ORNL
Oak Ridge
National
Laboratory
Operated by
Union Carbide Corporation for the
Department of Energy
Oak Ridge, Tennessee 37830
ORNL/EIS-80
EPA
United States
Environmental Protection
Agency
Office of Research and Development
Health Effects Research Laboratory
Cincinnati, Ohio 45268
EPA-600/1 -78-023
REVIEWS OF THE ENVIRONMENTAL
EFFECTS OF POLLUTANTS:
III. CHROMIUM
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL HEALTH EFFECTS RE-
SEARCH series. This series describes projects and studies relating to the toler-
ances of man for unhealthful substances or conditions. This work is generally
assessed from a medical viewpoint, including physiological or psychological
studies. In addition to toxicology and other medical specialities, study areas in-
clude biomedical instrumentation and health research techniques utilizing ani-
mals — but always with intended application to human health measures.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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ORNL/EIS-80
EPA-600/1-78-023
May 1977
Contract No. W-7405-eng-26
REVIEWS OF THE ENVIRONMENTAL EFFECTS OF POLLUTANTS: III. CHROMIUM
by
Leigh E. Towill, Carole R. Shriner, John S. Drury,
Anna S. Mammons, and James W. Holleman
Information Center Complex, Information Division
Oak Ridge National Laboratory
Oak Ridge, Tennessee 37830
operated by
Union Carbide Corporation
for the
Department of Energy
Reviewer and Assessment Chapter Author
James 0. Pierce
University of Missouri
Columbia, Missouri 65201
Interagency Agreement No. D5-0403
Project Officer
Jerry F. Stara
Office of Program Operations
Health Effects Research Laboratory
Cincinnati, Ohio 45268
Date Published: May 1978
Prepared for
HEALTH EFFECTS RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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This report was prepared as an account of work sponsored by an agency
of the United States Government. Neither the United States Government nor
any agency thereof, nor any of their employees, contractors, subcontractors,
or their employees, makes any warranty, express or implied, nor assumes any
legal liability or responsibility for any third party's use or the results
of such use of any information, apparatus, product or process disclosed in
this report, nor represents that its use by such third party would not
infringe privately owned rights.
This report has been reviewed by the Health Effects Research Laboratory,
U.S. Environmental Protection Agency, and approved for publication. Approval
does not signify that the contents necessarily reflect the views and policies
of the U.S. Environmental Protection Agency, nor does mention of trade names
or commercial products constitute endorsement or recommendation for use.
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CONTENTS
Figures vii
Tables ix
Foreword xiii
Acknowledgments xv
Abstract xvli
1. Summary 1
1.1 Discussion of Findings 1
1.1.1 Chemical Properties and Analytical Techniques. ... 1
1.1.2 Environmental Occurrence 2
1.1.3 Environmental Cycling and Fate 4
1.1.4 Biological Aspects in Microorganisms 5
1.1.5 Biological Aspects in Plants 5
1.1.6 Biological Aspects in Wild and Domestic Animals. . . 6
1.1.7 Biological Aspects in Humans and Test Animals. ... 7
1.1.8 Food Web Interactions 9
1.2 Conclusions 9
2. Physical and Chemical Properties and Analysis 12
2.1 Summary 12
2.2 Physical and Chemical Properties 13
2.2.1 The Element 13
2.2.2 Divalent Chromium 14
2.2.3 Trivalent Chromium 17
2.2.4 Tetravalent and Pentavalent Chromium 20
2.2.5 Hexavalent Chromium 21
2.2.6 Biochemistry of Chromium 23
2.2.7 Environmental Chemistry of Chromium 24
2.3 Analysis for Chromium 26
2.3.1 Considerations in Analysis 26
2.3.2 Analytical Procedures 28
2.3.3 Comparison of Analytical Methods 42
3. Biological Aspects in Microorganisms 56
3.1 Summary 56
3.2 Metabolism 56
3.2.1 Uptake 56
3.2.2 Concentration 57
3.2.3 Biotransformation and Elimination 57
3.3 Effects 57
3.3.1 Algae 59
3.3.2 Protozoa 64
3.3.3 Fungi 64
3.3.4 Bacteria 65
4. Biological Aspects in Plants 71
4.1 Summary 71
4.2 Metabolism 71
4.2.1 Question of Essentiality 71
4.2.2 Uptake 72
4.2.3 Translocation 73
4.2.4 Distribution 82
4.2.5 Plant Concentration and Pollution Sources 92
iii
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iv
4.2.6 Elimination 95
4.3 Effects 96
4.3.1 Smelter Waste Toxicity 96
4.3.2 Symptoms in Culture Experiments 96
5. Biological Aspects in Animals 107
5.1 Summary 107
5.2 Metabolism 107
5.2.1 Uptake and Absorption 107
5.2.2 Transport and Distribution 110
5.2.3 Elimination 117
5.3 Effects 120
5.3.1 Physiological Effects 120
5.3.2 Toxicity 121
6. Biological Aspects in Humans 141
6.1 Summary 141
6.2 Metabolism 142
6.2.1 Uptake and Absorption 142
6.2.2 Transport 143
6.2.3 Distribution 144
6.2.4 Chromium Interactions 151
6.2.5 Elimination 152
6.3 Effects 153
6.3.1 Effects on Biochemical Systems 153
6.3.2 Nutrition: Chromium Deficiency in Diets 165
6.3.3 Toxicity 168
7. Environmental Distribution and Transformation 199
7.1 Summary 199
7.2 Trends in Production and Usage 200
7.3 Distribution of Chromium in the Environment 208
7.3.1 Sources of Pollution 208
7.3.2 Distribution in Air 213
7.3.3 Distribution in Soil 226
7.3.4 Distribution in Water 235
7.3.5 Distribution in Sediments 240
7.4- Environmental Fate 242
7.4.1 Mobility and Persistence in Air 243
7.4.2 Mobility and Persistence in Soil 244
7.4.3 Mobility and Persistence in Water and Sediments. . . 244
7.5 Waste Management 247
8. Environmental Interactions and Their Consequences 264
8.1 Summary 264
8.2 Environmental Cycling 264
8.3 Human Exposure 265
8.4 Biomagnification in Food Chains 270
8.4.1 Terrestrial Food Chains 270
8.4.2 Aquatic Food Chains 271
9. Environmental Assessment ... 277
9.1 Summary 277
9.2 Quantity of Chromium Entering Various Environmental Media . 278
9.3 Judgment of Potential Toxicity 279
9.4 Toxicity and Human Health Effects 280
9.5 Persistence in the Environment 282
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9.6 Critical Environmental Pathways 282
9.7 Biomagnification 283
9.8 Summary Opinion and Research Needs 283
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FIGURES
3.1 The effect of different concentrations of chromium on the
growth of N. palea 62
3.2 Inhibitory effects of sodium chromate concentrations on
the alga Selenastvwn aapricornutum 63
4.1 The translocation of chromium(III)-EDTA in rice plants. ... 74
4.2 Chromium concentrations in vegetation illustrating the
transfer of increased quantities of the trace element by
cooling-tower drift to the landscape 93
4.3 Chromium concentrations in foliage of deciduous and
coniferous tree species 93
4.4 Accumulation of chromium by tobacco plants exposed to
cooling-tower drift 98
4.5 Effects of increased chromium concentrations on leaf size
in tobacco exposed to cooling-tower drift 99
5.1 Accumulation of 5lCr by Hermione hystrix from seawater
containing the radionuclide in the form of chromate .... 108
5.2 Uptake of hexavalent chromium by two groups of rainbow
trout exposed to 0.0100 and 0.0013 ppm chromium 110
5.3 Accumulation from solution of 51Cr by the crab, P. vigil. . . 118
5.4 Retention of 51Cr by Hermione hystrix following a 12-day
exposure to the radionuclide in high specific activity in
seawater in the form of chromate 119
5.5 Retention of 51Cr by Sigmodon hispidus 120
5.6 Time course of survival of Daphnia pulex exposed to high
concentrations of sodium dichromate 130
5.7 Percent survival of 12-day-old Daphnia pulex exposed to
various concentrations of sodium dichromate 131
5.8 Chromium toxicity of potassium dichromate and potassium
chromate to bluegills 135
6.1 Micrograms of chromium in lungs of guinea pigs after
intratracheal injections of 200 yg of chromium as
trivalent chromic chloride or chromates 147
6.2 Rate of urinary and fecal excretion and blood clearance of
intravenously injected trivalent 51Cr from male rats. . . . 154
6.3 Possible structure for the glucose tolerance factor 156
6.4 Relationship between chromium contents per milliliter of
aqueous alcohol extracts of foods and the corresponding
biological activities 167
7.1 Supply-demand relationships for chromium, 1968 205
vii
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viii
7.2 Chromium material flow, 1970 207
7.3 Chromium content of U.S. surficial materials 230
7.4 Chromium concentration in sediments from the southern
California basins 242
7.5 Flow diagram for precipitation treatment of wastes 250
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TABLES
2.1 Chromium isotopes 14
2.2 Physical properties of typical chromium compounds 15
2.3 Some mononuclear chromium(III) complexes of singly coordinat-
ing and bidentate chelating ligands 19
2.4 Solubility of chromium trioxide and selected chromates in
water 22
2.5 Trace element concentrations in different materials 28
2.6 Instrumental methods for the determination of chromium. ... 31
2.7 Mean chromium content in different types of sugars 36
2.8 Interlaboratory study of chromium analysis by atomic
absorption spectrophotometry 45
2.9 Interlaboratory comparison results from water analysis of
chromium 46
3.1 Microbial concentration of chromium 58
3.2 Chromium content of algae 59
3.3 Approximate concentration ranges of chromium which
completely inhibited growth in seven species of algae ... 60
3.4 Greatest concentration of chromium which permitted growth
equal to or better than controls (no chromium) in seven
algal species 61
4.1 The rate of chromium absorption by intact rice plants as a
function of the chromium concentration in nutrient
solution 73
4.2 Distribution pattern of chromium after absorption by intact
rice plants 74
4.3 Yield and chromium content of corn grown in greenhouse pot
experiments in soils with various amendments 76
4.4 Chromium concentrations in ten New Jersey soils and in corn
and ragweed grown on these soils 77
4.5 Distribution of 51Cr in wheat and beans grown in solution
culture with either 51Cr-labeled trivalent or hexavalent
chromium 79
4.6 Trivalent and hexavalent chromium in the ash of some plant
materials 80
4.7 Chromium-51 extracted by various methods from wheat and beans
grown in solution culture with 51Cr-labeled hexavalent
chromium 81
4.8 Distribution of slCr in various subcellular fractions after
differential centrifugation of leaf homogenates 82
ix
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4.9 Chromium concentrations in food plants 83
4.10 Chromium concentrations in crop plants 84
4.11 Chromium concentrations in plant and soil samples from a
serpentine area 86
4.12 Chromium content of major rock types in Finland and of the
soils formed over these rocks 87
4.13 Chromium concentrations in plants growing in soils overlying
silicic, ultrabasic, or calcareous rocks 88
4.14 Chromium concentrations in selected plant species growing on
different soils in Finland ; 89
4.15 Chromium concentrations in a variety of plants 90
4.16 Chromium content of fruits and vegetables from Panama .... 92
4.17 Chromium concentrations in plants grown on control and
sludge-amended soils 94
5.1 Chromium in wild and domestic animal tissues Ill
5.2 Chromium concentrations in the hair of several wild animal
species 112
5.3 Accumulation of chromium in various tissues of aquatic
organisms 114
5.4 Comparison of chromium distribution pattern in cotton rats
(S-igmodon hispidus) exposed to cooling-tower drift and in
control animals 116
5.5 Uptake of chromate by Tapes deoussatus exposed to different
chromium concentrations in seawater 116
5.6 The effect of exposure to 20 ppm chromium on the blood of
rainbow trout, Salmo ga-irdneT-i 122
5.7 Toxicity of chromium to aquatic biota 123
5.8 Sublethal doses of inorganic chromium for aquatic organisms . 129
5.9 Median tolerance limit values for chromate in the rotifer
Philodina roseola 132
5.10 Salinity effects on median tolerance limits for chromium in
the crab Rangia ouneata 133
5.11 Median tolerance limit values of trivalent chromium for
several fish species 134
5.12 Median tolerance limit values and 95% confidence limits of
chromium for four species of warmwater fishes 136
6.1 Chromium concentrations in the organs of rats given plain
water, basal water without chromium, and basal water with
chromium 146
6.2 Chromium concentrations in human tissues 148
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XI
6.3 Geographical distribution of chromium in human tissues. . . . 150
6.4 Mean hair chromium concentrations of human subjects ages
0 to 35 months 151
6.5 Biochemical actions of chromium 155
6.6 Effect of chromium on mean glucose tolerance 159
6.7 Summary and significance of the effect of chromium on the
impaired glucose tolerance of malnourished infants 161
6.8 Effects of chromium, nickel, molybdenum, and cadmium on
fasting serum cholesterol levels in rats on a starch diet . 162
6.9 Chromium levels in aortas of subjects dying from arterio-
sclerotic heart disease, other cardiovascular diseases,
and other conditions including accidents 164
6.10 Calculated chromium biological values of the edible portion
of selected foods as purchased 166
6.11 Chromium content of sugars 168
6.12 Toxicity and uses of some chromium compounds 170
6.13 Animal exposures to chromates 173
6.14 Fatal doses of trivalent chromium in animals 175
6.15 Nasal injuries in a chromium-plating plant 179
6.16 Clinical findings in workers employed in chromium-plating
plants 181
6.17 Microscopic pulmonary findings in rabbits, guinea pigs, rats,
and mice after inhalation and intratracheal injections of
chromate material 183
6.18 Death distribution and tumors observed in rats at site of
implants of chromium compounds and of sheep fat 185
6.19 Carcinomas produced with chromium compounds in rats 186
7.1 Chromium content of various materials 200
7.2 Estimated world reserves and resources of chromite ore. . . . 202
7.3 Estimated world chromite ore resources 203
7.4 Contingency forecasts of demand for chromium by end use,
year 2000 206
7.5 Sources and estimates of chromium-containing atmospheric
emissions in 1970 209
7.6 Regional distribution of principal chromium sources and
emissions 210
7.7 Chromium emission sources 211
7.8 Chromium concentrations in Belgian coal and coal ash 212
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xii
7.9 Composition of chromium-containing wastes from metal plating
industries 214
7.10 Chromium concentrations in urban and nonurban air, quarterly
composites and yearly averages, 1969 215
7.11 Levels of airborne chromium in U.S. cities, 1954-65 223
7.12 Chromium concentrations in air 225
7.13 Chromium content of soils in various countries 226
7.14 Chromium concentrations in selected soils 229
7.15 Chromium content of air-dried soils 231
7.16 Chromium content of various soils and their clay fractions. . 232
7.17 Total and extractable chromium from nonserpentine and
serpentine soils 234
7.18 Total and extractable chromium in soils exposed to cooling-
tower drift 235
7.19 Concentration of chromium in water supplies 236
7.20 Chromium in waters of the United States 237
7.21 Chromium composition of suspended material in rivers 239
7.22 Concentration of chromium in sediments 241
7.23 Chromium concentration in sediments of Wisconsin lakes. . . . 243
7.24 Chromium transported by five phases in the Yukon and
Amazon Rivers 245
7.25 Chromium concentrations in sewage sludge 252
8.1 Chromium content of fruits and vegetables 266
8.2 Chromium content in various foods 268
8.3 Chromium content of selected seafoods and fruit juices. . . . 271
8.4 Chromium content of selected food samples and biological
value of extracts containing chromium 272
8.5 Chromium concentration in selected trophic levels of a
forest ecosystem in East Tennessee 273
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FOREWORD
A vast amount of published material is accumulating as numerous
research investigations are conducted to develop a data base on the
adverse effects of environmental pollution. As this information is
amassed, it becomes continually more critical to focus on pertinent,
well-designed studies. Research data must be summarized and interpreted
in order to adequately evaluate the potential hazards of these substances
to ecosystems and ultimately to public health. The Reviews of the Environ-
mental Effects of Pollutants (REEPs) series represents an extensive com-
pilation of relevant research and forms an up-to-date compendium of the
environmental effect data on selected pollutants.
Reviews of the Environmental Effects of Pollutants: III. Chromium
includes information on chemical and physical properties; pertinent
analytical techniques; transport processes to the environment and sub-
sequent distribution and deposition; impact on microorganisms, plants,
and wildlife; toxicologic data in experimental animals including metabo-
lism, toxicity, mutagenicity, teratogenicity, and carcinogenicity; and an
assessment of its health effects in man. The large volume of factual
information presented in this document is summarized and interpreted in
the final chapter, "Environmental Assessment," which presents an overall
evaluation of the potential hazard resulting from present concentrations
of chromium in the environment. This final chapter represents a major
contribution by James 0. Pierce from the University of Missouri.
The REEPs are intended to serve various technical and administrative
personnel within the Agency in the decision-making processes, i.e., in
the development of criteria documents and environmental standards, and
for other regulatory actions. The breadth of these documents makes them
a useful resource for public health personnel, environmental specialists,
and control officers. Upon request these documents will be made available
to any interested individuals or firms, both in and out of the government.
Depending on the supply, the document can be obtained directly by writing
to:
Dr. Jerry F. Stara
U.S. Environmental Protection Agency
Health Effects Research Laboratory
26 W. St. Clair Street
Cincinnati, Ohio 45268
R. J. Garner
Director
Health Effects Research Laboratory
xiii
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ACKNOWLEDGMENTS
The authors are particularly grateful to F. G. Taylor, Jr., Environ-
mental Sciences Division, and L. N. Klatt, Analytical Chemistry Division,
Oak Ridge National Laboratory (ORNL), for reviewing preliminary drafts of
this report and for offering helpful comments and suggestions. The advice
and support of Gerald U. Ulrikson, Manager, Information Center Complex,
and Jerry F. Stara, EPA Project Officer, and the cooperation of the Toxi-
cology Information Response Center, the Environmental Mutagen Information
Center, and the Energy and Environmental Response Center of the Informa-
tion Center Complex, Information Division, ORNL, are gratefully acknowl-
edged. The authors also thank Carol Brumley and Maureen Hafford, editors,
and Donna Stokes and Patricia Hartman, typists, for preparing the manu-
script for publication.
Appreciation is also expressed to Bonita M. Smith, Karen L. Blackburn,
and Donna J, Sivulka for EPA in-house reviews and editing and for coordinat-
ing contractual arrangements. The efforts of Allan Susten and Rosa Raskin
in coordinating early processing of the reviews were important in laying
the groundwork for document preparation. The advice of Walter E. Grube
was valuable in preparation of manuscript drafts. The support of R. John
Garner, Director of Health Effects Research Laboratory, is much appreciated.
Thanks are also expressed to Carol A. Haynes and Peggy J. Bowman for typing
correspondence and corrected reviews.
xv
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ABSTRACT
This study is a comprehensive, multidisciplinary review of the
health and environmental effects of chromium and specific chromium com-
pounds. Approximately 500 references are cited.
Chromium is abundant in the earth's crust and is widely dispersed
in the environment. It is used extensively in refractory materials and
chemicals, as a plating to produce hard and smooth surfaces, to prevent
corrosion, and in manufacturing stainless and alloy steels. Major atmos-
pheric emissions of chromium arise from metal producing industries,
coal-fired plants, municipal incinerators, and cooling towers. Major
releases to water are chiefly from the electroplating metal-finishing,
textile, and tanning industries.
Harmful effects to man or animals seldom result from chromium in
ambient air or public drinking water. Reported chromium toxicity occurs
mainly from occupational exposure. Trivalent compounds are not highly
toxic, but excessive exposure to dusts or mists of hexavalent chromium
compounds produces dermatitis, skin lesions, and ulceration and perfora-
tion of the nasal septum, as well as liver and kidney damage. With long-
term exposure to hexavalent chromium compounds, incidence of human lung
cancer increases. No data suggest that these compounds are mutagenic or
teratogenic risks.
Trace levels of chromium are essential to mammalian life. Irreversi-
ble metabolic damage may result from long-standing chromium deficiency.
As a result of the refinement of many foods, diets in the United States
are often low in chromium; organs of Americans usually contain less chro-
mium than corresponding organs of people from other nations. Except in
the lungs, tissue chromium content decreases progressively with age, which
suggests that intake of biologically active chromium in the United States
is marginal.
This report was submitted in partial fulfillment of Interagency
Agreement No. D5-0403 between the Department of Energy and the U.S.
Environmental Protection Agency. The draft report was submitted for
review June 1976. The final report was completed in August 1977.
xvii
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SECTION 1
SUMMARY
1.1 DISCUSSION OF FINDINGS
1.1.1 Chemical Properties and Analytical Techniques
Chromium, a transition element, is a steel gray, lustrous, hard metal
which melts at 1857°C and boils at 2672°C and has valence states ranging
from -2 to +6 (Section 2.2). A variety of chromium compounds are prepared
from chromite ore. Most of these compounds contain chromium in the more
stable trivalent and hexavalent oxidation states. The chromium in essen-
tially all environmentally important chromium compounds is in one of these
two oxidation states. Although tetravalent and pentavalent chromium com-
pounds exist, they are unstable and decompose to hexavalent and trivalent
chromium in aqueous solution (Section 2.2.4). The major chromium compounds
produced are chromic oxide, chromic sulfide, chromic halides, and chromic
sulfate. In aqueous solution, trivalent chromium forms a large array of
hexacoordinate complexes with amines, water, urea, halides, sulfates, and
organic acids (Section 2.2.3.5). Coordination complexes also occur with a
variety of anions (Section 2.2.3.5). Olation occurs at alkaline pH; a wide
range of polynuclear complexes are formed and ultimately precipitate as the
olated complex Cr(OH)3«XH20. All stable hexavalent chromium compounds are
oxy compounds and are strong oxidants. Chromates (Cr042~) and dichromates
(Cr2072~) are used to prepare other chromium compounds (Section 2.2.5).
The biochemistry of chromium is not completely known (Section 2.2.6).
Chromium can react with nucleic acids and proteins. In reactions with pro-
teins, it binds to carboxyl groups of glutamic and aspartic acids. Hexa-
valent chromium is probably reduced in biological systems; thus, the
prevalent interacting species would be trivalent chromium. Complexes of
trivalent chromium with several organic acids (Krebs cycle acids) are known.
Several analytical techniques are sufficiently sensitive to detect
chromium concentrations in the parts per billion range in a variety of
samples (Section 2.3). Care in handling is necessary to avoid severe con-
tamination of the sample. Loss of chromium as a volatile organo-chromium
compound has also been suggested but recent careful work has failed to dem-
onstrate losses from this source.
Chromium can be collected from air by impingers, electrostatic precip-
itators, and filters (Section 2.3.2). Water samples are collected in con-
tainers which do not contain chromium (borosilicate, clean quartz, or
polyethylene); the water is acidified and then used for analysis. Inorganic
solids are solubilized (ignition, acid digestion, or alkali digestion)
before analysis. Biological samples need to be ashed carefully to avoid the
possibility of chromium loss. In samples with low chromium content, separa-
tion and concentration may be necessary before analysis. Precipitation with
hydroxyquinoline and tannic acid may be used. Oxidation in a basic medium
forms soluble chromates, whereas many trace elements will precipitate.
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Liquid-liquid solvent extraction with the complexing agent ammonium pyrro-
lidinedithiocarbamate and the solvent methyl isobutyl ketone can concentrate
the chromium sample. Prior oxidation of all chromium(III) to chromium(VI)
is necessary because this technique extracts only hexavalent chromium.
Chromatography can be used to separate chromium from some interfering ele-
ments and to concentrate chromium in the sample.
Atomic absorption spectrometry (flame and flameless) is the most common
method used to detect chromium in samples (detection limits of about 20 ppb
in the flame method and of about 0.2 ppb in the flameless method) (Section
2.3.2.3). With biological samples, the organically complexed chromium should
first be converted to inorganic chromium by low-temperature ashing. The
flameless atomic absorption method may become more useful for routine, prac-
tical analysis in the near future.
Neutron activation analysis is also widely used to determine chromium
concentrations, but this method is expensive and is best suited for multi-
element determinations. After prior treatment to separate and concentrate
the element, concentrations of a few parts per billion can be detected.
Molecular absorption spectrophotometry, which uses the diphenylcarbazide
complex, is a classical analytical method; however, atomic absorption, neu-
tron activation analysis, and emission spectroscopy are now more commonly
used. Emission spectroscopy can detect chromium concentrations down to 0.3
ppb and spark-source mass spectrometry can detect about 0.02 to 0.1 ppb. The
precision and accuracy of spark-source mass spectrometry can be increased by
combining it with the isotope dilution technique. Other methods of chromium
analysis include x-ray fluorescence, gas Chromatography—mass spectrometry,
and single-sweep polarography. These analytical methods, however, are not
used extensively.
The greatest problem with chromium analysis, and indeed with chromium
studies in general, is the large uncertainty in the analysis of some types
of biological and environmental samples. Differences of more than an order
of magnitude in the chromium content of NBS bovine liver have been reported
by collaborating laboratories and the differences have persisted in spite
of considerable time and effort in trying to resolve them. Quite recently,
some progress toward getting better interlaboratory agreement has been made,
but the reasons for the earlier disagreements remain obscure. Until more is
learned about the reasons for the analytical problems, extreme care must be
used when drawing eonclusions from past analytical results.
1.1.2 Environmental Occurrence
Environmentally, chromium is ubiquitous. Low concentrations (about
10 ppm) are present in granite and limestones, while extremely high concen-
trations (average about 1800 ppm) are found in ultramafic and serpentine
materials (Section 7.2). Chromite is the major mineral form of chromium;
all chromium and chromium compounds prepared in the United States are from
imported chromite ores. Importation is considerably more economical than
mining the U.S. chromite deposits, most of which have a low chromium con-
tent. About 75% of the imported ore comes from the U.S.S.R. and South
Africa.
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Sources of atmospheric chromium include emissions from coal-fired
power plants, iron and steel industries, municipal incinerators, and cool-
ing towers. Yearly average concentrations of chromium in urban air (1968
and 1969) ranged from below detection level to 0.1 pg/m3; concentrations
exceeded 0.1 yg/m3 in only 59 of 186 urban cities. Air from nonurban areas
did not contain measurable amounts of chromium. Seasonal and day-to-day
variations in the amounts of chromium in the air can be expected. Back-
ground levels of chromium in air are difficult to determine; a concentration
of 5.3 pg/m3 detected at the South Pole was attributed to weathering of
crustal materials.
Most chromium in the atmosphere is particulate. The form of chromium
in these particulates is unknown but most likely is the trivalent state.
Chromates, however, do occur in the drift from cooling towers. Chromium is
present in particulates of all sizes. Although there are conflicting data,
smaller particles of fly ash from coal combustion generally have somewhat
higher chromium concentrations than larger particles. The data suggest
that surface enrichment of particulates may occur during the combustion
process.
Chromium concentrations in most soils range from 5 to 300 ppm (Section
7.3.3). The chromium concentration can be considerably higher in soils
formed over serpentine rock (500 to 62,000 ppm, ash wt basis). The clay
fraction of most soils typically has a higher proportion of chromium. Chro-
mium concentration does not change significantly with depth. Chromium in
soils, even those derived from serpentine strata, is mainly in an insoluble
state in adsorbed, mineral, or precipitated form. The relative contribu-
tions of adsorption to clays, organic matter, and iron or manganese hydrous
oxides and of precipitation reactions in decreasing the soluble chromium
content are not known. Presumably, these factors would vary with the phys-
ical and chemical characteristics of the soil. In most cases, these reac-
tions make chromium relatively unavailable for uptake by plants. Water-
extractable chromium in soils is usually less than 0.01 ppm. Chromium
amounts extractable by 2.5% acetic acid are likewise low — about 1 ppm in
many soils.
Chromium content in soils decreases with distance away from cooling
towers. In one study, background levels were reached at about 300 m from
the tower. Although chromium in the cooling-tower drift was in the form
of chromate, the amount of extractable chromium in the soils was quite low
(0.4 to 1.9 ppm). These findings suggest that reduction occurs in the soil
and that trivalent chromium is readily adsorbed or precipitated.
Trace quantities of chromium can be found in both surface water and
groundwaters. Dissolved chromium concentrations in fresh water ranged from
about 0 to 112 ppb, with an average of 9.7 ppb (Section 7.3.4). Higher
concentrations were observed in more industrialized areas. Concentrations
of chromium were considerably lower in seawater (0 to 0.5 ppb) than in fresh
water. In the early 1960s, most waters used as sources of drinking water
contained less than 8 ppb chromium. Only 4 of 969 public water supply sys-
tems examined in 1969 had finished drinking waters which contained more than
50 ppb chromium.
-------
Electroplating and metal finishing account for the major release of
chromium to wastewaters (Section 7.3.4). In addition, the textile and
tanning industries release some chromium. Significant amounts can also be
contributed by runoff from urban and residential areas (about 9% of the
total chromium received at sewage plants in New York City). Relative con-
tributions from different pollution sources to the total amount of chromium
found in wastewaters have not been reported for most cities.
In water with little organic matter, both trivalent and hexavalent
chromium can exist. Both forms are also found in seawater, but hexavalent
chromium is usually the major species (Section 7.3.4).
Significant amounts of chromium occur in particulate form in water.
For example, 67.6% of the total chromium in the Walker Branch Watershed
(Tennessee) was in particulate form. Chromium concentrations in the sus-
pended particles varied considerably (from 37 to 2000 ppm).
Most sediments contain chromium. Chromium concentrations of 90 to 140
ppm in some California basin sediments and of 1 to 49 ppm in Wisconsin lake
sediments were reported (Section 7.3.5). Concentrations of up to 1240 ppm
chromium have been found (Rhine River sediments). Slightly higher chromium
concentrations were reported in surface sediments. Although anthropogenic
input of chromium occurs, the amount has not been great enough to cause
large surface concentrations in sediments from most areas.
1.1.3 Environmental Cycling and Fate
Although some aspects of the environmental cycling of chromium are
known, quantitative data on the amount cycled are lacking (Section 7.4).
Atmospheric chromium, mainly in particulate form, is deposited on land or
water by fallout and precipitation (Section 7.4.1). Chromium concentrations
in rain ranged from 0.6 to 60 ppb; a monthly deposition of 11 g of chromium
per hectare was reported.
Chromium in the soil is rather immobile. It is mainly in the trivalent
state because hexavalent chromium is reduced in the presence of organic
matter (Section 7.4.2). Little information on chromium loss by leaching and
surface runoff exists. Anaerobic conditions in some soils may slightly en-
hance chromium solubility. Weathering and wind action probably contribute
a small amount of chromium to the atmosphere, but this amount has not been
quantified.
Flowing water transports vast amounts of chromium (for example, 790
metric tons per year by the Susquehanna River). In one study, most chromium
was found to be transported in the form of crystalline sediments. Existing
data suggest that mobilization of chromium from sediments to soluble form
does not occur when the suspended material of a river is deposited in an
estuary. In water, hexavalent chromium is effectively adsorbed and precipi-
tated with Mn02»nH20 but not with Fe203«nH20, apatite, or clay. The rela-
tive amounts of chromium supplied to many basins by various sources, such
as wind, sewer outfalls, storms, runoff, and river flow, have not been
determined.
-------
Little information is available on the fate of chromium in sediments.
Currents determine the pattern of sediment deposition. Storms and other
violent weather could stir sediments, especially in shallow areas, and re-
distribute the chromium within the sediments. Probably, little chromium is
recycled. Chelating agents, such as nitrilotriacetic acid used in detergents,
are released to the environment and may occur in concentrations which would
serve to solubilize metals. However, present data suggest that little chro-
mium is solubilized in this way.
Waste management of chromium in water usually involves reduction of any
hexavalent chromium to trivalent chromium followed by precipitation at alka-
line pH (Section 7.5). The precipitate is normally disposed of as landfill.
Care must be taken to avoid acidification of these landfill sites since
chromium (and other metals) would be solubilized. Ion exchange, ion flota-
tion, electrochemical conversion, activated carbon adsorption, liquid-liquid
extraction, and reverse osmosis processes are potential waste treatments for
chromium removal, but none of these methods are economically practical at
present.
The efficiency of chromium removal from sewage varies with treatment
plant design and discharge procedure. Overall removal efficiencies of 17%
to 18% were reported in one study. Sewage sludge has a wide range of chro-
mium concentrations (20 to 40,000 ppm), most of which is insoluble. Moder-
ate deposition of sewage sludge on land only slightly increases the available
chromium content of the soil.
1.1.4 Biological Aspects in Microorganisms
Because of the ubiquity of chromium in the environment, all organisms
are exposed to chromium and chromium has been found in all organisms exam-
ined. Chromium has not been shown to be an essential element for microbes
(Section 3.2). Most microbes take up chromium and those examined contained
up to a few parts per million. Microorganisms near pollution sources may
contain higher concentrations. Mechanisms of uptake have not been adequately
studied; chromate uptake in Neupospora is by the sulfate transport system.
Growth inhibition is the major effect observed for chromium additions
to growth media (Section 3.3). Different species exhibit different toler-
ances for chromium. In some cases, other trace elements can overcome the
growth inhibition of a specific chromium concentration. Chromium inhibi-
tion of photosynthesis has been observed in some algae; inhibition of ger-
mination in fungi has also been observed. Chromium inhibits nitrogen
fixation in Azotobacter. Hexavalent chromium reportedly is mutagenic to
Esoheviohia col-i,
1.1.5 Biological Aspects in Plants
Considerably more information is available on the metabolism and
effects of chromium in higher plants. Although some reports show chromium
to be beneficial to plant growth, it has not been found to be an essential
element for higher plants (Section 4.2.1).
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Plants take up chromium mainly from the soil (Section 4.2.2). Trans-
location of chromium, supplied as either trivalent or hexavalent chromium,
from roots to aerial portions of the plant is small; thus, the highest
chromium concentrations occur in roots. If chromium is supplied as the
chelate, large amounts are translocated; however, the role of natural che-
lates within soil in supplying chromium to plants is unknown (Section
4.2.3). Generally, the concentration of chromium within the plant increases
as the external available chromium concentration increases.
Chromium concentrations in plants growing on most soils are usually
only a few parts per million (Section 4.2.4). However, some plants growing
on infertile serpentine soils contain much higher chromium concentrations.
The endemic species of physiological races living in serpentine areas seem
either to exclude chromium or to tolerate high chromium levels in tissues.
The infertility of serpentine soils does not seem to be directly due to the
chromium concentration, although it may be a contributing factor. Plants
growing on soils amended with sewage sludge have slightly higher chromium
concentrations than control plants. These concentrations of chromium
apparently produce no toxic effects in the plants.
In solution and pot experiments, excess chromium in the growth medium
decreases both shoot and root growth and inhibits seed germination (Section
4.3.2). Growth inhibition can occur at concentrations of less than 1 ppm;
at higher concentrations death can occur. Growth inhibition takes the form
of decreased size, stunted roots and shoots, or abnormal inflorescence
development. Chlorosis occurs in some species.
The symptoms produced by excess chromium and the concentrations which
induce them are species specific. Interacting factors such as the content
of other elements in the medium can affect the results. Such data are
sparse for chromium interactions and plant growth. No data are available
on the effects of chromium on cellular metabolism or on how these effects
interact to produce the physiological effects observed.
1.1.6 Biological Aspects in Wild and Domestic Animals
Chromium uptake by animals is most easily studied in aquatic species.
Both hexavalent and trivalent chromium are taken up by aquatic organisms
(Section 5.2.1). Trivalent chromium in waters is often in particulate form
and can be ingested; therefore, it is found in the digestive tract of bottom
dwellers. Hexavalent chromium compounds are soluble and can be rapidly
sorbed by the gut and body walls. Surface adsorption of particulates can
occur on shells, gills, mantle, and other body surfaces. Chromium uptake
has been demonstrated in clams, polychaete worms, oysters, crabs, and fishes.
The effects of high chromium concentrations on these animals include reduced
growth and weight, increased oxygen consumption, and increased hematocrits.
Both trivalent and hexavalent compounds can be toxic to organisms. In
aquatic organisms, toxicity varies with pH, water hardness, temperature,
species, and size of the organism (Section 5.3.2). The lethal level of
chromium reported for some aquatic invertebrates was approximately 0.05 ppm;
for other organisms, lethal concentrations were greater. In soft water
trivalent chromium is more lethal to fish than hexavalent chromium, but'in
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hard water the opposite appears true. Toxic concentrations of chromium
vary considerably among different species of fish. For example, median
tolerance limits for trivalent chromium in soft water at 24 hr were 4 ppm
for guppies, 11 ppm for goldfish, 67 ppm for bluegills, and 5 ppb for fat-
heads. Values at 48 and 96 hr did not differ greatly. Various insects
have reportedly survived exposure to chromium concentrations in the 1 to
64 ppm range. No data were found for chromium interactions in birds, am-
phibians, or wild and domestic mammals.
1.1.7 Biological Aspects in Humans and Test Animals
Chromium is an essential trace element for humans. Most chromium is
taken up by ingestion; lesser amounts are taken up by the respiratory tract
and through damaged skin (Section 6.2.1). Absorption can occur through the
gastrointestinal and respiratory tracts. Natural chromium complexes, such
as the glucose tolerance factor, are absorbed to a greater extent than in-
organic trivalent chromium. Hexavalent chromium is reduced to trivalent
chromium by acid gastric juices. Inhaled chromium can be trapped in the
bronchi and subsequently swallowed (ingested), deposited in the alveoli
where it may remain in insoluble form (trivalent compounds), or absorbed
into the bloodstream (for example, chromates). Chromium complexes with
plasma proteins (g-globulins) of the blood and is distributed to body
tissues (Section 6.2.2).
The tissue uptake of chromium administered experimentally depends on
the chemical form. Soluble complexes such as acetate and citrate are ex-
creted before much uptake can occur. Compounds which give rise to colloidal
or protein-bound forms, such as chromite and chromic chloride, are retained
longer and uptake is greater. Phagocytosis of colloidal particles probably
explains the uptake of chromite by the reticuloendothelial system, liver,
spleen, and bone. Chromium as chromic chloride is also taken up by these
organs and accumulates in the spleen. The fetus has an affinity for chro-
mium which may result in marginal chromium deficiency in the mother. The
chromium level in the fetus starts to rise during the third month of preg-
nancy and reaches a peak in the seventh month. In the newborn, the level
of chromium decreases. Chromium transferred across the placenta must be in
the form of the glucose tolerance factor.
Simple chromium complexes administered in drinking water (5 ppm) in-
creased the chromium levels in the heart, lung, and kidney of test animals
(Section 6.2.3.1). Intravenous injection of tracer amounts of chromium as
chromic chloride showed that tissue uptake and retention differed among
organs. At four days after injection, heart, lung, pancreas, and brain
showed a decrease in labeled chromium, whereas spleen, kidney, testis, and
epididymis concentrated the labeled chromium.
Adult human tissues generally contain about 0.02 to 0.04 ppm chromium.
Lung tissue contains about 0.22 ppm chromium, urine about 1.8 to 11 ppb,
and hair about 0.69 ppm. Reports of chromium in blood plasma vary consid-
erably (2 to 520 ppb). Chromium has the greatest affinity for the reticulo-
endothelial system, spleen, liver, and bone marrow. Hair of newborn humans
has a higher chromium content than that of older children. Some organs of
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Americans contain less chromium than corresponding organs of people from
other nations, which suggests that Americans have a chromium deficiency.
Except for the lungs, chromium levels in tissues decrease with age.
Individuals are exposed to chromium mainly through the diet. In humans,
daily chromium intake ranges from 5 to 115 yg (Sections 6.3.2 and 8.3). No
significant relationship exists between biologically active chromium and
total chromium content in foods; thus, certain foods are better sources of
available chromium (brewer's yeast, meats, grain, and seafoods). Diets in
the United States are often low in chromium as a result of the refinement
of most foods.
Elimination of chromium from rats showed three half-lives (0.5, 5.9,
and 83.4 days); in humans, overall elimination is slow (Section 6.2.5).
Chromium is excreted mainly through urine, although some may be eliminated
through feces. About 7 to 15 yg of chromium is excreted daily by humans.
In many cases, this amount may be more than is taken in, which results in
a slow drain of chromium reserves.
From a biochemical viewpoint, chromium interacts with a variety of
ligands; the best-known interaction with proteins is that with collagen
during the tanning process (Section 6.2.4). Chromium inhibits some enzymes
(for example, 3-glucuronidase), but stimulates others. It is an essential
component of the glucose tolerance factor. Chromium can also form complexes
with nucleic acids, but their biological significance is unknown.
The major role of chromium in metabolism is as a part of the glucose
tolerance factor. This complex, which is necessary for normal glucose
metabolism, acts by potentiating the action of insulin. Altered tolerance
to glucose is the first indication of a deficiency of the glucose tolerance
factor and of chromium. Glucose fails to enter the cells because of a lack
of the combined action of the factor and insulin. Irreversible metabolic
damage may result from long-standing chromium deficiency. The relationship
of chromium to diabetes is uncertain, but increased chromium supply has in-
creased glucose tolerance in some diabetics. Lipid metabolism is also al-
tered with chromium deficiency; serum cholesterol levels are higher in
chromium-deficient rats and humans. Atherosclerosis is less evident in
areas of the world where the population has higher chromium levels. Chro-
mium deficiency also decreases amino acid incorporation into proteins.
Chromium deficiency is widespread enough that supplementation with glucose
tolerance factor has been suggested as a public health measure.
Chromium is not considered particularly toxic; the amount of chromium
needed to produce toxic symptoms is many times higher than the amount needed
to relieve symptoms of deficiency. Due to insolubility, trivalent chromium
compounds are almost nontoxic when given orally. Hexavalent chromium com-
pounds are strong oxidizing agents and are highly irritating to tissues.
They are also easily absorbed and cross cell barriers easily and are there-
fore more of a toxicity hazard than are trivalent chromium compounds.
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Chromium toxicity, which is mainly a problem of occupational exposure,
occurs most often with workers directly exposed to dusts or mists of hexa-
valent chromium compounds. Workers exposed to chromates may develop primary
irritations with ulcers and nonulcerative contact dermatitis (eczematous and
noneczematous). Duration of contact, susceptibility, and hygiene affect the
incidence and extent of these maladies. Improved working conditions can
decrease the incidence of skin effects. Treatment with ascorbic acid to
reduce hexavalent chromium aids healing of skin irritations.
The major respiratory effects caused by exposure to chromatic dusts or
chromic acid mists are ulceration and perforation of the nasal septum. An
increased incidence of lung cancer is associated with long-term exposure to
hexavalent chromium (Section 6.3.3.2.2). The latent period between first
exposure and occurrence of cancer generally appears to be between 10 and 20
years. Dose-response curves for lung cancer are not known. Exposure to
chromium compounds for relatively brief periods (days to weeks) can also
cause sneezing, rhinorrhea, redness of the throat, bronchospasm, headaches,
and dyspnea. Chronic exposure and incidents of high exposure can cause
systemic poisoning and result in liver and kidney damage.
In experimental animals, carcinomas, mainly sarcomas, have been pro-
duced at the site of implantation of chromium compounds; however, the inci-
dence of occurrence has not allowed a dose-response relationship to be
established. No data suggest that chromium poses any mutagenic or terato-
genic risk.
The maximum workplace concentration of airborne carcinogenic chromium(VI)
recently recommended by the National Institute for Occupational Safety and
Health is 1 yg/m3 of breathing zone air. Air quality standards for the
general population can be expected to be more stringent because the exposure
periods are longer and because the population has a wider age variation and
range of health complications.
1.1.8 Food Web Interactions
Although some organisms apparently concentrate chromium, no biomagnifi-
cation in food chains has been observed (Section 8.4). Aquatic ecosystems
have been better studied than terrestrial ecosystems. The existing data
from both ecosystems indicate that organisms at lower trophic levels contain
higher chromium concentrations than organisms at higher trophic levels. The
explanation may be that hexavalent chromium absorbed by lower forms is re-
duced in situ to the less soluble trivalent form, which is not subsequently
absorbed by the predator.
1.2 CONCLUSIONS
1. The environmentally important oxidation states of chromium are the
trivalent and hexavalent forms. Organic matter reduces hexavalent
to trivalent chromium.
2. With suitable analytical procedures, chromium concentrations of less
than 1 ppb can be detected. However, continued poor results from
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10
interlaboratory comparison studies indicate that extreme caution
should be used when drawing conclusions which depend on the accuracy
of analytical results.
3. Major atmospheric emissions of chromium are from the chromium alloy
and metal-producing industries; lesser amounts come from coal combus-
tion and cement production. Major emissions to water occur from the
electroplating industry.
4. Chromium is ubiquitous in soils and is typically present in the range
of 5 to 300 ppm. Most soil chromium is unavailable for plant uptake.
5. Data on the amounts of chromium cycled by environmental factors are
lacking. Little chromium is leached from soils; chromium in waters
is deposited in sediments.
6. All organisms contain measurable amounts of chromium. Uptake of both
trivalent and hexavalent chromium can occur.
7. Mammals appear to be the only group of organisms for which chromium
is an essential element.
8. Chromium can reduce both root and shoot growth in plants and can
inhibit photosynthesis and nitrogen fixation in microbes. Various
organisms have different tolerances and no specific mechanisms of
action are known.
9. Chromium is acquired by humans mainly through ingestion and dis-
tributed to tissues by the blood.
10. Altered glucose tolerance is the first observed symptom of chromium
deficiency. Chromium is involved in glucose metabolism as part of
the glucose tolerance factor, which acts with insulin to govern the
entry into cells of sugars as well as amino acids and lipids.
11. Diets in the United States are often low in chromium as a result of
the refinement of many foods. Some evidence suggests a deficiency
of chromium and of the glucose tolerance factor which becomes more
severe with age.
12. Chromium toxicity is mainly an occupational concern. Trivalent chro-
mium compounds are not a great toxicity hazard. Industrial exposure
to dusts or mists of hexavalent chromium compounds produces dermatitis,
skin lesions, and ulceration and perforation of the nasal septum.
Systemic effects may also result. With long-term exposure, the
incidence of lung cancer increases.
13. No biomagnification of chromium has been observed in organisms of a
food chain. Chromium concentrations are highest in members of the
lower trophic levels.
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11
14. Probably the greatest single concern in drawing conclusions on chro-
mium effects in the environment is the analytical uncertainty shown
by interlaboratory comparison data. Drawing firm conclusions in the
face of these unresolved problems can be quite hazardous.
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SECTION 2
PHYSICAL AND CHEMICAL PROPERTIES AND ANALYSIS
2.1 SUMMARY
The inorganic chemistry of chromium has been well studied and under-
stood. However, its biologic and environmental interactions are obscure
and poorly characterized. This dichotomy is the direct result of the
chemical complexity of the element and the extremely low chromium concen-
trations often found in living matter. Chromium occurs in valence states
ranging from -2 to +6. The tripositive state, the most stable form, ex-
hibits a very strong tendency to form six-coordinate octahedral complexes
with a great variety of ligands such as water, ammonia, urea, halides,
sulfates, ethylenediamine, and organic acids. In neutral and basic solu-
tions, trivalent chromium forms polynuclear compounds in which adjacent
chromium atoms are linked through OH or 0 bridges. These compounds may
eventually precipitate as Cr203»nH20. Hexavalent chromium compounds have
the greatest economic importance as well as biological and environmental
significance. All stable hexavalent chromium compounds are oxy species
(such as Cr03, Cr.042~, and Cr02Cl2) which strongly oxidize organic matter
on contact. The other valence states of chromium are too unstable to be
significantly involved in the biochemical process with the possible ex-
ception of the very stable zero-valent state of "sandwich" complexes, such
as dibenzene chromium. There is no evidence that such compounds occur in
biologic media.
A variety of analytical techniques is available for the determination
of chromium in environmental samples down to the parts per billion level.
Although this sensitivity is adequate for most inorganic samples, it can
sometimes be achieved only at the expense of costly and time-consuming
preanalysis steps. There is a continuing need for more rapid and inex-
pensive methods of analysis which do not require pretreatment of samples.
The analysis of chromium in organic media is the most serious problem
currently confronting researchers interested in the biochemistry of this
element. Sometimes present only at the parts per billion level, chromium
in organic media is subject to severe contamination from equipment such as
knives, needles, and containers. Moreover, there is now little doubt that
chromium naturally present in some biological materials behaves differently
from inorganic chromium and that it may not be detected by flameless atomic
absorption spectrometry when it is introduced directly into the graphite
atomizer. The discovery of this disparate behavior of organically bound
chromium has rendered suspect much previously reported quantitative data,
particularly data defining characteristic levels of chromium in various
biological media. Some workers have suggested that the behavior is due to
volatile forms of chromium which are lost during ashing, but recent careful
attempts to demonstrate volatile chromium species failed. Confidence will
be restored to this area of research only when causes of the anomalies are
identified and previous assays are verified or amended by new analyses
which are beyond suspicion.
1 9
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13
2.2 PHYSICAL AND CHEMICAL PROPERTIES
Chromium has been known for more than 175 years and has been an item
of commerce during most of this time. Despite this long history, however,
many aspects of the element and its interactions with man and the environ-
ment remain obscure. Thus, although our knowledge of the inorganic chem-
istry of simple chromium compounds is well established, our understanding
of the biochemistry of chromium is, at best, only rudimentary. This cir-
cumstance arises partly from the chemical complexity of the element itself
and also from the low concentrations in which it is normally encountered in
biological media (Mertz, 1969). A similar lack of information exists con-
cerning the cycling of chromium in the environment (National Academy of
Sciences, 1974, p. 108).
In view of the state of the art, this section will necessarily deal
chiefly with the inorganic chemistry of chromium; characteristic reactions
useful in understanding the behavior of the element will be stressed. How-
ever, interactions of biological and environmental relevance will be dis-
cussed as fully as existing data permit.
2.2.1 The Element
Chromium was discovered in 1797 by Louis Vauquelin, a French chemist,
in the red Siberian ore, crocoite (PbCrO/,) . The production of chromium
chemicals on a commercial basis started soon afterwards in 1816 and has
continued without interruption. Chromium compounds now have great economic
importance in the paint and dye industries as pigments and mordants, in
metallurgy for the production of stainless steel and other alloys, in the
chrome tanning of leather goods, in the production of high-melting refrac-
tory materials, and, of course, in chrome plating. The steel gray, lus-
trous, hard metal melts at 1857 ± 20°C, boils at 2672°C, and has a specific
gravity of 7.18 to 7.20 at 20°C (Weast, 1974). There is disagreement in
the literature concerning the numerical values of measurements involving
high temperatures, such as boiling points and melting points. Such meas-
urements should be accepted with reservation.
As found in nature, chromium is a mixture of four stable isotopes of
mass numbers 50, 52, 53, and 54. The natural abundances and thermal neutron
cross sections of these isotopes are listed in Table 2.1. Also included in
this table are descriptions of the five established radioactive isotopes of
chromium. The radioisotope commonly used in tracer work is 51Cr. Commer-
cially available chemical forms of this nuclide include chromium(III) in
dilute acid and chromate.
Chromium, the 24th element of the periodic chart, belongs to the first
series of transition elements. The electronic configuration of the element
is {Ar}3^54s1. Oxidation states of chromium range from -2 to +6, but it
most commonly occurs in the trivalent and hexavalent forms. Hexavalent
chromium compounds have the greatest economic importance and also appear to
be the most environmentally and biologically significant forms of chromium.
Chemically, the most stable and important state is Cr3+, d3. In this spe-
cies chromium has a strong tendency to form octahedral complexes of
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14
Table 2.1. Chromium isotopes
Natural
Isotope abundance
(%)
Chromium
Cr-48
Cr-49
Cr-50 4.31
Cr-51
Cr-52 83.76
Cr-53 9.55
Cr-54 2.38
Cr-55
Cr-56
Mode
At°mic Lifetime of
mass ,
decay
51.996
23 h Electron capture
41.9 m Electron emission
49.9461
27.8 d Electron capture
51.9405
52.9407
53.9389
3.5 m Electron emission
5.9 m Electron emission
Decay
energy
(MeV)
1.4
5.26
0.752
2.59
1.6
Thermal neutron capture
cross section
(b)
3.1 + 0.2
16.0 + 0.5
0.76 + 0.06
18.2 + 1.5
380 + 40
Source: Adapted from Weast, 1977, p. B-278. Reprinted by permission of the publisher.
coordination number six with ligands such as water, ammonia, urea, ethyl-
enediamine, halides, sulfate, and organic acids. Each t2g level in these
complexes is singly occupied, which produces a sort of half-filled shell
stability (Cotton and Wilkinson, 1962, p. 567). This arrangement results
in extremely slow ligand exchange rates and imparts a pseudostability to
the complex, even under conditions in which these complexes are thermo-
dynamically very unstable. Oxidation states lower than chromium(III) are
strongly reducing; in aqueous solutions only the divalent state is known.
Chromium(V) and chromium(IV) are formed as transient intermediates in the
reduction of chromium(VI) solutions. They have no stable solution chem-
istry because of disproportionation to trivalent and hexavalent chromium;
however, a few solid compounds are known. The highest oxidation state,
chromium(VI), corresponds to the loss of the total number of 3d and 4s
electrons. Stable compounds of this state exist only in the oxy species,
such as Cr03, Cr042~, Cr2072~, and Cr02Cl2, which are strongly oxidizing.
The strong inclination of hexavalent chromium compounds to be reduced to
the trivalent state, particularly by organic materials, and the tendency
of the resulting trivalent chromium to form very stable complexes with
common biological ligands afford obvious mechanisms by which chromium can
interact with the normal biochemistry of man. The physical properties of
typical chromium compounds are shown in Table 2.2.
2.2.2 Divalent Chromium
Chromium forms divalent compounds with oxygen, the halogens, sulfur,
organic acids, and a number of complexing agents. In aqueous solution and
in many of its salts, the chromous ion is bright blue. Its chemical be-
havior is similar to that of the ferrous ion, except that the tendency to
pass from the divalent to the trivalent state is much stronger with chro-
mium than with iron. In fact, chromous ions are among the strongest
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Table 2.2. Physical properties of typical chromium compounds
Compound
Oxidation state 0
Chromium carbonyl
Dibenzene-
chromium(O)
Oxidation state + 1
Bis(biphenyl)-
chromium(I)
iodide
Oxidation state +2
Chromous acetate
Chromous chloride
Chromous ammonium
sulfate
Oxidation state +3
Chromic chloride
Chromic acetyl-
acetonate
Chromic potassium
sulfate (chrome
alum)
Chromic chloride
hexahydrate
Chromic chloride
hexahydrate
Chromic oxide
Oxidation state +4
Chromium (IV) oxide
Formula
Cr(CO)6
(C6H6)2Cr
(C6HsC6H5)2CrI
Cr2(C2H302K-2H20
CrCl2
CrSOi,-(NHA)zSOt,»6H20
CrCl3
Cr(CH3COCHCOCH3)3
KCr(SOi.)2-12HzO
[Cr(HaOKCla]Cl»2H20
[Cr(H20)6]Cl3
Cr203
Cr02
Appearance
Colorless
crystals
Brown
crystals
Orange plates
Red crystals
White
crystals
Blue crystals
Bright purple
plates
Red-violet
crystals
Deep purple
crystals
Bright green
crystals
Violet
crystals
Green powder
or crystals
Dark-brown or
black powder
Crystal system Density
and space group (g/cm3)
Orthorhombic, C2p 1. 77 i8
Cubic, Pa3 1.519
1.61716
Monoclinic, C2/a 1.79
Tetragonal, D^ 2.93
5
Monoclinic, C^Tz
3 or 5
Hexagonal, Z?3 2.872S
Monoclinic 1.34
Cubic, Afi 1.82615
Triclinic or 1.83525
monoclinic
6
Rhombohedral , D^d
Rhombohedral, D^rf 5.2225
Ik
Tetragonal , D^fo 4 . 98
(calculated)
Melting Boiling
point point Solubility
150 (decomposes) 151 (decomposes) Slightly soluble in
(sealed tube) CClz,; insoluble in
H20, (C2H5)20,
C2HSOH, C6H6
284-285 Sublimes 150 Insoluble in H20;
(vacuum) soluble in C6H6
178 Decomposes Soluble in
C2HSOH, CSH5N
Slightly soluble in
H20; soluble in
acids
815 1120 Soluble in H20 to blue
solution, absorbs 02
Soluble in HZ0,
absorbs 02
Sublimes 885 Insoluble in H20,
soluble in pres-
ence of Cr2+
208 345 Insoluble in HaO;
soluble in CSHS
89 Soluble in H20
(incongruent)
95 Soluble in H20, green
solution turning
green-violet
90 Soluble in H20, violet
solution turning
green-vio'let
2435 ca. 3000 Insoluble
Decomposes Soluble in acids to
to Cr203 Cr3+ and Crs+
Ul
-------
Table 2.2 (continued)
Compound
Chromium (IV)
chloride
Oxidation state +5
Barium chromate (V)
Oxidation state +6
Chromium(VI)
oxide
Chromyl chloride
Ammonium
dichromate
Potassium
dichromate
Sodium dichromate
Potassium chromate
Sodium chromate
Potassium chloro-
chromate
Silver chromate
Barium chromate
Strontium chromate
Lead chromate
Formula
CrCU
Ba3(Cr04)2
Cr03
Cr02Cl2
(NH4)2Cr20?
K2Cr207
Na2Cr207-2H20
K2CrOi,
Na2CrO<,
KCr03Cl
Ag2Cr04
BaCr04
SrCrO,,
PbCrOa
Appearance
Black-green
crystals
Ruby-red
crystals
Cherry-red
liquid
Red-orange
crystals
Orange-red
crystals
Orange-red
crystals
Yellow
crystals
Yellow
crystals
Orange
crystals
Maroon
crystals
Pale yellow
solid
Yellow solid
Yellow solid
Orange solid
Red solid
, _ Melting Boiling
Crystal system Density . ...
, , , ,-. point point
and space group (g/cm3) (°c) (°C)
Stable only at 830
high temp
Same as
Ca3(P04)2
Orthorhombic, C2$ 2.725 197 Decomposes
1.914525 -96.5 115.8
Monoclinic 2.1552S Decomposes
180
Triclinic 2.67625 398 Decomposes
Monoclinic 1.34823 84.6 Decomposes
(incongruent)
Orthorhombic 2.732,8 971
Orthorhombic, D2ft 2.72325 792
Monoclinic 2.49739 Decomposes
Monoclinic 5.62525
Orthorhombic 4.49825 Decomposes
Monoclinic, C2fr 3.895i3 Decomposes
Orthorhombic
Monoclinic, C2h 6.12l= 844
Tetragonal
Solubility
Slightly decomposes
in H20; soluble in
dilute acids to
Cr3 + and Cr6*
Very soluble in H20;
soluble in CH3-
COOH, (CHSCO)20
Insoluble in H20,
hydrolyzes; soluble
in CS2 , CCli,
Soluble in H20
Soluble in H20
Very soluble in H20
Soluble in H20
Soluble in H20
Soluble in H20,
hydrolyzes
Very slightly soluble
in H20; soluble in
dilute acids
Very slightly soluble
in H20; soluble in
strong acids
Slightly soluble in
H20; soluble in
dilute acids
Practically insoluble
in H20; soluble in
strong acids
Source: Adapted from Hartford and Copson, 1964, Table 3, p. 480-481. Reprinted by permission of the publisher.
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17
known reducing agents in aqueous solution; the standard reduction poten-
tial for the chromium(II)/chromium(III) couple is -0.4 V (Weast, 1974).
Due to this tendency to oxidize, chromous compounds are not found in
nature (National Academy of Sciences, 1974, p. 4), nor is there yet any
evidence that divalent chromium plays any biochemical role (Schroeder, 1970).
2.2.3 Trivalent Chromium
The trivalent state of chromium is the most stable oxidation state of
the element and the most important chemically. The foremost characteristic
of this state is the strong tendency to form kinetically inert hexacoordi-
nate complexes. Because of the very slow ligand exchange rate, many of
these complexes can be isolated as solids even though they are quite un-
stable thermodynamically. This characteristic has great relevance in
studies of the behavior of chromium(III) in biological systems. In acid
solutions, even the simple ion is coordinated with the solvent as
[Cr(OH2)e]3+• The tendency to coordinate is as marked in the trivalent
chromium species as in any other known element and extends to all kinds of
ligands; it is especially strong with nitrogen compounds such as amines
(Sidgwick, 1950, p. 1014).
2.2.3.1 Chromic Oxide — This green, insoluble, crystalline oxide (Cr203)
is formed by burning chromium metal in oxygen, by thermal decomposition
of chromium trioxide or ammonium dichromate, or by roasting the hydrous
oxide (Cr203«nH20). The latter compound, frequently called chromic hydrox-
ide, is precipitated by addition of hydroxide to solutions of chromium(III)
salts (Cotton and Wilkinson, 1962, p. 685). Chromic oxide is insoluble in
both acid and base if it is too strongly ignited; otherwise, it and its
hydrous form are amphoteric and dissolve readily in acid to yield aquo ions,
[Cr(H20)s]3+, and in concentrated alkali to give chromite, [Cr(OH)
-------
18
important chromium halides. Anhydrous chromic chloride does not dissolve
appreciably in cold water, alcohol, acetone, or ether, but it goes into
solution readily in the presence of a small amount of chromium(II) ion or
a reducing agent such as stannous chloride (Cotton and Wilkinson, 1962,
p. 68). Mineral acids, including aqua regia, have no action on the anhy-
drous chloride salt. Fused alkali hydroxides or carbonates, in the pre-
sence of nitrates, react with CrCl3 to form chromates. A considerable
number of hydrated chromic chlorides are known. In concentrated solutions
above 30°C, the dark green hexahydrate, [CrCl2(H20)4]C1»2H20, is the stable
species. This commercial solution is sometimes used as a mordant, in tan-
ning, and in the preparation of chromium complexes. Usually, however, the
basic chloride is preferred for these uses (Hartford and Copson, 1964) .
The other chromic halides are generally similar to the chloride.
Fluoride is used for printing and dyeing woolens, mothproofing woolen
fabrics, and coloring marble.
2.2.3.4 Other Simple Salts — Only a few salts are pertinent to this dis-
cussion. Anhydrous chromic sulfate, which can be prepared from the oxide
with sulfuric acid, has the color of a peach blossom and, like the chromic
chloride, is insoluble in water except in the presence of a chromous salt
or other reducing agent. It forms a series of green and violet hydrates
which contain up to 18 molecules of water (Cotton and Wilkinson, 1962,
p. 687). These salts are used extensively in manufacturing paints, var-
nishes, and inks, as well as frits for coloring porcelain. A deep violet
hydrated nitrate, Cr(N03)3»9H20, is used along with several lower hydrates
in preparation of chromium catalysts and in textile printing. Upon de-
hydration, these salts decompose to chromic oxide and oxides of nitrogen.
A variety of chromic salts of organic acids are used for printing cotton
in skeins and in the experimental tanning of leather.
2.2.3.5 Hexacoordinated Complexes — The most characteristic feature of
the solution chemistry of chromium is the pronounced tendency of chromium-
(III) to form coordination compounds. Literally thousands of these com-
plexes exist and they appear to be always hexacoordinate (Cotton and
Wilkinson, 1962, p. 687). Although a large number of chromium complexes
are known, they can be classified into a relatively small number of types,
as outlined below.
2.2.3.5.1 Ammines — The group of complexes in which chromium is attached
to nitrogen is probably the largest and most stable. It includes the pure
ammines, (CrAm6)3+; the mixed amine-aquo complexes, [CrAm6-n(H20)n]3+
(n = 0 to 4, 6); the mixed amine-acid complexes, (CrAm6-nXn)(3~n)+; and
the mixed amine-aquo-acido complexes, [CTcAia.6-n-m(R20)n'Xm] (3-m) + t where Am
represents the monodentate NH3 or half of a bidentate amine such as ethyl-
enediamine and X represents a univalent acido ligand such as a halide or
nitro ion (Rollinson, 1973, p. 666). Examples of specific complexes which
have been prepared are given in Table 2.3.
2.2.3.5.2 Aquo ions — The hexaquo ion, [Cr(OH2)6]3+, occurs in aqueous
solutions of all simple chromic salts and in many of their crystals as well
(Cotton and Wilkinson, 1962, p. 687). Among these are the violet hexa-
-------
19
Table 2.3. Some mononuclear chromium(III) complexes of
singly coordinating and bidentate chelating ligands
Type
Ligands
[CrA6]3+
[CrA5B]3+
[CrA5X]2+
[CrA3B2X]z+
[CrAAX2]+
[CrA3BX2]+
[CrA3X3]°
[Cr(AX)3]°
[CrAXs]2"
[CrX6]3"
A = H20; NH3; NH2CONH2; % en; % pn; % dipy, % phen;
% biguanide
A, B = NH3, H20
A, X = H20, Cl"; H20, N03 ; NH3, Cl"; NH3 , Br"; NH3 ,
N03-; NH3, N02"
A, B, X = NH3, H20, Cl"; NH3 , H20, Br"
A, X = % en, ONO~; % en, Cl" (ois); % en, SCN" (trans);
% dipy, Cl"; % phen, Cl~; % dipy, % ox~; % phen, % ox"
A, B, X = NH3, H20, Cl'; NH3, H20, Br"
A, X = H20, Cl"; C2H5OH, Cl~; NH3, Cl"; THF, Cl"; py,
Cl~; ^-substituted amide, Cl~
AX = acac; hfa, 3-bromoacetylacetone; formylacetone;
malonaldehyde; glycine; alanine; methionine
A, X = NH3, SCN"; C2H5NH2, SCN"; py, SCN"; H20, % ox";
% dipy, % ox"; % phen, % ox"
A, X = H20, Br"
X = CN"; SCN"; % ox"
A, B = singly coordinating neutral molecule or % bidentate chelat-
ing neutral molecule; X = singly charged negative ion or % bidentate
doubly charged chelating ion; AX = bidentate chelating ligand coordinat-
ing via one neutral and one negative group.
^en = ethylenediamine; pn = propylenediamine; dipy = dipyridyl;
phen = 1,10-phenanthroline; py = pyridine; acac = acetylacetone; hfa =
hexafluoroacetylacetone; THF = tetrahydrofuran; ox = oxalate.
Source: Adapted from Rollinson, 1973, Table 16, p. 667. Reprinted
by permission of the publisher.
hydrates of the chloride and the bromide and an extensive series of alums,
MlCr(SO/,)2»12H20. Examples of mixed aquo-ammine complexes are given in the
preceding section.
2.2.3.5.3 Acido complexes — Trivalent chromium also forms anionic complexes
of the type (CrX6)3~, where X is a monodentate anion such as F~, Cl", CN",
SCN" or part of a polydentate anion such as oxalate. As was the case with
ammine and aquo complexes, mixed acido-aquo and acido-ammine species also
occur. A commonly occurring complex of the latter type is Reinecke's salt,
NHi,[Cr(SCN)i,(NH3)2]«H20, which is widely used to precipitate large cations
(Kleinberg, Argersinger, and Griswold, 1960, p. 526).
-------
20
2.2.3.5.4 Polynuclear complexes — In alkaline media, chromium(III) tends
to form a variety of polynuclear complexes through olation (Rollinson,
1973):
[Cr(H20)6
3+
[Cr(H20)5OH]
V
0
(H20)5CrX \Cr(H20)5
5+
+ H20 ,
2[Cr(H20)5OH]
(H20)4Cr
H
.0..
•0'
H
;Cr(H20)4
2H20
The diol produced by the second reaction, and any other polynuclear prod-
ucts containing water molecules, can release further hydrogen ions, creat-
ing more coordinated OH groups and a higher state of aggregation. Under
appropriate conditions, the aggregates may attain colloidal dimensions and
ultimately precipitate a three-dimensional olated complex, Cr(OH)3»XH20.
This tendency frequently causes difficulties in carrying out reactions in
neutral or basic solutions. Olation is favored by heat, increased concen-
tration, increased basicity, and time. Thus, the biological activity of
simple chromium complexes may be a function of the age of such solutions,
a factor not always given sufficient consideration (Mertz, 1969). If
olated compounds are heated sufficiently, still more acid is eliminated
and the chromium atoms are then linked through oxygen atoms (oxolation):
heat
(H20)4Cr
C12 + 2HC1
Mesmer and Baes (1975) have critically reviewed the hydrolysis be-
havior of metal-containing cations of a number of metals, including chro-
mium, by applying molecular orbital and ligand field theory. Chromium(VI)
is extensively hydrolyzed in water and gives only neutral or anionic
species. Chromium(III) compounds can give rise to polymers, as discussed
above, which exhibit sluggish kinetic behavior due to the stabilization of
this d3 ion against ligand displacement reactions.
2.2.4 Tetravalent and Pentavalent Chromium
These valence states are irrelevant to the aqueous chemistry of chro-
mium; no stable solutions are known. However, various nonaqueous tech-
niques may be utilized to prepare a limited number of tetravalent and
pentavalent chromium compounds.
-------
21
2.2.5 Hexavalent Chromium
Hexavalent chromium is the highest oxidation state and the second most
stable valency, next to that of chromium(III). All stable hexavalent chro-
mium compounds are exclusively oxy molecules and potent oxidizing agents
(Cotton and Wilkinson, 1962, p. 689). The hexafluoride (CrF6) is sometimes
cited as an exception to this statement, but this thermally unstable yellow
halide decomposes to CrF5 and F2 at -100°C (Rollinson, 1973). Hexavalent
chromium occurs rarely in nature, apart from man's invention, because it is
readily reduced in the presence of organic matter. However, after intro-
duction by man, hexavalent chromium frequently remains unchanged in many
natural water sources because of the low concentration of reducing matter.
Hexavalent chromium occurs most commonly in the form of chromate or dichro-
mate, both of which are high-tonnage industrial products (National Academy
of Sciences, 1974, p. 5).
2.2.5.1 Chromium Trioxide — Chromium trioxide (chromic anhydride, Cr03)
is readily precipitated in the form of bright red needles by the addition
of sulfuric acid to aqueous solutions of sodium or potassium dichromates.
The trioxide melts at 197°C, but it is unstable at higher temperatures,
gradually losing oxygen until Cr203 is formed. Chromium trioxide is very
hygroscopic; its solubility in water as a function of temperature is
given in Table 2.4. The trioxide is a very powerful oxidizing agent.
Hydrogen, ammonia, and hydrogen sulfide are oxidized in the gaseous state.
Certain organic materials such as alcohol or paper are ignited on brief
contact with Cr03 (Udy, 1956, p. 135). Chromic acid (H2CrO<, or Cr03«H20),
the hydrated form of chromium trioxide, does not occur in the free state,
but it is readily formed in solution. Most metals dissolve in chromic
acid solutions. Iron, however, soon develops a passivity for further reac-
tion when it is exposed to certain concentrations of the acid. Anodized
aluminum is also resistant to oxidation by chromic acid.
Chromium trioxide is widely used in chrome plating and other metal-
finishing operations and in recirculating water systems and cooling towers
as a corrosion inhibitor for ferrous alloys (International Agency for
Research on Cancer, 1973).
2.2.5.2 Chromates, Dichromates, and Polychromates — Sodium chromate and
sodium dichromate, primary products of the chemical industry, are produced
by roasting chromite ore in the presence of soda ash. The soluble chro-
mates are removed by leaching with water and are converted to sodium
dichromate by treatment with sulfuric acid.
All of the metallic chromates, except those of the alkalies and the
light alkaline earths, are insoluble in water. As the pH is lowered,
solutions of chromate ions turn orange because of the formation of dichro-
mate ions:
2Cr042~ + 2H+ = Cr20-,2~ + H20, K = 4.2 x 1014.
Acid solutions of dichromate are powerful oxidizing agents:
Cr20?2~ + 14H+ + 6e = 2Cr3+ + 7H20, E = 1.33 V vs SHE.
-------
Table 2.4. Solubility of chromium trioxide and selected chromates in water
Temperature
0
10
20
30
40
50
60
70
80
90
100
Solubility (wt %)
Chromium
trioxide
61.70
62.08
62.49
62.91
63.39
63.90
64.46
65.08
65.79
66.59
67.46
Ammonium Sodium
chromate chromate
19.78 24.21
32.11
44.36
28.8 46.84
48.84
34.40 51.04
37.21 53.54
55.2
55.5
55.8
56.1
Potassium
chromate
37.14
38.05
38.96
39.80
40.61
41.40
42.15
42.88
43.60
44.31
45.00
Ammonium
dichromate
15.16
21.06
26.67
31.98
36.99
41.72
46.14
50.27
54.10
57.65
60.89
Sodium
dichromate
70.60
71.67
73.16
75.00
77.09
79.46
82.04
84.98
88.39
90.60
91.43
Potassium
dichromate
4.3
7.8
11.7
16.1
20.9
26.0
31.3
36.6
42.0
46.5
50.2
Source: Adapted from Udy, 1956, Tables 6.5 and 6.33, pp. 131, 161-162, Volume I, ACS Monograph
No. 132, 1956. Reprinted by permission of the publisher.
to
-------
23
Basic solutions of the chromate ion are much less oxidizing:
Cr042~ + 4H20 + 3£ = Cr(OH)3(s) + 50H~, E =-0.13 V vs SHE.
The solubilities of the most important chromates and dichromates are given
as a function of temperature in Table 2.4.
Potassium dichromate, once the leading commercial form of chromium,
has now been largely replaced by the less costly sodium dichromate, from
which almost all other chromium chemicals are prepared. In view of the
ubiquity of sodium dichromate, this compound, more than any other, is
probably responsible for the pollution of our waterways with hexavalent
chromium.
2.2.5.3 Other Compounds — Hexavalent chromium also occurs in several other
types of compounds: the halochromates, the chromyl halides, and the peroxy-
chromates. None of these have the chemical or economic importance of the
chromates.
2.2.6 Biochemistry of Chromium
Chromium interacts in some manner with a wide assortment of biologi-
cally relevant compounds. As discussed later, the chief biochemical func-
tion of chromium apparently relates to insulin and the membrane transport
of cell metabolites. Insulin requires chromium at the site of action to
exert its maximal effect. On the other hand, without insulin, chromium
and its complexes are inert. The mechanisms by which these interactions
occur are not yet apparent (Mertz, 1969). Chromium also interacts strongly
with nucleic acids. Wacker and Vallee (1959) found more than 1000 ppm
chromium in a ribonucleoprotein from beef liver. Whether or not this high
concentration of chromium associated with ribonucleoprotein has any bio-
chemical significance has not yet been established. Chromium also appears
to interact with enzymes, bacteria, yeasts, red blood cells, and a variety
of substances with low molecular weight (Mertz, 1969).
The chemistry of these interactions is unknown. Based upon the estab-
lished inorganic chemistry of trivalent chromium, interaction could be ex-
pected to occur by the formation of chromium complexes with oxygen or
nitrogen donors in the substrate. This mechanism is known to occur in the
chrome tanning of leather. Here, chromium reacts mainly with the free
carboxyl groups of the acidic amino acids of the protein (glutamic and
aspartic acids), forming stable complexes between different chains of pro-
tein (Mertz, 1969). Other binding sites such as hydroxyl groups, peptide
bonds, and amino groups probably play only a minor role; masking these
does not impair the tanning process appreciably. On the other hand, methyl-
ation of the free carboxyl groups prevents tanning completely. Other
relevant factors have also been unequivocally established: (1) only tri-
valent chromium has tanning activity; hexavalent chromium acts only after
reduction to the trivalent sites; (2) tanning involves the coordination
sites of trivalent chromium; (3) mononuclear trivalent chromium complexes
do not tan. The tanning action is initiated by raising the pH of the
solution, which causes the formation of olated polynuclear complexes.
-------
24
These complexes act by accepting carboxyl groups of the collagen strands
into their coordination sphere at the expense of previously bound water
molecules. Chrome tanning results in nearly total saturation of protein
with the metal; various leathers have chromium concentrations of 4% to 6%
(Mertz, 1969).
2.2.6.1 Complexes with Biologic Ligands — The fate of chromium ingested
into the mammalian system depends on the chemical form and concentration
of the chromium species and on the competition for the chromium by hydroxyl
ions and other ligands of the biological system. In media of physiological
pH, the expected reaction of chromium(III) is olation, except when it is
prevented or minimized by competition of ligands other than hydroxyl ions
(Rollinson, 1973). One net result of such competition is the establishment
of a characteristic state of aggregation of the chromium(III) products for
given conditions. This characteristic state of aggregation can be measured
by observing the rate of transport of the chromium(III) species through a
membrane by the method of sequential dialysis. In this procedure, succes-
sive samples of the buffered reaction mixtures are dialyzed at intervals
and data are plotted showing the fractional attainment of dialysis equilib-
rium vs time. The area under the dialysis curve is proportional to the rate
of diffusion of chromium(III) and, thus, inversely proportional to the
molecular weight of the diffusing species. It is, therefore, a measure of
the effectiveness of the ligand in preventing polymerization and, hence,
the ligand's coordinating tendency. Measured in this manner, the order of
coordinating tendencies of the Krebs-cycle compounds is citrate > iso-
citrate > malate > oxalacetate > a-ketoglutarate > aconitate > fumarate >
succinate. The most effective of the many biological ligands tested are
histidine, ATP, ADP, thiamine pyrophosphate, fructose-1, 6-diphosphate,
3-phosphoglycerate, citrate, isocitrate, and tartonate. Glucose does not
influence diffusion rates in these experiments, but oleate decreases them
strongly, probably through the formation of large, chromium-containing
micelles (Rollinson, 1973).
2.2.6.2 Oxidation States — Only trivalent and hexavalent chromium are
known to occur in biological media and only the trivalent state is stable
in such an environment (Mertz, 1969). The hexavalent form is readily re-
duced to the trivalent form by a variety of organic species, including
tissue in vitro (National Academy of Sciences, 1974, p. 23). There is no
evidence that hexavalent chromium may be protected from such reduction by
complex formation (Mertz, 1969). Stable "sandwich" complexes in which
chromium has a valence of zero have been mentioned as possibly being in-
volved in the binding of chromium to ribonucleic acids (Wacker and Vallee,
1959). However, no experimental evidence exists to support this suggestion.
2.2.7 Environmental Chemistry of Chromium
2.2.7.1 Air — Low atmospheric levels of chromium occur as a result of
industrial activity, such as the manufacturing of chromium chemicals,
cement, or certain steels. End-product use, such as the burning of coal,
paper matches, and fireworks, contributes a share (Schroeder, 1970). Soil-
derived aerosols may also be important (John et al., 1973). Chromium air
pollution usually occurs as particulate emissions, although mists and
-------
25
sprays may be present at specific locations. Little information exists in
the literature regarding the nature of the chemical species present in the
atmosphere away from obvious sources of pollution. Sullivan (1969, p. 2)
stated that chromium trioxide is perhaps the most important hexavalent com-
pound in the air. This molecule is the anhydride of chromic acid; its chem-
istry is described in Section 2.2.5. Soil-derived aerosols may contain
chromic oxide whose chemistry is treated in Section 2.2.3.1. Further studies
are needed to identify other forms of particulate emissions.
2.2.7.2 Water — Chromium appears in some surface waters and in most rivers
as hexavalent chromates. Soluble trivalent chromium is not usually en-
countered in fresh water (Mertz et al., 1974). Seawater contains lower
chromium concentrations than the adjoining rivers, apparently because the
hexavalent metal is reduced to less soluble trivalent forms which settle to
the ocean floor (National Academy of Sciences, 1974, p. 10). About half of
the chromium in seawater is thought to be trivalent (Mertz et al., 1974).
The chemistry of both trivalent and hexavalent chromium is discussed in
Sections 2.2.3 and 2.2.5. Little is known of the aqueous species of chro-
mium present in natural brines.
2.2.7.3 Soil — During weathering, chromium in rocks tends to be oxidized
to soluble complex anions (Goldschmidt, 1945). Most soils contain small,
varying amounts of chromium (trace to 250 ppm). Very little information
is available concerning the chemical form of the element in soils, but it
is generally assumed to occur as the trivalent chromic oxide (National
Academy of Sciences, 1974, p. 8). Only a small fraction (<1%) of the chro-
mium in soils derived from glacial till can be extracted with acetic acid
(Mertz et al., 1974), whereas up to 6% of the total can be extracted from
soils derived from bedrock residuum (Taylor et al., 1975). Chromium avail-
ability is strongly influenced by the pH of the soil. According to Davis
(1956, p. 106), little or no uptake of chromium by plants occurs above pH 4.
Therefore, conclusions relative to the availability of chromium in a soil
can not be drawn solely on the basis of a total chromium analysis. The
chemistry involved in fixing chromium in soils of high pH has not been in-
vestigated. However, the fixation chemistry of the six elements adjacent
to chromium in the first transition series was studied by Jenne (1968).
He concluded that primary fixation occurred by sorption of these heavy
metals on the hydrous oxides of manganese and iron, which are commonly
present in most soils. Jenne ascribed lesser roles to fixation by organic
matter, clays, and carbonates and to precipitation as the discrete oxide or
hydroxide. However, Baker (1973) ascribed a more significant role to heavy
metal binding by organic matter although he did not present data on chromium.
The chromium content of soils may be greatly increased by repeated
applications of phosphate fertilizers and sludges from certain sewage plants.
The concentration of chromium in phosphorites from the Idaho-Wyoming-Utah
region averages about 1000 ppm (National Academy of Sciences, 1974, p. 9);
sludges from selected sewage plants greatly exceed even this concentration
(Adams, Eckenfelder, and Goodman, 1973).
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26
2.3 ANALYSIS FOR CHROMIUM
2.3.1 Considerations in Analysis
A variety of methods are available for the determination of chromium
in environmental samples. Several of these methods are sufficiently sensi-
tive to detect chromium in the low parts per billion concentration range
(Table 2.6). Nevertheless, no one method can be characterized as best for
the analysis of chromium in every application; sample load, equipment avail-
ability, and cost are key considerations in the method selection. Detec-
tion limits, sample matrix, specificity, analysis time, and accuracy must
also be considered. These and other factors pertinent to the selection of
an analytical method and the evaluation of reported analytical data are
summarized in this section.
Although some samples may contain chromium in relatively high concen-
trations, the element is present at the trace level in most environmental
samples. In nutritional research, variations in the concentration of chro-
mium at the nanogram level appear pertinent (Mertz, 1974). At these levels,
the accurate analysis of chromium presents a challenge to the analytical
chemist which has only recently been solved, if indeed it is solved now.
The problem can best be illustrated by interlaboratory comparison data on
NBS bovine liver (SRM 1577). Parr (1974) studied this carefully homog-
enized sample which involved ten laboratories. The results ranged from
<0.005 to 1.57 ug/g. Pierce et al. (1976) reported on a study that in-
volved several sample types, including bovine liver. Results from neutron
activation analysis, gas liquid chromatography, and flame and furnace
atomic absorption were included. Agreement between laboratories and methods
was obtained for certain types but not for others. The range for bovine
liver was 0.045 to 0.206 yg/g. The existance of volatile forms of chro-
mium was suggested as one possible explanation for the disagreements.
In another study, Greig (1975) compared atomic absorption and neutron
activation analysis methods for chromium in marine organisms. Each method
was precise but disagreements up to a factor of three existed between
methods. Since sample preparation varied with both the method and the
organism, the source of the disagreement is hard to establish.
The National Bureau of Standards first issued its bovine liver SRM in
1972. The chromium content has been extensively studied in many laborato-
ries and has only now been established (Dunstan and Garner, 1977). It is
soon to be certified at 90 ± 15 ng/g. The existence of this reference
material with established chromium values, in addition to the orchard
leaves (SRM 1571) and brewer's yeast (SRM 1569), will be of tremendous
help in resolving any remaining analytical problems.
In dealing with day-to-day samples containing chromium at the nanogram
per gram level, sampling handling techniques assumes greater importance
than in ordinary analytical determinations. For example, carefully pre-
pared standards or samples may be invalidated by adsorption of the metal on
the container walls or by leaching of contaminants from the container. This
problem is obviously aggravated by prolonged storage of such solutions prior
-------
27
to use. Shendrikar and West (1974) studied the adsorption of chromium(III)
and chromium(VI) on the walls of Pyrex, flint, and polyethylene beakers as
a function of pH and time. Solutions of pH 6.95 initially containing 1 ppm
chromium(III) showed negligible losses during the first 24 hr. After this
induction period, however, progressive adsorption occurred until 17% to 25%
of the element was lost after 15 days. Clearly, neutral or basic solutions
of trivalent chromium require acidification prior to storage if adsorption
losses are to be avoided. Chromium in the hexavalent state is not appre-
ciably adsorbed under these conditions. In a similar study, Gilbert and
Clay (1973) spiked 4 liters of unacidified seawater with 10 yg/liter chro-
mium(III), stored it in a polyethylene bottle, and analyzed 400-ml portions
for chromium after 0, 1, 2, 3, 7, and 14 days. The half-life of chromium-
(III) in solution was only 1.8 ± 0.3 days. Obviously, such samples must be
analyzed promptly if serious errors are to be avoided.
The composition of samples can be drastically altered by contaminated
reagents used in various preanalysis treatments, such as acidification,
dissolution, digestion, and extraction. Care should be taken that only
reagents of the highest purity are used; even so, the quantity added should
be limited to avoid unnecessary buildup of contaminants. The conventional
chromic acid cleaning solution should not be used for equipment in which
trace-level chromium samples are to be processed. In most instances,
nitric acid is a suitable substitute.
Precautions must also be taken to avoid contamination of trace-level
samples by equipment which may contain chromium. Although some authori-
ties stated that biologic tissues may be safely collected by dissection
with stainless steel knives and scissors (National Academy of Sciences,
1974, p. 116), other workers reported unacceptable contamination by their
use (Webb, Niedermeier, and Griggs, 1973). The use of grinding or homog-
enizing equipment apparently can introduce chromium as a result of the
pressure and heat generated in the grinding process (National Academy of
Sciences, 1974, p. 116). Grinding such samples with an agate mortar and
pestle is a safer procedure. Versieck and Speecke (1972) observed a three-
fold increase of chromium in the initial fraction of blood samples taken by
venipuncture with disposable needles. Their studies also showed that chro-
mium introduced by taking liver biopsies with a Menghini needle sometimes
exceeded the normal chromium concentration in human liver tissue.
Chromium is generally regarded as a nonvolatile element not subject
to losses in mild laboratory heating processes. Conflicting data are re-
ported on the existance of highly volatile, and therefore readily lost,
organo-chromium compounds in biological samples. Maxia et al. (1972),
Mertz (1974), and Masironi, Wolf, and Mertz (1973) all reported signifi-
cant losses from some samples even at rather low temperatures. However,
Jones, Buckley, and Chandler (1975) conducted very careful experiments
with 51Cr-labeled brewer's yeast and found no significant volatility loss
up to 800°C. Koirtyohann and Hopkins (1976) labeled rat tissues with 51Cr
and found no loss on dry ashing except for blood ashed at 700°C. Very
recently, Rook and Wolf (1977) conducted very careful experiments with
brewer's yeast and reached the conclusion that <1% of the chromium was
lost on heating up to 350°C. Also, the fact that the NBS bovine liver is
-------
28
being certified at a value near the low end of the initially reported
range indicates that contamination was probably a greater problem than
volatility losses in the earlier work. However, until more data are re-
ported, the validity of the laboratory processing technique must be care-
fully verified for samples which could contain volatile chromium.
2.3.2 Analytical Procedures
2.3.2.1 Sampling and Sample Handling — Since chromium is ubiquitous
(Schroeder, 1970), an essential micronutrient for man (Mertz, 1974), and
a toxic environmental pollutant (National Academy of Sciences, 1974,
p. 17), many kinds of samples are of interest. The principal requirements
for each sample class are discussed below.
2.3.2.1.1 Chromium in air — Because of the chemical nature of chromium,
gaseous forms in the air are unlikely. Dusts and fumes of chromium com-
pounds may be collected by any method suitable for the collection of other
dusts and fumes; impingers, electrostatic precipitators, and filters are
commonly used. The National Air Sampling Network uses a high-volume fil-
tration sampler (Sullivan, 1969). Typical filter media include cellulose,
polyethylene, polystyrene, and glass. Begnoche and Risby (1976) used a
low-volume sampler with porous polymer filters. Analytical "blanks"
should be determined for the chosen filter media because some filter media
are contaminated with surprisingly large amounts of chromium (Table 2.5).
Dams, Rahn, and Winchester (1972) presented additional data for ten fre-
quently used filter materials. Chromic acid mists may be collected in an
impinger using water or caustic solutions.
Skogerboe (1974) and Johnson (1974) have reviewed current methods of
monitoring trace, metal particulates.
Table 2.5. Trace element concentrations in different materials
Material
Polyethylene
Borosilicate glass
Kimwipe tissue
Millipore filter
Double distilled water
Double distilled nitric acid
Concent rat ion
(ppb)
Zinc
25
730
48,800
2,370
1
2
Iron
10,600
280,000
1,000
330
< <0.2
1
Cobalt
0.31
81
24
13
<0.02
0.03
Chromium
19
Not measured
500
17,600
2
13
Source: Adapted from Bhagat et al., 1971, Table IV, p. 2419. Reprinted by
permission of the publisher.
-------
29
2.3.2.1.2 Chromium in environmental waters — The process of sampling
environmental waters for chromium is generally complicated and depends on
the homogeneity of the water source, the number of locations sampled, the
size of the individual sample, and the manner in which the samples are
collected. A more representative sample can usually be obtained by collect-
ing several small samples from different parts of the water body than by
collecting one large sample at a single point. Brown, Skougstad, and
Fishman (1970) discussed this subject extensively. Descriptions of sampling
systems are given in Standard Methods for the Examination of Water and
Wastewater (American Public Health Association, American Water Works
Association, and Water Pollution Control Federation, 1971).
2.3.2.1.3 Chromium in inorganic solids — Chromium can sometimes be deter-
mined in solids with little or no prior sample preparation (Murrmann,
Winters, and Martin, 1971). Frequently, however, the sample must be dis-
solved before analysis. The method of solubilization must be adapted to
the nature of the sample as well as to the method of determination chosen.
Three classical procedures are still generally used: ignition, digestion
with acid, and digestion with alkali. If a residue remains, it may be
solubilized by fusion with sodium carbonate, followed by treatment with
0.5 M sulfuric acid or treatment with hydrofluoric acid. Extraction of the
chromium into an immiscible organic solvent, such as methyl isobutyl ketone,
may be necessary to eliminate interfering elements or to provide increased
sensitivity through concentration of the sample. In this event, any tri-
valent chromium in the aqueous phase is first oxidized to the hexavalent
form to ensure complex formation. The oxidation step may be accomplished
by treatment of the sample with silver nitrate and potassium peroxydisulfate
(Pinta, 1966, p. 277) or with potassium permanganate and sodium azide
(Brown, Skougstad, and Fishman, 1970).
2.3.2.1.4 Chromium in biological media — Although the analysis of chromium
in many inorganic samples is routine, even at the trace level, serious prob-
lems are currently associated with the determination of chromium in biologi-
cal materials. Mertz (1974) asserted that analysis is the "most difficult
and important" problem facing workers in this area of research. He stated
that although analyses of chromium obtained by one laboratory in one tissue
may be relatively consistent, results obtained by different investigators
and efforts to establish "normal" chromium concentrations in various tissues
must be viewed with skepticism until the composition and volatility of chro-
mium compounds in organic media are established. These problems are dis-
cussed in Section 2.3.1.
2.3.2.2 Separation and Concentration — Environmental samples often contain
chromium in such small amounts that concentration or separation from poten-
tial contaminants is required. Evaporation is sometimes used as a concen-
tration procedure; however, more specific techniques are usually required
to eliminate interfering constituents.
2.3.2.2.1 Precipitation — Chromium can be precipitated from aqueous solu-
tions by a number of reagents; hydroxyquinoline (oxine) and tannic acid are
used for this purpose. However, this procedure is not generally recommended
for environmental samples containing low chromium concentrations because the
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30
risk of loss is great. Another application of precipitation for the separa-
tion of chromium involves oxidation in a basic medium, whereby chromate is
formed and remains in solution while a great many other metals such as iron,
manganese, titanium, nickel, and cobalt are precipitated. The oxidation can
be effected in hot solution with sodium peroxide, hydrogen peroxide, and
sodium hydroxide or with bromine and sodium hydroxide (Sandell, 1959, p. 388).
Methods in which a trace component is to be retained in solution while inter-
ferences are precipitated often fail due to coprecipitation of the analyte.
2.3.2.2.2 Solvent extraction — Liquid-liquid solvent extraction is a
widely used method for separating and concentrating chromium in environ-
mental samples. This technique can be highly selective and, unlike pre-
cipitation, can be used for very small quantities of material (Andelman,
1971). In this method, an immiscible organic solvent is equilibrated with
an aqueous solution containing chromium in a complexed state; the phases
are then separated and the organic phase, in which the chromium species
preferentially concentrates, is used as required, either for further separa-
tion and concentration or directly in analysis. The smaller the volume of
the extracting solvent, the greater will be the concentration factor.
Ammonium pyrrolidinedithiocarbamate is a commonly used complexing agent for
chromium extraction (Goulden, Brooksbank, and Ryan, 1973). Typically,
methyl isobutyl ketone is used as the organic solvent (Brown, Skougstad,
and Fishman, 1970). This technique recovers only hexavalent chromium; if
trivalent chromium is to be extracted, it must first be oxidized (Section
2.3.2.1.3). The efficiency of the extraction process should be verified
for the concentrations and sample types of interest.
2.3.2.2.3 Chromatographic methods — Trivalent chromium can be separated
from iron(III), aluminum, uranium, cerium, titanium, nickel, copper, molyb-
denum, manganese, cobalt, thorium, zinc, vanadium(V), tungsten, gallium,
indium, and thallium by adding excess 8-hydroxyquinaldine to precipitate
chromium and most of the other metals, dissolving the dried precipitate in
chloroform, diluting this with an equal volume of benzene, and passing the
solution through a column of activated alumina. Chromium is eluted with a
mixture of chloroform and benzene; the other metals remain on the alumina.
In the absence of aluminum, cobalt, and vanadium, 8-hydroxyquinoline can be
used as the complexing agent (Sandell, 1959, p. 390). The technique would
probably not be applicable to samples at low concentrations. Wolf et al.
(1972) used the gas chromatographic technique to concentrate and separate
picogram amounts of chromium in human blood plasma and serum.
2.3.2.3 Methods of Analysis — Chromium can be determined by a variety of
analytical procedures. Methods which are currently important or show
future promise are described in this section. Emphasis is placed on per-
formance and limitations of each procedure rather than on minute details.
Table 2.6 lists various instrumental methods for the determination of chro-
mium. Detection limit, precision, accuracy, and optimum concentration
ranges of samples vary not only among different methods, but also among
various models of particular instruments. The tabulated data are, there-
fore, representative rather than definitive.
-------
Table 2.6. Instrumental methods for the determination of chromium
Analytical method
Atomic absorption
spectroscopy
(flameless)
Atomic absorption
spectroscopy
(flame)
Neutron activation
analysis
Spec tropho tome trie
Important
application
Biologic solids and
fluids: tissue,
blood, urine;
industrial waste-
waters
Fresh and saline
waters , indus-
trial waste
fluids, dust and
sediments , bio-
logic solids
and liquids,
alloys
Air pollution
particulates,
fresh and saline
waters , biologic
liquids and
solids , sediments ,
metals , foods
Natural water and
industrial waste
solutions having
5 to 400 yg/liter
hexavalent
chromium may be
analyzed . Higher
concentrations
must be reduced
by dilution
Precision
n ,-j i-f -ft- (relative standard
deviation/sample
size)
0.2 yg/litera 15% (6 yg/liter)G
0.05 yg/liter^ 5% (3 pg/liter)d
Sensitivity varies 3% (8 ng/$r
with sample and 6% (5 yg)t
processing con-
ditions. Typical
sensitivites are:
0.2 ng/g/ (petro-
leum), 30 ng/g&
(environmental
samples), 0.2
yg/g" (biologic
material)
3 yg/liter^ 3% (400 yg/liter) l
Relative error Interfering
Relative error substances
7% (5 yg/liter)a No interfering
substances are
reported for
samples of
urine and
blood J3 Less
than 10% inter-
ference is ob-
served for Na+,
K+, Caa+, Mg2+,
Cl , F~, SOt, ,
and PO*3" in
certain indus-
trial wastewaters,
3% (5 pg/liter)e Interfering sub-
stances present
in the original
sample are usual-
ly not extracted
into the organic
solvent .
25% (100 ng/cu m)*7 Interference may
(air pollution arise from gam-
particulates) ma ray activity
20% (2.4 yg/g)« from other ele-
(orchard ments , especially
leaves) Na-24, Cl-38, K-4;
and Mn-56. Brems-
strahlung from
P-32 may be
troublesome.
2% (0.4 yg/g) Iron, vanadium,
and mercury may
interfere.
Selectivity
Total chromium is
measured .
o
All of the
extracted chro-
mium is measured.
but only Cr(VI)
is extracted froi
the original
sample unless
oxidative pre-
treatment is
used.
Total chromium is
measured.
1
This method
determines only
the hexavalent
chromium in
solution.
u>
-------
Table 2.6 (continued)
Precision
A , fc. , ._, , Important „ , , . . (relative standard „ -
Analytical method ;. . Detection limit , , Relative error
application deviation/sample
size)
X-ray fluorescence Atomospheric parti- 2 to 10 ug/g (liver)" 4% (25 Ug/g)° 1% to 4% (120 ug/
culates, geologic 1.5 ug/g (coal)° (coal) cm2) (air partic-
materials ulates)P
Interfering Selectivity
substances
The particle size Total chromium is
of the sample determined.
and the sample
matrix may in-
fluence the
observed measure-
ments .
Gas chromatography
(electron-capture
detection)
Gas chromatography
(atomic spectroscopic
detection)
Gas chromatography
(mass spectrometric
detection)
Emission spectroscopy
(arc)
Emission spectroscopy
inductively coupled
plasma source
Blood, serum, urine,
natural water
samples
Blood, serum,
orchard leaves
Blood plasmas,
serum
A wide variety of
environmental
samples
A wide variety of
biological and
environmental
samples
0.03
1 ng
<6% (1 ng)'
20% (2 ug/g)'
0.5 pg°
0.5 ng
0.0003," 0.001"
Pg/ml
9% (10 ng/g)"
19% (0.2 ug/m3)
6% to 12% (50 ug/
liter)"
20% (10 ng/g)°
10% to 16% (50
Ug/liter)"
Excess chelating
agent or other
electron-captur-
ing constituents
in the sample
may lead to er-
roneous results.
No interfering is
reported.
No interferences
are reported.
No interfering
substances are
reported.
Only chromium that
is chelated and
extracted is
measured; other
electro-negative
substances may
elute from the
column and be
detected at the
same time as the
Cr chelate.
Only chromium that
is chelated and
extracted is
detected. Atomic
spectroscopic
methods of detec-
tion are inher-
ently more selec-
tive for Cr in
complex samples,
however.
Only chromium that
is chelated and
extracted is
capable of being
detected.
Total chromium is
determined.
Total chromium is
determined.
10
-------
Table 2.6 (continued)
Analytical method Important Detection limit
application
Mass spectrometry A wide variety of 0.05-1 ug^
solid , liquid , or
gaseous samples
Chemiluminescence Fresh, natural 30 ng/liter
waters
Precision
(relative standard Relative error
deviation/sample
size)
20% (photographic)^
3% ((electrical)^
0.5% (isotope dilu-
tion)^
12% (2 Pg/g)2 5% (2.3 ug/g)0"2
5% (2.3 JJg/g) (orchard leaves)
(orchard leaves)
Interfering Selectivity
substances '
Potential inter- Total chromium
ferences may determined.
arise from any
ion having the
same mass/charge
ratio as the
chromium nuclide.
Co (II), Fe(II), Only trivalent
and Fe(III) chromium ion
interfere but may measured.
be measured by ,1
running a blank.
is
is
Sources:
"Schaller et al., 1973.
Environmental Instrumentation Group, 1973ez.
^Morrow and McElhaney, 1974.
Gilbert and Clay, 1973.
e"-oulden et al., 1973.
?'
Jsi
Shah et al., 1970.
JJBhagat et al., 1971.
.Spyrou et al., 1974.
biarrison et al., 1971.
^Dams et al., 1970.
pe Geoij et al., 1974.
American Public Health Association, American Water Works
Association, and Water Pollution Control Federation, 1971.
mSandell, 1959.
"Kemp et al., 1974.
°Kuhn, 1973.
^Jaklevic et al., 1974.
^Savory et al. , 1969.-
PWolf, 1976.
"
et al., 1972.
Seeley and Skogerboe, 1974.
"Barnard and Fishman, 1973.
^Fassel and Kniseley, 1974.
Boumanns and deBoer, 1972.
Elser, 1976.
Ahearn, 1972.
Seitz and Hercules, 1973.
Li and Hercules, 1974.
Seitz et al., 1972.
LO
-------
34
Several of the terms used in Table 2.6 are defined variously in the
literature. Detection limit (column 3) denotes the smallest quantity that
can be determined reliably by the designated technique or instrument. In
most techniques, detection limit is defined as two or three times the stand-
ard deviation of blank readings (Kaiser, 1973). The precision of the tabu-
lated methods is stated in terms of the relative standard deviation, that
is, the standard deviation of a set of samples expressed as a percentage of
the mean. Since precision varies with sample size, this information is
also indicated in column 4 of Table 2.6. Data in column 5 indicate results
of analyzing samples of known composition such as Bureau of Standards mate-
rial, synthetic standard samples, or samples prepared by the addition of
small, successive increments of the component to be determined (differential
addition technique). Accuracy is expressed as the relative error. Litera-
ture values for the accuracy of a given method vary widely; only a small
number of interlaboratory or interprocedural comparisons are available.
Consequently, these data must be used cautiously. The following sections
briefly describe the various classes of instrumental methods.
2.3.2.3.1 Atomic absorption spectrometry (flame) — In this method of
analysis, a previously prepared sample is injected into an air-acetylene
flame through which light of 357.9-nm wavelength is passed. The flame
atomizes the sample and light from the lamp is selectively absorbed by
chromium atoms in proportion to their concentration in the vapor. A photo-
detector measures the intensity of the 357.9-nm radiation after its passage
through the flame and compares it with the intensity of the original line
spectrum emitted by the lamp. The results are usually converted and cali-
brated to read out directly in concentration values. Variations of the
above procedure may be desirable with certain samples. The air-acetylene
flame may be replaced with a nitrous oxide—acetylene flame which provides
greater sensitivity and freedom from chemical interference.
The sensitivity of this method varies with different combinations of
the processing variables mentioned above and with sample type, size, and
treatment. For example, the absorption of chromium is suppressed by iron
and nickel (Ottaway et al., 1973). If the analysis is performed in a lean
flame, this interference can be lessened, but the sensitivity will also be
reduced. The interference by iron and nickel does not occur in the nitrous
oxide—acetylene flame (U.S. Environmental Protection Agency, 1974). Al-
though chromium is not detected as readily as some metals, good detection
limits can be obtained under favorable conditions. Thus, Gilbert and Clay
(1973) reported a detection limit of 0.05 yg/liter with an extraction for
the determination of chromium in seawater. A more conservative detection
limit of 0.02 mg/liter (direct aspiration) is reported in the Manual of
Methods for Chemical Analysis of Water and Wastes (U.S. Environmental Pro-
tection Agency, 1974).
Although many environmental samples can be analyzed by atomic absorp-
tion spectrometry without prior preparation, an extraction procedure is
recommended for samples containing less than 50 yg/liter chromium. Typ-
ically, such samples are extracted with ammonium pyrrolidinedithiocarbamate
in methyl ethyl ketone.
-------
35
In general, the precision and accuracy of atomic absorption analyses
using flame spectrophotometry are adequate for most inorganic environmental
samples such as fresh and saline waters, industrial wastes, dusts and sedi-
ments, and metals. A relative standard deviation of ±5% is commonly re-
ported for specialized samples down to the parts per billion level (Gilbert
and Clay, 1973; Goulden, Brooksbank, and Ryan, 1973); recoveries of chro-
mium from spiked samples (accuracy) are reported with similar errors. The
average precision reported by multipurpose laboratories is somewhat higher
than the above figures: 30% to 60% relative standard deviation for samples
containing 7 to 400 yg/liter chromium, with an average relative error of
about 10% (U.S. Environmental Protection Agency, 1974).
At present, atomic absorption spectrometry with flame atomization is
the most widely used procedure for determining chromium in environmental
samples (National Academy of Sciences, 1974, p. 117).
2.3.2.3.2 Atomic absorption spectrometry (flameless) — Flameless atomic
absorption spectrometry is a relatively new variation of the previously
described method in which the sample is atomized directly in a graphite
furnace, carbon rod, or tantalum filament instead of a flame. This innova-
tion frequently results in a tenfold to thousandfold increase in sensitiv-
ity for many elements (Environmental Instrumentation Group, 1973£>, p. 16)
and may eliminate the need for sample preparation in certain sample types.
The technique may be used for many types of samples of environmental
interest, but it is probably most attractive for the analysis of solid and
liquid biological samples since the danger of loss or contamination during
sample preparation is reduced. Using this technique, Schaller et al. (1973)
reported a detection limit (1% absorption) of 0.2 yg/liter chromium in
urine, which corresponds to only 10 pg of the metal in the sample analyzed.
Replicate analyses of urine containing 6 yg/liter chromium had a relative
standard deviation of ±15% and recovery of chromium from spiked samples
averaged 93%. These data reflect favorable developmental laboratory con-
ditions; under the routine conditions customarily found in commercial
laboratories greater analytical variance may be expected.
The analysis of chromium by the flameless atomic absorption technique
is influenced by a number of factors. Henn (1974) observed a variation in
absolute sensitivity as a function of sample volume and ascribed the effect
to the manner in which the sample was distributed in the graphite furnace.
Schaller et al. (1973) found that the specificity of the method was influ-
enced by smoke and nonspecific absorption during the atomization of urine
samples. This difficulty was satisfactorily resolved by modifying the
charring procedure to destroy the smoke-causing components. Barnard and
Fishman (1973) evaluated the heated graphite atomizer for the routine,
practical analysis of water samples and concluded that trace metal analysis
of water by direct comparison with aqueous standards is impractical because
of matrix interference. However, analysis by combining chelation and sol-
vent extraction with subsequent atomization proved satisfactory. Analysis
by the method of standard additions was also acceptable.
-------
36
Background or nonspecific absorption effects are much more severe in
flameless absorption than in flame atomic absorption. Fortunately, all
major manufactures offer instruments with automatic simultaneous background
correction capability. Flameless atomic absorption done without background
correction is automatically suspect.
The uncritical use of the flameless atomic absorption technique to
determine chromium in organic matrices was questioned by Masironi, Wolf,
and Mertz (1973), Wolf, Mertz, and Masironi (1974), and Mertz (1974).
These authors investigated the chromium content of different sugar samples
and observed large discrepancies depending on whether the samples were ashed
in oxygen plasma at 150°C, in a muffle furnace at 450°C, or in the graphite
furnace of the atomic absorption spectrometer at 1000°C. As shown in Table
2.7, ashing in a muffle furnace at 450°C resulted in chromium losses of 52%,
46%, 17%, and 0% for molasses and unrefined, brown, and refined sugar, re-
spectively, as compared to the oxygen plasma procedure. Ashing of the same
types of sugar in the graphite furance at 1000°C resulted in losses of 89%,
77%, 52%, and >50%, respectively, as compared to the oxygen plasma method.
After extensive additional tests the authors concluded,
(a) inorganic chromium in a sugar matrix can be deter-
mined by direct addition of the sample to the graphite fur-
nace; (b) chromium naturally present in sugar and probably
in other food-stuffs and biological materials occurs in an
organically bound complex that is lost to detection by atomic
absorption upon direct placement of the sample in the graphite
furnace, i.e., it behaves differently from inorganic chromium;
(c) in order to determine organically bound chromium by graph-
ite furnace atomic absorption, it is necessary to convert it
to inorganic chromium by oxygen plasma ashing before introduc-
tion of the sample into the furnace.
Table 2.7. Mean chromium content in different types of sugars
Type
of
sugar
Molasses
Unrefined
Brown
Refined
Number
of
samples
3
8
5
7
Chromium content (ng/g
Oxygen plasma
ashing,
150 C
266 + 50
162 + 36
64 + 5
20 + 3
Muffle furnace
ashing,
450 C
129 + 54
88 + 20
53 + 8
25 + 3
of sample)
Graphite
ashing,
(direct
29
37
31
<10
furnace
1000 C
analysis)
+ 5
+ 13
+ 2
Values listed are averages of means of multiple determinations of each
type + standard mean error of this average.
Source: Adapted from Wolf, Mertz, and Masironi, 1974, Table III, p. 1039.
Reprinted by permission of the publisher.
-------
37
These observations cast doubt on the validity of many published analyses
of chromium in biological materials. At the present state of knowledge,
analyzing and cross-checking analyses of this type by different techniques
apparently are essential. Low-temperature ashing also appears to be an
essential step in the analysis of some biological samples.
2.3.2.3.3 Neutron activation analysis — Neutron activation analysis is one
of the most sensitive modern analytical techniques for the determination of
trace elements. Samples and known standards are irradiated in a nuclear
reactor during which time neutrons are captured by various nuclides in the
sample. Usually, the production of radioactive isotopes makes it possible
by appropriate measurements to identify the daughter activities and relate
them to the parent isotope. By comparison with the activity induced in the
standards, the amount of sought isotope can be calculated. The induced
activity, and, hence, the sensitivity for determining the parent nuclide,
is proportional to the amount of the parent isotope present. Neutron fluxes
of 1012 to lO1* neutrons cm"2 sec"1 are easily available in modern reactors;
thus, for irradiations of reasonable length (a few seconds to a few days)
most elements can be determined at levels of 10"8 to 10"10 g (Fulkerson and
Goeller, 1973, p. 436).
The commonly used reaction for chromium activation analysis is
50Cr(n,Y)sJCr. Chromium-50 has a thermal neutron absorption cross section
of 17.0 barns and a natural abundance of 4.31% (Robertson and Carpenter,
1974). The resulting 51Cr decays with a half-life of 27.8 days and is
usually determined by measuring the intensity of the 320-keV gamma ray.
The minimum chromium concentration which can be detected varies with
sample type and processing conditions. The following sensitivites have been
reported for samples and analyzed without chemical processing: 0.2 ng/g in
petroleum (Shah, Filby, and Haller, 1970), 30 ng/g in fresh water (Bhagat
et al., 1971), and 0.2 yg/g in biologic material (Spyrou et al., 1974).
Greater sensitivities generally can be achieved for given irradiation con-
ditions if the sample is chemically processed to separate and concentrate
the element to be determined. For example, after chemically processing
the sample, Robertson and Carpenter (1974) cited a sensitivity of 0.1 ng/g
for chromium in river water and 3 ng/liter for seawater. McClendon (1974)
reported sensitivities at the parts per billion level for chromium extracted
from previously irradiated biological and environmental samples.
The precision and accuracy of neutron activation analyses of chromium
also vary with sample type and processing conditions but may be generally
characterized as good to excellent for most samples. Relative standard
deviations of ±10% have been commonly reported for samples containing chro-
mium in the microgram per gram and nanogram per gram ranges (Harrison et
al., 1971; Shah, Filby, and Haller, 1970). The relative error was fre-
quently less than 25% (Dams et al., 1970; De Goeij et al., 1974) and may
be less than 5% under favorable conditions (McClendon, 1974).
One distinct advantage of neutron activation analysis is reduced
problems due to reagent contamination. Even if chemical processing is
required, postirradiation contamination is of no consequence in the final
result.
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38
Neutron activation analyses are applicable to many kinds of environ-
mental samples including air pollution particulates, dusts, soils, fresh
and marine waters, sediments, biologic liquids and solids, and foods. The
samples most often are irradiated without prior chemical treatment. How-
ever, the procedure is relatively expensive and is normally used only when
a multielement determination is required. Since additional elements are
determined at small incremental cost, the average cost per element is low
if many elements are assayed. The method has another disadvantage when
used for the analysis of chromium. Due to intense x-ray or bremsstrahlung
activity from 2ANa, 38C1, "2K, 56Mn, and 32P in many samples, the irradi-
ated sample usually must be cooled several weeks before measuring the chro-
mium concentration. The procedure is thus not amenable to rapid or on-line
applications. The lengthy cooling period can be reduced to about 24 hr by
chemically separating the offending nuclides from the irradiated chromium
(McClendon, 1974).
2.3.2.3.4 Molecular absorption spectrophotometry — This analytical method
involves forming colored molecular species which absorb radiation in the
visible or near ultraviolet range of the spectrum. The amount of radia-
tion absorbed is compared with a previously obtained calibration plot and
is related to the metal concentration by the calibration data. The molecu-
lar species used to determine chromium is usually the diphenylcarbazide
complex, which is reddish purple in slightly acid solutions (American
Public Health Association, American Water Works Association, and Water
Pollution Control Federation, 1971, p. 156). Photometric measurements at
concentrations near 400 yg/liter can be made with a precision of about 30%.
Accuracy depends on the promptness of the analysis; spectrophotometric com-
parisons should be made at least 5 min but not more than 15 min after the
reagent is added to the sample (American Public Health Association,
American Water Works Association, and Water Pollution Control Federation,
1971, p. 158).
The molecular absorption method for determining chromium can be used
for natural water samples, industrial waste solutions, and solutions of
ores and metals if the concentration of hexavalent chromium is in the range
of 5 to 400 yg/liter. The technique was used extensively several years
ago; now, however, it has been largely supplanted by more sensitive and
convenient techniques such as atomic absorption spectroscopy, nuclear acti-
vation analysis, and emission spectroscopy.
2.3.2.3.5 Emission spectroscopy — In emission spectroscopy, prepared sam-
ples are excited with a flame, arc, spark, or plasma; the resulting light
is dispersed with a monochromator, and the characteristic emission lines
of each excited element are recorded electronically or on a photographic
plate. The concentration of each element is determined by comparing the
density of its emission line with that of an internal or external standard.
Sample preparation depends in part on the mode of excitation; in general,
samples are dissolved and the liquid is deposited on metal or graphite
electrodes which are dried before analysis. Precision and accuracy vary
with sample type and chromium concentration; standard reference water
samples containing 10 to 50 yg/liter chromium can be determined with an
apparent accuracy of ±10% to 16% and a relative precision of ±6% to 12%
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39
(Barnard and Fishman, 1973). Seely and Skogerboe (1974) monitored air con-
taining 0.2 yg/liter chromium with a precision of ±19%. Webb, Niedermeier,
and Griggs (1973) observed comparable precision in the analysis of biolog-
ical tissues, but they found that serious errors were introduced if ex-
ternal reference standards and the unknown samples did not contain similar
concentrations of matrix elements.
The above examples illustrate that emission spectroscopy is an attrac-
tive procedure for analyzing a variety of environmental samples, especially
when multielement analysis is required. Adequate precautions must be taken,
however, to eliminate bias from matrix effects (Niedermeier, Griggs, and
Webb, 1974).
Emission spectroscopy, using an inductively coupled plasma as a light
source, has been studied extensively (Boumans and deBoer, 1972, 1975;
Fassel and Kniseley, 1974; Olson, Haas, and Fassel, 1977). Sensitivities
down to 0.3 ppb have been reported (Environmental Instrumentation Group,
1973Z?, p. 5) using direct aspiration of sample solutions. Precision and
convenience are similar to atomic absorption methods and multielement
determinations are readily carried out. Although it has not been adequately
tested, plasma emission spectroscopy appears to be very promising for the
future.
2.3.2.3.6 Spark-source mass spectrometry — Chromium can be determined by
exciting a sample with a radio-frequency spark, followed by spectrometric
measurement of the resulting ions according to their mass. The ions of
different mass-to-charge ratios describe different radial paths through the
magnetic field of the electromagnetic analyzer. As a result, they impinge
on different points along the detector, usually a photographic plate. The
chromium concentration in the sample is measured by the density of the
appropriate spectral line on the photographic plate, as compared to that of
an element previously added to the sample in known amount. This technique
is applicable to virtually any matrix, but results are only semiquantita-
tive. Typically, the detection limits for chromium are 0.02 to 0.1 yg/g,
with a relative standard deviation of ±20% (Environmental Instrumentation
Group, 1973&, p. 14).
The precision and accuracy of the spark-source mass spectrometric
method can be greatly improved by using the isotope dilution technique.
In this variation, a known quantity of S3Cr is added to the sample and the
whole is refluxed with acid until isotopic equilibrium is achieved. A
portion of the solution is then transferred to an electrode and is excited
by a radio-frequency spark as previously described. The ratio of 52Cr to
53Cr is determined and compared with that of the initial S3Cr spike. The
chromium concentration in the original sample is related to the extent of
dilution observed in the spiked sample. Relative errors of 0.5% to 3% are
typical for samples containing chromium in concentrations varying from
micrograms to picograms (Farrar, 1972). This method was recently used to
establish the chromium content of NBS bovine liver (Dunstan and Garner,
1977).
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40.
The spark-source mass spectrometric technique is relatively expensive
in terms of labor and equipment charges per sample, especially if the iso-
tope dilution procedure is used; consequently, it is rarely the method
chosen for chromium unless multielement analyses are required. An excep-
tion is the analysis of reference materials, such as bovine liver. When
economically justified, the method can be applied to a wide variety of
environmental samples, such as atmospheric particulates, natural water
samples, industrial waste solutions, fuels, and biologic materials. Care
must be taken to avoid mass interferences from polynuclear ions having the
same mass to charge ratio as the measured chromium nuclides (Brown and
Taylor, 1975).
2.3.2.3.7 X-ray fluorescence — Due to recent development in x-ray sources
and instrumentation, energy-dispersive x-ray fluorescence is gaining accept-
ance as a nondestructive method of simultaneously determining groups of
elements in a variety of environmental samples (Environmental Instrumenta-
tion Group, 1973&, p. 11). In this technique, the sample is irradiated
with low-energy x-ray or gamma photons which displace K or L orbital
electrons from elements of interest. A series of characteristic x-ray
lines are then emitted as the electron defects are filled by electrons
from higher orbitals. Typically, silicon solid-state detectors are used
in conjunction with multichannel analyzers to record and analyze the result-
ing spectrum (Jaklevic et al., 1974). The intensity of the fluorescence is
related to the concentration of the metal in the sample by comparison with
radiation from an internal standard. Sample preparation is important; par-
ticle size and shape affect the extent to which the irradiating beam is
scattered or absorbed. Also, quantitative measurements of trace elements
may be complicated by radiation from surrounding atoms. Solid samples can
be pressed into thin wafers to minimize these matrix effects. Liquid sam-
ples can be processed directly, provided the metal concentrations of interest
are at least 1 yg/g; preanalysis enrichment is required for samples of lower
concentration.
The precision and accuracy of the method varies with sample type and
concentration level; for orchard leaves containing 2.3 ppm chromium, the
relative standard deviation and relative error reported by one laboratory
were ±64% and 15%, respectively (Environmental Instrumentation Group, 1973£>,
p. 13). In contrast to these data, Kuhn (1973) reported a relative stand-
ard deviation of ±4% for coal samples containing 25 yg/g chromium, and
Jaklevic et al. (1974) cited a relative error of 1% to 4% in analyzing
samples of air particulates containing 120 yg/cm2 chromium.
The energy-dispersive x-ray fluorescence technique is not yet in wide-
spread use. It appears to have considerable potential for rapid, multi-
element analysis of certain environmental samples, particularly those which
can have more or less homogeneous surfaces, such as filtered air particu-
lates, solutions, and finely divided solids which can be readily pressed
into homogeneous pellets.
2.3.2.3.8 Gas chromatography — Gas chromatography is a method of separation
in which the components to be separated are distributed between two phases:
a stationary bed of large surface area and a gas which percolates through
-------
41
and along the stationary bed. Typically, the stationary hed is a column
filled with a finely divided, inert packing which is evenly coated with a
suitable liquid sorbent. Alternatively, the stationary bed may be a 0.01-
to 0.02-in. inner diameter column onto which a 0.5-ym layer of liquid
phase is coated. These columns are known as "capillary" or "open tubular"
columns. Helium, hydrogen, or nitrogen is usually used as the gaseous
phase. When a sample is placed into a chromatographic column, the unabsorbed
carrier gas moves the sample constituents through the column at a rate deter-
mined by the interaction of each constituent with the sorbent. Ideally,
since each constituent has a different affinity for the sorbent, each com-
ponent of the sample leaves the column completely resolved from the other
components. The composition of the original sample is determined by identi-
fying and measuring each of these fractions. The chromatographic detector
serves to identify sample components, and therefore the particular sample
constituents under investigation dictate which type of detector to use.
Chromium can be analyzed by gas chromatography as a volatile metal
chelate (Moshier and Sievers, 1965; Guiochon and Pommier, 1973). The
general procedure is as follows. The sample is first digested to get the
chromium in solution. The chromium is then quantitatively chelated with
1,1,1-trifluoro-2,4-pentanedione to form a thermally stable, volatile
chromium(III) complex. This complex is subsequently extracted into an
organic solvent (usually benzene or hexane), and an aliqout of this extract
is injected into the gas chromatograph. It should be noted that only chro-
mium(III) will form the desired complex; therefore, chromium(VI) is re-
duced to chromium(III) with sodium sulfite immediately after digestion.
Using this procedure, investigators have determined chromium by gas
chromatography with a variety of detectors. Savory, Mushak, and Sunderman
(1969) and Savory, Glenn, and Ahlstrom (1972) determined chromium in human
serum samples using electron capture detection. The limit of sensitivity
was reported to be 0.03 pg of chromium. Electron capture detection has
also been used to determine chromium in natural waters at picogram levels
(Lovett and Lee, 1976; Gosink, 1976) and physiological levels of chromium-
(III) in urine (Ryan and Vogt, 1977). Wolf (1976) used atomic absorption
detection to determine chromium in NBS SRM 1571 orchard leaves, reporting
a detection limit of 1 ng chromium. A specially constructed microwave
emission detector was utilized by Black and Sievers (1976) to analyze chro-
mium in blood plasma. The 357.9-nm emission line of chromium was monitored
to detect as little as 0.9 pg/yl chromium. Wolf et al. (1972) coupled a
mass spectrometer to a gas chromatograph to determine chromium in serum and
blood. A detection limit of 0.5 pg was reported with a relative error of 20%.
The gas chromatographic analysis of chromium in a variety of biological
and environmental samples is very sensitive. Of the detection methods used,
the electron capture method is the least specific and therefore requires a
very clean extract. Spectroscopic detection methods respond directly to
chromium and appear promising. Gas chromatography, with a mass spectrom-
eter detector, is an extraordinarily sensitive and specific method. The
high equipment cost will not allow the method to become popular, but it may
find an important application in the analysis of biological materials.
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42
2.3.2.3.9 Polarography — Polarographic techniques have a long and honorable
history in analytical chemistry, but they have not been applied extensively
to chromium analysis. Two recent variations of the method — single-sweep
polarography and differential pulse polarography — hold promise as poten-
tially sensitive and rapid techniques. The single-sweep method was applied
to chromium in water (with a detection limit of 0.01 ppm) (Whitnack, 1975).
Similar detection capability is shown by the differential pulse method
(Crosmun and Mueller, 1975; Neeb, 1974). These methods must be regarded as
potentially useful but are currently not popular for chromium analysis.
2.3.2.3.10 Chemiluminescence' — Luminol (5-amino-2,3-dihydrophthalazine-
1,4-dione) emits light when oxidized by hydrogen perioxide. Oxidation occurs
only in basic solution in the presence of certain metal ions which catalyze
the reaction. In the presence of excess reagents, the intensity of light
emission is proportional to the metal catalyst concentration, a property
that can be made the basis for trace metal catalyst analysis. The intrinsic
sensitivity of the luminol system to small metal concentrations greatly ex-
ceeds that of most analytical procedures. For example, the minimum detect-
able quantity of trivalent chromium in natural water samples is about 25 pg
(Seitz, Suydam, and Hercules, 1972).
Chemiluminescence analyses may be performed in static or flowing
systems. A typical flowing system was described in detail by Seitz, Suydam,
and Hercules (1972). Normally, an analysis is performed in less than 30 min.
The precision and accuracy of the Chemiluminescence method are not well
documented; however, the available data are encouraging. On the basis of a
limited number of analyses of NBS orchard leaves (SRM No. 1571) containing
about 2.3 yg/g chromium, relative standard deviations by two different
analysts varied from ±5% to ±12% and accuracies (recovery from standard
sample) exceeded 95% (Li and Hercules, 1974; Seitz and Hercules, 1973).
Recently a centrifugal fast analyzer was used for a rapid Chemiluminescence
analysis of chromium(III) in water (Bowling et al., 1975).
The Chemiluminescence method of analysis is not a mature, established
analytical procedure; much more experience is required to define its use-
fulness and limitations. However, its economy, speed, and extraordinary
sensitivity offer promise of usefulness in the analysis of metals at the
ultratrace level, especially for chromium in biologic materials.
2.3.3 Comparison of Analytical Methods
Until the last decade or two, the spectrophotometric method utiliz-
ing the chromium diphenylcarbazide reaction was the most widely used
technique for determining chromium. During the last few years, however,
this method has been largely replaced by the more sensitive and convenient
atomic absorption spectrometry. Through use of the flame technique, chro-
mium can usually be determined at concentrations equal to or less than
that established for drinking water standards without prior concentration.
Considerably greater sensitivity can be achieved using the newer flameless
variations of atomic absorption spectrometry, with some loss of convenience.
In general, the sensitivity, precision, and accuracy attainable by atomic
-------
43
absorption techniques are adequate for most inorganic samples of environ-
mental interest. The usefulness of atomic absorption techniques for analy-
sis of chromium in organic media is not so well defined. The concentration
of chromium in many such samples is below the detection level of the flame
method unless unusually large samples are used. However, even if large
samples are available, the extensive preanalysis processing required by
such samples can introduce considerable error. In principle, this dilemma
should be resolved by the use of flameless atomic absorption; however,
evidence is accumulating that chromium in some biological media behaves
differently from inorganic chromium: it may be lost to detection by atomic
absorption upon direct placement of the sample in the graphite furnace
(Masironi, Wolf, and Mertz, 1973; Maxia et al., 1972; Mertz, 1974; Wolf,
Mertz, and Masironi, 1974). The flameless atomic absorption method can
still be applied to the determination of chromium in some organic samples
such as sugars, however, if the element is converted to the inorganic form
by oxygen plasma ashing before introducing the sample into the furnace
(Wolf, Mertz, and Masironi, 1974). Conventional techniques for converting
chromium in organic samples to the inorganic form should be considered
suspect until their validities are rigorously established by the use of
appropriate reference standards (Mertz, 1974) (see also Section 2.3.1).
Neutron activation analysis is widely used to determine chromium and
other elements in environmental samples; it is probably second only to
atomic absorption spectroscopy in frequency of use. This popularity stems
from three factors: the great sensitivity of the method, its applicability
to a variety of sample types with little or no preanalysis processing, and
its ability to determine a variety of elements with the irradiation of a
single sample. If many elements must be determined, the cost per element
is small by this technique. The use of neutron activation analysis to
determine chromium normally requires a cooling period of several weeks if
postirradiation separations are not performed. Thus, the technique is not
suited for on-line or rapid analyses of chromium. However, if postirradia-
tion separations are made, very precise analyses can be obtained in about
a day (McClendon, 1974).
Emission spectroscopy is a well-established analytical method capable
of satisfactorily determining many elements simultaneously in a variety of
environmental samples. With plasma excitation, the method is adequately
sensitive and accurate for most environmental samples. Similar comments
apply to spark-source mass spectroscopy with isotope dilution.
The importance of x-ray fluorescence as an analytical method for
environmental samples has been greatly expanded by the recent development
of the energy-dispersive mode of operation. With this feature, rapid, as
well as sensitive, multielement analyses can be performed. This variant
of the standard x-ray analysis technique is not yet mature; also, problems
relating to sample preparation exist. However, with seasoning, this tech-
nique appears very attractive for sensitive multielement analysis of
environmental samples.
2.3.3.1 Standardization — Trace-level determinations of chromium are re-
quired in an extensive variety of samples: atmospheric particulates and
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44
mists, fresh and marine waters, industrial waste effluents, sludges, soils
and sediments, and ores and metals as well as plant and animal tissues and
fluids. Reliable analyses require standard procedures for the collection,
preparation, and storage of these specimen types and standard methods for
concentrating or separating the chromium from the various materials.
Achievement of this task is only in the initial stages; earliest efforts
have been directed toward development of procedures for drinking water,
groundwater and surface waters, and domestic and industrial waste effluents.
Standard Methods for the Examination of Water and Wastewater, 13th ed.,
1971, published jointly by the American Public Health Association, the
American Water Works Association, and the Water Pollution Control Federation,
prescribes standard sample handling techniques and analytical procedures for
many metals and includes spectrophotometric and atomic absorption techniques
for chromium at the trace level. More recently, the U.S. Environmental Pro-
tection Agency (EPA) published the Handbook for Analytical Quality Control
in Water and Wasteuater Laboratories, 1972, which defines standards useful
in many aspects of the work. In a companion volume, Manual of Methods for
Chemical Analysis of Water and Wastes, 1974, the EPA established standard
procedures for determining many constituents of water samples, including
the analysis of trace levels of chromium by atomic absorption spectrometry.
However, much remains to be done in this area.
One of the most pressing needs is the greater availability of standard
materials representative of environmental samples. The National Bureau of
Standards (NBS) supplies orchard leaf, tuna meal, bovine liver, and brewer's
yeast as standard reference materials for the analysis of biological material.
Chromium concentrations in most of these materials are now being certified.
The EPA in cooperation with the NBS has made up four environmental standards:
fly ash, coal, oil, and gasoline. Concentrations of many of the elements
of prime.environmental concern in these reference materials are established.
Thus far, no standard reference natural water samples are available, but the
EPA will supply six concentrated water reference samples which, when diluted
as prescribed, will give different concentrations of arsenic, cadmium, chro-
mium, copper, lead, selenium, and zinc in the parts per billion concentra-
tion range. These samples are available from J. A. Winter, Methods Per-
formance Evaluation Activity, National Environmental Research Center, U.S.
Environmental Protection Agency, Cincinnati, Ohio 45268 (Robertson and
Carpenter, 1974).
2.3.3.2 Interlaboratory Comparisons — Relatively few interlaboratory com-
parisons of chromium analyses at the trace level were reported in the
literature. In a study conducted by the Methods Development and Quality
Assurance Research Laboratory, Cincinnati, Ohio, six synthetic concentrates
containing varying levels of aluminum, cadmium, chromium, iron, manganese,
lead, and zinc were added to natural water samples (U.S. Environmental Pro-
tection Agency, 1974). Samples were distributed to various laboratories
for analysis by atomic absorption spectrometry. The statistical results
for chromium are given in Table 2.8. With the exception of one sample,
good accuracies were reported by the participating laboratories; however,
interlaboratory precision was poor.
The United States Geological Survey (Water Resources Laboratory, Denver,
Colorado) conducts a continuing interlaboratory comparison program for water
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45
Table 2.8. Interlaboratory study of chromium analysis by
atomic absorption spectrophotometry
Number
of labs
74
76
72
70
47
47
True values
(yg/liter)
370
407
74
93
7.4
15.0
Mean value
(yg/liter)
353
380
72
84
10.2
16.0
Standard
deviation
(yg/liter)
105
128
29
35
7.8
9.0
Accuracy as
percent bias
-4.5
-6.5
-3.1
-10.2
37.7
6.8
Source: U.S. Environmental Protection Agency, 1974, p. 106.
analysis. Chromium results from several of these samples, which cover a
period of approximately five years (^1971 to 1976), are given in Table 2.9.
Relative standard deviations show definite improvement during the period,
dropping from 70% to 100% in the early rounds to 20% to 30% for the later
ones. The total range of reported values remains disturbingly large.
Parr (1974) reported on a study of NBS bovine liver that involved ten
laboratories and the range between the high and low result was over 300
(see Section 2.3.1). Pierce et al. (1976) used bovine liver, urine, serum,
and wheat in an interlaboratory comparison which also compared results from
several methods of analysis. The quality of the results seemed to depend
more on the sample matrix than on the analytical method. The range between
high and low results for bovine liver was about a factor of four. Chromium
in bovine liver is soon to be certified at 90 ± 15 ng/g (Rook and Wolf,
1977).
In a recent study (Von Lehmden, Jungers, and Lee, 1974) by the EPA to
monitor trace elements in fuels, nine laboratories using similar analytical
methods were asked to determine the concentration of 28 elements, including
chromium, in the same fuel and fly-ash matrices. The analytic methods in-
cluded neutron activation analysis, atomic absorption spectrometry, spark-
source mass spectrometry, optical emission spectrometry, anodic stripping
voltammetry, and x-ray fluorescence. The reported values of chromium in
coal ranged from 3.4 to ^30 ppm; in fly ash, from 80 to 500 ppm; in resid-
ual fuel oil, from 0.7 to 4 ppm; and in gasoline, from <0.001 to <0.3 ppm.
There appears to have been significant improvement in the ability to
measure chromium during the past five years but the ranges reported are
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46
Table 2.9. Interlaboratory comparison results
from water analysis of chromium
SRW
number
28
32
38
39
44
45
48
49
52
53
56
57
59
Total
range
(yg/liter)
0-90
0-40
4-50
7-70
15-45
10-32
3-40
10-90
10-110
0-25
14-43
Mean + standard
deviation
(outliers rejected)
19.2 + 14.3
11 + 11
45 + 24
7.9 + 6.3
8.2 + 2.8
18.9 + 6.2
31.8 + 7.0
16.5 + 5.9
6.3 + 2.3
20.0 + 5.0
39.4 + 11.9
9.5 + 1.7
30.2 + 6.5
Relative
standard
deviation
74
100
33
80
34
32
22
36
36
25
30
18
21
Source: U.S. Geological Survey Water Resources
Laboratory, Denver, Colo.
still disturbingly large. The ranges illustrate the difficulties in measur-
ing traces of chromium and emphasize anew the importance of certified ref-
erence materials such as those now being provided by the National Bureau of
Standards.
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47
SECTION 2
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SECTION 3
BIOLOGICAL ASPECTS IN MICROORGANISMS
3.1 SUMMARY
The limited data on the metabolism and toxicity of chromium show that
most microbes are able to absorb some chromium. Internal chromium con-
centrations for microbes vary, but many samples have about 1 ppm chromium,
a value similar to that found in many plants. Chromium has not been shown
to be an essential element for any group of microorganisms. Toxicity for
many microbes occurs at chromium concentrations of 0.05 to 5 ppm, although
exact tolerances depend on the particular species. Chromium inhibits a
variety of metabolic processes such as nitrogen fixation, photosynthesis,
and protein synthesis; no data defining mechanisms of toxicity were found.
Comparative data indicate that chromium(VI) is more toxic than chromium(III)
3.2 METABOLISM
The metabolism of chromium in microbes has scarcely been studied. Al-
though isolated reports have given evidence that chromium addition stimu-
lated growth (Pratt and Dufrenoy, 1947) or certain metabolic systems
(Horecker, Stotz, and Hogness, 1939), most reports have shown growth inhi-
bition at moderate chromium concentrations. No studies have conclusively
demonstrated that chromium is an essential element in microbes.
3.2.1 Uptake
Little information was found on the mechanisms or kinetics of chromium
uptake by microbes. Roberts and Marzluf (1971) demonstrated that chromate
was actively taken up by the sulfate transport system in Neurospora crassa.
A similar mode of transport apparently exists in the bacterium Salmonella
typhimuriwn (Ohta, Galsworthy, and Pardee, 1971; Pardee et al. , 1966) and
in the fungus Aspevg-il'lus nidulans (Arst, 1968). In fact, a common method
for selecting microbial mutants deficient in sulfate uptake is by selection
for chromate resistance (Ohta, Galsworthy, and Pardee, 1971). Resistance
is assayed by the ability to grow in the presence of 26 ppm chromium(VI)
(0.5 mM Na2CrO<,) (Pardee et al. , 1966).
Radiochromate (picocuries per gram wet wt) was measured in plankton
from the Columbia River (Watson et al., 1969). Chromium is released into
the river by the Hanford Reactor. Uptake by these plankton was assumed to
occur by adsorption rather than by assimilation. However, no experimental
evidence was given to support this contention. The chemical form of chro-
mium in natural waters must also be considered in the assessment of adsorp-
'tion and assimilation phenomena.
Experiments with 51Cr have shown that the alga Naviaula sp. and a
bacterium (species not specified) sorbed chromium (ca. 40% to 50% of 51Cr
taken up in 24 hr) under those particular experimental conditions (Calow
and Fletcher, 1972). The data did not distinguish between adsorption and
56
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57
absorption. The amount of 51Cr lost from Navicula and bacteria over a
48-hr period was less than 4% of 51Cr absorbed.
An interesting relation between chromium (as trivalent chromium) uptake
and glucose concentration occurs in brewer's yeast. Whereas uptake of tri-
valent 51Cr did not occur in Sabouraud medium in either log or stationary
phase cells, addition of glucose increased chromium uptake 2000% after 13
days. Uptake of manganese or iron was not increased. Uptake was independ-
ent of the trivalent chromium concentration (0.0001 to 1 ppm); these con-
centrations did not stimulate growth (Burkeholder and Mertz, as cited in
Mertz, 1969).
3.2.2 Concentration
Information on chromium concentration in microbes is rather sparse,
but existing data illustrate that a rather broad concentration range can
be found and that the internal concentration is probably related to the
concentration in the external medium (Table 3.1).
Chromium concentrations for a variety of plants, including algae and
fungi, are listed in Table 4.15. The concentrations ranged from 0.65 to
27 ppm chromium and are similar to concentrations found in higher plants.
Table 3.2 gives chromium concentrations in some multicellular marine algae;
the observed range is from about 0.4 to 12 ppm chromium with a typical con-
centration of about 1 ppm. No data on the relationship between chromium
concentrations in water and in the plants were found. Fukai and Brokey
(1965) suggested that surface contamination of water plants may account for
part of the observed chromium content. Soothe and Knauer (1972) reported
that the brown algae Maerocystis pyrifera contained 5.0 ± 3.5 ppm chromium
on an ash weight basis.
Data such as these must be used with caution, however, because of the
analytical uncertainties discussed in the previous chapter. Relative chro-
mium values from a given laboratory are probably trustworthy but absolute
values and comparative values between laboratories must be regarded as very
uncertain. This situation will remain, especially for older data, until
the reasons for the large analytical errors are explained.
3.2.3 Biotransformation and Elimination
No information was found on the metabolism of chromium within the cell
when supplied as either trivalent or hexavalent chromium or on the possible
elimination of chromium from living cells.
3.3 EFFECTS
The major effect reported for chromium- is growth inhibition of a
variety of organisms. However, in most cases, studies were not designed
to determine the maximum concentrations tolerated without metabolic
impairment.
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58
Table 3.1. Microbial concentration of chromium
Organism
Sphaerotilus sp.
(bacterium)
Zooplankton
Microplankton
Phytoplankton
Plankton
Fungi
Coral
SolenosmiUa
Desmophyllum
Cory ophy Ilia
Tvoahoayathus
Dendrophyllia
Madraeis
Cladocora
Anomoaora
Bathyayathus
Unidentified
Lichens
Umbiliaaria
hyperborea
Pcumelia eonsperea
Leaanova rub-ina
Caloplaoa elegans
Chromium
concentration
(ppm dry wt)
284
6-12
7-11
8-137
0.6-3.7
1.3-21.4
3.5
1.5
<2
1-1.2
<2-3
1.5
2
4
2
2
4
33
100-150
50
30
150
Sample area
Japanese river,
below pollution
effluent outfall
Control region of
N.Y. Bight
Acid-iron waste
disposal area,
N.Y. Bight
Monterey Bay,
Calif.
Monterey Bay,
Calif.
Pacific Ocean
Jamaican deep-
ocean region
Jamaican deep-
ocean region
Jamaican deep-
ocean region
Jamaican deep-
ocean region
Jamaican shallow-
ocean region
Jamaican shallow-
ocean region
Jamaican shallow-
ocean region
Jamaican shallow-
ocean region
Jamaican shallow-
ocean region
Collected from
sandstones
Reference
Loutit, Patrick, and
Malthus, 1973
Vaccaro et al. , 1972
Vaccaro et al. , 1972
Martin and Knauer,
1973
Martin and Knauer,
1973
Martin and Knauer,
1973
Schroeder, Balassa,
and Tipton, 1962
Schroeder, Balassa,
and Tipton, 1962
Livingston and
Thompson, 1971
LeRoy and Koksoy,
1962
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59
Table 3.2. Chromium content of algae
Species
Enteromorpha linza
(green algae)
Enteromorpha ralfsii
(green algae)
Enteromorpha sp.
(green algae)
Ulva lactuoa
(green algae)
Codiwn elongation
(green algae)
Cystoseira myriophylloides
(.brown algae)
Cystose-ira firribriata
(brown algae)
FUGUS oeranoides
(brown algae)
Fucus vesiaulosus
(brown algae)
Jania rubens
(red algae)
L-ithophyllwn inerustans
(red-calcarious algae)
Place and date
of
collection
Toulon (M)a
Aug. 1963,
Cap Breton (A)
Jan. 1964
St. -Raphael (M)
July 1964
Arcachon (A)
Jan. 1964
St.-Raphael(M)
July 1964
Monaco (M)
Sept. 1963
Toulon (M)
Aug. 1963
St. -Raphael (M)
July 1964
Bayonne (A)
Jan. 1964
Cap Breton (A)
Jan. 1964
Arcachon (A)
Jan. 1964
Toulon (M)
Aug. 1963
Cap Martin (M)
June 1962
Chromium
content
(ppm)
1.6
0.9
0.4
1.4
0.4
0.4
1.4
1.0
0.6
1.0
0.6
4.1
12.1
?M = Mediterranean coastal waters.
A - French Atlantic littoral.
Source: Adapted from Fukai and Broquet, 1965, Table 1,
4. Reprinted by permission of the publisher.
3.3.1 Algae
Growth inhibition data reported by Hervey (1949) for seven algal species
demonstrated that certain species were more tolerant of chromium (added as
K2Cr207) than others (Table 3.3). Additionally, small amounts of chromium
stimulated growth (Table 3.4). Optimal growth, however, in five of the seven
species was at chromium concentrations of <0.32 ppm.
Wium-Andersen (1974) found a decrease in growth over a four-day period
in the algal species Nitzschia palea (diatom) and Chlofella pyrenoidosa at
-------
Table 3.3. Approximate concentration ranges of chromium which completely
inhibited growth in seven species of algae
(ppm)
Organism
ChoTella variegatus
Chlorocoecwn hwni-aota
Scenedesmus obliquus
Lepocinalis steinii
Flagellate #46
Diatom #26
Diatom #47
H-2 growth medium
15 days
1.6-3.2
1.6-3.2
3.2-6.4
0.032-0.32
0.032-0.32
No growth
No growth
33 days
1.6-3.2
3.2-6.4
3.2-6.4
0.32-1.6
0.32-1.6
0.032-0.32
0.032-0.32
56 days
6.4-16.0
3.2-6.4
3.2-6.4
0.32-1.6
0.32-1.6
0.32-1.6
0.032-0.32
H-2 modified growth medium
15 days
1.6-3.2
3.2-6.4
1.6-3.2
0.032-0.32
0.32-0.32
0.32-1.6
0.032-0.32
33 days
3.2-6.4
3.2-6.4
1.6-3.2
0.32-1.6
0.32-1.6
0.32-1.6
0.032-0.32
56 days
6.4-16.0
3.2-6.4
1.6-3.2
0.32-1.6
1.6-3.2
0.32-1.6
0.32-1.6
The lag period for both these organisms was so extended in H-2 medium that even the controls showed
no growth in 15 days.
Source: Adapted from Hervey, 1949, Table 2, p. 6. Reprinted by permission of the publisher.
o\
o
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61
Table 3.4. Greatest concentration of chromium which permitted growth equal to
or better than controls (no chromium) in seven algal species (ppm)
Organism
H-2 growth medium
H-2 modified growth medium
15 days 33 days 56 days 15 days 33 days
56 days
Chorella variegatus
Chloroooccwn himioola
Saenedesmus obliquus
Lepocinclis steinii
Flagellate #46
Diatom #26
Diatom #47
0.0001
0.32
0.32
0.032
0.032
a
a
0.32
0.32
0.32
0.032
0.032
0.32
0.032
1.6
0.32
0.32
0.32
0.32
0.32
0.032
0.00032
0.0
0.0
0.032
0.0
0.032
0.032
0.32
0.32
0.32
0.032
0.032
0.32
0.032
3.2
0.32
0.32
0.32
0.32
0.32
0.32
No growth in any tubes, including controls.
Source: Adapted from Hervey, 1949, Table 2, p. 6. Reprinted by permission of the
publisher.
Cr2072 concentrations of 50, 150, and 300 ppb (Figure 3.1). No growth
stimulation was observed at any of the concentrations used; increased iron
concentration (24 ppb) did not counteract the toxicity. In this study,
photosynthesis in Nitzschia was inhibited 25% at a Cr2072~ concentration
of about 350 ppb and 50% at a concentration of about 750 ppb. In Chlorella,
about ten times more chromium was necessary to inhibit photosynthesis by the
same degree as in Nitsschia. Since chromium had no inhibitory effect at low
light intensities (where light would be the limiting factor), the authors
concluded that chromium inhibition occurred in the dark processes of photo-
synthesis. More information is needed, however, on the mechanism of growth
inhibition because the kinetics of inhibition of growth and photosynthesis
are not similar.
Chromium concentrations between 0.01 and 0.50 ppm did not stimulate
growth in Chlorella cultures. Growth inhibition occurred at concentrations
greater than 0.50 ppm (Nollendorf, Pakalne, and Upitis, 1972). Toxicity of
chromium could be decreased by increasing the concentrations of other trace
elements, by adding ethylenediaminetetraacetic acid (EDTA) to the medium,
or by increasing the iron concentration. Chromium adsorption increased at
toxic chromium levels. A 50% reduction in cell number occurred in Nitzsohia
linearis W. Sm. after 120 hr of culture with 0.21 ppm trivalent chromium
(Patrick, Cairns, and Scheier, 1968).
Upitis, Pakalne, and Nollendorf (1973) found 102%, 86%, 71%, 62%, and
36% of control biomass of Chlorella sp. grown in culture with 0.1, 1, 2, 3,
and 5 ppm chromium, respectively (form of chromium not specified). Although
several trace elements essential to growth were tested, only iron (10 and
45 ppm) eliminated the growth inhibition of 2 ppm chromium in the culture
solution. Similar phenomena of amelioration by addition of trace elements
were shown for growth inhibition by cadmium and nickel. The existence of
specific antagonistic ions which decrease chromium ion toxicity is well
documented in certain cases (Epstein, 1972).
-------
62
109
ORNL-DWG 76-2445
10
Q.
it)
ppb CHROMIUM
0
150
150
01234
TIME (days)
Figure 3.1. The effect of different concentrations of chromium on
the growth of N. palea. Source: Adapted from Wium-Andersen, 1974,
Figure 1, p. 309. Reprinted by permission of the publisher.
Carton (1973) grew the alga Selenastmm oaprioovnutwm in culture with
chromate concentrations ranging from 0.0139 to 13.9 ppm (Figure 3.2) and
observed almost complete inhibition of growth at concentrations greater
than 1.39 ppm chromium. The object of the study was to identify toxic
components found in cooling-tower blowdown. Concentrations of CrO<,2~ with-
in the range used in this study are found in cooling-tower blowdown; thus,
a potential environmental hazard exists. As indicated by the author, tox-
icity data are needed not only for individual compounds found in the blow-
down but also for various combinations of these compounds. The concentrations
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63
^2..
ORNL-DWG 76-346)
^SIGNIFICANT DIFFERENCE FROM CONTROL
AT 0.01 ppm LEVEL
t CONTROL
* 0.0139 ppmCr04
I 0.139 ppmCr04*
.,-0.139 ppmCr04*
+ 1.39 ppmCrQ4*
H 1.39 ppm Cr04*
x 13.9 ppm Cr04*
8 (2 16
TIME (days)
20 24
Figure 3.2. Inhibitory effects of sodium chromate concentrations
on the alga Selenastrwn capTicoTnutwn. Source: Adapted from Carton,
1973, Figure 2, p. 291. Reprinted by permission of the publisher.
of Cr2072~ which inhibited growth of the algae Soenedesmus, Navioula
semi.nulwn, and Macroaystis pyrifera were 0.7, 0.2, and 1.0 ppm, respec-
tively (North, Stephens, and North, 1973).
Pollutants may have a differential effect on members of a mixed popula-
tion. In studies aimed at delineating the role of trace elements in the
management of nuisance growths in aquatic systems, Patrick, Boot, and Larson
(1975) studied the effects of several trace elements, including chromium, on
algal community structures. Experiments were conducted during different
months of the year to determine whether changes in natural conditions in-
fluenced the effects of the trace elements. Mixed filamentous and diatom
algal populations were suspended in test chambers in stream waters. While
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64
other characteristics were held constant, various concentrations of the
trace element compounds were added to the water. At a chromium concentra-
tion (potassium dichromate) of 40 to 50 ppb, diatoms remained dominant and
diversity was high. At average concentrations of 95 to 97 ppb, the diatom
diversity was reduced although the diatoms remained dominant; at average
concentrations of 397 ppb, diatoms were completely replaced by blue-green
algae and the green alga St-igeocloniwn lubrioim. Differences in biomass
and in uptake of chromium occurred during the year. For instance, at 50
ppb chromium in the water the accumulation was 1450 ppm (micrograms chro-
mium per gram of dried biomass) in March to April, whereas in May it was
only 500 ppm. However, biomass was higher in May and dilution was there-
fore a more important factor. At 100 ppb chromium results were similar,
while at 400 ppb the difference was accentuated — an accumulation of 3350
ppb in March to April and only 900 ppb in May. In the period July to
August, accumulation at the 400-ppb level was 2000 ppm. In general, there
was a good correlation between the amount of accumulation of chromium per
gram of biomass, the 14C uptake, and the development of a blue-green algal
flora.
Because blue-green and green algae are less subject to predator pres-
sure (mostly aquatic insect larvae) than are diatoms, their growth should
be restrained. These studies indicate the need for regulation of trace
element levels so that diversity, productivity, and openness of waterways
can be maintained.
3.3.2 Protozoa
Concentrations of chromium(VI) (supplied as K2Cr207) which were "lethal"
to various protozoa varied from 160 ppm for Pevanema to 5000 ppm for Para-
mec-Lum eaudatum, while "tolerated" concentrations ranged from 718 ppm for
Chilomonas to 1000 ppm for P. aaudatim (Ruthven and Cairns, 1973). "Lethal"
concentration was defined as the lowest concentration at which all organisms
died within 10 min of exposure, and "tolerated" concentration was the highest
concentration at which "some" organisms remained alive after 3 hr. These
data are of limited value because of the high concentration of chromium used
and because of unsuitable viability criteria.
Chromate concentrations from 10 to 100 yAf accelerated growth of pro-
mastigotes of Leishnan-ia tarentolae, a protozoan blood parasite, cultured
in medium with [3SS]taurine as the sole sulfur source (Sheets and Krassner,
1974). Chromate also enhanced incorporation of 35S label from taurine
into cell fractions. Increased growth with chromate did not occur, how-
ever, when inorganic sulfate was the sole sulfur source. Presumably, the
chromium effect is related to sulfur metabolism in the promastigotes.
3.3.3 Fungi
Mertz (1969) has reviewed the sparse literature on the effects of
chromium on yeast. Chromates in broad range of concentrations (6 to 800
ppm) can stimulate yeast fermentation, although similar stimulation can be
caused by other agents (acidity, heat, salts, and hypotonic solutions).
Toxicity of trivalent chromium to brewer's yeast was reported at concen-
trations of 200 ppm chromium.
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65
In studies to determine how the incorporated metal influenced yeast
metabolism, Burkeholder and Mertz (1966) added 0.1 ppm trivalent chromium
to cultures and observed increased C02 production (after a 3-hr lag) as
compared with unsupplemented controls. Addition of glucose tolerance
factor, a chromium complex required for normal glucose utilization (Section
6.3.1.1), or yeast cell fractions containing chromium produced an immediate
stimulation of C02 production. Thus, chromium is important for biological
activity, although the exact mechanism of its role in metabolism is undefined.
Sulfuric acid—dichromate mixtures have long been used to clean glass-
ware. Even exhaustive rinsing of the glassware does not remove all the
Cr2072 ions that are sorbed onto the glass surface and the amount remain-
ing can inhibit some enzymes and the growth of certain microbes. Richards
(1936) found that as little as 0.1 ppb Cr2072~ inhibited growth of yeast
and "other microbes."
Few studies were found on chromium effects on fungi other than yeast.
The median effective dose of trivalent chromium [as Cr(N03)3] which inhib-
ited germination of the fungi Altemaria tenuis and Botvytis fabae was
4.5 x 10~6 and 12.5 x 10~6 M, respectively (Somers, 1961). Natural in-
fections of corn kernels with AspeTgillus flavus were associated with
increased levels of trace elements in the kernel (Lillehoj, Garcia, and
Lambrow, 1974). Addition of 5 to 10 yg of chromium, manganese, cobalt,
or cadmium per gram of germ to a growth medium of defatted corn germ in-
creased aflatoxin production by Aspepg-iltus. Since phytate (inositol hexa-
phosphate) present in corn germ strongly binds trace elements, these ele-
ments might not be biologically available for microbial growth. Results
of Lillehoj, Garcia, and Lambrow (1974) suggested that aflatoxin production
may be a method of measuring availability of trace elements to the fungus.
Ashida (1965), who reviewed fungal adaptation to metal toxicants, cited
only one case of acquired resistance to chromium, and that case occurred
in yeast.
With any organism the possibility exists of finding a strain with in-
creased tolerance or sensitivity to the chemical under study. For instance,
although the type of resistance involved is not clear, strains of the brown
rot fungus (Poria vaUlantii") which demonstrate increased resistance to a
copper-chrome-arsenate wood preservative have been isolated (Da Costa, 1959).
However, the resistance may be due to increased resistance to arsenic. The
diversity, density, and succession of microbial invaders on exposed woods
have been studied by a number of workers (Greaves, 1972); the results suggest
that some microbes have a certain tolerance to these preservatives.
3.3.4 Bacteria
Little information was found for effects of chromium on bacteria. In
Bacillus megatherium, LDSO values were 144 ppm chromium(III) and 76 ppm
chromium(VI) (Ludvick, as cited in Eye, 1974). Growth of Staphylocooeus
awceus in a dilute synthetic medium was inhibited by the addition of 1 ppm
Cr2072~. Growth inhibition in a beef extract—peptone broth medium required
a concentration of almost ten times as much, presumably because protection
was conferred by the macromolecular constituents of the broth (Henry and
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66
Smith, 1946). Nitrogen fixation in Azotobacter chTOOOOcewn was stimulated
by 10"5 to 10~il g/liter of K2Cr04 and was inhibited by 10"3 g/liter of
K2CrC<, (Egorova and Shohegiov, 1970). In higher concentrations, K2CrO<,
inhibited growth of these bacteria.
Weinberg (1964) found that "subbactericidal" concentrations of various
trace elements (chromium, molybdenum, tungsten, selenium, and tellurium)
supplied before or within 2 hr after manganese addition suppressed sporula-
tion in Bacillus. Manganese, in concentrations larger than that required
for vegetative growth, was necessary for sporulation. Chromium (60 x 10 M)
added 3 hr after manganese addition actually increased the sporulation.
Increased sensitivity to chromium has been observed in a mutant of
Salmonella typhimurium (Corwin et al., 1966). The authors first observed
that ethylenediaminetetraacetic acid (EDTA) in the solid growth medium
allowed growth of tryptophan-deletion mutants and found that their agar
contained chromium. Experiments showed that the chromium concentration in
the agar was sufficient to inhibit growth of the mutant but not growth of
the normal type. Differences in toxicity susceptibility to other trace
elements could not be demonstrated between mutant and normal type. At
500 uM CrCl3, normal strains showed little decrease in growth, whereas
CrCl3 at concentrations as low as 10 to 20 uAf caused complete growth in-
hibition in the mutants. The nature of the mutation is unknown; trivalent
chromium concentrations within the normal and mutant strains were not
determined.
Two Esohefiohia aoli tonB-trp deletion mutants which are sensitive to
chromium(III) and require high iron concentrations for optimal growth were
described by Wang and Newton (1969a). The chromium sensitivity can be
reversed with high iron concentrations. These data, along with other lines
of evidence, suggest that the deleted genetic information is responsible
for active iron transport and that "residual iron transport" is inhibited
by the chromium(III) ion.
A point mutant of E. aoli which is sensitive to trivalent chromium
and requires a high concentration of iron for growth had the active iron
uptake system but could not synthesize a natural chelator, 2,3-dihydroxy-
benzoylserine (DHBS), specific for iron (Wang and Newton, 1969&). The
mechanism by which chromium(III) inhibits residual iron uptake is not
known, but it may involve competition with iron(III) for entry.
3
There is evidence that hexavalent chromium compounds are mutagenic.
Tryptophan revertants in the E. aoli mutation assay system were produced
by Na2CrO<,, K2CrO<,, and CaCrOA (0.05 to 0.20 micromole per culture plate).
No revertants were found using the soluble compound Cr2SO<,K2SO<,«2H20 or
with soluble salts of tungsten or molybdenum (neighboring class VI-B
elements), which indicated specificity. Only hexavalent chromium was
mutagenic in this system (Venitt .and Levy, 1974). These authors suggested
that chromium specifically attacks GC base pairs within the DNA molecule,
giving GC-AT transitions.
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67
SECTION 3
REFERENCES
1. Arst, H. N. 1968. Genetic Analysis of the First Steps of Sulphate
Metabolism in Aspergillus nidulans. Nature (London) 219:268-270.
2. Ashida, J. 1965. Adaptation of Fungi to Metal Toxicants. Annu.
Rev. Phytopathol. 3:153-174.
3. Boothe, P- N., and G. A. Knauer. 1972. The Possible Importance of
Fecal Material in the Biological Amplification of Trace and Heavy
Metals. Limnol. Oceanogr. 17(2) :270-274.
4. Burkeholder, J. N., and W. Mertz. 1966. Incorporation and Effect
of Chromium(III) in Brewer's Yeast (abstract). Fed. Proc. Fed.
Am. Soc. Exp. Biol. 25:759.
5. Calow, P., and C. R. Fletcher. 1972. A New Radiotracer Technique
Involving C-14 and Cr-51, for Estimating the Assimilation
Efficiencies of Aquatic, Primary Consumers. Oecologia (Berlin)
9:155-170.
6. Corwin, L. M., G. R. Fanning, F. Feldman, and P. Margolin. 1966.
Mutation Leading to Increased Sensitivity to Chromium in Salmonella
typhimtrium. J. Bacteriol. 91:1509-1515.
7. Da Costa, E.W.B. 1959. Abnormal Resistance of Poria va-illantii
(B.C. ex Fr.) Cke. Strains to Copper-Chrome-Arsenate Wood Preserv-
atives. Nature (London) 183:910-911.
8. Egorova, E. A., and A. T. Shohegiov. 1970. Effect of Chromium
Preparations on the Nitrogen Fixing Capability of Asotobaeter
chroooooewn. Tr. Stavropol. Sel'skokhoz Inst. (USSR) 2:118-119.
9. Epstein, E. 1972. Mineral Nutrition of Plants: Principles and
Perspectives. John Wiley and Sons, Inc., New York. 412 pp.
10. Eye, J. D. 1974. Tannery Waste. J. Water Pollut. Control Fed.
46:1283-1286.
11. Fukai, R., and D. Brokey. 1965. Distribution of Chromium in
Marine Organisms. Bull. Inst. Oceanogr. (Monaco) 65(1336):3-19.
12. Carton, R. B. 1973. Biological Effects of Cooling Tower Slowdown.
Water 69(129) :284-292.
13. Greaves, H. 1972. Microbial Ecology of Untreated and Copper-
Chrome-Arsenic Treated Stakes Exposed in a Tropical Soil: I.
The Initial Invaders. Can. J. Microbiol. (Canada) 18:1923-1931.
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68
14. Henry, R. J., and E. C. Smith. 1946. Use of Sulfuric Acid-Dichromate
Mixture in Cleaning Glassware. Science 104:426-427.
15. Hervey, R. J. 1949. Effect of Chromium on the Growth of Unicellular
Chlorophyceae and Diatoms. Bot. Gaz. (Chicago) 111:1-11.
16. Horecker, B. L., E. Stotz, and T. R. Hogness. 1939. The Promoting
Effect of Aluminum, Chromium, and the Rare Earths in the Succinic
Dehydrogenase—Cytochrome System. J. Biol. Chem. 128:251-256.
17. LeRoy, L. W., and M. Koksoy. 1962. The Lichen — A Possible Plant
Medium for Mineral Exploration. Econ. Geol. 57:107-113.
18. Lillehoj, E. B., W. J. Garcia, and M. Lambrow. 1974. Aspergillus
flavus Infection and Aflatoxin Production in Corn: Influence of
Trace Elements. Appl. Microbiol. 28(5):763-767.
19. Livingston, H. D., and G. Thompson. 1971. Trace Element Concentra-
tions in Some Modern Corals. Limnol. Oceanogr. 16(5):786-796.
20. Loutit, M. W., F. M. Patrick, and R. S. Malthus. 1973. The Role of
Metal-Concentrating Bacteria in a Food Chain in a River Receiving
Effluent. Proc. Univ. Otago Med. Sch. (New Zealand) 5:37-38.
21. Martin, J. H., and G. A. Knauer. 1973. The Elemental Composition of
Plankton. Geochim. Cosmochim. Acta (England) 3:1639-1653.
22. Mertz, W. 1969. Chromium Occurrence and Function in Biological
Systems. Physiol. Rev. 49(2):163-230.
23. Nollendorf, A., D. Pakalne, and V. Upitis. 1972. Little Known Trace
Elements in Chlorella Culture. Latv. PSR Zinat. Akad. Vestis (Latvian
S.S.R.) 7:33-43.
24. North, W. J., G. C. Stephens, and B. B. North. 1973. Marine Algae
and Their Relation to Pollution Problems. In: Marine Pollution in
Sea Life, M. Ruivo, ed. Fishing News Limited, London, pp. 330-340.
25. Ohta, N., P. R. Galsworthy, and A. B. Pardee. 1971. Genetics of
Sulfate Transport by Salmonella typhirmviwn. J. Bacteriol. 105:
1053-1062.
26. Pardee, A. B., L. S. Prestidge, M. B. Whipple, and J. Dreyfuss. 1966.
A Binding Site for Sulfate and Its Relation to Sulfate Transport into
Salmonella typhirmriim. J. Biol. Chem. 241(17):3962-3969.
27- Patrick, R., T. Boot, and R. Larson. 1975. The Role of Trace Elements
in Management of Nuisance Growths. EPA-660/2-75-008, U.S. Environ-
mental Protection Agency, Corvallis, Ore. 250 pp.
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69
28. Patrick, R., J. Cairns, Jr., and A. Scheier. 1968. The Relative
Sensitivity of Diatoms, Snails, and Fish to Twenty Common Constit-
uents of Industrial Wastes. Prog. Fish Cult. 30:137-140.
29. Pratt, R., and J. Dufrenoy. 1947- Comments by Readers. Science
105:574.
30. Richards, 0. W. 1936. Killing Organisms with Chromium as from In-
completely Washed Bichromate-Sulfuric-Acid Cleaned Glassware. Physiol.
Zool. 9(2):246-253.
31. Roberts, K. R., and G. Marzluf. 1971. The Specific Interaction of
Chromate with the Dual Sulfate Permease System of Neurospora cvassa.
Arch. Biochem. Biophys. 142:651-659.
32. Ruthven, J. A., and J. Cairns, Jr. 1973. Response of Fresh-Water
Protozoan Artificial Communities to Metals. J. Protozool. 20(1):
127-135.
33. Schroeder, H. A., J. J. Balassa, and I. H. Tipton. 1962. Abnormal
Trace Metals in Man — Chromium. J. Chronic Dis. 15:941-964.
34. Sheets, E. G., and S. M. Krassner. 1974. "Trace Metabolites" —Effect
of High Concentrations on Le'ishmania tapentolae Promastigotes. J.
Protozool. 21(5):742-744.
35. Somers, E. 1961. The Fungitoxicity of Metal Ions. Ann. Appl. Biol.
(England) 49:246-253.
36. Upitis, V- V., D. S. Pakalne, and A. F. Nollendorf. 1973. The Dosage
of Trace Elements in the Nutrient Medium as a Factor in Increasing the
Resistance of Chlorefia to Unfavorable Conditions of Culturing. Micro-
biology (USSR) 42:758-762.
37. Vaccaro, R. F., G. D. Grice, G. T. Rowe, and P- H. Wiebe. 1972. Acid-
Iron Waste Disposal and the Summer Distribution of Standing Crops in
the New York Bight. Water Res. (England) 6:231-256.
38. Venitt, S., and L. S. Levy. 1974. Mutagenicity of Chromates in Bac-
teria and Its Relevance to Chromate Carcinogenesis. Nature (London)
250:493-495.
39. Wang, C. C., and A. Newton. 1969a. Iron Transport in Esohevichia aoli\
Relationship between Chromium Sensitivity and High Iron Requirement in
Mutants of Esoheriahia aoli. J. Bacteriol. 98:1135-1141.
40. Wang, C. C., and A. Newton. 1969&. Iron Transport in Eschevichia
coli: Roles of Energy-dependent Uptake and 2,3'-Dihydroxybenzoylserine,
J. Bacteriol. 98:1142-1150.
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70
41. Watson, D. G. , C. E. Gushing, C. C. Coutant, and W. L. Templeton.
1969. Effect of Handford Reactor Shutdown on Columbia River Biota.
In: Symposium on Radioecology, D. J. Nelson and F. C. Evans, eds.
University of Michigan, Ann Arbor, Mich. pp. 291-299.
42. Weinberg, E. D. 1964. Manganese Requirement for Sporulation and Other
Secondary Biosynthetic Processes of Bacillus. Appl. Microbiol.
12(5):436-441.
43. Wium-Andersen, S. 1974. The Effect of Chromium on the Photosynthesis
and Growth of Diatoms and Green Algae. Physiol. Plant (Sweden)
32:308-310.
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SECTION 4
BIOLOGICAL ASPECTS IN PLANTS
4.1 SUMMARY
Chromium is present in all soil types (Section 7) and in plants grow-
ing on these soils, but it has not been shown to be an essential element
for plants. Plants take up chromium through either root or leaf surfaces,
but little chromium is translocated from the site of adsorption unless it
is supplied in chelated form. Natural chelates of chromium within the soil
probably occur, but they have not been studied.
Chromium concentrations in plants growing on normal soils range from
about 0.1 to 5 ppm, with most values less than 1 ppm. Plants growing on
serpentine soils show a much wider concentration range, from 1 ppm to 3000
ppm chromium in ash. Subterranean plant parts have higher chromium concen-
trations than do aerial parts.
Plants growing near cooling towers contain elevated levels of chromium.
Concentrations of chromium in plants growing near smelters have not been
reported. Wastes from chromate-producing smelters are very toxic to vegeta-
tion necessitating revegetation techniques for reclamation of contaminated
areas.
Serpentine soils contain high levels of chromium which contribute to
the low fertility of these soils. The major factors are probably low abso-
lute calcium levels, low calcium to manganese ratios, low trace element
levels, or nickel toxicity. The cause of infertility may vary with the
specific serpentine soil under examination.
High chromium concentrations caused chlorosis in beans and oats and
stunting in tobacco, an especially sensitive plant, and maize. There is a
lack of experimental work on the effects of the different chemical forms of
chromium on plants. From limited data, hexavalent chromium appears to be
more toxic than trivalent chromium; both forms affect plants at relatively
low concentrations (about 1 to 10 ppm).
4.2 METABOLISM
The metabolism of chromium in plants includes uptake, translocation,
concentration and distribution, and elimination. Chromium can undergo few
chemical changes within the cell other than oxidation-reduction. Although
complex formation could occur within the cell (Section 4.2.3), few studies
on subcellular distribution or interactions of chromium in plant systems
have been reported.
4.2.1 Question of Essentiality
The question of whether chromium is an essential element for plants
has not been answered. Some authors reported that the addition of chromium
71
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72
compounds to soil resulted in increased yield. In reviewing these reports,
Pratt (1966) concluded, "These stimulative effects have been small and
others have been erratic; most have remained unverified." A review by Mertz
(1969) cited reports of increased crop yields in Germany, France, Poland,
and Russia as a result of chromium application to soils. Mertz concluded
that small amounts of chromium are beneficial for plant growth, but he noted
the complexity of assessing chromium availability in soils and of determin-
ing how chromium stimulates yield. Additional support for this view comes
from increased yields of wheat, rye, oats, corn, and peas grown in a sand
and water culture containing trivalent chromium (Scharrer and Schropp, 1935,
cited in Mertz, 1969).
Huffman and Allaway (19732?), however, demonstrated that romaine lettuce,
wheat, and beans grew normally in culture solution experiments with purified
salts. Final chromium concentration was 3.8 x 10"4 micromole. Thus, if
chromium is required by these plants, it is required at concentrations less
than 3.8 x lO"* micromole.
Improved plant response after addition of the element to soil is not
conclusive evidence for essentiality. Arnon and Stout (1939) stated,
An element is not considered essential unless (a) a
deficiency of it makes it impossible for the plant to complete
the vegetative or reproductive stage of its life cycle; (b)
such deficiency is specific to the element in question, and
can be prevented or corrected only by supplying this element;
and (c) the element is directly involved in the nutrition of
the plant quite apart from its possible effects in correcting
some unfavorable microbiological or chemical condition of the
soil or other culture medium. From that standpoint a favor-
able response from adding a given element to the culture
medium does not constitute conclusive evidence of its indis-
pensability in plant nutrition.
Thus, while chromium is an essential element for humans (Section
6.3.2), no conclusive evidence exists for its essentiality in plants.
4.2.2 Uptake
Plants take up many substances by absorption through either root or
leaf surfaces. Absorption of most minerals typically occurs through root
uptake, but it can also occur through aboveground surfaces exposed to mate-
rials in the air. Several factors affect chromium absorption by plants and
the availability of chromium in the soil: physical and chemical properties
of the chromium compounds, pH effects on reactivity and solubility phenom-
ena, presence of organic chelating compounds within the soil, interactions
with other soil minerals, and the ability of the given species to absorb
chromium under a range of environmental factors such as carbon dioxide and
oxygen concentrations (Black, 1968).
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73
The mechanism of chromium uptake is speculative; it may involve the
absorption of soluble ions from the soil solution, from adsorbed ions in
soil by contact exchange, and from soluble organic-chelated forms (Black,
1968). The specific methods of chromium absorption from the soil are
unknown.
The kinetics of absorption of chromium(III)-ethylenediaminetetraacetic
acid (EDTA), chromium(III) [as Cr(N03)3], and chromium(VI) (as K2CrOA) from
nutrient solutions were studied in rice (Verfaillie, 1974). Chromium sup-
plied in chelated form entered roots more slowly than either chromium(III)
or chromium(VI); the chelated form, however, was transported throughout the
plant. Chromium(III) and CrO<,2~ were absorbed more quickly (Table 4.1),
although less than 2% was transported to aerial parts (Table 4.2). Chro-
mium(III)-EDTA was continuously taken up over the five-day period; stems
attained the greatest chromium concentration (Figure 4.1). Chromium(III)
has a strong tendency to form chelates and these probably occur in soils,
but no data are available to indicate a role in chromium uptake in field
situations. The kinetics of chromium(III) uptake were divided into three
phases: (1) a rapid phase of adsorption onto root surfaces, (2) absorp-
tion [second order kinetics between chromium(III) and an existing pool of
biochemical compounds], and (3) a prolonged phase (<10 hr) of metabolic
uptake involving delivery to shoots. The kinetics of chromium(VI) uptake
showed two stages or mechanisms which could be fitted into the Michaelis
equation. Although he had no direct evidence, Verfaillie concluded from
kinetic data that chromate was reduced to the chromic state [chromium(III)]
by organic matter on the root prior to physiological uptake.
Table 4.1. The rate of chromium absorption by intact rice plants as a function
of the chromium concentration in nutrient solution
Concentration
level
10-'
2 x 10"7
5 x 10-'
io-6
2 x 10'6
5 x 10~6
io-5
2 x IO"5
3 x 10'5
5 x 10"5
7 x 10'5
Cr(III)-EDTA
uptake
(nmole hr"1 gFR"l)a
0.031
0.13
KzCrO,,
intake
(nmole hr"1 gFR"1)
0.39
0.58
0.97
1.44
1.87
4.06
6.70
12.1
21.1
Cr(N03)3
uptake phase
(nmole hr"1 gFR"1)
0.012
0.020
0.047
0.088
0.13
0.28
0.35
0.77
1.70
2.39
2.92
0.29 24.9 3.14
Saturation Vmax = 0.35b Vmax =34.2 Vmax =4.0
fnmole"1 hr J gFR'1 = nanomoles per hour per gram of fresh weight of root.
Vmax = maximum uptake rate.
Source: Adapted from Verfaillie, 1974, Table I, p. 321. Reprinted by
permission of the publisher.
-------
74
Table 4.2. Distribution pattern of chromium after
absorption by intact rice plants
Plant
tissue
Roots
Collars
Stems
Leaves
Total
Percent of total chromium in each plant part
Cr(III)-EDTA
9.4
38.8
33.2
18.6
100.0
K2CrOit
95.7
2.8
0.7
0.8
100.0
Cr.(N03)3
95.3
2.9
0.9
0.9
100.0
Source: Adapted from Verfaillie, 1974, Table II,
p. 322. Reprinted by permission of the publisher.
ORNL-DWG 76-3444
15-
in
-------
75
In sand culture experiments, the uptake of CrO<,2 into tobacco leaves,
tobacco roots, and corn leaves increased with increasing chromium concen-
trations in the external medium (Soane and Saunder, 1959). The chromium
concentration in corn leaves increased from 4 to 8 ppm when the external
chromium concentration was increased from 0 to 10 ppm. Amounts of chromium
in tobacco leaves increased from 4 to 34 ppm when the plants were cultured
in concentrations of 0 to 10 ppm chromium; over the same range of external
concentrations, the chromium content of tobacco roots increased from 13 to
410 ppm. Tobacco was extremely sensitive to chromium; abnormal development
occurred at 1 ppm chromium in the culture medium (175 ppm chromium in roots).
Eckert and Blincoe (1970) evaluated the uptake of 14 gamma-emitting
isotopes, including 51Cr, from range soil by various forage and weed species.
The uptake of chromium was rated as very good in the upper soil horizons for
several range species. Decreased uptake was noted for chromium in the lower
soil horizons; this was attributed to the decreased solubility of chromium
with increasing pH.
Corn grown on soil amended with sludge to give total soil chromium
concentrations of 3 to 1360 ppm contained only 1.2 to 2.3 ppm chromium in
the tops (Table 4.3) (Mortvedt and Giordano, 1975&). Incubation of sludge-
amended soils for 21 and 36 weeks prior to planting of corn in the pots did
not greatly affect final chromium concentration in the tops. Addition of
Na2Cr207 to soil to give 1, 5, 20, 80, and 320 ppm chromium increased chro-
mium concentrations in corn from the control level (1.5 ppm) to 5.0 and 16.1
ppm at the two highest soil values. Repetition of the above experiment at
soil pH 5.5 and 7.0 gave similar results; large increases of chromium in
the tissue occurred only at 320 ppm soil chromium.
Again, a note of caution must be added concerning uncertainties in
older analytical procedures. Comparisons based on data sets generated in
different laboratories, or in one laboratory at different times, may be
subject to large errors. Since the data given here are the best available,
however, they must suffice for at least tentative comparisons.
The ability of the living cell to take up chromium has led to its use
in estimating viability in a cell population (Kumanishi and Yamamoto, 1968).
Bourque, Vittorio, and Weinberger (1967) found that increased hexavalent
51Cr incorporation (supplied as CrO*,2") into sectioned wheat root tips
accompanied the increased metabolic state which occurred during vernaliza-
tion. However, they found little radioactivity in roots incubated with
ascorbic acid (to reduce hexavalent to trivalent chromium) prior to incuba-
tion with 51Cr-labeled CrO*,2" and thus concluded that only hexavalent chro-
mium could penetrate cells. These data disagree with the results of other
experiments (Section 4.2.3) and may possibly be explained by the extensive
washing of the root sections in this study. No data were given for chromate
added at the same time as the ascorbate.
The chemical form of chromium in a given soil depends on the origin of
the chromium compounds. Native chromite, a major form of chromium in the
lithosphere, is a mixture of oxides of magnesium, calcium, chromium, iron,
and aluminum and is essentially insoluble. Anthropogenic sources could
-------
76.
Table 4.3.
Yield and chromium content of corn grown in greenhouse pot experiments
in soils with various amendments'2
Treatment
Rate of
chromium
application
(ppm)
Yield (g/pot) Chromium in tissue (ppm)
Crop 1 Crop 2 Crop 3 Crop 1 Crop 2 Crop 3
Control
Sludge A
Sludge B
Compost
Control
(uncontrolled pH)
(uncontrolled pH)
Control
(pH 5.5)
68
340
1360
3
13
50
3
13
50
1
5
20
80
320
31
33
35
30
32
34
19
34
36
37
31
32
32
27
4
1
55
48
50
45
50
49
48
51
51
47
46
48
49
50
50
55
6
30
34
32
31
27
34
36
31
41
40
1.3
1.2
1.2
1.4
2.3
1.4
1.4
1.1
1.1
2.0
1.3
1.5
1.5
2.3
5.0
16.1
1.6
2.1
1.7
3.0
1.5
2.3
3.5
1.4
1.9
1.6
1.2
2.1
1.4
1.9
1.9
2.2
9.3
2.0
2.3
5.4
2.0
3.0
1.3
0.6
2.8
1.8
0.7
Na2Cr207
(pH 5.5)
Na2Cr207
(pH 7.0)
Cr2(S04)3
(pH 5.5)
5
20
80
320
0
5
20
80
320
5
20
80
320
56
55
40
1
60
60
58
29
1
58
56
52
25
0.8
2.5
7.4
55.0
0.5
1.4
2.7
9.6
57.0
1.3
1.4
2.4
2.8
aCrops were grown in the amended soils in three different ways: (1) crop was grown for
7 weeks in soil immediately after amendment; (2) soil with amendment was incubated in a moist
chamber for 21 weeks prior to planting crop (7-week growth period) ; (3) soil with amendment
was incubated for 36 weeks prior to planting crop (7-week growth period).
Source: Adapted from Mortvedt and Giordano, 1975fc, Tables 2, 3, and 7, pp. 171-173.
Reprinted by permission of the publisher.
contribute trivalent chromium in oxide form or hexavalent chromium as either
chromate (CrOA2 ) or dichromate (Cr2072~). In the presence of organic
matter, hexavalent chromium would be reduced to trivalent chromium and would
either precipitate as the hydroxide, carbonate, or sulfide; trivalent chro-
mium would adsorb on clays, iron oxides and hydrous oxides, and organic
matter. Chromates are rare in nature and are stable only in alkaline, oxi-
dizing conditions (Allaway, 1968). The adsorption phenomenon may be the
-------
77
main mechanism of retention in dilute soil solutions (Murrmann and Koutz,
1972). Jenne (1968) presented arguments for the significance of hydrous
iron and manganese oxides in the binding of manganese, iron, cobalt, nickel,
copper, and zinc in soils, and Baker (1973) argued for the significance of
soil organic matter. Although chromium was not discussed in either of these
publications, a similar binding may occur because chromium is in the same
transitional series as these elements.
Prince (1957a, 1957&) used spectrographic analyses to study the rela-
tionship between trace element concentrations in corn and ragweed and in
the soil in which they were grown. Chromium concentrations in corn were
not closely related to soil chromium concentrations; however, ragweed chro-
mium concentration did increase with soil chromium concentration (Table 4.4).
Since chromium values in corn decreased with age of the leaf, uptake over a
period of time was not constant. Data on the relationship .between available
chromium in the soil and chromium concentrations in the root of corn would
be more valuable information because chromium is not usually translocated
(Section 4.2.3).
Table 4.4. Chromium concentrations in ten New Jersey soils and in
corn and ragweed grown on these soils
(ppm)
Corn leaves
Soil type
Annandale loam
Collington sandy loam
Coltz loam
Cossayuna loam
Croton silt loam
Lansdale loam
Norton loam
Sassafras sandy loam
Squires loam
Washington loam
Soil
32
20
40
20
38
30
75
45
46
39
Young
1.13
0.74
1.84
2.07
0.88
Tassel
stage
0.84
0.69
1.15
1.22
1.16
Mature
1.37
1.69
0.47
0.44
2.18
1.61
0.80
0.50
1.28
0.68
Ragweed
2.74
1.31
6.77
4.90
4.09
Source: Adapted from Prince, 1957a, Tables 5-7, pp. 402-404, and Prince
I957b, Tables 1 and 3, pp. 414-415. Reprinted by permission of the publisher.
No information was found relating soil organic matter to plant uptake.
Both dichromate and chromate ions are oxidizing agents which, when discharged
onto soils, would oxidize organic matter (Section 2.2.5). Also, an increased
soil organic content generally allows for both increased adsorption and in-
creased cation-exchange capacity. Therefore, an increased organic content
might be expected to allow more available chromium to be retained within the
soil. The organic content could be of particular importance in serpentine
soils, which are characterized by high chromium and nickel contents in addi-
tion to a low calcium to magnesium ratio.
-------
78
Few reports have emphasized the relationship between soil pH and chro-
mium uptake. Most metals are more soluble at low pH values (pH 4 to 5) and,
thus, are more available for uptake than at high pH values (pH 7 to 8). For
landfills, pH should be maintained at 6.5 or above (Chaney, 1973). While
chromium, like other metals, is considered to be more available at lower pH
values (Murrmann and Koutz, 1972), Patterson (1971) has shown that uptake of
both trivalent and hexavalent chromium into barley roots increased with an
increase in soil pH from 5.6 to 7.8. Injury, however, only occurred with
hexavalent chromium. No explanation for this apparent contradiction was
presented.
Interactions occurring between various elements within the soil can
affect the exchangeable and soluble soil concentrations of a particular
element (Black, 1968). No specific data were found for interactions be-
tween chromium and other elements in the soil.
Interactions among elements can affect their concentrations in and
toxicity to the plant. The only data found for chromium were those of
Wallace, Sufi, and Romney (1971), who studied the effects of calcium and
chelating agents on heavy metal concentrations in bush beans grown in solu-
tion cultures. Increasing calcium concentrations decreased the toxic effect
of 10"* M chromium (as measured by decreased wet weight). Addition of ethyl-
enediaminetetraacetic acid (EDTA) to the optimum calcium concentration re-
stored the toxic effect of chromium. No specific mechanisms have been
proposed for the observed interactions among calcium, EDTA, and chromium.
4.2.3 Translocation
The fate of absorbed chromium in plants is unknown. Soluble organic
complexes of some trace elements have been observed within plants (Tiffin,
1972), but the only report for chromium has been by Lyon, Peterson, and
Brooks (1969a, 1969Z?) in experiments with Leptospermwn seopa.ri.um. The
xylem exudate from both roots and shoots of plants cultured in 51Cr-labeled
NaCrO/, solutions contained only chromate, while the 80% ethanol extract of
root, leaf, and stem contained three chromium complexes, one of which was
identified as the trioxalatochromate ion. Most of the 51Cr was found in
the root (267 counts min"1 mg"1 dry wt in shoots; 17,300 counts min"1 mg"1
dry wt in roots). Thus, hexavalent chromium was absorbed by the plant but
little was transported in the xylem to the shoot. The site of complexation
was not determined. Myttenaere and Mousny (1974) also showed in rice that
little radiochromium [supplied to the roots as either chromium(III) or
CrOi,2"] was transported to the shoots. If chromium was supplied to the
roots as chromium-EDTA, less total absorption occurred; however, signif-
icant amounts were transported to the leafy shoots. Similar results were
found for rice by Verfaillie (1974) (Table 4.2). DeKock (1956) failed to
find significant chromium concentrations in the leaves and stems of mustard
plants exposed to solutions containing 2 ppm chromium. He also observed
that the chromium content of roots was less when chromium was supplied in
the chelated form.
Chromium-51-labeled trivalent or hexavalent chromium supplied for 14
days was taken up by both flowering wheat and bean plants (Huffman and
-------
79
Allaway, 1973a). At maturity, the wheat roots contained 95% of the hexa-
valent chromium and 96% of the trivalent chromium; bean roots contained 93%
of the hexavalent form and 92% of the trivalent form (Table 4.5). Thus,
chromium was not significantly translocated from the root to the shoot of
the plants studied.
Table 4.5. Distribution of 51Cr in wheat and beans grown in solution culture
with either 51Cr labeled trivalent or hexavalent chromium
Bean
Wheat
Plant
tissue
Seed
Chaff (pods)
Stems
Leaves
Roots
Cr(VI)
(ng/g)
3
32
26
144
3791
(%
total
Cr)
0.03
0.5
1.1
5.1
93.2
Cr(III)
(ng/g)
2
50
37
166
3096
(%
total
Cr)
0.02
0.9
1.5
6.5
91.5
Cr(VI)
(ng/g)
1
18
21
74
5378
(%
total
Cr)
0.1
0.9
3.0
1.1
94.9
Cr(III)
(ng/g)
1
16
15
64
3982
(%
total
Cr)
0.1
1.1
1.7
1.4
95.7
Source: Adapted from Huffman and Allaway, 1973a, Table II, p. 984. Reprinted by
permission of the publisher.
Levi, Dalschaert, and Wilmer (1973) observed little translocation in
bean and lettuce of foliarly applied 51Cr (drop or spray methods) added as
either CrCl3 or Na2CrOi.. Although slightly greater amounts of activity
were exchanged with the carrier when chromium was added as Na2Cr04, the
increase did not exceed 7% of the total. The results indicated that most
of the added trivalent and hexavalent chromium was retained within the
tissue in an unexchangeable form. No data were presented to show that
chromium was retained in the hexavalent form within the tissue.
Data for plants growing on serpentine soil (Section 4.2.4.2.1) showed
that chromium is mainly concentrated in subterranean parts, although some
high values given for aerial parts indicate that some translocation occurs
(Lounamaa, 1956).
The subcellular localization of chromium and its exact chemical form
within the cell have not been adequately characterized. Schroeder, Balassa,
and Tipton (1962) reported trivalent and hexavalent content of dry-ashed
plant material and found species variations (Table 4.6). The assumption
that the oxidation state is unchanged during dry ashing is very hazardous
and the differences are as likely to represent minor changes in ashing
conditions as they are the original chromium chemistry.
When rice plants were grown in nutrient solutions containing low levels
of chromium (0.073 ppb trivalent chromium, 0.075 ppb CrO/,2") and subjected
to a sequential extraction procedure, protoplasmic fractions contained
84.50% of the label when trivalent chromium was added and 92.81% of the
-------
80
Table 4.6. Trivalent and hexavalent chromium
in the ash of some plant materials
Plant
sample
Thyme
Black pepper
Tomato , raw
Maple leaves
Red oak leaves
Pine needles
Chromium content
(yg/g wet wt)
Cr(III)
3
1
0
0
0
.38
.02
.14
.03
.14
Cr(VI)
0.
1.
0.
0.
0.
41
24
03
05
07
Cr(III)
Total
3.
2.
0.
0.
0.
0.
79
26
01
17
08
21
89.
45.
82.
37.
66.
4
1
3
5
7
Source: Adapted from Schroeder, Balassa, and
Tipton, 1962, Table 9, p. 959. Reprinted by permission
of the publisher.
label when CrO/,2" was added. The cell wall fractions contained 15.50% of
the trivalent chromium and 7.19% of the CrO/,2' (Myttenaere and Mousny,
1974). Although this experiment showed that chromium supplied as either
trivalent or hexavalent chromium will ultimately enter the cell, no infor-
mation on whether CrO<,2~ was reduced prior to uptake was given.
Data from the cellular fractionation of bean and wheat plants previ-
ously incubated in 51Cr-labeled hexavalent chromium solutions are given in
Table 4.7 (Huffman and Allaway, 1973£>) . The most notable difference between
the data for wheat and for bean was the chromium content of the 0.2 N HC1
extract of the root. The authors suggested that most of the chromium in
wheat may have been in a soluble, and hence, acid-extractable form (perhaps
in the vacuole), while bean root may have retained the chromium in an in-
soluble form in the cell walls. However, distribution in the various sub-
cellular fractions from differential centrifugation of plant homogenates
(Table 4.8) showed most of the activity in the supernatant fraction (homog-
enization). Since the cell walls were probably largely pelleted, most
chromium was apparently not in the cell wall fraction. The results ob-
tained by the extraction and fractionation procedures apparently differed
considerably. Analysis of the fractionation supernatant from bean leaves
gave one peak with gel permeating chromatography (Sephadex G-10) and with
paper electrophoresis, but this peak did not coincide with known standards
of chromium citrate, chromium aconitate, chromium oxalate, or chromate.
Preliminary work indicated that the chromium was present predominantly as
an anionic complex with a low molecular weight. Blincoe (1974) identified
chromium in lucerne as an anionic complex with a molecular weight of about
2900.
-------
Table 4.7. Chromium-51 extracted by various methods from wheat and beans grown
in solution culture with 51Cr—labeled hexavalent chromium
(percent)
Plant
Wheat
Grain
Chaff
Stems
Leaves
Roots
Bean
Grain
Pods
Stems
Leaves
Roots
80%
ethanol
49
9
16
4
3
41
10
22
16
5
Ether
2
0
0
0
1
2
0
1
Boiling
water
24
67
47
9
42
28
39
6
0.2 N
HC1
31
5
29
58
17
17
25
2
Acetone
precipitate
from HC1-
soluble
2
3
1
1
4
4
1
0
0.5 N
HClOit
18
1
12
9
10
18
12
13
Acetone
precipitate
from HC104-
soluble
3
2
0
1
1
1
0
1
2 N
NaOH
5
3
5
14
6
4
4
37
Residue
6
4
2
4
9
4
3
34
Extractions were done sequentially from dried materials.
Source: Adapted from Huffman and Allaway, 1973&, Table III, p. 984. Reprinted by permission of the
publisher.
oo
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82
Table 4.8. Distribution of 51Cr in various subcellular fractions
after differential centrifugation of leaf homogenates
Chromium-51 in fraction (%)
Plant Treatment Nuclei
and Mitochondria Microsome Supernatant
debris
Wheat
Bean
Cr(III)
Cr(VI)
Cr(III)
Cr(VI)
3
4
4
4
2
2
4
3
1
1
2
1
89
87
79
86
values do not add to 100% because pellet washings were not
recombined.
Source: Adapted from Huffman and Allaway, 1973a, Table IV, p. 985.
Reprinted by permission of the publisher.
Apparently, significant amounts of chromium can be moved into tissues
in certain instances. A single application of Elgetol, a blossom thinner
containing 4,6-dinitro-o-cresol and 1.9% sodium bichromate, to apple trees
at blossom led to high chromium contents in the young fruit (about 0.34 ug/g
two weeks after application) (Coahran, Maxwell, and Zucker, 1973). Although
the tissue chromium concentration in both treated and untreated trees
dropped during the 19 weeks of fruit development due to growth of the fruit,
the total amount of chromium in the apple fruit increased considerably in
both treated and untreated trees. Thus, in apple development, chromium
appeared to be transported to the fruit in measurable amounts and this chro-
mium flow was apparently a normal physiological process. The authors sug-
gested that the soil was the source of the chromium which flowed to the
fruit.
4.2.4 Distribution
The concentration of chromium found within a plant depends on the type
of plant and the chromium content of the soil. In general, chromium con-
centrations in soil range from 5 to 3000 ppm, with a mean of 100 ppm (Bowen,
1966) (Section 7.3.3). Chromium concentrations in the plant could range
from <1 to >3000 ppm (Lounamaa, 1956), but the more normal range would be
0.2 to 1.0 ppm (Allaway, 1968). Allaway (1968) stated that chromium is not
concentrated at any stage in the cycle from soil to plant to animal, but
data are inadequate to support this generalization. Since few studies on
the available chromium content of soils have been reported, bioaccumulation
of chromium in plants is difficult to assess.
4<2-4-1 Crop Plants - Few data were found on chromium concentrations in
crop plants. Chromium concentrations on a wet weight basis, given by
Schroeder, Balassa, and Tipton (1962) for various food plants, suggest that
most crop species have similar chromium levels (0 to 0.09 ppm), although
radishes and parsnips (root crops) have somewhat elevated levels (Table 4.9).
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83
Table 4.9. Chromium concentrations in food plants
Plant
sample
Chromium content
(ppm wet wt)
Vegetables
Potato, white
Beans, dried, navy
Beans, dried, yellow-eye
Beans, wax
Beans, green string
Lentils, dried
Beets
Radishes
Parsnips
Parsnip leaves
Turnip leaves
Carrots
Onions
Spinach
Swiss chard
Squash, summer
Cucumber
Kohlrabi
Cauliflower
Cabbage
Sauerkraut
Rhubarb, raw
Lettuce, garden
Lettuce, head
Fruits
Peach, Elberta, raw
Raisins
Blackberries, wild
Tomato, raw
Apple, Macintosh
Pear
Plum
Grains and cereals
Corn, fresh on cob
Corn meal
Rye, seed
Rye, whole
Wheat, whole (Japanese)
Rice, (Japanese) 204 samples
Rice
Oatmeal, dry
0.0
0.08
0.05
0.03
0.02
0.09
0.01-0.03
0.0
0.13
0.08-0.19
0.04-0.06
0.0-0.03
0.01-0.02
0.0-0.05
0.06
0.02
0.01-0.03
0.0
0.02
0.01-0.06
0.03
0.02
0.07
0.02-0.13
0.01
0.02
0.0
0.01
0.02
0.01
0.02
0.02
0.05
0.05
0.04
0.08
0.04
0.05
0.06
Source: Adapted from Schroeder, Balassa, and Tipton,
1962, Table 6, p. 949. Reprinted by permission of the
publisher.
-------
84
Since chromium is not translocated to any great extent, the roots of these
food plants might be expected to have higher chromium concentrations than
other plant parts.
Trace elements within grains may be concentrated in germ (Lillehoj,
Garcia, and Lambrow, 1974). Data for chromium showed that whole kernel
corn contained 0.075 ppm chromium, while germ contained 1.43 ppm chromium.
The amounts of trace elements present also influenced the production of
aflatoxin by Aspergillus flavus infections of corn (Section 3.3.3). Data
from several other studies, summarized by Pratt (1966), illustrate that a
broad range of concentrations can be found among different plant species
(Table 4.10). Although these data give an overall view of chromium con-
centrations in plants, they are of limited value unless available chromium
concentrations in soils are determined and the usual analytical uncertainty
also limits their utility.
Table 4.10. Chromium concentrations in crop plants
Plant
Barley
Cherry
Corn
Tissue
Leaves
Fruit
Leaves
Leaves
Leaves
Stalks
Grain
Cobs
Husks
„ , Chromium
Growth _ , . .
Conditions concentration
stage . , .
(ppm dry wt)
Mature
Young
Tassel
Mature
Mature
Mature
Mature
Mature
7
0
0
0
0
0
0
0
0
.6
.032
.74-2.07
.69-1.22
.50
.22
.48
.53
.34
Oat
Leaves and stem
Growing on serpentine soil
3.0-11.0
Orange
Pear
Potato
Wheat
Leaves
Leaves
Leaves
Whole fruit
Pericarp
Peel
Tuber
Leaves
Greenhouse
Field
Seedling
Mature
Ma tun;
Ma ture
0.2-0.
10.0
0.50-1
0.03
0.50
0.85
0.002
4.5-14
3
.00
.8
Source: Adapted from Pratt, 1966, Table 1, p. 138.
4.2.4.2 Noncrop Plants
4.2.4.2.1 Serpentine soil flora — Serpentine soils, which overlie serpen-
tine rocks, are characterized by high concentrations of chromium, nickel,
and cobalt; a high magnesium to calcium ratio; and a deficiency of other
essential plant elements such as phosphorus, potassium, and molybdenum.
They are typically unproductive as farm or timberland but do support endemic
species with distinct ecotypes (Whittaker, 1954). In the United States,
-------
85
major serpentine areas occur in the Appalachian chain from western Massa-
chusetts to Georgia and along the Pacific Coast mountain ranges in Cali-
fornia, Oregon, and Washington (Whittaker, 1954). The specific cause of
the infertility of serpentine soils is unknown and it may vary from site
to site.
A wide range of chromium concentrations can be found in plants growing
on serpentine soils (Lounamaa, 1956; Lyon et al., 1970, 1971). Table 4.11
illustrates the variability among species. Some plants take up chromium in
an amount roughly proportional to total soil chromium concentration (for
example, Leptospermwn seoparium), while others apparently can exclude chro-
mium (for example, Phylloeladus alpi-nus). Lack of apparent correspondence
between plant and soil chromium concentrations for some other species may
be due to the difficulty of determining the available chromium content in
the specific soil near the plant.
In a study of shrubs growing on high nickel-chromium soils, Cole (1973)
showed no shrub species to contain high chromium amounts and suggested that
most species are able to restrict chromium entry. For example, the nickel
accumulator Hybanthus floribundus did not contain high levels of chromium
(0.04 to 12 ppm chromium, dry wt basis).
Additional data on chromium concentrations in plants growing on high
chromium soils are discussed in the next section.
4.2.4.2.2 Herbaceous and woody plants — The most comprehensive study of the
relationship between trace element composition of plants and the type of rock
in the substratum was made by Lounamaa (1956) in Finland. Lichens, mosses,
ferns, conifers, deciduous trees and shrubs, dwarf shrubs, and grasses and
herbs were examined. Table 4.12 gives chromium concentrations in soils and
rocks of Finland. Ultrabasic rocks and the soils overlying them contained
the highest chromium concentration. Chromium concentrations in plants
growing on these rocks and soils are given in Tables 4.13 and 4.14. Chro-
mium concentrations were lower in plants than in corresponding soils and
rocks, although relatively high chromium concentrations were found in plants
growing on ultrabasic rock and soil. Subterranean plant parts had higher
concentrations than aboveground parts, again suggesting that chromium is not
easily translocated throughout the plant.
No other comprehensive studies of the relationship between the plants
and soils were found. Chromium concentrations in a variety of plants are
given in Table 4.15. In the various groups analyzed, concentrations ranged
from undetectable amounts to 27 ppm chromium (Aspergillus miarocystiaus);
the typical range was from 0.2 to 5.0 ppm chromium (dry wt basis). Ewing,
Howes, and Price (1969) determined concentrations of several trace elements
in fruits and vegetables from Panama (Table 4.16). The range observed for
chromium (0.003 to 8.0 ppm) is similar to that found in other studies.
The chromium content of a variety of plant foods has been determined by
several research groups (Section 8.3). The reported range of chromium con-
centrations in edible portions of these plants was similar to that found in
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86
Table 4.11. Chromium concentrations in plant and soil samples
from a serpentine area
Chromium
concentration
in soil
(ppm)
150
930
5,300
62,000
4,200
7,600
3,800
1,500
500
23,000
4,900
Plant
species
Cassinia vauvilliersii var. sevpentina
Leptospermum soopavium
Copvosma pawiflora
Draaophyllum filifoliwn var. collinwm
Metvosideros umbellate.
Podosarpus totara
Lichen (species unknown) on rock
L. eoopariwn
Myosotis monroi
D. pvonwn
Hymenanthera alpina
Myvsine divariaata
Stellavia roughii
Pimelea suteri
Cassinia vauvilliersii var. serpentina
Hebe odova
L. soopariim
Gentiana corymbifera
Phovmiwn colensoi
H. odova
L. scoparium
Myosotis monroi
Notothlaspi austvale
Hymenanthera alpina.
C. vauvillievsii var. serpentina
Coprosma pavviflora
Nothofagus solandvi var. aliffortioides
Phylloaladus alpinus
Cassinia vauvillievsii var. serpentina
Hebe odova
Coprosma parviflora
N. solandri var. sliffortioides
P. alpinus
C. aunninghamii
Daorydium biforme
Mypsine divariaata
N. solandvi var. cliffortioides
P. alpinus
C. bariksii
C. aunninghamii
D. bi forme
N. menziesii
P. alpinus
H. odora
L. saoparium
Myosotis monroi.
Cassinia vauvillievsii var. sevpentina
H. odora
L. saopaviwm
Dvaaophyllw uniflovwn
Lyoopodium australiamm
Chromium
concentration
in plant sample
(ppm of ash)
370
210
120
300
20
80
34,000
1,100
3,500
4,400
70
125
3,600
3,200
4,600
8,500
9,000
5,400
700
380
840
2,000
1,300
1,200
60
740
36
52
13
13
44
36
20
60
44
52
44
20
52
52
36
28
13
36
3,800
460
1,500
1,000
700
2,900
7,700
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87
Table 4.11 (continued)
Chromium
concentration
in soil
(ppm)
21,000
5,000
8,200
3,200
Plant
species
C. vamri.'l'l'ie'PS'ii var. eevpenti.no.
H. odora
Leptospermum saoparium
M. monroi
D. fiUfolium var. aollinum
Myvsine divaricata
C. vauvilUersii, var. serpentina
H. odora
Notothlaspi australe
Anisotome aromatica
B. odora
L. scopariwn
G. eorymbifeTo.
Hymenanthera alp-ina
C. vauvilliers-ii. var. serpentina
Hebe odara
L. saopariim
G. aom/mbifera
M. divaricata
S. roughii
Chromium
concentration
in plant sample
(ppm of ash)
360
105
2,300
600
300
580
2,700
1,150
200
115
1,500
4,100
400
6,000
2,200
90
650
780
850
350
Source: Adapted from Lyon et al., 1970, Table 2, pp. 136-137.
Reprinted by permission of the publisher.
Table 4.12. Chromium content of major rock types in Finland
and of the soils formed over these rocks
Chromium content
(ppm)
K.OCK
type
Silicic
Ultrabasic
Calcareous
Rock
Mean
87 + 14
2200 + 260
380 + 98
Range
<3-1000
300-6000
<3-3000
Soil
Mean
140 + 18
4000 + 310
110 + 23
Range
10-300
2000-6000
<3-300
Source: Adapted from Lounamaa, 1956, Table 3, pp. 52-53.
Reprinted by permission of the publisher.
-------
Table 4.13. Chromium concentrations in plants growing in soils overlying
silicic, ultrabasic, or calcareous rocks
Chromium concentration (ppm of ash)
Plant
Lichens
Mosses
Ferns
Conifers
Deciduous trees
and shrubs
Dwarf shrubs
Herbs
Grasses
Tissue
Frond
Subterranean parts
Needles
Twigs
Leaves
Twigs
Leaves
Stems
Inflorescences
Leaves
Stems
Subterranean parts
Inflorescences
Leaves and steins
Subterranean parts
Plants growing
on
silicic rock
Mean
39 + 6
48 + 18
7 + 1
55 + 13
7 + 2
12 + 2
5 + 1
6 + 1
7 + 1
17 + 4
12 + 5
6 + 3
7 + 2
31 + 8
9 + 3
9+3
87 + 30
Range
10-300
10-100
<1-30
1-300
<1-60
<1-60
<1-30
<1-60
<1-30
3-100
<1-100
<1-60
<1-30
<1-100
<1-30
1-30
3-300
Plants growing
on
ultrabasic rock
Mean
650 + 160
200 + 45
230 + 90
740 +270
18 + 5
25 + 10
26 + 9
26 + 9
73 + 32
160 + 68
160 + 47
160 + 72
60 + 21
910 + 260
62 + 23
46 + 12
420 + 99
Range
300-1000
100-300
10-1000
100-3000
3-60
1-100
1-100
3-100
3-300
3-600
3-600
3-1000
3-300
30-3000
3-300
3-100
3-1000
Plants growing
on
calcareous rock
Mean Range
23+7 10-30
6+2 3-10
120 + 64 10-300
4+1 <1-10
10+4 <1-30
4+1 <1-10
3+1 <1-10
11+7 1-80
25 + 13 3-60
oo
oo
Source: Adapted from Lounamaa, 1956, Tables 5, 8, 10, 14, 22, 28, 34, and 36, pp. 64-65, 70-71, 80-81, 98-99,
118-119, 132-133, 160-161, and 168-169. Reprinted by permission of the publisher.
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89
Table 4.14. Chromium concentrations
in selected plant species growing on
different soils in Finland
Plant Chromium
concentration
species .
(ppm of ash)
Lichens
Peltigera aan-ina 6-30
Cladina alpestvis 10-1,000
Stereocaulon pasahale 10-300
Parmelia aentrifuga 200-10,000
Parmelia saxatilis
Mosses
Tortella tortuosa 10-300
Rhaeom-itnum lanuginosum 100-300
Hyloaomium splendens 10-100
Ferns
Woods-La ilvensis 3-30
Cystopteris fragilis 3-300
Lastrea phegopteris 3-300
Aspleniwn trichomanee 1-100
Asplenium septentrionale 1-1,000
Polypodium vulgare 1-300
Conifers
Pioea abies 1-100
Pinus s-ilvestris 1-60
Junipems aormunis 1-30
Deciduous trees and shrubs
Populus tremula 3
Betula vevruaosa 1-60
Almis inaana 1-30
Rosa majalis 100
Sorbus auauparia 1-30
Daphne mezevewn 3rlOO
Loni-aefa xylostewn 1-10
Dwarf shrubs
Vaao-Lni-wn vit-is-idaea 1-100
Calluna vulgaris 1-100
Empetrum nigrum 3-600
Grasses and herbs
Molinia aoerulea 3-60
Festuea ovina 3-100
Deschampsia aaespitosa 3-100
Alli-im sahoenoprasum 1-10
Polygonatum adoration 1-60
Rumex aaetosella 1-10
Visaafia vulgavis 1-300
Dianthus superbus 3-100
Sedum telephiwn 1-1,000
Saxifraga granulata 1-10
Rubus idaeus 1-30
Vi-a-La evaaaa 10-100
Thymus serpyllum 3-100
Source: Adapted from Lounamaa, 1956,
Tables 4, 7, 9, 13, 17, 26, and 31, pp. 60-
61, 69, 74-78, 92-96, 106-112, 128-130, and
142-154. Reprinted by permission of the
publisher.
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90
Table 4.15. Chromium concentrations in a variety of plants
Species
Chromium
concentration
(ppm)
Reference
Dry wt
Ash wt
Algae
Anaeystis nidulas 1.2
Aphanizomenon flos-aquae 9
Laminaria saccharina 6
Ahnpheltia pliaata 2.9
Caulerpa prolifera 11
Chora fragiUs 0.82
Fungi
Aspergillus miarocystieus 27
Hypoxylon fragiforme 0.65
Alauria aurantia 2.7
Bulgaria inquinans 1.1
Elaphomyaes granulatus 0.43
Clavulina ai.nerea 1.1
Steveum hirsutum 3.3
Lyooperdon pyriforme 3.0
Saleroderma veruaosa 9
Lichens
Cladonia retipora 4.6
Mosses
Marchantia polymorpha 1.0-14
Sphagnum aeutifoliwn 7
Polytrichum commune 2.5
Hypnim aupressiforme 8
fiypmrn awpressiforme 5-14.0
Ferns and fern allies
Psilotum triquetrwn 0.27-0.97
Selagi-nella willdencwii. • 0.43
Lycopodium aireinatwn 0.33-0.59
Equisetwn gigantewn 0.45
Ophioglossum pedunculoswn 0.45
Salvinia aurioulata 1.0-4.4
Gytnnosperms and angiosperms
Enaephalartos lehmanii 0.05-0.53
Ginkgo biloba 0.20
Juniperus aommunis 0.37-0.64
Ephedva gevardiana 0.45-0.56
Liriodendron tulip-ifera 0.37
Pulmonaria eaoaharata 0.43
Elodea aanadens-iB 0.43
Carex pendula 0.12
Prwus serotina (wild cherry) leaves 0.57
Betula papyrifera (white birch) 0.19
leaves
Fagus grandifolia (beech) leaves 0.29
Acer rubmm (red maple) green leaves 0.11
Acer rubvum (red maple) red leaves 0.20
Queraus rubra (red oak) leaves 0.17
Queraue rubra (red oak) acorns 0.02
Thuya occidentalis (arborvitae) 0.35
leaves
Thuya oecidentalis (arborvitae) buds
Pyvue ameriaana (ash) leaves 0.70
Populus trernuloides (quaking aspen) 0.25
leaves
Horovitz, Schock, and
Horovitz-Kisimova, 1974
7.9
3.2
5.6
1.8
3.2
9.2
0.9
6.7
0.0
7.7
4.0
Horovitz, Shock, and
Horovitz-Kisimova, 1974
Horovitz, Shock, and
Horovitz-Kisimova, 1974
Horovitz, Shock, and
Horovitz-Kisimova, 1974
Horovitz, Shock, and
Horovitz-Kisimova, 1974
Horovitz, Shock, and
Horovitz-Kisimova, 1974
Schroeder, Balassa, and
Tipton, 1962
-------
91
Table 4.15 (continued)
Species
Chromium
concentration
(ppm)
Dry wt
Ash wt
Reference
Gymnosperms and angiosperms
Pyrus mains (apple) leaves 0.33 3.2
Pyrus mains (apple) apples 0.13 5.9
Pinus strobus (white pine) needles 0.49 15.8
Juniperus aommunis berries 0.49 14.5
Picea rubva (spruce) needles 0.24 6.9
TrifoHum vepens (clover) shoot 0.34 2.3
Mediaago sativa (alfalfa) shoot 0.09 1.0
Dactylis glomerata (pasture grass) 1.30 22.5
shoot
Quercus' palustvis (pin oak) leaves 3.8 + 0.8
Queraus palustris (pin oak) twigs 2.8 + 0.4
Acer sacchamm (sugar oak) leaves 1.9 + 0.3
Aoev saechamm (sugar oak) twigs 2.3 + 0.2
Acer platano-ides (Norway maple) 2.8 + 0.2
leaves
Acer- platanoides (Norway maple) twigs 1.6 + 0.1
Tsuga aanadensis (hemlock) leaves 2.8 + 0.4
Tsuga aanadensis (hemlock) twigs 3.5 + 0.4
Taxus spp. (yew) leaves 3.9 + 0.3
Taxus spp. (yew) twigs 6.0 + 1.4
Piaea abies (spruce) leaves 2.6 + 0.4
Piaea db-ies (spruce) twigs 4.9 + 0.4
Acer pubnm (red maple) leaves 0.27-0.38
Acer saadhavimm (silver maple) 0.27
leaves
Aaev sacaharum (sugar maple) leaves 0.38
Fagus grandifolia (beech) leaves 0.26
Ilex opaca (holly) leaves 0.06-0.37
Kalmia latifolia (mountain laurel) 0.08-0.62
leaves
Pieris japonica (heath) leaves 0.01-0.60
Pinus strdbus (white pine) leaves 0.25-2.4
Platanus occidentalis (sycamore) 0.23
leaves
Quereus palustns (oak) leaves 0.10-0.58
Rhododendron roseum leaves 0.06-0.38
Tsuga oanadensis (hemlock) leaves 0.37-0.56
Tritisum spp. (wheat) seed 0.003-0.043
Aloe spp. 17
Amaranthus spp. 38
Juniperus vi.rgini.ana (cedar) 1.8-4.5
Schroeder, Balassa, and
Tipton, 1962
Smith, 1973
Hanna and Grant, 1962
Welch and Gary, 1975
Baumslag and Keen, 1972
Connor, Shacklette, and
Erdman, 1971
both crop and wild plants. However, the relative biological value of chro-
mium in foods used for animal nutrition was not necessarily related to the
chromium concentration in the food (Toepfer et al., 1973).
4.2.4.2.3 Water plants — Little information was found on the chromium con-
centrations in water plants. Fukai and Brokey (1965) found that the marine
taxa Zostera sp. and Posidonia ooeanica (eelgrass) contained 4.2 ppm and an
average of 1.6 ppm chromium on a dry weight basis, respectively.
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92
Table 4.16. Chromium content of
fruits and vegetables from Panama
Chromium content
Fruit , , .v
(ppm dry wt)
Plantain, dried
Banana
Breadfruit
Sugarcane
Coconut
Cocoa beans
Avocado
Kidney beans
Rice
Corn
Yam (name)
Yam (otoe)
Cassava
0
0
2
0
0
0
0
0
0
0
0
8
0
.1-1.2
.1-0.5
.0
.7
.15
.50
.003
.05
.6
.25
.1-0.2
.0
.15-1.5
Source: Adapted from Ewing,
Howes, and Price, 1969, Table 3,
p. 14.
4.2.5 Plant Concentration and Pollution Sources
One type of chromium pollution results from chromate present as a
corrosion inhibitor in cooling towers and used, for example, with nuclear-
powered steam generators and process facilities requiring closed cycle cool-
ing (Taylor et al., 1975). Drift from these facilities transports chemicals
to adjacent terrestrial areas and surface waters. Although similar species
were not examined at each distance from the cooling towers in this study.
chromium concentrations in grasses, forbs, trees, and litter decreased con-
siderably with distance. Some contamination was evident at 1230 m (4000 ft)
from the cooling tower (Figures 4.2 and 4.3). No information was given on
whether increased amounts of chromium were due simply to surface deposition
or to actual plant uptake.
A regional and historical study of the heavy metal content of the moss
Hynum oupressiforme in Sweden showed that a small increase in chromium con-
tent occurred from 1870 to 1969 (5.8 to 7.7 ppm dry wt) in samples from the
more industrialized areas (Ruhling and Tyler, 1969). Since moss generally
obtains a large proportion of its mineral content from airborne particles,
an increase in chromium air pollution can be inferred.
-------
1000
125 250
500
93
DISTANCE (m)
1000
ORNL-DWG 76-2446
1500
1000
2000 3000 4000 5000
DISTANCE FROM COOLING TOWER (ft)
6000
Figure 4.2. Chromium concentrations in vegetation illustrating the
transfer of increased quantities of the trace element by cooling-tower drift
to the landscape. Background concentrations (parts per million ± 1 standard
error) were: grass, 0.40 ± 0.03; forb, 0.65 ± 0.05; litter, 2.65 ± 0.74.
Source: Adapted from Taylor et al., 1975, Figure 3, p. 414.
100
125 250
500
DISTANCE(m)
1000
ORNL-DWG 76-2447
1500
BROADLEAF (DECIDUOUS)
1000 2000 3000 4000 5000
DISTANCE FROM COOLING TOWER (ft)
6000
Figure 4.3. Chromium concentrations in foliage of deciduous and
coniferous tree species. Background concentrations (parts per million ±
1 standard error) ranged from 1.32 ± 0.42 for deciduous broadleafs to
1.25 ± 0.30 for conifers. Source: Adapted from Taylor et al., 1975,
Figure 4, p. 415.
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94
Although total and available chromium amounts within sludge-amended
soils have been reported, there are few reports on the chromium content of
plants grown in these soils (Page, 1974). The chromium data of LeRiche
(1968) had certain anomalies (Table 4.17), the most striking of which was
that chromium concentrations were higher in tops than in roots. Although
treated soils contained up to 17 times the chromium concentration of un-
treated soils, chromium concentrations in plants grown on the two soils
were similar.
Sewage sludge application to soils increased the content of chromium
(and other elements) in fodder rape. Application of sewage containing 176
ppm chromium (dry wt basis) to soil (background level 36.1 ppm chromium) at
the rate of 7 metric tons dry matter per hectare every second year for 12
years increased the soil content to 61 ppm chromium and increased the fodder
rape concentration from 2.6 ± 0.17 ppm to 4.1 ppm chromium (Andersson and
Table 4.17- Chromium concentrations in plants grown on control
and sludge-amended soils
Sample
(0.5 N acetic acid)
b
Leeks
Chromium concentration (ppm dry wt)
Control soil
Plot 4
Plot 8
0.42
1.00
Amended soil
Plot 3
0.28
Plot 39
Soil2'
0.7
0.2
2.0
3.5
0.80
Globe beets
Tops
Roots
0.9
0.3
0.8
0.3
0.8
0.5
1.2
1.1
Potatoes
Tops
Roots
2.20
0.08
1.20
0.10
2.50
0.01
3.50
0.05
Soil0
(0.5 N acetic acid)
1.5
0.33
1.8
3.4
Carrots
Tops
Roots
0.44
0.03
0.38
0.03
0.82
0.09
0.94
0.04
-, Sludge applications discontinued after 1961.
Samples taken from 1959 to 1961.
Samples taken in 1967.
Source: Adapted from LeRiche, 1968, Tables 1-6, pp. 205-206.
Reprinted by permission of the publisher.
-------
95
Nilsson, 1972). However, lettuce grown on sewage-amended soils (80 and 160
metric tons added per hectare, containing 9.5 and 2 ppm of 0.5 acetic acid-
extractable chromium) did not contain detectable chromium levels (Dudas and
Pawluk, 1975).
Mortvedt and Giordano (1975&) showed that high chromium concentrations
in sludge did not reduce yield of corn or increase tissue chromium concen-
trations, which suggests that most chromium in sludge is unavailable for
plant uptake. Amounts of available chromium are usually very low because
of the insoluble nature of most chromium compounds. The land disposal of
municipal sludges may not result in a serious problem of chromium uptake
into the food chain because the chromium is in the unavailable trivalent
state. Other elements within the sludge present a greater problem. Chaney
(1973) has discussed the important factors in soil retention of these ele-
ments (cadmium, zinc, copper, and nickel) and in their uptake by plants.
Small amounts of heavy metals are also supplied to the soil through
application of commercial fertilizers. Mortvedt and Giordano (1975a) showed
that plant uptake of chromium (and of other heavy metals with the exception
of zinc) was not significantly increased with the usual application rates of
phosphorus fertilizers. Plant uptake of heavy metals was lower on limed
soil than on acid soil. Uptake of chromium did not increase even when CrCl3
was added in rather high amounts to pots supplied with phosphorus additions
of 200 and 600 rag/pot.
4.2.6 Elimination
No information on the bioelimination of chromium from living plant
organs was found. Since a small, but measurable, quantity of chromium is
translocated from root to shoot, small amounts could be lost from the plant
by leaf, branch, fruit, and flower drop and by rain leaching. However,
natural chromium is typically in an insoluble, immobile form; therefore,
extensive leaching of chromium by rain would appear unlikely.
Studies concerned with the direct contamination of field plants with
radioactive nuclides released from bomb tests or nuclear accidents have
suggested that field plants lose chromium with time, which indicates
elimination from the plants. A small amount of chromium, sprayed on barley
as 51Cr-labeled Cr(N03)3, was absorbed by foliage and translocated to develop-
ing husks and grain. This translocation indicated that field loss occurs and
is perhaps greatest in the earliest part of the growing season (Aarkrog and
Lippert, 1971). Mechanisms of loss were not discussed; however, initial re-
tention was related to the surface of the plant (where surface was defined
as the ratio of dry weight to height). Thus, a portion of the activity was
probably adsorbed or retained on the plant surface and never absorbed by the
plant. Spraying slCr-labeled Na2CrO<, on a grassland area gave similar results.
A definite field loss of chromium occurred and a small amount of activity
appeared in new growth after removal of the sprayed foliage (Chadwick and
Chamberlain, 1970).
Fescue grass in a field was contaminated with radiolabeled sodium
chromate to quantify the retention of simulated drift from a cooling tower
-------
96
(Taylor, Gray, and Parr, 1976). All applied chromate was retained during
the first week after application. Two rains during the second week removed
about 50% of the initial deposition. By the fifth week, less than 5% re-
mained, which suggested that contamination was primarily a surface phenomenon
and that the contamination remained soluble. Drift-contaminated foliage and
litter from the field plots were sampled and covered with distilled water to
simulate six successive 1-in. rainfalls. Approximately 7% to 9% of the
total chromium applied was removed from the foliage with each rainfall simu-
lation, whereas only 3% was removed from the litter. These results suggest
that chromium in litter is less soluble and not as easily removed by weather-
ing phenomena.
4.3 EFFECTS
Studies on the effects of various chromium compounds (trivalent and
hexavalent) in different concentrations on plant growth have centered on
symptoms of toxicity; no studies providing information on molecular mech-
anisms or explanations for toxicity were found. The minimum chromium con-
centration required to produce visible symptoms varies for different species
and depends on chemical form and a host of environmental factors affecting
availability. In some cases, addition of chromium has been beneficial for
plant growth and yield (Section 4.2.1); however, most of these reports were
for field experiments. Studies with controlled culture experiments are
necessary to clarify the question of possible beneficial responses.
4.3.1 Smelter Waste Toxicity
During the production of metallic chromium and other chromium compounds
from chromite, considerable quantities of waste containing soluble chromates
are disposed on land adjacent to the smelters. Revegetation of these areas
is necessary after the smelters are abandoned. Examples reported were for
smelters in Great Britain. In tests with Si-nccpis aiba, Gemmell (1973) deter-
mined that the combined effects of high chromate concentration and high pH
inhibited plant growth. As little as 1% of the unweathered wastes (in 99%
sand) completely inhibited germination, while 0.02% reduced shoot growth by
50%. Weathered waste was about 10% as toxic as the unweathered waste.
Breeze (1973) concluded that neither sand nor topsoil would be successful as
a diluent in decreasing waste toxicity and that chemical detoxification
methods would be necessary. Addition of FeSOi, decreases toxicity of chro-
mate wastes by reducing chromate to chromium(lll) (which subsequently pre-
cipitates as Cr203) and/or by pH effects, depending upon the chemical
composition of the substrate (Gemmell, 1972). For long-term success, how-
ever, additional revegetation methods are necessary because of the recurrence
of metal toxicity on treated soils. Gemmell (1974) determined that covering
the waste with a 25- to 30-cm layer of granular free-draining subsoil
followed with top coverings of soil, peat, or sewage sludge was the best
revegetation technique. Incorporation of FeSO/, within the soil and subsoil
should further aid in counteracting chromium toxicity.
4.3.2 Symptoms in Culture Experiments
Toxicity studies can be performed by treating plants in culture with a
balanced mineral solution containing added chromium concentrations. Soybeans
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97
grown in nutrient culture (0 to 5 ppm hexavalent chromium) showed decreasing
concentrations (and uptake) of calcium, potassium, phosphorus, iron, and
manganese in shoots and of potassium, phosphorus, iron, and manganese in
roots at culture levels as low as 0.5 ppm chromium (Turner and Rust, 1971).
A significant decrease in fresh weight of tops occurred at 0.5 ppm chromium
and of roots at 1.0 ppm chromium. Toxicity symptoms, which occurred at 5 ppm
chromium, consisted of severe wilting of the tops. Soil pot culture experi-
ments (0 to 6 ppm hexavalent chromium) showed similar decreasing trends in
element content with increasing chromium content and similar toxicity symp-
toms. Death of plants occurred within three days of treatment with 30 and
60 ppm chromium. Plant chromium concentrations were not determined.
Bean plants cultured in nutrient solutions showed a reduction in leaf
dry weight with as little as 0.01 ppm hexavalent chromium, but the greatest
decrease in weight occurred in solutions containing from 0.1 to 1 ppm chro-
mium (Rediske, Cline, and Selders, 1955). Root dry weight decreased at
chromium concentrations greater than about 0.2 ppm. Hexavalent chromium
apparently affects carbohydrate metabolism; both reducing sugars and sucrose
amounts decreased with increasing hexavalent chromium concentrations. Addi-
tions of trivalent chromium to the nutrient medium produced increasing
amounts of reducing sugars and sucrose in leaves. Protein nitrogen was not
decreased significantly in either roots or leaves with concentrations of
hexavalent or trivalent chromium (0.1 to 100 ppm). The primary visible
symptom of chromium toxicity in bean plants was chlorosis; leaf chlorophyll
concentration decreased with increased hexavalent chromium concentrations
from 0.01 to 1 ppm (Rediske, 1956). Both iron and manganese uptake from
nutrient solutions containing these chromium concentrations were reduced.
Sludge from municipal wastes was added to soils to supply up to 1360
ppm chromium. Chromium contained in these wastes did not affect yield
(weight per pot) of corn (Table 4.3) (Mortvedt and Giordano, 1975&), whereas
the addition of Na2Cr207 to soils to give final chromium concentrations of
80 and 320 ppm decreased weight of corn plants by 87% and 97%. Addition of
Cra(50^)3 to 320 ppm in soil (pH 5.5) reduced yield by about 50%.
Tobacco and maize showed abnormal growth and development when grown in
sand cultures containing various chromium concentrations (Soane and Saunder,
1959). At 5 and 10 ppm chromium (as KaCr207), intense stunting of tobacco
plants occurred; 1 ppm chromium also inhibited stem elongation and inflores-
cence development. Severe root abnormalities led these authors to suggest
that chromium had a "specially toxic effect on root development." However,
since chromium is not translocated, it is difficult to estimate whether one
tissue or organ is inherently more sensitive when it contains a particular
chromium concentration.
Tobacco plants exposed to cooling-tower drift accumulated rather high
levels of chromium at 15 m from the tower (Figure 4.4) (Parr, Taylor, and
Beauchamp, 1976; Taylor et al., 1975). At distances farther from the cool-
ing tower, accumulation was not as great. Tobacco was sensitive to increased
chromium levels and showed about 75% reduction in leaf size or weight at 15 m
and 200 m from the tower as compared to plants at 600 m and 1400 m (Figure
-------
98
ORNL-DWG 76-2448
345
TIME (weeks)
Figure 4.4. Accumulation of chromium by tobacco plants exposed to
cooling-tower drift. Source: Adapted from Taylor et al., 1975, Figure
5, p. 417.
4.5). The inhibition to leaf growth at 200 m occurred at foliar concentra-
tions of <10 ppm chromium, a value similar to the 5 ppm chromium shown to be
toxic to tobacco by Soane and Saunder (1959).
Hunter and Vergnano (1953) observed that some oat plants grown in
nutrient solutions in sand culture showed diffuse leaf chlorosis at 5 ppm
hexavalent chromium; all plants were slightly chlorotic and stunted at 10
ppm. Root growth appeared normal at 5 and 10 ppm. At 25 and 50 ppm chromium,
plants were stunted and had poor root development and brownish red necrotic
areas on the leaves. Little chromium (0.4 to 3.9 ppm) was found in the
leaves of plants cultured in 5 and 10 ppm chromium, but leaves cultured at
25 ppm contained 252 ppm chromium (dry wt). The authors reported that trace
metals produced chlorosis in the following order: Ni > Cu > Co > Cr > Zn >
Mo > Mn. However, Anderson, Meyer, and Mayer (1973) did not observe chloro-
sis in potted oats over a three-week period when chromium was applied as
potassium dichromate, chromium trioxide, or chromium sulfate (75 to 225 ppm).
Many reports related iron deficiency chlorosis to high concentrations
of trace metals. Hewitt (1948) found that the descending order of elements
producing chlorosis in sugar beet was Co2+ >
Cr3+ >
-2 +
Cu2+ >
Zn
2 +
CrO
2-
M2+ >
Pb2T. Specific elements also gave toxic effects not obviously
related to chlorosis. Plants growing with CrO<,2' were dwarfed while those
with chromium(III) appeared normal. Severity of toxicity was in the order
Ni > Co2 > Zn2+ > Cu2+ > CrO,2' > Cr3+ = Mn2+ = Pb2+. Hewitt (1953) also
found that hexavalent chromium decreased the vigor of tomato, potato, oats,
-------
99
ORNL-DWG 76-2449
2400
15 200 600 1400
DISTANCE FROM COOLING TOWER (m)
Figure 4.5. Effects of increased chromium concentrations on leaf
size in tobacco exposed to cooling-tower drift. Source: Adapted from
Taylor et al., 1975, Figure 6, p. 418.
and kale to a greater extent than did trivalent chromium. In sugar beet,
tomato, and potato, both hexavalent and trivalent chromium produced chlorosis
that could be diagnosed as iron deficiency.
DeKock (1956) investigated the effect of heavy metals in ionic or che-
lated form on iron chlorosis in mustard plants (Sinapsis alba) and observed
no chlorosis with 2 ppm chromium, although yield was slightly reduced. With
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100
ionic chromium, roots appeared stunted; however, with chelated chromium no
chlorosis or inhibition of root growth was observed. The order of effective-
ness of the metals in producing chlorosis was Cu > Ni > Co > Zn > Cr > Mn.
DeKock postulated that the metals acted in the root to prevent translocation
of iron, which is necessary for chlorophyll formation to tops and thus
induced chlorosis. The order of heavy metal toxicity to rice was Cd > Cu >
Ti > Zn > Cr > Mo for water-filled paddies; the order in a dry field was
Cd > Cu > Zn > Mo > Cr (Nagai, 1973a). Growth inhibition for the Kanamachi
turnip decreased in the order Na > Cd > Zn > Cu > Ti > Cr > Mo (Nagai, 1973&).
Verfaillie (1974) reported that no abnormal physiological effects were
observed in rice plants maintained in nutrient solutions supplemented with
10~4 M chromium(III) over a 2.5-day period or with 10"" M chromium(III)-EDTA
over a 5-day period. With chromium(VI) (as CrOi,2") concentrations greater
than 2 x 10"5 M, some leaves and stems began to turn yellow and to wither.
Stanley (1974) found 50% inhibition of root weight of the water milfoil
at 1.9 ppm Cr2072~ and at 9.9 ppm chromium(III); 50% inhibition of shoot
weight occurred at 2.6 ppm Cr2072~ and 14.6 ppm chromium(III).
Breeze (1973) compared the toxicity of chromium(III) and chromium(VI)
(as Cr2072~) in LoUwm perenne seedlings. Germinated seeds were exposed
to solutions containing 10, 50, 100, and 500 ppm chromium for 60 hr prior
to planting in soil; survival was measured a week later. At 10, 50, 100,
and 500 ppm chromium(III), survivals were 84%, 63%, 35%, and 1%, respec-
tively. Survivals for 10, 50, 100, and 500 ppm Cr2072" were 84%, 72%, 47%,
and 2%, respectively.
Thus, chromium can be toxic to plants; the concentration at which
effects are first observed depends on the species. Because chromium is
not easily translocated, effects on root growth might be expected. At high
chromium concentrations, inhibition and stunting of root growth as well as
chlorosis and inhibition of shoot growth have been observed. There appears
to be no single characteristic symptom of chromium injury (Yopp, Schmid,
and Hoist, 1974). The above symptoms are all gross phenotypic abnormali-
ties which must certainly be preceded by altered metabolic patterns. How-
ever, no data on abnormal metabolism in plants exposed to low or high
chromium concentrations or on the mechanisms responsible for the observed
symptoms have been reported.
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101
SECTION 4
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27. Hewitt, E. J. 1948. Relation of Manganese and Some Other Metals to
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28. Hewitt, E. J. 1953. Metal Interrelationships in Plant Nutrition:
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29. Horovitz, G. T., H. H. Schock, and L. A. Horovitz Kisimova. 1974.
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32. Hunter, J. G., and 0. Vergnano. 1953. Trace-Element Toxicities in
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34. Kumanishi, T., and T. Yamamoto. 1968. Cr-51 Release Test for
Determination of Optimum Conditions of Low Temperature Preservation
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35. LeRiche, H. H. 1968. Metal Contamination of Soil in the Woburn
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40. Lyon, G. L., P. J. Peterson, and R. R. Brooks. 1969a. Chromium-51
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SECTION 5
BIOLOGICAL ASPECTS IN ANIMALS
5.1 SUMMARY
Most studies of the effects of chromium on animals have used aquatic
species: fish, crustaceans, polychaete worms, and insects. Effects on
birds or on wild and domestic mammals have not been reported, but some
concentration data were found. The effect of chromium on mammals and chro-
mium metabolism are discussed in Section 6.
Experimental evidence has indicated that trivalent and hexavalent chro-
mium are the forms most significant to biological systems; both species are
readily adsorbed to body surfaces. Hexavalent chromium is accumulated by
marine animals, whereas the trivalent form is not. Absorption and accumula-
tion are passive actions dependent on chromium concentration.
High chromium concentrations can produce several physiological changes
in aquatic species. Growth reduction, decreases in hematocrit values and
protein content, impairment of reproduction, and increased oxygen consump-
tion have occurred in animals exposed to chromium.
Although trivalent chromium has been found to be toxic to several
animals, hexavalent chromium is generally more toxic. Water properties
such as pH, temperature, alkalinity, and hardness are factors influencing
chromium toxicity. In addition, various animal species display different
sensitivities to chromium. The lethal chromium level for invertebrates has
been reported as 0.05 ppm (National Academy of Sciences and National Academy
of Engineering, 1972); therefore, any water quality standards should be well
below this level.
5.2 METABOLISM
5.2.1 Uptake and Absorption
Investigations of chromium uptake by animals have primarily used marine
and freshwater species. In their natural environment, mollusks accumulate
trace metals at various rates. Accumulation of these metals in tissues is
affected by the species involved, water temperature and pH, concentration
of the metal, and physiological and biochemical activity of the animal.
Chromium ions are adsorbed to shells and passively taken into aquatic species
through gills which act as ion exchangers. Although chromium can exist in
several valence states, the trivalent and hexavalent forms are the ones
important in biological systems. These forms behave differently when added
to aqueous solutions. Trivalent chromium added as chromic chloride results
in hydroxide formation and precipitation (Chipman, 1967); the particles
formed readily adsorb.to surfaces. Hexavalent chromium (sodium chromate)
forms a true solution containing no particulate matter.
107
-------
108
Baudouin and Scoppa (1974a) reported that accumulation of trivalent
51Cr In zooplankton (Eudiaptomus> Cyclops, and Daphnia) occurred rapidly
and that uptake increased with increasing external concentrations, which
suggests that uptake is a passive process. Surface adsorption of trivalent
slCr was small; however, in organisms which do not accumulate chromium to
any large extent, this adsorption may account for up to 30% of total uptake.
In oxygenated natural waters with high alkaline values, chromate ions are
stable. Copepods (Eudiaptomus and Cyclops) did not accumulate hexavalent
51Cr, whereas Daphnia did so rapidly.
Chipman (1967) investigated the accumulation of 51Cr by Hermione
hystrix, a polychaete worm. The worms were placed in seawater suspensions
containing either chromic chloride or sodium chromate. Worms in seawater
suspensions with trivalent chromium present in the bottom silt had chromium
on body surfaces and within the digestive tract. Accumulation did not occur
because the trivalent form was not absorbed from the digestive tract. When
Hermione was exposed to seawater which contained chromate, uptake of hexa-
valent chromium was rapid. Accumulation, which occurred slowly with no
diminution, was expressed as the ratio of radioactivity per gram of live
worm to that of a milliliter of seawater (Figure 5.1). Uptake of hexavalent
chromium increased as the chromium concentration in seawater increased,
which indicated that chromium uptake by Hermione was a passive process.
Accumulation possibly occurred by the binding of chromium to some body
proteins.
Chromium was absorbed by the polychaete worm Nereis virens (Raymont
and Shields, 1963). In a solution containing 1 ppm chromium as sodium
chromate, Nereis reduced the chromium concentration by amounts ranging from
0.06 to 0.1 ppm. This reduction apparently was due to chromium uptake by
15
cc
10
a:
UJ
o
§
o
ORNL-OWG 76-2450
10 15
TIME (days)
20
Figure 5.1. Accumulation of 51Cr by Hermione hystrix from seawater
containing the radionuclide in the form of chromate. Source: Adapted from
Chipman, 1967, Figure 1, p. 935. Reprinted by permission of the publisher.
-------
109
the worm. Chromium was absorbed through the gut and body walls; the para-
podial region had a high chromium concentration because the body wall was
thinner in this area.
Uptake of metal ions from aquatic systems by shellfish has been studied.
Chipman (1966) investigated 51Cr uptake by the clam, Tapes deaussatus. Clams
placed in seawater containing trivalent 51Cr rapidly became radioactive from
their filtering activity and adsorption of chromium particles on shells,
folds of gills, mantle, and other surfaces in contact with the seawater.
These particles were quickly eliminated by the clam; the body tissues did not
accumulate trivalent 51Cr. Trivalent chromium chelated with ethylenediamine-
tetraacetic acid (EDTA) was not taken up by the clam. Clams in contact with
seawater containing hexavalent chromium rapidly took up the chromium ions by
adsorption and accumulated a small amount of chromium in the tissues. Amounts
of chromium entering the clam were related to the chromium concentration in
the seawater, which indicated that uptake was a passive process. These re-
sults corroborated Chipman's earlier investigations of chromium uptake by
Hermione sp.
Chromium was found in shells of the oyster Crassostrea virginiaa in
higher concentrations than in the seawater from which the oysters were taken
(Ferrell, Carville, and Martinez, 1973). Since chromium can form carbonates,
the oyster possibly incorporated chromium as the shell formed. Soft tissues
of the oyster Crassostpea gi-gas were analyzed for uptake of various metals
(Ayling, 1974). The concentration of chromium in the oyster was independent
of the concentration in the water. In contrast to previous reports, this
study suggested that chromium had been absorbed by some physiological proc-
ess up to a maximum concentration that depended on oyster size.
Physiological movement of chromium has also been studied in the crab
Canoe? magister (Tennant and Forster, 1969). Chromium was found in the
gills, setae, and hepatopancreas. Since chromium is adsorbed on surfaces,
it is associated with organs having a high surface-area to volume ratio.
The setae and gills have this high ratio, which suggests that chromium was
adsorbed to their surfaces. However, chromium present in the hepatopancreas
must have been ingested and/or diffused across gill membranes. The authors
suggested that a metabolic movement of chromium was involved, which indi-
cated a physiological process in chromium uptake. Chromium was taken up in
greatest concentration by the gills of the crab Podophthalmus vigil exposed
to 1 yCi 51Cr per liter (Sather, 1967). Sather proposed that 51Cr was bound
to proteins and possibly to mucopolysaccharides.
A study using rainbow trout, Salmo gairdneri, showed that chromium up-
take was passive (Fromm and Stokes, 1962). Uptake occurred with fish ex-
posed to 0.0013 and 0.0100 ppm chromium as potassium chromate. The amount
of chromium accumulated was proportional to the amount of chromium present
in the water and leveled off after 10 days of exposure. Each point on Fig-
ure 5.2 represents the mean value for four fish. Broken lines show the mean
maximum uptake and solid lines are regression lines for uptake. At chromium
concentrations of 0.01 and 0.0013 ppm in water, the mean maximum chromium
concentrations in the trout were 133.6 and 16.6 ppm, respectively. Rainbow
trout exposed to 18.6 ppm chromium had a total chromium uptake by the liver,
-------
110
ORIML DWG 76-2451
200
in
E
§,100
50
u>
E 0
Z
g. 20
i_
u
"E
cc 10
o
o
• 0.0100 ppm CHROMIUM
o 0.0013 ppm CHROMIUM
I
I
8 12 16 20
TIME OF EXPOSURE (days)
24
Figure 5.2. Uptake of hexavalent chromium by two groups of
rainbow trout exposed to 0.0100 and 0.0013 ppm chromium. Source:
Fromm and Stokes, 1962, Figure 1, p. 1152. Reprinted by permission
of the publisher.
spleen, kidney, and gall bladder of 72.5 yg per fish during a 24-hr exposure
(Schiffman and Fromm, 1959).
5.2.2 Transport and Distribution
Table 5.1 gives the chromium distribution in tissues of some wild and
domestic mammals; Table 5.2 lists chromium content of hair in various animal
species. Chromium distribution in some aquatic species is summarized in
Table 5.3.
Elemental analyses of tissues of cotton rats chronically subjected to
ingestion and inhalation pathways (cooling-tower drift) have been compared
to those of animals remote from exposure (Table 5.4) (Taylor, 1975). Signif-
icant differences (P < 0.01) in chromium concentrations in pelt, hair, and
bone were identified between exposed and control animals. Chromium concen-
trations in bones of exposed and control animals ranged from 0.46 to 0.16
ppm, whereas concentrations in hair and pelt of animals exposed to drift
ranged from 4.4 to 1.1 ppm, respectively. These elevated levels in exposed
animals were contrasted to 0.4 and 0.1 ppm in hair and pelt of control
-------
Ill
Table 5.1. Chromium in wild and domestic animal tissues
Wild animals
Domestic animals
Tissue
Liver
Kidney
Heart
Lung
Spleen
Muscle
Stomach
Placenta
Number of
samples
9
12
11
3
5
4
1
1
Chromium
concentration
(ppm wet wt)
0.16
0.20
0.14
0.24
0.48
0.11
0.04
0.07
Chromium
Number of concentration
samples , . ,.
(ppm wet wt)
16 0.15
7 0.16
11 0.0
Source: Adapted from Schroeder, 1970, Table 5, p. 9. Reprinted
by permission of the publisher.
animals. With the exception of the gastrointestinal tract, chromium was
evenly distributed among organs of control animals. Little evidence of bio-
accumulation was found among animals exposed to elevated levels of chromium.
Huckabee, Cartan, and Kennington (1972) analyzed the hair of several
mammals from Idaho and Wyoming for concentrations of trace metals, includ-
ing chromium (Table 5.2). Chromium was found in 61% of the samples; levels
varied widely among members of the same species from the same geographic
area as well as among different species.
Trivalent chromium concentrations in Hermione were 10,373, 5,410, and
3,713 counts min"1 g"1 at 9, 15, and 22 days of exposure, respectively
(Chipman, 1967). Trivalent chromium was not concentrated to any large ex-
tent; concentration factors were 0.59 at 9 days, 0.31 at 15 days, and 0.21
at 22 days. Hexavalent chromium concentrations ranged from 0.4 mg/g (live
wt) at 1 day of exposure (0.3 ppb added as sodium chromate) to 3.6 mg/g
(live wt) at 19 days of exposure. The concentration factor was approxi-
mately 10 at 19 days.
Other studies showed that chromium was absorbed by Nereis in several
areas of the body (Raymont and Shields, 1963). The blood vessels had high
chromium concentrations. Chromium was transported from the body and gut
walls to small blood vessels in these regions. A chromium gradient was
-------
112
Table 5.2. Chromium concentrations in the hair of
several wild animal species
Species
Antiloaapra ameriaana
(pronghorn antelope)
Odoaoileus hemionus
(mule deer)
CBTVUB canadensis
(elk)
Ovecamos amevicanus
(mountain goat)
Sov&x vagvans (shrew)
Miarotus pennsylvani-cus
(meadow vole)
Miarotus montanus
(mountain vole)
Location
Lemhi Range, Idaho
Lemhi Range, Idaho
Lemhi Range, Idaho
Lemhi Range, Idaho
Lemhi Range, Idaho
Lemhi Range, Idaho
Lemhi Range, Idaho
Lemhi Range, Idaho
Lemhi Range, Idaho
Lemhi Range, Idaho
Lemhi Range, Idaho
Lemhi Range, Idaho
Lemhi Range, Idaho
Lemhi Range, Idaho
Lemhi Range, Idaho
Lemhi Range, Idaho
Lemhi Range, Idaho
Lemhi Range, Idaho
Laramie Basin, Wyo.
Laramie Basin, Wyo.
Wamsutter Area, Wyo.
Wamsutter Area, Wyo.
Shirley Basin, Wyo.
Shirley Basin, Wyo.
Shirley Basin, Wyo.
Lemhi Range, Lost River Mts., Idaho
Lemhi Range, Lost River Mts., Idaho
Lemhi Range, Lost River Mts., Idaho
Lemhi Range, Lost River Mts., Idaho
Lemhi Range, Lost River Mts., Idaho
Lemhi Range, Lost River Mts., Idaho
Lemhi Range, Lost River Mts., Idaho
Lemhi Range, Lost River Mts., Idaho
Lemhi Range, Lost River Mts., Idaho
Soldier Mts . , Idaho
Soldier Mts., Idaho
Soldier Mts. , Idaho
Soldier Mts. , Idaho
Soldier Mts. , Idaho
Soldier Mts. , Idaho
Soldier Mts. , Idaho
Soldier Mts., Idaho
Soldier Mts. , Idaho
Soldier Mts . , Idaho
Lemhi Range, Idaho
Lemhi Range, Idaho
Jackson Hole, Wyo.
Jackson Hole, Wyo.
Jackson Hole, Wyo.
Gros Ventre Range, Wyo.
Jackson Hole, Wyo.
Jackson Hole, Wyo.
Jackson Hole, Wyo.
Chromium concentration
in sample
(ppm)
44
120
18
36
110
4.7
6.6
160
480
1.9
98
640
370
120
6.8
Trace
440
55
130
9.9
2.8
0.3
30
6.7
9.0
13
22
48
57
310
51
92
420
630
570
83
240
9
84
57
16
1.9
13
13
4.0
5.5
15
5.6
8.8
8.2
16
180
85
-------
113
Table 5.2 (continued)
Species
Location
Chromium concentration
in sample
(ppm)
Microtus montanus
(mountain vole)
Zapits pvinaeps
(western jumping mouse)
Erethizon dovsatwn
(rodent)
Eutamis sp. (rodent)
Miarotus riehardsoni
(rodent)
Microtus longicandus
(rodent)
Can-Is latrans
(coyote)
Jackson Hole, Wyo.
Jackson Hole, Wyo.
Jackson Hole, Wyo.
Jackson Hole, Wyo.
Jackson Hole, Wyo.
Jackson Hole, Wyo.
Jackson Hole, Wyo.
Jackson Hole, Wyo.
Jackson Hole, Wyo.
Jackson Hole, Wyo.
Jackson Hole, Wyo.
Gros Ventre Range, Wyo.
Jackson Hole, Wyo.
Jackson Hole, Wyo.
White Cloud Peaks, Idaho
White Cloud Peaks, Idaho
Gros Ventre Range, Wyo.
Gros Ventre Range, Wyo.
Gros Ventre Range, Wyo.
Gros Ventre Range, Wyo.
White Cloud Peaks, Idaho
White Cloud Peaks, Idaho
White Cloud Peaks, Idaho
Jackson Hole, Wyo.
Jackson Hole, Wyo.
Jackson Hole, Wyo.
Jackson Hole, Wyo.
Jackson Hole, Wyo.
Jackson Hole, Wyo.
Jackson Hole, Wyo.
Jackson Hole, Wyo.
Jackson Hole, Wyo.
Jackson Hole, Wyo.
Jackson Hole, Wyo.
Jackson Hole, Wyo.
Jackson Hole, Wyo.
Jackson Hole, Wyo.
Jackson Hole, Wyo.
160
21
150
23
82
44
9.9
30
58
49
21
4.7
45
24
0.7
4.3
0.9
0.8
29.1
10
0.7
4.3
1.7
5.8
1.6
1.5
12
0.9
5.3
4.8
0.6
4.2
3.5
0.7
2.0
6.2
2.1
3.3
Source: Compiled fromLHuckabee, Cartan, and Kennington, 1972.
found across the gut wall into the blood vessels. Actual chromium concen-
trations in tissues were not reported. Chromium concentrations in limpets
(Patella vulgata) collected near a sewage outfall ranged from 9.7 to 23.2
ppm in the soft tissues and from 9.3 to 10.4 ppm in skeletal parts (Navrot,
Amiel, and Kronfeld, 1974).
In the clam, Tapes deeussatus, chromium was distributed throughout the
absorptive surfaces of the body (Chipman, 1967). Most trivalent 51Cr was
found in shells, folds of gills, and the mantle. The concentration ratio
was <1.0. Hexavalent 51Cr was found primarily in soft tissues, with only
a small percentage in shells. At 20 days of exposure, the concentration
factor was 12 to 16. Chromium concentrations in clam shells and meats are
given in Table 5.5.
-------
Table 5.3. Accumulation of chromium in various tissues of aquatic organisms
Chromium
Species concentration issue
in seawater or or§an
Crassius auratus 10-13.0 yCi injected into Intestine
air bladder Liver
Pancreas
Spleen
Kidney
Head kidney
Gill
Muscle
Backbone
Gonad
Air bladder
Lampsilis vadiata 0.204 pCi/ml Soft tissues
Hernrione (whole) 17,804 counts min"1 g"1
17,833 counts min'1 g"1
18,226 counts min"1 g"1
0.31 ppb
0.1 ppb
0.3 ppb
0.3 ppb
0.3 ppb
0.3 ppb
0.3 ppb
0.3 ppb
0.3 ppb
0.3 ppb
3.0 ppb
3.0 ppb
3.0 ppb
3.0 ppb
10 ppb
10 ppb
10 ppb
10 ppb
Chromium
concentration
in tissue
25 counts min"1 mg"1
25-40 counts min"1 mg"1
25-40 counts min"1 mg"1
60-100 counts min"1 mg"1
200 counts min"1 mg"1
275 counts min"1 mg"1
40-60 counts min"1 mg"1
10 counts min"1 mg"1
30-40 counts min"1 mg"1
30-60 counts min"1 mg"1
1,000 counts min"1 mg"1
89.6 pCi/g
10,373 counts min"1 g"1
(9 days)
5,410 counts min"1 g"1
(11 days)
3,713 counts min"1 g"1
(22 days)
8.1 ppm (1 day, dry)
0.4 ppm (2 days, live)
0.7 ppm (3 days, live)
0.9 ppm (5 days, live)
1.1 ppm (7 days, live)
1.3 ppm (9 days, live)
1.7 ppm (12 days, live)
2.3 ppm (15 days, live)
2.7 ppm (19 days, live)
14.0 ppm (4 days, live)
22.0 ppm (8 days, live)
26.0 ppm (11 days, live)
34.0 ppm (15 days, live)
24 ppm (2 days)
40 ppm (4 days)
53 ppm (8 days)
68 ppm (11 days)
Concentration
factor
440
0.59
0.31
0.21
3.0 (5 days)
3.5 (7.5 days)
5.0 (9.0 days)
7.5 (12.5 days)
8.0 (15.0 days)
12.0 (19.0 days)
-------
Table 5.3 (continued)
Chromium
Species concentration
in seawater
10 ppb
10 ppb
100 ppb
100 ppb
100 ppb
100 ppb
500 ppb
500 ppb
500 ppb
500 ppb
. Chromium
Tlssue concentration
or organ
e in tissue
84 ppm (11 days)
108 ppm (13 days)
206 ppm (3 days)
288 ppm (6 days)
428 ppm (11 days)
495 ppm (14 days)
856 ppm (3 days)
1139 ppm (6 days)
1436 ppm (11 days)
1834 ppm (14 days)
*-i _ _ _ _i
Concentration
factor
f\ f\
Mummichog
Zooplankton, postlarvae
fish (whole)
Podophthalmus vigil
1 = concentration of
phytoplankton culture —
chromium transferred
down food chain
132 MCi/mg = initial
concentration in
phytoplankton
culture
1 yCi CrCl3 per liter
1 yCi CrCl3 per liter
1 pCi CrCl3 per liter
1 yCi CrCl3 per liter
1 yCi CrCl3 per liter
Gonad
Muscle
Gills
Spleen
Liver
Digestive tract
Gills
Muscle
Midgut gland
Carapace
Blood
5000 dio min"1 mg"1
(max, 2 days)
79-80 dis min"1 mg"1
(max, 2-4 days)
75 dis min"1 mg"1
(max, 6 days)
50 dis min"1 mg"1
(max, 14 days)
10 dis min"1 mg"1
(max, 16 days)
9.0
0.5
1.7
6.9
1.7
2.2
9.9
7.3
6.2
Source: Adapted from National Academy of Sciences and National Academy of Engineering, 1972, Table 3, pp. 469-
480. Data collected from various sources.
-------
116
Table 5.4. Comparison of chromium distribution pattern in cotton rats (Sigmodon hispidus")
exposed to cooling-tower drift and in control animals
Organ or tissue
Heart
Liver
Kidney
Spleen
Lung
Bone
Muscle
Gastrointestinal tract
Pelt
Hair ,
Residual
"ORGDP = Oak Ridge
Six pooled samples
Number of
Control
6
6
6
6
6
6
6
6
6
6
6
Gaseous Diffusion
of four animals
animals
ORGDPa
%
6b
6b
6b
6b
6b
6b
6b
24
24
24
Plant, Oak
each.
Chromium concentration (ppm + 1 SE)
Control
0.105 + 0.013
0.046 + 0.016
0.087 + 0.014
0.493 + 0.123
0.289 + 0.072
0.160 + 0.008
0.234 + 0.043
1.046 + 0.277
0.092 + 0.007
0.395 + 0.021
0.200 + 0.032
Ridge, Tennessee.
ORGDPa
0.124 + 0.016
0.160 + 0.039
0.124 + 0.040
0.713 + 0.084
0.292 + 0.063
0.460 + 0.024
0.288 + 0.029
1.006 + 0.183
1.056 + 0.133C
4.397 + 0.555°
0.311 + 0.025
"Blood, reproductive organs, brain, salivary glands, and thyroid.
Source: Adapted from Taylor, 1975, Table 6, p. 4.
Table 5.5. Uptake of chromate by
Tapes deaussatus exposed to
different chromium concentrations
in seawater
Chromium uptake
Exposure
(days)
at the
seawater concentrations
indicated (ppb)a
3 ppb 10 ppb
5
10
15
20
5
10
15
20
7.0
15.5
21.5
27.3
37.4
44.2
80.7
84.0
Shells
5.1
13.6
18.0
26.0
Meats
55.8
129.4
231.8
275.1
100 ppb
5.0
9.8
16.0
18.0
775
1879
2750
2470
Calculated from the specific
activities of 51Cr.
Source: Adapted from Chipman,
1966, Table II, p. 579. Reprinted by
permission of the publisher.
-------
117
Harvey (1969) found the 51Cr concentration in soft tissues of fresh-
water clams exposed to 0.204 pCi/ml was 89.6 pCi/g, with a concentration
factor of 440. Oyster shells from various parts of the United States were
analyzed for heavy-metal concentrations (Ferrell, Carville, and Martinez,
1973). Chromium concentrations, which ranged from 0.05 to 7.26 ppm, were
considerably higher in shells than in seawater and represented at least a
thousandfold increase. Ayling (1974) found that the Pacific oyster, Cras-
sostvea gigas, contained 1 to 37 ppm chromium (dry wt) in soft tissues.
Mud samples from beds inhabited by these oysters contained 2 to 88 ppm chro-
mium; thus, a very small concentration factor for oysters was indicated.
Ayling noted that care must be taken in interpreting concentration factors
since values based on seawater and mud vary widely. In a survey of various
mollusks, Pringle et al. (1968) reported chromium concentrations of 0.04 to
3.40 ppm (wet wt) for U.S. East Coast oysters, 0.1 to 0.3 ppm (wet wt) for
U.S. West Coast oysters, 0.1 to 5 ppm (wet wt) for soft shell clam, and
0.19 to 5.80 ppm (wet wt) for northern quahaug.
Sather (1967) found that the gills of crabs probably regulated the
amount of chromium absorbed by blood. Chromium passed through the gills
and was transported by the blood to other tissues. Intrapericardial in-
jection of radiochromium resulted in loss of 51Cr from the blood to the
gills, where it was internally bound. Muscle tissues had greater affinity
for chromium than other tissues and thus reached equilibrium shortly after
the gills. Chromium concentrations in various organs are shown in
Figure 5.3.
Several studies concerning chromium concentrations in fish have been
conducted. Tong et al. (1974) reported that the chromium concentration in
lake trout (Salvelinus namayoush) from Lake Cayuga in New York generally
increased with trout age. At 1 year of age, chromium content was 5.2 ppb
(fresh wt); at 12 years, the chromium concentration was 90 ppb (fresh wt).
Several species of fish from the Great Lakes were analyzed for trace ele-
ments (Lucus, Edgington, and Colby, 1970). Chromium concentrations (micro-
grams per gram of tissue) in whole fish were: Lake Michigan alewife, 1.1 ±
0.5; Lake Michigan spottail shiner, 0.9 ± 0.5; Lake Erie spottail shiner,
10; Lake Michigan trout-perch, 1.6 ± 0.2; and Lake Superior trout-perch, <3.
Uthe and Bligh (1971) surveyed several fish species from Canadian lakes.
The chromium concentrations of dressed fish in parts per million wet weight
were: lake whitefish (Moose Lake), 0.033; lake whitefish (Lake Ontario),
<0.017; northern pike (Moose Lake), <0.035; northern pike (Lake St. Pierre),
<0.026; northern pike (Lake Erie), <0.031; rainbow smelt (Lake Erie), 0.034;
and yellow perch (Lake Erie), <0.065.
Again, it is necessary to add a note of caution about the analytical
uncertainty of numbers such as those given above. All values must be re-
garded as tentative until the methods of analyses for traces of chromium
are better understood. Comparison of numbers from different laboratories
or different methods is particularly hazardous.
5.2.3 Elimination
Marine polychaete worms have been used to investigate the retention
and rate of loss of slCr. Hevmione sp. exposed 12 days to seawater with
-------
118
ORNL-DWG 76-3842R
10,000
1,000 -
o>
E
\
Q.
1OO -
6 8 10 12
TIME (days)
14 16
Figure 5.3. Accumulation from solution of 51Cr by the crab,
P. vigil. Source: Sather, 1967, Figure 1, p. 951. Reprinted by
permission of the publisher.
chromate added showed more than one rate of loss (Chipman, 1967). The bio-
logical half-life was 123 days for the long-lived component and 7.95 days
for the short-lived component (Figure 5. A). In Hermione, chromium seemed
to be present in two components with a different type of binding in each.
The slow turnover rate indicated a component that was bound differently.
The long, steady rate of accumulation indicated that the larger part of
Cr accumulated from long-term exposure was bound in a body component
haying a slow turnover rate.
v, i Z4 a1"tfntion study using the freshwater clam, Lompallis radiata, the
biological half-life of slCr also had both short- and long-lived components
(Harvey, 1969). The half-life of the short-lived component was 5 days and
that of the long-lived component was 52 days. In comparison with the
marine worm Hewmone, 51Cr has a shorter biological half-life in clams than
in marine worms.
Studies by Sather (1967) indicated that the gills of crabs exposed to
lost chromium at a daily rate of 263 dis min"1 mg'1 when the gills were
in water without chromium. The biological half-life was nine to ten
-------
119
100
I 50
z
s
ui
or
>-
K
>
t-
U
< 20
u
ORNL-OWG 76- 2452A
2 6 10 14 18 22 26 30 34 38 42 46 50 54 58 62
TIME (days)
Figure 5.4. Retention of 5lCr by Hermione hystvix following a 12-day
exposure to the radionuclide in high specific activity in seawater in the
form of chromate. Source: Adapted from Chipman, 1967, Figure 2, p. 938.
Reprinted by permission of the publisher.
days. Chromium loss was attributed to mobilization of chromium by the blood
and its deposition in other tissues.
Brown crickets were fed radiolabeled chromium (as chromium chloride),
were transferred to nonradioactive food, and then their whole-body reten-
tion was measured (Van Hook and Crossley, 1969). The retention of 51Cr was
described in a two-component model. From a single ingestion, an estimated
95% of the initial body burden was eliminated within 48 hr with a biological
half-time of 4 hr. Less than 6% of the nuclide ingested was actually assim-
ilated by the tissues. The assimilated fraction (short-time component) was
eliminated at a slower rate with a biological half-time of 83 hr. The low
assimilation and moderate excretion rates indicate that the 5lCr concentra-
tion would probably be reduced at each trophic transfer.
The significance of chronic exposure to chromium by ingestion was deter-
mined in retention studies of native mammals (Taylor, 1975). Elimination of
slCr (as Na251CrOi,) by cotton rats resulted in a two-component curve — a
short component representing gut clearance and a long component illustrating
loss of the assimilated fraction. The percent assimilated was 0.8% of the
initial whole-body radioactivity. Within three days after feeding, 99% was
eliminated (Figure 5.5), whereas the remaining fraction (<1%) , which repre-
sented loss of the assimilated radionuclide, was eliminated at a slower
rate. The biological half-time of the assimilated chromium was calculated
to be 693 days. These data confirm the lack of any bioaccumulation from
contaminated food as depicted in stable analyses (Table 5.4) and suggest the
reduced probability of a toxic effect due to the low assimilation and rapid
excretion rates.
-------
120
ORNL-DWG 75-14703
g
z
o
too
50
20
10
5
2
1
0.5
0.2
n i
V —
^
?
\
•
\—
— V-
\
\
\
*
\
\j
— ^
=•— — j
• OBSERVED
o CALCULATED
— ft-
• —
.
46 8 10 (2
TIME (doys postfeeding)
14
16
Figure 5.5. Retention of 51Cr by Sigmodon hispidus.
from Taylor, 1975, Figure 1.
Source: Adapted
5.3 EFFECTS
5.3.1 Physiological Effects
Biesinger and Christensen (1972) reported the effects of several metals
on the metabolism of Daphnia magna. Animals exposed to 0.619 ppm trivalent
chromium (added as chromic chloride) in Lake Superior water (pH 7.4) had a
weight reduction of 11% when compared with control animals. The amount of
total protein per animal was reduced by 3%. The effect of chromium on metab-
olism was measured by glutamic oxalacetic transaminase (GOT) activity. The
GOT activity per animal exposed to 0.619 ppm chromium was reduced by 4% when
compared with controls. Reproduction was also affected; a chromium concen-
tration of 0.33 ppm resulted in a 16% reproduction impairment. When Daphnia
pulex was exposed to sodium dichromate, a hexavalent chromium compound,
oxygen consumption was altered (Sherr and Armitage, 1973). The oxygen con-
sumption per animal was approximately doubled in the group exposed to 0.01
ppm dichromate (temperature 21°C) as compared with the control group.
Fromm (1970) studied the effects of chronic chromium exposure on rain-
bow trout, Salmo ga^rdner^. Fish exposed to 0.2 ppm chromium for one week
had plasma cortisol levels almost double that of controls (0.54 yg/ml for
exposed fish, 0.27 wg/ml for controls). After exposure for two and three
weeks, exposed fish had plasma levels similar to those of controls. Effects
of chromium on the blood of S. gaivdneri were also reported by Schiffman
and Fromm (1959). Trout exposed to 20 ppm chromium showed a significant
increase in red blood cells. Both splenectomized and intact fish exposed
to 20 ppm chromium had hematocrits significantly higher than controls.
M^r°h Splf?f °mlzed fish exP°sed to chromium also had a significantly
hxgher hemoglobin content than did the blood from nonexposed splenectomized
-------
121
fish. The chromium-exposed intact fish had larger blood cells than did the
controls. These effects are summarized in Table 5.6. The authors suggested
that the increase in hematocrits resulted from decreased plasma volume and
increased cell number and cell size. A chromium concentration of 2 to 4 ppm
affected the hematocrit.
5.3.2 Toxicity
Because heavy-metal salts in solution are stable compounds, they con-
stitute a serious form of pollution. Chromium toxicity to aquatic organisms
has been shown to vary with solution pH, water hardness, temperature, species,
size of organism, and the chemical form of chromium. A few studies have
reported trivalent chromium to be only slightly toxic to several organisms.
In soft water, trivalent chromium appears to be the form most lethal to fish,
whereas in hard water, hexavalent chromium has the greatest toxicity. In
hard water, the toxicity of trivalent chromium is reduced by the formation
of precipitates; hexavalent chromium remains toxic under these conditions.
The susceptibility of organisms to trivalent chromium is complicated by the
acidity of most trivalent chromium salts.
Fish appear to be more tolerant of chromium salts than lower forms of
aquatic organisms. Exposure to low chromium concentrations over a long
period produces a more detrimental effect on the organism than does a high-
dose exposure for a brief period. Toxic effects to aquatic organisms are
summarized in Tables 5.7 and 5.8.
Studies of chromium toxicity in mammals have been concerned primarily
with experimental animals (rats, mice, and guinea pigs) and man and thus
will be discussed in Section 6.
Nereis sp. showed sensitivity to hexavalent chromium salts (Raymont
and Shields, 1963). Responses to sodium and potassium chromates and dichro-
mates did not differ. Chromium concentrations of 2 to 10 ppm produced heavy
mortality in two to three weeks. The threshold toxicity level for Nereis
was just under 1 ppm chromium.
Several studies concerning the effects of chromium on Daphnia sp. have
been reported. For example, chromium was added to Lake Erie water in the
form of chromic chloride to determine its effects on Daphnia magna (Anderson,
1948). The approximate 50% lethal concentration (LC50) for chromic chloride
was <3.6 ppm (0.000023 M). At this concentration the solution became acid
and a precipitate formed. This precipitate may have been responsible for
immobilizing the daphnids either by mechanical means or by a specific toxic
action. Daphnids were found to be particularly susceptible during molting.
After three weeks, the LC50 reported for Daphnia magna by Biesinger and
Christensen (1972) was 2.0 ppm chromium in Lake Superior water. For Lake
Erie water, the 64-hr approximated threshold was <1.2 ppm. These results
tend to substantiate the work of Anderson (1948).
The survival of Daphnia pulex exposed to various concentrations of
sodium dichromate showed that Daphnia displayed no adverse reaction to low
-------
Table 5.6. The effect of exposure to 20 ppm chromium on the blood of rainbow trout, Salmo gaivdneiri.
.a
Treatment
Intact trout
Clean tap water
Chromium water
Splenectomized trout
Clean tap water
Chromium water
Hematocrit
(ml/ 100 ml)
31.8 + 1.39
43.8 + 1.56
28.5 + 1.42
40.6 + 2.92
Hemoglobin
(g/100 ml)
6.5 + 1.27
6.6 + 0.25
5.6 + 1.13
7.4 + 0.51
Red blood
cells count
(million
HUil )
1.11 + 0.098
1.25 + 0.032
1.04 + 0.18
1.38 + 0.11
Red blood
cells length
00
14.69 + 0.24
14.93 + 0.15
Plasma
volume
(ml/100 g)
2.13 + 0.14
1.61 + 0.12
2.44 + 0.12
1.74 + 0.10
Blood
volume
(ml/100 g)
3.24 + 0.16
3.01+0.18
3.85 + 0.16
3.16 + 0.14
,A11 values are given as mean and standard error.
Concentration of 20 ppm.
Source: Adapted from Schiffman and Fromm, 1959, Table I, p. 207. Reprinted by permission of the
publisher.
to
-------
Table 5.7. Toxicity of chromium to aquatic biota
Chemical
compound
Ammonium chromate
Chromic chloride
Chromic sulfate
Chromic sulfate
and sodium
dichromate
Chromium
Chromium
(chromate)
Chromium
(dichromate)
Chromium
(hexavalent)
Test
organism
Gambusia affinis
Gambusia affinis
Daphnia magna
Daphnia magna
(cladocera)
Daphnia magna
(cladocera)
Lyrmaea sp. (snail)
Daphnia magna
(cladocera)
Daphnia magna
Daphnia magna
Gasterosteus
aculeatus
Salmo gairdneri
Salmo gairdneri
Criaotopus bicinctus
(midgefly)
Lepomis maaroahirus
Lepomis maarochirus
Lepomis maeroahims
Salmo gaivdneri
Salmo gairdneri
Lepomis maspochims
Lepomis maopoahims
Lepomis maapoohipus
Lepomis macrochirus
Lepomis maepoehipus
Lepomis maopochipus
Lepomis macpoahivus
Test
conditions
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
FW, FS
FW, FS
(river)
FW
FW
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
FW
SB, FW, LS
SB, FW, LS
Chromium
concentration Remarks
(ppm)
270.0
212.0
«3.6
0.1
0.03
0.17
2.0
0.6
0.33
1.0
20.0
31.0
<25
170
110
170.0
5.0
10.0-12.5
48.4
113.0
176.8
0.2
<50
<70
48-hr TI^ (median tolerance limit) ,
acute; turbid water
48-hr TLjj,, acute; turbid water
Threshold concentration, dose just
immobilizing in 64 hr; Lake Erie water
24-hr TL,,,, acute
48-hr TI^, acute (standard reference
water)
24-hr TI^, acute (standard reference
water)
3-week TI^, chronic; 18 °C
50% reproduction loss in 3 weeks
16% reproduction loss in 3 weeks
Toxic limit , acute
No toxic effect noted
No kill in 96 hr
Survived and matured; resistant species
96-hr TI^; chromate
96-hr TI^; dichromate
40% kill, 15 days
80% kill, 15 days (tissue accumulation
study)
96 hr, 100% survival
96-hr TLj,,, acute
96 hr, 100% kill
96-hr TI^ continuous exposure
Can survive 30 days
Can survive at least 7 days (hard water,
ro
GO
pH 7.7-8.2)
-------
Table 5.7 (continued)
Chemical
compound
Chromium
(hexavalent)
Chromium (trivalent)
Chromium diboride
Chromium potassium
sulfate
Chromium sulfate
Chromium sulfate
(6H20)
Chromium sulfate
Chromium sulfate
(trivalent)
*
Test
organism
Lepomis maavoohivus
Salmo gairdnevi
Young salmon
Young salmon
Young salmon
Young salmon
Oncorhynchus kisutah
0. tshawytsaha
Ptyohoaheilus
oregonensis
Pimephales promelas
Lepomis macroahirus
Lepomis macroahims
Cavassius auvatus
Lebistes retiaulatus
Anthoaidavis sp.
(sea urchin)
Anthoaidaris sp.
Hemicentrotus sp.
(sea urchin)
Mytilus sp. (mussel)
Mytilus sp.
Fish
Fish
Gasterosteus aauleatus
Gasterosteus aauleatus
Gasterosteus aauleatus
Oncorhynchus kisutah
Onaovhynahus kisutah
Test
conditions
SB, FW,
SB, FW,
SB, FW,
SB, FW,
SB, FW,
SB, FW,
SB, FW,
SB, FW,
SB, FW,
SB, FW,
SW, LS
SW, LS
SW, LS
SW, LS
SW, LS
FW, LS
FW, LS
SB, FW,
SB, FW,
SB, FW,
CB, FW,
CB, FW,
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
Chromium
concentration Remarks
(ppm)
110.0
2.5
<10.0
<17.8
50.0
>50.0
10.0
10.0
10.0
5.07 (S)fo
6.74 (H)
7.46 (S)
71.9 (H)
4.10 (S)
3.33 (S)
3.2
10.0
10.0
3.2
10.0
170-200
130-160
5.0
2.0
1.2
50.0
>50.0
96-hr TLn,, acute, soft water, alkalinity
and hardness reduced toxicity
Tissue accumulation-elimination study,
2.5-ppm exposure level up to 24 days
Minimum lethal concentration, freswater
Minimum lethal concentration, seawater
Minimum lethal concentration, freshwater
Minimum lethal concentration, seawater
No kill in 24 hr; 10.0°C
No kill in 24 hr; 10.0°C
No kill in 24 hr; 10.0CC
96-hr TI^, acute, in hard and soft water
No effect on development of eggs; 27 °C
Effect on development of eggs; 27 °C
Effect on development of eggs; 11-16°C
No effect on development of embryos ;
13-17°C
Effect on development of embryos;
13-17°C
Minimum lethal dose; distilled water
21°C
Minimum lethal dose; distilled water,
21°C
Survived 24 hr; pH 6.0, 15-18°C
Survived 48 hr
Lethal concentration limit
100% kill in 3 days
Critical level
-------
Table 5.7 (continued)
Chemical
compound
Potassium chromate
Potassium chromate
[Cr(II)]
Potassium chromate
(hexavalent
chromium)
Test
organism
Anthoaidaris sp.
Hemieentrotus sp.
(sea urchins)
Mytilus sp. (mussel)
CrassotTea gigas
(oyster)
Gambusia affinis
Gambusia affinis
Gambusia affinis
Lepomis macroahirus
Lepomis macroahirus
Lepomis macro ahipus
Lepomis maovoohims
Pimephales pvomelas
Pimephales pvomelas
Pimephales pvomelas
Salmo gaivdnevi
Salmo gaivdneri
Salmo gairdnein
Salmo gairdneri
Salmo gairdneri
Salmo gairdnevi
Nitzsahia lineavis
(diatom)
Physa heterostropha
(snail)
Lepomis mearoahifus
Miaropterus salmoides
Microptevus salmoides
Oncorhynchus kisutoh
Oneorhynchus kisutah
Oneorhynchus kisutoh
Oncorhynahus kisutah
Onaovhynchus kisutah
Test
conditions
SW,
SB,
SB,
SB,
CB,
CB,
CB,
SB,
SB,
SB,
SB,
SB,
SB,
SB,
SB,
SB,
SB,
SB,
SB,
SB,
SB,
CB,
CB,
CB,
CB,
CB,
LS
FW,
FW,
FW,
FW,
FW,
FW,
FW,
FW,
FW,
FW,
FW,
FW,
FW,
FW,
FW,
FW,
FW,
FW,
FW,
FW,
FW,
FW,
FW,
FW,
FW,
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
Chromium
concentration Remarks
(ppm)
3.2
10.0
3.2
10.0
722
480
400
450
630
550
^620.0
109
60.4
45.6
100
20
1000
500
200
20
0.8-0.82
16.8
168.8
195
94
31.8
100.0
31.8
31.8
56.3
No effect on development of eggs; 27°C
and 15-16°C
Effect on development of eggs; 27°C and
11-16°C
No effect on development of embryos;
13-17 and 27°C
Effect on development of embryos; 13-17
and 27 °C
24-hr TI^, acute; (all data, turbid
water, 17-21°C)
48-hr TL,,,, acute
96-hr Tl^, acute
96-hr TL,,,, acute; small fish, 20°C
96-hr TI^, acute; medium fish, 20°C
96-hr TI^, acute; large fish, 20°C
96-hr TL,,,, acute, soft water; alkalinity
and hardness reduced toxicity
24-hr TLjjj, acute
48-hr TL,,,, acute
96-hr TL,],, acute (soft water)
24-hr TLjjj, acute
Increased hepatocrit values from 31.8 to
43.8
79 min, mean equilibrium loss; 18 °C
172 min, mean equilibrium loss; 18°C
374 min, mean equilibrium loss; 18°C
3580 min, mean equilibrium loss; 18°C
120-hr TL,,,
96-hr TL,,,; 18-22°C
96-hr TL,,,, acute; 16-20°C
48-hr TL,,!, acute; 20-21°C
Increase, then decline in 02 consumption;
dead in 80 hr
73% kill in 13 days
67% kill in 5 days
100% kill in 11 days
33% kill in 5 days
33% kill in 3 days
to
Ul
-------
Table 5.7 (continued)
Chemical
compound
Potassium chromic
sulfate [Cr(III)]
Potassium dichromate
Test
organism
Daphnia magna
(cladocera)
Carassius auratus
Carassius auratus
Gambusia affinis
Gambusia affinis
Gambusia affinis
Lepomis maorochirus
Daphnia magna
Physa heterostropha
(snail)
Lepomis maoroohirus
Brachydanio rerio
Braohydanio rerio
Bradhydanio rerio
Lepomis maorochirus
Snail
Snail
Lepomis maoroohirus
Lepomis maoroohirus
Lepomis maorochirus
Lepomis maorochirus
Lepomis macrodhirus
Lepomis macrodhirus
Lepomis maoroohirus
Lepomis maoroohirus
Daphnia magna
(cladocera)
Morone saxatilis
Morone saxatilis
Morone saxatilis
Morone saxatilis
Morone saxatilis
Test
conditions
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
SB, FW, LS
CB, FW, LS
CB, FW, LS
CB, FW, LS
CB, FW, LS
CB, FW, LS
Chromium
concentration
(ppm)
42
100
500
370
320
280
739.0
0.4
17.3
113.0
180
1500
280
440
17.3
40.6
320
137
320.0
320.0
382.0
369.0
320
320.0
«0.6
150
100
300
125
100
Remarks
Toxicity threshold, 2 days at 23°C
Apparently not harmful in 108 hr, hard
water
Lethal in 3 days
24-hr TLn,, acute
48-hr TL,,,, acute
96-hr TL^, acute (turbid water, 21-23°C)
24-hr TL,,,, acute
100-hr TL^,, acute
96-hr T^; 18-22°C
96-hr 11^,, acute; 16-20°C
48-hr TL,,,, acute; adults (all data at
24°C; soft water)
48-hr TLjj, acute; eggs
24-hr Tl^,, acute; adults
48-hr TL,,,, acute
TI^, soft water, 20°C
TL,,,, hard water, 20°C
96-hr TI^, acute; low 02
100% survival; low 02
96-hr TL^,, acute; small, medium, and
large fish
96-hr Tl^n,, acute; soft water, 18 and
30°C
96-hr TL^; hard water, 18°C
96-hr TLn,; hard water, 30°C
96-hr TI^, acute <18 and 30°C) , toxicity
values up to 20% more in hard water
96-hr TI^, acute; both normal and low
02 content
Highest concentration not immobilizing
under prolonged exposure; 25°C
24- and 48-hr TI^, acute; 21.1°C, larvae
72- and 95-hr TL,,,, acute; larvae
24-hr TI^, acute; 21.1°C, fingerlings
48-hr TLn,, acute; fingerlings
72-hr TI^, acute; fingerlings
-------
Table 5.7 (continued)
Chemical
compound
Potassium dichromate
Potassium dichromate
[Cr(VI)]
Sodium chromate
Sodium chromate,
sodium carbonate
Sodium chromate,
sodium silicate
Sodium chromate,
sodium sulfate
Sodium chromate,
sodium silicate
sodium sulfate
Test
organism
Morone saxatilis
LepomLs macvoahivus
Pimephales promelas
Lepomis maeroohivus
Carassius auratus
Lebistes reticulatus
Hy dropsy ehe spp.
(caddis fly)
Stenonema mbnm
(mayfly)
Salmo gairdnepi
Salno gairdneTi
Salmo gaifdneTi
Salmo gairdneri.
Daphnia magnet
(cladocera)
Garribusia affinis
Nereis sp .
(polychaete)
Cavcinus maenas
(crab)
Leander squilla
(prawn)
Leander squilla
(prawn)
Daphnia magna
(cladocera)
Daphnia magna
(cladocera)
Daphnia magna
(cladocera)
Daphnia magna
(cladocera)
Test
conditions
CB,
SB,
SB,
SB,
SB,
SB,
SB,
SB,
SB,
SB,
SB,
SB,
SB,
SB,
SB,
SB,
SB,
SB,
SB,
SB,
SB,
SB,
SB,
FW,
FW,
FW,
FW,
FW,
FW,
FW,
FW,
FW,
FW,
FW,
FW,
FW,
FW,
SW,
SW,
SW,
SW,
SW,
FW,
FW,
FW,
FW,
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
Chromium
concentration Remarks
(ppm)
75
3*430.0
f.
17.6 (S)D
27.3 (H)
118.0 (S)
133.0 (H)
37.5 (S)
30.0 (S)
280
3.5
1000
500
200
20
0.7
500.0
0.5-10
60
50
sao
^5
0.33
408.0
0.21
130.0
0.28
3044.0
0.28
122.0
2255.0
96-hr TI^, acute; fingerlings
96-hr TL,,,, acute, soft water; alkalinity
and hardness reduced toxicity
96-hr TI^, acute; in hard and soft water
48-hr TI^, acute soft water, 20-22°C
(all data for larvae)
54.6 min, mean equilibrium loss; 18°C
60.6 min, mean equilibrium loss; 18°C
188 min, mean equilibrium loss; 18°C
4342 min, mean equilibrium loss; 18°C
Toxicity threshold, 2 days at 23°C
48-hr TI^, acute; high turbidity
Sublethal effect, 21 days
12-day TI^,, acute
Sublethal effect, 12 days
Threshold toxicity, adults
Threshold toxicity, young
50% immobilization in 100 hr, acute
100-hr TLj,,; standard reference water
100-hr TL,,,; standard reference water
100-hr TL • standard reference water
to
-------
Table 5.7 (continued)
Chemical
compound
Sodium chromate,
sodium silicate,
sodium sulfate
Sodium chromate,
sodium bisulfite
Sodium chromate,
sodium bisulfite
Sodium chromate,
sodium sulfate
Sodium chromate,
sodium silicate
Sodium chromate,
sodium carbonate,
sodium sulfate
Sodium dichromate
Test
organism
Daphnia magna
(cladocera)
Daphnia magna
(cladocera)
Daphnia magna
(cladocera)
Daphnia magna
(cladocera)
Daphnia magna
(cladocera)
Daphnia magna
(cladocera)
Onaorhynchus
tshawytseha
Salmo gairdneri
Lepomis macrodh-irus
Lepomis macrodhirus
Lepomis macrodhirus
Gambusia affinis
Daphnia magna
(cladocera)
Cyprinus carpio
Daphnia magna
(cladocera)
Daphnia magna
(cladocera)
Test
conditions
SB
SB
SB
SB
SB
SB
CB
CB
SB
SB
SB
SB
SB
FW
SB
SB
, FW,
, FW,
, FW,
, FW,
, FW,
, FW,
, FW,
, FW,
, FW,
, FW,
, FW,
, FW,
, FW,
, FS
(tank)
, 'FW,
, FW,
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
LS
Chromium
concentration
(ppm)
0.201
119.0
2180.0
0.286
70.0
0.278
67.0
0.276
2984.0
0.159
93.0
0.192
240.0
2079.0
0.08
0.013-0.022
500
410
76
420.0
<0.31
20
22.0
10.0
Remarks
50% immobilization in 100 hr, acute
50% immobilization in 100 hr, acute
100-hr TL,,,; standard reference water
(Data on other combinations of sodium
salts were provided)
50% immobilization in 100 hr, acute
50% immobilization in 100 hr, acute
50% immobilization in 100 hr, acute
(Data on other three combinations of
sodium salts were provided)
Sublethal, survival impaired; hatchery
rearing
Sublethal, growth inhibited, hatchery
rearing
21-hr TI^, acute; 20°C
48-hr TL^, acute; 20°C
Safe concentration
48-hr TLj,, acute; turbid water
Near immobilization in 48 hr; Lake Erie
water, 25°C
Survived but did not reproduce; 25°C
24-hr TI^, acute
48-hr Tl^d, acute (standard reference
water)
SB
study.
static bioassay; CB = constant-flow bioassay; FW = freshwater; SW = sea (salt) water; LS = lab study; FS = field
S = soft water; H = hard water.
Source: Adapted from U.S. Atomic Energy Commission, 1973, Table I, pp. I.3-1.10. Data collected from several sources.
00
-------
12ft
Table 5.8. Sublethal doses of inorganic chromium for aquatic organisms
Species
Daphnia magna
Chronic
dose
(ppm)
<0.6
<3.6
Conditions
Chromic acid; threshold of immobilization
Threshold of immobilization; chromic chloride;
64 hr
Lepomis maarochirus 728 Hydration of tissues of body due to coagulation
of mucous covering body; 22.5 C; pH 5.9
Fish 0.2 Retarded rate of growth and resulted in
increased mortality; hexavalent chromium
Sdlmo ga-irdneri Not given Change in erythrocyte surface area and
increase or decrease in hematocrit value
2-4 Raising of hematocrits
2.5 Chromium as chromate; lab bioassay; tap water;
glucose transport by gut segments reduced
40% from controls
Fish 10-50 Decreased extractable protein content of blended
fish muscle
Source: Adapted from National Academy of Sciences and National Academy of Engineering,
1972, Table 2, p. 462. Data collected from several sources.
chromium levels (Sherr and Armitage, 1973). Figure 5.6 illustrates a re-
peating pattern of mortality, a slow rate followed by a rapid rate. The
percentage of survival of 12-day-old Daphnia is shown in Figure 5.7. At
hour 0, each group contained 40 animals. Because of the small number of
animals used in this study, the results should be viewed with some reserva-
tion. The slowing of the mortality rate shown in Figure 5.7 may have been
a result of the small sample size.
Warnick and Bell (1969), who examined the effects of several heavy
metals on various aquatic insects, reported a 96-hr median tolerance limit
(TLm) for trivalent chromium (as chromium chloride). The water used for
the studies had a temperature of 18 ± 2°C, pH 7.25, and a hardness of 44
ppm. A 96-hr TLm value was not determined for Acroneux"La lycorias (stone
fly) because the insects did not die in 96 hr at the maximum chromium con-
centration tested (64 ppm). The 96-hr TLm value was 2 ppm chromium for
Ephemerella. subvar-ia (mayfly) and 64 ppm chromium for Hydropsyehe betteni
(caddis fly). These results indicate that aquatic insects are not as sensi-
tive to chromium as many fish. Analysis of water samples from polluted
stretches of the Clinton River in Michigan gave hexavalent chromium concen-
trations as high as 25 ppm (Surber, 1959). The midgefly, Cricotopus bioino-
tus, was able to survive and reproduce in these concentrations, which indi-
cates that it is very resistant to hexavalent chromium.
-------
13Q
100'
ORNL-DWO 76-24S3
CONTROL
3 4
TIME (hr)
24
Figure 5.6. Time course of survival of DapTmia pulex exposed to
high concentrations of sodium dichromate. Source: Adapted from Sherr
and Armitage, 1973, Figure 1, p. 53. Reprinted by permission of the
publisher.
The effect of temperature on hexavalent chromium toxicity was investi-
gated using the rotifer Phi-lodina roseola (Schaefer and Pipes, 1973).
Median tolerance limit values for chromium at various temperatures are pre-
sented in Table 5.9. Chromium was more toxic at higher temperatures, but
as exposure time increased, the effect of temperature on TLm values was
diminished. The longer the exposure time, the less effect temperature had
on the chromium concentration which caused a 50% mortality rate.
Toxicity data for freshwater zooplankton were presented by Baudouin
and Scoppa (1974Z?). Median lethal concentrations (at 48 hr) for Cyclops
adyssorwnt Eudiaptomus padanus, and DapTmia hyalina were 10, 10.1, and
0.022 ppm hexavalent chromium, respectively. Toxicity was measured as time
for 50% mortality versus concentration of chromate. Combined temperature
and concentration studies relevant to the question of the effects of thermal
discharges on the uptake and toxicity of pollutants were done with one of
the organisms, the copepod Eudiaptomus. Mortality at 15°C was higher than
and parallel to that at 10°C fo.r all concentrations; however, the curve of
mortality at 20°C crossed these two and was higher than either at concen-
trations above about 7 ppm and lower at concentrations below about 3 ppm.
In a preliminary investigation, the crab Caveinus maenas was sensi-
tive to hexavalent chromium (Raymont and Shields, 1963). A sharply defined
threshold was not determined. At concentrations of 20 and 40 ppm chromium,
-------
131
ORNL-DWQ 76-2454
90
70
W50
o
85
0.
30
10-
o
A
A
CONTROL
o.ooi ppm
o.oos ppm
o.oi ppm
o.os ppm
o.io ppm
12 24 36 48 60 72
TIME IN DICHROMATE (hr)
84
96
Figure 5.7. Percent survival of 12-day-old Daphnia pulex exposed
to various concentrations of sodium dichromate. Source: Adapted from
Sherr and Armitage, 1973, Figure 4, p. 59. Reprinted by permission of
the publisher.
the survival rate of the exposed crabs equaled that of the controls in sea-
water; however, at 60 ppm chromium, a 50% mortality was reached after 12
days. The threshold level was slightly less than 5 ppm chromium for small
prawns (Leandev squilla) and 10 ppm chromium for larger prawns. A fresh-
water snail (Physa heterostrapha), a diatom (N-itzschia 1i,neari,s), and the
bluegill (Lepomis maarochirus) were exposed to divalent and trivalent chro-
mium (Patrick, Cairns, and Scheier, 1968). The 96-hr TL^ was 113 ppm tri-
valent chromium and 168.8 ppm divalent chromium for the fish and 17.3 ppm
trivalent chromium and 16.8 ppm divalent chromium for the snails. Diatoms
were the most sensitive to trivalent chromium and fish were the least
sensitive.
-------
132
Table 5.9. Median tolerance limit values for
chromate in the rotifer Philodina roseola
Time
Temperature
Chromate as chromium,
95% confidence limits
(ppm)
(hr)
24
48
72
96
(°C)
5
15
20
25
30
35
5
15
20
25
30
35
5
15
20
25
30
35
5
15
20
25
30
Median
tolerance
limit
65
43
37
28
23
18
31
22
18
14
11
9.1
16
12
11
7.0
6.4
5.3
12
8.9
7.4
5.5
4.4
Lower
limit
50
39
30
23
19
15
27
19
15
12
9.2
7.4
14
10
9.1
5.7
5.2
4.5
10
7.4
6.2
4.3
3.5
Upper
limit
84
52
45
33
28
22
36
26
21
17
13
11
19
14
13
8.7
7.9
6.3
14
12
9.1
7.0
5.6
Source: Adapted from Schaefer and Pipes,
1973, Table 3, p. 1785. Reprinted by permission
of the publisher.
Salinity affects the toxicity of chromium ions (Olson and Barrel, 1973),
A brackish water clam, Rangia ouneata, was exposed to various concentrations
of hexavalent chromium at several salinities. Chromium was more toxic in
fresh water than in saline water (Table 5.10) and was most toxic at a salin-
ity of <1 ppt and least toxic at the highest salinity (22 ppt).
Calabrese et al. (1973) investigated the effect of heavy metals on
oyster (.Cvassostrea virginied) embryos. Trivalent chromium as chromium
chloride was relatively nontoxic as compared with mercury, silver, copper,
and zinc. The LC50 for chromium was 10.3 ppm in water with pH 7.8 to 8.5,
temperature of 26 ± 1°C, and 25% salinity.
-------
133
Table 5.10. Salinity effects on
median tolerance limits for chromium
in the crab Rangia cuneata
Chromium ion concentration
_ , . . for median tolerance limit
Salinity . .
(ppt) (ppm)
48 hr 72 hr 96 hr
<1
5.5
22
0.96
66.0
86.0
0.32
32.0
73.0
0.21
14.0
35.0
Source: Adapted from Olson and
Barrel, 1973, Table I, p. 10. Reprinted
by permission of the publisher.
Several workers have investigated the effects of trivalent and hexa-
valent chromium on fish. Chemical and physical characteristics of water
affect the toxicity of chromium. Also, different fish species show varying
degrees of sensitivity to chromium ions. For example, Strik et al. (1975)
observed a mortality of 5 out of 20 trout after 15 days of exposure to 10
ppm chromium (K2Cr207), but no mortality was observed in roach exposed to
the same chromium concentration for 32 days. Mearns et al. (1976) studied
relative toxicities of chromium(VI) and chromium(III) to two coastal species,
the speckled sanddab (Cithariohthys stigmaeus) and a polychaete worm (Nean-
thes avenaceodentata). Hexavalent chromium was found to be much more toxic
to the marine worm than the marine fish (LC50 in four days of 3.1 mg/liter
and 30 mg/liter, respectively). Hexavalent chromium (as K2Cr207 and Cr03)
was found to be more toxic to both species than trivalent chromium (as
CrCl3).
In contrast to the positive effect of temperature on chromium toxicity
to rotifers, Rehwoldt et al. (1972) found that temperature had no signifi-
cant effect on the TLm of trivalent chromium in several fish species.
Median tolerance limit ranges were 10.3 to 31.6 ppm chromium at 15°C and
13.9 to 26.3 ppm chromium at 28°C. In water with temperature of 28°C,
pH 8.0, and hardness of 55 ppm, the TLm values for trivalent chromium at
three time periods are listed in Table 5.11.
In very soft water (pH near 5.7), hexavalent chromium (as a chromate
or dichromate) was much less toxic to fish than the trivalent form in simple
solutions of chromic salts (Doudoroff and Katz, 1953). Concentrations below
20 ppm hexavalent chromium were nontoxic in any water; trivalent chromium
was toxic at concentrations less than 2 ppm in soft water.
-------
134
Table 5.11. Median tolerance limit values
of trivalent chromium for
several fish species
Species
Fundulus diaphanus
(banded killifish)
EOOGUS saxatilis
(striped bass)
Lepomis gibbosus
(pumpkinseed)
ROOGUS canevioanus
(white perch)
Anguilla rostvata
(American eel)
Cypri-nus carp^o
(carp)
Cr(III)
median
24 hr
26.3
19.3
19.1
17.5
19.5
21.2
concentration for
tolerance limit
(ppm)
48 hr
20.8
18.8
17.8
16.0
16.3
18.4
96 hr
16.9
17.7
17.0
14.4
13.9
14.3
Source: Adapted from Rehwoldt et al., 1972,
Table II, p. 93. Reprinted by permission of the
publisher.
The toxicity of hexavalent chromium to bluegills (Lepomis maaroah-irus)
was investigated by Trama and Benoit (1960). Two salts, potassium dichro-
mate and potassium chromate, were used in the study. The 96-hr TL was
113 ppm chromium for the dichromate and 170 ppm chromium for the chVomate
salts. The water had a temperature of 20 ± 1°C and a hardness of 45 ppm.
When either salt was added, the pH of the water tended to shift toward
neutrality. When 155 ppm potassium dichromate was added, the pH ranged
from 6.3 to 6.8; with 320 ppm potassium chromate, the pH range was 7.5 to
8.5. Figure 5.8 illustrates the survival of bluegills with various concen-
trations of both salts. Under the test conditions, ionic partition gave
more hydrochromate ion in the dichromate solution than in the chromate solu-
tion; the authors believed that the differences in TL^ values for the two
salts were due to this condition. The singly charged hydrochromate ion was
more readily absorbed than the doubly charged chromate or dichromate ions
and was the dominant toxic species in both cases. The higher level of
hydrochromate ions in the dichromate-derived solution accounted for its
higher toxicity.
Several investigators have studied trout to determine the effects of
chromium on fish. Carton (1973) found that with young steelhead trout no
-------
135
ORNL-DW6 76-2455
100
so
CO
I-
Ul
o
tC. 40
tu
0.
20
KzCr04
IOO ISO ZOO
CHROMIUM CONCENTRATION (ppm)
250
Figure 5.8. Chromium toxicity of potassium dichromate and potassium
chromate to bluegills. Adapted from Trama and Benoit, 1960, Figure 2,
p. 874. Reprinted by permission of the publisher.
mortalities occurred during a 96-hr exposure to 31 ppm sodium chromate
(water pH, 7; hardness, 20 ppm; temperature, 10°C). Schiffman and Fromm
(1959) reported a 24-hr TLm for rainbow trout exposed to 100 ppm chromium.
The water hardness was 334 ppm; temperature, 14°C to 15°C; and pH, 8.5 to
8.8 (see Section 5.3.1).
Chromium toxicity to four warmwater fish species was studied by
Pickering and Henderson (1966) (Table 5.12). Soft water had pH 7.5 and
hardness of 20 ppm; hard water had pH 8.2 and hardness of 360 ppm. Chro-
mium toxicity differed for each species studied and was also influenced by
water characteristics. Trivalent chromium salts formed a precipitate when
they were added to the hard water, whereas hexavalent chromium did not.
Because of its various hydrates, trivalent chromium was an unusual toxicant.
At 48-hr, mortality of bluegills in two assays was greater at 10.41 ppm
trivalent chromium than at two higher concentrations. Results showed 90%
mortality at 10.41 ppm and only 20% mortality at higher concentrations.
For each species in soft water, the 96-hr TLffl value was significantly lower
for trivalent chromium than for hexavalent chromium. For all species, the
96-hr TL value was lower than the 24-hr TL^ value when hexavalent chromium
was used.
These studies concerned with toxic effects of chromium on aquatic
species have demonstrated that species differences, chemical and physical
characteristics of water, and the form of the chromium ion all affect the
action of chromium on animals. Trivalent and hexavalent chromium display
different levels of toxicity, depending on species and water characteristics.
Water hardness, pH, and temperature are prime considerations in determining
sensitivity to chromium.
-------
Table 5.12. Median tolerance limit values and 95% confidence limits of chromium
for four species of warmwater fishes
(ppm)
Salt
Chromium
potassium sulfate,
CrK(SOi.)2«12H20
Potassium
dichromate,
K2Cr207
Potassium
chroma te,
K2Cr204
Dilution
water
Soft
Hard
Soft
Hard
Soft
Soft
Soft
Hard
Soft
Hard
Soft
Soft
Soft
Test
fish
Fatheads
Fatheads
Bluegills
Bluegills
Goldfish
Guppies
Fatheads
Fatheads
Bluegills
Bluegills
Goldfish
Guppies
Fatheads
24
Median
tolerance
limit
5.37
77.5
67.4
84.0
11.0
4.10
39.6
63.5
284.
228.
122.
•f~t
133. a
109.
hr
Confidence
limits
4.58-6.17
65.4-102.
59.5-78.6
68.7-124.
7.68-14.3
3.21-5.13
34.6-46.6
53.0-75.9
232. -421.
202. -266.
107. -144.
89.5-161.
48
Median
tolerance
limit
5.22
67.4
38.7
71.9
5.37
3.85
19.7
35.4
171.
180.
58.8
61.7
60.4
hr
Confidence
limits
4.47-5.93
59.5-78.6
11.4-82.8
62.2-88.1
4.58-6.17
2.97-4.80
13.6-25.6
25.8-44.4
137. -221.
145. -236.
45.1-83.3
47.4-89.0
46.0-81.9
96
Median
tolerance
limit
5.07
67.4
7.46
71.9
4.10
3.33
17.6
27.3
118.
133.
37.5
30.0
45.6
hr
Confidence
limits
4.37-5.71
59.5-78.6
5.56-9.84
62.2-88.1
2.81-4.98
2.47-4.15
14.0-20.9
20.1-32.7
88.8-147.
103. -166.
24.4-50.9
23.0-41.2
32.2-59.6
value determined by graphical interpolation.
Source: Adapted from Pickering and Henderson, 1966, Table 2, pp. 456-458. Reprinted by permission of the publisher.
Co
-------
137
SECTION 5
REFERENCES
1. Anderson, B. G. 1948. The Apparent Thresholds of Toxicity to Daphnia
magna for Chlorides of Various Metals When Added to Lake Erie Water.
Trans. Am. Fish. Soc. 78:96-113.
2. Ayling, G. M. 1974. Uptake of Cadmium, Zinc, Copper, Lead, and
Chromium in the Pacific Oyster, Crassostrea gi-gas, Grown in the Tamar
River, Tasmania. Water Res. (England) 8:729-738.
3. Baudouin, M. F., and P. Scoppa. 1974a. Accumulation and Retention
of Chromium-51 by Freshwater Zooplankton. Commission of the European
Communities, Joint Nuclear Research Centre, Italy, pp. 15-23.
4. Baudouin, M. F., and P. Scoppa. 1974&. The Influence of Environ-
mental Factors on the Toxicity of Heavy Metals to Aquatic Organisms.
In: Annual Report 1973. Commission of the European Communities,
Joint Research Centre, Italy. 4 pp.
5. Biesinger, K. E., and G. M. Christensen. 1972. Effects of Various
Metals on Survival, Growth, Reproduction, and Metabolism of Daphnia
magna. J. Fish. Res. Board Can. (Canada) 29:1691-1700.
6. Calabrese, A., R. S. Collier, D. A. Nelson, and J. R. Maclnnes.
1973. The Toxicity of Heavy Metals to Embryos of the American Oyster
Crassostrea vivg-in-ica. Mar. Biol. 18:162-166.
7. Chipman, W. A. 1966. Uptake and Accumulation of Chromium-51 by the
Clam, Tapes deaussatus in Relation to Physical and Chemical Form. In:
Disposal of Radioactive Wastes into Seas, Oceans, and Surface Waters.
International Atomic Energy Agency, Vienna, pp. 571-582.
8. Chipman, W. A. 1967. Some Aspects of the Accumulation of Cr-51 by
Marine Organisms. In: Radioecological Concentration Processes,
B. Aberg and F. P- Hungate, eds. Pergamon Press, London, pp. 931-941.
9. Doudoroff, P., and M. Katz. 1953. Critical Review of Literature on
the Toxicity of Industrial Wastes and Their Components to Fish: II.
The Metals, as Salts. Sewage Ind. Wastes 25:802-839.
10. Ferrell, R. E., T. E. Carville, and J. D. Martinez. 1973. Trace
Metals in Oyster Shells. Environ. Lett. 4(4):311-316.
11. Fromm, P. 0. 1970. Toxic Action of Water Soluble Pollutants on
Freshwater Fish. U.S. Environmental Protection Agency, Washington, B.C.
12. Fromm, P. 0., and R. M. Stokes. 1962. Assimilation and Metabolism of
Chromium by Trout. J. Water Pollut. Control Fed. 34:1151-1155.
-------
138
13. Carton, R. B. 1973. Biological Effects of Cooling Tower Slowdown.
Water 69(129):284-292.
14. Harvey, R. S. 1969. Uptake and Loss of Radionuclides by the Fresh-
water Clam Lampsilis vadiata (Gmel.). Health Phys. (England)
17:149-154.
15. Huckabee, J. W., F. 0. Cartan, and G. S. Kennington. 1972. Environ-
mental Influence on Trace Elements in Hair of 15 Species of Mammals.
ORNL-TM-3747, Oak Ridge National Laboratory, Oak Ridge, Tenn. 38 pp.
16. Lucas, H. F., Jr., D. N. Edgington, and P. J. Colby. 1970. Concen-
trations of Trace Elements in Great Lakes Fishes. J. Fish. Res.
Board Can. (Canada) 27:677-684.
17. Mearns, A. J., P- S. Oshida, M. J. Sherwood, D. R. Young, and D. J.
Reish. 1976. Chromium Effects on Coastal Organisms. J. Water Pollut.
Control Fed. 48:1929-1939.
18. National Academy of Sciences and National Academy of Engineering.
1972. Water Quality Criteria 1972. U.S. Environmental Protection
Agency, Washington, D.C. 533 pp.
19. Navrot, J., A. J. Amiel, and J. Kronfeld. 1974. Patella vulgata:
A Biological Monitor of Coastal Metal Pollution — A Preliminary Study.
Environ. Pollut. (England) 7:303-308.
20. Olson, K. R., and R. C. Harrel. 1973. Effect of Salinity on Acute
Toxicity of Mercury, Copper, and Chromium for Rangia ouneata
(Pelecypoda, Mactridae). Contrib. Mar. Sci. 17:9-13.
21. Patrick, R., J. Cairns, Jr., and A. Scheier. 1968. The Relative
Sensitivity of Diatoms, Snails, and Fish to Twenty Common Constituents
of Industrial Wastes. Prog. Fish Cult. 30:137-140.
22. Pickering, Q. H., and C. Henderson. 1966. The Acute Toxicity of Some
Heavy Metals to Different Species of Warmwater Fishes. Air Water
Pollut. (England) 10:453-463.
23. Pringle, B. H., D. E. Hissong, E. L. Katz, and S. T. Mulawka. 1968.
Trace Metal Accumulation by Estuarine Mollusks. J. Sanit. Eng. Am.
Soc. Civ. Eng. Div. 94:455-475.
24. Raymont, J.E.G., and J. Shields. 1963. Toxicity of Copper and Chro-
mium in the Marine Environment. Int. J. Air Water Pollut. (England)
7:435-443.
25. Rehwoldt, R., L. W. Menapace, B. Nerrie, and D. Alessandrello. 1972.
The Effect of Increased Temperature upon the Acute Toxicity of Some
Heavy Metal Ions. Bull. Environ. Contam. Toxicol. 8(2):91-96.
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139
26. Sather, B. T. 1967. Chromium Absorption and Metabolism by the Crab,
Podophthalmus vigil. In: Radioecological Concentration Processes,
B. Aberg and F. P- Hungate, eds. Pergamon Press, London, pp. 943-976.
27. Schaefer, E. D., and W. 0. Pipes. 1973. Temperature and the Toxicity
of Chromate and Arsenate to the Rotifer, Philodina roseola. Water Res.
(England) 7:1781-1790.
28. Schiffman, R. H., and P- 0. Fromm. 1959. Chromium-Induced Changes in
the Blood of Rainbow Trout, Salmo gairdnerii. Sewage Ind. Wastes
31:205-211.
29. Schroeder, H. A. 1970. Chromium. Air Quality Monograph No. 70-15,
American Petroleum Institute, Washington, D.C. 28 pp.
30. Sherr, C. A., and K. B. Armitage. 1973. Preliminary Studies of the
Effects of Bichromate Ion on Survival and Oxygen Consumption of Daphnia
pulex (L.). Crustaceana (Leiden) 25:51-69.
31. Strik, J.J.T.W.A., H. H. delongh, J.W.A. vanRijn van Alkemade, and
T. P. White. 1975. Toxicity of Chromium(VI) in Fish, with Special
Reference to Organoweights, Liver and Plasma Enzyme Activities, Blood
Parameters, and Histological Alterations. In: Sublethal Effects of
Toxic Chemicals on Aquatic Animals, J. H. Koeman and J.J.T.W.A. Strik,
eds. Elsevier Science Publishers, Amsterdam, pp. 31-41.
32. Surber, E. W. 1959. Cricotopus bicinatus, a Midgefly Resistant to
Electroplating Wastes. Trans. Am. Fish. Soc. 88:111-116.
33. Taylor, F. 1975. Distribution and Retention of Chromium in Small
Mammals from Cooling Tower Drift (presented at National Symposium on
Radioecology, Corvallis, Ore., May 12-14, 1975). 5 pp.
34. Tennant, D. A., and W. 0. Forster. 1969. Seasonal Variation and
Distribution of Zn-65, Mn-54 and Cr-51 in Tissues of the Crab Cancer
magister Dana. Health Phys. (England) 18:649-657.
35. Tong, S.S.C., W. D. Youngs, W. H. Gutenmann, and D. J. Lisk. 1974.
Trace Metals in Lake Cayuga Lake Trout (Salvelinus namaycus'h) in
Relation to Age. J. Fish Res. Board Can. (Canada) 31:238-239.
36. Trama, F. B., and R. J. Benoit. 1960. Toxicity of Hexavalent Chro-
mium to Bluegills. J. Water Pollut. Control Fed. 32:868-877.
37. U.S. Atomic Energy Commission. 1973. Toxicity of Power Plant Chemicals
to Aquatic Life. WASH-1249, Washington, D.C. pp. 1.1-1.12.
38. Uthe, J. F., and E. G. Bligh. 1971. Preliminary Survey of Heavy Metal
Contamination of Canadian Freshwater Fish. J. Fish Res. Board Can.
(Canada) 28:786-788.
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140
39. Van Hook, R. I., and D. A. Crossley. 1969. Assimilation and Bio-
logical Turnover of Cesium-134, Iodine-131, and Chromium-51 in Brown
Crickets, Aoheta domesticus (L.). Health Phys. (England) 16:463-467.
40. Warnick, S. L., and H. L. Bell. 1969. The Acute Toxicity of Some
Heavy Metals to Different Species of Aquatic Insects. J. Water
Pollut. Control Fed. 41:280-284.
-------
SECTION 6
BIOLOGICAL ASPECTS IN HUMANS
6.1 SUMMARY
Chromium is an essential trace element for humans. Total individual
daily intake ranges from 5 to 115 yg. No toxic symptoms from this daily
intake are known.
Chromium is absorbed through both the respiratory and gastrointestinal
tracts, with hexavalent chromium being more easily absorbed in both tracts
than the trivalent form. Much of the chromium ingested is not absorbed due
to insolubility unless it exists as natural complexes in food (i.e., the
glucose tolerance factor). In biological reactions, hexavalent chromium
is reduced to the trivalent form, which coordinates with organic compounds
such as nucleic acids and proteins. The hexavalent form readily penetra-
tes the red blood cell membrane and becomes bound to the globin fraction
of hemoglobin; the trivalent form, which cannot pass through the membrane,
is bound to the 3-globulin fraction of the plasma proteins. Trivalent
chromium bound to siderophilin is thus transported to various tissues.
Chromium is consistently found in higher concentrations in the fetus
and newborn than in the mother. Simple chromium compounds are not trans-
ferred across the placenta, however, the glucose tolerance factor is.
Distribution of chromium depends on its chemical state and the amount
administered. Adult human tissues normally retain chromium levels ranging
from 0.02 to 0.04 ppm on a dry weight basis, but levels vary with geograph-
ical distribution. Tissue chromium concentrations, except for those in the
lungs, decrease with age.
In rats, three main components of elimination have half-lives of 0.5,
5.9, and 83.4 days; however, it is not known if these components are the
same in humans. Urinary excretion is the major route. Small amounts are
also lost through feces, and possibly the skin.
Chromium deficiency affects glucose, lipid, and protein metabolism.
Supplementation with chromium improves glucose tolerance in the elderly,
in malnourished children, and in noninsulin-dependent diabetics who have
a chromium deficiency. Chromium affects cholesterol levels in rats, sug-
gesting that human cholesterol levels may rise as a result of chromium
deficiency.
Chromium deficiency, as evidenced by improvement of glucose tolerance
with chromium supplementation, may be fairly widespread. Supplementation
with chromium in a biologically available form, such as preformed glucose
tolerance factor, has been recommended as a public health measure.
141
-------
142
Chromium, particularly in the trivalent form, is not very toxic.
Trivalent chromium compounds are poorly absorbed due to their insolubility.
Hexavalent compounds are more toxic as a result of their oxidizing power
and ease of penetration into tissues. Hexavalent chromium compounds can
cause ulceration and perforation of the nasal septum, but apparently not
cancer of the skin or nasal septum. A high incidence of bronchogenic car-
cinoma occurs in chromium chemical workers. The latent period between
first exposure and disease onset is between 10 and 20 years. A dose-
response relationship has not been established.
Systemic chromium poisoning effects, which include damage to the liver
and tubular necrosis of the kidney, may occur from either chronic exposure
or a high-exposure incident.
Threshold limit values for occupational exposure to chromium have been
recommended. The maximum workplace concentration of airborne carcinogenic
chromium(VI) recently recommended by the National Institute for Occupa-
tional Safety and Health is 1 yg/m3 of breathing zone air. More stringent
air quality standards for the general population can be expected because of
longer exposure periods and a wider range of ages and health complications.
6.2 METABOLISM
6.2.1 Uptake and Absorption
6.2.1.1 Entry — Humans are primarily exposed to chromium through ingestion.
Ingested chromium includes dietary chromium as well as inhaled chromium that
is cleared to the pharynx and swallowed. Ingestion contributes the largest
portion of chromium intake. A typical institutional diet provides an aver-
age of approximately 78 yg chromium per day (Schroeder, Balassa, and Tipton,
1962). Under ordinary conditions, chromium intake from air, probably less
than 1 yg/day, does not contribute significantly to total intake of avail-
able chromium (National Academy of Sciences, 1974). Atmospheric chromium is
mainly particulate matter in the form of trivalent chromium compounds. A
small amount of chromium is absorbed through the skin, but this uptake prob-
ably occurs only through damaged skin.
Various methods for administering chromium have been used in animal
studies. Chromium can be added either to the diet or to the atmosphere.
Intraperitoneal, intrapleural, and subcutaneous injections, as well as
implantation in tissue, allow for the introduction of chromium into a
specific body area and permit greater control of chromium concentration in
the animal.
6.2.1.2 Absorption — Chromium is absorbed through both the gastrointestinal
and respiratory tracts. The amount absorbed differs in each system and de-
pends on the form of chromium.
Discrepancies in values reported for chromium absorption from the
digestive tract appear in the literature; exact values are not known.
Trivalent chromium is poorly absorbed, whereas chromate absorption appears
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143
to be higher (Mertz, 1969). From 0.1% to 1.2% of trivalent chromium salts
were absorbed, whereas 25% of glucose tolerance factor (GTF), a chromium
complex necessary for normal glucose tolerance, was absorbed. Donaldson
and Barreras (cited by Underwood, 1971) found that orally administered tri-
valent chromium was poorly absorbed regardless of dose or the dietary chro-
mium status of the subjects. Natural chromium complexes in the diet seem
to be more available for absorption than simple salts. The contents of the
digestive tract can influence the amount of chromium absorbed; the presence
of foods may decrease chromium absorption.
Acid gastric juice reduces hexavalent chromium ions to trivalent chro-
mium ions, which are poorly absorbed (Underwood, 1971). The mechanism by
which chromium is carried across the intestinal wall and the site of absorp-
tion are not known (Mertz, 1969). Chromium can precipitate in the form of
large, insoluble complexes if it is not protected from the alkaline intes-
tinal contents by coordination. The degree of absorption may depend on how
efficiently suitable ligands protect against olation (Section 2.2.6.1).
Chromium absorption through the respiratory tract can be as compli-
cated as absorption through the digestive tract. The absorption of chromic
compounds is slightly greater through the respiratory tract than through
the digestive tract (Baetjer, 1956). Absorption of inhaled chromium seems
to occur through one of three mechanisms (National Academy of Sciences,
1974). Inhaled chromium with a particle size greater than 1 y is usually
trapped in the bronchi and does not enter the alveoli (Schroeder, 1970).
These particles are moved by ciliary action and swallowed (National Acad-
emy of Sciences, 1974). Pulmonary chromium may be in either soluble or
insoluble form (Schroeder, 1970). Insoluble particles small enough to
penetrate into the alveoli can be trapped in tissue; soluble particles
penetrate into the blood to be distributed throughout the body. Water-
and serum-soluble chromates are absorbed into the blood system, whereas in-
soluble trivalent chromium particles and relatively inert oxides and hydrox-
ides of trivalent chromium remain in lung tissue.
6.2.2 Transport
6.2.2.1 Transport in Blood — Chromium compounds are bound by proteins in
the blood (Gray and Sterling, 1950). Intravenously injected anionic hexa-
valent chromium passes through the membrane of red blood cells and binds
to the globin fraction of hemoglobin. Gray and Sterling (cited in Baetjer,
1956) hypothesized that before hexavalent chromium is bound by hemoglobin,
it is reduced to trivalent chromium by an enzymatic reaction within red
blood cells. Once inside the blood cell, chromium ions are unable to re-
penetrate the membrane and move back into the plasma. In physiological
amounts, cationic trivalent chromium is bound to siderophilin and trans-
ported to other tissues (Hopkins and Schwarz, 1964). The distribution in
plasma protein fractions is dose dependent. Large concentrations of chro-
mium ions saturate the binding sites of siderophilin and will then bind to
other proteins, but not in red blood cells.
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144
Subsequent tissue uptake depends on the chemical state of chromium
(Visek et al., cited in Mertz, 1969). Acetate and citrate complexes are
efficiently excreted, whereas chromite and chromic chloride, which are
colloidal or protein bound, give rise to a high chromium concentration in
tissues. Chromium disappears quickly from the blood and is taken up by
other tissues, where it is 10 to 100 times more concentrated than in the
blood (National Academy of Sciences, 1974). Therefore, blood chromium
concentration is not a good indicator of chromium nutritional status (Mertz,
1969). Furthermore, various tissues retain chromium longer than plasma
does; hence, there is no equilibrium between tissue-stored and circulating
chromium (Underwood, 1971).
6.2.2.2 Placental Transfer — Chromium has been found consistently in the
fetus and newborn (Mikosha, cited in National Academy of Sciences, 1974).
In the human fetus, the chromium concentration increases at 2.5 to 7 months
(Mikosha, cited in Mertz, 1969). Following this increase, the chromium
concentration shows a sharp drop at birth.
The chromium concentration in newborn rats was not increased by feed-
ing the mother chromium chloride in drinking water, but the concentration
was increased by natural sources of chromium in the diet (Mertz et al.,
1969). Results from intravenous injection of one dose of [51Cr]chromic
chloride (5 pCi per rat) at the time of mating indicated that none of the
51Cr in the mother was lost to the young at birth. Repeated doses of salt
administered by stomach tube throughout pregnancy produced a small amount
of labeled chromium in the offspring. However, 51Cr extracted from brewer's
yeast and fed to pregnant rats by stomach tube was transported into the
fetus. These results indicated active transport of chromium across the
placenta against a gradient. Fetal chromium must be derived from specific
chromium complexes in the diet. It has been demonstrated that chromium is
transported into the fetus in the glucose tolerance factor (National Acad-
emy of Sciences, 1974).
6.2.3 Distribution
Chromium is distributed in human tissues in variable, low concentra-
tions. Chromium analysis has not been standardized; therefore, caution
should be used in comparing chromium concentrations in human tissues,
especially in comparing results from different laboratories. Distribution
of administered chromium depends on chemical state and amount given; it is
not certain whether the affinity of chromium for certain body systems, such
as the reticuloendothelial system, is due to a physiological dependency or
to an overload of the system (National Academy of Sciences, 1974). The
affinity of chromium for the reticuloendothelial system as well as for the
spleen, liver, and bone marrow probably represents phagocytosis of the col-
loidal particles (Mertz, 1969). The accumulation of radiolabeled chromate
in the spleen may represent the chromium bound to red blood cells. Chromium
levels in tissues other than the lungs decline with age. The chromium con-
centration in the lungs increases in later life because of the deposition
of insoluble chromium by inhalation. Schroeder, Balassa, and Tipton (1962)
found that chromium levels in the heart, lung, aorta, and spleen decrease
during the first ten years of life; liver and kidney levels remain stable
until the second decade, when a decrease occurs. In studying trace metal
content in coronary arteries of Nigerians, Taylor and Williams (1974) found
that chromium levels decreased with age in males but not in females.
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145
6.2.3.1 Administered Chromium Distribution in Rats and Guinea Pigs —
Schroeder and Nason (1974) found that adding 5 ppm chromium to drinking
water significantly increased chromium levels in the lung, heart, and
kidney of rats (Table 6.1). Increased chromium concentrations were found
in the spleens of these rats compared to those in rats given plain water
and basal water containing manganese, cobalt, copper, zinc, and molybdenum.
The heart and spleen concentrated chromium when the sole source was dietary
intake. The feeding of cadmium and its subsequent accumulation appeared to
suppress chromium levels in the heart and in male kidneys.
High chromium levels in the heart, lung, and kidney of mature and im-
mature rats were also reported by Hopkins (1965). Chromium-51 trichloride
at concentrations of 0.001 and 0.1 ppm body weight was injected intrave-
nously. Dose level, diet, and sex had no effect on tissue distribution.
Tissue retention differed among various organs. At four days after in-
jection, the heart, lungs, pancreas, and brain retained 10% to 31% of
initial radioactivity, whereas the spleen, kidney, testis, and epididymis
concentrated chromium and had 104% to 200% activity. The brain had the
least affinity for chromium. Chromium levels of mature rats were higher
than those of immature rats in the spleen, kidney, testis, and epididymis;
immature animals showed higher chromium levels in the bones. The mature
testis took up chromium more than any other organ; during the 4-hr period
following injection, accumulation increased 400%.
Water-soluble chromate injected intratracheally was retained only
slightly (15%) in the lungs of guinea pigs, whereas 69% of chromic chlo-
ride was retained (Baetjer, Damron, and Budacz, 1959). Thus, trivalent
chromium was retained in the lungs longer and at a higher level than hexa-
valent chromium (Figure 6.1). Chromium retained in both animal and human
lung tissues was present either in a hydrated or acid-soluble form which
was absorbed by cell membranes or cellular debris or was combined with
nuclei. The lung tissue of humans possesses the same ability to bind
chromium as that of guinea pigs.
6.2.3.2 Distribution in Human Organs — Adult human tissues generally con-
tain 0.02 to 0.04 ppm chromium on a dry weight basis (Underwood, 1971).
Several investigators have studied chromium distribution in healthy human
tissues (Table 6.2).
Chromium levels in human liver and kidneys vary with geographic loca-
tion (Schroeder, Balassa, and Tipton, 1962). Chromium was not detected in
the liver and kidneys of some Americans but was found in the liver and
kidneys of all foreigners examined. Foreigners had higher chromium levels
than Americans in all tissues except lung tissue of Far Eastern subjects,
heart and lung tissues of Near Eastern subjects, and aorta, kidney, pan-
creas, and testis tissues of Swiss subjects (Table 6.3) (Schroeder, 1970).
These data indicate that Americans may be deficient in chromium.
A mean concentration of 0.22 ppm chromium (wet wt) was found in lung
tissue of subjects from various locations in the United States (Schroeder,
1970). A rough correlation existed between chromium levels in lungs and
in air from 1954 to 1959. Tipton and Shafer (cited in Schroeder, 1970)
-------
Table 6.1. Chromium concentrations in the organs of rats given plain water,
basal water without chromium, and basal water with chromium
Type
of
water
Plain water
Basal water without
chromium
Basal water with
5 ppm chromium
Number
number of
samples
23/12
31/6
66/11
age
(days)
360
838
863
Chromium Chromium in organs (ppm)a
diet + water L±ver Lung Heart Kidney
(ppm)
0.14+0 0.19+0.015 0.47+0.664 1.27+0.235 0.57+0.442
0.14 + 0 0.15 + 0.053 0.20 + 0.031 0.48 + 0.031 0.51 + 0.233
0.14 + 5 0.49 + 0.197 2.14 + 0.795 2.30 + 0.673 2.47 + 0.555
Spleen
2.02 + 0.357
1.33 + 0.466
3.01 + 1.090
aValues for both sexes combined.
Source: Adapted from Schroeder and Nason, 1974, Table 2, p. 171. Reprinted by permission of the publisher.
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147
I40-,
120-
100-
s
o
K
O
60-
40-
20-
!
i!
ORNL-DWG 76-2456
30 40 50
TIME AFTER INJECTION (days)
60
Figure 6.1. Micrograms of chromium in lungs of guinea pigs after
intratracheal injections of 200 yg of chromium as trivalent chromic
chloride or chromates. Source: Adapted from Baetjer, Damron, and
Budacz, 1959a, Figure 2, p. 60/142. Reprinted by permission of the
publisher.
also found significant correlations between levels of chromium and levels
of aluminum, titanium, and vanadium in lungs.
Sanders et al. (1971) studied the distribution of chromic oxide par-
ticles in pulmonary alveoli by exposing hamsters to chromic oxide dust
(0.5 to 1.0 ppm in air for 4 hr). Large numbers of chromic oxide aggre-
gates were free in the alveolar lumens or within the alveolar epithelium,
the granular pneumonocytes. The median diameter for the chromic oxide
particles was 0.17 ym. Over 90% of the oxide was found in macrophages
and 4% was found in type I alveolar epithelium.
6.2.3.3 Distribution in Blood and Urine — A wide range of values for
chromium content in blood and urine has been reported. Analysis of low
chromium concentrations in blood and urine has not been standardized;
therefore, these values should be regarded with caution (National Academy
of Sciences, 1974). Schroeder, Balassa, and Tipton (1962) reported chro-
mium levels of 0.52 and 0.17 ppm in serum, whereas Doisy et al. (cited in
National Academy of Sciences, 1974) found a chromium concentration of only
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148
Table 6.2. Chromium concentrations in human tissues
Tissue
Chromium
concentration
(ppm)
Ash wt
Wet wt
Reference
Adrenal
Aorta
Bladder
Bone
Brain
Larynx
Liver
Lung
Lymph node
Muscle
Omentum
9.4
0.1-56.0
2
3.4
'0.1
0.2
Cecum
Diaphragm
Duodenum
Esophagus
Fat
Heart
Ileum
Je j unum
Kidney
6.2
2.3
2.3
3.0
3.2
1.5
0.1-3.9
0.005-0.075
4.0
1.7
1.0
2.3
0.1
0.7
= 0.1-
1.6
13
0.5-115
1.0
12
Tipton and Cook, 1963
Tipton, 1960
Tipton and Cook, 1963
Tipton and Cook, 1963
Tipton and Cook, 1963
Tipton and Cook, 1963
0.01 Hamilton, Minski, and
Cleary, 1973
Tipton, 1960
Tipton and Cook, 1963
Tipton and Cook, 1963
Tipton and Cook, 1963
Tipton and Cook, 1963
Tipton and Cook, 1963
Tipton and Cook, 1963
Tipton, 1960
Wester, 1972
Tipton and Cook, 1963
Tipton and Cook, 1963
Tipton and Cook, 1963
Tipton, 1960
Schroeder, Balassa,
and Tipton, 1962
0.03 Hamilton, Minski, and
Cleary, 1973
Tipton and Cook, 1963
Tipton and Cook, 1963
Tipton, 1960
Schroeder, Balassa,
and Tipton, 1962
0.08 Hamilton, Minski, and
Cleary, 1973
0.5 Hamilton, Minski, and
Cleary, 1973
Tipton and Cook, 1963
Tipton, 1960
2.2 Hamilton, Minski, and
Cleary, 1973
0.005 Hamilton, Minski, and
Cleary, 1973
Tipton and Cook, 1963
Tipton and Cook, 1963
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149
Table 6.2 (continued)
Tissue
Chromium
concentration
(ppm)
Reference
Ash wt
Wet wt
Ovary
Pancreas
Prostate
Rectum
Sigmoid colon
Skin
Spleen
Stomach
Testis
Thyroid
Trachea
Uterus
2.2
0.1-510
1.6
0.2-100
0.9
0.1-8
4.1
3.9
17
0.5
<0.1-8
2.0
1.6
0.1-18
1.5
3.4
1.6
Tipton and Cook,
Tipton, 1960
0.06 Hamilton, Minski
Cleary, 1973
Tipton and Cook,
Tipton, 1960
Tipton and Cook,
Tipton, 1960
Tipton and Cook,
Tipton and Cook,
Tipton and Cook,
Tipton and Cook,
Tipton, 1960
Tipton and Cook,
Tipton and Cook,
Tipton, 1960
0.03 Hamilton, Minski
Cleary, 1973
Tipton and Cook,
Tipton and Cook,
Tipton and Cook,
1963
, and
1963
1963
1963
1963
1963
1963
1963
1963
, and
1963
1963
1963
2 ppb in serum. Chromium values found by others (cited in Underwood, 1971)
ranged from 0.011 to 55 ppb in human plasma and from 5 to 54 ppb in red
blood cells. Imbus et al. (1963) found blood chromium levels ranging from
13 to 55 ppb with a median of 27 ppb for U.S. subjects, while Hamilton,
Minski, and Cleary (1973) reported a blood level of 70 ppb chromium for
subjects from the United Kingdom. Hambidge (cited in National Academy of
Sciences, 1974) found chromium levels in urine of 8.4 ppb for adults and
5.5 ppb for children over a 24-hr period. Imbus et al. (1963) reported
urinary levels from 1.8 to 11 ppb chromium with a median of 2.77 ppb.
6.2.3.4 Distribution in Hair — As reported by Schroeder and Nason (1969),
chromium concentrations in hair were relatively constant with age rather
than duplicating the pattern of decreased amounts of chromium in tissues.
Levels were similar for both males and females; the mean chromium concen-
trations were 0.69 ± 0.063 ppm for men and 0.96 ± 0.049 ppm for women.
Hambidge, Franklin, and Jacobs (1972) measured chromium concentrations
in hair at various distances from the root. They found that the concentra-
tion did not depend on the time the hair had been exposed to the external
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150
Table 6.3. Geographical distribution of chromium in human tissues
(ppm, ash)
a
Tissue United States Africa
Aorta
Brain
Heart
Kidney
Liver
Lung
Pancreas
Spleen
Testis
1.9
0.2
1.6
0.8
0.8
14
1.6
0.5
1.6
5.5
0.6
0.9
2.0
1.3
16
2.5
1.3
4.2
Near East Far East
11* 15*
b b
2. if 2.T
4.0 6.3 >C
f~\ S9 rj
5.3D>° 3.3°
b b
2.r 2.0°
22 23
h h
4.2° 6.7°
3.1b>° 3.lb>°
7.0* 8.3*
Switzerland
8.8*
1.9
4.6
b
2.5
2.9
62
b
5.9
4.5
7.3*
TMales, ages 20 to 59, median values.
Differs from U.S. values, P < 0.001.
CDiffers from African values, P < 0.001.
Source: Adapted from Schroeder, 1970, Table 7, p. 12.
permission of the publisher.
Reprinted by
environment, but that concentration changes were due to past fluctuations
in chromium nutritional status. However, in disagreement with Hambidge,
Franklin, and Jacobs (1972), Creason et al. (1975) reported that chromium
levels in children's hair were significantly associated with environmental
exposure gradients.
Hambidge and Rodgerson (1969) found higher chromium levels in hair of
nulliparous women (0.2 to 2.81 ppm) than in hair of parous women (0.04 to
1.14 ppm), though a later study (Hambidge and Droegnueller, 1974) found
changes in hair concentrations due to pregnancy that were not statistical-
ly significant. Mahalko and Bennion (1976) used furnace AA to obtain
values for hair chromium concentrations of nulliparous and parous women
who had just given birth. Mean hair chromium concentrations of nulli-
parous and parous women were 309 ± 23 and 117 ± 10 ppb, respectively. No
further significant decrease in hair chromium was observed in women who
had borne more than one child. It was observed that hair chromium con-
centration increased significantly with the amount of time between preg-
nancies, especially when at least four years had passed since the end of
the last pregnancy. The data suggest a state of suboptimal chromium
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151
nutrition during pregnancy. A study of hair chromium concentrations of
children revealed that chromium levels in 3- to 8-month-old infants were
significantly higher than in those of 2- to 3-year-old children (Hambidge
and Rodgerson, 1969). Mean chromium levels in hair declined during the
latter part of the first year and during the second year approached levels
present in older humans (Table 6.4).
Table 6.4. Mean hair chromium concentrations
of human subjects ages 0 to 35 months
Age of
subjects
0-7 days
3-6 months
8 months
10-12 months
1-2 years
2-3 years
Number of
subjects
25
6
8
11
23
20
Hair chromium
concentration
(ppb)a
910 + 139
1493 + 386
850 + 106
631 + 62
525 + 59
412 + 47
+ standard error of the mean.
Source: Adapted from Hambidge and
Baum, 1972, Table 1, p. 277. Reprinted by
permission of the publisher.
6.2.4 Chromium Interactions
The solubility of trivalent chromium in biological material is based
on the variety of small compounds which coordinate to chromium in biolog-
ical fluids (Rollinson, 1966). In the absence of ligands, olation would
cause the formation of large chromic hydroxide complexes of a colloidal
nature with no biological activity. Ligands in the intestines prevent
olation and precipitation, keep chromium soluble, and make it available
for absorption.
6.2.4.1 Proteins — The tanning process is the best-known interaction of
chromium with proteins. Hexavalent chromium is reduced to trivalent chro-
mium, which is then coordinated to carboxyl groups of collagen strands
(Mertz, 1969). However, chrome tanning is a total saturation of protein
with chromium and does not occur at physiological chromium concentrations.
At these concentrations (100 ppm) , chromium cross-links protein without
tanning. Trivalent chromium strongly binds to egg protein and human plasma
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152
proteins (Grogan and Oppenheimer, 1955). Hexavalent chromium, however,
reacts with protein through weak bonds only at low pH.
6.2.4.2 Enzymes — Chromium inhibits enzyme reactions when concentrations
excessive for a particular enzyme are added in vitro. Either trivalent or
hexavalent chromium inhibits thromboplastic activity (Chargaff and Green,
cited in National Academy of Sciences, 1974) and g-glucuronidase activity
(Fernley, cited in National Academy of Sciences, 1974). Amounts of chro-
mium exceeding saturation levels of the specific receptor site react with
other sites, and if these sites are essential to activity, a depression of
function will result (Mertz, 1969). Chromium seems to be an integral part
of the digestive enzyme trypsin (Langbeck et al., cited in National Acad-
emy of Sciences, 1974). Removing chromium from trypsin resulted in a loss
of activity which was restored by adding chromium.
Chromium also has the ability to stimulate enzyme activity. Horecker
et al. (cited in Mertz, 1969) found that trivalent chromium stimulated
oxygen consumption in a succinic dehydrogenase-cytochrome system. The
enzyme phosphoglucomutase, which functions in glucose metabolism, is stim-
ulated by chromium (Strickland, cited in Mertz, 1969), as is the conversion
of acetate to carbon dioxide, cholesterol, and fatty acids by rat liver in
vitro (Curran, cited in Mertz, 1969).
6.2.4.3 Nucleic Acids — Hexavalent chromium has been shown to react with
nucleic acids. Tissues treated with chromate become green, which suggests
that the reaction is a reduction from hexavalent to trivalent chromium
followed by complex formation with nucleic acids (National Academy of
Sciences, 1974). Nucleic acids contain high chromium concentrations.
Analysis of beef heart tissue and ribonucleic acid (RNA) for trace elements
showed that chromium in RNA was enriched by several times over chromium in
whole heart tissue (Wester, 1972). Chromium levels in RNA ranged from 0.049
to 6.0 ppm. Wacker and Vallee (1959) found the chromium content of RNA from
calf pancreas, calf thymus, horse kidney, rabbit reticulocytes, and rat
liver to be 140, 77, 180, 140, and 630 ppm, respectively. Chromium is very
firmly bound to RNA; it possibly plays a role in maintaining the configura-
tion of the RNA molecule by linking purine and pyrimidine bases through
covalent bonds.
6.2.4.4 Other Trace Elements — Schroeder and Nason (1976) found that chro-
mium levels were depressed in heart, kidney, and spleen when germanium was
administered and elevated in these same tissues by indium and rhodium.
Feeding of hexavalent chromium elevated chromium levels in all tissues ex-
cept the heart.
6.2.5 Elimination
6.2.5.1 Biological Half-life — The excretion of trivalent chromium meas-
ured by whole-body counting is independent of the amount administered and
the chromium dietary status (Mertz, Roginski, and Reba, 1965). In rats,
three main components of the retention curve have half-lives of 0.5, 5.9,
and 83.4 days. In humans, chromium turnover appears to be very slow (Nat-
ional Academy of Sciences, 1974). The estimated fraction of chromium ab-
sorbed by man through ingestion (International Commission on Radiological
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153
Protection, 1966) is similar (<0.005) to the fraction assimilated by native
cotton rats (0.008) (Taylor, 1975). Similarly, the biological half-times
of the fraction (long component) assimilated by man and cotton rats are
616 and 693 days, respectively. If humans have the three-component excre-
tion rate, the first component may be an effective way of rapidly eliminat-
ing excess chromium.
6.2.5.2 Routes of Elimination — Chromium is excreted in both urine and
feces. Urinary excretion is the major route with at least 80% of injected
chromium excreted in this manner (Mertz, 1969). The intestine plays only
a minor part in chromium elimination. Visek et al. (1953) found that rats
eliminated up to 20% of intravenously injected trivalent chromium in feces.
The site of chromium excretion in the intestines is not known. Reported
ranges of daily chromium excretion in urine vary; a representative range
of 1.6 to 21 ppb chromium was reported by Hambidge (1971).
Colling et al. (cited in Mertz, 1969) studied urinary excretion in
dogs following intravenous injection of chromium. Chromium coordinated to
small molecular ligands was filtered at the glomerulus; however, up to 63%
was then reabsorbed in the tubuli from the filtrate. Only a very small
portion of protein-bound chromium is excreted; almost all urinary chromium
is in a dialyzable form. Urinary excretion of injected chromium (0.1 yg
chromium per 100 g body wt) in male rats had two components over a four-
day period (Figure 6.2) (Hopkins, 1965). Only 6% to 7% of injected tri-
valent chromium was excreted in the feces.
Davidson, Burt, and Parker (1974) studied the effect of a standard
glucose load or a water load on the renal excretion of chromium in normal
subjects. A standard glucose load (75 g) resulted in a significant decrease
in the urinary excretion of chromium in fasting rats. A water load in-
creased excretion by more than 100% due to diuresis.
6.3 EFFECTS
Chromium is necessary for glucose and lipid metabolism and for utili-
zation of amino acids in several mammalian systems. It is also important
in the prevention of common chronic diseases such as mild diabetes and
atherosclerosis in humans.
6.3.1 Effects on Biochemical Systems
Table 6.5 summarizes the effects of chromium on several biochemical
systems and functions.
6.3.1.1 Glucose Metabolism — Chromium is involved in glucose metabolism
as part of the glucose tolerance factor (GTF). This factor is a natural-
ly occurring chromium complex that is found in brewer's yeast and other
foodstuffs. The complex itself has not been completely identified, al-
though partial characterization has been achieved (Mertz, 1974, 1975; Mertz
et al., 1974; Polansky, 1974; Toepfer, 1974; Toepfer et al., 1973, 1977).
These investigators postulate that the primary configuration of the glucose
tolerance factor is a niacin-Cr-niacin axis. A suggested structure of the
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154
ORNL-DWG 76-2457
96
TIME AFTER INJECTION (hr)
• BLOOD FROM RATS (AV OF
INTACT AND KILLED) INJECTED
WITH 0.1 M9 CHROMIUM PER 100 g
BODYWT
O BLOOD FROM RATS (AV OF
INTACT AND KILLED) INJECTED
WITH 0.01 M9 CHROMIUM PER 100 g
BODYWT
D URINE
• FECES FROM FOUR INTACT
RATS (AV) INJECTED WITH
0.1 MS CHROMIUM PER 100 g
BODY WT
Figure 6.2. Rate of urinary and fecal excretion and blood clearance
of intravenously injected trivalent 51Cr from male rats. Source: Adapted
from Hopkins, 1965, Figure 1, p. 733. Reprinted by permission of the
publisher.
complex is shown in Figure 6.3. Toepfer et al. (1977) and Mertz et al.
(1974) have also synthesized a material which possesses almost identical
chemical and biological characteristics as glucose tolerance factor ex-
tracted from brewer's yeast. Detection of nicotinic acid, chromium,
glycine, glutamic acid, and cysteine in GIF extracted from brewer's yeast
led to this synthesis.
The glucose tolerance factor is required for normal glucose tolerance
and appears to act by potentiating the action of insulin. In animals whose
diets are deficient in chromium, glucose is removed from the bloodstream
only half as fast as it is normally removed. This impairment is the first
sign of chromium deficiency. With long-term deprivation, additional com-
plications may develop (Mertz, 1969), including impaired growth, aortic
and corneal lesions, and reduced life span. The GTF appears in certain
foods and is especially rich in brewer's yeast, which results in quick
relief of impaired glucose tolerance when added to the diet. Feeding with
chromium compounds may also relieve impairment of glucose tolerance. In
the experiments of Schwarz and Mertz (1959) which led to the discovery of
chromium as the active element in GTF, feeding with a number of trivalent
-------
155
Table 6.5. Biochemical actions of chromium
System or function
Animal
Deficiency
state
Effect of
chromium
Glucose metabolism
Glucose tolerance
Diabetic state
Insulin response
Blood glucose
Glycogen formation
Glucose tolerance
Glucose tolerance
Lipid metabolism
Cholesterol synthesis
Fatty acid synthesis
Serum cholesterol
Serum cholesterol
Aortic lipids and plaques
Amino acid metabolism
Protein synthesis, growth
Utilization
Survival and life span
Eye
Rat, monkey
Rat
Rat
Rabbit, mouse
Rat
Man
Man (diabetes)
Rat
Rat
Rat
Man
Rat
Rat, mouse
Rat
Mouse, rat
Rat
Reduced Restored
Induced Cured
Reduced Restored
Elevated Lowered
Delayed Increased
Restored to normal
Slightly improved
+ Increased
+ Increased
Elevated Reduced
Elevated Slightly reduced
Increased Prevented and lowered
Reduced Increased
Reduced Increased
Reduced Increased
Corneal Prevented
opacity
a+ indicates animal is capable of synthesis.
Source: Adapted from Schroeder, 1970, Table 14, p. 18. Reprinted by permission of
the publisher.
chromium compounds at a level of 20 to 50 yg chromium per 100 g body weight
resulted in overnight improvement of glucose tolerance. However, only a
small part of most complexes is absorbed; equivalent improvement was
achieved in 2 hr by intravenous injection of only 0.25 to 0.50 yg chro-
mium, as the neutralized chrome alum complex, per 100 g of rat body weight
(Mertz, Roginski, and Reba, 1965).
Relief of impaired glucose tolerance by feeding of chromium has also
been shown in other animals. For instance, trivalent chromium (10 ppm) as
the acetate added to drinking water relieved impairment of glucose toler-
ance in squirrel monkeys which were chromium deficient (Davidson and
Blackwell, 1968). The glucose removal rate per minute was 1.38% before
chromium supplementation and 2.23% after supplementation. The effect of
chromium depended on the valence state and apparently also on the chemical
form of the trivalent state. Divalent chromium given to monkeys with
normal glucose tolerance caused an impairment of tolerance. The authors
suggested that the divalent chromium may have interfered with either the
absorption of the trivalent chromium (which is the biologically active
form) or its effect at the cellular level. Trivalent chromium given at
acid pH was not effective in relieving impairment; the authors postulated
that this was due to formation of complexes which were poorly absorbed.
-------
156
ORNL-DWG 78-7448
COOH
GLYCINE
COOH ?
GLYCINE
COOH ?
NH2 '
HOOC
Figure 6.3. Possible structure for the glucose tolerance factor.
Source: Adapted from Mertz et al., 1974, Figure 4, p. 2279. Reprinted
from Federation Proceedings 33:2275-2279, 1974.
Three levels of dietary chromium (0.125, 0.625, and 50 ppm) were fed
to nonpregnant, pregnant, and F-l offspring guinea pigs by Preston et al.
(1976). All groups had similar weight gain patterns and dietary intake
levels. Mortality rates during pregnancy were less for pigs fed the two
higher chromium levels than for those on the base diet. Glucose tolerance,
glucose peak time, and serum cholesterol appeared to be more affected by
pregnancy and generation of guinea pigs than by the levels of dietary
chromium.
Chromium also plays an important role in human glucose metabolism.
In a study by Levine, Streeten, and Doisy (1968), chromium supplementation
(150 yg daily) was given orally over a period of two to four months to ten
elderly human subjects who were apparently healthy and who had no family
history of diabetes but whose oral glucose tolerance tests were abnormal.
In four of these subjects glucose tolerance became normal, but in six it
remained abnormal. Insulin and insulin-like activity levels in all the
subjects were normal and rose normally in response to the glucose loads.
-------
157
Thus, the beneficial effect of the chromium in the glucose tolerance res-
ponders did not result from an increased release of insulin. Significant-
ly, the serum chromium concentrations increased in response to glucose
load in both old and young (control group subjects), but the increase was
less in the elderly nonresponders. These results suggest that an adequate
rise in serum chromium might be necessary for a normal response to glucose.
In direct contrast to these observations, however, Pekarek et al. (1975)
found a precipitous fall in serum chromium (1.50 to 0.85 ppb) on administra-
tion of a 30 g intravenous glucose load. Analytical uncertainty may contri-
bute to this contradiction.
In analyzing studies such as the above, Underwood (1971) hypothesized
that patients respond by improved glucose tolerance when their low-chromium
state has not been irreversibly complicated by other factors. If tissue
stores of chromium have been long depleted, supplementation for longer peri-
ods than in the above study might be needed for a threshold of response to
be reached. Levine, Streeten, and Doisy (1968) noted that the group which
responded had a much milder impairment than the nonresponders, which im-
plicates damage as the chief reason for nonresponse. However, depletion
not relieved in the time period of the trial could also have been a factor
in the lack of response of some subjects in the nonresponding group. Poor
absorption and deficient synthesis of GIF are other possible reasons for
lack of response to chromium supplementation.
Clearance of glucose from the blood in the glucose tolerance test
depends on uptake of glucose into cells. Chromium has been shown to
interact with insulin in this process. Using epididymal fat tissue of rats
fed GTF-deficient diets, Mertz, Roginski, and Schwarz (1961) showed up to
94% increases in uptake of glucose and incorporation of glucose carbon into
the tissue after small amounts of chromium were added. The presence of in-
sulin was indispensable. Insulin alone was without effect. In experiments
using D-galactose as substrate (Mertz and Roginski, 1963), addition of
0.01 yg chromium per 100 mg tissue increased entry rates of the sugar by a
factor of 3.8 over controls in the presence of 1 milliunit of insulin.
Again, neither chromium nor insulin alone was effective. While galactose
is metabolized in the liver, it is poorly metabolized in peripheral tissues;
hence, these results indicate that the chromium with insulin acts at the
level of sugar entry into the cells from the extracellular fluid.
Chromium is involved in other insulin-sensitive processes, including
the oxidation of glucose, utilization of glucose for lipogenesis, swelling
of mitochondria, and incorporation of certain amino acids into proteins
(Mertz, 1974). These and other actions of insulin (activation and induc-
tion of some enzymes, inhibition of other enzymes, inhibition of lipolysis)
may not be as unrelated as they seem. Insulin acts in a generalized manner
on the plasma membrane of the target cells, which causes changes that lead
to enhanced entry not only of glucose and other sugars but also of amino
acids, lipids, and the potassium ion (Lehninger, 1975). This action is
followed by increased synthesis of protoplasm and storage products.
On the basis of polarographic shifts observed in experiments with
liver mitochondria, Mertz (1967, 1969) postulated that chromium could act
-------
158
as a catalyst in the initial reaction between insulin and specific membrane
sites. A ternary complex would be formed that would facilitate the di-
sulfide interchange between membrane sulfhydryls and disulfide bonds of
insulin that have been postulated by some authors (Cadenas et al., 1961;
Fong et al., 1962) as being part of the mechanism of insulin action. It
is not clear whether chromium acts as a simple compound, an extended com-
plex, or as part of GIF. Some studies on the metabolism of chromium have
suggested that it may act as a simple compound (Mertz, 1974); however, the
effect of GIF is always greater and it is likely that chromium, to be fully
effective, must be part of a GIF complex. According to Hopkins (1971),
following absorption and transport, GIF is stored in a pool before it re-
sponds to a glucose load. Inorganic trivalent chromium taken in as part of
the diet is transported to various metabolic sites, one of which is the
site of GIF synthesis. The synthesized GIF then joins the storage pool
for utilization. Hopkins hypothesized that persons who do not respond to
chromium supplementation may be deficient in the ability to synthesize GIF.
It is not known if mammals are capable of GIF synthesis. If the capa-
bility exists, either in the mammal itself or in its intestinal flora,
it does not seem to be very efficient in the majority of adults and may
be the limiting factor in chromium metabolism (Mertz, 1974).
6.3.1.1.1 Hypoglycemia — In a severe chromium deficiency state, rats and
mice showed glycosuria and hypoglycemia (Mertz, 1967). Mertz and Roginski
(cited in Mertz, 1969) found that rats injected subcutaneously with 100
milliunits of insulin per 100 g body weight had a hypoglycemic response
which was significantly less than that of chromium-supplemented controls.
Incorporation of glucose carbon 1 hr after injection of 1 milliunit of
insulin per 100 g body weight was greater in chromium-supplemented rats
than in nonsupplemented rats. Rats raised in conditions of maximal chro-
mium exclusion had fasting hypoglycemia and glycosuria (Schroeder, cited
in National Academy of Sciences, 1974). Half of the chromium-deficient
rats had a positive test for urine sugar, whereas 9 of 87 chromium-supple-
mented rats had positive urine sugar. Hypoglycemia precedes the terminal
phase of dietary necrotic liver degeneration (Mertz, 1969). Thus, a
higher blood glucose level in chromium-supplemented rats may reflect some
protection by chromium against hypoglycemia.
6.3.1.1.2 Diabetes — The response to chromium supplementation in diabetes
is directly dependent on whether or not the case is complicated by a chro-
mium deficiency (Mertz, 1969). However, no data identify chromium de-
ficiency as a primary causative agent in diabetes even though correlations
between chromium metabolism and the diabetic state exist (Mertz, 1974).
Insulin-dependent diabetics absorbed two to three times more orally ad-
ministered chromium chloride than normal human subjects (Doisy et al.,
1969, 1971). These diabetics also excreted twice as much chromium chlo-
ride as normal control subjects. Maturity-onset diabetics did not show
increased absorption and excretion of chromium. Hambidge et al. (cited in
Mertz, 1974) suggested that the disturbance in chromium metabolism may be
a result rather than a cause of diabetes.
Short-term supplementation of 1.0 mg chromium chloride to seven dia-
betics for one to seven days had no effect on impaired glucose tolerance
-------
159
(Glinsmann and Mertz, 1966). Four diabetics were given daily oral doses
of 150 to 1000 yg of chromium for 15 to 120 days. Three of these subjects
showed significant improvement in oral glucose tolerance. The improvement
usually was preceded by a slight impairment of tolerance. Table 6.6 shows
the changes in glucose tolerance of one subject during chromium supple-
mentation. Two diabetic outpatients were given the same chromium supple-
mentation; one showed improvement and the other was unaffected. The authors
suggested that even though chromium chloride was not particularly useful as
a therapeutic agent in diabetes, a certain chromium level may be required
for optimal glucose metabolism.
Table 6.6. Effect of chromium on mean glucose tolerance
supplemental ion
None
60 pg,
60 pg,
60 pg,
None
60 pg,
None
1 rag,
3
3
3
3
3
times
times
times
times
times
a day
a. day
a day
a day
a day
Days
0-32
33-74
75-119
120-140
180-194
195-211
256-313
337-340
Number
of
tests
10
12
13
5
1
5
10
1
Mean blood glucose concentration
(mg/100 ml)
Fasting
84
85
84
84
96
83
87
68
Time after glucose load (min)
30
217
224
210
203
207
196
220
148
60
229
238
213
201*
290,
193*
245
162
90
195
209
186
175
293
175
224
151
120
156
162
141,
112°
237,
118*
166
96
^Subject was maturity-onset diabetic, controlled on diet. Oral glucose tolerance test
consisted of constant noon meal and 100 g of glucose.
"Mean values significantly different from control (P < 0.025).
Source: Adapted from Glinsmann and Mertz, 1966, Table 2, p. 515. Reprinted by permis-
sion of the publisher.
Schroeder (1968) reported that glucose metabolism was improved in 4 of
12 diabetic outpatients given up to 1 mg chromic chloride daily for six
months. One subject was able to reduce the insulin dose and another ceased
taking oral hypoglycemia agents.
The distribution of slCr in organs of rats with induced diabetes was
not significantly different from that of normal rats (Mathur and Doisy,
1972). However, by inducing diabetes or by feeding high-fat diets, the
distribution of 51Cr in the liver fraction was altered. Chromium moved
from the nuclear to the microsomal fraction when the rate of hepatic lipog-
enesis was either normal or elevated. Morgan (1972) found a significant
difference in hepatic chromium concentrations between diabetic and normal
human subjects. The mean concentration of hepatic chromium was 12.7 yg/g
of ash for the normal group and 8.59 yg/g of ash for the diabetic group.
-------
160
Three hypotheses have been proposed concerning the relationship of
chromium to diabetes (Schroeder, 1968):
(1) Chromium has no role in glucose metabolism in diabetes
mellitus. (2) Chromium plays a role in the utilization of
glucose by insulin, but absorption of the chloride or acetate
is erratic. (3) Chromium deficiency is causal for some part
of the disturbed glucose tolerance in some patients with
diabetes mellitus, but the proportion cannot be definitely
proved until tissue stores are depleted, which has not
occurred.
None of these hypotheses have been proven.
6.3.1.1.3 Malnutrition in children — A severe and responsive chromium
deficiency in relation to protein-calorie malnutrition exists in several
areas of the world (National Academy of Sciences, 1974). Hypoglycemia and
impaired glucose tolerance, two symptoms of impaired glucose metabolism,
are generally associated with kwashiorkor and marasmus in malnourished
children. In a study by Hopkins, Ransome-Kuti, and Majaj (1968), six mal-
nourished infants from the Jordanian hills and six from the Jordan River
Valley were given 250 yg chromium chloride. The infants from the hills
had severely impaired tolerance (fasting blood glucose levels of 58 mg/100
ml, glucose removal rate of 0.7% increment glucose per minute), whereas
tolerance was normal in children from the valley (70 mg/100 ml, 3.8%/min).
The children from the valley used drinking water with chromium levels
three times that found in water in the hills. Six malnourished Nigerian
children with impaired glucose tolerance (1.2%/min) were also given 250 yg
chromium chloride. The glucose removal rates of the children from the
Jordanian hills improved significantly from 0.6%/min to 2.9%/min (Table
6.7). Lower chromium states apparently occur in parts of Jordan and Nigeria
and are associated with impaired glucose tolerance in malnourished children.
However, not all cases of malnutrition are complicated with low chromium
states and chromium treatment can be expected to improve only those cases
which are caused by a low chromium state. In a study of malnourished in-
fants from Turkey, the glucose removal rate significantly improved in 9 of
14 cases after supplementation with 250 yg of chromium chloride (Gurson
and Saner, 1971). Similar supplementation caused a significant weight in-
crease in infants with marasmus when compared with a nonsupplemented control
group (Gurson and Saner, 1973).
A study in Cairo, Egypt, of 34 infants with kwashiorkor showed that
not all cases of impaired glucose tolerance associated with malnutrition
are due to chromium deficiency (Carter et al., 1968). The impaired glu-
cose tolerance of the infants in one group improved following consumption
of a high-protein, high-calorie diet for one to two weeks. A supplement
of 250 yg of chromium as chromic chloride given to another group of children
had no effect. Thus, the reversible impaired glucose utilization did not
seem to be due to the low chromium diet which the infants habitually
received.
-------
161
Table 6.7. Summary and significance of the effect of chromium on the
impaired glucose tolerances of malnourished infants
Subjects
Number
of
infants
Glucose
removal rate
(%/min)
Significance
of
difference
Jordanian infants from hill area with 10
0.5 ppb chromium in drinking water
Jordanian infants from valley with 9
1.6 ppb chromium in drinking water
Jordanian infants
Initial glucose tolerance test 6
After chromium treatment 6
Nigerian infants
Initial glucose tolerance test 6
After chromium treatment 6
Nontreated infants
Initial glucose tolerance test 5
Repeated glucose tolerance test 5
0.7
3.8
0.6
2.9
1.2
2.9
1.9
2.1
P < 0.001
P < 0.001
P < 0.05
Not
significant
Source: Adapted from Hopkins, Ransome-Kuti, and Majaj, 1968, Table V,
p. 208. Reprinted by permission of the publisher.
6.3.1.2 Lipid Metabolism — Trivalent chromium increased the synthesis of
cholesterol and fatty acids from acetate in rats (Curran, cited in Schroeder,
1968). These early experiments indicated that chromium is essential for
lipid metabolism. The effects on lipid metabolism could be the result of
the stimulation of glucose metabolism by chromium. In rats, elevated blood
cholesterol levels and changes in the major arteries resembling the fatty
deposits of arteriosclerosis are signs of chromium deficiency (Schroeder,
Kitchener, and Nason, 1971). The addition of 1 ppm chromium to drinking
water of male rats significantly lowered serum cholesterol levels as com-
pared to serum cholesterol levels in chromium-deficient rats. Addition of
5 ppm chromium resulted in further reductions in cholesterol levels. Feed-
ing the rats white sugar plus chromium, brown sugar, or raw sugar slowed
the rise in serum cholesterol. The addition of 50 ppm cadmium had no con-
sistent effects, whereas 50 ppm molybdenum produced effects similar to
those of chromium (Table 6.8).
The relationship between chromium and cholesterol metabolism in rats
suggests that human cholesterol levels may rise as a result of chromium
deficiencies. Because several other metals cause reductions in cholesterol
levels, the action of chromium on circulating cholesterol may not be
specific (Mertz, 1969).
A significant difference in the incidence of spontaneous aortic plaques
was found between chromium-fed rats and chromium-deficient rats (Schroeder
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162
Table 6.8. Effects of chromium, nickel, molybdenum, and
cadmium on fasting serum cholesterol levels in rats
on a starch diet
Metal in
basal water
Control 1
(0 ppm chromium)
5 ppm chromium
5 ppm cadmium
Control 2
(1 ppm chromium)
5 ppm chromium
Control 3
(5 ppm chromium)
12 ppm chromium
5 ppm nickel and
5 ppm chromium
10 ppm molybdenum
and 5 ppm chromium
50 ppm cadmium
and 5 ppm chromium
Age
(days)
360
510
761
360
510
761
360
510
760
405
657
668
718
402
718
342
663
151
315
231
576
917
Males
Cholesterol
levela
(mg/100 ml)
102 + 4.5
108 + 4.4
123 + 8.2
91 + 4.8
77 + 6.6
93 + 7.6
76 + 4.7
68 + 2.8
89 + 8.7
111 + 8.7
76 + 2.9
78 + 2.1
92 + 5.3
86 + 3.2
67 + 5.1
75 + 2.6
49 + 4.8
79 + 4.2
76 + 5.8
74 + 4.2
107 + 6.1
111 + 12.4
Females
Age
(days)
j
510
761
510
761
510
760
405
657
698
718
709
405
726
480
912
342
663
158
315
331
677
1020
Cholesterol
levela
(mg/100 ml)
80 + 7.3
95 + 11.2
101 + 8.2
114 + 9.5
87 + 9.8
113 + 9.0
72 + 5.3
120 +9.3
116 + 6.1
109 + 4.0
63 + 4.1
72 + 5.2
77 + 5.2
62 + 2.7
86 + 3.4
75 + 3.8
80 + 4.7
77 + 2.4
83 + 5.4
64 + 2.4
88 + 2.8
84 + 5.9
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163
Table 6.8 (continued)
Males
Metal in
basal water
Age
(days)
Cholesterol
levela
(mg/100 ml)
Females
Age
(days)
Cholesterol
levela
(mg/100 ml)
Control 4
(5 ppm chromium)
50 ppm molybdenum
(in doubly
deionized water)
50 ppm cadmium
and 5 ppm chromium
Control 5
(5 ppm chromium)
No chromium
129
476
810
135
477
813
719
90
115
228
571
46 + 1.7
88 + 2.4
100 + 7.3
51 + 2.2
76 + 4.6
76 + 3.5
99 + 5.2
84+1.9
114 + 5.0
123 + 10.1
78 + 4.8
129
476
810
135
477
813
719
90
127
228
571
60 + 3.4
94 + 3.7
85 + 5.8
57 + 1.5
74 + 5.4
97 + 4.2
97 + 4.3
74 + 4.0
110 + 2.7
91 + 6.1
86 + 6.0
fllean + standard error of mean.
Source: Adapted from Schroeder, Mitchener, and Nason, 1971,
Table 4, p. 252. Reprinted by permission of the publisher.
and Balassa, 1965). Examination of aortas at the end of the rat's natural
life showed the incidence of plaques in chromium-fed rats was 2%, whereas
the incidence in the chromium-deficient animals was 19%.
People living in areas of the world where atherosclerosis is mild or
virtually absent had higher chromium levels in tissues than people from
areas where the disease is endemic (Schroeder, 1968). The greatest differ-
ence between foreign and American chromium levels was in the aorta (Schroeder,
Nason, and Tipton, 1970). Table 6.9 compares chromium levels in the aortas
of subjects who died from arteriosclerotic heart disease to those in subjects
who died from other causes. Chromium levels in the aorta were generally
lower in patients who died from arteriosclerotic heart disease. Circulating
cholesterol levels declined 12.2% in seven of ten patients after five months
of chromium supplementation given as 2 mg of the acetate daily (Schroeder,
1968). In patients not receiving chromium supplementation, circulating
cholesterol levels decreased only 2.5% to 5.7%. Serum cholesterol levels in
three of five diabetics declined to nearly 200 mg/100 ml after they received
larger doses of chromium.
-------
164
Table 6.9. Chromium levels in adrtas of subjects dying from
arteriosclerotic heart disease, other cardiovascular diseases,
and other conditions including accidents
Location
Cause of
death
Number of
cases'2
Ash ,
(% dry wt)
Chromium ,
(ppm dry wt)
P°
San Francisco
AHD 15(13) 8.3 + 1.46
AHD, mild 3(3) 5.4 + 0.37
or moderate
Accidents 10(2) 5.7 + 2.46
0.048 + 0.009
0.028 + 0.003
0.228 + 0.076
<0.005
United States,
nine cities
Africa
Middle East
Far East
AHD
CVD-'
Accidents
CVD
Accidents
Other
CVD
Accidents
Other
ADH
CVD
Accidents
Malignancy
Other
13(7)"
15(6)^
103(13)
2
5(1)
11(1)
3(1)
8(2)
11
5
20(3)
8
25(1)
21
5.2 + 0.71
5.1 + 0.98
5.1 + 0.38
3.8 + 0.35
1.7 + 0.62
5.4 + 0.72
4.3 + 0.40
3.7 + 1.33
4.8 + 1.31
4.5 + 1.03
2.9 + 0.39
2.7 + 0.50
3.1 + 0.26
4.0 + 0.78
0.052 + 0.088
0.196 + 0.090
0.260 + 0.067
0.116 + 0.026
0.072 + 0.020
0.193 + 0.025
0.216 + 0.084
0.360 + 0.143
1.284 + 0.831
0.246 + 0.132
0.311 + 0.073
0.970 + 0.532
0.533 + 0.107
0.438 + 0.077
<0.005
<0.025
^Numbers in parentheses are numbers of cases deficient in aortic chromium.
Mean values are shown.
Q
P is significance of difference between mean for coronary heart .disease or
cardiovascular disease and other causes of death.
<^AHD = Arteriosclerotic heart disease with occlusion.
-Differs from accident by chi-square analysis, P < 0.001
Jr-
CVD
9P
Cardiovascular and cerebrovascular disease other than AHD.
< 0.025.
Source: Adapted from Schroeder, Nason, and Tipton, 1970, Table 10, p.
Reprinted by permission of the publisher.
132.
Even with these data, the effect of chromium on cholesterol levels is
difficult to assess. The evidence indirectly points to chromium deficiency
as a cause of human atherosclerosis (Schroeder, 1973; Schroeder, Nason, and
Tipton, 1970). When large doses of chromium complexes are given orally,
elevated cholesterol levels are lowered and glucose metabolism is improved.
Human aortas and other arteries with a chromium deficiency may not be
capable of oxidizing lipids.
6.3.1.3 Amino Acid Metabolism - Rats fed diets deficient in chromium and
protein could not incorporate several amino acids into their heart protein
(Roginski and Mertz, 1969). Trivalent chromium supplementation with added
insulin significantly improved amino acid incorporation. Glycine, serine
and methionine were the amino acids affected. Lysine and phenylalanine
-------
165
were not affected. Cell transport of an amino acid analog was stimulated
to a greater extent by insulin in rats fed low-protein diets with chromium
supplementation than in chromium-deficient rats. Chromium may be a co-
factor with insulin in two insulin-responsive processes of amino acid
metabolism.
6.3.1.4 Eye Lesions — Rats fed a diet containing less than 100 ppb chro-
mium developed visible eye lesions (Roginski and Mertz, 1967). Approxi-
mately 10% to 15% of the animals were affected. Final stages of the lesion
were opacity of the cornea, dilation of the vessels, and neovascularization
of the cornea. Chromium supplementation prevented eye lesions but did not
reverse the defect (Mertz, 1969). Corneal opacity in chromium-deficient
rats may be a nonspecific reaction to the deficiency.
6.3.2 Nutrition: Chromium Deficiency in Diets
Chromium nutrition in humans depends on the intake of readily absorbed
dietary factors (Reinhold, 1975). Total chromium provided daily from a
typical institutional diet is about 78 yg (Schroeder, Balassa, and Tipton,
1962). However, daily dietary chromium intake varies from 5 to 115 yg
(Mertz, 1969). Drinking water may also provide significant amounts of ab-
sorbable chromium. Levander (1975) has reviewed the nutritional aspects
of chromium. Hambidge (1974) suggests that chromium nutritional levels are
suboptimal in the United States, especially for pregnant women. He feels
that supplementation with inorganic chromium would be ineffective in
correcting the problem. Hopkins (1971) found, however, that oral trivalent
chromium improved glucose tolerance, though GTF supplementation would be
better. Chromium deficiencies can be corrected by intake of foods high in
glucose tolerance factor (Reinhold, 1975).
Biological values of foods containing available chromium show brewer's
yeast to be a good source of usable chromium, followed by meats, grain,
and certain seafoods (Mertz, 1974).
Toepfer et al. (1973) also examined the relationship between chromium
content of foods and chromium biological activity. Relative biological
activity was determined by measuring the carbon dioxide production from
glucose oxidation using glucose-l-carbon-14 in the presence of rat epi-
didymal tissue and 100 microunits of insulin. The calculated relative
biological activity for various foods is presented in Table 6.10; Tables
8.1 to 8.4 give chromium concentrations in foods. No significant rela-
tionship was found between biological activity and total chromium content
of foods. A significant relationship existed for chromium extracted with
alcohol in meats, fungi, seeds, and seafoods (Figure 6.4).
Chromium-deficient diets are common in the United States because of
the amount of refined food which is consumed. Refined fats are generally
low in chromium. Milling wheat into refined white flour removes 40% of
the chromium. White flour provides approximately 6.6 yg chromium per
kilocalorie, whereas whole wheat flour supplies 53 yg/kcal (Schroeder,
1968). Ingestion of refined sugars which contain little or no chromium
depletes chromium pools in humans, but this depletion may not occur if the
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166
Table 6.10. Calculated chromium
biological values of the edible portion
of selected foods as purchased
Food sample
Yeast, brewer's (dried)
Pepper, black
Liver, calf's
Cheese, American
Wheat germ
Bread, whole wheat
Cornflakes cereal
Bread, white
Spaghetti
Beef round
Wheat grain
Butter
Bread, rye
Margarine
Oysters
Cornmeal, yellow
Peppers, chili (fresh)
Wheat bran and middlings
Vegetarian chicken
Cornmeal, white
Shrimp
Grits
Lobster
Mushrooms
Chicken leg
Haddock
Patent flour
Beer
Egg white
Chicken breast
Vegetarian choplets
Skimmed milk
Relative
biological
value
44.88
10.21
4.52
4.39
4.05
3.59
3.01
2.99
2.89
2.89
2.96
2.81
2.67
2.48
2.43
2.35
2.27
2.21
2.16
2.09
2.03
1.97
1.95
1.92
1.89
1.86
1.86
1.77
1.77
1.75
1.72
1.59
Source: Adapted from Toepfer et al.,
1973, Table II, p. 72. Reprinted by per-
mission of the publisher.
sugar contains absorbable chromium. Most of the chromium in raw sugar is
removed during refining (Table 6.11). Refined sugar contains 0.5 to 2.5 yg
chromium per 100 kcal, whereas raw sugar provides 6.0 to 8.8 yg/100 kcal.
Thus, most of the energy in the diet of the average American is obtained
from sources that do not supply needed chromium.
-------
167
• SHRIMP
3.00
2.00
1.00
ORNL-DW6 76-2458
• MUSHROOMS
VEGETARIAN
CHICKEN/
•GRITS
HADDOCK
CHICKEN BREAST*
-RYE BREAD*
WHEAT*
YELLOW CORN MEAL •
EN LEG
SKIMMED MILK*
• UVER
•CHIU PEPPER
BRAN
•BEEF »8EER
• BEER
* VBEE
WHOLE WHEAT BREAD
0.2
0.4
0.6
0.8
.10
1.2
1.4
CHROMIUM (ft,g/m\)
Figure 6.4. Relationship between chromium contents per milliliter
of aqueous alcohol extracts of foods and the corresponding biological
activities. Source: Toepfer et al., 1973, Figure 1, p. 70. Reprinted
by permission of the publisher.
This suboptimal dietary chromium intake may be a cause of the continu-
ous decline of tissue chromium levels with age. Dietary chromium may not
be high enough to compensate for the utilization and excretion of chromium,
thus causing increasingly lower levels in the body as aging occurs. The
high chromium levels in newborns place a stress on chromium concentrations
in the mother's body stores (Mertz, 1969). Chromium in the fetus must be
supplied from the mother's chromium pool rather than from simple chromium
compounds. The mean chromium concentration in hair of parous women was
less than a third of that found in hair of nulliparous women (Hambidge and
Rodgerson, 1969). Decreasing chromium levels may be a factor in the
impairment of glucose tolerance with an increase in the number of offspring
(Mertz, 1969).
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168
Table 6.11. Chromium content of sugars
Sugar sample
Chromium
(ppm) (yg/100 kcal)
Sugar cane, Virgin Islands 0.07
Sugar cane, Puerto Rico 0.12
Sugar cane, bark, 0.15
Puerto Rico
Raw sugar, Philippines 0.24 6.0
Raw sugar, Colombia 0.35 8.8
White sugar, United States 0.08 2.0
White sugar, France 0.13 3.3
White sugar, superfine, 0.02 0.5
United States
Brown sugar, dark 0.12 3.0
Brown sugar, light 0.06 1.5
Brown sugar, Irish 0.07 1.8
Fructose 0.18 4.5
Glucose 0.03 0.8
Lactose 0.17 4.3
Cerelose 0.17 4.3
Molasses, household 0.11 4.3
Molasses, blackstrap 0.22 8.6
Molasses, refinery 0.27 10.5
Affination syrup 0.75 29.2
Molasses, final 1.21 47.0
Honey, purified 0.29 10.0
Maple syrup
Corn syrup
Orange juice
Grape juice
0.18
0.15
0.13
0.47
6.0
5.0
34.0
94.0
Source: Adapted from Schroeder, 1968,
Table VII, p. 240. Reprinted by permission of
the publisher.
6.3.3 Toxicity
Chromium, especially trivalent chromium, has low toxicity; amounts
needed to produce toxic symptoms are much higher than amounts required to
remove symptoms of deficiency. The LD50 reported for trivalent chromium
-------
169
injected intravenously into rats was 1 mg chromium per 100 g body weight
(Underwood, 1971), an amount more than 10,000 times the dose needed to
relieve impairment of glucose tolerance in these same animals. Given orally,
trivalent compounds are practically nontoxic due to their insolubility. As
reported by Mertz (1969)., feeding trivalent chromium to experimental animals
at levels of even hundreds of milligrams daily failed to produce toxic symp-
toms. Schroeder (1968) found only beneficial effects of feeding small
amounts of trivalent chromium in lifetime studies with rats and mice. Eaton
et al. (1975) studied extractable chromium from printers ink in children's
comic magazines. The extraction experiments were designed to simulate ab-
sorption after ingestion of paper. Extracted chromium ranged from 100 to
570 ppm and constituted no apparent hazard.
In contrast, symptoms of toxicity have been observed in several
species of animals given water containing more than 5 ppm hexavalent
chromium (Mertz, 1969). Hexavalent chromium compounds are highly irritat-
ing because of the oxidizing power of the hexavalent state. Also, the
anions of hexavalent chromium compounds are easily absorbed and penetrate
cell membranes easily. However, except for its oxidizing ability, the
toxicity of injected hexavalent chromium is not greatly different from that
of injected trivalent chromium. Table 6.12 gives the toxicity and uses of
some trivalent and hexavalent chromium compounds. Toxic effects of chro-
mates on experimental animals are summarized in Table 6.13; Table 6.14 shows
the doses of trivalent chromium which were necessary to produce death.
Chromium toxicity in man is mainly an occupational concern. Indus-
trial exposure to chromium primarily affects the skin, nasal mucous mem-
brane, and lungs (Browning, 1969). Systemic poisoning from chromium, with
resulting damage to liver and kidneys, has also been described. Similar
lesions have been found in the nonindustrial population after ingestion or
external application of chromium compounds.
6.3.3.1 Skin Effects — Workers exposed to chromates in various industries,
such as textile dyeing, manufacturing of paint pigments, leather tanning,
metal plating, cement masonry, metal and wood polishing, and blueprinting,
develop various types of skin injuries (National Academy of Sciences, 1974).
Skin reactions to chromium have been classified into two categories: (1)
primary irritations with ulcers and nonulcerative contact dermatitis and
(2) allergic contact dermatitis with eczematous and noneczematous dermatitis.
Samitz and Katz (1963) demonstrated that hexavalent chromium was re-
duced by the skin to the trivalent form and then bound to the skin. The
chromium reduction may involve divalent sulfur. A correlation was found
between the rate of percutaneous absorption and the inactivation of epi-
dermal SH groups (Samitz, 1955).
6.3.3.1.1 Primary dermatoses — Chromium ulcers known as chrome holes are
caused by contact with chromate dust and solutions such as chromic acid,
sodium or potassium chromate or dichromate, or ammonium dichromate (Nat-
ional Academy of Sciences, 1974). Harmful effects result when chromate
comes in contact with a break in the skin (Baetjer, 1956). The incidence
of ulcers, which can be high, is related to duration of contact, suscepti-
bility, and hygiene. Chrome holes are generally found on the hands, arms,
-------
170
Table 6.12. Toxicity and uses of some chromium compounds
Compound
Toxicity
Ammonium chromic sulfate,
Ammonium dichromate(VI) ,
(NlU)2Cr207
Basic cupric chromate,
CuCr04Cu(OH)2,
CuCr0^2Cu(OH)2,
CuCrO,.-3Cu(OH)2
Chromic acetate,
Cr(C2H302)3
Chromic bromide, CrBrs
Chromic carbonate,
Cr2Os-xC02-yH20
Chromic chloride, CrCl3
Chromic fluoride, CrF3
Chromic formate,
Cr(HCOO)3
Chromic hydroxide,
Cr(OH)3
Chromic nitrate, Cr(N03)3
Chromic oxide, Cr203
Chromic phosphate, CrP04
Chromic potassium oxalate,
K3[Cr(C2Ot)3]
Chromic potassium sulfate,
KCr(S04)2
Chromic sulfate,
Cr2(SO*)3
Causes skin irritation, ulceration,
"chrome sores," perforation of nasal
septum, pulmonary irritation
Should be kept tightly closed. MLD
(intravenous) in mice 801,000 ppb
(see chromium trioxide)
See chromium trioxide
MLD (intravenous) in mice 247,000 ppb
Chromite, FeCra04
As mordant in textile industry; in manu-
facture of electrolytic chromium metal
As source of pure nitrogen, especially
in the laboratory; in pyrotechnics
(Vesuvius fire); in lithography and
photoengraving; in special mordants,
catalysts, and porcelain finishes
In fungicides, seed protectants, and
wood preservatives; as mordant in
dyeing textiles; in protecting textiles
against insects and microorganisms;
copper-chromium oxide as a selective
hydrogenation catalyst
As a mordant in dyeing; in tanning; in
hardening photographic emulsions; to
improve light stability and dye affin-
ity of textiles and polymers; in cata-
lyst for polymerization of olefins
In catalysts for polymerization of
olefins
In preparation of chromic salts
In chromizing; in manufacture of chromium
metal and compounds; as catalyst for
polymerization of olefins and other
organic reactions; as textile mordant;
in tanning; in corrosion inhibitors; as
waterproofing agent
Hydrates used in printing and dyeing
woolens, coloring and hardening marble,
mothproofing woolen fabrics, treating
silk, polishing metals, and as halo-
genation catalyst
In printing cotton skeins; in leather
tanning and waterproofing
As pigment such as Guignet's green; in
tanning industry, as mordant; as
catalyst for organic reactions
In preparation of chromium catalyst; in
textile printing; as corrosion
inhibitor
In abrasives; as refractory materials,
electric semiconductors; as pigment,
particularly in coloring glass; in
alloys, printing fabrics, and bank-
notes; as catalyst for organic and
inorganic reactions
As green pigment; in wash primers; in
catalysts for dehydrogenation of hydro-
carbons and polymerization of olefins
In tanning industry; in dyeing chromate
colors on wool
As mordant for dyeing fabrics uniformly;
in tanning leather, printing calico;
for rendering glue and gum insoluble;
in manufacture of ink, other chromium
salts; for waterproofing fabrics,
hardening photographic emulsions
For insolubilization of gelatin; in cata-
lysf preparation; as mordant in tex-
tile industry; in tanning of leather;
in chrome plating; in manufacture of
Cr, CrO,, and Cr alloys; to Improve
dispersibility of vinyl polymers In
water; in manufacture of green var-
nishes, paints, inks, glazes for
porcelain
As only important commercial ore
-------
171
Table 6.12 (continued)
Compound
Toxlcity
Chromium, Cr
See chromium trioxide
Chromium carbonyl,
Cr(CO)6
Chromium tetrafluoride,
CrF4
Chromium trioxide, Cr03
Chromous acetate,
Cr(C2Ha02)2
Chromous bromide, CrBr2
Chromous chloride, CrCla
Chromous fluoride, CrF2
Chromous formate ,
Cr(HCOO)2
Chromous oxalate,
LDso (intravenous) in mice 100,000 ppb
A strong irritant
Dermal contact can cause primary irrita-
tion and ulceration as well as aller-
gic eczema. Inhalation can cause
nasal irritation, septal perforation.
Pulmonary irritation, bronchogenic
carcinoma may result from breathing
chromate dust. Ingestion causes
violent gastrointestinal irritation
with vomiting, diarrhea. Renal injury
has been reported in experimental
animals.
See chromium trioxide
See chromium trioxide
A strong irritant (see chromium trioxide)
In manufacture of chrome-steel or chrome-
nickel-steel alloys (stainless steel);
for greatly increasing resistance and
durability of metals; for chrome plat-
ing of other metals; man-made Cr-51
isotope used as tracer in various
blood diseases and in determination of
blood volume (as the chloride or as
sodium chromate)
In catalysts for olefin polymerization
and isomerization; as gasoline addi-
tive to increase octane number; in
preparation of chromous oxide, CrO
In chromium plating, copper stripping,
aluminum anodizing; as corrosion
inhibitor; in photography, purifying
oils and acetylene, hardening micro-
scopical preparations; medical and
veterinary uses: 5% solution as
topical antiseptic and astringent, 20%
solution as caustic
In preparation of other chromous salts;
as 03 absorber in gas analyses
In chromizing
In chromizing; in preparation of Cr
metal; in catalysts for organic
reactions; as 02 absorbent; in
analysis
In chromizing; in catalytic cracking of
hydrocarbons; as alkylation catalyst;
in nuclear reaction fuels
In baths for chromium electroplating; in
catalysts for organic reactions
Chromous oxalate,
CrC20<,
Chromous sulfate, CrSOh
Chromyl chloride,
Cr02Cl2
Chromyl fluoride, Cr02F2
Copper chromium oxide,
a mixture of CuCraO/,
and CuO
Cupric chromate(III),
CuCraO*
Cupric chromate(VI),
CuCrO*.
Ferric chromate(VI),
Fc3(CrOfc)3
Burns and blisters the skin; should be
handled only in well-ventilated hood
See chromium trioxide
As analytical reagent; for absorption of
Oz from gas mixtures; as dehydrohalo-
genating and reducing agent
As catalyst for polymerization of ole-
fins; in oxidation of hydrocarbons, in
Etard reaction for production of alde-
hydes and ketones; in preparation of
various coordination complexes of
chromium
As fluorination catalyst; to increase
olefin-polymer receptivity for dyes
Same as cupric chromate(III)
In fungicides, seed protectants, and
wood preservatives; as mordant in
dyeing textiles; in protecting tex-
tiles against insects and micro-
organisms; copper chromium oxide as
selective hydrogenation catalyst
Same as cupric chromate(III)
As pigment for ceramics, glass, and
enamels
-------
172
Table 6.12 (continued)
Compound
Toxlclty
Uses
Lead chromate (chrome
yellow), PbCrO»
Potassium chromate(VI),
KjCrO,.
Potassium dichromate(VI),
K2Cr207
Sodium chromate(VI),
Na2CrO<,-4H20
Sodium dichromate(VI),
Na2Cr207-2H20
LD5(> (intraperitoneal) in guinea pigs
400,000 ppb
LD (subcutaneous) in rabbits 12,000 ppb
(see chromium trioxide)
Internally, a corrosive poison—30 g
reported fatal within 35 min. Indus-
trial contact may result in ulceration
of hands, destruction of mucous mem-
branes, and perforation of nasal
septum. Chromates have been reported
as causing cancer of the lung.
LD (subcutaneous) in rabbits 243,000 ppb
Irritant and caustic to skin, mucous
membranes (see chromium trioxide)
As pigment in oil and water colors; in
printing fabrics, decorating china and
porcelain; in chemical analysis of
organic substances. Basic lead chro-
raates of colors from brown-yellow to
red are used as pigments
Has a limited application in enamels,
finishing leather, rustproofing of
metals, being replaced by the sodium
salt; as a reagent in analytical
chemistry
In tanning leather, dyeing, painting,
decorating porcelain, printing, photo-
lithography, pigment prints, staining
wood, pyrotechnics, safety matches;
for bleaching palm oil, wax, and
sponges; in waterproofing .fabrics; as
an oxidizer in the manufacture of
organic chemicals; in electric bat-
teries; as a depolarizer for dry cells.
As corrosion inhibitor in preference
to sodium dichromate where lower solu-
bility is advantageous; medical use:
externally as astringent, antiseptic,
caustic; veterinary use: as caustic
for superficial growths
In protecting iron against corrosion and
rusting
As oxidizing agent in manufacture of
dyes, many other synthetic organic
chemicals, inks, etc.; in chrome-
tanning of hides; in electric bat-
teries; in bleaching fats, oils,
resins, sponges; in refining petroleum;
in manufacture of chromic acid, other
chromates, and chrome pigments; in
corrosion inhibitors, corrosion-
inhibiting paints; in many metal treat-
ments; in electroengraving of copper;
as mordant in dyeing; for hardening
gelatin; for defoliation of cotton
plants and other plants and shrubs;
medical use: in solution as anti-
septic, astringent, caustic
Source: Adapted from Sullivan, 1969, Table 7, pp. 49-58.
and feet. The first sign of chrome ulcers is the appearance of papules
which change to pustules. These pustules become deep ulcers with thickened,
indurated, undermined tissue around the ulcer. Ulcers, if neglected, pene-
trate to the bone, are difficult to heal, and persist for long periods of
time.
Chrome holes may be caused by the oxidizing properties of hexavalent
chromium (Samitz, Shrager, and Katz, 1962), which causes denaturation of
skin proteins. This corrosive action of the chromate ion is independent
of its sensitizing properties. The toxic effects of hexavalent chromium
can be prevented by reducing chromium to the trivalent form.
In a study of workers from a chromate manufacturing plant, Edmundson
(1951) found that of 285 workers, 60.5% had chrome ulcers or scars. The
distribution of ulcers and scars was: hands, 31% to 46%; arms, 19.5%;
ankles and feet, 10.1%; legs, 6.0%; back, 4.1%; knees, 3.6%; thighs, 3.3%;
-------
Table 6.13. Animal exposures to chromates
Species
Rabbits
and cats
Rabbits
Cats
Mice
Mice
Mice
Rats
Rabbits and
guinea pigs
Rats
Mature rats
and mice
Young rats
Type of
exposure
Inhalation
Inhalation
Inhalation
Inhalat ion
Inhalation
Inhalation
Inhalation
Inhalation
Ingestion
Ingestion
Ingestion
Material
Chromates
Dichromates
Dichr ornate
Mixed dust
containing chromates
Mixed dust
containing chromates
Mixed dust
containing chromates
Mixed dust
containing chromates
Mixed dust
containing chromates
Potassium chromate
added to drinking
water
Zinc chromate
in feed
Zinc chromate
in feed
Average dose or
concentration
1-50 mg/m3
11-23 mg/m3
11-23 mg/m3
1.5 mg/m3 as Cr03
16-27 mg/m3 as CrOs
7 mg/m3 as CrC>3
7 mg/m3 as CrC>3
5 mg/m3 as Cr03
500 pg/g
10 mg/g
1.2 mg/g
Duration
14 hr/day
1-8 months
2-3 hr for
5 days
2-3 hr for
5 days
4 hr/day, 5 days /week
for 1 year
% hr/day
intermittently
37 hr over 10 days
37 hr over 10 days
4 hr/day, 5 days /week
for 1 year
Daily
Daily
Daily
Effect
Pathological changes
in lungs
No effect
Bronchitis,
pneumonia
No harmful effects
Fatal to some strains
Fatal
Barely tolerated
No marked effects
Maximum nontoxic
level
Maximum nontoxic
level
Maximum nontoxic
level
Young rats
Ingestion
Dogs, cats Ingestion
and rabbits
Potassium chromate
in feed
Mono- or dichromates
1.2 mg/g
Daily
1.9-5.5 mg chromium per 29-685 days
kilogram body wt
Maximum nontoxic
level
No harmful effects
Dogs
Ingestion
Potassium dichromate
2.8-5.7 g
Daily
Fatal in 3 months
-------
Table 6.13 (continued)
Species
Dogs
Monkeys
Dog
Guinea pigs
Rabbits
Rabbits
Rabbits
Rabbits and
guinea pigs
Mice
Mice
Mice
Rabbits
Dogs
Dogs
Dog
Dog
Type of
exposure
Stomach tube
Subcutaneous
Subcutaneous
Subcutaneous
Subcutaneous
Subcutaneous
Subcutaneous
Subcutaneous
or intravenous
Intravenous
Intravenous
Intravenous
Intravenous
Intravenous
Intravenous
Intravenous
Intravenous
Material
Potassium dichromate
Potassium dichromate
Potassium dichromate
Potassium dichromate
Potassium dichromate
Potassium dichromate
Potassium dichromate
Sodium chromate
Zinc chromate
Zinc chromate
Barium chromate
Potassium dichromate
Potassium chromate
Potassium chromate
Potassium dichromate
Potassium dichromate
Average dose or Duration
concentration
2.8-5.7 g
20-700 mg of 2% solution
594 mg
10 mg
1.5 g of 1% solution per
kilogram body wt
20 mg
0.5-1.0 g of 0.5%
solution per kilogram
body wt
162-486 mg
100 pg/month 10 months
750 vg One dose
2.5 mg Nine doses at 6-week
intervals
0.7 g of 2% solution per
kilogram body wt
10 g
23 mg
594 mg
3 mg/100 ml blood Two doses
Effect
Rapidly fatal
Fatal
Rapidly fatal
Lethal
80% fatal
Lethal
Nephritis
Rapid death
Tolerated
Fatal
Tolerated
Fatal
Fatal
Survived
Rapidly fatal
Marked kidney damage
Source: Adapted from Sullivan, 1969, Table 9, pp. 60-63.
-------
175
Table 6-. 14. Fatal doses of trivalent chromium in animals
Animal
Route
a
Material
Chromium dose
(g/kg)
Effect
Dog SC Chromic chloride 0.8
Rabbit SC Chromic chloride 0.52
Rat IV Chrome alum 0.01-0.018
Chromium-hexaurea chloride
a
Fatal
Fatal
Mouse IV
IV
IV
IV
IV
IV
Chromic chloride
Chromic acetate
Chromic chloride
Cr(III)
Chromic sulfate
Chromium carbonyl
0.8
2.29
0.4
0.25-2.3
0.085
0.03
MLD
MLD
MLD
MLD
MLD
LD50
SC = subcutaneous; IV = intravenous.
Source: Adapted from National Academy of Sciences, 1974, Table 8-3,
p. 79.
abdomen, 3.0%; face, 1.9%; neck, 1.6%; and chest, 0.6%. Contact with
alkali chromates or chromic acid, the number of abrasions as a result of
job conditions or worker's carelessness, and inadequate care given to the
abrasions were factors in the occurrence of the ulcers. Exposure to
chromic acid or its alkali salts did not sensitize workers to potassium
dichromate.
The incidence of chrome ulcers among chromate workers has decreased
over the years. More efficient ventilating systems reduce the concentra-
tion of chromate mist in the air and thus reduce the amount of contact
with chromium by workers. Henning (1972) reported that the entrance of
chromic acid mist into workroom air can be prevented by using lip exhaust
ventilation at the chromic acid bath and chemical suppressants which re-
duce surface tension or by building a layer of foam to act as a physical
barrier to the mist. Covering skin areas where abrasions appear prevents
chromium penetration. Samitz, Scheiner, and Katz (1968) found ascorbic
acid to be an effective antichromium agent. The mechanism for hexavalent
chromium inactivation by ascorbic acid involved reduction to trivalent
chromium followed by complex formation of the trivalent form. Ten percent
aqueous ascorbic acid applied to abrasions treated with potassium dichro-
mate significantly re.duced healing time of chromate ulcers in guinea pigs
-------
176
(Pirozzi, Gross, and Samitz, 1968). If more time elapsed before the appli-
cation of ascorbic acid, more time was required for healing. Even after
a 30-min delay, however, healing time was reduced. Ascorbic acid acted by
reducing the hexavalent chromium salt to the trivalent state. These results
agree with the findings of Samitz, Shrager, and Katz (1962).
6.3.3.1.2 Contact dermatitis and allergic responses — A diffuse dermatitis
results from skin contact with low concentrations of hexavalent chromium
compounds. Eczematoid dermatitis is considered an allergic reaction to
chromates; sensitization may take place within a few days or after several
years of exposure (Baetjer, 1956).
Even though dermatitis is often caused by hexavalent chromium, it is
just as prevalent with trivalent compounds (Hamilton and Hardy, 1974).
Mali, Malten, and Van Neer (1966) reported, however, that a higher concen-
tration of trivalent chromium was needed to cause an allergic reaction.
A level of at least 20 times that of hexavalent chromium was needed for an
epicuticular reaction and 50 times as much for an intracutaneous reaction.
Individual chromium sensitivities also differ between hexavalent and tri-
valent compounds. Those persons slightly sensitive to dichromate may not
react to trivalent chromium. Samitz and Gross (1961) tattooed guinea pigs
with both trivalent and hexavalent chromium compounds. They reported no
significant difference in the absorption of these compounds. As a result
of other experiments with guinea pigs, Scheiner and Katz (1973) proposed
that the binding of chromium by protein depends on the concentration of
free trivalent chromium ions in solution. In the presence of strong
ligands such as oxalate, little chromium is bound because most of it is
complexed and is not available to the protein. With a weak ligand, a
higher concentration of free ions allows more binding. The presence of
strong ligands may inhibit formation of the complete antigen with respect
to eliciting allergic reactions.
Cases of chromatic dermatitis have been reported in several industries.
Morris (1955) reported dermatitis in persons making and using chrome glue
manufactured from leather trimmings which contained chromium. Levin et al.
(cited in National Academy of Sciences, 1974) showed that dermatitis in
lithographers was principally caused by chromium compounds. Eczematous
contact dermatitis was prevented by workers soaking their hands and fore-
arms in 10% ascorbic acid solution (Samitz and Shrager, 1966).
An outbreak of dermatitis developed in 60 of 250 automobile-factory
workers engaged in wet-sanding primer painting (Engel and Calnan, 1963).
The latent period before dermatitis appeared was four to six months. Patch
tests showed that zinc chromate was the causal agent. Symptoms varied from
erythema to dyshidrotic and exudative eczema. In another study of 230 auto-
mobile assemblers, potassium dichromate was the most common sensitizing
agent out of nine common sensitizing substances tested. Positive reactions
occurred in 36% of the workers (Newhouse, 1963). Incidence of chromium
sensitivity was four times greater among assemblers than among those with
other jobs. The chromate source was a dip used in chromium plating and
zinc coating.
-------
177
Shelly (1964) found that inhalation of chromium fumes generated from
acetylene welding rods caused a severe eczematous eruption on the palms of
a chromium-sensitive patient. Some welding rods contain up to 18% chromium.
Fregert and Ovrum (1963) found that close exposure to chromium vaporized
from welding rods elicited contact dermatitis on the face of a chromium-
sensitive welder.
Four patients with shoe-leather dermatitis reacted positively to patch
tests with 0.2% trivalent basic chromic sulfate, which is the material used
to tan shoe leather (Morris, 1958). Leather workers with chromium dermati-
tis reacted to the trivalent material; a diesel engine inspector exposed to
hexavalent chromium reacted to the hexavalent material but not to trivalent
chromium. The author concluded that shoe-leather dermatitis could be caused
by sensitization to the basic chromic sulfate leached from the shoe by the
patient's sweat.
Samitz and Gross (1960) and Samitz, Katz, and Gross (1960) proved that
human sweat could extract both trivalent and hexavalent chromium compounds
from shoe leather. They theorized that hexavalent compounds were more
likely to cause sensitization because they have a higher sensitizing index
and are more diffusible. The hexavalent chromium may either have been a
contaminant from the tanning process or have been oxidized from trivalent
chromium by some readily reducible substance. In another study, Samitz
and Gross (1961) found no evidence for cross-sensitization between hexa-
valent and trivalent chromium compounds. An anti-chrome agent was developed
to reduce hexavalent to trivalent chromium without harming the skin (Samitz,
Gross, and Katz, 1962). The reagent contained sodium pyrosulfite to reduce
the chromium and tartaric acid to chelate the trivalent chromium formed.
The application of an ointment containing these compounds effectively
blocked reactions in two chromate-sensitive patients 15 and 30 min after
0.25% potassium dichromate was applied.
Fregert (1961) reported that the hexavalent chromium content in un-
burnt match heads was as high as 1.7%. The chromate caused allergic
eczematous contact dermatitis in sensitive people because the match heads
partly dissolved when held by moist fingers. The pockets of many of these
people contained chromate from matches. The eczema cleared up in some
people when contact with the matches was eliminated.
Studies by Mali, Van Kooten, and Van Neer (1963) to investigate the
capacity of chromium salts to bind with serum and dermal proteins, chro-
mium diffusion, membrane potentials, reduction of dichromate by skin com-
ponents, permeation of chromium salts through living skin, chromium
sensitivity of patients, and animal sensitization lead to several conclus-
ions about behavior of chromium compounds in the skin. Trivalent chromium
salts have a strong affinity for the epithelial and dermal structures, but
affinity of hexavalent compounds is weak. Because trivalent chromium salts
possess this strong affinity and tend to form large complexes, their dif-
fusibility through tissues is reduced and, therefore, their ability to
induce sensitization is low. However, small amounts of the trivalent com-
pound formed by the interaction between dichromate and tissues would be
predisposed to form a hapten-protein complex as the first step in sensitiz-
ation. The possible in vitro reduction of dichromate and the fact that
-------
178
guinea pigs injected with trivalent chromium were sensitized to hexavalent
chromium point to the formation of a chromium-protein complex as the first
step in the sensitization process.
Allergic reactions in several patients with green tattoos have been
reported (Loewenthal, 1960). There appeared to be an association of dermal
granulomatous and epidermal eczematous allergic reactions. These reactions
may be the result of contamination of the trivalent chromium used in the
tattoos with some hexavalent chromium.
In sensitization studies, Fregert and Rorsman (1964) found that humans
allergic to hexavalent chromium are usually also allergic to trivalent chro-
mium. Patch testing with trivalent chromium showed that a response was pro-
duced if the concentration of the test material was high enough. Basophil
leukocytes were increased in the inflammatory exudates produced by both
trivalent and hexavalent chromium. In a later study, hexavalent compounds
elicited stronger allergic reactions than trivalent compounds; the intensity
of the reactions to trivalent chromium compounds depended on the anions
(Fregert and Rorsman, 1966).
In guinea pigs, sensitization, once induced, was long-lived (Gross,
Katz, and Samitz, 1968). Cross-sensitization between hexavalent and tri-
valent chromium salts occurred; potassium dichromate was the most effective
sensitizer tested. The trivalent chromium ion appeared to be responsible
for sensitization. Sensitization differences were a result of the avail-
ability of the chromium to form a complete antigen by conjugation with a
carrier protein. The subcutaneous injection of relatively large doses of
potassium dichromate (10 mg in Freund's complete adjuvant) to guinea pigs
temporarily inhibited sensitization (Jansen and Berrens, 1968). The guinea
pigs gradually returned to the original sensitivity level as shown by
allergic responses to various chromium compounds. Schneeberger and Forck
(1974) produced contact sensitization and allergic responses in guinea pigs
with both hexavalent and trivalent chromium salts. The sensitization cap-
abilities of the trivalent complexes were proportional to the release of
chromium from the complex. In chromium-sensitized guinea pigs, serum
albumin was an active carrier of chromium (Katz et al., 1974). Chromium-
globulin complexes were not directly involved in the allergic response
mechanism.
6.3.3.2 Respiratory Effects
6.3.3.2.1 Perforation of the nasal septum — A common effect of chromate
dust or chromic acid mist inhalation is ulceration and perforation of the
nasal septum (Baetjer, 1956). The incidence of this condition varies with
degree of exposure — the greater the exposure, the higher the incidence
rate. The perforation is limited to the cartilage of the septum; the
mucous membrane covering this area is less vascular than the membrane
lining the rest of the nasal passage and is easily destroyed (National
Academy of Sciences, 1974). Blood supply to the cartilage is stopped and
necrosis occurs. The first symptom is a hyperemic reaction with sneezing,
swelling, and secretion (Baetjer, 1956). A mucous crust forms about the
perforation and is later expelled. Some irritation may be noticed but
-------
179
there is practically no pain. The perforation is not disabling and is
sometimes unnoticed by the workers. Nasal irritation seems to occur at
atmospheric concentrations of 0.1 mg chromic acid per cubic meter and may
occur at even lower levels (U.S. Department of Health, Education, and
Welfare, 1973).
In a survey of various electroplating factories, Gomes (1972) found
86.8% of the workers exposed to chromic acid mist had symptoms ranging
from scarring to perforation of the nasal septum. Perforated nasal septums
were present in 24%; 38.4% had ulcerations of the septum. The threshold
limit of exposure (0.1 mg/m3) was exceeded by more than 50% of the workers;
in one case, the atmospheric concentration was 1.40 mg/m3.
Kleinfeld and Rosso (1965) examined nasal injuries in nine workers in
a chrome-plating plant. Table 6.15 summarizes their findings. Air sample
analyses showed chromium concentrations of 0.18 to 1.4 mg/m3. The effect
of time at a fixed chromium concentration was not reported. Ulceration of
the septum was found in seven workers and four showed perforation of the
septum. Chromic acid was the responsible agent.
Table 6.15. Nasal injuries in a
chromium-plating plant
Case
Age
(years)
Duration of
exposure
(months)
Findings
1
2
3
4
5
6
7
8
30
19
19
18
47
45
23
20
48
6
2
12
9
10
6
1
0.5
Perforated septum
Perforated septum
Perforated septum
Perforated septum
Ulcerated septum
Ulcerated septum
Ulcerated septum
Moderate injection
of septum and
turbinates
Moderate injection
of septum
Source: Adapted from Kleinfeld and Rosso,
1965, Table I, p. 242. Reprinted by permission of
the publisher.
-------
180
Workers who inhaled a mist from 5% chromic acid solution were affected
in varying degrees (Zvaifler, 1944). In 50% to 60% of the cases, only the
anterior part of the septum showed a superficial ulceration. About 35% had
deeper ulcerations, usually of the anterior part of the inferior turbinate.
Symptoms similar to those of atrophic rhinitis developed in 5% to 10% of the
workers. The injury to the nasal mucosa caused by exposure to the anodizing
mist differed from that of chrome plating; the involvement, while wide-
spread, did not include perforation. In another study, Edmundson (1951)
found 61.4% of the chrome workers examined had perforated septa.
Bloomfield and Blum (cited in National Academy of Sciences, 1974)
examined workers in six U.S. chrome-plating plants. Their findings are
reported in Table 6.16. They concluded that continuous daily exposure to
chromic acid concentrations greater than 0.1 mg/m3 caused injury to nasal
tissue. Concentrations below 0.1 mg/m3 generally have not been studied;
therefore, their effects are not known.
6.3.3.2.2 Cancer of the respiratory tract — Increased incidence of lung
cancer is a long-term effect of exposure to hexavalent chromium from the
manufacturing of dichromate from chromite ore (National Academy of Sciences,
1974). The incidence of cancer at other body sites is not increased. Res-
piratory cancer usually occurs only after several years of exposure and may
not appear until long after exposure has ended. The dose-response relation-
ship between chromium and respiratory cancer is not known. The chromium
concentration in factories usually has not been measured. Even if the con-
centration was measured at the time of cancer diagnosis, it was not neces-
sarily the same as that at the time of exposure. It is not known which
specific compounds in chromate manufacturing are responsible for the in-
creased incidence of cancer (Baetjer, 1956). Most cases of cancer of the
respiratory tract have been bronchogenic carcinomas. A few cases of can-
cer have occurred in the upper respiratory tract, including the sinus,
pharynx, and oral region.
Bidstrup (1951) examined chest x rays of 724 workers in an English
chromate-producing industry and found one pulmonary carcinoma. A later
study of chromate workers in three chromate-producing factories showed a
significant increase in mortality from carcinoma of the lung above that
of the general population (Bidstrup and Case, 1956). Only 3.3 deaths from
lung cancer were expected, but 12 deaths were reported. The mean latent
period was calculated to be 21 years with a standard deviation of 10 years.
The authors concluded that carcinoma of the lung was an occupational hazard
of the chromate-producing industry.
In a survey of pulmonary carcinoma in chromate workers by Baetjer
(1950a), the duration of exposure varied greatly. Variations in the latent
period may have been related to the degree of exposure. In most cases, the
onset of illness occurred while the men were employed at the chromate
plant. Atmospheric chromate concentrations were not known. Pathological
examination showed that the tumors usually arose from the main bronchi;
oat, squamous, undifferentiated epithelial, or anaplastic tumors were iden-
tified. Baetjer (1950&) compared the number of chromate workers among
patients with lung cancer and the number of chromate workers among other
-------
Table 6.16. Clinical findings in workers employed in chromium-plating plants
Case
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Time employed in
„ _. chromium-plating
Occupation "
room
(months)
Chromium plater
Chromium plater
Foreman plater
Foreman plater
Chromium plater
Chromium plater
Chromium plater
Chromium plater
Chromium plater
Chromium plater
Chromium plater
Chromium plater.
Chromium plater
Chromium plater
Nickel plater0
Racker
Racker
Racker
Wiper d
Foreman ,
Foreman
Clerk^
Inspector
6
20
7
8.5
3.5
0.75
0.25
7
3
36
5
0.75
12
0.67
1.5
8
0.75
0.75
1.5
0
0
0
0
Time over
tank
(hr/day)
4
4
2
3
4
7
7
7
7
4
6
6
4
2
0
0
0
0
0
0
0
0
0
Approximate
CrOs exposure
(mg/cu m)
1.5
2.8
2.5
2.5
5.6
0.12
0.12
0.12
0.12
0.2
0.12
0.12
2.8
2.8
0
0
0
0
Perforated Ulcerated Inflamed „ . , .
a a a Nosebleed
septum septum" mucosa"
++ - -H- Yes
++ - + Yes
- ++ -H- Yes
- ++ ++ Yes
- -H- -H- Yes
- - -H- Yes
- - -H- Yes
- - ++ Yes
-H- No
-H- No
- - + Yes
- - + No
No
No
- + + Yes
+ - + Yes
- - + No
- - + No
- - + No
- - + No
- - + No
No
+ No
Chrome
holes
Yes
Yes
No
No
Yes
Yes
No
No
Yes
No
Yes
No
No
No
No
No
No
No
No
No
No
No
No
,++, marked; +, slight; -, negative.
Used vaseline in nose.
Xyanide burns.
Worked in other departments of factory.
Source: Adapted from Bloomfield and Blum as reported in National Academy of Sciences, 1974, Table 7-1, p. 44.
oo
-------
182
hospitalized groups selected as controls. The percentage of lung cancer
patients who had been exposed to chromates was significantly higher than
would be expected on the basis of the control hospitalized groups.
In an epidemiologic study of lung cancer deaths among workers of a
U.S. chromate plant, Mancuso and Hueper (1951) reported a lung cancer death
rate which was approximately 15 times that of the general population living
in the county in which the plant was located. The latent period was 10.6
years. The authors suggested that insoluble chromium compounds may produce
lung cancer because these compounds are retained in the lung over long
periods of time. Brinton, Frasier, and Koven (1952) also reported a higher
frequency of respiratory cancer among chromate workers than among workers
in other industries. Langard and Norseth (1975) found an increased inci-
dence of bronchial carcinoma among workers in a factory producing zinc chro-
mate. The risk ratio for exposed workers was approximately 38. All workers
had been exposed mainly to zinc chromate dust; the exposure levels of the
workers who developed bronchial cancers probably were from 0.5 to 1.5 mg
chromium per cubic meter for six to nine years.
Attempts to produce lung tumors with chromium by inhalation have been
unsuccessful in experimental animals. Baetjer et al. (1959) exposed mice
and rats to various chromium compounds. Animals were exposed by inhalation
of air from a chromate-producing plant where the concentration of chromium
trioxide was 1 to 3 mg/m3. Other animals were given intrapleural or intra-
tracheal injections of chromium trioxide. No bronchogenic carcinomas were
found in any of the animals. Intratracheal injection of zinc chromate pro-
duced an epithelization of the alveoli. Nettesheim et al. (1970) did not
affect the lung tumor incidence in mice exposed daily for 5% hr/day, 5
days/week to an aerosol of chromium oxide dust at a concentration of
25 mg/m3. Autopsy and histopathological examinations were performed at
6, 12, and 18 months. Steffee and Baetjer (1965) were unable to produce
malignant tumors in rabbits, guinea pigs, rats, and mice by inhalation
and/or intratracheal injection of various chromium compounds under condi-
tions simulating the exposures in old chromate-refining plants. The effects
caused by the chromium compounds are summarized in Table 6.17.
Other experimental data have shown that sarcomas can be produced local-
ly by injection and by implantation of various chromium compounds, but no
dose-response relationship is available from the data. Payne (1960a) ex-
posed mice to calcium chromate, sintered calcium chromate, and sintered
chromium trioxide (10 mg of chromium compound) by implantation into the
thigh muscle and subcutaneous injection. After 7 to 13 months, spindle
cell or fibrosarcomatous tumors occurred at the site of implantation of
calcium chromate or sintered calcium chromate. No tumors were produced
by subcutaneously injected sintered chromium trioxide or sintered calcium
chromate. A summary of results from an experiment with rats by Hueper
and Payne (1959) is presented in Table 6.18. Calcium chromate, sintered
calcium chromate, sintered chromium trioxide, and barium chromate (25 mg
of chromium compound) were implanted intramuscularly and intrapleurally.
The cancers produced were mainly sarcomas which occurred at the site of
implantation. This effect was related to the degree of solubility of these
compounds in an aqueous medium. Barium chromate with low solubility did
-------
Table 6.17. Microscopic pulmonary findings in rabbits, guinea pigs, rats, and mice
after inhalation and intratracheal injections of chromate material
Number of
Method
of
exposure
Total number of
animals
ri
g
"O
w
Hyperemia
Hemorrhage
Emphysema
Atelectasis
animals exhibiting various symptoms
Bronchiectasis
Abscesses
Bronchopneumonia
Interstitial
pneumonitis
Alveolar & intersti-
tial inflammation
Alveolar hyperplasia
Interstitial fibrosis
CO
iH
•-)
CO
O
U
g
•H
O
Granulomas
Alveologenic adenomas
Lymphosarcoma
Rabbits
Inhalation
Mixed dust
Controls
Intratracheal experimental
Dry mixed dust
Zinc chromate
Lead chromate
Residue
Controls
Dry portland cement
Saline
No injection
Inhalation
Mixed dust
Controls
Intratracheal experimental
Mixed dust
Zinc chromate
Lead chromate
Residue
Controls
Dry portland cement
Wet portland cement
8
5
10
7
7
7
2
5
2
50
44
19
21
13
19
8
7
3
3
6
4
7
3
1
4
0
13
22
4
7
1
4
1
0
5
1
3
3
4
2
0
2
1
14
14
7
6
4
2
2
1
4
1
2
4
4
3
0
2
1
16
10
3
6
3
7
2
2
0
0
0
1
0
0
0
0
0
32
28
10
13
6
5
3
2
6
4
6
0
7
7
2
3
1
Guinea
34
32
9
8
7
9
4
4
0
0
0
0
0
0
0
0
0
pigs
0
0
8
0
0
1
0
0
0
1
3
3
1
2
1
1
1
7
4
0
7
3
6
1
2
3
1
4
2
3
3
0
2
0
18
9
4
14
7
8
2
2
1
0
2
1
0
1
0
1
0
4
6
1
5
1
5
0
0
4
1
0
4
3
2
0
0
1
23
6
11
12
6
9
1
3
1
0
2
6
1
2
0
0
0
11
0
2
13
2
1
0
2
0
0
1
0
0
0
1
0
0
6
0
0
5
1
0
1
1
1
0
0
0
0
0
1
0
0
3
3
2
2
1
2
1
0
1
0
1
2
0
2
0
0
0
1
0
1
4
2
3
0
0
0
0
0
0
0
0
0
0
0
3
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
0
0
0
1
0
0
oo
-------
Table 6.17 (continued)
Number of animals exhibiting various
Method
of
exposure
Inhalation
Mixed dust
Control
Intratracheal
Chromate, then virus
Virus, then chromate
Virus only
Chromate only
Intratracheal
Zinc chromate early
Zinc chromate
Zinc carbonate early
Zinc carbonate
No injections
Total number of
animals
78
75
32
35
38
38
11
62
7
12
18
•a
16
33
13
13
6
13
4
20
2
2
5
Hyperemia
15
14
14
24
21
19
2
22
1
2
9
01
00
01
EC
19
17
8
12
13
9
7
24
3
7
6
Emphysema
37
44
24
32
23
32
0
12
0
2
2
Atelectasis
Rats
37
49
28
33
22
28
Mice
5
21
0
6
7
Bronchiectasis
24
41
19
17
11
21
0
16
0
0
4
Abscesses
40
17
15
11
8
14
0
2
0
0
1
Bronchopneumonia
57
35
11
17
13
23
0
8
1
3
10
Interstitial
pneumonitis
5
5
8
3
11
2
0
18
1
1
1
Alveolar & intersti-
tial inflammation
22
12
3
1
2
4
6
45
1
1
2
symptoms
Alveolar hyperplasia
5
2
7
8
2
8
4
28
0
1
2
Interstitial fibrosis
0
0
1
3
0
0
0
2
0
0
0
01
01
CJ
4J
pi
a
•H
o
25
4
4
3
1
1
0
0
0
0
0
Granulomas
12
1
1
0
0
0
0
1
0
0
0
Alveologenic adenomas
3
2
0
2
1
0
0
31
0
3
7
Lymphosarcoma
4
4
1
1
3
2
0
2
0
0
2
aThe groups designated "early" include those animals that died or were killed within the first 6 months. The first tumors
appeared at 6% months in the zinc chromate and zinc carbonate groups.
Source: Adapted from Steffee and Baetjer, 1965, Table 1, p. 67. Reprinted by permission of the publisher.
I-1
00
-------
Table 6.18. Death distribution and tumors observed in rats at site of implants of chromium compounds and of sheep fat
Deaths in periods of months after administration
Chromium
compound
CaCrO,,
Sintered
CaCrO,.
Sintered
Cr03
BaCrO,.
Sheep fat
Site of
implant
Thigh
Pleural
Thigh
Pleural
Thigh
Pleural
Thigh
Pleural
Thigh
Pleural
0-3
With
tumor
0
0
0
0
0
0
0
0
0
0
No
tumor
1
3
1
2
0
1
2
0
1
0
4-6
With
tumor
3
7
6
3
4
2
0
0
0
0
No
tumor
4
1
2
4
3
1
1
3
1
1
7-9
With
tumor
5
13
2
13
8
8
0
0
0
0
No
tumor
0
5
1
2
0
2
1
1
1
3
of material
10-12
With
tumor
0
1
0
1
3
4
0
0
0
0
No
tumor
0
5
2
1
1
2
1
1
3
1
Duration
of
exposure
(months)
13
12
14
14
12
12
12
12
12
12
Number
dead
13
35
14
26
19
20
5
5
6
5
No
tumor
at
site
8
21
8
17
15
14
0
0
0
0
Percent
of dead
with
tumors
62
60
57
65
79
70
0
0
0
0
1— '
00
(Ji
Number of rats at beginning of experiment: 35 (20 male and 15 female) for each material at each site.
Source: Adapted from Hueper and Payne, 1959, Table I, p. 275. Reprinted by permission of the publisher.
-------
186
not produce tumors in rats during the same period of time. Thus, chromium
was capable of producing carcinomas of the lung and sarcomas of the soft
tissues of the mediastinum and thigh. Laskin, Kuschner, and Drew (1970)
used intrabronchial pellets in rats to determine the carcinogenic effect
of ore-roast residue, calcium chromate, chromic oxide, and chromium tri-
oxide. Lung cancers were produced that closely duplicated human lung
pathology (Table 6.19). The mean cancer induction time was 540 days. All
carcinomas occurred at the site of pellet implantation.
Table 6.19. Carcinomas produced with chromium compounds in rats
Material
Number of Squamous cell Adeno- Hepatocell
animals carcinoma carcinoma carcinoma
Process residue
Calcium chromate
Chromic chromate
Chromic oxide
Chromic trioxide
Cholesterol control
100
100
100
98
100
24
1 1
6 2
1
2
Source: Adapted from Laskin, Kuschner, and Drew, 1970, Table 5,
p. 334.
Zinc chromate, widely used as an anticorrosive paint pigment, may also
possess carcinogenic properties since it is slightly more soluble than the
carcinogenic strontium chromate. Chromite ore roasts implanted into the
pleural cavity and into the thigh muscle of rats produced squamous cell
carcinomas along with sarcomas of the lung (Hueper, 1958). Fibrosarcomas
were found in the thighs of the rats. Further studies by Payne (1960&) in
which roasted chromite ore fractions (10 mg) were injected subcutaneously
into rats indicated that intermediate products in the production of chro-
mium chemicals and the discarded residue may be harmful. Implantation of
these fractions produced sarcomas in 4 of 70 rats. Calcium chromate in-
jected intramuscularly into rats produced spindle cell and pleomorphic cell
sarcomas in 75% of the test rats (Roe and Carter, 1969). Sarcomas were pro-
duced at the injection site and were locally invasive. Schoental (1975)
hypothesized that the mechanism of action involved oxidation of glyceral
and fatty acids by the hexavalent chromium to yield carcinogenic aldehydes
and epoxyaldehydes. However, proof is lacking.
Hueper and Payne (1962) found in experiments with rats that both hexa-
valent and trivalent chromium possessed carcinogenic properties. Sodium
-------
187
dichromate (2 mg) injected intrapleurally produced an adenocarcinoma of
the right lung. Chromic acetate (25 mg), a trivalent chromium compound,
induced only a weak carcinogenic response from muscular tissue. One ana-
plastic spindle cell sarcoma was found at the site of implantation.
6.3.3.2.3 Other respiratory effects — Dusts and mists which contain low
concentrations of hexavalent chromium irritate the respiratory system and
can cause sneezing, rhinorrhea, redness of the throat, and general broncho-
spasm (National Academy of Sciences, 1974). Higher chromium concentrations
may cause coughs, headaches, dyspnea, and substernal pain.
In two cases where large amounts of chromic acid mist were inhaled,
the nasal mucosa was only mildly hyperemic, but deep pulmonary structures
were severely damaged (Meyers, 1950). Weight loss, coughing, chest pain,
and pleural effusion were present in both cases. Six months after exposure
both patients still experienced sharp, burning chest pains on deep inspira-
tion. Williams (1969) reported two asthma cases which were related to chro-
mium inhalation. One patient was exposed to chromic acid mist and the other
to zinc chromate in a primer paint. The asthmatic conditions subsided when
the patients were gradually removed from contact with the chromium source.
6.3.3.3 Systemic Effects — Although explicit proof of systemic poisoning
due to occupational exposure to chromium compounds is lacking, a relation-
ship between the two may exist. A study of several workers in a chromium-
plating plant (Pascale et al., 1952) investigated hepatic injury due to
exposure to chromium trioxide from chromic acid mist. Of five patients
with high urinary chromium concentrations, two showed clinical evidence of
hepatic involvement and another had no physical evidence of systemic
disease. One of the patients with symptoms was jaundiced and one patient
had hepatic tenderness. Biopsy on four of the five patients showed abnor-
malities in hepatic structure. The authors concluded that subtle systemic
intoxication to employees in the chromium industry may be a definite health
hazard.
Evan and Bail (1974) studied structural changes in the kidney following
chromate treatment. Sodium chromate (10 or 20 mg/kg wt) injected intra-
peritoneally into rats induced changes which correlated with the amount of
lysozyme in the urine. The chromate selectively affected the cells in the
convoluted portion of the proximal tubule; progressive changes were swell-
ing and loss of microvilli, formation of intracellular vacuoles, mitochon-
drial swelling, and cytoplasmic liquefaction followed by desquamation.
Higher chromate doses and longer exposure caused greater damage. Urinary
lysozyme concentrations increased as damage to the tubule cells became more
severe.
The effects of adding chromium to the drinking water of animals have
been studied. For four years dogs were given water containing from 0.45
to 11.2 ppm chromate (Anwar et al., 1961). Chromium accumulated in the
liver, kidney, and spleen independent of the chromium concentration in
water. No significant pathological changes were found in any of the
animals. Administering both trivalent and hexavalent chromium (25 ppm) in
drinking water to rats for a year produced no toxic symptoms. Hexavalent
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188
chromium produced higher tissue chromium concentrations than trivalent chro-
mium; therefore, its ingestion may be potentially more hazardous. Byerrum
(1960) also introduced hexavalent chromium into the drinking water of rats.
In agreement with Anwar et al. (1961), he found no toxicity due to the
chromium.
6.3.3.4 Mutagenesis and Teratogenesis — No data were found implicating
chromium as either a mutagen or a teratogen.
6.3.3.5 Recommended Threshold Limit Values — The threshold limit values
(TLV) recommended by the American Conference of Governmental Industrial
Hygienists in 1970 for airborne chromium compounds in the work environment
vary according to the chromium form. For chromic acid and chromates ex-
pressed as Cr03, the TLV is 0.1 mg/m3. For other soluble chromic and
chromous salts, the TLV is 0.5 mg/m3 expressed as chromium. For the metal
and its insoluble salts, the TLV is 1 mg/m3 (Smith, 1972). The same
organization has recommended a TLV of 0.1 mg/m3 for some insoluble chro-
mates (National Academy of Sciences, 1974).
The National Institute for Occupational Safety and Health (NIOSH) of
the U.S. Department of Health, Education, and Welfare has recommended that
the TLV for chromic acid be 0.05 mg/m3 as chromium trioxide, with a ceil-
ing concentration of 0.1 mg/m3, as determined by a sampling time of 15
min (U.S. Department of Health, Education, and Welfare, 1973). These levels
may be low enough to prevent manifestation of most effects of chromium ex-
posure. However, according to Smith (1972), if an air quality standard for
chromium is adopted for the general population, it can be expected to be
very much lower than the TLV.
Controls more stringent than those indicated by the limits cited above
have recently been recommended by NIOSH for both soluble (noncarcinogenic)
and insoluble (carcinogenic) airborne chromium(VI) compounds. The maximum
workplace concentration of airborne carcinogenic chromium(VI) recommended
is 1 yg/m3 of breathing zone air; carcinogenic chromium(VI) is defined
as poorly soluble monochromates and dichromates (U.S. Department of Health,
Education, and Welfare, 1975). The maximum recommended concentration for
airborne, noncarcinogenic hexavalent chromium — defined as the readily
soluble monochromates and dichromates — is considerably higher: 25 yg
chromium(VI) per cubic meter of breathing zone air determined as a time-
weighed average exposure for up to a 10-hr workday, 40-hr workweek. For
any 15-min sample, the permissible maximum concentration is 50 yg chromium-
(VI) per cubic meter of breathing zone air.
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189
SECTION 6
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34. Gurson, C. T., and G. Saner. 1973. Effects of Chromium Supplementation
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35. Hambidge, K. M. 1971. Chromium Nutrition in the Mother and the Growing
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37. Hambidge, K. M., and J. D. Baum. 1972. Hair Chromium Concentrations
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38. Hambidge, K. M., M. L. Franklin, and M. A. Jacobs. 1972. Changes in
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48. Hueper, W. C. 1958. Experimental Studies in Metal Cancerigenesis.
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51. Imbus, H. R., J. Cholak, L. H. Miller, and T. Sterling. 1963. Boron,
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54. Katz, S. A., D. M. Scheiner, A. W. Klein, and M. H. Samitz. 1974.
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Contaminants and Human Health, D.H.K. Lee, ed. Academic Press,
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120. Steffee, C. H., and A. M. Baetjer. 1965. Histopathologic Effects of
Chromate Chemicals. Arch. Environ. Health 11:66-75.
121. Sullivan, R. J. 1969. Preliminary Air Pollution Survey of Chromium
and Its Compounds. U.S. Department of Health, Education, and Welfare,
Raleigh, N.C. 75 pp.
122. Taylor, F. 1975. Distribution and Retention of Chromium in Small
Mammals from Cooling Tower Drift (presented at Fourth National
Symposium on Radioecology, Corvallis, Ore., May 12-14, 1975). 5 pp.
123. Taylor, G. 0., and A. 0. Williams. 1974. Lipid and Trace Metal
Content in Coronary Arteries of Nigerian Africans. Exp. Mol. Pathol.
21:371-380.
-------
198
124. Tipton, I. H. 1960. The Distribution of Trace Metals in the Human
Body. In: Metal-Binding in Medicine, M. J. Seven, ed. J. B.
Lippincott Co., Philadelphia, Pa. pp. 27-42.
125. Tipton, I. H., and M. J. Cook. 1963. Trace Elements in Human Tissue:
Part II. Adult Subjects from the United States. Health Phys. (England)
9:103-145.
126. Toepfer, E. W. 1974. Separation from Yeast of Chromium Containing
Material Possessing Glucose Tolerance Factor Activity. Fed. Proc.
33:659.
127. Toepfer, E. W., W. Mertz, M. M. Polansky, E. R. Roginski, and W. R.
Wolf. 1977. Preparation of Chromium-Containing Material of Glucose
Tolerance Factor Activity from Brewer's Yeast Extracts and by Synthesis.
J. Agric. Food Chem. 25:162-166.
128. Toepfer, E. W., W. Mertz, E. E. Roginski, and M. M. Polansky. 1973.
Chromium in Foods in Relation to Biological Activity. J. Agric. Food
Chem. 21:69-73.
129. Underwood, E. J. 1971. Chromium. In: Trace Elements in Human and
Animal .Nutrition. 3rd ed. Academic Press, New York. pp. 253-266.
130. U.S. Department of Health, Education, and Welfare. 1973. Occupational
Exposure to Chromic Acid. pp. 15-43.
131. U.S. Department of Health, Education, and Welfare. 1975. Occupational
Exposure to Chromium(VI). HEW Publication No. (NIOSH) 76-129. 200 pp.
132. Visek, W. J., I. B. Whitney, U.S.G. Kuhn, III, and C. L. Comar. 1953.
Metabolism of Cr-51 by Animals as Influenced by Chemical State. Proc.
Soc. Exp. Biol. Med. 84:610-615.
133. Wacker, W.E.C., and B. L. Vallee. 1959. Nucleic Acids and Metals:
I. Chromium, Manganese, Nickel, Iron and Other Metals in Ribonucleic
Acid from Diverse Biological Sources. J. Biol. Chem. 234:3257-3262.
134. Wester, P. 0. 1972. Trace Elements in RNA from Beef Heart Tissue.
Sci. Total Environ. (Netherlands) 1:97-103.
135. Williams, C. D. 1969. Asthma Related to Chromium Compounds. N.C. Med.
J. 30:482-491.
136. Zvaifler, N. 1944. Chromic Acid Poisoning Resulting from Inhalation
of Mist Developed from Five Percent Chromic Acid Solution: I. Medical
Aspects of Chromic Acid Poisoning. J. Ind. Hyg. Toxicol. 26:124-126.
-------
SECTION 7
ENVIRONMENTAL DISTRIBUTION AND TRANSFORMATION
7.1 SUMMARY
Chromium is an abundant element. Large amounts are used in the trans-
portation industry, construction, machinery, and refractory products. Les-
ser amounts are also used for home appliances, pigments and paints, leather
tanning, and metal plating. The entire U.S. chromium ore supply is imported
from other countries, including South Africa, the U.S.S.R., Turkey, the
Philippines, and Albania. The world supply of chromium is adequate to meet
U.S. demands until at least the year 2000.
Chromium is emitted into the atmosphere mainly from ore refining, chemi-
cal processing, refractory processing, fossil fuel combustion, cement proc-
essing, asbestos production, and incineration of a variety of materials.
Air chromium concentrations exceeded 10 ng/m3 in 59 of 186 urban areas ex-
amined and are below the detection limit in most nonurban areas. Atmospheric
chromium is usually in particulate form. Background levels are difficult to
estimate but may be about 5 pg/m3.
Total soil chromium concentrations vary, ranging from <5 to about 300
ppm except in serpentine soils which may have up to 1% to 2%. Available
chromium is quite low (0.01 to 4 ppm) even in serpentine soils. Most chro-
mium in soil is in an insoluble or tightly bound trivalent form.
Chromium concentrations in fresh water range from 0 to about 100 ppb.
Seawater concentrations are lower (0 to 0.36 ppb). Both trivalent and
hexavalent chromium exist in water, but the trivalent form may eventually
precipitate or be absorbed from the water. Hexavalent chromium is the major
stable form in seawater.
Chromium concentrations in sediments range from <1 to about 100 ppm,
which corresponds to background levels. The anthropogenic input has not
been high.
Precipitation and fallout remove chromium from the atmosphere to both
land and water. Chromium within soil is insoluble and leaching removes
very little. Surface runoff supplies some chromium to natural waters,
where it is eventually deposited in sediments. Management of aqueous chro-
mium wastes usually involves converting any hexavalent chromium to the tri-
valent form. The pH is raised to 9.5 and chromic hydroxide precipitates.
The dried precipitate is placed in landfills.
Sewage sludge contains a wide range of chromium concentrations (20 to
40,000 ppm) and is often added to soils as fertilizer. The chromium within
these amended soils is not easily extractable and, thus, is neither available
for plants nor lost by leaching. Other toxic elements in sludges are of much
greater concern.
199
-------
2QO
7.2 TRENDS IN PRODUCTION AND USAGE
Chromium is present in a variety of rocks (Mertz et al., 1974) (Table
7.1). Ultramafic and serpentine rocks contain the largest chromium con-
centrations; granitic rocks, limestones, and dolomites contain the smallest
amounts. Chromium in igneous rocks, usually in the mineral form of chromite,
shows positive correlation with magnesium and nickel content. Argillaceous
sedimentary rocks also contain chromium, which is usually concentrated in
the phosphorites and in bauxite and lateritic iron ores. Frohlich (1960)
in his study of the geochemistry of chromium found:
The analyses show that chromium is concentrated in the
basic and ultrabasic rocks, while the granites investigated
generally contained only about 1 p.p.m. Cr. In the basic
rocks, the chromium is present in specific chromium minerals
such as chromite and picotite, and also in magnetites and
pyroxenes. The felspar contains almost no chromium.
Table 7.1. Chromium content of various materials
(ppm)
Chromium content
Type of material
Ultramafic and serpentine
Basalts and gabbros
Andesites, diorites
Granitic rocks
Limestones and dolomites
Sandstones
Clays and shales
Soils
Phosphorites
Coal
Usual range
reported
1100-3400
60-420
10-200
2-60
1-200
10-150
30-3000
Average
1800
200
50
5
11
35
90
40
300a
10
Phosphorites from Idaho, Wyoming, and Utah
average close to 1000 ppm chromium.
Source: Adapted from Mertz et al., 1974, Table 10,
p. 30. Reprinted by permission of the publisher.
-------
201
The chromium content of volcanic rocks decreases
steadily with increasing Si02 content. Thus, the melilite
basalt of Gotzenbruhl with 34.7% Si02 contains 1380 p.p.m.
Cr, while the Aar granite with 77% Si02 contains but
1 p.p.m. Cr.
Among the sedimentary rocks, high chromium contents are
found in bauxites and in sedimentary iron ore deposits. In
the bauxites this is due to relative (secondary) enrichment
of chromium, while in the iron ores chromium may be associated
with the iron in a colloidal state.
Pelitic sediments show a very uniform chromium content.
Of 40 samples investigated, 24 contained between 70 and 100
p.p.m. Cr, while the remainder were also fairly close to these
values.
For the most part, the chromium in sediments is concen-
trated in the micas and clay minerals, particularly in illite.
Chromite, which may be represented as (Mg, Fe)0»(Cr, Al, Fe)203,
is the major chromium mineral of commercial importance. In the United
States, unaltered forms range in composition from 16.4% to 60.4% Cr203
(Thayer and Miller, 1962). United States chromite deposits occur in Mary-
land, Montana, North Carolina, Pennsylvania, Texas, Wyoming, California,
in beach-sand deposits in Oregon and Washington, and in lateritic iron ores
in Washington. These deposits are small and presently of no commercial
value (Mertz et al., 1974). Major minable reserves of chromite (contain-
ing 33% to 55% Cr203) exist in Brazil, Cuba, Rhodesia, and the Republic
of South Africa; several other countries have smaller minable amounts
(Thayer, 19.73) (Table 7.2). Additional estimates of chromite ore resources
are given in Table 7.3.
Because of its importance for various defense purposes, chromium ore
is stockpiled, and "due to the politically unstable nature of the supply of
chromium ore, stockpiles tend to be larger than ordinarily expected" (GCA
Corporation, 1973). Stockpile inventories for 1972 were 826,000 metric tons
of chemical-grade chromite, 1,061,000 metric tons of refractory-grade chro-
mite, 1,413,000 metric tons of metallurgical-grade chromite, 366,000 metric
tons of high-carbon ferrochromium, 290,000 metric tons of low-carbon ferro-
chromium, 54,000 metric tons of ferrochromium-silicon, and 7300 metric tons
of chromium metal (Morning, 1974).
The United States currently imports all of its chromium ore. In 1968,
about 75% came from South Africa and the U.S.S.R. and about 25% from Turkey,
the Philippines, and Albania (Brantley, 1970). Amounts of chromite imported
in 1972 were 394,000 metric tons from the U.S.S.R, 92,000 metric tons from
Turkey, 225,000 metric tons from the Republic of South Africa, 84,000 metric
tons from Southern Rhodesia, 119,000 metric tons from the Philippines,
25,000 metric tons from Pakistan, 12,000 metric tons from the Malagasy
Republic, and 13,000 metric tons from Iran (Morning, 1974).
-------
202
Table 7.2. Estimated world reserves and resources of chromlte ore
(metric tons)
Area
Western Hemisphere
United States
Brazil
Canada
Cuba
Greenland
Other areas
Hemisphere total
Eastern Hemisphere
Republic of South Africa
Rhodesia
U.S.S.R.
Turkey
Finland
India
Philippine Republic
Malagasy Republic
Iran
Greece
Other areas
Hemisphere total
World total
(rounded)
Type of ore
and -,
deposit
A (P)
B, B- (S, PI)
C (P)
A (S)
B (S)
C (P)
A (P)
B, B- (S)
A (P)
C (P)
B- (S)
A
B
B-
c
Other
All types
A (S)
B (S)
A (S, PI)
B (S)
A (P)
B- (S)
C (P)
A (C) (P)
B (S)
A (S, P)
B (S)
A (P)
C (P)
A (S)
B (S)
A (P)
A (P)
C (P)
A (C) (P)
B (S)
A
B
B-
C
All types
Identified fl
chromium resources
d
Reserves
None
None
None
2,500
3,500
100
250
2,500
3,500
350
6,350
500,000
1,000,000
500,000
50,000
10,000
1,000
10,000
5,000
10,000
5,000
2,000
700
4,000
4,000
1,000
1,500
50
50
2,000
577,250
1,064,020
1,000
14,050
1,656,300
1,663,000
Conditional
resources6
350
5,000
100
3,000
2,000
150
100
2,500
100
1,000
10,000
200
3,650
19,500
1,200
200
24,550
500,000
2,000,000
500,000
50,000
10,000
2,000
• 10,000
5,000
5,000
4,000
2,000
500
2,000
3,000
2,000
1,000
100
2,000
574,550
2,060,000
2,000
12,050
2,648,600
2,675,000
f
Hypothetical
and speculative^
resources
500
2,000
100
5,000
5,000
1,000
10,000+
200
5,500
17,000+
1,100
200
23,800+
3,000,000+
500,000+
25,000
5,000
10,000
20,000
1,000
5,000
7,000
5,000
250
2,500
3,581,250
3,581,250
3,600,000
Types of ore: A, high chromium ore, Cr203 more than 46%, Cr:Fe is more than 2:1; B,
high-iron ore, Cr203 40-46%, Cr:Fe is 1.5:1 to 2:1; B-, high iron ore, Cr203 less than 40%,
Cr:Fe is 1.5:1 or less; C, high-aluminum ore, A1203 is more than 20%, Al20a + Cr203 is more
than 60%.
"Types of deposit: (S), layered or stratiform; (P) , pod-shaped; (PI), placer,
subordinate; (C), amount not estimated.
"Identified resources: Specific, identified mineral deposits that may or may not be
evaluated as to extent and grade, and whose contained minerals may or may not be profitably
recoverable with existing technology and economic conditions.
"Reserves: Identified deposits from which minerals can be extracted profitably with
existing technology and under present economic conditions.
^Conditional resources: Specific, identified mineral deposits whose contained
minerals are not profitably recoverable with existing technology and economic conditions.
tHypothetical resources: Undiscovered mineral deposits, whether of recoverable or
subeconomic grade, that are geologically predictable as existing in known districts.
^Speculative resources: Undiscovered mineral deposits, whether of recoverable or
subeconomic grade, that may exist in unknown districts or in unconventional form.
Source: Adapted from Thayer, 1973, Table 24, pp. 117-118. Data collected from
several sources.
-------
Table 7.3. Estimated world chromite ore resources
Area
Republic of South Africa
Southern Rhodesia
Turkey
United States
Philippines
Finland
Canada
Other
Free world total
U.S.S.R. and other
Communist countries
World total (rounded)
Total
(thousand
metric
tons)
2,000,000
600,000
10,000
8,000
7,500
7,500
5,000
11,350
2,649,350
51,500
2,701,000
High chromium
Percent
5
50
90
5
20
72
16
51
17
Quantity
(thousand
metric
tons)
100,000
300,000
9,000
400
1,500
8,175
419,075
26,500
446,000
High
Percent
95
50
92.5
100
100
2
84
29
83
. b
iron
Quantity
(thousand
metric
tons)
1,900,000
300,000
7,100
7,500
5,000
200
2,220,100
15,000
2,235,000
s*
High aluminum
Percent
10
10
2.5
80
26
0.4
20
1
Quantity
(thousand
metric
tons)
1,000
1,000
200
6,000 g
2,975
10,175
10,000
20,000
,Cr203, 45% or more, metallurgical ores.
Cr203, 40% or more, chemical ores.
CA1203, 20% or more, refractory ores.
Source: Adapted from Brantley, 1970, Table 2, p. 251.
-------
204
In 1972, the U.S. chromium consumption was 320,000 metric tons, which
represented 1,034,000 metric tons of chromite ore; 63.8% was used by the
metallurgical industry, 19.6% by the refractory industry, and 16.6% by the
chemical industry (Morning, 1974). Figure 7.1 presents the chromium supply-
demand relationships for 1968. Most uses of chromium depend upon its
decorative and corrosion-resistant properties. The breakdown of chromium
distribution into specific categories (Figure 7.1 and Table 7.4) shows that
construction products, transportation machinery and equipment, and refrac-
tory products consumed most of the 458,000 metric tons which were used in
1968 (Brantley, 1970). Metallurgical uses include iron castings, chrome
alloys, steels and stainless steel, and various chrome-plated items (Brantley,
1970). Because chromite has a high melting point [2038°C (3700°F)] and is
chemically inert, it is used in manufacturing bricks for lining metallur-
gical furnaces. A flow diagram shows the amounts of chromium used to pro-
duce various materials in 1970 (Figure 7.2).
The major chromium compounds produced in the chemical industry are
chromate and dichromate, which serve as starting compounds for manufactur-
ing all other chromium chemicals (Sullivan, 1969). This process involves
roasting finely ground chromite ore with sodium carbonate and calcium car-
bonate and then leaching with hot water to extract "sodium monochromate"
(Na2CrO<.) (Buckell and Harvey, 1951). Addition of dilute sulfuric acid
produces sodium dichromate (Na2Cr207). Chromates are used for oxidation in
the production of various organic materials (such as saccharin, benzoic
acid, and camphor), in purification of chemicals, and in inorganic oxida-
tions (Sullivan, 1969). A major percentage of chromic acid is used for
chrome plating. Dichromate can be converted to chromium(III) sulfate, which
is used in the tanning industry (6800 metric tons of Cr203 per year).
Chromates and chromic oxide, in combination with other metals, produce a
variety of pigments and mordants. Table 6.12 lists some important chromium
compounds and their industrial uses. Fungicides and wood preservatives
consume an estimated 1300 metric tons of chromium annually. Chromates are
also used as rust and corrosion inhibitors.
Projected chromium demands for the year 2000 (Table 7.4) show an
increase in most of the consumption categories (Brantley, 1970). The
accuracy of these estimates depends on many factors. For example, the
projected amount of chromium to be used in transportation depends on the
total number of automobiles produced in 2000; their size, decorative require-
ments, and pollution control devices; the number of commercial and family
vehicles; and the number of pleasure crafts, vessels, and military ships.
The supply of chromium is estimated to be adequate to meet the pro-
jected demand (for the year 2000, between 0.78 and 1.16 million metric
tons); however, with the present price structure, the U.S. chromium supply
will be obtained entirely from foreign sources (Brantley, 1970). If domes-
tic resources were used (U.S. reserves: 20.4 million metric tons of chro-
mite ore with an 11.4% average Cr203 content), costs would be about $1280
per ton of chromium, compared to about $100 per ton from foreign sources.
Part of the domestic demand will be supplied by recovery of chromium from
stainless steel scrap and home materials scrap (<25% total).
-------
WORLD PRODUCTION
1664(1834le
ORNL-DWG 76-2459
GOVERNMENT STOCKPILE BALANCE - 2256(2487)
TRANSPORTATION
(SIC 371
77(851
CONSTRUCTION
PRODUCTS
(SIC 15, 161
105(116)
MACHINERY AND
EQUIPMENT
(SIC 35, 36)
72(79)
HOME APPLIANCES
AND EQUIPMENT
(SIC 363)
25(281
REFRACTORY PRODUCTS
(SIC 33, 32971
68(751
PLATING OF METALS
(SIC 3471 1
20(221
PIGMENTS AND PAINTS
(SIC 281 6. 3479)
15(161
LEATHER PRODUCTS
(SIC 3111)
10111)
KEY
e - ESTIMATE
SIC - STANDARD INDUSTRIAL CLASSIFICATION
UNITS' THOUSAND METRIC TONS OF CHROMIUM WITH THOUSAND
SHORT TONS IN PARENTHESES.
OTHER
66(73)
N>
O
Ul
Figure 7.1. Supply-demand relationships for chromium, 1968. Source: Adapted from
Brantley, 1970, Figure 1, p. 253.
-------
Table 7.4. Contingency forecasts of demand for chromium by end use, year 2000
End use
Transportation
Construction products
Machinery and
equipment
Home appliances and
equipment
Refractory products
Plating of metals
Pigments and paints
Leather products
Other
Total
Demand, 1968
(thousand
metric tons)
77
105
72
25
68
20
15
10
66
458
U.S. forecast
base, 2000
(thousand
metric tons)
165
196
191
89
50
70
51
9
232
Dnited
Low estimate
(thousand
metric tons)
135
186
168
45
36
35
45
9
209
868
Demand
States
High estimate
(thousand
metric tons)
204
263
259
91
68
78
65
11
256
1295
, 2000
Rest of
Low estimate
(thousand
metric tons)
NAa
NA
NA
NA
NA
NA
NA
NA
NA
2542
the world
High estimate
(thousand
metric tons)
NA
NA
NA
NA
NA
NA
NA
NA
NA
3903
NA = Not available.
Source: Adapted from Brantley, 1970, Table 4, p. 258.
NJ
O
-------
ORNL-DWG 76-2460
SECONDARY
METAL AND SCRAP
•GCA ESTIMATES
UNITS: THOUSAND METRIC TONS CONTAINING CHROMIUM WITH
THOUSAND SHORT TONS IN PARENTHESES
Figure
Figure 1, p
7.2.
, 3.
Chromium material flow, 1970. Source: Adapted from GCA Corporation, 1973,
-------
2Q8
With advances in technology, use of substitute materials, and develop-
ment of new uses, changes in demand could occur. From a production view-
point, the substitution of chemical grades of chromite for metallurgical
grade is to be expected in the near future for some uses (Brantley, 1970).
In the production of stainless steels, lower cost high-carbon ferrochromium
is increasing in use compared to low-carbon ferrochromium. These steels
have a slightly lower chromium content than the steels they replace and
have a comparable strength and corrosion resistance. The trend is toward
expanded use of heat- and corrosion-resistant materials and use of lower
grades of chromite for their production in some cases.
7.3 DISTRIBUTION OF CHROMIUM IN THE ENVIRONMENT
7.3.1 Sources of Pollution
Major sources of atmospheric chromium emissions are from different
aspects of the chromium industry, such as ore refining, chemical processing,
refractory processing, metallurgical processing, and "inadvertent" sources
such as coal and oil combustion, cement production, incineration, and
asbestos production (GCA Corporation, 1973) (Table 7.5). Ferrochromium
production is by far the major source of atmospheric emissions (68.2% of
the U.S. total). Emission control procedures decreased total chromium
emissions by 54% [16,463 metric tons per year (18,136 tons per year) after
control compared with 36,106 metric tons per year (39,775 tons per year)
before control] with a 40% reduction in the ferrochromium industry (Table 7.5).
Data for geographical distribution of atmospheric chromium emissions
in the United States, divided according to the U.S. Environmental Protec-
tion Agency regions, are presented in Table 7.6. The more populated, in-
dustrial areas of the United States received the most emissions. The Great
Lakes area received 29% of the total chromium emissions, while the three
East Coast regions were next with 19.0%, 18.5%, and 17.3%. The rest of the
United States received very little.
Another study of atmospheric chromium emissions (Goldberg, 1973) gave
similar estimates for primary chromium production, but it did not consider
emissions from the ferrochromium industry (Table 7.7). In addition, esti-
mated total emissions from coal and oil combustion were considerably higher.
Thus, from these two studies, total emissions were estimated to be between
11,000 and 16,000 metric tons per year.
Chromium air pollution comes mainly from the industrial production of
chrome alloys and chromium metal, from chemical industries, and from the use
of chromium chemicals or end products. Chromium has not been mined in the
United States since 1961, so no air pollution can be attributed to this source.
Cement production also releases chromium to the atmosphere and to water.
A typical analysis of portland cement showed 41.2 ppm chromium (range 27.5
to 60 ppm), of which 4.1 ppm was soluble and of this amount, 2.9 ppm was hexa-
valent (Schroeder, 1970). In 1970, about 250 metric tons of chromium was
released to the atmosphere by cement production industries (GCA Corporation,
1973).
-------
Table 7.5. Sources and estimates of chromium-containing atmospheric emissions in 1970
• •*
Source
Mining
None in United States
Refining
Ferrochromium
Electric furnace
Material handling
Electrolytic chromium
Refractory
Noncast
Electric cast
Chemical processing
Dichromate
Other chemicals
Steel and alloys
Chromium steels
Cast iron
Super alloys and
alloys
Genera,! steel making
Inadvertent sources
Coal combustion
Oil combustion
Cement production
Incineration
Asbestos
Total
Uncontrolled
emission
factor
(kg/103 kg)
(100-415)
250a
5
0.024
75
112
15
12
38
12
f3
NAC
NA
NA
NA
NA
NA
Production
level
(metric
tons/year)
341,000
341,000
8,200
55,000
6,000
55,400
172,000
4,500
11,000
NA
30,700,000
261,000
848,000
845,000
6,000
Chromium in
emissions
(%)
22
65
51
b
b
b
b
b
b
NA
0.026
0.13
0.03
0.017
0.15
Emissions
of chromium
before
controls
(metric
tons/year)
0
18,700
1,100
Negligible
4,100
684
835
2,100
171
136
NA
7,900
336
NA
NA
9.1
36,100
Estimated
level of
emission
control
(%)
40
32
95
64
77
90
78
99
78
NA
82
0
NA
NA
99
54
Emissions
of chromium
after
controls
(metric
tons/year)
11,200
750
Negligible
1,500
150
84
22
472
1.8
30
91
1,420
336
254
143
0
16,500
Percent of
total U.S.
chromium
emissions
68.2
4.6
9.0
1.0
0.6
2.9
0
0.2
0.6
8.6
2.0
1.5
0.9
.Intermediate value.
Emission factor multiplier equal to tons of chromium processed or handled annually.
NA = Not applicable.
Source: Adapted from GCA Corporation, 1973, Table 2, p. 12.
to
O
VO
-------
Table 7.6. Regional distribution of principal chromium sources and emissions
Environmental
Protection Agency
region
I. Conn. , Me. ,
Mass., N.H.,
R.I., Vt.
II. N.J., N.Y.,
P.R., V.I.
III. Del., Md.,
Pa., Va.,
W.Va., D.C.
IV. Ala., Fla.,
Ga., Ky.,
Miss., N.C.,
S.C., Tenn.
V. 111., Ind.,
Mich., Minn.,
Ohio, Wis.
VI. Ark., La.,
N.M. , Okla.,
Tex.
VII. Iowa, Kan.,
Mo., Neb.
VIII. Col., Mont.,
N.D., S.D.,
Utah, Wyo.
IX. Ariz., Calif.,
Nev., Hawaii,
South Pacific
X. Alaska, Idaho,
Ore., Wash.
Total
Ferrochrome
production12
Chromium
Number emissions
of (metric
plants tons per
year)
0 0
3 2,600
2 1,700
3 2,600
4 3,500
0 0
0 0
0 0
0 0
1 860
13 11,300
Refractory
production*2
Number
of
plants
0
4
15
2
14
0
2
1
2
0
40
Chromium
emissions
(metric
tons per
year)
0
160
610
82
570
0
82
41
82
0
1,630
Chrome steel
production0
Chromium
Number emissions
of (metric
plants tons per
year)
9 30
56 180
33 110
3 9
33 110
1 3.6
2 6.3
0 0
5 16.3
1 3.6
143 470
Cement ,
production
Number
of
plants
1
13
28
27
30
27
20
9
19
7
181
Chromium
emissions
(metric
tons per
year)
1.8
18
39
38
41
38
28
13
27
10
254
Chromium
emissions
from coal
production"
(metric .-
tons total
per. oil
year) derived
10 0.7
81 5.7
310 21.7
300 21.0
580 44.1
20 1.4
58 4.1
47 3.3
10 0.7
4.5 0.3
1,420 100
Chromium
emisj
>ions
from oil
combustion*
(metric
tons
per
year)
61
98
50
32
25
13
2.7
6.3
39
9
336
Percent
of
total
oil
derived
18.0
29.1
15.0
9.6
7.6
3.7
0.9
1.8
11.6
2.7
100
Total
chromium
emissions
(metric
tons
per
year)
103
3,140
2,800
3,000
4,830
74
177
107
174
898
15,300
Percent
of total
U.S.
chromium
emissions
0.6
19.0
17.3
18.5
29.0
0.5
1.1
0.7
1.1
5.4
93.2
Si
M
O
,Chromium industry source.
Inadvertent source.
Source:, Adapted from GCA Corporation, 1973, Table 4, p. 22.
-------
211
Table 7.7. Chromium emission sources
Chromium emission
Source
(metric
tons)
Percent
of this
pollutant
Asbestos mining 7.3 0.07
Kraft pulp mill recovery furnace Negligible Negligible
Sulfite pulp mill Negligible Negligible
Primary chromium production 3,800 34.98
Asbestos products Negligible Negligible
Refractory brick production 6.3 0.06
Installation of asbestos material Negligible Negligible
Spray-on fireproofing Negligible Negligible
Use of insulating cement Negligible Negligible
Power plant boilers
Pulverized coal 5,100 46.40
Stoker coal 580 5.33
Cyclone coal 170 1.60
All oil 20 0.18
Industrial boilers
Pulverized coal 220 2.06
Stoker coal 780 7.20
Cyclone coal 110 1.02
All oil 15 0.14
Residential/commercial boilers
Coal 70 0.64
Oil 34 0.32
Total 10,900
Source: Adapted from Goldberg, 1973, Appendix A, p. 107.
The combustion of natural materials is another source of atmospheric
chromium. For example, coal has a relatively high chromium content which
can be released during industrial and residential burning of coal (1400 metric
tons of chromium for 1970). Wood and leaf burning and forest fires are also
likely to release chromium, although estimated amounts were not found.
Coal combustion releases many environmental pollutants, the most abundant
of which are NO^. and S02 (Rancitelli, Abel, and Weimer, 1974). Considerable
quantities of trace elements are also released; the extent and the effects of
such emissions need to be determined. Chromium emissions from the power plant
in Centralia, Washington, were estimated to be 720 kg/year, with an estimated
yearly deposition on soil between 3.7 and 12.9 mg/m2. Eighty-two coal
samples from the Illinois Basin contained 4.00 to 54.00 ppm chromium with a
mean of 14.10 ppm (Ruch, Gluskoter, and Shimp, 1974). Concentrations in Bel-
gian coal samples and in the Illinois samples were similar (Table 7.8) (Block
-------
212
Table 7.8. Chromium concentrations in
Belgian coal and coal ash
(ppm)
Sample
Coal
Coal ash
Use
Home heating
Electric power
Coke production
Industrial processes
Home heating
Electric power
Coke production
Chromium
content
12.0
55.0
14.2
24.5
320
180
330
Source: Adapted from Block and Dams,
1975, Table II, p. 148. Reprinted by per-
mission of the publisher.
and Dams, 1975). Chromium in Belgian coal ash ranged from 180 ppm in coal
used for electric power generation to 330 ppm in coal used for coke production,
Coal used in the Allen Steam Plant in Memphis, Tennessee, contained 21 ppm
chromium, while slag contained 180 ppm and precipitated fly ash contained 356
ppm (White et al., 1974). Shiebly (cited in Lee and von Lehmden, 1973) re-
ported that chromium concentrations in coal ranged between 1 and 100 ppm.
Chromium apparently has not been concentrated in coal during formation
processes (Ruch, Gluskoter, and Shimp, 1974). In eight coal samples from
the western United States, the ratio of the mean values of chromium in coal
(9 ppm) to the clarke value for average crustal abundance of chromium (100
ppm) indicated an exclusion process. However, the significance of such esti-
mates based on average crustal abundance figures is in doubt.
Although trace element concentrations in coal are small, the use of
large amounts of coal releases considerable quantities of these elements to
the environment. Metals have been effectively removed by grinding coal with
water and then using oil to agglomerate the carbonaceous material (Capes et
al., 1974). The average chromium content of feed coal was 652 ppm and that
of the agglomerates was 186 ppm.
Nord and Bingham (1972) reported that Utah coals contained 22 ppm
chromium and Pennsylvania coals contained 0.4 ppm chromium. They demon-
strated that blood serum, lung wash fluid, and normal saline extracted
various percentages of metals (magnesium, calcium, iron, and nickel) from
coal samples; however, no chromium, cadmium, or lead was detected in
extracts.
-------
213
The use of commercial fertilizers supplies trace amounts of heavy
metals to soils. Mortvedt and Giordano (1975) reported that fertilizers
prepared from phosphate rock of the western United States contained higher
concentrations of most heavy metals (344 ppm chromium) than those prepared
from phosphate rock of the eastern United States (175 ppm chromium).
The plating and finishing industry is the major source of chromium
pollution in natural waters. In New York City, electroplaters accounted
for 43% of chromium received in sewage plant influent (Klein et al., 1974).
Surprisingly, residential runoff accounted for 21% of chromium in the in-
fluent. This runoff perhaps came from settling of atmospheric chromium
and subsequent washing into sewage waters. Chromium is released from plat-
ing processes as the result of rinsing operations; spillage; mists from hot
tanks; and chromate pickling, washing, and post-plating baths (Ottinger et
al., 1973). Although chromium pollution from the plating bath itself is
small, the overall loss of chromium as chromates or chromic acid is very
high - about 20,000 metric tons in 1970 in the United States; between 80%
and 90% of the chromium becomes wastes. Recovery procedures recycle only
about 30% of the wastes. Composition of some chromium-containing wastes
from metal-plating industries is given in Table 7.9. Typical waste treat-
ment involves reducing chromium(VI) to chromium(III) and subsequent raising
of the pH to precipitate the hydroxide (Section 7.5).
A new process for chromium plating using chromium(III) instead of
chromium(VI) is currently being tested (O'Sullivan, 1975). Advantages of
this process include elimination of the spray hazard, easier disposal of
spent electrolytes, more uniform chromium deposition, production of micro-
cracked finishes, and more economical operation.
The textile industry also releases significant amounts of chromate
waste, most of which is subsequently treated in the same manner as chromate
wastes from other sources.
Significant progress has been made in reducing the chromium content of
tannery discharge water (Eye, 1974). Examples cited for chromium removal
were 97% in one instance and a decrease of chromium from 2900 ppm in the
spent liquor to 0.4 ppm in the discharge solution. Chromium is usually
removed by precipitation with lime.
In 1970, use of chromate compounds as pigments accounted for about 40%
of the dichromates consumed in the United States (Chemical Profiles, Sodium
Bichromate and Chromic Acid, as cited in Ottinger et al., 1973). Ottinger
et al. (1973) estimated that 62,000 kg of chromium are lost annually in the
sludge of solvent-based paints and 437,000 kg as discarded paint residues.
7.3.2 Distribution in Air
The chromium concentration in air varies with location. Sullivan (1969)
cited data from the National Air Sampling Network for 1964 which gave the
national average for chromium as 0.015 yg/m3 with a maximum of 0.350 yg/m3.
Table 7.10 gives chromium content of air in 1968-1969 for both urban and non-
urban areas (U.S. Environmental Protection Agency, 1973). Although chromium
-------
214
Table 7.9. Composition of chromium-containing wastes from metal plating industries
Waste description
Form
Source
3000 ppm of a mixture of chromium, 20% aluminum sulfate,
and 35% sulfuric acid (trace of copper, nickel, lead)
12.5% chromic acid-dichromate in 10% to 30% sulfuric
acid with 5000 to 120,000 ppm chromium [85% as
Cr(III)] with 100 to 1000 ppm lead, copper, and iron
Dilute chromic acid solution containing Cr(III) at 100
to 200 ppm and Cr(VI) at 2000 to 4000 ppm with traces
of organics (combined wash waters)
Partially neutralized aqueous plating waste containing
5 to 10% zinc chromate, and 5 to 10% zinc phosphate
contaminated with various organic oils
Solutions of chromates and dichromates in sulfuric acid
(6 to 12%) containing 5000 to 170,000 ppm chromium
with copper, lead, and traces of organics
0.1 to 0.5% chromium, 100 to 400 ppm copper, 100 to 600
ppm nickel in 5 to 10% aqueous hydrofluoric-hydro-
chloric acid
1 to 20% chromium in solids concentrations of 10 to 80%
from settling and/or dewatering processes; includes
copper in varying amounts with varying amounts of
inert filter aids
100 to 1000 ppm chromium as alkaline cyanide solutions
(6 to 20%) with copper in varying amounts with
possible traces of organics, nickel, lead, and zinc
5 to
chromic acid in water solution with
chromic acid in 13% aqueous sulfuric acid
0.1 to 1% sodium or potassium dichromate in water,
usually sulfuric acid present in a 1 to 15%
concentration
Liquid Aluminum anodizing bath
with drag out
Liquid Metal finishing
Liquid Metal plating
Liquid Zinc plating
Liquid Formation of protective
and decorative coat-
ings (metals)
Liquid Plating preparation
(metal)
Sludge Chemical process
(plating operations,
manufac turing,
metallurgical)
Liquid Metal plating (formation
of protective and
decorative coatings)
Liquid Metal plating, ship-
building
Liquid Metal finishing and
plating
Liquid Metal finishing, ship-
building, plating
Source: Adapted from Ottinger et al., 1973, Table 1, p. 147.
concentrations in most nonurban areas, and even in many urban areas, were
below detection levels, certain areas did have measurable levels at some time
during the year. Yearly average concentrations in urban areas varied from
below detection level to as high as 0.120 yg/m3 in Baltimore, Maryland.
Yearly averages were greater than 0.010 yg/m3 in only 59 of 186 urban areas.
In fact, chromium in the air has apparently declined in many, but not all,
U.S. cities since 1959 (Table 7.11) (Schroeder, 1970). Table 7.12 reports
chromium values in air compiled from several sources; these values are
similar to those found by the National Air Surveillance Network.
Lee, Patterson, and Wagman (cited in Bond, Straub, and Prober, 1972)
found that the air in Cincinnati, Ohio, and in suburban Fairfax, Ohio, had
similar chromium content (0.31 and 0.28 yg/m3, respectively), while a wild-
life preserve had a somewhat lesser concentration. On another day, air
-------
215
Table 7.10. Chromium concentrations in urban and nonurban air,
quarterly composites and yearly averages, 1969
(Pg/m3)
Location
Alabama
Gadsden
Huntsville
Mobile
Montgomery
Alaska
Anchorage
Fairbanks
Arizona
Maricopa County
Phoenix
Tucson
Arkansas
Little Rock
Texarkana
West Memphis
California
Anaheim
Burbank
Fresno
Glendale
Long Beach
Los Angeles
Oakland
Ontario
Riverside
Sacramento
San Bernardino
San Diego
San Francisco
San Jose
Santa Ana
Torrance
Colorado
Denver
Montezuma County
Connecticut
Bridgeport
Hartford
New Haven
Waterbury
First
quarter
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.013
0.0
0.010
0.0
0.0
0.0
0.015
0.011
0.0
0.0
0.0
0.011
0.022
0.0
0.0
0.0
0.0
0.010
0.0
0.0
0.0
0.009
0.014
Second
quarter
Urban areas
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.010
0.0
0.0
0.012
0.018
0.014
0.014
0.012
0.0
0.020
0.017
0.0
0.0
0.0
0.010
0.017
0.0
0.027
0.0
0.0
0.017
Third
quarter
0.0
0.0
0.013
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.017
0.0
0.014
0.0
0.0
0.014
0.019
0.017
0.012
0.009
0.0
0.016
0.010
0.0
0.0
0.0
0.016
0.014
0.0
0.013
0.014
0.0
0.013
Fourth
quarter
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.015
0.0
0.0
0.0
0.019
0.014
0.012
0.010
0.0
0.023
0.013
0.0
0.0
0.0
0.0
0.0
0.0
0.008
0.011
0.0
0.019
Yearly
av
0.012
0.018
0.014
0.010
0.009
0.017
0.015
0.011
0.013
0.016
-------
216
Table 7.10 (continued)
Location
Delaware
Wilmington
Dist Columbia
Washington
Florida
Jacksonville
Miami
St. Petersburg
Tampa
Georgia
Atlanta
Columbus
Savannah
Hawaii
Honolulu
Idaho
Boise City
Illinois
Chicago
East St. Louis
Joliet
North Chicago
Peoria
Rockford
Springfield
Indiana
East Chicago
Evansville
Fort Wayne
Gary
Hammond
Indianapolis
New Albany
South Bend
Terre Haute
Iowa
Davenport
Des Moines
Dubuque
Kansas
Kansas City
Topeka
Wichita
First
quarter
0.017
0.0
0.020
0.0
0.010
0.015
0.0
0.0
0.0
0.0
0.0
0.014
0.012
0.012
0.0
0.0
0.0
0.0
0.041
0.089
0.013
0.018
0.024
0.015
0.018
0.0
0.0
0.013
0.0
0.0
0.011
0.0
0.0
Second
quarter
0.013
0.016
0.0
0.0
0.0
0.014
0.0
0.0
0.0
0.0
0.0
0.012
0.0
0.015
0.0
0.016
0.010
0.016
0.053
0.011
0.010
0.016
0.021
0.013
0.013
0.010
0.0
0.011
0.0
0.0
0.0
0.0
0.0
Third
quarter
0.020
0.0
0.013
0.0
0.015
0.020
0.015
0.0
0.0
0.008
0.0
0.016
0.0
0.017
0.013
0.014
0.019
0.009
0.100
0.0
0.022
0.013
0.015
0.012
0.010
0.0
0.0
0.032
0.0
0.0
0.012
0.0
0.0
Fourth
quarter
0.0
0.0
0.013
0.0
0.009
0.012
0.0
0.0
0.011
0.0
0.0
0.024
0.120
0.0
0.015
0.010
0.014
0.0
0.061
0.009
0.0
0.016
0.018
0.013
0.012
0.010
0.0
0.017
0.0
0.0
0.016
o n
\j . \j
0.0
Yearly
av
0.013
0.012
0.009
0.015
0.016
0.012
0.011
0.011
0.064
0.028
0.012
0.016
0.019
0.013
0.013
0.018
0.010
-------
217
Table 7.10 (continued)
Location
Kentucky
Ashland
Covington
Louisville
Louisiana
Baton Rouge
New Orleans
Shreveport
Maryland
Baltimore
Massachusetts
Boston
Fall River
Springfield
Worchester
Michigan
Dearborn
Detroit
Flint
Grand Rapids
Lansing
Saginaw
Trenton
Minnesota
Duluth
Minneapolis
St. Paul
Missouri
Kansas City
St. Louis
Montana
Helena
Nebraska
Omaha
Nevada
Las Vegas
Reno
New Hampshire
Concord
First
quarter
0.019
0.021
0.019
0.0
0.011
0.0
0.140
0.0
0.0
0.0
0.0
0.014
0.019
0.012
0.015
0.013
0.0
0.015
0.0
0.012
0.012
0.0
0.018
0.0
0.0
0.0
0.0
0.0
Second
quarter
0.018
0.018
0.010
0.0
0.017
0.008
0.110
0.0
0.010
0.0
0.009
0.014
0.016
0.010
0.008
0.0
0.0
0.010
0.0
0.0
0.012
0.0
0.012
0.0
0.0
0.0
0.0
0.0
Third
quarter
0.025
0.010
0.012
0.0
0.021
0.0
0.092
0.0
0.0
0.0
0.0
0.017
0.020
0.011
0.011
0.0
0.0
0.0
0.0
0.0
0.0
0.010
0.023
0.0
0.0
0.011
0.0
0.0
Fourth
quarter
0.017
0.018
0.016
0.0
0.0
0.0
0.066
0.008
0.009
0.0
0.0
0.047
0.019
0.0
0.0
0.0
0.0
0.010
0.014
0.012
0.0
0.0
0.018
0.0
0.011
0.0
0.0
0.0
Yearly
av
0.020
0.017
0.014
0.013
0.102
0.015
0.018
0.009
0.009
0.009
0.018
-------
218
Table 7.10 (continued)
Location
New Jersey
Burlington County
Elizabeth
Glassboro
Hamilton
Jersey City
Newark
Paterson
Perth Amboy
Trenton
New Mexico
Albuquerque
New York
Albany
Buffalo
New York City
Niagara Falls
Rochester
Syracuse
Utica
North Carolina
Charlotte
Durham
Greensboro
Winston-Salem
North Dakota
Bismarck
Ohio
Akron
Canton
Cincinnati
Cleveland
Columbus
Dayton
Toledo
Youngs town
Oklahoma
Oklahoma City
Tulsa
Oregon
Medford
Portland
First
quarter
0.008
0.009
0.011
0.0
0.030
0.015
0.017
0.011
0.011
0.0
0.009
0.010
0.027
0.052
0.012
0.043
0.0
0.011
0.009
0.012
0.0
0.0
0.015
0.025
0.022
0.011
0.014
0.013
0.0
0.026
0.0
0.012
0.0
0.010
Second
quarter
0.0
0.009
0.0
0.010
0.025
0.031
0.011
0.011
0.0
0.0
0.010
0.031
0.025
0.027
0.017
0.016
0.0
0.0
0.0
0.0
0.0
0.0
0.017
0.020
0.026
0.015
0.015
0.0
0.012
0.024
0.0
0.0
0.0
0.0
Third
quarter
0.0
0.0
0.0
0.018
0.082
0.022
0.0
0.009
0.0
0.0
0.0
0.016
0.014
0.0
0.0
0.014
0.0
0.0
0.0
0.0
0.0
0.0
0.019
0.048
0.048
0.026
0.012
0.0
0.0
0.020
0.0
0.0
0.0
0.014
Fourth
quarter
0.008
0.011
0.0
0.009
0.071
0.029
0.019
0.010
0.016
0.0
0.011
0.013
0.011
0.046
0.0
0.0
0.0
0.0
0.0
0.0
0.010
0.0
0.015
0.049
0.047
0.030
0.009
0.015
0.010
0.054
0.0
0.0
0 0
\J • \J
0.0
Yearly
av
0.008
0.010
0.052
0.024
0.012
0.010
0.008
0.017
0.019
0.032
0.019
0.016
0.035
0.036
0.020
0.013
0.031
-------
219
Table 7.10 (continued)
Location
Pennsylvania
Allentown
Bethlehem
Erie
Harrisburg
Hazleton
Johnstown
Philadelphia
Pittsburgh
Reading
Scranton
Warminster
West Chester
Wilkes-Barre
York
Puerto Rico
Bayahon
Catano
Guayanilla
Ponce
San Juan
Rhode Island
East Providence
Providence
South Carolina
Columbia
Greenville
Tennessee
Chattanooga
Knoxville
Memphis
Nashville
Texas
Dallas
El Paso
Fort Worth
Houston
Pasadena
San Antonio
Utah
Ogden
Salt Lake City
First
quarter
0.0
0.012
0.0
0.012
0.0
0.014
0.017
0.020
0.049
0.0
0.010
0.0
0.0
0.022
0.009
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.023
0.009
0.022
0.013
0.013
0.0
0.0
0.011
0.010
0.0
0.0
0.0
Second
quarter
0.009
0.010
0.0
0.012
0.0
0.0
0.019
0.070
0.085
0.0
0.009
0.010
0.0
0.0
0.0
0.021
0.014
0.0
0.0
0.0
0.0
0.0
0.0
0.022
0.009
0.0
0.015
0.014
0.0
0.0
0.011
0.0
0.0
0.0
0.015
Third
quarter
0.016
0.020
0.029
0.034
0.0
0.012
0.036
0.069
0.070
0.011
0.0
0.0
0.0
0.012
0.0
0.013
0.009
0.0
0.013
0.0
0.0
0.0
0.0
0.011
0.014
0.0
0.012
0.0
0.0
0.0
0.0
0.036
0.0
0.0
0.023
Fourth
quarter
0.0
0.023
0.0
0.018
0.0
0.027
0.017
0.042
0.052
0.0
0.008
0.0
0.009
0.009
0.017
0.015
0.0
0.0
0.0
0.0
0.0
0.0
0.031
0.013
0.0
0.016
0.016
0.015
0.0
0.011
0.0
0.0
0.0
0.0
0.013
Yearly
av
0.016
0.019
0.014
0.022
0.050
0.064
0.007
0.011
0.013
0.017
0.009
0.014
0.011
0.013
-------
220
Table 7.10 (continued)
Location
Vermont
Burlington
Virginia
Danville
Hampton
Lynchburg
Newport News
Norfolk
Portsmouth
Richmond
Roanoke
Washington
Seattle
Spokane
Tacoma
West Virginia
Charleston
Wisconsin
Eau Claire
Kenosha
Madison
Milwaukee
Racine
Superior
Wyoming
Casper
Cheyenne
First
quarter
0.0
0.0
0.0
0.0
0.009
0.0
0.0
0.0
0.013
0.0
0.0
0.010
0.048
0.0
0.009
0.0
0.010
0.0
0.0
0.0
0.0
Second
quarter
0.010
0.012
0.0
0.0
0.0
0.0
0.015
0.0
0.0
0.0
0.0
0.0
0.040
0.0
0.015
0.0
0.010
0.0
0.0
0.0
0.0
Third
quarter
0.0
0.0
0.0
0.0
0.0
0.0
0.008
0.0
0.011
0.013
0.0
0.0
0.019
0.0
0.0
0.0
0.017
0.0
0.0
0.0
0.0
Fourth
quarter
0.0
0.011
0.0
0.0
0.0
0.0
0.012
0.0
0.012
0.0
0.0
0.0
0.034
0.0
0.019
0.0
0.026
0.0
0.0
0.0
0.0
Yearly
av
0.010
0.010
0.035
0.011
0.016
Arizona
Grand Canyon
National Park
Arkansas
Montgomery County
California
Humboldt County
Florida
Hardee County
Idaho
Butte County
0.0
Nonurban areas
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
-------
221
Table 7.10 (continued)
Location
Indiana
Monroe County
Parke County
First
quarter
0.0
0.0
Second
quarter
0.0
0.0
Third
quarter
0.0
0.0
Fourth
quarter
0.0
0.0
Yearly
av
Maine
Acadia National
Park
Maryland
Calvert County
Missouri
Shannon County
Montana
Glacier National
Park
Nebraska
Thomas County
Nevada
White Pine County
New Hampshire
Coos County
New York
Jefferson County
North Carolina
Cape Hatteras
National Park
Oklahoma
Cherokee County
Oregon
Curry County
Pennsylvania
Clarion County
Rhode Island
Washington County
South Carolina
Richland County
South Dakota
Black Hills
National Park
0.0
0.015
0.011
0.014
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.011
0.0
0.0
0.011
0.0
0.0
0.0
0.019
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.087
0.0
0.009
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.029
0.0
0.018
0.016
0.0
0.0
0.0
0.010
0.032
-------
222
Table 7.10 (continued)
Location
First
quarter
Second
quarter
Third
quarter
Fourth
quarter
Yearly
av
Tennessee
Cumberland County 0.0
Texas
Matagorda County 0.0
Vermont
Orange County 0.0
Virginia
Shenandoah 0.0
National Park
Wythe County 0.0
Wisconsin
Door County 0.0
Wyoming
Yellowstone 0.0
National Park
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Source: Adapted from U.S. Environmental Protection Agency, 1973,
Table 5-3, pp. 5-9 - 5-12.
chromium content in Cincinnati was 0.16 yg/ro.3. The mass median diameter of
particles, however, was very similar among the three locales (1.5 to 2.0 ym).
No reason was given for the relatively high chromium contents observed in
these three regions as compared to those found by the National Air Surveil-
lance Network. Daily variation in concentrations could be expected in such
studies depending upon atmospheric conditions; however, no data relating
air chromium content to atmospheric stability or meteorological conditions
were found. Sugimae (1975) found concentrations ranging from 0.017 to
0.087 yg/m3 in Osaka, Japan.
Little information exists on particle size distribution of the chromium
in air. Cawse (1974) gave data for chromium in air particulate matter at
Trebannos, United Kingdom. The mass median diameter was 1.5 ym; 12%, 12%,
12%, 17%, 10%, 7%, 9%, and 4% of total chromium was found on cascade im-
pactor stages having effective cutoff diameters of 0.47, 0.68, 1.1, 2.3,
3.1, 5.0, 7.5, and 11.0 ym, respectively. The backing filter contained 16%
of the chromium. Similar data were obtained from air in Chilton, United
Kingdom; the concentration of chromium in these particles ranged from 54 to
210 ppm. There was no trend toward higher concentrations in the smaller
particles.
The chromium content in fly ash from a coal-fired steam plant was 130
ppm for 25-ym particles, 130 ppm for 12.5-ym particles, 130 ppm for 10-ym
particles, 300 ppm for 3.5-ym particles, and 300 ppm for 1.5-ym particles
-------
223
Table 7.11. Levels of airborne chromium in
U.S. cities, 1954-65
(pg/m3)
City
Cities with
Birmingham , Ala .
Phoenix, Ariz.
Los Angeles, Calif.
Denver, Colo.
Atlanta, Ga.
Boise, Idaho
Ind ianap o 1 is , Ind .
Des Moines, Iowa
Wichita, Kan.
New Orleans, La.
Baltimore, Md.
Boston, Mass.
Detroit, Mich.
Minneapolis, Minn.
St. Louis, Mo.
Las Vegas, Nev.
Camden, N.J.
Newark, N.J.
Albuquerque, N.M.
New York, N.Y.
Charlotte, N.C.
Akron , Ohio
Cleveland , Ohio
Youngs town, Ohio
Portland, Ore.
Allentown, Pa.
Bethlehem, Pa.
Philadelphia, Pa.
Pittsburgh, Pa.
Chattanooga, Tenn.
Nashville, Tenn.
Houston, Tex.
El Paso, Tex.
Salt Lake City, Utah
Seattle, Wash.
Tacoma, Wash.
Charleston, W.Va.
Milwaukee , Wis .
Cheyenne , Wyo .
Mean
Year
Chromium
level Year
decreasing chromium
1959
1960
1959
1959
1959
1960
1959
1959
1959
1959
1959
1959
1959
1959
1959
1961
1962
1961
1960
1959
1959
1960
1959
1959
1959
1961
1961
1959
1959
1961
1959
1959
1962
1959
1959
1959
1959
1959
1959
0.038
0.084
0.037
0.019
0.023
0.020
0.024
0.019
0.017
0.025
0.094
0.051
0.029
0.020
0.041
0.031
0.014
0.046
0.057
0.021
0.023
0.041
0.043
0.047
0.025
0.036
0.048
0.026
0.028
0.041
0.029
0.025
0.006
0.019
0.047
0.018
0.097
0.029
0.011
0.0372
levels
1965
1964
1963
1964
1965
1965
1964
1964
1964
1963
1965
1964
1964
1964
1964
1964
1963
1964
1965
1964
1964
1965
1964
1963
1964
1965
1965
1964
1964
1964
1964
1964
1964
1964
1963
1964
1964
1964
1964
Chromium
level
0.005
0.007
0.015
0.005
0.002
0.001
0.008
0.003
0.001
0.011
0.018
0.007
0.014
0.002
0.007
0.001
0.010
0.020
0.002
0.006
0.002
0.009
0.014
0.012
0.004
0.000
0.005
0.011
0.021
0.015
0.011
0.004
0.000
0.001
0.015
0.001
0.044
0.010
0.000
0.0083
-------
224
Table 7.11 (continued)
Chromium Chromium
City Year level Year level
Cities with increased or unchanged chromium levels
Pasadena, Calif. 1959 0.002 1962 0.023
San Francisco, Calif. 1959 0.001 1962 0.020
San Jose, Calif. 1959 0.001 1963 0.002
Washington, D.C. 1959 0.004 1964 0.016
East St. Louis, 111. 1959 0.007 1963 0.029
East Chicago, Ind. 1959 0.013 1964 0.033
Rochester, N.Y. 1960 0.055 1962 0.036
Altoona, Pa. 1959 0.001 1965 0.002
Mean 0.0105 0.0201
Cities with high chromium levels
St. Paul, Minn.
Jackson Co., Miss.
Bayonne, N.J.
Paterson, N.J.
Buffalo, N.Y.
Glen Cove, N.Y.
Troy, N.Y.
Massena, N.Y.
Mt. Vernon, N.Y.
New Rochelle, N.Y.
Asheville, N.C.
Tulsa, Okla.
Johnstown, Pa.
Lancaster, Pa.
Scranton, Pa.
Spokane, Wash.
Huntington, W.Va.
Mean
1962
1965
1963
1963
1962
1962
1962
1961
1961
1961
1960
1961
1963
1962
1961
1961
1960
0.013
0.012
0.015
0.010
0.010
0.019
0.015
0.019
0.035
0.022
0.020
0.016
0.010
0.016
0.030
0.041
0.021
0.0191
Source: Adapted from Schroeder, 1970, Table 2, p. 4.
Reprinted by permission of the publisher.
(Lyons, cited in Lee and von Lehmden, 1973). Linton et al. (1976) demon-
strated by secondary ion mass spectrometry and electron-induced x-ray
spectrometry that" the surface of coal fly ash had a higher concentration of
chromium than material at a depth of 500 A within the particle.
Enrichment factor analysis (chromium/cerium concentrations in fly ash
or aerosol to those in soil) showed little chromium enrichment in aerosols
collected at the Walker Branch Watershed, Oak Ridge, Tennessee (enrichment
factor 2.0) or at the Allen Steam Plant, Memphis, Tennessee (enrichment
factor 4.5) (Andren, Lindberg, and Bate, 1975). Indirect evidence for in-
creased air chromium concentrations in the vicinity of a power plant also
comes from soil analyses in which soils near the power plant contained 6.5
ppm chromium and background soils contained 4.6 ppm (Klein and Russell 1973)
-------
225
Table 7.12. Chromium concentrations in air
Area
Chromium
concentration
range
Reference
Bronx, N.Y.
Lower Manhattan, N.Y.
Tuxedo, N.Y.
San Francisco, Calif.
Boston, Mass.
United Kingdom
Lerwick, England (background)
Northwest Canada (background)
Norway (background)
Urban England
Heidelberg, Germany
17-73 ng/m3
27-93 ng/m3
3-23 ng/m3
2-22 ng/m3
6.8 ng/m3
1-14 ng/kg air
0.9 ng/kg air
0.5 ng/kg air
0.5 ng/kg air
4.6-25 ng/kg air
4.6 ng/m3
Kneip et al., 1970
Kneip et al., 1970
Kneip et al., 1970
John et al., 1973
Gordon, Zoller, and
Gladney, 1973
Peirson et al., 1973
Cawse, 1974
Cawse, 1974
Cawse, 1974
Cawse, 1974
Bogen, 1974
Specific industrial activities increase the chromium content of air in
their vicinities. Lee and von Lehmden (1973) reported the chromium content
in particulate emissions from several sources. Chromium concentrations in
emissions ranged between 1 and 100 ppm for coal-fired power plants, between
100 and 1000 ppm for cement plants, between 10 and 100 ppm for iron and
steel industries, and between 100 and 1000 ppm for municipal incinerators.
Another locale with high chromium air concentrations is the area near
cooling towers. Cooling-tower drift consists of water droplets formed
mechanically within the tower and carried by wind into surrounding areas.
Chromium (usually CrO<,2~) is often used in the cooling-tower water as a
corrosion inhibitor. The droplets in the cooling-tower drift are assumed
to contain chromium in concentrations similar to those in the tower water.
Air concentrations of chromium near a cooling tower at the Oak Ridge Gaseous
Diffusion Plant, Oak Ridge, Tennessee, were about 50 ng/m3 for distances up
to 200 m (Alkezweeny et al., 1975). Hourly chromium deposition was about
1 mg/m2 at 30 m from the tower and about 0.01 mg/m2 at 1000 m.
Background contamination levels are difficult to estimate because of
uncertain amounts of anthropogenic input. Atmospheric chromium concentration
at the South Pole, a region distant from major anthropogenic sources, was
5.3 ± 3.0 pg/m3 with a range of 2.5 to 10 pg/m3 (Zoller, Gladney, and Duce,
1974). The ratios of chromium to aluminum, which were the same as in the
earth's crust, suggested that the chromium in the atmosphere at the South
Pole was due to weathering of crustal material. By statistical correlation
analysis, it was determined that chromium in air over the San Francisco Bay
area was derived from soil material (John et al., 1973).
-------
226
The chemical form of chromium in air depends on the source. Chromium
from metallurgical production is usually in the trivalent or zero state;
however, during chromate production, chromate dusts can be emitted. Aerosols
containing chromic acid can be produced during the chrome-plating process;
chromate is also the form found in air contaminated with cooling-tower drift.
7.3.3 Distribution in Soil
The chromium concentration in soil depends on geographic region, age of
soil, and underlying parent rock material. Total chromium content within
most soils (Tables 7.13 and 7.14) ranged from <5 ppm chromium to about 1000
ppm, although most soils contain <300 ppm (Swaine, 1955). In a detailed
study of element composition in U.S. surficial soils, Shacklette et al. (1971)
found that 64% of the soil samples contained total chromium concentrations in
the range of 25 to 85 ppm (Figure 7.3). In general, the clay fraction of
soil contains a higher chromium concentration than do other soil components
(Tables 7.14 and 7.15).
Table 7.13. Chromium content of soils in various countries
Location
Canada
Quebec
Cook Islands
Atiu, Mangaia, and Aitutaki
Lower Cook Islands
Mangaia, Atiu, and Mauke
Cuba
Czechoslovakia
Mohelno , Bohemia
Moravia, northwest Bohemia
Dominican Republic
Sierra de Bahoruco
Finland
France
Number
of
samples
5
3 surface
3 subsoil
8 surface
5 subsoil
4 surface
1 subsoil
Surface)
Subsoil f
11 surface
16 subsoil
3 surface
2 subsoil
10 surface
10 subsoil
1 surface
4 subsoil
1 surface
4 subsoil
1
16 surface
2 subsoil
34 surface
8 subsoil
Chromium
content
(ppm)
Found
500-1,650
(l,250)a
550-1,150
(900)
600-1,650
(1,100)
550-1,570
(920)
500-900
(750)
550
400-21,500
1,300-11,600
(3,900)
<350-21,500
(4,500)
350-24,600
(15,400)
2,900, 23,900
685-1,700
(1,245)
860-2,135
(1,355)
Found
1,830
1,040-2,050
(1,620)
3.9
2.9-4.0
(3.5)
700
<100
2-87
(30)
56, 88
1.8-114
(44)
16-64
Remarks
Surface and subsoil
Total
Total; two profiles; derived from basalt
Total; derived from basalt alluvium mixed
with limestone
Mean total values for six i-portant soil
types
Total; four profiles; representative soils
Total; one profile; infertile soils derived
from rocks high in Mg, Cr, and Ni
Total; five profiles; derived from
serpentine
Various parent materials
Total; one profile; forest soil derived from
serpentine; pines showed stunted growth
Extract 1% citric acid; one profile; forest
soil derived from serpentine; pines showed
stunted growth
Composite sample; aluminous lateritic soil
From peit bogs (some near ores)
Different types
Fused Na2C03-KN03; total; two profiles
-------
227
Table 7.13 (continued)
Location
Germany
Baden
Haiti
Rochelois Plateau
New Caledonia
New Zealand
North Auckland
Niue Island
Puerto Rico
Near Mayaguez
Russia
Along 40th meridian
Various parts
Scotland
Near Huntly
Northeast
Number
of
samples
13 surface
12 subsoil
16 surface
31 subsoil
1
1 surface
2 subsoil
1 surface
4 surface
1 subsoil
3 surface
2 surface
5 surface
1 surface
4 subsoil
4 surface
5 subsoil
3 surface
15 surface
35 subsoil
1 surface
7 subsoil
2
Surface
3
41 surface
110 subsoil
20 surface
66 subsoil
16 surface
53 subsoil
5 surface
Chromium
content
(ppm)
90-122
(107)
73-138
(107)
47-108
(85)
62-122
(87)
550
33,500
20,900, 21,400
4.5
350-550
(500)
500
1,150-1,500
(1,300)
400, 400
7,950-8,650
(8,450)
26,400
21,700-35,800
(26,100)
750-26,400
(11,600)
21,800-35,800
(27,200)
0.2-0.6
(0.4)
(approx) 50
29-570
(241)
5-760
(195)
145
154-321
(234)
1,720, 2,890
10-5,000
0.11-0.17
(0.14)
15-500
(140)
200-800
(210)
<0. 02-0. 56
(0.16)
<0. 02-0. 66
(0.18)
<0. 01-0. 10
(0.02)
<0. 01-0. 07
(0.01)
<0. 02-0. 06
(0.02)
Remarks
Fused Na202-NaOH; total; three profiles;
different types; various parent materials
Fused NaHS04; 15 profiles; different types;
various parent materials
Composite sample; aluminous lateritic soil
Total; one profile; derived from serpentine
Exchangeable; derived from serpentine
Ironstone soils; mostly on basalt
Total
Soluble in 21% HC1
Total; unproductive; laterites derived from
serpentine
Total; Nipe clay profile; derived from
serpentine
Total; one profile; infertile soils derived
from rocks high in Mg, Cr, and Ni
Extract neutral 1 N NH,,Ac; infertile soils
derived from rocks high in Mg, Cr, and Ni
Zonal soils of the Russian plain
13 profiles; different types
Total; profile formed from basic rocks
Total; derived from serpentine
Total
Extract 2.5% HAc; derived from granite,
norite, or old red sandstone
Total; 34 profiles; cultivated, uncul-
tivated; different parent materials
Extract 0.5 N HAc; 17 profiles; cultivated,
uncultivated; different parent materials
Extract 1 S NH4Ac, pH 7; 14 profiles; cul-
tivated, uncultivated; different parent
materials
Extract 1 N NHi,AC, pH 8.5; four profiles;
cultivated, uncultivated; different parenl
materials
17
<0. 01-0. 03
-------
228
Table 7.13 (continued)
Location
North
Aberdeenshire
Aberdeenshire
Whitecairns, Aberdeenshire
Solomon Islands
Siota, Gela
6
2
8
2
8
2
8
1
4
4
1
1
1
Number
of
samples
surface
subsoil
surface
subsoil
surface
subsoil
surface
subsoil
surface
surface
surface
surface
Chromium
content
(ppm)
5-700
(185)
3,000, 3,500
2,000-3,000
(2,500)
0.69, 2.1
0.10-3.2
(1.3)
0.02, 0.05
<0. 02-0. 12
(0.05)
0.33
0.39-1.1
(0.68)
0.39-0.76
(0.60)
8,000
450
0.1
Remarks
Total; cultivated; different parent
materials
Total; two profiles; cultivated; on ser-
pentine till
Extract 0.1 ff HC1; two profiles; cultivated;
on granite till and basic igneous till
Extract 0.0025 N HC1; two profiles; cul-
tivated; on granite till and basic
igneous till
Extract 0.5 N HAc; one profile; cultivated;
on serpentine till
Extract 2.5% HAc; serpentine parent
material; cultivated
Total; laterite
Soluble in 21% HC1; laterite
Exchangeable; laterite
South Africa
Transvaal
Sweden
1,400-2,700 Treated HF-HaSO,. and fused KjSa07; total;
derived from chromiferous rocks of
Bushveld igneous complex
Detected Chromite present; citrus-growing area
Near Uppsala and Stockholm
United States
Hawaiian Islands
Hyde Swamps, N.C.
Pennsylvania
Various parts
Peninsular Florida
Florida
Western Samoa
Vaitele and Savaii
8
11 surface
23 subsoil
3
1 surface
1 subsoil
13 surface
13 subsoil
16 surface
24 subsoil
11 surface
14 surface
44 subsoil
77 surface
55 subsoil
2 surface
16 subsoil
9 surface
5 surface
11 subsoil
2 surface
2 subsoil
1 surface
2 subsoil
3-30
(8)
400-1,800
(900)
250-1,850
(800)
195-245
(225)
14
14
<15-125
(50)
15-170
(65)
"None "-16, 200
(2,800)
"None "-4,600
(1,300)
0.3-2.0
(0.7)
4-62
(16)
0-34
(11)
<1-300
(approx 40)
<1-1,000
(approx 60)
30,300
<1-100
<10-500
950-3,350
(1,900)
900-2,350
(1,600)
1,100, 1,650
1,250, 1,800
250
400, 400
Each a composite of at least 20 cultivated
post-glacial clays
Total; six profiles; different types
derived from lava or volcanic ash
Total on ash; about 2% ash; peat
Total
Total; different parent materials
Total; 12 profiles; infertile soils
from rocks high in Mg, Cr, and Ni
Extract neutral 1 ff NHtAc; infertile
derived from rocks high in Mg, Cr,
;
derived
soils
and Ni
Heated HjSO,., HBr + Br2; probably total; 11
profiles
Cultivated, virgin; samples ignited
at 450°C
Two profiles; everglades peat and Okeechobee
muck
Citrus soils; samples ignited at 450
Total; five profiles; laterites
Total; laterites
Soluble in 21% HC1; laterites
°C
Average chromium content.
Source: Adapted from Swaine, 1955, pp. 29-34. Reprinted by permission of the publisher.
-------
229
Table 7.14. Chromium concentrations in selected soils
(ppm)
Material
Total soil
chromium
concentration
Reference
Soil, on road 71
Soil, off road 71
Soil 36.1 + 0.2
Soil 47
Clay 157
Annandale loam 32
Collington sandy loam 20
Coltz loam 40
Cossayuna loam 20
Croton silt loam 38
Lansdale loam 30
Norton loam 75
Sassafras sandy loam 45
Squires loam 46
Washington loam 39
Umiat bentonite 6.4
Kaolinite-7 48.1
Illite-35 79.0
Fairbanks silt 280
Barrow silt 126
Suffield silt 6.4
Surface soil
Residential area 3.2 + 3.3
Agricultural area 4.6 + 3.6
Industrial area 8.5 + 9.0
Airport 17.6 + 8.9
Calcareous soil 130-150
Muck soil 12-46
Soil in England 1.8-110
Conner et al., 1971
Conner et al., 1971
Andersson and Nilsson, 1972
Shimp et al., 1957
Shimp et al., 1957
Prince, 1957
Prince, 1957
Prince, 1957
Prince, 1957
Prince, 1957
Prince, 1957
Prince, 1957
Prince, 1957
Prince, 1957
Prince, 1957
Murrmann, Winters, and Martin, 1971
Murrmann, Winters, and Martin, 1971
Murrmann, Winters, and Martin, 1971
Murrmann, Winters, and Martin, 1971
Murrmann, Winters, and Martin, 1971
Murrmann, Winters, and Martin, 1971
Klein, 1972
Klein, 1972
Klein, 1972
Klein, 1972
Proctor, 1971
Chattopadhyay and Jervis, 1974
Cawse, 1974
-------
ORNL-DWG 76-3841
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-------
231
Table 7.15. Chromium content of air-dried soils
Chromium concentration (ppm)
Soil
Brown podzol, freely drained on
serpentine till
Brown podzolic with gleyed B- and
C-horizons imperfectly drained,
on olivine gabbro till
Brown forest soil freely
drained on andesitic moraine
Peaty gleyed podzol on
granitic till
Podzol, freely drained on
granitic gneiss till
Podzol, freely drained on
quartz mica schist till
Noncalcareous gley, poorly
drained on Silurian slate
till
Peaty podzol with iron pan
freely drained below pan
on sandstone till
Horizon
Surface
B2
B2
B-C
C
Surface
B2
B3
B3
C
Surface
B2
B-C
C
H
A
A2
T.^1
B2
B^-C
C
Surface
B2
B2
c3
Surface
B2
B2
B3
c3
Al
A2
B2
B,
gz
c3
A2
B2
B3
C3
LlUJ-J. UC^J
(cm)
5.1-17.8
20.3-30.5
45.7-55.9
66.0-76.2
96.5-109.2
0-20.3
30.5-38.1
40.6-48.3
50.8-61.0
91.4-111.8
2.5-17.8
25.4-35.6
45.7-66.0
73.7-83.8
17.8-22.9
25.4-35.6
43.2-53.3
53.3
53.3-63.5
78.7-91.4
101.6-116.8
0-25.4
30.5-35.6
40.6-50.8
61.0-76.2
94.0-104.1
0-17.8
33.0-48.3
61.0-68.6
81.3-96.5
101.6-116.8
5.1-12.7
12.7-22.9
27.9-35.6
40.6-50.8
61.0-76.2
91.4-106.7
2.5-5.1
12.7-35.6
55.9-68.6
88.9-101.6
1.11
(in.)
2-7
8-12
18-22
26-30
38-43
0-8
12-15
16-19
20-24
36-44
1-7
10-14
18-26
29-33
7-9
10-14
17-21
21
21-25
31-36
40-46
0-10
12-14
16-20
24-30
37-41
0-7
13-19
24-27
32-38
40-43
2-5
5-9
11-14
16-20
24-30
36-42
1-2
5-14
22-27
35-40
Total
3500
2000
2000
3000
3000
300
100
200
300
300
80
60
40
150
7
25
30
50
30
20
20
200
150
150
150
200
150
150
150
150
200
250
250
250
200
200
200
20
30
25
10
Extracted by Extracted by
neutral ammonium 2.5% acetic
acetate acid
0.10 0.31
0.04 1.10
0.01 0.39
0.01 0.60
0.01 0.63
0.01 0.15
0.01 0.08
<0.01 0.11
<0.01 0.08
<0.01 0.11
Source: Adapted from Swaine and Mitchell, 1960, Table 1, pp. 350-353 and Table 2, pp.
by permission of the publisher.
357-358. Reprinted
Soils formed on serpentine rock have much higher total chromium con-
centrations than other soils (Table 7.13). Proctor (1971) found that total
chromium concentrations ranged from 2500 to 4000 ppm (ash wt) for British
and Swedish serpentine soils, and Lyon et al. (1970) found extreme vari-
ability in concentrations for serpentine regions of New Zealand (500 to
62,000 ppm, ash wt basis).
The chromium content at different soil depths has not been studied to
any great extent. For Papua-New Guinea soils (serpentine) mean concentra-
tions for horizons A!, A2, ABi/Bu AB2/B2, B3/BC, and d were 946, 970, 771,
396, 677, and 294 ppm, respectively (Sleeker and Austin, 1970). Chromium
content of the parent material was 283 ppm. Chromium concentration was not
-------
232
correlated with clay content in these soils but was correlated with sand
content, especially in the 50- to 75-um and 150- to 210-ym fractions.
Swaine and Mitchell (1960) reported total and extractable chromium concen-
trations for soils derived from different rock materials (Table 7.15).
Content was similar in all three horizons. Chromium analyses of A-, B-,
and C-horizons of podzol, Squires, Annandale, Wethersfield, and Norton soils
and of their respective clay fractions (Table 7.16) showed that total chro-
mium content did not differ significantly with depth (Conner, Shimp, and
Tedrow, 1957). In a muck soil, total chromium concentrations were 12.1 to
14.3 ppm at the surface, 18.5 ppm at 0 to 7.5 cm, 30.2 ppm at 7.5 to 15.0 cm,
35.4 ppm at 15.0 to 22.5 cm, 45.8 ppm at 22.5 to 30.0 cm, 28.6 ppm at 30.0
to 37.5 cm, and 26.7 ppm at 37.5 to 45.0 cm (Chattopadhyay and Jervis, 1974).
Table 7.16. Chromium content of various soils
and their clay fractions
Chromium content (ppm)
Soil
Horizon
Total soil
Clay fraction
Podzol on Wisconsin drift
Podzol on Kansan drift •
Squires (derived from
calcareous materials)
Annandale (derived from
calcareous materials)
Wethersfield (derived from
acid red shale)
Norton (derived from
acid red shale)
A
B
C
A
B
C
A
B
C
A
B
C
A
B
C
A
B
C
17
48
43
12
44
51
22
7
8
28
30
8
10
18
21
20
15
33
101
177
140
81
102
160
83
108
94
43
34
31
134
134
167
167
157
164
pp.
Source: Adapted from Connor, Shimp, and Tedrow, 1957, Table 2,
67-68. Reprinted by permission of the publisher.
The important consideration, however, is not total chromium but rather
the chromium available for plant uptake; few studies have reported this
value. Bradford, Blair; and Hunsaker (1971) found water-extractable chromium
in only 8 of 68 California soil samples, with a mean chromium concentration
of 0.01 ppm and a range of 0.01 to 0.017 ppm. For Lassen Adobe Clay, the pH
of the water did not alter the amount of chromium extracted; <0.01 ppm was
extracted at pH values of 3.9, 5.1, 6.7, and 7.6.
-------
233
Swaine and Mitchell (1960) and Mitchell (1971) also reported a very low
extractable (by 2.5% acetic acid) chromium content from a variety of soils
even though the total chromium concentration was quite high in certain soils
(Tables 7.15 and 7.17). Mortvedt and Giordano (1975) found that the amounts
of chromium extractable with 0.1 N HC1 from soils amended with different
amounts of phosphate fertilizer were near their analytical detection limit
(0.05 ppm) in most cases.
The total soil chromium concentration in the vicinity of a cooling
tower decreased with distance from the pollution source; background levels
were reached at a distance of about 300 m (Taylor et al., 1975) (Table
7.18). In the immediate vicinity of the cooling tower (15 and 60 m), total
chromium concentrations were high at both 0- to 1-cm and 1- to 6-cm depths;
however, in all cases, extractable chromium (by ammonium acetate, pH 4.8)
was less than 6% of the total. Mean extractable concentrations from control
regions and regions with near background levels for total chromium were in
the range of 0.40 to 1.90 ppm.
In lysimeter experiments, Lehman and Wilson (1971) detected no measur-
able chromium extracted by sodium acetate from soils before or after appli-
cation of sewage wastewater effluent.
Certain authors have characterized some soils as chromium deficient,
where deficiency is defined as available chromium being below a level needed
by the plant. Although chromium has not been shown to be essential for
plants (Section 4.2.1), reports of increased crop yields following applica-
tion of chromium to soils have suggested that a certain level of available
chromium is needed for optimal plant growth and that some soils are defi-
cient in this respect (Mertz, 1969). However, until various indirect
effects are excluded and chromium is shown to be essential, such observa-
tions merely illustrate a beneficial effect from application of chromium
compounds to soils.
In most cases, the chemical form of chromium within soil is a matter
of conjecture, depending on parent rock material, anthropogenic input into
soil, pH, and oxidizing conditions of soil. Since the major mineral form
of chromium is chromite, a portion of chromium within soils, especially
serpentine soils, is in this form. The majority of other mineral forms of
chromium are rather inert and only sparingly soluble. During weathering of
rocks, some solubilization of chromium can occur. With intensive oxidation,
chromium(III) can be converted into the soluble chromate ion, CrOj,2", which
can be precipitated by certain heavy metals such as lead (Goldschmidt,
1954). This oxidation probably rarely occurs in soils. Anthropogenic in-
put of chromium is often as the CrO<,2~ ion, although it is usually initially
discharged into waters. Because chromium(VI) is a strong oxidizing agent,
it is usually converted to chromium(III), especially in the presence of
organic matter. No data giving relative amounts of chromium(III) and chro-
mium (VI) in soils were found. Chromium(III) tends to form six-coordinate
octahedral complexes and in many cases probably precipitates as Cr203«nH20
(Section 2.2.3). Precipitation would increase with an increase in pH. The
behavior of chromium(III) ions in soil has not been reported in any detail
in the literature. In chromium clays (artificially constructed by adding
-------
Table 7.17. Total and extractable chromium from nonserpentine and serpentine soils
Depth
Soil
Peaty podzol on felsitic
laval tilla
Freely drained brown
podzol on serpentine till
(mm)
25-50
100-200
255-330
330
330-430
610-710
50-175
200-305
450-560
670-760
965-1090
(in.)
1-2
4-8
10-13
13
13-17
24-28
2-7
8-12
18-22
26-30
38-43
Horizon
F
H
A-i , A?
B , pan
B2
B3
Surface
Bl
B2
B-C
C
Chromium concentration (ppm dry wt)
Total
5
8
80
80
100
100
3500
2000
2000
3000
3000
Extracted by 2.5%
acetic acid
0.04
0.06
0.53
0.83
0.68
0.34
0.31
1.10
0.39
0.60
0.63
a
Chromium content of vegetation on this soil was 1.3 ppm.
Source: Adapted from Mitchell, 1971, Table 4, p. 12 and Table 5, p.
the Controller of Her Britannic Majesty's Stationery Office.
oo
13. Reprinted by permission of
-------
235
Table 7.18. Total and extractable chromium in soils
exposed to cooling-tower drift
Distance
from
cooling
tower
(m)
15
60
180
300
600
900
1200
1500
1800
Control
0- to
Total0
chromium
(ppm)
458 + 150
172 + 23
67 + 4
53 + 4
53 + 5
52 + 6
50 + 5
39 + 9
52 + 6
50 + 5
1-cm soil depth
Extractable
chromium
(ppm)
26.99 + 4.74
8.34 + 1.52
3.17 + 0.78
0.65 + 0.15
0.81 + 0.17
1.38 + 0.6
1.61 + 0.95
1.50 + 0.72
0.43 + 0.02
0.49 + 0.01
Percent
extractable
5.89
4.84
4.73
1.22
1.52
2.65
3.22
3.84
0.82
0.98
1- to
Totala
chromium
(ppm)
267 + 135
108 + 13
70 + 6
50 + 4
54 + 5
46 + 6
52 + 6
56 + 12
53 + 6
58 + 2
6-cm soil depth
Extractable
chromium
(ppm)
11.36 + 2.91
4.05 + 0.37
3.03 + 1.0
0.46 + 0.11
0.40 + 0.12
0.89 + 0.31
1.90 + 0.94
1.40 + 0.83
0.45 + 0.02
0.59 + 0.06
Percent
extractable
4.25
3.75
4.32
0.92
0.74
1.93
3.65
2.51
0.84
1.01
.Total analyses determined by neutron activation techniques.
Extracted in 1 19 ammonium acetate adjusted to pH 4.8.
^Concentration in ppm + 1 standard error.
Source: Adapted from Taylor et al., 1975, Table 1, p.
419.
0.5 N Cr2(SO<,)3 to montmorillonite clay and centrifuging) , release of chro-
mium by monovalent cations was relatively small compared to release of cobalt
and nickel from their respectively constructed clays (Basu and Mukherjee,
1965). The order of ions arranged according to their ability to release
increasing amounts of chromium from chromium clay was Al > Mg > NHj, > K > Na.
The sequence of exchange of H from a formulated H-clay was Cr » Ni >. Co.
Thus, chromium appears to be bound more tightly to montmorillonite clays
than are either cobalt or nickel. Adsorbtion to clays, therefore, would
decrease the soluble trivalent chromium content in the soil. This adsorp-
tion would increase at higher pH values (>6.0). Chromium ions could also
adsorb to organic matter or form insoluble organometallic precipitates.
No data were found on the importance of organic material in decreasing
soluble chromium concentrations within soils.
In summary, while total chromium in soil varies, ranging up to 300
ppm in nonserpentine areas and to 1 to 2 wt % in serpentine soils, extract-
able chromium amounts are usually low (0.01 to 4.0 ppm) (Murrmann and Koutz,
1972). Most chromium in soil is apparently insoluble and, therefore, is
not readily available for plant uptake.
7.3.4 Distribution in Water
Chromium, like a variety of other trace metals, can be found in both
surface water and groundwaters in trace quantities (Table 7.19); the amount
is usually related to anthropogenic input. This relationship can be most
easily seen for stream and river water. No chromium was detected in 65
samples from California streams (Silvey, 1967), but 1250 ppb chromium was
once detected in a contaminated stream in Nassau County, New York (Lieber,
Perlmutter, and Frauenthal, 1964). A discussion of the problem of plating
and sewage wastes contributing to this contamination in Nassau County can
be found in Perlmutter and Lieber (1970). Abatement procedures have led to
-------
236
Table 7.19. Concentration of chromium in water supplies
Frequency
Water sample of
detection
Lake Tahoe, Nev. area
Tahoe City
Upper Truckee River
Trout Creek
Logan Creek
Incline Creek
Colorado River 12%
Columbia River 87%
Mississippi River 23%
Missouri River 10%
Ohio River 20%
Oak Ridge, Tenn.
Natural waters
Waters near cooling tower
U.S. surface waters 25%
U.S. surface waters 24.5%
New York City area
Uncontaminated stream
Contaminated stream
Uncontaminated well
Contaminated well
Illinois River
California
Spring water 4 of 72 samples
Well water 3 of 63 samples
Stream water 0 of 65 samples
Seawater 0 of 24 samples
U.S. water supplies
(2595 samples)
Rhine River, Germany
Qishon River, Israel
Poland
Biala Przemsza
Sztola
Wisla
Seawater
Chromium
concentration
(ppb)
Average Range
<0.07
<0.71
<0.91
<0.71
<0.71
10-30
1-10
3-20
8-10
4-10
50-120
2500-2790
<1 <1-19
9.7 1-112
<10
1250
<10
6000
21 5-38
0-21
0-13
2.3 0-79
18
<10
12-100
6-44
31-112
0.04-0.07
Reference
Bond, Straub, and Prober, 1973
Bond, Straub, and Prober, 1973
Bond, Straub, and Prober, 1973
Bond, Straub, and Prober, 1973
Bond, Straub, and Prober, 1973
Bond, Straub, and Prober, 1973
Bond, Straub, and Prober, 1973
Bond, Straub, and Prober, 1973
Bond, Straub, and Prober, 1973
Bond, Straub, and Prober, 1973
Crosmun and Mueller, 1975
Crosmun and Mueller, 1975
Durum and Hem, 1972
Kopp, 1969
Lieber, Perlmutter, and
Frauenthal, 1964
Lieber, Perlmutter, and
Frauenthal, 1964
Lieber, Perlmutter, and
Frauenthal, 1964
Lieber, Perlmutter, and
Frauenthal, 1964
Mathis and Cummings, 1973
Silvey, 1967
Silvey, 1967
Silvey, 1967
Silvey, 1967
Soukup, 1972
De Groot and Allersma, 1973
Kronfeld and Navrot, 1974
Pasternak, 1973
Pasternak, 1973
Pasternak, 1973
Krauskopf, 1956
significant decreases in hexavalent chromium in the aquifer. Major indus-
trialized rivers have variable chromium contents. A range of 5 to 38 ppb
was reported in the Illinois River (Mathis and Cummings, 1973), 3 to 20 ppb
in the Mississippi River (detection in 23% of samples), and 8 to 10 ppb in
the Missouri River (detection in 10% of samples) (Bond, Straub, and Prober,
1973).
In a five-year study of trace element content in U.S. waters, Kopp and
Kroner (1967) reported that dissolved chromium concentrations ranged from
0 to 112 ppb with a mean content of 9.7 ppb (Table 7.20). Concentrations
-------
Table 7.20. Chromium in waters of the United States
Basin
Northeast
North Atlantic
Southeast
Ohio River
Lake Erie
Upper Mississippi River
Tennessee River
Western Great Lakes
Missouri River
Lower Mississippi River
Colorado River
Western Gulf
Pacific Northwest
California
Summary
Number of
positive
occurrences
51
36
37
57
11
20
32
19
3
31
17
3
53
6
386
Frequency of
detection
(%)
56
21
41
24
23
18
47
29
17
20
17
6
33
21
25
Chromium
Minimum
1
1
1
1
6
1
2
1
1
2
3
5
1
2
1
concentration
Maximum
112
29
22
36
25
20
20
20
7
90
63
56
36
45
112
(ppb)
Mean
14
6
4
7
12
7
6
6
3
16
16
25
6
15
9.7
NJ
CO
Source: Compiled from Kopp and Kroner, 1967.
-------
238
were apparently related to industrial activity. For example, samples from
Lake Michigan near Milwaukee, Wisconsin, contained chromium in two of ten
samples (2 and 4 ppb), while in Lake Michigan near Gary, Indiana, an area
with greater industrial discharges, water contained chromium in three of
nine samples (5 to 19 ppb). Although not as completely analyzed, chromium
was found in suspended matter in 8% of the samples (18 of 288 samples), with
a mean chromium concentration of 30 ppb in water. The Northeast basin had
the largest frequency of detection. In an earlier study, Durum and Haffty
(1963) reported a range of 0.72 to 84 ppb chromium in rivers, with Atlantic
coastal rivers having "slightly enriched" concentrations compared to the
average for all U.S. streams.
Chromium concentrations in seawater are very low; no chromium was
detected in 24 samples from off the California coast (Silvey, 1967), and
a range of 0.5 to 0.25 ppb chromium was reported in another study (Bond,
Straub, and Prober, 1973).
In a tabulation of chromium concentrations in various waters used for
water supply, river waters contained amounts ranging from undetectable to
7.8 ppb; lake waters from 0.34 to 2.8 ppb; impoundment waters from undetect-
able amounts to 3.8 ppb; and groundwaters, wells, and infiltration galleries
from undetectable amounts to 1.1 ppb (Bond, Straub, and Prober, 1973).
In 1969, the Community Water Supply Survey (CWSS) found that hexa-
valent chromium concentrations in finished drinking water exceeded the
Public Health Service's mandatory limit for drinking water (50 ppb) in four
of the 969 public water supply systems examined (McCabe et al., 1970).
The suspended load (defined as being the material retained on a 0.45-vim
filter) and the trace element composition of this suspended material has
been determined in several U.S. rivers (Table 7.21). Analyses showed
chromium concentrations in this material to range between 37 and 460 ppm
on a dry weight basis (Turekian and Scott, 1967). Because most chromium
compounds are insoluble and suspended matter in water has both cation-
exchange capacity and adsorption properties and would therefore likely
take up any soluble chromium, most chromium would probably be in particulate
form. Chromium concentrations in dry-season suspended silts of southern
California were approximately 500 ppm in "natural" areas and 2000 ppm in
urbanized areas (Chen et al., 1974). Anthropogenic output of soluble chro-
mates would account for a higher soluble chromium content in pollution out-
falls; however, at low pH values in reducing situations, chromate would be
reduced to Cr203 (Section 2.2.5). Chromate was not found to adsorb onto
montmorillonite, illite, kaolinite, ferric oxide, manganese oxide, hydrated
ferric oxide, or peat (Kharkar, Turekian, and Bertine, 1968). In the Walker
Branch Stream, Walker Branch Watershed, Oak Ridge, Tennessee, 32.4% of the
total chromium was in soluble form (six-month average) (Andren, Lindberg,
and Bate, 1975).
Analysis of water from a Norwegian fjord showed that the chromium con-
tent in unfiltered water increased from about 0.56 ppm at a 1-m depth to
about 1.7 ppb at a 180-m depth (Piper, 1971). At a 1-m depth, about 0.2 ppb
chromium was in soluble form (passing through a 0.45-ym filter), whereas
-------
239
Table 7.21. Chromium composition of suspended
material in rivers
River
Brazos, Tex.
Colorado, Tex.
Red, La.
Mississippi, Ark.
Tombigbee, Ala.
Alabama , Ala .
Chattahoochie, Ga.
Flint, Ga.
Savannah , S . C .
Wateree, S. C.
Pee Dee, S. C.
Cape Fear, N. C.
Neuse, N. C.
Roanoke , N . C .
James , Va .
Rappahannock, Va.
Potomac, Va.
Susquehanna, Pa.
Rhone , France
Avignon, June 1966
Rio Maipo, Chile
Puente Alto, South of
Santiago, September 1966
Suspended
load
(mg/liter)
954
150
436
185
25
54
71
12
30
37
188
61
36
33
41
28
34
54
296
41
Chromium content
(ppm dry wt)
100
82
37
150
220
150
190
210
460
200
150
130
380
240
290
140
170
290
150
68
Source: Adapted from Turekian and Scott, 1967, Table I,
p. 942, Reprinted by permission of the publisher.
about 0.26 ppb was in particulate form. At a 40-m depth, filtered water
contained about 0.56 ppb chromium, while suspended chromium was only 0.04 ppb.
Apparently, chromium was present as a hydroxide in the more shallow depths
(pH 8.0, Eh 0.44 V) but solubilized at greater depths (pH 6.9). Although
chromium(VI), a potent oxidizing agent, is usually reduced in the presence
of organic matter, it can be retained in natural waters which contain low
concentrations of reducing matter (Section 2.2.5).
-------
240
The valence of chromium in seawater can be either six or three. Fukai
(1967) suggested that the stable chromium species in seawater was chromium(VI),
but provided data to show both forms were present. Surface seawater contained
from 0.02 to 0.14 ppb chromium(III) and from 0.28 to 0.36 ppb chromium(VI),
while seawater at depths of 5, 500, and 1000 m contained about 0.2 ppb chro-
mium(III) and 0.2 ppb chromium(VI). Studies of slCr release (initially as
Cr2072~) into the Columbia River at Hanford, Washington, have shown that most
51Cr entering seawater remains hexavalent (as CrO<,2~) and that any chromium-
(III) formed would usually be sorbed to sediment particles and removed from
true solution (Cutshall, Johnson, and Osterberg, 1966).
7.3.5 Distribution in Sediments
Although chromium concentrations have been determined for a variety of
sediments (Table 7.22), few detailed studies with depth of sediment, back-
ground level of chromium, chemical form of chromium, and relationship to
pollution sources have been reported. Chromium content of Rhine River sedi-
ments ranged from a few parts per million to over 1200 ppm (De Groot and
Allersma, 1973). Estimated background levels were between 20 and 40 ppm
chromium for southern Lake Michigan (Leland, Shukla, and Shimp, 1974) and
64 ppm chromium in the Firth of Clyde Estuary (MacKay, Halcrow, and Thornton,
1972).
In the San Pedro, Santa Monica, Santa Barbara, and Soledad basins of
California, chromium concentrations did not change to any great extent with
depth (Figure 7.4) (Bruland et al., 1974). Chromium concentrations in the
upper sediments increased slightly for the San Pedro and Santa Monica basins
and decreased slightly in the Santa Barbara and Soledad basins. Background
values for each basin are roughly 100 ppm chromium, assuming that little
anthropogenic chromium deposition occurred before 1900.
The chromium concentration in sediments of several Wisconsin lakes did
not significantly decrease with depth (Table 7.23) (Iskandar and Keeney,
1974). No reason was suggested for enrichment of surface layers in Lakes
Mendota, Monona, and Waubesa. If sediments greater than 50-cm in depth are
considered "precultural" in origin, then reasonable estimates for background
levels of chromium in sediments would be from <1 to 35 ppm. Although quanti-
tative estimates of the contributions from diverse transporting agencies were
not possible, outfall wastes probably accounted for the chromium observed in
the sediments.
Surface sediments of southern Lake Michigan contained an average of 77
ppm chromium (range of 35 to 165 ppm), while the 15- to 100-cm depth sedi-
ment contained 52 ppm chromium (range of 32 to 68 ppm) (Leland, Shukla, and
Shimp, 1974). Although the significance of values was not stated, apparently
chromium was not greatly increased in Lake Michigan sediments. The wider
range in surface sediments, however, suggested that chromium has been depos-
ited more sporadically in recent times. The chromium concentrations were
more closely related to the organic carbon content of the surficial sediment
than to clay particle size.
Other studies, however, suggested that chromium was accumulating in the
upper 10 cm of lower Lake Michigan sediments. Gross et al. (1972) stated,
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241
Table 7.22. Concentration of chromium in sediments
Sample area
Delaware Bay
New York City Bight
Background
Sludge dumping area
Puget Sound
Seattle area
Tacoma area
Southern region
Hood Canal
Texas
Houston ship channel
Neches River
Sabine River (low industrial activity)
Southern Lake Michigan
Surface sediments
Sediments from >15- to 100-cm depth
Estimated background
Illinois
Illinois River (Peoria)
Nonindustrial streams
Long Island Sound (mud)
Buzzards Bay, Mass.
Canada
Ottawa River
Rideau River
Silt
Medium-size particles
Rhine River
Meuse River
Scheldt River
Ems River
Chao Phya, Thailand
Tji Tarum, Java
Rotterdam Harbor
Inner
Intermediate
Outer
Firth of Clyde
Background
Sludge dumping area
Clyde Estuary
Gulf of Paria, Trinidad
Saanich Inlet, British Columbia
Chromium
concentration
(ppm)
Average Range
33-447
106 2-310
105 50-209
70-139
43-154
58-135
80-126
39-254
8-288
41-89
77 35-165
52 32-68
20-40
17 2-87
6 3-7
190-450
33
22
21
27
9
1240
620
380
180
100
40
868
434
186
64 + 20 38-106
164 + 84 48-308
624
93
81
Reference
Bopp and Biggs, 1972
Carmody, Pearce, and Yasso, 1973
Carmody, Pearce, and Yasso, 1973
Crecelius, Bothner, and Carpenter, 1975
Crecelius, Bothner, and Carpenter, 1975
Crecelius, Bothner, and Carpenter, 1975
Crecelius, Bothner, and Carpenter, 1975
Hann and Slowey, 1972
Hann and Slowey, 1972
Hann and Slowey, 1972
Leland, Shukla, and Shimp, 1974
Leland, Shukla, and Shimp, 1974
Leland, Shukla, and Shimp, 1974
Mathis and Cummings, 1973
Mathis and Cummings, 1973
Wogman, Rieck, and Kosorok, 1974
Mackay, Halcrow, and Thornton, 1972
Oliver, 1973
Oliver, 1973
Oliver, 1973
Oliver, 1973
De Groot and Allersma, 1973
De Groot and Allersma, 1973
De Groot and Allersma, 1973
De Groot and Allersma, 1973
De Groot and Allersma, 1973
De Groot and Allersma, 1973
De Groot and Allersma, 1973
De Groot and Allersma, 1973
De Groot and Allersma, 1973
Mackay, Halcrow, and Thornton, 1972
Mackay, Halcrow, and Thornton, 1972
Mackay, Halcrow, and Thornton, 1972
Mackay, Halcrow, and Thornton, 1972
Mackay, Halcrow, and Thornton, 1972
"In many cores these accumulations are 5 to 20 times as great as concentra-
tions of the same trace elements found 1 m deeper in the core." These chro-
mium concentrations correlated best with concentrations of organic carbon.
In sediments of the Ottawa and Rideau rivers, Oliver (1973) observed
a significant correlation between surface area of particles and their metal
content. Silt (0.004 to 0.062 mm) contained 27 ppm chromium, while medium-
sized particles (0.5 to 2.0 mm) contained 9 ppm. In Puget Sound sediments,
-------
SAN PEDRO
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242
SANTA MONICA
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4 12 20 28
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I I I I
1800
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SANTA BARBARA
BASIN
4 12 20 28
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1940-*-
Figure 7.4. Chromium concentration in sediments from the southern
California basins. Source: Adapted from Bruland et al., 1974, Figure 3,
p. 426. Reprinted by permission of the publisher.
no elevated chromium levels attributable to input by man were observed
(Crecelius, Bothner, and Carpenter, 1975). In addition, statistical anal-
yses did not demonstrate a strong relationship between chromium concentra-
tions and sediment grain size.
Site and rate of deposition of suspended matter carried by a river
into a lake depends on many factors, such as area water turbulence and size
of suspended particles. In Lake Michigan at Grand Haven, Michigan, Robbins
and Edgington (1973) found that fine particles did not begin to settle for
about a 6 mile distance, and then the prevailing north-south internal and
wind-induced currents in the lake produced a north-south band of deposition
in the sediments from 4 to 17 miles off the shoreline. Chromium concentra-
tions in surface sediments were from about 100 to 180 ppm and from 60 to
180 ppm in samples from various depths (up to 20 cm). Deposition within a
body of water, therefore, is not the same in all areas. Careful selection
of sample sites and analysis of factors influencing deposition at these
sites are necessary for a complete picture of metal accumulation within
sediments.
7.4 ENVIRONMENTAL FATE
No comprehensive studies on the resident times or fate of chromium
within the various media have been made. However, the few available reports
presented enough data to identify some of the mechanisms involved in move-
ment of chromium among the media. The most obvious lack of information is
in the quantitative aspects of such movements and, of course, the actual
amounts of each element would depend on the particular circumstances.
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243
Table 7.23. Chromium concentration in sediments
of Wisconsin lakes
(ppm dry wt)
Lake
0-5
5-10
10-15
Depth (cm)
15-20 20-25
25-50
>50
Northern Wisconsin lakes
Mary
Tomahawk
Minocqua
Phillips
Butternut
1
28
4.2
38
26
1
18
4.0
32
19
1.5
20
4.8
32
21
1.5
17 20
3.9 2.0
26 28
23
1.7
26
33
35
35
0.8
16
5.4
35
Southern Wisconsin lakes
Mendota
Monona
Waubesa
Kegonsa
Wingra
42
49
33
17
17
38
46
24
13
23
33
38
35
16
21
30
28 10
36 30
18 18
19
16
8
22
15
23
11
7
17
15
18
Source: Adapted from Iskandar and Keeney, 1974, Table III,
p. 167. Reprinted by permission of the publisher.
7.4.1 Mobility and Persistence in Air
Chromium is removed from air by fallout and precipitation. In New
York City, the average amount of chromium deposited monthly by precipita-
tion was 0.15 yg/m2, with a range of 0.05 to 0.25 yg/m2 (Volchok and Bogen,
1973). The average chromium concentration in precipitation was 0.025 yg/ml
with a range of 0.005 to 0.060 yg/ml over 11 months.
Cawse (1974) presented data on trace element contents of wet and dry
deposition in the United Kingdom. Rainwater contained between 0.64 and 34
ppb chromium in rural England and 9.3 ppb in central Swansea (urban area).
Total annual chromium deposition was between 0.12 and 1.9 yg/m2 with dry
deposition accounting for 0.023 to 0.44 yg/m2. Depending upon locale,
between 44% and 96% of total deposition occurred by wet precipitation.
Although data for chromium are sparse and exhibit a considerable range of
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244
values, urban areas have somewhat higher wet and total deposition amounts
than do rural areas. Concentrations of chromium in rainwater were 3.6 ppb
for Heidelberg, Germany; 2 ppb for Quiltayute, Washington; and 2.9 ppb for
Waymire, United Kingdom (Bogen, 1974).
At the Walker Branch Watershed, Oak Ridge, Tennessee, chromium concen-
trations in rainwater varied from 0.7 to 3.9 ppb over a 14-month period
(Andren et al., 1974; Andren, Lindberg, and Bate, 1975). Monthly total
amounts of chromium delivered to the watershed ranged from 0.6 to 10.7 g/ha,
with a monthly average of 3.9 g/ha. From January to June 1974, monthly
average rain deposition was 2.9 g/ha (range 0.6 to 8.4 g/ha), while dry
deposition was 0.76 g/ha (range 0.16 to 2.18 g/ha). Apparently, most chro-
mium is deposited on land by wet fall (rain or snow) and is obviously
related to the amount of rain or snow occurring during the sampling period.
Rainfall ash contained 420 and 450 ppm chromium in two samples from
England. These concentrations were higher than those in the fly ash
released to the environment from the neighboring generating stations
(Hallsworth and Adams, 1973). Thus, other unidentified sources contributed
to the rainwater ash.
7.4.2 Mobility and Persistence in Soil
Few studies which presented data on the fate of chromium in soils were
found. Most soil chromium is in mineral, adsorbed, or precipitate form and
is not easily transported to other media. On the basis of correlation
analysis, the chromium in aerosols over the San Francisco Bay area was shown
to be largely derived from soil (John et al., 1973). Atmospheric chromium
at the South Pole is probably derived partly from the ocean and partly from
crustal weathering (Zoller, Gladney, and Duce, 1974). Thus, weathering and
wind action can transport soil chromium to the atmosphere.
Chromium is also removed from soils by both runoff and by percolating
water, but data on this type of removal are lacking. Runoff could remove
both chromium ions and bulk precipitates of chromium, with final deposition
on either a different land area or a body of water. In addition, flooding
of soils and the subsequent anaerobic decomposition of plant matter may
increase dissolution of metal oxides in the soil (Kee and Bloomfield, 1962).
Rates of dissolution depend on the particular soil characteristics. For
example, water extracted 0.5 ppm chromium and 2.5% acetic acid extracted
0.8 ppm chromium from a 17.5-cm (7-in.) layer of grassy soil incubated for
39 days under anaerobic conditions. Aerobic incubation of the same soil
without grass for the same length of time resulted in 0.04 ppm chromium
extracted by water and 0.4 ppm extracted by 2.5% acetic acid. Before in-
cubation, water and 2.5% acetic acid extracted about 0.05 and 0.04 ppm
chromium, respectively, from the grassy soil samples and 0.01 and 0 ppm
chromium, respectively, from the soil without grass. Subsequent aeration
of samples resulted in partial immobilization of the trace elements.
7.4.3 Mobility and Persistence in Water and Sediments
No experimental studies describing the fate of chromium within natural
waters were found. Since most chromium in water is in particulate form, it
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245
would ultimately be deposited in sediments. Considerable amounts of material
could be transported in flowing waters. The Susquehanna River transports
approximately 790 metric tons of chromium per year (Turekian and Scott, 1967).
The chromium input from natural streams into Lake Michigan is estimated to be
about 30 metric tons per year; the input from air pollution is higher,
approximately 90 metric tons per year (Winchester and Nifong, 1971).
Various physical forms of metals in streams can be transported by river
current (Table 7.24) (Gibbs, 1973). The percentage transported in each form
was determined for iron, nickel, cobalt, copper, chromium, and manganese and
was different for each metal. Crystalline sediments were the major form of
chromium transported in the two rivers studied. De Groot and Allersma (1973)
found a metal-in-water to metal-in-suspended-matter ratio of 1 to 2.3 for the
Rhine River. In the heavily polluted Qishon-Gadura River system in Israel,
chromium concentrations in water were <10 ppb, while sediments in the con-
taminated region contained from 220 to 610 ppm chromium. Since this region
of the river system has relatively high pH values (10 to 11), efficient
removal of heavy metals from the water occurs. Even boiling water did not
extract any chromium from these sediments. Dean, Bosqui, and Lanouette
(1972) listed 5.3 as the pH above which most chromium(III) precipitates
from dilute solutions.
Table 7.24. Chromium transported by five phases
in the Yukon and Amazon Rivers
(percent)
Physical form
of chromium
In solution and organic complexes
Adsorbed
Precipitated and coprecipitated
In organic solids
In crystalline sediments
Amazon
River
10.4
3.5
2.9
7.6
75.6
Yukon
River
12.6
2.3
7.2
13.2
64.5
Source: Adapted from Gibbs, 1973, Table 1, p. 72.
Reprinted by permission of the publisher.
The trace-element mass balance for the Walker Branch Watershed, Oak
Ridge, Tennessee, showed that the six-month atmospheric input of chromium
for soil and water was 22.1 g/ha and the total stream output was 9.1 g/ha,
giving a retention in the watershed of 58.8% (Andren, Lindberg, and Bate,
1975). The suspended load in water also provides a major transport mech-
anism for chromium in this watershed (67.6% of chromium is in insoluble
form).
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246
Movement of metals can occur through aquifers. Finder (1973) demon-
strated that simulation of movement of groundwater contaminants can be
obtained with the Galerkin-finite element method. This method was used
for chromium-contaminated groundwaters of Long Island, New York.
As with chromium in air and soil, the exact chemical form of chromium
in water is not well defined. In contrast to soil, the small concentration
of organic matter in some streams is insufficient to reduce chromium(VI) to
chromium(III), and thus both chromium(III) and chromium(VI) ions exist.
Ultimately, however, chromium(VI) is reduced to chromium(III), which pre-
cipitates and is eventually deposited in sediments.
Mobilization of chromium can occur following the discharge of sus-
pended matter carried by rivers into estuaries (De Groot and Allersma, 1973).
This process, which has been demonstrated for the Rhine Estuary, apparently
occurs because the organic matter onto which chromium had been adsorbed
decomposes and the metals are released as soluble organo-metallic complexes.
As De Groot pointed out, this release may be the result of specific condi-
tions in the Rhine Estuary and may not generally occur in all estuaries.
Some data support the contention that salinity does not greatly affect the
distribution of chromium between soluble and suspended phases. In a study
by Evans and Cutshall (1973), about 94% of 51Cr was in dissolved form in
river water; after addition of seawater to river water, about 92% still
remained in the dissolved form. Seawater did not leach 51Cr from suspended
river matter (<1%) even after three weeks of contact time. Similarly, sea-
water did not leach 51Cr from bottom sediments of the Columbia River (Johnson,
Cutshall, and Osterberg, 1967).
Schroeder and Lee (1975) studied transformations between chromium(III)
and chromium(VI) in natural waters. They found that only 3% of chromium(III)
was oxidized by 02 in 30 days at ambient temperatures (22°C to 26°C). The
presence of manganese oxide increased rates dramatically but the significance
of this fact in natural waters is doubtful due to calcium and magnesium satu-
ration of reaction sites. Many compounds reduced chromium(VI). The authors
recommended that total chromium, not chromium(III), be used to assess water
quality because of possible transformations. The arguments are not very
convincing.
In the Upper James Bay Estuary, chromium is apparently removed from
water by adsorption to hydrous iron oxides and clay materials (Van Horn,
1973). The form of chromium in the water was not reported. Lu and Chen
(1976) found that chromium was not significantly released from sediments
into seawater under either oxidizing or reducing conditions.
Krauskopf (1956) addressed the problem of factors controlling the low
concentrations of rare metals in seawater. Seawater is "undersaturated" in
rare metals in spite of the large amounts supplied. Removal of chromium(VI)
by adsorption to Fe203»nH20, apatite, clay, and plankton varied from about
10% to 47%, while Mn02»nH20 was very effective, adsorbing between 89% and
94% of the initial chromium(VI). Chromium(VI) is the major stable form of
chromium in seawater (Cutshall, Johnson, and Osterberg, 1966; Fukai, 1967).
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247
Adsorption and precipitation as sulfides could not account for the low con-
centrations observed; however, Krauskopf (1956) suggested that in sulfide-
rich or reducing areas, chromium(VI) is converted to chromium(III) and is
then precipitated as Cr(OH)3. This approach is oversimplified because chro-
mium input is not entirely in the form of chromium(VI), nor is it all in
soluble form; thus, some chromium settles into sediments.
The identification of chromium sources and the quantification of input
into waters has not been well studied. Bruland et al. (1974) concluded that
it was "not possible to evaluate the contribution from different transport-
ing agencies —winds, sewer outfalls, storm runoff, and river runoff" for
basins of the southern California coast. Fluxes of chromium into sediments
of the San Pedro, Santa Monica, Santa Barbara, and Soledad basins had a
yearly average of 2.9 ug/m2 for anthropogenic chromium input and 5.2 yg/m2
for natural chromium input. Annual washout flux of chromium from atmos-
phere to water was calculated to be about 0.1 yg/m2. Thus, while Winchester
and Nifong (1971) concluded that the major input of chromium into Lake
Michigan was particulate deposition from airborne sources, the major input
of chromium into the California basin was from entering waters.
Chelating agents, such as nitrilotriacetic acid (NTA) and ethylene-
diaminetetraacetic acid (EDTA), release metal cations from sediments. Clay
Lake (Ontario) sediments, extracted by 10% NTA and EDTA solutions at a ratio
of 1 to 10, contained 190 and 210 ppb chromium, respectively, while dis-
tilled water extract contained only 8 ppb chromium (Barica, Stainton, and
Hamilton, 1973). At NTA concentrations of 1 mg/liter, little difference was
observed in extractable chromium compared to distilled water controls; how-
ever, some other metals were released in the order of Fe > Mn > Zn > Pb >
Cu > Cr. Since NTA may be used as a phosphate substitute in producing
detergents, the environmental impact of the release of NTA into waters is
of concern.
Concentrations are projected to be as high as 200 ppb NTA in some
natural waters. Natural and metallo-chelated forms of NTA are ultimately
broken down to nitrates, which may also become a problem. Actual rates of
degradation depend upon the particular NTA-metal complex (Chau and Shiomi,
1972). Degradation time of a chromium-NTA complex in Lake Ontario water,
pH 8.2, was six days.
7.5 WASTE MANAGEMENT
Chromium wastes released to air, land, and water are produced by
several major industries (Figure 7.1). By far the largest amount is re-
leased into water during treatments involved with the plating and finishing
industries (Table 7.9). In most cases, these waters must be treated before
being discharged. Since the maximum permissible chromium concentration in
public water supplies has been set at 0.05 ppm by the U.S. Environmental
Protection Agency, efficient chromium removal from wastewaters, especially
water from plating industries, and disposal of the chromium obtained are
necessary.
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248
Chromium concentrations in various water wastes were 10,000 to 50,000
ppm in bright dip wastes from metal plants, 600 ppm in pickle bath or plat-
ing wastes, 40 ppm in leather industry wastes, and 10 to 60 ppm in cooling-
tower blowdown waters (Cheremisinoff and Habib, 1972). The major technique
for chromium removal from these waters is by precipitation. Chromium(VI)
is usually first reduced to chromium(III) with ferrous sulfate, sodium bi-
sulfite or metabisulfite, or sulfur dioxide at low pH values (Ottinger et
al., 1973). The pH is then raised to about 9.5, and chromic hydroxide and
ether metal hydroxides precipitate. The precipitate is collected in set-
tling ponds, dried, and then disposed of by landfill, ocean dumping, or in-
cineration. At present, recovery of chromium from these-precipitates is
not economically feasible. Ion exchange, another process which can remove
chromium from wastewaters, is not used as extensively as precipitation, but
it may be feasible in certain cases, especially where the flow rate can be
adequately controlled.
Some chromium wastes are discharged into municipal sewers and can help
precipitate sulfide from water. Such chromium wastes are usually reduced
to chromium(III) and precipitated during transit to the sewage plant. This
precipitate is removed by sewage treatment processes. Other removal methods,
such as precipitation, ion flotation, electro-chemical conversion, electro-
dialysis, activated carbon adsorption, liquid-liquid extraction, and re-
verse osmosis are being developed and may be commercially used in the future.
Combinations of two or more methods may be necessary for more effective
concentration reductions. Furthermore, novel advances in technology may
produce versatile methodology. For example, Netzer, Wilkinson, and Beszedits
(1974) reported that discarded pulverized automobile tires effectively re-
moved chromium from solutions, and when preceded with a lime precipitation
step, reduced chromium concentrations to below 0.1 ppm (99% removal) over
the pH range 6 to 11.
Each disposal method for precipitated wastes as well as municipal
wastes poses potential problems involving release of chromium to the environ-
ment. Leaching is the primary means by which chromium is removed from land-
fill and could possibly contaminate groundwater and surface waters. Leachate
from simulated sanitary landfills, however, did not contain measurable amounts
of chromium (Pohland, 1975). Care must be taken to avoid acidification of the
landfill, which would solubilize a portion of the trivalent chromium and thus
allow it to be leached out.
Incineration is another method for disposal of municipal wastes.
Municipal incinerators in Milwaukee, Wisconsin, produced stack effluents
which contained 0.1% to 1.0% chromium in ash (Jens and Rehm, 1966). Col-
lector catch and residues each contained 0.01% to 0.1% chromium. Over a
five-day period, 5.3 metric tons of dry stack emissions was produced from
the incineration of 1281 metric tons of refuse (variable water content).
Impinger-water residues (obtained from a sampling train for measuring
particulates in stack emission of incinerators) contained <0.5 ppm chro-
mium (Achinger and Daniels, 1970). The magnetic metallic fraction of the
residue from municipal solid waste incinerators contained an average of
0.009% chromium (0.001% to 0.0187% range) (Ostrowski, 1971). A portion of
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249
the chromium may have come from discarded tin-free steel beer cans, which
have been reported to contain 60 ppm chromium (0.12 Ib/ton).
Wastewater from plating industries does not contain just chromium,
however, and an integrated procedure for efficient removal of all metals
in the wastewater must be developed. A flow diagram for precipitation
treatment of wastes (Figure 7.5) illustrates the steps necessary to pro-
duce a low-contamination effluent from a plating company (Cave, 1971).
Watson (1973) gave a more detailed examination of all methods of hexavalent
chromium removal from water and the current level of technology for each
method.
The overall efficiency of chromium removal from sewage influent varied
from 17% to 78% (average 37%) in a study of seven midwestern sewage treat-
ment plants (Brown et al., 1973). Systems with primary treatments averaged
only 27% removal, a trickling-fliter secondary treatment effected 38% chro-
mium removal, and an activated sludge secondary treatment removed 78% of the
chromium. From sewage influent (no influent chromium data listed), the
Hyperion Wastewater Treatment Plant in Los Angeles produced primary effluent
containing about 300 ppb chromium and a secondary effluent containing 60 ppb
chromium (activated sludge process and sedimentation) (Chen et al., 1974).
Approximately 60% of chromium in the primary effluent and 30% in the secon-
dary effluent were in particulate form. Concentrations of dissolved chromium
(defined as that passing through a 0.2-ym filter) in two samples dropped
from 147 and 100 ppb in primary effluent to 30 and 47 ppb in the secondary
effluent, reductions of 80% and 53%, respectively. Particle size distri-
bution for primary effluent was 19% of total chromium retained on 0.2- to
8-ym filters, 75% on 8- to 44-ym filters, and 6% on >44-ym filters. For
the secondary effluent, 33% was retained on 0.2- to 8-ym filters, 51% on
8- to 44-ym filters, and 16% on >44-ym filters. Discharge from the plant
consisted of primary effluent, mixtures of primary effluent and secondary
effluent, and mixtures of effluent and digested sludge. The composite
sample of final effluent released contained about 200 ppb chromium; about
50% of the chromium in the final effluent was retained on filters with pore
size of less than 8 ym.
In New York City, about 676 kg/day (0.04 to 0.50 ppm influent chromium
concentration) is discharged into wastewaters and received at various sewage
plants (Klein et al., 1974). Most of the chromium was discharged from the
metal-plating industry, although contributions also came from other sources
(for example, residential wastewaters, 0.008 to 0.15 ppm chromium; surface
runoff, 0.16 ppm chromium). Of the total chromium received at sewage plants,
43% came from electroplaters, 9% from other industries, 9% from runoff, 28%
from residential sources, and 11% was unaccounted for. Sewage plant dis-
charge effluent contained from 0.04 to 0.19 ppm chromium (weighted average
0.08 ppm), representing a 48% reduction in chromium content of the water.
Estimates of chromium in waters discharged to the harbor were 353 kg/day
for sewage plant effluents, 313 kg/day for runoff, and 259 kg/day for un-
treated wastewater, totaling 925 kg/day of discharge (about 0.12 ppm chro-
mium, weighted average). Harbor waters contained from <0.5 to 10 ppb chromium,
while the adjacent regions contained about 0.5 ppb; area rivers contained
from <0.5 to 5.8 ppb.
-------
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OIL-BEARING MIXING TANK AND »' | » rcM^7'0" ~
,,, ~ 1 iniinHS DICHROMATE ^±^ ,,.,.
SAJHtNINl, nFmirTinw ^ \
SLUDGE iirii.ii.iiii« » 1 |
1| i 1
ii FILTRATION «-
SURPLUS 1 ' * PUMP TANK AND
WATER TO •- CONCENTRATION EMULSION
nnicn lu ANP STORAfiF •> nnCAKINC
btnviots | 1 - _.....,...,.- FIITFRCAKF
1 STORAGE '
IIJ: i 1
„ FILTER CAKE
TO WASTE TIP
/"•';,'! AERATION FLOW OCCURS ONLY
| ^ ! ! CELLS WHEN CONDITIONS WARRANT IT
\: \ i 1 . . 1
-- i - l^A.'.^U_ _ FISH | * 1 SLUDGE
11 t rnrnvp" POND CLAHIHCAI IUN | • TRANSFER «J
i i'
iU-
Figure 7.5. Flow diagram for precipitation treatment of wastes. Source: Adapted from
Cave, 1971, Table 2, p. 207. Reprinted by permission of the publisher.
-------
251
In some waste treatment facilities, stabilization ponds are used to
remove various elements from effluent (Bulthuis, Craig, and McNabb, 1973).
Organisms in the ponds help to produce a purified water supply. Data from
a study of such ponds in Michigan showed that chromium concentration of the
effluent dropped from 8.5 to 3.5 ppb as water moved from an anaerobic pond,
to a facultative pond, to a facultative-aerobic pond, and then to an aerobic
pond. Of the total chromium entering into the facultative-aerobic and the
aerobic ponds, between 1% and 2% was incorporated into higher plant materials
and 18% to 20% was incorporated into sediments. Thus, some chromium was
immobilized during the purification process.
Sewage sludge contains a wide range of chromium concentrations (Table
7.25) — from about 20 ppm to over 40,000 ppm, with a mean concentration
range of 86 to 380 ppm (Page, 1974). In a study of 42 sludges from England,
chromium (but not other metals) was found to increase in concentration with
the size of the city; apparently, the amounts chiefly reflected the use of
chromium compounds in the tanning industry (Berrow and Webber, 1972). Most
of the chromium in sludge, however, is in insoluble form. In a study of the
effluents from sludge, Argo and Gulp (1972) reported that while sand filtra-
tion only reduced the concentration of chromium(VI) from 50 to 49 ppb, carbon
adsorption reduced the concentration to 17 ppb. Lime coagulation, which was
only slightly more effective than the sand filtration, only reduced the
chromium(VI) from 56 to 50 ppb in one effluent. Total chromium concentra-
tions of sewage effluents in 57 Michigan treatment plants studied by Page
(1974) were in the range of 0.0005 to 1.46 ppm (median 0.02 ppm), most of
which was soluble (0.01 to 1.0 ppm, median 0.02 ppm). Available chromium
(defined as being soluble in 2.5% acetic acid) in 42 sewage sludges from
England ranged from <0.9 to 170 ppm (mean 22 ppm, median 4.4 ppm) (Berrow
and Webber, 1972). This amount was between 0.7% and 8.5% of the total chro-
mium content of sludge and was considerably higher than the 0.01 to 1.0 ppm
in 2.5% acetic acid extracts of soils.
As mentioned earlier, most of the chromium in sludge is insoluble and
apparently remains so during treatment. Blakeslee (cited in Page, 1974)
studied the concentrations of trace elements, including chromium, in sludges
from a number of sewage treatment plants at various stages of treatment.
Undigested sludge contained from 66 to 7800 ppm chromium, secondary digestor
sludge from 22 to 9600 ppm, and vacuum filter cake from 28 to 10,600 ppm.
Although mass balances were not given, these figures, when considered with
the generally low chromium concentrations in sewage effluents, infer that
chromium in sludge is solubilized to only a small extent by the treatment
the sludge undergoes.
The application of sewage sludges to soils presents both advantages
(source of irrigation water, plant nutrients, improvements of properties,
reclamation of wastewater) and disadvantages (e.g., potential toxicity of
trace elements); however, few references present data concerned with chro-
mium in sludge-amended soils. Seven years after sludge application was
discontinued (66 metric tons of sludge per hectare per year for 19 years;
the 0.5 N acetic acid—extractable concentration of sludge was 3.5 ppm
chromium), the 0.5 N acetic acid—extractable content of soil was 2.6 ppm
chromium compared to the 0.9 ppm chromium from untreated soil (Le Riche,
-------
Table 7.25. Chromium concentrations in sewage sludge
Locale
Sweden
Michigan
England
Southern California
Toronto , Canada
Oklahoma
Indiana
„ , Chromium concentration Number of samples in concentration range
Number . . r °
f (ppm dry wt;
sludges _ „ „, , .
Range Mean Median ppm ppm ppm ppm
93 20-40,615 872 86 0 48 39 2
57 22-30,000 2,031 380 0 19 18 18
42 40-8,800 980 250 0 13 19 10
<40-600
60-16,000
0-600
50-19,600
Ln
Source: Modified from Page, 1974, compiled from Tables 1, 2, 3, and 5, pp. 9, 11, 12, and 15.
-------
253
1968). No information was found on the chemical form of chromium in sludge,
sewage effluents, or sludge-amended soils.
Trace elements supplied by sludge added to soils are slowly removed by
processes such as leaching, plant uptake, and runoff. For example, at two
different sludge application rates, total amounts of 118 and 164 ppm chro-
mium were added to soils over a three-year period, yet at the end of this
period only 26% and 19%, respectively, of chromium added was recovered
(Page, 1974). Le Riche (1968) found that extractable chromium (0.5 N acetic
acid) in sludge-amended soils decreased little over an eight-year period
after the last sludge application (2.8 ppm for 1959 and 2.6 ppm for 1967).
Chromium concentrations of water "saturation" extracts of sludge (0.01 ppm),
of soil beneath sludge drying ponds (0.01 to 0.40 ppm), and of soil from
fields irrigated with sewage effluent (0.01 to 0.40 ppm) were within the
range found for extracts of a wide variety of soils. Nevertheless, these
data indicate that a certain amount of chromium can be removed from amended
soils and transported in drainage water (Page, 1974).
-------
254
SECTION 7
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262
101. Schroeder, D. C., and G. F. Lee. 1975. Potential Transformations of
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American Petroleum Institute, Washington, D.C. 28 pp.
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-------
SECTION 8
ENVIRONMENTAL INTERACTIONS AND THEIR CONSEQUENCES
8.1 SUMMARY
Chromium is released to the environment from many sources and is cycled
among air, land, and water; small amounts are taken up by a wide variety of
organisms. Although environmental interactions of chromium have been inade-
quately studied, chromium does not appear to be biomagnified in either aquatic
or terrestrial food chains, even though certain organisms can accumulate it.
The relative immobility of chromium in biological systems, due to the poor
solubility of a number of its compounds, partially explains the lack of bio-
magnification observed.
The average daily chromium intake for humans is approximately 100 yg.
Most of this amount is the result of dietary intake; lesser amounts are con-
tributed by water and air. This chromium, however, may not be in a form
available for utilization by man. Few studies exist on the chromium content
of organisms growing in polluted regions, but the general trend seems to be
an increased chromium content in lower trophic level organisms in response
to an increased environmental level of chromium.
8.2 ENVIRONMENTAL CYCLING
Data on removal rates from each medium are given in Section 7. Chromium
released into the atmosphere, either as chromate mist from cooling towers or
plating operations or as particulate matter from ore extraction processes or
incineration of chromium-bearing materials, is eventually deposited on land
or water. In soil which has low pH and contains organic matter, hexavalent
chromium is reduced to trivalent chromium; in well-aerated water with little
organic matter, hexavalent chromium is more stable and can persist.
Soil chromium is generally in an insoluble, unavailable form, mainly
either as the weathered form of parent chromite or as Cr203»nK20. A small
amount of soil chromium is water extractable and slightly larger amounts are
extractable with ammonium acetate or acetic acid. Therefore, leaching could
be expected to remove only a small amount of soil chromium; however, litera-
ture on the quantitative aspects of this process is sparse. Surface runoff
into waters can be expected to remove a small amount of soil chromium.
Surface runoff, deposition from air, and release of wastewaters (vari-
ously treated for chromium removal) are sources of chromium in waters.
Sedimentation is apparently an effective removal mechanism, as shown by the
very low concentrations of chromium in most waters. Chromium, therefore,
accumulates in sediments. In rivers, considerable suspended material which
contains chromium can be transported and eventually deposited in estuaries
or bays.
264
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265
8.3 HUMAN EXPOSURE
Human exposure to chromium in the general environment occurs mainly
through the diet. The amount of chromium ingested per day depends on the
amount of food ingested and the chromium content of each food. Estimates
of the amount of chromium ingested have come from analyses of institutional
diets. One such study for institutions in the United States showed the
average chromium content of all foods served to be between 0.175 and 0.472
mg/kg (Murthy, Rhea, and Peeler, 1971). Statistical analysis of the data
showed significant variation in chromium amounts from one sampling period
to the next and from one institution to another. Average amounts ingested
daily ranged from 0.455 to 0.880 mg chromium. During 1967, the average
amount of chromium consumed was about 0.63 mg/day; the amount consumed was
slightly less in summer than in fall and spring.
An average of 0.019 mg chromium per lunch (range of 0.009 to 0.088
mg per lunch) was found in school lunches sampled from 300 schools in 19
states (Murphy, Page, and Watt, 1971). Schroeder, Balassa, and Tipton
(1962) found 0.078 mg chromium in a one-day institutional diet. Thus,
studies estimating daily dietary intake of chromium are in agreement.
The chromium content of a variety of foods is presented in Table 8.1
(Thomas, Roughan, and Watters, 1974), Table 8.2 (Schroeder, Balassa, and
Tipton, 1962), Table 8.3 (Meranger and Somers, 1968; Meranger, 1970; Zook
et al., 1976), and Table 8.4 (Toepfer et al., 1973). The chromium data pre-
sented by these five research groups show fair agreement for most foods.
The results of Thomas, Roughan, and Watters (1974) showed a range from
<0.01 to 1.13 ppm chromium with a mean of 0.15 ppm for fresh foods and 0.23
ppm for frozen vegetables. Schroeder, Balassa, and Tipton (1962) gave a
range of 0.01 to 0.13 ppm chromium for fruits and vegetables with a mean of
0.03 ppm, and Toepfer et al. (1973) found chromium amounts between 0.04 and
0.27 ppm in vegetable samples. Thomas, Roughan, and Watters (1974) expressed
concern about the chromium concentrations in these reports; while they found
a nickel content similar to that reported by Schroeder, Balassa, and Tipton
(1962), they found higher chromium and lower cobalt values. Murphy, Page,
and Watt (1971) observed wide geographical and seasonal variation in trace
element content of total diets, which could explain the discrepancies. The
nutritional significance of chromium in diets is discussed in Section 6.3.2.
Community air and drinking water contribute smaller quantities of chro-
mium to the total daily exposure than does the diet. In the Community Water
Supply Survey (CWSS), only 4 of 969 water supplies exceeded the U.S. Public
Health mandatory limit of 50 ppb chromium (Section 7.3.4). Since the CWSS
did not present concentration data for the finished drinking water supplies,
it is difficult to determine amounts of chromium actually received from
drinking water. A reasonable estimate from the discussion in Section 7.3.4
is about 10 ppb. If a daily intake of 1 to 2 liters of water is assumed
(Friberg et al., 1974) , consumption of chromium from drinking water would
be between 10 and 20 yg/day.
The need for caution in interpretation due to analytical uncertainty
in these results must be kept in mind. Large errors are found in current
-------
266
Table 8.1. Chromium content of fruits and vegetables
Food
Fresh fruits and vegetables
Beetroot
Broccoli
Brussels sprouts
Cabbage
Carrots
Celery
Cucumber
Leeks
Lettuce
Mushrooms
Onions
Potatoes
Spinach
Swedes
Watercress
Miscellaneous
Dried herbs
Apples
Skin
Flesh
Pears
Skin
Flesh
Whole fruit
Plums
Rhubarb
Tomatoes
Total
Frozen vegetables
Peas
Spinach
Beans
Sweet corn
Broad beans
Brussels sprouts
Asparagus
Total
Number
of
samples
2
5
19
23
10
3
3
3
2
6
11
14
2
8
7
8
6
2
4
7
7
6
6
5
10
179
6
2
5
2
3
3
3
22
Chromium content
(ppm)
Range
0.04-0.12
0.06-0.33
0.01-0.64
0.05-0.29
<0. 01-0. 13
0.08-0.12
0.15-0.20
0.02-0.16
0.12-0.21
0.06-0.72
0.04-0.83
0.06-0.40
0.12-0.28
<0. 01-0.19
0.05-0.31
<0. 01-0. 15
<0. 01-0. 22
0.07-0.13
0.06-0.16
0.20-0.50
0.07-0.32
0.23-0.88
<0. 01-0. 01
0.01-0.09
0.16-0.37
<0. 01-0. 88
0.12-1.13
0.03-0.09
0.17-0.24
0.35-0.39
0.11-0.40
0.08-0.25
<0.01
<0. 01-1. 13
Mean
0.08
0.19
0.14
0.15
0.08
0.11
0.17
0.08
0.17
0.25
0.19
0.15
0.20
0.09
0.16
0.08
0.11
0.10
0.11
0.30
0.18
0.44
<0.01
0.04
0.24
0.15
0.38
0.06
0.22
0.37
0.22
0.16
<0.01
0.23
-------
267
Table 8.1 (continued)
Food
Canned fruits and vegetables
Apples
Apricots
Black currants
Grapefruit
Oranges
Peaches
Prunes
Damsons
Plums
Pineapples
Rhubarb
Tomatoes
Baked beans
Sweet corn
Spinach
Asparagus
Mushrooms
Total
Number
of
samples
7
3
4
3
3
4
6
2
12
5
8
4
7
3
7
3
3
84
Chromium content
(ppm)
Range
<0. 01-2. 64
0.02-0.08
0.02-0.08
0.01-0.07
<0. 01-0. 05
0.03-0.06
0.53-2.15
0.72-2.04
<0. 01-2. 64
0.02-0.09
0.01-1.84
0.02-0.04
<0. 01-0. 64
0.06-0.54
0.01-0.08
<0. 01-0. 18
0.23-0.47
<0. 01-2. 64
Mean
1.39
0.04
0.03
0.04
0.02
0.05
1.01
1.39
1.04
0.04
0.66
0.03
0.24
0.22
0.04
0.11
0.33
0.39
Source: Adapted from Thomas, Roughan, and Watters, 1974,
Table 1, p. 774, Table 2, p. 774, and Table 3, p. 775.
Reprinted by permission of the publisher.
chromium analyses (Section 2), and it is likely that older data are even
less reliable. Until the reasons for the analytical problems are dis-
covered, we will not know how much reliance to place on these numbers.
The quantity of chromium inhaled varies with the environment. No
measurable chromium was found in rural air, whereas urban air contained
values up to 0.1 yg/m3 (Section 7.3.2). A more reasonable estimate for
chromium concentrations in urban air would be about 0.01 yg/m3 (Section
7.3.2). If one assumes that an individual inhales about 20 m3 of air per
day (Friberg et al., 1974), then airborne chromium exposure would be about
0.2 yg/day for each individual.
Therefore, total daily chromium intake approximates 100 yg per indi-
vidual; food accounts for about 80 yg of this amount. This level of ex-
posure apparently does not cause any chromium toxicity symptoms. Indeed,
daily supplements of 250 yg chromium have been used to improve glucose
tolerance in cases of malnutrition (Section 6.3.1.1).
-------
268
Table 8.2. Chromium content in various foods
. Chromium content
Food sample (ppm)
Condiments and spices
Pepper, black 3.70
Thyme 10.00
Cloves 1.50
Chili powder 0.86
Green pepper, whole fresh 0.19
Red pepper, whole, fresh, hot 0.01
Salt, table 0.0
Salt, sea 0.0
Dairy products
Milk, whole, homogenized 0.01
Milk, dried, skim 0.07
Eggs, hen 0.16
Butter 0.17
Cheese, Wisconsin swiss 0.11
Mean 0.10
Meat and fish
Haddock 0.02
Halibut, meat 0.01
Halibut, skin 0.18
Lobster, claw meat 0.0
Lobster, tail meat 0.0
Lobster, digestive gland 0.33
Lobster, shell 0.0
Oyster, canned, gulf 0.09
Clams, hard shell 0.44
Clams, soft shell 0.36
Shrimp, fresh 0.01
Scallop, fresh 0.11
Beef marrow 0.03
Beef chuck 0.09
Lamb chop 0.12
Pork chop 0.10
Partridge gizzard 0.13
Chicken gizzard 0.11
Chicken breast 0.26
Chicken skin 0.27
Tripe 0.04
Mean, excluding skins, shells, and organs 0.11
-------
269
Table 8.2 (continued)
_ , . Chromium content
Food sample , .
(ppm)
Vegetables
Potato, white 0.0
Beans, dried, navy 0.08
Beans, dried, yellow-eye 0.05
Beans, wax 0.03
Beans, green string 0.02
Lentils, dried 0.09
Beets 0.01-0.03
Radishes 0.0
Parsnips 0.13
Parsnip leaves 0.08-0.19
Turnip leaves 0.04-0.06
Carrots 0.0-0.03
Onions 0.01-0.02
Spinach 0.0-0.05
Swiss chard 0.06
Squash, summer 0.02
Cucumber 0.01-0.03
Kohlrabi 0.0
Cauliflower 0.02
Cabbage 0.01-0.06
Sauerkraut 0.03
Rhubarb, raw 0.02
Rhubarb, cooked in stainless steel 0.05
Lettuce, garden 0.07
Lettuce, head 0.02-0.13
Mean 0.03-0.05
Fruit
Peach, Elberta, raw 0.01
Peach, stewed in stainless steel 0.01
Raisins 0.02
Blackberries, wild 0.0
Tomato, raw 0.01
Tomato, stewed in stainless steel 0.14
Apple, Macintosh 0.02
Pear 0.01
Plum 0.02
Cranberry jelly 0.0
Mean 0.02
-------
270
Table 8.2 (continued)
„ , , Chromium content
Food sample (ppm)
Grains and cereals
Corn, fresh on cob 0.02
Corn meal 0.05
Corn flakes 0.04
Corn oil margarine 0.37
Corn oil 0.47
Vegetable shortening 0.16
Rye, seed 0.05
Rye, whole 0.04
Flour, wheat (all purpose) 0.0
Wheat, whole 0.03
Flour, wheat (Japanese) 0.0
Wheat, whole (Japanese) 0.08
Rice (Japanese) 204 samples 0.04
Rice 0.05
Oatmeal, dry 0.06
Mean, excluding fats 0.04
Animal food
Dog food pellets 4.24
Rat diet, special 0.07-0.17
Source: Adapted from Schroeder, Balassa, and Tipton, 1962, Table
6, pp. 949-950. Reprinted by permission of the publisher.
8.4 BIOMAGNIFICATION IN FOOD CHAINS
Examination of the chromium content in organisms of higher trophic
levels in known food chains has not shown significant biomagnification.
Chromium is a relatively immobile element in biological systems, as ex-
emplified by the lack of gastrointestinal absorption of chromium(III) com-
pounds (Section 6.2.1.2) and by lack of translocation of chromium from the
site of absorption in plants (Section 4.2.3). This immobility may par-
tially explain the lack of biomagnification observed. Lack of biomagnifica-
tion could also occur because the chromium content of foods for a particular
trophic level is highly variable.
8.4.1 Terrestrial Food Chains
Little information was found on the chromium concentration in compo-
nents of terrestrial food chains. In a study of forest food chains, con-
centration data of selected components showed no large biomagnification.
However, according to Andren et al. (1973), such data "must be viewed cau-
tiously, since specific dietary constituents and food chain linkages were
-------
271
Table 8.3. Chromium content of selected seafoods and fruit juices
Food sample
Chromium
content
(ppm)
Reference
Salmon 0.47
Clam chowder 0.71-0.85
Tuna 0.13
Oyster 0.58
Sardine 0.35-0.37
Crab meat 0.57
Channel catfish, wild 0.12
Pacific halibut 0.18
Ocean perch 0.10
Spiny lobster 0.14
Alaskan shrimp 0.15
Atlantic scallops 0.05
Grape juice 0.08
Prune juice 0.15
Hawaiian Punch, pineapple, <0.01
apple, orange, grapefruit
juices
Tangerine juice <0.01
Lime juice 0.24
Lemon juice 0.05
Meranger and Somers, 1968
Meranger and Somers, 1968
Meranger and Somers, 1968
Meranger and Somers, 1968
Meranger and Somers, 1968
Meranger and Somers, 1968'
Zook et al., 1976
Zook et al., 1976
Zook et al., 1976
Zook et al., 1976
Zook et al., 1976
Zook et al., 1976
Meranger, 1970
Meranger, 1970
Meranger, 1970
Meranger, 1970
Meranger, 1970
Meranger, 1970
not determined." Table 8.5 gives the chromium concentration in selected
components of a typical forest ecosystem. Earthworms and cryptozoa con-
tained high chromium concentrations, but more data are necessary to deter-
mine if specific organisms feeding on earthworms or cryptozoa biomagnify
chromium.
8.4.2 Aquatic Food Chains
Aquatic ecosystems are easier to study than terrestrial ecosystems and
more information exists for them. In an experimental study of "an unnatural
and simple, but reproducible, food chain" under controlled environmental
conditions, Baptist and Lewis (1969) found that concentration levels of
slCr-labeled trivalent chromium declined through the food chain. The chain
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272
Table 8.4. Chromium content of selected food samples and biological value of extracts containing chromium
Chromium content
Sample
Meats and fish
Liver, calf's
Beef, round
Chicken, breast
Chicken, leg
Shrimp
Haddock
Lobster tail
Oysters
Grains , grain products
Wheat, grain
Wheat , germ
Wheat, bran and middlings
Wheat, flour
Bread, white
Bread, whole wheat
Bread , rye
Spaghetti
Cornflakes
Cornmeal , yellow
Cornmeal , white
Grits
Fruits
Bananas
Apple, peel
Apple, pared
Oranges
Strawberries
Blueberries
Vegetables
Carrots
Potatoes , old
Potatoes, new
Spinach
Miscellaneous
Mushrooms
Yeast , brewer ' s
Cheese, American
Beer
Vegetarian
Choplets
Chicken slices
Pepper
Black, table
Chili, fresh
Butter
Margarine
Milk, skimmed
Ginger ale
Sugar, cane
Egg white
Egg yolk
Total
solids
a>
30
34.
.2
.1
29.2
26
.2
15.2
19,
19,
.8
.9
12.2
88
94
91
.7
.6
.1
90.2
62
64
62
91
94
.2
.5
.7
.4
.3
91.2
91
90
27
18
14
14
8
22
11
Q
47
37
9
3
95
.1
.0
.3
.6
.4
.7
.5
.0
.6
.4
.0
.4
.7
.8
61.9
4
20
21
90
23
85
90
9
10
100
12
47
.6
.1
.5
.5
.4
.4
.9
.5
.5
.2
.8
Total
Wet wt
(ppm)
0.55
0.57
0.11
0.18
0.07
0.07
0.05
0.26
0.28
0.23
0.38
0.23
0.26
0.42
0.30
0.15
0.14
0.10
0.12
0.05
0.10
0.27
0.01
0.05
0.03
0.05
0.09
0. 04
0.27
0.21
0.10
0.04
1.12
0.56
0.03
0.10
0.07
0.35
0.30
0.13
0.18
0.01
<0.01
0.08
1.83
Dry wt
Cppm)
1.77
1.67
0.37
0.70
0.48
0.34
0.23
2.16
0.32
0.24
0.42
0.25
0.42
0.66
0.49
0.16
0.15
0.11
0.13
0.06
0.38
1.48
0.09
0.31
0.34
0.22
0.78
0.55
0.57
1.03
1.27
1.17
0.92
0.61
0.48
0.32
0.38
1.28
0.15
0.20
0.13
0.05
0.02
0.65
3.84
Chromium
removed with
50% ethanol
m
33.6
1817
24.6
21.9
69.4
51.5
93.6
30.2
37.8
85.0
15.8
14.3
42.9
32.8
29.7
75.0
80.0
74.8
47.0
90.0
99.5
52.5
40.0
80.7
26.5
100
48.0
53.6
86.6
48.2
30.4
100
24.6
87.8
100
22.5
80.0
50.0
84.4
36.0
50.4
Biological
Acid hydrolysate
Biological
value
2
2
2
1
0
1
2
1
2
1
2
1
2
2
1,
2.
1.
3.
1.
2.
2.
2
2.
1.
2,
1.
1.
1,
1.
I
3,
1.
3.
1.
1.
2.
2,
1.
1
1.
2.
1
1.
.95
.60
.42
.99
.91
.24
.06
.95
.29
.82
.08
.86
.98
.26
.70
.34
.60
.18
.80
.19
.02
.65
.30
.95
,96
,92
, 33
,75
.72
91
.88
.34
.39
,60
.18
.15
,35
,81
,32
.35
.00
.74
.20
.59
Chromium
(ppm)
0.220
0.220
0.086
0.146
0.059
0.053
0.007
0.089
0.022
0.024
0.030
0.018
0.077
0.023
0.027
0.006
0.014
0.021
0.024
0.011
0.056
0.258
0.064
0.029
0.060
0.101
0 . 192
0.076
0.077
0.200
0.169
0.070
0.034
0.083
0.077
0.055
0.076
0.120
0.030
0.070
0.030
0.023
0.088
0.065
activity"
50% Ethanol extract
Biological
value
1
1
2
.88
.65
.19
2.41
3
2
5
1
2
1
1
1
1
1
2
1,
1,
2.
1.
2.
0.
1,
3.
4,
1,
1,
3.
2,
1,
1,
1.
1
1
1
0
.46
.26
.09
.56
.08
.55
.58
.40
.47
.25
.15
.38
.09
.02
.44
,43
.99
.04
.19
.06
.40
.66
,72
,86
.99
.82
.20
.28
.90
.08
.96
Chromium
(ppm)
0.077
0.044
0.054
0.080
0.101
0.052
0.065
0.013
0.042
0.020
0.003
0.002
0.008
0.005
0.039
0.012
0.011
0.040
0.028
0.027
0.057
0.064
0.147
0.007
0.024
0.063
0.047
0.090
0.076
0.068
0.010
0.008
0.032
0.048
0.025
See Section 6.4.2 for discussion of biological activity.
Source: Adapted from Toepfer et al., 1973, Table 1, p. 71. Reprinted by permission of the publisher.
consisted of the alga Chlamydomonas sp. (first trophic level), brine shrimp
Avtem-la sal-ina (second trophic level), post-larval croaker (Mi,CTopogon
undulatus) or post-larval mojarra (Eucinostorms sp.) (third trophic level),
and the mummichog (Fundulus heteroclitus') (fourth trophic level) . Measur-
able uptake of 51Cr from water was observed for all trophic levels; however,
for Artemia and the mummichog, uptake through food was much greater, whereas
post-larval fish accumulated slightly more 51Cr from water than from food.
Mathis and Cummings (1973) also found decreased chromium concentrations
in higher trophic level organisms of aquatic ecosystems (about 10 ppm in
worms, about 5 ppm in clams, about 1.2 ppm in omnivorous fish, and about
1 ppm in carnivorous fish).
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273
Table 8.5. Chromium concentration in
selected trophic levels of a forest
ecosystem in East Tennessee
Ecosystem
component
Substrate
Soil
Litter
Producers
Tree leaf
Tree branch
Tree root
Acorn
Consumers
Insect
Squirrel
Sparrow
Mouse
Predators
Hawk
Owl
Omnivores
Crow
Oppossum
Fox
Cryptozoa
Earthworm
Source: Adapted
1973.
Chromium
concentration
(ppm dry wt)
7
2
4
0.3
9
0.1
3
0.8
1
1
1
0.2
1
0.6
0.8
10
5
from Andren et al..
In the Tamar River, Tasmania, chromium concentrations in the Pacific
oyster CrassostTea gigas (average 7.9 ppm chromium, dry wt basis) were
poorly correlated with concentrations of chromium in the mud (average 87.8
ppm chromium, dry wt basis) (Ayling, 1974). According to Ayling, "accumula-
tion factors describing the ability of oysters to concentrate heavy metals,
based upon their ability to extract metals dissolved in water, appear mean-
ingless, where there are high concentrations of metals in muds." Since the
contribution to total chromium intake of chromium dissolved in water, of
chromium in particulates filtered from water, and of chromium in ingested
muds is unknown, an accumulation factor is difficult to determine. The
author pointed out that microorganisms within the muds may have concentrated
heavy metals by adsorption and thus made them more available to the oyster.
No data were found to either support or refute this contention.
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274
Concentration of heavy metals in fecal material in water may allow for
biomagnification in certain food chains. Boothe and Knauer (1972) studied
the concentration of a number of metals, including chromium, in the feces
of the crab Pugettia produeta, which feeds on the brown alga Macrocystis
pyrifera. While the concentration ratios (concentration in feces to con-
centration in the alga) were >2 for cobalt, arsenic, zinc, copper, lead,
and iron, the ratio for chromium was 0.8, which indicated no concentration
of that element in the fecal pellet.
Davis, cited in Foster (1963), showed that lower trophic levels in the
Columbia River ecosystem (algae, sponges, insect larvae, and snails) have
higher concentrations of 51Cr than do higher trophic levels (fish and cray-
fish). Levels of 51Cr in the organisms of various trophic levels were ob-
served to be higher in winter than in summer (Watson et al., 1971)- The
51Cr is released into the river from the cooling waters used in the Hanford
reactors. Sodium dichromate is added to the reactor water as a corrosion
inhibitor and becomes radioactive due to neutron bombardment. This slCr
can also enter terrestrial ecosystems through sorption by crops grown on
lands irrigated with Columbia River water (Perkins et al., 1960). Concen-
trations of about 1 yyCi/g of 51Cr were found in several crops; however,
milk and meat of cattle did not contain measurable amounts. No 51Cr activ-
ity could be detected in humans who lived in the area and consumed these foods.
Lack of assimilation of chromium present in foods is probably the major
reason organisms of the higher trophic levels contain lesser amounts of chro-
mium. In fact, the poor absorption of chromium by many animals makes 51Cr-
labeled trivalent chromium a valuable tracer when used in conjunction with
lilC for measuring assimilation efficiencies (Calow and Fletcher, 1972).
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275
SECTION 8
REFERENCES
1. Andren, A. W., J.A.C. Fortescue, G. S. Henderson, D. E. Reichle,
and R. I. Van Hook. 1973. Environmental Monitoring of Toxic Materials
in Ecosystems. In: Ecology and Analysis of Trace Contaminants.
ORNL-NSF-EATC-1, Progress Report, June 1972-January 1973. Oak Ridge
National Laboratory, Oak Ridge, Tenn. pp. 61-119.
2. Ayling, G. M. 1974. Uptake of Cadmium, Zinc, Copper, Lead, and
Chromium in the Pacific Oyster, Crassostrea gigas, Grown in the Tamar
River, Tasmania. Water Res. (England) 8:729-738.
3. Baptist, J. P., and C. W. Lewis. 1969. Transfer of Zn-65 and Cr-51
Through an Estuarine Food Chain. In: Symposium on Radioecology,
D. J. Nelson and F. C. Evans, eds. University of Michigan, Ann Arbor,
Mich. pp. 420-430.
4. Boothe, P. N., and G. A. Knauer. 1972. The Possible Importance of
Fecal Material in the Biological Amplification of Trace and Heavy
Metals. Limnol. Oceanogr. 17(2):270-274.
5. Calow, P., and C. R. Fletcher. 1972. A New Radiotracer Technique
Involving C-14 and Cr-51 for Estimating the Assimilation Efficiencies
of Aquatic, Primary Consumers. Oecologia (Berlin) 9:155-170.
6. Foster, R. F. 1963. Environmental Behavior of Chromium and Neptunium.
In: Radioecology, V. Schultz and A. W. Klement, Jr., eds. Reinhold
Publishing Corporation, New York. pp. 569-576.
7. Friberg, L., M. Piscator, G. F. Nordberg, and T. Kjellstrom. 1974.
Cadmium in the Environment. CRC Press, Inc., Cleveland, Ohio.
pp. 19-20.
8. Mathis, B. J., and T. F. Cummings. 1973. Selected Metals in Sediments,
Water, and Biota in the Illinois River. J. Water Pollut. Control Fed.
45:1573-1583.
9. Meranger, J. C. 1970. The Heavy Metal Content of Fruit Juices and
Carbonated Beverages by Atomic Absorption Spectrophotometry. Bull.
Environ. Contam. Toxicol. 5:271-275.
10. Meranger, J. C., and E. Somers. 1968. Determination of the Heavy Metal
Content of Sea-Foods by Atomic Absorption Spectrophotometry. Bull.
Environ. Contam. Toxicol. 3:360-365.
11. Murphy, E. W., L. Page, and B. K. Watt. 1971. Trace Minerals in
Type A School Lunches. J. Am. Diet. Assoc. 58:115-122.
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276
12. Murthy, G. K., U. Rhea, and J. T. Peeler. 1971. Levels of Antimony,
Cadmium, Chromium, Cobalt, Manganese, and Zinc in Institutional Total
Diets. Environ. Sci. Technol. 5:436-442.
13. Perkins, R. W., J. M. Nielsen, W. C. Roesch, and R. C. McCall. 1960.
Zinc-65 and Chromium-51 in Foods and People. Science 132:1895-1897.
14. Schroeder, H. A., J. J. Balassa, and I. H. Tipton. 1962. Abnormal
Trace Metals in Man — Chromium. J. Chronic Dis. 15:941-964.
15. Thomas, B., J. A. Roughan, and E. D. Watters. 1974. Cobalt, Chromium,
and Nickel Content of Some Vegetable Foodstuffs. J. Sci. Food Agric.
(England) 25:771-776.
16. Toepfer, E. W., W. Mertz, E. E. Roginski, and M. M. Polansky. 1973.
Chromium in Foods in Relation to Biological Activity. J. Agric. Food
Chem. 21:69-73.
17. Watson, D. G., C. E. Gushing, C. C. Coutant, and W. L. Templeton. 1971.
Cycling of Radionuclides in Columbia River Biota. In: Trace Substances
in Environmental Health — IV, D. D. Hemphill, ed. University of Missouri
Columbia, Mo. pp. 144-157.
18. Zook, E. G., J. J. Powell, B. M. Hackley, J. A. Emerson, J. R.
Brooker, and G. M. Knobl. 1976. National Marine Fisheries Ser-
vice Preliminary Survey of Selected Seafoods for Mercury, Lead,
Cadmium, Chromium, and Arsenic Content. J. Agric. Food Chem. 24:47-53.
-------
SECTION 9
ENVIRONMENTAL ASSESSMENT
James 0. Pierce
University of Missouri
Columbia, Missouri
9.1 SUMMARY
In attempting to arrive at a satisfactory estimate of the ecological
distribution of chromium and its present fate and effect on man's environ-
ment, a number of factors must be carefully considered. Paramount among
these is the past and present state of the art in relation to the analyti-
cal methods employed for the analysis of chromium. In order to scientific-
ally and objectively determine environmental pathways, concentration factors
and biomagnification, and human health related factors, the basic data base
must be as accurate as possible. Unfortunately, the analytical methods used
in the past years for all of the studies involving chromium, especially in
many environmental media and plant and animal tissue, leave much doubt as to
the accuracy and validity of the data base. Even today the results from
many laboratories are questionable. This point cannot be over stressed,
since inaccurate and even erroneous conclusions can be drawn using such data,
especially older literature data. For example, only recentlyhaschromium
been accepted as an essential element for man and''itsrojLe_in^the' mainten-
arfC5~"bf the glucos^jtoTerlin^ An interesting comment
is -trtiSt nutiri^^ynists have greater concern for marginal deficiency of chro-
mium in humans than to overexposure. The basic reasoif behind the relative
lateness of this discovery~was the lack of a sensitive analytical method
for the measurement of chromium at low levels. However, the data base is
rapidly improving with the development and adoption of new analytical pro-
cedures in more laboratories. Enough data do exist to be able to determine,
on a semiquantitative basis, that chromium as far as thp t-.ni-.al prmJjaammenJ-
anji the general population are concerned, does not^re^res^ent an^enyiron-
mental haza^3T~™HoweverT'''iir the bccupatTonaTsettine. exposure to chromium,
especially in its hexavalent form, does represent a potential health hazard
and worker exposure should be limited.
The National Institute of Occupational Safety and Health recommends
two standards for hexavalent chromium designed to protect the health and
safety of workers up to a 10-hr workday, 40-hr workweek, over a working
lifetime. One standard addresses occupational exposure to a group of non-
carcinogenic, but otherwise hazardous, materials. The other pertains to
those instances where there is exposure to chromium(VI) materials associ-
ated with an increased incidence of lung cancer.
The problem is that there is no practical way, on the basis of chemi-
cal analysis of airborne chromium(VI), to distinguish between noncarcino-
genic and carcinogenic chromium materials. Thus for all practical purposes,
all airborne chromium(VI) shall be considered to be carcinogenic. The
current NIOSH recommended standard for carcinogenic chromium(VI) is 1 ug
277
-------
278
chromium(VI)/m3 of air. On the basis of current information, this rec-
ommended standard appears to be reasonable and obtainable in the workplace
and is thought to be adequate to protect the health of workers.
In summary, at present and with the available data, chromium does not.
except in the occupational setting, appear to be present in the general
environment in significant enough concentrations to cause concern. Path-
ways have yet to be determined for the ecological cycling and fate of chro-
mium and considerable research in these areas needs to be done. The major
area of needed research is the development of sensitive .analytical_te^h-
niques capable or distinguishing between the various valence states and
species of chromium. This is a critical need due to the vastf differences
in the potential toxicity of chromium, especially the differences between
chromium(III) and chromium(VTN
9.2 QUANTITY OF CHROMIUM ENTERING VARIOUS ENVIRONMENTAL MEDIA
No chromium ore is currently mined in the United States. Chromite
imports were estimated at 1,800,000 metric tons in 1972. United States
chromium consumption for the same year was 320,000 metric tons (Morning,
1974) of chromium, which corresponds to about 1,000,000 metric tons of ore.
The difference between the import and consumption figures represents re-
export of chromium in the form of manufactured products, increases in
stockpile storage, and uncertainties in the consumption estimates. For
example, Brantley (1970) estimated 1968 consumption at 458,000 metric tons
of chromium, the GCA corporation (1973) gave the 1970 demand as 389,000
metric tons, and the above estimate of 320,000 was for 1972. The figures
show almost a 50% reduction in consumption over a four-year-period which is
obviously not an accurate assessment of the trend. Chromium consumption is
increasing and is expected to continue to increase at least until the year
2000.
Industrial uses of chromium are about 64% in metallurgy, 20% in the
manufacture of refractories, and 16% in the chemistry industry. The pri-
mary chromium chemicals are sodium chromate and sodium dichromate. These
are converted as needed for many uses, including chrome plating, as an
oxidant in many synthetic processes, in leather tanning, as a component of
many pigments, in fungicides and wood preservatives, and as rust and corro-
sion inhibitors.
Chromium emissions into the atmosphere are estimated to be between
11,000 and 16,000 tons/year in the United States. Ferrochromium production
is the major source (about 68%) with ore refining, chemical processing, and
refractory processing all making major contributions. Sources of atmos-
pheric chromium not directly related to industrial uses of the metal include
coal and oil combustion, cement production incineration, and asbestos pro-
duction. Coal combustion is by far the largest contributor from these
"inadvertent" sources and was estimated to contribute 1420 metric tons in
1970. Coals contain a wide range of chromium concentration: Illinois coals
contain from 4 to 54 ppm with an average of 14 ppm; a Belgian study reported
12 to 55 ppm in coals; and the Allen Steam Plant, burning coal containing
21 ppm chromium, produced slag containing 180 ppm and precipitated fly ash
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279
with 356 ppm. Chromium used for corrosion inhibition contributed to the
atmospheric contamination around cooling towers, but the total amount is not
very large and the effect quite local.
Geographic distribution of atmospheric chromium closely parallels
areas of high population and industrial activity. Four of the EPA regions,
the Great Lakes and three East Coast regions, received over 80% of the
total emissions. Nonindustrial regions received very little.
The primary source of soil contamination is fallout and washout from
the atmosphere. Some soil chromium is added with fertilizers reported to
contain 175 ppm to 344 ppm. Sewage sludge can contribute significant
amounts of chromium when used as a fertilizer. Natural levels of chromium
in soils is reasonably high and quite variable, with 64% in the range 25
ppm to 85 ppm total chromium. Serpentine soils may contain several per-
cent chromium. Except for local situations, anthropogenic activity does
not appear to have altered soil chromium levels. Most soil chromium,
whether natural or added, is quite insoluble and not readily available to
plants.
The plating and finishing industries are a major source of chromium in \f
industrial waters. They accounted for 43% of the chromium input in New York,
sewage. Residential runoff accounted for 21% of the influent, possibly due
to atmospheric chromium that had settled. The overall loss of chromium
from the plating process is about 20,000 metric tons/year and only about 30|
is recycled. Discharges from the tanning and textile industries also con-
tribute chromium to waters.
The total amount of chromium transported by rivers is surprisingly
large; for example, 790 metric tons/year by the Susquehanna River. However,
most of it is in the rather insoluble trivalent form and closely associated
with sediments. When sediments are deposited, the chromium is not readily
mobilized. It remains effectively adsorbed and/or precipitated and is un-
available to biological systems.
9.3 JUDGMENT OF POTENTIAL TOXICITY
The toxicity of chromium is almost exclusively a problem of industrial
activity and in most cases the effects are relatively local. The metal is
quite toxic to fish and many other aquatic organisms, especially in its
hexavalent form which can persist in waters low in organic matter. Aquatic
organisms vary widely in their sensitivity to the element. The lethal level
for some invertebrates is 0.05 ppm while tests on other organisms, includ-
ing fish, indicate that several tens of ppm can be tolerated. Maximum per-
missible concentrations must be set, of course, based on the more sensitive
organisms.
In the presence of organic matter, hexavalent chromium is reduced to
the less toxic and relatively insoluble trivalent form in natural waters.
The trivalent chromium precipitates with, or is adsorbed on, sediments where
it is much less active biologically.
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280
Evidence of toxicity to plants in practical environmental situations
includes reduced growth of tobacco exposed to cooling tower drift (Section
4.3.2). A 75% reduction of leaf area occurred at 15m and 200m from the
tower. Some evidence indicates that high chromium levels contribute to the
low fertility of serpentine soils, but other factors such as low calcium
content and low calcium to magnesium ratio are probably more serious. Wastes
from chromium smelting can be highly toxic to plants (Section 4.3.1). In one
example, as little as 1% of the waste in sand completely inhibited germina-
tion. The affected area had to be covered with 25 cm to 30 cm of soil for
successful revegetation.
9.4 TOXICITY AND HUMAN HEALTH EFFECTS
The available information on the toxic effects of chromium compounds
on humans comes almost entirely from known occupational exposures to hexa-
valent chromium. Reports in the literature date back as far as 1827.
Chromium as a metal is essentially biologically inert and has not pro-
duced any known toxic or other harmful effects in either man or laboratory
animals. Trivalent compounds of chromium have no established toxicity.
They are poorly absorbed when ingested orally and do not give rise to local
or systemic effects; exposure by inhalation has not demonstrated any measur-
able biological effect. The trivalent compounds do react with the skin by
combining with proteins in the superficial layers, but they do not cause
ulceration. There are no known effects of trivalent chromium on animals or
humans exposed to normal levels of chromium generally found in uncontaminated
environmental media. The primary reason for the nontoxic nature of the tri-
valent compounds of chromium is their extr_ejne__im3olub. ility. As~~3±sCU!fsyd in
Section 6.3, feeding of trivalent chromium to experimental animals at levels
of even hundreds of milligrams daily failed to produce toxic symptoms. In
fact, other studies have found only beneficial effects of feeding small
amounts of trivalent chromium in lifetime studies with rats and mice. It
can be generally concluded, therefore, that chromium in its trivalent form
does not represent a potentially harmful chemical in man's environment.
Hexavalent chromium compounds, on the other hand, do represent potenti-
ally hazardous chemicals in the environment and exposure must be controlled,
especially in the occupational environment. These compounds when ingested,
inhaled, or absorbed are toxic even to the point of being carcinogenic. The
toxic nature of hexavalent chromium is discussed in detail in Section 6 of
this report.
There are presently three standards recommended by NIOSH for the
control of worker exposure to various forms of chromium. These standards
have been recommended after careful review of existing data and represent
the best opinion on safe levels of airborne chromium. They are considered
adequate to protect the health and safety of workers.
The first of these recommended standards pertains to chromic acid, de-
fined as chromium trioxide [chromium(VI) oxide or chromic acid anhydride]
and aqueous solutions. The NIOSH criteria document for chromic acid contains
the following recommendations: Occupational exposure to chromic acid shall
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281
be controlled so that no worker is exposed either to (1) a concentration of
chromic acid greater than 0.05 mg as chromium trioxide/m3 of air determined
as a time-weighted average exposure for an 8-hr workday, 40-hr workweek, or
(2) a ceiling concentration in excess of 0.1 mg as chromium trioxide/m3 of
air as determined by a sampling time of 15 min.
The other two NIOSH recommended standards pertain to hexavalent chro-
mium, defined as the chromium in all materials in the +6 (hexavalent)
state. One standard addresses occupational exposure to a group of noncar-
cinogenic, but otherwise hazardous materials, while the other pertains to
occupations and workplaces where there is exposure to other chromium(VI)
materials associated with an increased incidence of lung cancer.
On the basis of the chemical analysis of airborne chromium(VI) mate-
rials, there is no practical means of distinguishing between these two
groups of chromium(VI) materials. Until the airborne chromium(VI) in a
particular workplace is demonstrated by the employer to be of the type con-
sidered noncarcinogenic, all airborne chromium(VI) shall be considered to
comprise carcinogenic materials.
According to the NIOSH criteria document for chromium(VI), noncarcino-
genic chromium(VI) is the chromium(VI) in monochromates and bichromates of
hydrogen, lithium, sodium, potassium, rubidium, cesium, and ammonium, and
chromium(VI) oxide. Carcinogenic chromium(VI) comprises any and all chro-
mium (VI) materials not included in the above noncarcinogenic group.
The recommended standard is as follows:
(1) Carcinogenic chromium(VI) shall be controlled in the workplace so
that the airborne workplace concentration of chromium(VI), sampled and ana-
lyzed according to recommended procedures, is not greater than 1 yg chro-
mium (VI) /m3 of breathing zone air.
(2) Noncarcinogenic chromium(VI) shall be controlled in the workplace
so that the airborne workplace concentration is not greater than 25 yg
chromium(VI)/m3 of breathing zone air determined as a time-weighted average
(TWA) exposure for up to a 10-hr workday, 40-hr workweek, and is not
greater than 50 yg chromium(VI)/m3 of breathing zone air as determined by
any 15-min sample.
The present levels of hexavalent chromium found in the general environ-
ment do not appear to pose a human health problem; however, continuous
monitoring and further epidemiological research is needed, especially in
relation to levels of hexavalent chromium in public water supplies.
Present environmental levels of chromium in urban ambient air (0.01 to
0.03 yg/m3; in soils (traces to 250 ppm); in seawater (below 0.1 ppb); in
river water (1 to 10 ppb); in municipal drinking water (nondetectable —
35 ppb); and in foods (0.02 to 0.22 yg/g) are not of sufficiently high
concentration to cause concern. The total chromium intake per day in man,
estimated as between 5 to 115 yg in food and water and 0.04 to 0.08 yg in
air, has not demonstrated any measurable toxic effect even at the subclinical
level. If chromium is a problem it is probably because many U.S. diets are
regarded as at least marginally deficient in chromium.
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282
It is evident from the available data that chromium does not, currently,
appear to represent a significant hazard in the general environment. Occupa-
tional exposures do represent potential and real problems and need to be
controlled.
However, as recommended by the National Academy of Sciences report on
chromium, because some chromium compounds have caused serious health prob-
lems in persons through industrial exposure and because the hexavalent com-
pounds are irritating and corrosive to tissue, the role of chromium in the
environment requires careful consideration and much future research needs
to be developed.
9.5 PERSISTENCE IN THE ENVIRONMENT
Chromium is an element and is therefore not going to decompose into
harmless substances as many organic pollutants do. In that sense, it might
be regarded as infinitely persistant. In most natural systems, chromium(III)
is the most stable form of the element. In the presence of organic matter,
chromium(VI) is reduced, probably aided by complexation of the resultant
chromium(III). Chromium(III) is characterized by limited solubility near
neutral pH due to formation of hydrated oxides, and by a strong tendency to
sorb onto clays, sediments, and organic matter.
Atmospheric chromium falls out or is washed out into soils or water.
In aqueous systems the trivalent form of the element either precipitates or
is adsorbed onto particulate matter or organic matter. In either case, it
is rather quickly removed and is found in sediments. The hexavalent form
is stable only in waters with little organic matter. In all other cases,
it is reduced and later precipitated. In soil, hexavalent chromium is re-
duced to trivalent form and is then tightly bound to clay particles. It is
not readily leached except at low pH. Uptake by most plants is poor and
there is very little translocation to the above ground parts.
Few experiments on specific environmental sinks have been reported,
probably because the sinks, primarily soil and sediments, are fairly pre-
dictable from known chemistry of the element. In some cases the element
may bind to organic matter temporarily, but the binding is transferred to
soil or sediment particles as the organic matter decomposes. There is
little evidence that chromium(III) is likely to be oxidized to the more
soluble and toxic hexavalent state under environmental conditions.
9.6 CRITICAL ENVIRONMENTAL PATHWAYS
Conditions under which harmful levels of chromium are likely to persist
in the environment include the following:
a. Chromium(VI) is stable in water which is low in organic matter.
The chromates remain in solution and are quite toxic to certain aquatic
organisms, especially invertebrates.
b. An accepted method for removing chromium from wastestreams is re-
duction followed by precipitation of chromium(III) hydroxide. The precipi-
tate is often disposed of in land fills. There appears to be little
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283
leaching from the fills under normal conditions, but acid leach water could
be expected to solubilize and transport the chromium.
c. Chromates are used as corrosion inhibitors in cooling-tower water
and are subsequently deposited on the surrounding area as the mists drift
from the tower. The surrounding land and any vegetation growing on it are
contaminated by the airborne hexavalent chromium. Elevated chromium levels
in plants have been reported up to 1200m from a tower. It is not known how
much was deposited directly on the plants and how much was due to uptake
from the soil. Chromium deposited on plants apparently remains in the hexa-
valent form and most of it can be washed off by rain. In the soil the
chromium(VI) is reduced and bound as discussed earlier. No reports detail-
ing harmful effects due to cooling tower drift were found.
d. Sewage sludge is often put on soil and some sludges are quite high
in chromium. The element remains tightly bound to the sludge and/or soil
and is neither readily leached nor taken up by plants. However, some reports
indicate increased chromium levels in plants grown on sludge amended soil.
Again, no reports of harmful effects to the vegetation or to animals that
consumed it were found.
e. Large amounts of chromium are transported by major rivers, nearly
all of which are associated with particulates, and most probably results
from natural weathering.
f. Large amounts of chromium are released to the atmosphere from the
ferro-chromium and other industries as well as from fossil fuel combustion.
There is no evidence that these releases constitute a health hazard.
9.7 BIOMAGNIFICATION
No evidence exists for the biomagnification of chromium in food chains.
Animals in the higher trophic levels tend to have lower tissue chromium
concentrations than their prey. If the hexavalent state is ingested by man
or animals it is probably reduced in the stomach. Trivalent inorganic chro-
mium is inefficiently absorbed in the digestive tract of animals, while
chromium in certain organically bound forms is readily absorbed by the mam-
malian digestive system. The most significant of these forms is the glucose
tolerance factor. Organically bound chromium is also readily transferred
across the placenta to the fetus in contrast to very poor transfer of the
inorganic form. These facts are of profound significance in nutritional
aspects of the essential trace element chromium, but probably have little
bearing on chromium as an environmental contaminant.
9.8 SUMMARY OPINION AND RESEARCH NEEDS
At the present time, using data available from industrial and epidemio-
logical studies, chromium does not appear to represent an environmental
hazard to the general population. Occupational exposures require that levels
be controlled to the point that the health and safety of the worker is not
affected. Trivalent chromium in either case does not appear to represent a
potential hazard.
Future research is required with a view to not only potential over-
exposure, but also regarding deficiency. Almost no data exist concerning
the ecologic cycling of chromium in the environment. Data on the chemical
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284
valence of chromium in the ecosystem and the environment are not available.
Analytical techniques do not exist for species identification and accurate
determination of the chemical form of chromium in complex media, especially
in biological tissue. These questions can only be answered by properly de-
signed and executed research.
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285
SECTION 9
REFERENCES
1. Brantley, F. E. 1970. Chromium. In: Mineral Facts and Problems.
U.S. Department of the Interior, Washington, D.C. pp. 247-262.
2. GCA Corporation. 1973. National Emissions Inventory of Sources and
Emissions of Chromium. EPA-450/3-74-012, U.S. Environmental Protect-
ion Agency, Research Triangle Park, N.C. 33 pp.
3. Morning, J. L. 1974. Chromium. In: Minerals Yearbook 1972, Vol. I.
Bureau of Mines, Washington, D.C. pp. 289-299.
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28?
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Reviews of the Environmental Effects of Pollutants:
III. Chromium
5. REPORT DATE
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Leigh E. Towill, Carole R. Shriner, John S. Drury,
Anna S. Hammons. and James W. Holleman
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Information Center Complex/Information Division
Oak Ridge National Laboratory
Oak Ridge, Tennessee 37830
10. PROGRAM ELEMENT NO.
1HA616
11. CONTRACT/GRANT NO.
IAG D5-0403
12. SPONSORING AGENCY NAME AND ADDRESS
Health Effects Research Laboratory, Cin-OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45219
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
EPA/600/10
15. SUPPLEMENTARY NOTES
16. ABSTRACT
This report is a review of the scientific literature on the biological and
environmental effects of chromium. Included in the review are a general summary
and a comprehensive discussion of the following topics as related to chromium and
specific chromium compounds: physical and chemical properties; occurrence;
synthesis and use; analytical methodology; biological aspects in microorganisms,
plants, wild and domestic animals, and humans; distribution mobility and persist-
ence in the environment; assessment of present and potential health and environ-
mental hazards; and review of standards and governmental regulations. More than
500 references are cited.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
COSATI Field/Group
*Pollutants
Toxicology
Chromium
Health Effects
06F
06T
8. DISTRIBUTION STATEMENT
Release to public
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
288
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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