xvEPA
United States
Environmental Protection
Agency
Environmental Criteria and
Assessment Office
Research Triangle Park NC 27711
EPA-600/8-83-028A
August 1983
External Review Draft
Research and Development
Air Quality
for Lead
Volume II of IV
Review
Draft
(Do Not
Cite or Quote)
NOTICE
This document is a preliminary draft. It has not been formally
released by EPA and should not at this stage be construed to
represent Agency policy. It is being circulated for comment on its
technical accuracy and policy implications.
-------
EPA-600/8-83-028A
August 1983
_t f. External Review Draft
Draft
Do Not Quote or Cite
Air Quality Criteria
for Lead
Volume II of IV
NOTICE
This document is a preliminary draft. It has not been formally released by EPA and should not at this stage
be construed to represent Agency policy. It is being circulated for comment on its technical accuracy and
policy implications.
Environmental Criteria and Assessment Office
Office of Health and Environmental Assessment
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, N.C. 27711
-------
NOTICE
Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
ii
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ABSTRACT
The document evaluates and assesses scientific information on the health
and welfare effects associated with exposure to various concentrations of lead
in ambient air. The literature through 1983 has been reviewed thoroughly for
information relevant to air quality criteria, although the document is not
intended as a complete and detailed review of all literature pertaining to
lead. An attempt has been made to identify the major discrepancies in our
current knowledge and understanding of the effects of these pollutants.
Although this document is principally concerned with the health and
welfare effects of lead, other scientific data are presented and evaluated in
order to provide a better understanding of this pollutant in the environment.
To this end, the document includes chapters that discuss the chemistry and
physics of the pollutant; analytical techniques; sources, and types of
emissions; environmental concentrations and exposure levels; atmospheric
chemistry and dispersion modeling; effects on vegetation; and respiratory,
physiological, toxicological, clinical, and epidemiological aspects of human
exposure.
iii
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PRELIMINARY DRAFT
CONTENTS
VOLUME I
Chapter 1.
VOLUME II
Chapter 2.
Chapter 3.
Chapter 4.
Chapter 5.
Chapter 6.
Chapter 7.
Chapter 8.
VOLUME III
Chapter 9.
Chapter 10.
Chapter 11.
Volume IV
Chapter 12.
Chapter 13.
Executive Summary and Conclusions
Introduction
Chemical and Physical Properties
Sampling and Analytical Methods for Environmental Lead
Sources and Emissions
Transport and Transformation
Environmental Concentrations and Potential Pathways to Human Exposure
Effects of Lead on Ecosystems
Quantitative Evaluation of Lead and Biochemical Indices of Lead
Exposure in Physiological Media
Metabolism of Lead
Assessment of Lead Exposures and Absorption in Human Populations
Biological Effects of Lead Exposure
Evaluation of Human Health Risk Associated with Exposure to Lead
and It's Compounds
1-1
2-1
3-1
4-1
5-1
6-1
7-1
8-1
9-1
10-1
11-1
12-1
13-1
TCPBA/H
1v
7/1/83
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PRELIMINARY DRAFT
TABLE OF CONTENTS
2. INTRODUCTION 2-1
3. CHEMICAL AND PHYSICAL PROPERTIES 3-1
3.1 INTRODUCTION 3-1
3.2 ELEMENTAL LEAD 3-1
3.3 GENERAL CHEMISTRY OF LEAD 3-2
3.4 ORGANOMETALLIC CHEMISTRY OF LEAD 3-3
3.5 FORMATION OF CHELATES AND OTHER COMPLEXES 3-4
3.6 REFERENCES 3-8
4. SAMPLING AND ANALYTICAL METHODS FOR ENVIRONMENTAL LEAD 4-1
4.1 INTRODUCTION 4-1
4.2 SAMPLING 4-2
4.2.1 Regulatory Siting Criteria for Ambient Aerosol Samplers 4-2
4.2.2 Ambient Sampling for Particulate and Gaseous Lead 4-6
4.2.2.1 High Volume Sampler (hi-vol) 4-6
4.2.2.2 Dichotomous Sampler 4-8
4.2.2.3 Impactor Samplers 4-9
4.2.2.4 Dry Deposition Sampling 4-10
4.2.2.5 Gas Collection 4-11
4.2.3 Source Sampling 4-11
4.2.3.1 Stationary Sources 4-11
4.2.3.2 Mobile Sources 4-12
4.2.4 Sampling for Lead in Other Media 4-13
4.2.4.1 Precipitation 4-13
4.2.4.2 Surface Water 4-14
4.2.4.3 Soils 4-14
4.2.4.4 Vegetation 4-15
4.2.4.5 Foodstuffs 4-15
4.2.5 Filter Selection and Sample Preparation 4-15
4.3 ANALYSIS 4-16
4.3.1 Atomic Absorption Analysis (AAS) 4-17
4.3.2 Emission Spectroscopy 4-18
4.3.3 X-Ray Fluorescence (XRF) 4-19
4.3.4 Mass Spectrometry (IDMS) 4-21
4.3.5 Colorimetric Analysis 4-21
4.3.6 Electrochemical Methods: Anodic Stripping Voltammetry
(ASV), and Differential Pulse Polarography (DPP) 4-21
4.3.7 Methods for Compound Analysis 4-22
4.4 CONCLUSIONS 4-23
4.5 REFERENCES 4-24
5. SOURCES AND EMISSIONS 5-1
5.1 HISTORICAL PERSPECTIVE 5-1
5.2 NATURAL SOURCES 5-3
5.3 MANMADE SOURCES 5-5
5.3.1 Production 5-5
5.3.2 Utilization 5-5
5.3.3 Emissions 5-7
5.3.3.1 Mobile Sources 5-7
5.3.3.2 Stationary Sources 5-20
TCPBA/E v 7/1/83
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PRELIMINARY DRAFT
TABLE OF CONTENTS (continued).
5.4 SUMMARY 5-20
5.5 REFERENCES 5-22
6. TRANSPORT AND TRANSFORMATION 6-1
6.1 INTRODUCTION 6-1
6.2 TRANSPORT OF LEAD IN AIR BY DISPERSION 6-2
6.2.1 Fluid Mechanics of Dispersion 6-2
6.2.2 Influence of Dispersion on Ambient Lead Concentrations 6-4
6.2.2.1 Confined and Roadway Situations 6-4
6.2.2.2 Dispersion of Lead on an Urban Scale 6-6
6.2.2.3 Dispersion from Smelter and Refinery Locations 6-8
6.2.2.4 Dispersion to Regional and Remote Locations 6-8
6.3 TRANSFORMATION OF LEAD IN AIR 6-17
6.3.1 Particle Size Distribution 6-17
6.3.2 Organic (Vapor Phase) Lead in Air 6-22
6.3.3 Chemical Transformations of Inorganic Lead in Air 6-23
6.4. REMOVAL OF LEAD FROM THE ATMOSPHERE 6-25
6.4.1 Dry Deposition 6-25
6.4.1.1 Mechanisms of dry deposition 6-25
6.4.1.2 Dry deposition models 6~26
6.4.1.3 Calculation of dry deposition 6-27
6.4.1.4 Field measurements of dry deposition on
surrogate natural surfaces 6-29
6.4.2 Wet Deposition 6-30
6.4.3 Global Budget of Atmospheric Lead 6-31
6.5 TRANSFORMATION AND TRANSPORT IN OTHER ENVIRONMENTAL MEDIA 6-33
6.5.1 Soil 6-33
6.5.2 Water 6-37
6.5.2.1 Inorganic 6-37
6.5.2.2 Organic 6-38
6.5.3 Vegetation Surfaces 6-41
6.6 SUMMARY 6-42
6.7 REFERENCES 6-44
7. ENVIRONMENTAL CONCENTRATIONS AND POTENTIAL PATHWAYS TO HUMAN EXPOSURE 7-1
7.1 INTRODUCTION 7-1
7.2 ENVIRONMENTAL CONCENTRATIONS 7-1
7.2.1 Ambient Air 7-1
7.2.1.1 Total Airborne Lead Concentrations 7-3
7.2.1.2 Compliance with the 1978 Air Quality Standard 7-13
7.2.1.3 Changes in Air Lead Prior to Human Uptake 7-13
7.2.2 Lead in Soil 7-24
7.2.2.1 Typical Concentrations of Lead in Soil 7-26
7.2.2.2 Pathways of Soil Lead to Human Consumption 7-28
7.2.3 Lead in Surface and Ground Water 7-32
7.2.3.1 Typical Concentrations of Lead in Untreated Water 7-32
7.2.3.2 Human Consumption of Lead in Water 7-33
7.2.4 Summary of Environmental Concentrations of Lead 7-35
7.3 POTENTIAL PATHWAYS TO HUMAN EXPOSURE 7-36
7.3.1 Baseline Human Exposure 7-37
TCPBA/E v1 7/V83
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PRELIMINARY DRAFT
TABLE OF CONTENTS (continued).
7.3.1.1 Lead in Inhaled Air 7-39
7.3.1.2 Lead in Food 7-39
7.3.1.3 Lead in Drinking Water 7-47
7.3.1.4 Lead in Dusts 7-50
7.3.1.5 Summary of Baseline Human Exposure to Lead 7-55
7.3.2 Additive Exposure Factors 7-56
7.3.2.1 Special Living and Working Environments 7-56
7.3.2.2 Additive Exposures Due to Age, Sex, or Socioeconomic
Status 7-65
7.3.2.3 Special Habits or Activities 7-65
7.3.3 Summary of Additive Exposure Factors ™ . 7-67
7.4 SUMMARY 7-67
8. EFFECTS OF LEAD ON ECOSYSTEMS 8-1
8.1 INTRODUCTION 8-1
8.1.1 Scope of Chapter 8 8-1
8.1.2 Ecosystem Functions 8-4
8.1.2.1 Types of Ecosystems 8-4
8.1.2.2 Energy Flow and Biogeochemical Cycles 8-4
8.1.2.3 Biogeochemistry of Lead 8-7
8.1.3 Criteria for Evaluating Ecosystem Effects 8-8
8.2 LEAD IN SOILS AND SEDIMENTS 8-12
8.2.1 Distribution of Lead in Soils 8-12
8.2.2 Origin and Availability of Lead in Aquatic Sediments 8-13
8.3 EFFECTS OF LEAD ON PLANTS 8-14
8.3.1 Effects on Vascular Plants and Algae 8-14
8.3.1.1 Uptake by Plants 8-14
8.3.1.2 Physiological Effects on Plants 8-17
8.3.1.3 Lead Tolerance in Vascular Plants 8-20
8.3.1.4 Effects of Lead on Forage Crops 8-21
8.3.1.5 Summary of Plant Effects 8-21
8.3.2 Effects on Bacteria and Fungi 8-21
8.3.2.1 Effects on Decomposers 8-21
8.3.2.2 Effects on Nitrifying Bacteria 8-24
8.3.2.3 Methylation by Aquatic Microorganisms 8-24
8.3.2.4 Summary of Effects on Microorganisms 8-24
8.4 EFFECTS OF LEAD ON DOMESTIC AND WILD ANIMALS 8-25
8.4.1 Vertebrates 8-25
8.4.1.1 Terrestrial Vertebrates 8-25
8.4.1.2 Effects on Aquatic Vertebrates 8-27
8.4.2 Invertebrates ; 8-30
8.4.3 Summary of Effects on Animals 8-33
8.5 EFFECTS OF LEAD ON ECOSYSTEMS 8-33
8.5.1 Delayed Decomposition 8-34
8.5.2 Circumvention of Calcium Biopurification 8-35
8.5.3 Population Shifts Toward Lead Tolerant Populations 8-37
8.5.4 Mass Balance Distribution of Lead in Ecosystems 8-37
8.6 SUMMARY 8-39
8.7 REFERENCES 8-41
TCPBA/E vii 7/1/83
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PRELIMINARY DRAFT
LIST OF FIGURES
Page
3-1 Metal complexes of lead 3-6
3-2 Softness parameters of metals 3-6
3-3 Structure of chelating agents 3-7
4-1 Acceptable zone for siting TSP monitors 4-5
5-1 Chronological record of the relative increase of lead in snow strata, pond
and lake sediments, marine sediments, and tree rings 5-2
5-2 The global lead production has changed historically 5-4
5-3 Location of major lead operations in the United States 5-9
5-4 Estimated lead-only emissions distribution per gallon of combusted fuel 5-14
5-5 Trend in lead content of U.S. gasolines, 1975-1982 5-16
5-6 Trend in U.S. gasoline sales, 1975-1982 5-17
5-7 Lead consumed in gasoline and ambient lead concentrations, 1975-1982 5-18
5-8 Relationship between lead consumed in gasoline and composite maximum
quarterly average lead levels, 1975-1980 5-19
6-1 Isopleths are shown for annual average particulate lead in ug/m3 6-7
6-2 Spatial distribution of surface street and freeway traffic in
the Los Angeles Basin (10d VMT/day) for 1979 6-9
6-3 Annual average suspended lead concentrations for 1969 in the
Los Angeles Basin, calculated from the model of Cass (1975) 6-10
6-4 Profile of lead concentrations in the northeast Pacific 6-13
6-5 Midpoint collection location for atmospheric sample collected
from R. V. Trident north of 30°W, 1970 through 1972 6-14
6-6 The EFcrust values for atmospheric trace metals 6-14
6-7 Lead concentration profile in snow strata of northern Greenland 6-16
6-8 Cumulative mass distribution for lead particles in auto exhaust 6-18
6-9 Particulate lead size distribution measured at the Allegheny
Mountain Tunnel, Pennsylvania Turnpike, 1975 6-19
6-10 Particle size distributions of substances in gutter debris,
Rotunda Drive, Dearborn, Michigan 6-20
6-11 Predicted relationship between particle size and deposition velocity at
various conditions of atmospheric stability and roughness height 6-28
6-12 Variation of lead saturation capacity with cation exchange
capacity in soil at selected pH values 6-36
6-13 Lead distribution between filtrate and suspended solids in
stream water from urban and rural compartments 6-39
7-1 Pathways of lead from the environment to human consumption 7-2
7-2 Percent of urban stations reporting indicated concentration interval 7-6
7-3 Seasonal patterns and trends quarterly average urban lead concentrations 7-11
7-4 Time trends in ambient air lead at selected urban sites 7-12
7-5 Airborne mass size distributions for lead taken from the literature 7-21
7-6 Paint pigments and solder are two additional sources of potential lead
exposure which are not of atmospheric origin 7-36
7-7 Change in drinking water lead concentration is a house with lead
plumbing for the first use of water in the morning. Flushing rate
was 10 1 Hers/minute 7-47
7C-1 Concentrations of lead in air, in dust, and on children's hands, measured
during the third population survey. Values obtained less than 1 km from the
smelter, at 2.5 km from the smelters, and in two control areas are shown 7C-4
7C-2 Schematic plan of lead mine and smelter from Mexa Valley, Yugoslavia study ... 7C-7
8-1 The major components of an ecosystem are the primary producers,
grazers, and decomposers 8-6
TCPBA/F viii 7/1/83
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PRELIMINARY DRAFT
LIST OF FIGURES (continued).
Figure Page
8-2 The ecological success of a population depends in part on the
availability of all nutrients at some optimum concentration • 8-10
8-3 This figure attempts to reconstruct the right portion of a
tolerance curve 8-11
8-4 Within the decomposer food chain, detritus is progressively
broken down i n a sequence of steps 8-23
8-5 The atomic ratios Sr/Ca, Ba/Ca and Pb/Ca (0) normally
decrease by several 8-36
ix
TCPBA/F 7/1/83
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PRELIMINARY DRAFT
LIST OF TABLES
Table Page
3-1 Properties of elemental lead 3-2
4-1 Design of national air monitoring stations 4-3
4-2 TSP NAMS criteria 4-4
4-3 Description of spatial scales of representativeness 4-7
4-4 Relationship between monitoring objectives and
appropriate spatial scales 4-7
5-1 U.S. utilization of lead by product category 5-6
5-2 Estimated atmospheric lead emissions for the U.S., 1981, and the world 5-8
5-3 Light-duty vehicular particulate emissions 5-11
5-4 Heavy-duty vehicular particulate emissions 5-11
5-5 Recent and projected consumption of gasoline lead 5-12
6-1 Summary of microscale concentrations 6-5
6-2 Enrichment of atmospheric aerosols over crustal abundance 6-15
6-3 Comparison of size distributions of lead-containing particles in
major sampling areas 6-21
6-4 Distribution of lead in two size fractions at several sites
i n the Uni ted States 6-22
6-5 Summary of surrogate and vegetation surface deposition of lead 6-29
6-6 Deposition of lead at the Walker Branch Watershed, 1974 6-31
6-7 Estimated global deposition of atmospheric lead 6-32
7-1 Atmospheric lead in urban, rural and remote areas of the world 7-4
7-2 Cumulative frequency distributions of urban air lead concentrations 7-7
7-3 Air lead concentrations in major metropolitan areas 7-9
7-4 Stations with air lead concentrations greater than 1.0 ug/m3 7-14
7-5 Distribution of air lead concentrations by type of site 7-19
7-6 Vertical distribution of lead concentrations 7-22
7-7 Comparison of indoor and outdoor airborne lead concentrations 7-25
7-8 Summary of soil lead concentrations 7-28
7-9 Background lead in basic food crops and meats 7-28
7-10 Summary of lead in drinking water supplies 7-35
7-11 Summary of environmental concentrations of lead 7-35
7-12 Summary of inhaled air lead exposure 7-39
7-13 Lead concentrati ons in mi 1 k and foods 7-41
7-14 Addition of lead to food products 7-43
7-15 Prehistoric and modern concentrations in human food from a marine food
chain 7-44
7-16 Recent trends of lead concentrations in food items 7-45
7-17 Summary of lead concentrations in milk and foods by source 7-46
7-18 Summary by age and sex of estimated average levels of lead injested from
mi 1 k and foods 7-47
7-19 Summary by source of lead consumed from mi 1k and foods 7-50
7-20 Summary .by source of lead concentrations in water and beverages 7-51
7-21 Daily consumption and potential lead exposure from water and beverages 7-52
7-22 Summary by source of lead consumed in water and beverages 7-53
7-23 Current baseline estimates of potential human exposure to dusts 7-55
7-24 Summary of baseline human exposures to lead 7-56
7-25 Summary of potential additive exposures to lead 7-59
8-1 Estimated natural levels of lead in ecosystem 8-11
8-2 Estimates of the degree of contamination of herbivores,
omnivores, and carnivores 8-25
TCPBA/G x 7/X/83
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PRELIMINARY DRAFT
LIST OF ABBREVIATIONS
AAS
Ach
ACTH
ADCC
ADP/0 ratio
AIDS
AIHA
All
ALA
ALA-D
ALA-S
ALA-U
APDC
APHA
ASTM
ASV
ATP
B-cells
Ba
BAL
BAP
BSA
BUN
BW
C.V.
CaBP
CaEDTA
CBD
Cd
CDC
CEC
CEH
CFR
CMP
CMS
CO
COHb
CP-U
cBah
D.F.
DA
DCMU
DDP
DNA
DTH
EEC
EEC
EMC
EP
EPA
Atomic absorption spectrometry
Acetylcholine
Adrenocoticotrophic hormone
Antibody-dependent cell-mediated cytotoxicity
Adenosine diphosphate/oxygen ratio
Acquired immune deficiency syndrome
American Industrial Hygiene Association
Angiotensin II
Aminolevulinic acid
Aminolevulinic acid dehydrase
Aminolevulinic acid synthetase
Aminolevulinic acid in urine
Ammonium pyrrolidine-dithiocarbamate
American Public Health Association
Amercian Society for Testing and Materials
Anodic stripping voltammetry
Adenosine triphosphate
Bone marrow-derived lymphocytes
Barium
British anti-Lewisite (AKA dimercaprol)
benzo(a)pyrene
Bovine serum albumin
Blood urea nitrogen
Body weight
Coefficient of variation
Calcium binding protein
Calci urn ethylenedi ami netetraacetate
Central business district
Cadmiurn
Centers for Disease Control
Cation exchange capacity
Center for Environmental Health
reference method
Cytidine monophosphate
Central nervous system
Carbon monoxide
Carboxyhemoglobi n
Urinary coproporphyrin
plasma clearance of p-aminohippuric acid
Copper
Degrees of freedom
Dopami ne
[3-(3,4-dichlorophenyl)-l,l-dimethylurea
Differential pulse polarography
Deoxyribonucleic acid
Delayed-type hypersensitivity
European Economic Community
Electroencephalogram
Encephalomyocardi tis
Erythrocyte protoporphyrin
U.S. Environmental Protection Agency
TCPBA/D
xi
7/13/83
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PRELIMINARY DRAFT
LIST OF ABBREVIATIONS (continued).
FA Fulvic acid
FDA Food and Drug Administration
Fe Iron
FEP Free erythrocyte protoporphyrin
FY Fiscal year
G.M. Grand mean
G-6-PD Glucose-6-phosphate dehydrogenase
GABA Gamma-aminobutyric acid
GALT Gut-associated lymphoid tissue
GC Gas chromatography
GFR Glomerular filtration rate
HA Humic acid
Hg Mercury
hi-vol High-volume air sampler
HPLC High-performance liquid chromatography
i.m. Intramuscular (method of injection)
i.p. Intraperitoneally (method of injection)
i.v. Intravenously (method of injection)
IAA Indol-3-ylacetic acid
IARC International Agency for Research on Cancer
ICD International classification of diseases
ICP Inductively coupled plasma
IDMS Isotope dilution mass spectrometry
IF Interferon
ILE Isotopic Lead Experiment (Italy)
IRPC International Radiological Protection Commission
K Potassium
LAI Leaf area index
LDH-X Lactate dehydrogenase isoenzyme x
LCcn Lethyl concentration (50 percent)
LD?? Lethal dose (50 percent)
LH Luteim'zing hormone
LIPO Laboratory Improvement Program Office
In National logarithm
LPS Lipopolysaccharide
LRT Long range transport
mRNA Messenger ribonucleic acid
ME Mercaptoethanol
MEPP Miniature end-plate potential
MES Maximal electroshock seizure
MeV Mega-electron volts
MLC Mixed lymphocyte culture
MMD Mass median diameter
MMED Mass median equivalent diameter
Mn Manganese
MND Motor neuron disease
MSV Moloney sarcoma virus
MTD Maximum tolerated dose
n Number of subjects
N/A Not Available
TCPBA/D xff 7/13/83
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PRELIMINARY DRAFT
LIST OF ABBREVIATIONS (continued)
NA
NAAQS
NADB
NAMS
NAS
NASN
NBS
NE
NFAN
NFR-82
NHANES II
Ni
OSHA
P
P
PAH
Pb
PBA
Pb(Ac)?
PbB
PbBrCl
PBG
PFC
PH
PHA
PHZ
PIXE
PMN
PND
PNS
ppm
PRA
PRS
PWM
Py-5-N
RBC
RBF
RCR
redox
RES
RLV
RNA
S-HT
SA-7
scm
S.D.
SDS
S.E.M.
SES
SCOT
Not Applicable
National ambient air quality standards
National Aerometric Data Bank
National Air Monitoring Station
National Academy of Sciences
National Air Surveillance Network
National Bureau of Standards
Norepinephrine
National Filter Analysis Network
Nutrition Foundation Report of 1982
National Health Assessment and Nutritional Evaluation Survey II
Nickel
Occupational Safety and Health Administration
Potassium
Significance symbol
Para-aminohippuric acid
Lead
Air lead
Lead acetate
concentration of lead in blood
Lead (II) bromochloride
Porphobilinogen
Plaque-forming cells
Measure of acidity
Phytohemaggluti ni n
Polyacrylamide-hydrous-zirconia
Proton-induced X-ray emissions
Polymorphonuclear leukocytes
Post-natal day
Peripheral nervous system
Parts per million
Plasma renin activity
Plasma renin substrate
Pokeweed mitogen
Pyrimide-5'-nucleotidase
Red blood cell; erythrocyte
Renal blood flow
Respiratory control ratios/rates
Oxidation-reduction potential
Reticuloendothelial system
Rauscher leukemia virus
Ribonucleic acid
Serotonin
Simian adenovirus
Standard cubic meter
Standard deviation
Sodium dodecyl sulfate
Standard error of the mean
Socioeconomic status
Serum glutamic oxaloacetic transaminase
TCPBA/D
xiii
7/13/83
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PRELIMINARY DRAFT
LIST OF ABBREVIATIONS (continued).
slg
SLAMS
SMR
Sr
SRBC
SRMs
STEL
SW voltage
T-cells
t-tests
TBL
TEA
TEL
TIBC
TML
TMLC
TSH
TSP
U.K.
UMP
USPHS
VA
WHO
XRF
X^
Zn
ZPP
Surface immunoglobulin
State and local air monitoring stations
Standardized mortality ratio
Strontium
Sheep red blood cells
Standard reference materials
Short-term exposure limit
Slow-wave voltage
Thymus-derived lymphocytes
Tests of significance
Tri-n-butyl lead
Tetraethy1-ammoni urn
Tetraethyllead
Total iron binding capacity
Tetramethyllead
Tetramethyllead chloride
Thyroid-stimulating hormone
Total suspended particulate
United Kingdom
Uridine monophosphate
U.S. Public Health Service
Veterans Administration
Deposition velocity
Visual evoked response
World Health Organization
X-Ray fluorescence
Chi squared
Zinc
Erythrocyte zinc protoporphyrin
MEASUREMENT ABBREVIATIONS
dl
ft
g
g/gai
g/ha-mo
km/hr
1/min
mg/km
ug/m3
mm
umol
ng/cm2
nm
nM
sec
deciliter
feet
gram
gram/gallon
gram/hectare-month
kilometer/hour
liter/minute
mi 11igram/kilometer
microgram/cubic meter
millimeter
micrometer
nanograms/square centimeter
namometer
nanomole
second
TCPBA/D
xiv
7/13/83
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AUTHORS, CONTRIBUTORS, AND REVIEWERS
Chapter 3: Physical and Chemical Properties of Lead
Principal Author
Dr. Derek Hodgson
Department of Chemistry
University of North Carolina
Chapel Hill, NC 27514
The following persons reviewed this chapter at EPA's request:
Dr. Clarence A. Hall
Air Conservation Division
Ethyl Corporation
1600 West 8-Mile Road
Ferndale, MI 48220
Dr. David E. Koeppe
Department of Plant and Soil Science
Texas Technical University
Lubbock, TX 79409
Dr. Samuel Lestz
Department of Mechanical Engineering
Pennsylvania State University
University Park, PA 16802
Dr. Ben Y. H. Liu
Department of Mechanical Engineering
University of Minnesota
Minneapolis, MN 55455
Dr. Michael Oppenheimer
Environmental Defense Fund
444 Park Avenue, S.
New York, NY 10016
Dr. William Pierson
Scientific Research Labs.
Ford Motor Company
P.O. Box 2053
Dearborn, MI 48121
Dr. Gary Rolfe
Department of Forestry
University of Illinois
Urbana, IL 61801
Dr. Glen Sanderson
University of Illinois
Illinois Natural History Survey
Urbana, IL 61801
Dr. Rodney K. Skogerboe
Department of Chemistry
Colorado State University
Fort Collins, CO 80521
Dr. William H. Smith
Greeley Memorial Laboratory
and Environmental Studies
Yale University, School of
Forestry
New Haven, CT 06511
Dr. Gary Ter Haar
Toxicology and Industrial Hygiene
Ethyl Corporation
Baton Rouge, LA 70801
Dr. James Wedding
Engineering Research Center
Colorado State University
Fort Collins, CO 80523
XV
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Chapter 4: Sampling and Analytical Methods for Environmental Lead
Principal Authors
Dr. Rodney K. Skogerboe
Department of Chemistry
Colorado State University
Fort Collins, CO 80521
Contributing Author
Or. Robert Bruce
Environmental Criteria and Assessment Office
MD-52
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
The following persons reviewed this chapter at EPA's request:
Dr. James Wedding
Engineering Research Center
Colorado State University
Fort Collins, CO 80521
Dr. John B. Clements
Environmental Monitoring Systems Laboratory
MD-78
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Dr. Tom Dzubay
Inorganic Pollutant Analysis Branch
MD-47
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Or. Clarence A. Hall
Air Conservation Division
Ethyl Corporation
1600 West 8-Mile Road
Ferndale, MI 48220
Dr. Derek Hodgson
Department of Chemistry
University of North Carolina
Chapel Hill, NC 27514
Dr. Bill Hunt
Monitoring and Data Analysis Division
MD-14
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Dr. David E. Koeppe
Department of Plant and Soil Science
Texas Technical University
Lubbock, TX 79409
Dr. Samuel Lestz
Department of Mechanical
Engineering
Pennsylvania State University
University Park, PA 16802
Dr. Ben Y. H. Liu
Department of Mechanical
Engineering
University of Minnesota
Minneapolis, MN 55455
Dr. Michael Oppenheimer
Environmental Defense Fund
444 Park Avenue, S.
New York, NY 10016
Dr. William Pierson
Scientific Research Labs.
Ford Motor Company
P.O. Box 2053
Dearborn, MI 48121
Dr. Gary Rolfe
Department of Forestry
University of Illinois
Urbana, IL 61801
Dr. Glen Sanderson
University of Illinois
Illinois Natural History Survey
Urbana, IL 61801
xv i
-------
Mr. Stan Sleva
Office of Air Quality Planning and Standards
MD-14
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Dr. William H. Smith
Greeley Memorial Laboratory
and Environmental Studies
Yale University, School of Forestry
New Haven, CT 06511
Dr. Robert Stevens
Inorganic Pollutant Analysis Branch
MD-47
U.S. Environmental Protection
Agency
Research Triangle Park, NC 27711
Dr. Gary Ter Haar
Toxicology and Industrial Hygiene
Ethyl Corporation
451 Florida Boulevard
Baton Rouge, LA 70801
Chapter 5: Sources and Emissions
Principal Author
Dr. James Braddock
Mobile Source Emissions Research Branch
MD-46
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Contributing Author
Dr. Tom McMullen
Environmental Criteria and Assessment Office
MD-52
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
The following persons reviewed this chapter at EPA's request:
Dr. Clarence A. Hall
Air Conservation Division
Ethyl Corporation
1600 West 8-Mile Road
Ferndale, MI 48220
Dr. Derek Hodgson
Department of Chemistry
University of North Carolina
Chapel Hill, NC 27514
Dr. David E. Koeppe
Department of Plant and Soil Science
Texas Technical University
Lubbock, TX 79409
Dr. Samuel Lestz
Department of Mechanical Engineering
Pennsylvania State University
University Park, PA 16802
Dr. William Pierson
Scientific Research Labs.
Ford Motor Company
P.O. Box 2053
Dearborn, MI 48121
Dr. Gary Rolfe
Department of Forestry
University of Illinois
Urbana, IL 61801
Dr. Glen Sanderson
University of Illinois
Illinois Natural History Survey
Urbana, IL 61801
Dr. Rodney K. Skogerboe
Department of Chemistry
Colorado State University
Fort Collins, CO 80521
XV11
-------
Dr. Ben Y. H. Liu
Department of Mechanical Engineering
University of Minnesota
Minneapolis, MN 55455
Dr. Michael Oppenheimer
Environmental Defense Fund
444 Park Avenue, S.
New York, NY 10016
Dr. James Wedding
Engineering Research Center
Colorado State University
Fort Collins, CO 80523
Dr. William H. Smith
Greeley Memorial Laboratory
and Environmental Studies
Uale University, School of Forestry
New Haven, CT 06511
Dr. Gary Ter Haar
Toxicology and Industrial Hygiene
Ethyl Corporation
451 Florida Boulevard
Baton Rouge, LA 70801
Chapter 6: Transport and Transformation
Principal Author
Dr. Ron Bradow
Mobile Source Emissions Research Branch
MD-46
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Contributing Authors
Dr. Robert Elias
Environmental Criteria and Assessment Office
MD-52
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Dr. Rodney Skogerboe
Department of Chemistry
Colorado State University
Fort Collins, CO 80521
The following persons reviewed this chapter at EPA's request:
Dr. Clarence A. Hall
Air Conservation Division
Ethyl Corporation
1600 West 8-Mile Road
Ferndale, MI 48220
Dr. Derek Hodgson
Department of Chemistry
University of North Carolina
Chapel Hill, NC 27514
Dr. David E. Koeppe
Department of Plant and Soil Science
Texas Technical University
Lubbock, TX 79409
Labs.
Dr. William Pierson
Scientific Research
Ford Motor Company
P.O. Box 2053
Dearborn, MI 48121
Dr. Gary Rolfe
Department of Forestry
University of Illinois
Urbana, IL 61801
Dr. Glen Sanderson
Illinois Natural History Survey
University of Illinois
Urbana, IL 61801
xviii
-------
Dr. Samuel Lestz
Department of Mechanical Engineering
Pennsylvania State University
University Park, PA 16802
Dr. Ben Y. H. Liu
Department of Mechanical Engineering
University of Minnesota
Minneapolis, MN 55455
Dr. Michael Oppenheimer
Environmental Defense Fund
444 Park Avenue, S.
New York, NY 10016
Dr. William H. Smith
Greeley Memorial Laboratory
and Environmental Studies
Yale University, School of
Forestry
New Haven, CT 06511
Dr. Gary Ter Haar
Toxicology and Industrial Hygiene
Ethyl Corporation
451 Florida Boulevard
Baton Rouge, LA 70801
Dr. James Wedding
Engineering Research Center
Colorado State University
Fort Collins, CO 80523
Chapter 7: Environmental Concentrations and Potential Pathways to Human
Exposure
Principal Authors
Dr. Cliff Davidson
Department of Civil Engineering
Carnegie-Mellon University
Schenley Park
Pittsburgh, PA 15213
Dr. Robert Eli as
Environmental Criteria and
Assessment Office
MD-52
U.S. Environmental Protection
Agency
Research Triangle Park, NC 27711
The following persons reviewed this chapter at EPA's request:
Dr. Carol Angle
Department of Pediatrics
University of Nebraska
College of Medicine
Omaha, NE 68105
Dr. Lee Annest
Division of Health Examin. Statistics
National Center for Health Statistics
3700 East-West Highway
Hyattsville, MD 20782
Dr. Donald Barltrop
Department of Child Health
Westminister Children's Hospital
London SW1P 2NS
England
Dr. A. C. Chamberlain
Environmental and Medical
Sciences Division
Atomic Energy Research
Establishment
Harwell 0X11
England
Dr. Neil Chernoff
Division of Developmental Biology
MD-67
U.S. Environmental Protection
Agency
Research Triangle Park, NC 27711
Dr. Julian Chisolm
Baltimore City Hospital
4940 Eastern Avenue
Baltimore, MD 21224
xix
-------
Dr. Irv Billick
Gas Research Institute
8600 West Bryn Mawr Avenue
Chicago, IL 60631
Dr. Joe Boone
Clinical Chemistry and
Toxicology Section
Centers for Disease Control
Atlanta, GA 30333
Dr. Robert Bornschein
University of Cincinnati
Kettering Laboratory
Cincinnati, OH 45267
Dr. Jack Dean
Immunobiology Program and
Immunotoxicology/Cell Biology program
CUT
P.O. Box 12137
Research Triangle Park, NC 27709
Dr. Fred deSerres
Associate Director for Genetics
NIEHS
P.O. Box 12233
Research Triangle Park, NC 27709
Dr. Robert Dixon
Laboratory of Reproductive and
Developmental Toxicology
NIEHS
P.O. Box 12233
Research Triangle Park, NC 27709
Dr. Claire Ernhart
Department of Psychiatry
Cleveland Metropolitan General Hospital
Cleveland, OH 44109
Dr. Sergio Fachetti
Section Head - Isotope Analysis
Chemistry Division
Joint Research Center
121020 Ispra
Varese, Italy
Dr. Virgil Ferm
Department of Anatomy and Cytology
Dartmouth Medical School
Hanover, NH 03755
Mr. Jerry Cole
International Lead-Zinc Research
Organization
292 Madison Avenue
New York, NY 10017
Dr. Max Costa
Department of Pharmacology
University of Texas Medical
School
Houston, TX 77025
Dr. Anita Curran
Commissioner of Health
Westchester County
White Plains, NY 10607
Dr. Warren Galke
Department of Biostatisties
and Epidemiology
School of Allied Health
East Carolina University
Greenville, NC 27834
Mr. Eric Goldstein
Natural Resources Defense
Council, Inc.
122 E. 42nd Street
New York, NY 10168
Dr. Harvey Gonick
1033 Gayley Avenue
Suite 116
Los Angeles, CA 90024
Dr. Robert Goyer
Deputy Director
NIEHS
P.O. Box 12233
Research Triangle Park, NC 27709
Dr. Stanley Gross
Hazard Evaluation Division
Toxicology Branch
U.S. Environmental Protection
Agency
Washington, DC 20460
Dr. Paul Hammond
University of Cincinnati
Kettering Laboratory
Cincinnati, OH 45267
XX
-------
Dr. Alf Fischbein
Environmental Sciences Laboratory
Mt. Sinai School of Medicine
New York, NY 10029
Or. Jack Fowle
Reproductive Effects Assessment Group
U.S. Environmental Protection Agency
RD-689
Washington, DC 20460
Dr. Bruce Fowler
Laboratory of Pharmacology
NIEHS
P.O. Box 12233
Research Triangle Park, NC 27709
Dr. Kristal Kostial
Institute for Medical Research
and Occupational Health
Yu-4100 Zagreb
Yugoslavia
Dr. Lawrence Kupper
Department of Biostatisties
UNC School of Public Health
Chapel Hill, NC 27514
Dr. Phillip Landrigan
Division of Surveillance,
Hazard Evaluation and Field Studies
Taft Laboratories - NIOSH
Cincinnati, OH 45226
Dr. David Lawrence
Microbiology and Immunology Dept.
Albany Medical College of Union
University
Albany, NY 12208
Dr. Jane Lin-Fu
Office of Maternal and Child Health
Department of Health and Human Services
Rockville, MD 20857
Dr. Don Lynam
Air Conservation
Ethyl Corporation
451 Florida Boulevard
Baton Rouge, LA 70801
Dr. Ronald D. Hood
Department of Biology
The University of Alabama
University, AL 35486
Dr. V. Houk
Centers for Disease Control
1600 Clifton Road, NE
Atlanta, GA 30333
Dr. Loren D. Koller
School of Veterinary Medicine
University of Idaho
Moscow, ID 83843
Dr. Chuck Nauman
Exposure Assessment Group
U.S. Environmental Protection
Agency
Washington, DC 20460
Dr. Herbert L. Needleman
Children's Hospital of Pittsburgh
Pittsburgh, PA 15213
Dr. H. Mitchell Perry
V.A. Medical Center
St. Louis, MO 63131
Dr. Jack Pierrard
E.I. duPont de Nemours and
Compancy, Inc.
Petroleum Laboratory
Wilmington, DE 19898
Dr. Sergio Piomelli
Columbia University Medical School
Division of Pediatric Hematology
and Oncology
New York, NY 10032
Dr. Magnus Piscator
Department of Environmental Hygiene
The Karolinska Institute 104 01
Stockholm
Sweden
xx i
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Or. Kathryn Mahaffey
Division of Nutrition
Food and Drug Administration
1090 Tusculum Avenue
Cincinnati, OH 45226
Dr. Ed McCabe
Department of Pediatrics
University of Wisconsin
Madison, WI 53706
Dr. Paul Mushak
Department of Pathology
UNC School of Medicine
Chapel Hill, NC 27514
Dr. John Rosen
Division of Pediatric Metabolism
Albert Einstein College of Medicine
Montefiore Hospital and Medical Center
111 East 210 Street
Bronx, NY 10467
Dr. Stephen R. Schroeder
Division for Disorders
of Development and Learning
Biological Sciences Research Center
University of North Carolina
Chapel Hill, NC 27514
Dr. Anna-Maria Seppalainen
Institutes of Occupational Health
Tyoterveyslaitos
Haartmaninkatu 1
00290 Helsinki 29
Finland
Dr. Ellen Silbergeld
Environmental Defense Fund
1525 18th Street, NW
Washington, DC 20036
Dr. Robert Putnam
International Lead-Zinc
Research Organization
292 Madison Avenue
New York, NY 10017
Dr. Michael Rabinowitz
Children's Hospital Medical
Center
300 Longwood Avenue
Boston, MA 02115
Dr. Harry Roels
Unite de Toxicologie
Industrielle et Medicale
Universite de Louvain
Brussels, Belgium
Dr. Ron Snee
E.I. duPont Nemours and
Company, Inc.
Engineering Department L3167
Wilmington, DE 19898
Mr. Gary Ter Haar
Toxicology and Industrial
Hygiene
Ethyl Corporation
451 Florida Boulevard
Baton Rouge, LA 70801
Mr. Ian von Lindern
Department of Chemical
Engineering
University of Idaho
Moscow, ID 83843
Dr. Richard P. Wedeen
V.A. Medical Center
Tremont Avenue
East Orange, NJ 07019
Chapter 8: Effects of Lead on Ecosystems
Principal Author
Dr. Robert Eli as
Environmental Criteria and Assessment Office
MD-52
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
XX ii
-------
The following persons reviewed this chapter at EPA's request:
Dr. Clarence A. Hall
Air Conservation Division
Ethyl Corporation
1600 West 8-Mile Road
Ferndale, MI 48220
Dr. Derek Hodgson
Department of Chemsitry
University of North Carolina
Chapel Hill, NC 27514
Dr. David E. Koeppe
Department of Plant and Soil Science
P.O. Box 4169
Texas Technical University
Lubbock, TX 79409
Dr. Samuel Lestz
Department of Mechanical Engineering
Pennsylvania State University
University Park, PA 16802
Dr. Ben Y. H. Liu
Department of Mechanical Engineering
University of Minnesota
Minneapolis, MN 55455
Dr. Michael Oppenheimer
Environmental Defense Fund
444 Park Avenue, S.
New York, NY 10016
Dr. William Pierson
Scientific Research Labs.
Ford Motor Company
P.O. Box 2053
Dearborn, MI 48121
Dr. Gary Rolfe
Department of Forestry
University of Illinois
Urbana, IL 61801
Dr. Glen Sanderson
Illinois Natural History Survey
University of Illinois
Urbana, IL 61801
Dr. Rodney K. Skogerboe
Department of Chemistry
Colorado State University
Fort Collins, CO 80521
Dr. William H. Smith
Greeley Memorial Laboratory
and Environmental Studies
Yale University, School of
Forestry
New Haven, CT 06511
Dr. Gary Ter Haar
Toxicology and Industrial Hygiene
Ethyl Corporation
451 Florida Boulevard
Baton Rouge, LA 70801
Dr. James Wedding
Engineering Research Center
Colorado State University
Fort Collins, CO 80523
XXiii
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PRELIMINARY DRAFT
2. INTRODUCTION
According to Section 108 of the Clean Air Act of 1970, as amended in June 1974, a cri-
teria document for a specific pollutant or class of pollutants shall
. . . accurately reflect the latest scientific knowledge useful in
indicating the kind and extent of all identifiable effects on public
health or welfare which may be expected from the presence of such pollu-
tant in the ambient air, in varying quantities.
Air quality criteria are of necessity based on presently available scientific data, which
in turn reflect the sophistication of the technology used in obtaining those data as well as
the magnitude of the experimental efforts expended. Thus air quality criteria for atmospheric
pollutants are a scientific expression of current knowledge and uncertainties. Specifically,
air quality criteria are expressions of the scientific knowledge of the relationships between
various concentrations—averaged over a suitable time period—of pollutants in the same atmos-
phere and their adverse effects upon public health and the environment. Criteria are issued
to help make decisions about the need for control of a pollutant and about the development of
air quality standards governing the pollutant. Air quality criteria are descriptive; that
1s, they describe the effects that have been observed to occur as a result of external expo-
sure at specific levels of a pollutant. In contrast, air quality standards are prescriptive;
that is, they prescribe what a political jurisdiction has determined to be the maximum per-
missible exposure for a given time in a specified geographic area.
In the case of criteria for pollutants that appear in the atmosphere only in the gas
phase (and thus remain airborne), the sources, levels, and effects of exposure must be con-
sidered only as they affect the human population through inhalation of or external contact
with that pollutant. Lead, however, is found in the atmosphere primarily as inorganic partic-
ulate, with only a small fraction normally occurring as vapor-phase organic lead. Conse-
quently, inhalation and contact are but two of the routes by which human populations may be
exposed to lead. Some particulate lead may remain suspended in the air and enter the human
body only by inhalation, but other lead-containing particles will be deposited on vegetation,
surface waters, dust, soil, pavements, interior and exterior surfaces of hous1ng--in fact, on
any surface in contact with the air. Thus criteria for lead must be developed that will take
into account all principal routes of exposure of the human population.
This criteria document is a revision of the previous Air Quality Criteria Document for
Lead (EPA-600/8-77-017) published in December, 1977. This revision is mandated by the Clean
Air Act (Sect. 108 and 109), as amended U.S.C. §§7408 and 7409. The criteria document sets
forth what is known about the effects of lead contamination in the environment on human
health and welfare. This requires that the relationship between levels of exposure to lead,
D23PB2 2-1 7/1/83
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PRELIMINARY DRAFT
via all routes and averaged over a suitable time period, and the biological responses to those
levels be carefully assessed. Assessment of exposure must take into consideration the
temporal and spatial distribution of lead and its various forms in the environment.
This document focuses primarily on lead as found in its various forms in the ambient
atmosphere; in order to assess its effects on human health, however, the distribution and
biological availability of lead in other environmental media have been considered. The
rationale for structuring the document was based primarily on the two major questions of
exposure and response. The first portion of the document is devoted to lead in the environ-
ment—its physical and chemical properties; the monitoring of lead in various media;
sources, emissions, and concentrations of lead; and the transport and transformation of lead
within environmental media. The later chapters are devoted to discussion of biological
responses and effects on ecosystems and human health.
In order to facilitate printing, distribution, and review of the present draft materials,
this First External Review Draft of the revised EPA Air Quality Criteria Document for Lead
is being released in the form of four volumes. The first volume (Volume I) contains the
executive summary and conclusions chapter (Chapter 1) for the entire document. Volume II (the
present volume) contains Chapters 2-8, which include: the introduction for the document
(Chapter 2); discussions of the above listed topics concerning lead in the environment
(Chapters 3-7); and evaluation of lead effects on ecosystems (Chapter 8). The remaining two
volumes contain Chapters 9-13, which deal with the extensive available literature relevant to
assessment of health effects associated with lead exposure.
An effort has been made to limit the document to a highly critical assessment of the
scientific data base. The scientific literature has been reviewed through June 1983. The
references cited do not constitute an exhaustive bibliography of all available lead-related
literature but they are thought to be sufficient to reflect the current state of knowledge on
those issues most relevant to the review of the air quality standard for lead.
The status of control technology for lead is not discussed 1n this document. For infor-
mation on the subject, the reader is referred to appropriate control technology documentation
published by the Office of Air Quality Planning and Standards (OAQPS), EPA. The subject of
adequate margin of safety stipulated in Section 108 of the Clean Air Act also is not explicity
addressed here; this topic will be considered in depth by EPA's Office of Air Quality Planning
and Standards in documentation prepared as a part of the process of revising the National
Ambient Air Quality Standard for Lead.
D23PB2 2-2 7/1/83
-------
PRELIMINARY DRAFT
3. CHEMICAL AND PHYSICAL PROPERTIES
3.1 INTRODUCTION
Lead is a gray-white metal of bright luster that, because of its easy isolation and low
melting point (327.5°C), was among the first of the metals to be placed in the service of man.
Lead was used as early as 2000 B.C. by the Phoenicians, who traveled as far as Spain and
England to mine it, and it was used extensively by the Egyptians; the British Museum contains
a lead figure found in an Egyptian temple which possibly dates from 3000 B.C. The most
abundant ore is galena, in which lead is present as the sulfide (PbS), and from which metallic
lead is readily smelted. The metal is soft, malleable, and ductile, a poor electrical
conductor, and highly impervious to corrosion. This unique combination of physical properties
has led to its use in piping and roofing, and in containers for corrosive liquids. By the
time of the Roman Empire, it was already in wide use in aqueducts and public water systems, as
well as in cooking and storage utensils. Its alloys are used as solder, type metal, and
various antifriction materials. The metal and the dioxide are used in storage batteries, and
much metal is used in cable covering, plumbing and ammunition. Because of its high nuclear
cross section, lead is extensively used as a radiation shield around X-ray equipment and
nuclear reactors.
3.2 ELEMENTAL LEAD
In comparison with the most abundant metals in the earth's crust (aluminum and iron),
lead is a rare metal; even copper and zinc are more abundant by factors of five and eight,
respectively. Lead is, however, more abundant than the other toxic heavy metals; its
abundance in the earth's crust has been estimated (Moeller, 1952) to be as high as 1.6 x 10 3
percent, although some other authors (Heslop and Jones, 1976) suggest a lower value of 2 x
10 4 percent. Either of these estimates suggests that the abundance of lead is more than 100
times that of cadmium or mercury, two other significant systemic metallic poisons. More
important, since lead occurs in highly concentrated ores from which it is readily separated,
the availability of lead is far greater than its natural abundance would suggest. The great
environmental significance of lead is the result both of its utility and of its availability.
Lead ranks fifth among metals in tonnage consumed, after iron, copper, aluminum and zinc; it
is, therefore, produced in far larger quantities than any other toxic heavy metal (Dyrssen,
1972). The properties of elemental lead are summarized in Table 3-1.
023PB3/A 3-1 7/13/83
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PRELIMINARY DRAFT
TABLE 3-1. PROPERTIES OF ELEMENTAL LEAD
Property
Description
Atomic weight
Atomic number
Oxidation states
Density
Melting point
Boiling point
Covalent radius (tetradehral)
Ionic radii
Resistivity
207.19
82
+2, +4
11.35 g/cm3 at 20 °C
327.5 °C
1740 °C
1.44 A
1.21 A (+2), 0.78 A (+4)
21.9 x 10"6 ohm/cm
Natural lead is a mixture of four stable isotopes: 204Pb (*1.5 percent), 206Pb (23.6
percent), 207Pb (22.6 percent), and 208Pb (52.3 percent). There is no radioactive progenitor
for 204Pb, but 206Pb, 207Pb, and 208Pb are produced by the radioactive decay of 238U, 23SU,
and 232Th, respectively. There are four radioactive isotopes of lead that occur as members of
these decay series. Of these, only 21°Pb is long lived, with a half-life of 22 years. The
others are 211Pb (half-life 36.1 min), 212Pb (10.64 hr), and 214Pb (26.8 min). The stable
isotopic compositions of naturally occurring lead ores are not identical, but show variations
reflecting geological evolution (Russell and Farquhar, 1960). Thus, the observed isotopic
ratios depend upon the U/Pb and Th/Pb ratios of the source from which the ore is derived and
the age of the ore deposit. The 206Pb/204Pb isotopic ratio, for example, varies from
approximately 16.5 to 21 depending on the source (Doe, 1970). The isotopic ratios in average
crustal rock reflect the continuing decay of uranium and thorium. The differences between
crustal rock and ore bodies, and between major ore bodies in various parts of the world, often
permit the identification of the source of lead in the environment.
3.3 GENERAL CHEMISTRY OF LEAD
Lead is the heaviest element in Group IVB of the periodic table; this is the group that
also contains carbon, silicon, germanium, and tin. Unlike the chemistry of carbon, however,
the inorganic chemistry of lead is dominated by the divalent (+2) oxidation state rather than
023PB3/A 3-2 7/13/83
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PRELIMINARY DRAFT
the tetravalent (+4) oxidation state. This important chemical feature is a direct result of
the fact that the strengths of single bonds between the Group IV atoms and other atoms
generally decrease as the atomic number of the Group IV atom increases (Cotton and Wilkinson,
1980). Thus, the average energy of a C-H bond is 100 kcal/mole, and it is this factor that
stabilizes CH4 relative to CH2; for lead, the Pb-H energy is only approximately 50 kcal/mole
(Shaw and Allred, 1970), and this is presumably too small to compensate for the Pb(II) -»
Pb(IV) promotional energy. It is this same feature that explains the marked difference in the
tendencies to catenation shown by these elements. Though C-C bonds are present in literally
millions of compounds, for lead catenation occurs only in organolead compounds. Lead does,
however, form compounds like Na4Pb9 which contain distinct polyatomic lead clusters (Britton,
1964), and Pb-Pb bonds are found in the cationic cluster [Pb60(OH)6] 4 (01 in and Soderquist,
1972).
A listing of the solubilities and physical properties of the more common compounds of
lead is given in Appendix 3A. As can be discerned from those data, most inorganic lead salts
are sparingly soluble (e.g., PbF2, PbCl2) or virtually insoluble (PbS04, PbCr04) in water; the
notable exceptions are lead nitrate, Pb(N03)2, and lead acetate, Pb(OCOCH3)2- Inorganic lead
(II) salts are, for the most part, relatively high-melting-point solids with correspondingly
low vapor pressures at room temperatures. The vapor pressures of the most commonly
encountered lead salts are also tabulated in Appendix 3A. The transformation of lead salts in
the atmosphere is discussed in Chapter 6.
3.4 ORGANOMETALLIC CHEMISTRY OF LEAD
The properties of organolead compounds (i.e., compounds containing bonds between lead and
carbon) are entirely different from those of the inorganic compounds of lead; although a few
organolead(II) compounds, such as dicyclopentadienyllead, Pb(C5H5)2, are known, the organic
chemistry of lead is dominated by the tetravalent (+4) oxidation state. An important property
of most organolead compounds is that they undergo photolysis when exposed to light (Rufman and
Rotenberg, 1980).
Because of their use as antiknock agents in gasoline and other fuels, the most important
organolead compounds have been the tetraalkyl compounds tetraethyllead (TEL) and
tetramethyllead (TML). As would be expected for such nonpolar compounds, TEL and TML are
insoluble in water but soluble in hydrocarbon solvents (e.g., gasoline). These two compounds
are manufactured by the reaction of the alkyl chloride with lead-sodium alloy (Shapiro and
Frey, 1968):
4NaPb + 4C2H5C1 -» (C2H5)4Pb + 3Pb + 4NaCl (3-1)
023PB3/A 3-3 7/13/83
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PRELIMINARY DRAFT
The methyl compound, TML, is also manufactured by a Grignard process involving the
electrolysis of lead pellets in methyl magnesium chloride (Shapiro and Frey, 1968):
2CH3MgCl + 2CH3C1 + Pb -» (CH3)4Pb + 2MgCl2 (3-2)
A common type of commercial antiknock mixture contains a chemically redistributed mixture
of alkyllead compounds. In the presence of Lewis acid catalysts, a mixture of TEL and TML
undergoes a redistribution reaction to produce an equilibrium mixture of the five possible
tetraalkyllead compounds. For example, an equimolar mixture of TEL and TML produces a product
with a composition as shown below:
Component Mol percent
(CH3)4Pb 4.6
(CH3)3Pb(C2H5) 24.8
(CH3)2Pb(C2H5)2 41.2
(CH3)Pb(C2H5)3 24.8
(C2H5)4Pb 4.6
These lead compounds are removed from internal combustion engines by a process called
lead scavenging, in which they react in the combustion chamber with halogenated hydrocarbon
additives (notably ethylene dibromide and ethylene dichloride) to form lead halides, usually
bromochlorolead(II). Mobile source emissions are discussed in detail in Section 5.3.3.2.
Several hundred other organolead compounds have been synthesized, and the properties of
many of them are reported by Shapiro and Frey (1968). The continuing importance of organolead
chemistry is demonstrated by a variety of recent publications investigating the syntheses
(Hager and Huber, 1980, Wharf et al., 1980) and structures (Barkigia, et al., 1980) of
organolead complexes, and by recent patents for lead catalysts (Nishikido, et al., 1980).
3.5 FORMATION OF CHELATES AND OTHER COMPLEXES
The bonding in organometallic derivatives of lead is principally covalent rather than
ionic because of the small difference in the electronegativities of lead (1.8) and carbon
(2.6). As is the case in virtually all metal complexes, however, the bonding is of the
donor-acceptor type, in which both electrons in the bonding orbital originate from the carbon
atom.
The donor atoms in a metal complex could be almost any basic atom or molecule; the only
requirement is that a donor, usually called a ligand, must have a pair of electrons available
023PB3/A 3-4 7/13/83
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PRELIMINARY DRAFT
for bond formation. In general, the metal atom occupies a central position in the complex, as
exemplified by the lead atom in tetramethyllead (Figure 3-la) which is tetrahedrally
surrounded by four methyl groups. In these simple organolead compounds, the lead is usually
present as Pb(IV), and the complexes are relatively inert. These simple ligands, which bind
to metal at only a single site, are called monodentate ligands. Some ligands, however, can
bind to the metal atom by more than one donor atom, so as to form a heterocyclic ring
structure. Rings of this general type are called chelate rings, and the donor molecules which
form them are called polydentate ligands or chelating agents. In the chemistry of lead,
chelation normally involves Pb(II), leading to kinetically quite labile (although
thermodynamically stable) octahedral complexes. A wide variety of biologically significant
chelates with ligands, such as amino acids, peptides, nucleotides and similar macromolecules,
are known. The simplest structure of this type occurs with the amino acid glycine, as
represented in Figure 3-lb for a 1:2 (metal:ligand) complex. The importance of chelating
agents in the present context is their widespread use in the treatment of lead and other metal
poisoning.
Metals are often classified according to some combination of their electronegativity,
ionic radius and formal charge (Ahrland, 1966, 1968, 1973; Basolo and Pearson, 1967; Nieboer
and Richardson, 1980; Pearson, 1963, 1968). These parameters are used to construct empirical
classification schemes of relative hardness or softness. In these schemes, "hard" metals form
strong bonds with "hard" anions and likewise "soft" metals with "soft" anions. Some metals
are borderline, having both soft and hard character. Pb(II), although borderline,
demonstrates primarily soft character (Figure 3-2). The terms Class A may also be used to
refer to hard metals, and Class B to soft metals. Since Pb(II) is a relatively soft (or class
B) metal ion, it forms strong bonds to soft donor atoms like the sulfur atoms in the cysteine
residues of proteins and enzymes; it also coordinates strongly with the imidazole groups of
histidine residues and with the carboxyl groups of glutamic and aspartic acid residues. In
living systems, therefore, lead atoms bind to these peptide residues in proteins, thereby
preventing the proteins from carrying out their functions by changing the tertiary structure
of the protein or by blocking the substrate's approach to the active site of the protein. As
has been demonstrated in several studies (Jones and Vaughn, 1978; Williams and Turner, 1981;
Williams et al., 1982), there is an inverse correlation between the LD50 values of metal
complexes and ttie chemical softness parameter (op) (Pearson and Mawby, 1967). Thus, for both
mice and Drosophila, soft metal ions like lead(II) have been found to be more toxic than hard
metal ions (Williams et al., 1982). This classification of metal ions according to their
toxicity has been discussed in detail by Nieboer and Richardson (1980). Lead(II) has a higher
softness parameter than either cadmium(II) or mercury(II), so lead(II) compounds would not be
expected to be as toxic as their cadmium or mercury analogues.
023PB3/A 3-5 7/13/83
-------
PRELIMINARY DRAFT
H2O
H3C
CH3
Pb'
H3C CH3
Pb
CH9
CH2
^Q
(a)
I
I
I
H2O
(b)
Figure 3-1. Metal complexes of lead.
k.
sf
j£
UJ
Q
Z
UJ
_i
O
o
ff
o
CO
$
^
U
9.0
t
i
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
• III
, All*
p
—
• Afl' P£ptJ.
"*Ti* Hfl"
— %Cu'
• Pb"
— Sn"t* «Cu"
0Co"
Cr"
- M^Vv-""
~~ Mg"
C,' Ba" •
AK* *•• Ca"
%Na' Sr"
•
— Li'
I I I
I I I I I " I " I
4
•^
• Bi' •
w PbllV)
• Ti"
CLASS B _
• Sbllll)
As(lll)
In" • 0
• • Fe" Sn(IV)
Ga"* BORDERLINE "~
Gd" Lu"
A AW W Sc" 0
* Y" Al"
La" Y
Be"
CLASS A
I I I I I .A .A
023PB3/A
4 6 8 10 12 14 16 20 23
CLASS A OR IONIC INDEX, Z'/r
Figure 3-2. Softness parameters of metals.
Source: Nieboer and Richardson (1980).
3-6
7/01/83
-------
PRELIMINARY DRAFT
o o
I! I'
0-C-CH2 CH2-C-0- CH3 o
N-CH2-CH2-N HS-C-CH-C
-0-C-CH2 CHo-C-O- CH3 NH2 OH
II II
o o
EDTA PENICILLAMINE
Figure 3-3. Structure of chelating agents.
The role of the chelating agents is to compete with the peptides for the metal by forming
stable chelate complexes that can be transported from the protein and eventually be exreted by
the body. For simple thermodynamic reasons (see Appendix 3A), chelate complexes are much more
stable than monodentate metal complexes, and it is this enhanced stability that is the basis
for their ability to compete favorably with proteins and other ligands for the metal ions.
The chelating agents most commonly used for the treatment of lead poisoning are ethylenediami-
netetraacetate ions (EDTA), D-penicillamine (Figure 3-3) and their derivatives. EDTA is known
to act as a hexadentate ligand toward metals (Lis, 1978; McCandlish et a!., 1978). X-ray
diffraction studies have demonstrated that D-penicillamine is a tridentate ligand binding
through its sulfur, nitrogen and oxygen atoms to cobalt (de Meester and Hodgson, 1977a; Helis;
et al., 1977), chromium (de Meester and Hodgson, 1977b), cadmium (Freeman et al., 1976), and
lead itself (Freeman et al., 1974), but both penicillamine and other cysteine derivatives may
act as bidentate ligands (Carty and Taylor, 1977; de Meester and Hodgson, 1977c). Moreover,
penicillamine binds to mercury only through its sulfur atoms (Wong et al., 1973; Carty and
Taylor, 1976).
It should be noted that both the stoichiometry and structures of metal chelates depend
upon pH, and that structures different from those manifest in solution may occur in crystals.
It will suffice to state, however, that several ligands can be found that are capable of suffi-
ciently strong chelation with lead present in the body under physiological conditions to per-
mit their use in the effective treatment of lead poisoning.
023PB3/A 3-7 7/01/83
-------
PRELIMINARY DRAFT
3.6 REFERENCES
Ahrland, S. (1966) Factors contributing to (b)-behaviour in acceptors. Struct. Bonding 1: 207-
220.
Ahrland, S. (1968) Thermodynamics of complex formation between hard and soft acceptors and
donors. Struct. Bonding (Berlin) 5: 118-149.
Ahrland, S. (1973) Thermodynamics of the stepwise formation of metal-ion complexes in aqueous
solution. Struct. Bonding (Berlin) 15: 167-188.
Barkigia, K. M.; Fajer, J.; Adler, A. D.; Williams, G. J. B. (1980) Crystal and molecular struc-
ture of (5,10,15,20-tetra-n-propylporphinato)lead(II): a "roof" porphyrin. Inorg. Chem
19: 2057-2061.
Basolo, F.; Pearson, R. G. (1967) Mechanisms of inorganic reactions: a study of metal complexes
in solution. New York, NY: John Wiley & Sons, Inc.; pp. 23-25, 113-119.
Britton, D. (1964) The structure of the Pbg 4 ion. Inorg. Chem. 3: 305.
Carty, A. J. ; Taylor, N. J. (1976) Binding of inorganic mercury at biological sites. J. Chem.
Soc. Chem. Commun. (6): 214-216.
Carty, A. J. ; Taylor, N. J. (1977) Binding of heavy metals at biologically important sites:
synthesis and molecular structure of aquo(bromo)-DL-penicillaminatocadmium(II) dihydrate.
Inorg. Chem. 16: 177-181.
Cotton, F. A.; Wilkinson, G. (1980) Advanced inorganic chemistry. New York, NY: John Wiley &
Sons, Inc.
de Meester, P.; Hodgson, D. J. (1977a) Model for the binding of D-penicillamine to metal ions
in living systems: synthesis and structure of L-histidinyl-D-penicillaminatocobalt(III)
monohydrate, [Co(L-his)(D-pen)] H20. J. Am. Chem. Soc. 99: 101-104.
de Meester, P. ; Hodgson, D. J. (1977b) Synthesis and structural characterization of L-
histidinato-D-penicillaminatochromium (III) monohydrate. J. Chem. Soc. Oalton Trans. (17):
1604-1607.
de Meester, P.; Hodgson, D. J. (1977c) Absence of metal interaction with sulfur in two metal
complexes of a cysteine derivative: the structural characterization of Bis(S-methyl-L-
cysteinato)cadmium(II) and Bis(S-methyl-L-cysteinato)zinc(II). J. Am. Chem. Soc. 99: 6884-
6889;
Doe, B. R. (1970) Lead isotopes. New York, NY: Springer-Verlag. (Engelhardt, W.; Hahn, T.; Roy,
R. ; Winchester, J. W.; Wyllie, P. J., eds. Minerals, rocks and inorganic materials:
monograph series of theoretical and experimental studies: v. 3).
Dyrssen, D. (1972) The changing chemistry of the oceans. Ambio 1: 21-25.
Freeman, H. C. ; Stevens, G. N. ; Taylor, I. F., Jr. (1974) Metal binding in chelation therapy:
the crystal structure of D-penicillaminatolead(II). J. Chem. Soc. Chem. Commun. (10):
366-367.
Freeman, H. C.; Huq, F.; Stevens, G. N. (1976) Metal binding by D-penicillamine: crystal struc-
ture of D-penicillaminatocadmium(II) hydrate. J. Chem. Soc. Chem. Commun. (3): 90-91.
A03REF/A 3-8 7/13/83
-------
, PRELIMINARY DRAFT
Freeman, H. C. ; Huq, F.; Stevens, G. N. (1976) Metal binding by D-penicillamine: crystal struc-
ture of D-penicillaminatocadmium(II) hydrate. J. Chem. Soc. Chem. Commun. (3): 90-91.
Hager, C-D. ; Huber, F. (1980) Organobleiverbindungen von Mercaptocarbonsauren. [Organolead com-
pounds of mercaptocarboxylic acids.] Z. Naturforsch. 35b: 542-547.
Helis, H. M. ; de Meester, P.; Hodgson, D. J. (1977) Binding of penicillamine to toxic metal
ions: synthesis and structure of potassium(D-penicillaminato) (L-Penicillaminato)cobal-
tate(III) dihydrate, K[Co(D-pen)(L-pen)] 2H20. J. Am. Chem. Soc. 99: 3309-3312.
Heslop, R. B.; Jones, K. (1976) Inorganic chemistry: a guide to advanced study. New York, NY:
Elsevier Science Publishing Co.; pp. 402-403.
Jones, M. M.; Vaughn, W. K. (1978) HSAB theory and acute metal ion toxicity and detoxification
processes. J. Inorg. Nucl. Chem. 40: 2081-2088.
Lis, T. (1978) Potassium ethylenediaminetetraacetatomanganate(III) dihydrate. Acta Crystallogr.
Sec. B 34: 1342-1344.
McCandlish, E. F. K.; Michael, T. K.; Neal, J. A.; Lingafelter, E. C.; Rose, N. J. (1978) Com-
parison of the structures and aqueous solutions of [o-phenylenediaminetetraacetato(4-)]
cobalt(II) and [ethylenediaminetetraacetato(4-)] cobalt(II) ions. Inorg. Chem. 17: 1383-
1394.
Moeller, T. (1952) Inorganic chemistry: an advanced textbook. New York, NY: John Wiley & Sons,
Inc.
Nieboer, E. ; Richardson, D. H. S. (1980) The replacement of the nondescript term "heavy metals"
by a biologically and chemically significant classification of metal ions. Environ.
Pollut. Ser. B. 1: 3-26.
Nishikido, J. ; Tamura, N. ; Fukuoka, Y. (1980) (Asahi Chemical Industry Co. Ltd.) Ger. Patent
No. 2,936,652.
Olin, A.; SSderquist, R. (1972) The crystal structure of p-[Pb60(OH)6](C104)4 H20. Acta Chem.
Scand. 26: 3505-3514.
Pearson, R. G. (1963) Hard and soft acids and bases. J. Am. Chem. Soc. 85: 3533-3539.
Pearson, R. G. (1968) Hard and soft acids and bases, HSAB, part 1: fundamental principles. J.
Chem. Educ. 45: 581-587.
Pearson, R. G.; Mawby, R. J. (1967) The nature of metal-halogen bonds. In: Gutmann, V., ed.
Halogen chemistry: vol. 3. New York, NY: Academic Press, Inc.; pp. 55-84.
Rufman, N. M. ; Rotenberg, 2. A. (1980) Special kinetic features of the photodecomposition of
organolead compounds at lead electrode surfaces. Sov. Electrochem. Engl. Transl. 16:
309-314.
Russell, R.; Farquhar, R. (1960) Introduction. In: Lead isotopes in geology. New York, NY:
Interscience; pp. 1-12.
Shapiro, H.; Frey, F. W. (1968) The organic compounds of lead. New York, NY: John Wiley & Sons.
(Seyferth, D., ed. The chemistry of organometallic compounds: a series of monographs.)
03REF 3-9 7/1/83
-------
PRELIMINARY DRAFT
Shaw, C. F., III; Allred, A. L. (1970) Nonbonded interactions in organometallic compounds of
Group IV B. Organometallic Chem. Rev. A 5: 95-142.
Wharf, I.; Onyszchuk, M.; Miller, J. M. ; Jones, T. R. B. (1980) Synthesis and spectroscopic
studies of phenyllead halide and thiocyanate adducts with hexamethylphosphoramide. J.
Organomet. Chem. 190: 417-433.
Williams, M. W. ; Hoeschele, J. D. ; Turner, J. E. ; Jacobson, K. B. ; Christie, N. T. ; Paton,
C. L.; Smith, L. H. ; Witsch, H. R. ; Lee, E. H. (1982) Chemical softness and acute metal
toxicity in mice and Drosophila. Toxicol. Appl. Pharmacol. 63: 461-469.
Williams, M. W. ; Turner, J. E. (1981) Comments on softness parameters and metal ion toxicity
J. Inorg. Nucl. Chem. 43: 1689-1691.
Wong, Y. S.; Chieh, P. C.; Carty, A. J. (1973) Binding of methylmercury by amino-acids: X-ray
structures of p_J.-penicillaminatomethylmercury(II). J. Chem. Soc. Chem. Commun. (19)>
741-742.
03REF 3-10 7/1/83
-------
PRELIMINARY DRAFT
APPENDIX 3A
PHYSICAL/CHEMICAL DATA FOR LEAD COMPOUNDS
3A.1 DATA TABLES
Table 3A-1. PHYSICAL PROPERTIES OF INORGANIC LEAD COMPOUNDS1
Solubility, g/100 ml
Compound
Lead
Acetate
Azide
Bromate
Bromide
Carbonate
Carbonate,
basic
Chloride
Chlorobromide
Chromate
Chromate,
basic
Cyanide
Fluoride
Fluorochloride
Formate
Hydride
Hydroxide
lodate
Iodide
Nitrate
Formula
Pb
Pb(C2H302)2
Pb(N3)2
Pb(Br03)2-H20
PbBr2
PbC03
2PbC03-Pb(OH)2
PbCl2
PbClBr
PbCr04
PbCr04-PbO
Pb(CN)2
PbF2
PbFCl
Pb(CH02)2
PbH2
Pb(OH)2
Pb(I03)2
PbI2
Pb(N03)2
M.W.
207.
325.
291.
481.
367.
267.
775.
278.
322.
323.
546.
259.
245.
261.
297.
209.
241.
557.
461.
331.
19
28
23
02
01
20
60
10
56
18
37
23
19
64
23
21
20
00
00
20
S.
11.
3.
5.
6.
6.
6.
5.
6.
6.
8.
7.
4.
6.
6.
4.
G.
35
25
-
53
66
6
14
85
12
63
24
05
63
155
16
53
M.P.
327.5
280
expl.
d!80
373
d315
d400
501
844
855
601
d!90
d
d!45
d300
402
d470
Cold
water
i
44.
0.
1.
0.
0.
0.
3
023
38
8441
00011
i
99
6xlO~6
si
0.
0.
1.
0.
0.
0.
37.
i
s
064
037
6
0155
0012
063
65
Hot
water
i
22iso
0.0970
si s
4.71100
d
i
3.34100
i
i
s
0. 1081
20
si s
0.003
0.41
127
Other
solvents
sa
s glyc
-
-
sa
sa.alk
s HN03
i al
sa.alk
sa.alk
s KCN
s HN03
i al
sa.alk
s HN03
s.alk
s.alk
PBAPP/A
3A-1
7/1/83
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PRELIMINARY DRAFT
Table 3A-1. (continued). PHYSICAL PROPERTIES OF INORGANIC LEAD COMPOUNDS1
Compound
Nitrate, basic
Oxalate
Oxide
Dioxide
Oxide (red)
Phosphate
Sulfate
Sulfide
Sulfite
Thiocyanate
Formula
Pb(OH)N03
PbC204
PbO
Pb02
Pb304
Pb3(P04)2
PbS04
PbS
PbS03
Pb(SCN)2
M.W.
286.20
295.21
223.19
239. 19
685.57
811.51
303.25
239.25
287. 25
323.35
S.G.
5.93
5.28
9.53
9.375
9.1
7
6.2
7.5
3.82
M.P.
d!80
d300
888
d290
d500
1014
1170
1114
d
d!90
Cold
water
19.4
0.00016
0.0017
i
i
1.4xlO"s
0.00425
8.6xlO"5
i
0.05
Solubility, g/100 ml
Hot Other
water solvents
s sa
sa
s.alk
i sa
i sa
i s,alk
0.0056
sa
i sa
0.2 s.alk
Abbreviations: a - acid; al - alcohol; alk - alkali; d - decomposes;
expl - explodes; glyc - glycol; i - insoluble; s - soluble;
M.W. - molecular weight; S.G. - specific gravity; and
M.P. - melting point.
Source: Weast, 1975.
PBAPP/A
3A-2
7/1/83
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PRELIMINARY DRAFT
Table 3A-2. TEMPERATURE VARIATION OF THE VAPOR PRESSURES
OF COMMON LEAD COMPOUNDS
Temperature °
Name
Lead
Lead
Lead
Lead
Lead
Lead
Lead
bromide
chloride
flouride
iodide
oxide
sulfide
Formula
Pb
PbBr2
PbCl2
PbF2
PbI2
PbO
PbS
M.P.
327.4
373
501
855
402
890
1114
1 mm
973
513
547
solid
479
943
852
(solid)
10 mm
1162
610
648
904
571
1085
975
(solid)
40 mm
1309
686
725
1003
644
1189
1048
(solid)
100 mm
1421
745
784
1080
701
1265
1108
(solid)
C
400 mm
1630
856
893
1219
807
1402
1221
760 mm
1744
914
954
1293
872
1472
1281
Source: Stull, 1947
3A.2. THE CHELATE EFFECT
The stability constants of chelated complexes are normally several orders of magnitude
higher than those of comparable monodentate complexes; this effect is called the chelate
effect, and is very readily explained in terms of kinetic considerations. A comparison of the
binding of a single bidentate ligand with that of two molecules of a chemically similar mono-
dentate ligand shows that, for the monodentate case, the process can be represented by the
equations:
M + B .a M-B
Kb
M-B + B
MB,
(3A-1)
(3A-2)
The related expressions for the bidentate case are:
M + B-B 1 M-B-B
M-B-B
M
k4
B
B
(3A-3)
(3A-4)
The overall equilibrium constants, therefore, are:
Ki =
.
kbkd'
PBAPP/A
3 A- 3
7/1/83
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PRELIMINARY DRAFT
For a given metal, M, and two ligands, B and B-B, which are chemically similar, it is
established that ki and kfl have similar values to each other, as do k2 and k. and k4 and k.;
each of these pairs of terms represents chemically similar processes. The origin of the
chelate effect lies in the very large value of k3 relative to that of k . This comes about
because k3 represents a unimolecular process, whereas k is a bimolecular rate constant.
Consequently, K2 » Kx.
This concept can, of course, be extended to polydentate ligands; in general, the more
extensive the chelation, the more stable the metal complex. Hence, one would anticipate,
correctly, that polydentate chelating agents such as penicillamine or EDTA can form extremely
stable complexes with metal ions.
3A.3 REFERENCES
Stull, D.R. (1947) Vapor pressure of pure substances: organic compounds. Ind. Eng. Chem 39:
517-540.
Weast, R.C., ed. (1975) Handbook of chemistry and physics. Cleveland, OH; The Chemical Rubber
Co.
PBAPP/A 3A-4 7/1/83
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PRELIMINARY DRAFT
4. SAMPLING AND ANALYTICAL METHODS FOR ENVIRONMENTAL LEAD
4.1 INTRODUCTION
Lead, like all criteria pollutants, has a designated Reference Method for monitoring and
analysis as required in State Implementation Plans for determining compliance with the lead
National Ambient Air Quality Standard. The Reference Method [C.F.R. (1982) 40:§50] uses a
high volume sampler (hi-vol) for sample collection and atomic absorption spectrometry for
analysis. The reference method may be revised to require collection of a specific size frac-
tion of atmospheric particles. Size specific inlets will be discussed in Section 4.2.3.
Airborne lead originates principally from man-made sources, about 75 to 90 percent from
automobile exhaust, and is transported through the atmosphere to vegetation, soil, water, and
animals. Knowledge of environmental concentrations of lead and the extent of its movement
among various media is essential to control lead pollution and to assess its effects on human
populations.
The collection and analysis of environmental samples for lead require a rigorous quality
assurance program [C.F.R. (1982) 40:§58]. It is essential that the investigator recognize all
sources of contamination and use every precaution to eliminate them. Contamination occurs on
the surfaces of collection containers and devices, on the hands and clothing of the investi-
gator, in the chemical reagents, in the laboratory atmosphere, and on the labware and tools
used to prepare the sample for analysis. General procedures for controlling contamination in
trace metal analysis are described by Zief and Mitchell (1976). Specific details for the
analysis of lead are given in Patterson and Settle (1976). In the following discussion of
methods for sampling and analysis, it is assumed that all procedures are normally carried out
with precise attention to contamination control.
In the following sections, the specific operation, procedure and instrumentation involved
in monitoring and analyzing environmental lead are discussed. Site selection criteria are
treated briefly due to the lack of verifying data. Much remains to be done in establishing
valid criteria for sampler location. The various types of samples and substrates used to col-
lect airborne lead are described. Methods for collecting dry deposition, wet deposition,
aqueous, soil and vegetation samples are also reviewed along with current sampling methods
specific to mobile and stationary sources. Finally, advantages and limitations of techniques
for sample preparation and analysis are discussed.
023PB4/A 4-1 7/14/83
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PRELIMINARY DRAFT
4.2 SAMPLING
The purpose of sampling is to determine the nature and concentration of lead in the envi-
ronment. Sampling strategy is dictated by research needs. This strategy encompasses site
selection, choice of instrument used to obtain representative samples, and choice of method
used to preserve sample integrity. In the United States, sampling stations for air pollutants
have been operated since the early 1950's. These early stations were a part of the National
Air Surveillance Network (NASN), which has now become the National Filter Analysis Network
(NFAN). Two other types of networks have been established to meet specific data requirements.
State and Local Air Monitoring Stations (SLAMS) provide data from specific areas where pollu-
tant concentrations and population densities are the greatest and where monitoring of compli-
ance to standards is critical. The National Air Monitoring Station (NAMS) network is designed
to serve national monitoring needs, including assessment of national ambient trends. SLAMS
and NAMS stations are maintained by state and local agencies and the air samples are analyzed
in their laboratories. Stations in the NFAN network are maintained by state and local agen-
cies, but the samples are analyzed by laboratories in the U.S. Environmental Protection
Agency, where quality control procedures are rigorously maintained.
Data from all three networks are combined into one data base, the National Aerometric
Data Bank (NADB). These data may be individual chemical analyses of a 24-hour sampling period
arithmetically averaged over a calendar period, or chemical composites of several filters used
to determine a quarterly composite. Data are occasionally not available because they do not
conform to strict statistical requirements. A summary of the data from the NADB appears in
Section 7.2.1.
4.2.1 Regulatory Siting Criteria for Ambient Aerosol Samplers
In September of 1981, EPA promulgated regulations establishing ambient air monitoring and
data reporting requirements for lead [C.F.R. (1982) 40:§58] comparable to those already estab-
lished in May of 1979 for the other criteria pollutants. Whereas sampling for lead is accomp-
lished when sampling for TSP, the designs of lead and TSP monitoring stations must be comple-
mentary to insure compliance with the NAMS criteria for each pollutant, as presented in Table
4-1, Table 4-2, and Figure 4-1.
In general, the criteria with respect to monitoring stations designate that there must be
at least two SLAMS sites for lead in any area which has a population greater than 500,000 and/
or any area where lead concentration currently exceeds the ambient lead standard (1.5 ug/m3)
or has exceeded it since January 1, 1974. In such areas, the SLAMS sites designated as part
of the NAMS network must include a microscale or middlescale site located near a major roadway
(£30,000 ADT), as well as a neighborhood scale site located in a highly populated residential
sector with high traffic density (£30,000 ADT).
023PB4/A 4-2 7/14/83
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PRELIMINARY DRAFT
TABLE 4-1. DESIGN OF NATIONAL AIR MONITORING STATIONS
Criteria
TSP (Final Rule)
Air Pb (Final Rule)
Spatial scale
Category (a)
Category (b)
Number required
Stations required
Neighborhood scale
As per Table 4-2
Microscale or middle scale
Neighborhood scale
Minimum 1 each category
where population >500,000
OJ
Category (a)
High traffic and
population density
neighborhood scale
Meters from edge of
roadway
meters above ground 2-15
level
Category (b)
Meters from edge of roadway
Meters above ground level
As per Figure 4-1
Major roadway
microscale or
S30.000
5-15
2-7
Major roadway
middle scale
no, ooo
>15-50
2-15
20,000 ^40,000
>15-75 >15-100
2-15 2-15
High traffic and population density
neighborhood scale
^10,000
>50
2-15
20,000
>75
2-15
^40,000
MOO
2-15
Source: C.F.R. (1982) 40:§58 App E
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TABLE 4-2. TSP NAMS CRITERIA
Population Category
High -- >500,000
Medium -- 100-500,000
Low -- 50-100,000
Approximate Number
High1
6-8
4-6
2-4
of Stations Per Area
Concentration
Medium2
4-6
2-4
1-2
Low3
0-2
0-2
0
:When TSP Concentration exceeds by 20% Primary Ambient Air Standard of 75 ug/m3 annual
geometric mean.
2TSP Concentration > Secondary Ambient Air Standard of 60 ug/m3 annual geometric mean.
3TSP Concentration < Secondary Ambient Air Standard.
Source: C.F.R. (1982) 40:§58 App D
With respect to the siting of monitors for lead and other criteria pollutants, there are
standards for elevation of the monitors above ground level, setback from roadways, and setback
from obstacles. A summary of the specific siting requirements for lead is presented in Table
4-1 and summarized below:
• Samples must be placed between 2 and 15 meters from the ground and greater than 20
meters from trees.
• Spacing of samplers from roads should vary with traffic volume; a range of 5 to
100 meters from the roadway is suggested.
• Distance from samplers to obstacles must be at least twice the height the obstacle
protrudes above the sampler.
• There must be a 270° arc of unrestricted air flow around the monitor to include
the prevailing wind direction that provides the maximum pollutant concentration to
the monitor.
• No furnaces or incineration flues should be in close proximity to the monitor.
023PB4/A 4-4 7/14/83
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ZONE C (UNACCEPTABLE)
ZONE A (ACCEPTABLE
ZONE B(NOT RECOMMENDED
10 20 25 30
DISTANCE FROM EDGE OF NEAREST TRAFFIC LANE, meters
Figure 4-1. Acceptable zone for siting TSP monitors where the average daily traffic exceeds 3000
vehicles/day.
Zone A: Recommended for neighborhood, urban, regional and most middle spatial scales. All IMAMS are in this zone.
Zone B: If SLAMS are placed in Zone B they have middle scale of representativeness.
Source: 46 FR 44159-44172
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To clarify the relationship between monitoring objectives and the actual siting of a mon-
itor, the concept of a spatial scale of representativeness was developed. The spatial scales
are described in terms of the physical dimensions of the air space surrounding the monitor
throughout which pollutant concentrations are fairly similar. Table 4-3 describes the scales
of representativeness while Table 4-4 relates monitoring objectives to the appropriate spatial
scale.
The time scale may also be an important factor. A study by Lynam (1972) illustrates the
effect of setback distance on short-term (15 minute) measurements of lead concentrations
directly downwind from the source. They found sharp reductions in lead concentration with in-
creasing distance from the roadway. A similar study by PEDCo Environmental, Inc. (1981) did
not show the same pronounced reduction when the data were averaged over monthly or quarterly
time periods. The apparent reason for this effect is that windspeed and direction are not
consistent. Therefore, siting criteria must include sampling times sufficiently long to
include average windspeed and direction, or a sufficient number of samples must be collected
over short sampling periods to provide an average value consistent with a 24-hour exposure.
4.2.2 Ambient Sampling for Particulate and Gaseous Lead
Airborne lead is primarily inorganic particulate matter but may occur in the form of
organic gases. Devices used for collecting samples of ambient atmospheric lead include the
standard hi-vol and a variety of other collectors employing filters, impactors, impingers, or
scrubbers, either separately or in combination. Some samplers measure total particulate
matter gravimetrically; thus the lead data are usually expressed in ug/g PM or ug/m3 air.
Other samplers do not measure PM gravimetrically; therefore, the lead data can only be
expressed as ug/m3. Some samplers measure lead deposition expressed in ug/cm2. Some instru-
ments separate particles by size. As a general rule, particles smaller than 2.5 um are
defined as fine, and those larger than 2.5 um are defined as coarse.
In a typical sampler, the ambient air is drawn down into the inlet and deposited on the
collection surface after one or more stages of particle size separation. Inlet effectiveness
internal wall losses, and retention efficiency of the collection surface may bias the
collected sample by selectively excluding particles of certain sizes.
4.2.2.1 High Volume Sampler (hi-vol). The present SLAMS and NAMS employ the standard hi-vol
sampler (Robson and Foster, 1962; Silverman and Viles, 1948; U.S. Environmental Protection
Agency, 1971) as part of their sampling networks. As a Federal Reference Method Sampler, the
hi-vol operates with a specific flow rate range of 1.13 to 1.70 m3/min, drawing air through a
023PB4/A 4-6 7/14/83
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TABLE 4-3. DESCRIPTION OF SPATIAL SCALES OF REPRESENTATIVENESS
Microscale Defines ambient concentrations in air volumes associated
with areas ranging from several to 100 meters in size.
Middle Scale Defines concentrations in areas from 100 to 500 meters
(area up to several city blocks).
Neighborhood Scale Defines concentrations in an extended area of uniform
land use, within a city, from 0.5 to 4.0 kilometers in
size.
Urban Scale Defines citywide concentrations, areas from 4-50
kilometers in size. Usually requires more than one
site.
Regional Scale Defines concentrations in a rural area with homogeneous
geography. Range of tens to hundreds of kilometers.
National and Global Defines concentrations characterizing the U.S. and the
Scales globe as a whole.
Source: C.F.R. (1982) 40:§58 App. D
TABLE 4-4. RELATIONSHIP BETWEEN MONITORING OBJECTIVES AND
APPROPRIATE SPATIAL SCALES
Monitoring objective Appropriate spatial scale for siting air monitors
Highest Concentration Micro, Middle, Neighborhood (sometimes Urban).
Population Neighborhood, Urban
Source Impact Micro, Middle, Neighborhood
General (Background) Neighborhood, Regional
Source: C.F.R. (1982) 40:§58 App. D
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200 x 250 mm glass fiber filter. At these flow rates, 1600 to 2500 m3 of air per day are
sampled. Many hi-vol systems are presently equipped with mass flow sensors to control the
total flow rate through the filter.
The present hi-vol approach has been shown, during performance characterization tests, to
have a number of deficiencies. First, wind tunnel testing by Wedding et al. (1977) has shown
that the inlet characteristics of the hi-vol sampler are strongly affected by particle size,
windspeed, and wind direction. However, since most lead particles have been shown to have a
mass median diameter (MMD) in the range of 0.25 to 1.4 urn (Lee and Goranson, 1972), the hi-vol
sampler should present reasonably good estimates of ambient lead concentrations. However, for
particles greater than 5 urn, the hi-vol system is unlikely to collect representative samples
(McFarland and Rodes, 1979; Wedding et al., 1977). In addition, Lee and Wagman (1966) and
Stevens et al. (1978) have documented that the use of glass fiber filters leads to the forma-
tion of artifactual sulfate. Spicer et al. (1978) suggested a positive artifactual nitrate
while Stevens et al. (1980) showed both a positive and negative artifact may occur with glass
or quartz filters when using a hi-vol sampler.
4.2.2.2 Dichotomous Sampler. The dichotomous sampler collects two particle size fractions,
typically 0 to 2.5 um and 2.5 um to the upper cutoff of the inlet employed (normally 10 um).
The impetus for the dichotomy of collection, which approximately separates the fine and coarse
particles, was provided by Whitby et al. (1972) to assist in the identification of particle
sources. A 2.5 um cutpoint for the separator was also recommended by Miller et al. (1979) be-
cause it satisfied the requirements of health researchers interested in respirable particles,
provided adequate separation between two naturally occurring peaks in the size distribution,
and was mechanically practical. Because the fine and coarse fractions collected in most loca-
tions tend to be acidic and basic, respectively, this separation also minimizes potential par-
ticle interaction after collection.
The particle separation principle used by this sampler was described by Hounam and
Sherwood (1965) and Conner (1966). The version now in use by EPA was developed by Loo et al.
(1979). The separation principle involves acceleration of the particles through a nozzle.
Ninety percent of the flowstream is diverted to a small particle collector, while the larger
particles continue by inertia toward the large particle collection surface. The inertial
virtual impactor design causes 10 percent of the fine particles to be collected with the
coarse particle fraction. Therefore, the mass of fine and coarse particles must be adjusted
to allow for their cross contamination. This mass correction procedure has been described by
Dzubay et al. (1982).
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Teflon membrane filters with pore sizes as large as 2.0 urn can be used in the dichoto-
mous sampler (Dzubay et al, 1982; Stevens et al., 1980) and have been shown to have essen-
tially 100 percent collection efficiency for particles with an aerodynamic diameter as small
as 0.03 urn (Liu et al., 1976; See Section 4.2.5). Because the sampler operates at a flowrate
of 1 mVhr (167 1/min) and collects sub-milligram quantities of particles, a microbalance with
a 1 M9 resolution is recommended for filter weighing (Shaw, 1980). Removal of the fine par-
ticles via this fractionation technique may result in some of the collected coarse particles
falling off the filter if care is not taken during filter handling and shipping. However,
Dzubay and Barbour (1983) have developed a filter coating procedure which eliminates particle
®
loss during transport. A study by Wedding et al. (1980) has shown that the Sierra inlet to
the dichotomous sampler was sensitive to windspeed. The 50 percent cutpoint (D5o) was found
to vary from 10 to 22 |jm over the windspeed range of 0 to 15 km/hr.
Automated versions of the sampler allow timely and unattended changes of the sampler
filters. Depending on atmospheric concentrations, short-term samples of as little as 4 hours
can provide diurnal pattern information. The mass collected during such short sample periods,
however, is extremely small and highly variable results may be expected.
4.2.2.3 Impactor Samplers. Impactors provide a means of dividing an ambient particle sample
into subfractions of specific particle size for possible use in determining size distribution.
A jet of air is directed toward a collection surface, which is often coated with an adhesive
or grease to reduce particle bounce. Large, high-inertia particles are unable to turn with
the airstream and consequently hit the collection surface. Smaller particles follow the air-
stream and are directed toward the next impactor stage or to the filter. Use of multiple
stages, each with a different particle size cutpoint, provides collection of particles in
several size ranges.
For determining particle mass, removable impaction surfaces may be weighed before and
after exposure. The particles collected may be removed and analyzed for individual elements.
The selection and preparation of these impaction surfaces have significant effects on the
impactor performance. Improperly coated or overloaded surfaces can cause particle bounce to
lower stages resulting in substantial cutpoint shifts (Dzubay et al., 1976). Additionally,
coatings may cause contamination of the sample. Marple and Will eke (1976) showed the effect
of various impactor substrates on the sharpness of the stage cutpoint. Glass fiber substrates
can also cause particle bounce or particle interception (Dzubay et al., 1976) and are subject
to the formation of artifacts, due to reactive gases interacting with the glass fiber, similar
to those on hi-vol sampler filters (Stevens et al., 1978).
023P84/A 4-9 7/14/83
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Cascade impactors typically have 2 to 10 stages, and flowrates for commercial low-volume
versions range from about 0.01 to 0.10 mVmin. Lee and Goranson (1972) modified a commer-
cially available 0.03 m3/min low-volume impactor and operated it at 0.14 mVmin to obtain
larger mass collections on each stage. Cascade impactors have also been designed to mount on
a hi-vol sampler and operate at flowrates as high as 0.6 to 1.1 nrVmin.
Particle size cutpoints for each stage depend primarily on sampler geometry and flowrate.
The smallest particle size cutpoint routinely used is approximately 0.3 (jrn, although special
low-pressure impactors such as that described by Hering et al. (1978) are available with cut-
points as small as 0.05 |jm. However, due to the low pressure, volatile organics and nitrates
are lost during sampling. A membrane filter is typically used after the last stage to collect
the remaining small particles.
4.2.2.4 Dry Deposition Sampling. Dry deposition may be measured directly with surrogate or
natural surfaces, or indirectly using micrometeorological techniques. The earliest surrogate
surfaces were dustfall buckets placed upright and exposed for several days. The HASL wet-dry
collector is a modification which permits one of a pair of buckets to remain covered except
during rainfall. These buckets do not collect a representative sample of particles in the
small size range where lead is found because the rim perturbs the natural turbulent flow of
the main airstream (Hicks et al., 1980). They are widely used for other pollutants, espe-
cially large particles, in the National Atmospheric Deposition Program.
Other surrogate surface devices with smaller rims or no rims have been developed recently
(Elias et al., 1976; Lindberg et al., 1979; Peirson et al., 1973). Peirson et al. (1973)
used horizontal sheets of filter paper exposed for several days with protection from rainfall.
Elias et al. (1976) used Teflon® disks held rigid with a 1 cm Teflon ring. Lindberg et al.
(1979) used petri dishes suspended in a forest canopy. In all of these studies, the calcu-
lated deposition velocity (see Section 6.3.1) was within the range expected for small aerosol
particles.
A few studies have measured direct deposition on vegetation surfaces using chemical wash-
ing techniques to remove surface particles. These determinations are generally 4 to 10 times
lower than comparable surrogate surface measurements (Elias et al., 1976; Lindberg et al.,
1979), but the reason for this difference could be that natural surfaces represent net accumu-
lation rather than total deposition. Lead removed by rain or other processes would show an
apparently lower deposition rate.
There are several micrometeorological techniques that have been used to measure particle
deposition. They overcome the major deficiency of surrogate surfaces, the lack of correlation
between the natural and artificial surfaces, but micrometeorological techniques require expen-
sive equipment and skilled operators. They measure instantaneous or short-term deposition
023PB4/A 4-10 7/14/83
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only, and this deposition is inferred to be to a plane projected surface area only, not neces-
sarily to vegetation surfaces.
Of the five micrometeorological techniques commonly used to measure particle deposition,
only two have been used to measure lead particle deposition. Everett et al. (1979) used the
profile gradient technique by which lead concentrations are measured at two or more levels
within 10 m above the surface. Parallel meteorological data are used to calculate the net
flux downward. Droppo (1980) used eddy correlation, which measures fluctuations in the ver-
tical wind component with adjacent measurements of lead concentrations. The calculated dif-
ferences of each can be used to determine the turbulent flux. These two micrometeorological
techniques and the three not yet used for lead, modified Bowen, variance, and eddy accumula-
tion, are described in detail in Hicks et al. (1980).
4.2.2.5 Gas Collection. When sampling ambient lead with systems employing filters, it is
likely that vapor-phase organolead compounds will pass through the filter media. The use of
bubblers downstream of the filter containing a suitable reagent or absorber for collection of
these compounds has been shown to be effective (Purdue et al., 1973). Organolead may be col-
lected on iodine crystals, adsorbed on activated charcoal, or absorbed in an iodine mono-
chloride solution (Skogerboe et al., 1977b).
In one experiment, Purdue et al. (1973) operated two bubblers in series containing iodine
monochloride solution. One hundred percent of the lead was recovered in the first bubbler.
It should be noted, however, that the analytical detection sensitivity was poor. In general,
use of bubblers limits the sample volume due to losses by evaporation and/or bubble carryover.
4.2.3 Source Sampling
Sources of lead include automobiles, smelters, coal-burning facilities, waste oil combus-
tion, battery manufacturing plants, chemical processing plants, facilities for scrap proces-
sing, and welding and soldering operations (see Section 5.3.3). A potentially important
secondary source is fugitive dust from mining operations and from soils contaminated with
automotive emissions (Olson and Skogerboe, 1975). Chapter 5 contains a complete discussion of
sources of lead emissions. The following sections discuss the sampling of stationary and
mobile sources.
4.2.3.1 Stationary Sources. Sampling of stationary sources for lead requires the use of a
sequence of samplers at the source of the effluent stream. Since lead in stack emissions may
be present in a variety of physical and chemical forms, source sampling trains must be de-
signed to trap and retain both gaseous and particulate lead. A sampling probe is inserted
023PB4/A 4-11 7/14/83
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PRELIMINARY DRAFT
directly in the stack or exhaust stream. In the tentative ASTM method for sampling for atmos-
pheric lead, air is pulled through a 0.45 urn membrane filter and an activated carbon adsorp-
tion tube (American Society for Testing and Materials, 1975a). In a study of manual methods
for measuring emission concentrations of lead and other toxic materials, Coulson et al.
(1973), recommended use of a filter, a system of impingers, a metering system, and a pump.
4.2.3.2 Mobile Sources. Three principal procedures have been used to obtain samples of auto
exhaust aerosols for subsequent analysis for lead compounds: a horizontal dilution tunnel
plastic sample collection bags and a low residence time proportional sampler. In each proce-
dure, samples are air diluted to simulate roadside exposure conditions. In the most commonly
used procedure, a large horizontal air dilution tube segregates fine combustion-derived parti-
cles from larger lead particles ablated from combustion chamber and exhaust deposits. In this
procedure, hot exhaust is ducted into a 56-cm diameter, 12-m long, air dilution tunnel and
mixed with filtered ambient air in a 10-cm diameter mixing baffle in a concurrent flow
arrangement. Total exhaust and dilution airflow rate is 28 to 36 mVmin, which produces a
residence time of approximately 5 sec in the tunnel. At the downstream end of the tunnel,
samples of the aerosol are obtained by means of isokinetic probes using filters or cascade
impactors (Habibi, 1970).
In recent years, various configurations of the horizontal air dilution tunnel have been
developed. Several dilution tunnels have been made of polyvinyl chloride with a diameter of
46 cm, but these are subject to wall losses due to charge effects (Gentel et al., 1973; Moran
et al., 1972; Trayser et al., 1975). Such tunnels of varying lengths have been limited by
exhaust temperatures to total flows above approximately 11 mVmin. Similar tunnels have a
centrifugal fan located upstream, rather than a positive displacement pump located downstream
(Trayser et al., 1975). This geometry produces a slight positive pressure in the tunnel and
expedites transfer of the aerosol to holding chambers for studies of aerosol growth. However,
turbulence from the fan may affect the sampling efficiency. Since the total exhaust plus
dilution airflow is not held constant in this system, potential errors can be reduced by main-
taining a very high dilution air/exhaust flow ratio (Trayser et al., 1975).
There have also been a number of studies using total filtration of the exhaust stream to
arrive at material balances for lead with rather low back-pressure metal filters in an air
distribution tunnel (Habibi, 1973; Hirschler et al., 1957; Hirschler and Gilbert, 1964;
Sampson and Springer, 1973). The cylindrical filtration unit used in these studies is better
than 99 percent efficient in retaining lead particles (Habibi, 1973). Supporting data for
lead balances generally confirm this conclusion (Kunz et al., 1975).
023PB4/A 4-12 7/14/83
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In the bag technique, auto emissions produced during simulated driving cycles are air-
diluted and collected in a large plastic bag. The aerosol sample is passed through a filtra-
tion or impaction sampler prior to lead analysis (Ter Haar et al., 1972). This technique may
result in errors of aerosol size analysis because of condensation of low vapor pressure
organic substances onto the lead particles.
To minimize condensation problems, a third technique, a low residence time proportional
sampling system, has been used. It is based on proportional sampling of raw exhaust, again
diluted with ambient air followed by filtration or impaction (Ganley and Springer, 1974;
Sampson and Springer, 1973). Since the sample flow must be a constant proportion of the total
exhaust flow, this technique may be limited by the response time of the equipment to operating
cycle phases that cause relatively small transients in the exhaust flow rate.
4.2.4 Sampling for Lead in Other Media
Other primary environmental media that may be affected by airborne lead include precipi-
tation, surface water, soil, vegetation, and foodstuffs. The sampling plans and the sampling
methodologies used in dealing with these media depend on the purpose of the experiments, the
types of measurements to be carried out, and the analytical technique to be used. General
approaches are given below in lieu of specific procedures associated with the numerous possi-
ble special situations.
4.2.4.1 Precipitation. The investigator should be aware that dry deposition occurs continu-
ously, that lead at the start of a rain event is higher in concentration than at the end, and
that rain striking the canopy of a forest may rinse dry deposition particles from the leaf
surfaces. Rain collection systems should be designed to collect precipitation on an event
basis and to collect sequential samples during the event. They should be tightly sealed from
the atmosphere before and after sampling to prevent contamination from dry deposition, falling
leaves, and flying insects. Samples should be acidified to pH 1 with nitric acid and refrig-
erated immediately after sampling. All collection and storage surfaces should be thoroughly
cleaned and free of contamination.
Two automated systems have been in use for some time. The Sangamo Precipitation
Collector, Type A, collects rain in a single bucket exposed at the beginning of the rain event
(Samant and Vaidya, 1982). These authors reported no leaching of lead from the bucket into a
solution of 0.3N HN03. A second sampler, described by Coscio et al. (1982), also remains
covered between rain events; it can collect a sequence of eight samples during the period of
rain and may be fitted with a refrigeration unit for sample cooling. No reports of lead
analyses were given. Because neither system is widely used, their monitoring effectiveness
has not been thoroughly evaluated.
023PB4/A 4-13 7/14/83
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4.2.4.2 Surface Water. Atmospheric lead may be dissolved in water as hydrated ions, chemical
complexes, and soluble compounds, or it may be associated with suspended matter. Because the
physicochemical form often influences environmental effects, there is a need to differentiate
among the various chemical forms of lead. Complete differentiation among all such forms is a
complex task that has not yet been fully accomplished. The most commonly used approach is to
distinguish between dissolved and suspended forms of lead. All lead passing through a 0.45 pm
membrane filter is operationally defined as dissolved, while that retained on the filter is
defined as suspended (Kopp and McKee, 1979).
When sampling water bodies, flow dynamics should be considered in the context of the pur-
pose for which the sample is collected. Water at the convergence point of two flowing
streams, for example, may not be well mixed for several hundred meters. Similarly, the heavy
metal concentrations above and below the thermocline of a lake may be very different. Thus,
several samples should be selected in order to define the degree of horizontal or vertical
variation. The final sampling plan should be based on the results of pilot studies. In cases
where the average concentration is of primary concern, samples can be collected at several
points and then mixed to obtain a composite.
Containers used for sample collection and storage should be fabricated from essentially
&
lead-free plastic or glass, e.g., conventional polyethylene, Teflon , or quartz. These con-
tainers must be leached with hot acid for several days to ensure minimum lead contamination
(Patterson and Settle, 1976). If only the total lead is to be determined, the sample may be
collected without filtration in the field. Nitric acid should be added immediately to reduce
the pH to less than 2 (U.S. Environmental Protection Agency, 1978). The acid will normally
dissolve the suspended lead. Otherwise, it is recommended that the sample be filtered upon
collection to separate the suspended and dissolved lead and the latter preserved by acid addi-
tion as above. It is also recommended that water samples be stored at 4°C until analysis to
avoid further leaching from the container wall (Fishman and Erdmann, 1973; Kopp and Kroner,
1967; Lovering, 1976; National Academy of Sciences, 1972; U.S. Environmental Protection
Agency, 1978).
4.2.4.3 Soils. The distance and depth gradients associated with lead in soil from emission
sources must be considered in designing the sampling plan. Beyond that, actual sampling is
not particularly complex (Skogerboe et al., 1977b). Vegetation, litter, and large objects
such as stones should not be included in the sample. Depth samples should be collected at 2
cm intervals to preserve vertical integrity. The samples should be air dried and stored in
sealed containers until analyzed.
023PB4/A 4-14 7/14/83
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4.2.4.4 Vegetation. Because most soil lead is in forms unavailable to plants, and because
lead is not easily transported by plants, roots typically contain very little lead and shoots
even less (Zimdahl, 1976; Zimdahl and Koeppe, 1977). Before analysis, a decision must be made
as to whether or not the plant material should be washed to remove surface contamination from
dry deposition and soil particles. If the plants are sampled for total lead content (e.g., if
they serve as animal food sources), they cannot be washed. If the effect of lead on internal
plant processes is being studied, the plant samples should be washed. In either case, the
decision must be made at the time of sampling, as washing cannot be effective after the plant
materials have dried. Fresh plant samples cannot be stored for any length of time in a
tightly closed container before washing because molds and enzymatic action may affect the dis-
tribution of lead on and in the plant tissues. Freshly picked leaves stored in sealed poly-
ethylene bags at room temperature generally begin to decompose in a few days. Storage time
may be increased to approximately 2 weeks by refrigeration.
After collection, plant samples should be dried as rapidly as possible to minimize chem-
ical and biological changes. Samples that are to be stored for extended periods of time
should be oven dried to arrest enzymatic reactions and render the plant tissue amenable to
grinding. Storage in sealed containers is required after grinding. For analysis of surface
lead, fresh, intact plant parts are agitated in dilute nitric acid or EDTA solutions for a few
seconds.
4.2.4.5 Foodstuffs. From 1972 to 1978, lead analysis was included in the Food and Drug
Administration Market Basket Survey, which involves nationwide sampling of foods representing
the average diet of an 18-year-old male, i.e., the individual who on a statistical basis eats
the greatest quantity of food (Kolbye et al., 1974). Various food items from the several food
classes are purchased in local markets and made up into meal composites in the proportion that
each food item is ingested; they are then cooked or otherwise prepared as they would be con-
sumed. Foods are grouped into 12 food classes, then composited and analyzed chemically.
Other sampling programs may be required for different investigative purposes. For those foods
where lead may be deposited on the edible portion, the question of whether or not to use
typical kitchen washing procedures before analysis should be considered in the context of the
experimental purpose.
4.2.5 Filter Selection and Sample Preparation
In sampling for airborne lead, air is drawn through filter materials such as glass fiber,
cellulose acetate, or porous plastic (Skogerboe et al., 1977b, Stern, 1968). These materials
often include contaminant lead that can interfere with the subsequent analysis (Gandrud and
Lazrus, 1972; Kometani et al. 1972; Luke et al., 1972; Seeley and Skogerboe, 1974). If the
023PB4/A 4-15 7/14/83
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PRELIMINARY DRAFT
sample collected is large, then the effects of these trace contaminants may be negligible
(Witz and MacPhee, 1976). Procedures for cleaning filters to reduce the lead blank rely on
washing with acids or complexing agents (Gandrud and Lazrus, 1972). The type of filter and
the analytical method to be used often determines the ashing technique. In some methods,
e.g. , X-ray fluorescence, analysis can be performed directly on the filter if the filter
material is suitable (Dzubay and Stevens, 1975). Skogerboe (1974) provided a general review
of filter materials.
The main advantages of glass fiber filters are low pressure drop and high particle col-
lection efficiency at high flow rates. The main disadvantage is variable lead blank, which
makes their use inadvisable in many cases (Kometani et al., 1972; Luke at al., 1972). This
has placed a high priority on the standardization of a suitable filter for hi-vol samples
(Witz and MacPhee, 1976). Other investigations have indicated, however, that glass fiber
filters are now available that do not present a lead interference ^problem (Scott et al.,
1976b). Teflon filters have been used since 1975 by Dzubay et al. (1982) and Stevens et al.
(1978), who have shown these filters to have very low lead blanks (<2 ng/cm2). The collection
efficiencies of filters, and also of impactors, have been shown to be dominant factors in the
quality of the derived data (Skogerboe et al., 1977a).
Sample preparation usually involves conversion to a solution through wet ashing of solids
with acids or through dry ashing in a furnace followed by acid treatment. Either approach
works effectively if used properly (Kometani et al., 1972; Skogerboe et al., 1977b). In one
fS\
investigation of porous plastic Nuclepore filters, some lead blanks were too high to allow
measurements of ambient air lead concentrations (Skogerboe et al., 1977b).
4.3 ANALYSIS
The choice of analytical method depends on the nature of the data required, the type of
sample being analyzed, the skill of the analyst, and the equipment available. For general
determination of elemental lead, atomic absorption spectroscopy is widely used and recommended
[40 C.F.R. (1982) 40:§50]. Optical emission spectrometry (Scott et al., 1976b) and X-ray
fluorescence (Stevens et al., 1978) are rapid and inexpensive methods for multielemental
analyses. X-ray fluorescence can measure lead concentrations reliably to 1 ng/m3 using sam-
ples collected with commercial dichotomous samplers. Other analytical methods have specific
advantages appropriate for special studies. Only those analytical techniques receiving wide-
spread current use in lead analysis are described below. More complete reviews are available
in the literature (American Public Health Association, 1971; Lovering, 1976; Skogerboe et al.,
1977b; National Academy of Sciences, 1980).
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With respect to measuring lead without sampling or laboratory contamination, several in-
vestigators have shown that the magnitude of the problem is quite large (Patterson and Settle,
1976; Patterson et al., 1976; Pierce et al., 1976; Patterson, 1982; Skogerboe, 1982). It
appears that the problem may be caused by failure to control the blank or by failure to stan-
dardize instrument operation (Patterson, 1982; Skogerboe, 1982). The laboratory atmosphere,
collecting containers, and the labware used may be primary contributors to the lead blank pro-
blem (Murphy, 1976; Patterson, 1982; Skogerboe, 1982). Failure to recognize these and other
sources such as reagents and hand contact is very likely to result in the generation of arti-
ficially high analytical results. Samples with less than 100 ug Pb should be analyzed in a
clean laboratory especially designed for the elimination of lead contamination. Moody (1982)
has described the construction and application of such a laboratory at the National Bureau of
Standards.
For many analytical techniques, a preconcentration step is recommended. Leyden and
Wegschelder (1981) have described several procedures and the associated problems with control-
ling the analytical blank. There are two steps to preconcentration. The first is the removal
of organic matter by dry ashing or wet digestion. The second is the separation of lead from
interfering metallic elements by coprecipitation or passing through a resin column. New sepa-
ration techniques are continuously being evaluated, many of which have application to specific
analytical problems. Yang and Yeh (1982) have described a polyacrylamide-hydrous-zirconia
(PHZ) composite ion exchanger suitable for high phosphate solutions. Corsini, et al. (1982)
evaluated a macroreticular acrylic ester resin capable of removing free and inorganically
bound metal ions directly from aqueous solution without prior chelation.
4.3.1 Atomic Absorption Spectroscopy (AAS)
Atomic absorption spectroscopy (AAS) is a widely accepted method for the measurement of
lead in environmental sampling (Skogerboe et al., 1977b). A variety of lead studies using AAS
have been reported (Kometani et al., 1972; Zoller et al., 1974; Huntzicker et al., 1975; Scott
et al., 1976b; Lester et al., 1977; Hirao et al., 1979; Compton and Thomas, 1980; Bertenshaw
and Gelsthorpe, 1981).
The lead atoms in the sample must be vaporized either in a precisely controlled flame or
in a furnace. Furnace systems in AAS offer high sensitivity as well as the ability to analyze
small samples (Lester et al., 1977; Rouseff and Ting, 1980; Stein et al., 1980; Bertenshaw et
al., 1981). These enhanced capabilities are offset in part by greater difficulty in analyti-
cal calibration and by loss of analytical precision.
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Pachuta and Love (1980) collected particles on cellulose acetate filters. Disks (0.5
cm2) were punched from these filters and analyzed by insertion of the nichrome cups containing
the disks into a flame. Another application involves the use of graphite cups as particle
filters with the subsequent analysis of the cups directly in the furnace system (Seeley and
Skogerboe, 1974; Torsi et al., 1981). These two procedures offer the ability to determine
particulate lead directly with minimal sample handling.
In an analysis using AAS and hi-vol samplers, atmospheric concentrations of lead were
found to be 0.076 ng/m at the South Pole (Maenhaut et al., 1979). Lead analyses of 995 par-
ticulate samples from the NASN were accomplished by AAS with an indicated precision of H
percent (Scott et al., 1976a, see also Section 7.2.1.1). More specialized AAS methods for the
determination of tetraalkyl lead compounds in water and fish tissue have been described by
Chau et al. (1979) and in air by Birnie and Noden (1980) as well as Rohbock et al. (1980).
Atomic absorption requires as much care as other techniques to obtain highly precise
data. Background absorption, chemical interference, background light loss, and other factors
can cause errors. A major problem with AAS is that untrained operators use it in many labor-
atories without adequate quality control.
Techniques for AAS are still evolving. An alternative to the graphite furnace, evaluated
by Jin and Taga (1982), uses a heated quartz tube through which the metal ion in gaseous
hydride form flows continuously. Sensitivities were 1 to 3 ng/g for lead. The technique is
similar to the hydride generators used for mercury, arsenic, and selenium. Other nonflame
atomization systems, electrodeless discharge lamps, and other equipment refinements and tech-
nique developments have been reported (Horlick, 1982).
4.3.2 Emission Spectroscopy
Optical emission spectroscopy is based on the measurement of the light emitted by
elements when they are excited in an appropriate energy medium. The technique has been used
to determine the lead content of soils, rocks, and minerals at the 5 to 10 ug/g level with a
relative standard deviation of 5 to 10 percent (Anonymous, 1963); this method has also been
applied to the analysis of a large number of air samples (Scott et al., 1976b; Sugimae and
Skogerboe, 1978). The primary advantage of this method is that it allows simultaneous meas-
urement of a large number of elements in a small sample (Ward and Fishman, 1976).
In a study of environmental contamination by automotive lead, sampling times were short-
ened by using a sampling technique in which lead-free porous graphite was used both as the
filter medium and as the electrode in the spectrometer (Copeland et al., 1973; Seeley and
Skogerboe, 1974). Lead concentrations of 1 to 10 ug/m3 were detected after a half-hour flow
at 800 to 1200 ml/min through the filter.
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Scott et al. (1976a) analyzed composited particulate samples obtained with hi-vols for
about 24 elements, including lead, using a direct reading emission spectrometer. Over 1000
samples collected by the NASN in 1970 were analyzed. Careful consideration of accuracy and
precision led to the conclusion that optical emission spectroscopy is a rapid and practical
technique for particle analysis.
More recent activities have focused attention on the inductively coupled plasma (ICP)
system as a valuable means of excitation and analysis (Garbarino and Taylor, 1979; Winge et
al., 1977). The ICP system offers a higher degree of sensitivity with less analytical inter-
ference than is typical of many of the other emission spectroscopic systems. Optical emission
methods are inefficient when used for analysis of a single element, since the equipment is
expensive and a high level of operator training is required. This problem is largely offset
when analysis for several elements is required as is often the case for atmospheric aerosols.
4.3.3 X-Ray Fluorescence (XRF)
X-ray emissions that characterize the elemental content of a sample also occur when atoms
are irradiated at sufficient energy to excite an inner-shell electron (Hammerle and Pierson,
1975; Jaklevic et al., 1973; Skogerboe et al. , 1977b; Stevens et al., 1978). This fluores-
cence allows simultaneous identification of a range of elements including lead.
X-ray fluorescence may require a high-energy irradiation source. But with the X-ray
tubes coupled with fluorescers (Jaklevic et al., 1973; Dzubay and Stevens, 1975; Paciga and
Jervis, 1976) very little energy is transmitted to the sample, thus sample degradation is kept
to a minimum (Shaw et al., 1980). Electron beams (McKinley et al., 1966), and radioactive
isotope sources (Kneip and Laurer 1972) have been used extensively (Birks et al., 1971; Birks,
1972) as energy sources for XRF analysis. To reduce background interference, secondary fluor-
escers have been employed (Birks et al., 1971; Dzubay and Stevens, 1975). The fluorescent
X-ray emission from the sample may be analyzed with a crystal monochromator and detected with
scintillation or proportional counters (Skogerboe et al., 1977b) or with low-temperature semi-
conductor detectors that discriminate the energy of the fluorescence. The latter technique
requires a very low level of excitation (Dzubay and Stevens, 1975; Toussaint and Boniforti,
1979).
X-ray emission induced by charged-particle excitation (proton-induced X-ray emission or
PIXE) offers an attractive alterative to the more common techniques (Barfoot et al., 1979;
Hardy et al., 1976; Johansson et al., 1970). Recognition of the potential of heavy-particle
023PB4/A 4-19 7/14/83
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PRELIMINARY DRAFT
bombardment for excitation was demonstrated by Johansson et al. (1970), who reported an inter-
ference-free signal in the picogram (10 12 g) range. The excellent capability of accelerator
beams for X-ray emission analysis is partially due to the relatively low background radiation
associated with the excitation. The high particle fluxes obtainable from accelerators also
contribute to the sensitivity of the PIXE method. Literature reviews (Folkmann et al., 1974;
Gilfrich et al., 1973; Herman et al., 1973; Walter et al. , 1974) on approaches to X-ray
elemental analysis agree that protons of a few MeV energy provide a preferred combination for
high sensitivity analysis under conditions less subject to matrix interference effects. As a
result of this premise, a system designed for routine analysis has been described (Johansson
et al., 1975) and papers involving the use of PIXE for aerosol analysis have appeared (Hardy
et al., 1976; Johansson et al., 1975). The use of radionuclides to excite X-ray fluorescence
and to determine lead in airborne particles has also been described (Havranek and Bumbalova,
1981; Havranek et al., 1980).
X-radiation is the basis of the electron microprobe method of analysis. When an intense
electron beam is incident on a sample, it produces several forms of radiation, including
X-rays, whose wavelengths depend on the elements present in the material and whose intensities
depend on the relative quantities of these elements. An electron beam that gives a spot size
as small as 0.2 urn is possible. The microprobe is often incorporated in a scanning electron
microscope that allows precise location of the beam and comparison of the sample morphology
with its elemental composition. Under ideal conditions, the analysis is quantitative, with an
accuracy of a few percent. The mass of the analyzed element may range from 10 14 to Ifl"16 g
(McKinley et al., 1966).
Electron microprobe analysis is not a widely applicable monitoring method. It requires
expensive equipment, complex sample preparation procedures, and a highly trained operator.
The method is unique, however, in providing compositional information on individual lead par-
ticles, thus permitting the study of dynamic chemical changes and perhaps allowing improved
source identification.
Advantages of X-ray fluorescence methods include the ability to detect a variety of
elements, the ability to analyze with little or no sample preparation, low detection limits (2
ng Pb/m3) and the availability of automated analytical equipment. Disadvantages are that the
X-ray analysis requires liquid nitrogen (e.g., for energy-dispersive models) and highly
trained analysts. The detection limit for lead is approximately 9 ng/cm2 of filter area
(Jaklevic and Walter, 1977), which is well below the quantity obtained in normal sampling
periods with the dichotomous sampler (Dzubay and Stevens, 1975).
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4.3.4 Mass Spectrometry
Isotope dilution mass spectrometry (IDMS) is an absolute measurement technique. It
serves as the standard to which other analytical techniques are compared. No other techniques
serve more reliably as a comparative reference. Its use for analyses at subnanogram concen-
trations of lead and in a variety of sample types has been reported (Chow et al., 1969, 1974;
Facchetti and Geiss, 1982; Hirao and Patterson, 1974; Murozumi et al., 1969; Patterson et al.,
1976; Rabinowitz et al., 1973).
The isotopic composition of lead peculiar to various ore bodies and crustal sources may
also be used as a means of tracing the origin of anthropogenic lead. Other examples of IDMS
application are found in several reports cited above, and in Rabinowitz and Wetherill (1972),
Stacey and Kramers (1975), and Machlan et al. (1976).
4.3.5 Colon'metric Analysis
Colorimetric or spectrophotometric analysis for lead using dithizone (diphenylthiocarba-
zone) as the reagent has been used for many years (Anonymous, 1963; Horowitz et al., 1970;
Sandell, 1944). It was the primary method recommended by a National Academy of Sciences
(1972) report on lead, and the basis for the tentative method of testing for lead in the
atmosphere by the American Society for Testing and Materials (1975b). Prior to the
development of the IDMS method, colorimetric analysis served as the reference by which other
methods were tested.
The procedures for the colorimetric analysis require a skilled analyst if reliable
results are to be obtained. The ASTM conducted a collaborative test of the method (Foster et
al., 1975) and concluded that the procedure gave satisfactory precision in the determination
of particulate lead in the atmosphere. In addition, the required apparatus is simple and
relatively inexpensive, the absorption is linearly related to the lead concentration, large
samples can be used, and interferences can be removed (Skogerboe et al., 1977b). Realization
of these advantages depends on meticulous attention to the procedures and reagents.
4.3.6 Electrochemical Methods: Anodic Stripping Voltammetry (ASV), Differential Pulse
Polarography (DPP)"
Analytical methods based on electrochemical phenomena are found in a variety of forms
(Sawyer and Roberts, 1974; Willard et al., 1974). They are characterized by a high degree of
sensitivity, selectivity, and accuracy derived from the relationship between current, charge,
potential, and time for electrolytic reactions in solutions. The electrochemistry of lead is
based primarily on Pb(II), which behaves reversibly in ionic solutions having a reduction po-
tential near -0.4 volt versus the standard calomel electrode (Skogerboe et al., 1977b). Two
023PB4/A 4-21 7/14/83
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PRELIMINARY DRAFT
electrochemical methods generally offer sufficient analytical sensitivity for most lead mea-
surement problems. Differential pulse polarography (DPP) relies on the measurement of the
faradaic current for lead as the voltage is scanned while compensating for the nonfaradaic
(background) current produced (McDonnell, 1981). Anodic stripping voltammetry (ASV) is a two
step process in which the lead is preconcentrated onto a mercury electrode by an extended but
selected period of reduction. After the reduction step, the potential is scanned either
linearly or by differential pulse to oxidize the lead and allow measurement of the oxidation
(stripping) current. The preconcentration step allows development of enhanced analytical
signals; when used in combination with the differential pulse method lead concentrations at
the subnanogram level can be measured (Florence, 1980).
The ASV method has been widely applied to the analysis of atmospheric lead (Harrison et
al., 1971; Khandekar et al., 1981; MacLeod and Lee, 1973). Landy (1980) has shown the applic-
ability to the determination of Cd, Cu, Pb, and Zn in Antarctic snow while Nguyen et al.
(1979) have analyzed rain water and snow samples. Green et al. (1981) have used the method to
determine Cd, Cu, and Pb in sea water. The ASV determination of Cd, Cu, Pb, and Zn in foods
has been described by Jones et al., 1977; Mannino, 1982; and Satzger et al., 1982, and the
general accuracy of the method summarized by Holak (1980). Current practice with commercially
available equipment allows lead analysis at subnanogram concentrations with precision at the 5
to 10 percent on a routine basis (Skogerboe et al., 1977b). New developments center around
the use of microcomputers in controlling the stripping voltage (Kryger, 1981) and conforma-
tional modifications of the electrode (Brihaye and Duyckaerts, 1982).
4.3.7 Methods for Compound Analysis
The majority of analytical methods are restricted to measurement of total lead and cannot
directly identify the various compounds of lead. The electron nricroprobe and other X-ray
fluorescence methods provide approximate data on compounds on the basis of the ratios of
elements present (Ter Haar and Bayard, 1971). Gas chromatography (GC) using the electron cap-
ture detector has been demonstrated to be useful for organolead compounds (Shapiro and Frey,
1968). The use of atomic absorption as the GC detector for organolead compounds has been
described by DeJonghe et al. (1981), while a plasma emission detector has been used by Estes
et al. (1981). In addition, Messman and Rains (1981) have used liquid chromatography with an
atomic absorption detector to measure organolead compounds. Mass spectrometry may also be
used with gas chromatography (Mykytiuk et al., 1980).
Powder X-ray diffraction techniques have been applied to the identification of lead com-
pounds in soils by Olson and Skogerboe (1975) and by Linton et al. (1980). X-ray diffraction
techniques were used (Harrison and Perry, 1977; Foster and Lott, 1980; Jacklevic et al., 1981)
to identify lead compounds collected on air filters.
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4.4 CONCLUSIONS
To monitor lead particles in air, collection with the hi-vol and dichotomous samplers and
analysis by atomic absorption spectrometry and X-ray fluorescence methods have emerged as the
most widely used methods. Sampling with the hi-vol has inherent biases in sampling large par-
ticles and does not provide for fractionation of the particles according to size, nor does it
allow determination of the gaseous (organic) concentrations. Sampling with a dichotomous
sampler provides size information but does not allow for gaseous lead measurements. The size
distribution of lead aerosol particles is important in considering inhalable particulate
matter. To determine gaseous lead, it is necessary to back up the filter with chemical
scrubbers such as a crystalline iodine trap.
X-ray fluorescence and optical emission spectroscopy are applicable to multi-element
analysis. Other analytical techniques find application for specific purposes. The paucity of
data on the types of lead compounds at subnanogram levels in the ambient air is currently
being addressed through development of improved XRF analyzer procedures.
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5. SOURCES AND EMISSIONS
5.1 HISTORICAL PERSPECTIVE
The history of global lead emissions has been assembled from chronological records of
deposition in polar snow strata, marine and freshwater sediments, and the annual rings of
trees. These records are important for two reasons. They aid in establishing natural
background levels of lead in air, soils, plants, animals, and humans. They also place current
trends in atmospheric lead concentrations in the perspective of historical changes. Most
chronological records document the sudden increase in atmospheric lead at the time of the
industrial revolution, and a later burst during the 1920's when lead-alkyIs were first added
to gasoline.
Tree ring analyses are not likely to show the detailed year-by-year chronological record
of atmospheric lead increases. In situations where ring porous tree species that retain the
nutrient solution only in the most recent annual rings are growing in heavily polluted areas
where soil lead has increased 100-fold, significant increases in the lead content of tree
rings over the last several decades have been documented. Rolfe (1974) found 4-fold increases
in both rural and urban tree rings using pooled samples from the period of 1910-20 compared to
samples from the period from 1963-73. Symeonides (1979) found a 2-fold increase during a
comparable interval at a high lead site but no increase at a low lead site. Baes and Ragsdale
(1981) found significant post-1930 increases in oak (Quercus) and hickory (Carya) with high
lead exposure, but only in hickory with low lead exposure.
Pond sediment analyses (Shirahata, et al. 1980) have shown a 20-fold increase in lead
deposition during the last 150 years (Figure 5-1), documenting not only the increasing use of
lead since the beginning of the industrial revolution in western United States, but also the
relative fraction of natural vs. anthropogenic lead inputs. Other studies have shown the same
magnitude of increasing deposition in freshwater sediments (Christensen and Chien, 1981;
Galloway and Likens, 1979; Edgington and Robbins, 1976), and marine sediments (Ng and
Patterson, 1982). The pond and marine sediments also document the shift in isotopic
composition caused by the recent opening of the New Lead Belt in Missouri, where the ore body
has an isotopic composition substantially different from other ore bodies of the world.
Perhaps the best and certainly the most controversial chronological record is that of the
polar ice strata of Murozumi et al. (1969), which extends nearly three thousand years back in
time (Figure 5-1). The data of Jaworowski et al. (1981) and Herron et al. (1977) do not agree
with the value found by Murozumi et al. (1969) for the early period around 800 B.C. Ng and
Patterson (1981) have shown that the 1ce cores of Herron et al. (1977) were contaminated with
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1750
1775
1950
1975
Figure 5-1. Chronological record of the relative increase of lead in snow strata, pond
and lake sediments, marine sediments, and tree rings. The data are expressed as a
ratio of the latest year of the record and should not be interpreted to extend back in
time to natural or uncontaminated levels of lead concentration.
Source: Adapted from Murozumi et al. (1969) (O), Shirahata et al. (1980) (D), Edgington
and Bobbins (1976) (A), Ny and Patterson (1979) (A), and Rolfe (1974) (• ).
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industrial greases. Patterson (1983) has also discussed the probable errors made by
Jaworowski et al. (1981) in their determination of manmade lead in glacial ice samples. At
the South Pole, Boutron (1982) observed a 4-fold increase of lead in snow from 1957 to 1977
but saw no increase during the period 1927 to 1957. The observed increase was attributed to
global rather than local or regional pollution. The author suggested the extensive
atmospheric lead pollution which began in the 1920's did not reach the South Pole until the
mid-1950' s. This interpretation agrees with that of Maenhaut et al. (1979), who found
atmospheric concentrations of lead of 0.000076 ug/m3 at the same location. This concentration
is about 3-fold higher than the 0.000024 ug/m3 estimated by Patterson (1980) and Servant
(1982) to be the natural lead concentration in the atmosphere. In summary, it is likely that
atmospheric lead emissions have increased 2000-fold since the pre-Roman era, that even at this
early time the atmosphere may have been contaminated by a factor of three over natural levels
(Murozumi et al. 1969), and that global atmospheric concentrations have increased dramatically
since the 1920's.
The history of global emissions may also be determined from total production of lead, if
the fraction of that lead released to the atmosphere during the smelting process, the fraction
released during industrial consumption and the amount of lead emitted from non-lead sources
are known. The historical picture of lead production has been pieced together from many
sources by Settle and Patterson (1980) (Figure 5-2). They used records of accumulated silver
stocks to estimate the lead production needed to support coin production. Until the
industrial revolution, lead production was determined largely by the ability or desire to mine
lead for its silver content. Since that time, lead has been used as an industrial product in
its own right, and efforts to improve smelter efficiency, including control of stack emissions
and fugitive dusts, have made lead production more economical. This improved efficiency is
not reflected in the chronological record because of atmospheric emissions of lead from many
other anthropogenic sources, especially gasoline combustion (see Section 5.3.3). From this
knowledge of the chronological record, it is possible to sort out contemporary anthropogenic
emissions from natural sources of atmospheric lead.
5.2 NATURAL SOURCES .
Lead enters the biosphere from lead-bearing minerals in the lithosphere through both
natural and man-made processes. Measurements of soil materials taken at 20-cm depths in the
continental United States (Levering, 1976; Shacklette et al. 1971) show a median lead
concentration of 15 to 16 ug Pb/g soi]. .Ninety-five percent of these measurements show 30
ug/g of lead or less, with a maximum sample concentration of 700 ug/g.
023PB5/A 5-3 7/13/83
-------
PRELIMINARY DRAFT
SPANISH PRODUCTION
OF SILVER
IN NEW WORLD
INDUSTRIAL
REVOLUTION
EXHAUSTION
OF ROMAN
LEAD MINES
SILVER
PRODUCTION
IN GERMANY
INTRODUCTION
OF COINAGE
DISCOVERY OF
CUPELLATION
RISE AND FALL
OF ATHENS
\
ROMAN REPUBLIC
AND EMPIRE
10°
5500 5000 4500 4000 3500 3000 2500 2000 1500 1000
YEARS BEFORE PRESENT
Figure 5-2. The global lead production has changed historically in response to
major economic and political events. Increases in lead production (note log
scale) correspond approximately to historical increases in lead emissions shown
in Figure 5-1.
Source: Adapted from Settle and Patterson (1980).
In natural processes, lead is first incorporated in soil in the active root zone, from
which it may be absorbed by plants, leached into surface waters, or eroded into windborne
dusts (National Academy of Sciences, 1980; Chamberlain, 1970; Patterson, 1965; Chow and
Patterson, 1962).
Natural emissions of lead from volcanoes have been estimated by Nriajgu (1979) to be 6400
t/year based on enrichment over crustal abundance. That is, 10 X 109 kg/year of volcanic dust
are produced, with an average concentration of 640 ug/g, or 40 times the crustal abundance of
16 ug/g. The enrichment factor is based on Lepel et al. (1978), who measured lead in the
023PB5/A
5-4
7/13/83
-------
PRELIMINARY DRAFT
plume of the Augustine volcano in Alaska. Settle and Patterson (1980) have calculated
emissions of only 1 t/year, based on a measured Pb/S ratio of 1 X 10 7 and estimated sulfur
emissions of 6 X 10 t/year. This measured Pb/S ratio was from volcanoes reported by
Buat-Menard and Arnold (1978), and is likely to be a better estimate of lead emissions from
volcanoes.
Calculations of natural contributions using geochemical information indicate that natural
sources contribute a relatively small amount of lead to the atmosphere. For example, if the
typical 25 to 40 ug/m3 of rural airborne particulate matter consisted solely of wind-entrained
soils containing 15 M9/9, and rarely more than 30 ug of lead/g, as cited above, then the
natural contribution to airborne lead would range from 0.0004 to 0.0012 ug/m3. It has been
estimated from geochemical evidence that the natural particulate lead level is less than
0.0005 ug/m3 (National Academy of Sciences, 1980; United Kingdom Department of the
Environment, 1974). In fact, levels as low as 0.000076 pg/m3 have been measured at the South
Pole in Anarctica (Maenhaut et al., 1979). In contrast, average lead concentrations in urban
suspended particulate matter range as high as 6 ug/m3 (Akland, 1976; U.S. Environmental
Protection Agency, 1979, 1978). Evidently, most of this urban particulate lead stems from
man-made sources.
5.3 MANMADE SOURCES
5.3.1 Production
Lead occupies an important position in the U.S. economy, ranking fifth among all metals
in tonnage used. Approximately 85 percent of the primary lead produced in this country is
from native mines, although often associated with minor amounts of zinc, cadmium, copper,
bismuth, gold, silver, and other minerals (U.S. Bureau of Mines, 1975). Missouri lead ore
deposits account for approximately 80 to 90 percent of the domestic production. Approximately
40 to 50 percent of annual lead production is recovered and eventually recycled.
5.3.2 Utilization
The 1971-1980 uses of lead are listed by major product category in Table 5-1 (U.S. Bureau
of Mines, 1972-1982). Total utilization averaged approximately 1.36xl06 t/yr over the 10-year
period, with storage batteries and; gasoline additives accounting for ~70 percent of total use.
The gasoline antiknocks listed in Table 5-1 include additives for both domestic and import
markets. The additive fraction of total lead utilization has decreased from greater than 18
percent in 1971-1973 to less than 9.5 percent in 1981. Certain products, especially
batteries, cables, plumbing, weights, and ballast, contain lead that is economically
recoverable as secondary lead. This reserve of lead in use is estimated at 3.8 million metric
023PB5/A 5-5 7/13/83
-------
TABLE 5-1. U.S. UTILIZATION OF LEAD BY PRODUCT CATEGORY (1971-1981), METRIC TONS/YEAR
(U.S. BUREAU OF MINES, 1981, 1982)
Product category
Storage batteries
Gasoline antiknock
additives3
Pigments and ceramics
AMunitlon
Solder
Cable coverings
Caulking lead
Pipe and sheet lead
Type Metal
Brass and bronze
Bearing netals
Other
TOTAL
1971
616,561
239,666
73,701
79,423
63,502
47,998
27,204
41,523
18,876
18,180
14,771
56,958
1.298,383
1972
661,740
252,545
80,917
76,822
64,659
41,659
20,392
37,592
18,089
17,963
14,435
63,124
1,349,846
1973
697,888
248,890
98,651
73,091
65,095
39,006
18,192
40,529
19,883
20,621
14,201
61,019
1,397,876
1974
772,656
227,847
105,405
78,991
60,116
39,387
17,903
34,238
18,608
20,172
13,250
62,106
1,450,679
1975
634,368
• 189,369
71,718
68,098
52,011
28,044
12,966
35,456
14,703
12,157
11,051
54,524
1,176,465
1976
746,085
217,508
95,792
66,659
57,448
14,452
11,317
34,680
13,614
14,207
11,851
68,181
1,351,794
1977
858,099
211,296
90,704
62,043
58,320
13,705
8.725
30,861
11,395
15,148
10,873
64,328
1,435,497
1978
879,274
178,473
91,642
55,776
68,390
13,851
9,909
23,105
10,795
16,502
9,510
75,517
1,432.744
1979
814,332
186,945
90,790
53,236
54,278
16,393
8,017
27,618
10,019
18,748
9,630
58,329
1.358,335
1980
645,357
127,903
78,430
48,662
41,366
13,408
5,684
28,393
8,997
13,981
7,808
50,314
1,070,303
1981
770,152
111,367
80,165
49,514
29,705
12,072
5,522
28,184
7,838
13,306
6,922
52,354
1,167,101
-o
TO
m
r—
»— *
20
o
g
'includes additives for both domestic and export Markets.
-------
PRELIMINARY DRAFT
tons, of which only 0.5 to 0.8 million metric tons are recovered annually. Lead in pigments,
gasoline additives, ammunition, foil, solder, and steel products is widely dispersed and
therefore is largely unrecoverable.
5.3.3 Emissions
Lead or its compounds may enter the environment at any point during mining, smelting,
processing, use, recycling, or disposal. Estimates of the dispersal of lead emissions into
the environment by principal sources indicate that the atmosphere is the major initial
recipient. Estimated lead emissions to the atmosphere are shown in Table 5-2. Mobile and
stationary sources of lead emissions, although found throughout the nation, tend to be
concentrated in areas of high population density, with the exception of smelters. Figure 5-3
shows the approximate locations of major lead mines, primary and secondary smelters and
refineries, and alkyl lead plants (International Lead Zinc Research Organization, 1982).
5.3.3.1 Mobile Sources. The majority of lead compounds found in the atmosphere result from
leaded gasoline combustion. Several reports indicate that transportation sources, which
include light-duty, heavy-duty, and off-highway vehicles, contribute over 80 percent of the
total atmospheric lead (Nationwide [lead] emissions report, 1980, 1979; U.S. Environmental
Protection Agency, 1977). Other mobile sources, including aviation use of leaded gasoline and
diesel and jet fuel combustion, contribute insignificant lead emissions to the atmosphere.
The detailed emissions inventory in Table 5-2 shows that 86 percent of the lead emissions in
the United States are from gasoline combustion. Cass and McRae (1983) assembled emissions
inventory data on the Los Angeles Basin and determined that 83 percent of the fine particle
emissions originated from highway vehicles. Lead is added to gasoline as an antiknock
additive to enhance engine performance in the form of two tetralkyl lead compounds, tetraethyl
and tetramethyl lead (see Section 3.4). Lead is emitted from vehicles primarily in the form
of inorganic particles, although a very small fraction (<10 percent) of lead emissions are
released as volatile organic compounds, i.e., lead alkyls (National Academy of Sciences,
1972).
The factors which affect both the rate of particulate lead emissions and the
physicochemical properties of the emissions are: lead content of the fuel, other additives,
vehicle fuel economy, the driving speed or conditions, and type of vehicle, as well as design
parameters, maintenance, ages of the engine, exhaust, and emission control systems. The major
types of vehicles are light-duty (predominantly cars) and heavy-duty (trucks and buses). The
important properties of the particulate emissions include the total amount emitted, the size
distribution of the particles, and the chemical composition of these particles as a function
of particle size. The most commonly used index of particle size is the mass median equivalent
023PB5/A 5-7 7/13/83
-------
PRELIMINARY DRAFT
TABLE 5-2. ESTIMATED ATMOSPHERIC LEAD EMISSIONS FOR THE
UNITED STATES, 1981, AND THE WORLD
Source category
Gasoline combustion
Waste oil combustion
Solid waste disposal
Coal combustion
Oil combustion
Wood combustion
Gray iron production
Iron and steel production
Secondary lead smelting
Primary copper smelting
Ore crushing and grinding
Primary lead smelting
Other metallurgical
Zn smelting
Ni smelting
Lead alkyl manufacture
Type metal
Portland cement production
Miscellaneous
Total
Annual
U.S.
emissions
(t/yr)
35,000
830
319
950
226
--
295
533
631
30
326
921
54
245
85
71
233
40,739a
Percentage of
U.S. total
emissions
85.9%
2.0
0.8
2.3
0.6
— —
0.7
1.3
1.5
0.1
0.8
2.3
0.1
0.6
0.2
0.2
0.5
100%
Annual
global
emissions
(t/yr)
273,000
8,900
14,000
6,000
4,500
50,000
770
27,000
8,200
31,000
16,000
2,500
7,400
5,900
449,170
Inventory does not include emissions from exhausting workroom air, burning of lead-painted
surfaces, welding of lead-painted steel structures, or weathering of painted surfaces.
Source: For U.S. emissions, Battye (1983), for global emissions, Nriagu (1979).
023PB5/A
5-8
7/13/83
-------
GJ
•o
09
in
01
i
*—5'•*
')T —.^
/ \
^-j—
T '--,
!>
X.
I.J'-^f
—1
yo
a
/'^.
• MINES (15)
A SMELTERS AND REFINERIES (7) *
O SECONDARY SMELTERS AND REFINERIES (56)
• LEAD ALKYL PLANTS (4)
oo
CO
Figure 5-3. Locations of major lead operations in the United States.
Source: International Lead Zinc Research Organization (1982).
-------
PRELIMINARY DRAFT
diameter (MMEO), which is defined as the point in the size distribution of particles such that
half the mass lies on either side of the MMED value (National Air Pollution Control Adminis-
tration, 1970). Table 5-3 summarizes a recent study estimating the participate emission rates
and particle composition for light-duty vehicles operated on a leaded fuel of 1.8 g Pb/gallon
(Hare and Black, 1981). Table 5-4 estimates particulate emission rates for heavy- duty
vehicles (trucks) operated on a leaded fuel of 1.8 g Pb/gallon (Hare and Black, 1981). The
lead content of 1.8 g Pb/gallon was chosen to approximate the lead concentration of leaded
gasoline during 1979 (Table 5-5). Another recent study utilizing similar composite emission
factors provides estimates of motor vehicle lead emissions for large areas (Provenzano, 1978).
Lead occurs, on the average, as PbBrCl in fresh exhaust particles (Hirschler et al.,
1957). This lead compound is 64.2 percent lead by mass and is a common form of lead emitted
due to the presence of the scavengers ethylene dichloride and ethylene dibromide in normal
leaded fuel. PbBrCl has theoretical mass ratios for lead, bromine, and chlorine of 0.64,
0.25, and 0.11, respectively. The particle compositional data in Table 5-3 indicate that mass
ratios for lead, bromine, and chlorine are approximately 0.60, 0.30, and 0.10, respectively,
from both pre- and post-1970 vehicles. Data from another study (Lang et al., 1981), involving
1970-1979 vehicles, indicated that mass ratios for lead, bromine, and chlorine were 0.62,
0.30, and 0.08, respectively.
The fate of emitted lead particles depends upon their particle size (see Section 6.3.1).
Particles initially formed by condensation of lead compounds in the combustion gases are quite
small (well under 0.1 pm in diameter) (Pierson and Brachaczek, 1982). Particles in this size
category are subject to growth by coagulation and, when airborne, can remain suspended in the
atmosphere for 7 to 30 days and travel thousands of miles from their original source
(Chamberlain et al., 1979). Larger particles are formed as the result of agglomeration of
smaller condensation particles and have limited atmospheric lifetimes (Harrison and Laxen,
1981). The largest vehicle-emitted particles, which are greater than 100 urn in diameter, may
be formed by materials flaking off from the surfaces of the exhaust system. As indicated in
Table 5-3, the estimated mass median equivalent diameter of leaded particles from light-duty
vehicles is <0.25 [im, suggesting that such particles have relatively long atmospheric
lifetimes and the potential for long-distance transport. Similar values for MMEO in
automobile exhausts were found in Britain (0.27 urn) (Chamberlain et al. 1979) and Italy (0.33
Mm) (Facchetti and Geiss, 1982). Particles this small deposit by Brownian diffusion and are
generally independent of gravitation.
The size distribution of lead exhaust particles is essentially bimodal (Pierson and
Brachaczek, 1976) and depends on a number of factors, including the particular driving pattern
in which the vehicle is used and its past driving history (Ganley and Springer, 1974; Habibi,
023PB5/A 5-10 7/13/83
-------
PRELIMINARY DRAFT
TABLE 5-3. LIGHT-DUTY VEHICULAR PARTICULATE EMISSIONS*
Rate or property
Exhaust participate emissions, g/mi
Particle mass median equivalent diameter, pm
Data
Pre-1970
0.29
<0.25
by vehicle category
1970 & later
without catalyst
0.13
<0.25
percent of particulate mass as:
Lead (Pb)
Bromine (Br)
Chlorine (Cl)
Trace metals
Carbon (C), total
Sulfate (S04=)
Soluble organics
22 or greater
11 or greater
4 or greater
1
33 or greater
1.3
~30 or less
36 or greater
18 or greater
6 or greater
1 or greater
33 or less
1.3 or greater
-10
*Rate estimates are based on 1.8 Pb/gal fuel.
Source: Hare and Black (1981).
TABLE 5-4. HEAVY-DUTY VEHICULAR PARTICULATE EMISSIONS*
Particulate emissions by model year
Heavy-duty category
Pre-1970
1970 and later
Medium-duty trucks
(6,000 to 10,000 Ib GVW)
Heavy-duty trucks
(over 10,000 Ib GVW)
0.50
0.76
0.40
0.60
*Rate estimates are based on 1.8 g Pb/gal fuel, units are g/mi.
Source: Hare and Black (1981).
023PB5/A
5-11
7/13/83
-------
PRELIMINARY DRAFT
TABLE 5-5. RECENT AND PROJECTED CONSUMPTION OF GASOLINE LEAD
Average lead content
(g/gai)
Gasoline volume
Calendar
year
1975a
1976
1977
1978
1979
1980
1981
1982
1983b
1984
1985
1986
1987
1988
1989
1990
(billions
Total
102.3
107.0
113.2
115.8
111.2
110.8
102.6
100.0
96.1
92.3
89.2
86.1
83.8
81.5
79.2
77.7
of gallons)
Leaded
92.5
87.0
79.7
75.0
68.1
57.5
51.0
40.6
41.7
35.4
29.7
25.3
22.1
19.5
17.0
14.7
Sales
weighted
total
pool
1.62
1.60
1.49
1.32
1.16
0.71
0.59
0.64
0.50
0.50
0.50
0.50
0.50
0.50
0.50
Total
lead Air- lead
(10at) (ng/m3)d
Leaded
1.81
1.97
2.12
2.04
1.90
1.37
1.19
1.44
1.10
1.10
1.10
1.10
1.10
1.10
1.10
0.5 gpg
pooled std
165.6
171.0
168.7
153.3
129.5
78.5
61.0
62.0
48.1
46.1
44.6
43.0
41.9
40.7
39.6
38.8
1.1 gpg
leaded std
___
—
—
—
—
—
—
— H
47.0
39.0
32.7
27.8
24.3
21.4
18.7
16.2
1.23
1.22
1.20
1.13
0.93
0.60,.
0.47^
0.45C
aOata for the years 1975-1982 are taken from U.S. Environmental Protection Agency
(1983b), in which data for 1975-1981 are actual consumption of lead and for 1982,
estimates of consumption.
bData for 1983-1990 are estimates taken from F.R. (1982 October 29).
cEstimated (this work)
Data from Hunt and Neligan (1982), discussed in Chapter 7, are the maximum
quarterly average lead levels from a composite of sampling sites.
023PB5/A
5-12
7/13/83
-------
PRELIMINARY DRAFT
1973; 1970; Ter Haar et al., 1972; Hirschler and Gilbert, 1964; Hirschler et al., 1957). As
an overall average, it has been estimated that during the lifetime of the vehicle,
approximately 35 percent of the lead contained in the gasoline burned by the vehicle will be
emitted as small particles (<0.25 [im MMED), and approximately 40 percent will be emitted as
larger particles (>10 |jm MMED) (Ter Haar et al., 1972). The remainder of the lead consumed in
gasoline combustion is deposited in the engine and exhaust system. Engine deposits are, in
part, gradually transferred to the lubricating oil and removed from the vehicle when the oil
is changed. A flow chart depicting lead-only emissions per gallon of fuel charged into the
engine is shown in Figure 5-4. It is estimated that 10 percent of the lead consumed during
combustion is released into the environment via disposal of used lubricating oil (Piver,
1977). In addition, some of the lead deposited in the exhaust system gradually flakes off, is
emitted in the exhaust as extremely large particles, and rapidly falls into the streets and
roads where it is incorporated into the dust and washed into sewers or onto adjacent soil.
Although the majority (>90 percent on a mass basis) of vehicular lead compounds are
emitted as inorganic particles (e.g., PbBrCl), some organolead vapors (e.g., lead alkyls) are
also emitted. The largest volume of organolead vapors arises from the manufacture, transport,
and handling of leaded gasoline. Such vapors are photoreactive, and their presence in local
atmospheres is transitory, i.e., the estimated atmospheric half-lives of lead alkyls, under
typical summertime conditions, are less than half a day (Nielsen, 1982). Organolead vapors
are most likely to occur in occupational settings (e.g., gasoline transport and handling
operations, gas stations, parking garages) and have been found to contribute less than 10
percent of the total lead present in the atmosphere (Gibson and Farmer, 1981; National Academy
of Sciences, 1972).
The use of lead additives in gasoline, which increased in volume for many years, is now
decreasing as automobiles designed to use unleaded fuel constitute the major portion of the
automotive population (Table 5-1). The decline in the use of leaded fuel is the result of two
regulations promulgated by the U.S. Environmental Protection Agency (F.R., 1973 December 6).
The first required the availability of unleaded fuel for use in automobiles designed to meet
federal emission standards with lead-sensitive emission control devices (e.g., catalytic
converters); the second required a reduction or phase-down of the lead content in leaded
gasoline. Compliance with the phase-down of lead in gasoline has recently been the subject of
proposed rulemakings. The final action (F.R., 1982 October 29) replaced the present 0.5 g/gal
standard for the average lead content of all gasoline with a two-tiered standard for the lead
content of leaded gasoline. Under this proposed rule, large refineries would be required to
meet a standard of 1.10 g/gal for leaded gasoline while certain small refiners would be
subject to a 1.90 g/gal standard until July 1, 1983, at which time they were made subject to
the 1.10 g/gal standard.
023PB5/A 5-13 7/13/83
-------
en
01
'VJB'K
en
i
LEADED FUEL
(Pb = 1.0 g/gal)*
1000 mg (100%)-
TOTAL MASS OF LEAD
CHARGED INTO THE
ENGINE
AUTO
ENGINE
CMC
TAILPIPE DEPOSITION ^ 16% /..
150 mg RETAINED ON
INTERIOR SURFACES OF
ENGINE AND EXHAUST
SYSTEM
m 350 mg Pb EMITTED ;££
m TO ATMOSPHERE AS:$S
'?'•' LEAD AEROSOL WITH '*%
. MASS MEDIAN DIAMETER:
5;:. OF <0.25 Mm, POTENTIAL.-;
i* FOR LONG RANGE M
;; TRANSPRT/PLLUTION'
= 400 mg Pt EMlto TO:;§:
ROADWAY AS PARTICLES i
;;:: WITH MASS MEDIAN .,:^
; DIAMETERS >10 /im wK
LOCALIZED POLLUTION.?;?
-<
o
100 mg Pb RETAINED BY
LUBRICATING OIL
EXHAUST PRODUCTS
(760 mg TOTAL
Pb EMITTED)
Figure 5-4. Estimated lead-only emissions distribution per gallon of combusted fuel.
00
CJ
-------
PRELIMINARY DRAFT
The trend in lead content for U.S. gasolines is shown in Figure 5-5 and Table 5-5. Of
the total gasoline pool, which includes both leaded and unleaded fuels, the average lead
content has decreased 63 percent, from an average of 1.62 g/gal in 1975 to 0.60 g/gal in 1981
(Table 5-5, Figure 5-5). Accompanying the phase-down of lead in leaded fuel has been the
increased consumption of unleaded fuel, from 11 percent of the total gasoline pool in 1975 to
50 percent in 1981 (Table 5-5 and Figure 5-6). Since 1975, when the catalytic converter was
introduced by automobile manufacturers for automotive exhaust emissions control, virtually all
new passenger cars have been certified on unleaded gasoline (with the exception of a few
diesels and a very few leaded-gasoline vehicles). Because of the yearly turnover rate in the
vehicle fleet, the demand for unleaded gasoline is forecast to increase to 58 percent of the
total gasoline pool in 1982 and ~75 percent by 1985. As the demand for unleaded fuel
increases, it may become uneconomical to distribute leaded gasoline for light-duty vehicles in
low-volume localities.
The lead content of leaded gasoline (Table 5-5) is forecast to increase from 1.19 to 1.44
g/gal in 1982 (DuPont de Nemours, 1982). The reason for this increase is that under the 1982
0.5 g/9al total pool standard, refiners could add ever-increasing amounts of lead to each
gallon of leaded gasoline (up to the level at which it would no longer be economically
justified) as the amount of unleaded gasoline produced by the refinery increases. Thus, as
the amount of unleaded gasoline increased, the amount of lead in leaded gasoline could also
increase under the former regulations. The recent EPA decision (F.R., 1982 October 29)
eliminated this practice, thereby ensuring that the amount of lead used in gasoline will
decline after 1982 to 1.1 g/gal. Further decreases in lead emissions from gasoline combustion
will depend on continued reductions in the sales of leaded gasoline.
Data describing the lead consumed in gasoline and average ambient lead levels (composite
of maximum quarterly values) versus calendar year are listed in Table 5-5 and plotted in
Figure 5-7. The 1975 through 1979 composite quarterly lead averages are based on 105
lead-monitoring sites, primarily urban. The 1980 composite average is based on 58 sites with
valid annual data. The EPA National Aerometric Data Base is still receiving the 1980 data.
The linear correlation (Figure 5-8) between lead consumed in gasoline and the composite
maximum average quarterly ambient average lead level is very good with r2 = 0.99. The 1981
and 1982 composite averages shown in Table 5-5 and Figures 5-7 and 5-8 are derived using the
linear equation of Figure 5-6. Between 1975 and 1980, the lead consumed in gasoline decreased
52 percent (from 165,577 metric tons to 78,679 metric tons) while the corresponding composite
maximum quarterly average of ambient lead decreased 51 percent (from 1.23 ug/m3 to 0.60
fjg/m3)- This indicates that control of lead in gasoline over the past several years has
effected a direct decrease in peak ambient lead concentrations, at least for this group of
monitoring sites.
023PB5/A 5-15 7/13/83
-------
2.40
PRELIMINARY DRAFT
2.00
CO
0>
(0
LU
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o
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Z
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1.00 -
0.50 -
0.00
I
I
LEADED FUEL
SALES-WEIGHTED TOTAL
GASOLINE POOL
(LEADED AND UNLEADED
"AVERAGE")
UNLEADED FUEL
I
t
I
1975
1976
1977
1981
1982"
1978 1979 1980
CALENDAR YEAR
Figure 5-5. Trend in lead content of U.S. gasolines, 1975-1982. (DuPont, 1982).
•1982 DATA ARE FORECASTS.
023PB5/A
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PRELIMINARY DRAFT
120
I I
TOTAL GASOLINE SALES
1975 1976 1977
1978 1979 1980
CALENDAR YEAR
1981 1982*
Figure 5-6. Trend in U.S. gasoline sales, 1975-1982. (DuPont, 1982).
•1982 DATA ARE FORECASTS.
023PB5/A
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g
&
I
i
1
200 r-
180
200
LU
O
UJ
3
I
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160
140
120
100
80
60
40
20 _
180
160
140
120
100
80
60
40
20 -
I I I I
I I
AMBIENT LEAD CONCENTRATION
LEAD CONSUMED IN GASOLINE
1 I I I
I
I I
I
1.20
1.10 §
2
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
O
1976 1978
1977 1978 1979 1980
CALENDAR YEAR
1981* 1982*
Figure 5-7. Lead consumed in gasoline (Du Pont, 1982) and ambient lead con-
centrations, 1975-1982. (Hunt and Neligan, 1982).
•DASHED LINES ARE ESTIMATES.
5"18 7/01/83
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180 F=
160 —
140
I
g
3
.2 120
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o
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60
40
20
AVERAGE Pb = 6.93 x 10* (Pb CONSUMED) + 0.05
r2 = 0.99
1978
1975
1979
'1980
1981
y
• 1982*
I
I
I
I
I
0.20 0.40 0.60 0.80 1.00 1.20
COMPOSITE MAXIMUM QUARTERLY AVERAGE LEAD LEVELS, pg/m*
Figure 5-8. Relationship between lead consumed in gasoline and composite maximum
quarterly average lead levels, 1975-1980.
•1981 AND 1982 DATA ARE ESTIMATES.
5-19
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PRELIMINARY DRAFT
Furthermore, the equation in Figure 5-8 implies that the complete elimination of lead
from gasoline might reduce the composite average of the maximum quarterly lead concentrations
at these stations to 0.05 ug/m3, a level typical of concentrations reported for nonurban
stations in the U.S. (see Chapter 7). Even this level of 0.05 ug/m3 is regarded as evidence
of human activity since it is at least two orders of magnitude higher than estimates of
geochemical background lead concentrations discussed in Section 5.2.
5.3.3.2 Stationary Sources. As shown in Table 5-2 (based on 1982 emission estimates), solid
waste incineration and combustion of waste oil are the principal contributors of lead
emissions from stationary sources, accounting for two-thirds of stationary source emissions.
The manufacture of consumer products such as lead glass, storage batteries, and lead additives
for gasoline also contributes significantly to stationary source lead emissions. Since 1970,
the quantity of lead emitted from the metallurgical industry has decreased somewhat because of
the application of control equipment and the closing of several plants, particularly in the
zinc and pyrometallurgical industries.
A new locus for lead emissions emerged in the mid-1960s with the opening of the "Viburnum
Trend" or "New Lead Belt" in southeastern Missouri. The presence of ten mines and three
accompanying lead smelters in this area makes it the largest lead-producing district in the
world and has moved the United States into first place among the world's lead-producing
nations.
Although some contamination of soil and water occurs as a" result of such mechanisms as
leaching from mine and smelter wastes, quantitative estimates of the extent of this
contamination are not available. Spillage of ore concentrates from open trucks and railroad
cars, however, is known to contribute significantly to contamination along transportation
routes. For example, along two routes used by ore trucks in southeastern Missouri, lead
levels in leaf litter ranged from 2000 to 5000 (jg/g at the roadway, declining to a fairly
constant 100 to 200 ug/g beyond about 400 ft from the roadway (Wixson et al., 1977).
Another possible source of land or water contamination is the disposal of participate
lead collected by air pollution control systems. The potential impact on soil and water
systems from the disposal of dusts collected by these control systems has not been quantified.
5.4 SUMMARY
There is no doubt that atmospheric lead has been a component of the human environment
since the earliest written record of civilization. Atmospheric emissions are recorded in
glacial ice strata and pond and lake sediments. The history of these global emissions seems
closely tied to production of lead by industrially oriented civilizations.
023PB5/A 5-20 7/13/83
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Although the amount of lead emitted from natural sources is a subject of controversy,
even the most liberal estimate (25 X 103 t/year) is dwarfed by the global emissions from
anthropogenic sources (450 X 103 t/year).
Production of lead in the United States has remained steady at about 1.2 X 106 t/year for
the past decade. The gasoline additive share of this market has dropped from 18 to 9.5
percent during the period 1971 to 1981. The contribution of gasoline lead to total
atmospheric emissions has remained high, at 85 percent, as emissions from stationary sources
have decreased at the same pace as from mobile sources. The decrease in stationary source
emissions is due primarily to control of stack emissions, whereas the decrease in mobile
source emissions is a result of switchover to unleaded gasolines. The decreasing use of lead
in gasoline is projected to continue through 1990.
023PB5/A 5-21 7/13/83
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5.5 REFERENCES
Akland, G. G. (1976) Air quality data for metals, 1970 through 1974, from the National Air
Surveillance Network. Research Triangle Park, NC: U.S. Environmental Protection Agency,
Office of Research and Development; EPA report no. EPA 600/ 4-76-041. Available from*
NTIS, Springfield, VA; PB 260905.
Baes, C. F. , III; Ragsdale, H. L. (1981) Age-specific lead distribution in xylem rings of
three tree genera in Atlanta, Georgia. Environ. Pollut. Ser. B 2: 21-36.
Battye, B. (1983) Lead emissions inventory, 1981 [Memo to John Haines]. January 31. Avail-
able for inspection at: U.S. Environmental Protection Agency, Environmental Criteria and
Assessment Office, Research Triangle Park, NC.
Boutron, C. (1982) Atmospheric trace metals in the snow layers deposited at the South Pole
from 1928 to 1977. Atmos. Environ. 16: 2451-2459.
Buat-Menard, P.; Arnold, M. (1978) The heavy metal chemistry of atmospheric particulate matter
emitted by Mount Etna volcano. Geophys. Res. Lett. 5: 245-248.
Cass, G. R.; McRae, G. J. (1983) Source-receptor reconciliation of routine air monitoring data
for trace metals: an emission inventory assisted approach. Environ. Sci. Technol. 17;
129-139.
Chamberlain, A. C. (1970) Interception and retention of radioactive aerosols by vegetation.
Atmos. Environ. 4: 57-77.
Chamberlain, A. C.; Heard, M. J.; Little, P.; Wiffen, R. D. (1979) The dispersion of lead from
motor exhausts. In: Proceedings of the Royal Society discussion meeting, pathways of
pollutants in the atmosphere; 1977; London, United Kingdom. Philos. Trans. R. Soc. London
290: 577-589.
Chow, T. J. ; Patterson, C. C. (1962) The occurrence and significance of lead isotopes in
pelagic sediments. Geochim. Cosmochim. Acta 26: 263-308.
Christensen, E. R. ; Chien, N. (1981) Fluxes of arsenic, lead, zinc, and cadmium to Green Bay
and Lake Michigan sediments. Environ. Sci. Technol. 15: 553-558.
Edgington, D. N. ; Robbins, J. A. (1976) Records of lead deposition in Lake Michigan sediments
since 1800. Environ. Sci. Technol. 10: 266-274.
F.R. (1973 December 6) 38: 33734-33741. Regulation of fuel additives: control of lead ad-
ditives in gasoline.
F.R. (1982 October 29) 47: 49322-49334. 40 CFR Part 80: Regulation of fuels and fuel ad-
ditives: final rule.
Galloway, J. N.; Likens, G. E. (1979) Atmospheric enhancement of metal deposition in
Adirondack lake sediments. Limnol. Oceanogr. 24: 427-433.
Ganley, J. T.; Springer, G. S. (1974) Physical and chemical characteristics of particulates In
spark ignition engine exhaust. Environ. Sci. Technol. 8: 340-347.
023PB5/A 5-22 7/13/83
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Gibson, M. J.; Farmer, J. G. (1981) Tetraalkyl lead in the urban atmosphere of Glasgow.
Environ. Technol. Lett. 2: 521-530.
Habibi, K. (1970) Characterization of particulate lead in vehicle exhaust—experimental tech-
niques. Environ. Sci. Technol. 4: 239-248.
Habibi, K. (1973) Characterization of particulate matter in vehicle exhaust. Environ. Sci.
Technol. 7: 223234.
Hare, C. T. ; Black, F. M. (1981) Motor vehicle particulate emission factors. Presented at:
74th meeting and exposition of the Air Pollution Control Association; June. Pittsburgh,
PA: Air Pollution Control Association; paper no. 81-56.5.
Harrison, R. M.; Laxen, D. P. H. (1981) Lead pollution: causes and control. New York, NY:
Chapman and Hall.
Herron, M. M.; Langway, C. C., Jr.; Weiss, H. V.; Cragin, J. H. (1977) Atmospheric trace
metals and sulfate in the Greenland ice sheet. Geochim. Cosmochim. Acta 41: 915-920.
Hirschler, D. A.; Gilbert, L. F. (1964) Nature of lead in automobile exhaust gas. Arch.
Environ. Health 8: 297-313.
Hirschler, D. A.; Gilbert, L. F.; Lamb, F. W.; Niebylski, L. M. (1957) Particulate lead com-
pounds in automobile exhaust gas. Ind. Eng. Chem. 49: 1131-1142.
Hunt, W. F.; Neligan, R. E. (1982) National air quality and emissions trends report, 1974-
1980. Research Triangle Park, NC: U.S. Environmental Protection Agency, Office of Air
Quality Planning and Standards.
International Lead Zinc Research Organization (1982) Locations of major lead operations in the
United States [Map]. New York, NY: International Lead Zinc Research Organization.
Jaworowski, Z.; Bysiek, M.; Kownacka, L. (1981) Flow of metals into the global atmosphere.(
Geochim. Cosmochim. Acta 45: 2185-2199.
Lang, J. M.; Snow, L.; Carlson, R.; Black, F.; Zweidinger, R.; Tejada, S. (1981) Characteriza-
tion of particulate emissions from in-use gasoline-fueled motor vehicles. New York, NY:
Society of Automotive Engineers; SAE paper no. 811186.
Lepel, E. A.; Stefansson, K. M.; Zoller, W. H. (1978) The enrichment of volatile elements in
the atmosphere by volcanic activity: Augustine volcano 1976. J. Geophys. Res. 83:
6213-6220.
Levering, T. G., ed. (1976) Lead in the environment. Washington, DC: U.S. Department of the
Interior, Geological Survey: Geological Survey professional paper no. 957. Available
from: GPO, Washington, DC; S/N 024-001-02911-1.
Maenhaut, W.; Zoller, W. H.; Duce, R. A.; Hoffman, G. L. (1979) Concentration and size distri-
bution of particulate trace elements in the south polar atmosphere. J. Geophys. Res. 84:
2421-2431.
Murozumi, M.; Chow, T. J.; Patterson, C. (1969) Chemical concentrations of pollutant lead aer-
osols, terrestrial dusts and sea salts in Greenland and Antarctic snow strata. Geochim.
Cosmochim. Acta 33: 1247-1294.
023PB5/A 5-23 7/13/83
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National Academy of Sciences. (1972) Lead: airborne lead in perspective. Washington, DC:
National Academy of Sciences. (Biologic effects of atmospheric pollutants.)
National Academy of Sciences, Committee on Lead in the Human Environment. (1980) Lead in the
human environment. Washington, DC: National Academy of Sciences.
National Air Pollution Control Administration. (1970) Control techniques for particulate air
pollutants. Washington, DC: U.S. Department of Health, Education and Welfare; publication
no. AP-51. Available from: NTIS, Springfield, VA; PB 190253.
Nationwide [lead] emissions report. (1979) From: NEDS, National Emissions Data System [Data
base]. Research Triangle Park, NC: U.S. Environmental Protection Agency, Office of Air
Quality Planning and Standards. Printout. Available for inspection at: U.S. Environmental
Protection Agency, Environmental Criteria Assessment Office, Research Triangle Park, NC.
Nationwide [lead] emissions report. (1980) From: NEDS, National Emissions Data System [Data
base]. Research Triangle Park, NC: U.S. Environmental Protection Agency, Office of Air
Quality Planning and Standards. Printout. Available for inspection at: U.S. Environmental
Protection Agency, Environmental Criteria Assessment Office, Research Triangle Park, NC.
Ng, A.; Patterson, C. (1981) Natural concentrations of lead in ancient Arctic and Antarctic
ice. Geochim. Cosmochim. Acta 45: 2109-2121.
Ng, A.; Patterson, C. C. (1982) Changes of lead and barium with time in California off-shore
basin sediments. Geochim. Cosmochim. Acta 46: 2307-2321.
Nielsen, T. (1982) Atmospheric occurence of organolead compounds. In: Grandjean, P., ed. Bio-
logical effects of organolead compounds. Boca Raton, FL: CRC Press; PAGES. (IN PRESS)
Nriagu, J. 0. (1979) Global inventory of natural and anthropogenic emissions of trace metals
to the atmosphere. Nature (London) 279: 409-411.
Patterson, C. C. (1965) Contaminated and natural lead environments of man. Arch. Environ
Health. 11: 344-360.
Patterson, C. C. (1980) An alternative perspective - lead pollution in the human environment:
origin, extent and significance. In: National Academy of Sciences, Committee on Lead in
the Human Environment. Lead in the human environment. Washington, DC: National Academy of
Sciences; pp. 265-350.
Patterson, C. C. (1983) Criticism of "Flow of metals into the global atmosphere [Letter],
Geochim. Cosmochim. Acta 47: 1163-1168.
Pierson, W. R.; Brachaczek, W. W. (1976) Particulate matter associated with vehicles on the
road. Warrendale, PA: Society of Automotive Engineers; SAE technical paper no. 760039
SAE transactions 85: 209-227.
Pierson, W. R.; Brachaczek, W. W. (1982) Particulate matter associated with vehicles on the
road II. J. Aerosol Sci. VOL: PAGES. (IN PRESS)
Piver, W. T. (1977) Environmental transport and transformation of automotive-emitted lead
Environ. Health Perspect. 19: 247-259.
023PB5/A 5-24 7/13/83
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Provenzano, G. (1978) Motor vehicle lead emissions in the United States: an analysis of
important determinants, geographic patterns and future trends. J. Air Pollut. Control
Assoc. 28: 1193-1199.
Rolfe, G. L. (1974) Lead distribution in tree rings. For. Sci. 20: 283-286.
Servant, J. (1982) Atmospheric trace elements from natural and industrial sources. London,
United Kingdom: University of London, Monitoring and Assessment Research Centre.
Settle, D. M.; Patterson, C. C. (1980) Lead in albacore: guide to lead pollution in Americans.
Science (Washington D.C.) 207: 1167-1176.
Shacklette, H. T.; Hamilton, J. C. ; Boerngen, J. G. ; Bowles, J. M. (1971) Elemental composi-
tion of surficial materials in the conterminous United States: an account of the amounts
of certain chemical elements in samples of soils and other regoliths. Washington, DC:
U.S. Department of the Interior, Geological Survey; Geological Survey professional paper
no. 574-D.
Shirahata, H.; Elias, R. W.; Patterson, C. C.; Koide, M. (1980) Chronological variations in
concentrations and isotopic compositions of anthropogenic atmospheric lead in sediments
of a remote subalpine pond. Geochim. Cosmochim. Acta 44: 149-162.
Symeonides, C. (1979) Tree-ring analysis for tracing the history of pollution: application to
a study in northern Sweden. J. Environ. Qual. 8: 482-486.
Ter Haar, G. L.; Lenane, D. L. ; Hu, J. N.; Brandt, M. (1972) Composition, size, and control of
automotive exhaust particulates. J. Air Pollut. Control Assoc. 22: 3946.
U.S. Bureau of Mines. (1972-1982) Lead. In: Minerals yearbook. Volume I: Metals and minerals.
Washington, DC: U.S. Government Printing Office.
U.S. Environmental Protection Agency. (1977a) Control techniques for lead air emissions:
volumes I and II. Durham, NC: U.S. Environmental Protection Agency, Office of Air Quality
Planning and Standards; EPA report nos. EPA-450/2-77-012A and EPA-450/2-77-012B.
Available from: NTIS, Springfield, VA; PB80-197544 and PB80-197551.
U.S. Environmental Protection Agency, Health Effects Research Lab. (1977b) Air quality cri-
teria for lead. Research Triangle Park, NC: U.S. Environmental Protection Agency,
Criteria and Special Studies Office; EPA report no. EPA-600/8-77-017. Available from:
NTIS, Springfield, VA; PB 280411.
U.S. Environmental Protection Agency. (1978) Air quality data for metals 1975 from the
National Air Surveillance Networks. Research Triangle Park, NC: U.S. Environmental
Protection Agency; Office of Research and Development; EPA report no. EPA-600/4-78-059.
Available from: NTIS, Springfield, VA; PB 293106.
U.S. Environmental Protection Agency. (1979) Air quality data for metals 1976 from the
National Air Surveillance Networks. Research Triangle Park, NC: U.S. Environmental
Protection Agency, Office of Research and Development; EPA report no. EPA-600/4-79-054.
Available from NTIS, Springfield, VA; PB80-147432.
U.S. Environmental Protection Agency. (1983) Summary of lead additive reports for refineries.
Washington, DC: U.S. Environmental Protection Agency, Office of Mobile Source: draft
report.
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United Kingdom Department of the Environment, Central Unit on Environmental Pollution. (1974)
Lead in the environment and its significance to man. London, United Kingdom: Hep
Majesty's Stationery Office; pollution paper no. 2.
Wixson, B. G. ; Bolter, E.; Gale, N. L.; Hemphill, 0. D.; Jennett, J. C. (1977) The Missouri
lead study: an interdisciplinary investigation of environmental pollution by lead and
other heavy metals from industrial southeastern Missouri: vols. 1 and 2. Washington, DC:
National Science Foundation. Available from: NTIS, Springfield, VA: PB 281859 and PR
274242.
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6. TRANSPORT AND TRANSFORMATION
6.1 INTRODUCTION
This chapter describes the transition from the emission of lead particles into the
atmosphere to their ultimate deposition on environmental surfaces, i.e. , vegetation, soil, or
water. At the source, lead emissions are typically around 10,000 ug/m3 (see Section 5.3.3),
while in city air, lead values are usually between 0.1 and 10 ug/m3 (Dzubay et al., 1979;
Reiter et al., 1977; also see Chapter 7). These reduced concentrations are the result of
dilution of effluent gas with clean air and the removal of particles by wet or dry deposition.
Characteristically, lead concentrations are highest in confined areas close to sources and are
progressively reduced by dilution or deposition in districts more removed from sources.
At any particular location and time, the concentration of lead found in the atmosphere
depends on the proximity to the source, the amount of lead emitted from sources, and the
degree of mixing provided by the motion of the atmosphere. It is possible to describe
quantitatively the physics of atmospheric mixing in a variety of ways and, with some limiting
assumptions, to develop simulation models that predict atmospheric lead concentrations. These
models are not sensitive to short-term variations in air motion over a period of weeks or
months because these variations are suppressed by integration over long periods of time.
In highly confined areas such as parking garages or tunnels, atmospheric lead
concentrations can be ten to a thousand times greater than values measured near roadways or in
urban areas. In turn, atmospheric lead concentrations are usually about 2% times greater in
the central city than in residential suburbs. Rural areas have even lower concentrations.
Because lead emissions in the United States have declined dramatically in the past few
years, the older lead concentration data on which recent dispersion studies are based may seem
not to be pertinent to existing conditions. Such studies do in fact illustrate principles of
atmospheric dispersion and may validly be applied to existing concentrations of lead, which
are described in Section 7.2.1.1.
Transformations which may occur during dispersion are physical changes in particle size
distribution, chemical changes from the organic to the inorganic phase, and chemical changes
in the inorganic phase of lead particles. Particle size distribution stabilizes within a few
hundred kilometers of the sources, although atmospheric concentration continues to decrease
with distance. Concentrations of organolead compounds are relatively small (1 to 6 percent of
total lead) except in special situations where gasoline is handled or where engines are
started cold within confined areas. Ambient organolead concentrations decrease more rapidly
than inorganic lead, suggesting conversion from the organic to the inorganic phase during
transport. Inorganic lead appears to convert from lead halides and oxides to lead sulfates.
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Lead is removed from the atmosphere by wet or dry deposition. The mechanisms of dry
deposition have been incorporated into models that estimate the flux of atmospheric lead to
the Earth's surface. Of particular interest is deposition on vegetation surfaces, since this
lead may be incorporated into food chains. Between wet and dry deposition, it is possible to
calculate an atmospheric lead budget that balances the emission inputs discussed in Section
5.3.3. with deposition outputs.
6.2 TRANSPORT OF LEAD IN AIR BY DISPERSION
6.2.1 Fluid Mechanics of Dispersion
Particles in air streams are subject to the same principles of fluid mechanics as
particles in flowing water (Friedlander, 1977). On this basis, the authors of several texts
have described the mathematical arguments for the mixing of polluted air with clean air
(Benarie, 1980; Dobbins, 1979; Pasquill, 1974). The first principle is that of diffusion
along a concentration gradient. If the airflow is steady and free of turbulence, the rate of
mixing is determined by the diffusivity of the pollutant. In the case of gases, this
diffusivity is an inherent property of the molecular forces between gases. For particles,
diffusivity is a property of Brownian movement, hence a function of particle size and
concentration. For both cases, the diffusivity for dilute media is a constant (Dobbins,
1979).
If the steady flow of air is interrupted by obstacles near the ground, turbulent eddies
or vortices may be formed. Diffusivity is no longer constant but may be influenced by factors
independent of concentrations, such as windspeed, atmospheric stability, and the nature of the
obstacle. By making generalizations of windspeed, stability, and surface roughness, it is
possible to construct models using a variable transport factor called eddy diffusivity (K), in
which K varies in each direction, including vertically. There is a family of K-theory models
that describe the dispersion of particulate pollutants.
The simplest K-theory model assumes that the surface is uniform and the wind is steady;
thus, turbulence is predictable for various conditions of atmospheric stability (Pasquill,
1974). This model produces a Gaussian plume, called such because the concentration of the
pollutant decreases according to a normal or Gaussian distribution in both the vertical and
horizontal directions. These models have some utility and are the basis for most of the air
quality simulations performed to date (Benarie, 1980). However, the assumptions of steady
windspeed and smooth surface place constraints on their utility.
Several approaches have been used to circumvent the constraints of the Gaussian models.
Some have been adapted for studying long range transport (LRT) (more than 100 km) of
pollutants. Johnson (1981) discusses 35 LRT models developed during the 1970s to describe the
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dispersion of atmospheric sulfur compounds. A few models that address specific problems of
local and regional transport merit further discussion because they emphasize the scope of the
modeling problem.
One family of models is based on the conservative volume element approach, where volumes
of air are seen as discrete parcels having conservative meteorological properties, such as
water vapor mixing ratio, potential temperature, and absolute vorticity (Benarie, 1980). The
effect of pollutants on these parcels is expressed as a mixing ratio. These parcels of air
may be considered to move along a trajectory that follows the advective wind direction. These
models are particularly suitable for dealing with surface roughness, but they tend to
introduce artifact diffusion or pseudodiffusion, which must be suppressed by calculation (Egan
and Mahoney, 1972; Liu and Seinfeld, 1975; Long and Pepper, 1976).
An approach useful for estimating dispersion from a roadway derives from the similarity
approach of Prandtl (1927). A mixing length parameter is related to the distance traveled by
turbulent eddies during which violent exchange of material occurs. This mixing length is
mathematically related to the square root of the shear stress between the atmosphere and the
surface. Richardson and Procter (1925) formulated these concepts in a law of atmospheric
diffusion which was further extended to boundary layer concepts by Obukhov (1941). At the
boundary layer, the turbulent eddy grows and its energy decreases proportionately with time
and distance away from the source.
Although physical descriptions of turbulent diffusion exist for idealized circumstances
such as isolated roadways and flat terrain, the complex flow and turbulence patterns of cities
has defied theoretical description. The permeability of street patterns and turbulent eddy
development in street canyons are two major problem areas that make modeling urban atmospheres
difficult. Kotake and Sano (1981) have developed a simulation model for describing air flow
and pollutant dispersion in various combinations of streets and buildings on two scales. A
small scale, 2 to 20 m, is used to define the boundary conditions for 2 to 4 buildings and
associated roadways. These subprograms are combined on a large scale of 50 to 500 meters.
Simulations for oxides of nitrogen show nonlinear turbulent diffusion, as would be expected.
The primary utility of this program is to establish the limits of uncertainty, the first step
toward making firm predictions. It is likely that the development of more complete models of
dispersion in complex terrains will become a reality in the near future.
An important point in this discussion is that none of the models described above have
been tested for lead. The reason for this is simple. All of the models require sampling
periods of 2 hours or less in order for the sample to conform to a well-defined set o1
meteorological conditions. In most cases, such a sample would be below the detection limits
023PB6/A 6-3 7/13/83
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for lead. The common pollutant used to test models is S02, which can be measured over very
short, nearly instantaneous, time periods. The question of whether gaseous S02 can be used as
a surrogate for particulate lead in these models remains to be answered.
6.2.2 Influence of Dispersion on Ambient Lead Concentrations
Dispersion within confined situations, such as parking garages, residential garages and
tunnels, and away from expressways and other roadways not influenced by complex terrain
features depends on emission rates and the volume of clean air available for mixing. These
factors are relatively easy to estimate and some effort has been made to describe ambient lead
concentrations which can result under selected conditions. On an urban scale, the routes of
transport are not clearly defined, but can be inferred from an isopleth, i.e., a plot
connecting points of identical ambient concentrations. These plots always show that lead
concentrations are maximum where traffic density is highest.
Dispersion beyond cities to regional and remote locations is complicated by the fact that
there are no monitoring network data from which to construct isopleths, that removal by
deposition plays a more important role with time and distance, and that emissions from many
different geographic location's sources converge. Some techniques of source reconciliation
are described, but these become less precise with increasing distance from major sources of
lead. Dispersion from point sources such as smelters and refineries is described with
isopleths in the manner of urban dispersion, although the available data are notably less
abundant.
6.2.2.1 Confined and Roadway Situations. Obviously, the more source emissions are diluted by
clean air, the lower ambient air concentrations of lead will be. Ingalls and Garbe (1982)
used a variety of box and Gaussian plume models to calculate typical levels of automotive air
pollutants that might be present in microscale (within 100 meters of the source) situations
with limited ventilation. Table 6-1 shows a comparison of six exposure situations, recomputed
for a flat-average lead emission factor of 6.3 mg/km for roadway situations and 1.0 mg/min for
garage situations. The roadway emission factor chosen corresponds roughly to values chosen by
Dzubay et al. (1979) and Pierson and Brachaczek (1976) scaled to 1979 lead-use statistics.
The parking garage factor was estimated from roadway factors by correction for fuel
consumption (Ingalls and Garbe, 1982).
Confined situations, with low air volumes and little ventilation, allow automotive
pollutant concentrations to reach one to three orders of magnitude higher than are found in
open air. Thus, parking garages and tunnels are likely to have considerably higher ambient
lead concentrations than are found in expressways with high traffic density or in city
streets. Purdue et al. (1973) found total lead levels of 1.4 to 2.3 ug/m3 in five of six U.S.
cities in 1972. In similar samples from an underground parking garage, total lead was 11 to
12 pg/m3.
023PB6/A 6-4 7/13/83
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PRELIMINARY DRAFT
Table 6-1 also shows that the high concentration of automotive lead near roadways
declines significantly at distances greater than 100 meters. Dzubay et al. (1979) found lead
concentrations of 4 to 20 ug/m3 in air over Los Angeles freeways in 1976; at nearby sites off
the freeways, concentrations of 0.3 to 4.7 |jg/m3 were measured.
TABLE 6-1. SUMMARY OF MICROSCALE CONCENTRATIONS
Data are recalculated from Ingalls and Garbe (1982) using 1979 lead emission factors. They
show that air lead concentrations in a garage or tunnel can be two or three orders of magni-
tude higher than on streets or expressways. Typical conditions refer to neutral atmospheric
stability and average daily traffic volumes. Severe conditions refer to maximum hourly
traffic volume with atmospheric inversion. Data are in ug/m3. Emission rates are given in
parentheses.
Situation
Air lead
concentration
Residential garage (1 mg Pb/min)
Typical (30 second idle time) 80
Severe (5 min idle time) 670
Parking garage (1 mg Pb/min)
Typical 40
Severe 560
Roadway tunnel (6.3 mg Pb/km)
Typical 11
Severe 29
Street canyon (sidewalk receptor) (6.3 mg Pb/km)
Typical a) 800 vehicles/hr 0.4
b) 1,600 vehicles/hr 0.9
Severe a) 800 vehicles/hr 1.4
b) 1,600 vehicles/hr 2.8
On expressway (wind: 315 deg. rel., 1 m/sec) (6.3 mg Pb/km)
Typical 2.4
Severe 10
Beside expressway
Severe
1,
(6.
1
10
100
000
3 mg Pb/km)
meter
meters
meters
meters
30
~8~
6
2
0
min
.25
Annual
1.2
1.0
0.3
0.03
average
023PB6/A
6-5
7/13/83
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PRELIMINARY DRAFT
Tiao and Hillmer (1978) and Ledolter and Tiao (1979) have analyzed 3 years (1974-1977) of
ambient air lead data from one site on the San Diego Freeway in Los Angeles, California.
Participate lead concentrations were measured at five locations: in the median strip and at
distances of 8 and 30 to 35 meters from the road edge on both sides of the road. Average lead
concentrations at the 35 meter point were two- to four-fold lower than at the 8 meter location
(Tiao and Hillmer, 1978). An empirical model involving traffic count and traffic speed, which
are related to road emissions, required only windspeed as a predictor of dispersion
conditions.
Witz et al. (1982) found that meteorological parameters in addition to windspeed, such as
inversion frequency, inversion duration, and temperature, correlate well with ambient levels
of lead. At a different site near the San Diego freeway in Los Angeles, monthly ambient
particulate lead concentrations and meteorological variables were measured about 100 meters
from the roadway through 1980. Multiple linear regression analysis showed that temperature at
6 AM, windspeed, wind direction, and a surface-based inversion factor were important variables
in accurately predicting monthly average lead concentrations. In this data set, lead values
for December were about five-fold higher than those measured in the May to September summer
season, suggesting that seasonal variations in wind direction and the occurrence of
surface-based inversions favor high winter lead values. Unusually high early morning
temperatures and windspeed during the winter increased dispersion and reduced lead
concentration. The success of this empirical model depends on the interplay of windspeed and
atmospheric stability (Witz et al., 1982).
6.2.2.2 Dispersion of Lead on an Urban Scale. In cities, air pollutants including lead that
are emitted from automobiles tend to be highest in concentration in high traffic areas. Most
U.S. cities have a well-defined central business district (CBD) where lead concentrations are
highest. To illustrate the dispersion of lead experienced in cities, two cases are presented
below.
Trijonis et al. (1980) reported lead concentrations for seven sites in St. Louis,
Missouri; annual averages for 1977 are shown in Figure 6-1. Values around the CBD are
typically two to three times greater than those found in the outlying suburbs in St. Louis
County to the west of the city. Bradow (1980) presented results from the Regional Air
Monitoring System Gaussian plume model (Turner, 1979) for St. Louis for the 1977 calendar
year. Figure 6-1 also presents isopleths for lead concentration calculated from that model.
The general picture is one of peak concentrations within congested commercial districts which
gradually decline in outlying areas. However, concentration gradients are not steep, and the
whole urban area has levels of lead above 0.5 ug/m3.
023PB6/A 6-6 7/13/83
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PRELIMINARY DRAFT
ST. CHARLES COUNTY. MO
92,954
MADISON COUNTY. ILL
250,934
ST. LOUIS COUNTY, MO
951.353
ST. CLAIR COUNTY
285.176
Figure 6-1. Isopleths are shown for annual average paniculate lead in
RAM Model calculations predict lead concentrations in St. Louis for 1977.
Numerical values below place names are 1970 population counts for these
areas.
Source: Calculated from Bradow (1980) on the basis of a fleet average lead
emissions factor of 54 mg/mile for 1977.
023PB6/A
6-7
7/01/83
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PRELIMINARY DRAFT
For the South Coast Basin of Southern California, the area of high traffic density is
more widespread than is characteristic of many cities. Ambient concentrations of lead tend to
be more uniform. For example, Figures 6-2 and 6-3 show the average daily traffic by grid
square and the contour plots of annual average lead concentration, respectively, for 1969
(Kawecki, 1978). In addition, Figure 6-3 shows annual average lead measured at eight sites In
the Basin for that year. It is clear that the central portion had atmospheric particulate
lead concentrations in the range of 3 ng/m3; the outer areas were about 1 to 2 pg/m3.
Reiter et al. (1977) have shown similar results for the town of Fort Collins, Colorado
for a 5.5-hr period in May of 1973. In that study, modeling results showed maximum lead
concentrations in the center of town around 0.25 ug/m3, which decreased to 0.1 ug/m3 in the
outermost region. Presumably, still lower values would be found at more remote locations
Apparently, then, lead in the air decreases 2^-fold from maximum values in center city
areas to well populated suburbs, with a further 2-fold decrease in the outlying areas. These
modeling estimates are generally confirmed by measurement in the cases cited above and in the
data presented in Section 7.2.1.
6.2.2.3 Dispersion from Smelter and Refinery Locations. The 15 mines and 7 primary smelters
and refineries shown in Figure 5-3 are not located in urban areas. Most of the 56 secondary
smelters and refineries are likewise non-urban. Consequently, dispersion from these point
sources should be considered separately, but in a manner similar to the treatment of urban
regions. In addition to lead concentrations in air, concentrations in soil and on vegetation
surfaces are often used to determine the extent of dispersion away from smelters and
refineries.
6.2.2.4 Dispersion to Regional and Remote Locations. Beyond the immediate vicinity of urban
areas and smelter sites, lead in air declines rapidly to concentrations of 0.1 to 0.5 ug/m3
Two mechanisms responsible for this change are dilution with clean air and removal by
deposition (Section 6.4). In the absence of monitoring networks that might identify the
sources of lead in remote areas, two techniques of source identification have been used.
Vector gradient analysis was attempted by Everett et al. (1979) and source reconciliation has
been reported by Sievering et al. (1980) and Cass and McRae (1983). A third technique, isoto-
pic composition, has been used to identify anthropogenic lead in air, sediments, soils
plants, and animals in urban, rural, and remote locations (Chow et al. 1975), but this
technique is not discussed here because it provides no information on the mechanism of
transport.
023PB6/A 6-8
7/13/83
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PRELIMINARY DRAFT
342
937
BOO
55
WE!
118
*•*•—•-
710
1037
983
10
TLOS
363
•^-\
1306
1812
1971
1295
ANGELI
2492
*SAI
\ 531
\
>
596
1644
2006
1324
ES
•)
2596
JTAMC
2179
1809
k '
|N
\753
)
X433
\ 94
V^H
207
919
1607
2714
2833
MICA
1609
1490
86
339
•Q
1659
2982
•
4562
2409
1672 (
' LENNOX
1371
^^
1071
396
5
1738
3RRAN
1428
rP;
iCJ
1*^363
/
5
6
2S6
692
EN DA
1668
OS AN
3626
1868
KYNW
1797
2335
CE
2411
-*u>
3*s\*
(T
301
6
143
fPAS/
.E
1178
1696
GELES
1088
2043
FOOD
2159
3133
2099
MG BEX
383
^V
V,
4
4
kDENA
900
1666
720
799
881
997
705
kCH
929
\ 226
1
0
487
1327
854
294
635
1499
1128
1329
655
V64
X
0
1
t)AZ
420
1413
•WES
347
272
534
1759
*AI\
1610
4
4
USA
265
674
TCOV
218
114
194
772
AHEIM
-
1082
0
0
24
356
INA
111
6
12
146
41
§ GARDEN GROVE
1060
1447
•
136
SANTA ANA
1142
946
k.
• ^s
1004
187
,196
203
0
0
Figure 6-2. Spatial distribution of surface street and freeway traffic in the Los
Angeles Basin (103 VMT/day) for 1979.
Source: Kawecki (1978).
023PB6/A
6-9
7/01/83
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PRELIMINARY DRAFT
KEY TO CONTOUR CONCENTRATIONS
Figure 6-3. Annual average suspended lead concentrations for 1969 in the Los
Angeles Basin, calculated from the model of Cass (1975). The white zones between
the patterned areas are transitional zones between the indicated concentrations.
Source: Kawecki (1978).
023PB6/A
6-10
7/01/83
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PRELIMINARY DRAFT
In vector gradient analysis, the sampler is oriented to the direction of the incoming
wind vector, and samples are taken only during the time the wind is within a 30° arc of that
vector. Other meteorological data are taken continuously. As the wind vector changes, a
different sampler is turned on. A 360° plot of concentration vs. wind direction gives the
direction from which the pollutant arrives at that location. Only one report of the use of
this technique for lead occurs in the literature (Everett et al., 1979), and analysis of this
experiment was complicated by the fact that in more than half the samples, the lead con-
centrations were below the detection limit. The study was conducted at Argonne National
Laboratory and the results reflected the influence of automobile traffic east and northeast of
this location.
Source reconciliation is based on the concept that each type of natural or anthropogenic
emission has a unique combination of elemental concentrations. Measurements of ambient air,
properly weighted during multivariate regression analysis, should reflect the relative amount
of pollutant derived from each of several sources (Stolzenberg et al., 1982). Sievering et
al. (1980) used the method of Stolzenberg et al. (1982) to analyze the transport of urban air
from Chicago over Lake Michigan. They found that 95 percent of the lead in Lake Michigan air
could be attributed to various anthropogenic sources, namely coal fly ash, cement manufacture,
iron and steel manufacture, agricultural soil dust, construction soil dust, and incineration
emissions. This information alone does not describe transport processes, but the study was
repeated for several locations to show the changing influence of each source.
Cass and McRae (1983) used source reconciliation in the Los Angeles Basin to interpret
1976 NFAN data (see Sections 4.2.1 and 7.2.1.1) based on emission profiles from several
sources. They developed a chemical element balance model, a chemical tracer model, and a
multivariate statistical model. The chemical element balance model showed that 20 to 22
percent of the total suspended particle mass could be attributed to highway sources. The
chemical tracer model permitted the lead concentration alone to represent the highway profile,
since lead comprised about 12 percent of the mass of the highway generated aerosol. The
multivariate statistical model used only air quality data without source emission profiles to
estimate stoichiometric coefficients of the model equation. The study showed that single
element concentrations can be used to predict the mass of total suspended particles.
A type of source reconciliation, chemical mass balance, has been used for many years
by geochemists in determining the anthropogenic influence on the global distribution of ele-
ments. Two studies that have applied this technique to the transport of lead to remote
areas are Murozumi et al. (1969) and Shirahata et al. (1980). In these studies, the influence
of natural or crustal lead was determined by mass balance, and the relative influence of
023PB6/A 6-11 7/13/83
-------
PRELIMINARY DRAFT
anthropogenic lead was determined. In the Shirahata et al. (1980) study, the influence of
anthropogenic lead was confirmed quantitatively by analysis of isotopic compositions in the
manner of Chow et al. (1975).
Harrison and Williams (1982) determined air concentrations, particle size distributions,
and total deposition flux at one urban and two rural sites in England. The urban site, which
had no apparent industrial, commercial or municipal emission sources, had an air lead
concentration of 3.8 ug/m3, whereas the two rural sites were about 0.15 ug/m3. The average
particle size became smaller toward the rural sites, as the mass median equivalent diameter
(MMED) shifted downward from 0.5 \im to 0.1 pm. The total deposition flux will be discussed
in Section 6.4.2.
Knowledge of lead concentrations in the oceans and glaciers provides some insight into
the degrees of atmospheric mixing and long range transport. Tatsumoto and Patterson (1963),
Chow and Patterson (1966), and Schaule and Patterson (1980) measured dissolved lead
concentrations in sea water off the coast of California, in the Central North Atlantic (near
Bermuda), and in the Mediterranean, respectively. The profile obtained by Schaule and
Patterson (1980) is shown in Figure 6-4. Surface concentrations in the Pacific (14 ng/kg)
were found to be higher than those of the Mediterranean or the Atlantic, decreasing abruptly
with depth to a relatively constant level of 1 to 2 ng/kg. The vertical gradient was found to
be much less in the Atlantic. Tatsumoto and Patterson (1963) had earlier estimated an average
surface lead concentration of 200 ng/kg in the northern hemispheric oceans. Chow and
Patterson (1966) revised this estimate downward to 70 ng/kg. Below the mixing layer, there
appears to be no difference between lead concentrations in the Atlantic and Pacific. These
investigators calculated that industrial lead currently is being added to the oceans at about
10 times the rate of introduction by natural weathering, with significant amounts being
removed from the atmosphere by wet and dry deposition directly into the ocean. Their data
suggest considerable contamination of surface waters near shore, diminishing toward the open
ocean (Chow and Patterson, 1966).
Duce et al. (1975), Taylor (1964), and Maenhaut et al. (1979) have investigated trace
metal concentrations (including lead) in the atmosphere in remote northern and southern
hemispheric sites. The natural sources for such atmospheric trace metals include the oceans
and the weathering of the Earth's crust, while the anthropogenic source is particulate air
pollution. Enrichment factors for concentrations relative to standard values for the oceans
and the crust were calculated (Table 6-2); the mean crustal enrichment factors for the
North Atlantic and the South Pole are shown in Figures 6-5 and 6-6. The significance
of the comparison in Figure 6-6 is that 90 percent of the particulate pollutants in the global
023PB6/A 6-12 7/13/83
-------
PRELIMINARY DRAFT
rrnrrn
• DISSOLVED Pb
Q PARTICULATE Pb
I I I I I I I I
5000
2 4 6 8 10 12 14 16 0
CONCENTRATION, ng Pb/kg
Figure 6-4. Profile of lead concentrations in the
central northeast Pacific. Values below 1000 m are
an order of magnitude lower than reported by
Tatsumoto and Patterson (1963) and Chow and
Patterson (1966).
Source: Schaule and Patterson (1980).
023PB6/A
6-13
7/01/83
-------
80 W
PRELIMINARY DRAFT
60; 40°
Figure 6-5. Midpoint collection location for at-
mospheric samples collected from R.V. Trident
north of 30 N, 1970-1972.
Source: Duce et al. (1975); Zoller et al. (1974).
023PB6/A
ELEMENT
Figure 6-6. The EFcrust values for atmospheric
trace metals collected in the North Atlantic
westerlies and at the South Pole. The horizontal
bars represent the geometric mean enrichment fac-
tors, and the vertical bars represent the geometric
standard deviation of the mean enrichment factors.
The EFcrust for lead at the South Pole is based on
the lowest lead concentration (0.2 mg/scm).
Source: Duce et al. (1975); Zoller et al. (1974).
6-14
7/01/83
-------
PRELIMINARY DRAFT
troposphere are injected in the northern hemisphere (Robinson and Robbins, 1971). Since the
residence times for particles in the troposphere (Poet et al., 1972) are much less than the
interhemispheric mixing time, it is unlikely that significant amounts of particulate
pollutants can migrate from the northern to the southern hemisphere via the troposphere;
however, this does not rule out stratospheric transfer.
TABLE 6-2. ENRICHMENT OF ATMOSPHERIC AEROSOLS OVER CRUSTAL ABUNDANCE
Using the crustal abundances of Taylor (1964), the enrichment of atmospheric aerosols, rela-
tive to aluminum, has been calculated by Duce et al. (1975). An enrichment factor signifi-
cantly above one implies a source other than crustal rock for the element in question.
Element
Al
Si
Fe
Co
Mn
Cr
V
Zn
Cu
Cd
Pb
Sb
Se
Concentration
range, ng/m3
8-370
0:0008-0.011
3.4-220
0.006-0.09
0.05-5.4
0.07-1.1
0.06-14
0.3-27
0.12-10
0.003-0.62
0.10-64
0.05-0.64
0.09-0.40
Enrichment
factor3
1.0
0.8
1.4
2.4
2.6
11
17
110
120
730
2,200
2,300
10,000
aBased on the geometric mean of the concentration.
Murozumi et al. (1969) have shown that long range transport of lead particles emitted
from automobiles has significantly polluted the polar glaciers. They collected samples of
snow and ice from Greenland and the Antarctic. As shown in Figure 6-7, they found that the
concentration of lead varied inversely with the geological age of the sample. The authors
023PB6/A 6-15 7/13/83
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PRELIMINARY DRAFT
T
0.20 h-
AGE OF SAMPLES
Figure 6-7. Lead concentration profile in snow
strata of Northern Greenland.
Source: Murozumi et al. (1969).
attribute the gradient increase after 1750 to the Industrial Revolution and the accelerated
increase after 1940 to the increased use of lead alkyls in gasoline. The most recent levels
found in the Antarctic snows were, however, less than those found in Greenland by a factor of
10 or more. Before 1940 the concentrations in the Antarctic were below the detectable level
(<0.001 ug/kg) and have risen to 0.2 ug/kg in recent snow.
Jaworowski (1967) found that lead concentrations in two glaciers have increased by a
factor of 10 during the last century. The concentrations in the most recent ice layers were
extremely high (148 ug/kg). Jaworowski et al. (1975) also studied stable and radioactive
pollutants from ice samples from the Storbreen glaciers in Norway. The mean stable lead
concentration in Storbreen glacier ice in the 12th century was 2.1 ug/kg. The mean for more
recent samples was 9.9 ug/kg. Around 1870 the average lead concentration in Norwegian glacier
ice was 5.9 ^9/kg, whereas that for glaciers in Poland was 5.0 ug/kg. A century later, the
mean concentration in the Norwegian glacier was 9.9 ug/kg, while the mean concentration in the
Polish glacier reached 148 ug/kg. Jaworowski et al. (1975) attributed the large increase of
lead concentrations in the Polish glacier to local sources.
023PB6/A
6-16
7/01/83
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PRELIMINARY DRAFT
Evidence from remote areas of the world suggests that lead and other fine particle
components are transported substantial distances, up to thousands of kilometers, by general
weather systems. The degree of surface contamination of remote areas with lead depends both
on weather influences and on the degree of air contamination. However, even in remote areas,
man's primitive activities can play an important role in atmospheric lead levels. Davidson et
al. (1982) have shown that there are significant levels of fine particle lead, up to 0.5
pg/m3, in remote villages in Nepal. The apparent source is combustion of dried yak dung,
which contains small amounts of naturally occurring lead derived from plant life in those
remote valleys.
6.3 TRANSFORMATION OF LEAD IN AIR
6.3.1 Particle Size Distribution
Whitby et al. (1975) placed atmospheric particles into three different size regimes: the
nuclei mode (<0.1 urn), the accumulation mode (0.1 to 2 urn) and the large particle mode (>2
urn). At the source, lead particles are generally in the nuclei and large particle modes.
Large particles are removed by deposition close to the source and particles in the nuclei mode
diffuse to surfaces or agglomerate while airborne to form larger particles of the accumulation
mode. Thus it is in the accumulation mode that particles are dispersed great distances.
In Figure 6-8, size distributions for lead particles in automobile exhaust are compared
with those found in air samples at a receptor site in Pasadena, California, "not in the
immediate influence of traffic" (Huntzicker et al., 1975). The authors conclude that the
large particle mode found in exhaust (>9 urn) is severely attenuated in ambient air samples.
Therefore, large particle lead must be deposited near roadways. Similar data and conclusions
had been reported earlier by Daines et al. (1970).
Pierson and Brachaczek (1976) reported particle size distributions that were larger in
ambient air than in a roadway tunnel, where vehicle exhaust must be dominant (see Figure 6-9).
The large particles may have been deposited in the roadway itself and small particles may have
agglomerated during transport from the roadway to the immediate roadside. Since 40 to 1,000
urn particles are found in gutter debris (Figure 6-10), deposition of large particles appears
confirmed.
Little and Wiffen (1977, 1978) reported a MMEO for lead of 0.1 pm in the roadway but
0.3 pi" * meter from the road edge in an intercity expressway in England. Further, particle
size distributions reported by Huntzicker et al. (1975) show bimodal distributions for on-
roadway samples, with peak mass values at about 0.1 and 10 urn. For off-roadway Pasadena
samples, there is no evidence of bimodality and only a broad maximum in lead mass between 0.1
and 1 urn.
023PB6/A 6-17 7/13/83
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PRELIMINARY DRAFT
2
I
o
o
cc
UJ
I-
01
5
5
UJ
_j
O
Q.
o
o
o
QC
UJ
10.0
8.0
6.0
4.0
2.0
1.0
0.8
0.6
0.4
I I
PASADENA Pb
(11/72)
(2/74)
I I I I
20
40
60
80
90
95
MASS IN PARTICLES < O . percent
P
Figure 6-8. Cumulative mass distribution for lead particles in
auto exhaust and at an urban site in Pasadena, Calif, some
distance from high traffic density roadways.
Source: Huntzicker et al. (1975).
023PB6/A
6-18
7/01/83
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PRELIMINARY DRAFT
10
8 -
6
|
0.8
0.6
0.4
0.2
0.1
I T
Pb
1 I T
AMBIENT AEROSOL Pb
I
I I
I
VEHICLE AEROSOL Pb
I Illlllll 1 1
1 10 ~ 50 80 90 96 98 99
% OF MASS IN PARTICLES SMALLER THAN STATED p%d
Figure 6-9. Particulate lead size distribution measured at the
Allegheny Mountain Tunnel, Pennsylvania Turnpike, 1975.
Source: Pierson and Brachaczek (1976).
023PB6/A
6-19
7/01/83
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PRELIMINARY DRAFT
»
cc
LU
fc
<
Q
3
o
1000
500
100
60
10
I I I I
I I I
I I
I I II
0.1 1 2 6 10 50 90 95 9899
PERCENT OF MASS IN PARTICLES SMALLER THAN STATED SIZE
99.9
Figure 6-10. Particle size distributions of substances in gutter
debris. Rotunda Drive, Dearborn, Michigan.
Source: Pierson and Brachaczek (1976).
023PB6/A
6-20
7/01/83
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PRELIMINARY DRAFT
In cities or in rural areas, there is a remarkable consistency in lead particle size
range. For example, Robinson and Ludwig (1964) report cascade impactor MMED values for lead
ranging from 0.23 to 0.3 urn in six U.S. cities and three rural areas as shown in Table 6-3.
Stevens et al. (1978) have reported dichotomous sampler data for six U.S. cities, as shown in
Table 6-4, and Stevens et al. (1980, 1982) have reported similar results for remote locations.
Virtually every other study reported in the literature for Europe, South America, and Asia has
come to the conclusion that ambient urban and rural air contains predominantly fine particles
(Cholak et al., 1968; De Jonghe and Adams, 1980; Durando and Aragon, 1982; Lee et al., 1968;
Htun and Ramachandran, 1977).
TABLE 6-3. COMPARISON OF SIZE DISTRIBUTIONS OF LEAD-CONTAINING
PARTICLES IN MAJOR SAMPLING AREAS
Distribution
25%a
No. of
Sample area samples
Chicago
Cincinnati
Philadelphia
Los Angeles
Pasadena
San Francisco
Vernon (rural)
Cherokee (rural)
Mojave (rural)
12
7
7
8
7
3
5
1
1
0
0
0
0
0
0
0
0
Avg.
•19(7)b
.15(3)
.14(3)
.16(7)
.18
.11
.17(4)
.25
-
0.
0.
0.
0.
0.
0.
0.
Range
10-0.29
09-0.24
09-0.25
10-0.22
05-0.25
06-0.13
12-0.22
Avg.
0.30
0.23
0.24
0.26
0.24
0.25
0.24
0.31
0.27
by particle size, urn
MMED
0.
0.
0.
0.
0.
0.
0.
Range
16-0.64
16-0.28
19-0.31
19-0.29
08-0. 32
15-0.31
18-0.32
75%a
Avg.
0.40(10)
0.44
0.41
0.49(7)
0.48(6)
0.45(2)
0.40
0.71
0.34
Range
0.28-0.
0.30-0.
0.28-0.
0.39-0.
0.13-0.
0.44-0.
0.28-0.
63
68
56
60
67
46
47
*% refers to the percentile of the mass distribution. Thus in the column labeled 25% are the
particle sizes at which 25% of the particle mass is in smaller sizes. Similarly, the 75%
column contains values of particle sizes at which 75% of the mass is in smaller sizes.
bNumbers in parentheses indicate number of samples available for a specific value when dif-
ferent from total number of samples.
Source: Robinson and Ludwig (1964).
023PB6/A
6-21
7/13/83
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PRELIMINARY DRAFT
TABLE 6-4. DISTRIBUTION OF LEAD IN TWO SIZE FRACTIONS AT
SEVERAL SITES IN THE UNITED STATES
(ug/m3)
Location
New York, NY
Philadelphia, PA
Charlestown, W. WA
St. Louis, MO
Portland, OR
Glendora, CA
Average
Date
2/1977
2-3/1977
4-8/1976
12/1975
12/1977
3/1977
Fine
1.1
0.95
0.62
0.83
0.87
0.61
Coarse
0.18
0.17
0.13
0.24
0.17
0.09
F/C ratio
6.0
5.6
4.6
3.4
5.0
6.7
5.2
Source: Stevens et al. (1978).
It appears that lead particle size distributions are stabilized close to roadways and
remain constant with transport into remote environments (Gillette and Winchester, 1972).
6.3.2 Organic (Vapor Phase) Lead in Air
Although lead additives used in gasoline are less volatile than gasoline itself (see
Section 3.4), small amounts may escape to the atmosphere by evaporation from fuel systems or
storage facilities. Tetraethyllead (TEL) and tetramethyllead (TML) photochemically decompose
when they reach the atmosphere (Huntzicker et al., 1975; National Air Pollution Control
Administration, 1965). The lifetime of TML is longer than that of TEL. Laveskog (1971) found
that transient peak concentrations of organolead up to 5,000 ug/m3 in exhaust gas may be
reached in a cold-started, fully choked, and poorly tuned vehicle. If a vehicle with such
emissions were to pass a sampling station on a street where the lead level might typically be
0.02 to 0.04 ug/m3, a peak of about 0.5 ug/m3 could be measured as the car passed by. The
data reported by Laveskog were obtained with a procedure that collected very small (100 ml)
short-time (10 min) air samples. Harrison et al. (1975) found levels as high as 0.59 pg/m3
(9.7 percent of total lead) at a busy gasoline service station in England. Grandjean and
Nielsen (1977), using GC-MS techniques, found elevated levels (0.1 ug/"i3) of TML in city
streets in Denmark and Norway. These authors attributed these results to the volatility of
TML compared with TEL.
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A number of studies have used gas absorbers behind filters to trap vapor-phase lead
compounds. Because it is not clear that all the lead captured in the backup traps is, in
fact, in the vapor phase in the atmosphere, "organic" or "vapor phase" lead is an operational
definition in these studies. Purdue et al. (1973) measured both particulate and organic lead
in atmospheric samples. They found that the vapor phase lead was about 5 percent of the total
lead in most samples. The results are consistent with the studies of Huntzicker et al. (1975)
who reported an organic component of 6 percent of the total airborne lead in Pasadena for a
3-day period in June, 1974, and of Skogerboe (1975), who measured fractions in the range of 4
to 12 percent at a site in Fort Collins, Colorado. It is noteworthy, however, that in an
underground garage, total lead concentrations were approximately five times those in ambient
urban atmospheres, and the organic lead increased to approximately 17 percent.
Harrison et al. (1979) report typical organolead percentages in ambient urban air of 1 to
6 percent. Rohbock et al. (1980) reported higher fractions, up to 20 percent, but the data
and interpretations have been questioned by Harrison and Laxen (1980). Rohbock et al. (1980)
and De Jonghe and Adams (1980) report one to two orders of magnitude decrease in organolead
concentrations from the central urban areas to residential areas.
6.3.3 Chemical Transformations of Inorganic Lead in Air
Lead is emitted into the air from automobiles as lead halides and as double salts with
ammonium halides (e.g., PbBrCl • 2NH4C1). From mines and smelters, PbS04, PbO-PbS04, and PbS
appear to be the dominant species. In the atmosphere, lead is present mainly as the sulfate
with minor amounts of halides. It is not completely clear just how the chemical composition
changes in transport.
Biggins and Harrison (1978, 1979) have studied the chemical composition of lead particles
in exhaust and in city air in England by X-ray diffractometry. These authors reported that
the dominant exhaust forms were PbBrCl, PbBrCl'2NH4C1, and a-2PbBrCl'NH4C1, in agreement with
the earlier studies of Hirschler and Gilbert (1964) and Ter Haar and Bayard (1971).
At sampling sites in Lancaster, England, Biggins and Harrison (1978, 1979) found
PbS04'(NH4)2S04, and PbS04-(NH4)2BrCl together with minor amounts of the lead halides and
double salts found in auto exhaust. These authors suggested that emitted lead halides react
with acidic gases or aerosol components (S02 or H2S04) on filters to form substantial levels
of sulfate salts. It is not clear whether reactions with S04 occurs in the atmosphere or on
the sample filter.
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PRELIMINARY DRAFT
The ratio of Br to Pb is often cited as an indication of automotive emissions. From the
mixtures commonly used in gasoline additives, the mass Br/Pb ratio should be about 0.386 if
there has been no fractionation of either element (Harrison and Sturges, 1983). However,
several authors have reported loss of halide, preferentially bromine, from lead salts in
atmospheric transport (Dzubay and Stevens, 1973; Pierrard, 1969; Ter Haar and Bayard, 1971).
Both photochemical decomposition (Lee et al., 1971; Ter Haar and Bayard, 1971) and acidic gas
displacement (Robbins and Snitz, 1972) have been postulated as mechanisms. Chang et al.
(1977) have reported only very slow decomposition of lead bromochloride in natural sunlight;
currently the acid displacement of halide seems to be the most likely mechanism. O'Connor
et al. (1977) have reported no loss in bromine,in comparison of roadside and suburban-rural
aerosol samples from western Australia; low levels of S02 and sulfate aerosol could account
for that result. Harrison and Sturges (1983) warn of several other factors that can alter the
Br/Pb ratio. Bromine may pass through the filter as hydrogen bromide gas, lead may be
retained in the exhaust system, or bromine may be added to the atmosphere from other sources,
such as marine aerosols. They concluded that Br/Pb ratios are only crude estimates of
automobile emissions, and that this ratio would decrease with distance from the highway from
0.39 to 0.35 less proximate sites and 0.25 in suburban residential areas.
Habibi et al. (1970) studied the composition of auto exhaust particles as a function of
particle size. Their main conclusions follow:
1. Chemical composition of emitted exhaust particles is related to
particle size.
a. Very large particles greater than 200 urn have a
composition similar to lead-containing material deposited
in the exhaust system, confirming that they have been
emitted from the exhaust system. These particles contain
approximately 60 to 65 percent lead salts, 30 to 35
percent ferric oxide (Fe203), and 2 to 3 percent soot and
carbonaceous material. The major lead salt is lead
bromochloride (PbBrCl), with (15 to 17 percent) lead oxide
(PbO) occurring as the 2PbO-PbBrCl double salt. Lead
sulfate and lead phosphate account for 5 to 6 percent of
these deposits. (These compositions resulted from the
combustion of low-sulfur and low-phosphorus fuel.)
b. PbBrCl is the major lead salt in particles of 2 to 10 um
equivalent diameter, with 2PbBrCl-NH4Cl present as a minor
constituent.
c. Submicrometer-sized lead salts are primarily 2PbBrCl-NH4Cl.
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PRELIMINARY DRAFT
2. Lead-halogen molar ratios in particles of less than 10 urn MMED
indicate that much more halogen is associated with these solids
than the amount expected from the presence of 2PbBrCl-NH4C1, as
identified by X-ray diffraction. This is particularly true for
particles in the 0.5 to 2 urn size range.
3. There is considerably more soot and carbonaceous material
associated with fine-mode particles than with coarse mode
particles re-entrained after having been deposited after
emission from the exhaust system. This carbonaceous material
accounts for 15 to 20 percent of the fine particles.
4. Particulate matter emitted under typical driving conditions is
rich in carbonaceous material. There is substantially less
such material emitted1 under continuous hot operation.
5. Only small quantities of 2PbBrCl-NH4Cl were found in samples
collected at the tailpipe from the hot exhaust gas. Its
formation therefore takes place primarily during cooling and
mixing of exhaust with ambient air.
Foster and Lott (1980) used X-ray diffractometry to study the composition of lead
compounds associated with ore handling, sintering, and blast furnace operations around a lead
smelter in Missouri. Lead sulfide was the main constituent of those samples associated with
ore handling and fugitive dust from open mounds of ore concentrate. The major constituents
from sintering and blast furnace operations appeared to be PbS04 and PbO-PbS04, respectively.
6.4 REMOVAL OF LEAD FROM THE ATMOSPHERE
Before atmospheric lead can have any effect on organisms or ecosystems, it must be
transferred from the air to a surface. For natural ground surfaces and vegetation, this
process may be either dry or wet deposition.
6.4.1 Dry Deposition
6.4.1.1 Mechanisms of Dry Deposition. Transfer by dry deposition requires that the particle
move from the main airstream through the boundary layer to a surface. The boundary layer is
defined as the region of minimal air flow immediately adjacent to that surface. The thickness
of the boundary layer depends mostly on the windspeed and roughness of the surface.
Airborne particles do not follow a smooth, straight path in the airstream. On the
contrary, the path of a particle may be affected by micro-turbulent air currents, gravitation,
or its own inertia. There are several mechanisms which alter the particle path sufficient to
cause transfer to a surface. These mechanisms are a function of particle size, windspeed, and
surface characteristics.
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PRELIMINARY DRAFT
Particles larger than a few micrometers in diameter are influenced primarily by
sedimentation, where the particle accelerates downward until aerodynamic drag is exactly
balanced by gravitational force. The particle continues at this velocity until it reaches a
surface. Sedimentation is not influenced by windspeed or surface characteristics. Particles
moving in an airstream may be removed by impaction whenever they are unable to follow the
airstream around roughness elements of the surface, such as leaves, branches, or tree trunks.
In this case, the particle moves parallel to the airstream and strikes a surface perpendicular
to the airstream. A related mechanism, turbulent inertia! deposition, occurs when a particle
encounters turbulence within the airstream causing the particle to move perpendicular to the
airstream. It may then strike a surface parallel to the airstream. In two mechanisms, wind
eddy diffusion and interception, the particle remains in the airstream until it is transferred
to a surface. With wind eddy diffusion, the particle is transported downward by turbulent
eddies. Interception occurs when the particle in the airstream passes within one particle
radius of a surface. This mechanism is more a function of particle size than windspeed. The
final mechanism, Brownian diffusion, is important for very small particles at very low
windspeeds. Brownian diffusion is motion, caused by random collision with molecules, in the
direction of a decreasing concentration gradient.
Transfer from the main airstream to the boundary layer is usually by sedimentation or
wind eddy diffusion. From the boundary layer to the surface, transfer may be by any of the
six mechanisms, although those which are independent of windspeed (sedimentation,
interception, Brownian diffusion) are more likely.
6.4.1.2 Dry deposition models. A particle influenced only by sedimentation may be considered
to be moving downward at a specific velocity usually expressed in cm/sec. Similarly,
particles transported to a surface by any mechanism are said to have an effective deposition
velocity (Vd), which is measured not by rate of particle movement but by accumulation on a
surface as a function of air concentration. This relationship is expressed in the equation:
vd = j/c
where J is the flux or accumulation expressed in ng/cm2-s and C is the air concentration in
ng/cm3. The units of V . become cm/sec.
Several recent models of dry deposition have evolved from the theoretical discussion of
Fuchs (1964) and the wind tunnel experiments of Chamberlain (1966). From those early works,
it was obvious that the transfer of particles from the atmosphere to the Earth's surface
involved more than rain or snow. The models of Slinn (1982) and Davidson et al. (1982)
are particularly useful for lead deposition and were strongly influenced by the theoretical
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PRELIMINARY DRAFT
discussions of fluid dynamics by Friedlander (1977). Slinn's model considers a multitude of
vegetation parameters to find several approximate solutions for particles in the size range of
0.1 to 1.0 |jm. In the absence of appropriate field studies, Slinn (1982) estimates deposition
velocities of 0.01 to 0.1 cm/sec.
The model of Davidson et al. (1982) is based on detailed vegetation measurements and wind
data to predict a Vd of 0.05 to 1.0 cm/sec. Deposition velocities are specific for each
vegetation type. This approach has the advantage of using vegetation parameters of the type
made for vegetation analysis in ecological studies (density, leaf area index (LAI), height,
diameter) and thus may be applicable to a broad range of vegetation types for which data are
already available in the ecological literature.
Both models show a decrease in deposition velocity with decreasing particle size down to
about 0.1 to 0.2 urn, followed by an increase in V. with decreasing diameter from 0.1 to 0.001
cm/sec. On a log plot of diameter vs. V., this curve is v-shaped, and the plots of several
vegetation types show large changes (10X) in minimum Vd, although the minima commonly occur at
about the same particle diameter (Figure 6-11).
In summary, it is not correct to assume that air concentration and particle size alone
•x
determine the flux of lead from the atmosphere to terrestrial surfaces. The type of vegetation
canopy and the influence of the canopy on windspeed are important predictors of dry
deposition. Both of these models predict deposition velocities more than one order of
magnitude lower than reported in several earlier studies (e.g., Sehmel and Hodgson* 1976).
6.4.1.3 Calculation of Dry Deposition. The data required for calculating the flux of lead
from the atmosphere by dry deposition are leaf area index, windspeed, deposition velocity, and
air concentration by particle size. The LAI should be total surface rather than upfacing
surface, as used in photosynthetic productivity measurements. Leaf area indices should also
be expressed for the entire community rather than by individual plant, in order to incorporate
variations in density. Some models use a more generalized surface roughness parameter, in
which case the deposition velocity may also be different.
The value selected for Vd depends on the type of vegetation, usually described as either
short (grasses or shrubs) or tall (forests). For particles with an MMED of about 0.5, Hicks
(1980) gives values for tall vegetation deposition velocity from 0.1 to 0.4 cm/sec. Lannefors
and Hansson (1983) estimated values of 0.2 to 0.5 cm/sec in the particle size range of 0.06 to
2.0 urn in a coniferous forest. For lead, with an MMED of 0.55 urn, they measured a deposition
velocity of 0.41.
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PRELIMINARY DRAFT
I I I Mill I I I II
UPPER LIMIT:
NO RESISTANCE BELOW AND
ATMOSPHERIC DIFFUSION FROM
1 cm TO 1 m
LOWER LIMIT:
ONLY BROWN) AN BELOW AND
ATMOSPHERIC DIFFUSION ABOVE
INDICATED HEIGHT
— — 4.0
p-PARTICLE DENSITY
zQ« ROUGHNESS HEIGHT
U ' FRICTION VELOCITY
10
10''
10
10"' 1
PARTICLE DIAMETER,
Figure 6-11. Predicted deposition velocities at 1 m for ^*=30 cm s"1
and particle densities of 1, 4, and 11.5 g cm'9.
Source: Sehmel (1980).
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6.4.1.4 Field Measurements of Dry Deposition on Surrogate and Natural Surfaces. Several in-
vestigators have used surrogate surface devices similar to those described in Section 4.2.2.4.
These data are summarized in Table 6-5. The few studies available on deposition to vegetation
surfaces show deposition rates comparable to those of surrogate surfaces and deposition velo-
cities in the range predicted by the models discussed above. In Section 6.4.3, these data are
used to show that global emissions are in approximate balance with global deposition. It is
reasonable that future refinements of field measurements and model calculations will permit
more accurate estimates of dry deposition in specific regions or under specific environmental
conditions.
TABLE 6-5. SUMMARY OF SURROGATE AND VEGETATION SURFACE DEPOSITION OF LEAD
Flux
Depositional surface ng Pb/cm2-day
Air cone
ng/m3
Deposition velocity
cm/sec Reference
Tree leaves (Paris) 0.38
Tree leaves (Tennessee) 0.29-1.2
Plastic disk (remote 0.02-0.08
California)
Plastic plates
(Tennessee)
0.29-1.5
1. Servant, 1975.
2. Lindberg et al., 1982.
3. Eli as and Davidson, 1980.
4. Lindberg and Harriss, 1981.
5. Davidson et al., 1981.
6. Davidson et al., 1982.
7. Lannefors et al., 1983.
13-31
110
0.086
0.05-0.4
0.05-0.06
1
2
3
Tree leaves (Tennessee)
Snow (Greenland)
Grass (Pennsylvania)
Coniferous forest (Sweden)
—
0.004
—
0.74
110
0.1-0.2
590
21
0.005
0.1
0.2-1.1
0.41
4
5
6
7
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6.4.2 Wet Deposition
Wet deposition includes removal by rainout and washout. Rainout occurs when particulate
matter is present in the supersaturated environment of a growing cloud. The small particles
(0.1 to 0.2 urn) act as nuclei for the formation of small droplets, which grow into raindrops
(Junge, 1963). Droplets also collect particles under 0.1 (jm by Brownian motion and by the
water-vapor gradient. The nucleation process may also occur on particulate matter present
below cloud level, producing droplets large enough to be affected by sedimentation. These
processes are referred to as rainout. Washout, on the other hand, occurs when falling
raindrops collect particles by diffusion and impaction on the way to the ground. Although
data on the lead content of precipitation are rather limited, those that do exist indicate a
high variability.
Results on lead scavenging by washout are conflicting. In a laboratory study employing
simulated rainfall, Edwards (1975) found that less than 1 percent of auto exhaust lead
particles could be removed by washout. However, Ter Haar et al. (1967) found that intense
rainfall removed most of the atmospheric lead. As a result, the lead content of rain water is
smaller for intense rainfall than in steady showers, presumably because the air contains
progressively less lead. It is not clear which of the two phenomena, nucleation or washout,
is responsible.
Lazrus et al. (1970) sampled precipitation at 32 U.S. stations and found a correlation
between gasoline used and lead concentrations in rainfall in each area. Similarly, there is
probably a correlation between lead concentration in rainfall and distance from large
stationary point sources. The authors pointed out that at least twice as much lead is found
in precipitation as in water supplies, implying the existence of a process by which lead is
removed from the soil solution after precipitation reaches the ground. Russian studies
(Konovalov et al., 1966) point to the insolubility of lead compounds in surface waters and
suggest removal by natural sedimentation and filtration.
Atkins and Kruger (1968) conducted a field sampling program in Palo Alto, California, to
determine the effectiveness of sedimentation, impaction, rainout, and washout in removing lead
from the atmosphere. Rainfall in the area averages approximately 33 cm/year and occurs
primarily during the late fall and winter months. Airborne concentrations at a freeway site
varied from 0.3 MS/1"3 to a maximum of 19 pg/m3 in the fall and winter seasons, and were a
maximum of 9.3 ug/m3 in the spring. During periods of light rainfall in the spring, the
maximum concentration observed was 7.4 ug/m3. More than 90 percent of the lead reaching the
surface during the one-year sampling period was collected in dry fallout. Wet deposition
accounted for 5 to 10 percent of the lead removal at the sampling sites.
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PRELIMINARY DRAFT
Andren et al. (1975) evaluated the contribution of wet and dry deposition of lead in a
study of the Walker Branch Watershed in Oak Ridge, Tennessee, during the period June 1973 to
July 1974. The mean precipitation in the area is approximately 130 cm/yr. Results reported
for the period January through June 1974 are presented in Table 6-6. Wet deposition
contributed approximately 67 percent of the total deposition for the period.
TABLE 6-6. DEPOSITION OF LEAD AT THE WALKER BRANCH WATERSHED, 1974
Period
January
February
March
April
May
June
Total
Average
Wet
34.1
6.7
21.6
15.4
26.5
11.1
115.4
19.2
Lead deposition (g/ha)
Dry
<16.7
< 3.3
<10.6
< 7.5
<13.0
< 5.4
56.5
9.4
aTotal deposition ~172 g/ha. Wet deposition ~67 percent of total.
Source: Andren et al., 1975.
6.4.3 Global Budget of Atmospheric Lead
The geochemical mass balance of lead in the atmosphere may be determined from
quantitative estimates of inputs and outputs. Inputs are from natural and anthropogenic
emissions described in Section 5.2 and 5.3. They amount to 450,000 to 475,000 metric tons
annually (Nriagu, 1979). There are no published estimates of global deposition from the
atmosphere, but the data provided in Sections 6.4.1 and 6.4.2 can provide a reasonable basis
on which to make such an estimate. Table 6-7 shows an average concentration of 0.4 ug Pb/kg
precipitation. The total mass of rain and snowfall is 5.2 x 107 kg, so the amount of lead
removed by wet deposition is approximately 208,000 t/yr. For dry deposition, a crude estimate
may be derived by dividing the surface of the Earth into three major vegetation types based on
surface roughness or LAI. Oceans, polar regions, and deserts have a very low surface rough-
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TABLE 6-7. ESTIMATED GLOBAL DEPOSITION OF ATMOSPHERIC LEAD
Deposition from atmosphere
Mass
10 17 kg/yr
Wet
To oceans 4. 1
To continents 1.1
Area
Dry 1012 km2
To oceans, ice caps, deserts 405
Grassland, agricultural
areas, and tundra 46
Forests 59
Concentration C
10"6 g/kg
0.4
0.4
Deposition rate
10 3 g/m2*yr
0.2
0.71
1.5
Total dry:
Total wet:
Global:
leposition
106 kg/yr
164
44
Deposition
106 kg/yr
89
33
80
202
208
410
Source: This report.
ness and can be assigned a deposition velocity of 0.01 cm/sec, which gives a flux of 0.2
ug/m2tyr assuming 75 ng Pb/m3 air concentration. Grasslands, tundra, and other areas of
low-lying vegetation have a somewhat higher deposition velocity; forests would have the
highest. Values of 0.3 and 0.65 can be assigned to these two vegetation types, based on the
data of Davidson et al. (1982). Whittaker (1975) lists the global surface area of each of the
three types as 405, 46, and 59 x 1012 km2, respectively. In the absence of data on the global
distribution of air concentrations of lead, an average of 0.075 yig/m3 is assumed. Multiplying
air concentration by deposition.velocity gives the deposition flux for each vegetation type
shown on Table 6-7. The combined wet and dry deposition is 410,000 metric tons, which
compares favorably with the estimated 450,000 to 475,000 metric tons of emissions.
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Mass balance calculations of this type serve to accentuate possible errors in the data
which are not otherwise obvious. The data used above are not held to be absolutely firm.
Certainly, more refined estimates of air concentrations and deposition velocities can be made
in the future. On the other hand, the calculations above show some published calculations to
be unreasonable. In particular, values of 36 pg/kg rain reported by Lazrus (1970) would
account for more than 50 times the total global emissions. Likewise, deposition fluxes of
0.95 pg/cm2'yr reported by Jaworowski et al. (1981) would account for 10 times global
emissions. Chemical budgets are an effective means of establishing reasonable limits to
environmental lead data.
6.5 TRANSFORMATION AND TRANSPORT IN OTHER ENVIRONMENTAL MEDIA
6.5.1 Soil
Soils have both a liquid and solid phase, and trace metals are normally distributed
between these two phases. In the liquid phase, metals may exist as free ions or as soluble
complexes with organic or inorganic ligands. Organic ligands are typically humic substances
such as fulvic or humic acid, and the inorganic ligands may be iron or manganese hydrous
oxides. Since lead rarely occurs as a free ion in the liquid phase (Camerlynck and Kiekens,
1982), its mobility in the soil solution depends on the availability of organic or inorganic
ligands. The liquid phase of soil often exists as a thin film of moisture in intimate contact
with the solid phase. The availability of metals to plants depends on the equilibrium between
the liquid and solid phase.
In the solid phase, metals may be incorporated into crystalline minerals of parent rock
material, into secondary clay minerals, or precipitated as insoluble organic or inorganic
complexes. They may also be adsorbed onto the surfaces of any of these solid forms. Of these
categories, the most mobile form is in soil moisture, where lead can move freely into plant
roots or soil microorganisms with dissolved nutrients. The least mobile is parent rock
material, where lead may be bound within crystalline structures over geologic periods of time.
Intermediate are the lead complexes and precipitates. Transformation from one form to another
depends on the chemical environment of the soil. For example at pH 6 to 8, insoluble
organic-Pb complexes are favored if sufficient organic matter is available; otherwise hydrous
oxide complexes may form or the lead may precipitate with the carbonate or phosphate ion. In
the pH range of 4 to 6, the organic-Pb complexes become soluble. Soils outside the pH range
of 4 to 8 are rare. The interconversion between soluble and insoluble organic complexes
affects the equilibrium of lead between the liquid and solid phase of soil.
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Even though the equilibrium may shift toward the insoluble form so strongly that 99.9
percent of the lead may be immobilized, 0.01 percent of the lead in total soil can have a
significant effect on plants and microorganisms if the soils are heavily contaminated with
lead (Chapter 8).
The water soluble and exchangeable forms of metals are generally considered available for
plant uptake (Camerlynck and Kiekens, 1982). These authors demonstrated that in normal soils,
only a small fraction of the total lead is in exchangeable form (about 1 ug/g) and none exists
as free lead ions. Of the exchangeable lead, 30 percent existed as stable complexes, 70
percent as labile complexes. The organic content of these soils was low (3.2 percent clay,
8.5 percent silt, 88.3 percent sand). In heavily contaminated soils near a midwestern
industrial site, Miller and McFee (1983) found that 77 percent of the lead was in
exchangeable or organic form, although still none could be found in aqueous solution. Soils
had a total lead content from 64 to 360 ug/g and an organic content of 7 to 16 percent.
Atmospheric lead may enter the soil system by wet or dry deposition mechanisms described
earlier. There is evidence that this lead enters as PbS04 or is rapidly converted to PbS04 at
the soil surface (Olson and Skogerboe, 1975). Lead sulfate is relatively soluble and thus
could remain mobile if not transformed. Lead could be immobilized by precipitation as less
soluble compounds [PbC03, Pb(P04)2], by ion exchange with hydrous oxides or clays, or by
chelation with humic and fulvic acids. Santillan-Medrano and Jurinak (1975) discussed the
possibility that the mobility of lead is regulated by the formation of Pb(OH)2, Pb3(P04)2,
Pbs(P04)3OH, and PbC03. This model, however, did not consider the possible influence of
organic matter on lead immobilization. Zimdahl and Skogerboe (1977), on the other hand, found
lead varied linearly with cation exchange capacity (CEC) of soil at a given pH, and linearly
with pH at a given CEC (Figure 6-12). The relationship between CEC and organic carbon is
discussed below.
Some of the possible mechanisms mentioned above can be eliminated by experimental
evidence. If surface adsorption on clays plays a major role in lead immobilization, then the
capacity to immobilize should vary directly with the surface-to-volume ratio of clay. Two
separate experiments using the nitrogen BET method for determining surface area and size
fractionation techniques to obtain samples with different surface-to-volume ratios, Zimdahl
and Skogerboe (1977) demonstrated that this was not the case. They also showed that precipi-
tation as lead phosphate or lead sulfate is not significant, although carbonate precipitation
can be important in soils that are are carbonaceous in nature or to which lime (CaC03) has
been added.
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Of the two remaining processes, lead immobilization is more strongly correlated with
organic chelation than with iron and manganese oxide formation (Zimdahl and Skogerboe, 1977).
It is possible, however, that chelation with fulvic and humic acids is catalyzed by the
presence of iron and manganese oxides (Saar and Weber, 1982). This would explain the positive
correlation for both mechanisms observed by Zimdahl and Skogerboe (1977). The study of Miller
and McFee (1983) discussed above seemed to indicate that atmospheric lead added to soil is
distributed to organic matter (43 percent) and ferro-manganese hydrous oxides (39 percent),
with 8 percent found in the exchangeable fraction and 10 percent as insoluble precipitates.
If organic chelation is the correct model of lead immobilization in soil, then several
features of this model merit further discussion. First, the total capacity of soil to
immobilize lead can be predicted from the linear relationship developed by Zimdahl and
Skogerboe (1977) (Figure 6-12) based on the equation:
N = 2.8 X 10"6 (A) + 1.1 X 10"5 (B) - 4.9 X 10"5
where N is the saturation capacity of the soil expressed in moles/g soil, A is the CEC of the
soil in meq/100 g soil, and B is the pH. Because the CEC of soil is more difficult to
determine than total organic carbon, it is useful to define the relationship between CEC and
organic content. Pratt (1957) and Klemmedson and Jenny (1966) found a linear correlation
between CEC and organic carbon for soils of similar sand, silt, and clay content. The data of
Zimdahl and Skogerboe (1977) also show this relationship when grouped by soil type. They show
that sandy clay loam with an organic content of 1.5 percent might be expected to have a CEC of
12 meq/100 g. From the equation, the saturation capacity for lead in soil of pH 5.5 would be
45 umoles/g soil or 9,300 ug/g. The same soil at pH 4.0 would have a total capacity of 5,900
ug/g.
The soil humus model also facilitates the calculation of lead in soil moisture using
values available in the literature for conditional stability constants with fulvic acid. The
term conditional is used to specify that the stability constants are specific for the
conditions of the reaction. Conditional stability constants for HA and FA are comparable.
The values reported for log K are linear in the pH range of 3 to 6 (Buffle and Greter, 1979;
Buffle et al., 1976; Greter et al., 1979), so that interpolations in the critical range of pH
4 to 5.5 are possible (Figure 6-12). Thus, at pH 4.5, the ratio of complexed lead to ionic
lead is expected to be 3.8 x 103. For soils of 100 ug/g, the ionic lead in soil moisture
solution would be 0.03 ug/g. The significance of this ratio is discussed in Section 8.2.1.
It is also important to consider the stability constant of the Pb-FA complex relative to
other metals. Schnitzer and Hansen (1970) showed that at pH 3, Fe3+ is the most stable in the
023PB6/A 6-35 7/13/83
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PRELIMINARY DRAFT
x
S
x
o.
O
z
o
I
I
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
pH = 8
pH = 6
• — pH = 4
25
50 75
CEC, meq/100 g
100
125
Figure 6-12. Variation of lead saturation capacity with cation exchange
capacity in soil at selected pH values.
Source: Data from Zimdahl and Skogerboe (1977).
023PB6/A
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PRELIMINARY DRAFT
sequence Fe3+ > A13+ > Cu2+ > Ni2+ > Co2+ > Pb2+ > Ca2+ > Zn2+ > Mn2+ > Mg2+. At pH 5, this
sequence becomes Ni2 = Co2 > Pb2 > Cu2 > Zn2 = Mn2 > Ca2 > Mg2 . This means that at
normal soil pH levels of 4.5 to 8, lead is bound to FA + HA in preference to many other metals
that are known plant nutrients (Zn, Mn, Ca, and Mg). Furthermore, if lead displaces iron in
this scheme, an important function of FA may be inhibited at near saturation capacity. Fulvic
acid is believed to play a role in the weathering of parent rock material by the removal of
iron from the crystalline structure of the minerals, causing the rock to weather more rapidly.
In the absence of this process, the weathering of parent rock material and the subsequent
release of nutrients to soil would proceed more slowly.
6.5.2 Water
6.5.2.1 Inorganic. The chemistry of lead in an aqueous solution is highly complex because
the element can be found in a multiplicity of forms. Hem and Durum (1973) have reviewed the
chemistry of lead in water in detail; the aspects of aqueous lead chemistry that are germane
to this document are discussed in Section 3.3.
Lead in ore deposits does not pass easily to ground or surface water. Any lead dissolved
from primary lead sulfide ore tends to combine with carbonate or sulfate ions to (1) form
insoluble lead carbonate or lead sulfate, or (2) be absorbed by ferric hydroxide (Lovering,
1976). An outstanding characteristic of lead is its tendency to form compounds of low
solubility with the major anions of natural water. Hydroxide, carbonate, sulfide, and more
rarely sulfate may act as solubility controls in precipitating lead from water. The amount of
lead that can remain in solution is a function of the pH of the water and the dissolved salt
content. Equilibrium calculations show that at pH > 5.4, the total solubility of lead in hard
water is about 30 ug/1 and about 500 ug/1 in soft water (Davies and Everhard, 1973). Lead
sulfate is present in soft water and limits the lead concentration in solution. Above pH 5.4,
PbCOs and Pb2(OH)2C03 limit the concentration. The carbonate concentration is in turn
dependent on the partial pressure of C02 as well as the pH. Calculations by Hem and Durum
(1973) show that many river waters in the United States have lead concentrations near the
solubility limits imposed by their pH levels and contents of dissolved C02. Because of the
influence of temperature on the solubility of C02, observed lead concentrations may vary sig-
nificantly from theoretically calculated ones.
Lazrus et al. (1970) calculated that as much as 140 g/ha-mo of lead may be deposited by
rainfall in some parts of the northeastern United States. Assuming an average annual rainfall
runoff of 50 cm, the average concentration of lead in the runoff would have to be about
330 ug/1 to remove the lead at the rate of 140 g/ha-mo. Concentrations as high as 330 ug/1
023PB6/A 6-37 7/13/83
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PRELIMINARY DRAFT
could be stable in water with pH near 6.5 and an alkalinity of about 25 ng bicarbonate ion/1
of water. Water having these properties is common in runoff areas of New York State and New
England; hence, the potential for high lead concentrations exists there. In other areas, the
average pH and alkalinity are so high that maximum concentrations of lead of about 1 pg/l
could be retained in solutions at equilibrium (Levering, 1976).
A significant fraction of the lead carried by river water may be in an undissolved state.
This insoluble lead can consist of colloidal particles in suspension or larger undissolved
particles of lead carbonate, -oxide, -hydroxide, or other lead compounds incorporated in other
components of particulate lead from runoff; it may occur either as sorbed ions or surface
coatings on sediment mineral particles or be carried as a part of suspended living or
nonliving organic matter (Lovering, 1976). A laboratory study by Hem (1976) of sorption of
lead by cation exchange indicated that a major part of the lead in stream water may be
adsorbed on suspended sediment. Figure 6-13 illustrates the distribution of lead outputs
between filtrate and solids in water from both urban and rural streams, as reported by Rolfe
and Jennett (1975). The majority of lead output is associated with suspended solids in both
urban and rural streams, with very little dissolved in the filtrate. The ratio of lead in
suspended solids to lead in filtrate varies from 4:1 in rural streams to 27:1 in urban
streams.
Soluble lead is operationally defined as that fraction which is separated from the
insoluble fraction by filtration. However, most filtration techniques do not remove all
colloidal particles. Upon acidification of the filtered sample, which is usually done to
preserve it before analysis, the colloidal material that passed through the filter is
dissolved and is reported as dissolved lead. Because the lead in rainfall can be mainly
particulate, it is necessary to obtain more information on the amounts of lead transported in
insoluble form (Lovering, 1976) before a valid estimate can be obtained of the effectiveness
of runoff in transporting lead away from areas where it has been deposited by atmospheric
fallout and rain.
6.5.2.2 Organic. The bulk of organic compounds in surface waters originates from natural
sources. (Neubecker and Allen, 1983). The humic and fulvic acids that are primary complexing
agents in soils are also found in surface waters at concentrations from 1 to 5 mg/1,
occasionally exceeding 10 mg/1. (Steelnik, 1977), and have approximately the same chemical
characteristics (Reuter and Perdue, 1977). The most common anthropogenic organic compounds
are NTA and EDTA (Neubecker and Allen, 1983). There are many other organic compounds such as
oils, plasticizers, and polymers discharged from manufacturing processes that may complex with
lead.
023PB6/A 6-38 7/13/83
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PRELIMINARY DRAFT
I
OJ
O
0
o
Q
<
LU
100
75
50
25
SUSPENDED SOLIDS
FILTRATE
URBAN
RURAL
Figure 6-13. Lead distribution between filtrate and suspended
solids in stream water from urban and rural compartments.
Source: Hem (1976); Rolfe and Jennett (1975).
023PB6/A
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PRELIMINARY DRAFT
The presence of fulvic acid in water has been shown to increase the rate of solution of
lead sulfide 10 to 60 times over that of a water solution at the same pH that did not contain
fulvic acid (Bondarenko, 1968; Levering, 1976). At pH values near 7, soluble lead-fulvic acid
complexes are present in solution. At initial pH values between 7.4 and about 9, the
lead-fulvic acid complexes are partially decomposed, and lead hydroxide and carbonate are
precipitated. At initial pH values of about 10, the lead-fulvic acid complexes again
increase. This increase is attributed to dissociation of phenolic groups at high pH values,
which increases the complexing capacity of the fulvic acid. But it also may be due to the
formation of soluble lead-hydroxyl complexes.
The transformation of inorganic lead, especially in sediment, to tetramethyllead (TML)
has been observed and biomethylation has been postulated (Schmidt and Huber, 1976; Wong et
al., 1975). However, Reisinger et al. (1981) have reported extensive studies of the
methylation of lead in the presence of numerous bacterial species known to alkylate mercury
and other heavy metals. In these experiments no biological methylation of lead was found
under any condition. Chemical alkylation from methylcobalamine was found to occur in the
presence of sulfide or of aluminum ion; chemical methylation was independent of the presence
of bacteria.
Jarvie et al. (1977, 1981) have recently shown that tetraalkyllead (TEL) compounds are
unstable in water. Small amounts of Ca2 and Fe2 ions and sunlight have been shown to cause
decomposition of TEL over time periods of 5 to 50 days. The only product detected was
triethyllead, which appears to be considerably more stable than the TEL. Tetramethyllead is
decomposed much more rapidly than TEL in water, to form the trimethyl lead ion. Initial
_4
concentrations of 10 molar were reduced by one order of magnitude either in the dark or
light in one day, and were virtually undetectable after 21 days. Apparently, chemical
methylation of lead to the trialkyllead cation does occur in some water systems, but evolution
of TML appears insignificant.
Lead occurs in riverine and estuarial waters and alluvial deposits. Laxen and Harrison
(1977) and Harrison and Laxen (1981) found large concentrations of lead (~1 mg/1) in rainwater
runoff from a roadway; but only 5 to 10 percent of this is soluble in water. Concentrations
of lead in ground water appear to decrease logarithmically with distance from a roadway.
Rainwater runoff has been found to be an important transport mechanism in the removal of lead
from a roadway surface in a number of studies (Bryan, 1974; Harrison and Laxon, 1981; Hedley
and Lockley, 1975; Laxen and Harrison, 1977).
023PB6/A 6-40 7/13/83
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PRELIMINARY DRAFT
Apparently, only a light rainfall, 2 to 3 mm, is sufficient to remove 90 percent of the lead
from the road surface to surrounding soil and to waterways (Laxen and Harrison, 1977).
The Applied Geochemistry Research Group (1978) has reported elevated lead concentrations
(40 ug/g and above) in about 30 percent of stream bed sediment samples from England and Wales
in a study of 50,000 such samples. Abdullah and Royle (1973) have reported lead levels in
coastal areas of the Irish sea of 400 ug/g and higher.
Evidence for the sedimentation of lead in freshwater streams may be found in several
reports. Laxen and Harrison (1983) found that lead in the effluent of a lead-acid battery
plant near Manchester, England, changed drastically in particle size. In the plant effluent,
53 percent of the lead was on particles smaller than 0.015 urn and 43 percent on particles
greater than 1 urn. Just downstream of the plant, 91 percent of the lead was on particles
greater than 1 urn and only I percent on particles smaller than 0.015 urn. Under these
conditions, lead formed or attached to large particles at a rate exceeding that of Cd, Cu, Fe
or Mn.
The lead concentrations in off-shore sediments often show a marked increase corresponding
to anthropogenic activity in the region (Section 5.1). Rippey et al. (1982) found such
increases recorded in the sediments of Lough Neagh, Northern Ireland, beginning during the
1600's and increasing during the late 1800's. Corresponding increases were also observed for
Cr, Cu, Zn, Hg, P, and Ni. For lead, the authors found an average anthropogenic flux of 72
mg/m2'yr, of which 27 mg/m2-yr could be attributed to direct atmospheric deposition. Prior to
1650, the total flux was 12 mg/m2
-------
PRELIMINARY DRAFT
particles via an electrostatic mechanism.- Other types of leaves are covered with a cuticular
wax sufficiently sticky to retain particles. Thus, rainfall does not generally remove the
deposited particles (Arvik and Zimdahl, 1974). Animals or humans consuming the leafy portions
of such plants can certainly be exposed to higher than normal levels of lead. Fortunately, a
major fraction of lead emitted by automobiles tends to be deposited inside a highway
right-of-way, so at least part of this problem is alleviated.
The particle deposition on leaves has led some investigators to stipulate that lead may
enter plants through the leaves. This would typically require, however, that the lead
particles be dissolved by constituents of the leaf surface and/or converted to the ionic form
via contact with water. The former possibility is not considered likely since cuticular waxes
are relatively chemically inert. Arvik and Zimdahl (1974) have shown that entry of ionic lead
through plant leaves is of minimal importance. Using the leaf cuticles of several types of
plants essentially as dialysing membranes, they found that even high concentrations of lead
ions would not pass through the cuticles into distilled water on the opposite side.
The uptake of soluble lead by aquatic plants can be an important mechanism for depleting
lead concentrations in downstream waterways. Gale and Wixson (1979) have studied the
influence of algae, cattails, and other aquatic plants on lead and zinc levels in wastewater
in the New Lead Belt of Missouri. These authors report that mineral particles become trapped
by roots, stems, and filaments of aquatic plants. Numerous anionic sites on and within cell
walls participate in cation exchange, replacing metals such as lead with Na+, K+, and H+ ions.
Mineralization of lead in these Missouri waters may also be promoted by water alkalinity.
However, construction of stream meanders and settling ponds have greatly reduced downstream
water concentrations of lead, mainly because of absorption in aquatic plants (Gale and Wixson,
1979).
6.6 SUMMARY
From the source of emission to the site of deposition, lead particles are dispersed by
the flow of the airstream, transformed by physical and chemical processes, and removed from
the atmosphere by wet or dry deposition. Under the simplest of conditions (smooth, flat
terrain), the dispersion of lead particles has been modeled and can be predicted (Benarie,
1980). Dispersion modeling in complex terrains is still under development and these models
have not been evaluated (Kotake and Sano, 1981).
Air lead concentrations decrease logarithmically away from roadways (Edwards, 1975) and
smelters (Roberts et al., 1974). Within urban regions, air concentrations decrease from the
central business district to the outlying residential areas by a factor of 2 to 3. In moving
023PB6/A 6-42 7/13/83
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PRELIMINARY DRAFT
from urban to rural areas, air concentrations decrease from 1 to 2 pg/m3 down to 0.1 to 0.5
ug/m3 (Chapter 7). This decrease is caused by dilution with clean air and removal by
deposition. During dispersion to remote areas, concentrations decrease to 0.01 [ig/m& in the
United States (Elias and Davidson, 1980), to 0.001 M9/m3 in the Atlantic Ocean (Duce et al.,
1975), and to 0.000076 |jg/m3 in Antarctica (Maenhaut et al., 1979).
Physical transformations of lead particles cause a shift in the particle size
distribution. The bimodal distribution of large and small particles normally found on the
roadway changes to a single mode of intermediate sized particles with time and distance
(Huntzicker et al., 1975). This is probably because large particles deposit near roadways and
small particles agglomerate to medium sized particles with an MMED of about 0.2 to 0.3 [an.
Particles transform chemically from lead halides to lead sulfates and oxides. Organolead
compounds usually constitute 1 to 6 percent of the total airborne lead in ambient urban air
(Harrison et al., 1979).
Wet deposition accounts for about half of the removal of lead particles from the
atmosphere. The mechanisms may be rainout, where the lead may be from another region, or
washout, where the source may be local. The other half of the atmospheric lead is removed by
dry deposition. Mechanisms may be gravitational for large particles or a combination of
gravitational and wind-related mechanisms for small particles (Elias and Davidson, 1980).
Models of dry deposition predict deposition velocities as a function of particle size,
windspeed, and surface roughness. Because of their large surface area/ground area ratio,
vegetation surfaces receive the bulk of dry deposited particles over continental areas. Wet
and dry deposition account for the removal of over 400,000 t/year of the estimated 450,000
t/yr emissions (Nriagu, 1979).
Lead enters soil as a moderately insoluble lead sulfate and is immobilized by
complexation with humic and fulvic acids. This immobilization is a function of pH and the
concentration of humic substances. At low pH (*4) or low organic content (<5 percent),
immobilization of lead in soil may be limited to a few hundred ug/g (Zimdahl and Skogerboe,
1977), but at 20 percent organic content and pH 6, 10,000 pg Pb/g soil may be found.
In natural waters, lead may precipitate as lead sulfate or carbonate, 'or it may form a
complex with ferric hydroxide (Levering, 1976). The solubility of lead in water is a function
of pH and hardness (a combination of Ca and Mg content). Below pH 5.4, concentrations of
dissolved lead may vary from 30 ng/1 in hard water to 500 pg/1 in soft water at saturation
(Levering, 1976).
Particles deposited by dry deposition on vegetation surfaces (leaves and bark) are
retained for the lifetime of the plant part. The particles are not easily washed off by rain
nor are they taken up directly by the leaf (Arvik and Zimdahl, 1974).
023PB6/A 6-43 7/13/83
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6.7 REFERENCES
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7. ENVIRONMENTAL CONCENTRATIONS AND POTENTIAL PATHWAYS TO HUMAN EXPOSURE
7.1 INTRODUCTION
In general, typical levels of human lead exposure may be attributed to four components of
the human environment: food, inhaled air, dusts of various types, and drinking water. This
chapter presents information on the ranges and temporal trends of concentrations in ambient
air, soil, and natural waters, and discusses the pathways from each source to food, inhaled
air, dust, and drinking water. The ultimate goal is to quantify the contribution of anthropo-
genic lead to each source and the contribution of each source to the total lead consumed by
humans. These sources and pathways of human lead exposure are diagrammed in Figure 7-1.
Chapters 5 and 6 discuss the emission, transport, and deposition of lead in ambient air.
Some information is also presented in Chapter 6 on the accumulation of lead in soil and on
plant surfaces. Because this accumulation is at the beginning of the human food chain, it is
critical to understand the relationship between this lead and lead in the human diet. It is
also important where possible to project temporal trends.
In this chapter, a baseline level of potential human exposure is determined for a normal
adult eating a typical diet and living in a non-urban community. This baseline exposure is
deemed to be unavoidable by any reasonable means. Beyond this level, additive exposure factor
s can be determined for other environments (e.g., urban, occupational, smelter communities),
for certain habits and activities (e.g., pica, smoking, drinking, and hobbies), and for varia-
tions due to age, sex, or socioeconomic status.
7.2 ENVIRONMENTAL CONCENTRATIONS
Quantifying human exposure to lead requires an understanding of ambient lead levels in
environmental media. Of particular importance are lead concentrations in ambient air, soil,
and surface or ground water. The following sections discuss environmental lead concentrations
in each of these media in the context of anthropogenic vs. natural origin, and the contribu-
tion of each to potential human exposure.
7.2.1 Ambient Air
Ambient airborne lead concentrations may influence human exposure through direct inhala-
tion of lead-containing particles and through ingestion of lead which has been deposited from
the air onto surfaces. Although a plethora of data on airborne lead is now available, our
understanding of the pathways to human exposure is far from complete because most ambient mea-
surements were not taken in conjunction with studies of the concentrations of lead in man or
in components of his food chain. However, that is the context in which these studies must now
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INDUSTRIAL
EMISSIONS
SURFACE AND
GROUND WATER
DRINKING
WATER
Figure 7-1. Pathways of lead from the environment to human consumption. Heavy
arrows are those pathways discussed in greatest detail in this chapter.
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be interpreted to shed the most light possible on the concentrations likely to be encountered
in various environmental settings.
The most complete set of data on ambient air concentrations may be extracted from the
National Filter Analysis Network (NFAN) and its predecessors (see Section 4.2.1). These data,
which are primarily for urban regions, have been supplemented with published data from rural
and remote regions of the United States. Because some stations in the network have been in
place for about 15 years, information on temporal trends is available but sporadic. Ambient
air concentrations in the United States are comparable to other industrialized nations. In
remote regions of the world, air concentrations are two or three orders of magnitude lower,
lending credence to estimates of the concentration of natural lead in the atmosphere. In the
context of the NFAN data base, the conditions are considered which modify ambient air, as
measured by the monitoring networks, to air as inhaled by humans. Specifically, these
conditions are changes in particle size distributions, changes with vertical distance above
ground, and differences between indoor and outdoor concentrations.
7.2.1.1 Total Airborne Lead Concentrations. A thorough understanding of human exposure to
airborne lead requires detailed knowledge of spatial and temporal variations in ambient con-
centrations. The wide range of concentrations is apparent from Table 7-1, which summarizes
data obtained from numerous independent measurements. Concentrations vary from 0.000076 ijg/m3
in remote areas to over 10 ug/m3 near sources such as smelters. Many of the remote areas are
far from human habitation and therefore do not reflect human exposure. However, a few of the
regions characterized by low lead concentrations are populated by individuals with primitive
lifestyles; these data provide baseline airborne lead data to which modern American lead expo-
sures can be compared. Examples include some of the data from South America and the data from
Nepal.
Urban, rural, and remote airborne lead concentrations in Table 7-1 suggest that human ex-
posure to lead has increased as the use of lead in inhabited areas has increased. This is
consistent with published results of retrospective human exposure studies. For example,
Ericson et al. (1979) have analyzed the teeth and bones of Peruvians buried 1600 years ago.
Based on their data, they estimate that the skeletons of present-day American and British
adults contain roughly 500 times the amount of lead which would occur naturally in the absence
of widespread anthropogenic lead emissions. Grandjean et al. (1979) and Shapiro et al. (1980)
report lead levels in teeth and bones of contemporary populations to be elevated 100-fold over
levels in ancient Nubians buried before 750 A.D. On the other hand, Barry and Connolly (1981)
report excessive lead concentrations in buried medieval English skeletons; one cannot discount
the possibility that the lead was absorbed into the skeletons from the surrounding soil.
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TABLE 7-1. ATMOSPHERIC LEAD IN URBAN, RURAL,
AND REMOTE AREAS OF THE WORLD
Location Sampling period
Urban
Miami
New York
Boston
St. Louis
Houston
Chicago
Salt Lake City
Los Angeles
Ottowa
Toronto
Montreal
Berlin
Vienna
Zurich
Brussels
Turin
Rome
Paris
Rio de Janeiro
Rural
New York Bight
Framingham, MA
Chadron, NE
United Kingdom
Italy
Belgium
Remote
White Mtn. , CA
High Sierra, CA
Olympic Nat. Park, WA
Antarctica
South Pole
Thule, Greenland
Thule, Greenland
Prins Christian-
sund, Greenland
Dye 3, Greenland
Eniwetok, Pacific Ocean
Kumjung, Nepal
Bermuda
Spitsbergen
1974
1978-79
1978-79
1973
1978-79
1979
1974
1978-79
1975
1975
1975
1966-67
1970
1970
1978
1974-79
1972-73
1964
1972-73
1974
1972
1973-74
1972
1976-80
1978
1969-70
1976-77
1980
1971
1974
1965
1978-79
1978-79
1979
1979
1979
1973-75
1973-74
Lead cone, (jjg/m3) Reference
1.3
1.1
0.8
1.1
0.9
0.8
0.89
1.4
1.3
1.3
2.0
3.8
2.9
3.8
0.5
4.5
4.5
4.6
0.8
0.13
0.9
0.045
0.13
0.33
0.37
0.008
0.021
0.0022
0. 0004
0.000076
0. 0005
0.008
0.018
0.00015
0.00017
0.00086
0.0041
0.0058
HASL, 1975
see Table 7-3
see Table 7-3
see Table 7-3
see Table 7-3
see Table 7-3
HASL, 1975
see Table 7-3
NAPS, 1975
NAPS, 1975
NAPS, 1975
Blokker, 1972
Hartl and Resch, 1973
Hogger, 1973
Roels et al. , 1980
Facchetti and Geiss, 1982
Colacino and Lavagnini, 1974
Blokker, 1972
Branquinho and Robinson, 1976
Duce et al., 1975
O'Brien et al. , 1975
Struempler, 1975
Cawse, 1974
Facchetti and Geiss, 1982
Roels et al. 1980
Chow et al . , 1972
Eli as and Davidson, 1980
Davidson et al. , 1982
Duce, 1972
Maenhaut et al . , 1979
Murozumi et al . , 1969
He i dam, 1981
Heidam, 1981
Davidson et al., 1981c
Settle and Patterson, 1982
Davidson et al. , 1981b
Duce et al . , 1976
Larssen, 1977
Source: Updated from Nriaga, 1978
PB7/A
7-4
7/14/83
-------
PRELIMINARY DRAFT
The remote area concentrations reported in Table 7-1 do not necessarily reflect natural,
preindustrial lead. Murozumi et al. (1969) and Ng and Patterson (1981) have measured a 200-
fold increase over the past 3000 years in the lead content of Greenland snow. In the opinion
of the authors, this lead originates in populated mid-latitude regions, and is transported
over thousands of kilometers through the atmosphere to the Arctic. All of the concentrations
in Table 7-1, including values for remote areas, have been influenced by anthropogenic lead
emissions.
Studies referenced in Table 7-1 are limited in that the procedures for determining the
quality of the data are generally not reported. In contrast, the two principal airborne lead
data bases described in Section 4.2.1 include measurements subjected to documented quality as-
surance procedures. The U.S. Environmental Protection Agency's National Filter Analysis Net-
work (NFAN) provides comprehensive nationwide data on long-term trends. The second data base,
EPA's National Aerometric Data Bank, contains information contributed by state and local
agencies, which monitor compliance with the current ambient airborne standard for lead (1.5
ug/m3 averaged over a calendar quarter) promulgated in 1978.
7.2.1.1.1 Distribution of air lead in the United States. Figure 7-2 categorizes the urban
sites with valid annual averages (4 valid quarters) into several annual average concentration
ranges (Akland, 1976; Shearer et al. 1972; U.S. Environmental Protection Agency, 1978, 1979;
Quarterly averages of lead from NFAN, 1982). Nearly all of the sites reported annual averages
below 1.0 ug/m3. Although the decreasing number of monitoring stations in service in recent
years could account for some of the shift in averages toward lower concentrations, trends at
individual urban stations, discussed below, confirm the apparent national trend of decreasing
lead concentration.
The data from these networks show both the maximum quarterly average to reflect compli-
ance of the station to the ambient airborne standard (1.5 ug/ma), and quarterly averages to
show trends at a particular location. Valid quarterly averages must include at lease five
24-hour sampling periods evenly spaced throughout the quarter. The number of stations comply-
ing with the standard has increased, the quarterly averages have decreased, and the maximum
24-hour values appear to be smaller since 1977.
Table 7-2 provides cumulative frequency distributions of all quarterly lead concentra-
tions for urban NFAN stations (1st quarter = Jan-Mar, etc.). Samples collected by the NFAN
from 1970 through 1976 were combined for analysis into quarterly composites. Since 1977, the
24-hour samples have been analyzed individually and averaged arithmetically to determine
the quarterly average. These data show that the average lead concentration has dropped
markedly since 1977. An important factor in this evaluation is that the number of reporting
stations has also decreased since 1977. Stations may be removed from the network for several
PB7/A 7-5 7/14/83
-------
PRELIMINARY DRAFT
(0
_l
i
u.
O
I I I I I I
0.5-0.9
. — • — . 1.0-1.9
2.0-3.9 Mg/m3
10 —
1966 67 68
(95) (146)
70 71 72 73 74 75 76 77 78 79 80
(159) 1180) (130) (162) (72) (57)
YEAR
Figure 7-2. Percent of urban stations reporting indicated concentration interval.
PB7/A 7-6 7/1/83
-------
TABLE 7-2. CUMULATIVE FREQUENCY DISTRIBUTIONS OF URBAN AIR LEAD CONCENTRATIONS*
Percenti le
Year
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
No. of
Station
Reports
797
717
708
559
594
695
670
533
282
167
220
10
0.47
0.42
0.46
0.35
0.36
0.37
0.37
0.37
0.27
0.22
0.14
30
0.75
0.71
0.72
0.58
0.57
0.58
0.58
0.57
0.43
0.33
0.21
50
1.05
1.01
0.97
0.77
0.75
0.78
0.74
0.75
0.57
0.43
0.30
70 90
1.37
1.42
1.25
1.05
1.00
0.96
0.96
0.95
0.74
2.01
2.21
1.93
1.62
1.61
1.54
1.41 |
1.67
1.19
0.63 1.09
0.38 0.55
95
2.59
2.86
2.57
2.08
1.97
2.02
1.72
2.13
1.49
1.33
0.66
99
4.14
4.38
3.69
3.03
3.16
3.15
3.07
3.29
2.40
2.44
0.84 1
Max.
Qtrly.
Avg
5.83
6.31
6.88
5.83
4.09
4.94
4.54
3.96
3.85
3.59
1.06
Arithmetic
Mean
1.19
1.23
1.13
0.92
0.89
0.89
0.85
0.91
0.68
0.56
0.32
dev.
0.80
0.87
0.78
0.64
0.57
0.59
0.55
0.80
0.64
0.58
0.27
Geometric
Mean
0.99
1.00
0.93
0.76
0.75
0.74
0.72
0.68
0.50
0.39
0.24
dev.
1.80
1.89
1.87
1.87
1.80
1.82
1.80
1.79
1.87
1.89
1.88
•o
73
70
CO
<*>
*The data reported here are all valid quarterly averages reported from urban stations from 1970 to 1980,
in ug/m3. The vertical line marks compliance with the 1978 1.5 pg/m3 EPA National Ambient Air Quality
Standard. In 1980, the quarterly average for all but the highest 1 percent of the stations was 0.84. The
sources of the data are Akland, 1976; U.S. EPA, 1978, 1979; Quarterly averages of lead from NFAN, 1982.
-------
PRELIMINARY DRAFT
reasons, the most common of which is that the locality has now achieved compliance status and
fewer monitoring stations are required. It is likely that none of the stations removed from
the network were in excess of 1.5 MS/1"3, and that most were below 1.0 ug/m3.
The summary percent!les and means for urban stations (Table 7-2) have decreased over the
period from 1970 to 1980, with most of the decrease occurring since 1977; the 1980 levels are
in the range of one-third to one-fourth of the values in 1970. The data from non-urban loca-
tions are given in Appendix 7A. While the composite nonurban lead concentrations are approxi-
mately one-seventh of the urban concentrations, they exhibit the same relative decrease over
the 1979-1980 period as the urban sites.
Long-term trends and seasonal variations in airborne lead levels at urban sites can be
seen in Figure 7-3. The 10th, 50th, and 90th percentile concentrations are graphed, using
quarterly composite and quarterly average data from an original group of 92 urban stations
(1965-1974) updated with data for 1975 through 1980. Note that maximum lead concentrations
typically occur in the winter, while minima occur in the summer. In contrast, automotive
emissions of lead would be expected to be greater in the summer for two reasons: (1) gasoline
usage is higher in the summer, and (2) lead content is raised in summer gasolines to replace
some of the more volatile high-octane components that cannot be used in summertime gasolines.
The effect is apparently caused by the seasonal pattern of lower dispersion capacity in
winter, higher capacity in summer.
Figure 7-3 also clearly portrays the significant decrease in airborne lead levels over
the past decade. This trend is attributed to the decreasing lead content of regular and pre-
mium gasoline, and to the increasing usage of unleaded gasoline. The close parallel between
these two parameters is discussed in detail in Chapter 5. (See Figure 5-4 and Table 5-6.)
The decrease in lead concentrations, particularly in 1979 and 1980, was not caused by the
disappearance from the network of monitoring sites with characteristically high concentra-
tions; the quarterly values for sites in six cities representing the east coast, the central,
and the western sections of the country (Figure 7-4) indicate that the decrease is widespread
and real.
Table 7-3 shows lead concentrations in the atmospheres of several major metropolitan
areas of epidemiological interest. Some of the data presented do not meet the stringent re-
quirements for quarterly averages and occasionally there have been changes in site location or
sampling methodology. Nevertheless, the data are the best available for reporting the history
of lead contamination in these specific urban atmospheres. Further discussions of these data
appear in Chapter 11.
PB7/A 7-8 7/14/83
-------
s
TABLE 7-3. AIR LEAD CONCENTRATIONS IN MAJOR METROPOLITAN AREAS (yg/m3) (quarterly averages)
I
VO
Station
Year
1970
1971
1972
1973
1974
1975
Type
Quarter
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
Boston
MA
1
0.8
1.2
1.2
0.7
1.0
0.6
2.5.
0.6
0.9
1.0
1.2
0.6a
l.Oa
0.9a
New York
NY
1
1.2
1.5
1.9
1.4
1.6
l.fl
1.7
0.9
1.3
1.0
1.1
0.8
1.3
0.9
0.5
1.1
0.9
0.9
0.8
0.8
1.0
1.1
Phi la. Wa*h.
PA OC
141
0.9
0.9
1.2
1.1
1.3
1.3
2.1
1.7
1.2
1.1
0.5
1.1
Octroi I Chicago
HI 1L
1 123
1.2
1.4
1.4
1.3
1.0
1.8
1.6
2.2
0.9
0.9
0.8
0.7
1.2
1.2
Houston
TX
1 4
1.8
2.0
1.9
2.5
1.9
1.6
1.7
2.7
2.3
1.0
0.9
2.3
2.9
1.8
1.7
1.7
1.8
2.0 0.6a
1.8 0.6
2.6 0.5
2. la 0.7
1.7 0.7
2.1 0.6
2.4 1.1
Dal
1
3.8
2.3
2.8
3.7
3.4
1.8
2.5
2.7
3.4
1.8
2.2
2.8
1.9
1.3
1.9
1.3
1.4
2.8
3.3
2.9
2.3
3.0
2.9
las/Ft. Worth
TX
2 4
0.2a
0.4
0.6
0.3
0.3
0.4
0.5 0.3
Los
1
5.7
3.5
5.1
3.9
6.0
2.9
3.3
6.3
3.1
2.0
2.6
4.7
2.7
2.0
2.7
1.9
2.0
1.4
3.2
1.2
1.9
3.2
Angeles
CA
2
3.2
2.2
3.3
1.9
1.6
1.5
2.1
1.6
2.5
1.6
1.7
1.9
2.6
1.7
1.2
1.7
2.2
00
CO
-------
-o
CD
•vj
TABLE 7-3. (continued)
I
I—>
o
CO
Station
Year
1976
1977
1978
1979
1980
1981
1982
Station
Type
Quarter
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
type: 1.
2.
3.
4.
Boston
MA
1
0.6a
0.7
0.8
l.Oa
0.9
1.3
1.0
0.4
0.6
0.8a
0.9a
0.5
0.6
0.4
0.3
1.0
center
center
center
New York. Phi la. Wash. Detroit Chicago
NY PA
1 1
1.3
1.6
1.4
1.3
1.2
1.1
1.4
1.3 1.6
l.Oa 1.1
0.9 1.2
1.0
1.2
0.7
0.4
0.7
0.7
0.5
0.4
0.4
0.4
0.5
0.5
0.8a
city commercial
city residential
city industrial
4
1.0
0.8
0.9
1.0
0.8
0.7
0.7
1.2
0.7
0.6
0.6
0.8
0.4
0.4
0.4
0.5
0.4a
0.3
0.2
0.3
0.3
0.3
0.3
0.4
DC
1
1.2a
1.4
0.4a
1.2
0.9a
2.1
2.2
1.1
1.1
3.3
1.8
1.3
1.6
1.9
HI
1 1
1.1
0.9
1.0
0.7
0.5
0.3 0.4
0.3 0.7
0.3 1.0
0.4a 0.5
0.3 0.2
0.3 0.4
0.3 0.3
0.3a 0.4
0.4
0.2
0.3
0.4
1L
2
0.9
0.6
0.3
0.4
0.5
0.4
0.3
0.3
0.3
0.2a
0.3
0.4
0.3
0.3
3
0.8
0.8
0.3
0.6
0.5
0.4
0.2
0.3
0.2
0.3
0.3
0.3
0.2
0.3
Houston
TX
1 4
0.8a 0.5
0.7a 0.5
1.1 0.7
0.3a 0.2
0.8 0.3
1.3 0.7
1.0 0.5
0.8 0.4
0.8 0.5
1.7 0.9
0.9 0.4
0.8 0.4
0.5a O.ba
0.7a 0.5
0.6a 0.3
0.3a 0.3a
0.2
0.4
0.7 0.5
0.2 0.2
0.5 0.3
0.8 l.Oa
Dallai/Ft.
TX
1 2
0.7a 0.3
0.7 0.3
l.la 0.3
2.3
1.2 0.2
1.1 0.2
1.6a 0.5
1.7a 0.4
1.1 0.4
1.3 0.4
. 1.7 0.5
1.2a 0.4
0.6a 0.2
l.la 0.4
O.Sa 0.3
0.3a 0.3
0.6a 0.1
0.3 0.1
0.4 0.3
0.6 0.3
0.3 0.1
0.2
0.3
Worth
Los Angeles
CA
1
0.2
0.4
0.3
0.2
0.2
0.5
0.3
0.3
0.3
0.6
0.4
0.3
0.6
0.4
0.2
0.2
0.1
0.3
0.3
0.2
0.3
0.4
1
4.1
3.3
1.7
1.8
3.8
2.2a
1.6
1.9
1.5
0.9
l.Oa
0.6a
0.7
l.la
1.3
0.7
0.8
1.3
0.8
O.S
0.8
1.1
2
3.0
2.4
1.4
1.6
2.9
1.6
1.1
0.8
1.0
1.7
1.0
0.7
0.8
1.1
0.7
0.6
suburban residential
-o
70
-<
u
a:
less than required number of 24-hour sampling periods to meet composite criteria
-------
PRELIMINARY DRAFT
4.0 i i i i i i i i i i i i i i i i i i i I i i i i i i i
90th PERCENTILE
60th PERCENTILE
10th PERCENTILE
I I ! I . I I I I I I I I I I I I , . I . , , I
I I I I I I I I I I I I I I I I I I
65666768697071 7273 74 757677787980
YEAR
Figure 7-3. Seasonal patterns and trends in quarterly average urban lead concentrations.
7.2.1.1-2 Global distributions of air lead. Other industrialized nations have maintained
networks for monitoring atmospheric lead. For example, Kretzschmar et al. (1980) reported
trends from 1972 to 1977 in a 15"station network in Belgium. Annual averages ranged from 0.16
ug/m at rural sites to 1.2 ug/m3 near the center of Antwerp. All urban areas showed a
maximum near the,,center of the city, with lead concentrations decreasing outward. The rural
background levels appeared to range from 0.1 to 0.3 ug/m3. Representative data from other
nations appear in Table 7-1.
7.2.1.1-3 Natural concentrations of lead in air. There are no direct measurements of pre-
historic natural concentrations of lead in air. Air lead concentrations which existed in pre-
historic times must be inferred from available data. Table 7-1 lists several values for re-
mote areas of the world, the lowest of which is 0.000076 ug/m3 at the South Pole (Maenhaut et
al., 1979). Two other reports show comparable values: 0.00017 ug/m3 at Eniwetok in the
Pacific Ocean (Settle and Patterson, 1982) and 0.00015 at Dye 3 in Greenland (Davidson et al.,
1981a). Since each of these studies reported some anthropogenic influence, it may be assumed
that natural lead concentrations are somewhat lower than these measured values.
PB7/A
7-11
7/1/83
-------
CO
1
O
g
a:
UJ
o
o
u
o
oc
<
1.4
1.2
1.0
0.8
0.6
0.4
0.2
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
WORCHESTER, MA
NEWARK, NJ
I II J I
I I I I
DES MOINES, IA
AKRON, OH —
I I L
PB7/A
1975 76 77 78 79 80 1975 76 77 78 79 80
YEAR
Figure 7-4. Time trends in ambient air lead at selected urban sites.
7-12 7/1/83
-------
PRELIMINARY DRAFT
Another approach to determining natural concentrations is to estimate global emissions
from natural sources. Nriagu (1979) estimated emissions at 24.5 x 106 kg/yr, whereas Settle
and Patterson (1980) estimated a lower value of 2 x 106 kg/yr. An average troposheric volume,
to which surface generated particles are generally confined, is about 2.55 x 1010m3. Assuming
a residence time of 10 days (see Section 6.3), natural lead emissions during this time would
be 6.7 x 1014 ug. The air concentrations would be 0.000263 using the values of Nriagu (1979)
or 0.0000214 ug/m3 using the data of Settle and Patterson (1980). It seems likely that the
concentration of natural lead in the atmosphere is between 0.00002 and 0.00007 ug/m3. A value
of 0.00005 ug/m3 will be used for calculations regarding the contribution of natural air lead
to total human uptake in Section 7.3.1.
7.2.1.2 Compliance with the 1978 Air Quality Standard. Table 7-4 lists stations operated by
state and local agencies where one or more quarterly averages exceeded 1.0 ug/m3 or the cur-
rent standard of 1.5 ug/m3 in 1979 or 1980. A portion of each agency's compliance monitoring
network consists of monitors sited in areas expected to yield high concentrations associated
with identifiable sources. In the case of lead, these locations are most likely to be near
stationary point sources such as smelters or refineries, and near routes of high traffic den-
sity. Both situations are represented in Table 7-4; e.g., the Idaho data reflect predominant-
ly stationary source emissions, whereas the Washington, D.C. data reflect predominantly
vehicular emissions.
Table 7-5 summarizes the maximum quarter lead values for those stations reporting 4 valid
quarters in 1979, 1980, and 1981, grouped according to principal exposure orientation or in-
fluence—population, stationary source, or background. The sites located near stationary
sources clearly dominate the concentrations over 2.0 ug/m3; however, new siting guidelines,
discussed in Section 7.2.1.3.2, will probably effect some increase in the upper end of the
distribution of values from population-oriented sites by adding sites closer to traffic emis-
sions.
The effect of the 1978 National Ambient Air Quality Standard for Lead has been to reduce
the air concentration of lead in major urban areas. Similar trends may also be seen in urban
areas of lower population density (Figure 7-4). Continuous monitoring at non-urban stations
has been insufficient to show a trend at more than a few locations.
7,2.1.3 Changes in Air Lead Prior to Human Uptake. There are many factors which can cause
differences between the concentration of lead measured at a monitoring station and the actual
inhalation of air by humans. The following sections show that air lead concentrations usually
decrease with vertical and horizontal distance from emission sources, and are generally lower
indoors than outdoors. A person working on the fifth floor of an office building would be ex-
posed to less lead than a person standing on a curb at street level. The following dis-
cussions will describe how these differences can affect individual exposures in particular
circumstances.
PB7/A 7-13 7/14/83
-------
TABLE 7-4. STATIONS WITH AIR LEAD CONCENTRATIONS GREATER THAN 1.0 pg/m3
Data are listed from all stations, urban and rural, reporting valid quarterly averages greater than 1.0
ug/m3. Some stations have not yet reported data for 1981.
1979 Max 1980
No. of Quarters Qtrly No. of Quarters
Station # >1.0 >1.5 Ave >1.0 >1.5
Troy, AL
Glendale, AZ
Phoenix, AZ
ii H
ii n
H ii
Scottsdale, AZ
Tucson, AZ
Nogales, AZ
Los Angeles, CA
Anaheim, CA
Adams Co, CO
Arapahoe Co, CO
Arvada, CO
Brighton, CO
Colorado Springs, CO
Denver, CO
n n
n n
n n
u ii
n n
Englewood, CO
Garfield, CO
Grand Junction, CO
Longmont, CO
Pueblo, CO
n n
Routt Co, CO
New Haven, CT
Waterbury, CT
Wilmington, DE
(003)
(001)
(002A)
(002G)
(004)
(013)
(003)
(009)
(004)
(001)
(001)
(001)
(001)
(001)
(001)
(004)
(001)
(002)
(003)
(009)
(010)
(012)
(001)
(001)
(010)
(001)
(001)
(003)
(003)
(123)
(123)
(002)
2
1
1
2
2
2
2
1
1
1
2
1
1
1
1
2
4
3
1
2
2
1
1
2
2
1
1
1
3
2
2
2
0
1
0
0
0
1
0
1
0
1
0
0
1
3
1
1
1
1
1
0
1
0
0
0
0
0
0
2.78
1.06
1.54
2.59
1.48
1.55
1.41
1.18
1.51
1.11
1.77
1.10
1.60
1.17
1.37
1.70
3.47
2.13
1.57
1.67
1.67
1.80
1.20
1.53
1.07
1.03
1.03
1.33
1.57
1.41
1.21
2
2
2
1
1
1
2
1
2
1
1
0
0
0
0
0
0
1
0
0
0
0
Max 1981 Max
Qtrly No of Quarters Qtrly
Ave >1.0 >1.5 Ave
1.13 2 2
1.29 1 0
1.49 2 0
1 0
1.06
1.13 1 0
1.10
2 0
1.53
1.03
1.23
1.10
1.27
4.32
1.17
1.39
1.04
1.08
1.43
-o
70
TO
ya
-------
TABLE 7-4. (continued)
t—»
tn
Station #
Washington, DC
H n
it n
n n
n n
Oade Co, PL
Miami, FL
Perrine, FL
Hillsborough, FL
Tampa, FL
Boise, ID
Kellogg, ID
n n
Shoshone Co, ID
n n
n n
a n
a n
n n
Chicago, IL
it n
n n
n n
n ii
Cicero, IL
Elgin, IL
Granite City, IL
» n
it H
n n
Jeffersonville, IN
East Chicago, IL
n n
ii ii
n n
(005)
(007)
(008)
(Oil)
(015)
(017)
(020)
(016)
(002)
(082)
(043)
(003)
(004)
(006)
(015)
(016)
(017)
(020)
(021)
(027)
(022)
(030)
(005)
(036)
(037)
(001)
(004)
(007)
(009)
(010)
(Oil)
(001)
(001)
(003)
(004)
(006)
1979 Max
No. of Quarters Qtrly
>1.0 >1.5 Ave
1
4
1
2
2
1
1
3
1
2
3
4
4
2
1
4
2
4
4
1
1
1
1
1
4
4
4
3
2
2
1
2
0
1
0
0
0
0
0
0
0
4
0
1
4
0
0
0
0
0
0
4
0
0
0
1
0
1.49
1.89
1.90
1.44
1.06
1.45
1.16
1.46
1.01
1.31
1.50
9.02
8.25
1.21
2.27
4.57
4.11
13.54
10.81
1.05
1.02
1.14
1.00
1.04
1.15
3.17
1.33
1.38
2.19
1.42
1.67
1.34
1980 Max 1981 Max
Ho. of Quarters Qtrly No of Quarters Qtrly
>1.0 >1.5 Ave >1.0 >1,5 Ave
2
1
1
1
2
4
1
3
2
4
3
1
1
1
3
1
1
0
0
0
0
4
0
4
0
0
1
2
0
0
1.10
1.09
1.07
1.01
6.88
8.72 4 4
1.02
3. 33 2 2
2. 15 1 0
13. 67 4 4
7.18
1.02
1.06
1.95
2.97 4 3
1.43 1 0
1.04
6.67
1.54
1.49
11.82
7.27
1.13
-------
TABLE 7-4. (continued)
O>
1979 Max 1980
No. of Quarters Qtrly No. of Quarters
Station # >1.0 >1.5 Ave >1.0 >1.5
Hammond, IN
ii ii
Indianapolis, IN
Oes Moines, IA
Buechel, KY
Covington, KY
ii ii
Greenup Co, KY
Jefferson Co, Ky
Louisville, KY
ii ii
n ii
ii n
n n
n n
Newport, KY
Okolona, KY
Paducha, KY
n n
St. Matthews, KY
Shively, KY
Baton Rouge, LA
Portland, ME
Anne Arundel Co,
n n
Baltimore, MO
n n
n n
n n
n n
Cheverly, MD
Essex, MD
Hyattsville, MD
Springfield, MA
Boston, MA
(004)
(006)
(030)
(051)
(001)
(001)
(008)
(003)
(029)
(004)
(009)
(019)
(020)
(021)
(028)
(002)
(001)
(004)
(020)
(004)
(002)
(002)
(009)
MD (001)
(003)
(001)
(006)
(008)
(009)
(018)
(004)
(001)
(001)
(002)
(012)
2
1
1
1
2
1
1
1
1
1
1
1
1
1
1
1
1
1
2
1
2
2
1
1
1
2
4
2
2
1
1
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
1
1
0
0
0
0
0
0
0
0
1
0
0
1
0
1.18
1.46
1.16
1.30
1.12
1.16
1.42
1.05
1.01
1.29
1.06
1.06
1.51
1.41
1.22
1.20
1.56
1.57
1.02
1.27
1.45
1.06
1.09
1.24
1.08
1.12
1.51
1.15
1.18
1.68
1.01
1
1
1
1
1
1
1
2
1
1
0
1
1
1
1
1
1
1
1
0
Max 1981 Max
Qtrly No of Quarters Qtrly
Ave >1.0 >1.5 Ave
1.41
1.78
2.41
1.75
1.59
2.52
1.42
2.31
1.83
1.04
O
yo
-------
TABLE 7-4. (continued)
I
I—•
^J
1979 Max 1980 Max 1981 Max
No. of Quarters Qtrly No. of Quarters Qtrly No of Quarters Qtrly
Station # >1.0 >1.5 Ave >1.0 >1.5 Ave >1.0 >1.5 Ave
Minneapolis, MN
ii ii
Richfield, MN
St. Louis Park, MN
St. Paul, MN
n ii
Lewis & Clark Co, MT
II H
Omaha, NE
Las Vegas, NV
Newark, NJ
Perth Amboy, NO
Paterson, NJ
Elizabeth, NJ
Yonkers, NY
Cincinnatti, OH
Laureldale, PA
Reading, PA
E.Conemaugh, PA
Throop, PA
Lancaster City, PA
New Castle, PA
Montgomery Co, PA
Potts town, PA
Phi la., PA
ii »
n ii
n n
Guaynabo Co, PR
Ponce, PR
San Juan Co. , PR
E. Providence, RI
Providence, RI
n ii
Greenville, SC
(027)
(055)
(004)
(007)
(031)
(038
(002)
(008)
(034)
(001)
(001)
(001)
(001)
(002)
(001)
(001)
(717)
(712)
(804)
(019)
(315)
(015)
(103)
(101)
(026)
(028)
(031)
(038)
(001)
(002)
(003)
(008)
(007)
(015)
(001)
1
4
2
1
1
4
1
1
1
1
1
1
1
1
4
1
3
3
1
1
1
1
3
4
2
1
2
1
4
2
4
1
2
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
2.44
3
1.95 2 0
2.87 4
1.04
1.36 3
4.19 4
1 0
1.08
1.15
1.17
1.08
1.42
1.16
1.08
1.15
3.30 2
1.11
1.28
1.13
1.18
1.01
1.23
1.16
1.21
2.71 3 0
1.29
1.06
1.60 1 0
1.08
3.59
1.10
1.92 2 0
1.34
1.38
2.41 3 1 1.52
1.18
3.04
1.82 2 2 3.11
2.75 2 2 3.19
1.19
1.86 4 3 2.18
1.26 1 0 1.30
1.06 1 0 1.02
1.16
-<
o
-------
TABLE 7-4. (continued)
c»
1979 Max 1980 Max 1981 Max
No. of Quarters Qtrly No. of Quarters Qtrly No of Quarters Qtrly
Station # >1.0 >1.5 Ave >1.0 >1.5 Ave >1.0 >1.5 Ave
Nashvi 1 1 e/Oavi dson ,
TN
San Antonio, TX
Dallas, TX
it n
ii it
n n
ii n
ii ii
El Paso, TX
n ii
n n
n ii
II H
II II
II II
II II
II II
II II
II 11
II II
Houston, TX
n n
n n
ii ii
Ft. Worth, TX
Seattle, WA
Tacoma, WA
Charleston, WV
(006)
(034)
(018)
(029)
(035)
(046)
(049)
(050)
(002A)
(002F)
(002G)
(018)
(021)
(022)
(023)
(027)
(028)
(030)
(031)
(033)
(001)
(002)
(037)
(049)
(003)
(057)
(004)
(001)
1
1
1
1
1
1
1
2
1
1
4
2
1
2
2
2
1
1
1
2
2
1
3
2
1
1
1
0
0
1
0
0
0
0
0
1
1
0
0
1
1
0
0
0
0
0
0
0
0
1.05
1.23
1.59
1.07
1.12
1.22
1.01
1.13
1.90
1.90
2.60
1.91
1.02
1.84
2.12
2.15
1.02
2.47
1.97
1.35
1.39
1.26
1.13
1.14
1.36
1.06
1.09
2.12
4 1 1.79
2 1.74 4 2 1.75
1 0 1.16
1 1 1.96
-------
PRELIMINARY DRAFT
TABLE 7-5. DISTRIBUTION OF AIR LEAD CONCENTRATIONS BY TYPE OF SITE
Concentration ranges (ug/m3)
Site- type
Population
Stationary
source
Background
Total
(site-years)
£.5
300
50
21
371
>.5
Sl.O
173
12
0
185
>1.0
31.5
46
10
0
56
>1.5
£2.0
7
2
0
9
>2.0
5
21
0
26
Total no. of
site-years
531
95
21
647
Percent of sites
in concentration
range
57%
29%
9%
4%
100%
Data are the number of site years during 1979-81 falling within the designated quarterly aver-
age concentration range. To be included, a site year must have four valid quarters of data.
7.2.1-3-1 Airborne particle size distributions. The effects of airborne lead on human health
and welfare depend upon the sizes of the lead-containing particles. As discussed in Chapter
6, large particles are removed relatively quickly from the atmosphere by dry and wet deposi-
tion processes. Particles with diameter smaller than a few micrometers tend to remain
airborne for long periods (see Section 6.3.1).
Figure 7-5 summarizes airborne lead particle size data from the literature. Minimum and
Maximum aerodynamic particle diameters of 0.05 urn and 25 urn, respectively, have been assumed
unless otherwise specified in the original reference. Note that most of the airborne lead
mass is associated with small particles. There is also a distinct peak in the upper end of
many of the distributions. Two separate categories of sources are responsible for these dis-
tributions: the small particles result from nucleation of vapor phase lead emissions (pre-
dominantly automotive), while the larger particles represent primary aerosol emitted from com-
bustion or from mechanical processes (such as soil erosion, abrasion of metal products, re-
suspension of automobile tailpipe deposits, and flaking of paint).
Information associated with each 1n the distributions in Figure 7-5 may be found in Table
7A-1 of Appendix 7A. The first six distributions were obtained by an EPA cascade impactor
network established in several cities during the calendar year 1970 (Lee et al., 1972). These
PB7/A
7-19
7/14/83
-------
PRELIMINARY DRAFT
distributions represent the most extensive size distribution data base available. However
the impactors were operated at excessive air flow rates that most likely resulted in particle
bounceoff, biasing the data toward smaller particles (Dzubay et al., 1976). Many of the later
distributions, although obtained by independent investigators with unknown quality control
were collected using techniques which minimize particle bounceoff and hence may be more reli-
able. It is important to note that a few of the distributions were obtained without backup
filters that capture the smallest particles. These distributions are likely to be inaccurate
since an appreciable fraction of the airborne lead mass was probably not sampled. The distri-
butions of Figure 7-5 have been used with published lung deposition data to estimate the frac-
tion of inhaled airborne lead deposited in the human respiratory system (see Chapter 10).
7.2.1.3.2 Vertical gradients and siting guidelines. New guidelines for placing ambient air
lead monitors went into effect in July, 1981 (F.R. , 1981). "Microscale" sites, placed between
5 and 15 meters from thoroughfares and 2 to 7 meters above the ground, are prescribed, but
until now few monitors have been located that close to heavily traveled roadways. Many of
these raicroscale sites might be expected to show higher lead concentrations than that measured
at nearby middlescale urban sites, due to vertical gradients in lead concentrations near the
source. One study (PEDCo, 1981) gives limited insight into the relationship between a micro-
scale location and locations further from a roadway. The data in Table 7-6 summarize total
suspended particulates and particulate lead concentrations in samples collected in Cincinnati
Ohio, on 21 consecutive days in April and May, 1980, adjacent to a 58,500 vehicles-per-day
expressway connector. Simple interpolation indicates that a microscale monitor as close as 5
meters from the roadway and 2 meters above the ground would record concentrations some 20 per-
cent higher than those at a "middle scale" site 21.4 meters from the roadway. On the other
hand, these data also indicate that although lead concentrations very close to the roadway
(2.8 m setback) are quite dependent on the height of the sampler, the averages at the three
selected heights converge rapidly with increasing distance from the roadway. In fact, the
average lead concentration (1.07 ug/m3) for the one monitor (6.3 m height, 7.1 m setback) that
satisfies the microscale site definition proves not to be significantly different from the
averages for its two companions at 7.1 m, or from the averages for any of the three monitors
at the 21.4 m setback. It also appears that distance from the source, whether vertical or
horizontal, can be the primary determining factor for changes in air lead concentrations. At
7.1 m from the highway, the 1.1 and 6.3 m samplers would be about 7 and 11 meters from the
road surface. The values at these vertical distances are only slightly lower than the
corresponding values for comparable horizontal distances.
PB7/A 7-20 7/14/83
-------
PRELIMINARY DRAFT
1.00
0.76
0.60
0.26
0
1.00
0.76
0.50
0.26
0
1.00
0.76
0.60
0.26
0
1.00
0.76
•» 0.60
0.26
0
1.00
0.76
0.60
0.26
0
1.00
0.76
0.60
0.26
0
1.00
0.76
0.60
076
0
1.00
0.76
0.60
0.25
1 CHICAGO, IL
2 CINCINNATI, OH
3 DENVER. CO
4 PHILADELPHIA. PA
S ST. LOUIS, MO
6 WASHINGTON, D.C.
rV,
7 CINCINNATI, OH
I FAIRFAX. OH
ALTON. IL
..
NEAR SMELTER
0 CENTKVILLE. IL
SVILLE, IL
2 KMOX n 1ADIO
• 11 TRANSMITS
_dL
13 PERE n MARQUETTE
PARK. IL 11
14 WOOD ,
RIVER. IL
15 CINCINNATI, OH
FREEWAY
1» GLASGOW, SCOTLAND
1.646
7 S.E. MISSOURI,
I S.E. MISS
FAR FROM
SMELTER
iURI.
4nri
I! NEW BRUNSWICK. NJ
HIGHWAY
20 SAN FRANCISCO. CA
21 LOS ANGELES. CA
22 LOS ANGELES. CA
FREEWAY
23 PASADENA. CA
24 PASADENA, CA
26 GREAT SMOKIES
NAT'L PARK. TN
2« PITTSBURGH. PA
27 NEPAL . HIMALAYAS
21 EXPORT, PA
29 PACKWOOO, WA
30 OLYMPIC NAT'L
PARK. WA
31 BERMUDA
1.20
32 BERMUDA
i3ANN ARBOR. MI
34 ANN ARBOR. Ml
_J
3B CHICAGO. IL
LINCOLN. NE
37 TALLAHASSEE. FL
1.S01'
31 CHILTON. ENGLAND
3* TREBANO8. ENGLAND
40 NEW YORK. NY
0.01 0.1 1 10 0.01 0.1 1 10 0.01 0.1 1 10 0.01 0.1 1 10 0.01 0.1 1 10
dp. nm
Figure 7-5. Airborne mass size distributions for lead taken from the literature. AC represents
the airborne lead concentration in each size range, Cj is the total airborne lead concentra-
tion in all size ranges, and dp is the aerodynamic particle diameter. A density of 6 g/cm3 for
lead-containing particles has been used to convert aerodynamic to physical diameter when
applying the lower end of the lung deposition curves of Figures 7-3 through 7-5.
PB7/A
7-21
7/1/83
-------
PRELIMINARY DRAFT
TABLE 7-6. VERTICAL DISTRIBUTION OF LEAD CONCENTRATIONS
Kansas City
east of road
Kansas City
west of road
Cincinnati
east of road
Cincinnati
west of road
Cincinnati
Cincinnati
Cincinnati
Setback
distance
(m)
3.0*
3.0*
3.0*
3.0*
2.8
7.1
21.4
Height
(m)
6.1
1.5
6.1
1.5
6.1
1.5
6.1
1.5
10.5
6.3
1.1
10.5
6.3
1.1
10.5
6.3
1.1
Effective1
distance
from
source
(m)
6.4
3.2
6.4
3.2
6.4
3.2
6.4
3.2
10.4
6.4
2.9
12.3
9.2
7.1
23.6
22.2
21.4
Air lead
cone.
(ug/m3)
1.7
2.0
1.5
1.7
0.9
1.4
0.6
0.8
0.81
0.96
1.33
0.93
1.07
1.16
0.90
0.97
1.01
Ratio to
source
0.85
S
0.88
S
0.64
S
0.75
S
0.61
0.72
S
0.69
0.80
0.87
0.68
0.73
0.77
S = Station closest to source used to calculate ratio.
Effective distance was calculated assuming the source was the edge of the roadway at a height
of 0.1 m.
*Assumed setback distance of 3.0 m<
Other urban locations around the country with their own characteristic wind flow patterns
and complex settings, such as multiple roadways, may produce situations where the microscale
site does not record the highest concentrations. Collectively, however, the addition of these
microscale sites to the nation's networks can be expected to shift the distribution of
reported quarterly averages toward higher values. This shift will result from the change in
composition of the networks and is a separate phenomenon from downward trend at long estab-
lished sites described above, reflecting the decrease in lead additives used in gasoline.
PB7/A
7-22
7/14/83
-------
PRELIMINARY DRAFT
Two other studies show that lead concentrations decrease with vertical distance from the
source. PEDCo-Environmental (1977) measured lead concentrations at heights of 1.5 and 6.1 m
at sites in Kansas City, MO and Cincinnati, OH. The sampling sites in Kansas City were des-
cribed as unsheltered, unbiased by local pollution influences, and not immediately surrounded
by large buildings. The Cincinnati study was conducted in a primarily residential area with
one commercial street. Samplers were operated for 24-hour periods; however, a few 12-hour
samples were collected from 8 AM to 8 PM. Data were obtained in Kansas City on 35 days and in
Cincinnati on 33 days. The range and average values reported are shown in Table 7-7. In all
cases except two, the measured concentrations were greater at 1.5 meters than at 6.1 meters.
Note that the difference between the east side and west side of the street was approximately
the same as the difference between 1.5 m and 6.1 m in height.
Sinn (1980) investigated airborne lead concentrations at heights of 3 and 20 m above a
road in Frankfurt, Germany. Measurements conducted in December 1975, December 1976, and Janu-
ary 1978 gave monthly mean values of 3.18, 1.04, and 0.66 \tg/m3, respectively, at 3 m. The
corresponding values at 20 m were 0.59, 0.38, and 0.31 ug/nis, showing a substantial reduction
at this height. The decrease in concentration over the 2-year period was attributed to a de-
crease in the permissible lead content of gasoline from 0.4 to 0.15 g/liter beginning in Janu-
ary 1976.
Two reports show no relationship between air concentration and vertical distance. From
August 1975 to July 1976, Barltrop and Strehlow (1976) conducted an air sampling program in
London at a proposed nursery sita under an elevated motorway. The height of the motorway was
9.3 m. Air samplers were operated at five to seven sites during the period from Monday to
Friday, 8 AM to 6 PM, for one year. The maximum individual value observed was 18 pg/m3. The
12 month mean ranged from 1.35 pg/m3 to 1.51 M9/n»3» with standard deviations of 0.91 and 0.66,
respectively. The authors reported that the airborne concentrations were independent of height
from ground level up to 7 m.
Ter Haar (1979) measured airborne lead at several heights above the ground, using
samplers positioned 6 m from a heavily traveled road in Detroit. A total of nine 8-hour day-
time samples were collected. The overall average airborne lead concentrations at heights of
0.3, 0.9, 1.5, and 3.0 m were 4.2, 4.8, 4.7, and 4.6 ug/m3, respectively, indicating a uniform
concentration over this range of heights at the measurement site. It should be noted that at
any one height, the concentration varied by as much as a factor of 10 from one day to the
next; the importance of simultaneous sampling when attempting to measure gradients is clearly
demonstrated.
Data that show variations with vertical distance reflect the strong Influence of the geo-
metry of the boundary layer, wind, and atmospheric stability conditions on the vertical gradi-
ent of lead resulting from automobile emissions. The variability of concentration with height
PB7/A 7-23 7/14/83
-------
PRELIMINARY DRAFT
is further complicated by the higher emission elevation of smokestacks. Concentrations
measured from sampling stations on the roofs of buildings several stories high may not reflect
actual human exposure conditions, but neither would a single sampling station located at
ground level in a building complex. The height variation in concentration resulting from
vertical diffusion of automobile emissions is likely to be small compared to temporal and
spatial variations resulting from surface geometry, wind, and atmospheric conditions. Our
understanding of the complex factors affecting the vertical distribution of airborne lead is
extremely limited, but the data of Table 7-6 indicate that air lead concentrations are pri-
marily a function of distance from the source, whether vertical or horizontal.
7.2.1.3.3 Indoor/outdoor relationships. Because people spend much of their time indoors, am-
bient air data may not accurately indicate actual exposure to airborne lead. Table 7-7 sum-
marizes the results of several indoor/outdoor airborne lead studies. In nearly all cases, the
indoor concentration is substantially lower than the corresponding value outdoors; the only
indoor/outdoor ratio exceeding unity is for a high-rise apartment building, where air taken in
near street level is rapidly distributed through the building air circulation system. Some of
the studies in Table 7-7 show smaller indoor/outdoor ratios during the winter, when windows
and doors are tightly closed. Overall, the data suggest indoor/outdoor ratios of 0.6 to 0.8
are typical for airborne lead in houses without air conditioning. Ratios in air conditioned
houses are expected to be in the range of 0.3 to 0.5 (Yocum, 1982).
The available data imply that virtually all airborne lead found indoors is associated
with material transported from the outside. Because of the complexity of factors affecting
infiltration of air into buildings, however, it is difficult to predict accurately indoor lead
concentrations based on outdoor levels. Even detailed knowledge of indoor and outdoor air-
borne lead concentrations at fixed locations may still be insufficient to assess human expo-
sure to airborne lead. The study of Tosteson et al. (1982) in Table 7-7 included measurement
of airborne lead concentrations using personal exposure monitors carried by individuals going
about their day-to-day activities. In contrast to the lead concentrations of 0.092 and 0.12
ug/m3 at fixed locations, the average personal exposure was 0.16 ug/m3. The authors suggest
this indicates an inadequacy of using fixed monitors at either indoor or outdoor locations to
assess exposure.
7.2.2 Lead in Soil
Much of the lead in the atmosphere is transferred to terrestrial surfaces where it is
eventually passed to the upper layer of the soil surface. The mechanisms which determine the
transfer rate of lead to soil are described in Section 6.4.1 and the transformation of lead in
PB7/A 7-24 7/14/83
-------
PRELIMINARY DRAFT
TABLE 7-7. COMPARISON OF INDOOR AMD OUTDOOR AIRBORNE LEAD CONCENTRATIONS
Airborne lead concentration
(ug/m3)
Type of building Indoor Outdoor
Library
City hall
Office building 1
Office building 2
House 1
House 2
Apartment building 1
Second floor
Roof
Apartment building 2
Third floor
Eleventh floor
Eighteenth floor
Roof
1.12
1.31
0.73
0.55
1.37
0.94
1.46
1.50
--
1.68
1.86
--
2.44
1.87
1.44
1.09
2.48
1.34
2.67
1.38
1.21
--
—
1.42
Indoor/outdoor
ratio Location Ref
0.46
0.70
0.51
0.51
0.55
0.70
0.55
1.09
--
—
—
--
Hartford, CT (1)
1
1
1
1
'
New York, NY (2)
it
ii
H
ii
H
New air conditioned
apartment
Older non-air condi-
tioned apartment
Air conditioned public
building
Non-air conditioned
storeroom in public
building
Houses
University buildings
Public schools
Store
Commercial office
Houses
Houses with gas stoves
Houses with electric
stoves
Office buildings
House 1
Before energy conser-
vation retrofit
After energy conser-
vation retrofit.
House 2
Before energy
conservation retrofit
After energy
conservation retrofit
0.12-0.40 0.13-0.50
0.14-0.51 0.17-0.64
0.15-0.79 0.33-1.18
0.45-0.98 0.38-1.05
0.092
0.12
0.039
0.037
0.035
0.038
0.070
0.084
0.045
0.112
0.82
0.87
0.63
0.81
0.53
0.28
0.28
0.31
0.27
0.74
0.65
0.68
0.42
0.56
0.44
0.78
0.34
New York, NY
(3)
Pittsburgh, PA (4)
Topeka, KS
Boston, MA
(5)
(6)
Medford, OR (7)
1. Yocum et al., 1971.
2. General Electric Company, 1972.
3. Hal pern, 1978.
4. Cohen and Cohen, 1980.
5. Tosteson et al., 1982.
6. Moschandreas et al., 1981.
7. Berk et al., 1981.
7-25
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PRELIMINARY DRAFT
soil in Section 6.5.1. The uptake of lead by plants and its subsequent effect on animals may
be found in Section 8.2. The purpose of this section is to discuss the distribution of lead
in U.S. soils and the impact of this lead on potential human exposures.
7.2.2.1. Typical Concentrations of Lead in Soil.
7.2.2.1.1 Lead in urban, smelter, and rural soils. Shacklette et al. (1971) sampled soils at
a depth of 20 cm to determine the elemental composition of soil materials derived from the
earth's crust, not the atmosphere. The range of values probably represent natural levels of
lead in soil, although there may have been some contamination with anthropogenic lead during
collection and handling. Lead concentrations in soil ranged from less than 10 to greater than
70 |jg/g. The arithmetic mean of 20 and geometric mean of 16 jjg/g reflect the fact that most
of the 863 samples were below 30 ug/g at this depth. McKeague and Wolynetz (1980) found the
same arithmetic mean (20 ug/g) for 53 uncultivated Canadian soils. The range was 5 to 50 ng/g
and there was no differences with depth between the A, B and C horizons in the soil profile.
Studies discussed in Section 6.5.1 have determined that atmospheric lead is retained in
the upper two centimeters of undisturbed soil, especially soils with at least 5 percent
organic matter and a pH of 5 or above. There has been no general survey of this upper 2 cm of
the soil surface in the United States, but several studies of lead in soil near roadsides and
smelters and a few studies of lead in soil near old houses with lead-based paint can provide
the backgound information for determining potential human exposures to lead from soil.
Because lead is immobilized by the organic component of soil (Section 6.5.1), the concen-
tration of anthropogenic lead in the upper 2 cm is determined by the flux of atmospheric lead
to the soil surface. Near roadsides, this flux is largely by dry deposition and the rate de-
pends on particle size and concentration. These factors vary with traffic density and average
vehicle speed (see Section 6.4.1). In general, deposition flux drops off abruptly with
increasing distance from the roadway. This effect is demonstrated in studies which show that
surface soil lead decreases exponentially up to 25 m from the edge of the road. The original
work of Quarles et al. (1974) showed decreases in soil lead from 550 to 40 ug/g within 25 m
alongside a highway with 12,500 vehicles/day in Virginia. Their findings were confirmed by
Wheeler and Rolfe (1979), who observed an exponential decrease linearly correlated with traf-
fic volume. Agrawal et al (1981) found similar correlations between traffic density and road-
side proximity in Baroda City, as did Garcia-Miragaya et al. (1981) in Venzuela and Wong and
Tarn (1978) in Hong Kong. The extensive study of Little and Wiffen (1978) is discussed in
Chapter 6. These authors found additional relationships between particle size and roadside
proximity and decreases with depth in the soil profile. The general conclusion from these
studies is that roadside soils may contain atmospheric lead from 30 to 2000 ug/g in excess of
natural levels within 25 meters of the roadbed, all of which is in the upper layer of the soil
PB7/A 7-26 7/14/83
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PRELIMINARY DRAFT
profile. It is assumed that particles deposited directly on the roadway are washed to the
edge of the pavement, but do not migrate beyond the shoulder.
Near primary and secondary smelters, lead in soil decreases exponentially within a 5 to
10 km zone around the smelter complex. Soil lead contamination varies with the smelter emis-
sion rate, length of time the smelter has been in operation, prevailing windspeed and direc-
tion, regional climatic conditions, and local topography (Roberts, 1975).
Little and Martin (1972) observed decreases from 125 to 10 ug/g in a 6 km zone around a
smelting complex in Great Britain; all of the excess lead was in the upper 6 cm of the soil
profile. Roberts (1975) reported soil lead between 15,000 and 20,000 ug/g near a smelter in
Toronto. Kerin (1975) found 5,000 to 9,000 ug/g adjacent to a Yugoslavian smelter; the con-
tamination zone was 7 km in radius. Ragaini et al. (1977) observed 7900 ug/g near a smelter
in Kellogg, Idaho; they also observed a 100-fold decrease at a depth of 20 cm in the soil pro-
file. Palmer and Kucera (1980) observed soil lead in excess of 60,000 ug/g near two smelters
in Missouri, decreasing to 10 ug/g at 10 km.
Urban soils may be contaminated from a variety of atmospheric and non-atmospheric
sources. The major sources of soil lead seem to be paint chips from older houses and deposi-
tion from nearby highways. Lead in soil adjacent to a house decreases with distance from the
house; this may be due to paint chips or to dust of atmospheric origin washing from the
rooftop (Wheeler and Rolfe, 1979).
Andresen et al. (1980) reported lead in the litter layer of 51 forest soils in the north-
eastern United States. They found values from 20 to 700 ug/g, which can be compared only
qualitatively to the soil lead concentration cited above. This study clearly shows that the
major pathway of lead to the soil is by the decomposition of plant material containing high
concentrations of atmospheric lead on their surface. Because this organic matter is a part of
the decomposer food chain, and because the organic matter is in dynamic equilibrium with soil
moisture, it is reasonable to assume that lead associated with organic matter is more mobile
than lead tightly bound within the crystalline structure of inorganic rock fragments. This
argument is expressed more precisely in the discussions below.
Finally, a definitive study which describes the source of soil lead was reported by
Gulson et al. (1981) for soils in the vicinity of Adelaide, South Australia. In an urban to
rural transect, stable lead isotopes were measured in the top 10 cm of soils over a 50 km dis-
tance. By their isotopic compositions, three sources of lead were identified: natural, non-
automotive industrial lead from Australia, and tetraethyl lead manufactured in the United
States. The results indicated that most of the soil surface lead originated from leaded gaso-
line. Similar studies have not been conducted in the United States.
PB7/A 7-27 7/W83
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PRELIMINARY DRAFT
7.2.2.1.2 Natural and anthropogenic sources of soil lead. Although no study has clearly
identified the relative concentrations of natural and anthropogenic lead in soil, a few clari-
fying statements can be made with some certainty. Lead may be found in inorganic primary
minerals, on humic substances, complexed with Fe-Mn oxide films, on secondary minerals or in
soil moisture. All of the lead in primary minerals is natural and is bound tightly within the
crystalline structure of the minerals. Most of this lead can be released only by harsh treat-
ment with acids. The lead on the surface of these minerals is leached slowly into the soil
moisture. Atmospheric lead forms complexes with humic substances or on oxide films that are
in equilibrium with soil moisture, although the equilibrium strongly favors the complexing
agents. Consequently, the ratio of anthropogenic to natural lead in soil moisture depends
mostly on the amounts of each type of lead in the complexing agents and very little on the
concentration of natural lead in the inorganic minerals.
Except near roadsides and smelters, only a few ug of atmospheric lead have been added to
each gram of soil. Several studies indicate that this lead is available to plants (Section
8.3.1.1) and that even with small amounts of atmospheric lead, about 75 percent of the lead in
soil moisture is of atmospheric origin. A conservative estimate of 50 percent is used in the
discussions in Section 7.3.1.2. A breakdown of the types of lead in soil may be found in
Table 7-8.
TABLE 7-8. SUMMARY OF SOIL LEAD CONCENTRATIONS!
Matrix
Total soil
Primary minerals
Humic substances*
Soil moisture
Natural
lead
8-25
8-25
20
0.0005
Atmospheric
lead
Rural
3
60
0.0005
Urban
50-150
2000
0.0150
Total
lead
Rural
10-30
8-25
80
0.001
Urban
150-300
8-25
2000
0.0155
t All values in ug/g.
*Assumes 5% organic matter, pH 5.0; may also include lead in Fe-Mn oxide films.
Source: Section 6.5.1
7.2.2.2 Pathways of Soil Lead to Human Consumption.
7.2.2.2.1 Crops. Lead on the surfaces of vegetation may be of atmospheric origin, or a com-
bination of atmospheric and soil in the internal tissues. As with soils, lead on vegetation
surfaces decreases exponentially with distance away from roadsides and smelters (Cannon and
Bowles, 1962; see also Chapter 8). This deposited lead is persistent. It is neither washed
PB7/A
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7/14/83
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PRELIMINARY DRAFT
off by rain nor taken up through the leaf surface. For many years, plant surfaces have been
used as indicators of lead pollution (Garty and Fuchs, 1982; Pilegaard, 1978; Ratcliffe, 1975;
Ruhling and Tyler, 1969; Tanaka and Ichikuni, 1982). These studies all show that lead on the
surface of leaves and bark is proportional to traffic density and distance from the highway,
or more specifically, to air lead concentrations and particle size distributions. Other
factors such as surface roughness, wind direction and speed are discussed in Chapter 6. The
data also show that lead in internal plant tissues is directly related to lead in soil.
In a study to determine the background concentrations of lead and other metals in agri-
cultural crops, the Food and Drug Administration (Wolnik et al., 1983), in cooperation with
the U.S. Department of Agriculture and the U.S. Environmental Protection Agency, analyzed over
1500 samples of the most common crops taken from a cross section of geographic locations.
Collection sites were remote from mobile or stationary sources of lead. Soil lead concentra-
tions were within the normal range (8-25 pg/g) of U.S. soils. Extreme care was taken to avoid
contamination during collection, transportation, and analysis. The concentrations of lead in
crops found by Wolnik et al. (1983) are shown as "Total" concentrations in Table 7-9. The
breakdown by source of lead is discussed below. The total concentration data should probably
be seen as representing the lowest concentrations of lead in food available to Americans. It
is likely that lead concentrations in crops harvested by farmers are somewhat higher for
several reasons: some crops are grown closer to highways and stationary sources of lead than
those sampled by Wolnik et al. (1983); some harvest techniques used by farmers might add more
lead to the crop than did Wolnik et al.; and some crops are grown on soils significantly
higher in lead than those of the Wolnik et al. study because of a history of fertilizer ad-
ditions or sludge applications.
Because the values reported by Wolnik et al. are of better quality than previously
reported data for food crops, it is necessary to disregard many other reports as being either
atypical or erroneous. Studies that specifically apply to roadside or stationary source con-
ditions, however, may be applicable if the data are placed in the context of these recent
findings by Wolnik et al. (1983). Studies of the lead associated with crops near highways
have shown that both lead taken up from soil and aerosol lead delivered by deposition are
found with the edible portions of common vegetable crops. However, there is enormous vari-
ability in the amount of lead associated with such crops and in the relative amounts of lead
in the plants versus on the plants. The variability depends upon several factors, the most
prominent of which are the plant species, the traffic density, the meteorological conditions,
and the local soil conditions (Welch and Dick, 1975; Rabinowitz, 1974; Arvik, 1973; Dedolph et
PB7/A 7-29 7/14/83
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PRELIMINARY DRAFT
TABLE 7-9. BACKGROUND LEAD IN BASIC FOOD CROPS AND MEATS+
Crop
Wheat
Potatoes
Field corn
Sweet corn
Soybeans
Peanuts
Onions
Rice
Carrots
Tomatoes
Spinach
Lettuce
Beef (muscle)
Pork (muscle)
Natural
Pb
0.0015
0.0045
0.0015
0.0015
0.021
0.050
0.0023
0.0015
0.0045
0.001
0.0015
0.0015
0.0002
0.0002
Indirect
atmospheric
0.0015
0.0045
0.0015
0.0015
0.021
0.050
0.0023
0.0015
0.0045
0.001
0.0015
0.0015
0.002
0.002
Direct
atmospheric
0.034
—
0.019
—
—
--
—
0.004
--
—
0.042
0.010
0.02
0.06
Total1"
0.037
0.009
0.022*
0.003
0.042
0.100
0.0046*
0.007*
0.009*
0.002*
0.045*
0.013
0.02**
0.06**
±A11 units are in ug/g fresh weight.
^Except as indicated, data are from Wolnick et al. (1983).
*Preliminary data provided by the Elemental Analysis Research Center, Food and Drug Adminis-
tration, Cincinnati, OH.
**Data from Penumarthy et al. (1980).
al., 1970; Motto et al., 1970; Schuck and Locke, 1970; Ter Haar, 1970). These factors,
coupled with the fact that many studies have neglected differentiation between lead on plants
versus lead in plants, make it difficult to generalize. Data of Schuck and Locke (1970)
suggest that in some cases (e.g., tomatoes and oranges) much of the surface lead is readily
removed by washing. But as noted in Section 6.4.3, this is not universally true; in some
cases, much more vigorous washing procedures are necessary.
Ter Haar (1970) found that inedible portions of several plants (bean leaves, corn husks,
soybean husks, and chaff from oats, wheat, and rice) had two to three times the lead concen-
tration when grown near a busy highway compared with similar plants grown in a greenhouse sup-
plied with filtered air. The edible portions of these and other plants showed little or no
difference in lead content between those grown in ambient air and those grown in the filtered
air. However, the lead concentrations found by Ter Haar (1970) for edible portions of crops
grown in filtered air in the greenhouse were one to two orders of magnitude higher than those
PB7/A
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7/14/83
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PRELIMINARY DRAFT
of the same types of crops taken from actual agricultural situations by Wolnik et al. (1983).
Dedolph et al. (1970) found that while ryegrass and radish leaves grown near a busy highway
contained deposited airborne lead, the edible portion of the radish was unaffected by varia-
tions in either soil lead or air lead.
To estimate the distribution of natural and atmospheric lead in food crops (Table 7-9),
it is necessary to recognize that some crops of the Wolnik et al. study have no lead from
direct atmospheric deposition, that all lead comes through soil moisture. The lowest concen-
trations of lead are found in those crops where the edible portion grows above ground and is
protected from atmospheric deposition (sweet corn and tomatoes). Belowground crops are also
protected from atmospheric deposition but have slightly higher concentrations of lead, partly
because lead accumulates in the roots of plants (potatoes, onions, carrots). Leafy above-
ground plants (lettuce, spinach, wheat) have even higher lead concentrations presumably
because of exposure to atmospheric lead. The assumption that can be made here is that, in the
absence of atmospheric deposition, exposed aboveground plant parts would have lead concentra-
tions similar to protected aboveground parts.
The data on these ten crops suggest that root vegetables have lead concentrations between
0.0046 and 0.009 ug/g, all soil lead, which presumably is half natural and half anthropogenic
(called indirect atmospheric lead here). Aboveground parts not exposed to significant amounts
of atmospheric deposition (sweet corn and tomatoes) have less lead internally, also equally
divided between natural and indirect atmospheric lead. If it is assumed that this same con-
centration is the internal concentration for aboveground parts for other plants, it is ap-
parent that five crops have direct atmospheric deposition in proportion to surface area and
estimated duration of exposure. The deposition rate of 0.04 ng/cm2-day in rural environments
(see Section 6.4.1) could account for these amounts of direct atmospheric lead.
In this scheme, soybeans and peanuts are anomalously high. Peanuts grow underground in a
shell and should be of a lead concentration similar to potatoes or carrots, although peanuts
technically grow from the stem of a plant. Soybeans grow inside a sheath and should have an
internal lead concentration similar to corn. The fact that both soybeans and peanuts are
legumes may indicate species differences.
The accumulation of lead in edible crops was measured by Ter Haar (1970), who showed that
edible plant parts not exposed to air (potatoes, corn, carrots, etc.) do not accumulate atmo-
spheric lead, while leafy vegetables do. Inedible parts, such as corn husks, wheat and oat
chaff, and soybean hulls were also contaminated. These results were confirmed by McLean and
Shields (1977), who found that most of the lead in food crops is on leaves and husks. The
general conclusion from these studies is that lead in food crops varies according to exposure
to the atmosphere and in proportion to the effort taken to separate husks, chaff, and hulls
from edible parts during processing for human or animal consumption.
PB7/A 7-31 7/14/83
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PRELIMINARY DRAFT
These discussions lead to the conclusion that root parts and protected aboveground parts
of edible crops contain natural lead and indirect atmospheric lead, both derived from the
soil. For exposed aboveground parts, any lead in excess of the average found on unexposed
aboveground parts is considered to be the result of direct atmospheric deposition.
Near smelters, Merry et al. (1981) found a pattern different from roadside studies cited
above. They observed that wheat crops contained lead in proportion to the amount of soil
lead, not vegetation surface contamination. A similar effect was reported by Harris (1981).
7.2.2.2.2 Livestock. Lead in forage was found to exceed 950 ug/g within 25 m of roadsides
with 15,000 or more vehicles per day (Graham and Kalman, 1974. At lesser traffic densities,
200 ug/g were found. Other reports have observed 20 to 660 ug/g with the same relationship to
traffic density and distance from the road (see review by Graham and Kalman, 1974). A more
recent study by Crump and Barlow (1982) showed that the accumulation of lead in forage is di-
rectly related to the deposition rate, which varied seasonally according to traffic density.
The deposition rate was measured using the moss bag technique, in which bags of moss are
exposed and analyzed as relative indicators of deposition flux. Rain was not effective in
removing lead from the surface of the moss.
7.2.3 Lead in Surface and Ground Water
Lead occurs in untreated water in either dissolved or particulate form. Dissolved lead is
operationally defined as that which passes through a 0.45 urn membrane filter. Because atmos-
pheric lead in rain or snow is retained by soil, there is little correlation between lead in
precipitation and lead in streams which drain terrestrial watersheds. Rather, the important
factors seem to be the chemistry of the stream (pH and hardness) and the volume of the stream
flow. For groundwater, chemistry is also important, as is the geochemical composition of the
water-bearing bedrock.
Of the year-round housing units in the United States, 84 percent receive their drinking
water from a municipal or private supply of chemically treated surface or ground water. The
second largest source is privately owned wells (Bureau of the Census, 1982). In some communi-
ties, the purchase of untreated bottled drinking water is a common practice. The initial con-
centration of lead in this water, depends largely on the source of the untreated water.
7.2.3.1. Typical Concentrations of Lead in Untreated Water.
7.2.3.1.1 Surface water. Durum et al. (1971) reported a range of 1 to 55 ug/1 in 749 surface
water samples in the United States. Very few samples were above 50 ug/1, and the average was
3.9 H9/1- Chow (1978) reviewed other reports with mean values between 3 and 4 ug/1. The
National Academy of Sciences (1980) reported a mean of 4 ug/1 with a range from below
detection to 890 ug/1. Concentrations of 100 ug/1 were found near sites of sewage treatment,
urban runoff, and industrial waste disposal.
PB7/A 7-32 7/14/83
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PRELIMINARY DRAFT
Because 1 ug/1 was at or below the detection limit of most investigators during the
1970's, it is likely that the mean of 3 to 4 |jg/l was unduly influenced by a large number of
erroneously high values at the lower range of detection. On the other hand, Patterson (1980)
reports values of 0.006 to 0.05 ug/1 for samples taken from remote streams. Extreme care was
taken to avoid contamination and analytical techniques sensitive to less than 0.001 ug/1 were
used.
Streams and lakes are influenced by their water chemistry and the lead content of their
sediments. At neutral pH, lead moves from the dissolved to the particulate form and the part-
icles eventually pass to sediments. At low pH, the reverse pathway generally takes place.
Hardness, which is a combination of the Ca and Mg concentration, also can influence lead con-
centrations. At higher concentrations of Ca and Mg, the solubility of lead decreases.
Further discussion of the chemistry of lead in water may be found in Sections 6.5.2.1 and
8.2.2.
7.2.3.1.2 Ground water. Municipal and private wells account for a large percentage of the
drinking water supply. This water typically has a neutral pH and somewhat higher hardness
than surface water. Lead concentrations are not influenced by acid rain, surface runoff, or
atmospheric deposition. Rather, the primary determinant of lead concentration is the geo-
chemical makeup of the bedrock that is the source of the water supply. Ground water typically
ranges from 1 to 100 ug Pb/1 (National Academy of Sciences, 1980). Again, the lower part of
the range may be erroneously high due to difficulties of analysis. It is also possible that
the careless application of fertilizers or sewage sludge to agricultural lands can cause con-
tamination of ground water supplies.
7.2.3.1-3 Natural vs. anthropogenic lead in water. Although Chow (1978) reports that the na-
tural lead concentration of surface water is 0.5 ug/1, this value may be excessively high. In
a discussion of mass balance considerations (National Academy of Sciences, 1980), natural lead
was suggested to range from 0.005 to 10 ug/1. Patterson (1980) used further arguments to
establish an upper limit of 0.02 ug/1 for natural lead in surface water. This upper limit
will be used in further discussions of natural lead in drinking water.
Because ground water is free of atmospheric lead, lead in ground water should probably be
considered natural in origin as it occurs at the well head, unless there is evidence of
surface contamination.
7.2.3.2 Human Consumption of Lead in Water. Whether from surface or ground water supplies,
municipal waters undergo extensive chemical treatment prior to release to the distribution
system. There is no direct effort to remove lead from the water supply. However, some treat-
ments, such as flocculation and sedimentation, may inadvertently remove lead along with other
undesirable substances. On the other hand, chemical treatment to soften water increases the
solubility of lead and enhances the possibility that lead will be added to water as it passes
through the distribution system.
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PRELIMINARY DRAFT
7.2.3.2.1 Contributions to drinking water. For samples taken at the household tap, lead con-
centrations are usually higher in the initial volume (first daily flush) than after the tap
has been running for some time. Water standing in the pipes for several hours is intermediate
between these two concentrations (Sharrett et al., 1982; Worth et al., 1981). Common plumbing
materials are galvanized and copper pipe; lead solder is usually used to seal the joints of
copper pipes. Lead pipes are seldom in service in the United States, except in the New
England states (Worth et al., 1981).
Average lead content of running water at the household tap is generally lower (8 |jg/1)
than in some untreated water sources (25 to 30 |jg/l) (Sharrett et al., 1982). This implies
either that treatment can remove a portion of the lead or that measurements of untreated water
are erroneously high. If first flush or standing water is sampled, the lead content may be
considerably higher. Sharrett et al. (1982) showed that in both copper and galvanized pipes,
lead concentrations were increased by a factor of two when the sample was taken without first
flushing the line (see Section 7.3.1.3).
The age of the plumbing is an important factor. New copper pipes with lead solder ex-
posed on the inner surface of the joints produce the highest amount of lead in standing water.
After six years, this lead is leached away and copper pipes subsequently have less lead in
standing water than galvanized pipes. Because lead pipes are rarely used in the United
States, exposure from this source will be treated as a special case in Section 7.3.2.1. The
pH of the water is also important; the acid water of some eastern United States localities can
increase the leaching rate of lead from lead pipes or lead solder joints and prevent the
buildup of a protective coating of calcium carbonate plaque.
Table 7-10 summarizes the contribution of atmospheric lead to drinking water. In this
determination, the maximum reported value for natural lead (0.02 M9/1) was used, all ad-
ditional lead in untreated water is considered to be of atmospheric origin, and it is assumed
that treatment removes 85 percent of the original lead, and that any lead added during distri-
bution is non-atmospheric anthropogenic lead.
7.2.3.2.2 Contributions to food. The use of treated water in the preparation of food can be
a significant source of lead in the human diet. There are many uncertainties in determining
this contribution, however. Water used in food processing may be from a municipal supply or a
private well. This water may be used to merely wash the food, as with fruits and vegetables,
or as an actual ingredient. Water lead may remain on food that is partially or entirely de-
hydrated during processing (e.g., pasta). Water used for packing or canning may be used with
the meal or drained prior to preparation. It is apparent from discussions in Section 7.3.1.3
that, considering both drinking water and food preparation, a significant amount of lead can
be consumed by humans from treated water. Only a small fraction of this lead is of atmo-
spheric origin, however.
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TABLE 7-10. SUMMARY OF LEAD IN DRINKING WATER SUPPLIES*
Natural
Untreated
Lakes
Rivers
Streams
Groundwater
Treated
Surface
Ground
Pb
0.02
0.02
0.02
3
0.003
0.45
Indirect
atmospheric
Pb
15
15
2.5
--
2.5
— —
Direct
atmospheric
Pb
10
15
2.5
--
1.5
— ••
Non-atmospheric
anthropogenic
Pb
—
—
—
—
4
7.5
Total
Pb
25
30
5
3
8
8
*units are ug/1.
7.2.4 Summary of Environmental Concentrations of Lead
Lead concentrations in environmental media that are in the pathway to human consumption
are summarized on Table 7-11. These values are estimates derived from the preceding discus-
sions. In each category, a single value is given, rather than a range, in order to facilitate
further estimates of actual human consumption. This use of a single value is not meant to
imply a high degree of certainty in its determination or homogeneity within the human popula-
tion. The units for water are converted from ug/1 as in Table 7-10 to pg/g to facilitate the
discussions of dietary consumption of water and beverages.
TABLE 7-11. SUMMARY OF ENVIRONMENTAL CONCENTRATIONS OF LEAD
Medium
Air urban (ug/m3)
rural (ug/m3)
Soil total (ug/g)
Food crops (ug/9)
Surface water (ug/g)*
Ground water (ug/g)*
*note change in units
PR7/A
Natural
Pb
0.00005
0.00005
8-25
0.0025
0.00002
0.003
from Table
Atmospheri c
Pb
0.8
0.2
3.0
0.027
0.005
—
7-12.
7-35
Total
Pb
0.8
0.2
15.0
0.03
0.005
0.003
7/14/83
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PRELIMINARY DRAFT
Because concentrations of natural lead are generally three to four orders of magnitude
lower than anthropogenic lead in ambient rural or urban air, all atmospheric contributions of
lead are considered to be of anthropogenic origin. Natural soil lead typically ranges from 10
to 30 ug/g, but much of this is tightly bound within the crystalline matrix of soil minerals
at normal soil pHs of 4 to 8. Lead in the organic fraction of soil is part natural and part
atmospheric. The fraction derived from fertilizer is considered to be minimal. In undis-
turbed rural and remote soils, the ratio of natural to atmospheric lead is about 1:1, perhaps
as high as 1:3. This ratio persists in soil moisture and in internal plant tissues. Thus,
some of the internal lead in crops is of anthropogenic origin, and some is natural. Informa-
tion on the effect of fertilizer on this ratio is not available. Lead in untreated surface
water is 99 percent anthropogenic, presumably atmospheric except near municipal waste out-
falls. It is possible that 75 percent of this lead is removed during treatment. Lead in un-
treated ground water is probably all natural.
In tracking air lead through pathways to human exposure, it is necessary to distinguish
between lead of atmospheric origin that has passed through the soil (indirect atmospheric
lead), and atmospheric lead that has deposited directly on crops or water. Because indirect
atmospheric lead will remain in the soil for many decades, this source is insensitive to pro-
jected changes in atmospheric lead concentrations. Regulation of ambient air lead concentra-
tions will not affect indirect atmospheric lead concentrations over the next several decades.
The method of calculating the relative contribution of atmospheric lead to total poten-
tial human exposure relies heavily on the relationship between air concentration and deposi-
tion flux described on Section 6.4. Estimates of contributions from other sources are usually
based on the observed value for total lead concentration from which the estimated contribution
of atmospheric lead is subtracted. Except for the contribution of lead solder in food cans
and paint pigments in dust, there is little or no direct evidence for the contribution of non-
atmospheric anthropogenic lead to the total lead consumption of humans.
7.3 POTENTIAL PATHWAYS TO HUMAN EXPOSURE
The preceding section discussed ambient concentrations of lead in the environment, focus-
ing on levels in the air, soil, food crops, and water. In this section, environmental lead
concentrations are examined from the perspective of pathways to human exposure (Figure 7-1).
Initially, a current baseline exposure scenario is described for an individual with a minimum
amount of daily lead consumption. This person would live and work in a nonurban environment
eat a normal diet of food taken from a typical grocery shelf, and would have no habits or ac-
tivities that would tend to increase lead exposure. Lead exposure at the baseline level is
PB-7/A 7-36 7/14/83
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PRELIMINARY DRAFT
considered unavoidable without further reductions of lead in the atmosphere or in canned
foods. Most of the baseline lead is of anthropogenic origin, although a portion is natural,
as discussed in Section 7.3.1.5.
7.3.1 Baseline Human Exposure
To arrive at a minimum or baseline exposure for humans, it is necessary to begin with the
environmental components, air, soil, food crops, and water, which are the major sources of
lead consumed by humans (Table 7-11). These components are measured frequently, even
monitored routinely in the case of air, so that many data are available on their concentra-
tions. But there are several factors which modify these components prior to actual human ex-
posure. We do not breathe air as monitored at an atmospheric sampling station, we may be
closer to or farther from the source of lead than is the monitor. We may be inside a
building, with or without filtered air; the water we drink does not come directly from a
stream or river. It has passed through a chemical treatment plant and a distribution system.
A similar type of processing has modified the lead levels present in our food.
Besides the atmospheric lead in environmental components, there are two other sources
that contribute to this baseline of human exposure: paint pigments and lead solder (Figure
7-6). Solder contributes directly to the human diet through canned food and copper water dis-
tribution systems. Chips of paint pigments are discussed later under special environments.
But paint and solder are also a source of lead-bearing dusts. The most common dusts in the
baseline human environment are street dusts and household dusts. They originate as emissions
from mobile or stationary sources, as the oxidation products of surface exposure, or as pro-
ducts of frictional grinding processes. Ousts are different from soil in that soil derives
from crustal rock and typically has a lead concentration of 10 to 30 ug/g, whereas dusts come
from both natural and anthropogenic sources and vary from 1,000 to 10,000 (ag/g.
The discussion of the baseline human exposure traces the sequence from ambient air to in-
haled air, from soil to prepared food, from natural water to drinking water, and from paint,
solder and aerosol particles to dusts. At the end of this section, Table 7-24 summarizes the
four sources by natural and anthropogenic contributions, with the atmospheric contribution to
the anthropogenic fraction identified. Reference to this table will guide the discussion of
human exposure in a logical sequence that ultimately presents an estimate of the exposure of
the human population to atmospheric lead. To construct this table, it was necessary to make
decisions based on sound scientific judgment, occasionally in the absence of conclusive data.
This method provides a working approach to identifying sources of lead that can be easily
modified as more accurate data become available.
PB7/A 7-37 7/14/83
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-a
CD
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PRELIMINARY DRAFT
7.3.1.1 Lead in Inhaled Air. A principal determinant of atmospheric lead is distance from
the source. At more than 100 m from a major highway or more than 2 km from a stationary
source, lead concentrations generally drop to constant levels (see Section 6.3), and the par-
ticle size distribution shifts from a bimodal distribution to a unimodal one with a mass
median equivalent diameter of about 0.2 \im. Because the concentration of atmospheric lead at
nonurban stations is generally from 0.05 to 0.15 ng/">3> a value of 0.1 ug/m3 may reasonably be
assumed. A correction can be made for the indoor/outdoor ratio assuming the average individ-
ual spends 20-22 hours/day in an unfiltered inside atmosphere and the average indoor/outdoor
ratio for a nonurban location is 0.5 (Table 7-7). The adjusted air concentration becomes 0.05
jjg/m3 for baseline purposes.
The concentration of natural lead in the atmosphere, discussed in Section 7.2.1.1.3, is
probably about 0.00005 ug/m3. This is an insignificant amount compared to the anthropogenic
contribution of 0.2 ug/m3. A summary of lead in inhaled air appears in Table 7-12.
TABLE 7-12. SUMMARY OF INHALED AIR LEAD EXPOSURE
Children (2 year-old)
Adult-working inside
Adult-working outside
Adjusted
air Pb
cone. *
Mg/m3
0.05
0.05
0.10
Amount
inhaled
(mVday)
10
20
20
Total
lead
exposure
(pg/day)
0.5
1.0
2.0
Natural
Pb
(Mg/day)
0.001
0.002
0.004
Direct
atmospheric
Pb
(pg/day)
0.5
1.0
2.0
iy/alues adjusted for indoor/outdoor ratio of lead concentrations and for daily time spent
outdoors.
7.3.1.2 Lead in Food. The route by which many people receive the largest portion of their
daily lead intake is through foods. Several studies have reported average dietary lead inakes
in the range 100 to 500 pg/day for adults, with individual diets covering a much greater range
(Schroeder and Tipton, 1968; Tepper, 1971; Mahaffey, 1978; Nutrition Foundation, Inc. 1982).
Gross (1981) analyzed results of the extensive lead mass balance experiments described by
Kehoe (1961), which were conducted from 1937 to 1972. According to these data, total dietary
lead intake decreased from approximately 300 pg/day in 1937 to 100 pg/day in 1970, although
there is considerable variability in the data. Only a fraction of this lead is absorbed, as
discussed in Chapter 10.
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PRELIMINARY DRAFT
The amount of lead typically found in plants and animals is discussed in Section 7.2.2.2.
The sources of this lead are air, soil, and untreated waters (Figure 7-1). Food crops and
livestock contain lead in varying proportions from the atmosphere and natural sources. From
the farm to the dinner table, lead is added to food as it is harvested, transported, pro-
cessed, packaged, and prepared. The sources of this lead are dusts of atmospheric and indus-
trial origin, metals used in grinding, crushing, and sieving, solder used in packaging, and
water used in cooking.
The American diet is extremely complex and variable among individuals. Pennington (1983)
has described the basic diets, suppressing individual variation but identifying 234 typical
food categories, for Americans grouped into eight age/sex groups (Table 7-13). These basic
diets are the foundation for the Food and Drug Administration's revised Total Diet Study,
often called the market basket study, beginning in April, 1982. The diets used for this dis-
cussion include food, beverages and drinking water for a 2-year-old child, the adult female 25
to 30 years of age and the adult male 25 to 30 years of age. The 234 typical foods that com-
prise the basic diets approximate 90 percent or more of the food actually consumed by partici-
pants in the two surveys which formed the basis of the Pennington study. These 234 categories
have been further reduced to 26 food categories (Table 7-13) and 6 beverage categories (Table
7-20) based on known or presumed similarities in lead concentration, and a weighted average
lead concentration has been assigned to each category from available literature data. A com-
plete list of the Pennington categories and the rationale for grouping into the categories of
Tables 7-13 and 7-20 appears in Tables 7D-1 and 7D-2 of Appendix 7D.
Milk and foods are treated separately from water and other beverages because the pathways
by which lead enters these dietary components are substantially different (Figure 7-1), as
solder and atmospheric lead contribute significantly to each. Data for lead concentrations on
Tables 7-13 and 7-20 came from a preliminary report of the 1982 Total Diet Study provided by
the U.S. Food and Drug Administration (1983) for the purpose of this document. In 1982, the
Nutrition Foundation published an exhaustive study of lead in foods, using some data from the
National Food Processors Assocation and some data from Canadian studies by Kirkpatrick et al.
(1980) and Kirkpatrick and Coffin (1974, 1977). A summary of the available data for the
period 1973 to 1980 was prepared in an internal report to the FDA prepared by Beloian (1980).
Portions of these reports were used to interpret the contributions of lead to food during
processing.
Many of the food categories in Table 7-13 correspond directly to the background crop and
meat data presented in Table 7-9. The following section evaluates the amounts of lead added
during each step of the process from the field to the dinner table. In the best case, re-
PB7/A 7-40 7/14/83
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PRELIMINARY DRAFT
liable data exist for the specific situation in question and conclusions are drawn. In some
cases, comparable data can be used with a few reasonable assumptions to formulate acceptable
estimates of lead contributions. For a portion of the diet, there are no acceptable data and
the contributions of lead must, for the time, be listed as of undetermined origin.
TABLE 7-13. LEAD CONCENTRATIONS IN MILK AND FOODS
Dietary consumption
Child
(2-yr-old)
Milk
Dairy products
Milk as ingredient
Beef
Pork
Chicken
Fish
Prepared Meats
Other Meats
Eggs
Bread
Flour as ingredient
Non-wheat cereals
Corn flour
Leafy vegetables
Root vegetables
Vine vegetables
Canned vegetables
Sweet corn
Canned sweet corn
Potatoes
Vegetable oil
Sugar
Canned fruits
Fresh fruits
Pureed baby food
Subtotal
350
24
7
33
12
12
5
14
1
33
42
23
33
14
7
3
19
39
4
5
38
5
15
14
49
11
812
(3/day)
Adult
female
190
36
11
61
21
20
15
11
7
34
56
26
13
12
39
7
49
53
6
4
52
12
21
11
57
--
824
Adult
male
280
49
15
120
40
29
18
23
5
53
75
79
34
20
38
7
62
62
7
7
85
15
34
13
49
—
1219
Lead Summary
concentration* food
(ug/g) category
in Table 7-16
0.01
0.03
0.01
0.035
0.06
0.02
0.09
0.013
0.07
0.017
0.015
0.013
0.025
0.025
0.05
0.025
0.025
0.25
0.01
0.21
0.02
0.03
0.03
0.22
0.02
0.03
A
A
A
B
B
B
B
B
B
B
C
C
C
C
C
C
C
D
C
0
C
C
C
D
C
Water and
beverages
Total
647
1459
1286
2110
1804
3023
See
Table 7-21
"Data are summarized from preliminary data provided by the U.S. FDA; complete data appear in
Appendix 7D.
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PRELIMINARY DRAFT
7.3.1.2.1 Lead added during handling and transportation to processor. Between the field and
the food processor, lead is added to the food crops. It is assumed that this lead is all of
direct atmospheric origin. Direct atmospheric lead can be lead deposited directly on food
materials by dry deposition, or it can be lead on dust which has collected on other surfaces
then transferred to foods. For the purposes of this discussion, it is not necessary to dis-
tinguish between these two forms, as both are a function of air concentration.
There are no clear data on how much lead is added during transportation, but some obser-
vations are worth noting. First, some fresh vegetables (e.g., potatoes, lettuce, carrots,
onions) undergo no further processing other than trimming, washing and packaging. If washed
water without soap is used; no additives or preservatives are used. An estimate of the amount
of atmospheric lead added during handling and transportation of all food crops can be made
from the observed increases in lead on those fresh vegetables where handling and transpor-
tation would be the only source of added lead. Because atmospheric lead deposition is a
function of time, air concentration, and exposed surface area, there is an upper limit to the
maximum amount of direct atmospheric lead that can be added, except by the accumulation of
atmospheric dusts.
7.3.1.2.2 Lead added during preparation for packaging. For some of the food items, data are
available on lead concentrations just prior to the filling of cans. In the case where the
food product has not undergone extensive modification (e.g., cooking, added ingredients), the
added lead was most likely derived from the atmosphere or from the machinery used to handle
the product. As with transportation, the addition of atmospheric lead is limited to reason-
able amounts that can be added during exposure to air, and reasonable amounts of atmospheric
dust accumulation on food processing surfaces. One process that may increase the exposure of
the food to air is the use of air in separating food items, as in wheat grains from chaff.
Where modification of the food product has occurred, the most common ingredients added
are sugar, salt, and water. It is reasonable that water has a lead concentration similar to
drinking water reported in Section 7.3.1.3 (0.008 ug/g) and that sugar (Boyer and Johnson,
1982) and salt have lead concentrations of 0.01 ug/g. Grinding, crushing, chopping, and
cooking may add lead from the metallic parts of machinery and from industrial greases. A
summary of the data (Table 7-14) indicates that about 30 percent of the total lead in canned
goods is the result of prepacking processes.
7.3.1.2.3 Lead added during packaging. From the time a product is packaged in bottles, cans
or plastic containers, until it is opened in the kitchen, it may be assumed that no food item
receives atmospheric lead. Most of the lead which is added during this stage comes from the
solder used to seal some types of cans. Estimates by the U.S. FDA, prepared in cooperation
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PRELIMINARY DRAFT
with the National Food Processors Association, suggest that lead in solder contributes more
than 66 percent of the lead in canned foods where a lead solder side seam was used. This lead
was thought to represent a contribution of 20 percent to the total lead consumption in foods
(F.R., 1979 August 31).
TABLE 7-14. ADDITION OF LEAD TO FOOD PRODUCTS
Food
Soft Packaged
Wheat
Field corn
Potatoes
Lettuce
Rice
Carrots
Beef
Pork
Metal cans
Sweet corn
Tomatoes
Spinach
Peas
Applesauce
Apricots
Mixed fruit
Plums
Green beans
In the
field
0.037
0.022
0.009
0.013
0.007
0.009
0.01
0.06
0.003
0.002
0.045
After
preparation
for packaging
0.04
0.06
0.43
0.08
0.08
0.07
0.08
0.09
0.16
After
packaging
0.065
0.14
0.018
0.07
0.10
0.05
0.07
0.10
0.27
0.29
0.68
0.19
0.24
0.17
0.24
0.16
0.32
After
kitchen
preparation
--
0.025
0.02
0.015
0.084
0.017
0.035
0.06
0.58
—
0.86
0.22
0.17
—
0.20
0.16
Total Pb
added
after harvest
—
0.003
0.011
0.002
0.077
0.008
0.025
--
0.28
0.82
0.14
0.09
0.10
0.12
0.07
~"
This table summarizes the stepwise addition of lead to food products at several stages between
the field and the dinner table. Data are in ug/g fresh weight.
The full extent of the contribution of the canning process to overall lead levels in
albacore tuna was reported in a benchmark study by Settle and Patterson (1980). Using rigor-
ous clean laboratory procedures, these investigators analysed lead in fresh tuna, as well as
in tuna packaged in soldered and unsoldered cans. The data, presented in Table 7-15, show
that lead concentrations in canned tuna are elevated above levels in fresh tuna by a factor of
4,000, and by a factor of 40,000 above natural levels of lead in tuna. Nearly all of the in-
crease results from leaching of the lead from the soldered seam of the can; tuna from an
unsoldered can is elevated by a factor of only 20 compared with tuna fresh from the sea. Note
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PRELIMINARY DRAFT
that when fresh tuna is dried and pulverized, as in the National Bureau of Standards reference
material, lead levels are seen to increase by a factor of 400 over fresh sea tuna. Table 7-15
also shows the results of analyses conducted by the National Marine Fisheries Service.
TABLE 7-15. PREHISTORIC AND MODERN CONCENTRATIONS IN HUMAN FOOD
FROM A MARINE FOOD CHAIN1
Estimated
prehistoric
Surface seawater 0.0005
Albacore muscle, fresh 0.03
Albacore muscle from die-punched
unsoldered can
Albacore muscle, lead-soldered can
Anchovy from albacore stomach 2.1
Anchovy from lead-soldered can
Modern
0.005
0.3
7.0
1400
21
4200
1Values are ng/g fresh weight.
Source: Settle and Patterson (1980).
7.3.1.2.4 Lead added during kitchen preparation and storage. Although there have been
several studies of the lead concentrations in food after typical meal preparation, most of the
data are not amenable to this analysis. As a part of its compliance program, the U.S. FDA has
conducted the Total Diet Study of lead and other trace contaminants in kitchen-prepared food
each year since 1973. Because the kitchen-prepared items were composited by category, there
is no direct link between a specific food crop and the dinner table. Since April, 1982, this
survey has analyzed each food item individually (Pennington, 1983).
Other studies which reflect contributions of lead added during kitchen preparation have
been conducted. Capar (1978) showed that lead in acidic foods that are stored refrigerated in
open cans can increase by a factor of 2 to 8 in five days if the cans have a lead-soldered
side seam not protected by an interior lacquer coating. Comparable products in cans with the
lacquer coating or in glass jars showed little or no increase.
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PRELIMINARY DRAFT
7.3.1.2.5 Recent changes of lead in food. As a part of its program to reduce the total lead
intake by children (0 to 5 years) to less than 100 M9/day by 1988, the U.S. FDA estimated lead
intakes for individual children in a large-scale food consumption survey (Beloian and
McDowell, 1981). To convert the survey of total food intakes into lead intake, 23 separate
government and industry studies, covering the period from 1973 to 1978, were statistically
analyzed. In spite of the variability that can occur among individuals grouped by age, the
authors estimated a baseline (1973-78) daily lead intake of 15 ug/day for infants aged 0 to 5
months, 59 ug/day for children 6 to 23 months, and 82 ug/day for children 2 to 5 years. Bet-
ween 1973 and 1978, intensive efforts were made by the food industry to remove sources of lead
from infant food items. By 1980, there had been a 47 percent reduction in the lead consump-
tion of the age group 0 to 5 months and a 7 percent reduction for the 6 to 23 month age group
(Table 7-16). Most of this reduction was accomplished by the discontinuation of soldered cans
used for infant formula.
TABLE 7-16. RECENT TRENDS OF LEAD CONCENTRATIONS IN FOOD ITEMS
Canned food1
Green beans
Beans w/pork
Peas
Tomatoes
Beets
Tomato juice
Applesauce
Citrus juice
Infant food2
Formula concentrate
Juices
Pureed foods
Evaporated milk
Early 70 's
(ug/g)
0.32
0.64
0.43
0.71
0.38
0.34
0.32
0.14
0.10
0.30
0.15
0.52
1976-77
(ug/g)
data
not
available
0.055
0.045
0.05
0.10
1980-81
(ng/g)
0.32
0.26
0.19
0.29
0.24
0.08
0.04
0.11
0.01
0.015
0.02
0.07
1982
(M9/g)
0.16
0.17
0.22
—
0.12
0.067
0.17
0.04
ifioyer and Johnson (1982); 1982 data from U.S. Food and Drug Administration (1983).
2pre-1982 data from early 70's and 1976-79 from Jelinek (1982); 1980-81 data from Schaffner
et al. (1983).
The 47 percent reduction in dietary lead achieved for infants prior to 1980 came about
largely because there are relatively few manufacturers of foods for infants and it was compar-
atively simple for this industry to mount a coordinated program in cooperation with the U.S.
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PRELIMINARY DRAFT
FDA. There has not yet been a similar decrease in adult foods (Table 7-16) because only a few
manufacturers have switched to non-lead cans. As the switchover increases, lead in canned
food should decrease to a level as low as 30 percent of the pre-1978 values, and there should
be a corresponding decrease of lead in the total adult diet, perhaps as much as 25 to 30 per-
cent. The use of lead-soldered cans in the canning industry has decreased from 90 percent in
1979 to 63 percent in 1982. By the end of 1984, the two leading can manufacturers expect to
produce no more lead-soldered cans for the food industry. A two-year time lag is expected
before the last of these cans disappears from the grocery shelf. Some of the 23 smaller
manufacturers of cans have announced similar plans over a longer period of time. It is likely
that any expected decrease in the contribution of air lead to foods will be complemented by a
decrease in lead from soldered cans.
7.3.1.2.6 Summary of lead in food. The data of Table 7-13 have been condensed to four cate-
gories from the 26 categories of food in Table 7-17. The total lead concentrations are
weighted according to consumption from Table 7-13, then broken down by source based on the in-
formation provided in Tables 7-9 and 7-14, which show estimates of the atmospheric lead added
before and after harvest. The same weighted total lead concentrations are used to estimate
milk and food lead consumption in Table 7-18 for three age/sex categories. The total dietary
lead consumption is then broken down by source in Table 7-19, using the distributions of Table
7-17. Because the percent distribution by source is approximately the same for the three age/
sex categories, only the data for adult males are shown.
TABLE 7-17. SUMMARY OF LEAD CONCENTRATIONS IN MILK AND FOODS BY SOURCE*
Major
food
category
A. Dairy
B. Meat
C. Food crops
D. Canned food
Total
lead
0.013
0.036
0.022
0.24
Direct
atmospheric
lead
0.007
0.02
0.016
0.016
Pb from
solder &
other metals
0.02
0.20
Pb of
undeter-
mined
origin
0.007
0.016
0.002
0.02
%
Direct
atmospheric
lead
54%
56%
73%
7%
*Foods have been categorized from Table 7-13. Data are in ug/g. The natural and indirect
atmospheric lead concentrations in dairy and meat products are estimated to be 0.0002
from each source. In food crops and canned foods, these values are 0.002 ug/g.
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It is apparent that at least 35 percent of lead in milk and food can be attributed to
direct atmospheric deposition, compared to 26 percent from solder or other metal sources. Of
the remaining 34 percent for which the source is as yet undetermined, it is likely that
further research will show this lead to be part atmospheric in origin and part from solder and
other industrial metals.
This dietary lead consumption is used to calculate the total baseline human exposure in
Section 7.3.1.5 and is the largest baseline source of lead. Possible additions to dietary
lead consumption are discussed in Section 7.3.2.1.1 with respect to urban gardens.
TABLE 7-18. SUMMARY BY AGE AND SEX OF ESTIMATED AVERAGE LEVELS
OF LEAD INGESTED FROM MILK AND FOODS
Dietary consumption
(Q/day)
A. Dairy
B. Meat
C. Food crops
D. Canned food
Total
2-yr-old
child
381
113
260
58
812
Adult
female
237
169
350
68
824
Adult
male
344
288
505
82
1219
Lead cone.
in food
ug Pb/g*
0.013
0.036
0.022
0.24
Lead consumption
ug/day
2-yr-old
child
5.0
4.1
5.7
13.9
28.7
Adult
female
3.1
6.1
7.7
16.3
33.2
Adult
male
4.5
10.4
11.1
19.7
45.6
'Weighted average lead concentration in foods from Table 7-13.
Because the U.S. FDA is actively pursuing programs to remove lead from adult foods, it is
probable that there will be a decrease in total dietary lead consumption over the next decade
independent of projected decreases in atmospheric lead concentration. With both sources of
lead minimized, the lowest reasonable estimated dietary lead consumption would be 10 to 15
ug/day for adults and children. This estimate is based on the assumption that about 90 per-
cent of the direct atmospheric lead, solder lead and lead of undetermined origin would be re-
moved from the diet, leaving 8 ug/day from these sources and 3 pg/day of natural and indirect
atmospheric lead.
7.3.1.3 Lead in Drinking Water. The U.S. Public Health Service standards specify that lead
levels in drinking water should not exceed 50 ug/1. The presence of detectable amounts of
lead in untreated public water supplies was shown by Durum (1971) to be widespread, but only a
few samples contained amounts above the 50 ug/1 standard.
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The major source of lead contamination in drinking water is the water supply system it-
self. Water that is corrosive can leach considerable amounts of lead from lead plumbing and
lead compounds used to join pipes. Moore (1977) demonstrated the effect of water standing in
pipes overnight. Lead concentrations dropped significantly with flushing at 10 1/min for five
minutes (Figure 7-7). Lead pipe currently is in use in some parts of New England for water
service lines and interior plumbing, particularly in older urban areas. The contributions of
lead plumbing to potential human exposure are considered additive rather than baseline and are
discussed in Section 7.3.2.1.3.
There have been several studies in North America and Europe of the sources of lead in
drinking water. A recent study in Seattle, WA by Sharrett et al. (1982) showed that the age
of the house and the type of plumbing determined the lead concentration in tap water. Stand-
ing water in copper pipes from houses newer than five years averaged 31 ug/1; those less than
18 months average about 70 ug/1. Houses older than five years and houses with galvanized pipe
averaged less than 6 ug/1. The source of the water supply, the length of the pipe and the use
of plastic pipes in the service line had little or no effect on the lead concentrations. It
appears certain that the source of lead in new homes with copper pipes is the solder used to
join these pipes, and that this lead is eventually leached away with age.
The Sharrett et al. (1982) study of the Seattle population also provided data on water
and beverage consumption which extended the scope of the Pennington (1983) study of all Ameri-
cans. While the total amount of liquids consumed was slightly higher in Seattle (2200 g/day
vs. 1800 g/day for all Americans), the breakdown between water consumed inside and outside the
home can prove useful. Men, women and children consume 53, 87, and 87 percent respectively of
their water and beverages within the home.
Bailey and Russell (1981) have developed a model for population exposure to lead in home
drinking water. The model incorporates data for lead concentration as a function of stagna-
tion time in the pipes, as well as probability distributions for times of water use throughout
the day. Population surveys conducted as part of the United Kingdom Regional Heart Survey
provided these water-use distributions.
Other studies have been conducted in Canada and Belgium. Lead levels in water boiled in
electric kettles were measured in 574 households in Ottawa (Wigle and Charlebois, 1978). Con-
centrations greater than 50 ug/1 were observed in 42.5 percent of the households, and ex-
cessive lead levels were associated with kettles more than five years old.
PB7/A 7-48 7/14/83
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PRELIMINARY DRAFT
10
TIME OF FLUSHING, minutes
Figure 7-7. Change in drinking water lead concentration in a house with
lead plumbing for the first use of water in the morning. Flushing rate was
10 liters/minute.
Source: Moore (1977).
023PB8/B
7-49
7/01/83
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PRELIMINARY DRAFT
TABLE 7-19. SUMMARY BY SOURCE OF LEAD CONSUMED FROM MILK AND FOODS*
A. Dairy
B. Meat
C. Food crops
D. Canned foods
Total
% of total
Total
lead
4.5
10.4
11.1
19.7
45.7
100%
Natural
lead
0.1
0.1
1.0
0.2
1.4
3.1%
Atmospheric
Indirect
lead
0.1
0.1
1.0
0.2
1.4
3.1%
lead
Direct
lead
2.3
5.7
8.1
1.3
17.4
38.1%
Pb from
solder and
other
metals
—
--
--
16.4
16.4
35.9%
Lead of
undeter-
mined
origin
2.0
4.5
1.0
1.6
9.1
19.9%
*Distribution based on adult male diet. Data are in ug/day. There may be some direct
atmospheric lead and solder lead in the category of undetermined origin.
The potential exposure to lead through water and beverages is presented in Tables 7-20,
7-21 and 7-22. In Table 7-20, typical concentrations of lead in canned and bottled beverages
and in beverages made from tap water (e.g., coffee, tea, drinking water) are shown by source.
The baseline concentration of water is taken to be 0.01 ug/g, although 0.006 to 0.008 are
often cited in the literature for specific locations. It is assumed that 2/3 of the original
lead is lost during water treatment and that only 0.005 ug/g remains from direct atmospheric
deposition. The water distribution system adds 0.001 ug/g, shown here as lead of undetermined
origin. The source appears to be the pipes or the solder used to seal the pipes. These
values are used for water in canned and bottled beverages, with additional amounts added from
solder and other packaging procedures.
The lead concentrations in beverages are multiplied by total consumption to get daily
lead consumption in Table 7-21 for 3 age/sex categories. For adult males, these are
summarized by source of lead in Table 7-22; distribution by source would be proportional for
children and adult females. The data of Table 7-22 are used for the overall summary of base-
line human exposure in Section 7.3.1.5.
7.3.1.4 Lead in Dusts. By technical definition, dusts are solid particles produced by the
disintegration of materials (Friedlander, 1977) and appear to have no size limitations.
Although dusts are of complex origin, they may be placed conveniently into a few categories
relating to human exposure. Generally, the most convenient categories are household dusts,
soil dust, street dusts and occupational dusts. It is a characteristic of dust particles that
they accumulate on exposed surfaces and are trapped in the fibers of clothing and carpets.
Ingestion of dust particles, rather than inhalation, appears to be the greater problem in the
baseline environment, especially ingestion during meals and playtime activity by small chil-
dren.
023PB8/B 7-50 7/14/83
-------
TABLE 7-20. SUMMARY BY SOURCE OF LEAD CONCENTRATIONS IN WATER
AND BEVERAGES*
Canned juices
Frozen juices
Canned soda
Bottled soda
Canned beer
Water & beverages
Total
lead
0.052
0.02
0.033
0.02
0.017
0.008
Di rect
atmospheric
lead
0.0015
0.0015
0.0015
0.0015
0.0015
0.0015
Lead from
solder and
other metals
0.048
0.014
0.029
0.014
0.013
0.004
Percent
di rect
atmospheric
2.9%
7.5
4.5
7.5
8.8
18.9
o
*Data are in ug/g. Natural and indirect atmospheric lead are estimated to be 0.00002 and
0.0025 ug/g respectively, for all beverage types.
-------
TABLE 7-21. DAILY CONSUMPTION AND POTENTIAL LEAD EXPOSURE FROM
WATER AND BEVERAGES
I
en
Consumption*
(a/day)
Beverage
Canned juices
Frozen juices
Canned soda
Bottled soda
Coffee
Tea
Canned beer
Wine
Whiskey
Water
Water as ingredient
Total
2 yr old
child
53
66
75
75
2
32
-
-
-
320
24
647
Adult
female
28
66
130
130
300
160
35
35
5
400
20
1286
Adult
male
20
73
165
165
380
140
300
11
9
510
31
1804
Beverage
lead
conc.t
(kig/g)
0.052
0.02
0.033
0.02
0.01
0.01
0.017
0.01
0.01
0.008
0.008
Lead consumption
(uq/day)
2 yr old
child
2.8
1.3
2.5
1.5
-
0.3
-
-
-
2.6
0.2
11.2
Adult
f emal e
1.5
1.3
4.3
2.6
3.0
1.6
0.6
0.1
0.1
2.6
0.2
17.9
Adult
male
1.0
1.5
5.4
3.3
3.8
1.4
5.1
0.1
0.1
3.2
0.2
25.1
JO
o
ya
* Data from Pennington, 1983.
t Data from U.S. Food and Drug Administration, 1983.
-------
PRELIMINARY DRAFT
TABLE 7-22. SUMMARY BY SOURCE OF LEAD CONSUMED IN WATER AND BEVERAGES*
Canned juices
Frozen juices
Canned soda
Bottled soda
Canned beer
Water &
beverages
Total
Percent
Total
Pb
1.0
1.5
5.4
3.3
5.1
8.8
25.1
100%
Natural and
indirect
atmospheric
Pb
0.05
0.18
0.42
0.50
0.8
2.8
4.8
19.1%
Direct
atmospheric
Pb
0.03
0.11
0.25
0.3
0.5
1.6
2.8
11.1%
Lead in
solder and
other metals
Pb
0.92
1.2
4.7
2.5
3.8
4.4
17.5
69.7%
*Data are for adult males, expressed in ug/day. Percentages are the same for children
and adult females. Total consumption for children and adult females shown on Table 7-21.
Two other features of dust are important. First, they must be described in both concen-
tration and amount. The concentration of lead in street dust may be the same in a rural and
urban environment, but the amount of dust may differ by a wide margin. Secondly, each cate-
gory represents some combination of sources. Household dusts contain some atmospheric lead,
some paint lead and some soil lead. Street dusts contain atmospheric, soil, and occasionally
paint lead. This apparent paradox does not prevent the evaluation of exposures to dust, but
it does confound efforts to identify the amounts of atmospheric lead contributed to dusts.
For the baseline human exposure, it is assumed that workers are not exposed to occupational
dusts, nor do they live in houses with interior leaded paints. Street dust, soil dust and
some household dust are the primary sources for baseline potential human exposure.
In considering the impact of street dust on the human environment, the obvious question
arises as to whether lead in street dust varies with traffic density. Nriagu (1978) reviewed
several studies of lead in street dust. The source of lead was probably flue dust from burn-
ing coal. Warren et al. (1971) reported lead in street dust of 20,000 M9/9 in a heavily traf-
ficked area. In the review by Nriagu (1978), street dust lead concentrations ranged from 300
023PB8/B
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PRELIMINARY DRAFT
to 18,000 ug/g in several cities in the United States. In Hong Kong, lead in street dust
ranged from 960 to 7400 (jg/g with no direct relationship to traffic volume (Ho, 1979). In
other reports from Hong Kong, Lau and Wong (1982) found values from 130 ug/g at 20 vehicles/
day to 3,900 ug/g at 37,000 vehicles/day. Fourteen sites in this study showed close correla-
tion with traffic density.
In the United Kingdom, lead in urban and rural street dusts was determined to be 970 and
85 pg/g, respectively, by Day et al. (1975). A later report by this group (Day et al. , 1979)
discusses the persistency of lead dusts in rainwashed areas of the United Kingdom and New
Zealand and the potential health hazard due to ingestion by children. They concluded that,
whereas the acidity of rain was insufficient to dissolve and transport lead particles, the
potential health hazard lies with the ingestion of these particles during the normal play
activities of children residing near these areas. A child playing at a playground near a
roadside might consume 20 to 200 ug lead while eating a single piece of candy with unwashed
hands. It appears that in nonurban environments, lead in street dust ranges from 80 to 130
ug/g, whereas urban street dusts range from 1,000 to 20,000 ug/g- For the purpose of esti-
mating potential human exposure, an average lead value of 90 ug/g in street dust is assumed
for baseline exposure on Table 7-23, and 1500 ug/g in the discussions of urban environments in
Section 7.3.2.1.
Dust is also a normal component of the home environment. It accumulates on all exposed
surfaces, especially furniture, rugs and windowsills. For reasons of hygiene and respiratory
health, many homemakers take great care to remove this dust from the household. Because there
are at least two circumstances where these measures are inadequate, it is important to
consider the possible concentration of lead in these dusts in order to determine potential ex-
posure to young children. First, some households do not practice regular dust removal, and
secondly, in some households of workers exposed occupationally to lead dusts, the worker may
carry dust home in amounts too small for efficient removal but containing lead concentrations
much higher than normal baseline values.
In Omaha, Nebraska, Angle and Mclntire (1979) found that lead in household dust ranged
from 18 to 5600 M9/9- In Lancaster, England, a region of low industrial lead emissions
Harrison (1979) found that household dust ranged from 510 to 970 ug/g, with a mean of 720
ug/g. They observed soil particles (10 to 200 urn in diameter), carpet and clothing fibers,
animal and human hairs, food particles, and an occasional chip of paint. The previous Lead
Criteria Document (U.S. Environmental Protection Agency, 1977) summarized earlier reports of
lead in household dust showing residential suburban areas ranging from 280 to 1,500 ug/g,
urban residential from 600 to 2,000 ug/g, urban industrial from 900 to 16,000 M9/g- In El
Paso, Texas, lead in household dust ranged from 2,800 to 100,000 ug/g within 2 km of a smelter
(Landrigan et al. 1975).
023PB8/B 7-54 7/14/83
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PRELIMINARY DRAFT
It appears that most of the values for lead in dust in nonurban household environments
fall in the range of 50 to 500 ug/g. A mean value of 300 ug/g is assumed. The only natural
lead in dust would be some fraction of that derived from soil lead. A value of 10 M9/9 seems
reasonable, since some of the soil lead is of atmospheric origin. Since very little paint
lead is included in the baseline estimate, most of the remaining dust lead would be from the
atmosphere. Table 7-23 summarizes these estimates of human exposure to dusts for children and
adults. It assumes that children ingest about 5 times as much dust as adults, most of the ex-
cess being street dusts from sidewalks and playgrounds. Exposure of children to occupational
lead would be through contaminated clothing brought home by parents. Most of this lead is of
undetermined origin because no data exist on whether the source is dust similar to household
dust or unusual dust from the grinding and milling activities of factories.
7.3.1.5 Summary of Baseline Human Exposure to Lead. The values derived or assumed in the
preceeding sections are summarized on Table 7-24. These values represent only consumption,
not absorption of lead by the human body. The key question of what are the risks to human
health from these baseline exposures is addressed in Chapter 13. The approach used here to
evaluate potential human exposure is similar to that used by the National Academy of Sciences
(1980) and the Nutrition Foundation (1982) in their assessments of the impact of lead in the
human environment.
TABLE 7-23. CURRENT BASELINE ESTIMATES OF POTENTIAL HUMAN EXPOSURE TO DUSTS
Child
Household dusts
Street dust
Occupational dust
Total
Percent
Adult
Household dusts
Street dust
Occupational dust
Total
Percent
Dust
lead
cone.
M9/9
300
90
150
300
90
150
Dust
ingested
g/day
0.05
0.04
0.01
0.10
0.01
0.01
0.02
Dust
lead
consumed
pg/day
15
4.5
1.5
21.0
100%
3
1.5
4.5
100%
Source of lead
Natural
0.5
0.1
0.6
2.8
0.1
0.1
0.2
4.5
Atmos .
14.5
4.5
19.0
90.5
2.9
2.9
64.4
(yq/day)
Undetermi ned
1.4
1.4
6.7
1.4
1.4
31.1
023PB8/B
7-55
7/14/83
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PRELIMINARY DRAFT
TABLE 7-24. SUMMARY OF BASELINE HUMAN EXPOSURES TO LEADt
Soil
Source
Child-2 yr old
Inhaled air
Food
Water & beverages
Dust
Total
Percent
Adult female
Inhaled air
Food
Water & beverages
Dust
Total
Percent
Adult male
Inhaled air
Food
Water & beverages
Dust
Total
Percent
Total
lead
consumed
0.5
28.7
11.5
21.0
61.4
100%
1.0
33.2
17.9
4.5
56.6
100%
1.0
45.7
25.1
4.5
76.3
100%
Natural
lead
consumed
0.001
0.9
0.01
0.6
1.5
2.4%
0.002
1.0
0.01
0.2
1.2
2.1*
0.002
1.4
0.1
0,2
1.7
2.2%
Indirect
atmospheric
lead*
-
0.9
2.1
-
3.0
4.9%
-
1.0
3.4
-
4.4
7.8%
-
1.4
4.7
-I-
6.1
8.0%
Direct
atmospheric
lead*
0.5
10.9
1.2
19.0
31.6
51.5%
1.0
12.6
2.0
2.9
18.5
32.7%
1.0
17.4
2.8
2.9
24.1
31.6%
Lead from
solder or
other metals
-
10.3
7.8
-
18.1
29.5%
-
11.9
12.5
•
24.4
43.1%
-
16.4
17.5
— I—
33.9
44.4%
Lead of
undetermined
origin
-
17.6
-
1.4
19.0
22. 6X
-
21.6
-
1.4
23.0
26.8%
-
31.5
-
1.4
32.9
27.1%
"Indirect atmospheric lead has been previously incorporated into soil, and will probably remain in the
soil for decades or longer. Direct atmospheric lead has been deposited on the surfaces of vegetation
.and living areas or incorporated during food processing shortly before human consumption.
'Units are in ug/day.
7.3.2 Additive Exposure Factors
There are many conditions, even in nonurban environments, where an individual may
increase his lead exposure by choice, habit, or unavoidable circumstance. The following sec-
tions describe these conditions as separate exposures to be added as appropriate to the base-
line of human exposure described above. Most of these additive exposure clearly derive from
air or dust, while few derive from water or food.
7.3.2.1 Living and Working Environments With Increased Lead Exposure. Ambient air lead con-
centrations are typically higher in an urban than a rural environment. This factor alone can
contribute significantly to the potential lead exposure of Americans, through increases in
023PB8/B
7-56
7/14/83
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PRELIMINARY DRAFT
inhaled air and consumed dust. Produce from urban gardens may also increase the daily con-
sumption of lead. Some environmental exposures may not be related only to urban living, such
as houses with interior lead paint or lead plumbing, residences near smelters or refineries,
or family gardens grown on high-lead soils. Occupational exposures may also occur in an urban
or rural setting. These exposures, whether primarily in the occupational environment or
secondarily in the home of the worker, would be additive with other exposures in an urban
location or with special cases of lead-based paint or plumbing.
7.3.2.1.1 Urban atmospheres. Urban atmospheres have more airborne lead than do nonurban
atmospheres, therefore there are increased amounts of lead in urban household and street dust.
Typical urban atmospheres contain 0.5 to 1.0 ug Pb/m3. Other variables are the amount of in-
door filtered air breathed by urban residents, the amount of time spent indoors, and the
amount of time spent on freeways. Dusts vary from 500 to 3000 ug Pb/g in urban environments.
It is not known whether there is more or less dust in urban households and playgrounds than in
rural environments. Whereas people may breathe the same amount of air, eat and drink the same
amount of food and water, it is not certain that urban residents consume the same amount of
dust as nonurban. Nevertheless, in the absence of more reliable data, it has been assumed
that urban and nonurban residents consume the same amount of dusts.
The indoor/outdoor ratio of atmospheric lead for urban environments is about 0.8 (Table
7-7). Assuming 2 hours of exposure/day outdoors at a lead concentration of 0.75 ug/m3, 20
hours indoors at 0.6 ug/m3, and 2 hours in a high traffic density area at 5 ug/m3, a weighted
mean air exposure of 1.0 ug/m3 appears to be typical of urban residents.
7.3.2.1.2 Houses with interior lead paint. In 1974, the Consumer Product Safety Commission
collected household paint samples and analyzed them for lead content (National Academy of
Sciences; National Research Council, 1976). Analysis of 489 samples showed that 8 percent of
the oil-based paints and 1 percent of the water-based paints contained greater than 0.5
percent lead (5000 ug Pb/g paint, based on dried solids), which was the statutory limit at the
time of the study. The current statutory limit for Federal construction is 0.06 percent. The
greatest amounts of leaded paint are typically found in the kitchens, bathrooms, and bedrooms
(Tyler, 1970; Laurer et al., 1973; Gilbert et al., 1979).
Some investigators have shown that flaking paint can cause elevated lead concentrations
in nearby soil. For example, Hardy et al. (1971) measured soil lead levels of 2000 ug/g next
to a barn in rural Massachusetts. A steady decrease in lead level with increasing distance
from the barn was shown, reaching 60 ug/g at fifty feet from the barn. Ter Haar (1974)
reported elevated soil lead levels in Detroit near eighteen old wood frame houses painted with
lead-based paint. The average soil lead level within two feet of a house was just over 2000
Ug/g; the average concentration at ten feet was slightly more than 400 ug/g. The same author
023PB8/B 7-57 7/14/83
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PRELIMINARY DRAFT
reported smaller soil lead elevations in the vicinity of eighteen brick veneer houses in
Detroit. Soil lead levels near painted barns located in rural areas were similar to urban
soil lead concentrations near painted houses, suggesting the importance of leaded paint at
both urban and rural locations. The baseline lead concentration for household dust of 300
ug/g was increased to 2000 ug/g for houses with interior lead based paints. The additional
1700 ug/g would add 85 ug Pb/day to the potential exposure of a child (Table 7-25). This in-
crease would occur in an urban or nonurban environment and would be in addition to the urban
residential increase if the lead-based painted house were in an urban environment.
7.3.2.1.3 Family gardens. Several studies have shown potentially higher lead exposure
through the consumption of home-grown produce from family gardens grown on high lead soils or
near sources of atmospheric lead. Kneip (1978) found elevated levels of lead in leafy vege-
tables, root crops, and garden fruits associated qualitatively with traffic density and soil
lead. Spittler and Feder (1978) reported a linear correlation between soil lead (100 to 1650
pg/g) and leafy or root vegetables. Preer et al. (1980) found a three-fold increase in lead
concentrations of leafy vegetables (from 6 to 16 ug/g) in the soil lead range from 150 to 2200
ug/g. In none of these studies were the lowest soil lead concentrations in the normal range
of 10 to 25 ug/g, nor were any lead concentrations reported for vegetables as low as those of
Wolnik et al. (1983) (see Table 7-9).
In family gardens, lead may reach the edible portions of vegetables by deposition of at-
mospheric lead directly on aboveground plant parts or on soil, or by the flaking of lead-
containing paint chips from houses. Traffic density and distance from the road are not good
predictors of soil or vegetable lead concentrations (Preer et al., 1980). Air concentrations
and particle size distributions are the important determinants of deposition on soil or vege-
tation surfaces. Even at relatively high air concentrations (1.5.ug/m3) and deposition velo-
city (0.5 cm/sec) (see Section 6.4.1), it is unlikely that surface deposition alone can
account for more than 2-5 ug/g lead on the surface of lettuce during a 21-day growing period.
It appears that a significant fraction of the lead in both leafy and root vegetables derives
from the soil.
Using the same air concentration and deposition velocity values, a maximum of 1000 ug
lead has been added to each cm2 of the surface of the soil over the past 40 years. With cul-
tivation to a depth of 15 cm, it is not likely that atmospheric lead alone can account for
more than a few hundred ug/g of soil in urban gardens. Urban soils with lead concentrations
of 500 ug/g or more must certainly have another source of lead. In the absence of a nearby
(<5 km) stationary industrial source, paint chips seem the most likely explanation. Even if
the house no longer stands at the site, the lead from paint chips may still be present in the
soil.
023PB8/B 7-58 7/14/83
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PRELIMINARY DRAFT
TABLE 7-25. SUMMARY OF POTENTIAL ADDITIVE EXPOSURES TO LEAD
Baseline exposure:
Child
Inhaled air
Food, water & beverages
Dust
Total baseline
Additional exposure due to:
Urban atmospheres1
Family gardens2
Interior lead paint3
Residence near smelter4
Secondary occupational5
Baseline exposure:
Adult male
Inhaled air
Food, water & beverages
Dust
Total baseline
Addi tonal exposure due to:
Urban atmospheres1
Family gardens2
Interior lead paint3
Residence near smelter4
Occupational6
Secondary occupational5
Smoking
Wine consumption
Total
lead
consumed
(Mg/day)
0.5
39.9
21.0
61.4
99
800
85
1300
150
1.0
70.8
4.5
76.3
28
2000
17
370
1100
21
30
100
Atmospheric
lead
consumed
(ug/day)
0.5
12.1
19.0
31.6
98
200
1300
1.0
20.2
2.9
24.1
28
500
370
1100
27
7
Other
lead
sources
(|jg/day)
-
27.8
2.0
29.8
600
85
-
50.6
1.6
52.2
1500
17
3
7
lincludes lead from household and street dust (1000 ug/g) and inhaled air (.75 pg/m3).
2assumes soil lead concentration of 2000 ug/g; all fresh leafy and root vegetables, sweet corn
of Table 7-13 replaced by produce from garden. Also assumes 25% of soil lead is of atmos-
pheric origin.
^assumes household dust rises from 300 to 2000 ug/g. Dust consumption remains the same as
baseline.
^assumes household and street dust increases to 25,000 ug/g.
5assumes household dust increases to 2400 ug/g.
«assumes 8 hr shift at 10 ug Pb/m3 or 90% efficiency of respirators at 100 ug Pb/ms, and occu-
pational dusts at 100,000 ug/m3.
023PB8/B
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7/14/83
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PRELIMINARY DRAFT
Studies of family gardens do not agree on the concentrations of lead in produce. At the
higher soil concentrations, Kneip (1978) reported 0.2 to 1 |jg/g in vegetables, Spittler and
Feder (1978) reported 15 to 90 ug/g, and Freer et al. (1980) found 2 to 16 ug/g. Since the
Spittler and Feder (1978) and Freer et al. (1980) studies dealt with soils in the range of
2000 ug/g, these data can be used to calculate a worst case exposure of lead from family
gardens. Assuming 15 ug/g for the leafy and root vegetables [compared to 0.01 to 0.05 ug/g of
the Wolnik et al. (1983) study] family gardens could add 2000 ug/day if the 137 g of leafy and
root vegetables, sweet corn and potatoes consumed by adult males (Table 7-13) were replaced by
family garden products. Comparable values for children and adult females would be 800 and
1600 ug/day, respectively. No conclusive data are available for vine vegetables, but the
ranges of 0.08 to 2 H9/9 f°r tomatoes suggest that the contamination by lead from soil is much
less for vine vegetables than for leafy or root vegetables.
7.3.2.1.4 Houses with lead plumbing. The Glasgow Duplicate Diet Study (United Kingdom
Department of the Environment, 1982) reports that children approximately 13 weeks old living
in houses with lead plumbing consume 6 to 480 ug Pb/day. Water lead levels in the 131 homes
studied ranged from less than 50 to over 500 ug/1. Those children and mothers living in the
homes containing high water-lead levels generally had greater total lead consumption and
higher blood lead levels, according to the study. Breast-fed infants were exposed to much
less lead than bottle-fed infants. Because the project was designed to investigate child and
mother blood lead levels over a wide range of water lead concentrations, the individuals
studied do not represent a typical cross-section of the population. However, results of the
study suggest that infants living in homes with lead plumbing may have exposure to consid-
erable amounts of lead. This conclusion was also demonstrated by Sherlock et al. (1982) in a
duplicate diet study in Ayr, Scotland.
7.3.2.1.5 Residences near smelters and refineries. Air concentrations within 2 km of lead
smelters and refineries average 5 to 15 ug/m3. Assuming the same indoor/outdoor ratio of
atmospheric lead for nonurban residents (0.5), residents near smelters would be exposed to in-
haled air lead concentrations of about 6 ug/m3, compared to 0.05 ug/m3 for the background
levels. Household dust concentrations range from 3000 to 100,000 ug/g (Landrigan et al.,
1975). A value of 25,000 ug/g is assumed for household dust near a smelter. Between inhaled
air and dust, a child in this circumstance would be exposed to 1300 ug Pb/day above background
levels. Exposures for adults would be much less, since they consume only 20 percent of the
dusts children consume.
7.3.2.1.6 Occupational exposures. The highest and most prolonged exposures to lead are found
among workers in the lead smelting, refining, and manufacturing industries (World Health
Organization, 1977). In all work areas, the major route of lead exposure is by inhalation and
023PB8/B 7-60 7/14/83
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ingestion of lead-bearing dusts and fumes. Airborne dusts settle out of the air onto food,
water, the workers' clothing, and other objects, and may be transferred subsequently to the
mouth. Therefore, good housekeeping and good ventilation have a major impact on exposure. It
has been found that levels might be quite high in one factory and low in another solely
because of differences in ventilation, or differences in custodial practices and worker edu-
cation. The estimate of additional exposure on Table 7-25 is for an 8 hour shift at 100 yg
Pb/m3. Occupational exposure under these conditions is primarily determined by occupational
dust consumed. Even tiny amounts (e.g., 10 mg) of dust containing 100,000 pg Pb/g dust can
account for 1,000 ug/day exposure.
7.3.2.1.6.1 Lead mining, smelting, and refining. Roy (1977) studied exposures during mining
and grinding of lead sulfide at a mill in the Missouri lead belt. Primary smelting operations
were 2.5 miles from the mill, hence the influence of the smelter was believed to be negligible.
The total airborne lead levels were much greater than the concentrations of respirable lead,
indicating a predominance of coarse material.
The greatest potential for high-level exposure exists in the process of lead smelting and
refining (World Health Organization, 1977). The most hazardous operations are those in which
molten lead and lead alloys are brought to high temperatures, resulting in the vaporization of
lead. This is because condensed lead vapor or fume has, to a substantial degree, a small
(respirable) particle size range. Although the total air lead concentration may be greater in
the vicinity of ore-proportioning bins than it is in the vicinity of a blast furnace in a
smelter, the amount of particle mass in the respirable size range may be much greater near the
furnace.
A measure of the potential lead exposure in smelters was obtained in a study of three
typical installations in Utah (World Health Organization, 1977). Air lead concentrations near
all major operations, as determined using personal monitors worn by workers, were found to
vary from about 100 to more than 4000 ug/m3. Obviously, the hazard to these workers would be
extremely serious if it were not for the fact that the use of respirators is mandatory in
these particular smelters. Maximum airborne lead concentrations of about 300 ug/m3 were mea-
sured in a primary lead-zinc smelter in the United Kingdom (King et al., 1979). These authors
found poor correlations between airborne lead and blood lead in the smelter workers, and con-
cluded that a program designed to protect these workers should focus on monitoring of biologi-
cal parameters rather than environmental levels.
Spivey et al. (1979) studied a secondary smelter in southern California which recovers
lead mainly from automotive storage batteries. Airborne lead concentrations of 10 to 4800
ug/m3 were measured. The project also involved measurement of biological parameters as well
as a survey of symptoms commonly associated with lead exposure; a poor correlation was found
023PB8/B 7-61 7/14/83
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between indices of lead absorption and symptom reporting. The authors suggested that such
factors as educational level, knowledge of possible symptoms, and biological susceptibility
may be important factors in influencing symptom reporting. In a second article covering this
same study, Brown et al. (1980) reported that smokers working at a smelter had greater blood
lead levels than nonsmokers. Furthermore, smokers who brought their cigarettes into the work-
place had greater blood lead levels than those who left their cigarettes elsewhere. It was
concluded that direct environmental contamination of the cigarettes by lead-containing dust
may be a major exposure pathway for these individuals (See Section 7.3.2.3.1).
Secondary lead smelters in Memphis, Tennessee and Salt Lake City, Utah were studied by
Baker et al. (1979). The former plant extracted lead principally from automotive batteries,
producing 11,500 metric tons of lead in the eleven months preceding the measurements. The
latter plant used scrap to recover 258 metric tons of lead in the six months preceding the
measurements. Airborne concentrations of lead in the Tennessee study exceeded 200 ug/m3 in
some instances, with personal air sampler data ranging from 120 |jg/m3 for a battery wrecker to
350 ug/m3 for two yard workers. At the Utah plant, airborne lead levels in the office, lunch-
room, and furnace room (furnace not operating) were 60, 90, and 100 ug/m3, respectively. When
charging the furnace, the last value increased to 2650 ug/m3. Personal samplers yielded con-
centrations of 17 ug/m3 for an office worker, 700 ug/m3 for two welders, and 2660 ug/m3 for
two furnace workers. Some workers in both plants showed clinical manifestations of lead poi-
soning; a significant correlation was found between blood lead levels and symptom reporting.
High levels of atmospheric lead are also found in foundries in which molten lead is al-
loyed with other metals. Berg and Zenz (1967) found in one such operation that average con-
centrations of lead in various work areas were 280 to 600 ug/m3. These levels were sub-
sequently reduced to 30 to 40 ug/m3 with the installation of forced ventilation systems to
exhaust the work area atmosphere to the outside.
7.3.2.1.6.2 Welding and cutting of metals containing lead. When metals that contain lead or
are protected with a lead-containing coating are heated in the process of welding or cutting,
copious quantities of lead in the respirable size range may be emitted. Under conditions of
poor ventilation, electric arc welding of zinc silicate-coated steel (containing 4.5 mg Pb/cm2
of coating) produced breathing-zone concentrations of lead reaching 15,000 ug/m3, far in
excess of 450 ug/m3, which is the current occupational short-term exposure limit (STEL) in
the United States (Pegues, 1960). Under good ventilation conditions, a concentration of
140 ug/m3 was measured (Tabershaw et al., 1943).
In a study of salvage workers using oxyacetylene cutting torches on lead-painted struc-
tural steel under conditions of good ventilation, breathing-zone concentrations of lead aver-
aged 1200 ug/m3 and ranged as high as 2400 ug/m3 (Rieke, 1969). Lead poisoning in workers
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dismantling a painted bridge has been reported by Graben et al. (1978). Fischbein et al.
(1978) discuss the exposure of workers dismantling an elevated subway line in New York City,
where the lead content of the paint is as great as 40 percent. The authors report that one
mm3 of air can contain 0.05 g lead at the source of emission. Similarly, Grandjean and Kon
(1981) report elevated lead exposures of welders and other employees in a Baltimore, Maryland
shipyard.
7.3.2.1.6.3 Storage battery industry. At all stages in battery manufacture except for
final assembly and finishing, workers are exposed to high air lead concentrations, particular-
ly lead oxide dust. For example, Boscolo et al. (1978) report air lead concentrations of
16-100 ug/m3 in a battery factory in Italy, while values up to 1315 ug/m3 have been measured
by Richter et al. (1979) in an Israeli battery factory. Excessive concentrations, as great as
5400 ug/m3, have been reported by the World Health Organization (1977).
7.3.2.1.6.4 Printing industry. The use of lead in typesetting machines has declined in
recent years. Air concentrations of 10 to 30 ug/m3 have been reported where this technique is
used (Parikh et al., 1979). Lead is also a component of inks and dyes used in the printing
industry, and consequently can present a hazard to workers handling these products.
7.3.2.1.6.5 Alkyl lead manufacture. Workers involved in the manufacture of alkyl lead
compounds are exposed to both inorganic and alkyl lead. Some exposure also occurs at the
petroleum refineries where the two compounds are blended into gasoline, but no data are avail-
able on these blenders.
The major potential hazard in the manufacture of tetraethyl lead and tetramethyl lead is
from skin absorption, which is minimized by the use of protective clothing. Linen et al.
(1970) found a correlation between an index of organic plus inorganic lead concentrations in a
plant and the rate of lead excretion in the urine of workers. Significant concentrations of
organic lead in the urine were found in workers involved with both tetramethyl lead and tetra-
ethyl lead; lead levels in the tetramethyl lead workers were slightly higher because the reac-
tion between the organic reagent and lead alloy takes place at a somewhat higher temperature
and pressure than that employed in tetraethyl lead production.
Cope et al. (1979) used personal air samplers to assess exposures of five alkyl lead
workers exposed primarily to tetraethyl lead. Blood and urine levels were measured over a
six-week period. Alkyl lead levels ranged from 1.3 to 1249 ug/m3, while inorganic lead varied
from 1.3 to 62.6 ug/m3. There was no significant correlation between airborne lead (either
alkyl or inorganic) and blood or urine levels. The authors concluded that biological monito-
ring, rather than airborne lead monitoring, is a more reliable indicator of potential exposure
problems.
023PB8/B 7-63 7/14/83
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7.3.2.1.6.6 Other occupations. In both the rubber products industry and the plastics
industry there are potentially high exposures to lead. The potential hazard of the use of
lead stearate as a stabilizer in the manufacture of polyvinyl chloride was noted in the 1971
Annual Report of the British Chief Inspector of Factories (United Kingdom Department of
Employment, Chief Inspector of Factories 1972). The inspector stated that the number of
reported cases of lead poisoning in the plastics industry was second only to that in the lead
smelting industry. Scarlato et al. (1969) reported other individual cases of exposure. The
source of this problem is the dust that is generated when the lead stearate is milled and
mixed with the polyvinyl chloride and the plasticizer. An encapsulated stabilizer which
greatly reduces the occupational hazard is reported by Fischbein et al. (1982).
Sakurai et al. (1974), in a study of bioindicators of lead exposure, found ambient air
concentrations averaging 58 ng/m3 in the lead-covering department of a rubber hose manufactu-
ring plant. Unfortunately, no ambient air measurements were taken for other departments or
the control group.
The manufacture of cans with leaded seams may expose workers to elevated ambient lead
levels. Bishop (1980) reports airborne lead concentrations of 25 to 800 ug/m3 in several can
manufacturing plants in the United Kingdom. Between 23 and 54 percent of the airborne lead
was associated with respirable particles, based on cyclone sampler data.
Firing ranges may be characterized by high airborne lead concentrations, hence instruc-
tors who spend considerable amounts of time in such areas may be exposed to lead. For exam-
ple, Smith (1976) reports airborne lead concentrations of 30 to 160 u/m3 at a firing range in
the United Kingdom. Anderson et al. (1977) discuss lead poisoning in a 17 year old male
employee of a New York City firing range, where airborne lead concentrations as great as 1000
(jg/m3 were measured during sweeping operations. Another report from the same research group
presents time-weighted average exposures of instructors of 45 to 900 ug/m3 in three New York
City firing ranges (Fischbein et al., 1979).
Removal of leaded paint from walls and other surfaces in old houses may pose a health
hazard. Feldman (1978) reports an airborne lead concentration of 510 ug/m3, after 22 minutes
of sanding an outdoor post coated with paint containing 2.5 mg Pb/cm2. After only five min-
utes of sanding an indoor window sill containing 0.8 to 0.9 mg Pb/cm2, the air contained 550
|jg/m3. Homeowners who attempt to remove leaded paint themselves may be at risk of excessive
lead exposure. Garage mechanics may be exposed to excessive lead concentrations. Clausen and
Rastogi (1977) report airborne lead levels of 0.2 to 35.5 ug/m3 in ten garages in Denmark; the
greatest concentration was measured in a paint workshop. Used motor oils were found to con-
tain 1500 to 3500 ug Pb/g, while one brand of unused gear oil contained 9280 ug Pb/g. The
023PB8/B 7-64 7/14/83
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authors state that absorption through damaged skin could be an important exposure pathway.
Other occupations involving risk of lead exposure include stained glass manufacturing and re-
pair, arts and crafts, and soldering and splicing.
7.3.2.1.7 Secondary occupational exposure. Winegar et al. (1977) examined environmental con-
centrations as well as biological indicators and symptom reporting in workers in a secondary
lead smelter near St. Paul, Minnesota. The smelter recovers approximately 9000 metric tons of
lead per year from automotive batteries. The lead concentrations in cuff dust from trousers
worn by two workers were 60,000 and 600,000 ug/g. The amount of lead contained in pieces of
cloth 1 cm2 cut from the bottoms of trousers worn by the workers ranged from 110 to 3000 ug,
with a median of 410 ug. In all cases, the trousers were worn under coveralls. Dust samples
from 25 households of smelter workers ranged from 120 to 26,000 ug/g, with a median of 2400
ug/g. No significant correlations were found between dust lead concentrations and biological
indicators, or between symptom reporting and biological indicators. However, there was an in-
creased frequency of certain objective physical signs, possibly due to lead toxicity, with in-
creased blood lead level. The authors also concluded that the high dust lead levels in the
workers' homes are most likely due to lead originating in the smelter.
7.3.2.2 Additive Exposure Due to Age. Sex, or Socio-Economic Status.
7.3.2.2.1 Quality and quantity of food. The quantity of food consumed per body weight varies
greatly with age and somewhat with sex. A 14 kg, 2-year-old child eats and drinks 1.5 kg food
and water per day. This is 110 g/kg, or 3 times the consumption of an 80 kg adult male, who
eats 39 g/kg. Teenage girls consume less than boys and elderly women eat more than men, on a
body weight basis.
It is likely that poor people eat less frozen and pre-prepared foods, more canned foods.
Rural populations probably eat more home-grown foods and meats packed locally.
7.3.2.2.2 Mouthing behavior of children. Children place their mouths on dust collecting sur-
faces and lick non-food items with their tongues. This fingersucking and mouthing activity
are natural forms of behavior for young children which expose them to some of the highest con-
centrations of lead in their environment. A single gram of dust may contain ten times more
lead than the total diet of the child.
7.3.2.3 Special Habits or Activities.
7.3.2.3.1 Smoking. Lead is also present in tobacco. The World Health Organization (1977)
estimates a lead content of 2.5 to 12.2 ug per cigarette; roughly two to six percent of this
lead may be inhaled by the smoker. The National Academy of Sciences (1980) has used these
data to conclude that a typical urban resident who smokes 30 cigarettes per day may inhale
roughly equal amounts of lead from smoking and from breathing urban air.
023PB8/B 7-65 7/14/8,3
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7.3.2.3.2 Alcoholic beverages. Reports of lead in European wines (Olsen et al., 1981;
Boudene et al. , 1975; Zurlo and Graffini, 1973) show concentrations averaging 100 to 200 ug/1
and ranging as high as 300 ug/1. Measurements of lead in domestic wines were in the range of
100 to 300 ug/1 for California wines with and without lead foil caps. The U.S. Food and Drug
Administration (1983) found 30 ug/1 in the 1982 Market Basket Survey. The average adult con-
sumption of table wine in the U.S. is about 12 g. Even with a lead content of 0.1 ug/g, which
is ten times higher than drinking water, wine does not appear to represent a significant
potential exposure to lead. At one I/day, however, lead consumption would be greater than the
total baseline consumption.
McDonald (1981) points out that older wines with lead foil caps may represent a hazard,
especially if they have been damaged or corroded. Wai et al. (1979) found that the lead con-
tent of wine rose from 200 to 1200 ug/1 when the wine was allowed to pass over the thin ring
of residue left by the corroded lead foil cap. Newer wines (1971 and later) use other means
of sealing. If a lead foil is used, the foil is tin-plated and coated with an acid-resistant
substance. Lead levels in beer are generally smaller than those in wine; Thalacker (1980)
reports a maximum concentration of 80 ug/1 in several brands of German beer. The U.S. Food
and Drug Administration (1983) found 13 ug/1 in beer consumed by Americans.
7.3.2.3.3 Pica. Pica is the compulsive, habitual consumption of non-food items, such as
paint chips and soil. This habit can present a significant lead exposure to the afflicted
person, especially to children, who are more apt to have pica. There are very little data on
the amounts of paint or soil eaten by children with varying degrees of pica. Exposure can
only be expressed on a unit basis. Billick and Gray (1978) report lead concentrations of 1000
to 5000 ug/cm2 in lead-based paint pigments. A single chip of paint can represent greater ex-
posure than any other source of lead to a child who has pica. A gram of urban soil may have
150 to 2000 ug lead.
7.3.2.3.4 Glazed earthenware vessels. Another potential source of dietary lead poisoning is
the use of inadequately glazed earthenware vessels for food storage and cooking. An example
of this danger involved the severe poisoning of a family in Idaho which resulted from drinking
orange juice that had been stored in an earthenware pitcher (Block, 1969). Similar cases,
sometimes including fatalities, have involved other relatively acidic beverages such as fruit
juices and soft drinks, and have been documented by other workers (Klein et al., 1970; Harris
and Elsen, 1967). Because of these incidents, the U.S. Food and Drug Administration (1979)
has established a maximum permissible concentration of 7 ug Pb/g in solution after leaching
with 4 percent acetic acid in the earthenware vessel for 24 hours.
Inadequately glazed pottery manufactured in other countries continues to pose a signifi-
cant health hazard. For example, Spielholtz and Kaplan (1980) report 24 hour acetic
acid-leached lead concentrations as great as 4400 ug/g in Mexican pottery. The leached lead
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decreased with exposure time, and after several days appears to asymptotically approach a
value which may be as great as 600 ug/g. These investigators have also measured excessive
lead concentrations leached into acidic foods cooked for two hours in the same pottery.
Similarly, Acra et al. (1981) report that 85 percent of 275 earthenware vessels produced in
primitive Lebanese potteries had lead levels above the 7 ug/g limit set by the U.S. FDA. How-
ever, only 9 percent of 75 vessels produced in a modern Beirut pottery exceeded the limit.
Cubbon et al. (1981) have examined properly glazed ceramic plates in the United Kingdom, and
have found a decrease in leached lead with exposure time down to very low levels. The authors
state that earthenware satisfying the 7 ug/g limit will contribute about 3 ug/day to the
dietary intake of the average consumer.
7.3.2.3.5 Hobbies. There are a few hobbies where the use of metallic lead or solder may pre-
sent a hazard to the user. Examples are electronics projects, stained glass window construc-
tion, and firing range ammunition recovery. There are no reports in which the exposure to
lead has been quantified during these activities.
7.3.3 Summary of Additive Exposure Factors
Beyond the baseline level of human exposure, additional amounts of lead consumption are
largely a matter of individual choice or circumstance. Many of these additional exposures
arise from the ingestion of atmospheric lead in dust. In one or more ways probably 90 percent
of the American population are exposed to lead at greater than baseline levels. A summary of
the most common additive exposure factors appears on Table 7-25. In some cases, the additive
exposure can be fully quantified and the amount of lead consumed can be added to the baseline
consumption. These may be continuous (urban residence), or seasonal (family gardening) expo-
sures. Some factors can be quantified only on a unit basis because of wide ranges in exposure
duration or concentration. For example, factors affecting occupational exposure are air lead
concentrations (10 to 4000 ug/m3), use and efficiency of respirators, length of time of expo-
sure, dust control techniques, and worker training in occupational hygiene.
7.4 SUMMARY
Ambient airborne lead concentrations have shown no marked trend from 1965 to 1977. Over
the past five years, however, distinct decreases have occurred. The mean urban air concentra-
tions has dropped from 0.91 ug/m3 in 1977 to 0.32 ug/m3 in 1980. These decreases reflect the
smaller lead emissions from mobile sources in recent years. Airborne size distribution data
indicate that most of the airborne lead mass is found in submicron particles.
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Atmospheric lead is deposited on vegetation and soil surfaces, entering the human food
chain through contamination of grains and leafy vegetables, of pasture lands, and of soil
moisture taken up by all crops. Lead contamination of drinking water supplies appears to
originate mostly from within the distribution system.
Most people receive the largest portion of their lead intake through foods. Unprocessed
foods such as fresh fruits and vegetables receive lead by atmospheric deposition as well as
uptake from soil; crops grown near heavily traveled roads generally have greater lead levels
than those grown at greater distances from traffic. For many crops the edible internal por-
tions of the plant (e.g., kernels of corn and wheat) have considerably less lead than the
outer, more exposed parts such as stems, leaves, and husks. Atmospheric lead accounts for
about 30 percent of the total adult lead exposure, and 50 percent of the exposure for chil-
dren. Processed foods have greater lead concentrations than unprocessed foods, due to lead
inadvertently added during processing. Foods packaged in soldered cans have much greater lead
levels than foods packaged in other types of containers. About 45 percent of the baseline
adult exposure to lead results from the use of solder lead in packaging food and distributing
drinking water.
Significant amounts of lead in drinking water can result from contamination at the water
source and from the use of lead solder in the water distribution system. Atmospheric deposi-
tion has been shown to increase lead in rivers, reservoirs, and other sources of drinking
water; in some areas, however, lead pipes pose a more serious problem. Soft, acidic water in
homes with lead plumbing may have excessive lead concentrations. Besides direct consumption
of the water, exposure may occur when vegetables and other foods are cooked in water contain-
ing lead.
All of the categories of potential lead exposure discussed above may influence or be in-
fluenced by dust and soil. For example, lead in street dust is derived primarily from vehic-
ular emissions, while leaded house dust may originate from nearby stationary or mobile
sources. Food and water may include lead adsorbed from soil as well as deposited atmospheric
material. Flaking leadbased paint has been shown to increase soil lead levels. Natural con-
centrations of lead in soil average approximately 15 ug/g; this natural lead, in addition to
anthropogenic lead emissions, influences human exposure.
Americans living in rural areas away from sources of atmospheric lead consume 50 to 75 ^a
Pb/day from all sources. Circumstances which can increase this exposure are: urban residence
(25 to 100 ug/day), family garden on high-lead soil (800 to 2000 ug/day), houses with interior
lead-based paint (20 to 85 ug/day), and residence near a smelter (400 to 1300 ug/day). Occu-
pational settings, smoking, and wine consumption also can increase consumption of lead accord-
ing to the degree of exposure.
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A number of manmade materials are known to contain lead, the most important being paint
and plastics. Lead-based paints, although no longer used, are a major problem in older homes.
Small children who ingest paint flakes can receive excessive lead exposure. Incineration of
plastics may emit large amounts of lead into the atmosphere. Because of the increasing use of
plastics, this source is likely to become more important. Other manmade materials containing
lead include colored dyes, cosmetic products, candle wicks, and products made of pewter and
silver.
The greatest occupational exposures are found in the lead smelting and refining indus-
tries. Excessive airborne lead concentrations and dust lead levels are occasionally found in
primary and secondary smelters; smaller exposures are associated with mining and processing of
the lead ores. Welding and cutting of metal surfaces coated with lead-based paint may also
result in excessive exposure. Other occupations with potentially high exposures to lead in-
clude the manufacture of lead storage batteries, printing equipment, alkyl lead, rubber pro-
ducts, plastics, and cans; individuals removing lead paint from walls and those who work in
indoor firing ranges may also be exposed to lead.
Environmental contamination by lead should be measured in terms of the total amount of
lead emitted to the biosphere. American industry contributes several hundred thousand tons of
lead to the environment each year: 35,000 tons from petroleum additives, 50,000 tons from am-
munition, 45,000 tons in glass and ceramic products, 16,000 tons in paint pigments, 8,000 tons
in food can solder, and untold thousands of tons of captured wastes during smelting, refining,
and coal combustion. These are uses of lead which are generally not recoverable, thus they
represent a permanent contamination of the human or natural environment. Although much of
this lead is confined to municipal and industrial waste dumps, a large amount is emitted to
the atmosphere, waterways, and soil, to become a part of the biosphere.
Potential human exposure can be expressed as the concentrations of lead in these environ-
mental components (air, dust, food, and water) that interface with man. It appears that, with
the exception of extraordinary cases of exposure, about 100 ug of lead are consumed daily by
each American. This amounts to only 8 tons for the total population, or less than 0.01 per-
cent of the total environmental contamination.
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7.5 REFERENCES
Acra, A.; Dajani, R.; Raffoul, Z.; Karahagopian, Y. (1981) Lead-glazed pottery: a potential
health hazard in the Middle East. Lancet 1(8217): 433-434.
Agrawal, Y. K.; Patel, M. P.; Merh, S. S. (1981) Lead in soils and plants: its relationship to
traffic volume and proximity to highway (Lalbag, Baroda City). Int. J. Environ. Stud 16-
222-224.
Akland, G. G. (1976) Air quality data for metals, 1970 through 1974, from the National Air
Surveillance Network. Research Triangle Park, NC: U.S. Environmental Protection Agency
Office of Research and Development; EPA report no. EPA 600/ 4-76-041. Available from'
NTIS, Springfield, VA; PB 260905.
Anderson, K. E. ; Fishbein, A.; Kestenbaum, D. ; Sassa, S.; Alvares, A. P.; Kappas, A. (1977)
Plumbism from airborne lead in a firing range: an unusual exposure to a toxic heavv
metal. Am. J. Med. 63: 306-312. y
Andresen, A. M.; Johnson, A. H.; Siccama, T. G. (1980) Levels of lead, copper, and zinc in the
forest floor in the northeastern United States. J. Environ. Qual. 9: 293-296.
Angle, C. R.; Mclntire, M. S. (1979) Environmental lead and childrea: the Omaha study J
Toxicol. Environ. Health 5: 855-870.
Annual averages of lead from NFAN as of September 1982. (1982) From: NFAN, National Filter
Analysis Network [Data base]. Research Triangle Park, NC: U.S. Environmental Protection
Agency, Environmental Monitoring Systems Laboratory. Printout. Available for inspection
at: U.S. Environmental Protection Agency, Environmental Criteria and Assessment Office
Research Triangle Park, NC. '
Bailey, R. J.; Russell, P. F. (1981) Predicting drinking water lead levels. Environ. Technol
Lett. 2: 57-66.
Baker, E. L. , Jr.; Landrigan, P. J. ; Barbour, A. G.; Cox, D. H.; Folland, D. S.; Ligo, R. N. •
Throckmorton, J. (1979) Occupational lead poisoning in the United States: clinical and
biochemical findings related to blood lead levels. Br. J. Ind. Med. 36: 314-322.
Barltrop, D.; Strehlow, C. D. (1976) Westway nursery testing project: report to the Greater
London Council. London, United Kingdom. Available for inspection at: U.S. Environmental
Protection Agency, Environmental Criteria and Assessment Office, Research Triangle Park
NC. '
Barltrop, D. ; Strehlow, C. D. ; Thornton, I.; Webb, J. S. (1975) Absorption of lead from dust
and soil. Postgrad. Med. J. 51: 801-804.
Barry, P. S. I.; Connolly, R. (1981) Lead concentrations in mediaeval bones. Int. Arch Occun
Environ. Health 48: 173-177. H'
Beloian, A. (1982) Use of a food consumption model to estimate human contaminant intake
Environ. Monitor. Assess. 2: 115-127.
Beloian, A.; McDowell, M. (1981) Estimates of lead intakes among children up to 5 years of
age, 1973-1978 and 1980. Washington, DC: U.S. Food and Drug Administration, Bureau of
Foods; Division of Nutrition final internal report. Available from: U.S. Food and Drua
Administration, Bureau of Foods, Washington, DC. a
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Berg, B. A.; Zenz, C. (1967) Environmental and clinical control of lead exposure in a non-
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PRELIMINARY DRAFT
APPENDIX 7A
SUPPLEMENTAL AIR MONITORING INFORMATION
7A.1 AIRBORNE LEAD SIZE DISTRIBUTION
In Section 7.2.1.3.1, several studies of the particle size distributions for atmospheric
•V J|->l.
lead were discussed. The distributions at forty locations were given in Figure 7-5. Supple-
mentary information from each of these studies is given in Table 7A-1.
7A.2 NONURBAN AIR MONITORING INFORMATION
Section 7.2.1.1.1 describes ambient air lead concentrations in the United States,
emphasizing monitoring network data from urban stations. Table 7-2 gives the cumulative fre-
quency distributions of quarterly averages for urban stations. Comparable data for nonurban
stations are given in Table 7A-2. The trends shown by the two tables are similar, but the
numbers of reports for nonurban stations has decreased markedly since 1977. Table 7A-2 does
not include nonurban stations located near specific point sources. The detection limit has
decreased over the years, thus there are fewer reports of air concentrations below the
detection limit since 1975.
The distributions of annual averages among specific concentration intervals are given in
Table 7A-3 for nonurban stations. Comparable data were presented graphically in Figure 7-2
for urban stations.
7APPB/B 7A-1 7/1/83
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PRELIMINARY DRAFT
TABLE 7A-1.
INFORMATION ASSOCIATED WITH THE AIRBORNE LEAD SIZE
DISTRIBUTIONS OF FIGURE 7-5
Graph
no. Reference
Dates of sampling
Location of sampling
CT
Type of sampler (jg/™3
Approx.
MMD pm
3>
rsj
Lee et al. (1972)
Lee et al. (1972)
Lee et al. (1972)
Lee et al. (1972)
Lee et al. (1972)
Lee et al. (1972)
Jan. - Dec. 1970
Average of 4 quarterly
composited samples,
representing a total of
21 sampling periods of
24 hours each
Mar. - Dec. 1970
Sane averaging as
Graph 1, total of 18
sampling periods
Jan. - Dec. 1970
Sane averaging as
Graph 1, total of
21 sampling periods
Mar. - Dec. 1970
Sane averaging as
Graph 1, total of 20
sampline periods
Jan. - Dec. 1970
Same averaging as
Graph 1, total of 22
sampling periods
Jan. - Dec. 1970
Same averaging as
Graph 1, total of 23
sampling periods
Chicago, Illinois
Cincinnati, Ohio
Denver, Colorado
Philadelphia,
Pennsylvania
St. Louis, Missouri
Washington, D.C.
Modified Anderson 3.2
impactor with backup
filter
Modified Andersen 1.8
impactor with backup
filter
Modified Andersen 1.8
impactor with backup
filter
Modified Andersen 1.6
impactor with backup
filter
Modified Andersen 1.8
impactor with backup
filter
Modified Andersen 1.3
impactor with backup
filter
0.68
0.48
0.50
0.47
0.69
0.42
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PRELIMINARY DRAFT
TABLE 7A-1. (continued)
Graph
no
7
fi
9
10
11
12
13
Reference
Lee et al. (1968)
Lee et al. (1968)
Peden (1977)
Peden (1977)
Peden (1977)
Peden (1977)
Peden (1977)
Dates of sampling
September 1966
Average of 14 runs,
24 hours each
February 1967
Average of 3 runs
4 days each
Summer 1975
Average of 4 runs,
average 8 days each
Suamer 1972
Average of 3 runs,
average 10 days each
Summer 1973
Average of 2 runs
average S days each
SuMaer 1973
Average of Z runs,
average 6 days each
Summer 1972
Location of sampling
Cincinnati, Ohio
Fairfax, Ohio
suburb of Cincinnati
Alton, Illinois,
industrial area near
St. Louis
Centreville, Illinois,
downwind of a zinc
smelter
Collinsville, Illinois
Industrial area near
St. Louis
KMOX radio transmitter,
Illinois, industrial
area near St. Louis
Pere Marquette State
Type of sampler
Andersen impactor with
backup filter, 1.2m
above the ground
• Andersen impactor with
backup filter, 1.2m
above the ground
Andersen impactor
no backup filter
Andersen impactor
with backup filter
Andersen inpactor
with backup filter
Andersen Impactor
with backup filter
Andersen Impactor
CT
ug/n»
2.8
0.69
0.24
0.62
0.67
0.60
0.15
Approx.
HMD pm
O.Z9
0.42
2.1
0.41
0.24
0.31
0.51
14 Peden (1977)
Average of 9 runs,
average 9 days each
Summer 1975
Average of 4 runs,
average 8 days each
Park, Illionis, upwind
of St. Louis
Wood River, Illinois,
industrial area near
St. Louis
with backup filter
Andersen Impactor,
no backup filter
0.27
1.8
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PRELIMINARY DRAFT
TABLE 7A-1 (continued)
Graph
no
IS
16
17
18
19
20
21
22
Reference
Cholak et al.
(1968)
McDonald and
Duncan (1979)
Corn et al. (1976)
Dorn et al. (1976)
Dairies et al.
(1970)
Martens et al.
(1973)
Lundgren (1970)
Huntzicker et al.
(1975)
Dates of sampling
April 1968
average of several runs,
3 days each
June 1975
One run of 15 days
Winter, spring,
suMer 1972
Average of 3 runs,
27 days each
Winter, spring,
summer 1972
Average of 3 runs,
14 days each
1968
Average of continuous
1-week runs over an
8-month period
July 1971
One run of 4 days
November 1968
Average of 10 runs,
16 hours each
May 1973
One run of 8 hours
Location of sampling
3 sites: 10,400 and
3300* from Interstate
75, Cincinnati, Ohio
Glasgow, Scotland
Southeast Mi ssouri ,
800m from a lead
shelter
Southeast Missouri,
75 km from the lead
swelter of Graph 17
3 sites: 9, 76, and
530m from U.S. Route 1,
New Brunswick,
New Jersey
9 sites throughout
San Francisco area
Riverside, California
Shoulder of Pasadena
Freeway near downtown
Type of sampler
Andersen impactor
with backup filter
Casella impactor
with backup filter,
30m above the ground
Andersen impactor,
no backup filter,
1. 7m above the ground
Andersen impactor,
no backup filter,
1.7m above the ground
Cascade impactor with
backup filter
Andersen impactor
with backup filter
Lundgren impactor
Andersen impactor
with backup filter,
C
T Approx.
ug/m3 HMO \im
7.8*
1.7 0.32
1.1
0.53 0.51
1.0 3.8
0.11 2.4
4.5 0.35
2.2
1.5
0.84 0.49
0.59 0.50
14.0 0.32
Los Angeles, California
2m above the ground
-------
DRAFT
TABLE 7A-1 {continued)
I
en
Graph
no
23
24
25
26
Z7
Reference
Huntzlcker et al.
(1975)
Davidson (1977)
Davidson et al.
(1980)
Davidson et al.
(1981a)
Davidson et al.
(19816)
Dates of sampling
Februray 1974
One run of 6 days
May and July 1975
Average of 2 runs,
61 hours each
October 1979
One run of 120 hours
July-Sep. 1979
Average of 2 runs,
90 hours each
December 1979
One run of 52 hours
Location of sampling
Pasadena, California
Pasadena, California
Clingaan's Doae
Great Smokies National
Park, elev. 2024*
Pittsburgh, Pennsylvania
Nepal Himalayas
elev. 3962*
c
T Approx.
Type of sampler iig/m3 HMD pm
Andersen impactor 3.5 0.72
with backup filter,
on roof of 4 story
building
Modified Andersen 1.2 0.97
iapactor with backup
filter on roof of 4
story building
2 Modified Andersen 0.014 1.0
inpactors with backup
filters, 1.2M above
the ground
Modified Andersen 0.60 0.56
iiipactor with backup
filter, Am above the
ground
Modified Andersen 0.0014 0.54
iapactor with backup
28 Soold and
Davidson (1962)
29 Goold and
Davidson (1962}
June 1980
One run of 72 hours
July 1980
One run of 34 hours
Export, Pennsylvania
rural site 40 )(•
east of Pittsburgh
Packwood, Washington
rural site in 61fford
Pinchot National Forest
filter, 1.2« above
the ground
2 Modified Andersen 0.111
inpactors with backup
filters, 1.2m above
the ground
Modified Andersen 0.016
{•pactor with backup
filter, 1.5» above
the ground
1.2
0.40
-------
PRELIMINARY DRAFT
TABLE 7A-1 (continued)
Graph
no
30
31
32
33
•^j
3>
1
OS
34
35
36
37
Reference
Goo Id and
Davidson (1982)
Ouce et al.
(1976)
Duce et al.
(1976)
Harrison et al.
(1971)
Gillette and
Winchester (1972)
Gillette and
Winchester (1972)
Gillette and
Winchester (1972)
Johansson et al .
(1976)
Dates of sampling
July-Aug. I960
One run of 92 hours
Hay - June 1975
One run of 112 hours
July 1975
One run of 79 hours
April 1968
Average of 21 runs,
2 hours each
Oct. 1968
Average of 15 runs,
24 hours each
May - Sept. 1968
Average of 10 runs,
8 hours each
Oct. 1968
Average of 3 runs,
24 hours each
June - July 1973
Average of 15 runs,
Location of sampling
Hurricane Ridge
Olympic National
Park elev. 1600m
Southeast coast of
Bermuda
Southeast coast of
Bermuda
Ann Arbor, Michigan
Ann Arbor, Michigan
Chicago, Illinois
Lincoln, Nebraska
2 sites in Tallahassee,
Florida
C
T
Type of sampler ug/m3
Modified Andersen 0.0024
impactor with backup
filter, 1.5m above
the ground
Sierra high-volume 0.0085
impactor with backup
filter, 20m above the
ground
Sierra high-volume 0.0041
impactor with backup
filter. 20m above the
ground
Modified Andersen 1.8
impactor with backup
filter, 20m above the
ground
Andersen impactor with 0.82
backup filter
Andersen impactor with 1.9
backup filter
Andersen impactor with 0.14
backup filter
Delron Battelle-type 0.24
impactor, no backup
Approx.
MMD urn
0.87
0.57
0.43
0.16
0.28
0.39
0.42
0.62
average 50 hr each
filter, on building roofs
-------
PRELIMINARY DRAFT
38
39
40
Cawse et al.
(1974)
Pattenden et al.
(1974)
Bernstein and
Rahn (1979)
TABLE 7A-1 (continued)
Graph
no Reference
Dates of sampling
C
T
Location of sampling Type of sanpler \ig/m3
Approx.
HMD \M
July - Dec. 1973
May - Aug. 1973
Average of 4 runs,
1 nonth each
Aug. 1976
Average of 4 runs,
1 week each
Chilton, England
Trebanos, England
New York City
Andersen impactor with 0.16
backup filter, 1.5m above
the ground
Andersen inpactor with 0.23
backup filter, l.S> above
the ground
Cyclone sampling
system with backup
filter, on roof on
15 story building
1.2
0.57
0.74
0.64
"Airborne concentrations for filters run at the sane sites as the i«pactor, but during different tine periods. Inpactor concentrations not available.
•si
>
-------
TABLE 7A-2. CUMULATIVE FREQUENCY DISTRIBUTIONS OF QUARTERLY LEAD MEASUREMENTS
AT NONURBAN STATIONS BY YEAR, 1970 THROUGH 1980
(pg/m3)
I
00
Percentile
Year
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
No. of
station
reports
124
85
137
100
79
98
98
84
20
16
12
Minimum
qtrly.
avg.
LD
LD
LD
LD
LD
LD
LD
0.006
0.002
LD
LD
10
LD
LD
LO
LD
LD
LD
LD
0.01
0.007
0.02
0.01
30
LD
LD
LD
LO
0.053
LD
LD
0.04
0.04
0.02
0.005
50
LD
LO
0.107
LO
0.087
LD
LD
0.08
0.06
0.10
0.03
70
LD 0.
LD 0.
0.166 0.
0.132 0.
0. 141 0.
0.144 0.
0.105 0.
0.11 0.
0.09 0.
0.14 0.
0.05 0.
90
267
127
294
233
221
255
240
18
24
21
11
95
0.383
0.204
0.392
0.392
0.317
0.311
0.285
0.20
0.33
0.27
0.13
99
0.628
0,783
0.950
0.698
0.496
0.431
0.336
0.25
0.33
0.32
0.13
Arithmetic Geometric
Std. Std.
Max. Mean dev. Mean dev.
qtrly.
avg.
1.471
1.134
1.048 0.139 0.169 0.90
0.939
0.534 0.111 0.111 0.083
0.649
0.483
0.40 0.09 0.10 0.07
0.33 0.08 0.10 0.07
0.11 0.11 0.13 0.11
0.13 0.04 0.06 0.05
—
--
2.59
--
2.30
--
--
3.19
2.84
3.45
3.33
TO
m
70
o
TO
Sources: Akland (1976); U.S.
(1982).
Environmental Protection Agency (1978; 1979); Quarterly averages of Lead from NFAN
-------
PRELIMINARY DRAFT
TABLE 7A-3. NUMBER OF NASN NONURBAN STATIONS WHOSE DATA FALL WITHIN
SELECTED ANNUAL AVERAGE LEAD CONCENTRATION INTERVALS, 1966-1980
Concentration interval,
Year
— ••
1966
1967
1968
1969
1970-
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
No. stations
Percent
No. stations
Percent
No. stations
Percent
No. stations
Percent
No. stations
Percent
No. stations
Percent
No. stations
Percent
No. stations
Percent
No. stations
Percent
No. stations
Percent
No. stations
Percent
No. stations
Percent
No. stations
Percent
No. stations
Percent
<0.03
—
1
5
1
5
— .
10
29
9
39
3
19
0
0
0
0
5
24
1
20
1
25
1
33
0.03-0.096
10
52
7
35
15
75
11
52
—
4
12
7
31
5
31
0
0
0
0
8
38
3
60
1
25
2
67
0.10-0.19
6
32
10
50
4
20
9
43
7
70
9
26
6
26
6
38
1
20
3
50
7
33
1
20
1
25
0
0
|jg/m3
0.20-0.45
3
16
2
10
—
1
5
3
30
11
33
1
4
2
12
4
80
3
50
1
5
0
0
1
25
0
0
Total
19
100
20
100
20
100
21
100
10
100
34
100
23
100
16
100
5
100
6
100
21
100
5
100
4
100
3
100
Sources: Akland (1976); Shearer et al. (1972); U.S. Environmental Protection Agency (1978;
1979); Annual averages of lead from NFAN (1982).
7APPB/B
7A-9
7/1/83
-------
PRELIMINARY DRAFT
APPENDIX 7B
SUPPLEMENTAL SOIL AND DUST INFORMATION
Lead in soil, and dust of soil origin, is discussed in Section 7.2.2. The data shov,
average soil concentrations are 8 to 25 M9/9, and dust from this soil rarely exceeds 80 to 100
(jg/g. Street dust, household dust and occupational dusts often exceed this level by one to
two orders of magnitude. Tables 7B-1 and 7B-2 summarizes several studies of street dust.
Table 7B-3 shows data on household and residential soil dust. These data support the
estimates of mean lead concentrations in dust discussed in Section 7.3.1.4. Table 7B-4 gives
airborne lead concentrations for an occupational setting, which are only qualitatively related
to dust lead concentrations.
7APPB/C 7B-1 7/1/83
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PRELIMINARY DRAFT
TABLE 7B-1. LEAD DUST ON AND NEAR HEAVILY TRAVELED ROADWAYS
Sampling site
Concentration,
Hg Pb/g
Washington, DC:
Busy intersection
Many sites
Chicago:
Near expressway
Philadelphia:
Near expressway
Brooklyn:
Near expressway
New York City:
Near expressway
Detroit:
Street dust
Philadelphia:
Gutter (low pressure)
Gutter (high pressure)
Miscellaneous U.S. Cities:
Highways and tunnels
Netherlands:
Heavily traveled roads
13,000
4000-8000
6600
3000-8000
900-4900
2000
970-1200
1500
210-2600
3300
280-8200
10,000-20,000
5000
Reference
Fritsch and Prival (1972)
Kennedy (1973)
Lombardo (1973)
Pinkerton et al. (1973)
Ter Haar and Aronow (1974)
Shapiro et al. (1973)
Shapiro et al. (1973)
Buckley et al. (1973)
Rameau (1973)
TABLE 7B-2. LEAD CONCENTRATIONS IN STREET DUST IN
LANCASTER, ENGLAND
Site
Car parks
Garage forecourts
Town centre streets
Main roads
Residential areas
Rural roads
No. of
samples
4
16
2
7
13
19
7
4
Range of
concentrations
39,700 -
950 -
44,100 -
1,370 -
840 -
740 -
620 -
410 -
51,900
15,000
48,900
4,480
4,530
4,880
1,240
870
Mean
46,300
4,560
46,500
2,310
2,130
1,890
850
570
Standard
deviation
5,900
3,700
--
1,150
960
1,030
230
210
Source: Harrison (1979).
7APPB/C
7B-2
7/1/83
-------
PRELIMINARY DRAFT
TABLE 7B-3. LEAD DUST IN RESIDENTIAL AREAS
Sampling site
Concentration,
ug Pb/g
Reference
Philadelphia:
Classroom
Playground
Window frames
Boston and New York:
House dust
Brattleboro, VT:
In home
New York City:
Middle Class
Residential
Philadelphia:
Urban industrial
Residential
Suburban
Derbyshire, England:
Low soil lead area
High soil lead area
2000
3000
1750
1000-2000
500-900
610-740
3900
930-16,000
610
290-1000
830
280-1500
520
130-3000
4900
1050-28,000
Shapiro et al. (1973)
Needleman and Scanlon (1973)
Darrow and Schroeder (1974)
Pinkerton et al. (1973)
Needleman et al. (1974)
Needleman et al. (1974)
Needleman et al. (1974)
Barltrop et al. (1975)
Barltrop et al. (1975)
TABLE 7B-4. AIRBORNE LEAD CONCENTRATIONS BASED ON PERSONAL SAMPLERS, WORN BY
EMPLOYEES AT A LEAD MINING AND GRINDING OPERATION IN THE MISSOURI
LEAD BELT
Air lead concentration (ug/m3)
Occupation
Hill operator
Flotation operator
Filter operator
Crusher operator
Sample finisher
Crusher utility
Shift boss
Equipment operator
N
6
4
4
4
2
1
5
1
High
300
750
2450
590
10,000
—
560
--
Low
50
100
380
20
7070
—
110
--
Mean
180
320
1330
190
8530
70
290
430
H denotes number of air samples.
Source: Roy (1977).
7APPB/C
7B-3
7/1/83
-------
PRELIMINARY DRAFT
APPENDIX 7C
STUDIES OF SPECIFIC POINT SOURCES
OF LEAD
This collection of studies is intended to extend and detail the general picture of lead
concentrations in proximity to identified major point sources as portrayed in Chapter 7.
Because emissions and control technology vary between point sources, each point source is
unique in the degree of environmental contamination. The list is by no means all-inclusive,
but is intended to be representative and to supplement the data cited in Chapter 7. In many
of the studies, blood samples of workers and their families were taken. These studies are
also discussed in Chapter 11.
7C.1 SMELTERS AND MINES
7C.1.1 Two Smelter Study
The homes of workers of two unidentified secondary lead smelters in different geograph-
ical areas of the United States were studied by Rice et al. (1978). Paper towels were used to
collect dust from surfaces in each house, following the method of Vostal et al. (1974). A
total of 33 homes of smelter workers and 19 control homes located in the same or similar
neighborhoods were investigated. The geometric mean lead levels on the towels were 79.3 pg
(smelter workers) versus 28.8 ug (controls) in the first area, while in the second area mean
values were 112 ug versus 9.7 ug. Also in the second area, settled dust above doorways was
collected by brushing the dust into glassine envelopes for subsequent analysis. The geometric
mean lead content of this dust in 15 workers' homes was 3300 ug/g, compared with 1200 ug/g
in eight control homes. Curbside dust collected near each home in the second area had a
geometric mean lead content of 1500 ug/g, with no significant difference between worker and
control homes. No significant difference was reported in the paint lead content between
worker and control homes. The authors concluded that lead in dust carried home by these
workers contributed to the lead content of dust in their homes, despite showering and changing
clothes at the plant, and despite work clothes being laundered by the company. Storage of
employee street clothes in dusty lockers, walking across lead-contaminated areas on the way
home, and particulate settling on workers' cars in the parking lot may have been important
factors. Based on measurement of zinc protoporphyrin levels in the blood of children in these
homes, the authors also concluded that the greater lead levels in housedust contributed to in-
creased child absorption of lead.
7APPB/D 7C-1 7/1/83
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PRELIMINARY DRAFT
7C.1.2 British Columbia. Canada
Neri et al. (1978) and Schmitt et al. (1979) examined environmental lead levels in the
vicinity of a lead-zinc smelter at Trail, British Columbia. Total emissions from the smelter
averaged about 135 kg Pb/day. Measurements were conducted in Trail (population 12,000), in
Nelson, a control city 41 kilometers north of Trail (population 10,000), and in Vancouver.
The annual mean airborne lead concentrations in Trail and in Nelson were 2.0 and 0.5 ug/m3,
respectively. Mean lead levels in surface soil were 1320 \ig/Q in Trail (153 samples), 192
^g/g in Nelson (55 samples), and 1545 vg/g in Vancouver (37 samples).
Blood lead measurements shows a positive correlation with soil lead levels for children
aged 1-3 years and for first graders, but no significant correlation for ninth graders. The
authors concluded that small children are most likely to ingest soil dust, and hence deposited
smelter-emitted lead may pose a potential hazard for the youngest age group.
7C.1.3 Netherlands
Environmental lead concentrations were measured in 1978 near a secondary lead smelter in
Arnhem, Netherlands (Diemel et al., 1981). Air and dust were sampled in over 100 houses at
distances of 450 to 1000 meters from the smelter, with outdoor samples of air, dust, and soil
collected for comparison. Results are presented in Table 7C-1. Note that the mean indoor
concentration of total suspended particulates (TSP) is greater than the mean outdoor concen-
tration, yet the mean indoor lead level is smaller than the corresponding outdoor level. The
authors reasoned that indoor sources such as tobacco smoke, consumer products, and decay of
furnishings are likely to be important in affecting indoor TSP; however, much of the indoor
lead was probably carried in from the outside by the occupants, e.g., as dust adhering to
shoes. The importance of resuspension of indoor particles by activity around the house was
also discussed.
7C.1.4 Belgium
Roels et al. (1978; 1980) measured lead levels in the air, in dust, and on childrens1
hands at varying distances from a lead smelter in Belgium (annual production 100,000 metric
tons). Blood data from children living near the smelter were also obtained. Air samples were
collected nearly continuously beginning in September 1973. Table 7C-2 lists the airborne con-
centrations recorded during five distinct population surveys between 1974 and 1978, while
Figure 7C-1 presents air, dust, and hand data for Survey #3 in 1976. Statistical tests showed
that blood lead levels were better correlated with lead on childrens1 hands than with air
lead. The authors suggested that ingestion of contaminated dust by hand-to-mouth activities
7APPB/D 7C-2 7/1/83
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PRELIMINARY DRAFT
such as nail-biting and thumb-sucking, as well as eating with the hands, may be an important
exposure pathway. It was concluded that intake from contaminated hands contributes at least
two to four times as much lead as inhalation of airborne material.
TABLE 7C-1. LEAD CONCENTRATIONS IN INDOOR AND OUTDOOR AIR, INDOOR AND OUTDOOR
DUST, AND OUTDOOR SOIL NEAR THE ARNHEM, NETHERLANDS SECONDARY LEAD SMELTER
(INDOOR CONCENTRATIONS)
Parameter
Suspended parti cul ate matter
dust concentration (ug/m3)
lead concentration (ug/m3)
dust lead content (ug/kg)
Dustfall
dust deposition (mg/ms*day)
lead deposition (ug/m3 -day)
dust lead content (mg/kg)
Floor dust
amount of dust (mg/m3)
amount of lead (ug/m3)
Dust lead content (mg/kg)
in "fine" floor dust
in "coarse" floor dust
Arithmetic
mean
140
0.27
2670
15.0
9.30
1140
356
166
1050
370
Range
20-570
0.13-0.74
400-8200
1.4-63.9
1.36-42.4
457-8100
41-2320
18-886
463-4740
117-5250
*
n
101
101
106
105
105
105
107
101
107
101
*N number of houses.
(OUTDOOR CONCENTRATIONS)
Parameter
Arithmetic mean
Range
Suspended particles
dust concentration (ug/n>3)
lead concentraton (ug/m3)
(high-volume samplers, 24-hr
samples, 2 months' average)
Lead in dustfall
(ug/m3«day)
(deposit gauges, weekly
samples, 2 months' average)
Lead in soil
(mg/kg 0-5 cm)
Lead in streetdust
(mg/kg <0.3 mm)
64.5
0.42
508
322
860
53.7-73.3
0.28-0.52
208-2210
21-1130
77-2670
Source: Diemel et al (1981).
7APPB/D
7C-3
7/1/83
-------
Pb IN AIR
Pb IN DUST
n
18 o-
20 9
Pb ON HAND L
760
1600
2250
160
300
«so
MQ'hand
AT LESS THAN 1km FROM LEAD SMELTER
AT 25 km FROM LEAD SMELTER
URBAN - BRUSSELS
AIR
DUST
HANDcr
HAND 9
RURAL - HERENT
CHILDREN 1976
3RD SURVEY
Figure 7C-1. Concentrations of lead in air, in dust, and on children's hands, measured
during the third population survey of Table E. Values obtained less than 1 km from the
smelter, at 2.5 km from the smelter, and in two control areas are shown.
Source: Roels et al. (1980).
7APPB/D
7C-4
7/1/83
-------
PRELIMINARY DRAFT
TABLE 7C-2. AIRBORNE CONCENTRATIONS OF LEAR DURING FIVE
POPULATION SURVEYS NEAR A LEAD SMELTER IN BELGIUM*
Study populations
1 Survey
(1974)
2 Survey
(1975)
3 Survey
(1976)
4 Survey
(1977)
5 Survey
(1978)
<1 km
2.5 km
Rural
<1 km
2.5 km
Rural
<1 km
2.5 km
Urban
Rural
<1 km
2.5 km
<1 km
2.5 km
Urban
Rural
Pb-Air
(ug/m3)
4.06
1.00
0.29
2.94
0.74
3.67
0.80
0.45
0.30
3.42
0.49
2.68
0.54
0.56
0.37
*Additional airborne data in rural and urban areas obtained as controls are also shown.
Source: Roels et al. (1980).
7C.1.5 Meza River Valley, Yugoslavia
In 1967, work was initiated in the community of Zerjav, situated in the Slovenian Alps on
the Meza River, to investigate contamination by lead of the air, water, snow, soil, vegeta-
tion, and animal life, as well as the human population. The mselter in this community pro-
duces about 20,000 metric tons of lead annually; until 1969 the stack emitted lead oxides
without control by filters or other devices. Five sampling sites with high-volume samplers
operating on a 24-hr basis were established in the four principal settlements within the Meza
River Valley (Figure 7C-2): (1) Zerjav, in the center, the site of the smelter, housing 1503
inhabitants, (2) Rudarjevo, about 2 km to the south of Zerjav with a population of 100;
(3) Crna, some 5 km to the southwest, population 2198, where there are two sites (Crna-SE and
Crna-W); and (4) Mezica, a village about 10 km to the northwest of the smelter with 2515
7APPB/D 7C-5 7/1/83
-------
PRELIMINARY DRAFT
inhabitants. The data in Table 7C-3 are sufficient to depict general environmental contami-
nation of striking proportions.
7C.1.6 Kosova Province, Yugoslavia
Popovac et al. (1982) discuss lead exposure in an industrialized region near the town of
Kosova Mitrovica, Yugoslavia, containing a lead smelter and refinery, and a battery factory.
In 1979, 5800 kg of lead were emitted daily from the lead smelter alone. Ambient air concen-
trations in the town were in the range 21.2 to 29.2 ug/m3 in 1980, with levels occasionally
reaching 70 ug/m3. The authors report elevated blood lead levels in most of the children
tested; some extremely high values were found, suggesting the presence of congenital lead
poi soni ng.
7C.1.7 Czechoslovakia
Wagner et al. (1981) measured total suspended particulate and airborne lead concentra-
tions in the vicinity of a waste lead processing plant in Czechoslovakia. Data are shown in
Table 7C-4. Blood lead levels in 90 children living near the plant were significantly greater
than in 61 control children.
7C.1.8 Australia
Heyworth et al. (1981) examined child response to lead in the vicinity of a lead sulfide
mine in Northhamptom Western Australia. Two samples of mine tailings measured in 1969
contained 12,000 ug/g and 28,000 pg/g lead; several additional samples analyzed in 1978 con-
tained 22,000 ug/g to 157,000 ug/g lead. Surface soil from the town boundry contained 300
ug/g, while a playground and a recreational area had soil containing 11,000 ug/g and 12,000
ug/g lead respectfully.
Blood lead levels measured in Northhamptom children, near the mine, were slightly greater
than levels measured in children living a short distance away. The Northhampton blood lead
levels were also slightly greater than those reported for children in Victoria, Australia
(DeSilva and Donnan, 1980). Heyworth et al. concluded that the mine tailings could have
increased the lead exposure of children living in the area.
7C.2 BATTERY FACTORIES
7C.2.1 Southern Vermont
Watson et al. (1978) investigated homes of employees of a lead storage battery plant in
southern Vermont in August and September, 1976. Lead levels in household dust, drinking
water, and paint were determined for 22 workers' homes and 22 control homes. The mean lead
7APPB/D 7C-6 7/1/83
-------
Figure 7C-2. Schematic plan of lead mine and smelter from Meza Valley,
Yugoslavia, study.
Source: Fugas (1977).
7APPB/D
7C-7
7/1/83
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PRELIMINARY DRAFT
Table 7C-3. ATMOSPHERIC LEAD CONCENTRATIONS (24-hour) IN THE
MEZA VALLEY, YUGOSLAVIA, NOVEMBER 1971 TO AUGUST 1972
Pb concentration, |jg/m3
Site Minimum
Mezica 0.1
Zerjav 0.3
Rudarjevo 0.5
Crna SE 0. 1
Crna W 0. 1
Source: Fugas (1977).
Maximum Average
236.0 24.2
216.5 29.5
328.0 38.4
258.5 33.7
222.0 28.4
TABLE 7C-4. CONCENTRATIONS OF TOTAL AIRBORNE DUST AND OF AIRBORNE LEAD IN THE
VICINITY OF A WASTE LEAD PROCESSING PLANT IN CZECHOSLOVAKIA,
AND IN A CONTROL AREA INFLUENCED PREDOMINANTLY BY AUTOMOBILE EMISSIONS
TSP Lead
Exposed n
x (ng/m3)
S
range
95% c.i.
Control n
x (pg/m3)
S
range
95% c. i.
300 303
113.6 1.33
83.99 1.9
19.7-553.4 0.12-10.9
123.1-104.1 1.54-1.11
56.0 87
92.0 0.16
40.5 0.07
10-210 0.03-0.36
102.7-81.3 0.17-0.14
n - number of samples; x = mean of 24-hour samples
s = standard deviation; 95% confidence interval.
Source: Wagner et al. (1981).
7APPB/D
7C-8
7/1/83
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PRELIMINARY DRAFT
concentration in dust in the workers' homes was 2,200 (jg/g, compared with 720 ug/g in the
control homes. Blood lead levels in the workers' children were greater than levels in the
control children, and were significantly correlated with dust lead concentrations. No sig-
nificant correlations were found between drinking water lead and blood lead, or between paint
lead and blood lead. It is noteworthy that although 90 percent of the employees showered and
changed clothes at the plant, 87 percent brought their work clothes home for laundering. The
authors concluded that dust carried home by the workers contributed to increased lead absorp-
tion in their children.
7C.2.2 North Carolina
Several cases of elevated environmental lead levels near point sources in North Carolina
have been reported by Dolcourt et al. (1978; 1981). In the first instance, dust lead was
measured in the homes of mothers employed in a battery factory in Raleigh; blood lead levels
in the mothers and their chldren were also measured. Carpet dust was found to contain 1,700
to 48,000 ug/g lead in six homes where the children had elevated blood lead levels (>40
pg/dl). The authors concluded that lead carried home on the mothers' clothing resulted in
increased exposure to their children (Oolcourt et al. , 1978). In this particular plant, no
uniforms or garment covers were provided by the factory; work clothing was worn home.
In a second case, discarded automobile battery casings from a small-scale lead recovery
operation in rural North Carolina were brought home by a worker and used in the family's
wood-burning stove (Dolcourt et al., 1981). Two samples of indoor dust yielded 13,000 and
41,000 ug/g lead. A three-year-old girl living in the house developed encephalopathy
resulting in permanent brain damage.
In a third case, also in rural North Carolina, a worker employed in an automobile battery
reclamation plant was found to be operating an illicit battery recycling operation in his
home. Reclaimed lead was melted on the kitchen stove. Soil samples obtained near the house
measured as high as 49 percent lead by weight; the driveway was covered with fragments of
battery casings. Although no family member had evidence of lead poisoning, there were
unexplained deaths among chickens who fed where the lead waste products were discarded
(Dolcourt et al., 1981).
7C.2.3 Oklahoma
Morton et al. (1982) studied lead exposure in children of employees at a battery manu-
facturing plant in Oklahoma. A total of 34 lead-exposed children and 34 control children were
examined during February and March, 1978; 18 children in the lead-exposed group had elevated
blood lead levels (>30 ug/dl), while none of the controls were in this category.
7APPB/D 7C-9 7/1/83
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PRELIMINARY DRAFT
It was found that many of the battery factory employees also used lead at home, such as
casting lead into fishing sinkers and using leaded ammunition. A significant difference in
blood lead levels between the two groups of children was found even when families using lead
at home were deleted from the data set. Using the results of personal interviews with the
homemaker in each household, the authors concluded that dust carried home by the employees
resulted in increased exposure of their children. Merely changing clothes at the plant was
deemed insufficient to avoid transporting appreciable amounts of lead home: showering and
shampooing, in addition to changing clothes, was necessary.
7C.2.4 Oakland, California
Environmental lead contamination at the former site of wet-cell battery manufacturing
plant in Oakland, California was reported by Wesolowski et al. (1979). The plant was opera-
tional from 1924 to 1974, and was demolished in 1976. Soil lead levels at the site measured
shortly after demolition are shown in Table 7C-5. The increase in median concentrations with
depth suggested that the battery plant, rather than emissions from automobiles, were respons-
ible for the elevated soil lead levels. The levels decreased rapidly below 30 cm depth. The
contaminated soil was removed to a sanitary landfill and replaced with clean soil; a park has
subsequently been constructed at the site.
TABLE 7C-5. LEAD CONCENTRATIONS IN SOIL AT THE FORMER SITE OF A WET-CELL
BATTERY MANUFACTURING PLANT IN OAKLAND, CALIFORNIA
Depth
Surface
15 cm
30 cm
N
24
23
24
Range
(ug/g)
57-96,000
13-4200
13-4500
Mean
(pg/g)
4300
370
1100
Median
(i-'g/g)
200
200
360
Source: Wesolowski et al. (1979).
7C.2.5 Manchester, England
Elwood et al. (1977) measured lead concentrations in air, dust, soil, vegetation, and tap
water, as well as in the blood of children and adults, in the vicinity of a large battery
factory near Manchester. It was found that lead levels in dust, soil, and vegetation
decreased with increasing distance from the factor. Airborne lead concentrations did not show
a consistent effect with downwind distance, although higher concentrations were found downwind
7APPB/D 7C-10 7/1/83
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PRELIMINARY DRAFT
compared with upwind of the factor. Blood lead levels were greatest in the households of
battery factor employees: other factors such as distance from the factory, car ownership, age
of house, and presence of lead water pipes were outweighed by the presence of a leadworker in
the household. These results strongly suggest that lead dust carried home by the factor
employees is a dominant exposure pathway for their families. The authors also discussed the
work of Burrows (1976), who demonstrated experimentally that the most important means of lead
transport from the factory into the home is via the workers' shoes.
7APPB/D 7C-11 7/1/83
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PRELIMINARY DRAFT
APPENDIX 70
SUPPLEMENTAL DIETARY INFORMATION FROM THE
U.S. FDA TOTAL DIET STUDY
The U.S. Food and Drug Administration published a new Total Diet Food List (Pennington,
1983) based on over 100,000 daily diets from 50,000 participants. Thirty five hundred
categories of foods were condensed to 201 adult food categories for 8 age/sex groups.
Summaries of these data were used in Section 7.3.1.2 to arrive at lead exposures through food,
water, and beverages. For brevity and continuity with the crop data of Section 7.2.2.2.1, it
was necessary to condense the 201 categories of the Pennington study to 25 categories in this
report.
The preliminary lead concentrations for all 201 items of the food list were provided by
U.S. Food and Drug Administration (1983). These data represent three of the four Market
Basket Surveys, the fourth to be provided at a later time. Means of these values have been
calculated by EPA, using one-half the detection limit for values reported below detection
limit. These data appear in Table 7D-1.
In condensing the 201 categories of Table 70-1 to the 25 categories of Table 7-15,
combinations and fractional combinations of categories were made according to the scheme of
Table 7D~2. In this way, specific categories of food more closely identified with farm
products were summarized. The assumptions made concerning the ingredients in the final
product, (mainly water, flour, eggs, and milk) had little influence on the outcome of the
summarization.
7APPB/E 70-1 7/1/83
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PRELIMINARY DRAFT
TABLE 7D-1. FOOD LIST AND PRELIMINARY LEAD CONCENTRATIONS
Category Food
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
Whole milk
Low fat milk
Chocolate milk
Skim milk
Butter milk
Yogurt, plain
Milkshake
Evaporated milk
Yogurt, sweetened
Cheese, American
Cottage cheese
Cheese, Cheddar
Beef, ground
Beef, chuck roast
Beef, round steak
Beef, sirloin
Pork, ham
Pork chop
Pork sausage
Pork, bacon
Pork roast
Lamb chop
Veal cutlet
Chicken, fried
Chicken, roasted
Turkey, roasted
Beef liver
Frankfurters
Bologna
Salami
Cod/haddock filet
Tuna, canned
Shrimp
Fish sticks, frozen
Eggs, scrambled
Eggs, fried
Eggs, soft boiled
Pinto beans, dried
Pork and beans, canned
Cowpeas , dried
Lima beans, dried
Lima beans, frozen
Navy beans, dried
Red beans, dried
Lead concentration*
(pg/g)
0.02
0.06
0.08
0.04
0.03
0.05
0.04
0.09
0.03
0.05
0.04
0.11
0.02
0.18
0.03
0.04
0.41
0.03
0.02
T T
0.04
0.05
0.07 0.18
0.11
0.03
0.03
0.03
0.05
0.22
0.03
0.12
0.07
0.27 0.08
0.10
0.03
0.02
0.07 0.04
0.03
0.03
0.06
Mean
0.01
0.017
0.02
0.01
0.01
0.01
0.04
0.11
0.02
0.97
0.023
0.020
0.043
0.043
0.01
0.01
0.017
0.017
0.030
0.093
0.01
0.017
0.01
0.020
0.01 '
0.01
0.08
0.01
0.013
0.01
0.03
0.18
0.04
0.017
0.01
0.017
0.01
0.023
0.17
0.01
0.017
0.017
0.017
0.03
7APPB/E
7D-2
7/1/83
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PRELIMINARY DRAFT
TABLE 7D-1. (continued)
Category Food
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
Peas, green, canned
Peas, green, frozen
Peanut butter
Peanuts
Pecans
Rice, white
Oatmeal
Farina
Corn grits
Corn, frozen
Corn, canned
Corn, cream style, canned
Popcorn
White bread
Rolls, white
Cornbread
Bi scui ts
Whole wheat bread
Tortilla
Rye bread
Muffins
Crackers, sal tine
Corn chips
Pancakes
Noodles
Macaroni
Corn flakes
Pre-sweetened cereal
Shredded wheat cereal
Raisin bran cereal
Crisped rice cereal
Granola
Oat ring cereal
Apple, raw
Orange, raw
Banana, raw
Watermelon, raw
Peach, canned
Peach, raw
Applesauce, canned
Pear, raw
Strawberries, raw
Fruit cocktail, canned
Grapes , raw
Cantaloupe, raw
Pear, canned
Plums, raw
Grapefruit, raw
Pineapple, canned
Lead concentration*
(|jg/g)
0.14
0.03
0.15
0.03
0.05
0.06
0.03
T
0.22
0.09
0.03
0.04
0.05
0.02
0.03
0.04
0.03
0.03
0.04
0.18
0.02
0.21
0.02
0.03
0.23
0.03
0.24
T
0.03
0.10
0.28
0.08
0.19
T
0.56
0.06
0.07
0.06
0.03
0.04
0.03
0.05
0.02
0.04
0.06
0.02
0.04
0.03
0.23
0.04
0.19
0.03
0.24
0.02
0.08
0.22
0.08
0.25
0.06
0.11
0.08
0.02
0.02
0.03
0.02
0.02
0.03
0.03
0.03
0.02
0.02
0.04
0.02
0.02
0.28
0.10
0.13
0.17
0.05
Mean
0.22
0.04
0.56
0.01
0.017
0.084
0.027
0.017
0.01
0.013
0.28
0.09
0.053
0.01
0.037
0.01
0.023
0.03
0.023
0.02
0.01
0.017
0.02
0.017
0.033
0.013
0.02
0.033
0.01
0.017
0.013
0.02
0.03
0.03
0.02
0.01
0.013
0.23
0.023
0.17
0.02
0.017
0.20
0.013
0.04
0.31
0.012
0.017
0.08
7APPB/E
7D-3
7/1/83
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PRELIMINARY DRAFT
TABLE 70-1. (continued)
Category Food
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
Cherries, raw
Raisins, dried
Prunes, dried
Avocado, raw
Orange juice, frozen
Apple juice, canned
Grapefruit juice, frozen
Grape juice, canned
Pineapple juice, canned
Prune juice, bottled
Orange juice, canned
Lemonade, frozen
Spinach, canned
Spinach, frozen
Col lards, frozen
Lettuce, raw
Cabbage, raw
Coleslaw
Sauerkraut, canned
Broccoli, frozen
Celery, raw
Asparagus, frozen
Cauliflower, frozen
Tomato, raw
Tomato juice, canned
Tomato sauce, canned
Tomatoes, canned
Beans, snap green, frozen
Beans, snap green, canned
Cucumber, raw
Squash, summer, frozen
Pepper, green, raw
Squash, winter, frozen
Carrots, raw
Onion, raw
Vegetables, mixed, canned
Mushrooms, canned
Beets, canned
Radish, raw
Onion rings, frozen
French fries, frozen
Mashed potatoes, instant
Boiled potatoes, w/o peel
Baked potato, w/ peel
Potato chips
Scalloped potatoes
Sweet potato, baked
Sweet potato, candied
Spaghetti , w/ meat sauce
Beef and vegetable stew
Lead
0.04
0.05
0.03
0.02
0.06
0.03
0.06
0.08
0.02
0.05
0.04
0.80
0.05
0.05
0.03
0.13
0.77
0.04
0.02
0.03
0.16
0.26
0.19
0.03
0.14
0.04
0.07
0.02
0.25
0.17
0.03
0.07
0.11
0.03
0.04
0.04
0.11
concentration*
(pg/g)
0.03
0.07
0.09
0.04
0.11
0.02
0.03
0.07
1.65
0.10
0.27
0.39
0.03
0.04
0.31
-
0.23
T
0.02
0.02
0.03
0.05
0.17
0.25
0.11
0.03
0.02
T
0.02
0.04
0.02
0.05
0.04
0.12
T
0.04
0.04
0.02
0.04
0.05
0.02
0.02
0.12
0.06
0.04
0.12
T
0.12
0.23
0.02
0.12
0.02
0.06
0.12
0.08
0.02
0.04
0.02
0.08
Mean
0.017
0.03
0.033
0.037
0.013
0.054
0.027
0.07
0.05
0.017
0.033
0.03
0.86
0.07
0.12
0.01
0.017
0.05
0.43
0.027
0.01
0.013
0.01
0.017
0.072
0.23
0.21
0.02
0.16
0.012
0.023
0.033
0.013
0.017
0.027
0.08
0.21
0.12
0.023
0.033
0.012
0.043
0.013
0.023
0.017
0.023
0.033
0.033
0.10
0.012
7APPB/E
7D-4
7/1/83
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PRELIMINARY DRAFT
TABLE 70-1. (continued)
Category
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
Food
Pizza, frozen
Chi li , beef and beans
Macaroni and cheese
Hamburger sandwich
Meatloaf
Spaghetti in tomato sauce,
canned
Chicken noodle casserole
Lasagne
Potpie, frozen
Pork chow mein
Frozen dinner
Chicken noodle soup, canned
Tomato soup, canned
Vegetable beef soup, canned
Beef bouillon, canned
Gravy mix
White sauce
Pickles
Margarine
Salad dressing
Butter
Vegetable oi 1
Mayonnaise
Cream
Cream substitute
Sugar
Syrup
Jelly
Honey
Catsup
Ice cream
Pudding, instant
Ice cream sandwich
Ice milk
Chocolate cake
Yellow cake
Coffee cake
Doughnuts
Danish pastry
Cookies, choc, chip
Cookies, sandwich type
Apple pie, frozen
Pumpkin pie
Candy, milk chocolate
Candy, caramels
Chocolate powder
Gelatin dessert
Soda pop. cola, canned
Lead c
(
0.06
0.12
0.02
0.06
0.06
0.11
0.04
0.32
0.02
0.07
0.04
0.02
0.05
0.10
0.06
0.03
0.06
0.10
0.07
0.06
0.12
0.03
0.05
0.07
0.13
0.16
0.04
0.02
0.06
0.04
0.03
0.04
0.05
0.09
0.06
0.02
0.03
0.05
0.46
0.06
0.11
0.04
0.32
0.02
0.07
0.04
0.02
0.05
0.10
0.06
0.03
0.02
0.04
0.06
0.03
0.03
0.02
0.02
0.04
0.02
0.02
0.09
0.06
0.06
0. 14
0.03
0.04
0.06
T
0.04
0.04
0.05
0.05
0.06
0.02
0.02
0.04
0.03
0.03
0.03
0.03
0.02
0.04
0.04
0.03
0.02
Means
0.03
0.04
0.06
T
0.04
0.02
0.03
0.02
0.05
0.03
0.04
0.02
0.03
0.09
0.04
O.OB
T
0.033
0.06
0.01
0.013
0.17
0.03
0.02
0.067
0.027
0.13
0.01
0.033
0.035
0.04
0.013
0.013
0.027
0.67
0.043
0.033
0.053
0.01
0.01
0.027
0.05
0.043
0.027
0.023
0.063
0.013
0.027
0.01
0.027
0.043
0.057
0.06
0.04
0.013
0.037
0.033
0.027
0.023
0.033
0.07
0.03
0.06
0.015
0.013
7APPB/E
7D-5
7/1/83
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PRELIMINARY DRAFT
TABLE 7D-1. (continued)
Category Food
192
193
194
195
196
197
198
199
200
201
Soda pop
Soft dri
Soda pop
canned
Coffee,
Coffee,
Tea
lemon-lime, canned
nk powder
, cola, low cal . ,
instant
instant, decaf.
Beer, canned
Wi ne
Whiskey
Water
0.
0.
0.
0.
0.
T
Lead concentration*
(M9/9)
.13
,05
.02
03
02
0.
0.
0.
0.
0.
0.
02 0.02
02
.02
02
.02
03 0.03
Mean
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
06
013
027
01
013
01
17
03
013
012
Individual values for three Market Basket Surveys. "T" means only a trace detected, missing
+value means below detection limit.
Means determined by EPA using 0.01 (% of detection limit) for missing values and
0.015 for "T".
7APPB/E 7D-6 7/1/83
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PRELIMINARY DRAFT
TABLE 7D-2. CONDENSATION, TO 25 CATEGORIES, OF THE
201 CATEGORIES OF FOOD
Table 7-13
category
Categories and fractional categories*
from Pennington (1983) (Table 7D-1)
Milk
Dairy Products
Milk as ingredient
Beef
Pork
Chicken
Fish
Prepared meats
Other meats
Eggs
Bread
Flour as ingredient
Non-wheat cereals
Corn flour
Leafy vegetables
Root vegetables
Vine vegetables
Canned vegetables
Sweet corn
Canned sweet corn
Potatoes
Vegetable oil
Sugar
Canned fruits
Fresh fruits
1-6, 9
7, 10-12, 164, 167, 174, 176, 177
0.5(156), 0.2(178-187)
13-16, 0.1(143), 0.3(145), 0.6(147, 0.4(142, 149)
17-21
24-26
31-34
28-30
22-23, 27
35-37, 0.15(142, 144, 146, 149), 0.2(178-187), 0.3(69, 70)
58, 59, 61, 62, 65, 66, 0.4(147)
159, 160, 0.3(142, 144, 146, 149, 178-187), 0.6(69, 70)
50-52, 64, 75-77
53, 60, 63, 67, 71
107-111, 113-116
127, 128, 132
38, 40-44, 46, 117, 121, 123-126, 161, 173
39, 45, 106, 112, 118-120, 122, 129-131, 0.1(142, 145, 149)
0.2(144), 0.5(155-157)
54
55, 56
134-141
162, 163, 165, 166
169-172, 188, 0.3(178-187)
82, 84, 87, 90, 93
78-81, 83, 85, 86, 88, 89, 91, 92, 94-97
*In some cases, only a fraction of a category, e.g., milk in tomato soup, was used, and this
fraction is indicated by a decimal fraction before the category number in parenthesis.
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7E REFERENCES
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8. EFFECTS OF LEAD ON ECOSYSTEMS
8.1 INTRODUCTION
8.1.1 Scope of Chapter 8
This chapter describes the potential effects of atmospheric lead inputs on several types
of ecosystems. An effect is any condition attributable to lead that causes an abnormal phy-
siological response in individual organisms or that perturbs the normal processes of an eco-
system. A distinction is made among natural, cultivated, and urban ecosystems, and extended
discussions are included on the mobility and bioavailabi1ity of lead in ecosystems.
There are many reports on the effects of lead on individual populations of plants and
animals and a few studies on the effects of lead in simulated ecosystems or microcosms.
However, the most realistic studies are those that examine the effects of lead on entire
ecosystems, as they incorporate all of the ecological interactions among the various popu-
lations and all of the chemical and biochemical processes relating to lead (National Academy
of Sciences, 1981). Unfortunately, these studies have also had to cope with the inherent
variability of natural systems and the confounding frustrations of large scale projects.
Consequently, there are only a handful of ecosystem studies on which to base this report.
The principle sources of lead entering an ecosystem are: the atmosphere (from automotive
emissions), paint chips, spent ammunition, the application of fertilizers and pesticides, and
the careless disposal of lead-acid batteries or other industrial products. Atmospheric lead
is deposited on the surfaces of vegetation as well as on ground and water surfaces. In
terrestrial ecosystems, this lead is transferred to the upper layers of the soil surface,
where it may be retained for a period of several years. The movement of lead within eco-
systems is influenced by the chemical and physical properties of lead and by the biogeo-
chemical properties of the ecosystem. Lead is non-degradable, but in the appropriate chemical
environment, may undergo transformations which affect its solubility (e.g., formation of lead
sulfate in soils), its bioavailability (e.g., chelation with humic substances), or its toxi-
city (e.g., chemical methylation).
The previous Air Quality Criteria for Lead (U.S. Environmental Protection Agency, 1977)
recognized the problems of atmospheric lead exposure incurred by all organisms including man.
Emphasis in the chapter on ecosystem effects was given to reports of toxic effects on specific
groups of organisms, e.g. domestic animals, wildlife, aquatic organisms, and vascular and non-
vascular plants. Forage containing lead at 80 ug/g dry weight was reported to be lethal to
horses, whereas 300 ug/g dry weight caused lethal clinical symptoms in cattle. This report
will attempt to place the data in the context of sublethal effects of lead exposure, to extend
the conclusions to a greater variety of domestic animals, and to describe the types and ranges
of exposures in ecosystems likely to present a problem for domestic animals.
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Research on lead in wildlife has traditionally fallen into the following somewhat arti-
ficial categories: waterfowl; birds and small mammals; fish; and invertebrates. In all these
categories, no correlation could be made in the 1977 report between toxic effects and environ-
mental concentrations. Some recent toxicity studies have been completed on fish and inverte-
brates and the data are reported below, but there is still little information on the levels of
lead that can cause toxic effects in small mammals or birds.
Information on the relationship between soil lead and plants can be expanded somewhat
beyond the 1977 report, primarily due to a better understanding of the role of huntic sub-
stances in binding lead. Although the situation is extremely complex, it is reasonable to
state that most plants cannot survive in soil containing 10,000 ug/g dry weight if the pH is
below 4.5 and the organic content is below 5 percent. The specifics of this statement are
discussed more extensively in Section 8.3.1.2.
Before 1977, natural levels of lead in environmental media other than soil were not well
known. Reports of sublethal effects of lead were sparse and there were few studies of total
ecosystem effects. Although several ecosystem studies have been completed since 1977 and many
problems have been overcome, it is still difficult to translate observed effects under speci-
fic conditions directly to predicted effects in ecosystems. Some of the known effects, which
are documented in detail in the appropriate sections, are summarized here:
Plants. The basic effect of lead on plants is to stunt growth.
This may be through a reduction of photosynthetic rate,
inhibition of respiration, cell elongation, or root deve-
lopment, or premature senescence. Some genetic effects
have been reported. All of these effects have been ob-
served in isolated cells or in hydroponically-grown plants
in solutions comparable to 1 to 2 ug/g soil moisture.
These concentrations are well above those normally found
in any ecosystem except near smelters or roadsides.
Terrestrial plants take up lead from the soil moisture and
most of this lead is retained by the roots. There is no
evidence for foliar uptake of lead and little evidence
that lead can be translocated freely to the upper portions
of the plant. Soil applications of calcium and phosphorus
may reduce the uptake of lead by roots.
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Animals. Lead affects the central nervous system of animals and
their ability to synthesize red blood cells. Blood con-
centrations above 0.4 ppm (40 (jg/dl) can cause observable
clinical symptoms in domestic animals. Calcium and phos-
phorus can reduce the intestinal absorption of lead. The
physiological effects of lead exposures in laboratory
animals are discussed in extensive detail in Chapters 10
and 12 of this document.
Mi croorgani sms.There is evidence that lead at environmental concen-
trations occasionally found near roadsides and smelters
(10,000 to 40,000 |jg/g dw) can eliminate populations of
bacteria and fungi on leaf surfaces and in soil. Many of
those micoorganisms play key roles in the decomposition
food chain. It is likely that the affected microbial
populations are replaced by others of the same or differ-
ent species, perhaps less efficient at decomposing organic
matter. There is also evidence that microorganisms can
mobilize lead by making it more soluble and more readily
taken up by plants. This process occurs when bacteria
exude organic acids that lower the pH in the immediate
vicinity of the plant root.
Ecosystems. There are three known conditions under which lead may
perturb ecosystem processes. At soil concentrations of
1,000 ug/g or higher, delayed decomposition may result
from the elimination of a single population of decomposer
microorganisms. Secondly, at concentrations of 500 to
1,000 ug/g, populations of plants, microorganisms, and
invertebrates may shift toward lead tolerant populations
of the same or different species. Finally, the normal
biogeochemical process which purifies and repurifies
calcium in grazing and decomposer food chains may be
circumvented by the addition of lead to vegetation and
animal surfaces. This third effect can be measured at all
ambient atmospheric concentrations of lead.
Some additional effects may occur due to the uneven dis-
tribution of lead in ecosystems. It is known that lead
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accumulates in soil, especially soil with high organic
content. Although no firm documentation exists, it is
reasonable to assume from the known chemistry of lead in
soil that: 1) other metals may be displaced from the
binding sites on the organic matter; 2) the chemical
breakdown of inorganic soil fragments may be retarded by
the interference of lead on the action of fulvic acid on
iron bearing crystals; and 3) lead in soil may be in
equilibrium with moisture films surrounding soil particles
and thus available for uptake by plants.
To aid the reader in understanding the effects of lead on ecosystems, sections have been
included that discuss such important matters as how ecosystems are organized, what processes
regulate metal cycles, what criteria are valid in interpreting ecosystem effects, and how soil
systems function to regulate the controlled release of nutrients to plants. The informed
reader may wish to turn directly to Section 8.3, where the discussion of the effects of lead
on organisms begins.
8.1.2 Ecosystem Functions
8.1.2.1 Types of Ecosystems. Based on ambient concentrations of atmospheric lead and the dis-
tribution of lead in the soil profile, it is useful to distinguish among three types of eco-
systems: natural, cultivated, and urban. Natural ecosystems include aquatic and terrestrial
ecosystems that are otherwise unperturbed by man, and those managed ecosystems, such as com-
mercial forests, grazing areas, and abandoned fields, where the soil profile has remained un-
disturbed for several decades. Cultivated ecosystems include those where the soil profile is
frequently disturbed and those where chemical fertilizers, weed killers, and pest-control
agents may be added. In urban ecosystems, a significant part of the exposed surface includes
rooftops, roadways, and parking lots from which runoff, if not channeled into municipal waste
processing plants, is spread over relatively small areas of soil surface. The ambient air
concentration of lead in urban ecosystems is 5 to 10 times higher than in natural or culti-
vated ecosystems (See Chapter 7). Urban ecosystems may also be exposed to lead from other
than atmospheric sources, such as paint, discarded batteries, and used motor oil. The effects
of atmospheric lead depend on the type of ecosystems examined.
8.1.2.2 Energy Flow and Biogeochemical Cycles. Two principles govern ecosystem functions:
1) energy flows through an ecosystem; and 2) nutrients cycle within an ecosystem. Energy
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usually enters the ecosystem in the form of sunlight and leaves as heat of respiration.
Stored chemical energy may be transported into or out of an ecosystem (e.g., leaf detritus in
a stream) or be retained by the ecosystem for long periods of time (e.g., tree trunks).
Energy flow through an ecosystem may give structure to the ecosystem by establishing food webs
which efficiently regulate the transfer of energy. Segments of these food webs are called
food chains. Energy that flows along a grazing food chain is diverted at each step to the
detrital food chain.
Unlike energy, nutrient and non-nutrient elements are recycled by the ecosystem and
transferred from reservoir to reservoir in a pattern usually referred to as a biogeochemical
cycle (Brewer, 1979, p. 139). The reservoirs correspond approximately to the food webs of
energy flow. Although elements may enter (e.g., weathering of soil) or leave the ecosystem
(e.g., stream runoff), the greater fraction of the available mass of the element is usually
cycled within the ecosystem.
Two important characteristics of a reservoir are the amount of the element that may be
stored in the reservoir and the rate at which the element enters or leaves the reservoir.
Some reservoirs may contain a disproportionately large amount of a given element. For exam-
ple, most of the carbon in a forest is bound in the trunks and roots of trees, whereas most of
the calcium may be found in the soil (Smith, 1980, p. 316). Some large storage reservoirs,
such as soil, are not actively involved in the rapid exchange of the nutrient element, but
serve as a reserve source of the element through the slow exchange with a more active reser-
voir, such as soil moisture. When inputs exceed outputs, the size of the reservoir increases.
Increases of a single element may reflect instability of the ecosystem. If several elements
increase simultaneously, this expansion may reflect stable growth of the community.
Reservoirs are connected by pathways which represent real ecosystem processes. Figure
8-1 depicts the biogeochemical reservoirs and pathways of a typical terrestrial ecosystem.
Most elements, especially those with no gaseous phase, do not undergo changes in oxidation
state and are equally available for exchange between any two reservoirs, provided a pathway
exists between the two reservoirs. The chemical environment of the reservoir may, however,
regulate the availability of an element by controlling solubility or binding strengths. This
condition is especially true for soils.
Ecosystems have boundaries. These boundaries may be as distinct as the border of a pond
or as arbitrary as an imaginary circle drawn on a map. Many trace metal studies are conducted
in watersheds where some of the boundaries are determined by topography. For atmospheric
inputs to terrestrial ecosystems, the boundary is usually defined as the surface of vegeta-
tion, exposed rock, or soil. The water surface suffices for aquatic ecosystems.
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GRAZERS
PRIMARY
PRODUCERS
INORGANIC
NUTRIENTS
Figure 8-1. This figure depicts cycling processes within the major components of a
terrestrial ecosystem, i.e. primary producers, grazers and decomposers. Nutrient and
non-nutrient elements are stored in reservoirs within these components. Processes
that take place within reservoirs regulate the flow of elements between reservoirs
along established pathways. The rate of flow is in part a function of the concentra-
tion in the preceding reservoir. Lead accumulates in decomposer reservoirs which
have a high binding capacity for this metal. It is likely that the rate of flow away
from these reservoirs has increased in past decades and will continue to increase for
some time until the decomposer reservoirs are in equilibrium with the entire
ecosystem. Inputs to and outputs from the ecosystem as a whole are not shown.
Source: Adapted from Swift et al. (1979).
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Non-nutrient elements differ little from nutrient elements in their biogeochemical cy-
cles. Quite often, the cycling patterns are similar to those of a major nutrient. In the
case of lead, the reservoirs and pathways are very similar to those of calcium.
The important questions are: Does atmospheric lead interfere with the normal mechanisms
of nutrient cycles? How does atmospheric lead influence the normal lead cycle in an eco-
system? Can atmospheric lead interfere with the normal flow of energy through an ecosystem?
8.1.2.3 Biogeochemistry of Lead. Naturally occurring lead from the earth's crust is commonly
found in soils and the atmosphere. Lead may enter an ecosystem by weathering of parent rock
or by deposition of atmospheric particles. This lead becomes a part of the nutrient medium of
plants and the diet of animals. All ecosystems receive lead from the atmosphere. More than
99 percent of the current atmospheric lead deposition is now due to human activities (National
Academy of Sciences, 1980). In addition, lead shot from ammunition may be found in many
waterways and popular hunting regions, leaded paint chips often occur in older urban regions
and lead in fertilizer may contaminate the soil in agricultured regions.
In prehistoric times, the contribution of lead from weathering of soil was probably about
4 g Pb/ha-yr and from atmospheric deposition about 0.02 g Pb/ha-yr, based on estimates of
natural and anthropogenic emissions in Chapter 5 and deposition rates discussed in Chapter 6.
Weathering rates are presumed to have remained the same, but atmospheric inputs are believed
to have increased to 180 g/ha-yr in natural and some cultivated ecosystems, and 3,000 g/ha-yr
in urban ecosystems and along roadways (see Chapter 6). In every terrestrial ecosystem of the
Northern Hemisphere, atmospheric lead deposition now exceeds weathering by a factor of at
least 10, sometimes by as much as 1,000.
Many of the effects of lead on plants, microorganisms, and ecosystems arise from the fact
that lead from atmospheric and weathering inputs is retained by soil. Geochemical studies
show that less than 3 percent of the inputs to a watershed leave by stream runoff (Siccama and
Smith, 1978; Shirahata et al., 1980). In prehistoric times, stream output nearly equalled
weathering inputs and the lead content of soil probably remained stable, accumulating at an
annual rate of less than 0.1 percent of the original natural lead (reviewed by Nriagu, 1978).
Due to human activity, lead in natural soils now accumulates on the surface at an annual rate
of 5 to 10 percent of the natural lead. One effect of cultivation is that atmospheric lead is
mixed to a greater depth than the 0 to 3 cm of natural soils.
Most of the effects on grazing vertebrates stem from the deposition of atmospheric parti-
cles on vegetation surfaces. Atmospheric deposition may occur by either of two mechanisms.
Wet deposition (precipitation scavenging through rainout or washout) generally transfers lead
directly to the soil. Dry deposition transfers particles to all exposed surfaces. Large
particles (>4 urn) are transferred by gravitational mechanisms, small particles (<0.5 pm) are
also deposited by wind-related mechanisms.
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About half of the foliar dry deposition remains on leaf surfaces following normal rain-
fall (Elias et al., 1976; Peterson, 1978), but heavy rainfall may transfer the lead to other
portions of the plant (Elias and Croxdale, 1980). Koeppe (1981) has reviewed the literature
and concluded that less than 1 percent of the surface lead can pass directly into the internal
leaf tissues of higher plants. The cuticular layer of the leaves is an effective barrier to
aerosol particles and even to metals in solution on the leaf surface (Arvik and Zimdahl,
1974), and passage through the stomata cannot account for a significant fraction of the lead
inside leaves (Carlson et al., 1976; 1977).
When particles attach to vegetation surfaces, transfer to soil is delayed from a few
months to several years. Due to this delay, large amounts of lead are diverted to grazing
food chains, bypassing the soil moisture and plant root reservoirs (Elias et al., 1982).
8.1.3 Criteria for Evaluating Ecosystem Effects
As it is the purpose of this chapter to describe the levels of atmospheric lead that may
produce adverse effects in plants, animals, and ecosystems, it is necessary to establish the
criteria for evaluating these effects. The first step is to determine the connection between
air concentration and ecosystem exposure. If the air concentration is known, ecosystem inputs
from the atmosphere can be predicted over time and under normal conditions. These inputs and
those from the weathering of soil determine the concentration of lead in the nutrient media of
plants, animals, and microorganisms. It follows that the concentration of lead in the nutri-
ent medium determines the concentration of lead in the organism and this in turn determines
the effects of lead on the organism.
The fundamental nutrient medium of a terrestrial ecosystem is the soil moisture film
which surrounds organic and inorganic soil particles. This film of water is in equilibrium
with other soil components and provides dissolved inorganic nutrients to plants. It is chemi-
cally different than ground water or rain water and there is little reliable information on
the relationship between lead in soil and lead in soil moisture. Thus, it appears impossible
to quantify all the steps by which atmospheric lead is transferred to plants. Until more
information is available on lead in soil moisture, another approach may be more productive.
This involves determining the degree of contamination of organisms by comparing the present
known concentrations with calculated prehistoric concentrations.
Prehistoric concentrations of lead have been calculated for only a few types of organ-
isms. However, the results are so low that any normal variation, even of an order of magni-
tude, would not seriously alter the degree of contamination. The link between lead in the
prehistoric atmosphere and in prehistoric organisms may allow us to predict concentrations of
lead in organisms based on present or future concentrations of atmospheric lead.
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It is reasonable to infer a relationship between degree of contamination and physio-
logical effect. It seems appropriate to assume that natural levels of lead which were safe
for organisms in prehistoric times would also be safe today. It is also reasonable that some
additional atmospheric lead can be tolerated by all populations of organisms with no ill
effects, that some populations are more tolerant than others, and that some individuals within
populations are more tolerant of lead effects than others.
For nutrient elements, the concept of tolerance is not new. The Law of Tolerance
(illustrated in Figure 8-2) states that any nutrient may be present at concentrations either
too low or too high for a given population and that the ecological success of a population is
greatest at some optimum concentration of the nutrient (Smith, 1980, p. 35). In a similar
manner, the principle applies to non-nutrient elements. Although there is no minimum concen-
tration below which the population cannot survive, there is a concentration above which the
success of the population will decline (point of initial response) and a concentration at
which the entire population will die (point of absolute toxicity). In this respect, both
nutrients and non-nutrients behave in a similar manner at concentrations above some optimum.
Certain variables make the points of initial response and absolute toxicity somewhat
imprecise. The point of initial response depends on the type of response investigated. This
response may be at the molecular, tissue, or organismic level, with the molecular response
occurring at the lowest concentration. Similarly, at the point of absolute toxicity, death
may occur instantly at high concentrations or over a prolonged period of time at somewhat
lower concentrations. Nevertheless, the gradient between these two points remains an appro-
priate basis on which to evaluate known environmental effects, and any information which
correctly positions this part of the tolerance curve will be of great value.
The normal parameters of a tolerance curve, i.e., concentration and ecological success,
can be replaced by degree of contamination and percent physiological dysfunction, respectively
(Figure 8-3). Use of this method of expressing degree of contamination should not imply that
natural levels are the only safe levels. It is likely that some degree of contamination can
be tolerated with no physiological effect.
Data reported by the National Academy of Sciences (1980) are used to determine the typi-
cal natural lead concentrations shown in various compartments of ecosystems in Table 8-1.
These data are from a variety of sources and are simplified to the most probable value within
the range reported by NAS. The actual prehistoric air concentration was probably near the low
end of the range (0.02-1.0 ng/m3), as present atmospheric concentrations of 0.3 ng/m3 in the
Southern Hemisphere and 0.07 ng/m3 at the South Pole (Chapter 5), would seem to preclude natu-
ral lead values higher than this.
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MAXIMUM
NON NUTRIENT
INITIAL
RESPONSE
g
u>
o
a
3
o
o
/
/
/ NUTRIENT
/
/
LOW
HIGH
CONCENTRATION OF ELEMENT
Rgure 8-2. The ecological success of a population depends in part on the availability
of all nutrients at some optimum concentration. The dashed line of this diagram
depicts the rise and decline of ecological success (the ability of a population to grow.
survive and reproduce) over a wide concentration range of a single element. The
curve need not be symmetrically bell-shaped, but may be skewed to the right or left.
Although the range in concentration that permits maximum success may be much
wider than shown here, the important point is that at some high concentration, the
nutrient element becomes toxic. The tolerance of populations for high concentrations
of non-nutrients (solid line) is similar to that of nutrients, although there is not yet
any scientific basis for describing the exact shape of this portion of the curve.
Source: Adapted from Smith (1980).
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g
5
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PRELIMINARY DRAFT
In prehistoric times, the rate of entry of lead into the nutrient pool available to
plants was predominantly determined by the rate of weathering of inorganic minerals in frag-
ments of parent rock material. Geochemical estimates of denudation and adsorption rates
(Chapter 6) suggest a median value of 12 M9/9 as the average natural lead content of total
soil, with the concentration in the organic fraction at approximately 1 ug/g.
Studies have shown the lead content of leafy vegetation to be 90 percent anthropogenic,
even in remote areas (Crump and Barlow, 1980; Elias et al., 1976, 1978). The natural lead
content of nuts and fruits may be somewhat higher than leafy vegetation, based on internal
lead concentrations of modern samples (Elias et al., 1982). The natural lead concentrations
of herbivore and carnivore bones were reported by Elias et al. (Elias and Patterson, 1980;
Elias et al. , 1982). These estimates are based on predicted Pb/Ca ratios calculated from the
observed biopurification of calcium reservoirs with respect to Sr, Ba, and Pb, on the system-
atic evaluation of anthropogenic lead inputs to the food chain (Section 8.5.3), and on
measurements of prehistoric mammalian bones.
8.2 LEAD IN SOILS AND SEDIMENTS
8.2.1 Distribution of Lead in Soils
Because lead in soil is the source of most effects on plants, microorganisms, and eco-
systems, it is important to understand the processes that control the accumulation of lead in
soil. The major components of soil are: 1) fragments of inorganic parent rock material;
2) secondary inorganic minerals; 3) organic constituents, primarily humic substances, which
are residues of decomposition or products of decomposer organisms; 4) Fe-Mn oxide films, which
coat the surfaces of all soil particles and appear to have a high binding capacity for metals;
5) soil microorganisms, most commonly bacteria and fungi, although protozoa and soil algae may
also be found; and 6) soil moisture, the thin film of water surrounding soil particles which
is the nutrient medium of plants. Some watershed studies consider that fragments of inorganic
parent rock material lie outside the forest ecosystem, because transfer from this compartment
is so slow that much of the material remains inert for centuries.
The concentration of lead ranges from 5 to 30 ug/g in the top 5 cm of most soils not
adjacent to sources of industrial lead, although 5 percent of the soils contain as much as
800 ug/g (Chapter 5). Aside from surface deposition of atmospheric particles, plants in North
America average about 0.5 to 1 ug/g dw (Peterson, 1978) and animals roughly 2 ug/g (Forbes and
Sanderson, 1978). Thus, soils contain the greater part of total ecosystem lead. In soils,
lead in parent rock fragments is tightly bound within the crystalline structures of the
inorganic soil minerals. It is released to the ecosystem only by surface contact with soil
moisture films.
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Hutchinson (1980) has reviewed the effects of acid precipitation on the ability of soils
to retain cations. Excess calcium and other metals are leached from the A horizon of soils by
rain with a pH more acidic than 4.5. Most soils in the eastern United States are normally
acidic (pH 3.5 to 5.2) and the leaching process is a part of the complex equilibrium main-
tained in the soil system. By increasing the leaching rate, acid rain can reduce the availa-
bility of nutrient metals to organisms dependent on the top layer of soil. Tyler (1978)
reports the effect of acid rain on the leaching rate (reported as residence time) for lead and
other metals. Simulated rain of pH 4.2 to 2.8 showed the leaching rate for lead increases
with decreasing pH, but not nearly as much as that of other metals, especially Cu, Mn, and In.
This would be as expected from the high stability constant of lead relative to other metals in
humic acids (see Section 6.5.1). It appears from this limited information that acidification
of soil may increase the rate of removal of lead from the soil, but not before several major
nutrients are removed first. The effect of acid rain on the retention of lead by soil mois-
ture is not known.
8.2.2 Origin and Availability of Lead in Aquatic Sediments
Atmospheric lead may enter aquatic ecosystems by wet or dry deposition (Dolske and
Sievering, 1979) or by the erosional transport of soil particles (Baier and Healy, 1977). In
waters not polluted by industrial, agricultural, or municipal effluents, the lead concentra-
tion is usually less than 1 ug/1. Of this amount, approximately 0.02 ug/1 is natural lead and
the rest is anthropogenic lead, probably of atmospheric origin (Patterson, 1980). Surface
waters mixed with urban effluents may frequently reach lead concentrations of 50 ug/1, and
occasionally higher (Bradford, 1977).
In aqueous solution, virtually all lead is divalent, as tetravalent lead can exist only
under extremely oxidizing conditions (reviewed by Rickard and Nriagu, 1978; Chapter 3). At pH
higher than 5, divalent lead can form a number of hydroxyl complexes, most commonly PbOH ,
Pb(OH)2, and Pb(OH)3 . At pH lower than 5, lead exists in solution as hydrated Pb. In still
water, lead is removed from the water column by the settling of lead-containing particulate
matter, by the formation of insoluble complexes, or by the adsorption of lead onto suspended
organic particles. The rate of sedimentation is determined by temperature, pH, oxidation-
reduction potential, ionic competition, the chemical form of lead in water, and certain bio-
logical activities (Jenne and Luoma, 1977). McNurney et al. (1977) found 14 ug Pb/g in stream
sediments draining cultivated areas and 400 ug/g in sediments associated with urban eco-
systems. Small sediment grain size and high organic content contributed to increased reten-
tion in sediments.
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8.3 EFFECTS OF LEAD ON PLANTS
8.3.1 Effects on Vascular Plants and Algae
Some physiological and biochemical effects of lead on vascular plants have been detected
under laboratory conditions at concentrations higher than normally found in the environment.
The commonly reported effects are the inhibition of photosynthesis, respiration or cell
elongation, all of which reduce the growth of the plant (Koeppe, 1981). Lead may also induce
premature senescence, which may affect the long-term survival of the plant or the ecological
success of the plant population. To provide a meaningful evaluation of these effects, it is
necessary to examine the correlation between laboratory conditions and typical conditions in
nature with respect to form, concentration, and availability of lead. First, the reader must
understand what is known of the movement of lead from soil to the root to the stem and finally
to the leaf or flower. Most notably, there are specific barriers to lead at the soil: sol]
moisture interface and at the root: shoot interface which retard the movement of lead and
reduce the impact of lead on photosynthetic and meristematic (growth and reproduction) tissue.
8.3.1.1 Uptake by Plants. Most of the lead in or on a plant occurs on the surfaces of leaves
and the trunk or stem. The surface concentration of lead in trees, shrubs, and grasses
exceeds the internal concentration by a factor of at least five (Elias et al, 1978). There is
little or no evidence of lead uptake through leaves or bark. Foliar uptake, if it does occur,
cannot account for more than 1 percent of the uptake by roots, and passage of lead through
bark tissue has not been detected (Arvik and Zimdahl, 1974; reviewed by Koeppe, 1981; Zimdahl,
1976). Krause and Kaiser (1977) were able to show foliar uptake and translocation of lead
mixed with cadmium, copper, and manganese oxides when applied in large amounts (122 mg/m2)
directly to leaves. This would be comparable to 100,000 days accumulation at a remote site
(0.12 ng/cm2-d) (Elias et al., 1978). The uptake of lead was less than that of other metals
and application of sulfur dioxide did not increase the foilar uptake of these metals. The
major effect of surface lead at ambient concentrations seems to be on subsequent components of
the grazing food chain (Section 8.4.1) and on the decomposer food chain following litterfall
(Elias et al. , 1982). (See also Section 8.4.2.)
Uptake by roots is the only major pathway for lead into plants. The amount of lead that
enters plants by this route is determined by the availability of lead in soil, with apparent
variations according to plant species. Soil cation exchange capacity, a major factor, is
determined by the relative size of the clay and organic fractions, soil pH, and the amount of
Fe-Mn oxide films present (Nriagu, 1978). Of these, organic humus and high soil pH are the
dominant factors in immobilizing lead (Chapter 6). Under natural conditions, most of the
total lead in soil would be tightly bound within the crystalline structure of inorganic soil
fragments, unavailable to soil moisture. Available lead, bound on clays, organic colloids,
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PRELIMINARY DRAFT
and Fe-Mn films, would be controlled by the slow release of bound lead from inorganic rock
sources. Since before 3000 B.C., atmospheric lead inputs through litter decomposition have
increased the pool of available lead bound on organic matter within the soil reservoir (see
Section 5.1).
Because lead is strongly immobilized by humic substances, only a small fraction (perhaps
0.01 percent in soils with 20 percent organic matter, pH 5.5) is released to soil moisture
(see Chapter 6). In soil moisture, lead may pass along the pathway of water and nutrient
uptake on either a cellular route through the cell membranes of root hairs (symplastic route)
or an extracellular route between epidermal cells into the intercellular spaces of the root
cortex (apoplastic route) (Foy et al. , 1978). Lead probably passes into the symplast by mem-
brane transport mechanisms similar to the uptake of calcium or other bivalent cations.
At 500 ug Pb/g nutrient solution, lead has been shown to accumulate in the cell walls of
germinating Raphinus sativus roots (Lane and Martin, 1982). This concentration is much higher
than that found by Wong and Bradshaw (1982) to cause inhibition of germinating root elongation
(less than 2.5 ug/g), absence of root growth (5 MQ/Q), or 55 percent inhibition of seed ger-
mination (20 to 40 pg/g) in the rye grass, Col ium perenne. Lane and Martin (1982) also ,
observed lead in cytoplasmic organelles which appeared to have a storage function because of
their osmiophillic properties. It was suggested that the organelles eventually emptied their
contents into the tonoplast.
The accumulation of lead in cell walls and cytoplasmic bodies has also been observed in
blue green algae by Jensen et al. (1982), who used X-ray energy dispersive analysis in con-
junction with scanning electron microscopy to observe high concentrations of lead and other
metals in these single celled procaryotic organisms. They found the lead concentrated in the
third of the four layered cell wall and in polyphosphate bodies (not organelles, since they
are not membrane-bound) which appeared to be a storage site for essential metals. The nutri-
ent solution contained 100 ug Pb/g. The same group (Rachlin et al., 1982) reported morpholo-
gical changes in the same blue green alga (Plectonema boryanum). There was a significant
increase in cell size caused by the lead, which indicated that the cell was able to detoxify
its cytoplasm by excreting lead with innocuous cell wall material.
It appears that two defensive mechanisms may exist in the roots of plants for removing
lead from the stream of nutrients flowing to the above ground portions of plants. Lead may be
deposited with cell wall material exterior to the individual root cells, or may be sequestered
in organdies within the root cells. Any lead not captured by these mechanisms would likely
move with nutrient metals cell-to-cell through the symplast and into the vascular system.
Uptake of lead by plants may be enhanced by symbiotic associations with mycorrhizal fungi
The three primary factors that control the uptake of nutrients by plants are the surface area
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PRELIMINARY DRAFT
of the roots, the ability of the root to absorb particular ions, and the transfer of ions
through the soil. The symbiotic relationship between mycorrhizal fungi and the roots of
higher plants can increase the uptake of nutrients by enhancing all three of these factors
(Voigt, 1969). The typical ectomycorrhiza consists of a mantle or sheath of mycelia that com-
pletely surrounds the root. The physical extension of the sheath may increase the volume of
the root two to three times (Voigt, 1969). Mycorrhizal roots often show greater affinities
for nutrients than do uninfected roots of the same species grown in the same conditions. In
many soil systems, where the bulk of the nutrients are bound up in parent rock material, effi-
cient uptake of these nutrients by plants depends on the ability of organisms in the rhizo-
sphere (plant roots, soil fungi, and bacteria) to increase Lhe rates of weathering. Mycorrhi-
zal fungi are known to produce and secrete into their environment many different acidic com-
pounds (e.g., malic and oxalic acids). In addition, mycorrhizal roots have been shown to
release more carbon dioxide into the rhizosphere than do non-mycorrhizal roots as a result of
their increased rates of respiration. Carbon dioxide readily combines with soil moisture to
produce carbonic acid. All of these acids are capable of increasing the weathering rates of
soil particles such as clays, and altering the binding capacity of organic material, thereby
increasing the amount of nutrients in the soil solution. Mycorrhizae are known to enhance the
uptake of zinc by pine roots (Bowen et al. , 1974), and it is likely that lead uptake is simi-
larly increased, by inference to the ability of mycorrhizae to enhance the uptake of calcium
by pine roots (Melin and Nilsson, 1955; Melin et al., 1958).
The translocation of lead to aboveground portions of the plant is not clearly understood.
Lead may follow the same pathway and be subject to the same controls as a nutrient metal such
as calcium. This assumption implies that the plant root has no means of discriminating
against lead during the uptake process, and it is not known that any such discrimination
mechanism exists. There may be several mechanisms, however, that excrete lead back out of the
root or that prevent its translocation to other plant parts. The primary mechanisms may be
storage in cell organelles or adsorption on cell walls. The apoplast contains an important
supply of plant nutrients, including water. Lead in the apoplast remains external to the
cells and cannot pass to vascular tissue without at least passing through the cell membranes
of the endodermis. Because this extracellular region is bounded on all sides by cell walls,
the surface of which is composed of layers of cellulose strands, the surface area of the
apoplast is comparable to a sponge. It is likely that much of the lead in roots is adsorbed
to the apoplast surface. Dictyosomes, cytoplasmic organelles which contain cell wall
material, may carry lead from inside the cell through the membrane to become a part of the
external cell wall (Malone et al., 1974), possibly replacing calcium in calcium pectate. Lead
may also be stored and excreted as lead phosphate in dictyosome vesicles (Malone et al.,
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PRELIMINARY DRAM
1974). Nevertheless, some lead does pass into the vascular tissue, along with water and
dissolved nutrients, and is carried to physiologically active tissue of the plant.
Evidence that lead in contaminated soils can enter the vascular system of plants and be
transported to aboveground parts may be found in the analysis of tree rings. Rolfe (1974)
found four-fold increases in both rural and urban trees using 10 year increments of annual
rings for the period 1910-20 and comparing these to annual rings of the period 1963-73.
Symeonides (1979) found a two-fold increase from 1907-17 to 1967-77 in trees at a high-lead
site, with no increase in trees from a low-lead site. Finally, Baes and Ragsdale (1981),
using only ring porous species, found significant, post-1930 increases in Quercus and Carya
with high lead exposure, but only in Carya with low lead exposure. These chronological
records confirm that lead can be translocated from roots to the upper portions of the plant
and that the amounts translocated are in proportion to the concentrations of lead in soil.
8.3.1.2 Physiological Effects on Plants. Because most of the physiologically active tissue of
plants is involved in growth, maintenance, and photosynthesis, it is expected that lead might
interfere with one or more of these processes. Indeed, such interferences have been observed
in laboratory experiments at lead concentrations greater than those normally found in the
field, except near smelters or mines (Koeppe, 1981). It is likely that more is known of these
effects because these are the physiological processes studied more vigorously than others.
Studies of other plant processes, especially maintenance, flowering, and hormone development,
have not been conducted and no conclusion can be reached concerning possible lead effects on
these processes.
Inhibition of photosynthesis by lead may be by direct interference with the light reac-
tion or the indirect interference with carbohydrate synthesis. At 21 pg Pb/g reaction solu-
tion, Miles et al. (1972) demonstrated substantial inhibition of photosystem II near the site
of water splitting, a biochemical process believed to require manganese. Homer et al. (1979)
found a second effect on photosystem II at slightly higher concentrations of lead. This
effect was similar to that of DCMU [3-(3,4-dichlorophenyl)-l,l-dimethylurea], a reagent com-
monly used to uncouple the photosynthetic electron transport system. Bazzaz and Govindjee
(1974) suggested that the mechanism of lead inhibition was a change in the conformation of the
thylakoid membranes, separating and isolating pigment systems I and II. Wong and Govindjee
(1976) found that lead also interferes with P700 photooxidation and re-reduction, a part of
the photosystem I light reaction. Homer et al. (1981) found a lead tolerant population oi tne
grass Phalaris arundinacea had lowered the ratio of chlorophyll a/chlorophyll b, believed to
be a compensation for photosystem II inhibition. There was no change in the total amount of
chlorophyll, but the mechanism of inhibition was considered different than that of Miles et
al. (1972). Hampp and Lendzian (1974) found that lead chloride inhibits the synthesis of
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chlorophyll b more than that of chlorophyll a at concentrations up to 100 mg Pb/g. Devi
Prasad and Devi Prasad (1982) found 10 percent inhibition of pigment production in three spe-
cies of green algae at 1 pg/g, increasing to 50 percent inhibition at 3 pg/g. Bazzaz et al.
(1974, 1975) observed reduced net photosynthesis which may have been caused indirectly by
inhibition of carbohydrate synthesis. Without carbohydrates, stomatal guard cells remain
flaccid, transpiration ceases, carbon dioxide fixation decreases, and further carbohydrate
synthesis is inhibited.
The stunting of plant growth may be by the inhibition of the growth hormone IAA (indole-
3-ylacetic acid). Lane et al. (1978) found a 25 percent reduction in elongation at 10 |jg/g
lead as lead nitrate in the nutrient medium of wheat coleoptiles. This effect could be re-
versed with the addition of calcium at 18 ug/g. Lead may also interfere with plant growth by
reducing respiration or inhibiting cell division. Miller and Koeppe (1970) and Miller et al.
(1975) showed succinate oxidation inhibition in isolated mitochondria as well as stimulation
of exogenous NADH oxidation with related mitochondrial swelling. Hassett et al. (1976),
Koeppe (1977), and Malone et al. (1978) described significant inhibition of lateral root
initiation in corn. Inhibition increased with the simultaneous addition of cadmium.
Sung and Yang (1979) found that lead at 1 pg/g can complex with and inactivate ATPase to
reduce the production and utilization of ATP in kidney bean (Phaseolus vulgaris) and buckwheat
leaves (Fagopyrum esculentum). The lead was added hydroponically at concentrations up to
1,000 pg/g. Kidney bean ATPase showed a continued response from 1 to 1,000 pg/g, but buck-
wheat leaves showed little further reduction after 10 M9/9- Neither extracted ATP nor chemi-
cally added ATP could be used by the treated plants. Lee et al. (1976) found a 50 percent
increase in the activity of several enzymes related to the onset of senescence in soybean
leaves when lead was added hydroponically at 20 pg/g. These enzymes were acid phosphatase,
peroxidase, and alpha-amylase. A build-up of ammonia was observed along with a reduction in
nitrate, calcium, and phosphorus. Glutamine synthetase activity was also reduced by 65 per-
cent. Continued increases in effects were observed up to 100 pg/g, including a build-up of
soluble protein. Paivoke (1979) also observed a 60 percent increase in acid phosphatase acti-
vity during the first 6 days of pea seedling germination (Pisum sativum) at 2 pg/g, under low
nutrient conditions. The accumulation of soluble protein was observed and the effect could be
reversed with the addition of nutrients, including calcium.
The interaction of lead with calcium has been shown by several authors, most recently by
Garland and Wilkins (1981), who demonstrated that barley seedlings (Hordeum vulgare), which
were growth inhibited at 2 pg Pb/g sol. with no added calcium, grew at about half the control
rate with 17 pg Ca/g sol. This relation persisted up to 25 pg Pb/g sol. and 500 pg Ca/g sol.
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These studies of the physiological effects of lead on plants all show some effect at
concentrations from 2 to 10 (jg/g in the nutrient medium of hydroponically-grown agricultural
plants. It is certain that no effects would have been observed at these concentrations had
the lead solutions been added to normal soil, where the lead would have been bound by humic
substances. There is no firm relationship between soil lead and soil moisture lead, because
each soil type has a unique capacity to retain lead and to release that lead to the soil
moisture film surrounding the soil particle. Once in soil moisture, lead seems to pass freely
to the plant root according to the capacity of the plant root to absorb water and dissolved
substances (Koeppe, 1981).
Chapter 6 discusses the many parameters controlling the release of lead from soil to soil
moisture, but so few data are available on observed lead concentrations in soil moisture that
no model can be formed. It seems reasonable that there may be a direct correlation between
lead in hydroponic media and lead in soil moisture. Hydroponic media typically have an excess
of essential nutrients, including calcium and phosphorus, so that movement of lead from hydro-
ponic media to plant root would be equal to or slower than movement from soil moisture to
plant root. Hughes (1981) adopted the general conclusion that extractable soil lead is typi-
cally 10 percent of total soil lead. However, this lead was extracted chemically under lab-
oratory conditions more rigorous than the natural equilibrium between soil and soil moisture.
Ten percent should therefore be considered the upper limit, where the ability of soil to
retain lead is at a minimum. A lower limit of 0.01 percent is based on the only known report
of lead in both soil and soil moisture (16 ug/g soil, 1.4 pg/g soil moisture; Elias et al. ,
1982). This single value shows neither trends with different soil concentrations nor the soil
component (organic or inorganic) that provides the lead to the soil moisture. But the number
(0.01 percent) is a conservative estimate of the ability of soil to retain lead, since the
conditions (pH, organic content) were optimum for retaining lead. A further complication is
that atmospheric lead is retained at the surface (0-2 cm) of the soil profile (Martin and
Coughtrey, 1981), whereas most reports of lead in soil pertain to samples from 0 to 10 cm as
the "upper" layer of soil. Any plant that absorbs solely from the top few centimeters of soil
obviously is exposed to more lead than one with roots penetrating to a depth of 25 cm or more.
Agricultural practices that cultivate soil to a depth of 25 cm blend in the upper layers with
lower to create a soil with average lead content somewhat above background.
These observations lead to the general conclusion that even under the best of conditions
where soil has the highest capacity to retain lead, most plants would experience reduced
growth rate (inhibition of photosynthesis, respiration, or cell elongation) in soils of 10,000
ug Pb/g or greater. Concentrations approaching this value typically occur around smelters
(Martin and Coughtrey, 1981) and near major highways (Wheeler and Rolfe, 1979). These con-
PB8A/B 8-19 7/13/83
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PRELIMINARY DRAFT
elusions pertain to soil with the ideal composition and pH to retain the maximum amount of
lead. Acid soils or soils lacking organic matter would inhibit plants at much lower lead
concentrations.
The rate at which atmospheric lead accumulates in soil varies from 1.1 mg/m2-yr average
global deposition (Table 6-7) to 3,000 rng/m2-yr near a smelter (Patterson et al. , 1975).
Assuming an average density of 1.5 g/cm3, undisturbed soil to a depth of 2 cm (20,000 cmVm2)
would incur an increase in lead concentration at a rate of 0.04 to 100 ug/g soil-yr. This
means remote or rural area soils may never reach the 10,000 ug/g threshold but that undis-
turbed soils closer to major sources may be within range in the next 50 years.
8.3.1.3 Lead Tolerance in Vascular Plants. Some plant species have developed populations
tolerant to high lead soils (Antonovics et al., 1971). In addition to Homer et al. (1981)
cited above, Jowett (1964) found populations of Agrostis tenuis in pure stands on acidic spoil
banks near an abandoned mine. The exclusion of other species was attributed to root inhibi-
tion. Populations of A. tenuis from low-lead soils had no tolerance for the high lead soils.
Several other studies suggest that similar responses may occur in populations growing in
lead-rich soils (reviewed in Peterson, 1978). A few have suggested that crops may be culti-
vated for their resistance to high lead soils (Gerakis et al., 1980; John, 1977).
Using populations taken from mine waste and uncontaminated control areas, some authors
have quantified the degree of tolerance of Agrostis tenuis (Karataglis, 1982) and Festuca
rubra (Wong, 1982) under controlled laboratory conditions. Root elongation was used as the
index of tolerance. At 36 ug Pb/g nutrient solution, all populations of A. tenuis were com-
pletely inhibited. At 12 ug Pb/g, the control populations from low lead soils were completely
inhibited, but the populations from mine soils achieved 30 percent of their normal growth
(growth at no lead in nutrient solution). At 6 ug/g, the control populations achieved 10 per-
cent of their normal growth, tolerant populations achieved 42 percent. There were no measure-
ments below 6 ug/g. Wong (1982) measured the index of tolerance at one concentration only,
2.5 ug Pb/g nutrient solution, and found that non-adapted populations of Festuca rubra which
had grown on soils with 47 ug/g total lead content were completely inhibited, populations from
soils with 350 to 650 ug/g achieved 3 to 7 percent of normal growth, and populations from
5,000 ug/g soil achieved nearly 40 percent of normal growth.
These studies support the conclusion that inhibition of plant growth begins at a lead
concentration of less than 1 ug/g s°il moisture and becomes completely inhibitory at a level
between 3 and 10 ug/g. Plant populations thai: are genetically adapted to high lead soils may
achieve 50 percent of their normal root growth at lead concentrations above 3 ug/g. These
experiments did not show the effect of reduced root growth on total productivity, but they did
show that exposure to high lead soils is a requirement for genetic adaptation and that, at
PB8A/B 8-20 7/13/83
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PRELIMINARY DRAFT
least in the case of F. rubra, plant lead concentrations increase with increasing concentra-
tions in the soil.
8.3.1.4 Effects of Lead on Forage Crops. In the 1977 Criteria Document (U.S. Environmental
Protection Agency, 1977), there was a general awareness that most of the lead in plants was
surface lead from the atmosphere. Most studies since then have addressed the problem of dis-
tinguishing between surface and internal plant lead. The general conclusion is that, even in
farmlands remote from major highways or industrial sources, 90 to 99 percent of the total
plant lead is of anthropogenic origin (National Academy of Sciences, 1980). Obviously, the
critical agricultural problem concerns forage crops and leafy vegetables. In Great Britain,
Crump and Barlow (1982) determined that within 50 m of the highway, surface deposition is the
major source of lead in forage vegetation. Beyond this range, seasonal effects can obscure
the relative contribution of atmospheric lead. The atmospheric deposition rate appears to be
much greater in the winter than in the summer. Two factors may explain this difference.
First, deposition rate is a function of air concentration, particle size distribution, wind-
speed, and surface roughness. Of these, only particle size distribution is likely to be inde-
pendent of seasonal effects. Lower windspeeds or air concentration during the summer could
account for lower deposition rates. Second, it may be that the deposition rate only appears
to change during the summer. With an increase in biomass and a greater turnover in biomass,
the effective surface area increases and the rate of deposition, which is a function of sur-
face area, decreases. During the summer, lead may not build up on the surface of leaves as it
does in winter, even though the flux per unit of ground area may be the same.
8.3.1.5 Summary of Plant Effects. When soil conditions allow lead concentrations in soil
moisture to exceed 2 to 10 |jg/g, most plants experience reduced growth due to the inhibition
of one or more physiological processes. Excess calcium or phosphorus may reverse the effect..
Plants that absorb nutrients from deeper soil layers may receive less lead. Acid rain is not
likely to release more "lead until after major nutrients have been depleted from the soil. A
few species of plants have the genetic capability to adapt to high lead soils.
8.3.2 Effects on Bacteria and Fungi
8.3.2.1 Effects on Decomposers. Tyler (1972) explained three ways in which lead might inter-
fere with the normal decomposition processes in a terrestrial ecosystem. Lead may be toxic to
specific groups of decomposers, it may deactivate enzymes excreted by decomposers to break
down organic matter, or it may bind with the organic matter to render it resistant to the
action of decomposers. Because lead in litter may selectively inhibit decomposition by soil
bacteria at 2,000 to 5,000 ug/g (Smith, 1981, p. 160), forest floor nutrient cycling processes
may be seriously disturbed near lead smelters (Bisessar, 1982; Watson et al., 1976). This is
PB8A/B 8-21 7/13/83
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PRELIMINARY DRAFT
especially important because approximately 70 percent of plant biomass enters the decomposer
food chain (Swift et al. , 1979, p. 6), If decomposition of the biomass is inhibited, then
much of the energy and nutrients remain unavailable to subsequent components of the food
chain. There is also the possibility that the ability of soil to retain lead would be re-
duced, as humic substances are byproducts of bacterial decomposition.
During decomposition, plant tissues are reduced to resistant particulate matter, as solu-
ble organic and inorganic compounds are removed by the chemical action of soil moisture and
the biochemical action of microorganisms (Odum and Drifmeyer, 1978). Each group of micro-
organisms specializes in the breakdown of a particular type of organic molecule. Residual
waste products of one group become the food for the next group. Swift et al. (1979, p. 101)
explained this relationship as a cascade effect with the following generalized pattern (Figure
8-4). Organisms capable of penetrating hard or chemically resistant plant tissue are the
primary decomposers. These saprotrophs, some of which are fungi and bacteria that reside on
leaf surfaces at the initial stages of senescence, produce a wide range of extracellular
enzymes. Others may reside in the intestinal tract of millipedes, beetle larvae, and termites
capable of mashing plant tissue into small fragments. The feces and remains of this group and
the residual plant tissue are consumed by secondary decomposers, i.e., the coprophilic fungi,
bacteria, and invertebrates (including protozoa) specialized for consuming bacteria. These
are followed by tertiary decomposers. Microorganisms usually excrete enzymes that carry out
this digestive process external to their cells. They are often protected by a thick cell
coat, usually a polysaccharide. Because they are interdependent, the absence of one group in
this sequence seriously affects the success of subsequent groups, as well as the rate at which
plant tissue decomposes. Each group may be affected in a different way and at different lead
concentrations. Lead concentrations toxic to decomposer microbes may be as low as 1 to 5 ug/g
or as high as 5,000 ug/g (Doelman, 1978).
Under conditions of mild contamination, the loss of one sensitive bacterial population
may result in its replacement by a more lead-tolerant strain. Inman and Parker (1978) found
that litter transplanted from a low-lead to a high-lead site decayed more slowly than high-
lead litter, suggesting the presence of a lead sensitive microorganism at the low-lead site.
When high-lead litter was transplanted to the low-lead site, decomposition proceeded at a rate
faster than the low-lead litter at the low-lead site. In fact, the rate was faster than the
high-lead litter at the high-lead site, suggesting even the lead tolerant strains were some-
what inhibited. The long term effect is a change in the species composition of the ecosystem,
which will be considered in greater detail in Section 8.5.2.
Delayed decomposition has been reported near smelters (Jackson and Watson, 1977), mine
waste dumps (Williams et al., 19/7), and roadsides (Inman and Parker, 1978). This delay is
PB8A/B 8-22 7/13/83
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PRELIMINARY DRAFT
RAW
DETRITUS
D,
GROUP I
GROUP II
D,
GROUP III
D.
INORGANIC
NUTRIENTS
Figure 8-4. Within the decomposer food chain, detritus is progressively broken down
in a sequence of steps regulated by specific groups of decomposers. Because of the
cascade effect of this process, the elimination of any decomposer interrupts the sup-
ply of organic nutrients to subsequent groups and reduces the recycling of inorganic
nutrients to plants. Undecomposed litter would accumulate at the stages preceding
the affected decomposer.
Source: Adapted from Swift et al. (1979).
generally in the breakdown of litter from the first stage (Ot) to the second (02) with intact
plant leaves and twigs accumulating at the soil surface. The substrate concentrations at
which lead inhibits decomposition appear to be very low. Williams et al. (1977) found inhibi-
tion in 50 percent of the bacteria and fungal strains at 50 ug Pb/ml nutrient solution. The
community response time for introducing lead tolerant populations seems very fast, however.
Doelman and Haanstra (1979a,b) found lead-tolerant strains had replaced non-tolerant bac-
teria within 3 years of lead exposure. These new bacteria were predominately thick-coated
gram negative strains and their effectiveness in replacing lead-sensitive strains was not
evaluated in terms of soil decomposition rates.
Tyler (1982) has also shown that many species of wood-decaying fungi do not accumulate
Pb, Ca, Sr, or Mn as strongly as they do other metals, even the normally toxic metal, cadmium.
PB8A/B
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PRELIMINARY DRAFT
Accumulation was expressed a"s the ratio of the metal concentration in the fungus to its sub-
strate. A ratio of greater than one implies accumulation, less than one, exclusion. Of 11
species, manganese was excluded by ten, strontium by nine, lead by eight, and calcium by
seven. Potassium, at the other end of the spectrum, was not excluded by any species. The
species which appeared to accumulate calcium and lead were described as having harder, less
ephemeral tissues.
This relationship among calcium, strontium, and lead is consistent with the phenomenon of
biopurification described in Section 8.5.2. From the date of Tyler (1982) it appears that
some of the species of fungi receive lead from a source other than the nutrient medium, per-
haps by direct atmospheric deposition.
8.3.2.2 Effects on Nitrifying Bacteria. The conversion of ammonia to nitrate in soil is a
two-step process mediated by two genera of bacteria, Nitrosomonas and Nitrobacter. Nitrate is
required by all plants, although some maintain a symbiotic relationship with nitrogen-fixing
bacteria as an alternate source of nitrogen. Those which do not would be affected by a loss
of free-living nitrifying bacteria, and it is known that many trace metals inhibit this nitri-
fying process (Liang and Tabatabai, 1977,1978). Lead is the least of these, inhibiting nitri-
fication 14 percent at concentrations of 1,000 ug/g soil. Many metals, even the nutrient
metals, manganese and iron, show greater inhibition at comparable molar concentrations.
Nevertheless, soils with environmental concentrations above 1,000 ug Pb/g are frequently found.
Even a 14 percent inhibition of nitrification can reduce the potential success of a plant
population, as nitrate is usually the limiting nutrient in terrestrial ecosystems. In cul-
tivated ecosystems, nitrification inhibition is not a problem if nitrate fertilizer is added
to soil, but could reduce the effectiveness of ammonia fertilizer if the crops rely on nitri-
fying bacteria for conversion to nitrates.
8.3.2.3 Methylation by Aquatic Microorganisms. While methyllead is not a primary form of
environmental lead, methylation greatly increases the toxicity of lead to aquatic organisms
(Wong and Chau, 1979). There is some uncertainty about whether the mechanism of methylation
is biotic or abiotic. Some reports (Wong and Chau, 1979, Thompson and Crerar, 1980) conclude
that lead in sediments can be methylated by bacteria. Reisinger et al. (1981) report that
biomethylation of lead under aerobic or anaerobic conditions does not occur and such reports
are probably due to sulfide-induced chemical conversion of organic lead salts. These authors
generally agree that tetramethyl lead can be formed under environmental conditions when
another tetravalent organolead compound is available, but methylation of divalent lead salts
such as Pb(N03)2 does not appear to be significant.
8.3.2.4 Summary of Effects on Microorganisms. It appears that microorganisms are more sen-
sitive than plants to soil lead pollution and that changes in the composition of bacterial
PB8A/B 8-24 7/13/83
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PRELIMINARY DRAFT
populations may be an early indication of lead effects. Delayed decomposition may occur at
750 ug Pb/g soil and nitrification inhibition at 1,000 pg/g. Many of the environmental vari-
ables which can raise or lower these estimates are not yet known. In certain chemical en-
vironments, the highly toxic tetramethyllead can be formed, but this process does not appear
to be mediated by aquatic microorganisms.
8.4 EFFECTS OF LEAD ON DOMESTIC AND WILD ANIMALS
8.4.1 Vertebrates
8.4.1.1 Terrestrial Vertebrates. Forbes and Sanderson (1978) have reviewed reports of lead
toxicity in domestic and wild animals. Lethal toxicity can usually be traced to consumption
of lead battery casings, lead-based paints, oil wastes, putty, linoleum, pesticides, lead shot,
or forage near smelters. Except for lead shot ingestion, these problems can be solved by pro-
per management of domestic animals. However, the 3,000 tons of lead shot distributed annually
along waterways and other hunting grounds continues to be a problem. Of the estimated 80 to
90 million waterfowl in North America, 3.5 million die of poisoning from lead shot annually
(U.S. Fish and Wildlife Service, 1976).
A single pellet of lead shot weighs about 110 mg, and 70 percent of this may be eroded in
ringed turtle dove gizzards over a period of 14 days (Kendall et a!., 1982). Their data
showed an immediate elevation of blood lead and reduction of ALA-D activity within 1 day of
swallowing two pellets.
Awareness of the routes of uptake is important in interpreting the exposure and accumula-
tion in vertebrates. Inhalation rarely accounts for more than 10 to 15 percent of the daily
intake of lead (National Academy of Sciences, 1980). Much of the inhaled lead is trapped on
the walls of the bronchial tubes and passes to the stomach embedded in swallowed mucus.
Because lead in lakes or running stream water is quite low, intake from drinking water may
also be insignificant unless the animal drinks from a stagnant or otherwise contaminated
source.
Food is the largest contributor of lead to animals. The type of food an herbivore eats
determines the rate of lead ingestion. More than 90 percent of the total lead in leaves and
bark may be surface deposition, but relatively little surface deposition may be found on some
fruits, berries, and seeds which have short exposure times. Roots intrinsically have no sur-
face deposition. Similarly, ingestion of lead by a carnivore depends mostly on deposition on
herbivore fur and somewhat less on lead in herbivore tissue.
The type of food eaten is a major determinant of lead body burdens in small mammals.
Goldsmith and Scanlon (1977) and Scanlon (1979) measured higher lead concentrations in insect-
ivorous species than in herbivorous species, confirming the earlier work of Quarles et al.
PB8A/B 8-25 7/13/83
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PRELIMINARY DRAFT
(1974), which showed body burdens of granivores < herbivores < insectivores, and Jeffries and
French (1972) that granivores < herbivores. Animals in these studies were analyzed whole
minus the digestive tract. It is likely that observed diet-related differences were somewhat
diluted by including fur in the analysis, because fur-lead might be similar for small mammals
from the same habitats with different feeding habits.
Since 1977, there has been a trend away from whole body analyses toward analysis of iso-
lated tissues, especially bones and blood. Bone concentrations of lead ara better than blood
as indicators of long term exposure. Because natural levels of blood lead are not well known
for animals and blood is not a good indicator of chronic exposure, blood lead is poorly suited
for estimating total body burdens. One experiment with sheep shows the rapid response of
blood to changes in lead ingestion and the relative contribution of food and air to the total
blood level. Ward et al. (1978) analyzed the blood in sheep grazing near a highway (0.9 |jg/g
ml) and in an uncontaminated area (0.2 ug/ml). When sheep from the uncontaminated area were
allowed to graze near the roadway, their blood levels rose rapidly (within 1 day) to about
3.0 ug/ml, then decreased to 2.0 ug/ml during the next 2 days, remaining constant for the
remainder of the 14-day period. Sheep from the contaminated area were moved to the uncon-
taminated area, where upon their blood dropped to 0.5 ug/ml in 10 days and decreased to 0.3
ug/ml during the next 180 days. Sheep in the uncontaminated area that were fed forage from
the roadside experienced an increase in blood lead from 0.2 to 1.1 ug/ml in 9 days. Con-
versely, sheep from the uncontaminated area moved to the roadside but fed forage only from the
uncontaminated site experienced an increase from 0.2 to 0.5 ug/ml in 4 days. These data
show that both air and food contribute to lead in blood and that blood lead concentrations are
a function of both the recent history of lead exposure and the long term storage of lead in
bone tissue.
Chmiel and Harrison (1981) showed that the highest concentrations of lead occurred in the
bones of small mammals (Table 8-2), with kidney and liver concentrations somewhat less. They
also showed greater bone concentrations in insectivores than herbivores, both at the control
and contaminated sites. Clark (1979) found lead concentrations in shrews, voles, and brown
bats from roadside habitats near Washington, D.C., to be higher than any previously reported.
His estimates of dosages (7.4 mg Pb/kg-day) exceed those that normally cause mortality or
reproductive impairment in domestic mammals (1.5-9 mg Pb/g-day) (Hammond and Aronson, 1964;
James et al., 1966; Kelliher et al., 1973). Traffic density was the same as reported by Chmiel
and Harrison (1981), nearly twice that of Goldsmith and Scanlon (1977) (See Table 8-2). The
body lead burden of shrews exceeded mice, which exceeded voles. Beresford et al. (1981) found
higher lead in box turtles within 500 m of a lead smelter than in those from control sites.
Bone lead exceeded kidney and liver lead as in small mammals.
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PRELIMINARY DRAFT
There are few studies reporting lead in vertebrate tissues from remote sites. Elias et
al. (1976, 1982) reported tissue concentrations in voles, shrews, chipmunks, tree squirrels,
and pine martens from the remote High Sierra. Bone concentrations were generally only 2
percent of those reported from roadside studies and 10 percent of the controls of roadside
studies (Table 8-2), indicating the controls were themselves contaminated to a large degree.
Furthermore, biogeochemical calculations suggest that even animals in remote areas have bone
lead concentrations 50 to 500 times natural background levels. The natural concentration of
lead in the bones of herbivores is about 0.04 ng/g dry weight (Table 8-1). This value may
vary regionally with geochemical anomalies in crustal rock, but provides a reasonable indica-
tor of contamination. Natural levels of lead in carnivore bone tissue should be somewhat
lower, with omnivores generally in between (Elias and Patterson, 1980; Elias et al. , 1982).
Table 8-2 shows the results of several studies of small animal bone tissue. To convert
reported values to a common basis, assumptions were made of the average water content, calcium
concentration, and average crustal concentration. Because ranges of natural concentrations of
lead in bones, plants, soils, and air are known with reasonable certainty (Table 8-1), it is
possible to estimate the degree of contamination of vertebrates from a wide range of habitats.
It is important to recognize that these are merely estimates that do not allow for possible
errors in analysis or anomalies in regional crustal abundances of lead.
8.4.1.2 Effects on Aquatic Vertebrates. Two requirements limit the evaluation of literature
reports of lead effects on aquatic organisms. First, any laboratory study should incorporate
the entire life cycle of the organism studied. It is clear that certain stages of a life
cycle are more vulnerable than others (Hodson, 1979, Hodson et al., 1979). For fish, the egg
or fry is usually most sensitive. Secondly, the same index must be used to compare results.
Christensen et al. (1977) proposed three indices useful for identifying the effects of lead on
organisms. A molecular index reports the maximum concentration of lead causing no significant
biochemical change; residue index is the maximum concentration showing no continuing increase
of deposition in tissue; and a bioassay i ndex is the maximum concentration causing no mortal-
ity, growth change, or physical deformity. These indices are comparable to those of physio-
logical dysfunction (molecular, tissue, and organismic) discussed in Section 8.1.4.
From the standpoint of environmental protection, the most useful index is the molecular
index. This index is comparable to the point of initial response discussed previously and is
equivalent to the "safe concentration" originally described by the U.S. Environmental
Protection Agency (Batelle, 1971) as being the concentration that permits normal reproduction,
growth, and all other life-processes of all organisms. It is unfortunate that very few of the
toxicity studies in the aquatic literature report safe concentrations as defined above.
Nearly all report levels at which some or all of the organisms die.
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PRELIMINARY DRAFT
TABLE 8-2. ESTIMATES OF THE DEGREE OF CONTAMINATION OF HERBIVORES,
OMNIVORES, AND CARNIVORES
Data are based on published concentrations of lead in bone tissue (corrected to dry weight as
indicated). Degree of contamination is calculated as observed/natural Pb. Natural lead con-
centrations are from Table 8-1. Concentrations are in ug Pb/g dw.
Organism
Herbivores
Vole- roadside
Vole- roadside
-control
Vole-orchard
-control
Vole- remote
Deer mouse- roadside
-control
Deer mouse- roadside
-control
Deer mouse- roadside
-control
Mouse- roadside
-control
Mouse-roadside
-control
Average herbivore
roadside (7)
control (7)
remote (2)
Omm'vores/frugivores
Woodmouse- roads i de
-control
Composite- roadside
-control
Chipmunk- remote
Tree squirrel -remote
Feral pigeon-urban
-rural
Feral pigeon- urban
-suburan
-rural
Starling-roadside
-control
Bone
Pb cone.
38
17
5
73
9
2
25
5.7
29
7.2
52
5
19
9.3
109
18
41
8.5
2
67
25
22
3
2
1.3
670
5.7
250
33
12
210
13
Ref.
1
2
2
5
5
11
2
2
3
3
4
4
2
2
2
2
1
1
7
7
1
11
6
6
12
12
12
7
7
Estimated degree of
contamination
bone
320
140
42
610
75
17
210
48
240
60
430
42
160
78
910
150
340
71
17
840
310
280
37
25
16
8400
71
3100
410
150
2600
160
(continued)
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PRELIMINARY DRAFT
TABLE 8-2. (continued)
Organism
Bone
Pb cone.
Ref.
Estimated degree
contamination
bone
of
Robin-roadside 130
-control 41
Sparrow-roadside 130
-control 17
Blackbird-roadside 90
-control 7
Grackle-roadside 63
-control 22
Rats-roadside 310^
-control 15
Average omnivore
roadside (7) 102
urban (1) 670
control (7) 18
remote (2) 1.7
Carnivores
Box turtle-smelter 91a
-control 5^7
Egret-rural 12*
Gull-rural 11
Shrew-roadside 67
-control 12
Shrew-roadside 193
-control 41
Shrew-remote 4.6
Pine marten-remote 1.4
Average carnivore
7
7
7
7
7
7
7
7
9
9
8
8
10
10
2
2
1
1
1
11
1600
510
1600
200
1100
88
790
280
10000
500
1260
8400
230
21
3000
190
400
370
2200
400
6400
1400
150
47
roadside (3)
smelter (1)
rural (2)
control (4)
remote (2)
190
91
11
18
3
6200
3000
385
620
99
aDry weight calculated from published fresh weights assuming 35 percent water.
1. Chmiel and Harrison, 1981
2. Getz et al., 1977b
3. Welch and Dick, 1975
4. Mierau and Favara, 1975
5. Elfving et al., 1978
6. Hutton and Goodman, 1980
7. Getz et al., 1977a
8. Beresford et al., 1981
9. Mouw et al. , 1975
10. Hulse et al., 1980
11. Ellas et al., 1982
12. Johnson et al., 1982b
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Hematological and neurological responses are the most commonly reported effects of
extended lead exposures in aquatic vertebrates. Hematological effects include the disabling
and destruction of mature red blood cells and the inhibition of the enzyme ALA-D required for
hemoglobin synthesis. At low exposures, fish compensate by forming additional red blood
cells. These red blood cells often do not reach maturity. At higher exposures, the fish
become anemic. Symptoms of neurological responses are difficult to detect at low exposure,
but higher exposure can induce neuromuscular distortion, anorexia, and muscle tremors. Spinal
curvature eventually occurs with time or increased concentration (Hodson 1979; Hodson et al.,
1977). Weis and Weis (1982) found spinal curvature in developing eggs of killifish when the
embryos had been exposed to 10 ug Pb/ml during the first 7 days after fertilization. All
batches showed some measure of curvature, but those that were most resistant to lead were
least resistant to the effects of methyl mercury.
The biochemical changes used by Christensen et al. (1977) to determine the molecular
index for brook trout were 1) increases in plasma sodium and chloride and 2) decreases in
glutamic oxalacetic transaminase activity and hemoglobin. They observed effects at 0.5 ug/1,
which is 20-fold less than the lower range (10 ug/1) suggested by Wong et al. (1978) to cause
significant detrimental effects. Hodson et al. (1978a) found tissue accumulation and blood
parameter changes in rainbow trout at 13 ug/1- This was the lowest experimental level, and
only slightly above the controls, which averaged 4 ug/1. They concluded, however, that
because spinal curvature does not occur until exposures reach 120 ug/1, rainbow trout are ade-
quately protected at 25 ug/1.
Aside from the biochemical responses discussed by Christensen et al. (1977), the lowest
reported exposure concentration that causes hematological or neurological effects is 8 ug/1
(Hodson, 1979). Christensen1s group dealt with subcellular responses, whereas Hodson's group
dealt primarily with responses at the cellular or higher level. Hodson et al. (1978a) also
reported that lead in food is not available for assimilation by fish, that most of their lead
comes from water, and that decreasing the pH of water (as in acid rain) increases the uptake
of lead by fish (Hodson et al., 1978b). Patrick and Loutit (1978), however, reported that
tissue lead in fish reflects the lead in food if the fish are exposed to the food for more
than a few days. Hodson et al. (1980) also reported that, although the symptoms are similar
(spinal deformation), lead toxicity and ascorbic acid deficiency are not metabolically
related.
8.4.2 Invertebrates
Insects have lead concentrations that correspond to those found in their habitat and diet.
Herbivorous invertebrates have lower concentrations than do predatory types (Wade et al.,
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PRELIMINARY DRAFT
1980). Among the herbivorous groups, sucking insects have lower lead concentrations than
chewing insects, especially in regions near roadsides, where more lead is found on the sur-
faces of vegetation. Williamson and Evans (1972) found gradients away from roadsides are not
the same as with vertebrates, in that invertebrate lead decreases more slowly than vertebrate
lead relative to decreases in soil lead. They also found great differences between major
groups of invertebrates. Wood lice in the same habitat, eating the same food, had eight times
more lead than millipedes.
The distribution of lead among terrestrial gastropod tissues was reported by Ireland
(1979). He found little difference among the foot, skin, mantle, digestive gland, gonad, and
intestine. There are no reports of lead toxicity in soil invertebrates. In a feeding experi-
ment, however, Coughtrey et al. (1980) found decreased tolerance for lead by microorganisms
from the guts of insects at 800 |jg Pb/g food. Many roadside soils fall in this range.
In Cepaej hortensis, a terrestrial snail, Williamson (1979) found most of the lead in the
digestive gland and gonadal tissue. He also determined that these snails can lose 93 percent
of their whole body lead burden in 20 days when fed a low-lead diet in the laboratory. Since
no analyses of the shell were reported, elimination of lead from this tissue cannot be evalu-
ated. A continuation of the study (Williamson, 1980) showed that body weight, age, and day-
length influenced the lead concentrations in soft tissues.
Beeby and Eaves (1983) addressed the question of whether uptake of lead in the garden
snail, Helix aspersa, is related to the nutrient requirement for calcium during shell forma-
tion and reproductive activity. They found both metals were strongly correlated with changes
in dry weight and little evidence for correlation of lead with calcium independent of weight
gain or loss. Lead in the diet remained constant.
Gish and Christensen (1973) found lead in whole earthworms to be correlated with soil
lead, with little rejection of lead by earthworms. Consequently, animals feeding on earth-
worms from high lead soils might receive toxic amounts of lead in their diets, although there
was no evidence of toxic effects on the earthworms (Ireland, 1977). Ash and Lee (1980)
cleared the digestive tracts of earthworms and still found direct correlation of lead in
earthworms with soil lead; in this case, soil lead was inferred from fecal analyses. These
authors found differences among species of earthworms. Ireland and Richards (1977) also found
species differences in earthworms, as well as some localization of lead in subcellular organ-
dies of chloragogue and intestinal tissue. In view of the fact that chloragocytes are be-
lieved to be involved with waste storage and glycogen synthesis, the authors concluded that
this tissue is used to sequester lead in the manner of vertebrate livers. Species differences
in whole body lead concentrations could not be attributed to selective feeding or differential
absorption, unless the differential absorption occurs only at elevated lead concentrations.
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PRELIMINARY DRAFT
The authors suggested that the two species have different maximum tolerances for body lead but
gave no indication of physiological dysfunction when the maximum tolerance was reached. In
soils with a total lead concentration of 1,800 ug/g dry weight (Ireland, 1975), Lumbricus
rube11 us had a whole body concentration of 3,600 ug/g, while Dendrobaene rubida accumulated
7,600 |jg/g in the same location (Ireland and Richards, 1977). Because this difference was not
observed at the control site (15 ug/g soil), it can be assumed that at some soil concentration
between 15 and 1,800 ug/g, different species of earthworms begin to accumulate different
amounts of lead. The authors concluded that D. rubida can simply tolerate higher tissue lead
concentrations, implying that soil concentrations of 1,800 ug/g are toxic to L. rubellus. This
concentration would be considerably lower than soil lead concentrations that cause effects in
plants, and similar to that which can affect soil microorganisms.
Aquatic insects appear to be resistant to high levels of lead in water. To be conclu-
sive, toxicity studies must observe invertebrates through an entire life cycle, although this
is infrequently done. Anderson et al. (1980) found LC5o's for eggs and larvae of Tanytarsus
dissimilis, a chironomid, to be 260 ug/1. This value is 13 to 250 times lower than previously
reported by Warnick and Bell (1969), Rehwoldt et al. (1973), and Nehring (1976). However,
Spehar et al. (1978) found that mature amphipods (Gammarus pseudolimnaeus) responded nega-
tively to lead at 32 ug/1. Fraser et al. (1978) found that adult populations of a freshwater
isopod (Asellus aquaticus) have apparently developed a genetic tolerance for lead in river
sediments.
Newman and Mclntosh (1982) investigated freshwater gastropods, both grazing and burrow-
ing. Lead concentrations in the grazers (Physa Integra, Pseudosuccinea columella, and Helisoma
trivolvis) were more closely correlated with water concentrations than with lead in the food.
Lead in the burrowing species, Campeloma decisum, was not correlated with any environmental
factor. These authors (Newman and Mclntosh, 1983) also reported that both Physa integra and
Campeloma decisurn are able to eliminate lead from their soft tissue when transferred to a
low-lead medium, but that tissue lead stabilized at a level higher than found in populations
living permanently in the low-lead environment. This would seem to indicate the presence of a
persistent reservoir of lead in the soft tissues of these gastropods.
Borgmann et al. (1978) found increased mortality in a freshwater snail, Lymnaea palutris.
associated with stream water with a lead content as low as 19 ug/1. Full life cycles were
studied to estimate population productivity. Although individual growth rates were not af-
fected, increased mortality, especially at the egg hatching stage, effectively reduced total
biomass production at the population level. Production was 50 percent at 36 ug/1 and 0 per-
cent at 48 ug Pb/1.
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PRELIMINARY DRAFT
The relationship between LCS0 and initial physiological response is not immediately
obvious. It is certain that some individuals of a population experience physiological dys-
function well before half of them die. For example, Biesinger and Christensen (1972) observed
minimum reproductive impairment in Daphnia at 6 percent of the LC50 (450 ug/1) for this
species.
8.4.3 Summary of Effects on Animals
While it is impossible to establish a safe limit of daily lead consumption, it is reason-
able to generalize that a regular diet of 2 to 8 mg Pb/kg-day body weight over an extended
period of time (Botts, 1977) will cause death in most animals. Animals of the grazing food
chain are affected most directly by the accumulation of aerosol particles on vegetation sur-
faces and somewhat indirectly by the uptake of lead through plant roots. Many of these
animals consume more than 1 mg Pb/kg-day in habitats near smelters and roadsides, but no toxic
effects have been documented. Animals of the decomposer food chain are affected indirectly by
lead in soil which can eliminate populations of microorganisms preceeding animals in the food
chain or occupying the digestive tract of animals and aiding in the breakdown of organic
matter. Invertebrates may also accumultate lead at levels toxic to their predators.
Aquatic animals are affected by lead at water concentrations lower than previously con-
sidered safe (50 ug Pb/1) for wildlife. These concentrations occur commonly, but the contri-
bution of atmospheric lead to specific sites of high aquatic lead is not clear.
8.5 EFFECTS OF LEAD ON ECOSYSTEMS
There is wide variation in the mass transfer of lead from the atmosphere to terrestrial
ecosystems. Even within the somewhat artificial classification of undisturbed, cultivated,
and urban ecosystems, reported fluxes in undisturbed ecosystems vary by nearly 20-fold. Smith
and Siccama (1981) report 270 g/ha-yr in the Hubbard Brook forest of New Hampshire; Lindberg
and Harriss (1981) found 50 g/ha-yr in the Walker Branch watershed of Tennessee; and Elias et
al. (1976) found 15 g/ha-yr in a remote subalpine ecosystem of California. Jackson and Watson
(1977) found 1,000,000 g/ha-yr near a smelter in southeastern Missouri. Getz et al. (1979)
estimated 240 g/ha-yr by wet precipitation alone in a rural ecosystem largely cultivated and
770 g/ha-yr in an urban ecosystem.
One factor causing great variation is remoteness from source, which translates to lower
air concentrations, smaller particles, and greater dependence on wind as a mechanism of depo-
sition (Elias and Davidson, 1980). Another factor is type of vegetation cover. Deciduous
leaves may, by the nature of their surface and orientation in the wind stream, be more suit-
able deposition surfaces than conifer needles. Davidson et al. (1982) discussed the influence
of leaf surface on deposition rates to grasses.
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The history of lead contamination in roadside ecosystems has been reviewed by Smith
(1976). Recent studies have shown three areas of concern where the effects of lead on eco-
systems may be extremely sensitive (Martin and Coughtrey, 1981; Smith, 1981). First, decom-
position is delayed by lead, as some decomposer microorganisms and invertebrates are inhibited
by soil lead. Secondly, the natural processes of calcium biopurification are circumvented by
the accumulation of lead on the surfaces of vegetation and in the soil reservoir. Thirdly,
some ecosystems experience subtle shifts toward lead tolerant plant populations. These pro-
blems all arise because lead in ecosystems is deposited on vegetation surfaces, accumulates in
the soil reservoir, and is not removed with the surface and ground water passing out of the
ecosystem. Other potential effects are discussed that may occur because of the longterm
build-up of lead in soil.
8.5.1 Delayed Decomposition
The flow of energy through an ecosystem is regulated largely by the ability of organisms
to trap energy in the form of sunlight and to convert this energy from one chemical form to
another (photosynthesis). Through photosynthesis, plants convert light to stored chemical
energy. Starch is only a minor product of this energy conversion. The most abundant sub-
stance produced by net primary production is cellulose, a structural carbohydrate of plants.
Terrestrial ecosystems, especially forests, accumulate a tremendous amount of cellulose as
woody tissue of trees. Few animals can digest cellulose and most of these require symbiotic
associations with specialized bacteria. It is no surprise then, that most of this cellulose
must eventually pass through the decomposer food chain. Litter fall is the major route for
this pathway. Because 80 percent or more of net primary production passes through the decom-
posing food chain (Swift et al., 1979), the energy of this litter is vital to the rest of the
plant community and the inorganic nutrients are vital to plants.
The amount of lead that causes litter to be resistant to decomposition is not known.
Although laboratory studies show that 50 pg Pb/ml nutrient medium definitely inhibits soil
bacterial populations, field studies indicate little or no effact at 600 ug/g litter (Doelman
and Haanstra, 1979b). One explanation is that the lead in the laboratory nutrient medium was
readily available, while the lead in the litter was chemically bound to soil organic matter.
Indeed, Doelman and Haanstra (1979a) demonstrated the effects of soil lead content on delayed
decomposition: sandy soils lacking organic complexing compounds showed a 30 percent inhibition
of decomposition at 750 ug/g, including the complete loss of major bacterial species, whereas
the effect was reduced in clay soils and non-existent in peat soils. Organic matter maintains
the cation exchange capacity of soils. A reduction In decomposition rate was observed by
Doelman and Haanstra (1979a) even at the lowest experimental concentration of lead, leading to
the conclusion that some effect might have occurred at even lower concentrations.
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PRELIMINARY DRAFT
When decomposition is delayed, nutrients may be limiting to plants. In tropical regions
or areas with sandy soils, rapid turnover of nutrients is essential for the success of the
forest community. Even in a mixed deciduous forest, a significant portion of the nutrients,
especially nitrogen and sulfur, may be found in the litter reservoir (Likens et al. 1977).
Annual litter inputs of calcium and nitrogen to the soil account for about 60 percent of root
uptake. With delayed decomposition, plants must rely on precipitation and soil weathering for
the bulk of their nutrients. Furthermore, the organic content of soil may decrease, reducing
the cation exchange capacity of soil.
8.5.2 Circumvention of Calcium Biopurification
Biopurification is a process that regulates the relative concentrations of nutrient to
non-nutrient elements in biological components of a food chain. In the absence of absolute
knowledge of natural lead concentrations, biopurification can be a convenient method for esti-
mating the degree of contamination. Following the suggestion by Comar (1966) that carnivorous
animals show reduced Sr/Ca ratios compared to herbivorous animals which, in turn show less
than plants, Elias et al. (1976, 1982) developed a theory of biopurification, which hypothe-
sizes that calcium reservoirs are progressively purified of Sr, Ba, and Pb in successive
stages of a food chain. In other words, if the Sr/Ca and Ba/Ca ratios are known, the natural
Pb/Ca ratio can be predicted and the observed Pb/Ca to natural Pb/Ca ratio is an expression of
the degree of contamination. Elias et al. (1976, 1982) and Elias and Patterson (1980)
observed continuous biopurification of calcium in grazing and detrital food chains by the pro-
gressive exclusion of Sr, Ba, and Pb (Figure 8-5). It is now believed that members of grazing
and decomposer food chains are contaminated by factors of 30 to 500, i.e., that 97 percent to
99.9 percent of the lead in organisms is of anthropogenic origin. Burnett and Patterson
(1980) have shown a similar pattern for a marine food chain.
The mechanism of biopurification relies heavily on the selective transport of calcium
across membranes, the selective retention of non-nutrients at physiologically inactive binding
sites, and the reduced solubility of non-nutrient elements in the nutrient medium of plants
and animals. For example, lead is bound more vigorously to soil organic complexes and is less
soluble in soil moisture (Section 6.5.1). Lead is also adsorbed to cell walls in the root
apoplast, is excluded by the cortical cell membrane, and is isolated as a precipitate in sub-
cellular vesicles of cortical cells (Koeppe, 1981). Further selectivity at the endodermis
results in a nutrient solution of calcium in the vascular tissue which is greatly purified of
lead. Similar mechanisms occur in the stems and leaves of plants, in the digestive and circu-
latory systems of herbivores and carnivores, and in the nutrient processing mechanisms of
insects.
PB8A/B 8'35 7/13/83
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PRELIMINARY DRAFT
10
<3
£
?
co
«3
&
u
10-
I
ROCKS SOIL PLANT HERBI GARNI
MOISTURE LEAVES VORES VORES
PB8A/B
Figure 8-5. The atomic ratios Sr/Ca, Ba/Ca and Pb/Ca (O)
normally decrease by several orders of magnitude from the
crustal rock to ultimate carnivores in grazer and decomposer
food chains. Anthropogenic lead in soil moisture and on the
surfaces of vegetation and animal fur interrupt this process
to cause elevated Pb/Ca ratios (•) at each stage of the
sequence. The degree of contamination is the ratio of Total
Pb/Ca vs. Natural Pb/Ca at any stage. Ba/Ca and Sr/Ca ratios
are approximate guidelines to the expected natural Pb/Ca
ratio.
Source: Adapted from Elias et al. (1982).
8-36
7/01/83
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PRELIMINARY DRAFT
Atmospheric lead circumvents the natural biopurification of calcium. Deposition on plant
surfaces, which accounts for 90 percent of the total plant lead, increases the ratio of Pb/Ca
in the diet of herbivores. Deposition on animal fur increases the Pb/Ca ratio in the diet of
carnivores. Atmospheric lead consumed by inhalation or grooming, possibly 15 percent of the
total intake of lead, represents sources of lead which were non-existent in prehistoric times
and therefore were not present in the food chain.
8.5.3 Population Shifts Toward Lead Tolerant Populations
It has been observed that plant communities near smelter sites are composed mostly of
lead tolerant plant populations (Antonovics et al. , 1971). In some cases, these populations
appear to have adapted to high-lead soils, since populations of the same species from low-lead
soils often do not thrive on high-lead soils (Jowett, 1964). Similar effects have been ob-
served for soils enriched to 28,000 ug/g dry weight with ore lead (Holland and Oftedal, 1980)
and near roadsides at soil concentrations of 1,300 ug/g dry weight (Atkins et al., 1982). In
these situations, it is clear that soil lead concentration has become the dominant factor in
determining the success of plant populations and the stability of the ecological community.
Soil moisture, soil pH, light intensity, photoperiod, and temperature are all secondary fac-
tors (Antonovics et al., 1971). Strategies for efficient use of light and water, and for
protection from temperature extremes, are obliterated by the succession of lead-tolerant plant
populations. Smith and Bradshaw (1972) concluded that lead-tolerant plant populations of
Festuca rubra and Agrostis tenuis can be used to stabilize toxic mine wastes with lead concen-
trations as high as 80,000 ug/g.
8.5.4 Mass Balance Distribution of Lead in Ecosystems
Inputs of natural lead to ecosystems, approximately 90 percent from rock weathering and
10 percent from atmospheric sources, account for slightly more than the hydro!ogic lead out-
puts in most watersheds (Patterson, 1980). The difference is small and accumulation in the
ecosystem is significant only over a period of several thousand years. In modern ecosystems,
with atmospheric inputs exceeding weathering by factors of 10 to 1000, greater accumulation
occurs in soils and this reservoir must be treated as lacking a steady state condition
(Heinrichs and Mayer, 1977, 1980; Siccama and Smith, 1978). Odum and Drifmeyer (1978)
describe the role of detrital particles in retaining a wide variety of pollutant substances,
and this role may be extended to include non-nutrient substances.
It appears that plant communities have a built-in mechanism for purifying their own
nutrient medium. As a plant community matures through successional stages, the soil profile
develops a stratified arrangement which retains a layer of organic material near the surface.
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PRELIMINARY DRAFT
This organic layer becomes a natural site for the accumulation of lead and other non-nutrient
metals which might otherwise interfere with the uptake and utilization of nutrient metals.
But the rate accumulation of lead in this reservoir may eventually exceed the capacity of the
reservoir. Johnson et al. (1982a) have established a baseline of 80 stations in forests of
the northeast United States. In the litter component of the forest floor, they measured an
average lead concentration of 150 ug/g. Near a smelter, they measured 700 ug/g and near a
highway, 440 (jg/g. They presented some evidence from buried litter that predevelopment con-
centrations were 24 ug/g. On an area basis, the present concentrations range from 0.7 to
1.8 g Pb/m2. Inputs of 270 g/ha-yr measured in the Hubbard Brook forest (see Section 8.5)
would account for 1.0 g Pb/m2 in forty years if all of the lead were retained. The 80 sta-
tions will be monitored regularly to show temporal changes. Evidence for recent changes in
litter lead concentrations is documented in the linear relationship between forest floor lead
concentration and age of forest floor, up to 100 years.
Lead in the detrital reservoir is determined by the continued input of atmospheric lead
from the litter layer, the passage of detritus through the decomposer food chain, and the rate
of leaching into soil moisture. There is strong evidence that soil has a finite capacity to
retain lead (Zimdahl and Skogerboe, 1977). Harrison et al. (1981) observed that most of the
lead in roadside soils above 200 ug/g is found on Fe-Mn oxide films or as soluble lead car-
bonate. Elias et al. (1982) have shown that soil moisture lead is derived from the Teachable/
organic fraction of soil, not the inorganic fraction. Lead is removed from the detrital
reservoir by the digestion of organic particles in the detrital food chain and by the release
of lead to soil moisture. Both mechanisms result in a redistribution of lead among all of the
reservoirs of the ecosystem at a very slow rate. A closer look at the mechanisms whereby lead
is bound to humic and fulvic acids leads to the following conclusions: 1) because lead has a
higher binding strength than other metals, lead can displace other metals on the organic
molecule (Schnitzer and Khan, 1978); 2) if calcium is displaced, it would be leached to a
lower soil horizon (B), where it may accumulate as it normally does during the development of
the soil profile; and 3) if other nutrient metals, such as iron or manganese, are displaced,
they may become unavailable to roots as they pass out of the soil system.
Fulvic acid plays an important role in the development of the soil profile. This organic
acid has the ability to remove iron from the lattice structures of inorganic minerals, result-
ing in the decomposition of these minerals as a part of the weathering process. This break-
down releases nutrients for uptake by plant roots. If all binding sites on fulvic acid are
occupied by lead, the role of fulvic acid in providing nutrients to plants will be circum-
vented. While it is reasonably certain that such a process is possible, there is no informa-
tion about the soil lead concentrations that would cause such an effect.
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PRELIMINARY DRAFT
Ecosystem inputs of lead by the atmospheric route have established new pathways and
widened old ones. Insignificant amounts of lead are removed by surface runoff or ground water
seepage. It is likely that the ultimate fate of atmospheric lead will be a gradual elevation
in lead concentration of all reservoirs in the system, with most of the lead accumulating in
the detrital reservoir.
8.6 SUMMARY
Because there is no protection from industrial lead once it enters the atmosphere, it is
important to fully understand the effects of industrial lead emissions. Of the 450,000 tons
emitted annually on a global basis, 115,000 tons of lead fall on terrestrial ecosystems.
Evenly distributed, this would amount to 0.1 g/ha-yr, which is much lower than the range of
15 to 1,000,000 g/ha-yr reported in ecosystem studies in the United States. Lead has per-
meated these ecosystems and accumulated in the soil reservoir where it will remain for decades
(Chapter 6). Within 20 meters of every major highway, up to 10,000 ug Pb have been added to
each gram of surface soil since 1930 (Getz et al., 1979). Near smelters, mines, and in urban
areas, as much as 130,000 pg/g have been observed in the upper 2.5 cm of soil (Jennett et al.,
1977). At increasing distances up to 5 kilometers away from sources, the gradient of lead
added since 1930 drops to less than 10 ug/g (Page and Ganje, 1970), and 1 to 5 ug/g have been
added in regions more distant than 5 kilometers (Nriagu, 1978). In undisturbed ecosystems,
atmospheric lead is retained by soil organic matter in the upper layer of soil surface. In
cultivated soils, this lead is mixed with soil to a depth of 25 cm.
Because of the special nature of the soil reservoir, it must not be regarded as an infi-
nite sink for lead. On the contrary, atmospheric lead which is already bound to soil will
continue to pass into the grazing and detrital food chains until equilibrium is reached,
whereupon the lead in all reservoirs will be elevated proportionately higher than natural
background levels. This conclusion applies also to cultivated soils, where lead bound within
the upper 25 cm is still within the root zone.
Few plants can survive at soil concentrations in excess of 20,000 ug/g, even under opti-
mum conditions. Some key populations of soil microorganisms and invertebrates die off at 1000
ug/g. Herbivores, in addition to a normal diet from plant tissues, receive lead from the sur-
faces of vegetation in amounts that may be 10 times greater than from internal plant tissue.
A diet of 2 to 8 mg/daykg body weight seems to initiate physiological dysfunction in many
vertebrates.
Whereas previous reports have focused on possible toxic effects of lead on plants,
animals, and humans, it is essential to consider the degree of contamination as one measure of
safe concentration. Observed toxic effects occur at environmental concentrations well above
P88A/B 8-39 7/13/83
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PRELIMINARY DRAFT
levels that cause no physiological dysfunction. Small animals in undisturbed ecosystems are
contaminated by factors of 20 to 600 over natural background levels, and in roadside and urban
ecosystems by 300 to 6200. Extrapolations based on sublethal -effects may become reliable when
these measurements can be made with controls free of contamination. The greatest impact may
be on carnivorous animals, which generally have the lowest concentrations of natural lead, and
may thus havet he greatest percent increase when the final equilibrium is reached.
Perhaps the most subtle effect of lead is on ecosystems. The normal flow of energy
through the decomposer food chain may be interrupted, the composition of communities may shift
toward more lead-tolerant populations, and new biogeochemical pathways may be opened, as lead
flows into and throughout the ecosystem. The ability of an ecosystem to compensate for atmos-
pheric lead inputs, especially in the presence of other pollutants such as acid precipitation,
depends not so much on factors of ecosystem recovery, but on undiscovered factors of ecosystem
stability. Recovery implies that inputs of the perturbing pollutant have ceased and that the
pollutant is being removed from the ecosystem. In the case of lead, the pollutant is not
being eliminated from the system nor are the inputs ceasing. Terrestrial ecosystems will
never return to their original, pristine levels of lead concentrations.
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8.7 REFERENCES
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Borgmann, U.; Kramar, 0.; Loveridge, C. (1978) Rates of mortality, growth, and biomass pro-
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Bradford, W. L. (1977) Urban stormwater pollutant loadings: a statistical summary through 1972.
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Brewer, R. (1979) Principles of ecology. Philadelphia, PA: W. B. Saunders Company.
Burnett, M. W.; Patterson, C. C. (1980) Perturbation of natural lead transport in nutrient cal-
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Carlson, R. W. ; Stukel, J. J. ; Bazzaz, F. A. (1977) Aerosol studies. In: Rolfe, G. L. ;
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Carlson, R. W.; Bazzaz, F. A.; Stukel, J. J.; Wedding, J. B. (1976) Physiological effects, wind
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chloride, and lead nitrate on six biochemical factors of the brook trout (Salve!inus
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