United States Office of Water October 1981
Environmental Protection Regulations and Standards (WH-553) EPA-440/4-85-011
Agency Washington DC 20460
Water
&EPA An Exposure
and Risk Assessment
for Mercury
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DISCLAIMER
This is a contractor's final report, which has been reviewed by the Monitoring and Data Support
Division, U.S. EPA. The contents do not necessarily reflect the views and policies of the U.S.
Environmental Protection Agency, nor does mention of trade names or commercial products
constitute endorsement or recommendation for use.
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50772-101
REPORT DOCUMENTATION »• R*«>RT NO. 2.
PAGE EPA-440/4-85-011
4. Title and Subtitle
An Exposure and Risk Assessment for Mercury
7. Author^ Perwak, J.; Goyer, M. ; Nelken, L.;
Scow, K.; Wald, M. ; and Wallace, D.
9. Performing Organization Name and Address
Arthur D. Little, Inc.
20 Acorn Park
Cambridge, MA 02140
12. Sponsoring Organisation Name and Address
Monitoring and Data Support Division
Office of Water Regulations and Standards
U.S. Environmental Protection Agency
Washington, B.C. 20460
3. Recipient's Accession No.
5. Report Date Final Revision
October 1981
6.
8, Performing Organization Rept. No.
10. Project/Task/Work Unit No.
11. Contrsct(C) or Grant(G) No.
C-68-01-3857
C-68-01-5949
(G)
13. Type of Report & Period Covered
Final
14.
15. Supplementary Notes
Extensive Bibliographies
16. Abstract (Limit: 200 words)
This report assesses the risk of exposure to mercury. This study is part of a program
to identify the sources of and evaluate exposure to 129 priority pollutants. The
analysis is based on available information from government, Industry, and technical
publications assembled in August of 1980.
The assessment includes an identification of releases to the environment during
production, use, or disposal of the substance. In addition, the fate of mercury in
the environment is considered; ambient levels to which various populations of humans
and aquatic life are exposed are reported. Exposure levels are estimated and
available data on toxicity are presented and interpreted. Information concerning all
of these topics is combined in an assessment of the risks of exposure to mercury for
various subpopulations.
17. Document Analysis a. Descriptors
Exposure
Risk
Water Pollution
Air Pollution
b. Identlflers/Open-Cnded Terms
Pollutant Pathways
Risk Assessment
c. COSATI Field/Group Q6F 06T
Effluents
Waste Disposal
Food Contamination
Toxic Diseases
Mercury
It. Availability Statement
Release to Public
19. Security Class (This Report)
Unclassified
20. Security Class (This Page)
Unclassified
21. No. of Pages
218
22. Price
$19.00
ee ANSI-239.18)
See Instructions on Reverse
OPTIONAL FORM 272 (4-77)
(Formerly NTIS-35)
Department of Commerce
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EPA-440/4-85-011
August 1980
(Revised October 1981)
AN EXPOSURE AND RISK ASSESSMENT
FOR MERCURY
by
Joanne Perwak
Muriel Goyer, Leslie Nelken, Kate Scow
Margo Wald, and Douglas Wallace
Arthur D. Little, Inc.
Gregory Kew
Project Manager
U.S. Environmental Protection Agency
EPA Contract 68-01-3857
68-01-5949
Monitoring and Data Support Division (WH-553)
Office of Water Regulations and Standards
Washington, D.C. 20460
OFFICE OF WATER REGULATIONS AND STANDARDS
OFFICE OF WATER AND WASTE MANAGEMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
Agency
• .'[";<•<' "• = • •-. ;
^<-f.o_.r • - . ,J,
IL 6C604-oa90
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FOREWORD
Effective regulatory action for toxic chemicals requires an
understanding of the human and environmental risks associated with the
manufacture, use, and disposal of the chemical. Assessment of risk
requires a scientific judgment about the probability of harm to the
environment resulting from known or potential environmental concentra-
tions. The risk assessment process integrates health effects data
(e.g., carcinogenicity, teratogenicity) with information on exposure.
The components of exposure include an evaluation of the sources of the
chemical, exposure pathways, ambient levels, and an identification of
exposed populations including humans and aquatic life.
This assessment was performed as part of a program to determine
the environmental risks associated with current use and disposal
patterns for 65 chemicals and classes of chemicals (expanded to 129
"priority pollutants") named in the 1977 Clean Water Act. It includes
an assessment of risk for humans and aquatic life and is intended to
serve as a technical basis for developing the most appropriate and
effective strategy for mitigating these risks.
This document is a contractors' final report. It has been
extensively reviewed by the individual contractors ?nd by the EPA at
several stages of completion. Each chapter of the draft was reviewed
by members of the authoring contractor's senior technical staff (e.g.,
toxicologists, environmental scientists) who had not previously been
directly involved in the work. These individuals were selected by
management to be the technical peers of the chapter authors. The
chapters were comprehensively checked for uniformity in quality and
content by the contractor's editorial team, which also was responsible
for the production of the final report. The contractor's senior
project management subsequently reviewed the final report in its
entirety.
At EPA a senior staff member was responsible for guiding the
contractors, reviewing the manuscripts, and soliciting comments, where
appropriate, from related programs within EPA (e.g., Office of Toxic
Substances, Research and Development, Air Programs, Solid and
Hazardous Waste, etc.). A complete draft was summarized by the
assigned EPA staff member and reviewed for technical and policy
implications with the Office Director (formerly the Deputy Assistant
Administrator) of Water Regulations and Standards. Subsequent revi-
sions were included in the final report.
Michael W. Slimak, Chief
Exposure Assessment Section
Monitoring & Data Support Division (WH-553)
Office of Water Regulations and Standards
111
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TABLE OF CONTENTS
Page
LIST OF FIGURES viii
LIST OF TABLES ix
ACKNOWLEDGMENTS xi
I. EXECUTIVE SUMMARY 1
II. INTRODUCTION g
III. MATERIALS BALANCE X1
A. Introduction •]_•,
B. Production 17
1. Introduction ]_7
2. Process Description u
3. Environmental Releases from Mining and Production
Processes 2.8
C. Uses 18
1. Introduction 10
2. Electrical Apparatus 3.8
a. Introduction j_g
b. Batteries 21
c. Electric Lamps 21
d. Switches, Rectifiers, etc. 22
3. Electrolytic Preparation of Chlorine and Caustic Soda 22
4. Industrial Instruments 24
5. Mercury Compounds 25
a. Introduction 25
b. Catalysts . 25
c. Paint Manufacturing 25
d. Fungicides and Bactericides 26
e. Pharmaceuticals 26
f. General Laboratory Use 95
g. Dental Preparations 27
D. Natural and Inadvertent Sources 27
1. Natural Sources 27
2. Fossil Fuel Combustion 28
3. Mining and Smelting Operations 28
4. Mercury as an Impurity 28
5. Publicly Owned Treatment Works 28
6. Urban Runoff 29
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TABLE OF CONTENTS (Continued)
Page
E. Conclusions 29
References 31
IV. FATE AND DISTRIBUTION OF MERCURY IN THE ENVIRONMENT 35
A. Monitoring Data 35
1. Introduction 35
2. Water 35
3. Sediment 40
4. Rocks and Soil 43
5. Air 43
6. Aquatic Biota 47
7. Terrestrial Biota ^
B. Environmental Fate 54
1. Overview 54
a. Methodology 54
b. Major Environmental Pathways 55
c. Important Fate Processes 55
2. Physicochemical Pathways 59
a. General Fate Discussion 59
i. Aqueous Complexation 59
ii. Mercury Transport in Aqueous Systems ^
iii. Atmosphere 62
iv. Soils 64
v. Methylation 64
b. Atmospheric Transport 69
i. Overview 69
ii. Municipal Solid Waste and Sewage Incineration JQ
iii. Chlor-Alkali Plants 70
iv. Coal and Other Fossil Fuel Combustion 72
v. Metallurgical Plants 72
vi. House Paints 72
vii. Summary Statement 72
c. Solid Wastes and Agricultural Applications 73
i. Overview 73
ii. Mine Tailings and Coal Piles 74
iii. Acid Mine Drainage 74
iv. Solid Waste Disposal Sites 74
v. Flyash Disposal Ponds 75
vi. Agricultural Applications 75
vii. Summary Statement 76
d. Aqueous Industrial Discharges 77
i. Sources and Treatment 77
ii. Distribution in Surface Waters 77
iii. Sludge Disposal 78
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TABLE OF CONTENTS (continued)
iv. Ultimate Sinks 73
v. Summary Statement 73
e. POTW 80
i. Treatment Schemes 80
ii. Sludge Disposal 81
iii. Surface Water Discharge 82
iv. Summary Statement 82
Biological Fate 82
1= Introduction 82
2. Uptake of Mercury 33
3. Bioconcentration 85
4. Route of Exposure 35
5. Elimination gj_
6. Biomagnification in the Food Chain 94
7. Terrestrial Biological Fate 04
Summary 07
1. Monitoring Data 97
2. Environmental Fate 93
3. Biological Fate 99
References
101
V. HUMAN EFFECTS AND EXPOSURE 115
Human Toxicity 115
1. Introduction 115
2. Metabolism and Bioaccumulation 115
3. Animal Studies 122
a. Carcinogenicity 122
b. Mutagenicity 122
c. Adverse Reproductive Effects 123
d. Other Toxicological Effects j^25
e. Interactions With Other Metals 127
4. Human Studies -]_27
a. Acute Exposure
b. Chronic Exposure
c. Adverse Reproductive Effects
5. Overviexv
Exposure 133
1. Introduction
2. Ingestion
a. Drinking Water
b. Food
3. Inhalation 139
4. Dermal Absorption 139
5. Users of Mercury-containing Products 142
vi
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TABLE OF CONTENTS (continued)
6. Overview
References
VI. BIOTIC EFFECTS AND EXPOSURE 151
A. Effects on Biota 151
1. Introduction 151
2. Freshwater Organisms 151
a. Chronic and Sublethal Effects 151
b. Acute Effects 152
3. Marine Organisms 152
a. Chronic and Sublethal Effects 152
b. Acute Effects 156
4. Other Studies 156
5. Factors Affecting the Toxicity of Mercury 159 i
6. Terrestrial Biota 161
a. Animals 161
b. Plants 161
7. Conclusions 152
B. Exposure to Biota 163
1. Introduction 163
2. Monitoring Data for Aquatic Systems 163
3. Factors Affecting Aquatic Exposure to Mercury 166
4. Exposure of Terrestrial Organisms 166
5. Conclusions 167
References 169
VII. RISK CONSIDERATIONS 175
A. Risks to Humans 175
1. Introduction 175
2. Major Exposure Routes and Effects Levels
3. Risk Considerations for the General Population
4. Risk Considerations for Subpopulation
a. Fisheaters 181
b. Fetuses 182
c. Children 182
d. Users of Mercury-containing Products 132
B. Risks to Biota 184
APPENDIX A: Notes to Table 1 ' 185
APPENDIX B: Status of Restrictions on Commercial and Sport
Fishing Due to Mercury Contamination 197
vii
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Figure
No.
LIST OF FIGURES
Page
1 Flow Diagram for the Cycle of Production,
Consumption, and Disposition of Mercury in
the United States, 1976 ' 14-15
2 Materials Balance for Mercury, 1976 16
3 Locations of Mercury Cell Chlor-Alkali Plants
in the U.S. 23
4 Maximum and Mean Ambient Concentrations of
Mercury in Surface Water of the United States,
1970-1979 — A Ten Year Trend 38
5 Mean Levels of Mercury in Major River
Basins in 1972 and 1979 39
6 Mercury Concentrations in Sediment, United States,
1970-1978 — A Ten Year Trend 41
7 Major Environmental Pathways of Mercury 56-57
8 Schematic Diagram of Major Pathways of
Anthropogenic Mercury Released to the Environment
in the U.S. (1976) 58
9 Stability Fields of Mercury Aqueous Species as a
Function of pE and pH 60
10 Adsorption of Trace Metals in Oxidizing Fresh Waters 63
11 Concentration of Mercury in Moss Samples as a
Function of Distance from a Chlor-alkali Plant
in Sweden 71
12 Predicted Values of the Average Concentration of
Mercury Dissolved in the Lower Great Lakes 79
13 Apparent Mercury Pathways in Fish 84
14 Status of Fishery Restrictions and Closures
in the United States, 1977 135
viii
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LIST OF TABLES
Table
No.
Page
1 Production and Use/Releases of Mercury
in the United States, 1976 13
2 Consumption of Mercury in the United States,
1965-1978 19
3 Concentrations of Mercury Detected in Water 36
4 Concentrations of Mercury Detected in Sediment 42
5 Concentrations of Mercury Detected in Rocks and Soil 44
6 Concentrations of Mercury Detected in the Atmosphere 46
7 Mercury Concentrations Detected in Aquatic Biota 48
8 Mercury Concentrations Detected in Terrestrial Biota 52
9 Distribution of Mercury in the Ottawa River 61
10 Percentage of Mercury Evolved From Soil in
144 Hours 65
11 Methyl Mercury Formation over Time and Relationship
with Concentrations of Mercury in Anaerobic Cultures 67
12 Bioconcentration Factors for Aquatic Species 86
13 Mercury Distribution in Ottawa River Ecosystem 87
14 Observations Regarding Route of Exposure of
Aquatic Biota to Mercury 88-89
15 Distribution of Mercury Mass in the Ottawa River 92
16 Biological Half-Lives of Methyl Mercury in
Various Species go
17 Biological Magnification of Mercury in the
Aquatic Food Chain 95
18 Concentrations of Mercury in Human Tissue 119-121
19 Clinical Correlations of Neurotoxicity and
Levels of Mercury in Blood 130
ix
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LIST OF TABLES (continued)
Table
' Page
20 Percent of Population Exceeding the Recommended
ADI for Mercury Due to Fish Consumption 137
21 Maximum Intakes of Mercury for Two Fisheaters 138
22 Methylmercury Contant of Fish 140
23 Inhalation Exposure to Mercury 141
24 Acute Toxicity of Inorganic Mercury to
Freshwater Finfish ' 153
25 Acute Toxicities of Organic Mercury Compounds
to Freshwater Finfish 154
26 Acute Toxicity of Inorganic Mercury to Freshwater
Invertebrates ^55
27 Sublethal Effects of Mercury on Marine Fauna 157
28 Acute Toxicity of Inorganic Mercury to Marine
Organisms -^g
29 Lowest Mercury Concentrations Having Toxic Effects
on Aquatic Organisms 164
30 Minor River Basins With Mean Total Mercury Levels
Exceeding 0.5 ug/1 and/or Maximum Levels Exceeding
10.0 ug/1 S 165
31 Estimated Exposure of Humans to Mercury 176-177
32 Adverse Effects of Mercury on Mammals 179
33 Estimated Exposure of the General Population 180
34 Fish Species Consumed by Seafood Eaters With
Mercury Intake Exceeding 0.43 ug/kg/day 183
x
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ACKNOWLEDGMENTS
The Arthur D. Little, Inc., task manager for this study was Joanne
Perwak. Other major contributors were Muriel Goyer (human effects),
Leslie Nelken (environmental fate), Kate Scow (biological fate) Margo
Wald (monitoring data), and Douglas Wallace (biotic effects and exposure)
The materials balance for mercury (Chapter III) was adapted from a
draft report by Versar, Inc., produced under contract 68-01-3852 to the
Monitoring and Data Support Division, Office of Water Regulations and
Standards, U.S. EPA. Justine Alchowiak was the task manager for Versar
Inc. '
xi
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CHAPTER I.
EXECUTIVE SUMMARY
The Monitoring and Data Support Division, Office of Water Regulations
and Standards, the U.S. Environmental Protection Agency, is conducting an
ongoing program to identify the sources of, and evaluate the exposure to,
129 priority pollutants. This report assesses the exposure to and risk
associated with mercury.
RISK CONSIDERATIONS
Humans
Mercury occurs naturally in many rock strata and soils at trace
levels, and as a consequence, virtually all surface water and ground
water contain very low levels of mercury (generally less than 1 ug/1).
Because mercury is relatively volatile, atmospheric contamination can
occur from natural and industrial sources. Human activities are clearly
associated with increases in regional background levels, even considering
natural sources. For instance, ambient air levels in urban areas appear
to be about three times those in rural areas. Also, mercury levels in
all media are higher in the immediate vicinity of large sources such as
copper smelters, chlor-alkali plants and steam power plants.
Consideration of the sources and fate of mercury in the environment
suggests a number of potential exposure routes for humans. Human intake
of total mercury from food in the U.S. typically ranges from 5-15 ug/day
and inhalation exposure in general ranges from 0.1-0.6 ug/day. Average
ingestion of total mercury from drinking water is less than 1 ug/day.
Highest exposures are very likely attained by dentists (60-6000 ug/day, by
inhalation) and a small subpopulation who derive most of their diet from fish.
Mercury compounds can be absorbed through the gastrointestinal
tract, the respiratory tract, and through the skin. The absorption rate
and toxicity, however, vary with the route and the form of mercury and
thus exposures are not additive. Of special significance is methyl-
mercury, which is 80% to 100% absorbed from the gastrointestinal tract
and has a longer half-life (70 days) than other forms of mercury.
The critical organ systems in man are the central nervous system
and the kidneys. Mercury poses a particular hazard to the developing
embryo. Elemental and methylmercury readily cross the placental barrier,
inducing a variety of developmental anomalies and fetal death. A wide
variety of malformations has been produced in laboratory animals exposed
to mercury in utero at doses as low as 2.5 mg/kg maternal body weight.
The human fetus, and specifically the fetal nervous system, appears to be
particularly susceptible to methylmercury, as indicated by the mercury
poisoning episodes at Minamata and Niigata. (There is no evidence to'
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suggest that mercury compounds are carcinogenic, although methylmercury
has been implicated as a mutagen.)
The primary route of human exposure to mercury appears to be through
eating fish or shellfish. The World Health Organization (WHO) has recom-
mended that weekly intake be limited to less than 200 ug of methylmercury
and less than 300 ug total mercury. Similarly, a critical daily intake
of 30 ug mercury, which corresponds to a mercury blood level of 20 ng/g,
has been estimated by some researchers to be a safe intake for an average
70-kg man. However, there is some disagreement as to what constitutes a
"safe intake." A safe fetal exposure has not been established.
An estimated 0.1% to 0.2% of the population receives more than the
estimated "acceptable daily intake" (0.43 ug/kg/day) of methylmercury
for neurological disturbances due to consumption of seafood containing
mercury. However, the sensitivity to mercury varies within this subpopu-
lation. In addition, a very small population (estimated to be less than
0.01% of the U.S. population) may receive exposures of greater than
1.4 ug/kg/day through seafood consumption.
With the raising of the FDA action level to 1.0 ug/g mercury in
fish, a consumption of 30 g/fish/day containing the allowable level of
mercury will result in exposure equaling the estimated "acceptable daily
intake." Though this consumption level is probably very common in the
United States at this time, mercury levels in seafood are generally
below 1.0 ug/g.
An examination of the areas of the country in which fisheries have
been restricted due to mercury contamination showed that in many cases
the sources are unknown. Natural sources, abandoned chlor-alkali plants,
and an abandoned gold mine appear to be the sources of contamination when
they could be identified.
Both fetuses and children may be at risk due to large exposures to
mercury; however, the risk potential cannot be quantified at the present
time.
The accidental exposure of consumers to mercury through the use of
mercury-containing products does represent a risk, albeit unquantifiable,
to a very small subpopulation. Among these is the ingestion of small
mercury batteries by children, since these batteries are becoming more
widely used in the home. Degradation of the casing may expose the child
to a potentially lethal dose.
Biota
Monitoring data obtained in 1979 indicate that mercury levels in
surface waters at a number of locations are above the laboratory
threshold for sublethal effects on the "most sensitive" aquatic species.
However, LC^Q values for "most sensitive" species are generally more than
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10 times the average river basin concentrations. Fish-eating wildlife
living near contaminated waters may be at significant risk due to
faioaccumulation of mercury in fish.
The lowest concentration at which effects have been observed in
aquatic organisms is <0.01 ug/1 methylmercury, a chronic effects value
for Daphnia magna. Growth was inhibited in rainbow trout at methyl-
mercury concentrations as low as 0.04 ug/1.
The acute toxicity of mercury to fish is generally in the ug/1
range, with the organic compounds, especially methylmercury, more toxic
than the inorganic compounds. Mercury toxicity to invertebrates varies;
aquatic insects appear to be relatively tolerant.
Selenium appears to mitigate the adverse effects of mercury on
aquatic organisms as it does for humans. However, the mechanism is not
well understood.
Aquatic organisms may be commonly exposed to mean total mercury
levels of greater than 0.5 ug/1 in the North Atlantic, Ohio River, South
Central Lower Mississippi River, Pacific Northwest and California River
Basins. In general, levels of mercury appear to be decreasing with time,
and maximum levels of >10 ug/1 occur only rarely. In addition, no fish
kills attributed to mercury have been reported.
Thus, aquatic organisms may be at risk due to mercury exposure in
some locations. However, methylmercury, which is the more toxic form
in the laboratory, is found only at very low levels in natural waters.
The risk to aquatic organisms cannot be quantified with the available
data. However, the lack of evidence of fish kills associated with
mercury suggests that risk due to mercury is low.
Studies of the effects of mercury on terrestrial organisms have
been limited. Dietary concentrations of 3 mg/kg methylmercuric
chloride produced adverse reproductive effects in mallards and black
ducks. Oral doses of 13 mg/kg and 60 mg/kg were lethal to goshawks
and ducklings, respectively.
Most terrestrial organisms do not appear to be at risk, except
perhaps in the vicinity of anthropogenic sources. Elevated mercury
residues have been found in plant and animal specimens collected near
chlor-alkali plants, although no toxic responses have been reported.
Piscivorous mammals and birds may be exposed to more mercury than other
animals due to their position in the food chain.
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MATERIALS BALANCE
Production
Mercury production in the United States in 1976 totaled 2,428 kkg.
Of this amount, about 800 kkg were mined domestically in California and
Nevada, secondary production from mining and extraction of other ores
amounted to about 120 kkg, and the remainder (about 1,500 kkg) was
imported.
Uses
The pattern of mercury use in the United States has changed and the
amounts consumed have been declining slowly over the last 15 years. This
is largely the result of increasing concern over the toxic and persistent
nature of elemental mercury and its compounds.
Mercury consumption in the manufacture of electrical apparatus has,
however, been increasing, possibly because of the increased use of
mercury cells in smoke alarm devices. In addition to mercury cells,
mercury is used in other batteries, lamps, switches, and rectifiers.
This industry category consumed about 1,000 kkg of mercury in 1976.
The second largest user of mercury is the mercury-cell component of
the chlor-alkali industry, which uses mercury as a flowing cathode for
the electrolytic preparation of chlorine and caustic soda. Approximately
550 kkg of mercury were consumed in this way in 1976.
Other commercial applications for mercury compounds include use as
a mildewcide or preservative in paint (270 kkg), as a constituent of
Pharmaceuticals (2 kkg), and as a catalyst in the synthesis of vinyl
chloride and vat dyes (44 kkg). Elemental mercury is used in the
manufacture of industrial instruments (175 kkg). About 70 kkg of
mercury are consumed as an amalgam in dental work.
Releases
Recognized natural and manmade sources are estimated to release
3,700 to 3,900 kkg of mercury to the environment each year. By far
the largest initial receptors of this release are che air and land
compartments (1,662 kkg and 1,807 kkg, respectively). Approximately
300 kkg are released to the aquatic environment.
Mercury can be detected in the earth in nearly all crustal deposits.
Consequently, outgassing of the earth's crust and runoff from natural
erosion together contribute about 1,200 kkg in releases each year, or
31% of the known releases. The releases to the atmosphere from out-
gassing (-1,000 kkg) account for about 60% of all known releases to
this medium, those from runoff (-200 kkg) constitute nearly two-thirds
of known releases to the aquatic environment.
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Releases from anthropogenic sources are estimated to total about
2,300 kkg each year. Major anthropogenic sources to the atmosphere
include paint volatilization (-200 kkg) and fossil fuel combustion
(-180 kkg). Releases to land are largely attributed to disposal of
electrical apparatus (-780 kkg) and wastes from chlor-alkali plants
(-530 kkg).
Mercury in fertilizer, POTW sludges, discarded paints and painted
items, catalysts, and industrial and control instruments account for
most of the remainder of releases to the land. Sources to water include
manufacture and disposal of electrical apparatus (-16 kkg), application
of mercury-containing paint (-24 kkg), and dental uses (-17 kkg). About
1% of known releases go to POTWs. In addition, mercury is known to
contaminate urban runoff.
Considerable uncertainty is associated with the estimates of
releases from mercury-containing industrial and consumer products
(primarily paint and electrical equipment). Since these two product
classes consumed about one-half of the 2,400 kkg used in the United
States in 1976, the inability to characterize reliably the fate of
mercury in these products is troublesome.
FATE AND DISTRIBUTION ON THE ENVIRONMENT
Monitoring Data
Mercury is virtually ubiquitous in the environment though elevated
levels are found consistently near anthropogenic sources and occasionally
near natural sources .
Mercury levels in uncontaminated freshwater and saltwater are
generally low (0.04 ug/1 to 0.3 ug/1). Values of up to about 50 ug/1
mercury have been reported for water in contaminated areas. Sediment
levels range from -0.05 rag/kg in unpolluted areas to over 2.0 mg/kg near
industrial sources of contamination. Rocks and uncontaminated soils
contain 0.02 mg/kg to 0.15 mg/kg mercury, with concentrations of up to
250 mg/kg reported for sites near natural mercury deposits.
Atmospheric mercury in remote areas is primarily in the form of a
vapor and is usually in the elemental form. The ratio of mercury vapor
to mercury adsorbed to particulates is quite variable in urban areas.
Background concentrations range from 1 ng/m3 to 50 ng/m3 while urban
levels vary from 2 ng/m3 to 60
Freshwater fish usually have slightly higher mercury levels
(0.05 mg/kg to 1.80 mg/kg) than do marine fish (below 0.3 mg/kg).
Terrestrial biota also contain detectable levels of mercury. Trees
and herbaceous growth in unpolluted areas have concentrations ranging
from 0.02 mg/kg to 0.03 mg/kg, with levels up to 1.25 mg/kg in areas
contaminated by anthropogenic or natural sources of mercury. Levels in
birds and mammals vary depending on such parameters as species and
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geographical region. Feeding habits can also influence mercury accumula-
tion in mammals and birds.
Environmental Fate
Mercury in the water column is concentrated on suspended solids and
in sediments. Methylation of mercury is promoted both biologically and
abiologically in low pH environments, and under slightly reducing condi-
tions. In the atmosphere, most of the mercury (>90%) occurs as a vapor,
while the remainder exists adsorbed to sub-micron particulate matter.
Fallout and washout will remove nearly all of the adsorbed mercury; the
vapors are more prone to wide dispersal with a mean residence time of 4
to 11 days, and eventually contribute to background concentration levels.
Mercury has a great affinity for organic matter, clays, and hydrous
metal oxides, and in soils remains bound, provided the pH remains neu-
tral to alkaline. Mercury may be lost from soils by volatilization;
this tendency increases as the soil organic matter and moisture content
decrease.
( Mercury disposed of on the ground in mine tailings, coal piles, or
solid wastes is a major source of mercury to the environment. However,
little evidence exists to suggest that mercury enters surface or ground
waters as a result of acid mine drainage, or leaching from tailings and
landfills. Clays and organic matter in soils effectively reduce the
quantity of mercury leached from these systems. Soil environments
favoring transportation of mercury would be low in pH and contain little
clay and organic matter.
Phenylmercurials, which constitute most pesticidal forms of mercury,
are easily leachable, as well as subject to loss by vaporization and
surface runoff.
Mercury enters POTWs at an average concentration of 0.4 ug/1.
Aerobic and anaerobic biological treatment partition more than 90% of
the mercury into the sludge portion of the waste; the remainder exists
adsorbed onto suspended solids. The sludge generated by POTWs is
disposed of in landfills, by landspreading, or is incinerated. Sludge
spread as a soil amendment is not likely to enhance the solubility or
mobility of mercury. Landfill leachate analysis for mercury demonstrated
concentrations no higher than 0.2 tng/1. Aqueous effluents of wastewater
treatment contain mercury principally in the insoluble state. Discharge
to freshwaters will most likely result in elevated sediment concentra-
tions, and the possibility of methylation; discharge to marine waters
causes solubilization and oxidation of the mercury due to dilution.
Biological Fate
Methylmercury, which is the most common form of mercury found in
aquatic organisms, is rapidly accumulated and retained for long periods,
with a half-life of 1000 days in some species of fish. Both ingestion
and gill absorption are exposure routes for mercury, with the
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former appearing to play a more significant role in upper-trophic-level
organisms. Once absorbed, methylmercury tends to be associated with
muscle tissue — the edible part of fish — and liver and kidneys.
Bioconcentration levels range from one to six orders of magnitude
higher than background water concentrations and biomagnification of
mercury appears to occur in at least certain aquatic food chains.
Terrestrial plants generally do not accumulate mercury to very
significant levels compared with aquatic biota, though conversion of
phenyl and other mercury compounds to methylmercury may take place in
some plants. The forms of mercury present in soil and their influence
on uptake rates have not yet been determined.
-------
CHAPTER II.
INTRODUCTION
The Office of Water Regulations and Standards, Monitoring and Data
Support Division, the U.S. Environmental Protection Agency, is conducting
a. program to evaluate the exposure to and risk of 129 priority pollutants
in the nation's environment. The risks to be evaluated included poten-
tial harm to human beings and deleterious effects on fish and other biota.
The goal of the task under which this report has been prepared is to
integrate information on cultural and environmental flows of specific
priority pollutants and estimate the risk based on receptor exposure to
these substances. The results are intended to serve as a basis for
developing suitable regulatory strategy for reducing the risk, if such
action is indicated.
This report provides a brief, but comprehensive, summary of the
production, use, distribution, fate, effects, exposure, and potential
risks of mercury. There are a number of problems with attempting such
an analysis for this chemical. Mercury is an element commonly found in
the earth's crust and releases to the atmosphere and to water" from
natural sources can be significant in some locations. However, the
estimation of the contributions of these important sources is difficult.
In addition, the number of different forms of mercury make exposure
and risk assessment complex because the absorption and toxicity varies
with the route of exposure and the compound. Therefore, the form of
mercury has been specified where possible.
The evaluation of risk due to mercury is also complicated by the
fact that much of the toxicity data for mercury is epidemiological in
nature. Thus, it is often difficult to associate observed effects with
specific doses. However, the data collected at the several incidents
of widespread mercury poisoning have provided invaluable insight into
the effects resulting from mercury exposure.
The report is organized as follows:
Chapter III presents a materials balance for mercury
that considers quantities of the chemical consumed in
various applications and produced naturally, the form
and amount of pollutant released to the environment,
the environmental compartment initially receiving it.
and, to the degree possible, the locations and timing
of releases.
-------
Chapter IV describes the distribution of mercury in
the environment by presenting available monitoring
data for various media, by considering the physico-
chemical and biological fate processes that transform
or transport mercury, and by characterizing the major
environmental pathways for releases to the environment.
Chapter V describes the available data concerning the
toxicity of mercury for humans and laboratory animals
and quantifies the likely level of human exposure via
major known exposure routes.
Chapter VI considers toxicological effects on and
exposure to biota, predominantly aquatic biota.
Chapter VII presents a range of exposure conditions
for humans and other biota and compares these with
the available data on effects levels from Chapters V
and VI, in order to assess the risk presented by
various exposures to mercury.
Appendix A contains notes concerning computations
in Chapter III.
Appendix B presents an overview of the present
status of restrictions on commercial and sport
fisheries in the U.S. due to mercury contamination
-------
CHAPTER III.
MATERIALS BALANCE
A. INTRODUCTION
This chapter presents the materials balance for mercury in the
contiguous United States for the year 1976. It was adapted from a draft
report written by Versar, Inc.* The materials balance summarizes the
principal sources, uses, and environmental releases of mercury from use
categories believed to contribute more than 0.1 kkg per year to all
environmental media. Releases from both anthropogenic and natural
sources are considered. Potential anthropogenic sources were identified
by a review of activities in which the material participates from its
extraction and use in various forms to its ultimate disposal. For each
major source of pollutant release, the amount of material released is
estimated, the environmental compartments (air, land, water) initially
receiving and transporting the material are identified, and the locations
at which the pollutant loadings take place are specified to the degree
possible.
Data were obtained from a large number of published and unpublished
reports. The publication of greatest use in developing this materials
balance was the comprehensive report on mercury and its compounds pre-
pared by URS Research Corporation for the U.S. Environmental Protection
Agency (Van Horn 1975). This URS report pertains to the early 1970s,
and some of the data have been supplanted by subsequent data from actual
field measurements. In these cases, the more recent data, which are
thought to be more accurate, have been used. For example, URS cites the
emission factors for mercury used in the chlor-alkali industry as 0.035
to air, 0.004 to water, 0.501 to land, and 0.46 to inventory and recycle
A study by Versar, Inc. (1976a), conducted during 1975 and 1976, included
visits to 16 of the mercury-cell chlor-alkali plants in the continental
U.S., and data developed indicate that environmental distribution factors
are more accurately reflected in the following numbers: 0.033 to air,
0.001 to water, 0.005 to the product caustic, and 0.962 to land
(including non-discharging brine wells, evaporation ponds, and sludge
ponds, sludge pits and landfills). Similarly, screening and verification
sampling data collected by the Effluent Guidelines Division of EPA were
available for several industries (U.S. EPA 1979=). For aquatic dis-
charges and discharges to POTWs, these data are assumed to be the best
available and were used in the materials balance.
The year 1976 was selected for the analyses because it is the most
recent year for which a complete set of data were readily available.
*
Environmental Materials Balance for Mercurv. Draft report to the
Monitoring and Data Support Division, Office of Water Planning and
Standards, U.S. EPA, 1979.
11
-------
However, data on reported and apparent mercury consumption supplied by
the Department of Commerce for the period 1976-1977 indicate that mercury
use patterns did not change significantly between 1976 and 1978, the
latest year for which there are useful data from which to construct at
least a partial materials balance. The uncertainties in the data on
environmental releases far exceed any variations in the apparent and
reported consumption levels. Therefore, the environmental releases
reported for 1976 are probably representative of the releases for 1978
also.
Table 1 presents a breakdown of the amount of mercury discharged to
the U.S. environment from recognized natural and man-made sources during
1976. Of the approximately 3700-3900 kkg of mercury identified as entering
the total environment each yeas 31% (~1200 kkg) is derived from natural
sources. Figure 1 shows the total mercury flow in the U.S. in 1976,
tracing the cycle from production sources to disposition in the environ-
ment. Figure 2 displays the same data in a schematic diagram that
combines both flows and volumes in order to illustrate the relative
contributions of sources to each environmental compartment.
Although the amount of mercury released by natural sources is
probably relatively constant from year to year, man-made releases are
probably roughly proportional to consumption and thus more variable,
except that the release of mercury from some products may be delayed a
number of years until the containment vessels decay. During 1976,
consumption of mercury was 25% to 40% greater than in 1975, and was the
largest since 1969. The increase in mercury consumption in 1976 was
primarily due to an increase in electrical apparatus manufacture and,
within that industrial category, to a large increase in the use of
mercury cells in smoke alarm devices.
The distribution of mercury released to the environment in 1976, as
shown in Table 1 and Figures 1 and 2 is summarized below:
Mercury Release
Environmental Receptor Total (kkg) %
1625-1696 43
Water 308-312 8
POTWs 41 l
Solid Waste 1754-1858 48
The major recipients of the various mercury releases are the air com-
partment and the land. However, virtually all of the mercury that
goes to land is derived from industrial operations of one kind or
other (manufacturing, fossil fuel combustion, and mining and smelting
operations), whereas only about 40% of emissions to air are anthro-
pogenic, the rest being from natural, and therefore, uncontrollable
12
-------
TABLE 1. PRODUCTION AND USE/RELEASES (JF MERCURY IN THE UNITED STATES, 1976
l\'odu,J_lon tkk,^
I'UTW l.aiul
'"*""rt>' , /4^» MfB. ol U,. cury l.oill.ilnlil|S rioducl* 1681 M. dlj lolals ll.l.J luu
Mine. ..,,d rrlury IV ,d. ' 797 Hcc rlr.l A,.,Mrutu»2 94U R,.,,,,.. „„„,,„. „, ^(cut, k Hl,,Ju, ,„"• '"• " ,_„ '" „
|1"I1""S '515 Inju t. Control lost.2 175 M-liml jc-tlil.- ol 1 Mm In.. 1. r.,,, ,| ", ' S" ^'^ 1)'J °^4
17 tu .. Ifent 1 Hruoaraltoliti^ 69 Us*? of Morttty font A 1 n 1 »K VriHUit.!!!
K.,,11 luul •...bullion"-1"-" I9J C,tJ ,..1 (tonufactur^2 44 ll^lr,t.,l A|,,.Jt jtus"' ... ,„ „
P»|,url.v ,,r by,.ro.l,ul'''-''""'"'/ r,l K,U>K clde»/ll,,cturloldt....4 ^1 Paint /,.,.! l< Jt Ions' I99 „ „
rVrHlliisi" 190 1:ul"! al '.uboratory USL-^ 20 ludiutil.il Control I,,:,| i ,„»,,, I •, t.9 II u
<.ll .intl 1HH Kxnorlti^ 17 Ilililis
'•r. Mindu.it. i" Iliiaccoiuili-.d lor (Including " ' ° <••<> 1 )
Ki-'l t II IE1-I IllliJIII 1 t It's _
U "' "I'«'"BI> 40. U o U
"tllc'r H».» 4.8 11.7
16 „
K'.ul Hunoll and liroundwjl, i6 o (BB ,,
lliit.asi.lilK "1 Edrlb'b trust" 1019 0 0
K»M>II->'!
lliLiciouuttd lor (in. ludlnK Industrial
lota) Su|>|i|y 4077 unknown lulua^fs)
luo/
0.4
11.4
5)1.1
779
47
97
17.1
1.4
41. 1
II. /
III 5
19O. •»
50
l>
O
1/6 1
I/
-"I/
Detailed noli.:, exululnhiw tin.1 dt--rlv.itIon of nuuhtfr!. In thia
dre Klveii I" Appc-ndlx A.
-------
SOURCES
Hg Secondary Pro-
duction (fleprocesang
of Water and
Defective Products)
1 16
Imports
1
t
— *
— »
c
*
•
«
*•
•*»
••»
•^
*
ONSUMPTIVE USES
Electrical Apparatus
948
Electrical Preparation of
SS3
Paint Manufacturing
270
Industrial ana
175
Dental Preparations
683
Catalysts Manufacture
43.S
Fungicides & Bacteneides
20.9
General Laboratory Use
20.5
2.1
Other
134
Exports
17.3
Hg to Industrial Stockoile
175
INADVERTENT
SECONDARY USES ' SOURCES AIR WATER POTW LAIS
' ' " 7.8 0 0 0.4
** 0.2 0.1 NA 9.6
Eltctnca. Aopmwi ^ 143 1C rjA 7-9
"" 18.5 0.3 -0 531
^oo 0.4 o
— Pamt Apolicat.cn * igg ^ NA ^
*' 0 0 0 1.8
Instruments Use
" '""" 0 U NA NA
— Caul»its Um - •> 000 43.3
" 0 0 0 0
, fc Agricultural Use of ]
Fungicides and Bacteneides ] 0 3.1 0 179
•• it NA 5J 1.4
_^ Pharmaceutical __
Aool.cat.on, ° °-6 U 02
*" NA NA NA NA
Note: Values are given in kkg.
FIGURE 1 FLOW DIAGRAM FOR CYCLE OF MERCURY PRODUCTION,
CONSUMPTION AND DISPOSITION IN THE UNITED STATES
14
-------
SOURCES
CONSUMPTIVE USES
INADVERTENT
SECONDARY USES SOURCES
AIR WATER f>OTW LAND
92.5 0.8-4.5 0 8.7
34 0.1 0 1.3
-0 188 0 0
1019
0 0
Coal Mining
Copper Mining
Copper Smelting
Zinc Smelting
Lead Smelting
Cement
NA NA 0 190.5
IMA 0.6 0 NA
NA 0.1 <0.1 NA
NA 0 0.7 NA
NA 3.2 0 NA
NA 0 0 0.1
40.8 0 0 2.3
4.6 OJ 0 0.3
4.8 0.3 0 OJ
0.5 0.3 0 1.8
0.1
0 03
NA 42.2 NA NA
36
NA NA 25
NA NA 25
FIGURE 1 CONTINUED
15
-------
Commercial Production
2428
Secondary
Production
5%
Natural Sources
1207
Produced as Impurity
or By-Product
Mining & Primary
Production 33%
Degassing of Earth
f 84%
Manufacture of Mercury Products
1683
Rural
Runoff 16%
electrical
Apparatus
56%
Pain
Other 28%
Use of
Electrical Apparatus
938
Paint Application
Chlorine and
ustic Manufactur
Use of Control
Instruments
Unaccounted
for
292
104
Use of Other
Products
Released to Environment
> 3768 kkg
Water 8%
Note: All amounts are in kkg. FIGURE 2 MATERIALS BALANCE OF MERCURY-1976
16
Fossil Fuel
.Combusti
-------
sources. In addition to these sources, some portion of the air emissions
contributes to mercury levels in urban runoff, which in turn may contri-
bute significant amounts of mercury to the aquatic environment and POTWs,
3-5-350 kkg and 0.8-80 kkg, respectively.
B. PRODUCTION
1. Introduction
Mercury can be detected in the earth in nearly all crustal deposits
in concentrations ranging from parts per billion to parts per million.
For an ore deposit to be economically desirable, the ore must contain
at least 1.8 kg of mercury per metric ton (MT) of rock. Cinnabar
(mercuric sulfide, HgS) is the principal ore of mercury. Mercury
deposits in the United States are primarily located in Nevada and
California, and seven mines were in operation in 1976: New Almaden,
Oat Hill, Manhattan-One-Shot, Aetna and Knoxville in California and
McDermitt and Carlin in Nevada. At the Carlin mine, mercury is recov-
ered as a coproduct of gold refining (Van Horn 1975).
In recent years the mercury mining industry has shown great varia-
bility. In 1971 there were 71 mines in operation, which produced 616
kkg of mercury. After 1971 most of the mines discontinued their opera-
tion when the mercury price dropped and because they were unable to meet
air quality standards. Mercury production in the United States fell to
75 kkg in 1974. In May 1975, a new mine with an annual capacity of
700 kkg became active in Nevada and mercury production increased to 254
kkg in 1975 and 797 kkg in 1976 (Bureau of Mines 1976). (In 1979, only
the McDermitt mine was producing.) As of 1980, there are only two pro-
ducing mercury mines, both in Nevada (Bureau of Mines 1979, 1980).
Secondary production of mercury provided 116 kkg of mercury in 1976.
Over 60% (1515 kkg) of mercury consumed in the United States in 1976
was imported.
2. Process Description
Mercury ore is obtained from open pit surface mines and underground
mines. The ore is crushed, sized, and then fed from the storage bin into
a rotary kiln or a retort, where it is heated. The mercuric sulfide is
decomposed at about 96% efficiency. The mercury vapors are passed through
a condenser, where they are cooled below the dewpoint to form liquid
mercury. The mercury is then bottled in 76-lb flasks (Van Horn 1975).
The McDermitt mine in Nevada employs a new technology. The ore,
which has a very high mercury content (about 4.6 kg per metric ton of
ore) is crushed and sized and then concentrated by flotation techniques.
The concentrate from the flotation operation is fed through a six-hearth
furnace, where the mercury in the concentrate is vaporized. The mercury
vapors are cooled, condensed, sent through a cleaning process, and
stored in 1000-kg shipping containers (Van Horn 1975).
17
-------
The new technology used in the McDermitt mine is claimed to mini-
mize the mercury discharges to the environment. All of the process water
is recycled. Water used in the condensers is non-contact water and is
discharged or recycled. The tailings from the flotation process are
discharged to a pond for permanent storage. Leaching from the tailings
does not appear to present a problem. Exhaust gases containing sulfur
dioxide and traces of mercury vapor are discharged through a low stack
and the mercury content in these vapors is not allowed to exceed the
2.3-kg per day EPA compliance level (Van Horn 1975).
-=b Environmental Releases from Mining and Production Processes
Aquatic discharges from mercury mining are estimated to be zero (Van
Horn 1975, Calspan 1979) because, though there are no aqueous discharges
associated with mercury mining processes, there is also very little rain-
fall in the Western states where mercury is mined; therefore, leaching
and runoff are considered insignificant. Air emissions from secondary
production facilities are estimated to amount to 7.8 kkg, and solid
waste is estimated to be 0.4 kkg (Van Horn 1975). None of the secondary
production facilities has an effluent discharge (U.S. EPA 1979a); there-
rore, the discharge to water is estimated to be zero.
In addition, there are numerous inactive or abandoned mercury mines
in the United States. Release of mercury from these sites is improbable
since little mercury is expected to be found in the tailings of a mer-
cury mine (Martin and Mills 1976).
C. USES
1. Introduction
Mercury use in the United States is given in Table 2 for the period
1965-1978. As can be readily seen, the pattern of mercury use in the
U.S. has been significantly altered over this period. The probable
reasons for such changes are the wide publicity given to the toxic and
pervasive nature of mercury and its compounds, and the availability of
feasible alternatives and substitutions. However, in use areas in
which there are no feasible alternatives, total mercury use has been
relatively constant or has increased.
2. Electrical Apparatus
a. Introduction
The product category of electrical apparatus, which consists of
batteries, lamps, switches, and rectifiers was the largest single
consumer of mercury in 1976. Consumption in this category rose to 948
kkg, an increase of 62% over 1975 consumption. This increase was
primarily due to the surge in use of smoke detector devices, many of
which use mercury cells. Compared with total mercury consumption,
however, emissions from this category during manufacturing are small.
IS
-------
TABLE 2. CONSUMPTION OF HERCURY IN THE UNITED STATES. 1965-1978
End Use
Agriculture
Amalgamation
Catalyst
Dental preparations
Electrical apparatus
Electrolytic prepara-
tion of chlorine and
caustic soda
General laboratory
use
Industrial and
control Instruments ,
t-> Paint: ant 1 fouling
V£>
'Paint: mildew-
proofing
Paper nod pulp
manufacture
Unknow.i
Pharmaceuticals
Other
TOTAL
196S
107.4
9.2
31.8
110.2
6S1.0
301.7
80.4
356.0
8.8
283.0
21.3
_
14.4
560.1
2,535.4
1966
81.8
8.5
66.6
73.6
607.9
397.8
76.4
251.4
4.8
302.9
21.1
8.0
563.8
2,464.7
1967
i:!8.6
7.5
115.8
82.2
559. 2
4)3.1
66.9
257.1
5.2
242.2
15.4
9.8
443.1
2,396.1
1968
118.2
9.2
66.0
106.1
676.6
601.6
68.6
275.0
13.5
350.7
14.4
14.6
285.2
2,599.6
1969
92.7
6.7
102.0
99.3
637.3
714.2
66.7
229.4
8.4
327.0
19.2
24.5
314.8
2,666.8
Consumption (kkg)
1970 1971 1972
62.4
7.5
77.1
78.8
549.8
517. 4
62.2
166.5
6.8
349.9
7.8
23.8
209.7
2,119.8
50.9
34.9
81.4
582.0
418.9
62.0
167.9
14.3
282.3
0.1
~
23.5
83.1
1.801.1
63.3
27.6
102.8
636.1
397.0
20.4
225.4
1.1
282.3
0.03
*~
19.9
147.5
1,823.6
1973 1974
6M 33.8
23.2 44.7
93.3 1C4.2
620.4 678.2
450.5 582.4
22.7 16.4
246.6 213.8
1.1
261.0 234.6
-
20.9 20.6
6*. 2 121.1
1,871.0 2,050.1
1Q7S 1Q7A
( *•* t J 4.7/0
20.7 20.9
23.7 43.6
61.1 68.6
559.6 947.7
524.7 553.3
9.6 20.5
141.4 174.6
238.7 207.4
33.4
14.9 2.1
59.8 100.7
1,761.4 2,235.8
1977 1978
20.1 w2
53.2 W2
42.4 17.6
1005.7 598.1
370.3 384.8
14.0 14.5
180.0 120.3
288.3 308.9
_ _
Vt2 W2
89.2 216.1
2,063 1,660
Original sources of these data reported aercury volumes In units of 76-lb flasks;
these units have been converted to kkg by use of the factor of 0.0342 kkg/flask.
W - Withheld to avoid disclosing confidential Information.
Sources: Van Horn (1975); Cammarota (1975); Personal communication, M.J. Drake, Bureau of Mines
(for 1976-1978).
-------
Air
112.6
30.6
Water
15.6
Land
637.8
47.5
93.7
Total
750.4
93.7
93.7
Only about 10 kkg of the mercury are estimated to be lost to the environ-
ment during manufacturing processes. The balance of the mercury consumed
by this category (938 kkg) is in the manufactured products.
These manufactured products vary both in their useful lifetimes,
and in the durability of their construction. No detailed studies have
been conducted in order to determine the rate of mercury release to the
environment, but it is possible to make some reasonable estimates to
bound the problem. By far the largest portion (80%) of mercury used in
this category goes into batteries (see Note 16 to Table 1) with the
"lamps", and the "tubes and switches" subcategories each accounting
for 10%. As explained in the following paragraphs, rough assumptions
about the use and disposal of these products suggests the following
approximate releases (Arthur D. Little, Inc., estimate):
Release (kkg)
Air Wate
Batteries
Lamps
Switches, etc
Total Released 143.2 IJTi 7~797l93778
About 94 kkg of mercury is consumed in the manufacture of mercury
lamps of all types (10% of the total in this category), and for this
analysis no recycling is assumed to occur. Since no data were found with
which to estimate releases, a number of assumptions were made for the
purposes of providing perspective on the sources. It was first assumed
that one-half of the mercury used in lamps goes to mercury vapor street
lamps. It was assumed that these are replaced only when they are
broken, and have released one-third of their contents to the atmosphere,
and the remaining two-thirds either to the soil or pavement, contributing
to surface runoff. It was further assumed that the remaining one-half
of the mercury used in lamps goes to production of lamps for indoor use,
which are not broken before replacement. After they are replaced, these
lamps may be broken in trash barrels, in transit to waste disposal
centers (landfills or incinerators) or at the landfills. In this
process it was assumed that 20% of the mercury is released directly to
the atmosphere and that of the remaining 80%, 15% is incinerated (all
of which goes to the atmosphere), and 85% goes to landfills. These
assumptions result in the following estimated releases (Arthur D. Little,
Inc., estimate):
Release (kkg)
Air Water Land
Street lamps 15.6 15.6 15.6
Indoor lamps breakage 9.4 31.9
incinerated 5.6
Total Released 30.6 15.6 47.5
20
-------
b. Batteries
Mercury is used in the manufacture of 2inc-carbon dry cells, carbon-
zinc air cells, alkaline-manganese dioxide dry cells, mercury cells,
(Ruben, Weston, and mercury-cadmium cells), and zinc-silver oxide cells.
The zinc-carbon dry cell dominates the primary battery market. However,
new superior electrode materials will decrease demand for the standard
zinc-carbon batteries, and production of alkaline-manganese dioxide
batteries and mercury cells will probably increase (Versar 1975).
In the standard zinc-carbon cell, mercury is used in the form of
an amalgam with the zinc components in order to reduce corrosion of the
zinc and the subsequent electrical shorting that the corrosion products
could cause. In the carbon-zinc air cells, mercury is also amalgamated
with the zinc component, which is used to make the electrodes, and, in
the alkaline-manganese dioxide dry cells, mercury is used in combination
with zinc to make corrosion-resistant anodes (Versar 1975).
Mercury cells are classified according to three types: the Ruben
cell, the Weston cell, and the cadmium-mercury cell. In the Ruben cell,
the cathode consists of mercuric oxide and graphite and the anode is
zinc-mercury amalgam. In the Weston cell, the anode is made of cadmium
amalgam and the cathode is made of mercury metal. The mercury-cadmium
cell is very similar in construction to the Ruben cell, but with certain
proprietary changes in the electrode composition; the anode consists of
mercuric oxide and the cathode is of cadmium that is amalgamated with
up to 20% mercury by weight (Versar 1975).
The zinc-silver oxide dry cell is similar to the Ruben cell, except
that only the anode contains mercury and it is in the form of zinc
amalgam (Versar 1975).
Rejected batteries are the major waste products generated by battery
manufacturing operations. Some of the mercury is reclaimed from these
batteries and the remaining is landfilled. It is estimated that only a
minor amount of mercury is lost to air (0.2 kkg) and water (0.1 kkg)
during battery manufacturing. Disposal of used batteries has been esti-
mated to result in releases of about 113 kkg to air and 638 kkg to land.
c. Electric Lamo s
Mercury is used in the manufacture of fluorescent, mercury vapor,
metal halide, and high-pressure sodium lamps. These lamps are primarily
used in street lights, high-ceiling rooms, motion picture projectors,
photography, dental examinations, photochemistry, heat lamps, and water
purification. GTE-Sylvania, Westinghouse Electric, General Electric,
and North American Philips are the largest manufacturers of these
lamps (Van Horn 1975).
Mercury lamps are produced by injection of the liquid mercury, vapor,
21
-------
a starting gas, and other materials into a sealed quartz tube. Mercury
losses during manufacturing are relatively small. Substantial mercury
losses to the environment occur when consumers discard the spent tubes.
In all 0.2 kkg is estimated to be released to the atmosphere and 3.6
kkg to landfills.
d. Switches, Rectifiers, etc.
No information is available concerning the amount of mercury re-
leased during manufacturing and use of this product. However, its
characteristics suggest a relatively long lifetime, no recycling, and
ultimate disposal of all 93.8 kkg of the mercury consumed each year for
this use in a landfill.
3. Electrolytic Preparation of Chlorine and Caustic Soda
The second largest user of mercury is the mercury-cell segment of
the chlor-alkali industry. In this process, mercury serves as a flowing
cathode for the electrolytic decomposition of salt brine into chlorine
sodium hydroxide, and hydrogen. Theoretically, the mercury can be used
repeatedly without any losses. However, mercury losses do occur and
mercury is replaced at a rate of about 0.7-1.0 kg of mercury per metric
ton of chlorine.
A typical mercury-cell plant produces 270 kkg (300 tons) per day.
The smallest plant produces 94 kkg/day (104 tons/day) of chlorine; the
largest 600 kkg/day (725 tons/day). Figure 3 shows the locations of
mercury-cell chlor-alkali plants in the U.S.
Airborne mercury emissions from mercury-cell chlor-alkali plants
consist of mercury vapor in cell room air and mercury loss along with
byproduct hydrogen gases, which are scrubbed and filtered to remove most
of the mercury. In the mercury-cell process, the mercury flows through
the cells as a flowing cathode, and in order to maintain the flow,
mercury must be added at one end of the cell and removed at the other
end by means of inlet and outlet "end boxes." The end boxes are usually
kept under a slight vacuum, and the chlorine-containing gases that are
captured and scrubbed from the end boxes usually contain some elemental
mercury that is not completely recovered (Versar 1976a).
Present National Emission Standards for Hazardous Air Pollutants
(NESHAP) require that no more than 2,300 g per day of mercury vapor be
lost to the atmosphere from each mercury-cell plant regardless of size.
In practice, all plants cool the hydrogen to a temperature of 13°C
(55°F) or less to condense and recycle most of the mercury in this
stream. Most mercury plants further treat the hydrogen with activated
carbon or molecular sieves that amount to but a few grams a dav
(Versar 1976a).
Three types of solid wastes are generated from the mercury-cell
chlor-alkali plants (Versar 1976a):
22
-------
tsJ
Co
A Plants in existence in 1964, but not in
existence in 1978
• Plants in 1978 list of Chlorine Industry Association
FIGURE 3 LOCATION OF MERCURY CELL CHLOR-ALKALI PLANTS IN THE U.S.
-------
(1) the brine purification sludge that primarily
consists of calcium carbonate and magnesium
hydroxide, with minor amounts of sodium chloride
and mercury. The mercury is present either in
elemental form or as a complex HgCl s;
(2) mercury cell "butter," which is primarily an
amalgam; and
(3) mercury spills and cleanouts, which are flushed
into sumps below the cell room floor to become
waterborne wastes.
No waterborne wastes are generated from the mercury-cell operation
itself. However, wastewaters from mercury-cell plants are generated
from collected mercury spills, cell end-box purges, cell washings, and
brine leaks and spills. Due to the very low levels of mercury allowed
in plant wastewater, cell plants have wastewater treatment for mercury
removal. Available data from 1976 show that the mercury discharge at
every plant having effluent outfalls is within the applicable NPDES
and^h Tffi °f °;°13 t0 °'35 kg/day f°r BPT (best Practicable treatment)
and the Effluent Limitation Guideline which is generally given in
kg/kkg of product (Versar, Inc. 1976a).
Over 530 kkg of mercury is discharged to land annually by chlor-
alkali plants. The number of plants has remained relatively stable
over the past 15 years, and the major growth in the chlorine industry
has occurred using technology that does not require mercury cells.
However, there are apparently nearly 30 sites in the country that have
accumulated large amounts of solid waste material from mercury-cell
plants, some of which are no longer active. No estimate can be made of
the mercury that is contained in these disposal sites. In addition,
these areas represent a potential source to the aquatic environment,
although the extent of releases is unknown.
4. Industrial Instruments
Mercury is used in the manufacture of switchgear and switchboard
apparatus and mechanical measuring and control instruments because of its
high thermal conductivity and well-known thermal expansion properties.
Some of the major types are thermometers, thermostats, thermoregulators,
flowmeters, pressure-sensing devices and barometers, gages, valves,
pump seals, switches and relays, navigational devices, and medical
devices.
In the manufacturing of industrial instruments, mercury is lost to
the environment from spillage, from volatilization, and in cleaning of
old instruments that require servicing. The majority of the mercury
losses to the environment, however, occur from disposal of damaged
consumer products containing mercury (Van Horn 1975). as is shown in
Table 1.
24
-------
5. Mercury Compounds
a. Introduction
Mercury compounds are used in the production of fungicides and
bactericides, catalysts, paints, and Pharmaceuticals and in general
laboratory use.
The manufacturing process for mercury compounds involves conversion
of the metal into one of several inorganic mercurials that are appropri-
ate intermediates to the production of other inorganic or organic
compounds. There are about 16 manufacturers of mercury compounds in
the United States. Often the same facility produces both inorganic
feedstock and organic mercurials (Van Horn 1975).
Mercury compounds are low-volume chemicals. The most common
mercurials are mercuric chloride, red and yellow mercuric oxide, mer-
curous chloride, and aminomercuric chloride.
b. Catalysts
Manufacture of catalysts consumes 43.6 kkg of mercury each year.
This is a small but important use of mercury compounds. Mercury
catalysts are used in the synthesis of vinyl chloride and vat dyes.
Vinyl chloride monomer produced from acetylene and hydrogen chloride
uses a mercuric chloride catalyst. Most of the mercury losses occur
when carbon pellets impregnated with mercuric chloride are discarded
(Van Horn 1975).
Anthroquinone vat dyes are sulfonated in the presence of mercuric
sulfate to yield two dyestuff intermediates (1,5 and 1,8-disulfonic
acid). These vat dyes are easily reduced to a soluble, colorless form
in which the fibers are readily impregnated; the dyes are then oxidized
to produce the insoluble color in the fibers (Van Horn 1975).
Environmental releases from catalysts manufacturing each year are
estimated to amount to 0.1 kkg to air and 0.2 kkg to water. Losses of
mercury to the products of catalyzed reactions are considered to be
insignificant. The bulk of the releases from this category is from the
disposal of spent catalysts, all of which are assumed to be disposed of
in land, since recovery of mercury from mercurial catalysts is not
economically feasible.
c. Paint Manufacturing
The paint industry consumed about 12% of the mercury produced in
1976. A small amount of this mercury was used for mildew-proofing
substances; the remainder was used in paint additives. Phenylmercuric
compounds, primarily phenylmercuric acetate, are used as in can preser-
vatives in water-based paints and coatings at levels of 50-100 rag/1.
25
-------
Exterior water-based paints may contain phenylmercuric acetate as a
mildewcide at levels of 250-1500 mg/1 to prevent fungus growth on the
applied paint film (U.S. EPA 1976a). Although the mercury levels in
paints are low, large quantities of paints are used, so that the amount
of mercury involved is quite significant.
Paint manufacturing plants are estimated to discharge 0.4 kkg to
POTWs each year. Airborne emissions and solid wastes are considered
to be negligible. However, mercury emissions from paint applications
are^ expected to equal the mercury content. Air emissions are expected
to be 65% after application. The remaining 35% is expected to be
distributed between incineration (air), landfill, land fallout (from
paint peeling), and runoff.
d. Fungicides and Bactericides
In 1970, USDA banned the use of all alkylmercury pesticides. As a
result, phenylmercuric acetate (PMA) became the major organomercurial
used in agriculture. In August 1976, the U.S. EPA passed a regulation
that allows for the temporary use of mercury biocides to treat summer
golf turf diseases and certain farm seeds (barley, wheat) until
August 31, 1978, or when the equivalent of 2 years' production of the
latter biocides has been attained, but as of that date these uses were
cancelled. Use of mercury-based biocides on xjinter golf turf diseases
is allowed by the U.S. EPA under strictly controlled conditions
(U.S. EPA 1966).
Mercury lost to the environment during the manufacturing process is
expected to be negligible. The bulk of the mercury in pesticides reaches
the land upon application. Losses to water occur from the leaching of
mercury into groundwater supplies and from rain runoffs.
e. Pharmaceuticals
The use of mercury in Pharmaceuticals has decreased greatly in
recent years. Organic mercury compounds are used in diuretics and anti-
septics. Inorganic salts are used in solutions to sterilize instruments.
Ammoniated mercury, mercury oxides, and metallic mercury are used in
skin preparations. Phenylmercury compounds are used as preservatives
in cosmetics and soaps (Van Horn 1975).
Due to the decline in mercury use, environmental discharges from
the manufacturing operations are judged to be negligible. The bulk of
the mercury released to the environment from pharmaceutical use is
likely discharged primarily to POTWs, since mercurials are discarded
from the body along with other waterborne body wastes.
f. General Laboratory Use
Metallic mercury and mercurial compounds are used for many general
laboratory purposes: as reagents and indicators, for calibration and
26
-------
sealing, and occasionally in vacuum pumps. In hospitals, mercury is
used for diagnosis by means of radioactive markers and as a fixative
for tissues. In 1976, 20.5 kkg of mercury were consumed for general
laboratory uses (Van Horn 1975).
The distribution of mercury losses among particular environmental
media reflects primarily the type of the use of the chemical rather than
the type of laboratory (Van Horn 1975). Mercury is lost to the atmos-
phere through volatilization; mercury is lost to POTWs as a result of
discarding the chemicals down the drain when the experiment has been
completed; some mercury is also lost from spillage and from washing
glassware that contained mercury compounds. Most laboratories, however
have instituted techniques for recycling mercury wastes. It is expected
that between 55% and 60% of the mercury that is consumed is recycled.
g. Dental Preparations
Mercury is used as an amalgam in dental work. Fillings are prepared
by combining a silver-tin alloy in powdered form with metallic mercury.
A metallic putty is formed composed of silver-mercury, tin-mercury
compounds, and some residual silver-tin alloy. This putty is then
placed in the drilled tooth cavity. The putty is condensed and polished
and the excess amalgam is removed by filing during the condensing pro-
cess. This excess amalgam is normally released to the wastewater system
unless a trap to catch the amalgam is installed on the drain (Van Horn
"Premises" are now available in which the mercury and silver-tin
alloy are in measured quantities to prevent the losses of mercury during
the preparation of the filling (Van Horn 1975). It is estimated that
22% of the mercury consumed is lost to water and 2% is lost to air during
application of dental preparations. The remainder of the mercury is in
the dental work of the patients. However, it can be assumed that the
remainder will eventually be lost to the environment as well.
D. NATURAL AND INADVERTENT SOURCES
Approximately 40% of the total identified mercury released to the
environment is from natural sources and 11% is from inadvertent sources,
such as mining operations and fossil fuel' combustion.
1. Natural Sources
Mercury is naturally present in the environment as a result of the
outgassing of the earth's crust and as runoff from natural erosion
processes. Natural processes add mercury to the biosphere at a constant
rate. In the United States, the outgassing process releases over
1000 kkg of mercury (approximately 60% of the identified total mercurv
released to this medium) to the atmosphere. Runoff contributes almost
200 kkg of mercury to the water (approximately 63% of the known mercury
released to the water). These discharges of mercury are quite large
but they are widely distributed in the U.S., although mercurv deposit's
and mineralized areas are concentrated in the western U.S., resultin-
in higher rates of degassing from this region (Van Horn, 1975)
27
-------
2. Fossil Fuel Combustion
Fossil fuel combustion contributes about 5% (~190 kkg) to the
identified mercury released to the environment. The bulk of this emis-
sion (180 kkg) is airborne. The concentration of mercury in coal and
other fuels is very low (0.066 mg/kg to 0.2 mg/kg) (Van Horn 1975). Th«
releases of mercury to the air via combustion of fossil fuels are
substantial only because of the enormous quantities of fuels burned
The airborne emissions of mercury are primarily in the metallic form.
Land-destined wastes of mercury from these operations result from the
disposal of the bottom ashes.
3. Mining and Smelting Operations
Since mercury is present as an impurity in the ores of other metals
and minerals, it enters the environment as a byproduct of mining and
smelting operations.
Verification data from the Effluent Guidelines Division indicate
that coal mines discharge 3.2 kkg of mercury each year to the waters
(U.S. EPA 1979a). Other mining and smelting operations contribute
0.9 kkg to water (Van Horn 1975). Airborne emissions and solid waste
discharges from this category are 50.8 kkg and 5.1 kkg, respectively
(Van Horn 1975).
The gold milling process originally used mercury amalgam plates to
recover gold particles, although this process has been replaced by
cyanide leaching. While no releases of mercury can be attributed to
this source, the past use of mercury may represent a source of exposure
through highly contaminated sediments in the vicinity of gold mining
areas (Martin and Mills 1976).
4. Mercury as an Impurity
Approximately 191 kkg of mercury enter the environment as a result
of its occurrence as an impurity in fertilizers. Some of this mercury
may also enter the aquatic environment as a result of runoff.
The Effluent Guidelines Division's screening and verification data
(1979c) reveal mercury in the effluents of the Timber Products Proces-
sing Industry, Petroleum Refining, and Auto and Other Laundries.
Mercury is not expected to be used by these industries; therefore, it
must be present in the effluent as an impurity. These industries have
been estimated to discharge 0.7 kkg of mercury to waters and 0.7 kkg to
POTWs.
5. Publiclv Owned Treatment Works
The amount of mercury found in sewage effluents and sludges varies
greatly. It has been estimated that 42.2 kkg are discharged to the
28
-------
aquatic environment (see Note 25, Table 1). Sources to POTUs include
domestic and industrial waste, and urban runoff.
An estimated 3.6 million kkg of sewage sludge solids containing
between 0.36 and 203.2 kkg of mercury are collected annually in the
United States (SRI 1979). About 25% of this sludge is applied to land
as^a result of the sale of sludge for use as commercial fertilizers or
soil conditioners. The remainder is disposed of by incineration (35%),
in landfills (25%), and in the ocean (15%) (SRI 1979).
6. Urban Runoff
Mercury has been found in urban runoff at levels of about 0.2-85 ua/1
(Murphy and Carleo 1978). The mean value for a residential area of 720
acres in Rochester, N.Y. was found to be 18.1 ug/1 with the median value
for the same set of 10 data points in the range of 4-5 ug/1. A second
study involving less intensive sampling of stormwater and combined sewer
runotf in 11 cities across the U.S. (including Rochester. N.Y.) revealed
concentrations ranging from less than 0.2 ug/1 to 0.6 ug/1 (Turkeltaub and
Iveisman 1981). The mean and median values for this data set were both
equal to 0.3 ug/1. (The mercury concentration reported for Rochester in
this study was 0.25 ug/1.) Lacking further information, a range of 0.2-20
ug/1 in urban runoff was used to show the possible magnitude of the source
Thus, at volumes of runoff of 17.3 x 1012 1/yr and 3.6 x 1Q12 i/yr goim?
to surface waters and POTWs respectively (U.S. EPA 1977a). 3.5-350 kk^
goes to surface waters, and 0.8-80 kkg to POTWs each year. °
The most likely sources of mercury in urban runoff are air emissions
(subsequently deposited) from smelters, incinerators, fossil fuel combus-
tion, and various other industrial activities, as well as mercury vola-
tilized from paint. Since these releases have already been included in
the materials balance shown in Table 1, the urban runoff figures have not
been included in Table 1.
E. CONCLUSIONS
The published literature provides very little information regarding
the amounts and the fate of mercury wastes resulting from manufacturing
operations and from use of mercury-containing products. In general, it
appears that considerably more effort has been devoted to assessing the
amounts and fates of mercury wastes resulting from manufacturing opera-
tions than to those from the application of mercury-containing products,
in spite of the fact that manufacturing wastes may represent only a
minute quantity compared with potential wastes from manufactured' indus-
trial and consumer products, as indicated by the following:
29
-------
Mercury Segment of Amount Ha
Input (kkg) .Industry, Environaent
Electrical Equipment 948 Manufacturing 9.9
Products 938.1
Paint O7n *.. ~
Manufacturing 3.2
Products 266.8
r^v h-
(1) The product mix of short-lived and long-lived
consumer and industrial products containing mercury.
(2) The failure or replacement rate for products that
will last beyond the year of their manufacture.
(3) The fate of both short-lived and long-lived products
containing mercury.
.1,0
. eo .
^
r^j-^^^^
, dlsposa! of POIU sludges, and disposal
previous1^' numerous uncertainties exist in this
as a naral so "rSeSt^rr0rS *" Pr°bably in the ""mation of mercury
as a natural source, or mercury released from product use and disposal
and of mercur cont aisposai,
and of mercury contained in urban runoff.
30
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REFERENCES
Association of Metropolitan Sewage Agencies (AMSA)- Field report on
current practices and problems of sludge management. 1976: 25-29.
Battelle Columbus Laboratories. Multimedia levels: Mercury. Report No.
EPA-560/6-77-031. Washington, DC: Office of Toxic Substances, U.S.
Environmental Protection Agency; 1977.
Bureau of Mines. Minerals yearbook. Volume I. U.S. Department of
Interior; 1972: 909-910. Available from: Bureau of Mines, Pittsburgh,
PA.
Bureau of Mines. Preprint from the 1976 Bureau of Mines Minerals year-
book - Mercury. U.S. Department of Interior; 1976. Available from:
Bureau of Mines, Pittsburgh, PA.
Bureau of Mines. Mineral commodity profiles - Mercury. U.S. Department
of Interior; January 1978. Available from: Bureau of Mines, Pittsburgh,
PA.
Bureau of Mines. Mineral commodity profiles - Mercury. U.S. Department
of Interior; 1979: 96-97. Available from: Bureau of Mines, Pittsburgh,
PA.
Bureau of Mines. Minerals yearbook. Mercury in 1979. Non-ferrous
metals section, U.S. Department of Interior; January 2, 1980. Available
from: Bureau of Mines, Pittsburgh, PA.
Bureau of Mines. Mercury in the first quarter 1980. Mineral commodity
profiles - Mercury. Non-ferrous metals section, U.S. Department of
Interior; May 30, 1980. Available from: Bureau of Mines, Pittsburgh, PA.
Burns and Roe, Inc. Revised development document for the paint industry
point source category. U.S. Environmental Protection Agency; 1979.
Calspan Corporation. Development document for effluent limitations
guidelines and new source performance standard for the ore mining and
dressing industry. Contract No. 68-01-3281. U.S. Environmental
Protection Agency; 1979.
Davis, J.A.; Jacknow, J. Heavy metals in wastewater in three urban
areas. J. Water Pollut. Control Fed.: 9(9); 1975.
Furr, A.K.; Lawrence, A.W.; long. S.S.C.; Grandolfo, M.C.; Hofstader, R.A.;
Bache, C.A.; Gutenmann, W.H.; Lisk, D.J. Multielement and chlorinated
hydrocarbon analysis of municipal sludges of American cities. Environ.
Sci. Technol. 10:683-687; 1976.
31
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Jacobs Engineering Company. Development document including the data
base for effluent limitations guidelines and new source performance
standards and pretreatment standards for the inorganic chemical manufac-
turing industry point source category. Draft. Contract No. 68-01-4492.
U.S. Environmental Protection Agency; 1979.
Martin, H.W.; Mills, W.R. Jr. Water pollution caused by inactive ore
and mineral mines — a national assessment. Report No. EPA-600/2-76-298.
Cincinnati, OH: Office of Research and Development, U.S. Environmental
Protection Agency; 1976. Available from: NTIS, Springfield, VA:
PB-264-936.
Murphy, C.B. Jr; Carleo, D.J. The contribution of mercury and chlori-
nated organics from urban runoff. Wat. Res.: 12:531-533; 1978.
National Coal Association. Steam Electric Plant Factors. 1976.
Stanford Research Institute. Agricultural sources of mercury. Draft
report. Contract No. 68-01-3867. Monitoring and Date Support Division,
U.S. Environmental Protection Agency; 1979.
Turkeltaub, R.; Weisman. D. Collection and analysis of stormwater/
combined sewer overflows and sediment samples for priority pollutants.
Draft Report. Edison, NJ: Municipal Environment Research Laboratory
(MERL), U.S. Environmental Protection Agency; 1981.
US. Environmental Protection Agency (USEPA). Emission factors for
trace substances. Report No. EPA 450/2-73-001. 1973: ch. 7:9-15
U.S. Environmental Protection Agency (USEPA). Consolidated mercury
cancellation: hearing. Chapman Chemical Company. Federal Register
41(76): 16497; April 19, 1976.
U.S. Environmental Protection Agency (USEPA). Consolidated mercury
cancellation hearing: supplement and order. Chapman Chemical Company.
Federal Register 41(167): 36068; August 26, 1976.
U.S. Environmental Protection Agency (USEPA). Development document for
interim final effluent limitations guidelines and proposed new source
performance standards for the pharmaceutical manufacturing point source
category. Report No. EPA 440/1-75/060. 1976: 141.
U.S. Environmental Protection Agency (USEPA). Federal guidelines for
state and local pretreatment programs. Washington, DC; 1977a.
U.S. Environmental Protection Agency (USEPA). Survey of needs for
municipal wastewater treatment facilities. EPA EISD No. 10100. 1977b.
U.S. Environmental Protection Agency (USEPA). Development document for
effluent limitations guidelines and new source performance for the
nonferrous metals industry. Report No. EPA 440/l-79/019a. 1979a.
32
-------
U.S. Environmental Protection Agency (USEPA). Development document
for erfluent limitations guidelines and new source performance stan-
dards for the petroleum refining point source category. Report No
EPA 440/1-79/014-6. 1979b. '' "
U.S. Environmental Protection Agency (USEPA). Water quality analysis
branch priority pollutant data base. November 8, 1979. Monitoring
and Data Support Division; 1979c.
United Technologies, Hamilton-Standard Division. Development document
for the effluent limitation guidelines and proposed new source perfor-
mance standards for the machinery and mechanical products manufacturing
point source category. Draft. Contract No. 68-01-2914. U.S.
Environmental Protection Agency; 1975.
University of Illinois. Recycling of municipal sludges and effluents
on land. Proceedings of the joint conference; 1978.
Van Horn, W. Materials balance and technology assessment of mercury
and its compounds on national and regional bases. Report No. EPA 560/3-
75-007. Washington, DC: Office of Toxic Substances, U.S. Environmental
Protection Agency; 1975. Available from: NTIS, Springfield, VA'
PB 247 000.
Versar, Inc. Assessment of industrial hazardous waste practices,
storage and primary batteries industries. U.S. Environmental Protection
Agency; 1975.
Versar, Inc. Assessment of mercury wastewater management technology
and cost for mercury cell users in the chlor-alkali industry. Contract
No. 68-01-3557. U.S. Environmental Protection Agency; 1976a.
Versar, Inc. Development document for effluent limitations guidelines
and proposed new source performance standards for the storage and
primary batteries segment of the machinery and mechanical products
point source category. Contract No. 68-01-3273, task 2, U.S. Environ-
mental Protection Agency; 1976b.
Versar, Inc. Priority pollutant field survey. Data summary. 1978-
7:119-122, 302-352.
33
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CHAPTER IV.
FATE AND DISTRIBUTION OF MERCURY IN THE ENVIRONMENT
A. iMONITORING DATA
1. Introduction
The following collection of data represents levels of mercury
observed in the U.S. environment from 1970 through 1979, gathered from
published reports and computerized monitoring data bases. Levels of
mercury have been measured in water, sediment, rocks and soils, the
atmosphere, and terrestrial and aquatic biota, and the available data
concerning concentrations in these media are presented in the following
sections. Natural sources appear to account for a significant proportion
of the mercury in the environment. Mercury levels in all media tend to
be higher in urban areas than in rural areas. Studies that enable a
comparison of environmental mercury levels over time indicate a percep-
tible reduction in mean levels and a significant leveling off of mercury
levels in locations with high levels, due to reductions in releases to
the environment in many industrial sectors. A tremendous amount of
monitoring data is available for mercury. However, only a few examples
are included here. For more detailed discussions, the reader is referred
to Battelle (1977) and WHO (1976).
2. Water
Numerous analyses of mercury levels in water have been conducted.
Table 3 summarizes the results of a few studies.
Studies of uncontaminated ocean waters (Williams and Weiss 1973,
Hosohara 1961) found mercury concentrations ranging from 0.029 ug/1 to
0.27 ug/1. A reported mean mercury level in oceans of 0.1 ug/1 (Goldberg
1972) is consistent with this data.
Mercury concentrations in freshwater are similar to those found in
oceans. Various studies support the observation that mercury levels in
uncontaminated streams, rivers and lakes are usually between'0.01 ug/1
and 0.1 ug/11 (Jonasson and Boyle 1971). Garcia and Kidd (1979) found
an average of 0.027 ug/1 mercury in New Mexico's
Values above 0.1 ug/1 are probably caused by natural or anthropogenic
contamination (Jonasson and Boyle 1971).
35
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TABLE 3. CONCENTRATIONS OF MERCURY DETECTED IN WATER
Location
Ocean
Ocean
Concentration
(ug/1)
0.04-0.27 (range)
0.1 (mean)
Source
(Williams and Weiss (1973)
JHosohara (1961)
NSF(1972)
Comments
Uncontaminated areas
Uncontaminated areas
Freshwater
New Mexico (reservoir)
England ( lake)
Great Lakes
Northern Mississippi
Streams and Lakes
Minimata Bay, Japan
Rochester, NY urgan runoff
0.01-0.1 (range)
0.027 (mean)
0.12-0.029 (range of
mean values)
.16 (mean)
0.0-0.4 (range)
0.28 (mean)
1.6-3.6 (range)
18.1 (mean)
Jonasson and Boyle (1971) Uncontaminated areas
Garcia and Kidd (1979)
Gardner (1978)
Chau and Saitoh (1973)
Rihan ejt aj_^ (1978)
Hosohara ej^ al. (1961)
Murphy and Carleo (1978)
Uncontaminated area;
116 samples
Uncontaminated area;
116 samples
Agricultural area witli
mercurial fungicides;
10 samples
Contaminated area
Urban area
-------
second largest reservoir. In England, Gardner (1978) reported mean
mercury concentrations in an uncontaminated lake ranging from 0.012 ug/1
to 0.029 ug/1.
Slightly higher levels of mercury are found in freshwaters located
near possible sources of contamination. In a two-year study of the Great
Lakes, Chau and Saitoh (1973) reported a mean mercury concentration of
.16 ug/1, with values ranging from undetected to 0.4 ug/1. Rihan et al.
(1978) studied streams and lakes in northern Mississippi, an agricultural
area where mercurial fungicides are used. The average mercury level in
these waters was 0.28 ug/1.
Water in highly industrialized and/or contaminated areas may have
greatly elevated mercury concentrations. In Minimata Bay, a contaminated
area in Japan, mercury concentrations were reported to range from 1.6
ug/1 -3.6 ug/1 (Hosohara et al. 1961). Murphy and Carleo (1978) report
average mercury levels of 18.1 ug/1 in urban runoff in Rochester, N.Y.
The STORET water quality data system provides sampling information,
which indicates the distribution of reported ambient concentrations of
mercury in surface water. These data were retrieved for the time period
1970 to 1979 and aggregated on a national level and for major river
basins. Trends in ambient concentrations were investigated over the
past 10 years for both the continental United States and the geographical
regions delineated by major river basins.
The 10-year trend of maximum and mean concentration values for the
United States is presented in Figure 4. During this period, over
100,000 observations of total mercury were made at roughly 13,000 water
quality stations.
From 1970 to 1974, mean mercury concentration values over the U.S.
exceeded 1.0 ug/1 annually. Since 1975, the annual mean concentration
values have fallen to between 0.5 ug/1 and 0.7 ug/1. Likewise, sampling
records prior to 1975 show maximum values over 500 ug/1 in several areas
in the country. These maximum levels decreased such that these localized
maximum concentration values typically are below 200 ug/1 nationwide.
These reductions may represent improved analytical techniques, but more
likely reflect actual reductions in mercury levels.
In order to examine these trends in greater detail, data were
examined for a total of 23 major river basins. Figure 5 illustrates
a significant decrease in mean concentration values for major river
basins from 1972 to 1979.
Measurements of mercury in water are usually of total mercury due
to the limitations of the analytical techniques available for organic
mercury. The most sensitive organic test has a detection limit of
2 x 10-1 g Hg/g water (ORPG, 1979) which exceeds typical concentrations of
the compound in ambient waters. However, organic mercury levels in water
may be estimated by examining other water parameters. Using a partition
37
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10000
1000
o
3
w
I
100
10
Maximum
_L
_L
J.
• Mean
_L
I
1970 1971 1972
1973 1974 1975 1976 1977 1978 1979
Year
Number of Observations: 107,016
Number of Stations: 13,443
Source: STORE!
FIGURE 4 MAXIMUM AND MEAN AMBIENT CONCENTRATIONS OF MERCURY
IN SURFACE WATERS OF THE UNITED STATES 1970-1979 -
A TEN-YEAR TREND
38
-------
c
o
I
11.0
10.5
10.0
9.5
9.0
8.5
8.0
7.G
7.0
6.5
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
River Basins
Noitheast
North Atlantic
Southeast
Tennessee River
Ohio Biver
1.
2.
3.
4.
5.
6.
/. Upper Mississippi
8. Lake Michigan
9. MISSOIIII River
10. Lower Mississippi
11. Colorado Rivur
12. Western Gulf
13. Pacific Northwest
14. California
15. Great Basin
21. Lake Huron
22. Lake Superior
A
M
/ \
n
Legend
1972 (10.909 Samples)
1979 (797 Samples)
/\
7 8 9 10
Major River Basins
11
12
13 14
15
21 22
Source: STORET
FIGURE 5 MEAN LEVELS OF MERCURY IN MAJOR RIVER BASINS IN 1972 AND 1979
-------
7
coefficient of sediment to water of 1704" (Akagi et_a_l. , in press),
organic mercury levels in the Ottawa River were estimated to be approxi-
mately 0.0018 ug/1, which is 24% of the total mercury (ORPG, 1979).
Preliminary laboratory studies revealed organic fractions of 10-20%,
which are consistent with the preceding estimate (ORPG 1979). How
typical these fractions are of aquatic systems in general is unknown
due to a lack of sampling data for verification.
3. Sedir.ent
From the STORE! data retrieved, mercury concentrations in sediment
were not continually declining from 1970 to 1978 as were concentrations
in water. However the mean concentration dropped from 8 rag/kg in 1970
to 3 mg/kg in 1972 and remained below 3 mg/kg until 1978. Figure 6
exhibits the maximum and mean concentrations of mercury in sediment from
1970 to 1978 for the United States.
Table 4 briefly summarizes mercury concentrations reported in
sediment. Mercury concentrations in sediments near sources of contamina-
tion are higher than those in unpolluted areas. Price and Knight (1978)
found a mean mercury concentration of 0.0481 mg/kg in sediment from a
relatively uncontaminated lake and reservoir in Mississippi. In contrast,
Jackson (1979) found a mean mercury level of 1.27 mg/kg in the sediment
of a lake downstream from an area of high industrial activity, including
a chlor-alkali plant and a pulp and paper mill.
Other studies of contaminated areas also indicate high mercury
concentrations in sediments. Gardner et al. (1978) studied sediments
of a Georgia salt marsh located near a chlor-alkali plant. This factory
had discharged approximately 1 kg mercury/day of Hg from 1966 until
1972, when the discharges were discontinued. Sediments in a nearby salt
marsh contained mean mercury levels of 0.56 mg/kg in samples taken at a
depth of 0-5 cm., and 0.28 mg/kg in sediments 5-10 cm deep. In Palos
Verdes shelf sediments in California, samples located near a major waste-
water outfall were examined by Eganhouse et al. (1978). Aqua regia
digestion of sediment samples showed that they contained a mean mercury
concentration of 2.54 mg/kg. Roberts et al. (1975) found similar mercury
levels (mean values from 2-3 mg/kg) in sediments from Boston Harbor.
The form of mercury in the sediment represents an important issue
in determining exposure. The Ottawa River Project Group (ORPG 1979)
estimates that usually no more than 1% of the total mercury in sediment
is in the organic form. Roberts et al. (1975) found that 0.1-0.5% of
the mercury in Boston Harbor sediments was in the form of methylmercury.
A study of sediment in the Florida Everglades reported that similarly
low percentages (0.03-0.07%) of total mercury were methylmercury (Andren
and Harnss 1973). In the Palos Verdes sediments studied by Eganhouse _et al
(1978) up to 2% of the total mercury was in the organic form.
7
"For sandy sediment, using methylmercurv.
40
-------
10000 -
I" 1000
u
V
o
e
100 -
c
u
1970 1971 1972 1973 1974 1975 1976 1977 1978 1979
Year
Source: STORET
FIGURE 6 MERCURY CONCENTRATIONS IN SEDIMENT, UNITED STATES,
1970-1978 - A TEN-YEAR TREND
41
-------
TABLE 4. CONCENTRATIONS OF MERCURY DETECTED IN SEDIMENT
Location
Mississippi Lake and
Reservoir
Ontario (2 lakes)
Georgia (salt marsh)
California (Palos
Verdes Shelf)
Concentration
(mg/kg)
0.0481 (mean)
1.27 (mean)
0.56 (mean at 0-5 cm)
2.54 (mean)
Source
Price and Knight (1978)
Jackson (1979)
Gardner et al. (3978)
Eganhouse et al. (1978)
Commen t s
Uncontaminated area;
19 samples
Contaminated areas;
18 samples
Contaminated area; 10
amples at each depth
Contaminated area; samples
from 14 stations
Boston Harbor
2.0-3.0 (range of mean values) Roberts et al. (1975)
-------
Thus, it appears that methylnercury, as well as other organic
forms, generally .represents only a small portion of the total mercury
present in the sediment.
4. Rocks and Soil
Mercury is prevalent in almost all soils and rock formations.
Table 5 lists mercury concentrations found in these media. Background
concentrations of mercury in these media have been reported to range
0.001 mg/kg to over 0.5 mg/kg (D'ltri 1972). Jonasson and Boyle (1971)
estimate a narrower range of 0.02-0.15 mg/kg mercury for normal soils and
rocks, with values as high as 250 mg/kg occurring in soils near mercury
deposits.
Jonasson and Bovle (1971) studied the mercury content of various types
of sedimentary, igneous, and metamorphic rocks. Their data are presented
in Table 5. Since soils are derived from rocks, one would expect mercury
levels in uncontaminated soils to be similar to mercury concentrations in
rocks (Battelle 1977).
Data from Shacklette et al. (1971) supports this hypothesis. Soils
and other regoliths were sampled throughout the United States at sites
approximately 59 miles apart. The geometric mean of all mercury concen-
trations was 0.071 mg/kg, and 0.112 mg/kg was the arithmetic mean. Sixty-
seven percent of the locations had less than 0.080 mg/kg mercury, while
only 16% of the sites had values exceeding 0.175 mg/kg. The data were
also segregated according to that found east and west of the 97th
eridian, with geometric means of 0.096 mg/kg and 0.055 mg/kg for eastern
and western soils, respectively.
Wiersma and Tai (1974) surveyed cropland and noncropland soils in
29 eastern states and found no statistical difference between the two
soil types. Mean mercury levels ranged from 0.05 mg/kg to 0.10 mg/kg.
In two studies conducted as part of the National Soils Monitoring
Program, mercury concentrations in 10 urban areas were compared with
concentrations in the corresponding suburban areas (Gowen et al. 1973,
USEPA 1974a). At 9 of the 10 sites mercury concentrations were signifi-
cantly higher in the urban soils. Urban values ranged from undetected to
15.39 mg/kg while suburban levels varied between undetected and 1.12 mg/kg.
5. Air
Atmospheric mercury may exist as a vapor or associated with parti-
culates. In addition, airborne mercury may be present in elemental,
organic or inorganic forms. Therefore, monitoring data for mercury in
air must be interpreted with regard to the type of mercury being measured.
Various studies indicate that atmospheric mercury is primarily a
vapor (NRG 1978). However, the ratio of particulate mercury to mercury
vapor may vary with the location. Airborne mercury over oceans and in
43
-------
TABLE 5. CONCENTRATIONS OF MERCURY DETECTED IN ROCKS AND SOIL
Concentration
Location
Unspeci fled
Unspecified
Unspecified
Unspecified
Unspecified
Unspecified
Sites throughout the
United States
29 Eastern States
10 urban areas throughout
the United States
10 suburban areas throughout
the United States
0.001->0.5 (range)
0.02-0.15 (range)
up to 250
(0.025-.437 (range of mean
values)
0.010-3.25 (range)
0.020-.450 (range of mean
values)
.002-1.4 (range)
fO.050-.225 (range of mean
i values)
i0.010-1.0 (range)
0.071 (geometric mean)
0.112 (arithmetic mean)
0.05-0.10 (range of mean
values)
0.0-15.39 (range)
0.0-1.12 (range)
Source
D'ltri (1972)
Jonasson and Boyle (1971)
Jonasson and Boyle (1971)
Comments
Background concentrations
in rocks and soils
Background concentrations
in rocks and soi is
Background concentrations
near mercury deposits
Jonasson and Boyle (1971) Sedimentary rocks
Jonasson and Boyle (1971) Igneous rocks
Jonasson and Boyle (1971) Metamorphic rocks
Shacklette
-------
rural areas is reported to be almost completely in the vapor form,
although the proportion of vaporous atmospheric mercury may vary in
urban areas (NRC 1978).
Studies indicate that the major portion of airborne mercury (primarily
the vapor) is in the elemental form (NRC 1978, Spittler 1976). Johnson
and Braman (1974) collected air samples at eleven sites near Tampa, Florida
and found different mercury species present in the vapor fraction in the
following percentages: Hg(II) - 25%, methylmercury - 21%, elemental mercury
49% and dimethyl mercury - 1% (particulate mercury comprised the remain-
ing 4% of the sample material). Spittler's (1976) analysis of air
samples in North Carolina showed even higher percentages of elemental
mercury, including at least one sample that was entirely composed of
elemental mercury. Soldano et al. (1974, 1975) studied airborne mercury
near sewage treatment plants and found that the prevalence of certain
mercury species depended upon the species and distance from the source.
Levels of elemental mercury varied inversely with distance from the
plant, while levels of alkyl mercury halides increased with increasing
distance from the plant.
Cooper et al. (1974) report that background mercury vapor concen-
trations generally range from 1 ng/m3 to 5 ng/m3, while levels in urban
areas are in the range 2-60 ng/m3. According to the NRC (1978), typical
total mercury concentrations are approximately 0.7 ng/m in remote
oceanic areas, 4.0 ng/m3 in rural areas, and usually less than 10 ng/m^
in urban areas. Table 6 summarizes these as well as other data on
concentrations of mercury in air.
In the study by Johnson and Braman (1974) referred to above, total
mercury levels in Tampa ranged from 1.8 ng/m3 to 298 ng/m3, with mean
values of 4.48 ng/m3 during the day and 8.40 ng/m3 at night.
Spittler (1976) analyzed a variety of air samples from nine states,
with most of the samples coming from the New England area. Over 90%
of the samples contained mercury levels within the 2-60 ng/m3 range
reported by Cooper et al. (1974). High values appeared in the plumes of
an incinerator (200 ng/m3), a burning dump (275 ng/m3) and a power plant
(5,820 ng/m3). Cooper et al. (1974) also reported atmospheric mercury
levels in 10 cities located in the west and midwest. Values ranged from
5.0 ng/m3 near a freeway in Nashville, TN to 29.6 ng/m3 near an indus-
trial area in El Paso, TX.
The mercury content of petroleum may result in transportation
sources contributing significant amounts of mercury to the atmosphere.
Cooper et al. (1974) found that automobile exhaust gases contained
95-160 ng/m-* mercury. (The unburned fuel was not analyzed for mercury
content.) In addition Cooper_et _al. (1974) report that atmospheric
mercury concentrations near highways increase from 5 ng/m3 during low-
traffic periods to 10-12 ng/m3 during periods of heavy traffic.
45
-------
TABLE 6. CONCENTRATIONS OF MERCURY DETECTED IN THE ATMOSPHERE
Location
Unspecified
Unspecified
Unspecified
Unspeci fied
Unspecified
Tampa, KL
9 States
10 Cities (Western and
Midwestern United States)
Unspecified
Unspecified
Concentration
(ng/m3)
1-5 (range)
2-60 (range)
0.7 (typical value)
4.0 (typical value)
<10.0 (typical values)
f1.8-298 (range
j 4.48 (daytime mean)
<8.40 (nightime mean)
2-60 (range for 90% of
the samples)
5.0-29.6 (range)
5 (typical value)
10-12 (typical values)
Source
Cooper £t_ al. (1974)
Cooper et^ al. (1974)
NUC (1978)
NRC (1978)
NRC (1978)
Johnson and Braman (1974)
Spittler (1976)
Cooper e^ a I. (1974)
Cooper £t al. (1974)
Cooper et aJ. (1974)
Comments
Background concentrations
in rural areas
Urban areas
Remote oceanic areas
Rural areas
Urban areas
Near highway during
low traffic period
Near highway during
heavy traffic period
-------
6. Aquatic Biota
A large amount of data concerning mercury levels in aquatic biota
is available in the literature. Many of these studies have focused on
the threat of human exposure from mercury in seafood. Table 7 summarizes
data on aquatic biota which is discussed in this section.
Some studies of aquatic biota have focused specifically on freshwater
fish. A comprehensive survey of mercury levels in freshwater fish was
conducted by the National Pesticide Monitoring Program in 1969 and 1970
(Henderson _et _al. 1972). Various species of fish were sampled at 50
locations throughout the United States in 1969. These sites were reexam-
ined in the following year, along with 50 additional stations. Total
mercury residues above the detection limit (0.05 mg/kg) were present in
129 of 145 samples in 1969 and in 373 of 393 samples in 1970. The median
mercury level was 0.15 mg/kg for both years. Values ranged from £0.05 mg/kg
to 1.25 mg/kg in 1969 and from <0.05 mg/kg to 1.80 mg/kg in 1970.
The data from this study indicate some general patterns. High
mercury levels occurred most frequently in fish from Atlantic coastal
streams and Columbia River System. Most fish containing high levels
were species near the top of the food chain, a finding indicating
possible biomagnification of mercury (see Biological Fate). The lowest
mercury concentrations were reported in the two samples from Alaskan
streams and in samples from the Colorado River System and Mississippi
River tributaries in the Great Plains region (Henderson et^ al. 1972).
Various studies have shown that fish caught in reservoirs have
higher mercury concentrations than those caught in free-flowing sections
of rivers (Battelle 1977). One explanation for this phenomenon is that
when mercury-rich sediments are deposited in reservoirs, these ares pro-
vide ideal conditions for bacterial formation of methylmercury (Battelle
1977). This form of mercury is readily accumulated by fish (see
Biological Fate).
Data are available concerning freshwater biota in contaminated and
uncontaminated areas. Price and Knight (1978) studied Lake Washington
and the Sardis Reservoir, two unpolluted freshwater bodies in Mississippi.
They found a mean mercury level of 0.4 mg/kg in plankton and a mean value
of 0.11 mg/kg in clams. Sediment samples from this reservoir contained
an average of 0.05 mg/kg mercury. The authors noted that the mercury
concentration in the clams was only slightly higher than that in the'
sediments, a phenomenon reported in observations of clams in other
relatively uncontaminated areas. Also, trophic conditions of the water
may result in higher mercury levels in plankton as compared with those in
clams (Price and Knight 1978). Knight and Herring (1972) studied 73
largemouth bass (Micropterus salmoides) in the Ross Barnett Reservoir in
Mississippi. Since there are few industrial sources of mercury near
this reservoir it is hypothesized that mercury in the impoundment comes
from natural sources, waste items disposed of by the public and agri-
47
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TABLE 7. CONCENTRATIONS OF MERCURY DETECTED IN AQUATIC BIOTA
Concentration
Location
Sites throughout the
United States
Lake Washington and Sardis
Reservoir, Mississippi
Ross Barnett Reservoir,
Mississippi
Wisconsin River
Two Canadian Lakes
Ceorgia (salt marsh)
00
Sites throughout the
United States
North Atlantic
Offshore Waters
Sites in the United States,
Canada and Europe
California (Palos Verdes
Shelf)
Georgia (salt marsh)
0.15 (median value)
0.4 (mean value-plankton)
0.11 (mean value-clams)
<0.05-0.74 (range)
0.07-0.56 (range)
0.20-3.79 (range of means)
0.3-9.4 (range for
invertebrates)
0.1-2.4 (range for benthic
organisms)
0.0-6.98 (range)
0.154 (mean)
.02-.46 (range for mussels)
<.01-.19 (range for herring)
.08-3.85 (range for pike)
all mean values 0.5
0.008-0.104 (range)
Source
Henderson et al. (1972)
Comments
Price and Knight (1978) Uncontaminated area; 19
samples of each species
Knight and Herring (1972) Uncontaminated area; 73
fish
Sheffy (1978) 34 crayfish
Moore and Sutherland (1980) Contaminated area
Gardner et^ al. (1978) Contaminated area
NMFS (1975)
Greig et^ al. (1975)
Holder, (1973)
41 species of fish
Contaminated and uncon-
taminated areas
Eganhouse and Young (1978) Contaminated area
(Standiford et^ al. (1973)
I Potter et al. (1975)
Area with high natural
mercury levels
-------
cultural products. The bass contained mercury levels of <0.05-0.74
mg/kg. Average mercury concentrations varied according to the weight
of the fish, with the lightest fish containing an average of <0.12 mg/kg
mercury and the heaviest fish containing an average of 0.45 mg/kg.
Sheffy (1978) conducted mercury analyses on 34 crayfish from the
Wisconsin River and compared values found in industrialized and non-
industrialized sections of the river. Mercury was present in the
abdominal muscle of crayfish in concentrations of 0.07-0.56 mg/kg (wet
weight), with higher mean values occurring in the southern (industrialized)
section of the river. Sheffy (1978) noted, however, that the highest
mercury levels were found in crayfish approximately 30 km from the
industrial plants. This finding was attributed to physical character-
istics of the Wisconsin River, which appear to have influenced the
transport and accumulation of mercury. (See Battelle 1977)
A number of studies have focused exclusively on contaminated fresh-
waters and the organisms that inhabit them. Moore and Sutherland (1980)
investigated two polluted Canadian lakes. Discharge of mercury-laden
wastes from a gold mine into Giauque Lake was terminated in 1968, and
discharges into Thompson Lake from a different gold mine were discon-
tinued in 1949. Although mercury levels in the water of these two lakes
were usually below detection limits, the sediment was contaminated. In
Giauque Lake average mercury levels were 3.79 mg/kg in lake trout, 1.75
mg/kg in northern pike, and 1.22 mg/kg in round whitefish. Northern
pike in Thompson Lake had mean mercury concentrations of 1.69 mg/kg and
mercury values for whitefish averaged 0.20 mg/kg. Moore and Sutherland
(1980) concluded that northern pike in Thompson Lake are still accumu-
lating mercury from tailings deposited 30 years ago. They also noted
that while only a small part of these lakes had been contaminated, fish
throughout the lake had elevated mercury levels. Presumably this was
due to movement of fish between contaminated and uncontaminated areas.
Gardner et_ al. (1978) studied a variety of organisms from a salt
marsh ecosystem, which had been contaminated by discharges from a chlor-
alkali plant. Mercury levels in salt marsh invertebrates ranged from
0.3 mg/kg to 9.4 mg/kg while mercury levels varied between 0.1 mg/kg and
2.4 mg/kg in benthic organisms inhabiting a river in the area.
Phillips e_t al. (1980) determined levels of mercury in fish in the
Tongue River Reservoir, Montana. This area is in the vicinity of min-
ing activity, and was investigated due to the future prospect of exten-
sive coal mining in the area. Samples taken in 1978 showed that Northern
pike had the highest concentrations of total mercury, with a maximum of
1.53 ug/g wet weight. In addition, 29% of the samples showed levels
greater then 0.5 ug/g, the FDA limit in effect at that time. The authors
suggested that future development of coal mining might result in in-
creased mercury levels in fish in the area.
While mercury contamination from anthropogenic sources usually
results in elevated mercury levels in aquatic biota, it should be noted
49
-------
that high mercury concentrations may also result from natural sources.
In a study of fish in Saskatchewan waters, Sumner et al. (1972) found
elevated mercury levels (0.11 mg/kg - 1.3 mg/kg) in fish from four
lakes which were located far from industrial areas. The authors sug-
gested that bedrock containing high levels of mercury might be the
source of the contamination.
Mercury has been found in marine fish, as well as in freshwater
species, although it has been observed that, overall, saltwater fish
contain slightly lower mercury concentrations (NRC 1978, Battelle 1977).
A study by Koli et al. (1978) of freshwater and saltwater fish species
from South Carolina supports this conclusion.
A preliminary study by the National Marine Fisheries Service (NMFS
1975) investigated fish in coastal waters throughout the United States.
Out of 106 species tested, only six had median levels greater than 0.05
mg/kg. The highest mercury concentrations were reported in fish from
the southeastern coastline. Concentrations ranged from 0.0-6.98 mg/kg
in East Coast fish, from 0.003-3.57 mg/kg in Wast Coast fish and from°
0.001-1,511 mg/kg in Gulf Coast fish. '
In contrast to this NMFS study, Roberts et al. (1975) report that
the highest mercury levels in shellfish are found off the coast of
Massachusetts and the Brunswick area of Georgia, while the lowest values
were found in the Gulf of Mexico (with one exception in Texas).
A later, more comprehensive study of trace metals in aquatic biota
was conducted by NMFS (Hall et al. 1978). Tissues of 204 species of
fish, mollusks and crustaceans gathered from 198 sites throughout the
coastal United States (including Alaska and Hawaii) were analyzed.
Most fish and all crustaceans had mean mercury concentrations below
0.3 mg/kg. All mercury levels in mollusks were less than 0.1 mg/kg.
Extrapolation of the data by the authors of the study indicates that
less than 2% of the United States fish catch intended for consumption
contains mercury levels greater than 0.5 mg/kg.
Greig et al. (1975) studied invertebrates, plankton and fish from
North Atlantic offshore waters. Mercury levels in invertebrates were
generally less than 0.1 mg/kg and all plankton sampled had mercury
values less than 0.05 mg/kg. Forty-one species of fish were sampled
and their average mercury concentration was 0.154 mg/kg. The author
notes that this level is consistent with values reported in other
studies. Fish with relatively high levels of mercury were the cusk
(mean: 0.49 mg/kg) and the spiny dogfish (means: 0.44-0.53 mg/kg).
Marine animals have been studied in polluted, as well as unpolluted
areas. An international cooperative study reported mercury levels in
various species of freshwater and saltwater fish (Holden 1973). Data
for mussels, herring and pike are summarized in Table 7. There was
considerable overlap in concentration ranges in fish from polluted and
50
-------
unpolluted areas. Eganhouse and Young (1978) sampled tissues of six
benthie animals living in a contaminated area near the Palos Verdes
Peninsula in California. The Los Angeles County municipal wastewater
outfalls were the sources of this contamination. For all samples, mean
levels of total mercury were below 0.5 mg/kg while mean levels of organic
mercury were below 0.05 mg/kg (wet weight). These data were compared
with findings from other studies. The authors concluded that despite
the contamination of the organisms' habitat, mercury levels in these
animals were relatively low and similar to values found in related
animals in other areas of the world.
These data indicate that marine biota located in contaminated
water do not always have high mercury concentrations. These data are
in contrast to studies of freshwater fish, which usually show elevated
mercury levels in polluted areas.
This finding might be related to the observation (noted earlier)
that overall, marine fish tend to have lower mercury values than fresh-
water species. Possible explanations for this phenomenon include the
greater dilution and dispersion capacity of oceans and the far-ranging
habits of many large marine organisms (Battelle 1977).
Various studies indicate that methylmercury comprises 61-100% of
the total mercury in fish (Henderson et al. 1972, Buhler et al. 1973,
Huckabee et al. 1974, Gardner _e_t al_._ 1975, Knauer and Martin 1972).
Gardner et al. (1978) reported that 21-100% of the total mercury present
in the muscle of fish from a contaminated salt marsh was methylmercury.
Most studies of mercury in aquatic biota have focused on the threat
of human exposure from mercury in seafood. However, there are some data
available concerning aquatic plants and plankton.
Plants were analyzed in Lake Powell, Arizona, an area of high natural
mercury levels (Standiford et al. 1973, Potter et al. 1975). Mercury
concentrations ranged from 0.008 mg/kg to 0.104 mg/kg in vascular plants.
Knauer and Martin (1972) found that 12-67% of the total mercury
content of phytoplankton was methylmercury. In contrast, Gardner et al.
(1978) found only trace amounts of methylmercury in plants in a con--
taminated salt marsh in Georgia.
7. Terrestrial Biota
Mercury concentrations in terrestrial vegetation have been found
to vary between different types of vegetation, and also between polluted
and unpolluted areas. Table 8 summarizes these data, as well as other
data presented in this section.
Mercury levels in trees in a number of unpolluted areas averaged
0.02-3.03 mg/kg (Shacklette 1970, Huckabee 1973), while averages ranged
from 0.2 to 1.0 mg/kg in urban areas (Shacklette 1970, Smith
51
-------
TABLE 8. MERCURY CONCENTRATIONS DETECTED IN TERRESTRIAL BIOTA
Location
Unspecified
Unspec if led
Tacoma , WA
Concentrations
(mg/kg)
0.02-0.03 (range of mean
values)
0.2-1.0
1.1-4.0
Type of
Biota
Trees
Trees
Garden
Vegetables
Source
fShacklette(1970)
lHuckabee(1973)
(ShaclUette (1970)
(Smith (19 72)
Rats ch (19 74)
Oi
Oak Ridge, TN
Cades Cove, TN
Florida
Georgia
State of Washington
Jackson, Mississippi
0.025 Grass
0.092-0.118 Mosses
Huckabee(l973)
Huckabee (1973)
2.65-10.1 (range of mean
values)
40.1 (high values)
0.13-37.6
Raccoon Hair (Curable (1975a)
(Cumbie and Jenkins (1974)
Mammal Hair {Cumbie (1975a, b)
I Curable and Jenkins (1974)
0.02-11.67 Came Birds
.014-.085 (range) Pigeons
Ad ley and Brown (1972)
Knight and Harvey (1974)
Comments
Uncontaminated areas
Urban areas
Near a copper smelter
Near a stack emitting
fly ash
Unpolluted area
246 birds
Values in claws
-------
Shacklette (1970) also reported that trees growing over a cinnabar vein
in Alaska contained high levels of mercury (1.0-1.25 rag/kg).
Herbaceous growth in unpolluted areas contains mercury levels
similar to those found in trees in similar areas (Devendorf 1975,
Standiford et al. 1973, Gay 1976). Values increase near sources of
contamination. Analysis of garden vegetables growing within 3.2 km
of a copper smelter in Tacotna, Washington, showed mercury concentrations
of 1.1-4.0 mg/kg (Ratsch 1974).
Grasses do not appear to accumulate mercury as readily as other
types of vegetation. Huckabee (1973) reported a mercury level of
0.025 mg/kg in grass near a stack emitting fly ash in Tennessee.
Studies indicate that mosses and lichens tend to accumulate more
mercury than other types of vegetation. For example, mercury concen-
trations in mosses ranged from 0.092 to 0.118 mg/kg in Cades Cove,
Tennessee (an unpolluted area), while other vegetation in the area had
average mercury levels of 0.02-0.03 mg/kg (Huckabee 1973).
The far-reaching influence of anthropogenic sources of mercury on
vegetation is evident in some observations in Connecticut (Mondano and
Smith 1974). At distances up to 14 km from New Haven, mercury levels
in trees are similar to those found in trees located in the city.
Mercury levels in mammals vary with geographical area, as well as
among and within species (Battelle 1977). Cumbie (1975a, 1975b) and
Cumbie and Jenkins (1974) studied mammals in the southeastern United
States. Concentrations were reported for mammal hair, as mercury burdens
tend to be relatively high in that part of the animal. In Florida,
mean mercury values in raccoon hair ranged from 2.65 mg/kg in juveniles
to 10.1 mg/kg in adults, with one report of what appears to be an
unusually high mean value of 40.1 mg/kg in juvenile raccoons in Dade
County. In Georgia, mean values ranged from 0.13 mg/kg for white-tailed
deer in the Piedmont to 15.9 mg/kg for raccoon in the same area, and
37.6 mg/kg for otter in the Lower Coastal Plain. (All measurements are on
a dry weight basis in hair.)
Feeding habits influence mercury accumulation in mammals. The
highest mercury levels are found in carnivores whose diets include
aquatic organisms. Herbivores tend to have lower levels than carnivores
and omnivores (Battelle 1977). Lynch (1973) noticed that squirrels in
rural areas had higher mercury burdens than those near cities, a situ-
ation that may have resulted from their ingestion of seeds treated with
mercurial fungicides.
Mercury has been found in birds throughout the United States with
residues varying between years, seasons, regions and species (Battelle
1977). However, one nationwide monitoring program for starlings found
no differences in mercury levels between birds in urban and rural areas
(Battelle 1977).
53
-------
Clark and McLane's (1974) study of 329 xroodcock from 23 eastern and
midxj-estern states indicates a trend of higher mercury concentrations in
southern woodcock. Other regional variations were noted by Heath and
Hill (1974) who found mercury levels were higher in ducks from the
Atlantic and Pacific flyways than in samples from the Mississippi and
Central flyways.
Differences in diet may also influence mercury accumulation in
birds. Heath and Hill (1974) found that black ducks had mercury burdens
about twice those of the less carnivorous mallard ducks. Consumption
of mercury-treated seeds may also significantly increase residues in
birds (Lynch 1973).
Adley and Brown (1972) studied 246 game birds in the State of
Washington. The highest mean mercury levels were 11.67 mg/kg and 0.29
mg/kg found in the livers of mergansers and teal, respectively. The
authors noted that, out of all the species they studied, these two were
the only ones whose diets included aquatic organisms. Other average
mercury levels ranged from 0.02 mg/kg mercury in livers of grouse to
0.16 mg/kg in geese.
Knight and Harvey (1974) studied pigeons in Jackson, Mississippi
to collect data on mercury levels in wild birds in urban areas. Brains
of the birds contained an average of .022 mg/kg and values in claws
ranged from .014- to .085 mg/kg. The authors suggested that these mercury
residues may have accumulated from ingestion of treated grains and seeds,
as well as from exposure to natural sources of mercury.
Some studies have shown declining mercury levels in some birds in
recent years (Battelle 1977). They have attributed these reductions to
declines in the use of pesticides and improved disposal practices for
natural wastes.
B. ENVIRONMENTAL FATE
1. Overview
a. Methodology
This section characterizes the environmental fate of anthropogenic
mercury released by processes that contribute significant quantities of
the metal to the air, water and soil. The discussion emphasizes the form
of mercury for each discharge, and the processes that determine its sub-
sequent transport upon release to the environment. A general overview
of the environmental chemistry of mercury produced by Versar, Inc.
(1978a) has been the basis for this section. Other studies available
in the literature that support the observations noted are discussed as
relevant. Biological pathways have been treated separately from physico-
chemical and bulk transport pathways (see IV.c), although'the processes
promoting the biological production of inethylmercury are detailed here.
54
-------
b. Major Environmental Pathways
The major pathways of physical transport and relative rates at
which they occur are designated in Figure 7. Atmospheric emissions
(Pathway 1) have been segregated into point source and dispersive
emissions. Combustion processes, such as incineration, smelting, and
coal combustion, are point sources contributing to highly localized
pollution; dispersive sources such as volatilization of mercury from
paints and outgassing from the earth contribute to the concentration of
mercury found in background levels.
Pathway 2 follows the flow of mercury originating from disposal
sites for solid waste and mine tailings. As environmental controls
restrain further discharges to air and water, the quantity of mercury
disposed of upon land surfaces can be expected to increase. It is
also the pathway for agricultural applications.
Mercury discharged with industrial process effluents into local
surface waters or publicly-owned treatment works (POTW) is reviewed in
Pathway 3. The fate of mercury in POTWs is described in Pathway 4.
Figure 8 gives a more general overview of all major pathways of
anthropogenic mercury and the relative total contributions of the mer-
cury-consuming activities to each environmental compartment. The major
recipients are the land (mostly at specific.disposal sites) and air
compartments. The migration of mercury in groundwaters to nearby sur-
face waters has not been shown in this figure, but under the proper
conditions, the process can occur very rapidly. The importance of this
transport pathway, however, is not well understood at this time. Also
not represented in the figure is the high concentration of mercury in
sediments compared with the overlying water and in soils subject to'con-
tamination by airborne mercury.
c. Important Fate Processes
In aquatic systems, mercury is concentrated in the sediments in
aerobic waters, sorbed primarily onto hydrous iron and manganese oxides,
clays, and organic material. The bulk of mercury transported in the
water column in at least some cases is in association with the dissolved
solids (Perhac 1974). The primary species are organic complexes such
as with humic acid; the aqueous chloride and hydroxide are the predom-
inant inorganic species. In anaerobic waters,'the solubility of mercury
decreases; under reducing conditions, mercury will be precipitated
as mercury sulfide. In slightly reduced sediments, methylation of
mercury results, especially in acidic waters. Most mercury species
are available for methylation [upon conversion to Hg(II)], except for
the insoluble HgS. Demethylating bacteria also exist, but the rate of
demethylation is much slower than the rate of methylation.
55
-------
Pathway No.
1.
Atmospheric Emissions
Hg Production
Smelling
Fossil Fuel Combustion
Incineration
Chlor-alkali Plants
Atmospheric Emissions
House Paints
Outgassing
Solid Waste & Tailings,
Coal Piles &
Open Pit Mines
Agricultural Applications
Piimary Hg Pioduction
Coal Mining
Ore Mining and Beneficial ion
Chlor-alkali Plants
Batteries
Electric Lamps
Pavement & Local
Road Soils
Dissolved Solids
Susp. Sediment
FIGURE 7 MAJOR ENVIRONMENTAL PATHWAYS OF MERCURY EMISSIONS
-------
Aqueous Dischaiges
Chlor-alkali Plants
Dental Uses
Paint Application
Treatment
System
Hazardous/
Solid Waste
Dump
4.
POTW
Influent
.»
— _
Primary
. — .^.
"
Biological
Treatment
1
Sludge
Elfliient
Ocean Humping
Incin-
eration
Land-
till
..-_ J _ — ^.
Air
-i I.
Soil
Slow
Surface Water
Sediments
c
L
^- Ocuans
' /
\
Gioundwaler
/'
FIGURE 7 MAJOR ENVIRONMENTAL PATHWAYS OF MERCURY EMISSIONS (Continued)
-------
Ln
00
Atmospheric Emissions <~ 44% of Total)
Combustion
Metal Smelting
Paint Vapors
Chlor-alkah Pioductjon
Aqueous Dischaige (~ 8% of Total)
Lakes & Oceans
POTW
(~2%of Total)
Land Disposal (~47% of Total)
Solid Wastes
failings
Landfills
Lagoons
Agricultural Uses
Note: Quantities of anthropogenic mercury emissions moving in each pathway are roughly in proportion to the
th-ckness of each pathway shown. The figu,e is derived from the material balance of .nercury7^ by Chap,* „,.
FIGURE 8 SCHEMATIC DIAGRAM OF MAJOR PATHWAYS OF ANTHROPOGENIC MERCURY
RELEASED TO THE ENVIRONMENT IN THE U.S. (1979)
-------
Atmospheric emissions of mercury consist of mercury sorbed onto
submicron particulate matter and the elemental mercury vapor. Particu-
late mercury (about 5% of the total) is expected to be short-lived in
the atmosphere; dry fallout and washout of mercury particulates con-
tribute to mercury deposition upon local soils, urban pavements, and
surface waters. Mercury, as a vapor, may be longer lived in the atmos-
here, contributing to background concentrations.
Mercury is present in soils as a result of atmospheric deposition,
solid waste and sludge disposal, and agricultural uses. Most of this
mercury remains in the top few centimers of soil, sorbed onto organic
matter, clays, and iron and manganese oxides, above a pH of about 5.
The potential for translocation of mercury to the groundwater is generally
small, but is greater in sandy, porous sites or in low pH environments,
with a high water table. Volatilization from soils is probable, especially
in dry soil containing little organic material or clay.
2. Phvsicochemical Pathways
a. General Fate Discussion
i. Aqueous Complexation
The concentration of soluble mercury in water is directly related
to parameters such as pH, the oxidizing potential of the water, the
presence of other competing ions (e.g., calcium, magnesium and iron),
the concentration of precipitating agents (e.g., OH~, S=, P04~3, CO^) ,
and the concentration of complexing agents. Generally, at low pH values,
and in low alkalinity waters, mercury will be more soluble; at high
pH levels, and in high alkalinity waters, mercury is usually found
complexed with organic ligands, chlorides, and hydroxides. In natural
aerated waters, mercuric mercury [Hg (II)] is the stable form. Less
soluble forms of mercury typically found in aerated natural water in-
clude the oxide (.0053 g/lOOg); in anaerobic waters, the insoluble sul-
fide predominates. Figure 9 illustrates the presence of aqueous mer-
cury species as a function of pH and pE (Rubin 1974).
ii. Mercury Transport in Aqueous Systems
Mercury distribution and transport in river systems have been
researched by Rubin (1974), Khalid et al. (1975), and the Ottawa River
Project Group (1979). Mercury in the water column is concentrated
by inorganic hydrous oxides, clays, and organic suspended solids to
approximately 5-25 times the concentration found in the water (Rubin
1974). The work of Perhac (1974), which dealt with metals other than
mercury, shows that, although most metals are concentrated in suspended
sediments, the ratio of the mass of suspended sediments to the mass of
water is so low that metals are transported in most cases as dis-
solved solids. This observation is supported for mercury by the work
of the ORPG (1979), which determined the distribution of mercury in
bed sediments, suspended solids, and water. Table 9 summarizes their
59
-------
20- --
HgClg ' oq
10-
aq
-IQ
-15
io~3cr
aq
ct
Ok %'\"' -
Hg° oq
•V,,
pH
1. _
10
12
I
14
Note: 25"C and 1 atm total pressure. Solution contains 10"3 M S04~
and 10"3 or lO'^w CT . Dashed line represents expanded field
boundary of HgCI2. High solubilities exist over the upper one-
third and extreme lower right of the diagram.
Source: Rubin (1974)
FIGURE 9 STABILITY FIELDS OF Hg AQUEOUS SPECIES AS A
FUNCTION OF pE AND pH
60
-------
TABLE 9. DISTRIBUTION OF MERCURY IN THE OTTAWA RIVER
Component
Water
Suspended Solids
Bed Sediment (4cm)
Total Hg
(ug/kg)
.03
4401
4101
rumuci.L r _LUW OL
Mercury Through
Systems (kg)
1.3 x 103
3.4
2.9 x 10
Dry weight
Source: Ottawa River Project Group (1979),
61
-------
findings, which confirm that dissolved mercury in the water column is
the principal species transported.
Mercury is more easily adsorbed than most other metals. Figure
10 shows that although less easily sorfaed than copper, mercury is
adsorbed more readily than nickel, cobalt, zinc and cadmium
(Vuceta and Morgan 1978). Mercury adsorption onto sediments is
strongly influenced by the redox potential and pH and the sediment
characteristics. Khalid et al. (1975) determined that mercury added
as HgCl2 to Mississippi River sediment is adsorbed at high pH (6.5-8.0)
levels and reducing conditions. The pH dependence of adsorption is
seen by the following data generated for an invariant redox potential:
at pH 5, 50-75% of the added mercury remained soluble, at pH 6.5, the
percentage was 1-13% at pH 8.0, less than 0.5% remained in solution
(Khalid et al. 1975).
Desorption is also determined by pH and redox potential. For all
pH levels, desorption is negligible in reduced waters. In aerated
waters, the rate of desorption increases inversely with pH.
The Ottawa River Project Group (1979) determined that the mercury
concentration in sediment of a localized section of a river channel
fluctuated according to the organic fraction in the sediment. Mercury
concentrations ranged from 0.05 mg/kg for pure sand to 1.8 mg/kg for
organic material. These authors also inferred a mercury half-life
in the sediment of 1-2.5 years, on the basis of mercury concentrations
monitored for 3 years. The clearance mechanisms cited were sediment
transport, desorption and transport, bioaccumulation, volatilization,
or "removal" created by burial from new sediments.
iii. Atmosphere
Mercury is released as a vapor or aerosol into the atmosphere. The
aerosol fraction reported is about only 5% of the total mercury in air
(WHO 1976). Vapor species encountered in an analysis of air in Florida
were distributed as follows: 25% Hg(II), 21% CH3Hg+, 49% Hg(0), and
1% (CH3)?Hg (Johnson and Braman 1974). Since the concentration of mercury
in the atmosphere depends upon the temperature, concentrations tend to be
higher during the summer than in the winter (Krenkel 1973). Versar
(1978a) estimates that a mean residence time for mercury in the atmos-
phere is 4-11 days. Transformation of organic mercury compounds and
elemental mercury, which can occur during this period, are promoted by
UV light for the former group and oxidation to the divalent ion in the
presence of water for the latter (WHO 1976).
Mechanisms for removal of mercury from the atmosphere include wet
and dry deposition. Some dispute has arisen as the the efficiency of
wet deposition in the removal of mercury from the atmosphere. Krenkel
(1973) cites several examples of near 100% removal of mercury during a
rainfall. Van Horn (1975), on the other hand, cites examples in which
the particulate mercury is removed, but the remaining vaporized mercury
component (-90% of total) remains in the atmosphere despite rain and
snowfall.
62
-------
Note: pH = 7, pe = 12, pCQ2 = 10'3's atm, pCr = 4.16
Source: Vuceta and Morgan (1978)
FIGURE 10 ADSORPTION OF TRACE METALS IN
OXIDIZING FRESH WATERS AS A FUNC-
TION OF SURFACE AREA OF SiO: (s)
63
-------
The form of mercury in rainwater is not known (NRC 1977), but it
may be an adsorbed species on particulate matter or the divalent ion,
resulting from the oxidation of elemental mercury or methylmercury
particularly if the rain is acid in nature. The' divalent" and methyl-
mercury forms are available for further translocation within the air,
soil and water.
iv. Soils
The fate of mercury in soils follow three routes: volatilization,
leaching, and conversion to methylmercury, Rogers (1978) determined the
relative volatilization rates of various mercury species applied to
sandy, loam, and clay soils. The most soluble mercury species [HgCl?,
Hg(NC>3)2, and Hg(CH311302)2] disappeared from soil more quickly than
the less soluble, HgO, and insoluble HgS. The volatility rate was
progressively lower in sand, loam, and clay soils. Table 10 summarizes
some of the data Rogers (1978) generated for soils saturated at 50%
of field capacity, at pH 8-9.
Mercury transport via soil solution is dependent upon soil pH, soil
content, microbial activity, and the species of mercury present. In-
organic mercury species fHg(O) and HgS] undergo principally oxidation-
reduction reactions; Hg(0) to the divalent ion and HgS to soluble sul-
phates or sulfites in the presence of oxygen. The divalent ion is
capable of complexing and chelating to organic matter. Organic mercury
species, such as those used in fungicides, are very unstable, and are
transformed in acid soils to the divalent ion (WHo'l976).
The extent of inorganic mercury adsorption is related directly to
the organic and clay content in soils. Versar (1978b) reports that
mercury has an affinity for the sulfhydrylgroups in organic matter, and
montmorillonite and illite clays. Soil horizon profiles indicate that
soils rich in clay and organic matter do not permit significant trans-
location of mercury. At low pH levels, however, some of these species
are solubilized and translocated.
v. Methylation
Biological; Mercury may undergo biological methylation under both
aerobic and anaerobic conditions in water and soil solution. In an-
aerobic, mildly reducing systems, mercury, as the divalent ion, reacts
with methylated vitamin B-12 (CH3 B-12) to form methyl and dimethyl-
mercury. Microbes in the environment that are dependent upon CH3 B-12
are capable of methylating inorganic divalent mercury. It is important
to note that the form of mercury must be the divalent inorganic species
for methylation to occur. Most mercury compounds introduced by anthro-
pogenic releases into the environment are eventually transformed to
Hg (II). Some examples are elemental mercury, phenyl mercuries, alkyl
mercuries, and alkoxy-alkyl mercury (NRC 1977). Excluded from this
list is HgS, which due to its extremely low solubility and the prevailing
anaerobic conditions, is not available for methylation (Lexmond et al.
1976).
64
-------
TABLE 10. PERCENTAGE OF >ERCURY EVOLVED FROM SOIL IN 144 HOURS
% Removed in Type of Soil
Hg
Hgd2
HgO
HgS
Sand
33.8
19.6
0.2
Loam
32.9
15.0
0.3
Clay
14.2
6.4
0.2
Source: Rogers (1978).
65
-------
Aerobic and facultative anaerobic bacterial species recognized as
being capable of methylating mercury are Klebsiella pneumoniae, Escherichia
coli, and Clostridium cochlearum. The amount of mono- versus dimethyl
mercury formed is a function of initial mercury concentrations, and the
pH of the system (D'ltri 1972). Low initial concentrations of Hg (II)
and neutral to alkaline waters favor formation of dimethyl mercury.
The low water solubility and the high vapor pressure of this species
result in rapid volatilization from the system. Monomethyl mercury
may be returned to the system in acid rains, although methylmercury has
not been detected in rain (WHO 1976).
Higher initial concentrations of mercury and pH levels less than
neutral, promote CHsHg* formation. A slight degree of acidity pushes
the mono-di-methlymercury equilibrium toward the formation of CHoRe4"
(D'ltri 1972).
Berdicevsky _e_t al. (1979) researched the formation of methylmercury
in sterile and unsterile marine sediments under both aerobic and anaerobic
conditions. Mercuric chloride was used as the initial mercury species.
No methylmercury was produced in the sterile medium. Methylmercury
production was also shown under aerobic conditions. The anaerobic cul-
tures produced methylmercury in amounts that varied inversely with the
initial concentration and decreased over time, unlike the trend noted
for aerobes. Losses of methylmercury were attributed to evaporation
and adsorption onto the experimental glassware. Table 11 shows pro-
duction of methylmercury as a function of initial concentration and
time.
Abiological Methylation; Rogers (1978) found that mercury could
be methylated in sterile soils. He isolated a substance as something
belonging to the low molecular weight fraction of soil organic matter,
which he concluded promoted methylation. The conversion rate from
inorganic to methylmercury was directly proportional to increasing
temperature, decreasing pH (at pH levels greater than 5), and increasing
concentration of mercury ion. Of the clay, loam, and sand soils tested,
clay had the greatest ability to methylate mercury, followed by loam
and then sand.
Demethylation; Methylmercury may be decomposed abiotically or with
the aid of microbes. Chemical demethylation results from photolytic
decomposition of methylmercury-sulfur complexes, which are the principal
form of environmentally available methlymercury species. The reaction
sequence is shown below CLexmond 1976):
CH3HgS uv CH3- + HgS
light *"
CH3HgSR CH' + SR' + Hg(0)
66
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TABLE 11. METHYLMERCURY FORMATION OVER TIME AND RELATIONSHIP WITH
CONCENTRATIONS OF MERCURY IN ANAEROBIC CULTURES
Starting Methylmercury Levels (as Hg)
Total Hg
ug/ml
0.1
3.1
10.0
30.1
ug
77.3
n.d
n. d
n.d
Dav 2
%Total Hg
77.3
n.d
n. d
n.d
Dav
ug %
98.0
97.9
23.3
20.4
5
Total Hg
98.0
3.1
0.2
0.1
ug
5.2
2.6
2.4
2.4
Day 12
% Total Hg
5.2
.08
.02
.01
In.d. =* not detected
Source: Berdicevsky et al. (1979)
67
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Methylmercury is also chemically decomposed when the mono-dimethyl-
mercury equilibrium is shifted toward production of dimethylmercury
under some conditions such as in slightly alkaline waters.
In both aerobic and anaerobic waters microbial demethylation is
accomplished by several bacterial species capable of forming elemental
mercury and methane from methylmercury. Shariat et al._ (1979) found
that 21 of 40 bacterial strains isolated from soil, sewage, and sedi-
ments were able to demethylate mercury. The organisms are believed to
have developed a resistance to methlymercury poisoning by evolving
enzymes capable of hydrolyzing the methyl-carbon bond, and reducing
the Hg (II) produced to Hg(0) (NRC 1977). The high volatility of Hg(0)
permits escape of mercury from the soil or water system. The rate of
demethylation is reported to be several orders of magnitude slower than
methylation. In the presence of demethylating organisms, however,
steady-state concentration of CH3Hg+ is lower than it would be other-
wise (NRC 1977).
Summary Statement; The concentration and speciation of soluble
mercury in the water column is dependent upon the pH and redox potential
of the water and the nature of complexing ligands. In natural aerated
waters, Hg (II) is complexed with organic ligands, chlorides and hydrox-
ides. In reduced environments, mercury will be present as mercurous
oxide and HgS.
Mercury adsorbs onto iron and manganese oxides, clays, and organic
matter in the sediments. Its tendency to adsorb exceeds that of all
other divalent metals, with the exception of copper. Suspended solids
concentrate mercury; this concentration may exceed that of the sediments
due to a greater number of adsorption sites on suspended sediment. How-
ever, the amount of suspended sediments is usually small enough that the
major quantity of mercury in water bodies is found in the sediments and
water column as the dissolved solid. Methylation of mercury occurs in
slightly reduced, anaerobic and to a lesser extent, aerobic sediments.
Biological methylation proceeds at a rate faster than biological de-
methylation. Acidic waters favor the formation of nionomethyl mercury,
while neutral to alkaline waters favor production of water-insoluble
dimethylmercury,
In soils, mercury is adsorbed above a pH of 5; organic ligands, especially
humic acid and clays enhance adsorption. Compared with other metals (ex-
cepting copper), mercury demonstrates the greatest tendency to adsorb.
In acid environments, mercury will be available in the soil solution,
although to a lesser extent than other metals.
68
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b. Atmospheric Transport
i. Overview
y Pf OOUCH
Ch'Or-"'*»ii F(*nti
trie Srmuiont
Anthropogenic releases of mercury to the atmosphere result from a
number of point and dispersive sources. The primary point source
emissions are due to thermal processes that release mercury as the
elemental vapor or sub-micron aerosol (<4.5 urn). Principal thermal
sources are solid waste and sludge incineration, chlor-alkali production
plants, fossil-fueled power plants, and metal smelters (such as copper
smelters). Dispersive sources include such processes as volatilization
of paints containing and outgassing from the earth (see Chapter III).
Thermal processes release mercury as a vapor or as a sub-micron
aerosol. The elemental mercury vapor tends to be concentrated and
adsorbed onto particulate matter in the atmosphere. This sorptive
process is often cited as the reason for 100% removal of mercury by
rainfall via washout of particulates. As discussed above, only about
5% of the total mercury resides on the particulate fraction in the
atmosphere. Versar (1979) cites a mean residence time in air of 4-11
days.
Deposition of mercury in urban areas was not specifically documented
in the literature available, although mercury levels in urban runoff
69
-------
suggest that it is occurring. Particulate washout will deposit mercury
trom local point sources on pavement, where it will be transported to a
POTW or local surface waters. The behavior of mercury in surface waters
will be similar to that detailed in the general chemical fate section.
The available literature also did not document incidences of atmos-
pheric fallout of mercury into surface waters. Due to the tendency of
mercury to vaporize and be widely dispersed, washout and dry fallout
should contribute to mercury concentrations in the oceans. Vaporization
and re-entrainment of aerosols from the water surface will continue the
atmospheric mercury cycle.
ii. Municipal Solid Waste and Sexjage Incineration
Soldano et al. (1975) conducted a survey of airborne mercury emis-
sions from sewage treatment plant incinerators in order to determine the
transport differences of organomercury and elemental mercury. The survey
indicated that the concentration of inorganic mercury [as Hg(II)]
decreased as a function of distance from the source, whereas the concen-
tration of monomethyl mercuric chloride (Cl^HgCl) increased with distance.
The reasons proposed for this observation were (1) that the alkyl mercury
species comprise the major fraction of mercury emanating from the plant,
and (2) that the high volatility of this particular species would allow
for more rapid transport upon release than would the inorganic fraction.
In another study concerning municipal solid waste incinerators, Lav
and Gordon (1979) analyzed the combustible and non-combustible portions
of the waste to ascertain which fraction contributed significant metal
releases to the atmosphere. The combustible portion of solid waste was
thought to contain most of the mercury. Actual measurements were not
reported for mercury, as they were for other metals.. Negligibly low
quantities of mercury were thought to be in the flyash and fine bottom
ash remains of the incinerated waste; no mercury was; accounted for by
the non-combustible fraction of the waste.
iii. Chlor-Alkali Plants
Airborne emissions of mercury from chlor-alkali plants have been
studied extensively in Sweden and Canada. Pollution control devices have
curtailed mercury emissions to the air by more than 90% (Flewelling 1971).
The fallout pattern of these emissions has been studied as reflected in
concentrations of mercury in moss (Wallin 1976) and snow (Jernelov and
Wallin 1973). Figure 11 illustrates the decrease in mercury concentra-
tions in moss as a function of distance from a chlor-alkali plant. The
same trend was observed in snow. The greatest concentrations of mercury
are seen within 1 km of the plant, as a result of wet and dry deposition
and sedimentation. The quantity of mercury accumulated by the moss was
only 20% of that reported for snow. Reasons postulated for these
observations are (1) that mercury fallout is a temperature-dependent
70
-------
Hg
ng/g
Plant 1
2000
1500-
1000
500
0
Source: Wallin (1976)
10
15
km
FIGURE 11 CONCENTRATION OF MERCURY IN MOSS
SAMPLES AS A FUNCTION OF THE DIS-
TANCE FROM A CHLOR-ALKALI PLANT
IN SWEDEN
71
-------
process and proceeds more rapidly in cold weather, and (2) concentrations
reported for moss are complicated by tissue decomposition, absorption
efficiency of the moss, and direct water losses to the ground through the
moss mat. However, the important conclusions of both of these studies are
that the highest concentrations of mercury are found close to the chlor-
alkali plant emission stack, but surprisingly that this deposition repre-
sents only a small percentage of the total plant emissions. Dilution to
background concentrations in fact appears to be the fate of most of the
airborne mercury.
iv. Coal and Other Fossil Fuel Combustion
Mercury emissions from coal combustion are significant, not because
of concentrations of mercury existing in coal, but because of the enor-
mous quantities of coal used to generate power. Coal combustion is esti-
mated to contribute about 93 MT of mercury to the atmosphere each year,
with other fossil fuels releasing 84 MT of mercury (see Chapter III).
Billings and Matson (1972) studied a series of coal samples contain-
ing an average of 0.3 mg/kg Hg, and found that approximately 95% of the
mercury is released with the flue gas. The fate of the mercury emissions
from and deposition near a coal-fired power plant was studied at Four
Corners, New Mexico, and the findings differ from concentrations normally
reported for mercury in soil close to a combustion point source (Crockett
and Kinnison 1979). The mean mercury concentrations in soil (ng/g)
samples obtained at sites around the plant in concentric circles with
radii measuring 1.0, 2.9, 6.8, 15 and 30 km, were 22, 16, 14, 15, 13,
and 16 ng/g, respectively. Thus, it would appear that mercury levels
above background are found at distances of 1 km or less from the plant.
v. Metallurgical Plants
Zinc and copper deposits can contain about 100-300 mg/kg Hg (Habashi
1978), which is released during smelting as a vapor associated with SC>2
gas. Prior to the implementation of pollution controls, the mercury was
released directly to the atmosphere. Since then, sulfur dioxide scrub-
bers concentrate approximately one-half of those mercury releases
(Habashi 1978).
vi. House Paints
Mercury is present in water-based house paints as a bactericide and
a fungicide. It can apparently volatize quite rapidly from painted
surfaces. On the tenth day following application to an indoor surface,
the indoor concentration was 1000 times the exterior ambient air level
of mercury. Elemental mercury and phenyl mercuric acetate, with small
amounts of methyl mercuric chloride were detected (U.S. EPA 1976).
vii. Summary Statement
Mercury enters the atmosphere from point source combustion processes
and from widely dispersed sources from which vaporization occurs. Mer-
cury is sorbed onto sub-micron particulates, which have a residence
72
-------
time in the atmosphere that is subject to meteorological conditions
such as washout and fallout. Localized pollution of soils, pavements
and surface waters results from point source emissions. Mercury as the
vapor will be longer lived in the atmosphere, eventually contributing
to background concentrations.
c. Solid Wastes and Agricultural Applications
i. Overview
Pathway 2
Air
Solid Wastes,
Coal Piles &
Open Mines
Agricultural
Application
\
Surface
Water ,
Sediment
f*
\
Ocean
Groundwater
Most of the mercury-containing solid wastes arise from mineral ore
processing and coal mining or from municipal or hazardous wastes. Solid
waste from mining operations results from the overburden of surface
mining, and the low-grade portions of mineral-ore deposits. The tailings,
which contain highly concentrated minerals, are produced as a final waste
product of mineral concentration operations (Martin and Mills 1976).
Mercury is also released to land during landfilling and lagooning of
industrial and municipal sludges; flyash disposal; and the abondonment
of mercury-containing products such as batteries, scientific instrumen-
tation, and paint. Another major source of mercury released to land is
the application of mercury for agricultural purposes.
The oceans or lakes that are fed by streams or groundwater from mined
areas, solid and hazardous waste sites, or agricultural areas, may serve
as the ultimate sinks for mercury released from solid waste. However,
these sites are probably themselves the ultimate sink for mercury, in
the form of the insoluble sulfide or sorbed tightly onto clay minerals
and organic matter.
73
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ii. Mine Tailings and Coal Piles
Mercury was mined in both surface and underground mines, which in
the United States exist in the West, primarily in Nevada and California.
The principal ore of mercury is cinnabar, HgS, which is very insoluble
and stable. The amount of mercury lost during mining and primary pro-
duction is reportedly minimal. The tailings produced contain, on the
average, 5 mg/kg of mercury (Van Horn 1975). The tailings and waste
produced since 1850 are estimated to be total 60 million MT in the U.S.
(Martin and Mills 1976). Mercury is also associated with other sulfide-
rich ores such as copper, zinc, and coal. Localized leaching of mercury
from these mineral ores and coal tailings does not appear to present
a problem, as will be discussed below (Van Horn 1975).
iii. Acid-Mine Discharge
Leachate from controlled coal piles and mine tailings contains
low concentrations of mercury. Acid mine drainage from abandoned mines
solubilizes metals and aids in their transport. Acid mine drainage
results from the exposure of fine particulates to air, which oxidizes
the metal sulfides (e.g., HgS) to sulfuric acid. The impact of acid
mine drainage and extent of metal transport within streams depend upon
the buffering capacity (alkalinity) of the stream. Letterman and Mitsch
(1978) studied the impact of acid mine drainage emanating from several
abandoned coal mines in Pennsylvania. One discharge tested was typical
of concentrated acid mine discharge (pH 2.6, alkalinity as CaC03 = 0
mg/1); another was closer to neutral (ph 6.0) and buffered by contact
with the limestone strata underneath the mine. In both cases the mer-
cury concentration in the leachate was less than 0.0003 mg/1. The
low concentrations of mercury may be due to (1) a low concentration of
mercury originally present in the coal (.which is probable since it is
an Eastern coal), (2) adsorption of the mercury within the coal pile,
or (3) volatilization.
Martin and Mills (1976) in their studies of the problems associated
with abandoned mines did not feel that mercury presented a problem. In
cases where high levels of mercury in the sediment were reported, they
were thought to be due to discharges occurring when the mine was active.
The principal fate of mercury discharged to local streams with acid
mine drainage is probably adsorption to suspended particulates in the
water column, with subsequent deposition in the stream bed, or quiescent
lake system. Methylation is a probable occurrence over time, releasing
mercury for biotic uptake and transport via volatilization.
iv. Solid Waste Disposal Sites;
Mercury losses from municipal waste are principally released to
the land. The main contributors to mercury in solid waste are batteries,
control instruments, lamps, and tubes and switches (Van Horn 1975).
Losses of mercury via leachate from properly designed landfills have not
been documented (Van Horn 1975).
74
-------
Roulier (1975) reports on two studies of metal transport with
landfill leachate. In the first study, leachate collected under an-
aerobic conditions from municipal refuse was passed through columns of
well-characterized soils. The concentration of mercury in the leachate
was below the detection limit of 0.0005 mg/1.
The second study was a more realistic simulation of a properly-
designed landfill. Leachate was collected anaerobically from two
operating landfills and passed through columns packed with clay and
quartz sand at a rate of 2 pore volumes per month. The initial mer-
cury concentrations in the landfill leachates were 0.2 mg/1 and 0.0008
mg/1. The results demonstrated that 96.8% of the mercury was atten-
uated by the column. The principal mechanism responsible for the
attenuation was attributed to precipitation (the pH was neutral to
alkaline). The researchers of this study concluded that clay-lined
landfills will provide suitable preventive measures against metal
transport by landfill leachate (Roulier 1975).
The conclusion to be drawn from both of these studies is that
mercury migration to groundwater is probable in poorly operated land-
fill sites. Van Horn (1975) found that over one-half of the landfill
sites operating at the time of this study did not comply with regula-
tory requirements. A properly operated site, on the other hand, should
not release mercury to the environment.
v. Flyash Disposal Ponds
Only minimal mercury is translocated from flyash disposal ponds
(Theis et al. 1978). Groundwater from wells surrounding the ponds
consistently contained mercury levels below 0.2 ug/1.
vi. Agricultural Applications
Mercury has been applied to agricultural fields as a fungicide seed
dressing, insecticidal foliar spray, and as a minor constituent of fert-
ilizer and sludge used for the purposes of soil amendment. Alkyl mer-
curials are no longer used for fungicidal or insecticidal uses due to
the problems associated with methylmercury. Phenyl mercurial compounds
are now used most frequently. Mercury in fertilizer results from, reuse
of the sulphuric acid originally used in S0£ scrubbers, which concentrate
uercury vapor along with the S02 sas (Habashi 1978).
Translocation of mercury applied in agriculture within the soil
profile has been cited in a literature review by Krenkel (1973). In
soil profiles of rice paddies and orchard fields, the mercury concen-
tration profile was found to be a direct function of the clay fraction
and type in the soil. One soil, containing insignificant mercury con-
centrations, despite 10 years of continual application, was found to be
underlaid by a gravelly sand, which permitted loss of mercury by leaching.
A soil containing higher mercury concentrations was found to contain
a large fraction of montmorillonite clay. In subsequent studies of
75
-------
the adsorption tendencies of phenyl mercuric acetate (PMA) and HgCl?,
adsorption on clays decreased according to the type of clay and in the
following order: montmorillonite > allophane > kaolinite. Adsorption
was greatest at pH 6. Van Horn (1975) states that PMA and other phenyl
mercurials are not immobilized in the surface soil layer, and are easily
leachable. The PMA remaining in the soil (approximately 50% of that
applied) is also subject to loss via vaporization. Mercury is also
subject to loss from the soil surface by erosion and runoff. Mercury
in this case will be transported as an adsorbed species to surface
waters.
Little information was available concerning mercury contamination
through sludge and fertilizer application to agricultural sites. One
can assume that mercury in the sludge will be in a form less available
for biological uptake and leaching. Accumulation in the soil surface
is likely for mercury applied in this form.
vii. Summary Statement
Solid wastes, coal piles, and tailings are point sources of mercury
disposed of on land. Of these sources, mercury exposed as a result of
mining practices is potentially subject to greater translocation in the
environment due to the acid nature of the leachate, but there is no
evidence of such movement occurring.
Studies of municipal waste landfills have revealed mercury concen-
trations in leachate ranging from 0.0005 mg/1 to .2 mg/1. Mercury is
quickly attenuated by the soil, provided a high clay content exists and
the pH is alkaline. No data were found regarding groundwater contamina-
tion, though such contamination should not occur in a properly operated
landfill disposal site.
Mercury used in agricultural settings can be translocated through
leaching or volatilization. The importance of the former pathway is
dependent upon the clay content of the soil. Erosion and consequent
runoff are likely to be important pathways for mercury used for agricul-
tural purposes.
76
-------
d. Aqueous Industrial Discharge
i. Sources and Treatment
Pathway 3
Effluent
f
Aqueous
Discharge
Dental Preparations
Paint Applications
Chlor-alkali Plants
Hazardous
Waste/Dump
Sites
Pathway 4
Pathway 3, shown above, considers the fate of mercury discharged
with industrial wastewater effluents. The industries and uses that
contribute to these discharges are dental preparations, paint appli-
cations, and ase of electrical apparatus. The effluents from these
sources are discharged with or without treatment into natural waters or
municipal wastewater treatment systems. Waters discharged to the latter
are treated in Pathway 4-
The quantity of mercury discharged from chlor-alkali plants and
paper and pulp industries has been slight since regulations were im-
posed on these industries in 1970. No mercurials have been used in
Canada's paper and pulp industry since 1970 (Paavila 1971), and the
abatement measures have reduced mercury emissions from Canada's chlor-
alkali plants by 99% (Flewelling 1971). Mercury releases from these
industries have also been reduced in the U.S.
ii. Distribution in Surface Waters
The fate of mercury discharged as an industrial process effluent
was not well described in the available literature. Krenkel (1973)
concluded that mercury is concentrated in the sediment below outfalls
from chlor-alkali plants.
77
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Cooke and Beitel (1971) have performed a mass balance on mercury
entering the Great Lakes, partially from chlor-alkali plants. According
to their calculations, if mercury released to the Great Lakes from chlor-
alkali plants were eliminated after 1970, then the mercury entering
the watershed per year would be reduced from 2.2 million Ib per
year to 1.5 million Ib. They attribute some of the remaining mer-
cury discharges to urban runoff. Other sources considered were losses
from ore reduction, fuel consumption, laboratory use, agriculture, dental
uses, and disposal of manufactured products. Figure 12 illustrates
the predicted concentrations of dissolved mercury in the Great Lakes
as a result of mercury discharges from chlor-alkali plants.
Jackson (1979) analyzed the mercury concentrations in the sedi-
ments of two lakes, the first of which is fed by a river receiving
paper and pulp and chlor-alkali plant discharges, and the second of
which is fed by the outflow of the first lake. The ratio of mercury to
organic carbon for the first lake was significantly greater than that
for the second lake.
Similar ratios for four other metals did not vary between the two
lakes, a finding suggesting that concentrations of these metals resulted
from normal weathering and erosion of the x^atershed. In the contrast,
the results for mercury clearly implied that the first lake was acting
as a sink for mercury introduced into the river upstream. Mercury
reaching the sediment would be subject to methylation as described
previously.
iii. Sludge Disposal
The sludge generated by industrial effluent treatment is normally
disposed of in a solid or hazardous waste dump, or a settling pond.
A properly designed hazardous waste dump should prevent further trans-
location of mercury due to leaching. At some sites, the leachate is
collected and sent to a POTW (with or without further treatment).
Groundwater contamination is possible in a poorly operated landfill
or settling pond. The speed with which mercury is translocated in
this pathway is fairly fast in soils of low organic matter and clay.
The fate of mercury in solid waste sites was reviewed in Pathway 2.
iv. Ultimate Sinks
The major sinks for mercury associated with treated industrial
effluents are, in the short term, hazardous waste dumps, settling
ponds, or sites used for the disposal of sludge generated by POTWs.
The long-term sinks, as discussed earlier, are the oceans and lake
sediments.
v. Summary Statement
A major fraction of the mercury in aqueous industrial discharges
appears to be concentrated in the sediments in the vicinity of the
78
-------
l.Or
8-
• PREDICTED
CURVE
\"NO CHANGE"
z
g •
H ;
< 5-
rf*
z
01
Z 4'
o
8
p- ;
MEASURED
VALUE i
\
\
L
V
ASSUMED S
START X
\
\
\
\
^
/•
j
'''I
^-"' /
' /
/
P
/•
ai
' /
-2r
POIiNT
PREDICTED
CURVE
"CHLORALKALI
MERCURY"
REMOVED
1919 1944 1969 1994 2Ci9
YEAR
Source: Cookeefa/. (1971).
FIGURE 12 PREDICTED VALUES OF THE AVERAGE
CONCENTRATION OF MERCURY DISSOLVED
IN THE LOWER GREAT LAKES
79
-------
source. It is distributed principally with the organic, sulfide, and
clay components of the sediments, which are subject to methylation.
Disposal of sludge generated by waste treatment in a properly-operated
landfill should prevent further translocation of mercury.
e.
POTW
i.
Treatment Schemes
Pathway 4
Effluent
POTW
Inflow
Primary
Treatment
t
Biological
-Treatment .
*
Surface
Waters
Ocean
Incineration
Land Disposal^
Ocean Disposal-
x
Sludge
Pathway 4, shown above, describes the fate of mercury in waste-
waters that are introduced into a Publicly-Owned Treatment Works (POTW).
The inflow to the POTW may consist of combinations of industrial and
commercial effluents, domestic wastes, and runoff. Though the nature
of the influent is consequently quite varied, typical concentrations
of mercury in the influent will be about .0004 mg/1 (Levins et_ al.
1979).
The degree to which mercury is removed from the raw wastewaters,
and thus the concentration of mercury in the discharged wastewaters and
sludges, depends on the type of treatment involved. Levins et al.
(1979) report that average removal efficiencies of treatment processes
are 37.2% for primary treatment and 58.4% for secondary. Oliver and
Cosgrove (1974) report mercury concentrations in the effluent following
primary and secondary treatment as follows:
Treatment Stage
Raw Sewage
Primary Effluent
Secondarv Effluent
Hg Concentration (mg/1)
Total Dissolved
.007 .0006
.003 .00003
.001 .00005
80
-------
The efficiency of biological treatment systems in removing large
slugs of mercury has been studied by Neufeld and Hermann (1975) for
aerobic sludge digesters, and by Lingle and Hermann (1975) for anaerobic
systems. In the latter study, phenyl mercuric chloride and mercuric
chloride were introduced into a simulation of an anaerobic sludge di-
gestor at concentrations of up to 2,200 mg Hg/1. For both the mercury
species and all concentrations, about 96% of the mercury was partitioned
into the sludge solids, with 4% remaining with the sludge supernatant,
on suspended solids greater than 0.45 urn. The authors also determined
that the largest concentration of mercury (2,200 mg/1) inhibited diges-
tion, while 1,560 mg/1 did not. Analysis for methlymercury produced
during digestion revealed negative results.
The study by Neufeld and Hermann (1975) of aerobic sludge digesters
determined that mercury (added in concentrations of up to 1000 mg/1)
reached almost complete equilibrium and was nearly all removed (95%)
by the biological floe within 3 hours. Toxicity studies revealed that
aerobic treatment is inhibited temporarily at concentrations equal to or
greater than 2.5-5.0 mg/1 Hg-2+ (Ghosh and Zugger 1973). The biological
floe becomes acclimated to larger doses within a few hours.
Conclusions contrary to those indicated by the preceding two studies
are seen in the work of Mytelka et al. (1973) on treatment plant effi-
ciencies as obtained from a survey of POTWs in New Jersey, New York and
Connecticut. In this study, 90% of the plants surveyed had influent
mercury concentrations of 6.0052 mg/1 entering an aerobic digestor, and
0.0050 mg/1 exiting in the effluent. This implies that very little
of the mercury is partitioned in the sludge portion, although initial
concentrations were quite low. The authors use these findings as support
for recommendating mandated pre-treatment of waste effluents by indus-
tries prior to discharge into the sewers.
ii. Sludge Disposal
Sludge disposed of on land may go to a sanitary landfill, or be
spread for the purpose of amending the soil. The form of mercury in
sludge has not been revealed in this literature search, but it is
known that the metal remains bound to the organic matter of the sludge
and is converted into an insoluble state (Oliver and Cosgrove 1974).
Thus, disposal of the sludge in sanitary landfill sites should not
create major problems since the potential for leaching into the ground-
water is minimized by the form of mercury in sludge.
Sludge that is incinerated will contribute close to 100% of its
mercury content to the atmosphere. More detailed information can be
found in the description of atmospheric emissions (Pathway 1).
81
-------
iii. Surface Water Discharge
The behavior of mercury discharged with POTW effluents into local
waters will be similar to that described for aqueous pathways (Pathway
•j/ •
Morel et al. (1975) used a chemical equilibrium model to trace the
fate of metals present in sewage upon discharge in the ocean. The sew-
age used in this model was in the reduced state, so mercury was present
as the sulfide. The model predicts that dilution and oxidation will
solubilize the sulfide to the mercuric ion. This transformation will
occur some distance from the outfall and mercury will reach concentra-
tions similar to background levels.
The validity of this model is supported by the work of Eganhouse
.et _al. (1978) who studied the distribution and speciation of mercury
from a sewage outfall in Palos Verdes. They found that mercury near
the diffusers was inorganic in nature, probably the sulfide, whereas
moving away from the outfall, increasing concentrations of mercury were
associated with organics. Schell and Nevissi (1977) and Whaling et al.
(1977) found that the intertidal organisms — Ulva fuscus, mussels, and
clams — tended to reveal increased uptake near the outfall, but the
results were within sample variability. The second study of North
Carolina estuaries showed slight mercury elevations between control and
discharge estuaries in the roots of Spartina alterniflora (0.13-0.14
mg/kg). Mercury concentrations were increased in snails toward the
outfall, while they were not in the small sample of oysters analyzed.
The authors concluded that the current practices for effluent disposal
into the estuaries of North Carolina were acceptable to the ecology of
those systems.
iv. Summary Statement
The concentration of mercury in POTW influent averages about 0.4
ug/1. The effectiveness of its removal appears to be very high for
biological treatment processes, in which mercury is partitioned into the
sludge portion of the waste. Sludge spread for the purposes of soil
amendment is not likely to enhance the solubility or mobility of mer-
cury. In municipal landfills, the concentration of mercury in leachate
ranged from 0.0005 mg/1 to 0.2 mg/1. Mercury is expected to be quickly
adsorbed in soils containing clays and organic matter. Mercury in aqueous
effluents is principally sorbed onto suspended solids. Discharges to
marine systems can result in solubilization of mercury due to oxidation and
dilution. In fresh waters, mercury is expected to be partitioned into the
sediments, or be associated with dissolved solids in the water column.
C. BIOLOGICAL FATE
1. Introduction
Mercury is commonly found in the tissues of biota, especially in
aquatic species. The following section describes the fate of mercury
82
-------
in biota and discusses:
(1) The significance of the form of mercury, environmental
parameters, and route of exposure on rate of uptake;
(2) Half-lives and bioconcentration factors in biota;
(3) Biomagnification in trophic levels; and
(4) Bioaccumulation in terrestrial ecosystems.
2. Uptake of Mercury
Most mercury found in fish tissue is in the form of methylmercury
(Uthe et al._ 1973, Hildebrand et al. 1976, Phillips and Russo 1978).
Although in vitro liver preparations have been reported tc methylate
inorganic mercury (Matsumara et al. 1975), most researchers attribute
methylmercury in tissues to direct uptake of that form of the metal
(Phillips and Russo 1978). Methylmercury is rarely detected in the
water column even directly above methylating sediments, an observation
that is attributed to immediate biotic uptake of the newly formed com-
pound (WHO, 1976). DeFreitas et al. (1974) found in fish'that the
methyl form of mercury was taken up 100 times as rapidly as the in-
organic form from water and five times as rapidly from food. Other
differences between the behavior of the two forms are discussed below.
Methylmercury is absorbed very efficiently through biological
membranes. Gut absorption efficiency in fish is 90% for methylmercury
and 15% for the inorganic form (Norstrom et^ al. 1976). The methyl
form is excreted more slowly (Miettinen et_ al.. 1976). Once inside the
body, most of the methylmercury quickly becomes bound to sulfhydryl
groups in protein in a non-diffusible form (WHO, 1976). Figure 13
schematically describes the pathway of mercury in a finfish. Within
muscle tissue, mercury has a greater affinity for myofibrin and sacro-
plasmic protein than for non-protein nitrogenous compounds and insol-
uble muscle residues (Arima and Umemoto 1976).
The variables affecting the rate of mercury uptake include tempera-
ture, pH, and mercury concentration in water. Findings on such effects
have been reported for several species and are assumed, at this time,
to be applicable to fish in general. The rate of uptake conforms to
zero-order kinetics during the initial uptake phase, with a linear relation-
ship to water temperature (Hartung 1976). Cember ^t al._ (1978) found
a 0.066 exponential increase in rate of uptake per degree increase in
temperature between 9°C and 33°C in bluegills. This is attributable
to the increased pumping of water over the gills as a function of an
increase in metabolic rate with temperature rise (Burkett 1974). Burkett
(1974) found the temperature dependence to drop off above a temperature
of^21"C, an observation suggesting interference by the substance at that
point reducing efficiency of membrane transfer. Mercury uptake (of
mercuric chloride) increased as pH decreased, especially below pH 7.0
83
-------
Gills
Environment
V
Intestinal
Track
Blood Stream
Hg (inorganic)
Liver
Spleen
•Excretion
Muscle -SH (retained)
MeHg
Source: Windom era/. (1976)
FIGURE 13 APPARENT MERCURY PATHWAYS IN FINFISH
84
-------
(Tsai _et al_._ 1975). The concentration of mercury in water was import-
ant to uptake kinetics in fathead minnows (Olson'et_ al. 1975) and rain-
bow trout (McKim_et _al. 1976). Greater bioconcentration factors were
observed at the higher water concentrations.
3. Bioconcentration
Bioconcentration factors (3CF) for mercury in biota commonly
range from two to five orders of magnitude over water levels. Table 12
presents examples of SCFs reported for laboratory and field studies
in aquatic systems. Laboratory-measured BCFs are commonly greater
than values measured in natural systems (Burkett 1974). Invertebrates
tend to exhibit the highest BCFs of aquatic species, on the order of
106 (see Battelle 1977).
In a field study in the Ottawa River Project (ORPG 1979), concen-
trations in various species ranged from three to four orders of magni-
tude above water conconcentrations (see Table 13). The organic fraction
of the total mercury content varied by species, ranging from 0.3 to 0.85
and highest in fish. Due to differences in absorption efficiency in the
gut (90% for methylmercury, 15% for inorganic) (Norstrom et al.'1976),
higher organic concentrations were expected in upper trophic level
species, which would be exposed to potentially higher levels of methyl-
mercury in their prey. Lower trophic level organisms would be exposed
to low levels in water and sediment.
Mercury (both total and methyl) tends to be concentrated in the
muscle, heart, liver, and kidneys of fish, based on observations on
five species of fish (Bishop and Neary 1977). Considerably lower con-
centrations were measured in skin, scales, and bone. A negative cor-
relation was found between mercury levels and fat content in bottom
feeders and no observable correlation was found for other species.
Fromm (1977), however, found the gill in rainbow trout to be a more
important site of accumulation than the gastro-intestinal tract for
both methyl and inorganic mercury. The inorganic form tended to be
bound to the gill mucus, however, and was less likely to enter the body.
Nearly 50% of mercuric chloride in two species of fish was found to be
associated with external mucus (Tsai et al. 1975).
4. Route of Exposure
The routes of exposure of aquatic organisms to mercury have been
a matter of some controversy. As discussed above, it is generally
thought that the source of organic mercury in aquatic organisms is due
to the presence of low levels ot that form in the water. However,
ingestion of mercury may also be an important exposure route, in
addition to gill absorption. Table 14 describes these three inter-
related hypotheses.
iThe ratio of the concentration in biota tissue to the concentration in
water.
85
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TABLE 12. BIOCONCENTRATION FACTORS FOR AQUATIC SPECIES
Species
Concentration
in Water (me/1)
Concentration Approxi-
in Biota (mg/kg mate
wet wet) BCF
Marine Plants
Marine Mollusks
Crustaceans
Marine Fish
Freshwater Plants
Freshwater Inverts
Freshwater Fish
Barnacle
Crab1
Oyster
Clam1
Polychaeta
3 x
3 x
3 x
1 x
1 x
1 x
9 x
(sediment
io-5
10'5
10~5
io-4
ID'4
io-4
10~3
II
It
II
II
3
1
5
1
1
1
3
5
7
1
1
x 10"2
x 10°
x 10" 2
x 10
x IO1
x 10"1
x 10'1
x 10"3
x 10"2
x 10"1
x 10"1
io3
io5
io3
IO3
io5
io3
io2
io1
io1
io2
io2
Thompson et al.
Thompson et al.
Thompson et al.
Thompson et al.
Thompson et al.
Thompson et al.
Guthrie et al.
Guthrie _e_t al.
Guthrie ^t al.
Guthrie _ejt al.
Guthrie _et al.
(1972)
(1972)
(1972)
(1972)
(1972)
(1972)
(1979)
(1979)
(1979)
(1979)
(1979)
Rice Fish Eggs
(Oryzias latipes)
2,3
3 x 10
Pike
Pike
3 x 10
-2
6 x 10
3 x 10
0
10 Heisinger and Green
(1975)
3
10 Johnels et al. (1967)
2
10 Hannerz (1968)
Field Study.
y
"Exposed to mercuric chloride.
*T
Japanese species.
86
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TABLE 13. MERCURY DISTRIBUTION IN OTTAWA RIVER ECOSYSTEM
Total Hg Fraction Approximate
Component Cone, ug/1 ug/kg) Organic BCF
Water ~ 0.03
Bed Sediment 41 0.01 10^
Suspended Solids 440 ~0.3 1Q4
Benthic Invertebrates 220 ~0.3 1Q4
i
Higher Plants 100 0.20 1Q4
Fish 180 0.85 104
wet wgt for biota.
Source: Ottawa River Project Group (1979).
87
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TABLE 14. OBSERVATIONS REGARDING ROUTE OF EXPOSURE
OF AQUATIC BIOTA TO MERCURY
• Organic mercury concentrations in water are usually either
extremely low or not detectable.
• Usually >90% of the total mercury content found in fish and
shellfish tissue is in the methyl form (NRC 1978).
Hypothesis 1 - Fish take up inorganic mercury and convert it to the
methyl form in vivo
Supporting Evidence
• Inorganic mercury is accumulated by fish to concentration
factors of 1 to 50 (NRC 1978).
• Evidence of in vitro conversion of inorganic to
me thy liner cury (Matsumara _e_t ajL. 1975).
Counter Evidence
• Fish experimentally exposed only to mercuric ion exhibit
primarily the inorganic form in their tissue (Hannerz
1968, Cox et al. 1975).
• Uptake of methyl form is much more efficient than of
inorganic mercury.
• Evidence of in vivo conversion of methylmercury to
inorganic mercury in fish (Sharpe _et _al. 1977), which
would counteract methylation proceTs.
Hypothesis 2 - Methylmercury in water is the source of the methylmercury
found in fish and is directly taken up through gill
absorption
Supporting Evidence
• Although methylmercury is often non-detectable it is
found to comprise 10-30% of the mercury found in water
(ORPG 1979). In addition, current analytical methods
are not sensitive enough to detect methylmercury at the
concentrations at which it normally occurs.
• Gill uptake of methylmercury is extremely efficient and
rapid and the compound's biological half-life is long;
both factors lead to high bioaccumulation.
88
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TABLE 14. OBSERVATIONS REGARDING ROUTE OF EXPOSURE
OF AQUATIC BIOTA TO MERCURY (Continued)
Counter Evidence
• Methylmercury concentrations in water are often too
low to account for tissue levels.
Hypothesis 3 - Methylmercury is transferred primarily through the
lood chain, entering it via bottom feeders ingesting
contaminated bacteria and invertebrates associated
with bottom sediment
Supporting Evidence
• Methylation of mercury takes place primarily in upper
layer of sediment and methylmercury concentrations there
are relatively high compared with concentrations in other
aquatic compartments.
• Uptake efficiency of methylmercury from food is high, with
an associated 80% efficiency as compared to a 12% efficiency
for gill uptake for some fish (Norstrom e_t _al. 1976).
• Studies show that higher trophic-level species associated
with the water column accumulate more methylmercury from
food (60% of total) than bottom feeders (25% of total),
indicating significance of diet as a mercury source to
species not associated with sediment.
Counter Evidence
• Does not explain extremely high concentrations in low
trophic-level invertebrates not associated with sediment.
• Puts too much emphasis on benthic population as prime
component of total aquatic food chain; doesn't account for
producers such as algae.
39
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Hypothesis 1 is the weakest and, alone, cannot justify the high
methylmercury levels found in fish. Existing laboratory observations
on methylation in higher organisms are limited and do not indicate a
fast conversion rate.
Hypotheses 2 and 3 are more popular in the literature (NRC 1978,
ORPG 1979) and together contribute most significantly to methylmercury
levels in fish. Speculations abound as to which of the two exposure
routes is more significant. In yellow perch, 80% of methylmercury in
food and 12% in water passing over the gills is taken up (Norstrom _et al.
1976). Results of research by various investigators (Terhaar et al.
1977, Suzuki and Hatanaka 1974) conclude that ingestion in fish is the
more significant uptake route.
On the other hand, other researchers (Fagerstrom and Asell 1976)
claim that uptake from water is more significant. These authors, however,
assumed that northern pike assimilated 15% methylmercury in the diet, and
100% passing over respiratory surfaces. Phillips and Buhler (1978) found
that rainbow trout assimilated 10-12% of methylmercury passing over the
gills, and northern pike assimilated 15-20% o,f the methylmercury they
ingested (Phillips 1978).
The position of the fish in the food chain may influence the rela-
tive contribution of each pathway; for the upper trophic-level species
such as pike, 60% of its body burden of mercury was attributed to uptake
from food, while for bottom feeders only 25% was believed to result
from ingestion (Jernelov and Lann 1971, Olson et_ suL, 1973), even though
absorption efficiencies were similar in the two species.
Phillips et al. (.1980) have reviewed this point: recently. They
concluded that Norstrom et al. (1976) have correctly assumed a 12%
efficiency for respiratory methylmercury absorption, and that Fagerstrom
and Asell (1973) appropriately assumed a 14% efficiency for dietary
absorption. However, planktivores accumulate most of their methyl-
mercury body burden from water, and piscivores derive methylmercury
from both diet and water.
2
Using a pollutant accumulation model developed by Norstrom et al.
(1976) for uptake of mercury from water and assuming the efficiency" of
20-40% for gill absorption of methlymercury, the following calculations
were made (ORPG 1979). At a methylmercury concentration of 0.004 ug/1
in water, net uptake of 2 ug at one week for a 1-kg fish was estimated.
If a uniform distribution in the body is assumed, this would result in
a tissue concentration at one week of 2.0 ug/kg and a resulting concen-
tration ratio of 5 x 102. This value is compatible with observed values
(see Chapter IV-B). Therefore, accepting the assumptions of this model,
3The model uses pollutant biokinetics and fish energetics taking into
account a growth dependent metabolic rate, a gill uptake pollutant based
on respiratory rate, ingestion uptake based on caloric requirements
(by age class) tines an efficiency of absorption and excretion based
on body weight multiplied by a tissue turnover rate coefficient. See
publication- for more detail.
90
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a very low methylmercury concentration in water can contribute signifi-
cantly to typical tissue concentrations, and this supports Hypothesis
2 above.
The significance of food as a source of methlymercury can be illus-
trated by the following example. Assuming DeFreitas et al.'s (1977)
gut-absorption efficiency of 90% for methylmercury and 15% for inorganic,
the following equation (ORPG 1979) predicts the organic mercury fraction
in food assimilated and, therefore, in the predator's body:
«* 0.90
f* =
where f = organic mercury fraction in food (unassimilated)
f* = organic mercury fraction in predator.
Therefore, assuming retention of the mercury ingested, inverte-
brates could achieve a 30% organic mercury fraction from a 7% organic
fraction in sediment ingested, fish a 72% fraction from ingesting
invertebrates, and higher trophic level fish 94% from ingesting fish
with a 72% fraction. It is important to remember that the total amount
of mercury associated with biota in an aquatic system is small relative
to the mass contained in the water and sediment compartments (ORPG 1979)
Table 15 shows the mercury (total) distribution in the Ottawa River in
the summer of 1973. The mass in biota is six orders of magnitude lower
than the mass in water and eight orders of magnitude lower than in
bottom sediment. Therefore, the amount taken up by biota is small
relative to the total mercury load in the system.
5. Elimination
Elimination of mercury from tissue occurs very slowly. Only after
2 years in a mercury-free pond were mercury levels in yellow
perch (Perca flavescens) and rock bass (Ambloplites rupestris) reduced,
and the loss was attributed to tissue dilution through growth (Laarman
et al. 1976). Freshwater clams (Anodonta grandis) retained methylmer-
cury, but not inorganic forms, after transfer to clean waters (Smith
et al. 1975). A longer retention time for methylmercury has also been
reported in guppies (Kramer and Neidhart 1975).
Table 16 illustrates the variability in biological half-lives
reported for methylmercury in various species. Half-life may vary by
organ as found in the freshwater clam (Unio) (Renzoni and Bacci 1976).
In addition, there is evidence that biological half-lives are tempera-
ture dependent; residence time was shorter at higher temperatures in
oysters and bacteria (Cunningham and Tripp 1975a, Hamdy and Prabhu 1978).
Methylmercury, as suggested earlier, has a longer half-life in biota
than do inorganic or other organic forms of mercury (Miettinen 1976).
91
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TABLE 15. DISTRIBUTION OF MERCURY MASS IN THE OTTAWA RIVER
Instantaneous Mass of Mercury
Component Present in 4.8 km Test Segment
Inorg (g) Org (g)
Water
350
Bed Sediment 13,530 135
Suspended Solids 93 29
2
Biota 10 2>9
Sediments measured to 4 cm deep.
2
Biota include benthic invertebrates,
macrophytes, and fish.
Source: ORPG (1979).
92
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TABLE 16. BIOLOGICAL HALF-LIVES OF METHYLMERCURY
IN VARIOUS SPECIES
Species
Mouse
Monkey/Man
Seal
Fish:
Flounder (Pleuronectes flesus)
Pike (Esox lucius)
Eel (Anguilla vulgaris)
Rainbow Trout
Mussel (Pseudanodonta complanata)
2
Bacteria (Bacillus licheniformis)
Biological Half-Life
(days)
7
70
500
700 -
640 -
910 -
346
100 -
7 -
12001
7801
10301
400
12
Dependent on route of exposure
2
From Hamdy and Prabhu (1977).
Sources: UHO (1976), Miettinen (1975).
93
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6. Siomagnification in the Food Chain
Information on biomagnification of mercury in the upper trophic
levels is conflicting. A major cause of this is that field measurements
or residues in different trophic levels are usually of total mercury
not methylmercury (see Battelle 1977). On the other hand, methylmercury,
being more prevalent and persistent in biota, is more likely to'be trans-
ferred in a food chain. Total mercury measurements indicate no magnifica-
tion in higher trophic levels, while measurements of organic mercury do
indicate bioaccuinulation (ORPG 1979).* The mean level in predators has
been estimated to be 15 times the level in primary consumers (see Battelle
1977). Table 17 shows biomagnification (according to the arithmetic mean)
of mercury (presumably total) in an aquatic food chain. In a model food
chain study, however, Hamdy and Prabhu (1979) found inorganic mercury
accumulation in bacteria and mosquito larvae, but no magnification of
inorganic or organic mercury in guppies and their predators, cichlids.
Species variability in uptake rate and biological half-lives must be
taken into account before biomagnification of mercury can be understood.
Fish-eating birds — such as herons, ducks and gulls — are often
found to have mercury concentrations in their tissues and feathers, both
in North America (Hoffman and Curnow 1973, Vermeer and Armstrong 1972,
Hough and Zabik 1972, Stendell et al. 1976, Dustman jejr al. 1972? Adley
and Brown 1972) and in Scandinavia (Berg jet al. 1966, Sarka et al. 1978,
Holt 1969, Karppanen _et al. 1970). Concentrations have been detected as
high as 23 mg/kg in muscle tissue, 175 mg/kg in liver, and 65 mg/kg in
feathers (see NRC 1978). Residue concentrations in ducks have exceeded
guideline levels at times (see NRC 1978). A more detailed discussion
of mercury accumulations in birds can be found in the NRC's report on
mercury (NRC 1978).
7. Terrestrial Biological Fate
Most terrestrial plants are able to concentrate at least small
amounts of mercury (NRC 1978). The chemical form of mercury and the
soil characteristics affect uptake. Elemental mercury and alkylmercuric
compounds are more readily taken up by plants than the ionic inorganic
form (Dolar _e_t _al. 1971). Alkoxyalkyl- and phenylmercury compounds are
not taken up as efficiently by plants or are more rapidly degraded to
inorganic mercury than is methylmercury; this led to the'elimination of
the latter as a fungicide in Sweden (WHO 1976). In aerated soils, the
rapid accumulation of gaseous mercury results in residues of 0.2-10 mg/kg
(dry weight) in plants grown in soils where gaseous mercury is released
by decaying sulfides. In reducing soils where the mercury'present is
bound to soil constituents, typical plant concentrations are an order of
magnitude lower (Kothny 1973).
'''Increasing concentrations of organic mercury while total mercury remains
the same suggests that concentrations of other forms of mercury'are
decreasing.
94
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TABLE 17. BIOLOGICAL MAGNIFICATION OF MERCURY
IN THE AQUATIC FOOD CHAIN
Concentration (mg/kg)
Organisms
Algae eaters
Zooplankton eaters
•
Omnivores
No.
Samples
39
9
9
Range
0.01-01.8
0.01-0.07
0.04-1.16
Arithmetic
Mean
0.05
0.04
0.45
Detritus eaters
Predators
12
25
0.13-0.59
0.01-5.82
0.54
0.73
More Numerous Organisms
Zooplankton, snails,
mayfly nymphs
Insect larvae, minnows
Insect larvae and adults,
scuds
Worms, clams, insect
larvae
Insect larvae and adults,
frogs
Source: Bligh (1971).
95
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Terrestrial plants accumulate mercury from three sources: from
mercury fungicide treatment of seeds, from foliar application of
phenylmercuric sprays, and from mercury contaminated soils via root
uptake. The first two sources primarily affect food crops, while the
third is the most likely source of mercury residues in wild plants.
Since mercury use as pesticide is extremely limited, it is expected
that the direct contamination of plants, including food crops, would
be limited.
Root uptake of mercury into plants from soil is most important in
the vicininty of mercury sources. Natural background levels in soil
exist on the order of 0.01-1.0 mg/kg, averaging 0.071 mg/kg in the
U.S. (NRC 1978). In mineralized areas soil concentrations may be as
high as 500 mg/kg (NRC 1978). The behavior of mercury on reaching
the soil will affect plant uptake: if volatilized it is most likely
to be absorbed by roots, if converted to mercuric sulfide or an organic
mercury compound, it is less likely to be (NRC 1978).
3ull_et_al. (1977) studied the effects of proximity to a chlor-
alkali plant on the mercury content of topsoils and various organisms.
In the case to topsoils, grass (Festuca rubra), and earthworms (Lumbri-
cus terrestris), mercury residues in specimens collected within 0.5 km
of the plant were 30-40 times higher than specimens taken 10-30 km
away. However, the authors did not clarify, in the case of the grass
(F- rubra), whether the mercury was deposited on the leaf surfaces or
whether the mercury was actually absorbed into the tissues. A range
8-13% of the mercury in the earthworms was in the methylated form; the
organic fraction was not determined for other media. Woodmice (Apodemus
sylvaticus) and bank voles (Clethrionomys glaredus) collected near the
works had significantly greater concentrations of total mercury in the
liver, kidney, brain, and hair than control animals. No greater than
10% of the total mercury in the rodents was in the methyl form. Since
no methylmercury was known to be used in the area, the authors attributed
its presence in biota to methylation of the inorganic form in soil; no
mention was made of possible methylation by the organisms in which the
compounds were measured.
Soils surrounding a mercury mine in Nevada also proved to supply
quantities of mercury for uptake in three plant species (Gay 1976). 'in
samples of Bromus rubens, Spharalcea ambigua, and Boraginaceae sp. col-
lected in November and December (during dormancy), no significant resi- •
dues were detected. When specimens collected during the growing season
(in May) were examined, mercury was found in the range of 2.5-10 ug/kg.
The developing seeds of !L_ rubens in particular concentrated mercury to
relatively high levels. Unfortunately, the author failed to report the
residues found during the winter, and did not analyze the mercury con-
tent of the soil. Consequently, no uptake rates or concentration factors
were determined by this study.
Gardner et_ al. (1978) examined a variety of species for elevated
mercury residues in a salt marsh near a chlor-alkali chemical plant.
Concentrations in the roots of the marsh grass, Spartina alterniflora,
reflected the variations in the mercury content of the "lurrounding sur-
96
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face sediments, suggesting that uptake is related to substrate concen-
trations. With the exception of the specimens from one collection
site, however, other plant tissues did not have high mercury levels.
In hydroponic solutions, various crop species rapidly accumulated
methylmercury hydroxide (MMH) as high as three orders of magnitude
greater than the 0.006 mg/1 MMH in solution (Lipsey 1972). These
conditions would be relatively conducive to uptake compared with up-
take from soil.
In a microcosm study, less than 1% of the total mercury applied to
soil ended up in plants (Huckabee and Blaylock 1974); most remained
bound to soil. Plant concentrations were not available. The insignifi-
cance of plant uptake has been supported by field studies, in which very
low residues where found in plants grown in mercury-treated soils (Matti
et al. 1975, Smart 1968, Blanton et al. 1975). Concentrations of mer-
cury in plants grown in well-aerated soils apparently range from less
than 0.1 mg/kg to 0.7 mg/kg (wet weight), regardless of soil mercury
concentration (see NRC 1978).
D. Summary
1. Monitoring Data
Mercury has been detected in all components of the environment,
including water, sediment, rocks and soils, the atmosphere, and ter-
restrial and aquatic biota. Elevated levels often result from anthro-
pogenic sources, and occasionally from natural sources.
Mercury levels in uncontaminated water are generally low (.04-
0.3 ug/1) and are similar for freshwater and saltwater. Values of up
to about 20 ug/1 mercury have been reported for water in contaminated
areas. It is likely that 10-20% of mercury in water is in the form
of methylmercury.
Mercury concentrations in sediment are generally higher than
those in water. Levels range from ~0.05 mg/kg in unpolluted areas to
over 2.0 mg/kg near industrial sources of contamination. Methylmercury
generally represents no more than 1% of the mercury in sediment.
Rocks and uncontaminated soils contain similar levels of mercury.
Values generally range from 0.20 mg/kg-0.15 mg/kg, with concentrations
of up to 250 mg/kg reported for sites near natural mercury deposits.
Atmospheric mercury is primarily a vapor rather than adsorbed on
particulates, and is usually in the elemental form. Background concen-
trations range from 1 ng/m^-5 ng/rn-^ while urban levels vary from 2-60
ng/nH. High values result from sources of contamination such as incin-
erators and power plants. Automobile exhaust may also contribute to
atmospheric mercury pollution.
97
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Many data are available concerning mercury in aquatic biota. Fresh-
water fish usually have slightly higher mercury levels than do marine
fish. Most saltwater organisms contain mercurv levels below 0.3 mcr/kg.
Values for freshwater fish generally range between <0.05 mg/kg and 1.80 mg/kg.
Mercury contamination from anthropogenic sources usually is the cause of
elevated mercury levels in freshwater fish; concentrations in marine
organisms are less likely to be affected.
Terrestrial biota also contain detectable levels of mercury. Trees
and herbaceous growth in unpolluted areas have concentrations ranging
from 0.02 mg/kg to 0.03 mg/kg, with levels up to 1.25 mg/kg in areas con-
taminated by anthropogenic or natural sources of mercury. Levels in
birds and mammals vary depending on such parameters as species, and
geographical region. Feeding habits can also influence mercury accumu-
lation in mammals and birds.
2. Environmental Fate
^Mercury in the water column is concentrated on suspended solids
and in sediments. Methylation of mercury is promoted both biologically
and abiologically in low pH environments, and under slightly reducing
conditions. In the atmosphere, most of the mercury (>90%) occurs as°
a vapor, while the remainder exists adsorbed to sub-micron particulate
matter. Fallout and washout will remove nearly all of the adsorbed
mercury; the vapors are prone to wide dispersal, and eventually con-
tribute to background concentration levels. Mercury has a great affin-
ity for organic matter, clays, and hydrous metal oxides, and in soils
remains bound, provided the pH remains neutral to alkaline. Mercury
may be lost from soils by volatilization; this tendency increases as
the soil organic matter and moisture content decrease.'
Atmospheric releases of mercury include point sources such as coal
combustion, ore smelting, and solid waste incineration, and dispersive
sources such as volatilization from house paints and outgassing from
the earth. Mercury emissions from point sources are concentrated with-
in 1 km of the source in surface soils and waters. This accounts for
only a small percentage of total emissions, however, and the remainder
is subject to dispersal according to local meteorology.
Land disposal of mercury in chlor-alkali wastes, mine tailings, coal
piles, or solid wastes is a major source of mercury to the environment.
However, little evidence exists to suggest that mercury enters surface or
ground waters as a result of acid mine drainage, or leaching from tailings
and landfills. Clays and organic matter in soils effectively reduce the
quantity of mercury leaching from these systems. Soil environments favor-
ing transportation of mercury would be low in pH and contain little clay
and organic matter. Municipal landfill leachate analyses performed to
date have shown mercury concentration less than or equal to 0.2 mg/1.
98
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Mercury also reaches the soil through its use for agricultural
purposes as pesticide, although this use is limited. It is lost from
the soil by volatilization or retained as an adsorbed species to clays
and organic matter. Phenylmercurials, which constitute most pesticidal
forms of mercury, are easily leachable, as well as subject to loss by
vaporization and surface runoff.
Mercury enters POTWs at an average concentration of 0.4 ug/1.
Aerobic and anaerobic biological treatment partition more than 90% of
the mercury into the sludge portion of the waste. Most of the remainder
is adsorbed to suspended solids. Most sludges generated by POTWs are
disposed of in landfills, by ocean dumping, by incineration or by land-
spreading. Land-spreading of sludges to amend soils should not result
in enhanced solubility or mobility of added mercury species relative to
mercury already present in the soil because in both cases the mercury is
strongly adsorbed, chelated or is in an insoluble form.
Discharge of mercury-containing effluents to freshwaters, whether
direct or from POTWs, may result in elevated sediment concentrations for
several kilometers downstream. There is a distinct prospect of methyla-
tion of the mercury in freshwater sediments. Discharges to marine waters
usually result in oxidation and solubilization of the mercury followed by
dilution.
3. Biological Fate
The folloxjing conclusions may be drawn concerning the fate of mer-
cury in biota:
• Methylmercury is the most common form of mercury found in
aquatic organisms.
• Methylmercury is rapidly accumulated and retained for long
periods (>300 days in some species of fish).
• Both ingestion and gill absorption are exposure routes for
mercury, with the former appearing to play a more significant
role in upper-trophic-level organisms.
• Methylmercury tends to be associated with muscle tissue—the
edible part of fish—and liver and kidneys.
• Bioconcentration levels range from one to six orders of
magnitude higher than background water concentrations.
• Biomagnification of mercury appears to occur in at least
certain aquatic food chains, however, further research in
this area is reauired.
99
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Terrestrial plants generally do not accumulate mercury to
very significant levels compared with aquatic biota.
Plant residues may be higher (up to 10 mg/kg dry weisht
equivalent to approximately 5 mg/kg wet weight)'in soils
where gaseous mercury is available for uptake.
Conversion of phenyl and other mercury compounds to methyl-
mercury may take place in some plants.
Clarification is needed regarding the form of mercury
present in soil and its influence on uptake rates.
100
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CHAPTER V.
HUMAN EFFECTS AND EXPOSURE
A. HUMAN TOXICITY
1. Introduction
Mercury exists in several forms, each with different toxicity.
It is important, therefore, to distinguish among the different
chemical forms of mercury. Mercury compounds can be categorized
as either inorganic or organic. The inorganic classification includes
mercury in the form of (1) the elemental metal (Hg°) and its vapor,
(2) the mercurous ion (Hg+) and its salts, (3) the mercuric ion'(Hg++)
and its salts, and (4) mercuric ion complexes, which are capable of
forming reversible bonds with the thiol group in proteins. The organo-
mercurial classification includes compounds in which mercury is attached
to at least one carbon atom by a covalent bond. Due to their toxicity,
the most important class of organomercurials to be considered is com-
prised of methylmercury and related short-chain alkyl mercurial compounds.
Much information is available concerning the effects of mercury on
man. The occurrence of "Minamata disease" and incidents of poisoning due
to the ingestion of methyl-mercury-coated seed in Guatemala, Iraq, and
Pakistan within the past 20 years have prompted additional research on
the toxicity of mercury compounds. Indeed, several detailed reviews are
available on the human health hazards associated with mercury exposure
(Friberg and Vostal 1972, NRC 1978, Nordberg 1976, WHO 1976)'. Conse-
quently, no attempt was made to present the extensive experimental data.
Rather, the general findings of these reports have been summarized,
supplemented by data from recently published papers in areas of concern.
2. Metabolism and Bioaccumulation
Mercury compounds may be absorbed by the body through the gastro-
intestinal tract, respiratory tract, or skin. The toxicity of
mercury depends on the chemical form at entry in that this affects
absorption, distribution, and biological half-life.
The rate of absorption, and, therefore, the oral toxicity of various
compounds of mercury, increases in the following order: Hg° < Hg+ < Hg-H-
< CHsHg. Metallic mercury (HgO) is not appreciably absorbed by the gastro-
intestinal tract (<0.01%) and the dangers of poisoning from liquid
mercury by this route appear slight (Hugunin and Bradley 1975, WHO 1976).
Mercuric ions (Hg-H-) are absorbed somewhat more efficiently from the
gastrointestinal tract; about 5% to 15% of the total amount ingested is
absorbed by this route (Koos and Longo 1976). Mercurous ions are less
water soluble than mercuric ions and, thus, are not well absorbed when
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ingested. The most toxic forms of mercury are the alkylmercurials, which
a.e almost completed absorbed from the gastrointestinal tract (80-100%)
but much or the amount absorbed is subsequently secreted in bile (WHO
19/6, Hugunin and Bradley 1975).
Harmful levels of mercury may also be absorbed through the respira-
ihnVJS*'* MTVrI VSPOr Can be readUy absorbed *y the lungs, with
about W/, of inhaled mercury taken up by the alveoli (WHO 1976) The
vaporized metal quickly enters the bloodstream, where appreciable amounts
persist unchanged for several minutes before undergoing final oxidation
to mercuric ions. In sharp contrast to the mercuric form, methylmercurv
and inhaled elemental mercury vapor cross the blood-brain barrier and
Placenta more readily than other types of mercury (Gerstner and HuS 1977).
19? Cherian et^al. (1978) had five human volunteers inhale 4-10.7 yci
"_ Hg or 1 ud 203Hg vapor in air and reported approximately 74% reten-
tion. Of the retained dose, approximately 7% was deposited in red blood
cells. Another If, of the retained dose was exhaled in expired air; the
half-time for exhalation via this pathway was 14-25 hours. Cumulated
urinary and fecal excretion over 7 days was 11.6% of the retained dose
Fecal excretion accounted for approximately 80% of this amount: i.e
9.2% of the retained dose.
Monoalkylmercurials are also very volatile and diffuse readily across
lung alveoli; absorption is believed to be on the order of 80% of the
inhaled amount (WHO 1976). Inhaled aerosols of mercuric salts are also
absorbed by the lungs, but not as readily as mercury vapor (Hugunin and
Bradley 1975).
Mercury in its various forms (elemental, inorganic salts, and organic
compounds) can also be absorbed through the skin, but the extent of pene-
tration is unknown and is generally believed to be too slow a process to
be of much importance in comparison with other exposure routes. Use of
skin-lightening, mercury-containing facial creams by black African females
however, has resulted in episodes of hysteria, depression, uncontrollable
tremor, and ataxia (Baily et al. 1977). No record of the frequency of use
or amounts applied could be obtained. While this finding does indicate
absorption of mercury through the skin, the possibility of some inhalation
exposure cannot be excluded.
Little Information is available on the distribution of mercury in human
organs following well documented exposure to elemental mercury vapor but
in the brain are generally several times higher than those in liver and
other organs (WHO 1976). Studies on a variety of experimental animals
incicate that the kidney is the chief depository for mercury after the
administration of inorganic salts or elemental mercury vapor (WHO 1976).
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Urine and feces are the main routes of elimination of mercury from
the body. The percentage contribution of each pathway varies according
to the chemical form of mercury and the time that has elapsed since
exposure. The biotransformation of elemental mercury to mercuric ion
by red blood cells has been demonstrated ±n vitro, as has the rapid
conversion of aryMercurials to inorganic mercury in the body. The
short-chain alkylmercurials are converted more slowly to inorganic mer-
cury, with methylmercury compounds being converted the most slowly (WHO
1976).
Landry et al. (1979) recently reported that diet differentially
affected retention and whole-body elimination of an apparently non-toxic
dose of methylmercury (0.46 mg Hg/kg, oral dose) in 8-month-old female
BALB/c mice. Animals fed a chemically defined liquid diet excreted
(seven days after dosing) a greater proportion of inorganic mercury to
total mercury (0.91 ratio) than mice on either an evaporated whole milk
diet (0.72) or standard pelleted rodent diet (0.75). Mercury concentra-
tions in organs and blood (two weeks after exposure was initiated) gen-
erally correlated with whole-body retention of mercury.
In the case of repeated daily exposure, elimination depends on the
total body burden and not on daily dose. The time needed to reach steady-
state depends upon the biological half-life of the compound. In man,
these values are 40 days for inorganic mercury, 58 days for elemental
mercury, and 70 days for methylmercury. However, subpopulations exist
with half lives as long as 120 days (WHO 1976, NRC 1978).
Mercury levels in human tissues and body fluids vary considerably,
but the highest levels are generally found in the kidney and liver.
Gabica _e_t al. (1975) found that 76% of 242 tissues taken at autopsy in
Idaho during 1973-74 contained detectable levels of mercury. Mean levels
detected were 1.04 ug/g in kidney, 0.34 ug/g in liver, and 0.08 ug/g in
brain. In general, levels of mercury were higher in women than in men
once they approached or exceeded 1 ug/g tissue. Women over 65 years of
age had more mercury in their tissues than had men in the same age group.
These higher levels of mercury in females of advanced age remain to be
explained.
In another study of 40 cadavers ranging in age from 1 year to 90
years, Schmidt and Wilber (1978) found that mercury levels in kidney
tended to increase linearly with age. An earlier study of 113 people by
Mottet and Body (1974), however, found no statistically significant
increase in mercury burden occurring with increasing age. Regardless of
the organ or age of the subject, 70% of the assays had a mercury burden
of 0.25^ug/g wet tissue or less. The levels in kidney varied the most,
with 29% of the concentrations above 0.75 ug/g wet tissue. Levels as
high as 6.6 ug/g, 4.0 ug/g and 0.5 ug/g in kidney, liver, and brain,
respectively, have been found in Japanese fetuses who succumbed to
Minamata disease (Matsumoto _ejt _al. 1965).
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Roels jat al. (1978) determined the concentration of mercury in the
placentas from 474 Belgian women. The median value for placenta was
1.06 ug/lOOg wet tissue (range of 0.11-10.31). Mercury levels in
placenta were unrelated to corresponding levels in maternal and cord
blood.
Yugoslavian workers engaged in the chemical industry, active mercury
miners, and workers producing pesticides containing mercury accumulate
significant amounts of mercury in hair. The mean values of the mercury
content of hair were: 10.28 ug/g, 14.51 ug/g, and 20.94 ug/g, respec-
tively, compared with 0.70 ug/g in the general population (Stankovic
et al. 1977).
Thus, mercury levels in tissues of normal and exposed humans vary
considerably. The mercury burden in the general population, however,
appears to be below 1-2 ug/g in kidney, 0.35-0.75 ug/g in liver, and
less in other tissues. Table 18 contains a summary of human tissue levels
of mercury.
Nordberg (1976) summarized the known relationships between exposure
levels and tissue levels, based primarily on ingestion exposures of
methylmercury:
• A specific relationship exists between levels in
each organ and total body burden of methylmercury.
• Definite relationships exist among the levels of
methylmercury in various organs.
• Elimination is correlated with body burden, i.e.,
a specific fraction of body burden is eliminated
per unit of time.
• A linear relationship exists between daily dose
and mercury levels in blood and hair.
• Levels in blood and hair are related in a linear
fashion, with the hair levels about 250 to 300
times levels in whole blood. Thus, hair is of
greatest potential value as an index medium for
exposure to methylmercury. Also, hair provide
a record of the history of past exposure.
• At levels below which symptoms of toxicity can be
observed, brain levels may be estimated accurately
on the basis of blood levels.
• Urine values are of little value in estimating
body burden because not only are there low levels
of methylmercury present in the urine but also the
relatively larger proportion of inorganic mercury
present in urine introduces analytical difficulties.
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TABLE 18. CONCENTRATIONS OF MERCURY IN HUMAN TISSUE
Geographic
Population Region
General Idaho
population, 1973-1974
post-mortem
General popula- State of
tion, post- Washington
mortem, 26 wks. 1970-1972
of gestation to
88 yrs.
General popula- Northeastern
tion, post- Colorado
mortem, age 1
to 90 yrs.
Tissue
Kidney
Liver
Brain
Kidney
Liver
Heart
Muscle
Lung
Spleen
Pancreas
Cerebellum
Spinal Cord
Skin
Bone
Brain
' Kidney
Liver
Muscle
No.
Sampled
94
84
61
95
95
57
67
77
41
32
60
59
60
39
Distribution
mean ug Hg/g. wet tissue
1.04
0.34
0.08
mean ug Hg/R, wet tissue
0.757
0.250
0.102
0.126
0.251
0.122
0.065
0.132
0.087
0.193
mean ug Hg/g. wet tissue
+ S.D.
0.004 + 0.009
0.000 + 0.000
1.456 + 2.683
0.176 + 0.305
—
0.006 + 0.009
Remarks Reference
Mercury found in Gablca et al
76% of tissues tested; (1975)
The mean value was 0.73
ug/g with highest levels
found in kidney.
Irrespective of age Mottet and
or organ, over 70% of Body (1974)
the assays had burdens
less than 0.25 ug/g.
The amount of mercury Schmidt and
in kidney tended to in- Wilber (1978)
crease linearly with
age with a mild increase
in liver but no change
in bone and muscle.
Utilized atomic absorp-
tion spectroscopy.
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TABLE 18. CONCENTRATIONS OF MERCURY IN HUMAN TISSUE (Continued)
Population
General popula-
tion, Women
Genera] popula-
tion
General popula-
tion, Mothers,
Newborn child
Geographic
Region
Belgium
Yugoslavia
Japan
Tissue
Placenta
Hair
Blood
No.
Sampled
474
9
9
Distribution Remarks
median 0.0106 ug/g wet
tissue
0.70 ug/g
22.9 ug/l + 11.9*
30.8 ug/l + 21.6*
Reference
Roels et al.
(1978)
Stankovic et a]
(1977)
Suzuk i ejt al.
(1971)
General
populat ion
10
o
California
Ohio
New York
General popula-
tion, dieters
eating tuna fish
General popula-
tion with low
or zero fish
consumption
Whole Blood 33
Blood
Hair
Blood
Hair
40
87
79% of all samples had
concentrations below
5 ug/l; highest level
reported 51 ug Ug/l.
85% of all samples had
concentrations below
5 ug/l; highest level
reported 240 ug llg/1.
83% of all samples had
concentrations below
5 ug/l; highest level
reported 45 ug llg/1.
25% of population had
average level of 17.3 ug/l
and averaged hair concentra-
tion of 14 ug/g.
<1 to 6 ug/l
<1 to 5 ug/g
WHO (1966)
McDuffle (1975)
Berglund e^t al.
(1971)
*Tlie standard deviation.
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TABLE 18. CONCENTRATIONS OF MERCURY IN HUMAN TISSUE (Continued)
Pop 11 la Lion
General
population
Geographic
Region Tissue
New York
California
Ohio
Urine
No.
Sampled
363
31
Distribution
80% samples below 0.5 ug/1;
highest level reported 97 ug/1
87% samples below 0.5 ug/1; high
est level reported 15 ug/1
93% samples below 0.5 ug/1; high
est level reported 221 ug/1
Remarks
Reference
WHO (1966)
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3. Animal Studies
a. Carcinogenicity
Little information is available on the carcinogenicity of mercury
compounds. Schroeder and Mitchener (1975) reported no significant dif-
ference in tumor frequencies between control, unexposed, and exposed
random-bred albino Swiss mice following lifetime exposures to methyl-
mercury in drinking water (5000 ng/ml for 70 days, then 1000 ng/ml
thereafter). &
_ Prolonged exposure of mice to 1000 ng/g or 10,000 ng/g methlymercury
in their feed also did not alter the course of neoplasia following inocula-
tion with Rauscher leukemia virus (Roller 1975).
Localized sarcomas were reported in rats injected intraperitoneally
with metallic mercury (Druckrey et al. 1957), but no metastases were
observed. Carcinogenesis resulting from injection in which tumors are
induced only at the site of application is generally regarded as irrele-
vant to human exposure. ;
The available data (a single lifetime exposure in one species, the
mouse) are inadequate to permit a reliable assessment of the carcinogenic
potential or mercury, but at this time mercury is not indicated as a
carcinogen.
b. Mutagenicity
Mutagenicity studies conducted in plants and laboratory animals have
shown the ability of methylmercury to block mitosis in plant cells
human lymphocytes treated ±n vivo, and human cells in tissue culture and
to cause chromosome breakage in plant cells and point mutations in
Drosophila (NAS 1978, U.S. EPA 1979, Friberg and Vostal 1972, Voss et al
1978, Mathew and Al-Doori 1976).
Reports of mutagenic effects in humans resulting from methylmercury
exposure are few. Skerfving et al. (1974) reported a statistically
significant correlation between the frequency of chromosome breaks and
blood mercury concentrations in individuals with elevated blood methyl-
mercury levels (range 13-1100 ng/g) due to the ingestion of fish contain-
ing methylmercury.
Recently, Popescu _et al. (1979) reported that the incidence of
chromosome aberrations (mostly acentric fragments) in peripheral blood
of 22 men exposed to either mercury vapor or organic mercury was signifi-
cantly higher than in controls. Although the number of chromatid gaps
and breaks was increased in the exposed men (38 versus 16 in controls),
the increase was not statistically significant. Mercury concentration'
in the chemical plant in which these men were exposed had ranged between
0.15 mg/m-> and 0.44 mg/m3 during the past year.
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Rozynkowa and Raczkiewicz (1977) found severe mitotic toxicity in
human lymphocytes exposed to 40 ug/ml methylmercuric chloride for 2 hours
in culture. This type of damage is probably not of mutagenic significance,
since the cells cannot survive and carry the alteration of the genetic
material.
Similarly, Umeda and Nishimura (1979) found that mercuric chloride
was relatively toxic to FM3A mammary mouse carcinoma cells, but failed
to induce chromosomal aberrations at subtoxic concentrations
(3.2 x ID'5M).
In another study, Fiskesjo (1979) tested the mutagenicity of two
organic mercury compounds, methylmercuric chloride (MMC) and methoxyethyl
mercury chloride (MO) in the Chinese hamster cell line, V79-4. A weak
mutagenic effect was noted, but acute toxic effects obtained with both
compounds limited dose-response curves for mutagenicity to a very narrow
concentration range: MMC 0.1 mg/kg (no effect) to > 0.5 mg/kg
(poor survival);
MO 0.05 mg/kg (no effect) to > 0.3 mg/kg
(poor survival).
At 0.2 mg/kg, the number of mutants per 10^ survivors was 18.3, 30.7,
and 4.3 for MMC, MO and controls, respectively.
Casto _e_t al. (1979) tested mercuric chloride for its capacity to
enhance transformation of Syrian hamster embryo cells by a simian adeno
virus, SA7. Mercury showed moderate enhancement of viral transformation
following 18-hour exposure to 0.05 mM; an enhancement ratio of 5.6 above
control was recorded at 0.05 mM.
In summary, methylmercury has been shown to be a weak mutagen in
Drosophila. It can interfere with mitotic and meiotic chromosome segra-
gation in plants and animals and has been reported to produce chromosomal
aberrations in vitro in lymphocytes of individuals exposed to methyl-
mercury. Contradictory data exist on its ability to induce chromosomal
breaks in man. The significance of these observations for human health
remains unclear.
c. Adverse Reproductive Effects
Due to its great affinity for sulfhydryl groups, mercury poses a
particular hazard to the developing embryo. Methylmercury readily
crosses the placental barrier, inducing a variety of developmental
anomalies and death. The mechanisms by which methylmercury interferes
with fetal development, growth, and viability are not well known.
Although prenatal exposure to mercury has proved to cause a number of
harmful effects on the human fetus, to date, epidemiological studies
from human poisoning episodes have been inadequate to fully define
dose-response relationships or to conclude that the full range of
possible teratogenic effects has been identified.
Embryotoxicity and teratogenicity of mercury in animals, however,
have been well documented (Mottet 1978, Koos and Longo 1976). Hamsters,
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rats, or mice given acute high doses of organic mercurials during sensi-
tive periods of gestation have demonstrated a spectrum of malformations,
including cleft lip and/or palate, micrognathia, encephalocele/excenceph-
aly, microphthalmia, rib fusions, and syndactyly. Growth retardation,
litter resorption, and stillbirths occurred frequently. Methylmercury
compounds particularly affect nervous tissue, resulting in cerebellar'
malformations, nerve degeneration, and hydrocephalus. Differences in
species, dosing regimen, and chemical form of mercury administered,
however, make direct comparisons among studies difficult.
Recent studies serve as typical examples of the effect of mercury
on the developing embryo. Fuyuta et al. (1978) administered daily oral
doses of 2.5 mg/kg, 5.0 mg/kg, 6.0 mg/kg, or 7.5 mg/kg methylmercuric
chloride (MMC) to pregnant C57BL mice on days 6-13 of gestation and found
that it was teratogenic at the lowest dose tested. The highest dose,
7.5 mg/kg MMC, was embryocidal (i.e., 98.7% dead and resorbed embryos).
At^a dose of 6 mg/kg, a high incidence of fetal death (34.2%) was noted,
while both the 6 mg/kg and 5 mg/kg groups showed decreases in fetal body
weight and marked increases in malformations (cleft palate, fused thoracic
vertebrae). The incidence of malformations for 6 mg/kg, 5 mg/kg, 2.5 mg/k»
and 0 mg/kg MMC groups was 97.9, 75.7, 11.3 and 0%, respectively.
A concurrent experiment conducted with Wistar rats by these inves-
tigators resulted in a high incidence of fetal deaths and resorptions
(42.4%) and an 80.3% incidence of malformations, especially cleft palate,
generalized edema, and brain lesions, in rats given 7.5 mg/kg orally on
days 7-14 of gestation. Rats similarly treated with 5 mg/kg, 2.5 mg/kg,
or 0 mg/kg MMC had incidences of malformations of 6.8, 0.0 and 0.4%,
respectively.
Olson and Boush (1975) reported decreased learning capacity in
Holtzman rats exposed pre- and post-natally to 2 mg mercury/kg of diet.
Olson and Massaro (1977) reported that methylmercury (5 mg Hg/kg
maternal body weight) given subcutaneously to gravid Swiss Webster CFW
mice on day 12, hour 6 of gestation induced a high incidence of cleft
palate in fetuses examined on days 15 (72%), 16 (62%), and 17 (40%).
Palate closure (100%) occurred by 14 days in control animals.
Eccles and Annau (1978) orally exposed Long Evans rats to 0 mg/kg,
5 mg/kg, or 8 mg/kg methylmercury in utero on day 7 of gestation. At a
dose of 8 mg/kg, 40% of litters were resorbed, but litters that were
delivered were of normal size and weight.
Gale (1979) injected LVG hamsters subcutaneously with a single
15-mg/kg dose of mercuric acetate at 8 A.M., Noon or'5 P.M. on day 7, 8,
or 9 of gestation. Treatment resulted in fetal death and external,
internal, and skeletal abnormalities in survivors. Treatment at each
of the nine injection times was equally as effective in producing many,
but not all defects. Pericardial cavity distension arid ventral body
wall defects were observed in fetuses taken on day 12, but not in those
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gathered on day 15, a finding suggesting a transient nature to this
defect. Fetuses taken on day 15 exhibited cleft palates, hydrocephalus,
skeletal defects, and abnormal hearts characterized by dilation of the
walls of the right ventricle and/or conus cordis.
Mottet (1978) examined the effects of chronic low subcutaneous doses
of methylmercuric hydroxide to the developing rat at dose levels ranging
from slightly in excess of the environmental burden (2 mg/kg maternal
body weight) to overt clinical toxicity (16 mg/kg maternal body weight).
Rats were dosed from day 0 to day 20 of gestation. No detectable
increase in specific malformations was noted, but a dose-related decrease
in fetal size was observed; i.e., 4.2 g, 3.7 g, and 2.1 g for the control,
2 mg, and 16 mg Hg/kg levels. Decreased size appears to be associated
with a decreased number 'of cells per organ or tissue. Fetal death and
fetal mercury burden were also dose-related.
Decreased fertility has also been noted in male mice given a single
intraperitoneal dose of 1 mg/kg methylmercury hydroxide. Fertility
profiles from serial matings suggest an effect on spermatogonial cells
and premeiotic spermatocytes (Lee and Dixon 1975). Similar results have
been reported by Suter (1975) and Ramel (1972) at somewhat higher doses.
In summation, elemental and methylmercury have been shown to readily
cross the placenta, inducing a variety of developmental anomalies and
fetal death. Laboratory animals exposed to organic mercury _in_ utero
exhibit a wide spectrum of malformations including cleft palate, micro-
gnathia, encephalocele, etc., at doses as low as 2.5 mg/kg maternal
body weight. Methylmercury compounds appear to be particularly predis-
posed to concentrate in nervous tissue, producing cerebellar malforma-
tions, nerve degeneration and hydrocephalus.
d. Other Toxicologies! Effects
The toxicologic responses noted after the administration of mercury
vary depending upon the formulation or the chemical form administered
(organic or inorganic). Regardless of the form of the chemical, however,
the two major responses noted after mercury administration are neuro-
toxicity and renal damage.
The neurotoxic effects of mercury-containing compounds are well
characterized for only a few of the more common forms, e.g., methyl-
mercury and inorganic mercurials such as HgCl.. Considerable variation
among mercury compounds in gastro-intestinal absorption, metabolism, and
elimination from the body, as well as differences in uptake, distribution,
and elimination from the brain and other nervous tissue, all serve to
produce different neurological responses.
The neurotoxic effects follow from the ability of mercury compounds,
both organic and inorganic, to penetrate, bind, and significantly alter
biological membranes. Damage to the blood-brain barrier, a highly
selective complex of biological membranes, reduces the active transport
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of crucial nutrients such as amino acids, and permits the penetration of
blood solutes normally barred from the cerebro-spinal space, and these
cause neurocellular disintegration (Chang 1977). The monovalent alkvl
(
affinitv for ave a str°ng
affmxty for sulfhydryl groups of proteins, and the cellular membranes
are rich in sulfhydryl groups. Electronmicroscopic studies have shown
large amounts of mercury localized to membranes of the mitochondria
golgi apparatus, endoplasmic reticulum, and nuclear envelope (Chang'
et al. 1972). &
Studies on experimental animals have provided information on mecha-
nisms and sites of action for the mercurials, but need to be interpreted
carefully with respect to dose-effect relationships. There is consider-
able species variation in the uptake of mercurials into the brain from
the_blood. At approximately steady state, the blood-brain concentration
ratio is approximately 10-15 for rats, 1 for mice, 1-2 for cats, 0.5 for
dogs and pigs, and 0.1 for monkeys (Chang 1977). Neurotoxic signs occur
in most species at brain concentrations within an order of magnitude of
each other (i.e., between 1-10 mg/kg) although corresponding blood
concentrations may differ widely due to species differences in blood
to brain ratios (U.S. EPA 1979).
There is evidence, however, that primates may be more sensitive to
low levels of mercury in the brain than rodents. In rats, motor defi-
ciency has been detected at brain levels no lower than 5-10 mg/kg
following divided doses of methylmercury totalling 34 mg/kg of body
x^eight. In young monkeys dosed with divided or single doses of methyl-
mercury (4.6-6.9 mg/kg), severe neurotoxic effects were observed when
brain levels had reached only 1-2 mg/kg. These monkeys became physically
incapacitated and comatose at brain levels of 6-12 mg/kg (Hoskins and
Hupp 1978). Species differences in biological half-lives of mercury
compounds, together with the differences in blood-brain barrier and
possible intrinsic neural sensitivity, all contribute to species varia-
tion in dose-effect relationships for neurotoxic symptoms.
The other major irreversible effect associated with mercury exposure
is renal damage. Irrespective of chemical form at entry, kidneys concen-
trate more mercury than any other organ, often to an extent that is
incompatible with normal renal function and morphology. Renal damage
can result in oliguria, anuria, uremia, and death. Morphologic damage
to renal tubule cells has been demonstrated in rats following either
acute or chronic exposure to methylmercury (Fowler and Woods 1977
Hinglais et al. 1979, Fowler 1972). Similar results have been reported
following treatment with other mercurials (Friberg and Vostal 1972).
A recent report by Goldman and Blackburn (1979) indicates that
mercury may also influence thyroid function in the rat. Oral administra-
tion of 3 mg/day of mercuric chloride for 6 consecutive days accelerated
the release rate of thyroidal radioiodine (131];) . Administration of
approximately the same dose (2.5 mg/day) by stomach tube for 40 days
resulted in continued enhancement of thyroid activity. A reduction in
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the fraction of labelled triiodothyronine (13) was found and may indicate
a coupling defect in the synthesis of 13 exerted by mercury. Subchronic
exposure to 100 mg/kg mercuric chloride in the diet for 90 days (which
approximated the 2.5-mg/day dose by gavage), however, resulted in mani-
fest signs of mercury poisoning, together with decreased thyroid radio-
iodine uptake and depression of thyroid secretion rate, which was
irreversible even after 3 months on a control diet.
Thus, the toxic effects of mercury have been shown to vary depending
on chemical form administered, species variation in absorption, brain
uptake, etc. Neurotoxicity and renal damage are the two major toxic
effects noted after mercury exposure. Neurotoxic signs occur in most
species at brain concentrations between 1 and 10 mg/kg with primates
apparently more sensitive to the minimally effective brain concentration
than rodents, morphological damage to renal tubule cells have been
demonstrated in laboratory animals following either acute or chronic
mercury exposure irrespective of chemical form at entry.
e. Interactions With Other Metals
A complete discussion of the complex interactions of mercury with
other metals is beyond the scope of this report. There is no question,
however, that the toxic effects of mercury are modified to some extent
in the presence of selenium and other metals.
Selenium appears to diminish the acute and subchronic toxicity of
mercury in rodents (Skerfving 1978). Excess mercury provokes a pattern
of selenium retention similar to that found in cases of selenium defi-
ciency (Kristensen and Hansen 1979). Dietary selenium also influences
tissue distribution of inhaled mercury vapor in rats (Nygaard and
Hansen 1978). The protective mechanism of selenium against mercury
toxicity is not well understood, but selenium appears to eliminate the
stimulation of metallothionein biosynthesis induced by mercury
(Chmielnicka and Brzezhicka 1978). Of note, however, is the finding
that selenium-treated animals remain unaffected even when they have
attained tissue mercury levels otherwise associated with toxic effects.
This subject has been reviewed in detail by Skerfving (1978), Berlin
(1978), and Parizek (1978).
With respect to other metals, manganese, which is present in all
waters, has been shown to be an avid scavenger of mercury, and iron has
a similar action (Anderson 1973, Lockwood and Chen 1973). Conversely,
the toxic effects of mercury are accentuated by the presence of copper
(Corner and Sparrow 1956).
4. Human Studies
Both natural and cultural sources contribute to widespread, low-level
mercury contamination of the environment, as discussed in Chapter III.
As a result, all humans are exposed to low levels of mercurv through
inhalation and most are also exposed to low levels through ingestion of
127
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water and rood. Occupational exposures and effects have been recognized,
it not well characterized, for centuries in some cases. These are°dis-
cussed at more length in Section b. Chronic Exposure, as are three inci-
dents of widespread human toxicity due to ingestion of methylmercury.
A number of other accidental or incidental cultural sources have
been reported. These include poisonings due to inhalation of elemental
mercury vapor from broken thermometers (Agner and Jans 1978), from mercu-
rochrome therapy for an infected umbilicus (Yeh _ejt al. 1978), due to
release^of mercury from amalgam dental fillings "(Gay~£t al. 1979), and
due to ingestion of small mercury batteries by children (Reilly 1979,
Barros-D'Sa and Barros-D'Sa 1979). While a considerable number of such
incidents have been reported, most of the reports have been anecdotal
in nature, often not including information on the dose received (although
reasonable estimates may be made later in some cases) and rarely provide
information on incidence or exposed population, although again estimates
of differing reliability may be made later.
a. Acute Exposure
The acute symptoms resulting from the ingestion of any mercury-
containing compound may initially be noted by an ashen-grey appearance
of the mouth and pharynx. This condition results from precipitation of
the protoplasm of the mucous membrane, and is often accompanied by a
burning sensation in the mouth and throat and eschar formation on the
mouth and lips. Extreme salivation and thirst often follow. The mucous
membrane of the stomach is similarly affected. Consequently, gastric
pain, nausea and vomiting of blood-stained mucus result. If a high
concentration of mercury reaches the small intestine, severe, profuse,
and bloody diarrhea result, often accompanied by shreds of intestinal
mucosa. Due to loss of fluids and electrolytes, shock may be accompanied
by a rapid, weak pulse; cardiac arrhythmias; cold, clammy skin; pallor;
slow breathing; and peripheral vascular collapse (D'ltri 1972).
If the patient survives, the following delayed actions may occur
within 1 to 14 days: ulcerative colitis; salivary gland swelling;
excessive salivation; metallic taste, stomatitis/foul breath, loose
teeth; soft spongy gums; and a blue-black gum line caused by a mercury-
sulfhydryl complex. Systemic signs, referable to the central nervous
system,^include lethargy, excitement, hyper-reflexia. and tremor (Harvey
1970, D'ltri 1972). Oliguria is often present, with anuria, uremia,
albuminuria, hematuria, proteinuria, and acidosis. Death at this stage
is ascribed to uremia. Autopsies reveal inflammation and extensive
corrosion along the alimentary tract, severe renal tubular necrosis,
and possibly, central necrosis of the liver (D'ltri 1972).
b. Chronic Exposure
The onset of chronic mercury poisoning is often slow and insid-
ious, typically beginning with progressive numbness of the distal
parts of the extremities and often of the lips and tongue. This is
followed by an ataxic gait, clumsiness of the hands, dysarthria,
dysphagia, deafness, and blurring of vision. Voluntary movements are
128
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limited in most individuals although muscle atrophy is rare. Spasticity
and rigidity are often present, muscle stretch reflexes are usually
preserved or become hyperactive, and extensor plantar responses are
occasionally elicited during the later stages. Insomnia, agitation,
hypomania, and the loss of emotional control are frequently noted and
most individuals have abnormal involuntary movements, including
choreoathetosis, myoclonus, and coarse resting and action tremors
(D'ltri 1972).
Three major outbreaks of methylmercury poisoning have occurred in
man. In Minamata, Japan, the poisoning was caused by marine fish. In
Niigata, Japan, the methylmercury was carried by freshwater fish, and
in Iraq, methyl-mercury-contaminated grain was ingested by the rural
population. Individuals involved in these outbreaks have'demonstrated
a wide range of neurologic symptoms. Feelings of malaise have been
observed, progressing to severe bodily discomfort with muscular weakness,
paresthesia, loss of coordination of the digits, ataxia, speech distur-
bances, disturbances of vision (blurring and constriction of field of
vision) and loss of hearing, among many other manifestations of neuro-
toxicity. Character disorders and mental deficiency have also occurred.
Symptoms were similar in children and adults. Recovery from methylmer-
cury intoxication is inversely related to the severity of symptoms, and
ranges from complete functional recovery in persons experiencing minor
symptoms, such as slight paresthesia, to indefinitely protracted physical
and mental disabilities in severely poisoned individuals. Tokuomi (1968)
reported that neurological abnormalities were still apparent after 10
years in some patients who had experienced Minamata disease. Tremor of
fingers was apparent in 70% of the patients. Takeuchi et. _al. (1970)
noticed that some symptoms of central and peripheral nervous system
disturbances persisted unchanged, while symptoms such as mental abnormali-
ties worsened over 10 years in patients with Minamata disease.
Evaluation of human populations following large-scale exposure to
methylmercury compounds has been used to estimate the threshold dose
and corresponding blood levels that produce certain neurologic effects.
These estimates have been used to estimate the "safe" exposure levels at
which neurological symptoms should not occur. The Swedish Expert Group
(Berglund et al. 1971) made two estimates of the critical daily intake
based on the Japanese exposures at Minamata Bay and Niigata. Using the
metabolic method, which incorporated data on brain levels, absorption,
distribution, and a biological elimination half-life of 70 days, they
obtained a critical daily intake of - 10 ug/kg. The epidemiologic method,
which correlated blood levels and clinical symptoms in both poisoned
and non-poisoned individuals with methylmercury consumption in fish,
gave an estimate -5 ug/kg. When the lower of the two estimates is
used with a safety factor of 10, 30 ug/day of methylmercury appears to
be a safe level of intake for a 70-kilogram man. This would correspond
to an acceptable level of methylmercury in blood of approximately 20 ng/mi.
Subsequent epidemiologic studies summarized in Table 19 seemed to verify
that the 200 ng/ml blood level is approximately the level at which certain
neurologic effects would begin to occur. It is not known whether a safety
factor of 10 is sufficient, particularly for developing fetuses and infants
(see Chapter V.4.c.) and in some individuals in whom biological half-lives
for mercury compounds are as long as 120 days (Al-Shahristani and Shibab
1974).
129
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TABLE 19. CLINICAL CORRELATIONS OF NEUROTOXICITY
AND LEVELS OF MERCURY IN BLOOD
Blood Levels Incidence of Neurological Reference
(ng/ml) Symptoms
200 ~ 5% Bakir _et al. (1973)
5'330 42% Clarkson (1975)
Harada et al. (1976)
2
D° <50% Barbeau et al. (1976)
11-275 0% Turner et al. (1974)
mean 82
Extrapolated background level for paresthesia (earliest clinical sign)
2
Considered suspect because of likely inclusion of patients suffering
from alcoholism.
130
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WHO (1976) has established a provisional weekly intake of 0.3 mg
total mercury, of which no more than 0.2 mg should be present as methyl-
mercury. These doses correspond to daily intakes of 43 ug and ?9 ug/
respectively for a 70 kg person, slightly higher than those recommended
by Berglund _e_t _al. (1971).
Chronic inhalation exposure to mercury vapor in the workplace has
resulted in tremors, mental disturbances and gingivitis at air concen-
trations above 0.1 mg/m3; lower concentrations (0.06 to 0.1 mg/m3) are
associated with such non-specific signs as insomnia, loss of appetite,
weight loss. Occupational exposure to an air concentration of 0.05 mg/m3
mercury vapor would be equivalent to continuous environmental exposure
to an ambient air level of ~ 0.015 mg/m3 (based on a daily ventilation
of 10 m3 during working hours, 20 m3 for a 24-hour day, 225 working days/
year) (WHO 1976).
c. Adverse Reproductive Effects
^ human fetus appears to be very susceptible to mercury poisoning.
The information available concerning the human reproductive-teratogenic
effects of mercury is epidemiological in nature; the Minamata and
Niigata studies are prime examples. Although these studies indicate
that organic mercury passes the human placenta, the actual concentration
of mercury ingested by the mother, together with the duration of exposure,
cannot be determined.
Six percent of the children born near Minamata Bay between 1954 and
1959 were afflicted with mild to moderate spasticity, ataxia, chorea,
coarse tremors, seizures and severe intellectual deficiencies (Scanlon
1972). Since mercury can be excreted in breast milk (Berlin and Ullberg
1963) , many of these affected children may have acquired high mercury
levels both in utero and from their mothers' milk.
In all 19 reported cases of congenital infantile cerebral paresis
in Minamata and Niigata, the mothers displayed few or no clinical neuro-
logical symptoms (Eyl _et al. 1970). This absence of symptoms may be due
partially to the fact that fetal erythrocytes concentrate higher levels
of mercury than do maternal erythrocytes.
Typically, abnormalities were recognized at the beginning of the
sixth month after birth. Symptoms included instability of the neck,
convulsions, and failure of the eyes to follow. Patients also developed
severe mental and neurologic symptoms including: intelligence distur-
bance (100%), disturbance of body growth and nutrition (100%), hyper-
kinesia (95%), hypersalivation (95%), paroxysmal symptoms (82%),
strabismus (77%) and pyramidal symptoms (75%). Clinical evidence of
fetal brain damage was observed when maternal blood levels of mercury
of approximately 400 ng/ml were achieved (Harada 1978, NRC 1978).
In 1971, barley and wheat grain treated with methylmercury were used
to make bread containing about 4 mg of Hg/loaf; ingestion of this bread
resulted in a widespread epidemic of mercury poisoning in Iraq. Infants
131
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born to women pregnant during this period suffered severe brain damage.
Breast milk was shown to contain 5-6% of maternal blood Hg levels and
may have contributed to the problem (Koos and Longo 1976).
The harmful fetal effects of methylmercury were further implicated
in a male child born to a woman who had ingested contaminated pork
during the third through sixth months of pregnancy. The meat became
contaminated after hogs were inadvertently fed seed grain treated with
a methylmercury fungicide. Examinations of the mother were "normal" for
the remainder of the pregnancy, except for elevated levels of mercury
in the urine (0.18 mg/1 at 8 months). The male infant (3.06 kg) was'
delivered at term. Intermittent gross tremulous movements of the
extremities developed within 1 minute of birth and persisted for several
days. The child was normal in all other respects except for a high
urinary level of mercury (2.7 mg/1 at 1 day of age). At 6 weeks, the
infant was hypertonlc and irritable; no mercury could be detected in
his urine. At 8 months of age, the baby was irritable, began to have
myoclonic seizures, and was now hypotonic, grossly retarded, and had
nystagmoid eye movements without evidence of visual fixation. Since
this infant was never breast fed, this case presumably resulted from
actual intrauterine poisoning with organic mercury. The mother was
asymptomatic, in striking contrast to the symptomatology seen in the
infant, a finding that may indicate a special susceptibility of the
developing human nervous system to damage from mercury (Snyder 1971).
The most perplexing aspect of this circumstantial evidence that
methylmercury is a teratogenic agent for human fetuses is the lack of
symptomology in the mother during pregnancy while the child has marked
neurotoxic symptoms soon after birth. Whether this divergent response
to methylmercury exposure is due to the ability of the fetus to concen-
trate mercury _in utero, or because the developing nervous system of the
fetus may be hypersensitive to the toxic effects of methylmercury, cannot
be determined. Both factors may play a role in methylmercury's terato-
genicity since the embryo has been shown to concentrate greater amounts
of mercury in red blood cells than its mother; the nervous system may be
more sensitive because myelination may not have been completed at the
time of exposure.
5. Overview
Mercury compounds may be absorbed through the gastrointestinal tract,
respiratory tract and through the skin. In man, toxicity increases in
accordance with the extent of absorption, i.e., with increasing toxicity
of mercurial compounds as follows: Hg°
-------
Except for the production of local sarcomas at the point of
injection of metallic mercury in rats (findings that are generally
regarded as irrelevant to human exposure), there are no data available
to indicate that mercury compounds are carcinogenic.
Methylmercury is a weak mutagen in Drosophlla and can interfere
with mitotic and meiotic chromosome segregation in plants and animals.
Methylmercury also produces chromosomal aberrations in human lymphocytes
iH vitr° and has been implicated in the induction of chromosomal breaks
in man.
Mercury poses a particular hazard to the developing embryo. Ele-
mental and methylmercury readily cross the placental barrier, inducing
a variety of developmental anomalies and fetal death. A wide spectrum
of malformations including cleft palate, micrognathia, encephalocele,
etc., have been produced in laboratory animals exposed to mercury in
utero at doses as low as 2.5 mg/kg maternal body weight. The human"
fetus, and in particular, the fetal nervous system, appears to be
particularly susceptible to methylmercury as indicated by the Minamata
and Niigata episodes.
Most of the human data available on mercury exposure are epidemi-
ological in nature. The critical organ systems in man are the central
nervous system and the kidneys. The onset of chronic poisoning is often
slow and insidious and typically begins with numbness of the distal parts
of the extremities, and often of the lips and tongue. This is followed
by progressive neurological disturbances including dysarthria, ataxia,
concentric constriction of the visual fields, blurred vision, blindness,
deafness, and ultimately, death.
A critical daily intake of 30 ug Hg, which corresponds to a mercury
blood level of 20 ng/g, has been estimated to be a safe intake for an
average 70-kg man. However, there is some disagreement as to a "safe
intake." A blood mercury concentration of 200 ng/g is the approximate
blood level at which observable neurological effects occur.
B. EXPOSURE
1. Introduction
describes the toxicity of mercury to humans,
methylmercury. Because effects have been observed following
exposure to low levels of mercury, there has been a great emphasis on
developing exposure estimates over the past 5-10 years. Since numerous
authors have taken considerable effort to review and analvze available
rt!^'i T W°rk " Primarily summarized here, without going into great
VPP rh7J°rTmcre lnformaV-°n and background, the reader is referred to
NRG (1978), U.S. EPA (1979), and WHO (1976) for excellent reviews of this
31*63. •
133
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Though much still remains to be learned regarding the toxt'city of
mercury, it is clear that effective exposure and toxicity depend on the
route of exposure and the chemical form of mercury. Thus, exposure esti-
mates for different routes cannot simply be summed. Therefore, the
following section considers separately each exposure route and the form
of mercury generally associated with it.
2. Ingestion
a. Drinking Water
The intake of mercury in drinking water is generally considered to
be low. Battelle (1977) cites an EPA survey of finished drinking water
conducted in 1975-76. Of the 512 water supplies sampled, 460 were less
than the detection limit of 0.5 ug/1. Six samples had concentrations
greater than 2 ug/1. Thus, according to these data, most persons con-
suming 21 per day would be exposed to less than 1 ug/day in drinking
water, and a very small subpopulation would receive 4 ug/day.
The primary form of mercury in drinking water is probably soluble
inorganic compounds. NRC (1978) reviewed available data for evidence
of methylmercury in natural waters. The authors found very low levels,
generally less than 0.0002-0.001 ug/1 in nonpulluted waters (See
Chapter IV).
b. Food
Food has been considered to be the primary route of human exposure
to mercury. Almost all of the methylmercury in the human diet comes from
fish; however, other foods may contribute to the total mercury exposure
(NRC 1978). The U.S. FDA has recently raised the action level* for
mercury in fish, shellfish, crustaceans, and other aquatic animals from
0.5 to 1.0 mg/kg (FR 44:4012). NRC (1978) reports that this level is
generally exceeded only by the larger marine species and freshwater
species from particularly contaminated areas. For example, fishing
locations and catches are restricted in many areas of the U.S. Figure 14
shows the status of state restrictions on fishing due to mercury in 1977.
Appendix B contains an update of the status of these fisheries. At this
time many of them remain restricted, though restrictions have been
lifted in some states.
In addition, numerous incidents of food contamination due to mercury
have been reported. State agencies reported 19 such incidents from
1968 to 1978, and federal agencies reported 85 cases in the same time
period (OTA 1979). These incidents are defined as cases in which an
agency has taken regulatory action against a contaminated food, and,
therefore, represent only some portion of the total incidents that have
actually occurred, most of which are probably attributable to contami-
nated fish that had exceeded the previous action level of 0.5 mg/kg set
by FDA in 1969.
'''Level at which FDA can take action to remove fish from the market place.
134
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Sidles where closures of sport or commercial
fishunes and health warnings are now in «I feel
Stales with current health warnings about the
consequences of edling iiwrcury-coi^tammiited
Itsh or otlier seafood front selected watercourses
in the bldtu
D
Slates that liave reopened spot t or commercial
fisheries nr rescinded health warnings issued
since 1970
States that report no closuies of spoil or
commercial fisheries, and no health warnings
aboul mercury pollution since 1970.
Source: NRC0978)
FIGURE 14 STATUS OF FISHERY RESTRICTIONS AND CLOSURES IN THE UNITED STATES. 1977
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Though there are considerable data concerning mercury contamination
of fish (see Chapter IV, WHO 1976, and NRC 1978), most of"it is 5 or more
years old. Levels do not appear to vary much in marine species with
time, but levels in freshwater species vary to a greater degree. The
most recent and comprehensive survey of levels of mercury in fish was
conducted by Hall et_ al. (1978). These authors found that muscles of
most finfish had mean mercury levels below 0.3 mg/kg. Thirty-one species
contained mean levels in excess of the previous action level (0.5 mg/kg);
however, less than 2% of the U.S. catch was in excess of the 0.5 mg/kg
action level. Detailed information on contamination levels can be found
in Hall _et _al. (1978).
These data on concentrations of mercury in aquatic organisms, as
well as data from other sources, have been used by other authors to
calculate exposures to mercury for various subpopulations. The various
assumptions used in each resulted in widely variable estimates. The
most detailed estimate was performed by NMFS (1978). They used the
extensive monitoring of Hall et_ al. (1978), as well as a fish consump-
tion survey which included 25,947 participants. The amounts of each
species consumed by an individual were combined with the concentration
of mercury for that species as measured in the Hall ejt al. (1978) survey
(using the value at the 95% confidence limit) in order to estimate the
intake in an individual. NMFS (1978) used various action limits to deter-
mine the chance of a person's exceeding their Allowable Daily Intake (ADI),
The ADI was 30 ug/70 kg, adjusted to individual body weights". The
results of this exercise are shown in Table 20 These data suggest that
if the sample of the human population, as well as the seafood survey,
are representative, approximately 0.1-0.2% of the population is exposed
to mercury in seafood (with 95% confidence limits) amounting to more than
0.43 ug/kg body weight/day.
Other authors (U.S. EPA 1979, NRC 1978) have used levels in tuna
for calculating mercury intakes, using the assumption that tuna makes
up 75% of the fish intake. This would appear to underestimate exposure
for consumers of large amounts of seafood. The consumption patterns
of the persons exceeding their ADI (NMFS 1978) showed that, in many
cases, the greatest proportion of mercury intake was due to consumption
of less common, but more highly contaminated species of fish. Table 21
shows intake for two such persons, who represent the maximum calculated
intakes based on consumption patterns in the survey. The upper limit
daily intake in the table was calculated using the mercury concentration
value at the 95% confidence level for a given species, while the maximum
intake calculation in the table uses the maximum reported contamination
for a given species and assumes that levels in fish consumed are not
being restricted (no action limit). This table shows that a small
percentage of the population (<.008% may be receiving intakes of mercury
in seafood in excess of 100 ug/day. With the 0.5 ug/g action limit,
the upper limit daily intake was reduced to 80 ug/day, but the maximum
(again with the action limit) for the same individual was 222 ug/day.
136
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TABLE 20. PERCENT OF POPULATION EXCEEDING THE RECOMMENDED
ADI FOR MERCURY DUE TO FISH CONSUMPTION1
Grouf
Total
No.
Persons
24,652
No Action Limit 0.5 mg/kg action limit
0.19 0.11
Women of child-
bearing age
3,884
0.15
0.10
Children
4,423
0.34
0.20
Data based on intakes caluclated using consumption data for population
combined with 95% CL for concentration data for species consumed. A
75% compliance with the action limit was assumed.
Source: NMFS (1978).
137
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TABLE 21. MAXIMUM INTAKE OF MERCURY FOR TWO FISI1EATERS
oo
Person
Species
Person 1 Pike
Bass
Perch (marine)
Not identified
Person 2 Pike
Bass
Perch (marine)
££serving
206
167
144
150
253
218
181
Serving/
month
15
3
2
1
19
4
2
Concen
in Fisl
Avg.
0.01
0.75
0.13
0.01
0.75
0.13
itration 95% confidence limits No 0.5 ug/
L-(!i£/£i No action 0.5 ug/g action action
Max. limit action limit limit- lin.ir
1.7 78.84
2.0
0.59
1.7 119.27
2.0
0.59
51.37 2i7 141
79.46 342 222
Source: Taken from NMFS (1978).
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The above discussions apply to a small proportion of the population
at higher risk. Most of the population (99.89%) is subject to exposure
to lower levels, less than 0.43 ug/kg/day or 30 ug for a 70-kg person.
U.S. EPA (1979) reported that for an average consumption of fish (17 g/
day), 3.0 ug/day of mercury would be consumed. This exposure assumed a
consumption of 17 g fish/day, 75% of which was tuna (containing 0.2 ug/g
mercury). The remaining 25% of the diet consisted of other fish con-
taining 0.1 ug/g of mercury.
Seafood is not the only source of mercury in the diet, although
other foods appear to have lower concentrations. Peyton ^jt al. (1975)
reported that intake of total mercury would range from 5.T~ug7day to
14.6 ug/day for a standard diet and a range of mercury concentrations
in food. The meat, poultry, and fish component of this diet contributed
2.9-8.4 ug/day. The same authors reported a maximum value from the
literature of 22.62 ug/day for this group of foods.
The source of methylmercury in the diet, however, is primarily
seafood, although other foods also contribute to the total mercury
intake (NRC 1978). There is, however, some controversy over how much
of the mercury in seafood is methylmercury. Table 22 shows the range of
reported results. Cox_et_al. (1979) point out that the ratio of methyl-
mercury to total mercury is highly dependent on the size of the fish
They found no methylmercury in a 23-cm sample, but 0.55 mg/kg in the
35-cm sample.
Thus, without actual measurement of mercury in diets, there seems
to be no basis for estimating doses of methylmercury. Both U.S. EPA
(1979) and NRC (1978) have assumed that the total mercury intake in fish
is in the form of methylmercury. This assumption will certainly provide
a worst case estimate of risk.
3. Inhalation
Levels of mercury in air have been discussed in Chapter IV. A, with
a wide range of total mercury concentrations reported. The form of
mercury in air is generally elemental mercury vapor (NRC 1978) and the
inhalation exposure route is expected to contribute little to the body-
burden of methylmercury. Table 23 shows the inhalation exposure esti-
mates utilized here. The results show that most exposure routes are
insignificant compared with the estimated intake through food. Only
laboratory or dental office exposures would be in a similar range, and
these are occupational exposures, that are subject to the threshold
limit of 0.05 mg Hg/m3. More typical exposures of persons periodically
visiting these areas would be considerably lower.
4. Dermal Absorption
Though dermal absorption of mercury ions or compounds in solution
may be an important exposure route in certain occupational settings
(WHO 1976), it is probably not significant for the general population
due to the low concentration of mercury ion or methylmercury usually
encountered in natural waters.
139
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TABLE 22. METHYLMERCURY CONTENT OF FISH
Location
Swedish
Japan, Italy, France,
Holland
Tennessee, U.S.
Maine
Freshwater
Methylmercury
(% of Total Mercury)
Source
>90 Suzuki et al. (1973), as
cited in Grieg and
Krzynowek (1979)
25-30 Vi (1971), as cited in
Krenkel (1973)
<50 Krenkel e_t al. (1972), as
cited in Krenkel (1973)
-100 Rivers et al. (1972), as
cited in Krenkel (1973)
58 Cox et. al. (1979)
Blue marlin was the exception - <25%.
140
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TABLE 23. INHALATION EXPOSURE TO MERCURY
u 1 a t i oi
Concentration in Air
Outdoors
rural
urban
near sources
(natural or
anthropogenic)
Endoors
general
laboratory
dental
30 (max.)
150-1,500
100-200
200-10,000
10,000-100,000
Exposure
(ng/day)
100
600
3,000-30,000
2,000-4,000
4,000-200,000
57,000-570,000'
Source
(see Chapter IV)
(see Chapter IV)
(see Chapter £V)
Battelle (1977)
Battelle (1977)
Battelle (1977)
1 3
Assumes 20 m /day respiratory rate.
2 3
Assumes 10 m inhalation/working day, 5-day work week
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5. Users of Mercury-Containing Products
The consumer is commonly exposed to products containing mercury,
specifically thermometers, batteries, lamps, instruments, and paints.
With the exception of paints, these exposures are accidental, and thus
difficult to quantify. Certainly, the sub-populations associated with
such exposures are small, Consumers may also be exposed to mercury
through the use of mercury-containing medical or cosmetic products.
The dermal absorption of mercury from these sources is expected to be
low, although inhalation can occur. In any case, such exposures would
generally be insignificant compared with food.
Two incidents of swallowing camera batteries by children have been
described in the literature. When new, these batteries contain approxi-
mately 2 g mercuric oxide, which could be lethal if released. Unfortu-
nately, these batteries degrade after ingestion and then may come apart.
In one case, the battery was extracted, while in the second"case it
passed through with the child's stool. In neither case was long-term
toxicity observed. However, this type of accident may not be unusual,
and the increasing use of these batteries is cause for concern.
6. Overview
The primary route of exposure of humans to mercury is through food,
especially seafood, which contains methylmercury. An average intake of
total mercury in food has been estimated as 5.4-14.6 ug/day. Average
consumption of mercury in seafood (methylmercury) is estimated to be
3.0 ug/day. A small proportion (0.1%) of the population (predominantly
fisheaters) is subject to exposures of greater than 30 ug/day. An even
smaller subpopulation (<0.01%) may be exposed to intakes of mercury of
greater than 100 ug/day.
14:
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REFERENCES
Agner, E.; Jans, H. Mercury poisoning and nephrotic syndrome in two
young siblings. The Lancet 2(8096):951; 1978.
Al-Shahristani H.; Shibab, K.M. Variation of biological half-life of
methylmercury in man. Arch. Environ. Health 28:342-344; 1974. (As cited
by NRC 1978)
Anderson, A. The rape of the seabed. SR/World, November 6:16-21; 1973.
(As cited by Goldwater 1974)
Baily, P.; Kilroe-Smith, T.A.; Rendell, R.E.G. Some aspects of biochem-
istry of absorption and excretion of lead and mercury. In: Clinical
chemistry and chemical toxicology of metals. New York: Elsevier/North
Holland Biomedical Press; 1977: 131-136.
Bakir, F.; Damluji, S.F.; Amin-Zaki, L.; Murtadha, M.; Khalidi, A.;
Al-Rawi, N.Y.; Kriti, S.T.; Dhahir, H.I.; Clarkson, T.W.; Smith, J.C.;
Doherty, R.A. Methylmercury poisoning in Iraq. Science 181:230-241;
1973. (As cited by NRC 1978)
Barbeau, A.; Nantel, A.; Dorlot, F. Etude sur les effets medicaux et
toxicologiques du mercure organique dans le nord-ouest Quebecois. Comite
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149
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CHAPTER VI.
BIOTIC EFFECTS AND EXPOSURE
A. EFFECTS ON BIOTA
1. Introduction
This section presents the available information about the levels
of mercury that disrupt the normal behavior and metabolic processes of
aquatic and terrestrial organisms. Although mercury has received wide-
spread publicity as an extremely toxic substance, the experimental data
for biota are not as extensive as might be expected.
A certain amount of inconsistency in the results of bioassay (even
for individual compounds) is to be expected, owing to several factors.
Some differences may be attributed to the nature of the bioassay proce-
dure (static versus continuous flow), or the use of calculated versus
measured concentrations. In addition, water parameters such as tempera-
ture and salinity have been shown to affect the toxicity of mercury to
various aquatic organisms. Other factors include the species and '
developmental stage of the test organisms used. Some species and
developmental stages may be more sensitive to mercury than others.
Variations in these parameters may yield different experimental results
and make comparisons among studies difficult.
2. Freshwater Organisms
a. Chronic and Sublethal Effects
Exposure to low levels of mercury may result in acclimation by
aquatic organisms, or in behavioral alterations such as ataxia, inappe-
tance, increased respiration, and reproductive inhibition. Prolonged
exposure, even to low concentrations of mercury, may ultimately lead to
mortality of sensitive species or otherwise decrease the vigor and
diversity of local populations to the point that they are endangered.
Panigrahi and Misra (1978) exposed climbing perch (Anabas scandens)
to 3 mg/1 mercuric nitrate for 36 days. After 5 days, the fish became'
letnargic and reduced their feeding, but regained pre-test behavior
3 days later. After 28 days, however, 71% of the fish had become blind
or exophthalmic, and this observation coincided with a marked loss of
weight. After 48 hours of exposure to 3 ug/1 mercuric chloride (HgClo)
brook trout (Salvelinus fontinalis) had increased cough frequency (an
effort by the fish to remove accumulated mucus in the gills) (Drummond
et al. 1974).
151
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Drummond _et _al. (1974) reported the same effect in brook trout after
8 days exposure to 3 ug/1 methyl mercuric chloride (CHsHgCl). Rainbow
trout (Salmo gairdneri) exhibited a loss of appetite during a 1^0-day
bioassay in 860 ug/1 CH3HGC1, and a loss of nervous control after 269
days in 1,600 ug/1 CH3HGC1 (Matida et al. 1971). In the same study, the
growth of the trout was inhibited in concentrations as low as .04 ug/1
during an exposure period of 64 days. The growth of alevin brook trout
was also reduced in 0.79 ug/1 in a chronic bioassay by Christensen
The only available information on chronic or sublethal toxicity to
freshwater invertebrates was from Biesinger _et al. (1979). Minimum'
chronic effects levels for Daphnia magna were 0.9 ug/1 and <0 01 ug/1
for HgCl2 and CH3HgCl, respectively.
Sufalethal effects in algae from exposure to inorganic mercury
(HgCl2) have been reported for concentrations ranging from 60 ug/1 for
mixed algae (Bllnn et al. 1977) to 2,590 ug/1 for Ankistrodesmus braunil
(Matson _et al. 1972). The effects observed included retarded growth
and inhibited rates of chlorophyll synthesis, respiration, and photo-
synthesis. Enzyme inhibition was reported in the latter species at a
concentration of 1,598 ug/1 CH3HgCl.
b. Acute Effects
Data on the acute toxicity of mercury to freshwater biota are
compiled and condensed in Tables 24-26. With respect to intra- and
inter-species differences, it should be noted that the LC^0 (concentra-
tions lethal to 50% of test organisms) values given were derived under
a variety of conditions.
Surprisingly few species of freshwater finfish have been bioassayed
for their sensitivity to inorganic mercury. On the basis of the limited
data, rainbow trout appears to be the most sensitive species.
Of the many organic mercury compounds, the five most frequently
used in freshwater bioassays are listed, with LC5o values, in Table^25.
Although the data are sparse, merthiolate and pyridylmercury acetate
appear to be less toxic than methylmercury, phenylmercury acetate, or
ethylmercury phosphate.
A number of invertebrates have been tested for sensitivity to
inorganic mercury (usually HgCl2). All available data are listed in
Table 26; no information was found on the toxicity of organomercurics
to invertebrates.
3. Marine Organisms
a. Chronic and Sublethal Effects
Information on sublethal mercury toxicosis in marine finfish is
152
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TABLE 24. ACUTE TOXICITY OF INORGANIC
MERCURY TO FRESHWATER FINFISH
Fish Species
LC_0 (ug/1 as Hg++)
Reference
Rainbow trout (Salmo gairdneri) 33-903
Striped Bass (Roccus saxatilis) 90
Banded killifish (Fundulus diaphamus) 110
American eel (Anguilla rostrata) 140
Carp (Cyprinus carpio) 180
White perch (Roccus americanus) 220
Coho salmon (Oncorhynchus kisutch) 240
Pumpkinseed (Lepomis gibbosus) 300
Johanna gachua 1,400
Wobeser (1973), Hale (1977)
Rehwoldt et_ al. (1972)
Rehwoldt _et al. (1972)
Rehwoldt _e_t _al. (1972)
Rehwoldt _e_t _al. (1972)
Rehwoldt _et al. (1972)
Lorz _et al. (1978)
Rehwoldt _et al. (1972)
Hanumante and Kulkarni
(1979)
153
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TABLE 25. ACUTE TOXfCTTIES OF ORGANIC MERCURY
COMPOUNDS TO FRESHWATER FINFISH
Cn
-P-
values (ug/1 as Ug-»-f)
Fish Species
Rainbow trout (Salmo gairdnerl)
Brown trout (Salmo trutta)
Brook trout (Salvelinus fontlnalis) 65-84
Lake trout (Salvelinus namaycush)
Channel catfish (Ictalurus punctatus)
Bluegill sunfish (Lepomis macrochirus)
Blue gourami (Trichogaster trichopterus) 89.5
Methylmercury
CH3 Hg Cl
24-42
-
65-84
-
-
-
Ethylmercury Phenylmercury
Phosphate Acetate
Et Hg P0/, Ph Hg Ac Merthiolate
43 5.1-1,781 10,505
26,760
39,910
1,055
50 35-3,750 2,800
31,960
PyridyJme
Aceta
-
2,954
5,082
3.6JO
-
7,600
Roales and Perlmutter (1974).
Source: See U.S. EPA (1979).
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TABLE 26. ACUTE TOXICITY OF INORGANIC MERCURY
TO FRESHWATER INVERTEBRATES
Species
Daphnia magna
Scud (Gammarus sp.)
Midge (Chironomous sp.)
Crayfish (Oronectes limosus)
Sludgeworm (Tubifex tublfex)
Rotifer (Philodina acuticornis)
Bristleworm (Nais sp.)
Damsel fly larvae
Caddis fly larvae
Stonefly (Acroneuria lycorius)
Mayfly (Ephemerella subvaria)
Snail (Amnicola sp.)
Crayfish (Procambarus clarki)
Crayfish (Faxonella clypeata)
LC,n (ug/1 as Hg++)
Reference
5
10
20
Biesinger and Christensen (1972)
Rehwoldt_et_al. (1973)
Rehwoldtjat_al. (1973)
50-1,000 (LC6Q) Dayle_et_al. (1976)
82-100 Brkovic-Popovic and Popovic (1977a)
518-1,185 Buikema_et al. (1974)
1,000
1,200
1,200-2,000
2,000
2,000
2,100
200-20,000a
200-20,000a
Rehwoldt et al. (1973)
Rehwoldt _et _al. (1973)
Rehwoldt _et al. (1973)
Warnick and Bell (1969)
Warnick and Bell (1969)
Rehwoldt ejt al. (1973)
Heit and Fingerman (1977)
Heit and Fingerman (1977)
24-96 hour test
155
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limited to a very few species, and excludes most of the organic mercury
compounds. The lowest concentration of mercury resulting in sublethal"
efrects was 10 ug/1 HgCl2, causing abnormal development in the mummichog,
Fundulus heteroclitus (Weis and Weis 1977a) and decreased respiration
in the winter flounder, Pseudopleuronecies americanus (Calabrese et al.
1975). " ~~ — —
In a study by Cunningham and Grosch (1978), brine shrimp were
exposed in different experiments to HgCl2 and CH3HgCl. Adult reproduc-
tive lifespans were significantly reduced at concentrations of 10 ug/1
HgCl2 and 5 ug/1 CH^HgCl. The mean number of broods declined as well
in concentrations of 1 ug/1 and 10 ug/1 HgCl2 and in 1 ug/1 CH,HgCl (no
lower concentrations were used). However. 10 ug/1 HgCl2 had no effect
on the average number of offspring produced in each brood, while 1 ug/1
CH3HgCl significantly reduced the fecundity of the shrimp.
The fiddler crab (Uca pugilator) exhibited an increased metabolic
rate when exposed to 1.8 ug/1 HgCl2- Sublethal effects in other inver-
tebrates included decreased egg and feces production, reduced shell
growth, and inhibition of limb regeneration. A summary of these and
other data is given with references in Table 27. [For a more complete
review of the literature, see Table 13 in U.S. EPA (1979).]
The lowest effects concentrations for marine plants (including
algae, diatoms, and kelp) have been reported by Berland et al. (1976),
who observed growth inhibition in 18 species of algae in~5~"ug/l to
15 ug/1 HgCl2. Other sublethal effects such as abnormal development,
decreases in chlorophyll mass, and reduced C02 consumption have been
observed at higher concentrations. Among the nine organomercuric com-
pounds tested, three used by Harriss et al. (1970) reduced photosynthesis
in the diatom (Nitzchia delictissima) at a concentration of 0.1 ug/1.
[For more detailed information on the toxicity of mercury to marine
plants, see Table 11 in U.S. EPA (1979).]
b. Acute Effects
The mummichog is apparently the only saltwater fish that has been
tested for acute mercury toxicosis. Both the highest and lowest LC50
values (200 ug/1 and 6,800 ug/1) have been reported by Dorfmann (1977).
For a number of invertebrate species that have been tested, the LC5Q
concentrations range from 3.6 ug/1 to 32,000 ug/1. The most sensitive
species was the mysid shrimp, closely followed by the hardshell clam
and the Eastern oyster. The available data are compiled in Table 28.
4. Other Studies
The only available information on the impact of mercury on ecosys-
tems is a study by Sigmon _et al. (1977) on a freshwater community
composed of primary producers, herbivores, and carnivorous midges. A
one-year exposure to HgCl9 at concentrations of >0.1 ug/1 resulted in
reduced algae populations, and numbers and diversity of faunal species.
No effect on the midges was apparent.
156
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TABLE 27. SUBI.ETUAT, EFFECTS OF MERCURY ON MARINE FAUNA
Spec ieH
Concentration
Compound^ (li8/JL as Hg-H )
Test
Duration
Effect
Muniiiiicliog (J^njdulusi he_terocli_tus)
embryo
adult
adult
Winter flounder (j^seiidopleurone£tes
illO££icamis_) adult
Fiddler Crab (Utea jnig i latoj;)
<-ri zoea
Copepods (_fi_ve genera)
Copepod (_Ps eud oca la n us mi nut us)
Barnacle (Balanus balanoides)
cypr id
Eastern oyster (Crassojstrea virginica)
adult
Pacific oyster (Crassostrea gigas)
larva "
Polycliaete (Ct_enod_Hus serratus)
Fiddler cral) (Uca sp.)
adult
HgCl2
HgCl2, CH3lIgCl
HgCl
"X2
HgCl2
HgCl2
HgCU
UgCb2COOH
HgCl.
HgCl,
10-20
125
1,150
10
1.8
10
32
50
300-500
72 h.
24 h.
96 h.
60 d.
24 h.
2-10
5
10
10 d.
70 d.
<2 h.
Some development
abnormalities
Disrupted osmoregulation
Aberrant behavior
Decreased respiration,
blood chemistry changes
Increased metabolic rate
Decrease in egg and fecal
pellet production
Growth inhibition
Substrate attachment
inhibition
15 half days Reduced shell growth
24 h.
Abnormal development
21 d. Reproduction inhibited
32 d. No limb regeneration
Source: Table 13 in U.S. EPA (1979).
-------
TABLE 28. ACUTE TOXICITY OF INORGANIC
MERCURY TO MARINE ORGANISMS
Fish Species
Mummichog (Fundulus heteroclitus)
Invertebrate Species
Mysid shrimp (Mysidopsis bahia)
Hardshell clam (Mercenaria mercenaria)-embryo
Eastern oyster (Crassostrea virginica)-embryo
Copepod (Acartia clausi)
Grass shrimp (Palaemonetes vulgaris)-larva
Copepod (Acartia tonsa)
LC5() (ug/1 as Hg++)
References
200-6,800 Dorfman (1977)
3.6-3,9
4.8
5.6
10
10
10-20
Polychaete (Capitella capitata)-larva 14
Crab (Carcinus maenus) 14-1,200
White shrimp (Peneus setiferus)-adult 17
Lobster (Homarus americanus) 20
Polychaete (Neanthes arenaceodentata) 22-100
Hermit Crab (Pagarus longicarpus)-adult 50
Starfish (Asterias _forbesi)-adult) 60
Sandworm (Nereis virens_)-adult 70
Copepod (Pseudodiaptomus coronatus) 79
Prawn (Pandalus montaqui) 80
Bay Scallop (Argopecten irradians)-juvenile 89
Copepod (Eurytemora affinis) 158
Copepod (Tigriopus japonicus) 223
Softshell clam (Mya arenaria)-adult 400
Ambassis safgha 2,800
Platicthys flesus 3,300
Clam (Rangia cuneata)-adult 5,100
Mud snail (Nassarius absoletus)-adult 32,000
Sosnowski et al,
Calabrese et al,
(1979a)
(1977)
Calabrese et_ al. (1977)
Gentile e_t al. (1979)
Shealy and Sandifer (1975)
Sosnowski and Gentile (197S
Sosnowski e_t al. (1979b)
Reish et_ al. (1976)
Conner (1972)
Portmann (1968)
Green e_t al. (1976)
Johnson and Gentile (1979)
Reish e_t al. (1976)
Eisler and Hennekey (1977)
Eisler and Hennekey (197 )
Eisler and Hennekey (1977)
Gentile et. al. (1979)
Portmann and Wilson (1971)
Nelson e_t al. (1976)
Gentile _e_t al. (1979)
Sosnowski e_t al. (1979b)
Eisler and Hennekey (1977)
Portmann and Wilson (1971)
Portmann and Wilson (1971)
Olson and Harrel (1973)
Eisler and Hennekey (1977)
158
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5. Factors Affecting the Toxicity of Mercurv
Several variables in a natural aquatic environment may strongly
influence the availability and toxicity of mercury to biota. Among these
parameters are temperature and salinity; other important factors that
have not been adequately tested are pH and water hardness. Fish size
and sex have been studied for their association with sensitivity to
mercury. The interaction of mercury with other aqueous chemicals may
modify its toxicity either by synergy or inhibition; however, such rela-
tionships remain to be studied in detail. Perhaps the most important
aspect of mercury affecting its toxicity is its chemical form. Although
the data are inconsistent, organic forms appear to be generally more
toxic than inorganic mercury.
According to MacLeod and Pessah (1973), "temperature is the most
important environmental factor controlling rates of biological process"
in aquatic biota. In a bioassay with rainbow trout, they found that
increasing the temperature from 5° to 20°C decreased the 96-hour LC50
from 400 ug/1 to 220 ug/1 mercuric chloride. In an experiment with six
Hudson River fish species, Rehwoldt _et al. (1972) determined an acute
toxicity range of 370-740 ug/1 inorganic mercury at 15°C. When the
temperature was increased to 28°C, the range of LC50 values decreased
to 80-420 ug/1. The same effect has been noted for both freshwater and
marine invertebrates. Heit and Fingerman (1977) exposed crayfish
(Faxonella clypeata) to HgCl2 solutions varying between 10"7M and
4 x 10~6M, and found that the specimens maintained at 20°C survived in
greater numbers than those at 30°C. Jones (1973) has reported substan-
tially higher mortality in two estuarine isopods (Jaera albifrons and
j;. nordmanni) with a rise of only 5°C (from 10° to 15°C) in 1 mg/1 HgCl2.
Similar, but somewhat less pronounced results were also observed with
two species of marine sowbugs, Idotea neglecta and _I. emarginata.
The effects of variations in salinity are not as well documented,
and consequently are less understood. Jones (1973) exposed four species
of isopods (above) to 1.0 mg/1 and 0.1 mg/1 mercury at salinities
ranging from 1% to 100% seawater. All species were more sensitive in
the less saline solutions, with the most pronounced change in the two
estuarine (Jaera) species. The combined effect of decreasing salinity
and increasing temperature was particularly lethal, possibly because
of changes in the rates of absorption. The only other study on the
effects of salinity changes on mercury toxicity (Dorfman 1977) indicated
no significant trends for the mummichog.
Two studies on mercury toxicity have reported sex-related differ-
ences in sensitivities. In two species of crayfish, Procambarus clarki
and Faxonella clypeata, females exhibited substantially more resistance
to mercury than males. For example, 50% of the male _?'. clarki test
group exposed to lO^M HgCl2 died within 72 hours, while all the females
survived in good health until the end of the experiment at 30 days (Heit
and Fingerman 1977). However, a bioassay with brine shrimp (Artemia
salina) found that females were "physiologically more stressed" than
159
-------
males after exposure to 1 ug/1 and 2 ug/1 CH3HgCl. Any differences that
do exist between sexes with regard to mercury sensitivitv mav be species-
specific.
Heit and Fingerman (1977) also found that larger specimens of the
two crayfish species tested were more resistant to HgCl2 than smaller
specimens. In this respect, the results were similar for both males and
females.
Heavy metals and other substances often act together to produce or
mitigate toxic effects, although few such interactions have been studied
in the case of mercury. Calamari and Marchetti (1973) exposed rainbow
trout to mixtures of mercury and surfactants. Each surfactant was tested
separately in a mercury-detergent pair. The combinations of mercury and
anionic surfactants (ABS and LAS) produced toxic effects that were "more-
than-additive," while the mixture of nonylphenol ethoxylate (a non-ionic
surfactant) and mercury seemed to produce "less-than-additive" effects.
An antagonistic relationship between methylmercury and copper was
observed by Roales and Perlinutter (1974) in a bioassay with the blue
gourami (Trichogaster trichopterus). While 90 ug/1 copper killed 44%
and 90 ug/1 CH3HgCl killed 56% of a test group separately, many fewer
mortalities occurred when the two metal solutions were mixed in varying
proportions. In solutions of 20% Cu/80% CH3HgCl and 60% Cu/40% CH3HgCl,
all the fish survived the 96-hour exposure period. The authors suggested
that the less toxic copper protected the fish from the effects of methyl-
mercury, but no mechanism was hypothesized.
An interaction between mercury and selenium in the natural environ-
ment has also been observed. Beijer and Jernelov (1978) report that
these two metals coaccumulate in all marine organisms that have been
investigated. They hypothesize that this phenomenon occurs in normal
homeostatic regulation, and that the mercury helps the organism retain
essential levels of selenium. The authors note that experiments in
animals have shown that selenium compounds exert a "protective effect"
and decrease the toxic action of organic and inorganic mercury. However,
this Hg-Se relationship may have deleterious effects, as it results in
increased retention of mercury by the organism which may, in turn, lead
to a higher mercury body burden in the individual and an increased rate
of biomagnification in the food chain.
It should be noted, however, that the presence of selenium in the
tissues is not necessarily a fail-safe protection for all organisms.
Harbor seals found along the Netherlands coast exhibited definite signs
of mercury toxicosis despite a strong correlation of mercury and
selenium in their livers (Koeman _et_ _al. 1973).
Although the toxicity data discussed previously in this chapter are
subject to various interpretations, organic compounds of mercury are
generally considered to be more toxic than inorganic forms. Intone
comparative study available, Cunningham and Grosch (1978) concluded that
160
-------
methylmercury produced sublethal and lethal effects in brine shrimp at
lower concentrations than mercuric chloride. Boney _e_t _al (1959) com-
pared the effects of different organomercurics on the red alga, Plumaria
elegans, and found that toxicity increased with an increase in the number
or carbon atoms in the side chain. For example, n = C3H7HgCl was found
to be approximately four times as toxic to P_. elegans as CHoHgCl. Non-
alkyl forms such as phenyl- and diphenylmercuries also appear to be
substantially more toxic than inorganic mercury. This order of relative
toxicity for organomercurials may be reversed in mammals, including man,
where methylmercury is very toxic and preliminary data suggest that
toxicity of other alkylmercurials decreases with increasing alkyl chain
length. Phenyl and diphenylmercury seem even less toxic in mammals,
possible due to rapid conversion to inorganic forms in the blood (WHO
1976) .
6. Terrestrial Biota.
a. Animals
„ - StUdy °f the effects °f methylmercury dicyandiamide,
Heinz 1974) exposed mallard ducks (Anas platyrhynchos) continuously to
0.3 mg/kg Hg in the diet. At the end of the study, no health effects
were apparent in the adult ducks. Reproductive effects included the
production of smaller eggs than controls, and ducks fed 3 mg/kg Hg had
only 46 o% as many 1-week-old ducklings as the controls due to hatch
failure and mortality. The offspring of the ducks fed 0.5 mg/kg Hg had
an increased growth rate compared with the controls and the 3 mg/kg
group. No eggshell thinning was observed. The calculated LC50 for
10-day-old mallard ducklings over 8 days was reported at 60 mg/kg methvl-
mercury dicyandiamide (Hill, unpublished data). Heinz and Locke (1976)
observed that mallard ducklings did not die when ingesting 3 mg/kg
methylmercury in their diets, whereas ducklings (fed a clear diet) whose
parents were fed 3 mg/kg Hg perished within 3 to 6 days.
A similar experiment on black ducks (Anas rubripes) was conducted
by Finley and Stendell (1978). Adults were fed 3 mg/kg methylmercury
dicyandiamide for 28 weeks in two consecutive breeding seasons. The
only apparent effect in adults was hyperactivity in several individuals,
which suggested possible mercury poisoning. Again, reduced hatching and
higher duckling mortality was found in the test group compared with the
control group. However, a slight improvement in reproduction was noted
during the second year and residues in eggs, embryos and ducklings of
that year were lower than those of earlier offspring. The form of the
mercury in these tissues was not determined. Thus, the possibility exists
that the hens were better able to metabolize the mercury during the
second year. Partial demethylation of the mercury by the hens could
account for the improved reproduction and lower embryo residues observed.
The authors noted that biotransformation of mercury has been shown to
occur in the rat (Norseth and Clarkson 1970) and in guinea pigs (Iverson
and Hierlihy 1974) .
_ _ _ Studies cited by Heinz (1974) reported mortality in goshawks fed
cnicKen livers containing 13 m^/kg Hg (Borg _et al. 1970).
161
-------
b. Plants
Kn,5 :^T °?ly formation on mercury toxicosis in plants available for
trtis report was a study by Lipsey (1975) on maize seedlings (Zea navs^
Signif icant amounts of mercury were absorbed and translocated~bv" The" '
seedlings germinating in CH3HgOH. Root growth was inhibited when the
roots contained >10 mg/kg Hg, while shoot growth was reduced at 0.6 mg/kg,
7. Conclusions
The lowest concentration at which effects were observed in an aqua-
tic organism was <0.01 ug/1 CH3HgCl, a chronic effects value for Daohnia
S^; asTS* ^hibited in "^ov trout at CH3HgCl concentring
Adverse effects on reproduction occurred in brine shrimp at CH.HgCl
concentrations of 1 ug/1. In marine finfish, sublethal effects were
observed in 10 ug/1 HgCl2 and CH3HgCl in the mummichog, and in 10 ug/1
HgCl2 in the winter flounder. The minimum effects concentration for a
marine diatom was 0.1 ug/1 for three different organic forms of mercury.
_ Rainbow trout were again the most sensitive fish in acute bioassavs
with LC50 values of 5.1 ug/1 and 33 ug/1 for phenylmercuric acetate and
HgCl2, respectively. For all other groups of organisms, only toxicitv
data for inorganic mercury were found. The LC50 for Daphnia' was 5 u-/l.
The mummichog was the only marine fish tested for acute' toxicosis and
had a minimum LC50 of 200 ug/1. The most sensitive marine invertebrate
was apparently the mysid shrimp, with an LC50 of 3.6 ug/1.
Studies indicate that the toxicity of mercury increases with
increasing water temperature. Some species, particularly estuarine
organisms, may be more susceptible to mercury as salinity decreases.
It has been suggested that increasing temperature and decreasing salinity
act synergistically to increase absorption rates, thus rendering an
aquatic organism more susceptible to mercury toxicosis.
According to one study, copper interacts antagonistically with
methylmercury, thus effectively reducing the latter 's toxicity to
aquatic life. Selenium and mercury occur in 1:1 molar ratios in the
tissues ot all aquatic organisms tested. Apparently selenium mitigates
the adverse effects of mercury, but the relationship is not well under-
stood.
Mercury can appear in a variety of compounds, both inorganic and
organic, in the environment. The evidence suggests that the organic
compounds (particularly alkyl- and phenylmercurics) are more toxic than
inorganic forms, and that methylmercury is more ubiquitous than inorganic
forms.
Studies of the effects of mercury on terrestrial organisms have been
limited. Dietary concentrations of 3 mg/kg CH3HgCl produced adverse
reproductive effects in mallards and black ducks; oral doses of 13 mg/kg
and 60 ing/kg were lethal to goshawks and ducklings, respectively. Resi-
dues of ^0.6 mg/kg and 10 mg/kg in maize seedlings resulted in growth
inhibition in the shoots and roots, respectively.
162
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B. EXPOSURE TO BIOTA
1. Introduction
The previous section shows that mercury, especially organic forms,
can be toxic to biota. However, as discussed in Chapter IV. A, organic
forms of mercury are not predominant in the environment, although levels
of organic mercury can be high in the tissues of aquatic organisms.
Chapter IV also discussed the routes of exposure to organic mercury and
generally concluded that bioaccumulated organic mercury originates from
consumption of lower trophic organisms containing these forms, as well
as through the rapid accumulation and relatively slow clearance of
methylmercury formed in the sediment.
Thus, the implications for aquatic exposure and risk are unclear.
Although aquatic organisms are apparently more susceptible to the organic
.orms of mercury, these forms are rarely found at high levels in natural
waters. Aquatic organisms can accumulate methylmercury, although the
levels of accumulation have not been specifically correlated with effects
on aquatic organisms as they have for humans.
i
Therefore, although differing by on the order of one to two orders of
magnitude for some species, the toxicities of organic versus inorganic
forms of mercury were not distinguished in the exposure analysis. °The
lowest reported effects concentrations, regardless of the form of mercury
involved were combined to provide a conservative reference point for use'
in evaluation of ambient concentrations of total mercury.
2. Monitoring Data for Aquatic Systems
Information on the levels of mercury in the environment is readily
available from numerous sources but ambient levels reported are often
quite close to the detection limits of analytical methods used during
the 1970s. As a consequence, caution is needed when attempting to com-
pare ^ observed levels. In the analysis of aquatic exposure, STORET
provided the most comprehensive and internally consistent set of data,
and so was the main source used. The main problem with these data was
that they do not distinguish between the inorganic and organic fraction
of the total. Both organic and inorganic toxicity data for the more
sensitive species were used to determine "threshold" mercury concentra-
tions that might be harmful. On the basis of the data summarized in
Table 29, mean and maximum values for total mercury of >0.5 ug/1 and
>10.0, respectively, were chosen for use in the exposure analysis.
Concentrations of 0.5 ug/1 mercury were selected as an approximate level
above^which chronic and sublethal toxicosis might appear in sensitive
aquatic biota. Since concentrations exceeding 10.0 ug/1 are lethal for
a number of species under laboratory conditions, this was considered a
potential fish -kill level. The U.S. EPA (1980) has set the ambient water
quality criterion to protect freshwater aquatic life at 0.20 u*/l (total
recoverable mercury) as a 24 hr. average, and 4.1 ug/1 as a maximum.
163
-------
TABLE 29. LOWEST MERCURY CONCENTRATIONS HAVING TOXIC
EFFECTS ON AQUATIC ORGANISMS
Lowest Reported Effect Level (ug/1)
Form of
Mercury
Inorganic
Freshwater
1 nvertebra te
0.9a (Daphnla
magna)
Freshwater
Fish
t (Salvelinus
fontinalis)
Marine
Invertebrate
5b (Pseudocal unus
minutus)
Marine
Fish
10 b (Fundulus
Jieterocl
£
5 (Daplinta
magna)
33. O (Salmo
gairdneri)
3 . 6 c (Mys tdopsis
bahia)
200 (Fundulus
heterocli tux)
Organic 0.1
a
(Daplmia
magna)
0.04 (Salmo
gairdneri)
1.2 (Mysidopsis
hahia)
125 a (Fundulus
heteroclitus)
5.1 (Salmo
gairdneri
150 (Ganimarus
duebeni)
-3
Chronic value
bSublethal effect
'Acute value (LC )
Source: Tables 24-28.
-------
TABLE 30. MINOR RIVER BASINS WITH MEAN TOTAL MERCURY LEVELS
EXCEEDING 0.5 ug/1 AND/OR MAXIMUM MERCURY LEVELS
EXCEEDING 10.0 ug/1, 1979
Mercury Level (ug/1)
Basin
1-32
1-33
1-34
2-3
2-5
2-6
2-7
2-8
2-12
3-7
3-24
3-32
5-2
5-6
5-10
5-21
7-19
7-22
9-4
9-10
10-3
10-5
10-9
10-14
10-15
10-21
12-5
12-6
13-2
13-3
13-7
13-8
14-3
14-5
14-6
14-7
Middle Hudson R.
Lower Hudson - N.Y. Metropolitan Area
New Jersey Coast
Delaware R., Zone 1
Delaware R., Schuykill
Delaware R., Zone 2
Delaware R., Zone 3
Delaware R., Zone 4
Susquehanna R.
Yadkin - Pee Dee - Lower Pee Dee Rivers
Tampa Bay Area
Choctawhatchee R.
Monongahela R.
Hocking R.
Scioto R.
Ohio R., Main stem, minor tributaries
Meramec R.
Mississippi R. - Cape Girardeau Area
S. Central Missouri R.
S. Platte R.
Verdigris R.
White R.
Arkansas R. - Tulsa to Van Buren
Washita R.
Upper Red R. - Above Denison
Lower Mississippi R. - Natchez to Gulf
Colorado R.
Guadelupe Lavaca & San Antonio Basin
Clark Fork - Pend Oreille R.
Spokane R.
Central Snake R.
Middle and Lower Snake R.
San Francisco Bay Region
Santa Clara R.
Los Angeles R.
Santa Ana R.
Mean
0.6
1.1
1.0
1.2
1.8
1.6
1.4
0.8
0.7
0.8
1.8
0.6
-
0.6
0.7
0.7
1.0
2.2
-
0.6
0.6
0.6
0.6
0.7
0.6
-
1.5
1.0
1.0
0.6
0.6
0.7
0.7
2.4
2.7
3.2
Maximum
.
33.0
-
-
25.0
-
-
-
-
-
34.0
-
18.0
-
-
-
—
40.0
20.0
-
12.0
11.0
-
-
-
20.0
-
-
-
-
-
50.0
-
-
-
-
No. Samples
35
546
305
174
85
67
76
396
26
536
78
9
181
24
63
187
1
19
265
45
102
202
105
30
72
147
35
22
25
483
336
204
37
32
415
143
Source: U.S. EPA, STORET (1979).
165
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The highest mean levels of mercury in surface x.;ater in 1978-1979
occurred mainly in the North Atlantic, Ohio River, South Central Lower
Mississippi River, Pacific Northwest, and California basins (see Table 30)
The maximum values (> 10 ug/1) appear to reflect isolated events rather
than ambient conditions, and are distributed throughout the country.
STORET data for mercury levels in ambient water between 1970 and
1979 indicate generally decreasing levels over this period (see Chapter
IV). However, the significance of the changes is uncertain, for example,
1970 may have had unusually high concentrations of mercury, thus dis-
torting any real trend. In order to determine more accurately the trend
of aqueous mercury levels, it would be necessary to analyze the data for
previous years as well. Data for sediment and fish tissue levels were
insufficient to permit a trend analysis. Numerous events of exposure of
fish to mercury in the environment have been reported. Incidents of high
accumulation levels (exceeding FDA guidelines) are reported occasionally.
A discussion of mercury levels and sources of contamination is contained
in Chapter IV as well as the Appendix. No fish kills attributed to
mercury have been reported in the HDSD Fish Kill Incident files in the
last decade.
3. Factors Affecting Aquatic Exposure to Mercury
Certain environmental conditions increase the availability of
sediment-bound mercury to aquatic organisms. Rates of mercury methyla-
tion in sediment have been observed to increase when a removal mechanism
is present. In undisturbed stream beds, methylmercury is generally
released very slowly. It is more likely to be released in sediment that
is turned over and has greater contact with water, such as in fast flow-
ing streams with bed rolling, in systems supporting active benthic macro-
faunal populations, and during spring floods or after rainfall events.
Laboratory studies indicate that the half-life of mercury in undisturbed
sediment is 6-20 years. However, under natural conditions the half-life
is shorter; a half-life of 1-3 years was estimated in sediment in various
sections of the Ottawa River (ORPG 1979).
The physical removal of mercury from a local aquatic system occurs
via: (1) sediment transport; and (2) desorption from sediment to water
and subsequent water transport, with the latter process more significant
(ORPG 1979). Chemical variables, such as pH and the composition of the
sediment, influence the rate and degree of desorption of mercury from
sediment, and thus directly control the availability of mercury for
uptake. (Discussion of the adsorption process can be found in Chapter V.
B.).
4. Exposure of Terrestrial Organisms
Existing data on the exposure of biota to mercury indicate that
terrestrial organisms rarely encounter levels greater than natural
background concentrations. With the recent severe reduction in the use
of mercury as a fungicide in grain seed, the significance of a major
166
-------
are
* "'"—'In.
and
are exposed to ele ed ccentrations'of""113 *" "hlch "rcu1*" ls
hand, sine, the species of concern ar Wghly Jli^ih °° '^ °ther
be intan.ittenc and perhaps tnsignif icantln^e ^sef '" eXPOS"re ""
..Conclusions
tota! mercury i
to
°th"
pat^s,
food
residues in biotic tissue
tO high methylmercury
Ohio River, South Centr Lower
and California regl0ns ? InLden s
10 ug/1 were distributed throughout
with any particular region or indusv
Of
N°rth Atlantic,
thweSt
exceedin§
""
ated with the followin ndustries
mills, and waste disposal ponds from
reporting of incidents represents onlv n
it is likely that other sources identlfiedln'cL^
Potential sources of exposure for ^at ie'organ^s
or raore
„ "*
H°Wever' since the
167
-------
The use of mercury in grain seed treatment has been considerably
reduced in the last decade, thus obviating one of the more important
paths for the entry of mercury into food chains. However, certain
industrial and mining operations produce emissions that can increase
local mercury concentrations to potentially toxic levels. Tissue
samples from animals collected near such sources reveal mercury resi-
dues well above the levels in control specimens.
168
-------
REFERENCES
Beijer, K. ; Jernelov, A. Ecological aspects of mercury - selenium inter-
actions in the marine environment. Environ. Health Persp. 5:43-45;
1978.
Berland, B.R. et al. Action toxique de quatre metaux lourds sur la
croissance d'algues unicellulaires marines. C.R. Acad. Sci. Paris,
282, Ser. D:633; 1976. (As cited by USEPA 1979)
Biesinger, K.E.; Christensen, G.M. Effects of various metals on survival,
growth, reproduction, and metabolism of Daphnia magna. J. Fish. Res.
Bd. Can. 29:1691; 1972. (As cited by USEPA 1979)
Biesinger, K.E. .et al. The chronic toxicity of mercury to Daphnia magna
1979. (As cited by USEPA 1979) —
Blinn, D.W. et_ a±. Mercury inhibition on primary productivity using
large volume plastic chambers in situ. J. Phycol. 13:58; 1977.
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Boney, A.D. Sub-lethal effects of mercury on marine al°-ae. Marine Poll
Bull. 2:69-71; 1971.
Boney, A.D. Jit al. The effects of various poisons on the growth and
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Pharmacol. 2:37-49; 1959. (As cited by Boney 1971)
Borg, K. et al. Environ. Pollut. 1:91; 1970. (As cited in Heinz
1974)
Brkovic-Popovic, I.; Popovic, M. Effects of heavy metals on survival
and respiration rate of tubificid worms: Part I — Effects on survival.
Environ. Pollut. 13:65-72; 1977a. (As cited by USEPA 1979)
Buikema, A.L. Jr. Rotifers as monitors of heavy metal pollution in
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Calabrese, A. .et al. Sublethal physiological stress induced by cadmium
and mercury in winter flounder, Pseudopleuronectes americanus. In:
Sublethal effects of toxic chemicals on aquatic animals. Amsterdam:
Elsevier Science Publishing Company; 1975:15. (As cited by USEPA 1979)
Calabrese, A. _et al. Survival and growth of bivalve larvae under heavy-
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169
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Calamari, D.; Marchecti, R. The toxicity of mixtures of metals
and surfactants to rainbow trout (Salmo gairdneri Rich.)- Water Res.
7:1453-1464; 1973.
Christensen, G.M. Effects of metal cations and other chemicals
upon the in vitro activity of two enzymes in the blood plasma of the
white sucker, Catostomus commersoni (Lacepede). Chem. Biol. Int. 4:351
1975. (As cited by USEPA 1979)
Connor, P.M. Acute toxicity of heavy metals to some marine larvae.
Marine Pollut. Bull. 3:90; 1972. (As cited by USEPA 1979)
Cunningham, P.A.; Grosch, D.S. A comparative study of the effects of
mercuric chloride and methyl chloride on reproductive performance in
the brine shrimp, Artemia salina. Environ. Pollut. 15:83-99; 1978.
Dorfman, D. Tolerance of Fundulus heteroclitius to different
metals in salt waters. Bull. N.J. Acad. Sci., 22(2):21-23; 1977.
Doyle, M. ; Koepp, S.; Klaunig, J. Acute toxicological response of the
crayfish (Orconectes limosus) to mercury. Bull. Environ. Contam. Toxicol.
16:422-424; 1976. (As cited by USEPA 1979)
Drummond, R.A. et a_l. Cough response and uptake of mercury by brook
trout, Salvelinus fontinalis, exposed to mercuric compounds at different
hydrogen-ion concentrations. Trans. Am. Fish. Soc., 103:244; 1974.
(As cited by USEPA 1979)
Eisler, R.; Hennekey, R.J. Acute toxicities of Cd+2, Cr+6, Hg+2, Ni+2,
and Zn+2 to estuarine tnacrofauna. Arch. Environ. Contam. Toxicol.
6:315; 1977. (As cited by USEPA 1979)
Finley, M.T.; Stendell, R.C. Survival and reproductive success
of black ducks fed methylmercury. Environ. Pollut. 16:51-64; 1978.
Gentile, J.H. et_ jtl. Manuscript. 1979. (As cited by USEPA 1979)
Green, F.A. Jr. et al. Effect of mercury on the survival, respiration
and growth of postlarvae white shrimp, Penaeus setiferus. Marine Biol.
37:75; 1976. (As cited by USEPA 1979)
Hale, J.G. Toxicity of metal mining wastes. Bull. Environ. Contam.
Toxicol. 17:66; 1977. (As cited by USEPA 1979)
Hanumante, M.M.; Kulkarni, S.S. Acute toxicity of two mollusci-
cides, mercuric chloride and pentachlorophenol to a freshwater fish
(Channa gachua). Bull. Environ. Contam. Toxicol. 23:725-727; 1979.
Harriss, R.C. _e_t _al. Mercury compounds reduce photosynthesis by
plankton. Science 170:736; 1970. (As cited by USEPA 1979)
170
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Heinz, G. Effects of low dietary levels of methylmercury on mallard
reproduction. Bull. Environ. Contain. Toxicol. 11:386-392; 1974.
Heinz, G.; Locke, L.N. Brain lesions in mallard ducklings from parents
fed methylmercury. Avian Dis. 20:9-17; 1976. (As cited by Finley and
Stendell 1978)
Heit, M. ; Fingerman, M. The influences of size, sex, and temperature
on the toxicity of mercury to two species of crayfishes. Bull. Environ.
Contam. Toxicol. 18:572-580; 1977.
Hill, E.F. Unpublished data. (As cited by Heinz 1974)
Iverson, F.; Hierlihy, S.L. Biotransformation of methylmercury in the
guinea pig. Bull. Environ. Contam. Toxicol. 11:85-91; 1974. (As cited
by Finley and Stendell 1978)
Johnson, M.W. ; Gentile, J.H. Acute toxicity of cadmiu, copper
and mercury to larval American Lobster (Homarus americanus). Bull.
Environ. Contam. Toxicol. 22:258-264; 1979.
Jones, M.B. Influence of salinity and temperature on the toxicity
of mercury to marine and brackish water isopods (Crustacea). Est. Coastal
Marine Sci. 1:425-431} 1973.
Kemp, H.T. _et al. Water quality criteria data book. Volume 5: Effects
of chemicals on aquatic life. U.S. Environmental Protection Agency; 1973.
Koeman, J.H.; Peeters, W.H.M.; Koudstaal-Hol, C.H.M.; Tjioe, P.S.;
de Goeij, J.J.M. Mercury-selenium correlations in marine mammals.
Nature 245:385-386; 1973.
Lipsey, R.L. Accumulation and physiological effects of methyl-
mercury hydroxide on maize seedlings. Environ. Pollut. 8:149-155; 1975.
Lorz, H.W. _et al. Effects of several metals on smelting of Coho
Salmon. U.S. Environmental Protection Agency. 600/3-78-090. 1978.
MacLeod, J.C.;.Pessah, E. Temperature effects on mercury accumulation,
toxicity, and metabolic rate in rainbow trout (Salmo gairdneri).
J. Fish. Res. Bd. Can. 30:485-492; 1973.
Matida, Y. et al. Toxicity of mercury compounds to aquatic organisms
and accumulation of the compounds by the organisms. Bull. Freshwater
Fish Res. Lab. 21:197; 1971. (As cited by USEPA 1979)
Matson, R.S.; Mustoe, G.E.; Chang, S.B. Mercury inhibition on
lipid biosynthesis in freshwater algae. Environ. Sci. Technol. 6:158-
160; 1972. (As cited by USEPA 1979)
171
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Nelson, D.A.; Calabrese, A.; Nelson, B.A.; Maclnnes, J.R.; Wenzloff, D.R.
Biological effects of heavy metals on juvenile bay scallops, Argopecten
irradians, in short-term exposures. Bull. Environ. Contam. Toxicol.
16:275-282; 1976. (As cited by USEPA 1979)
Norseth, T.; Clarkson, T.W. Biotransfonnation of methylmercury salts in
the rat studied by specific determination of inorganic mercury. Biochem.
Pharmacol. 19:2775-2783; 1970. (As cited by Finley and Stendell 1978)
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Contrib. Marine Sci. 17:9; 1973. (As cited by USEPA 1979)
Ottawa River Project Group (ORPG). Mercury in the Ottawa River.
Environ. Res. 19:231-243; 1979.
Panigrahi, A.K.; Misra, 3.N. Toxicological effects of mercury
on a freshwater fish, Anabas scandens, Cuv. & Val. and their ecological
implications. Environ. Pollut. 16:31-39; 1978.
Portmann, J.E. Progress report on a programme of insecticide analysis
and toxicity-testing in relation to the marine environment. Meeresunter-
suchungen 17 (1-4):247; 1968. (As cited by USEPA 1979)
Portmann, J.E. ; Wilson, K.W. The toxicity of 140 substances
to the brown shrimp and other marine animals. Ministry of Agriculture,
Fisheries and Food, Fisheries Laboratory, Burnham-on-Cr-.iuch, Essex,
England. Shellfish Information Leaflet No. 22. ARUC-7701. December
1971. (As cited in Kemp _et al. 1973)
Rehwoldt, R.; Menapace, L.W.; Nerrie, B.; Allesandrello, D. The
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of some heavy metal ions toward benthic organisms. Bull. Environ.
Contam. Toxicol. 10:291-294; 1973.
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metals on laboratory populations of two polychaetes with comparisons to
the water quality conditions and standards in southern California marine
waters. Water Res. 10:299-302; 1976. (As cited by USEPA 1979)
Roales, R.R. ; Perlmutter, A. Toxicity of methylmercury and
copper, applied singly and jointly, to the Blue Gourami, Trichogaster
trichopterus. Bull. Environ. Contam. Toxicol. 12:633-639; 1974.
Shealy, M.H.; Sandifer, P.A. Effects of mercury on survival and develop-
ment of the larval grass shrimp, Palaemonetes vulgaris. Marine Biol.
33:7; 1975. (As cited by USEPA 1979)
172
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Sigmon, C.F. _et _al. Reductions in biomass and diversity resulting
from exposure to mercury in artificial streams. J. Fish Res. Bd. Can.
34:3395; 1977. (As cited by USEPA 1979)
Sosnowski, S.L.; Gentile, J.H. Toxicological comparison of natural and
cultured populations of Acartia tonsa to cadmium, copper, and mercury.
J. Fish. Res. Bd. Can. 35:1366; 1978. (As cited by USEPA 1979)
Sosnowski, S.L. et al. The effects of chronic mercury exposure on the
mysid shrimp, Mysidopsis bahia. Abstracts of the New England Fish and
Wildlife Conference. 1979 April 1-4, Providence, R.I. (As cited by
USEPA 1979)
STORE! water quality data system. Monitoring and Data Support Division,
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U.S. Environmental Protection Agency (USEPA). Mercury. Ambient water
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Office of Water Planning and Standards; 1979.
Warnick, S.L. ; Bell, H.L. The acute toxicity of some heavy metals to
different species of aquatic insects. J. Water Pollut. Control Fed.
41:380-384; 1969. (As cited by USEPA)
Weis, P.; Weis, J.S. Effects of heavy metals on development of the
killfish, Fundulus heteroclitus. J. Fish Biol. 11:49; 1977a. (As cited
by USEPA 1979)
Wobeser, G.A. Aquatic mercury pollution: Studies of its occurrence and
pathologic effects on fish and mink. Ph.D. Thesis, University of
Saskatchewan (Canada). (As cited by USEPA 1979)
173
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CHAPTER VII.
RISK CONSIDERATIONS
A. RISKS TO HUMANS
1. Introduction
^Previous chapters have described the production and use of mercury
and its fate in the environment. It is useful to review the points made
previously in order to identify the sources of exposure. Mercury is
used primarily in the production of chlorine, in paint manufacture, in
the production of instruments, and in the production of electrical
equipment, especially batteries. The relative importance of the sources
of mercury releases to the environment varies in different regions of
the country. In general, sources associated with population centers
include losses to air from fossil fuel combustion, incineration of
industrial and municipal waste, and from application of paints containing
mercury. Losses to the aquatic environment associated with population
centers include urban runoff losses from paint and dental applications,
and industrial discharges. In some regions, the major sources are copper,
zinc and lead mining and smelting, chlor-alkali manufacture, and natural
sources, including degassing from the earth and erosion of soils contain-
ing mercury.
The monitoring data discussed previously showed that mercury levels
in air and soil of urban areas are consistently higher than background
levels, and this finding suggests that the sources identified above
contribute to exposure of persons in urban areas. Land is the environ-
mental medium which receives the majority of mercury-containing industrial
and municipal wastes. Though mercury releases are not expected from
properly operated disposal sites, mercury movement from improperly
operated sites can be rapid.
The purpose of this section is to compare exposure pathways to
humans as described previously in Chapter V with exposure levels at
which effects may occur (also described in Chapter V). Consideration
of these two elements will aid in the identification of subpopulations
that may be exposed to different levels of mercury in its various forms.
2. Major Exposure Routes and Effects Levels
Table 31 summarizes the estimated exposure levels for the major
exposure routes. As can be seen, mercury in food represents the largest
single source of exposure for the largest number of people. Drinking
water and air appear to contribute relatively little to exposure of the
general population, although inhalation can be an important exposure
route in certain situations, such as near natural or anthropogenic
sources.
175
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TABLE 31. ESTIMATED EXPOSURE OF HUMANS TO MERCURY
Route
Drinking water
Food
Seafood
Total diet
Exposure (ug/day)
Intake Absorbed^ F
3.0
>30
80
>100
<0.4
3.0
>30
80
>100
5.3-14.6 2.8-7.9
2.5-7.1 2.5-7.1
orm
inorganic
inorganic
largely methyl-
mercury
Sul) population Assumptions
large Cone. <0.5 tig/1, consumption of 2 1
very small
average
largely methyl- pop. 0.1-0.2%
mercury
largely methyl
mercury
largely methyl
mercury
total mercury
methylmercury
- <0.0089%
- <0.0089%
large
large
Cone. 2 ug/1 , consumption of 2 1
Average value of .220 ug/g Ilg in
tuna, 75% of fjsh consumption tuna,
.100 ug/g in other fish, 17 g/day
fish consumption.
Based on survey at measured con-
centration and actual consumption.
Based on survey at measured con-
centrations and actual consumption.
0.05-ug/g action limit.
Based on survey at measured con-
centration and actual consumption.
No act ion 1 inii t.
Range of cone, in food items, FDA
standard diet.
Range of cone, in food items, FDA
standard diet. 85% of mercury In
meat, poultry and fish assumed to
be methyl.
-------
TABLE 31. ESTIMATICI) EXPOSURE 01* HUMANS TO MKRCURY (Continued)
Route
Inhalat ion
Outdoors
rural
urban
_ Exposure (ug/clay)
Intake
0.1
0.6
near
sources 3-30
Indoors
general 2-4
laboratory 4-200
dental 57-570
Absorbed Form
0.08 mercury vapor
0.5 mercury vapor
2.4-24 mercury vapor
1.6-3.2 mercury vapor
3.2-1.60 mercury vapor
40-460 mercury vapor
Subpopujat ion
large
large
small
large
sma] 1
small
i ons
5 ng/m In air, respiratory rale
of 20 m3/day.
3
30 ng/m in air max.
150-1500 ng/m jn air.
100-200 ng/m In air.
200-10,000 ng/m3 in air.
10,000-100,000 ng/m1 in air;
10 m ^ inhalation,
working day, 5-day work week.
1
A 10% absorption of ingested inorganic mercury and 100%
of methylmercury was assumed. An 80% absorption of
inhaled mercury was assumed.
Source: Chapter V.
-------
Table 32 summarizes the lowest observed effect levels, no observed
effect levels and "tolerable" or "acceptable daily intake" for mercury
as discussed in Chapter V. Of concern are the neurological disturbances
and fetal brain damage occurring at relatively low mercury levels in man.
Attempts have been made to correlate these blood levels with doses that
are also shown in the table. The lowest reported effect levels are
based on epidemiologic data and thus represent only obvious effects
occurring in the population. Other, more subtle effects may result from
lower levels of mercury exposure. The "tolerable" level of 0.43 ug/kg/
day was estimated by use of several different methods as described in
Chapter V.
Other adverse effects that may be of concern include chromosomal dam-
age, teratogenic effects, and reduction in male fertility. Although these
effect! have been observed in animals, or in human cells in vitro, the
significance of these findings to human health effects is unknown.
The following sections will consider the general population and
various subpopulations and their exposures to mercury. The exposure
levels for these groups will be compared with the "threshold" level
believed to result in neurologic disturbances, since at present this is
the only effect for which an associated dosage has been estimated.
Exposure to fetuses will also be discussed.
3. Risk Considerations for the General Population
Table 33 summarizes estimates of daily absorbed exposure levels for
the general population. It is apparent that food is the primary source
of methylmercury for this large group. The "acceptable" intake of
0.43 ug/kg/day as discussed in Chapter V is for methylmercury, and thus
can only be compared directly with exposure levels of methylmercury.
For the FDA standard diet and maximum residues in food, an exposure of
0.1 ug/kg/day can be estimated. There is no direct evidence at this time
to indicate that effects would be observed in a population receiving this
level of exposure. Statistical analysis of data from several poisoning
incidents suggests that the long-term methylmercury intake which produces
the earliest symptons in about 5% of the adult population could be 3-7
ug/kg/day (see Chapter V), so any effects associated with this maximum
exposure level from food (0.1 ug/kg/day) would probably only be observed
in a very small percentage of the total population.
Levels of exposure of the "average" person to mercury through
innalation can approach those from food in some situations. However,
mercury in the atmosphere is usually in the form of a vapor, aerosol'
or particulate, and these forms do not necessarily have the same dose-
response relationship as the forms commonly found in food. At this
time it is not possible to establish an acceptable level for inhalation
exposures. As shown in Table 32, exposure to concentrations of
0.015 mg/m3 on a continuous basis may result in effects such as loss
of appetite or insomnia. This level is far above the normal range of
atmospheric mercury concentrations found in urban or rural areas, though
levels near sources (natural or anthropogenic) can approach this effects
level and may be of concern.
178
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TABLE 32. ADVERSE EFFECTS OF MERCURY ON MAMMALS
Adverse Effects Species
Chromosomal
damage in vitro Man
Fetal brain Man
damage
Lowest Reported
Effect Level
13 ng/g erythrocytes
(methylmercury)
400 ng/g methylmercury
in maternal blood
186 mg/kg methylmerucry
in maternal hair
No Apparent Effect
Level
Neurological
disturbances
Teratogenicity
Carcinogenicity
Man
Mouse
Mouse
Reduction of
male fertility Mouse
Appetite loss, Man
insomnia (Hg vapor)
Minimum lethal
dose
Man
1 200 ng/g blood
(methylmercury)
= body burden 28-42 mg/kg,
dose 3-7 ug/kg/day
2.5 mg methylmercuric
chloride Hg/kg maternal
body weight
1 mg/kg methylmercury(ip)
0.06 mg/m mercury
vapor (workplace)
0.015 mg/m ambient,
estimated
1-4 g HgCl7
20 ng/g blood
(methylmercury)
0.43 ug/kg/day
estimated dose
5000 ng/ml methyl-
mercury drinking
water x 70 days;
1000 ng/ml for life
Effect level unknown.
Source: Chapter V.
179
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TABLE 33. ESTIMATED EXPOSURE OF THE GENERAL POPULATION TO MERCURY
CO
o
Exposure
Med him
Drinking Water
Food
Air
Absorbed Dose
ug/day
2.8-7.9
(2.5-7.1)
1.2-2.5
ijg/ kg/day
0.001
0.04-0.11
(0.04-0.10)
(0.02-0.04)
Form
Inorganic mercury
total mercury
methy]mercury
mercury vapor
Combines indoor and outdoor exposures with
the assumption that 75% of time is spent indoors.
Source: Table 31.
-------
Occupational exposures may be high in dental offices, as well as in
other occupational settings. However, exposures of occasional visitors
to these locations would be much lower.
As discussed previously in Chapter V, humans can be exposed to
mercury from silver-mercury dental fillings. Though this type of expo-
sure has been observed, it has not been quantified in a way which permits
evaluation of risk to this large exposed population at the present time.
4. Risk Considerations for Subpopulations
a. Fisheaters
Table 31 shows that 0.1% to 0.2% of the U.S. population may receive
more than 30 ug/70 kg person/day or 0.43 ug/kg/day methylmercury in
seafood. The data on consumption patterns and mercury concentrations
in various fish species used in this estimate are based on two separate
surveys. In the consumption survey, the actual concentrations in the
seafood consumed were not measured. Although the FDA action level of
1.0 ug/g mercury is in effect for fish, 100% compliance is not expected.
In addition, in setting the guideline the FDA assumed a consumption level
of 30 g fish per day, and a small percentage of the population probably
consumes more than this. Effects of mercury exposure would not necessarily
be observed in the 0.2% of the population, since the sensitivity to
mercury varies.
Geographic areas in which levels of mercury in seafood are high can
be identified to some extent. They have been discussed in Chapter V and
in the Appendix. The localized areas in which consumption of contami-
nated fish is high are not easily identified. A survey conducted by
the National Marine Fisheries Service showed that consumers of large
amounts of seafood were concentrated in the North and Mid-Atlantic states
the Southeast, the Great Lakes states, and in Texas, California and
Oregon (see Chapter V). Thus, it appears that a small portion of the
population from these areas, although they are large, may be at risk due
to consumption of mercury.
The types of fish eaten by persons with a mercury intake exceeding
0.43 ug/kg/day include both freshwater and saltwater species (see Table
34). Possible sources of mercury for freshwater species containing
high mercury concentrations include natural sources, chloralkali plants
mining, copper smelters, and power plants. Electric lamp, battery,
instrument, and paint manufacturers may also be sources in local areas.
Sources contributing to large bodies of water, like the Great Lakes,
would be numerous. The sources mentioned above would probably contribute
as well as runoff, agricultural use of fertilizer and pesticides, emissions
from paint applications and POTWs.
Mercury levels in saltwater species appear to be largely due to
natural bakcground" levels rather than a specific source. Accumulation
181
-------
of high mercury levels are probably due to the large size of some marine
species.
An examination of the areas of the country where freshwater fisheries
have been restricted due to mercury showed that the cause of contamiantion
included natural sources, abandoned chlor-alkali plants, and an abandoned
gold mine. However, in many cases the sources could not be identified.
b. Fetuses
Fetal brain damage has been shown to result from mercury exposure
to the mother, as discussed in Chapter V, 4, c. Minimum effects levels
have not yet been established, but clinical evidence of fetal brain
damage has been observed in a study involving 20 mother-infant pairs
when peak maternal hair mercury concentration rose above 100 mg/kg
(estimated to be equivalent to 400 ng/ml blood concentration). In a
separate incident, severe fetal brain damage was correlated with a peak
maternal hair concentration of 186 mg/kg. However, it has been estimated
that the earliest effects of mercury toxicity would be observable in the
most sensitive adult population at blood levels in the range of 200-500
ng/g. Taken in conjunction with the fact that neurological effects have
not always been obvious in mothers of infants with clinical evidence of
brain damage from mercury, there is some basis for inferring that minimum
effects levels for fetal brain damage may be less than or equal to 200
ng/ml maternal blood concentrations.
Since only 30 mother-infant pairs were involved in these studies on
fetal brain damage, it was not necessarily a representative sample. To
deal with this uncertainty, some state governments which have closed or
otherwise limited fisheries have recommended that pregnant women not
consume certain species of fish.
c. Children
The risk to children due to mercury exposure may be of concern due
to the indications of higher susceptibility of this subpopulation.
Because relatively little is known regarding the dose-response relation-
ship for mercury in children, detailed exposure analyses were not included
for them. However, the risk to children should be at least as great as
that for adults.
d. Users of Mercury-Containing Products
The accidental exposure of consumers to mercury does occur in a
very small subpopulation. Although this exposure is unquantifiable, it
is probably low relative to food exposure.
The swallowing of camera batteries by children is one such route
since these batteries are becoming more widely used in the home. The
corrosion of the casing may expose the child to potentially lethal dose.
182
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TABLE 34. FISH SPECIES CONSUMED BY SEAFOOD EATERS WITH
MERCURY INTAKE EXCEEDING 0.43 ug/kg/day
No. persons
Species eating (of 47)
tuna (light) 24
bass (sea and striped) 16
pike 15
flounder 12
perch - marine 10
mackerel (other than jack) 8
halibut 4
haddock 4
swordfish 2
Note: Other species such as crappie, sunfish, trout, shrimp,
lobster, salmon, etc., were consumed, but infrequently.
Source: See Hall _et ail. (1978), discussed in Chapter V.
183
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B. RISKS TO BIOTA
The exposure analysis for biota (Chapter VI) suggested that mercury
levels have gradually decreased in the major river basins of the U.S.
since 1970. Monitoring data on levels in bottom sediment and fish
residues, however, are inadequate to permit a similar trend analysis
for these media.
STORET data from 1978 to 1979 indicate that the highest mean
mercury concentrations were in the North Atlantic, Ohio River, South
Central Lower Mississippi, Pacific Northwest, and California basins.
In all of these regions, total aqueous mercury levels often exceeded
0.5 ug/1, a concentration which has sublethal effects in several species
in the laboratory. In addition, there are a few instances of maximum
mercury concentrations exceeding 10.0 ug/1, which is an acute toxicity
level for some aquatic organisms. Such incidents are not concentrated
in any one area, but appear to have occurred across the country.
The main difficulty in interpreting these data is an uncertainty
with regard to the chemical form of the mercury at any given location
The data as reported in STORET do not distinguish between organic and
inorganic mercury, but rather describe total mercury levels in water,
sediment, and fish tissues. The toxicity information presented in
Chapter VI suggest that methylated mercury is usually more toxic than
inorganic mercury. A conservative approach would be to assume that all
mercury is in this, its most toxic form, despite the fact that most
aqueous mercury is inorganic. Even with this assumption, however, the
risk to aquatic organisms cannot be quantified on the basis of the
available data. Consequently, the minor basins listed in Table 30
(Chapter VI) do not necessarily reflect aquatic populations at risk; at
best, they represent regions where the greatest hazards may exist.
Most marine fish are probably protected from mercury toxicosis
as a result of the relatively high selenium levels in ambient seawater.
In inland waters, however, selenium is normally a much less significant
component, and so, consequently, freshwater fish are probably more
susceptible to mercury. Toxicity data are not extensive enough to allow
confident identification of the more sensitive species. The rainbow
trout and the daphnids seem to be among the most sensitive groups;
however, these are also among the most frequently bioassayed species.
One group of special interest is crayfish, for some of which the LC5ns
for mercury are several orders of magnitude below those for other fresh-
water species.
Most terrestrial organisms do not appear to be at risk, except
perhaps in the vicinity of certain anthropogenic sources. Elevated
mercury residues have been found in plant and animal specimens taken
near chlor-alkali chemical plants, although no toxic responses were
noted. Piscivorous mammals and birds may be exposed to more mercury
than other animals because of their position of the top of the food
pyramid.
184
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APPENDIX A
NOTES TO TABLE 1
1. Bureau of Mines (1978).
2. Bureau of Mines (1976).
3. SRI (1979).
4. The U.S. Bureau of Mines (1976) reports that 607 flasks of mercury
(at 76 Ibs each) were consumed in the production of fungicides and
bactericides. This amount corresponds to approximately 20.9 kkg.
SRI (1979) found similar results.
5. The amount of mercury deposited in industrial stockpiles is taken
to be the difference between the total for production and imports
(2428 kkg) and the total for known consumption (2253 kkg) for 1976.
6. Van Horn (1975). Emission volumes have been rounded to one decimal.
7.
Assumptions regarding the relative amounts of mercury used in the
three principal subcategories of electric apparatus (tubes/switches,
lamps, and batteries) were made by Versar, Inc., after reviewing
the literature (Van Horn 1975, Battelle 1977, Versar, Inc. 1976b,
United Technology 1975) and contacting the battery industry
(Personal communication, Irwin Frankel, Mallory Battery Co.,
Tarreytown, NY, 1976). Factors relating to fraction of mercury
lost, and emission factors were obtained from Van Horn (1975):
Elect.
App.
Tubes/
Switches
% of
Total
10
Con-
sumption
(kkg)
94.8
Fraction
Lost(%)
0.025
Distribution to En-
vironmental Media (%)
Air H00 Landfill
1.00
Hg lost
Air H_0 L
^_
(kkg)
andf il
2.4
1
Lamps
Batter-
ies
10
80
94.8
758.4
0.04
0.005
.05
.05 .02
.95
.95
0.2
0.2 0.1
3.6
3.6
TOTAL
100
948
0.4 0.1 9.6
948.0 kkg consumed in manufacturing
- 10.1 kkg lost to environment during manufacturing
937.9 kkg in products, generally having extended lives
Data are not available concerning the amount of mercury discharged
to POTWs, but some small part of the aquatic discharge is assumed
to go to POTWs.
185
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8. Since all mercury purchased by the chlor-alkali industry is
eventually lost by a variety of routes, and since no additional
mercury-cell plants have come into existence in recent years, it
can be assumed that the equivalent of the purchased mercury ends
up in the environment or in the product. Reasonably accurate
data are available for 1975 regarding the amount of mercury that
is discharged to air, in plant effluents and caustic soda.
Most of the remainder ends up in landfills, or in land-locked
slurry ponds, evaporation ponds, or is recycled to deep brine
wells, all of which are also considered to be the land compartment
In 1975, data from 16 of the 27 chlor-alkali plants showed that
the average loss of mercury to the air was 1.73 kg/day/plant
(including losses to byproduct hydrogen) (Versar, Inc. 1976a).
For an assumed operating factor of 98%, losses to air were:
1.73 kg/day x 27 plants x 365 day/yr x .98 = 16.7 kkg/yr
When the above is adjusted to account for the somewhat greater
use of mercury by the industry in 1976, the total is computed as:
16 7 kkz/vr x 10-06 x 106 tons of Clo in 1976
10. / k«cg/yr x b ' - 18.5 kkg
Similarly, loss of mercury to caustic product at 16 plants was
0.27 kg/day/plant (Versar, Inc. 1976a)
.27 kg/day x 27 plants x 365 days/yr , .98 ,
=2.9 kkg/yr in NaOH product in 1976
Mercury losses via plant effluents for 23 plants were
0.046 kg/day/plant, therefore
27 plants x 0.046 kg/day x 365 days/yr x 0.98 x I0'°6
i
9.1 x 10b tons 1000 kg
.5 kkg/yr to plant effluent in 1976
According to Jacobs (1979) , the average mercury discharge for
12 plants was 10~4 kg/kkg of C12. The amount of chlorine produced
by this process is reported to be 2,750,000 kkg (in 1977). In the
total subcategory for the electrolytic preparation of chlorine and
caustic soda, there are 77 plants, 72 of which discharge directly,
and five that discharge to POTWs. There are 27 plants in the
subcategory that use the mercury-cell process. Hence:
Aquatic Discharge = 10~4 kg/kkg x 2,750,000 kkg x 1 kkg/1000 kg
= 0.3 kkg
Because the total aquatic discharge of mercury is small, and the
number of plants discharging to POTWs from the entire subcategory
186
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is small, it is assumed that all of the mercury is discharged
directly and that the discharge to POTWs is negligible.
Since the total consumption of mercury by this industry in 1976 was
553 kkg, and losses to air, water, and product can be accounted for,
it can be assumed that all the difference goes into landfills (or
sludge ponds, evaporative ponds, and brine wells). This difference,
in 1976, was:
553 kkg - 18.5 kkg - 2.9 kkg - 0.3 kkg = 531.3 kkg to land
Approximately 270 kkg of mercury were used in paint manufacture
during 1976, largely in the form of mildewcides, such as phenyl
mercuric acetate and phenyl mercuric oleate or succinate. The
portion of mercury lost from paint manufacture is 0.1% (0.27 kkg)
Wan Horn 1975). If 5% of losses are assumed to be to air, 5% to
land, and 90% to water (Van Horn 1975), then the amounts of mercury
lost to the media are:
Air: 0.05 x 0.27 kkg = 0.015 kkg = ~0 kkg
Water: 0.9 x 0.27 kkg = 0.24 kkg = "0.2 kkg
Land: 0.05 x 0.27 kkg = 0.015 kkg = ~0 kkg
However, during the screening and verification sampling and analysis
programs for the paint manufacturing industry, 22 plants were
sampled. The mercury concentrations in treated effluent ranged
from 0 ug/1 to 2900 ug/1, with an average concentration of 580 ug/1
(U.S. EPA 1979c). The total daily water discharge for direct dis-
chargers is 25,000 gal/day and for indirect (POTW) dischargers it
is 750,000 gal/day (Burns and Roe 1979). For 250 operating days
per year:
Direct discharge = 580 ug/1 x 25,000 gal/day x 3.785 1/gal
x 250 days/yr x 10~12 kkg/ug
= 0.01 kkg
= ~ 0 kkg
Discharge to POTWs = 580 ug/1 x 750,000 gal/day x 3.785 1/gal
x 250 days/yr x 10"12 kkg/ug
=0.4 kkg
Since these estimates for the aquatic discharge and discharge to
POTWs are based on actual sampling data, they are given in Table 1.
The amount of mercury that is actually used in paint products is
the amount consumed by the industry (270 kkg) less the amount lost
during production (0.4 kkg), or 269.6 kkg.
After application of paint, 65% of the mercury is volatilized to the
air (U.S. EPA 1973); thus of the 269.6 kkg of mercury used in paints,
175.2 kkg is lost to the air. If the remaining 94.4 kkg is assumed
187
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to be evenly distributed among landfills, land fallout (due to paint
Uaking), runoff, and the air (as a result of incineration), then
the total environmental distribution from paint use is:
Air: 23.6 + 175.2 = 198.8 kkg
Water (runoff): 23.6 kkg
Landfill: 23.6 kkg .,,..,
Land Fallout: 23.6 kkg 47<2 kkg
There are no data by which to partition the mercury between direct
aquatic sinks and POTWs; therefore, the entire amount has been put
under the aquatic discharge heading.
10. Approximately 175 kkg of mercury were used in the manufacture of
industrial and control instruments. According to Van Horn (1975),
the emission factor for the industry is 1% of the amount consumed,'
and all of this is assumed to be in the form of solid waste:
Solid waste discharge = 0.01 x 175 kkg » 1.75 kkg = 1.8 kkg
During the use of these instruments, all of the mercury is expected
to either enter the environment or to be recycled.
Total mercury available = 175 kkg - 1.8 kkg = 173.2 kkg
The following emissions distribution was reported by Van Horn (1975)
as follows:
Air: 4% 6.9 kkg
Water:
Lan
-------
Of the 73% in wastewater, two-thirds are assumed to go to POTWs.
Thus the annual mercury burden to the various environmental media
is as follows:
Air: 1.4 kkg
Water: 16.5 kkg
POTWs: 33.6 kkg
Land: 17.1 kkg
12. Approximately 43.6 kkg of mercury was used in catalyst manufacture
in 1976, mostly in catalysts for vinyl chloride and manufacture of
vat dyes. About 0.25% ( 0.1 kkg) was lost to air and 0.5% ( 0.2 kkg)
to wastewater during manufacture (Van Horn 1975). There are no data
available from which to determine the amount of mercury that is
discharged directly or to POTWs; therefore, the entire'amount esti-
mated is listed as an aquatic discharge. Data are not available by
which to estimate the solid wastes from this industry; however, it'
is not expected to be significant.
It is assumed, but has not been verified that the remainder (43.3
kkg) was disposed of in landfills, when the spent catalysts are
discarded.
13. Approximately 21 kkg of mercury are used in agricultural pesticides
(Bureau of Mines 1976). Negligible amounts are lost during manu-
facture. When the pesticides are used, it is estimated that 15%
(3.1 kkg) is lost in runoff and reaches the aquatic environment and
85% (17.9 kkg) goes to land (Van Horn 1975).
14. In 1976, approximately 20.5 kkg of mercury was used in various
laboratories, including college, high school, hospital, and
independent research laboratories. The following distribution
was estimated by Van Horn (1975).
Air:
Water:
Landfill:
Recycle:
10%
26%
7%
57%
2.1 kkg
5.3 kkg
1.4 kkg
11.7 kkg
TOTAL 20.5 kkg
Data are not available by which to determine the amount of mercury
that is discharged to POTWs or discharged directly to the aquatic'
environment. Since most of the laboratories are located in cities,
it is assumed that the major portion of this discharge would be to'
POTWs.
15. About 2.1 kkg of mercury is used in the manufacture of pharmaceuti-
cals, and only about 0.001 to 0.002 kkg is lost during manufacture-
this is considered to be negligible (U.S. EPA 1976c).
139
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During the consumer use of mercury-bearing Pharmaceuticals, it is
estimated that 90% is lost to water (i.e., 60% goes to POTWs plus
30% to direct discharge), and 10% goes to landfills. Thus the
annual releases to the various compartments total:
Water 0.63 kkg
POTWs: 1.26 kkg
Landfills: 0.21 kkg
16. Batteries manufactured from mercury are contained in a metal case
with a plastic seal. Therefore, little if any mercury is likely to
be released during use. However, in the United States (unlike Japan
and some European countries), there is no organized recycling pro-
gram, and substantially all batteries enter the municipal solid
waste stream (Arthur D. Little, Inc., estimate). Though the mercury
cells contain the highest concentration of mercury, a larger total
quantity of mercury is consumed in the manufacture of alkaline-
manganese dry cells, and nearly all dry cells contain some mercury.
In general, the batteries containing the highest concentrations of
mercury are also the ones that are built most ruggedly, and are,
therefore, most likely to survive waste handling processes such as
compaction. The seal is the weakest point in the battery and will
probably be oxidized (over time) and release the contained mercury.
If one assumes a relatively benign environment at the landfill
site, one can speculate that mercury cells, and to some extent
alkaline-manganese dry cells, may act as leak-proof containers
of mercury for 20-50 years (and perhaps longer). If corrosive con-
ditions prevail in the landfill, then the lifetime would be shorter.
(Arthur D. Little, Inc., estimate). Dry cells in that portion of
municipal solid waste that is incinerated would presumably rupture,
and allow most of the mercury to escape to the atmosphere.
For the purpose of this materials balance, it is assumed that 758.4
kkg of mercury was consumed in batteries in 1976 (80% of the total
in this category), and that 15% of municipal solid waste is incin-
erated, with the remaining 85% placed in landfills. Thus, 637.8 kkg
of mercury will go to land, and 112.6 kkg will go to the atmosphere
from the disposal of batteries containing mercury.
The remaining sources of mercury to the environment from electrical
apparatus are described in the text.
17. Mercury emissions arise from the combustion of three fossil fuels:
coal, oil, and natural gas. Most steam electric power generating
plants can be classified as predominantly coal burning, oil burning,
or gas burning. Power generation and fuel consumption in 1975 was
as follows (National Coal Association 1976):
190
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208,632 MW from 483,588,000 tons of coal in 381 coal plants
66,362 MW from 456,032,000 bbls oil in 533 oil plants
72,326 MW from 295,915 x 107 ft3 natural gas in 422 gas plants
During 1976, new plants were brought in with total additional power
ratings of (National Coal Association 1976):
11,976 MW for coal
4,410 MW for oil
1,436 MW for gas
The fuel consumption for 1976 was therefore:
483,588,000 x (208,632 + 11,976) = 511.35 x 106 tons coal
208,632
456,032,000 x (66,762 + 4,410) = 486.2 x 106 bbl. oil
66,762
(295,915 x 107) x (72,326 + 1,436) = 3.018 x 1012 ft3 natural gas
72,326 '
Mercury contents of these fuels are as follows:
0.2 mg/kg for coal (U.S. EPA 1973)
0.066 mg/kg for distillate oil (Van Horn 1975)
0.13 mg/kg for residual oil (U.S. EPA 1973)
0.04 mg/kg in natural gas (Van Horn 1975)
In 1972, the total fuel oil used in the U.S. was 1,066 x 106 bbl.
of distillate and 973,707,000 bbl. of residual or 53% and 47%,
respectively (Bureau of Mines 1972). The amount of each used for
electric power generation is not known, but if the same proportions
are assumed to have been used for power generation, both in 1972
and 1976, the average mercury concentration in fuel oil is:
(.066) (.53) + (.13) (.47) = .096 mg/kg
The mercury emitted by the combination of fossil'fuels is:
(511.35 x 106 tons coal) (.2 mg/kg) (.907 kkg/ton) =
92.8 kkg Hg from coal
(486.2 x 106 bbl) (7.82 Ib/gal) (0.096 mg/kg) (0.907/2000) =
6.95 kkg Hg from oil
(3.018 x 1012 ft3) (76.4 lb/1000 ft3) (0.554) (0.04 mg/kg
(0.907) = 2.32 kkg Hg from natural gas
(Note: 0.554 = sp. gr. of methane, and methane constitutes
>98% of natural gas.)
191
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When coal is burned: 90% of mercury goes to flue gas
9.4% goes to "land (ash)
0.6% goes to water (ash pond overflows)
Mercury in environmental media as a result of fuel combustion for
steam electric power generation is, therefore (Van Horn 1975):
Fuel
Coal
Oil
Gas
TOTAL
Hg in
fueKkka!
92.8
6.95
2.32
102.1
Distribution to
Environmental
Media (%)
Air Water
.90 .006
.999
.999
Land
.094
.001
.001
Hg to Media
(kke)
Air Water Land Total
83.5 0.56 8.7
7.0 - 0.006
2.3 - 0.002
92.5 0.56 8 7-
102.1
Quantities less than (<) 0.1 kkg/year are disregarded.
18. Coal use was as follows according to the Bureau of Mines (1979):
665,000,000 tons bituminous coal mined in 1976
1,150,000 tons bituminous coal imported
(60,000,000) tons bituminous coal exported
6,200,000 tons anthracite coal mined
612,350,000 tons = total used in U.S.
~ 511,350,000 tons coal for steam electric power generation
101,000,000 tons = total coal combusted, other than in steam
electric power generation
Hg discharged from coal = (101 x 106) (0.2 mg/kg)
(.907 kkg/ton) « 18.3 kkg Hg
Natural gas use in the U.S. in 1976 was distributed roughly as
follows (Bureau of Mines 1979):
9 3
19,500 x 109 ft^ = total natural gas used
- 3,018 x 10 ft = natural gas used for steam electric
power generation
16,500 x 10y ftj = natural gas used for other than steam
electric power generation
Hg discharged from gas =
(16,500 x 109 ft3) (76.4 lb/1000 ft3) (0.554 sp. gr.) (0.04 mg/kg)
(0.907/2000) = 12.7 kkg Hg.
Oil use in the U.S. in 1976 was approximately as follows (National
Coal Association 1976):
192
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19.
4810 x 10 bbls (42 gal/bbl) - total domestic oil demand
(90/£ used for fuel)
486.10 x 10° bbl used for steam electric power generation
Thus: (.9) (4810 x 106) - 486.2 x 106 = 3842.8 x 106 bbl
oil was used for other than steam electric power generation
Hg discharged from oil=
Mercury in Environmental Media (Van Horn 1975)
Fuel
Hg in
.Fuel (kkg)
Distribution to
Environmental
Media (%)
Hg to media (kkg)
Air Water Land
According to SRI (1979), 35% of sewage sludge is incinerated 157
is dumped in the ocean, 25% is spread on land as agricultural
fertilizer, and 25% is placed in landfills. SRI also stalls th^
and* 20°3a2 ST"*^ ^^ ln S^e Sl^ '• b^Jeenl kkg
and 203.2 kkg. Thus, the partition of mercury in sewage sludge
between the various environmental media is: §
Air (incineration)
Land (fertilizer):
Land (landfilling)
0.13 to 71.1 kkg (assuming most of the
Hg is volatilized during incineration
and that the rest is landfilled)
0.09 to 50.8 kkg
0.09 to 50.8 kkg
20.
Intermediate values were chosen for Table 1 and Figure 1.
on for Ore Mining (Calspan
the only producing mine in the U.S. - the McDermitt Mine
has a zero effluent discharge, except, of course, fo^on-procesi
Further3' WMCh arS aSSUmed t0 be -^^ibly contaminated
Furthermore, since most mining operations are in the western states
where rainfall is rare, runoff from tailing and other mine
piles is also assumed to be negligible.
21.
op l7Q for Nonferrous Metals
(U.S. EPA 1979a), primary and secondary production plants for
mercury have a zero effluent discharge. (See Note 20)
193
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22.
Only limited screening and verification data are available for the
Steam Electric Power Generation Industry (U.S. EPA 1979c). Mercury
was detected in the effluents at relatively low concentrations in '
all but one subcategory. Five of the seven subcategories have a
significant discharge. The following data were available (U.S
EPA 1979c):
23.
Subcategory
No.
No. Plants
Plants in the Average
Sampled Industry Flow (MGD)
Dis-
Average charge
Cone, (ug/1 (kkg)
Cooling Tower
Slowdown
Fly Ash Trans-
port
Metal Cleaning
Wastes
Low Volume
Wastes
Air Pollution
Control System
Slowdown
250 2.4 3.9 3.2
312 2.0 0.1 0.1
750 3.3 x 10"° 21,286 0.7
1068 0.28 0.6 0.3
10 0.98 16 Q.2
TOTAL 4.5 kkg
(Note: Discharge - (No. of plants) (Avg. Flow) (Avg. Cone.)
(365 days/yr) (3.785 1/gal) (10'12 kkg/ug)
There is low confidence in this estimate because only a few plants
were sampled (usually less than 15 per subcategory), and the numbers
were extrapolated to subcategories with a large number of plants and
large flow volume per plant.
Mercury was detected in the effluents of the Timber Products
Processing Industry during the verification sampling and analysis
program (U.S. EPA 1979c). Mercury is discharged in significant
amounts from two subcategories - Hardboard SIS and Insulation Board
(Therraochemical). The following data were available (U.S
1979a):
Industry
Subcategory
No. No. Dis-
Plants in Plants Avg. Flow Avg. Cone, charge
Subcategory Sampled (gal/dav/plant) (ug/1) (kkg)
Hardboard SIS 8
Insulation Board
(Thermochemical 4
1 8,236,600
2 13,803,190
5.5
TOTAL
0.3
0.3
0.6
194
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(Note: Discharge = (No. of plants) (Avg. Flow) (Avg. Cone.)
(250 days/yr) (3.785 1/gal) (10-12 kkg/ug)
24. Mercury was detected in the effluents of petroleum refineries during
the verification sampling and analysis program (U.S. EPA 1979c)
The average concentration was 0.16 ug/1 and average flow per plant
was 3.3 x 106 gal/day. There are 182 direct dischargers and 48
indirect (POTW) dischargers (U.S. EPA 1979b). Thus:
Direct discharge = (182 plants) (0.16 ug/1) (3.3 x 106 gal/dav)
(365 days/yr) x (10-12 kkg/ug) (3.785 1/gal)
=0.1 kkg
The mercury discharge to POTWs is considered to be negligible since
"
Erectly "^ °* ^ °™ ^"^ °f the am°Unt
25. The amount of mercury discharged from POTWs was taken to be the
average of three separate sets of data.
Data Set #1 - Municipal treatment plants generate 0.017 kkg of
sludge per person per year, and 1.6 x 10* people are serviced bv
POTWs (ASMA 1976). In a 1976 study of the' sludge. from iTcities,
turr £t_al. (1976) report a mercury concentration of 8.6 mg/kg
The annual discharge of mercury in sludge is, therefore:
(0.017 kkg/person) (1.6 x 108 people) (8.6 x 10"6)
= 23.4 kkg
It is assumed that 65% of all mercury entering sewage plants is
l!T 11o7^Udg^bef°re wastewate" are discharged (Davis and
Jacknow 1975). Thus, the total amount of mercury discharged both
as sludge and in POTW effluents is:
23.4 kkg/0.65 = 36.0 kkg
The amount of mercury discharged in the effluent is the difference
between the total and that remaining in the sludge:
36.0 kkg - 23.4 kkg = 12.6 kkg
~ °f 56 S6Wage treatm<^ facilities indi
effluent concentration of mercury was
7
SUrVey °f disch*rge monitoringrePorts
alS° indicated a mercury concentration of
nUj'm c6 t0tal efflU6nt fl°w for POTWs 1* estimated to be
0 MGD (U.S. EPA 1976b). The estimated annual discharge is:
(<0.003 x 10-3gm/l) (22.67 x 10^ gal/day) (3.785 1/gal)
(36:j days/yr) (1Q-6 kkg/gm) =< 94.0 kkg
195
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26.
27.
This amount is considered to be the maximum amount of mercury dis-
charged from treatment plants.
Data Set #3 - It has been reported that 19.9 kkg of mercury is
released annually to public waters from POTWs (University of
Illinois 1978).
The total reported in Table 1
above three calculations:
is the average of the results of the
(12.6 kkg + 94.0 kkg + 19.9 kkg)/3 = 42.2 kkg
Mercury was detected in the effluents of the Auto and Other
Laundries Industry during the verification sampling and analysis
program (U.S. EPA 1979c). Almost all of the plants in this industry
discharge to POTWs. Therefore, the direct aquatic discharge for this
industry is considered to be negligible. The following data were
available for this industry (U.S. EPA 1979c).
Industry
Subcategorv
No.
plants
Avg. Flow
(gal/dav)
Avg. Cone.
(ug/1)
Discharge
(kkg)
Industrial
Laundries 1,020 75,000
Power Laundries 3,094 10,000
Car Washes 77,693 5,000
Linen Supply 1,314 60,000
2.3 0.2
2.3 0.1
0.8 0.3
1.6 0.1
TOTAL 0.7 kkg
According to SRI (1979), 190.5 kkg of mercury is added to the
environmental burden each year as a result of the mercury contained
in fertilizers. Some of this mercury may enter the aquatic environ-
ment by means of runoff, but the amount is not known and there is
no basis for an estimate.
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APPENDIX B
STATUS OF RESTRICTIONS ON COMMERCIAL AND SPORT
FISHING DUE TO MERCURY CONTAMINATION
1970 M^ I ' an lnventory was take« °f states that have, since
1970, closed sport or commercial fisheries and/or issued health waminaa
concerning the consequences of eating fish or other seafood contlSnatfd
TotCl!?,7 (MS, \978)' ?±nCe ^ °f 1977' tw° main Actors h"e Ld
the act £ T§ f/^ bans/varninSs ^ **ny states: the FDA has raised
the action level for mercury in fish tissue from 0.50 ug/g to 1.00 uz%
and many industries that were discharging mercury-containing effluent'
their wasteT ""^ d±S^^ altogether or currently treat
Three levels of restrictions are addressed in the following summary:
(1) states with current closures, restrictions or
advisories;
(2) states in which consumption warnings are in effect;
(3) states in which prior closures, restrictions or
advisories have been rescinded.
In the description that follows, changes that have occurred since the
D?lLTry ^e rep°rted; if no chan^ occurred, the 1977 status is
presented. For states with restriction categories (1) and (2) above
the appropriate state health or environmental official was contacted.'
The rationale for limiting this effort was that those areas with the
most serious existing or past mercury pollution problems warranted the
most attention and states that fall into category (3) were not contacted.
STATE CURRENT STATUS - - ' - — - • -
Alabama* A 1970 restriction on commercial fishing in the Tombigbee,
Tensaw, and Mobile Rivers and their respective tributaries,
* !jSeS.that havVesci*ded closures of sport and/or commercial
tisheries or health warnings issued since 1970.
States in which health warnings are in' effect about the consequences
fish or other
***
197
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STATES
CURRENT STATUS
as well as the waters of Upper Mobile Bay, was lifted on
July 7, 1972. However, all of the Pickwick Reservoir in
Alabama was closed to commercial fisheries between 1970 and
1975. There are no consumption advisories in effect (Samuel
Spencer; Department of Conservation and Natural Resources,
State of Alabama; personal communication, April 1980).
California** A warning to eat only one meal per week of striped bass and
catfish from the Sacramento-San Joaquin Delta and San
Francisco Bay area was issued by the State Department of
Health and is still in effect. In addition, in 1972,
warnings were issued by the Santa Clara County Park and
Recreation District that fish (largemouth bass, sunfish,
catfish, and rainbow trout) taken from Calero, Almaden, and
Guadalupe reservoirs may contain high levels of mercury and
should not be eaten (NAS 1978).
Georgia* In 1970 the Savannah River and New Savannah Dam on Highway 17,
as well as the Brunswick Estuary, were closed to sport fishing,
The Brunswick Estuary was also closed to commercial fishing.
All restrictions and closures for the Brunswick Estuary were
removed on October 19, 1970, and were removed for the
Savannah River in September 1972 (NAS 1978).
Idaho*
Illinois**
No state restrictions or fishery closures are currently
in effect. Conditional warnings (no person should eat more
than 1/2 Ib of fish per week; and pregnant women, infants,
and children should not eat any fish taken from American
Falls Reservoir) were issued by the State Health Department
for selected species of fish in the American Falls Reservoir
(January 1971 and 1972), Hells Canyon Dam, Jordan Creek, and
other reservoirs on the Snake River (January 1971), but have
since been removed. Sources of mercury to these water bodies
are thought to be industrial or agricultural (American Falls
Reservoir and Hells Canyon Dam), an abandoned gold mine
(Jordan Creek), and natural sources (the Snake River) (Stacy
Beghards; Fisheries Division, Department of Fish and Game,
State of Idaho; personal communication, April 1980).
Before 1970, there were sport or commerical fishery closures
and no health warning advisories to fishermen or the public
about the consequences of eating mercury-contaminated fish.
In 1970, however, certain species of fish taken from three
reservoir lakes (Rend Lake, Cedar Lake, and Lake Shelbyville)
exceeded the FDA action level at that time of 0.5 ug/mercury.
As a result, the public was warned to limit consumption to no
more than 1/2 Ib per week of largemouth bass, shorthead
redhorse, black buffalo, bullhead, and yellow bullhead from
these lakes. The advisory has since been dropped for Cedar
and Shelbyville Lakes. No mercury problems have been
198
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STATES
CURRENT STATUS
Kentucky*
Louisiana*
Massachusetts*
identified that affect commercial fisheries. Sources of
mercury to the waters of the restricted lakes, are unknown-
however, it is likely that the mercury is naturally
occurring [William Fritz; Department of Conservation
Pers°nal communication,
The health warning and restrictions issued in 1970 for
have b~en ^^ ,th! Tennessee River at Calvert, Kentucky,
have been relaxed due to a drop in mercury levels A
state-run sampling program involving 30 stations is "
In^r? yiSiPr08re88f ^ the rSSultS WU1 be ^liable
in early 1981 to verify the levels of mercurv in the
Tennessee River (Robert Logan; Division of Water Qualitv
Department of Natural Resources and Environmental '
Personal communication,
In 1970, Louisiana issued a health warning regarding fish
°e CalaSleU "^^ ^ St°PPed the -te?
she t,
shipment of these fish. All state restrictions were
removed in 1975 because the mercury concentrations in
fish were below the FDA tolerance level of 0.5 ug/g then
in effect (NAS 1978). B s
In 1970, minor fisheries were closed and health warnings
were issued for three specific areas. As a result of
mercury contamination above the FDA action level of
U§ I,' tW° Shellfish areas were closed in December
PPTCa^rb°r ln Mari°n and Quisset Harbor in
In 1975, portions of these harbors were
reopened to shellfishing because mercury levels had
declined. Neither area was heavily industrialized, and
the source of mercury was believed to be marinas in which
mercury-based paint was being used in boat yard work.
Also in 1970, a health warning was issued for persons
who were engaged in recreational finishing in the
Taunton River. Fish could be taken, but people were
advised not to consume those from the northern boundary
of the Town of Fall River north to the northern boundary
of the Town of Dighton. This warning was the result of
an industrial discharge, which has since been terminated.
All health warnings have since been withdrawn (John
CoTtrfl sSerirMBi°10?iSt' DiViSi°n °f Water Dilution
April 1980) Massachusett^ Personal communication,
199
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STATES
CURRENT STATUS
Michigan*
Minnesota**
Mississippi**
On April 15, 1970, sport fishing was banned and health
warnings posted on the St. Clair River and Lake St Clair
Commercial fishing for walleye in Lake Erie was banned on'
April 29, 1970. On May 20, 1970, the sport fishing
restrictions were reduced to "catch and release" status
in the St. Clair and Detroit Rivers and Lake St. Clair.
In Lakes Erie, Huron (south of Port Sanilac), and St.
Clair, sport fishermen could keep all fish except wall-
eye, white bass, and freshwater drum, while commercial
fishermen could keep all species except walleye. A
public health advisory remains in effect for Lake
Superior (lake trout), Lake Michigan (salmon), Lake St.
Clair (large and small mouth bass). Sport fishing con-
tinues to be restricted in the Detroit and St. Clair
Rivers. The sources of mercury in Lake Michigan and
Lake Superior are unknown; it is believed that the
mercury contamination in the other water bodies is
attributable to industrial discharges or runoff (James
Forney; Toxic Materials Branch, Fisheries Division, State
of Michigan; personal communication, April 1980).
There have been no closures of sport or commercial
fisheries in the State. On December 11, 1970, the
Department of Health advised anglers to restric intake
of fish from certain waters to once a week due to high
mercury levels. Subsequent analyses of fish for mercury
resulted in modification of the warning between 1970 and
1976. The following four watercourses were found to
contain some fish exceeding the FDA action level of
0.5 ug/g: (1) the St. Louis River below Coloquet,
(2) the Upper Mississippi River between Grand Rapids and
Brainerd, (3) the Red River along the Dakota border,
and (4) Crane Lake near the Canadian border. The latest
modification to health advisories occured on May 14, 1976,
when the Department of Health advised that fish from Crane
Lakes be eaten no more than once a week (Larry Gust;
Environmental Health Division, Minnesota Department of
Health; personal communication, June 1980).
On August 1, 1975, the Mississippi portions of Pickwick
Lake were reopened to commercial fishing. The Mississippi
State Board of Health also issued a warning that pregnant
women should restrict consumption of fish from Pickwick
Lake to a minimum and that all other persons should limit
their normal intake of fish from this lake to not more
than two meals per week (Charles Chisholm; Director of
Air and Water Pollution Control Commission, State of
Mississioui: personal communication; June 1980).
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STATE
CURRENT STATUS
New Hampshire*
New Mexico**
New York***
No state restrictions are in effect. The warnings issued
in 1970 for pickerel, yellow perch, and smallmouth bass
from the Merrimack and Connecticut Rivers have been
removed because public health officials believe that the
current creel limits preclude anyone from eating suffi-
cient quantities of fish to be harmful to health (Charles
Thoits; Inland and Marine Fisheries Branch, Fish and Game
Department, State of New Hampshire; personal communication,
April 1980).
Sport fishery health cautions for the Navajo and Ute Lakes
were issued by the Health and Social Services Department
(HSSD) in 1970 and are still in effect. The public has
been advised not to eat more than 2 Ib per week of any
species of fish taken from Navajo Lake. If walleye and
largemouth bass weighing more than 1.5 Ib were taken from
Ute Lake, the recommended consumption was to be limited
to less than 1 Ib per week per adult person, and the
recommended consumption of catfish weighing more than
5 Ib was limited to 2 Ib per week per person. Warnings
were also issued against eating large amounts of fish
taken from Summer, Elephant Butte, and Caballo Lakes.
The HSSD stressed that it was safe to eat the fish pro-
vided that the recommended consumption limits were
observed. No point sources of mercury contamination
have been identified. Local authorities have speculated
that a possible source is runoff from abandoned placer
mines, which used "quick silver" (David Tague; Bureau of
Water Pollution Surveillance, Health and Social Services
Department, State of New Mexico; personal communication,
April 1980).
With the exception of fish from three bodies of water,
officials have proclaimed that it is safe to eat fish'
once a week without fear of mercury contamination.
Onondaga Lake is closed to fishing. People were advised
not to eat lake trout from Lake George or muskellung
from the St. Lawrence River, but the warning has been
lifted. Pregnant women and infants are advised not to
eat any freshwater fish. Some lakes in the Adirondacks
have been found to contain borderline concentrations of
mercury but no action has been taken in that area.
There are no restrictions on commerical fishing. The
source of mercury pollution appears to be natural,
except in the case of Onandaga Lake where a chlor-alkali
plant had a significant daily discharge. Wastes from
this plant are now being treated and the condition is
expected to improve (Edward Horn; Bureau of Environmental
Protection, State of New York; personal communication
April 1980).
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STATE
CURRENT STATUS
Oregon*
North Carolina* For the inland fisheries, the general danger warnings
issued in 1970 to fishermen are no longer in effect.
No closures or health warnings have been issued for the
marine fisheries. However, the FDA ban on swordfish
resulted in the closure of a small fishery for this
species on the northern coast of this State (Robert
Benton; Marine Fisheries, Department of Natural Resources
and Community Development, State of North Carolina;
personal communication, April 1980).
Ohio* In 1970 the Lake Erie commercial fishery was closed for
all fish except perch. An embargo was placed on white
bass and a sport fishery health warning announced.
Since then the 1970 restrictions were ruled unconstitu-
tional by the Ohio Supreme Court because "the Division
of Wildlife is not and was not responsible for consumer
protection." No state restrictions or health warnings
are presently in effect (NAS 1978).
There are no commercial fishery closures in effect.
However, in 1970 health warnings were issued for rainbow
trout, black crappie, suckers, and largemouth bass taken
from the Antelope and Owyhee reservoirs and parts of the
Willamette River. A curtailed intake of any fish taken
from these waters was recommended, particularly for
infants and pregnant women. In 1975 a health warning
was issued for striped bass (NAS 1978).
In 1970 the Department of Environmental Resources issued
an advisory that large predator game fish, such as
walleye, drum, smallmouth bass, and white bass, may
exceed the FDA action level of 0.5 ug/g mercury, and,
therefore, some restriction of the consumption of these
fishes by humans may be advisable. At the present time
there are no official restrictions on catching game fish,
and no health warnings have been issued with respect to
eating the species (NAS 1978).
South Carolina**In 1970 the sport and commercial fisheries were closed
on the Savannah River from Augusta, Georgia, to the
coast. These restrictions were removed in 1972. In
1972 an advisory was issued that recommended limiting
the consumption of fish taken from Lake Jocassee to
1.5 Ib of dressed fish per week and eliminating intake
by pregnant women. The elevated levels of mercury in
fish from Lake Jocassee were the result of natural
conditions, such as the slightly higher soil mercury
levels in the lake area and, more significantly, the
oligotrophic condition of the lake. The advisory is
Pennsylvania*
202
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STATE
CURRENT STATUS
currently in effect, and the mercury levels are being
monitored (J. Luke Hause; Division of Shellfish and
Recreational Waters, Department of Water and Natural
Resources, State of South Dakota; personal communication
April 1980).
South Dakota**
Tennessee***
Texas**
In 1970, the State reported no closures or advice to
fishermen about health hazards associated with eating
fish taken from South Dakota waters. Since then, only
the Cheyenne Arm of Oahe Reservoir has been posted by
the State's health officer. In June 1973, commercial
and sport fishermen were warned not to eat more than
1.5 Ib of fish from this water per week. This health
warning is still in effect. The source of mercury is
believed to be runoff from an abandoned gold mine in the
Black Hills (James Nelson; Water Quality and Hygiene,
Department of Water and Natural Resources, State of South
Dakota; personal communication, April 1980).
In September of 1970, the Tennessee River and Pickwick
Lake commercial fisheries were closed, a health warning
was issued, and a catch and release policy instituted for
sport fishing in these areas. Both the commercial and
sport fisheries restrictions were removed for Pickwick
Lake and the Tennessee River in August of 1971. A catch
and release restriction and health warning imposed on
sport fishing in the North Fork Holston River'in
September 1970 is still in effect and commercial fishing
is also not allowed. The source of mercury is runoff
from a closed chlor-alkali plant in Virginia (Elmo Lunn;
Water Quality Control Division, State of Tennessee;
personal communication, April 1980).
In 1970 approximately 19,900 acres of Lavaca Bay were closed
to commercial oyster harvest because of an accidental
spill from a chlor-alkali plant. This was a single
occurrence, and any detectable mercury levels today can
be Attributed to runoff of residual mercury from the
spill or from natural sources. In September 1971 the
size of the restricted area was reduced from 19,900 acres
to 11,000 acres. Currently safety warnings are in effect
for^only a small area adjacent to the site of the spill.
Additionally, the restrictions on the harvesting of
oysters were not entirely because of mercury pollution-
prior to its reclassification in 1970, Lavaca Bay had
approximately 8500 acres that were closed because of
sanitary and bacteriologic reasons (Lloyd Crabb; Shellfish
Program, Bureau of Environmental Health, State of Texas-
personal communication, April 1980). " '
203
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STATE
CURRENT STATUS
Vermont*
Virginia**"
West Virginia*
Wisconsin*
In 1970 Lake Champlain and its tributaries were closed
to the commercial harvest of walleye. In addition, an
embargo was placed on commercial sales of walleye from
Lake Champlain, its tributaries, and Lake Memphremagog,
and the embargo is still in effect. On April 25, 1973,
the sport fishery danger warnings imposed in 1970 were
continued for the consumption of walleye from Lake
Champlain, its tributaries, and Lake Memphremagog.
After a state sampling program, all other restrictions
were lifted in the mid 1970s. Mercury concentrations
are attributable to natural sources (Wally McClane;
Water Resources Division, State of Vermont; personal
communication, April 1980).
In 1970 the sport fishery on the North Fork of the Holston
River below Saltville was closed by the Virginia Depart-
ment of Health due to contaminated runoff from a closed
chlor-alkali plant. In 1975 this restriction was relaxed
to permit fishing under a catch and release regulation,
and the restriction was completely lifted in 1977. A
health warning was issued in 1970 and again in 1975
concerning the danger of eating fish taken from these
waters; this warning is still in effect. On June 6, 1977,
the Virginia Department of Health closed the sport fishery
on the South River, the south fork of the Shenandoah
River between Waynesboro and the Page County line, which
is restricted to a "catch and release" policy. Citizens
are warned that fish taken from these waters are unfit
for human consumption (Robert Stroube; Bureau of Toxic
Substances, Department of Health, State of Virginia;
personal communication, April 1980).
Sport and commercial fisheries in West Virginia are
presently not restricted due to mercury pollution. The
Ohio River commercial fishery, which was closed on
August 29, 1970, was reopened on July 1, 1973. Currently,
West Virginia has no health warnings in effect about the
consumption of mercury-contaminated fish (NAS 1978).
In 1970 a catch and release policy was recommended for
the Wisconsin River, along with a health warning that
not more than one meal of fish taken from this river
should be consumed each week. As of 1977, there were
no state restrictions because mercury levels in the
Wisconsin River system had dropped below the FDA action
level of 0.5 ug/g. Contracts for commercial fishing are
now being granted for the Wisconsin River and its impound-
ments, and warnings on fish consumption limits are no
longer being issued (NAS 1978).
204
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REFERENCE
9 -J- -7 / *J •
205
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