EPA 560/3-75-005
TECHNICAL AND MICROECONOMIC ANALYSIS
OF
CADMIUM AND ITS COMPOUNDS
June 1975
Final Report
Contract 68-01-2926, Task 1
Project Officer
David Garrett, P.E.
Prepared For
Environmental Protection Agency
Office of Toxic Substances
Washington, D.C. 20460
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ABSTRACT
\
The role of cadmium (and its compounds) in the environment and in
the economy of the United, States was studied, to evaluate the need for
and the projected effect of controlling its production, use and dissipa-
tion. Technologically and economically feasible control alternatives
were developed from:
(1) A systematic documentation of cadmium production,
uses, prevalence, and sources of pollution; and
(2) An evaluation of the present and projected health
hazards.
Available information was then used to directly compare and optimize the
various alternatives.
The results led to two sets of recortmended controls. The first,
aimed at preventing increases in the present cadmium health hazards,
consists of continued air and water pollution abatement, environmentally-
sound land disposal of industrial wastes and residuals, and regulation of
application rates to agricultural lands of cadmium-bearing materials. The
second set of controls exhibits a more aggressive posture towards limit-
ing cadmium dissipation, which could be implemented in the future should
a more precise definition of the health hazard justify such a posture.
This second set of controls includes limitation of the cadmium impurities
in products of the zinc industry, reduction in the demand for cadmium by
voluntary action of several key industries and government, and the restric-
tion or abolition of cadmium imports.
11
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TABLE OF CONTENTS
I INTRODUCTION 1
II SUMMARY AND CONCLUSIONS 5
III RECOMMENDATIONS 20
IV PRIMARY ZINC INDUSTRY 23
V CADMIUM ELECTROPIATING 58
VI CADMIUM IN PLASTICS 67
VII NICKEL-CADMIUM BATTERIES 84
VIII SECONDARY METALS INDUSTRY 91
IX CADMIUM AS AN IMPURITY 105
X CADMIUM TOXICITY 120
XI ASSESSMENT OF HEALTH HAZARDS 131
XII QUANTITIES OF CADMIUM RELEASED TO THE ENVIRONMENT . 140
XIII THE MARKET FOR CADMIUM 152
XIV COSTS OF ALTERNATIVE REGULATIONS 177
XV REFERENCES 197
ill.
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LIST OF TAPT.F,S
Page
1. Composition of Zinc Concentrate 23
2. Material Balances for Zinc Ore Concentration 26
3. Trend of Domestic Zinc Ore and Metal Production 32
4. U.S. Zinc Plants 34
5. Metal Content of Roaster Feed and Product 37
6. Material Balance Around Zinc Ore Roasters 40
7. Metal Content of Sinter Feed and Product 44
8. Metal Contents Around Horizontal Retorts 48
9. 1971-72 Cadmium Waterborne Discharges from the
Primary Zinc Industry 55
10. Cadmium Consumed in Electroplating 59
11. Consumption of Cadmium Pigments 68
12. Plastics Colorant Consumption 69
13. Recent Prices of Plastics Colorants 71
14. Colorant Consumption by Resin Type 73
15. Yellow, Orange, Red and Maroon Colorants Widely
Used with Various Resins 74
16. Consumption of Heat Stabilizers 82
17. Secondary Copper and Zinc Processed in 1967 92
18. Use of No. 2 Scrap, Millions of Metric Tons Per
Year 96
19. Change in Steel Production for Each Major
Process 102
IV
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LIST OF TABLES (Cont.)
20. Consumption of Zinc Oxide 106
21. Galvanizing Efficiencies and Coating Weights 109
22. Corrosion of Zinc in Various Atmospheres Ill
23. U.S. Bituminous Coal Statistics (Million Metric
Tons/Year) 118
24. Acute Toxicity of Cadmium and its Salts 121
25. Comparison of Toxicological Effects of Cadmium
in Animals and Man 125
26. Cadmium in Foods 135
27. Plant Uptake of Cadmium from Soils 136
28. Fulkerson-Goeller Emission Estimates (1968)
for U.S 141
29. Revised Cadmium Emission Estimates 147
30. Supply Statistics for Cadmium Data in Metric Tons
Per Year 154
31. U.S. Demand Statistics for Cadmium Data in Metric
Tons Per Year (Elemental Cadmium) 157
32. Estimates for Maximum Recovery of Secondary
Cadmium in 1985 167
33. Effects of Secondary Cadmium Recovery in 1985 170
34. Estimated Effects of Bans on Cadmium Use 172
35. Estimated Maximum Costs for Disposal of Excess
Cadmium 191
36. Summary of Costs of Selected and Total Bans 195
v
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LIST OF FIGURES
Page
1. Vapor Pressures of Metals and Compounds 39
2. Solubility of Cadmium Vs. pH Source 54
3. Cadmium Pigments Manufacture 77
4. Simplified Diagram of Major Operations in Nickel-
Cadmium Sintered-Plate Storage Battery Manufacture .... 88
5. U.S Cadmium Supply 153
6. Baseline U.S. Cadmium Demand 160
7. Projected 1985 U.S. Cadmium Demand 164
8. Cadmium Supply and Demand 165
9. Estimated Effect of Bans of Cadmium - Baseline
Period (1968-1972) 173
10. Estimated Effect of Bans of Cadmium - 1985
Projections 174
11. Foregone Benefits 182
VI
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This report was prepared by the staff of Versar Inc., Springfield,
Virginia with the aid of the staff of Jack Faucett Associates, Chevy
Chase, Maryland. Mr. Donald H. Sargent of Versar was the program manager,
and Mr. John R. Metz was the principal investigator for Faucett. Impor-
tant contributions were made by Dr. Sidney Kuniansky of Versar; Dr. Eugene
E. Vogin, a consultant to Versar; and Dr. Ernest J. Mosbaek and Ms. Judith
P. Goodrow of Faucett.
The considerable aid furnished by personnel of the Environmental
Protection Agency, Office of Toxic Substances, is acknowledged. Mr. David
Garrett and Mr. David Wagner served as Project Officers. Valuable guidance
and support was furnished by Dr. Herbert M. Katz, a consultant to EPA.
Appreciation is also extended to the International Lead Zinc
Research Organization, the Dry Color Manufacturers Association, the
National Association of Metal Finishers, the Metal Finishers Suppliers
Association, the American Iron and Steel Institute, and the Institute of
Scrap Iron and Steel; and to the individual companies that cooperated in
this effort.
VII
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SECTION I
INTRODUCTION
Objectives of the Study
Efforts by various parts of the U.S. Environmental Protection
Agency, EPA contractors, other Government agencies and other workers in
the field are making increasingly apparent the present and potential dan-
gers to man and the environment from unrestricted production and use of
certain toxic chemical substances. For many of these substances, there
is ample evidence of an inminent catastrophe to the general popula-
tion resulting from current production and use practices. Moreover, these
substances have, in general, beneficial uses and are of value to the pri-
vate and public sectors of the U.S. economy. Hence, the atmosphere for
regulation of these substances is neither a blanket endorsement of current
and projected practices as presenting no real danger; nor is it, at the
other extreme, a total and immediate ban of the production and use of
these substances. Realistically, for many of these toxic substances,
a careful assessment is required of the dangers, of the options reasonably
available for reducing the dangers and of the economic impact resulting
from implemention of such options.
This report is the result of a study specifically intended to
provide such objective data for several toxic chemical substances. The
substances covered in this report are elemental cadmium and cadmium com-
pounds; subsequent reports will address other substances.
The specific objectives of this study of cadmium (and its compounds)
are:
1. To objectively and quantitatively evaluate the real
dangers (both present and projected) to man and to
the environment, without the implementation of new
and specific control measures.
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2. To make an accounting of how, where, and how much-
cadmium is entering the environment in accessible
(and possibly dangerous) forms.
3. To identify control alternatives which may be
technologically and economically feasible,
and to evaluate the effectiveness of each
of these control alternatives in reducing
the overall danger of cadmium to man and
the environment.
4. To delineate the present and projected role
of cadmium (and its compounds) in the U.S.
economy, and to evaluate the impact of each
of the control alternatives upon the economy.
Scope of This Study and Report
Much has already been published on the various aspects of cadmium
and the environment. Fulkerson and Goeller performed a rather complete
resource analysis of the cadmium system, and their January 1973 report
serves to gather and organize the information available at that time.
Their work systematically covers the properties of cadmium and its com-
pounds (physical, chemical and biological); the natural abundance and
polluted levels found in air, water, and food; the estimated human dose
rate ranges; the toxicology; the movement and effects of cadmium in the
ecosystem; the flow of cadmium in society (i.e., in the economy); the
identification of pollution sources and of abatement practices; the costs
of abatement and of use restrictions; the potential for substitutes; and
the control of cadmium flow in society.
In light of the breadth of the Fulkerson and Goeller report, no
attempt was made in this current study to provide another (albeit newer)
complete resource analysis of cadmium. Hence, this report is not intended
to be an encyclopedia for cadmium, nor it is intended to provide to the
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reader all of the background and history pertinent to the subject. The
reader is strongly urged to use the Fulkerson-Goeller report for these
purposes.
In addition, the study described in this report did not have the
time, funds, or mandate to generate any new experimental data to shed
light on areas previously identified as needing additional research.
Reaching the overall objective (to provide an assessment of the
dangers, a definition of the control options, and an evaluation of the
costs and effectiveness of these options), with the previously-published
work as a baseline, led to the following guidelines for emphasis in this
study:
1. Ihe critical review of previously-published analyses,
where significant differences in results and inter-
pretation of results existed.
2. The further investigation of areas pointed out by
previous efforts as needing attention, and where
important data has become available.
3. The investigation of areas not adequately covered
in previous efforts.
4. The evaluation of new research (since the previous
resource analysis), which has to some measure been
spurred by the Fulkerson-Goeller effort.
5. The evaluation of the significant changes in the
zinc production patterns and changes in the
cadmium consumption patterns.
6. The evaluation of the very significant changes
in pollution abatement practices and information
available, resulting from intensive EPA efforts
in the past few years.
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7. The specific emphasis upon the role of cadmium
in the U.S. economy.
8. The specific emphasis upon the definition of
control alternatives and upon the evaluation
of their respective effectiveness and economic
impact.
In essence, then, this report is composed of selected areas of
investigation (rather than being a complete documentation of all that is
known about cadmium), leading to the discussion of the viable control
alternatives. The first major part of the report (Sections IV-IX) syste-
matically covers the important areas of cadmium production and use, the
associated sources of pollution, the technology and costs for pollution
abatement, the potentials for substitutions, and the control alternatives
(identified but not as yet evaluated). These discussions build upon pre-
viously published analyses, and therefore include only a minimum of intro-
ductory material. The second major part (Sections X-XII) assesses the
toxicology and the health hazards of cadmium and summarizes the various
estimates previously made of cadmium dissipation into the environment.
The third and last major part of this report (Sections XIII-XV) discusses
the role of cadmium in the U.S. economy, the relative costs and effective-
ness of the control alternatives, and the microeconomic impact of these
control alternatives.
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SECTION II
SUMMAEY AND CONCLUSIONS
•Hie table on the succeeding page is a quantitative summary of where
cadmium is found, produced, converted, used, and inadvertently altered. Of
the cadmium in the commercial flow in the United States, this summary table
presents estimates of the amounts dissipated in end products, and of the
amounts accessible to the environment via air, water, and land discharges.
The results of this study are grouped into four broad categories.
First are those giving an overview of the role cadmium plays in our ecology
and in our economy. The second group deals with the technologies of
cadmium production, use, inadvertent appearance, and emissions. Third
are the results and conclusions dealing with the industrial economics
of cadmium. Last are the control alternatives deserving of further con-
sideration.
Overview of the Role of Cadmium
1. Cadmium has unquestioned chronic toxicity leading to serious
pathological consequences when ingested in quantities only 3
to 13 times greater than present average intake rates.
2. Cadmium in the soil is transported to the food chain; the
cadmium concentration in plants has an approximately 1:1
relationship with the cadmium concentrations in the soil, over
the entire range of concentrations down to the "unpolluted"
level of 0.1 ppm.
3. It is likely that much of the cadmium dissipated by man becomes
bound (in an environmentally-acceptable manner) in soil,
sediment, and ocean sinks.
4. An accounting of cadmium emissions reveals that (by difference)
approximately 90 per cent of the cadmium intentionally used in
our economy becomes apparently immobile and is thus removed from
circulation in an apparently adequate manner.
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SIM-RRY OF U.S. CADMIUM FI£W, DISSIPATION, AND EMISSIONS
METRIC TONS PER YEAR (1968-1972)
In Domestic Zn Ores
Losses in Beneficiation
In Domestic Zn Concentrates
In Imported Zn Concentrates
Total to Zn Smelters
Losses in Zn Smelting
In Zn for Galvanizing
Corrosion of Galvanized Pdts.
Losses in Scrap Processing
In ZnO for Rubber
Rubber Tire Wear
Net from Zn Smelting
In Domestic Flue Dusts
In Imported Flue Dusts
Domestic Cd Mstal Production
Cd Metal from GSA Stockpile
Cd Metal Imports
Total Cd Metal Supply
Cd Mstal to Electroplaters
Losses in Electroplating
In Electroplated Products
Losses in Scrap Processing
Cd Matal to Pigments
Losses in Processing
In Plastics
Losses in Incineration
Cd Mstal to Heat Stabilizers
Losses in Processing
In Plastics
Losses in Incineration
Cd Matal to Batteries
Losses in Processing
In Batteries
Cd Mstal to Alloys & Other Uses
Losses in Processing
In Alloys, etc.
Losses in Scrap Processing
From Phosphate Fertilizers
From Phosphate Detergents
Collected in Sewage Sludge
From Coal Combustion
From Oil Contoustion
From Lubricating Oils
Commercial
Flow
2,250
2,000
600
2,600
2,300
700
400
3,400
500
1,700
5,600
3,100
700
1,170
230
390
Dissipations
in End
Products
160
15
3,000
675
1,170
220
390
Airborne
Emissions
0.2
102
0.4
5.2
10
9.5
6
2.7
10
0.7
2.3
2.2
20
80
50
0.8
Waterborne
Effluents
7
7
0.8
0.3
10
land-Destined
Wastes
250
40
12
77
318
16.5
26
44
9
20
100
250
370
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5. There is. a lack of definitive cause-and-effect evidence, or even
of a precise analytical projection, between, cadmium dissemination
and chronic diseases in the United States.
6. Of the total cadmium released to the environment through the
activities of man, 20 per cent is accountable to the primary
non-ferrous metals industry (including ore mining and benefi-
ciation); 30 per cent is accountable to the conversion, use,
and disposition of cadmium in our economy; while the remaining
50 per cent is inadvertent (derived from fossil fuels, phosphate
fertilizers, and sewage sludge) and not at all linked to the
production or use of cadmium metal and its derivatives.
7. Of the total cadmium released to the environment through the
activities of man, only 15 per cent is in the form of air
pollution from stationary sources, and only one per cent is
in the form of water pollution from point sources. These
quantities appear to be decreasing, according to a comparison
of 1968 emission levels with 1974-75 levels. This decrease re-
flects investments in abatement equipment already made and
reflects the concerted efforts made by the government and pri-
vate sectors to abate the readily-identifiable sources of
pollution.
8. The great bulk of the total cadmium released to the environment
is in the form of land-destined solid wastes, slimes, and sludges.
Two categories may be defined for these materials. Less than
10 per cent of this cadmium (the first category) is in a
relatively small total volume of wastes, at relatively appreci-
able concentrations (0.1 per cent or greater). Much of these
wastes are the residuals from air and water pollution control;
and there is considerable progress in either disposing of these
wastes in an environmentally-adequate manner at relatively low
cost or in processing these wastes to reclaim the cadmium and
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other materials. More than 90 per cent of this land-destined
cadmium, however, (the second category) exists in an enormous
total waste volume and at relatively low concentrations (less
than 0.1 per cent). These concentrations are still up to 4
orders of magnitude higher than natural cadmium concentrations
in soil; the only apparently-feasible posture is the dispersing
of this cadmium on our lands in the least-damaging manner.
9. While the emissions of cadmium to air and water are not expected
to increase (improved pollution abatement should at least
compensate for industrial growth); the release of cadmium to
the land is expected to grow by 20 per cent by 1980. The primary
sources of these land-destined wastes, all increasing in volume,
are the combustion of coal, the use of phosphate fertilizers, the
isolation of sewage sludge, and the production of steel.
Technology of Cadmium-RelatedActivities
1. The domestic'primary zinc production capacity has shrunk signi-
ficantly over the past few years, with the closing of many of
the older pyrometallurgical plants. All new plants probably will be
electrolytic. This trend has both reduced the emissions of
cadmium from the primary zinc industry and has reduced the
cadmium dissipated as an impurity in zinc and zinc byproducts.
2. Cadmium, while accounting for only 0.5 per cent of the quantity
of zinc, provides approximately 5 per cent of the revenues as
compared to zinc. Its financial importance to the industry,
therefore, cannot be discounted.
3. The beneficiation of zinc ores is not selective with respect
to cadmium. Although the cadmium in ore tailings is not at
high concentrations, the cadmium quantities amount to 250
metric tons per year. The environmental mobility of this cadmium
in ore tailings is not well understood, but the partial use of
these tailings as an agricultural liming agent is a suspected
route into the food chain.
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4. The roasting of zinc concentrates usually results in very little,
if any, loss of cadmium. However, when, roasting is conducted at
temperatures greater than 1,000°C, cadmium will be vaporized.
Data for the cadmium content of the byproduct sulfuric acid (from
the roasting operation) has been widely conflicting, from a
range of 20 to 60 ppm previously reported by Fulkerson and
Goeller, to values less than 0.1 ppm newly reported by indus-
try. A route of cadmium into the food chain, via the cadmium
content of sulfuric acid used in the manufacture of phosphate
fertilizers, is therefore of questionable validity.
5. Since all but two large pyrometallurgical zinc plants will be
closed within the year, the wholesale release of cadmium to
the air via sintering is limited to these two plants. However,
they account for half of the domestic zinc capacity. The
volatization of cadmium is an intentional objective of sintering;
it results in the removal of 90 to 99 per cent of the cadmium
in the zinc calcine. Subsequent retorting is not a large source
of cadmium emissions, primarily because sintering serves to
first remove the cadmium.
6. The Icwer grades of zinc, primarily used for galvanizing and
the product of the pyrometallurgical plants, dissipate an
estimated 160 metric tons per year of cadmium. Although no
definitive data exists for how much of this cadmium is released
to the environment, the lifetime of galvanized coatings in severe
industrial or seacoast environments is as short as 4 to 12 years.
Zinc may be refined to virtually eliminate this source of cadmium
dissipation, but it would impart a competitive cost disadvantage
to the pyrometallurgical segment of the zinc industry.
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7. American Process zinc oxide has an estimated 100 ppm of cadmium
as an impurity, amounting to 15 metric tons per year, primarily
in rubber tires. The alternate French. Process zinc oxide con-
tains one-twentieth the cadmium.
8. Although cadmium electroplating is only a small fraction of the
total metal finishing industry, it is the largest consumer of
cadmium. The higher price for cadmium electroplating and the
emphasis upon reducing cadmium in wastewater effluents have
served to divert some of the demand to substitute metal
finishes. Much of the cadmium plating is for high-quality
and/or critical small parts, or in applications (military and
aircraft) where firm specifications impede changes and sub-
stitutions. Significant further reductions in cadmium electro-
plating are unlikely in a free marketplace; conversely, a 3
per cent per year growth rate was estimated.
9. The use of cadmium pigments in plastics is expected to grow
at 2 per cent per year. The relatively high price compared
to other pigments has already made the demand for cadmium pig-
ments highly selective, where no real substitutes are aval Table.
Many potential substitutes have similar toxicity problems.
However, if the specific color requirements for end items were
to be foregone, adequate, economical, and plentiful substitutes
are available.
10. Barium-cadmium heat stabilizers for polyvinyl chloride plastics
are in a reverse situation as compared to other cadmium uses.
The stabilizers enjoy almost half of their market, and are the
cheapest of the stabilizers; whereas cadmium in other uses is
a relatively expensive and minor part of their markets. Adequate
substitutes for barium-cadmium stabilizers are expected to be
fully competitive from both performance and price standpoints
in the near future; much substitution has already occurred. The
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Food and Drug Administration is expected to broaden the end-
item categories where bariura-cadinium stabilizers may not be
used. Because of these factors, a zero growth rate was pro-
jected for barium-cadmium stabilizers.
11. The demand for nickel-cadmium batteries is expected to grow at
a rate of 15 per cent per year. Of the major uses for cadmium,
only the battery end-items contain a sufficient quantity of
cadmium (8 to 10 per cent) to make reclamation feasible. There
already is some recycling practised, and more is expected.
Several consumer products which depend upon the nickel-cadmium
power source are in a rapid growth mode.
12. Two independent calculations of the quantity of cadmium involved
in steelmaking (via scrap iron and steel) resulted in an estimate
of 340 metric tons per year, compared to previous estimates of
Fulkerson and Davis three times higher. Automotive scrap
accounts for 75 to 85 per cent of this cadmium.
13. Although dust collection is efficient in nrijiimizing the cadmium
air emissions from steelmaking, the collected dusts contain several
hundred ppm of cadmium, and thereby present an environmental
hazard. However, the quantities of dusts involved are very
large, and safe land disposal would amount to a large cost.
Moreover, the trend in the steel industry towards decentralized,
smaller capacity mills presents problems of ensuring effective
air pollution control and disposition of collected dusts in a
dispersed industry.
14. Recent and comprehensive data indicates that the mean concentra-
tion of cadmium in sewage sludge is 75 ppm, five times higher
than the previous estimate of Fulkerson. The total quantity
of cadmium in sewage sludge was estimated at 300 metric tons
per year, and increasing.
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15. Cadmium from the combustion of coal is expected to increase
rapidly as more coal is mined and used for electric power
generation. Coal conversion processes offer the potential
for removing and recovering cadmium.
16. Cadmium from phosphate fertilizers is expected to increase
rapidly, in parallel with the growth of that industry. There
are presently no means used in the United States for removing
the cadmium from phosphoric acid.
Industrial Economics of Cadmium
1. The domestic production of cadmium is projected to be 4,700
metric tons per year by 1985. The domestic cadmium demand
calculated as the sum of the demand for each major consuming
sector, is projected to be 9,200 metric tons per year by 1985.
About 40 per cent of this demand, therefore, is expected to be
met by imported cadmium. The slightly higher projected demand
as compared to the total projected supply would result in an
increase in cadmium price by 1985 to about $11 per kilogram.
The domestic consumption of cadmium is growing at 4 per cent
per year.
2. The demand for cadmium, for most of the major uses and for the
total, is highly inelastic (i.e., the quantity demanded is very
insensitive to price). The application of a tax on cadmium sales
or on cadmium imports would therefore be largely ineffective in
reducing consumption.
3. A partial or total ban on cadmium use is a feasible alternative
for reducing or eliminating cadmium dissipation related to its
commercial use. Since cadmium is a byproduct of zinc production,
its domestic supply cannot be eliminated. A partial or total
ban on cadmium imports would substantially reduce its dissipative
uses.
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4. The costs for reducing cadmium consumption would be $16 per
kilogram. The major element of these costs, for all consuming
industries, is the long-run loss (ultimately paid by the many
consumers of cadmium-containing products) in using substitutes
which may cost more, may provide reduced quality, or may not
last as long. Only the battery industry would have compara-
tively significant idle capital and unemployment costs.
5. A total ban on cadmium imports would result (in a free market-
place) in a cadmium price of over $20 per kilogram and in an
increase in revenues to domestic cadmium producers of $40 to
$50 million per year.
6. A significant reduction in the demand for cadmium electroplating
might be possible through the voluntary actions of a few key
consuming segments. The government (including the military),
the automotive industry, the aircraft industry, the shipbuilding
industry, and similar consumers are all large consumers, the
prime producers are relatively few in number, they have an
established prime contractor/subcontractor hierarchy, and they
have a formal specification system.
7. The reclamation of used nickel-cadmium batteries should serve
to significantly reduce the quantities of "new" cadmium imported
into the United States, thereby directly decreasing the cadmium
dissipated.
Summary of Control Alternatives
A summary of the various control alternatives, each with a concise
statement of feasibility, effectiveness, and cost, is included at the end
of this section. These alternatives have passed a screening process and are
deserving of further consideration. Some alternatives identified in the
body of this report are not included in this tabulation; some were rejected
because they were not feasible, not effective, or too costly on an a priori
basis; others have been amended or replaced in an optimization process.
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SECTION III
There appear to be sufficient grounds, on the basis of potential
health hazards, for prudent measures to be taken to prevent any large
increases in the dissipation of cadmium in our environment; to reduce
or eliminate those discharges which are readily identifiable and po-
tentially controllable; to carefully monitor the movement of cadmium
in our ecology; and to support further research aimed at both quantify-
ing the problem and developing ways to ameliorate the problem.
However, in light of the lack of definitive cause-and-effect evidence
between cadmium dissemination and chronic diseases in the United States,
the lack of evidence that ingested cadmium is increasing, the likelihood
that much of the dissipated cadmium becomes bound in soil, sediment and
ocean sinks; the indication that much progress is being made in air and
water pollution abatement; and the fact that half of the man-made dissi-
pation of cadmium is not at all related to the cadmium producing and
using industries; no urgent program of bans on cadmium production, im-
ports, or use is justified at this time.
We are faced with the dilerrma that if the projections of this study
are qualitatively valid, the quantities of cadmium dissipated are in-
creasing at a substantial rate. It is therefore not possible to prevent
cadmium proliferation by simply maintaining our present posture.
In response to this dilemma, we recommend one set of control measures
deemed prudent for the present, and another set of control measures which
may be implemented in the future should new data justify a more aggressive
control posture.
Control Alternatives Recommended for the Present
A. Continued promulgation and enforcement of stringent regu-
lations for air pollution abatement from stationary sources
and for water pollution abatement from point sources. The
-20-
-------
specific control alternatives recommended, referring
to the tabulation in Section IX, are numbers 11, 12,
13, 14, 15, 16, 18, 19, 21, 22, 24, 26, 27, 29, 30,
and 32.
B. Promulgation and enforcement of regulations for en-
suring that cadmium-bearing industrial wastes destined
for land disposal be treated and disposed of in en-
vironmentally adequate ways. The specific control
alternatives recommended, referring to the tabulation
in Section II, are numbers 17, 20, 23, 25, and 28.
Control alternative 31 (for the iron and steel indus-
try) , while falling into this category, is associated
with extremely high costs; further information is
needed regarding the technology and costs of treating
these flue dusts for the removal of cadmium.
C. Regulation of the application rate to agricultural
lands of cadmium-bearing fertilizers, sewage sludges,
zinc ore tailings, and solid wastes from combustion
and incineration processes (control alternative
number 33). Further efforts are needed to precisely
define the limitations and the variations of limitations.
D. Encouragement of research for the removal of the
cadmium impurity in fertilizers and coal (control
alternatives 34 and 35).
E. Encouragement of the reclamation of cadmium, pri-
marily from used nickel-cadmium batteries. (Control
alternative 7).
F. Encouragement of continued research and monitoring
to define with greater precision the health hazards
presented by cadmium.
-21-
-------
Control Alternatives Recommended for the Future
Should further research and monitoring provide justification in terms of
definitive health hazards for more aggressive control measures, and should new
data verify the projections of this study that cadmium dissipation will in-
crease, then the following control alternatives could be adopted after more
detailed evaluation:
A. Regulation to very low levels of the cadmium
impurity in products and byproducts of the pri-
mary zinc industry tcontrol alternatives 37, 38,
and 39).
B. Reduction in the demand for cadmium, through
voluntary actions of major consumers, starting
with the federal government (control alternative
9).
C. Restriction on cadmium imports, the quota to be
determined by assessing the severity of the pro-
blem; and imposing a total ban on imports as an
extreme measure (control alternative 10).
-22-
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SECTION IV
PRIMARY ZINC INDUSTRY
Cadmium occurs naturally in zinc ores (and in lead-zinc and
copper-lead-zinc ores) in the approximate ratio of one part of cadmium
to 200 parts of zinc. As such, and because there is no separate ore of
cadmium, these zinc ores are the sources for primary cadmium, either as
a byproduct in the recovery of primary zinc or in the processing of the
residuals from the recovery operations for other metals.
Cadmium occurs wherever zinc is found. The average worldwide
abundance of cadmium and zinc, respectively, are 0.18 ppm and 80 ppm,
for a Cd/Zn ratio of 0.23 per cent. In zinc ores and lead-zinc ores,
the Cd/Zn ratio averages 0.5 per cent, according to Fulkerson, Page,
and Hallowell.(3)
The zinc ores, lead-zinc ores, and ccpper-lead-zinc ores are pro-
cessed by several methods, primarily flotation and heavy-media separation,
to produce a zinc concentrate which may contain 49.0 to 53.6 per cent
zinc and 0.24 per cent cadmium (for a Cd/Zn ratio of 0.47 per cent).
(4)
Five zinc ore concentrates sampled by Yost had an average Cd/Zn ratio
of 0.31 per cent. Other published data for zinc concentrates are listed
in Table 1.
These data show that while 0.50 per cent may be a representative
value for the Cd/Zn ratio, there is significant variation around this
value for individual ores and concentrates. Hence, to analyze the fate
of cadmium in the mining, beneficiation, and recovery of zinc, material
balances must be made upon individual operations rather than upon ag-
gregate values.
Ore Beneficiation
The zinc ores (and lead-zinc ores) that are processed are, of
course, mostly gangue, which is principally dolomite with minor amounts
-23-
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of calcite present. The extremely fine interlocking distribution
of the sphalerite (the zinc sulfide ore) necessitates grinding to typi-
cally 90 per cent minus 200 mesh to liberate the sphalerite so that it
may be separated from the gangue. Typical material balances for ore
beneficiation (based upon 1000 units of ore heads) are listed in Table 2.
Three important observations may be made from these data:
1. The cadmium/zinc ratio does not change as a result
of beneficiation; i.e., the cadmium in the ore is
carried quantitatively with the zinc to the lead
concentrate, the zinc concentrate and the residue:
Ore
Cd/Zn, Per Cent:
Ore Heads
Pb Concentrate
Zn Concentrate
Residue
Broken Hill
BHS
-
0.50
0.41
-
Broken Hill
BHN
0.42
0.43
0.42
0.47
Broken Hill
ZC
0.36
0.31
0.38
—
2. The beneficiation does a rather effective job from
a process engineering viewpoint of removing the
zinc (and so the cadmium), so that the residue has
a very low quantity of zinc and cadmium by compari-
son with the original ore:
Ore
Broken Hill
Avg. (5)
Average '-'-'
Average'''
Average'
Zn Content of Tailings, %
0.16
1.02
0.27
0.18
0.38
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3. The quantity of tailings is of the same magnitude
as the quantity of ore heads, since only a minor
quantity is removed as concentrates. Ihe annual
quantity of tailings from U.S. mines is 16,750,000
kkg.(1)
While the mine overburden usually contains less than 50 ppm cad-
mium, the tailings contain only about 15 ppm cadmium as 0.5 per cent
of a zinc content of 0.3 per cent). From a process engineering view-
point, therefore, it appears that the removal of cadmium from the land-
destined tailings has been entirely adequate.
However, from an environmental viewpoint, the adequacy is highly
suspect. The level of cadmium in the tailings, 15 ppm, is two orders of
magnitude greater than the average crustal abundance, although it is ob-
viously of the same magnitude as the soil in the mine vicinity. Ihe
environmental problem is that these tailings have become mobilized in
the environment as a result of the grinding, hydroclassifying, and flo-
tation operations (as opposed to their previous dormant state in nature
where they were locked into the gangue matrix). The mobility of the
tailings is a result of the very fine particle size, 86 per cent at minus
325 mesh, and of the physical state as a slime. As with most slime
ponds, the dried fines tend to dust during windy weather. Abatement
techniques in use in the United States include spraying with water or
soil covering to minimize dusting. Trees have been planted around the
ponds to act as windbreaks, and vegetative coverings have been planted.
Another potential environmental hazard is occasional release of slimes
during periods of heavy rainfall by overflowing of the banks of the
ponds; no pond in a climate with a positive rainfall/evaporation balance
can be designed to accomodate all storms without overflows. Accidental
breaks of earthen dams containing slime ponds may result in huge losses
to the environment. The cadmium content of a zinc ore tailings pond
effluent was found to be 0.0 to 0.02 mg/1. An EPA-sponsored effort
to develop effluent limitations guidelines for zinc ore mining and pro-
cessing is nearing completion, and more definite data on the waterborne
-27-
-------
cadmium losses should become available.
'Jhero has been considerable utilization of tailings in the United
States for road stone (particularly the coarse fractions), for railroad
ballast, as an asphalt filler and as mortar sand. Since the domestic
tailings are dolomitic (typically 30 per cent CaO, 18 per cent MgO and
10 per cent SiO,,) and contain trace elements, agricultural uses as a
liming agent and soil conditioner have been relatively popular for to-
bacco, cotton and peach growing. ^ ' ' ' In 1971, 23 per cent of the
/Q\
domestic zinc ore was mined in Tennessee , so that the tailings were
geographically situated for use on these crops. Additional data is
needed to determine whether any correlation exists between the use of
zinc ore tailings as agricultural lime and the surprisingly high cadmium
(9)
levels found in tobacco, peanuts, and beet pulp.
The mobility of cadmium in an aqueous system is highly dependent
upon pH. Cadmium carbonate is relatively insoluble in alkaline waters
(such as would be expected with the associated dolomite). However, if
ammoniaca! fertilizers are used, there is a danger of dissolved cadmium
resulting from the formation of the soluble cadmium-ammonia complex ions,
CdtNty*2 and Cd(NH3)*2.
The total cadmium in domestic mine tailings may be estimated at
250 metric tons per year (at 15 ppm). Only a portion, however, is re-
leased to the environment. While quantitative data on this fraction is
not available, evidence that it is significant at least in some cases
is the cadmium content of surface waters downstream of beneficiation
sites. The most prominent instance has been the Jintsu River in Japan,
the site of the infamous Itai-Itai disease. Upstream of the zinc mine,
the bottom sediments contained less than 0.2 ppm cadmium; downstream,
the cadmium content of the sediment measured 238 ppm. The downstream
Jintsu River water contained 1 to 9 yg/1 cadmium, not unusual for natural
waters in zinc-bearing formations, indicating either that the cadmium
pollution was in the form of suspended solids or that the sediments
-28-
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adsorbed and accumulated the cadmium from the water (as is typical of such
(2 4)
sediments). ' Other reported instances of very high cadmium concentra-
tions in surface waters near zinc mines include the Coeur d'Alene River
(1 2)
in Idaho, where 450 yg/1 was measured by USGS. ' In comparison, the
proposed EPA toxic pollutant effluent standards for cadmium are based
upon a fresh-water receiving body concentration after mixing of 0.24 yg/1
(cronic) and 4.0 yg/1 (acute).
The release to the air of ore tailing dusts was estimated by Davis
as one part of cadmium for each 10,000 parts of cadmium in the ore.
Since it was previously shown that only about 10 per cent of the cadmium
in the ore winds up in the residue, the Davis emission factor is an air
loss from tailings of one part per thousand. This is equivalent, then,
to an air emission in the U.S. of 0.25 kkg per year of cadmium.
In summary, then, the mine tailings may constitute a real hazard
due to the mobility of the wastes. Although quantitative data on this
mobility are not available, evidence of the results of this mobility at
several sites has been reported in terms of cadmium pollution of surface
waters.
It should be emphasized that at this point, little quantitative
information exists for the mobility of the tailings in the environment.
It appears that technology for minimizing the release of cadmium from
zinc ore tailings to the environment does exist, and in fact, is prac-
tised to a large extent. The regulatory options include:
1. Limiting the cadmium content of the wastewater
effluent from the slime ponds (which the proposed
toxic guidelines would do). If the cadmium con-
tent of the tailings is 15 ppm, the chronic limita-
tion of 0.24 yg/1 is equivalent to a total suspended
solids limitation of 16 mg/1 in the effluent, with-
out counting any cadmium contribution as dissolved
solids. Such a 16 mg/1 suspended solids regulation
-29-
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is mrginally attainable with settling pond
technology; it may require polishing filter
technology.
2. Requiring that slime ponds be sized for a severe
storm situation, perhaps for a 10-year, 24-hour
rainfall event, to minimize the frequency of
overflowing.
3. Requiring that any effluent resulting from an
excess of precipitation over evaporation be
treated before discharge. Lime treatment and
settling should result in a total cadmium
/O TO)
concentration of no more than 0.5 mg/1. '
4. Imposing extremely stiff penalties for failure
of slime pond dams, which would encourage in-
dustry to effectively construct, inspect and
maintain these dams.
5. Requiring that drainage from existing and
future tailings piles be collected and
treated, rather than be allowed to dis-
charge directly into ground waters or into
surface waters.
6. Imposing regulations for the effective control
of dusting from the dried tailings, such as
earth covering, vegetative covering, and wind-
breaks.
7. Restricting the use of tailings for agricultural
purposes especially, and perhaps for road and
railroad bed purposes. The agricultural restric-
tions may involve application as well as distri-
bution; so that the cadmium content of soils after
tilling is within the normal range and so that
-30-
-------
concurrent application of ammonia fertilizers
does not lead to solubilization of the cadmium.
If, in fact, there is a cause-and-effect relation-
ship between the use of tailings as high-cadmium
aglime and the high cadmium content of tobacco
(as has yet to be demonstrated), then a ban of
this use should be considered owing to the high
retention by the human body of cadmium in cig-
arette smoke.
U.S. Production of Zinc Ore Concentrates and Slab Zinc
The domestic production of zinc ore concentrates and of slab zinc
have been decreasing, in relation to the rest of the free world, in a
rather dramatic fashion, as is shown in Table 3.
Since cadmium production is intimately tied to zinc production,
these drastic changes in zinc demand a very thorough update of previous
cadmium material balances.
Prior to 1964, U.S. smelter capacity exceeded U.S. zinc consump-
tion, and we were a net exporter of zinc. The U.S. imported large quan-
tities of zinc concentrate as feedstock for domestic production essen-
tially matched the domestic consumption. However, domestic smelter clos-
ings since 1968 have caused a widening gap, to the point where the U.S.
is a significant net importer of zinc. It appears that the U.S. metal
production has shrunk to the point where it can service the domestic
mine production of concentrates.
The main driving force for domestic contraction has been the rapid
growth of foreign consumption of zinc. In 1950, the U.S. consumed 50
per cent of the free world's zinc supply. Between 1950 and 1970, the U.S.
consumption grew at a rate of only 1.6 per cent, compared to 4.4 per cent
in Europe, 13.7 per cent in Japan, and 7.2 per cent in the rest of the
free world. Consequently, the U.S. consumption in 1970 was only 30 per
cent of the free world total. Since the U.S. always had to import ore
-31-
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concentrates, the domestic competitive position deteriorated as its share
of demand decreased and as foreign metal production capacity increased.
Two other major factors contributed to the domestic decline in
zinc production. One has been the expensive pollution control equipment
demanded recently for older smelters, and the other has been the high
production cost of the older labor-intensive domestic smelters. Table 4
lists the domestic zinc plants by process, with production capacities
and age. It is apparent from Table 4 that:
1. Until the new New Jersey Zinc plant (now under
construction) comes on stream, the newest
plant in the U.S. is 33 years old.
2. A rash of recent plant closings has ac-
counted for the drastic decrease in domestic
zinc production.
3. Older pyrometallurgical plants, especially
horizontal retort plants, are closing because
they are labor-intensive, because they have
severe air pollution problems, and because
they cannot manufacture the high grades of
zinc. Only two small U.S. horizontal retort
plants are still in operation, and account
for only 13 per cent of the total U.S. pro-
duction capacity of 689,000 metric tons per
year. The two large pyrometallurgical plants
(one vertical retort plant and one electro-
thermal plant) account for 48 per cent of the
U.S. capacity, and the three electrolytic
plants account for the remaining 39 per
cent.
The following distribution of the free-vorld zinc manufacturing
processes also illustrates the recent widespread closings of horizontal
-33-
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retort plants:
(5,13)
Process
Horizontal Retort
Electrolytic
Vertical Retort
Electro thermic
Imperial Smelting
Year of Commercial
Adaptation
1800
1915
1930
1936
1950
Pet. of Total
Production
1958
32%
50%
7%
3%
8%
1970
15%
56%
10%
7%
12%
The two critical points to be emphasized, with respect to this
drastic change in the domestic zinc production picture, are:
1. The decreases in U.S. zinc production reduce the
release of cadmium to the environment in the U.S.
resulting from zinc production,
2. The replacement of "dirty" retorting with "clean"
electrolytic plants results in less cadmium re-
lease to the environment during zinc production,
in less cadmium content of the product zinc, and
in a potentially greater supply of primary cadmium.
With, these dramatic changes in mind, the zinc recovery processes
will be reviewed from the standpoint of the fate of the cadmium in the ore
concentrates.
Zinc Recovery from Ore Concentrates
All domestic zinc plants subject the ore concentrate to a roasting
process, to convert the zinc sulfide to the oxide (and some sulfate).
Itoasting prior to pyrometallurgical zinc recovery is geared to remove a
maximum of the sulfur in the concentrate, while roasting prior to
-35-
-------
hydrometallurgical (i.e., electrolytic) zinc recovery is tailored so that
a controlled amount of zinc sulfate may be produced.
Three methods of roasting are in use: a multiple-hearth furnace,
a flash roaster, and a fluid-bed roaster. Table 5 lists the relative
metal content of feed and product for several specific roasting operations
(it was previously pointed out that because of variations in the cadmium
content of concentrates, aggregate data has limited value). Also listed
in Table 5 are the ratios of cadmium to zinc in the feed and product;
and the ratios of cadmium to zinc in the feed and product; and the ratios
of Zn, Cd, Pb, and Cu to Fe in the feed and product. This latter set of
ratios was calculated because iron (and its compounds) is the least
volatile and because iron is present in appreciable quantities; hence,
it is used in this analysis as a tracer material. Finally, the feed/
product ratios of the metal ratios are shown in Table 5.
From these last sets of ratios, a set of statistics was calculated
to determine if these ratios were significantly different from unity; i.e.,
if there was significant loss of any metal relative to other metals.
(The last three columns of Table 5 were not included in this set of
statistics, for reasons explained below.)
Feed/Product
Ratio
Cd/Zn
Zn/Fe
Cd/Fe
Pb/Fe
Cu/Fe
No. Data
Points
8
7
7
4
6
Average ,
R"
1.02
0.96
1.02
0.93
0.99
Std. Dev. ,
S
0.11
0.05
0.05
0.15
0.02
These data show that the roasting process does not result in any
significant loss of cadmium relative to zinc, nor of any of the more
volatile metals relative to iron.
-36-
-------
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-37-
-------
The last three columns of Table 5 are for three streams at the
St. Joe Minerals Corporation plant, where high grade (H.G.), intermediate
(Int.), and prime western (P.W.) zinc are manufactured. It is apparent
from the feed/product ratios for cadmium and lead for the three grades
that the roasting process selectively removes Cd and Pb from the higher
grade concentrates. MDst likely, this is accomplished by running the
roaster (at least in a first stage) at an oxygen deficit; as Figure 1
shows, the vapor pressures of PbS and CdS are appreciable at 1000 to
1200°C while that of ZnS is two orders of magnitude lower. In addition,
the data from Table 5 would indicate that flue dusts from the high-grade
and intermediate roaster, rich in Pb and Cd, would be added as feed to
the prime western roaster.
The vapor pressure curves in Figure 1 demonstrate that the roast-
ing process is conducted on the borderline of the temperature range where
the oxides as well as the sulfides have appreciable vapor pressures.
MDSt plants with fluid-bed roasters control the temperature to 900 to
1000°C by use of a water spray.
The data in Table 6 from the Canadian Electrolytic Zinc plant for
1969 provide the basis for a direct material balance (in tons) around two
fluid-bed roasters, based upon independent analyses of the roaster feed
and product. Within the analytical precision, these data verify the
conclusions that there is little selective loss of cadmium in normal
roasting (i.e., with an excess of oxygen and at temperatures controlled
to less than 1000°C); and that the total losses in the flue gas are small
compared to the quantity of cadmium in the concentrate.
The flue gas typically goes through a waste heat boiler and at
least two stages of solids separation, a cyclone and an electrostatic
precipitator, with the solids returned to the zinc process and with the
gases (containing 9 to 13 per cent SCL) used to manufacture sulfuric acid.
Even after dust collection, the flue gas feed to the sulfuric acid plant
(4)
may contain 0.097 per cent Zn and 0.00071 per cent Cd. Analysis of
-38-
-------
TEMPERATURE (°C)
aoooi
1000/TEMPERATURE (°K)
FIGURE I
VAPOR PRESSURES OF METALS AND COMPOUNDS
-39
-------
TABLE 6
MATERIAL, BALANCE AROUND ZINC ORE ROASTERS
SOURCE: AIME(5)
Ore Concentrate, Total
Zinc
Cadmium
Copper
Iron
Calcine, Total
Zinc
Cadmium
Copper
Iron
CEZ
134,300
71,500
360
830
13,600
116,800
71,600
360
860
13,500
Allied
124,200
65,300
140
470
12,900
106,300
63,100
130
480
12,500
-40-
-------
the byproduct sulfuris acid £76, per centl fron zinc smelters., as reported
by Fulkerson, shows a cadmium concentration of 20. to SO ppm; any
cadmium not collected as a solid oxide will be an iirpurity in. the acid
since CdO is soluble in sulfuric acid.
For a typical concentrate containing 54 per cent zinc and 31 par
cent sulfur, the theoretical quantity of byproduct 76 per cent sulfuric
acid will be 2.3 kkg per kkg of zinc produced. Even at a cadmium con-
centration of 60 ppm, the quantity of cadmium in the acid would be only
140 grams per metric ton of zinc produced. In comparison, the quantity
of cadmium in the ore concentrate before roasting is equivalent to 5,000
grams per metric ton of zinc. Hence, the inferred loss of cadmium from
roasting that winds up as an impurity in the sulfuric acid is of the or-
der of 1 to 3 per cent of the total cadmium. This is consistent with the
data of Table 6, which show that almost all of the cadmium is retained
with the calcine.
The Pulkerson-Goeller study revealed that the cadmium concentra-
tion of 76 per cent sulfuric acid from zinc smelters was 20 to 60 ppm. New
data was obtained from industry sources in this study. One source said
that to the best of their experience, the cadmium content of their by-
product sulfuric acid is in the range of 0.005 ppm. A second source said
that a recent analysis of their sulfuric acid showed 0.06 ppm cadmium.
This large discrepancy may, of course, be attributed to erroneous
data, to a change in the situation between the 1968 time frame and the
present, or to a real discrepancy among producers. If the more recent
data is in fact representative of the current situation, then of course
no controls are required. If there are producers (other than those quoted
above) who do have appreciable cadmium in byproduct sulfuric acid, then a
regulation is in order, especially in light of the feasibility of such a
regulation as demonstrated by the results of the quoted industry sources.
-41-
-------
One such control option is to regulate the maximum cadmium content
of sulfuric acid used by phosphate fertilizer manufacturers to about 2 ppm
(such that the cadmium oxlginating from phosphate rock would not be ap-
preciably augmented). This control option would divert any high-cadmium
sulfuric acid (if there in fact is any) to non-fertilizer applications.
An alternate option is to directly regulate the maximum cadmium concentra-
tion of all byproduct sulfuric acid, ragardless of its intended use (with
the exception, of course, of captive uses within the primary zinc/cadmium
production cycle). This option prevents the dissipation of cadmium, as
opposed to diversion, and places the burden at the source of the cadmium
rather than at a single consuming industry.
After roasting, the next step in the pyrometallurgical route is
sintering, in which coal or coke is mixed with the calcine, a binder may
be added, nodules or briquettes are formed, and the green briquettes are
fired with air at about 1200 °C. The primary goal for sintering is to
produce a feed for smelting in the form of a manageable briquette which
has sufficient mechanical strength to avoid clogging and dusting in the
retorts. In the sintering process, the volatile fractions of the coal
are burned off, and any residual sulfur in the calcine (and in the coal)
is oxidized.
"In addition to preparing a product with desirable physical charac-
teristics for smelting, it was also discovered that certain volatile im-
purities could be removed and the resultant zinc produced therefrom was
of higher quality than had been possible with previous practices."^ '
This viewpoint of the industry (in 1953) truly expresses why sintering
is the source of so much cadmium pollution - the loss of cadmium (and of
lead) was intentional! At temperatures above 1200°C, the vapor pressures
of lead and cadmium sulfides and oxides are sufficient to cause their
-42-
-------
volatization. To enhance this process, chlorides are added to the sin-
tering machine to drive off volatile chlorides of lead and cadmium. At
most plants, a significant fraction of the sinter is recycled through the
sintering machine to further reduce the cadmium and lead content; at some
plants, two full passes through sintering are practised.
Table 7 lists, for several sinter plants, the zinc, cadmium, and
lead contents of the feed, product, and collected fume streams. For
Eagle-Picher, four representative runs are listed, varying significantly
from each other in terms of both feed composition and sinter product com-
position. The sinter machine operator has a great deal of flexibility in
adjusting the feed mix (including the recycled sinter), the air flow, and
the temperature.
A similar degree of flexibility is exhibited by the ASARCO Mexi-
cana data; starting with the same calcine, two drastically different
grades of sinter may be made. St. Joe Minerals performs the same type
of classification, with material segregated at the roasting stage. New
Jersey Zinc performs a two-stage sintering and coking operation, with
coal added between stages. If is concluded, therefore, that aggregate
industry data and data at any one particular plant may be widely mis-
leading as to the effectiveness of removing cadmium and lead from the
zinc in the sintering process. It is apparent from Table 7 that the
cadmium/zinc ratio, nominally 0.5 per cent in the calcine, is reduced by
sintering to no greater than 0.05 per cent and to as little as 0,003 per
cent. Hence, the sintering process removes from 90 to 99 per cent of the
cadmium in the calcine.
The dust is collected in a baghouse and is used (or sold) for the
production of primary cadmium. ASAKCO claims 99.5 to 99.9 per cent ef-
ficiency of collection. The following chart, based upon 5 kg of Cd
per kkg of Zn in the calcine, relates the Cd emitted to the atmosphere
to the percentage removal of Cd from the calcine by sintering and to the
collection efficiency of the baghouse:
-43-
-------
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-44-
-------
Values of Cadmium Emissions
ka Cd/kka Zn
Cd Removal
by
Sintering, %
90
95
99
Collection Efficiency of Baghouse
90
0.450
0.475
0.495
95
0.225
0.238
0.248
99
0.045
0.048
0.050
As these values show, the cadmium emissions are not greatly af-
fected by the sintering process variations. However, they are directly
affected by the baghouse efficiency.
If the domestic zinc production via sintering (i.e., non-
electrolytic) is estimated at 417,000 kkg per year, then the total cad-
mium emitted by sintering in the U.S. would be about 100 kkg per year,
based upon a 95 per cent collection efficiency for baghouses. Should 99
per cent efficiency be achieved by the entire sintering industry, the
cadmium emissions would be 20 kkg per year from these sources.
Others have generated cadmium emission factors for the sintering
operation. Yost measured the metal content of stack emissions from
the "coker" at the N.J. Zinc Palmerton, Pa. plant. This coking is a second-
stage sintering step, after approximately 70 per cent of the cadmium and
lead have already been removed from the calcine. At an attempt at making
a material balance, up to 20 per cent of the cadmium input to the coker
was still unaccounted for. The Yost emission factors are:
Cadmium,
Lead,
Zinc,
Copper,
0.96 kg/kkg Zinc in Feed
0.51 kg/kkg Zinc in Feed
10.4 kg/kkc Zinc in Feed
0.008 kg/kkg Zinc in Feed
These values must be regarded, however, as unique to the Palmerton plant
for two reasons:
1. They apply only to the second stage of the sin-
tering process as it is set up at this plant.
-45-
-------
2. There apparently is no baghouse or other dust
catcher in the exhaust train from this coker.
The first stage sintering unit process does
have precipitators, and the captured dust is
the primary source for the cadmium plant. The
only cadmium values apparently recovered from
the coker, however, are those at the bottom of
the exhaust stack.
Hence, it appears that the Yost data are not representative of the sin-
tering process in the industry. As Yost points out, moreover, the metal
emissions are very sensitive to temperature changes and to air flow
changes. The variation in the data of Table 7 reinforce this conclusion.
The next major unit process in the pyrometallurgical route to zinc
is retorting, to reduce the zinc oxide in the sinter to metallic zinc.
The coal or coke in the sinter is the reducing agent. Three major varia-
tions of retorting are practised in the U.S.; horizontal retorts, vertical
retorts, and the electrothermic process (see table of U.S. zinc plants).
The reaction is carried out at about 1200°C to 1600°C, with metallic zinc
vaporizing and subsequently collected in a condenser.
The oldest process is the horizontal retort process. It is con-
ducted as a batch operation in batteries of small units, since the size
of each retort is limited by heat transfer considerations (the retort is
externally heated). The process is labor intensive (because of its batch-
wise nature), it is energy inefficient (about 5 per cent efficiency), it is
inefficient in zinc recovery (about 10 per cent of the zinc remains in the
retort residue), and it is very bad from an air pollution standpoint
("blue powder" or flue dust production is high). Impure zinc dust (90 -
92 per cent Zn) formed in the retort is used commercially as the zinc
dust in hydrosulfite plants and as the pigment in zinc paints. This zinc
dust varies widely in quality and price and is also derived from galvani-
(18)
zer's waste, from scrap diecastings, and from sweater billets.
-46-
-------
The charge to the horizontal retort is about 60 per cent sinter,
15 per cent coke and coal, about 22 per cent recycled blue powder, and
minor amounts of dross, salt and fluorspar. The "stuffing" and loam are
essentially sinter, with some coke breeze and clay. Typical metal con-
tents around the horizontal retorts of ASARCO Mexicana are listed in
Table 8.
The off-grade product (about 10 per cent of the furnace produc-
tion) is refined either by liquation, redistillation or electrolysis.
The table above shows that the little amount of cadmium remaining in the
sinter (less than 10 per cent of the original cadmium in the ore con-
centrate and in the roaster calcine) is carried along with the zinc to
the smelter product and to blue powder and dross.
Approximately 15 per cent of the zinc (and cadmium) in the furnace
charge winds up as blue powder, which is largely zinc oxide formed in
the condenser which does not coalesce in the liquid phase but is carried
out as flue gas. At a dust collection efficiency of 95 per cent, the
emission to the atmosphere is 0.003 kg of cadmium per kkg of zinc pro-
duced. For a domestic horizontal-retort production level of zinc of
100,000 kkg per year, the emissions would amount to 0.3 kkg of cadmium
per year from horizontal retorting.
The vertical retort is a continuous process which uses the carbon
monoxide produced by the reaction for subsequent heating; it achieves a
10 per cent energy efficiency and achieves a higher zinc recovery with
only about 3 per cent blue powder formation. ' Hbwsver, the inter-
mittent charging of new briquettes to the top of the furnace results in
the release of some metal vapors to the air collection system upstream
of the zinc condenser (this is not the case in the closed system of the
batch-process horizontal retort). The zinc is condensed in a splash con-
denser, and the off-gases are scrubbed; any solids are collected in a
baghouse, and the cleaned gases (containing CD) are burned to provide heat
for the reaction before being released to the atmosphere.
-47-
-------
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r- OJ <3< rj- ro
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0 O O O O
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Spelter (Product) :
Regular Prime Western
Off-Grade P.W.
Refined Prime Western
Dry Cell Alloy
Galvanizing Alloy
-48-
-------
The metal content of the streams around the vertical retort at the
N.J. Zinc plant at Palmerton, Pa., are:
(4)
Coked Briquette Feed
Condensed Zinc Product
Retort Residue (bottoms)
Retort Scrubber Solids
Retort Baghouse Solids
% Zn
42
99.8
7.2
91
61
% Cd
0.011
0.018
0.0013
0.198
0.22
% Pb
0.15
0.054
0.08
0.056
0.21
Cd/Zn,
%
0.026
0.018
0.018
0.22
0.36
The above data indicate that fractionation of the cadmium does
occur in the vertical retort condenser; the blue powder has a tenfold
greater cadmium concentration than horizontal retort blue powder. If
3 per cent of the zinc charged winds up as entrained solids, the emission
factor (at 95 per cent collection efficiency) is 0.006 kg of cadmium per
kkg of zinc produced. For a domestic vertical-retort production level of
zinc of 103,000 kkg per year, the emission would amount to 0.6 kkg of
cadmium per year from vertical retorting.
The electrothermal process achieves 25 to 30 per cent energy ef-
ficiency by virtue of internal heating (as opposed to heat transfer
through firebrick for the horizontal and vertical retorts). However,
more expensive metallurgical coke must be used. The Cd/Zn ratio of the
sinter feed (St. Joe Minerals) is about 0.026 per cent, the same as for
the Palmerton vertical retort; and except for the mode of energy transfer,
the processes are basically the same. Hence, the same emission factor,
0.006 kg of cadmium per kkg of zinc produced, will be assumed. For a
domestic production rate of 227,000 kkg per year of zinc, the cadmium
emissions would be 1.4 kkg per year.
In the electrolytic route to zinc, the roasting of ore concentrate
is the same as in the pyrometallurgical route (except that some more sul-
fate is tolerated in the calcine). Rather than submitting the calcine to
-49-
-------
a sintering step, the electrolytic plants process the impure zinc oxide
using wet chemistry technology. This basic difference means, for practi-
cal purposes, that electrolytic plants do not have air pollution problems
(downstream of roasting) that pervade the smelting plants.
The calcine in electrolytic plants is dissolved in sulfuric acid,
leaving behind the insoluble lead, iron, arsenic, gold and silver. This
sludge is processed or sold for the metal content. Two-stage leaching
is generally practised to limit the amount of zinc co-precipitated. Re-
cently, a significant process iirprovement has been instituted which cir-
cumvents the loss of zinc as the insoluble ferrite, ZnO-Fe20., (the cal-
cine contains 5-12 per cent iron) ; excess sulfuric acid, at 80 to 95°C,
dissolves Fe^O^). Subsequent addition of a sodium, potassium or ammonium
salt precipitates the iron as the crystalline jarosite, such as
NH4Fe (S04) (OH) , which is readily separated (as opposed to the hard-to-
settle iron hydrate). The importance of this Jarosite process is that it
boosts zinc recovery from the conventional 85 to 93 per cent to the 96 to
98 per cent plateau and also enhances the recovery of byproduct cadmium,
copper, silver and lead. The effect is to make the electrolytic route
much superior from an economics viewpoint to existing pyrometallurgical
processes (where it was highly competitive before), so that virtually all
zinc plants now under study, design or construction are electrolytic.
Other improvements to the electrolytic process, also enhancing its econo-
mics, have included fluid-bed roasters, continuous leaching and purifica-
tion, improved electrolysis, and improved materials handling such as anode
. • • (13,19)
stripping.
The filtered solution from leaching is treated with zinc dust to
precipitate cadmium, copper, nickel and cobalt; the resultant filter cake
is an important source of primary cadmium. This purification of the zinc
sulfate may be conducted in two steps: first, a deficit of zinc dust is
added to precipitate copper (lowest in the electromotive series), which
is filtered; the filtrate is then treated with more zinc dust to precipi-
tate the other impurities. The second purification sludge typically
-50-
-------
contains 80 per cent cadmium and 5 per cent zinc. Hie effectiveness of
this purification is such that the resultant solution contains less than
0.2 mg/1 of cadmium; the electrolytic zinc product typically contains
0.00002 per cent cadmium.(3f5) Ohe spent electrolyte which contains no
cadmium is recycled as leach acid, so that there is no fundamental reason
for significant waterborne wastes from this process. The leach residue
and purification sludges are recovered for their metal values, so that
land-destined pollution is avoided. It may be concluded that the electro-
lytic process for zinc recovery is essentially pollution-free, as compared
to the pyrometallurgical processes.
Others have estimated cadmium emissions to the air from zinc smel-
ters. EPA^20^ developed a factor of 150 kg per kkg of cadmium in the ore
(21)
concentrate, equivalent to 1.0 kg per kkg of zinc produced. EPA lists
the following emission factors for total particulates prior to any control
Treasures (in kg per kkg of ore concentrate):
Roasting (multiple-hearth) 60
Sintering 40
Horizontal Retorts 4
Vertical Retorts 50
Electrolytic Process 1.5
Davis ^ published a factor of 142 kg of cadmium per kkg of cadmium in
the ore concentrate; it apparently was the basis for the estimates of
EPA and of Fulkerson.
the air emission factors developed in this analysis are;
Process
Roasting
Sintering
Horizontal Retort
Vertical or Electrothermal Retort
Electrolytic Process
kg Cd emitted
per kkg of Zn
~0
0.24
0.003
0.006
~0
kg Cd emitted
per kkg of Cd
charged
~ 0
48
0.6
1.2
~0
-51-
-------
These factors were based upon a realizable collection efficiency
of 95 per cent for airborne solids. EPA's ratings for collection effi-
ciency are 90 - 96 per cent for electrostatic precipitators and 97 - 99
(21)
per cent for baghouses. Lower efficiencies may be attained by indi-
vidual installations for any number of reasons, including:
1. The lack of dust collectors
2. Aerodynamic or particulate overloading
3. Fouling of precipitators
4. Torn fabric bags or leaks in ducts
5. Smaller particles than designed for.
However, this analysis assumes that currently-available technology
of design, operation and maintenance of dust collectors will be imple-
mented in the very near future if not yet practised.
Water pollution from the primary zinc (and cadmium) industry was
(8)
studied intensively for the EPA Effluent Guidelines Division, and the
EPA Office of Solid Waste Management Programs is currently sponsoring a
study of hazardous wastes from this industry. Earlier data, prior to the
effluent guidelines study, gave cadmium concentrations in the effluents
from two zinc smelters of 0.39 and 0.9 mg/1. Data from the effluent
guidelines study showed that the cadmium concentration in raw (untreated)
wastes could be quite high and are highly variable; several measured raw
waste concentrations were 0.6, 33, 0.05, 0.3, 0.15. 0.6, 0.16, 0.51, and
0.31 mg/1. Cadmium shows up in the raw wastes from the acid plant blow-
downs and from the retort flue gas scrubber liquors.
Of particular significance was the cadmium concentration of 33
mg/1 in the raw acid plant blowdown from the N.J. Zinc plant at Palmerton,
Pennsylvania. This concentration translates into a cadmium loss in the
blowdown of 134 grams per metric ton of zinc produced, or of approximately
3 per cent of the total cadmium in the zinc ore concentrate. This signi-
ficant blowdown loss from the process, plus the cadmium lost in byproduct
acid and cadmium lost in other raw aqueous wastes f offers at least a
-52-
-------
partial answer to the "unaccounted-for" losses of cadmium from this same
(4)
plant, as reported by Yost.
Treatment of the raw aqueous wastes, which contain cadmium as well
as arsenic, mercury, selenium, and zinc, and suspended solids, is accom-
plished by liming and sedimentation. The effluent limitation guidelines
are based upon an achievable cadmium concentration, after liming to pH
of 10.5 and settling, of 0.5 mg/1, as shown in Figure 2. Upon applica-
tion of the effluent flow for BPCTCA (1977) and BATEA (1983), the effluent
guidelines for cadmium (30-day averages) are:
BPCTCA BATEA
Wastewater Flow, liters/kkg 8,350 5,425
zinc
Cadmium in Effluent, kg/kkg 0.004 0.0027
zinc
These effluent limitations guidelines apply to the entire primary
zinc (including cadmium production) industry, regardless of process.
Based upon a total production level for the industry of 490,000 metric
tons of zinc per year (Table 3), the projected waterborne cadmium dis-
charges from this industry would be 1.96 kkg (1977) and 1.32 kkg (1983).
Table 9 lists the cadmium discharges from six of the eight plants
in the industry (as of the 1971/1972 time period). The total waterborne
cadmium discharge, without the missing two plants, was about 7.5 metric
tons per year. Hence, compliance with the effluent guidelines would re-
duce this cadmium discharge by a factor of at least 4 to 5. The effluent
(8)
guideline development document also estimated that the following addi-
tional costs (in 1971 dollars) would be associated with compliance by
the entire industry:
BPCTCA BATEA Total
Capital Costs $1,515,000 $1,054,000 $2,569,000
Annual Costs 458,000 450,000 908,000
-53-
-------
(OCX)
100
10
1.0
O.I
\1
ID'2
10"
to
-4
_J
V.
V)
10
10
-6
0.011 I I I l I I I JO"7
7 8 9 K) II 12 13
pH VALUE
FIGURE 2
SOLUBILITY OF CADMIUM vs, pH
SOURCE: EPA(I2)
-54-
-------
00
I
"O 5-i
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Q ££
S*
(U
ra C
oj
w tn
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^ 11 1
£ g S
-55-
-------
These costs, of course, cannot be totally attributed to cadmium removal,
since the same lime-and-settle treatment is effective in treatment of other
heavy metals or suspended solids.
Trends in the Primary Zinc Industry
Two trends are evident in the production of primary zinc. First
is the dramatic reduction in the domestic zinc production level over the
last 20 years, and the second is the rapid phase-out of older pyrometallur-
gical smelters in favor of electrolytic plants. Both of these trends are,
of course, directly beneficial in reducing the quantity of cadmium emitted
to the air from U.S. zinc smelting operations. A side benefit of the world-
wide switchover from retorting to electrolytic zinc is that much less cad-
mium is being dissipated to consumers as an impurity in zinc. Since the
trend is towards less cadmium loss to the environment and less cadmium
dissipated in the zinc products, the result is that more recoverable cad-
mium is becoming available for the primary cadmium industry. Compared to
a ratio of cadmium to zinc in ore of 0.5 per cent, the following ratios
of primary cadmium production to primary zinc production indicate that the
maximum ratio is being approached:
.(1)
Years
1901-1910
1910-1920
1920-1930
1930-1940
1940-1950
1950-1960
1960-1968
Ratio of Cadmium Production
to Zinc Production
0.002%
0.009%
0.056%
0.17%
0.25%
0.27%
0.33%
The regulatory alternative proposed is that extremely stringent
air pollution controls be imposed. This would have the effect of en-
couraging those older smelters still with air pollution problems to close
-56-
-------
in favor of newer electrolytic plants rather than absorb the high costs
for very efficient particulate control. For example, the imposition of
a 99 per cent collection efficiency standard would reduce the estimated
cadmium emissions from sintering to 0.05 kg per kkg of zinc. A mechanism
for setting such a standard for a particular plant is to impose a limi-
tation as a small percentage of the cadmium originally in the ore concen-
trate; in this way, there is no need for determining a complete cadmium
material balance around every unit process for enforcement purposes.
Such an emission regulation should be accompanied by regulating
the maximum percentage of cadmium in the zinc produced, to prevent the
smelter from complying with the emission standard by allowing cadmium to
be dissipated in zinc.
Other accompanying regulations would effectively prohibit the
unsecured land disposal of cadmium-bearing flue dusts and sludges. The
water-borne waste limitations already exist (or are already formally pro-
posed) .
-57-
-------
SECTION V
CAEMIUM ELECTROPLATING
The data in Table 10 show that the domestic consumption of cadmium,
as a percentage of all cadmium consumed, has remained at approxiinately
the same level since 1963.
All of the cadmium used in "transportation" is for electroplating.
In 1968, of the total of 950 kkg consumed in transportation, 590 kkg was
used in motor vehicles and 360 kkg in aircraft and boats. At a production
level of motor vehicles of about 12 million per year, each vehicle would
contain about 50 grams of cadmium as electroplate (this number will be
used as the basis for estimating the cadmium flow in ferrous scrap at
steel plants). The parts plated are small springs, screws, other fasten-
ers, electrical contacts, and other small components. The use of cadmium-
plated hardware in boats is due to the superior performance of this coat-
ing in a marine environment. Cadmium-plated fasteners are used exten-
sively in aircraft; for example, of the 3.3 million fasteners in each
Boeing 747, 2.8 million do not require a coating (aluminum alloys and
titanium alloys), but 500,000 are steel alloys which are coated, many
with cadmium.
The non-transportation end items which are cadmium-plated include
nuts, bolts, washers, springs, nails, rivets, radio and television parts,
malleable fittings, electrical parts, wire screen, appliance hardware,
tools, and even casket hardware.
The thickness of most cadmium electroplate is about 0.0007 cm,
equivalent to a deposition of about 60 grams per square meter. For an
annual consumption of 3,000 kkg of cadmium for all electroplating, the
area plated is approximately 50 million square meters.
The electroplating industry is characterized by the great diversity
among the approximately 20,000 separate shops. There are captive shops,
-58-
-------
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^ r~ i — t —
-59-
-------
and there are job shops which do electroplating under contract for manu-
facturers. Half of the shops have less than 15 employees per shift, while
90 per cent have less than 50 employees per shift. Conversely, 10 per
cent of the shops account, for one-third of the total industry capacity;
and only 10 per cent of the value added for electroplating is attributed
to non-captive job shops. Both the plant size and the cadmium percentage
vary widely: cadmium plating is more than 50 per cent of the workload in
some plants and is a negligible part in other plants.
Some insight may be gained by an analysis of a representative job
(22)
plating shop. In one month, this shop plated a total of 24,260 square
meters, broken down as follows (as per cent of the total):
Plating Metal
Copper, Nickel,
Chrome
Zinc
Cadmium
TOTAL
Automatic
Rack
36.4
26.1
_2J9
65.4
Automatic
Barrel
2.4
20.3
0
22.7
Miscellaneous
Barrel
2.1
0.3
9.5
11.9
Total
40.9
46.7
12-d
100.0
Typically, this shop combines the zinc and cadmium plating in the same
department; both use cyanide baths, the same plating technology, and
(23)
(except for the anode cost) have the same plating costs.
Of interest is the breakdown, by metal, between rack (large parts)
and barrel (small parts) plating. The copper-nidcel-chrome plating is 90
per cent rack plating, the zinc plating is 60 per cent rack plating, while
the cadmium plating is only 20 per cent rack plating. Hence, at least for
this shop, cadmium plating is predominantly applied to the smaller parts.
Further, this shop is representative in that only a minor fraction of its
total plating is with cadmium, and the volume of zinc plating is signifi-
cantly higher than the volume of cadmium plating.
Each 36 cm x 91 cm barrel may typically contain 70 kg of small
-60-
-------
steel parts with a total surface area of 4.5 square meters. Hence, a
representative small parts ratio is 65 square meters per metric ton. If
60 grams of cadmium are applied per square meter, an equivalent ratio
would be 3.9 kg cadmium per metric ton of plated parts. Of course, larger
parts (rack-plated) would have a much lower cadmium-to-steel ratio.
Ihe raw waterborne metal wastes from electroplating arise pri-
marily from dragout of plating solution, by the plated parts, from the
plating baths to the rinse tanks. Other important sources of raw aqueous
wastes are discarded plating baths, spills and overflows from plating
baths, equipment cleanup wastes, and sludges which accumulate in plating
baths. Many plating shops treat wastewaters for cyanide by oxidation
with chlorine or with sodium hypochlorite, but prior to 1972, few plating
(2)
(4)
shops treated wastewaters for cadmium removal. Some extreme cases of
cadmium pollution from electroplating have been noted in the literature,
such as a 3.2 mg/1 cadmium concentration in ground water in Long Island,
and a cadmium concentration of 300 mg/1 in an effluent in Southern Cali-
fornia (with resultant soil concentrations of up to 30 ppm cadmium).
The standard treatment for cadmium (and other metals) in electro-
plating wastewater is the precipitation as the hydroxide or carbonate
n ?? ?4i
(using lime, caustic soda, or soda ash) at pH 9.2 to 10.9,Vi' ' ' with
subsequent clarification or filtration. Efforts to reduce the raw wastes
are also being implemented, such as the countercurrent flow of rinse wa-
ter, and "housekeeping" improvements in the process area. Some approaches,
such as segregation of cadmium wastes from other metal wastes with subse-
quent recovery via ion exchange and the use of caustic soda/soda ash solu-
tions as a first rinse after the plating bath, have been implemented in a
.. , . (22,24)
few plants.v '
The raw waste load varies substantially in the electroplating in-
dustry. The raw waste from zinc plating (using similar equipment and
technology to cadmium plating) may be estimated from a zinc concentration
prior to treatment of 32 mg/1 and from a water use of 0.65 liters per amp-
(24)
hour at one plant. Using a typical current efficiency of 60 per cent
-61-
-------
for zinc plating from a cyanide bath, the calculated raw waste load is
28 kg per metric ton plated (2.8 per cent of the zinc plated).
A correlation of seven electroplating shops revealed that the 1972
state-of-the-art of wastewater treatment could be expressed (regardless of
metal plated) as a treated discharge of 3.5 kg metal per metric ton plated
(24)
(0.35 per cent of the plated metal). Hence, comparison of this factor
with the above raw waste factor indicates that average treatment is close
to 90 per cent effective in the 1972 time frame. In addition, the use of
these two factors applied to 3,000 kkg per year of cadmium plated means
that the cadmium discharged in the effluent is 10.5 kkg per year and that
the cadmium in the waste treatment sludge is 73.5 kkg per year.
(24)
The proposed 1977 effluent guidelines for zinc, copper, nickel,
and chromium electroplating are 80 mg of metal per square meter plated
(per plating operation). Assuming that since cadmium plating is virtually
2
the same as zinc plating, the 80 mg/m limitation would be equivalent to
1.33 kg cadmium per metric ton of plated cadmium (0.133 per cent). Using
the above raw waste load factor of 28 kg per kkg plated, an implied treat-
ment efficiency is 95 per cent. Applying these 1977 projections to 3,000
kkg per year of cadmium plated means that the cadmium discharged in the
effluent would be 4.0 kkg per year and that the cadmium in the waste treat-
ment sludge would be 80 kkg per year.
The proposed 1983 effluent guidelines for electroplating (again
extrapolated to cadmium) is zero discharge of cadmium. The technology
basis for this limitation includes in-process changes to reduce the raw
waste load (i.e., countercurrent rinses) plus total recycle of process
water after chemical treatment, plus recovery of the metals by evaporation,
ion-exchange, or reverse osmosis. This technology implies that neither
waterborne nor land-destined wastes would occur from electroplating in
1983.
In the case of cadmium, the separately-proposed toxic substances
effluent limitations may hasten the zero-discharge iitplementation.
-62-
-------
The capital investment required to achieve the 1977 BPCTCA ef-
fluent limitation was estimated to be $150,000 per 100 square meters per
hour of plating capacity; and the additional capital investment for
achieving the 1983 BATEC zero discharge effluent limitation was estimated
(24)
to be $100,000 to $200,000 per 100 square meters per hour. On the
basis of a total cadmium plating industry capacity of 25,000 square meters
per hour (50 million square meters per year and 2,000 operating hours per
year), the investment costs for the industry would be $37.5 million for
BPCTCA plus $25 to $50 million for BATEC. For comparison, the value added
from cadmium plating is approximately $3.20 per square meter or $160 mil-
lion per year. It was estimated that the incremental cost of pollution
control would be less than 5 per cent of the plating cost for BPCTCA and
(24)
would be approximately 10 per cent for BATEC.
In addition to the wastewater treatment costs, the residual sludges
must be either processed for cadmium recovery or disposed of in an environ-
mentally adequate manner. The disposal costs are estimated to be $400 per
kkg (dry solids basis) for chemical fixation and landfill, or $600 per kkg
(dry solids basis) for secured landfill of the sludge. ' The quantity
of dry solids as Cd(OH)~ in residual sludges implied by the 1977 guidelines
is 104 kkg per year for the entire cadmium plating industry. Hence, the
disposal costs would be about $50,000. In contrast, the value of the
cadmium in this sludge, at $8.80 per kg, amounts to $720,000 per year as
an incentive for recovery.
The costs for electroplating, exclusive of the metal costs, are
in the range of $2.70 per square meter. For cadmium plating, about 60
grams are used per square meter, with a cost (at $8.80 per kg) of about
$0.55 per square meter plated, bringing the total cost to $3.25 per square
meter. In comparison, the cost of zinc (at $0.50 per kg and at 100 grams
per square meter) is about $0.05 per square meter plated, for a total
plating cost of $2.75 per square meter.
Pollution control requirements imposed by local, state, and federal
standards, have increased the costs for electroplating. Most platers
-63-
-------
have already adopted some type of waste treatment; the initial emphasis
has been on cyanide and on hexavalent chromium, but recent attention has
been on other heavy metals including cadmium. The higher toxicity of
cadmium relative to zinc has brought about, and will continue to generate,
much more restrictive effluent standards for cadmium. This is expected
to cause the cost of cadmium plating to rise faster (compared to zinc
electroplating). There is a movement away from cadmium in electroplating
because of pollution control requirements, because the cost of cadmium is
a larger percentage of the total electroplating cost than it is for zinc,
and because the price of cadmium has increased and its availability has
been curtailed.
Auto manufacturers have begun to use chromate and oil corrosion
protection in place of cadmium plating for some applications, and others
have begun to use zinc plating in place of cadmium plating for corrosion
protection and tin for electrical parts. However, it seems probable that
since cadmium has always been more expensive than its potential substi-
tutes, substitutes have been already made where possible. Much of cadmium
plating is for high-quality parts, or critical parts, or in applications
(military and aircraft) where firm specifications impede changes and sub-
stitutions. Cadmium plating is already (and always has been) a very small
part of the metals finishing industry. Hence, since cadmium plating is an
expensive specialty, and, as such, is demanded where substitutes are not
totally equivalent, the price of cadmium would have to be significantly
higher (perhaps $20 per kg) before price would have a substantial effect
on demand.
The control alternatives include, of course, the effluent limita-
tion guidelines and the toxic substances guidelines discussed earlier.
Since wastewater treatment would result in an inter-media transfer of
cadmium from water to land-destined waste, an effective control strategy
must include regulations for environmentally-adequate land disposal of
residuals as well as waterborne waste regulations.
-64-
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Many electroplating shops are in highly-industrialized cities, and
have historically discharged into municipal sewer systems. Of 53 electro-
plating facilities evaluated in the development of effluent guidelines,
25 discharged into municipal sewer systems rather than directly to
.rms <
(27)
(24)
streams. New York City alone has 250 electroplating firms discharging
a total of 30 kg of cadmium per day into the city's sewers.
Four kinds of undesirable effects occur as a result of the dis-
charge of cadmium into municipal wastewater systems:
1. In those areas with combined sewers and with fre-
quent overflows, a portion of the cadmium is
directly released to the receiving waters.
2. Much of the cadmium will not be removed by
municipal sewage treatment plants, and will
be released to the receiving waters.
3. Cadmium in excessive quantities may poison
biological treatment operations, such as
secondary wastewater treatment or anerobic
sludge digestion.
4. Some of the cadmium will be adsorbed into the
sludge. If the sludge is incinerated, the
volatile cadmium oxide wDuld not likely remain
as part of the ash. Scrubbing systems would
return the cadmium to the wastewater plant,
eventually leading to discharge in the ef-
fluent. The cadmium oxide not scrubbed out
of the flue gas would be directly released to
the environment. If the sludge is landfilled,
it is likely that some would be leached, pol-
luting surface and ground waters. If the
sludge is applied to agricultural land, the
cadmium uptake by plants would lead it into
the food chain.
-65-
-------
For the above reasons, it is imperative that effluent limitation
guidelines also include pretreatment standards which effectively pro-
hibit the discharge of cadmium into municipal sewer systems.
Another control strategy is a full or partial ban on cadmium
electroplating. Besides the direct elimination of cadmium pollution
from the electroplating industry, the limitation or cessation of
cadmium electroplating would result in a major reduction in the cadmium
emitted by the steel industry in their processing of scrap. Moreover, a
ban on cadmium electroplating would halve the cadmium use (and dissipation)
and reduce imports to zero. It is implied, of course, that such an
option would be coupled with control measures restricting cadmium emissions
at zinc smelters.
-66-
-------
SECTION VI
CADMIUM IN PLASTICS
Cadmium compounds are used extensively for formulating plastics
molding compounds in tws ways: as a heat stabilizer and as a pigment.
Much of the plastic products containing cadmium wind up in tne municipal
solid waste stream, and the portion of this stream that is incinerated
releases cadmium to the environment via the inefficiency of incinerator
flue gas scrubbing systems, the wet scrubber effluents, and the land-
filling of incineration residues.
Cadmium Pigments - Use Pattern
Table 11 lists the quantity of cadmium used in manufacturing pig-
ments for all uses, and the quantity of cadmium colorants used in the
plastics industry. The actual cadmium content in colorants depends upon
the particular pigment (cadmium sulfide or cadmium sulfoselenide) and
whether the colorant is a pure toner or a lithopone. Of the total quantity
of cadmium colorants consumed for all uses (2,500 metric tons per year),
approximately 700 kkg is in the form of C.P. toners (i.e., pure compounds)
with an average cadmium content of 70 per cent; and 1,800 kkg is in the
form of lithopones with an average cadmium content of 25 per cent. Hence,
the overall percentage of cadmium in all colorants is about 38 per cent.
This infers that approximately 75 per cent of all cadmium pigments are
consumed in plastics; an independent industry estimate was 90 per cent.
The pigments are also used in interior water-base paints, durable
enamels, coated fabrics, textiles, rubber, printing inks, artists' colors,
glass, and ceramic glazes.
The data in Table 12 show the cadmium colorant consumption in plas-
tics in relation to other colorants used in plastics. These data show that
white and black colorants constitute 86 per cent of the total consumption in
plastics; and that cadmium colorants account for only 2 per cent of all
-67-
-------
TABLE 11
CONSUMPTION OF CADMIUM PIGMENTS
(28)
SOURCES: BUREAU OF MINES,
MODERN PLASTICS
(29)
1968
1969
1970
1971
1972
1973
1974
Cd Content in Pigments for
All Uses, kkg of Cadmium
per Year
1,110
1,100
970
1,010
1,230
Cd Colorants for
Plastics, kkg of
Colorants per yr
2,000
2,140
2,090
2,180
2,300
2,630
2,750
-68-
-------
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8
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r^
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o o m o O
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rH in rH rH CTl
-------
colorants and 13 per cent of the non-black-or-white colorants. Much of
this distribution is a result of the wide range in colorant prices, shown
in Table 13. The very high price for the cadmium reds and maroons is the
result of the high price of selenium.
The plastics molder will generally use the cadmium lithopone over
the C.P. toners, since they provide more tinctorial power per dollar.
However, the C.P. toners are used where physical properties of the plas-
tic are critical since less is used. In a great many cases the cadmium
colorants are used together with titanium dioxide to give a range of color
shades.
Colorants are generally used in the range of 1 to 4 per cent of the
resin (depending to a large extent upon the tinctorial power of the col-
orant) , with, an average of about 1.25 per cent. Hence, the colorant costs
per kilogram of resin fall into these general ranges:
Iron Oxides, Carbon Black, TiCL 0.4 - 1.1 cents/kg
Chrome Yellows, Iron Blues, Molybdate 1.8 - 2.8 cents/kg
Orange
Organics 6 - 20 cents/kg
Cadmium Lithopones 7 - 16 centsAg
CP Cadmiums 16 - 36 cents/kg
A perspective is gained by these representative (1973) resin price levels;
the cost of the orqanics and cadmium colorants are a maior portion of the
materials cost:
Low-density polyethylene, Polyvinyl chloride $0.27Ag
High-density polyethylene, Polystyrene 0.31Ag
Polypropylene 0.37/kg
Polyvinyl Acetate, Melamine/Urea 0.44/kg
Phenolics 0.48/kg
ABS/SAN 0.55Ag
Acrylics 0.80 Ag
Epoxies 1.30 Ag
Nylon l.SOAg
-70-
-------
TABLE 13
RECENT PRICES OF PLASTICS COLORANTS
SOURCES: MODERN PLASTICS,(29) DCMA(30)
Colorant
Titanium Dioxide
Carbon Black
Iron Oxides (Yellow &
Iron Blues
Chrome Yellows
Molybdate Oranges
Cadmium Lithopones:
Yellows
Oranges
Reds
Maroons
CP Cadmiums:
Yellows
Oranges
Reds
Maroons
Organics
Price, $Ag (June 1974)
$ 0.88
0.30
Red) 0.45
2.20
1.45
1.85
5.90
7.90
9.80
12.70
13.30
19.00
24.00
28.70
5.00-15.00
-71-
-------
The data of Table 14 showing the 1974 colorant consumption by
resin type indicates that colorants are widely disseminated among resin
types (and so among end products) . However, the high price of cadmium
colorants discourages their use in cheap, disposable end items; these
colorants are more generally used for durable, high-quality end items.
Table 15 lists the yellow, orange, red, and maroon colorants (the
colors of cadmium pigments) widely used for each type of resin. It is
apparant that cadmium pigments are widely used in all types of resins and
so are widely disseminated in plastic end products. It may therefore be
concluded that the distribution of the 500 metric tons per year of ele-
mental cadmium in plastics (as colorants) is homogeneous with respect to
ultimate incineration of plastic end-items.
Table 15 also shows that the list of alternate colorants is fairly
extensive for many of the resins, particularly for low density polyethylene
and polyvinylchloride. On the other hand, few if any substitutes are
available for ABS, acetal, nylon, polycarbonate, fluoroplastics, diallyl
phthalate, and silicones. Of these resins, several have critically high
heats of processing which limit the choice of colorant; among these are
the fluorocarbons, the nylons, and polycarbonates. Silicones, while
not processed at high temperatures, are used in service at high tempera-
tures. Others of these resins exhibit chemical reactivity which limits
colorant selection; included are the acetals, acrylics, polyesters, epoxies,
and urethanes. It should be noted that where cadmium colorants have few
alternates, the resins are also relatively high-priced, so that cadmium
colorants may be justified.
It is important to emphasize that cadmium pigments have properties
which cannot be matched by any potential substitute (for the same color) .
The cadmium pigments are totally non-bleeding (not soluble in the resin)
and are alkali-resistant; these properties make them especially suitable
for plastic automobile interiors. Cadmium pigments yield very high opacity
(for applications where this is important), and extremely bright colors
(where identification, visibility, or safety is involved). The high-
temperature properties of cadmium pigments, as mentioned previously,
-12-
-------
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-73-
-------
TABLE 15
YELLOW, ORANGE, RED AND MAROON COLORANTS
WIDELY USED WITH VARIOUS RESINS
(32)
SOURCE: MDDERN PLASTICS ENCYCLOPEDIA.
Colorant
Inorganics -
Cadmium Sulfide
Cadmium Sulfoselenide
Iron Oxide Yellow, Red
Chrome Yellow, Orange
Molybdate Orange
Ultramarine Red
Organics -
Quinacridone Red
Anthrapyrimidine Yel.
B.O.N. P.ed
Itiioindigo Red
Rod Lake R Red
Pyra'-solone Red
Anthraquinone Red
Isoindolinone Red
Perylene Red
Anthraguinone Yellow
Benzictene Yellow, liR
Hansa Yellow
Dis-Azo Yello, Or. , Rec
Pyranthrone Orange
GR Ferinone Orange
Isoindolinone Or. , Yel.
Flavanthrone Yellow
X
X
X
X
Acetal 1
X
X
X
X
•H
rH
I
X
X
X
X
X
X
Cellulosics 1
X
X
X
X
X
X
X
X
X
I
X
X
X
X
I
iH
"o
9
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
HD Polyethylene |
X
X
X
X
X
X
X
X
X
X
X
Polypropylene |
X
X
X
X
X
X
X
X
X
Polycarbonate |
X
X
X
Fluoroplastics |
X
X
Polystyrene-GP |
X
X
X
X
X
X
X
X
Polystyrene-IR |
X
X
X
X
X
X
Vinyls-Flexible |
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
I
in
1
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Amino Resins |
X
X
X
X
X
X
X
X
X
Diallyl phthalate j
X
X
X
X
X
Phenol Formaldehyde]
X
X
X
X
X
X
X
X
X
X
X
X
Polyester, Alkyd |
X
X
X
X
X
X
X
X
X
X
X
Silicones |
X
X
X
X
5?
^r
X
X
X
V
X
X
X
X
X
X
Po lyur ethane |
X
X
X
X
X
X
X
X
X
X
X
-74-
-------
are quite important in certain resin systems. It should be mentioned that
the entire heat history of a pigmented resin is critical; even though some
organic pigment may survive a once-through molding process, it may not be
suitable for scrap rework (and so the molding economics would suffer).
Potential substitutes for cadmium colorants, such as the chrome
colors, the lead colors, and the polynuclear aronatics, pose their own
toxicity problems which must, of course, be taken into account in formu-
lating control regulations.
The difficulties in finding direct substitutes for cadmium colorants
are, to a large measure, dictated by aesthetics. At one extreme, either
white (titanium dioxide) or black (carbon black) might be used for all
resin systems at low prices and with high performance. Realistically,
however, the aesthetics of color (other than white or black) are part
of our commercial world, and price differentials are being justified for
this purpose.
In summary, then, it appears that the high price of cadmium pig-
ments, as compared to others, has already made the choice of cadmium pig-
ments highly selective (i.e., where no cheaper substitute will suffice to
meet the coloring requirements of the resin system and of the end-item
application).
In light of the above discussion, a potential control strategy
would be a partial ban on the use of cadmium colorants in plastics. Exemp-
tions might be based upon:
1. The necessity for the specific color and color
quality in the end item.
2. The necessity for the particular resin system for
the end item (i.e., would an alternate resin-
colorant combination satisfy product requirements).
3. Ihe demonstration that the end item would not
quickly or largely enter the municipal solid
waste stream.
-75-
-------
4. The demonstration that the quantity of such end
items is not large.
5. The demonstration that substitutions create
pollution problems equal in magnitude and
severity.
Manufacture of Cadmium Pigments
Cadmium pigments (red, orange, yellow and cadmium lithopone) are
all generally produced by the method described on Figure 3. The amounts
and types of reactants are varied to produce the desired color. Cadmium
red is essentially cadmium selenide; the yellow is a mixed cadmium-zinc
sulfide, and the orange is somewhere in betoken. Cadmium lithopone is a
mixed barium sulfate-cadmium sulfide co-precipitate made by using barium
sulfide to precipitate the product instead of sodium sulfide used for the
other cadmium colors. The quantities noted on Figure 3 are a material
balance referenced to 1000 mass units of pigment produced.
The losses to the atmosphere from the calcination step were esti-
mated by Davis to be 8 kg per kkg processed (0.8 per cent). The Davis
estimate is based upon efficient dust collection equipment (i.e., baghouses)
which return much of the calcination dust to the process.
Waterborne wastes arise from the filtration and washing operation,
both as dissolved cadmium salts in the spent mother liquor and washings,
and as suspended solids. The raw waste load (before treatment) was de-
termined for similar inorganic pigment processes (chrome pigments, lead
pigments and zinc pigments) to be in the range of 10 to 20 kg per kkg
(33)
product. ' Neutralization and precipitation with lime, with subsequent
clarification in settling ponds, was found to remove 90 to 95 per cent of
the heavy metals, resulting in a waterborne discharge of about 0.3 kg of
metal per kkg of product pigment. The estimated capital cost for this
treatment is about $55 per kkg of annual production, and the estimated
total costs (capital recovery and operating cost) are about $20 per kkg
-76-
-------
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-77-
-------
produced. Further, it was found that the majority of the inorganic pig-
ments industry already meets this level of treatment. An independent EPA
(34)
study gave results consistent with the above data.
Technology for treating zinc yellow waterborne wastes, first by
ion exchange and then with soda ash (to precipitate the highly insoluble
zinc carbonate) resulted in a further reduction in the effluent to approxi-
mately 0.02 kg of metal per kkg of product. This technology seems directly
transferable to cadmium pigments.
In plants producing only cadmium colors, the solid waste generated
by wastewater treatment can be (and is) recycled back to the process. This
cannot be done at large chrome pigment complexes where cadmium colors are
made and a single large treatment facility exists for the entire complex.
The other solid waste stream destined for land disposal contains slightly
contaminated dry chemical bags and in-plant product transfer containers
(non-metallic) .
The quantity of the cadmium pigments in the land-destined waste
stream was estimated as 10 to 20 kg per kkg of product as wastewater treat-
ment residuals plus 0.5 kg per kkg of product as residuals in discarded
(25)
containers. In addition, this waste stream contains, on a dry basis,
approximately 200 kg/kkg product of non-hazardous materials such as filter
aids, calcium sulfate (from lime treatment of sulfates), water treatment
residuals, and discarded containers.
At present, although the pigments industry has spent large sums of
money for wastewater treatment, the land-destined waste stream is not dis-
posed of in an environmentally-acceptable manner. Land dumping, disposal
in general-purpose landfills, pond storage, and even disposal into municipal
sewer systems are prevalent. Leaching of the cadmium to contaminate both
surface and ground water is a distinct probability. A small fraction of
the plants, expected to increase drastically by 1977, practice waste dis-
posal in a secured landfill (landfill integrity with leachate control and
monitoring of surface and ground water). It is also estimated that 25 per
-78-
-------
cent of the industry's cadmium residuals may be recovered instead of dis-
posed by 1983; and that chemical fixation of the non-recoverable wastes
(now in the pilot-plant stage) would become operational.
Cost estimates for land-dumping or unsecured landfill disposal
were $1.90 per kkg of product pigment; costs for secured landfilling or
chemical fixation are estimated as $7.50 per kkg of product pigment.
The quantity of cadmium pigments produced in 1974 is estimated as
2,500 kkg (of which 1,100 kkg is elemental cadmium). Using the factors
developed above, the annual emission of cadmium in effluent water is 0.75
kkg. The quantity of cadmium pigments currently disposed of to land in
an inadequate manner is 37.5 kkg per year, containing 16.5 kkg per year
of elemental cadmium. Hence, the total estimated loss of elemental cad-
mium to the environment is 26 kkg per year from the manufacture of cadmium
pigments.
Based upon the implementation of EPA regulations for the land dis-
posal of hazardous wastes and for waterborne wastes, only the 9 kkg per
year of airborne cadmium (increased to perhaps 13 kkg per year by growth
of the industry) is projected for the 1983 time period. The additional
abatement cost to the industry is estimated as $19,000 per year for
environmentally-adequate land disposal; to be added to the existing cost
of $60,000 per year for wastewater treatment and to the existing cost for
air pollution control.
Heat Stabilizers for Plastics
Cadmium-containing heat stabilizers find widespread use in retarding
discoloration due to the breakdown of polyvinyl chloride resin during the
molding operation. Without stabilizers, HC1 starts to evolve at about
95°C, and discoloration of the resin occurs with a loss of 0.1 per cent
HC1. High molding temperatures are needed for polyvinyl chloride because
of its relatively high melt viscosity. For rigid compositions (with little
plasticizer), a molding temperature of about 230°C is typical; for flexible
compositions with higher levels of plasticizer, molding temperatures of
-79-
-------
150°C are typical. Recently, multi-screw extruders have been developed
which reduce the temperature-time exposure of PVC resins, thereby re-
ducing the stabilizer requirement by 50 to 74 per cent.
There are four major categories of heat stabilizers for PVC. First
are metal soaps of zinc or cadmium, which prevent early discoloration for
a short period of time, after which discoloration proceeds rapidly. Second
are metal soaps of calcium or barium (or lead), which are not effective in
preventing early slight discoloration but which resist serious discoloration
for substantially longer periods. Combinations of these two types of
stabilizers are effective in preventing both early and later discoloration;
actually, their longer-time effectiveness is much greater together than would
be expected from the effect of each alone.
This synergism may be illustrated by the following data:
Parts per 100 of PVC Resin
Barium Ricinoleate
3.0
2.0
1.5
1.0
0.0
Cadmium Ricinoleate
0.0
1.0
1.5
2.0
3.0
Heat Stability,
Minutes
420
780
720
450
390
Further synergism is obtained by the addition of a third category
of stabilizers to the above two. This third category includes epoxy com-
pounds and phosphites, which have no color-retarding effect by themselves
but which appreciably increase the effectiveness of the metal carboxylate
stabilizers. The fourth category of heat stabilizers are the organotin
compounds, which are extremely effective at low concentrations.
The barium-cadmium stabilizers presently dominate the flexible PVC
market. They are used extensively for calendering and plastisols. The
lead stabilizers are used primarily for electrical products because of
their low water absorption. Calcium-zinc stabilizers are used primarily
-30-
-------
for food-grade flexible PWC, since the Food and Drug Administration does
not permit the use of barium-cadmium (or lead) in food-contacting
(packaging) applications. The tin stabilizers find use in rigid PVC formu-
lations; the FDA permits the use of octyl tin stabilizers for bottles, and
they are used for PVC pipe and conduit.
The stabilizers vary widely in price:
Barium - cadmium stabilizers, $0.65 - $1.30Ag
Calcium - zinc stabilizers, $1.10 - $2.20Ag
Butyl tin stabilizers, $2.75 Ag
Octyl tin stabilizers, $6.00 Ag
The consumption of heat stabilizers, of total PVC resin, and of
the elemental cadmium consumed in heat stabilizers, is listed in Table 16.
The consumption of all heat stabilizers is between 2.0 and 2.5 per cent
of the PVC resin consumption; and the barium-cadmium stabilizers have
accounted for almost 50 per cent of the total stabilizers consumed.
Furthermore, the average cadmium content in barium-cadmium stabilizers
is about 7 per cent.
The dominance of barium-cadmium stabilizers has been the combined
result of good performance and lowest cost. The organotin stabilizers have
superior performance characteristics, but they are relatively higher priced
per unit of resin processed despite lower stabilizer requirements. Calcium-
zinc stabilizers are used as direct substitutes for barium-zinc stabilizers
in flexible food packaging, and the FDA has proposed (Federal Register,
April 12, 1974) extending the ban on cadmium colorants and stabilizers to
food-contact articles in household, food service, and food-dispensing use
(containers, pitchers, tumblers, measuring scoops, mixing bowls, canisters,
butter dishes, ice buckets, etc.). The plastics industry, responding to
increased pressure based on toxicological reasons, has been developing
calcium-zinc stabilizer formulations which, taking advantage of the syn-
ergistic action of other ingredients, are approaching the performance of
the barium-cadmium stabilizers.
-81-
-------
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-82-
-------
In summary, then, it appears that the organotins are at present
direct substitutes for the cadmium-containing stabilizers; but are higher-
priced. In addition, the calcium-zinc stabilizers have already been sub-
stituted for the barium-cadmium stabilizers where food considerations have
demanded, and the technology appears close at hand to permit the complete
substitution of calcium-zinc for barium-cadmium in terms of both perfor-
mance and costs. The apparent regulatory alternative, therefore, is a com-
plete ban on cadmium-containing heat stabilizers, with perhaps a two-year
transition period for industry to accomplish the substitution.
-83-
-------
SECTION VII
MCKEL-CAI3"fflJM BATTERIES
The manufacture of nickel-cadmium storage batteries is the fastest-
growing segment of the cadmium industry. The demand for nickel-cadmium
batteries almost doubled in 1973 and is expected to settle into an annual
growth pattern of between 15 and 20 per cent over the next few years. A
major constraint to even more rapid expansion is the limited availability
of cadmium to the battery industry.
In 1972, a total of 16.3 million nickel-cadmium batteries were
produced (11.7 million sealed and 4.6 million vented). The total value
of shipments was 47.6 million dollars. The total 1972 production of nickel-
cadmium batteries was 4,005.6 kkg. Battery sizes ranged from small button
cells less than 14 mm in diameter to large rectangular cells of 113 mm
high by 91 mm long by 38 mm wide. Ten plants produce nickel-cadmium bat-
teries; the four largest are General Electric (Gainesville, Fla.),
Burgess Division of Gould (St. Paul, Minn.), Union Carbide (Cleveland,
Ohio), and Marathon (Waco, Tex.)
Nickel-cadmium rechargeable storage batteries are used for alarm
systems, emergency lighting, calculators, pacemakers, portable appliances
and tools, walkie-talkies, and for heavy equipment uses in buses, diesel
locomotives, airplanes, and spacecraft. Calculators are currently the
biggest market for the battery. A new nickel-cadmium cell, introduced
in 1973, charges to 90 per cent of its capacity in 15 minutes and is use-
ful for portable garden and power tools and for hobby equipment.
There are two distinct types of nickel-cadmium cells — the pocket
plate (Jungner type) cell and the sintered plate cells. Industry sources
have indicated that only a limited number of pocket plate type batteries
-84-
-------
are now being produced in the U.S. The production has switched to the
sintered plate cell.
The positive and negative plates of the pocket plate cell are
usually similar in construction, consisting of perforated pockets which
contain the active materials. The pockets for both positive and negative
plates are made from nickel-plated perforated steel ribbon. Pockets of
the negative plates are filled initially with cadmium oxide or cadmium
hydroxide, either of which is reduced to metallic cadmium on charging.
Some manufacturers of these cells add iron (5 to 30 per cent) to the
cadmium in order to obtain the required degree of fineness of the cadmium.
The pockets of the positive plate are filled with nickel powder.
(37)
Wilson dismantled a number of 36 kilogram aircraft batteries
and analyzed their constituents:
Cadmium 8.1 per cent
Nickel 25.3 per cent
Iron 6.5 per cent
Cobalt 0.5 per cent
KOH electrolyte 16 per cent
The plates were separately analyzed:
Negative Plate, 39.9% Cd, 42.9% Ni
Positive Plate, 2.2% Cd, 76.2% Ni
The half-reactions of the nickel-cadmium cell are:
Negative Plate, 2NiOOH + 2H20 + 2e~ = 2Ni(OH)2 +
Positive Plate, Cd + 2OH~ + Cd(OH)2 + 2e~
20H
The cell must be protected against absorption of carbon dioxide
from the atmosphere; otherwise, CdGO, and NiCO 'NiO are readily formed.
Industry sources indicate that the production of pocket-plate type
batteries does not generate any water-borne hazardous waste. This is
because the active chemicals used are solids and not solutions or pastes.
When good housekeeping methods are used within the plant, cells rejected
-85-
-------
in quality control operations are the only waste generated. These cells
/og\
are reclaimed through, sale to scrap processors.
The manufacture of sintered plate batteries, however, does generate
hazardous waste. This type of cadmium battery differs materially in con-
struction and performance from the pocket plate battery described above.
This variety of battery contains a cadmium anode, a potassium hy-
droxide electrolyte, and a nickel oxide cathode. For the electrodes,
sintered placques containing the active materials are used. In one pro-
cess, the placques are made by impregnating binder materials with nickel
and cadmium nitrate salts. The nickel and cadmium nitrates are converted
to hydroxides in potassium hydroxide solution. The plates are then washed
thoroughly and dried in a hot oven. The impregnation cycle is repeated to
deposit the desired amount of active material. The plates then go through
a formation treatment which removes impurities and brings the active
materials to a condition similar to that existing in working electrodes.
The cell is assembled into final form using an absorbent plastic separator
and a nickel-plated steel case. With the addition of the alkaline electro-
lyte, they are ready for electrical testing, packing, and shipping.
There are currently three distinct manufacturing processes used for
preparing the electrodes of the sintered plate batteries. The preceding
paragraph described the worst case from an environmental standpoint of the
three, due to the high concentration of cadmium and nickel compounds con-
tained in the wash water. The other processes in use are:
a) An electrolytic deposition process which deposits
active materials directly on the sintered plates -
this process produces wastewater containing nickel
and cadmium compounds, though the amount is not as
great as in the impregnation process described
above; and
b) A pressed powder process involving active materials
mixed with binders in a dry powder form - the powder
-86-
-------
mix is pressed onto a wire mesh or expanded metal
grid in a mold. This is a dry process and no
wastewater is involved.
A mass-balanced process flow diagram for the impregnation-sintered
plate process is shown in Figure 4. The wastes from the production of this
type of battery include the following:
a) Wastewaters containing cadmium and nickel salts
together with potassium hydroxide. The source of
this waste is the washing steps. This waste is
estimated to amount to 3.24 kg nickel nitrate and
7.96 kg cadmium nitrate per 1000 kg of product in
the untreated wastewater.
b) Solid wastes recovered from treatment of wastewaters.
These are estimated to contain cadmium hydroxide
(5.339 kg) and nickel hydroxide (1.660 kg) per 1000
kg of product; and
c) Rejected batteries from the test and package step.
They contain 1.47 kg nickel and 5.20 kg cadmium per
1000 kg of product.
This data represents information supplied by three plants repre-
senting 42 per cent of the U.S. production. The waste factors for nickel
and cadmium in the rejected cells were calculated from plant supplied
data. The waste factors for cadmium hydroxide and nickel hydroxide in
the wastewater treatment sludge were estimated on the basis of the amount
of cadmium in the treated effluents from two plants and the reported ef-
(38)
ficiencies of the impregnation process.
The total quantity of cadmium in the sludges from wastewater treat-
ment and in the scrap battery waste stream is 9.30 kg per kkg of product.
These two solid waste streams are not, however, universally destined for
land disposal; an estimated 50 per cent of the plants sell wastewater treat-
ment sludges for reclamation, and an estimated 75 per cent of the plants
-87-
-------
NICKEL PLATED STEEL ^
NICKEL POWDER — ^
NICKEL NITRATE
SATURATED SOLUTION
* r
IMPREGNATING
KOH 20% SOLUTION — ^
2.6 FELTED NYLON
364 NICKEL PLATED — ^
STEEL CASE
52.8 KOH.LiOH — fel
SIM
516
SINTERED
STRIP FORMED
CADMIUM
NITRATE SOLUTION
~~* r~
DRYING
^
IMMERSION
*
WASHING
|
ASSEMBLY
|
ELECTROLYTE
ADDITION
|
TEST
AND
PACK
* *
IMPREGNATING
WATER EFFLUENT
/ 3.24 Ni(NOj)2
/ 7.96 Cd (N0j)z
r CAUSTIC
^ TREATMENT
TO SEWER SLUDGE (DRY)
OX»5« CdfOH)2 5.339 Cd(OH)2
OI33 Ni(OH>2 1.660 Ni(OH)2
^ REJECT
•* CELLS
IOOO PRODUCT W7 Ni
5.20 Cd
FIGURE 4
PLIFIED DIAGRAM OF
MAJOR OPERATIONS IN NICKEL-CADMIUM SINT
STORAGE BATTERY MANUFACTURE
-PLATE
-88-
-------
sell reject batteries to reprocessors. As a result of the above solid
waste factors and of the estimated extent of reclamation, the total quantity
of cadmium (as elemental Cd) disposed of on land in 1973 was estimated as
8.4 kkg. This disposal is currently environmentally inadequate, consisting
of simple land dumping and on-site ponding of sludge, since leaching and
contamination of both surface and ground waters are probable. Such dis-
posal methods are estimated to cost $133 per metric ton of solid waste
(dry basis), or $320 per metric ton of elemental cadmium in the waste;
for a total 1973 cost of $2,700.
The projected quantity of cadmium (for 1977) to be disposed of on
land in the same inadequate manner is 11.4 kkg; the increase over 1973
due to a projected growth of the industry is partially offset by some
increase in either reclamation of the wastes or secured land disposal.
The disposal costs would amount to $3,700.
By 1983, it is projected that no solid wastes will be disposed of
on lard in an environmentally unacceptable manner. In all likelihood
(especially in view of the increased price and short supply of cadmium)
most of the cadmium in the irxlustry's solid wastes will be reclaimed;
where reclamation is impractical, either secured landfill or chemical
fixation of sludge should cost $200 per metric ton of solid waste (dry
basis), or $480 per metric ton of elemental cadmium in the waste. The pro-
jected quantity of cadmium to be disposed of by 1983 is 9.1 kkg, so that
the total cost would be $4,400.
These total disposal costs are low chiefly because the cadmium-
containing wastes are highly concentrated; this is quite a different situa-
tion from many where the hazardous contituent is dispersed in a much larger
quantity of other materials.
According to Figure 4, the treated wastewater still contains 0.0735 kg
of elemental cadmium per kkg of product; at a 1973 production level of
4005.6 kkg, the cadmium loss to wastewater amounts to 0.294 kkg per year.
According to Davis, the cadmium emissions to the atmosphere
-89-
-------
from the manufacture of nickel-cadmium batteries is 1 kg per kkg of
cadmium charged. Hence, the annual emission to the atmosphere is about
1 kkg.
Wilson investigated the reclamation of cadmium from discarded
batteries and reported 94 per cent cadmium recovery. This process was
based upon a roasting step at 288° to 316°C (550° to 600°F), a leaching
of the cadmium oxide with ammonium nitrate to form the highly soluble
+2
Cd(NH_). complex ion and subsequent precipitation of cadmium carbonate
with carbon dioxide. Alternately, 99 per cent recovery of cadmium from
the plates was achieved by vacuum distillation (0.1 mm Hg at 650° to
800°C). These emerging technologies, plus the existing reclamation of
prompt battery scrap, plus the stripping technology used in the cadmium
electroplating industry, provide evidence that recycling of nickel-cadmium
batteries is technically feasible. The institutional aspects of battery
recycling are already in effect for larger storage batteries (i.e., the
lead-acid battery industry regularly practices trade-in as well as re-
covery from junk automobiles). However, the mechanism for recovery of
spent smaller batteries (a large proportion of the nickel-cadmium battery
market) is not yet developed.
In addition to the cadmium reclamation technologies of vacuum dis-
tillation and leaching with an ammonium salt, another process is amalgam
electrolysis. Many companies are now processing nickel-cadmium battery scrap
but primarily for the nickel values rather than for the cadmium values. It
appears, then, that as the nickel-cadmium battery use increases, a cortmeasurate
increase in reclamation will follow. A special incentive such as a refundable
deposit, or a requirement for nickel-cadmium batteries to be labelled with re-
clamation instructions, are two ways to encourage recycle of used batteries..
-90-
-------
SECTION VIII
SECONDARY METALS INDUSTRY
Secondary Non-Ferrous Metals
The secondary zinc and copper industries may initially be suspect
as a source of cadmium pollution because of the high-temperature processing
involved. The Bureau of Mines Office of Mineral Resource Evaluation esti-
mates that in the 28-year period from 1940 to 1968 the accumulation of these
metals in the in-use reservoir was 23/200,000 kkg of copper and 3,820,000
kkg of zinc. Of this reservoir, the secondary metals industry processed
(in 1967) the quantities listed in Table 17.
Although the total zinc-base scrap processed amounts to 155,000
kkg per year, the bulk of the scrap is zinc die-casting alloys. These
alloys utilize special high-grade zinc only, which contains no more than
0.004 per cent cadmium. Hence, the cadmium in the zinc-base secondary
metals processed amounts to an estimated 6.2 kkg. In addition, since the
basic recovery process for secondary zinc is distillation and collection
of zinc and zinc oxide, effective dust collection is universally practised.
At a 90 per cent collection efficiency, the quantity of cadmium emitted
would be only 0.6 kkg per year.
A total of 1,168,000 kkg per year of copper-base scrap is processed
in high-temperature blast furnaces, melting furnaces, and sweating furnaces;
of which 60 per cent is brass and bronze (the remaining 40 per cent contains
(39)
no cadmium). The zinc content of these alloys as as follows:
Per Cent Zinc
Commercial bronze 10
Red brass 15
Low brass 20
Cartridge brass 30
Yellow brass 35
Muntz metal 40
-91-
-------
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-92-
-------
Free-cutting brass 34
Naval brass 39
Architectural bronze 40
Of the 1,168,000 kkg per year of copper-base scrap processed, 60
(28)
per cent is brass or bronze. If these alloys contain an average of
30 per cent zinc, the quantity of zinc in processed scrap is 210,000 kkg
per year. However, much of this zinc is directly reused in the production
of secondary copper alloys; in 1971, a total of 148,000 kkg of secondary
zinc (70 per cent of the total processed) was so used. The remainder of
the secondary zinc processed, 62,000 kkg per year, is refined at high
temperatures, and the cadmium in this zinc would be in the form of dusts
and fumes.
Although the ASTM grades of zinc primarily used for copper-based
alloys permit up to 0.5 per cent cadmium, the data of Tables 7 and 8 indi-
cate that pyre-metallurgical zinc contains no more than 0.035 per cent
cadmium, and electrolytic zinc typically contains 0.00002 per cent cadmium.
At the higher cadmium level, the 62,000 kkg of refined secondary zinc
would contain 22 kkg of cadmium; and if the dust collection efficiency
were 90 per cent, the quantity of cadmium emitted would be 2.2 kkg per
year.
This estimate of cadmium loss may be high since the cadmium content
of secondary copper-base metals might be appreciably lower than was assumed.
For one, much of the zinc in the scrap brass and bronze might actually be
electrolytic, with much less cadmium than the assumed 0.035 per cent. For
another, it must be recognized that the recycle ratio of copper-base metals
is quite high; from 1967 through 1971, the secondary copper production was
about equal to domestic mine production. The implication of this extensive
recycling is that the cadmium in scrap can, of course, only be lost once;
secondary brass as scrap must contain less cadmium than primary brass as
scrap.
-93-
-------
It must be emphasized that the cadmium concerns in the non-ferrous
secondary metals industry are not the result of the intentional use of
cadmium (i.e., cadmium electroplating), but are the direct result of the
cadmium impurity in zinc/copper alloys. One potential regulatory posture
would be to require the use of only high-grade zinc in the production of
primary brass and bronze; i.e., to prohibit the use of high-cadmium zinc
for these alloying purposes. Although a significant time lag would be
involved before the total effects are felt in the secondary metals indus-
try (since there is so much recycling of copper-base metal), this alterna-
tive regulation would in the long run prove most effective. The technology
for almost totally removing cadmium at the primary zinc source is proven
and economical electrolytic plants are now favored over retort plants for
reasons other than eliminating cadmium pollution. Conversely, regulations
aimed at the secondary copper-base metals industry to strengthen existing
air pollution control regulations (i.e., to enforce universal use of bag-
houses to collect cadmium-bearing dusts) would be an alternative with
shorter-term effectiveness.
Secondary Ferrous Metals
Cadmium enters the primary iron-and-steel industry as cadmium-
bearing ferrous scrap, in the form of cadmium electroplate or cadmium-
contaminated galvanized coatings. The cadmium is entirely volatilized
at steel-making temperatures so that the product steel contains no cadmium.
Some of the cadmium is released to the environment via the inefficiencies
in dust-catching equipment, while the cadmium in the captured dusts may
also enter the environment because of inadequate disposal and/or use of
these dusts.
Previous estimates of the quantity of cadmium involved in steel-
making ' used aggregate data for a cadmium-to-steel ratio in scrap,
basically derived from the total quantities of cadmium used in electro-
plating and galvanizing as compared to the total quantities of steel
produced. The estiitate made in this study is intended to differentiate
-94-
-------
among steel products consumed so that a cadmium-to-steel ratio specific
to scrap may be estimated and used.
The ferrous scrap specifications for No. 1 heavy melting steel,
No. 1 bundles, and other No. 1 grades exclude scrap that is metal coated
and old automobile body and fender stock. It is clear, therefore,
that No. 1 ferrous scrap contains no cadmium. No. 2 scrap (heavy melting
and bundles) is the grade where auto stock and other coated iron and steel
is classified; actually, No. 2 scrap is largely composed of obsolete auto
and truck bodies.
Approximately 7 million junk automobiles per year are processed by
(41)
the secondary ferrous metals industry. A typical junk automobile,
(40 41)
weighing 1,450 kg, yields 1,150 kg of No. 2 bundle steel. ' Hence,
junk automobiles are the source for about 8 million metric tons per year
of No. 2 ferrous scrap. Table 18 lists the recent movement of No. 2
(28,40)
scrap.
These data show that the 8 million kkg per year of No. 2 scrap from
auto bodies constitutes about 85 per cent of all domestic generation of old
No. 2 scrap, and about 75 per cent of all such scrap (including the home
scrap). Hence, the assumption that the cadmium content of the No. 2 scrap
consumed in steel making is equivalent to the cadmium content of auto
scrap is justified.
The discussion of electroplating resulted in a cadmium content of
50 grams per auto via electroplated steel. Virtually all should show up
in the No. 2 ferrous scrap portion of the processed junk auto, since no
cadmium plating of nonferrous metal (or plastics) is conducted. The
question also arises whether cadmium from sources other than electroplating
is in an automobile. Cadmium colors and stabilizers in the polyvinyl
chloride would not be retained in the ferrous scrap portion; the plastic
would either be burned off or left behind in the magnetic recovery of
a shredded auto. Similarily, cadmium in the zinc oxide of tires would
not be carried with the No. 2 scrap portion.
-95-
-------
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-96-
-------
A typical auto contains 25 kg of zinc die-cast alloy, but at
(23)
a maximum cadmium concentration of O.OQ4 per cent for the Special High
Grade used in die-casting, the quantity of cadmium per auto would amount
to only one gram. Moreover, much of the Special High Grade zinc is electro-
(3 5)
lytic, with a typical cadmium content of 0.00002 per cent, ' much less
than the maximum; and in any event, most of the zinc die cast alloy is not
carried with shredded ferrous scrap but is rejected by the magnetic separa-
(42)
tion. Hence, compared to the cadmium from electroplated steel, the
cadmium from zinc die cast may be neglected.
The cadmium in an auto's galvanized parts most likely would be
carried into the processed ferrous scrap. Prime Western grade zinc, used
widely for galvanizing, typically contains 0.035 per cent cadmium. The
quantity of galvanizing zinc used for automobiles is not directly known,
but a maximum value may be obtained by difference. In 1968, the consump-
(43)
tion of all zinc by the transportation industry was 360,000 metric tons.
It has also been estimated that of the total die-cast alloy consumed
(500,000 kkg), approximately 60 per cent (or 300,000 kkg) is consumed by
(43)
automobile manufacturers. Hence, the zinc consumption by automobile
manufacturers for galvanizing is no greater than 60,000 kkg per year;
equivalent to 5 kilograms per car. The maximum amount of cadmium, then,
would be 1.75 grams per car from galvanizing.
The conclusion reached, then, is that the total quantity of cadmium
per car distributed in the 1,150 kg of No. 2 scrap is 52 grams; and so the
cadmium concentration of No. 2 scrap is deduced to be 0.045 kg per metric
ton.
Based upon the above reasoning, the conclusion that only No. 2 scrap
contains cadmium, and the annual consumption of No. 2 scrap by the iron and
steel industry (about 7.6 million metric tons per year), the calculated
quantity of cadmium entering the iron and steel industry is 340 metric tons
per year.
Other estimates have been made based upon aggregate factors for the
-97-
-------
concentration of cadmium in scrap iron and steel. Davis used concen-
tration factors of 0.025 kg cadmium from electroplating and 0.0015 kg
cadmium from galvanizing per metric ton of all old steel scrap; which
when applied to a consumption of 35 million metric tons per year of old
scrap yielded a quantity of cadmium entering the iron and steel industry
of 930 metric tons per year. Fulkerson recalculated this quantity
based upon concentrations of cadmium in finished steel to be 0.037 (electro-
plated) and 0.00125 (galvanized) kg per metric ton; and an annual consump-
tion of 26 million metric tons of steel scrap; to yield a quantity of cad-
mium entering the iron and steel industry of 990 metric tons per year.
An independent estimate of the quantity of cadmium involved in
steel-making was made in this study, using the uncontrolled dust emission
(21)
factors for each process of EPA,v ' the 1972 and 1985 steel production
statistics for each process, ' and tte experimental cadmium concen-
(4)
trations in flue dusts from each process of Yost: '
Dust Produced, kg/kkg steel
Steel Produced, Million
kkg/yr
Cd concentration in
dusts, ppm
Dust Produced, kkg/yr
Cd in Dusts, kkg/yr
1972
1985
1972
1985
1972
1985
Open
Hearth
4.15
31.7
12.7
250
132,000
53,000
33
13
Basic
Oxygen
25.5
67.6
115.2
80
1,720,000
2,940,000
137
235
Electric
Arc
4.6
21.5
53.5
580
99,000
246,000
57
143
Total
-
120.8
181.4
-
1,951,000
3,239,000
227
391
-98-
-------
The total cadmium, 227 kkg/yr (1972) and 391 kkg/yr (1985), is in good
agreement with the 340 kkg/yr estimated from the analysis of scrap flow,
and verifies this lower estimate (as compared to previous estimates). The
total quantity of dusts is very high; at an average cost for secured land-
fill of $70 per metric ton, the costs for land disposal in an environ-
mentally adequate manner (considering the high cadmium concentrations)
are:
1972, $137 million per year
1985, $227 million per year
The lower quantity (340 kkg per year) calculated in this study is
believed to be the more precise value because it is based upon the specific
scrap grade that contains cadmium rather than upon aggregate values for all
scrap. The data of Yost at an open hearth furnace with an electrostatic
precipitator yielded a factor of 0.085 x 10~6 kkg of cadmium emissions per
kkg of steel produced; or a factor of 1.4 x 10~6 kkg of cadmium emissions
per kkg of No. 2 scrap consumed at this furnace. Applying this factor to
the total U.S. consumption of No. 2 scrap, 7.6 million kkg per year, yields
a cadmium emission from the iron and steel industry of 10.5 kkg per year.
This emission is 3.1 per cent of the 340 kkg/year of cadmium entering the
industry in No. 2 scrap; a percentage entirely consistent with the operating
efficiencies achieved by electrostatic precipitators.
(4)
The data of Yost for the cadmium concentrations in the collected
dusts from the three major steel processes show a direct correlation with
the relative quantities of scrap used in the charge:
Total Scrap Used,
kkg per kkg of Product
Cd Concentration in
Collected Dusts, ppm
Open Hearth
Basic Oxygen
Electric Furnace
0.50
0.33
1.00
250
80
580
-99-
-------
The reason for this wide variation is fundamentally that the carbon
in pig iron is a fuel in the open hearth and basic oxygen processes for
providing the required heat in steel making. The basic oxygen process
utilizes more of this heat of combustion, thereby conserving auxiliary
fuel, than the open hearth process. Hence, the basic oxygen process needs
more carbon-containing pig iron (and therefore may use less scrap) than
the open hearth process. At the other extreme, the electric furnace pro-
cess provides all of the heat from an auxiliary source, and therefore may
use 100 per cent scrap. Recent efforts have been directed towards in-
creasing the allowable scrap content of the basic oxygen process, by
preheating the scrap and by adding a fuel such as calcium carbide.
On the other hand, the utilization of No. 2 scrap is product-
oriented. The permissible level of No. 2 scrap, regardless of process,
is determined by the permissible level of impurities in the product steel.
Copper, nickel and tin are neither removed in the steel making slag (as
is aluminum), nor are they removed by vaporization (as is Cd, Zn, and Pb);
they are carried through, to the finished steel. The desired copper con-
tent of finished steel is:
Low quality steels, 0.5 per cent
Average quality, 0.3 per cent
High quality, 0.1 per cent
Deep-drawing quality, 0.05 per cent
In contrast, the copper content of ferrous scrap is:
No. 1 Factory Bundles, 0.06 per cent
No. 1 Industrial Heavy Malting, 0.10 per cent
No. 1 Railroad Heavy Melting, 0.16 per cent
No. 1 Dealer Bundles, 0.12 per cent
No. 2 Car Sides, Bundles, 0.27 per cent
No. 2 Dealer Heavy Metal, 0.40 per cent
No. 2 Dealer Bundles, 0.48 per cent
No. 2 Shredded Scrap, 0.22 per cent
-100-
-------
Other factors influence the utilization of No. 2 scrap. One is the
availability of home scrap in the steel mill; the use of purchased scrap
(including No. 2 scrap) nay be influenced by the difference between total
scrap requirements and home scrap availability. Another factor is that
the impure No. 2 scrap requires more fuel, more heat time, and more lime
than factory bundles. A very important factor is that No. 2 scrap intro-
duces uncertainty into steel making; a margin of safety is applied so that
the highly-variable impurities of No. 2 scrap do not compromise product
quality.
In projecting the flow of cadmium junto steel making via No. 2 scrap,
two points must be made. First, the recent efforts towards improving the
quality of No. 2 scrap (i.e., shredding and magnetic separation) may in-
crease the utilization of No. 2 scrap; the cadmium content of the scrap
would not be lowered by these techniques, so that more cadmium would flow
into steel making. Second, the recent growth of the electric-furnace
"minimills" scattered around the country and heavily utilized to make
lower-grade steels from local No. 2 scrap would decentralize the cadmium
flow and therefore make it more difficult to control. As the data of
Table 19 indicate, the steel industry has been experiencing a major change
in the relative importance of the three major processes.
In past years, the collected dusts from steelmaking furnaces
(which contain iron oxide) were sent to the sintering plants along with
ore fines, coke breeze, limestone and recycled material from various mill
processes. The purpose of the sintering process is to form larger ag-
glomerates from the fines for recycle to the blast furnace. However, the
sintering operation has been under recent attack because of its poor record
of air pollution, and the recent trend has been to dispose of cadmium-
bearing furnace dusts as landfill rather than to recover the iron values
by sintering and recycling. Little is presently known of the environmental
hazards of land-destined dusts containing cadmium, which of course involve
much more cadmium than the cadmium emitted to the atmosphere.
-101-
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TABLE 19
CHANGE IN STEEL PRODUCTION FOR EACH MAJOR PROCESS
SOURCES: BUREAU OF MINES,(28) REGAN(
Year
1950
1955
1960
1965
1968
1969
1970
1971
1972
1980*
1985*
Production, Millions Metric Tons Per Year
Open Hearth
78.1
95.5
78.3
85.5
59.6
55.1
43.5
32.2
31.7
22.7
12.7
Basic Oxygen
—
0.3
3.0
20.8
44.3
54.6
57.4
57.9
67.6
95.2
115.2
Electric
5.4
7.3
7.6
12.5
15.3
18.2
18.3
19.0
21.5
40.8
53.5
Total
83.5
103.1
88.9
118.8
119.2
127.9
119.2
109.1
120.8
158.7
181.4
Projections
-102-
-------
The sintering operation itself, being a high-temperature process,
results in some cadmium being released to the atmosphere despite dust con-
trol equipment. In this case, from the standpoint of cadmium (as opposed
to total dusts), the sintering operation is contraproductive, since double
exposure of furnace dusts occurs (once in the furnace and once in the sinter
plant). The cadmium in the furnace dusts that winds up in the sintered
agglomerates is most likely an ultimate constituent of the blast furnace
slag (if it is not emitted again as blast furnace dust or even downstream
as steel furnace dust).
Apparently the cadmium in the ferrous scrap, being relatively
volatile, is exposed to at least one and possibly multiple high-temperature
operations where some of it escapes to the atmosphere. Since no cadmium
leaves the steel mill with the steel, the cadmium not lost to the atmosphere
is a constituent of other waste streams from the steel mill.
Several regulatory alternatives are suggested to control the re-
lease of cadmium into the environment from the steel industry:
1. Banning or severely restricting the use of cadmium
electroplating in automobile manufacturing. If
technically feasible, this option would effectively
reduce the flow of cadmium into steel making since
auto scrap is the dominant route.
2. Stringent air pollution control regulations for
steel making, including the mini-mills. A dust
capturing efficiency of 97 per cent or better
should be imposed. It may be feasible to im-
pose guidelines in terms of cadmium emissions
permitted per unit of No. 2 scrap used. If a
guideline was based on the finished steel pro-
duction level, the effect would be a disincentive
for using No. 2 scrap.
-103-
-------
Stringent regulations regarding the handling and
disposal of the collected dusts from steel making,
since this waste stream contains the bulk of the
cadmium. The fine dusts should be prevented from
being dispersed by the wind or by storm water
drainage. Land disposal should be adequately pro-
tected so that surface and ground waters are not
contaminated. Research aimed at recovering the
cadmium (and zinc and lead) values, as well as the
iron values in this steel making dust, should be
encouraged.
-104-
-------
SECTION IX
CADMIUM AS AN IMPURHY
The dissemination of cadmium to the environment is attributable not
only to the production and use of cadmium and its compounds as discussed
in the previous sections, but also to the unintentional prevalence of
cadmium as an impurity in several important materials.
Rubber Tires
The estimate of cadmium emissions from rubber tire wear made by
Davis, widely quoted by others, ' ' is 5.2 metric tons per year.
This estimate is based upon a cadmium content in tread rubber of 20 ppm,
a loss of 1.27 kg of tread rubber per tire in 32,200 km (20,000 miles) of
12
use, and a total United States travel of 1.62 x 10 vehicle-kilometers
(1.01 x 10 vehicle-miles).
The source of cadmium in rubber tires is the cadmium impurity in
the zinc oxide, which is used as an activator for organic accelerators
for the vulcanization process. From 3 to 5 kilograms of zinc oxide are
used per hundred kilograms of rubber. Table 20, which lists the recent
consumption data for zinc oxide, shows that 53 per cent of the total is used
in rubber manufacturing.
Three processes are in use for making zinc oxide. The American, or
direct process, for making zinc oxide is similar to the primary zinc pro-
cess; it is made from roasted zinc ore concentrate. As in the primary zinc
process, the roasted ore is sintered with coal and the sinter is then re-
torted. In the manufacture of zinc oxide, the retorting is conducted in the
presence of air, so that finely-divided zinc oxide is recovered rather than
molten zinc. In the French, or indirect, process variation, zinc metal is
first recovered, then vaporized and oxidized. The third process is a pro-
prietary wet process for purifying crude z.inc oxide recovered from lead
smelters.
-105-
-------
TABLE 20
CONSUMPTION OF ZINC OXIDE
SOURCE: BUREAU OF MINES
1967
1968
1969
1970
1971
1972
Total Consumption,
kkg/year
165,000
194,000
199,000
193,000
206,000
223,000
Consumption in Rubber,
kkg/year
86,000
101,000
105,000
101,000
113,000
117,000
-106-
-------
•Ihe wet process accounts for approximately 10 per cent of the total
production. C33) In 1972, 47,100 kkg of slab zinc were used for the produc-
tion of zinc oxide, C28} so. that the French process accounted for 58,700 kkg
of zinc oxide, or 26 per cent of the total. Hence, the American process
(by difference) accounted for 64 per cent of the total production.
Ihe quantities of impurities in commercial zinc oxide manufactured
by St. Joe Minerals are:
PbO, %
CdO, %
Fe203, %
American Process
ZnO
0.009
0.010
0.015
French Process
ZnO
0.0015
0.0006
0.005
A more recently-acquired estimate from an industrial source for
American Process ZnO was 100 to 300 ppm of cadmium. Hence, assuming 100
ppm in American Process ZnO and assuming a production level of 150,000
kkg per year of American Process ZnO, there are 15 metric tons per year
of cadmium impurity in American Process zinc oxide.
The price differential between the two grades of zinc oxide is
rather small (Chemical Marketing Reporter, March 31, 1975):
ZnO pigment, American Process (lead-free), $0.88 - $0.92/kg
ZnO pigment, French Process (regular), $0.92 - $0.94/kg
The American (or direct process) zinc oxide contains comparable
quantities of cadmium to the metallic zinc products; the processes are
directly comparable. The French (or indirect process) zinc oxide contains
much less cadmium since a zinc purification step may be added or since
electrolytic zinc may be used.
-107-
-------
At an average zinc oxide usage ratio of 4 parts per hundred of
rubber, the cadmium content of the rubber would be 4 ppm (American ZnO)
and 0.2 ppm (French ZnO). These levels are considerably lower than the
:ires
(ID
(45)
20-90 ppm reported for rubber tires by Lagerwerff and Specht, used as
a basis for the Davis estimate.
A possible explanation for this large difference in cadmium content
(less than 4 ppm vs 20-90 ppm) is that other zinc oxide producers permit
higher cadmium concentrations, on the order of 0.05 to 0.25 per cent. This
is likely if zinc oxide is made from collected dusts and fumes (which may
contain up to 25 per cent cadmium).
The straightforward control strategy would be to regulate the
cadmium content of rubber tires to 4 ppm, which would force the cadmium
content of the zinc oxide used to 100 ppm or less. Such a regulation,
while permitting the use of American process zinc oxide, would reduce the
cadmium emissions from the estimated 5.2 kkg per year to approximately 1
kkg per year.
Of course, the corollary regulation would be the stringent control
of cadmium emissions from the zinc oxide manufacturing process.
Zinc for Galvanizing
The grades of zinc used for galvanizing contain approximately
0.035 per cent cadmium. From 1968 to 1972, the quantity of zinc
used for galvanizing has been relatively stable at 450,000 metric tons
per year, and has remained at approximately 37 per cent of the total zinc
consumed. Hence, it is estimated that approximately 160 metric tons per
year of cadmium is unintentionally involved in galvanizing.
Goitroercial quality zinc coating on steel sheet has an average
thickness of about 0.003 centimeters, and the weight of zinc is about
2 (23)
0.191 kg/m . More than 50 per cent of all the zinc used for gal-
vanizing is consumed for sheet and strip. However, the specific quantities
of zinc vary considerably with the shape of the steel work, as Table 21
indicates.
-108-
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TABLE 21
GALVANIZING EFFICIENCIES AND COATING WEIGHTS
SOURCE: DAESEN '
Product
Sheet
Pipe
Wire
Sheet Ware
Wire Cloth
Pole Line Hardware
Structural
Castings
Zinc Melted,
kg/kkg Product
84
83
42
228
240
79
62
104
Pet. of Zn Melted
Remaining on Work
83
68
65
82
80
45
67
48
Coating Weight,
Pet. of Product
7.4
6.0
2.7
18.6
19.8
3.5
4.1
4.9
-109-
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Galvanized steel products are used widely in construction; in
heating, ventilating and air conditioning; in plumbing, and in many other
applications. The corrosion protection afforded by the zinc coating is
by two mechanisms: first, because zinc covers the steel (and corrodes
more slowly), and second, because in galvanic corrosion, zinc sacrifically
oxidizes. The point is that the zinc coating (and of course the 0.035 per
cent of cadmium) is expected to be released to the environment.
The data of Table 22 indicate that corrosion is very rapid in
atmospheres containing SCL and moisture, as in industrial indoor or out-
door use. In only a few (4 to 12) years, all of the cadmium in galvanized
coatings in such atmospheres is released to the environment. For estimating
purposes, it is hypothesized that the cadmium annually released to the
environment is 25 per cent Cor 40 kkg/yr) of the cadmium in new galvanized
products each. year. The remainder is assumed to be in non-corrosive atmos-
pheres, otherwise protected from corrosion (painted or masked by other parts),
consumed in the scrap metal industry, or disposed of in the solid waste
stream.
As in the zinc oxide case, the straightforward control strategy
vould be the regulation of the cadmium content. In 1972, virtually 50
(28)
per cent of all the slab zinc produced was special high grade, v ' with
(23)
a maximum cadmium content of 0.004 per cent. Much of this, used
primarily in die-cast alloys, was electrolytic zinc. Approximately 60
per cent of the domestic zinc production is pyrometallurgical, and this
is the primary source for the lower grades of zinc (Prime Western and
Select) that are used for galvanizing.
Some of the pyrometallurgical zinc is presently refined to meet
the large market for special high grade zinc. Two processes are in common
use for the refining of zinc to remove cadmium: redistillation and electro-
lytic. An appropriate control alternative, based upon existing technology,
-110-
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00
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-111-
-------
would be to require that all zinc used meet the 0.004 per cent cadmium
specification. This would eventually reduce the cadmium emission from the
corrosion of galvanized steel by ten-fold. A long lead time is involved
in reducing the cadmium emissions because of the huge quantities of galvanized
steel already produced over the years.
As previously stated, such a restriction must be accompanied by
restricting cadmium emissions during zinc production.
Given sufficient lead time to enable the industry to install
sufficient pyrometallurgical zinc refining capacity, the problem of
limiting the cadmium content in zinc may be defined as one of equity be-
tween the pyrometallurgical producers and the electrolytic producers.
The current price differential is only about $Q.Q2 per kilogram
(American Metal Market, March. 24, 19751:
Prime Western Grade, $0.85 - $0.86/kg
High Grade, $0.87 - $0.88/kg
Special High Grade, $0.87Ag
In comparison, it is estimated that in light of increased energy costs,
the cost of refining Prime Western zinc would be $0.04 per kilogram. The
value of the recovered cadmium (perhaps 0.35 grams per kilogram of zinc)
would be no more than $0.003 per kilogram of zinc. Hence, there would be
a net penalty of about $0.02 per kilogram for the pyrometallurgical zinc
producers as compared to the electrolytic producers.
More must be learned of the economic impacts of a regulation ban-
ning the sale of all zinc and zinc products with more than about 40 ppm
of cadmium before such a regulation is promulgated. The decision comes
down to a case of conflicting inequities. On the one hand, it may be
inequitable to penalize the pyrometallurgical zinc producers with respect
to the electrolytic zinc producers. On the other hand, it may be inequitable
to penalize one class of cadmium dissipators (i.e., requiring costly waste-
water treatment for electroplaters to reduce their 80 kkg/year effluent
while permitting the zinc industry to dissipate 160 kkg/year of cadmium).
-112-
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Phosphate Fertilizers
Fulkerson estimated that the cadmium content of commercial
phosphate fertilizers (at 2 to 20 ppm) amounted to 23-230 metric tons
per year; based upon a 1968-69 consumption of about 11,000,000 kkg per
year of fertilizers with a P^ content of 3,800,000 kkg.
The consumption of fertilizers is expanding at a 5 to 7 per cent
(47)
growth rate in North. America:
1965
1970
1975
1980
3.6 million metric tons P205/year
5.0 million metric tons
^
6.3 million metric tons PJX/year
8.0 million metric tons P^C^/year
Hence, the Fulkerson estimate of cadmium in consumed fertilizers would
double before 1980.
The zinc and cadmium concentrations in several commercial fertilizers
were measured by Yost:
.(4)
Fertilizer
Diammonium Phosphate
Diammonium Phosphate
lybnoammonium Phosphate
Triple Super Phosphate
Composite Data
Fertilizer
Composition
18-46-0
16-48-0
13-52-0
0-46-0
Zinc,
ppm
122
160
92
95
114
Cadmium,
ppm
9.0
14.3
3.5
7.2
7.8
Zn/Cd
13.6
11.2
26.3
13.2
14.7
It is readily apparent that the Zn/Cd ratio is much lower than the
(2)
value of 200 normally found in natural materials. Page attributes
this to the cadmium accumulations by marine animals from sea water, and
the deposition of the hard parts of these animals to form marine phos-
phorite deposits such as the Florida phosphate fields.
-113-
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If Yost's composite cadmium concentration of 7.8 ppm is used, this
is equivalent to a value of about 16 ppm based on P2°^' so t^iat t^le cadmium
estimate for 1975 becomes 100 kkg/year and that for 1980 becomes 130 kkg/year.
The cadmium, and zinc in phosphate rock exists as replacement atoms
for calcium in. the apatite, and so accompany the P^O in the ore beneficia-
^* *J
tion process (which concentrates P^O- from 15 to 31 per cent) and in the
manufacture of phosphoric acid (by either the wet or dry process). Cadmium
and zinc are highly soluble in mineral acids, so that the normal phosphoric
acid clarification step does not remove them. The treatment with sulfide
to remove arsenic from food-grade phosphoric acid probably would not be ef-
fective, since cadmium sulfide has a solubility in the range of 5,000 ppm
(12)
at low pH. The fate of cadmium in the solvent-extraction commercial
process for recovering and purifying phosphoric acid is not known, but it
is possible that the cadmium salts are not extracted by the organic sol-
(47 48)
vents, so that they may be separated from the phosphoric acid. '
For the sake of completeness, the possibility of cadmium entering
phosphate fertilizers via the sulfuric acid (in addition to the phosphate
ore source) was investigated. It has been previously mentioned that by-
product sulfuric acid from zinc smelters may contain 20 to 60 ppm of
cadmium. It is also likely that by-product sulfuric acid from copper
and lead smelters also contains cadmium in smaller concentrations.
Of the total U.S. sulfuric acid production (in 1973) of 37.2
million metric tons (as 100 per cent H^SO.); only 10.9 per cent, or 4.05
million kkg, was produced from all smelter off-gases; and only 2.6 per
cent, or 0.97 million kkg, was produced from the roasting of zinc con-
(49)
centrates. Hie zinc smelters (Table 4) are located in Pennsylvania,
Texas, Oklahoma, Idaho, and Illinois — far removed from the Florida
phosphate fields; but a significant amount of wet-process phosphoric
acid is manufactured close enough to the smelters so that by-product
sulfuric acid may conceivably be used.
-114-
-------
The total quantity of wet-process phosphoric (as P~CL) manufactured
(49)
in 1973 was 5.7 million kkg. Since approximately 2.8 kkg of 100 per
/47\
cent H2SO is required per kkg of P2°5' t^ie sulfuric acid consumed
in wet-process phosphoric acid manufacture was approximately 16 million
metric tons. This is 43 per cent of the total demand for sulfuric acid,
enhancing the probability that at least some zinc smelter acid is being
used for fertilizer manufacture.
The possibility was also investigated for cadmium entering the
fertilizer process via an impurity in elemental sulfur used for sulfuric
acid manufacture. This possibility was discounted, however, as Frasch pro-
cess sulfur typically contains less than 5 ppb of cadmium.
In summary, the dissipation of cadmium via phosphate fertilizers is
large, and is growing at a rate which would double the Pulkerson estimate
before 1980. Since phosphoric acid is the precursor for most phosphate
fertilizers, any control options aimed at removing the cadmium from ferti-
lizers would logically be applied to the phosphoric acid manufacturing
segment. The technology for removing cadmium is not apparent, and it is
recommended that research be aimed at this objective.
Another control option is the regulation of the cadmium content of
sulfuric acid that is used for phosphoric acid manufacture, with the ob-
jective of preventing the use of smelter by-product sulfuric acid for this
purpose.
Wst-process phosphoric acid is also used in the manufacture of
calcium phosphates for animal feeds. The potential for cadmium entering
the food chain in this manner should be investigated.
Coal
The Fulkerson^ ' estimate for cadmium in coal was based upon an
annual consumption of 450 million metric tons (500 million short tons);
and upon a cadmium content in coal of 0.25 to 2.0 ppm. These data resulted
in a cadmium quantity associated with coal of 110 to 900 kkg per year. At
a representative single value of 1 ppm, the annual quantity of cadmium is
450 kkg.
-115-
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Because of the uncertain fate of the cadmiura, FulkersorL did not
(97}
apply a factor for air pollution abatement. Klein and Russell, based
upon the work of Billings and Matson, used a 90 per cent collection
efficiency for cadmium (and for other metals in coal except mercury) for
(4)
a power generation station's electrostatic precipitator. Yost measured
an emission rate for cadmium in the stack gas of a coal-burning power plant
(downstream from an electrostatic precipitator) of 0.324 mg/sec. With an
assumed coal consumption rate of 1.7 kg/sec (commeasurate with a reported
steam generation rate of 13.9 kg/sec), the cadmium emission rate was 0.19
mg per kg of coal burned; compared to a representative value of cadmium
in coal of 1 mg/kg. The primary zinc industry achieves 95+ per cent
collection efficiency for cadmium in electrostatic precipitators and
baghouses. In comparison, Yost's data for a municipal refuse incinerator
with a wet scrubbing-system resulting in less than one per cent collection
(4)
efficiency for cadmium.
Based upon these observations, a cadmium collection efficiency of
85 per cent has been assumed for present-day coal-burning electric power
stations, generally equipped with electrostatic precipitators. Since
about 97 per cent of all the coal is burned in such facilities, and 3 per
cent is burned in residential or commercial furnaces with no air pollution
control, then the overall distribution of the cadmium will be:
Air Emissions, 17.5 per cent or 80 kkg/yr
Residues and Captured Fly Ash, 82.5 per cent or 370 kkg/yr
The cadmium in the fly ash will, in general, be partially accessible to
the environment via dusting and via leaching.
Of major importance in this estimate of cadmium emissions from
coal is the projected increases in coal utilization due to the energy
situation. Table 23 lists the rather stable coal statistics for the past
five years, but the 1980 projection reflects an annual growth rate of
over 6 per cent. The impact is that the domestic consumption in 1980 is
-116-
-------
expected to be around 760 million metric tons, 70 per cent higher than
the base for the Fulkerson estimate. Hence, the cadmium quantity could
be increased to around 760 kkg per year by 1980.
The data of Table 23 also show that in 1974, 72 per cent of the
total coal consumed was for electric power generation. Of the remainder,
17 per cent was consumed by coke plants, 11 per cent by other manufacturing
(15)
and mining industries, and only 1 per cent was delivered by retail dealers.
The proportion for electric utilities is expected to increase by 1980.
Much research is currently underway in developing coal conversion
processes (synthetic oil and synthetic low-and-high-Btu gas). The EPA is
actively investigating the fate of the heavy metals in these conversion
processes. In one preliminary study of a high-Btu gasification pro-
cess, starting with Pittsburgh No. 8 coal containing 0.78 ppm of cadmium,
24 per cent of the cadmium was volatilized in the first stage (430°C and
1 atmosphere), an additional 23 per cent in the second stage (650°C and 74
atmospheres), and an additional 15 per cent in the third stage (1000°C and
74 atmospheres), leaving 38 per cent of the original cadmium in the residue.
As expected, the more volatile trace elements (Cd, Eg, Pb, As, Se) wound
up prijnarily in the prpduct gas, while most of the less volatile trace
elements (Cr, Ni, and V) remained primarily in the residues.
The research, emphasis on removal of trace elements from synthetic
gas and oil, plus the regulatory emphasis on air pollution abatement from
power generation stations and other stationary sources, should result in
proportionately less cadmium being emitted to the air from coal (or coal
products) combustion. If a 95 per cent overall capture efficiency is pro-
jected for 1980, the air emissions of cadmium vrould be 80 kkg per year
(about what they were in the 1970 time period), while the captured fly
ash and residues would contain 680 kkg per year of cadmium.
The growth of coal consumption is expected to continue well past
1980; the U.S. recoverable reserves are estimated to be 394 billion metric
tons.
-117-
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TABLE 23
U.S. BITUMINOUS COAL STATISTICS (MILLION METRIC TONS/YEAR)
SOURCE: BUREAU OF MINES(15)
Year
1970
1971
1972
1973
1974
1980*
Production
547
501
540
537
535
812
Exports
64
51
51
48
55
(54)
U.S. Consumption
(total)
468
449
469
505
490
(758)
U.S. Consumption
(electric power)
290
299
317
351
355
580
*Projection
-118-
-------
The control options suggested are:
1. Continued stringent a.ir pollution controls,
esjpecially for coal-burning electric power
generation stations.
2. Research emphasis upon removal of the
cadmium from synthetic oil or gas prior
to combustion.
3. Research and regulation on the disposal of
residues and of collected fly ash in en-
vironmentally-adequate ways.
-119-
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SECTION X
CADMIUM TQXICITY
Although a deadly poison in high concentrations, cadmium levels
necessary to cause acute toxic episodes have not been found environmen-
tally in the United States except in isolated cases of occupational
exposure. Chronic cadmium poisoning has occurred as a result of occu-
pational exposure, and, in Japan, as a result of environmental sources.
Table 24 provides a summary of the acute toxic dosages in a variety of
(52)
animal species for cadmium and several of its salts. In man,
critical threshold levels for observed effects is about 200 ppm of cadmium
in the renal cortex.
Chronic studies have been performed by a number of investigators.
Cadmium stearate fed orally to rats for 90 days caused decrease in growth
(54)
and histopathologic changes of the stomach, intestines and testicles.
Ingestion of 5 ppm of cadmium with drinking water by mice resulted in
tissue concentrations comparable to that seen in man, with increased male
(54)
mortality. At 10 ppm in rats for 60 days, cadmium inhibits the follow-
ing enzyme systems: oxidative phosphorylation, phosphatase and succinic
oxidase. In rabbits, cadmium can evoke hypocalcemia.
The effects of cadmium on the immune response have not been re-
solved. Studies in rats show that a dose of 0.6 mg/kg at 14 and 7 days
prior to antigen injection, cadmium respectively enhanced and suppressed
antibody synthesis. In vitro, cadmium cytophagic effects on erythro-
cytes and platelets is similar to that seen with other heavy metals and is
(58)
attributed to a toxic effect on sulfhydryl enzymes. Thus the anemia
is manifested, and cadmium has been shown to be transported to bone marrow
where it inhibits hemoglobin synthesis by being incorporated into the
(59)
molecule. Cadmium does not exert any observable mutagenic effects or
chromosome abnormalities. Although it readily crosses the placenta no
teratogenic changes have been manifested.
-120-
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TA3LK 24
ACUTE TOXIOITY 0? CADMIUM AND ITS SALTS
Cadmium (fumes)
Cadmium Chloride
Cadmium Fluoborate
Cadmium Fluoride
Cadmium Pluosilicate
Cadmium Lactate
Cadmium Oxide
Cadmium Phosphate
Cadmium Stearate
Cadmium Succinate
Cadmium Sulfate
Cadmium Sulfate
Tetrahydrate
Cadmium Sulfide
Spoci es
human
rat
rat
dog
rat
guinea pig
rat
mouse
Mouse
rat
Mouse
rat
rat
rat
dog
Route
Toxic Dose
inhalation TCLo 9 mg/M
intramuscular TDLo 700 mg/kg
rat
rat
oral
s.c.
i.v.
inhalation
oral
oral
s.c.
oral
inhalation
s.c.
oral
inhalation
s.c.
inhalation
oral
intravenous
i .p.
oral
s.c.
s.c.
s.c.
LD^O 88 rag/kg
TDLo 2.2 mp/kg
ID£0 1+.U8 mg/kg
LCLo 320 mg/M
LDLo 250 mg/kg
LD50 150 mg/kg
LDLo 200 mg/kg
LDlo 100 mg/kg
LCLo 670 mg/M
LD50 13.9 mg/kg
LD50 72 mg/kg
LC50 500 mg/M
TDLo 12 mg/kg
LCLo 650 mg/M
s.c.
ABBREVIATIONS
LD50
LD50 9.31 mg/kg
LD50 11.38 mg/kg
LD£0 660 mg/kg
TDLo 22mg/kg/10WI
LD£0 27 mg/kg
TDLo 8mg(Cd)/kg/10WI
TDLo HOmg/kg
TCLo Lowest toxic concentration evoking an adverse response
TDLo Lowest toxic dosage evoking an adverse response
LD50 The dose causing death in %Q% of the animal population
LCLo Lowest lethal concentration
LDLo Lowest lethal dose
LC5>0 The concentraction causing death in %0% of the animal population
10WI 10 weeks of dosing at a specified intermittent interval
s.c. subcutaneous
i.v. intravenous
i.p. intrape^i^oneal
-121-
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Although injections of cadmium chloride into male rats resulted
in pleomorphic sarcomas at the injection site 10 to 16 months later, pro-
bably as a result of injury to tissues of mesenchymal-mesodermal origin,
this response is not indicative of a carcinogenic effect since many sub-
stances, when similarly administered to rats, induce the same changes.
Rather, it is a local response to tissue (fibroblast) injury. Cadmium
(62)
has not been implicated in lung cancer in animals or man. Analysis
of zinc and cadmium levels in patients who died of emphysema, bronchitis
and pulmonary cancer and emphysema in comparison to levels in patients
who had only lung cancer or who died with no renal, hepatic or lung in-
volvements indicated that there was no specificity for cadmium in primary
tumors. However, one group of investigators showed a correlation
between air pollution and increased incidence of prostatic cancer in white
males in Nashville, Term. Since cadmium oxide dust is known to be present
in the air they inferred a possible causal relationship but offered no
definitive proof.
Exposure of rats to an aerosol of cadmium chloride solution for 1
hour on 5, 10 or 15 occasions resulted in acute vascular congestion and
alveolar hemorrhage followed by polymorphonuclear cell infiltration.
Localized granulation tissue subsequently developed about the bronchioles.
By the 10th day after exposure, the granulation tissue had undergone change
to fine scar tissue with destruction of adjacent alveoli, resembling human
centrilobular emphysema. Cadmium content of lungs was proportional to
the number of exposures. It has been previously shown that renal and liver
levels of cadmium increase with chronic obstructive lung disease and body
burden is well correlated with the number of pack-years of cigarettes
smoked. These changes cause a decrease in lung compliance and dyspnea. *
The mechanism of the cadmium toxicity may involve inhibition of Na , K ,
i <
Mg ATPase systems of pulmonary alveolar macrophages and cellular mem-
branes. (b7)
0.5 mg per kg, s.c., of cadmium chloride or stearate causes glyco-
suria and proteinuria in mice. 0.25 mg per kg, s.c., to rabbits also
-122-
-------
resulted in nephropathy with alterations of proximal tubules and mild
//-OS
glomerular changes. The proteinuria was characterized by a low al-
bumin level and fairly high alpha and beta fractions, and a distinct
fraction in the anterior gamma region. A basic protein in the renal
(CQ\
cortex migrated as muramidase.
Comparisons were made of urine protein levels in normal and 40
cadmium exposed workers. Normal levels of excretion were 50 mg per
day, while the cadmium exposed workers excreted between 80 and 2600 mg
per day. Subjects with greater than 150 mg per day proteinuria showed
electrophoretic patterns with low albumin, high alpha-2, beta and gamma-
globulins. Proteinuria of greater than 400 mg per day also yielded a
distinct beta peak. There was little variation in the electrophoretic
patterns noted at 6 month intervals. The proteinuria had a high mucoid
content. Battery workers with 10 years exposure to cadmium showed anosmia
and proteinuria but no correlation to other disease states.
Metallothioneins are low molecular weight proteins found in a
variety of tissues and are responsible for the transport of a variety of
metals within the body. The accumulation of cadmium in the kidney and
liver is dependent on the storage of cadmium in the metallothionein. This
protein readily passes through the glomeruli and can subsequently be found
in urine. As a result of the concentrating activity of cadmium in the
kidneys, cadmium will evoke renal tubular dysfunction when threshold limits
are exceeded.
Rats given 5 meg per ml of cadmium in drinking water from time of
weaning began to develop hypertension after about 1 year. This increased in
incidence with age and females were affected more than males, but mortality
was greater in males. There is a correlation between cardiovascular death
rates and cadmium present in air as an industrial pollutant as well as
hypertension and water softness due to cadmium. Atherosclerosis is also
(72)
associated with water softness as well.
-123-
-------
Cadmium produces persistent hypertension in rabbits and dogs. It
is predominately deposited in the kidney and liver and to a lesser extent
in the blood vessels of cadmium hypertensive rabbits. Cadmium was capable
of inhibiting vasopressor induced renal vasoconstriction.
Some epidemiologic studies have been carried out in the U.S. In
a survey of 77 midwestern cities, no correlation was found between cadnriim
(74)
in air fallout and cardiovascular disease. However there appeared to
be a simple correlation between cadmium content of milk and cardiovascular
disease in 59 U.S. cities. Cadmium concentration in air was corre-
lated with deaths from heart disease and arteriosclerotic heart disease
in 28 cities (R = 0.76). Zinc, with which cadmium is often associated,
also had a good correlation (R = 0.56). Patients with increased blood
pressure have increased cadmium levels in renal tissue. This may contri-
bute to the pathophysiology of cardiovascular disease.
Studies have indicated that cadmium oxide is more toxic than cadmium
dust or other cadmium salts. Threshold limits have been established at
0.1 mg of cadmium oxide per m of air. Table 25 corrpares the toxicological
effects of cadmium poisoning in experimental animals and in man.
In man the most common symptoms of acute cadmium poisoning are
xerostomia, vomiting, headache, cough, chest pain, and anorexia. High
concentrations may result in severe respiratory difficulty and uncon-
sciousness followed by bronchopneumonia and even death. Chronic exposure
to lew levels of cadmium can result in the following symptoms: fatigue,
nervousness, cough, shortness of breath and gastric disturbance, impair-
ment of sense of smell, kidney function and pulmonary function - often
leading to emphysema. Often a yellow ring forms on the teeth of workers.
In chronic cadmium poisoning the typical systems present are
shortness of breath due to emphysema with urinary excretion of a character-
istic lew molecular weight protein. The mortality rate resulting from the
acute pneumonitis is about 15-20%, and this acute toxicity has no resem-
(78)
blance to the chronic form of the disease.
-124-
-------
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Kidney biopsies of cadmium poisoned individuals showed thickening
of the small arteries and a slight degeneration of the tubules while pul-
monary function tests showed constrictive ventilatory impairment. Pro-
(79)
teinuria and glycosuria were predominate findings.
One group of investigators could not show any correlation
beto*een chronic cadmium exposure and hypertension, cardiovascular disease
or hypercholesterolemia.
Itai-Itai disease involves renal tubular dysfunction accompanied
by osteomalacia and osteoporosis. Its symptoms include:
- severe pain at regions of groin, loins, back and joints,
- duck gait
- a tendency to fracture of bones
- proteinuria and glycosuria
- an increase in serum alkaline phosphatase and a decrease
in serum inorganic phosphorous.
IVbst victims are women who have borne several children and are now meno-
pausal. Itai-Itai disease occurs in Japan in the Jintsu River Basin and
is the result of chronic cadmium poisoning resulting from a daily diet
(81)
contaminated by cadmium released through mining activities. Research
studies showed that the chronic poisoning leading to this condition
occurred because of such factors as pregnancy, lactation, aging and
calcium deficiency.
Whole body retention studies were carried out in rats using 4
(82)
routes of administration. Ihe following results were obtained:v '
Route of Administration Per Cent Absorption
intraperitoneal 9 3
intravenous 91
inhalation 41
oral 2.3
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Immediately after inhalation, 9.7% of total inhaled cadmium was
the lungs. The route of administration did not influence the rate of
elimination or the biological half-life. In female monkeys, within 5
days of administering 1 meg of cadmium, 43.5% was excreted, 46.8% remained
in the gastrointestinal tract, 7.21% was in the walls of the gastro-
intestinal tract and 0.65% was distributed in the body. Maximum absorp-
(83)
tion was 1.3%. In mice, maximum absorption increases acutely with in-
creased dose, but in chronic exposure absorption decreases as tolerance
develops. Following oral dosage to mice, 50 - 70% is absorbed from the
gastrointestinal tract and 50 - 60% of this level was excreted by the
kidneys on the first day. The remainder was stored primarily in the
liver and kidney. Intestinal absorption in mice was shown to be
(85)
2-3% with a half life of 50 days. A 55 year old man has an absorp-
tion rate of 5.34%. The accumulation of cadmium reaches a ceiling level
after about 30 years of age.
The data below are from a number of studies of cadmium levels in
human tissue:
Blood
Blood
Urine
Urine
Hair
Kidney
Kidney
Kidney
Petal tissue, first
trimester
Fetal tissue, second
trimester:
Liver
Kidney
Brain
0.2 meg/100 ml
0.7 mog/100 ml
0.82 meg/liter
1.15 meg/liter
0.7 ppm
4
> 10 mcg/gm (ash weight)
55 mcg/gm (wet weight)
upper limit of 5000 mcg/gm (ash weight)
0.032-0.07 mcg/gm (wet weight)
0.113 mcg/gm (wet weight)
0.05 mcg/gm (wet weight)
0.140 mcg/gm (wet weight)
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Liver/kidney ratios of cadmium in various Japanese populations
are given below:
Type Individual Ratio
Normal 0.10 to 0.20
Exposed > 0.35
Itai-Itai Disease 1.4 to 3.7
Residents of Cadmium Polluted Areas 0.05 to 1.25
TWo studies have been carried out in the United States and have
shown a mean weighted average of 16 ppm of cadmium iji renal tissue. In
studies where disease victims and smokers were not excluded from the
tabulation, mean renal levels of 50 and 25 ppm have been reported. '
No studies of cadmium concentration on the existence of renal tubular
dysfunction have been made of environmentally exposed populations in the
United States. No correlations have been made between renal cadmium levels
and hypertension. But there appears to be a correlation between neoplasia
and renal cadmium content, though it is not a cause and effect relation-
,,. (86)
ship.
In summary, cadmium is highly toxici with a rating of 5 on a scale
of 1 to 6. The acute lethal dose by ingestion is estimated to be between
5 and 50 mg per kg or between 0.35 and 3.5 g for a 150 pound man. The
maximum permissible level in drinking water is 0.01 ppm. This standard
(U.S. Public Health Service) is based on a tenfold reduction of the
lowest tested level (0.1 ppm) that results in cadmium accumulation in rat
kidneys. The following illustrates the toxicity scale for ingested cadmium:
Level (mg) Response
3 to 90 emetic threshold, non-fatal incidents
15 experimentally induced vomiting
10 to 326 reported severe but non-fatal toxic symptoms
350 to 3500 estimated lethal dose
8900 reported lethal dose
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By inhalation cadmium has a toxicity rating of 6. The recommended
maximum atmospheric concentration of cadmium fumes is 0.1 mg per cubic
meter of air for an 8 hour period. The inhalation of 40 mg of cadmium
with pulmonary retention of 4 mg is considered fatal to man.
Aside from Itai-Itai Disease, which occurs in only one section of
Japan and only amongst menopausal women, cadmium has not been associated
definitively with other specific disease states - particularly in the
United States. However, that is not to say that cadmium is non-toxic.
(81)
On the basis of extensive reviews carried out by Friberg et.al. the
following conclusions may be made:
1. Cadmium can be a very serious health problem in industrial
settings and in the general environment. Environmental con-
tamination is particularly serious since the metal accumu-
lates in the body during long-term exposure.
2. Prolonged exposure to cadmium dust can cause emphysema in
industrial workers, and some evidence exists that persons
in the general population who have chronic bronchitis and
emphysema have larger-than-normal body burdens of cadmium,
although a definite cause-and-effeet relationship has not
been established.
3. The internal organs affected most critically by cadmium are
the kidneys. Damage to the tubules produces excessive pro-
teinuria. Extensive damage causes acute secondary defects
including osteomalacia, the softening of the bones that
characterizes Itai-Itai disease.
4. Experimental and autopsy findings demonstrate that serious
kidney impairment has already occurred if concentration of
cadmium in the kidney cortex reaches 200 ppm.
5. Hypertension has developed in some experimental animals after
prolonged exposure to cadmium. No conclusive evidence exists
that cardiovascular disease in human beings is caused by
cadmium exposure but epidemiological studies statistically
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linking the two merit further investigation. Other internal
diseases caused by excessive exposure include anemia and
liver damage.
Research is needed on concentrations of the metal in body
organs other than the kidney, such as the liver, pancreas,
and thyroid gland. Additional studies should be carried out
regarding the carcinogenic, teratogenic and mutagenic effects
of cadmium.
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SECTION XI
ASSESSMENT OF HEALTH HAZARDS
most direct way of assessing the chronic health hazards pre-
sented by cadmium is to compare the measured 50-year level of accumulated
cadmium in the renal cortex (presently estimated at 16 to 50 ppm) with the
threshold level for renal dysfunction (200 ppm). This comparison results
in a "safety factor" of between 4 and 12.5, which has caused a large measure
of concern because it is not a comfortable margin of many orders of magni-
tude. Other reasons for concern include the Japanese public health problem
(in the Jintsu River Basin) of environmentally-caused cadmium poisoning,
which emphasizes the narrow safety factor; the rather large changes in
cadmium release to the environment (as discussed in Sections IV through
IX); and the built-in lag between a long-term buildup of cadmium in the
human body and the emergence of disease symptoms.
The very recent few years has produced both mounting concern and
considerable progress towards understanding; both the result of the develop-
ment of refined atomic absorption spectrophotometric procedures which per-
mit the determination of cadmium at concentration levels ooimon in the
biosphere.
One key question which has received much attention is whether the
cadmium being released to the environment as the result of man's activities
is finding its way into the food chain, or, instead, being assimilated by
natural sinks such as the soil and the oceans. Some of the more recent
work is discussed below.
Another key subject is the relationship of daily cadmium intake
levels (which can be monitored) to the long-term accumulation in the renal
cortex (which cannot be continuously monitored). The objective is to
determine the "safety factor" in terms of current average daily intake,
which is estimated as 75 ± 25 micrograms, as compared to the critical
daily intake (associated with the critical 50-year accumulation of 200 ppm
in the renal cortex). This subject is also discussed below.
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However, the definitive and quantitative assessment of the health
hazard is still not available. Some observers at one extreme rlouht whether
the long-term accumulations in man are any different from what they always
have been, since cadmium is a widely-dissipated element in natural soils
and waters, and so they see no cause for alarm or for regulation of cad-
mium emissions. Some observers at the other extreme advocate the fail-
safe course in dealing with a toxic material which may only show health
effects after many years of exposure; they would strictly regulate cadmium
emissions without a definitive cause-and-effect relationship.
Observers at both extremes agree to actively seek definitive answers
and to carefully monitor the situation (now that the analytical tools are
available). In the interim, a middle-of-the road approach seems to be that
reconnended in 1972 by the Joint FAQ/WHO Expert Conmittee on Food Addi-
(87}
tives to not permit any increase in the present daily intake level:
"In view of the critical level (of cadmium in wet renal
cortex) of 200 mg/kgr the Committee feels that present
day levels of cadmium in the kidney should not be al-
lowed to rise further. If the total intake of cadmium
does not exceed 1 ygAg body weight per day, it is un-
likely that the levels of cadmium in the renal cortex
will exceed 50 mg/kg, assuming an absorption rate of
5 per cent and a daily excretion of only 0.005 per
cent of the body load (reflecting the long half-life
of cadmium in the body). T?he Conmittee therefore
proposes a provisional tolerable weekly intake of
400-500 ug per individual. However, because of the
many uncertainties involved, this estimate should be
revised when more precise data and better evidence
become available.
"At the present time the cadmium intake of many popu-
lations is unknown and analytical methods, although
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adequate, require further standardisation. There
are uncertainties regarding the absorption and
excretion of cadmium in various nutritional and
metabolic states, and it is not known whether popu-
lations with excessive cadmium loads derived from
the diet have developed proteinuria.
"Such diet surveys as have been performed indicate
that in some areas cadmium levels approach or even
exceed the values recommended above, because of
environmental pollution. At present, cadmium in-
haled from the urban atmosphere does not contribute
a significant proportion to the total body burden.
However, significant absorption through heavy
smoking is possible. The continuing contamination
of the environment from industrial and other sources
is likely to increase the cadmium concentration in
food, and in the future this may lead to hazardous
levels. The Committee recommends that every effort
should be made to limit, and even reduce, the exist-
ing pollution of the environment with cadmium."
Cadmium Transport in the Food Chain
A number of papers have recently shed light on the relationship
between cadmium pollution and the appearance of higher-than-normal levels
of cadmium in soils and plants. The sources of cadmium pollution have
(4 92)
included generally-industrialized urban areas, ' coal-burning power
plants,(97) zinc smelters,(87'9°'91) and heavily-travelled roads.(45'92)
The addition to soil of cadmium-rich phosphate fertilizers and sewage
(4 93 94 95 96)
sludge ' ' ' ' has been studied, and investigators have determined
the plant take up resulting from delibrate doses of cadmium to the
(89 90 98)
soil. ' ' Relevant data is also available from the Jintsu River
(87)
Basin in Japan. The transport of cadmium to land animals and to
(4 88)
aquatic organisms has also been investigated. '
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The cadmium content of natural (unpolluted) soils is reported to be
generally less than 1 ppm, with, one "common" level of Q.Q6 ppm, an
"average" level of 0.88 ppm in certain Canadian agricultural soils,
(4)
an "average" level of 0.04 ppm in certain U.S. (mid-^west) agricultural
soils, and an overall crustal abundance of 0.15 ppm. In comparison,
the cadmium content of common foodstuffs in the U.S., listed in Table 26,
is generally below 0.10 ppm, but values in selected foods (not known to
(87}
be contaminated) have been higher.
The uptake of soil cadmium by plants is dependent upon a great
number of factors, particularly soil type and organic content, pH, and
plant species. Cadmium in soils seems to be tightly bound and not readily
removed by leaching; it may be adsorbed on aluminum oxide or iron oxide
and it may be complexed by organic materials of low solubility. Sediments
in rivers and lakes have been shown to accumulate cadmium (as has sewage
sludge) from waters.
Despite the above mechanisms for binding cadmium, the recent evi-
dence accumulated by the investigators (listed above) of plant uptake is
conclusive in that plants will reflect higher-than-normal cadmium levels
in soil over the entire range of cadmium concentrations. Prior to
1970, the evidence was inconclusive for plant uptake at cadmium concen-
trations in the soil in the 0.1 to 50 ppm range; but positive evidence
has since been reported. Representative experimental results of recent
work is listed in Table 27.
The impact of this evidence is that cadmium contamination of soil
(in the concentration ranges observed in the vicinity of smelters, power
plants, and roads, and resulting from the application of fertilizer and
sludge) does result in comparable cadmium contamination of the food
chain.
Relationship Between Intake and Accumulation
The modeling of the human intake-retention-excretion balance for
cadmium has been sought over the past few years, so as to relate daily
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TABLE 26
CADMIUM IN FOODS
SOURCE: OECD(87)
Pood
A. Composite Classes (USA survey)
Dairy products
Meat, fish, poultry
Grain, cereal products
Leafy vegetables
Legume vegetables
Root vegetables
Garden fruits
Fruits
Oils, fats, etc.
Sugar and adjuncts
Beverages
Potatoes
B. Some Extreme Individual
Measurements
Olive oil .(Spanish)
Ementhaler cheese
Cod Liver oil
Tea (Japanese) green
leaves
Oysters, fresh
Anchovies, canned
Beef kidney (F.R.G.)
Max. Cadmium Cone.
(mg/kg wet weight)
1968-1969 1969-1970
0.09(10)a
0.06(21)
0.08(27)
0.08(27)
0.03(16)
0.08(24)
0.07(25)
0.38(15)
0.13(27)
0.07(18)
0.04(8)
—
0.01(9)
0.03(22)
0.06(27)
0.14(28)
0.04(10)
0.08(27)
0.07(27)
0.07(10)
0.04(28)
0.04(27)
0.04(9)
0.08(29)
1.22
1.48
1.71
2.50
3.66
5.39
12.00
a = Samples were taken from 30 markets in 24 different U.S. cities.
The number in brackets is the number of samples whose measured
cadmium concentration was above 0.01 mgAg (max. 30).
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TABLE 27
PLftNT UPTAKE OF CADMIUM FROM SOILS
Investigator
Haghiri(98)
Haghiri{98)
John(90)
i
Lagerwerff(45)
«(99)
Lagerwerff
1
Plant
Soybean Tops
1
Wheat Tops
1
Oat Shoots
Oat Roots
Oat Shoots
Oat Boots
Grass
1
1
Radish Roots
1
Cd in Soil,
ppm
2.5
5
10
15
20
30
40
50
2.5
5
10
15
20
30
40
50
1.3
1.3
46.4
46.4
0.22
0.40
1.45
0.11
0.34
0.56
Cd in Plant,
ppm
7
10
13
14
18
20
23
24
3
5
8
9
10
12
14
16
0.51
1.11
16.1
36.3
0.50
0.73
0.95
0.90
1.1
1.2
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intake (a quantity which, may be continuously monitored) with long-term
accumulation in the renal cortex Ca quantity which is a direct indicator
of chronic cadmium poisoning, but which cannot be continuously monitored).
(87}
One such model was constructed from the following arguments,
each based upon experimental data:
1. Five per cent of ingested cadmium is absorbed into the
bloodstream (inhalation of cadmium is neglected);
2. Cadmium accumulates in bodily organs from 90 per
cent of the absorbed cadmium (assuming as experi-
ments have shown, that about 10 per cent of ab-
sorbed cadmium is rapidly excreted);
3. The kidney, the critical organ from the point of
view of the health effects of cadmium, contains
one-third the body burden of cadmium;
4. The concentration of cadmium in renal cortex is
one and a half times that in the kidney taken
as a whole;
5. Well-established experimental data allow adjust-
ment for the variation of kidney weight and food
intake with age; and
6. Cadmium is excreted at the rate of 0.005 per cent
(per day) of body burden, implying a whole-body
half-life of 33 years.
The tWD questionable parameters in this model are the 5 per cent
absorption rate and the 0.005 per cent excretion rate; the precision of
the empirical evidence may allow a ±50 per cent variation in this 5 per
cent absorption rate. The excretion rate was apparently adjusted so that
the model, with appropriate time functions for kidney weight and food intake,
resulted in a 50-year renal cortex cadmium concentration of 50 ppm for an
adult daily cadmium intake rate of 62 micrograms. Assuming the form of
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the model is appropriate, a mich. higher excretion rate would be needed to
match, another set of reported data, a 5Q-^ear renal cortex concentration
of 16 ppm for a daily intake rate of 75 ± 25 micrograms.
Without further refinement of the model, values for a critical
daily intake rate (corresponding to the threshold renal cortex concen- -
tration of 200 ppm) may be anywhere between 200 and 1,000; implying a
"safety factor" of between 3 and 13.
The key result of this exercise is not that the "safety factor" on
daily intake may be as low as 3 (which would imply a near-panic situation);
but that the safety factor probably is no larger than 13. This implies
a situation of caution and careful monitoring, especially in light of the
recent evidence that cadmium can be transported into the food chain from
contaminated soil on an approximately one-to-one concentration basis.
The total agricultural land, of course, is a vast sink for the
assimilation of cadmium, assuming the cadmium contamination is distributed
evenly. At a "natural" cadmium concentration in soil of 0.15 ppm, the top-
most meter of the continental lithosphere contains approximately 100 million
metric tons of cadmium. The instance of Itai-Itai disease in the Jintsu
River Basin of Japan could be cited as an example where a large quantity of
cadmium contamination was not distributed over a large agricultural area
and where the inhabitants did not balance their home-grown food with "imported"
food. In this instance, the Jintsu Valley was close to a closed ecology;
the consumption ratio of locally-grown foods to "imported" foods ranged from
0.7 up to 2.4.(87)
To a great extent, the United States represents the reverse situation,
where foodstuffs are widely disseminated across the country for consumption.
Moreover, the U.S. population is much more mobile, so that the chances are
smaller for very locally-high levels of cadmium being a continuing factor
over a 50-year period.
The other side of the argument, however, has merit as well. There
is a significant proportion of the U.S. population which is not mobile,
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and which might live for many years in the cadmium shadow of an indus-
trialized area, a coal-burning power plant, a municipal incinerator, a
steel plant, a zinc smelter, or a heavily-travelled roadway. Some of
these individuals may eat a larger-than-average proportion of home-grown
food (i.e., backyard vegetable gardens, home canners, etc.) or of bio-
concentrating seafood. The accumulation of cadmium in some individuals
may be promoted by heavy smoking or by occupational factors, or by varia-
tions from average intake/absorption/excretion rates.
Further research to relate intake to accumulation is quite clearly
needed. At this point, arguments made above (on both sides of the question)
are highly qualitative. While the sensitive analytical tools for measuring
and monitoring cadmium levels in the environment have been developed, the
means for quantitatively assessing the hazards associated with these levels
have not as yet been developed.
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SECTION XII
QUANTITIES OF CADMIUM RELEASED TO THE ENVIKDNMENT
Fulkerson and Goeller compiled an estimate, by source, of the
annual quantities of cadmium entering the environment in 1968. This esti-
mate is reproduced as Table 28. The total emissions to air, water and
soil were estimated as 2,500 to 3,600 metric tons per year (as elemental
cadmium). In the time since that estimate was made, additional data has
become available, and some of the production, use, and emission patterns
have significantly changed. Previous sections of this report have dis-
cussed these later data and changes in detail; the revisions and additions
are summarized below.
Zinc Ore Mining and Beneficiation
The total cadmium in domestic mine tailings is estimated at 250 kkg
per year. Little or no waterborne cadmium is assumed to result from adequate
water reuse and containment pond technology.
Zinc Recovery from Ore Concentrates^
The cadmium emissions to the air (based upon 95 per cent collection
efficiencies) are estimated as follows:
Roasting ~ 0
Sintering 100 kkg/year
Horizontal Retort 0.3 kkg/year
Vertical or Electrothermal 2.0 kkg/year
Retort
Electrolytic Plants ~0
Total 102 kkg/year
The total estimate is only one-tenth the previous estimate, and reflects
the closing of many older plants (especially pyrometallurgical plants)
and the addition of efficient dust collection equipment.
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TABLE 28
FULKERSCN-GOELLER EMISSION ESTIMATES (1968) FOR U.S.
UNITS: METRIC TONS PER YEAR AS ELEMENTAL CADMIUM
Source
Air Emissions
Soil and Water
Emissions
Zinc Ore Mining & Beneficiation
Primary Zinc Industry
Electroplating Shops
Pigment Manufacture
Stabilizer Manufacture
Alloy Manufacture
Battery Manufacture (& Misc.)
Iron and Steel Industry
Incineration
Rubber Tire Wear
Phosphate Fertilizers
Coal Ccnfoustion
Diesel & Fuel Oil Combustion
Lubricating Oils
Sewage Sludge Disposal
0.2
953
~ 0
9.5
2.7
2.3
0.7
<100
86
5.2
113-907
18-90
0.8
181
294
0.2
<900
23-230
22-57
-J.41-
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Cadmium as waterborne effluents is estimated as:
1971 -72 10 kkg/year
1977 2.0 kkg/year
1983 1.3 kkg/year
The significant decrease is the result of water pollution abatement practices.
The prior estimate of 294 kkg/year is of questionable validity, since it was
derived by difference (and not by direct measurement).
Electroplating Shops
No previous estimate was made for the water and land emissions
from this industry. The estimates in this study are:
Waterborne Wastes, kkg/year
Waste to Land Disposal, kkg/year
1972
10.5
73.5
1977
4.0
80
1983
0
0
This industry exemplifies the results of pollution abatement
practices.
Pigment Manufacture
The 1974 emissions (as elemental cadmium) are estimated as:
Waterborne effluents, 0.75 kkg/year
Land-destined wastes, 16.5 kkg/year
Battery Manufacture
The wateriDorne effluents are estimated to contain 0.3 kkg/year of
cadmium. The land-destined wastes are estimated to contain the following
quantities of elemental cadmium:
1973, 8.4 kkg/year
1977, 11.4 kkg/year
1983, 9.1 kkg/year
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Secondary Nbn-Ferrous Metals Industry
The emissions of cadmium to the air are estimated to be less than
2.2 kkg/year.
Iron and Steel Industry
The emissions of cadmium to the air are estimated to be 10.5
kkg/year. The collected dusts, destined for land disposal, are estimated
to contain 330 kkg/year of cadmium.
These estimates, much lower than the prior estimates, are based
upon data specific to the scrap grades used in steel-making. The results
of effective air pollution abatement practices are also reflected in the
new estimate.
Galvanized Products
The release of cadmium to the environment via the corrosion of
galvanized products was very crudely estimated to be 40 kkg/year.
Phosphate Fertilizers
The quantity of cadmium applied to the land via phosphate fertil-
izers is projected to be 100 kkg/year in 1975 and 130 kkg/year in 1980.
A continued annual growth rate of 5 to 7 per cent is- estimated.
Coal Combustion
The estimate of cadmium release via coal combustion is:
Air Emissions, kkg/year
Land-Destined Wastes, kkg/year
1974
80
370
1980
80
680
The increase in land-destined wastes reflects a large growth rate
in coal utilization for electric power generation; the air emissions are
stable reflecting very stringent controls for new power stations and more
stringent controls retrofitted to existing power stations (to increase the
overall cadmium collection efficiency from 85 per cent in 1974 to 90 per
cent in 1980).
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Savage Sludge
lhe Fulkerson-Goeller estimate in Table 28 was based •upon a per
capita dry sludge solids quantity of 0.091 kilograms per day for 120 million
(out of 200 million) people; and upon an average cadmium content of dry
sludge solids of 15.6 ppm (which was derived from Swedish data).
In the 1971 and 1973 time period, a revise of about 100 literature
references, and analysis of 80 additional sludge samples collected from
United States sewage treatment plants, were conducted by the Environmental
Protection Agency's National Environmental Research Center in Cincinnati.
The statistical distribution of heavy metal values tended to be log-normal,
with a few very high values that could ordinarily be traced to specific
industrial discharges. For cadmium, the results from the literature were
a geometric mean of 61 ppm, with a spread (the antilog of the standard
deviation of the log-normal distribution) of 5.89; and a geometric mean of
93 ppm for the atomic absorption determinations for the sludge samples.
Using an intermediate value of 75 ppm for cadmium, the quantity of cadmium
in sewage sludge becomes 300 metric tons per year.
The source of such a large quantity of cadmium could not be attributed
to excretions of man. Using the values of Section XT (an average per capita
daily intake of 75 micrograms and an excretion rate of 95 per cent), the
cadmium excreted by 120 million people amounts to only 3 metric tons per
year. Nor can this large quantity of cadmium in sewage sludge be primarily
attributed to industrial effluents; it has been previously estimated that
the primary zinc industry, the electroplating industry, and other industrial
waterborne sources amount to perhaps 25 kkg per year of cadmium, only a
fraction of which is discharged into municipal sewer systems. Although air
emissions from all sources amount to about 300 kkg/year of cadmium, it is
difficult to conceive of any large percentage of this quantity, once pre-
cipitated to the land, entering the municipal sewer systems via storm water
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into combined sewers or via inflow and infiltration. Rather, it appears rea-
sonable that most of this airborne cadmium would either retrain on the land or
would run off directly into surface waters. Similarly, only a rather small
fraction of the 100 kkg/year of cadmium in phosphate fertilizers could conceivably
enter municipal sewer systems.
The cadmium impurity in phosphate detergents is a suspected source of the
cadmium in sewage sludge. Using the impurity level of 16 ppm cadmium based upon
PJDj. (the same as in phosphate fertilizers) , the 1.1 million metric tons per year
(49)
of sodium tripolyphosphate produced would contain 10.2 metric tons per year of
cadmium. Hence, the detergent contribution is also only a small fraction of the
cadmium in sewage sludge.
Municipal sewage sludge (like river sediments and like other biological
organisms) is an efficient collector of metals, including cadmium. As part of
other research at a 28 mgd sewage treatment plant, Versar has determined that 85
per cent of the cadmium in the raw sewage is collected in the dewatered sludge.
The average concentration of cadmium in the intake of community water supplies was
measured to be 1.3 yg/liter, and the quantity of municipal wastewater is ap-
12
proximately 200,000 liters per capita per year, or 24 x 10 liters per year for
120 million people. Hence, the quantity of cadmium in municipal water intakes
(which is collected in municipal sewage sludge) is approximately 31 metric tons.
The balance of the 300 kkg per year of cadmium in sewage sludge; less
the human excretions (3 kkg/yr) , industrial sources (25 kkg/yr) , phosphate de-
tergents (10 kkg/yr) , and "natural" cadmium in water (31 kkg/yr) ; is about 230
kkg per year. A possible source for this balance is the cadmium in galvanized
water and sewer pipes and in PVC sewer pipe. While the Brattleboro, Vermont,
reservoir had only 2.1 ppb cadmium, the running tap water contained 8.3 ppb (cold)
and 21.0 ppb (hot) . The Conrnunity Water Supply Survey, which collected 2,216
water samples at the consumer's tap in 969 water systems, resulted in an average
cadmium concentration of 8 ppb in the 556 samples where the pH was between 7.0
and 7.4, but much less in other pH ranges. By comparison, the 230 kkg/yr of
cadmium unaccounted for in sewage sludge is equivalent to 9.6 ppb in sewage.
-145-
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While galvanized pipe is suspect as the large source of cadmium in
sewage sludge, the evidence is not conclusive* The quantity of zinc used for
galvanizing tubes, pipe, fittings, tanks, and containers is approximately
(14)
72,500 metric tons per year; at 0.035 per cent cadmium, the cadmium involved
is only 25 kkg per year.
The total quantity of cadmium in sewage sludge, estimated as 300 kkg
per year, is an increasing one for the following reasons:
1. The huge investment over the past few years in new, expanded,
and upgraded sewage collection and treatment facilities is
resulting in a commensurate increase in sludge quantities.
2. Recent restrictions on ocean dumping of sludge have increased
the quantities intended for land disposal.
3. The increased cost of auxiliary fuels has influenced the choice
of sludge incinerators for new facilities, increasing the
quantities of sludge intended for land disposal.
Of the cadmium-containing sewage sludge, approximately 60 per cent
is directly applied to land, 10 per cent is still ocean-dumped, and 30 per
cent is incinerated. If the cadmium collection efficiency of sewage sludge
incinerator scrubbers is 80 per cent, then the cadmium emitted to the air
would be about 20 kkg per year, and the cadmium disposed of on land
(including the sludge ash) would be about 250 kkg per year.
Municipal Incinerators
If an 80 per cent collection efficiency is applied to the previous
estimate, then the cadmium emissions to the air from incinerators would
be about 16 kkg per year, and the land-destined wastes would include about
70 kkg per year of cadmium.
Sunmary of Revised Estimates
Table 29 summarizes the revised emissions. The revised total re-
lease of cadmium to the environment is about 2,000 metric tons per year;
-146-
-------
TABLE 29
REVISED CADMIUM EMISSION ESTIMATES
UNITS: METRIC TONS PER YEAR AS ELEMENTAL CADMIUM
Source
Zinc Ore Mining &
Beneficiation
Primary Zinc Industry
Total: Extraction,
Refining & Production
Electroplating Shops
Pigment Manufacture
Stabilizer Manufacture
Alloy Manufacture
Battery Manufacture
Total: Industrial Conversion
Secondary Non-Ferrous Matals
Iron and Steel Industry
Galvanized Products
Rubber Tire Wear
Incineration
Total: Consumption &
Disposal of
Cd-containing products
Phosphate Fertilizers
Phosphate Detergents
Coal Carbustion
Diesel & Fuel Oil
Combustion
Lubricating Oils
Sewage Sludge
Total: Inadvertent Sources
Grand Totals
Airborne
Emission-.
0.2*
102
102
~1
9.5*
2.7*
2.3*
0.7*
15
2.2
10.5
-0
5.2*
16
34
~0
-0
80(1974)
80(1980)
50*
0.8*
20
151
300
Waterbome
Effluents
~0
10(1971-72)
2.0(1977)
1.3(1983)
-7(1974-75)
-2(1980)
10.5(1972)
4.0(1977)
0(1983)
0.75
-0
-0
0.3
-8(1974-75)
-3(1980)
-0
-0
~0
-0
-0
~0
-0
10.2
-0
-o
~0
-0
-0
10
25(197-1-75)
15(1980)
Land-Destined
Wastes
250
-0
250
73.5(1972)
80(1977)
0(1983)
16.5
-0
~0
8.4(1973)
11.4(1977)
9.1(1983)
-102(1974-75
~ 75(1980)
20
330
40
~0
70
460
100(1975)
130(1980)
-0
370(1974)
680(1980)
-0
~0
250
720(1974-75)
1,060(1980)
1,500(1974-75)
1,800(1980)
Total
Emissions
359(1974-75)
354 (1980)
125(1974-75)
93(1980)
494
831(1974-75)
1,221(1980)
1,800(1974-75]
2,100(1980)
•Estimates Unchanged from Fulkerson-Goel'ler Estimates.
-147-
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Less than the previous estimate (Table 28) of 2,500 to 3,600 metric tons
par yoar. 'Lhe main reasons for this lower new value are:
1. Effective air and water pollution abatement by industry,
prompted by the promulgation of specific guidelines and
regulations by Federal and state governments.
2. The contraction of the zinc industry, and particularly the
closing of older pyrometallurgical smelters.
3. New calculations of emissions, particularily for the steel
industry and for the zinc industry.
The totals of Table 29 show that the waterborne cadmium effluents
from industry are close to and approaching a comparatively negligible
quantity. The reasons are that wastewater treatment technology for cadmium
removal is well established and is effective; that Federal legislation
for controlling waterborne pollution is far-reaching and effective; and
that the analytical technique for monitoring cadmium in effluents is well-
developed and in wide use.
The air emissions data of Table 29 reflect a moderate (i.e., 80
per cent) efficiency attainable for collecting cadmium fumes and dusts
from installations such as electric power generation stations and in-
cinerators. These data also reflect the high (95 per cent or better)
cadmium collection efficiencies attainable with installations specifically
intended for relatively high flue gas concentrations of heavy metals, such
as are found in zinc smelters, steel furnaces, and pigment calcining
equipment.
Of the 300 metric tons per year of cadmium estimated to be the air
emissions, the emissions from the primary zinc industry are 100 metric tons
per year. Pyrometallurgical processes (with sintering operations) account
for half the U.S. zinc production, and even with very efficient collectors,
this large quantity of cadmium is lost. Any large reduction in this loss,
short of abandoning the pyrometallurgical plants, would require unknown
-148-
-------
new technology to be applied to the flue gases. It must be remembered
that the sintering operation is intended to purify the zinc calcine by
volatilizing cadmium (and other iitpurities), and that the standard oper-
ating procedure is to recycle the collected flue dusts through the high-
tenperature processes in order to build up the cadmium concentration to
where recovery is more economical.
Large total quantities of cadmium are also released to the air via
combustion of fossil fuels and incineration processes. These quantities
are large only because the quantities of fuels and solid waste burned are
enormous; the cadmium is present only in trace concentrations.
By comparison to the water and air emissions, the data of Table 29
show that land-destined wastes contain much more of the cadmium released
to the environment. Much of these cadmium-containing land-destined wastes
are the residuals from air and water pollution abatement practices; the
inter-media transfer has been especially iirportant in the iron-and-steel
industry, in electroplating, in pigment and battery manufacture, and in
sewage treatment. Actually, even the cadmium released to the air and to
water is transformed into land-destined waste via relatively rapid at-
mospheric fallout and via absorption onto river sediments.
The land-destined cadmium falls into two categories. The first
category is made up of vast quantities of solid wastes, in which cadmium
is only a very minor constituent. Included are the zinc ore tailings,
the residues from coal combustion, incineration residues, and sewage
sludge. The second category is made up of industrial wastes of much
smaller total quantities and with much higher concentrations of cadmium;
included are the residuals from electroplating, from pigment and battery
manufacture, and the dusts collected from steel furnaces. Ways and means
for either disposing of (in an environmentally adequate manner) or of
recycling the industrial wastes of the second category are being developed
and implemented. However, the enormous quantities of wastes of the first
category imply that the near-term control strategy is the dispersing upon
land of these wastes so as to prevent locally-high concentrations of
cadmium (and other toxic substances).
-149-
-------
Hence, for the land application of sewage sludges, phosphate
fertilizers, zinc ore tailings, coal ash, incinerator ash, or other materials
with cadmium concentrations significantly higher than those found in "normal"
soils; the resulting cadmium content should not exceed the "natural" maxi-
(93)
mum of 0.6 ppm , which is an order of magnitude greater than the "typical"
natural value of 0.06 ppm.
Ihe application of cadmium-rich materials to soil is also dependent
upon(96):
1. The soil pH. A pH of less than 6.5 makes cadmium much more
available to plants.
2. The organic matter in the soil. Organic matter chelates the
cadmium and makes it less available.
3. The cation exchange capacity of the soil. A soil with a high
cation exchange capacity binds cadmium, and makes it less
available.
4. The crop to be grown in the soil. Crops vary widely in their
susceptibility to different toxic elements.
Dissipation vs. Emissions
The data of Table 29 may be analyzed from another viewpoint. Of the
total estimated cadmium emission of around 2,000 metric tons per year,
approximately 30 per cent (600 kkg/year) had its origin as primary cadmium
metal. The emissions from zinc ore mining, beneficiation, and from zinc
production amount to 20 per cent of the total emissions, and the remaining
50 per cent (and growing) are attributable to sources not associated with
the primary zinc/cadmium industry (i.e., fertilizers, fossil fuels, and
sewage sludge).
Hence, the emissions originating as primary cadmium metal are ap-
proximately 10 per cent of the consumption of primary cadmium. The con-
verse of this statement is that the present situation of wide dissipation
is 90 per cent effective in removing cadmium from circulation in an
-150-
-------
(apparently) environmentally adequate manner! Certainly the cadmium in
plastics that are not incinerated remains bound in the resin matrix for
a long time. The very good atmospheric corrosion resistance of cadmium
leads to the conclusion that unless electroplated parts are subjected to
an acidic environment, incinerated, or recycled as ferrous scrap, the cad-
mium remains immobile for a long time.
This argument does not, of course, relieve the concern for the 10
per cent that is emitted. Every prudent effort should be made to reduce
this quantity. However, the control options must be thoroughly analyzed
because there is a real danger of disturbing this balance and causing the
remaining 90 per cent to become either more mobile in the environment or
to be present in much higher (and much irore hazardous) concentrations.
-151-
-------
SECTION XIII.
THE MARKET FOR CADMIUM
The market for cadmium differs markedly from the typical economic
model of supply and demand responses to price changes for tvro reasons:
1. Cadmium Supply - Since cadmium is a by-product of
zinc production, the supply is relatively insensi-
tive to price changes;
2. Cadmium Demand - Since cadmium represents a small
percentage of the total cost of most consumer pro-
ducts containing cadmium and since no adequate
substitutes exist in many cases, even large price
changes have little effect on demand.
This section contains supply and demand curves for 1974 and 1985
which are later used to estimate future cadmium discharges for the base-
line situation (no regulation beyond present controls), and to estimate
reductions in cadmium usage and cadmium discharges for a given cadmium
regulatory alternative.
Cadmium Supply
Because there is no separate ore of cadmium, it is produced ex-
clusively as a by-product material, either in the recovery of primary
zinc from its ore or in the processing of secondary materials such as
collected flue dusts and small quantities of secondary metal scrap. In
addition, the General Services Administration, which had stockpiled cad-
mium from 1948 through 1963, has since been releasing significant quan-
tities to industry. Cadmium supply statistics for recent years are listed
in Table 30.
Figure 5 shows the U.S. cadmium supply as related to the price
(in constant 1974 dollars). as Figure 5 indicates, the domestic supply
of cadmium is inelastic, i.e., relatively insensitive to price level,
-152-
-------
20r
0 4,000 8,000 12,000 16,000
U.S. CADMIUM SUPPLY (METRIC TONS/YEAR)
FIGURE 5
U.S. CADMIUM SUPPLY
-153-
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-154-
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above a price of $5 per kilogram. Since cadmium is a minor by-product
of zinc production (0.5 per cent of the quantity and 5 per cent of the
value of shipments), the cadmium domestic supply is intimately related
to the zinc supply and is xelatively insensitive to cadmium price changes.
As Table 30 indicates, the world production of cadmium is in the
range of 17,000 metric tons per year (of which about 13,000 is free-jworld
production). The total U.S. supply curve (defined as U.S. production plus
imports) has been constructed with considerable price elasticity, reflecting
that there is an active world market in cadmium.
Without the benefit of an independent evaluation of cadmium pro-
duction costs, it appears (assuming the recovery of cadmium-rich flue
dusts and sludges is a requirement of zinc purification and pollution
abatement regulations regardless of the market for cadmium) that the extra
costs for cadmium recovery and refining should be no more than $2 per
kilogram. This is based on the prices for zinc, lead, and copper, (all
within $1.50Ag) i and the basic similarities between the refining process
for all of these nonferrous metals. The conclusion reached is that the
price for cadmium is 3 to 5 times the production costs, so that the quan-
tity produced is not closely correlated to price.
The corollary of this argument is that the supply would become
elastic at prices less than $2 per kilogram. For this reason, the supply
curve of Figure 5 has been extrapolated below $5 per kilogram in the
manner shown.
Assuming an annual increase in the world's zinc production of 3
per cent, and assuming that some additional secondary cadmium would
become available in the U.S. (because of pollution abatement and reclama-
tion) the 1985 supply would be about 40 per cent higher than the 1974
supply. The projected supply curve is also shown in Figure 5, with the
-155-
-------
understanding that this projection should reflect the uncertainty about
the level of zinc production, cadmium recovery efficiency, extent of re-
clamation, and other unknown variables.
Cadmium Demand
Table 31 lists the cadmium demand statistics for recent years, as
published by the Bureau of Mines.(14'15'16/43) included is a BOM projec-
tion for the 1985 demand level. Although some minor inconsistencies exist
between these BOM historical data and the data included in the earlier
sections of this report (which incorporated other sources), the study of
cadmium demand in this section is based upon the BOM historical data.
However, the BOM projection for 1985 was not entirely adopted because of the
following two points of disagreement:
1. BOM projects the battery demand for cadmium to
conform to that of the QSEP growth, rate, 4 per
cent. The discussion in Section VII of this
report results in a projected growth rate of
15 per cent.
2. BOM projects the cadmium demand for PVC heat
stabilizers to conform to that of the GNP
growth rate, 4 per cent. The discussion in
Section VI of this report projects FDA ex-
tensions of cadmium restrictions, the use of
multi-screw extruders to reduce the temperature-
time history, and the development of calcium-
zinc stabilizers with equivalent performance
and costs. Hence, a 4 per cent growth rate is
not justified. The projection used in this
study is of zero growth in demand to 1985.
-156-
-------
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The demand schedules used in this study are as follows:
Electroplating
Pigments
Heat Stabilizers
Batteries
Other
Total
1968-1972 Baseline
kkg/year
3,100
700
1,170
230
390
5,590
1985 Projection
kkg/year
4,850*
950*
1,170
2,200
810*
9,980
Growth Rate
Per Cent Per
Year
3
2
0
15
5
3.9
*BOM Projections
As is apparent, the total projected industrial demand for cadmium
in 1985 is not very different, regardless of whether the BOM projections
or the projections of this study are used.
Four uses - electroplating, plastic stabilizers, pigments and
Ni-Cd batteries - are responsible for 95 per cent of the cadmium consumed
annually. The means by which cadmium is supplied to the users are varied.
Much of cadmium is bought by consumers who buy enough to deal directly
with the smelter. In the electroplating industry, however, many of the
chemical manufacturers who supply plating shops with the necessary
chemicals act as distributors, purchasing large quantities of cadmium
from the smelter and selling it to the platers along with their chemicals.
Some of these "middlemen" import cadmium and distribute it in like fashion.
In addition, GSA has supplied cadmium in recent years through its authori-
zation to decrease the stockpile of cadmium; many distributors and large
users of cadmium have purchased the excess reserves from GSA rather than
from smelters. However, the GSA inventory as of November 30, 1974, was
2,920 metric tons, compared to a stockpile objective of 2,010 kkg; leaving
an excess of only 910 kkg.
-158-
-------
In order to develop a demand curve, the effects of price changes
on demand must be examined. The demand for cadmium is a derived demand
in each industry; it is the demand for the final good containing cadmium
which causes the producer of that good to purchase cadmium. Therefore,
the effect which a change in the price of cadmium has on demand will be a
result of two effects:
1. the demand response to changes in the price of
final goods as a result of changes in the cost
of cadmium contained in them; and
2. the substitution of other materials for cadmium
as the price of cadmium changes.
In all of the final goods, the cost of cadmium is such a small
fraction of the cost of the total good that a 2 to 3 fold change in the
price of cadmium should cause only a slight shift in the supply curve for
a final good and hence a slight decrease in demand. However, the same
change in price, while not affecting demand for the final good, may greatly
affect the demand for cadmium in that final good if an adequate substitute
exists.
Figure 6 shows the baseline (i.e., 1968-1972) cadmium demand curves
for each of the major uses, drawn from the data of Table 31). As the data
of Table 31 indicate (by inspection), the quantity of cadmium consumed for
each use is not strongly correlated to the cadmium price. The following
correlation coefficients were calculated for the 1968-1972 data:
Cadmium for electroplating 0.24
Cadmium for pigments 0.40
Cadmium for heat stabilizers 0.60
Cadmium for batteries 0.22
Cadmium for other uses 0.04
Hence, for all except pigments and heat stabilizers, the regression of
quantity upon price accounts for less than 10 per cent of the variance in
quantity consumed, and so the demand curves in Figure 6 were drawn vertically
-159-
-------
24r
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KILOGRAN
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^BATTERIES
1 1 1 1 1 1 I 1
Q
0 2.000 4,000 6,000 8,0
U.S. CADMIUM DEMAND (METRIC TONS/YEAR)
FIGURE 6
U.S. CADMIUM DEMAND
BASELINE PERIOD (1968-1972)
-160-
-------
(e.g., completely inelastic demand) in the range of the historical data
($5 to $11 per kilogram) . For both pigments and heat stabilizers, the
demand curves of Figure 6 in this price range were drawn with the least-
square slopes of the historical data, which are each about -25 metric tons
per year/dollars per kilogram. The total cadmium demand curve of Figure 6
is the sum of the individual demand curves.
The individual demand curves of Figure 6 were extrapolated based
upon the relevant discussions in previous sections. For electroplating,
the costs (exclusive of metal costs) are in the range of $2.70 per square
meter. The cost of cadmium is an additional $0.55 per square meter, while
the cost of zinc is about $0.05 per square meter. The electroplating de-
mand curve of Figure 6 was drawn with very little elasticity below the range
of data; even if the cadmium price was $2 per kg rather than $8 per kg,
cadmium would still be much more expensive than zinc and substitution for
zinc should not occur. At the upper end, the curve shows no elasticity
since those substitutions for cadmium on the basis of metal cost have al-
ready been made (i.e., cadmium at the present price of $8 per kg is already
much more expensive than zinc). As the cost of cadmium reaches $20 per kg,
however, the total plating costs become 50 per cent higher, and discussions
with industry personnel indicate that demand would drop off at this level.
Cadmium pigments are economically similar to the case of cadmium
electroplating. These cadmium pigments cost $13 to $25 per kg, and even the
lithopones cost $6 to $10 per kg; compared to chrome colors at $1.50 to $2
per kg and to iron oxides at less than $0.50 per kg. The demand curve of
Figure 6 was constructed with some elasticity at $2 to $3 per kg of cadmium,
reflecting a potential use of cadmium pigments at that price level instead
of chrome colors. Since cadmium pigments are presently much more expensive
than potential substitutes, little elasticity in demand was projected as the
cadmium price rises even more. As a level of $20 per kg of cadmium is
reached, however, industry sources indicate a drop in. demand (probably by
substituting other colors for the yellows, oranges, reds, and maroons).
-161-
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The heat stabilizers curve of Figure 6 shows a different situation,
however. The bariun^adniiurn heat stabilizers are already the cheapest and
enjoy 50 per cent of the market, so that an even lower cost of cadmium
should not greatly increase? the demand. Calcium-zinc stabilizers are pre-
sently twice as expensive, so a drop in cadmium demand is projected at about
$15 per kg of cadmium, where significant substitution should occur not only
from the Ca-Zn system but also from the organotins.
The batteries demand curve of Figure 6 has been drawn to be highly
inelastic. In 1972, the quantity of cadmium used in batteries (410 kkg) was
10 per cent of the total quantity of nickel-cadmium batteries produced
(4,600 kkg). The value of the cadmium, at $8 per kg, amounted to $3.3
million, which was 7 per cent of the total value of shipments for the bat-
teries, $47.6 million. Hence, the impact of cadmium price should be rela-
tively minor below $20 per kg of cadmium.
The total industrial demand curve is the sum of the individual de-
mand curves; this is also shown in Figure 6.
In developing the baseline demand curve, all variables except price
and quantity were held constant. From an examination of cadmium demand,
it is apparent that many other variables affect demand. For instance, if
a new battery were developed to replace the Ni-Cd battery, the curve would
shift to the left and if a new use for cadmium pigments was developed, the
curve would shift to the right. If a substitute stabilizer was developed,
the shape of the curve might change or it might shift depending upon its
price and adequacy as a replacement. Changes in uses of cadmium and cad-
mium containing products, availability of substitutes for cadmium and cad-
mium containing products, and the relative prices of cadmiiim-containing
products and their substitutes, are all of prime importance in determing
the shape and position of the demand curve.
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For all uses except heat stabilizers, the 1985 demand projections
shown in Figure 7 were developed by shifting the curves of Figure 6 accord-
ing to the ratio of the projected demand levels (listed previously) to the
baseline demand levels. For heat stabilizers, it is projected that other
systems will be directly competitive from a cost standpoint, resulting in
a much more elastic demand curve for cadmium in this industry. The total
industrial demand curve of Figure 7 was obtained by summing the individual
curves.
Relation of Supply and Demand
Figure 8 combines, on one graph, the baseline and projected supply
curves of Figure 5 and the baseline and projected total demand curves of
Figures 6 and 7. Ihe projected 1985 cadmium consumption is 9,100 metric
tons per year (an increase of 60 per cent over the 1968-1972 market) and
the projected 1985 equilibrium price is $10.80 per kilogram (in constant
1974 dollars). This price is higher than the 1968-1972 price of $8.50
because the projected demand is greater than the projected supply relative
to the baseline market.
It must be emphasized that these projections are not at all precise;
both the projected supply curve and the projected demand curve could be
shifted.
The development of a substitute or a price change for a final good
containing cadmium will cause a shift in the entire demand curve; a new
substitute for cadmium as a factor of production or a change in the rela-
tive prices of cadmium complements and substitutes will cause a change in
the shape of the curve.
The unknown variables with the greatest effect on the results are:
Supply: 1. price of zinc
2. growth in zinc production
3. impediments to foreign trade
4. recovery from secondary sources
Demand: 1. technological change (i.e., a new
substitute or a new use for cadmium)
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24r
0 2,000 4,000 6,000 8,000 10,000 12,000
U.S. CADMIUM DEMAND (METRIC TONS/YEAR)
FIGURE 7
U.S. CADMIUM DEMAND
1985 PROJECTIONS
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V)
oc.
24|-
22
20
18
16
14
12
10
8
6
4
I I
4,000 8,000 12,000 16,000
CADMIUM QUANITY ( METRIC TONS /YEAR)
FIGURE 8
CADMIUM SUPPLY AND DEMAND
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2. changes in the prices of substi-
tutes and complements for cadmium
and cadmium containing products
3. changes in the demand for cadmium
containing products
In the baseline period, the domestic cadmium production (3,300 kkg/yr)
satisfies 60 per cent of the U.S. cadmium demand. Based upon the projections
of Figures 5, 7, and 8, the 1985 domestic cadmium production (4,600 kkg/yr)
would satisfy only 50 per cent of the domestic demand (9,100 kkg/yr).
An informative exercise is the evaluation of the potential change
in the domestic cadmium supply by the maximum recovery of cadmium from
secondary sources. The incentive for such recovery (in addition to the
environmental pressures for removing cadmium from products and residues)
might be the projected increase in cadmium price to $10.80 per kilogram.
Table 32 outlines the estimates (based upon the emissions of Table 29) for
maximum recovery of secondary cadmium. The potential exists, then, for
increasing the domestic cadmium supply, by 2,400 kkg per year from secondary
sources, to a total of 7,000 kkg per year. At this level, only about 35
per cent of the U.S. cadmium demand would be satisfied by imports.
While batteries should consume about 25 per cent of the total cad-
mium by 1985 (as Figure 7 shows), the data of Table 32 shows that more than
half of the reclaimable cadmium from secondary sources is from used batteries.
In 1985, the value of the cadmium in batteries would be about $17 million
per year, which should provide incentive for industry to develop institu-
tional mechanisms for reclamation (the technology is already developed) .
In actuality, the nickel values from nickel-cadmium batteries provide a
greater return than the cadmium. At least one manufacturer of nickel-
cadmium batteries has already begun to encourage recycle by labeling and
other inducements. It appears, then, that there will be sufficient
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TABLE 32
ESTIMATES FOR MAXIMUM RECOVERY OF SECONDARY CADMIUM IN 1985
Source
Primary Zinc Industry
Electroplating Shops
Pigment, Stabilizer,
Alloy, and Battery
Manufacture
Used Batteries
Secondary Metals
Galvanized Products
Zinc Oxide
Phosphate Fertilizers
Coal
Total
Recoverable
Quantity,
kkg/year
80
80
40
1,500
350
150
15
130
50
2,395
Basis for Estimates
Increase dust collection effi-
ciency to 99 per cent
Reclaim wastewater treatment
sludges
Increase dust collection effi-
ciency and reclaim wastewater
treatment sludges
Recycle 75 per cent of used
batteries
Process flue dusts
Use higher-grade zinc for gal-
vanizing and recover the
cadmium at the zinc smelter
Recover cadmium in ZnO
manufacture
Remove cadmium from phosphoric
acid with new technology
Recover cadmium in coal gasifi-
cation and liquefaction pro-
cesses
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incentive in the private sector to reclaim much, of the cadmium from bat-
teries. The government's posture should be one of encouragement of such
reclamation.
The use of cadmium in batteries offers far greater potential for
recovery of the cadmium than any other present use. Conversely, all other
present uses are inherently dissipative; and therefore of prime concern
from the standpoint of health hazards. If 75 per cent of the cadmium in
batteries was recycled in 1985, the imports of "new" cadmium would be re-
duced from 4,500 kkg per year to 3,000 kkg per year.
Control Alternatives Based Upon Supply and Demand
One external market force to be considered is a tax and import
duty on cadmium production and/or use. As previous discussions have in-
dicated, however, the domestic cadmium demand curve is highly inelastic
until the price reaches perhaps $20 per kilogram. Hence, a tax must be
very high indeed before it becomes effective in curbing demand. As
Figure 8 shows, the projected increase in cadmium consumption is not ac-
companied by lower prices; if this were the case, then a tax might be
effective in the elastic region of the demand curve. However, in light
of the consumption and price projections, a tax is not suitable for this
situation.
An alternative control option is a quota on cadmium imports, or
carrying it to the extreme, a ban on cadmium imports. Since the present
level of imports accounts for 40 per cent of the U.S. cadmium demand; and
since the projected level of imports would account, in 1985, for 33 to 50
per cent of the U.S. cadmium demand (depending upon the extent of reclama-
tion of secondary cadmium); a partial or full ban on imports should be an
extremely effective means for reducing the quantity of cadmium consumed in
the United States. It is not anticipated that the domestic supply would
increase appreciably in reaction to such an import restriction. Despite
the importance of cadmium revenues to the zinc industry, cadmium has not
in the past been a determining factor for deciding whether a zinc (or
copper-zinc or lead-zinc) ore is economical, or whether a new primary zinc
plant should be built.
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With a total ban on cadmium imports, the 1974 domestic supply would
be equivalent to the domestic production capacity, 3,300 kkg/year, and
would be highly inelastic (as Figure 5 shows). At this quantity, the mar-
ket price would be around $21 per kilogram, according to the baseline
demand curve of Figure 8. Hence, the domestic producers may benefit from
an extra revenue of $41 million per year. This excess may be scrutinized
by the government in terms of an excess profits situation, in terms of
compensating for the imposition of stringent emission controls and of pos-
sible product and byproduct quality regulations upon the primary zinc/
cadmium industry, and in terms of making domestic zinc more competitive
in the world market.
In 1985, the domestic supply with a total ban on imports would be
at least 4,700 kkg/year (the projected domestic primary cadmium production
capacity). At this quantity, the estimated market price (according to
Figure 8) would be $21.60 per kilogram in the absence of an import ban.
This would generate $51 million per year in extra revenue for the domestic
cadmium producers.
However, Table 32 indicates that another 2,400 kkg per year of
secondary cadmium is potentially available in 1985. The very high price
for cadmium resulting from an import ban would serve to encourage reclama-
tion. Batteries would have the largest potential (as Table 32 shows), but
there should be strong incentives for reclaiming cadmium from flue dusts,
industrial sludges, and even from phosphoric acid and coal. Such reclama-
tion would only partially make up for the decrease in domestic supply
brought on by an import ban. Table 33, which summarizes the estimated
effects of several assumed levels of secondary cadmium recovery, shows
that the market price would be above $20 per kilogram regardless of the
fraction recovered. At this price level, the various cadmium consumers
would be expected to develop and use substitutes.
In order for an import ban on cadmium to be effective, it must
cover not only metallic cadmium, but also cadmium-bearing flue dusts,
sludges, and other residues from abroad. Moreover, it must cover products
derived from cadmium, such as electroplated parts, pigments, heat stabilizers,
and batteries.
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TABLE 33
EFFECTS OF SECONDARY CAQyUUM RECOVERY IN 1985
(WITH A TOTAL BAN ON CADMIUM IMPORTS)
Fraction of Potential
Actually Recovered
0.0
0.25
0.50
0.75
1.00
Recovered
Quantity,
kkg/yr
0
600
1,200
1,800
2,400
Total
Domestic Supply
kkg/yr
4,700
5,300
5,900
6,500
7,100
Market
Price,
$Ag
21.60
21.40
21.30
21.10
20.80
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In addition to reducing the cadmium consumption level, an ijtiport
restriction or ban would also serve to encourage secondary cadmium re-
covery from domestic sources. The market price of $20 per kilogram should
be a very real incentive not only for reclamation of battery cadmium, but
also for the various other sources listed in Table 32.
Another alternative control option for reducing cadmium consumption
would be a ban (either total or selective) upon the use. of cadmium. Figures
9 and 10 were constructed to (respectively) estimate the baseline and 1985
demand curves resulting from hypothetical selective bans on each of the uses
in turn. The estimated equilibrium price, the total U.S. consumption of
cadmium, and quantity of cadmium diverted for each selective ban, are sum-
marized in Table 34.
Prompting Significant Reductions in Cadmium Demand for Electroplating
An alternate control strategy to a ban on cadmium electroplating is
a reduction in the supply and demand for cadmium electroplating. The
supply of cadmium electroplating may be reduced since stringent effluent
guidelines would force some platers to cease this activity. This may be
especially true for job platers whose present cadmium business is only a
minor fraction of their total output, or for captive platers who can con-
vert to alternate finishes.
On the demand side, cadmium electroplating has been distributed
among the following end items:
End Use
Industrial Fasteners & Other Uses
Electronics and Communications
Aircraft, Aerospace, Shipbuilding,
Ordnance
Automotive Parts
Per Cent
32.8
26.3
20.5
20.4
kkg/yr
1,020
820
640
630
-171-
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Diverted
>ns/Year
3 o
S3
O H
g( >H
§1
Total C
Metric
1
n
l&
F
u
o o o o o o
o o o o o
rH CN in
o o o o o o
o o o o o
LO LO ^f ^*1* ^^
o o o o o
in o H CN o
oo oo r^ vo ro
CO 4J
W CD rH
CD CO N Qi
•iH 4-> -H O
QJ S M-l 4J
CD 4J « ^3 U
C 4-> &) 13 CD rH
ft (8 -iH 4J rH r-H
13 CQ CM W W t-^ oo oo in
o o o o o
oo <£> o CN in
o oo o o in
rH rH rH
CO 4J
u id
CO (D rH
0) CO N ft
•H -P -iH O
>H C rH &
0) 3 -iH 4J
CD 4J S J3 O
C 4-> BI f3 CD rH
0 5} -H 4J rH H
!? (M Pi rO TT1 *^i
i ^
in
CO
CT>
l-i
-172-
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UJ
O
0 2,000 4,000 6,000 8,000
CADMIUM QUANTITY( METRIC TONS /YEAR)
FIGURE 9
ESTIMATED EFFECT OF BANS OF CADMIUM
BASELINE PERIOD (1968-1972)
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24
22
20
18
to 16
H 14
I "
L_ 10
8
" 6
UJ
<%? 4
Q.
2,000 4,000 6,000 8pOO 10,000 12,000
CADMIUM QUANTITY (METRIC TONS/YEAR)
FIGURE 10
ESTIMATED EFFECT OF BANS OF CADMIUM
1985 PROJECTIONS
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In addition to the cadmium electroplating demand of the automobile
industry, some cadmium-copper alloying stock-has been used in radiators,
cadmium pigments are used for the plastics, and cadmium heat stabilizers
are used for vinyls used in interior and exterior moldings and in calen-
dered stock for coverings. It was previously shown that the recycling
ratio for automobiles (as ferrous scrap) is much, higher than for most
other cadmium-using end items, and that a very large fraction of the
No. 2 bundles of ferrous scrap is automotive scrap.
An alternative control strategy to regulation of the automobile
manufacturing industry is to seek the voluntary cooperation of this
highly-concentrated industry (with respect to the small number of prime
domestic producers).
Falling into a similar category are the electronics, aircraft,
aerospace, shipbuilding, ordnance, and similar industries, which, to a
large extent are suppliers of government (including military) requirements.
Perhaps one main reason for the high inelasticity of demand for cadmium
plating (and therefore for all cadmium) is simply the built-in inertia
against change of longstanding, self-perpetuating, and intransigent
government specifications. The military specification for surface treat-
ments and inorganic coatings for metal surfaces of weapon systems,
MH-S-50002C, lists many alternatives to cadmium plating, but states that
zinc may not be used for aerospace and missile systems due to its bulky
corrosion products. A great many hardware and components military speci-
fications call for the use of cadmium plating. Much may be accomplished
in reducing these demands for cadmium electroplating. The Department of
Defense specifications preparation activity is vested in two groups, the
Defense Electronics Supply Center (for electrical connectors and electro-
nics) and the Defense Industrial Supply Center (for fasteners and other
mechanical parts). Hence, the organization exists for reviewing military
specifications calling for cadmium-plated parts, to justify such speci-
fications against alternate means for metal finishing.
It should also be feasible for a review and justification of
specifications to be conducted by the aircraft, shipbuilding, electronics,
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and similar industries, all large consumers of cadmium electroplating. They
are all highly structured industries (with- relatively few major prime con-
tractors, with, a well-established hierarchy of subcontractors, and with a
well-established formality of rigid specifications}. Furthermore, much, of
the cadmium plating in these industries is captive.
Further study is required of the quantitative potential for signi-
ficantly reducing the demand for cadmium without the requirement of a
formal ban.
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SECTION XD7
POSTS OF ALTERNATIVE REGULATIONS
In previous sections, alternatives for controlling various dis-
charges of cadmium into the environment have been identified. In this
section the costs associated with these alternatives will be quantified.
In each case, the estimated cost is the difference between the course of
events when no action is taken and the course of events given a specified
cadmium regulation.
The costs of a control alternative can be broken into two broad
categories: (1) long-run costs are derived from the differences between
the two "steady states", one without a control alternative and one with;
these costs extend indefinitely. The short-run costs are those incurred
while moving from the steady state without a control alternative to one
with a control alternative; these costs have a termination when the steady
state with a control alternative is reached. If an effluent guideline were
adopted, then the purchase of treatment equipment is a short-run cost for
once the machinery is in place the new "steady state" is achieved. The
upkeep of the machinery is a long-run cost, however, for it will occur
every year in the future.
A second important distinction among costs is that between those
involving direct monetary outlays and those which are felt in other ways.
If an effluent guideline were adopted, then the treatment equipment is an
out-of-pocket expense, but if the quantity produced decreases as a result,
then the foregone consumer surplus is a cost despite the fact that there
is no direct monetary outlay.
The costs estimated for each control alternative are in terms of
dollars per kilogram of cadmium diverted from dissipation via the use in
question. It is tempting to assume that all cadmium diverted by a speci-
fied control measure is harmless. This is not necessarily true. The
costs presented here represent the cost of having cadmium in one form
rather than another. The flow of cadmium through the environment is
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much like the flow of blood through the body — closing one vessel or
channel simply forces blood through, another. If, for example, cadmium
is no longer dumped into a stream, it will be deposited as landfill; if
it cannot be used in electroplating, it can be used as a pigment or other
alternative. The metal will be mined as long as zinc ore is mined; how-
ever, the network of dispersion can be affected by regulation. The cost
estimates in this study represent the costs of altering this flow, not
the costs of rendering the cadmium harmless.
A comparison of control options on the basis of dollars per kilo-
gram of cadmium diverted is also potentially misleading unless recognition
is made of the benefits to human health and to environmental quality from
each such diversion. The eventual choice of control measures should ideally
be based upon the cost per unit reduction in health damage. Although the
correlation between quantities of cadmium emitted and health damage was
discussed in Sections X, XI, and XII, the basis for a quantitative estimate
of health damage does not yet exist. For the purposes of this section,
therefore, the benefits of a control alternative will be assessed in terms
of quantity of cadmium diverted from dissipation, with the results regarded
as the results of a screening mechanism of candidate options. Without a
more precise measure of health benefits, it is not possible to identify
the most cost-effective options or to determine the amount of diversion
societally desirable. The purpose of this section is to provide an indi-
cation of the available options, their likely effects, and the probable
costs — important steps in selecting controls to be instituted.
The control options evaluated here are those which seemed most
feasible in preliminary review. Many alternatives were considered and
some were rejected for detailed analysis because the costs appeared too
great for the perceived benefit on an a priori basis; others were rejected
because their effectiveness was shown to be too small.
Costs of a Ban on the Use of Cadmium
A ban can be selective or all-encompassing. In this report, costs
of banning the use of cadmium in each of the four major industries and in
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all uses will be considered. As has been pointed out, the costs can be
broken most simply into two categories, long-run and short-run. An out-
line of the costs which can be applied to each case will be developed, but
the way in which the costs arise will be explained first.
Most of the costs of a cadmium ban are those one would expect in
any industry. However, due to the peculiarity of the cadmium market,
certain unexpected costs are incurred. Because cadmium is produced solely
as a byproduct, and because the quality requirements of the primary pro-
duct (zinc) and emission regulations force the isolation of most of this
byproduct, the cadmium supply is highly inelastic, i.e., highly insensitive
to price (as Figures 5 and 8 show). Moreover, the marginal costs for re-
fining cadmium (once it is isolated in dusts and sludges at appreciable
concentrations) are likely much less than the market price for cadmium;
it was earlier estimated that these marginal production costs are less
than $2 per kilogram, compared to a price of $7 to $11 per kilogram.
Since a decrease in cadmium demand resulting from a total or partial
ban on its use will decrease sales and therefore revenues and profits to
the smelters, the zinc industry would be affected by a ban, either selec-
tive or all-encompassing, on the use of cadmium. Approximately 4 kg of
cadmium are refined from a metric ton of zinc in the production process
which means $40 in revenues are returned from cadmium sales for every
$800 in zinc sales. If the profit margin on zinc sales is assumed to be
10 per cent (or $40 per metric ton), and if it is assumed that the profit
margin on cadmium sales is $5 per kilogram (or $20 per metric ton of zinc),
then the following illustrates the relative importance of cadmium to the
zinc industry:
Cadmium quantity, 0.4 per cent of zinc quantity
Cadmium revenues, 5 per cent of zinc revenues
Cadmium profits, 25 per cent of zinc profits
It must be emphasized that the above comparison of profit is
without any real basis in data or in substantive analysis. Of course,
the method of allocating production costs would influence the comparison
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of cadmium and zinc profits; if the costs for removal of cadmium from
zinc calcines and if a proportion of the mining, beneficiation, and
roasting costs were charged to cadmium, then the profit comparison would
be entirely different. However, the fact remains that a total ban on
cadmium, resulting in stockpiling of cadmium dusts and sludges at primary
zinc plants, would have a relatively large effect on the overall industry
profit margin.
Through instituting a ban, society suffers a cost equal to the
difference between the benefits which would be derived by producing the
cadmium and the benefits which can result from using those resources in
their next most productive capacity. The lowered level of production
will free resources to move into other uses and idle capital and unemploy-
ment will result from their partial immobility. This is a short-run
phenomenon resulting in short-term costs.
The primary cost of a ban is the foregoing of the benefits from
cadmium usage, a long-run cost. If the market system is functioning prop-
erly, then the resources presently used to produce cadmium are being used
in their most productive capacity, that is, they would produce fewer bene-
fits if employed elsewhere. Therefore, by prohibiting a form of cadmium
consumption one forces them into alternative production and suffers a cost
equal to the difference between the benefits if used in cadmium production
and the benefits if used elsewhere — the consumer surplus. The following
subsection explains in greater detail the definition of foregone benefits
and the techniques for their estimation.
Definition and Estimation of Foregone Benefits
Cadmium pollution can be reduced by control devices that prevent
cadmium emissions or by a ban on cadmium uses. Whereas control devices
involve extra cost in cadmium production or use, a ban on cadmium involves
a cost in forcing people to use cadmium substitutes — forcing users to
forego the benefits of cadmium over and above the next best substitute.
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Although there are substitutes in virtually every use of cadmium,
they are not perfect substitutes. Sometimes they cost more, sometimes
they don't provide the same quality product, and sometimes they don't last
as long. The mere fact that cadmium is being used verifies that it has
advantages over the next best substitutes. It is possible that some uses
are not justified at current market prices, but it is inconceivable that
all uses are unjustified.
There is a question whether cadmium use would be justified
(economical) if the cost of environmental damages were added to current
market prices. This project does not include estimating cost of the en-
vironmental damage; however, it does include estimating the cost of a ban
on cadmium use — one means bo avoid environmental damage. The cost of
a ban is the cost to society of foregoing the benefits of present and
future cadmium use:
1. Benefits to users — the difference between market
price and the value of cadmium in various uses.
2. Benefit to producers — the difference between.
market price and the cost of producing cadmium
for the market.3
By estimating and adding the twD foregone benefits we can determine
the minimum environmental damage cost that will justify a ban on cadmium
use.
Figure 11 is a simple market description illustrating foregone
benefits from a ban which prohibits the Q consumption of cadmium for, say,
pigments. Users forego benefits equal to area P^P^A while producers forego
benefits equal to area P-P^A. In other words, users pay only the P~ mar-
ket price, but the actual value/unit of cadmium to them is the average value
on the demand curve between P_ and A. Likewise, producers receive price
since cadmium is a by-product and there can be disposal costs if it is
not sold, the production cost must be calculated carefully.
-181-
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FIGURE 11
FOREGONE BENEFITS
-182-
-------
?„, but the average cost/unit is only the average value on the oost curve
between P, and A.
By determining the value of cadmium from demand curves, we auto-
matically consider the possibility of cadmium substitutes. The difference
between the D, specified demand for pigments and the lower D~ demand for
cadmium as a specific pigment reflects opportunities for substitutes.
Stated otherwise, the foregone benefits to users from a ban on cadmium would
be P->P4B instead of the smaller P2P^A ^ cadmium had no substitute.
There are two basic ways to determine foregone benefits to cadmium
users and producers. One approach is an engineering analysis— an analysis
that a user himself would employ in determining what he is willing to pay for
cadmium and its substitutes, or that a producer himself would employ in deter-
mining how much to produce at each price. A second approach is to trace out
the demand curve (e.g., the curve P.~A in Figure 11) from (1) observed changes
in market prices and quantities and (2) opinions of experts among suppliers
and consumers.
The estimates for this study were developed under the second
approach. The first approach is very expensive and subject to significant
errors from inaccurate or incomplete information.
Cadmium demand curves developed for this study indicate that sub-
stitutes for some uses are very good and, therefore, a ban would produce
few foregone benefits. In other uses, substitutes are so inferior that the
current $7 to $9 per kg market prices could increase to $22 per kg and users
vould still prefer cadmium over substitutes. By definition, the cadmium
user who would pay as much as $22 per kg would forego a minimum of $15 benefit
per kilogram if the cadmium he can now purchase at $7 per kg is banned.
The cadmium demand curve P_A in Figure 11 is drawn to indicate that
market price is nearly equal to consumer value for part of the uses, but
consumer value is significantly above market price in other uses.
In the long run, foregone benefits are paid by the many consumers
of products in which cadmium is a component. It is erroneous to think that
the benefits of cadmium uses are obtained by a few producers acting against
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the public interest while the benefits of less cadmium pollution are to be
enjoyed by the general public. In the short run, producers of cadmium and
manufacturers that use cadmium in their products will suffer losses from a
ban. However, in the long-run, suppliers reach a new equilibrium via zinc
prices and the consumers bear the loss of foregone benefits via higher zinc
prices and via higher prices or lower quality of products containing sub-
stitutes for cadmium.
Estimates of foregone benefits are certainly subject to error.
However, they are often a significant cost to society whenever there is
a ban on products for environmental or any other reason; therefore, fore-
gone benefits must be estimated to provide a complete accounting of social
costs and they must be analyzed if we expect to make rational decisions on
cadmium controls. Estimates in this report are objective estimates of
cost consequences of specified cadmium control alternatives.
Outline of Cost Elements
A. Long-Run
1. Foregone Benefits — If cadmium can no longer be
used for a certain purpose, then society must fore-
go the benefits in excess of the best alternative
use of resources. The cost is equal to the amount
society would have been willing to pay to have
cadmium available for that purpose, the area under
the demand curve, less the amount which would have
been paid in alternate uses, the area under
the marginal cost curve. This cost occurs each
year the ban is operative.
One factor which affects this cost is the de-
velopment of new substitutes. Whereas the
presently available substitutes are represented
in the demand curve, new substitutes that could
be developed are not included, even though they
can reduce the cost significantly.
-184-
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2. New Discharges — when cadmium is selectively
banned from one industry it may be used in
other industries which will result in new dis-
charges. The magnitude of this cost depends
upon the industry or industries which use the
freed cadmium and how much they use. Since the
estimation of foregone benefits already allocates
the freed cadmium to alternate uses, the quantity
of new discharges will be equal to the increment
in consumption for each use. Hence, under the
assumption of equivalent environmental damage
per unit of cadmium dissipated (regardless of
the mechanism or form of dissipation), no addi-
tional costs will result. For the case of a
total cadmium ban, there is a priori no new dis-
charge costs.
3. Disposal of Excess Cadmium — Since the quantity
of cadmium in the zinc is fixed, when less cad-
mium is recovered, more cadmium is distributed
elsewhere. In the long-run this quantity should
be deposited as a secured landfill. It should
be pointed out that, by placing a ban on a
certain form of consumption, domestic demand
is unlikely to fall by an amount equal to that
form of consumption. As a result of decreasing
domestic production and increasing domestic
consumption, future slacks in demand are more
likely to result in decreased imports than de-
creased domestic demand. Carried further, suf-
ficient slacks in demand would result in esqports
-185-
-------
of primary cadmium. This aspect further confuses
an. estimate of this cost and the costs of new dis-
charges.
4. Smelter Impact — Since a ban will decrease
demand for cadmium, revenues to the smelter
will decline and one might expect an impact
on this industry. The comparison of zinc and
cadmium quantities, revenues, and profits made
previously (while having no real basis in fact
or data) indicates that some increase in zinc
price would be expected to make up for any
lost cadmium revenues and profits. Without
explicitly evaluating the zinc price increase
or the long-run costs of such an increase; it
will be assumed that the zinc price will in-
crease about $0.02 per kilogram for a total
cadmium ban, equivalent to the lost cadmium
profits. Further, it will be assumed that
this 2.5 per cent increase in zinc prices will
not result in a significant decrease in domestic
zinc consumption. If this domestic price in-
crease is sufficient to cause a competitive dis-
advantage with respect to imported zinc, the U.S.
could conceivably increase the import tariff
from the present value. U/l/75) of $0.015 per
kilogram to the statutory limit of $0.039 per
kilogram.
For these reasons, then, the long-run smelter
impact costs will be assumed negligible for the
purposes of this study. The authors invite
-186-
-------
other estimates, however, in light of the gross
and unsubstantiated assumptions made in this
estimate.
B. Short-Run
1. Capital that becomes obsolete or reduces in value.
If cadmium is not available for a specific pro-
duction process, then either the capital will be
used for other purposes in its present state, it
will be converted for other purposes, or it will
lie idle, depending upon the costs of conversion
and the perceived productivity of the capital in
a new function. The cost of a cadmium ban to
society depends upon how much of the benefits
which could have been provided by the existent
capital can be reclaimed. By introducing a
tdjre lag between the announcement of a ban and
its institution, these costs can be reduced
significantly.
2. Unemployment — As a specific production is
halted by a ban on cadmium, the labor involved
in that production could become unemployed. The
cost depends upon the amount of time unemployed
and their productivity in new jobs relative to
the old jobs. By introducing a time lag between
the announcement of a ban and its institution,
these costs can be reduced significantly.
3. Stockpiling — If the demand for cadmium is
reduced, stockpiling is likely to occur as a
short-run response. The cost is the oppor-
tunity cost of using the resources which go
into stockpiling. The drop in demand will
-187-
-------
result in fewer imports and a short-run stock-
piling at the smelter for a ban on electro-
plating (where the total demand will be signi-
ficantly reduced). For a total ban on cadmium,
stockpiling would probably not occur since the
smelters would have no reason to refine the
cadmium to stockpile.
Because an estimate of the amount stockpiled
is dependent on so many unknown variables,
this cost will not be quantified. However,
since the cost is probably small and it only
exists in the short-run, this will not affect
the results appreciably.
4. Lag Time for Substitutes — In considering the
benefits foregone by the use of cadmium in
specific areas, the benefits which can be
provided by substitutes have been accounted
for. However, these substitutes will not
be readily available when the cadmium ban
is effected. During the conversion to sub-
stitutes, the benefits from these substitutes
are also foregone. The introduction of a
time lag can reduce this cost also.
5. Miscellaneous — Depending upon the particular
industry and use, there may be additional short-
run costs. For instance, if Ni-Cd batteries are
banned, further costs are incurred since these
batteries are component parts of other consumer
goods:
changing machinery producing these
goods so that they can use another
power source,
-188-
-------
. converting the goods already pro-
duced to use another power source,
and/or
goods left unused because Ni-Cd
batteries are not available and the
costs of power conversion are too
high.
These costs will not be estimated; in general,
they will be insignificant when compared to the
rest.
Using the above outline as a guide, the costs resulting from a
selective ban on each of the primary uses of cadmium will be considered,
as well as a total ban on all forms of cadmium consumption.
Foregone Benefits (Long-Run Costs)
Using the estimated cadmium demand curves of Figures 9 and 10, the
foregone benefits for each ban was calculated as the area, above the supply
curve, between the demand curve without bans and the appropriate demand
curve for each ban. Hence, the foregone benefits for a ban on nickel-
cadmium batteries is the area within ABCEDA; those for a ban on cadmium
pigments is the area within ABCGFA; etc. The results are tabulated below
in terms of the annual foregone benefits for each selective ban, and the
foregone benefits per kilogram of cadmium diverted for each ban (the quanti-
ties of cadmium diverted are listed in Table 34).
-189-
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Cadmium Use Ban
Assumed
Baseline-i
Period
1985
None
Batteries
Pigments
Stabilizers
Electroplating
.All
None
Batteries
Pigments
Stabilizers
Electroplating
.All
Foregone Benefits,
Million Dollars/Year
0
3.3
7.4
9.3
48.8
92.2
0
26.6
8.1
0.4
64.3
149.3
Foregone Benefits,
DollarsAg Diverted
_
16.70
10.60
8.40
18.10
16.40
_
16.60
13.60
0.80
17.30
16.20
The foregone benefits for bans on batteries or electroplating, or
for a total ban on cadmium use, are approximately $16 per kilogram of cad-
mium diverted from these uses. The foregone benefits from banning pig-
men ts are somewhat lower (approximately $12 per kilogram diverted)
reflecting the slight elasticity in the pigment demand, curves of Figures 6
and 7. Banning cadmium heat stabilizers would involve foregone benefits
of $8 per kilogram in the baseline period, and less than $1 per kilogram
in 1985, since substitutes are available at much lower price levels than
substitutes for other cadrnium-consuming commodities.
Disposal of Excess Cadmium (Long-Run Costs)
The 1974 domestic cadmium production capacity is 3,300 metric tons
per year, and the projected 1985 capacity is 4,600 metric tons per year.
Comparing these to the estimates of total consumption of Table 34 for as-
sumed cadmium use bans results in the data of Table 35, the maximum esti-
mates for the quantities and costs for disposal of excess cadmium. A unit
cost for environmentally adequate land disposal (i.e., secured landfill)
of cadmium-rich sludges or dusts was taken as $320 per metric ton of ele-
mental cadmium in the waste (see Section VTI). In lieu of estimating any
-190-
-------
TABLE 35
ESTIMATED MAXIMUM COSTS FOR DISPOSAL OF E3CESS CADMIUM
Cadmium Use Ban
Assumed
Baseline
Period *
1985
None
Batteries
Pigments
Stabilizers
Electroplating
.All
None
Batteries
Pigments
Stabilizers
Electroplating
.All
Excess Cadmium,
kkg/yr
0
0
0
0
400
3,300
0
0
0
0
0
4,600
Cost of Disposal,
Million Dollars/Year
0
0
0
0
0.12
1.05
0
0
0
0
0
1.47
-191-
-------
excess quantities (of domestic production over domestic consumption) ex-
ported, i.e., an analysis of the world cadmium market, the maximum costs
for disposing of excess cadmium are estimated by assuming no exports.
Idle Capital (Short-Run Costs)
In the nickel-cadmium battery industry, it is felt that if cadmium
were unavailable, the existent plant and equipment would have no alterna-
tive uses and, therefore, a zero salvage value. This is probably an over-
statement; buildings could surely be converted to another function at a
certain cost; however, for purposes of this report, we shall consider the
statement to be essentially true. Since machinery has a productive capacity
which would not be utilized in any fashion, society foregoes certain bene-
fits by allowing it to lie idle. The true loss is difficult to estimate
since members of the industry are reluctant to divulge any pertinent data.
Even the National Electrical Manufacturers Association, an organization
which includes the battery manufacturers among its members, has been un-
able to obtain such data. A very crude estimate is possible, however.
One firm estimated the original cost of plant and equipment at $14
million. Since their annual sales are approximately 15 per cent of the
Ni-Cd battery market, it is reasonable that the total original value of
industry plant and equipment would be about $100 million. Considering
that most of the productive capacity has been built in recent years,
depreciation to date should not be large, and this figure seems a reasonable
estimate of present value. If this present value is amortized over 15 years,
the annual cost is $7 million per year.
A more precise estimate would be desirable, but the error should
not affect the final cost estimate appreciably.
In the cadmium electroplating industry, state and federal effluent
controls will probably create a trend towards concentration in fewer shops.
At present, there appear to be many shops with only one cadmium bath — a
small cadmium plating capacity. If effluent limitations are much more
-192-
-------
stringent for cadmium than for zinc, the additional cost would price most
of them out of the cadmium plating market because there are larger opera-
tions which can spread the cost over a larger output. As an example, the
job plating shop described earlier in this report plated cadmium on only
12 per cent of its work; it is possible that such a shop may elect to dis-
continue cadmium plating should effluent guidelines dictate segregation and
separate treatment and recovery of cadmium wastes.
Although much of cadmium plating is manual barrel plating, the baths
would likely be used (if cadmium plating were banned) for barrel plating of
zinc, copper, nickel, chrome, or other metals. The idle capital costs due
to a cadmium plating ban, therefore, should not be significantly higher
than the idle capital costs resulting from stringent effluent guidelines.
Hence, no separate costs will be attributed to banning cadmium plating.
The equipment used in manufacturing barium-cadmium heat stabilizers
can be used to produce the substitute calcium-zinc stabilizers. Therefore,
beyond some small transition costs, the costs of idle capital should be
negligible.
The production process for cadmium pigments is unlike that of any
other type pigment so their plant and equipment would have no reclaim
value. Six companies manufacture cadmium pigments and the approximate
cost of a "typical plant" is $5 million. The plant itself should last
forty years and the production equipment 10 years. Assuming that half
the value of the plant and equipment of the six companies has been used
thus far, a cost of nearly $1 million per year for the next twenty years
from idled capital would result.
Unemployment (Short-Run Costs)
As the capital is idled, labor is unemployed. Unlike capital, how-
ever, labor can find substitute employment and so the cost exists for a
shorter duration. The same battery firm mentioned above, whose annual
sales are approximately 15 per cent of the market, employs 400 persons.
Based upon this employment-output rate, industry-wide employment is 3,000.
-193-
-------
The average salary in. the storage battery industry is $9,000 (1972 Census
of Manufacturers, Preliminary Report). If the average length, of unemploy-
ment caused by the ban v/ere 6 months, the associated cost would be $13.5
million.
In the electroplating industry, some unemployment will probably
occur if a. ban is instituted; some shops will have to lay off workers
while they find new demand to replace their cadmium contracts. Even if
a shop replaces its cadmium plating demand with substitutes, it is possible
that more highly skilled workers would be required (cadmium plating is a
less critically-controlled operation). The unemployment or shifts in em-
ployees are likely to be short run, and of an insignificant magnitude
compared to the costs already cited. The unemployment cost might become
significant if many shops were to close, but as stated before, the costs
over and above the costs resulting from stringent effluent guidelines
would probably be small.
No significant unemployment costs (beyond some small transition
costs) are expected for the heat stabilizers industry, where substitutes
may be made by the same workers.
A "typical" cadmium pigments plant employs 15 hourly and 2 to 3
salaried employees. If their average annual salary wjere $10,000. and six
months expired before alternative employment could be found, a cost of
$85,000 would occur in the first year of the ban. For the entire industry
(six companies), the unemployment costs in the first year would be $510,000.
Sunnary of the Costs for Banning Cadmium Use
Table 36 summarizes the costs for each- selective ban and for a
total ban on cadmium use. As Table 36 shows, the foregone benefits are the
overwhelming costs for all except the battery industry (where idle capital
and unemployment costs are large). The additional short-run costs for a
total ban on cadmium would be (based upon an estimated 1975 cadmium con-
sumption of 6,000 metric tons) $3.60 per kilogram for the first year and
$1.30 per kilogram for each of the next 15 to 20 years.
-194-
-------
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ro
8
•*
r-
a\
b
% 3
&
1
to
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00 O 00
2 ° 2
** >*
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ro o ro
Annual Costs:
Benefits
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* •
O O 0
rH rH
CO O CO
vo ^>
VO O *i)
CN CN
tonual Costs:
Benefits
(U rH
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m
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0 0
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0101
0101
in
rH O O rH
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-195-
-------
Costs of Banning Cadmium
The costs of an import ban were estimated in the same way as the
costs of a use ban. The foregone benefits were calculated by integrating
to the left of the total supply and demand curves Gas they intersect at
Point A on Figure 8) , and subtracting the integral to the left of the
domestic production and demand curves (as they intersect at Point B) .
These long-run costs are $24.4 million per year $11.10 per kilogram of
cadmium diverted) for the 1985 time frame.
The short-run costs for the domestic cadMAmi-consuming industries
would be approximately 40 per cent of those costs shown in Table 36 Csince
the decrease in consumption would be approximately 40 per cent of a total
ban on each use) :
Idle Capital Costs*
Duration, Years
Unemployment Costs*
Duration, Years
Cadmium-Using Industry
Batteries
2.8
15
5.4
1
Pigments
0.4
20
C.2
1
Stabilizers
0
-
0
—
Electroplating
0
-
0
—
All
3.2
15-20
5.6
1
*Millions of Dollars Per Year
-196-
-------
SECTION XV
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78. Bonnell, J.A., Ann. Occup. Hyg., £, 45-49, 1965.
79. Harada, A., and Y. Shibuya, Preprint in Japanese, p. 18-24, 1973.
80. Hammer, D.I., J.F. Finklea, J.P. Creason, S.H. Sandifer, J.E. Keil,
L.E. Priester, and J.F. Stara, Preprint, Missouri Univ., Columbia,
1971.
81. Friberg, L., M. Piscator, G. Nordberg and T. Kjellstrom, Cadmium in
the Environment, II. EPA-R2-73-190, 1973.
82. Moore, W. Jr., J.F. Stara, W.C. Crocker, M. Malanchuk, and R. Iltis,
Environ. Res. 6_, 473-478, 1973.
83. Suzuki, S. and T. Tanaka, Proc. Sci. Res. Meet. Itai-Itai Disease
Cadmium Poisoning, Tokyo, Japan 1971.
84. Nakagawa, A., T. Hirono, and I. Murata, ibid.
85. Kitamura, S., ibid.
86. Morgan, J.M., Arch. Environ. Health, 24, 364-368, 1972.
87. Cadmium and the Environment: Toxicity, Economy, Control; Organization
for Economic Cooperation and Development, Environment Directorate,
Paris, 1975.
88. Kneip, T.J., and G.J. Laner, Trace Metal Concentration Factors in
Aquatic Ecosystems, N.Y. University Medical Center, NYC, May 1973.
89. John, M.K., C.J. VanLaerhoven, and H.H. Chuah, Factors Affecting
Plant Uptake and Phytotoxicity of Cadmium Added to Soils,
Environmental Science & Technology 6_, 12, 1005-9 (Nbv 1972).
90. John, M.K., H.H. Chuah, C.J. VanLaerhoven, Cadmium Contamination of
Soil and Its Uptake by Oats, Environmental Science & Technology 6_,
6, 555 (6/72).
-202-
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91. Helena Valley, Montana, Area Environmental Pollution Study,
PB-207126.
92. Pitt, R.E. and G. Amy, Toxic Materials Analysis of Street Surface
Contaminants, EPA-R2-73-283 (Aug 1973).
93. Page, A.L., Fate and Effects of Trace Elements in Sewage Sludge
When Applied to Agricultural Lands, EPA Advanced Waste Treatment
Research Laboratory, Jan 1974, PB 231171.
94. Pound, C.E., and R.W. Crites, Wastewater Treatment and Reuse by Land
Application, EPA-660/2-73-006a (Vol I) and - 006b (Vol II), Aug 1973.
95. Land Application of Sewage Effluents and Sludges: Selected Abstracts,
EPA-660/2-74-042 (June 1974).
96. Proceedings of the Joint Conference on Recycling Municipal Sludges
and Effluents on Land, Champaign, 111., July 1973.
97. Klein, D.H., and P. Russell, Heavy Metals: Fallout Around a Power
Plant, Environ. Science and Technology "]_, 4, 357-8 (Apr 1973).
98. Haghiri, F., Cadmium Uptake by Plants, J. Environ. Quality 2_, 1,
93-6 (1973).
99. Lagerwerff, J.V., Uptake of Cadmium, Lead and Zinc by Radish from
Air and Soil, Soil Science 111, 129-33 (1971).
100. Athanassiadis, Y.C., Air Pollution Aspects of Cadmium and its Compounds,
NAPCA/HEW, PB 188086 (Sept 1969).
101. Compilation of Air Pollution Emission Factors (Second Edition), EPA
Office of Air Quality Planning and Standards (April 1973).
102. Illinois Institute for Environmental Quality, Health Effects and
Reconrnendations for Atmospheric Lead, Cadmium, Mercury, and Asbestos,
PB-220224 (March 1973).
103. Schroeder, H.A., Air Pollution by Metals, Archives of Environmental
Health, Vol 21 (Dec 1970).
104. "Trends in Usage of Cadmium", National Materials Advisory Board,
National Academy of Sciences - National Academy of Engineering,
Washington, D.C. November 1969.
105. Minerals Industry Surveys, "Cadmium in the First Quarter 1974,"
Bureau of Mines, U.S. Department of the Interior, Washington, D.C.
20240.
106. Billings, C.E., and W.R. Matson, Science 176_, 1233-43 (1972).
107. Private Communications, National Association of Metal Finishers,
Metal Finishers Suppliers Association, and member companies.
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BIBLIOGRAPHIC DATA
SHEET
1. Report No.
3. Recipient's Accession No.
4. Title and Subtitle
Technical and Microeoonomic Analysis of Cadmium and its
Compounds
5. Report Date
March 1975
6.
7. Author(s) Jack Faucett
Donald H. Sargent (Versar Inc.) and John R. Metz (Associates) "
8. Performing Organization Kept.
NO. 454^
9. Performing Organization Name and Address
Versar Inc.
6621 Electronic Drive
Springfield, Virginia 22151
10. Project/Task/Work Unit No.
II. Contract/Grant No.
68-01-2926
12. Sponsoring Organization Name and Address
U.S. Environmental Protection Agency
Office of Toxic Substances
Washington, D.C. 20460
13. Type of Report & Period
Covered
Final Report, Task 1
14.
15. Supplementary Notes
16. Abstracts
The role of cadmium (and its compounds) in the environment and in the
economy of the United States was studied, to evaluate the need for and the
projected effect of controlling its production, use and dissipation. Techno-
logically and economically feasible control alternatives were developed from.:
(1) A systematic documentation of cadmium production, uses, prevalence, and"
sources of pollution; and (2) An evaluation of the present and projected
health hazards. Available information was then used to directly compare and
optimize the various alternatives.
The results led to t\n sets of recortmended controls. The first, aimed
at preventing increases in the present cadmium health hazards, consists of
continued_air and water pollution abatement, environmentally-sound land dis-
posal of industrial wastes and residuals, and regulation of application rate:;
to agricultural lands of cadmium-bearing materials. The second set of controls
exhibits a more aggressive posture towards limiting cadmium dissipation, which
could be implemented in the future should a irore precise definition of the health
hazard justify such a posture. This second set of controls includes limitation
of the cadmium impurities in products of the zinc industry, reduction in the
demand for cadmium by voluntary action of several key industries and govern-
ment, and the restriction or abolition of cadmium imports.
17. Key Words and Document Analysis. 17o. Descriptors
Cadmium
Cadmium ProdBCtion
Cadmium Use
Cadmium Toxicology
Zinc Production
Cadmium Electroplating
Cadmium Pigments
Barium-Cadmium Heat Stabilizers
Nickel-Cadmium Batteries
Cadmium Microeconomics
7b. Identifiers/Open-Ended Terms
Cadmium Control Alternatives
Cadmium in Sewage Sludge
Cadmium in Phosphate Fertilizers
Cadmium in Coal
Cadmium in Scrap Iron and Steel
Cadmium Air Pollution Control
Cadmium Water Pollution Control
Cadmium in Land-Destined Wastes
17c. COSATI Field/Group
8. Availability Statement
Release Unlimited
19. Security Class (This
Report)
UNCLASSIFIED
20. Security Class (This
a
21. No. of Pages
209
22. Price
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