United States
environmental Protection
Agency
Office of Water
Regulations and Standards
Criteria and Standards Division
Washington DC 20460
EPA 440/5-30-021
Octooer 1980
vvEPA
Ambient
Water Quality
Criteria for
Arsenic
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AMBIENT WATER QUALITY CRITERIA FOR
ARSENIC
Prepared By
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Water Regulations and Standards
Criteria and Standards Division
Washington, O.C.
Office of Research and Development
Environmental Criteria and Assessment Office
Cincinnati, Ohio
Carcinogen Assessment Group
Washington, D.C.
Environmental Research Laboratories
Corvalis, Oregon
Duluth, Minnesota
Gulf Breeze, Florida
Narragansett, Rhode Island
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DISCLAIMER
This report has been reviewed by the Environmental Criteria and
Assessment Office, U.S. Environmental Protection Agency, and approved
for publication. Mention of trade names or commercial products does not
constitute endorsement or recommendation for use.
AVAILABILITY NOTICE
This document is available to the public through the Nationa'
Technical Information Service, (NTIS), Springfield, Virginia 22161.
11
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FOREWORD
Section 304 (a)(l) of the Clean Water Act of 1977 (P.L. 95-217),
requires the Administrator of the Environmental Protection Agency to
publish criteria for water quality accurately reflecting the latest
scientific knowledge on the kind and extent of all identifiable effects
on health and welfare which may be expected from the presence of
pollutants in any body of water, including ground water. Proposed water
quality criteria for the 65 toxic pollutants listed under section 307
(a)(l) of the Clean Water Act were developed and a notice of their
availability was published for public comment on March 15, 1979 (44 FR
15926), July 25, 1979 (44 FR 43660), and October 1, 1979 (44 FR 56628).
This document is a revision of those proposed criteria based upon a
consideration of comments received from other Federal Agencies, State
agencies, special interest groups, and individual scientists. The
criteria contained in this document replace any previously published EPA
criteria for the 65 pollutants. This criterion document is also
published in satisifaction of paragraph 11 of the Settlement Agreement
in Natural Resources Defense Council, et. a], vs. Train, 8 ERC 2120
(D.O.C. 1976), modified, 12 ERC 1833 (O.O.C. 1979).
The term "water quality criteria" is used in two sections of the
Clean Water Act, section 304 (a)(l) and section 303 (c)(2). The term has
a different program impact in each section. In section 304, the term
represents a non-regulatory, scientific assessment of ecological ef-
fects. The criteria presented in this publication are such scientific
assessments. Such water quality criteria associated with specific
stream uses when adopted as State water quality standards under section
303 become enforceable maximum acceptable levels of a pollutant in
ambient waters. The water quality criteria adopted in the State water
quality standards could have the same numerical limits as the criteria
developed under section 304. However, in many situations States may want
to adjust water quality criteria developed under section 304 to reflect
local environmental conditions and human exposure patterns before
incorporation into water quality standards. It is not until their
adoption as part of the State water quality standards that the criteria
become regulatory.
Guidelines to assist the States in the modification of criteria
presented in this document, in the development of water quality
standards, and in other water-related programs of this Agency, are being
developed by EPA.
STEVEN SCHATZOW
Deputy Assistant Administrator
Office of Water Regulations and Standards
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ACKNOWLEDGEMENTS
Aquatic Life Toxicology
Charles E. Steohan, ERL-Ouluth
U.S. environmental Protection Agency
John H. Gentile ERL-Narragansett
U.S. Environmental Protection Agency
Mammalian Toxicology and Human Health Effects
Dan Greathouse (author)
U.S. Environmental Protection Agency
Oebdas Mukerjee (doc. mgr.), ECAO-Cin
U.S. Environmental Protection Agency
Jerry F. Stara (doc. mgr.), ECAO-Cin
U.S. Environmental Protection Agency
Jeff Gaba, OGC
U.S. Environmental Protection Agency
Paul Hammond
University of Cincinnati
Steven 0. Lutkenhoff
U.S. Environmental Protection Agency
Robert McGaughy, CAG
U.S. Environmental Protection Agency
Ed Wool son
U.S. Department of Agriculture
Roy E. Albert*
Carcinogen Assessment Group
U.S. Environmental Protection Agency
Thomas Clarkson
University of Rochester
Patrick Durkin
Syracuse Research Corporation
Lester Grant, ECAO-RTP
U.S. Environmental Protection Agency
Terri Laird, ECAO-Cin
U.S. Environmental Protection Agency
Bill Marcus, OOW
U.S. Environmental Protection Agency
Harry Ska!sky
Reynolds Metal Company
Technical Support Services Staff: D.J. Reisman, M.A. Garlough, B.L. Zwayer,
P.A. Daunt, K.S. Edwards, T.A. Scandura, A.T. Pressley, C.A. Cooper,
M.M. Denessen.
Clerical Staff: C.A. Haynes, S.J. Faehr, L.A. Wade. D. Jones, 3.J. Bordicks,
B.J. Quesnell. P. Gray, B. Gardiner.
*CAG Participating Members:
Elizabeth L. Anderson, Larry Anderson, Dolph Arnicar, Steven Bayard,
David L. Bayliss, Chao w. Chen, John R. Fowle III, Bernard Haberman,
Charalingayya Hiremath, Chang S. Lao, Robert McGaughy, Jeffrey Rosen-
blatt, Oharm V. Singh, and Todd W. Thorslund.
w
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TABLE OF CONTENTS
Page
Criteria Summary
Introduction A-l
Aquatic Life Toxicology 8-1
Introduction B-l
Effects 8-4
Acute Toxicity B-4
Chronic Toxicity B-6
Plant Effects B-7
Residues B-7
Miscellaneous B-8
Summary B-10
Criteria B-12
References B-26
Mammalian Toxicology and Human Health Effects C-l
Exposure C-l
Ingestion from Water C-l
Ingestion from Food C-2
Inhalation C-10
Dermal C-12
Pharmacokinetics C-12
Absorption C-13
Distribution C-20
Metabolism C-24
Excretion C-33
Effects C-36
Acute, Subacute, and Chronic Toxicity C-36
Subacute and Chronic Toxicity C-47
Synergism and/or Antagonism C-70
Teratogenicity C-73
Mutagenicity C-75
Carcinogenicity C-78
Criterion Formulation C-l10
Existing Guidelines and Standards C-110
Current Levels of Exposure C-110
Special Groups at Risk C-112
Basis and Derivation of Criterion C-112
References C-117
Appendix C-156
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CRITERIA DOCUMENT
ARSENIC
Aquatic Life
^reshwatef aauatic life the concentration of total recoverable
valent inorganic arsenic should not exceed 440 ug/1 at any time. Short-term
effects on embryos and larvae of aquatic vertebrate species have been shown
to occur at concentrations as low as 40 ug/1.
The available data for total recoverable trivalent inorganic arsenic in-
dicate that acute toxicity to saltwater aquatic life occurs at concentra-
tions as low as 508 ug/1 and would occur at lower concentrations among spe-
cies that are more sensitive than those tested. No data are available con-
cerning the chronic toxicity of trivalent inorganic arsenic to sensitive
saltwater aauatic life.
Human Health
For the maximum protection of human health from the potential carcino-
genic effects due to exposure of arsenic through ingestion of contaminated
water and contaminated aquatic organisms, the ambient water concentrations
should be zero based on the non-threshold assumption for this chemical.
However, zero level may not be attainable at the present time. Therefore,
the levels which may result in incremental increase of cancer risk over the
lifetime are estimated at 10 , 10 , and 10 . The corresponding
recommended criteria are 22 ng/1, 2.2 ng/1, and 0.22 ng/1, respectively. If
the above estimates are made for consumption of aquatic organisms only, ex-
cluding consumption of water, the levels are 175 ng/1, 17.5 ng/1, and 1.75
na/1, respectively.
vi
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INTRODUCTION
Arsenic is a naturally occurring element often referred to as a metal,
although chemically classified as a metalloid. Arsenic and its compounds
are used in the manufacturing of glass, cloth, and electrical semiconduc-
tor, as fungicides and wood preservatives, as growth stimulants for plants
and animals, as well as in veterinary applications (U.S. EPA, 19765). The
United States consumes half of the world production of arsenic, or about
37,500 tons per year, and produces about 18,000 tons per year itself. The
principal emission source for arsenic in the United States is thought to be
coal-^uel power plants, which emit approximately 3,000 tons of arsenic per
year (Nelson, 1977).
Environmental concentrations of arsenic have been reported at 5 mg per
kg in the earth's crust (U.S. EPA, 1976a). Arsenic is found also in air and
in all living organisms. Analysis of 1,577 U.S. surface waters showed arse
nic to be present in 87 samples, with concentrations ranging from 5 to 336
uq/1 and a mean level of 64 ug/1 (Kopp, 1969). Bowen (1966) reported 3.0
ud/1 in sea water.
A member of Group VB of the periodic table, arsenic has five electrons
in its outer shell, giving rise to the oxidation states of *5, +3, 0, and
-3. Arsenic as a free element (0) is rarely encountered in natural waters.
Soluble inorganic arsenate (+5) predominates under normal conditions since
it is thennodynamical ly more stable in water than arsenite (+3) (Ferguson
and Gavis, 1972). Elemental arsenic is a gray, crystalline material with a
molecular weight of 74.92, a density of 5.727, a melting point (at 28 atmos-
pheres) of 817°C, and a boiling point (sublime) of 613°C (Weast, 1975).
The low toxicity of elemental arsenic is attributed to its virtual insolu-
bility in water or in the body fluids (U.S. EPA, 1976b).
A-l
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A distinction should be made between different means of classifying
arsenic compounds. The compounds of arsenic may be classified according to
the oxidation state of arsenic (As ", As , and As ) and according to
whether or not arsenic is in the organic form (i.e., the arsenic atom is
covalently attached to at least one carbon atom).
Conditions of low pH, low Eh (standard oxidation-reduction potential)
and TOW dissolved oxygen in water favor the formation of lower oxidation
state arsenicals such as arsenite (+3) and arsine (-3) whereas more basic,
oxygenated waters result in an increase in the percentage of arsenic present
in the oentavalent state. The reducing action of certain organisms may also
cause arsenite to be the predominate form. In waters of high organic con-
tent, a considerable amount of arsenic may be bound to colloidal humic mat-
ter (Ferguson and Gavis, 1972).
Both arsenate and arsenite can be removed from the water column by co
precipitation or adsorption onto iron oxides (LaPeintre, 1954; Gupta and
Ghosh, 1953). Arsenate species can also be removed by adsorption onto alum-
inum hydroxide and clays, while arsenite is readily adsorbed onto metal sul -
fides (Ferguson and Gavis, 1972).
Oxidation of arsenite to arsenate occurs slowly at neutral pH (faster in
strongly acid or alkaline solutions), while methylation of arsenic to methyl
and dimethylarsine by methanogenic bacteria is known to occur (McBride and
Wolfe, 1971).
Arsine (AsH-j) and its methyl derivatives are the most acutely toxic
compounds of arsenic. However, they do not occur in drinking water or in
ambient water. Human exposure has occurred only through generation of these
compounds in occupational settings. Thus, arsine compounds are not further
considerated in this document.
A-2
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The organic' '"hich are not naturally occurring, are the largest group
of arsenic compounds. The two most common organic arsenic compounds are the
arsonic adds, R-AsO-(OH)2, and the arsinic acids, R,R'-AsO-OH, where R
and R1 refer to a variety of organic (alkyl) groups (U.S. EPA, 1976b). The
organic arsenic compounds considered to be of environmental importance are
those containing methyl groups, the aromatic arsenic derivatives employed as
feed additives and in veterinary medicine, and others which may have impor-
tance in biological systems (U.S. EPA, 1976a).
Arsenic forms a complete series of trihalides, while arsenic (V) fluor-
ide is the only simple pentahalide known. All of the arsenic halides are
covalent compounds that hydrolyze in the presence of water (Standen, 1967).
Additional information on inorganic arsenic compounds is given in Table 1.
A-3
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TABLE 1
Properties of Some Inorganic Arsenic Compounds*
Compound
Formula
Hater Solubility
Specific Properties
Arsenic trloxlde
Arsenic pentoxide
Arsenic hydride
(arsine)
Arsenic (HI) sulfide
Arsenic sulfide
Arsenic (V) sulfide
As203
As?05
12 x 10* wg/1 • O'C
21 x 106 wg/l • 25'C
2,300 x 10* Mg/l • 20"C
20 Ml/100 g
cold water
520 »g/l • 18*C
1.400 i.g/1 O O'C
Dissolves in water to
form arsenious acid
(H3As03:
K . 8 xlO-10H 25"C)
Dissolves in water to
form arsenic acid
2.5 x 10~4
5.6 x 10
3 x 10-13)
*3
This compound and Its
methyl derivatives are
considered to be the
most toxic.
Burns in air forming
arsenic trioxide and
sulfur dioxide; occurs
naturally as orpiment.
Occurs naturally as
Realgar.
*Source: Standen, 1967; U.S. EPA, 1976a,b
A-4
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REFERENCES
Alderdice, D.F. and F.FL Brett. 1957. Toxicity of sodium arsenite to young
chum salmon. Prog. Sep. Pacific Coast Stat. Fish. Res. Board Can. 108: 27.
Ancel, P. 1946. Recherche experimental e . sur le spina bifida. Arch. Anat.
vier. M0rph. Exo. 36: 45.
Anderson, 3.G. 1946. The toxicity thresholds of various sodium salts
determined by the use of Daphnia magna. Sewage Works Jour. 18: 82.
Beaudoin, A.R. 1974. Teratogenicity of sodium arsenate in rats.
toloay. 10: 153.
Biesinger, K.E. and C-.M. Christensen. 1972. Effects of various metals on
survival, growth, reproduction, and metabolism of Oaphm'a magna. Jour.
Fish. Res. Board Can. 29: 1691.
Bowen, H.J.M. 1966. Trace Elements in Biochemistry. Academic Press,
London -New York.
Browning, E. 1961. Toxicity of Industrial Metals. Buttersworth, London.
Calabrese, A., et al. 1973. The toxicity of heavy metals to embryos of t.he
American oyster, Crassostrea virginica. Mar. Biol. 18: 162.
A-5
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Car-dwell, 3-D., et al. 1976. Acute toxicity of selected to- : to six
soecies of *ish. Ecol. Res. Ser. EPA 600/3-76-008. U.S. • 1. Prot.
Aqency, Washington, D.C.
Clemens, H.P. and K.E. Sneed. 1959. Lethal doses of several commercial
chemicals for fingering channel catfish. U.S. Fish Wildl. Ser. Spec. Sci.
Sep. Fish. No. 316. U.S. Dep. Inter., Washington, O.C.
Ferguson, J.F. and J. Gavis. 1972. A review of the arsenic cycle in natu-
ral waters. Water Res. 6: 1259.
Fenn, V.H. and S.J. Carpenter. 1968. Malformation induced by sodium arse-
nate. Jour. Reprod. Fertil. 17: 199.
Gilderhus, P.A. 1966. Some effects of sublethal concentrations of sodium
arsenite on bluegills and the aquatic environment. Trans. Am. Fish. Soc.
95: 289.
Guota, S.R. and S. Ghosh. 1953. Precipitation of brown and yellow hydrous
iron oxide. III. Adsorption of arsenious acids. Kolloid-Z. 132: 141.
Hood, R.D. and S.L. Bishop. 1972. Teratogenic effects of sodium arsenate
in mice. Arch. Environ. Health. 24: 62.
Hughes, J.S. and J.T. Davis. 1967. Effects of Selected Herbicides on Blue-
gill Sunfish. In: Proc. 18th Annu. Conf., S.E. Assoc. Game Fish Comm.,
October 13-21, 1964. Clearwater, Florida. S.E. Assoc. Game Fish Comm.,
Columbia, South Carolina, p. 480.
A-6
-------
KODP, J«p« 1969, The Occurrence of Trace Elements in Water, In: o.D.
Hemphill fed.}. Proc, 3rd Annu. Conf. Trace Substances in Environ, Health.
University of Missourif Columbia,
LaPeintre, M. 1954. Solubilization oar les eaux natjrelles de 1'arsenic
lie' au fer dans les roches sedimentaires. C.R. Acad. Sci. 239: 359.
McBride, B.C. and R.C. Wolfe. 1971. Biosynthesis of dimethylarsine by
Vethanobacterium. Biochem. Jour. 10: 4312.
Nelson, D.A., et al. 1976. Biological effects of heavy metals on juvenile
bay scallops, Argooecten irradians, in short-term exposures. Bull. Environ.
Contam. Toxicol. 16: 275.
Nelson, K.W. 1977. Industrial contributions of arsenic to the environment.
Environ. Health Persoect. 19: 31.
Ridgeway, L.P. and O.A. Karnovsky. 1952. The effects of metals on the
chick embryo: Toxicity and production of abnormalities in development. Ann.
N.v. Acad. Sci. 5: 203.
Sanders, H.O. and O.B. Cope. 1968. The relative toxicities of several
oesticides to naiads of three species of stoneflies. limnol. Oceanogr.
13: 112.
Sorenson, E.^.B. 1976. Toxicity and accumulation of arsenic in green sun-
fish, Lepomis cyanellus, exposed to arsenate in water. Bull. Environ. Con-
tarn. Toxicol. 15: 756.
A-7
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Soehar, R.L. Comparative toxicity of arsenic compounds and their accumula-
tion in invertebrates and fish. Manuscript.
Standen, A. fed.) 1967. Kirk-Othmer Encyclopedia of Chemical Technology.
Interscience Pub., New York.
Tseng, W.P., et al. 1968. Prevalence of skin cancer in an endemic area of
chronic arsenicism in Taiwan. Jour. Natl. Cancer Inst. 40: 453.
U.S. EPA. 1976a. Arsenic. Subcommittee on Arsenic, Com. on Med. and Biol.
Effects of Environ. Pollut. NRC/NAS, EPA 600/1-76-036. U.S. Environ. Prot.
Agency, Washington, O.C.
U.S. EPA. 1976b. Arsenic and its compounds. EPA 560/6-76-016. U.S. Envi-
ron. Prot. Agency, Washington, O.C.
Weast, P.C. (ed.) 1975. Handbook of Chemistry and Physics. 56th ed. CRC
Press, Cleveland, Ohio.
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Aquatic Life Toxicology*
INTRODUCTION
Arsenical compounds are found in all living organisms including those in
aquatic systems. Althougn important sources of arsenic in the environment
are industrial (Nelson, 1977; Fowler, 1977), such as smelters of nonferrous
ores and coal-fired power plants using arsenic-rich coal, suostantial arsen-
ic contamination of water can also occur from the improper use of arsenical
pesticides such as sodium arsenite which is often used as an aquatic
herbicide.
The chemistry of arsenic is quite complex, consisting of chemical, bio-
chemical, and geochemical reactions which together control the amount of
dissolved arsenic concentrations in aquatic systems. A cycle for arsenic in
natural waters has been diagrammed in an extensive review by Ferguson and
Gavis (1972).
Arsenic is stable in water in four oxidation states (+5, +3, 0, -3) as
both inorganic and organometallic species and in dissolved and gaseous
states. Common arsenic species are arsenate, arsenite, methanearsonic acid
and dimethyl arsenic acid (cacodylic acid). Arsenic as the free element (0)
is rarely encountered in water but appears to be thermodynamically stable at
lower Eh (standard oxidation reduction potential) values. At very low Eh,
AsH-j (arsine, -3) may be formed which is only slightly soluble. Arsenic
sulfides have low solubilities and occur as stable solids at pH values below
5.5 and lower Eh conditions. Arsenite (+3) may also be present if the Eh is
*The reader is referred to the Guidelines for Deriving Water Quality Crite-
ria for the Protection of Aquatic Life and Its Uses in order to better un-
derstand the following discussion and recommendation. The following tables
contain the appropriate data that were found in the literature, and at the
bottom of the appropriate table are calculations for deriving various mea-
sures of toxicity as described in the Guidelines.
8-1
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less than 0.1V. Arsenic (+3) has a strong affinity for sulfur and reaaily
adsorbs or coprecipitates with metal sulfides.
In aerobic water, reduced forms of arsenic tend to be oxidized to arse-
nate (*5), the predominant form in these waters. The rate of oxidation of
arsenite to arsenate by oxygen is slow at neutral pH, but proceeds measurab-
ly in several days in strongly alkaline or acidic conditions (Ferguson and
Gavis, 1972). This oxidation, however, probably never proceeds to comple-
tion. Arsenate can coprecipitate with or adsorb on nydrous iron oxides and
form insoluble precipitates with calcium, sulfur, aluminum, and oarium com-
pounds (Holm, et al. 1979). Arsenate is chemically similar to pnosphate and
may be enriched in phosphate minerals, although arsenic affinity to iron is
predominant. The adsorption of arsenate by metal oxides and the formation
of arsenic sulfide appears to remove arsenic from solution to the sediments
and prevent nigh arsenic concentrations from being present in solution.
Studies by Holm, et al. (1979) and others on the heterogeneous interactions
of arsenic in aquatic systems indicate that arsenate is more strongly ab-
sorbed to sediments than are other arsenic forms. Generally, adsorption
processes are very dependent on arsenic concentration, sediment characteris-
tics, pH, and ionic concentration of other compounds. Arsenic can be re-
moved from the sediments by volatilization and recycled in the water.
Inorganic arsenic can be converted to organic alkyl arsenic acids (+3
and +5) and to methylated arsines (-3) under anaerobic conditions by fungus,
yeasts and bacteria, although biomethylation may occur under aerobic condi-
tions as well.
Little is known about the mechanism of arsenic toxicity to aquatic or-
8-2
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ganisms; however, arsenic readily forms kinetically stable bonds to sulfur
and carbon in organic compounds. Like mercury, arsenic (+3) reacts with
sulfhydryl groups of proteins; enzyme inhibition by tnis mechanism may be
the primary mode of arsenic toxicity. Arsenate does not react with
sulfhydryl groups as readily but may uncouple oxidative pnosphorylation
(Anderson, 1979).
Although considerable information has been published on the effects of
arsenic on freshwater organisms, knowledge of its toxicity is less than com-
plete since much of the work has been devoted to monitoring or field assess-
ment studies or were studies that contained information that was not useful
for deriving a water quality criterion. Virtually no data on chronic ef-
fects of arsenic on fish species exist, and only one invertebrate chronic
test was found acceptable. Only two references dealing with arsenic biocon-
centration by freshwater species accurately reported exposure concentrations
or calculated useful bioconcentration factors.
The arsenic data base for saltwater organisms is inadequate to assess
comparative sensitivity among a variety of organisms and their life stages
or to assess the importance of water quality parameters sucn as salinity to
arsenic toxicity. In addition, these data do not distinguish differences,
if any, among various oxidation states.
The present data base for arsenic is separated into trivalent inorganic
arsenic, pentavalent inorganic arsenic, and other arsenic compounds since
the majority of toxicity tests were conducted with the trivalent form, par-
ticularly sodium arsenite, and because toxicity may be related to the form
of arsenic present in solution. All results are expressed in terms of ar-
senic, not as the compound.
B-3
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EFFECTS
Acute Toxicity
Seven acute tests with freshwater invertebrate species have been report-
ed with trivalent inorganic arsenic ana all were testea with sodium arsenite
(Table 1). Only one {U.S. EPA, 1980) was a flow-through test with measured
concentrations; the others were static tests with unmeasured concentrations.
Crustaceans, comprised of three cladoceran and one scud species, showed some
variation among species but were more than four times more sensitive than a
stonefly species, an aquatic insect. Tne range of acute values for crusta-
ceans was 812 to 5,278 ug/1. Daphnia magna appeared to be the most tolerant
cladoceran although it was difficult to compare sensitivities due to the
small data base. All crustacean species were more than twice as sensitive
to trivalent inorganic arsenic as were the fish species tested. Stonefly
sensitivity was within the range of sensitivity of fish based on 12 acute
tests with fish.
The acute toxicity of trivalent inorganic arsenic to freshwater fishes
is also summarized in Table 1. One-half of the tests were static with un-
measured concentrations and the others were flow-through tests with measured
concentrations. Seven fish species are represented and sodium arsenite was
used in all tests. Rainbow trout and brook trout were the most sensitive
species and bluegills were the most tolerant. The total range of LCcQ
values was narrow for the seven species (13,340 to 41,760 ug/1). The three
values reported for bluegills by Inglis and Oavis (1972) were for tests con-
ducted in soft, medium and hard water (50, 200» and 370 mg/1 as CaCO^, re-
spectively). No significant difference was demonstrated to indicate that
hardness had any effect on arsenic toxicity.
3-4
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Values reported for two invertebrate and four fish species exposed to
pentavalent inorganic arsenic and other arsenic comoounds are listed in
Table 1. All tests were static with unmeasured concentrations except for
one flow-through, measured test with rainbow trout and sodium arsenate.
Values reported for Daphnia magna and rainbow trout exposed to sodium
arsenate (*5) are comparable to those for exposures with these species and
sodium arseoite (+3K Although this data base is limited, the two valence
States appear to be similarly toxic. The extremely high values reaorted for
crayfish, channel catfish, and smallmouth bass exposed to monosodium
methanearsonate indicate that organic arsenic may be much less toxic than
both trivalent and pentavalent inorganic arsenic. The 96-hour LC^« value
of 82.400 ug/1 shown for fathead minnows and arsenic trisulfide (Table 6)
was aooroximately 5 times higher than the value for this species exposed to
sodium arsenite (Table 1). This is probably because arsenic trisulfide is
less soluble than sodium arsenite.
Based on the above data base, the Freshwater Final Acute Value for tri-
valent inorganic arsenic, based on calculations described in the Guidelines,
is 440 ug/1 (Table 3).
Acute toxicity data representative of trivalent inorganic arsenic and
saltwater aauatic life are limited to two fish and three invertebrate spe-
cies (Table 1). Nelson, et al. (1976) employed a renewal test to determine
the toxicity of sodium arsenite to juvenile bay scallop, and Calabrese, et
al. (1973) evaluated toxicity to American oyster embryos using sodium arse-
nite in static tests. Toxicity tests with unmeasured concentrations defined
B-5
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a 96-hour LC^ Of 3,490 ug/1 for bay scallops and a 48-hour LC5Q of
7,500 ug/l for American oyster. The lowest arsenic acute value reported
(508 ug/1) was for a cooepod tested in static toxicity tests with sodium
arsenite.
Alderdice and Brett (1957) assessed the toxicity of arsenic trioxide to
chum salmon using a renewal test with unmeasured concentration to determine
the 48-hour LCgg of 8,330 ug/1 (Table 6). The 96-hour LC5Q values for
arsenic for the fourspine stickleback and Atlantic silverside were deter-
mined to be 15,000 and 16,000 ug/1, respectively (Table 1).
Toxicity of arsenic trisulfide to juvenile white shrimp was tes ?d by
Curtis, et al. (1979). A 96-hour LCgQ of 24,700 ug/1 was determined for
this less soluble form of the element in static tests (Table 6). No compar-
able data are available with this species for any other form of trivalent
arsenic, but the highest of the five available values is 16,033 wg/1.
Chronic Toxidty
Only one chronic test was reported that could be used to calculate a
chronic value for arsenic and freshwater aauatic organisms. A life-cycle
test with Daphnia magna (U.S. EPA, 1980) (Table 2) exposed to sodium arse-
nite resulted in a chronic value of 912 ug/1 based on chronic limits of 633
and 1,315 ug/1. A life-cycle test with the same species (Table 6) exposed
to sodium arsenate could not be used in the calculation of a chronic value
because the test concentrations were not measured as specified in the Guide-
lines. However, the upper and lower chronic limits in this test, based on
reproduction growth, and enzyme Inhibition were nearly identical (520 to
1,400 ug/1) to that reported above for Daphnia magna. Both tests were con-
8-6
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ducted in Lake Superior water. The similar toxicity reported in these tests
using trivalent and oentavalent inorganic arsenic suggests that these forms
are similarly toxic as was noted previously with acute tests.
Because less than the required number of chronic tests were reported for
arsenic according to the Guidelines, a Freshwater Final Chronic Value cannot
he calculated.
No data are available on the chronic toxicity of arsenic to saltwater
fish or invertebrate species.
Plant Effects
The effect of trivalent inorganic arsenic on three species of algae and
one submerged plant are reported in Table 4. All tests were conducted with
sodium arsenite (Cowell, 1965). The sensitivity of aouatic plants is com-
parable to that for sensitive invertebrate species exposed in acute tests.
No data are available for saltwater algae or vascular plants.
Residues
Bioconcentration factors for freshwater organisms and arsenic are shown
in Table 5. Values were obtained for four invertebrate and two fish species
for trivalent inorganic arsenic compounds. Six species were tested with
other arsenic compounds. Numerous other studies reporting bioconcentration
factors for aouatic organisms were not used since they did not meet the
requirements described in the Guidelines.
In the study by Spehar, et al. (1980), arsenic was tested to compare tne
bioconcentration of four arsenic compounds after approximately 28 days of
exposure. Results indicated that Oaphnia magna and one snail, Helisoma cam-
panulata, had the highest residues when exposed to trivalent inorganic ar-
senic. Another snail species, Stagnicola emarginata, and stoneflies exposed
to trivalent inorganic arsenic had values similar to organisms exposed :?
3-7
-------
the other compounds. Sioconcentration factors for rainbow trout and scuds
were reported as zero because residues in exposed animals were not different
from those in the controls. No value was reported for scuds and trivalent
inorganic arsenic (arsenic trioxide) because the concentration tested was
lethal after 2 weeks of exposure.
A bioconcentration factor of 4 was obtained for bluegills and arsenic
trioxide in another study (U.S. EPA, 1978). The half-life in bluegill tis-
sue was one day. The low bioconcentration and short half-life of arsenic in
fish tissue suggest that no residue problem will occur at concentrations
that are not directly toxic.
A bioconcentration factor of 350 was obtained for the oyster, Crassos-
trea virqinica, after 112 days of exposure (U.S. EPA., 1980b)
No Residue Limited Toxicant Concentration (RLTC) for arsenic could be
determined since no maximum permissible tissue concentration for arsenic is
available.
Miscellaneous
Data on other toxicological effects show that there is a wide range of
sensitivity of freshwater invertebrate and fish species to arsenic (Table
6). Comparison of these data for fish with the fish acute values (Table 1)
indicates that 1n almost all cases, arsenic toxicity was increased with in-
creased duration of exposure. One value for bluegills (Hughes and Davis,
1967) was an exception resulting in a 48-hour LCg* of 290 ug/1. This
value was Included in the document because it was verified by the author and
because there was no reason to exclude the data. A specialized pelletized
form of sodium arsenite was used which may have accounted for its high tox-
icity. The invertebrate data were too variable to indicate a trend in tox-
icity in regard to duration of exposure.
B-3
-------
Not enough data were obtained to compare the toxicity of trivalent inor-
ganic arsenic to that of other arsenic compounds. As with the acute tests,
me trivalent form, particularly sodium arsenite, was the compound most
extensively tested.
T-emperature was the only variable tested to determine effects of envi-
ronmental factors on arsenic toxicity to freshwater organisms. Sorenson
(1976c) found that increased water temperature decreased the median letnal
time of green sunfish after exposure to two concentrations of sodium arse-
nate (Table 6).
Generally, the lowest freshwater toxicity values for arsenic were OD-
tained in exposures witn early life stages of fish. Values for early life
stage exposures with rainbow trout and goldfish embryos and larvae were sev-
eral times lower than those for older juvenile stages of these, species.
Data for bluegills showed that fingerling stages exposed to sodium arsenite
were more sensitive than juveniles and adults of this species. Acute data
{Table 1) also showed that channel catfish fingerlings were slightly more
sensitive than juvenile stages exposed to sodium arsenite. The lowest value
obtained for all of the arsenic data was for an early life stage exposure
with the toad which resulted in a 7-day LC50 of 40 ug/1 (Birge, 1979).
Values obtained for early life stages of fish species were lower than
those obtained for the most sensitive invertebrate species (Table 1) and
were below the limits obtained for a life cycle test with Daphnia magna
(Table 2).
Bryan (1976) exposed the saltwater polychaete worm, Nereis diversicolor,
to sodium arsenite and estimated the 192-hour LCcQ to be greater than
14,500 ug/l (Table 6).
B-9
-------
Sodium arsenite caused other effects which include depressea oxygen con-
sumption rate and behavioral changes in mud snails exposed to sodium arse-
nite at concentrations of arsenic greater than 2,000 ug/1 for 72 hours (Mac-
Innes and Thurberg, 1973) and arrested development of red alga sporelings
following exposure to 577 ug/l for 18 hours and a post-exposure period of
seven days (Soney, et al. 1959).
Holland, et al. (1960) determined tolerance levels of pink salmon to ar-
senic trioxide and determined a 96-hour LC1QQ of 12,307 ug/1; a 7-day
LC100 of 7'195 u9/1; and a 10~day LC54 of 3»787 u9/]<
The Dioconcentration factor of 15, calculated from Nelson, et al. (1976)
for the bay scallop after only a 4-day exposure, has been included for in-
formational value.
Summary
The chemistry of arsenic in water is complex and the form present in
solution is dependent on such environmental conditions as Eh, pH, organic
content, presence of suspended solids, and sediment characteristics. Based
on freshwater data, trivalent inorganic arsenic (with the exception of ar-
senic trisulfide) and the pentavalent form appear to be imilarly toxic to
aquatic organisms. Organic arsenic compounds and arser : trisulfide were
much less toxic but additional data are needed to adequately determined
their effect on aquatic life.
Acute data for 14 freshwater species show that differences in toxicity
were not related to the type of exposure (i.e., static or flow-through
tests). Acute values for trivalent inorganic arsenic ranged from 312 to
41,760 ug/1. A life cycle test was conducted with Daphnia magna which gave
a chronic value of 912 ug/1. No chronic tests with freshwater fish species
were reported.
3-10
-------
The freshwater residue data indicate tnat arsenic is not bioconcentrated
to a high degree and that lower foms of aouatic life may accumulate Mgher
arsenic '•esidues than fishes. Arsenic accumulation in freshwater aiuatic
oraam'sms does not apoear to be qreat'y affected by the form of arsenic ore-
sent, although the highest residues were seen in exposures with the triva-
-------
CRITERIA
For freshwater aquatic life the concentration of total recoverable tri-
valent inorganic arsenic should not exceed 440 ug/1 at any time. Short-tern
effects on embryos and larvae of anuatic vertebrate soecies nave been shown
to occur at concentrations as low as 40 ug/1
The available data for total recoverable trivalent inorganic arsenic in-
dicate that acute toxicity to saltwater aquatic life occurs at concentra-
tions as low as 508 ug/1 and would occur at lower concentrations among soe-
cies that are rcore sensitive than those tested. No data are available con-
cerrnnq the chronic toxicity of trivalent inorganic arsenic to sensitive
saltwater aouatic life.
3-12
-------
Table I. Acute values for arsealc
Species
Method*
Cheatcat
LCM/EC90
Specie* Neaa
Acute Value
Reference
FRESHWATER SPECIES
Cladoceran.
Oaphnla aagaa
Cladoceran,
Oaphnla pulax
Cladoceran,
Oaphala pulax
Cladoceran,
SlMocephalus serrulatus
Scud.
GeaMrus pseudol lanaeus
Stonefly.
Ptaroaarcys call torn lea
Stonefly.
Ptaronarcys call torn lea
Rainbow trout,
Satan galrdnari
Brook trout,
Salvellnus tontlnalls
Goldfish (Juvenile),
Car ass 1 us auratus
Fathead Minnow
(Juvenile),
Channel catfish
(Juvenile).
S. U
s. u
s. u
s. u
FT, M
s. u
S, U
s. u
FT, M
FT, N
FT, M
FT, M
Trlvalent
Sodlua
arsanlte
SodliM
arsanlte
Sodliw
arsanlte
Sodlu*
arsenlte
SodliM
arsanlta
SodliM
arsanlte
SodliM
arsanlta
SodliM
arsanlta
Sod lim
arsanlta
SodliM
arsanlta
Sodlua
ar sen! ta
SodliM
arsanlte
Inorganic Arsenic
5,278
1,044
1,740
812
879
22.040
22.040
13,340
14,964
26.042
15,660
18.096
5,278
1.348
812
879
22,040
13,340
14,964
26,042
15.660
Anderson, 1946
Sanders A Cope,
FPRL, I960
Sanders & Cope,
U.S. EPA, 1980a
Sanders & Cope.
FPRL. I960
FPRL, 1980
Car dwell, et al.
Car dwell, et al.
Cardwell, et al.
Cardwell. et al.
1966
1966
1968
1976
1976
1976
1976
Ictalurus punctatus
B-13
-------
Table I. (Continued)
Species Hethod*
Channel catfish S, U
(tlngerl Ing),
Ictalurus punctatus
FlagtUh (fry). FT. H
Jordanella I lor Ida*
eiuegill (juvenile),, FT, H
Lepoals mecrochlrus
Bluoglll. S, U
LepoMls wacrochlrus
Blueglll. S, U
lepoals Mcrochlrus
Blueglll, S, U
L«po*ls Mcrochlrus
Blueglll, S, U
LepoMlt Mcrochlrus
Cladoceran, S, U
Oaphnla maq/na
Rainbow trout (Juvenile), FT, M
Sat ao ^alrdaerl
Crayfish. S. U
Proca«barufc sp.
Channel cattish, S, U
Ictalurus punctatus
Chemical
SodliM
Sodlu«
arsenlt*
SodliM
ar sen 1 te
SodliM
arsenl te
SodliM
arsanlte
SodliM
arsenl te
SodliM
arsenite
Pentavalent
LC50AC50
(»fl/l)M
15.022
28.130
41.760
15,370
16,240
15,486
17,400
Inorganic Arsenic
SodliM 7,400
ar senate
Sodlua 10.800
ar senate
Other Arsenic Compounds
HooosodliM
•at hanear sooa t e
HooosodliM
•etnanearsonat*
506,000
1.403.000
Species Mean
Acute Value
(ug/l)"*
18,096
28.1)0
41,760
7.400
tO. 800
506,000
1,403,000
Reference
Clttftuits & Sneed, 1959
CardMul 1. et at. 1976
Card*«l 1, et al. 1976
Inylls 1 Udvls, 1972
Inglls 1 Udvls. 1972
Inglls A Davis. 19/2
FPRL, I960
Bleslnger &
Clrlstensun. 1972
Hale. 1977
Anderson, et al. 1975
Anderson, et al. 1975
B-14
-------
Table I. (Continual)
Species Method8
Sinai inouth bass S. U
( Hngarl Ing),
Micropterus doioaiMj
Bay scallop (Juvenile), R, U
Argopecten I r radians
Aserlcsn oyster, S, U
Crassostrea virgin lea
Copepod, S, U
Acartla clausl
Foursplne stickleback, S, U
Ape It as guadracus
Atlantic silver si da S. U
(Juvenile),
Menldla eanldla
LC50AC50 Acute Value
Cheat cai <|ig/)i" CM9/i)BB Reference
Monoiodiu- 4i4,000 414,000 Andar&on, or a\ . 1975
•at hanear sona te
SALTWATER SPECIES
Trlvalont Inorganic Arsenic
Sodltm 3,490 3,490 Nelson, et al. 1976
arseftite
Sod Jus 7,300 7,500 Calebruse, el -!,
arsenlte 1973
SodluM 506 506 U.S. LPA, I980b
arsenlte
SodluM 14,953 15,000 U.S. EHA, I960b
arsenlte
Sodlu* 16,033 16,000 U.S. LPA, I980b
arsenl te
* S • static, R - reneMal, FT • flow-through, U » unmeasured, H *> Measured
•"KesulTs are expressed as arsenic, not as the compound.
3-15
-------
TabU 2. Chronic values for arsenic
Specie*
Test1 Chemical
Limit*
(Hfl/l)11
Chronic Value
(HO/1 )" Reference
FRESHWATER SPECIES
Cladoceran,
Daphnla Mgna
Trlvalent Inorganic
LC Sodium
arsenlte
Arsenic
633-1.315
912 U.S. EPA. I960a
• LC » IIU cycle or partial life cycle
"Results are expressed as arsenic, not as the compound
Cladoceran,
Daphnla aagna
Acute-Chronic Ratio
Chemical
Acute
Value
Trlvalent Inorganic Arsenic
Sodium 5,270
arsenlte
Chronic
Value
(U9/I) Ratio
912
5.8
B-16
-------
TabU 3. Spacla* Bean acut« valuas and aoita-chronlc ratio* tor arsmlc
Spaclcs Maan Spael*s Maa*
Ae»ita Vain* Acuta-Chronlc
nk» SpMlas (Mfl/D Ratio
FRESHWATER SPECIES
12
II
10
9
8
7
6
5
4
3
2
1
Trlvalont Inorganic
Bluoglll,
Lapo*ls Mcrochlrus
Flagtlsh.
Jordaiwlia tlorldae
Goldtlsti,
Car ass 1 us aura t us
Stonef ly,
Ptaronarcys call torn lea
Chaonal catfish,
Ictalurus punctatus
Fathead Minnow,
Plaaphal«s proa* las
Brook trout,
Salvallnus fontlnalls
Rainbow trout,
Sal«o ifalrdnwl
Cladocaran,
Daphnla aagna
Cladocaran,
Daphnla pulax
Scud,
Ga««arus psaudollanawis
Cladoceran,
SlMOcaphalus s«rrulatus
Arsenic
41,760
28,130
26,042
22,040
18,096
15,660
14,964
13,340
5,278 5.8
1,348
879
812
B-17
-------
3.
Baolt*
Saaclaft
Aorta Valva
(M/l>
AcMta-Caroalc
Ratio
SAtTMATER SPECIES
Triwalaat laorgjalc Arsaalc
5
4
2
1
Atlantic •llvarslda.
Fowrsalaa stick 1 aback,
Apaltas ^uadracus
Aaarlcaa oyctar,
Cra»«o«traa vlrglalca
Bay scallop.
Copapod.
Acartla clausl
16.033
14,953
7,500
3.490
500
-
Ranked fro* l«a»t sansltlva to «o»t tancltlv* ttascd on spacias aaan
acuta valua.
Frashnatar Fl«al Acuta Valua for trlvalant Inorganic arsanlc - 440 ug/l
3-18
-------
Tobl* 4* Plant valves for arsenic
Specie*
Chealcal
Effect
(pa/!)* Reference
FRESHMATER SPECIES
Trivalent inorganic Arsenic
Aiga.
Cladophora sp.
Alga,
Spirogyra sp.
Aiga,
Zygnema sp.
Submerged plant,
PotaaogstoB sp.
SodiiM
arsenlte
Sodium
orsenite
Sod Jus
arsenlte
SOdllM
iOO> kiii in
2 «ks
1001 kill In
2 wks
!OC$ ki i ! ir.
2 wks
95| kill In
! so
2,520 Coweii, 1965
2.320 Cowell, 1965
2,320 Cows!!, 5965
2.320 Cowel 1, 1965
* Results are expressed as arsenic, not as the coapound.
B-19
-------
Spaclas
Tissue
Tabla 5. Raslduas tor arsanlc
Chaalcal
Bloconcantrat Ion
Factor
Duration
(days) Rafaranca
FRESHWATER SPECIES
Trlvalant Inorganic Arsanlc
Ctadocaran,
Daphnla tugna
Snail.
HallsoM cMpanulata
Snail,
Stagnlcola aaarglnata
Stonatly,
Pteronarcys dor sat a
Rainbow trout,
Sal«o galrdnarl
Bluaglll,
Lapoals Mcrochlrus
Cladocaran,
Daphnla «agna
Scud,
Gaawarus psaudollamaaus
Sna 1 1 ,
HallsoM cjMNMWulata
Snail,
Stagnlcola eaarglnata
S tonal ly,
Ptaroaarcys dor sat a
Rainbow trout,
Salao galrdnerl
Whola body
Whola body
Whola body
Whola body
Whola body
Whola body
Whola body
Whola body
Whola body
Whola body
Whola body
Whola body
Arsenic
trloxlda
Arsanlc
trloxlda
Arsanlc
trloxlda
Arsanlc
trloxlda
Arsanlc
trloxlda
Arsanlc
trloxlda
Pantavalant Inorganic
Arsanlc
pantox 1 da
Arsanlc
pantoxlda
Arsenic
pantoxlda
Arsanlc
pent oxide
Arsenic
pantoxlda
Arsanlc
pantoxlda
10
17
3
9
0
4
Arsanlc
4
0
6
3
7
0
21
28
28
28
28
28
21
28
28
28
28
28
Speh
-------
TabU 5. (Continued)
Sj>sc!ss
Tissue
B loconcmtrat 1 on
Cheaica! Factor
Duration
iday»}
Haler«nc«
Other Arsenic Compounds
Cladocaran,
Oaphnla Magna
Cladoceran,
Oaphnla Maona
Scud,
GawMrus ps«udol tMnaeus
Scud,
GAMMBTUS pseudol iMnaeus
Snail,
He 1 1 sowa caMpanu 1 at a
Snail,
Heiisoma caMpanulata
Snaii,
Stagnicola eMarglnata
Snail,
Staynicoia uMTyinata
Stonaiiy,
Pteronarcys dor sat a
Stonetly,
Ptsroftarcys dcrsata
Ratabos trout.
Sal MO galrdner 1
Kalnbow trout.
Sat BO gaJrdner 1
Whole body
Whole body
Whole body
Whole body
Whole body
Whole body
Whoie body
Whole body
Whole body-
Whole body
Whole body
Whole body
Dl sod I UK M«thy 1
ar senate
SodluM dlMethyl
ar senate
DIsodliM Methyl
ar senate
£odluM dlMethyl
ar senate
DIsodluM Methyl
ar senate
SodluM dlMethyl
ar senate
DisodiuM Methyi
arsenatn
SodluM dlMethyl
arsenafv
DisOuiuM «etny t
ar senate
SodluM dlMethyl
ar senate
Oisodtua asthy!
ar senate
Sodlui* dlMethyl
ar senate
4
4
0
0
4
5
3
2
9
7
0
0
2!
21
28
28
28
28
28
28
28
28
28
28
Spehdr, et a!.
Spdhor, et ol.
bpahar . et sU
Spehar , et at.
Spohar, et al.
Sptthar, et
-------
Tatt* S.
-------
Table 6. Other data for arsenic
Chemical
Result
« Reference
«B^U^_«B^B» •— «^»^™™.— «»^»W^B~i«»— • 4MB— M«^^ -»*«^M» 1 . ' ' ~ -
FRESHWATER SPECIES
Trlvalent Inorganic Arsenic
C 1 adoceran,
(not specified)
Cl«doceran,
Papnnla Magna
Cladoceran,
(not specified)
Copepod 1 ado It),
(not specified)
Copopod,
(not spec Ml ad)
Rotifer,
(not specified)
Rotifer,
(not specified)
AwpMpod,
HyaUUtt knlcKwboctierl
A^blpod.
GaMurus psaudol lonaeus
Mayfly (ny^th),
Caen Is dlalnuta
Hayfly (ny^in),
Caen Is dlalnuta
Mayf ly.
Calllbaatls sp.
Toad (eabryo- larval) .
Gastruphryne carol Inensls
Sodium
arsenlte
Sodlun
arsenlta
SodluM
arsenlte
SodliM
arsenlte
Sodlun
arsenite
SodliM
arsenlte
Sodlu*
arsenl te
Arsenic
trlGKlde
Arsenic
trloxlde
Arsenic
trloxlde
Ar sen 1 c
trloxlde
Arsenic
trloxlde
Sodium
arsenlte
1 ok
26 nrs
16 «ks
16 wKs
1 Mk
t *k
16 Mks
5 days
7 days
5 days
5 days
5 days
7 days
Significant pop-
ulat Ion reduction
IC50 (Median
(Mobilization)
Reduced population
(one treatment)
Reduced population
(weekly treatments)
Significant popu-
lation reduction
Significant popu-
lat Ion reduction
Reduced population
(•onthly treatments)
70$ Mortality
80| Mortality
25> Mortality
62} Mortality
94$ Mortality
LC50
2,120
3,770
690
690"
2,320
2,320
690"»
4,469
961
2,234
5.958
4,469
40
Cowell, 1965
Crosby & Tucker. 1966
Glldernus, 1966
Gllderhus, t%6
Cowell, 1965
Cowell. 1965
Gllderhus, 1966
Surlier & Meehean,
1931
Spehar, et al. I960
Surber I Meehean,
1931
Surber & Meehean,
1931
Surber 1 Meuhuan,
1931
Utry». 1979
B-23
-------
Table 6. (CoetlMUed)
Result
Species
Rainbow trout
(e»bryo-larval).
Sales galrdnerl
Rainbow trout (Juvenile),
Sales galrdnerl
Brook trout,
Sal veil BUS tontlnalls
Goldfish (Juvenile),
Carasslus auratus
Goldfish (e*bryo- larval),
Carasslus auratus
Spot tall shiner,
Motropls hudson 1 us
Fathead *lnnow (juvenile),
PlMphalas promelas
Fathead •Innow,
PlneplMtles proaalas
Olueglll (Juvenile),
Lepoals *acrochlrus
Blueglll (adult),
Lepoals Mcrochlrus
Blueglll (Juveniles),
Lepoals *acrochlrus
Blueglll (flngerllng),
Lepoals *acrochlrus
Cheeiical
Sodlu*
arsenlte
Arsenic
trloxlde
Sodlu*
arsenlte
Sodlu*
arsenlte
Sodlu*
arsenlte
Sodlu*
arsenlte
Sodlu*
arsenlte
Arsenic
trlsulflde
Sodlu*
arsenlte
Sodlu*
arsenlte
Sodlu*
arsenlte
Sodlu*
arsenlte
(palletized)
Duration
28 days
21 days
262 hrs
336 hrs
7 days
72 hrs
336 hrs
96 tirs
16 wks
)6 wks
336 hrs
48 hrs
Effect
LC50
Decrease In fat
weight gain
LC50
LCM
LC50
LOO
LC50
LC50
Reduced survival
(one treatment)
Hlstoparhologlcal
alterations
(weekly treat*ents)
LCSO
LC50
MO
1,000
10,440
18,618
490
27,000
82,400
690
690"
18,328
290
Reference
Blrgo. 1979
Speyer, 1974;
Speyer & Leduc, I97i
Cardwel 1. et al. 1976
Cardwell, et al. 1976
tilrye, 1979
Boschettl 4
McLoughlln, 1957
Cardwell, et al . 1976
Curtis, et al. 1979
Gllderhus, 1966
GHderhus, 1966
Cdrdwell, et al. 1976
Huyhes &, Davis. 1967
3-24
-------
Table 6.
Result
Spaclas
Reference
Pentavalent Inorganic Arsenic
Cladocaran.
Daphnla aaana
Cladocaran.
Oaphala »agna
Green Minflsh C Juvenile).
Lepoals cy ana II us
Green sunflsh,
LepOMlS cyanallus
Green sunflsh,
Lepoals cyan* II us
Green sunflsh,
LefKMls cyanellus
Green sunflsh,
Leoomts Chanel lus
Green tuntlsh,
Lepceils cyanallus
Green sunflsh,
Leponls cyanallus
Sodlua
ar senate
SodliM
ar senate
Sodlu*
ar senate
SodliM
ar senate
SodliM
ar senate
SodliM
ar senate
ar senate
ar senate
SodliM
ar senate
3 MkS
3 «ks
39 hrs
2 Mks
678 hrs
210 hrs
124 hrs
527 hrs
209 hrs
SALTWATER
LC50
Chronic Malts
LT50
Ultrastructural
changes In liver
LT50 at 10 C
LT50 at 20 C
LT50 at 30 C
LT50 at 20 C
LT50 at 30 C
SPECIES
2.850
520-
1,400
40.000
31,700
60,000
60,000
60,000
30.000
30,000
Bleslnyer &
Chrlstensen, 1972
Bleslnger A
Chrlsten&en. 1972
Sorenson, I976a
Sorenson, I976b
Sorenson, I976c
Sorenson, I976c
Sorenson, I976c
SoreniOfi, 1976c
Sorenson, I976c
Trlvalent Inorganic Arsenic
Red alga,
Pluaarla a lagans
Polychaeta wor«,
Nereis dlverslcolor
SodliM
arsenlte
SodliM
arsenlte
16 hrs
192 hrs
7 day post expo-
sure - arrested
development o<
spore) Ings
LC50
577
>I4,500
booey, at ol. 1959
bryan, 1976
B-25
-------
Tabla 6. (CoKtlawad)
Spacla»
Mud SMll.
NaSSarluS ObSOlatMS
Bay scallop (Juvanlla),
Argopactln Irradlans
Mhlta ihrlap
(Juvanlla).
Paftaauft sallfarus
Pink sal»on,
Oncorhynchus oprfauscha
Pink calaon,
Oncorhynchus ggrbuscha
Pink MlMon,
Oncorhynchu* oprbuscha
Chua sal aon,
Oncortiynchut kata
Cnwilcal
Sod) u>
ar$*nlta
SodlUM
arsanlt*
Arsanlc
trlMilflda
Arsanlc
trloKloa
Arsanlc
trlCKlda
Arsanlc
trlOKlda
Arsanlc
trlcKlda
Racult
Duration EMaet (na/l»* Rataranca
72 hrs 09 consuaption >2,OOU Haclnnas 1 Thurbarg
rtta 4*pratsad and 1973
abnormal bahawlor
4 days Btoconcantrat Ion - Nalson, at al. 1976
factor * 13
96 hrs LC50 24,700 CurtU, at at. 1979
96 hrs LCI 00 12,507 Holland, at at. I960
7 days LCIOO 7,195 Holland, at al. I960
10 days LC54 3,787 Holland, at al . I960
48 hrt LC50 6,330 Alderdlce t Bratt,
1957
• Rasults ara axprassad as arsenic, not as tha co*pound«
*• Maasurad concantratlon attar 16 waaks was 9.040 |tg/l
••"Maasurad concantratlon attar 16 waaks «as 2,280 tig/1
B-26
-------
REFERENCES
Alderdice, O.F. and J.R. Brett. 1957, Toxicity of sodium arsenlte to young
salmon. Prog. Rep. Pacific Coast Stat. Fish. Res. 8d. Canada. 108: 27.
Anderson, A.C., et al. 1975. The acute toxlclty of MSMA to black bass (Mj_-
cropterus dolomieu), crayfish (Procambarus sp.), and channel catfish ( Ictal-
urus lacustris). Bull. Environ. Contam. Toxicol. 14: 330.
Anderson, B.G. 1946. The toxicity thresholds of various sodium salts de-
termined by the use of Daphnla maqna. Sewage Works Jour. 18: 82.
Anderson, M.A. 1979. Personal communication. University of Wisconsin,
Water Chemistry Program, Madison, Wisconsin.
Biesinger, K.E. and G.M. Christensen. 1972. Effects of various metals on
survival, growth, reproduction, and metabolism of Daphnia maqna. Jour.
Fish. Res. Board Can. 29: 1691.
Birge, W.J. 1979. Aauatic Toxicology of Trace Elements in Coal and Fly
Ash. In: Energy and Environmental Stress 1n Aouatlc Systems. Thomas Hunt
Morgan School of Biological Sciences, Lexington, Kentucky. Sel. Water Res.
Abs. 12, W79-09248.
B-27
-------
Boney, A.O., et al. 1959. The effects of various poisons on the growth and
vitality of soorelings of the red alga Plumaria elegans. (Bonnem.) Schm.
Schm. Biochem. Pharmacol. 2: 37.
Boschetti, M.M. and T.F. Mclouohlin. 1957. Toxicity of sodium arsenite to
minnows. Sanitalk. 5: 14.
Bryan, G.W. 1976. Heavy Metal Contamination in the Sea. Ir±' Marine Pollu-
tion, Part 3. Academic Press.
Calabrese, A., et al. 1973. The toxicity of heavy metals to embryos of the
American oyster, Crassostrea virginica. Mar. Biol. 18: 162.
Cardwell, R.D., et al. 1976. Acute toxicity of selected toxicants to six
species of fish. Ecol. Res. Series EPA 600/3-76-008. U.S. Environ. Prot.
Agency, o. 125.
Clemens, H.P. and K.E. Sneed. 1959. Lethal doses of several commercial
chemicals for fingerling channel catfish. U.S. Fish Wildl. Serv. Sci. Rept.
Fish. No. 316, Washington, D.C., U.O. Oep. Inter, p. 10.
Cowell, B.C. 1965. The effects of sodium arsenite and silvex on the plank-
ton populations in farm ponds. Trans. Am. Fish. Soc. 94: 371.
Crosby, O.G. and R.K. Tucker. 1966. Toxicity of aauatic herbicides to
Oaohnia magna. Science. 154: 289.
B-28
-------
Curtis, M.W., et al. 1979. Acute toxicity of 12 industrial chemicals to
freshwater and saltwater organisms. Water Res. 13: 137.
Ferguson, J.F. and J. Gavis. 1972. A review of the arsenic cycle in natu-
ral waters. Water Res. 6: 1259.
Fish Pesticide Research Laboratory. 1980. Unpublished laboratory data.
Columbia, Missouri.
Fowler, 8.A. 1977. International conference on environmental arsenic: An
overview. Environ. Health Perspect. 19: 239.
Gilderhus, P.A. 1966. Some effects of sublethal concentrations of sodium
arsenite on bluegills and the anuatic environment. Trans. Am. Fish. Soc.
95: 289.
Hale, J.G. 1977. Toxicity of metal mining wastes. Bull. Environ. Contam.
Toxicol. 17: 66.
Holland, A.A., et al. 1960. Toxic effects of organic and inorganic pollu-
tants on young salmon and trout. State of Washington, Dep. Fish. Res.
3ull. No. 5.
Holm, T.R., et al. 1979. Reprinted from ACS Symposium Series No. 93.
Chemical Modeling in Aoueous Systems, E.A. Jenne, (ed.). Am. Chem. Soc.
B-29
-------
Huqhes, J.S. and J.T. Oavis. 1967. Effects of Selected Herbicides on Blue-
gill Sunfish. ]£: Proc. 18th Ann. Conf., S.E. Assoc. Same Fish Comm.,
October 18-21, 1964. Clearwater, Florida. S.E. Assoc. Game Fish Comm.
Columbia, S.C. D. 480.
Inglis, A. and E.L. Davis. 1972. Effects of water hardness on the toxici-
ty of several organic and inorganic herbicides to fish. Bur. Sport Fish
Wildl. Tech. Paper 67. U.S. Deo. Inter, p. 22.
Maclnnes, J.R. and R.P. Thurberg. 1973. Effects of metals on the behavior
and oxygen consumption of the mud snail. Mar. Poll. Bull. 4: 185.
Nelson, O.A., et al. 1976. Biological effects of heavy metals on juvenile
bay scallops, Arqooecten irradians, in short-term exposures. Bull. Environ.
Contam. Toxicol. 16: 275.
Nelson, K.W. 1977. Industrial contributions of arsenic to the environment.
Environ. Health Perspect. 19: 31.
Sanders, H.O. and O.B. Cope. 1966. Toxicitles of several pesticides to two
soedes of cladocerans. Trans. Am. Fish. Soc. 95: 165.
Sanders, H.O. and O.B. Cope. 1968. The relative toxicities of several pes-
ticides to naiads of three species of stoneflies. Limnol. Oceanogr.
13: 112.
8-30
-------
Sorenson, E.M.8. 1976a. Toxicity and accumulation of arsenic in qrsen
fish, Lepomis cyanellus, exposed to arsenate in water. Bull. Environ. Con-
tarn. Toxicol. 15: 756.
Soreson, E.M.8. 1976b. Ultrastructura! changes in the hepatocytes of green
sunfish, Lepomis cyanellus Rafinesoue, exoosed to solutions of sodium arse-
nate. Jour. Fish 3iol. 8: 229.
Sorenson, E.M.3. 1976c. Thermal effects on the accumulation of arsenic in
green sunfish, Leoomis cyanellus. Arch. Environ. Contam. Toxicol. 4; 3.
Soehar, R.L., et al. 1980. Comparative toxicity of arsenic compounds and
their accumulation in invertebrates and fish. Arch. Environ. Contam.
Toxicol. 9: 55.
Soeyer, M.R. 1974. Some effects of combined chronic arsenic and cyanide
ooisoning on the physiology of rainbow trout. M.S. Thesis, Concordia Univ.,
Montreal, Canada.
Soeyer, M.R. and G. Leduc. 1975. Effects of Arsenic Trioxide on Growth of
Rainbow Trout. In: International Conference on Heavy Metals in the Environ-
ment. Toronto, Ontario, Canada. October, 1975.
Surber, E.W. and O.L. Meehean. 1931. Lethal concentrations of arsenic for
certain aauatic organisms. Trans. Am. Fish. Soc. 61: 225.
8-31
-------
U.S. EPA. 1978. In-deoth studies on health and environmental impacts of
selected water pollutants. U.S. Environ. Prot. Agency. Contract No. 68-01-
4646.
U.S. EPA. 1980a. Unpublished laboratory data. Environ. Res. Lab., Duluth,
Minnesota.
U.S. EPA. 1980b. Unpublished laboratory data. Environ. Res. Lab.,
Narragansett, Rhode Island.
8-32
-------
Mammalian Toxico1ogy and Human Health Effects
EXPOSURE
Inqestion from Water
In a U.S. Environmental Protection Agency national study of residential
tao water, 66.3 percent of the one-time grab samples collected from 3,834
"esidences had arsenic levels greater than 0.1 ug/1. The average, minimum,
and maximum arsenic levels of the samples were 2.37, 0.50, and 213.6 ug/1,
respectively (Greathocise and Oaun, 1978). In 1975 it was reported that 5
out of 566 samples collected from Interstate Carrier Water Supplies exceeded
10 ug/1 and that the maximum level was 60 ug/1 (U.S. EPA, 1975). Well water
samples collected during 1976 at 59 residences in a Fairbanks. Alaska sur-
burban community had a mean arsenic content of 224 ug/1 with a range from
1.0 to 2,450 "9/1 (u-s- Public Health Service, 1977). Valentine, et al.
(1979) reported that arsenic levels in the water supply from five communi-
ties (Fairfax and Edison in Sakersfield. California; and Virginia Foothills,
Hidden Valley, and Fallon in Nevada) to be 6, 393, 51, 123. and 98 ug/7, re
spectively.
There have been a number of other reports of isolated instances of high-
er than usual concentrations of arsenic in well waters. Goldsmith, et al.
(1972) reported on a study, in Lassen County, California, of the health ef-
fects associated with drinking well waters with arsenic levels ranging from
100 ug/1 or less to 1,400 ug/1. In Perham, Minnesota, a newly bored well
was associated with illness in 13 people whose hair samples contained arsen-
ic at 37-1,680 ug/g. The well water serving these patients contained arsen-
ic from 11,800 to 21,000 ug/1; this was later determined to come from ground
contamination by residual arsenical grasshopper bait (Feinglass, 1973).
C-l
-------
forty-five out °f 558 water samples collected from Lane County, Oregon had
arsenic values greater than 50 ug/1. The mean, maximum, and minimum values
detected were 9.6, 2,150, and 0 ug/1, respectively (Morton, et al. 1976).
^ch information nas been collected concerning the levels of arsenic in
fresh surface waters (Table 1). Arsenic occurrence is very widespread and
even occurs in some rain water. Most of the high values reported in rivers
and lakes are probably due to industrial contamination [National Academy of
Sciences (NAS), 1977al. Angino, et al. (1970) have shown that household de-
tergents (mostly of the high-phosphate type) widely used in the United
States contained arsenic at 1-73 ug/g; their use probably contributes sig-
nificant amounts of arsenic to surface sources. Sollins (1970), however,
felt that, after dilution during use, the concentration would be well below
the recommended maximum and constitute no particular hazard. It has been
Generally assumed that surface waters, like the ocean, are "self-purifying"
with respect to arsenic - i.e., arsenic is removed from solution by deposi-
tion with sediments; but quantitative studies are lacking. Sediments are
always higher in arsenic than the waters with which they are associated
(NAS, 1977a).
Inoestion from Food
A 1966 food survey found arsenic in 3.2 percent of the samples at a
range of 0.10 to 4.7 ug/g (Cummings, 1966). In a 1967 market-basket survey,
arsenic was present in 10 percent of the composite samples (Ouggan and Lips-
comb, 1969). In 1968, arsenic occurred in 18 percent of the samples.
Whether arsenic occurred naturally or as a result of man's activities was
not known.
Schroeder and Balassa (1966) sampled foods and beverages from American
chain stores (Table 2). Fish and seafoods contained the most arsenic
C-2
-------
TABLE 1
Arsenic in Fresh Surface Waters
Arsenic Concentration
Water
Reference
United States
Lakes:
New York, Chautauqua
Michigan
Superior
Wisconsin
California, Searles
Florida, Echols
Florida, Magdelene
Rivers:
Hillsborough
Withlacoochee
Fox (polluted watershed)
Yellowstone
Narrow
Providence
Seekoink
Sugar Creek
(contaminated)
Columbia
Schuylkill
Canals:
Florida
3.5-35.6
0.5-2.4
0.1-1.6
4.0-117
198,000-243,000
0.0-llOa
0.0-2,000b
3.58
1.75
0.25
0.42
100-6,000
4.5
0.90
0.75-0.90
2.48-3.45
10-1,100
1.6
30-180
10-20
Lis and Hopke, 1973
Seydel, 1972
Seydel, 1972
Chamberlain and Shapiro, 1969
White, et al. 1963
Livingston, 1963
Livingston, 1963
Braraan and Foreback, 1973
Braman and Foreback, 1973
Braman and Foreback, 1973
Braman and Foreback, 1973
Brown, et al. 1973
Ellis, 1934
Ray and Johnson, 1972
Ray and Johnson, 1972
Ray and Johnson, 1972
Durum et al. 1971:
Wilder, 1972
Onishi, 1969
Kopp, 1967
Grantham and Sherwood, 1968
03
-------
TABLE 1 (cont.)
Water
Arsenic Concentration
ng/1
Reference
Puget Sound
Rainwater:
Rhode Island
Washington, Seattle
Chile
Formosa, Mel) water
1.5-1,200
0.82
17
800
800
Crecelius, et al. 1975;
Crecelius and Carpenter, 1974
Ray and Johnson 1972
Crecelius, et al. 1975
Borgono and Greiber, 1972
Fan and Yang, 1969
Dissolved solids, <2,000 mg/1
Dissolved solids, >2,000 mg/1
C-4
-------
TABLE 2
Arsenic in Foods*
(wet weight)
Arsenic Micrograms of
Food Sample Concentration Arsenic
(ug/D 100
Fish and sea food
Haddock
Kingf ish
Oysters, fresh
Oysters, frozen
Scalloos, fresh
Shrimp, fresh frozen
Shrimo Shells
Clams, fresh frozen
Conch, fresh
Conch, dried, whole
Meats
Beef, stewing
Pork loin
Pork liver, No. 1
°ork liver, No. 2
Pork kidney
Lamt choo
Chicken breast
Gelatin
Egg lecithin
Vegetables and grains
Wheats, whole
Rye, seed
Corn
Corn meal
Corn oi 1
Corn oil lecithin
Rice, Madagascar
Rice, U.S.
Puffed rice
Kelloggs' Special K*
Cottonseed oil
Beets
2.17
8.86
2.9
2.7
1.67
1.50
15.3
2.52
3.1
5.63
1.3
0.06
1.07
1.4
0.0
0.35
0.0
0.19
0.0
0.17
0.16
0.11
0.78
0.0
0.0
0.48
0.13
1.6
0.66
0.0
0.0
305
886
580
540
160
132
—
525
311
311
58
21
75
98
0
19
0
6
0
5
5
3
22
0
0
13
3
46
19
0
0
05
-------
TABLE 2 (cont.
Food Sample
Arsenic
Concentration
(ug/i)
*Source: Schroeder and Balassa, 1966
aCalorie values from McCance and Widdowson, 1947
Micrograms of
Arsenic per
100 cala
Vegetables and grains (cont'd)
Seet greens
Swiss charci
Rhubarb
Red pepper
Garlic, fresh
Cherry tomatoes
Yellowpear tomatoes
Turnip
Mushrooms
Soy lecithin
Vegetables, St. Thomas, V.I.
Carrots
Peas, dried
Peas, fresh
Tomatoes, fresh
Egg plant
Ginger
Fruits
Apple
Orange
Pear
Grapes, wild
Miscel laneous
Cocoa, Hershey's®
Coffee
Tea
Salt, table
Salt, sea
Sugar, lump
Sugar, granulated
Milk, evaporated
Milk, dry skimmed
Butter, unsalted
0.24
0.56
0.48
0.06
0.24
0.37
0.10
0.0
2.9
0.0
0.0
0.09
0.0
0.0
0.82
0.0
0.0
0.0
0.0
0.17
0.59
0.0
0.89
2.71
2.83
0.10
0.0
0.17
0.0
0.23
240
215
800
„_
__
264
70
0
414
0
0
3
0
0
546
0
0
0
34
13
0
«.
_
_
3
0
11
0
3
C-6
-------
and fruits contained the least. Generally, the only foods which are high in
arsenic are seafoods. Chapman (1926) found that mussels, oysters, and scal-
lops contained very high levels of arsenic (means of up to 30 yg/g). In
comparison, mixed freshwater fish contained a mean of 0.65 ug/g arsenic.
Zook, et al. (1976) reported that in a survey of selected seafoods for metal
content, the overall arsenic mean content was 2.6 ug/g. The lowest mean
arsenic value was found in wild catfish -0.1 ug/g. Thus, arsenic appears
to be present in small amounts in nearly all foods, with marine inverte-
brates containing the highest arsenic levels (Table 3).
A bioconcentration factor (BCF) relates the concentration of a chemical
in aauatic animals to the concentration in the water in which they live. An
appropriate BCF can be used with data concerning food intake to calculate
the amount of arsenic which might be ingested from the consumption of fish
and shellfish. Residue data for a variety of inorganic compounds indicate
that bioconcentration factors for the edible portion of most aquatic animals
are similar, except that for some compounds bivalve molluscs (clams,
oysters, scallops, and mussels) should be considered a separate group. An
analysis (U.S. EPA, 1980a) of data from a food survey was used to estimate
that the per capita consumption of freshwater and estuarlne fish and
shellfish is 6.5 g/day (Stephan, 1980). The per capita consumption of
bivalve molluscs is 0.8 g/day and that of all other freshwater and estuarine
fish and shellfish is 5.7 g/day.
Spehar, et al. (1980) obtained bioconcentration factors of zero for four
different arsenic compounds in rainbow trout, but a 8CF of 4 was obtained
with the blueqill (U.S. EPA, 1978). Thus, the BCF for arsenic is probably
about 1.0 for many aquatic animals a BCF of 350 was obtained for sodium
arsenite with in oysters. If the values of 350 and 1 are used with the
C-7
-------
TABLE 3
Bioaccumulation Ratio Values for Arsenic
in Acuatic Organisms3*
Species
Haddock
Kingf ish
Crustacea and shellfish
Assorted fish
Assorted fish
Shrimp
Mackerel
Cod
Assorted freshwater fish
Arsenic in
Tissue
(ug/I)
2-10.8
8.86
1.5-3.1
0.018-1.06
0.076-2.27
-------
consumption data, the weighted average bioconcentration factor for arsenic
and the edible portion of all freshwater and estuaHne aauatic organisms
consumed by Americans is calculated to be 44.
Oecelius (1977a) has analyzed 19 samples of domestic table wines for
several species of arsenic; 13 varieties of white and red wines were in-
cluded. The Canoes of concentrations were <1-420 ug/1, <1-110 ug/1, and
<1-530 ug/1 for arsenite, arsenate, and total arsenic, respectively. Mean
levels were 127, 32, and 153 ug/1, respectively. Clearly, the majority of
the arsenic was present as arsenite. Both dimethylarsinic acid and methyl -
arsonic were below the detection limit of 1 wg/1 in these wine samples.
In 1966 Schroeder and Balassa (1966) estimated that the average daily
diet contains 900 ug of arsenic. This estimate was based on the results of
arsenic determinations for meats, sea food, and vegetables purchased from
Vermont chain stores. Arsenic in an institutional diet was estimated to be
400 ug per day. One reason for this lower level is that the institutional
diet did not contain any seafood. The World Health Organization reported
that arsenic intakes vary from 7 to 60 ug per day (NAS, 1977a). Jelinek and
Corneluissen (1977) reported that the Food and Drug Administration (FOA) has
monitored for arsenic in its Total Diet Survey since inception of the pro-
gram. The data from this program indicated that the average daily intake
for arsenic trioxide has decreased from about 130 wg/day in 1968 to about 20
ug/day in 1974. It is likely that the differences among the estimates of
total daily intake are partially due to variations in the species of arsenic
considered.
Arsenic was known as a therapeutic agent to the ancient Greeks and Ro-
mans. The introduction of Salvarsan (arsphenamine) by Ehrlich at the turn
C-9
-------
of the century gave rise to intense activity on the part of the organic
chemists, and it is estimated that more than 32,000 arsenic compounds were
synthesized (NAS, 1977a).
The advent of penicillin disposed of antiluetic arsenicals, and other
newer drugs have nearly eliminated the use of other organic arsenicals. In
current Human therapeutics, arsenicals are of importance only in the treat-
ment of certain tropical diseases (Harvey, 1975).
Inhalation
Suta (1978) has evaluated atmospheric arsenic concentration data for
1974 in 267 locations representing a resident population of more than
58,000,000 people. The annual average concentrations for all sites ranged
from below the detection limit to 83 mg/m . The mean of the annual average
concentrations for all locations was 3 mg/m . The average concentration
for eiaht locations near nonferrous smelters was 30 mg/m , and the average
concentration for eight locations in remote rural areas was 0.4 mg/m , as-
suming a concentration of zero for samples reported as below detection lim-
it. The lower detection limit for an individual arsenic sample is 1 mg/m
(Suta, 1978).
Suta (1978) has estimated air arsenic concentrations and exposed popula-
tion numbers associated with major manmade sources of arsenic in the atmos-
phere (Table 4). He states that due to the paucity of relevant data and in-
formation, the large number of required assumptions, and the inherent inac-
curacies of the modeling approach, the accuracy of these exposure estimates
cannot be judged quantitatively. It should be noted that the exposure
concentrations shown in the table are annual averages. Exposures for se-
lected times may be much higher or lower than the annual averages. Popula-
tion exposures for concentrations below 3 mg/nr are not given because they
C-10
-------
TABU 4
Estimates of Collation Exposures to Arsenic far Selected Emission Sources'
Emission Source
Average Annual
Concentration*
<«9/«5)
I.O-5.9
1.0-?. 9
0.60-0.99
0.30-0.59
0. 10-0.?9
O.t)6<>-0. 099
0.030-0.059
0.010-0.029
O.OOS-0.009
0.003-0.004
Copper
Smelters*
2.200
--
17.500
2H.OOO
92,000
2Btt,000
20,000
Mb ,000
23/.000
lead
Shelters':
JJOO
2.600
5,100
38.000
46.000
67,000
I\*c
Shelters'*
22.000
48.000
134.000
6V). 000
1.202,000
1.642.000
Cotton Pestle Me
Gin* Manufacturer'
5
100
200
700
2.000
J.OUO
5.900
20.000 60
Sb.OOO BOO
1)5,000 11.900
Gloss
Manufac tun ni)9
ISO
2«.,OOO
169.000
1. 251.000
1,534.000
6.0b<4,000
9,490.0m)
•Sroirce: Sula. 1978
*Aver*oe QMiiillrect ion«l concentrations. With the exception of cotton gin exposures, 24-hr worst-case
c*n be estiMted by MMilliplyinq the <»muj*l averiqes of 12.5. The 24-hr worst-case exposures for cotton yini may be
obtained by «wltiplyinq the concentrations by 81.
leased on EPA's esti«ale of stack emissions. Assumes 10 percent fugitive emissions.
cHased on an emission of 0.5 Ib of arsenic per each ton of lead produced. Fugitive emissions are estiHMieil lu be
10 percent of stack Missions.
''Based on an emission of (.3 Ib of arsenic per ton of tine produced by pyrometal lurgical ^Melters and no sldik
Missions at electrolytic shelters, fugitive emissions assumed to be 10 percent of the I.) Ib/ton slack emtbiiitm
for all spellers.
eAnnual averaqe exfHisure. assuming that ginnlitg exposures occur during 15 percent of lite year and that there are no
exposures duftiM) the reminder of the year.
'ASSUMES that all large plant pesticide enisslons are well control led.
lAssuwes that 25 percent of pressed and blown glass is manufactured with arsenic and that only certain «idiiufjitur-
ers use arsenic in all of their pressed and blown glass production.
C-ll
-------
are assumed to be equal the average urban background concentration. Popula-
tion exposures are not given for concentrations below 10 mg/rrr for some
cocoer smelter alternative estimates, because to do so would have required
extrapolation of modeling results beyond 20 km for the source. At these
areater distances, the accuracy of the modeling results became increasingly
uncertain.
It is quite apparent from these qualified estimates that in some areas
of the country, the general population is exposed to high levels of atmos-
oheric arsenic when compared to ambient levels in uncontaminated areas.
Klemmer, et al. (1975) analyzed 61 samples of dusts collected from homes in
Hawaii for arsenic content and found that the levels ranged from 33 to 1,080
ug/g. Since house dust has been implicated as a significant source of human
oesticide burden, it may also be a significant source of arsenic exposure in
some homes.
Dermal
No information was found concerning the levels and/or duration of dermal
exoosure to arsenic. Since arsenic compounds are used in insecticides,
herbicides, fungicides, algicides, sheepdips, wood preservatives, and dye-
stuffs and for the eradication of tapeworm in sheep and cattle (NAS, 1977a),
it seems likely that the dermal route may be a source of arsenic exposure
for some segments of the population.
PHARMACOKINETICS
Adequate understanding of arsenic toxicology is heavily dependent upon
clear delineation of differences between various arsenic forms or compounds,
e.g., organic versus inorganic arsenic compounds or tHvalent versus penta-
valent inorganic arsenic species, in terms of various pharmacokinetic as-
oects, e.g., adsorption, metabolism (especially in vivo biotransformations),
C-12
-------
distribution, and excretion. Important new information regarding different-
ial characteristics of various arsenic forms in regard to such aspects has
emerged in the scientific literature during the past 5 years, but has only
recently begun to be critically evaluated in regard to its full meaning and
implications. In addition, newly emerging evidence has recently been re-
oorted suggesting a possible essential role for arsenic in some mammalian
soecies, carrying with it potential implications for analyses of arsenic
toxicology. A thorough critical assessment of literature bearing on the
above issues appears in the recently prepared EPA Health Assessment Document
for Arsenic (U.S. EPA, 1980b).
Absorption
The major routes of arsenic exposure of significance for general public
health are inhalation and ingestion, either via direct intake of food and
water or secondary to the inhalation of arsenic in a form and size whereby
it undergoes retrocilliary movement and is eventually swallowed. Inhalation
is probably of more significance in occupational settings, while oral intake
is a more widespread exposure route for the population at large. Percutan-
eous absorption of arsenic, while poorly studied, can occur in man, based on
isolated reports, but appears to be a relatively minor route of exposure ex-
cept under certain occupational exposure conditions.
Confusing the picture of arsenical absorption is the importance of the
chemical form of the arsenical. In some studies, this has been known with
more certainty than in other studies and it is difficult at times, to dis-
cern clearly relative uptake or absorption characteristics for various ar-
senic forms under different exposure conditions.
The extent of respiratory absorption of arsenic adsorption depends on
chemical species of arsenic and the particulate size, assuming that the air-
borne arsenic comoound is in the form of an aerosol. Smaller-sized parti
cles (
-------
greater subsequent absorption likely via the alveolar parenchyma than for
larger-sized particles. Larger particles tend to be deposited mainly in the
upper portion of the respiratory tract, undergo retrodliary movement, and
ultimately are swallowed, with arsenic absorption then determined by the
characteristics of gastrointestinal uptake. Precise relative rates of up-
take and absorption of airborne arsenic compounds, therefore, depend upon
the size of arsenic-associated particles generated from particular emission
sources. In the case of emissions from high-temperature combustion sources,
such as smelters and coal-fired power plants, emissions of arsenic and other
toxic trace metals were found by Natusch, et al. (1974) to be mainly in the
highly respirable size range of
-------
Animal data have also been reported on arsenic absorption via the respi -
ratory tract. Bencko and Symon (1970) observed that hairless mice breathing
a solid aerosol of fly ash containig 180 ug As/nr for several weeks had
increases in tissue arsenic values. Since the particle size was determined
to be only less than 10 urn, part of this intake may have occurred via the GI
tract. Increases in tissue arsenic in two exposure groups also occurred
when rats were exposed to arsenic trioxide (condensation aerosols: 1.0,
3.7, and 46 ug/m^) for 90 days (Rozenshtein, 1970). Similarly, relatively
rapid absorption of pentavalent arsenic was noted by Outkiewicz (1977) when
rats were exposed intratracheally (arsenate solution labeled with arsenic -
74; 0.1 and 4.0 mg/kg). Arsenic tissue distribution dynamics were similar
for the intratracheal and a companion intravenous exposure study, indicating
that the rate of arsenic uptake intratracheally resembles parenteral admini-
stration more than oral or percutaneous exposure.
In man and experimental animals, factors which govern gastrointestinal
absorption of arsenic include both the chemical form of the element and its
physical characteristics. It can be stated that soluble arsenicals will be
generally more extensively absorbed than the insoluble forms. On the other
hand, one should be cautious in extending data for simple water solubility
to the chemical milieu existing in the GI tracts of various species.
Taken collectively, the reports of Coulson, et al. (1935), Ray-3ettley
and O'Shea (1975), Oecelius (1977), and Mappes (1977) demonstrate that very
substantial gastrointestinal absorption of soluble inorganic tHvalent
arsenic occurs. Greater than 95 percent of inorganic arsenic taken orally
by man appears to be absorbed, with less than 5 percent of the administered
amount appearing in feces (Coulson, et al., 1935; Ray-8ettley and O'Shea,
1975).
C-15
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Consistent with this, Mappes (1977) observed that daily intake orally of
an aqueous solution of -0.8 mg tnvalent arsenic led to a daily urinary ex-
cretion rate of 69 to 72 percent of the daily intake by a human subject.
Also, Oecelius (1977) reported that ingestion of 50 ug trivalent and 13 ug
oentavalent inorganic arsenic in a wine sample led to 80 percent of the
total 63 ug of arsenic appearing in urine within 61 hours. Oecelius
(1977), however, reported that ingestion of well water mainly containing
identified pentavalent inorganic arsenic led to urinary clearance of half of
the intake of -3 days. Absence of fecal arsenic data preclude determining
fecal loss or body retention of the remaining half.
In contrast to the relatively high absorption rate for soluble inorganic
arsenic, Mappes (1977) reported that insoluble arsenic triselenide
(AsjSe^), when taken orally, passes through the GI tract with negligible
absorption.
While available data for human GI tract absorption of As£03 taken UP
via inhalation are sparse, the report of Smith, et al. (1977) strongly sug-
gests that levels of arsenic trioxide entering the GI tract of smelter work-
ers strongly correlate with urinary arsenic levels.
Analysis of arsenic intake via the diet of nonoccupationally exposed
populations requires that one consider the issue of bioavailability and dif-
ferences in the manner in which arsenic forms are incorporated into the mat-
rix of various foodstuffs. In terms of concentration levels and bioavaila-
bility factors, the arsenic content of crustaceans and other marine foods
warrants special comment.
The so called "shrimp" or "seafood" arsenic present in crustaceans and
other fish appears to represent a complex organic form of the element which
has recently prompted considerable study (LeBlanc and Jackson, 1973; Westoo
C-16
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and Rydalv, 1972; Munr0, 1976; Edmonds, et al. 1977; Penrose, et al. 1977;
Oecelius, 1977; Edmonds and Francesconi, 1977). In brief, the results of
such studies indicate that the arsenic present in shellfish and other marine
foods appears to be extensively absorbed and rapidly excreted intact as a
complex organoarsenical by man and animals and, as such, does not appear to
oose a oarticular health threat to man. Thus, it is not appropriate to con-
sider high human arsenic intake from diets heavy with "seafood" arsenic as
representing relevant exposure inputs for estimating the likely toxicity po-
tential associated with overall exposure of population segments to inorganic
arsenic via multimedia routes.
Studies of the oral intake and absorption of arsenicals in experimental
animals generally confirm the findings derived from the above human studies.
More specifically, soluble inorganic arsenic, in either trivalent or penta-
valent solutions, is almost completely absorbed from the GI tract of rats
(Coulson, et al. 1935), with 88 percent absorption was observed for arsenic
trioxide solution (Urakabo, et al. 1975; Dutkiewicz, 1977) and 70 to 90 per-
cent for arsenate solution. Similar observations have been made in pigs
(Munro, et al. 1974), with 90 percent of arsenic trioxide solution being
absorbed, and monkeys (Charfaonneau, et al. 1978a) with 98 percent of arsenic
trioxide being absorbed. Charbonneau, et al. (1978a) fed arsenic-containing
fish (Atlantic grey sole) to adult female monkeys as a homogenate (1 mg fish
arsenic/kg body weight) and noted that about 90 percent was absorbed, of
which about 75 percent appeared in urine after 24 days. In a related study,
swine and adolescent monkeys were seen to absorb approximately 70 to 50 per-
cent, respectively. On the other hand, arsenic trioxide in suspension given
orally to rabbits and rats was reported to result in only about 40 and 30
oercent absorption, respectively (Ariyoshi and Ikeda, 1974).
C-17
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The effect of nutritional status or dietary factors on arsenic absorp-
tion has not been well studied, although interactive relationships between
arsenic and elements such as selenium are known. Tamura et al. (1977)
showed that rats given arsenic trioxide in either milk or cereal diets had
no differences in fecal excretion patterns of arsenic over a 6-month period.
Nozaki, et al. (1975), using ligated rabbit intestine, demonstrated that
phosphate, casein, and a casein hydrolysate all inhibited trivalent arsenic
uotake. Tsutsumi and co-workers (1976) found that co-administration of
metal chelanting agents, such as dimercaprol (BAL), thioctic acid (TA), or
74
diisopropylaminodichloroacetate (DAOA), with As labeled arsenate into
the GI tract of the rat resulted in markedly retarded enteric absorption of
the arsenical, compared to controls receiving the labeled arsenate alone.
Little information exists on the extent of cutaneous absorption into the
bloodstream of inorganic arsenic by human subjects. Evidence for skin
absorption sufficient to induce clinical manifestations of arsenic poisoning
stems from case reports of either individual accidents with arsenic tri-
chloride (Delepine, 1922,1923; Buchanan, 1962), arsenic acid solution (Carb
and Hine, 1977), or (arsenical paste) (Robinson, 1975). Patty (1948) notes
that arsenic passage through epidermal lesions is more rapid than with nor-
mal skin suggesting that, in the case of industrial activity, the skin burns
elicited by arsenic contact permit easier passage of arsenic into the deeper
layers of the integument.
Dutkiewicz (1977) found that skin absorption of arsenic in the rat using
solutions of arsenate, was significant and the uptake rate via the tail was
as high as 33.1 wg/cm /hour using concentrations up to 0.2 molar. The
2
corresponding absorption in man, using 700 cm as the surface area for
C-18
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both hands, was calculated to be as much as 23.2 mg/hour; and tissue levels
of arsenic from dermal contact resembled the distribution dynamics of oral
exoosure.
Potential fetal exposure to toxic elements via transplacental passage
from the mother is of major importance given the potential sensitivity of uj_
uterp development to diletarious impacts of exogenous toxic agents.
In a study of maternal-newborn tissue sets for arsenic, Kagey, et al.
(1977) reported that cord blood levels approximate those of mothers in 101
subject sets. Tissue analysis (Kadowaki, 1960) of fetus arsenic in a pre-
sumably healthy Japanese population indicated measurable arsenic levels at
least by the fourth month of gestation and increasing to the seventh month.
Of importance here is the observation that brain levels, as well as those of
bone, liver, and skin, were the highest of all tissue tested. Since the
relative amounts of arsenic passing the blood-brain barrier in adult animals
appears to be small relative to uptake in other soft tissues, these data
sugaest that the human fetal nervous system may be particularly vulnerable
to arsenic exposure early in development.
Complicating the issue is the chemical nature of the tissue arsenic as-
sayed in either of the two studies noted above, inasmuch as precise chemical
speciation was not attempted. Also, the Japanese study presumably did not
select material in a manner such that dietary histories could be discerned.
Thus, Questions can be raised regarding full implications of these data for
toxicological analyses.
Transplacental transfer of arsenic has also been demonstrated in experi-
mental animals, For example, rapid transplacental transfer has been demon-
strated in hamsters given arsenate parenterally (Perm, 1977; Hanlon and
C-19
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Perm, 1977), with embryonic tissues showing levels close to those in mater-
nal blood 24 hours after dosing. Tnvalent arsenic, given as such, also re-
sults in transplacental passage in pregnant rats. Arsenic has been detected
in newborn rats when the dams received arsenic trioxide in the diet.
Distribution
Analysis of the -available literature dealing with the tissue distribu-
tion of inorganic arsenic must be tempered by current awareness that i_n_ vivo
biotransformations of arsenic occur in many species and distribution dynam
ics involve the transformation products as well as any intermediates or
original exposure forms.
Blood is the main vehicle for transport of arsenicals from absorption
sites to various tissues, with the hemokinetic character of arsenic being
dependent on the animal species studied. It is readily apparent from the
literature that the rat constitutes an anomalous model for studies of the
fate of inorganic arsenicals vn vivo and this includes the clearance behav-
ior of blood-borne arsenic in the rat (Hunter, et al. 1942; Ducoff, et al.
1948; Lanz, et al. 1950; Ariyoshi and Ikeda, 1974; Klaassen, 1974; Tsut
sumi and Kato, 1975; Outkiewicz, 1977). In the case of the rat, arsenic in
blood is only slowly cleared following exposure, with about 80 percent of
the total blood arsenic content localized in the erythrocyte. The half-
times of blood clearance for inorganic arsenic in the rat (trivalent or
pentavalent) is of the order of 60 to 90 days (Lanz, et al. 1950; Ariyoshi
and Ikeda, 1974). Given the recent data of Odanaka, et al. (1978), cited
earlier, it 1s possible that erythrocyte arsenic is present as the dimethyl -
ated form.
Arsenic in the blood of other species — man (Ducoff, 1948; Mealey, et
al. 1959), mice (Lanz, et al. 1950; Oema, 1955), rabbit (Hunter, et al.
C-20
-------
; Ducoff, 1948; Klaassen, 1974), dog (Lanz, et al. 1950; Hunter, et al.
1942), and the primate (Hunter, et al. 1942; Klaassen, 1974) —whether
given as the pentavalent form or as trivalent form, is rapidly cleared.
In some of these species, a three-compartment model for clearance is ap-
parent. Qverby and FredMckson (1963) calculated half-times of ~6 hours for
the raoid phase, a slightly longer time for the second phase and a slow
ohase of -60 hours.
Clearance of arsenic in dog and man was also found to fit a three com
oartment model by Charbonneau, et al. (1978b) with half-times of 1, 5, and
35 hours, respectively. When contrasted with the work of Tarn, et al.
(1978a), which reported the time dependent j_n vivo methylation of arsenic
and excretion, the various components presumably relate to initial excretion
of inorganic arsenic, followed by clearance of dimethylarsenic.
Very little information is available concerning the molecular character
of binding in either erythrocytes or plasma, and what little older data is
available must be viewed in the light of what is presently known about i_n_
vivo changes in arsenical forms.
In the rat erythrocyte, arsenic appears to be associated with the pro
tein moiety of hemoglobin (Hunter, et al. 1942; Lanz, et al. 1950). Labeled
arsem'te (As), when given to a human subject, appeared to be associated
in plasma with *1-globulin (Musi! and Oejmal, 1957).
Biliary transport of arsenic has been reported for a number of species.
8ile excreted arsenic is reabsorbed. Cikrt and Sencko (1974) noted that the
rat had a higher biliary excretion rate for trivalent than for the
oentavalent form (-10:1). Klaassen (1974) noted that the biliary excretion
rate was much greater for the rat than for either the rabbit or the dog.
Biliary transport data for man is not available.
C-21
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The tissue partitioning of arsenic in man has been studied using both
autopsy and dosing data. Kadowaki (1960) found that heart, kidney, liver,
and lung contained the highest levels of arsenic (0.04 to 0.05 ppm, wet
weight) of the soft tissues, with skin, hair, teeth, bone, and nails --
arsenic storage organs -- housing the highest absolute amount. Brain tissue
(0.03 ppm wet weight) had an arsenic level slightly lower than other soft
tissue. Uebscher and Smith (1968), analyzing tissue samples from nonex-
posed sources in Scotland, observed lung to have the highest levels (0.08
ppm dry weight), with liver and kidney levels (0.03 ppm dry weight) not
materially different from other soft tissue. Like the Kadowaki study, stor-
age organs such as bone, hair, nails, and teeth had the highest overall
levels.
In addition to the autopsy studies by Kadowaki (1960) and Uebscher and
Smith (1968), Larsen, et al. (1979) have recently reported on a detailed
study of the topographical distribution of arsenic in normal human brain
tissue. The study results (for 5 persons, 15 to 81 years of age) revealed
widespread distribution of arsenic throughout essentially all of 24 brain
areas sampled, with markedly higher concentrations of arsenic in white mat-
ter (2.4-5.2 ng/g wet tissue) than in grey matter (1.2-2.6 ng/g wet tis-
sue). These arsenic concentrations in centra.l nervous system white matter
are not significantly different from arsenic concentrations reported earlier
for peripheral nerves (Larsen, et al. 1972), leading to the interpretation
by Larsen, et al. that the metal is likely preferentially accumulated in
neural tissue components (e.g., myelin) high in lipids, phospholipids, or
phosphatides. This interpretation is consistent with the proposition by
Schroeder and Balassa (1966) that arsenic has a predilection for accumula-
tion in fat.
C-22
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The above findings appear to be rather consistent in regard to the over-
all patterns of tissue distribution of arsenic based on human autopsy mate-
rial. However, since the above studies were carried out with little atten-
tion to dietary histories, particularly the predominance of seafood in diet,
it is difficult to compare the study results in absolute quantitative terms
or to draw orecise conclusions from them regarding trends in tissue accumu-
lation with age. Kadowaki's data for infants and elderly subjects, never-
theless, suggest some age-dependent accumulation in skin and kidney. Also,
the above studies do not provide a basis for assessing possible differential
tissue distribution of tri - or pentavalent-inorganic arsenic. Other studies
indicate, however, that when human subjects are exposed to trivalent arsenic
parenterally, highest levels of arsenic are seen in liver and kidney
(Hunter, et al. 1942; Ducoff, et al. 1948; Mealey, et al. 1959).
Exposure of various species to either tri- or pentavalent arsenic leads
to the initial accumulation of the element in liver, kidney, lung, spleen,
aorta, and skin (Hunter, et al. 1942; Ducoff, et al. 1948; Lanz, et al.
1950; Peoples, 1964; AriyosM and Ikeda, 1974; Cikrt and Bencko, 1974; Kla-
assen, 1974; Tsutsumi and Kato, 1975; Urakabo, et al. 1975; Dutkiewicz,
1977). With the exception of the rat, a species in which metabolism of
arsenic is only a very limited model for study of this element (vide supra),
clearance from soft tissue is rather rapid except for the skin, where the
high sulfhydryl group content probably promotes tight arsenical binding. As
also seen with human tissue, arsenic is apparently lodged in the brain of
experimental animals exposed to arsenic, with slow clearance reported
(Crema, 1955).
The more-or-less similar tissue distribution profiles for both tri- and
pentavalent arsenic in various species probably reflects the common bio-
C-23
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transformation oathways for inorganic arsenic that have been described ear-
lier. It should be noted, however, that since presacnfice perfusion of
animals in these studies was not carried out, part of the arsenic tissue
burdens reported may be attributable to trapped blood. This might, for ex-
ample, account for at least part of markedly elevated tissue levels noted
for spleen.
Metabolism
The understanding of assimilation of inorganic arsenic by man and other
mammalian soecies is substantially complicated by a series of ne«1y-
-------
Oecelius (1977) reported the urinary excretion of form variable arsenic
when a human subject ingested arsenic in known oxidation state or other
chemical forms. Ingestion of a wine sample of known arsenic content and
fori (50 ug trivalent and 13 ug pentavalent) was followed in about 61 hours
by major clearing of the 63 ug of arsenic: 50 oercent as dimethylarsenic
acid, 14 aercent as monomethyl arsenic, and 8 percent each in the two
inorganic forms.
Consumotion of well water containing 200 ug arsenic as arsenate by a
subject in the same study showed urinary trivalent arsenic at near back-
ground levels with an elevation in pentavalent form as well as increased ex-
cretion of dimethylarsenic. Determining exact percentages of eacn excreted
form was complicated by recovery of but half of the ingested amount. Arsen-
ic as contained in canned crab tissue was also studied in this experiment.
It would appear that arsenic is present in marine foods in an organic form
which is excreted intact, but from which dimethylarsenic may be liberated by
chemical treatment.
The study of Smith, et al. (1977), using basically the same speciation/
analysis techniaues noted in the previous study and involving urinary pro-
files for a group of copper smelter wokers, also confirmed transformation
processes i_n_ vivo (Table 5). In controls as well as in three study groups
that varied as to intensity of airborne trivalent arsenic oxide exposure,
dimethylarsenic was the dominant species in urine, followed by methyl arsen-
ic, trivalent arsenic, and pentavalent arsenic.
Interestingly, the correlation of dimethylarsenic with airborne exposure
composed a tighter fit than total arsenic. Furthermore, both fine resp-ir.
able and larger (>5 urn) fractions of arsenic trioxide particulate correlated
with all four forms measured, with a stronger relationship seen for t"e
C-25
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TABLE 5
Concentration of Arsenic In Urine and Airborne Samples
Test and Control Groups*
Urinary
Species
AS (III)a
As (V)a
Methyl arsonic adda
Dimethylarsinic acid*
Total urinary arsenic
Arsen1cb
Control
(n-41)
1.3(1.58)
1.31(1.59)
3.4(1.63)
11.5(1.47)
21.2(2.04)
3.6(1.56)
Low As
Exposure
(n-30)
2.2(2.19)
1.6(2.32)
4.9(2.13)
17.0(1.96)
24.7(2.01)
8.3(3.43)
As concn. (SD)a
Medium As
Exposure
(n-23)
4.8(2.08)
2.4(2.86)
9.7(1.90)
32.7(1.71)
51.8(1.61)
46.1(3.05)
High As
Exposure
(n-30)
8.6(2.62)
3.1(3.64)
20.8(2.55)
64.1(2.42)
66.1(2.14)
52.7(6.61)
*Source: Smith, et al. 1977
aAll concentatlons are expressed as yg/1 of elemental arsenic, geometric mean (standard deviation).
^All constituent concentrations are expressed as ng/m^ geometric mean (standard deviation). Con-
trols had 56.1 percent of samples less than detectable (<1.2 ug As/m3) and the low group had 20
percent less than detectable.
C-26
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portion, i.e., that portion wnich mainly enters the body via the GI
tract. It may be seen that while the relative amount of dimethylarsenic
acid, (which may be considered a detoxification form) is invariant over the
various exposure groups, the relative amount of trivalent arsenic (particu-
larly in comparison to pentavalent arsenic) increases almost linearly with
increasing exposure. This increase in trivalent arsenic with increasing ex-
posure to airborne arsenic is further suggestive evidence that it is the
trivalent form of arsenic j£ vivo that mainly accounts for toxic effects
seen in man and is consistent with dose-response relationships for various
health effects found in epidemiologic studies.
Reports in the literature dealing with the interconversion of trivalent
and pentavalent arsenic in man are sketchy. Mealey, et al. (1959) noted
that administration of As trivalent arsenic parenterally to human clini-
cal subjects resulted in excretion of levels of "pentavalent" arsenic that
ranged from about 60 percent 1 day post-dosing up to 80 percent with further
time. The method employed involved the acidification of urine samples with
hydrochloric acid followed by benzene extraction. Trivalent arsenic is ex-
tracted by benzene, but the pentavalent form remains. Since this separation
approach differentiates tri - and pentavalent inorganic arsenic {later bio-
analytically confirmed by both Mushak, et al. 1977 and Reinke, et al. 1975)
as well as methyl arsonous from methylarsonic and dimethyl arsinous from
cacodylate (Mushak, et al. 1977), it is probable that the "arsenate" frac-
tion was a mixture of cacodylic, methyl arsenic, and inorganic pentavalent
arsenic. Since the amount of "arsenate" determined was greater proportion-
ally than any contaminating level in the parenteral dose, conversion to
arsenate and methylated forms had occurred.
'-27
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One subtle aspect of this Deport, however, is that mono- and, more im-
portantly, dimethylarsenic in these urine samples existed as dimethylarsenic
(cacodylic) rather than dimethylarsinous acid. Were the case otherwise,
i.e., methylated arsenic in lower oxidation state, then extraction into ben-
zene from hydrochloric acid solution of the lower-state methyl arsenicals
would have occurred, as indicated by the observations of tfushak, et al.
^1977). This does not preclude the possibility that sufficient oxygenation
of urine samples occurs in the process of collection to allow oxidation j_n
situ, but the work of both Smith, et al. (1977) and Oecelius (1977) indi-
cates that whatever artifactive oxidation in urine post-collection may oc-
cur, at least measurable inorganic trivalent arsenic remains and at levels
proportional to exposure to the trivalent form.
A number of animal studies also provide data regarding the character and
Quantitative aspects of in vivo transformation processes of inorganic arsen-
ic. Of necessity, the weight placed on these studies is tied to the quality
of the methods of analysis and their ability to chemically speciate the var-
ious forms. This also necessitates retrospective scrutiny of methods used
in the earlier literature since the more reliable speciation techniques -e
of recent origin.
To date, transformation processes involving arsenic and experimental
animals have been reported for the dog (Lakso and Peoples, 1975; Tarn, et al.
1978,1979; Charbonneau, et al. 1979), cow (Peoples, 1964; Lakso and Peoples,
1975), mouse (Bencko, et al. 1976), and rat (Winkler, 1962; Ginsburg, 1965;
Odanaka, et al. 1978).
Lakso and Peoples (1975) noted that the oral exposure of both dogs and
cows to either arsenite or arsenate led to conversion of either valency form
C-28
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to methylated arsenic with about 50 percent conversion to methyl arsenic,
which may formally be considered pentavalent. The method used did not per
nit distinction between valency forms of inorganic arsenic.
Several more recent studies Have provided more detailed data as to arse-
nic transformation processes in the dog. Tarn, et al. (1978,1979) exposed a
arouD of docs to radiolabeled f As) arsenic acid given intravenously.
The levels of inorganic, monomethyl -, and dimethylarsenic were then timemon
itored in urine and plasma using an ion-exchange chromatographic tecnnigue.
While inorganic arsenic is the major species in plasma up to about 2 hours
post-dosing, dimethyl arsenic formation can be detected as early as 10 min-
utes affc?r administration. By 6 hours, virtually all (90 percent) plasma
arsenic is in the dimethyl form, with little monomethyl species detected.
Oimethylarsem'c was the major form in the urine from days 1-6. In a compan-
ion study, Tarn, et al. (1978b) used thin-layer chromatography to further
speciate the inorganic arsenic fraction into both pentavalent and trivalent
arsenic. Charbonneau, et al. (1978a,b) noted that when labeled arsenic acid
(As) was given to dogs intravenously, about four-fifths of the arsenic
lodged in the red cells, with dimethylarsenic being detected in those cells
about 10 minutes after dosing. With time, the arsenic content is partition-
ed between cells and plasma, total conversion being seen by 6 hours. At
about 1 hour, dimethylarsenic is detected in the urine. These data indicate
participation of the erythrocytes and liver in dimethylation and transport
of the dimethylated species.
Of interest, here are the data of Odanaka, et al. (1978), who fed ferric
methanearsonate to adult male rats and analyzed the blood, urine, and feces
for the amount of various speciated arsenical forms. Dimethyl arsenic was
detected in urine, feces, and blood, indicating methylation of monomethyl
C-29
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arsenic j_n vivo. While dimethylarsenic was in minor amounts in urine and
feces, blood arsenic was mainly present as dimethylarsenic. For analysis,
these workers used thin-layer chromatography for separation of the arseni
cals and gas-1iauid chromatography in tandem with mass spectrometry to con
clusively determine the structure of the organoarsenicals as mono- and di-
methylarsenic.
The Odanaka, et al. (1978) oaper is of significance on several counts:
(1) it demonstrates that methyl arsenic can be methylated to dimethylarsenic
and, hence, the monomethyl form can be an intermediate in the inorganicdi
methylarsenic transformation (since these authors took pains to assure the
purity of the methyl arsenic administered, it is ^niikely that the dimethyl
form arose from contaminating inorganic arsenic); (2) mass spectral analysis
confirms the presence of dimethylarsenic in arsenic transformations in the
rat and, by inference, other animal models reported; (3) the minor amounts
of dimethylarsenic in urine or feces and the major amounts in blood suggest
selective retention of dimethylarsenic by rat erythrocytes. When contrasted
with the Charbonneau, et al. (1978a,b) data noted previously, it appears
that in both rat and dog the erythrocyte is at least the transport vehicle
for dimethylarsenic, but, unlike the dog erythrocyte, release of dimethyl -
arsenic into rat plasma is much slower. This is consistent with other known
facts of arsenic distribution in the rat as noted below.
In light of the preceding reports regarding methylation processes, ear-
lier reports dealing with trivalent-to-pentavalent-arsenic conversion or the
reverse must be viewed carefully.
_In vivo conversion of trivalent inorganic arsenic to the pentavalent
form has been reported by several authors. Infusion of arsenite (trivalent)
intravenously in dogs led to the detection of tri - and pentavalent arsenic
C-30
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in olasma, urine, and glomerular filtrate (Ginsberg, 1965). tinkler fi962!
noted that livers of rats fed arsenite contained mainly arsenate. *^e "lore
Decent study of Bercko, et a". (1976) is particularly significant in that
fivalent arsenic conversion to the pentavalent form in mice was demonstrat-
ed using oaper chromatographic techniaues for separation and removal of
urine samples through the bladder to minimize artifactive oxidation of tri-
valent arsenic. It was noted that the relative amounts of pentavalent arse-
nic formed from radio-isotopic ( As) arsenite hinged on the time lapse
after pretreatment with a large dietary level (250 mg/1) in drinking water.
In animals preexposed for 13 days prior to dosing with the labeled arsenate,
virtually no trivalent arsenic was found in urine. Since dimethylarsenic
acid was not tested in Bencko's chromatographic system, it is possible that
this was the form being identified as pentavalent inorganic arsenic.
The case for HI vivo reduction of pentavalent arsenic to the trivalent
fonn is sketchier, mainly due to analytical methods employed. The aporoach
of Lanz, et al. (1950), who reported some reductive conversion of arsenate,
entailed precipitation as a mixed salt, the residual solubility of which
could have been enough to account for the amount labeled as soluble triva-
lent arsenic (MAS, 1977a). The Ginsberg (1965) report employed an extrac-
tion/chelation separation method involving acidified samples and removal of
trivalent arsenic wfth chloroform containing ethyl xanthate. Since ethyl
xanthate is a thioli'c chelanting agent and pentavalent arsenic is very lab-
ile in acid, interaction of the chelatinq agent with pentavalent arsenic to
form arsenic (III) and some disulfide (R-S-S-R) cannot be discounted. Using
doos dosed with arsenate, the origin of the trivalent portion of the inor-
ganic arsenic fraction as isolated and measured, i.e., _i_n vitro versus jjn
vivo formation, cannot be definitely established (Tarn, 1978).
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As can best be oresently determined, demethylation of methylated arsen-
ics formed jji vivo does not occur. Support for this is chiefly from data of
Stevens, et al. (1977), who saw no evidence of j_n_ vivo demethylation when
animal were exposed to dimethylarsinic acid (cacodylic acid).
Several experimental animal studies suggest that some induction of a
tolerance to arsenicals may arise in arsenic pretreated animals that are re-
exoosed. Bencfco and co-workers (Bencko and Symon, 1969, 1970; Sencko, et
al. 1976) have found that arsenic pretreatment of mice will markedly alter
the subseauent tissue distribution and excretion data of a radio-isotopic
arsenic pulse. The mechanism of this process is not understood,, but must
include the efficiency of the i_n_ vivo methylation process(es) described ear-
lier.
In summary;
1. Pentavalerit and trivalent arsenic in both man and animals undergo
jm vivo transformation mainly to dimethylarsinic acid, which pro-
bably was misidentified as pentavalent inorganic arsenic in early
studies.
2. The i_n vivo conversion of pentavalent inorganic arsenic to the tri -
valent forms remains to be conclusively demonstrated, but cannot De
ruled out based on presently available information.
3. Methylation of inorganic arsenic can be considered as detoxifica-
tion in that cacodylic acid is much less toxic than the inorganic
forms,
4, As a detoxification process, methylation efficiency appears con-
stant as a fraction of total speciable arsenic, although the rela-
tive amount of trivalent arsenic will increase with increasing ex-
posure.
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5. However, as a detoxification process, it can eventually be over-
whelmed or Codified as is apparent from the extensive literature on
arsenic toxicology in man and animals.
5. At least in some species, dimethylarsenic formation involves the
erythrocyte and the liver in biosynthesis and transport.
Excretion
3enal clearance appears to be the major route of excretion of absorbed
arsenic in man and animals, biliary transport of the element leading to
enteric reabsorption with little carriage in feces.
In a study assessing the utility of urine arsenic measurement in occupa-
tional exposure settings, Nappes (1977) reported excretion data for both
single and multiple daily dosing for a human subject ingesting arsenite sol-
ution. By 3 hours, renal excretion was maximal, with about one-auarter of
the single dose appearing in the urine by day 1 post-exposure. With succes-
sive arsenite ingestion (0.8 rng As), daily urinary clearance after 5 days
was two-thirds of daily intake.
Crecelius (1977) noted that arsenic in wine [50 ug As (III), 13 ug As
(V)l after ingestion led to a measured level in urine of -80 percent after
61 hours. Oral ingestion of arsenic (V) in well water (200 ug), however,
led to about 50 percent urinary excretion by 3 days after ingestion. Mealey
(1959) measured urine arsenic in patients given trivalent arsenic by intra-
venous administration, with -60 percent of the dose amount appearing in the
urine by 24 hours. Hunter, et al. (1942) noted considerable variance, 30 to
80 percent after 4 to 5 days, in urinary clearance of arsenic given parent-
erally in a group of human subjects.
As might be predicted from the j£ vivo behavior of arsenicals in the
rat, urinary excretion of arsenic in this species is very slow, due to
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erythrocyte retention on the order of 2 to 5 percent of the arsenic intake
by several days post-dosing (Coulson, et al. 1935; Ariyoshi and Ikeda,
1974). Urakabo, et al. (1975) calculated a half-time of 84 days for arsenic
in the rat.
Slow clearance of arsenic from the rat gave rise to the widely held as-
sumption for many years that arsenic is one of the elements that accumulate
in the body. Other species excrete arsenic rapidly. Mice, rabbits, swine,
dogs, and monkeys clear the majority of injected trivalent arsenic within 24
hours, with excretion usually being ^70 percent within that time period (Ou-
coff, et al. 1948; Oema, 1955; Munro, et al. 1974; Lakso and Peoples, 1975;
Tarn, et al. 1978a; Charbonneau, et al. 1978b). Other studies also indicate
rapid urinary clearance of arsenic given in the pentavalent form to species
other than the rat (OuPont, et al. 1942; Ginsberg and Lotspeich, 1963; Peo-
ples, 1964; Lakso and Peoples, 1975). Some calculated half-times for either
tri- or pentavalent arsenic urinary clearance are: mice, injected trival-
ent, -4.5 hours; dogs and cows, oral tri- or pentavalent, -36 hours.
Deposition of arsenic in such organs as hair and nails can be considered
an excretory mechanism for arsenic. Although hair analysis has had a long
history in arsenic's chemical and forensic literature, for reasons of both
analytical convenience and the possibility of establishing an exposure his-
tory from sectional analysis, many questions remain unanswered. The rela-
tionhsip between arsenic deposition in hair and various exposure parameters
has not been well defined on a Quantitative basis nor are the physiological
mechanisms well understood. The chemical nature of hair arsenic is also
largely unknown.
The long-held view of arsenic as an element that accumulates in the body
was mainly based on the behavior of arsenic in the rat, an animal model
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which in retrospect was the least helpful in understanding the fate of the
toxicant i_n vivo for other mammalian species and man.
Based on current arsenic elimination data for all mammalian species
studied other than the rat (vide supra), one concludes that marked long-term
accumulation of arsenic generally does not occur in physiologically vital
components of the body. This is in contrast to, say, marked long-term lead
accumulation in bone or cadmium accumulation in renal cortex. Autopsy tis-
sue data for human subjects of different ages is not conclusive regarding
possible long-term tissue accumulation. Kadowaki (1960) did observe higher
mean levels of arsenic in skin and kidney samples of subjects about 50 years
of age versus infant values, but dietary histories of the subjects were not
available to allow for differentiation of increases in arsenic levels due to
current versus past exposures for the older subjects. Deposition in hair is
really excretory in nature, not accumulative.
Brune, et al. (1980) have reported that lung tissue from retired smelter
workers, on autopsy, had median values for- arsenic which were approximately
8 times higher than that for a control group. Kidney and liver values, how-
ever, were not significantly different between smelter worker groups and
controls. Arsenic accumulation in the lung of smelter workers even after
several years of retirement and removal from workplace exposure (interval of
2-19 years) suggests that a very insoluble form of arsenic exists in smelter
ambient air and is inhaled by these workers. That this form may be arsenic
sulfide is further suggested by the study of Smith, et al. (1976) who *ound
that the respirable air within the confines of a copper smelter contained
arsenic sulfide. These two studies have implications for the issue of occu-
pational respiratory carcinogenesis associated with arsenic exposure.
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EFFECTS
Acute. Subacute, and Chronic Toxicity
The multiplicity of organ systems and tissues affected in the manifesta-
tion of clinical symptoms of acute poisoning and in the production of sys-
temic health effects associated with subacute or chronic exposure to the
metal reflect well the widespread impact of arsenic in certain subcellular/
biochemical processes common to cellular components of many different types
of tissues. At the same time, certain distinctive features of arsenic sys-
temic toxicity, e.g., its marked effects on the skin, are better understood
in light of the intercession of the metal into particular biochemical pro-
cesses most intensely characteristic of selected cells or tissue types,
e.g., those comprising the integumentary system. The possibility of arsenic
playing a beneficial role, at very low trace levels, as hinted at by newly
emerging evidence for its essentiality 1n some mammalian species, is also
best evaluated within the context of a discussion of the impact of the metal
in subcellular/biochemical mechanisms.
The following discussion focuses on those data dealing with inorganic
arsenic interactions at the biochemical and subcellular level which have the
most relevance for understanding the i_n vivo toxic effects of the agent in
man and experimental animals.
Several reviews (Peters, 1955; Vallee, et al. 1960; Johnstone, 1963;
Webb, 1966) have described the effects of various arsenicals on enzymes and
enzyme-mediated processes in a number of species. Many of these studies
have entailed either purified preparations, where question of relevance to
J_n vivo conditions can be raised, or heterogeneous, complex systems where
the site of interaction(s) is left in doubt.
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The literature dealing with effects of trivalent arsenic on enzymes is
rather extensive, while that for pentavalent arsenic is considerably more
soarse. This stems in large measure from the widely accepted fact that it
is the trivalent form which can chemically interfere directly with enzyme
action via formation of arsenic-sulfur bonds with those thiol groups which
oarticipate ^n either enzyme structure or function.
Webb (1966) has tabulated no less than 78 enzymes from a wide variety of
soecies which have been reported to be inhibited to a varying degree by tri-
valent arsenic (arsenite) at concentrations of 0.01 to >10 millimolar. Al-
though various classes of enzymes are sensitive to arsenite, the oxidizing
enzyme systems appear to be particularly vulnerable, including: pyruvate
oxidase, 0-amino acid oxidase, 2-glutamic acid oxidase, monoamine oxidase,
liver choline oxidase, and glucose oxidase.
Evidence in support of thiol binding as the biochemical site of enzyme
inhibition includes: (1) all of the oxidase systems noted above can be re-
activated with glutathione, a thiolic biochemical factor (Sarron and Singer,
1943); (2) lipoic acid is a cofactor in a number of these enzyme systems and
possesses proximal thiol groups expected to react readily with trivalent
arsenic to form a highly stable five-membered heterocycle (Vallee, et al.
1960). Such effects not only provide good clues as to the biochemical basis
for arsenic toxicity but also support the premise that arsenicals are gen-
eral metabolic poisons.
One particularly important oxidizing enzyme systems sensitive to arsenic
is the pyruvate dehydrogenase (POH) complex which plays a crucial role in
cellular energetics. The pyruvate dehydrogenase complex consists of three
distinct enzymes: (1) pyruvate dehydrogenase (pyruvate decarboxylase), (2)
C-37
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dehydrolipoate transacetylase, and (3) dihydrolipoated hydrogenase. Arsen-
ite could interfere with the latter two enzymes via binding to the proximal
thiol groups of lipoic acid, while any effects on pynjvate decarboxylase are
likely to be associated with the inactivation/activation reaction controlled
by a phosphorylation/dephosphorylation process (Linn, et al. 1969).
Decently, Schiller, et al. (1977) studied the pynjvate oxidation system
using liver mitochondria from rats fed pentavalent arsenic (up to 85 ppm As
in drinking water) in order to pinpoint the site of arsenic interaction in
the enzyme complex. Pynjvate dehydrogenase (enzyme 1 of the complex) activ-
ity was measured before and after activation |£ vitro. Basal activity be-
fore activation was reduced by 48 percent at 3 weeks in the animals fed 85
ppm As. The inhibition of pymvate dehydrogenase activity both before and
after activation suggests a direct effect on pyruvate utilization not invol-
ving lipoic acid.
Since the activation/deactivation process for POH requires that phos-
phate bind at some point to both POH and the phosphatase and kinase enzymes
involved in activation/deactivation, arsenate presumably interferes by com-
peting with inorganic phosphate. Thus, in this particular system, effects
are imparted by both pentavalent (Schiller, et al. 1977) and trivalent arse-
nic (Webb, 1966). Inhibition of the POH system by arsenic influences the
operation of the tricarboxylic acid cycle, with decreased acetyl-Co A forma-
tion and subsequent decrease in NADH generated for ATP formation. Fatty
acid synthesis and storage triglycerides are also affected.
Inorganic arsenic in the trivalent form has also been known to interfere
with active transport processes and this literature has been critically re
viewed by Webb (1966). Substance transport that is inhibited includes: po
tassium, sodium, rubidium, hydrogen Ion, halide, monohydrogen phosphate,
C-38
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water, proplonate, glucose, certain amino acids, marker dyes, and streptomy-
cin. According to Webb (1966), it is difficult to ascertain whether arsen-
ate has a specific effect on transport or whether the process reflects a
general lesioning of cellular respiration by the arsenical. Some evidence
suggests that the chief mechanism of transport inhibition involves pyruvate
oxidation inhibition (Davenport, 1955).
Arsenite is known to be a potent inhibitor of chicken liver xanthine
dehydrogenase and related molybdoflavoproteins (Rajagopalan and Handler,
1964, 1967; Peters and Sanadi, 1961; Palmer, 1962) and probably interacts
with the molybdenum center in these enzymes (Coughlan, et al. 1969). John-
son and Rajagopalan (1978), using electron paramagnetic resonance (EPR) sig-
nal modification from molybdenum, found the site of arsenite interaction to
be a reactive group within the molybdenum complex required for electron
transfer from purine substrate to the enzyme and is probably a sulfhydryl
unit binding the metal atom, a persulfide residue, or possibly the metal it-
self.
Although inhibition of enzymes due to arsenicals has been more heavily
studied, enzyme activation by arsenicals is also known to occur (Webb,
1966). This includes activation of cytochrome oxidase of rat brain at an
arsenate concentration of 1.0 millimolar, catalase malate dehydrogenase of
pig heart at 30 milUmolar and, apparently, enzyme systems associated with
drug detoxification. For example, Ribeiro (1971) noted that trivalent arse-
nic oxide reduced hexobarbitone anesthesia time in mice although
hexobarbitone oxidation and amlnopyrene demethylation rates were unaltered.
Also, Wagstaff (1978), studying the effects of dietary arsenic trioxide on
hexobarbitone sleeping time, oxidation cleavage of 0-ethyl-0-p-nitrophenyl
C-39
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phenylphosphonothioate (EPN), and 0-domethylation of p-nitroanisole in rats
at 100 to 5,000 ppm As, found moderate enzyme induction by trivalent arsenic
but phenobarbital induction of the enzyme system was unaffected.
Unlike arsenite, pentavalent arsenate appears to exert biochemical ef-
fects via interference with phosphate transport and phosphorylation (NAS,
1977a; Fowler, et al. 1977), through uncoupling of mitochondria! oxidative
phosphorylation, presumably via competitive replacement of inorganic phos-
phate by arsenate to form a highly labile arsenate ester that decomposes.
Also, arsenate stimulates succinate-controlled respiration of rat liver mi-
tochondria, an effect retarded by addition of phosphate (Crane and Lipman,
1953); and mitochondrial ATPase is stimulated by arsenate (Azzone and Erns-
ter, 1961; Wadkins, 1961), the stimulation being offset by inorganic phos-
phate. Arsenate inhibition of mitochondrial respiration may occur via com-
petition with phosphate during oxidative phosphorylation and/or inhibition
of NAD reduction by succinate (Mitchell, et al. 1971). Rats chronically ex-
posed to arsenate show decreased state 3 respiration and respiratory control
ratios in renal and liver mitochondria (Brown, et al. 1976), associated with
swelling of the organelle in both organs.
From the above, it can be seen that the mitochondrion is one cellular
organelle particularly vulnerable to the effects of inorganic arsenic either
as arsenite or arsenate (Webb, 1966; Fowler, 1977a; NAS, 1977a). Mitochon-
dria readily take up arsenic and various i_n_ vivo and i_n_ vitro studies indi-
cate that biochemical lesioning includes NAD-coupled mitochondrial
respiration, uncoupled oxidative phosphorylation and interference with steps
in the heme blosynthetic pathway which are intramitochondrial (Fowler,
19775).
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Arsenate causes mitochondria! swelling both j_n vitro (Packer, 1961; De-
Master and Mitchell, 1970; Mitchell, et al. 1971) and in vivo (Fowler, 1974,
1975; Brown, et al. 1976). Effects on liver mitochondria after prolonged
oral exposure of rats to arsenate (20, 40, 85 ppm in drinking water) were
found by Fowler et al. (1977) to include pronounced UT_ situ mitochrondrial
swelling in the 40 and 85 ppm^As exposure group animals, as well as lipidic
vacuolization and fibrosis. These structural changes were associated with:
(1) decreased state 3 respiration and respiratory control ratios for pyruv-
ate/malate but not succinate; and (2) marked increase in specific activity
of monoamine oxidase and cytochrome oxidase, sited in inner mitochondria!
membranes. Effects of arsenate on these membrane marker enzymes suggests
direct interaction with membranes, resulting in increased permeability or
conformational change. The mechanism of these effects is probably arsenate
interference in phosphorylation processes required for functioning of pyruv-
ate dehydrogenase, the first enzyme in the pyruvate oxidation complex
(Schiller, et al. 1977).
In a related study, Woods and Fowler (1977) saw a pronounced effect of
oral arsenate administration (1.2, 2.2, and 3.5 mg As/kg; 6 weeks) on rat
mitochondria! heme biosynthesis, with heme synthetase activity decreased to
63 percent of control levels at the highest exposure level, 3.5 mg As/kg,
and a resulting porphyrin urea.
Incubation of respiratory rat liver mitochondria with arsenate for 20
minutes at 2*C followed by removal of the agent results in uncoupled respir-
ation with succinate (Bhuvaneswaran, et al. 1972). Since most of the arsen-
ate in this study was removed prior to oxidative phosphorylation assay, un-
coupling of succinate oxidation is not an arsenolytic process. Interesting-
ly, the mitochondria! preparation was capable of limited glutamate/malate or
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3-hydroxybutyrate oxidation (AOP/0 values of 1.3 to 1.6). Further study of
this system (Bhuvaneswaran and Wadkins, 1978) indicates that arsenate treat-
ment preferentially decreases the coupling capacity of mitochondria at sites
2 and 3. In related work, Bhuvaneswaran and Wadkins (1977) found that a
small fraction of arsenate added to the mitochondrial preparation could not
be amoved even with trichloroacetic acid treatment. Since arsenic binding
does not occur with cyanide, oligomycin, or inorganic phosphate, the binding
is associated with an electron transport chain and energy-coupling reac-
tions. Dissociation of the complex could be achieved after partial restora-
tion of oxidative coupling at sites 2 and 3, i.e., ATP addition.
Harris and Achenjang (1977) found that uptake of arsenite by rat liver
mitochondria to be energy-dependent and inhibited by mersalyl or N-ethymale-
imide. Two modes of uptake were kinetically discernible and may involve
both membrane thiol attachment and accumulation of free or bound arsenite in
matrix space.
Fowler et al. (1978) studied microsomal and mitochondrial oxidative in-
teractions in preparations from livers of rats exposed orally to arsenate
(40 ppm in drinking water, for 6 weeks). Morphometric studies showed a
doubling of the ratio between rough endoplasmic reticulum surface density
and mitochondria! volume density in the arsenic treated animals. Microsomes
from arsenic-treated animals contained 20 percent less aminopyrine demethy 1-
ase activity compared to controls after mixing with mitochondria from con-
trol animal livers. These data point to an j_n_ vivo functional interaction
between mitochondria and microsomes with regard to oxidative processes, with
arsenate disturbing mitochondria! NAD-linked oxidative capability and reduc-
ing microsomal mixed-function oxidative capability.
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Tn addition to characterization of mitochondria! effects, numerous stud-
ies have focused on the interaction of arsenic with ONA as it relates to
chromosomal effects. Knowledge that arsenate can compete with phosphate in
phosphorylation processes, as noted earlier, has prompted suggestions that
arsenate occasions chromosomal abnormalities by substituting far phosphate
in the DNA chain (Petres and Hundelker, 1968; Petres, at al= 1970), This
hypothesis ignores the fact that arsenate esters are so much more labile
thermodynamicany than the phosphorus analogs that it is questionable if
such esters have other than transitory existence.
More likely is interference with DNA repair processes. Jung (1969.
1971) demonstrated decreased ONA repair following ultraviolet irradiation
and incubation of skin grafts in arsenate solution, concluding that "dark
repair" of DNA in these cells is inhibited. Results of studies by Rossman.
et al. (1977) on effects of UV light and arsenite on strains of £._ coll dif-
fering in DNA repair functions further implicate arsenite as interferring
with ONA repair processes. Observations by Grunicke. et al. (1973) that DNA
removal from tumor cells is retarded by either arsenate or arsenite suggests
that cross-linking of ONA and protein may be occurring.
In regard to the possible role of arsenic as an essential element at low
trace levels, early reports attempting to show a nutritional requirement for
the element in animals were inconclusive (MAS. 1977a; Underwood. 1977).
Part of the problem was undoubtedly technical In nature, i.e.. the diffi-
culty of carrying out such studies in an experimental environment where
rigorous exclusion of a ubiquitous element from the diet 1s necessary. More
recently, however, several carefully controlled studies appear to demon-
strate nutritional essentiality for arsenic in some mammalian species. For
example. Nielsen, et al. (1978) observed that feeding of arsenic-deficient
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diets to pregnant rats resulted in greater perinatal mortality among pups
from arsenic-deprived dams and post weaning deficits in growth, enlarged
spleens, and increased red cell osmotic fragility.
Anke, et al. (1978) also studied nutritional reouirements for arsenic,
using goats and mini-pigs and a semi-synthetic diet containing less than 50
ppb arsenic. Effects attributed to arsenic deficiency in both species oc-
curred in adult animals and their offspring. Arsenic deficiency increased
the mortality of adult goats as well as altering their mineral profiles for
copper and manganese. Significant reproductive effects for both arsenicde-
ficient goats and mini-pigs included reduction of normal birth percentages
and litter sizes; and the mortality of kids and piglets from the As-defic-
ient groups was significantly increased. Manganese levels were elevated in
As-deficient kids and piglets, but no perturbation of hematological indices
(hemoglobin, hetnatocrit, or mean corpuscular concentration) was noted.
This is in contrast to observations with rat (Nielson, et al. 1974),
where decreased hematocrits, elevated iron content in spleen, and increased
osmotic fragility of cells were seen. Given that the rat is known to be an
anomalous animal model for arsenic metabolism (see Metabolism section) how-
ever, these differences are probably peculiar to that species. Other evi-
dence for the likely essentiality of arsenic in the rat, includes the find-
ings of Schwartz (1977), who noted enhanced growth effects of arsenite on
rats fed an arsenic-supplemented diet. An optimal effect was seen at 0.25
to 0.5 pom, but pentavalent arsenic as sodium arsenate was less effective.
Despite the above evidence for possible arsenic essentiality in some
mammalian species, any physiological role for arsenic, the existence of any
specific carrier agent in the body, or other evidence of arsenic essentially
C-44
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in man remains to be independently demonstrated. Another factor complicat-
ing the issue is the fact that one usual feature of essential element meta-
bolism is homeostatic control of levels and movement of a particular element
j_n vivo. Based on information considered earlier, there appears to be no
effective absorption barrier for most soluble inorganic arsenicals, but ef-
ficient excretory mechanisms (kidney, hair) and biotransformation appear to
provide possible control over an absorption-excretion balance. The Question
of arsenic essentially in man is made even more interesting by the study of
Liebscher and Smith (1968) (see Metabolism section), who showed that arsenic
in human tissue appears in a log-normal distribution, a commonly observed
biostatistical characteristic of environmental contaminants rather than es-
sential elements. Put in terms of physiology, this says that contaminant
levels occur in tissues in simple proportion to the level of exposure, i.e.,
not under homeostatic control. However, such a biostatistical criterion
added to those of Mertz (1970) is complicated in the case of arsenic if one
does not know the specific partitioning of various chemical forms both uj.
vivo and in the human diet.
The more physiologically subjective issue of arsenic beneficiality,
particularly to man, merits some comment because the distinction between
beneficiality and essentiality is not always made. Given the historical
toxicological character of arsenic in man and animals, beneficial effects
from the past (or present) use of such "therapeutics" as Fowler's solution
(arsenite base), and arsenic pastes have not always been considered ;n a
framework of benefit-risk balance. The beneficiality of agents such as Fow-
ler's solution has required that the margin of risk perhaps be too narrow
between levels associated with both beneficial dose-effect and toxic'ty
C-45
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dose-effect resoonses. By contrast, the limited data on arsenic essentially
suggest a requirement for only very small trace amounts, leaving a huge gap
between essentiality and toxicity.
The Question of possible beneficial effects of arsenic also substantial-
ly involves the issue of interactive effects between arsenic and other sub-
stances, including certain important protective effects exerted by arsenic
in relation to reducing toxicity effects associated with excess exposure to
certain other trace metals.
Acute Toxicity
The typical systemic manifestations of arsenic poisoning due to inges-
tion usually include gastrointestinal disturbances (Dreisbach, 1971). The
intensity and onset of symptoms are determined to some extent by the physic-
al form of the arsenical, quantity ingested, and whether or not a meal has
been recently eaten. Hemolysis is the primary manifestation of arsine poi-
soning.
The first symptom of acute poisoning is often a feeling of throat con-
striction followed by difficulty in swallowing, epigastric discomfort, and
violent abdominal pain accompanied by vomiting and watery diarrhea (Buch-
mann, 1962). Intense thirst is usually present (Rentoul and Smith, 1973).
Cramps may be present in muscles of the lower limbs. Systemic collapse with
severe hypotension probably reflects widespread damage to the muscular sys-
tem. Death which is generally preceded by restlessness, convulsions, or
coma, may result from cardiac failure. In subacute poisoning, symptoms are
less intense. If death is not immediate, jaundice and oliguria or anuria
occur after 1 to 3 days (Oreisbach, 1971). The toxic action of arsenic on
the gut lining epithelium is seen microscopically as a cloudy swelling and
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fatty infiltration (Buchmann, 1962). In less severe cases of occasional oc-
cupational exposure, recovery often occurs and may either be complete or
followed by recurrent manifestations of symptoms characteristic of chronic
DOT soni ng.
Subacute and Chronic Toxicity
Several reports of acute arsenical posioning by ingestion have been
cited in the older literature (Reynolds, 1901; Mizuta, et al. 1956; Takane-
hara, et al. 1956; Yoshikawa, et al. 1960). An acute poisoning episode also
occurred more recently in two Indonesian orphanages from the ingestion of
arsenic-contaminated rice which was prepared independently in each orphanage
(Tjaij and Aziz, 1971). Laboratory analyses showed small amounts of arsenic
in the urine of five children and in the vomit of one child. Symptoms of
vomiting, abdominal pain, diarrhea, lassitude, dizziness, and headache ap-
peared in 109 children and 48 adults 1 to 2 hours after ingestion of the
rice. These symptoms were similar to these typically seen with the earlier
incidents and accidental poisonings.
The acute oral toxicity of arsenic trioxide using commercial grade
(97.77 AsjO-j with 1.18 percent Sb20^) and highly purified arsenic
trioxide (99.99 percent As^O^) was tested in mice and rats by Harrison,
et al. (1958). Test solutions were administered intraesophageally. For
Webster Swiss mice, acute oral LD^Q was estimated as 39.9 mg As/kg body
weight for purified As^ and 42.9 mg As/kg body weight for the commerc-
ial grade. The LD^Q for Sprague Oawley albino rats was 15.1 mg As/kg for
the pure ^2^2 and 23.6 mg As/kg for the crude form. While the IDjg
for the purified arsenic was lower in both species, the purified arsenic was
a less severe gastrointestinal irritant than the commercial form of arsenic
trioxide. Retching and gastrointestinal damage were attributed to the pre-
sence of antimony in the unpurified preparation.
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Several points regarding acute arsenic poisoning are of considerable in-
terest. For example, trivalent arsenic is widely held to be more toxic sys-
temically than the pentavalent form, based on both lethality data and
sublethal experimental studies. Although it is rarely possible to establish
precisely the exposure level in acute arsenic poisoning, Vallee, et al.
(1960) have estimated a human lethality dose of trivalent arsenic as the
oxide to be on the order of 70 to 180 mg. Individual susceptibility may be
much less. Holland (1904) described one patient showing subacute symptoms
to -8 mg of arsenic in Fowler's solution (alkaline arsenite).
The matter of reversibility or nonreversibility of acute poisoning symp-
toms is also quite important. Survivors of acute arsenic poisoning display
sequelae which involve the peripheral nervous, hematopoietic, cardiovascu-
lar, hepatic, and integumentary systems. The peripheral neuropathy, with an
onset of several weeks, usually involves the lower extremities and histolo-
gically, is manifested by long axon Wallerian degeneration, and can persist
for years (Ohta, 1970). Cardiac abnormalities range from certain electro-
cardiographic disturbances, included T-wave abnormalities, to eventual con-
gestive heart failure.
The anemia and leukopenia of acute arsenic poisoning appear to be re-
versible features. These are in contrast to the longer-lasting symptoms
such as skin lesions, Including erythematous eruptions followed by pigmenta-
tion and keratoses of the extremities, which are late-emerging sequelae of
subacute or chronic arsenic exposure. More detailed discussion of the organ
systems involved in subacute and chronic arsenic toxlcity is presented below.
Systemic exposure to amounts of arsenic sufficient to cause symptoms but
inadequate to produce systemic collapse is of particular interest for de-
velopment of human health criteria for arsenic exposure. The exposed pat-
ient may go for weeks or months with gradually increasing or variable signs
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and symptoms related to several organ systems and giving the appearance of a
progressive chronic disease state. If death occurs, it may appear to have
been the conseauence of the inexorable course of an obscure "natural" dis-
ease. Information bearing on the induction of arsenic toxicity effects by
subacute or chronic exposure of humans has been derived from case reports
and epidemiologic studies of people exposed via use of therapeutic arsenic-
als, homicidal or accidental poisonings, and occupational or environmental
exposures.
The literature describing the constellation of health effects observed
in connection with various such exposure conditions or circumstances is
briefly reviewed next, before assessment of salient information, including
data on dose-effect or dose-response relationships, bearing on arsenic-in-
duction of different specific classes or types of systemic health effects
delineated by the organ systems affected.
Health effects associated with medicinal or therapeutic uses arsenicals
have been best delineated in relation to the use of Fowler's solution. The
method of arriving at a therapeutic dose of Fowler's solution is based on
establishing a patient's tolerance to increasingly higher, but nontoxic
doses of arsenic. As described by Holland (1904), the patient was typically
given 5 drops (about 9 mg of arsenic trioxide, or 6.8 mg of arsenic) well
diluted, after meals (i.e., three times a day), increasing the dose one drop
daily until the disease is under control or until the eyelids puff and the
bowels move too freely. The dose is then reduced to a safer quantity, and
continued until the warning returns, when it is again reduced. For some
persons even the minimum dose will produce unpleasant effects; one case of
erythroderma has been reported after a patient received 10 mg of arsenic
trioxide (7.6 mg of arsenic) taken over a 2-day period.
C-49
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There are other case reports in the literature of subacute to chronic
arsenic poisoning due to the use of Fowler's solution. Silver and Waiimian
(1952) described a patient who ingested approximately 8,8 mg of arsenic tri-
oxide as Fowler's solution daily for a total period of 23 months, as a reme-
dy for asthma. Signs of arsenic poisoning, manifested as increased freckl-
ing and as darkening of the nipples, first appeared in association with gas-
trointestinal symptoms after 13 months; redness and puffiness about the eyes
and hyperkeratoses developed at approximately 1.5 years. Neurologic symp-
toms in the form of paresthesias and weakness were the last to be noted, oc-
curring after 2 years. When the arsenic intake was stopped, the pigmenta-
tion lightened, but the hyperkeratoses remained, and the asthma became more
difficult to control.
Also, Fierz (1965) examined 262 patients who had received long courses
of medicinal arsenic 6-25 years previously and found keratoses in 40 percent
and typical skin cancer in 8 percent. There was evidence of a dose rela
tionship for both keratoses and skin cancer. Patients who had received more
than 400 ml of Fowler's solution (4 g of arsenic trioxide) had an incidence
of hyperkeratoses of greater than 50 percent, but as little as 60 ml (600 mg
of arsenic trioxide) had resulted in keratotic changes in one patient. As
little as 75 ml (750 mg of arsenic trioxide) had been consumed by one pat-
ient with skin cancer. The shortest time to cancerous change was 6 years,
with an average of 14 years, compared with Neubauer's estimate of 18 years
(Neubauer, 1947). Fierz (1965) noted that 1,450 invitations for a free ex-
amination had been sent to patients who had been given the therapeutic arse-
nic. Beside the 262 who came for examination, 100 patients provided written
reports, and information was obtained about the deaths of 11. Five of the
11 deaths were due to systemic cancer, and three to lung cancer. Sixteen of
the 21 patients with cancer had typical keratoses (Fierz, 1965).
C-50
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In regard to health effects observed with homicidal and accidental poi-
soning cases, Holland (1904) used the information gained from personal ob-
servation and reports of suicide and criminal cases which used rat or fly
ooison, as well as Fowler's solution, to describe the effects of subacute
and chronic arsenic exposure. Occasionally, enthusiastic patients would
overdo their use of medicinal arsenic, but this was uncommon, because of the
associated discomfort. Holland described subacute poisoning as producing
loss of appetite, fainting, nausea and some vomiting, dry throat, shooting
pains, diarrhea, nervous weakness, tingling of the hands and feet, jaundice,
and erythema. Longer exposure resulted in dry, falling hair; brittle, loose
nails; eczema; darker skin; exfoliation; and a horny condition (hyperkera-
toses) of the palms and soles.
Mizuta, et al. (1956) reported on 220 Japanese patients of all ages who
had been poisoned by contaminated soy sauce, with an average estimated in-
gest ion of roughly 3 mg of arsenic (probably as calcium arsenate) daily for
2-3 weeks. In this group, 85 percent had facial edema and anorexia; fewer
than 10 percent had exanthemata, desquamation, and hyperpigmentation; and
about 20 percent had peripheral neuropathy. Except for headaches and fever,
the findings in these patients appeared to be very similar to those reported
by Reynolds (1901). Although the majority of patients' livers were en-
larged, relatively few abnormalities were found in liver-function tests; and
the histopathologic description of five liver biopsies did not reveal severe
degenerative changes. There were no findings suggestive of congestive fail-
ure, but electrocardiograms were abnormal in 16 of 20 patients, and this co-
nfirmed the reports of Josephson, et al. (1951) and Nagai, et al. (1956).
The symptoms tended to diminish after 5 or 6 days, despite continued intake
of arsenic, and neurologic symptoms became prominent as much as 2 weeks
C-51
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after arsenic ingestion was discontinued, at which time urinary arsenic con-
tent remained high. Hair was found to contain arsenic at 2.8-13.0 ug/g near
the root, compared with 0-1.5 ug/g near the end and 0.4-2.8 ug/g in hair
from control patients.
For a few months in 1955, a large number of babies in Japan received a
formula made from powdered milk contaminated with arsenic (Masahika and
Hideyasu, 1973; Okamura, et al. 1956a,b; Satake, 1955).
The subacute symptoms of poisoning in these infants included the usual
coughing, rhinorrhea, conjunctivitis, vomiting, diarrhea, and melanosis, but
the striking presenting features were fever and abdominal swelling secondary
to hepatomegaly. Abnormal laboratory findings included anemia, granulocyto-
penia, abnormal electrocardiograms, and increased density at epiphyseal ends
of long bones similar to the familiar "lead line". Nagai, et al. (1956) re-
ported on a group of these children who were followed for more than 6
months. Except for a measurable retardation in ulnar growth, they found
that all other features of the syndrome had disappeared, including melanos-
is. Follow-up is continuing, and a report by the Japanese Pediatric Society
(1973) indicated that growth was still reduced and that there was a probable
incidence 15-30 percent of leukomelanodemia in the children (at the ages of
17-20 months). The children had a 15 percent incidence of keratosis (vama-
shita, 1972). Of greater concern, however, was the observation of increased
incidences of mental retardation, epilepsy, and other findings that suggest-
ed brain damage in the arsenic-exposed children. Presumably, future studies
in this population (more than 10,000 exposed infants) will help to resolve
some of the standing questions regarding the latent effects of arsenic expo-
sure.
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In regard to occupational arsenic exposures, it Mas noted by Perry, et
al. (1948) that all of a group of chemical workers handling inorganic arsen-
ic compounds had pigmentary changes and that one third of them had "warts,"
although these were not well described. They reported that the cutaneous
"changes were so evident that (the examiner) could readily tell whether the
man . . , was a chemical worker." All these workers had increased urinary
arsenic compatible in degree with the extent of exposure; this indicates
systemic absorption of the arsenic from dust, probably through the lungs and
skin. High-exposure areas of the plant had arsenic concentrations ranging
from about 250 to 700 ug/m ,
Holmqvist (1951) also reported ezcematous and follicular dermatitis in
smelter workers, primarily on exposed skin. Patch tests showed sensitivity
to both trivalent and pentavalent arsenic. Birmingham, et al. (1965) re-
ported similar lesions that developed within a few months of the startup of
a gold smelter that handled ores containing large amounts of arsenic sul-
fide. Dermatitis developed 1n half the mill workers and 1n 32 of 40 stud-
ents in a nearby elementary school.
Butzengeiger (1940) reported that, of 180 vlnedressars and cellar-men
with symptoms of chronic arsenic poisoning, about 23 percent had evidence of
vascular disorders of the extremities. Arsenical insecticides were used in
the vineyards, and exposure occurred not only with spraying, but during work
in the vineyards by Inhalation of contaminated dusts and plant debris.
Sulfur and lime-sulfur were frequently applied in the same solution, or as a
dust with lead arsenate. In either event, arsenite is formed as a func-
tion of the contact time between the two materials. Most of the workers
consumed 1-2 liters of wine per day, especially that made from musk. It has
recently been shown by Crecelius (1977) that wine contains high levels of
C-53
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arsenite from reductioan during fermentation. Wine made from the musk con-
tains even higher levels of arsenite than normal. Exposure, therefore, to
arsenite would seem to be convincing in this population, with lesser expo-
sures of arsenate. All 15 workers with vascular disorders had hyperpigmen-
tation, and all but two had palmer and plantar keratosis; six of the 15 had
gangrene of the fingers and toes.
The same association of vascular disorders, hyperpigmentation, and kera-
tosis was observed in Taiwan (veh, 1963). Urinary arsenic content average
0.324 mg/liter, and hair arsenic, 0.39 ug/g. Butzengeiger (1949) reported
that the electrocardiograms of 36 of 192 vinegrowers with chronic arsenic
intoxication were definitely abnormal, with no other evident cause. The ao-
normalities included prolongation of the Q-T interval and a flattened
T-wave. In treated cases, these abnormalities diminished with the other
evidence of toxicity. Similar findings were reported by Barry and Herndon
(1962) and GTazener, et al. (1968).
Turning to health effects induced by various environmental exposures, in
the early 1960s, physicians in Antofagasta, Chile, noted demiatologic mani-
festations and some deaths, particularly among children, that were traced to
a water supply containing 300 ug/1 of arsenic. This water supply had been
in operation only since 1958. Borgono and Graiber (1972) have reported on
studies of the inhabitants of this city. They compared 180 inhabitants of
Antofagasta with 98 people who lived in a city (iQuique, Chile) with a nor-
mal water supply. Most of the people studied were less than 10 years old.
Among the residents of Antofagasta the primary symptoms reported were abnor-
mal skin pigmentation (80 percent); chronic coryza (60 percent); hyperkera-
tosis (36 percent); various cardiovascular manifestations, i.e., Raynaud's
C-54
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syndrome (30 percent); acrocyanosis (27 percent); abdominal pain (39 per-
cent); chronic diarrhea (7 percent); and lip herpes (13 percent). The inci-
dence of these symptoms in the control population was substantially lower or
nonexistent.
Two additional reports on the Antofagasta studies are worthy of note.
Zaldivar (1974) further described a study on a total of 457 patients (208
males, 249 females) bearing cutaneous lesions (leukoderma, melanoderma,
hyperkeratosis, squamous-cell carcinoma). Children (up to 15 years of age)
accounted for 69.2 percent of male cases, and for 77.5 percent of female
cases. These patients exhibited high arsenic content in the hair. The mean
concentration of arsenic in drinking water in the period 1968-1969 was 380
ug/g versus 80 ug/g in 1971. Such difference was attributed to a new filter
plant, which started operation in May, 1970. The average incidence rates
per 100,000 population for cases with cutaneous lesions in 1968-1969 were
145.5 for males and 160.0 for females. The Incidence rates decreased in
1971 to 9.1 for males and 10.0 for females.
Among the 337 registered children, 5 died showing thrombosis of brain
arteries, thrombosis of mesenteric artery, restriction of lumen of coronary
arteries, and/or myocardlal Infarction. Of the 64 registered adult males, 2
developed multiple skin carcinoma with lymph node metastases.
A number of questions are raised regarding this report. For example,
the decrease in cutaneous lesions seemed to be too rapid, following instal-
lation of the water-treatment plant, suggesting other factors were involved.
The 8- to 10-year-old age group recovered in three years. Adults exposed
for more than 15 years also had a decrease 1n incidence rate of cutaneous
lesions.
C-55
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In a follow-up study, Borgano, et al. (1977) investigated clinical and
epidemiologic aspects of the cases first reported in 1971. Arsenic content
in hair and nail clipping samples of the inhabitants of Antofagasta were de
termined and compared to the levels measured in the initial study reported
in 1971. Similar measurements and comparisons were performed for cultivated
vegetables and carbonated beverages. Also, a clinical study was made in
school children, looking for cutaneous lesions attributed to arsenicism.
Six years after the water treatment plant started to operate the problem had
diminished considerably. Arsenic determination of hair and nails of child
ren 6 years of age or less, born since the water treatment plant went into
operation, indicated no cutaneous lesions in this age group. However, those
over 6 years of age still had significant arsenic residues in hair and
nails. Although the clinical manifestations have improved, arsenic content
of water, soft drinks, and in some foods are still considerably above safe
levels and reouire additional sanitary engineering improvements.
Arguello, et al. (1938) reported on a large group of patients seen for
arsenical skin cancers in the Cordoba region in Argentina, which had a high
arsenic content in the drinking water {Bergoglio, 1964) and found keratoder-
ma in 100 percent of the patients. Most patients also had associated hyper -
hidrosis and abnormalities of pigmentation, whereas those reported by Fierz
(1965) did not. Arguello, et al. (1938) noted that the pigmentation ap-
peared early and was variable among the patients. It was described as small
dark spots 1 to 10 mm in diameter, with a tendency to coalesce, and appear-
ing predominantly on the trunk, that is, in the areas not exposed to the
sun. These and other authors have noted that atrophy may be associated with
telangiectasia and loss of color, or leukoderma, between the hyperpigmented
areas (the "raindrop" appearance) cited by Reynolds (1901).
C-56
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In another study of large-scale environmental contamination exposure,
Tseng, et al. (1968) surveyed a group of 40,421 residents of the southwest
coast of Taiwan (from a population "at risk" of 103,154) exposed to arsenic
via well water and found that they suffered from a number of dermatologic
and peripheral vascular problems. The overall male and female prevalence
rates for the clinical findings are as follows: hyperpigmentation 18.4 19.2
percent, 17.6 oercent; keratotic lesions 7.1 - 7.5 percent, 6.8 percent; and
black foot disease 0.9 - 1.2 percent, 0.7 percent for males and females re-
spectively. The reason for the range of values for males was not ex-
plained. Skin cancer prevalence rates corresponded directly to age and
arsenic exposure gradients (Table 6) (Tseng, 1977). The concentration of
arsenic in the wells ranged from 17 to 1,097 1.3/1. No cases of melanosis or
keratosis were found in a group of 2,552 people living in an area where the
wells contained almost no arsenic.
In considering arsenic health effects in terms of specific organ systems
or tissues effected, the effects of arsenic on skin are clearly among the
more notable and striking manifestations of the systemic toxicity of the
metal. The characteristics of the skin malignancies found in chronic arsen-
ism have been reviewed by Yeh (1963) and Yen, et al. (1968) in their reports
on the Taiwan cases. A prominant, even necessary, clinical feature of arse-
nical skin cancer is its association with the characteristic keratoses or
pigment irregularities on the trunk. Several authors have cited a similar
association in exposed workers as evidence that arsenic may cause internal
cancers, especially of the lung (Braun, 1958; Currie, 1947; Htieper, 1951;
Osburn, 1957; Robson and JeHiffe, 1963; Rosset, 1958; Roth, 1957). In ad
dition, the skin lesions are characteristically multiple and predominantly
on the areas of the body that are protected by clothing. Both these fea-
tures are notable, inasmuch as "ordinary" skin cancers tend to be single and
C-57
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TABLE 6
Prevalence of Skin Cancer for Males*
mq/1 20-39 yr 40-59 yr >60 yr
(30) (50) (70)
0 -0.29 0.0015 0.0065 0.0481
(0.15)
0.30-0.59 0.0043 0.0477 0.1634
(0.45)
>0.6 0.0224 0.0983 0.2553
(1.2)
*Source: Tseng, 1977
c-59
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have b^en shown to Kave a body distribution directly correlated with the
amount of Sun exposure (Birmingham, 1971; Miescher, 1934). Arsenical les-
ions (both keratoses and cancers) also appear at an earlier average age than
do solar (senile) keratoses and related carcinomas (NAS, 1977a). The induc-
tion of skin lesions had been a characteristic result of oral ingestion of
arsenic under all exoosure situations discussed above.
The histopathology of the multiple and varied lesions seen in arsenism
has been the subject of considerable interest among dermatopathologists (An-
derson, 1932; Ayres and Anderson, 1934; Miescher, 1934; Montgomery, 1935;
Pinkus and Mehregan, 1969; veh, 1963; Veh, et al. 1968). Lesions that clin-
ically are keratoses may show proliferation of keratin of a verrucous na-
ture, may exhibit precancerous derangement of the squamous portions of the
epithelium equivalent to those seen in Bowen's disease and solar keratosis,
or may even be frank sauamous cell carcinomas. Lesions that are less kera-
totic and more erythematous may contain either squamous cell or basal cell
carcinoma or a mixture of cell types. Most authors seem to agree that kera-
totic lesions appear to be able to progress to frank carcinoma, but observa-
tion of such an event is rare, and most cancers appear to arise independent-
ly of the keratoses.
The question of the association of Bowen's disease with arsenism has
stimulated considerable controversy. Graham and Helwig (1959) analyzed 36
autopsies of patients with Bowen's disease in whom arsenic intake had been
ruled out as much as possible. It is striking that this group of patients
differed from patients with arsenism in several respects: they lacked the
typical keratoses and pigmentation; they had a tendency for the "typical
Bowenoid" squamous cell carcinoma uj_ situ to precede the other cutaneous
malignancies by an average of 6 years; there was an incidence of approxi-
mately 80 percent of associated internal malignancies (some diagnosed only
C-59
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at autopsy); and they had suggestive evidence of a familial predisposition
to the condition. Of more than 100 living patients with the dignosis of
Bowen's disease surveyed by the same authors, internal malignancy had been
diagnosed in 23. These features seem sufficient to distinguish Bowen's dis-
ease from chronic arsenism, despite the confusion later introduced by Grah-
am, et al. (1961). If Graham and Helwig's cases are representative, the as-
sociation of systemic cancers is much higher in Bowen's disease than has
ever been suggested for chronic arsenism (MAS, 1977a).
The effects of arsenic exposure on skin may occur many years after ces-
sation of exposure (NAS, 1977a). For example, Braun (1958) reported on 16
patients who had been exposed to arsenic in their occupation as vintners
many years before. No known exposure to arsenic had occurred since. All
had keratoses, nine had leukomelanoderma of the trunk, and seven had skin
cancer or intraepidermal carcinoma j£ situ. Eight had lung cancer.
Roth (1957) also studied 47 vintners whose arsenic exposure had occurred
8-14 years earlier. His population was selected by having come to autopsy.
He found that 33 of the 47 had cancer. A total of 75 malignant tumors (40
of which were skin cancers) of various tissues were observed: 18 cases had
lung cancer, 6 with hemangiosarcoma of the liver, 5 with esophageal carcin-
ima, and 1 with bile duct carcinoma.
Cardiovascular effects of arsenic have been demonstrated to occur with
acute and subacute exposure of humans to inorganic arsenic and may include
quite severe cardiovascular involvement, with congestive heart failure
identified as a cause of death in fatalities encountered in one posioning
outbreak (Reynolds, 1901). More recent clinical assessments of subacute and
chronic arsenic poisoning of large numbers of people (Mizuta, et al. 1956;
Hamamoto, 1955; Borgono and Greiber, 1972; Tseng, et al. 1968) indicate that
C-60
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the extent of cardiovascular injury with the nature of exposure, subject,
geographic area, and level of arsenic intake.
Hamamoto's (1955) clinical findings of cardiovascular injury in 12,000
infants consuming arsenic-contaminated milk included elevation of the
ST-wave and extension of the QT-interval, cardiographic changes which were
slow to revert to normal after exposure and ceased. Similar cardiographic
data for 200 patients who consumed arsenic-contaminated soy sauce were noted
(Mizuta, et al. 1956).
In the clinical survey by Sorgono and Greiber (1972) of both pediatric
and young adult victims of chronic arsenic exposure via a drinking water
supply, cardiovascular symptoms seen included Raynaud's syndrome, acrocyano
sis, angina pectoris, hypertension, myocardial infarction, and mesenteric
thrombosis.
Tseng (1968, 1977) described the incidence of "black foot disease" in
Taiwanese consuming well water containing relatively high levels of arsenic.
The disorder, a peripheral vascular derangement arising from arteriosclero
sis and thromboangitis obliterans, results in gangrene of the feet and shows
an increasing prevalence with increasing arsenic content of drinking water.
Chronic exposure to arsenic in occupational settings has also been re
ported to be associated with various cardiovascular disorders. Vine dres-
sers who had been exposed to trivalent arsenic showed late onset (30 years
post-exposure, exposure time of 20 years) peripheral vascular sequelae in
the form of endangiitis obliterans and acrodermatitis atrophicans (Grobe,
1976). The role of arsenic in increased cardiovascular disease mortality is
suggested by the epidemlological investigations of smelter workers by both
Lee and Fraumeni (1969) and Axelson, et al. (1978).
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Little information is available regarding useful animal models of the
cardiovascular effects seen in arsenic-exposed human subjects. However,
oral exposure (1.5 mg As/kg body weight) of cats to either arsenate or arse
nite in feed (Massmann and Opitz, 1954) was followed by flattened T-wave and
lengthened QT-time in the electrocardiogram.
Neurotoxic effects of arsenic have long been recognized as being associ-
ated with acute, subacute, and chronic exposures to relatively high levels
of inorganic arsenic. These effects include both clinically significant
peripheral nervous system (PNS) and central nervous system (CNS) damage re-
ported as occurring in cases of accidental or homicidal arsenic poisonings,
prolonged occupational exposures, and certain therapeutic applications of
arsenical compounds. Such marked neurotoxic effects have been fairly well
characterized in terms of their major pathophysiological features, clinical
courses and sequalae, and associated histopathology. Much less well char-
acterized are quantitative dose effect/dose response relationships defining
arsenic exposure parameters associated with Induction of neurotoxic effects
in humans.
Reynolds (1901) provided one of the earliest detailed descriptions of
arsenic-induced neurotoxic effects in reporting on clinical findings for
more than 500 patients that had consumed arsenic-contaminated beer. As de
scribed elsewhere (NAS, 1977a), Reynolds (1901) reported that neurologic
signs and symptoms began before the appearance of classical skin lesions,
but followed such an Insidious course of development so as to have gone un-
diagnosed for several weeks. Neurological Involvement started with sensory
changes, e.g., paresthesias, hypersthesias, and neuralgias, accompanied 3y
considerable muscle tenderness. Varying degrees of motor weakness, progres-
sing from distal to proximal muscle groups, also occurred and culminated at
C-62
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times in paralysis of affected muscle groups or extremities. Certain indi-
cations of central nervous system (CNS) damage, e.g., loss of memory and
general mental confusion, were also observed but were discounted by Reynolds
(1901) as being less likely due to arsenic than chronic alcoholism or con-
current excessive selenium intake.
Perpherial nervous system (PNS) effects similar to those described by
Reynolds (1901) have since been observed in numerous other cases of acute,
subacute, and chronic arsenic exposures (Silver and Wainman, 1952; Mizuta,
et al. 1956; Heyman, et al. 1956; Jenkins, 1966; Hara, et al. 1968; Chut-
tani, et al. 1967; Ishinishi, et al. 1973; Nakamura, et al. 1973; Nagamatsu
and Igata, 1975; O'Shaughnessy and Kraft, 1976; Frank, 1976; Garb and Hine,
1977; LeQuesne and Mcleod, 1977) and are now recognized as classic clinical
symptoms of arsenic poisoning. Such symptoms include peripheral sensory ef-
fects characterized by the appearance of numbness, tingling, or "pins and
needles" sensations in the hands and feet, as well as decreases in touch,
pain, and temperature sensations in a symmetrical "stocking glove" distribu-
tion. These symptoms are often variously accompanied by burning sensations,
sharp or shooting pains, and marked muscle tenderness in the extremities.
Peripheral neuritis symptoms originate distally and, over the course of a
few weeks, often progressively become more widespread in both lower and up-
per extremities, usually appearing first in the feet and later in the
hands. Signs and symptoms of peripheral motor nerve effects include: sym-
metrical muscular weakness of the extremities, predominantly distal but at
times extending to proximal muscle groups and, rarely, the shoulder or pel-
vic girdle; evidence of foot and/or wrist drop; and, in some cases, rapidly
developing paralysis and atrophy of lower leg muscles and small muscles of
the hand.
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Collectively, the above components of the classical clinical syndrome
associated with excessive arsenic exposure are highly indicative of progres-
sive peripheral polyneuropathy, involving both sensory and motor nerves, and
most intensively affecting long-axon neurons. Several studies (Jenkins,
1966; Nagamatsu and Igata, 1975; O'Shaughnessy and Kraft, 1976; Garb and
Mine, 1977; LeQuesne and McLeod, 1977) have provided quantitative electro-
physiologic data, in the form of electromyographic (EMG) or nerve conduction
velocity (NCV) recordings, confirming arsenic induced peripheral nerve func-
tional deficits in association with the manifestations of frank clinical
signs and symptoms of the above type. In addition, biopsy and autopsy stud-
ies have provided histopathological evidence verifying peripheral nerve dam-
age, especially Wallerian degeneration of long-axon myelinated nerve fibers,
in cases of human arsenic exposure where frank neurological signs and symp-
toms were manifested (Heyman, et al. 1956; Jenkins, 1966; Chuttani, et al.
1967; Ohta, 1970; LeQuesne and McLeod, 1977). Such degenerative changes in
myelinated long-axon neurons are consistent with human autopsy findings dis-
cussed earlier regarding the uptake of arsenic into peripheral nerves (Lar-
sen, et al. 1972) and preferential accumulation of the metal in CNS white
matter with high content of "fatty" components of neural tissue, e.g., mye-
linated nerve fibers (Larsen, et al. 1979).
Several additional points regarding arsenic-induced peripheral neuro-
pathies warrant special attention here for present health assessment pur-
poses, including consideration of such issues as: (1) arsenical forms
identified as inducing clinical neuropathies; (2) pattern(s) of development
of neuropathic effects; (3) persistence of, available therapy for, and re-
covery from such effects; and (4) effective exposure or dosage parameters
associated with their induction.
C-64
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In regard to such issues, clinically-manifest cases of peripheral neuro-
oathies have been demonstrated to occur as the result of exposure to many
different inorganic arsenic forms under a variety of circumstances. For ex-
ample, peripheral neuropathy effects have been documented in clinical cases
of acute homicidal, suicidal, or accidental poisonings involving ingestion
of various commercially available herbicides, pesticides, and animal poisons
containing inorganic arsenic compounds such as: lead arsenate; sodium arse-
nate; calcium tn'arseniate; copper acetoarsenite (Paris Green); arsenious
oxide; and arsenic trioxide (Heyman, et al. 1956; Jenkins, 1966; Ohta, 1970;
O'Shaughnessy and Kraft, 1976). Similarly, peripheral neuropathy have been
observed following acute, subacute, or chronic occupational exposures to
many of the same arsenic compounds, e.g., in the course of agricultural ap-
plications of calcium or lead arsenate insecticide sprays, or occupational
exposure to arsenicals such as: arsenious acid and other tri- and pentaval-
ent inorganic arsenic compounds encountered in a coal gas desulfurization
processing facility (Hara, et al. 1968); and arsenic trihydride or arsine
(Frank, 1976). Thus, regardless of the particular inorganic arsenic form or
valence state involved, it appears that excessive exposure to arsenic from
any of the above substances can result in severe peripheral neuropathy.
In regard to the development and persistence of peripheral neuropathy
associated with arsenic exposure, somewhat variable patterns of onset, per-
sistence, and response to treatment have been observed, depending in part on
the nature of specific exposure parameters. LeQuesne and McLeod (1977), for
example, reported fairly rapid onset of peripheral neuropathies involving
both motor dysfunctions and paresthesias, which appeared in four patients
within 10 days to 3 weeks after ingestion of single large doses of inorganic
arsenic compounds (e.g., sodium arsenate and arsenious oxide). Further de
terioration occurred for a few days in 3 of the patients and progressively
C-65
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worsened for 5 weeks for the fourth, as indexed by NCV recordings and other
observations of clinical signs and symptoms. All improved slowly there-
after, but after 6 to 8 years, 3 patients still had abnormal neurological
signs and symptoms; NCVs, too, were still not in the normal range and marked
atrophy of affected muscles was evident in some cases. The pattern of onset
and persistence of neuropathy signs and symptoms observed by others (Heyman,
et al. 1956; Jenkins, 1966; Nagamatsu and Igata, 1975; O'Shaughnessy and
Kraft, 1976; Garb and Hine, 1977) for acute arsenic poisoning are consistent
with those reported by LeQuesne and McLeod (1977); that is, the neuropathy
typically become clinically manifest within a week or two after exposure and
slow incomplete recovery is seen over a course of years, with some patients
continuing to require the aid of leg braces to walk. Delayed onset of symp-
toms, 1 to 6 months after acute exposure to arsine has been reported (Frank,
1976) for six industrially exposed workers.
Under more chronic occupational exposure conditions to lower levels of
arsenic compounds, the development of neuropathy symptoms can be more grad-
ual and insidious and not only bilateral but unilateral polyneuropathies
without motor paralysis have been reported (Ishinishi, et al. 1973; Naka-
mura, 1973). Again, the time course for recovery from the neuropathies,
once induced, tends to be slow and on the order of years. Gradual onsets of
peripheral neuropathies and slow recoveries have also been reported with
subacute or chronic exposures to arsenic via ingestion of contaminated soy
sauce (Mlzuta, et al. 1956) or anti-asthmatic herbal preparations containing
arsenic trloxlde or asenic sulfide (Tay and Shea, 1975).
In regard to effective dosage parameters for induction of peripheral
neuropathies by arsenic, it is usually not possible to determine precise
doses involved or periods of exposure. For most acute poisonings, it is us-
ually evident that high level exposure (on the order of tens or hundreds of
C-66
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mg or more) occurred, frequently involving only a single dose. For subacute
or chronic poisoning situations, information exists from few studies by
which effective exposure parameters can be estimated. Mizuta, et al.
(1956), for example, reported that peripheral neuropathies occurred in 20
percent of 220 patients of all age groups poisoned by ingestion of arsenic
contaminated soy sauce, with approximately 3 mg arsenic (likely as calcium
arsenate) estimated to be ingested daily for 2-3 weeks resulting in total
effective doses up to approximately 60 mg. Also, Tay and Shea (1975) re-
ported polyneuropathies in approximately 50 percent of 74 patients poisoned
by daily ingestion of 3.3 or 10.3 mg/day of arsenic trioxide or arsenic sul-
fide in antiasthmatic medicinal pills. Similarly, Silver and Wainman,
(1952) reported on a patient that had ingested approximately 8.8 mg of arse-
nic trioxide daily for 28 months as an asthma treatment. Signs of peripher-
al neuropathy appeared at about two years, well after the onset of other
arsenic-related effects, e.g., skin changes; assuming regular ingestion of
the arsenical each day for two years, then, the neuropathy appear to be as-
sociated with gradual exposure to a maximum total dose of up to 650 mg of
arsenic. Comparison of this estimate (650 mg) with that from the Mizuta, et
al. (1956) study (60 mg) suggests marked variation in individual suscepti-
bility to neurotoxic effects of arsenic resulting in frank clinical neuro-
pathies.
The above studies characterizing clinically-flianifest peripheral neuro
pathies with relatively high acute, subacute, or chonlc exposure, have
raised Questions as to whether similar but subtle neurotoxic effects are in-
duced by chronic exposure to lower levels of arsenic. Takahashi (1974), for
example, reported that abnormal electromyograms (EMG) were found in the ab-
sence of subjective symptoms among population groups living in the vicinity
of an arsenic mine and smelter in Japan.
C-67
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Few other epidemiology studies have attempted to delineate more precise-
ly qualitative or quantitative relationships between chronic arsenic expo-
sure and the induction of peripheral neurotoxic effects indexed by EMG or
NCV recordings and neurologic examinations. Landau, et al. (1977) reported
relationships between length and intensity of occupational arsenic exposure
(mainly to arsenic trioxide via inhalation) of smelter workers and altera-
tions in peripheral nerve functioning. The manner in which the data were
reported, however, precludes precise characterization of dose-effect/dose-
response relationships. Similar difficulties exist in terms of attempting
to characterize such relationships for arsenic-induced peripheral nerve de-
ficits demonstrated by EMG recording in studies of two other chronically ex-
posed populations: (1) an Indian population exposed partly via occupational
contact with arsenic in a gold mining and smelting facility in Yellow Knife,
Canada, or via arsenic emissions from the facility into the ambient environ-
ment (Canadian Public Health Assoc., 1978); and (2) a Nova Scotia population
exposed via geologically natural arsenic contamination of wells used for
drinking water (Hindmarch, et al. 1977).
Several of the clinical reports dicussed above not only document peri-
pheral nerve damage induced by exposure to arsenic, but also contain de
scriptions of arsenic-induced central nervous system (CNS) disturbances or
encephalopathic effects ranging in severity from memory losses and general
mental confusion to convulsions, stupor, coma, and even death (e.g., Heyman,
et al. 1956; Jenkins, 1966; Frank, 1976; Nagamatsu and Igata, 1975;
O'Shaughnessy and Kraft, 1976; Garb and Hine, 1977). The onset and courses
of such CNS effects have not been well defined, but appear to parallel
rather closely the development of peripheral neuropathy; and cases of pro-
longed encephalopathy indexed by electroencephalogram (EEG) recordings of
abnormal brain wave patterns up to a year after cessation of exposure have
C-68
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been reported (Freeman and Couch, 1978; BentaT, et al. 1961). Very little
information regarding dose-effect/dose-response relationships for arsenicin-
duction of CNS effects can be derived from these studies, however, and such
effects appear to be a much less constant feature of arsenic-induced neuro-
toxic effects in adults than are peripheral neuropathies.
Certain studies suggest, in contrast, that children may be more suscept-
ible to arsenic-induced CNS damage. Severe CNS deficits were observed in
children exposed for several months as babies to arsenic-contaminated pow-
dered milk formulas in MoHnaga, Japan (Hamamoto, 1955; Okamura, et al.
1956b; Vamashita, et al. 1972; Masahiki and Hideyasau, 1973; Japanese Pedia-
tric Society, 1973). Follow-up studies on the children exposed to arsenic
as infants have revealed: (1) increased incidence of severe hearing loss
(>30 dB) in 18 percent of 415 children examined, compared to less than 1
percent incidence of hearing loss in corresponding age group children; (2)
increased incidence of abnormal electroencephalographic (EEC) brain wave
patterns in 14 percent of the exposed children, more than double the ex-
pected rate for comparable normal pediatric populations; and (3) observa-
tions of increased incidences of persisting mental retardation, epilepsy,
and other indications of severe brain damage. In additon, Ohira and Aoyama
(1972) reported not only increased EEG abnormalities but also visual system
damage, including pathological eye changes, in children fed the arsenic con-
taminated powdered milk in comparison to nonexposed breast-fed infants.
Taking into account known information regarding length of exposure and dose
levels, it can be calculated that the above persisting (probably permanent)
types of CNS damage effects resulted from ingestion of approximately 3.5
mg/day of arsenic resulting in a total intake of about 90-140 mg.
In another study (Bencko and Syman, 1970), hearing losses in children
were reported to be associated with arsenic exposure derived from emissions
C-69
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from a nearby power plant combusting high-arsenic content coal. Both air
and bone conduction hearing losses were observed, suggesting inner ear dam-
age. Failure to find analogous hearing losses in children exposed to atmos-
pheric arsenic emitted from a nearby copper smelter in the United States
(Milham, 1977) has raised questions regrading arsenic-induced damage to the
inner ear in children. Evidence supportive of the possible occurrence of
such effects has been obtained in an animal toxicology study (Aly, et al.
1975) that demonstrated hearing losses and histopathological confirmations
of destruction of the organ of Corti and other inner ear damage in guinea
pigs exposed to arsenic over a two-month period via intraperitoneal (i.p.)
injections of sodium arsenate solutions at a dosage level of 0.2 mg/kg body
weight.
Very few animal toxicology studies have focused on investigation of
neurotoxic effects of arsenic on the CNS. Rozenshstein (1970), for example,
reported evidence of CNS functional deficits, as indexed by altered condi -
tioned reflexes, as well as histopathologic evidence of CNS structural dam-
age, e.g., pericellular edema and neuronal cytolysis in the brain, in rats
exposed for three months to an arsenic trioxide aerosol resulting in an
arsenic concentration of 46 ug/m . Similar but less severe effects were
also obtained with exposure of other rats to a 3.7 ug As/m3 aerosol. CNS
deficits, indexed by impaired avoidance conditioning in the absence of
demonstrable histopatholotic changes in brain tissue, were also reported
(Qsata, 1977) for suckling rats administered 2 or 10 mg arsenic trioxide via
stomach intubation over a 40 day period.
Synergism and/or Antagonism
Moxon (1938) first demonstrated the protective effect of arsenic against
selenium poisoning when he found that arsenic at 5,000 ug/1 as sodium asen-
ite in the drinking water largely prevented liver damage in rats whose diet
C-70
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contained selenium at 15 ug/g as seleniferous wheat. Moxon and Dubois
(1939) then showed that arsenic was unique in its ability to prevent selen-
ium toxicity; all other elements studied were unable to protect against all
manifestations of chronic selenosis. Sodium arsenite and sodium arsenate
were equally effective against seleniferous grain, but the arsenic sulfides
were ineffective (Dubois, et al. 1940). Arsanilic acid and 3-nitro-4-hydr-
oxyphenylarsonic acid, two organic arsenicals used as "growth-promoters" for
livestock, also exhibited a beneficial action against selenium poisoning in
rats when given in the drinking water (Hendrick, et al. 1953). There is
evidence that it would be practical to use these two agents to protect swine
and poultry in high-selenium regions (Carlson, et al. 1954; Wahlstrom, et
al. 1955). Amor and Pringle (1945) even suggested the use of an arsenic-
containing tonic as a prophylactic agent against selenium poisoning in ex-
posed industrial workers.
The metabolic basis for the beneficial effect of arsenic in selenium
poisoning remained confused for some time, because arsenic was known to
block the biosynthesis of dimethylselenide, a detoxification product in ani
mals that received subacute doses of selenium by injection (Olson, et al.
1963). Moreover, the protective effect of arsenic against dietary selenium
was not seen if the arsenic was given in the diet, instead of the drinking
water (Ganther and Baumann, 1962a). Frost (1967) has shown that the toxici-
ties of arsenic and selenium are additive if both elements are given in the
drinking water. These results agree with those of Obenneyer, et al. (1971)
who recently observed an additive toxicity between arsenite and trimethyl-
selenonium chloride or dimethylselenide.
Ganther and Saumann (1962) studied the influence of arsenic on the meta-
bolism of selenium when both elements are injected in subacute doses and
found that the excretion of selenium into the gastrointestinal tract was
C-71
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markedly stimulated by arsenic. Levander and Baumann (1966a) observed an
inverse relationship in arsenic-treated rats between the amount of selenium
retained in the liver and the amount excreted into the gut; and they con-
cluded that the bile might be the route by which selenium was appearing in
the gastrointestinal tract. This hypothesis proved correct when it was dis-
covered that in three hours over 40 percent of the selenium injected could
be recovered in the bile of rats that also received arsenic, whereas only 4
percent of the selenium was excreted into the bile of rats not given arsenic
(Levander and Baumann, 1966b). This effect of arsenic on the biliary excre
tion of selenium was not confined to subacute toxlcity experiments: a re
sponse of selenium to arsenic was seen at doses approaching a rat's daily
intake of selenium when fed some crude commercial diets. Sodium arsenite
was the most effective form of arsenic in enhancing the biliary excretion of
selenium, but arsenate and 3-nitro-4-hydroxylarsonate were also active to
some extent. In experiments with radioactive arsenic, it was found that
selenium stimulated the biliary excretion of arsenic, Just as arsenic stimu-
lated the excretion of selenium. Initial attempts to characterize the forms
of selenium in rat bile suggested that the element is probably present in
several forms, including some macromolecularly bound selenium.
Although these studies provide physiologic information concerning the
interaction of arsenic and selenium, the chemical mechanism of the process
is still far from clear. The most logical hypothesis to account for the
arsenic-selenium antagonism from the molecular point of view assumes that
arsenic combines with selenium--perhaps, in analogy with sulfur chemistry,
by reacting with selenol (-SeH) groups to form a detoxification conjugate
that passes readily into the bile (NAS, 1977a).
C-72
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Teratogenicity
Although few human epidemiologic studies have provided evidence of arse
m'c-induced reproductive or teratogenic effects, several studies have shown
that sodium arsenate induces developmental malformations in a variety of
test animals: embryo chick, hamster, rat, and mouse (Ancel, 1946; Ridgeway
and Karnovsky, 1952; Perm and Carpenter, 1968; Hood and Bishop, 1972; Beau
doin, 1974).
Pregnant golden hamsters injected with sodium arsenate (15 to 25 mg/kg
body weight) produced offspring with a range of developmental malformations
including anencephaly, renal agenesis, rib malformation, cleft lip and pal-
ate, and anoohthalmia. The percentages of living embryos with various se-
lected malformations following maternal treatment with 20 mg/kg sodium arse
nate on the 8th day of gestation were as follows: nearly 90 percent with
all malformations; over 80 percent with anencephaly; nearly 70 percent with
rib malformations; and 30 percent with exencephaly. The spectrum of malfor-
mations varied with the time of injection during critical stages of embryo
genesis. Malformations induced by arsenate differed from those induced by
other teratogenic agents including certain heavy metals (Ferm, et al. 1971).
In another study, single intrapen'toneal injections of sodium arsenate
(45 mg/kg) in Swiss-Webster mice between the 6th and llth days of gestation
consistently caused an increase in fetal resorptions, a significant decrease
(p<0.05) in fetal weights compared to controls, and a number of fetal mal-
formations, most frequently the following: exencephaly, shortening of the
jaws with consequent protrusion of the tongue, exophthalinos, missing pinna,
cleft lip, hydrocepnalus, umbilical hernia, ectrodactyly, micromelia, and
shortened or twisted tail or limb, or both. Malformations were dependent on
the stage of embryogenesis. Exencephaly occurred in 54 percent of the fet-
uses when the injection was administered on day 9 of gestation; fusion of
C-73
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the ribs occurred in 100 percent of the fetuses when the injection was given
on day 9; and fusion of the vertebrae occurred in 73 percent when the injec-
tion was given on day 10 (Hood and Bishop, 1972).
In a later report, Perm (1977) demonstrated that administration of 20
mg/kg of sodium arsenate intravenously or intraperitoneally to golden ham-
sters during days 8 to 9 of gestation induced a specific spectrum of malfor-
mations including exencephaly, encephaloceles, skeletal defects, and malfor-
mations of the genitourinary system. The last effect, which appears to be
uniaue to arsenate, occurred in both sexes and with high frequency.
Perm (1977) further showed that radioactive arsenic ( As) injected
intravenously into Golden hamsters on day 8 of gestation was transmitted
across the placenta during the critical stage of embryogenesis and appeared
in the fetal tissues. Perm (1977) refers to a report concerning a case of
arsenic trioxide poisoning during human pregnancy, which demonstrated the
"ease with which inorganic arsenic crosses the human placenta at term with
extremely high levels in the fetal liver, brain, and kidneys" (Perm, 1977).
Introduction of arsenic into fertilized bird eggs has led to malformations
of beak and brain (Peterkova and Puzanova, 1976).
Hood, et al. (1977) compared the prenatal effe s of oral and intraperi-
toneal administration of sodium arsenate in mice. Intraperitoneal admini -
stration had a considerably greater effect than oral administration on pre
natal mortality, reduction of fetal weights, and occurrence of fetal malfor-
mations. The dosages were 40 mg/kg (intraperitoneal) and 120 mg/kg (oral).
Hood, et al. (1977) further noted that although arsenite is considerably
more toxic than arsenate, it has received less attention from teratologists.
Intraperitoneal injection of mice i_n utero with 10 to- 12 mg/kg arsenate on
one of days 7 to 12 of pregnancy caused significant increases in prenatal
mortality (o
-------
gross and skeletal malformations similar to but less frequent than those
induced by comparably toxic levels of arsenate (Hood, et al. 1977).
In another study, Tamura (1978) found no effects on growth and develop-
ment of rats fed arsenic trioxide from the 7th to the 21st day postnatal ly
at a dose level of 1.5 mg/kg/day in comparison to a 50 percent mortality
rate at a 15 mg/kg dose.
Mutagenicity
Most mutagenesis research has centered on chromosomal reactions to sod-
ium arsenate. There are no data based on the host-mediated assay or the
dominant lethal technique (NAS, 1977a).
One of the earliest observations that has meaning today was made by
Levan (1945). Root men'stem cultures of A11 iurn cepa were treated for 4
hours with an unspecified arsenic salt at 10 concentrations, from lethal to
a no-effect. Chromosomal changes were observed, including spindle distur-
bances and metaphase arrests. Similar effects, with minor variations, were
observed after treatment with salts of 24 other metals (mostly nitrates).
The changes resembled those caused by colchicine, but they cannot be consid-
ered serious damage (NAS, 1977a).
Petres and Hundeiker (1968) and Petres, et al. (1970, 1972) have re-
ported chromosomal breakage in human leukocyte cultures after short-term J_n
vitro exposure to sodium arsenate and in cultures obtained after long-term
exposure to arsenical compounds in vivo.
The cytotoxic and mutagenic effects of sodium arsenate were tested j_n
vitro on phytohemagglutinin-stimulated lymphocyte cultures at concentrations
of 0.05-30 ng/ml of culture medium (Petres, et al. 1970). It was reported
that 33 percent of metaphase plates were pulverized at 0.1 ug/ml and 80-100
Descent at concentrations of 2 ug/ml or greater. The "mitosis index" and
the "( H)thymidine-labeling index" were decreased. Arsenate has also
C-75
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found to increase the total frequency of exchange chromosomes in Drosophl la
melanoqaster treated with selenocystine, (Walker and Bradley, 1969). The
overall significance of these chromosomal studies is difficult to assess,
inasmuch as many unrelated compounds may cause similar effects. The fact
that arsenic compounds have caused chromosomal damage in a number of biolog-
ic systems, however, should alert toxicologists to a possible role of arsen-
ic in chemically-induced mutagenesis (NAS, 1977a).
_In_ vivo studies were made on 34 patients at the University of Freiburg
Skin Clinic (Petres, et al. 1970). Thirteen of these patients had recieved
intensive therapy, some more than 20 years before the experiment; most of
these were psoriasis patients. The control group (21 patients) consisted of
14 psoriasis patients and seven with eczema, none of whom had had arsenic
treatment. Phytohemagglutinin-stimulated lymphocyte cultures were prepared
from each patient for evaluation of chromosomal aberrations. The incidence
of aberrations was remarkedly greater in the cultures of patients who had
been treated with arsenic. Expressed as the frequency per 1,000 mitoses, 49
secondary constrictions occurred in the arsenic group and 12 in the control;
gaps were found in 51 in the arsenic group and seven in the control; 26
"other" lessions occurred in the arsenic group and one in the control; and
broken chromosomes appeared at the rate of 65 per 1,000 mitoses in the arse-
nic group and two in the control. Aneuploidy was found at the expected fre
auency in the arsenic group. The extent of abnormalities attributed to
treatment with arsenicals is impressive; it is important that this study be
repeated (NAS, 1977a).
The occurrence of chromosome aberrations was studied by Beckman, et al.
(1977) in short-term cultured leukocytes from mine workers exposed to arsen-
ic at the Ronnskar smelter in northern Sweden. In the smelter workers, 87
aberrations were found in 819 mitoses (Table 7). The number of aberrations
C-76
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TABLE 7
Oromosome Aberrations in Workers Exposed to Arsenic
from Ronnskar, Sweden and Controls*
No. of cells
No. of aberrant cells
No. of aberrations
Gaps
Chromatid aberrations
Chromosome aberrations
Total
No. of aberrations per cell
Freauency of aberrant cells, %
Arsenic
Workers
819
71
56
12
19
87
0.1062
8.7
Controls
1,012
13
9
3
1
13
0.0128
1.3
*Source: Seckman, et al. 1977
TABLE 8
ancer, by Site*
C-77
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increased from 0 to 25 aberrations per 100 cells. In the control material
10 aberrations were found by these investigators in 1,012 mitoses. Thus, it
was found that the freauency of aberrations was significantly higher
(p<0.001) among the arsenic-exposed workers. The three types of aberrations
observed in this study,, gaps (p<0.001), chromatid aberrations (p<0.01), and
chromosome aberrations (p<0.001) were significantly increased.
Paton and Allison (1972) investigated the effect of sodium arsenate,
sodium arsenite, and acetylarsan on chromosomes in cultures of human leuko-
cytes and diploid fibroblasts. Subtoxic dose of the arsenicals were added
to leukocyte and fibroblast cultures at various times between 2 and 48 hours
before fixation. In leukocyte cultures treated with sodium arsenate at
0.29-1.8 x 10~^M for the last 48 hours of the culture period, 60 percent
of 148 metaphases examined were found to have chromatid breaks. No signifi-
cant breaks were found in cultures treated with sodium arsenate at 0.58 x
10~^M, the highest nontoxic concentration. However, treatment with acety-
larsan at 6.0 x 10~^M resulted in 20 percent chromatid breaks in 50 meta-
phases examined. Sodium arsenate caused chromosomal damage in diploid
fibroblasts to which sodium arsenite {0.29-5.8 x IQ^M) was added to the
medium for the last 24 hours of culture; chromatid breaks were found in 20
percent of 459 metaphases examined. These results supported the j_n vitro
observations of Petres, et al. (1972) and Petres and Hundeiker (1968).
Carcinogenicity
The case for the association of inorganic arsenic with skin and lung
cancer, as well as other visceral carcinomas, has been extensively reviewed
(IARC, 1973; NIOSH, 1975; Hernberg, 1977; and others). The most salient
points concerning pertinent literature and reviews are evaluated below.
C-78
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The clinical association of skin cancer with the oral administration of
arsenic compounds began with a report by Hutchinson (1888). He described
six patients in whom skin cancer occurred and who had suffered for very long
periods from diseases o^ the skin (five with psoriasis, one with pemphigus)
typified by multiple lesions. Multiple lesions occurred even when sauamous
cancers arose in keratoses; there was an average of two lesions per case.
The elapsed time from the beginning of administration of the arsenical
drug to the beginning of the epitheliomatous growth was variable, but aver-
aged 13 years, regardless of the type of lesion. In cases with keratosis,
the latent period to the onset of keratosis was about half the latent period
to the onset of the epithelioma, i.e., about 9 years. In spite of the long
induction period, arsenic-related skin cancers started when the patients
were relatively young, 33 percent when they were 40 or younger, and 70 per-
cent when they were 50 or younger.
Of the 143 patients, 13 had or developed miscellaneous cancers at other
sites, but such cases were not reported systematically; the reports commonly
presented one or a few case histories. For example, Regelson, et al. (1968)
reported a case of hemangioendothelial sarcoma of the liver in a 49-year-old
man who had taken Fowler's solution intermittently for 17 years to control
osoriasis.
There have been numerous reports of arsenic-induced occupational cancer,
such as those of the excess lung-cancer mortality among Southern Rhodesian
miners of gold-bearing ores containing large amounts of arsenic (Osburn,
1957), and of the occurrence of lung and liver cancer and clinical arsenism
among German vineyard workers exposed to arsenic-containing insecticides
(Braun, 1958; Roth, 1957, 1958). The association of cancer with a high
degree of arsenic exposure has often been based on the existence of oalmar
and plantar keratoses (Sommers and McManus, 1953). However, because of the
C-79
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increased concentration of arsenic in the lesions of Bowen's disease, arsen-
ic has been considered as a possible cause of the disease and accompanying
visceral tumors (Graham, et al. 1961), without overt prior exposure to
arsenicals.
A number of relatively quantitative studies of cancer attributable to
occupational exposure to arsenicals exists as discussed in this document.
A death-record examination was made of a British plant that manufactured
sodium arsenite sheep dip (Hill and Faning, 1948; Perry, et al. 1948). The
factory was in a small country town within a specific birth and death regis-
tration subdistrict. In this and adjacent subdistHcts, death certificates
of 75 workers and 1,216 men (not factory workers) in three other occupation-
al groups were obtained for the period 1910-1943. Of the 75 deaths among
factory workers, 22 (29 percent) were due to cancer; of the other 1,216
deaths, 157 (13 percent) were due to cancer. The proportion of deaths due
to cancer was even higher among men who actually worked with the manufacture
and packaging of the arsenic-containing material: 16 of the 31 deaths of
men so classified were due to cancer. The number of deaths due to cancer
according to site for the two groups is shown in Table 8, in which those
deaths are expressed as a ~>action of cancer deaths and as a fraction of
total deaths. The absolute numbers of deaths and the fraction of cancer
deaths are from the author's paper; the fractions of total deaths were cal-
culated for this report. The data suggest a relative excess in the factory
workers of cancers of the respiratory system and skin, whether calculated on
the basis of cancer deaths or of total deaths; the corresponding deficits in
cancers of the digestive organs and peritoneum disappear when calculated on
the basis of total deaths.
C-80
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TABLE 8
Death Due to Cancer, by Site*
No. Cancer Deaths
Buccal cavity and
pharynx
Digestive organs and
peritoneum
Respiratory organs
Genitourinary
Skin
Other or unspecified
Total
Factory
Workers
2
5
7
2
3
_3
22
Other 3
Occupational
Groups
10
91
25
13
2
16
157
Fraction of
Cancer Deaths, Xa
Other 3
Factory Occupational
Workers Groups
9.1
22.7
31.8
9.1
13.6
13.6
99.9
6.4
58.0
15.9
8.3
1.3
10.2
100.1
Fraction of
Total Deaths, %«
Other 3
Factory Occupational
Workers Groups
2.7
6.7
9.3
2.7
4.0
4.0
29.4
0.8
7.5
2.1
1. 1
0.2
1.3
13.0
'Source: Hill and Faninqt 1948
dThere were 75 deaths among the factory workers and 1,216 deaths in the other three occupational
groups (see text).
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Although Hill and Faning (19*8) stated that the numbers of cancer deaths
are small, they concluded that "there is a suggestion in the figures that
the factory workers have been especially affected in the lung and skin."
Hence, there was an investigation of the environmental conditions at the
factory and the clinical condition of the workers in question, compared with
employees in other branches of the factory who were not exposed to arsenic
(Perry, et al. 1948), The median air arsenic content for the chemical work-
ers at the various operations ranged from 254 to 696 ug/mr. As an upper
limit, this was stated to represent the inhalation of about 1 g of arsenic
per year. This amount of arsenic is roughly equivalent to the amount re-
ceived by patients using arsenic medication for skin diseases.
The excretion of arsenic in the urine of 127 current employees was de-
termined; the scatter of these values was very wide. Some exposed workers
excreted from 1 to nearly 2 mg/day, whereas many excreted less than 100
ug/day. A few of the persons in the control group had very high excretion
rates, for which the authors found no explanation. It is important to note
that 20 of the 31 factory workers had been exposed to airborne sodium arsen-
ite for more than 20 years, and five of them for 40-50 years. Furthermore,
the median age of the 31 exposed workers was 52 years, and the average age
was 50. None of these men's lungs had pathologic signs attributable to
their exposure to sodium arsenite (radiographs were made, and vital capacity
and exercise capacity were measured).
The mortality experience of 8,047 white male smelter workers exposed to
arsenic tr1oxide during 1938-1963 was compared by Lee and Fraumani (1969)
with that of the white male population in the same state. There was a
threefold excess total mortality from respiratory cancer in smelter workers,
and this reached an eightfold excess for employees working more than 15
C-82
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years and heavily exposed to arsenic. When respiratory cancer deaths were
grouped according to degree of arsenic exposure, the observed mortality was
significantly higher than expected in all three groups: approximately 6.7,
4.8, and 2.4 times the expected mortality in the heavy-, medium-, and light -
exposure groups, respectively. In addition to arsenic tHoxide dust, smelt-
er workers were concurrently exposed to sulfur dioxide. Exposure to silica
and ferromanganese and lead dusts occurred in parts of the refineries where
arsenic concentrations were low. Therefore, a similar classification was
made for relative sulfur dioxide exposure. Respiratory
-------
by Milham and Strong (1974). They criticized the methods of the Pinto and
Bennett study. The records of workers from the same plant revealed 40
deaths from lung cancer, which was significantly higher than the 18 expected
on the basis of rates in the general U.S. population. Recent data on mor-
tality experience of arsenic exposed workers by Pinto, et al. (1977) is pre
sented in Table 9.
Snegireff and Lombard (1951) made a statistical study of cancer mortal-
ity in a metallurgic plant (A) in which arsenic was handled and in a control
plant (Z) in which "working conditions approximate those of Plant A except
that no arsenic is handled." From 1922 to 1949, there were 146 deaths among
the employees of Plant A who handled large quantities of arsenic trioxide.
Of these deaths, 18 were due to cancer, including seven cases of cancer of
the respiratory system. In the control plant, 12 of 109 deaths between 1941
and 1949 were due to cancer, including six due to lung cancer. The authors
stated that total cancer mortality in the two plants was not significantly
different from the figures for the state as a whole, and they concluded that
handling of arsenic trioxide in the industry studied does not produce a sig-
nificant change in cancer mortality of the plant employees. However, as
pointed out by the National Institute for Occupational Safety and Health
(NIOSH, 1975), there are a number of deficiencies in the report. Specifi-
cally, reanaJyses of the data have revealed that actually there was a large
excess (approximately fivefold) of lung-cancer deaths relative to mortality
from all causes among workers in both plants. Thus, the data demonstrated
evidence of a carcinogen for the respiratory system among the workers of
both the plant in which arsenic trioxide was handled and the control plant.
Findings of increased risk of lung cancer among copper-smelter workers
are not limited to the United States. A retrospective study by Kuratsune,
et al. (1974) in Japan revealed that, of 19 males who died of lung cancer in
C-84
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TABLE 9
Observed Ooatlts and Standardised Mortality Ratios (SHH) at Ages 66 and Over fur the Period
January 1.1949. through December 31. 19/3. Mong 5JO Hen Ketlrlng fro* the Tacoaa Swelter
by Cause of Death and Arsenic Exposure Index at Retirement 4. >>
Arsenic Exposure lndexc
Cause of Death
All causes
Cancer (140-205)
Digestive (150-159)
Respiratory (160-164)
ty*phatic (200-203. 205)
Urinary (I80.IUI)
Oilier cancer
Stroke (330-334)
Heart disease (400-443)
foroiiary (420)
Other heart disease
Respiratory disease
(41« 493, 500-602)
AM oliv«r causes
Total
Under
3.000
3.000-5.999
6.000-8.999
9.000 11.999
I2.000*
Obs
324
69
20
32
2
3
12
43
144
120
24
II
57
SHR
.12.21
148.90
122.0
304. ft1*
95.2
90.9
84. 5
113.2
108.8
108.9
108.6
101. 8
92.2
Obs
87
15
6
5
1
3
18
33
25
8
4
"
SMR
98.1
107.9
121.2
165.6
166.1
56.3
150.3
81.4
74.9
111.5
116.8
89.2
Obs
124
28
9
11
1
7
12
63
52
II
3
18
SMR
110.3
156. Of1
140.4
279. 4*1
126.1
102.8
80.0
122.4
122.2
123.2
70.9
74.8
Obs
70
14
2
7
0
5
J
36
31
5
1
12
SHI
129.2J
151.6
62.7
306.90
0.0
150.4
104.5
I44.241
145.10
138.4
52.4
104.1
Obs
24
,
1
4
0
0
6
5
4
1
2
4
SMR
117.7
2IU.7
264.7
668. !>0
0.0
0.0
218.4
53.6
SI. 7
62.9
?!>O.U
91. 1
Obs
17
S
0
5
0
0
I
.,
5
0
0
6
SHH
130.0
217.2
0.0
810. 5J
0.0
0.0
64.7
BJ.2
95.5
0.0
0.0
212.4
4'.niiri .•: Pinto, et al.
I'l •!•'•' ''•«! 'li->!<«< ct^uisuo' tiwU'i ilei ivfil I KM Hart jer. el al.
•'•.I jl isl it .IMI'>).
C-85
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a particular town, 11 had been employed as smelter workers in a local copper
refinery, and in all cases the disease Had become manifest after the men had
stopped working at the refinery. The author's conclusion was that prolonged
sxoosure to arsenic, and oossibly also other compounds, seemed to be associ-
ated with cancer of the lings. Additional groups exposed to inorganic arse
nic such as gold miners in Rhodesia (Osburn, 1969), hard-rock miners in the
United States (Wagoner, et al. 1963), and nickel refinery workers (Rock-
stroh, 1959) have shown an increased mortality from lung cancer, but evalua-
tion of the role of arsenic is difficult because of the presence of other
carcinogens in the working atmosphere.
A study at the Dow Chemical Company examined the incidence of respira
tory cancer among 173 descendents who were exposed primarily to lead arsen
ate and calcium arsenate «>nd 1,809 descendents who worked in the same plant
and were not exposed to those compounds (Ott, et al. 1974). Data were pre-
sented on the relationship between cumulative arsenic exposure and the ratio
of observed to expected deaths from lung cancer. The average exposure of
each worker was calculated on the basis of records of job assignments and
data on the arsenic content of the air in various parts of the plant.
Deaths from respiratory malignancy were seven times greater than expected
for total inhaled quantitites of 29.8 g and 2-4 times greater for 0.13-6.56
g. There was no association between the extent of exposure and the time
from beginning of exposure to death; most of the respiratory cancers occur-
red 20-40 years after initial exposure, regardless of total exposure.
The ratio of observed to expected deaths was even higher (3.85:1) in
another category, malignant neoplasms of the lymphatic and hematopoietic
tissues except leukemia, than it was in malignant neoplasms of the respira-
C-86
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tory system (3.45:1). Six lymphomas were reported, with the following diag-
noses on the death certificates: four cases of Hodgkin's disease, one of
lymphoblastoma, and one of reticulum cell sarcoma.
By contrast with the Dow Chemical Company workers, orchard workers who
sprayed lead arsenate were reported as showing no evidence of increased can-
cer (Nelson, et al. 1973). A mortality study involving a cohort of 1,231
morbidity survey of the effects of exposure to lead arsenate insecticide
scray was conducted in 1968-1969. Air concentrations of arsenic during
spraying averaged 0.14 mg/m . The population was grouped according to ex-
posure in three categories and compared in terms of standardized mortality
ratios with the mortality experience of the state of Washington. There was
no evidence of increased mortality from cancer, heart disease, or vascular
lesions.
In 1974, the mortality experience of retired employees of an Allied
Chemical Company pesticide plant in Baltimore was analyzed (Baetjer, et al.
1975; NAS, 1977a). The employees had been exposed to a number of industrial
chemicals, including arsenicals; there were no data on the extent of expo-
sure to the various chemicals. Incidence of death among the retirees was
3.5 times that among the general Baltimore population. The excess mortality
was concentrated in cancer-caused deaths (14 times the expected),
particularly respiratory cancer and lymphatic cancer. The noncancer deaths
were at the expected rates. These calculations were based on a total of 22
deaths in men from all causes during the period 1960-1972.
Several human studies not generally available were reviewed in the Na-
tional Institute of Occupational Safety and Health document on occupational
exposure to inorganic arsenic (NIOSH, 1975), including unpublished reports
to Kenncott Copper Corporation in 1971 and 1974; unpublished papers pre-
sented at the Conference on Occupational Carcinogenesis in New York City on
C-87
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March 24=27, 1975; and an evaluation by NIOSH of the study by Nelson, et al.
(1973). In the latter case, independent sources of information investigated
by NIOSH contradicted, ratisr than confirmed, the rgpcrt by Nelson, et al.
(1973). The conclusion drawn was that the report apparently did not accur-
ately depict the cancer incidence of persons exposed to lead arsenate spray
in the Wenatchee Valley (NIQSH, 1975),
High incidences of skin cancer have been reported in several population
groups exoosed to high concentrations of arsenic in drinking water, inriijcj-
ing people in the district of Reichenstein in Silesia. (Geyer. 1898), Cor-
doba Province in Argentina, (Bergoglio, 1964), and Taiwan (Tseng, et al.
1968).
Chronic arsenical poisoning, including skin cancer and a gangrenous con-
dition of the hands and feet called Blackfoot's disease, has occurred in
several communities exposed to arsenic in drinking water. The best docu-
mented instance of such arsenical poisoning is in Taiwan (veh, et al. 1968;
veh, 1963, 1973; Tseng, et al. 1968; Tseng, 1977). In a house to-house sur-
vey of 40,421 people in 37 villages along the southwest coast of Taiwan,
Tseng, et al. (1968) found that the prevalence of skin cancer, hyperpigmen-
tation, and keratosis each correlated with the arsenic content of the water.
The highest range of concentrations was greater than 0.6 ppm, and the lowest
range was less than 0.29 ppm. From a general survey of these inhabitants,
the prevalence rate for arsenical skin cancer was 10.6 per 1,000 residents
in 1965. The skin cancer --ate for well water containing <0.60 ppm was 21.4
per 1,000 people, while at. <0.29 ppm it was 2.6 (Tables 10 and 11; Figures
1, 2, and 3).
The sources of drinking water for these areas were deep artesian wells,
used from around 1910 until 1966, when a tap water supply was installed.
C-88
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TABLE 10
Age-specific and Sex-soecific Drevalence 3ate
for Skin Cancer*
Age
0-19
20-29
30-39
40-49
50-59
80-60
70*
Total
Male
Per 1,000
_
1.0
9.7
25.9
80.8
124.8
209.6
16.1
Female
Number
0
2
20
40
99
92
__57
310
Per 1,000
__
1.1
1.5
8.0
28.9
57.0
53^8
5.6
Number
0
3
4
16
38
40
_17_
118
Total
Per 1,000
._
1.1
5.0
15.7
53.7
91.9
12L1
10.6
Number
0
5
24
56
137
132
74
428
*Source: Tseng, 1977
c-89
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TABLE 11
Causes of Death in Patients wit" Skin Cancer and
Patients with Blackfoot Disease*
Skin Cancer
Patients
Cause of Death
Cancer
Lung
Skin
Bladder
L i ver
Colon
Kidney
Stomach
Nasal cavity
3one
Uterus
Esoohagus
Miscellaneous
Cardiovascular disease
Gangrene
Cerebrovascular disease
Respiratory disease
Pulmonary tuberculosis
Pneumonia
Others
No.
68
15
15
10
6
5
5
3
2
2
1
—
4
30
7
32
46
10
17
19
*
27.9
6.1
6.1
4.1
2.5
2.0
2.0
1.2
0.8
0.8
0.4
0
1.6
12.3
2.9
13.1
18.9
4.1
7.0
7.8
Blackfoot
Disease
Patients
No.
99
21
12
17
21
3
—
4
5
4
2
4
6
83
70
63
100
41
28
31
%
18.8
4.0
2.3
l'.2
4.0
0.6
0
0.8
0.9
0.8
0.4
0.8
1.1
15.7
13.3
12.0
18.9
7.8
5.3
5.9
General
Pooulation in
Endemic Area
No.
125
21
3
16
17
12
—
13
16
2
6
2
17
87
—
91
231
55
117
67
*
13.1
2.2
0.3
1.7
1.3
1.3
0
1.4
1.7
0.2
0.6
0.2
1.8
9.1
0
9.5
25.1
5.8
12.3
7.0
Disease of
alimentary tract
Senility
13
12
5.3
4.9
34
22
6.4
4.2
118
50
12.4
5.3
Renal disease
Miscellaneous
Unknown
Total
7
13
16
244
2.9
5.3
6.6
21
30
6
528
4.0
5.7
1.1
34
207
—
951
3.6
21.3
0
*Source: Tseng, 1977
c-90
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200
Molt
Tata I
100-
40 90 «0 TO «0
FIGURE 1
Age and Sex-soecific - Prevalence Rate for Skin Cancer
Source: Adapted from Tseng, 1977.
Both Sexes
200
ISO
too
I
looo
H> M M
< — IM T
10. »
M
40-
in
H H^n QjM ft Ov«r
M M*4 030 - 0-59
I L«w OAO - 0.2*
V
Total
FIGURE 2
Age-specific Prevalence Rate (1/1,000) for Skin Cancer by Arsenic
Concentration in Well Water
Source: Tsenq, 1977
C-9L
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>< 20 1—
«
o
u
e
-*
w
0.3 - 0.6 mg/1
8 —
4
0
FIGURE 3
GracMca! Representation of Figure 2
c-92
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The concentrations of arsenic in the water ranged from 0.01 to 1.82 ppm
(median range was 0.4 + 0.6 ppm). The chemical form of arsenic in the water
was not clearly determined, but it may have been either tn'valent (because
the well water is probably anaerobic) or a methylated arsine (because the
authors observed a combustible gas, perhaps methane, bubbling from the water
storage tanks). Initial attempts to measure the arsenate to arsenite ratio
of the water have been confined to measurements in a United States labora-
tory of a sample shipped from Taiwan with no special precautions to preserve
the speciation occurring at the collection point (Table 12) (Irgolic,
1979). Therefore, from the best available information, people in that re-
gion of Taiwan could have been exposed to both tHvalent and pentavalent
arsenic compounds.
Assessing the Taiwan situation is more complex than simply identifying
the two oxidation states of arsenic, as suggested recently by Lu, et al.
(1975, 1977a,b). These workers have observed nonarsenical fluorescent com-
pounds in water samples from the areas where Blackfoot disease is endemic
and have identified one of the fluorescent components as an alkaline hydro-
lysate of ergotamine, lysergic acid, or a related compound (Lu, et al.
1977b). They have also shown that one of the fluorescent components pro
duced abnormalities in developing chick embryos (Lu, et al. 1977a). It is
not known whether ergotamine was the compound that produced these abnormal-
ities.
The evidence of arsenical waters in an eastern area of the province of
Cordoba, Argentina, has been known for many decades and is associated with
the occurrence of hyperpigmentation, keratosis, and skin cancer. A study
made in 1949-1959 indicated a higher proportion of deaths from cancer in the
arsenical region than in the rest of the province — 23.8 percent versus
C-93
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TABLE 12
Analysis Results for the Taiwan Water Samples*
Geographic Location
Element Pei Men Pu Tai
Arsenite^, ppm As
Arsenate^, ppm As
Arsenite and Arsenate
total As, ppm (AAS)2
total As, ppm (NAA)3
0.05
0.52
0.57
0.72
0.76
0.09
0.63
0.72
0.76
Sodium, ppm 282 223
Cooper, pom <0.1 <0,
Manganese, ppm <0.1 <0.
Zinc, ppm <0.1 <0,
Iron, ppm <0.1 <0,
•Source: Irgolic, 1979.
^Determined by GC-MES
2F1ameless Atomic Absorption Spectrometry
^Neutron Activation Analysis
C-94
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15.3 percent (Bergoglio, 1964), The excess was due mainly to cancer of the
respiratory and digestive tracts in both men and women. The excess cancer
was unrelated to socioeconomic differences.
In contrast to the above epidemiology studies yielding evidence for in-
creased cancer rates in populations exposed to arsenic via drinking water
supplies, a study conducted by Morton, et al. (1976) failed to demonstrate
any increased incidence of cancer in Lane County, Oregon, the only area in
the United States where the drinking water supply has elevated levels of
arsenic. Several possible explanations can be offered for the lack of
effects seen in Lane County in comparison to positive observations in other
areas, e.g., Taiwan. These include the following:
(1) arsenic concentrations in the Lane County drinking water supply were
distinctly lower than those measured in Taiwan;
(2) the predominant form of arsenic in the Taiwanese water was trivalent
arsenic which tends to be more toxic than the pentavalent form found in
Lane County;
(3) an insufficient number of subjects to reveal small increases in cancer
rates may have been studied in the Lane County area, an area much less
densely populated than Taiwan and having fewer total numbers of subjects
available for study;
(4) differences in racial characteristics and nutritional status between the
two experimental populations may have affected the results;
(5) the presence of other carcinogenic contaminants in the Taiwanese water
but not in the Lane County water may have increased the cancer rate in-
dependent of the presence of arsenic.
C-95
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While none of the above explanations can be ruled out as crucial factors,
neither can the observed differences in cancer rates be conclusively attH -
buted to any one of them.
In general, animal studies have not shown carcinogenicity for arsenic
compounds, even when administered at near the maximally tolerated dosage for
long periods. Certain notable exceptions are described first, and then
several of the negative studies.
Askanazy (1927) noted benign and malignant teratomas in rat embryos
transplanted into the peritoneal cavity of rats whose drinking water con-
tained arsenic. Embryonal cells are especially sensitive to arsenic which
provoked in them signs of degeneration even in concentrations of 0.25 ug/1
of cultivation medium (Goeckerman and Wilheim, 1940).
In 1962, Halver reported the occurrence of hepatomas in trout fed a syn-
thetic diet containing carbarsone at 4.8 mg/g of diet (the data were re-
viewed by Kraybill and Shimkin (1964); the original report is not readily
available). Of 50 trout exposed to carbarsone, five developed hepatomas.
There were no hepatomas in a large control group fed the synthetic diet
without carbarsone. However, aflatoxin contamination of the diet may have
been a confounding variable.
More recently, Osswald and Goerttler (1971) reported that subcutaneous
injections of sodium arsenate in pregnant Swiss mice caused a considerable
increase in the incidence of leukemia in both the mothers and their off-
spring. A 0.005 percent aqueous sodium arsenate solution was injected daily
during pregnancy for a total of 20 injections, each containing arsenic at
0.5 mg/kg. Some groups of offspring from the arsenic-treated females were
C-96
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given an additional 20 subcutaneous injections of arsenic (0.5 Tig/kg) at
weekly intervals. Leukemia occurred in 11 of 24 mothers (46 percent), 7 of
34 male offspring (21 percent), 6 of 37 female offspring (16 percent), and,
in the offspring given the additional 20 injections, 17 of 41 males (41 per-
cent) and 24 of 50 females (48 percent). Leukemia developed in only 3 of 35
males (9 oercent) and in none of 20 female offspring of untreated control
mice. Furthermore, 11 of 19 mice (58 percent) developed lymphoma after 20
weekly intravenous injections of 0.5 mg each of arsenic as sodium arsenate.
Long-term studies of effects of arsanilic acid on chickens, pigs, and
rats were reoorted by Frost, et al. (1962). No adverse effects were seen in
the chickens and pigs after 4 years of feeding, nor in pigs fed 0.01 percent
arsanilic acid for three generations. Male and female weanling rats from
the F£ generation of a six-generation breeding study in which 0.01 percent
and 0.05 percent arsanilic acid was fed were held on the 0.01 percent arsan-
ilic acid diet or on the control diet for 116 weeks. The overall tumor in-
cidence was the same in all groups and resembled the historical incidence of
tumors in the colony, 35-45 percent. The significance of these data lies in
the fact that transplacental exposure to a carcinogen followed by lifetime
exposure to the same carcinogen is often the most sensitive technique for
detecting carcinogenicity of a substance (Tomatis and Mohr, 1973), but this
test was negative.
Soutwetl (1963) used female mice (Rockland and a specially bred strain
highly susceptible to skin tumors) in a test for cocarcinogenicity of potas-
sium arsenite. It was tested as an initiator, both orally by stomach tube
(a total of 2.4 mg in five days) and locally (a total of 1.2 mg in eight ap-
plications during five days). This initiating treatment was followed by
topical application of croton oil twice a week for 18 weeks. He also tested
C-97
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potassium arsenite as a promoter by daily applications (a total of 2.3
mg/week) after a single 75 ug dose of dimethylbenzanthracene (OMBA). The
prolonged skin applications of potassium arsenite were hyperkeratotic and
ulcerogenic. Other experiments were done to determine whether arsenic would
increase the yield of skin cancers caused by a suboptimal regimen of DMBA
plus croton oil given either at the time OM8A initiation or during the
24-week period of croton oil promotion. Under the latter condition, the
mice were fed potassium arsenite at 169 ug/g of food. This dietary concen-
tration of 169 wg/g {as potassium arsenite) is very high, compared with the
0.5 ug/g usually found in the human diet. In no case was there an effect of
arsenite on skin carcinogenesis in these experiments. Many tumors developed
in the positive control mice, beginning as early as six weeks after treat-
ment began.
Baroni, et al. (1963) carried out a similar study with male and female
Swiss mice, testing the oral effects of potassium arsenite (100 mg/1 in
drinking water) as an initiator with croton oil promotion and as a promoter
with OMBA and urethane initiation. Local skin applications of sodium arsen -
ate were tested as a promoter after initation with OMBA or urethane. The
arsenicals had no effect on tumorigenesis: and only a very slight degree of
keratosis was observed.
Milner (1969) used three strains of mice that differed in susceptibility
to the induction of skin tumors by the application to the skin of methyl -
cholanthrene-impregnated paraffin disks for 2-3 weeks. The treated site was
transplanted syngenetlcally and observed for eight weeks for tumor forma-
tion. Arsenic trioxid« (100 mg/1 in drinking water) was administered either
during methylcholanthrene exposure, to animals with transplanted skin, or
C-98
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both. Arsenic exposure produced a small increase in the yield of papillomas
in the low-susceptibility strain, a small decrease in the high-susceptibil-
ity strain, and no effect in the intermediate susceptibility strain.
Byron, et al. (1967) fed either sodium arsenite or sodium arsenate to
Osborne-Mendel rats in a 2-year study at dietary concentrations of 15-250
ug/g for arsenite and 30-400 ug/g arsenate. No carcinogenic activity of
either material was found. These investigators also did a 2-year arsenic
feeding experiment on dogs, with negative results; however, this was an in-
adequate observation period for studying carcinogenic responses in dogs.
Hueper and Payne (1962) incorporated arsenic trioxide in the drinking
water (either plain or with 12 percent ethanol) of groups of rats and mice.
The initial concentration of 4 mg/1 was increased by 2 mg/1 each month to a
maximum of 34 mg/1 at 15 months. Thus, the daily intake of arsenic trioxide
ranged from 0.1 to 0.8 mg/rat. The administration of arsenic trioxide was
continued until 24 months. Neither the rats nor the mice developed any can-
cers in suspected target organs — skin, lung, and liver.
Kanisawa and Schroeder (1969) and Schroeder, et al. (1968) found no car-
cinogenic effects on mice exposed to potassium arsenite at 5 mg/1 in drink-
ing water from weaning to senescence (Kanisawa and Schroeder, 1969) or on
rats on the same regimen (Schroeder, et al. 1968).
Kroes, et al. (1974) studied the carcinogeniclty of lead arsenate and
sodium arsenate with SPF-W1star-derived male and female rats. In addition,
some groups were intubated with a subcarcinogenic dose of diethylnitrosamine
to investigate a possible synergistic action leading to lung tumors. Food
intake and body weights were recorded, and complete gross and microscopic
examinations were made on all animals. Lead arsenate that was incorporated
in the diet at 1,350 ug/g was toxic and caused increased mortality; an ade-
noma of the renal cortex and a bile duct carcinoma were found in this group,
C-99
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but no significance can be attached to one OF two tumors in any group. No
cancer was associated with the feeding of lead arsenate at 463 ug/1 or sod-
ium arsenate at 416 ug/1. No synergism with the nitrosamines was observed.
There was a high spontaneous-tumor incidence in this experiment. The test
diets were fed to female rats from the time of parturition until the young
were weaned, and these young were the test animals. Surviving rats were
killed after 29 months of feeding.
As Fraumeni (1975) has pointed out, it 1s largely because laboratory
studies have not succeeded in producing tumors in animals that arsenic has
not been accepted universally as a carcinogen. There is evidence from clin-
ical observations and occupational and population studies that inorganic
arsenic is a skin carcinogen in man. There 1s a characteristic sequence of
skin effects of chronic exposure to arsenic that Involves hyperpigmentation
initially, then hyperkaratosls (keratosis), and finally skin cancer (Yeh, et
als 1968), This sequence has been oserved under a variety of circumstances
involving chronic exposure: potassium arsenlte (Fowler's solution) was used
medicinally (Neubauer. 1947), vineyard workers used sprays and/or dusting
powders containing arsenic compounds and drank arsenic-contaminated wine
(8raun4 1958: Roth. 1957, 1958). chemical workers manufactured sodium arsen-
ite for use as i sheep dip (Perry, et al. 1948), and residents of a south-
west area of Taiwan had. as their only source of drinking water for over 45
years, artesian wells eontaminattd by arsenic from geologic deposits (Tseng.
et aU 1968), The similarity of responses under these diverse circumstances
is important* because studies in human populations always involve variables
that cannot be controlled as in laboratory t.xn*rimtnts; htncts the credibil-
ity of information derived from human studies depends on the demonstration
of comparable effects under different conditions. This requirement has been
amply met regarding arsenic as a cause of skin cancer (NAS, I977i)s
C-100
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The earliest skin effect of chronic arsenic exposure, hyperpigmentat ion
(melanosis), occurs in a dappled pattern predominantly in unexposed areas.
After the onset of melanosis, the skin begins to atrophy in a patchy way in
hyperpigmented areas, with the formation of keratoses that are the pathogon-
omom'c lesions of chronic arsenic exposure (Yen, et al. 1968). Only a small
proportion of the keratoses evolve into skin cancer, and this takes place
only after many years. The sequence is illustrated by the Taiwan data the
prevalence of melanosis, keratosis, and skin cancer reached 10 percent in
the male population roughly at ages of 18, 30, and 60 years, respectively
(Tseng, et al. 1968). Chronic exposure to inorganic arsenic thus causes a
slowly progressive form of patchy skin damage involving the epidermis and
adnexal structures, as well as the underlying dermis, with the precancerous
keratoses and cancers forming in the areas of chronic atrophy. The chronic
damage and tumorigenesis resulting from arsenic are similar to the effects
of ionizing and ultraviolet radiation on the skin (HAS, 1977a).
Arsenical skin cancer is readily distinguished from skin cancer induced
by sunlight, in that it occurs predominantly on surfaces that are shielded
from sunlight and multiple lesions are much more common in arsenic-induced
cases; for example, in 428 of the 429 cases of skin cancer studied in Tai-
wan, there was more than one cancer (veh, et al. 1968).
Substantial doses of inorganic arsenic are required to produce an appre-
ciable incidence of skin cancer. The average intake of persons treated with
Fowler's solution who developed skin cancer was around 20-30 g. The preval-
ence of skin cancer 1n Taiwanese men exposed to drinking water containing
arsenic at 300-600 mg/1 was about 15 percent at age 60 and over. The normal
incidence is 2-3 percent. On the basis of a 2 I/day water intake for the
period over which the artesian wells were used (45 years), the total arsenic
C-101
-------
intake must have been about 15 g, which is roughly in the same domain as
that in clinical cases of the use of Fowler's solution. Thus, the Taiwanese
data that demonstrated the requirement for large doses of arsenic to obtain
even a modest yield of skin cancer are consistent with the relatively low
frequency of skin cancer in patients treated with Fowler's solution. The
low potency of inorganic arsenic may explain why no skin effects have been
reported in people treated for syphilis with organic arsenicals, inasmuch as
the total doses amounted to only a few grams. However, It is also possible
that the metabolism of the organic arsenicals is sufficiently different to
preclude the occurrence of skin cancer and other forms of arsenical damage
even at higher doses (MAS, 1977a).
The relative frequency of melanosis, keratosis, and skin cancer was
roughly similar in the Taiwanese population and the chemical workers who
manufactured sheep dip. On direct examination, the latter showed a 90 per-
cent prevalence of melanosis and 30 percent prevalence of keratosis, for a
ratio of melanosis to keratosis of 3:1. At comparable ages, the Taiwanese
showed a ratio of about 4:1. Two of the nine keratosis patients in the
sheep dip factory had already been treated for skin cancer, and the propor-
tionality between keratosis and skin cancer was about the same in Taiwan.
As in the Taiwan experience, the sheep dip chemical workers had been exposed
to large doses of Inorganic arsenic (up to 1 g/year), but much of this was
by inhalation (MAS, 1977a).
It 1s possible that the trivalent and pentavalent forms of inorganic
arsenic produce the same effects on skin. This is of interest, particularly
in view of the different metabolic patterns of trivalent and pentavalent in-
organic arsenic with the former by interaction with sulfhydryl groups and
the latter by substituting for phosphate. The clinical use of Fowler's
C-102
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solution and the manufacture of sodium arsenite as a sheep dip both involved
exposure to trivalent inorganic arsenic. The two categories of people de-
veloped similar skin responses. The Rhodesian gold miners, in whom the in-
cidence of typical arsenical keratoses was very high, were exposed to arsen-
opyrlte, 1n which the arsenic becomes trivalent on weathering; the reactions
of arsanopyrite in the body are unknown (NAS, 1977a). The chemical form of
arsenic in the Taiwanese artesian-well water is still being investigated,
but, the reported occurrence of methane gas 1n the water could preclude the
existence of arsenic 1n the pentavalent form (MAS, 1977a) and certain pre
Umlnary results by Irgollc (1979) suggest that the trivalent form of arsen
1c predominates. The failure to find Increased incidence of cancer in Lane
County, Oregon, where pentavalent, inorganic arsenic tends to predominate in
water supplies lends some support to the possibility that trivalent arsenic
has the greatest carcinogenic potential and 1s of the greatest concern.
Of the published reports on mortality from respiratory cancer in copper
smelters, the most Impressive is that of Lee and Fraumenl (1969). The study
involved a population of 8,047 white male smelter workers who were followed
for 26 years; for each employee, Information was available on time, place,
and duration of employment, maximal arsenic and sulfur dioxide exposures
(descriptive, rather than numerical), and cause of death. The life-table
method was used to evaluate age-specific mortality rates for the various
causes of death, and the rates were compared with those of the states in
which the smtlters were. The number of deaths available for analysis was
very substantial; 1,877. The study demonstrated a systematic gradient for
respiratory cancer according to the magnitude and duration of exposure to
both arsenic and sulfur dioxide. These agents, however, were inseparably
linked, because of the nature of the smelter operations. The amount of ex-
cess cancer was impressive, with an eightfold increase in the workers who
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had the heaviest arsenic exposure for the longest duration, i.e., more than
15 years. The latent period -- the interval between first employment and
death from respiratory cancer --was extraordinarily long and was inversely
related to the magnitude of exposure: 34, 39, and 41 years for the categor-
ies of heavy, medium, and light arsenic exposure. There were deficiencies
in the study, some of which were unavoidable. For example, no indication
was given of whether the study population was representative of the total
workers population; the exposure rankings were based on the maximal arsenic
concentrations, rather than weighted averages derived from work histories.
No quantitative data were available on exposure. No attempt was made to
validate the stated causes of death. No smoking histories were obtained.
However, none of these deficiencies could be seriously regarded as invalida-
ting the conclusions of the study (MAS, 1977a).
The Kuratsune, et al. (1974) report dealt with a smaller study that com-
pared lung-cancer mortality rates calculated from the 22 deaths that occur-
red in a 30-year period in a smelter town with the lung cancer experience in
the same period in a neighboring city and in Japan as a whole. The stan-
dardized mortality rate for males in the smelter towns was four times higher
than that for the rest of the country, but equal to that for women. This
4-fold excess is comparable with the 3.3-fold excess observed in the Lee and
Fraumeni (1969) study. Although many of the men 1n the town worked in the
refinery, a much higher proportion of the lung-cancer cases, compared with
controls, occurred in men who were heavily exposed to arsenic as smelter
operators. As 1n the case of the Lee and Fraumeni (1969) study, the latent
period from first exposure to the diagnosis of lung cancer was very long,
ranging from 26 to 48 years. The duration of employment was also very long,
with a median of about 30 years, although two cases occurred in people who
worked for only 2-3 years.
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Two lung cancer studies of the American Smelting and Refining Company
smelter have produced conflicting results. The 1963 Pinto and Bennett re-
port examined the proportional mortality from lung cancer in a total of 229
deaths in the period 1946-1960. This study dealt only with pensioners and
workers who died during their employment and did not include people who had
left the plant. The reported data showed that the 18 lung-cancer deaths in
the plant population as a whole was higher than the rate in the state of
Washington. However, the excess lung cancer for the plant as a whole was
due to the high occurrence in controls, i.e., in workers who were considered
not to have arsenic exposure. Milham and Strong (1974) by contrast, found
in the years 1950-1971, that there were records of 39 deaths due to respira
tory cancer in Pierce County (the smelter locale) in people who were stated
to have worked at the smelter. Application of U.S. mortality rates to the
published figures for the smelter population at risk yielded an expected
number of 18 respiratory cancer deaths, compared with the 39 deaths observed
(MAS, 1977a).
Pinto, et al. (1977) recently resolved the discrepancy between the Pinto
and Bennett (1963) and Milham and Strong (1974) papers in a study of the
same smelter that Devaluated the exposure categories used in the Pinto and
Bennett paper (1963) (which were apparently in error) and also included a
longer observation period and therefore more deaths. The data included a
total of 32 respiratory cancer cases and show a progressive increase in
standardized mortality ratio with increasing arsenic exposure. The arsenic-
exposure index was calculated as a weighted average based on urinary arsenic
concentration and duration of employment. It is of interest that the eight-
fold excess in respiratory cancer for workers with the highest exposures and
C-105
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the threefold excess for all the smelter workers reported by Pinto et al.
(1977) were very close to the figures reported by Lee and Fraumeni (1969)
and Kuratsune, et al. (1974).
The studies described here indicated that excess respiratory cancer oc-
curs in copper-smelter workers as a function of the magnitude and duration
of exposure to arsenic, with latent periods of three to four decades from
the time of initial exposure. However, the studies do not permit a conclus-
ive resolution of the issue of whether concomitant exposure to sulfur diox-
ide and other smelter dusts is necessary for the carciogenic response. Evi-
dence from studies involving entirely different circumstances of exposure
including workers in three pesticide manufacturing plants (Hill and Faning,
1948; Ott, et al. 1974), vintners who applied pesticides (Braun, 1958), and
Rhodesian gold miners (Osburn, 1969), however, suggests that sulfur dioxide
and other unspecified smelter dusts are not essential cofactors for the
respiratory carcinogenicity of arsenic. All the nonsmelter studies had
obvious limitations, but the lung cancer excess 1n each study was relatively
large and, taken as a group, they provide significant evidence that arsenic
is a lung carcinogen (MAS, 1977a).
The Hill and Faning (1948) study of 75 deaths in a sheep dip factory
used the indirect method of proportional mortality to evaluate the small
group of 22 deaths from cancer; seven of them were cancers of the respira
tory tract, compared with an expected 2.4 deaths. The Dow arsenic workers
(Ott, et al. 1974) were evaluated in two ways: (1) by an analysis of death
records of those who died from lung cancer (28, or 16.2 percent, of 173
chemical-worker deaths, compared with 104, or 5.7 percent, of the 1,809 con-
trol-case deaths), and (2) then, as a retrospective cohort study, a compari-
son of the mortality from respiratory cancer (obtained from the records used
C-106
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in the first approach) among 603 persons identified as having worked in the
arsenic plant from 1940 to 1973 with the mortality among the corresponding
U.S. white population. The two approaches gave essentially the same re-
sults - a threefold to fourfold excess. However, the puzzling aspect of the
data is that almost 60 percent of the respiratory-cancer deaths were in peo
pie who had worked with arsenic for less than a year, three decades earlier.
Most of the arsenic workers were unskilled short-term employees, of whom a
large proportion left the company after a brief period of employment. The
follow-up study, however, dealt only with the people who remained in the
company. A confirmation of the excess lung cancer in a follow-up of short-
term arsenic workers who left the company would be very useful. Neverthe
less, there were about a dozen cases in people who worked longer than a year
and who were in the highest dose categories, where the excess risk was maxi-
mal (fourfold to sixfold). It is possible that the apparent twofold excess
in lung cancer in the lower exposure categories, including those who worked
with arsenic for less than a year, would not be ascribable to arsenic, be-
cause there was no change in cancer risk over a wide range of total doses
(0.04-1.56 g). Furthermore, these low dose categories consisted predomin-
antly of short-term unskilled workers who as a group might have had higher
exposures to other hazardous chemicals than the controls (MAS, 1977a).
The Allied Chemical Company pesticide manufacturing operations produced
a range of products, including some arsenical compounds. A preliminary
study of the proportional mortality among retired employees showed a seven-
fold excess of lung cancer that accounted for about 40 percent of all
deaths. Both the Dow and Allied studies also showed a few excess deaths
from lymphoma and Hodgkin's disease. The results of a more detailed study
of the Allied Chemical Company that is now in progress will be very useful
(MAS, 1977a).
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Arsenic sprays and dusts were widely used in Germany between 1925 and
1942, at which time they were banned (Braun, 1958; Roth, 1957, 1958). Vine-
yard workers also drank wine containing arsenic. Hundreds of workers de-
veloped acute and chronic arsenic poisoning. In the 1950's, vineyard work-
ers with lung cancer began to appear in hospitals serving the vineyard re-
gions. An association between arsenic and lung cancer is further suggested
by the high proportion of vineyard workers with lung cancer who had the
characteristic hyperpigmentation and keratoses associated with chronic arse-
nic exposure (MAS, 1977a).
The same high degree of association of skin arsenism and lung cancer oc-
curred in Rhodesian gold miners who were heavily exposed to arsenopyrite
dust (Osburn, 1969). In the period 1957-1963, the occurrence of 37 cases of
lung cancer in gold miners represented an incidence of 206/100,000 compared
with 34/100,000 for adult males in the Gwanda region of Rhodesia. This re-
presents a sixfold difference in lung cancer in miners (MAS, 1977a).
The probability of death from lung cancer in persons with keratosis,
ranges from 32 to 56 percent, which is roughly 5-10 times higher than might
be expected. The data suggest that there is a very high risk of lung cancer
when the exposure to inorganic arsenic dust is high enough to cause keratos-
es (MAS, 1977a).
The only evidence that arsenic is a liver carcinogen comes from German
vintners. Thirteen of the 47 persons whose autopsies were reported by Roth
(1957, 1958) had cirrhosis, and six had angiosarcoma, a rare form of liver
cancer associated with exposure to vinyl chloride and Thorotrasr*, and one
with a duct carcinoma. Only two cases of angiosarcoma have been reported in
people treated with Fowler's solution (Regelson, et al. 1968). There is no
evidence of either cirrhosis or liver damage in any of the other studies on
C-108
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arsenic. It is possible that the combined effect of a high alcohol intake
and arsenic is responsible for the unusual forms of cirrhosis and liver can-
cer observed in vintners. It should also be pointed out that the chemical
form of arsenic in wine is unknown (NAS, 1977a).
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CRITERION FORMULATION
Existing Guidelines and Standards
In 1942, the U.S. Public Health Service set a maximum allowable level of
50 ug/Hter for arsenic in drinking water supplied by interstate Carrier
Water Supplies. The arsenic standard remained at that level in the 1962 re-
vision of the Drinking Water Standards and has been continued in the U.S.
Environmental Protection Agency Drinking Water Standards which became effec-
tive in June of 1977.
The American Conference of Governmental and Industrial Hygienists
(ACGIH, 1977) has set 0.5 mg/m3 as the Threshold Limit Value-Time Weighted
Average (TLV-TWA) for airborne arsenic. This means that the time-weighted
average concentration of airborne arsenic for a normal 8-hour workday or
40-hour workweek should not exceed 0.5 mg/m3. The Conference has issued a
Notice of Intended Change (for 1977} which to reduce the TLV-TWA from 0.5
mg/m3 to 0.05 mg/m3 (ACGIH, 1977).
The National Institute of Occupational Safety and Health has recommended
a ceiling level of 2 vg/m3 for airborne inorganic arsenic for any 15 min-
ute period of the workday.
The new (August, 1978) Occupational Safety and Health Administration
(OSHA) standard for airborne inorganic arsenic is 10 wg/m3 TWA.
Current Levels of Exposure
A broad range of arsenic levels have been found in drinking water sam-
ples. In a U.S. Environmenal Protection Agency national study of resident-
ial tap water, 66.8 percent of the one time grab samples collected from
3,834 residences had arsenic levels greater than 0.1 ug/1. The average,
minimum, and maximum levels of the samples with detectable arsenic were
2.37, 0.05, and 213.6 ug/1, respectively (Greathouse and Craun, 1978). In
C-110
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1975 it was reported that 5 out of 566 samples collected from Interstate
Carrier Water Supplies exceeded 10 ug/1 and that the maximum level was 60
ug/liter (U.S. EPA, 1975). Well water samples collected during 1976 at 59
residences in a Fairbanks, Alaska suburban community had a mean arsenic con-
tent of 224 yg/liter with, a range from 1.0 to 2,450 ug/1 (U.S. Public Health
Service, 1977). Moderately elevated levels of arsenic, 10 to 330 ug/1, are
present in potable waters of some smaller communities in Nevada and Cali-
fornia (Valentine, 1979). There have been a number of other reports of iso-
lated instances of higher than usual concentration of arsenic in well waters
(Goldsmith, et al. 1972; Feinglass, 1973; Morton, et al. 1976). The highest
value reported in these studies was 21,000 ug/1 in well water contaminated
by arsenical grasshopper bait.
There is a wide diversity in the estimates of daily intake of arsenic in
foods. Schroeder (1968) has estimated that the average diet provides an
arsenic intake of about 1,000 ug/day. Arsenic in a sample institutional
diet amounted to about 400 ug/day (Schroeder and 8alassa, 1966). This lower
level is attributed, at least partially, to the absence of seafood, a pri-
mary source of arsenic, in the institutional diet. In contrast to these
levels, the World Health Organization (WHO) reported that average arsenic
intakes for Canada, the United Kingdom, the United States, and France varied
from 25 to 33 ug/day; specific values ranged from 7 to 60 ug/day (WHO, 1973).
According to Suta (1978), the levels of atmospheric arsenic in locations
where major arsenic emitting sources are absent range from below the detec-
tion limit of 1 ng/nr to 83 ng/rrr with an average of 3 ng/rrr. The an-
nual average near major emission sources (copper, lead, and zinc smelters,
cotton gins, pesticide manufacturers, and glass manufacturers) ranged from 3
•j •} •>
ng/'nij to 5,900 ng/m- with most below 290 ng/mj. Assuming normal daily
-111
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inhaled volumes of 21.2 and 11.1 cubic meters for men and women, respective-
ly, the ranges of daily airborne arsenic exposures in uncontaminated areas
are 760 ng and 11-921 ng for men and women respectively. In areas where
arsenic emitting sources are located daily, inhaled exposure levels may be
as high as 6,148 to 125,080 ng and 3,219 to 65,490 ng for men and women,
respectively.
No quantifiable information was found concerning present levels of expo-
sure from drugs or dermal contact.
Special Groups at Risk
Adverse effects have been demonstrated in all age groups of both sexes.
Children may have an increased susceptibility to arsenic-induced CNS damage
(Hamamoto, 1955; Okamura, et al., 1956; Yamashita, et al., 1972).
Basis and Derivation of Criterion
As described in the Carcinogenicity Section, a number of studies have
shown that arsenic is important in the etiology of human cancers. Clinical,
occupational, and population studies have demonstrated that both ingestion
and inhalation exposures to arsenic compounds increase the risk of cancer
induction in the tissues of the lung and skin and possibly other sites.
There appears to be general agreement that arsenic is a human carcinogen,
despite of the fact that there has been general failure to demonstrate this
effect in any animal model. Hence, it is necessary to rely totally on human
data rather than supplement it with appropriate animal toxicity and carcino-
genic data. This limitation causes serious problems since animal studies
are the only practical means to effectively evaluate relative toxicities,
absorption rates, etc. for different compounds and routes of administra-
tion. Instead, these types of questions must be answered based on effects
and observation of exposed populations recognizing the numerous unknowns
C-112
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(levels of arsenic and other environmental exposures, dietary patterns,
genetic differences, etc.) and different routes of exposure.
The only study that relates levels of arsenic ingestion to skin cancer
is the one conducted by Tseng (1968) in southwest Taiwan. He found a con-
sistent dose response relationship between the exposure variable levels of
arsenic in drinking water and age and stein cancer prevalence. Questions
concerning comparability between the U.S. and Chinese populations must be
raised since some areas in the U.S. have similar arsenic levels without the
reported dermatological manifestations. It is very possible that major dif-
ferences in dietary patterns (the Chinese diet is low in protein and fat)
(Veh, 1973), other environmental and/or occupational coexposures, socioeco-
nomic status, etc. may account for the differences. However, since similar
health responses have been observed in Antofagasta, Chile (Borgono and Grei -
ber, 1972), Cordoba, Argentina (Bergoglio, 1964), German vineyard workers
(Oenk, et al. 1969), and those who ingest Fowler's Solution (Neubauer,
1947), it must be assumed that arsenic is at least one component of the en-
vironmental exposures responsible for the observed effects. Secondly, the
clear dose response relationships both by length of exposure, as indicated
by age, and by level of waterborne arsenic provide additional evidence that
arsenic is at least one of the agents responsible for the observed effects.
It seems auite unlikely that other environmental, occupational, or socio
economic factors which might be responsible for variations in skin tumor in
cidence would have a similar gradient to the waterborne arsenic gradient.
Hence it appears reasonable to use the Taiwan data as a basis for estimating
a level which will not increase the lifetime risk of cancer by more than
1/100,000. It is recognized the calculated level may be quite conservative
since the Taiwan experience may represent a worst ease situation due to ex-
posures and other agents, possibly dietary deficiencies.
C-113
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The EPA Cancer Assessment Group has developed a mathematical prediction
model for estimating an acceptable level based on the published Taiwan data
(Tseng, 1977). Their material is included in Appendix I to explain the
model and the calculated estimates.
Under the Consent Decree in NRDC v. Train, criteria are to state "recom-
mended maximum permissible concentrations (including where appropriate,
zero) consistent with the protection of aquatic organisms, human health, and
recreational activities." Arsenic 1s suspected of being a human carcinogen.
Because there is no recognized safe concentration for a human carcinogen,
the recommended concentration of arsenic in water for maximum protection of
human health is zero.
Because attaining a zero concentration level may be infeasible in some
cases and in order to assist the Agency and states in the possible future
development of water quality regulations, the concentrations of arsenic cor-
responding to several incremental lifetime cancer risk levels have been
estimated. A cancer risk level provides an estimate of the additional inci-
dence of cancer that may be expected in an exposed population. A risk of
lO"^ for example, indicates a probability of one additional case of cancer
for every 100,000 people exposed, a risk of 10"6 indicates one additional
case for every million people exposed, and so forth.
In the Federal Register notice of availability of draft ambient water
quality criteria, EPA stated that it is considering setting criteria at an
interim target risk level of 10"5, 10"6, or 10"7 as shown in the fol-
lowing table.
Exposure Assumptions Risk Levels and Corresponding Criteria (1)
(per aay;ng/i
10-7 10-6 10-5
2 liters of drinking water 0772 772 ~72
and consumption of 6.5 g
grams fish and shellfish. (2)
Consumption of fish and 1.75 17.5 175
shelIfish only.
C-114
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(1) Calculated by applying a relative risk model for epidemiology stud-
ies, as discussed in the Human Health Methodology Appendices to the
October 1980 Federal Register notice which announced the availabil-
ity of this document and as discussed in Appendix I. Since the ex-
trapolation model is linear at low doses, the additional lifetime
risk is directly proportional to the water concentration. There-
fore, water concentrations corresponding to other risk levels can
be derived by multiplying or dividing one of the risk levels and
corresponding water concentrations shown in the table by factors
such as 10, 100, 1,000, and so forth.
(2) Thirteen percent of the arsenic exposure results from the consump-
tion of aquatic organisms which exhibit an average bioconcentration
potential of 44-fold. The remaining 87 percent of arsenic exposure
results from drinking water.
Concentration levels were derived assuming a lifetime exposure to var-
ious amounts of arsenic, (1) occurring from the consumption of both drinking
water and aquatic life grown in waters containing the corresponding arsenic
concentrations and, (2) occurring solely from consumption of aquatic life
grown in the waters containing the corresponding arsenic concentrations.
Although total exposure information for arsenic is discussed and an
estimate of the contributions from other sources of exposure can be made,
this data will not be factored into ambient water quality criteria formula-
tion until additional analysis can be made. The criteria presented, there-
fore, assumed an Incremental risk from ambient water exposure only.
The criterion as estimated by the methodology may appear unreasonably
low. However, Inorganic arsenic is clearly established as a human carcino-
gen including ingestion in drinking water. Further, negative findings in
C-115
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large population groups (Harrington, st al. 1980; norton, et al. 1976;
Southwick, st al. 1980) have been carefully evaluated by the Agency to check
if the criteron predicts an incidence above what was found in these stud=
ies. The Agency concludes that the Taiwan experience is not invalidated by
the lack of skin cancer incidence in areas of the United States where people
are exposed to arsenic through drinking water.
C-11S
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APPENDIX
Mathematical Prediction Model
Due to the stable copulation in a rural area along the southwest coast
of Taiwan, the data collected by Tseng, et al. (1968) may be viewed as a
lifetime feeding study where measured amounts of arsenic in well water are
consumed by a study population of 40,421 individuals. Thus, this data may
be used to predict the lifetime probability of skin cancer caused by the
ingestion of arsenic.
A model estimating the cancer rate as a function of drinking water arse-
nic concentration was generated using the information in its published form,
which is a summary of data collected by the investigators. If the original
data had been available, a more exact mathematical analysis would have been
possible.
Doll (1971) has suggested that the relationship between the incidence of
some site specific cancers, age, and exposure level of a population may be
expressed as:
(1) I(x,t) - vBxV'1
where x is the exposure level of a carcinogen, t is the age of the popula-
tion, and B, m, v are unknown parameters.
However, the data collected by Tseng, et al. (1968) was obtained at one
point in time, and since skin cancer has only a marginal effect on the death
rate, the obtained rates may be viewed more accurately as the probability of
having contracted skin cancer by time t. The relationship between this
probability, often referred to as the cummulatfve probability density or
prevalence, and the incidence or age specific or hazard rate may be ex-
pressed as:
(2) F(x,t) - 1 - exp [ ("^(x.s) dsl
o'
C-156
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Utilizing the suggestion of Doll (1971) for the form of the incidence
rate, the prevalence may be expressed as:
(3) F(x.t) » 1 - exp (-8xmtv)
which is a Welbull distribution.
In Table 1, based on information in Tseng, et al. (1968), we have esti
mates of F(x.t) for different age and exposure groupings for males.
To use this data, specific values for x and t had to be obtained for the
intervals. Where the intervals were closed the midpoint was utilized. For
the greater than 0.6 ppm group, the midpoint between 0.6 and the greatest
recorded value 1.8 was taken, resulting in 1.2 ppm. For age 60 or greater,
a value of 70 was utilized somewhat arbitrarily, being the same increase
over the lower level as that in the other two age intervals. The values for
(x,t) to relate to the prevalence estimates are shown in parentheses in
Table 1.
From eauation (3) it follows that:
(4) ln(-ln[l-F(x,t)]) - ln(B) * m ln(x) * v ln(t)
which is multiple linear in form. Estimating the parameters by the usual
least square techniques, we obtained the relationship:
(5) ln( - ln[l - F(x.t)]) » 17.548 * 1.192 ln(x) * 3.881 ln(t)
which is an excellent fit having a multiple correlation coefficient of
0.986.
Eauation (5) may be expressed as:
(6) F(x,t) - 1 - expC-10"7 x 0.2429x 1>192 t3-881] .
- 1 -expC-H (t) x 1.192]
If the coefficient m • 1.192 was in fact equal to 1, then for a given value
of t equation (6) would be "one-hit" in form.
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TABLE 1
Age - Exposure - Specific Prevalence Rates*
ppma
0 - ,29
(0.15)
0.30 - 0.59
(0.450)
>0.6
(1.2)
20-39
(30)
0.0013
0.0043
0.0224
40-59
(50)
0.0065
0.0477
0.0983
>60
770)
0.0481
0.1634
0.2553
*Source: Tseng, et al. 1968
aRange given. Midpoint is In parenthesis,
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To test this Hypothesis (i.e., Ho: in « 1) the student "t" test is used,
giving the result:
-1
which is r»ot significant at the 0.1 level. The value 0.138 is the standard
e^or of m. Thus there is insufficient evidence to reject the hypothesis
that the dose response relationship is "one-hit" even at the 0.1 level even
though the standard error of the regression coefficient is quite small.
Fixing m » 1 we have the relationship:
(7) Ffx.t) . 1 - exp[-g(t)x]
Transforming this equation to its linear form and obtaining the least square
estimates of B and v, we find that:
g (t) » exp(-17.5393) t3'853, where 8 - 2.41423 x LO"8, v - 3.853
In this case, the fit is still quite good as represented by a correlation of
0.971. The data used to obtain the estimates is shown in Table 2 and the
goodness of fit is illustrated in Figure 1.
The function F(x,t) . 1 -exp[ -2. 41423x1 O"8 x t3*853], is the proba-
bility of contracting skin cancer by age t given that a individual had a
life-time exposure to x ppm in his drinking water (and lived until age t).
In Appendix ! of the CAG (1978) coke oven document, the lifetime proba-
bility of cancer in the presence of competing mortality was derived from the
age-specific incidence rate. For the case where the cancer rate in the ab-
sence of exposure is near zero (as in this case where the skin cancer is of
3 rats form that was virtually unknown in other parts of Taiwan) the life-
time probability may be expressed as:
Q(*) * Bx/(8xV)
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TABLE 2
Data Utilized to Obtain Predictor Equation and Figure 1
pp»
Arsenic
X
0.15
0.45
1.20
Age at Medical
Examination
t
30
50
70
30
50
70
30
50
70
Skin Cancer Prevalence
Observed
Rate
0.0013
0.0065
0.0481
0.0043
0.0477
0.1634
0.0224
0.0983
0.2553
Rate
F(x,t)
Expected
Rate
0.0031
0.0127
0.0455
0.0053
0.0375
0.1304
0.0141
0.0969
0.3110
Transformed
Skin Cancer
Prevalence Rate
-ln( -ln[l-
-17.5393 + 3
Observed
6.64474
5.03269
3.00993
5.44699
3.01849
1.72368
3.78739
2.26844
1.22155
.8531nt+lnx
Expected
6.33160
4.36341
3.06695
5.23299
3.26480
1.96834
4.25216
2.28397
0.98751
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F(x,t) -
0.0009 7.0
t-30
0.0025 6.0
0.0067 5.0
0.0181 4.0
0.0486 3.0
0.1266 2.0
0.3078 1.0
U50
0.6321 0.0
-2. -1.6 -1.2 -.8 -.4 .0 .4 Ine(ppm)
0.135 0.202 0.301 0.449 0.670 1.000 1.492 ppm
FIGURE 1
Relationship between Transfonned
Prevalence and log ppm Arsenic in Water, log age
C-161
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whe»-e p » In t^, (where tffl is the median lifetime of tne popu-
lation). Assuming tm » 68 and v * 3.853, is the same for total mortality
as the appearance of skin cancer, we have:
0 t \ 2.41423 x
2 > " 2.41423 x * 6.02793
The level of x that results in a lifetime probability of skin cancer equal
to 1C"5 is found by solving Q (» ) . 10"5 for x giving X « 2.4969 x
10"5 mg/liter or 0.025 ug/liter.
Under the assumption that the average consumption of water is two liters
in both the U.S. and Taiwan we estimate a water criteria concentration of:
2(.025) - C(2 * 0.0065 x 44) or
C - —1^5 - 0.0219 ug/1
2.2860
Where 0.0065 is the average fish consumption in kilograms and 44 is the bio-
accumulation factor for fish (supplied by Don Mount of U.S. EPA).
A standard for waterborne arsenic of 22 ng/1 would thus insure a life-
time risk of cancer of less than 10 .
It is recognized that inorganic and organic compounds differ in terms of
toxicity and likely in terms of carcinogenic potential. However, since the
recommended level is to be based on carcinogenic potential and no informa-
tion is available concerning the relationship(s) of specific arsenic species
and cancer a single all inclusive limit must be set. Even if the data were
available to permit separate standards, the level of development of the re-
quired analytical methodology is not sufficient to permit reliable and re-
oeatable speciation measurements, a necessity before setting a standard (Or.
Irgolic, Texas AAM University, personal communication).
C-162
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For comparative purposes, the Stockinger and Woodward (1958) method was
applied to the present and proposed airborne arsenic standards to compute
comparable waterborne arsenic levels.
American Conference of Governmental Industrial Hygienists:
1. Existing threshold limit value - time-weighted average - 500 ug/m
500 ug x 10 m3 x 5 work days x 20X absorption m 5 000 g/week
m3 work day week
5,000 ug x 1 week x 1 x Allowed » 445 ug/i
week 7 days Z liters 8055 absorption
Applying the recommended safety factor of 100 the comparable drinking
water limit is 4.46 ug/1.
2. Proposed threshold limit value - time-weighted average - 50 ug/m^
50 ug x 10 m3 x 5 work days x 2056 absorption ^ ^n Q/wk
m3 work day week
500 ug x 1 week x 1 x Allowed . 44.5 vg/]
week 7 days 2 liters 8056 absorption
Applying the recommended safety fator of 100 the comparable drinking
water limit is 0.45 ug/1.
Occupational Safety and Health Administration:
1. Eight-hour average - 10 ug/m3
10 ug x 10 m3 x 5 work days x 2055 absorption m 10Q ug/week
week work days week
100 ug x 1 week x 1 x Allowed « 3.93 ug/l
week 7 days 2 liters so* aosorption
Applying the recommended safety factor of 100, the comparable drinking
water limit is 0.09 ug/1.
C-163
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Assuming that the absorption factors (air.-20 percent, water-80 percent)
and methods recommended by Stockinger and Woodward (1958) are reasonable and
that the safety of 100 is appropriate, it is dear that the recommended
water standard is even more restrictive than the air standards. The differ-
ences are likely due at least partially to variations in extrapolation meth-
ods and levels of acceptable risk.
It is of interest to see what cancer risk would be associated with an
air exposure equivalent to the recommended water standard of 0.02 wg/1. If
we make the following assumptions:
(1) Total daily average absorbed arsenic from water is:
0.8 x 0.02 (2 + 0.0065 x 44) > 0.0366 ug, where 80 percent is the
absorption rate.
(2) The breathing rate is 1 m /hr and 20 percent of the arsenic is
absorbed.
Then, the air concentration, X, required to obtain the same absorbed amount
of arsenic is:
0.2 x 24 x X - 0.0366 ug or
X - 0.008 ug/m3
From the 1978 CAG report on the risk associated with airborne arsenic
the lifetime cancer risk associated with X ug/M3 of arsenic in the air is
estimated to be:
P » 3.418 x 10"3X
If instead of basing our risk on the most sensitive study we use the geo-
metric mean of the three studies, the lifetime cancer risk would be:
P . 1.95 x 10'3 X
C-164
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The risks associated with X . 0.008 are thus 2.73 x 10"5 and 1.56 x
10"^. Thus, if our water standard was based on the geometric mean of the
human epidemiological air studies, it would be 0.013 ug/1 instead of 0.02
ug/1, which 1s a remarkably consistent result.
C-165
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