&EPA
United States
Environmental Protection
Agency
Office of
Toxic Substances
Washington DC 20460
EPA-560/2-79-001
April 1979
Toxic Substances
The Health and
Environmental Impacts
of Lead
An Assessment of the
Need for Limitations,
-------
DREXEL
UNIVERSITY
V
W.W. Hagerty Library
32nd and Chestnut Streets
Philadelphia, Pennsylvania 19104
August 21, 1997
U.S. EPA OPPT Library (7407)
401 M St. SW
Northeast Mall 8606
Washington DC 20460
Hello:
We are returning the enclosed book lent to us on ILL#6163567. The book was received
damaged.
Dage, E.L. "The health and environmental impact
of lead and assessment of a need for
limitations"
Considering the poor condition and also to avoid any further damage to the book, we did not
give it to our patron.
Please void any charges associated with this loan.
Thank you,
~~~~
Deidre Harper
-------
EPA-560/2-79-00l
APRIL, 1979
OPTS~XECHNICAL !NFOID~!IO~ CEi~lD'
THE HEALTH AND ENVIRON~lliNTAL IMPACTS
OF LEAD M~D fu~ ASSESSMENT OF A
NEED FOR LIMITATIONS
Contract No. 68-01-4318
Project Officer
Elbert L. Dage
Office of Toxic Substances
Washington, D.C. 20460
OFFICE OF TOXIC SUBSTANCES
U.S. Environmental Protection Agency
Washington, D.C. 20460
-------
DISCLAIMER
This report has been reviewed by the Office of Toxic Substances,
U.S. Environmental Protection Agency, and approved for publication. Approval
does not signify that the contents necessarily reflect the views and policies
of the U.S. Environmental Protection Agency, nor does mention of trade names
or commercial products constitute endorsement or recommendation for use.
ii
-------
ABSTRACT
This study was performed to assess the health and environmental impacts
of lead and its compounds and the need for additional limitations upon its
production, use, or disposal. The investigation included an analysis of
the lead industry and the uses of lead, estimates of the nature and quanti-
ties of lead dispersed to the environment and their effects on the ecosystem
and on man, and an analysis of the scope and status of present limitations.
An evaluation of candidates for the application of limitations disclosed
that leaded gasoline and canned or processed foods ranked highest. Since
the former has already been addressed and new limitations promulgated, atten-
. tion was focused on lead intake from foods and beverages.
Food may account for from 60 to as much as 90 percent of lead intake
for the general population. Lead is naturally present in foods and this
fraction of the body burden is probably unavoidable. However, significant
lead contamination is inadvertently introduced into processed foods, pri-
marily from the lead solder used in food cans. It has been estimated that
as much as two-thirds of the lead in canned foods results from the solder.
No other lead limitation considered appeared to offer as great a potential
benefit to the entire population as a reduction of lead in canned foods.
Limitations directed at the dietary mode of exposure will benefit sensitive
segments, e.g. children, and the general population alike.
Analysis of dietary intakes and blood lead concentrations indicated that
reductions in mean blood leads of l~g/dl or more, provide a significant and
beneficial reduction in normal blood lead levels in the general population.
This level of reduction can be achieved by improvements in food can manu-
facturing technologies and procedures, while still retaining the economic
and technological benefits of soldered can construction.
Considerable progress toward these goals is presently being made by
the can industry, in cooperation with the Food and Drug Administration; it
is recommended that the results of these efforts be evaluated before further
action is taken.
Other potential sources of lead ingestion considered included lead-
glazed foodware, leaded glass, decal-decorated glass tumblers, solder-
joined food vessels, and pewter ware. On the basis of the evidence avail-
able, all of these appeared to be minor sources, not requiring further in-
vestigation at this time.
This report was submitted in fulfillment of Contract No. 68-01-4318
by Battelle Memorial Institute under the sponsorship of the U.S. Environ-
mental Protection Agency. This report covers the period September 30, 1976,
to April 30, 1979, and work was completed as of May 30, 1979.
Hi
-------
Abstract
Tables.
Figures.
THE HEALTH AND ENVIRONMENTAL IMPACTS OF LEAD M~D
ASSESSMENT OF A NEED FOR LIMITATIONS
TABLE OF CONTENTS
. . . .
. . . .
. . . .
. . . . . . . . . . . .
. . . . .
. . . . . . . . .
. . . . .
. . . .
. . . . . . . . . . . .
. . . . .
. . . . . .
. . . . . . . . .
. . . .
Acknowledgement.
4.0
. . . . . .
. . . . . .
. . . . . . . .
1.0
General Summary/Environmental Assessment. .
. . . . .
2.0
Introduction.
. . . . .
. . . . . .
. . . . . . .
. . . . . . . .
3.0
Properties of Lead and Its Compounds. .
. . . . . . .
. . . . . .
3.1
Physical and Chemical Properties. . . . . . . . . . .
3.1.1 Inorganic Compounds of Lead. . . . . . . . . . . . .
3.1.2 Organic Compounds of Lead. . . . .
3.1.3 Isotopes of Lead. . . . . . . . . . . . . . . .
3.2
References. .
. . . .
. . . .
. . . . . . .
. . . . .
The Lead Industry. .
4.1
. . . .
. . . . .
. . . .
. . . . . .
Overview/History
. . . . . .
. . . .
. . . . . . . . .
4.2
Lead Producing Industry. .
. . . . .
. . . .
. . . . .
4.2.1
Primary Lead. . . . . . . . . . . . . . . . . .
4.2.1.1 Mining. . . . . . . . . . . . . . . . . . .
4.2.1.2 Beneficiation. . . . . . . . . . . . . . . .
4.2.1.3 Smelting and Refining. . . . . . . . .
4.2.1.4 Production and Products. . . . . . . .
Secondary Lead. . . . . . . . . . . . . .
4.2.2.1 Scrap Pretreatment. . . . . . . . . .
4.2.2.2 Smelting. . . . . . . . . . . . . . . . . .
4.2.2.3 Refining. ... . . . . . . . . . . . . . . .
Supply/Demand Relationships . . . . . . . . . .
4.2.3.1 Stockpiling. : . . . . . . . . . . . .
4.2.2
4.2.3
iv
Page
. . iii
. xii
. xvii
. xix
1
10
12
12
15
17
21
23
25
25
28
28
28
31
32
34
38
42
43
43
45
48
-------
1- -
4.4
5.0
4.3
TABLE OF CONTENTS (Continued)
4.2.3.2
4.2.3.3
yage
48
Sl
Refined Lead Prices. . . . . . . . . . .
Reserves. . . . . . . . . . . . . . . . .
Lead Consuming Industries. . . . .
4.3.1
4.3.2
4.3.3
4.3.4
4.3.5
4.3.6
References.
. . . . . . . . . . .
52
Storage
4.3.1.1
4.3.1.2
4.3.1.3
Gasoline
4.3.2.1
4.3.2.2
4.3.2.3
Ba t teries. . . . . . . . . . . . . . . . .
Manufacture. . . . . . . . ~ . . . . . .
Production and Industry Structure. . . .
Future Projections. . . . . . . . . . . .
Antiknock Additives. . . . . . . . . . .
Manufacture. . . . . . . . . . . . . . .
Production and Industry Structure. . . .
Future Projections. . . . . . . . . . . .
53
53
60
63
64
64
71
78
84
84
87
90
90
95
96
105
. . . 106
107
108
109
109
110
110
Lead Oxides and Pigments. . . . . . . . . . . . .
4.3.3.1 Manufacturing. . . . . . . . . . . . . .
4.3.3.2 Production and Industry Structure. . . .
4.3.3.3 Future Projections. . . . . . . . . . . .
Inorganic Lead Compounds. . . . . . . . . . . . .
4.3.4.1 Manufacturing. . . . . . . . . . . . .
4.3.4.2 Production and Industry Structure. .
4.3.4.3 Future Projections. . . . . . . .
Miscellaneous Uses of Metallic Lead. . . . .
4.3.5.1 Ammunition. . . . . . . . . . . . .
4.3.5.2 Solder. . . . . . . . . . . . . . . . . .
4.3.5.3 Sheet Lead. . . . . . . . . .
4.3.5.4 Cable Covering. .
4.3.5.5 Weights and Ballast. . . . . . . .
4.3.5.6 Type Metal. . . . . . . . . . . . . . . .
4.3.5.7 Pipes, Traps, and Bands, and Caulking
Lead. . . . . . . . . . . . . . . . . . . 111
4.3.5.8 Brass and Bronze and Bearing Metals. .. 112
4.3.5.9 Casting metal. . . . . . . . . . . . .. 113
4.3.5.10 Collapsible Tubes and Foil. . . . . .. 113
4.3.5.11 Miscellaneous Uses. . . . . 114
Organic Lead Compounds. . . . . . . . . . . . .. 114
. . . .
115
. . . . . . . . . . . .
. . . . . .
Introduction of Lead Into the Environment.
5.1
5.2
Summary.
. . . .
121
. . . . .
121
. . . . . . . . . . . . . . . . . . .
Sources. . . . . . . . . .' . .
5.2.1
5.2.2
. . . ... . . . . . . . . . 121
121
Lead Producing Industry. . . . . . . . . . . . . . 121
5.2.1.1 Primary Lead. . . . . . . . . . . . . .
5.2.1.2 Secondary Lead. . . . . . . . . . . . . . 127
5.2.1.3 Secondary Brass and Bronze. . . . . . .. 128
Lead Consuming Industry. . . . . . . . . .. 129
5.2.2.1 Storage Battery Manufacture. . . . . .. 129
v
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TABLE OF CONTENTS (Continued)
Page
Gasoline Antiknock Additives. . . . . . 129
Lead Oxides and Pigments. . . . . . 135
Inorganic Lead Compounds. . . . . . . . . 137
Miscellaneous Uses of Metallic Lead. .. 138
Sources of Lead. . . . . . . . . . . . . 140
Iron and Steel Production. . . . . . . . 140
Cement manufacture. . . . . . . . . . . 141
Combustion of Fossil Fuels. . . . . . . . 142
Solid Waste Incineration. . . . . . . . 143
Sludge Disposal: . . . . . . . . . 143
5.2.2.2
5.2.2.3
5.2.2.4
5.2.2.5
Indirect
5.2.3.1
5.2.3.2
5.2.3.3
5.2.3.4
5.2.3.5
5.2.3
5.3
References. .
. . . . . . . . . . . 145
. . . . . . . . '" . .
6.0
Ecological Effects
151
. . . . . . . . . . . '" '" . . . . . . . .
6.1
Summary. . .
. .151
. . . . . . .
. . . ill
'" '" '" '" '" '" '"
6.2
Effects on Terrestrial and Aquatic Protista. . . . . . . .153
6.2.1
6.2.2
Terrestrial Protista. .
Aquatic Protista. . . .
. . . .154
. .155
'" '" '" '"
'" '" '" '" '" '"
'" '" '" '" '"
'" '" '" '"
6.3
Effects on Plants. . . . . . .
. .1~6
'" '" '" '"
'" '" '" '" '"
6.3.1
6.3.2
6.3.3
Metabolism, Uptake, and Absorption. . . . . .
Yie Ids. . . . . . . . . .. . . . . . . . .
Organolead Compounds. . . . . . . . . . . . . .
. . . 157
. 159
. . 160
6.4
Effects on Aquatic Biota.
. '160
'" '" '" '"
'" '" '" '" '" '" '"
'" '" '" '"
6.4.1
6.4.2
Invertebrates. . . . . . . . . . . . . . . . 160
Fishes. . . . . . . . . . . . . . . . . . . . . . . 161
Effects on Terrestrial Biota. . .
6.5
. 163
'" '" '" '" '"
6.5.1
6.5.2
Invertebrates. . . . . . . . . . 163
Vertebrates. . . . . . . . . . . 163
6.5.2.1 Birds. . . . . . . . . . . . '163
6.5.2.2 Mammals. . . . . . . . . . . . . . . . . '165
. . 166
6.6
Environmental Interactions. . . . . . . . . . .
Physical and Chemical Behavior. . . . .. . .166
Environmental Transport and Transfers. . . . 171
6.6.2.1 Air/Plants. . . . . . . . . . . . . . . .171
6.6.2.2 Soil/Plants. . . . . . . . . . . . 175
6.6.2.3 Plants/Animals. . . . . . . 176
6.6.2.4 Aquatic Systems. . . . . . . 177
6.6.1
6.6.2
vi
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1- -
7.0
6.7
TABLE OF CONTENTS (Continued)
Page
Ref erences . . . . . . . . . . . . . . . . . . . . . . . . 180.
Effects on Humans.
. . . . .
. . . .
. . . .
. . .192
7.1
7.2
7.3
7.4
7.5
7.6
. . . .
. . . . . . . .
. . . .
. .197
Summary. .
. . . .
Biological Pathways.
. . . .
. . . . .
. . . . .
. . . . .197
7.2.1
7.2.2
7.2.3
Uptake and Absorption. . . . . . . . . . . . . . 197
7.2.1.1 Inhalation. . . . . . . . . . . . . . . . 197
7.2.1.2 Ingestion. . . . . . . . . . .. . . . . .197
7.2.1.3 Skin Absorption. . . . . . . . . . . . . .200
7.2.1.4 Placental Transfer. . . . . . . . . . . . 200
Transport and Distribution. . . . . . . . . . . . .202
Elimina tion. . . . . . . . . . . . . . . . . . . . 211
212
Toxic Effects. . . . . .
7.3.1
7.3.2
7.3.3
. . . .
. . . . . .
Toxicities of Inorganic Lead Compounds. . . .212
Reproductive Effects. . . . . . . . . . . . .215
7.3.2.1 Fertility Reduction. . . . . . . . . . . .215
7.3.2.2 Mutagenicity. . . . . . . . . . . . . . . 217
7.3.2.3 Teratogenicity. . . . . . . . . . . 217
Carcinogenicity. . . . . . . . . . . . . . . . . . 218
219
Lead Poisoning in Children. . .
7.4.1
7.4.2
7.4.3
. . . . . .
. . . .
Adverse Effects of Lead. . 220
Lead Dose Necessary to Produce Adverse Effects. . . 220
Estimated Lead Intake in a Child with Pica for
Pain t . . . . . . . . . . . . . . . . . . . .
226
. . . . .
229
Epidemiology.
7.5.1
7.5.2
7.5.3
. . . . . . . . . . .
Studies of General Population. . . . . . . . . . . 230
Intermediate Level Studies. . . . . . . . . . . . . 242
7.5.2.1 Mobile Emissions Sources. . . . . . . . . -243
7.5.2.2 Populations Impacted by Stationary
Sources. . . . . . . . . . . . . . . . . . 245
Studies of Occupational Groups. . . . . . . . . . . 252
7.5.3.1 Threshold Levels for Clinical and
Subclinical Effects. . . . . . . . . . . . 252
. . . . . . . . . .
264
Organic Lead. .
7.6.1
7.6.2
7.6.3
7.6.4
. . . . .
. . . . . .
Uptake and Absorption. . . . . . . . .
Tissue Distribution. . . . . . . . . . . . . . . .
Elimination. . . . . . . . . . . . . . . . .
Toxic Effects. . . . . . . . . . . . .
266
267
268
268
vii
-------
7.7
7.6.5
TABLE OF CONTENTS (Continued)
7.6.4.1 Acute Toxicity of Various Organolead
Compounds. . . . . . . . . . . . . . . .
7.6.4.2 Neuropathology. . . . . . . . . . . . . .
7.6.4.3 Metabolic Effects. . . . . . . . . . . .
7.6.4.4 Enzyme Effects. . . . . . . . . . . . . .
7.6.4.5 Reproductive Effects. . . . . . . . . . .
Epidemiologi~ Studies. . . . . . . . . . . . . . .
References. . . . . . . . . . . . . . . . . . . . . . . .
Lead in the Environment.
. . . . . . . . . . . . . . . . . . .
8.0
8.1
8.2
8.3
8.4
8.5
Summary
. . . . . . . .
. . . . . .
. . . . .
. . . . .
--------
Lead in Air.
8.2.1
8.2.2
8.2.3
. . . . . .
. . . .
Air Lead Concentrations in the U.S. .
Localized Source-Oriented Studies. . . . . . . .
8.2.2.1 Antiknock-Related Studies. . . . . . . .
8.2.2.2 Smelter-Related Studies. . . . . . . . .
Trends in Atmospheric Lead Concentrations. . . .
Lead in Hater. .
8.3.1
8.3.2
8.3.3
. . . . . . . .
. . . . . .
. . . . .
Water Lead Concentrations in the U.S. . . . . .
Lead Concentrations in Drinking water. . . . . .
Trends in Water Lead Concentrations. . . . . . .
Lead in Soils. .
8.4.1
8.4.2
8.4.3
8.4.4
. .. . . . . .
. . . . . . . . .
Soil Lead Concentrations in the U.S.. . . . . .
Localized Source-Oriented Studies. . . . . . . .
Lead in Urban Dusts. . . . . . . . .. ....
Trends in Soil Lead Concentrations. . . . . . . .
Lead in Foods and Beverages. . . . .
8.5.1
8.5.2
8.5.3
Determinants of Lead Content. . . . . . . . . .
Lead Content of Individual Food Commodities. . .
8.5.2.1 Food and Forage Plants. . . . . . . . .
8.5.2.2 Processed Fruit and Vegetable Products.
8.5.2.3 Meat, Fish, and Poultry Products. . . .
8.5.2.4 Milk and Infant Formulas. . . . . . . .
8.5.2.5 Beverages, Bakery Products, Sugar, and
Condiments. . . . . . . . . . . . . . .
Adventitious Lead in Processed Food. . . . . . .
viii
Page
268
269
269
271
271
271
273
292
292
296
297
301
301
305
309
314
316
320
324
324
325
325
328
330
331
332
333
333
336
337
339
341
344
-------
8. 7
8.6
TABLE OF CONTENTS (Continued)
Page
Source Contributions to Lead Intake by Humans. . . . . . . 351
Lead Intake From Air. . . . . . . . . . . . . 351
Lead Intake From Drinking Water. . . . . . . . . 355
Lead Intake From Soil and Other Non-Food Items. . . 356
Lead Intake From Foods and Beverages. . . . . . . . 357
Relative Contributions of Various Media to Body
Burdens. . . . . . . . . . . . . . . . . . . . . .
8.6.5.1 Adults' . . . . . . . . . . . . . . . . .
8.6.5.2 Children' . . . . . . . . . . . . . . . .
Recommendations Concerning Safe Levels of Dietary
Lead. . . . . . . . . . . . . . . . . . . . . . . . 373
Effects of Reducing Adventitious Lead in Canned
Foods on Dietary Lead Intake. . . . . . . . . . . . 376
8.6.7.1 Methods for Deriving Food Consumption
Levels. . . . . . . . . . . . . . . . . . . 376
8.6.7.2 Daily Dietary Lead Intakes from Different
Foods for Various Age-Sex Groups. . . . . . 384
364
364
367
Lead Uptake/Blood-Lead Relationships. . .
9.2.1
9.2.2
. . . .
. . . .
. 390
Relationship of Blood Lead Levels to Lead
Exposure in Humans. . . . . . . . . . . . . . . . .
Distributional Characteristics of Blood Lead
Values in General Populations. . . . . . . . . . . .
Effects of Reducing Dietary Intake on Mean Blood
Lead Levels. . . . . . . . . . . . . . . . . . . . .
8.7.3.1 Approach to Estimation' . . . . . . .
8. 7 . 3. 2 Examp le Case' . . . . . . . . . . . . . . .
390
392
393
395
8.6.1
8.6.2
8.6.3
8.6.4
8.6.5
8.6.6
8.6.7
8.7.1
8.7.2
8.7.3
1.8
References. .
. . . . . . . . . . . . .
. . . . . . .
. . . .
401
1.0
Assessment of the Need for and Possible Approaches to
Limitations on Lead' . . . . . . . . . . . . . . . . . . .
415
. . . . . . . . . .
. . . . . . . . . .
415
1.1
Summary. . . .
. . . 418
9.2
9.3
Need for Limitations. . . . . .
. . . . . . .
. . . .
Acute Lead Poisoning. . . . . . .
Limitations at Low Lead Levels.
. . . . . . . . . . 418
. . . . . . . . 419
Approaches to Limitations. . .
. . . . .
. . . . . . . 426
9.3.1
9.3.2
Criteria for Prioritization. . . . . . . . . . 426
Prioritization of Possible Limitations. . . . . . . . 427
9.3.2.1 Leaded Gasolines . . . . . . . . . . . . . . 428
9.3.2.2 Adventitious Lead in Food and Beverages. . . 430
ix
-------
,-
9.4
9.3.3
9.3.2.3
9.3.2.4
9.3.2.5
9.3.2.6
9.3.2.7
9.3.2.8
9.3.2.9
9.3.2.10
9.3.2.11
TABLE OF CONTENTS (Cant.)
Page
High-Lead Paint in Homes. . . . . . . . . 431
Lead-Based Paints. . . . . . . . . . . . 432
Printing Inks. . . . . . . . . . . . . . 433
Lead-Acid Storage Batteries. . . . . . . 434
Lead in Plastics and Rubber. . . . . . . 434
Lead Ammunition. . . . . . . . . . . . . 435
Miscellaneous Uses of Metallic Lead. . . 435
Emissions from Lead in Industry
Processes. . . . . . . . . . . . . . . . 436
Emissions from Indirect Sources. . 436
. . . . . . .
437
Non-Structural Approaches. .
.438- .
Existing and Proposed Limitations. .
9.4.1
9.4.2
. . . . . .
. . . .
Direct Limitations on Lead. . . . . . . . . . . . 441
9.4.1.1 Nonferrous Ore Mining and Milling. . . . .441
9.4.1.2 Ferroalloy Ore Mining and Milling. . . . .442
9.4.1.3 Primary Lead. . . . . . . . . . . . 442
9.4.1.4 Primary Copper. . . . . . . . . . . 442
9.4.1.5 Electroplating. . . . . . . . . . . 442
9.4.1.6 Lead Storage Battery Manufacture. '. . . . 443
9.4.1.7 Chlorine-Caustic. . . . . . . . . 443
9.4.1.8 Lead Monoxide. . . . . . . . 443
9.4.1.9 Chrome Pigments. . . . . . . 443
9.4.1.10 Television Picture Tubes. . . . . 443
9.4.1.11 Hand Pressed and Blown Glass. . . . . . .444
9.4.1.12 Lead-Sheathed Rubber Hose. . . . . ., 444
9.4.1.13 Gasoline Antiknock Additives. . . . . . 444
9.4.1.14 Lead-Based Paint. . . . . . . . . . . . 445
9.4.1.15 Lead-Based Paint in Federally-Owned
or Assisted Housing. . . . . 446
Occupational Exposure to Lead. . . . . . 447
Drinking Water Standard. . . . . . 447
Evaporated Milk. . . . . . . . . . 447
Ambient Air Standards. . . . . . . 448
Lead Arsenate. . . . . . . . . . . . . . 448
Lead Shot. . . . . . . . . . . . . . . . 449
Ocean Dumping. . . . . . . . . . . . . 449
Limitations. . . . . . . . . . . . . . . 449
Primary Lead Smelters. 449
Primary Copper Smelters. . . . . . 450
Secondary Lead Smelters. . . . . . . . . 450
Secondary Brass and Bronze Ingot
Production Plants. . . . . . . . . 450
Ferroalloy Production Facilities. . . . .450
Electric Arc Steel Furnaces. . . . . . . 450
Incinerators. . . . . . . . . . . . . . .450
Sludge Incinerators. . . . . . . . . . . 4sn
9.4.1.16
9.4.1.17
9.4.1.18
9.4.1.19
9.4.1.20
9 . 4 . 1. 21
9.4.1.22
Indirect
9.4.2.1
9.4.2.2
9.4.2.3
9.4.2.4
9.4.2.5
9.4.2.6
9.4.2.7
9.4.2.8
x
-------
9.5
9.6
9.4.3
TABLE OF CONTENTS (Continued)
9.4.2.9 Portland Cement Plants. . . . . . .
9.4.2.10 Petroleum Storage. . . . . . . . . . . .
9.4.2.11 Gasoline Vapor Recovery. . . . . .
Recent Enabling Legislation. . . . . . . . .
Case Study: Analysis of Alternatives for Limitations on
Lead Intake from Foods and Beverages. . . . . . . . . . .
9.5.1
9.5.2
9.5.3
Lead in
9.5.1.1
9.5.1.2
9.5.1.3
9.5.1.4
Processed Foods and Beverages. . . . . . .
Food Can Technology. . . . . . . . . . . .
Alternatives to Lead-Soldered Food Cans. .
Good Manufacturing Practices. . . .
Economic Effects of Limitations
Alternatives. . . . . . . . . . . . . . .
Industry Trends and Outlook. . . . . . . .
9.5.1.5
Lead-Glazed Foodware. . . . . . . . . . . . . . . .
9.5.2.1 Glaze Technology. . . . . . . . . . . . .
9.5.2.2 Historical Perspective. . . . . . . . . .
9.5.2.3 Alternatives to Lead Glazes. . . . . . . .
Miscellaneous Sources of Ingested Lead. . . . . . .
9.5.3.1 Decal-Decorated Tumblers . . . . . .
9.5.3.2 Lead Glass. . . . . . . . . . . . .
9.5.3.3 Solder-Joined Food Vessels. . . . .
9.5. 3.4 Pewter. Ware. . . . . . . . . . . .
9.5.3.5 Drinking Water. . . . . . . .
References. . .
Appendix. .
. . . . . . . .
. . . .
. . . .
. . . . . . . . . . . . . . . .
. . . . . .
Lead Intakes from Various Foods for Selected Age-Sex
Groups. . . . . . . . . . . . . . . . . . . . . . . . .
xi
Page
450
450
451
451
452
452
452
458
460
463
471
,472
473
475
476
477
477
478
478
479
479
481
484
484
-------
TABLES
Number
3.1 Physical Constants for Lead. . . . . . . . . . . . . . . . . .
3.2 Oxidation-Reduction Potentials for Lead. . . . . . . . .
Solubilities of Inorganic Compounds of Lead. . . . . . . . . .
Properties of Tetraethyllead and Tetramethy1lead .
Consumption Patterns for Lead in Selected Countries, 1976. . .
Lead Smelters and Refineries. . . . . . '. . . . . . . . . . .
U.S. Production of Refined Lead and Antimonial Lead at Primary
Refineries, by Source Material, 1966-1975. . . . . . . . . .
4.4 Standard Specifications for Pig Lead (B29-55). . . . . . . . .
4.5 Lead Recovered from Scrap Processed in the United States, 1966-
1975 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.6 Supply of Lead in the United States, 1967-1977 . . . . . . . .
4.7 U.S. Imports of Lead by Types of Material, 1967-1977 . . . . .
4.8 U.S. Exports of Lead by Type of Product, 196701977 . . .
4.9 Selected Compounds of Lead and Their Uses. . . . . . . .
4.10 U.S. Lead Consumption by Class of Product, 1967-1976 . . . . .
4.11 Lead Consumption in the United States, By Products, 1973-1976.
4.12 Estimated Structure of Storage Battery Industry. . . . . . . .
4.13 Lead Alkyl Manufacturers and Estimated Capacities. . . . . . .
4.14 Production and Consumption of Lead Alkyls, 1966-1976 . . . . .
4.15 Average Lead Content of Gasolines, 1965-1978 . . . . . . . . .
4.16 Consumption of Gasoline and Lead Anti-Knock, 1955-1978 .
4.17 Gasoline Consumption Forecast. . . . . . . . . . . . . .
4.18 Effect of PhasedoWli on Consumption of Lead in Gasoline.
4.19 Lead Pigments--U.S. Shipments, By Industry, 1971-1975. .
4.20 Plants Producing Lead Pigments. . . . . . . . . . . . . . . .
4.21 Inorganic Lead Compounds and Their Uses. . . . . . . . . . . .
4.22 Producers of Lead-Based Plastic and Rubber Stabilizer-Type
Materials. . . . . . . . . . . . . . . . . . . . . . . . . .
4.23 Estimated Consumption of Lead-Based Stabilizers in Plastics and
Rubber Indus~ries, 1974. . . . . . . . . . . . .
4.24 Producers of Lead-Based Paint Driers. . . . . . .
4.25 Production of Selected Lead-Based Paint Driers. .
4.26 Producers of Miscellaneous Lead-Based Chemicals Produced
than One Company. . . . . . . . . . . . . . . . . . .
4.27 Miscellaneous Lead-Based Chemicals Produced by Only One
Company. . . . . . . . . . . . . . . . . . . . .
5.1 Estimated Releases of Lead to the Environment. . . . . .
6.1 Concentrations of Lead Reported Toxic or Lethal to rish.
6.2 Lead in the Above-Ground Portion of Grasses as a Function of
Distance from Traffic or Industries. . . . . . .
6.3 Lead in Crops, Greenhouse Studies. . . . . . . . . . . .
6.4 Lead in Crops, Highway Studies. . . . . . . . . . . . .
3.3
3.4
4.1
4.2
4.3
Page
13
14
16
20
27
36
37
39
41
46
47
49
54
58
59
62
65
73
74
77
80
83
89
91
93
98
99
101
102
by More
103
xii
104
127
162
172
173
173
-------
TABLES (Continued)
Number
6.5 Mean Concentration of Lead in Tissue of Small Mammals from
Roadside and Control Sites. . . . . . . . . . . . . . . . .
7.1 Lead Ingestion and EKcretion of a Normal Human Subject. . . .
7.2 ALA-D Activity in Liver and Distribution of Lead in Various
Organs in Rats. . . . . . . . . . . . . . . . . . . . . . .
7.3 Tissue Lead Concentration in Children and Adolescents. . . . .
7.4 Variation in Human Tissue Lead Concentration with Geographical
Locations. . . . . . . . . . . . . . . . . . . . . . . . . .
7.5 Tissues Ranked on the Basis of Overall Mean Concentrations of
Lead. . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.6 Age-Related Increases of Lead Concentration in Body Tissues. .
7.7 Representative Toxicities and Occupational Standards for Seven
Commercially Important Inorganic Lead Compounds. . . . . . .
7.8 Calculated Lead Intake and Absorbed Dose from Paint Pica. . .
7.9 Calculated Daily External Dose and Associated Internal Dose. .
7.10 Blood Lead Levels of Selected Human Populations. . . . . . . .
7.11 Mean Air Lead Exposure for the Five Groups Examined by Azar,
e t a1. (1975). . . . . . . . . . . . . . . . . . . . . . . .
7.12 The Impact of Air Lead on Blood-Lead Levels; A Comparison of
Actual Data to Predictions Using Mathematical Model. .
7.13 Descriptions of Lead Plants Investigated, 1975-1976. . .
7.14 Blood-Lead Levels in Lead Plant Workers. . . . . . . . .
7.15 Percentage of Workers with Symptoms of Lead Poisoning by Blood
Lead and Erythrocyte Protoporphyrin Level at Three Lead
Plants. . . . . . . . . . . . . . . . . . . . . . . .
7.16 Frequency of Symptoms Among 22 Cases of Lead Poisoning, Utah,
1976 . . . . . . . . . . . . . . . . . . . . . .
7.17 Frequency of Symptoms in Lead Smelting Plant Employees,
Minnesota, 1976. . . . . . . . . . . . . . . . . . . .
7.18 Cutaneous Absorption of Lead Compounds. . . . . . . . . . . .
7.19 Representative Toxicities and Occupational Standards for
Tetraethyl and Tetramethyl Lead. . . . . . . . . . . .
8.1 Lead Concentrations in Surface Air From Selected Sites Along
the 80th Meridian, 1967. . . . . . . . . . . . .
8.2 Concentration of Lead in the Atmosphere of Three Cities, 1961-
1962 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.3 National Average Ambient Atmospheric Lead Concentrations:
Quarterly Composites. ... . . . . . ..... . . . . . . . ...
8.4 List of 31 Urban Areas with Quarterly Lead Concentrations
Equalling or Exceeding 1.5 ~g/m3 in 1975 . . . . . . . . . .
8.5 Effect of Proximity to Highway in an Urban Environment on Air
and Blood Lead Concentrations. . . . . . . . . . . . . . . .
Lead Content of Various Marine Waters. . . . . . . . . . . . .
Regional Summary of Lead in Surface Water of the U.S. . . . .
Number of Samples of Surface Waters Exceeding Specified Concen-
trations of Lead. . . . . . . . . . . . . . . . . . . . . .
8.9 Lead Content of Tap Water From Two Surveys of Distributed
Water. . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.6
8.7
8.8
xiii
Page
177
199
201
203
207
209
210
213
227
228
231
237
241
255
257
257
259
259
267
270
298
300
302
303
306
314
317
319
322
-------
Number
8.10 Lead Content of Roadside Soil and Grass as a Function of Dis-
tance From Traffic and Soil Depth. . . . . . . . . . .
8.11 Lead in Dirt in Detroit. . . . . . . . . . . . . . . . .
8.12 Lead Content of Cereals and Vegetables. . . . . . . . .
8.13 Lead Content of Fruits. . . . . . . . . . . . . . . . .
8.14 Lead Content of Processed Fruits and Vegetable Products.
8.15 Lead Content of Meatt Fish and Poultry Products. . . . .
8.16 Lead Content of Milk and Infant Formulas. . . . . . . .
8.17 Lead Content of Beverages. . . . . . . . . . . . . . . .
8.18 Lead Content of Bread and Baked Products. . . . .
8.19 Lead Content of Sugart Spicest Condimentst and Miscellaneous
Foods. . . . . . . . . . . . . . . . . . . . . . . .. 343
8.20 Variations in Lead Concentrations with Time in Selected Canned
Food Products. . . . . . . . . . . . . . . . . . . . . . . .
8.21 Potential Daily Intake of Lead by Inhalation. . . . . .
8.22 Deposition of Lead Inhaled by Man. . . . . . . . . . . .
8.23 Estimated Dietary Intake of Lead by Food Class. . . . . . . .
8.24 Rank Order of Lead Findings by Food Class. . . . . . . . . . .
8.25 The Effects of Various Assumptions of the Value of Trace and
Non-Detections on Estimates of Dietary Intake. . . . .
8.26 Lead Content of Adult Foods Sampled by FDA Heavy Metals in
Foods Survey; FY 1974. . . . . . . . . . . . . . . . . . . . 363
8.27 Lead Content of Baby Foods Sampled by FDA Heavy Metals in
Foods Survey; FY 1974. . . . . . . . . . . . . . . . . . . . 364
8.28 The Relative Contributions of Various Media to Lead Intake and
Absorption: Adult Males. . . . . . . . . . . . . . .. 366
8.29 Estimated Total Absorbed Dose at Varying Air Lead Concentrations:
Young Adult Males. . . . . . . . . . . . . . . . . . . 369
8.30 The Relative Contribution of Various Media to Lead Intake and
Absorption in 3-Year Old Children. . . . . . . .
8.31 Total Daily Lead Absorbed By 3-Year Non-Pica Child and
Percentage Attributable to Various Media under Varying
Environmental Conditions. . . . . . . . . . . . . . .
TABLES (Continued)
8.32
8.33
Estimated Lead Content of Various Foods. . . . . . . . .
Food Consumption in Grams Per Day for Various
Age-Sex Groups. . . . . . . . . . . . . . . . . . . . ..
Daily Dietary Intake of Lead for Various Age-Sex
Groups and The Effect of Reducting Lead in Canned Foods
by One-Half or Two-Thirds. . . . . . . . . . . .
Reduction in Daily Lead Intake for Children from
Various Food Classes after Elimination of 1/2 or 2/3
of the Lead in Canned Foods. . . . . . . . . . . . . .
Reduction in Daily Lead Intake for Adults from Various
Food Classes after Elimination of 1/2 or 2/3 of the Lead
in Canned Foods. . . . . . . . . . . . . . . . . . . . .
Geometric Mean Air- and Blood-Lead Values for 11 Study
Populations. . . . . . . . . . . . . . . . . . . .
Frequency Distribution of Blood Lead Values in Two Hypo-
thetical Populations of Adult Females. . . . . . .
8.34
8.35
8.36
8.37
8.38
xiv
Page
326
329
334
336
337
338
340
342
343
348
352
353
359
360
361
371
374
377
380
385
386
387
391
398
-------
Blood-Lead Levels versus Lowest-Observed-Effect Levels.
9.2 Assessment of Factors Characterizing a Need and
Feasibility of Limitations on Lead. . . . . . . . . . .
Summary of Existing and Proposed Federal Regulations
Governing Limitations on Lead. . . . . . . . . . . . . .
Comparison of Results of 1974 and 1976 Canned
Food Surveys. . . . . . . . . . . . . .
Lead Content of Infant Juices Packed in Metal
Containers. '. . . . . . . . . . . . . . . . . . . . . .
Major U.S. Merchant Producers of Metal Cans, 1975. . .
Summary of Estimated Costs of Alternative Food Can
Manufacturing Techniques. . . . . . . . . . . . . . . .
Number
9.1
9.3
9.4
9.5
9.6
9.7
Table A-l.
TABLES
.
(Cont.)
. . . . .
TABLES
APPENDIX A
Daily Intake of Lead From Various Foods and the Effect
of Reducing Lead Content of Canned Foods: Males and
Females Under l-year Old. . . . . . . . . . . . . . . . .
A-2.
Page
422
42.9
439
462
464
465
470
A-l
Daily Intake of Lead From Various Foods and the Effect
of Reducing Lead Content of Canned Foods: Males and
Females 1-2 Years Old. . . . . . . . . . . . . . . . . . . A-2
A-3.
Daily Intake of Lead From Various Foods and the Effect
of Reducing Lead Content of Canned Foods: Males and
Females 3-5 Years Old. . . . . . . . . . . . . . . . . . . A-3
A-4.
Daily Intake of Lead From Various Foods and the Effect
of Reducing Lead Content of Canned Foods: Males and
Females 6-8 Years Old. . . . . . . . . . . . . . . . .
xv
. . A-4
-------
A-5.
A-6.
A-7.
A-8.
A-9.
A-lO.
TABLES
APPENDIX A (Cont.)
Daily Intake of Lead From Various Foods and the Effect
of Reducing Lead Content of Canned Foods: Males
15-17 Years Old. . . . . . . . . . . . . . . . . . . . . .
Daily Intake of Lead From Various Foods and the Effect
of Reducing Lead Content of Canned Foods: Females
15-17 Years Old. . . . . . . . . . . . . . . . . . . . . .
Daily Intake of Lead From Various Foods and the Effect
of Reducing Lead Content of Canned Foods: Males
20-34 Years Old. . . . . . . . . . . . . . . . . . . . . .
Daily Intake of Lead From Various Foods and the Effect
of Reducing Lead Content of Canned Foods: Females
20-34 Years Old. . . . . . . . . . . . . . . . . . . . . .
Daily Intake of Lead From Various Foods and the Effect
of Reducing Lead Content of Canned Foods: Males
55-64 Years Old. . . . . . . . . . . . . . . . . . . . . .
Daily Intake of Lead From Various Foods and the Effect
of Reducing Lead Content of Canned Foods: Females
55-64 Years Old. . . . . . . . . . . . . . . . . . . . . .
xvi
A-5
A-6
A-7
A-8
A-9
A-lO
-------
FIGURES
.
Number
3.1 Solubility and species distribution for Pb(II) in soft
water. . . . . . . . . . . . . . . . . . . . . . . .
3.2 Solubility and species distribution for Pb(II) in hard
water. . . . . . . . . . . . . . . . . . . . . . . .
4.1 Simplified flow sheet for production of primary lead. . . .
4.2 Geographic locations of domestic primary lead smelters
and refineries. . . . . . . . . . . . . . . . . . . . . .
Lead scrap flow. . . . . . . . . . . . . . . . . . . . . . .
Secondary lead smelting process. . . . . . . . . . . . . . .
Trends in the lead industry in the United States. . . . . .
Simplified flow sheet for storage battery manufacture. . . .
Sodium-lead alloy process for the manufacture of tetraethyl
lead. . . . . . . . . . . . . . . . . . . . . . . . . . .
4.8 Electrolysis process for the manufacture of tetramethyl
lead. . . . . . . . . . . . . . . . . . . . . . . . . . .
4.9 Nationwide trends in gasoline lead content, 1965-1985. . . .
4.10 Passenger car use of premium gasoline. . . . . . . . . . . .
4.11 Projected consumption of grades of gasoline, 1970-1990. . .
4.12 Estimated lead content of leaded and total gasoline pool,
1970-1985. . . . . . . . . . . . . . . . . . . . . . . . .
4.13 Simplified flow sheet of processes for the manufacture of
lead-based white pigments. . . . . . . . . . . . . . . . .
4.14 Simplified flow sheet of processes for manufacture of lead
chromate-based pigments. . . . . . . . . . . . . . . . . .
6.1 Ecologic flow chart for lead showing possible cycling
pathways and compartments. . . . . . . . . . . . . . . . .
7.1 Levels of blood lead in volunteers exposed to 10.9 ~g/m3
lead sesquioxide. . . . . . . . . . . . . . . . . . . . .
7.2 Dose-response relationship for the effects of internal
doses of lead ad Pb-B on erythrocyte protoporphyrin. . .
7.3 Mean blood lead concentration for epidemilogic and
experimental respiratory exposures. . . . . . . . . . . .
Blood lead levels and corresponding mean air lead levels. .
Blood lead versus total air lead. . . . . . . . . . . . . .
Hypothetical distribution curves of blood lead concentra-
tions of a population exposed first to 200 ~g Pb/m3 and
then to 500 ~g/m3. . . . . . . . . . . . . . . . .
8.1 Air lead values as a function of traffic volume and
distance from the highway. . . . . . . . . . . . .
8.2 Concentrations of metals in air as a function of distance
from the E1 Paso smelter. . . . . . . . . . . . .
8.3 Concentration of particulate lead in air. . . . . . . . .
8.4 Relative abundance of lead in airborne particulates and
in soil samples. . . . . . . . . . . . . . . . . . . . .
8.5 Average urban ambient air lead concentrations vs. lead
anti-knock consumption, with phasedown. . . . . . . . .
8.6 Depth profiles of common lead concentration in the central
northeast Pacific. . . . . . . . . . . . . . . . . . . .
8.7 Annual mean level of lead in U.S. streams, 1975. . . . . .
8.8 Percentage of Boston tap water samples exceeding lead
standard. . . . . . . . . . . . . . . . . . . . . . . .
4.3
4.4
4.5
4.6
4.7
7.4
7.5
7.6
xvii
Page
18
19
29
35
40
44
50
61
66
69
75
76
81
81
86
88
167
205
221
232
234
239
253
304
308
310
310
312
315
318
323
-------
Number
8.9
8.10
8.11
8.12
8.13
8.14
8.15
8.16
8.17
8.18
FIGURES (Cont.)
Mean lead concentrations of Boston tap water samples
by type of samp le. . . . . . . . . . . . . . . . . . .
Distribution of lead in canned and bottled products. . .
Lead distribution in single cans of tomato paste. . . . .
Lead distribution in single cans of tomato paste
after storage at room temperature. . . . . . . . . . .
Effect of seam length/volume ratio on the lead level of
can contents. . . . . . . . . . . . . . . . . . . . . .
Lead absorbed by man. . . . . . . . . . . . .
The relative contribution of various media to total
absorbed lead dose. . . . . . . . . . . . . . . . . . .
Daily dietary intake of males, by age. . . . . . . . . .
Daily dietary intake of females, by age. . . . . .
Predicted distribution of blood lead levels at
two different mean blood leads for adult women,
20-34 years old. . . . . . . . . . . . . . . . .
xviii
Page
323
345
345
347
347
365
368
388
389
397
-------
ACKNrn{LEDGEMENTS
Other Battelle-Columbus staff members contributed specialized
expertise in the preparation of this document, including Mr. John B.
Hallowell in the area of nonferrous metals, Mr. James L. Otis on alkyl
leads, Mrs. J. Caroline War ling and Mr. David A. Savitz on the com-
pilation and analysis of diets and lead intakes, and Mr. Raymond ~v. Hale
on general industry economics.
We also wish to express our appreciation for the cooperation
received from EPA staff of The Office of Toxic Substances, particulary
the project officer, Elbert L. Dage, who provided support throughout the
program.
xix
-------
1.0
GENERAL SUMMARY
This general summary is intended to serve as an overview of the investi-
gation and highlight the principal findings; more detailed summaries are
included within the individual chapters.
Analysis of the findings of this investigation of the health and envi-
ronmental effects of lead supports the conclusions of prior investigators
examining this problem, and leads to a number of general conclusions on the
need for additional controls on lead, and suggested ways and means for apply-
ing these limitations most advantageously.
Lead is already a highly regulated substance, and most of the exposure
hazards leading to acute lead poisoning have already been closely regulated.
These are primarily occupational exposures, to which the population in general
is not exposed. Less intense, but more pervasive sources of lead intake,
which may affect the general population, such as lead in gasoline antiknock
additives, have also been addressed in recent years, and the combination of
the gasoline lead phasedown and the ambient air quality standard for lead has
placed this major environmental source of lead finally under control.
Of the ten remaining
gested lead, specifically
source of lead intake for
investigation.
candidates for consideration of limitations, in-
lead in foods, was identified as the preeminent
the general population, and was selected for further
Mostof the lead intake from food is attributed to lead accidentally
introduced during the canning process. Methods for achieving large reductions
in this adventitious lead, short of the total elimination of lead-soldered
food cans, are available, and the can-making industry is vigorously pursuing
this approach, in cooperation with the Food and Drug Administration. The
reductions in mean blood lead concentration of the general population which
can be achieved by these evolutionary improvements are calculated to be so
significant that they should not be overlooked. The ongoing efforts of the
FDA in this area are proving so effective that it is recommended that the
results of this program be awaited and evaluated before further action is
taken.
-
L
-------
Lead is a dense, soft, malleable, easily fused, non-corroding metal,
almost as durable in the environment as a noble metal. As described in
Chapter 3, most lead compounds are moderately to highly insoluble. This
characteristic has an important bearing on the lack of mobility of lead in
soil and in water, and partially explains why lead has not posed a large
problem in ecosystems, in spite of the fact that man has over the years
discarded and dispersed millions of tons of lead to the biosphere.
Lead is also a rare metal. Its average abundance in the earths crust
has been estimated to be only about 16 ppm. Nevertheless, there are a
surprising number of commercially exploitable deposits, and lead is a
commercially important base metal. Lead is durable and relatively easy to
refine or rerefine. Thus, secondary lead is recovered from scrap and
recycled, on a scale comparable to that of primary lead (See Chapter 4).
The United States is the leading producer of primary lead, producing
approximately 500,000 to 600,000 metric tons per year, mostly from deposits
in southeastern Missouri. About the same quantity of secondary lead is
produced each year.
Consumption of lead in the U.S. is inextricably related to the
automobile industry. In recent years, from 800,000 to 1,000,000 metric
tons (from 60 to 70 percent of total lead consumption) have gone to the
manufacture of storage batteries and gasoline antiknock additives. Lead
storage batteries represent the only large segment of the lead industry
with a foreseeable significant growth potential. Except for a few
relatively minor uses, all other uses of lead are relatively stagnant or
declining. Much of this decline is directly related to increasing
pressures to find substitutes for or to minimize the use of this toxic
metal. Lead-containing paints and paint driers are one example of this
trend; whereas lead-based house paints were formerly very widely used,
no house paint manufactured today may contain in excess of 0.06 percent
lead, i.e. must be lead-free.
Lead's uses vary from those that are totally dissipative to those
almost non-dissipative; as described in Chapter 5, most of the introduction
of lead to the environment arises directly from dissipative uses. Alkyllead
gasoline antiknock additives is the premier example of a dissipative
use which has accounted for almost all of the lead dissipated initially to
the air, and ultimately to s01l and water. On the other hand, lead in
storage batteries, the largest single use (consuming typically about
750,000 tons/yr of lead) is an essentially non-dissipative use. The lead
in batteries is not consumed in service, and an estimated 80 percent is
recycled. Even that which escapes recovery and recycle is in such a
compact and immobile form that its dispersion and transfer through the
ecosystem is minimal.
Lead is also introduced to the environment to some extent by indirect
routes not associated at all with the use of lead or lead compounds, for
example, from the combustion of coal or the firing of cement calcine. Other
indirect sources include iron and steel production and the incineration of
solid wastes or sewage sludges. Fortunately, as discussed in Chapter 5, the
quantities of lead emitted from these indirect sources are small in comparison
2
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to the major sources of lead emissions. Part of the reason for this is that
required control of particulate emissions concomitantly also provides control
of particulate lead. The contribution from these sources to the body burden
of the general population is small, estimated to possibly be from a fraction
of a percent to 1-2 percent at the worst.
The ecological effects of lead (Chapter 6) tend to be unspectacular
and subtle. Although excessive levels of lead in the environment have the
same kinds of effects upon terrestial and aquatic systems as most other toxic
substances, such excessive levels are the exception. Most such incidents
appear to have been associated with large-scale emissions of lead from
industrial point sources. The massive amounts of lead which have been released
to the environment from the combustion of leaded gasolines have not elicited
propartionallyseriou3 ecological effects, possibly because the dispersion
is so uniform, and environmental concentrations are below the level at which
effects are apparent. Although lead has been shown to bioconcentrate in
some fish species, there is no evidence of biomagnification. The poisoning of
waterfowl from eating lead shot has prompted regulatory action to substitute
iron shot in the principal U.S. flyways to reduce this hazard. Laboratory
and field studies have shown .that lead inhibits plant growth and produces
other adverse biochemical phenomena, although such effects are minimal
at usual ambient concentrations. Ecologically speaking, the indications
are that lead is a nonessential element that exhibits a 10.J degree of potential
toxicity to plants and a high degree of potential toxicity to animals.
The major toxic effects of lead have been upon people (Chapter 7).
Lead poisoning has been recognized as an occupational problem for centuries;
and many restrictions have been placed upon conditions in the work place to
reduce this hazard. Within the past year the Occupational Safety and Health
Administration promulgated regulations reducing by one-half the allowable
workroom air lead concentration, from 100 to 50 ~g/m3; and this had a few
years ago been halved from the earlier 200 ~g/m3 level. This category of
exposure to lead can be characterized as one of very high occupational risk
to a small group of people, which is being addressed by OSHA, but is not an
environmental risk to which the general population is exposed.
Lead's toxic effects range from acute lead poisoning (seen in some
occupationally exposed individuals and in children who ingest large quantities
of lead by eating paint chips) about which there is general agreement on
its manifestations and epidemiology, to the other extreme, found at threshold
exposures, where there is considerable scientific controversy about the
effects. There is still controversy as to the maximum level of lead exposure
which produces no adverse effects, arising in part from the subtle nature of
these threshold effects.
Attempts to establish a dose-response relationship between environmental
lead concentrations and adverse health effects and/or the relative contribu-
tion of each of the various sources of exposure to body burden have met with
only limited success. The underlying difficulty in such an analysis may be
traced to the multiplicity of sources of lead exposure and the difficulty in
accurately quantifying individual exposure.
3
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1_-
Although it suffers from some drawbacks, blood lead, expressed as micro-
grams of lead per 100 milliliters of blood (~g/dl), is generally accepted as
the best available analytical measure of recent lead exposure and readily
available body lead. Also for the purposes of this study, the effects
criteria proposed by EPA in presenting ambient air quality criteria for lead
were adopted. At the same time it was recognized that these estimated no-
effect levels are based on limited populations, and there is no evidence
that they apply to the population in general.
Lead may be absorbed into the body by inhalation, ingestion, skin
absorption, or placental transfer. Various studies indicate that 37-50 per
cent of inhaled lead is deposited in the lungs. In adults, approximately
7.5-10 percent of ingested lead is absorbed in the gastrointestinal tract;
recent data indicate that this is not the case with children, in children
absorption is much higher, 44-50 percent. These recent results for children
suggest that earlier estimates of acceptable daily intake for young children
may have been grossly overestimated, and points up the desirability of in-
clusion of adequate safety margins in establishing allowable intakes, and in
considering possible limitations on lead.
The critical effect of inorganic lead compounds is interference with
heme synthesis. Short-term inhalation of organic lead compounds primarily
affects the central nervous system. However, organic lead poisoning is
fundamentally a wholly occupational risk, to which the general population
is not normally exposed, and was, therefore, not considered further in this
study.
Lead appears also tOo have an effect on reproductive ability; and may
have teratogenic effects in man, although the evidence for this is not de-
finitive. Evidence to date does not indicate that lead is carcinogenic for
humans.
Lead poisoning in children is a serious but preventable problem. The
primary source of this is ingestion of paint chips containing lead and to
a lesser degree, ingestion of dust and dirt contaminated by weathering of
leaded paints, automotive emissions, and in some limited areas, smelter
emissions. Regulation of lead levels in paint, together with phasedown of
leaded gas and ambient air quality standards should be expected to reduce
future risks effectively. Much leaded paint is still present in older
housing. This source of exposure will remain significant until pre-World
War II housing is replaced with newer dwellings.
Prevention of lead poisoning in children residing in these older homes
is primarily a matter of parental education (especially regarding good
housekeeping to minimize the amount of paint chips, dust, etc. available to
the young child) early detection and follow-up of lead poisoned children to
detect and eliminate the specific source(s) of exposure from the child's
environment. Unless the source is eliminated or controlled following
diagnosis and treatment, recurrance of lead poisoning is probable.
4
-------
One source of lead intake for the general population is air. The con-
sensus of studies of diverse general populations suggests that, the contribu-
tion of ambient air lead to blood lead is in the range of 0.6-2.0 ~g/dl per 1
~g/m3 in air, although the correlation of air lead and blood lead is not high
over the narrow ranges of lead concentration found in ambient air. The
correlation is more definitive at high air leads with indications that the
rate of change in blood lead decreases with increasing air lead.
Lead is found in all three media, air, water, and soil, although most
attention in recent years has been focused on lead in air. As discussed
in Chapter 7, lead in the atmosphere is a potentially significant contributor
to intake and body burdens, from the annual combustion of 150,000 tons of
lead in gasoline antiknock additives. As the consumption of lead antiknock
has begun to decrease, from the peak of 220,000 metric tons, achieved in
1970, improvements in air lead concentrations are beginning to become apparent.
The annual average for urban stations in the National Air Sampling Networks
(NASN) decreased from 1.23 ~g/m3 in 1971 to 0.89 ~g/m3 in 1975. On the basis
of the relationship derived between gasoline antiknock consumption and annual
average air lead concentration, it is estimated that the annual average for
1978was about 0.58 ~g/m3, and following the leaded gasoline phasedown, will
decline to about 0.3 ~g/m3 by 1980 and thereafter. When air lead concentra-
tions attain this level, inhalation will become a rather minor contributor
of .lead to man's body burden.
Lead concentrations in U.S. surface waters are essentially all below 50
ppb (~g/l), about the solubility of lead in hard water. The available data
suggest that the median concentration for U.S. drinking water supplies is
about 10 ppb, and 80 percent of public water supplies are below 20 ppb lead.
Thus, it is not surprising that the contribution of drinking water to the
lead burden of the general population is small. A few localized trouble
spots exist in New England and the Pacific Northwest, where lead water pipe
was formerly used in domestic water systems, and where the water is soft
and has a low pH.
The mean soil lead concentration in the U.S. is approximately 16 ppm,
and is changing only slowly. The lead in soils is relatively unavailable
to crops, and does not appear to pose a health risk to the general population.
Urban dust and dirt is another matter. Lead concentrations in dust and dirt
in and around dwellings as high as 1,000 to 11,000 ppm have been found; the
latter levels represent extreme cases. Adults are essentially unaffected
by high dust and dirt lead concentrations, but these high concentrations
represent a real health risk to inner city children living in deteriorated
housing, because of the hand-to-mouth tendencies of small children.
It is generally accepted that the major source of lead for the average
person is food. Neither air nor water compare with food as a source of lead;
depending on the specific contributions of these other sources, food may
represent from 60 to as much as 90 percent of lead intake. All foods
naturally contain lead in varying concentrations, though for many foods this
may be only a few hundreths ppm. Fresh milk, an important food for infants
and small children, will contain 0.05 ppm or less, for example. This part of
man's daily intake of lead is probably unavoidable, but also probably not
harmful. Most of the adventitious lead in the average diet arises from canned
5
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foods, and is derived from the lead solder seam of the can. It is generally
accepted that this is a very substantial fraction, as much as one-half to
two-thirds of the total lead content of the foods, as eaten. Some of this
lead is dissolved by the food, especially the more acid and agressive foods,
but the evidence indicates that a probably more important source is particu-
late lead (spatter, dust, powder) which lodges inside the can during the
soldering process.
Adventitious lead in food is controllable, either by abandonment of the
three-piece lead-soldered can (which would totally eliminate the problem) or
by improving can-making technology and quality control. The latter option has
much to recommend it.
Using the latest publicly-available FDA and Department of Agriculture
dietary data, and estimates of lead contents of foods, both fresh and packed,
drawn from the literature, lead intakes were calculated for a number of age-
sex groups. By similar calculations, it was possible to estimate the
reductions in lead intake accruing if one-half or two-thirds of the lead in
canned food could be eliminated by modifications in can-making technology.
Data were available on the mean blood lead level of one special group
(20 - 34 year-old females) which permitted the calculation of the population
distribution curve as a function of blood lead level with and without the
projected reduction. These calculations indicated that a reduction of 1.3
~g/dl in blood lead would result for this group if two-thirds of the lead in
canned food were eliminated, which would reduce by about half the number of
women in this age group with blood lead levels (above the standard cut-off
point of 25 ~g/dl) in the range where evidence of hematological changes
begin to appear. Similar benefits can be projected for other population
segments, using the same technique.
Even after levels of lead in the environment are determined, the
routes by which this lead enters man are identified, and the contributions
of the various media estimated. the question still remains as to whether
there exists a need for additional limitations on lead. The answer to this
is not immediately self-evident since lead is already controlled by a multi-
plicity of existing or imminent Federal regulations. More than 30 regula-
tions limiting exposure to lead either directly or indirectly were identified
(Section 9). Addressing the need for additional limitations on lead, the
answer to this question depends in part on the answer to the two other
questions: (1) What is the present level of exposure in various segments
of the population, and (2) Does sustained exposure at these levels represent
a significant health hazard?
An unequivocal answer is not possible to either of these questions and
therein lies some of the problem surrounding lead. Presently there are no
data concerning blood lead levels of representative national samples, although
as an approximation the evidence indicates 15-20 ~g/dl as a reasonable estimate
for adults, and perhaps 20-25 ~g/dl for children. The answer to the second
question is even more uncertain, depending as it does on the consensus evalu-
ation of the significance of the subtle biochemical effects of lead at low
doses, and whether or not these are reversible, and what their long term
effect is, especially on children. As has been made evident in the discussions
6
-------
concerning the establishment of an ambient air lead standard, this is a
question surrounded by a considerable scientific controversy.
Nevertheless, upon examination of the broadly-stated problem the con-
clusion was reached that the question that whether or not a "threshold"
blood lead level at which effects could have long-term significance overlapes
the existing blood lead concentration in the populace did not need to be
answered. Even if there is no overlap, the gap between the two does not
provide the safety factor needed, and prudence dictates that this safety
margin be increased. Acceptance of this premise leads naturally to the
conclusion that additional limitations of some sort on lead warrant consider-
ation.
Analysis of eleven candidates for limitations were made to establish
priorities for their further consideration. Although the needed data were not
available to permit quantifying possible benefits, as in the case of the 20-34
year-old females with respect to lead reductions in ingested food, a compara-
tive evaluation was possible. Adventitious lead in food and leaded gasolines
ranked well above other candidates.
Analysis of the limitations already enacted to control lead in gasoline
and projections of their effects on lead emissions, led to the conclusion that
there is no pressing need for additional limitations in this area at this time,
with a recommendation that the results of these regulations be awaited and
evaluated before further action is taken.
As noted above, analysis of the relative lead intakes from inhalation and
ingestion demonstrated conclusively that the ingestion of food and water was
the most predominant source of average daily lead intake for the general
population unless air lead concentrations reached abnormally high levels.
Additionally, in considering specific limitations, one should concentrate first
on those producing the maximum benefit to the largest group of persons or the
most sensitive segments of the population, or ideally, to both. Limitations
directed toward the dietary mode of exposure would benefit sensitive segments
and the general population alike.
An exception to the generalization that food constitutes the maximum
source of lead intake is, of course, the child with pica who eats lead-
containing paint chips, plaster or dirt. Ingestion of relatively minute quanti-
ties of such materials can far outweigh all other. sources of exposure for these
children and all too often has led to clinical lead poisoning (Section 7.4).
However, a mode of application of a limitation on lead to eliminate this very
important source of lead was not identified. Increased emphasis on parental
education programs and early detection and treatment appears to offer the most
effective solution to this problem at this time.
Thus, for the general population, reduction of lead accidentally introduced
into food appeared to be the limitation candidate offering the greatest benefit
to the largest number of people, in addition to especially benefiting the
sensitive population segment of young children.
There are alternatives to the standard three-piece can with a soldered
side seam, and billions of cans are made without a soldered seam. Steel three-
piece cans may be made with welded or cemented side seams; or two-piece cans with
7
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po side seam at all can be formed by the drawing and redrawing or drawing
and ironing processes. Billions of two-piece aluminum cans are manufactured
for beer containers. However, none of these alternatives are well suited
to the rigors of aseptic canning, nor to the economic manufacture of the
wide variety of sizes of cans needed by the food industry.
However, significant reductions in adventitious lead in foods packed in
three-piece soldered cans have been shown to be possible, and the can industry
has already embarked on an evolutionary program in cooperation with the Food
and Drug Administration, to accomplish this, still based on the three-piece
soldered can. This program involves some modifications of the can line
solder station, to prevent the entrance or to clean up the lead solder spatter
and dust from the interior of the can, since it has been shown that this was
the primary contributor to lead pickup, rather than dissolution of the
structural lead in the soldered seam.
An important element in this improvement program is the Good Manufacturing
Procedures (GMP) concept utilized by FDA in its monitoring efforts over the
manufacture of foods and drugs, which includes strong emphasis on quality
control. The effectiveness of this evolutionary approach was demonstrated in
an industry test in 1976 on a number of can making lines which had been
modified to reduce accidental lead pickup. Lead contents of thirteen foods
(selected as those likely to be fed to young children) averaged 0.19 ppm,
a 41 percent reduction from the 0.32 ppm average of the comparable 1974 survey.
When the entire sanitary food can industry has been similarly modified and
GMP applied, a 40 to 50 percent reduction in lead content in all canned food
can be anticipated, with a significant benefit to mean blood lead values.
Capital costs to incorporate these can making line modifications and
cleanup improvements into the approximately 1,085 lines in the U.S. producing
sanitary food cans was estimated by the Can Manufacturers Institute at about
$45,000 per line, or nearly $50 million for the entire industry. Added
operating costs (investment amortization only) were estimated to be a nominal
$0.10 - 0.30/M cans.
Capital costs for the alternatives of adding an organic polymer stripe
over the seam, or a 360-degree spray over the entire interior were $70,000 and
$660,000-930,000 per line, respectively. Added operating costs were in the
$0.20 - 0.75/M can range. All of the lead-free alternative forming methods
were much more costly, ranging from $1 to 3 million in new capital cost per
line, and from $3-6/M can added operating costs.
Limitations on the lead content in foods would have to take into account
the varying and unknown lead content of the original raw food, which pretty
well rules out the approach of specifying a maximum lead content of processed
foods. The GMP approach, already utilized by FDA for similar product quality
control problems, appears to be a more flexible and adaptable control
mechanism, which should accomplish the desired objective, and is recommended,
at least as an interim measure. If this approach is successful, the much more
costly solution of total elimination of lead from food cans may not be necessary.
8
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Other potential sources of ingested lead considered for possible limit-
ation included: lead glazed foodware; lead glass; decal-decorated glass
tumblers, solder-joined food vessels; and pewter. Although quantitative data
on these potential sources of lead intake were sparse, it was clear that they
contribute very little to the body burden of the general population, and they
were accorded a low priority for more detailed investigation. No further
investigation of these minor sources of ingested lead is recommended at this
time.
9
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2.0
INTRODUCTION
Lead is an ubiquitous element in the biosphere, not surprising for a
metal which has been used by man since antiquity. Therefore, it will be present
in the human body, with the body burden depending on the level of environmental
exposure. It is clear that lead levels in the environment have been gradually
increasing ever since the beginning of the industrial revolution; and the rate
of increase accelerated when gasoline antiknock additives came on the scene.
Hopefully, the controls now being applied to this foremost dissipative use of
lead will reverse this trend; there is some evidence that this has begun to
happen.
The U.S. Environmental Protection Agency has been charged by the U.S.
Cungress with the general responsibility of protecting man's environment. The
Agency has also been charged with the implementation and enforcement of numerous
specific acts aimed at this goal. Some of the major acts include The Clean Air
Act, The Federal Water Pollution Control Act, The Resources Conservation and
Recovery Act., The Safe Drinking Water Act, and The Toxic Substances Control
Act. Under the latter act, EPA has the responsibility of controlling and
regulating substances posing an "unreasonable risk or injury to health or the
environment."
Lead is a known toxic substance and the toxic properties of lead have been
recognized for centuries, along with its special properties which have been
beneficially utilized by man. Which, if any, of the manifold uses of lead and
its compounds pose an "unreasonable risk" was a matter requiring further
definition. There have been numerous studies of various aspects of the health
and safety hazards posed by some specific uses of lead, e.g., in paint, but
there do not appear to have been any studies examining the uses and releases of
lead on an overall basis, relative to performing an assessment of the need for
and nature of possible limitations.
Such an overall assessment was the objective of this investigation. A
further, more specific objective, was to assess the present and future need for
limitations, and if a need were indicated, to identify the types of limitations
which appear to be the most justified and most effective.
This study, then, evaluates the nature and structure of the lead industry,
the myriad uses of lead and its compounds, the losses of lead to the environ-
ment and their fate, the resultant level of health and environmental hazards,
and where the most effective reduction of those hazard levels might be
effected.
10
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Lead is so ubiquitous in the environment that a portion of man's intake
is essentially irreducible. Thus, efforts to minimize this intake necessarily
focus on the reducible fraction.
As the investigation proceeded it became evident that while all foods and
beverages naturally contain lead in trace concentrations, the sources of this
lead are so widespread and diffuse as to be almost uncontrollable. Thus,
significant reductions in the lead content of unprocessed food appeared unlikely.
On the other hand, a substantial fraction of the lead intake from food of the
general population was determined to be adventitious, added accidentally in the
processing and packing of food, and significant reductions in this portion of
man's lead intake appeared to be attainable.
Since the resources available to this study permitted investigation of
but a few limited avenues of approach to possible limitations on lead, lead
intake via ingestion was selected as the limitation candidate of highest priority,
focusing primarily on the reducible fraction associated with canned food.
11
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3.0
PROPERTIES OF LEAD AND ITS COMPOUNDS
3.1
PHYSICAL AND CHEMICAL PROPERTIES
Lead is a soft metal with a bluish-gray color when freshly cut. Its
bright luster soon disappears upon exposure to air because of the formation
of lead oxide. The important physical constants of lead are presented in
Table 3.1. It is assigned atomic number 82 in the periodic classification
of the elements, and has several naturally occurring isotopes which result
in an average atomic weight of 207.19. Because lead has four electrons in
its outer shell, it falls in Group IV of the periodic table, and conse-
~uently, might be expected to show a normal valence of +4 in its compounds.
However, the 2 "s" electrons are difficult to ionize and as a result the
usual valence of lead in ionic compounds is +2 rather than +4. In acid
solutions lead is a fair reducing agent; in alkaline solutions it is a
rather strong reductant. The more important oxidation-reduction potentials
for lead and its compounds are presented in Table 3.2 (Latimer, 1952).
Lead has good resistance to neutral solutions, here the oxide and
carbonate are the corrosion products, and is fairly resistant to alkaline
sclutions. Lead is resistant to sulfuric, sulfurous, phosphoric and chromic
acids, but it is moderately attacked by hydrochloric and hydrofluoric
acids. It is strongly corroded by nitric, acetic and formic acids and
moderately affected by organic chlorides and aqueous solutions of metal
chlorides. In the presence of oxygen most organic acids react with lead to
form the corresponding organolead salts (Hamner, 1974).
Lead's high density (11.3 grams per cubic centimeter), its softness,
and relatively low melting point enable easy forming and casting. These
physical characteristics account for the numerous uses of lead (see Section
4.3). Lead forms low-melting alloys with tin, arsenic, antimony, bismuth,
cadmium, and calcium, singularly and collectively. These alloys are fab-
ricable by commercial processes (Hack, 1967). Alloys are also made from
secondary lead which is recovered from scrap. Lead does not readily alloy
with zinc, iron, nickel, and other high-melting metals. Alloys of lead can
be extruded, drawn, rolled, cast, stamped, spun, and applied as a coating
to other metals by hot dipping, electroplating, or spraying (Lead Indus-
tries Association, 1952). Thick layers of lead can be bonded to steel
and other metals.
12
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Table 3.1
PHYSICAL CONSTANTS FOR LEADa
=
Melting point, C
Boiling point, C
Specific gravity, at 20 C
at 327.43 C
at 650.0 C
at 850.0 C
Vapor pressure, at 987 C, mm Hg
at 1167 C
at 1417 C
at 1508 C
at 1611 C
Surface tension, at 350 C, dyn/cm2
at 400 C
at 500 C
Viscosity, at 441 C, cp
at 551 C
at 703 C
at 844 C
Specific heat, at 0 C, cal/g
at 20 C
at 100 C
at 327 C
at 500 C
Latent heat of fusion, cal/g
Latent heat of vaporization, cal/g
Thermal conductivity, at 20 C, cal/(cm2) (C/cm) (see)
at 100 C
at 327.43 C
at 600 C
at 800 C
Magnetic susceptibility, 10-6 egs units
Brinell hardness (cast)
Element bond length, Pb-Pb- at 25 C, A
Electrical resistivity, micro-ohms/cc at 20 C
Refractive index, sodium light
Velocity of sound, em/see x 105
Tensile strength, lb/sq in at 20 C
Linear coefficient of expansion, per C x 10-5
347.43
1740
11.3437
10.686
10.302
10.078
1.0
10.0
100.0
200.0
400.0
442
438
431
2.116
1. 700
1. 349
1.185
0.0297
0.0306
0.0320
0.0390
0.037
5.86
203
0.083
27.021
94.6
107.2
116.4
0.12
4.2
3.5003
20.648
2.01
1. 227
1920
2.93
aAdapted from McKay. In: Encyclopedia of Chemical Technology, Vol. 12,
A. Standen (ed.), Used by permission of Interscience Publishers,
New York. (c) John Wiley and Sons, Inc., 1967.
13
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Table 3.2
a
OXIDATION-REDUCTION POTENTIALS FOR LEAD
Reaction
t.EO volts
,
Pb + Pb+2 + Ze
Pb+2 + Pb+4 + 2e
-2
Pb + S04 + PbS04 + 2e
Pb + 20H + PbO + H20 + 2e
+2' +
Pb + 2H20 + PbOZ + 4H + Ze
+ -Z
PbS04 + 2H20 + PbOZ + 4H + S04 + Ze
PbO + 20H- + Pb02 + H20 + 2e
Pb + 2Cl- + PbC1Z + 2e
Pb + 2Br- + PbBrZ + 2e
Pb + 21- + PbIZ + 2e
Pb + S-2 + PbS + 2e
+ 0.126
- 1. 7
+ 0.356
+ 0.58
- 1. 455
- 1. 685
- 0.Z48
+ 0.268
+ 0.280
+ 0.365
+ 0.980
aAdapted from Latimer, The Oxidation State of the Elements and
Their Potentials in Aqueous Solutions, 2nd Edition, (c) 1952,
pp 151-155. ~eprinted by permission of Prentice-Hall, Inc.,
Englewood Cliffs, Ne~ Jersey.
14
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3. 1 . 1
Inorganic Compounds of Lead
The divalent lead compounds resemble those of the alkaline earth ele-
ments. The sulfate, nitrate, and carbonate compounds of lead are isomorphic
with the corresponding barium and strontium compounds. Many lead compounds
have two or more crystalline forms. The common inorganic compounds of lead
(nitrate chlorate, and acetate) are water-solublej the chloride is spar-
ingly soiublej and the sulfate, carbonate, chromate, phosphate, and sulfide
are insoluble.
Lead monoxide (PbO), one of the most important industrial lead com-
pounds, exists in two forms. At ordinary temperatures, the monoxide exists as
reddish-yellow, tetragonal crystals commonly referred to as litharge. At 480 C
this transforms into yellow orthorhombic crystals known as massicot. Neither
form of the oxide is appreciably soluble in water. Litharge disolves only to
the extent of 0.0017 gram/100 ml of water at 20 C, and massicot, 0.0023
gram/100 mI. The melting point of PbO is 888 Cj it has appreciable volatility.
below this. PbO reacts readily with all common acids to form the corresponding
salts and dissolves in alkali, though with more difficulty. Hence, PbO serves
~s a starting point for the preparation of many lead compounds (Thompson,
1967). The major uses of the inorganic and organic compounds of lead are
discussed in Section 4.3.
Red lead, Pb104' contains both divalent and tetravalent lead atoms in a
complex crystallIne structure. It is prepared by the oxidation of PbO in air at
500 C.
Lead dioxide, PbO , is a dark brown solid in which the lead atoms are
tetravalent. It is a ~igorous oxidizing agent when heated (290 C). Pb02 can be
produced in the laboratory by the anodic oxidation of solutions of leaa
compounds. Commercially, it is produced by the treatment of an alkaline slurry
of red lead with chlorine (Klug and Brasted, 1958).
Values for the solubilities of common inorganic compounds of lead are
presented in Table 3.3 (Lange, 1967j Weast, 1974). Lead sulfide has a very
low solubility (approximately 0.8 mg/l) and its formation can serve as a
convenient method for the removal of lead from aqueous systems. Its
solubility is higher than might ~~gexpected on consideration of the low
solubility product (Ksp = 7 x 10 ). This is due mainly to the hydro-
lysis of the sulfide ion. (Kolthoff, et al., 1964).
The equilibrium model for the chemistry of aqueous lead developed by
Stumm and Morgan (1970) indicates that at low pH and low pe (reducing
conditions) elemental lead can be readily dissolved. This has health
implications, where soft water with little or no buffering capacity is at a
low pH and lead piping is used for potable water. Excessive lead
concentrations in such water have been observed in Great Britain and in
certain locations in the United States (see Section 8.3).
15
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Table 3.3
SOLUBILITIES OF INORGANIC CO~~OUNDS OF LEADa,b
Name
Compound
Formula
Acetate
Bromide
Carbonate
Chlorate
Chloride
Chromate
Fluoride
Hydroxide
Iodide
Nitrate
Oxalate
Oxide, mono-
Oxide, tetra-
Phosphate
Sulfate
Sulfide
Pb(OOCCH3)2' 3H20
PbBr2
PbC03
Pb(C103)2'H20
PbC12
PbCr04
PbF2
Pb(OH)2
PbI2
Pb(N03)2
Pb(OOC)2
PbO
Pb304
Pb3(P04)2
PbS04
PbS
Water Solubility,
gl100 m1
44.3
0.844
1.1 x 10-4
151. 3
0.99
5.8 x 10-6
0.064
0.0155
0.063
56.5
1.6 x
10-4
1.7 x 10-3
5.3 x 10-5
1.4 x 10-5
4.25 x 10-3
8.6 x 10-5
Temperature,
C
20
20
20
18
20
20
20
20
20
20
18
20
20
20
25
20
lath edition,
~eprinted with permission from Handbook of Chemistry,
N.S. Lange (ed.) (c) McGraw-Hill Book Company, 1967.
bReprinted with permission from Handbook of Chemistry
55th Edition, R.D. Weast Ced.). Cc) CRC Press, Inc.,
16
and Physics,
1974.
-------
In the absence of suspended solids, the solubility of lead in water is
dependent on pH, salt content and partial C02 pressure. Equilibrium
calculations by Davies and Everhart (1973) indicate the solubility of lead
to be about 30 ppb in hard water and 500 ppb in soft water. As illustrated
by Figure 3.1, below a pH of about 5.4, PbSO is the species limiting
solubility. Above pH 5.4, PbCO~ and Pb2(OH)/~03 are the limiting factors in
lead concentrations in solution. In hard water a pH greater than 6.0 is the
level at which the above carbonates are present and cause a corresponding
limitation (Figure 3.2). The most important factor in determining lead
solubilities is the carbonate concentration which in turn depends on the
partial pressure of C02 and the pH. The envelope boundary line Cpb shows
concentrations of lead in solution. The minimum occurs at a pH just above 9
in soft water and just below pH 9 in hard water.
3.1.2
Organic Compounds of Lead
Organolead compounds are those in which the lead atom is bound directly
to one or more carbon atoms. Since Lowig's first synthesis of an organolead
compound in 1853, organolead chemistry has developed into one of the
largest areas of organometallic chemistry. It has been estimated that about
1200 organolead compounds were known in 1965 (Shapiro and Frey, 1968). Only
a few of these achieved commercial status.
The tetraorganolead compounds in which a tetravalent lead atom is
bonded to four organic groups through carbon represent the most stable
class of compounds. The four organic groups may be alkyl, aryl, cycloalkyl,
arylalkyl, thienyl, furyl, and substituted derivatives thereof. The most
important of these compounds are the fuel additives, tetraethyllead (TEL)
and tetramethyllead (TML).
In general, the alkyl derivatives of lead are highly toxic compounds,
and are readily absorbed through the skin (see Section 7.6). TEL and TML
are clear, colorless liquids, volatile, nonpolar, nonionic, and soluble in
many organic solvents such as hydrocarbons, chloroform, ether, and absolute
ethanol. They have very low water solubilities, and are relatively
unreactive in air, water or alkaline solutions (Shapiro and Frey, 1968).
They are, however, light-sensitive and undergo photochemical decomposition
when they reach the atmosphere; because they are readily broken down by
light and heat, their presence in the atmosphere is transient (National
Academy of Sciences, 1972).
At 50 millimeters of mercury, TEL boils at 108.4 C, and TML at 33.2 C.
TML decomposes on heating at 265 C, and TEL at 100 C (Shapiro and Frey,
1968). Some of the other physical properties " as summarized by Gerarde
(1964), are presented in Table 3.4.
These compounds decompose readily during the combustion process, thus
freeing the radicals to prevent the extremely rapid burning of gasoline.
The so-called "regular" gasoline contains 3 to 4 milliliters of the
tetralead compounds per gallon. This concentration represents from about
1.8 to 2.5 grams of lead per gallon. To scavenge the lead from the engine,
17
-------
7
3 ,
Cpb
5 -
[Pb(C03)~-J
U
0\ 9
o
.-
I
[PbC12J
11
[Pb OH3+]
2
[Pb(OH)~-J
13
15
3
7
13
5
9
11
pH
Figure 3.1
Solubility and species distribution for Pb (II)
in soft water Source: Davies and Everhart (1973).
18
-------
3
~.- ~...- ~'" . ...
5
[Pb(C03)~-]
[Pb2+]
7
[Pb(OH)~-J
[PbOH+]
9
[Pb(OH)3]
[PbC12J
11
13
[Pb(OH)2]
15
3
8
11
13
7
5
9
,
, ..
pH
Figure 3.2
Solubility and species distribution for Pb (II)
in hard water Source: Davies and Everhart (1973).
19
-------
Table 3.4
PROPERTIES OF TETRAETHYLLEAD "AND TETRAMETHYLLEADa
Physical Properties
Tetramethyllead
Tetraethyllead
Physical form
Chemical formula
Odor
IV
a
Saturated liquid density
at 20 C
Vapor pressure at 20 C
Boiling point
Freezing point
Flash point (open cup)
Viscosity at 20 C
Refractive index nD20
Solubility in water at 22 C
Solubility in gasoline
Watery white oily liquid
~~t~~~4~~Uity
Watery white oily liquid
(CH3) lb
Faint, fruity (probably
in chern. pure state)
odorless
1. 65 glml
0.27 mm Hg
199 C
130.2 C
85 C
0.87 cps
1.520
0.18 ppm
Soluble in
1. 99 glm1
22.5 mm Hg
110 C
30.3 C
About 38 C
0.53 cps
1. 512
18.0 ppm
Soluble in
all proportions
all proportions
a
Source: Gerarde. Reprinted with permission from Annual Reviews Pharmacology. (c) Annual Reviews,
Inc., 1964.
-------
standard antiknock fluids also contain ethylene dibromide and/or ethylene
dichloride. The chief lead emission products are (in particles of
equivalent diameter between 2 and 10 micrometers) the alpha and beta forms
of ammonium chloride and lead bromochloride (NH4Cl.2PbCl Br,
2NH Cl.PbC1.Br), minor quantities of lead sulfate (PbS04) and the mixed
oxi~e and halide. (PbO.PbCl-BroH20) (National Academy of Sciences, 1972).
These combustion products, present as solids, are the largest source of
atmospheric lead pollution (see Section 5.2.2).
In addition to the tetralead derivatives, other types of organolead
compounds are of environmental significance, for example, hexamethyldilead,
which consists of six organic groups surrounding a pair of lead atoms:
(CH3)3Pb-Pb(CH3)3.
Lead can also be bonded to organic groups through an oxygen atom giving
rise to a variety of alkoxides, such as triemethyllead methoxide,
(CH ) PbOCH . Peroxide structures, an example being tert-butyl
tr~eihylle~d peroxide (CH3)3PbOOC(CH3)3 are also known, (Shapiro and Frey,
1968) .
Organolead compounds are also formed with Group VI-A elements. A large
number of organolead compounds also are known in which the lead is bonded
to sulfur, for example, (CHi)iPbSCHi. A few compounds have been prepared in
which the sulfur is replace~ ~y selenium or tellurium. Organolead compounds
in which the lead is bonded to nitrogen are types in which the nitrogen is
part of a heterocyclic ring:
. .,,/CH:::::::,...
(C2H5)3Pb-N " ~ ~ (Shapiro and Frey, 1968)
"CH~
There are, additionally, a number of lead salts of organic acids, such as
lead naphthenate, lead di-2-ethyl hexanoate, etc., used in the paint and
plastic industries which are, by industry convention, classified as
inorganic compounds.
3.1.3
Isotopes of Lead
There are four natural stable isotopes of lead, with the following
abundances (Lederer, et al., 1967):
Isotope
Percent
Pb-204
Pb-206
Pb-207
Pb-208
1 .4
25.1
21.3
52.7
21
-------
Pb-204 has no radioactive progenitor. Pb-206, Pb-207, and Pb-208 are
produced by the radioactive decay of uranium-238, uranium-235, and
thorium-232, with half-lives of 4.5, 0.7, and 14 billion years,
respectively (Lederer, et al., 1967). There are four radioactive isotopes
of lead occurring as members of these decay series. Pb-211, Pb-212, and
Pb-214 have short half-lives, 36.1 min., 10.64 hr., and 26.8 min.,
respectively. Pb-210 (Radium-D), the longest lived, however, has a
half-life of about 20 years, sufficiently long to be useful in
environmental studies.
The stable isotope composition of naturally occurring lead ores is
known to vary, depending on its geological evolution, and this can be used
to determine the geological age of lead deposits. Because of these
differences, in some instances isotopic composition may be used, with the
assistance of mass spectrometry, to determine the sources of lead
contamination. However, because lead is so durable and so much of it is
recycled, the pool of recycled scrap, and products derived from it (e.g.,
TEL) tend to average toward a fairly uniform composition. While this
complicates the tracing of the origines) of environmental lead by isotopic
ratio measurements, the technique has still proven useful.
22
-------
3.2
REFERENCES
Davies, P. H., and W. H. Everhart. 1973. Effects of Chemical Variation
in Aquatic Environments. Vol. III. Lead Toxicity of Rainbow Trout and
Testing Application Factor Concept. EPA-R3-73-011c. Office of Research
and Monitoring, U.S. Environmental Protection Agency, Washington, D.C.
80 pp.
Hack, C. H., 1967, Lead Alloys. In: Kirk-Othmer Encyclopedia of Chemical
Technology, Vol 12, A. Standen (ed.) Interscience Publishers, John
Wiley and Sons, Inc., New York, New York. pp 248-266.
Hamner, N. E. (compiler). 1974. Corrosion Data Survey. Metals Section,
5th Ed., National Association Corrosion Engineers, Houston, Texas. 283
pp.
Klug, H. P. and R. C. Brasted (eds.). 1958. Comprehensive Inorganic
Chemistry, Vol. 7 D. Van Nostrand Co., Inc., Princeton, New Jersey. 302
pp.
Kolthoff, I. M., P. Elving, and E. B. Sandell, 1964, Treatise on Analyti-
cal Chemistry, Part II, Vol. 6, Interscience Publishers, John Wiley
and Sons, Inc., New York, New York. pp 69-171.
Lange, N. A. (ed.) 1967), Handbook of Chemistry 10th ed., McGraw-Hill
Book Company, New York, New York. pp 276-280.
Latimer, W. M. 1952. Oxidation Potentials. Prentice-Hall, Inc.,
Englewood Cliffs, N.J. pp 151-155.
Lead Industries Association. 1952. Lead in Modern Industry. New York,
New York. 230 pp.
Lederer, C. M., J. M. Hollander, and I. Perlman. 1967. Table of
Isotopes. 6th Ed., John Wiley and Sons, Inc., New York, New York. 594
pp.
McKay, J. E. 1967. Lead. In: Encyclopedia of Chemical Technology. Vol.
12, A. Standen (ed.), Interscience Publishers, John Wiley and Sons,
Inc. New York, New York. pp 207-247.
National Academy of Sciences, Committee on Biologic Effects of Atmos-
pheric Pollutants. 1972. Biologic Effects of Atmospheric Pollutants.
Lead. Airborne Lead in Perspective. Washington, D.C. 341 pp.
Shapiro, H., and F. W. Frey. 1968. The Organic Compounds of Lead. Inter-
Science Publishers, John Wiley and Sons, Inc., New York, New York. 486
pp.
23
-------
Stumm, W., and J. J. Morgan. 1970. Aquatic Chemistry. An Introduction Em-
phasizing Chemical Equilibria in Natural Waters. Interscience
Publishers, John Wiley and Sons, Inc., New York, New York. 583 pp.
Weast, R. C. (ed.). 1974. Handbook of Chemistry and Physics. CRC Press,
Cleveland, Ohio. 2278 pp. B-100-B-103.
24
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4.0
THE LEAD INDUSTRY
4.1
OVERVIEW - HISTORY
As stated by Callaway (1962), "The discovery of lead is lost,in
antiquity. The earliest known writings are rich in references to lead. They
emphasize its prominence among the metals used by civilized man."
Physical evidence supports the contention that the Egyptians in the
7000-5000 B.C. period used lead, as well as copper, silver, and gold. Also
in the pre-Christian era, the Chinese may have circulated flatened lead
pieces as coins, while fabled lead deposits were worked by the Phoenicians
in Spain, Sardinia, and Cyprus and later by the Carthaginians in Greece. By
the time of the Roman empire, the metallurgy of lead was well enough known
that a large share of Roman wealth was supplied by silver extracted from
the lead ores of Sardinia, Spain, and Britain..
The ancients used lead for coinage and ornamentation. As noted above,
the Romans refined lead to recover the silver. Additionally, recent
excavations of Roman ruins reveal that they also fabricated the refined
lead into pipes and spigots for their water distribution systems, which
after 2000 years remain functional. However, the .big impetus for lead
consumption was the introduction into Europe of gunpowder during the 14th
century and the subsequent development of the rifle that fired a malleable
metal pellet--a lead shot. Otherwise, lead's corrosion resistance was
utilized in roofing for cathedrals and protective encasement of underground
pillars.
As western civilization struggled out of the dark ages, Northern
European nonferrous metals deposits were discovered and exploited between
700 and 1200 A.D. This was followed by widespread resumption of mining
throughout Europe starting about 1400 A.D. Four hundred years of
exploitation depleted the high-grade European deposits and by the start of
the 19th century European geologists and mining companies were turning to
overseas colonies for base metals, including lead.
In the New World, the first authenticated lead mine was established by
English settlers in 1721 at Falling Creek, Virginia, to supply metal
primarily for bullets and shot. By 1650, the industry was established in
New England while concurrently Jesuit missionaries worked some outcrop
deposits in Arizona. Expansions of the eastern industry supported the
exploration and settlement of territories west of the Alleghenies until
25
-------
1763 when the southeastern Missouri deposits were opened up on a permanent
basis. Then, to protect this burgeoning industry, the First Congress of the
United States enacted legislation in 1789 imposing a tariff on lead imports.
After the Civil War and the completion of the transcontinental railway
in 1869, mining in Colorado, Utah, Nevada, and eastern California expanded
rapidly in response to industrial growth in the northeastern United States.
Between 1876 and 1880, the United States surpassed both Germany and Spain
as miners and refiners of lead, and has continued to lead in the output of
refined lead to the present. With respect to domestic mine production, the
United States remained in first place until 1957, when Australia captured
the lead, and fell to third place in 1958 behind Australia and the USSR.
The opening of the "new lead belt" in Missouri in 1967 revived mining in
the United States, which since then has produced at an annual level of
450,000 to 550,000 metric tons (500,000 to 600,000 short tons). In 1975,
the United States was the leading country in producing lead from mine
sources, accounting for 16 percent of the world total (U.S. Bureau of
Mines, 1976). The United States, Russia, Australia, and Canada are the top
producers at both the mine and smelter level. These four countries have
accounted for 46 percent of world smelter output in the last 10 years.
Modern usage of lead and its alloys probably followed by a short period
of time the development of economical methods for producing iron and steel
in the 18th and early 19th centuries. Through the late 19th and early 20th
centuries, metallic uses of lead dominated the market -- sheet lead for
construction and corrosion-resistant chemical equipment and for cable
coverings, lead shot for ammunition, lead-tin alloys for pewter-type metal,
solders, and bronze (copper-tin) alloys. Red and white lead and chromate
pigmments were the principal non-metallic applications. Automotive
batteries (during the 1920's) and tetraethyl lead (during the 1930's)
emerged as major new uses in the post World War I era. Radiation shielding
appears to be the principal new application in the post World War II period
although sound attenuation and vibration dampening are expected to have
near-term promise.
Consumption patterns for lead vary from country to country because of
degree of industrialization, availability of alternative materials, housing
customs, and personal transportation modes. Table 4.1 presents appare~t
consumption patterns in 1976 for the United States, the big four of Europe
(France, West Germany, Italy, United Kingdom), and Japan, as reported by
the World Bureau of Metal Statistics (1977). The importance of personal
automotive transportation in the United States and Japan is readily
apparent from the storage battery category. The differences in pigments and
chemicals and alloys is less ~triking. Use for ammunition is either
negligible in the other countries, or it is categorized under miscellaneous
uses. Europe and Japan still use lead for cable sheathing to a larger
extent than in the United States where polymeric sheathings have been
preferred. Similarly, constructional applications (pipe, traps, bends),
foil applications (collapsible tubes), and corrosion resistant equipment
utilize lead in Europe and Japan. In the United States more use is made of
copper and plastic pipe, aluminum foil, and stainless steel, rubber
26
-------
TABLE 4.1.
CONSUMPTION PATTERNS FOR LEAD IN SELECTED COUNTRIES, 1976a
End-Use Designationb
Thousands of Metric Tons or Percent
United States European Big Fourc Japan
Quantity Percent Quantity Percent Quantity Percent
Storage batteries
613
47.2
392
34.1
93
40.4
Cable sheathing
14
1.1
145
12.6
16
7.0
Pigments and chemicals
303
23.4
294
25.6
62
27.0
Alloys
75
5.8
50
d
4.4
d
15
__d
6.5
d
Ammunition
66
5.1
Other soft lead products
and miscellaneous
226
17.4
267
23.3
44
19.1
Total
1297
100.0
1148
100.0
230
100
a
Source: World Metal Statistics. Used by permission of ~vorld Bureau of
Metal Statistics (C)(1977).
bEnd-use designations not specifically defined but believed to be roughly comparable.
c
France, West Gernmany, Italy, and United Kingdom.
d
Not reported.
27
-------
linings, glass linings, or asphaltic compounds, for these uses. Still, the
United States consumes nearly one-fourth of all the refined lead used
annually.
Depending on the stage of processing, lead ranks third, fourth, or
fifth among the industrial metals of the United States. It is third in
terms of recoverable metal in domestically mined ores, behind iron ore and
copper. It is fourth in terms of primary metal production, behind iron,
aluminum, and copper. It is fifth in terms of domestic consumption, behind
steel, aluminum, copper, and zinc.
In the following sections, the elements comprising the lead producing
and lead consuming segments of the lead industry are described and
discussed, including technology, uses, production, geographic locations,
and future projections. Although many of the important sources of pollutant
emissions are identified in the course of the technology descriptions,
their detailed consideration is deferred to the following chapter.
4.2
LEAD PRODUCING INDUSTRY
The producing segment of the lead industry breaks down into two
distinct parts, primary lead and secondary lead. The primary lead segment
includes the original recovery of lead from ores and concentrates. Since
lead is a durable metal, one that is relatively easy to refine or rerefine,
there is, accordingly, a major secondary market, comparable in size to the
primary metal market. A large fraction of annual U.S. lead consumption
conists of recycled secondary lead.
4.2.1
Primary Lead
The primary lead segment is considered to include the mining,
beneficiating, smelting, and refining of lead ores and concentrates. The
principal operations involved are shown schematically in Figure 4.1.
4.2.1.1
Mining-
In terms of occurrence in the earth's crust, lead is a rare metal. Its
relative abundance has been estimated at 16 parts per million (ppm), in
contrast to 80 ppm for copper, 125 ppm for zinc, 4800 ppm for iron, or 8000
ppm for aluminum. In spite of this statistical disparity, commercially
exploitable deposits of lead-bearing ores occur with remarkable frequency
and are widely distributed. Geologically, lead is most frequently
associated with zinc and subordinate quantities of silver in replacement
deposits in sedimentary rocks. Fissure-vein deposits may have a similar
composition but usually are far more complex, including iron and copper as
additional major constituents with arsenic, antimony, and bismuth as minor
impurities. .
Three general types of lead-containing ore are mined in the United
States, essentially all from underground mines; they are -- lead ores,
lead-zinc ores, and complex ores. Lead ores contain lead as the predominant
28
-------
Zinc- Lead Ores
LJr'~erground
Mining
Waste Rock
Or e
$
Ground Ore
Lead Concentrate
Zinc Concentrate
Zinc
Concentrate
to Zinc
Smelter
Lead Ores
IJnderg roun d
Mining
Waste Rock
Ore
$
Ground Ore
Lead Concent ra te
r
Concentrate
Rooster
Sulfur Dioxide
Refinery
Drosses
Refined Lead
Complex Ores
Underground
Mining
Waste Rock
~
Or e
$
Ground Ore
Tailings
Zinc Cor.centrate
.....
Copper
Concentrate
to Copper
Smel fer
Figure 4.1.
Simplified flow sheet for production of primary lead.
Source: Battelle - Columbus
29
-------
nonferrous metal present and for which the concentrates are treated.
Recoverable quantities of other metals mayor may not be isolated from
waste streams at appropriate stages of processing, depending on economics.
Lead-zinc ores have readily recoverable quantities of both lead and zinc
and are treated, usually at the beneficiating stage, for segregation of
each component. Complex ores contain at least three primary nonferrous
metals in quantities and ratios such that economic segregation of
individual metals is possible, frequently at the beneficiating stage. The
bulk of the complex ores in the United States and Canada contain lead,
zinc, and copper as principal constituents plus up to four other
recoverable by-products.
Most lead ore deposits contain the sulfide, galena (PbS), commonly
associated with sphalerite (ZnS), pyrite (FeS2)' chalcopyrite (CuFeS2) and
other sulfides or sulfasalts, any of which may be recovered to yield
by-products or coproducts. The near-surface part of some galena ore bodies
may be alt~red to cerussite (PbC03), anglesite (PbS04), or other oxidized
lead minerals. Mineralization may include marcasite, tetrahedrite,
dolomite, calcite, quartz, barite and minerals containing antimony,
bismuth, gold and silver. Not all of these materials occur in any given
~eposit. Lead, as lead, in ore ranges from 1 percent to over 7 percent.
There are about 50 mines in the United States that could recover ores
with a significant lead content. The number that actually operate in any
given year depends on general economic conditions, world lead prices, and
the availability of miners. Under favorable marketing conditions in 1973,
the 36 operating mines of that year expanded to 49 in 1974, but fell to 33
in 1975 as markets shrank. Obviously, the variation is attributable,
primarily, to the small marginal operations that produce only when supply
tends to lag behind demand. The domestic mining industry in 1977 was
comprised of about 50 mines in 14 states. Twenty-five mines produced 99
percent of the 1977 output, and the leading 8 mines, all in Missouri,
yielded 80 percent of the year's total mine production of ores and
concentrates (U.S. Bureau of Mines, 1978b).
At the ore stage, the lead content of the material mined ranges from a
high of between 7 and 8 percent to a low of less than 0.01 percent. Lead
ores are those in which lead is the predominant nonferrous metal value, as
illustrated by the Missouri deposits and selected mines in Colorado and
Idaho. Zinc-lead ores contain more zinc than lead, among which the eastern
replacement deposits and many western fissure-vein deposits are examples.
Complex ores include copper-Iead-zinc, silver-lead, copper-lead, and other
combinations in which lead is a minor constitutent that usually follows the
major nonferrous constituent through several stages of concentration until
an economic separation can be made.
The old lead belt in Missouri was averaging a little over 5 percent
lead in the hoisted ore in the first part of the 1966-1975 decade. The new
lead belt started out at 6.5 to 7.0 percent of lead but was averaging less
than 6.7 percent in 1974. Production of ores mined predominantly for lead
(i.e., "lead ores") increased from 5.2 million metric tons (5.7 million
30
-------
short tons) in 1966 to a high of 8.4 million metric tons (9.3 million short
tons) in 1974, while recoverable lead rose from 148,000 metric tons
(164,000 short tons) to 527,000 metric tons (581,000 short tons) in 1974.
In underground mining, access to the orebody is achieved by digging a
shaft and underground passage ways in barren rock close to the ore. The ore
is then extracted by a mining technique appropriate to the size, location,
and outline of commercial ore and the strength and cohesion of the
surrounding rock. On the average, lead mines in the United States excavate
1 ton of waste rock for every 17.25 tons of ore sent to the beneficiation
plant. The waste rock, over 544,000 metric tons, (600,000 short tons) per
year is piled on waste dumps and will contain traces of ore from fringe
areas of the orebody removed to gain access to commercial ore. With
effective grade control in mining, the waste dump will receive less than
1.0 percent of the ore removed and the average lead content of the dump
will be less than 0.1 percent. The waste dump is exposed to rainfall with
subsequent leaching and runoff. However, waste rock tends to be coarse,
presenting only moderate exposure of surface area to the moisture.
4.2.1.2
Beneficiation--
Coarsely crushed ore is hoisted to ground level and transported by
truck or conveyor belt to the mill. Secondary and tertiary crushing are
followed by wet grinding to liberate individual mineral species for
flotation. Lead, zinc, and copper concentrates can be segregated, with
pyrite and the gangue (worthless rock) materials reporting in the tailings.
Ores are beneficiated by gravity or froth flotation processes to yield
concentrates containing a concentration of 70 to 80 percent of lead, and
minor amounts of zinc, copper, and other nonferrous metals. Depending on
the type of ore treated and processing conditions, recovery of lead in the
form of concentrates may range from over 96 percent to less than 50 percent
of mill feed. For lead-dominant ores, some 95 percent of the lead content
of the feed reports in the lead concentrate, containing a concentration of
lead of 75 percent or better; a further 1 percent is contained in the zinc
concentrate, and the balance of 4 percent remains in the tailings.
(Hallowell et aI, 1973).
Industrywide data are not published on the eventual disposition of the
recoverable lead in each class of ore. However, direct losses to tailings
from the beneficiation step are believed to be less than 7 percent of the
recoverable lead mined annually in the United States, based on a 98 percent
recovery from lead ores, 85 percent from lead-zinc ores, and 50 percent
from all other ores. (Hallowell, et aI, 1973).
Other than accidental spillage or equipment breakdown, physical losses
occur as dusts from dry crushing and screening operations or as trace
residues left in storage tanks, processing vessels, transfer lines, and
equipment. The dusts are evacuated by exhaust systems and separated from
the air stream by cyclones, electrostatic precipitators, or wet scrubbers,
31
-------
and added to the flotation conditioning tanks with the finely ground feed.
The trace residues usually are flushed to floor drains that discharge to
the tailings thickener.
The solids, largely pyrite and inert gangue materials with about 0.2
per cent each of major metals in the ore, are disposed of to large tailings
ponds which allow settling of solids and recycle of processing water. From
9.07 million metric tons of ore milled annually, about 8.20 million metric
tons of tailings solids are impounded.
Two products -- lead concentrates and zinc concentrates -- are
forwarded to appropriate smelters. Zinc concentrates exit from the lead
flowchart at this point. Lead concentrates, containing up to 6 percent
moisture, are transported to a smelter by conveyor belt for contiguous
concentrator-smelter locations, or by truck or railcar for noncontiguous
locations. The latter shipments usually are bulk transport in dump trucks
or open gondola cars.
4.2.1.3
Smelting and Refining--
This major segment consists of three important processing steps --
sintering, smelting, and refining. The sintering step converts lead sulfide
to lead oxide with the potential of recovering sulfur dioxide as by-product
sulfuric acid. The smelting step reduces lead oxide to elemental lead (lead
bullion) containing most of the metallic impurities that were in the
concentrate. The refining step separates refined lead (99.99 percent
purity) from the metallic impurities, which report in various drosses.
After analysis, lead concentrates are blended with fluxes and recycled
slags, dusts, and sinter fines. The blend is loaded onto a continuous
sinter belt, ignited, and burned by oxygen in the air. During the initial
sintering stages, the strong offgases contain 6 to 8 percent S02 which is
diverted to the sulfuric acid plant. Weak offgases from sinter cooling
stages are piped to the smelter baghouse for recovery of any dust. Cooled
sinter is crushed and separated into a coarse stream and a recycle fines
stream. Between 30 and 50 percent of the sinter feed consists of recycled
material to promote suitable porosity on the belt, and to dilute the
sulfide content sufficiently to prevent the attainment of excessively high
temperatures which would cause fusion during sintering.
The gases from the sintering operation, averaging about 4 percent S02
are passed through a gas-cleaning system to remove particulates and then to
a contact sulfuric acid plant. While the gas-cleaning effectively removes
the metal-containing dusts there is sufficient carry-over of volatile
organics from flotation reagents to produce a dark color sulfuric acid,
usually sold at a discount, principally for use in making fertilizer.
The coarse sinter is conveyed to the smelting operation where it is
combined with coke and recycled refinery drosses and charged intermittently
to a blast furnace where the coke ignites, and heats the sinter to
incipient fusion, and provides the reducing gas that converts lead oxide to
32
-------
metallic lead. Fluxes in the sinter become slag which is tapped from the
bottom of the furnace with molten lead to a settler. Lead overflows a weir
in the settler and is transferred in ladles to the refinery or cast into
cakes as lead bullion. Slag overflows to an inclined iron trough where it
is granulated by water jets for recycle, as a diluent, to the sinter plant
or for discharge to a dump. Offgases from the furnace pass through a
baghouse for dust removal before discharge to the atmosphere. Baghouse dust
is recycled to the sinter preparation area.
Although all the lead smelters in the United States are essentially
based on the same process, the western smelters employ more complicated
flow sheets because of the more complex nature of the western concentrates,
complex imported materials, and their interrelationship with copper and
zinc plants. For example, the slag in Missouri is sufficiently low in zinc
to discard, but at Western smelters, slag is treated for zinc recovery in a
slag fuming furnace. (U.S. Environmental Protection Agency, 1975a).
Lead from the southeast Missouri lead belt is relatively free of
arsenic, antimony, and bismuth and is usually refined immediately after
smelting. Although there are variations, the refining process is
essentially as follows. Molten lead from the smelter is decoppered by
stirring with soda ash, sand, coke, and recycled sulfur dross while cooling
to 510 C (950 F). The resulting dry dross is skimmed off and smelted in a
reverberatory furnace yielding copper matte, lead bullion, and a small
amount of slag. The cooled lead is stirred with sulfur to complete
decoppering, the dross being recycled to the prior step. Next, the molten
lead is desilvered in two stages using recycled zinc-silver skim and fresh
zinc powder. After a number of recyclings, the zinc-silver skim contains
over 15 percent silver and is treated to distill off the zinc while the
impure silver is cast into bars for shipment to a silver refinery. After
desilvering, the still molten lead is subjected to a vacuum in which the
residual zinc distills. The resulting 99.99 percent pure lead is cast into
pigs for shipment as refined lead (U.S. Environmental Protection Agency,
1975b). .
Lead from western lead-zinc and complex ores contains significant
amounts of arsenic, antimony, and bismuth in addition to copper, zinc,
silver, and gold. Lead bullion from a smelter -- melted if necessary -- is
stirred with soda ash and coke while cooling to precipitate copper in a
lead dross treated, as before, in a reverberatory furnace yielding copper
matte, lead bullion, and slag. Decoppered lead is given two sequential
Harris process treatments (molten caustic soda) to remove firstly, arsenic
and tin, if any, and secondly, antimony. The resulting lead bullion is
further decoppered by stirring with sulfur, then desilvered and de zinced as
described above. Then, the dezinced lead is stirred with a mixture of
calcium and magnesium metals which form intermetallic compounds with the
bismuth impurity. Finally, dissolved calcium and magnesium are removed by
treating the lead with caustic soda. The refined lead is cast into pigs for
sale or the preparation of lead alloys. Harris process slags are treated to
recover arsenic and antimony as the oxides. Calcium-magnesium-bismuth slags
are treated with chlorine to recover commercially pure bismuth. (U.S.
Environmental Protection Agency, 1975b).
33
-------
4.2.1.4
Production and Products--
Primary lead smelting and refining increased in the 1966-1975 decade,
in keeping with the growth of domestic mining. In 1966, four smelters, two
smelter-refiners, and four refineries produced 428,000 tons (472,000 short
tons) of refined lead. In the following 10 years, two smelters and one
refinery were deactivated while two refiners switched solely to secondary
production, but two new smelter-refineries were built and a third expanded
extensively. Thus, refined lead output in 1972 (the peak year) was 631,000
metric tons (696,000 short tons), an increase of 47 percent, equivalent to
an annual compound rate of nearly 4 percent.
Locations of the present primary lead smelters and refineries are shown
in Figure 4.2. Pertinent information on their capacities and
characteristics are contained in Table 4.2.
u.s. production of refined lead and antimonial lead during the
1966-1975 decade is shown in Table 4.3. There was a dramatic increase in
primary lead production from domestic areas, beginning in 1969:
Thousands of Thousands of
Year Metric Tons Year Metric Tons
1965 273 1972 562
1966 297 1973 547
1967 288 1974 602
1968 326 1975 564
1969 462 1976 528(e)
1970 519 1977 488(e)
1971 525
This coincided with the commissioning of the first mine in the "new lead
belt", following the discovery of massive replacement deposits in
southeastern Missouri in geological formations different from those
containing the deposits opened up in 1763. Since that time the "new lead
belt" has dominated United States production. Production has ceased at the
mines in Kansas and Oklahoma, and declined significantly from the
fissure-vein deposits in the western states. Production from the eastern
replacement deposits continues to contribute only minor tonnages.
Lead bullion is the designation given lead as produced from the blast
furnace. While lead from Missouri ores is generally pure enough for most
commercial uses without sophisticated refining, and is termed "chemical
lead", that from western and most foreign ores contains enough gold and
silver to make their extraction profitable.
Other metals, especially antimony, must be reduced to very low levels
to have "soft" lead, which is easily workable and the type used for most
applications. Antimonial lead, containing as much as 8 percent antimony, is
34
-------
,
- - ------ ~---
\
.
-ASAIm (
1: ~R) - -
t
I
1., ~
--
.._-~ ----.
(El Paso)
,
. (,' Bunker IIill (Ke
\ (5 + R)
l. . ASARCO (E.
\ (S)
'--~-
, -- ------
(
f
- ,
---. - ,
.' --/. -
--
. . -.
... - -
,
,
.
.
I
_\
(
\
..---
.
.
.
.
.
.
.
.
.
---
I
I
,
.-... .. -
.. . . .
...f -.. -.-... -----....
.
.
,
.
"----
.
,
,
.
.
(5) = Smelter only.
(R) = Refinery only.
(5 + R) = Smelter and refinery.
55).
Figure 4.2.
Geographic locations of domestic primary lead smelters and refineries
Source: U.S. Environmental Protection Agency (l975a)
-------
TABLE 4.2.
LEAD SMELTERS AND REFINEkIESa
Annual Tons
of Lead
Containing First
Material Year Of Raw Materials Slag Acid
Company Location Treated 1972 Operation Used Treatment Plant Products
American Smelting and Glover. 159.600 1968 Lead Cone. None None Refined Lead
Refining Company Missouri Waelz Residue Copper Dross
Lead Residues Retort Bullion
East Helena. 192.000 1888 Lead Cone. Slag None Lead Bullion
Montana Siliceous Ores Fuming Soda Ash Matte
Zinc Residue Furnace Soda Ash Speiss
Lead Baghouse Dust
Zinc Fume
El Paso. not reported 1887 Slag None Lead Bullion
Texas Fuming Zinc Fume
UJ
'"
Omaha. 136.000 1870 Lead Bullion None None Refined Lead
Nebraska Secondary 'Lead Antimonal Lead
Solder
Misc. Lead Alloys
Bismuth
Copper Matte
Sodium Telluride
Slag.
Bunker Hill Co. Kellogg. 550.000 1918 Lead Cone. Slag 300 TPD Refined Lead.
Idaho Fuming Gold, Silver,
Antimony
St. Joe Minerals Herculaneum. 336.000 1892 Lead Cone. None 300 TPD Refined Lead.
Missouri Silver Bullion.
Copper Matte
Missouri Lead Boss. 192.500 1968 Lead Cone. None 225 TPD Refined Lead
Operating Co. Missouri Copper Matte
Dross
Silver Bullion
aSource: 1. S. Environmenta. Protection Agency( .975a).
-------
TABLE 110 3. U.S. PRODUCTION OF REFINED LEAD AND ANTUIONIAL LEAD
AT PRIHARY REFINERIES, BY SOURCE NATERIAL, 1966-19758
-- -
----_._------"- -*-
Production, Thousands of Metric Tons
1966 1967 1968 1969 1970 1971 1972 1973 1974 1975
Refined Lead
From ~~imary sources:
Domestic ores and
base bullion 289 235 317 466 479 520 524 515 526 481
Foreign ores and
base bullion 111 110 107 113 126 70 94 97 84 96
From secondary sources 8 2 2 -2 ~ 1 1
408 b 347 426 584 609 591 619 612 611 577
w
'-I Antimonial LeCid
From primary sources:
Domestic ore 5 5 14 11 8 11 6 8 5 2
Foreign ore 5 3 3 4 3 4 2 4 4
From secondary sources 10 7 6 6 7 2 5 1 1 3
20 15 24 21 17 17 13 13 10 5
Total Primary Sources 410 353 442 59/.. 616 604 625 624 620 579
Total Secondary Sources 18 9 8 10 11 3 6 1 1 3-
GRAND TOTAL 428 362 450 605 627 607 631 625 621 582
a Source: U.S. Bureau of Mines Minerals Yearbooks.
b Totals may not equal sum of figures shown because
of rounding.
-------
a specialty lead favored for battery use. Standard specifications for pig
lead, as specified by ASTM Designation B29-55, are shown in Table 4.4.
4.2.2
Secondary Lead
Lead is a durable metal and is one that is relatively easy to refine or
rerefine. There is, accordingly, a major secondary market, comparable in
size to the primary metal market. Secondary lead is recovered from scrap,
wastes, drosses, and residues. Because of its excellent resistance to
corrosion, many lead products remain virtually unchanged during their
lifetime, and recovery is not difficult. The chief source of secondary lead
is from automobile storage batteries that have been scrapped after 3- to
4-year service. In the U.S. about 80 percent of the lead used in the
manufacture of storage batteries is recycled; in some foreign industrial
countries the percentage is higher. An indication of the flow of scrap is
given by Figure 4.3. (Ryan and Hague, 1976).
In the recycle industry scrap is classified into two categories, "new"
or prompt industrial scrap, and obsolete or old scrap. "New" scrap is that
resulting from metal industry operations, e.g., punchings, borings,
t.rimmings, imperfect products, etc. It is easily kept segregated with
respect to composition, and finds a ready market. A recent study
(Battelle-Columbus, 1972) estimated that, for most metals, recycle of "new"
scrap approaches 100 percent of that generated.
Obsolete scrap, or old scrap, consists of metal products (industrial or
consumer) that have been in use, served their purpose, and been discarded.
For lead, obsolete scrap in recent years accounts for about 85 percent of
. total scrap, as illustrated by Table 4.5. The largest source of obsolete
scrap is battery-lead plates, and accordingly, the principal recovered
product is antimonial lead.
The breakdown of scrap receipts is illustrative of the general origins
of lead scraps. Another annual tabulation of the U.S. Bureau of Mines is of
stocks and consumption of new and old scrap; the 1975 figures are
illustrative of the origins and rel~tive significance of the various types
of scrap:
Soft Lead
Hard Lead
Cable Lead
Battery-Lead Plates
Mixed Common Babbitt
Solder and Tinny Lead
Type Metals
Drosses and Residuals
Scrap Receipts,
Metric Tons, Gross Weight
New Scrap Old Scrap
30,430
24,610
44, 140
561,180
2,970
9,920
17,450
121,320
690,700
Total
121,320
38
-------
TABLE 4.4.
STANDARD SPECIFICATIONS FOR PIG LEAD (B29-55)a
Acid Common
CorroU~g Chemical Copper Desilverized
Lead Lead (c) '. Lead Cd) ," Lead(e)
Max Min Max Min Nax Min Nax Hin
Silver 0.0015 0.020 0.002 0.002 0.002
Copper 0.0015 0.080 0.040 0.080 0.040 0.0025
Silver and copper 0.0025
Arsenic. antimony and 0.002 0.002 0.002 0.005
tin, together
Zinc 0.001 0.001 0.001 0.002
VJ Iron 0.002 0.002 0.002 0.002
\0
Bismuth 0.050 0.005 0.025 0.150
Lead (by difference) 99.94 99.90 99.90 99.85
a Source:
Annual Book of ASTM Standards, 1978.
for Testing and Materials, (C) 1971.
Reprinted by permission of the American Society
b Corroding lead is a designation that has been used in the trade for many years to describe
lead which has been refined to a high degree of purity.
C Chemical lead has been used in the trade to describe the undesi1vered lead produced from
Southeastern Missouri ores.
d Acid-copper lead is made by adding copper to fully refined lead.
e Common desi1vered lead is a designation used to describe fully refined desi1vered lead.
-------
Q
I
.
L -.------.
B
t
I
I
I
I
I
CONSUMERS OF MILL PRODUCTS AND CASTINGS
CMA.~IJFACTURF.RS Of ENO PROOUCTSI
B
I
I
--______1..
flow.
Figure 4.3.
Source:
Lead scrap
Ryan and Hague
40
(1976).
-------
TABLE 4.5.
LEAD RECOVERED FROM SCRAP PROCESSED IN THE UNITED STATES. 1966-1975a
Thousands of Metric Tons
1966 1967 1968 1969 1970 1971 1972 1973 1974 1975
Kind of Scrap
New Scrapb
Lead-base 72 65 67 74 79 93 103 100 84 82
Copper-and tin-base 7 5 5 6 4 4 5 4 4 3
Total 79 70 72 80 83 97 108 105 88 85
Old Scrap
Battery lead plates 259 275 281 317 318 302 315 335 379 379
All other lead-base 163 141 130 134 126 129 122 140 152 123
Cooper-and-tin base 18 16 16 17 15 13 14 13 13 9
~ Total 440 432 427 468 459 444 451 488 545 511
f-'
Grand Total 519 502 499 548 542 541 559 592 633 596
Form of Recovery
As soft lead 142 136 126 140 144 136 157 169 206 246
In antimonial lead 257 262 280 311 316 311 314 341 337 286
In other alloys 121 104 94 97 82 94 88 84 81 65
Total 520 502 500 548 542 541 541 594 634 597
-----.--
-------
aSource: u.S. Bureau of Mines Annual Minerals Yearbooks.
bNew Scrap consists primarily of drosses and residues.
-------
Scrap receipts are not directly comparable to lead recovered, being on a
gross weight basis inflated by an unknown amount, since substantial amounts
of non-lead materials are included in the gross weights.
According to the U.S. Bureau of Mines (1976) in 1975 approximately 115
secondary lead plants were engaged in recovering lead and lead alloys from
recycled scrap material; five plants closed during the year. Important.
secondary smelters are located in major metropolitan areas, such as New
York, Philadelphia, Baltimore, Cleveland, Chicago, Baton Rouge, Dallas, Los
Angeles, and San Francisco. Lead-bearing scraps of copper or tin alloys,
and selected lead alloys usually are merely melted and adjusted for proper
alloy composition.
4.2.3.1
Scrap Pretreatment--
Because obsolete scrap makes up 85 percent of the lead scrap consumed,
it can be obtained from a wide variety of sources. These scraps may contain
organic materials such as insulation, grease, and oil. The major metallic
elements found in the scrap are antimony, tin, arsenic, copper, cadmium,
zinc, silver, indium, tellurium, and bismuth.
Lead scrap must be treated by densification and/or partial removal of
metallic and nonmetallic contaminants in order to make it more amenable for
further processing. Large pieces of lead-bearing scrap such as drosses,
residues, and slags must be reduced in size before further processing.
These are crushed in a jaw crusher to the desired size for processing to
recover the lead content. Handling and crushing of these scrap materials
gives rise to dust emissions which need to be controlled.
A number of relatively impure lead scraps (tooling dies, type metal
drosses, lead sheathed cable and wire, and lead drosses and skimmings from
a number of sources) are usually given a pretreatment to recover the lead
values. One process is the rotary/tube sweating route where the scrap is
charged to a furnace, the lead melted from the remaining materials, and the
molten lead poured from the furnace, leaving the higher-melting residues
behind. The sweated lead normally is given another furnace treatment to
refine or alloy the recovered lead into an acceptable product.
Reverberatory sweating is used to treat lead scrap with a higher lead
content than that charged to a rotary/tube furnace. The charge materials
usually are battery plates, lead oxides, drosses, lead scrap, and certain
residues. The process steps are the same as for rotary tube sweating. That
is, charging the solid material to the reverberatory furnace, melting, and
pouring the lead away from the solid residue. .
Zinc-bearing scraps will produce a zinc-containing
collected by the baghouse may be leached with sulfuric
recover the zinc. The lead-bearing residue is returned
for refining.
dust, and the dust
acid to remove and
to the blast furnace
42
-------
4.2.2.2
Smelting--
Smelting is commonly used to purify scrap by removing some of the
metallic and nonmetallic contaminants. The scrap may consist of new scrap,
pretreated scrap, type metals, babbit metals, mixed scrap, metallics from
batteries, or flue dusts. The secondary lead industry is basically the
recovery of lead from .automobile batteries; in 1975 almost 69 percent of
the lead scrap consumed was in the form of obsolete, discarded automobile
batteries. In this process any liquid remaining in the battery is drained
out, the battery is crushed to break the lead and lead compounds from the
non lead portion, and the mixture screened to separate the lead from the
organic materials that form the battery case. The recovered lead scrap can
then be fed into a reverberatory furnace or blast furnace for further
processing. The smelting scheme is illustrated by Figure 4.4 (U.S.
Environmental Protection Agency, 1977a).
Soft lead is recovered by reverberatory smelting. Because of the low
melting point of lead, it rapidly separates from the other metals. The
molten material is agitated by bubbling air or steam through it to oxidize
impurities such as antimony that then rise to the surface and enter the
~lag. The slag, containing a mixture of lead oxides and antimony, is
charged to the blast furnace for further processing. The fairly pure molten
lead is poured into ingots.
Particulate matter consisting of metallic oxides, sulfides, and
sulfates of lead, tin, arsenic, copper, and antimony is collected by
passing the flue gases through a baghouse and recycling the dust to the
furnace for lead recovery.
In blast furnace smelting a hard antimonial lead is produced by
charging a mixture of pretreated scrap, reverberatory slag, battery scrap,
drosses and rerun slag to the furnace along with coke and scrap iron and
heating. The lead and antimony from the slags are reduced to the metallic
state by carbon monoxide produced by combustion of the coke. The molten
lead is withdrawn almost continually from the furnace; the slag is tapped
at intervals. As the material in the furnace melts down and is tapped,
additional charges, consisting of 4.5 percent scrap iron, 3 percent
limestone, 5.5 percent coke, 4.5 percent rerun slag, and 82.5 percent
drosses, oxides, reverberatory slag, and residues are added. The molten
lead is cast into ingots or transferred to refining kettles.
4.2.2.3
Refining--
Intermediate products such as soft lead and antimonial lead from the
blast furnace and reverberatory furnaces require further refining to obtain
final lead products. Some lead oxide materials are made in addition to
metal products.
In kettle (softening) refining, hard lead, either cast or molten, and
fluxes are charged to a preheated kettle and melted. After mixing the flux
into the molten charge, the drosses are skimmed off and the metal cast into
43
-------
WASTE S/\TTE~IES
SPENT ELECTRO '- ','TE
TO TRE)..n~E~H
~
SCp. ,\? L:: A::
FRO;\18ATTERIES
OTHER
LEAD.BASE
SCRAP
REVERBERATORY
FURNACE
SOFT LEAD
(PURE LEAD)
BARTON
OXIDATION
LEAD
OXIDE
. = ALTERNATIVE
ROUTES
Figure 4.4.
BLAST
FURNACE
SLAG
HARD LEAD
(ANTIMONIAL LEAD)
REMELT
KETTLES
(REFINING OR
ALLOYING)
REFINED
LEAD OR
LEAD
ALLOYS
ANTIMONIAL
LEAD
PRODUCTS
Secondary lead smelting process
Source: u.S. Environmental
Protection Agency (l977a).
44
-------
ingots. Several fluxes, including sodium hydroxide, sodium nitrate,
aluminum chloride, aluminum, sawdust, and sulfur, are added to remove
deleterious metals, including antimony. These metals are removed in the
dross. The solid wastes contain skimmings, flux, and metals separated from
the melt during refining. These wastes are also returned to the blast
furnace for lead recovery.
Kettle (alloy) refining is the process of adjusting the metal
composition of reverberatory or blast furnace lead to produce the desired
lead alloy. The process is essentially the same as in the previous process.
The charge is melted, flux stirred in, the alloying agents added, the
skimmings removed, and the molten lead alloy cast. Antimony, copper, tin,
and silver are common alloying agents.
The kettle oxidation process is used to produce battery lead oxide,
which is essentially lead monoxide (PbO) containing about 20 percent of
lead metal. The operation consists of charging molten led to a kettle,
agitating the molten material rapidly while air is passed over the melt,
drawing the air through a duct to a baghouse, and collecting the lead oxide
plus lead metal product
Reverberatory oxidation is used to produce either lead monoxide or red
lead (Pb 04). PbO is made by oxidizing lead under careful control. Red lead
results from overoxidizing the lead. The process involves charging the,hot
furnace with molten lead, agitating and simultaneously oxidizing the molten
lead with air, and removing the lead oxide from the furnace.
4.2.3
Supply/Demand Relationships
Estimating the total supply of lead available for United States
consumption each year is an almost impossible task to accomplish with
accuracy. The analysis is complicated by the varying percentages of lead in
the multiplicity of lead-containing materials and lead scraps in varying
stages of processing by domestic producers, and further compounded by the
imports and exports of these same materials. However, by focusing on the
main factors and neglecting the minor aberrations such as the above a close
approximation can be derived. This can be done by defining the total supply
as the total of primary and secondary production plus imports, adjusted for
the net change in producers and consumers stocks. On this basis, the total
supply of lead in the United States varied during the years 1967-1977 as
) shown in Table 4.6, from a minimum of 1,163,000 metric tons in 1967 to a
maximum of 1,497,000 metric tons in 1977. It will be noted that there has
been a gradual, if irregular, decline in imports as the new rich Missouri
deposits were exploited and began to affect market balance. There was,
however, an increase in imports in 1977. Total imports of all types of
lead-containing material during this same period are shown in Table 4.7.
Concurrently, exports of refined lead and lead scrap materials were-- ,
inconsequential until 1972 when world demand surpassed supply. The
continuing world shortage during 1973 and early 1974 provided unusual
opportunities for the American producers to penetrate foreign markets at a
profit. By 1975, the worldwide economic stagnation had eliminated much of
45
-------
TABLE 4.6.
SUPPLY OF LEAD IN THE UNITED STATES, 1967-1977a
Thousands of Metric Tons
Primary Secondary Net Stock Total
Year Production Production Importsb ChangeC Supply
1967 353 503 330 (23) 1163
1968 442 500 307 47 1296
1969 594 548 253 (44) 1351
1970 616 542 222 (89) 1291
1971 604 542 177 72 1395
1972 625 560 220 (15) 1390
1973 624 594 162 45 1425
1974 620 634 107 (67) 1294
1975 579 596 91 ( 2) 1264
1976 598 645 135 107 1485
1977 555 648 244 44 1497
aSource:
U.S. Bureau of Mines Annual Minerals Yearbooks, (1966-1976)
U.S. Bureau of Mines Mineral Industry Surveys, August, 1977;
March, 1978.
bImports for consumption of. pigs and bars (lead content).
cInc1udes stocks at both producers' and consumers' plants.
parentheses, 0, indicate net addition to inventory.
Figures in
46
-------
TABLE 4.7.
U.S. IMPORTS OF LEAD BY TYPES OF MATERIAL, 1967-1977a,b
Thousands of Metric Tons of Lead Content
are, flue dust Base Pigs and Reclaimed
Year and matte Bullion Bars Scrap, etc TotalC
1967 113 1 330 9 453
1968 80 <1 307 6 393
1969 99 2 253 6 360
1970 102 <1 222 6 330
1971 60 <1 177 3 240
19. 72 92 1 220 3 317
1973 100 <1 162 3 264
1974 86 1 107 1 195
1975 79 <1 91 5 176
1976 69 2 132 4 207
1977 66 7 237 6 316
aSource:
U.S. Bureau of Mines Minerals Yearbooks (1967-1976)
U.S. Bureau of Mines Mineral Industry Surveys, August, 1977;
March, 1978.
bDoes not include imports of pigments and lead compounds.
CTota1s may not equal sums of figures shown because of rounding.
47
-------
I-
I
,
the foreign premium price
traditional levels (Table
consisted of contaminated
processing to recover the
for lead and U.S. exports were returning to
4.8). Historically, much of the scrap exports
dross and baghouse dusts requiring extensive
valliable metals.
Long-term trends in the lead industry are illustrated by Figure ~~1 in
which the total of annual primary and secondary production is compared to
total annual consumption. Approximate balance of supply and demand was
achieved by imports, which normally ranged between about 175,000 and
350,000 metric tons per year, except for a few high years in the early
1950's. Secondary production is less erratic and more stable than primary
production, but has also exhibited a steady upward trend for the last two
decades. During most of the 1960's, secondary lead production exceeded
primary production; in fact, it was not until the "new lead belt" mines in
Southeastern Missouri came into production that primary production regained
the lead.
Employment in the lead producing industry has held
the last five years although decreasing slightly. Mine
has gradually decreased from 4,900 in 1973 to 4,700 in
refinery employment decreased only from 2,450 to 2,400
period (U.S. Bureau of Mines, 1978b).
fairly constant over
and mill employment
1977; smelter and
during the same
4.2.3.1
Stockpiling--
During World War II and again in 1951-1952, the government regulated
the lead industry to provide adequate supplies for all essential purposes.
Stocks were reduced during World War II, but stockpiling was resumed in
1950, and by the end of 1958 the domestic purchase program was completed.
Disposal of excesses began in 1964. The government stockpile had a
substantial impact on the lead industry, particularly during 1972-1974,
when 473,500 metric tons of stockpile excess was sold. In 1974, withdrawals
from the stockpile provided approximately 14 percent of the new supply of
lead. (Ryan and Hague, 1976). Actual physical drawdown of government stocks
was only about 6,300 metric tons during 1975, a year of depressed demand
for lead. There were no withdrawals in 1976 and 1977 and stockpile status,
as of November 30, 1977, was 545,700 metric tons, with a goal of 785,000
metric tons, 865,000 short tons, and none authorized for disposal (U.S.
Bureau of Mines, 1978b).
4.2.3.2
Refined Lead Prices--
In the early part of the 1966-1975 period, common pig lead was priced
for marketing at either St. Louis (Missouri) or New York (New York).
Starting in 1972, the quotation basis is "delivered common pig, lead" with
New York as the site for posting. The London price is that derived from
daily trading on the London Metal Exchange, the accepted indicator of world
pricing trends. London lead prices traditionally are lower than those in
the United States. Frequently, the difference is enough to cover ocean
freight and insurance costs plus a little extra for the import agent, a
matter of 2 to 2.5 cents per pound. This relationship was maintained from
48
-------
TABLE 4.8.
u.s. EXPORTS OF LEAD BY TYPE OF PRODUCT, 1967-1977a,b
Thousands of Metric Tons
Pigs, Bars, and Anodes
Unwrought Lead Wrought Lead Grand
Year and Alloys and Alloys Total Scrap Tota1d
1967 5.9c 0.4 6.3
1968 7.5c 0.9 8.4
1969 2.3 2.2 4.5 2.1 6.6
1970 4.5 2.5 7.0 3.8 10.9
1971 3.4 2.0 5.4 15.5 20.9
1972 6.0 1.6 7.6 32.0 39.6
1973 47.1 13.4 60.4 54.3 114.7
1974 48.6 7.6 56.2 53.9 110.1
1975 16.7 2.6 19.3 45.3 42.5
1976 5.3 42.5 47.8
1977 8.9 77.5 86.4
aSource:
U.S. Bureau of Mines. Minerals Yearbooks (1967-1976)
U.s. Review of Mines Mineral Industry Surveys,August, 1977;
March, 1978
bDoes not include exports of lead compounds.
cPrior to 1969, pigs, bars, and anodes not subdivided.
dTota1s may not equal sums of figures shown because of rounding.
49
-------
1600
1200
" ,.-- ---"""...... ",'"
'\.--.....'" "
1400
I
I
I
I
I
~ 1000 I
~. I
""-'-, . I
u --..... -~-' ",
..... ------, /' ",
- , / "
~ 600 - ,,... , /
'+- " /,... ',/ / Total Production
o ,/
VI v>
o --g
o
~ 600
o
~
I-
400
Secondary Product ion
~~----------~
"....
--"
- ,.'
-...."",
Primary Production
200
o
1952
1955
1960
1965
Year
1970
1975
Figure 4.5.
Trends in the lead industry in the United States.
Source:
1 . S. Bureau of
ines tinera.s Yearbooks.
-------
I~-
1966 until the early part of 1973 when worldwide shortages drove London
prices above those in the United States.
Refined lead has the status of a commodity on world markets and its
price is quite responsive to shortages or surpluses, both short term and
long term. Lead prices trended downward in the 1966-1968 period under the
increasing pressure of surplus production, largely overseas. Prices firmed
in 1969 and early 1970 until the slowdown in the U.S. economy triggered a
period of excess stocks well into 1971. After reasonable balance in 1972,
booming economies worldwide in 1973 and 1974 liquidated producers' and
dealers' stocks and the London price exceeded the United States price,
creating a good export m~ket for the new production in southeastern
Missouri. The worldwide downturn in 1975 was reflected in falling prices
and a return to the traditional spread between U.S. and London quotations.
However, production costs for the "new Missouri lead belt" tend to maintain
a floor price under U.S. quotations at 19 cents per pound, 5 cents higher
than the lowest quote in 1972, the last "normal" year.
Since 1975, additional increases in the U.S. quotations have been
introduced without regard to the status of producers' or dealers' stocks.
rhe average U.S. producer price in January-March, 1978, for common lead was
33.0 cents per pound, a 2 cent increase above mid-1977 prices, and a full
10 cents above the average 1976 price. (U.S. Bureau of Mines, 1978a)
4.2.3.3
Reserves--
New discoveries since 1965 have substantially increased the United
States resource base for lead, and annual mine production has more than
doubled.
According to the latest U.S. Bureau of Mines estimates, United States
reserves are an important part of world totals:
Region
Lead Content, Thousands
of Metric Tons
United States
Australia
Canada
Mexico
Peru
Other Latin American Countries
Other Market Economy Countries
Central Economy countries
25,800
17,000
11,700
4,100
3,200
4,100
27,600
30,000
123,500
U.S. -lead reserves represent a decrease from previous estimates because
certain inferred reserves not having near-term potential have been
excluded. (U.S. Bureau of Mines, 1978b).
51
-------
Including hypothetical undiscovered economic and some identified
marginally economic resources doubles the world total. If speculative and
economically submarginal lead deposits as well as undiscovered lead
deposits in new areas of the world are considered, then the total resource
of lead may be as high as 1.5 billion tons (Ryan and Hague, 1976).
Ryan and Hague estimated the distribution of United States reserves by
states as follows:
States
Lead Content,
Millions of Metric tons
Missouri
Washington, Idaho, Montana
Colorado, Utah, New Mexico,
Arizona, California
46.9
4.5
1.6
Virginia, New York, Maine,
Wisconsin, and others
0.5
53.5
In the opinion of the U.S. Bureau of Mines (Ryan and Hague, 1976) the
United States resource base is more than adequate to support the domestic
component of primary lead demand to 2000.
4.3
LEAD CONSUMING INDUSTRIES
The consumption of lead in the United States is inextricably related to
the automobile industry. During the last several years from 800,000 to
1,000,000 metric tons of lead, accounting for from 60 to over 70 percent of
total anAual lead consumption, have gone into storage batteries and
gasoline antiknock additives. Lead-acid storage batteries, as described
later, represent the only large segment of the lead industry with
significant growth potential. Traditional lead-based metal products and
pigments face declining or stagnant rather than growing markets, and the
use of lead in gasoline is mandated to be drastically reduced within the
next several years. The world consumption of lead is slowing, and Bank of
America economists predict consumption to grow at only a 2 per cent rate
through 1985, compared with a 3 per cent annual growth rate during the past
20 years (Anonymous, 1976).
Lead and lead compounds have many other smaller, but nevertheless
important uses. Metallic lead is used for ammunition, bearing metals,
covering, pipe caulking, collapsible tubes, foil, solder, type metal,
weights and ballast, radiation attenuation, and in sheet form, for
attenuation of noise or vibration.
cable
Lead compounds also have a wide diversity of uses. There are scores of
inorganic compounds and over 1000 organolead compounds. Some illustrative
52
-------
uses of lead compounds are listed in Table 4.9, although some of the
possible use shown are minor or insignificant.
u.s. lead consumption, grouped into five broad classes of products, is
shown in Table 4.10 for the 1967-1976 decade. As is evident in this
tabulation, storage batteries, an essentially nondissipative use, account
for over half of annual lead consumption. Most of the remaining lead uses
would have to be classified as dissipative, either totally and prompt, such
as gasoline antiknock additives, or totally and slowly, such as pigments in
paint. A smaller third class would include the mostly metallic uses, where
the lead is in a reclaimable form, but which mayor may not be recovered.
A more detailed breakdown of consumption uses for 1973-1976, the most
recent years for which data are available, is shown in Table 4.11. The
various use categories shown are discussed in the following sections.
These data are derived from U.S. Bureau of Mines sources. The Bureau of
Mines has for a number of years compiled probably the most complete lists
of lead consumption in the United States by product. The classifications
used have been consistent in that they provide continuity, but the
breakdown in some cases is ~ather broad, so that some important end uses of
compounds do not show as line items. An example of this is the class of
"red lead and litharge" under pigments. Litharge (PbO) has many uses other
than as a pigment. A signficant fraction of the litharge reported is used
in the manufacture of batteries; a new significant use is the preparation
of a number of lead compounds used as stabilizers in plastics and
elastomers. Nevertheless, the Bureau of Mines breakdown of lead use by
products provides the best overall picture currently available of the
relative importance of most lead uses.
4.3.1
Storage Batteries
Storage batteries represent by far the largest single category of lead
use. Approximately 93 percent of the storage batteries produced in this
country are classified as SLI (starting, lighting, and ignition) and are
used for equipping new cars or as replacement batteries for existing
vehicles. The remaining 7 percent are industrial batteries used as
emergency power sources, to power industrial and mining vehicles, in
submarines, etc. Although battery design and manufacture have been improved
to extend the useful life of batteries, expansion in the number of
automobiles on the road and the development of new transportation
modes--i.e., industrial lift trucks, golf carts, snowmobiles, etc.--has
broadened the markets for batteries (Short and Associates, 1976).
4.3.1.1
Manufacturing--
The manufacturing process for making storage batteries is complex, but
a simplified version follows. The battery grids are cast, then filled with
a lead oxide (black oxide) paste to form a porous lead oxide plate, and
cured to increase strength. The plates and separators are assembled into
elements and placed in the battery case. The elements are welded together,
53
-------
TABLE 4.9
SELECTED LEAD COMPOUNDS AND THEIR USESa
Chemical Compounds
Uses
Lead acetate
Dyeing and printing cottons
Manufacture of lead salts
Astringent (veterinary)
Paint drier
Lead coating of metals
Lead alloys
Slush coatings
Type metals for printing
Batteries
Battery grids
Bearing metals
Solders
Fusible alloys
Communication cables
Pipe and sheet in chemical
installations
Corrosion protection coatings
Lead antimonate
Pigment
Staining glass
Crockery and porcelain
Lead arsenate
Insecticides
Veterinary medicine
Lead azide
Primer in explosives
Lead borate
Paint drier and production of
conductive coatings
Glass
Pottery
Porcelain
Chinaware
Lead carbonate
Paints
Ceramics
Glazes
Processing
of parchment
Lead chloride
Manufacturing of white lead dyes
Solder and flux
Lead chromate
Pigment
Printing of fabrics
Decorating china and porcelain
54
-------
TABLE 4.9
SELECTED LEAD COMPOUNDS fu~D THEIR USESa
( Con t . )
Chemical Compounds
Uses
Lead cyanamide
Corrosion inhibitors
(Antirust paints)
Lead dioxide
Electrodes
Dyes
Rubber substitutes
Manufacture pigments
Analytical purposes
Lead fluosilicate
Electrolyte in electrolytic
refining of lead
Lead formate
Rubber compounding
Lead fumarate
Plastisols
Phonograph records
Electrical insulation
Lead iodide
Bronzing, printing
Photography
Lead linoleate
Driers in paints
Lead molybdate
Paint
Pigment
Lead monoxide,
litharge
Ointments
Plasters
Glaze
Flux
Pigments
Analytical
Driers
Lead naphthenate
Driers in paint
Lead nitrate
Match industry
Pyrotechnics
Chemical intermediates
Lead oleate
Driers in paint
55
-------
TABLE 4.9
SELECTED LEAD COMPOUNDS AND THEIR USESa
(Cont.)
Chemical Compounds
Uses
Lead orthophosphate
Lead perchlorate
Lead phosphate
Lead selenide
Lead silicate
Lead stannate
Lead styphnate
Lead subactate
Lead sulfate
Lead sulfide
Lead telluride
Lead tetroxide,
red lead
Lead tetramethyl
Stabilizer for plastics
Pigments
Anticorrosive agents
Analytical reagent
Stabilizer for plastics
Semiconductor
Infrared detector
Glass, ceramics
Ceramics
Explosives detonator
Sugar analysis
Pigments
Batteries
Lithography
Fabrics
Photoelectric cell
Infrared detector
Photosensitive resistor circuits
Photoelectric cell
Infrared detector
Photosensitive resistor circuits
Pigments
Dyes
Chemicals
Matches
Pryotechnics
Curing agents
(rubber substitute)
Antiknock
Fungicide
Filling of Geiger counters
56
-------
TABLE 4.9
SELECTED LEAD COMPOUNDS AND THEIR USESa
(Cont.)
Chemical Compounds
Uses
Trialkyl or alkyl
aryl lead
Polymerization
Catalysts
Stabilizers for PVC
Electroplating
Lubricating oils
Biocidal agents
Lead thiocyanate
Primer in explosives
Matches
Dyes
Lead thiosulfate
Rubber accelerator
Lead mirrors
Lead titanate
Pigment
Ceramics
Lead tungstate
Pigmen t
Lead vanadate
Pigment
Lead zirconate
Pigment
a
Source:
Lutz, et al. ,(1970)
-------
TABLE 4.10.
u.s. LEAD CONSUMPTION BY CLASS OF PRODUCT, 1967-1976a
Consumption, Thousands of Metric Tons
Product 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976
Metal products 331 331 322 287 333 307 308 298 240 238
Storage batteries 423 466 529 539 617 659 698 773 635 746
Pigmentsb 92 97 92 89 73 81 99 105 72 96
Chemica1sc 225 238 247 253 240 253 260 228 189 218
IJ1
00
Miscellaneous and
unclassified 35 37 38 34 36 48 44 47 ~ ~
-
Tota1d 1,106 1,169 1,227 1,202 1,299 1,348 1,398 1,451 1,177 1,352
aSource:
U.s. Bureau of Mines Minerals Yearbooks.
bSorne o~ the oxides in this category are used in battery manufacture.
CPrincipa1 components of this category are gasoline antiknock additives (TEL and TML).
dTota1s may not equal sum of figures shown because of rounding.
-------
TABLE 4.11.
LEAD. CONSUMPTION IN THE UNITED STATES, BY PRODUCTS, 1973-l976a
Metal Products
Ammunition
Bearing metals
Brass and bronze
Cable covering
Caulking lead
Casting metals
Collapsible tubes
Foil
Pipes, traps, and bends
Sheet lead
Solder
Storage batteries
Grids, posts
Oxides
Terne metal
Type metal
Total
Pigments
White lead
Red lead and litharge
Pigment colors
Otherb
Total
Chemicals
Antiknocks
Miscellaneous
Total
Miscellaneous Uses
Annealing
Galvanizing
Lead plating
Weights and ballast
Total
Other, unclassified uses
Grand Tota1C
==-=---- - -- ------ ='-
aSource:
1973
. Consumption; Metric Tons
1974 1975
73,901
14,200
20,620
39,005
18,191
6,550
2,594
4,521
19,310
21,218
65,095.
331,560
366,328
2,410
19,883
1,005,386
1,586
81,228
15 ,385
432
98,631
248,889
856
249,745
3,604
1,174
675
18,909
24,362
19,726
1,397,850
78,990
13,250
20,170
39,390
17,900
6,610
2,255
6,250
14,925
19,315
60,115
335,070
417,585
2,090
18,610
1,072 ,525
1,310
87,220
15,725
650
105,405
227,205
640
227,845
3,715
1~510
450
19,425
25,100
21,855
1,452,730
68,100
11,050
12,160
20,045
12,965
6,990
2,010
4,915
12,910
22,550
52,010
296,330
338,040
. 1,370
14,700
876,145
2,265
59,370
9,630
455
71,720
189,205
165
189,370
2,385
1,110
340
18,155
25,990
19,250
1,178,475
U.S. Bureau of Mines Annual Minerals Yearbooks.
=--~_.:==
bInc1udes lead content of leaded. zinc oxide and other pigments.
clncludes lead which went directly from scrap to fabricated products.
59
1976
66,664
11,848
14,203
14,448
11. 314
6,084
2,112
4,649
12,506
22,165
57,434
348,146
397,773
1,446
13,611
984,403
2,714
77,460
15,087
508
95,769
217,460
133
217,593
2,625
1,135
350
20,285
24,395
29,345
1,351,505
-------
posts connected to them and the battery filled with sulfuric acid. The
battery is then charged, washed, painted, and shipped. Process steps are
shown schematically in Figure 4.6. .
.---
Grids, the structural part of the lead plates, are cast by pouring
molten lead into the casting machine. Antimonial lead was favored
heretofore for this use because of its greater structural strength; as
described later it is being challenged by other lead alloys. After removal
from the casting machine, the grids are inspected and sent to the pasting
operation.
Lead oxide is produced by the fuming process in some battery plants
while other plants purchase the oxide. The black oxide (lead oxide
containing 20 to 40 percent metallic lead) is mixed with dilute sulfuric
acid and various additives such as wood fiber to add strength. The grids
are then coated with the oxide paste and flash dried to remove surface
water. The plates are then dried under controlled (curing) rates for 2-3
days.
After curing, the plates plus separators are assembled into elements
~nd welded, with lead, to form an electrical connection between the
positive and negative plates. These elements are placed in electrolytic
baths filled with acid and "formed" by passage of electrical current in the
dry-charged battery process. This operation converts the paste to lead
peroxide in the positive plate and to sponge lead in the negat,ive plate.
The elements are removed from the bath, rinsed with water, and dried. The
dried elements are then assembled in a case, the posts welded in and the
cover sealed to the case..
Wet-charged storage battery manufacture is somewhat different. The
elements are assembled in a case, welded together, the posts connected, and
acid added. The batteries are then "formed" by the passage of electrical
current as above, and the acid removed for recovery. New acid is added and
the battery is boost charged. The final operations are washing and painting.
4.3.1.2
Production and Industry Structure--
The domestic battery industry is dominated by six large corporations
operating 65 facilities which produce an estimated 90 percent of all SLI
and industrial batteries in the U.S. The remaining 10 percent is
distributed among an estimated 110 independent nonintegrated battery
manufacturers serving specialized or regional markets. The principal
companies and their estimated market shares are shown in Table 4.12. These
data are not claimed to be accurate but do roughly approximate the-
structure of the industry. It is apparent from the data that the industry
is an oligopoly containing a fringe of small independents, which, for
regional or specialized reasons, can compete with the six national
companies which have roughly 90 percent of the total market. The small
number of major producers would make easier the implementation of
limitations on production or use (Short and Associates, 1976).
60
-------
Piq Lead
SOlids
,
Oxide L.DuSIS
ProduClion I ,Gaseous
Addiil ives
Separators
Dry BaHery Line
Battery
Case
Cover
Figure 4.6.
II Particu!Oles
Wasle w~
Acid
~
Wash, Poinl
Wasle Water
Simplified flowsheet for storage
battery manufacture.
Source:
C.randall and Rodenberg (1974)
Reprinted by permission of Purdue
University.
61
..
60 Ilery
Case and
Cover
Acid,
Solids
-------
TABLE 4.12.
ESTIMATED STRUCTURE OF STORAGE BATTERY INDUSTRya
Estimated
Estimated 1974 Estimated Number of
Number of Production, Percent of Employees
Holding Company Facili ties 106 Batteries Market Share Exposed to Lead
ESB, Inc. 20 10.00 17.1 3,035
General Battery 10 8.94 15.3 2,934
Company
Globe-Union 10 8.96 15.3 2,059
Gould 13 9.60 16.4 2,181
CJ\ E1tra Corp. 9 7.02 12.0 1,592
N
De1co- Remy 3 7.98 13.7 1,275
Total large 65 52.60 89.8 13,076
producers
Independents 110 5.90 10.1 3,500
Total 175 58.50 100.0 16,575
a Adapted from Short and Associates, (1976).
Source:
-------
It should be noted that storage batteries constitute a nondissipative
use of lead, so that a large fraction of this consumption is recycled
secondary lead rather than virgin primary lead. Estimates of extent of
recycle of storage batteries are conflicting. One recent industry estimate
was that about 50 percent of those scrapped in a given year are reclaimed,
via secondary refiners (Anonymous, 1977). Industry sources claim that the
recycling of 75 percent of the batteries scrapped would represent a
realistic maximum level that probably could be achieved between 1980 and
1985. On the other hand, a Bureau of Mines estimate (Ryan and Hague, 1976)
states that about 80 percent of the lead used in the manufacture of storage
batteries is recycled.
Thus, battery manufacturing
refiners, though geographically
more populous urban states, led
Illinois.
plants, like their supporting secondary
widely distributed, are concentrated in the
by California, New York, Pennsylvania, and
Paralleling the increase in automobile population, storage batteries
have comprised the one growth area of the lead industry (See Table 4.10).
Approximately 47.2 million SLI batteries were produced in 1975, 8.5 million
less than 1974. Of this total, about 40.7 million were replacement
batteries and 6.5 million were original equipment. As shown in Table 4.11,
in 1975 the battery grids and posts consumed over 296,000 metric tons of
lead, and the oxides for filling the grids consumed over 338,000 metric
tons; the two combined represented 53 per cent of total lead consumption in
1975 for all purposes (U.S. Bureau of Mines, 1976).
4.3.1.3
Future Projections--
In the view of Short and Associates (1976) lead storage batteries are
technologically and economically superior to any known substitute. Demand
for batteries is almost totally a function of automobile production and the
number of vehicles in operation, and is, therefore, relatively inelastic.
The Bureau of Mines projects a growth in lead demand for batteries to range
between 1.08 and 1.9 million metric tons by 2000, with a most probable
value of 1.45 million tons, based on the expected rate of growth (about 3.5
percent) of the gross national product (GNP), and evolutionary improvements
in lead-acid batteries. The higher value envisions a significant growth in
electrically powered vehicles; the lower value is predicated on an
accelerated growth of non-lead storage batteries.
A somewhat more optimistic estimate is suggested by Wright and Kubulak
(1976) who describe the rate of growth of SLI batteries (each containing
about 9 kg of lead) at 4 to 5 percent per year, to which must be added the
larger industrial batteries and standby power batteries--markets growing at
an estimated 8 to 10 percent per year.
Some major technological and economic changes appear to be in store as
a result of the recent development of the "maintenance-free" battery, which
will affect not only the lead-acid battery industry, but also the secondary
lead industry.
63
-------
One battery manufacturer recently announced a new heavy-duty battery
based on a lead-calcium alloy, impervious to vibration, corrosion-free, and
requiring no water make-up. This lead-calcium battery retains its charge 6
to 8 times longer than ordinary batteries and has up to 30 percent more
cranking power (U.S. Bureau of Mines, 1975). Competing manufacturers have
developed lead alloys containing strontium, or cadmium - antimony in
response. This new alloys are expected to virtually replace the
conventional antimonial lead heretofore used by all manufacturers. One
estimate is that by 1980, 70 percent of all automotive batteries will be
made without filler caps (using the new alloys), and conventional
antimonial lead's share of the market (61 percent in 1976) will drop to 10
percent. (Walsh, 1977).
This development will have a significant impact upon the secondary lead
industry, which up to now has had only one alloy to deal with. In the
future scrap battery alloys may contain antimony, calcium, strontium,
cadmium, arsenic, tin, aluminum, and possibly other metals (Walker, 1977).
This will pose some serious metallurgical problems for secondary refiners.
Additionally, there is a very large pool of antimony contained in the
present battery population, which will be excess for future battery needs.
~eeded will be a lead-antimony separation process, and new uses for
antimony.
4.3.2
Gasoline Antiknock Additives
The second largest use of lead, and one which is totally dissipative
over the entire country, is for the manufacture of gasoline antiknock
additives. Lead alkyls, tetraethyl lead (TEL) and tetramethyl lead (TML),
provide the least expensive way to raise the octane rating of gasoline, and
in recent years all gasolines have contained from 1.5 to 3 g/gal of lead.
In general, and for larger refiners, this need for octane improvement
resulted in the use of about 2.4 g/gal in the 1960's.
4.3.2.1
Manufacture--
Tetraethyl and tetramethyl lead are produced by two major generic
processes--the sodium-lead alloy process and the electrolytic process. Most
of these alkyls are produced by the sodium-lead alloy process operated in
batch fashion. One major manufacturer operates the sodium-lead alloy
process in continuous fashion in two plants and a small manufacturer
operates the electrolytic process in one plant. (See Table 4.1~) Many of
the details of lead alkyl manufacture are proprietary. The general outlines
of the processes have been described by Shapiro and Frey (1968) of the
Ethyl Corporation, on which the following discussion is partially based.
Some supplementary information was obtained in plant visits and discussions
with plant personnel.
4.3.2.1.1 Sodium-lead alloy process--A simplified block diagram of the
sodium-lead alloy process as applied to tetraethyl lead is presented in
Figure 4.7. In this process, the major unit processes are:
-
64
-------
TABLE 4.13.
LEAD ALKYL MANUFACTURERS AND ESTIMATED CAPACITIESa
Thousands of metric tons
1976 Estimate Total Annual
Location Process Production a --a Capuci tyb
Capacity
Deepwater ;U Cor.tinuollS 86 95
Antioch CA Na-Pb alloy 27 59 154
Baton Rouge LA Batch 91 104
Pasadena TX Na-Pb alloy 27 54 158
Freeport LA Electrolytic
(TML only) 13.6 18 18
Beaumont TX Batch
Na-Pb alloy 41 54 54
(TEL on1y)'c
285 385
E. 1. duPan t de Nemours & Co., Inc.
Organic CheIT~ca1s Department
Petroleum Cheffiica1 Division
Ethyl Corporation
0'
VI
Nalco Chemical Company
Petrol~um and Process
Che~icals Division
rFG Industries, Inc.
Chern Div1.sion
:IOU3 ton Chemical Co.
Tot",l
a
Source:
Battelle - Columbus estimates.
b
c
Chr.m. ~arketing Reporter, 109 (26), 9 (June 28, 1976).
TI~u purchased from Nalco Chemical Company.
-------
Vent
I Ethyl Chloride
Vent
Ethyl
Chloride
TEL
Vent
Water
Steam
Sti II
Wash
Water
Vent
~~~:rl
!
,Sludge Pit l
Sol ids L
~ Waste Wa ter
I Treatment
Decanted Wash Water
( Recycle)
Air
OXidizer-rJ
Wash Tanl~
T
Spent Solids
TEL
Scavengers
Dye.
Antioxidant
Ig ni tion Contrul! ~ r
Solveni
Lead
,vent
Secondary
Smelter
->-Slag
Blend
Tonk
Figure 4.7.
Sodium-lead alloy process for the
manufacture of tetraethyl lead.
Source:
13attel:1.~-ColuT"bus, based on
Shapiro and Frey (1968) .
66
-------
.
.
.
Preparation of the sodium-lead alloy
Reaction of the alloy with ethyl chloride
Steam distillation of excess ethyl chloride and
tetraethyl lead from a mixture of sodium chloride
and lead
Oxidation and washing
Lead recovery operations.
.
.
The initial step in the process is to melt metallic lead and sodium
which are then alloyed in a vessel by combining 90 parts lead with 10 parts
sodium. The alloy is then solidified on flakers and conveyed (often in
hopper cars) to the autoclaves. Because of the high reactivity of metallic
sodium and sodium-lead alloy with oxygen, moisture, and carbon dioxide, all
of the steps involving these materials are conducted under a nitrogen
atmosphere.
The reaction of ethyl chloride with sodium-lead alloy is performed in
autoclaves where temperatures somewhat in excess of 75 C and pressures
exceeding about 5 atmospheres pressure (absolute) are employed. The
chemical reactions involved are:
4Na + 4Pb ~ 4NaPb
4NaPb + 4 C2H5C1, ~ (C2H5)4 Pb + 4NaC1 + 3Pb.
Based on these equations, it is apparent that 75 percent of the lead
introduced to the autoclave must be recycled.
If tetramethyl lead (TML) is to be produced, methyl chloride is used
instead of ethyl chloride. In addition, a Lewis acid such as aluminum
chloride or triethyl aluminum and a solvent such as toluene are autoclaved
at more severe temperatures and higher pressures.
These reactions are exothermic and significant cooling is provided by
condensing volatilized ethyl chloride (or methyl chloride--toluene) and
returning the liquid to the autoclave. In the case of TEL manufacture,
significant amounts (about 10 percent of theoretical) of ethyl chloride are
lost by side reactions to yield ethane, ethylene, and butane which are
ultimately vented to an incinerator.
After the reaction is complete, most of the reaction mass is dumped to
a steam still, after the autoclave has been depressurized through a
condenser to recover a portion of the ethyl chloride (or methyl chloride
and toluene). The steam stills are typically operated in batch fashion but
may be operated continuously. In the batch distillation, the low boiling
ethyl chloride (or methyl chloride and toluene) is the first material
distilled; this is condensed and is recycled after purification. TEL (or
TML) mixed with steam is volatilized next and is condensed and forwarded to
an oxidation-wash operation. The solids, consisting principally of lead and
sodium chloride, are discharged to a sludge pit.
67
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The TEL-water mixture is oxidized by sparging air into the mixture,
primarily to oxidize and precipitate unwanted metal compounds such as
bismuth. (This step is not used with TML manufacture). After oxidation, the
TEL (or TML) is washed with water, decanted, and forwarded to the blending
operation where scavengers (ethylene dichloride and ethylene dibromide),
dye, antioxidant, solvent (kerosene), and a surface ignition control agent,
are added to produce the finished antiknock gasoline additive.
The solids which were discharged from the steam still to the sludge pit
are washed (or leached) with water to dissolve out the sodium chloride in a
covered sludge pot. Air from the covered pot is vented through a carbon bed
and subsequently to a stack. Water solution containing the dissolved salt
along with fine lead particles and residual TEL constitutes a significant
aqueous lead emission and, therefore, receives careful attention from
antiknock producers as a waste disposal problem. Treatment may be by
proprietary processes which inlude pH adjustment to produce relatively
insoluble basic lead carbonate and lagooning, followed by treatment of the
effluent with activated carbon. The residual solids are dried in an
enclosed dryer so that the volatiles, consisting primarily of water and
ethyl chloride, may be condensed. The dried solids are then refined in a
conventional secondary smelting operation to recover the lead.
4.3.2.1.2 Electrolytic process--A simplified block diagram of the
electrolytic process as applied to tetramethyl lead is presented as Figure
4.8. In this process, the major steps are:
.
Preparation of Grignard reagent (methyl magnesium chloride
etherate in ether)
.
Electrolysis of the Grignard reagent using lead as the anode
to produce tetramethyl lead and magnesium chloride
.
Recovery of the methyl chloride and ether for recycle and
purification of tetramethyl lead from magnesium chloride
.
Blending to produce finished antiknock compounds.
Grignard reagent is produced by reacting finely divided metallic
magnesium with methyl chloride in the presence of ether which forms a
methyl magnesium chloride etherate in ether solution. This solution is
introduced to an electrolytic cell which uses lead pellets as the anode and
the walls of the cell as the cathode. The overall electrochemical reaction
is as follows:
2CH3MgC1 + 2CH3C1 + Pb
~ (CH3)4Pb + 2MgC12
Excess methyl chloride is removed by distillation. The specific process
employed to separate TML, ether, and magnesium chloride is not known but
probably uses distillation for recovery of the ether and a proprietary
solvent extraction process combined with distillation to separate magnesium
chloride from TML and to purify the TML.
68
-------
Lead Pellets
(for anode)
Meth I
TML Ether
MgCI2
CH3CI
Figure 4.8.
Ether
Magnesium
Methyl Chlori,je
CH3MgCI eth~rate
(Grignord reagent)
Methyl Chloride (to recycle)
Still
E th e r
(to recycle)
TML
Purification
TML (to blending)
MgCI2
(to magnesium recovery)
Electrolysis process for the
manufacture of tetramethyl lead.
Source:
Battelle-Columbus, based on
Shapiro and Frey (1968).
69
-------
4.3.2.1.3 Mixed TEL-TML antiknocks--TML and TML-TEL mixtures are most
applicable to high octane gasolines containing high aromatics
concentrations. Two types of TEL-TML mixtures are produced--simple physical
mixtures and reacted mixtures. Preparation of the reacted mixtures involves
adding TML to TEL in the presence of a catalyst to yield a mixture of
triethyl (mono) methyl lead, diethyl dimethyl lead, and (mono) ethyl
trimethyl lead plus unreacted TEL and TML.
4.3.2.1.4.. Environmental management practices--The manufacturers are
very aware of the high toxicity of the lead alkyls and generally discharge
vented gases containing TML and TEL to high stacks or incinerators. When
possible, tanks and vessels being filled with liquids containing alkyls are
vented back to the tanks being emptied.
The industry has evidently unofficially adopted a 100 ug/m3 lead level,
as proposed by the Department of Labor (1975) for inorganic lead
compounds.* Blood and urine samples are regularly taken from employees and
monitored to assure that individuals do not become overly exposed.
A significant liquid stream containing lead alkyl is generated from the
washing operation after the oxidation step. This stream is recycled to the
steam still to recover valuable TEL or TML. A particularly troublesome
waste stream is generated during the water wash (or leach) of the salt from
the material dumped to the sludge pit. This waste would contain residual
TEL or TML plus metallic lead. This waste stream is handled differently by
the manaufacturers, by proprietary processes in some cases. One company
first applies a treatment to adjust pH and subsequently forms insoluble
basic lead carbonate. Next the waste is lagooned followed by passage of the
supernate through activated carbon. According to a company representative
the final discharge is about 5 pounds per day of lead--about 1 ton per year.
The principal solids generated by the plant are the dried solids from
the sludge pit. Lead from this material is 'recovered by in-plant and in
some cases off-site secondary recovery smelting operations in reverberatory
furnaces. Slag from this operation receives some treatment and particulates
are collected by either baghouses or in venturi scrubbers.
4.3.2.1.5 Transportation and handling--Lead alkyls are recognized as
hazardous substances requiring extreme care in transportation and handling.
Nearly all antiknock gasoline additives are transported in the United
States by specially designed 3000- to 9600-gallon railroad tank cars or
1000- to 3000-gallon over-the-road tank trucks approved by the I.C.C.
However, 775- to 3000-gallon portable tanks and 55-gallon drums are often
employed in export shipments; such tanks are approved by the Coast Guard
(E. I. DuPont de Nemours and Company, 1964; industry sources).
Because of the toxicity of antiknock gasoline additives the producers
have been vitally concerned with the proper handling of such products since
their introduction to the market. As a consequence, these producers require
* Final standard promulgated (U.S. Department of Labor, 1978) is 50 ug/m3.
70
-------
that refineries install blending facilities that have been approved at the
design and final inspection stages by representatives of alkyl
manufacturers. The principal feature of the blending plants is that they
operate under vacuum to avoid spills. If spills or leaks do occur in the
systems, repairs and corrective measures must be conducted with the advice
or personal attendance of the alkyl manufacturer's factory representative.
For example, pipelines or tanks that have been used to handle concentrated
lead alkyls may not be opened for repair unless a factory representative is
in attendance (E. I. DuPont de Nemours and Company, 1964). The
manufacturers of lead alkyls control adherence to such rules by simply
refusing to ship their product.
The manufacturers of lead alkyls have published 10- to 15-page books of
"regulations" or "guides" which were based on the advice of a committee
appointed by the Surgeon General of the U.S. Public Health Service. (E. I.
DuPont de Nemours and Company, 1964; Ethyl Corporation, undated). Matters
regulated include selection of blending personnel, emergency procedures,
tank car and drum unloading procedures, cleanup of spills, laboratory
procedures, precautions for men entering tanks that have contained
antiknocks, required clothing and equipment, bathing procedures, required
posted notices, and many other important aspects. These regulations or
guides generally appear to be those of the manufacturer. However, analysis
of the regulations of the two largest lead alkyl manufacturers reveal many
similarities; therefore,it is believed that the committee appointed by the
Surgeon General required many specifics to be incorporated~
The guidelines emphasize that concentrated lead antiknocks should under
no circumstances be heated in the laboratory or distilled" even under
vacuum, because of the danger of explosion.
4.3.2.2
Production and Industry Structure--
There are four manufacturers of TEL and TML as shown in Table 4.13.
DuPont and Ethyl Corporation dominate the industry, each possessing about
40 percent of the business, with Houston Chemical and Nalco sharing the
remainder. Industry capacity is estimated at 1.35 billion to 1.45 billion
lb of finished antiknock mix (Anderson, 1978), which translates to 375,000
to 395,000 metric tons/yr of 100 percent alkyl. At the present time the
industry has significant over-capacity relative to current demands; as
discussed in the following section, this situation will inevitably become
worse as the lead phasedown proceeds.
It is estimated that in 1976 about 277,000 metric tons (305,000 short
tons) of lead alkyls were produced, and thus, the industry was operating at
about 75 percent capacity. Because of the special environmental situation
in California, it is believed that DuPont's Antioch, California plant is
operating at a disproportionately lower rate than the other plants. In
addition, it is believed that Ethyl's Pasadena (Houston) plant is operating
at a lower operating rate than its Baton Rouge plant.
71
-------
Alkyl lead production, sales, and domestic consumption for the period
i966-1976 are presented in Table 4.14. The apparent discrepancy between
production and sales is principally due to double counting, i.e., the
manufacturers may report production of tetraethyl lead when produced and
again when such TEL is used to produce mixed TEL and TML. A large number of
antiknock additives are sold. In addition to TEL and TML, mixtures
containing triethyl methyl lead, diethyl dimethyl lead, or ethyl trimethyl
lead are also manufactured. Value of annual sales in recent years has been
in the 500 to 600 million dollar range.
The high compression engines of the early 1960's required high-octane
gasoline, and the average lead content of the gasoline pool peaked in the
late 1960's (Table 4.15 and Figure 4.9). Since about the 1970 model year,
automobiles have been built with lower compression engines--ones requiring
lower octane gasoline and thus gasoline with lower lead content. As a
result of this change, practically all new cars built since 1970 are able
to use regular gasoline instead of highly leaded premium fuels. (Faoro and
McMullen, 1977). The percentage of cars on the road requiring premium
gasoline is now down to about 6.5 percent, as illustrated by Figure 4.10
(National Petroleum News, 1978). The result of the engine modifications can
be clearly seen in the lower lead content in gasoline (in both regular and
premium grades) after 1969.
Thus, the average lead content of the total gasoline pool has also been
in a steady decline since 1969, when it peaked at 2.53 g/gal. In 1975 the
average lead content of the pool was for the first time below that of
regular gasoline; by 1978 the estimated average lead content of the pool
was 1.20 g/gal. If the EPA phase-down schedule is met, this will further
decrease to 0.59 g/gal after October 1, 1979.
Historical consumption data for total gasoline and lead are shown in
Table 4.16. Gasoline consumption data are based on Ethyl Corporation
surveys, adjusted to compensate for the approximately 95 per cent coverage
of refiners. Average pool lead contents are based on the semi-annual
surveys of the Bartlesville Energy Technology Center. Lead consumption
peaked in 1970; the peak in gasoline consumption does not appear to have
yet been reached. Lead consumption so calculated does not agree with
consumption data reported by the U.S. Bureau of Mines. For example, lead
consumed in 1975 for antiknock additive manufacture, according to the U.S.
Bureau of Mines data (Table 4.11), was 189,200 metric tons. However,
according to the accounting system used this includes all lead sold to
antiknock additive manufacturers for the manufacture of lead alkyls. Thus,
lead for alkyls destined for export (40 to 50 thousand tons annually in
recent years) is included in this figure (U.S. Bureau of Mines, 1978) Also,
utilization of the lead is not 100 percent, and some is presumed to be
sufficiently degraded to drosses, etc., during alkyl manufacture such that
it is recycled to the secondary lead-segment of the industry. The 1975
estimate of 162,800 metric tons, based on actual lead content of gasolines, .
is believed to be a better estimate and is used for purpose of calculating
emissions.
72
-------
TABLE 4.14.
PRODUCTION AND CONSUMPTION OF LEAD ALKYLS, 1966-1976a
Thousands of metric tons
TML/TEL Exports and U.S.
Year TELa TMLa Mixturesa,b Consumptionc Consumption
1966 247 50 311 280
1967 251 43 92 315 283
1968 220 53 139 327 298
1969 168 35 195 336 313
1970 147 229 342 312
1971 128 327 297
1972 137 304 337 305
1973 161 347 335 299
1974 210 207 317 262
1975 142 160 277 238
d d
1976 277 238
aSource: Synthetic Organic Chemicals, U.S. Production and Sales, U.S.
International Trade Commission (formerly Tariff Commission) (1977.)
bInc1udes tetramethy1 lead, mixtures of TML and TEL, and other organic lead
compounds.
'CSource: Chemical Economics Handbook, Stanford Research Institute (1976),
except as noted.
dBatte11e-Co1umbus estimates.
73
-------
TABLE 4.15.
AVERAGE LEAD CONTENT OF GASOLINES, 1965-1978
Average Lead Co~tent
By Grade, g/gal
Percentage of
Total Automotive
Gasoline Sales b
Year
Leaded
Premium
Leaded
Regular
Leaded
Premium
Leaded
Regular
Unleaded
Average
Lead Content
in Gasoline
Pool, glgal
1965 2.76 2.11 37.2 62.7 2.35
1966 2.81 2.19 39.0 60.9 2.43
1967 2.81 2.27 39.7 60.2 2.49
1968 2.79 2.28 41.2 58.7 2.49
1969 2.80 2.34 41.9 58.0 2.53
1970 2.73 2.28 42.6 57.4 2.47
1971 2.59 2.09 41.1 58.9 2.29
1972 2.45 1. 94 38.1 61.9 2.13
1973 2.34 1.87 32.4 67.6 2.02
1974 2.23 1. 76 24.5 75.5 1.88
1975 2.19 1.73 19.0 68.0 13.0 1. 60
1976 2.37 1.85 17.1 62.7 20.2 1.57
1977 2.36 1. 82 14.8 58.6 26.6 1. 42
1978 2.70c 1. 68c 12.3d 54.4d 33.3d 1. 20d
a Data from Shelton, E.M., Bartlesville Energy Research Center.
b Data from yearly Report of Gasoline Sales, By States, 1977, compiled by
Ethyl Corporation.
c Battelle-Columbus estimate based on partial 1978 data.
d Battelle-Columbus estimates.
74
-------
o
pool average ~o
o
o
o
Q
o
o
o
rooooo 000000
L. 0.59g/gal ~aximum after
3.0
Leaded premium
2.5
,,-.....,
,,- - "
,," \
'" \
\
\
\
\
\
--\(
,
\
\
"'6
C\
"
C\
- 2.0
en
Q)
c
"0
en
o
(.!)
Leaded regular
....
o
c
~
c
o
U
"0
o
Q)
...J
Q)
C\
o
...
Q)
>
~
1.5
1.0
Projected
0.5
o
1965
1970
Total gasoline pool
\
\
-...
,
,
,
,
\
\
\
\
1975
1980
1985
10/1/79
1990
Figure 4.9.
Nationwide trends in gasoline lead content, 1965-1978.
Year
Source:
Shelton, E.M.
75
-------
V)
I-
o
U
-
o
-
c
(1)
<..)
I-
(1)
a.. 20
501
/\
/'. / \
, ,.../ ~.....~,
---~-- 1 ,
...------ ,
~ \ \
,
\
I
~
Premium recommended \
for model year ,
. \
I
\
I
\
I
\
I
\
'-L-
1970 1972
Year
40
30
10
o
1964
1966
1968
Figure 4.10.
Premium Sales
\
\
,
\
,
,
,
\
\
,
,
\
\
,
\
,
,
,
\
\
Premium /'\
recommended "
for cars on
road
- J.... -
1976
1978
1974
Passenger car use of premium gasoline
Source: National Petroleum News (1978).
76
-------
TABLE 4.16.
CONSUMPTION OF GASOLINE AND LEAD ANTI-KNOCK, 1955-1978
Total Gasoline Average
Sales, Pool Lead, Lead,
Year Billion Gala g/galb Metric Tons/Yr
1955 51. 8 2.38 123,300
1956 54.0 2.44 131,800
1957 55.5 2.38 132,100
1958 56.9 2.14 121,800
1959 59.8 2.12 126,800
1960 61.0 2.04 124,400
1961 61. 8 1. 94 119,900
1962 63.9 2.01 128,500
1963 66.2 2.15 142,300
1964 69.1 2.25 155,500
1965 71. 7 2.35 168,500
1966 74.9 2.43 181,900
1967 77.2 2.49 192,200
1968 81. 6 2.49 203,200
1969 85.3 2.53 215,900
1970 89.1 2.47 220,200
1971 92.9 2.29 212,700
1972 97.3 2.13 207,200
1973 101.8 2.02 205,600
1974 99.2 1. 88 186,500
1975 101. 8 1.60 162,800
1976 106.9 1.57 167,800
1977 109.1 1.42 154,900
1978 112.8c 1. 20c 135 ,400
a Based on Ethyl Corporation data. increased 4 per cent to adjust for 95-96
b percent industry coverage of survey.
Based on Bartlesville Energy Technology Center semi-annual data.
c
Estimated.
77
-------
4.3.2.3
Future Projections--
In addition to promulgating regulations to control hydrocarbon
emissions, which led to the adoption of catalytic converters as the
preferred abatement measure (and consequently, to no-lead gasoline for
vehicles so equipped), the U.S. Environmental Protection Agency also
promulgated regulations reducing the average lead content of all gasoline
sold to 0.5 g/gal by October 1,1979 (U. S. Environmental Protection Agency,
1973; 1976). This has had and is having a major impact upon the petroleum
refining industry as well as upon the average lead content of gasolines now
and in the future.
The use of lead for gasoline antiknock additivives has already begun to
decline, and the decline will accelerate as the more drastic steps of the
lead phase down are implemented. Initially, the average lead content of
the total pool was to have been reduced to 0.8 g/gal by January 1, 1978.
However, this proved to be an overly ambitious goal, and the EPA
Administrator was empowered to grant waivers to refiners exhibiting "good
faith" efforts to reach the 0.8 g/gal goal. Most refiners qualified for
such waivers, which accounts for the 1.2 g/gal pool average for 1978. What
the average lead content of the total gasoline pool will be by 1980 and
beyond is a matter of some speculation, compounded by numerous and
ill-defined factors. A level not exceeding 0.5 g/gal is mandated by EPA
regulations.* It may be lower than this. One uncertain factor is how much
gasoline will be consumed in future years. Total car mileage is projected
to increase, more or less proportionately to population growth and
long-term secular trends. However, gasoline demands are less certain, as is
the fraction of that demand represented by pre-1974 cars and light trucks
able to utilize leaded gasoline.
Significant improvements in average automobile fuel economy have been
mandated by EPA. Also, it is well known that older cars are driven fewer
miles per year than new cars. For example, a typical 10-year-old car is
driven half as many miles per year as the "average" car, and one-third the
number of miles per year as the .car less than one year old (Sobotka, 1976).
On the basis of this and similar considerations, Sobotka estimated the
following projection of motor gasoline grade distribution:
Year
Percent of Volume
Leaded
Regular Premium
Unleaded
1976
1980
1985
1990
20
56
77
87
64.5
37
21
13
15.5
7
2
* Although the originally promulgated maximum lead content for total pool
was 0.50 g/gal, exemptions for small refiners have raised the national
target limit to approximately 0.59 g/gal.
78
-------
Similar estimates are projected by the "ESCON" model developed by one of
the major TEL manufacturers (E.I. DuPont de Nemours and Co., Inc., 1978).
Estimates of total gasoline consumption through 1990 are summarized in Table
4.17, and illustrated by Figure 4.11. It will be noted that according to this
forecast, total gasoline consumption is predicted to peak in 1980-81, and
decline slightly thereafter. This forecast is consistently below the one made
in 1977, resulting from a lower forecast of motor vehicle sales, and a more
conservative projection of vehicle use. The model assumes that automobile
manufacturers will meet Federal targets on fuel economy.
The effect of emission control regulations will be that by 1980 unleaded
gasoline will have captured half the total market, and its share will continue
to increase, reaching 78 to 80 percent of the total by 1985 and 85 percent by
1990. This will permit increasing lead levels in the decreasing volume of
leaded gasoline while still maintaining the required 0.5 g/gal average for the
total pool. Anderson (1978) estimates that by 1985 the lead content of leaded
gas will be back up to what it was in 1971 (Figure 4.12).
Another factor which will increase unleaded gasoline's share of the
market was the shift, beginning with the 1979 model year, in maximum weight
rating for light duty vehicles from 6,000 lbs to 8,500 lbs, gross vehicle
weight (GVW). Previously, EPA exempted trucks over 6,000 lbs from emission
control, and as Prescott (1976) pointed out, even most full-size pickup
trucks weigh more than this amount. Since light trucks account for nearly
20 percent of gasoline consumed and about half fall in the 6,000 to 8,500
lb weight bracket, a significant use of leaded gasoline is being eliminated.
The possibility of an "octane crunch" about 1980-1981 has been
suggested, especially if gasoline demand exceeds forecasts, and there is a
shortfall in supply of high-octane gasoline feedstocks. Octane quality of
all three grades of gasoline appears to have been reasonably satisfactory
through 1978. As indicated by Table 4.15, market share of leaded premium
gasoline peaked in 1970-71 at about 42.6 percent. As lower compression
engines were adopted in succeeding model years, the need for leaded premium
gasoline decreased; by 1978 it retained only about a 12 percent market
share (Figure 4.10). The lessened need for high-octane premium gasoline
permitted refiners to achieve desired octane levels by increasing the
content of high octane components and reducing the rate of lead addition
during the 1970-75 period. As the demand for unleaded gasoline increased
beginning in 1975, it became necessary to divert more of the high-octane
feedstocks from premium to unleaded gasoline. The resulting octane
deficiency in leaded premium gasoline has been made up by increasing its
lead content, as illustrated by lead levels for the last several years
(Figure 4.9). However, utilization of this strategy will lose much of its
"effectiveness after October 1, 1979, when the lead content of the total
pool must be reduced to the 0.59 g/gal maximum limit. After that date the
possibility of an "octane crunch" increases significantly. This is perhaps
best illustrated by developing a scenario and calculating the probable
outcome.
79
-------
TABLE 4.17.
GASOLINE CONSUMPTION FORECASTa
Total Gasoline Use, All Vehicles
Billion Gallons per year Percentage of Sales
Leaded Leaded Leaded Leaded
Year Premium Regular Unleaded Total Premium Regular Unleaded
1979 11.2 55.1 48.3 114.5 9.8 48.1 42.1
1980 8.7 48.6 57.8 115.0 7.5 42.2 50.3
1981 6.5 42.1 66.1 114.7 5.7 36.7 57.5
1982 4.8 36.4 71.3 112.5 4.3 32.4 63.3
1983 3.5 31.4 75.2 110.1 3.2 28.5 68.3
1984 2.6 27.3 78.3 108.2 2.4 25.2 72.4
1985 1.9 24.1 80.9 106.9 1.7 22.5 75.7
ex> 1986 1.3 21. 4 82.2 104.9 1.2 20.4 78.3
o 1987 0.8 19.2 82.9 103.0 0.8 18.6 80.5
1988 0.5 17.4 83.5 101.4 0.5 17.1 82.3
1989 0.3 15.8 83.8 100.0 0.3 15.8 83.8
1990 0.2 14.5 84.1 98.8 0.2 14.7 85.1
a Source: Data from ESCON model (E. 1. DuPont de Nemours and Co. Inc., 1978)
-------
120
I I r I , I I I
. Tolal - -
,.~ "........
'" ,
;' "
" '.....
~,.......,"'" ..... .......
/
/
/
/
100
80
'"
c
,g
;3
~ 60
c
~
CD
20
o
1970
Figure 4.11.
1975
1990
Source:
Projected consumption of grades of gasoline, 1970-1990
E.1. DuPont de Nemours (1978).
3
c
o
o
01
....
8. 2
on
E
E
CI
-
c
I T,
1970
Leaded pool
....
,
'"
--\
\.
'" ~
Totol pool ',- - - - - -
I I I I I I I I
1980 1985
Figure 4.12.
1975
Year
Estimated lead content of leaded and total gasoline
pool, 1970-1985.
Source:
Anderson (1978). Reprinted with permission
from Chemical and Engineering News. (c)
.~erican Chemical Society (1978).
81
-------
Principal assumptions of the proposed scenario are that quantities and
grades of gasoline are as projected by the ESCON model (Table 4.17); that
without phasedown the refining industry can achieve the slight increase in
clear pool octane required to maintain quality; and that leaded regular and
premium gasolines contain 2.0 and 2.5 g/gal, respectively. As illustrated
by Table 4.15, these values are representative of recent ranges.
Results of the analysis are summarized in Table 4.18. Assuming that
octane levels are maintained, this estimate suggests that the critical
years may be 1980-81 when octane improvement of the leaded gasoline pool
will be needed which is equivalent to that which, under normal industry
practice, would be achieved by an additional 30,000 to 50,000 metric tons
of lead.
An octane deficiency may " be overcome by increasing industry capacity
for catalytic reforming, catalytic cracking, alkylation, and isomerization
to boost the octane level of the clear pool. Whether this increase can or
will occur by 1980 is problematical. Alternatively, some octane deficiency
may be met by some lowering of average octane levels. This cannot all come
from the leaded pool; a proportionate share must come from the unleaded
pool. However, if engine performance suffers as a result, there will be an
increased tendency towards "misfueling" i.e., the use of leaded gasoline in
cars equipped with catalytic converters, promoting catalyst poisoning, and
a consequent increase in emissions of hydrocarbons.
If the phasedown proceeds as planned, lead consumption will be
reduced to about 67,850 metric tons per year in 1980, and remain below this
level thereafter (Table 4.18). Interestingly, beginning in 1984, lead
emissions would be lower with the assumed lead contents of 2.0 and 2.5
g/gal for regular and premium gasoline than with a 0.59 g/gal limit for the
total pool. At these lead levels, average lead concentrations in the total
pool would be 0.50 g/gal in 1985, and only 0.30 g/gal by 1990.
The lead consumption data reported has been that used for domestic gasoline
supplies. Exports of lead alkyls have been at about the 40,000 tons/yr
level and are estimated to continue at that level. Exports are expected by
some industry representatives to grow significantly in the future years.
However, recent European actions indicate that decreases in lead contents
of gasoline will be comparable to those in the U.S. Prescott (1976) reports
that the latest European Economic Community objective is to reduce lead in
premium gasoline to 0.4 g/l (1.5 g/gal) and in regular to 0.15 g/l (0.6
g/gal) by January 1, 1978. West Germany has been at 0.6 g/gal since the
beginning of 1976. These and other similar developments suggest that the
European lead alkyl export market can also expect some shrinkage; however,
it is also estimated that increases in markets in Latin America and other
areas will offset this decrease.
Because of the projected decline in lead alkyl production in the United
States, it is quite improbable that any new production facilities will be
constructed. In fact, it is believed that DuPont's Antioch, California
82
-------
I
TABLE 4.18.
EFFECT OF PHASEDO~~ ON CONSUMPTION OF LEAD IN GASOLINE
Total Lead, metric tons/yr
Gasoline, At 0.59 Lead Required for Leaded Gasoline
Billion g/ga1 at !ITypica1" Levels,
Year Gal. in Pool Premium Regular Total
1979 114.5 ll9,940b 28,000 110,200 138,200
1980 115.0 67,850 21,750 97,200 118,950
1981 114.7 67,670 16,250 84,200 100,450
1982 112.5 66,380 12,000 72 ,000 84,000
1983 110.1 64,960 81,750 62,800 71,550
1984 108.2 63,840 6,500 54,600 61,110
1985 106.9 63,070 4,750 48,200 52,950c
1986 104.9 61,890 3,250 42,800 46,050
1987 103.0 60,770 2,000 38,400 40,400
1988 101. 4 59,830 1,250 34,800 36,050
1989 100.0 59,000 750 31,600 32,350
1990 98.8 58,290 500 29,000 29,500d
a Based on projected gasoline consumption (Table 4.17) and 2.00 g/ga1 lead
in regular and 2.50 g /ga1 in premium (Table 4.15).
b 1978 pool average of 1.20 g/ga1 for first 3/4 year.
Assumes
c of pool = 0.50 g/gal
Average
d of pool = 0.30 g/gal
Average
83
-------
plant will be closed in about 1979. In addition, other smaller plants
including Ethyl's Pasadena, Texas and Nalco's Freeport, Texas plant may
close shortly thereafter. The development of new products and processes is
unlikely except that PPG Industries may produce more TML at Beaumont, Texas
if Nalco's plant is closed.
4.3.3
Lead Oxides and Pigments
Lead oxides and pigments is a conventional industry grouping in which
there are some overlaps; Black oxide is used for batteries and never as a
pigment. Litharge (PbO), formerly used as a pigment, is very seldom so used
now, but is the most important start{ng lead compound for the manufacture
of other lead compounds. Red lead (Pb304), another oxide, is still widely
used as a primer coating for steel.
4.3.3.1
Manufacture--
4.3.3.1.1 Litharge--Litharge or lead monoxide contains about 93
percent lead. Its color ranges from yellow to reddish yellow, depending on
its crystalline structure. (U.S. Tariff Commission, 1968) While it can be
used as a pigment, it is used primarily in the manufacture of products
other than paint pigments, e.g., batteries, ceramics, glazes, lead glasses,
vitreous enamels, and is a convenient and chemically reactive starting
material for a wide variety of other lead compounds.
There are several principal processes for producing litharge, all
involving the oxidation of elemental lead at elevated temperature. Molten
lead may be held in a cupelling furnace at about 1020 C until oxidized to
molten litharge, or molten lead at about 510 C may be atomized into a
flame, where it burns vigorously, forming "sublimed" or "fumed" litharge.
Aternatively, molten lead is fumed from the surface and collected in a
baghouse. In all of the processes, the product must be cooled quickly to
below about 300 C to avoid further oxidation, forming red lead. (Beltz, et
al., 1973)
4.3.3.1.2 Black oxide~-Black oxide is a mixture of lead monoxide and
finely divided elemental lead, which is used in the manufacture of lead-acid
storage batteries. It can be made in the same furnace as used for litharge
manufacture; the desired ratio of lead oxide to metallic lead is controlled
by the temperature of the charge and the amount of air swept through the
furnace. The product is caught in a baghouse, and may be further milled
before use.
4.3.3.1.3 Red lead--Red lead, or minium (also known as orange mineral),
contains about 91 percent lead by weight. Its color ranges from bright red
to orange-red depending on the true red lead content. Its major use is in
protective coatings to prevent rusting and corrosion of steel products; the
bright color of a prime coat of red lead is a familiar sight on new bridges
and other steel structures. It is also used in battery manufacture, and some
is used in the manufacture of ceramics.
84
-------
Red lead is made by further oxidation of litharge, sometimes in the same
furnace.
4.3.3.1.4 Leaded zinc oxides--Leaded zinc oxides find some use as white
pigments in oil-based exterior paints. They can be prepared by confuming
zinc and lead sulfide ores or by physical mixing of lead and zinc oxides.
They have largely been replaced by other pigments, and are now almost
obsolete pigments. Production data are no longer published in Bureau of
Mines tabulations, to avoid disclosing individual company data.
4.3.3.1.5 White lead--The commercial varieties of white lead include
basic lead carbonate, basic lead sulfate, and basic lead silicate. As
illustrated by the schematic flow sheet in Figure 4.13, basic lead carbonate
is made by a wet process involving the reaction of lead with dilute acetic
acid and then precipitation with C02 as the basic carbonate. The acetic acid
liberated by the C02 reaction is free to digest more lead. The process is
generally carried out as a batch operation. In the older methods, the CO
was generated by fermentation; in the newer processes, combustion produc€s
are the source of C02' (Beltz, et al., 1973).
As illustrated by Figure 4.13, basic lead sulfate and basic lead
silicate are generally produced by thermal processes. Lead sulfate fume is
produced by spraying molten lead into a combustion chamber along with S02'
The high temperature causes volatilization and oxidation of the lead. The
resulting oxide then reacts with the S02 and excess air to yield a basic
lead sulfate fume. The fume and flue gas are passed directly to a baghouse
filter for collection, and the product is suitable for direct use as the
pigment. Basic lead silicate is produced by fusion of litharge (PbO) with
silica. This process is carried out at about 1000 C (1800 F). When the
fusion is complete, the melt is drained from the furnace into water which
serves to quench and granulate the product. The resulting lead silicate is
then ready for final finishing by grinding to form the pigment (Battelle-
Columbus, 1975).
White-lead paints were for years the traditional exterior house paints
for wood (and were used for interior paints as well). This is, of course, a
totally dissipative use, although the rate of dissipation to the environment
is quite speculative. The quantity of lead that has been applied to
structures in the form of paint is truly enormous. Ewing and Pearson (1974)
quote the estimate of Ziegfeld (1964) that in the preceding 40 years over 3
million tons of lead paint had been applied, of which a significant fraction
was white lead paint on houses.
White-lead pigment is subject to discoloration from sulfur in the
atmosphere, and it has been largely replaced by zinc oxide and titanium
dioxide but small quantities still are produced annually. (See Table 4.11).
However, with the prohibition of the lead content in paint for dwellings
exceeding, first 1 percent, then 0.5 percent, and finally now 0.06 percent,
as described in a later section, white lead is almost an obsolete pigment.
85
-------
Dlgl!5tlon of
ltad
"2°
[H10, acetic]
acid, C02
finishing
Comb us t Ion
of I tad
Mechanical
collection
00
0\
[fuel, Ilr.]
5°2
Ox Ida tlon
0' Ic.d
fusion, litharge
and silica 25
finishing
Hut, air
Silica
Figure 4.13.
Simplified flow sheet of processes for the manufacture of lead-based
white pigments.
Source:
Battelle-Columbus (1975).
-------
Its consumption has fallen from 32,800 metric tons in 1950 to 2,700 tons in
1975, a decr~ase of 92 percent, and it can be expected to decline still
further.
4.3.3.1.6 Lead chromate-based pigments--Lead-based pigment colors
include yellows, oranges, and greens, starting with lead chromate as the
basic product. Lead chromate (PbCr04) is a yellow pigment with good color
retention, produced by solubilizing litharge (PbO) by reaction with nitric
acid then precipitating the lead chromate by the addition of sodium
dichromate. The precipitated pigment is carefully washed and dried at a
temperature below 90 C. It mayor may not be diluted with a co-produced or
admixed lead sulfate, or lead silicosulfate.
Basic lead chromate (PbO.PbCr04) is an orange pigment whose color
depends upon the proportions of lead chromate and basic lead chromate that
are present. The processing is essentially the same as for the preparation
of normal lead chromate, mixing a soluble lead salt such as lead nitrate or
lead acetate with soluble sodium chromate or dichromate. The precipftate is
then washed and dried. In order to increase the basic lead chromate
proportion of the mixture, it is common practice to use more sodium
chromate than sodium dichromate.
Molybdenum (molybdate) oranges may be made by coprecipitating lead
chromate and lead molybdate, and may contain lead sulfate as well. Chrome
green may be made by blending chrome yellows with iron blues.
Chrome yellow is principally used in paints, and its increase in recent
years is largely attributable to its application in marking highway traffic
lanes. Because of their vivid, bright colors, lead chromate pigments also
find use in printing inks.A simplified schematic flow sheet for the
manufacture of lead chromate-based pigments is shown in Figure 4.14.
4.3.3.2
Production and Industry Structure--
The traditional uses for lead oxide and pigments are either essentially
stagnant or decreasing.
Areas where lead oxide is a starting material for the preparation of
other products, e.g., heat stabiizers for plastics, provide the only growth
factors. Illustrative are the data on white lead, red lead, and litharge
(Table 4.19). White lead has consistently decreased, although it may
plateau at about its current levels. Red lead paints appear to have
stabilized at the 4,000 to 6,000 metric ton/yr level.
The utilization of litharge (PbO) in ceramics (primarily for glazes)
has shown growth in recent years, as has its use in rubber compounding,
however its use in oil refining has essentially disappeared. Most of the
litharge in the "other" category went to the manufacture of batteries,
which was adversely affected by the economic slowdown in 1975.
87
-------
H20 [4, No additive ]
b. N4011
c. N42504 + NaZHo04
d. I ran b' ue
00
00
figure 4.14.
ftnhhtng
Simplified fow sheet of processes for manufacture of
lead chromate-based pigments.
Source:
Battelle-Columbus (1975).
-------
TABLE 4.19.
LEAD PIGMENTS - U.S. SHIPMENTS,
BY INDUSTRY, 1971-1975a
Thousands of Metric Tons
1971 1972 1973 1974 1975
White lead (dry and in oil) 3,987 6,138 2,900
Paints 3,987 6 ,138 2,900
Ceramics 31 28 16
Other 2,132 2,963 5,739 5,355 3,021
. Total 6,150 9,129 8,655 5,355 3,021
Red lead
Pain ts 7,906 4,452 5,903 4,847 4,129
Storage batteries Wb W W W W
Other 11,130 13 ,482 6,629 7,207 9,562
Total 19,036 17,933 12,532 12,054 13,691
Litharge
Ceramics 22,074 21,031 32,570 42,264 30,784
Insecticides H W W W W
Oil refining 1,282 1,145 562 694 W
Paints 2,798 6,636 2,823 4,850 2,946
Rubber 1,887 1,961 4,606 5,886 5,306
Other 106,054 103,120 121,923 92 ,736 70,234
Total 134,095 133,893 162,383 146,430 109,270
aSource:
US Bureau of Mines (1976).
bW = Withheld to avoid, disclosing individual company confidential data;
included with "other".
89
-------
"-
The major producers and plants are listed in Table 4.20; the number of
companies producing these pigments is down to less than a dozen.
4.3.3.3
Future Projections--
The U.S. Bureau of Mines forecast for lead demand for paints by the
year 2000 (Ryan and Hague, 1976) projects a demand ranging between 120,000
and 180,000 metric tons, with 135,000 tons as the most probable demand.
(This forecast was made before the legislation establishing a maximum of
0.06 percent lead in consumer product paints, and may therefore now be
overly optimistic). The pigments category has shown essentially no growth
over the past decade, and this appears likely to continue.
4.3.4
Inorganic Lead Compounds
For the purposes of this report inorganic lead compounds are defined as
lead compounds other than oxides or pigments which contain no carbon or no
direct attachment of a carbon atom to a lead atom; as a consequence of this
definition, several lead compounds that contain organic structures are
classified herein as inorganic lead compounds. This definition is
consistent with industry usage of the term and will facilitate further
discussion.
None of these are individually tracked in Bureau of Mines tabulations,
and production and consumption data are uncertain. Almost all of the
inorganic lead compounds appear to fall under the "litharge" category,
since this is the basic starting material. Except for stabilizers for
plastics and dryers for paints most of them are relatively small volume,
specialty products.
A number of these compounds and industries in which they are used are
listed in Table 4.21. One of the salient features of the chart is that,
although there are numerous chemical compounds of lead made and used in the
"compounding" industries, the generalized classes of compounded products
may be considered as few. Further, it may be seen that some compounded
products contain more than one lead compound. For example, paint may
contain one lead compound as a pigment and another compound as a drier.
Similarly, polyvinyl chloride may be stabilized with one lead compound and
colored by another. It may also be noted that the classes of products are
not mutually exclusive in that a lead compound used as a pigment may be
later used for one of the other uses, i.e., paint, dyes, inks, textiles,
and/or printing.
With the exception of uses in batteries, the uses shown in the chart
are all dissipative, i.e., the lead in these compounds is never recycled,
but is diffused through the environment by processes of weathering, wear
and erosion, or is disposed of as a component of discarded materials.
90
-------
TABLE 4.20.
PLANTS PRODUCING LEAD PIGMENTSa
1;fuite Lead
Lead Carbonate
Dimensional Pigments, Inc.
NL Industries, Inc.
Industrial Chemicals Div.
Bayonne, New Jersey
Chicago, Illinois
Oakland, California
Richardson-Merrell, Inc
J.T. Baker Chemical Co. (Subsidiary)
Smith Chemical & Color Co.
\fuittaker Corp.
Rona Pearl Div.
Inc.
Phillipsburg, New Jersey
Jamaica, New York
Bayonne, New Jersey
Lead Sulfate, tribasic
NL Industries Inc.
Industrial Chemicals Div.
Perth Amboy, New Jersey
Philadelphia, Pennsylvania
St. Louis, Missouri
Oakland, California
Lead Silicates
Eagle-Picher Industries, Inc.
Chemicals & Fibers Div.
Joplin, Missouri
NL Industries, Inc.
Industrial Chemicals Div.
Perth Amboy, New Jersey
Philadelphia, Pennsylvania
St. Louis, Missouri
Colored Pigments
Red Lead (Orange mineral)
Eagle-Picher Industries, Inc.
Chemicals & Fibers Division
Joplin, Missouri
Mallinckrodt Chemcial Works
Industrial Chemicals Division
NL Industries, Inc.
Industrial Chemicals Div.
St. Louis, Missouri
Atlanta, Georgia
Charleston, West Viriginia
Chicago, Illinois
Dallas, Texas
Oakland, California
Philadelphia, Pennsylvania
St. Louis, Missouri
Los Angeles, California
91
-------
TABLE 4.20.
(Continued)
Colored Pigments.
Red Lead
RSR Corporation
Quemetco, Inc., subsidiary
Indianapolis, Indiana
Middletown, New York
Seattle, Washington
City of Industry, California
Lead oxide, yellow (litharge)
American Smelting and Refining Company
Eagle-Picher Industries, Inc.
Chemicals and Fibers Division
Denver, Colorado
Joplin, Missiouri
NL Industries, Inc
Industrial Chemicals Div.
Atlanta, Georgia
Charleston, Hest Virginia
Chicago, Illinois
Dallas, Texas
Oakland, California
Philadelphia, Pennsylvania
St. Louis, Missouri
Los Angeles, California
Portland, Oregon
RSR Corporation
Quemetco, Inc., subsidiary
Indianapolis, Indiana
Middletown, New York
Seattle, Washington
City of Industry, California
Lead Chromate
Hercules Incorporated
Coatings & Specialty
Glens Falls, New York
Kewanee Oil Company
Harshaw Chemical Company, division
Pigment and Ceramic Department
Mineral Pigments Corporation
Chemical Color Division
Louisville, Kentucky
Beltsville, Maryland
Richardson-Merrell, Inc.
J.T. Baker Chemcial Co. (subsidiary)
Phillipsburg, New Jersey
a
Source:
Directory of Chemical Producers, Stanford Research Institute (1976)
92
-------
TABLE 4.21.
INORGANIC LEAD COMPOUNDS AND THEIR USES
Compound
Acetate X X X I
I
Antimonate X " I X
~ ~~
Azide j I X
I I
Beta Resorcylate ' I
X I
Borate X X I X
,
I
Carbonate X I ! X
Chloride X X I
Chlorosilicate ; X
Chromate X X X X ' X
I
Cyanamid X !
Fluoborate X
Fumarate X X
Hydroxy Neodecanoate X X
Iodide X X
Isocarboxylate X
Linoleate X
Maleate X
Manganese naphthenate X
Manganese tallate X
Molybdate x[ X
Naphthenate X
Neo-deconoate X X
Nitrate X
Oleate X
Orthophosphate X i X
I
Oxides X X X l X X X X X
I
93
-------
TABLE 4.21.
INORGANIC LEAD COMPOUNDS AND THEIR USES (Continued)
Compound
Phosphate Xi X
I
Phosphate, dibasic I X
I
I
Phthalate, dibasic I X
I
Salicylate I iX
Selenide , Ix
I
Silicate X X I I j
I I
Silico sulfate I :X \
I ! I
Silico chromate I iX I
I
; , I
Stannate X I '
I I
; I I
I I
Stearate xi IX I
I
j j i
Stearate, dibasic xl I ! I
! I
Styphnate xl X I i
I
I
I I
Sulfate X I X X IX
Sulfide I X
I
Tallate X
Telluride X
Thiocyanate X X X
Titanate X X X
Tungstate X
2-Ethylhexanoate X X
Vanadate X
Zirconate X
94
-------
4.3.4.1
Manufacturing--
In general, the inorganic lead compounds are produced by typical,
non-proprietary processes as follows:
(a)
(b)
Litharge is reacted with an acid or soluble salt of an acid to
produce the desired product. Products that can be produced in
this manner include the following lead compounds: acetate,
benzoate, borate, cyanide, formate, nitrate, perchlorate,
subacetate, and tribasic lead sulfate.
A soluble lead salt (often lead acetate) is reacted with an acid
or a soluble salt of an acid often to form a precipitate which is
then filtered, washed, and dried. The soluble lead salt may be
formed in situ, such as by adding a small quantity of acetic acid
to litharge. Products that can be produced in this manner include
the following lead compounds: arsenate, benzoate,borate, bromide,
carbonate, chloride, citrate, fumarate, iodate, iodide, lactate,
maleate, metaborate, molybdate, oxalate, phosphate, dibasic
phosphate, phosphite, phthalate, pyrophosphate, salicylate,
sesquichloride, stannate, succinate, sulfate, tartrate,
thiocyanate, thiosulfate, and tungstate.
(c)
Litharge may be fused with an oxide of the desired metallic
compound. Products that can be produced in this manner include
the following lead compounds: bisilicate, chlorosilicate (by post
treatment with hydrochloric acid), metavanadate,molybdate,
silicate, silico sulfate, silico chromate (by post treatment with
sulfuric or chromic acid, respectively), stannate, titanate ,
zirconate, and zirconate titanate.
(d)
Paint dryers may be manufactured by a fusion process wherein
litharge or a soluble lead salt is added slowly to the acid form
of the organic material, such as a soap. The temperature is
allowed to rise as the lead compound is added; the reaction mass
is then externally heated to 110 to 150 C to complete the
reaction and to evaporate water from the product. The product may
then be filtered, cooled, and packaged, or alternatively
filtered, cooled, blended with solvent, and then packaged.
(e)
Paint dryers may also be prepared by a precipitation process, by
the addition of a soluble lead salt (i.e., lead acetate or
nitrate) in water to the soluble sodium soap of a fatty acid in
water to form a "precipitate" of an insoluble lead dryer. (In the
case of lead naphthenate, the "precipitate" coagulates and
floats.) The water layer is removed (decanted) and the product is
washed with water and filtered. Finally, the lead dryer is heated
to 110 to 150 C to dry the product, cooled, and packaged. It may
also be blended with solvent.
95
-------
(f)
Paint dryers may also be produced by dissolving finely divided
metal in heated organic acids (100 to 200 C) over 4 to 12 hours
using catalysts, such as air, air and water, or acetic acid.
Volatilized material is refluxed during the reaction. After the
reaction is complete, the catalyst is allowed to evaporate and'
the product is filtered, cooled, and packaged or blended with
solvent and packaged.
(g)
Other specific processes:
(1)
Lead iodide may be produced by the reaction of lead
metal with iodine.
(2)
Lead bromide may be produced by reacting bromide with
lead iodide.
(3)
Lead nitrate may be prepared by the reaction of nitric
acid with metallic lead or with several of the oxide
forms of lead.
(4)
Lead tetraacetate may be formed by the reaction of red
lead with glacial acetic acid.
(5)
Lead fluoride or tetrafluoride may be produced by the
reaction of lead carbonate with hydrogen fluoride.
Descriptions of processes employed to produce lead acetylacetonate,
fluoborate, hydroxide, and mononitroresorcinol were not identified.
4.3.4.2
Production and Industry Structure--
Although there is some overlap, the inorganic lead chemicals industry
can be subdivided into three general groups: lead stabilizers, paint
driers, and miscellaneous lead chemicals (frequently small-volume specialty
produc ts )' .
4.3.4.2.1 Lead stabilizers--In the manufacture of some plastics,
particularly polyvinyl chloride (PVC) types, it is necessary to heat them
to relatively high temperatures to soften them during fabrication
operations. The amount of heat that can be applied is limited in degree and
duration by the tendency of the compounds to decompose, resulting in some
deterioration in physical properties, accompanied by a progressive
darkening in color. Additive compounds which promote heat stabilization
include metal soaps, organotins, lead compounds, nitrogen compounds,
organophosphites, epoxies, and phenols (Weinberg, 1976).
Lead has been employed as a stabilizer for plastics for a longer period
than any other product. Initially, lead carbonate was used. Later tribasic
lead sulfate, lead silicate, dibasic lead stearate, dibasic lead phthalate,
lead stearate, dibasic lead phosphite, and tribasic lead maleate were
introduced.
96
-------
Lead stabilizers have good heat and weather resistance. They are low in
price, their good workability ensures high productivity, and they exhibit
good dielectric properties (low volume resistivity) and low water
absorption. They are used extensively in PVC electrical wire and cable
insulation and in opaque rigid PVC extruded and injection molded products,
where they confer weather resistance as well as protection against heat
during molding. Sulfur staining, lack of clarity, and toxicity of lead
stabilizers are some of their drawbacks. (Weinberg, 1976).
Typically, plastics formulations may contain about 0.5 percent lead. At
one time a few producers used lead stabilizers in DWV (drain, waste, and
vent) pipe, but since Schedule 40 plastic pipe may also be used for potable
water piping, this application has been abandoned. Industry sources state
that no lead is used in any PVC pipe. If any plasticizer is used it is more
likely to be 0.1 to 0.2 percent of organotin (Furno,1978).
The use of lead stabilizer in PVC pipe for potable water service is
effectively precluded by National Sanitation Foundation Standard No. 14
(1965). This standard, applicable to thermoplastic pipe, fittings, valves,
traps, and joining materials, specifies a maximum lead concentration of
0.05 mg/l after a 72-hour leach in 1 percent nitric acid, which will be
exceeded if a lead stabilizer is present (National Sanitation Foundation,
1977).
A list of producers of lead-based stabilizer materials utilized in the
manufacture of plastics and rubber products is presented in Table 4.22. The
major manufacturer of the lead based plastic and rubber types of stabilizer
materials presented in Table 4.22 is NL Industries, which dominates sales
of these materials, accounting for about 67 percent of the business. Other
significant suppliers include Eagle-Picher, Gulf Resources (Bunker Hill
Division), American Cyanamid (MacGregor Lead Division) and Hammond Lead
Products (Halstab Division). Although F. D. Davis has a significant raw
material position, it is believed that this company sells most of its
material for pigment use. It is not believed that Dimensional Pigments,
Rona Pearl, or Smith Chemical sell significant quantities of materials for
stabilizer use. Finally, J. T. Baker and City Chemical probably only sell
reagent grade material for other uses.
Consumption of the lead compounds shown in Table 4.22 in the plastics
and rubber industries in 1974 has been estimated as presented in Table
4.23. Their use in plastics has been in a gradual decline in recent years,
perhaps prompted by increasing environmental regulations, as evidenced by
one industry estimate of 1973-1976 consumption:
97
-------
TABLE
4.22. PRODUCERS OF LEAD-BASED PLASTIC AND RUBBER STABILIZER-TYPE MATERIALS a
Company b
American Cyanamid & Company
MacGr~gor Lead Division
City Chemical CompanyC
F. D. Davis CompanyC
c,d
Dimensional Pigments
Eagle-Picher Industrie..
Location
Wayne, NJ
Chicago, IL
Jersey City, NJ
South Plainfield, NJ
Bayonne, NJ
Joplin, MO
New York, NY
Cincinnati, OH
\0
ex>
Gulf Resources & Chemical Corp. Soutla Plainfield, NJ
Bunker HIll Divis~on
Hammond Lead Products Company
Halstab Division
1,1. lndustriese
Industrial Chemicals Div.
Metals Division
c
Richardson--Mcrrell, Inc.
J. T. Baker ~hemical Co.
Rona Pearl, lnc.d
Smith Chemical & Color Co. d
Hammond, IN
Charleston, WV
Philadelphia, rA
St. Louis, MO
Chicago, IL
rhillipsburg, IIJ
See fOOLnote e
Jamaica, NJ
Lead Stabilizer
x
X
X
X
X
x
X
X
X
X
X
X
X
X
a
Source:
Chemical Economics Handbook, Stanford Research InsLitute (197~).
Active stabilizer suppliers to the trade include Argus (Witco subsidiary), American Cyanamid, Eagle-Picher, Ferro, Halstab, Interstab, Mooney, NL,
Tenneco, Witco, RT Vanderbilt Company, Inc., American-Hoescht, and M.R.S. Chemicala. It is believed that Vanderbilt, Hoechst, and M.R.S. do Dot
manufacture such compounds in the United States.
Believed to be a producer of pig1llent or reagent gtade only and not sold as stabilizer.
Carbonate to supply Dimensional Pigments Bnd Rona Pearl is produced at one plant.
b
c
d
e
x
x
x
X
X
x
x
x
X
x X X X X
X X
X
X
~~
The Oakland, California plant waB shut down prior to 1977 and the Perth Amboy plant WBS shut down Karch 15, 1977.
-------
TABLE 4.23. ESTIMATED CONSUMPTION OF LEAD-BASED STABILIZERS.
IN PLASTICS AND RUBBER INDUSTRIES, 1974a
Millions of kg (lb)
7.3
(16)
Tribasic lead sulfate
ChIaro silicates
Dibasic lead stearateb
3.6
Blends of chlorosilicates and
dibasic lead stearatesb
Lead carb onate
2.7
2.3
1.4
Dibasic lead phthalate
Dibasic lead phosphate
Silica-chromate
0.5
0.5
Silica sulfate
Fumarate, maleate, phosphate,
salicylate, silicate, and
bisilicate
Negligible
(8)
(6)
(5)
(3)
(1)
(1)
Total
18.3
(40)
a
Source:
Battelle - Columbus estimate, based on industry estimates.
b
Actual consumption of dibasic lead stearate is small.
99
-------
Consumption of Heat Stabilizers
(In Metric Tons)
Stabilizer 1973 1974 1975 1976
Barium-Cadmium 23,000 22,300 17,500 22,000
Lead 14,600 14,600 6,400 8,200
Calcium-zinc 1,360 1,400 1,000 1,300
Tin 7,600 7,500 5,800 7,000
Total 46 , 560 41,600 30,700 38,500
Source: Modern Plastics (1976).
4.3.4.2.2 Paint driers--Producers of paint driers are listed in Table
4.24. Major producers of lead-based driers presented in Table 4.24 include
Ferro,Interstab, Mooney, Norac,Shepherd, Sherwin-Williams, Tenneco, Troy,
and Witcoj the relative positions of Diamond Shamrock, NL Industries, and
Smith Color are believed to be small. The major manufacturers of these
driers produce other metallic driers in the same or similar equipment and,
thus, capacity figures are not meaningful.
Historical production rates of selected lead driers are presented in
Table 4.25. Total production of the three most popular lead driers peaked
in 1969 at more than 10 million kg (23 million pounds). Drier production
then entered a period of decline, as water-based latex paints more and more
supplanted traditional oil-base paints. Additionally, more recently the
restrictions on the use of lead in paints have caused the replacement of
lead driers by other materials. By 1975, total production of lead-based
driers had declined to about 3 million kg (6.5 million pounds) or to 28
percent of the peak production rate. Lead consumed in these products in
1975 was about 1,360 metric tons (1,500 short tons), when total sales
revenue of such driers were estimated to have been about 4.5 to 5.0 million
dollars.
As is noted in the footnotes to Table 4.24 some of the lead 2-ethyl
hexanoate, hydroxy neodecanoate, neodecanoate, stearate, and dibasic
stearate produced by Ferro, Interstab, Mooney, NL Industries, Tenecco, and
Witco are also used as rubber and plastic stabilizers.
4.3.4.2.3 Miscellaneous lead compounds-~A number of lead compounds are
produced in limited quantity .or to industrial order for special
applications. Some of these are produced by more than one manufacturer
(Table 4.26); others by only one manufacturer (Table 4.27). The diversity
of the inorganic lead compound industry is illustrated by the fact that in
the tables contained in this section 46 companies are shown, producing 60+
chemicals at 50+ locations.
100
-------
TABLE 4.24.
PRODUCERS OF LEAD-BASED PAINT DRIERS
,.
,
Lead Drier .Compound
Company Location
Dia..,nd Sha..rock Corp. Cedar town , GA
Process Chemicals
DivisIon
. Ferro Corp. Bedford, OH X X
Ferro Chemical Div.
Interstab Chemicals,
1m'. New Brunswick,NJ X X X
I-' Mooney Chemicals,
a Inc. Franklin, PA X X X X X X
I-'
NL Industric3, Inc.
In~ustrial Chemicals
Di vi.il".. Philadelphia, PA
NOlac Company, Inc. Lodi, IU X
Mathe Division
Shepherd Chemical Co. Cincinnati, OH X X X X
ShervJ.n-1-HIUams Co. Cleveland, OM X
EmeryvUle, CA X
Garland, TX X
Smith Chemical and
Color Company Jamaica. NY
Tenneco Inc. Elizabeth, N.J X X
Tenneco Chemicals Long Beach, CA X X
Troy Chemical Corp. Newark, NJ X X X
l./itco Chemical Corp. Clea ring, IL X X
Organics Divis 10n Lynwood, CA X X
X X
X
X
X
X
x ..x X
x X X
X
x X
X X
X X
X
aSource:
Chemical Economics Handbook, Stanford Research Institute (1975).
bSeveral lead compounds classified herin as paint driers are used aa lead stabilizers including 2-ethyl hexanote, hydroxy neodecanoate, nedecanoate,
stearate, and dibasic stearate.
-------
TABLE 4.25.
PRODUCTION OF SELECTED LEAD-BASED PAINT DR!ERSa
Year
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
Production, millions of kg (lb)
2-Ethy1
Hexanoate
Naphthenate
6.47 (14.27)
6.06 (13.37)
7.73 (17.04)
8.19 (18.06)
6.51 (14.36)
5.48 (12.08)
5.19 (11.45)
5.26 (11. 61)
4.10 (9.04)
1.87 (4.12)
a
Sources:
0.11 (0.24)
0.09 (0.19)
0.47 (0.82)
0.39 (0.87)
0.69 (1.52)
0.20 (0.45)
1.57 (3.47)
0.40 (0.89)
1.11 (2.44)
0.80 (1.77)
Ta11ate
1.64 (3.61)
1.62 (3.58)
1. 78 (3.92)
1.99 (4.38)
1.90 (4.16)
1.18 (2.60)
0.91 (2.00)
0.60 (1.33)
0.51 (1.13)
0.42 (0.65)
8.22
6.41
9.88
10.57
9.09
6.86
7.67
6.27
5.72
2.97
Total
(18.12)
(14.14)
(21.78)
(23.31)
(20.04)
(15.13)
(16.92)
(13.83)
(12.61)
(6.54)
Current Industrial Reports, Series M28A, U.S. Department
of Commerce, Bureau of the Census 1966 through 1973.
Synthetic Organic Chemicals, U.S. Production and Sales,
U.S. International Trade Commission.
102
-------
TABLE 4.26.
PRODUCERS OF MISCELLANEOUS LEAD-BASED CHEMICALS PRODUCED BY MORE
a
THAN ONE CaMP ANY
Company Location
Alli..d Chemical Corporation Marcus lIook, PA X
C. P. Chemicals, Inc. Swa reo. NJ X
Chempa r ChemIcal Company Portland, ORe 0
City ChemIcal Corporation Jersey City, NJ X X
Deepwater Chemical Comps"y Irvine, CA X X
Dimensional Pigments, Inc. Bayonne, NJd 0
lIurstan ChemIcal Corporation Brooklyn, NY X
lIulJ:lllel t:hcClical Compsny South Plilinfield, NJ X
t-' X,.ical Company Co LumbuH, 011 X
Transeloo, Inc. Pennyan, NY X
Woolf.olk Chemical Works, Inc. Fort Valley, GA 0
8Source: Chemi cal Ecunomics lIandbook, Stanford Research Institute (1975).
bNo lead arsenate i6 being produced at the present time according Lo these companies.
CUntil recently. Cl,empar had acquired its lead arsenate from Woolfolk.
dproduct is (or was) produ.:ed in one plallt to serve both Rona Pearl and Dimensionsl Pigmenta.
eIt is believ..d that ~arsha~ no longer produces lead fluoborate.
-------
TABLE 4.27.
~1ISCELLANEOUS LEAD-BASED CHEMICALS PRODUCED BY ONLY ONE
COMPANY .
City Chemical Corporation (Jersey City, NJ)
benzoate
bromide
citrate
cyanide (metallurgy reagent)
hydroxide
lactate
metavanadate
molybdate
oxalate
pyrophosphate
sesquichloride
stannate-(ceramic electronic bodies)
succinate
tartrate
thios~lfate. (rubber accelerator)
tungstate (pigment)
MacKenzie Chemi~~l Works (Central Islip, NY)
acetylacetoate
NL Industries
Philadelphia, PA - formate (rubber compounding)
Niagara Falls, NY - titanate (pigment and ceramics)
zirconate- (electronic devices)
Pennwalt Corporation, Ozark-Mahoning Co. (Tulsa, OK)
fluoride
tetrafluoride (potential fluorinating agent for hydrocarbons)
Olin Corporation, Winchester (Niagara Falls, NY and East Alton, IL)
styphnate- (detonator for explosives)
Richardson-Merrell, Inc., J. T. Eaker Chemical Company (Phillipsburg, NJ)
chloride- (artist pigment, solder, and solder flux)
G. Frederick Smith (Columbus, OH)
perchlorate (analytical reagent)
Syntex Corporation, Arapahoe Chemicals Division (Boulder, CO)
tetraacetate
Thiokol Corporation, Ventron Corporation, Alfa Products Division (Danvers, MA)
telluride
Tyler Corporation, Atlas Powder Company (Tamaqua, PA)
nitroresorcinol
aSource;
Di.rectory of Chemical Producers, Stanford Research Institute (1976).
104
-------
Lead fluoborate, used in electroplating in negligible quantities, is
producd by electroplating supply firms including C. P. Chemicals, and
Harstan, but probably is no longer produced by Harshaw (Kewanee
Industries). Lead iodide is produced in small quantities for photographic
use and as a gold or bronze pigment by Deepwater Chemical R.S.A.
Corporation. (These companies also produce lead iodate for unknown uses).
City Chemical can also produce reagent grade iodide for specialty use.
Although lead nitrate is a water soluble form of lead that would be
useful for preparation of other lead materials or for match manufacture,
pyrotechnics, and dyeing, only Mallinckrodt, J. T. Baker,
(Richardson-Merrell) and G. Frederick Smith reportedly manufacture the
product, probably only reagent grade and in very small quantities.
Allied Chemical Corporation and J. T. Baker (Richardson-Merrell)
produce lead subacetate in minor quantities for sugar analysis. Similarly,
lead thiocyanate is produced in small quantities as a primer for explosives
and matches by Hummel Chemical Company and City Chemical.
Lead zirconate-titanate is produced in small quantities by NL
Industries and Transelco and is used as a dielectric.
Of the lead products listed in Table 4.27, lead styphnate (produced by
Olin for use as a detonator), lead chloride (produced by J. T. Baker for
use in artist pigments and solder), and lead tetraacetate (produced by
Arapahoe for textile dyeing) are the only materials that might be produced
in any significant quantity. Most materials produced by City Chemical are
used for reagent or for specialty purposes. Acetylacetonate is produced for
an unknown and probably specialty purpose by MacKenzie.
Less than 100 tons per year each of lead formate, lead titanate, and
lead zirconate are produced by NL Industries.
Consumption of the lead fluoride compounds produced by Ozark-Mahoning
(Pennwalt) is believed to be very small and for specialty purposes. G.
Frederick Smith produces lead perchlorate as a reagent chemical. No
significant uses for the nitroresorcinol and telluride produced by Syntex
and Alfa (Thiokol) are known.
In past years, lead arsenate was a popular insecticide, e.g., it was
the insecticide of choice for protecting apple orchards against the
coddling moth. The quantities produced and used were significant, as
evidenced by the following U.S. Department of Agriculture (1975) tabulation:
105
-------
Year Metric Tons
1967 2,700
1968 4,090
1969 4,170
1970 1,880
1971 2,800
1972 2,340
1973 1,790
1974 W *
1975
w
withheld to avoid disclosure of individual
companies.
now combined with all inorganic insecticides,
fungicides, and rodenticides
*
Since World War II, lead arsenate has been supplanted by various
organic insecticides. This trend was accentuated by concern of the FDA for
lead in foods, particularly in canned apple juice and applesauce for
infants. The refusal of food packers to accept apples sprayed with lead
arsenate effectively terminated its use in the U.S. A survey of all the
companies listed in Table 4.23 as lead arsenate producers revealed that all
manufacturers claim not to be a current producer. Also, no record of
importation of lead arsenate was located. Most recent status of lead
arsenate, as determined by EPA (U.S. Environmental Protection Agency, 1978)
is that none is being manufactured in the United States, and that sales, if
any, are less than 500 kg/yr of active ingredient.
This use was obviously a totally dispersive one, and considerable
residues of lead arsenate have been shown to have accumulated in orchard
soils (See Section 5.2.3).
4.3.4.3
Future Projections--
It is evident from the preceding discussion that the production of
inorganic lead compounds is a minor segment of the lead industry whose
future will be influenced primarily by the effects of environmental
considerations rather than by the growth prospects of the products in which
they are used, or their effectiveness in those uses. Thus, the projection
for these compounds is for stagnant or declining markets.
4.3.5
Miscellaneous Uses of Metallic Lead
Lead has a variety of uses in metallic form, either singly, or alloyed with
other metals. Most of these uses derive from one or more of the special
attributes of metallic lead--high density, corrosion resistance,
malleability, castability, and low melting point.
106
-------
The components of the metal end-use category, as compiled annually by the
Bureau of Mines (See Table 4.11), consist of a heterogenous collection
of products, alloys, and mill shapes. Several are specific--i.e.,
ammunition, bearing metals, cable covering, type metal, collapsible tubes,
and the construction-oriented pipes, traps, bends, and caulking lead. The
remainder designate alloys or mill product forms, each of which has a
variety of applications--viz., brass and bronze, casting metals, foil,
sheet lead, solder, and terne metal.
Uses of metallic lead have been declining in the post-World War
period. From a level of 360,000 metric tons in 1966, these gradually
to about 300,000 tons in 1974, a loss of 60,000 tons in 8 years, and
plummeted a further 60,000 tons in one year to about 240,000 tons in
continuing at this level in 1976 (Table 4.10).
II
fell
then
1975,
These end uses, except for ammunition, are potentially
non-dissipative, although reclamation and recycle of the product items are
erratic; the larger the physical size of the item, the higher the
probability of recycle. Also, a closed loop with recycle is a normal part
of some uses, such as for cable covering and type metal, and added lead is
primarily for makeup.
These miscellaneous uses are described briefly in the following pages,
in generally descending order of annual consumption.
4.3.5.1
Ammunition--
Lead continues to be the major metal used for sporting ammunition in
the form of shot and small-caliber rifle and handgun bullets. The alloy
used may contain up to one percent arsenic for shot, and up to 2 percent
antimony for bullet cores. Lead ammunition is still used in military
training (Ryan and Hague, 1976).
Except for target range shooting, where reclamation is feasible and
frequently practiced, ammunition would have to be classed as a dissipative
use. A particular problem with lead shotgun shot is that deposited on the
bottoms of ponds and marshes, where it is available to waterfowl. It is
being replaced for waterfowl hunting by steel shot, as discussed later.
Use of lead for ammunition declined from 79,000 metric tons in 1974 to
under 67,000 metric tons in 1976. Future projection of the U.S. Bureau of
Mines (Ryan and Hague, 1976) gave a forecast base of 100,000 short tons
(91,000 metric tons) in the year 2000, on a basis of paralleling population
growth. In view of the declining trend of the last several years, and the
proposed restrictions on the use of-lead shot for waterfowl hunting, this
estimate is considered to more probably represent the upper range of the
forecast. Lead consumption over the near term is believed to more likely
fall in the 70,000-80,000 metric ton range.
107
-------
4.3.5.2
Solder--
One of the commonest lead alloys is solder, the designation for a
series of relatively low-melting alloys of lead and tin. The half-and-half
grade (50 percent lead and 50 percent tin) is a general all-purpose grade.
Principal uses of solder are to form water-tight or electrically conductive
joints or to fill surface imperfections on automobile or appliance
surfaces. Food can manufacture, electronic component assembly, and
automobile manufacture are the major end-use categories. The quantity of
solder used per automobile is considerable; the average has been estimated
to be of the order of 10 kg. Solder is used in radiator fabrication and for
smoothing body surfaces at joints in manufacture. Its use in body repair
work is declining as competition from epoxy cold-set filling compounds
intensifies.
Common solder alloys range from the low melting (183-192 C) 70 percent
tin - 30 percent lead alloy used for coating metals, to 2 to 5 percent tin,
95 to 98 percent lead alloys, used for soldering cans. A 60-40 grade is
used for general purposes, but particularly where the temperature
requirements are critical. The 50-50 grade, a general purpose grade, is
most popular of all. The 40-60 alloy is a plumbers wiping solder for
joining lead pipes and cable sheaths, and the 20-80 solder is used for
filling dents or seams in automobile bodies (American Society for Testing
Materials, 1978b).
Lead consumption for solder has fallen off irregularly from the 71,560
metric tons used in 1966, as indicated by U.S. Bureau of Mines data
tabulated below:
1966 71 ,560 1972 64,620
1967 63,340 1973 65,095
1968 67, 180 1974 60,015
1969 65,870 1975 52,010
1970 63,220 1976 57,430
1971 63,500
Automated machinery has permitted a reduction in the amount of solder
needed for a given joint and alternative technologies--e.g., adhesive or
welded can seams, aluminum cans, crimp and clamp electrical connections,
epoxy body seam fillers, etc. have contributed to reductions in lead usage.
The forecast is for this contraction in the consumption of solder to
continue, fueled by the increasing concern about the health effects of lead
and the tightening regulatory climate. One particularly vulnerable segment
is the solder used in joining seams in food cans, estimated to have
consumed approximately 4,000 metric tons of lead in 1976 (U.S. Bureau of
Mines, 1978c). The environmental effects of the use of soldered food cans
are discussed at length in Chapter 8.
108
-------
4.3.5.3
Sheet Lead--
Sheet lead is used to line chemical equipment for corrosion
resistance, to fabricate radiation shielding in X-ray rooms and wherever
radioactive materials are used or handled, and as a sound barrier or
absorber. Sheet lead is used also in building construction as a roofing
material, for flashing for roof vents, and for shower stall pans.
Consumption of sheet lead is slightly lower than it was a decade ago,
but may be in the process of reversing that downtrend. Contrary to most
lead uses, 1975 consumption increased over that of 1974, and 1976
consumption held that gain (Table 4.11). The increasing emphasis by OSHA on
sound levels in industrial situations is expected to accentuate the use of
sheet lead for sound absorption.
The use of metallic lead in sheet form is not a particularly
dissipative use. The weight and value of sheet lead used in a given
industrial application is such as to favor recovery and recycle when the
equipment or building is retired and scrapped.
4.3.5;4
Cable Covering--
Cable coverings use lead in either of two distinct ways. Lead alloys
are extruded around assembled cables for underground or underwater
installation. Connections between cable sections are built up in place
(underground) or on the deck of a cable-laying vessel from thin-gage sheet
lead and sealed to the extruded covering of the cable lengths.
Intercontinental cables continue to rely on lead but plastic coverings have
supplanted lead in recent years in less critical services. Cable sheathing
is reclaimable as old scrap when the cable is replaced--5 to 25 years after
installation.
The second usage of lead in cable production is as a sheath for
retention of rubber-based coatings during curing. In this application, soft
unalloyed lead is extruded onto the uncured rubber covering of the
assembled cable and retained during a steam curing cycle, then stripped and
recycled to the melting tank for reuse. This is basically a non-dissipative
use, requiring additional lead only to make up for handling losses, e.g.,
drosses resulting from oxidation, which are removed from the melting pot
and recycled as lead scrap.
The decrease in the consumption of lead for lead-sheathed cable since
1966 has been dramatic, decreasing from over 60,000 metric tons to less
than 15,000 in 1976 (U. S. Bureau of Mines data):
1966 60,310 1972 41,660
1967 57,170 1973 39,000
1968 48,480 1974 39,390
1969 49,160 1975 20,045
1970 46,050 1976 14,450
1971 48,000
109
-------
This decrease is believed to reflect the increasing substitution of
other (plastic) coverings for lead. The greater reliance on microwave
domestic transmission and transmission via satellite for overseas
transmission in place of underwater cables is a contributing factor; this
trend is likely to continue. No expansion in this use is forecast.
4.3.5.5
Weights and Ballast--
Weights and ballast is a general subcategory consuming substantial
amounts of lead annually. Sailing vessel keels, submarine ballast, and
industrial weights for balancing probably are the largest items
dimensionally, but automobile tire balancing weights--from one-half ounce to
6 ounces each--account for the most lead. A major portion of the discarded
tire weights do not get recycled, but wind up in municipal dumps or land
fills. The total weights and ballast subcategory ranged from 14,000 to
19,000 metric tons of lead per year in the 1966 to 1975 decade, trending
upward slightly. .
4.3.5.6
Type Metal--
Type metal is a lead-based alloy with antimony and tin used by linotype
machines in the preparation of printed materials, such as newspapers and
books. The line of type is assembled from dies containing the appropriate
letter cavities. The dies are locked in place and molten type metal is
injected and cooled, forming a slug on the top of which the raised printing
characters are located. The slugs are assembled into frames and inserted
into a press where the printing takes place. When the printing run is
complete, the slugs are returned to the linotype machine and fed into the
melter for recycle. These electrically-or gas-heated pots hold up to several
tons of molten metal. Surplus ink on the slugs create fumes at the melting
pot which are objectionable to the type-setters. Due to the heat and the
irritating smoke, the pots are hooded and the area well ventilated.
Recently, new processes have been developed which do not require lead
use, the cold type (photo typesetting) and offset presses. Many firms have
already changed over to the cold process, and in 5 to 10 years all but 5-7
1/2 percent of the industry will have changed over (Short and Associates,
1976).
Type metal is a non-dissipative use, with total recycle by the user;
the only lead consumption is for makeup to replace dross losses and other
handling losses.
Consistent with the developments described above, the consumption of
lead for type metal has also exhibited a significant decrease since 1966,
dropping over 50 percent, from 27,590 metric tons to 13,610 in 1976 (U.S.
Bureau of Mines data):
110
-------
1966 27,590 1972 18,090
1967 25,900 1973 19,880
1968 25,380 1974 18,610
1969 23,270 1975 14,700
1970 22,200 1976 13,610
1971 18,880
The forecast is for the annual decrease to continue, with consumption
possibly leveling off at a few thousand tons per year after 1985.
4.3.5.7
Pipes, Traps, Bends, and Caulking Lead--
Lead pipe, traps, and bends are still specified by some building codes
(less for residential construction), and lead pipe is still used for
corrosive service by the chemical industry. Lead pipe used industrially is
probably reclaimed at the end of its service life; traps and bends in
domestic use are reclaimable, but the percentage may not be very high at
present. Thus, this use, while not necessarily dissipative, probably
results in a solid waste discharge to the environment. On the other hand,
lead in this form is quite immobile and resistant to degradation, so that
the insult to the environment is minimal.
Alternative materials, e.g., copper, brass, and stainless steel are
making major inroads into these traditional uses.
Lead is used to caulk bell joints in cast iron pipe, usually by
pouring molten lead into the joint, which has been sealed on the bottom by
stuffing oakum down in the joint. Many building codes still require this
type of joint, although more modern pipe and joint techniques, e.g., copper
pipe and soldered joints, and plastic pipe and cemented joints, are making
inroads into lead-caulked cast iron pipe, especially for such applications
as vent stacks.
Both of these applications of lead are in declining trends, as shown
by the U. S. Bureau of Mines consumption data since 1966:
Caulking
Lead Pipes, Traps and Bends
1966 57,380 18 , 120
1967 43,340 18,310
1968 45, 100 19,310
1969 40,690 17,600
1970 31,390 16,220
1971 27,200 16,480
1972 20,390 16 , 130
1973 18 , 1 90 19,130
1974 17,900 14,930
1975 12,970 12,910
1976 11,310 12,500
111
-------
The decline was especially severe, over 80 percent, for caulking lead; that
for pipes, traps, and bends was less so, and lead consumption for this
purpose may stabilize at about the 12,000 ton/yr level. Where the decline
in caulking lead will~plateau; if indeed it does, is uncertain. In any
case, like so many other segments of the lead industry, there are no
prospects for growth for these uses.
4.3.5.8
Brass and Bronze_aQg Bearing Metals--
~. .' . .. "., ....' . ~ .'''~ ...' -""""
---. .......
Brass is basically an alloy of copper and zinc. Lead is an alloying
additive used to,pr~rpq.ri+y:.:-improve its machinability. "Leaded brass"
'contains 62.5 per-centcopper, 35.15 percent zinc, and 1.15 percent lead. In
"high lead brass" the lead content is increased to 3 percent; a "low lead
brass" would have only 0.5 percent lead. Bronzes are basically alloys of
copper and tin; lead is also added to some bronzes. Automobile radiators,
,..,.-... plumbing 'fi-xtUr.es';' O:1iIlaii1g 'hardware, and corrosion-resistant industrial
! ,'. ~y'pipe~andfi tt'ings' :aiehna',for . end uses for these alloys. Competition for
'! brass and bro~~e,iI)u...~,h..e.SE? applications comes principally from plastics,
'F::' -, :.: alumiritini. a-nd"" st'aTnle'ss steel. Secondary recovery of brasses and bronzes is
'1 :'. ,;e_~tE:!n.~.~ y.e..",. ":::0':."";:.,: ;c.:. :'..::.;'.: :.-' :;;:.":,.
1;--
~. :," j.- ~I:":~:' :h;'3~~~"":;;'~ .~::::'~'
'. ' ,- ~_I .!
I;
I
q-:",:,.~:~. ..'.
;1
,,'.,:: ." TrC!-rspp.r;~g;t.;i."9n. Ir~q.uir.es:(lead in bearings, where its natural qualities
of lubrication and resistance to wear are the basis for applications in
'automotive:'eqtii'pment. arii:!" railroad ,car journals (Ryan and Hague, 1916). A
common ~omP9sition~Qr .raii~oad car bearings is 86 percent lead, 5 percent
.-t:tn-,:"~ana 9 'pe"i'ceiit antimony. Copper-lead bearing alloys may contain as much
as 40.percent lead. Leaded bronzes are essentially mixtures of lead,
copper, and:tin, wHh:.:a h:ad content -of 4 to 25 percent (Metals Handbook,
1 961) .
L.
. . - ...
, '
Ii
"
',;':Eead-oearing;':metals have been the traditional material for railroad
car journal boxes and for line-shaft support bearings. Both applications
have had. inc~easing,.coIJWetition from roller bearings and lead consumption
continues to decline. Minor wear occurs in such bearings in use but the
bulk of the material is recoverable.
.-.-, _.-+.- ..- ."
The consumption data reported in :the Annual Minerals Yearbooks (U.S.
BureaU of Mines) illustrate the decliriing lead demands since 1966 for both
of these use categories: ' :. .
... Bearing Metals
Brass and Bronze
)" ".') ~.
,\;
.1966,
1961
:.1968
1969
1910
.i 911
. -, .. 1912
1913
1"914
1915'
1916
. . .-
. J'
..
19,580
11,140
16,130
15,190
14,810
14,110
14,340
14,200
13,250
11 ,050
11 ,850
23,080
18,560
19,010
19,510
11,110
18, 180
11,960
20,620
20,110
12, 160
14,200
. ..J~
'," " (
. . , I' . ~ ,
I. . ,. .
112
-------
The consumption of lead for bearing metals has declined steadily and
consistently since 1966, and the decline has probably not yet run its
course. Brass and bronze fairly steadily demanded 18,000 to 20,000 metric
tons of lead per year up to 1974. In 1975 and 1976 lead consumption
cOllapsed to 12,000 to 14,000 tons per year, for reasons not clear. Both
uses will be fortunate to hold at present levels, and no growth is forecast
for either.
4.3.5.9
Casting Metal--
Casting metals provide easily formed structural parts for nonload
bearing industrial machinery and corrosion resistant equipment, such as
chemical pumps. Also, the nuclear industry widely utilizes cast lead for
lead bricks weighing about 12 kg (27 lb), for lead pigs for the shipment of
radioactive materials, and for lining the large casks used to ship spent
reactor fuel elements. Most of the lead in this use is recovered and
recycled.
Lead consumption for this use category varied irregularly between
6,000 and 9,000 metric tons per year during the past decade, and has ranged
between 6,000 to 7,000 tons since 1970. It appears likely to continue at
about this level, with essentially no prospects for significant growth.
4.3.5.10 COllapsible Tubes and Foil --
Collapsible tubes of lead pioneered the handy, disposable personal
package for toothpaste, creams and ointments, and similar personal care and
pharmaceutical products. Since World War II, increasing concern about the
health aspects of lead in such tubes has led to the adoption of other
materials. Aluminum, along with plastics, with their ready availability,
lower price, and better resistance to product discoloration or metal
contamination--have become dominant in this field.
Collapsible tubes of lead have become almost obsolete, except for a
few specialized uses such as for artists' colors in oil, and other minor
industrially-oriented products. After use, the tubes are discarded rather
than collected for recycling. Annual lead consumption for these uses has
declined about 80 percent from the approximately 11,000 metric tons per
year of the late 1960's to a little over 2,000 tons per year since 1973. It
gives evidence of stabilizing at about this level, with no prospects for
growth.
Lead foil is used to shield radioactive materials (gamma-ray
attenuation) during shipment and storage. Lead foil consumption has ranged
between 4,500 and 6,500 metric tons per year over the past decade, with no
strong trend either up or down; it can probably be expected to continue in
similar fashion.
113
-------
4.3.5.11 Miscellaneous Uses--
There are several miscellaneous uses for metallic lead, each consuming
no more than a few hundred to a few thousand metric tons per year. These
include annealing, galvanizing, and plating.
As an annealing bath, low-melting lead alloys provide a curing
for various metals. This is a modest use of lead, 3,700 metric tons
and 2,400 in 1975, which will probably continue at a nominal level.
appears to have no major growth potential. It is an essentially
nondissipative use, with apparently very little impact upon the environment.
medium
in 1974
It
Lead has a minor use in plating steel parts, such as nuts and bolts,
primarily to provide lubrication and as an anti-galling agent. Terne metal,
an alloy of lead and tin, is used to coat steel sheets to provide corrosion
resistance. Terne alloy contains 10 to 25 percent tin, with the remainder
lead. Lead coatings that contain as little as 2 to 2.5 percent tin are
increasingly popular (Metals Handbook, 1961). Major use for terne metal is
for automobile gasoline tanks (the inner suface) to prevent rusting of this
vital automobile component. Lead consumption for these uses has ranged
hetween 2,000 and 4,000 tons per year during the past decade, and is
expected to continue at about this level. No growth is forecast for this
segment of the lead industry.
4.3.~- Organic Lead Compounds
For the purposes of this report organic lead compounds are defined as
those compounds in which a lead atom is attached directly to a carbon atom.
A large number of compounds containing lead and carbon which do not fit
this definition were discussed as inorganic compounds in Section 4.3.4.
The major organic lead compounds are, of course, tetraethyl lead and
tetramethyl lead; these were discussed in Section 4.3.2.
Although a large number of organic lead compounds theoretically could
be produced, and over a thousand are known, only one specific product,
tetraphenyl lead, and two manufacturers were identified.
The Houston Chemical Company Division of PPG Industries, produces (or
did produce) unspecified organic lead compounds at Beaumont, Texas; the
Alfa Products Division of Ventron Corporation (subsidiary of Thiokol
Corporation) produces tetraphenyl lead at Danvers, Massachusetts.
The" list of possible types of organic lead compounds include:
Hexaorgano dilead
Tetraorgano lead
Triorgano lead halide
Triorgano lead compound
Di (Triorgano lead) oxide
Triorgano lead alkoxide
Triorgano lead organophosphide
Triorgano lead azide
R6Pb2
R4Pb2
R PbX
R3pbOR'
(~3Pb)20
R PbOR '
R3pbPR2,
R3PbN 2
3 3
114
-------
where Rand R' refers to an alkyl, aryl, or alkenyl group, and X refers to
an halide. These products may be produced by a variety of processes:
.
.
Reaction of a lead alloy with an organic ester
Grignard reaction mechanism using lithium or
magnesium chloride with an inorganic lead salt
Reaction of lead salts with trialkyl aluminum
Lead metal reacted with alkylhalides, phosphates or
sulfates
Lead metal with an alkyl chloride, reacted with magnesium
alkyl magnesium halide, alkyl lithium, sodium aluminum
alkyl, or sodium boron alkyl
Electrolysis using a lead anode and a Grignard reagent
(analogous to the electrolytic method for producing
(TML)
Trialkyl-lead chloride plus lithium aluminum hydride to
produce trialkyl lead hydride
Trialkyl lead hydroxide plus metallic sodium to produce
di (trialkyl lead) oxide
Di (Trialkyl lead) oxide plus an alkyl hydroxide to
produce a trialkyl lead alkoxide
Trialkyl lead chloride plus dialkyl hydrogen phosphide
to produce trialkyl lead dialkyl phosphide
Trialkyl lead hydroxide plus hydrogen azide to produce
trialkyl lead azide.
.
.
.
.
.
.
.
.
.
Although the following lead organic compounds have been produced, no
explicit current manufacturers were identified: tributyl lead acetate,
triethyl lead acetate, and triphenyl lead acetate, used as fungicidal
agents in paints; alkyl lead compounds for use as anti-mildewing agents in
the cotton industry; and mercuric chloride mixed with diethyl lead
dichloride, used for seed treatment.
Although not certain, it is most likely that Houston Chemical Company
has produced reactive lead alkyls and mixtures thereof for sale for the
manufacture of other compounds, such as ethyl mercuric chloride from
tetraethyl lead (TEL). This may explain a portion of the use of 164 tons
(181 tons) of metallic lead consumed in 1975 for chemicals other than
gasoline additives. The sodium-lead alloy processes would, of course, have
been used for the manufacture of such TEL. The process employed by Alfa
Products Division of Ventron Corporation was not established, but a very
good possibility is that triphenyl aluminum is reacted with a soluble lead
salt in a hydrocarbon solvent.
Capacity, production levels and other specifics about these compounds
are unknown. All are estimated to be quite minor, with negligible effect
upon the lead industry.
115
-------
4.4
REFERENCES
American Society for Testing and Materials. 1978a Part 8. Nonferrous
Metals. Standard B29-55 (Reapproved 1977). American Society for
Testing and Materials, Philadelphia, Pennsylvania. pp 51.
American Society for Testing and Materials. 1978b. Part 8.Nonferrous
Metals. Standard B32-76. Solder Metal. American Society for
Testing and Materials, Philadelphia, Pennsylvania. pp 57.
Anderson, E.V. 1978. Phasing Lead Out of Gasoline: Hard Knocks for Lead
Alkyl .producers. Chemical and Engineering News. February 6. pp 12-16.
Anonymous. 1976. World's Lead Use Rate Expected to Decline.
Dispatch, Columbus, Ohio. Sept. 6.
Columbus
Anonymous.
1977 .
Private communication from a battery manufacturer.
Battelle-Columbus. 1972. A Study to Identify Opportunities for Increased
Solid Waste Utilization. NTIS PB 212730.
Battelle-Columbus. 1975. Inorganic Color Pigments (Task 22) and Inorganic
White Pigments (Task 23). Draft report under Contract No. 68-02-1323
to U.S. Environmental Protection Agency, Control Systems Laboratory,
Research Triangle Park, North Carolina. 101 pp.
Beltz, P. R., R. H. Cherry, P.S.K. Choi, G. W. Collings, P.W. Cover, M.S.
Farkas, B.C. Kim, P.W. Lerro T.A. McLure, D.N. Williams, and E.T.
Yeager, 1973. Economics of Lead Removal In Selected Industry.
Battelle Memorial Institute, Columbus, Ohio. U.S. Environmental
Protection Agency. pp 53-70.
Callaway, H.M., 1962. Lead, A Materials Survey. Information Circular 8083,
U.S. Department of The Interior, Bureau of Mines, Washington, D.C.,
194 pp.
E. I. DuPont de Nemours and Company. 1964. Regulations Governing the
Handling and Blending of DuPont Lead Antiknocks for Locations
Receiving Antiknock in Tank Cars or Tank Trucks. E. I. DuPont de
Nemours and Company, Wilmington, Delaware. January. 13 pp.
116
-------
E. I. DuPont de Nemours and Company. Undated. DuPont Antiknocks. Product
Bulletin. Petroleum Chemicals Division, Wilmington, Delaware. 14 pp.
E. I. DuPont De Nemours and Company. 1978. Fall 1978 ESCON Forecast.
Technical Brief No. 7812. Hilmington, Delaware. September 22. 5 pp &
Attachments.
Ethyl Corporation. Undated. A Guide to the Safe Handling and Mixing of
rtEthylrt Antiknock compounds. Ethyl Corporation, Houston, Texas. 19 pp.
Ethyl Corporation. 1978. Yearly Report of Gasoline Sales, by States, 1977.
Petroleum Chemicals Division, Houston, Texas. pp2-12.
Ewing, B. B., and J. E. Pearson. 1974. Lead in the Environment, from
Advances in Environmental Science, and Technology, Vol. 3. Editors:
J. N. Pitts, and R. L. Metcalf. John Wiley & Sons, New York 126 pp.
Faoro, R. B. and T. B. McMullen. 1977. National Trends in Trace Metals in
Ambient Air EPA-450/l-77-003, U.S. Environmental Protection Agency,
Monitoring and Reports Branch, Research Triangle Park, North Carolina.
33 pp.
Furno, F. 1978. Personal communication from Celanese Piping Systems, Inc.
Hilliard, Ohio.
Hallowell, J. B., J. F. Shea, G.R. Smithson, Jr., A. B. TripIer, and B.W.
Gonser. 1973. Water Pollution Control in the Primary Nonferrous-
Metals Industry, Vol. I. Copper, Zinc, and Lead Industries, Office
of Research and Monitoring, U.S. Environmental Protection Agency,
Washington, D. C., EPA-R2-73-247a, 177.pp.
Lutz,
G. A., A.R. Levin, S. G. Bloom, K. L. Nielsen, J. L. Cross, and D. L.
Morrison. 1970. Technical Intelligence, and Project Information
System for the Environmental Health Service, Vol. III. Lead Model
Case Study, by Battelle Memorial Institute, Columbus, Ohio for U.S.
Department of Health~Education~and Welfare Environmental Health Service.'
McKay, J.E. 1967. Lead.ln: Kirk-Othmer Encyclopedia of Chemical Technology,
2nd Ed., Vol 12, A. Standen (ed.), Interscience Publishers, John Wiley
and Sons, Inc., New York pp 207-247.
Metals Handbook.
for Metals.
1961. Metals Handbook.
Cleveland, Ohio.
8th Ed. Vol. 1.
American Society
Modern Plastics.
September.
1976.
pp 43.
Heat Stabilizers.
Staff Article, Modern Plastics,
117
-------
National Petroleum News Factbook Issue. 1978. National Petroleum News,
McGraw-Hill Inc., New York, New York. June. ~ 193 pp.
National Sanitation Founcation. 1977. Standard No. 14 for
Materials, Pipe, Fittings, Valves, Traps, and Joining
Adopted 1965; Revised February, 1977.
National Sanitation Foundation, Ann Arbor, Michigan.
Thermoplastic
Materials.
86 pp.
Prescott, J. H. 1977. u.s. Oil Refiners Gird for Lead-in-Gasoline Cuts.
Chemical Engineering 84: 1 66-68, January 31.
Ryan,
J. P., and N.M. Hague. 1976. Mineral Facts and
Bulletin 667, 1975 Edition. Bureau of Mines, U.
Interior, Washington, D.C. pp. 591-610.
Problems. Lead.
S. Department of
Shapiro, H., and F. W. Frey. 1968. The Organic Compounds of Lead.
Kirk-Othmer Encyclopedia of Chemical Technology, 2nd Edition,
A Standen (ed), Interscience Publishers, John Wiley and Sons,
New York, New York. pp 282-299.
In:
Vol. 12.
Inc. ,
Shelton, E.M. Motor gasolines. Semi-Annual Summer and Winter Surveys, 1965-
1977. u. S. Department of Energy, Bartlesville Energy Technology Center
Bartlesville, Oklahoma.
Short
and Associates. 1976. Preliminary Technological Feasibility, Cost
of Compliance, and Economic Impact Analysis of the Proposed OSHA
Standard for Lead. Prepared for OSHA, U. S. Department of Labor, by
J. Short and Associates, Salt Lake City, Utah, .327 pp.
Sobotka. 1976. Economic Impact on Petroleum Refineries of Lead Additive
Phasedown. Final Report to U. S. Environmental Protection Agency
Contract No. 68-01-4174, Sobtka and Company, Inc., Montpelier,
Vermont, p 71.
U. S. Bureau of Mines. 1975. Lead. Preprint from the 1974 Minerals Year-
book. U. S. Department of the Interior, Washington, D. C. 26 pp.
U. S. Bureau of Mines, 1976. Lead. Preprint from the 1975 Minerals Year-
book. U. S. Department of The Interior, Washington, D. C. ~8 pp.
U. S. Bureau of Mines, 1977. Commodity Data Summaries, 1976.
Department of The Interior, Washington, D. C.
Lead.
U. S.
U. S. Bureau of Mines. 1978a. Lead Industry in March, 1978. Mineral
Industry Surveys, U. S. Department of The Interior, Washington, D. C.
7 pp.
U. S. Bureau of Mines. 1978b. Lead. Mineral Commodity Summaries.
Department of The Interior, Washington, D. C. pp 90-91.
U. S.
U. S. Bureau of Mines.
R. W. Hale.
1978c.
Personal communitation from J. Rathjen to
118
-------
u. S. Department of Agriculture. 1975. The Pesticides Review.
Stabilization and Conservation Service, Washington, D. C.
Agriculture
58 pp.
U. S. Department of Commerce. 1973. Bureau of Census, 1966-1973, U. S.
Department of Commerce, Washington, D. C.
U. S. Department of Labor. 1978. Occupational Exposure to Lead. Final Standard.
Occupational Safety and Health Administration, Washington D.C.
43 FR 52952-53014. November 14.
U. S. Environmental Protection Agency, 1973. Part 80. Regulation of Fuels
and Fuel Additives; Control of Lead Additives in Gasoline.
38 FR 33724-33711. December 6.
U. S.
Environmental Protection Agency, 1975 a. Economic Impact of Proposed
Water Pollution Controls on the Nonferrous Metals Manufacturing In-
dustry, Phase II, EPA 230/1-75-041 p/III-4, U. S. Environmental
Protection Agency, Washington, D. C. March. Various pagination.
U. S.
Environmental Protection Agency. 1975b. Development Document for
Interior Final Effluent Limitations guidelines and Proposed New Source
Performance Standards for The Lead Segment of The Nonferrous Metals
Manufacturing Point Source Category. EPA 440/1-75-032 a. February.
pp 124.
U. S. Environmental Protection Agency. 1976. Regulation of Fuels and Fuel
Additives; Control of Lead Additives in Gasoline. 41FR 42675-42677 Sept. 28.
U. S.
Environmental Protection Agency. 1977a. Control Techniques for Lead
Air Emissions. 2 Vols. EPA-450/2-77-012. Office of Air QuaLity Planning
and Standards, Research Triangle Park, North Carolina. Various
pagination.
Environmental Protection Agency. 1977b. Development Document for
Effluent Limitations guidelines and New Source Performance Standards
for the Miscellaneous Nonferrous Metals Segment of The Nonferrous
Metals Point Source Category. EPA-440/1-76/067. March. pp. 40-44. .
U. S.
U. S. Environmental Protection Agency.
communication to R. Ewing.
1978.
Pesticides Branch.
Personal
U. S. Tariff Commission. 1968. Summaries of Trade and Tariff Information,
Schedule 4, Vol. 10, U. S. Tariff Commission, Washington, D. C.
Walker, P. 1977. Maintenance - Free Battery Poses Problems for Secondary
Plants, Am. Metal Market, June 16.
Walsh, T. 1977. Maintenance - Free Battery Seen Changing The Industry.
Metal Market, June 15.
Am.
Weinberg, E. L. 1976. Heat Stabilizers. 1975-1976. Modern Plastics
Encyclopedia. McGraw-Hill, Inc., New York, New York. pp 208-209.
119
-------
World Metal Statistics. 1977. Principal End Uses of Lead.
World Bureau of Metal Statistics, London, England.
30 (12) 73-74.
Wright, J. A. and R. B. Kubalak. 1976. Lead/Zinc Industry Update - 1976,
Mining Congress Journal, ~2(11), p 44-46.
Ziegfeld, R. L. 1964.
R Feb.
The Importance and Uses of Lead, Arch. Env. Health,
120
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5.0
INTRODUCTION OF LEAD INTO THE ENVIRONMENT
5.1
SUMMARY
No complete material balance appears to have ever been made for
lead, perhaps because of the unquantifiable nature of some of the emissions
which proceed at an imperceptible rate from the enormous inventory of lead
as a "resource in use". Estimated air emissions are probably the most
completely identified and quantified. The recent EPA report (U.S. Environ-
mental Protection Agency, 1977a) covers most of the principal types of
emission sources, for which estimates are provided.
There appears to be no comparable inventory of water emissions.
Part of the problem here is that much, if not most, of the lead entering
the hydrosphere was originally an air emission, and double-counting is a
problem not amenable to an easy solution. Efforts are made in this section
to identify the significant sources of lead entering the waters of the United
States each year; the probable contributions of predecessor air emissions
to these flows are noted and estimated where a basis for estimation exists.
The estimation of solid waste disposed to landfills as solid waste from a
mineral processing or manufacturing operation is fairly straight-forward;
however, data are fragmentary on other more dispersed or unmeasured streams.
Existing information is summarized on the types and modes of dispersion,
the receiving media (air, water, and/or land), estimates of the amounts of
lead released, and when available, information on the impacts of such
releases. The available or derived estimates are given in Table 5.1 along
with comments as appropriate.
As a result of the widespread use of lead and its compounds described
in Chapter 4, and the losses to the environment associated with that use,
lead is detectable at above natural levels in all three compartments of
the environment--air, water, and soil. Concentrations of lead in t~e
environment and their e£fects on human intake are discussed in Chapter 8.
5.2
SOURCES
5.2.1
Lead Producing Industry
5.2.1.1
Primary Lead--
5.2.1.1.1 Mining and. smelting lead ores--The mining and milling of
lead ores results in the release of lead to all three media with the largest
quantity of lead, in mill tailings, disposed to the land.
121
-------
TABLE 5.1.
ESTIMATED RELEASES OF LEAD TO THE ENVIRONMENTa,b
:....;r-=-~.~~.-'-
Metric tons/year
To the To
Atmosphere Wastewater
893 200-500 21,000
112 3.7 1,010
1,314 12.5 1,590
750 Sewered 3,260
47 10 460
82 1-340 40
1,000 60 None
112 Sewered 200
40 Sewered 40
113 Minor Minor
435 Minor Minor
60 Unknown Minor
600 Unknown Minor
77 ~inor Minor
Source
Lead Producing Industry
Primary lead
Primary zinc
Primary copper
Secondary lead
Secondary brass
and bronze
Lead Consuming Industries
Battery manufacture
Lead alkyl manufacture
Lead oxide & Pigments
Lead stabilizers
Cable covering
Type metal
Can Soldering
Ceramics
Metallic lead products
Indirect Sources
Gasoline distribution
Gasoline combustion
Waste oil disposal
Coal combustion
Oil combustion
Cement manufacture
Iron and steel manufacture
Grey iron products
Ferro alloy production
Solid Waste incineration
Sludge disposal
420
122,100
3,400
225
100
312
605
1,080
30
1,170
5
None
Indeterminate
Indeterminate
Minor
Minor
Minor
Unknown
Unknown
Unknown
Unkown
Unknown
To the
Land
None
Final Sink
4,650
4,275
In As h .
Unknown
Unknown
Unknown
Minor
In Ash
2,400
aSource:
U.S. Environmental Protection Agency (1977a); Battelle-Columbus
estimates.
bBas is :
1975 data.
122
-------
The emissions to the air from the mining and milling of lead ores are
principally in the form of particulates emitted during blasting, transport,
crushing, and grinding of the ores. The largest portion of lead production
(80 percent) comes from underground mines in southeastern Missouri. The
particulate emissions from mining are those contained in the ventilation
air circulated through these mines, which are usually wet, so that no
general dusting is encountered within the mine (Hallowell, 1970). In
open-pit mines, associated with some mixed ores (i.e., Pb-Cu, Cu-Pb-Zn ores)
the dust from mining operations is more obvious in terms of blasting and
loading operations. Additional fugitive dust is generated during hauling
or transport by truck or conveyors from mine to mill, at transfer points
and during crushing, screening and dry grinding operations. Most dusty
operations are hooded and the dust is collected and returned to the process
stream. Other milling operations (e. g., wet grinding) are not a source of
dust.
All the above emissions consist of lead ore particles-basically
insoluble lead sulfides--relatively coarse in particle size, and fall
to earth within a short distance of the point of generation. The net
emission of lead to the atmosphere from the crushing and grinding of lead
ores is estimated to amount to 81 metric tons of contained lead annually.
However, lead is also recovered from copper ores (mined in very large
tonnages, generally in open-pit mines under dry conditions) and from
copper-lead-zinc ores, also mined in large tonnages. Crushing and grinding
of these other ores is estimated to release an additronal 412 metric tons,
for a total annual lead emission of 493 metric tons. (U.S. Environmental
Protection Agency, 1977a).
Losses of lead to the water from lead ore mining and milling operations
vary according to lead contents of mine drainage and mill tailings pond over-
flows. These two modes of release of lead are highly dependent on the
individual circumstances of the amount of water present in a mine, and the
climate (i.e., rainfall) in which the tailings pond operates. The amount of
mine drainage generated by a mine depends on the specific geology of an ore
deposit, i.e., whether the water in the mine is or becomes acid or alkaline
either from its instrinsic nature or after interaction with exposed strata
and ore. The Bonneterre Formation in which the southeastern Missouri mines
operate is a productive aquifer, and most mines must pump 18.9 to 26.5 cu
m/min (5,000 to 7,000 gpm) to prevent the mines from flooding (Jennett and
Wixson, 1972).
The milling or concentrating of ore results in the separation of a con-
centrate from a gangue, which is transported as a slurry to a tailings pond
for disposal on land. The local climate (i.e., rainfall) along with water-
use practice in the mill, determine whether an excess of water is discharged
from the tailings pond. Thus, any estimate of the amount of lead entering
surface waters from lead ore mining and milling operations is affected by
the highly individual circumstances of mine drainage quantity and chemistry
and the climate and water use practices of the milling operations. Additionally,
the estimate of lead losses to water from the mining and milling of lead ores
is further subject to judgments concerning the category of are included, in
that lead is extracted not only from lead ores but also from other ores
containing lead, e.g., lead-zinc ores and copper-lead-zinc ores.
123
-------
One approach to estimating the lead loss to surface waters from lead
ore mining and milling operations is the derivation of a "unit waste load" on
the basis of measured flows and concentrations. Some example values of
concentrations and flows from lead mining and milling operations are listed
below (U.S. Environmental Protection Agency, 1975b):
Flow, Plant A Plant B Plant C
cubic meters/day 8,300 29,000 1,426
gallons/day 2,190,000 7,700,000 377,280
Lead Concentration, mg/l 0.05 0.093 <0.024
Unit Waste Load,
kg Pb/metric ton of ore 0.00012 0.071 0.013
Average Unit Waste Load, '- ~ .
kg Pb/metric ton of ore 0.028
The flow, concentrations, and unit waste loads given above reflect
total discharge from mine and mill operations. Note the wide variation in
flows and resulting derived unit waste loads. While this approach is far
from rigorous, aggregated data on total flows are not available, and the
estimation is necessarily based on tonnages, which are recorded.
The classes of lead-containing ores to which the unit waste load may
be applied and their 1975 tonnages are (U.S. Bureau of t1~ines, 1976):
Class of Ore
Lead
Zinc
Lead-Zinc
Cu-Pb,Cu-Zn,
Cu-Pb-Zn
All Other
Metric Tons
Percent of Total
Lead Production
7,855,300
5,657,800
2,383,800
86
1
10
2,143,200
37,952,000
55,992,100
2
1
If the "unit waste load" derived as described above is applied to only
lead ores, the estimated annual loss of lead to water would be approximately
220 metric tons. Extending this factor to the other 1ead-copper-zinc ore
combinations would increase the estimate to about 500 metric tons/yr.
Extending this to the "all other" category of ores is less appropriate. Over
98 per cent of these, primarily copper ores, are mined and milled in Arizona
in net evaporation areas, and water discharges are minimal. For the purposes
of this estimate they can be neglected.
-
Another approach to estimating losses of lead to the water from mining
and milling operations utilizes the recently-promulgated Effluent Limitations
Guidelines for Base and Precious Metals (U.S. Environmental Protection Agency,
1978a). The effluent limitations are expressed in concentrations rather than
in units of production because it was not possible to develop an easily
applicable relationship between units of production and. waste water discharged
by mines and mills in this category. Allowable lead discharge limits, based
on best practicable technology (BPT), are 0.3 ~(1 (30-day average).
124
-------
The original guidelines development document (U.S. Environmental
Protection Agency, 1975b) modeled the lead mining and milling industry in
terms of representative mines and mills. Using this approach to estimating
produces estimated lead contents of wastewater discharges of 30 metric tons
in 1977. BAT (Best Available Technology) and NSPS (New Source Performance
Standards) regulations are to be proposed in 1979, which will further reduce
allowable discharges.
The solid wastes from milling of lead ores contain some residual lead
content since the recovery process (usually flotation) is not 100 percent
efficient. The lead content in concentrator tailings from various major U.S.
operations has been reported to range from 0.09 to 0.25 weight percent (AlME,
1970). The quantity of tailings may be taken as 93 to 95 percent of the ore
mined. These factors lead to an estimate of 18,000 metric tons per year of
contained lead being disposed of in the tailings from lead and major classes
of mixed ores (i.e., Pb, Pb-Zn, Cu-Pb-Zn). This lead is principally in its
initial galena form (lead sulfide). The potential for mobilization of this
lead would include the possible paths of the tailings pond overflow, seepage
into the underlying strata, and ~yeathering by wind and runoff.
The smelting of lead ores results in emissions of fume and particulate
to the atmosphere, the generation of lead~containing wastewaters, and the
generation of slags and sludges which are disposed of to the land. The
emissions of lead to the atmosphere from primary lead smelting include
emissions of lead-containing fume and particulate from the pyrometallurgical
unit processes of sintering, the blast furnace, and the dross reverberatory
furnace. In addition, fugitive emissions are generated from concentrate
handling, storage, and transfer, and leaks from ducts and furnace openings.
The estimated net emissions of lead to the atmosphere from primary lead
smelting operations are reported as 400 metric tons per year (U.S. Environ-
mental Protection Agency, 1977a). These emissions would include those
stemming from fume i.e., lead oxide particles of small size.
In a survey of water pollution control in the primary nonferrous metals
industry made for EPA by Battelle's Columbus Laboratories (Hallowell, et al.,
1973), the effluents from the tailings ponds were reported to contain anywhere
from no lead to 800 pg/l; these streams originally contained from 0 to 50 pg/l
as measured at points considered unaffected by plant effluents.
As part of the development of effluent limitations, the flows and lead
concentrations of all lead smelter wastewaters were determined in 1973 (U.S.
Environmental Protection Agency, 1975c). The estimated 1975 net release of
contained lead, based on those measurements, was 2.5 metric tons.
A recent survey for the Office of Solid Waste Management idenfified the
solid wastes generated by the primary lead smelting industry as slags, drosses,
and sludges. On the basis of average analyses, the contained lead content of
these wastes was reported as 2,640 metric tons. The lead in these wastes was
mostly in the form of slags with an unknown but probably slow rate of release.
Some lead was in the form of wastewater treatment sludges (i.e., most likely
the hydroxide form). These wastes were all discharged to the land on the
smelter sites. (Calspan, 1977).
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5.2.1.1.2 Mining and smelting of other lead-containing ores--Lead occurs
in varying amounts in many metal ore deposits and consequently travels with
the other materials during processing. Depending on the amount of lead present
and the particular process, the lead may be recovered as a by-product or appear
in the wastes and residues from various processes. The residues, depending on
their mode of formation, may be transferred between industries if their content
of metal values makes this economically advantageous. Examples of residues
which have been traditionally transferred between industries are lead-
containing flue dusts from the zinc and copper industries to the lead industry;
solution purification residues (lead cake) from the zinc to the lead industry,
and zinc-containing slags from the lead industry to the zinc industry. (In
some cases, slags from lead blast-furnaces are fumed at the lead plant to pro-
duce zinc oxide as a co-product of lead.) Several industries in this category
produce noteworthy releases of lead to the environment. Unfortunately, no
consistent data base exists for releases of lead to various media for all of
these industries. Estimates of lead releases from processing these ores are
presented below to the extent that available information allows.
As with lead ore the handling of other ores in processing results in the
generation of dusts generally consisting of relatively coarse particles. As
noted previously, these types of emissions are considered as fugitive; being
coarse, the particles settle rapidly and are less respirable and produce more
localized impacts (i.e., confined to the area of the operations) relative to
other process emissions from thermal processes, high stacks, or mobile sources.
The lead intrinsic to these other ores follows similar paths to water
and land as described for lead milling and tailings disposal. Depending on
the lead content of the ore and the nature of the process, lead will appear
in the process water discharge from the ore processing steps (e.g., in flota-
tion tailings pond overflow), and in the waste solids disposed of in tailings
ponds, as well as in dusts and runoff produced by weathering of the tailings
deposit, to the extent that lead is present in the ore or tailings. (U.S.
Environmental Protection Agency, 1976a).
The presence of lead in almost all mine and mill process water streams
and in discharge streams is indicated by the data obtained during a survey of
the metal ore mining and milling industry (U.S. Environmental Protection
Agency, 1975b). Examples of the data obtained are listed below:
Type of Mine
or Mill
Lead
Concentration,
mg/l
0.023
0.111
<0.05-0.40
Silver
Aluminum
Molyldenum
Copper-Molydenum
Uranium
Platinum
Emission Source
Mine
Mill
Process
Mine, Mill,
Process
Process
Process
Discharge
Discharge
Discharge
Process
0.05-0.25
<0.1
0.10
0.03
0.02
- 0.1
0.01
Iron
Iron
Copper
Lead-Zinc
126
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Although lead is present in many of the process streams~ the amount discharged
comprises only a few tons~ based on the estimated concentrations and actual
reported discharge flows. Many metal mining operations are in the western
desert and produce no discharge of water. Others in areas of net water
accumulation either do or are beginning to practice water recycle. Thus~
while lead is present in most mineral processing streams~ concentrations in
actual discharge streams are relatively low~ i.e.~ around the drinking water
level of 0.05 mg/l. These discharges still represent concentrations above
the levels generally encountered in surface waters. Thus~ metal ore mining and
milling operations may be characterized as diffusely scattered sources of low-
level contributions which generally raise the level of lead concentrations in
the receiving waters.
The contributions of lead to the environment from pyrometallurgical
processes is most significant in terms of emissions to the atmosphere from
a few high temperature processes~ the content of lead in some wastewaters~ and
in some metallurgical wastes disposed of to the land. Notable lead emissions
to the atmosphere are associated with the smelting processes for copper and
zinc~ and have been estimated to amount to 1~314 and 112 metric tons~ respec-
tively~ of contained lead for the year 1975. (U.S. Environmental Protection
Agency~ 1977a).
Lead was present in the wastewaters from electrolytic refining operations
in the copper industry "in a sufficient number of cases to allow the development
of analytical~ flow~ and unit waste load data. It is estimated that 12.5
metric tons of contained lead was discharged by those operations in the year
(1973) the data were developed (U.S. Environmental Agency~ 1975d). A study
of wastes destined for land disposal from copper smelting and refining
operations provided an estimate of 1~590 metric tons of lead as being con-
tained in all process wastes such as slags~ flue dusts, sludges and other
process wastes. (Calspan~ 1975).
Lead in the wastewaters discharged by zinc smelters was found to range
in concentration from 0.02 to 1.35 mg/l (U.S. Environmental Protection Agency~
1975a). Using data gathered on the concentrations and flows for five indivi-
dual smelters~ the total release of lead in the wastewaters is calculated to
have been approximately 3.7 metric tons for 1973.
The study of wastes generated by the primary zinc industry which are
deposited on the land (slags~ dusts~ sludges~ and water treatment residues)
resulted in an estimate of 1~010 metric tons of contained lead. These wastes
were almost all disposed of on the plant site where they were generated
(Calspan~ 1975).
5.2.1.2
Secondary Lead--
Secondary lead smelting is considered to include both the recovery of
storage batteries (the major segment of the secondary lead industry) and
various other processes which recover lead and lead alloys. The principal
operation of scrap battery smelting is the blast furnace~ while recovery of
other forms of lead involve rotary~ reverberatory or other fQrms of furnaces.
127
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Because of the diversity and lower grades of the feeds and operations of the
smaller segments of the industry, and a probably lower level of effective
pollution control, the estimated emissions of lead to the atmosphere (750
metric tons) (U.S. Environmental Protection Agency, 1977a) and the amounts of
lead wasted to land disposal (3,260 metric tons) (Calspan, 1975) exceed those
of the primary lead smelting industry. There was not discovered any reason-
able basis for estimation of losses of lead from this industry to wastewaters.
In general, it may be observed that storage battery recovery includes the
step of "battery breaking" in which the nonmetallic (rubber or ABS plastic)
case is separated from the inner assembly of plates and separators. The
battery-breaking operation obviously results in the liberation of acid and
sludge from the battery. Battery breaking is sometimes done on the battery
smelting plant site, sometimes as part of a diverse scrap metal operation,
and occasionally as the sole activity of a small independent company. In
cases of integrated battery smelting operations, the battery breaking operation
is acknowledged as a generator of acid wastes, and special concrete aprons
and runoff collection and treatment are provided. It is estimated that the
majority of scrap operations are sources of acid runoff and drainage which
is saturated with lead. These operations constitute a diffuse and unassessed
segment of industrial operations. They are estimated to account for a
portion of the release of lead in the flows of sewage and drainage from
municipal-industrial complexes.
The sweating process (See section 4.2.2.1) gives rise to both gaseous
and particulate atmospheric emissions. The gaseous portion consists of
sulfur oxides, nitrogen oxides, fuel combustion products, and air. The
particulates are unburned fuel, fumes, dusts, fly ash, and soot. These
emissions are controlled by baghouses, with scrubbers used in some plants.
Solid wastes from this process are the nonmetallics and other metallic
residues remaining after lead removal (U.S. Environmental Protection Agency,
1977a).
Both atmospheric emissions and solid wastes result from the reverber-
atory sweating process. Gases and particulate matter containing fumes and
dusts are the atmospheric emissions. The gases consist of combustion products,
sulfur oxides, unburned fuel, and hydrocarbons pyrolyzed from the organic
compounds mixed with the scrap. Lead, additive metals used to alloy lead,
antimony, and nonmetallic materials such as fluxes or organic contaminants
from the scrap are contained in the fumes and dusts. The atmospheric
emissions are controlled by use of a baghouse, scrubber, or both. There also
may be settling chambers or gas cooling devices. Wet lime scrubbers are used
in some plants to control sulfur oxide emissions.
5.2.1
Secondary Brass and Bronze
Lead is encountered in the brass and bronze industry, which to a large
extent coincides with the secondary copper industry, principally in the forms
of solder residue on recycled automobile radiators, and as deliberate additions
of up to 1 percent of lead to produce leaded (free-machining) brasses and as
deliberate additions of 10 to 20 percent by weight in specialty alloys such as
the red brasses. Emissions of lead to the atmosphere (estimated at 47 metric
128
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1-'--
tons per year) result from secondary copper blast furnace and reverberatory
smelting and melting, refining, and alloying furnaces (U.S. Environmental
Protection Agency, 1977a). Lead in wastewaters from secondary copper
operations results from operations such as slag quenching, wet-grinding of
residues, and wet air-pollution control measures. The total loss of lead to
the wastewaters by the secondary copper industry was estimated from (1973)
data developed during !effluent limitations guidelines studies as amounting to
10 metric tons (U.S. Environmental Protection Agency, 1975e). Another EPA
study on land-disposed wastes from the industry developed an estimate of 460
tons of lead contained in slags and sludges from the secondary copper smelting
industry (Calspan, 1975).
These lead emissions and wastes are generated largely in metropolitan
industrial areas, with many wastewater discharges being routed to municipal
sewer systems, and land-destined wastes being disposed of partly on the plant
site and partly to municipal landfills.
5.2.2
Lead Consuming Industry
5.2.2.1
Storage Battery Manufacture--
Storage battery manufacturing operations result in annual losses of lead
to the air estimated at 82 metric tons (U.S. Environmental Protection Agency,
1977a), 1 to 340 metric tons in wastewaters (Versar, 1975) and 39 metric tons
of contained lead in wastes destined for land disposal (Crandall and Rodenberg,
1974). The emissions of lead to the atmosphere arise from melting, casting,
oxide production operations, and the grinding and handling of dry metal and
oxide powders prior to their formation into a paste. The pasting operations
can be a source of air pollution because of the handling of finely divided
lead oxide «50 microns). These operations are carried out under well ventil-
ated hoods, with the hood effluent being passed through towers and washed with water
to remove particulate matter which goes into a sump.
The wide range in the estimate of losses of lead in wastewaters is due
to two factors: differences between two current manufacturing processes and
the wide range of wastewater management practices such as recycle and nature
of chemical treatment (if used). Plants making "dry-charge" batteries actually
fill batteries with acid, charge the battery, and drain the acid, resulting in
a larger amount of waste acid. Plants making "wet" batteries produce lead-
containing acid wastes only from spills, battery-washing, and general plant
washing and sump overflows from the paste-making operations. The wastes
destined for land disposal include water-pollution-control sludges, and
miscellaneous scrap and plant wastes.
5.2.2.2
Gasoline Antiknock Additives--
Lead is introduced into the environment at three points in the lead
alkyl cycle: from its manufacture; from the distribution and transfers of
129
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leaded gasoline on its way to the consumer; and finally, when it is burned
in an internal combustion engine.
5.2.2.2.1 Manufacture--The manufacture of lead-containing antiknock
compounds involves emissions to the atmosphere (1975) of an estimated 1,000
metric tons of contained lead (Versar, 1977). These losses are principally in
the form of the processed organic compounds and fume and lead oxide particulates
generated by the furnaces used to recover lead from process sludges. These
emissions occur only at the six antiknock manufacturing sites.
The losses of lead in wastewaters from lead alkyl manufacturing plants
was estimated at 60 metric tons (for the year 1975) on the basis of discharge
information obtained from three plants. A recent study for the Office of
Solid Waste Management Programs established that no process wastes were dis-
posed of to the land by these plants on a regular basis; that is, the only
lead-containing waste was the process sludge, which is reclaimed at all plants
(Processes Research, 1976).
The losses to the air and water are judged to be directly related to
production rates and will thus change with any change in production level.
5.2.2.2.2 Gasoline distribution--Most of the lead discharged into the
atmosphere as a result of the use of lead a1kyls as antiknock agents is, of
course, discharged in the exhaust gases from intera1 combustion engines. As
noted earlier (Table 4.16), the quantity of lead used in lead alkyl antiknock
fluid in 1977 was estimated to be approximately 155,000 metric tons. All of
this is presumed to eventually be dissipated, most of it in the exhaust gases.
However, losses also occur in the distribution chain leading to the vehicle
gasoline tank; at the refinery, at the transfer terminal, at the bulk station,
and finally, at the service station.
It should be noted that these losses of lead in antiknock compounds
prior to combustion are not necessarily additive to lead losses generally
estimated as being due to the use of leaded gaso1ines, since usual estimates
are based on total leaded gas production rather than on consumption, and,
hence, losses occurring before the actual combustion are included in the total
loss.
During the filling of tanks containing gasoline, including terminal
and bulk station tanks, as well as service station tanks and automobile
gasoline tanks, hydrocarbon-rich air is displaced by liquid. Sheppard, et. a1
(1976) estimated that this could release to the atmosphere as much as 0.2
percent by weight (~5.6 g/ga1) each time the gasoline is transferred. Similar
estimates for gasoline emission factors for vehicle fueling (4.5 g/gal) have
been made by EPA (U.S. Environmental Protection Agency, 1973d) as cited by
Dougherty, et al., (1977) who estimated 5.3 g/gal. At the 1977 average of
7,178,000 barrels of gasoline per day (U.S. Department of Energy, 1978), this
would represent a loss of approximately 200 million gallons of hydrocarbons
per year. Since only about 72 percent of gasoline in 1977 was leaded (U.S. Del
ment of Energy, 1978), at an estimated average lead content of 1.42 g/ga1 (Tab11
130
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4.16), estimated loss of lead alkyl (as lead) was approximately 200 metric tons
per year. To this must be added the gasoline vapors displaced from the under-
ground tanks when fuel is delivered to the station, estimated to also have
about the same emission factor, which would double the loss to 400 metric
tons per year. However, this is a maximum loss, since, as noted in the
1972 NAS report (Nation~Academy of Sciences, 1972), lead alkyls are less
volatile than gasoline, and tend to remain behind when gasoline vaporizes.
There are also losses in transfer and storage all the way back to the re-
finery. The annual emission losses for floating roof tanks, which are speci-
fied for gasoline storage by current EPA regulations, are estimated as follows:
Barrels
Tank Size
a .b
Annual Emission Losses'
50,000
100,000
150,000
117
180
269
a
b
Source: Sheppard, et al., (1976).
Estimates based on methods in API
Bulletin 2517.
In anticipation of the New Source Performance Standard, which became effect-
ive March, 1974, it was assumed that, starting in 1971 all new tanks were
floating roof. It was also assumed that currently 90 percent of all gasoline
tanks have floating roofs. Total petroleum industry capacity for gasoline
storage was taken as approximately 210,000,000 barrels, as of September 30,
1973, (National Petroleum Council, 1974). In the absence of specific data,
a 50,000-barrel storage tank was assumed to be standard, i.e., the popula-
tion was approximately 4,200 storage tanks. At the estimated annual loss of
117 barrels (4,914 gallons) per tank, the total loss of hydrocarbons is
put at approximately 20,640,000 gallons/year. Assuming that approximately
the same storage capacity was utilized in 1977, and that 72 percent was
leaded gasoline containing 1.42 g/gal of lead, a total lead loss of about
20 metric tons per year is estimated.
Projecting losses of lead alkyls in the transfer and distribution of
gasoline to 1980 and 1985 involves the use of a number of assumptions which
mayor may not be applicable, since the entire situation is presently very
fluid.
Total car mileage is projected to increase, more or less proportion-
ally to population growth and long-term secular trends. Gasoline consumption
patterns are less well defined. Sobotka (1976) estimated 1985 motor gasoline
consumption of 111.4 billion gallons/yr. A 1976 EPA estimate quoted by
Sobotka (1976) was that highway use of gasoline (97 percent of the total)
would peak in 1980 at about 107.3 billion gal/yr, producing a total use of
110.6 billion gal/yr. However none of these estimates appear to take into
131
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account the present life style in the United States as witnessed by the fact
that average 1976 gasoline consumption was 107.0 billion gallons, which in-
creased ~n 1~77 to about 110 billion gallons (U.S. Department of Energy, 1978);
consumpt~on ~n 1978 probably already exceeded all of the above estimates
(Table 4.16).
A more realistic forecast appears to be that provided by the ESCON model
(E.I. DuPont de Nemourn and Co., Inc. 1978). In this forecast, total gasoline
consumption is estimated to peak in 1980 at about 115 billion gallons per
year, gradually declining to about 107 billion gal/yr by 1985 and to 99 billion
by 1990. According to this same forecast, leaded gasoline consumption will drop
to 57.3 billion gallons in 1980, to 26 billion in 1985 and to 14.7 billion in
1990. With an assumed uncontrolled average loss rate of 5.1 g/gal, hydrocarbon
losses would be a little over 210 million gallons per year in 1980, decreasing
to about 195 million gal/yr in 1985. At the mandated average gasoline pool
lead content of 0.59 g/gal, annual losses of lead would be about 125 and 115
tons/yr, respectively.
The rapid decline in the use of leaded gas will cause a major
decline in the loss of lead alkyls in the distribution of leaded gas.
Reinforcing this trend will be EPA regulations on vapor recovery, designed
to control hydrocarbon emissions, which are now in the proposed rule stage.
The proposed regulations have a dual thrust. Stage I regulations will
require the recovery of 90 percent of the hydrocarbon vapors displaced
from gasoline storage tanks above a small size (varying from 250 to 2000
gallons) during refilling, in 16 air quality control regions (AQCR's).
In addition, the regulations will require vapor laden delivery vehicles
to refill only at facilities equipped with such a vapor recovery system.
Proposed Stage II regulations (U.S. Environmental Protection Agency,
1976 b) call for emissions during vehicle filling in 13 of these same
AQCR's not to exceed a specified value, not yet finalized but expected
to be within the range of 0.4 to 0.6 g/gallon of fuel dispensed. No actual
regulations have yet been promulgated and the ultimate form these regula-
tions will take is unclear. An exemption from vapor recovery requirements
for retail outlets owned by an independent small business marketers having
monthly sales of less than 50,000 gallons was written into (Sec. 325) the
1977 Amendments to the Clean Air Act (P.L. 95-95), which further complicates
forecasting ultimate emission from vehicle fueling.
Spills at filling stations are another source of loss of gasoline
and lead alkyls. Being of a random nature, they are even more difficult
to quantify than the vapor losses discussed above. It is estimated that
spillage is less than vapor losses, and might approximate no more than
0.1 percent loss (3 g/gallon) dispensed. The proposed Stage II vapor
recovery regulations also contain a limitation on spillage, which would
be permitted to occur in up to 15 percent of all vehicle refuelings
(but the quantity limits on spills are not specified).
No basis exists for an estimate of vehicle fueling losses in 1980 or
1985; it will certainly be less than the estimated uncontrolled loss of
~lOO metric tons, possibly amounting to no more than one-half..
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It is not possible to assign the volume of tankage at petroleum
refineries, tank farms, and bulk terminals which will in the future
be dedicated to the storage of leaded gasoline. However, it is expected
that the storage, and the losses, will decrease proportionally to the
decrease in consumption, so that losses of lead alkyls will diminish
significantly. If the decrease is proportional to average lead contents
(0.5 versus 1.4 g/gal), the 1977 loss of 21 metric tons per year will
decrease to only about 7 metric tons of lead per year by 1980, and
continue thereafter at about that level.
Losses of leaded gasoline at service stations represents a loss of
organic lead in the vapor phase, to which in previous years only a small
segment of the general population, service station attendants, would have
been exposed. Although the number of service stations has been decreasing
in recent years, there were still approximately 176,000 in 1977 (National
Petroleum News, 1978). Now, however, with the increasing trend toward
self-service automobile refueling, a large segment of the general popula-
tion is exposed. Percentage of self-service gasoline motorist market
share has increased from about 15 percent in January, 1975 to 40 percent
in December, 1977 (National Petroleum News, 1978), and is forecast to
continue to increase. Since there were an estimated 114,000,000 automobiles
registered in 1977 (National Petroleum News, 1978), conceivably 45 million
drivers could be exposed to lead alkyl fumes while refueling their cars.
Few studies of ambient alkyl lead air concentrations around service
stations appear to have been conducted. Harrison, et al., (1975) determined
an organic lead level of 0.59 ug/m 3 six meters from a gaoline pump (See
Section 5.3.2.2.1).
5.2.2.2.3 ConsumPtion--The use of lead in gasoline antiknock fluids
is a totally dissipative use as well as one which is totally dispersed;
there are no regions of the United States which are free from this source
of lead. However, the distribution, being a function of automobile use,
is population-related and hence is concentrated in metropolitan and urban
areas.
The emissions of lead from the combustion of leaded gaso1ines con-
constitute by far the largest introduction of lead into the atmosphere,
almost four times as large as all other atmospheric emissions combined.
The annual down~vard trend after years of steady increase, but in 1977
the amount was estimated to still be nearly 155,000 metric tons. (In
the peak year, 1970, consumption exceeded 220,000 tons).
Although not all of this is emitted directly to the a7mosphere, 7h:
bulk of it is, as both fine «0.5~) and coarse (>0.5~) par71cles. Hab1b1
(1970) showed approximately 10 percent of the exhaust part1cles to be
large "gritty" ones of 0.3 to 3 mm (300 to 3000~) in size, which fell to
the ground within a few (5 to 6) meters (16 to 20 feet) of the.c~r. The,
finer particles remain suspended for longer periods, but a def1n1te gra~1ent
with distance has been shown by numerous investigators, so that these f1ner
133
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particles are also concentrated
«O.lll) can remain suspended in
and thus can travel substantial
as discussed in Section 8.2.
near roadways.
the atmosphere
distances from
The very fine particles
for very long periods
the original sources,
Vehicle age (mileage) markedly influences the nature of the emissions:
these tend to be of lower quantity and smaller in size when a car is new
,
but both increase with mileage. Ter Haar, et aI, (1972) found that the
mass median diameter (MMED) of particles was about 1 Il at 7,250 miles, about
2 Il at 16,500 miles, and about 41lat 21,150 miles. Also, they estimated
that over the lifetime of the car, about 75 percent or more of the lead
burned was exhausted, 35 percent as fine particles, and 40 percent as
coarse. The remainder of the lead consumed deposited in the engine and
exhaust system. Engine deposits, e.g. those on the cylinder walls,
would transfer to the lubricating oil and be removed when the oil is changed.
Habibi, et al., found that about 10 percent of the lead was retained in the
oil and oil filter. Thus, waste oil is also an important route of dispersion
of lead to the environment. Most of the remaining 15 percent unaccounted for
is presumed to remain in the exhaust system.
Taking the estimate that the gasoline consumed in 1975 contained 162,800
metric tons of lead (Table 4.16) and assuming that of this quantity 75 percent
was exhausted and 10 percent was transferred to the lubricating oil, calculated
exhaust emissions were 122,100 metric tons, with another 16,300 metric tons
contained in the lubricating oil.
In 1975, approximately 50.1 million barrels (2.1 billion gallons) of
lubricating oil were sold in the United States (National Petroleum News,
1978). According to an estimate by Maugh (1976) about half of the lubri-
cating oil was consumed in use, discarded with filter cartridges, or lost
through leakage. He attributes to the Environmental Protection Agency
the following estimate of the fate of the 4.5 billion liters (1.2 billion
gallons) recovered:
Billions of
Liters
Millions of
Gallons
Percent
Burned as fuel
Used in road oil
Rerefined
Unaccounted for
and asphalt
2.26
0.76
0.42
1.10
4.54
600
200
no
290
1200
50.0
16.7
9.2
24.1
100.0
Automotive engine oils represented only about 38 percent (797 million
gals) of the total 2.1 billion gallons of lubricating base oils sold in the
United States in 1975 (National Petroleum News, 1978). Except for these oils,
none of the other lubricating oils are exposed to lead alkyls. Also, while
lead naphthenate is added to some lubricating oils as a detergent (U.S.
Environmental Protection Agency, 1977b), its use in engine oils is small
enough, relative to lead pickup, to be disregarded. Thus, with respect to
waste oils, only automotive engine oils are regarded as significant carriers
of lead, and the following estimate considers only automotive engine oils.
134
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The role of waste oil in the entry of lead to the environment can be
estimated with the assistance of several assumptions. The assumption of Maugh ,
that one-half of the oil added is consumed in use, lost through leakage, or
discarded with the filter cartridge appears reasonable and is adopted. (The
fraction discarded with the used oil filter is a contribution to solid waste).
Total engine oil recovered is then 398,500,000 gallons (1,355,400 metric tons).
These waste automotive lubricating oils are characterized by lead contents
ranging from 800 to 11,200 ppm with an average value variously quoted as 6,000
to 10,000 ppm (0.6 to 1.0 percent) (U.S. Environmental Protection Agency, 1977a).
The total lead content of the recovered oil (using an average concentration
of 10,000 ppm) is estimated to be approximately 13,550 metric tons. Assuming
that its disposition is distributed as estimated by Maugh, the disposition
of this lead would be as follows:
Metric Tons
Burned as fuel
Used in road oil
Rerefined
Unaccounted for
and asphalt
6,800
2,250
1,250
3,250
Available information on lead emissions from waste oil burned as fuel
indicates that about 50 percent is emitted with the flue gas during normal
operation (U.S. Environmental Protection Agency, 1977a) providing an estimate
that about 3,400 metric tons of lead are emitted. The other 3,400 tons in
the oil burned as fuel is presumed to report to the ash, and is disposed
of in a landfill.
It is estimated that the major portion of the lead in the waste oil rere-
fined would appear in the rerefiner's sludge, which is largely lagooned. There
remains about 3,250 metric tons of lead in waste oil unaccounted for, with
likely final fates including sewering, landfill, incineration, or wasting
to surface waters. The most mobile of these quantities of lead is the approx-
imately 3,400 tons estimated to be emitted to the atmosphere from combustion
of waste oil as a fuel. The next most mobile portion would most likely be
the parts of the 3,250 tons unaccounted for that are incinerated or released
to surface waters. That portion released to municipal sewers would be partly
abated by sewage treatment, with a portion going to sewage slude (discussed
elsewhere in this report). The least mobile portions of the lead in waste
oils would be those in landfilled ash, road surfacing, or that directly
disposed of to the land.
5.2.2.3 Lead Oxides and Pigments--
The path of lead-containing pigments and lead oxide through industrial
processing, compounding, consumption, and disposal is complex and not com-
pletely documented. Pigments constitute a completely dissipative use of
lead as do some uses of oxides, while the use of lead oxide in batteries
is largely nondissipative.
The production of the oxides, i.e., litharge (PbO), red lead (Pb304),
and lead dioxide (Pb02) are all furnace oxidation processes and involve the
collection of the product inbaghouseswith some potential for emissions of
lead oxides to the atmosphere but little or no potential for water pollution
135
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or solid waste. Because of the value of the products and for health reasons,
these emissions are generally well controlled. Annual emissions of lead to
the air from oxide production in 1975 were estimated to be 100 metric tons.
(U.S. Environmental Protection Agency, 1977a). Oxide production is performed
by battery manufacturers, pigment producers, and lead oxide is one of the
forms of reclaimed lead produced by secondary metal processors. One of the
products produced by furnace oxidation is the "black" oxide which is actually
a mixture of elemental lead metal particles and litharge (PbO). All black
oxide and the bulk (on the order of 80 percent) of litharge (PbO) is used in
battery manufacture. Some red lead (Pb304) is also used by battery manufac-
turers.
The losses of lead from oxide production are principally
emissions to the air, with essentially no estimated loss to the
the losses disposed to the land being included in those general
attributed to the secondary lead industry.
those
water and
losses
The production of basic lead sulfate (white) pigment also involves a
thermal process (See Figure 4.13) with the product collected in a baghouse
and handled in similar fashion to the oxides. The production processes
for other lead pigments, basic lead carbonate (white lead) and the lead
chromates (yellow, orange, and green), involve aqueous chemical processes
with little potential for emissions to the atmosphere, but some potential
for generation of wastewaters. The review of wastewater discharges from
these operations included in the development of water discharge limitations
for the inorganic chemicals segment of industry concluded that, with no
identifiable exceptions, the pigments industry discharged all wastewaters
to municipal sewer systems (U.S. Environmental Protection Agency, 1973b).
In this context, insufficient data were developed to identify how many
pigments manufacturers produced lead pigments (estimated as no more than
a dozen in this study) or what the specific or generalized rates of dis-
charge or contained lead might be.
lead
tons
A survey of wastes destined for land
in such wastes from pigment operations
for the year 1974 (Versar, 1977).
disposal estimated the contained
to amount to about 200 metric
The second largest segment of the flow of lead oxides to further
compounding or consumption is the litharge consumed in the ceramics industry
(on the order of 30,000 tons in 1975). Reportedly, this lead oxide is used
in glazes, the preparation of which involves the mixing of the lead oxide
into a water-based suspension (with or without other components), and the
spraying of the mixture onto the surfaces of ceramic ware, followed by
firing in an oven to produce a fused coating. The losses of lead during
spraying have not been quantified, but constitute an occupational exposure.
No basis is available for an estimate of the lead losses from this industry,
but at least one case is known in which lead appeared in the untreated
wastewaters in maximum and average concentrations of 1800 and 1160 ppm,
respectively (National Commission on Water Quality, 1975). The wastewater
was being treated, principally via flocculation and clarification to remove
lead in the form of suspended solids, but no discharge flow or final dis-
charge concentrations were reported. .
136
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Yet another route of consumption for lead oxides is in glass making.
Leaded glass is used in television tube manufacture, making of decorative
pressed and blown glassware, and in special glass used for radiation shielding.
It is estimated that these types of glass account for approximately three
percent of total glass production. The major release of lead to the environ-
ment from glassmaking occurs as an emission to the atmosphere during handling,
weighing, charging, and melting in the glass-making furnace. This emission
has been estimated to amount to 56 metric tons for the year 1975 (U.S.
Environmental Protection Agency, 1977a). Releases of lead in wastewater
from glass-making result principally from grinding and etching of lead glass
and are estimated to amount to 0.2 to 2 metric tons per year on the basis
of the information available (U.S. Environmental Protection Agency, 1974c).
No basis exists for the estimation of lead contained in industrial wastes
destined for land disposal. Depending on industry practices, air pollution
control residues and water pollution control, sludges disposed of to the
land might amount to more than the estimated releases mentioned above. Most
of the leaded glass (except radiation shielding) is estimated to eventually
reach municipal or industrial landfills.
Quantities of litharge (on the order of 6,000 metric tons per year)
are used in the making of rubber. The oxide is added to some rubbers in
proportions of approximately one to ten percent by volume to accelerate
the vulcanizing reaction. Litharge is added most often to rubber serving
as insulation on wire. No specific or noteworthy releases of lead to the
environment are judged to be associated with this use of lead, although
the use is totally dissipative. The final fate of such insulation is
judged to be divided among a minor portion of recycle, some incineration,
and disposal to the land.
5.2.2.4
Inorganic Lead Compounds--
The largest identifiable class of inorganic lead compounds, other
than oxides and pigments, discussed in Section 5.2.2.3, includes the
stabilizers used in plastics, principally in PVC polymers. Usage 6f
lead in the plastics industry in 1976 was estimated at approximately
8,200 metric tons per year (Modern Plastics, 1976). The estimated
8,200 tons of lead so consumed would be processed first into the
indicated compounds, and then be involved in the final formulation
and compounding of the plastic product. In view of the lack of de-
finitive information concerning the environmental aspects of any of
the specific industrial processes involved, no basis exists for the
calculation of lead losses to any media. It may be reasoned that some
losses of raw or input materials occur in any industrial process, and
that these generally are at least on the order of one percent of the
input, and that the consumption of 8,200 tons of lead would result in
at least 80 tons of losses in some form during manufacture. It could
be further reasoned that since the stabilized compounds are largely
produced in aqueous chemical processes, the most probable form of loss
would be that to wastewaters. However, the manufacturing plants pro-
ducing the compounds and the plastics mostly discharge wastewaters to
municipal sewer systems where other pollutants (e.g., biological and
chemical oxygen demand) are generally more significant than trace metals.
137
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The next large~identifiable portion of lead involved in any
class of compounds is an estimated 1,500 tons of lead consumed in paint
driers. Reasoning similar to that above would have to be applied to
these compounds in that they also undergo various compounding steps, i.e.,
conversion of lead to a specific compound, and formulation of the drier
into paints. However, the forms of release of paint driers would include
losses during the application of paints as well as losses during chemical
and paint compounding.
Lesser tonnages of lead (i.e., on the order of the 133 metric tons
assigned to the classification "Miscellaneous Chemicals" by the Bureau of
Mines) are consumed in preparation of other listed compounds (except oxides
and pigments). As noted in other portions of the text, some compounds are
produced in reagent grades and small quantities for analytical use. Losses
during such processing would be estimated to be proportionately smaller
than for bulk processing of industrial grades of compounds, and probably
are insignificant.
It can be concluded from the discussions in this and the preceding
section that essentially all inorganic lead compounds, except for a portion
of the oxides, are eventually dissipated through attrition or being disposed
of as waste; the lead in these compounds is never recycled.
5.2.2.5
Miscellaneous Uses of Metallic Lead--
The nature of the uses of metallic lead is such that individual
emission losses from their manufacture or use are modest, and they pale in
comparison to the quantities of lead introduced into the biosphere through
the combustion of leaded gasolines. Additionally, relatively small number
of point sources is involved so that the environmental impacts are localized,
5.2.2.5.1 Cable covering and rubber hose manufacture--As described
in Section 4.3.5.4, there .are two types of lead use in the manufacture of
electric cable; in one lead provides the final sheath, in the other it
supplies the necessary restraint while a rubber base covering is vul-
canized, and is then removed for recycle to the process.
The process of applying lead sheathing to preassembled electric
cable involves the manipulation of lead in and around machinery so as to
form a continuous envelope of lead around the cable. The sheathing may
be entirely metallic or a combination of lead and plastic, depending
on the degree of protection or the properties desired in the composite
product. The maintenance of molten lead supplies or baths and the routing
of the lead through the forming machinery result in the generation of fume,
particulate, and slivers which result in not only high exposure of the
machine operators but an estimated annual emission of 113 metric tons of
lead to the atmosphere. Cable covering processes normally do not incorporate
particulate collection devices (U.S. Environmental Protection Agency, 1977a).
Because of the non-aqueous nature of the process and the available opportu-
nity of returning scraps and wastes to the melting pot, lead in wastewaters
or other forms is estimated to be zero or negligibly small.
138
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Rubber sheathed cable and rubber hose are made in much the same
fashion. A lead sheathing is applied to the assembled uncured components
so that the lead sheath acts as a temporary pressure vessel or custom die
to keep coils of hose under pressure during curing or valcanizing. After
curing in a steam pressurized autoclave, the lead sheath is stripped and
the lead recycled to the sheathing operation. Lead appears as a wastewater
pollutant in the condensate from the autoclave when it is blown-down or
emptied. Based on information available from effluent limitation Guidelines
studies, the lead may occur in concentrations as high as 67 mg/l in the
raw wastewater. Using information from the guidelines studies, it is
estimated that the total potential release of lead from rubber hose manu-
facture is about 2.5 metric tons. This potential release would be associated
with approximately 30 plant sites, about 26 of which are estimated to dis-
charge to municipal sewers (U.S. Environmental Protection Agency, 1974d).
If the plants achieved the limits of lead discharge specified by the Effluent
Limitations Guidelines through pretreatment of wastes, the discharge to the
sewers would be reduced to about 60 kilograms of lead per year. The 2.4
metric tons removed from the wastewater would presumably be disposed of as
a sludge to a suitable landfill.
5.2.2.5.3 Can Manufacturing--Can making, actually the soldering and
cleaning or smoothing of the soldered seam, involves the maintenance of solder
baths, the handling of the molten metal and the wire or cloth brushing of the
frozen solder seam. These operations produce emissions to the atmosphere
of fume and particulate estimated to amount to 60 metric tons per year in 1975
(U.S. Environmental Protection Agency, 1977a). The potential for losses of
lead in wastewater or in wastes destined for land disposal is considered to
be zero or" negligibly small.
However, as will be developed later in this report,
food cans comprises one of the major sources of additions
of lead, but is one fo~ which alternatives are available.
ly speaking, an emission, it is one of the most important
of lead into the environment.
the use of solder in
to man's body burden
Though not, strict-
facets of the entry
5.2.2.5.4 Miscellaneous uses of metallic lead--Lead has numerous
miscellaneous uses, which are generally characterized by the consumption of
a relatively small tonnage, but for which lead fills a niche not easily filled
by competing materials. Most of these applications utilize the high density,
corrosion resistance, malleability and easy formability, or non-sparking
chacter of this metal. Included are the use of architectural sheet and foil
for flashing and sound proofing, and for linings of tanks and vessels for
purposes of corrosion resistance in chemical process vessels (a recent
noteworthy example is linings of electrostatic precipitators for cleaning
corrosive industrial gas streams. Lead plate is used for spark-proof flooring
in explosives plants and other hazardous areas. Lead foil, sheet and plate,
and thick-walled lead containers are used for radiation shielding in nuclear
applications~ and around industrial and medical x-ray equipment. A high-lead
glass is used for hot-cell windows. Lead is used for weights and ballast on
139
-------
automotive wheels, ships, rotating machinery, and as counterweights on fork-
lift trucks and other machinery, and in molten metal baths as for heat treat-
ing of steel wire. In essence, there are numerous uses of lead in prefabric-
ated and/or massive form with which there are associated no or negligible
losses of lead to the environment during use, and from which the lead, being
in recognizable, fairly massive form, will be largely reclaimed through re-
cycling to the secondary lead industry.
The major release of lead to the environment associated with these uses
is that occuring during the original melting and casting of the items to
shape. Subsequent fabrication of rolled sheet and foil are dry mechanical
processes in which releases are zero or negligibly small.
5.2.3
Indirect Sources of Lead
The sources of entry of lead to the environment described in
Sections 5.2.1 and 5.2.2 have all dealt with some segment of the lead industry
or with other industries in which lead products are utilized in some beneficial
fashion. There are, in addition, a number of sources of lead entry into the
environment where the lead is present in a process only as impurity or trace
component. While most of these processes have relatively low specific emission
factors, these are frequently associated with very large tonnages of process
materials, with the net result that some of the emissions are significant.
5.2.3.1
Iron and Steel Production--
Releases of lead from the iron and steel industry occur due to the
presence of lead in iron ore, coking coals, and in scrap which is remelted.
As indicated above, even trace contaminants produce substantial emissions
when multiplied by the enormous tonnages of this industry, as illustrated by
estimates of 1975 production (U.S. Environmental Protection Agency, 1977a):
Millions of Metric Tons
Grey iron
Sinter
Coke
Blast furnace
Basic oxygen furnace
Open hearth furnace
Electric arc furnace
16.7
27.9
43.8
72.5
65.1
20.1
20.6
The lead in coal appears as an emission from coke ovens with the net
emitted lead content estimated as 11 metric tons for the year 1975. The lead
content and emission factor is very low per ton of coal or coke, but the high
tonnage of coke production results in an appreciable estimated emission of
lead. Similarly, the presence of lead as a trace impurity in iron ore,
combined with the very large tonnage of iron ore processed results in another
appreciable estimated net emission of 18 metric tons of lead from iron ore
sintering operations. These sintering operations are thefirs~ ~igh-
temperature steps in the processing of the ore and the lead is volatilized.
140
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Similar reasoning applies to the presence of an appreciable net estimated
emission of 91 metric tons of lead from blast furnaces, wherein the coke and
sintered ore are processed at a successively higher temperature resulting in
continued volatilization of the residual lead (U.S. Environmental Protection
Agency, 1977a).
Lead is also emitted to the atmosphere from the various types of melting
furnaces in the steel (basic oxygen,: open hearth, and electric furnaces) and
gray iron (cupola and electric furnaces) industries. These emissions are
principally attributable to the presence of lead in scrap materials charged
to these furnaces. Scrap makes up various percentages of the charge, ranging
from 25 percent of the total iron charge up to 100 percent of the charge in
some electric furnace op~rations. The lead emission is attributed to the
presence of lead in automobile scrap (solder) and red lead paint on scrap
derived from ships, bridges, structures, and to a lesser extent, other scrap
containing solders, galvanizing and/or enamels. The total estimated net
emissions from these scrap remelting furnaces is approximately 1,564 metric
tons for the year 1975 (U.S. Environmental Protection Agency, 1977a).
While it may be reasoned that the principal source of wastewaters in
primary steel operations is air pollution control, and that wastewaters or
dry residues from air pollution control would thus show some lead content,
there is insufficient basis for estimating the losses of lead to water and
in land-destined wastes. Various individual analyses of process water streams
within steel plants show lead contents above intake waters but lead is not a
major pollutant controlled by any specific discharge regulation applicable to
wastewaters from the steel industry. Similarly, baghouse dust from electric
furnace operations (destined for land disposal) likewise show appreciable
concentrations of lead, but no basis exists for an estimate of the aggregate
lead released to water and land from steel melting operations. (U.S.
Environmental Protection Agency, 1974a).
Lead is also an appreciable emission, estimated at 30 metric tons in
1975, to the atmosphere from the production of ferromanganese. The lead is
present in manganese ore concentrate which is charged to electric furnaces
for smelting (with coke). The estimated lead emission is the net lead emitted
after control devices; an associated lead content is present in the dust
collected by control devices which are predominantly baghouses. The dust is
typically disposed of to a landfill because currently neither the manganese
nor the lead content are economically recoverable. No basis exists for an
estimate of the aggregate total of the lead content of these dusts which are
discharged to landfills.
5.2.3.2
Cement Manufacture--
Lead is present in cement in trace concentrations and is emitted to the
atmosphere during handling, transport, and especially from cement kilns. The
estimated net emission of contained lead was 312 metric tons in 1975 (U.S.
Environmental Protection Agency, 1977a). Review of the Guidelines Development
141
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Document for the cement industry gave factors of about 20 percent of plants
practicing dust leaching, wet slurry disposal (with possible discharge of
supernatant) or wet air pollution control, all of which allow a potential
release of lead to wastewater discharge (U.S. Environmental Protection Agency,
1973a). Using the unit waste load given for lead (0.99 grams per metric ton
of product) for 20 percent of production results in an estimated potential
release of lead in process wastewaters of approximately 14 metric tons for
68 million metric tons of production. This estimate does not include consider-
ation of runoff flows. The highest concentration (not specified) of lead
encountered was for wastewaters from a plant using oyster-shell marl for raw
material.
The intrinsic lead content of the raw materials of the cement industry
would be volatilized during the clinkering process in the kiln, with some
lead reporting in the wastewaters of plants where water contacts the kiln
dust. In other plants (an estimated 80 percent of the industry) the dusts are
returned to quarries, slurried to on-site lagoons, or hauled away by contract-
ors (presumable for land disposal). No data base is available to allow a
estimation of either the amount of dust disposed of to landfills or the lead
content of this dust. High alkalinity is the reason the dust is wasted, a
condition which would favor the minimum solubilization of any lead present.
(U.S. Environmental Protection Agency, 1973a).
5.2.3.3
Combustion of Fossil Fuels--
Lead is a trace metal impurity of highly variable occurrence in coals.
Gluskoter, et al., (1977), in their exhaustive study of the occurrence and
distribution of trace elements in coal, reported on the analysis of 165 U.S.
coals. Lead concentration ranged from 4 to 218 ppm; with considerable
differences between coals from different regions:
Coal Samples
23 Eastern Appalachian
114 Illinois Basin
28 Western
Lead, ppm
Arith. mean Geom. mean
5.9
32
3.4
4.7
15
2.6
It is evident from the above that much more data would be needed than are
available in order to estimate a weighted average lead content for the
coal burned in a given year. Most coal currently burned comes from Eastern
Appalachia and the Illinois Basin, and for purposes of calculation the two
are arbitrarily averaged (geometric means) at 10 ppm.
Annual U.S. coal consumption is currently of the order of 450 million
metric tons (500 million short tons), estimated (at 10 ppm) to contain about
4,500 tons of lead. On the basis of the study by Klein, et al., (1975), on
the pathways of 37 trace elements through a coal-fired power plant, approx-
imately 97.5 percent of the lead was trapped in the fly ash and- the bottom
ash, with only about 2.5 percent escaping. However, the plant tested was in
the exemplary class, and 95 percent is estimated to be a more realistic
national average. Using this latter value, lead emitted is estimated to be
approximately 225 metric tons/year.
142
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The other 95 percent of the lead, of the order of 4,275 metric tons
(4,700 short tons) remains with the ash, and in larger installations, is generally
disposed of to an ash pond.
Fuel oils also contain traces of lead; the EPA extimate of lead emissions
(U.S. Environmental Protection Agency, 1977a) was a nominal 100 metric tons
per year.
5.2.3.4
Solid Waste Incineration--
Quantitative data on the quantities of solid waste incinerated and its
lead content are lacking. One estimate (U.S. Environmental Protection Agency,
1977a) was that about 1.6 kg (3.5 Ib) of domestic refuse and garbage is
collected per capita per day in the United States. With a U.S. population
of about 210 million in 1975, total domestic solid waste is estimated to
have been approximately 123 million metric tons. In 1975 an estimated 16.5
million metric tons were burned in municipal incinerators. Based on limited
emission data, lead emissions were estimated at 1,170 metric tons (U.S. Envi-
ronmental Protection Agency, 1977a). These emissions arise from many of the
components of municipal refuse including most of the dissipative uses of
lead: pigments in paints, dyes, and inks, lead in plastics, rubber, insula-
tion, cans and other soldered components, and other forms. An important, but
somewhat uncertain, quantity is the lead in waste lubricating oil from auto-
mobiles. A substantial amount of this is discarded to solid waste and finds
its way to an incinerator.
5.2.3.5
Sludge Disposal~-
Lead is reported present in municipal sewage sludges in the range of
10 to 26,000 parts per million, with a median concentration of 500 parts per
million (Page and Chang, 1975). One EPA estimate is that 5.6 million dry
metric tons (6.2 million short tons) of municipal sludge are being produced
and disposed of in one manner or another each year. At the median concentra-
tion this represents about 3100 metric tons of contained lead. It may be
noted that this also represents the reappearance of some of the lead emissions
to water described in previous pages, with lead from used motor oil perhaps
the largest contributor. The estimated general breakdown for disposal is as
follows (U.S. Environmental Protection Agency, 1976c):
Method
Ocean Disposal
Incineration
Landfill
Land Application
(croplands) (20)
(other) ( 5)
Percent of Total
Municipal Sludge
15
35
25
25
Millions of
Metric Tons
0.8
2.0
1.4
1.4
100
5.6. -
143
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Ocean disposal has been favored by a number of large coastal cities.
The disposal of sludge to the ocean has been shown to result in elevated
l~vels of lead (and other metals) in bottom sediments around the point of
d1sposal. In one study of silts, sediments and sludges in the Los Angeles
and Southern California area, marine sediments affected by flows and sludges
from an urbanized area show lead contents 30 or more times those in natural
coastal sediments not affected by sludge or urbanization. The impact of this
release has produced no notable effects in terms other than the elevated lead
concentrations in the silts, i.e., no preferential concentrations in man or
aquatic organisms have been noted (Young, et al., 1973). However, some heavy
metals are known to bioaccumulate to where they interfere with reproduction
or cause toxic effects to certain marine organisms; those of immediate concern
are cadmium and mercury. Efforts are currently underway to phase-out most of
the ocean dumpers and pipe dischargers by 1981 or soon thereafter (U.S.
Environmental Protection Agency, 1976c).
Incineration is the most commonly used disposal option, and many incinerator
are located in large urban areas. This is related in part to the fact that
incineration accomplishes the greatest volume reduction (to 10 to 30 percent
of the original matter dry volume) and the locations with the largest inputs
of sludge are generally the areas with the least available space for disposal.
The release of lead to the atmosphere from sewage sludge incineration
may be estimated on the basis of a study of selected sites performed to deter-
mine the impact of anticipated increases in incineration if ocean dumping
were to be curtailed. All stack tests were on incinerators with wet scrubber
controls and showed net total particulate emission rates of 0.6 to 2.4 kilo-
grams per metric ton of charge (Battelle-Columbus, 1973). Assuming the
particulates also contained the median lead concentration of 500 ppm, the
1,200 to 4,800 metric tons of particulates emitted would contain 0.6 to 2.5
metric tons of lead; a negligible quantity. The balance of the lead in the
sludge would appear either in the ash or the air pollution control dust or
sludge, all of which would presumably be sent to a municipal landfill.
Approximately 25 percent of municipal sludge is disposed of by land
application; this disposal option has been preferred by communities with
suitable available land, generally inland cities and smaller rural communities.
Reportedly, trace metal concentrations may accumulate in soils so treated and
some metals may produce toxic effects to plants growing in such soils. How-
ever, in actual. field operations and in laboratory tests in which some metal
toxicity has been observed in terms of reduced growth, lead has not been
shown to be the cause of the toxicity. Interactions of lead with plants is
discussed in Section 6.3 and lead in foods is discussed in Section 8.5 and 8.6.
144
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7.0
EFFECTS ON HUMANS
7.1
SUMMARY
The metabolism of lead is concerned with uptake and absorption, transport
and distribution, and elimination.
Lead may be absorbed into the body by inhalation, ingestion, skin ab-
sorption, or placental transfer. Various studies indicate that approximately
37 - 50 percent of inhaled lead is deposited in the lungs. This amount is a
function of the size and solubility of lead particles as well as rate and depth
of breathing. Approximately 10 percent of ingested lead is absorbed by the
gastrointestinal tract in adults. This rate is thought to be much higher in
young children. Studies have also indicated that a reduction in dietary cal-
cium increases gastrointestinal lead absorption. It appears that inorganic
lead salts are not absorbed through the skin to any significant extent; how-
ever, this has not been studied extensively. Organic lead compounds, in
contrast, are absorbed significantly via the skin. Placental transfer of
inorganic lead has been widely reported. Exposure of the embryo or fetus to
lead via placental transfer has greater potential for injury than does expo-
sure during adulthood.
Following absorption, essentially all the lead in the body is associated
with the erythrocytes; it is then distributed to various tissues throughout
the body. More than 90 percent of the body burden of lead is a relatively non-
diffusible fraction in the skeleton. The concentration of lead is high in hair
as well as in bone, intermediate in liver, kidney and aorta, and lowest in the
heart and brain. The absorption, distribution and elimination of lead results
in an equilibrium state when exposure from all sources is relatively constant.
In this equilibrium state, blood lead and urine lead levels fairly accurately
reflect total body burden of lead. Under stable environmental conditions blood
lead levels of general populations appear to be fairly stable. They tend to be
higher in urban than in rural populations and in males than in females. One
study has suggested that concentrations of lead in bone and in most soft tis-
sues, such as the kidney, pancreas, and liver, rise until around the fourth or
fifth decade of life and then reaches a plateau or begins to decrease. Other
studies, however, have reported no such decline in the elderly.
The principal, routes of elimination of lead from the body are through the
feces and urine. Secondary routes are in sweat, milk, hair and desquamated
skin. Fecal lead excretion is greater than excretion of lead in the urine.
The toxicological effects of lead can be viewed at three levels. First,
there is the problem of sporadic episodes of acute lead intoxication; these are
usually accidental or the result of ignorance of the danger of lead.
192
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Second is the problem of clinical and subclinical intoxication of large
numbers of children in urban ghetto areas who are living in pre-World War II
housing. The third problem of concern in the toxicology of lead is the ques-
tion of the possible harmful effects of undesirably high body stores of lead
in general populations.
It has been shown that many body organs and systems are adversely affected
by lead. However, much of what is known concerning these effects has been in-
dicated only by isolated cellular or subcellular systems. The implications
for the health of man are uncertain in such cases.
The critical effect of inorganic lead compounds is adverse interference
with heme synthesis and, according to current knowledge, the critical organ
of inorganic lead effect is hematopoietic bone marrow. Short-term inhala-
tion of organic lead compounds results in central nervous system manifesta-
tions, suggesting that this is the critical organ of organic lead.
Lead appears to have an adverse effect on reproductive ability. Various
animal studies show that parents exposed to lead had increased numbers of
breeding failures, reduced litter size and weights of offspring, and reduced
survival rates of offspring. Teratogenic effects of inorganic lead in animals
are manifested by congenital skeletal malformations. Evidence concerning
the relationship between lead and chromosomal abnormalities in humans is not
definitive. Studies on chromosomal aberrations in workers professionally
exposed to lead seem to favor a positive relationship.
Renal, adrenal, thyroid, prostate and pulmonary adenomas, renal adeno-
carcinomas and testicular carcinomas have been found in rats and mice given
lead phosphate and lead acetate via dietary and parenteral routes. In con-
trast, epidemiological evidence to date does not indicate that lead has a
similar carcinogenic effect on humans.
Lead poisoning in children is a serious but preventable problem that
can be controlled in any of the three following ways: eliminating the
source of lead; controlling the means by which lead enters the body; or
finding and treating cases early. The sequelae of symptomatic lead poisoning
include seizure disorders as well as various behavioral and functional dis-
orders such as hyperactivity, impulsive behavior, prolonged reaction time and
slmved learning ability.
The extent of the effects of lead poisoning in children is dependent on
several factors. Children tend to exhibit more severe effects from lead poi-
soning when exposure is during a period of rapid growth. It appears that
the brain is especially vulnerable during growth spurts. Age also seems to
influence rate of gastrointestinal absorption of lead. In addition, both
dietary components and dietary deficiencies alter gastrointestinal lead
absorption rates.
Lead exerts its effects in the hematopoietic, neurologic and renal systems.
Among children, renal damage associated with severe lead intoxication is fre-
quently reversible. Permanent renal damage does occur among adults having
chronic (occupational) overexposure to lead. No published data are available
to suggest t~at renal damage occurs in asymptomatic cases.
193
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Considerable controversy exists concerning conflicting reports of neuro-
logical damage occuring in asymptomatic or mildly symptomatic cases. There-
fore, the hematopoietic system is considered the critical site for the effects
of lead.
In addition to laboratory studies, and clinical studies of small groups
of lead intoxicated children, a wide variety of epidemiologic studies have
sought to describe and quantify the health effects of lead in various general
populations. Although both gastrointestinal and respiratory absorption of
lead have long been recognized as primary routes of exposure, epidemiologic
studies have tended to focus upon the latter, presumable due to the relative
ease with which the respiratory exposure level of populations can be character-
ized (based on suitable environmental monitoring data). Deriving reasonably
accurate estimates of dietary lead intake has proven more difficult due to a
wider range of variability among individuals with respect to daily caloric
intake and composition of the diet. Thus, studies of the effects of dietary
lead exposures tend to be of the laboratory type and involve intensive obser-
vation of very small groups of individuals. Moreover, past studies of
metabolism of dietary lead in normal subjects have been confined almost ex-
clusively to adult males.
Studies of the effects of respiratory lead exposure have been conducted
in three general types of settings: (1) general populations, (2) groups sub-
jected to some unusual circumstance or mode of exposure (i.e., "intermediate
level" studies) and (3) studies of occupational groups. These three types
of populations represent a gradient of exposure from fairly low to moderate
to perhaps dangerously high.
Detailed examination of several studies of general populations is pro-
vided in the following sections. Consensus from studies of diverse general
populations suggests that the contribution of air lead to blood lead is ap-
proximately 0.6 - 2.0 ~g Pb/dl per 1 ~g/m3 in air. This relationship appears
to hold true in a variety of communities having ambient air lead in the range
from a few hundredth of 1 ppm to approximately 8-10 ppm. (See Three Cities
Study, Seven Cities Study and Azar, et al., 1975, reported below.) Many inter-
urban comparisons have failed to find significant differences in mean blood
lead levels between cities or a significant correlation between air and blood
lead levels within cities. Failure to establish such a relationship is
possibly due to the narrow range of ambient conditions studied and/or to the
relatively small contribution of air lead to total absorbed dose under the
ambient conditions prevailing at the sites investigated (generally well below
5 ~g/m3). The fact that an exceptionally well done multiple regression
analysis (Azar, et al., 1975) found only 43 percent of the variation in blood
lead is explained by air lead supports the contention that other factors,
including lead ingested from food and beverages are more important deter-
minants of blood lead.
Studies of persons regularly exposed to unusually high ambient lead
concentrations (over 10 ~g/m3 for all or part of the day) either from mobile
194
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or stationary sources have been much more suceessful in demonstrating rela-
tionships between levels of lead in air and those in blood. It is only under
these higher dose conditions that repiratory intake accounts for an appreci-
able percentage of total lead absorption. Chronic exposure to intermediate
levels of lead from mobile sources occurs among persons living in close prox-
imity to dense vehicular traffic (e.g., freeways, heavily travelled urban
thorofares) or from occupations which involve prolonged exposure to automo-
tive exhaust (e.g., policemen, taxi drivers, parking garage attendants,
mechanics). Populations residing near stationary sources of lead emissions
such as primary and secondary smelters have also been examined. Studies
conducted in each of these types of settings are reported in the text.
In general, comparisons of groups exposed to above average amounts of
auto exhaust reveal mean blood lead levels somewhat higher than control
groups not similarly exposed. Oftentimes, however, blood lead concentrations
of the heavily exposed persons lie within, or just slightly above normal
limits (with normal limits being defined as ~ 2 standard deviations of the
mean of some general population). Such findings are especially true of
studies examining groups residing near freeways or working in traffic. Groups
exposed to auto exhaust indoors, where ambient lead levels are presumably
higher, consistently reveal mean blood leads 20-40 percent higher than con-
trol goups from the general population as well as a higher percentage of
individuals exhibiting evidence of undue lead absorption (blood lead greater
than 40 ~g/dl).
Groups exposed to stationary emissions sources generally show moderate-
to-marked elevations of blood lead. Moreover, in many instances, populations
exhibit a gradient. in blood lead levels which is inversely related to distance
from the source of emissions. This type of relationship has been shown for
both primary and secondary smelter areas. Several studies focus specifically
on the possible effects on children living near smelting complexes. Results
of investigations in El Paso, Texas; East Helena, Montana; Kellogg, Idaho;
Omaha, Nebraska; Toronto (Canada) and several European countries are
discussed in the following sections. Elevated blood lead (> 40ug Pb/dl), hair
lead (> 100 ppm Pb in hair), metabolic changes (increased urinary excretion
of ALA or coproporphyrins), neurologic abnormalities (reduction in peripheral
nerve conduction velocity) or some combination of the above were considered
evidence of undue lead absorption. Children exhibited abnormalities with
respect to these parameters at all of the study sites, albeit to varying
degrees. Dust and dirt (in addition to airborne particulate) appear to be
important sources of lead intake for children living in smelter communities.
Occupational lead exposures represent the high end of the dose-response
spectrum. It is among workers who smelt, refine and manufacture lead-contain-
ing or lead-painted products that the highest and most prolonged lead
exposures are found. The clinical pattern of occupational lead intoxication
has changed in recent decades. Nowadays acute or fatal lead poisoning is
rare; today's cases are frequently diagnosed at an earlier, asymptomatic stage
based on abnormalities of biochemical, neurological, or renal function.
Despite these apparent advances, however, excessive lead absorption and its
attendant health effects remain a serious and all too prevalent occupational
195
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--
hazard in the lead industries today. Epidemiologic studies conducted between
1975 and 1976 in five major lead facilities throughout the United States
showed unacceptably high blood lead levels and symtoms of lead poisoning in
every plant studied (four secondary smelters and one lead chemicals plant).
Hematologic, neurologic, and renal damage were consistently reported. Be-
yond that, this series of investigations also provided evidence of medical
mismanagement of overexposed workers and poisoning o~ workers' children from
exposure to heavily contaminated work clothing which was taken home for
laundering. These and other findings from other epidemiologic studies of
lead workers clearly indicate that present occupational standards and work
practices do not adequately protect workers from adverse health effects.
The relationship between air lead and blood
has been the subject of several investigations.
this section in terms of the policy implications
setting more appropriate occupational standards.
lead among industrial workers
These studies are reviewed in
their findings may have for
The alkyl derivatives of lead are highly toxic compounds, which, like
inorganic forms, may also be absorbed by inhalation or ingestion. They are
readily absorbed through the skin. High solubility of alkyl lead compounds
in body fluids is the basis for percutaneous toxicity whereas the volatility
of these compounds underlies the hazard potential among workers engaged in
the production of these compounds. Persons chronically exposed to evaporating
gasoline may be at risk as well, although the requisite epidemiologic studies
to quantify this potential risk have not been conducted. Because alkyl lead
compounds are light sensitive and undergo rapid decomposition upon reaching
the atmosphere, their presence is transient and thought to amount to less
than 10 percent of inorganic lead levels. To date, no information is avail-
able on the effects of chronic, low level (non-occupational) exposure to
airborne alkyl lead.
From a toxicological viewpoint, the most significant organic lead com-
pounds are the tetraethyl and tetramethyl compounds. These compounds are
used in gasoline antiknock additives; consequently potentially toxic expo-
sures are thought to be restricted almost exclusively to the industrial sector.
Because of the known occupational hazard, extensive studies have been con-
ducted on the uptake and absorption, elimination, tissue distribution, and
toxic effects of tetraethyl- and tetramethyl lead. The results of these
studies are briefly summarized at the end of this chapter.
In addition to tetraethyl (TEL) and tetramethyl lead (TML), a number
of miscellaneous organic lead compounds find industrial uses. These include
lead soaps of organic acids such as lead stearates, tallates, naphthenates
and octoates (chiefly di-2-ethylhexanoare) produced and marketed in the United
States as paint driers. Any hazard encountered in the manufacture, handling
and use of these products is a function of the concentration of lead actually
present, the solvents contained and their activity as oxidation catalysts.
Although little data are available regarding the specific toxicities of
these "miscellaneous" compounds, in general, the LDSO values appear to be
several orders of magnitude higher (less toxic) than those of TEL and TML.
The behavior of these lead soaps in biological systems also appears more
similar to inorganic lead than to that of TEL and TML.
196
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7.2
BIOLOGICAL PATHWAYS
7.2.1
Uptake and Absorption
Lead may be taken into the body by inhalation, ingestion, skin absorp-
tion, and placental transfer.
7.2.1.1
Inhalation--
The uptake of any inhaled particulate material is a function of its
size and solubility. When inhaled, the small lead particles (less than 1 to
2 micrometers in diameter) tend to be retained by the respiratory tract to
be absorbed or coughed up and swallowed later. Particles of hygroscopic
material are deposited in the lungs in a higher percentage than non-
hygroscopic ones because as they take up water from the moist air in the
respiratory tract their size increases. Deposition of inhaled particles
will also vary with rate and depth of breathing. Minimum deposition occurs
during rapid, shallow conditions of respiration (Nozaki, 1966). Kehoe (1961
a, b; 1964) found that the deposition of lead sesquioxide particles in the
lung ranged from 35 percent of the amount inhaled when the mean particle
diameter was 0.05 micrometer, up to 54 percent for a diameter of 0.075
micrometer. When the mean diameter was approximately 1 micrometer, reten-
tion was 43 to 53 percent. Kehoe (1961 a-d) estimated that 40 percent of
the lead (as lead sesquioxide) deposited in the airways were transferred to
the gastrointestinal tract. This transfer probably involved particles ap-
proximately 2.9 ~m mass median equivalent diameter (MMED) and larger
(National Academy of Science, 1972). In a study of lead retention in the
lungs of lead workers and ship breakers, Mehani (1966) found that 37 to 47
percent by weight of the inspired lead was retained in the lungs of the
lead exposed workers. These concentrations varied with severity of effort
at work, (that is, with respiratory rate), size of particles including those
of 3 micrometers, and the number of particles being retained in the mouth
and throat and either expectorated or swallowed and excreted in the feces.
In this case, 50 percent of the lead particles were greater than 2.9 micro-
meters (MMED). It is believed that the particles in this range of diameter
were transferred to the gastrointestinal tract.
from
15 :!:
Rabinowitz et al., (1974) calculated that the quantity of lead absorbed
a typical urban atmosphere (lead concentration equals 1 to 2 ~g/m3) is
3 ~g per day.
7.2.1.2
Ingestion--
The absorption of lead in the intestine depends upon age, chemical form,
dietary calcium level, Vitamin D intake, diet composition, quantity consumed,
and gastric acidity. Other studies have shown that dietary iron, copper,
selenium, and ascorbic acid levels also influence lead absorption. Vitamin
D in the diet increases the concentration of lead in the blood and in the
femur (Sobel, et a1., 1938). Reduction of dietary calcium increases the
absorption of lead. Kostia1 (1971a) found that lead retention was 1.4 times
lower in 5 to 7 day old rats fed cow's milk with calcium and phosphate
197
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additives than in those fed pure cow's milk. Six and Goyer (1972) showed
that lowering dietary lead also increases lead absorption.
Net absorption of lead from the gastrointestinal tract has been found
to be quite low in those species which have been studied, and the percentage
absorbed does not appear to be proportional to the dose. In laboratory
animals, the amount of lead absorbed from the gastrointestinal tract appears
to be much less than that in man. Net absorption of lead in sheep is approxi-
mately 1.3 percent over a range of 2 to 108 milligrams Pb/day and is quite
similar for rabbits (Blaxter, 1950). The form in which lead is administered
to animals does not appear to have a major effect on its absorption. Calves,
poisoned with a series of lead salts, showed little difference in uptake when
the lead was given as the phosphate, oxide or carbonate, or even as dried
flakes. Only galena and metallic lead seemed to be absorbed poorly (Allcroft,
1950).
Generally, the uptake of lead from the gastrointestinal tract is less
complete than it is from the lungs, assuming that the amount of lead absorbed
from the lungs is equivalent to the amount deposited (that is, 37 - 40 percent
of the amount inhaled). Experimental studies have revealed that gastro-
intestinal absorption of lead varies with age. Kehoe (196la) found that,
in adults, absorption of lead from the gastrointestinal tract is approximately
10 percent of the amount ingested. (See Table 7.1). Alexander et al.,
(1973) reported that in children, aged 3 months to 8 1/2 years, 53 percent
of ingested lead is absorbed by the gastrointestinal tract with 18 percent
retention. More recently, Ziegler, et al., (1978) found that absorption
averaged 42 percent in a group of infants and toddlers.
Rabinowitz, et al., (1975) used stable isotope and balance studies to
investigate the human uptake of dietary and atmospheric lead. Five healthy
volunteers were maintained in a hospital metabolic unit for up to 6 months
in order to assess absorption, excretion, pool sizes and fluxes of lead under
typical urban conditions. Subjects were fed constant low-lead diets, supple-
mented with non-radioactive isotope tracers. The concentration of tracer
lead and total lead in diet, feces, urine, blood, hair, nail~ sweat, bile,
gastric and pancreatic secretions and bone were measured by mass spectrometry.
Alimentary absorption of both the tracer lead nitrate and food lead
varied from 6-14 percent in these subjects, while in rats as high as 70 per
cent absorption was observed when tracer was administered during fasting.
The data on the kinetics of tracer lead within the body could be adequately
described by a 3-compartment model. By transferrring 3 subjects to a room
with filtered air and observing the rate at which their blood lead fell, it
was determined that about 15 ~g/day of lead is inspired, about one-half as
much as originates in diet. This was confirmed by the lead balance and the
incomplete labelling to blood by a dietary tracer.
198
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TABLE 7.1 LEAD INGESTION AND EXCRETION OF
A NORMAL HUMAN SUBJECTa
Net Change
8-Week Lead Lead Excreted, mg in Body
Periods Ingested, mg Total" In Feces In Urine Lead, mg
1st 13.59 11.95 10.45 1.50 +1. 64
2nd 13.31 15.13 13.63 1.50 -1. 82
3rd 13.16 13.82 12.45 1.37 -0.66
4th 11.51 11.59 10.41 1.18 -0.08
5th 9.30 8.93 7.88 1.05 +0.37
6th 9.24 9.05 8.16 0.89 +0.19
7th 12.75 13.74 12.86 0.88 -0.99
Subtotal 82.86 84.21 75.84 8.37 -1.35
8th 22.21 17.61 15.85 1. 76 +4.60
9th 18.17 15.05 13.76 1.29 +3.12
Subtotal 40.38 32.66 29.61 3.05 +7.72
Total 123.24 116.87 105.45 11.42 +6.37
a Source: Kehoe (1961a-d). Reprinted from Journal Royal Institute
Public Health Hygiene.
199
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7.2.1.3
Skin Absorption--
Penetration of inorganic lead through the intact skin has not
studied extensively. Limited data indicate that inorganic salts of
not absorbed to any significant extent. (Laug and Kunze, 1948).
been
lead are
Hamilton and Hardy (1974) reported a case of skin absorption of inorgan-
ic lead from the application to the skin of a theatrical grease paint contain-
ing 40 percent lead oxide. Conceivably, the lead oxide might have been con-
verted to a liquid-soluble organic salt. Lead soaps, for example, naphthenate,
used in industrial lubricants, however, are absorbed significantly via skin
(Hine et al., 1969).
Rastogi and Clausen (1976) studied the absorption of lead through the
skin by comparing the effect produced by lead naphthenate or lead acetate
solution, when coated on the skin of rats, with data obtained from subcutan-
eous injections of these solutions. Body weight and liver size and weight
decreased in rats receiving the subcutaneous dose. o-Aminolevulinic acid
dehydrase (ALA-D) in liver was decreased in all rats that were treated with
lead compounds. The distribution of absorbed lead was evaluated by assay of
tIle lead content in brain, liver, kidney, spleen and muscle in the rats.
(Table 7.2). The results of this study seem to verify that absorption of lead
through the skin does occur. Also, the decline in ALA-D activity was either
equal to or more pronounced when lead naphthenate was administered than when
lead acetate was administered; however, the lead naphthenate produced lower
lead concentrations in the liver than did the acetate compound. These find-
ings seem to indicate that lead naphthenate is comparatively more toxic than
lead acetate.
In a study of the toxicity of lead naphthenate, Van Peteghem and DeVos
(1974) observed that 8 percent of the 102 employees having occupational con-
tact with lead-containing oils showed a blood lead content of over 40 ~g/dl
and also had an increase in a-amino levulinic acid excretion in the urine.
However, the observed increases were all below the maximum acceptable con-
centration for adults.
7.2.1.4
Placental Transfer--
The inorganic forms of lead have a greater potential for injury to the
embryo, fetus, neonate and child than to the mature adult. The fetus seems
most susceptible to the effects of lead during the phase of rapid growth and
it has been postulated that fetal tissues may be able to concentrate lead at
least during the first 16 weeks of gestation (Karlag and Moeller, 1958). Cord
blood was found to have lead concentrations approximating those found in
maternal blood (Scanlon, 1971, Harris and Holley, 1972, and Rajegowda et al.,
1972). Scanlon has found lead concentrations as high as 39 ~g/dl in the
umbilical cord. The blood of newborns contains lead in concentrations simi-
lar to that in cord blood (Robinson, et a1., 1958).
In a study on normal humans, Bar1trop (1969) observed that placental
transfer of lead began as early as the twelfth week of gestation and that the
200
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TABLE 7.2
a
ALA-D ACTIVITY IN LIVER AND DISTRIBUTION OF LEAD IN VARIOUS OItGA1JS IN RATS
Mean ALA-D Activitl Lead Content in llg/g Wet Tissue c
Experimental Group Parts cata1yzed/g liver Brain Kidney Liver Spleen Muscle
Control 619 :!: 24 11. 2 :!: 1. 7 7.9 :!: 2.3 5.0 :!: 0.8 8.8 :!: 1.4 2.9 :!: 0.5
Cutaneous lead 35d 55.4 :!: 5.2d + d 2.0d
acetate 544 :!: 13.0 :!: 1.8 18.8 - 2.5 8.9 :!: 1.2 7.7 :!:
Cutaneous lead 524 :!: 18d 3.2d 9.6 :!: 0.8d d
N naphthenate 12.8 :!: 1.6 34.8 :!: 8.8 :!: 1.1 11. 4 :!: 2.4
0
~ Subcutaneous lead
acetate 473 :!: 19d 15.8:!: 1.8d 321. 0 :!: 18.0d 108.0 :!: 10.0d 81. 9 :!: 6. 8d 17.8:!: 2.2d
Subcutaneous lead 24d 2.6d 7.7d 56.3 :!: 6.6d 2.2d d
naphthenate 473 :!: 21.3 :!: 184.0 :!: 50.6 :!: 25.2 :!: 2.1
aSource: Adapted from Rastogi and Clausen (1976). Reprinted,
Elsevier - North Holland Publishers, Inc., Amsterdam
bA d. . I'
ssaye 1n tr1p 1cate.
~Assayed in duplicate.
P <0.001.
with permission from Toxicology. (c)
(1976).
-------
lead content in fetal tissues increased throughout pregnancy. Fetal bone was
found to have the highest tissue-lead level (80 ~g/g). Lower lead levels were
found in the placenta, heart, kidney, liver, and blood. The total amount of
lead transferred per day during pregnancy appeared to be less than 303
micrograms.
Finklea et al., (1972) found that lead is bound to and crosses the
placenta, with fetal blood levels being lower than maternal levels, and with
erythrocyte levels showing a greater difference than whole blood. According
to Baumslag (1975), transplacental transfer might not occur in mothers with
sufficiently high copper levels (quantity not given) as copper may be protect-
ive.
Kostial and Momcilovic (1974), investigated the transfer of lead during
various stages of gestation and lactation to determine the period of maximal
transfer from mother to offspring. Tracer doses of lead-203 were given intra-
venously to rats on the 18th day of pregnancy and on the 4th and 15th day of
lactation. Calcium-47 was given at the same time to relate the results of
lead transfer to the transfer of calcium to offspring. The transplacental
transport of lead was eight times lower than that of calcium while trans-
mammary transport of lead was four times lower.
Chaube, et al., (1972) in a study of human embryonic and fetal lead
concentrations, detected lead in two-thirds of the first trimester specimens
without relation to age. Fifty embryos and fetuses ranging from 31 to 261
gestational age were used. In fetal tissues, lead was found in 77, 15, and
30 percent, respectively, of the liver, brain, and kidney samples analyzed.
In the embryos the concentration of lead ranged from 0.38 to 2.0 micrograms
per gram of wet tissue weight. Only two fetuses had detectable lead in the
brain. In the liver, the concentration ranged from 0.84 to 4.04 micrograms
per gram of wet tissue weight, and in the kidney from 0.9 to 2.3 micrograms
per gram of wet tissue weight.
Haas, et al., (1973), reporting on 294 sets of maternal and fetal blood
samples, found lead levels in maternal samples were 16.9 ! 8.6 ~g/dl; fetal
lead levels were 15.0 ! 7.9 ~g/dl. The coefficient of correlation of blood
levels in the newborn with levels in their mothers equaled 0.57.
Schroeder and Tipton (1968) found lead in significant concentrations in
young children of several nationalities, even in stillbirths, indicating con-
siderable placental transfer (see Table 7.3).
7.2.2
Transport and Distribution
Following absorption, essentially all the lead in the body is associated
with the erythrocytes. It is then distributed to various tissues with con-
centrations being highest in bone and hair, intermediate in liver, kidney, and
aorta, and lowest in heart and brain. Schroeder and Tipton (1968) have
observed that under conditions approximating steady state, more than 90 percent
of the lead resides as a relatively nondiffusible fraction in the skeleton.
The body tends to reject lead at a rate commensurate with the rate of ingestion.
202
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TABLE 7.3
TISSUE LEAD CONCENTRATION IN CHILDREN AND ADOLESCENTSa
Place of
Origin N Aorta Liver Kidney Pancreas Lung Testis Heart Brain Spleen Bone
Mean Lead Concentration, ppm ash
America
Stillborn 22 65 53 38 18 25 10 37
IV 0-19 23 24 74 62 31 18 9 5 0 10 2
o
l.U
Africa 5 100 39 18 23 0 13
India 9 82 100 90 44 68 76 33 10 50 10
Japan 3 27 64 98 26 34 72 15 13 23 27
a
Source: Schroeder and Tipton. Rep rin ted with permission from Archives Environmental Health.
(c) AmericAn ~edical Association, 1963.
N = Number of samples.
-------
Therefore, the biological fluid levels (blood and urine) fluctuate with the
amount of ingested lead. Since only about 10 percent of the ingested lead is
absorbed into the body, lead concentrations in the feces reflect short-term
fluctuations in the lead ingested while the urine and blood levels are more
indicative of lead concentrations over long periods of time.
Lead is associated with the erythrocytes or the plasma proteins, and a
small quantity is in the free, ionized state. Approximately 95 percent of
the lead in the circulating blood is attached to the red cell. The rate of
lead uptake from the plasma by the erythrocytes is temperature dependent.
Clarkson and Kench (1958), on reexamination of Mortensen and Kellog's data
(1944), showed that the ratio of the velocities of uptake at 10 and 20 C was
given by the equation:
k 20/k = 5.61 x 104/2.16 x 104
thus QlO = 2.8, and
minutes,
energy of activation = 15,800 cal/mole.
Since lipid-free stroma does not bind lead effectively, the lipids and lipid
proteins in the cell membrane seem to act as a stong binding site for lead
(Jung, 1947 and Vincent, 1958, cited in Waldron and Steffen, 1974; Teisinger,
et al., 1958). The fact that lead is bound to plasma proteins is not
surprising since other heavy metals like mercury and cadmium also show a
strong affinity for ligands such as phosphates, cysteinyl and histidyl side
crunnsof proteins, purines, pteridines, and porphyrins (Vallee and Ulmer, 1972).
Possibilities suggested for the manner in which lead is bound to the erythro-
cyte include a peptized lead phosphate sol (Clarkson and Kench, 1958), a
colloidal lead phosphate (Aub, et al., 1925), a diglyceryl phosphate
(Maxwell and Bischoff, 1929a,b) mixed salts with calcium and chloride (Jowett,
1932), and a protein-phenolic complex (Reddi, 1953). The affinity of lead
toward sulfhydryl (SH) groups suggests a series of reactions on the membrane
which lead to a S-Pb-S complex (Passow and Tillman, 1955, cited in Waldron
and Steffen, 1974).
Barltrop and Smith (1971) have reexamined the lead-binding properties
of human erythrocytes and investigated the cell fraction in which binding
occurs. Their results suggest that lead is bound to the cell contents rather
than to stromal material. This was confirmed by the absence of significant
binding of lead when washed stroma were tested in place of hemolyzed
erythrocytes. The observed interaction with the prehemoglobin band was attri-
buted to residual hemoglobin bound to that fraction. Comparison of the
elution characteristics of this band with a calibration graph indicated a
mean molecular weight of 240,000. Stromal proteins extracted from red cell
ghosts have been shown to have molecular weights ranging from 10,000 to
170,000; however, these values are unlikely to apply to material obtained by
simple hemolysis. The lack of correspondence between hemoglobin concentration
and lead binding in fractions obtained from the Sephadex column at elution
volumes of 350 milliliters and above suggests that there by be some low-
molecular-weight material in addition to hemoglobin that interacted with lead.
204
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Lead disappears from the blood at a rate which indicates first-order
reaction kinetics and may be the sum of three exponential functions
(Castellino and Aloj, 1964). Stover (1959) concluded that lead rapidly
transferred to the extravasular spaces from the plasma as the latter level
declined. To maintain dynamic equilibrium between red-cell and plasma lead,
on the one hand, and extracellular and intracellular lead on the other, it
is suggested that the ionic fraction of the plasma lead is transferred
slowly to other body compartments. A similar rationale applies to the lead
concentration in urine, with blood showing a somewhat lesser fluctuation
than urine (Kehoe, 1961a-d). The concentration of lead in the blood of the
general population is fairly stable. The lead content in th~ blood does
not change significantly with age, neither among North Americans (U.S.
Department of Health Education and Welfare, 1965) nor among some other
nationalities (Horiuchi, 1970, cited in TGOl1A, 1973; Horiuchi and Takada,
1954, and Horiuchi, et al., 1959, cited in National Academy of Sciences
(1972). There was no increase in the concentration of lead in serum with
age in U.S. residents (Butt, et al., 1964). Coulston (1973) and Knelson,
et al., (1973) described a study in which 20 human volunteers were exposed
to 10.9 ~g/m3 of lead sesquioxide 23 hours per day for 4 months (see
Figure 7.1).
IXPOStO
o
o
5 10 15
WEEI
-------
Goldwater and Hoover (1967) determined blood-lead levels of person~ jn
16 different countries. A total of 801 blood speciMens were analyzed for
lead content using the dithizone method. In general, urban means were higher
than rural means. There appeared to be no statistically significant differ-
ences between countries with respect to geographical location or degree of
industrialization. The blood lead level of their study was 17 ~g/dl of blood
with a st-anqarddeviation of 11 ~g/dl.
Kubota, et al., (1968) who made a detailed investigation of blood-lead
levels of male residents of 19 cities in the continental United States, found
that the means from one city to another varied widely as did individual values
within each city. Earlier, Hofreuter, et al., (1961) observed variations
among residents in Los Angeles with respect to both sex and urbanization.
Blood lead levels were significantly higher in males as compared to females
and in rural as compared to urban inhabitants.
Extensive studies of soft-tissue lead distrubution have been reported by
Schroeder and Tipton (1968), Schroeder and Balassa, (1961), Tipton and Cook
(1963), Tipton and Shafer (1964), and Tipton et al., (1965). Barry and
Mossman (1970) confirm these earlier data. Table 7.4 shows the variations in
lead concentration with geographical orgin. The brain and the heart show
consistently low values. The authors provide no explanation for the
geographic variation in these values other than to point out the fact that
most of the values are highest for the most urbanized/industrialized areas.
In general the aorta has the highest concentration followed by the liver
and kidney.
Schroeder and Balassa (1961) and Schroeder and Tipton (1968) found that
concentrations of lead in the soft tissue, for example, kidney, pancreas,
liver, lung, and aorta increase with age, the rise being particularly sharp
in the aorta. These values continue to rise until approximately age 40-50
(age 60-70 for the aorta), at which point they begin to level off. Age-linked
accumulations of lead in tissues of Americans were also found for larynx,
trachea, and prostate (Schroeder and Balassa, 1961). In aortas collected
at autopsy from 18 male residents of Baltimore the highest aortic levels of
lead were found in those persons 38 years or older (Poklis, 1975). All but
two of these subjects had dense atheromas present. The lead content of the
trachea at autopsy from 17 Balti~ore residents sampled in 1972 ranged from
0.6 to 8.8 microgrqms per gram of fresh tissue (Poklis and Freimuth, 1975).
Contrary to the observation of Schroeder and Tipton (1968), no significant
correlation of tracheal lead and age was demonstrated by these data. The
mean tracheal lead concentration of the samples collected in 1972 was compared
with the mean lead concentration of Baltimore residents reported in 1957.
From the increase in trachea lead, it may be concluded that from 1957 to 1972
there was an increase in the lead "body burden" of Baltimore residents. While
the increase may not have been sufficient to affect public health of Balti-
more residents, it does reflect an increase in lead exposure in the Baltimore
environment.
Bone contains approximately 90 percent of the total body burden of-lead,
which is deposited in the form of the insoluble tertiary lead phosphate. Data
by Schroeder and Balassa (1961) and Schroeder and Tipton (1968) indicate that
the concentration of lead in the bones rises steadily to about the 4th decade
206
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TABLE 7.4
VARIATION IN HUMAN TISSUE LEAD CONCENTRATION WITH GEOGRAPHICAL LOCATIONa
Place of origin N Aorta Liver Kidney Pancreas Lung Testis Heart Brain Spleen Bone
Mean Lead Concentration, ppm ash
Nine American 150 140 130 98 49 47 12 5 5 27 43
cities
San Francisco 27 220 160 54 65 38 20 10 5 44
N
a Switzerland 9 32 59 45 42 32 23 14 5 20
'-J
Africa 54 71 64 36 24 28 29 5 5 21
Middle East 37 140 70 62 34 42 32 24 14 40 26
Far East 74 91 97 63 39 43 35 19 10 33 30
a Schroeder and Tipton. Reprinted with
Source: permission from Archives Environmental Health.
(c) American Medical Association, 1968.
-------
and remains relatively constant and then decreases in the 7th or 8th decade.
However, the results reported by Schroeder and Tipton were based on only 3
individuals, and additional confirmation of this conclusion appears needed.
Barry and Mossman (1970) and Barry (1973) concluded that there is no
decrease in bone lead with old age and suggested that the drop reported by
some of the earlier investigators was due to the small number of samples.
This confirms earlier work by Morris (1940), who in calculating regression
coefficients between lead concentration in femur, ribs, and vertebrae, and
age found that lead contents rose significantly and gave correlation co-
efficients equal to 0.48, 0.36, and 0.28, respectively. He concluded that
more lead was stored in the long bones than in either ribs or the vertebrae,
however, there does not seem to be general agreement as to which bone contains
the greatest concentration of lead. Holtzman (1963) demonstrated that the
concentration of lead-210 was higher in trabecular than in cortical bone.
The lead in the skull bones seemed to be most representative of the total
skeleton since their concentration deviated least from the mean. Rib con-
centrations deviated most from the mean and concentrations in the tibia were
very low.
Gross, et al., (1975) assayed 29 tissues per individual from autopsies
of 46 white males ranging in age from 20 to 84 years (see Table 7.5) and found
the following: 43 had blood-lead concentrations of 40 ~g/dl or less; one had
a blood lead concentration of 41 ~g/dl, one a concentration of 43 ~g/dl and
one had a concentration of 106.5 ~g/dl. On a wet-weight basis (see Table
7.6), calcified tissues (bones and aorta) contained the highest concentration
of lead; the glandular tissues (liver, kidney, and pancreas) were inter-
mediate; and the remaining tissues which were mostly of a nonglandular nature
had the lowest concentrations. Table 7.6 shows the distribution of lead in
the bones and aorta. The low lead values for the bones of the individual
in the 5th decade may reflect a chance selection of individuals with low
lifetime lead exposures. A rapid increase of lead in the aorta was found
after the 5th decade.
Gross and Pfitzer (1975) found that'concentrations of more than 2 micro-
grams of lead per gram in the aorta were associated with severe atheroclerosis
involving calcium deposits. As re~lected in the skeletal lead, the overall
body content of lead increased with age, but the concentrations in many soft
tissues did not change and in several tissues lead concentrations decreased
with age.
Sumino, et al., (1975) determined the amounts of 15 heavy metals in 15
female cadavers (average weight 55 kilograms, average age 39 years.) The
highest level of lead was found in the adrenal glands (1.2 plus or minus
0.79 ppm). The average lead content of the female tissue samples was higher
than that in corresponding male tissue samples except in the liver. Signi-
ficant differences were found in small intestines (p = 0.011Iung, brain,
adrenal glands, and spleen (p = 0.05).
208
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Table
7.5
TISSUES RANKED ON THE BASIS OF OVERALL
~ffiAN CONCENTRATIONS OF LEADa,b
ppm, wet-weight basis
Tissue N X/SD r Tissue N X/SD r
Tibia 45 14.09/11. 22 O.53c Thyroid 40 0.17/0.11 0.30
Skull 44 13..81/9.09 0.50c Testes 43 0.15/0.09 -0-.26
Rib 45 7.14/4.19 0.38d Jejunum 45 0.12/0.05 -0.30d
Vertebrae 44 4.42/2.52 0.21 Brain, grey 39 0.11/0.05 -0.18
Aorta 45 1. 65/1. 82 0.52c Brain, white 41 0.11/0.04 -0.09
Liver 45 0.98/0.53 -0.34d Fascia 43 0.11/0.05 -0.05
Nodes 41 0.86/0.93 0.15 Stomach 45 0.10/0.05 -0.32
Kid. cor. 45 0.79/0.42 -0.53c Bladder 43 0.09/0.04 -0.02
Kid. med. 44 0.48/0.22 -0.38d Skin 43 0.08/0.03 -0.11
Pancreas 45 0.46/0.23 -0.45c Heart 43 0.08/0.04 -0.12
Spleen 43 .0.33/0.15 -0.02 Cecum 45 0.07/0.03 -0.07
Lung 42 0.36/0.12 0.13 Muscle 44 0.07/0.03 -0.23
Adrenal 41 0.25/0.12 -0.38d Urine 8 0.06/0.11 0.24
Blood 43 0.21/0.09 -0.29 Adipose 43 0.04/0.01 0.11
Prostate 41 0.20/0.22 -0.08
aSource: Gross, et a1. Reprinted with permission from Toxicology and
Applied Pharmacology. (c) Academic Press, Inc., 1975.
bShown are number of tissues (N), their means +SD and correlation of
tissue concentrations vs age.
cp <0.01-
dp <0.05.
N = Number of samples.
209
-------
TABLE 7.6 AGE-RELATED INCREASES OF LEAD CONCENTRATION IN
BODY TISSUESa.b (ppm. wet-weight basis)
Tissue
20-29
70-79
Tibia
6.6l:t0.92
(6)
N
I-'
o
Skull
7. 27i1. 76
(6)
Rib
4.06:1:1. 92
(6)
Vertebrae
3.48:1:1. 50
(6)
Aorta
0.40:!:0.18
(6)
30-39
9. 37:!:4.6l.
(4)
9. 07:!:4. 31
(4)
5.48:!:3.82
(4)
2. 98:!:1. 84
(4)
0.86:!:0.71
(4 )
Decade. years
40-49 50-59
10. 77:!:5.09
(8)
12.85:!:5.12
(8)
8.04:t4.13
(8)
4. 98:!:1. 52
(8)
0.75:!:0.16
(8)
9.68:!:4.43
(9)
10.13:!:4.21
(9)
4. 83:t1. 55
(9)
2. 88:!:1. 20
(9)
1. 14:!:0.46
(9)
60-69
18.57:!:8.34
(11)
19.60:!:8.17
(11)
9. 77:t4. 36
(11)
6.66:!:3.24
(11)
2.83:!:2.55
(11)
28. 36:!:21. 37
(6)
21. 76:!:18. 06
(5)
9.42:!:4.65
(6)
4.17:!:2.26
(6)
3.32:!:2.18
(6)
aSource: Gross. et al. Reprinted with
(c) Academic Press. Inc. 1975.
b
Shown are the decade means +SD.
permission from Toxicology and Applied Pharmacology.
The number of tissues in each decade are shown in parentheses.
-------
7.2.3
Elimination
The principal routes of elimination of lead from the body are through
the feces and urine. Secondary routes include sweat, milk, hair, and dis-
carded and desquamated skin. Lead concentrations of approximately 0.01 ppm
have been found in the milk of normal cows. This seems toxicologically
insignificant (Hammond and Aronson, 1964). In experimental animals, lead is
excreted into the bile, and injected lead may be found in the feces. For
example, Blaxter and Cowie (1946) after administration of lead acetate to
sheep, found that 7.5 percent of the dose was excreted in 6 days of which 81
percent was in the bile.
The classical studies of Kehoe (1961a-d) indicate that under normal
conditions not more than 10 percent of ingested lead is absorbed by adults.
However, under abnormal conditions the excretion of inorganic lead is en-
hanced by procedures or conditions that favor mobilization from bone and
soft-tissue burdens.
The excretion of lead into the urine is probably not as great as ex-
cretion in the bile. The excretion of lead through the kidney is hampered
by the interaction of lead and heavy metals in general with ligands present
in erythrocytes and/or plasma proteins. Vostal (1963 and 1966), cited in
TGOMA (1973) and Vostal and Heller (1968) investigated lead excretion in
man and dogs and found that the renal tubule reabsorbed a constant amount
of lead, with the effect being pH-dependent, increasing at low pH and decreas-
ing or entirely disappearing at high pH. More recently these same investigators
found that in the chicken, lead passes into the urine not only by glomeru-
lar filtration, but also by direct transport across the tubular wall.
Kehoe's work (196la-d) indicates that in conditions approximating a
steady-state in which oral input roughly parallels urinary and fecal output,
the urinary excretion is about 10 percent of the oral input and the fecal
output is close to 90 percent. Most of the lead in the feces represents
lead which h~s passed unabsorbed through the gut. The contribution to to-
tal excretion of inhaled lead was not determined, a factor which would have
likely elevated the estimated proportion of the total lead intake excreted
via the urine.
The estimates of half-time for lead in bone have varied from 64 days
in the spine of rats (Torvik, et al., 1974) to 7,500 days in the skeleton
of a dog (Fisher, 1969). The half-time varies with different bones, pre-
sumably due to the relative proportions of cortical and trabecular bone.
The International Commission on Radiological Protection (ICRP) has used
10 years as the biological half-life for lead in bones of humans (ICRP, 1959).
Following a single dose of 210Pb in dogs, disappearance of the label from
blood was followed for 280 days. The biological half-life of lead in the
body was estimated to be 1940 days (Hursh, 1973).
211
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7.3 TOXIC EFFECTS
The present-day environmental problem of lead may be viewed at three
levels. First~ there is the problem of sporadic episodes of acute lead
intoxication. These are largely accidental or the result of ignorance of
the danger of lead. Second is the problem of clinical and subclinical in-
toxication of large numbers of children in urban ghetto areas who are living
in pre-World War II housing. This is largely a socioeconomic problem but
corrective measures are possible; perhaps the most promising is increased
monitoring and surveillance for early detection and treatment (see Section
9.3.3). The third aspect of the environmental problem concerns the ques-
tion of the possible harmful effects of body stores of lead in general
populations.
An answer to this latter question depends on increased knowledge of
the biologic effects of lead~ particularly regarding the effect of trace
quantities on cellular function (Goyer~ 1971).
Many organs and systems have been shown to be adversely affected by
lead. However~ much of what is known concerning effects has been adduced
only in isolated cellular or subcellular systems. The implications for
the health of man are uncertain in such cases. The subject of enzymatic
and cellular responses to lead and organ system toxicities is a complex
topic~ which would require a much more detailed discussion than is possible
in this document. Information on this topic can be found in the recent
report on the environmental impacts of lead (Bell~ et al.~ 1978) which
treats this topic in detail~ including discussions of renal~ hematopoietic~
nervous system~ immune system~ cardiovascular system~ and endocrine sys-
tem toxicities and the factors influencing or modifying toxicity.
In this report~ discussion is restricted to representative acute tox-
icities~ the occupational standards derived from them and the toxic effects on
the reproductive system.
7.3.1
Toxicities of Inorganic Lead Compounds
Representative toxicities and occupational standards for industrial in-
organic lead compounds are shown in Table 7.7 (as noted earlier~ inorganic
compounds are considered to include all those where a carbon atom is not
directly connected to lead; this includes the lead salts of organic acids which
are used as paint driers, etc.).
U.S. Occupational Standards include those promulgated by the Occupa-
tional Safety and Health Administration; those shown are time-weighted
averages (TWA), based on continuous exposure for 8-hour day and a 40-hour work
week~ and are stated in terms of air lead concentrations (as lead). Also
shown are theTLV's (Threshold Limit Values) established by the American
Conference of Govermental Industrial Hygienists (ACGIH)~ which issues recom-
mended air lead concentrations, also time-weighted averages based on a 40-
hour work week.
212
-------
TABLE 7.7
REPRESENTATIVE TOXICITIES AND OCCUPATIONAL
STANDARDS FOR SEVEN COMMERCIALLY
IMPORTANT INORGANIC LEAD COMPOUNDS a
3
Compound and Standards, ug/m
U.S. OccupationalO TLVc,d f
Chemical Formula Toxicities, mg/kg
Lead arsenate oral, rat LDsO 100
PbHAS04 or 150 150 oral, human LDLO 1.4
Pb3(As°4)2
Lead chromate, basic ipr, guinea pie LD.o 400
PbO'PbCr04 200 150 scu, rat TD=> 150
Lo
Lead dioxide 200
Pb02
Lead monoxide
(litharge) PbO 200 ipr rat LDLo 430
Lead tetraoxide ipr rat LDLo 1,500
(red lead) Pb304 200 ipr rat LDsO 200
Lead naphthenate
CnH2n - 202 oral, rat LDsO 5,100
C H2 - 402 skn rat LD 520
n n 50
C H .- 602
n 2n
Lead stearate
(approx) Pb(C1SH3s02)2 oral, guinea pig LDLo 6000 mg/kg
Inorganic lead 50e
compounds (all)
213
-------
TABLE 7.7 (Continued)
Notes:
aSource:
Registry of Toxic Effects of Chemical Substances (NIOSH, 1977).
Thre~hold Limit Values for Chemiczl Scbstances and
Physical Agents in the Workroom Environment (ACGIH, 1977)
U.S. Department of Labor (1978).
bU.S. Occupational Standard (OSHA) based on time-weighted average
(TWA) for continuous exposure (8-hr day and 40-hr week).
cThreshold Limit Value - based on time - weighted average for continuous
exposure 8-hr day and 40-hr week (American Conference of Governmental
Industrial Hygienists (1977).
dTLV of 150 ~g/m3 applies to fumes and dusts of all inorganic lead compounds.
eRevised -standard for all inorganic lead compounds (U.S. Department of
Labor, 1978).
f
Toxicity data descriptors:
1.
routes of administration:
ipr - intraperitoneal
scu - subcutaneous
skn - dermal or cutaneous (intact skin)
ivn - intravenous
par - parenteral, unspecified.
inh - inhalation
2.
toxic response terms:
LD50 - Lethal Dose Fifty - A calculated dose of a chemical substance
which is expected to cause the death of 50 percent of an entire
defined experimental animal population, as determined from
the exposure to the substance, by any route other than
inhalation, of a significant number from that population.
LD -
Lo
Lethal Dose Low - the lowest dose of a substance other than LD50 introduced
by any route other than inhalation over any given period of time and
reported to have caused death in humans or animals when introduced in one or
more divided portions.
TDLe -
Toxic Dose Low - the lowest dose of a substance introduced by any route other
than inhalation over any given period of time and reported to produce any toxic
effect in humans or to produce carcinogenic, teratogenic, mutagenic, or
neop~astigenic effects in humans or animals.
MLD
- Minimum Lethal Dose.
LD50 -
Lethal Concentration Fifty - a calculated concentration of a substance
exposure to which for a specified length of time would cause the death
of an entire defined experimental animal population as determined from
to the substance of a significant number from that population.
in air,
of 50 percent
the exposure
214
-------
OSHA has promulgated new regulations which establish the maximum allow-
able concentration for lead and its inorganic compounds in work room air at
50 ~g/m3 (U.S. Department of Labor, 1978).
For inorganic lead compounds, the critical effect of lead is adverse
interference with heme synthesis and according to present knowledge, the
critical organ of lead effect is the hematopoietic bone marrow. For
organic lead compounds and, specifically, the alkyllead compounds, short-
term inhalation first results in central nervous system manifestations,
suggesting that this is the critical organ for organic lead. (See Section
7.6.4).
Lead salts of organic acids would be expected to show critical effects
more characteristic of inorganic lead compounds than alkylleads, although
absorption through the skin might lead to neurological manifestations. The
solubility of the lead compounds in tissue fluids is of prime importance
(more important than the physical nature - dust, fumes, mists, or vapors)
in determining their passage to the critical organs.
Generally the toxicity of the lead salts of organic acids (lead
naphthenate, lead tallate, lead stearate, and lead-2-ethylhexanoate) is
associated with (1) hydrolysis or decomposition products, resulting in inor-
ganic lead compound and (2) solvent systems employed in their commercial
utilization, which influence their absorption. Thus, the migration of
lead/lead compounds from polymeric films might result in increased toxicity
of lead.
7.3.2
Reproductive Effects
The effects of lead on human reproductive functions per se have
received little study in recent years. Consequently, much of what appears
in the literature concerning human reproductive effects comes from very
old studies of workers exposed to levels of lead orders of magnitude
higher than today's lead workers, or alternatively from rather unscientific
foreign reports of similar age. Lancranjan's (1975) study is the only recent
investigation focusing exclusively on human fertility effects (specifically
spermatogenic abnormalities) under reasonable well defined levels of lead
exposure. Some cell culture studies of mutational activity of lead are
also available.
7.3.2.1
Fertility Reduction--
When both male and female rats and mice were exposed to 25 micrograms
of lead (as lead acetate) per liter of drinking water, the offspring had
increased numbers of breeding failures, runts, young deaths and dead lit-
ters (Schroeder, 1973). Unspecified inorganic lead salts administered to
pregnant mice and rats in low doses (25 ppm) in drinking water produced
runting, reproductive failure and shortened life spans (Schroeder and
Mitchener, 1971).
215
-------
Hilderbrand et al., (1973) investigated the effect of lead acetate
on reproduction and metabolism in rats. Eighty sexually mature males and
eighty sexually mature females were maintained in a controlled environment
at a constant temperature of 25.5 C. The males and females were divided
into three groups with each group containing 20 rats. Group 1 served as
controls; group 2 was treated orally with 5 micrograms of lead acetate
for 30 days; and group 3 was treated with 100 micrograms of lead acetate
for 30 days. These dosages of lead were presumably administered daily,
although the authors do not specifically state. Results of this investiga-
tion revealed the following:
1) In males, wh~n the lead concentration in
14 micrograms per 100 milliliters to 26
prostatic hyperplasia resulted.
2) When the lead level increased to 50 ~g/dl, testicular damage
occurred and spermatogenesis was inhibited.
3) In the female, when lead concentration in blood increased from
14 ~g/dl to 30 ~g/dl, irregularity of estrus occurred.
4) When lead levels reached 30 ~g/dl, persistent vaginal estrus
occurred after normal estrus, and the development of ovarian
follicular systs with a reduction in the number of corpora
lutea was noted.
5) No toxicity or mortality occurred in the treated animals.
the blood increased from
~g/dl, impotence and
Stowe and Goyer (1971), also have observed that the reproductive
capacity of male rats is reduced as a result of lead exposures. The pater-
nally-transmitted effect includes reduction of litter size, weights of
offsprings and, reduced survival rates of the offsprings. Goyer and Rhyne
(1973) reported that lead workers having blood-lead levels equal to 62
to 88 ~.g/dl displayed gap-break type aberrations of chromatids similar to
to those reported in animal studies by Muro and Goyer, (1969). A
variety of nonspecific changes in chromosome morphology (adhesions and
spiralizing defects), and increases in tetraploid mitoses and the mitotic
index were also noted.
Lancranjan, et al., (1975) investigated the reproductive ability of
150 men occupationally exposed to lead at a storage battery plant. One
hundred of these men had a:range of occupational exposure to lead of 1 to 23
years (8.5 mean), and 50 were technicians and office workers who worked ina~n~:c
workrooms in a lead-polluted environment for 1 to 27 (mean 6) years. Lead-
poisoned workmen (23) had mean values of lead in blood of 74.5 ~ 26 pg/dl;
workmen with moderately increased absorption (42), 52.8 + 21 wg/dl; slightly
increased absorption (35), 41 + 12pg/dl; physiologic absorption (50),
23 + 14 pg/dl. Workmen having-lead absorption ranging from slight to high
exhibited a substantial increase in spermatogenic abnormalities (astheno-
spermia, hypospermia, or oligospermia and/or teratospermia). Because tests
for hypothalamo-pituitary influence were negative, it appeared that effects
on the testes were direct.
216
-------
7.3.2.2
Mutagenicity--
Nuclear polyploidy and abnormalities in mitosis resulting from lead
toxicity have been found in bone marrow cells by several investigators.
Chromosomes from leukocyte cultures from mice fed a diet containing 1 per-
cent lead acetate showed an increased number of gap-break-type aberrations
(Muro and Goyer, 1969). The observed chromosomal abnormalities largely
involved only single chromatids. Failure to have a paired defect (break
or gap) in both chromatids of a chromosome suggested that damage occurred
after the deoxyribonucleic acid (DNA) synthetic phase of the cell cycle.
There is a possible relationship between increased DNA'ase activity and
chromosome damage as a marked increase in deoxyribonuclease activity has
been demonstrated in urine from lead-poisoned rats (Muro and Goyer, 1969).
Studies on chromosomal aberrations in workers professionally exposed
to lead, lead and some of its compounds, and mixtures of lead, cadmium,
zinc, and tin, still do not answer the question whether lead can cause
chromosomal abnormalities. At best, evidence seems to be in favor of
there being a causal relationship. Whereas Bauchinger et al., (1972),
O'Riordan and Evans (1974), Schmid et al., (1972), and Speding et al.,
(1972) could not detect any severe chromosomal aberrations in workers
from different lead industries, Bauchinger et al., (1976), De Knudt et al.,
(1973), Forni and Secchi (1972), Forni et al., (1976), and Schwanitz et al.,
(1970, 1975) observed a significant increase in such aberrations. De Knudt
(1977) concludes that lead is not the only factor responsible for the severe
aberrations found in some workers in lead industries and that it can even
be surmised that other factors must be considered, for example diet, photo-
chemical effects, and intoxication with other heavy metals (cadmium, zinc).
7.3.2.3
Teratogenicity--
Although effects of lead on reproductive fitness have been surmised
to occur in individuals with increased body burden of lead, this effect
has not been clarified. Hamilton and Hardy (1974) reported that lead
poisoning in women industrial workers in the early 1900's resulted in
decreased fertility and an increased abortion rate. Exposure of women to
concentrations of lead prevalent in industry at that time no longer happens.
Consequently, the effect of lead on the human endocrine and reproductive
systems received relatively little attention in comparison with studies
on the hematopoietic, renal, and nervous systems. Observations concerning
the adverse effects of lead on animals and man are herein discussed.
Stowe and Goyer (1971) found that lead is toxic to gametes of both
male and female rats, resulting in decreased numbers and size of offspring
from poisoned rats. Vermande-Van Eck and Meigs (1960) observed histopatho-
logical changes in the ovaries of lead-poisoned rhesus monkeys. Such changes
217
-------
have not been observed in humans. Ferm and Carpenter (1967) were able to
induce specific congenital-skeletal malformations in golden hamster embryos.
On either day 7, 8, or 9 of pregnancy various salts of lead (acetate, chlo-
ride, nitrate) were injected into the mother through the lingual vein. The
dosage was 50 mg/kg made up in distilled water and the volume of the injec-
tion was 1 m1/100 g of body weight. The embryos were recovered between day
12 and day 15 of the normal 16-day gestation period. The use of lead nitrate
on 3 different days of gestation shows that the 8-day old embryo seems most
sensitive to the effect of this compound. The malformations caused by each
of the 3 lead compounds were primarily localized within the developing
sacral and tail vartebrae and were characterized by varying degree of tail
malformations.
Ferm (1969) examined the teratogenic effects of both cadmium and lead
when injected separately into pregnant hamsters. On the eighth day of
gestation the hamsters were anesthetized with pentobarbital and injected
with distilled water (controls), cadmium sulfate (2 mg Cd/kg), lead acetate
(25 or 50 mg Pb/kg) or combinations of cadmium sulfate and lead acetate.
The frequency and severity of clefts in the lip and palate usually caused
by cadmium were reduced in the presence of lead, while the posterior tail
malformations caused by lead appeared to be potentiated in the presence of
cadmium (Ferm, 1969). The possibility is suggested that in the case of
tail bud malformation, cadmium and lead interact additive1y on certain en-
zymes, but that lead blocks the effect of cadmium on the differentiating
visceral arch system, thus preventing the facial abnormalities.
Lead acetate injected intravenously into pregnant prairie moles,
Microtus ochrogaster, during organogenic stages was teratogenic at 32 mg/kg,
but not at 8 or 16 mg/kg (Kruckenberg, et a1., 1976). Total litter
resorption occurred only at doses of 64 mg/kg. No histopathologic changes,
such as eosinophilic intranuclear inclusion bodies in the proximal convoluted
tubules of the kidney, were observed in treated pregnant females.
Palmisano, et a1., (1969) attributed a case of neuromuscular abnorm-
alities and growth impairment of a child to lead poisoning as a result of
the consumption by the pregnant mother of illicit whiskey.
Summarizing, the teratogenic effect of lead needs additional clarifi-
cation and research.
7.3.3
Carcinogenicity
In contrast to man, rodents are susceptible to lead-induced cancers.
Renal, adrenal, thyroid, prostate, and pulmonary adenomas, renal adenocar-
cinomas, and testicular carcinomas have been observed in rats and mice which
had received lead phosphate, lead acetate, and basic lead acetate via dietary
and/or parenteral routes (Sunderman, 1971). Sunderman also reported
lymphomas resulting from the subcutaneous injection of lead.
218
-------
Oyasu, et al., (1970) found that cerebral gliomas (usually poorly
differentiated, malignant tumors) were induced in rats with dietary lead
subacetate and/or 2-acetylaminofluorene (AAF). The highest incidence (8.6
percent) of gliomas was in rats ingesting dietary lead subacetate. With
AAF the glioma incidence was 2.5 percent while in the controls it was 0.3
percent. An increased incidence of lung cancer has been reported in lead,
copper and zinc smelter workers, and in the residents of communities sur-
rounding smelters (Anonymous, 1975a). The report adds that arsenic emitted
from these plants may be the actual cause of cancer.
A followup study of 425 workers exposed to lead in a storage battery
factory was conducted by Dingwall-Fordyce and Lane (1963). They reported
"no evidence to suggest that malignant disease was associated with lead
absorption". Similarly, a recent epidemological study of causes of death
among U. S. lead workers indicated that although the deaths from malignant
neoplasms were slightly higher than expected, the incidence was not eleva-
ted to the point of statistical significance (Cooper and Gaffey, 1975).
Martell (1975) postulates that small, insoluble particles of radio-
active lead (lead-2l0) are absorbed by tobacco plants as they grow. The
radioactive lead is inhaled in the lungs with tobacco smoke, where it
gives off alpha rays that destroy the lung cells, or the radioactive lead
particles spread throughout the body, and may cause some bone, liver and
stomach cancers.
Summarizing, the research to date indicates that cancer cannot be
singled out as a particular risk for individuals with chronic lead poisoning.
7.4
LEAD POISONING IN CHILDREN
Lead poisoning is a preventable disease that generally can be con-
trolled in three ways: by eliminating the sources of lead; by control-
ling the means by which lead enters the body; or by finding and treating
cases early. Unless the source of lead poisoning in a child's environ-
ment is eliminated or contained following diagnosis and treatment, recurrence
of lead poisoning is probable. Thus, early diagnosis must be coupled with
efforts to identify and remove the sources of poisoning. The issue of
leaded paint (specifically, the issue of what constitutes a safe level of
lead in paint) has been addressed in a major report by the National Academy
of Sciences (1976). In this report it is noted that answer to the lead
in paint question presupposes answers to three preliminary questions, namely:
1)
2)
3)
What
What
What
pica
are the adverse effects of lead?
dose of lead is required to produce adverse effects?
is the estimated daily intake of lead in a child with
for paint.
and
Although it is recognized that the total amount of lead assimilated
may be derived from a variety of environmental sources, the NAS report is
concerned mainly with the absorption of lead from the ingestion of lead-
containing paints by young children.
219
-------
7.4.1
Adverse Effects of Lead in Children
According to National Academy of Sciences (1976) there are basically
three stages in childhood lead poisoning:
1) Asymptomaticlead poisoning in which no clinical symptoms are ap-
parent, but in which measurable metabolic changes occur,
2) Symptomatic lead poisoning in which clinical symptoms such as
anorexia, vomiting, apathy, atoxia, drowsiness or irritability
occur, and
3) Lead encephalopathy with cerebral edema, in which coma or convul-
sions occur.
The sequelae of lead encephalopathy, noted by the NAS panel, include
seizure disorders, severe mental retardation and death. Likewise, the
sequalae of symptomatic but less severe lead poisoning include seizure
disorders as well as various behavioral and functional disorders, usually
captioned under minimal brain dysfunction. Clinical studies indicate that
the latter syndrome may include hyperactivity, impulsive behavior, prolonged
reaction time, perceptual disorders, and slowed learning ability. Minimal
brain dysfunction might also result from asymptomatic lead poisoning.
Significantly, the sequelae in each diagnostic category of lead poisoning
do not nec~ssarily occur in every child with a diag~osis; each individual
is unique in his response.
The NAS panel concluded that the question of deciding on which organ
system is the most sensitive, i.e., defining the "critical effect" is very
important when setting "safe levels" of lead. Studies of both hematologic
effects and neurologic effects show varying degrees of response with
equivalent exposure to lead. For example, hematologic effects appear in
some 1 - 5 year old children when blood lead levels reach 30 - 40 ~g/dl,
while an increased frequency of neurologic effects have been shown only in
those children in the range of 50 - 60 ~g/dl or above.
Since the effects of lead in the hematopoietic system are reversible,
they do not constitute sequelae. Lead interferes with the formation of
hemoglobin at several stages, it reduces the life span of the red blood
cells which results in lead induced anemia. In encephalopathy, acute
renal injury (Fanconi syndrome) may also occur. In children this is
usually reversibile, assuming that the child is removed from the source of
lead which produced the toxicity in the first place
7.4.2
Lead Dose Necessary to Produce Ad~~!~e Effects
In the context of this discussion "dose" may mean (1) t;he quantity of lead ad-
ministered, (2) the quantity absorbed, or (3) the quantity present in the
affected organs, tissues or biological fluids. External dose refers to the
amount of lead entering the body. The internal dose represents the amount
of lead present in the organs, tissues, or biological fluids. Herein, blood
lead concentrations are used as indicators of internal dose.
Because individual variability influences the estimate of a dose neces-
sary to produce an adverse effect, any estimate of a safe dose level should
220
-------
allow a margin of safety for highly susceptible individuals who are affected
by relatively low doses (National Academy of Sciences,1976). This estimate
can be obtained from results of population surveys which measure both dose and
effect in each individual and may be expressed as dose-response curves. This
relationship is expressed in Figure 7.2, where blood lead is used as an indi-
cator of internal dose and erythrocyte protoporphyrin as an indicator of effect.
Positive reactors are those individuals who show an effect greater than the
anticipated mean plus two standard deviations. On plotting the percentage of
positive reactors for each blood lead group, it can be seen that highly
susceptible individual groups show a positive response at relatively low blood
lead levels, while highly resistant individuals show a normal response at
relatively high blood lead levels.
100
.!:
..
l; 60
a.
..
o
. a.
Q) 0
'0 {; (;0
cc ..
a.
iii
11>'0
C '11
0'-
o
g. ~ 40
Q)-
0:: Q)
C
ell
U
~ 20
a.
Figure 7.2
o
Totol N = 155
N:20
N:9
<30
30-39 40-49 50-59
Blood Lead, p.gPb/IOO ml whole bloed
;;60
Dose-response relationship for the effects
of internal doses of lead as Pb-B on erythrocyte
protoporphyrin.
Source: Chisolm (1977).
Reprinted from Clinical Chemistry (1977).
Zielhuis (1975a and 1975b) also plotted dose-response curves for each
measure of lead's effect to obtain a series of dos~esponse relationships. As
the NAS panel stated, while dose-response information is helpful in defining
safe levels of toxic substances, other parameters must be considered. These
are individual variability, age, and diet.
Individual variability influences the estimate of a dose required to
produce an adverse effect. In a heterogeneous population, some members seem to
be affected by comparatively low doses of lead, while other individuals will
show little or no effect at high doses. Generally, however, the percentage of
individuals in a population who show a specific effect will be dose-sensitive.
This condition must be recognized in identifying safe dose levels for the
entire population under investigation.
221
-------
Evidence in both animals and humans indicates that both age and diet
are primary factors influencing the absorption and effects of lead (National
Academy of Sciences, 1976). Dobbing and Sands (1973) report that the growth
spurt of the human brain begins during midpregnancy. They conclude that (1)
glial replication and differentiation extends to at least the end of the first
postnatal year and quite likely beyond 18 months, (2) myelination continues
into the third and fourth years and (3) cerebellar growth is most rapid
during the first 18 months of postnatal life. About 83 percent of the human
brain growth spurt is postnatal (Dobbing, 1974). Studies of malnutrition in
both experimental animals and human infants have demonst,:ated the vulner-
ability of the developing brain. Hyponutrition occurring during the growth
spurt of the brain of the rat produced a permanent reduction in both body
and brain weight as well as behavioral changes (Dobbing and Sands, 1973).
Hyponutrition before this period had less severe effect on the central
nervous system (CNS) development.
The growth spurt in rats occurs during the first 25 days after birth
along with glial cell multiplication during the first half of this period.
Rapid myelination, dendritic authorization, synaptic connections, dramatic
metabolic and neurochemical development and rapid cerebral growth occur
ouring this period. Permanent clumsiness associated with cerebral deficits
caused by hyponutrition occur during the growth spurt (Dobbing, 1974).
Studies of malnutrition in human infants also have shown that the brain
is especially vulnerable during the growth spurt. Pyloritis occurs between
birth and 3 months of age, is surgically correctable and is not associated
with any particular socioeconomic or cultural group (Klein, et a1., 1975).
Reduced I.Q. levels were found in school-age boys suffering from malnutri-
tion during the first two years of life (Hertzig, et a1., 1972).
Age also seems to alter the intestinal absorption rate for lead. It
has been hypothesized that gastrointestinal absorption of lead is more
efficient in children than in adults. Various animal studies support
this position as does a study by Alexander et ale (1973) involving children
aged 3 months to 8 1/2 years.
A more recent study leaves little doubt that a higher percentage of
gastrointestinal lead intake is absorbed in children than in adults (Ziegler,
et al., 1978). Twelve normal infants aged 14 to 746 days served as subjects
for this study. Eighty-nine metabolic balance studies were performed to
determine lead intake and fecal and urinary excretion. Net absorption and
retention were calculated from the results of these studies. Urinary ex-
cretion increased with increasing intake; however, it amounted to only a
small portion of total excretion. Lead intake and fecal excretion were
significantly correlated. Absorption, calculated as lead intake minus fecal
excretion and expressed as a percentage of intake, averaged 26.2 percent.
Average lead retention was 11.3 percent, expressed as a percentage of intake.
Both absorption and retention of lead were significantly correlated with intake.
222
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Ziegler, et aI, analyzed the results of balance studies with intakes
greater than 5 ].lg/kg/day separately, since it is likely that most children
have intakes higher than 5 ].lg/kg/day. Average net absorption was 42 percent
of intake, and net retention averaged 32 percent of intake when intakes were
greater than 5 ].lg/kg/day. Fecal excretion of lead exceeded intake in 7 of 28
studies with intake less than 5 j..lg/kg/day. This was true in only 3 of
61 studies with intakes higher than this value. Studies have shown that
gastrointestinal absorption of lead in adults is approximately 10 percent
of intake (Kehoe, 1961a; Rabinowitz et a1., 1975). Therefore, Ziegler's
work lends substantial weight to the hypothesis that gastrointestinal
absorption of lead is more efficient in children than in adults.
Both dietary components and dietary deficiencies alter the intestinal
absorption of lead (National Academy of Sciences, 1976). In experimental
animals, the intestinal absorption of lead is significantly increased if lead
is administered in oils, fats, or milk rather than in a dry diet. Similar
studies are not available, nor possible, in young children. Dietary
deficiencies such as calcium, copper, and iron increase the absorption of
lead in rats. Dietary deficiencies of calcium and, especially, iron have
been reported to be prevalent among preschool age children, especially
those in the lower socioeconomic groups. Because of the rapid growth rate
during early childhood, iron reserves may be marginal even in apparently
healthy children. An additional risk factor, pica, the repetitive ingestion
of non-food substances, occurs in at least 50 percent of preschool children
between 12 and 36 months of age (National Academy of Sciences, 1976).
Summarily, several factors make the young child less resistant to
lower levels of lead than the adult. Pica may lead to ingestion of lead-
containing paint chips; the young age makes the child susceptible to lead-
induced neurologic damage; and both age and diet may elevate the intestinal
absorption rate for lead (National Academy of Sciences, 1976).
Lead exerts its effects in the hematopoietic, neurologic, and renal
systems. Renal damage is a reversible effect observed in severe cases and
no published data are available to suggest that damage occurs in asymptom-
atic cases. Considerable controversy exists concerning conflicting re-
ports of neurologic damage occurring in asymptomatic or mildly symptomatic
cases. At least until this argument is resolved, the hematopoietic system
is considered the critical site for lead's effects. Thus, using blood lead
as a measure of the internal dose of lead, different effects can be observed
as blood lead levels increase. Le~d-induced anemia has been found in both
adults and children. Lead causes multiple interferences in the formation
of hemoglobin (National Academy of Sciences, 1972), including inhibition of
the enzymes, o-aminolevulinic acid dehyratase (ALA-D), and ferrochelatase
(Pentschew and Garro, 1966). "The inhibition of these enzymes results in an
accumulation of o-amino1evu1inic acid in urine (ALA-U) and free erythrocyte
protoporphyrin (FEP) in blood. It is now known that zinc protoporphyrin
and not the free protoporphyrin IX is present in excess in the circulating
erythrocytes in lead poisoning and iron deficiency (Lamola and Yamane, 1974).
Population studies of children in the United States have rarely included
enough children with <20 j..lg Pb/dl to determine this lower threshold level.
223
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A second threshold is observed in children when blood lead levels reach
35 - 40 ~g/dl (Chisolm, et al., 1975; Kammholz, et al., 1972, Piomelli,
et al., 1973, and Sassa, et al., 1973). When blood lead levels reach 40 -
50 ~g/dl, the excretion of ALA-U begins to rise in both adults and children
(Selander and Cramer, 1970, and Tola, et al., 1973). Pueschel, et al.,
(1972) found a significant negative relationship between hemoglobin and
blood lead levels in children. Blood lead levels> 60 ~g/dl were almost
always associated with hemoglobin levels <10 g/dl.Betts, et al., (1973)
found hemoglobin levels < 11 g/dl in 36 percent of children with 37-56~g
Pb/dl, 71 percent with 60 - 100 ~g Pb /dl, and 89 percent with> 100 ~g
Pb/dl. Rosen and Trinidad (1974) found a negative relationship between
hematocrit and blood lead concentrations in children at levels exceeding
40 ~g/dl.
Subtle neurological effects are difficult to measure in both adults
and children and even more difficult to attribute to a single cause such
as lead poisoning. There is currently no set of neurochemical tests for
measuring changes that is comparable to tests available for measuring
changes in the hematopoietic system. Present measurements of neurologic
changes accrmplished through the use of functional tests such as I.Q. tests.
Confounding factors such as parental I.Q., parental education level, socio-
economic status, and birth trauma also affect the results of these tests.
Studies aiming to show a relationship between I.Q. and exposure to lead
should include control/study matches for age, birth rank, parental I.Q.,
socioeconomic status, nutrition, and pica. In addtion, there should be
studies in which the presence or absence-6fexposure to lead in the early
years is well documented. Many reported studies lack a correct experimental
design, a proper control group, and firm documentation concerning lead exposure.
The studies of de la Burde and Choate (1972 and 1975) meet most of
the criteria of a prospective study. Both study and control children came
from an on-going Child Development Study at the Medical College of Virginia
in Richmond. ~lothers were followed during pregnancy and delivery and child-.
ren followed for eight postnatal years. The study group consisted of 67
asymptomatic children who had a positive history of pica for paint or plaster,
lived in deteriorated old housing, had positive urinary coproporphyrin tests
and either a blood lead level >40 ~g Pb/dl or blood lead >30 ~g Pb/dl and
positive radiographic findings for lead lines in the long bones. We feel
that this combination of criteria for selecting the study group was more
reliable than a selection based on blood lead levels alone. Even so, the
absence of serial blood levels, which were not feasible at the time, is
the major weakness of this study. This weakness is largely overcome by
dependence on x-rays (Betts et al., 1973) and positive urine coproporphyrin
tests (Benson and Chisolm, 1960) are generally associated with blood lead
concentrations equal to or greater than 60 ~g Pb/dl. Lead levels in shed
deciduous teeth were determined several years later on teeth from 29 of the
lead-exposed children and 32 of the control children. The mean tooth lead
level for the study group was significantly higher than the mean tooth lead
level of the control group. The control group consisted of 70 children who
had a negative history of pica for paint or plaster, lived in modern housing,
did not visit older housing for day care and had negative tests for copro-
224
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porphyrin in urine. In addition, all children were excluded from both groups
who showed neurologic abnormalities or developmental lag either during the
newborn period or at four months, if abnormalities were noted on the Bayley
scale at eight months, or if confirmed or suspected disease of the central
nervous system was noted anytime before seven years of age. In addition,
the groups were comparable in age, sex, race, mother's non-verbal I.Q.,
socio-economic status, family composition and possible sources of family
upheaval such as death in the family, foster home placement or working
mother.
Neurological and psychological tests were administered to both groups
at four years of age and again at seven years of age. Fifty-eight children
from each group also had tests repeated at eight years of age. At four years
of age, the most significant differences between the groups were in the
areas of fine motor coordination and behavior. Failure on fine motor
tests occurred almost twice as frequently in the lead-exposed group as in
the control group. Deviation in overall behavior ratings occurred almost
three times as frequently in the lead-exposed group. Mean I.Q. scores, as
measured by the Stanford-Binet test, were 89 + 13.1 for the lead-exposed
group and 94 ~ 10.5 for the control group. At seven years of age, neurologic
examination revealed deficits in more than twice as many children from the
study group as from the control group. Full-scale I.Q., as measured on the
Wechsler Intelligence Scale for Children revealed that the majority of
children from both groups had average intelligence, although the mean LQ. 's
were statistically significantly (p <0.01) lower in the lead-exposed group.
The frequency of results in the borderline or mentally defective range was
higher in the lead-exposed group. Short attention span and minimal goal
orientation occurred in 32 percent of lead-exposed children and 14 percent
of control children. Poor academic progress was noted in 27.8 percent of
lead-exposed children and 4.1 percent of control children. The number of
children repeating at least one grade was higher in the lead-exposed group
(25.9 percent) than in the control group (6.1 percent). Eleven lead-exposed
children and four control children were receiving speech therapy for speech
impediments.
De la Burde and Choate (1972, 1975) felt that the most significant
difference between the groups was in the area of behavior and that this was
the primary cause for poor school performance. Among the lead-exposed group,
five had been seen by psychiatrists, one had been institutionalized and
three were subject to seizures. None of these findings occurred in any of
the control children. A review of school records revealed that hyperactivity,
explosive behavior and frequent temper tantrums occurred in 19 lead-exposed
children and 5 control children. The behavior problems which had been ap-
parent at four years of age, but which were adequately handled in the home
environment, persisted at seven years and prevented appropriate functioning
in the school environment.
The results of several additional studies indicate a relationship be-
tween increased lead absorption and neurologic deficits in young children.
These include the studies by Albert, et al., (1974), Perino and Ernhart (1974),
Beattie, et al., (1975), and David et al.~ (1972).
225
-------
. Although no single study cited above represents a perfect model to
detect subtle neurologic differences between groups, an increased frequency
of irreversible neurobehavioral deficits seems to exist in those children
with blood lead levels in the range of 50 - 60 ~g Pb/dl or above. Reversible
neurobehavioral effects appear at somewhat lower blood levels. However, it
is not clear as to whether the exposure levels of 50 - 60 ~g/dl or above
represent the levels which were responsible for the behavioral deficits
observed.
7.4.3
Estimated Lead Intake in a Child with Pica for Paint
The National Bureau of Standards has published the results of mathe-
matical models together with the assumptions and data used to formulate
the models (Gilsinn, 1972). From this model it was estimated that approxi-
mately 600,000 children in 241 standard metropolitan statistical areas
(SMSA'S) had elevated blood lead levels (>40 ~g/dl). However, as Goyer
and Mehlman (1977) point out, at the present time the models and assumptions
are only partially validated. The study has also been criticized for using
only data from the east and midwest. (See also Section 8.6.3)
The incidence of lead poisoning is highest among one-to-five year old
children who live in run-down urban neighborhoods where peeling paint and
broken plaster often prevail (Pueschel, et al., 1972). A relatively small
number of cases result from exposure to improperly glazed pottery or
exposure to industrial sources, (e.g., smelters and battery factories).
The mechanism by which lead industries contribute to childhood lead
poisoning can be direct, as in the case of lead emissions to ambient air,
and fallout of particulate lead causing elevation of lead levels in dust and
dirt, and indirect, such as household contamination due to lead carried into
the house on leadworker's clothing.
Even in the absence of significant industrial sources, the preschool-
age child is exposed to multiple sources of lead, including dust, canned
foods and liquids, and paint. It is the cumulative intake and absorption
from these various sources that is important. Inhalation of average urban
air (1 - 3 ~g Pb/m3 is considered insignificant in comparison with the above
sources.
Paint provides the most concentrated source of lead potentially avail-
able to a young child. Dried house paint films containing 0.5 percent lead
would provide 5,000 ~g Pb/g paint. Comparison of model x-ray films of known
quantities of paint with abdominal x-ray films taken of children known to
have pica for paint indicated 7 of 10 randomly selected films showed radio-
pacities equivalent to an estimated one gram of paint consumed by each child
(King and Schaplowsky, 1974).
Since house dust lead levels in newer inner city houses were significantly
lower than in the older inner city houses (2 - 24 ~g Pb/square foot compared
with 33 - 456 ~g Pb/square foot floor surface, (Sayre, et al., 1974) concluded
that the source of lead probably originated from the powdering of old lead
paints. From a study of dirt samples around painted frame farm houses remote
from traffic Ter Haar and Aronow (1974) concluded that lead paint was the
226
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-principle cause of elevated soil lead levels and that lead from fallout dust
was an insignificant source of lead intake in the children studied.
Although wide variations in lead intake could occur as a result of
the parents' choice of food for their child, an estimate of 93 ! 36 ~g Pb/day
was obtained from the analysis of the dietary intake of 333 infants aged 1 to
12 months. (National Canners Association stud~ cited by Kolbye, et al., 1974).
This estimate corresponds to about half the total adult dietary intake. Stu-
dies by Alexander, et al., (1973) in 11 healthy children receiving a normal
diet showed a mean lead intake of 10.6 ~g Pb/kg body weight per day and a
mean fecal lead output of 5.1 ~g/kg/day. In Alexander's studies average daily
intake and outputs are calculated on a per kilogram basis for an average two-
year old child weighing 12.5 kilograms. Obviously in Kolbye's studies the
mean lead intake per kilogram of body weight was somewhat higher. Since
Kolbye did not determine the fecal lead output the percent of lead absorbed
cannot be calculated.
However, from Alexander's studies it is estimated that 50 per
cent of lead from foods is absorbed by a young child. This estimate will be
used in this discussion on the hazard of 0.5 percent lead paint. Studies in
~nimals indicate that lead compounds, incorporated into a paint matrix, are
absorbed only one-fourth to one-half as well as the free lead salts. (Gage
and Litchfield, 1969). Using an average of one-third for estimating the
child's absorption of lead from paint, experimental data indicate that chil-
dren will absorb one-third of 50 percent, or an average of 17 percent of the
lead from paint.
Table 7.8 (National Academy of Sciences, 1976) gives the estimated amounts
of lead abs~rbed and excreted, based on an absorption factor and estimates of
weekly intakes of 1, 2, or 3 grams of 0.5 percent paint. Average daily
intakes are also calculated on a per kilogram basis for an average two-year
old child weighing 12.5 kilograms.
Table 7.8
CALCULATED LEAD INTAKE AND ABSORBED DOSE FROM PAINT PICAa
Paint Ingested
Per Week, g
Calculated Lead Intakeb
~g/day ~g/kg/day
Lead Absorbedc
~g/day ~g/kg/day
d
Lead Excreted,
~g/day
1
2
3
714
1,429
2,143
56.1
114.3
171. 4
121
243
354
9.7
19.4
29.1
593
1,186
1,779
a
Source: National Academy of Sciences, (1976)
bAssumes paint contains 0.5 pecent lead
cAbsorption estimated at 17 percent
JExcretion in feces estimated at 83 percent
227
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Thus, from Table 7.8, a 12.5 kg child consuming 1 gram of 0.5 percent
lead paint per week would have a daily intake of 57.1 ].1g Pb/kg body weight,
a fivefold increase above that found in a normal diet. Two grams of paint
would produce an eleven-fold increase, and three grams, a sixteen-fold
increase.
Clinical evidence indicates that children with pica are apt to ingest
one to three grams of paint per week (National Academy of Sciences, 1976).
Since the ingestion of between one and two grams of 0.5 percent lead paint
per week would be enough to produce daily fecal outputs equivalent to those
found in children with >60 ].1g Pb/dl of blood, the NAS panel concluded a
level of 0.5 percent lead in paint cannot be considered a "safe level".* The
above method for determining the hazard of lead paint is premised on relating
lead intake to the appearance of early clinical illness and significant risk
of central nervous system (CNS) effects.
A s~cond method relates lead intake to blood lead levels associated with
the ~ppearance of metabolic effects in children. The average blood lead level
in normal children is approximately 20 ].1g Pb/dl (Lepow, et al., 1974). Early
metabolic changes in the hematologic system start when blood lead levels reach
the range of 30 to 40 ].1g/dl. Thus, it would be desirable to insure that
mean blood lead levels for groups do not exceed 20 ].1g/dl. Table 7.9 (National
Academy of Sciences, 1976) shows the effect of the ingestion of 0.5 per lead
paint on blood lead levels.
TABLE 7.9
CALCULATED DAILY EXTERNAL DOSE AND
ASSOCIATED INTERNAL DOSEa
Increase
in Blood
Lead,
].1g/dl
Lead Absorbed
Each Day,
].1g/kg/day
Corresponding
Lead Intake,
].1g/kg/dayb
Total Lead Intake Necessary For
10 kg Child, 12.5 kg Child,
].1g/day ].1g/day
17
34
1.43
2.86
8.41
16.82
84.1
168.2
105.1
210.3
a
bSource: National Academy of Sciences,
Assumes 17 percent absorption.
(1976)
*It may be pointed out that lead paints up until very recently contained
much more than 0.5 percent lead; the paints originally applied to now-
substandard housing may have contained as much as 60 - 65 percent lead.
228
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The ingestion of 16.8 mg paint/day or 33.6 mg paint per day containing
0.5 percent lead would raise blood levels by 17 ~g/dl or 34 ~g/dl in a 10 kg
child. Similarly, a 12.5 kg child would need to ingest either 21 mg paint/day
or 42.6 mg paint/day. It is not unusual for a child with pica for paint to
consume more than 1,000 mg paint per week or 143 mg paint per day (King and
Schaplowsky, 1974). This second method also shows that a level of 0.5 per
cent lead in paint clearly represents a hazard to a child with pica for
paint. However, because many factors modify lead intake, absorption rates,
and individual susceptibility, the foregoing two methods used for deter-
mining the hazard of 0.5 percent lead paint, cannot be considered suitable
for application to every child. Factors (discussed earlier) such as age,
diet, and nutrition affect the increase or decrease of lead absorption by
one individual. Only after these parameters are resolved can we hope to
get additional clarification of the hematopoietic, neurological, and renal
effects of lead and thereby define a safer daily permissible intake for all
groups.
However, with respect to the dose calculated by the NAS panel for a
child with pica (Table 7.8), at the new upper limit of 0.06 percent lead in
paints to be used in and on houses, the assumed 1 to 3 grams of chips in-
gested per week would produce an absorbed dose of only 14.5 to 42.8 ~g/day.
7.5
EPIDEMIOLOGY
A wide variety of epidemiologic studies have attempted to describe and
quantify the health effects associated with lead exposure. The identifica-
tion of especially susceptible segments of the population has also been a
constant objective of these studies. Although both gastrointestinal and
respiratory absorption of lead have long been recognized as contributors
to body burden, the vast majority of epidemiologic studies have chosen to
examine the effects of respiratory, rather than dietary exposures. This
apparent emphasis on respiratory exposures relates primarily to the rela-
tive ease with which the respiratory exposure level of populations may be
estimated (based on suitable environmental monitoring data). Characterizing
dietary lead exposures has proven more difficult due to a wider range of
individual differences in factors determining lead intake such as absolute
caloric intake and composition of diet. Consequently, studies of dietary
lead exposures tend to be often laboratory type and generally restrict them-
selves to intensive, long-term observation of a mere handful of individuals.
Several studies of dietary lead exposure are described in Section 7, and
alluded to again in Section 8.6, a discussion of the relative importance
of dietary vs. respiratory sources to total lead dosage. The remainder of
this section, however, is devoted to a discussion of the contribution of
airborne lead to blood lead, an indirect indicator of body burden.
Epidemiologic studies have been conducted in three general types of set-
tings based on the characteristic levels of exposure:
(1) Studies of general populations
(2) intermediate level studies in which groups are singled out for
study based on some unusual circumstance or mode of exposure. Typically,
these studies involve groups chronically exposed to ambient lead concentrations
229
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higher than those of the general population, but substantially lower than
industrial exposure levels. Persons residing in close proximity to freeways,
working in dense vehicular traffic or living near smelters or other stationary
sources of lead emissions are examples of "intermediate" groups for which
epidemiologic information is available.
(3) Occupational studies including persons who are exposed to air lead
concentrations many times higher than general populations or "intermediate"
groups; thus, they represent the high extremes of the dose-response spectrum.
Attempts to establish a dose-response relationship between environmental
lead concentrations and adverse health effects and/or the relative contribu-
tion of each of the various sources of exposure to body burden have met with
only limited success. The underlying difficulty in such an analysis may be
traced to the multiplicity of sources of lead exposure and the difficulty in
accurately quantifying individual exposure.
7.5.1
Studies of General Population
The risk to general populations from lead in air has become a matter of
considerable concern and the subject of many recent studies. As Hammond (1977)
has pointed out, studies of the fate of inhaled lead in man using conventional
deposition and clearance measurements have not provided much useful information
on the contribution of lead in ambient or industrial air to the internal dose
at specified air lead concentrations. A more indirect but nonetheless use-
ful approach to the problem proceeds from the assumption that the concentra-
tion of lead in the blood is proportional to the combined level of total up-
take. Although such a relationship has never been rigorously demonstrated,
taken together, the studies discussed in this section place the contribution
of air lead to blood lead in the range of about 0.6-2.0 ~g/d1 in blood per
~g lead/m3 in air.
The earliest large scale study of general populations was the "Three
Cities Study" conducted in Los Angeles, Philadelphia, and Cincinnati, Ohio,
in the early 1960's (U.S. Department of Health Education and Welfare, 1965).
In addition to the general population, several groups more appropriately in-
cluded in the "intermediate" exposure category (Le., policemen, traffic con-
trollers, garage employees, etc.) were also investigated as separate study
groups. The principal finding of the "Three Cities Study" was that signifi-
cant differences in blood lead means could not be found between the cities.
On the other hand, persons who lived or worked in close vicinity of dense
vehicular traffic such as traffic policemen, garage mechanics, and parking
lot attendants had higher blood lead levels than others not similarly ex-
posed. These data are shown in Table 7.10.
230
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TABLE 7.10 BLOOD LEAD LEVELS OF SELECTED
HUMAN POPULATIONS a
Type of Population
Nean Blood Lead,
)Jg/dl
Population \"ithout kno~m occupational
. exposures:
Remote California mountain
Composite Rural U.S.
Suburban Philadelphia
Composite Urban U. S.
Los Angeles Aircraft workers
Pasadena city ~mployees
Dmvnt0\oJ11 Philadelphia
Hale
Fcmales
12
16
13
21
19
19
24
( 9)
(10)
(13)
(16)
(17)
(12)
(18)
Population \.:ith known occupational
exposures:
Cincinnati policeman
Cincinnati trafficman
Cincinnati automobile test-lane
imspectors
Cincinnati garage workers
Boston Sur-ner-Tunnel c3ployee5
25
30
31
31
30
aSource:
U.S~ Department of Health, Education, and WelfRre (1965).
Goldsmith and Hexter (1967) calculated a logarithmic dose-response re-
gression of blood lead concentrations on air lead levels. The data were mean
blood lead levels and the associated average estimated ambient air exposure
from the cities included in the "Three Cities Study" (U.S. Dept. of Health,
Education, and Welfare, 1965). Under the assumption that the major source of
variation in ambient air lead was vehicular traffic, Goldsmith and Hexter cal-
culated particle sizes and consequent retention rates were calculated on the
basis of 50-80 percent (by weight) particles < 1.0 ~ equivalent diameter.
This is believed to be the characteristic particle size associated with
automotive emissions. In general, fixed samplers were used to measure ambient
levels; although it is recognized that they may not be truly representative
of individual exposures, the authors felt they represented reasonable
estimates of population averages. Goldsmith and Hexter concluded that a dose-
response relationship was suggested when blood lead concentration is plotted
against air lead concentration. Data for various groups/individuals are
plotted in Figure 7.3 The regression line shown in Figure 7.3 is calculated
on the basis of epidemiologic data from the "Three Cities Study" (Goldsmith
and Hexter, 1967). In addition, data from four human subjects experimentally
exposed to known, high concentrations of lead seoquioxide (Kehoe, 1966) are
also plotted along the regression line in order to reinforce the apparent
validity of the relationship depicted. The regression line seen in Figure 7.3
is described by the equation:
231
-------
10glO blood lead = 1.265 + 0.2433 10glO air lead
Thus, the Goldsmith and Hexter regression line may be interpreted to indicate
that each microgram of lead in air contributes about 1.3 ~g/lOOml to blood
lead in the range of exposure observed in the "Three Cities Study," (speci-
fically from less than 0.2 ~g/m3 to approximately 8.0 ~g/m3) as shown in
Figure 7.3.
1:1010
o
~40
'--
1:10
:::I
~
. ('IO~I.IIOLOGIC DATA
X LD
+.6
..
~
C'CI
C1)
""20
~
o
o
.-I
..c
c:
C'CI
~ '0
0.1
+
Ie
~...
Jt"X
:~.'+
,.~~
~,
.. .. ,"
~yt
. 0 a
o .
...00 a
o HI<
ass
EXPERIMENTAL
SUBJECTS
.
10.0
50.0
o.s
1.0
5.0
Estimated Average Respiratory Exposure, ug Pb/m3
Figure 7.3
Mean blood lead concentration for epidemiologic
and experimental respiratory exposures. (Re-
gression from epidemiologic data only.)
Redrawn from Goldsmith and Hexter.
Source:
National Academy of Sciences, (1972).
The authors concluded that "the close correspondence between the ex-
perimental and epidemiologic data (obtained from Kehoe, 1966 and "Three
Cities Study" respectively) make it seem likely that this relationship will
be valid for a population having a dietary, beverage and cigarette smoking
intake similar to that of American males."
Goldsmith and Hexter's proposed dose-response regression has been
criticized on several grounds. First, ambient exposures were estimated
only and were not necessarily measured at the same times and places at
which the populations were exposed. Thus, air and blood levels even within
the same exposure group (~ata points) are not related in any consistent,
specific fashion. Second, the validity of calculating a regression line
based on lead absorption from atmospheric lead has been challenged on the
basis of the variable contribution of lead from other, more important
sources of intake such as food and cigarettes (National Academy of Sciences,
1972). Thirdly, the authors do not describe the methods of deriving their
regression line nor do they present data on statistical tests of "goodness
of fit" of the calculated regression line. Their methods of deriving the
232
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estimated "average" exposures levels for occupational groups in policemen,
garage workers, and tunnel workers are described only as a weighted average
of presumed occupational and ambient exposure which, themselves were estimated.
In addition, Goldwater (1972) discusses the matter of confidence limits when
this type of statistical analysis is employed. Lines representing confidence
limits are hyperbolic and diverge markedly when applied to extrapolations at
either end of the regression line; there is little validity to extrapolations
beyond the ranges encompassed by actual observations. The NAS report also com-
ments on this phenomenon by stating, "the regression line cannot be applied
with confidence to exposure conditions affecting the general population; this
also applies to the general population of most large urban centers, inasmuch
as average ambient air concentrations even in these centers do not generally
exceed 2 jJg/m3."
In earlier studies such as the "Three Cities Study," multiple uncontrolled
variables associated with the various population groups have confused the ap-
praisal of actual integrated exposure and the construction of the correct dose-
response relationship. Because blood lead levels are determined by many fac-
tors in addition to respiratory absorption of lead in ambient air, the effects
of these variables must be either controlled through statistical procedures or
wqde as homogeneous as possible in the initial selection of the study subjects.
Unless personal monitoring devices are used, one cannot accurately quantify
total integrated exposure over months or years for police officers, garage
mechanics, "drivers", "commuters", aircraft workers or other similar groups.
Occupational exposures and geographic variability in lead concentrations in
various parts of the city are not reflected in air sampling at fixed locations
not clearly related to the population in question.
Tepper and Levin (1975) reported the findings of a survey of air and pop-
ulation lead levels in selected American communities, commonly referred to as
the "Seven Cities Study". The principal objective of the study was to evaluate
the relationship between atmospheric lead levels and the concentrations of
lead in blood of persons exposed to the atmospheres in question. Among the
cities surveyed were Cincinnati, Philadelphia, and Los Angeles, which had been
extensively surveyed in 1961-1962 as part of the "Three Cities Study" previously
described. Also included were New York City, Metropolitan Washington, D.C.,
Greater Chicago, Houston, and Los Alamos, New Mexico. These cities were sel-
ected on the basis of population density, industrialization and geographical
location to represent a broad spectrum of these variables.
Tepper and Levin (1975) focused particular attention on the definition
of populations having a specific, consistent relationship to known air levels
of lead. Unlike the Three Cities Study, populations sampled in the present
study were women volunteers living within a prescribed distance (within a 1-
mile radius) from the reference air sampling station. Moreover, the blood
lead and air measurements were made concurrently. In confining the observa-
tions to members of one sex, requiring that the subject reside not more than
1 mile from the sampling apparatus, and eliminating as completely as possible
extraneous, occupational lead exposures, the authors hoped to create a group
which would accurately reflect patterns of respiratory absorption of lead in
the ambient atmosphere in a general community setting.
233
-------
In addition to the groups of women described above, husbands of 100 Los
Alamos participants were also included as a separate study group. Estimates
of alimentary lead intake were obtained from measurement of the urine and
feces of a subsample of 20 volunteers in each region. Eact participant col-
lected all excrement for a 10-day period.
The principal findings of the Seven City Study were as follows:
1) Concerning changes in atmospheric levels of lead during the interval
1961-62 to 1968-69, the reported data demonstrate higher lead levels at most
of the study sites during the more recent of the two. periods. A careful
examination of experimental methodology tends to exclude the possibility that
this change is an artifact reflecting changes in technique.
2) The relationship between age and blood lead level was examined by
means of regression analysis and was found to be of no general significance.
3) The influence of smoking upon blood lead levels was determined to
be clearly significant. The blood lead level of smokers exceeded that of
nonsmokers and previous smokers. The relationship held true for males as
well as females in the husband-wife pairs in Los Alamos.
4) Since the F-ratio testing the difference in blood lead levels among
locations was significant, individual comparisons were conducted between urban
and suburban populations in the same metropolitan areas to examine whether or
not blood levels reflect degree of urbanization for smokers and nonsmokers.
In both smoker and nonsmoker categories, urban groups were consistently higher
than nonurban groups. Consequently, it appears that urban blood lead levels
are higher than those from related suburban areas.
5) Figure 7.4 presents mean blood lead levels and corresponding mean
air lead levels at the sites where both were measured. The association between
these mean values was measured by means of the Pearson Product
0.03
o "'-
8 =",
"''''
- 0-
~ ~-;
~0.02 ;: g
~ ~~
o -,0
as .-
.:
..,
o
.'
-' c.O\
o
o
.
'"
~ - 0
~ ~ ~
It ii I
.: E ,., -- 3
E~ ~ .. ~
~< . g
":: . . t3
If. S .
. .=
a;
g
'C
~
E
o
-'
;;
'5 ( ) : ;,urr.:.er of people
~
.
- floOd LeCd L.,els Cia
~ Function Qf Air laod
:::. ~vels
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~
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->
0-
f
~
5.0
Figure 7.4
:'0
2.0 3.0
Lead in Air ./,,9/rr.)
4.C
Blood lead levels
and corresponding
mean air lead levels.
Source:
Tepper and
Levin (1975)
234
-------
Moment Correlation Coefficient and Kendall's Rank Correlation Coefficient.
The values obtained were 0.412 and 0.354, respectively, for all data. Cor-
responding values for non-smokers only were 0.400 and 0.345. The values were
not: significant at the 5 percent level. It was therefore concluded that
there is no association between average blood and air lead concentrations in
the locations studied.
6) The observations that urban levels of blood lead are significantly
higher than suburban levels, but that air concentrations of lead are not
clearly reflected in blood lead levels generally, suggest that other var-
iables are more important than ambient air lead levels in determining con-
centrations of lead in the blood. The precise nature of the variables,
which evidently differ in the several regions studied, remains undefined.
Presumable alimentary lead intake plays a significant role; however this
was not clearly evident in the short-term metabolic study. Climatic factors
may also be relevant.
7) The analysis of fecal lead levels conducted to appraise alimentary
lead intake, did not demonstrate a reciprocal relationship between air and
food exposures, i.e. high alimentary intake compensating for respiratory
exposures so as to obscure effects of the latter.
8) The examination of blood lead levels in husband-wife pairs in Los
Alamos revealed a significant difference between males and females. The
basis for this difference was not established. Probably, it cannot be
attributed to occupational factors, for the work of each individual was
characterized and conducted under comprehensive and detailed industrial
hygiene supervision. Differences in smoking between the sexes could not
account for the differences in blood lead, either. The blood lead in males
remained higher than in females of the same smoking status.
Since men have generally higher hematocrit levels than women and lead
is transported in association with red blood cells, the authors suggested
that higher blood lead concentrations in men reflect a higher level of
circulating red cells. This hypothesis deserves further investigation.
Although both men and women of the studied Los Alamos couples consumed
diets presumably similar in composition, the men consumed a generally
greater quantity of food. It is therefore also likely that the alimentary
exposure of men to lead may be greater than that of women.
In summary, the Seven Cities Study failed to find a significant cor-
relation betwejn air lead and blood lead levels over an air lead range of
0.17-3.39 ~g/m. Such a finding should not be unexpected, however, due to
the narrow range of ambient conditions examined, the relatively small
(20-30 percent) contribution of air to total lead intake (See Section 8.6)
at such low exposure levels, and the fact that the air data were obtained
from fixed outdoor sampling stations which cannot estimate individual
exposure levels precisely.
Azar, et al., (1975) reported on the effects of air lead exposure as
measured with personal sampling devices on. such indices of lead absorption
as blood lead, urine lead, DALA (delta aminolevulinic acid) and ALAD
(aminolevulinic acid dehydratase) activity.
235
-------
The air lead exposure of 30 male subjects in each of 5 locations in
the United States was measured with personal air samplers for 24 hours a
day for periods ranging from 2-4 weeks. During this period, blood samples
were analyzed for lead and ALAD activity analyses and urine samples were
measured for lead, DALA excretion, osmolarity and creatinine. Smoking data
was obtained by means of a questionnaire. Two types of personal samplers
were used: one was an MSA unit equipped with a cyclone device capable of
differentiating between respirable and non respirable particles. These
were used in the two taxicab studies. The second type was a Casella unit
which was more portable, but since it did not have the cyclone device, only
total air lead exposure was measurable.
The five sites were selected to represent a wide range of air lead
exposures. Taxicab drivers were studied in Philadelphia and Los Angeles.
Participants at Starke, Florida, Barksdale, Wisconsin and Los Angeles were
employees of Du Pont de Nemours and Company and were thought to be repre-
sentative of non-occupationally exposed groups.
The average exposure, urine and blood responses were computed for each
subject in the study. Statistical ana~yses were based on these within sub-
ject averages. The site averages were subjected to an analysis of variance
to determine whether there were any significant differences between average
urine and blood responses at the five sites. The relationship between air
lead and the blood and urine responses were evaluated using regression tech-
niques. Homogeneity of the slopes were checked by multiple regression
techniques and analyses of the data in both natural physical units and log-
arithmic units (base 10 logarithms of the natural units) were performed. The
logarithmic relationship gave the best fit to the date.
Table 7.11 shows air-lead exposure levels which were calculated by
combining the work exposure ("on duty") with the home exposure ("off duty")
on a time-weighted basis. \Vhen a cyclone device was used, the data are
referred to as Respirable and when not used, as Total. Exposures ranged
from a low of 0.22 ~g/m3 at Starke to a high of 9.12 ~g/m3 obtained on a
Los Angeles cab driver. Respirable air lead exposures were significantly
less than total exposures, indicating that a large portion of "Total" lead
is composed of particles >10 microns in diameter which do not penetrate
the lung. (These large particles could be swallowed, however.)
Statistical analysis of the data showed that there was no significant
correlation between air and blood lead at any of the five sites, indicating
either (1) that there is in fact no correlation between air lead and blood
lead, or (2) thirty subjects is too few to demonstrate significance, or (3)
the range of data is too narrow to show significance, or (4) variables other
than air lead (lead ingested from food and drink) are overwhelming any effect
which air lead might have on blood lead. Analysis of the composite data (149
subjects) using a multiple regression technique indicated that unspecified
variables other than air lead were more important determinants of blood lead.
236
-------
TABLE 7. 11
MEAN AIR LEAD EXPOSURE FOR THE FIVE GROUPS EXAMINED BY AZAR, ET AL (1975)a
Site
_._9-~-- P-.l!..~I_n__._.-
Total
3
Lead Concentration, ~g/m I 1 S.D.
Off Duty
Total
Combined Exposure
Total Respirable
Respirable
Philadelphia, Pa
Cab drivers
5 . 10 + 1. 11
Starke, Fla.
2.01 + 2.52
N
W
'-I
Barksdale, Wise.
2.84 + 5.19
Los Angeles, Calif.
Cab drivers
9.42 +
.98
Los Angeles, Calif.
Office workers
3.05 +
.76
N.D.
4.34 + .86 1. 48 + .23 2.62 + .42
1. 39 + 2.39 0.37 + .31 0.81 + .82
b -
N.D. 0.36 + 0.14 1.01 + 1.43
7.48 + .92 4.22 + 1.28 6 . 10 + 1. 02
N.D. 3.07 + .81 3.06 + .75
2.37 +
.34
0.64 + 0.78
N.D.
5.37 + 1.02
aSource: Azar et a1. Reprinted from Lead: Environmental Quality and
Safety Supplement, Vol 2, T.B. Griffin, and J. H. l(nelson (Eds.)
(c) George Thiem Verlag, Stuttgart (1975).
bN.D. = Not determined.
-------
Figure 7.5 shows that the data tended to clump into five subgroups by
location. The average relationship between air lead exposure and blood
lead concentration was obtained by drawing a line with a slope of 0.153
through the average blood lead concentration for 149 subjects. This line
is defined by the equation:
log blood Pb = 1.2257 + 0.153 log air Pb
The slope of this regression was significantly (p < 0.01) different from
zero (95% Confidence Limits, C. 1. = :t 0.079). AP~roximatelY 56 percent of the
variance in blood Pb is not explained by air Pb (R = 0.436). Figure 7.5
also shows the regression lines obtained when the data from each site are
combined and adjusted to a common slope of 0.153. (This procedure is
justified since the slopes are homogeneous.) After pooling data from all
sites, there was a significant correlation between log air lead level and
log blood lead level. The contribution of air lead to blood lead was found
to be approximately 1.0 ~g of lead per 100 ml of blood per 1 ~g per m3 of
air in the range of air lead concentrations studied. This 1:1 estimate is
somewhat less than the 1:1.3 ratio estimated from Goldsmith and Hexter's
(1967) equation.
The slope of the regression line in Figure 7.5 (0.153) is less than
that found by Goldsmith and Hexter (1967) and considerably less than that
bAsed on calculations of the Environmental Protection Agency shown as in
Figure 7.5 as the "EPA line".
Hammond (1977, personal communication) has applied the mathematical
model described by Azar, et al., (1973) to empirical data published by
Rabinowitz (1974); Griffin, et al., (1975); Fugas, et al., (1973); Prpic-Majic,
et al., (1973); and Williams, et al., (1969) in order to compare actual data
to predictions derived from the model.
The formula developed by Azar, et al., (1973; 1975) is as follows:
log PbB = 1.226 + 0.153 . log ~g Pb/m3
where
PbB = blood lead level in ~g/dl
Pb/m3 = air lead level.
The above equation
tion the average PbB at
says, in effect, that for this particular popula-
1 ~g Pb/m3 was:
log PbB = 1.226 = 16.8 ~g/dl
log ~g Pb/m3 reduces to zero when air Pb = 1 ~g/m3.
since the term (0.153 .
For an3 other population under study, the constant for PbB at air lead
= 1 ~g Pb/m will be unique to that population and will depend upon all
sources of lead ~ntake. In order to solve for the constant describing log
PbB at 1 ~g Pb/m , baseline PbB at a known small air lead concentration
can be used. Taking an example, Coulston, et al., (1972) determined PbB
in a group of men known to breathe air lead at 0.2 ~g/m3 throughout the day.
Solving for the term b in a = b + c.
a = log observed PbB
b = unknown constant
c = 0.153 . log of observed air lead, ~g Pb/m3.
238
-------
1~2
8
7
6
5
4
3
g 2
Q
.....
C7>
:l
't:1
~ Igl
't:1 e
~ 7
CD 6
5
4
3
2
10°
l(j'
e.
. 0
. . e
.
e e
e
.
.
e
.
. -.......
Legend
Within Site Slope
Philo. Cab
L.A. Cab
l.A. Office
. --..----
0--
Log Blood Pb=1.226 + 0.153 Log Air Pb
e ----
Borksdoie, Wis.
Starke, Fla.
E.P.A. Line
. . . . .
o -..-
6 7 8 9 10'
2
3
5
6 7 8 9 10° 2
Total Air Lead, fL9/m3
4
5
3
4
FIGURE 7.5
BLOOD LEAD VERSUS TOTAL AIR LEAD
Source:
Azar, et al. Reprinted from Lead: Environmental
Quality and Safety Supplement, Vol. 2.
T. B. Griffin and J. H. Knelson (Eds.)
(c) George Thiem Verlag, Stuttgart, 1975.
239
-------
Using the Azar model, it is necessary to calculate a new constant for
any particular group, log PbB at 1 ~g Pb/m3. In Table 7.12, the baseline
data for PbB at low, known air lead is given. Data for log PbB at 1 ~g
Pb/m3 are then calculated. This is the constant b described above. Using
the calculated constant (log PbB at 1 ~g Pb/m3) the predicted PbB at the
high air lead concentration is compared to the actual PbB measured.
Finally, the contribution of air lead to PbB as actually observed is given.
Predictions are also provided for PbB values at several air lead
concentrations breathed for 40 hours per week against a background PbB of
23.5 with an assumed nonoccupational air lead of 1 ~g/m3.
It is evident from these data that the Azar model for regression of
blood lead on air lead predicts fairly accurately the mean blood lead
values for groups of workers and human volunteers whose air lead exposures
were fairly accurately known. It is also evident that as air lead increases,
its impact on blood lead, as designated in the last column of the table,
becomes progressively smaller. Thus, Hammond's (1977) data implies that
the impact of incremental additions to an alread3 high ambient lead expo-
sure, say over the suggested maximum of 100 ~g/m would have only modest
impact on internal dose (as reflected by blood lead) relative to equivalent
incremental additions at lower air lead levels. Obviously, such a state-
ment should not be construed to suggest that such high industrial levels
are safe.
Certain seeming discrepancies occur in Table 7.12. For example, an
average air lead exposure of 27 ~g/m3 (Prpic-Majic, 1973; Fugas, 1973)
yields a predicted PbB of 46.8 while an average air lead exposure of 72.2
~g/m3 is predicted (last horizontal row) to yield a somewhat lesser PbB
of 45.2. This discrepancy is due to the fact that in the former case PbB
at 1 ~g/m3 is 28.3 (antilog 1.4513) while in the latter case it is only
23.5. This only serves to highlight the fact that the impact of air lead
on blood lead is very much dependent upon the background of nonair sources
of lead.
It may be argued that the Azar model is invalid for industrial sit-
uations in which the particle size range and chemical composition of the
lead aerosols may be quite different from those encountered in the general
ambient air situation prevailing in the Azar study. Nevertheless, the
Azar regression equation is quite consistent with the limited experimental
data available concerning industrial exposure.
Experimental studies of prolonged exposure to artificially generated
lead aerosols have been reported by Griffin, et al., (1975). Lead aerosols
were produced by introducing lead-203 tetraethyl lead into gasoline, burning
this in an automotive engine, and employing diluted exhaust from the engine
as an exposure aerosol for a group of experimental subjects. Thus, the lead
aerosol employed in these experiments resembled that of ambient air in part-
icle size but different isotopically. Subjects were exposed for 23 hours a
day to lead levels of 3.2 and 10.9 ~g/m3. The experiments were continued
for over 4 months to allow time for equilibration of blood lead to the new
240
-------
TABLE 7.12. THE IMPACT OF AIR LEAD ON BLOOD-LEAD LEVELS; A COMPARISON OF ACTUAL DATA
TO PREDICTIONS USING MATHEMATICAL MODELa,b
Baseline
log PbB at "High" Air Exposure PbB,~g/dl I1g PbB/
PbB at I1g/m3 1 I1g Pb/m3 I1g Pb/m3 log jJ.& Pb/m3 Predicted Actual I1g/m3 Reference
11.2 0.2 1. 1561 1.6 0.2041 15.4 12.9 1.2 Rabinowitz, 1974
21.8 0.2 1.4454 3.2 0.5051 33.3 27.6 1.9 Griffin, et a1. 1975
20.1 0.2 1.4101 10.9 1. 03 74 37.1 36.4 1.5 Ditto
22.1 0.2 1.4513 35 1. 5441 48.7 44.3 0.64 Fugas, et a1., 1973
anu Prpic-Majic,
et a1., 1973
22.1 0.2 1.4513 27 1.4314 46.8 42.9 0.78 Ditto
23.5 1.0 1.3711 51 1. 7076 42.9 50.1 0.53 Williams, e t a1., 1969
tV
.p. 23.5 1.0 1.3711 37 1.5682 40.8 39.7 0.45 Ditto
~
23.5 1.0 1.3711 33 1.5185 40.1 39.5 0.42 "
23.Sc 1.0 1.3711 24.6 1. 3909 .~8.4
23. Sd 1.0 1. 3 711 36.5 1. 5623 40.7
23.5e 1.0 1. 3 711 48.4 1.6848 42.5
23.Sf 1.0 1. 3 711 72.2 1. 8585 45.2
a
Source: Hammond, P. B. (1977, personal communication).
bAzar, et a1., 1973.
c 3
Prediction assuming i.nha1ation of 100 Iig/m3 air lead 40h!\.,k. + 1 I1g/m for remainder of week (128 h)
(avg. = 24.6 fLg/m3).
dprediction assuming 150 \1g/m3 40h/wk.
e 3
PredictIon assuming 200 IJ.g/m 40h/wk.
fprediction assuming 300 I1g/m3 40h/wk.
3 128/wk. 3
+ 1 I-Lg/m (avg. = 36.5 jJ.g/m ).
3 128/wk. 3
+ 1 lig/m (avg. = 48.4 IJ.g/m ).
3 128/wk. 3
+ 1 \.Lg/m (avg. = 72.2 jJ.g/m ).
-------
exposure levels. The exposures resulted in increases of 2.0 and 1.4 ~g/m3
of blood per 1 ~g/m3 in air. In a similar study, Rabinowitz (1974) removed
most of the usual 2.0 ~g/m3 of air lead from the chamber in which one subject
was maintained. Following reduction of the air lead, Rabinowitz traced the
decline in the blood lead of this subject over the next 40 days. Examination
of these data suggest that blood lead appeared to decline approximately 1 ~g/dl
for each 1 ~g/m3 of lead removed from the air.
Studies have generally reported the regression equation describing the
relationship between blood lead and air lead in terms of logarithmic units.
Clearly, the contribution of each microgram of lead in air to blood lead
(in original units) will change considerably over the range of air lead
concentrations examined. Consequently, the ratios above represent the average
ratio over a range of air lead concentrations which vary from study to study.
These difficulties notwithstanding, there appears to be a fairly good consensus
that the contribution of each microgram of air lead to blood lead probably
lies in the range from 0.6 to 2.0 ~g/dl.
Furthermore, these studies are in close agreement with the data presented
earlier by Williams, et al., (1969), Prpic-Majic, et al., (1973), and Fugas,
et al., (1973), which estimate a concentration of about 1 ~g of lead per 100
ml of blood for each 1 ~g/m3 of air lead exposure.
7.5.2
Intermediate Level Studies
Studies of persons regularly exposed to unusually high ambient lead
concentrations (over 10 ~g/m3 for all or part of the day) both from mobile
and stationary sources have been much more successful at demonstrating
relationships between levels of lead in air ~nd those in blood. Actually,
it is only under these circumstances that respiratory intake of lead ac-
counts for a substantial percentage of total absorption. It should be
mentioned that few of the persons in the intermediate category are exposed
to sustained levels of over 10 ~g/m3 for more than a few hours a day.
Chronic exposure to intermediate levels of lead from mobile sources
may occur either as a result of residing in close proximity to high traf-
fic density (e.g., freeways) or from occupations which involve exposure
to above average amounts of automotive exhaust either indoors or outdoors.
Policemen, taxi drivers, garage attendants and mechanics are the most common
examples. Populations residing near stationary sources of lead emissions
such as primary and secondary smelters and battery plants have also been
studied. The effects of exposure to higher than average amounts of lead
among the Wenatchee orchardists and their families has also been reported.
7.5.2.1
Mobile Emission Sources--
Thomas, et al., (1967) conducted a study to determine whether persons
living near freeways in Los Angeles County have increased levels of lead
in blood. Fifty adults who had resided for at least 3 years within 76.2
meters (250 feet) of a freeway were compared with 50 who had resided for
a like period near the ocean or at least 1.6 kilometers (1 mile) from a
freeway. Average blood-lead levels were substantially higher in the pop-
ulation sample living near the freeway. However, these blood-lead levels
242
-------
were similar to other Los Angeles populations and lower than those reported
for some other urban populations. The observed di~ference between the two
population samples is consistent with the existence of coastal-inland atmos-
pheric lead and blood-lead gradients within the Los Angeles Basin.
The effect of distance of residence from highways upon blood-lead levels
among black females has been investigated by Daines, et al., (1972) (see
Table 8.5). Average annual air-lead levels on the front porches of homes
located 3.7, 38.1, and 121.9 meters away from a highway were 4.60, 2.41,
and 2.24 micrograms per cubic meter, respectively. There was no significant
difference between the outside air-lead concentrations at 38 and 122 meters,
but both were different from the air-lead concentration at 3.7 meters from
the highway. This rapid nonlinear decrease in airborne lead with distance
from the source has been observed for mobile as well as stationary lead
sources. Concentrations of lead in dustfall also decreased rapidly with
increasing distance from the roadway. Indoor air-lead levels measured in-
side the front room of houses at the three sampling points also reflected
this nonlinear decrease, being 2.3, 1.50, and 1.57 micrograms per cubic
meter as the distances increased.
Average ~lood-lead leavels in the study subjects wer 23.1, 17.4, and
17.6 ~g/lOO m of blood at 3.7, 38.1, and 121.9 meters, respectively. Just
as the air lead levels, the average blood-lead levels at the two more dis-
tant sampling sites differed significantly from the average at 3.7 met~rs,
but did not differ significantly from one another. Among the homes closest
to the highway (3.7 meters), air-lead and blood-lead levels were significantly
lower for subjects whose homes were air-conditioned than for similar
subjects in homes without air-conditioning.
~
Despite the fact that the air lead levels measured at the two locations
differed from one another statistically, this difference would not necessarily
be reflected in higher blood lead levels at the nearer site. Under the assump-
tion that each microgram of lead per cubic meter of air contributes 0.6 to 2.0
~g of lead per 100 ml of blood, one would not expect that the difference in
ambient lead exposure between the two sites (0..2J ~g/m3) to result in dif-
ferences in blood lead of more than about 0.4 ~~ lead/dl.
Groups exposed to above-average amounts of automotive exhaust outdoors,
such as policemen, mayor may not have lead levels above those of comparable
groups not so exposed according to a U.S. Environmental Protection Agency
(1977) report. Differences, when present, are small (10 to 20 percent), but
ranges are sometimes above normal limits. However, groups similarly exposed
indoors (U.S. Dept. of Health, Education and Welfare, 1965; Tola, et al.,
1972; Gothe, et al., 1973) such as parking garage employees, consistently have
20 to 40 percent higher levels than ordinary groups, with greater numbers of
individuals having blood leads above the normal range (blood lead of 40 ~g/dl
or higher). Groups exposed to lead at controlled stationary sources of lead ,pro-
duction have blood-lead levels similar to those of parking garage employees
or those of individuals exposed in automotive repair facilities. Groups ex-
posed in automotive repair facilities (U.S. Dept. of Health, Education and
Welfare, 1965; Tola et al., 1972) consistently have higher levels (20 to
100 percent higher) because exposure to solder, batteries, etc., is added
to exposure to automotive exhaust. The range of levels is increased, and
many are above 40 ~g/dl as demonstrated in the Three Cities Study.
243
-------
Lawther, et al., (1972) studied airborne inorganic lead and its uptake
by inhalation using three different types of data: (1) measurements of air-
borne concentrations of inorganic lead compounds taken in a busy London
street and at a control site away from traffic, (2) measurements of the
blood-lead concentrations in London taxi drivers using day workers as the
test group and night workers as the controls; and (3) visual appearance of
particles collected from the general atmosphere of London, from a busy
London street and from the exhaust gases of petroleum and diesel engines.
Blood-lead and carboxyhemoglobin levels were studied among London
taxi drivers on both the day and the night shift. Significant differences
were found in blood carboxyhemoglobin, but not in blood-lead levels, when
comparing smoking and non-smoking day-shift drivers to similar night-
shift drivers. Lawther, et al., (1972) concluded that the day drivers had
a greater exposure to motor car exhaust than the night-shift drivers be-
cause they had significantly higher blood carboxyhemoglobin levels and
therefore "it would seem that little of the lead found in their blood is
attributable to the lead they inhale while driving in London streets".
Unfortunately, the report does not provide any evidence of distinctively
different exposures of day and night drivers in terms of ambient lead
concentration. Also, the fact that differences in carboxyhemoglobin (COBb)
levels were found in day and night drivers does not really constitute valid
evidence of differences in lead exposure. Because the biological half-time
of carboxyhemoglobin in blood is 3 or 4 hours one might expect not only
rapid equilibration of blood COBb with atmospheric CO but also a diurnal
variation in COHb levels among the cab drivers. On the other hand, Kehoe
demonstrated that the half-time of lead may be as long as several weeks
(Kehoe, 1960 ) and similar diurnal patterns of blood lead levels would not
be expected. Consequently, the COBb cannot be used as a valid indicator of
lead exposure from automotive emissions. Furthermore, information was not
obtained regarding the exposure of the drivers when they were off duty (U.S.
Environmental Protection Agency, 1972). Thus, the relative contribution of
automotive exhaust versus other sources of lead remains unresolved.
Iwata, et al., (1971) described the effects of lead in auto exhaust
on traffic controllers. The study measured lead in areas representative of
the controller's work environment, along with medical examinations for signs
of lead toxicity. Lead concentrations in air ranged from 3.3. to 916 ~g/m3.
Medical examinations were carried out on 17 traffic controllers (Group I)
and 14 indoor policemen (Group II). Subjective symptoms included headache
and nettle rash, sore throat, nausea, constipation, lumbago, and dizziness.
More complaints were found in Group I. No difference was found between the
two groups in terms of whole blood specific gravity, amount of blood pigment,
and punctate, basophilic erythrocyte level. The average level of lead in
blood ranged from 12.3 to 24.5 ~g/dl in Group I and 10.1 to 17.3 ~g/dl in
Group II, indicating slightly higher levels in Group I, however, these differ-
ences were not large enough to be statistically significant.
Landrigan, et al., (1975c) discovered three cases of mild lead poisoning
among instructors at an indoor pistol range. These cases were characterized
by blood-lead levels greater than 100 ~g/dl of blood, free erythrocyte pro-
toporphyrin levels greater than 450 ~g/dl of red blood cells, abdominal pain,
244
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1---'--
I
and, in one instance, by slowing of motor and sensory nerve conduction vel-
ocity. Fragmentation of bullets during firing, explosive vaporization of
primer, and aerosolization of lead suboxide particles during bullett molding
appear to have been the major sources of airborne lead.
7.5.2.2
Populations Impacted by Stationary Sources--
Stationary sources of lead emissions can be divided into three cat-
egories:
1) Primary smelters where the lead bearing ore is processed.
Because lead ore generally will contain other metals (such as zinc, cadmium,
bismuth, and arsenic), effects observed in exposure studies may not always
be caused by lead alone. Consequently, establishing a dose response re-
lationship for health effects in such studies is difficult due to the con-
founding effects of other potentially toxic emissions.
2) Secondary lead smelters and lead processing plants.
3) Miscellaneous sources, consisting of those industrial processes
where the main objective is not to obtain or process lead. Examples include
battery manufacture, painting or torch cutting surfaces coated with leaded
paint, cable stripping, and other operations in which lead is incidentally
released into the environment.
..
7.5.2.2.1 Primary smelters--A recent Environmental Protection Agency report
has summarized very well the studies which have examined the effects of lead
exposure on persons residing near stationary lead emitting sources (U.S. Envi-
ronmental Protection Agency, 1977). Extensive investigations of the effects
of lead exposure on people living near primary smelters have been performed
in El Paso, Texas, Helena Valley, Montana, and Kellogg, Idaho. Several of
these studies are briefly summarized below.
The smelter at El Paso, Texas, has been operating since the late 1800's
and produces not only lead but also copper and zinc (Landrigan et al., 1975a;
Texas Morbidity and Mortality Weekly Report, 1973). In addition to these
metals, cadmium and arsenic are known to be emitted. The estimated lead
emissions were 292 metric tons in 1968; 511 metric tons in 1970, and 312
tons in 1971. These figures, however, are only for stack emissions; it is
not known how much lead may have been emitted from fugitive emissions via
ventilation, windows, etc. An epidemiologic study focused on the so-called
Smeltertown Section, a residential area less than 182.88 meters (200 yards)
west of the smelter, as well as some nearby communities farther downwind that
were also affected by the smelter emissions. The concentrations of lead in
air are presented in detail by U.S. Environmental Protection Agency (1977) and
in the published reports referred to above. Daily lead concentrations in
Smelter town in 1972 ranged from 0.49 to 75.0 ~g/m3. For 86 sampling days in
1972, the average level was 6.6 ~g/m3. Air lead levels fell off rapidly with
increasing distance from the smelter, declining to background levels at 4 to 5
km from the smelter (see Figure 8.2). High concentrations of lead were found
in the soil, being greatest in the area nearest the smelter (geometric mean
1791 ppm lead). High concentrations of lead in house dust were also found,
ranging from 400 to 58,800 ppm.
245
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Determinations of lead in blood revealed that 53 percent of the children
aged 1-9 residing within a distance of 1 mile or less from the smelter had
blood lead levels> 40 ~g/di, the level considered by many investigators to
be indicative of undue lead absorption. Of children residing between 1 and
approximately 4 miles (6.6 km) from the smelter, 18 percent had blood lead
levels above 40~g/dl. Beyond that distance and among older children (over
9) levels in blood were lower. Airborne lead levels of 8-10 ~g/m3 annual
mean were recorded in the area within 1 mile of the smelter. Household sam-
pling revealed that children within this 1 mile area with blood leads>
40 ~g/dl were exposed to as much as 3.1 times as much lead in dust (6447 vs.
2067 ppm) as the children with lower blood values. Paint, water, food and
pottery were also examined as potential sources of lead, however the authors
stated that they believed particulate lead in air and dust accounted for most
of the undue lead absorption in El Paso children (Landrigan, et al., 1975a).
A smelting complex in East Helena, Montana has also been investigated
as a source of airborne air pollution. Zinc, cadmium, and arsenic are
known to be emitted also, however the quantity of lead emissions is not
known (U.S. Environmental Protection Agency, 1977) Air concentrations of
lead were measured in 1969, and in East Helena the average concentration
at several stations varied from 0.4 to 4 ~g/m3; the maximum 24-hour value was
found to be 15 ~g/m3. In the city of Helena, the average concentration
was 0.1 ~g/m3. Lead in soil was found to be 4000, 600, and 100 ppm at
distances of 1.6, 3.2, and 6.4 km (1, 2, and 4 miles), respectively, from
the smelting complex; whereas, in uncontaminated soil near the Helena Valley
it was 16 ppm. Deposited lead (dustfall) was found to vary from 3 to 108
mg/m2/month in East Helena; whereas, in Helena it varied from 1 to 7 mg/m~month.
...
Studies on humans were limited to children; lead in hair and blood
were found to be higher in East Helena than in Helena. The respective
averages were 15.6 and 11.6 ~g/d1 in blood and about 40 and 13 ppm lead in
hair (Hammer, et al., 1972). Both blood lead and hair lead are suggestive
of greater exposures nearer the smelter. The blood values reported in-
dicate that lead absorption, although evidently elevated in residents near
the smelter was still essentially within normal limits. No other adverse
health effects have been noted among these children.
The U.S. Environmental Protection Agency (1977) reported preliminary
data on air lead in the vicinity of a lead-zinc smelter at Kellogg, Idaho
which showed that during 6 months in 1971 the average concentration of lead
in air was between 6 and 8 ~g/m3. Children from this area had a mean blood
level of 20.9 ~g/dl and a mean hair-lead level of about 100 ppm. Based on
lead in air determinations, the exposure seems to be about twice as high as
in East Helena, which is supported by the finding that lead in hair was twice
as high. This exposure resulted in about 5 ~g/dl higher lead values in blood.
In September 1973, a fire destroyed the main fume filtration system at the
smelte~ causing increased lead emissions. Records showed that emissions of
lead to the atmosphere averaged 8.3 metric tons per month from 1955-1964,
11.7 metric tons from 1965-Sept. 1973 and 35.3 metric tons from October 1973
to Sept. 1974 (Landrigan, et al., 1976). Following the hospitalization of
two children with symptoms of lead poisoning, the Center for Disease Control
246
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joined with the State of Idaho in a comprehensive study of children in the
area (Landrigan, et al., 1976; Yankel, et al., 1977).
In September, 1974, blood-lead levels> 40 ~g/dl were found in 385 (41.9
percent) of 919 children less than 10 years-old who were examined. About 99
percent of the 172 children living within 1.6 km of the smelter had blood-lead
values ~ 40 ~g/dl. The mean blood concentration declined with distance from
the point of emission. Blood-lead levels were consistently higher in
children 1 to 4 years old than in those 5 to 9 years old. In addition, higher
levels in children were associated with reported active ingestion of lead-
containing material (pica), with lower socioeconomic status, and with
parental employment at the smelter or at a lead mine. A significant negative
relationship between blood-lead level and hematocrit value was found. Seven
of 41 children (17 percent) with blood-lead levels ~ 80 ~g/dl were diagnosed
by the investigators as being anemic on the basis of hematocrit less than
33 percent, whereas only 16 of 1006 children (1.6 percent) with blood-lead
levels < 80 ~g/dl were so diagnosed (U.S. Environmental Protection Agency,
1977a) .
Subsequently, Yankel, et al., (1977) published additional information
concerning the 1974 study as well as the results of a follow-up study
conducted in 1975. The follow-up was undertaken to determine the effective-
ness of control measures initiated after the 1974 study.
Between August 1974 and August 1975, the mean annual air-lead levels
decreased at all stations monitored. In order of increasing distance from
the smelter, the relative concentrations in the two years were 18.0 to 10.3
~g/m3, 14.0 to 8.5 ~g/m3, 6.7 to 4.9 ~g/m3, and, finally, 3.1 to 2.5 ~g/m3 at
10 to 24 km. Similar reductions were noted in the housedust-lead concentra-
tions (U.S. Environmental Protection Agency, 1977a).
The report of Yankel, et al., showed that there were reductions in
environmental lead contamination between 1974 and 1975, and that the
correlations between blood-lead levels and environmental or demographic factors
were consistant from one year to the next. Five factors significantly
influenced the probability of a child's developing an excessive blood-lead
level:
1)
2)
Concentrations of lead in ambient air (~g/m3)
Concentration of lead in soil (ppm).
3)
Age (years).
4)
Cleanliness rating of the home (subjective evaluation coded 0, 1
and 2, with 2 signifying "dirtiest").
5)
General classification of the parents' occupation.
247
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These investigators developed a matematica1 model based on the 1974 data
that included each of the five factors that had been shown to be correlated
with increased blood-lead levels. The model, shown below, can be used to
estimate the effect of variations in the environmental factors on mean blood-
lead levels in children:
1n (Pb-B) = 3.1 + 0.041 (Air) + 2.1 x 10-5 (Soil) +
0.087 (Dust) + 0.018 (Age) + 0.024 (Occupation).
Although the strongest correlation found was between blood lead level and
air-lead level, the authors concluded that it was unlikely that inhalation of
contaminated air alone could explain the elevated blood-lead levels observed.
In another report, Von Lindern and Yankel reasoned that even though air lead
was the principal source, a major route of exposure was the ingestion of lead
in soil and dust. They proposed that to protect the health of the children
in this area the regulation of environmental standards must take into
account all of these routes of exposure (U.S. Environmental Protection Agency,
1977a).
It is clear from the preceding discussion that emissions from primary
smelters may cause elevated blood levels and other signs of increased lead
burdens in populations living near the emission sources. In E1 Paso and
Kellogg, the high concentrations of lead in blood of children in these areas
are comparable at or above levels associated with increases in ALA excretion.
Elevated lead levels in blood and urine and increases in ALA-U are, of course,
results of lead exposure. As pointed out earlier, primary lead smelters will
emit other metals, and nonspecific effects may well be caused by these or
other contaminants (U.S. Environmental Protection Agency, 1977). Efforts
should be made to separate effects of such contaminants from lead effects.
A recent EPA report (U.S. Environmental Protection Agency, 1976) in-
vestigated mortality patterns in counties containing primary smelters in
comparison with contiguous, non-smelter counties to determine whether
smelter emissions produced any noticeable health effects in terms of
disease-specific mortality.
Several findings were consistent among all, or most of the sites
examined. A majority of smelter counties showed an excess of deaths from
five categories of deaths:
1. All causes combined;
2. Cancer of the liver and biliary passages;
3. Cancer of the trachea, lung and bronchus;
4. Cancer of the kidney; and
5. Cancer of the bladder.
Excesses from other non-cancer causes of death were frequently found in
one or two of the smelter counties. These excesses were predominantly
from respiratory diseases such as bronchitis, emphysema, asthma and.
pneumonia. Excess deaths from arteriosclerosis and small vessel disease
were also seen in some smelter counties, however this pattern was not
consistent.
248
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These findings appear to conflict with the results of other studies.
Traditionally, lead has not been thought to be a carcinogen in man, although
it has been shown to induce cancer in rodents. Similarly, cancer has not
been shown to be excessive in several studies of ~ohorts of lead workers.
The study cited above suffers from several methodological weaknessess which
cast doubt on the validity of the findings. First, the failure to eliminate,
control for, or at least quantify the levels of other known carcinogens
present in smelter emissions suggests that even though there may be a
genuine excess of cancer in the smelter counties, the causal connection
between lead exposure and cancer has not been established convincingly.
Second, in comparative studies of inter-community variation in health
status, it is essential that demographic factors independently associated
with mortality risk (i.e. population density, age, race, and sex distri-
butions, socioeconomic and educational levels) be explicitly controlled in
the analysis, lest effects attributable to differing population compositions
in the areas being compared be erroneously ascribed to effects of exposure.
Adjustments for these factors in this study were remarkably inadequate.
Consequently, findings from this particular study should be viewed with
skepticism, however, this means of approach offers some possibilities if
an adequate study design could be developed.
7.5.2.2.2 Secondary smelters and lead processing plants--A good example
of exposure from secondary smelters has recently been given by Nordman,
et al., (1973). A random sample of 621 individuals 16 years old or older
in an area near a secondary smelter in Finland was selected; 334 individuals
responded, of whom 41 were rejected for various reasons. Lead and ALAD
in blood were determined in the remaining 293 individuals. The resu]ts
were related to distance from the source and to dustfall levels of lead,
which had been determined at 80 stations during a I-month period. Signi-
ficant negative correlations were found between distance from source and
lead or ALAD in blood. This was especially pronounced in a group of women
who spend most of their time at home. On a group basis, lead in blood was
also found to be correlated to dustfall. However, blood-lead levels were
generally below 30 ~g/dl, and only in a group of males living in a zone
where the dustfall was about 100 mg/m2/month was the mean blood level 30
~g/dl. Dustfall in this study was about the same as that reported from
East Helena.
Exposure from both a primary and secondary smelter in the inner city
area of Omaha, Nebraska,' has been reported (McIntyre and Angle, 1972;
Angle and McIntyre, 1974). In the report, the authors did not take into
account the city traffic, but in a more recent study reported by U.S. Environ-
Dlental Protection Agency (1976) these authors concluded that elevated blood
levels of lead could be related to proximity to a battery plant, traffic
intensity, and substandard housing. These reports illustrate some of the
difficulties involved in studying exposures from point sources in cities.
Martin (1974) reported an epidemiological survey of lead works of
various types to determine possible adverse health effects on mothers and
children living in the area. At a point approximately 100 meters from the
249
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factory chimney, average atmospheric lead concentrations of 3.0 ~g/m3 with
occasional 24-hour concentrations ranging up to a maximum of 28 ~g/m3 were
found. An extensive series of measurements of lead deposits was made in the
vicinity and monthly figures of up to 392 ~g/m2 were found; environmental
dusts contained concentrations of up to 5 percent, and soil concentrations
ranged from 0.15 to 4.9 percent. Initial results indicated that of 39
children under the age of 5 years living within 400 meters of the factory,
41 percent had blood levels of above 40 pg/dl whereas of 80 children living
at distances of 400 to 500 meters from the factory, only 13.7 percent had
blood-lead values above this level. Similarly, of 252 children attending
local schools, 44 were found with blood levels above 40 ~g/dl, 6 of these
being above 60 ~g/dl. Of the 26 mothers living within the 400 meter range,
3 had blood-lead levels over 40 ~g/dl, whereas of 53 living in the 400-to
500-meter range in none did the blood lead exceed this level. Of the 4
children under shcool age with the highest blood leads, 3 (with levels
of 75, 74, and 65 ~g/dl) were living close to the works and 2 of these had
fathers working there. In the third, the child's only known exposure to
abnormal quantities of lead was the result of his proximity to the works.
In the fourth, who lived in the 400- to 500-meter range, there was evidence
of pica. Where raised blood levels were found, investigations were carried
out in the home to exclude as far as possible sources of raised lead
intake other than those derived from the factory. Apart from the occasional
case of pica, no abnormal source was established and the principal cause
of the raised levels was presumably either emissions to the atmosphere
from the factory, windborne dusts, or dusts from vehicles entering and
leaving the works, or lead taken home on the person or clothing of a parent
working in the factory.
Roberts, et al., (1974) report on the dispersal of lead and on the
health effects of lead contamination around two secondary smelters located
in different parts of Toronto. Each smokestack is about 100 meters south
of a residential area and 100 to 200 meters north of an elevated expressway
carrying 50,000 to 150,000 cars per day. Lead emissions from the two
smelters were estimated at 15,000 to 30,000 kilograms per year. The high
rate of lead fallout around the secondary lead smelters was attributed to
episodal large-particulate emissions from low-level fugitive sources rather
than from stack fumes. The lead content of dustfall, and consequently of
soil, vegetation, and outdoor dust, decreased exponentially with distance
from the two smelters. Monthly geometric means of the lead concentrations
in suspended particulates close to the smelters ranged from 1 to 5.3
pg/m3 in air or approximately twice that of many urban sites.
Blood samples for lead analyses were collected from 286 people close
to the first smelter, 1425 people close to the second smelter, an urban
control group of 1231 individuals of similar socioeconomic status. To
determine the major source of increased lead absorption, blood and hair
samples were obtained during the same period as the above from 16 families
living within 15 meters of the first smelter and 8 urban control families
living in houses of similar age and upkeep.
Between 13 and 30 percent of the children living in the contaminated
areas had absorbed excessive amounts of lead (as evidenced by blood lead
of over 40 ~g/dl and more than 100 micrograms of lead per gram of hair) com-
250
-------
pared with less than 1 percent among the control group. A relationshiop
between blood and hair lead was established which indicated that the ab-
sorption was fairly constant for most children examined. Consequently it
appeared that the ingestion of contaminated dirt and dusts rather than
"paint pica" was the major route of lead intake. Metabolic changes (Le.
increased urinary excretion of ALA and coproporphyrins) were found in most
of the 21 children selected from those with excessive lead absorption; 10
to 15 percent of this group showed nonspecific neurological dysfunctions
and/or reduction in peripheral nerve conduction velocity.
7.5.2.2.3 Miscellaneous sources--There have been very few epidemiologic
studies of groups exposed to lead in which a large number of health para-
meters were measured and the results in different exposure groups compared.
One of the earliest of such studies concerned the orchardists in the
Wenatchee area of Washington state who were exposed to lead arsenate as
reported by Neal, et al., (1941) and followed up in a later study by Nelson,
et al., (1973).
The lead concentrations observed were not as high as those sometimes
seen in other industrial exposures, but that makes them particularly im-
portant because the urine-lead concentrations range from slightly higher
than commonly found in urban communities to the same as in moderate lead
exposures in industry.
Among the factors studied in assessing the health of the orchard-
ists were weight, blood pressure, diseases of the cardiovascular system,
skin disorders, eye irritation, chronic nervous diseases, blood dyscrasias,
kidney disease, pulmonary tuberculosis, visual acuity, syphilis, neoplastic
disease, and fertility. Each parameter was studied to find out whether
it had been modified by the lead arsenate exposure. Insofar as comparative
data for other populations were available, no evidence was found that any
of these factors was altered by the exposure. Special attention was given
to the medical examination of children because in the Wenatchee area,
where orchards surrounded the communities or the houses in which they lived,
there were unusual opportunities for children to be exposed to lead arsenate
insecticide sprays and spray residues on branches, leaves, and grass, in
addition to residues ingested on apples. In only one respect did these
children differ from children in other districts: their urinary lead and
arsenic concentrations were nearly twice as high as those of a group of 18
children measured at the same time in Washington, D.C. (who had a mean
urine lead content of 0.025 mg/l; standard deviation, 0.0128).
Serious questions might be raised concerning the relative importance
of the lead compared with the arsenical portion of the lead arsenate mole-
cule in the overall toxicity of the compound since any toxic action ob-
served might be attributable to arsenic. The National Academy of Sciences
(1972) reported that findings from animal studies indicate that the greater
toxicity of the lead arsenate molecule is attributable to the lead radical
rather than to the arsenic; no synergistic action of lead and arsenic
was reported. Based on its review of the Wenatchee orchardists study, the
same authors concluded that there was no indication of adverse effects of
lead arsenate exposure on the health of the Wenatchee children (National
Academy of Sciences, 1972).
251
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7.5.3
Studies of Occupational Groups
Occupational lead exposures represent the high end of the dose-
response spectrum. It is among workers who smelt, refine, and
manufacture lead-containing or lead-painted products that the highest
and most prolonged lead exposures are seen. Consequently, the study of
occupational groups provides valuable data on maximal human health effects
in terms of both high ambient concentration and chronicity of exposure. At
the outset it should be noted that the clinical pattern of occupational
lead poisoning has changed during the 20th century in that the incidence
and severity of poisoning has decreased substantially in recent years.
Whereas acute and occasionally fatal lead poisoning was seen early in the
20th century, today's cases of lead intoxication are frequently diagnosed
at an earlier, asymptomatic stage on the basis of abnormalities of bio-
chemical, neurological, or renal function. Nevertheless, excessive lead
absorption and its attendant health effects remain a serious and prevalent
occupational hazard in the lead industries today. The findings of several
recent surveys reported in this section indicate that present standards
and work practices of the lead industry do not adequately protect lead
workers from adverse health effects.
7.5.3.1 Threshold Levels ~or Clinical and Subclinical Effects--
It is perhaps useful in this discussion to work downward from the worst
effects which are universally regarded as adverse to health to those which
are of uncertain health significance. In this regard, it is customary to
distinguish between clinical and subclinical effects. For the purpose
of this review, clinical effects are those which a subject can perceive
and which? physician would normally seek to correct (i.e. biological
changes known to be indicative of disease). Subclinical effects are changes
of a more subtle nature and which, under normal circumstances do not result
in a perceptible decrement in bodily function. Such changes could possibly
reduce an individual's capability to cope with a coexistent body stress
(Hammond, 1978). Subclinical effects typically occur in asymptomatic indivi-
duals and are usually detectable only by sophisticated and generally non-
routine biological tests.
7.5.3.1.1 Dose-response relationships for clinical effects--Lead intoxica-
tion, in its severest forms, can cause permanent damage to the body or death.
Observed clinical effects include damage to: (1) the central nervous system,
including the brain, (i.e. acute and chronic encephalopathy), (2) the peri-
pheral nervous system, (3) the kidneys and (4) hematopoietic system (i.e.
anemia). Symptoms which may vary in severity include colic, abdominal pain,
loss of appetite, constipation, excessive tiredness and weakness, nervous
irritability, fine tremors, and weakness in the extensor muscles of the
hands and feet (U.S. Department of Labor, 1975).
A number of studies have sought to relate clinical symptoms and effects
caused by lead exposure to workers' blood-lead levels (National Academy
of Sciences, 1972; \villiams, 1975). Kehoe, (1961 a-d) based on observations
of occupationally-exposed men who were otherwise healthy, reports that clear-
cut symptoms of acute lead intoxication are associated with a blood-lead
level over 80 ~g/dl of whole blood. Moreover, he observed that as concen-
252
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trations of blood lead rise above 80 ~g/dl, the likelihood of lead intoxi-
cation increases. Although such concentrations do not necessarily result
in lead intoxication in all individuals, the probability of lead intoxica-
tion increases dramatically at blood lead levels above 80 ~g/d1 as shown in
Figure 7.6 (Williams, 1975). In addition, a number of studies have observed
symptoms and effects caused by exposure to lead at blood-levels below 80
~g/dl (National Academy of Sciences, 1972; U.S. Department of Labor, 1975).
E 100 - - - -
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o 0
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occur. Further, workers with blood-lead levels above 80 ~g/dl without
clear-cut symptoms may have milder symptoms caused by lead exposure. It
should be noted that in evaluating studies which seek to relate blood lead
levels to symptoms of lead exposure, it is rarely possible in clinical
situations to determine the amount of lead absorbed before the onset of
symptoms of lead intoxication."
Gibson, et al., (1968) examined a series of 100 workers from different
lead industries. Ninety one of these individuals were working and 9 were
hospitalized for lead poisoning at the time of the study. The objectives
of this investigation were to define more clearly the clinical and biochemi-
cal criteria of lead poisoning in three stages: (1) a presymptomatic
stage of lead exposure (37 men); (2) a stage involving mild symptoms or
mild anemia (45 men); and (3) frank lead poisoning with severe symptoms and
signs (18 men). Urinary lead values were similar for all three groups;
blood-lead tests were less sensitive in discriminating symptomatic cases than
hemoglobin and urinary coproporphyrin, and delta-aminolevulinic acid (ALA) esti-
mations. Although the latter three parameters correlated well with each
other, they were uncorrelated with urinary and blood-lead levels. Porpho-
bilinogen (PBG) levels became raised with symptoms of lead poisoning. A
hemoglobin of 13 grams per 100 milliliters or less was considered a cautionary
sign. Urinary coproporphyrin above 80 micrograms per 100 milligrams creati-
nine, ALA above 2.0 milligrams per 100 milligrams creatinine, and PBG above
0.15 milligram per 100 milligrams of creatinine were always associated
with symptoms and were therefore considered to be the upper safety limits.
Blood-lead values of 60 micrograms per 100 grams of blood were proposed
as the upper acceptable limit.
Among the occupational groups represented in this survey, scrap metal
burning, battery manufacturing, and shipbreaking constituted the gravest
lead hazards, whereas wire manufacturing constituted the least. Workers
in the most modern factory, a car-body pressing plant, had urinary copro-
porphyrin and ALA estimations just below the danger level for these para-
meters despite apparently efficient protective measures. This observation
underscores the importance of medical supervision of lead workers.
Epidemiologic studies conducted between 1975 and 1976 in five different
lead facilities across the United States have shown unacceptably high
blood-lead levels and symptoms of lead poisoning in every plant studied
(Center for Disease Control, 1977). The sites investigated included four
secondary smelters and one lead chemicals plant (Eagle-Picher Industries,
Joplin, Missouri), which produces such lead compounds as lead oxides, lead
peroxide, lead sulfate, and lead silicate.
Information concerning the plants included in the investigation is
given in Table 7.13. Hematologic, neurologic and renal damage due to
lead were consistently reported. Inappropriate mediaal management (misuse
of chelating drugs) and poisoning of workers' children from home contamina-
tion with lead dust were also observed in one or more of the plants.
Initial investigations at the Memphis, Tennessee, secondary lead
smelter were prompted by reports of excessive blood-lead levels and clinical
254
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TABLE 7.13
,
DESCRIPTIONS OF LEAD PLANTS INVESTIGATED, 1975-1976a
Date of Study
Location
Type of Plant
Date Plant Began Pounds of Lead
Lead Processing Processed per
Month
1948 2.3 million
<1930
1948 1. 5 million
1975 30,000-250,000
November 1975 Memphis, Tenn. Secondary smelter
March 1976 Joplin, Missouri Lead chemicals plant
May 1976 Eagan, Minnesota Secondary smelter
January 1976 Salt Lake City, Utah Secondary smelter
N March 1976 Atlanta, Georgia Secondary smelter
111
111
a
So urce :
Center for Disease Control, 1977.
-------
lead poisoning at this plant. Ninety-two percent of current employees and
one former employee were examined, revealing blood-lead levels up to 184
~g/dl with 67 percent above the currently proposed occupational standard
of 60 ~g/dl. Table 7...14' sunnnarizes the distribution of blood-lead
levels at the Memphis facility as well as from the other four sites. The
highest levels were seen in production area workers, who exhibited incidence
rates of classical signs of lead poisoning as follows:
Abdominal pain (17 percent)
Gastrointestinal dysfunction (22 percent)
Joint pain (28 percent)
Neuromuscular symptoms (27 percent)
Anorexia (23 percent)
Lead neuropathy (8.5 percent) weakness of wrist extensor muscles
Anemia (13 percent) defined by hemoglobin ~ 14 ~g/dl
Three workers were anemic, and neurological symptoms including wrist weak-
ness, ankle drop and tremors were noted in a few workers. Symptoms com-
patible with lead poisoning were noted in 38 percent of the 53 workers ex-
amined.
The most noteworthy finding at the Memphis plant was the high incidence
of renal disease; 32 percent of the workers qad elevated blood urea nit-
rogen (BUN ~ 20 mg/dl). Further studies revealed significant impairment of
renal tubular and glomerular function in 7 workers, a finding which may
represent early stages of lead nephropathy.
Investigations at the secondary lead smelter at Salt Lake City, Utah,
revealed unequivocal lead poisoning in 52 percent of those examined; two
hospitalized workers had blood lead levels over 250 ~g/dl. In addition,
36 percent of the workers were anemic. These cases of acute lead poisoning
were related to a change in progess involving the conversion of two small
rotary furnaces previously used to process antimony to lead processing.
Inadequate ventilation was felt to be responsible for the elevated air lead
levels in the plant.
The median blood lead level of 38 workers at the secondary lead smelter
at Eagan, Minnesota, was 72.5 ~g/dl. Seventy-six percent had levels> 60
~g/dl. Weakness of wrist and/or ankle extensor muscles was seen in 10.5
percent of the workers; 26 percent has tremor of the outstretched hands.
At the Atlanta, Georgia secondary lead smelter, 70 percent of the
plants' 39 employees had blood lead levels ~ 60 ~g/dl. The percentage
of workers with blood-lead levels ~ 80 ~g/dl varied between 43 percent in
January, 1975 (when a lead exposure problem was first identified) to 26
percent in February 1976. Workers at this plant who were treated with
intravenous chelation were permitted to remain on the job during therapy.
This practice is condemned by the medical profession.
An important finding of the overall study was that blood lead and
erythrocyte protoporphyrin (EP) were well correlated with symptoms of
lead toxicity. Persons reporting symptoms during the year previous to
testing had significantly higher blood lead levels than those without
256
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TABLE 7.14
BLOOD LEAD LEVELS IN LEAD PLANT WORKERSa
Number of \vorkers in Each Group, Percent at the Level Indicated
Blood Lead Level)
1Jg/d1 Hemphis, Joplin, Atlanta, Salt Lake Eagan,
Tenn. Mo. Ga. City, Utah Minn. Total
< 40 14(18%) 1(2%) 6(15%) 1(3%) 3(8%) 25(11%)
40-59 12(15%) 7(17%) 6 (15%) 5(17%) 6(16%) 36(16%)
60-79 26 (33%) 21(50%) 17(44%) 2(7%) 17(45%) 83(37%)
> 80 26 (33%) 13 (31%) 10(26%) 21(72%) 12(32%) 82 (36%)
Total Tested 78 42 39 29 38 226
a Source: Center for Disease Control (1977).
TABLE 7.15
PERCENTAGE OF WORKERS WITH SY~~TOMS OF LEAD POISONING
BY BLOOD LEAD AND ERYTHROCYTE PROTOPORPHYRIN LEVEL AT
THREE LEAD PLANTSa,b
Plant
Location
<40
Ratio, Percent, of Symptomatic Workers
by Blood Lead Level, 1Jg/dl
40-59 ' 60-79
>80
Tennessee
1/13 (8)
[0/1 (8) {
[0/2 (0)]
2/12 (17)
4/7 (57)
2/6 (33)
7/26 (27)
7/21 (33)
9/14 (64)
18/26 (69)
7/13 (54)
5/12 (42)
Missouri
Minnesota
Erythrocyte Protoporphyrin Level, 1Jg/d1
<100 100-199 200-299
>300
Tennessee
2/26 (~)
[1/1 (100)]
[0/2 (0)]
2/13 (15)
4/10 (40)
1/5 (20)
11/16 (69)
10/15 (62)
[0/4 (0)]
13/21 (62)
9/15 (60)
15/23 (65)
Missouri
Minnesota
:source: Adapted from Center for Disease Control (1977).
Two or more of symptoms of lead poisoning during past year.
cr ] = 5 members or less.
257
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symptoms. Erythrocyte protoporphyrin CEP} levels were also well corre-
lated (r = 0.76) with zinc protoprophyrin levels. Furthermore, the higher
the blood lead or EP level, the greater was the proportion of symptomatic
workers. This correlation was best in circumstances where the duration of
exposure was relatively short as in the Memphis facility (average duration
of employment was 5 months) than in plants where the average duration of
exposure was longer. In Eagan, Minnesota, and Joplin, Missouri, the average
duration of exposure was 4 and 20 years respectively. These data are shown
in Table 7.15.
Forty-nine percent of workers with blood-lead levels from 60-79
~g/d1 reported symptoms consistent with lead poisoning during the year
preceding examination. Twenty-three percent of workers with blood lead
levels from 60-79 ~g/d1 were experiencing symptoms at the time of the
examination. Since many of the symptoms reported were nonspecific, (i.e.,
headaches, joint pain, constipation) a similar questionnaire was adminis-
tered to a control group of workers residing in the same community but
without occupational lead exposure. The prevalence of reported symptoms
consistent with lead toxicity was much lower among unexposed workers than
in lead workers.
Anemia, (defined by hemoglobin levels < 14 g/d1) was noted in 14
percent of workers at the Memphis plant and 31 percent at the Salt Lake
City facility. The clinical significance of anemia depends upon the degree
of hemoglobin depression, however, classical symptoms of anemia (i.e.,
tiredness, fatigue, etc.) are not generally seen until hemoglobin decreases
below 8 g/100 m1. Impairment in work performance, however, has been doc-
umented at hemoglobin levels of 11-13 g/d1 according to the authors (Center
for Disease Control, 1977). A dose-response effect between hemoglobin
level and work performance was noted throughout the range of hemoglobin
levels from 3-17 g/d1 and no threshold effect was observed. Resistance
to infection is also depressed in anemic persons although no precise infor-
mation regarding the magnitude or threshold level for this effect is avail-
able.
The manifestations of lead toxicity varied with duration of exposure.
After brief exposure (2-3 months) gastrointestinal symptoms predominated
whereas constitutional symptoms and joint pains were relatively more common
after prolonged exposure (over 1 year). Also, conditions of acute expo-
sure led to relatively more gastrointestinal symptoms than chronically
exposed workers. Highest rates of gastrointestinal symptoms were noted
in lead poisoning cases in Salt Lake City (3-4 months duration) while
workers chronically exposed in the Eagan, Minnesota, plant exhibited more
nonspecific, constitutional symptoms such as tiredness, weakness, irrita-
bility, and joint pain (Tables 7.16 and 7.17).
A summary of dose-response data
1. Anemia - With one exception,
or more months of exposure.
2. Neuropathy - Several workers showed wrist extensor or ankle weak-
ness after 2-7 months of exposure. The lowest blood lead level
associated with neuropathy was 78 ~g/d1; most neuropathy cases had
blood lead levels above 80 ~g/dl.
258
for various symptoms is as follows:
anemia was observed only after two
-------
TABLE 7.16
FREQUENCY OF SYMPTOMS AMONG 22 CASES
OF LEAD POISONING. UTAH. 1976a
TABLE 7.17
FREQUENCY OF SYMPTOltS IN LEAD SMELTING
PLANT EMPLOYEES. MINNESOTA. 1976a
Symptom Number Percent Symptom Number Percent.
Abdominal cramps 19 86 Tiredness 17 52
Nausea 18 82 Loose bowel movements 11 33
Diarrhea 12 55 Irritability 9 27
Headache 12 55 Joint pains 9 27
N Dizziness 12 55 Muscle weakpess 9 27
VI Anorexia 12 55 Loss of appetite 7 21
\0 Vomiting 9 41 Headache 6 18
Paresthesias 9 41 Leg cramps 6 18
Constipation 8 36 Constigation 6 18
Fatiguability 8 36 Nausea 5 16
Myalgias 7 32 Trouble sleeping 4 12
Weight loss 6 27 Vomiting 4 13
Irritability 5 23 Abdominal pain 3 9
Chest pain 5 23 Weight lossc 2 6
Muscle weakness 4 18 Shakes 2 6
Tremor 4 18
Joint pains 4 18
a
bSource: Adapted from Center for Disease Control (1977).
aSource: Excluding 1 employee with symptom due to ulcers.
Adapted from Center for Disease c
Excluding 2 employees with symptom due to diet.
Control (1977). Of the 2 with weight loss not related to diet. 1 lost
20 pounds in 15 months and 1 lost 22 pounds in 7 months.
-------
3. Nephropathy - No definite relationships were noted between dur-
ation of exposure and development of overt lead nephropathy. Some
abnormalities of renal function were correlated with duration of
lead exposure. At the Missouri plant, 32 percent of workers tested
had elevated blood urea nitrogen (BUN). These workers. had worked
at the plant for 45 - 31 years. Eight percent of the Tennessee
workers had elevated BUN levels and 8 percent of the Minnesota workers
had elevated serum creatinine levels. With the exception of three
individuals, (all of whom had been exposed to lead less than two
months) no worker with less than 3 1/2 years of exposure had ab-
normal renal functions tests.
A survey of 228 children living in the area surrounding the Memphis,
Tennessee smelter showed no excessive lead absorption, however young
children of smelter workers were found to have elevated blood levels, with
eight of these children being hospitalized and treated for lead poisoning.
Examination of 31 children (ages 1-9) at the Eagan, Minnesota plant revealed
blood lead levels ~ 30 ~g/dl in 16 percent of the children, indicating in-
creased lead absorption.
Based on findings presented in the previous discussion, it is ob-
vious that the currently accepted guideline defining the upper limit of a
safe blood lead level (80 ~g/dl) does not provide adequate protection
against lead toxicity. If lead toxicity is to be prevented, the biologic
monitoring system must effectively remove the worker from exposure prior
to the onset of illness. Clearly, the present 80 ~g/dl level does not pro-
vide adequate protection since anemia and other overt symptoms of lead in-
toxication were observed at blood-lead levels below 80 ~g/dl.
In the five facilities investigated, no workers showed evidence of
lead related anemia, wrist weakness or lead related renal disease associated
with a blood lead level < 60 ~g/dl. In fact, very few workers with blood
lead levels < 60 ~g/IOO ml had any symptoms consistent with lead intoxication.
It was concluded that the data in the report clearly support the setting
of a biologic threshold limit value of 60 ~g/dl for occupationally exposed
populations, and furthermore, that this value should be revised downward in
the event that deleterious health effects at blood lead levels < 60 ~g/dl
can be demonstrated in the future (Center for Disease Control, 1977).
7.5.3.1.2 Effects of chronic lead exposure on mortality--Yet another pos-
sible means of investigating clinical effects of lead exposure is the
systematic examination of mortality patterns of lead workers. Customarily
such studies are retrospective in nature and involve a comparison of the
mortality rates for various causes among lead workers as opposed to "control
groups" having no unusual sources of lead exposure (i.e., general populations).
Findings of elevated rates or proportions of various causes of deaths among
lead workers suggests that lead may playa role in the etiology of that
particular disease. Although in general, occupational mortality studies of
the lead industry have produced essentially negative results, several such
investigations are summarized below.
Dingwall-Fordyce and Lane (1963) carried out a retrospective mortality
260
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study of British lead workers (with at least 25 years of service each)
who retired between the years 1926 and 1960. Workers were classified
according to three grades of exposure: heavy, medium or none based on
average urinary lead concentration records. The heavy exposure group
(average urinary lead 100-250 ~g/liter over the past 20 years of employment)
had higher than normal death rates from cerebrovascular diseases. Included
in this category are cerebral hemorrhage, thrombosis and arteriosclerosis.
Interestingly, the trend of excess deaths in the heavy exposure group was
most pronounced among men who retired prior to 1951. Such a finding is
probably related to technological changes which improved exposure conditions
over the years. Deaths from malignant neoplasms were not above the rate
expected (based on the general population rates) in any of the exposure
categories.
Malcolm (1971) also published the results of a mortality study which
examined men exposed to lead at "moderate" levels. The average blood lead
level of the group was 65 ~g/dl. He found no evidence of significant ex-
cess mortality from heart disease, pulmonary disease, cerebrovascular
accidents, cancer, renal disease or other miscellaneous causes among
the group.
Cooper and Gaffey (1975) undertook a study of men who worked in lead
production facilities and battery plants to determine whether or not their
mortality differed significantly from that of men not occupationally ex-
posed to lead. This investigation took the form of a prospective study
of mortality in six lead-production facilities and ten battery plants.
The former included one primary smelter, two refineries, and three recycling
plants. A group ot.70~2 men who had been employed in these plants between
1946 and 1970 was followed to determine whether they were still alive at
the end of 1970. Their observed mortality by cause was compared with that
of a comparable population of all United States males.
Lead absorption in many of the men was greatly in excess of currently
accepted standards based upon urinary and blood-lead concentrations avail-
able for a portion of the group. Seventy-eight percent of 47 smelter work-
ers had blood lead levels ~ 80 ~g/dl or more over the period from 1946-
1961. After 1965 data based on 489 workers showed 35 percent had blood
lead ~ 80 ~g/d1. Levels from the battery workers were somewhat lower than
those of the smelter workers. Over all levels of exposure, duration and
job classifications, 81.5 - 95.7 percent of the workers had blood lead
levels ~ 40 ~g/dl.
There were 1356 deaths reported; death certificates were obtained
for 1267. The standardized mortality ratio (St1R) for all causes was 107
for smelter workers and 99 for battery plant workers indicating a fairly
close approximation of the U.S. male population whose SMR = 100 by defini-
tion. Deaths from neoplasms were in slight excess in smelters, but not
significantly increased in battery plants. There were no excess deaths
from kidney tumors. The S~ffi for cardiovascular-renal disease was 96 for
smelter workers and 101 for battery plant workers, i.e., roughly the same
as for the general population but not as good as might be expected in an
employed population which commonly have lower SMRs for these causes than
the general population. There was definitely no excess in deaths from
261
-------
either stroke or hypertensive heart disease. However, deaths classified as
"other hypertensive disease" and "unspecified nephritis or renal sclerosis"
were higher than expected. The actual numbers of deaths in these last-
named categories combined (41 where 19.5 were expected) represented about
three percent of all certified deaths. In these observations, the possible
interactive effects between lead and other renal toxic agents, such as
cadmium cannot be ruled out, however. The life expectancy of lead workers
was calculated to be approximately the same as that of all U.S. males.
7.5.3.1.3 Subclinical effects: hematologic, neurologic, behavioral, and
nephrotoxic--As noted above, lead may produce changes in biochemical and
physiological parameters which occur at blood-lead levels well below those
usually associated with overt clinical effects. The point at which sub-
clinical changes became sufficiently serious to represent a threat to health
are neither clearly defined nor agreed upon.
Selander and Cramer (1970) and Haeger-Aronsen (1971) have reported
that the threshold level associated with the appearance of excess ALA in
the urine occurs at blood lead levels in the 40-60 ~g/dl range. An expon-
ential increase in urinary ALA (reflecting inhibition of ALAD by lead) is
s~en as blood lead increases above 40 ~g/dl. The physiological significance
of this disturbance of heme synthesis is that if sufficient inhibition occurs,
overt hematological changes such as anemia, and decreased life span of
erythrocytes may result.
Similarly, Tola, et al., (1973) reported a slight decrement in hemo-
globin and hematocrit at blood-lead levels as low as 40 ~g/dl. Their con-
clusion was based on a study of sequential changes in hemoglobin which oc-
curred among workers newly employed in an industrial lead environment.
Studies by Seppalainen, et al., (1975) revealed subclinical neuropathy
(slowing of the maximal conduction velocities of the median and ulnar
nerves) in storage battery workers whose blood lead levels never exceeded
70 ~g/dl. These changes may be precursors of more serious motor impairment
in view of the fact that these effects may represent a milder version of
the weakness of the extensors of the hands and feet which is frequently
observed in clinical lead intoxication. Subtle effects of the nervous
system take on added significance due to the possible irreversibility of
these changes and the limited regenerative capacity of the nervous system.
The data of Seppalainen, et al., (1975) agree reasonably well with
those of Repko, et al., (1975), who studied behavioral measures of task
performance among workers exposed to lead in storage-battery manufacturing
companies. While the intellectual functions tested were unaffected by
increases in body burden of lead, motor functions (i.e., hands), sensory
functions (hearing), neuromuscular or psychomotor (tremor, eye-hand coordin-
ation, muscular strength, and endurance) and psychological functions (as
measured by tests of hostility, aggression, and general dysphoria) were.
all affected by the body burden of lead. The strongest relationships between
exposure and effects were found with tests of neuromuscular and psychomotor
performance. Major changes on the preferred side of the body were observed
at blood levels between 70 and 79 ~g/lOOg (U.S. Department of Labor, 1975).
262
-------
Vitale, et al., (1975) performed various laboratory/diagnostic tests
of renal function on a group of lead workers. The tests revealed evidence
of decreased renal function in 4 of 8 persons with blood lead levels below
80 ~g/dl. These lead workers had been engaged in refining, welding
and cutting operations for variable lengths of time. The functional impair-
ment associated with this level of renal damage, if any, was not reported.
Similarly, Cramer, et al., (1974) observed renal damage including decreased
ability of proximal tubular cells to form inclusion bodies, decreased abil-
ity to excrete lead and moderate renal fibrosis in a group of workers exposed
to lead for 4 years or longer.
7.5.3.1.4 Policy implications of air to blood lead relationships for setting
occupational standards--A variety of recent studies have generated data
on the dose-response relationship between air lead and blood lead. Since
these studies are more relevant from the standpoint of implications for
standard setting (rather than documenting specific forms of toxicity which
occur at a given lead level) they are reported separately in the section
below. In reading this section, it is well to keep in mind that most in-
dustrial firms use blood lead as an indirect measure "dose" of air lead,
rather than direct monitoring of air lead, which may vary substantially
throughout the plant. Second, as reported in the previous sections, blood
lead levels are well correlated with a variety of health effects, both
clinical and subclinical. Hence periodic monitoring of blood lead levels
may be quite useful in preventing overexposure or failing that, in detecting
lead effects at an early and often reversible stage.
Preliminary findings of a study by National Institute for Occupational
Safety and Health (NIOSH) at the General Motors Corp. Delco-Remy battery
plant in Muncie, Indiana, provide new information on the relationship be-
tween air and blood-lead levels (Wall Street Journal, 1977b). NIOSH analyzed
the data on lead levels in the blood of about 500 plant workers as well
as the lead level in the air. Investigators found that the plant kept lead
levels in the blood of over 90 percent of its workers at 60 ~g/d1 or lower
by maintaining air exposures at a maximum of about 100 ~g/m3 in most work
areas.
The studies of Williams, et al., (1969) and Williams (1972) cited in
U.S. Department of Labor (1975) may be used to estimate the potential con-
tribution of lead in air to blood lead levels. The air exposure data used
by Williams, et al., (1969) was based on measurements obtained from workers
in various departments of a storage battery factory who wore personal sam-
plers for a full work shift for 2 weeks. Considerable variation was found
both among departments and among individual personal samples. The study
presents a correlation between the mean blood lead level, together with the
upper and lower ranges, with air lead levels. In order to provide a maxi-
mum blood lead value of 60 ~g/dl, the mean blood lead level in a population
of workers must be maintained at about 40 ~g/dl since a mean of about 40
~g/dl will result in a range in workers of approximately 20 ~g/dl at the
lower limits to 60 ~g/dl at the upper limits. The '~illiams data suggest
that air lead levels of 200 ~g/m3 correspond to a range of 48~92 ~g/dl of
lead in blood with a mean level of 70 ~g/dl (84 ~g/dl ~ 80 ~g/lOOg). Air
lead levels of 150 ~g/m3 correspond to a range of 38-82 ~g/dl with a mean
263
-------
blood lead level of 60 ].1g/dl. It is apparent, therefore, because of these
ranges, that airborne lead levels of 200 or even 150 j..Ig/m3 would result in
unacceptable blood lead levels, i.e., greater than 60 j..Ig/dl for a signifi-
cant number of employees (U.S. Department of Labor, 1975).
Based on data from 103 employees, air lead levels of 200 j..Ig/m3 pro-
duced a mean blood level of 70 j..Ig/dl with some workers having over 80 j..Ig
lead/dl in blood (Williams, 1975). Interestingly, the data on air lead and
corresponding blood lead levels reported by Short Associates (1976) tends
to confirm the relationship described above.
The correlation of somewhat lower blood lead levels, (i.e., < 60
j..Ig/dl) with air lead levels are not definitive. Thus, the regression equ-
ation relied upon in Williams' study is based upon data which do not con-
tain a critically important value--the blood lead level corresponding to an
air lead level of 50'j..Ig/m3. If it is assumed that the Williams regression
equation is correct, an air lead level of 50 j..Ig/m3 would correspond to a
mean blood lead level of 40 j..Ig/lOOg, with an upper limit of approximately
60 ].1g/100g. However, as noted above, critical data are missing, leaving
doubt as to the correctness of this projection. The regression equation
is unduly weighted by data at either extreme, and extrapolation of this
equation to predict the air lead-blood-lead relationship beyond the limits
of measured data is somewhat speculative. In any event, the study by
Williams, even with its limitations, provides the best available data with
respect to the air lead--blood lead relationship in industrial exposure
situations. Clearly, the Williams study shows that to achieve a mean blood
lead level of 40 j..I3/100g would require an 8-hour air lead concentration of
less than 150 j..Ig/m based on a time-weighted average (U.S. Department of
Labor, 1975). Based on Williams' (1969) calculations, it appears that an
increase of 1 j..Ig/m3 in the weekly time-weighted average concentration of
lead in air would correspond to an increase of approximately 1 pg/dl in
blood lead.
Prpic-Majec, et al., 1973 and Fugas, et al., 1973, report data from
a study of 52 workers in unspecified lead trades. The time-weighted aver-
age concentration of respirable lead particles was 35 j..Ig/m3; the mean
blood lead level of the group was 44.3 j..Ig/dl. A control group living in
an area having air lead at 0.2 j..Ig/m3 and a mean blood lead level of 22.4
j..Ig/dl was used to establish baseline levels of blood lead due to non-air
sources of 22.1 j..Ig!dl (0.3 j..Ig!dl in the control group was due to air).
Since the air lead level in the occupational environment was 35 j..Ig/m3,
it was concluded that 1 j..Ig of lead mer m3 in air contributes 0.6 ].1g/100
ml of blood (22.1 j..Ig/m3 + 35 j..Ig/m3).
As earlier indicated, the studies of Prpic - Majec, et al., (1973)
Fugas, et al., (1973) and Williams (1975) suggest that the incremental
increase in blood lead per unit increase in lead in air is somewhat less
at air lead levels characteristic of industry than those in the usual out-
door ambient range.
7.6
ORGANIC LEAD
In general, the alkyl derivatives of lead are highly toxic compounds,
264
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and are readily absorbed through the skin. Tetraethyl and tetramethyl
(JEL and TML) are clear, colorless liquids, volatile, nonpolar, nonionic,
and soluble in many organic solvents such as hydrocarbons, chloroform,
ether, and absolute ethanol. They have very low water solubilities, and
are relatively unreactive in air, water or alkali (Shapiro and Frey, 1968).
The high solubility of alkyl lead compounds in body fluids is the basis for
toxicity through percutaneous absorption whereas the volatility of these
compounds (particularly when added to gasoline) underlies the hazard poten-
tail among workers engaged in the production of these compounds. Those
chronically exposed to evaporating gasoline may also be at risk, although
few studies have been conducted. Because alkyl lead compounds are light-
sensitive and undergo photochemical decomposition when they reach the at-
mosphere; their presence in the atmosphere is transient (National Academy
os Sciences, 1972).
In cities, alkyl lead levels were reported "not to reach 10 percent
of inorganic levels" (National Academy of Science, 1972). In fact, much
of the lead burned in gasoline (see Section 6.6.1) is not exhausted in
forms which can remain suspended in the atmosphere. To date, no information
exists on the effects of chronic, low-level exposure to airborne alkyl lead.
From a toxicological viewpoint, the most significant organic lead
compounds are the lead alkyls, tetraetheyl and tetramethyl. Additionally,
a number of lead ompounds of organic acids, such as lead naphthenate, lead
octoate, etc., used in the paints and plastics industry are significant
although these are, by industry convention, classified as inorganic com-
pounds. Their behavior in biological systems also appears more similar
to inorganic lead than to that of the lead alkyls.
Lead soaps of organic acids are commonly used as driers by the paint,
varnish, printing ink and linoleum industries. Thus, exposure to these
compounds is limited mostly to industrial workers. Soaps of mixed acids
of linseed oil and rosin acids are known as linoleate driers and resinate
driers, respectively. Lead stearates, tallates, naphthenates, and octoates
(chiefly 2-ethylhexanoate) are also produced and marketed in the United
States as paint driers. The hazards encountered in the handling and use
of driers and metallic soaps are associated with the toxicity of the metal
present, the solvents contained, and their activity as oxidation catalysts.
Although little data are available regarding the specific toxicities of
these compounds, in general, the LDSO values appear to be several orders of
magnitude higher than those of TEL and TML.
In general, the alkyl (tri-and tetraalkyl) derivatives of lead are
highly toxic compounds which are absorbed by inhalation, ingestion or per-
cutaneous absorption. These compounds are probably distributed in a nonionic
form and, being lipid-soluble, are concentrated in the brain, body fat and
liver. Because of this selective distribution, manifestations of lead
poisoning are dominated by involvement of the central nervous system (CNS) and
differ from those of inorganic lead poisoning (Gerarde, 1964; Schepers, 1964).
While many of the symptoms of acute poisoning by inorganic and organic lead
are similar, they can be distinguished diagnostically. Organolead poisoning
results in elevated levels of lead in the urine but less consistently in
265
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the blood. Likewise, red blood cell stippling, anemia, and alterations in
urinary porphyrins are not consistently seen with organic lead exposure,
particularly in acute episodes.
Organic lead compounds, particularly the two alkyl leads used in anti-
knock additives, constitute primarily an occupational exposure problem, to
which the general population is not exposed. Because of the known occupa-
tional hazard, extensive studies have been conducted on uptake and absorp-
tion, elimination, tissue distribution, and toxic effects. The results of
these studies are summarized briefly in the following pages. A more de-
tailed discussion of the health effects of organic lead compounds is con-
tained in the recent review of the environmental effects of lead (Bell,
et al., 1978).
7.6.1
Uptake and Absorption
Kehoe (1925, 1927) showed that tetraethyllead vapor is readily
absorbed through the pulmonary epithelium. Using radium-D as a
marker, Mortensen (1942) studied the uptake of tetraethyllead in the lungs
of rats. The amount absorbed was proportional to the concentration of
vapor in the inhaled air, although the proportion decreased at high con-
centrations,(Mortensen, 1942). Because lead alkyls are broken down by
light and heat, their presence in the air is transient and it is believed
that they contribute little to the inhalation burden of general populations.
Ingestion is a much less probable route for uptake and absorption of
organic lead compounds than inhalation and skin absorption. In general,
lead soaps are hydrolyzed and possibly converted to metal chlorides and
free acids when ingested. Hazards from inhalation and skin contact may
also arise when solvents are combined with the lead soaps, particularly
in the liquid driers. In such situations, the solvents probably represent
a greater toxicological hazard than the lead in the paint driers. One
estimate places the total number of persons directly exposed to lead in the
manufacture of paint driers in the United States at less than 250; thus,
it is a relatively insignificant source of lead exposure compared to the
primary and secondary lead and storage battery industries which employ about
25,000 persons who are potentially exposed to much higher levels (Short
Associates, 1976). Further, the usage of many types of paint driers,
especially the linoleates, resinates, stearates, and tallates .has markedly
declined in the past decade, further reducing any possible hazard.
Pettinati, et al., (1959) and Rosetti, et al., (1961) point out that
percutaneous absorption is of importance only in the case of lead alkyls
and lead salts of naphthenic and fatty acids. Eldridge (1924) reported
that tetraethyllead was absorbed rapidly through the skin in both dogs
and guinea pigs.
Laug and Kunze (1948) found the amount of lead in the kidney from
application of tetraethyllead was significantly elevated relative to the
controls who received various forms of inorganic lead, demonstrating the
greater percuteneous absorption of tetraethyllead. (Table 7.18).
266
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Table 7.18-
CUTANEOUS ABSORPTION OF LEAD COMPOUNDSa
Lead
Quantity Concentration
Applied, in Kidneys,
Compound mg/g Wet Vlt. Control
Arsenate 102 0.85 0.55
Oleate 148 1.30 0.59
Acetate 77 1.80 0.82
Tetraethyl 106 64.20 0.82
aSource: Laug and Kunze (1948). Reprinted, with permission,
from J. Ind. Hygiene Toxicol.(c) Williams and Wilkins Co.(1948).
Tetraalkyl lead compounds are volatile, highly lipid-soluble, and
would be expected to pass through biological membranes including the
placenta. McClain and Becker (1972) reported that trimethyllead does
cross the placental barrier but to only a limited extent at low maternal
doses. At higher doses, however, transport was much greater, probably
because binding sites in maternal erythrocytes were saturated at the
higher dose.
7.6.2
Tissue Distribution
The distribution of the organic lead salts differs markedly from the
inorganic salts of lead. Bolanowska (1968) investigated the distribution
and excretion of triethyllead in rats following intravenous administration
of tetraethyllead. Twenty-four hours after administration of tetraethyllead,
50 percent of the total lead in the internal organs was in the form of tri-
ethyllead; the highest levels were found in the liver, blood, kidney, and
brain. Cremer (1959) found that tetraethyllead was rapidly converted to
triethyllead in the liver. Triethyllead then remained stable in vivo for
--
several days before it was excreted in the feces and urine at a rate equiva-
lent to not more than I percent of the daily dose. Inorganic lead consti-
tuded the remainder of the in vivo lead beginning 24 hours after injection.
---
The triethyllead ion is identified as responsible for the toxic effects
of tetraethyllead. There is evidence that tetramethyl- and tetrapropyllead
compounds are metabolized to the trialkyl form much more slowly than tet-
raethyllead is converted to triethyllead. This may account for their being
comparatively less toxic, although once formed, trimethyllead compounds are
as toxic as the triethyllead compounds (Cremer and Callaway, 1961). Unlike
those of inorganic lead, the organic lead compounds have no special affinity
for bone but a high affinity for lipid tissues, especially those constituting
the nervous system. Therefore, the central nervous system is the site of
greatest concentration.
267
-------
Schepers (1964) observed that the concentration in the brain is much
lower than in the liver and lungs, even though the effects of organic lead
compounds are mainly in the central nervous system in experimental animals.
After inhalation of toxic amounts of tetraethyllead the concentration of
lead in the skeleton and in blood is negligible, whereas after inhalation of
toxic amounts of tetramethyllead, the concentration of lead in blood may
exceed that in any other tissue including the skeleton. Following inhala-
tion by rats, tetraethyllead can be recovered unchanged from the liver
(Stevens, et al., 1956), although it is rapidly metabolized in the liver to
inorganic lead so that chronic exposure may result in distribution and a
toxic syndrome characteristic of inorganic lead (Cremer, 1959).
7.6.3
Elimination
There are few data on the excretion of alkyl lead compounds such as
tetraethyllead and tetramethyllead. Sanders (1964) states that in both
inorganic and organic lead intoxication the urine will probably be found to
have an abnormally high concentration of lead. In tetraethyllead intox-
ication, it is likely to be considerably higher than it is an inorganic
lead poisoning since lead absorbed percutaneously is more rapidly excreted.
In considering the kinetics of organic lead excretion, it should be
noted that TEL and TIlL have a far shorter residence time in the blood and
other tissues than does inorganic lead. Kehoe and Thamann (1931) found
that in rabbits, following skin absorption~ the absorbed tetraethyllead
decomposed in the tissues after a period of 3 to 14 days. Both its tissue
distribution and excretion followed quantitatively that of water-soluble
lead compounds. In a study of the excretion of triethyllead in rats,
Bolanowska (1968) found that 24 hours after the administration of TEL, 50
percent of the total lead in the soft organs was in the form of triethyl-
lead. Triethyllead concentration in vivo then remained steady for several
days, and was excreted in the feces and urine at a rate equivalent to not
more than 1 percent of the daily dose of TEL. Inorganic lead constituted
the remainder of the in vivo lead 24 hours after TEL injection, and no
diethyllead was found, even shortly after administration of TEL. Diethyl-
lead was fairly stable in vivo, but less so than triethyllead. Bolanowska
notes the presence of triethyllead in humans who died up to 20 days after
acute poisoning with TEL.
7.6.4
Toxic Effects
7.6.4.1
Acute Toxicity of Various Organolead Compounds--
The absorption of lipid-soluble alkyl lead compounds, either through
the skin or the lung~ may result in central nervous system manifestations
including insomnia, asthenia, tremors, headache, neuromuscular pain,
hallucinations, mania, delusions, and convulsions. The results of the ad-
ministration of single, lethal doses of TEL or TML progress from hyper-
irritability and tremors to convulsions and death. Chronic exposure to
alkyl lead also leads to neurotoxicity with similar symptomatology as
that following acute exposure.
268
-------
The toxicities of TEL and TML
TLV's (Threshold Limit Values) for
and 150 jlg/m3 for tetraethyl lead.
not for inhalation.
are shown in Table 7.19.
lead as tetramethyl lead
These are, however, for
As shown, the
is 100 jlg/m3,
skin exposure,
7.6.4.2
Neuropathology--
The pathological lesions noted in lead induced CNS anomalies include
cerebral edema, encephalopathy, increased cerebrospinal fluid pressure,
proliferation and swelling of endothelial cells, dilation of capillaries
and arterioles, glial cell proliferation, focal necrosis and neuronal
degeneration (Goyer and Rhyne, 1973).
Many of these symptoms are also common to inorganic lead poisoning
as well.
One investigator has attempted to distinguish between CNS toxicity
cau~ed by organic and inorganic lead compounds. This is the monograph
prepared by Pentschew (1958) based principally on earlier work of Tolgskaya
and Reznikov (1955). These authors discussed the physiologic differences
between encephalopathy caused by organic lead compounds versus that at-
tributable to inorganic lead.
Triethyllead inhibits catecholamine effect on smooth muscle contrac-
tion. Consequently, there has been some speculation that the toxicity
of triethyllead and particularly its action on the central nervous system
can be explained by a combination of effects which might result from an
upset of cholinergic and adrenergic contral pathways due to the formation
of endogenous psychotogenic complexes. This speculation is based on
unconfirmed claims that adrenochrome, which is an intermediate in the con-
version of catecholamines to trihydroxyindole products, is an hallucinogenic
agent. Galzigna, et a1., (1973) found that triethy11ead dramatically
increases the duration of the succinylcholine-induced myoneural block of
cholinergic transmission. This is explained by the competition between
triethy11ead and succinylcholine for serum cholinesterase. Triethy11ead
is able to antagonize the affect of norepinephrine in vivo but alone is
without any effect on normal contractile activity.
7.6.4.3
Metabolic Effects--
Few studies have focused specifically on the metabolic effects of
a1ky11ead compounds.
Trimethy1-and triethy11ead decrease oxygen consumption when added to
rat brain and cortex slices in vitro. Tetramethy1- and tetraethyllead
did not have this effect except at much higher concentrations (amount un-
known). A decrease in in vitro oxygen consumption was also found in brain
slices taken from rats previously exposed to triethy1- and tetraethyllead
(Gerarde, 1964). Glucose metabolism in brain slices is also inhibited by
the diethy1-, triethy1-, tripropyl- and trimethy11ead compounds.
269
-------
TABLE 7.19 REPRESE~TATIVE TOXICITIES AND OCCUPATIONAL STANDARDS
FOR TETRAETHYL LEAD AND TETRAMETHYL LEADa
Compound and Standards, ~~/m3 d
Chemical Formula U.S. Occupational TLVc Toxicities , mg/kg
Te trae thyl lead 75 (skn) 100 (skn) oral rat LD 17
Pb(C2H5)4 ipr rat LDLo 10
ivn rat LDLo 31
par rat LDLo lS
scu mouse LDLo 86
scu mouse TDLo 86
skn dog LDLo 500
ivn rabbit LDLo 23
skn guinea pig LDLo 990
inh rat LCLo 6ppm
50
Tetramethyl lead 70 (skn) 150 (skn) oral rat LDSO 190
Pb(CH3)4 ipr rat LD 73
par rat LDLo 105
ivn rabbit LD50 90
Lo
Notes:
a
Source:
Registry of Toxic Effects of Chemical Substances (NIOSH, 1977).
Threshold Limit Values for Chemical Substances and
Physical Agents in the Workroom Environment (ACGIH, 1977)
U.S. Department of Labor (1978).
b
U.S. Occupational Standard (OSHA) based on time-weighted average
(TWA) for continuous exposure (8-hr day and 40-hr week).
cThreshold Limit Value - based on time-weighted average for continuous
exposure 8-hr day and 40-hr week (American Conference of
Governmental Industrial Hygienists (1977).
dT . .
ox~c~ty data descriptors: See Table 7.7
270
-------
TEL has effects on neurotransmitter metabolism in the brain of experi-
mental animals (Cremer and Callaway, 1961). The mechanism of this action
was studied by assessing the effects of triethyllead in vitro on the cho-
linesterase activity of rat diaphragm and in vivo on serum cholinesterase
in the dog. The highest inhibition of acetylcholinesterase activity of
the rat diaphragm obtained with two concentrations (0.4 and 0.8 milliliter)
of the substrate acetylthiocholine was about 25 percent of normal activity.
The inhibition was noncompetitive. As with other aspecific cholinesterase
inhibitors, triethyllead was able to induce a maximal inhibition of 25
to 30 percent on the true cholinesterase activity of the rat diaphragm
preparation. Maximum inhibition of serum cholinesterase was observed 15
minutes after the administration of 6 milligrams per kilogram triethyllead
to dogs and full recovery occurred 45 minutes after administration (Gal-
zigna, et al., 1973).
7.6.4.4
Enzyme Effects--
In view of the high sensitivity of ALAD to lead, the levels of enzyme
activity in the blood of men occupationally exposed to lead alkyls, partic-
ularly tetraethyllead, were measured (Millar, et al., 1972). The enzyme
activity in an exposed group of men was significantly less (P less than
0.001) than in a control gr~up, the respective mean values being 220 and
677 units of enzyme activity.
Tetraethyllead is metabolized in the body via triethyllead and di-
ethyllead ions. Diethy11ead ion was found to inhibit ALA dehydratase
activity at concentrations greater than 5 x 10-5 M, although the degree of
inhibition was less than that obtained with Pb++. These results suggest
that exposure to tetraethyllead can cause a decrease in erythrocyte ALA
dehydratase activity (Millar, et al., 1972). The effect of known inhibitors
on ALA dehydratase activity, such as alcohol consumption and cigarette
smoking were not taken into account in the group of workers investigated.
7.6.4.5
Reproductive Effects--
McClain and Becker (1972) found that tetraethyl lead, tetramethyl
lead, and trimethylead chloride were essentially nonteratogenic in Sprague-
Dawley rats. Embryo or fetal toxicity accompanied the administration of
the organolead compounds and was characterized by growth retardation and
delayed ossification of bone. Marked fetal effects were observed only in
maternal animals that exhibited severe toxicity and were, therefore, severely
debilitated.
7.6.5
Epidemiologic Studies
Gerarde (1964) states that because of the large dilution factor (3
to 4 milliliters per gallon of gasoline) of TEL, the normal use of "leaded"
gasoline does not present a lead intoxication hazard. However, human ex-
posure to TEL during the cleaning of leaded-gasoline tanks has led to
fatalities (Shapiro and Frey, 1968). Robinson (1974) has presented evi-
dence of absorption of alkyl lead antiknock compounds among occupationally
exposed workers. Delta-aminolevulinic acid (ALA) and lead were measured in the
271
-------
urine of 123 men of various ages and lengths of service, all working as
operators or maintenance men in an area of production of alkyl lead anti-
knock compounds (tetraethyllead and tetramethyllead). The levels of ALA
and lead in urine were found to have a relatively low positive correlation
of 0.52 which suggests that a given elevation of urinary lead excretion
probably is associated with a lower level of urinary ALA excretion when the
exposure is to organic lead. It is not clear whether this difference might
be related primarily to differences in circumstances of exposure or to
differences in metabolism (biotransformation) due to exposure to a different
form of lead. For example, there have been no experimental studies re-
ported to indicate what effect, if any, tetraethyllead or tetramethyllead
might have on porphyrin metabolism and, hence, on urinary ALA excretion.
In summary, the investigation by Robinson (1974) shows that absorption of
organic lead as indicated by increased urinary levels, is associated with
an increase in urinary ALA levels. However, the mechanism through which
this effect is produced was not identified.
Proper protection .of workers has virtually eliminated the problem of
TEL or TML poisoning over the last 30 years. Robinson (1976) made a detailed
comparison of extensive medical information (results of periodic medical
examinations, of medical records of absence from work due to nonoccupational
illness, and of cumulative medical diagnoses) for workers with 20 years or
more tetraethyllead (TEL) service to a matched (for age, sex, race, and
length of service) group of workers with no occupational lead (TEL or
other) exposure. The comparison showed no significant health differences
between the two populations. Robinson (1976) concluded that under the con-
ditions that have existed at the Baton Rouge, Louisiana alkyllead plant,
workers having long occupational exposure to levels of lead (chiefly TEL)
sharply in excess of that of the general public, but within a range termed
"safe" by current industrial medical standards, have not suffered detectable
impairment of health.
272
-------
I -- ~-~~-
I
7.7
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Levels in Selected American Communities. In: Lead. T. B. Griffin
and J. H. Knelsor (eds.). Environmental Quality and Safety. Supple-
ment Vol. II. Georg. Thieme Publishers, Stuttgart. pp 152-196.
Ter Haar, G. L., and R. Aronow. 1974. New Information on Lead in Diet and
Dust as Related to the Childhood Lead Problem, Environ. Health
Perspect. Experimental Issue (7):83-89. May.
Texas Morbidity and Mortality Weekly Report. 1973. Human Lead Absorption,
Texas Morbidity and Mortality Weekly Report. 22(49):405-407. December 8.
Thomas, H. V., B. K. Milmore, G. A. Heidbreder and B. A. Kogan. 1967. Blood
Lead of Persons Living Near Freeways. Arch. of Environ. Health. 15(6):
695-705.
Tipton, I. H., and M. J. Cook. 1963. Trace Elements in Human Tissue. Part II.
Adult Subjects from the United States. Health Phys. 9(2):103-145.
Tipton, I. H., H. A. Schroeder, H. M. Perry, Jr., and M. J. Cook. 1965. Trace
Elements in Human Tissue. Part III. Subjects from Africa, The Near and
Far East and Europe. Health Phys. 11(5):403-451.
Tipton, I. H., and J. J. Shafer. 1964. Statistical Analysis of Lung Trace
Element Levels. Arch. Environ. Health. 8(1):58-67.
Tola, S., S. Hernberg and J. Nikkanen. 1972. Occupational Lead Exposure in
Finland. II Service Stations and Garages, Work, Environment, Health. 9:
102-105.
Tola, S., S. Hernberg, J. Nikkanen and S. Valkonen. 1973. Parameters Indicative
of Absorption and Biological Effect in New Lead Exposure, Brit. J. of Indust.
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288
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.
--------- -- --
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290
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Study. The Relationship Between Childhood Blood Lead Levels and Environ-
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291
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8.0
LEAD IN THE ENVIRONMENT
8.1
SUMMARY
It is the intention of this section to evaluate environmental concentra-
tions of lead in air, water, and fcod, and the relative contributions from each
of these media to total lead absorption and to blood lead levels. Also evalu-
ated is the effect of reducing adventitious lead in foods upon dietary lead
intake and, for a selected population sub-group, the effect upon mean blood-
lead levels. Much of the discussion centers upon adults in the normal, nonoc-
cupationally exposed general population, for whom the most data are available.
The exposure modes and responses of children are more complex and difficult to
quantify than those of adults and also critical aspects of the metabolic pro-
~ess, (particularly absorption/retention rates) for various modes of exposure
have not been adequately characterized in children as yet. Where it is known
that children differ from adults, separate estimates will be presented, if
possible. It should be understood that such estimates do not apply to children
with pica or other unquantifiable or unusual sources of lead intake.
Humans are exposed to environmental lead through inhalation, ingestion,
and in the case of organolead compounds, through cutaneous absorption. Under
normal conditions, the concentration of organic lead present in the environment
is so low that cutaneous absorption of organic lead can be ignored, except in
accidental or occupational exposure cases (U. S. Environmental Protection
Agency, 1977). Inhalation is of undisputed importance as the primary contribu-
tor to body burden among those occupationally exposed to lead. Furthermore,
relative to dietary lead, inhalation may provide an equal or more important
route of exposure for persons living in the immediate vicinity of major sta-
tionary sources or heavily traveled automobile freeways. These are special
exposure conditions which are not applicable to the general adult population,
however. Exposure patterns unique to children are discussed in Section 8.6.5.
For the general population, therefore, ingestion appears to be the most
important mechanism of exposure. Except in the special circumstances outlined
above, exposure via inhalation of ambient air by the general population is
clearly of secondary importance compared to exposure via ingestion of food,
water and cigarette use.
As indicated in Section 7.5.1, efforts to determine the absorption of lead
by the respiratory system at specified air lead concentrations, have been only
marginally successful for various technical reasons. It has been necessary to
resort to blood lead PbB as an indirect measure of "dose" of air lead. For
people who are breathing fairly constant air lead concentrations, averaged over
292
-------
months, the concentration of lead in the blood varies in accordance with the
air lead concentration. Analysis of data as to air lead vs. blood lead levels
in several studies of adults, indicate that over the range of general ambient
air lead concentrations, 1 ~g Pb/m3 of air contributes 1-2 ~g Pb/dl in blood.
This relationship seems also to apply to children. (Hammond, 1978).
Lead in the atmosphere, resulting, primarily, from the 150,000i. metric
tons of lead consumed annually in gasoline antiknock additives, is one signifi-
cant contributor to human intake and body burdens. Since concentrations are
directly related to gasoline consumption, it is not surprising that concentra-
tion gradients are seen in the vicinity of heavily traveled highways. Levels
above 10 ~g/m3 have been measured in heavy traffic. These concentrations
diminish rapidly, almost exponentially, with increasing distance from the high-
way and atmospheric lead concentrations stabilize at low levels (1-2 ~g/m3), ap-
proximately, 100 feet from the road due to the settling of particles (Ewing and
Pearson, 1974). Risks to health from airborne ambient lead occur, primarily,
among persons living in areas immediately adjacent to freeways and heavily-
trafficked urban streets (elevated blood lead seen) and among traffic policemen,
auto mechanics, and others who work in an atmosphere of heavy automotive usage
with poor ventilation. Persons residing in areas near lead-emitting industries
also show elevated blood levels which are indicative of increased absorption of
lead (U. S. Environmental Protection Agency, 1977).
However, improvements in air lead concentrations are on the way. After
reaching a peak in 1970, antiknock lead consumption has begun to decline, with
a corresponding improvement in ambient air quality. Average ~ational urban air
concentration has declin3d from 1.23 ~g/m3 in 1971 (1.00 ~g/m geometric mean)
to 0.89 ~g/m3 (0.74 ~g/m geometric mean) for the most recent average (1975).
The national arithmetic mean is estimated to have declined to 0.58 ~g/m3 in
1978, and is projected to decline to about 0.30 ~g/m3 in 1980 and thereafter,
after the target level of 0.5 g/gal lead average in the total gasoline pool is
achieved. As developed in Section 8.6, when air lead reaches these levels, in-
halation becomes a rather minor contributor to man's body burden of lead.
Overall, trends in ambient air lead levels are encouraging, and the limitations
now in place are already proving effective.
Lead has a relatively low solubility in water, as low as 50 ~g/l in hard
water, when analyzed as soluble lead (see APHA Standard Methods and Section
3.1.1 and Figures 3.1 and 3.2). Thus, it is not surprising that most U. S.
surface waters contain lead in concentrations below the drinking water standard
of 50 ~g/l. The extensive 1970 U. S. Geological Survey study found only 3 of
720 samples (0.4 percent) above 50 ~g/l. Similar results have been found in
surveys of public water systems, and the available data suggest that the median
concentration in U. S. drinking water supplies about 10 ~g/l. Water quality
is not as widely nor as routinely sampled and analyzed as is air quality; there
is no network system continuously sampling water analogous to the NASN, which
routinely samples air, and hence, annual U. S. averages for water are not
available. However, as with air, there is no evidence of an increasing concen-
tration trend in recent years. As compliance with effluent guidelines and
other waste disposal regulations improves, lead concentrations in water should
293
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decrease.
Although the lead content of city water supplies measured at the reser-
voirs seldom exceeds 50 ~g/l, water drawn from household taps occasionally ex-
ceeds this level. This is mainly due to the use of lead water pipes. Low
concentrations of dissolved solids (soft water) and an acidic pH exacerbate the
problem. Under extremely unfavorable conditions, the lead concentration may
exceed 1,000 ~g/l, as in Glasgow, Scotland, where lead-lined water storage
tanks are an additional problem.
The mean lead concentration in surficial soils in the U. S. is about 16
ppm. Average lead concentrations in soils, except for special cases such as
near smelters, heavily travelled highways, or other major lead emission sources,
are little above background and are changing only slowly. Lead concentrations
in urban dusts, on the other hand, may be quite high, from 1,000 ppm to as much
as 11,000 ppm for some house dusts, in extreme cases. Typically, such exces-
sively high lead levels are found in old, deteriorated, sub-standard housing,
and most of the lead content of the dusts is attributed to the disintegration
of high-lead paint or lead-containing plaster.
It is generally accepted that the major source of lead for the average per-
son is food and beverages. It was, for example, noted in the EPA Air Quality
Criteria for Lead document (U. S. Environmental Protection Agency, 1977) trlat
"In typical urban settings, food probably constitutes the body's
largest direct source of lead because almost every item in the
diet contains some measurable amount of the metal."
Neither air nor water compare with food as a source of lead. At an aver-
age of 20 m3 inhaled per day, and the 1975 mean air lead concentration of 0.89
~g/m3, total intake from air would be 18 ~g; and at 1.5 1 of water per day at
20 ~g/l, intake from water would be 30 ~g. This compares to an estimate of
lead intake from food of 254 ~g per day for a teenaged ~ale (U. S. Department
of Health, Education, and Welfare, 1977). Few people inhale an average air
lead concentration in excess of 2 ~g Pb/m3. At worst, this contribution to
circulating blood lead concentration is probably somewhere between 2 and 4
~g/dl. Assuming a normal PbB of approximately 15 ~g/dl, this leaves about 10-
12 ~g Pb/dl to be accounted for. In the absence of any other widespread
sources of lead intake for the average person, foods and beverages are general-
ly held responsible for the predominant remaining fraction of intake. It is
therefore important to consider the extent to which lead in foods and beverages
is reducible.
The lead content of most fresh foods is in the range of a few tenths ppm;
fresh milk will contain 0.05 ppm or less. However, significant amounts of lead
may be introduced in food through processing and packaging, particularly the
latter, due to the large role played by canned foods, for which substantial
amounts of lead solder are used for sealing seams. It is widely recognized
that the soldered seams of cans are potential sources of adventitous lead, and
the Acting Director of the Bureau of Foods, FDA, has testified that "about two-
294
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thirds of the lead in canned food is from the solder."
Certain foods have been found to double or triple their lead content as a
result of the transfer of lead from solder to filler, especially during storage
for substantial periods of time. The significance of this transfer is still
unknown, however. More information is needed as to: (1) the total dietary
contribution of such items and (2) the availability for absorption of the sol-
der contribution.
Hammond (1978) has noted that metallic lead particles such as are found in
the side seam region of lead soldered cans are very poorly absorbed compared to
lead acetate incorporated into the diet of experimental animals.
And thus, it is quite possible that contamination from solder in the form
of microscopic pellets of metallic lead are not nearly as readily absorbed from
the gastrointestinal tract as is lead present in foods in the form of simple
lead salts bound to natural ligands. There is a need for further studies to
establish more clearly the bioavailability of solder-derived lead.
Direct determination of absorption of lead from the digestive tract is not
beset with as many technical difficulties as in the case with inhaled lead.
Although the number of studies of lead absorption performed in people is
extremely limited"the conclusions drawn are fairly consistent. Approximately
8 percent of total, normal dietary lead is absorbed in adults and about 40 per-
cent is absorbed in the case of infants and preschool-age children. Dietary
intake of lead in the general adult population is about 150-250 ~g/d. Limited
information suggests that every 100 ~g Pb ingested in the diet daily contri-
butes about 6 ~g to blood lead,
In Section 8.6, estimates are developed of the potential benefits of re-
ducing the lead content in canned foods as a means of restricting lead exposure.
Various segments of the general population are analyzed as specific examples.
Such a reduction in the overall level of lead intake, while not directed at
specific "high risk" groups, is projected to have a significant beneficial ef-
fect, particularly for those individuals whose current levels of lead inges-
tion are in the marginally safe range. Since it has been shown in FDA surveys
that canned foods contribute approximately 30 percent of total dietary lead
intake and at least half, and possibly two-thirds of this 30 percent is attrib-
utable to canning itself, realistic savings of approximately 10 to 15 percent
of total dietary lead could be achieved if adventitious addition of lead from
cans can be prevented or reduced to negligible levels.*
* It was learned during the second phase of
a cooperative program underway with the can
duce drastic reductions in the average lead
this investigation that the FDA has
industry, which is expected to pro-
content of canned foods.
295
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1__-
Sample case calculations for the demographic group consisting of 20-34
year old females assuming a two-thirds reduction in lead in canned foods
indicated that this would reduce mean blood lead from 15.6 to 15.3 ~g/dl. While
this would b~ advantageous for the average individual, perhaps its greater
advantage would be in the reduction in the number of persons with blood lead
levels at the high end of the spectrum (> 25 ~g/dl), in the range where evidence
of hemotological changes begin to appear.
A reduction of 1.3 ~g/dl does not, at first glance, appear to constitute a
significant reduction in average blood lead. However, it represents a nearly 8
percent reduction, and a comparable reduction in lead intake and average body
burden is achievable in no other practical way (assuming that air lead has
already been taken care of by the new ambient air quality standard for lead
(U. S. Environmental Protection Agency, 1978b).
8.2
LEAD IN AIR
As discussed in Section 5.2.2, over one hundred thousand metric tons of
lead are being discharged from automobiles to the atmosphere each year, which
dwarfs all other discharges. Since this is distributed across the entire'
United States, there are no areas free from this pollutant, and it is a matter
of concern for human health.
,
Natural sources of lead are trivial in comparison to anthropogenic (man-
caused) sources. Natural sources include such items as forest fires and
volcanic smokes; most often cited for natural sources of lead are the estimates
of Patterson (1965). At that time Patterson estimated that the largest contri-
butor was silicate dust (contributing 5 x 10-4 ~g/m3 to the atmospheric total,
with volcanic halogen ae5osols contributing 3 x 10-5 ~g/m3 and forest fire
smoke only 6 x 10-6 ~g/m). More recently, Patterson has concluded that the
silicate dust figure is too high because it is based on too high an estimate
f~r dust levels. Latest measurement of lead in mid-Pacific air is 2 x 10-4 ~g/
m ; this lead is in 40-fold excess of crustal silicate values, indicative of
anthropogenic enrichment. Tge sam~ studies suggest a prehistoric natural am-
bient level of about 4 x 10- ~g/m in mid-ocean air (Patterson, 1978).
For the continental United States, the baseline concentration for ~tmos-
pheric lead has been suggested by Chow, et al., (1972) to be 0.008 ~g/m .
This value is an annual average, measured at White Mountain, California, in a
virtually uninhabited area at an elevation of 3,800 meters, far above the
thermal inversion. Patterson (1978) confirms the observation of average lead
concentrations of about 0.01 ~g/m3 in the most remote part of the California
High Sierras, but notes that this atmospheric lead is enriched about 100-fold
above crustal silicate concentrations as a consequence of anthropogenic inputs.
It is suggested by Patterson and his associates on the basis of these data
that a preh~storic natural ambient lead concentration may have been about
0.0001 ~g/m in continental air near ground level, mainly from silicate soil
particles (Patterson, 1978).
296
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8.2.1
Air Lead Concentrations in the D. S.
Only in recent years have ambient atmospheric lead concentrations been
measured in the D. S. Occupational atmospheric lead concentrations have, of
course, been monitored for many years because of health considerations, and
considerable data are available. For the purpose of this discussion, in-plant
air lead levels are considered to represent an occupational exposure problem,
not causally related to the release of lead to the general environment or to
environmental concentrations, and thus, beyond the scope of this study. This
matter has been intensively and exhaustively investigated by the Occupational
Safety and Health Administration (OSHA) of the Department of Labor, which has
promulgated (D. S. Department of Labor, 1978) new lower permissible occupation-
al lead air concentrations in the work place of 50 ~g/m3 (See Section 9.4.1.16).
Illustrative of the relationship of ambient atmospheric lead concentra-
tions to urban population centers and industrial development is the tabulation
presented by Harley (1970) of lead concentrations in surface air collected in
1967 by the D. S. Atomic Energy Commission along their 80th Meridan Network
(Table 8.1)
Systematic measurements of lead in the atmosphere of a city began in 1941
in Cincinnati, Ohio, but the work was interrupted by World War II and not re-
sumed until the 1950's, at which time a number of D. S. cities were includedj
The 1941 data from Cincinnati gave an average lead concentration of 5.1 ~g/m .
Cholak (1964) reported that investigations in Cincinnati from 1941 to 1962
showed a continual and gradual downward trend in both mean and median concen-
trations of lead in air. The mean concentration of 5.1 ~g/m3 in 1941 decreased
to 1.43 ~g/m3 in 1962 while the m~~ian level fell to ~.27 ~g/m3. After 1954,
no lead concentration above 8 ~g/m was found. The h~gher average values and
ranges found from 1941 to 1951 may have been partly due to the manner of sampl-
ing during this period, and, therefore, were somewhat biased. However, it was
concluded by the investigators that the downward trend was real, even though
the volume of traffic and consumption of leaded gasoline increased greatly
during this period. During the same period, consumption of coal for heating
purposes decreased, as did total dustfall (D. S. Department of Health, Educa-
tion and Welfare, 1965a).
An extensive study to determine the variation in the annual, seasonal,
monthly, and diurnal average distributions of lead and total particulate matter
in the atmosphere of Cincinnati, Los Angeles, and Philadelphia (3-Cities Study)
was carried out by continuous sampling from June 1961 through May 1962 (D. S.
Department of Health, Education, and Welfare, 1965a,b). A summary of the
297
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TABLE 8.1
LEAD CONCENTRATIONS IN SURFACE AIR FROM SELECTED
S~TES ALONG THE 80TH HERIDIAN, 1967a
Site Sampled Latitude Leadj
1Jg/m
Thule, Greenland 70° N <0.01
Moonsonee, Canada 56° N 0.06
New York, New York 41° N 2.5
Sterling, Virginia 39° N .74
Miami, Florida 26° N 1.7
Bimini, Bahama Islands 26° N 0.10
San Juan, Puerto Rico 18° N 0.80
Balboa, Panama go N 0.23
Guay aq ui1, Ecuador 2° S 0.35
Lima, Peru 12° S 0.50
Chacahaya, Peru 16° S 0.09
Antofagasta, Chile 24° S 0.06
Santiago, Chile 33° S 0.87
Punta Arenas, Chile 53° S 0.06
a:
Source:
Harley (1970). Reprinted, with permission from
Environmental Science and Technology. (C) American
Chemical Society. 1970
298
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results (Table 8.2) shows that the general urban concentrations ranged from
about 1 to 3 ~g/m3 depending on the area sampled. The average concentration of
lead for all samples collected during the year was 1.4 ~g/m3 in Cincinnati, 2.5
in Los Angeles, and 1.6 in Philadelphia. The highest average concentration for
all ~amples collected during a single month at any single sampling site was 3.1
~g/m in Cincinnati, 6.4 in Los Angeles and 4.4 in Philadelphia. The highest
individual concentrations were 6.4 ~g/m3 in Cincinnati, 11.4 in Los Angeles,
and 7.6 in Philadelphia. A uniform sampling procedure was used in each of the
cities, and the samples were analyzed by the same technique.
The results of a subsequent study conducted in 1968-1969 in these same
three cities, plus New York, Chicago, Houston, and Washington, D.C. (7-Cities
Study) have been described by Tepper and Levin (1975). (See Section 7.5.1).
These data indicated higher lead levels at most of the study sites during the
more recent of the two periods, consistent with the large increase in tetra-
ethyl lead consumption compared to 1961-62.
The overall situation in the United States with respect to atmospheric
lead was well summarized by the report on airborne lead by the National Academy
of Sciences National Research Council Committee on Biological Effects (1972),
and their findings are still valid. As pointed out in that report, the concen-
tration of lead in ambient air is closely correlated with the density of vehic-
ular traffic, being highest in large cities, lower in suburban areas, and low-
est in rural areas. These gradients are also subject to diurnal and seasonal
cycles, primarily as a result of meteorological differences.
Although the basic situation remains much the same as when the NAS-NRC
report was prepared, results of other investigations have appeared which further
elaborate the findings reported therein, and sampling and analysis have improved
considerably in the intervening years, so that an extension and update is appro-
priate.
It has only been in recent years that much attention was paid, on a nation-
al basis, to trace metal concentrations in the atmosphere. Prior to this,
analytical efforts tended to be localized and related to specific actual or
suspected problems. Beginning in 1953, an air quality sampling program was
begun under the auspices of the U. S. Health Service, albeit on a much more
linlited scale than today's efforts. This sampling effort was ultimately taken
over by the U. S. Environmental Protection Agency after its' formation, and is
now designated the National Air Surveillance Network (NASN), which routinely
monitors air pollutant concentration levels in urban and nonurban America.
Prj.ncipal concern has been with the tracking of changes in fossil fuel combus-
tion products (particulates and S02) and in the automobile-related "criteria"
pollutants, but data are now collected routinely on 11 metals, one of which is
lead. Air particulate samples have been collected since 1970 at approximately
300 urban and 35 nonurban sites (some of the latter have taken on the character-
istics of urban sites with time and expanding urban development). National
cumulative arithmetic and geometric means for the 1970-1975 period have been
reported by EPA (Akland, 1976; U. S. Environmental Protection Agency, 1978a),
299
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TABLE 8.2
CONCENTRATION OF LEAD IN THE AT~OSPHERE
OF THREE CITIES, 1961-1962
Atmospheric Lead Concentration, ~g/m3
Cincinnati
Los Angeles
Philadelphia
Annual average values
Downtown
Outlying area
All stations
Seasonal distributions
(all stations):
Summer
Fall
\,:inter
Spring
Diurnal distributions
(annual--al1 stations
stated as a fraction
of annual mean):
2300-0300
0300-0700
0700-1100
1100-1500
1500-1900
1900-2300
2
1
1.4
3
2
2.5
3
1
1.6
1.3
1.7
1.3
1.3
1.9
2.8
3.1
2.1
1.4
1.9
1.9
1.4
1.3
1.1
1.4
0.8
0.9
1.0
1.0
1.1
1.2
0.7
0.8
1.1
0.9
0.8
1.4
0.8
1.1
1.1
aAdapted from u.s. Department of Health, Education and Welfare (1965a).
300
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as shown in Table 8.3. The improving quality of urban ambient air with respect
to lead concentrations, since the peak year of 1971, is evident in these data.
For any given cumulative frequency, the lead level each year is lower, and
there has been a steady decline in the annual mean concentrations. In 1974 and
1975, the most recent years for which data are available, the annual geometric
means were 0.74-0.75 ~g/m3 (0.89 ~g/m3 arithmetic mean); and almost 90 percent
of the 1,300 urban quarterly averages were below the recently-promulgated 1.5
~g/m3 ambient air quality standard for lead (U. S. Environmental Protection
Agency, 1978b). .
The results from the 35 non-urban sampling sites indicate an arithmetic
mean for 1975 of 0.085 ~g/m3 (0.054 ~g/m3 geometric mean), about a factor of
ten lower than the comparable urban average. The nonurban means appear to have
varied somewhat randomly during the 1970-1975 period; there has not been a
steady improvement as shown in the urban average. These nonurban means may re-
present the minimum, ultimately attainable, for urban air lead concentration
averages.
In the discussion of requirements for state implementation plans to comply
with the 1.5 ~m3 ambient air quality standard (a standard not to be exceeded on
a quarterly basis), 31 urban areas were cited by EPA as having had quarterly
air lead concentrations equalling or exceeding 1.5 ~g/m3 in 1975 (U. S. Envi-
ronmental Protection Agency, 1978). These areas are listed in Table 8.4, along
with 1975 maximum quarterly and annual (where available) averages published in
the 1975 air quality data for metals (Rhodes and Fair, 1978). There appear to
be some discrepancies; a number of urban areas, e.g. Birmingham, Alabama,
Philadelphia, Pennsylvania, and Washington, D.C., are not recorded as having
exceeded 1.5 ~g/m3 in any quarter in 1975.
The "rollback" needed to bring many of these urban areas into compliance
is moderate, and is probably attainable with the planned lead phasedown.
Reduction in lead c.onsumption from 1975 reached 17 percent by 1978 (Table 4.16),
should r~ach 26 percent by 1979, and 60 percent by 1980 (Table 4.18), by which
time, almost all of the listed areas should be in compliance.
8.2.2
Localized Source-Oriented Studies
A considerable number of localized source-oriented studies of ambient air
lead concentrations have been conducted since the 1950's. Many of these have
been aimed at various facets of antiknock emissions and their influence on
close-in "microclimates". Others have attempted to develop lead concentration
profiles in the vicinity of point sources such as smelters.
8.2.2.1
Antiknock-Related Studies--
Illustrative of the "microclimate" type of study was the one by Daines,
et al., (1970), who investigated the lead content of the air as a function of
traffic volume, proximity to the highway, wind direction, and acceleration ver-
sus constant speed. One of their principal findings was that air lead levels
near busy (New Jersey) highways are relatively high, 2 to 7 ~g/m3, at 10 meters
distance, but drop off rapidly within a short distance (50 meters), beyond
which the rate of decrease is gradual. As shown by figure 8.1. at 180 meters
(500 feet), ambient air concentration had decreased to the 1-2 ~g/m3 range.
301
-------
TABLE 8.3
NATIONAL AVERAGE AMBIENT ATHOSPHERIC LEAD
CONCENTRATIONS: QUARTERLY COMPOSITES. (~g/m3)a
Minimum Arithmetic Geometric
Number Reported Cumulative Frequency Distributions, Percent Std. Std.
Year Stations Value 10 30 50 70 90 95 99 Max. Mean Dev. Mean Dev.
Urban
1970 797 LD b .47 .75 1.05 1. 37 2.01 2.59 4.14 5.83 1.19 .80 .99 1. 84
1971 717 LD .42 .71 1.01 1.42 2.21 2.86 4.38 6.31 1. 23 .87 1.00 1.89
1972 708 LD .46 .72 .97 1.25 1.93 2.57 3.69 6.88 1.13 .78 .93 1.87
1973 559 LD .35 .58 .77 1.05 1.62 2.08 3.03 5.83 .92 .64 .76 1.87
LV 1974 594 .08 .36 .57 .75 1.00 1.61 1. 97 3.16 4.09 .89 .57 .75 1.80
a
N 1975 695 LD .37 .58 .78 .96 1.54 2.02 3.15 4.94 .89 .59 .74 1. 82
Non Urban
1970 124 LD LD LD LD LD .267 .383 .628 1.471 .088 .190 .040 3.72
1971 85 LD LD LD LD LD .127 .204 .783 1.134 .047 .155 .008 4.80
1972 137 LD LD LD .107 .166 .294 .392 .950 1.048 .139 .169 .090 2.59
1973 100 LD LD LD LD .132 .233 ..192 .698 .939 .110 .149 .068 2.77
1974 79 LD LD .053 .087 .141 .221 .317 .496 .534 .111 .111 .083 2.30
1975 98 LD LD LD LD .144 .255 .311 .431 .649 .085 .126 .054 2.95
a Source: Rhodes and Fair, (1978).
bLimit of Detection
-------
LIST OF 31 URBAN AREAS WITH QUARTERLY AIR LEAD
CONCENTRATIONS EQUALLING OR EXCEEDING
1.5 ~g/m3 in 1975a
TABLE 8.4
Urban Area
1975 Data b
Average Max Q
Rollback
Needed,
Percent
Birmingham, Ala
Phoenix, Ariz
Fresno, Cal
L.A.-Long Beach, Cal
Sacramento
San Bernadino
San Diego
San Francisco-Oakland
Denver, Colo
NY, NY-N.E. N.J.
Waterbury, Conn.
Springfield, Chicago
Wilmington, De1-NJ
Philadelphia, Pa - NJ
Wash, D.C. - MD, Va
Chicago - N.W. Indiana
Minneapolis - St Paul
St. Louis -Ill
Las Vegas, Nev
Reno, Nev
Oklahoma City (1974)
Scranton, Pa
San Juan, Pr
Columbia, SC
Greensvi1le, SC
Knoxville, Tenn
Memphis, Tenn
Dallas, Tex
El Paso, Tex
Houston, Tex
0.68
2.07
0.95
2.45c
0.90
1. 37
1. 36
1. 45d
0.93
1. 52
1.13
1.07
2.69
2.16
1. 81
1.18
1. 92
1.89
1.43
1.00
1. 08
0.77
1. 82
2.77
1.57
1. 91
0.89
3.16
1. 59
3.45 c
1. 61
1.71
2.64
2.3ld
1. 75
1. 09
1. 74
1.50
1. 57
1.15
1.08
4.61
3.24
1. 73
2.91
2.15
3.75
2.28
1. 93
1. 85
1. 52
1. 20
1. 99
3.03
2.34
2.25
53
6
57
7
9
43
35
15
18
5
68
54
13
49
30
61
35
23
19
1
25
51
36
33
a
b
Source: 43 FR 46269, October 5, 1978.
Data from Rhodes and Fair (1978).
c
Sampling station Torrance, Cal.
Sampling station San Jose, Cal.
d
303
-------
At 3 meters (10 feet) from a highway carrying 58,000 cars/day, average annual
lead concentration was 10 ~g/m3. This was reduced about 50 percent at a dis-
tance of 10 meters (30 feet).
Another conclusion of this study was that over 65 percent of the lead in
the air from 10 to 530 meters (30 to 1750 feet), from a well-traveled highway,
consisted of particles under 2 ~m in diameter and over 85 percent consisted of
particles under 4 ~m. These fall, unfortunately, in the 0.1 to 10 ~m particle
size range shown by Natusch and Wallace (1974) to have maximum pulmonary depo-
sition.
'10
8
47,000 - ---0-
2
--{)-
o
0 100 200 300 400 500
Distance. feet
rt) 6
E
'-
0\
:t.
.0
a.. 4
Figure 8.1 Air lead values as a function of
traffic volume and distance from
the highway.
Source:
Daines, et ale (1970). Reprinted
with permission from Environmental
Science and Technology. (c)
American Chemical Society. 1970.
304
-------
In a later similar study, Daines, et al., (1972) compared the lead content
of air inside and outside homes located close (3.7 meters) to a busy New Jersey
street with similar homes at greater distances, 38 and 122 meters (125 and 400
feet). Continuous air samples were taken on front porches and in front rooms
inside the homes for 2 years; blood samples were also taken on two occasions.
Results of this study, summarized in Table 8.5 show that air samples taken in-
side homes were consistently less (an average of about 45 percent) than those
taken out of doors. There were no significant differences between the indoor
air samples at the three distances except during the open window (summer) sea-
son. The outdoor samples at homes 3.7 meters distant from the highway were
consistently greater than at those at 38 to 122 meters. Use of a room air con-
ditioner significantly reduced average indoor lead concentration at the close-
in homes, to a level comparable to the indoor concentrations in the more
distant homes. (Biological implications of this study are discussed in Section
7.5.2.1).
Several recent
sess the effects of
these are discussed
similar "microclimate" studies have been conducted to as-
lead emissions from gasoline antiknock on crops and soils;
in the sections on soils (8.4) and crops (6.3.2).
.Concern about levels of alkyllead compounds in the air have prompted
several localized studies of situations where gasoline is transferred, or burned
in confined spaces, as well as of general urban ambient levels. Purdue, et al.,
(1973) described the organic lead concentration in an underground parking garage
and in the general ambient air of six major cities in the U. S. In the parking
garage, the total air lead level was 11.7 ~g/m3, of which 16.7 percent was
organic lead. In the six major cities, the organic lead concentration was about
10 percent of the total lead (about 0.2 ~g/m3). Differences found in the
concentration of organic lead relative to particulate lead may be related to
differences in proximity to the emitting sources such as gasoline stations and
gasoline storage centers. Also, tetraethyllead and tetramethyllead undergo
rapid photochemical decomposition in the atmosphere, which can affect alkyllead
concentrations. Colwill and Hickman (1973) and Harrison, et al., (1974) found
alkyllead concentrations of 0.2 to 1.5 ~g/m3 in the vicinity of gasoline pumps,
and the concentration of tetraalkyllead emitted from the exhaust pipe of cars
varied from 50 to 1000 ~g/m3 when the engine was idling (Laveskog, 1971).
8.2.2.2
Smelter-Related Studies--
Other localized "micro scale" investigations have been conducted in the
vicinity of known or suspected "hot spots", quite often smelters. East Helena,
Montana is the site of a lead smelter which has been operating since 1888.
During the summer and fall of 1969, a source-oriented study of the Helena
Valley, Montana area was undertaken using dustfall bucket and high-volume sampl-
ing techniques (U. S. Environmental Protection Agency, 1972). During this
period, the city of Helena was exposed to an average daily concentration of 0.1
~g/m3 with maximum concentrations up to 0.7 ~g/m3. The residents of the East
Helena area were exposed to an average daily concentration of 0.4 to 4.0 ~g/m3,
depending upon proximity to the source, with maximum daily exposures up to 15
~g/m3. Within a 1.7 km (1 mile) radius of the smelter, the fallout of lead on
305
-------
TABLE 8.5
EFFECT OF PROXIMITY TO HIGHWAY IN AN URBAN
ENVIRONMENT ON AIR AND BLOOD LEAD
CONCENTRATIONS a
3
Pb Concentration, ~g/m
Time of Location of Area A Area B Area C
Year Sampler 3.7 m 38.1 m 122 m
Nov - April Front porch 4.56 2.63 2.37
Front room 1.85 1.55 1. 67
Nay - Oct Front porch 4.68 2.05 2.07
Front room 2.37 1.40 1.43
,
Entire year Front porch 4.60 2.41 2.24
Front room 2.30 1.50 1.57
Pb Concentration,
pg/100 g bloodb
April sample 22.3 16.9 17.9
November sample 23.9 17.9 17.4
Average 23.1 17.4 17.6
a
Source:
Adapted from Daines, et al. (1972).
Reprinted with permission from
Environmental Science and Technology
(c) American Chemical Society, 1970.
b
Blood from women living in homes.
the ground ranged from 30 to 140 mg/m2; an area of from O.O~ to 0.18 m2 would
contain the body burden limit for lead.
In a more recent study, an intensive investigation was conducted around
another old smelter, the one at El Paso, Texas which has been in operation
since 1887. This copper-lead-zinc smelting complex has been the subject of
studies of lead in blood, dust, soil, and air, with the conclusion that the
smelter was producing elevated levels of lead in all of these media for a dis-
tance of 0.6 kilometers and to lesser degrees in various media for up to 6.6
kilometers (Landrigan, et al., 1975). Epidemiological aspects of this study
306
-------
are discussed in Section 7.5.2.2.1.
The El Paso City-County Health Department estimated in 1971 that the
emissions from 1969 through 1971 had comprised 1010 metric tons of lead, 508 of
zinc, 11 of cadium, and 1 of arsenic. The pollution problem was accentuated by
the topography and meteorology of the area, which is surrounded by high moun-
tains and is extremely arid (10 to 25 cm of rainfall per year), so that fine
dust is frequently present. Thermal inversions occur on 70 percent of the
mornings. Air samples were collected upwind and downwind of the smelter at the
property boundary, 60 to 120 meters from the base of the main stack, and at 39
other locations in El Paso. The annual mean lead concentration at the property
boundary downwind of the smelter in 1971 was 92 ~g/m3, with the range from 15
to 269 ~g/m3. Levels fell rapidly with distance, and reached background values
at 4 to 5 km (Figure 8.2). From June, 1972 through July, 1973, jhe mean lead
concentration was again highest downwind of the smelter (43 ~g/m ), a consider-
able reduction over the 1971 values, but still excessively high (Landrigan, et
al., 1975).
Dustfall was also high, especially near the smelter (204 mg/m2/mo), de-
creasing with distance. As a result, children in the first 1.6 km with blood
lAvels of 40 ~g/dl or over were found to be exposed to dust with concentrations
of 6450 ppm lead; children with lower blood levels were exposed to dusts of
2070 ppm lead. High concentrations (around 1 percent by weight) of lead in the
soil around the smelter were attributed partly to the fact that the smelter had
been operating for 85 years.
Other aspects of possible exposure were also checked during this investi-
gation, including food, water, house paint, pottery soil, and dust. The data
appear to be conclusive in suggesting that particulate lead in dust and air ac- .
counted for most of the lead absorption in El Paso children, and that the
smelter was the principal source of the lead. In 1977, a multimillion-dollar
program of control measure was undertaken, including improved control of fugi-
tive emissions and collection of surface soil in the neighborhood of the plant.
The "New Lead Belt" in southeastern Missouri has also been investigated to
determine the effect of the lead mining and smelting operations on air quality
and distribution of pollutants. Since the commissioning of the first mine in
1969, this industrial district has become one of the world's largest lead-
producing areas, mining more than 392,277 metric tons of lead, or 75 percent
of the entire U. S. lead production during 1970 (U. S. Bureau of Mines, 1976).
Annual averages for suspended lead collected in Glover, Missouri, by high-
volume samplers were 3.4, 5.3, and 5.5 ~g/m3 in 1970, 1971, and 1972 respec-
tively (U. S. Environmental Protection Agency, 1977b).
Other similar studies have been conducted in Omaha,
Southern Solano County, California; the results of these
recent EPA document on air quality criteria for lead (U.
Protection Agency, 1977b).
Nebraska, and in
are summarized in a
S. Environmental
307
-------
.!:
100.0 -0
-t
50.0 \
t
\
\'
\\
\
10.0 -h
\',
5.0 \'
o ,
\b
\\.
"
\ '..........-
I 0 \ ---- Lead
1.0 0 ----0--
'" 0 ---
, ---..........
" 0 --
, --........
'-- Zinc 0
---- -.-- --- ----- ---- ---- ---
---
o Lead values
o
c:::(
to
E
"
C\
::to
o
0.5 t
\
\
, Cadmium
-
-----"'-A .
rsenlc
-
0.1
0.01
o
2
4
~....J
8 10 12 14 16 18 20 22
Kilometers From Smelter
Figure 8.2 Concentrations of metals in air as a function
of distance from the El Paso smelte~.
Source:
Landrigan, et al.. (1975). Reprinted,
by permission, from the New England
Journal of Medicine (1975).
308
-------
8.2.3
Trends in Atmospheric Lead
From their introduction till consumption reached a peak in 1970 (Table
4.16), quantities of alkyllead antiknock additives increased annually. Now
that this dominant source of lead in the atmosphere has finally begun to de-
crease, it seems inevitable that ambient lead air concentrations will also
similarly decrease.
The mass of detailed data in the NASN files for 1965 through 1974 was cor-
related and analyzed by Faoro and McMullen (1977). For this analysis, criteria
for selection of sample stations were length and continuity of record, in order
to maintain the comparison on a consistent basis. This reduced the data base
to 92 NASN urban sampling sites, a small number on which to base either region-
al or national averages; also, because of the selection of the sample popula-
tion for this analysis, the averages are not totally comparable with the nation-
al averages and means for all stations (Table 8.3). Nevertheless, they provide
useful measures of relative rather than absolute concentrations across time,
and illustrate national trends in air lead concentrations.
The composite 50th percentile of lead concentrations at urban sites in-
creased steadily after 1965, peaking at a little over 1.1 ~g/m3 in 1971 and
then declined, reaching 0.85 in 1974, about the level it had started from in
1965. This was a statistically significant decrease of .about 24 percent, with
most of it occurring between 1972 and 1973. This general trend was described
as being consistent at most sites studied. It was found that ambient air lead
concentrations were about 30 percent higher in the Far West (where California
sampling sites predominate) and in the Northeast, than in the other three geo-
graphic regions of the country. This is not surprising, and appears to corre-
late with the respective vehicle densities.
In another paper, McMullen and Faoro (1976) described the results of an
analysis of data covering 11 metals obtained on airborne particulate matter
samples from the NASN for the period 1965-1974. The analysis considered both
the concentrations per unit volume of air and the relative abundance compared
to crustal abundance. The frequency distribution curve (Figure 8.3) shows
that whil~ the average of urban mean air lead concentrations was approximately
0.75 ~g/m , about 30 percent of the analysis exceeded an average of 2 ~g/m3,
with some of t~ese as high as 6 ~g/m3. The mean of the nonurban sites was
0.04-0.05 ~g/m , with lead at the limit of detection for 30 percent of the
stations; and the maximum was less than 0.5 ~g/m3.
McMullen and Faoro also made the interesting comparison of abundance of
lead in particulate samples versus the average and range of lead contents in
soils, as reported by Shacklette, et al., (1971) in their very extensive
survey of U. S. soils. Urban particulate samples had a mean lead content of
appro~imately 10,000 ppm (1 percent) compared to the average soil lead content
of about 16 ppm (Figure 8.4).
Whereas the nonurban particulate samples had abundances of other metals
309
-------
c:c
w
.....
w
~
(.J
era
::::;
(.J
c:c
w
CI..
en
:E
<:t
c:c
e,:,
o
c:c
(.J
~
10
0.1
0.01
0.001
NON. -
URBAN
30 20 10 10 20 30
PERCENT OF STATIONS
Figure 8.3
Concentration of
particulate lead.
in air.
Source: McMullen and
Faoro (1977)
2 103
o
:J
-'
~
c:c
uJ
CI..
en
.....
c:c
<:t
CI..
102
310
105
104
NON.
URBAN
SOil,
AVERAGE.
10
~
DETECTION LIMIT
-1
j
I
30 20 10 10 20 30
PERCErJT OF STATIONS
Figure 8.4
Relative abundance
of lead in airborne
particulates and in
soil samples.
Source: McMullen and
,Faoro (1977\ A
-------
quite comparable to their abundances in soils, lead was an exception; the lead
content of nonurban samples was in some instances, up to the 1 percent level.
This was attributed to the fact that the data were significantly influenced by
the results from the station located at the Grand Canyon Visitors Center.
While this is a nonurban site, it is one with a high density of automobile
traffic and one which illustrates the influence of antiknock emissions on
ambient air lead concentrations.
.. The 0.5 g/gal maximum lead content for the entire gasoline pool, mandated
by EPA to be achieved by October 1, 1979 will reduce annual lead consumption
for alkyllead antiknock additives to an estimated 63,000 to 67,000 metric ton
range in the 1980-1985 period (See Table 4.18).
The estimated effect of this decrease on average ambient air lead concen-
trations is graphed in Figure 8.5. Historical air lead values are geometric
means from Table 9.3; historical lead consumption is from Table 4.16 and pro-
jected future lead consumption based on the present phasedown schedule is from
Table 4.18.
On the basis of the data for the six-year period between 1970 and 1975
(and adopting the conservative assumption that all of the lead measured in the
air resulted from the combustion of leaded gasolines) each 1000 metric ton
charge in antiknock lead consumption produces a change of 0.0043 ~g/m3 in mean
air lead concentration. This relationship may be used to project national
average ambient air lead concentrations beyond 1975. For 1976-1978, lead usage
is taken from Table 4.16. Future lead usage (Table 4.18) is estimated from the
gasoline consumptions projected by the ESCON model (E.I. du Pont de Nemours and
Co., Inc., 1978), summarized in Table 4.17.
For the base case, lead levels in the gasoline pool are assumed to contin-
ue at the 1978 average of 1.20 g/gal until October 1, 1979, and at the EPA-man-
dated level of 0.59 g/gal thereafter. Projected annual average ambient air
lead concentrations are estimated to have decreased to 0.58 ~g/m3 in 1978, to
further decrease to 0.52 ~g/m3 in 1979, and to 0.29-0.30 ~g/m3 in 1980 and
thereafter.
If, on the other hand, lead contents of leaded gasolines continue to
follow present industry practice, and contain no more than about 2.00 g/gal
lead in regular and 2.50 g/gal in premium (See Table 4.15), the pool average
will fall considerably below 0.59 g/gal as cars using leaded gasoline are
replaced by cars requiring unleaded gasoline. By 1990, the pool average could
be as low as 0.30 g/gal and total lead consumption no more than 29,500 metric
tons/yr. (Table 4.18). Under these conditions, an average urban air lead
concentration of 0.13 ~g/m3 is projected.
While national annual average ambient air lead concentrations can be
correlated with total annual lead antiknock consumption, there are no similar
direct relationships which can be employed to estimate or predict air lead
concentrations for smaller areas. Site-specific air quality calculations can
be performed for very small areas, provided that a suitable validated mathemat-
311
-------
I/)
c:
o
-
.~
~ 140 -
E
....
o
I/)
-0
g 120
I/)
~
o
.r;
-
:; 100
,=
o
III
o
C>
,= 80
-
c:
GJ
-
c:
o
t)
-0 60
o
GJ
-.J
220
200
Antiknock :ead
180
160
1.2
If)
E
......
0'1
::t.
~ 1.0
-0
0
GJ
-.J
,
,
,
,
,
,
,
,
,
,
\ Projected
Air lead ~
,
,
,
'--- --...
---
40
c:
o
-e 0.8
:::>
GJ
-
'j;;
o
a.
E 0.6
o
t)
c:
o
GJ
::E
,
,
,
,
,
,
,
----------
..
"
,
,
..
,
. '.
20
u 0.4
'\:
-
(I)
E
o
GJ
C> 0.2
10
0.1
o
. 1955
I
1960
1975
1965
1970
Year
Figure 8,5.
Average urban ambient air lead concentrations vs.
lead antiknock consumption, with phasedown,
Source:
Battelle-Columbus estimates.
312
1990
-------
ical model is available.
Numerous variables besides quantity of emitted lead can significantly
influence air lead concentrations. It is, for example, well-known that air
lead concentrations are inversely ,proportional to distances from high,"ays, and
that concentrations at 100 meters may be one-half to one-third or less those at
10 meters, e.g. see Figure 8.1, so that location of the measurement point is
very important. Topography, and its effects on local air movement can similar-
ly be quite important. Seasonal differe~ces, e.g., as in California, can have
major effects upon the air lead concentrations resulting from unit lead
_emission. Illustrative is a comparison of the 1975 quarterly air lead averages
in Northern California with quarterly gasoline consumption. Although 1975 gas-
oline consumption data are not available, the 1976 data reported in Highway
Statistics, 1976 (U. S. Department of Transportation, 1977) may be considered
representative:
1976 Gasoline Consumption,
Billions of Gallons
1975 Average3Air
Lead, ~g/m a
Ql
Q2
Q3
Q4
2.763
2.967
2.995
2.960
1.15
0.56
0.71
1. 62
a
Average of Sacramento, San Francisco, Oakland, Berkeley,
San Jose, and Fresno
The spring and summer quarters had slightly larger gasoline consumptions than
the fall and winter quarters, but air lead concentrations were less than one-
half as great.
Thus, it is apparent that a straight rollback may not be appropriate for
all areas, and seasonal modifications may be appropriate for some areas where
climatic or topographic considerations dictate.
As emissions from leaded gasolines decrease, so also will secondary im-
pacts derived from lead alkyl antiknock additives, such as lead in dustfall on
food crops, in nonpoint source runoff from the urban areas, and from the com-
bustion of used lubricating oil. There will be temporary aberrations,
certainly, most likely in those urban centers of highest density but, overall,
the prognosis appears extremely favorable.
The recently promulgated national ambient air quality standard for lead of
1.5 ~g/m3 (U. S. Environmental Protection Agency, 1978b), will provide the
313
-------
mechanism for controlling the few remaining localized point sources, e.g.,
existing battery plants and primary and secondary lead smelters, which have not
been regulated by New Source Performance Standards.
Overall, the effectiveness of the steps already taken suggest that, in
general, few additional limitations on atmospheric lead emissions are necessary
at this time.
8.3
LEAD IN WATER
The lead profiles in the major oceans of the world were determined by Chow
(1968), who used mass spectrometer techniques to analyze samples from various
depths as well as locations. The results indicated that there are no essen--
tial differences in lead concentration in deep waters below the 1000 meter
level, but in the surface layers, lead is present in greater amounts in the
Pacific and Mediterranean waters than in the central Atlantic, away from land
influences. Chow also cited data by other investigators (Table 8.6) which show
the wide range of values found in different places, from 0.02 micrograms per
kilogram (ppb) in ocean depths to 8 micrograms per kilogram in surface waters
0[£ Europe.
TABLE 8.6
LEAD CONTENT OF VARIOUS MARINE WATERSa
Source of Seawater
Concentration,
ppb
3-5b
2
3-8
5-8
4
5
Florida Key
North Sea--Surface
Brittany-Surface
Gullmarfjord-Surface
Japan Coast-Surface
English Channel-Surface
Washington Coast-to 100 m
English Channel
Atlantic-to 5,300 m
Pacific-to 4,000 m
Bermuda-to 3,000 m
0.1
0.6 -1.5
0.02-0.10
0.02-0.35
0.03-0.07
aSource: Chow. Reprinted with permission from
Journal of Water Pollution Control Federation.
(c) Water Pollution Control Federation, 1968.
bLimit of sensitivity of method.
314
-------
According to Patterson and associates, many of the previous analyses of
low concentrations of lead in ocean water have been seriously in error through
contamination. Schaule and Patterson (1978) have determined the lead profile
in the mid-Pacific, which, while in general agreement with the decreasing con-
centration with depth described by Chow, found lead concentrations to be
considerably lower. The lead profile essentially parallels those of unsupport-
ed lead-2l0 and tritium, as shown in Figure 8.6. The concentrations do not
change significantly to depths of 250 to 400 m, then decrease sharply within
small depth intervals to very small values, after which concentration changes
become more gradual. Below a couple thousand meters dissolved lead concentra-
tions seldom exceed 0.002 ~g/kg, only a tenth of the value reported by Chow.
Mass balance considerations indicate much of the lead introduced to the oceans
enters from the atmosphere, primarily from the combustion of leaded gasolines.
0°
2
(ng Pb/kgJ
8 10 12
4
6
c
iOOO
a)
2000
. Diss. Pb
c Part. Pb
~
c.
Q.)
a
3000
a
c
4000
5000
(IU.)
0 3 6 9 12
I I I I
(Pb210/Ra226)
2 3 4
l I ._..~....,.l :;;.::~;'::';")<:~.. ...= 1
""",'''''''.,'.. ",);",.., . ....,
..................-...,.;. . ....
"" !r
>"'1
J:
"'"
.<
):~
;:1
~I
'," I
"
.~,' I
I
..... Tritium
; '''.'' Pb210/Ra226
b)
Figure 8.6.
Depth profiles of common lead concentration and
general structure of tritium and lead -210
distribution in the central northeast Pacific.
Source:
Schaule and Patterson (1978).
315
-------
Since both tritium, as debris from nuclear bomb tests, and unsupported lead2l0,
derived from continental radon-222 emanations, enter by basically the same
route, the similarity in profiles is not surprising (Schaule and Patterson,
1978).
8.3.1
Water Lead Concentrations in the U. S.
The concentrations of lead in U. S. waters are generally low, almost uni-
formly below the 50 ~g/l (ppb) limit specified by the Interim Drinking Water
Standard (U. S. Environmental Protection Agency, 1975g). The generally low
values found for dissolved lead reflect the relative insolubility of the forms
(hydroxide, carbonate and hydroxy carbonate) likely to result from ambient
conditions. As noted in Section 3.1, equilibrium calculations indicate that
the total solubility of lead in hard water is about 30 ppb, and 500 ppb in soft
water (Davies and Everhart, 1973).
A number of surveys of heavy metals in raw and finished waters of the U. S.
have been conducted. One of the broadest geographically was the one investigat-
ing levels of heavy metals in lakes and rivers of the U. S. conducted by the
U. S. Geological Survey during autumn dry-weather flows in 1970 (Durum, et al.,
1971). More than 720 samples were obtained, in three categories:
Surface water sources for cities exceeding 100,000 population
(or largest city in state)
Water courses downstream of major municipal and/or industrial
complexes in each state
USGA hydrologic bench-mark stations (located near headwaters
of undeveloped drainage basins).
Samples were filtered before analysis (0.45 micron openings) to provide infor-
mation on sediment-free water like that normally supplied to the user; thus,
essentially only dissolved lead was measured. The results of this large recon-
naissance, as summarized by Durum (1974), were that detectable concentrations
of lead (> 1 ~g/£) were found in 63 percent of the river water samples. Only
three values exceeded 50 ppb; however, there was a distinct regional pattern
in the data as shown in Table 8.7. A larger proportion of the waters from the
northeastern and southeastern states contained lead above the detection limit,
and the largest share of the higher concentrations, i.e., > 10 ppb. Median
lead concentration for 727 samples was 2 ppb.
In some mineralized areas in the western state where water is scarce,
higher lead concentrations have been obser~ed, as indicated by Figure 8.7, from
the 1976 Annual Report of the Council on Environmental Quality (1976).
The U. S. Geological Survey maintains a computerized data bank for six
toxic substances, including lead, in water. Concentrations are determined for
the metals after filtration through a 0.45 micron filter (dissolved phase) and
in water containing suspended sediment (total phase). Dissolved values for
316
-------
TABLE 8.7
REGIONAL SUMMARY OF LEAD IN
SURFACE WATERS OF THE U. S.a
Concentration Range, ppb < 1 ppb,
Region Maximum Minimum Median percent
Ne~v England and Northeast 890 <1 6 8
Southeastern 44 <1 4 27
Central 84 <1 1 51
Southwestern 34 <1 1 61
No'rthwestern 23 <1 1 62
aSource:
Durum and Hem. 1972. Reprinted, with permission, from Annals of
New York Academy of Science. (c) New York Academy of Science (1972).
317
-------
[=:J 100 ppb
or less
~ over
100 ppb
~
o
"'-
<>
()
C=>
Figure 8.7. Total levels of lead in U. S. streams: 1975
Source: Council on Environmental Quality (1976).
lead are compared to the 50 ppb primary drinking water standard; "total values
are compared to the 30 ppb recommended for freshwater aquatic life and wildlife.
The data for lead concentrations in surface waters in the computer storage up
to mid-January, 1976, are presented in Table 8.8. It is apparent from these
data that while the northeastern and southeastern states might have more values
above 10 ppb, as noted by Durum, those with more than a nominal number in ex-
cess of 50 ppb were states with significant lead mineralization, e.g.,
Colorado, Missouri, and Washington. The reason for Florida's inclusion in this
list is unknown. Approximately 86 percent of the samples had detectable lead
concentrations (> 1 ppb), and 3.3 percent exceeded 50 ppb.
Analysis of 3,266 samples of ground water showed 65 percent (2,145) with
a detectable concentration of lead, and 2.9 percent (94) which exceeded 50 ppb.
Colorado was again in the group with a significant number of high values;
Pennsylvania and New Jersey also were in this group.
The potential sources for elevated lead concentrations in surface waters
are many.and varied. Rain water can be a direct source of lead to surface
waters and sediments. As shown by Lazrus, et a1., (1970), rain water can aver-
age 34 ppb, and reach values as high as 300 ppb. Rain water can also be an in-
direct source by washing lead-containing dustfa11 from roofs and streets into
surface water courses; some as dissolved lead or, more likely, as particulate
matter. Since most of the lead discharged from vehicle exhausts appears to
fallout in the near vicinity of its discharge, urban surfaces are the initial
receptors of much of the lead from gasoline. Thus, it is not surprising that
318
-------
TABLE 8.8. NUHBER OF SA:-IPI.ES OF SURFACE \.jATERS EXCEEDING SPECIFIED
CONCENTRATIONS OF LEADa,b
Dfssolved I Total
.
State N N>O N>SO Max. N N>O N>30 Max.
ppb ppb ppb ppb
Ala. 97 93 2 100 33 33 18 100
Alaska 113 95 4 130 72 67 53 6,500
Ariz. 21 19 1 100 12 12 12 300
Ark. 41 41 0 50 148 146 104 750
Calir. 156 115 8 270 125 110 85 3,200
Colo. 517 431 10 1,900 212 212 206 1,900
Conn. 64 55 2 70 2 2 1 75
Del. 10 10 0 8 0 - - -
Fla. 450 397 17 700 3.26 315 77 800
Ga. 170 106 1 50 10 10 5 230
Hawaii 9 9 1 100 67 65 16 200
Idaho 87 78 .3 181 49 49 46 2,500
Ill. 26 26 1 340 13 11 4 100
Ind. 45 42 0 38 19 18 3 200
Iowa 33 23 4 150 '5 5 4 100
Kans. 24 18 0 14 9 9 9 100
Ky. 103 97 3 80 74 69 32 1,700
La. 273 233 0 40 72 72 30 3,500
Maine 14 14 4 440 9 9 7 100
Md. 21 21 0 40 13 12 2 100
Mass. 30 29 2 124 9 9 3 1,000
Mich. 125 118 ' 120 39 38 6 90
Minn. 41 33 1 50 30 29 27 900
Miss. 22 15 0 46 68 68 10 110
Mo. 74 70 10 1,000 19 19 18 550
Mon to 102 84 0 35 86 84 . il 1,000
Nebr. 80 63 1 88 16 16 16 700
Nev. 13 12 0 13 10 10 10 200
N. H. 6 6 0 35 19 19 0 21
N. J. 67 66 3 240 40 40 8 100
N. Mex. 51 42 5 <2,142 63 63 63 1,600
N. Y. 203 193 2 160 248 242 60 7,800
N. C. 75 59 4 100 47 {,7 40 500
N. Dak. 80 72 1 100 65 :>5 58 500
Ohio 49 43 9 340 185 171 10 240
Okla. 55 50 1 200 61 61 61 1,200
Oreg. 25 25 1 60 13 13 13 100
Pa. 245 213 4 <21,000 207 203 179 <41,000
R. 1. 11 11 0 34 4 4 4 500
S. C. 34 33 2 73 11 11 5 110
S. Dak. 45 40 0 40 17 17 11 600
Tenn. 21 19 1 50 47 45 14 300
Tex. 170 155 9 150 29 29 29 500
Utah 122 110 2 85 19 19 19 300
Vt. 4 4 1 50 1 1 0 4
Va. 17 12 0 20 4 4 1 40
Wash. 154 148 21 1,100 30 30 23 1,100
W. Va. 57 53 2 370 56 56 5 91
Wis. 38 35 0 30 14 11 2 37
Wyo. 66 45 0 15 60 59 56 600
United States 4,356 3,781 J.45 1,900 I 2,787 2,709 1,546 7,800
i
BSource: Pickering (1976).
bStreams, lakes reservoirs
cExp1anation:
N
N>O
N>10\.lg/1I.
= ~umber or stations
= Number or stations
= Number of stations
specified.
= Maximum value round.
ror which data are aV3ilabl~.
that have an analysis result greater than zero.
that ha\Te an analysis result greater than amount
Max
319
-------
Sartor and Boyd (1972) found lead to be a prevalent fraction of street dirt in
12 U. S. cities. They found that the lead accumulated over a seven-day period
averaged 0.32 kg per linear kilometer (0.57 pound per curb mile). They furth-
er estimated that a storm occurring in a hypothetical city of 100,000 persons
five days after the preceding storm could transport 125 kg of lead to surface
streams. Erosion of soil is an analogous but much smaller source of lead.
Urban soils would contribute proportionally more lead per unit mass than soils
from rural areas.
Municipal wastewater may comprise another significant input of lead to
surface waters. Depending on the industrial nature of the city, lead content
of the wastewater can be several hundred ppb. The effectiveness of removal
varies, but typically will fall in the 30-60 percent range (Brown, et al.,
1973; Patterson, et al., 1975).
Areas in which lead has been mined might be expected to have greater than
average amounts in the waters. The Springfield region of Missouri, which has
been such a mining region, was surveyed by Proctor, et al., (1973) for lead
content of surface waters and wells. In some localized areas, the lead content
of the water exceeded the 50 ppb primary drinking water standard. However,
must water samples had a lead content below this limit. In the Helena, Montana
environmental pollution study (U. S. Environmental Protection Agency, 1972),
concentrations of 1 to 40 ppb were found, which are no greater than those found
in other parts of the country.
The impact of the lead mining and milling operations in Southeastern
Missouri has been monitored since before the onset of development in the mid-
1960's. In general, the lead (and other heavy metal) content of the streams
receiving effluents have remained at or near background levels. The apparently
minimum effect of these operations is attributed to the predominantly limestone
geology of the area. The effect of the limestone is to produce, by carbonate
precipitation, low concentrations of metals in original mine water, in mill
water in tailings ponds, and even to remove any metals which reach surface
waters. The local streams apparently undergo a natural purification process
(with respect to lead and other metals) as they flow over limestone outcrops.
8.3.2
Lead Concentrations in Drinking Water
Most public water supplies are filtered before distribution, so that only
dissolved lead is expected at the domestic tap. However, in earlier years,
lead piping has been used in potable water systems, and under some conditions,
high dissolved lead concentrations can be reached.
In 1969, the U. S. Public Health Service initiated an extensive community
water supply survey (CWSS) which was national in scope, and included 969 public
water supply systems. The samples included both surface and ground water, and
large and small systems (McCabe, et al., 1970). Samples were collected at the
consumer's tap rather than at the water treatment plant. Only 1.4 percent of
the samples exceeded 50 ppb lead; and the highest value recorded was 640 ppb.
320
-------
The U. S. Environmental Protection Agency (1976) has reported a more detailed
breakdown of the distribution of lead concentrations (Table 8.9). As shown,
the median concentration was about 10 ppb and only 19 of the 2,595 samples
(0.7 percent) exceeded twice the primary drinking water standard.
Prior to the formation of the U. S. Environmental Protection Agency, the
Public Health Service had the responsibility of certifying the water supply
systems used by interstate carriers and serving the traveling public. EPA now
has assumed the responsibility for monitoring the quality of drinking water
utilized by interstate carriers. The most recent compilation of these results
(U. S. Environmental Protection Agency, 1975f) shows that only two out of 592
analyses (0.3 percent) exceeded the 50 ppb interim primary drinking water
standard.
As noted above, the contribution of lead pipes to the level of lead in
drinking water can be significant. This problem is prevalent in New England
because of two basic factors. First, the nature of the water supplies in New
England is such that they are usually acidic and very low in naturally occurr-
ing substances such as calcium and magnesium which cause hardness, (this lead
problem, accordingly, does not arise in the limestone areas of the Midwest).
The second factor is the formerly widespread use of lead pipe for conveying
water to homes, generally between the water main and the home; the length in-
volved may be from 10 to 100 feet. The results of a 1974 EPA investigation of ,
the lead levels in drinking water supplied by the Metropolitan District
Commission (MDS) to the greater Boston area have been reported by Karalekas, et
al., (1975). The lead concentration was less than the detection limit (13 ppb)
at the treatment facility and before entering the distribution system. Based
on the results of analysis of 936 samples from 383 households, it was clear
that on prolonged contact with sections of lead pipe, lead content of the water
reached undesirable levels. As shown by Figure 8.8, almost 50 percent of the
first drawn samples in the morning exceeded the 50 ppb standard and the mean
morning sample contained over 100 ppb (Figure 8.9).
To overcome this lead corrosion problem, plans were drawn up to adjust the
pH of the water to reduce the aggressiveness of the water towards lead pipe; it
was estimated that 2,000 metric tons (2,200 short tons) of sodium hydroxide
would be required annually to accomplish this (Anonymous, 1975). Implementation
of this pH adjustment accompanied by fluoridation of the water supply, began in
May, 1977. The goal was to raise the pH from its former 6.5-7.2 range to 8.5.
As reported by Ryan (1978), although there were the usual initial shakedown
difficulties during the first several months (for example, pH varied from 7.5
to 9.2), corrosion mitigation is gradually being achieved. Evidence for this
was the decrease, after several months, in the averages of the three standard
grab samples (running, standing, and early morning) of the test homes from the
prior range of 100 to 58 ppb, to a range of 46 to 29 ppb, below the primary
water standard; and lead concentrations were still continuing to decrease.
Additional studies of five New England water systems conducted by Region
I of the U. S. Environmental Protection Agency (Karelekas, et al., 1977) indi-
321
-------
TABLE 8.9 LEAD CONTENT OF TAP WATER FROM TWO SURVEYS OF
DISTRIBUTED WATERa
Community Water
Supply Studyb
c
Chicago Study
Concentration,
~g/l
Frequency
Percent
> than
stated concn.
Frequency
Percent
> than
stated con en.
0-1
2-3
4-5
6-7
8-9
10-14
15-19
20-24
25-29
30-34
35-39
40-44
45-49
SOd-54
55-59
60-64
65-69
70-74
75-79
80-84
85-89
90-94
100-199
200-299
300-399
400-499
500-
663
2
15
45
130
909
335
236
121
33
40
16
9
4
2
2
1
4
5
1
1
o
2
12
2
3
2
100.0
74.5
74.4
73.8
72.1
67.1
32.0
19.1
10.0
5.4
4.1
2.5
11. 9
1.6
1.4
1.3
1.3
1.2
1.1
0.9
0.8
0.8
0.8
0.7
0.3
0.2
0.1
205
18
13
13
24
97
17
49
55
7
24
3
19
2
1
o
1
o
1
o
o
o
1
100.0
62.7
59.5
57.1
54.7
50.4
32.7
29.6
20.7
10.7
9.5
5.1
4.5
1.1
0.7
0.5
0.5
0.4
0.4
0.2
0.2
0.2
0.2
2595
550
aSource: U.S. Environmental Protection Agency, (1976)
bData from McCabe, et a1., (1970)
CData from Mc Cabe and Vaughn (1969)
dprimary drinking water standard.
322
-------
46.8 ~
'" ~
26.7 ~ ~
12.7 ~ ~ ~
5.5 - Z; ~
RUNNING STANDING COMPOSITE EARLY
MORNING
Figure 8.8
Percentage of Boston tapwater
samples exceeding lead standard
Source:
Karelekas, et al., (1975).
0.104
0.093
~
~ ~
LEAD STANDARD ~ ~
O.05mg/2 ~~ ~
~~ ~
~ ~-~-
~ ~ ~
.~. -~ ~ ~ ~
~ ~ ~ ~
MEAN
CONe.
mg/!
. LEAD 0.053
RUNNING
STANDING
COMPCSIT E
EARLY
MORNING
Figure 8. 9
Mean lead concentration of Boston tap water
samples by type of sample.
Source:
Karelekas, et al.,
(1975).
cated that the adjustment of pH alone to the range of 7.0 to 8.0 did not reduce
the lead concentrations below the standard, and that at pH's below 7, the use
of phosphate corrosion inhibitors (e.g. zinc orthophosphate, sodium zinc phos-
phate, and sodium hex am eta phosphate) did not eliminate above-standard concen-
trations. The 3 systems with above-standard lead concentrations characteris-
tically had very soft water, with har.dness values in the 10 to 20 ppm range,
along with a pH below 7.5. In contrast, the 2 systems which did not exhibit
above-standard lead concentrations had hardnesses of 40 ppm or higher, and a
pH above 7.1 (in one case, a pH of 10.1). Both of these systems adjusted pH
with lime, which also adds calcium hardness.
323
-------
1-
While these data are somewhat limited, the indications are
control of lead concentrations to below primary water standards
with relatively simple adjustments of water pH and composition.
clear that
can be achieved
Lead pipe is no longer used for potable water systems in this country, and
its use is contrary to most current building codes. Most new domestic water
piping systems employ copper pipe, which is generally joined (sweated) with
either a 50:50 or 40:60 lead: tin solder (see Section 4.3.5.2). Surprisingly,
there has been almost no research on lead pickup from such systems; only one
study has been identified (Wong and Berrang, 1976), and it is so briefly de-
scribed that intrepretation and evaluation is difficult. This study concerned
some simulated systems exposed to tap water from the Victoria, B. C., Canada
supply. Characteristics of the water were not disclosed, but it is known to be
similar to that of Boston, low in pH and dissolved minerals, and quite aggres-
sive. This study indicated that the 50 ppb limit could be exceeded in a system
with 20 soldered joints after one hour's standing, depending on the amount of
water which had been passed through the system. Tests on a real system in a
one-year-old house yielded a dissolution rate of 0.4 ~g/Pb/joint/hr. with lead
service pipe dissolution rates were 30-480 ~g/hr. Evaluation of the importance
of solder joints on lead exposure will have to await the conduct of some more
d~finitive and better documented investigations.
8.3.3
Trends in Water Lead Concentrations
There are no indications that lead concentrations of U. S. surface waters
are increasing; and ground water has always been low overall. Two principal
reasons for this can be hypothesized; the low solubility of lead in most natu-
ral waters; and the input of lead to the environment is diminishing as lead
antiknock usage declines, and as compliance with Federal air and water emission
regulations increases. The promulgation of new pretreatment guidelines will
reduce lead inputs to municipal wastewater treatment plants, which will have
beneficial effects on downstream lead concentrations.
Recognition of lead problems at the consumers tap in a few geographical
areas is well advanced. Methods of minimizing lead corrosion are available,
and it is anticipated that these problems will be overcome in the near future.
As these mitigating procedures are implemented, a gradual decrease in the
mean lead content of U. S. water should become evident.
8.4
LEAD IN SOILS
In terms of occurrence in the earth's crust, lead is a rare metal, amount-
ing to only a fraction of such other metals as copper, zinc, and iron. Earlier
work on measurement of lead in soils and rocks has been summarized by de
Treville (1964) who reported data which were compiled mainly at the Kettering
Laboratory. These data indicate that an average value for the earth's crust is
16 ppm, with alkaline rocks containing about 8 ppm and acidic rocks about 20
ppm.
324
-------
8.4.1
Soil Lead Concentrations in the U. S.
The U. S. Geological Survey has recently conducted an extensive survey of
the elemental composition of surficial materials in the conterminous United
States (Shacklette, et al., 1971). These results, summarized and updated with
new analyses by Tidball (1976), indicated that the moister soils of the eastern
half of the country had a mean lead concentration of 14 ppm, as compared with
18 ppm for the drier soils of the west. About 94 percent of the 964 samples
had lead concentrations of 30 ppm or below, and about 58 percent had concentra-
tions equal to or less than .the mean of 16 ppm.
Comparison of the lead content of urban soils in a region which included
industrial, agricultural, and residential areas showed that there was about 2.7
times as much lead in industrial soil as in residential soil (Klein, 1972).
The agricultural soils contained slightly less lead than those in residential
areas.
8.4.2
Localized Source - Oriented Studies
Numerous studies have been conducted to determine the effect of various
types of lead sources on the close-in deposition on soils. Not surprisingly,
automobile and highway-oriented studies lead the list, followed by smelter-
oriented investigations; a relatively limited number of studies have been con-
ducted to determine the effects of dispersion of lead from painted houses, and
of the cumulative accumulation in orchards from the application of lead arse-
nate insecticides.
Several studies illustrative of the highway-related investigations are
noted below and briefly summarized; details can be found in the original
reference. Lagerwerff and Specht (1970) present data typical of the depth pro-
files for lead found by various investigators. Table 8.10 summarizes the
results, and shows about a 65 to 75 percent reduction in lead content with
distance in the top 5 centimeters of soil for samples taken at points 8 to 32
meters from a highway. In every case, the amount of lead decreased with depth
of sample.
The accumulation of lead in soils over a period of about 40 years was com-
pared for areas of high and low motor vehicle traffic densities in the Los
Angeles area (Page and Ganje, 1970). The sampling sites were more than 1.6
kilometers from any major highway. No lead accumulations as a function of2time
were o~served where motor vehicle traffic was less than 80 vehicles/2.~ krn
(80/mi). In areas where the traffic density exceeded 580 vehicleslmi , the
surface concentration of lead (2.5-cm depth) increased by a factor of 2 to 3
during the 40 year period, which amounted to an accumulation of 15 to 36 ppm of
lead. The highest value recorded for any location was 52 ppm.
A very high lead concentration was found near a heavily-travelled express-
way in Chicago. The soil contained as much as 7,600 ppm at distances up to
13.7 meters from the expressway, and 900 ppm up to 45.7 meters (Khan, et al.,
325
-------
Tab Ie 8.10
LEAD CONTENT IN ROADSIDE SOIL AND GRASS AS A
FUNCTION OF DISTANCE FROM TRAFFIC AND SOIL
DEPTHa
Site
I 8 68.2 522 460 416
Hest of U.S. 1. near Plant 16 47.5 378 260 104
Industry Station. 32 26.3 164 108 69
Beltsville. Maryland
UJ
N II 8 51. 3 5/.0 300 98
(J'\
West of southbound lanes. 16 30.0 202 105 60
Washington-Baltimore Parkway. 32 18.5 140 60 38
Bladensburg. Maryland
III 8 21. 3 242 112 95
West of Interstate 29. 16 12.5 140 104 66
Platte City. Missouri 32 7.5 61 55 60
TV 8 31.3 150 29 11
North of Seymour Road. 16 26.0 101 14 8.2
Cincinnati. Oh:io 32 7.6 55 10 6.1
aSource: Lagerwerff and Specht. Reprinted with permission from Environmental Science and
Techno10~y. (c) American Chemical Society. (1970).
Distance
from
Road. m
Grass
Lead Content. ~g/g dry weight
Soil Profile Soil Profile Soil Prof He
Layer. Layer. Layer.
0-5 em 5-10 cm 10-15 cm
-------
1973). The amount of lead varied with the seasons in a fashion similar to the
seasonal variations in average monthly traffic volumes on the expressway. Lead
levels were lowest during fall and winter, increased during the spring, and
reached their highest values during the summer.
Hamphill, et al., (1974) studied roadside lead contamination in soils
along highways used for transport of lead concentrate in the Missouri lead belt.
Lead values approaching 3,800 ~g/g (ppm) of dry weight were found at zero
distance from the road. Along control routes, high lead values of 384 ~g/g of
dry weight were observed. The total lead in soils decreased rapidly at 100 to
300 meters. The investigators suggested that the elevated levels of lead in
the soil near the control routes 2re probably due to contamination from motor
fuel and possibly other sources.
The presence of a lead smelter can cause very high lead levels in nearby
soils. In the Helena, Montana study cited previously, the upper 2.5 centime-
ters of uncultivated soil were found to contain 4000, 600, and 100 ppm of lead
at distances from the smelter of 1.6, 3.2, and 6.4 kilometers (1, 2, and 4
miles), respectively (U. S. Environmental Protection Agency, 1972).
Roberts, et al., (1974) found that a high rate of lead fallout around two
secondary lead smelters originated mainly from large-particulate emissions from
low level fugitive sources rather than from stack fumes. The lead content of
dustfall and, consequently, of soil, vegetation, and outdoor dust, decreased
exponentially with distance from the two smelters. Lead emissions from the two
smelters were estimated to be 15 to 30 metric tons per year. Regression analy-
sis of the concentrations indicated an exponential decrease with distance, from
values of 40,000 and 16,000 ~g/g of soil close to smelter A and smelter B, re-
spectively; to an urban background of 100 to 500 micrograms per gram of soil,
which accounted for 60 to 80 percent of the variability in data. Although the
monthly geometric means of the atmospheric lead concentrations close to the
smelters (1 to 5.3 ~g/m3 of air) were only double those for urban sites (0.8 to
2.4 ~g/m3) the range of the daily concentrations was much greater, producing a
marked log normal distribution.
As a part of the environmental pollution investigation at a smelter in El
Paso, Texas (see Section 8.2.2.2) soil samples were also collected at 99 sites
in El Paso and at three remote sites. Samples were taken at the surface and at
depths of 2.5, 5.0 and 7.5 cm (1, 2 and 3 inches). Only trace amounts of lead
were found «50 ppm) at the remote sites. Within the city, highest levels in
1972 were found within 200 m of the smelter (mean of 3457 ppm and range of 560
to 11,450 ppm for 54 samples); lead content was consistently highest at the
surface. Concentrations fell rapidly over the first 2 to 3 krn from the smelter,
but remained above background for as far as 10 krn (Landrigan, et al., 1975).
The use of lead paints on the exterior of houses has been found to result
in locally high concentrations of lead in soils. Soil samples taken near old
houses in Cincinnati built prior to 1900 had lead concentrations which ranged
from 32.5 to 7,620 ppm. In general, there was a correlation between soil lead,
327
-------
and the lead content of the exterior paint on the houses (Bertinuson and C1arkt
1973). This work also demonstrated that much more lead could be accumulated in
the soil around a house with lead paint than at the roadside where heavy auto-
mobile traffic passed (10t200 vehicles per day). The house contribution to
soil lead was about 30 times greater than that from the road. This source of
lead can be accentuated if the old paint is chipped and scraped from the wood
and then allowed to disperse in the vicinity. One such measurement showed that
lead in the soil 15 to 30 meters from the house was 165 to 185 ppm when the old
paint was removed. A year latert the lead content had increased to 440 to 490
ppm (Bogden and Louris, 1975).
It has long been recognized that the eating of lead paint is a main cause
of lead poisoning and elevated blood leads of children living in dilapidated
housing. In this connection, Ter Haar and Aronow (1974) determined the source
of lead in dirt to which children are normally exposed. Dirt samples were
taken in old urban areas around 18 painted frame houses and 18 houses of brick
construction (Table 8.11). The data suggested that (1) weathered lead-based
paint is a major contributor to soil lead, and (2) vehicular sources probably
make a significant contribution to soil lead near the sidewalks.
High local concentrations of lead might be expected to occur in soils
where plants and trees have been sprayed with lead arsenate. In past yearst
. this compound was used as an insecticide but has been presently supplanted by
organic compounds. Howevert the soil of an orchard which had been sprayed with
lead arsenate for many years was found to contain about 50 to 65 ppm of lead.
This is not an unusually high value; however, it is significantly greater than
the 15 to 20 ppm which is typical of uncontaminated areas (Vandecaveyet et al.,
1936).
8.4.3
Lead in Urban Dusts
Street dust and house dust can also be a source of lead, especially for
young children prone to hand-to-mouth activity. In a survey of 77 midwestern
cities, it was found that the average lead concentration in the street dust of
residential areas was 1658 ppm, and that in commercial and industrial areas
the average concentrations were 2,334 and 1,386 ppm, respectively (Hunt, et a1.,
1971).
Day, et al., (1975) analyzed several hundred samples of urban dust and
dirt likely to be encountered by children as a normal part of their environment
in Manchester, England, with results in general agreement with those of Hunt,
et al. The average lead concentration in the urban samples was 970 ppm (median
concentration was 860 ppm). The highest value encountered was 10,200 ppm, and
the lowest 90 ppm. The higher values were unusual; only 10 percent of the
samples exceeded 1,500 ppm, and only 5 percent exceed 2,000 ppm.
Solomon and Natusch (1977) conducted an area-wide survey of settled dusts
and soils in a moderate-sized urban community (Urbana-Champaign, Illinois).
Approximately 1400 samples, both indoor and outdoor, were taken in residential
and nonresidential areas. The homes selected were in.good repair, painted with
328
-------
TABLE 8. 11
LEAD IN DIRT IN DETROITa
Lead Concentration, ppm
Painted Frame Houses Brick Houses
Location Mean Range Mean Range
Within 0.6 m of house
front 2349 (126-17590) 351 (78-1030)
back 1586 (162-4951) 501 (72-2350)
sides 2257 (140-7284) 426 (91-1160)
3 m from house
front 447 (58-1530) 156 (39-316)
back 425 (149-1410) 200 (72-480)
Near sidewalk 627 (152-1958) 324 (86-1130)
curb 572 (320-1957) 612 (147-2420)
Gutter 966 (415-1827) 1213 (304-3170)
a
Adopted from Ter Haar and Aronow (1974).
unleaded or low-lead paints, located in relatively
and were described as upper-middle-class abodes in
The average l~ad content of 239 floor dust samples
ppm (680 ~g/m floor surface).
low traffic density areas,
extremely good condition.
taken in 12 homes was 600
Lead was also determined in 228 outdoor soil and dust samples around the
same houses. Lead levels in dusts were high both near roads and near the
houses. The range in dust lead content was from 240 to 6640 ppm away from the
houses and from 130 to 11,760 ppm near them. Soil lead was lower and less
variable, 20 to 1060 ppm.
In 27 house dust samples collected in the adjacent and far suburbs of the
Boston and Cambridge, Massachusetts area (Kreuger, 1972, cited in Solomon and
Natusch), lead concentrations of 1,200 ppm were found. Lead concentrations in
house-dust samples collected in the core city averaged 2,000 ppm; core-city
gutter samples ranged from 400 to 9,000 ppm. Lead levels measured in these
studies are much lower than those usually found in truly dilapidated homes --
50,000 to 400,000 ppm (National Academy of Sciences, 1972).
Illustrative of the latter type of situation is the investigation of
Lepow, et al., (1975) in a deprived area of Hartford, Connecticut, to ascertain
the cause of the chronically elevated blood levels (> 40 ~g/dl) in ten 2-6 year
old children. The mean age was 52 months, and the blood levels were 40-70
329
-------
~g/dl. Several of the children had reached peak
~g/dl, and half had received at least one course
one had a previous history of pica, and 9 of the
some degree of excessive mouthing behavior.
blood lead levels of 70-120
of chelation therapy. All but
10 study children exhibited
The average lead concentration in outdoor play area dirt was 1,200 ppm
(range 700-1,750 ppm), and the average in house dust was 11,000 ppm (range
4,900-17,000 ppm). Dirt sampled from the hands of the study children averaged
2,400 ppm lead.
These averages from Hartford should not be regarded as typical, even for
urban environments. They do illustrate the dimensions of the problem in com-
batting the lead intoxication problem found in economically deprived children
living in old and deteriorated housing.
8.4.4
Trends in Soil Lead Concentrations
The mobility and persistence of anthropogenic lead in soil is influenced
by its chemical form. The nature of the lead compounds in soil that originate
in automobile exhausts and that are formed near roadways was determined by
Olson and Skogerboe (1975). Samples were collected from the top centimeter of
surface soil or from street dust in four different parts of the U. S. Lead
sulfate accounted for the major portion of the lead present in the samples. A
small amount of PbO.PbS04 and traces of lead oxides were found in some of the
specimens, while PbS was detected in a sample from the Missouri Lead Belt. In
view of the work by Ter Haar and Bayard (1971) which showed that only about 3
percent of the aerosol lead in "old" exhaust particulates was PbS04' it appears
that much of the conversion to lead sulfate occurs after the lead compounds are
deposited on the soil.
If the lead is of strictly inorganic origin, it apparently can be leached
from the soil at a fairly rapid rate. At the sites of permanently shutdown
smelters, it was found that badly contaminated surface soil (5-cm) (104 to 328
~g/g) lost lead at a rate that would reduce it to background values in 2 to 5
years (see Section 6.6.1).
In general, lead deposited on the soil is retained near the surface, and
its concentration drops off rapidly with depth of the soil (e.g. see Table
8.10). In most respects the soil can be considered as a near-total sink for
lead received by it. Thus, its lead content can be expected to increase with
time, although at an almost imperceptible rate except where emissions from
local point sources are large and concentrated.
If lead from the combustion of leaded gasolines is the major contributor
to the lead content of urban dusts, as seems likely from the available data,
the gasoline lead phasedown should result in proportional decreases in dust
lead contents. A concentration decrease of 2/3 or greater by 1980 from the
1970 peak would be compatible with the phasedown schedule.
330
-------
~,i 8.5
LEAD IN FOODS AND BEVERAGES
This section presents data on natural or "background" levels of lead in
foods, sources and mechanisms of lead uptake in foods and discusses the find-
ings of numerous investigations regarding the lead content in various types of
foods. Interpretation of the potential human health impact of these findings,
typical dietary dosages (human exposure patterns) and problem areas are dis-
cussed in Sections 8.6 and 8.7.
Lead is naturally present in foods because it is a normal constituent of
soils (averaging 16 ppm in the United States). The quantity of lead derived
from soils (unless contaminated) is generally low; of the order of a few tenth
of 1 ppm (Kehoe, 1961). Kehoe's early investigations (Kehoe, et al., 1933) re-
vealed lead in every food item both in the field and from dwellings of the in-
habitants of a primitive region unexposed to industrial or mining activities.
Patterson (1965) estimated that the natural lead content of food should be 0.01
~g/g wet weight or 0.01 ppm. Because the lead content of most foods today is
much higher than 0.01 ppm, this author concluded that most of the lead present
in today's foods arises from industrial sources of lead. National Academy of
Science (1972) cites the work of Schroeder, et al., (1961) who found approxi-
mate means and ranges as follows:
Lead Content, wet weight, ppm
Commodity
Mean Range
1. 2 ppm 0 - 1.5
0.5 ppm 0.2 - 2.5
0.2 ppm 0 - 0.37
0.4 ppm 0 - 1. 39
0.2 ppm 0 - 1.3
No detectable lead
Condiments
Fish and seafood
Meat and eggs
Grains
Vegetables
Fresh whole milk
The NAS document (National Academy of Sciences, 1972) cites evidence to suggest
that the average lead content in foods is about 0.2 ppm.
Soil, dustfall, and rainfall are potential sources of lead in plants which
are related, to some degree, to ambient air conditions. Other known sources of
lead in foods are: (1) usage (formerly) of lead arsenate pesticides, (2) sur-
face deposition of lead near roadways, (3) inadvertent addition of lead during
331
-------
food processing or canning, (4) leaching from improperly glazed utensils or
storage vessels and, possibly, leaching from some types of plastic containers.
8.5.1
Determinants of Lead Content
The lead content of food or forage plants is related to the amount of lead
applied topically to exposed areas of edible leaves, stems, and fruit by rain-
fall or dustfall, and to the amount that is translocated from soil and surface
and/or ground waters through the roots to stems, leaves, and fruit (Bethea and
Bethea, 1975; Ewing and Pearson, 1974; Kehoe et al., 1968; Haley, 1969; Leland
et al., 1975; see Section 6.6.2). Lead may accumulate differentially in dif-
ferent portions of plants, in varying quantities depending upon weather, proxi-
mity to highways, traffic patterns, etc. (Leland et al., 1975; Schuck, 1970;
Schuck and Locke, 1970). The lead content of portions that are eaten by humans
or livestock are most important from the health standpoint (Haley, 1969; Inter-
national Lead Zinc Research Organization, 1972; Kolbye, et al., 1974).
Lead appears to accumulate differentially in various portions of the plant.
In general, lead concentrations tend to be low in the fruit grain and tubers
(except for seeds) and higher in the roots and leaves (Motto, et al., 1970).
Tupical application of lead from airborne fallout is usually of minimal signif-
icance to humans because the edible portions tend to be protected by coverings
and because 1/2 - 2/3 of the lead deposited in this fashion washes off. Since
food for human consumption is normally washed before eating, the contribution
of topical lead is probably small. Note, however, that animals consuming these
commodities would not be similarly protected.
For meats, milk, eggs and other products from domestic livestock, the lead
content is related to that of the feed, forage and water consumed by the ani-
mals (Engel, et al., 1971; Ewing and Pearson, 1974; Guss, 1970; Lynch, et al.,
1974). Animals grazing near roadways or stationary sources of lead emissions
may be vulnerable to lead intake from heavily contaminated grasses and vegeta-
tion. Meats consumed by humans conceivably could be contaminated in this man-
ner, yet, the National Academy of Sciences (1972) reports that there is no evi-
dence that this is occurring. The lack of measurable changes in lead content
of meats and other animal food products over the past 30 years also supports
this contention.
In
that of
of lead
Leland,
the case of fish and shellfish, lead content in tissues is related to
the aquatic (fresh, brackish or marine) environment and to the uptake
by organisms such as plankton in the food chain (Dorn, et al., 1972;
et al., 1975; Loutit, et al., 1973).
In addition to the lead derived from air, aoil, and water, foods may con-
tain lead derived from glazed vessels and metal containers sealed with lead
solder (Clark, 1972; Harris and Elsea, 1967; Klein and Namer, 1970; Mitchell
and Aldous, 1974). Lead poisoning has occurred from the consumption of home-
made apple cider made in lead-lined earthenware vessels and illegal alcohol or
"moonshine" produced in old automobile radiators in the southwestern states
(Palmisano, et al., 1969; Walls, 1969).
332
-------
8.5.2
Lead Content of Individual Food Commodities
8.5.2.1
Food and Forage Plants--
A substantial body of published data exists on the lead content of food
and forage crops, including cereals, vegetables and fruits. Tables 8.12 and
8.13 summarize typical values for the lead content of cereals and vegetables,
and of fruits, respectively.
The available data on portions of crop plants whose lead content is de-
rived from both air and soil indicate that soil uptake is the more important
source. Lead from the air generally deposits on the leaves and outer portions
of edible plants such as husks, as well as on the soil. It appears that uptake
of lead through the stomata of leaves may be considerably less than that taken
up from soil through the roots. However, crops grown close to highways (with-
in 30.4 meters or 100 feet) having a heavy traffic volume may have high levels
of lead contamination on the leaves and outer portions. The question of
whether or not lead is translocated from the leaves or roots to other portions
of crops has not been resolved (see Section 6.6.2). The available data
indicate that the edible portions of crop plants including leaves, roots and
fruits generally have a lower lead content than inedible portions. Data
obtained by the Food and Drug Administration from analyses of "market basket"
samples of food purchased in retail establishments indicate that levels of lead
consumed in fresh fruits and vegetables are well below levels considered sig--
nificant from the human health standpoint (Kolbye, et al., 1974).
Leafy wastes from food crops that contain high levels of lead may be a
hazard to domestic livestock if used as a component of feed. For example, note
in Table 8.12 the considerably higher lead content of corn stalks, leaves, and
husks as compared to the kernels, and of unharvested cabbage leaves as compared
to the head. The type of lead poisoning in cattle and horses is more fully dis-
cussed in Section 6.5.2.
Possible hazards from lead contamination of homegrown vegetables has only
recently been considered. A warning, for example, was recently issued by the
Idaho Department of Health and Welfare to residents within a 6.4-km (4-mile)
radius of a lead smelter that homegrown vegetables may have high levels of lead
(Anon, 1975). It is likely, however, that vegetable contamination in smelter
areas is primarily a problem of deposition of lead, particularly on the exteLn-
al portions of the plants rather than high concentrations of lead in the plant
tissues themselves. Thus, thorough washing should remove most of the lead de-
posited on the surface. In any event, unless the garden provides a substantial
proportion of the total diet, the effects of lead contribution from contaminated
produce should be diluted in the total pool of food consumed so that this source
probably would contribute very little total lead in a well balanced diet.
333
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TABLE 8. 12 LEAD CONTENT OF CEREALS AND VEGETABLES
Lead Content,
Products .pp~. Sample State Reference
Wheat, heads 1. 0-2.0 Dry (1)
grain 0.16-0.113 Dry (2)
Oats, heads 0.3-2.0 Dry (1)
Corn, tassels 19-1742 Dry' (3)
leaves 30-329 Dry (3)
stalks 3.1-13 Dry (3)
kernels 0-2.6 Dry (3)
cobs 0.9-5.6 Dry (3)
Barley, heads 0.5-2.0 Dry (1)
Rye, heads 0.3-7.0 Dry (1)
grass 2.4-14.2 Dry (4)
Cabbage, heads 1. 0-1.1 Dry (2)
<0.01-0.51 Wet (5)
unharvested leaves 4.5-5.8 Dry (2)
Cauliflower, hearts 0.9 Dry (1)
leaves 2.0 Dry (1)
Broccoli, flowers 0.19-0.30 . Wet (6)
stalks 0.04 Wet (6)
Brusse1 sprouts <0.01-0.24 Wet (5)
Collards 0.25-0.50 Wet (6)
Ce1~ry <0.01-0.02 Wet (6)
0.01-0.02 Wet (5)
Spinarch 0.10-0.25 Wet (6)
Watercres.3 0.01-0.33 Wet (5)
Lettuce, leaves 8.7-159 Dry (3)
3.2-6.6 Dry (2)
1. 0-9,. 0 Dry (1)
roots 20-150 Dry (3)
Lettuce, Romaine, outer leaves 0.10-0.18 Dry (6)
inner leaves <0.01-0.01 Wet (6)
Artichokes, outer leaves 0.04 Wet (6)
inner leaves <0.01 Wet (6)
Potatoes, leaves 20-530 Dry (3)
stems 14-53 Dry (3)
roots 7.6-100 Dry (3)
tubers 1. 2-14 Dry (2)
0.30-0.33 Dry (2)
<0.01-0.14 Wet (5)
334
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TABLE 8.12
LEAD CONTENT OF CEREALS AND VEGETABLES a
(Continued)
Products
Ref!'rence
Lead Cont~nt,
ppm
Sample State
Potatoes, tubers, peel
tub!'rs, inner portion
Onions
Beets, roots
tops
Ca.rrots, tops
leaves
stems
roots
:i.nner portion
Leeks
RaG ish , leaves
roots
Peas, pods and peas
pods
p~as
Beans
Be~ns, leaves
Cucumbers
Tomatoes,
leaves
blades
petioles
stems
fruit
peels
pulp
Rhubarb, stems
leaves
Mushrooms
,
7.4-10.4
0.02
3.3-4.1
<0.01-0.38
1.6-6.0
1. 0-6. 0
2.0-10.0
25-218
4. 70- 7.0
83-152
16-23
0.05-0.06
3.3-24
1.7-2.1
(3)
(6)
(3)
(5)
(7)
(1)
(1)
(3)
(1)
(3)
(3)
(6)
(3)
(2)
(5)
(1)
(6)
(5)
(4)
(4)
(7)
(6)
(6)
(7)
(7)
(2)
(2)
(,)
(3)
(3)
(3)
(3)
(2)
(5)
(3)
(3)
0.)
(1)
(5)
Dry
Wet
Dry
'-let
Unspecified
Dry
Dry
Dry
Dry
Dry
Dry
Wet
Dt'y
Dry
Wet
Dry
Wet
Wet
Dry
Dry
Unspecified
\{et
Wet
Unspecified
Unspecifil!d
Dry
Dry
t.1~t
0"17
Dry
Dry
Dry
Dry
Wet
Dry
Dry
Dry
Dry
Wet
2.0
<0.01
0.04-0.07
2.3-16.4
0.8-2.0
0-0.2
<0.01-0.02
<0.01-0.02
0.03
0.15-0.26
1. 2-1. 4
7.9-20.0
0.01-0.03
37-276
31-87
8-16
3.9-166
0.59-0.72
0.01-0.14
3.6-16
3.1-6.8
2.0-4.0
8.0-11.0
0.03-0.04
8References:
(1)
(2)
(3)
(4)
(5)
(6)
(7)
Warun and De1avau1t (1962)
Ter Haar (1970)
Hotto, et ,,1., (1970)
Dedo1ph, et a1., (1970)
Thomas, et a!., (1972)
ILZRO (1972)
de Trevi11e (1964)
335
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TABLE 8.13" LEAD CONTENT OF FRUITS
Lead Content, a
Products ppm Sample State References
Apples, whole fruit 0.12-0.3 Unspecified (1)
<0.01-0.37 Wet (2)
skin <0.01-0.24 Wet (2)
flesh <0.01-0.05 Wet (2)
Pears, whole frui': 0.18 Unspecified (1)
0.02-0.04 Wet (2)
skin <0.01-0.23 Wet (2)
flesh <0.01-0.03 Wet (2)
Peaches 0.04-0.08 Unspecified (1)
Cherries 0.12 Unspecified (1)
Plums 0.06-0.16 Wet (3)
...
aReferences: (1) de Treville (1964). (2) Thomas, e t al., (1972). (3) Thomas
et al., (1973).
8.5.2.2
Processed Fruit and Vegetable Products--
Table 8.14 summarizes reports of analyses of lead contamination in canned,
frozen, and dehydrated fruit and vegetable products. The lead content of fro-
zen beans, peas and carrots was below the detectable limit of the analytical
method used. Interestingly, these products, together with frozen spinach and
frozen potatoes, had a lower lead content than that of the corresponding fresh
products given in Table 8.3. The canned fruit products listed in Table 8.14
had significantly higher lead contents (99.9 percent confidence level) than the
corresponding fresh products listed in Table 8.13.
Various studies have provided convincing evidence that the differences be-
tween fresh and canned products result from the release of lead from solder
used along the seam of the can or possibly from inadvertent addition of lead
during other phases of processing operations. These studies are discussed in
detail in Section 8.6.4.2.
336
-------
TABLE 8.14
LEAD CONTENT OF PROCESSED FRUITS
AND VEGETABLE PRODUCTSa
Products
Lead Content,
ppm
Sample State
a
References
Beans, frozen
Beans, baked
Carrots, frozen
Corn, canned
Peas, frozen
Peas, canned
Spinach, canned
Spinach, frozen
Potatoes, frozen
Tomatoes, canned
Apples, canned
Apricots, canned
Apricots, dried
Black currants, canned
Damsons, canned
Grapefruits, canned
Oranges, canned
Peaches, canned
Pineapples, canned
Plums, canned
Prunes, canned
Raisins
Rhubarb, canned
Strawberries, frozen
Fruits and vegetables,
dried
<0.01
0.19-0.67
<0.01
0.00-3.00
<0.01
0.00-1. 46
0.13-0.95
0.07
0.01
0.32-0.63
0.12-1.14
0.52-1.48
0.24
0.17-3.90
0.37-0.74
0.19-0.54
0.10-0.22
0.26-0.50
0.14-0.54
0.17-0.98
0.15-0.73
o
0.10-2.57
0.02
1. 0- 2 . 0
Wet
Wet
Wet
Wet
Wet
Wet
Wet
Wet
Wet
~.,ret
Wet
Wet
Unspecified
Wet
Wet
Wet
Wet
Wet
Wet
Wet
Wet
Unspecified
Wet
Wet
Unspecified
(1)
(2)
(1)
(3)
(1)
(3)
(2)
(1)
(1)
(2)
(2)
(2)
(4)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(2)
(4)
(2)
(1)
(4)
a
References:
(1) ILZRO (1972a)
(2) Thomas, et a1. (1973)
(3) National Food Processors
(4) de Trevi11e (1964)
Association (1977)
8.5.2.3
Meat, Fish and Poultry Products--
Table 8.15 presents a summary of the lead content of meat, fish and poul-
try products. The lead content of organ meats such as heart, kidney and liver
of swine and turkeys (not shown) is usually higher than that of muscle (Dalton
and Ma1anoski, 1969). However, the lead content of beef liver appears to be
337
-------
TARLE 8.15 LEAD CONTENT OF MEAT, FISH, AND POULTRY PRODUCTSa
Products
Referencesc
Beef, roast chuck
bone of leg
hamburger
liver
Lead Content,
ppm
o.nb
3.60
O.248b
0.089b
Pork, fresh, muscle
0.54-1. 33
Meat, canned, cureda
wieners (smoked or
unsmoked)
bologna
meat loaves
salami
pastrami and other
0.01-0.30
0.04-0.16
0.01-0.26
0.01-0.26
0.01-0.30
0.01-042
liverwurst
bacon
ham
picnic shoulders
corned beef products
1. 80- 7. 60
0.01-0.16
0.01-0.16
0.01-0.12
0.01-0.28
Fish, fresh
cod, fresh, Icelandic
clams, hard, Atlantic
crab, body meat, Pacific
lobster, Atlantic
shrimp, Alaskan
0.32
0.28
0.45
0.55
0.50
Fish, canned
tuna, initial
canned 6 months
after packing
ssrdines, Dutch
0.34
0.44
0.72
Poultry
chicken, fryer
turkey, fresh, muscle
0.127b
2.93-3.35
0.174b
Eggs, chicken
Meat, fish, and poultry
(composite)
0.015
(9)
(1)
(2)
(1)
(1)
(3)
(4)
(4)
(4)
(4)
(4)
(4)
(5)
( 4)
(4)
(4)
(4)
(6)
(6)
(6)
(6)
(6)
(7)
(7) .
(8)
(1)
(3)
(1)
~ata on canned,
b
Mean.
cReferences:
cured meats are expressed on a wet-weight basis.
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
U.S. Department H~w (1975)
Kehoe (1976)
Dalton and Malonaski (1969)
Kirkpatrick and Coffin (1973)
Hankin, et al., (1975)
Zook, et a1., (1976)
National Food Processors Assn. (1977)
Reith, et a1., (1974)
Kolbye, et a1., (1974)
338
-------
quite low compared to that of beef muscle.
The lead content for cured and smoked meat products given in Table 8.15
was reported by Kirkpatrick and Coffin (1973) on a fresh-weight basis. When
these are corrected to a dry-weight basis, the highest lead level of bacon, ham
and picnic shoulders will be lower than that for pork muscle reported by Dalton
and Malanoski (1969). According to Hankin, et al., (1975), seven market sam-
ples of fresh beef and pork liver that were analyzed by the atomic absorption
spectrometric method of Dalton and Malanoski (1969) contained 1.4 to 1.6 npm
Pb. Liverwurst sampled sporadically contained from 0 to 7.6 ppm Pb, apparently
depending upon the lead content of the ingredients used.
Fish reportedly contain lead in the range of 0.1-1.0 ppm. This is at
least 2-3 order of magnitude higher than the water from which they are harvest-
ed but is more nearly comparable to the concentrations in the flora and fauna
utilized as food by the fish (Ewing and Pearson, 1974). The National Marine
Fisheries survey of selected seafoods reported mean lead values among species
which tended to be rather uniform and only a few species averaged higher than
0.6 ppm. No species exceeded 1.0 ppm (Zook, et al., 1976). Unfortunately,
many data on lead in fish (i.e., wildlife surveys) report on a whole fish basis
i:L1cluding internal organs. "Edible portionsll analyses, relevant for humans,
are reported much less frequently. FDA's Market Basket studies composite fish
with meats and poultry and, therefore, no average values' f')r fish can be de-
rived from that data.
8.5.2.4
Milk and Infant Formulas--
There is considerable concern about the lead content of milk and proc-
essed milk pronucts since these foons comprise a substantial proportion of the
diet of infants and children. Various data, past and present, exist with re-
spect to lead levels in milk, processed milk products, infant formulas and
human milk. These data are assembled by product in chronological order in
Table 8.16.
Numerous articles in recent years have discussed the difficulty of accu-
rately quantifying lead in milk in the parts per billion range (Lamm and
Rosen, 1974; Brandt and Bentz, 1971; Kolbye, et al., 1974, and Dutilh and Das,
1971). Differences as large as tenfold between different investigators and/or
analytical techniques in analysis of the same product are not uncommon.
Cooperative studies involving several laboratories using standardized methods
of sample preparation and analytic techniques on identical samples have
revealed poor performance and extreme variability between laboratories. Accu-
racy becomes worse as the level of lead decreases, particularly as the lead
level decreases below 1 ppm, which is typical of milk products. In addition,
the ubiquity of lead magnifies the possibility for sample contamination. On
the other hand, trace metal loss during destruction of the sample matrix also
contributes to error. These problems notwithstanding, several generalizations
can be made from the data shown in Table 8.16.
339
-------
TABLE 8.16 LEAD CONTENT OF MILK A.~D INFANT FORMULAS
Year of Lead Content, ppm Analytic~l f
Milk Product Sampling Mean Range MethQd Reference
Canned evaporated milk AASd
skimmed 1971 1.04 0.30-2.30 (1)
1972-73 0.06 0.04-0.07 AAS (2)
regular 1968 0.81c AAS (3)
1971 0.36 0.30-0.40 (1)
1972-73 0.11 0.04-0.22 NAAS (2)
1972-74 0.14 0.03-0.91 undetermined (7)
1973 0.202 0.01-0.820 AAS (4)
1973-74 0.125 0.02-0.37 (5)
0.12 0.01-0.46 (11)
Infant Formula
Concentrate 1972-73 0.083 0.04-0.12 NAAS (2)
0.09 0.06-0.13 AAS (6)
Ready to serve (diluted)
Modified Milk I 1968 0.170 AAS (3)
Modified Milk II 1968 0.210 AAS (3)
Lamb Heat Base 1968 0.256 AAS (3)
Soya Base 1968 0.272b AAS (3)
1972-73 0.033 0.-0.08 NAAS (2)
1972-74 0.05 undertermined (7)
Homogenized Hilk (cow) 1971 0.04 AAS (1)
1972-73 0.005a NAAS (2)
1973 0.04 AAS (4)
1972-74 0.02 0.02-0.07 not stated (7)
0.005 dithizone (8)
0.042e 0.009-0.1540 AAS (9)
0.042 photon activation (10)
0.049 0.023-0.079
Human Breast ~li1k
1971 0.02 O. -0.065 AAS (1)
1972-73 0.005 NAAS (2)
O.OlSe 0.006-0.202 AAS (3)
0.012 AAS (3)
~etection limit 0.005 ppm.
Seamed cans and bottles averaged.
~Average of four brands.
AAS =f1ame atomic absorption spectrophotometry;
e
fMedian, rather than mean.
References:
(1) Lamm, et al., (1973)
(2) Lamm and Rosen (1974)
(3) Murthy and Rhea (1971)
(4) ~~tche11 and Aldous (1974)
(5) U.S. Dept. HEW (1975)
(6) Ko1bve. et a1... (1974)
NAAS = nonf1ame AAS.
~7). Ministry of Agriculture, Fisheries and Foqd
(8) Brandt and Bentz (1971)
(9) Pinkerton, et al., (1973)
(10) Duti1h and Das.(1971)
. .11) Schmidt (1974)
(1975)
340
-------
The lead content of human breast milk and fresh, homogenized cow's milk
(market milk) are quite low in comparison to those milk products which have
been canned, evaporated or mixed with additives (i.e., infant formulas). This
is as expected, for the lead concentration of the plasma is low and remarkably
constant over a wide range of whole blood lead levels (Lamm and Rosen, 1974).
Since lead is primarily associated with the erythrocytes rather than the plas-
ma, only a small amount of lead is excreted in milk. Therefore, a naturally
low level of lead in milk is expected. Nevertheless, the lead content of milk
can be influenced by the lead present in feed and grass and the licking of
metal objects or painted surfaces by cows.
Lynch, et al., (1974) also confirmed that very little lead is excreted via
the milk, even after administration of substantial amounts of lead. Eleven
milligrams of lead, as Pb (C03)2' per kilogram of body weight was administered
to Holstein cows. This lead level did not produce serious physiological
changes despite a large body burden. The lead content of whole milk (5.9 ppb),
was lower than the mean lead content (49 ppb) of market milk as determined in a
national survey by Murthy, et al., (1967). However, the lead content of milk
did not decrease to background levels until 34 days after dosing the cattle.
Pinkerton, et al., (1973) collected human milk from mothers in a breast-
feeding club in Cincinnati, Ohio, and bovine milk from individual cows on farms
producing milk for the Cincinnati area (Table 8.16). Chemical analyses re-
vealed that human breast milk contained about one-fourth the lead of bovine
milk. Median milk lead values were 0.010 and 0.042 ppm, respectively, for hu-
mans and cows. Based on this study, a bottle-fed infant could theoretically
take in about thirty times the lead of an exclusively breast-fed infant.
\Vhereas analyses of human milk and homogenized cow's milk have shown low
levels of lead, past studies have indicated serious contamination problems in
canned evaporated milk. Lead content of other processed milk products (e.g.,
infant formulas) is generally intermediate between the levels of "natural"
milks and those of canned evaporated milk (Table 8.16). Data in 1968 on four
brands of evaporated milk indicated concentrations of 0.8 ppm; four brands of
infant formulas averaged about 0.4 ppm lead (Murthy and Rhea, 1971). Detailed
information on the problem of lead contamination in canned milk products, along
with the results of several recent surveys of canned milk products, is given in
Section 8.4.5.
8.5.2.5
Beverages, Bakery Products, Sugar and Condiments--
Tables 8.17 to 8.19 present summaries of the lead content of beverages,
bakery products, sugar, condiments and miscellaneous foods. With the exception
of fruit juices, especially the infant type products, it does not appear that
any of these products contain sufficient quantities of lead to be of concern
from the standpoint of a totai dietary intake. Many fruit juices have a pH in
the range of 2.7 to 3.9. Mitchell and Aldous (1974) reported that the mean
lead level of canned, infant juice products was 202 micrograms per liter as
compared to 35 micrograms per liter in similar bottled products. They explain
the higher levels in cans on the basis of the acidity of these products com-
341
-------
bined with leaching of lead from the seams in cans possessing a high seam to
volume ratio.
TABLE 8.17
LEAD CONTENT OF BEVERAGES
Products
Lead Content,
ppm
0.015b
0.004
0.004
0.02
<0.008
0.20-0.74
a
References
Drinking water (U. S.)
Lemonade
Soda
Soft drinks (Holland)
Carbonated beverages
Tea
(1)
(2)
(2)
(3)
(4)
(3)(5)
ALCOHOLIC BEVERAGES
Beer (Cincinnati)
Beer (Holland)
Wine (Holland)
Brandy (India)
Rum (India)
Dry Gin (India)
Whiskey (India)
0.01-0.29
0.03
0.13
0.05-0.60
0.024-0.057
o
0.027
(2)
(3)
(3)
(2)
(2)
(2)
(2)
FRUIT JUICES
Lime juice
Lemon juice
Diluted fruit drinks, canned
Orange juice, canned frozen
concentrate
Tomato juice, canned
Orange juice, infant
Apple juice, infant
0.30
0.57
0.251
(4)
(4)
(6)
(6)
(6)
(6)
(6)
0.135
0.338
0.308-0.655
0.207-0.907
aReferences: (1)
(2)
(3)
(4)
(5)
(6)
bMedian value.
U. S. Environmental Protection Agency (1975)
de Treville (1964)
Reith, et al. (1974)
Meranger (1970)
Ministry of Agriculture, Fisheries, and Food
U. S. Dept. of Health, Education and Welfare
(1975)
(1975)
342
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TABLE 8.18 LEAD CONTENT OF BREAD
AND BAKED PRODUCTSa
Products
Lead Content
ppmb
Bread, whole wheat
Bread, white
Rolls, hamburger
Doughnuts, cake
Biscuit mix
Flour, all purpose
0.42
0.41
0.45
0.45
0.24
0.51
aSource: Zook et al., (1970).
bMean lead content, dry weight
basis.
TABLE 8.19
LEAD CONTENT OF SUGAR, SPICES, CONDIMENTS
AND MISCELLANEOUS FOODS
Products
Lead Content
ppm
a
References
Sugar
Corn Syrup
Pepper, black
red
Ginger
Turmeric
Mustard seed
Cloves
Cinnamon
Salt
Coffee
Cocoa beans
Baking powder
Refined soybean
Oils, fats, and
oil, canned
shortening
0.004-0.13
0.21-0.49
0.22
0.4
0.08
0.4
0.4
0.15
0.03
0.2-0.45
0.07
0.15
5.0-10.0
0.02-0.10
0.02
(1) (2) (3) (4)
(1)
(1) (2)
(1) (2)
(1)(2)
(1)(2)
(1) (2)
(1) (2)
(1) (2)
(1) (2)
(5)
(5)
(1)(2)
(6)
(3)
a
References:
(1)
(2)
(3)
(4)
(5)
(6)
de Treville (1964)
Haley (1969)
Ko1bye, et a1., (1974)
Ministry of Agriculture,
Reith, et a1., (1974)
Bergner and Rudt (1968)
343
Fisheries, and Food (1975)
-------
8.5.3
Adventitious Lead in Processed Foods
Significant amounts of lead may be introduced in food through processing
and packaging. Although the food industry uses stainless steel almost exclu-
sively in processing equipment, substantial amounts of lead are still
used in solder for sealing seams in food cans; it was estimated that approxi-
mately 4~000 metric tons of lead were used in 1976 (Rathjen~ 1978). In 1977~
the Assistant Director for Packaging Technology of the Food and Drug Adminis-
tration (FDA) stated that approximately 13 billion tin plated steel containers
used for food have a soldered side seam (Davis~ 1977). The solder composition
used is 98 percent lead and 2 percent tin (higher tin content solders are now
used for evaporated milk). Most of the solder is on the outside of the can and
only a small bead is on the interior of the can. Often the can is also lac-
quered. Nevertheless~ absorption of lead still occurs as evidenced by the
higher lead levels in canned foods than in similar foods packed in glass or
aluminum containers. The Acting Director of the Bureau of Foods~ FDA~ testi-
fied at the public hearing on the proposed national ambient air quality stand-
ard for lead that "about two-thirds of the lead in canned food is from the
solder" (Roberts~ 1978).
A study conducted by the National Canners' Association (now National Food
Processors Association) in 1972 was reported by Ewing and Pearson (1974). The
study showed that after 1 year of storage in a can, tomato juice averaged 0.36
ppm lead while tomato juices packed in glass averaged 0.26 ppm. Mitchell and
Aldous (1974) reported on a study comparing foods packed in metal cans with
soldered seams with similar bottled products (Figure 8.10). A comparison of
the identical product in different types of containers was possible only in a
few cases. Unfortunately, since identical products from the same factory and
batch could not usually be obtained~ a parallel comparison cannot be presented.
The data do, however, clearly indicate a higher mean lead concentration in the
canned products (0.167 ppm) than in the bottled products (0.042 ppm), sugges-
tive of the magnitude of the effect of packaging on the lead level of food
products.
FDA's Heavy Metals in Foods Survey reported the adult and baby categories
in canned foods (see Tables 8.26 and 8.27). Canned tomatoes had the highest
mean lead level of all adult foods (0.710 ppm). Such a fiuding might be anti-
cipated in view of the acidity of tomatos and the rated propensity of acid
foods for leaching lead from containers. What is surprising about the data in
Tables 8.26 and 8.27 are the high lead levels reported in a variety of other
non-acid canned products. Pork and beans, peas, vegetable soup and green beans
had lead concentrations of 0.64, 0.43, 0.33, and 0.32, respectively.
344
-------
Figure 8.10
Figure 8. 11
en 50
I-
U
~
o 25
o
Q::
a. 0
LL.
o
I- 75 97
Z BOTTLES
W
U
ffi 50
a.
75
122
CANS
MEAN 167 ~9/J
MEAN 42~9I.1
25
( 100 100-199 200-399 )400
LEAD CONCENTRATION CA9/.()
Distribution of lead in canned and bottled products.
Source:
1000
~
CI
::l. 750
-
c
o
-
E500
-
c
Q)
(.)
g 250
u
-c
c
Q)
....J
o
o
Mitchell and Aldous (1974).
,
6
Lead distribution in single cans of tomato paste.
Source:
Mitchell and Aldous, (1974).
Symbols represent five different cans.
345
-------
The ability of acid foods to accumulate lead from cans has been the sub-
ject of several investigations (Mitchell and Aldous, 1974; National Food
Processors Association, 1977). Lead solder was confirmed as a source by a
study in which tomato paste (viscous and unmixed) showed decreasing lead
concentration as the distance from the soldered seam increased (Mitchell and
Aldous, 1974). The results for 5 eight-oz. cans of tomato paste, sampled in
5 positions across a diameter passing through the seam, is shown in Figure 8.11
In all cases, position 1 (nearest the seam) showed a higher level than the
opposite side of the can. This effect was particularly evident after the open
cans had been stored at room te.mperature for 24 hours. Here, the lead distri-
bution is even more indicative of leaching from the seam and lead levels up to
5000 ~g/l (5.0 ppm) are indicated (Figure 8.12).
The authors hypothesized further, that if lead was entering the can via
the seam, there should be a relationship between the seam length/can volume
ratio and the lead level of the contents. The data from three groups of cans
selected from seam length/volume ratios of 1.25,0.75-1.25 and <0.75 confirm
this suspicion (Figure 8.13). Products in cans having a high seam length to
volume ratio (>1.25 and 0.75 to 1.25) had a higher lead content than those in
cans having a lower ratio «0.75). The high ratio cans included mainly baby
food and other s~all juice cans.
A survey conducted in 1974 by the National Food Processors Association
(1977) examined lead content of various common vegetables, fruits, and juices
prior to canning and aft~r storage in the can for 1-1/2, 3, 6, and 12 months,
simulating pre-consumption storage of canned foods. These data (Table 8.20)
offer strong support that: (1) food can acquire substantial quantities of lead
from cans, and (2) lead concentration in canned food increases with the length
of storage. Several foods such as grapefruit juice, orange drink, corn, and
tomatos, approximately, doubled their lead content after 1 year in storage.
These data provide some insight into the significant increase in lead con-
tent in foods ehich are not particularly agressive towards can seams and inter-
iors. The data in Table 8.20 show that in many cases, most of the lead pickup
occurr-edcetween the filler bowl of the packing machinery and the initial
analysis, which was performed after essentially no storage time, too soon for
leaching to have had a measurable effect. The presence of particulate solder
in the can would explain this increase; confirmation for this hypothesis is
suggested by the fact that extreme variability in lead concentrations were en-
countered when grab samples were analyzed, and it was found necessary to take
the entire contents of a can as a representative sample. Additional support
for the hypothesis is provided by the little or no further increase in lead
concentrations with storage time observed in some of these kinds of foods. A
possible explanation is that this lead results from the fine particulates of
solder ("spatter") formed during the soldering and post-soldering brushing of
excess solder from the seam.
As recently
milk when levels
tration of whole
suggest the need
as 1974, levels of 0.5 ppm were frequently found in canned
below 0,2 ppm would have been expected on the basis of concen-
milk (Kolbye, et aI" 1974), These and other available data
for further research, particularly with regard to solder and
346
-------
6000
- 5000
~
01
:t
-
54000
-
o
'-
-
~ 3000
(.)
c
o
U
"0 2000
o
(1)
-I
o
o
Figure 8.12
Figure 8.13
2 :; 4
Sample Position
5
6
Lead distribution in single cans of tomato paste
after storage at room temperature.
Second day after purchase, cans kept at room temperature
overnight. Symbols represent five different cans.
Source:
Mitchell and Aldous (1974).
60
(/)
z
«
(.)
u..
o 30
I-
Z
UJ
(.)
0::
~ 0
< 100 100-199 200-299 ~400
LEAD CONCENTRATION Vigl))
SEAM LENGTH/VOLUME RATIO
~>t.25 00.75 -1.25 li]<.75
m 53 CANS, MAINLY BABY FOODS AND OTHER
SMALL ( 60z) JUICE CANS
o 18 CANS, MAINLY SODA AND OTHER 120z CANS
I!J 21 CANS, MAINLY 460z JUICE CANS,I6oz
FRUIT CANS
Effect of seam length/volume ratio on the lead level
of can contents.
Source:
Mitchell and Aldous (1974).
347
-------
.----"
TABLE 8.20.
V~~IATIONS IN LEAD CONCENTRATIONS WITH TI}ffi
IN SELECTED CANNED FOOD PRODUCTS a
Food Product
Lead Concentration.
ppmb
Percent Contributed
by Can
Corn
filler bowl
initial
6 months
1 year
0.05
0.46
0.59
0.93
89
92
95
Green beans
.filler bowl
initial
6 months
1 year
0.18
0.48c
0.35
0.39
63
49
54
Peas
filler bowl
initial
6 months
1 year
0.08
0.33
0.40
0.37
76
80
78
Tomatoes
filler bowl
initial
6 months
1 year
0.06
0.31
0.55d
0.52
81
89
88
Applesauce
filler bowl
initial (mean)
6 months
1 year
0.08
0.27
0.32
0.38
79
75
79
Fruit
cocktail
filler bowl
initial
6 months
1 year
0.08
0.22c
0.21
64
62
Grapefruit juice
filler bowl
initial
6 months
1 year
0.04
0.09
0.30 .
100
100
100
Tomato juice
filler bowl
initial
6 months
1 year
0.05
0.25
0.28
80
82
Orange drink
filler bowl
initial
6 months
1 year
0.01
0.05
0.11
0.11
80
91
91
aSource:
1974 Lead in Canned Food Survey, National Food Processors
Association (1977).
b
Values are means of approximately 12-50 samples.
cAnoma1ous mean, caused by distribution extremely skewed to the right.
dAfter 9 months.
348
-------
flux operations in canning evaporated milk. Unlike other food products,
evaporated milk traditionally has been packed in a can having a soft solder
plug.
Murthy and Rhea (1971) reported that the ratio of tin to lead in the fil-
ling solder affected lead uptake by evaporated milk. When the ratio was 60:40
and large amounts of solder were allowed access to the milk, lead uptake of
0.34-1.60 ppm was observed, .~hereas samples not exposed to solder had 0.05-0.37
ppm. No significant difference was seen in lead uptake by evaporated milk
between a 50:50 filling solder and a 10:90 for internal seams. With solder
pellets present inside, canned milk showed 0.10-0.54 ppm lead (Engst and
Waggon, 1965).
The evaporated milk industry was informed of the need to reduce these
levels and the industry has responded by instituting changes in canning opera-
tions and improving quality control procedures. A general declining trend from
levels as high as 0.5 ppm to 0.1 ppm over the past 5 - 7 years is evident from
Table 8.16.
The data obtained by Lamm and Rosen (1974) showed a decrease in lead con-
tent of evaporated milk and infant formulas in a 1972-73 survey as compared to
that determined in a 1971-72 (Lamm, et al., 1973) survey. These results have
quite reasonably been questioned on the basis of a change from flame to non-
flame atomic absorption spectrometric analyses (Holliday, et al., 1974; Sarett,
1974). As shown in Table 8.16, Lamm and Rosen's (1974) data shows significant-
ly lower levels for all milk products (including market milk and human milk)
than Lamm, et al. 's (1973) study. Thus, much of the discrepancy between the
two studies is probably attributable to analytical techniques, rather than an
actual decrease of the magnitude suggested (ca lOX). Mitchell and Aldous
(1974) obtained higher lead levels in canned evaporation milk (mean, 0.20 ppm;
range, 0.01 to 0.28 ppm) using flame atomic absorption spectrometry than did
Lamm and Rosen (1974) using a nonflame method (mean, 0.10 ppm; range, 0.04 to
0.22 ppm).
More recent Food and Drug Administration (FDA) analyses indicated that the
mean lead content of 80 canned, evaporated milk samples was 0.125 ppm, with a
range of 0.02 to 0.37 ppm (Kolbye, et al., 1974). The results of an industri-
al survey of 3000 canned, evaporated milk samples using a FDA-approved method,
showed a mean value of 0.12 ppm Pb, with the highest level in the range of 0.01
to 9.46 (U. S. Department of Health, Education and Welfare, 1975). The food
industry has been moving toward elimination of the plug-type metal container.
This should aid in minimizing the levels of lead in evaporated milk and related
products.
In addition, the importance of evaporated milk in infant nutrition has
been in a long-term declining trend over the past 20 years. As reported by
Fomon (1974), whereas in 1958 the feeding of about 42 percent of infants
through 2 months of age was based on evaporated milk formulas, this had de-
creased to about 2 percent by 1972. Evaporated milk has largely been replaced
349
-------
by formulas based on soybeans, more nutritionally complete an~ more easily di-
gested by infants than cow's milk. Evidence in support of th~s comes from the
results of two surveys conducted by one of the major formula producers
(Martinez, personal communication, 1977), which indicated the following propor-
tions of infants using evaporated milk formulas:
Hospital period
to 2 months
3-4 months
5-6 months
Evaporated
1976
0.1
1.0
2.2
2.2
Milk, percent
1971
0.8
4.2
4.0
3.5
These infant formulas are available either concentrated, requiring dilution be-
fore use, or ready-to-use. Both types are packed in regular side-seamed cans,
and do not use the plug-type evaporated milk style can.
The use of canned milk (condensed and evaporated) has, in general, also
been in a long-term declining trend in the United States, as indicated by U. S.
Department of Agriculture 1978 Statistics.
Year
Millions of Ib
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1,572
1,497
1,376
1,214
1,186
1,102
1,057
1,000
924
862
788
Commercial infant formulas, packed in 8-ounce and 30-ounce seamed cans and
in 4-ounce glass nursettes, did not reveal any significant differences in the
lead content of the product in either of these types of containers (Lamm and
Rosen, 1974). This finding has not been replicated in other studies, however.
Lamm and Rosen's (1974) survey, as well as a National Food Processor's Associa-
tion survey, showed averages of 0.08 and 0.09 ppm,respectively. Similarly, FDA
spot analyses showed an average of 0.09 ppm in four major brands of infant
formula concentrates. Diluted for use, the lead values would be reduced by 50
percent, making them comparable to market milk.
350
-------
1he consensus of studies conducted by the Can Manufacturer's Institute, in
cooperation with the National Food Processors Association (1977), the Food and
Drug Administration (U. S. Dept. of Health, Education and Welfare, 1977), and
Aldous and Mitchell (1974), suggests that approximately one-half to two-thirds
of the lead content in canned foods is attributable to canning, rather than the
food itself. In addition, Mitchell and Aldous (1974) have demonstrated that
(1) lead solders appear responsible for increasing the lead content in canned
foods and (2) substantial quantities of lead may be leached from lead solder
seams and incorporated into foods. These results, taken together, indicate the
potential for reducing dietary lead through changes in canning technology (e.g.
substituting other types of solder, adhesives, or sealing methods for lead sol-
der in can joints or the use of coatings inside the can to act as a barrier to
prevent contact between lead soldered seams and food inside the can). Estimates
of the effects of instituting these types of changes in reducing both lead in-
take and (indirectly) body burden of lead among various population groups, are
provided in Sections 8.6 and 8.7.
8.6
SOURCE CONTRIBUTIONS TO LEAD INTAKE BY HUMANS
8.6.1
Lead Intake From Air
Inhalation of air is a smaller potential source of lead input for most
persons than ingestion of food. Due to the large variation of lead in air with
season and locale, the potential intake by this route is extremely variable de-
pending on location and personal physiologic characteristics. Data cited in
the NAS report (National Academy of Sciences, 1972) indicate that th~ median
concentration of lead in the air of Los Angeles in 1962 was 2.5 ~g/m , al-
though some stations in the city recorded individual concentrations as high as
11.4 ~g/m3. In contrast, the concentration of lead in most suburban atmospheres
seldom exceeds 0.5 ~g/m3, and for rural areas, 0.1 ~g/m3. As much as a five-
fold variation in atmospheric lead exposure has been observed within cities,
depending on the location of residence (i.e., downtown Los Angeles (2.5 ~g/m3)
or a typical suburb (0.5 ~g/m3). The variability of potential lead intake by
inhalation is further increased by the variability in total air inhaled which
depends, among other things, on the degree of physical activity and respiratory
volume. For example, a man doing light work for 8 hours a day would inhale
more than twice (22.8 m3 vs. 10.8 m3) as much air as a man at rest all day, as
shown in Table 8.21. According to the National Academy of Sciences (1972) cal-
culations, if one superimposes on this range, a 25 fold difference in atmo-
spheric lead concentration betwe~n urban and rural air, the potential daily in-
take of lead could vary from 1.1 ~g for a rural man at rest all day to 57.0 ~g
for a man engaged in light work in downtown Los Angeles, and residing there
while not at work. The comparable amount of lead potentially respired by a
suburbanite who commutes to the city for light work, is estimated to be 30.6
~g (4.8 + 1.8 + 24.0).
351
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TABLE 8.21
POTENTIAL DAILY INTAKE OF LEAD BY INHALATIONa
Activity Air Potential Lead Intake, ~g
Levelb Inhaled, m3 @ 0.1 ~g/m3 @ 0.5 ~g/m3 @ 2.5 ~g/m3
8 Hr. working
("light activity") 9.6 0.96 4.8 24.0
8 Hr. nonoccupation- 9.6 0.96 4.8 24.0
al activity
8 Hr. resting 3.6 0.36 1.8 9.0
-
Total 22.8 2.28 11.4 57.0
aSource: National Academy of
bOf a "standard manll weighing
surface area of 1.8 m2.
Sciences, (1972).
70 kg, 20-30 years old, 175 cm tall, and having a
Interestingly, as in the case of dietary intake, potential respiratory intake
in infants is greater than that of adults on a ~g/kg body weight basis for ex-
posure at comparable concentrations of airborne lead. The basis for this is
the greater volume of air respired by children per unit of body weight. A 1-
year-old child inhales 6 m3 of air per day compared with the 23 m3 per day in-
haled by an adult (National Academy of Science, 1972). The significance of
this proportionally greater inhalation of lead cannot be properly evaluated as
it is presently unknown whether the higher potential intake may be accompanied
by a correspondingly higher, equal, or lower rate of excretion than adults.
Although it is generally agreed that for most individuals, dietary lead
presents a more important (quantitative) source of exposure than air, there
are many uncertainties concerning their relative contributions to body burden.
One of the chief reasons for these uncertainties is the lack of specific know-
ledge concerning the fate of inhaled lead once it enters the lungs, and the
factors which may modify absorption rates. The contributions of food and water
to daily lead assimilation, in contrast, have been studied extensively in de-
tailed, long-term balance studies such as those of Kehoe (1961). The few
studies which have examined inhalation of lead in humans are reported below.
Mehani (1966) conducted an investigation to determine the degree of ini-
tial deposition and retention of inhaled lead in the lungs. That study
reported an average deposition of 37 percent for non-industrially exposed men
and 39 and 47 percent for two groups of industrially exposed men, respectively.
The particle size distribution was not reported.
352
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In general, the information concerning the size distribution of lead par-
ticles in the environment indicates that particle sizes of mass median equiva-
lent diameters (MMED) of 0.1 - 1.0 ~m should be of the greatest concern; the
average MMED in the general atmospheric environment is about 0.25 ~m (Robinson
and Ludwig, 1967).
Kehoe (1961) presented the results of a study in which both the deposition
rates in the lungs and the particle size was reported. Lead sesquioxide
produced by burning tetraethyllead was the source of the exposure; the parti-
cles generated were classified according to two size groups: an average
diameter of 0.05 ~m with 90 percent from 0.02 - 0.09 ~m; and a second group
having a median diameter of 0.9 ~m, with 90 percent less than 2 ~m in size.
The 0.05 ~m size corresponds to an MMED of 0.25 ~m reported for the general
atmospheric environment by Robinson and Ludwig (1967). The concentration of
lead used by Kehoe (1961) was 150 ~g/m3, much higher than that encountered in
the general environment, but not atypical of industrial exposure levels. The
deposition of the smaller particles in the respiratory tract was 36 percent
[which closely approximates the 37 percent estimated by Mehani (1966)) while
that of the larger particles (MMED = ~ 2.9 ~m was 46 percent.
Nozaki (1966) utilized a variety of particle sizes ranging from 0.05-1 ~m.
Rates of deposition under both. rapid, shallow, and slow, deep, respiration were
determined. For particles having a diameter of 0.05 ~m, the total deposition
in the respiratory tract under conditions of slow deep breathing was 42.5
percent but, as shown in Table 8.22, all deposition rates were appreciably
lower during rapid, shallow conditions of respiration.
TABLE 8.22
DEPOSITION OF LEAD INHALED BY MANa
10 Respirations/min; 1,350 cc Tidal Air
Particle Particle
Diameter, ~m Deposition, percent
30 Respirations/min; 450 cc Tidal Air
Particle Particle
Diameter, ~m Deposition; percent
1.0 63.2 1.0 35.5
0.6 59.0 0.6 33.5
0.4 50.9 0.4 33.0
0.2 48.1 0.2 29.9
0.1 39.3 0.1 27.9
0.08 40.0 0.08 26.5
0.05 42.5 0.05 21.0
a
Source:
Adapted from Nozaki (1966) by National Academy of Sciences (1972).
353
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In summary, the bulk of available experimental evidence suggests that the
deposition in the respiratory tract of lead from the ambient air is approximate-
ly 35-40 percent (National Academy of Sciences, 1972). Again, it must be noted
that these results may not be generalizable to groups such as women and child-
ren not included as experimental subjects in these studies. The NAS panel con-
cluded, "knowledge concerning the contribution of respired air to the total
amount of lead entering the body is insufficient to allow anything better than
general approximations. A reasonably sound estimate can be provided for the
fraction of the inhaled lead which is deposited in the airways, but very little
is known concerning its fate once deposited".
Under certain conditions, inhaled lead of large particle size may contri-
bute to gastrointestinal absorption. Lead particles deposited in the
nasorpharyngeal region may be swallowed or ejected by nose blowing or expecto-
ration. Similarly, ciliarymucus transport may cause migration upward to the
pharynx where swallowing or expectoration may occur, or they may enter the sys-
temic circulation. Particles deposited in the alveolar bed may be phagocytized
by migratory macrophages and conveyed back up the airways to be swallowed and
passed through the gastrointestinal tract, according to the National Academy of
Sciences' report (1972). A single study of Kehoe (1961), attempted to quantify
the importance of this mechanism under experimental conditions. Kehoe deter-
mined the.excretion of lead in urine before, during and after termination of
inhalation of small and larger particles of lead oxide (average MMED 0.25 ~m;
median MMED 2.9 ~m). During long periods of lead inhalation, Kehoe found that
excretion of lead of both size groups increased. Only during inhalation of the
larger particles was there an increase in fecal lead excretion. This increase
was presumably attributable to retrograde movement of larger particles from the
lungs to the nasopharynx followed by swallowing. National Academy of Sciences
(1972) estimated that 40 percent of the lead deposited in the airways was
transferred to the gastrointestinal tract; this transfer probably involved the
"large" particles (in the 2.9 ~m MMED range). The contribution of
"respiratory" lead intake to gastrointestinal absorption under normal environ-
mental conditions is unknown.
Various estimates of absorbed lead dosage from air have been derived. 3
Given 37 percent deposition and total retention/abso5ption, inhalation of 23 m
of air per day, and a lead concentration of 2.5 ~g/m , 21 ~g of lead per day
originating in the air would be absorbed compared with, roughly, 30 ~g/day
originating in foods and water (National Academy of Sciences, 1972). At the
maximum concentration permitted by the new lead air quality standard (1.5 ~g/
m3), daily absorption of inhaled lead would be reduced from 21 ~g to 12.6 ~g,
and at the 1975 geometric mean national urban air lead concentration of 0.75
~g/m3 (Table 8.3) daily lead absorbed from air would be further reduced to
6.3 ~g.
Other investigators, as cited by Ewing and Pearson (1974), suggest that
the previous assumption of 23 m3 of air inhaled per day is too high and esti-
mates would be more appropriately based on lower volumes of respired air. Ac-
cordingly, Ewing and Pearson (1974) estimated that a lead dosage of 20-25 ~g
354
-------
would result f30m an urban adult breathing air containing 3 ~g/m3 and respir-
ing about 15 m of air per day. This estimate would be similarly reduced at
the lower lead concentrations, more representative of current urban air lead
concentrations.
Data on percent absorption by children are scant, due, in part, to the
difficulties in the participation of child subjects in experimental studies.
For the purposes of estimating relative contributions from the various media,
an average absorption of 40 percent for inhaled lead was adopted for both
children and adults.
8.6.2
Lead Intake From Drinking Water
The environmental distribution and concentrations of lead found in U. S.
waters are discussed in Section 8.3.2. In this section, the relationship of
these lead levels to the total human exposure profile is considered. As noted
in Section 8.3.2, very few water supplies have lead concentrations in excess of
the 50 ~g/l drinking water standard. The median lead concentration in munici-
pal water supplies appears to be in the range of 10 ~g/l, based on the analyti-
cal data described in Section 8.3.2. A few localities in the U. S., notably
metropolitan Boston, have higher exposures due to very soft water and the pre-
sence of lead in domestic piping systems.
With the exception of a very few localities, (e.g., Boston), it is ap-
parent that drinking water contributes a minor percentage of ingested lead for
the average adult. Based on an examination of data from nationwide water
quality surveys, the National Academy of Sciences (1972) concluded that it is
doubtful that many people drink water containing greater than 50 ~g of lead/
liter with any consistency.
The absorption characteristics of ingested lead compounds have been stud-
ied by many investigators, beginning with the classic work of Kehoe in the ear-
ly 1960's. For adults, most of the estimates appear to cluster in the neigh-
borhood of 10 percent, and this value was adopted for both food and water for
the estimation of relative contributions of the several media.
Assuming, on the average, a lead content in drinking water of 10 to 20
~g/l and a daily consumption of 1 to 2 liters, the lead intake would range be-
tween 10 and 40 ~g/day, of which about 10 percent, or 1 to 4 ~g, would be
absorbed. This intake would represent less than 10 percent of the World Health
Organization (W.H.O.) recommended acceptable total intake of 3 mg/wk (429 ~g/
day) for adults. Depending on the levels of intake from other sources, water
may contribute between 10 and 20 percent of the daily absorbed dose of lead for
the average U. S. adult.
The efficiency of absorption of ingested lead by children is much greater
than the 10 percent of adults. Alexander (1973;1974) showed a value of 53 per-
cent. In a recent broader study conducted by Ziegler, et al., (1978), the
average absorption for 61 balance studies on children ranging from 14 days to
about 2 years in age was 41.5 percent. This latter value was adopted for
children for both ingested food and water.
355
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8.6.3
Lead Intake From Soil and Other Non-Food Items
It is generally accepted that ingested dietary lead constitutes the
body's largest direct source of lead. Lead intake from soil and dust is a neg-
ligible problem for adults and can be neglected. However, this may constitute
a very important route for lead intake by infants and pre-school children, as
suggested in Section 8.4.3, especially for young children with pica habits or
prone to hand-to-mouth activity. Lead intake may be estimated based on lead
concentrations in dirt and dusts and the mouthing behavior of the child. Un-
fortunately, there is a great deal of uncertainty on the availability of the
contained lead and, hence,'of its absorption. It is, undoubtedly, less well
absorbed than lead in ingested food or water; for purposes of calculation, a
conservative assumption might be that it is 3/4 as well absorbed, i.e., about
30 percent absorption.
In the study by Day, et al., (see Section 8.4.3), it was found that the
average concentration of lead in urban dust was 960 ppm (860 ppm median). The
authors found, through direct measurements, that from 5 to 50 mg of dirt can be
transferred from a child's hands (dirty from 30 minutes of normal play) to a
"sticky sweet". Therefore, approximately 100 ~g of lead could be ingested via
c0nsumption of two sweets.
Day, et al., calculated that children age~ one to nine ingest, approxi-
mately, 165 ~g of lead per day in food and water. Consumption of two sweets
during normal play would add to this amount considerably.
In the similar investigation by Lepow, et al., (1975) (see Section 8.4.3),
the transfer of lead from children's hands to their mouth was also observed and
measured. Hand dirt had an average lead concentration of 2400 ppm. Most of
the children were observed to have their hands or non-food objects in their
mouths frequently. A reasonable estimate of mouthing frequency was established
at ten times per day. The authors estimated, using the above figures, that a
child exhibiting this mouthing behavior and playing in a similarly contaminated
environment could ingest 240 ~g of lead per day, thus approaching the maximum
permissible daily intake from this source alone.
Given the combination of the high lead content of the house dust and the
mouthing proclivities of the study children the high blood leads of these
children are, perhaps, not surprising, and serve to point up the fact that
paint pica is not the only danger for small children living in substandard
housing. It is fortunate that the large majority of children are not so ex-
posed, else high blood lead levels would be far more prevalent.
A non-food item which may be a contributor to lead intake by adults is
lead from cigarette smoke. As pointed out by Mahaffey (1978), the concentra-
tions of lead in tobacco can vary widely; Cogbill and Hobbs (1957) found con-
centrations up to 39 ppm. Investigation of lead to arsenic ratios implicated
lead arsenate as the probable source of the lead in cigarettes. Surprisingly,
little information on the lead content of tobacco smoke is available. Cogbill
356
-------
and Hobbs estimated that the amount of lead transferred to mainstream smoke was
about 4-6 percent of the lead concentration in the cigarette, corresponding to
about 1-2 ~g per cigarette. Patterson (1965) estimated about 0.8 ~g of lead is
contained in each cigarette, resulting in about 6.4 ~g of lead absorbed per day
for a pack-a-day smoker. The 40 percent retention rate assumed by Patterson
does not appear to be documented specifically in the literature; selection of
this figure is probably based on analogy to deposition/retention rates of lead
observed in experimental inhalation studies (National Academy of Sciences,
1972).
A point to note here is that the references cited on lead content of to-
bacco in cigarettes are based on 15 to 20-year-old data, from a period when
lead arsenate was a widely used insecticide. As described in Section 4.3.4.2.
3, in recent years lead arsenate has been supplanted by organic pesticides to
the extent that it is no longer manufactured in the U. S. Thus, there appears
to be some question whether cigarettes may still be a significant source of
lead intake for smokers. There do not appear to be any recent studies bearing
on this question. For purposes of calculation, the 40 percent absorption for
inhaled lead is assumed to be also applicable to lead from cigarette smoke,
although there does not appear to be much experimental data on this either.
Lead Intake from Foods and Beverages h,
Daily dietary lead intake is determined by the amount and kinds of food
and beverages ingested and by the lead content of each of the various compo-
nents of the diet. As discussed earlier, a portion of inhaled lead may also
contribute to ingested lead if the inhaled lead moves from the lungs to the
nasopharyngeal area where it may be swallowed.
8.6.4
Several methodologic approaches have been used to derive estimates of
dietary lead intake. These include: (1) analysis of "typical diet" repli-
cates, (2) institutional total diet studies (i.e., composites), and (3) bal-
ance studies, which measure both intake and excretion of individuals
maintained under experimental conditions, and (4) estimates based on measure-
ment of fecal lead excretion.
Total dietary intake estimates, utilizing the techniques above, place the
typical adult daily lead intake in the range of 90-500 ~g/day with most of the
estimates converging on the 150-300 range. Much of the variation observed in
these studies is due to difference in absolute food intake. For example, in a
nationwide study of institutionalized children, Murthy, et al., (1971) reported
that the children's average food consumption ranged from 1.18 kg/day to 2.55
kg/day depending on the institution. Similarly, within single institutions,
individuals ranged between 0.92 - 3.10 kg/day of food. This threefold range of
intake level (or perhaps more) presumably applies to the general population as
well.
Kehoe (1961), Schroeder,
cited in the National Academy
ing from 100-500 ~g/day based
et al., (1961), Harley (1970), Lewis (1966), as
of Sciences (1972) have published estimates rang-
on food intake levels of about 2,000 g of food
357
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and beverages per day. Estimates of lead intake conducted over the past 30
years have been remarkably similar, suggesting that any trends in lead consump-
tion, if present, must be extremely subtle (National Academy of Sciences, 1972;
Ewing and Pearson, 1974).
Harley's (1970) study is particularly interesting. Lead concentrations in
various foods in New York City were determined. These values were then multi-
plied by U. S. Department of Agriculture estimates of food consumption. Find-
ings of the study revealed a weighted lead intake of approximately 280 ~g/day;
a food consumption of 1.75 kg/day per person; and a mean lead concentration in
food of 0.163 ppm.
Composition of the diet determined by food choice also influences lead in-
take. Lewis (1966) as cited by the National Academy of Sciences (1972), points
out that no food or group of foods is either a large or a constant contributor
to lead in man, because man's diet is composed of a wide variety of individual
items, and various food contribute various amounts of lead. Lewis (1966) esti-
mated the average daily dietary intake of lead at about 300 ~g, with a range
for most people of 100-2,000 ~g. The range can vary markedly from person to
person and from city to city, on the basis of choice, opportunity, and specific
h.qbits.
The Food and Drug Administration (FDA) conducts two major food surveil-
lance programs in the U. S. FDA's Total Diet Studies is a generalized program
to determine the levels of pesticide residues, PCB's, heavy metals (including
lead), and other contaminants in the diets of U. S. consumers. The information
generated by this program is based on continual monitoring of total diet
samples or "market baskets" from retail markets in 30 locations nationwide
(U. S. Dept. of Health, Education and Welfare, 1977). The specific foods
collected are designed to simulate the 2 week diet of a 15-20 year old male,
statistically the largest food consumer. Each market basket consists of 117
foods representative of 12 food groups (i.e., dairy; meat, fish and poultry,
fruits, etc.). The composition of the market baskets vary somewhat both in
relative amounts of various commodities and also there is minor variation in
the commodities sampled from region to region. These variations are intended
to reflect regional differences in diet.
Foods sampled under the Total Diet Studies program are purchased from
retail markets in amounts and types specified by FDA. The foods are then
prepared (washing, peeling, cooking, baking, etc.) according to uniform in-
structions. Foods are then divided into the 12 food groups and composited for
sampling by combining the foods in proportions reflective of average consump-
tion levels for each commodity as determined by a U. S. Department of
Agriculture household food consumption survey. (U. S. Department of
Agriculture, 1965). The lead content of each of the 12 food groups composites
is then measured. Consequently, the program does not provide data on the lead
content of individual foods.
Total Diet Studies, or "Market Basket Studies" have shown a very
generalized distribution of lead in foods, with no single food group or source
358
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assuming overwhelming importance. In general, however, highest levels are seen
in vegetables, particularly leafy ones (Mahaffey, et al., 1975; U. S. Department
of of Health, Education and Welfare, 1977). Market Basket Studies have
TABLE 8.23
ESTIMATED DIETARY INTAKE OF LEAD BY FOOD CLASSa
Lead
Jlg/day
Percent
total
I
II
III
IV
V
VI
VII
VIII
IX
X
XI
XII
Dairy products
Meat, fish, and poultry
Grain and cereal
Potatoes
Leafy vegetables
Legume vegetables
Root vegetables
Garden fruits
Fruits
Oil and fats
Sugars adjuncts
Beverages
0.0
4.00
4.16
0.70
3.03
18.80
3.83
11.36
9.49
0.67
0.55
3.81
0.0
6.6
6.9
1.2
5.0
31.1
6.4
18.8
15.7
1.1
0.9
6.3
Totals
60.4
a
Based on Fy 1973 Total Diet Survey data of the Food and
Drug Administration as reported by Mahaffey, et al., (1975).
consistently revealed the highest quantities of lead in food classes represent-
ing vegetables (either ,leafy, legume, or root) and in fruits and garden fruits
as shown in Tables 8.23 and 8.24. The fruits and garden fruits together com-
pose only 10.4 percent of the total diet. However, they provide 34 percent of
daily lead intake. Similarly, the vegetable groups (i.e., legume, root or
leafy vegetables) account for only 5.7 percent of total daily food intake, yet
they contribute 44 percent of daily intake. Together, fruits and vegetables
(Food Classes V, VI, VII, VIII, and IX) account for almost 80 percent of total
daily food intake. Estimated dietary intake from all food groups is shown in
Table 8.25.
359
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TABLE 8.24
RANK ORDER OF LEAD FINDINGS BY FOOD CLASS; FY 1973a,b
Food Class
Legume vegetables
Garden fruits
Root vegetables
Grains and cereal products
Leafy vegetables
Fruits
Meats, fish, and poultry
Oil, fats, and shortenings
Sugars and adjuncts
Potatoes
Beverages
Dairy products
Percent
Positive
Rank
Based on Mean
Highest
Concentration
100
87
83
73
83
73
77
50
63
57
17
33
1
2
3
4
5
6
7.5
7.5
9
10.5
10.5
12
Mean
Concentration
pprnc,d
0.26
0.12
0.11
0.10
0.05
0.042
0.013
0.013
0.0067
0.0033
0.0033
(O)e
aSource: Mahaffey, et al. (1975). (FDA Total Diet Study)
bSampling locations distributed over the United States
cLead determinations made by flameless atomic absorption
spectro photometry
dBased on 30 "Market Basket" samples of each commodity
eTraces count as positive occurrences but with no ppm
value.
Of the various methods of estimating daily dietary lead intake, the FDA
Total Diet studies have consistently provided the lowest estimates. For
example, the FY 1973 figure for lead intake was 60.4 ~g/day. The comparable
figure for FY 1974 was 90.2 ~g/day. Changes in the method of reporting which
allowed a lower minimum level to be reported in 1974, rather than actual
increases in intake, are thought to account for the 30 ~g/day discrepancy be-
tween FY 1973 and FY 1974 figures (U. S. Department of Health, Education and
Welfare, 1977). Kolbye, et al., (1974) has severely criticized the accuracy
of these estimations, suggesting that analysis of the foods as composites
rather than separate foods leads to substantial under-estimation of the quanti-
ties present, because trace values in the composites (near the detection
limits) have been counted as zeros. Determination of lead in foods, in general,
has presented difficulties because (1) the limits of detection for lead are
high relative to the other heavy metals (0.1 ppm for lead vs. 0.01 ppm for
360
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cadmium and mercury), (2) the quantities typically present in foods are low in
relation to detection limits.
Under differing assumptions about the actual values of these trace concen-
trations, Kolbye, et al., 1974, showed that a four-fold difference could exist
in the estimates of intake based on the 1973 Total Diet Study data (Table 8.25).
TABLE 8.25
THE EFFECTS OF VARIOUS ASSUMPTIONS OF THE VALUE OF TRACE AND NON-
DETECTIONS ON ESTIMATES OF DIETARY INTAKE a
Study Title and Method of Calculation
FY 73 Total Diet Studies (Traces and
Non-detections = 0) (See Table 8.11)
FY 73 Total Diet Studies as Reported by
Kolbye, et al., (1974)
(with traces assumed = 0.09 ppm
and non-detections assumed = 0.00 ppm)
(with traces assumed = 0.09 ppm
and non-detections assumed = 0.05 ppm)
Calculated ~g Lead
Per Day for Teenage Male
60
159
233
FY 74
Total Diet Studiesb
(with traces and non-detections = 0
(with traces assumed = 0.02 ppm, which
was half of lowest quantitated levels
in FY 74 and non-detections = 0
90
95
FY 74 Heavy Metals in Foods Survey
(using median levels of surveyed foods)
(using mean levels of surveyed foods)
141
254
a
Source: U. S. Department of Health, Education and Welfare, 1977.
bThe analytical method was the same during FY 73 and FY 74. However, in FY 74,
after additional experience in use of the method, the laboratory was requested
to estimate detected values lower than the 0.1 ppm. In FY 73, 0.1 ppm was the
lowest reportable level.
The range of values derived was 60-233 ~g lead per day for FY 1973. A similar
analysis of FY 1974 data revealed a range of 90-254 ~g/day depending on the
treatment of "trace" findings and the choice of median or mean levels for cal-
culations (U. S. Department of Health, Education, and Welfare, 1977). Thus,
361
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analytical sensitivity of the method becomes a factor along with how "traces"
or "non-detections" are treated. These factors significantly alter the calcu-
lation of daily intake levels.
In contrast, estimates of dietary lead intake derived from replicate diets
and fecal lead excretion in strictly controlled metabolic studies, place lead
intake from approximately 150-300 ~g Pb/day depending on total food intake
(Kehoe, 1961; Schroeder and Tipton, 1963).
In view of the difficulties in evaluating food composites, in 1974 FDA in-
stituted a second food monitoring program called the Heavy Metals in Foods
Survey, to examine lead in 41 different staple items of infant, child, and
adult diets. The last entry in Table 8.25, 141 - 254 ~g/day is based on this
survey. The Heavy Metals in Foods Survey is somewhat similar to the Total Diet
Studies program except that fewer food commodities are sampled and the food pro-
ducts are analyzed individually. The Heavy Metals in Foods Survey also distin-
guished between canned and non-canned foods in each commodity. A total of 41
fcods are surveyed in this program. The specific commodities sampled are
selected on the basis of: (1) relative importance to the diet. (2) past indi-
cations of high lead levels in the food, (3) balanced coverage of raw and pro-
cessed foods. The 41 foods surveyed are thought to account for at least 71
percent of the daily diet. Hopefully, this survey will provide important infor-
mation on the overall lead levels in infant and adult diets and identify areas
in which technological improvements need to be made and/or guidelines or
regulatory action may be appropriate.
Lead content of the 41 adult and baby foods sampled are reported in
Tables 8.26 and 8.27. Although only one year's data from the Heavy Metals in
Foods Survey has been released (FY 1974), several significant findings have
emerged with respect to lead in foods.
The mean lead content of canned commodities (averaged over all canned
foods surveyed) is between two and three times the lead content of all the non-
canned products. The respective average lead content of the canned and non-
canned groups were 0.376 ppm and 0.156 ppm (U. S. Dept. of Health, Education,
and Welfare, 1977).
For both adults and children, approximately 30 percent of daily lead
intake comes from canned foods although they represent only about 11 percent of
the diet by weight. These two findings underscore the importance of canned
foods as a potentially controllable source of lead intake. Further discussion
of this topic is included in Seciton 8.6.7.
362
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TABLE
8.26 LEAD CONTENT OF ADULT FOODS SAHPLED BY FDA
HEAVY METALS IN FOODS SURVEY, FY 1974a,b
- . . --.. ----. Concentration,
ppm
Upper
No. of Tolerance
Samples Mean Range Limit
Carrots, fresh 70 0.205 0-3.54 1. 234
Lettuce, raw 69 0.130 0-2.02 0.712
Potatoes, raw
white 71 0.050 0-0.762 0.251
Butter 71 0.068 0-0.151 0.455
Margarine 71 0.068 0-0.37 0.159
Eggs, whole fresh 69 0.174 0-4.02 0.792
Chicken, fryer, raw
whole or raw cut-up 71 0.127 0-1.30 0.507
Bacon, cured raw
sliced 71 0.099 0-1.685 0.598
F.ankfurters 69 0.198 0-2.87 1.087
Raw liver, beef 71. 0.089 0,..1.03 0.387
Hamb.urger, rm.
ground beef 71 0.248 0-8.29 1. 396
Roast, chuck beef 71 0.071 0-0.54 0.309
Wheat flour, white 70 0.052 0-1. 62 o.~oo
Cornmeal, yello.1 70 0.143 0-2.54 0.563
Rice, white milled 71 0.104 0-2.76 0.662
Breakfast cer~al
ready-to-eat 68 0.107 0-2.18 0.526
Sugar, refined
beet or cane 71 0.031 0-0. 4lf 0.146
Bread, ...hite 70 0.084 O~0.91 0.347
Beets, canned 71 0.381 0-3.47 1. 448
Tomato juice canned 71 0.338 0-3.08 0.803
Mixed vegetable
juice, canned 70 0.215 0-1. 76 0.770
Soup, vegetarian
vetetable 71 0.331 0-2.85 1. 382
Orange juice,
canned frozen
concentrate 71 0.135 0-5.2 1. 351
Green beans,
canned 71 0.318 0-1. 34 0.860
Beans canned with
pork and tomato 71 0.638 0-4.74 1. 959
Peas, camJed 70 0.425 0-6.95 1. 912
Tomatoes, canned 71 0.710 0-4.81 2.375
Diluted fruit: drin~~s,
canned 71 0.251 0-3.18 1.137
Peaches, canned 71 0.417 0-2.908 1.097
Pineapple, canned 71 0.402 0-7.10 1.306
Applesauce, cann~d 71 0.320 0-3.03 0.898
aSol\rce:
U.S. Department of Health. Education and Welfare (1975).
bSampling locations distributed throughout the United States.
cUp per linlit of 95% confidence interval; 95% of individual values in the population samples
are at or below this limit.
363
-------
TABLE 8.27
LEAD CONTENT OF BABY FOODS SAMPLED BY FDA
HEAVY METALS IN FOODS SURVEY, FY 1974a,b
Food Product
No. of
Samples
Mean
Concentration, ppm
Range Upper Tolerance
Limit
Vegetables and Beef
Mixed Vegetables
Spinach
Orange Juice
Apple Juice
Applesauce
Pears
Peaches
Apricots
0.070
0.072
0.085
0.375
0.321
0.160
0.079
0.094
0.082
71
71
69
71
71
71
71
71
71
0-0.67
0-1.12
0-0.55
0-3.66
0-1. 47
0-1. 37
0-0.494
0-0.458
0-0.63
0.245
0.406
0.270
1. 533
0.885
0.547
0.212
0.259
0.283
aSource: U. S. Department of Health, Education and Welfare,
bSampling locations distributed throughout the United States~
cUpper limit of 95 percent confidence interval; 95 percent of
individual values in the population samples are at or below
this limit.
8.6.5
(1975).
Relative Contribution of Various Media to Body Burden
8.6.5.1
Adults--
Of the major pathways of exposure to lead (air, food, water and sometimes
tobacco smoke), food represents the major contributor to body burden for the
general population. As indicated, general population as defined here refers to
normal, non-occupationally exposed adults and to older children whose exposure
through dust, dirt, and paint is negligible. Individuals exposed to unusually
high ambient concentrations of lead (say above 2.5 ~g/m3 in air) such as those
living in close proximity to major lead emitting industries or extremely high
density traffic are possible exceptions. For those groups, air may constitute
an equal or, perhaps, more important source of exposure. It should be noted
that unusual conditions of exposure outlined above apply to a very small per-
centage of the population, consequently, the bulk of the present discussion is
directed toward the more typical lead exposure profile. A discussion of the
special problems of high risk groups is deferred until Section 9.
Although food is the principal contributor to absorbed lead, the propor-
tionate contributions of various media (air, food, cigarettes, water) is quite
variable depending on the level of exposure from ambient air. Figure 8.14
shows that food contributes at least one-half of the body retention or uptake
for the urban man exposed to 1.3 ~g/m3 in air. For the nonsmoking rural inhab-
itant (ambient air at 0.05 ~g/m3) food contributes as much as 90 percent of
364
-------
50
10
- -
8
u
'"
n
0
r
'"- -
o
::! "
.a <
{!.
- Ajr
r- -- Water -- -
~
I- '8 ~ -
o
'"' ...
40
>-
..
~
~ 30
c
'"
:0
>
.&:
~
..
J:J
o
~ 20
"i
~
o
Rural
M;IO
Urban
Man
Figure 8.14.
Lead absorbed by man.
Source: Ewing and Pearson (1974)
Adapted from Patterson (1965).
absorbed lead dose. Note also that the absolute quantity of lead absorbed is
approximately 10 ~g per day greater for the urban resident as opposed to the
rural inhabitant.
Table 8.28 compares the amount of lead absorbed (~g/day) from air, water,
food and cigarettes under various levels of daily intake for young adult males
for each of the media. Assumptions regarding lead concentrations in the vari-'
ous media and the fraction of intake actually absorbed are based on data pre-
sented in previous sections regarding these parameters and especially on infor-
mation derived from the comprehensive reviews of Patterson (1965), National
Academy of Sciences (1972) and U. S. Environmental Protection Agency (1977).
365
-------
TABLE 8.28
THE RELATIVE CONTRIBUTIONS OF VARIOUS MEDIA TO LEAD INTAKE AND ABSORPTION: ADULT MALES
Daily Lead Daily Lead Uptake
Media Daily Intake Lead Concentration Intake, J.Jg/day Percent Absorbeda Absorption,J.Jg/day
Food Standard Diet in USDA Varies with diet compo- 150 1 11. 25
consumption data as sition. Average lead 200 15.00
used in Market Basket content approximately 250 > 7.5 18.75
Studies, kg/day 0.1 J.Jg/g 300 (254) J 22.50
400 30.00
Water 1.0 Q. 20 J.Jg/Q. 20 } 2.0
1.5 Q. 30 10 3.0
2.0 Q. 40 4.0
w Air 20 m3 0.10 J.Jg/m3 2.0 0.8
0'\
0'\ 0.25 5.0 2.0
0.50 10.0 4.0
1.00 20.0 8.0
1.50 30.0 12.0
2.00 40.0 40 16.0
2.50 50.0 20.0
3.00 60.0 24.0
3.50 70.0 28.0
4.00 80.0 32.0
4.50 90.0 36.0
5.00 100.0 40.0
Tobacco Smoke 10 cigarettes. 0.8 J.Jg/cigarette 8 } 3.2
20 cigarettes 0.8 16 40 6.4
30 cigarettes 0.8 24 9.6
a Source: Battelle estimates derived from literature
b FDA estimate for lead intake of teenage male (See Table 8.25).
-------
The companion table (Table 8.29 shows the total absorbed dose of lead received
per day under a variety of ambient air conditions). Note that non-air sources
including food and water (and cigarettes, for smokers) contribute 22.0 and 28.4
~g/day, respectively, to abosrbed lead. For both smokers and nonsmokers, the
proportionate contribution from ambient air increases as ambient air lead
increases. At approximately, 2.75 ~g/m3 ambient air supplies as much absorbed
1Jad per day as does diet. For smokers, the equivalent figure is about 3.5 ~g/
m lead in air. The absolute quantity of absorbed lead nearly triples from its
baseline value (at 0.01 ~g/m3 in air) to 62.0 ~g/day at ambient air lead levels
of 5.0 ~g/m3 for nonsmokers. For smokers, the increase is less dramatic, how-
ever, daily absorbed lead more than doubles, increasing from its baseline va1u3
of 28.4 ~g/day to 68.4 ~g/da3 absorbed when ambient lead in air is at 5.0 ~g/m .
The range of 0.1 to 4.0 ~g/m of lead in air approximates the usual range of
ambient conditions for general populations. As indicated in Section 8.2.1,
only 5 stations reported mean annual lead concentrations of over 2 wg/m3 and
none of the stations reported over 3.0 ~g/m3.
Figure 8.15 portrays the data from Table 8.28, assuming an absorbed dose
from food of 254 ~g/day, 3.0 ~g/day from water and 6.4 ~g/day from cigarettes.
The area beneath each of the lines (i.e., Food, Air, Smoke, and Water) corre-
sponds to the percent contribution to absorbed lead dose for each media for a
given ambient air concentration of lead. The total of all media for any given
air lead concentration is 100 percent. The actual absorbed dosage in ~g/day
for each ambient air concentration may be derived from Table 8.28. As indicat-
ed in Figure 8.15, at low to moderate levels of lead in air, food and water
account for a very large proportion of absorbed lead dose for the general adult
population. As air lead levels increase, however, air takes on an increasingly
prominent position and actually surpasses absorbed lead from food and water at
approximately 2.75 ~g/m3. Beyond that point (>2.75 ~j/m3 in air), food dimin-
ishes in importance whereas air increases. 2.75 ~g/m is well above average
annual means currently measured even in most densely urbanized areas; lead
levels in the vicinity of point sources such as primary and secondary smelters
may exceed 2.75 ~g/m3, however. Except at the lowest ambient air lead concen-
trations, water and cigarettes maintain a low and rather uniform contribution
to absorbed dose. If lead arsenate is the cause of the dose from cigarettes,
this source may be overestimated.
8.6.5.2 Children--
As suggested in previous sections, the exposure patterns of children
differ dramatically from those of adults. Several studies have demonstrated
that gastrointestinal absorption of lead is much more efficient in you~g
children than in adults. Ziegler, et a1., (1978) found a mean absorpt~on rate
of 41.5 percent based on metabolic balance studies of children. This implies
that at a given lead concentration in food, a child will actually absorb more
than 4 times more lead than an adult consuming the same item. Also, the
composition of children's diets is different from adults (see Table 8.33);
children consume larger amounts of food than adults on a grams/kg body weight/
day basis. Inputs from smoking can be ignored for children. Perhaps, the most
important difference in exposure patterns between children and adults is that
dust and dirt constitute a significant route of exposure for children.
Hand-to-mouth activity (e.g., thumb sucking and finger licking)
mal behavioral characteristic of children through five years of age.
is a nor-
This can
367
-------
Q) 80
o
'-
~
>-
.0
$
0
0 60
"0
0
Q)
U-) ...J
(j\ "0
():) Q)
.0
....
0
II> 40
.0
«
-
0
-
c
Q)
()
'-
II)
a.. 20
100
Legend.
Food
---- Air
-..- Water
--- Cigarettes
Air and food lines cross
at 2.3/Lg/m3
I
I
I
I
---
--...-- -
--
--
--
--
--
--
--
--
--
--
-
....-
--
-
"
... -'
----~
,. --
"" ----
" ------ - -- ------
" --- ---,-....-,-- --
;~..----.. -.. -..
""
""
..-..
o
o
5.0
5.5
4.0
4.5
3.5
1.0
1.5
2.0 2.5 3.0
Air Concentration of Lead .,.,.g/m3
0.5
Figure 8.15
The relative contribution of various media to
total absorbed lead dose.
Source:
Battelle-Columbus estimate, based on 254 ~g/day
from food, and 30 ~g/day from water.
-------
TABLE 8.29
ESTIMATED TOTAL ABSORBED DOSE AT
VARYING AIR LEAD CONCENTRATIONSa:
YOUNG ADULT MALES
Avg. Ambient
Air Lead, ]Jg/m3
Total Absorbed Daily Doseb
Nonsmoker Smoker
0.01
0.1
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
22.0
22.8
26.0
30.0
34.0
38.0
42.0
46.0
50.0
54.0
58.0
60.0
28.4
29.2
32.4
36.4
40.4
44.4
48.4
52.4
56.4
60.4
64.4
68.4
aSource: Battelle-Columbus Estimate
bA .
ssumpt~ons:
(1) Dietary intake of 254 ]Jg Pb/day (suggested as
intake level of young adult male in FDA Heavy
Metals in Foods Survey (U. S. Department of
Health, Education, and Welfare, 1977).
(2) Consumption of 1.5 liters of water/day at
average lead content of 20 ]Jg/l (= 30 ]Jg/day).
(3) Consumption of 1 pack of 20 cigarettes/day or
6.4 ]Jg Pb/day for smokers.
result in the ingestion of soil and/or dust. Within a contaminated environ-
ment, hand-to-mouth activity coupled with immature dieting habits (i.e., re-
trieval of food from dusty surfaces or soil, and subsequent consumption), pro-
vide a major source of ingested lead for young children. Day, et al., (1975)
estimated that under average urban conditions, after 30 minutes of normal
playground activity, 5 -to 50 mg. 'of dirt from a child's hands can be trans-
ferred to a typical "sticky sweet". A small child playing in dirt easily in-
gests 10 mg. of soil/dust with each episode of hand-to-mouth activity. A
conservative estimate of 10 hand-to-mouth activities a day would result in the
ingestion of 100 mg. of soil/dust per day (Lepow, et al., 1975). One hundred
mg. of ingested soil/dust per day' would seem to be an approximate, conservative
assumption for the average three year old on the empirical observations of
Lepow, et al.
369
-------
-
Pica, especially for paint, can also be a very important source, however,
this habit is not characteristic of the majority of young children and, there-
fore, will be considered as a special case. Ingestion of ~on-food items is so
- - -
variable that averages are not estimable for children with pica. Estimating
average lead intakes from unintentional ingestion of non-food items (i.e., dust
and dirt) among non-pica children is even difficult due to the apparent high
variability in lead content of dust and dirt on environmental surfaces.
These cautions notwithstanding, estimates of the relative contribution of
various media to lead absorption (dust/dirt, food, water and air) can be made
for non-pica children given certain reasonable assumptions. Estimates based on
three types of ambient air conditions and four different concentrations of lead
in dust and dirt for a 3 year old child are given in Table 8.30. Daily intakes
of food (1340 g/d) and daily dietary lead intake are based on figures from FDA's
Total Diet Studies described in detail in Section 8.6.7. The gastrointestinal
absorption rates of 41.5 used for food is suggested by Ziegler, et al.,
(1978). In the absence of estimated absorption rates for lead in water, the
same percentage as for food is assumed to apply. Estimates of daily intake of
water (1.4 ~) is based on reference man studies (ICRP, 1959) and is probably a
liberal estimate since fruit juices and beverages made with water are included
in FDA's analyses as foods. The level of 20 ~g Pb/~ of water was selected as a
value which would not be exceeded by more than a small percentage of households
(see Section 8.3.2). Three different ambient air conditions are examined,
since the relative contribution of other media varies as a function of air lead
exposure. The levels selected to represent rural conditions (0.11 ~g/m3) and
urban conditions (0.89 ~g/m3) appear realistic in view of the levels presented
in Section 8.2.1. The levels selected for lead concentrations in dust and dirt
(800, 1600, 2400, and 3000 ppm) were selected in order to include the range of
mean values reported from samples taken from varying indoor and outdoor environ-
ments. The specific studies are detailed in Section 8.4.3 and indicated in
footnote "k" of Table 8.30; It is believed that these concentrations are more
realistic than use of the 11,000 ppm dust lead concentration reported by Lepow,
et al., (1975), which has been used in some estimations. In support of this,
Lepow, et al., actually found 2,400 ppm lead in the dust and dirt sampled di-
rectly from the children's hands. As noted earlier, it was assumed that ab-
sorption from dust and dirt is only three-quarters of that of the lead con-
tained in food, or about 30-31 percent.
As shown in Table 8.30, food contributes a significant quantity of daily
absorbed lead. Depending on the concentration of lead present in dust and
dirt, food ranks either first or second (behind dust/dirt) as a source of lead
body burden. The absolute contribution of water and air is fairly constant and
low over the three environmental conditions depicted. Water contributes approx-
imately 11.6 ~g Pb/day and air, from 0.21 to 2.8 ~g Pb/day at air lead levels
up to the ambient air quality standard. The contribution from dirt and dust
varies by a factor of four or more, (in the example from 24.9 to 99.5 ~g Pb/day)
depending on the assumptions made about the lead content of ingested dust and
dirt. Consequently, it appears that in more heavily contaminated environments
where lead in housedust and outdoor dirt/dust averages over approximately
1535 ppm, this source will provide equal or greater input than food to the
"lead body burden of non-pica young children." This statement should, however,
370
-------
TABLE 8.30 THE RELATIVE CONTRIBUTION OF VARIOUS MEDIA TO LEAD INTAKE
AND ABSORPTION IN 3 YEAR-OLD CHILDREN
==r._~ -
Daily Lead Daily Lead
Lead Intake, Percent Absorption,
Media Daily Intake Concentration jJg/day absorbed ,jJg/day
Food 1340 g a 0.1-0.2 ppm U5b 41.5c 47.7
(variable)
Water 1.4R.d 20I'g/~e 28 41.5f 11.6
3 4.7 m3g 3 40h
Rural O.lllJg/m Air O.11lJg/m 0.52 0.21
800 ppm k 80 31.1 j 24.9
Dust/dirt 100 mg i 1600 ppm 160 II 49.8
2400 ppm 240 II 74.6
3200 ppm 320 II 99.5
lJ,) Food 1340g 0.1-0.2 ppm 115 41.5 47.7
-...J (Variable)
I--'
Water .1.4R. 201Jg/9 28 41.5 11.6
3 Air 4.7m3 3 4.2 40 1.7
Urban 0.89IJg/m . 891Jg/m
800 ppm 80 31.1 24.9
1600 ppm 160 II 49.8
Dust/dirt 100 mg 2400 ppm 240 II 74.6
3200 ppm 320 II 99.5
Food 1340 g 0.1 - 0.2 ppm 115 41.5 47.7 .
(Variable)
Water 1.41 20IJg!R. 28 41.5 11.6
4.7m3 3 2.8
At Ambient Air Air 1.5IJg/m 7.05 40
Quality
Standard 800 ppm 80 31.1 24.9
1600 ppm 160 II 49.8
Dust/dirt 100 mg 2400 ppm 240 II 74.6
3200 ppm 320 II 99.5
-------
TARLE 8.10.
(Continued)
Notes:
a1340g intake figure based on averaging FDA Total Diet Studies estimates for 1-2 year
old children (1290g/day) and 3-5 year old children (1390g/day). (See Table 8.33).
b
l15ug/day, Battelle estimate based 00 average of FDA Total Diet Studies for male and
female children 1-2 years of age (107ug/day) and children 3-5 years of age (123ug/day)
c4l.5 percent absorption rate based on Ziegler, et al., (1978) estimate.
d
1.4 liter per day intake based on 3 year old child as described by Drill, et al., (1978).
UJ
......
N
e20ug/t selected because at least 80 percent of households surveyed had tapwater below this
level (McCabe, et aI, 1976; U.S. Environmental Protection Agency, 1976).
f
41.5 percent absorption rate observed for foods by Ziegler, et aI, assumed to apply to
liquids as well.
g4.7m3/day estimated respiratory volume based on ICRP (1959)
h
40 percent absorption rate based on estimate by National Academy of Sciences, (1972).
ilOO mg/day intake based on estimate by Lepow, e.t aI, (1974).
j31.l percent based on assumption that gastrointestional absorption of lead from dust and dirt
is 75 percent as efficient as that from food.
k
Estimates of lead present in dirt and dust are representative of the range of means observed by the in-
vestigators below:
600 ppm
1200 ppm
1200 ppm
1386 pprn
658 .pm
2000 I 1m
2344 )pm
indoor house duse (clean
indoor house dust (aver.
outdoor play area dirt
outdoor street dust
outdoor street dust
indoor louse I ust (core
outdoor street. ust
area)
Boston and Manchester)
Solomon and Natusch, 1977
Kreuger, 1972
Lepow, et aI, 1974
Hunt, et a1., 1971
Hunt, et a1, 1971
Kreuger, 972
(unt, et a., .97.
city Boston)
-------
be qualified by suggesting that the above estimate was based on ingestion of
100 mg/day of dust and dirt and an absorption rate of 31.1 percent. Although
based on empirical studies (Lepow, et al., 1975), it is unknown whether this
seemingly high level of dust and dirt ingestion is representative of normal
children. (Lepow's estimate was based on observation of relatively disadvan-
taged urban children, all having blood leads over 40 ~g/dl).
Table 8.31 shows the total daily lead absorption under the same environ-
mental conditions described for Table 8.30. Once again, it is seen that food
contributes approximately 30-57 percent of total absorbed lead. Likewise,
dust/dirt contributes approximately 29-63 percent of total absorbed lead.
The relative contribution of food and water vary inversely with lead concen-
tration in dust and dirt. The contribution of air appears rather low and uni-
form, however, it should be realized that lead in air (along with weathering of
paint, etc.) contributes to dust/dirt lead. Therefore, the entries in the air
columns probably underestimate the full effects of lead in ambient air.
8.6.6
Recommendations Concerning Safe Levels of Dietary Lead
No evidence exists at the present time of any effect of lead as a benefi-
cial trace element in human nutrition. Various estimates have been reported in
Section 8.6.4 of the total human exposure to lead from food sources.
Data from the Total Diet Studies and the Heavy Metals in Foods Survey pro-
vide an estimate of daily lead intake for an American adult between 90-254 ~g/
day (U. S. Department of Health, Education, and Welfare, 1977). Consensus from
other types of studies places intake in the range of 100-400 ~g lead/day
(National Academy of Sciences, 1972). This intake is well below that which
produces toxicity in adults. Three hundred micrograms of lead per day has been
found to be a level of ingestion at which positive balance does not occur in
adults (Kehoe, 1961; U. S. Department of Health, Education, and Welfare, 1975).
The World Health Organization (WHO) has recommended 3.0 milligrams per week
(429 ~g/day) as an acceptable total level of intake for adults. An intake of
two hundred fifty four ~g/day reported by'the FY 1974 Heavy Metals in Foods
Survey is 59 percent below this recommendation. Sufficient variability in in-
take levels shown by balance studies and institutional studies is suggestive of
the possibility that some segments of the population may be consuming lead at
levels much nearer Maximum Permissible Daily Intake (MPDI) of 429 ~g. No pop-
ulation-based studies are available to confirm or deny this speculation,
however. It may be concluded that present levels of dietary intake among the
general population do not exceed maximum permissible intake as established by
WHO but the margin of safety between present average levels of intake and the
MPDI is not large. Certain segments of the population, particularly those
exposed to substantial quantities of airborne lead (especially from occupation),
receive additional ingested lead from air, and are possibly consuming lead at
or above the MPDI of 429 ~/day.
Studies aimed at determining daily dietary lead intake of normal, non-pica
children include studies of replicate diets, Total Diet Studies (FDA's Total
Diet Studies and Heavy Metals in Food surveys), institutional diet studies and
estimates based on fecal lead excretion.
373
-------
TABLE 8.31.
TOTAL DAILY LEAD ABSORBED BY 3 YR-OLD NON-PICA CHILD AND PERCENTAGE
ATTRIBUTABLE TO VARIOUS MEDIA UNDER VARYING ENVIRONMENTAL CONDITIONSa
Rural Conditions 3 Urban Conditions 3 Ambient Air Quality Standard
Air Lead = 0.11 ~g/m Air Lead = 0.89 ~g/m Air Lead = 1.5 ~g/m3
Total Daily Lead Percent Contribution Total Daily Lead Percent Contribution of Total Daily Lead Percent Contribution
Absorption under of Various Media Absorption under Various Media Absorption under of Various Media
Lead Cone. in Various Levels of Dust/ Various Levels of Dust/ Various Levels of Dust/
Dust/Dirt, Lead in Dust and Dirt Food Water Air Lead in Dust and Dirt Food Water Air Lead in Dust and Dirt Food Water Air
.PJ\m Dirt, j.1gb Dirt, Ugb Dirt. pgb
w 800 84.4 29 57 14 <1 85.9 29 55 14 2 87.0 29 55 J3 3
'"-I
.p.. 1600 109.3 46 44 10 d 110.8 45 43 10 2 111. 9 45 43 10 2
2400 134.1 56 36 8 <1 135.6 55 35 9 1 136.7 55 35 8 2
3000 159.0 63 30 7 <1 160.6" 62 30 7 1 161.6 62 30 7 1
Notes:
aSee Table 8.30 for assumptions underlying these calculations.
bSum of Column 6 of Table 8.30 for each of 4 lead levels in dust and dirt (i.e., : 800, 1600, 2400 and 3,000 ppm)
-------
Kolbye, et al., (1974) cited a dietary survey of 333 infants in the United
States, aged 1 to 12 months, in which the estimated dietary lead intake was 93
plus or minus 36 micrograms per day. Similarly, the U. S. Department of
Health, Education and Welfare (1975) has provided the following estimates for
infants and toddlers through 2 years of age:
Age
Estimated ~g/day Dietary Lead Intake
2 months
6 months
1 year
2 years
79
63
100
115
These estimates given above are based on survey data as well as on other
sources discussed in more detail in the FDA report (U. S. Department of Health,
Education, and Welfare, 1975). Based on examination of various surveys and
methods, the general consensus is that normal children aged 1-3 consume, ap-
proximately, 100-130 ~g of lead per day (Chisholm and Harrison, 1956; Barltrop
and Killala, 1967; Mitchell and Aldous, 1974; Mahaffey, et al., 1975; U. S.
Department of Health, Education, and Welfare, 1977).
The most significant inference to be drawn from these figures is that
children receive a much higher dietary dose of lead than adults on a per weight
basis. One survey showed that a diet consisting mostly of infant foods sup-
plied 120 ~g lead per day for a 6 month old child. As the child gets older and
the diet consists more and more of adult table foods, lead intake actually de-
creases slightly (97-100 ~g/day) due to the lower average lead content of adult
foods. (Mahaffey, et al., 1975). If 200 ~g/day is accepted as the average
adult intake, then children under 2 years old receive as much as 1/2 of the
adult dose.
The greater lead intake of infants, compared with adults, on a unit-body-
weight basis, probably is related to infant's higher caloric and water require-
ments. It is not known whether the apparent greater intake is accompanied by a
correspondingly greater total output; the critical balance studies have not
been conducted, as they have in adults (National Academy of Science, 1972).
Several studies do provide evidence of a higher rate of absorption from the
alimentary tract in children. According to King (1971) and Alexander, et al.,
(1973), absorption rates in infants and young children may be as high as 50
percent compared to 5-10 percent for adults. Ziegler's recent (1978) studies
indicating an average of 41.5 percent absorption confirm this high absorption
for young children. Thus, the higher dietary dosage may take on added signi-
ficance when coupled with a higher absorption rate.
Few official recommendations exist for acceptable lead intake levels in
children. King (1971) reported that an ad hoc committee of the Department of
Health, Education, and Welfare has suggested 300 ~g/day for all sources as a
maximum permissible intake for children. However, this recommendation was made
before it was established that children absorb greater amounts of lead from the
diet than adults. Lin-Fu (1972) estimated that the quantity of lead producing
375
-------
toxicity in children to be about 1000 ~g/day for children 4-6 months of age.
Barltrop (1972) has recommended a maximum permissible daily intake (MDPI) of
93-180 ~g/day.
The mean intake estimated by the FDA Heavy Metals in Foods survey is below
the 300 ~g/day maximum permissible total intake proposed by King (1971). Data
from the same survey (U. S. Department of Health, Education, and Welfare, 1975)
have shown reason to doubt that lead in foods is normally distributed (i.e.
there are substantially more high intakes than would be expected on the basis
of a normal distribution). Occasional intakes of very high levels of lead in
foods can and do occur. These occasional high findings greatly affect the
estimated mean intake and if they can be reduced, the average exposure will
substantially decrease. Also, it should be re-emphasized that the estimated
dietary dosages do not apply to children with pica, who in eating a single chip
of leaded paint, ingest many times the recommended maximum daily dose.
8.6.7
Effects of Reducing Adventitious Lead
in Canned Foods on Dietary Lead Intake
This section describes the methods developed to estimate the effects on
lead intake of reducing adventitious lead in canned foods. Estimates of cur-
rent daily dietary lead intake are developed for various age-sex groups. These
estimates are based on inventorying consumption of specific food commodities,
determining the average amount of lead present in each commodity, and calculat-
ing daily lead intake by constructing a typical daily diet for various
demographic groups. The amount of lead intake attributable to specific commod-
ities/groups is tabulated in order to pinpoint those foods which contribute
most significantly to total daily intake. (These tabulations do indeed verify
that canned foods supply inordinate amounts of lead per unit.) The reduction
in dosage, net and percentage, which would occur in the event of reducing lead
in canned foods by one-half or two-thirds, is calculated for the various age-
sex groups for which dietary data are available. Selection of these two reduc-
tion levels was based on two assumed possibilities. The maximum reduction of
two-thirds is, essentially, equivalent to the total elimination of adventitious
lead in canned food (since two-thirds of the total lead content is estimated to
result from lead pickup). A less rigorous re~uction assumes that total elimi-
nation of adventitious lead from canned food may not be practical, but that a
75 percent reduction in lead pickup can be achieved, equivalent to a 50 percent
(0.75 x 0.667) overall reduction. For technical and economic reasons developed
in Chapter 9, the 50 percent overall reduction is probably the more realistic
case.
8.6.7.1
Methods for Deriving Food Consumption Levels--
Data from the Household Food Consumption Survey (from the U. S. Department
of Agriculture, Agriculture Research Service, 1966) were modified to' produce
the data in Tables 8.32 to 8.36. The manipulations and assumptions made, de-
riving the information presented here from the published reports, are described
below.
376
-------
TABLE 8.32
ESTIMATED LEAD CONTENT OF VARIOUS FOODS
Lead
Content
Food Class Specific Food Commodity ppm Basis for Estimate
Hilk Hilk, fresh 0.021 FDA (1975b)
Hilk, processed, canned 0.12 FDA (1975a)
Hilk, processed, uther 0.07 Reith ,et al.,
(1974)
Cream 0.068 FDA (1975b)
Cheese and mixtures 0.12 MAFF (1975)
Eggs 0.174 FDA (1975b)
Heat Beef, canned 0.75 MAFF (1975)
v.J Beef, other 0.2 MAFF (1975)
-....J Pork, canned 0.13 Reith~ et al..I
-....J
(1974)
Pork, other 0.15 FDA (1975b)
Poultry 0.127 FDA (1975b)
Fish, canned 0.500 FDA (1975a)
Fish, other 0.500 FDA (1975a)
Other and mixtures, canned 0.28 CHI-NCA (1977b)
Other and mixtures, other 0.198 FDA (1975b)
Nuts and Oils Legumes and nuts 0.26 FDA (1975a)
Fats and oils 0.013 FDA (1975b)
Breads Bread 0.084 FDA (1975b)
Other baked goods 0.10 Bogen (1972)
Cereals, pastes 0.107 FDA (1975b)
Sugar Products Sugar 0.031 FDA (1975b)
Candy, jam, etc. 0.07 Reith, et al.)
(1974)
Beverages Tea 0.20 Reith,et al.l
(1974)
Coffee 0.07 Reith,et al.,
(1974)
-------
TABLE 8.32
(Continued)
Food Class
Beverages (cont'd)
lJ.)
.......
ex>
Tomatoes and Vegetables
Potatoes and Fruits
Specific Food Commodity
Lead
Content
ppm
Basis for Estimate
Ewing (1978)
Ewing (1978)
FDA (1975b)
CMI-NCA (1977b)
Reith, et al.J
(1974)
Reith) et al.,
(1974)
Reith,et al.,
(1974)
Schroeder (1974)
Schroeder (1974)
Reith, et al.)
(1974)
FDA (1975b)
CMI-NCA (1977a)
FDA (1975b)
CMI-NCA (1977b)
FDA (1975a)
FDA (1975b)
CMI-NCA (1977a)
CMI-NCA (1977b)
FDA (1973)
CMI-NCA (1977b)
CMI-NCA (1977a)
FDA (1975b)
FDA (1975b)
CMI-NCA (1977b)
FDA (1975a)
Cola,
Cola,
Fruit
Fruit
Other
canned a
other b
drinks, canned
drinks, other
soft drinks, canned
0.15
0.08
0.251
0.03
0.02
Other soft drinks, other
0.02
Beer, canned
0.17
Beer, other
Wine
Other alcoholic drinks
0.10
0.35
0.05
Tomatoes, canned
Tomatoes, other
Tomato juice, canned
Citrus, canned c.
Citrus, 'other
Citrus juice, canned
C. .. th d
1trus JU1ce, 0 er
e
Dark green vegetables, canned
Dark green vegetables, other
e
Deep yellow vegetables, canned
e
Deep yellow vegetables, other
f
Potatoes, canned
Potatoes, other
Other vegetables, canned g
Other vegetables, other
0.710
0.08
0.338
0.09
0.04
0.135
0.02
0.44
0.05
0.44
0.09
0.10
0.05
0.48
0.11
-------
TABLE 8.32
(Continued)
Food Class
Specific Food Commodity
Lead
Content
ppm
Basis for Estimate
Potatoes and Fruits
(cont'd)
Other
Other
Other
Other
Other
Other
vegetable juice, canned
vegetable juice, other
fruits, canned
fruits, other
fruit juice, canned h
fruit juice, other
0.215
0.04
0.346
0.04
0.09
0.04
W
--..J
-0
FDA (1975b)
CMI-NCA (1977b)
FDA (1975b)
FDA (1975a)
CMI-NCA (1977b)
CMI-NCA (1977a)
a For "canned" vs. "other" in
since this is the basis for
tially as bottled products.
bAssumed value of 1/2 of the canned cola lead content.
beverages, only lead-soldered cans were considered as canned
differentiation. Cans which do not leach lead are treated essen-
cBased on canned grapefruit juice.
dBased on fresh orange juice.
eBased on mean of vegetables in the category.
fAssumed value of twice that of fresh.
g Based on corn.
hBased on apple and grapefruit juices.
-------
TABLE 8.33 FOOD CONSUMPTION IN GRAMS PER DAY FOR VARIOUS AGE-SEX GROUPS
Male/Female, Male/Female, Male/Female, Male/FemalE', Male, Female, Male, Female, Male, Female,
Fnod Class & Substance Under 1 Year 1-2 Years 3-5 Years 6-8 Years 15-17 Years 15-17 Years 20-34 Years 20-34 Years 55-64 Years 55-64 Years
MILK
Nilk, fresh 515.04 438.08 376.66 398.12 444.74 283.42 235.32 150.96 150.22 111. 74
Milk, processed, canned 47.41 40.33 34.67 36.65 40.94 26.09 21.67 13.90 13.83 10.29
Nllk, processed, other 133.55 113.59 97.67 102.93 115.32 73.49 61.02 39.14 38.95 28.97
Cream 18.0 23.0 31.0 40.0 49.0 34.0 33.0 30.0 39.0 35.0
Cheese and mixtures 1.0 5.0 4.0 5.0 11.0 8.0 12.0 11.0 15.0 ' 14.0
Eggs 17.0 28.0 23.0 23.0 . 42.0 25.0 55.0 27.0 51.0 33.0
w ~IEATS
(;f:J
0 Ueef, canned 0.08 0.26 0.37 0.42 0.83 0.64 1.21 0.71 0.89 0.59
Beef, other 6.92 23.74 33.63 37.58 74.18 57.36 108.79 63.29 80.11 53.41
Pork, canned 0.17 1.18 1.68 1.85 3.44 2.35 4.12 2.25 3.82 2.06
Pork. other 3.83 26.82 38.32 42.15 78.56 53.65 93.88 51. 75 87.18, 46.94 ,
Poultry 3.0 11.0 16.0 25.0 27.0 18.0 32.0 21.0 28.0 25.0
Fish. canned 0.0 0.69 1.16 1.62 2.31 2.08 3.23 2.08 4.16 2.08
Fish. other 0.0 2.31 3.85 5.38 7.69 6.92 10.77 6.92 13.84 6.92
Other and mixtures, 4.42 4.82 4.02 5.36 9.11 6.57 10.59 6.43 6.83 5.90
canned
Other and mixtures, 29.58 33.18 28.98 36.64 62.89 46.43 74.41 46.57 55.17 44.10
other
NUTS & OILS
Legumes and nuts 13.0 16.0 28.0 36.0 47.0 29.0 13.0 24.0 25.0 17.0
Fats alld oils 2'.0 12.0 18.0 22.0 39.0 22.0 15.0 23.0 35.0 24.0
BREADS
Bread 5.0 39.0 63.0 77.0 135.0 79.0 120.0 71.0 107.0 67.0
Other baked goods 4.0 29.0 43.0 54.0 85.0 59.0 77.0 52.0 75.0 51.0
Cereals and pastes 48.0 75.0 83.0 84.0 93.0 65.0 84.0 75.0 73.0 52.0
-------
TABLE 8.33 (Continued)
Male/Female, Male/Female, Male/Female, Male/Female, Male, Female, ~la1e, Female, Male, Female,
Food Class & Substance Under 1 Year 1-2 Years 3-5 Years 6-8 Years 15-17 Years 15-17 Years 20-34 Years 20-34 Years 55-64 Years 55-64 Years
SUGAR PRODUCTS
Sug;tr 1.0 8.0 12.0 14.0 13.0 10.0 17.0 13.0 17.0 9.0
Candy, jam, etc. 9.0 22.0 31.0 33.0 .46.0 31.0 27.0 22.0 30.0 22.0
BEVERAGES
Tea 2.0 18.0 33.0 36.0 91.0 76.0 148.0 119.0 100.0 109.0
Coffee 0.0 2.0 5.0 4.0 59.0 65.0 422.0 400.0 558.0 522.0
Cola, canned 0.12 2.13 3.47 4.50 8.91 7.5 7.16 5.97 2.34 2.03
Cola, other 2.28 38.74 63.24 82.04 162.38 136.74 130.47 108.82 42.74 37.04
w Fruit drinks, canned 0.04 0.63 1.03 1.35 2.65 2.23 2.13 1. 78 0.70 0.61
00
I-' Fruit drinks, other 0.68 11.54 18.84 24.52 48.37 40.73 38.86 32.41 12.73 11.03
Other soft dr.inks, 0.05 0.78 1.27 1.65 3.26 2.75 2.62 2.19 0.86 0.74
canned
Other soft drinks, 0.83 14.18 23.15 30.03 59.44 50.05 47.76 39.87 15.64 13.56
other
Beer, canned 0.0 0.0 0.0 0.0 0.0 0.0 6.15 1.31 4.12 0.68
Beer, other 0.0 0.0 0.0 0.0 0.0 0.0 112.17 23.92 75.05 12.37
IHne 0.0 0.0 0.0 0.0 0.0 0.0 7.34 1.57 4.91 0.81
Other alcoholic drinks 0.0 0.0 0.0 0.0 0.0 0.0 10.34 2.20 6.92 1.14
Tu~~TOES & VEGETABLES
Tomatoes, canned 0.23 2.71 2.94 4.52 6.56 5.65 8.59 7.22 6.78 7.01
Tomatoes, other 0.56 6.71 7.27 11.18 16.21 13.98 21. 24 17 .90 16.77 17.33
Tomato juice, canned 0.21 2.58 2.79 4.30 6.23 5.37 8.17 6.88 6.45 6.67
CltrllR, cmancd 0.21 0.46 0.52 0.53 0.72 0.59 0.64 0.52 0.64 0.73
Citrus, other 13.06 28.48 32.04 32.M 44.5J. 36.19 39.16 35.65 39.16 45.10
Citrus juice, canned 4.36 9.53 10.72 10.92 14.89 12.11 13.10 10.92 13.10 15.09
Citrus juice, other 4.37 9.53 10.72 10.92 14.89 12.11 13.10 10.92 13.10 15.09
Dark greer. vegetables, 0.31 0.61 0.46 0.77 0.92 1.22 1.07 1.22 1.22 1.07
canned
Dark green vegetables, 1.69 3.39 2.54 4.24 5.08 6.78 5.93 6.78 6.78 5.93
other
~
-------
TABLE 8.33 (Continued)
Male/Female, ~Iale/Fema Ie, Male/Female, Male/Female, Male, Female, Male, Female, ~Iale, Female,
Food Class & Substance Under 1 Year 1-2 Years 3-5 Years 6-8 Years' 15-17 Years 15-17 Years 20-34 Years 20-34 Years 55-64 Years .55-64 Years
TOMATOES & VEGETABLES ------ - --.-- --.------.-- --~------ -. ------"------- ---".
(continued)
Deep yellow vegetables, 1.30 0.65 0.65 0.76 0.97 0.65 1.08 0.74 1.40 1.08
canned
Deep yellow vegetables, 10.70 5.35 5.35 6.24 8.03 5.35 8.92 6.26 11.60 8.92
othel-
w
00
N POTATOES & FRUITS
Potaotes, canned 0.10 0.58 0.73 0.90 1.55 0.85 1.63 1.06 1.29 0.82
Potatoes, other 5.90 33.42 42.27 52.10 89.45 49.15 9/;.37 54.94 74.71 47.18
Other vegetables, 14.28 13.71 13.71 16.28 26.57 21.14 32.28 22.90 28.58 22.85
canned
Other vegetables, 34.97 33.57 33.57 39.87 65.04 56.75 79.03 55.98 69.98 55.95
other
Other vegetable juice, 0.75 0.72 0.72 0.85 1.39 1.11 1.69 1.12 1.50 1.20
canned
Other fruits, canned 21. 99 19.63 19.83 22.18 23.16 22.18 18.85 12.46 21. 79 18.06
Other fruits, other 81. 72 72.97 73.70 82.46 86.11 82.46 70.05 46.42 81.0 67.13
Other fruIt juice, 7.56 6.75 6.81 7.62 7.96 7.62 6.48 4.71 7.49 6.21
canned
Other fruit juice, 0.73 0.65 0.66 0.74 0.77 0.74 0.62 0.41 0.72 0.60
other
-------
Report No.1, entitled "Food Consumption of Households in the United
States," gives detailed dietary information at the household level. The infor-
mation is described for several different regions of the United States, degrees
of urbanization (urban, rural farm, and rural non-farm) and household incomes.
Data which have been aggregated across some or all of these parameters are tab-
ulated as well.
Report No.6 gives specific household food consumption data (in grams per
day) for each food, separated according to its form (e.g. potatoes--fresh, po-
tatoes--canned, etc.) This information is sufficient to derive, for' any de-
sired demographic group, a distribution of specific food forms for any given
food. For example, assume a certain (demographic) household eats potatoes as
follows: 60 g/day fresh, 27 g/day frozen, and 13 g/day canned. This is equiv-
alent to a distribution of 60 percent fresh, 27 percent frozen, and 13 percent
canned. This information is essential in merging this household-level data
with individual-level data.
Report No. 11 (Food and Nutrient Intake of Individuals in the United
States) is concerned with individual's diets. Demographic subdivisions are
again provided, though in less detail, with the additional feature of diet
specification by sex and age group.' This provides the average grams per day
intake for specific age-sex groups, divided/aggregated according to a variety
of demographic descriptions.
This information is not, however, supplied in the same detail as the
household data in Report No.1. First, there is less specificity of the food
types. For example, the category "tomatoes": includes all forms of whole to-
matoes, tomato sauce, and tomato juice. The second difficulty involves fail-
ure to specify the form (i.e., fresh, frozen, or canned) of the product.
The household data were merged with the individual data in the following
manner (as illustrated for tomatoes): Report No.1 noted a household consump-
tion of 1.09 g/day fresh whole tomatoes, 0.44 g/day canned tomatoes and sauce,
and 0.42 g/day canned juice for an average income-region-urbanization house-
hold. This indicates that 78.5 percent of the tomatoes eaten were whole/sauce
and 21.5 percent were in the form of juice. Furthermore, 28.8 percent of the
whole/sauce products were canned while 100 percent of the juice was canned.
Note that these proportions are based on the entire household's consumption.
Consultation of Report No. 11 states that a 20-to-34-year-old male (aver-
aged over all incomes, urbanizations, and regions) eats 38 g of tomato
products daily. Assuming his tomato intake is in the same relative proportions
as the entire household, the above percentages are utilized. Thus, 78.5 per-
cent of 38 g (29.83 g) is eaten daily as whole tomatoes or sauce. Of these
29.83 g, 28.8 percent, or .8.59 g, are canned and 21.24 g are not canned.
Finally, 21.5 percent of the 38 g eaten daily is juice, all of which is canned
(8.17 g day). This exemplifies the method employed for all the components of
the diet.
In most cases, the basic nature of the product did not have to be
383
-------
extrapolated, e.g., meat did not have to be divided into beef, pork, etc.,
based on household averages since Report No. 11 supplied the meat and source.
In all cases, however, the dichotomy of "canned" versus "not canned" required
extrapolation. The only source used for extrapolation purposes, aside from the
Household Food Consumption Survey Report No.1, was a National Soft Drink Asso-
ciation (1970) report on canned beverages. This supplied the proportion of
soft drinks and beer in bottles and several types of cans.
The potential sources of inaccuracy in the above method should be noted
explicity. The food consumption survey' data are quite old (1965-1966) and are
in the process of being updated. In certain instances, where there are known
changes in consumption patterns (e.g., the recent dramatic decline in the use
of evaporated milk among infants), the changes of the past decade could be sub-
stantial. Another concern is the accuracy of assuming that all members of a
household eat food items in the same proportions. For most adults, this may be
reasonable, but deviations would be expected among extremely young children and
perhaps among the elderly. These potential inaccuracies cannot be quantified
but should be considered when evaluating the data presented. Unfortunately,
the updated data being compiled by FDA are still in process of evaluation and
verification, and have not yet been released, and were not available to this
study.
8.6.7.2
Daily Dietary Lead Intakes from Different
Foods for Various Age-Sex Groups--
Daily lead concentration and total daily consumption of various foods for
several age-sex groups are presented in Tables 8.32 and 8.33. Lead content was
multiplied by daily consumption in grams for each specific type of food to ob-
tain average daily lead intake. Details of these calculations for each age-sex
group are contained in Appendix A (Tables A-I through A-lO). These values were
also calculated for the same age-sex group among low income households (incomes
less than $3,000 per year). These values, however, were not sufficiently dif-
ferent from those based on the aggregate of all incomes to warrant their
separate consideration.
Tables A-I through A-lO also show the effects of reducing the lead in
canned foods by one-half or two-thirds. Data for the various age-sex groups
are summarized in Table 8.34. Distribution by age of amount of food ingested
daily is shown in Figure 8.16 for males and in 8.17 for females. The reduc-
tions in daily lead intakes resulting from these decreases are summarized, by
food group, in Table 8.35 for children and in Table 8.36 for adults.
As can be seen upon inspection of Table 8.34 and Figures 8.16 and 8.17,
males 20-34 years old have the largest daily lead intake. The distribution of
lead intake by age is similar in shape for males and females. However, the
values for adult females are lower than those of the corresponding adult male
age group. Also, the difference between female age groups is less than it is
between corresponding male groups. The largest absolute reduction in daily
lead intake is also in the male 20-34-year-old group, which is to be expected,
due to the fact that this group originally had the largest intake. The largest
384
-------
TABLE 8.34
DAILY DIETARY INTAKE OF LEAD FOR VARIOUS AGE-SEX
GROUPS AND THE EFFECT OF REDUCING LEAD IN CANNED
FOODS BY ONE-HALF OR TWO-THIRDSa
With Lead in With Lead in
Normal Canned Food Canned Food
Reduced by 1/2 Reduced by 2/3
Daily Daily Reduction, Daily Reduct10n,
Intake ,Jig Intake,j.lg Percent Intake,)lg Percent
Male/Female,
Under 1 year 75.42 63.47 15.8 60.04 20.4
Male/Female,
1-2 years 107.48 94.09 12.5 89.56 16.7
Male/Female
3-5 years 123.02 109.79 10.8 105.35 14.4
Male/Female,
6-8 years 143.60 127.80 11.0 122.20 14.9
Male,
15-17 years 222.64 200.95 9.7 193.73 13.0
Female,
15-17 years 168.03 150.63 10.5 143. 71 14.6
Male,
20-34 years 273.52 247.73 9.4 239.26 12.5
Female,
20-34 years 190.36 173.94 8.6 168.46 11.5
Male,
55-64 years 236.03 216.12 8.4 209.06 11.4
Female,
55-64 years 183.02 166.22 9.2 154.46 15.6
a
Source:
Battelle-Columbus estimates.
385
-------
TABLE 8.35.
REDUCTION IN DAILY LEAD INTAKE FOR CHILDREN FROM VARIOUS FOOD CLASSES
a
AFTER ELIMINATION OF 1/2 OR 2/3 OF THE LEAD IN CANNED FOODS
Age-Sex Groups
Proportion Hales/Females, Hales/Females, Males/Females, Males/Females,
of Under 1 Year 1-2 Years 3-5 Years 6-8 Years
Food Lead lJg Percent pg Percent lJg Percent lJg Percent
Group Removed Reduction Reduction Reduction Reduction Reduction Reduction Reduction Reduction
Milk 1/2 2.85 ( 9.7) 2.42 ( 8.3) 2.08 ( 8.2) 2.20 ( 8.1)
2/3 3.79 (13.0) 3.23 (11.1) 2.77 (10.9) 2.93 (10.8)
Meats 1/2 0.66 ( 6.9) 1.03 ( 5.1) 1.12" ( 4.6) 1.43 ( 4.8)
2/3 0.87 ( 9.2) 1.43 ( 7.2) 1.48 ( 6.1) 1.91 ( 6.4)
w
CX) Nuts, Oils, 1/2 0.0 ( 0.0) 0.0 ( 0.0) 0.0 ( 0.0) 0.0 ( 0.0)
'"
Breads, and 2/3 0.0 ( 0.0) 0.0 ( 0.0) 0.0 ( 0.0) 0.0 ( 0.0)
Sugar Products
Bev€.rages 1/2 . 0.01 ( 2.4) 0.25 ( 3.1) 0.41 ( 2.9) 0.53 ( 3.2)
2/3 0.02 ( 3.2) 0.33 ( 4.2) 0.55 ( 4.0) 0.70 ( 4.3)
Tomatoes and " 1/2 0.78 (23.9) 2.34 (32.5) 2.51 (32.6) 3.43 (34.1)
Vegetables 2/3 1.13 (35.0) 3.12 (43.3) 3.35 (43.5) 4.90 (48.7)
Potatoes and 1/2 7.62 (33.6) 7.36 (32.0) 7.14 (31. 0) 8.22 (30.7)
Fruits 2/3 13.10 (42.3) 9.81 (42.6) 9.52 (41. 3) 10.96 (40.9)
Totals 1/2 11.95 (15.8) 13.39 (12.5) 13.24 (10.8) 15.81 (11.0)
2/3 15.38 (20./1) 17.91 (16.7) 17.67 (14.4) 21.40 (14.9)
8Source: Battelle-Columbus estimate
-------
TABLE 8.36.
REDUCTION IN DAILY LEAD INTAKE FOR ADULTS FROM VARIOUS FOOD CLASSES
AFTER ELIMINATION OF 1/2 or 2/3 OF THE LEAD IN CANNED FOODS a
Age-Sex Croups
Proportion Hales, Females, Hales, Females, Males, Females,
of 15-17 Years 15-17 Years 20-34 Years 20-34 Years 55-64 Years 55-64 Years
Food Lead 11& Percent 118 Percent 118 Percent 118 Percent IIg Percent IIg Percent
Croup Removed Reduction Reduction Reduction Reduction Reduction Reduction Reduction Reduction Reduction Reduction Reduction Reduction
W Milk 1/2 2.46 ( 7.2) 1.31 ( 6.0) 1.30 ( 5.1) 0.84 ( 5.3) 0.83 ( 4.0) 0.72 ( 4.6)
CXI 2/3 3.27 ( 9.6) 2.09 ( 9.6) 1.73 ( 6.9) 1.11 ( 7.1) 1.13 ( 5.4) 0.92 ( 5.9)
'J 1/2 ( 4.7) 1.83 ( 4.8) 1.40 ( 2.2) 1.83 ( 4.7) 2.58 ( 4.6) 1.70 ( 4.6)
.lel1ts 2.39
213 3.18 ( 6.2) 2.44 ( 6.4) 2.41 ( 3.7) 2.44 ( 6.2) 3.44 ( 6.2) 2.26 ( 6.2)
Nuts, Oils 1/2 0.0 ( 0.0) 0.0 ( 0.0) 0.0 ( 0.0) 0.0 ( 0.0) 0.0 ( 0.0) 0.0 ( 0.0)
Bread's, and 2/3 0.0 ( 0.0) 0.0 ( 0.0) 0.0 ( 0.0) 0.0 ( 0.0) 0.0 ( 0.0) 0.0 ( 0.0)
Sugar Products
Beverages 1/2 1.03 ( 2.6) 0.87 ( 2.5) 1.35 ( 1. 5) 0.80 ( 1. 2) 0.32 ( 0.4) 0.29 ( 0.5)
2/3 1.38 ( 3.4) 1.16 ( 3.4) 1.80 ( 2.0) 1.06 ( 1.6) 0.83 ( 1.1) 0.39 ( 0.6)
Tomatoes and 1/2 4.83 (34.5) 5.62 (41.9) 8.46 (39.3) 4.93 (35.6) 4.99 (34.3) 5.14 (34.5)
Vegetables 2/3 6.45 (46.0) 7.01 (52.2) 11. 28 (52.3) 6.57 (44.5) 6.65 (47.5) 6.86 (46.1)
Potatoes "ad 1/2 10.97. (29.6) 9.80 (31. 0) 11. 66 (29.6) 8.04 (29.9) 11.19 (30.2) 9.06 (30.9)
Fruits 2/3 14.62 (39.5) 13.06 (41.3) 15.41 (39.2) 10.71 (40.0) 14.92 (40.2) 18.23 (62.1)
Torals 1/2 21. 69 ,( 9.7) 17.68 (10.5) 25.79 ( 9.4) 16.43 ( 8.6) 19.91 ( 8.4) 16.81 ( 9.2)
2/3 28.91 (13.0) 24.60 (14 .6) 34.26 (12.5) 21. 90 (11.5) 26.97 (11.4) 28.56 (15.6)
aScurce: Battelle-Columbus estimate
-------
280
w
()O
00
260
240
220
200
180
CI'
:t
~ 160
c
-
c
H 140
"C
c
Q)
..J
~120
c
Q)
0100
>.
Legend
No lead removed from canned foods
- --- 1/2 lead removed from canned foods
--- 2/3 lead removed from canned foods
c
o
40
20
0
0 5 10
Figure 8.16
Daily dietary intake of males, by age
Source:
Battelle-Co .UIT)US estima:e
65
-------
280
260
240
220
200 (190.4)
c>
::1...180
Q)
.)I:
.E 160
c
H
"'0
0
~ 140
>0 (123.0)
....
l".J 0
ex> Qj 120 -
\D 0 107.5
>-
'0100
0
40
20
083.0)
-- -- - . (166.2)
- , ------~r-~
---
- - - - - -"'t (1515)
----
Legend
No lead removed from canned foods
1/2 lead removed from canned foods
2/3 lead removed from canned foods
---
o
o
25
65
5
10
15
20
30 35
Age ,years
40
45
50
55
60
Figure 8.17. Daily dietary intake of females, by age
Source:
Battelle-Columbus estimate
-------
percentage reduction can be seen in children less than 1 year old.
Across all the age-sex groups, the food groups in which the largest reduc-
tion occurs are the "tomato and vegetable" and "potato and fruit" groups. How-
ever, the fact that these groups contribute only a small percentage of the
total daily food intake must be considered. This somewhat diminishes the
effect of the large percentage reduction within these groups.
8.7
LEAD UPTAKE/BLOOD-LEAD RELATIONSHIPS
8.7.1
Relationships of Blood-Lead Levels
to Lead Exposure in Humans
Various studies indicate the body burden of lead accumulates until middle
age and perhaps beyond (National Academy of Sciences, 1972); U. S. Environment-
al Protection Agency, 1977). Although the body burden is distributed through-
out a number of organs and systems within the body, the largest portion is
concentrated in the skeletal system. This is also where the accumulation
occurs, producing a reservoir of lead in the body that is not readily exchange-
able nor biologically available under normal conditions (National Academy of
Sciences, 1972). Thus, the non-accumulating portion of the body burden of lead
is more toxicologically significant than the lead reservoir in the skeletal
system which gradually increases with age (U. S. Environmental Protection
Agency, 1977). In contrast to the relatively nonexchangeable lead reserves in
the skeleton, much of the exchangeable portion of the body burden is stored in
the soft tissues such as the liver and kidney, which are perfused with blood.
In consideration of this, the blood lead level is often used as an indicator of
the concentration of lead in soft tissues. Blood lead is, therefore, considered
to be a more useful parameter than total body burden, since it is thought to be
representative of the exchangeable portion of the body burden. Moreover, blood
is more easily accessible than tissue for biological monitoring of lead.
There have been numerous attempts to demonstrate a dose-response relation-
ship between lead dosage received from various media and blood lead. Two main
approaches have been used. The first assumes that the concentration of blood
lead is proportional to the combined level of absorption via all the modes of
exposure to lead (mainly air, food, and water). Next, the percentage of the
total inhaled and ingested lead actually absorbed by the body is calculated
under various assumptions regarding retention rates for various media. It fol-
lows that each source of exposure contributes to the concentration of blood lead
in proportion to the amount absorbed from that source. (Bell, et a1., 1978).
In general, an adult ingests, approximately, 200-300 ~g of lead per day from
dietary sources. Assuming an intake of 250 ~g of lead per day and 7.5 percent
absorption of the dose, it follows that 18.75 ~g/day would be absorbed from
diet. From.an urban atmosphere averaging 2.0 ~g/m3 of lead, an assumed respir-
atory intake of 20 m3 per day and a retention rate of 37 percent, absorption of
14.8 ~g of lead would occur. An additional 5-10 ~g per day might be absorbed
by those who smoke cigarettes. The contribution to absorbed dose from drinking
390
-------
TABLE 8.37.
GEOMETRIC MEAN AIR-AND BLOOD-LEAD VALUES
FOR 11 STUDY POPULATIONS a
Geom. mean Blood lead, )Jg/dl
air, lead, Sample
Community )Jg/m3 Geom. mean GSD Size
Los Alamos, NM 0.17 14.9 1.28 185
Okeana, OH 0.32 15.6 1.39 156
Houston, TX 0.85 12.5 1.31 186
Port Washington, NY 1.13 15.4 1.28 196
Ardmore, PA 1.15 18.0 1.38 148
Lombard, IL 1.18 13.9 1.27 146
Washington, DC 1.19 19.2 1.26 219
Rittenhouse, PA 1.67 20.6 1.33 136
Bridgeport, IL 1. 76 17.6 1.27 146
Greenwich Village, NY 2.08 16.6 1.28 139
Pasadena, CA 3.39 17.5 1.31 194
aSource: U.S. Environmental Protection Agency (1977);
Calculated from data from Tepper and Levin (1975).
water amounts to, approximately, 3 )Jg/day, assuming intake of 1.5 liters of
water at 20 )Jg/2 and 10 percent absorption. Thus, it appears that the relative
contributions of dietary (including drinking water) and atmospheric sources to
the blood lead level of a non-smoking urban adult are, approximately, 67 and 33
percent, respectively, (14.8 )Jg from air divided by 18.75 from diet and 3.0 )Jg/
day from water) Ewing and Pearson, 1974; Environmental Health Resources Center,
1973; National Academy of Sciences, 1972. The proportion contributed by diet
in children is probably closer to 75 percent (Environmental Protection Agency,
1977; Environmental Health Resources Center, 1973). Presumably, this is at-
tributable to higher absorption rates of children. Ratios of ingested to
absorbed lead may be as high as 0.5 (50 percent absorption) for infants as
391
-------
opposed to 0.05 to 0.10 observed among adults. Although empirical data are
lacking, it is probable that the absorption ratio decreases gradually through-,
out childhood.
The second type of approach used to demonstrate this dose-response rela-
tionship is the comparison of lead exposure from diet and atmosphere with the
blood lead level. Qualitatively, the concentration of blood lead increases as
exposure from any or all sources increases. Studies have shown that this is
not a constant ratio over a broad range of exposures, however. (U. S.
Environmental Protection Agency, 1977; Bell, et al., 1978; World Health Organ-
ization, 1977). The relationship appears to be linear for low exposures and
logarithmic for very high exposures (U. S. Environmental Protection Agency,
1977). In the lower ranges of atmospheric ex~osure, blood lead levels increase
0.6 to 2.0 ~g/dl blood for every 1.0 ~g per m atmospheric lead (U. S. Environ-
nental Protection Agency, 1977; Bell et al., 1978; World Health Organization,
0977). A similar quantitative relationship for dietary exposure is not well
stablished. Various studies have shown increases in blood lead from 6 to 18
~ per dl blood for every 100 ~g lead ingested daily; European data provide a
re consistent picture of this relationship. U. S. Environmental Protection
~ncy (1977) indicates that each 100 ~g Pb/day from diet contributes about 6
Pb/dl to blood lead. This relationship, in turn, implies that the mean
Jd lead level of American adults exposed to low levels of atmospheric lead
~g/m3 average annual mean) shouldobe in the vicinity of 15 ~g Pb/dl, as-
ng a total dietary intake of 250 ~g/day:
(250/100)(6 ~g Pb/dl) = 15 ~g Pb/dl
cal observation confirms that this estimate closely approximates the mean
~U lead values given for eleven study populations shown in Table 8.37.
8.7.2
Distributional Characteristics of Blood
Lead Values in General Populations
Several studies have reported that evidence of adverse health effects (e.
g., increased urinary ALA) can be detected at blood-lead levels above 40 ~g/dl
(Environmental Health Resource Center, 1973; U. S. Environmental Protection
Agency, 1977; Tepper and Levin, 1975). The inhibition of aminolevulinate de-
hydratatase (ALA-D) can be detected at blood-lead levels as low as 10 ~g/dl
(U. S. Environmental Protection Agency, 1977). In evaluating the extent to
which members of general populations exhibit blood-lead levels above these
critical levels, it is essential to investigate the distribution of blood-lead
levels in large samples of the general population unexposed to unusual sources
of lead (i.e., normal populations).
It is reasonable to assume that even though average population blood-lead
levels are well below the threshold level for adverse effects, a certain per-
centage of individuals may still be above this level depending upon the average
and standard deviation of this distribution (Schubert, et al., 1967). Allow-
ance for biological variability is a critical issue in: (1) setting standards
for toxic substances based on avoidance of adverse health effects, (2)
392
-------
evaluating the effectiveness of such standards via biological monitoring, and
(3) evaluating changes in the population parameters. Specifically, the criti-
cal question to be answered concerns the effect on high risk groups of, signi-
ficantly, lowering the average population blood-lead level. Lowering the mean
blood-lead level of the population should, theoretically, reduce the number of
individuals above a specified critical level, provided that the scandard devia-
tion and the shape of the distribution remain unchanged.
In order to develop a method for predicti~g the response of blood-lead
levels in a population to a specified reduction in lead intake, it is necessary
to consider the distributional characteristics of blood lead values for various
populations and to examine the statistical properties implied by the form of
these distributions.
The distribution of blood-lead levels is most often described as being
log-normal; that is, skewed to the right (U. S. Environmental Protection
Agency, 1977; Tepper and Levin, 1972; Yanke1, et a1., 1977). The logarithm of
a variable that is log-normally distributed will be normally distributed and
will adhere to all the assumptions and rules of any other normally distributed
variable (Schubert, et a1., 1967; Aitchison and Brown, 1963). The median is a
more useful measure of central tendency for a skewed distribution such as this
than is the arithmetic mean. Since in the case of blood-lead distribution, the
arithmetic mean will lie to the right of the median by ap amount determined by
the standard deviation, the geometric mean is a better estimate of the central
tendency. Geometric Mean (GM) is defined as ~ollows:
n
(GM) = Exp ~ (In xiJ/n]
i=l
The standard deviation of this statistic, the Geometric Standard Deviation,
(GSD) , is defined as follows:
n
(GSD) = Exp {~
i=l
2 1/2
[In(xi) - 1n(GM)] /n-1}
(Aitchison and Brown, 1963; Schubert, et a1., 1967). In the following discus-
sion and ca1ucu1ations, the geometric statistics will be used rather than
arithmetic ones.
8.7.3
Effects of Reducing Dietary Intake on Mean Blood Lead Levels
Control strategies, directed toward the elimination of lead added in can-
ning, benefit, practically, the entire population, because consumption of
canned products is so universal. Consequently, it follows that substantial re-
ductions .in dietary lead would produce reductions in blood lead proportional to
current intake of canned products. Groups of consumers with higher than aver-
age consumption of canned products, e.g., infants, the poor, the institutional-
ized, the elderly and those living in remote areas might expect the greatest
393
-------
beneficial effect.
Changes, such as those projected, can also be thought of in terms of a
shift to the left (downward) of the frequency distribution of blood-lead levels
of a population. Providing: (1) baseline data are available for the popula-
tion group of interest (i.e., geometric mean, GM, and geometric standard devia-
tion, GSD) and, (2) the shape of the distribution can be assumed to remain con-
stant, then estimates of the percentage of the population at or above any
selected "biologicaL threshold level" can be ascertained. Again, assuming that
in the event of a reduction in dietary lead intake, the distribution curve
shifts to the left with no change in shape, estimates of the percentage reduc-
.tion in individuals at or above any desired level can be deduced. Moreover,
if estimates of the size of the specific population group of interest are
available from census or other sources, the percentage reduction can be ex-
pressed in terms of an absolute number of individuals. This provides an excel-
lent criterion for judging the potential effectiveness of any anticipated
program/limitation strategy, if the necessary data for such an analysis are
available. Unfortunately, this is the exception rather than the rule, and such
calculations are not possible for other limitation candidates. Even for
dietary intake of lead, sufficient data are available only for the demographic
g~oup consisting of 20-34-year-old females. This group is used as a test case
to demonstrate the approach (Section 8.7.3.2).
8.7.3.1
Approach to Estimation--
As suggested above, it appears that on the average for adults, diet con-
tributes, approximately, 6 ~g of lead/dl for each 100 ~g of lead ingested in
the diet. Assuming that this average might be applied to an hypothetical
individual with a blood-lead level of 15 ~g Pb/dl, it follows that if his diet
contains 200 ~g of lead per day, 12 ~g/dl or 80 percent of his total blood-lead
is accounted for by dietary sources, while the remaining 3 ~g/dl or 20 percent
comes from other sources, primarily, atmospheric lead (and, possibly, cigar-
ettes).
In order to calculate the amount of reduction in the blood-lead level
which would result from lowering dietary lead by a specific amount, it is
necessary to know the actual amount of lead ingested daily and the amount of
reduction achieved/desired. For example, if the same hypothetical individual
with a blood-lead level of 15 ~g/d1 ingests 200 ~g of lead daily and, subse-
quently, reduces his intake to 150 ~g/day, the reduction in blood-lead result-
ing from the lowering of dietary intake can be predicted, using the 6 ~g/dl per
100 ~g intake relationship.
The reduced dietary intake, 150 ~g/day would contribute 9.0 ~g/dl to the
blood-lead level to which the 3 ~g/day contributed by air would be added (since
it remains unchanged). Thus, a blood-lead level of 12.0 ~g/dl might be expect-
ed on the reduced dietary lead regimen as opposed to the original value of 15
~g/dl. (To achieve the same 3 ~g/dl reduction in blood-lead by reducing air
lead rather than dietary lead, air lead would have to be reduced, approximately,
2.0 ~g/m3 below present levels (assuming each 1 ~g/m3 of lead in air contributes
394
-------
about 1-2 ~g/dl ~o blood-lead). Since there are almost no NASN stations ex-
ceeding this value, it is apparent that, for practical purposes, reducing die-
tary intake is a more promising avenue to pursue.
Although the present example utilized a hypothetical individual case, sim-
ilar calculations can be made for specific population groups (i.e., children
under 5, women in childbearing years, etc.) using the actual (current) amounts
of lead ingested and estimates of the reductions which can be effected for each
group, using information regarding dietary lead intakes of various age-sex
groups as well as net and percentage reductions under various technological op-
tions such as that presented in Table 8.34.
Another application of analysis of the frequency distribution of blood-
lead levels in populations is in the determination of the proportion of the
population whose blood lead values exceed a selected critical, or "threshold"
level. For example, the percentage of a population with blood-lead above 40
~g/dl, regarded by many as a critical level, can be estimated using the loga-
rithms of geometric means and standard deviations derived from empirical data
(Aitchison and Brown, 1963; Schubert, et al., 1967; U. S. Environmental Protec-
tion Agency, 1977). Such a procedure allows prediction of the effects of any
contemplated change in exposure level, provided that the effect can be
expressed in terms of a change in the population mean. Starting from the base-
line or current levels, the percentage of the population exceeding a critical
level is determined. If the mean of that population changes by a given amount
due to some intervention, the projected change in percent of the population
above the selected critical level can be projected (assuming that the standard
deviation of the distribution remains the same, a reasonable assumption).
8.7.3.2
Demonstration of the Technique in a Test Case--
Although the change in percentage above a critical level may be small, the
absolute quantity of individuals shifting from above to below a critical
threshold level can be quite large. It is expected that many individuals at or
above critical levels will be shifted to safe "subcritical" levels as a result
of lowering the mean blood-lead level for the population, as shown in the
following example.
Several researchers have found that hematologic changes can be clearly
seen at blood-lead levels around 25 ~g/dl, especially in women and children,
(Committee on Toxicology, 1976; U. S. Environmental Protection Agency, 1977;
Environmental Health Resources Center, 1973). The effect of a reduction in
lead intake on the percentage of the population group of women 20-34 years old
with blood-lead values above 25 ~g/dl will be calculated as a specific example.
The geometric mean blood-lead level of this group has been estimated to be 16.6
~g/dl (Tepper and Levin, 1972; U. S. Environmental Protection Agency, 1977).
Theoretically, the geometric standard deviation is constant at 1.31 ~g/dl; this
has been empirically verified in several cases (Yankel, et al., 1977; Environ-
mental Protection Agency, 1977).
Using the 6 ~g/dl per 100 ~g dietary intake of lead, and the 190.4 ~g/day
395
-------
intake for this popu12tion subgroup (Table 8.34), it can be calculated that
11.4 ~g/dl of blood lead is derived from food, with the 5.2 ~g/dl difference
being attributable to air and other causes. This intake would be reduced to
168.5 ~g/day if two-thirds of the lead in the canned food portion of the diet
were eliminated (Table 8.34). The corresponding blood lead contribution from
diet would be 10.1 ~g/dl which, plus the 5.2 ~g/dl contriuution from non-
dietary sources, would give a new mean blood-lead level of 15.3 ~g/dl.
The percentage of the population with blood-lead values above 25 ~g/dl can
now be calculated for the two different means. In order to use the assumptions
of a normal distribution, Z values must be calculated using logarithmic trans-
formations of the geometric variables described above. The general formula for
Z is as follows: Z = (X - ~)/a, where ~ is the mean, and a is the standard
deviation.
Percentages of population corresponding to any desired blood levels are
easily calculated by computer. Data for the two populations of females 20-34
years of age, having blood-lead means of 16.6 ~g/dl and 15.3 ~g/dl, are used in
the following example: .
For GM = 16.6 ~g/dl:
Z = [In(25~g/dl) - In(16.6~g/dl]/ln(1.3l~g/dl) = 1.52
For GM = 15.3:
Z = [In(25~g/dl) - In(15.3~g/dl/ln(1.3l~g/dl = 1.81
Figure 8.18 shows two curves describing distributions of blood lead levels
in two hypothetical populations of women 20-34 years of age. The percentage
plotted versus any given level represents the proportion of the population ex-
pected to have blood lead levels greater than or equal to that given value.
Blood-lead levels in both populations were assumed to have lognormal distribu-
tions. For the first and second curves, the geometric means (GM) were taken to
be 16.6 and 15.3, respectively; for both curves, the geometric standard devia-
tion (GSD) was taken to be 1.31.
The proportions corresponding to the percentages plotted in the graph were
computed as follows. Since p is the proportion of people having blood lead
levels less than or equal to a given level x, 1 - P is the proportion having
levels greater than x. Also, p = Pr(Z < z), where z is set equal to (In(x) -
In(GM)/ln(GSD). Since the blood lead levels are lognormally distributed, this
last expression has a standard normal probability distribution. Therefore, "p"
values can be directly obtained from a table of cumulative normal distribution
function values (Z-scores). The percentage values of interest were then com-
puted as (1 - p) x 100.
The curves in Figure 8.18 were plotted after using this method to compute
percentages corresponding to blood lead levels (x) ranging from 15 to 45 for the
two hypothetical human populations. Table 8.38 shows the actual percentages at
396
-------
So?
j
.. \
" \
~I
~ JOI
--l .
LI'
(5
CI
"S i
g. 2:j t
c... i
'0 !
~ 15 t
~ .,j /. \., ...? .
jOistribution wijh 2/3 of \ Percent of population Wlrh blood lead> ...5 fLg;dl
leoe ~ ~ar;ned food remov~ "'1\,. \
G.M.-I:>.3fL9/dl ~~
" . ,-
oL-, ; " ~~
15.c.:xJ 1, .5tXJ 2;).CQJ 22 .&:oJ 2S.ooo 27 .S:.D :;C .OW :;2 .5a) ;E.OOO
\
\
\
I Initial distribution G.M. = 16.6 ,ug/dl
/
,
t
:;'7.C:OO
I
4Q .oro
.
\2 .QOJ
I
4S.QJJ
Blood Lead Leve I
Figure 8.18. Predicted distribution of blood lead levels at two
different mean blood levels for adult women,
20-34 years old.
Source:
Battelle-Columbus estimate
397
c
-------
TABLE 8.38.
FREQUENCY DISTRIBUTION OF BLOOD LEAD VALUES IN TWO HYPOTHETICAL
POPULATIONS OF ADULT FEMALESa
Blood Lead
Le vel .
I1g/dl
Percenta~e of Population at or above the Blood Lead Level Indicated in Column-l-
b P 1 i "C
Population 1 opu at on ..
tt;.OOOO
15.3000
..1.5...600IL
15.9000
.~6.200n.-
16.5000
..JA....aO IllL
11.1000
...11..& ltIlo.o..
11.7000
...1 4.. D.O 0 tL
18.3000
.J..a.a.6.Q.OJL
18.9000
...19...200.0..
19.5000
.~.9.. 8.0 O.n..
20.1000
, II. "0 OJL
20.7000
.21...0.1100
21.3000
.-2t....EOOIL.
21.9000
-Z.Z..2Q.0 n..
22.5QOO
._.22...8!10a...
23.1000
.-23...400 a..-
23.7000
-Z1t.....D.oa..n..
. 24.3000
..2ft_61l0 0-.
24.9000
..25..2000-.
25.5000
, C;. I\(J Q..IL
26.1000
..26..4000-.
26.7000
--21_00011-.
27.3000
-Z..Z..... flll...Q..D-
21.9000
..28..200 Q.-
28.5000
.-~8..800n.-
29.1000
~1ln.11-
29.1000
..3 Q... 0 0.0 n.
30.3000
...30... EO 0 Q.
30.9000
JJ.a.Z.0.Q IL
U.5000
.-Ji!t.-6z.~
61.8676
.--_S.9..099L
56.3383
.._.5.3.5988.-
50.8926
10/1. '3.1.2-
45.624"
_---43.0B1L.
40.6091
.__3.8.21.44.._.
35.CJ024
:1I3.67U-
31.5421
_.--.2.9.."991._.
27.5494
____25...6CJ3&._.
23.9314
, , - Z6z...IL
20.6838
---1.9..1. CJ5Zu
17.7931
----1.-6.47&.1_-
15.24H
1 I.. n"107
13.0034
..--U..99Ct.1.--
. 11.0534
.---1.0 ..1.1BO--
9.3642
----B....6.Q 8.9..-
7.9087
-_u..2.Z6Q.2_-
6.6604
----..6..1.062--
5.5946
C;.,2.2..L
4.6881
------4.2880_-
3.9200
;-~_-.3.5.818_-
3.2112
'-Q8~
2.124CJ
.----..2..4854_-
2.2661
--_u-2.0653--
1.8817
t.7139-
1.5605
--_u~. '+ 2 0.4_-
1.2925
_u--~.1158--
1.069"
.q723
.8839
~2.q2~1 --
50.0000
___42.13.3.6.-
..4.3361
--.41.618.0_.
38.9881
-3.6.aliS3.L
34.0201t
_-.31. 69Z.6-
29.4730
__-l.Z.36.;13-
25.3641
--23.1.7r;(]
21.6946
--- z.a..Q 21.1-
18.4516
---1.6..9 83.3-
15.612"
, I. - :n C;2..
13. 1475
--.3.Z..045l.-
11.0238
--.3.0...0.7-91.-
9.Z066
~".Q2JL
7.6612
--__6..97.99..
E.3543
---_5_1.803.-
5.2545
fa. 7..z3.L
4.3333
---_3_931.5--
3.5649
---_3.2306..
.2. CJ262
,.,,~
2.3971
-- -- 2...1 &.81-
1.9601
----1..17-1-"-
1.6002
__1...-'11t.S.L
1.3045
----1...1.l7Z..
1.0621
-._.-...9S.1~.
.8631
7766
.7011
----_....6.322..
.5696
-_u_....5.1.3Q..
.10619
.lt1r;q
.314,.
398
-------
TABLE 8.38
(Continued)
Blood Lead
Level
~g/dl
Percenta2e of Population at or above the Blood Lead Level Indicated in Column 1
b ~
Population 1 Population 2
:H . 80 Q'/l..--
32.1000
__32... !tQOD ----
32.1000
_.33.0000.-_--
33.3000
-3.3.. 6n nit
33.9000
-.3$t.. 200J1..__-
3'+.5000
..31+..800.l1..m
35.1000
J.5--.ItlJOlL-
35.7000
..36..11000._---
36.3000
.-36.60011.---
36.9000
..3.ZJOOll..-
37.5000
..31....600 a._---
38.1000
..38..1.000.--_-
38.7000
-3..9-JI 00 !l..-
39.3000
-.3 9... 6000.---.
39.'3000
_A O. 200 0..._--
'+0.5000
r. n. II a.Oll..-
'+1.1000
--A 1...'+0 0 0_- ---
U.7000
.-..r. 2..000 0-----
'+2.3000
..JL2....f OJl.1L.-
42.9000
-A J..2aO a.. m.
'+3.5000
--r.3...aoo a.---.
44.1000
..ltlt..1tD 0.D.-
"'+.7000
.J.s. .o.oOD.--_.
. M 3.3-
~7300
___...66.3 2.---
.6024
---.54.11.---
...967
--.ASia.-
.409ft
___...37.J.6.._-_-
.3372
___...3060,.----
..2777
--.25..1..9.-
.2285
___...20.13..___-
.1881
---...17. 0 0._--.
.1547
.1403
.1272
___..115~L_-
.1046
---..n 949_---
.0860
----07"n
. 0 70 7
-__..n6.1.2_oo-
.Q582
--- .0528-_--
.0478
.n434
.0393
.___.0.35.100_-
.0324
.---..0293--_-
.0266
. O~C.1
.0219
.---..019.9----
.00aO
---_..0 163--_.
.0148
-- 0131;
.0122
.-u~ 1.11..---
.337 L
.3033
__--.2.12.9---
.2456
._u.2.2.10-_-
.1988
-..1.l.AlL-
.1608
._--..1~."'1__-
.1301
---_..111.0__-
.1052
-...Q..9lt.6..-
.0851
-_u..n 1.65__-
.0688
-__-..Q619~--
.0557
. or;o 1
.0450
----.. D.lt 05._..
.0364
_--...0.32.7:_-
.0295
---.Jl2..1i5-
.0238
---...021.4..._.
.0193
_--...0.11.4__-
.0156
. II t/LCL-
.0126
...:_...0114.._.
.0102
._--...00.92..-
.0083
.nn7r;
.0067
.---...0051..__.
.0055
----... 0.0.49. -_.
. 0044
.00411-
.0036
.---- 4..1132 ---
aSee text for full description of how
b data were generated.
Geometric mean blood lead 16.6 ~g/dl
cGeometric mean blood lead 15.3 ~g/dl
these
399
-------
or above a given blood level for each of the hypothetical populations.
In a population with geometric mean at 16.6 ~g/d1, 6.55 percent of indi-
viduals would be expected to have blood lead levels at or above 25 ~g/d1. On
the other hand, in a population with geometric mean at 15.3, only 3.22 percent
would be expected to have blood lead levels at or above 25 ~g/dl. Had another
critical blood lead value been selected, say 40 ~g/dl, Table 8.38
shows that for the population with geometric mean of 16.6, over 5 percent of
the population would be at or above 40 ~g/d1 while in the second population
(geometric blood lead mean at 15.3) less than 2 percent would reach levels
as high as 40 pg/d1.
Extending these results to real world conditions. illustrates the dramat-
ic effect of a small reduction (1.3 ~g/d1) in the geometric mean blood level of
a population. According to the 1970 census, there were 21,143,824 women be-
tween the ages of 20 and 34 in the United States (U. S. Bureau of Census,
1975); 1,384,920 of these would be expected to have blood-lead levels above 25
~g/dl. However, as a result of lowering the mean blood-lead level in this
group as described above, the number with levels above 25 ~g/d1 can be reduced
to 680,831. Obviously, the reduction in mean blood-lead level described above
can have profound effects; it would lower by 1/2 the number of people in the
range where evidence of hematologic changes begin to appear. Furthermore,
since the highest fertility occurs among women of the 20-34 age group, addi-
tional benefits, in terms of protecting unborn children from undue lead expo-
sure, would also be expected.
400
-------
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1-
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104 pp.
Roberts, H. R. 1978. Statement before The EPA Public Hearing on Proposed
National Ambient Air Quality Standard for Lead. Washington, D. C.
February 15.
Roberts, T. M., T. C. Hutchinson, J. Paciga, A. Chattopadbyay, R. E. Van
Loon, and D. K. Parkinson. 1974. Lead Contamination Around Secondary
Smelters. Estimates of Dispersal and Accumulation by Humans.
Science. 186(4169):1120-1123.
Robinson, E., and F. Ludwig. 1967. Size Distributions of Atmospheric Lead
Aerosols. J. Air Poll. Control Assoc. 17: 664-669.
Ryan, C. R. 1978. Region I, U. S. Environmental Protection Agency.
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Sarett, H. D. 1974. Lead Contamination in Milks Fed to Infants:
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1972-1973
Sartor, J. D. and G. B. Boyd. 1972. Water Pollution Aspects of Street
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Schau1e, D., and C. C. Patterson. 1978. The Occurrence of Lead in The
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4(4):
410
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Shacklette, H. T., J. C. Hamilton, J. G. Boerngen, and J. M. Bowles. 1971.
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411
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414
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9.0 ASSESSMENT OF THE NEED FOR AND
POSSIBLE APPROACHES TO LIMITATIONS ON LEAD
9.1
SUMHARY
Lead is undeniably a toxic element, and lead poisoning has been a problem
for mankind for centuries. Adverse effects of lead on health vary from acute -~
lead poisoning, which is easily recognized and on which there is general
agreement down to levels where observable effects are debatable and sometimes
controversial. However, even low levels cannot be dismissed as inconsequential;
lead and its compounds do not biodegrade to innocuous residues, but persist
for an infinite time.
The evidence is overwhelming that there is a critical need for limitations
which will prevent the occurrence of acute lead poisoning, and regulations
have been enacted or proposed in this country which should minimize its future
occurrence from presently acceptable uses and processes involving lead. Some
occupational problems still remain, principally at primary and secondary lead
smelters, and in lead-acid storage battery plants (see Section 7.5.3); other
specialized employee groups susceptible to acute lead poisoning are painters,
scrapyard workers, and ship breakers.
This is primarily an occupational problem requiring specific control
measures. Such measures, e.g., recent regulations reducing allowable work
place air lead concentrations from 200 to 50 ~g/m3, have been promulgated
by The Occupational Safety and Health Administration of The Department of
Labor.
The major nonoccupational acute lead poisoning problem
of children, primarily as a result of exposure to high-lead
1n old substandard housing.
remaining is that
paint and dust
Although recently-enacted limitations on lead-based paint will prevent
today's paints from presenting future problems of this sort, no current limi-
tations appear able to solve this existing problem, nor do limitations appear
well suited to address this problem. Greatly expanded surveillance and ped-
iatric management appear to offer the optimum approach to this lead poisoning
problem.
The need for limitations that will protect the general public which is
nonoccupationally exposed is less conclusive than the need to prevent clinical
lead poisoning. Part of the uncertainty relates to the changing concentrations
of environmental lead.
415
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Historically, ambient concentrations and environmental exposure to lead
have been increasing almost since the Industrial Revolution. Fortunately,
the rate of increase in environmental concentrations appears to have stabilized
somewhat in recent years. Actually, the trend towards ever-increasing
concentrations may finally have been halted and reversed by some of the
limitations already enacted, e.g. the phasedown of leaded gasolines, but the
benefits of these are not yet fully realized, nor even totally predictable.
In spite of these impending improvements, exposure to lead cannot be
demonstrated to be below the level at which no adverse effects occur. Part
of the problem is that this level cannot be unequivocally defined, since the
health significance of the subtle biochemical disturbances is subject to
varying interpretations. Nevertheless, a case can be made on the basis that the
mean blood lead levels of the nonoccupationally exposed general population, at
15-20 Wg/dl, if not at the level where irreversible effects begin to occur, is
so close to it that the margin of safety is insufficient. Prudence dictates
that this margin be increased, if feasible, i.e. there is a need for
additional limitations to further reduce average blood lead levels.
The need is even greater to reduce blood lead levels in children, who
constitute an especially sensitive segment of the general population; the
m~rgin of safety between present levels of blood lead in children and tolerable
levels is relatively small, possibly the smallest for any toxic substance to
which children are exposed.
The optimum approach to a further reduction in exposure to lead was
identified by the analysis of man's sources of lead intake (Section 8), which
demonstrated the importance of ingested lead in determining blood lead levels,
and also that food and drink were the major contributors. An analysis of other
sources of lead exposure reinforced the importance of ingested lead and confirm-
ed that this approach to limitations should receive high priority. This does
not negate the importance of other limitations; however, a compilation of
existing and proposed Federal limitations (Section 9.4) shows that most of
the other pathways for lead exposure have already come under control.
Thus, control of adventitious lead in food and drink appeared to be the
principal limitations yet to be instituted. As witnessed by the testimony
presented at the EPA public hearing considering the proposed national ambient
air quality standard on lead on February 15, 1978 by The Acting Director of
the Bureau of Foods, Food and Drug Administration (Roberts, 1978}, the FDA
had concern for this problem and has an ongoing program designed for its
maximum mitigation within the bounds of existing food can technology. This
has been a cooperative program with the can manufacturing and food packing
industries, with promising results, some of which are described herein.
At the time of the selection of adventitious lead in food as a high
priority problem for consideration of possible limitations during the second
phase of this program, it was not known that an FDA program was in progress
in this area. The results of this program offer independent support to the
approach towards this problem which was adopted by FDA, and it is hoped that
they will be useful to the continuing FDA efforts.
416
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In Section 9.5.2 alternatives to lead-soldered cans for the packaging
of food are described and analyzed. These include cans with cemented and
welded side seams~ two-piece cans formed by drawing procedures, aluminum
cans, glass containers and retortable pouches. The latter, a very recent
development,are made of an aluminum-plastic laminate and have some significant
advantages in protecting flavor during the sterilization process, as well as
in eliminating lead. However, at this time the packing process is slow and
therefore costly. As this process is developed and perfected it can be
expected to become more competitive.
In contrast to the total replacement of the three-piece soldered can,
the can industry has demonstrated over the last several years that a signi-
ficant reduction in adventitious lead in canned foods is possible by a
combination of evolutionary improvements in can making technology and "good
manufacturing practices", including especially close attention to quality
control. Illustrative of this is the 40+ percent decrease in lead content
of 10 representative canned foods in a 1976 industry survey compared to the
results of the similar survey conducted in 1974. The average lead content
of the 10 foods surveyed was 0.19 ppm. Infant foods showed even larger
reductions; the average lead content of 16 canned frUit juices surveyed in
1977 was 0.06 ppm, compared to the 1973 average of 0.29 ppm.
If these improvements can be extended indust!y-wide a major reduction
in the average lead content of canned foods can be achieved rather quickly,
and without the need for a large capital inves.tment program by the industry.
Capital costs to adopt this approach of modifying present can making
lines and cleanup of soldering operations are estimated by The Can Manu-
facturers Institute as moderate, of the order of $50,000 per line, or about
$50 million for the industry. Adding equipment to apply an organic polymer
stripe over the solder seam would increase the capital cost per line by
approximately $20,000 or $20 million for the industry. It was estimated
that added operating costs of $0.10 to $0.45 per thousand cans would be
incurred.
The capital costs to entirely replace the three-piece soldered can with
any of the lead-free forming processes were estimated to be in the $600,000
to $2,500.000 range per can line, resulting in an industry investment in the
$1 to $3 billion dollar range. Added operating costs of perhaps $3 to 6 per
thousand cans were projected.
The benefit-cost ratios of the alternatives strongly favor the can line
modification approach now being implemented, and its adoption, at least as
an interim improvement, has much to recommend it. With the further improve-
ment of seam striping and/or sprayed organic polymer linings for infant
foods, most of the benefits to be gained by reduction of adventitious lead
in canned foods would be achieved.
Processed food is not the only possible source of ingested lead for the
general population. Another potential, though minor source of ingested
417
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lead is from the lead glaze used on dinnerware. Lead glazes are the most wide-
spread in use and are considered best for all ordinary purposes. If the glaze
is improperly formulated and/or fired, the lead in the glaze is extractable
by foods and beverages, and a few cases of clinical lead poisoning have occurred
from this cause. This problem is one of individuals, with negligible effect
on the general public. The u.s. Food and Drug Administration, which is respon-
sible for the regulation of this "indirect food additive," monitors both
domestic and foreign ware. Domestic dinnerware appears to have no problem
in meeting lead release limitations; some foreign ware does. As of now, no
fully suitable alternative to lead glazes appears to exist commercially.
Modern pewter contains no lead and hence poses a minimal lead ingestion
problem; antique pewter does, but its use appears to be so limited as to be
discounted. Almost no community drinking water systems exceed the primary
lead drinking water standard of 50 ppb; in a few soft-water areas lead service
piping to homes has caused high lead dontents in domestic water. This does
not appear to be a widespread problem. Some concern has been expressed recently
about the hazard from decal-decorated drinking glasses. Results obtained by
the interagency task force formed to investigate this potential hazard led to
the conclusion that no formal rule-making is required at this time.
9.2
NEED FOR LIMITATIONS
Lead is undeniably a toxic substance. The symptoms and effects of acute
lead poisoning have been known for centuries. Clinical, epidemo10gica1, and
toxicological studies have conclusively demonstrated that excessive exposure
to lead adversely affects human health. These adverse effects vary from acute
lead poisoning, easily recognized and on which there is general agreement,
down through sub-clinical effects to more subtle biochemical disturbances
of the heme-synthetic mechanism which occur at levels of lead exposure well
below those that cause any observable decrement in hemoglobin (Hammond, 1977).
Not only is this latter effect subtle but also variable, and not universally
acknowledged.
9.2.1
Acute Lead Poisoning
A need for limitations may be categorized by whether it applies to the
acute lead exposure case or to the low end of the scale. Considering first
the upper end, there is very little disagreement, on either the adverse effects,
the need to mitigate or eliminate the hazard, or the form of the limitations
required to accomplish this. The need to prevent excessive exposure to lead,
such as will induce acute lead poisonin~ has long been recognized, as evidenced
by the existence of numerous regulations designed to prevent or minimize such
exposures, especially occupational exposures, both in the United States and
abroad.
Although great strides have been made in the past half century in mitigating
occupational lead exposure and industrial lead poisoning, the problem has not
yet been entirely eliminated. Epidemiologic studies conducted by the Center
for Disease Control in 1975 and 1976 in 5 different U.S. lead facilities have
shown unacceptably high blood-lead levels and symptoms of lead poisoning in
every plant studied (see Section 7.5.3.1). On the basis of the findings of
418
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this and other studies it is obvious that the currently accepted upper limit
of a safe blood lead level (80 ~g/dl) does not provide adequate protection
against lead toxicity.
In the industrial situation the route of entry for lead is primarily
inhalation rather than absorption or ingestion, and high blood lead levels can
be correlated with high air lead concentrations. The data of Williams, cited
in the OSHA proposed occupational exposure standards (U'3' Department of Labor,
]975), showed that an air lead concentration of 200 ~g/m corresponded to a
mean blood lead level of 70 ~g/dl (48-92 ~g/dl range)3 Similarly, the Williams
data suggest that air lead concentrations of 150 ~g/m correspond to a blood
lead range of 38-82 ~g/dl, with a mean blood lead level of 60 ~g/dl.
Epidemiological studies are unequivocal in identifying a need for additional
limitations on occupational exposure to lead to prevent overexposure and lead
poisoning symptoms in lead industry workers. The Occupational Safety and Health
Administration of the U.S. Department of Labor, which has the primary
responsibility for safety in the workplace, has promulgated regulations to
minimize or eliminate this risk by reducing the time weighted overaje (8-hr day,
40-hr week) lead concentration in the workplace from 200 to 50 ~g/m (U.S.
D~partment of Labor, ]978). The regulations also provide for, among other things,
the monitoring of employee exposure, methods of compliance, housekeeping practices,
personal protective equipment and clothing, training, medical surveillance,
and record keeping.
On the basis
concluded that it
demonstrated need
exposure to lead.
of the data submitted in support of this regulation, it is
will indeed produce the desired results, and there is no
at this time for additional limitations on occupational
The major nonoccupational acute lead poisoning problem remaining, and
unfortunately, one striking at the most susceptible segment of the population,
children and infants, is that arising from ingestion of the high-lead interior
and exterior paints (and dusts) generally associated with substandard urban
housing. It has been estimated that several hundred thousand children in the
United States, primarily from areas where such substandard housing is prevalent,
may have blood leads in excess of 40 ~g/dl (see Section 7.4). Possible approaches
to this problem are discussed in Section 9.3.3.
While it is true that there have been a few isolated cases of acute lead
poisoning in the U.S. from illicit whiskey, from improperly glazed ceramic
beverage containers, from misuse of other lead products, and even from the
excessive comsumption of a calcium diet supplement derived from animal bones,
the frequency of such cases is small as compared to other sources of lead
exposure.
9.2.2
Limitations at Low Lead Levels
As indicated by the previous discussion, there is widespread agreement on
the characterization and the intrepretation of the effects of lead upon humans
with acute or chronic lead poisoning. As lead dose becomes smaller and smaller,
419
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it's effects are less and less definitive and unequivocal, and at just-
perceptible levels there is considerable uncertainty and disagreement upon its
effects. Although it has long been assumed that low levels of lead can be
tolerated in humans without demonstrable adverse effects, the exact levels of
exposure that define these thresholds have not been clearly established.
It is evident that there is scientific controversy about facts and
intrepretation of the health significance of subtle biochemical disturbances
associated with blood levels below traditional levels of concern.
In this context, clinical effects can be considered to be those which a
subject can perceive and which a physician would normally seek to correct.
Subclinical effects are those which under normal circumstances do not result
in a perceptible decrement in body function but which could possibly reduce an
individual's capacity to cope with a coexistent body stress (Hammond, 1978).
Hammond (1978), reviewing the effects of lead upon man, noted that the
principal organs affected by lead are the kidneys, the hematopoietic system,
and the central and peripheral nervous systems, and that in all four cases a
spectrum is seen, including both clinical and subclinical effects.
As Hammond (1978) points out:
"The effects of lead on the hematopoietic system are varied
in nature. They include shortened survival of circulating red
cells and decreased rate of hemoglobin synthesis in the bone marrow.
Both of these general effects contribute to the anemia which is
characteristic of lead poisoning. Anemia is clearly a clinical
effect, one which a physician would normally seek to correct.
The minimal level of lead exposure which is necessary to cause
anemia is difficult to specify, if only because the clinical
definition of anemia is imprecise. It is perhaps more to the
point to consider the minimal level of lead exposure at which
a downward drift in blood hemoglobin first appears, even within
the accepted normal range. This minimal level appears to be
PbB = 40 in children and PbB = 50 in adults.
Two enzymes in the pathway leading to heme synthesis are clearly
inhibited by lead at PbB's below 40. The first of these is heme
synthetase, a mitochondrial enzyme which catalyzes the final step
in heme synthesis, the insertion of iron into protoporphyrin IX.
Inhibition of this enzyme is reflected on the appearance of elevated
protoporphyrin IX in circulating red cells, an effect which occurs
at PbB's as low as 25 in adult males and as low as 20 in adult
females and children. At even lower levels of lead exposure (PbB = 15),
the enzyme aminolevulinic acid dehydratase (ALAD) which converts the
the heme precursor aminolevulinic acid (ALA) to the intermediate
porphobilinogen (PBG) is somewhat inhibited, both in blood and in
some other tissues. The consequence of inhibition of this enzyme
is thought to be elevation of the precursor ALA in blood plasma
and urine. This effect does occur, but only as PbB rises above 40.
420
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Thus, the significance of ALAD inhibition at very low levels of lead
exposure is uncertain and is considered by most to be a subcritical
effect.
The basic issue, for which there is no clear answer, is as to
whether elevation of erythrocytic protoporphyrin between PbB = 20
and PbB = 40 is to be considered a critical or subcritical effect.
The effect certainly is compensated since hemoglobin levels are
sustained at a normal level in this range of lead exposure. The
real issue is as to whether or not a person's capacity to cope with
a co-existent stress on hematopoiesis is in any way compromised.
Not much is known about this problem. There is a need for more
research to determine the health consequences of this compensated
state, and also to determine the implications of the effects of
lead on the synthesis of other hemoproteins essential to normal
body function."
It is well-known that very high lead exposure can cause severe, often fatal
damage to the brain in both adults and children. Effects at lower exposures
become increasingly difficult to define, and there has been much controversy in
rpcent years regarding the effect of lead on the central nervous system. A
number of recent studies examining possible neurological and behavioral effects
of lead in children have been reported. Nearly all of these studies ha¥e
been retrospective in nature, and have generally focused on children with
blood leads above threshold levels (i.e.>25 ~g/dl) for detectable changes in
the hematopoietic system. Also, the experimental designs of these studies are
flawed in one way or another, and the effects observed may have been a result
of the combined effects of lead and other stressors, both physical and social,
since these studies have almost invariably been conducted in socio-economically
deprived populations.
Thus, while there may be threshold levels of lead exposure for subtle
neurological and behavioral effects, it does not seem possible at this time to
correlate these unequivocally with specific levels of either blood lead or
lead intake.
Conceding that an unambiguous correspondence of cause and effect cannot
be established at threshold levels of lead exposure, possibly the question of
the most desirable course of action can be approached in another way.
As noted earlier, there is considerable scientific controversy about the
intrepretation of the health effects of lead, and about the level at which
irreversible effects corne into play. In the Air Quality Criteria for Lead
document (U.S. Enviromental Protection Agency, 1977) a tabulation of blood
lead levels versus lowest - observed - effects levels was presented
(Table 9.1).
421
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TABLE 9.1 BLOOD LEAD LEVELS VERSUS LOWEST-
OBSERVED-EFFECTS LEVELS
Lowest 'evel
tor ODserved
ellects, ,.9 Ptl/dl
whOle Dlood ODserve
-------
of 25.5 ~g/dl for 6151 children in 14 intermediate sized cities in
As an approximation, it can be assumed that the average blood lead
is in the 20-25 ~g/dl range.
Illinois.
for children
This lack of data hampers the evaluation of where the U.S. population
stands now with respect to blood lead, and also what effects various alternative
limitations might have. Nevertheless, the above approximations of blood lead
levels will suffice for development of the hypothesis that additional limitations
on lead intake are desirable for the general health. As noted in preceding
paragraphs elevated protoporphyrin can occur at blood lead levels as low as
25 ~g/dl in adult males and as low as 20 ~g/dl in adult females and in
children (Hammond,l978). There is continuing debate as to whether this is a
critical or subcritical effect. However, the disquieting fact is that these
effects extend down to potential threshold blood levels approaching the
general U.S. average; and if there is no overlap, neither is there any distance
between the two. Thus, even though the conclusion be accepted that threshold
concentrations (and effects) of blood lead are higher than the elevation in
erythrocyte protoporphyrin suggests, the fact remains that the margin of safety
is small, and prudence suggests that it be increased.
The concern here is for the general population, and for the most
susceptible segments of it, children and pregnant women. EPA has stated that
the agency believes that young children (ages 1-5 years) should be regarded
as the foremost critically sensitive population subgroup for setting of lead
standards (U.S. Environmental Protection Agency, 1978). This is because
hematologic and neurologic effects in children are shown to occur at lower
thresholds than adults. and because children have a greater risk of exposure
to non-food material containing lead, such as dust and soil (and old lead paint),
as the result of normal hand-to-mouth activity. Additionally, as was noted in
the supporting EPA Criteria Document (U.S. Environmental Protection Agency, 1977a)
other factors suggesting that children may be at greater risk include:
(1)
greater intake of lead via inhalation and ingestion
per unit body weight;
greater absorption and retention of ingested lead;
physiologic stresses due to rapid growth rate and
dietary habits;
incomplete development of metabolic defense
mechanisms;
greater sensitivity of developing systems.
(2)
(3)
(4)
(5)
Pregnant women and the fetus are at risk because of transplacental
movement of lead to the fetus and the possibility of maternal complications at
delivery. Because there is a balance between maternal blood lead levels and
fetal blood lead levels, concern exists that development of the nervous system
of the fetus may be impaired due to neurotoxicity of lead. Changes in fetal
heme synthesis and premature births have been associated with prenatal
exposure of the fetus to lead. However, available evidence does not indicate
that pregnant women and the fetus would require a more stringent standard
than young children. (U.S. Environmental Protection Agency, 1978).
The very small fraction of the total population occupationally exposed to
excessive levels of lead is a separate problem, requiring different measures.
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1-
The question of whether there is a need for limitations on lead has already
been answered in the affirmative with respect to this group. Numerous
limitations have already been enacted in the United States and around the
world in response to this need.
With respect to the need for additional (new) limitations for the
protection of the general population, one way to approach the analysis
posing a series of questions:
is by
(1)
Is a need indicated for reductions in blood leads
and body burdens?
As discussed above, there is believed to be an
insufficient margin of safety between present blood
lead levels and potentially undesirable ones.
This margin of safety needs to be increased.
(2)
What is the size of the population affected or at
risk?
If it is accepted that average blood lead levels,
in the 20 t 5 ~g/dl range, are at or close to
levels where adverse effects, even through subtle,
are possible, then the entire U.S. population (250+
million) may be affected or benefited, if the
limitation is one which applies universally.
(3)
Is any sensitive segment of the general population
affected, or exposed to specific risk?
It has been shown and generally accepted that
children, especially young children, are the most
sensitive group, for a variety of reasons: frequent
pica, speed of growth, susceptibility of the
central nervous system, among others. They are
closely followed by pregnant women: and women in
the prime childbearing years of 20-34 should be
protected against intake of too much lead, i.e.
their blood lead should be maintained below 25
~g/dl.
(4)
What is the prognosis for reductions in exposure
to lead, in the absence of new limitations?
There will definitely be reductions in the exposure
of the general population to lead from limitations
already enacted, notably the phasedown in leaded
gasoline use. As discussed in Section 8.2.3, this
should reduce the national annual ambient air le~d
concentration fro8 the 1975 mean of 0.7-0.8 ~g/m
to below 0.3 ~g/m3 by 1980 or shortly thereafter.
On the basis that 1 ~g/m3 in air lead in this
424
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concentration range is equivalent to approximately 1 to
2 ~g/dl blood lead, this may reduce mean blood lead
by about 0.5 to 1.0 ~g/dl.
The new ambient air lead standard of 1.5 ~g/m3,
will produce some reductions in lead exposure for
the small segment of the population which is in
the intermediate exposure category because of their
location in the proximity of a major air emission
source (e.g. smelter).
The general population, on the other hand, is
expected to receive little additional benefit from
an ambient air lead standard at 1.5 ~g/m3 in those
locations where the combustion of leaded gasoline
accounts for a high percentage of atmospheric lead.
On the basis of EPA data from the National Air
Surveillance Networks (NASN) there were very few
stations which had annual or quarterly means
exceeding this level in 1975 (Section 8.2.1). The
phasedown ma3 already have taken these areas below
the 1.5 ~g/m level, or will very soon. Accordingly,
this ambient air standard will do little or nothing
to reduce the air lead intake of the general population.
Extension of effluent guidelines and promulgation
of pretreatment standards will contribute to
reducing lead concentrations in industrial wastewaters
in special areas where it is now high. Since half
or more of the lead is removed from the wastewater
before discharge the benefit will be only partial.
The net effect on reducing mean daily lead intake
and mean blood lead will be slight, a few tenths
of a ~g/dl from the normal 2-3 ~g/dl attributed
to drinking water.
Thus, the sum total of the reductions in blood lead which will accrue to the
general public from proposed or recently enacted limitations can be estimated
to be in the range of 0.5-1.0 ~g/dl, a reduction of approximately 2 1/2 to 5
per cent from a present mean of about 20 ~g/dl. The banning of paint containing
more than 0.06 percent lead by The Consumer Product Safety Commission (1977)
will virtually eliminate the danger of childhood lead poisoning from the in-
gestion of paint hereafter produced and applied around the home. However, this
limitation does nothing for the hazard from ingestion of high-lead paints such
as were applied in previous years, and which are still the principal cause of
lead poisoning in children, and will have essentially no effect or reducing
present average blood lead values of children now so exposed. (Agencies such as
Housing and Urban Development might be able to devise and implement limitations
which would attach this problem, which is basically a housing problem).
Thus, while all of the above are helpful and desirable steps to limit
exposure to lead, they will increase the margin of safety of the general
population only slightly; more is desirable.
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Consideration of Section 8 shows that at low air lead concentrations
(as will soon exist generally, with the exception of occupational exposure and
possibly the immediate vicinity of major point sources) the principal source
of lead for the general population is through ingestion of food. For most
individuals, food contributes 60 percent or more of total absorbed dose, and
if the mean blood lead concentration of the general public is to be lowered,
reduction of dietary lead appears to be the most logical means of approaching
the problem.
In summary, there is a need for additional reduction in human lead intake,
and food is the one large contributor offering the greatest promise for
achieving additional significant reductions affecting the general population.
In Section 8, the present levels of lead in foods, fresh and processed,
were analyzed; the potentials for reductions were developed, and the benefits
such reductions can bring in reducing mean blood leads and the number of persons
with blood lead above any given level were described. Possible approaches to
limitations, both food and non-food, are briefly described and the benefits
and disadvantages of each are analyzed in Section 9.3, and a case study of food
canning processes is examined in Section 9.5.
9.3
APPROACHES TO LIMITATIONS
9.3.1
Criteria For Prioritization
Theoretically, any use at all of lead should be the starting point for
consideration of possible limitations on its use. However, lead, a metal that
has been used by man for thousands of years, has too many valuable and essential
uses to make its total abandonment a viable option, i.e. total prohibition is
not a feasible limitation. There are technically feasible options or alter-
natives for many, if not most of the dissipative uses of lead, and it is
theoretically possible to prohibit those uses, if this is the most desirable
solution to achieve exposure reductions.
There is no definitive evidence of demonstrable adverse biological effects
on the general adult population of the United States due to exposure to lead,
except in limited areas in the proximity of major point sources, such as
smelters, (except, of course, unusual situations such as illicit whiskey or
poorly-fired hand-crafted drinking utensils). Part of the reason for this may
be that there is not definitive evidence that lead has significant teratogenic,
mutagenic, or carcinogenic properties in man. Another reason is that the
evidence to date indicates that lead does not bioconcentrate or biomagnify in
man's food chain; and plants are not adversely affected at present mean
concentrations of lead in the atmosphere and in the soil.
On the other hand, there is no evidence that lead is an essential element,
even though it has been part of the body burden of man for centuries. Also,
the proof is conclusive that lead is a toxic element. Lead compounds do not
biodegrade to non-toxic residues; the lead moiety can persist infinitely, and
there is no form of lead which is non-toxic.
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Proceeding from these basic premises, it is possible to establish a set
of criteria for prioritizing potential limitations on lead. The criteria uti-
lized in this investigation included the following, not necessarily listed in
order of importance, for considering the various ways in which man is exposed
to lead and how these might be limited:
Fraction of man's total absorbed dose attributable to
that cause
Directness of exposure to man or biota from source in question
Dissipative or non-dissipative use
Quantity of lead released to the environment
Bioavailability of released lead
Number of individuals who would benefit from the limitation
Special benefits of the limitation to particularly sensitive
segments of the general population
Availability of alternatives for the use or process limited
Technical and economic feasibility of appropriate limitations
Cost of instituting limitation vs. health benefits derived
Cost of monitoring and enforcement of limitation
Absence of Existing limitations
9.3.2
Prioritization Of Possible Limitations
On the basis of the above criteria and the information described on human
health effects (Section 7) and the nonoccupational exposure of humans to lead
(Section 8) these sources of lead exposure were identified as those most
meriting consideration of possible limitations, in the following approximate
order of priority:
Leaded gasolines (including contaminated waste lubricating oil)
Adventitious lead in foods
Lead in drinking water
High-lead paints in homes
Lead-based paints
Lead in printing inks
Emissions from lead industry processes
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I ~ -
Lead ammunition
Lead in plastics and rubber
Emissions from indirect sources
Lead-acid storage batteries
Miscellaneous uses of metallic lead
These sources are discussed in the suceeding paragraphs, in terms of the
criteria listed above. An evaluation of the importance of each type of source
in terms of the individual criteria is helpful in prioritizing the consideration
and development of possible limitations, even though such an evaluation is
necessarily somewhat subjective. The importance of each factor was assessed as
major (large), moderate, or minor (small), signified by a +, 0, or - sign. The
rating scale had to be reversed for negative factors, such as the cost of
monitoring and enforcement. More weight was given to the factors determining
the degree of risk posed by the particular use. Although the ratings are not
numerically additive a general ordering of the need and feasibility of limita-
tions is possible, and a high score is suggestive of a need for a high priority
ranking. The evaluation is summarized in tabular form in Table 9.2.
Not surprisingly, leaded gasolines and adventitious lead in foods had a
preponderance of +'s and the highest scores of all. Also scoring high were
high-lead paints in place, printing inks, and emissions of lead from lead
industry processes.
A key final judgement factor is one presence or absence of limitations.
discussed later in this chapter many limitations to control exposure to lead
already exist.
As
9.3.2.1
Leaded Gasolines--
As pointed out in Section 5.2.2.2, upwards of 120,000 metric tons of lead
were dispersed to the environment in 1975 from the consumption of leaded
gasolines. Most of this was to the atmosphere, with a large portion of the
balance reporting to the waste lubricating oil. Some of this was burned,
some was discarded to sewers or to solid waste, and some was re-refined.
The quantity released was so enormous (far more than all other annual
releases combined) that it was assigned a + + ranking. It is a totally
dissipative use of lead, emitted in a form with high bioavailibility through-
out the United States, and exposing the entire population. Alternatives are
available, and limitations are technically and economically feasible. The
cost of monitoring and enforcement is categorized as moderate. The entire
population will benefit from limitations on the use of leaded gasolines,
including the susceptible population segment of children, especially inner-
city children. Accordingly, all of these factors were rated as +'s.
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TABLE 9.2
ASSESSMENT OF FACTORS CHARACTERIZI~IG A NEED AND
FEASIBILITY OF LINITATIO~S ON LEAD
Assessment Factor
Fraction of
dose 0 + + 0 0
Directness of
exposure + + + + + + 0 0
Dissipative vs.
nondissipative + + + + + + + + 0 + +
Quantity ++
released 0 0 0 + 0
Bioavailibility + + + + + + + + +
No. of individuals
benefited + + 0 0
Spec. benefit +
susceptible pop. + 0 + + 0 0
Availibility of + + + +
alternatives + 0 0 0 0
Technical and economic
feasibility + + + + + 0 + 0 0
Benefit/cost 0
ratio + + 0 0 0 0
Low cost monitoring 0 + 0
and enforce ment 0 0 + 0 +
Absence of existing
limitations 0 + 0 + 0 + + + 0 + 0
a
bSource: Battelle - Columbus estimate
Symbols
+ large, major
0 moderate
small, minor
429
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The combination of the above factors has, of course, already prompted the
placing of strict limitations on leaded gasolines, as discussed elsewhere in
this report (Section 5.2.2.2, 8.2.3 and 9.4.1). As noted therein, the
phasedown to an average gasoline content of 0.5 g/gal by 1980 is ~redicted to
reduce the mean national air lead concentration to about 0.3 ~g/m. At this
concentration the contribution of leaded gasoline to the average absorbed dose
will be about 0.2 ~g/dl, approximately 1 percent of the mean blood lead of u.s.
adults. Present dose is considered to more properly fall in the moderate
category (rated 0), especially in high-traffic urban areas.
This very large reduction in the use of leaded gasolines will concomitantly
automatically reduce the dispersion of lead to the environment through the
disposal of waste lubricating oil.
There will, however, still be a large release of lead to the environment
from the combustion of gasoline, possibly 40,000 to 45,000 metric tons per
year in 1980-1985. Thus, it is conceivable that additional limitations on
leaded gasolines might be indicated. One approach might be to extend the
no-lead fuel requirement to trucks and piston-engine aircraft, now exempt
from the restrictions which have been placed on new passenger cars.
Limitations could be placed on the disposal of waste lubricating oil,
but the operation, monitoring, and enforcement of such limitations could pose
almost insuperable problems, as well as being extraordinarily costly.
As evident from the projected ambient
attained upon completion or the phasedown,
absorbed dose for individuals from further
slight.
air concentrations which will be
the possible additional reduction in
limitations is estimated to be
The subject of additional limitations on leaded gasolines is extremely
complex, and the assemblage and analysis of the voluminous data which would
be required to validate any recommended changes was beyond the scope of this
investigation. On the basis of the basic parameters outlined above, the
conclusion is offered that there is no pressing need for additional limita-
tions in this area at this time with a recommendation that the results of the
phasedown be awaited and evaluated before further action is taken.
9.3.2.2
Adventitious Lead in Food and Beverages--
As discussed in Sections 8.5 and 8.6, most of the intake of lead for the
general adult population is from food, and as the lead phasedown proceeds and
ambient air lead concentrations diminish, this will become the predominant
source. A major source in food is canned food. At present from one-half to
two-thirds of the lead content of canned food is adventitious, arising from the
lead in the solder used to form aseptic seals in the side seams of the cans.
In testimony at the EPA hearing on the proposed national ambient air quality
standard for lead, the acting head of the FDA Bureau of Foods estimated that
about two-thirds of the lead in canned food is from the solder, with the remain-
der in the food itself prior to canning. It was further estimated that for a
two-year old child, with a total average daily dietary lead intake of 98 ~g, about
lR 1I~ or 18 percent comes from food packed in cans (Roberts, 1978). Thus, a
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significant fraction of the dose arises from this cause, and the exposure
route is direct, causing both of these factors to be rated as +'s.
Much the same relationship exists for adults; since canned foods, on
average, constitute about 30 percent of U.S. diets, upwards of 15 percent
of daily lead intake from food could be eliminated.
Preliminary analysis showed that adventitious lead in foods had a
priority ranking comparable if not greater than that of lead in gasoline, and
probably merited the development and adoption of limitations more than any
other candidate. Alternatives are available (+), with satisfactory tech-
nological and economic feasibility (+), and the benefits are large for the
costs involved (+), costs of monitoring and enforcement would be moderate to
low (0), the entire population will benefit from reduced lead in foods (+),
particularly the specially sensitive group, children (+). This limitation
candidate had 10 + factors, more than any other category, indicative of its
importance in considering prioritization of lead limitations.
Further discussion on the form and nature of such possible limitations
and their technological feasibility is deferred to Section 9.5, devoted to this
tQpic. It is hoped that this analysis will provide further confirmation and
support to the Food and Drug Administration's efforts already underway on this
problem. ,
9.3.2.3
High-Lead Paint in Homes--
The special problem of high-lead paint in homes has been alluded to
earlier. This is acknowledged to be the .principal cause of childhood lead
poisoning, probably affecting several hundred thousand children, peimarily
those in substandard and deteriorated housing in the cities of the U.S. Since
at the time these lead paints were applied, in the years prior to WW II, lead
contents of the paint were characteristically as high as 60 percent or greater,
even a few chips of paint eaten by a child will produce unacceptable doses.
For these children the fraction of dose from this cause can be overwhelming,
and obviously receives a + rating. The problems arise from ingestion, which
is a totally direct route (+).
As noted in Section 4.3.3, it has been estimated that several million
tons of lead-based paints have been applied to houses, a dissipative use (+).
As Chisolm (1977) has noted, there were, according to the 1970 U.S. Census,
30 million dwelling units built before 1950 and still in use. It is
generally estimated that at least 90 percent of this old housing stock
contains lead-pigment paints in areas accessible to children. As discussed in
Section 7.4.3, Gilsinn (1972) has estimated on the basis of census data that
approximately 7,000,000 housing units are old enough to contain paint made
with high concentrations of lead, and that as many as 600,000 children in
241 standard metropolitan statistical areas (SMSA's) had elevated blood lead
levels (>40 ~g/dl). While this is numerically but a small fraction of the
total population, the risk is high.
Although the tonnage of lead paint which has been applied to homes is in
the millions of tons, the rate of release of flaking lead paint and lead-
containing plaster released to the environment is relatively quite small (-).
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L--
Nevertheless, the location of the releases and their concentrated nature give
them a significance far beyond their quantities. Since the entry to the body
is by ingestion, the route of exposure is direct, (+), and the risk is
compounded by the high absorption of children. The bioavailibility is
reportedly less for lead in a paint film than for lead in some of the soluble
lead salts, but it is quite high enough to have caused numerous cases of
lead poisoning in children, and is rated +.
However, this situation is another facet of the "resource in use"
category comprising the huge inventory of millions of tons of lead already
in place, and is one which will not be effectively controlled by limitations
on future lead use.
There are few satisfactory alternatives (-). Elimination of the problem
by immediate demolition of the affected housing and its replacement by new
lead-free housing does not appear to be an economically feasible solution (-).
A process of applying a heat-set shrink film has been developed to cover and
effectively seal off painted interior woodwork (Mirick and Nowacki, 1977), but
the economics and practical feasibility of this approach is doubtful.
A simple and sure solution to the problem of high lead paint and plaster
(and the concomitant high lead contents of the associated house dust) in old
and deteriorated substandard housings has not been devised. Some legislation
does exist, e.g. HUD's regulations covering lead paint in Federally-owned
or assisted housing (See Section 9.4.1.15), but this legislation does nothing
for non-Federal housing.
Some states, e.g. Massachusetts, have enacted legislation which requires
removal or cover of paint, plaster, or other accessible materials containing
dangerous levels of lead in residential premises where a child under 6 years
of age resides. Painting over with non-lead-based paint does not constitute
compliance. As a result of this Act, it is estimated that during the 3-year
period 1975-1977, approximately 10,000 units were deleaded in Massachusetts
(which represents, however, only 3.3 percent of the 300,000 units throughout
Massachusetts still to be deleaded) (Feldman, 1978). Even this solution is
not without problems. In the effort to protect children from the hazards of
lead paint, some of those removing it are falling victim. Unsafe deleading
procedures are resulting in cases of lead intoxication among the de leaders
themselves (Feldman, 1978).
It is not clear how present-day limitations can overcome the adverse
effects of lead paint applied to houses perhaps 40 or more years ago. Some
possible non-structural approaches to mitigating the child poisoning problem
are discussed in Section 9.3.4.
9.3.2.3
Lead-Based Paints--
The Lead-Based Poisoning Prevention Act (LBPPA) defines as lead-based
any paint containing more than 0.06 percent lead and their use is banned as
a hazardous product in situations where there is a reasonable probability that
children would have access to them, i.e. around the home. Metal furniture was
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subsequently exempted from the ban, and The Consumer Product Safety Commission
also determined that paints used industrially were not "consumer products"
and hence were not within the scope of the LBPPA.
The lead exposure hazard of lead-based paints is only to the childhood
segment of the general population; the exposure to adults is minimal. (There
can be major risks to painters, scrap yard employees, and ship breakers, but
these are occupational problems, excluded from this analysis. OSHA has
addressed these problems in its latest regulations).
The recycling of painted steel scrap to steel furnaces is a contributor
to atmospheric lead emissions, but limitation of such emissions is better
controlled as a part of steel industry regulations than as a seperate category.
The reduction in average individual absorbed dose from such limitation would
be expected to be small; the benefits would accrue principally to residents
in the proximity of such furnaces.
Lead-based paints were rated as +'s as a dissipative use, with a high
bioavailibility, with technically and economically feasible alternatives
available, and with special benefits occruing to the susceptible childhood
segment of the population by their limitation. However, since lead has
effectively been banned for uses where children might be harmed, the problem
is a most one with respect to any need for additional limitations.
9.3.2.5
Printing Inks--
The brilliant colors provided by lead chromate pigments are utilized in
colored printing inks to a certain extent. Chief use appears to be for
colored pictures in magazines and books and in the gaily-colored gift wrapping
papers and foils. (The Consumer Products Safety Commission is now investi-
gating this area).
Tonnage data were not identified, but only a fraction of the 15,000
metric tons of pigment colors consumed in 1976 went to printing inks.
Ultimate fate of most printed matter appears to be a landfill or an inciner-
ator; the latter would contribute slightly to air emissions of lead.
The chief concern with printing inks is the exposure to small children
who might chew paper, one form of pica. This is presumed to be a less common
occurrence than chewing woodwork, and the lead content of printed colored
paper is only a fraction of that of lead-based paint; 0.12 percent was found
by Campbell (1976). This is only twice the 0.06 percent allowable content of
"lead-free" paints, and appears to present a minimal risk.
Printing inks received + ratings for directness of exposure (through
ingestion), a high bioavailibility, and as comprising a dissipative use.
However, the fraction of dose estimated to result from this cause was rated as
minor, and alternatives are available which are technically and economically
feasible.
A limitation on the use of lead pigments in inks used for children's
books might be considered, but the reduction in individual absorbed dose would
433
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probably be imperceptible.
limitation.
This appears to be a low-priority candidate for
9.3.2.6
Lead-Acid Storage Batteries--
Lead-acid storage batteries represents the largest single use of lead
(upwards of 750,000 metric tons of lead were consumed in 1976), and annually
consumes more than half of total consumption. However, it also represents an
outstanding example of an essentially non-dissipative use, not exceeded by
any other base metal. The lead in a storage battery is used in a closed
container, with no losses to the environment during use. The exposure of the
general public to lead from the use of batteries is virtually nil, and no
dose benefits would accrue if lead batteries were replaced by non-lead
battery substitutes. There is no apparent alternative or technically and
economically feasible substitute for the lead-acid battery. Noteworthy
developments in battery technology include the current trend to the mainte-
nance-free lead-calcium battery in place of the older lead-antimony type.
On a longer-term basis other battery systems are in the research and
development stage. Of these candidates, the zinc-air battery is judged to
be the one most likely to approach the lead-acid battery in its present
applicability to existing needs, but practical commercial forms of this
battery are projected to be at least five years away, with a price several
times higher than lead-acid storage batteries. Other lead-free systems are
being investigated, but it is estimated that it may be 10 to 15 years before
any of these could successfully replace lead storage batteries.
,
The above discussion considered the lead exposure hazard resulting from
the use and application of lead-acid storage batteries and found it to be
insignificant. The industrial processes associated with this endeavor;
battery breaking, secondary smelting of old batteries, oxide production, and
pasting of battery plates, are another matter. Significant air and water
emissions of lead are possible, and regulation of the operations is needed to
prevent creation of lead exposure hazards. However, these are the same
problems encountered throughout the lead processing industry, and are not
unique to storage batteries. These are better considered all together as
process emissions problems (see Section 9.3.2.10).
Lead-acid storage batteries ranked very low as a candidate for limita-
tions (See Table 9.2). This is a non-dissipative use, with a biologically
non-available form of lead, releases almost none to the environment, has no
technically or economically feasible alternatives, and even rigorous
limitations on the use of lead storage batteries would do essentially nothing
towards reducing average lead intakes.
9.3.2.7
Lead in Plastics and Rubber--
Lead stabilizers find use in plastics, primarily PVC, e.g., for electric
wire insulation, to protect the plastic from the heat necessary for their
processing and forming (this use consumed about 8,000 metric tons in 1975
(see Section 5.2.2.4). This is a wholly dissipative use (+); none of it is
recycled. The bioavailibility of the lead in the plastic is low (-), the
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likelihood of a direct exposure through ingestion of such items is also low
(-). The fraction of the average individual's dose attributable to this
source is estimated to be unmeasurable (-).
The lead-containing plastic items (perhaps 1-2 percent lead) are
eventually discarded to waste, probably either to a landfill or to an
incinerator, analogous to the fate of paper. In the one case lead could
leach out to groundwater, and comprise an atmospheric emission in the other.
No information was identified on the resultant health hazards; in the absence
of definite information the judgement is made that the quantities so
released would be small to moderate (0) and that they would not constitute
major lead exposure hazards.
Some alternative stabilizers are available for this use, primarily tin
compounds, which may also pose their own risk (0). Overall this application
did not appear to warrant a high priority for consideration of limitations.
9.3.2.8
Lead Ammunition--
Two problems have been identified with respect to the environmental
effects of lead ammunition, one widespread and one quite unusual and rare.
The use of lead shot has been proven to produce serious lead poisoning in
waterfowl, causing the death of up to 2.4 million annually, excluding
sublethal effects that make millions of additional birds more vulnerable to
disease and predation (Carter, 1977). This situation obviously called for
some kind of limitations, not because' of human health implications, but
for the public welfare.
In response to this need, the U.S. Fish and Wildlife Service has
instituted a prohibition against the use of lead shot in the flyways most
affected; steel shot has been substituted for lead shot.
The unique case concerned employees at an indoor pistol range who
developed clinical symptoms of lead poisoning, due apparently to excessive
air lead concentrations. No reports of similar cases have been identified,
and this case is so unusual that it would appear to have only a low priority
with respect to candidacy for environmental limitations; Perhaps the only
limitation needed would be an extension of OSHA regulations on occupational
exposure to lead to such establishments.
9.3.2.9
Miscellaneous Uses of Metallic Lead--
Metallic lead is employed for a variety of uses utilizing its high
density and corrosion resistance, and for many of these uses there are few
practical substitutes. Radiation attenuation, ballast, sound absorbers,
tire balancing weights, lead pipe, and flashings are a few examples of such
uses (see Section 4.3.5 and 5.2.2.5).
Although there are few data on the recycle of lead from such uses, as a
generalization it may be observed that the extent of retrieval and recycle is
inversely proportional to the diffuseness of the use and directly proportional
to the mass of the individual pieces. Thus, recycle may be relatively high for
435
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t-
large items used industrially, and near zero on little items widely scattered,
such as tire balancing weights. Recycling is basically a function of
economics, and will improve as it becomes more economically attractive, either
by natural increases in lead prices, or by the incorporation of some subsidy
arrangements.
However, the alternate destination besides recovery and recycle is most
probably to a landfill, from which its dispersal to the environment would be
negligible because of its chemically inert metallic form.
The factors in this category were characterized by - and 0 ratings
(Table 9.2) and the need for investigation of possible limitations was
assigned a low priority.
9.3.2.10
Emissions from Lead Industry Processes--
One non-negligible source of exposure to lead and its compounds is
the lead industry and its processes (along with lead emissions encountered
in processing other nonferrous base metal ores). These exposures arise
primarily from lead-containing air and water emissions. These will be found
at lead mines and mills, primary and secondary lead smelters, storage battery
plants, and pigment plants.
The present status of limitations on lead producing and consuming
industries is described in some detail in Section 9.4, and it is evident
from the variety of these that a high priority has been assigned to controlling
these emissions. Since this has been a continuing effort for a number of
years most of the major lead exposure problem areas have been taken care of.
Effluent guideline limitations remain to be promulgated for lead battery
manufacturing, and air emission standards specifically regulating lead
emissions from existing smelters, etc., have not yet been developed. The 3
newly-promulgated ambient air lead air quality standard for lead of 1.5 wg/m
(U.S. Environmental Protection Agency, 1978), will no doubt have the indirect
effect of controlling air emissions from these existing sources.
The acquisition of the detailed experimental and field data on emissions,
required to establish a basis for proposing additional limitations, was
beyond the scope of this program. No further recommendations can be offered
until the impacts of recent regulations are observed. Overall, the area of
lead emissions from lead producing and consuming industries appears to be
fairly well in hand.
9.3.2.11
Emissions from Indirect Sources--
A number of so-called indirect sources, not part of the lead industry,
are emitters of lead, primarily to the atmosphere. These are sources where
lead is present as a minor constituent, as in coal, fuel oil, or cement rock,
or as one component of a waste, as in solid waste or sewage sludge (see
Section 5.2.3). As noted therein, and tabulated in Table 5.1, these do not
comprise major point sources of lead emissions, although the sum of all such
emissions is estimated at several thousand tons. Lead-painted steel scrap
accounts for an indeterminate fraction of the lead emitted from iron and steel
furnaces. Discarded lead-bearing materials, e.g. colored magazine paper, lead
436
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containing rubber or plastics, waste lubricating oil, solder from tin cans,
tire weights, lead toys, collapsible tubes, lead storage batteries, etc.,
account for the approximately 1,200 metric tons emissions estimated for the
incineration of solid wastes (Section 5.2.3.4).
These sources are fairly diffuse geographically, and vary widely in
performance and emission characteristics. Limitations have been promulgated
for a number of the types of sources based on control of particulates, which
are regulated on a "process-weight" basis. Since lead is emitted as a
particulate, these regulations afford a fair degree of control of lead
emissions. The detailed experimental and field emission data needed to
propose additional limitations on lead emissions was not available to this
investigation, and no recommendations for additional limitations can be
offered. The 1.5 ~g/m3 ambient air lead standard may provide all the control
needed for these sources. In total, they contribute little to the average
individual lead intake, and additional limitations from point sources of
this type are not regarded as high priority items.
However, one other type of indirect source which has resulted in the
dispersion of lead and lead compounds to the environment is solid waste
dtsposal. One facet of this is the disposal of wastes of all sorts to
landfills; this has been largely uncontrolled in the past, and the Resource
Conservation and Recovery Act of 1976 (RCRA) was enacted in response to
this need. Another facet is the disposal of sewage sludge to agricultural
lands. Such sludges may contain lead and other heavy metals, cadmium being
the one of most current concern, and criteria are needed for these heavy
metals.
9.3.4.
Non-Structural Approaches
The inapplicability of new limitations on lead use, handling, and
disposal to mitigate the very serious problem of lead poisoning of children
living in substandard and deteriorated housing painted with high-lead paints
was alluded to in Section 9.3.2.3. This historical problem may well continue
until the lead-containing substandard housing is eventually replaced.
However, immediate demolition and replacement is probably an unattainable
solution because of the costs. It may also be impractical and near-impossible
to identify and eliminate all sources of exposure for these children from
product use or environmental sources, even with stringent controls on lead.
An alternative less-costly solution is available which should very
nearly attain the same objective. The screening of infants and young children,
with appropriate follow-up examinations, can identify the existence of an
incipient problem, before irreversible damage occurs, so that corrective
measures can be promptly instituted. The effectiveness of this approach in
eliminating childhood deaths from lead poisoning and in minimizing childhood
lead poisoning cases has been demonstrated in several cities, for example,
Baltimore (Lutz, et al., 1970) and in Chicago (Sachs, et al., 1970).
On the basis of these and other results demonstrating the effectiveness
of this approach for the control of childhood lead poisoning it seems likely
that intensified surveillance of the population at risk, through local lead
poisoning prevention and treatment centers throughout the nation, probably
437
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offers the most practical method to very significantly reduce, if not
virtually eliminate, the adverse effects of exposure to lead of this most
sensitive segment of the population to the extreme risk of acute lead
intoxication. It should be emphasized that the adverse effects in question
are not threshold effects of lead below traditional levels of concern, as
discussed in Section 9.2.1, but are those associated with clinical lead
poisoning.
Accordingly, the health benefits to be so gained should significantly
exceed those accruing to this particularly sensitive population group from
any other limitation on lead including the 1.5 ~g/m3 ambient air lead standard,
or from any of the limitations on adventitious lead entering food.
Thus, while this surveillance and treatment is not a limitation on lead,
per se, its potential health benefits are so large that it is strongly
recommended that the potential of additional local, state and Federal funding
of this approach be very seriously considered. Because such a substantial
stock of old lead-painted housing is still in use in this country, the need
for screening and pediatric management in high-risk areas will continue for
some years. The benefit: cost ratio for this approach is believed to be as
high or higher than any other action which has been instituted or proposed
for consideration.
Non-structural approaches can be applied to other areas, for example,
with proper labelling, lead-containing paints were exempted for certain uses
under the Lead-Based Paint Poisoning Prevention Act (See Section 9.4.1.14).
9.4
EXISTING AND PROPOSED LIMITATIONS
More than thirty existing or imminent Federal regulations governing the
manufacture, use, or disposal of lead and lead-containing compounds have been
identiFied. These fall into two broad general categories: direct regulations
specifically governing lead, and indirect regulations governing some associated
pollutant, the control of which has a high probability of also controlling lead
emissions. (Particulate regulations are a good example of the latter type).
Another way of categorizing existing limitations is whether they govern
a process, a product, or the quality of the environment. Most of the regula-
tions which derive from the Clean Air Amendments of 1970 (PL 91-604) and the
Federal Water Pollution Control Act of 1972 (PL 92-500) control processes
which produce air or water lead emissions through New Source Performance
Standards (NSPS) and Effluent Guidelines. A smaller number of regulations
control products which do or can contain lead, and the final group sets
limits on lead concentrations in air or water.
The known existing limitations are summarized in Table 9.3, and described
and discussed in the following pages. The table indicates the mode of control,
the numerical value of the limitation, the Federal agency exercising control,
and the section of the Code of Federal Regulations (CFR) containing the
official regulation (or Federal Register, if the regulation or proposed
regulation is not yet in the CFR).
At the conclusion of the section some of the recently-enacted enabling
legislation is briefly discussed, which does not specifically apply to lead
and its compounds either directly or indirectly, but which has the authority
438
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TABLE 9.)
SUMMARY OF EXISTING AND PROPOSED FEDERAL REGULATIONS
GOVERNING LIMITATIONS ON LEAD.
Activity
Controlled
Nonferrous ore
mining and milling
Ferroalloy ore min-
ing and milling
Primary lead
Primary copper
Electroplating
Lead battery
manufacture
Chlorine-caustic
Lead monoxide
Chrome pigments
Television picture
tubes
Hand pressed and
blown glass
Lead-sheathed
rubber hose
Gasoline antiknock
additives
Lead-based
paint
Lead-based paint
on housing
Occupational
exposure
Community
water systems
Evaporated milk
Ambient air
standards
Lead-decorated
glassware
Mode of
Control
Effluent
guidelines
Do
Do
Do
Do
Do
Do
Do
Do
Do
Do
Do
Air
programs
Lead
content
Lead content
+ other
Exposure
standard
Lead
content
Lead content
Air
programs
Voluntary
Standard
Limitationa,b
Direct Limitations
0.3 mg/l Pb
0.2 mg/l Pb (mining)
No limitation (milling)
No discharge
No discharge
80 mg/sq m plated
Regulations not yet
promulgated
0.0025 kg/kkg product
No discharge
0.14 kg/kkg of product
4.5 g/kkg glass (BPT)
0.45 g/kkg glass (BAT)
No limits (BPT)
0.1 mg/l (BAT)
0.007 kg/kkg raw
material (BPT & BAT)
0.8 g/gal 1/1/78
0.5 g/gal 10/1/79
0.06 percent Pb
0.06 percent Pb
Elim. in existing
)
50 J,lg/m
housing
50 J,lg/l
0.3 ppm tolerance (proposed)
0)
1. 5 ~,g/m
50 ppm leachable
from lip and rim
(Continued)
439
Agency
Exercising
Control
EPA
EPA
EPA
EPA
EPA
EPA
EPA
EPA
EPA
EPA
EPA
EPA
EPA
EPA
CPSC
HUD
OSHA
EPA
FDA
BPA
°EPA,
FDA,
CPSC
Citation
(40 CFR 440.20)
(43 FR 2977J. )
40 CFR 440.40
40 CFR 421. 70
40 CFR 421. 40
40 CFR 4l).12c
43 FR 6560d
40 CFR 415.60
40 CFR 415.440
40 CFR 415.340
40 CFR 426.110
40 CFR 426.130
40 CFR 428.20
40 CFR 80.20
(16 CFR 1303. )
(16 CFR 1500.17)
24 CFR 35.
29 CFR 1910. 1025
40 CFR 141.11
39 FR 42740
40 CFR 50.12
Under
consideration
-------
TABLE 9.3
(Continued)
Activity Mode of Agency
a b Exercising
Controlled Control Limitation' Control Citation
Direct Limitations
Lead arsenate Lead
residues on food con ten t 7 ppm Pb EPA 40 CFR 180.194
Duck hunting Lead shot Some prohibition DOI 50 CFR 50 CFR 2U.134
Dump ing
Ocean dumping permits Permit required EPA 40 CFR 227.
Indirect Limitations
Primary lead 50 mg/dscm (particulates)
smelters NSPS 0.065 percent S02 EPA 40 CFR 60.180-.186
Primary copper 50 mg/dscm (particulates)
smelters N5P5 0.065 percent 502 EPA 40 CFR 60.160-.166
Secondary lead
smelters N5PS 50 mg/dscm (particulates) EPA 40 CFR 60.120-.123
Ferroalloy produc~ 0.23-0.45 kg/~{-hr
tion facilities NSP5 (particulates) EPA 40 CFR 60.260-.266
Electric arc steel
furnaces N5PS 12 mg/dscm (particulates) EPA 40 CFR 60.270-.275
Incinerators N5PS 0.18 g/dscm (particulates) EPA 40 CFR 60.50-.54
Sludge 0.65 g/kg dry sludge
incinerators N5P5 (particulates) EPA 40 eFR 60.150-.154
Portland cement 0.15 kg/kkg of feed
manufacture N5PS (particulates) EPA 40 CFR 60.60-.64
Gasoline vapor Air 90 percent recovery
recovery programs (stage I)
0.4-0.6 g/gal (Stage II) EPA
Petroleum Air Floating roof or
liquid storage programs equivalent EPA 40 eFR 60.112
aEffluent guideline limitations given are 30-day averages.
bAbbreviations:
BPT - Best practical control technology currently available
BAT - Best available control technology economically achievable
N5PS - New Source Performance Standards
dscm - Dry standard cubic meter
cElectroplating effluent guidelines standards suspended December 3, 1976.
d
Pretreatment standards reproposed February 14, 1978.
440
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to set such regulations and may do so at some future date when fully
implemented.
9.4.1
Direct Limitations on Lead
Direct limitations include those governing water and air emissions from
the various manufacturing segments of the metals industries, and use-related
emissions; those establishing limits on lead concentrations in air or water,
and those governing disposal.
Emissions to waterways are governed by Effluent Limitations Guidelines,
established under the authority of the Federal Water Pollution Control Act
amendments of 1972 (P.L. 92-500). By the terms of the Act, two levels of
control are to be achieved; initially the "best practical control technology
currently available" (BPTCA, or colloquially, BPT) and at a later date a
higher level of control designated "best available technology economically
achievable" (BATEA, or, colloquially, BAT). BPT was to have been achieved by
July 1, 1977 and BAT by July 1, 1983, but for a number of reasons these dates
have been extended.
Effluent guidelines may be established for existing sources, for new
sources, and for pretreatment before discharge to a publicly-owned wastewater
, treatment plant. Another characteristic of Effluent Guidelines Limitations
is that they are source-oriented and control emissions from point sources;
the quality of the receiving body of water is not a factor in the limitations.
The scope of air emission regulations is narrower than those for aqueous
effluents. These are promulgated under the authority of the Clean Air Act, as
amended in 1974, and as further amended by the Clean Air Act Amendments of
1977 (P.L. 95-95). Federal standards apply only to new sources: standards
for existing sources are set by the states.
9.4.1.1
Nonferrous Ore Mining and Milling--
Under Ote Mining and Dressing, Subpart B, Base and Precious Metals
Subcategory (40 CFR 440.20) effluent limits on lead have been set on both mine
drainage and effluents from froth flotation mills at (0.3 mg/l)*. These limi-
tations cover mines operated to obtain copper-bearing ores, lead-bearing ores,
zinc-bearing ores, gold-bearing ores, silver-bearing ores, or any combination
of these ores from open-pit or underground operations. The limitations are for
BpT; no BAT limitations have yet been promulgated. These final limitations just
recently issued (43 FR 29771) supersede the interim final regulations and slightly
adjust lead concentrations.
As a general rule, large-scale, outdoor-type, indurtrial. and mining
operations, such as the ferrous and nonferrous industries, are also granted
a variance to discharge untreated overflow in excess of the quantity resulting
from specified maximum storm events, generally in the case of BPT defined
as the 10-year, 24-hour precipitation event.
*Values cited in this section for effluent guidelines are the 30-day averages
not to be exceeded. Daily maximums are higher, most frequently by a factor of 2.
441
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9.4.1.2
Ferroalloy Ore Mining and Milling--
Subpart D, the Ferroalloy Ores Subcategory of the Ore Mining and Dressing
Category, (40 CFR 440.40) places lead effluent limits on mines producing more
than 5,000 metric tons or more of ferroal1oy ores per year. Ferroalloy metals
include chromium, cobalt, columbium, tantalum, manganese, molybdenum, nickel,
tungsten, and vanadium. Effluent limits (BPT) for mine drainage for lead is
0.2 mg/l. There are no limits on effluents from flotation mills. The
ferroalloys are characteristically high-value, low-tonnage metals, and mine
tonnages are minor, compared to those of copper, lead, and zinc. For example
1975 tonnages of lead and zinc ores were 7.8 and 5.7 million metric tons,
respectively (Section 5.2.1.1). Losses of lead to effluents for the ferroalloy
ores are correspondingly minor.
9.4.1.3
Primary Lead--
Subpart G, the Primary Lead Subcategory of the Nonferrous Metals
Manufacturing Point Source Category (40 CFR 421.70), includes the production
of lead at primary lead smelters and refineries, but primary lead refineries
nnt located on-site with a smelter are not part of this subcategory.
BPT limitations are for "no discharge of process waste water into
navigable waters". There are two exceptions. If an impoundment is designed
to contain the 10-year, 24-hour precipitation event, process waste water equal
to the excess collected in such an event may be discharged. Discharges may be
made monthly of the excess of precipitation in the impoundment above evaporation,
except that the lead content of such discharges shall not exceed 0.5 mg/l.
BAT limitations are analogous to the BPT limitations, the principal
difference being that the storm event is increased to the 25-year, 24-hour
event.
9.4.1.4
Primary Copper--
Subpart D of the Nonferrous Metals Manufacturing Point Source Category
covers the Primary Copper Subcategory (40 CFR 421.40). As with lead, primary
refineries not on site with primary smelters are not included; in the case of
copper refining, there is a separate subcategory to cover these facilities.
Limitations on lead discharges from
as for primary l~ad; no_discharge except
discharges of such excess are limited to
events.
primary copper operations are the same
for excessive precipitation, and routine
0.5 mg/1 lead, except for maximum storm
9.4.1.5
E1ectrop1ating--
Limitations on lead discharges are specified only for the Electroplating
of Common Metals Subcategory (Subpart A) of the Electroplating Point Source
Category (40 CFR 413.12). Omitting some of the minor details, lead discharges
are not to exceed 80 mg per square meter per operation. Since areas of
irregular surfaces are essentially indeterminate, other parameters such as
442
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ampere-hours used in plating can be used, after calibration.
Effluent guidelines regulations were originally promulgated April 24, 1975
(40 FR 18130-18148). These were challenged by the industry, and the common
metals subcategory regulations were suspended December 3, 1976 (41 FR 53018).
Proposed pretreatment standards for existing sources were re-proposed February 14,
1978, (43 FR 6560-6573), and are still in the comment period.
9.4.1.6
Lead Storage Battery Manufacture--
Work is in progress on the establishment of effluent guidelines for the
manufacture of lead storage batteries, but no information on limits is yet
available.
9.4.1. 7
Chlorine-Caustic--
Subpart F of the Inorganic Chemicals Manufacturing Point Source Category
covers the Chlorine and Sodium or Potassium Hydroxide Production Subcategory
(40 CFR 415.60). Plants using the diaphragm cell process for the manufacture
of chlorine and caustic are limited to 1ead.discharges of not ~reater than
0.0025 kg/kkg of product (2.5 g/metric ton) to meet BPT guidelines.
Guidelines for BAT are "no discharge".
9.4.1.8
Lead Monoxide--
Lead monoxide (litharge) manufacture is covered by Subpart AR, Lead
Monoxide Production Subcategory of the Inorganic Chemicals Manufacturing
Point Source Category (40 CFR 415.440). BPT limitations are "no discharge of
process waste water pollutants to navigable waters".
9.4.1.9
Chrome Pigments--
The manufacture of chrome pigments is covered by Subpart AH, Chrome
Pigments Production Subcategory of the Inorganic Chemicals Manufacturing
Point Source Category (40 CFR 415.340). BPT limitations are 0.14 kg/kkg of
product (140 g/metric ton).
9.4 . 1. 10
Television Picture Tubes--
Lead glass is used in fabricating television picture tubes, and aqueous
lead discharges can result from the grinding and polishing of the tube
envelopes. Lead discharges are controlled by Subpart K, Television Picture
Tube Envelope Manufacturing Category of the Glass Manufacturing Point Source
Category (40 CFR 426.110), which covers the process by which raw materials are
melted in a furnace and processed into picture tube envelopes.
BPT limits on lead are 4.5 g/kg of furnace pull.
by a factor of 10, to 0.45 g/kkg of furnace pull.
443
BAT limits are lowered
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9.4.1.11
Hand-Pressed and Blown Glass--
Subpart M, the Hand-Pressed and Blown Glass Manufacturing Subcategory of
the Glass Manufacturing Point Source Category, covers the production of
handpressed and blown lead glassware (40 CFR 426.130). There are no lead
limitations for BPT. BAT imposes lead concentration limits of 0.1 mg/l in waste
discharges.
9.4.1.12
Lead-Sheathed Rubber Hose--
The discharge of lead from the manufacture of lead-sheathed rubber hose is
covered under Subpart G, the Large-Sized General Molded, Extruded and
Fabricated Rubber Plants Subcategory of the Rubber Manufacturing Point Source
Category (40 CFR 428.20). Both BPT and BAT lead limitations are 0.007 kg/kkg
(0.7 g/metric ton) of raw material.
9.4.1.13
Gasoline Antiknock Additives--
The dispersal of lead to the atmosphere through the combustion of leaded
gasoline is by far the largest loss of lead tQ the environment, dwarfing the
total of all other emissions combined. Thus, it was appropriate that EPA
regulations have been promulgated to reduce this major source of lead emissions.
The Environmental Protection Agency, on December 6, 1973, published
(38 FR 33734) regulations designed to phase down the average lead content of
gasoline by steps, down to 0.5 g/gal by January 1, 1979. The announcement
stated that it was "the Administrator's judgement that the promulgated
reduction schedule is reasonable from the standpoint of protection of health
and from the standpoint of economic and technological feasibility".
In spite of this judgement the regulations were the subject of lengthy
litigation until June, 1976, at which time the U.S. Supreme. Court denied
certiorari, effectively reinstating them. Due to the length of elapsed time,
the phase down time schedule had to be modified somewhat. The date for
compliance with the 0.5 g/gal level is now October 1, 1979. The January 1,
1978 standard of 0.8 g/gal remained in effect, but could be suspended if a
refiner could show due dilignece incompliance efforts. Most large refiners
were able to show due dilignece, and as a result the average lead content of
the gasoline pool in 1978 was 1.20 g/gal (Table 4.16).
The small refiners (producing less then 25,000 barrels/day of gasoline)
as facing proportionally higher costs to comply, with smaller financial resources
to support the modifications. Accordingly, an October 1, 1979 level of 1.0 g/gal
for small refiners was proposed by EPA (42 FR 3183, January 17, 1977). It was
estimated that this would raise the ultimate lead average level to about 0.52
g/gal, with the effect on ambient lead concentrations considered to be
negligible. However, the Congress included in the Clean Air Act Amendments of
1977 specific relief for the small refineries of small refiners. A new rule was promul-
gated by EPA in response to this amendment which provides for a sliding scale of
444
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lead content increasing to a maximum of 2.65 g/gal for a 5,000 barrels/day
refinery (43 FR 17841-17842, April 26, 1978). It is estimated that this
will affect about 5.5 percent of the U.S. gasoline supply and raise the average
gasoline pool lead to 0.59 g/gal.
9 . 4 .1. 14
Lead-Based Paint--
On September 1, 1977 (42 FR 44192-44202) the Consumer Product Safety
Commission (CPSC) issued regulations governing lead-containing paint and
certain consumer products bearing such paint, with an effective date of
February 28, 1978, which banned, as hazardous products:
(1)
Lead-containing paint and similar surface-coating materials
containing more than a safe level of lead.
(2)
Toys and other articles intended for use by children bearing
lead-containing paint or other similar surface-coating
material containing more than a safe level of lead.
(3)
Articles of furniture bearing lead-containing paint or other
similar surface-coating materials containing more than a
safe level of lead.
The question of what is a safe level of lead has gone thrnugh a series of
revisions. At one time this was any paint containing less than 1 percent lead
in the dried film. A later amendment to the Lead-Based Paint Poisoning
Prevention Act (LBPPPA) reduced this to 0.5 percent, and directed the CPSC to
determine if a level of lead in paint in excess of 0.06 percent but not over
0.5 percent was safe.
On February 16, 1977 (42 FR 9404), The Consumer Product Safety Commission
announced its decision that available scientific information is insufficient to
establish that a level of lead in paint above 0.06 percent but not over 0.5
percent is safe. The result of this decision was to classify any paint
manufactured after June 22, 1977 containing more than 0.06 percent lead
as lead-based paint, under the LBPPPA.
The regulations exempt major appliances such as refrigerators and ranges
and household items such as venetian blinds from the "furniture article"
category; and a subsequent amendment excludes metal furniture. Also exempted,
if properly labelled were the following coatings:
(1)
Agricultural, and industrial equipment refinish coatings.
(2)
Industrial (and commercial building) maintenance coatings,
including traffic and safety marking coatings.
(3)
Graphic arts coatings (products marketed solely
on billboards, road signs, and similar uses and
marking in industrial buildings).
for application
for identification
(4)
Touch-up coatings for automobiles, agricultural and industrial
equipment, lawn and garden equipment, boats, outboard motors,
motorized recreational vehicles, and appliances.
445
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Catalyzed coatings marketed sold solely for use on radio-controlled
model powered air craft.
Exempted without the labeling requirement were:
(5)
(1)
Lead-paint backed mirrors which are part of furniture articles.
(2)
Artists paints and similar materials.
Excluded as not qualifying as consumer products were automotive and
marine coatings.
9.4.1.15
Lead-Based Paint in Federally Owned or Assisted Housing--
TheLBPPPAwas first enacted in 1971 (P.L. 91-695) to deal with the problems
of childhood lead poisoning caused by the ingestion of lead-based paints. The
original act prohibited, after January 13, 1971, the use of lead-based paint
in residential structures constructed or rehabilitated by the Federal
government, or with Federal assistance in any form. The term "lead-based
pC'lint" was defined as any paint containing more than 1 percent lead in the
dried paint film.
The LBPPPA was amended in 1973 (P.L. 93-151), which among other things
redefined "lead-based paint" to mean any paint with over 0.5 percent lead in
the dried film. The LBPPPA was again amended in 1976 by enactment of the
National Consumer Health Information and Health Promotion Act (P.L. 94-317).
Pursuant to these various pieces of legislation, the Department of
Housing and Urban Development (HUD) issued July 13, 1976 (41 FR 28876)
regulations revising 24 CFR Part 35 governing numerous controls on HUD-
associated housing constructed prior to 1950. These regulations, among
things:
other
(1)
Require HUD to notify purchasers and tenants of HUD-
associated housing constructed prior to 1950 of the
hazards of lead-based paint poisoning.
(2)
Prohibit the use of lead-based paint in HUD-associated
housing.
(3)
Provide for the elimination, to the extent practicable,
of lead-based paint hazards in HUD-associated housing
(and similarly in Federally-owned housing prior to
sale for residential habitation).*
*
"All surface conditions identified as immediate hazards are to be
thoroughly cleaned (washed, sanded, wire-brushed, scraped or otherwise
cleaned) as to remove all cracked, scaling, peeling, chipping, and
loose paint on applicable surfaces. Surfaces shall then be repainted
with two coats of a suitable non-leaded paint."
446
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9.4.1.16
Occupational Exposure to Lead--
The Occupational Safety and Health Administration (OSHA) of the
Department of Labor proposed (41 FR 45934, October 3, 1975) to amend 29 CFR
Part 1910 to the effect that the permissible employee lead exposure limit to
an 8-hour time-weighted average concentration, based on a 40-hour work week
be 100 ~g/m3, rather than the present 200 ~g/m3 standard. The proposed
regulations also governed the determination of employee exposure, methods of
compliance, personal protective equipment and clothing, training, medical
surveillance, and recordkeeping.
The final standard was promulgated on November 14, 1978 (43 FR 52952-
53014), with an effective date of February 1, 1979. It differed from the proposed
regulations in thaS the maximum allowable 8-hour time-weighted-average was
reduced to 50 ~g/m , with compliance dates by which this must be achieved varying
from one year for "all other industries", to five years for lead pigment
manufacturing, nonferrous foundries, battery manufacturing, and secondary lead
production, and to ten years for primary lead production. The final regulations
also govern protective equipment, and clothing, monitoring, housekeeping,
hygiene facilities and practices, medical surveillance, medical removal protection,
and emp~oyee training.
It is of interest to note that these regulations govern only
occupational exposure of employees at their workplaces, and totally ignore
emissions to the general environment outside the workplace. Thus, it is
conceivable that the net result of the adoption of the 50 ~g/m3 limitation
may well be to increase air lead emissions, since increasing ventilating air
is one of the easiest and most economical means of reducing in-plant air lead
concentrations.
9.4.1.17
Drinking Water Standard--
The maximum contaminant level for lead, applicable to community water
systems (a public water system serving> 15 year-round service connections or
> 25 year-round residents) is 0.050 mg/1 (50 ~g/l). (40 CFR 141.11).
9.4.1.18
Evaporated Milk--
On December 6, 1974, the Food and Drug Commission published proposed
regulations limiting the lead content of evaporated milk and evaporated skim
milk to 0.3 ppm (39 FR 42740). The limitation was proposed as a tolerance.
"Limiting an unavoidable substance through use of a tolerance rather than an
action level is appropriate when there are no changes foreseeable in the near
future that might affect the appropriateness of the limitation established.
The commissioner concludes that additional improvements in can technology,
futher reducing the levels of lead in evaporated milk are not expected in the
near future".
447
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_..
On February 18, 1978, the Acting Director of The Bureau of Foods, outlined
a 5-year plan to reduce lead intake from soldered cans by 50 per cent as well
as to further reduce the background levels in canned and other foods. It was
indicated that an advance notice of proposed rulemaking would be issued in the
fall of 1978, and it is expected that the question of lead in evaporated milk
will be addressed in that document.
9.4.1.19
Ambient Air Standards--
The U.S. Environmental Protection Agency was mandated by the courts
to develop an ambient air quality standard for lead, on the grounds that it had
been judged a criteria pollutant. In response to this mandate a ambient air
quality standard was issued (U.S. Environmental Protection Agenc~, 1978), which
instituted a primary and secondary air lead standard of 1.5 ~g/m , quarterly
arithmetic mean.
As noted earlier, this ambient air quality standard, will indirectly govern
many point source emissions.
9.4. 1. 20
Lead Arsenate--
The tolerances for residues of lead arsenate in or on raw agricultural
commodities, as established by EPA (40 CFR 180.194) are as follows:
- 7 ppm of combined lead in or on apples, apricots, asparagus,
blackberries, blueberries, boysenberries, celery, cherries,
cranberries, currants, dewberries, eggplants, gooseberries,
grapes, loganberries, mangoes, nectarines, peaches, pears,
peppers, plums, quinces, raspberries, strawberries, tomatoes,
and young berries
- 1 ppm of combined lead in or on citrus fruits.
In view of the importance which has been shown for lead ingested with food,
this level is considered to be excessively high, and should be lowered.
However, as of now, there appears to be negligible or nil lead arsenate
being manufactured or used on food crops in the United States. Accordingly,
no objections to a reduction (or possibly even a banning) would be anticipated,
and the revision would be little more than a formality. Thus, such a limitation
would fall into the insurance category, to preclude the recurrence of this
lead exposure hazard at some possible future date.
9.4. 1. 21
Lead Shot--
On July 28, 1976, the Fish and Wildlife Service of the Department of
the Interior published (41 FR 31395) a proposed regulation amending 50 CFR
20 to govern the use of lead shot in certain specific areas of the Atlantic
Flyway. The amendment prohibits taking ducks, geese, and coots with a
shotgun containing shells loaded with shot composed of any metal other than
such material as may be determined to be non-toxic to migratory waterfowl.
At the present time the only shot type available and approved is steel shot.
448
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Over the past two seasons the FWS has required hunters along parts of
the Atlantic and Mississippi flyways to switch from lead to non-toxic
steel shot. By Fall, 1978, the regulations will apply to parts of the
Central and Pacific flyways as well (Carter, 1977).
9.4.1.22
Ocean Dumping--
While the ocean dumping of lead-containing materials is directly
controlled by the regulations embodied in 40 CFR 227, Criteria for the
Evaluation of Permit Applications, the limitation is applicable in a round-
about way. Lead is named as one of the group of materials requiring special
care, in the class of Strictly Regulated Dumping. This classification re-
quires that evidence of the acceptability of proposed acts of disposal will
be required from the applicant according to specified criteria. This will
involve demonstration that the material proposed for disposal meets the
limiting permissible concentration of total pollutants as defined, consider-
ing both the concentration of pollutants in the waste material itself, and
the total mixing zone available for initial dilution and dispersion.
It is evident from the above that this limitation is applied on a case-
by-case basis, which may be cumbersome at times, but which will not hamper
its effectiveness.
9.4.2
Indirect Limitations
There are a number of indirect limitations applied to various industrial
and manufacturing operations which to some extent also control the emission
of lead to the enYironment. The two preeminent indirect controls are those
on air borne particulates through New Source Performance Standards (NSPS),
and on hydrocarbon vapor losses. Except for the alkyl leads, as in gaso-
line, lead will be present in particulate form, and control of particulates
should also adequately control lead emissions. Data contained in the recent
EPA report on control techniques for lead air emissions (U.S. Environmental
Protection Agency, 1977c) indicate that excessive losses of lead are not
occurring.
9.4.2.1
Primary Lead Smelters--
On January 15, 1976 (41 FR 2332) the U.S. Environmental Protection
Agency promulgated New Source Performance Standards for Lead Smelters.
Covering basically air emissions of particulates and sulfur dioxide (FR 40
60.180-.186). Maximum allowable particulate concentration is 50 ~g/dscm
(dry standard cubic meter), equivalent to 0.022 grains/dry standard cubic
foot, and maximum allowable sulfur dioxide concentration was 0.065 percent
by volume.
These two regulations also effectively control emissions of lead
particulates. Compliance with the sulfur dioxide regulation essentially
requires a sulfuric acid plant, the gaseous feed of which must be free of
particulates to avoid plugging the contact catalyst bed, and this is a
considerably more stringent requirement than the 50 mg/dscm.
449
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9.4.2.2
Primary Copper Smelters--
. On the same date analogous NSPS regulations were promulgated for
pr~mary copper smelters (40 CFR 60.160-.166). The same considerations
apply here as to lead smelters. Also, identical limitations were promulgated
at the same time for zinc smelters, but these are an insignificant source
of lead.
9.4.2.3
Secondary Lead Smelters--
EPA regulations covering NSPS for secondary lead smelters were issued
March 8, 1974 (39 FR 9308), with the same 50 mg/dscm (0.022 gr/dscf) limits
as for primary smelters, but, of course, with no sulfur dioxide limitations.
(40 CFR 60.120-.123).
9.4.2.4
Secondary Brass and Bronze Ingot Production Plants--
Regulations for secondary brass and bronze plants, another potential
source of lead air emissions, were promulgated at the same time as those
for secondary lead smelters, also with the 50 mg/dscm (40 CFR 60.130-.133).
9.4.2.5
Ferroalloy Production Facilities--
Regulations have been issued to limit emissions of particulates from
ferroalloy electric submerged arc furnaces. Regulations are in terms of
emissions per unit of energy input, and range from 0.23 kg/mw-hr for one
group of alloys, to 0.45 kg/mw-hr for some of the silicon-based alloys
(40 CFR 60.260-.266).
9.4.2.6
Electric Arc Steel Furnaces--
Standard of performance for particulate matter is that gases discharged
from a control device shall not contain particulate matter in excess of
12 mg/dscm (0.0052 gr/dscf) (40 CFR 60.270-.275).
9.4.2.7
Incinerators--
NSPS limitations on incinerators (above 45 metric ton/day) have been
established by 40 CFR 60.52, at 0.18 g/dscm (9.08 gr/dscf).
9.4.2.8
Sludge Incinerators--
40 CFR 60.152 sets NSPS limitations for particulates from sewage
sludge incinerators at 0.65 g/kg dry sludge (1.30 Ib/ton).
9.4.2.9
Portland Cement Plants--
By 40 CFR 60.62, standards for particulate matter are set at 0.15
kg/metric ton of feed (dry basis) to the kiln.
9.4.2.10
Petroleum Storage--
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Emission of gasoline from storage vessels and hence of antiknock in
leaded gasolines is limited by the 40 CFR 60.112 requirements that petro-
leum liquids with a true vapor pressure of over 1.5 psia, but not greater
than 11.1 psia, be stored in vessels with floating roofs or with a vapor
recovery system. This will include all gasolines.
9.4.2.11
Gasoline Vapor Recovery--
Gasoline vapor recovery regulations (Stage I) have been proposed by
EPA, under Section 110(a) (1) of the Clean Air Act, via Transportation Con-
trol Plans to be incorporated into state implementation plans. As a part of
the plan for sixteen air quality control regions (AQCR's), regulations were
promulgated which required the recovery of 90 percent of the vapor (by
weight) displaced during the filling of gasoline storage tanks.
Also proposed are analogous (Stage II) regulations governing the filling
of vehicle gasoline tanks at the filling station. Instead of a percentage
reduction, which would be difficult both to measure and to enforce, a mass
loss is proposed. The final value has not yet been set, but is expected to
b~ in the range of 0.4 to 0.6 g/gal.
The proposed standard also contains a limitation on the amount of
spillage permitted. Spillage would be permitted to occur in up to 15
percent of all vehicle refuelings. This appears to be a rather unquanti-
fiable and vague regulation and it is difficult to see how it will be
applied.
9.4.3
Recent Enabling Legislation
Two acts have recently been passed by the U.S. Congress which have the
potential of influencing the manufacture, use, and disposal of substances
containing lead. The Toxic Substances Control Act (TSCA), P.L. 94-469 of
October 11, 1976 grants the Administrator of the U.S. Environmental Pro-
tection Agency broad powers to regulate chemical substances and mixtures.
Under Section 9 of that act, the Administrator is instructed to use the
authorities of other Federal laws administered by EPA, unless it is in
the public interest to use TSCA. The same philosophy applies to other Fed-
eral laws not administered by the Administrator, except that there is an
inter-agency protocol to follow. In any event, the act establishes the
possibility that lead could be regulated under TSCA, should this be deemed
to be the most desirable course.
The Resource Conservation and Recovery Act (RCRA) of 1976 (P.L. 94-580)
establishes requirements for the management of solid and hazardous wastes.
Like its predecessor, the Solid Waste Disposal Act, RCRA will leave the
promulgation of governing regulations and their enforcement to the indivi-
dual states; there will not be specific Federal limitations. The Federal
role is to consist of financial and technical assistance and leadership in
the development, demonstration, and application of new and improved methods
of waste management.
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However, Federal criteria are to be established for identifying, trans-
porting, treatment, and disposal of hazardous wastes; these are still in
the draft stage and have not yet been promulgated. These criteria, when es-
tablished, will very likely regulate how lead-bearing wastes are handled in
landfills, and may provide criteria for their disposal of agricultural lands.
9.5
CASE STUDY:
ANALYSIS OF ALTERNATIVES FOR LIMITATIONS ON
LEAD INTAKE FROM FOODS AND BEVERAGES
At the conclusion of the first phase of this program, it was evident that
the greatest opportunity for reducing the daily lead intake of the general
population was via the ingestion route, specifically food and beverages. Further,
the benefits of such a reduction would apply universally, and would include the
two most sensitive segments of the population, children and pregnant women.
Since the funds available for the second phase of the program were limited,
it was necessary to select one candidate limitation as a test case to develop
the possible approaches to limiting lead intake, to determine the reductions which
were attainable, their technological and economic feasibility, and to assess the
benefits which would be conferred if adopted. Given these constraints, selection
of adventitious lead in foods and beverages was an obvious choice for more'
detailed study, especially since the information available indicated that this
problem was not under investigation elsewhere.
After the program was well under way it was learned that the Food and Drug
Administration was engaged in a study of lead in foods with the objective of
reducing lead contents, especially in the foods consumed by infants and young
children. Thus, there may be some duplication between the two studies. However,
it is hoped that the findings of this study will be useful in corroboration and
support of the FDA efforts to reduce man's intake of lead from foods.
9.5.1
Lead in Processed Foods and Beverages
The lead concentrations in various foods, both processed and unprocessed,
are described and discussed in Section 8.5.2. Processed foods never have less
lead than the fresh food from which they were prepared, and often have more.
Freezing, drying, or packaging in glass or aluminum contributes little or no
lead to food. However the conventional three-piece lead-coldered can is still the
standard for the food canning industry, although an evolutionary trend towards
its replacement is evident, and this is a well-recognized source of lead in
canned foods. Examples of the increase in lead content upon packing foods in
cans with lead soldered side seams, and upon their continued storage were presented
in Section 8.5.3. As illustrated by Table 8.20, doubling and tripling of the lead
content was not unusual.
9.5.1.1
Food Can Technology--
Although soldered tin plate cans still dominate the processed food
industry, changes are being made, both in the familiar three-piece soldered
tinplate can as well as in other competing forming and joining techniques
for manufacturing cans. Additionally, other packaging techniques, glass,
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plastic, retortable pouches (See Section 9.5.1.2) are competing with cans
for the food market. In non-food items, other packages have often been
extremely successful, e.g., fibre and composite cans have seized 77 percent
of the 2.6 billion unit motor oil market (Kline & Company, 1977).
The demands of food canning are more rigorous than those for bever-
ages; the reactions between foods and cans are more varied, and the need
. to prevent them has until now favored the three-piece soldered tin-lined
can. For example, for many foods good substitutes for tin have not yet
been commercially available. Also, tinplate does not lend itself to
welding or cementing, although this can be accomplished by suitable edge
treatment. However, this removes the protective tin coating at the seam and
creates the problem of preventing contact of food and metal.
As other protective organic coatings are developed, and approved for
food use by FDA, the other joining techniques will be better able to replace
soldering. This trend seems to already be under way since it appears
that the can manufacturers are no longer installing three-piece soldered
can lines; new can lines are two-piece or use alternative joining tech-
nologies.
The other problem is the aseptic canning process. In simple terms, this
involves.packing food in oven top cans, heating the cans to exhaust air from
the food, sealing tops on the hot cans by a crimping operation, and then
heating in a retort (customarily at about 240F) for a definite length of time
adequate to destroy pathogenic organisms which might be present on the raw
food material. Since the closure is made hot, upon cooling of the sterilized
cans, the contraction of the contents produces a partial vacuum in the
container.
The total and complete effectiveness of lead soldered cans has been
demonstrated for many years; this is not so true for the newer processes.
The rigors of the aseptic canning process also has prevented aluminum from
enjoying much success. Aluminum, a higher cost metal, is competitive for
beverages by the use of very thin gages, and now has a large share of the
beverage market. However, the vacuum encountered during food canning is not
compatible with thin-walled aluminum cans, and thicker gages are too costly
to be competitive.
9.5.1.1.1 Lead-soldered cans--The lead-soldered food can has been used
for several generations and to considerable degree has been responsible for
the growth of the canned food industry. Canning of various products from the
agricultural, fishing, cattle, and beverage industries is an important market
outlet for these sections of the American economy. It is also an important
market for packaging, labels, sanitation supplies, and for food and beverage
processing machinery and equipment.
During recent years there has been a decline in the numbers of lead-
soldered cans used in the food and beverage industries. A number of
circumstances probably account for this including the advent of frozen food
packaging a few decades ago, development of alternate methods of manufac-
turing cans, and more recently the desire to eliminate as much lead as
possible from foods that are ingested by humans, especially small children.
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Kopetz (1978) lists the following advantages for the soldered can:
Equipment exists
Well known technology
Essentially no new capital requirements
No size limitations
Good abuse resistance
Good integrity
Adequate shelf life
Easily used in customer's equipment
There has developed a variety of choices in can forming and joining
alternatives. Materials have changed. The familiar tin plate has gradually
grown to have much thinner coatings; and the former hot-dipped tin plate
has been superseded by electrolytic tin plate; a less expensive substitute
for tin plate, electrolytic chromium coated-steel has been developed and
is designated TFS-CT (tin-free steel-chromium type) or TFS-CCO (tin-free
steel-chromium-chromium oxide). This material can be used for many pro-
ducts where the cathodic protection normally supplied by tin is not needed.
TFS is a primary material for cemented 'and welded beer and carbonated
beverage containers, and can be used in sanitary food cans (Beese and
Ludwigsen, 1974).
Aluminum, even though having a higher cost per pound than steel, is
competitive where thin gages are practical. It has made its greatest
penetration in the soft drink and beer can markets, where it claimed
about 23 percent and 61 percent of 1976 shipments, respectively (Can Manu-
facturers Institute, 1977). Aluminum had 29 percent of the total 1976 can
market, mostly due to its success in the beverage market.
Internal pressures are not high for beverages, and thin-walled alum-
inum cans will withstand them quite successfully. However, thin-walled
aluminum cans will not withstand the pressures, and more specifically
the vacuums of the aseptic canning necessary for foods; and using thicker
walls increases the material cost out of the competitive range. A prohi-
bition or severe limitations on lead solder in food cans might eliminate
this cost barrier for aluminum food cans.
In addition to soldered-seams, joining techniques for three-piece
cans include cemented and welded (forge-welded or wire-welded) seams;
or two-piece cans can be formed by a drawing and redrawing process, or
by the drawing and ironing process. The technology involved in each of
these is described briefly in the following paragraphs, based in large part
upon Kopetz's (1978) description. It should be remembered that these other
processes are all possible alternatives to the lead-soldered can which
have been reduced to practice and are in commercial use.
In the making of three-piece soldered cans the tin-coated plate
is first sheared or slit into individual body blanks, which are fed into
the bodymaker, where the blanks are notched, rolled into round cylindri-
cal shapes, hooks formed on both edges, flux applied to these edges, and
the edges hooked together to form the body of the can. In the next machine
the cans, with seam side down, pass over a disc rotating in a bath of mol-
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ten solder, which applies solder to the seam; the wetting action of
the solder causes it to penetrate fully into the seam. After passing
by a post heat burner, the excess solder is wiped from the outside of
the can, and the can proceeds to a cooling section where the solder solid-
ifies. The last operation may be the application of a stripe of lacquer
to the soldered seam inside and outside.
The next operation on the can line is the flanger, which puts a
flared rim on both ends of the can body. Finally, one end is double-
seamed onto the can body. A coat of lacquer or enamel may be sprayed
into the formed can body, in lieu of the stripe mentioned above. The
cans are then tested under air pressure in equipment which automatically
rejects any that have imperfect seams (Ellis, 1967).
The following advantages are recognized for the soldering process
(Kopetz, 1978):
Equipment exists
Well known technology
Essentially no new capital equipment
No size limitations
Uses wide range of plate thicknesses and tempers
Good abuse resistance
Strong end profile
Adequate shelf life
Easily used in customers' equipment
9.5.1.1.2 Cemented cans--There are two
cans. The first is similar to the soldered
replaced the solder. It has been used in a
applications.
types of cemented side seam
can, except that a cement has
number of non-thermally processed
The other cemented container has a lap seam construction. The body
blanks are preheated by direct flame and the adhesive transferred to the
edge of the blank before its transfer to the bodymaker. After forming
into cylinders and reheating the can is pressed together at the lap and
chilled to set the adhesive. The remainder of the forming process is the
same as for the soldered cans.
The technology has been used commercially for billions of beer and
soft drink containers, and for millions of processed luncheon meat cans.
However, the technology of this approach for sanitary food cans is still
in the early development stages. The advantages of this process are
taken to be:
Good can integrity
No solder, no flux
Capable of producing in all current sizes
Interchangeability with other three-piece cans
High speed production
Uses lower cost tin-free steel (TFS)
No changes to customer equipment
Good abuse resistance
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The disadvantages are that the containers cannot stand aseptic canningt
and the cements only work on enameled tin-free steel or aluminum surfaces.
Thereforet products requiring a plain tinplate inner surface cannot be
packed satisfactorily. Other problems involved in substituting cemented
seams for soldered cans are equipment lacks for many sizes of canst and the
probable need to have baked inside spray coatings at temperatures close
to the softening point of the adhesive. Alsot tin-free steel lap seam
cemented cans present problems of iron pickup by corrosive food products.
Sulfide-bearing seafood and meat products which react with iron may there-
fore require aluminum. Howevert cemented seam cans should eventually
reach the same level of efficiency as soldered cans (Kopetzt 1978).
9.5.1.1.3 Welded cans--Two types of welding processes (forge and wire)
are used in the manufacture of cans. Forge welding produces a lap welded
side seam on a container body. This process was developed for making
containers from tin-free steel that has been chromium treated. Wire weldingt
which also produces a lap welded side seamt is used for tin plate. Both
methods are in large scale commercial practicet forge welding for billions
of beer and soft drink containerst and wire welding principally for
household and industrial products. For sanitary food cans both techniques
are in limited commercial use.
Edge preparation for forge welding is required to remove the oxide
and chrome layers from about an l/8-in. strip so that clean steel is avail-
able for welding. With adequate edge preparation black plate and tin
plate can also be welded; protection of the welded area against corrosion
is required.
The can forming process is analogous to that for soldered or cemented
seam cans except that after forming the cylinder it is tack welded in a
few places before passing between roller-type electrodes to produce the
continuous welded seam. Thermoplastic or thermosetting powder resins are
applied in a stripe along the seam while the metal is still hot and fused
in place.
The wire welding process is based on the use of expendable wires
which act as the electrical contact between the wheel-type electrodes and
the can body. Otherwise the process is analogous to forge welding. For
food containers an inside stripe would have to be applied to cover the
weld area.
The advantages of these welding processes are (Kopetzt 1978):
Forge Welding
Uses lower cost tin-free steel
Wire Welding
Does not need edge
weld tinplate
Good can integrity
preparation to
Good can integrity
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Forge Weld~ng cont'd
High speed production
Tolerance to high processing
temperatures
Elimination of solder, fluxes,
cements
Less body material
Improved and more reliable double
seam
Interchangeable with other 3-
piece cans on customers equip-
ment
Good dent resistance
Wire Welding cont'd
High speed production
Tolerance to high processing
temperatures
Elimination of solder, fluxes,
cements
Less body material
Relatively quick size change
Interchangeable with other 3-piece
cans on customers equipment
Good dent resistance
.The ap~arent ~isadvantages of the welding processes are that forge
weldlng equlpment.1S not available for all can diameters, but all diameters
are available in wire welding. It would take several years to provide the
can making equipment for all can sizes and products required. Time also
would be required for development of economic coating materials.
9.5.1.1.0 Drawn and redrawn cans--Drawn cans are punched from flat
sheet stock. Drawing requires the fewest number of operations from sheet
stock to finished can and is considered a simple method. Cans can be made
from steel, tin-free steel, tinplate, or aluminum by this process, which
produces a two-piece can with no side seam. Shallow drawing can be done in
a single operation; deeper drawing requires multi-stage draws. This is a
slower operation than the three-piece can processes, resulting in a higher
unit production cost.
The advantages claimed for the drawn cans are:
Superior can integrity
No solder or flux
No side seam or bottom end seam
Uses chromium treated tin-free steel,
Cans are stackable
tinplate, or aluminum
9.5.1.1.5 Drawn and ironed cans--The D & I process is similar to the
draw and redraw process except that the punch forces the formed cup down
through successively smaller diameter dies, which thins the sidewall by
stretching the metal. For example, a 0.130-in. sheet blank can winds up as
a seamless can with an 0.0045-in. wall (Kaercher, 1972).
The can and dies are flooded with a mixture of coolant and lubricant
during the ironing step, which must be thoroughly washed from the cans
after the cans are completed. The variable height bodies must be trimmed
to a uniform height, and it may be necessary to form circular beads in
the side walls to supply rigidity. The advantages are essentially the
same as those for drawn and redrawn cans.
The drawn and ironed process is widely used for aluminum beer cans;
even in 1971 they had 10 percent of the total market (Kaercher, 1972).
457
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Aluminum is easier to draw than steel, and rather thin-walled containers
are compatible with beer packaging requirements.
The problems with both drawn and redrawn and D & I can technology for
food canning are the difficulty in producing the wide diversity, often
coupled with small volume, of the cans required by the food canning in-
dustry. Also, much of the can making industry's present equipment would
become obsolete.
9.5.1.1.6 Non-lead soldered cans--It is possible to make soldered
cans that are lead free. The solders used are all tin or tin-silver and
appear to work satisfactorily. There are, however, disadvantages in
depending on tin as a can material. First, only small quantities of tin
ore concentrates are produced in the United States. The only tin smelter
in this country, at Texas City, Texas, treats Bolivian tin concentrates.
The major sources of tin metal are Malaysia, Thailand, Bolivia, and
Indonesia. Reliance on imported raw materials and metal is always a
dangerous situation because exports from the foreign countries can be cut
off at any time for various reasons.
A major factor facing tinplate and can manufacturers is the scarcity
and high price of tin. Dr. Leon Katz of American Can Company is quoted
(Steinberg, 1977) as stating that tin may start losing its share of the
food-can market if prices continue at current record levels. While there
is no precise tin price level that will trigger a price move to tin-free
steel and other packaging forms, can makers are thinking about alternatives
to tin. Steinberg also quoted R. C. Stolk, vice president for procurement
of American Can as stating that if tin gets to $6 a pound it could conceiv-
ably permit the substitution of other coatings. American Metal Market,
June 15, 1978, quoted the market price of tin at $6.10 per pound and the
Government Services Administration (GSA) sold stockpile tin for $5.68
per pound. The price of tin often vacillates depending on the supply and
demand situation and actions of the International Tin Council.
Alloying silver with tin to make solder is also introducing a higher
priced material. The American Metal Market quoted price for silver on
June 15, 1978 was $5.29 per troy ounce or $76.96 per pound. About 66 per-
cent of the domestic supply of siLver is obtained as a byproduct of copper,
lead, and zinc mining and refining. In 1976, just over 50 percent of the
silver consumed in the United States was supplied by imports. Principal
foreign suppliers are Canada, Mexico, Peru, and United Kingdom.
It appears that going to all tin or tin-silver solders and increasing
the demand for these two metals at their high prices is not a feasible
general alternative to lead-soldered cans. This approach may be feasible
for special applications, and, in fact, tin solder is reported as being
used by some manufacturers for infant foods (Sulek, 1977a).
9.5.1.2
Alternatives to Lead Soldered Food Cans--
The welded, cemented, drawn and redrawn, and drawn and ironed cans
described above are all alternatives to lead soldered food cans, although
still cans, and possessing all the strengths and weaknesses of cans. The
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substitution of tin or tin-silver solders is
limited use. There are indications that the
pressed to obtain the tin for tin plate, let
solder.
a possibility only for very
can industry will be hard
alone tin for a high-tin
There are also other non-can alternatives. Glass is historically the
oldest, and has been used for many years. A very new package is the re-
tortable pouch, which is described in 9.5.1.2.2. Frozen foods are classified
as supplementary to canned foods, but not alternatives in the context ot
this analysis, which has the constraint that to serve the market served
by canned food storage at room temperature must be possible.
9.5.1.2.1 Glass containers--Glass containers have been used for pack-
aging various food items as well as beer, soft drinks and fruit juices.
The glass container producers are optimistic that they will continue to
gain a larger share of these markets. Makers of baby food say their fruit
juice sales have increased markedly since they switched from metal cans to
glass containers that can be used with the standard tops for nursing
bottles (Starr, 1978). According to Shakin (1977) the glass bottle is
capturing more business in beer and soft drink packaging and capacity has
been expanded by the major producers. A major reason for the increasing
use of glass containers is their price advantage over metal cans. Assuming
that the prices of steel and aluminum will rise faster than the prices for
glass, the glass container should continue to enlarge its share of the
market. Shipments of glass containers in 1976 ran to $3.4 billion, up
from $3 billion in 1975.
The replacement of soldered cans by glass containers
perature food processing is not envisioned because of the
of glass with respect to thermal shock and to impact.
in high tem-
characteristics
9.5.1.2.2 Retortable pouches--A recent development in food processing
and packaging is the advent of the retortable pouch. The pouch is made of
aluminum foil sandwiched between plastic sheets, and is basically a can with
flexible sides. As described by Howard (1978), the pouches are filled with
food on the canning line, the air evacuated, and the pouches sealed and
cooked under pressure until harmful bacteria are killed. Because the pouch
is long and thin, heat transfer is better, reducing processing time and
minimizing canning's tendency to overcook food; it is claimed the food
tastes as good as frozen food. The pouches can be stored at room temperature,
and cooked by dropping the pouch into boiling water. The technique,
originally developed by the military for canned combat rations, has been
described as the greatest development in food processing since the tin can.
There are obstacles that must be overcome before the retortable pouch
makes much of an inroad into the canned food market. The filling equip-
ment is crude, expensive, and scarce. The filling lines are also slow
compared to canning lines. The food companies are concerned whether the
large investment they would have to make for pouched food lines could really
payoff. Last, but n~ least, is whether consumers will buy food in pouches
because it is foreign to present day methods of preparing and packaging
food.
459
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Breaking into the food packaging market on any reasonable level
will be an uphill battle for the backers of retortab1e pouches.
9.5.1.3
Good Manufacturing Practices--
One alternative to changing solder compositions, or can making tech-
nology, is the rather simple one of improving manufacturing practices and
quality control; although simple, it can provide some very real benefits
in reducing the lead content of canned foods, as will be shown for some
specific foods.
The good manufacturing practice (GMP) concept is used frequently by
the Food and Drug Administration in regulating the industries which it
oversees. While the term is difficult to define absolutely, its meaning
is easily understood, and it has apparently been quite successful as a
general catch-all control tool for regulating the manufacture of foods
and drugs.
9.5.1.3.1 Evaporated mi1k--This approach appeared to in part be
responsible for the reduction achieved in the lead content of evaporated
~i1k over the 1972-1974 period. As described in the proposed 0.3 ppm
tolerance for lead in evaporated milk and evaporated skim milk (U.S.
Department of Health, Education, and Welfare, 1974), the FDA had conducted
an investigation early in 1972 to determine baseline values in raw and
evaporated milk. Raw milk ranged from none to 0.28 ppm (av. 0.09 ppm)
and evaporated milk ranged from 0.21 to 1.10 ppm (av. 0.52 ppm). These
results were supported by other investigations reported in the literature
(raw milk 0.05 ppm average; evaporated milk 0.35 ppm average). Illustrative
data of the decreasing lead concentrations are presented in Table 8.16.
The FDA informed the evaporated milk industry of the seriousness of
the problem and the need to develop a solution. After some industry studies,
some modification in can manufacturing procedured were made in an effort
to reduce lead levels in evaporated milk. These efforts were fairly suc-
cessful. Analysis of over 3,000 samples from the first half of 1973
showed an average of 0.12 ppm. Analysis of 3,015 samples from the second
half of 1973 and the first four months of 1974 also confirmed the 0.12 ppm
average (range 0.02 to 0.33 ppm). Refinements in analytical techniques
for better sensitivity at trace levels led to a lower value for raw milk,
0.021 ppm, based on the analysis of 80 samples. While a larger number
of samples would have been needed to verify this value, it was concluded
that the average was significantly less than the 0.09 ppm initially re-
ported.
The reduction in lead uptake has been maintained. Dr. H. R. Roberts,
Acting Director of the Bureau of Foods of FDA, stated recently (Roberts,
1978) that the average lead content of evaporated milk is about 0.1 ppm.
9.5.1.3.2 Canned Foods--The increases in lead content in canned foods,
as demonstrated by the Can Manufacturers Institute-National Canners
Association (CMI-NCA) 1974 canned foods survey (Sulek, 1977), were reported
in Section 8.4.5 (Table 8.20).
460
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i
The canning industry has since then been modifying can making pro-
cedures in an effort to reduce lead levels. The concept of GMP in preven-
ting or cleaning up lead solder spatter and dust from the interior of the
cans was an important element in the modified procedures. Of key importance
in this work was the knowledge that lead dust~ as opposed to structural
lead (lead used to solder the sideseam) was the primary contributor to
comtainer-oriented lead pick-up. Lead dust is a by-product of the soldering
operation and techniques have been found to greatly control this phase of
the operation. Structural 1ead~ on the other hand~ has been found to
contribute very little lead to most canned items except in very aggressive
products.
To follow up on the practical effectiveness of these equipment
modifications and improvements in manufacturing procedures~ another survey
was conducted in 1976 by The Can Manufactures Institute and The National
Food Processors Association (formerly The National Canners Association).
Prefacing the presentation of the resu1ts~ it should be noted that most of
these data were obtained from cans produced on lines which had been
modified to significantly minimize lead contamination of the containers.
Due to the time and expense involved in these modifications, not all can
manufacturing lines have been modified to date (Su1ek~ 1978). However~ it
is representative of what can be accomplished and comparable values should
be the norm after all lines have been upgraded.
Thirteen products~ suggested by FDA as among those likely to be fed to
young chi1dren~ were surveyed. Results for these selected foods are
presented in Table 9.4~ along with comparable data from the 1974 CMI/NCA
survey~ for those foods~ included in the earlier (pre-modification) survey.
As shown in Table 9.4 the average lead content for all foods tested was
0.19 ppm~ and no product exceeded 0.30 ppm. Twenty-five samples of each
product were to be surveyed. The sampling plan involved taking a 2-1b.
sample at the filler bow1~ and then 24 cans of finished product~ which
were stored 6 months before analysis (only 6 months storage was used in
this study as the previous 1974 study had indicated insignificant increases
beyond that time). In order to ensure that a representative sample was
analyzed~ 12 cans were composited~ and a I-lb. subsamp1e removed, which
was then totally solubilized in nitric acid for analysis.
The effectiveness of the process modifications is best illustrated by
comparing the 1976 results with those of the 1974 survey (Table 9.4). All
foods except vegetable soup showed a significant drop in lead levels. The
average reduction for the 10 foods for which a comparison could be made
was slightly above 40 percent.
Based on these results~ a 50 percent decrease in adventitious lead
from canned foods should be quite possib1e~ without any major changes in
packaging or in present can technology. Such a reduction would appear to
be highly desirable~ on an interim basis at least~ while the evolutionary
changes in the can industry needed to essentially eliminate all lead pick-
up are implemented.
461
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. -
TABLE 9.4
COMPARISON OF RESULTS OF 1974 ArID
1976 CANNED FOOD SURVEYSa
Lead content, ppm
Filler bowl Canned Productb Percent change
1974 1976 1974 1976 in lead level.
Applejuice 0.02 0.02 0.17 0.13 -24
Applesauce 0.08 0.01 0.32 0.20 -38
Beef stew 0.11 0.03 0.29 0.19 -34
Chicken noodle soup 0.25d 0.02 0.68 0.25 -63
Corn (whole kernel) 0.08 0.05 0.32 0.22 -31
Green beans 0.18 0.04 0.35 0.15 -57
Fruit drinks 0.03 0.13 0.11 -15
Orange juice 0.03 0.07c
Peas 0.08 0.03 0.40 0.23 -43
Peaches 0.07 0.21
Pork & beans 0.23e 0.03 0.50 0.17 -66
Spaghetti 0.05 O.l1c
Vegetable soup 0.07 0.02 0.25 0.29 +16
Overall average 0.12 0.03 0.32 0.19 -41
~Source: 1976-1977 CMI/NFPA Lead in Canned Food Survey (Sulek, 1978).
Samples stored for 6 months before analysis
~Not included in calculation of average since they were not surveyed in
Based on only one sample.
e
Based on three samples.
1974.
462
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Interestingly, while the lead content of the canned foods decreased
as a result of improved can making procedures, more accurate analyses re-
sulted in lower average lead contents of the raw foods. Where the average
lead content of samples from the filler bowl was 0.12 ppm in the 1974
survey this decreased to 0.03 in the 1976 survey. (During the entire survey
a total of 2276 unprocessed samples were analyzed, for which the overall
average was 0.06 ppm.) Taking the 0.03 ppm value, the raw food represents
16 percent of the total lead in these selected foods. Thus, according
to the 1976 survey data, the adventitious lead, instead of comprising 2/3
of the total as formerly estimated, and as confirmed by the 1974 survey,
now represents 84 percent of the total intake. However, this mathematical
quirk should not obscure the fact that the absolute lead intake from canned
food would be cut nearly in half at the new level.
9.5.1.3.3 Infant foods--Another food industry segment that has
exhibited continuing reduction in lead content is infant food, under the
sponsorship of the Infant Food Manufacturer's Lead Program. In order to
reduce lead levels, manufacturers have converted to either tin solder or a
double spray and bake can lining; both of these have increased can costs
(Sulek, 1978). However, the benefits to the most sensitive segment of the
general population have been significant, as illustrated by the analytical
data contained in Table 9.5. In 1973 the mean lead content in canned infant
juices was 0.29 ppm. In 1974, when new can making procedures were begun the
mean lead level was reduced 52 percent to 0.14 ppm. The reductions have
continued; in the first half of 1977 the level was down to 0.06, a reduc-
tion of nearly 80 percent from 1973, and approaching the "background" level.
9.5.1.4
Economic Effects of Limitations Alternatives--
The number of cans produced by the can industry is astronomical, over
84 billion in 1976. Food cans accounted for 29.4 billion, beverage cans
46.4 billion, pet food cans 3.1 billion, and general packaging cans (motor
oil, paints, aerosol cans, and all others) for 5.5 billion (Can Manufactur-
ers Institute, 1977). Of the 46.4 billion beverage cans, 19.5 billion were
soft drink cans, and 26.9 billion were beer cans. Aluminum cans had 61
percent (16.5 billion) of the beer can market and about 23 percent (4.4
billion) of the soft drink can market. It is evident from these data that
the can industry is characterized by a low-unit cost, very high-volume
product, and that changes in manufacturing costs of a fraction of a cent
per can are important.
Alternative processes for making cans not requiring a lead solder side
seam are available, as described in Section 9.5.1.2. None are as well
suited as sanitary food cans as the present 3-piece soldered can. One
approach uses other joining processes-cementing or welding. In another, the
cans are drawn, giving a 2-piece can with no side or bottom joint. A major
disadvantage of these alternative techniques is their requirement for a very
high volume of a single size to be economic. The food can industry is
characterized by many sizes, with no one size possessing a dominant volume
comparable, for example, to the standard l2-oz. beverage can. While some
standardization of food can sizes is undoubtedly possible, it appears
somewhat doubtful that the number cquld be reduced to a level suited to these
alternative processes. As described in the following pages, these alternative
463
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Table 9.5
LEAD CONTENT OF INFANT JUICES
PACKED IN METAL CONTAINERSa
Lead content, ppm 1977b
Infant Juice 1973 1974 1975
Apple 0.36 0.14 0.05 0.03
Apple-cherry 0.28 0.18 0.11 0.03
Apple-grape 0.26 0.16 0.12 0.03
Apple-apricot 0.16 0.21 0.20 0.06
Apple-plum 0.03
Apple-pineapple 0.26 0.16 0.13 0.06
Apple-peach 0.04 0.06
Apple-prune 0.19 0.14 0.03
Mixed fruit 0.39 0.16 0.09 0.07
Orange 0.47 0.14 0.08 0.07
Orange-apple 0.25 0.08 0.08
Orange-apricot 0.27 0.14 0.10
Orange-apple-banana 0.54 0.17 0.18 0.09
Orange-banana 0.11 0.08 0.07 0.02
Orange-pineapple 0.21 0.15 0.06 0.07
Prune-orange 0.27 0.10 0.08
Number of samples 841 1138 675
Average,ppm 0.29 0.14 0.10 0.06
Reduction from 1973 ,percent 52 66 79
aSource: 1976-1977 CMI/NFPA Lead in Canned Food Survey (Sulek, 1978).
bFirst half of 1977.
464
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processes are characterized by high capital costs, and their substitution
would require major expenditures by the can industry.
9.5.1.4.1 Industry structure and production--The manufacture of food
cans is but one part, although the largest part, of the can making industry.
According to Ellis (1967) cans then accounted for nearly one-third of all
units of consumer packaging, and were used for some 2,500 different products.
In more recent data Kopetz (1978) stated that the can makers had total sales
of $8 billion in 1977, and that about 58 percent of the metal can sales were
three-piece cans used by the food and beverage industries. The Bureau of
Census reports that the total number of cans shipped in 1976 was 84 billion
valued at $6.4 billion, up from a value of $5.9 billion in 1975. Employment
in can making establishments is about 60,000 people working in 433 plants
located in 277 different municipalities. The combined total payroll for
1976 was estimated at $1.2 billion. In addition, can makers have annual
capital expenditures of $142 million.
The can industry is among the most highly concentrated in packaging.
In 1975 two companies, American Can and Continental Can, accounted for
37 percent of the value of all production (down from 56 percent in 1970) and
50 percent of all merchant sales. National Can and Crown Cork & Seal accounted
for an additional 18 percent of merchant sales. The top eleven companies, all
with merchant can sales of $30 million or more, had 78 percent of the merchant
total. These companies and their estimated sales of cans in 1975 are shown in
Table 9.6.
Table 9.6
MAJOR U.S. MERCHANT PRODUCERS OF METAL CANS, 1975
Rank
Company
$ Million
1
2
3
4
5
6
7
8
9
10
10
Continental Group
American Can
National Can
Crown Cork & Seal
Reynolds Metals
Ball Corp.
Diamond International
Van Dorn
Kaiser Alum. & Chemical
J.L. Clark
Sherwin-Williams
Other merchant suppliers
Captive producers
TOTAL
$1,175
1,125
535
315
150
70
60
60
55
30
30
1,020
1,545
$6,170
Source: Estimates by C.H. Kline & Co. (1977)
465
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At least 30 firms make cans solely for their own use. They include
such well-known food processors as Borden, California Canners & Growers,
Campbell Soup, Carnation, Castle & Cooke, General Foods, Green Giant, H.J.
Heinz, Hershey Foods, Pet, Stokely-Van Camp, and Libby, McNeil & Libby.
Captive manufacturers for nonfood products include R. Reynolds, United
States Tobacco, and Texaco (Kline & Company, 1977).
Captive production grew at a rate of about 15 percent a year between
1970 and 1974, and is continuing to increase. It represented about 17
percent of total production, and had grown to nearly 30 percent by 1975.
During the same period merchant shipments rose only about 2.5 percent per
year. Due to the desire of large packers to reduce package costs, this
trend should continue (Kline & Company, 1977).
An example of this trend is the new Metal Container Corporation
(subsidiary of Anheuser-Busch, Inc.) can making plant in Columbus, Ohio.
This plant will produce 800 million steel drawn-and-ironed cans annually
for the Columbus brewery. The plant operates four can lines 24 hours a
day, 7 days a week, employs more than 250 hourly-rated workers and represents
an investment of over $25 million. Metal Container also operates an
aluminum can making plant in Jacksonville, Florida, to serve the Anheuser-
Busch brewery there.
Beer cans are standard at a 12-oz. size, as are soft drinks. However,
in food cans there is a very large number of sizes. For example, for three-
piece cans there are 270 different can sizes, with 16 different can diameters*
(Kopetz, 1978).
Food cans are a very important part of the U.S. food chain. In 1975,
almost 47 billion pounds of food and beverage (about 14 percent of the
337 billion pound total) was packed in three-piece containers, and was
valued at $27 billion. Food canning activity was carried out in over
1,700 food processing plants located in 47 states, American Samoa, and
Puerto Rico. Employment in the food canning industry averages about
140,000 during the seasonal low production period (February) and exceeds
275,000 at the seasonal peak of canning activity in September. The com-
bined payroll in this industry in 1975 was approximately $1.7 billion
(Kopet~~78).
9.5.1.4.2 Costs to adopt alternative can manufacturing processes--
Present sanitary food can manufacturing processes, and several leading
candidate alternative can manufacturing processes were described in Section
9.5.2.1. Several of these alternative processes require an organic
coating stripe along the seam, to protect the metal from the contents of
the can. A 360-degree spray coating on the inside of some food cans is
already used in some applications, primarily to prevent reactions between
can and contents. These organic coatings could also be used for the purpose
cans by a 3-digit numberi~g system of inches
x height, e.g., a 303x406 can is 33/l6-in
~~he can industry specifies
and sixteenths for diameter
dia x 4 3/8-in height.
466
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of preventing lead pickup in lead-soldered food cans, although this technique
is evidently used now only for special situations, e.g., infant foods.
The capital and incremental operating costs for nine alternative
production techniques have been estimated by representatives of the Can
Manufacturers Institute on the joint CMI/NFPA Committee on Lead In Canned
Foods. Preliminary findings of this study are contained in a recent draft
report (Can Manufacturers Institute, 1978). The following discussion is a
condensation and summarization of this draft report. One of the alternatives,
induction soldering, is not considered here, since this variation on present
soldering technology appeared to have little effect on the problem of lead
pickup.
The eight remaining alternatives considered, and a brief characterization
of each are as follows:
(1)
Line Modification and Clean-Up
This involves modifying certain equipment, primarily that
at the solder station, and the introduction of more sophis-
ticated housekeeping procedures and equipment, buttressed by
rigorous quality control procedures. This is the basic
approach followed in achieving the 40 percent reduc~ons in
lead content described in Section 9.5.1.3. Adoption of these
measures is also a prerequisite for the following three
alternatives which also retain the lead soldered side seam.
There are few technological problems with this approach, and
costs to upgrade existing systems are low to moderate.
(2)
Inside Side Seam Stripe Using Organic Coatings
A stripe of an organic coating is applied to the side seam
post-soldering. Incorporation of alternative (1) is
required to realize the optimum benefits from this process.
Some cans are already being produced using this technique.
There are few technological problems with
costs to modify existing systems would be
coatings compatible with all products are
further development will be required.
this approach, and
moderate. Organic
not available, and
,(3)
Inside 360-Degree Spray Organic Coating
This alternative requires coating material to be sprayed
uniformly on the inside of the can after the side seam has
been soldered. Some cans are currently being manufactured
by this process. Incorporation of alternative (1) is also
required to realize the maximum benefit from this process.
There will be technological problems in perfecting coatings
suitable for the majority of food products and in obtaining
467
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FDA approval of their
testing costs will be
spray coating process
mated to be major.
safety, and coatings development and
significant. Costs to add a separate
operation to existing lines are esti-
(4)
Combination Inside Side Seam Stripe and 360-Degree Spray Organic Coating
This alternative includes the combination of alternatives
(2) and (3) for greater protection; again incorporation
of alternative (1) is a prerequisite to realize maximum
benefits.
Costs are slightly higher than for alternative (3).
(5)
Pure Tin Solder
This alternative would require almost no change to existing
lines, but would require more tin than is annually produced.
The low melting point of tin would pose some problems in the
high temperature presterilization of formed cans prior to
aseptic canning.
(6)
Cemented Side Seam
This alternative is used widely for beer and soft drink cans,
but is not suitable in its present state of development for
aseptic canning (See Section 9.5.1.1.2). Considerable devel-
opment in cements, coatings, and in forming processes would
be required. Twenty-five percent of current investment in
food can lines would become obsolete if this alternative is
adopted. Cost to convert would approach $1 million per line,
and changeover is estimated to require at least a five- year
period, depending on rapidity of solution of technological
problems.
(7)
Welded Side Seam
Two types of welding processes, forge and wire welding, are
used in the manufacture of cans (See Section 9.5.1.1.3), both
methods are in large scale use, e.g. for beer, soft drinks,
and household products, but the techniques have to date had
only limited application to sanitary food cans.
The replacement of existing can manufacturing equipment would
be costly and loss of 25 to 50 percent of current in - place
investment may result. A major technological problem would
be the adoptation of this high-volume single-size can process
to the smaller volume of a multiplicity of can sizes
characteristic of sanitary food cans.
468
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(8)
Drawn and Redrawn/Drawn and Ironed
Drawn and redrawn and drawn and ironed cans are described
and discussed in Sections 9.5.1.1.4 and 9.5.1.1.5. This
method of forming produces a two-piece can with no side
seam, and hence no lead at all. Both of these processes
are particularly suited to the production of massive
volumes of one size of can, e.g. a l2-oz. beverage can.
Much of the current can manufacturing equipment would
become obsolete if this replacement were made; cost per
line was estimated as in excess of $1 million. Current
cost studies do not justify this type of equipment for
sanitary food can manufacture.
Capital and incremental operating costs above present costs are
summarized in Table 9.7. The costs are necessarily generalized; for
example, they assume a line speed of 400 cans/minute, although line speeds
vary in practice from 100 to 800 cans/minute, and assume an average of 30
million cans/line/year (actual rates vary from 20 to 60 million). Total
industry costs are based on the existing approximately 1,085 lines in
~he U.S. producing sanitary food cans, and all costs are based on current
dollars.
The pure tin solder alternative can be dismissed as a general solution
for the food can manufacturing industry on the grounds of an insufficient
supply; it may be appropriate for special problems such as canning infant
foods and formulas. Of the remaining alternatives, the most cost-
effective would appear to be the line modification and cleanup and/or the
side seam stripe.
Total elimination of lead (options 6,7,8) would require new industry
investment in the billion dollar range, and cause a significant disruption
of the food can manufacturing industry. As pointed out by Dr. Howard R.
Roberts, Acting Director, Bureau of Foods, in a speech before the National
Food Processors Association (Roberts 1978b):
Based on industry data, it is estimated that about 33 billion
cans are used each year to package 10-15 percent of all food.
Since alternative containers (glass, 2-piece cans, plastics)
are not immediately available, eliminating the soldered 3-piece
can overnight would mean unacceptable disruption of the food
supply, especially with respect to fruits, vegetables, meat,
and seafood. Further impacts of eliminating the soldered 3-
piece can would be those on the over 140,000 permanent and
135,000 seasonal employees in these industries; the $3.7 bil-
lion spent on materials, and the $204 million spent on new
equipment. But even neglecting this economic impact, elimin-
ating the tin can would bring an unacceptable impact on the
food supply and on the nutritional status of major segments
of the population. Immediate elimination of the 3-piece can
is thus not a viable alternative.
469
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TABLE 9.7
SUMMARY OF ESTIMATED COST OF ALTERNATIVE
FOOD Ck~ MANUFACTURING TEC&~IQUESa
Capital Cost,b
Industry Total,
Million Dollarsc
Alternative
Per Line
(1) Line modification and
cleanup
$45,000
(2) Side seam stripe
Side seam stripe plus
line modification and
cleanup
18,500
63,500
(3) 360-Degree Spray
610,000-
860,000
(4) Side seam stripe plus
360-Degree Spray
625,000-
875,000
5,000
(5) Pure Tin Solder
(6) Cemented Side Seam
986,000
(7) Welded Side Seam
880,000
(8) Drawn and Redrawn
Drawn and Ironed
1,300,000
2,500,000
Added Operating
Cost/lOOO Cans
$
48.8
$0.10 to 0.30
20.1
0.20 to 0.45
68.9
0.30 to 0.75
661. 9 -
933.1
4.00 to 6.00
678.1 -
949.4
4.20 to 6.45
5.4
5.00 to 7.00
3.85b
3.l0b
4.30b
1,069.8
954.8
1,410.5
2,712.5
a
Source:
Can Manufacturers Institute (1978)
b Cost reflects only depreciation on investment, other operating costs
undetermined pending further development.
c
Based on 1,085 sanitary food can lines in U.S.
470
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9.5.1.4.3 Economic impacts upon materials suppliers--The major
materials used in can manufacture are steel, tinplate, chromium treated
steel, and aluminum. Tinplate and lead solder are the prime materials
in the soldered cans. For the years 1970-1976 tinplate shipments
averaged about 4.5 million metric tons annually, or about 5.5 percent of
total steel shipments. The U.S. Bureau of Mines (1978) estimates that,
in 1977, 31 percent or 16,000 metric tons of tin was used in cans and
containers. The bulk of the tin was used in tinplate and a much smaller
amount was in the solder.
Cans can be manufactured from tinplate by all of the newer can making
processes--cemented, forged, or drawn. Some producers prefer to use chromium
treated steel because it is cheaper. However, the elimination of the 1ead-
soldered can would not affect steel shipments per se, because steel sheet
will still be used for making cans by the other processes. Glass and alum-
inum are strong competitors to steel as containers for food and beverages.
Capture of a greater share of this market by either or both of these mat-
erials would lower the amount of steel in containers.
Widespread acceptance of the retortable pouch would also restrict
the quantities of steel, aluminum, and glass in food containers.
The loss of the market for the small quantities of tin in lead solder
used for soldered cans should not adversely affect the tin industry.
The U.S. Bureau of Mines (Rathjen, 1978) estimates that 4,000 metric
tons of lead were used in soldered food cans during 1976. The total lead
consumption in cans and containers of all kinds was estimated at 20,000
metric tons. Total annual lead consumption in 1976 and 1977 was about 1.34
million metric tons. This includes both primary and secondary lead. The
loss of a 4,000 metric ton market should have little impact on the lead
industry, especially in relation to the much larger loss of lead for the
gasoline anti knock market.
In summary, elimination of the lead-soldered can over a reasonable
period of time should have little impact on most material suppliers. The
quantities of lead and tin used in solder are reasonably small and the loss
of this market would be minimal. The present competition between steel,
aluminum, and glass as food and beverage containers will continue even if
the soldered can is phased out. Suppliers of coating materials could see an
expanding market as cans are manufactured by the newer processes.
9.5.1.5
Industry Trends and Outlook--
The' conclusion drawn from the results of the analysis described in
the preceding paragraphs is that a large fraction of the reduction sought
in adventitious lead in canned food can be achieved without precipitously
abandoning the three-piece lead soldered can, by relatively minor adjust-
, ments in can making technology and by adopting strict "good manufacturing
practices". This might involve intensive rinsing or brushing and rinsing
of the formed cans to remove all lead solder dust and spatter, or a double
stripe over the soldered seam, or even a double spray and bake interior
471
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lining. From the viewpoint of least capital investment requirement and
least disruption of the industry, while at the same time reducing
adventitious lead down nearly to target levels, this approach has much to
recommend it.
Some industry trends are already in motion, which will have a bearing
on the lead problem. According to one industry observer (Menke, 1978),
three-piece can lines are no longer being installed; all new can lines
are two-piece, aluminum or steel. Such competitive pressures will help
to accentuate the phasing out of three-piece soldered can lines. For
example, Reynolds Metals Company, a large producer of aluminum cans. will soon
be making steel cans in its new plant at Salisbury, North Carolina. The
company says it will be able to switch from aluminum to steel cans "at a
moment's notics". One objective is to develop data on comparative costs
for the two kinds of cans. It is assumed that these are drffiYn cans (Starr,
1978),
The soft drink industry is perhaps most rapidly phasing out three-piece
cans. There were a total of 19.5 billion soft drink cans in 1976 (Can
Manufacturers Institute). According to Mr. Korab of the National Soft
Drink Association, cans represented 34.5 percent of total soft drinks, and
lead soldered cans were only 35 percent of that, or 12 percent of the total
cans. (The rest were two-piece steel or aluminum, or three-piece cemented
or welded seam cans.) The use of soldered cans is rapidly phasing down, and
by 1980 only 0 to 5 percent of the cans (i.e., less than 2 percent of soft
drinks) will be marketed in soldered cans (Korab, 1978). These are being
replaced predominantly by aluminum cans.
Similarly, in beer cans the trend is away from three-piece cans to two-
piece. Within the last year Anheuser-Busch has gone from three-piece steel
cans to two-piece steel cans; the next move will likely be to aluminum
(Abel, 1978). Three-piece beer can shipments decreased from 14.7 billion
in 1972 to 6.6 billion in 1976, by which time they had only about 25 percent
of the market (Can Manufacturer's Institute, 1977).
While possibly not classifiable as an industry trend, at least one
infant formula manufacturer is featuring in advertisements that its formula
"is now available in a new l4-oz. can that is free of lead solder. Elimina-
ting solder reduces the infant's environmental exposure to lead." General
adoption of this advertising approach could hasten the complete replacement
of lead solder in infant foods.
rnfant foods are probably a special case. For adult foods, the more
probable action will be for the industry to adopt an evolutionary approach
to minimize lead pickup from three-piece soldered cans while conducting the
research and development necessary to achieve the ultimate lead-free goal.
9.5.2
Lead Glazed Foodware
A ceramic glaze is a thin glassy coating, generally containing silica,
which is applied and fused onto a clayware body. After firing, during
which the glaze becomes molten, the glaze closely resembles a glass. It
472
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is continuous, impervious, and almost completely insoluble when.prope~ly
formulated, applied, and fired. Glazes are as varied as the var~ous k~nds
of pottery and each kind is best with its appropriate glaze. Lead.glazes
are the most widespread in use and considered the best for all ord~nary
purposes. The glazes used by commercial dinnerware makers s:al the sur-
face of the dinnerware to make it shiny and very smooth, eas~er to clean,
more resistant to wear, and less likely to hold germs and bits of foods.
Thus, glazes not only have aesthetic reasons for their use, but some very
important functional ones.
9.5.Z.1 Glaze Technology--
Glazes are usually applied to unglazed ceramic ware by dipping,
brushing, or spraying an aqueous slurry of powdered g~aze constituents,
after which the ware is fired at a temperature sufficient to melt and
fuse the glaze. Glazes are multi-component mixtures, thus the possible
variations are almost endless. Typical of the clear glazes used on hotel
china is the following, which is contained in the ILZRO Manual, Lead
Glazes for Dinnerware (International Lead Zinc Research Organization, Inc.,
1974):
Base Glaze (mols)
0.066 KZO
0.179 Na20
0.261 PbO
0.494 CaO
0.340 A1203
0.314 B203
3.669 SiOZ
One of the purposes of the lead oxide is to serve as a flux, which reacts
at high temperatures and helps dissolve all of the glaze components to
form a glass. Lead oxide under these conditions is an active solvent, and
in addition to its fluxing action, also lowers the glazing temperature.
9.5.3.1.1 Variables influencing lead release from glazed ceramic ware--
The composition of the glaze is one of the major variables affecting its
durability, and with respect to lead, the ease and rate of lead solubility
and release. Copper, for example, is known to significantly increase the
lead solubility of a glaze, and is therefore, avoided in dinnerware. Strong
cautions are expressed against its use, as for example, the caution,
emphasized by italics, in a booklet for art potters and hobbyists (Lead
Industries Association, Inc., 197Z):
Under no conditions should copper exide be added to a lead
glaze intended for food surfaces.
Through trial and error, and research conducted by the ceramics industry
going back to the 1930's, glaze formulations have been developed, whose
lead loss when properly fired is extremely low, a few tenths ppm.
Firing temperature is another very important variable. Temperatures
in the ceramics industry are measured by Orton cones, which soften and sag
over at different temperature ranges (at a specified standard heating rate),
depending on the particular clay mixture used for that number cone. Cones
range in number in descending order from 022 to 01 and then in ascending
order from 1 to 36 with increasing temperature. The range of interest for
ceramics is from No. 010 (equivalent temperature 894 C) to No. 12 (1326 C).
Cones 3 - 5 (1168 C to 1196 C) are typical of production glazing tempera-
tures.
473
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The manual on glazes issued by the International Lead and Zinc Research
Organization (ILZRO) stated that "tests made on a large number of Cone 3 - 5
clear lead glazes (commercial plant production samples) show lead releases
values of less than 0.5 ppm, and in a number of cases, less than 0.1 ppm.
Thus, the cone 3 - 5 glazes, which constitute the large part of all
commercial dinnerware glazes used in this country, show very low lead
releases, as has been found in a number of other laboratories during the
past three decades." (ILZRO, 1974)
As reported by Eppler (1976), speaking at the 1974 International Con-
ference on Ceramic Foodware Safety, '1t has been shown conclusively that the
typical cone 3 - 5 formulas used to glaze both vitreous and semivitreous
dinnerware in the United States produce consistently low lead release values,
in most cases less than 0.5 ppm and with low scatter. Although medical
journals have reported some cases of lead poisoning resulting from the use
of certain imported and hand-crafted dinnerware, we know of no case where
the glaze allegedly responsible even approached the type of glaze used by
major American dinnerware manufacturers."
Hobbyists, not having the kiln capabilities of manufacturers, tend to
fire glazes in the 07 to 02 cone range (984 to l120C), which is one of the
reasons why hobbyist (and hand-crafted cottage-industry) ceramic ware has
sometimes caused lead poisoning problems.
Another variable is glaze thickness. With thin application, a glaze
will dissolve body constituents, which will change the composition and
structure of the glaze, thereby making it more acid resistant. Conversely,
with a heavier application (above 3 mils), the body constituents may not
penetrate through to the glaze surface, and if the glaze is not of an
inherently acid resistant type, higher lead release rates will result.
Here again the commercial manufacturer has more control over glaze thickness
(as well as the incentive to minimize glaze materials costs) than the hobby-
ist and excessive glaze application in commercial dinnerware is unlikely.
9.5.2.1.2 Lead release/glaze testing--Lead extractability is
measured by an acid extraction test, in which the ware being tested is
nearly filled with 4 percent acetic acid and allowed to stand at room
temperature for 24 hours. Lead concentrations in the extractant above
7ppm (7 mg/l) are considered evidence of unacceptable extraction (based
on average results for six units).
This method, originally published as FDA Laboratory Information
Bulletin No. 834, is still the standard test in the United States. The
ASTM has essentially the same test as ASTM C738-76 (American Society for
Testing Materials, 1977). The ASTM Manual describes this as a severe test
that is unlikely to be matched under the conditions of usage of such ceramic
ware.
In 1974, a group
auspices of the World
ards, and legislation
of experts met in Geneva, Switzerland, under the
Health Organization, to review testing methods, stand-
and enforcement procedures. A second meeting, held
474
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in Geneva, in 1976, resulted in the development of slightly revised test
procedures, but more importantly, some recommended new standards governing
lead release (World Health Organization, 1976).
One of the key changes was the establishmentof new dinnerware cate-
gories, as summarized below:
Category
Flatware
Holloware
Small
Large
Cookware
Characteristics
Internal depth below rim <25 mm
Internal depth >25 mm
1.1 1 or less
1. 1 1 or more
Glazed articles specifically in-
tended for cooking
Allowable Lead,mg/l
7.0
5.0
2.5
5.0*
*First 2-hours of 24-hour test at '\, 100C
Subsequently the International Standards Organization (ISO/TC 166 SC1)
circulated a slightly revised version (N14) of the one considered in
1976 to the appropriate recipients for a vote; voting is expected to be
completed in about 9 months, with the expectation that the proposed tests
and standards will be adopted (McLaren, 1978). The U.S. FDA is cognizant
of these developments, and has had a representative at these meetings,
and is now reviewing the draft proposal. It would appear that there is
a fair chance that the FDA will adopt these new standards, or something
very much like them.
9.5.2.2
Historical Perspective--
The involvement of the Food and Drug Administration in the testing
of ceramic ware for extractable lead evidently began in 1970, as the result
of an article in Good Housekeeping describing a lead poisoning incident
from a piece of imported foreign ceramic ware. FDA considers lead from
ceramic glazes an indirect food additive. Initially samples of ware from
10 to 12 countries were tested and numerous violations were discovered.
This program has continued, and from 2,000 to 3,000 samples per year
may be tested (Steele, 1978). These are not intended to be representa-
tive samples, statistically selected, but are selected because the inspect-
ors suspect they may have high release. Thus, the percentages violations
are skewed, and are in no way representative of total imports. A major
improvement has taken place since testing began in 1970. The 1970 -
1973 period violations were typically in the 10 - 11 percent range; now
they are less than 5 percent. However, this does not tell the whole story.
In the early days many leach solutions exceeded 1,000 ppm, and some were
2,000 to 10,000 ppm. Now, even those with release rates above the. 7 ppm
limit do not have these gross excesses. Whereas violations have occurred
in a number of imported products, problems of any significance appear to
be limited to a handful of foreign countries.
475
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In 1971 FDA conducted a sampling program covering domestically pro-
duced glazed ceramic foodware. Since then the industry association, the
U.S. Potters Association, has assumed the responsibility of conducting an
extensive volunteer program with twice-a-year sampling; the results
are forwarded to FDA. FDA periodically makes spot checks of the entire
domestic industry. Since periodic testing has not recently indicated
any problem with domestically produced dinnerware, it would indicate that
the problem is correctable through good quality control, and is fully
under control with respect to the hazard of extractable lead.
Although there have been a few well-publicized instances of lead
poisoning arising from this cause, they are so rare as to be newsworthy
enough to be made the subject of magazine articles. Also, if these arti-
cles are examined, it is seen that the ware falls into two classes: hand-
crafted, or imported foreign ware (possibly also handcrafted). In fact,
at least in some instances they were souveniers of foreign travel, and would
never be called upon to pass FDA inspection. Thus, the control of such
ware may be beyond the reach of Federal regulatory agencies.
As far as the general public is concerned, the problem of excessive
lead intake from improperly glazed dinnerware seems to be one of very low
probability. The FDA domestic monitoring and the self-policing of the
industry appears to be fully adequate to protect the public against even
marginal lead exposure hazards from this source. Whereas continued import
surveillance is required, the problem with imported dinnerware also seems
to be well under control.
9.5.2.3
Alternatives to Lead Glazes--
Before considering alternatives to lead glazes it is worth summarizing
the benefits that lead glazes confer, which would perhaps be lost by
their abandonment. These have been well summarized by Eppler (1976):
(1)
The strong fluxing action permits lower temperatures, and also
increases flexibility in formulation to achieve low expansion
and smooth surface.
Lead reduces viscosity and widens allowable firing range.
Lead produces low surface tension chiefly responsible for the
flatness and high gloss; also contributes to ability of the
glaze to heal over small surface imperfections.
Imparts a high index of refraction which results in a brilliant
appearance.
Reduces tendency towards surface crystallization or devitrification.
(2)
(3)
(4)
(5 )
This combination of desirable properties cannot yet entirely be reproduced
on a production scale in the leadless type glazes.
There are leadless glazes, and much research has been conducted aimed
at developing a satisfactory substitute for lead glazes. Many of these in-
creased quantities of alkali and boron oxides to help provide the low fusion
properties found in leaded glazes, but lose other properties in so doing, for
example in effects on underglaze colors and crazing (Lead Industries As-
sociation, 1972). None appear to have been sufficiently successful to per-
suade the industry to switch from lead glazes.
476
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One alternative would be to forego glazing entirely. However, apart
from the aesthetic loss there are serious health objections. Unglazed
pottery presents a different problem due to the fact that it can permit
the growth of pathogenic bacteria which potentially may constitute a far
more serious health hazard than that resulting from possible exposure to
lead in the glaze. Thus, the glazing of pottery does in practice confer
a beneficial health effect in terms of better hygiene.
9.5.2.3.1 Economic implications--If the present mode of control is
continued, either with the present limitations on extractable lead, or
the proposed ISO standards, there will be no major impacts upon the industry,
although there may be limited economic consequences for certain
manufacturers. Present glaze formulations and processing procedures,
combined with adequate quality control, appears to already be fulfilling
the objective of protecting the public health, and no changes are needed.
Should the abandonment of lead glazes be required, the industry dis-
ruption would be large. The new lead-free products would be more expensive,
and probably inferior with respect to durability. There are, however,
no indications that such drastic action is necessary or desirable.
9.5.3
Miscellaneous Sources of Ingested Lead
,
There are several miscellaneous potential sources of ingested lead
which need to be briefly discussed. Each of them has but a negligible
effect on the absorbed lead dose of the general population, and appears
to be important only in exceptional and unusual situations. Data on the
actual degree of risk are scant, and judgements are necessarily based
largely on conjecture.
9.5.3.1
Decal-Decorated Glass Tumblers--
In July of 1977, the Massachusetts Department of Public Health
announced that they had analyzed the exterior portion of a promotional
glass tumbler decorated with a lead glaze decal and were able to extract
some lead. An interagency task force (FDA, EPA, and CPSC) was formed
to examine the issue and decide upon an appropriate course of action.
The principal findings of the Interagency task force can be summarized
as follows (Hill, et al., 1978):
(1)
The industry and the involved agencies agreed that
under certain conditions, lead and cadmium can be
extracted from decorated glass tumblers and that
excessive levels can pose undesirable health risks.
(2)
Most glasses tested were well within acceptable
levels.
(3)
The glassware industry expressed a willingness for
a voluntary standard and adequate quality control.
477
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(4)
The task force concluded that the proposed positive
steps are likely to be adequate to reduce whatever
risk may be present, therefore, no formal rule-making
is required at this time.
9.5.3.2
Lead Glass--
The situation with lead glass dinnerware in part resembles that of
glazed ceramics and in part that of antique pewter. Lead is added to
glass to give it a high index of refraction, which when decorated by the
cutting of grooves, provides a brilliant appearance, much fancied for
such items as decorative fruit bowls. Some stemware is also manufactured
from lead glass. Characteristically, such lead glassware is expensive,
which tends to limit its use. Lead glassware is not customarily used as
everyday dinnerware, in this respect resembling antique lead pewter.
Like lead glazed ceramic ware, lead glass is subject to leaching if
the ware was not properly manufactured. Some foreign decanters have shown
up to 50 ppm by the standard acetic acid leach test (Ott, 1978). As in the
glazed dinnerware, the problem appears to be one of quality control. West
German and U.S. lead glassware has no problem in passing the test, and the
problem is only with one or more other countries. The present FDA
inspection program appears to be adequately coping with this limited pro-
blem, and no need for additional limitations is evident at this time.
9.5.3.3
Solder-Joined Food Vessels--
One source of ingested lead, whose extent was not determined in this
investigation, is from the lead solder which has, in the past at least,
been used to join assemblies of metallic vessels of various sorts which
are used to contain or to prepare foods or beverages, e.g. electric
coffee pots.
A recent article by Wigle and Charlebois (1978) described a clinical
lead poisoning case of an infant in Toronto, Canada, which was traced to
the solder used to seal the heating element into the base of the electric
kettle used to prepare the infant's formula. A subsequent survey of 574
households in Ottawa showed that 42.5 percent of water samples boiled in
this type of electric kettle exceeded the 50 ppb 1~O (and U.S.) standard,
and 9 percent exceeded 110 ppb. However, the conclusion of the investiga-
tion was that lead exposure from electric kettles may be a significant
problem only in infants receiving formula prepared with boiled water.
As indicated above it is not known how serious the problem is in the
U.S. It is known that at least a small number of industrial applications
have substituted a tin solder (described as a 95% tin-5% silver composition)
for lead-containing solders in coffee pots, kitchen and bathroom appliances,
and ice-making equipment (The Silver Institute, 1975). The technical be-
havior of these nonlead solders is reported as equivalent or superior in
terms of lower melting point, high-temperature strength, good wetting, and
better hygienic properties.
478
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This problem, if it is one, 'needs to be better defined before recom-
mendations can be made.
9.5.3.4
Pewter Ware--
Pewter is the historical name for an alloy of tin and lead, the lead
serving to harden the tin. High quality pewter had relatively low percent-
ages of lead, because of the known ill effects from lead on humans. From
about the twelfth century the trade in pewter in all Europear countries
appears to have been well organized and by the fourteenth century pewterers
were everywhere bound by statutes and edicts designed to prevent the ruin
of their business by unscrupulous competitors (Hedges, 1960). However,
lead was then, as now, so much cheaper than tin that the alloys were de-
based by excessive lead. This became a particular problem after the intro-
duction of better glazes for dinnerware led to the displacement of pewter
tableware. Some debased pewters contained as much as 40 to 50 percent lead.
There was a lead health hazard from the use of pewter, particularly
that with excessive lead content. However, this antique pewter now occupies
a predominantly decorative function, which has effectively eliminated it
dS a health hazard.
In the middle of the eighteenth century Britannia Metal was invented.
This is an alloy of 90-95 percent tin with 4-8 percent antimony, and 1-2
percent copper, and should contain no more lead than is justifiable as
an impurity. The best grades contain no lead. Modern pewter is Britannia
Metal.
The tin accounts for its soft sheen, ductility, and resistance to
corrosion. The antimony serves to whiten the metal and impart a hardness
unknown to old pewter. The copper adds ductility and desirable working
properties, but if present in more than a small percentage, adds an unde-
sirable yellow color. Utensils made from modern pewter (Britannia Metal)
have a high resistance to the action of almost all acids. Foods and drink
may be served in them without fear of chemical action (Osburne and Wil-
ber, 1938).
Summarily, modern pewter offers a minimum of lead ~xposure hazard,
and the exposure of the general public to antique pewter vessels appears
so unlikely that it can be neglected.
9.5.3.5
Drinking Water--
As discussed in Section 5.3.2, the general public, with few exceptions,
is not exposed to drinking water containing more than the 50 ppm limit of
the interim primary drinking water standard. The exceptions are in areas
of soft, low pH water; even here, the public water supplies are well below
the 50 ppm limit. The problem arises from the use of lead service pipe
between the distribution main and the house, and the size of the problem
is a function of the length of lead pipe for each individual case. The
areas concerned are primarily in New England, where the water is soft and
many houses are old enough to have had lead service pipes installed, with
apparently some similar problems in the Pacific Northwest.
479
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'-
There are two alternatives. The certain and absolute cure is to re-
move the offending pipe and replace it with non-lead pipe. The second would
necessitate that water distributed throughout the city be treated to make it
non-corrosive to lead pipe. Increasing the pH to a substantially alkaline
level (pH 9-10), and possible also adding a little carbonate hardness to
the water seems, on the basis of evidence from EPA Region I, to offer a
viable solution.
Since this is a rather unique situation, local in its effect, it is
not regarded as a strong candidate for national limitations; it can
probably best be handled as a local problem.
480
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9.6
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-------
Sulek, A. 1977a. CMI-NCA 1974 Lead in Canned Food Survey. Unpublished
Paper. National Food Processors Association, Washington, D. C. 10 pp.
Sulek, A. 1977b. CMI-NCA 1976 Lead in Raw Product Survey. Unpublished
Paper. National Food Processors Association, Washington, D. C. 8 pp.
Sulek, A. 1978. The Evaluation of Lead in Raw and Canned Food. Unpublished
Paper. National Food Processors Association. Washington, D. C. 11 pp.
Tepper, L. D. and L. S. Levin. 1975. A Survey of Air and Population Lead
Levels in Selected American Communities. In: Lead. T. B. Griffin and
J. H. Kue1son (Eds.) Environmental Quality and Safety, Supplement Vol.
II. Georg Thieme Publishers, Stuttgart. 152-196 pp.
U. S. Bureau of Mines. 1978. Mineral Commodity Summaries, 1978.
Department of the Interior. Washington, D. C.
U. S.
U. S.
Department of Health, Education, and Welfare. 1974. Lead in
Evaporated Milk and Evaporated Skim Milk. Proposed Tolerance.
and Drug Administration, Washington, D. C. 39 FR 42740-42748.
December 4.
Food
U. S. Department of Labor. 1978a. Occupational Exposure to Lead: Final
Standard. Occupational Safety and Health Administration, Washington,
D. C. 43 FR 52952-53014. November 14.
U. S.
Department of Labor. 1978b. Occupational Exposure to Lead.
Attachments to the Preamble for the Final Standard. Occupational
Safety and Health Administration, Washington, D. C. 43 FR 54354-
54509. November 21.
U. S.
Environmental Protection Agency. 1977a. Air Quality Criteria for
Lead. U. S. Environmental Protection Agency. EPA-600/3-77-017.
Office of Research and Development, Washington, D. C. December.
Various pagination.
U. S.
Environmental Protection Agency. 1977b. Control Techniques for Lead
Air Emissions. 2 Vo1s. EPA-450/2-77-012. Office of Air Quality
Planning and Standards Research Triangle Park, North Carolina.
December. Various pagination.
U. S. Environmental Protection Agency. 1978a.
Secondary Air Quality Standard for Lead.
October 5.
National Primary and
43 FR 46246-46263.
U. S. Environmental Protection Agency. 1978b. Implementation Plans for
Lead National Ambient Air Quality Standard. 43 FR 46264-46271.
October 5.
\vig1e, D. T., and E. J. Charlebois. 1978. Electric Kettles as a Source
of Human Lead Exposure. Arch. Env. Health. 72-78 pp.
World Health Organization. 1976. Ceramic Foodware Safety, Sampling,
Analysis, and Limits for Lead and Cadmium Release. Report of Meeting.
IVHO/Food Add/77.44.
484
-------
APPENDIX A
-------
TABLE A-l.
DAILY INTAKE OF LEAD FROM VARIOUS FOODS AND THE EFFECT OF
REDUCING LEAD CONTE~T OF CANNED FOODS: MALES AND FEMALES
UNDER i-YEAR OLD
Lead Intake, ug/day. with Lead In
Normal Daily Canned Food R,-,duced
Food Cla"s and Substance Lead Intake, ug Reduced 1/2 Reduced 2/ 1
~
Milk, fr'-'sh 10.82 10.82 10.82
Milk, proc~ssed. cann~d 5.69 2.845 1. 897
Milk, processed, other 9.35 9.35 9.35
Cream 1. 22 1.22 1.22
Ch..ese iJnd mixtures 0.12 0.12 0.12
Eg~s 2.04 2.04 2.04
~
8eef, canned 0.06 0.03 0.02
Beef, other 1. 38 1.38 1. 38
Pork, canned 0.02 0.01 0.0067
Pork, other 0.57 0.57 0.57
Poultry 0.381 0.381 0.381
Fish, c;.altned 0.0 0.0 0.0
Fisl" other 0.0 0.0 0.0
Other and mIxtures, canned 1.23 0.615 0.41
Other and mixtures, other 5.86 5.86 5.86
NUTS ANO OILS
Legumes and nuts 3.38 3.38 3.38
Fats and oils 0.01 0.03 0.03
BREADS
Bread 0.42 0.42 0.42
Other baked goods 0.40 0.40 0.40
Cereals, pastes 5.136 5.136 5.136
SUGAR PRODUCTS
Sugar 0.031 0.031 0.031
Candy, jam. etc. 0.63 0.63 0.63
BEVERAGES
Tea 0.4 0.4 0.4
Coffee 0.0 0.0 0.0
Cola, canned 0.02 0.01 0.0067
Cola, other 0.18 0.18 0.18
Fruit drinks, canned 0.01 0.005 0.003
Fruit drinks, oth~r 0.02 0.02 0.02
Other soft drinks, canned 0.001 0.0005 0.0003
Other soft drinks, ocher 0.02 0.02 0.02
Beer. canned 0.0 0.0 0.0
Beer, other 0.0 0.0 0.0
Wine 0.0 0.0 0.0
Other alcoholic drinks 0.0 0.0 0.0
TOMATOES AND VEGETABLES
Tomatoes, canned 0.16 0.08 0.0533
Tomatoes, other 0.04 0.04 0.04
Tomato juice, canned 0.07 0.035 0.0233
Citrus, canned 0.02 0.01 0.0067
Citrus, other 0.52 0.52 0.52
Citrus julc'-' , canned 0.59 0.295 0.197
Citrus juice, other 0.09 0.09 0.09
Dark gre..n vegetables, canned 0.14 0.07 0.047
Dark green vegetables, other 0.08 0.08 0.08
Deep yellow vegetables, canned 0.57 0.285 0.19
Deep yellow ve~etables, other 0.96 0.96 0.96
POTATOES AND FRUITS
Potato"s, cann"d 0.01 0.005 0.003
Potatoes, other 0.30 0.30 0.30
Other v~gctabJ~st canned 6.85 3.425 2.833
Other vegetables, other 3.85 3.85 3.85
Other vegetab1" Jutce, canned 0.16 0.08 0.053
Other fruits, canned 7.61 3.805 2.537
Oth~r fruits, other 3.27 3.27 3.27
Other f ru t t jutce. c:lnned 0.1>8 0.34 0.227
Other fruIt juice. other 0.03 0.03 0.03
TOTAL 75.419 63.4735 60.042
A-i
-------
TABLE A-2.
DAILY INTAKE OF LEAD FROM VARIOUS FOODS AND THE EFFECT
OF REDUCING LEAD CONTENT OF C~ED FOODS: MALES AND
FEMALES 1-2 YEARS OLD.
Lead Intake, ug/day, with Lead In
Normal Daily Canned Food Reduced
Food Class and Suhstance Lead Intake, IIg Reduced 1/2 Reduced 2/3
MI1.K
Milk, fresh 9.20 9.20 9.20
Milk, proc\!SSCU, CUIlIH!U 4.84 2.42 1.613
Milk, processed, other 7.95 7.95 7.95
Cream 1.56 1.56 1.56
Chaese and mixtures 0.60 0.60 0.60
Eggs 4.87 4.87 4.87
MF.A TS
Beef, canned 0.20 0.1 0.007
Beef, other 4.75 4.75 4.75
Pork, canned 0.15 0.075 0.05
Pork, other 4.023 4.023 4.023
Poultry 1.4 1.4 1.4
Fish, canned 0.35 0.175 0.117
Fish, other 1.16 1.16 1.16
Other and mixtures, canned 1. 35 0.675 0.45
Other and mixtures, other 6.57 6.57 6.57
NUTS AND OILS
Legumes and nuts 4.16 4.16 4.16
Fats and oils 0.156 0.156 0.156
~
Bread 3.276 3.276 3.276
Other baked goods 2.9 2.9 2.9
Cereals, pastes 8.03 8.03 8.03
SUGAR PRODUCTS
Sugar 0.25 0.25 0.25
Candy, jam, etc. 1. 54 1.54 1.54
BEVERAGES
Tea 3.6 3.6 3.6
Coffee 0.14 0.14 0.14
Cola, canned 0.32 0.16 0.107
Cola, other 3.1 3.1 3.1
Fruit drinks, canned 0.16 0.08 0.053
F:,uit drinks, other 0.35 0.35 0.35
Other soft drinks, canned 0.02 0.01 0.007
Other soft drinks, other 0.28 0.28 0.28
Beer, canned 0.0 0.0 0.0
Beer, other 0.0 0.0 0.0
Wine 0.0 0.0 0.0
Other alcoho lie drinks 0.0 0.0 0.0
TOMATOES AND VEGETABLES
Tomatoes, canned 1.92 0.96 0.64
Tomatoes, other 0.54 0.54 0.54
Tomato juice, canned 0.87 0.435 0.29
Citrus, canned 0.04 0.02 0.013
Citrus, other 1.14 1.14 1.14
Citrus juice, canned 1.20 0.645 0.43
Citrus juice, other 0.19 0.19 0.19
Dark green vegetables, canned 0.27 0.135 0.09
Dark green vegetables, other 0.17 0.17 0.17
Deep yellow vegetables, canned 0.29 0.145 0.097
Deep yell.ow v~~utltbtesJ other 0.48 0.48 0.48
POTATOES !\NIJ rRU ITS
Potatoes, canned 0.58 0.29 0.193
Potatoes, othar 1.67 1.67 1.67
Other vegetables, canned 6.58 3.29 2.193
Oth~~ v~get3blcs. other 3.69 3.69 3.69
Other vegetable Juice, canned 0.15 0.075 0.05
Other fruits, c~lnncd 6.79 3.395 2.263
Oth..r rnlits, other 2.92 2.92 2.92
Other ftuit Juice, canned 0.61 0.305 0.203
Other ftui t juice, ochur 0.03 0.03 0.03
TOTAt. 107.475 94.085 89.561
A-2
-------
TABLE A- 3.
DAILY INTAKE OF LEAD FROM VARIOUS FOODS AND THE EFFECT
OF REDUCING LEAD CONTENT OF CANNED FOODS: MALES ~~D
FE~~LES 3-5 YEARS OLD.
Lead Intake, ug/day, with Lead In
Normal Daily Canned Food Reduced
Food C)"s~ and Sub~t.:1n..:~ Lead Intake, ug Reduced 1/2 Reduced 2/3
~
Milk, fresh 1.91 1.91 1.91
Milk, proccs:;crJ, canned 4.16 2.08 1.381
Milk, processed, oth..r 0.84 0.84 6.84
CrQom 2.il 2.11 2.11
Chee~e and mixtures 0.48 0.48 0.48
Eggs 4.0 4.0 4.0
MEATS
Beef, canned 0.28 0.14 0.093
Beef, oth~r 6.13 6.13 6.13
Pork, canned 0.22 0.11 0.013
Pork, other 5.15 5.15 5.15
Poultry 2.03 2.03 2.03
Fish, canned 0.58 0.29 0.193
Fish, other 1.93 1.93 1.93
Other and mixtures, canned 1.13 0.565 0.311
Other and mixtures, 0 ther 5.14 5.14 5.14
NUTS AND OrLS
Legumes and nuts 1.28 1.28 1.28
Fats and oils 0.24 0.2!1. 0.24
~
Bread 5.29 5.29 5.29
Other baked goods 4.3 4.3 4.3
Cereals, pastes 8.88 8.88 8.88
SUGAR PRODUCTS
Sugar 0.31 0.31 0.31
Candy, jam, etc. 2.11 2.11 2.11
BEVERAGES
Tea 6.6 6.6 6.6
Coffee 0.35 0.35 0.35
Cola, canned 0.52 0.26 0.113
Cola, other 5.06 5.06 5.06
Frui t drinks, canned 0.26 0.13 0.081
Fruit drinks, other 0.51 0.51 0.51
Other soft drinks, canned 0.03 0.015 0.01
Cther soft drinks, other 0.46 0.46 0.46
Beet', canned 0.0 0.0 0.0
Beer, other 0.0 0.0 0.0
Wine 0.0 0.0 0.0
Other alcoholic drinks 0.0 0.0 0.0
TOMATOES AND VEGETABLES
Tomatoes, canned 2.09 1.045 0.691
Tomatoes, other 0.58 0.58 0.58
Tomato juice, canned 0.94 0.41 0.313
Citrus, canned 0.05 0.025 0.011
Citrus, other 1.28 1. 28 1.28
Citrus JuIce, canned 1.45 0.125 0.483
Citru~ juice, other 0.21 0.21 0.21
Dark green vegetables, canned 1~.20 0.10 0.061
Dark green vegetables, other 0.13 0.13 0.13
Deep yellow vegetables, canned 0.29 0.145 0.0961
Deep yellow vegetables, other 0.48 0.48 0.48
POTATOES AND FRUITS
Potatoes, cann"d 0.013 0.0365 0.0243
Potatoes, otht:r 2.11 2.11 2.11
Other veg"tables, canned 6.58 3.29 2.193
Other vegetable~, other 3.69 3.69 3.69
Other vegetable Juice, canned 0.15 0.015 0.05
Other fruits, canned 6.86 3.43 2.281
Othcr fru les, uther 2.95 2.95 2.95
Other fruit juic.., c:1nned 0.61 0.305 0.203
Other fruit juice, other 0.03 0.03 0.03
TOTAL 123.023 109.186 105.354
A-3
-------
TABLE A-4.
DAILY INT~~E OF LEAD FROM VARIOUS FOODS &~D THE EFFECT
OF REDUCING LEAD CONTENT OF CANNED FOODS: MALES AND
FEMALES 6-8 YEARS OLD.
Food Clas,; and Sub,;eance
HllK
Normal Daily
Lead ineake. \18
Lead Ineake, \lg/day, wieh lead In
Canned food Reduced
Reduced 1/2 Reduced 2/3
Milk,
Milk,
Milk,
Cream
Chee,;e and
E!;!;s
fresh
proce,;sed, canned
processed, ottlcr
mix Cures
~
Beef, canned
Beef, ocher
Pork, canned
Pork, ocher
poulery
Fish, canned
Fish, ocher
Ocher and mixeures,
Other and mixeures,
canned
ocher
NUTS AND OILS
legumes and nues
Faes and oils
8.36
4.40
7.20
2.72
0.60
4.002
8.36
2.20
7.20
2.72
0.60
4.002
8.36
1.467
7.20
2.72
0.60
4.002
0.315
7.52
0.24
6.32
3.175
0.81
2.69
1.50
7.25
0.1575
7.52
0.12
6.32
3.175
0.405
2.69
0.75
7.25
0.105
7.52
0.08
6.32
3.175
0.27
2.69
0.5
7.25
BREADS
9.36
0".29
9.36
0.29
9.36
0.29
Bread
Other baked goods
Cereals, pastes
SUGAR PRODUCTS
Sugar
Candy, jam, eec.
BEVERACES
Tea
Coffee
Cola, canned
Cola, ocher
Fruie drinks, canned
Fruie drinks, oCher
Other sofe drinks, canned
Ocher sofe drinks, other
Beer, canned
Beer, ocher
Wine
Ocher alcoholic drinks
TOMATOES AND VECETABlES
Tomaeoes, canned
Tomaeoes, other
Tomaeo juice, canned
Citrus, canned
Cierus, ocher
Cierus juice, canned
Cierus juice, ocher
Dark green vegeeables, canned
Dark green vegeeables, ocher
Deep yellow vegeeables, canned
Deep yellow vegecables, ocher
POTATOES AND FRUITS
Poeaeoes, canned
Poeatoes, ocher
Ocher vegeeables, canned
Ocher v~g~t"blcs, other
Ocher vegeeahle Juice, canned
Other frules, canned
Ocher frule,;, oeh"r
Ocher frule Julce, canned
Other fruie juice, ocher
6.47
5.40
8.99
6.47
5.40
8.99
6.47
5.40
8.99
0.43
2.31
0.43
2.31
0.43
2.31
7.2
0.28
0.68
6.56
0.34
0.74
0.03
0.60
0.0
0.0
0.0
0.0
7.2
0.28
0.31.
6.56
0.17
0.74
0.015
0.,60
0.0
0.0
0.0
0.0
7.2
0.28
0.227
6.56
0.113
0.74
0.01
0.60
0.0
0.0
0.0
0.0
3.21
0.89
1.45
0.05
1.31
1.47
0.2~
0.34
0.212
0.34
0.56
1. 605
0.89
0.725
0.025
1.31
0.735
0.22
0.17
0.212
0.17
0.56
1.07
0.89
0.483
0.0167
1.31
0.49
0.22
0.113
0.212
0.113
0.56
0.09
2.61
7.81
4.39
0.18
7.67
3.30
0.69
0.03
0.045
2.61
3.905
4.39
0.09
3.835
3.30
0.345
0.03
0.03
2.61
2.603
4.39
0.06
2.557
3.30
0.23
0.03
TOTAL
143.604
127.796
122.202
A-4
-------
EFFECT
DAILY INTAKE OF LEAD FROM VARIOUS FOODS AND THE
OF REDUCING LEAD CONTENT OF CANNED FOODS: MALES
15-17 YEARS OLD.
TABLE A-5.
Food Clas>! and Substanct!
HlLK
Normal Daily
Lead Intake, ug
Lead Intake, ug/day, with Lend In
Canned Food Rcduced
Reduced 1/2 Reduced 2/3
fresh
processed, cann~d
proc~sscd. other
Mllk,
Milk,
Milk.
Crcum
Cheesc and
~ggs
mixtures
~
Beef, canned
Beef, other
Pork, canned
Pork, other
Poultry
Fish, canncd
Fish, othcr
Other and mixtures,
Other and mixtures,
canned
other
NUTS AND OILS
Legumes and nuts
~'ats and oils
BREADS
Bread
Other baked goods
Cercals. pastes
SUGAR PRODUCTS
Sugar
Candy, 1am. etc.
BEVERAGES
Tea
Coffee
Cola, canned
Cola, other
Fruit drinks, canned
Fruit drinks, other
Other soft drinks, canned
Other soft drinks. other
Beer, canned
Beer, other
WIne
Other alcoholic drinks
TOMATOES A~D VEGETABLES
Tomatoes, canned
Tomatoes, other
Tomato juice, canned
Citrus, canned
Citrus, other
Citrus juice, canncd
Citrus juice, other
Dark green vegetables. canned
Dark green vegetables. other
Deep yellow vCGt!tablcs. canned
Deep yellow vc~~t<..lbl~s I otlu~r
POTATOES ANI) FRUITS
Potatoes, canncd
Potatoes, other
Other vegetables, canned
Other vegetables. other
Other vegetable juice, canned
Other fruits, canned
Other fruits, other
Other fruit juicc, canned
Other fruit juice, other
9.34
4.913
8.072
1. '112
1.320
7.308
9.34
2.4565
8.072
1.1U
1. 320
7.308
9.34
1.638
8.072
1.332
1. 320
7.308
0.623
14.836
0.447
11.784
3.429
1.155
3.845
2.551
12.452
0.3115
14.836
0.2235
11.784
3.429
0.5775
3.845
1. 2755
12.452
0.2077
14.836
0.149
11.784
3.429
0.385
3.845
0.8503
12. 452
12.22
0.507
12.22
0.507
12.22
0.507
11.34
8.5
9.951
11.34
8.5
9.951
11. 34
8.5
9.951
0.403
3.22
0.403
3.22
0.403
3.22
18.20
4.13
1. 337
12.991
0.666
1. 451
0.065
1.189
0.0
0.0
0.0
0.0
18.20
4.13
0.6685
12.991
0.333
1.451
0.0325
1.189
0.0
0.0
0.0
0.0
18.20
4.13
0.4457
12.991
0.222
1.451
0.0217
1.189
0.0
0.0
0.0
0.0
4.658
1. 297
2.106
0.065
1. 780
2.010
0.298
0.405
0.254
0.427
0.723
2.329
1.297
1.053
0.0325
1. 780
1.005
0.298
0.2025
0.254
0.2135
0.723
1.553
1. 297
0.702
0.0217
1. 780
0.67
0.298
0.135
0.254
0.1423
0.723
0.155
4.473
12.754
7.154
0.299
8.013
3.444
0.716
0.031
0.0775
4.473
6.377
7.154
0.1495
4.0065
3.444
0.358
0.031
0.0517
4.473
4.2513
7.154
0.0997
2.671
3.444
0.2387
0.031
TOTAl.
222.639
200.95
193.73
A-5
-------
TABLE A-6.
DAILY INTAKE OF LEAD FROM VARIOUS FOODS AND THE
EFFECT OF REDUCING LEAD CONTENT OF Cfu~NED FOODS:
FEMALES 15-17 YEARS OLD.
Food Class and Substance
lli.!:!
1'111. k,
Milk,
Milk,
Cream
Cheese
Eggs
fresh
proccssed, c~lnncd
processed, other
and mixtures
~
Bee f, canned
Beef. other
Pork, canned
Pork, other
Poultry
Fish, canned
Fish, other
Other and mixtures,
Other and mixtures,
canned
other
NUTS AND OILS
Legumes and nuts
Fats and oils
BREADS
Bread
Other baked goods
Cereals, pastes
SUGAR PRODUCTS
Sugar
Candy, jam, etc.
BEVERAGES
Tea
Coffee
Cola, canned
Cola, other
Fruit drinks, canned
.ruit drinks, other
Other soft drinks. canned
Other soft drinks, other
Beer. canned
Beer, other
Wine
Other alcoholic drinks
TOMATOES ANn VEGETABLES
Tomatoes, canned
Tomatoes, other
Tomato juice, canned
Citrus, canned
Citrus, other
Citrus juice. canned
Citrus juice, other
Dark greer. vegetables. canned
Dark green vegetables, other
Deep yellow ve~etables, canned
Deep yellow v"~etables, other
POTATOES ,\ND FRUITS
Potatoes. canned
Potatues, uth~r
Other vegetables, canned
Ocher vegetables, other
Other ve~etable juice, canned
Oth~r fruits, canned
Other fruits, other
Other fruit juice, canned
Other fruit juice. other
TOTAL
Normal Daily
Lead Intake, ug
Lead Intake, ug/day, with Lead In
Canned Food Reduced
Reduced 1/2 Reduced 2/3
5.95
3.13
5.14
2.312
0.96
4.35
5.95
1.565
5.14
2.312
0.96
4.35
5.95
1.04
5.14
2.312
0.96
4.35
0.48
11.47
0.30
8.05
2.29
1.04
3.46
1.84
9.19
0.24
11,47
0.15
8,05
2.29
0.52
3.46
0.92
9.19
0.16
11. 47
0.10
8.05
2.29
0.347
3.46
0.613
9.19
7.54
0.286
7.54
0.286
7.54
0.286
6.64
5.90
6.96
6.64
5.90
6.96
6.64
5.90
6.96
0.31
2.17
0.31
2.17
0.31
2.17
15.2
4.55
1.13
10.94
0.56
1.22
0.055
1. 001
0.0
0.0
0.0
0.0
15.2
4.55
0.565
10.94
0.028
1.22
0.61
1.001
0.0
0.0
0.0
U.O
15.2
4.55
0.377
10.94
0.187
1.22
0.018
1. 001
0.0
0.0
0.0
0.0
4.01
1.12
1.82
0.053
1.45
1.~3
0.24
0.54
0.34
0.29
0.48
2.005
1.12
0.91
0.0265
1.45
0.815
0.24
0.27
0.34
0.145
0.48
1.337
1.12
0.607
0.018
1.45
0.543
0.24
0.18
0.34
0.097
0.48
0.85
2.46
10.15
6.24
0.24
7.67
3.30
0.69
0.03
0.425
2.46
5.075
6.24
0.12
3.835
3.30
0.345
0.03
0.283
2.46
3.383
6.24
0.08
2.56
3.30
0.23
0.03
168.027
150.631
143.709
A-6
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TABLE A-7.
DAILY INTAKE OF LEAD FROM VARIOUS FOODS AND THE EFFECT OF
REDUCING LEAD CONTENT OF CANNED FOODS: MALES 20-34 YEARS
OLD.
Lead Intake, ug/day, with Lead In
Normal Daily Canned Food Reduced
Food Class and Substance Lead Intake, ug Reduced 1/2 Reduced 2/3
M£T.K
Milk, (c(!sh 4.94 4.94 4.94
Mil k, procc!is~d, cnnn~d 2.60 1.30 0.867
Milk, proccss"d, other 4.27 4.27 4.27
Cream 2.24 2.24 2.24
Cheese and mixtures 1.44 1.44 1.44
Eggs 9.57 9.57 9.57
MEATS
8eef, canned 0.91 0.455 0.303
Beef, other 21. 76 21. 76 21. 76
Pork, canned 0.54 0.27 0.18
Pork, other 14.08 14.08 14.08
Poultry 4.06 4.06 4.06
Fish, canned 1.62 0.B1 0.54
Fish, other 5.39 5.39 5.39
Other and mixtures, canned 2.97 1. 485 0.99
Other and mixtures, other 14.73 14.73 14.73
NUTS AND -on.s
Legumes and nuts 3.38 3.38 3.38
Fats and oils 0.20 0.2 0.2
~
Bread 10.08 10.08 10.08
Other baked goods 7.70 7.70 7.70
Cereals, pastes 8.99 8.99 8.99
SUGAR PRODUCTS
Sugar 0.53 0.53 0.53
Candy. jam, etc. 1.89 1.89 1.89
BEVERAGES
Tea 29.60 29.60 29.60
Coffee 29.54 29.54 29.54
Cola, canned 1.074 0.537 0.358
Cola, other 10.44 10.44 10.44
Fruit drinks, canned 0.53 0.265 0.177
Fruit drinks, other 1.17 1.17 1.17
Other soft drinks, canned 0.05 0.025 0.017
Other soft drinks, other 0.96 0.96 0.96
Beer, canned 1.05 0.525 0.35
Beer, other 11.22 11. 22 11. 22
Wine 2.569 2.569 2.569
Other alcoholic drinks 0.517 0.517 0.517
TOMATOES AND VEGETABLES
Tomatoes, canned 6.10 3.05 2.033
Tomatoes, other 1. 70 1. 70 1. 70
Tomato juice, canned 2.76 1.38 0.92
Citrus, canned 0.06 0.03 0.02
Citrus, other 1.57 1.57 1.57
Citrus juice, canned 1. 77 0.885 0.59
Citrus juice, ocher 0.26 0.26 0.26
Dark green v~getabies, canned 5.76 2.88 1.92
Dark green vegetables, other 0.30 0.30 0.30
Deep yellow vegetables, canned 0.47 0.235 0.157
Deep yellow ve~etubl~s, other 0.80 0.80 0.80
POTATOES AND FRUITS
Potatoes, canned 0.16 0.08 0.053
Potato~s, ocher 4.72 4.72 4. i2
Other vegetables, canned 15.50 7.75 5.167
Other vegetahles, other 8.70 a. 70 8.70
Ocher ycgecnhle Juice. canned 0.36 0.18 0.12
Other fruIts, canned 6.52 3.26 2.173
Other fruits, IJth~r 2.80 2.80 2.80
Other fruit juice, canned 0.58 0.19 0.19
Other fruit juice, ocher 0.02 0.02 0.02
TOTAL 273.52 247.73 239.26
A-7
-------
TABLE A-8.
DAILY INTAKE OF LEAD FROM VARIOUS FOODS AND THE EFFECT OF
REDUCING LEAD CONTENT OF CANNED FOODS: FEMALES 20-34 YEARS
OLD.
Normal Daily Lead Intake, ~g/day, with Lead In
Canned Food Reduced
Food Class and Substance Lead Intake, ug Reduced 1/2 Reduced 2/3
~
Milk, fr.:sh 3.17 3.17 3.17
Milk, processed, c.:1nn~d 1.67 0.835 0.557
Milk, processed, other 2.74 2.74 2.74
Cream 2.04 2.01, 2.04
Cheese and mixtures 1. 32 1.32 1.32
Eggs 4.70 4.70 4.70
MFA TS
Beef, canned 0.53 0.265 0.177
Beef, other 12.66 12.66 12.66
Pork, canned 0.293 0.1465 0.098
Pork, other 7.76 7.76 7.76
Poultry 2.667 2.667 2.667
Fish, canned 1.04 0.52 0.347
Fish, other 3.46 3.46 3.46
Other and mixtures, canned 1.80 0.90 0.60
Other and mixtures, other 9.22 9.22 9.22
NUTS ANt> OILS
Legumes and nuts 6.24 6.24
Fats and oils 0.30 0.30 0.30
~
Bread 5.96 5.96 5.96
Other baked goods 5.20 5.20 5.20
Cereals , pastes 8.03 8.03 8.03
SUGAR PRODUCTS
Sugar 0.40 0.40 0.40
Candy, 1am. etc. 1. 54 1. 54 1.54
BEVERAGES
Tea 23.80 23.80 23.80
Coffee 28.0 28.0 28.0
Cola, cann"d 0.59 0.445 0.297
Cola, other 8.71 8.71 8.71
Fruit drinks, canned 0.45 0.225 0.15
l"ruit drinks, other 0.97 0.97 0.97
Other soft drinks, canned 0.04 0.02 0.013
Other soft drinks, other 0.80 0.80 0.80
Beer, canned 0.22 0.11 0.073
Beer, other 2.39 2.39 2.39
Wine 0.55 0.55 0.55
Other alcoholic drinks 0.11 0.11 0.11
TOMATOES AND VEGETABLES
Tomatoes, canned 5.13 2.565 1.71
Tomatoes, other 1. 432 1.432 1.432
Tomato juice, canned 2.33 1.165 0.777
Citrus, c.lnned 0.05 0.025 0.017
Citrus, other 1.43 1.43 1.43
Citrus juice. canned 1.47 0.735 0.49
Citrus juice. other 0.22 0.22 0.22
Dark green vegetables. canned 0.54 0.27 0.18
Dark green vegetables, other 0.34 0.34 0.34
Deep yellow vegetables, canned 0.33 0.165 0.11
Deep yellow ve~etables. other 0.56 0.56 0.56
POTATOES AND FRUITS
Potatoes. canned 0.11 0.055 0.037
Potatoes, other 2.75 2.75 2.75
Other vegetables, canned 10.99 5.495 3.663
Other vegetables, other 6.16 6.16 6.16
Other vegetable Juice, canned 0.24 0.12 0.08
Other fruits, canned 4.31 2.155 1.437
Other fruits. other 1.86 1.86 1.86
Other fruit juice. canned 0.42 0.21 0.14
Other fruit juice, other 0.02 0.02 0.02
TOTAL 190.36 173.935 168.463
A-8
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TABLE A-g.
DAILY INTAKE OF LEAD FROM VARIOUS FOODS AND THE
EFFECT OF REDUCING LEAD CONTENT OF CANNED FOODS:
MALES 55-64 YEARS OLD.
Lead Intake. ~g/day. with Lead In
Normal Da1.ly Canned Food Reduced
Food Class and Substance Lead Intake, ~g Reduced 112 Reduced 2/3
~
MlIk, fresh 3.15 3.15 3.15
Milk, processed, cOlnned 1.66 0.83 0.533
Milk, processed, other 2.73 2.7J 2.73
CreOlm 2.65 2.65 2.65
Cheese and mixtures 1.80 1.80 1.80
ER!!S 8.87 8.87 8.87
~
Beef, canned 0.67 0.335 0.223
Beef, other 16.02 16.02 16.02
Pork, canned 0.50 0.250 0.167
Pork, other 13.08 13.08 13.08
Poultry 3.56 3.56 3.56
Fish, canned 2.08 1.04 0.693
Fish, other 6.92 6.92 6.92
Other and mixtures, canned 1.91 0.935 0.637
Other and mi~tures. other 10.92 10.92 10.92
NUTS AND OILS
Legumes and nuts 6.50 6.50 6.50
Fats and olls 0.46 0.46 0.46
~
Bread 8.99 8.99 8.99
Other baked goods 7.50 7.50 7.50
Cereals, pastes 7.81 7.81 7.81
SUGAR PRODUCTS
Sugar 0.53 0.53 0.53
Candy, jam, etc. 2.10 2.10 2.10
BEVERACES
Tea 20.0 20.0 20.0
Coffee 39.06 39.06 39.06
Cola, canned 0.35 0.175 0.117
Cola, other 3.42 3.42 3.42
Fruit drinks, canned 0.18 0.09 0.06
Fruit drinks, other 0.38 0.38 0.38
Other soft drinks, canned 0.02 0.01 0.007
Other soft drinks, other 0.31 0.31 0.31
Beer, canned 0.70 0.35 0.233
Beer, other 7.51 7.51 7.51
Wine 1.72 1. 72 1.72
Other a lcoho lic drinks 0.35 0.35 0.35
TOMATOES AND VEGETABLES
TCIIk'ltoes, canned 4.81 2.405 1. 603
Tomatoes, other 1.34 1.34 1.34
Tomato juice, canned 2.18 1.09 0.727
Citrus, canned 0.06 0.03 0.02
Citrus, other 1.57 1.57 1.57
Citrus juice, canned 1.77 0.885 0.59
Citrus juice, other 0.26 0.26 0.26
Dark green vegetabies, canned 0.54 0.27 0.18
Dark green vegetables, other 0.34 0.34 0.34
Deep yeliow vegetables, canned 0.62 0.31 0.207
Deep yellow ve~etables, other 1.04 1.04 1.04
POTATOES MID FRUITS
Potatoes, c.:anncd 0.13 0.065 0.043
Po ta toes. other 3.74 3.74 3.74
Other vegetables, canned 13.72 6.86 4..573
Other vegetables, other 7.70 7.70 7.70
Other vegetable juice. canned 0.32 0.16 0.107
Other fruits. canned 7.54 3.77 2.51
Other fruits, other 3.24 3.24 3.24
Other fruit juice, cann~d 0.67 0.335 0.223
Other fruit juice, oth~r 0.03 0.03 0.03
TOTAL 236.03 216.12 209.06
A-9
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