CHLORINATED BENZENES
Ambient Water Quality Criteria
Criteria and Standards Division
Office of Water Planning and Standards
U.S. Environmental Protection Agency
Washington, D.C.
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CRITERION DOCUMENT
CHLORINATED BENZENES
CRITERIA
Aquatic Life
Chlorobenzene
The data base for freshwater aquatic life is insuffi-
cient to allow use of the Guidelines. The following recommenda-
tion is inferred from toxicity data on 1,2,4,5-tetrachlorobenzene
and saltwater organisms and 1,2-dichlorobenzene and freshwater
organisms.
For chlorobenzene the criterion to protect freshwater
aquatic life as derived using procedures other than the Guidelines
is 1,500 ug/1 as a 24-hour average and the concentration should
not exceed 3,500 ug/1 at any time.
The data base for saltwater aquatic life is insufficient
to allow use of the Guidelines. The following recommendation is
inferred from toxicity data on 1,2,4,5-tetrachlorobenzene and
saltwater organisms and 1,2-dichlorobenzene and freshwater
*
organisms.
For chlorobenzene the criterion to protect saltwater
aquatic life as derived using procedures other than the Guidelines
is 120 ug/1 as a 24-hour average and the concentration should not
exceed 280 ug/1 at any time.
1,2,4-trichlorobenzene
The data base for freshwater aquatic life is insuffi-
cient to allow use of the Guidelines. The following recommenda-
tion is inferred from toxicity data on 1,2,4,5-tetrachlorobenzene
and saltwater organisms and 1,2-dichlorobenzene and freshwater
organisms.
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For 1,2,4-trichlorobenzene the criterion to protect
freshwater aquatic life as derived using procedures other than the
Guidelines is 210 ug/1 as a 24-hour average ano the concentration
should not exceed 470 ug/1 at any t nec
The data base for saltwatt-c aquatic life is insufficient
to allow use of the Guidelines. Tht following recommendation is
inferred from toxicity data on 1, 2, ' , 5-tetrachlorobenzene and
saltwater organisms and 1,2-dichlorcbenzene and freshwater
organisms.
For 1,2,4-trichlorobenzene the criterion to protect
saltwater aquatic life as derived using procedures other than the
Guidelines is 3.4 ug/1 as a 24-hour average and the concentration
should not exceed 7.8 ug/1 at any time.
1/2,3 t5-tetrachlorobenzene
The data base for freshwater aquatic life is insuffi-
cient to allow use of the Guidelines. The following recommenda-
tion is inferred from toxicity data on 1,2,4,5-tetrachlorobenzene
and saltwater organisms and 1,2-dichlorobenzene and freshwater
organisms.
For 1,2,3,5-tetrachlorobenzene the criterion to protect
freshwater aquatic life as derived using procedures other than the
Guidelines is 170 ug/1 as a 24-hour average and the concentration
should not exceed 390 ug/1 at any time.
The data base for saltwater aquatic life is insufficient
to allow use of the Guidelines. The following recommendation is
inferred from toxicity data on 1,2,4,5-tetrachlorobenzene and
saltwater organisms and 1,2-dichlorobenzene and freshwater
organisms.
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For 1,2,3,5-tetrachlorobenzene the criterion to protect
saltwater aquatic life as derived using procedures other than the
Guidelines is 2.6 ug/1 as a 24-hour average and the concentration
should not exceed 5.9 ug/1 at any time.
1,2,4,5-tetrachlorobenzene
The data base for freshwater aquatic life is insuffi-
cient to allow use of the Guidelines. The following recommenda-
tion is inferred from toxicity data on 1,2,4,5-tetrachlorobenzene
and saltwater organisms and 1,2-dichlorobenzene and freshwater
organisms.
For 1,2,4,5-tetrachlorobenzene the criterion to protect
freshwater aquatic life as derived using procedures other than the
Guidelines is 97 ug/1 as a 24-hour average and the concentration
should not exceed 220 ug/1 at any time.
For 1,2,4,5-tetrachlorobenzene the criterion to protect
saltwater aquatic life as derived using the Guidelines is 9.6 ug/1
as a 24-hour average and the concentration should not exceed 26
ug/1 at any time.
pentachlorobenzene
The data base for freshwater aquatic life is insuffi-
cient to allow use of the Guidelines. The following recommenda-
tion is inferred from toxicity data on 1,2,4,5-tetrachlorobenzene
and saltwater organisms and 1,2-dichlorobenzene and freshwater
:
organisms.
For pentachlorobenzene the criterion to protect fresh-
water aquatic life as derived using procedures other than the
Guidelines is 16 'ug/1 as a 24-hour average and the concentration
should not exceed 36 ug/1 at any time.
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The data base for saltwater aquatic life is insufficient
to allow use of the Guidelines. The following recommendation is
inferred from toxicity data on 1,2,4,5-tetrachlorobenzene and
saltwater organisms and 1,2-dichlorobenzene and freshwater
organisms.
For pentachlorobenzene the criterion to protect salt-
water aquatic life as derived using procedures other than the
Guidelines is 1.3 ug/1 as a 24-hour average and the concentration
should not exceed 2.9 ug/1 at any time.
Human Health
For the prevention of adverse organoleptic or toxicological
effects, the recommended criteria for chlorinated benzenes are as
follows:
Substance Criterion Basis for Criterion
Monochlorobenzenel 20 ug/1 Organoleptic effects
Trichlorobenzene 13 ug/1 Organoleptic effects
Tetrachlorobenzene 17 ug/1 Toxicity studies
Pentachlorobenzene .5 ug/1 Toxicity study
IA toxicological evaluation of monochlorobenzene resulted in
a level of 450 ug/1; however, organoleptic effects have been
reported at 20 ug/1.
For the maximum protection of human health from the potential
carcinogenic effects of exposure to hexachlorobenzene (HCB)
through ingestion of water and contaminated aquatic organisms, the
ambient water concentration is zero. Concentrations of HCB esti-
mated to result in additional lifetime cancer risks ranging from
no additional risk to an additional risk of 1 in 100,000 are pre-
sented in the Criterion Formulation section of this document. The
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Agency is considering setting criteria at an interim target
risk level in the range of 10~5/ 10~6, or 10~? with corres-
ponding criteria of 1.25 ng/1, 0.125 ng/1, and 0.0125 ng/1,
respectively.
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Introduction
The chlorinated benzenes, excluding dichlorobenzenes,
are monochlorobenzene (CgHcCl) , 1, 2, 3-tr ichlorobenzene (CgH-,
Clo), 1,2,4-trichlorobenzene (CgHoClo), 1,3,5-trichlorobenzene
(CgH3Cl3), 1,2,3,4-tetrachlorobenzene (CgH2Cl4), 1,2,3,5-
tetrachlorobenzene (CgH3Cl4), 1,2,4,5-tetrachlorobenzene
(CgH2Cl4), pentachlorobenzene (CgHCl,-), and hexachlorobenzene
(CgClg). Based on annual production in the U.S., 139,105
kkg of monochlorobenzene was produced in 1975, 12,849 kkg
of 1,2,4-trichlorobenzene, 8,182 kkg of 1,2,4,5-tetrachloroben-
zene and 318 kkg of hexachlorobenzene were produced in 1973
(West and Ware, 1977; U.S.I.T.C., 1975; EPA, 1975a).
The remaining chlorinated benzenes are produced mainly
as by-products from the production processes for the above
four chemicals. Production and use of chlorinated benzenes
results in 34,278 kkg of monochlorobenzene, 8,182 kkg of
trichlorobenzenes and about 1,500 kkg of tetra-, penta-,
and hexa-chlorinated benzenes entering the aquatic environment
yearly. Annual amounts on monochlorobenzene (690 kkg) and
hexachlorobenzene (1,628 kkg) contaminate solid wastes.
Yearly estimates of atmospheric contamination of monochloro-
benzene and tetrachlorobenzenes are 362.and 909 kkg, respec-
tively (West and Ware, 1977).
Monochlorobenzene is used for the synthesis of ortho
and para nitrochlorobenzenes (50 percent), solvent uses
(20 percent), phenol manufacturing (10 percent) and DDT
manufacturing (7.5 percent). 1,2,4-trichlorobenzene is used
as a dye carrier (46 percent), herbicide intermediate (28
percent), a heat transfer medium, a dielectric fluid in
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transformers, a degreaser, a lubrica ; aad a _ .-. antial ir.--.cr.i-
cide against termites. The other tr h]or^V ;-..- I'fjort:. -
are not used in any quantity. 1,2,4 -; .-.' _,^e. j;ene
is the only tetrachloro-isomer used . id. ' qu-.ntities.
Fifty-six percent of the annual con? .? .: . 2,4 S-tetjd-
chlorobenzene is used in the product! n "£ t'~ - 'foliant,
2 , 4 , 5-trichlorophenoxy acetic acid, . p^rcenc a the synthe-
sis of 2,4,5-trichlorophenol and 11 > rcsnt e~ a fungicide.
*
Pentachlorobenzene is used in small c ar.ti iea as a captive
intermediate in the synthesis of specialty chemicals (West
and Ware, 1977). Hexachlorobenzene in 1972 was used as a
fungicide (23 percent) to control wheat bunt and smut on
seed grains. Other industrial uses (77 percent) included
dye manufacturing, an intermediate in organic synthesis,
porosity controller in the manufacturing of electrodes,
a wood preservative and an additive in pyrotechnic composi-
tions for the military (EPA, 1975a).
In recent years, hexachlorobenzene has become of concern
because of its widespread distribution as an environmental
contaminant and a contaminant of food products used for
human consumption (Grant, et al. 1974). Hexachlorobenzene
has been found in adipose tissue and milk of cattle being
raised in the vicinity of an industrialized region bordering
the Mississippi River between Baton Rouge and New Orleans,
Louisiana. Hexachlorobenzene residues have been found in
adipose tissue of sheep in western Texas and eastern California
(EPA, 1975b). The occurrence and effects of hexachlorobenzene
have been reported in many organisms, e.g. birds (Vos, et
al. 1971; Cromartie, et al. 1975), rats (Medline, et al.
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1973), man (Cam and Nigogosyan, 1963) and fishes (Holden,
1970; Johnson, et al. 1974, ,Zi.tko, 1971) . .'Magnification
in the natural food.chain .is indicated by Gilbert-son and
Reynolds (1972) observation of hexachlorobenzene in the
eggs of common terns, which had apparently eaten contaminated
fish. This compound has also been found -in samples of ocean
water and its persistence in the environment has been acknowl-
edged (Seltzer, 1975).
Specimens of levee soil taken from along the Mississippi
River, known to be contaminated with hexachlorobenzene waste,
had levels of the compound ranging from 107.0 to .874.. 0 /jg/kg
(wet weight) (EPA, 1976a).
Among seven samples of sediments taken from the lower
Mississippi River, only one had detectable amounts of hexa-
chlorobenzene. The concentration found was .231,jug/L. This
site was known to be contaminated ,by hexachloroben'zene in
the past (Laska., et al. 1976) .
The National Organics Reconnaissance Survey tested
ten water supplies for a variety of organic chemicals. Mono1-
chlorpbenzene was detected but not quantified in three of
the ten .drinking water supplies. Drinking water supplies
from 83 locations in Region V, EPA were analyzed for various
pesticides and organic chemicals. Hexachlorobenz-ene was
detected in three locations with concentrations ranging
from 6 to 10 ng/1.
The National Organics Reconnaissance Survey tested
ten finished drinking waters fcr a variety of organic chemi-
cals (EPA, 1975c).
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Some physical properties of the chlorinated benzenes
are given below in Table 1 (Weast, 1975.
TABLE 1
Compound
MW
mp(°C) bp(°C)
density logoctanol
water
partition
monochlorobenzene
tr ichlorobenzene
1,2,3-
1,2,4-
1,3,5-
tetrachlorobenzene
1,2,3,4-
1,2,3,5-
1,2,4,5-
pentachlorobenzene
hexachlorobenzene
112.56
181.45
215.90
250.34
284.79
-45.6
52.6
17
63.4
47.5
54.5
138-140
86'
230
131-132
218-219
213.5
208
254
246
243-246
277
322
1.107
143
1.454
145
146
--
1.858
1.834
2.044
2.83
4.23
4.93
5.63
6.43
Monochlorobenzene, which is the most polar compound,
is soluble in water to the extent of 488 mg/1 at 25° (Mellan,
1970; Mardsen and Marr, 1963). Solubilities of the other
chlorobenzenes in water were not available. The chlorinated
benzenes are generally good solvent for fats, waxes, oils
and greases. The lipid solubility of these compounds is
high and are expected to accumulate in ecosystems (Mardsen
and Marr, 1963; Mellan, 1970).
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REFERENCES
Cam, C. , and G. Nigogosyan. 1963. Aoqu'.red toxic porphyria
cutanea tarda due to hexachlorobenzrne. Jour. Am. Med. Assoc.
183: 88.
Cromartie, E.W. 1975. Residues of organochlorine pesticides
and polychlorinated biphenyls and autopsy data for bald
eagles, 1971-1972. Pestic. Monit. Jour. 9: 11.
Gilbertson, M., and L.M. Reynolds. 1972. Hexachlorobenzene
(HCB) in the eggs of common terns in Hamilton Harbour, Ontario.
Bull. Environ. Contain. Toxicol. 7: 371.
Grant, D.L., et al. 1975a. Hexachlorobenzene accumulation
and decline of tissue residues and relationship to some
toxicity criteria in rats. Environ. Qual. Safety Suppl.
3: 562.
Grant, D.L., et al. 1975b. Effect of hexachlorobenzene on
rat reproduction. Toxicol. Appl. Pharmacol. 33: 167. (Author
abstract.)
Hampel, C., and G. Hawley. 1973. The Encyclopedia of Chemistry,
3rd ed. Van Nostrand Reinhold Co., N.Y.
Holden, A.V. 1967. International co-operative study of organo-
chlorine pesticide residues in terrestrial and aquatic wild-
life, 1967, 1968, 1970. Pestic. Monit. Jour. 4: 117.
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Johnson, J.L., et al. 1975. Hexachlorobenzene (HCB) residues
in fish. Bull. Environ. Contam. Toxicol. 11: 393.
Kirk, R.E., and D.F. Othmer. 1963. Kirk-Othmer Encyclopedia
of Chemical Technology, 2nd ed. Vol. 4, and Vol. 5. John
Wiley and Sons, New York.
Laska, A.L., et al. 1976. Distribution of hexachlorobenzene
and hexachlorobutadiene in water soil and selected aquatic
organisms along the lower Mississippi River, Louisiana.
Bull. Environ. Contam. Toxicol. 15: 535.
Mardsen, C., and S. Marr, 1963. Solvents Guide. Cleaver-Hume
Press Ltd., London.
Medline, A., et al. 1973. Hexachlorobenzene and rat liver.
Arch. Pathol. 96: 61.
Mellan, I. 1970. Industrial Solvents. Noyes Data Corp. Park
Ridge, N.J.
Seltzer, R.J. 1975. Ocean pollutants pose potential danger
to man. Chem. Engr. News 53: 19.
Snell, D., et al. 1969. Encyclopedia of Industrial Chemical
Analysis. Vol. 9. Interscience Publishers, N.Y.
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Stecher, P.G., ed. 1968. The Merck Index. An encyclopedia
of chemicals and drugs. 9th ed. Merck and Co., Inc., Rahway,
N.J.
U.S. EPA. 1975a. Survey of Industrial Processing Data: Task
I, Hexachlorobenzene and hexachlorobutadiene pollution from
chlorocarbon processes. Mid. Res. Inst. EPA, Off. Toxic
Subs. Washington, D.C.
U.S. EPA. 1975b. HCB review report: Fifth 90-day HCB meeting
and status of HCB studies.
U.S. EPA. 1976a. An ecological study of hexachlorobenzene.
EPA-560/6-76-009.
Varshavskaya, S.P. 1967. The hygienic standardization of
mono- and dichlorobenzenes in reservoir waters. Nov. Tr.
Aspir. Ordina. Pervyi Moskov. Medit. Instit. 175.
Vos, J.G., et al. 1971. Toxicity of hexachlorobenzene in
Japanese quail with special reference to porphyria, liver
damage, reproduction, and tissue residues. Toxicol. and
Applied Pharmacol. 18: 944.
Weast, R.C., ed. 1975. Handbook of Chemistry and Physics.
The Chemical Rubber Co., Cleveland, Ohio.
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West, W.L., and S.A. Ware, 1977. Preliminary Report, Investiga-
tion of Selected Potential Environmental Contaminants: Halo-
genated Benzenes. Environ. Prot. Agency, Washington, D.C.
r
Zitko, V. 1971. Polychlorinated biphenyls and organochlorine
pesticides in some freshwater and marine fishes. Bull. Environ.
Contain. Toxicol. 6: 464.
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AQUATIC LIFE TOXICOLOGY*
FRESHWATER ORGANISMS
Introduction
This discussion does not include the dichlorobenzenes which
are treated in a separate criterion document. Toxicity of the
remaining compounds in this class have been determined with
several fish species, Daphnia magna and Selenastrum capricornutum.
No chronic effects data are available.
Acute Toxicity
All data reported for freshwater fish are 96-hour, static
toxicity tests with unmeasured concentrations. Pickering and
Henderson (1966) reported unadjusted 96-hour LC50 values for
goldfish, guppy, and bluegill to be 51,620, 45,530, and 24,000
ug/1, respectively, for chlorobenzene (Table 1). Two 96-hour LC50
values for chlorobenzene and fathead minnows were 33,930 ug/1 in
soft water (20 mg/1) and 29,120 ug/1 in hard water (360 mg/1)
(Table 1). This indicates that hardness does not significantly
*The reader is referred to the Guidelines for Deriving Water
Quality Criteria for the Protection of Aquatic Life [43 FR 21506
(May 18, 1978) and 43 FR 29028 (July 5, 1978)] in order'to better
understand the following discussion and recommendation. The
following tables contain the appropriate data that were found in
the literature, and at the bottom of each table are the calcula-
tions for deriving various measures of toxicity as described in
the Guidelines.
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affect the toxicity of chlorobenzene. U.S. EPA (1978) reported
96-hour LC50 values for bluegill exposed to chlorobenzene, 1,2,4-
trichlorobenzene, 1,2,3,5-tetrachlorobenzenef 1,2,4,5-tetrachloro-
benzene and pentachlorobenzene to be be 15,900, 3,360, 6,420,
1,550 and 250 ug/1/ respectively. Comparable tests (U.S. EPA,
1978) were conducted with three dichlorobenzenes and the 96-hour
LC50 values ranged from 4,280 to 5,590 ug/1. Only 1,2,3,5-tetra-
chlorobenzene is an apparent anomaly in the trend to increasing
toxicity with chlorination.
Unadjusted 48-hour EC50 values reported for Daphnia magna
(U.S. EPA, 1978) are: chlorobenzene - 86,000 ug/1; 1,2,4-tri-
chlorobenzene - 50,200 ug/1; 1,2,3,5-tetrachlorobenzene - 9,710
ug/1; and pentachlorobenzene - 5,280 ug/1 (Table 2). The 48-hour
EC50 value for 1,2,4,5-tetrachlorobenzene was greater than the
highest exposure concentration, 530,000 ug/1 (Table 5). The
48-hour EC50 for three dichlorobenzenes and Daphnia magna ranged
from 2,440 to 28,100 ug/1. For Daphnia magna the toxicity of
chlorinated benzenes generally tended to increase as the degree of
chlorination increased.
No marked difference in sensitivity between fish and inverte-
brate species is evident from the available data. The Final Acute
Values for the chlorinated benzenes are: chlorobenzene - 3,500
ug/1; 1,2,4-trichlorobenzene - 470 ug/1; 1,2,3,5-tetrachloro-
benzene - 390 ug/1; 1,2/4,5-tetrachlorobenzene - 220 ug/1; and
pentachlorobenzene - 36 ug/l« The Final Acute Values for chloro-
benzene and 1,2,3,5-tetrachlorobenzene are based on Daphnia magna
data whereas all others are based on fish data.
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Chronic Toxicity
No chronic toxicity data are available for fish or inverte-
brate species.
Plant Effects
Ninety-six-hour EC50 tests, using chlorophyll a^ inhibition
and cell number production as measured responses, were conducted
with the green alga, Selenastrum capricornuturn (Table 3). The
effects of chlorinated benzenes on this alga generally increased
as chlorination increased, but the trend was not smooth. The alga
was considerably less sensitive than fish and Daphnia magna. The
Final Plant Values are 220,000 ug/1 for chlorobenzene, 35,000 y.g/1
for 1,2,4-trichlorobenzene, 17,000 ug/1 for 1, 2, 3,5-tetrachloro-
benzene, 47,000 ug/1 for 1,2,4,5-tetrachlorobenzene and 6,600 ug/1
for pentachlorobenzene.
Residues
Data which are adequate for computing acceptable bioconcen-
tration factors are available for two chlorinated benzenes. After
28-day exposures, the steady-state bioconcentration factors for
bluegill for pentachlorobenzene and 1,2,3,5-tetrachlorobenzene are
3,400 and 1,800, respectively (Table 4). The half-lives for these
compounds were between 2 and 4 days for 1,2,3,5-tetrachlorobenzene
and greater than 7 days for pentachlorobenzene (U.S. EPA, 1978).
For three dichlorobenzenes the bioconcentration factors obtained
using the same procedures (U.S. EPA, 1978) ranged from 60 to 89.
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No measured steady-state bioconcentration factors (BCF) are
available for other chlorinated benzenes. However, BCFs can be
estimated using the octanol-water partition coefficients of 290,
18,000, 93,000, and 2,500,000 for chlorobenzene, 1,2,4-trichloro-
benzene, 1,2,4,5-tetrachlorobenzene, and hexachlorobenzene,
respectively. These coefficients are used to derive estimated
BCFs of 44, 1,000,' 3,500, and 42,000 for chlorobenzene, 1,2,4-tri-
chlorobenzene, 1,2,4,5-tetrachlorobenzene, and hexachlorobenzene,
respectively, for aquatic organisms that contain about 8 percent
lipids. If it is known that the diet of the wildlife of concern
contains a significantly different lipid content, appropriate
adjustments in the estimated BCFs should be made.
Bioconcentration factors correlate well with an increase in
chlorine content. The sequence of measured and estimated biocon-
centration factors are 44 (chlorobenzene), 72 (mean of dichloro-
benzene data), 1,000 (1,2,4-trichlorobenzene), 1,800 (1,2,3,5-
tetrachlorobenzene), 3,500 (1,2,4,5-tetrachlorobenzene), 3,400
(pentachlorobenzene), and 42,000 (hexachlorobenzene).
Miscellaneous
A variety of data on other adverse effects is presented in
Table 5. Bioconcentration factors derived from a model ecosystem
(Isensee, et al. 1976) ranged from 730 to 9,870 but it could not
be determined whether these were steady-state results.
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CRITERION FORMULATION
Freshwater-Aquatic Life
Summary of Available Data
The concentrations below have been rounded to two significant
figures.
chlorobenzene
Final Fish Acute Value = 4,900 u_g/l
Final Invertebrate Acute Value = 3,500 ug/1
Final Acute Value = 3,500 ug/1
Final Fish Chronic Value = not available
Final Invertebrate Chronic Value = not available
Final Plant Value = 220,000 ug/1
Residue Limited Toxicant Concentration = not available
Final Chronic Value= 220,000 ug/1
0.44 x Final Acute Value = 1,500 ug/1
1,2,4-trichlorobenzene
Final Fish Acute Value = 470 ug/1
Final Invertebrate Acute Value = 2,000 ug/1
Final Acute Value = 470 ug/1
Final Fish Chronic Value = not available
Final Invertebrate Chronic Value = not available
Final Plant Value = 35,000 ug/1
Residue Limited Toxicant Concentration = not available
Final Chronic Value = 35,000 ug/1
0.44 x Final Acute Value = 210 ug/1
1,2,3, 5-tetrachlorobenzene
Final Fish Acute Value = 900 ug/1
- Final Invertebrate Acute Value = 390 ug/1
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Final Acute Value = 390 ug/1
Final -Fish Chronic Value = not available
Final Invertebrate Chronic Vajue - not available
Final Plant Value = 17,000 ug/-1
Residue Limited Toxicant Concentration - not available
Final Chronic Value = 17,',00 ug/1
0.44 x Final Acute Value 170 ug/1
1,2,4,5-tetrachlorobenzene
Final Fi-sh Acute Value = 220 yx;/l
Final Invertebrate Acute Value = not available
Final Acute Value = 220 ug/1
Final Fish Chronic Value = not available
Final Invertebrate Chronic Value = not available
Final Pla'nt Value = 47,000 ug/1
Residue Limited Toxicant Concentration = not available
Final Chronic Value = 47,000 ug/1
0.44 x Final Acute Value = 97 ug/1
pentachlorobenzene
Final Fish Acute Value = 36 ug/1
Final Invertebrate Acute Value = 210 ug/1
Final Acute Value = 36 ug/1
Final Fish Chronic Value = not available
Final Invertebrate Chronic Value = not available
Final Plant Value = 6,600 ug/1
Residue Limited Toxicant Concentration = not available
Final Chronic Value = 6,600 ug/1
0.44 x Final Acute Value = 16 ug/1
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No freshwater criterion can be derived for any chlorinated
benzene using the Guidelines because no Final Chronic Value for
either fish or invertebrate species or a good substitute for
either value is available, and there are insufficient data to
estimate a criterion using other procedures.
However, data for 1,2,4,5-tetrachlorobenzene and saltwater
organisms and 1,2-dichlorobenzene and freshwater organisms can be
used as the basis for estimating criteria.
For 1,2,4,5-tetrachlorobenzene and saltwater organisms 0.44
times the Final Acute Value is 11 ug/1. This concentration is
close to the Final Chronic Value of 9.6 ug/1 derived from an
embryo-larval test with the sheepshead minnow. Also, for 1,2-
dichlorobenzene and freshwater organisms 0.44 times the Final
Acute Value is less than the Final Chronic Value based on an
embryo-larval test with the fathead minnow. Therefore, a reason-
able estimate of criteria for chlorinated benzenes and freshwater
organisms would be 0.44 times the Final Acute Value.
chlorobenzene
The maximum concentration of chlorobenzene is the Final Acute
Value of 3,500 ug/1 and the estimated 24-hour average concentra-
tion is 0.44 times the Final Acute Value. No important adverse
effects on freshwater aquatic organisms have been reported to be
caused by concentrations lower than the 24-hour average concentra-
tion.
CRITERION: For chlorobenzene the criterion to protect fresh-
water aquatic life as derived using procedures other than the
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Guidelines is 1,500 ug/1 as a 24-hour average and the
concentration should not exceed 3/500 ug/1 at any time.
1,2,4-trichlorobenzene
The maximum concentration of 1,2,4-trichlorobenzene is the
Final Acute Value of 470 U9/1 and the estimated 24-hour average
concentration is 0.44 times the Final Acute Value. No important
adverse effects on freshwater aquatic organisms have been reported
to be caused by concentrations lower than the 24-hour average
concentration.
CRITERION: For 1,2,4-trichlorobenzene the criterion to
protect freshwater aquatic life as derived using procedures other
than the Guidelines is 210 ug/1 as a 24-hour average and the
concentration should not exceed 470 ug/1 at any time.
1,2,3,5-tetrachlorobenzene
The maximum concentration of 1,2,3,5-tetrachlorobenzene is
the Final Acute Value of 390 ug/1 and the estimated 24-hour
average concentration is 0.44 times the Final Acute Value. No
important adverse effects on freshwater aquatic organisms have
been reported to be caused by concentrations lower than the
24-hour average concentration.
CRITERION: For 1,2,3,5-tetrachlorobenzene the criterion to
protect freshwater aquatic life as derived using procedures other
than the Guidelines is 170 ug/1 as a 24-hour average and the
concentration should not exceed 390 ug/1 at any time.
B-8
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1,2,4 ,5-tetrachlorobenzene
The maximum concentration of 1,2,4,5-tetrachlorobenzene is
the Final Acute Value of 220 ug/1 and the estimated 24-hour
average concentration is 0.44 times the Final Acute Value. No
important adverse effects on freshwater aquatic organisms have
been reported to be caused by concentrations lower than the
24-hour average concentration.
CRITERION: For 1,2,4,5-tetrachlorobenzene the criterion to
protect freshwater aquatic life as derived using procedures other
than the Guidelines is 97 ug/1 as a 24-hour average and the con-
centration should not exceed 220 ug/1 at any time.
pentachlorobenzene
The maximum concentration of pentachlorobenzene is the Final
Acute Value of 36 ug/1 and the estimated 24-hour average concen-
tration is 0.44 times the Final Acute Value. No important adverse
effects on freshwater aquatic organisms have been reported to be
caused by concentrations lower than the 24-hour average concentra-
tion.
CRITERION: For pentachlorobenzene the criterion to protect
freshwater aquatic life as derived using procedures other than the
Guidelines is 16 ug/1 as a 24-hour average and the concentration
should not exceed 36 ug/1 at any time.
.-9
-------
Table 1. Freshwater fish acute values for chlorinated benzenes
Dioucsay Test
' Giaauisffl . Method* cone
Goldfish. S U
Carassius aurotus
Fathead minnow, S U
Pimcphales promelas
Fathead minnow, S U
Pimcphales pronielas
Fathead minnow, S U
Pimcphales promelas
Guppy. S U
Poeciila retlculatus
0, Bluegill. S U
i l.epomis macrochirns
0 Bluegill, S U
Lcpomis macrochirus
Bluegill, S U
Lcpomis macrochirus
Blue gill, S U
l.epomis macrochirus
Bluegill. ' . S U
l.epomis macrochiijus
Bluegill. S U
l.epomis macrochirus
" S = static
** U - unmeasured
Geometric mean of adjusted values:
Chemical Time
.** Peace i lotion (tire)
Chlorobenzene 96
Chlorobenzenc 96
Chlorobenzene 96
Chlorobenzene 96
Chlorobenzenc 96
Chlorobenzene 96
Chlorobenzene 96
1,2.4-trichloro- 96
benzene
1.2.3.5-tetra- 96
Chlorobenzenc
1.2.4,5-tetra- 96
Chlorobenzene
Pcntachloro- 96
benzene
Chlorobcnzune - 19,100 ng/l
IXbo
51.620
33.930
29.120
33.930
45.530
24.000
15.900
3.360
6.420
1.550
250
19JOO
~3^9^-
Adjusted
LCbO
(u<|/l( Ketoienct
28.220
18.550
15,920
18.550
24.890
13.120
8.690
1.837
3.510
847
140
- 4.900
1 , 2 ,4-trichlorobenzene = 1,837 Mg/l \ -n
1 , 2, 3, 5-tetrachlorobenzene =
1 ,2.4,5-tetrachlorobenzene =
Pentachlorobenzene » 140 Mg/l
3,510 Mg/
847 ,,g/l
i-S =
Pickering &
Henderson, 1966
Pickering &
Henderson . 1966
Pickering &
Henderson, 1966
Pickering &
Henderson, 1966
Pickering &
Henderson, 1966
Pickering &
Henderson, 1966
U.S. EPA. 1978
U.S. EPA, 1978
U.S. EPA. 1978
U.S. EPA, 1978
U.S. EPA, 1978
Mg/l
470 Mg/l
3 510
847'
379 =
36 ,,g/l
220 Mg/l
-------
Table 2. KrcuhwaLcr invertebrate acute values for chlorinated benzenes (U.S. El'A, 1978)
Cladoceran,
Oaphnia magna
Cladoceran,
Daplinla magna
Cladoceran,
Oaphnia magna
Cladoceran,
Daphnia magna
* S = static
** u . unmeasured
03 Geometric mean of
1
bioabtiay Tett cheinicdi Time
Method* Cone .** Description (Ilia)
S U Chlorobenzene 48
S U 1.2.4-trichloro- 48
benzene
S U 1.2,3.5-tetra- 48
Chlorobenzene
S U fentachloro- 48
benzene
Adjusted values: Chlorobenzene - 73,000 pg/1
Adjusted
LC'j(J LCbU
(IKI/1I (uq/1)
86.000 73,000
50.200 42,500
9.710 8.220
5.280 4.470
2^- - 3.500 ig/1
1,2.4-trlchlorobenzene - 42.500 Mg/l A2^°° - 2.000 Mg/l
1.2,3,5-tetrachlorobenzene = 8.220 ng/1
- 390 ng/1
Pentachlorobenzene = 4.470
-W - 210 pg/1
-------
Table 3. Freshwater plant effects for chlorinated benzenes (U.S. EPA. 1978)
Organism
Alga.
Selenastrum
capricornutum
.Alga.
Sclenaatrum
capricornucuin
Alga.
Sglcnastrum
capricornutum
Alga.
Selenastrum
capricornutum
Alga.
Selenastrum
capricornutum
Alga.
Selcnastrum
capricornutum
Effect
Concentration
(yy/11
Chlorobenzene
EC50 96-hr 232.000
chlorophyll a
EC50 96-hr 224.000
cell numbers
1.2,A-trtchlorobenzene
EC50 96-hr
chlorophyll a
EC50 96-hr
cell numbers
35.300
36.700
1,2,3,S-tctrachloroben2ene
EC50 96-hr
chlorophyll a
EC50 96-hr
cell numbers
17.200
17,700
1,2 ,4.5-tctrachlprobenzenc
Alga.
Selenastruiii
£ifli£i£P.- ""turn
Alga.
Selenasirurn
capricornutuiii
Alga.
So It: pas I. rum
£ H R r I £.
EC50 96- hr 52.900
chlorophyll a
EC50 96- hr /t6.800
cull numbers
Puntachlorohenzcno
EC50 96-hr 6.780
chlorophyll a
-------
Table 3. (Continued)
Organism
Alga.
Selenastrum
caprlcornutum
EC50 96-hr
cell numbers
Concentration
6.630
CD
I
M
Ul
Lowest plant value: Chlorobenzene - 22A.OOOiig/l
l.2.4-trichlorobenzene= 35.300 ug/1
1.2.3.5-tetrachlorobenzene = 17.200 vgfl
1,2.4.5-tetrachlorobenzene = A6.800 jig/1
Pentachloroben^ene = 6.630 Mg/1
-------
en
i
Bluegill.
l.eppnila macrochirua
UlueRill.
Lcnomis macrochlrua
I'entaclilorobenzene
3.AGO
28
1.2,3, S-Tetracjylorobenzene
1.800 23
-------
Table 5. Other freshwater data for chlorinated benzenes
03
I
Ul
Organism
Ri-d uwump crayfish,
Procambarus clurki
l.art'emouth bass,
Mjcropcurua salmoides
Alga.
Chlorella pyrenoidosa
Alga.
Ocdogpnluin cardiacum
Snail,
He]isnma sp.
Cladoceran,
Daphnia niaRna
.Atlantic salmon,
Salmo salar
Channel catfish,
Tctalurug punctatus
Test
Result
Mosqui tofish,
Gamhuuia af finis
ClaJoceran.
Daphnia inugna
'
unknown
10 days
6,
15 days
3 mo a
33 days
33 days
30 days
2 days
8 days
3 days
48 hrs
Mexachlorobenzene
Mortality
Mortality
Growth
I.C50 not La ska. et al. 1978
reached
at 27.3 iig/l
No l.aska. et al. 1978
difference
from controls
at 25.8 ,,g/l
and 10 iig/1
1 to
10,000
Bioconcentration
factor = 730
Bioconcentration
factor = 1,500
Bioconcentration
factor - 910
Uloconcentratlon
factor = 690
Bioconcentratlon
factor = 9.870
Bioconcentration
factor = 1.580
1,2.4,5-Tetraghlorobenze n e
1.050
Ceike 6. Parasher, 1976b
l
Iscnsee, et al. 1976
Isensee, et al . 1976
Isensee, et al. 1976
Zitko & llutzinger. 1976
Isensee, et al. 1976
Isensee. et al. 1976
>530,000 U.S. EPA. 1978
-------
SALTWATER ORGANISMS
Introduction
The data base for chlorinated benzenes (not including the di-
chlorobenzenes discussed in another document) and saltwater or-
ganisms is limited to chlorobenzene, 1,2,4-trichlorobenzene, 1,2,
3,5-tetrachlorobenzene , 1,2,4,5-tetrachlorobenzene, pentachloro-
benzene, and hexachlorobenzene. The effects of salinity, tempera-
ture, or other water quality factors on toxicity of the chlori-
nated benzenes are unknown. Separate criteria are necessary for
each chlorinated benzene because toxicity generally increases with
increas.ed chlorination and toxicity may vary depending on the
positions of chlorine in the compounds.
Acute Toxicity
Toxicity tests with the sheepshead minnow have been conducted
(U.S. EPA, 1978) with five chlorinated benzenes (Table 6). All
tests were conducted under static conditions and concentrations in
water were not measured. Concentrations acutely toxic to this
saltwater fish were relatively high for the lower chlorinated ben-
zenes and toxicity generally increased with increasing chlorina-
tion; unadjusted 96-hour LC50 values for dichlorobenzenes (7,440
to 9,660 ug/D to sheepshead minnows were slightly lower than that
for chlorobenzene. The sheepshead minnow was generally more
acutely sensitive to the chlorinated benzenes, except for 1,2,4-
trichlorobenzene and pentachlorobenzene, than were four freshwater
fish species (Table 1); 96-hour LC50 values of sheepshead minnows
and bluegills differed by factors of 1.5 to 6.4. The unadjusted
96-hour LC50 values for sheepshead minnows ranged from 21,400 ug
1,2,4-trichlorobenzene/l to 830 ug pentachlorobenzene/1. Since
B-16
-------
Since only one test was completed with each chemical, when the ad-
justed LC50 values are divided by the sensitivity factor (3.7),
the following Final Fish Acute Values are obtained: chloroben-
zene, 1,600 ug/1; 1,2,4-trichlorobenzene, 3,200 ug/1; 1,2,3,5-
tetrachlorobenzene, 540 ug/1; 1,2,4,5-tetrachlorobenzene, 120
ug/1; and pentachlorobenzene, 120 ug/1-
Mysidopsis bahia, the only invertebrate species tested, was
more sensitive to three of five chlorinated benzenes than the
sheepshead minnow and more sensitive to all chlorinated benzenes
tested than the freshwater cladoceran, Daphnia magna (Tables 6,7,
and 2). Chlorobenzene (96-hour LC50 = 16,400 ug/D was the least
toxic, while pentachlorobenzene was the most acutely toxic (96-
hour LC50 = 160 ug/1). As with sheepshead minnows, sensitivity to
the chlorinated benzenes (including the dichlorobenzenes) general-
ly increased as chlorination increased. When the adjusted LC50
values for each of the five compounds tested with Mysidopsis bahia
are divided by the species sensitivity factor (49), the Final In-
vertebrate Acute Values are: 280 ug chlorobenzene/1; 7.8 ug 1/2,
4-trichlorobenzene/l; 5.9 ug 1,2,3,5-tetrachlorobenzene/l; 26 ug
1,2,4,5-tetrachlorobenzene/l; and 2.9 ug pentachlorobenzene/1.
Chronic Toxicity
Only one study has been c inducted to determine the chronic
toxicity of chlorinated benzer >s to saltwater organisms (Table 8).
In an embryo-larval study vv>tr. the sheepshead minnow in which
survival of hatched fi.sh wa-- effected, the limits for 1,2,4,5-
tetrachlorobenzene ::c*e .2 o 80 ug/1 (U.S. EPA, 1978). Since
data on only one test are a/aiiable, when the chronic value of
64.5 ug/1 is divided by the species sensitivity factor (6.7), th'e
B-17
-------
Fish Chronic Value is 9.6 ug/1/ a value lower than the Final Acute
Value of 26 ug/1 for this chlorinated benzene.
Plant Effects
The saltwater alga, Skeletonema costatum, was less sensitive
to the chlorinated benzenes than the mysid shrimp or sheepshead
minnow (Table 9). Ninety-six-hour EC50 values for growth, based
on concentrations of chlorophyll a_ in culture, were comparable to
96-hour EC50 values calculated from cell numbers and, except for
chlorobenzene, EC50 values for Skeletonema costatum were 3 to 25
times lower than EC50 values for the freshwater alga. Those EC50
values for the saltwater alga based on chlorophyll a^ and cell num-
bers, respectively, are: 343,000 ug and 341,000 ug chloroben-
zene/1; 8,750 ug and 8,930 ug 1,2,4-trichlorobenzene/l; 830 ug and
>
700 ug If2,3,5-tetrachlorobenzene/l; 7,100 ug and 7,320 ug 1,2,4,
5-tetrachlorobenzene/l; and 2,230 ug and 1,980 ug pentachloroben-
zene/1. There are no data reported on effects of chlorinated ben-
zenes on saltwater vascular plants.
Residues
Hexachlorobenzene (HCB) is bioconcentrated from water into
tissues of saltwater organisms (Tables 10 and 11). Bioconcentra-
tion factors (BCF, concentration in tissue divided by concentra-
tion in water) range from 1,964 to 23,000 for fish and shellfish
(Parrish, et al. 1974). However, the BCF's for fishes and inver-
tebrate-species exposed- for 96-hours probably underestimate
steady-state BCF's for organisms chronically exposed to hexa-
chlorobenzene. Bioconcentration factors for grass shrimp, pink
shrimp, and sheepshead minnows exposed for 96-hpurs ranged from
1,964 to 4,116 while the BCF for pinfish was 15,203 (Table 11).
-I a
-------
Concentrations of HCB in these whole-body samples were probably
not at equilibrium due to the short exposure period; highly
chlorinated compounds generally do not reach chemical equilibrium
in exposed animals in short exposure periods.
The BCF in the flesh of pinfish, Lagodon rhomboides, chronic-
ally exposed for 42 days to HCB was 23,000 (Table 10) for the five
exposure concentrations tested (0.06 to 5.2 ug/1). Analysis of
the concentrations of HCB in pinfish indicate that HCB concentra-
tions after 7 days of exposure were approximately one-quarter of
the total concentration after 42 days of exposure; concentrations
after 42 days of exposure appear to be near chemical equilibrium.
Concentrations of HCB in pinfish muscle were reduced only 16 per-
cent after 28 days of depuration and this slow rate is similar to
that for DDT in fish (Parrish, et al. 1974). Since HCB bioconcen-
trated to high concentrations in all tissues of pinfish and de-
puration was slow as compared to several other organochlorine pes-
ticides (Parrish, et al. 1974), HCB has a high potential to trans-
fer through and be retained in aquatic food webs.
Additional BCFs for other chlorinated benzenes are discussed
in the freshwater section of this document.
Miscellaneous
Data on other toxicological effects (Table 11) indicate that
adverse growth effects on one species of protozoa, Tetrahymena
pyriformis, result from 10-day exposure to 1 ug hexachloro-
benzene/1.
B-19
-------
CRITERION FORMULATION
Saltwater-Aquatic Life
Summary of Available Data
The concentrations below have been rounded to two significant
figures.
Chlorobenzene
Final Fish Acute Value = 1,600 ug/1
Final Invertebrate Acute Value = 280 ug/1
Final Acute Value = 280 ug/1
Final Fish Chronic Value = not available
Final Invertebrate Chronic Value = not available
Final Plant Value = 340,000 ug/1
Residue Limited Toxicant Concentration = not available
Final Chronic Value = 340,000 ug/1
0.44 x Final Acute Value = 120 ug/1
1,2,4-trichlorobenzene
Final Fish Acute Value = 3,200 ug/1
Final Invertebrate Acute Value = 7.8 ug/1
Final Acute Value = 7.8 ug/1
Final Fish Chronic Value = not available
Final Invertebrate Chronic Value = not available
Final Plant Value = 8,800 ug/1
Residue Limited Toxicant Concentration = not available
Final Chronic Value = 8,800 ug/1
0.44 x Final Acute Value =3.4 ug/1
-------
1,2/3,5-tetrachlorobenzene
Final Fish Acute Value = 540 ug/1
Final Invertebrate Acute Value = 5.9 ug/1
Final Acute Value = 5.9 ug/1
Final Fish Chronic Value = not available
Final Invertebrate Chronic Value = not available
Final Plant Value = 700 ug/1
/ Residue Limited Toxicant Concentration = not available
Final Chronic Value = 700 ug/1
0.44 x Final Acute Value = 2.6 ug/1
1,2 , 4,5-tetrachlorobenzene
Final Fish Acute Value = 120 ug/1
Final Invertebrate Acute Value = 26 ug/1
Final Acute Value = 26 ug/1
Final Fish Chronic Value =9.6 ug/1
Final Invertebrate Chronic Value = not available
Final Plant Value = 7,100 ug/1
Residue Limited Toxicant Concentration = not. available
Final Chronic Value = 9.6 ug/1
0.44 x Final Acute Value = 11 ug/1
pentachlorobenzene
Final Fish Acute Value = 120 ug/1
Final Invertebrate Acute Value = 2.9 ug/1
Final Acute Value =2.9 ug/1
Final Fish Chronic Value = not available
Final Invertebrate Chronic Value = not available
Final Plant Value = 2,000 ug/1
B-21
-------
Residue Limited Toxicant Concentration = not available
Final Chronic Value = 2,000 ug/1
0.44 x Final Acute Value =1.3 ug/1
1,2,4/5-tetrachlorobenzene
The maximum concentration of 1,2,4,5-tetrachlorobenzene is
the Final Acute Value of 26 ug/1 and the 24-hour average concen-
tration is the Final Chronic Value of 9.6 ug/1. No important
adverse effects on saltwater aquatic organisms have been reported
to be caused by concentrations lower than the 24-hour average
concentration.
CRITERION: For 1, 2,4,5-tetrachlorobenzene the criterion to
protect saltwater aquatic life as derived using the Guidelines is
9.6 ug/1 as a 24-hour average and the concentration should not
exceed 26 ug/1 at any time.
No saltwater criterion can be derived for any other chlori-
nated benzene using the Guidelines because no Final Chronic Value
for either fish or invertebrate species or a good substitute for
either value is available.
However, data for 1,2,4,5-tetrachlorobenzene and saltwater
organisms and 1,2-dichlorobenzene and freshwater organisms can be
used as the basis for estimating criteria.
For 1,2,4,5-tetrachlorobenzene and saltwater organisms 0.44
times the Final Acute Value is 11 ug/1 and this concentration is
close to the Final Chronic Value of 9.6 ug/1 derived from an
embryo-larval test with the sheepshead minnow. Also, for
.1,2-dichlorobenzene and freshwater organisms 0.44 times the Final
Acute Value is less than the Final Chronic Value based on an
embryo-larval test with the fathead minnow. Therefore, a
B-22
-------
reasonable estimate for other.chlorinated benzenes and saltwater
organisms would be 0.44 times the Final Acute Value.
chlorobenzene
The maximum concentration of chlorobenzene is the Final Acute
Value of 280 ug/1 and the estimated 24-hour average concentration
is 0.44 times the Final Acute Value. No important adverse effects
on saltwater aquatic organisms have been reported to be caused by
concentrations lower than the 24-hour average concentration.
CRITERION: For chlorobenzene the criterion to protect
saltwater aquatic life as derived using procedures other than the
Guidelines is 120 ug/1 as a 24-hour average and the concentration
should not exceed 280 ug/1 at any time.
1 / 2,4-trichlorobenzene
The maximum concentration of 1,2,4-trichlorobenzene is the
Final Acute Value of 7.8 ug/1 and the estimated 24-hour average
concentration is 0.44 times the Final Acute Value. No important
adverse effects on saltwater aquatic organisms have been reported
to be caused by concentrations lower than the 24-hour average
concentration.
CRITERION: For 1,2,4-trichlorobenzene the criterion to
protect saltwater aquatic life as derived using procedures other
than the Guidelines is 3.4 ug/1 as a 24-hour average and the
concentration should not exceed 7.8 ug/1 at any time.
1,2/3,5-tetrachlorobenzene
The maximum concentration of 1,2,3,5-tetrachlorobenzene is
the Final Acute Value of 5.9 ug/1 and the estimated 24-hour
average concentration is 0.44 times the Final Acute Value. No
important adverse effects on saltwater aquatic organisms have been
B-23
-------
reported to be caused by concentrations Icver than the 24-hour
7'
average concentration.
CRITERION: For 1, 2, 3, 5-tetraci- ' robenzens the criterion to
protect saltwater aquatic life as a.. .v d ,i3ir;_ procedures oLher
than the Guidelines is 2.6 ug/1 as e 24 hour a ^ge and the
concentration should not exceed 5.9 j/' ac any time
pentachlorobenzene
The maximum concentration of pe tachlorobenzene is the Final
Acute Value of 2.9 ug/1 and the estimated 24-hour average concen-
tration is 0.44 times the Final Acute Value. No important adverse
effects on saltwater aquatic organisms have been reported to be
caused by concentrations lower than the 24-hour average concentra-
tion.
CRITERION: For pentachlorobenzene the criterion to protect
saltwater aquatic life as derived using procedures other than the
Guidelines is 1.3 ug/1 as a 24-hour average and the concentration
should not exceed 2.9 ug/1 at any time.
B-24
-------
Table 6. Marine fish acute values for chlorinated benzenes (U.S. EPA. 1978)
Adjusted
03
NJ
cn
Sheepshead minnow,
Cyprinodon varlcgatus
Shcepshead minnow,
Cyprinodon varie^atus
Sheep sheud. minnow,
Cyprinodon varlcgatus
Sheepshead minnow,
Cyprinodon variegatus
Slieupshuad minnow.
Cypvi nuilon vjriegacus
UiOatieay
Mtt]iod*_
S
S
S
S
S
Test
U
U
I)
U
U
Description
Chlorobenzene
1.2.4-
trichloro-
benzene
1.2.3.5-
tetrachloro-
bunzene
1.2.4.5-
tetrachloro-
benzene
Pentachloro-
benzcne
Time LCbo l.c5o
96 10.500 5,740
96 21.400 11.699
96 3.670 2.010
96 840 460
96 830 450
S = static
U = unmeasured
Geometric mean of adjusted values: chlorobenzene = 5,740
1.2,4-trlchlorobenzene = 11.699 ng/1
1.2.3,5-tetrachlorobenzene = 2,010
1.2,4.5-tetrachlorobenzene = 460 |ig/l
450
~rrr~" 1-600 "B/1
3.200
» 540 pg/1
= 120 ng/1
pentachlorobenzene = 450 |ig/l 3-7 = 120 |ig/l
-------
Table /.
Bioassay Tost
StililQiSH! Hgthpd* cousi*
Mysid shrimp. S U
Mysidopsts bahia
Mysid shrimp, S U
Mystdopsis bahia
Mysid shrimp. S U
Myaldopsiji bahia
Mystd shrimp, S U
My_sidop_ais bahia
Mysid shrimp. S U
Mysidopsia bahta
* S « static
*' U = unmeasured
Geometric mean of adjusted values:
Chemical Time LC'jU
Description |jt»a) ("'!/*>
Chlorobcnzene 96 16.400
1.2.4- 96 450
trichlorobenzene
1.2.3.5- 96 340
tetrachloro-
bcnzenu
1.2.4.5- 96 1,480
tetrachloro-
bcnzene
Pentachloro- 96 160
benzene
chlorobenzene » 13.890 iig/1 £g
1,2.4-trichlorobenzene = 381 yg/1
1,2 ,3.5-tetrachlorobenzene » 290 yg/1
Adlusted
LC5o
13.890
381
290
1,250
140
- 280 Mg/1
Hl - 7.8 Mg/1
I?- 5.9 ,g/l
1,250
1,2,4.5-tetrachlorobenzene ° 1,250 iig/i
pentachlorobenzene = 140 iig/1
140
jfg a 2.9 ng/1
-------
03
I
Chronic
Limits Value
Organism Test* lmi/i> (ug/1)
Sheepshead minnow. E-L 92-180** 64.5
Cyprinodon vartegatus -
* E-L ~ embryo-larval
**1.2.A.5-tetrachlorobenzene
Geometric mean of chronic values » 6A.5 Mg/1 ~~STJ
Lowest chronic value > 6A.5 iig/1
-------
Marine plant effects for chlorinated benzenes (U.S. EPA. 1978)
Concentration
tt
I
Oiganlam
Alga.
Skeletonema coscatum
Alga.
Skeletonema costatum
Alga.
Skeletonema costatum
Alga.
Skeletonema costatum
Alga.
Skeletonema costatum
Alga.
Skeletonema costatum
Alga,
Skeletonema costatum
Alga.
Skeletonema costatum
Alga.
Skeletonema costatum
Alga.
Skelbtonema costatum
Effect
EC50 96-hr
cell numbers
EC50 96-hr
chlorophyll a
Chlorobenzcne
341.000
343.000
EC50 96-hr
cell numbers
EC50 96-hr
chlorophyll a
1,2,4-trlchlorobenaene
8.930
8.750
EC50 96-hr
cell numbers
EC50 96-hr
chlorophyll a
1,2,3,5-tetrachlorobenaene
700
830
EC50 96-hr
cell numbers
EC50 96-hr
chlorophyll a
1.2,4,5-tetrachlorobenzene
7.320
EC50 96-hr
cell numbers
EC50 96-hr
chlorophyll a
7.100
Pcntaclilorobenzene
1.980
2,230
Final plant value:
Chlorobenzene = 341.000 pg/1
1.2,4-trichlorolienzene - 8,750 |ig/l
1.2,3,5-tetrachlorobeni:ene = 700 ng/1
1,2,4,5-tetrachlorobeni:ciie = 7,100 Mg/1
Pentachloiobenzene - 1.9UO Mg/1
-------
00
I
M
VO
Table 10. Marine residues for chlorinated benzenes (Parrish, ec al. 1974)
Time
Organism cioconcentratioii Factor (days)
Pinflsh. 23,000* 42
I.agocJon rhomboides
* Mean concencracion factor in 25 muscle samples for hexachlorobenzene.
-------
Table 11. Other marine JuLu chlorinated benzenes*
Organism
Protozoan,
Tetrahymena pyritortnis
Grass shrimp.
Paliiemonctcs puglo
Pink shrimp,
1'enaeus dnorarum
Pink shrimp,
Pcnacus duorarum
Test
puratjpn Ettect
10 Jays Decreaued growth
96 hrs Mean bioconccntration
factor = ft .116
96 hrs Mean bioconcentration
factor = 1,964
96 hrs 33% mortality during
exposure to 25 pg/1;
Result
Jug/1} pet eteijCg
Gelke & Praslier, 197S
Parrish, et al. 1974
Parrlsh, et al. 1974
Parrish. et Hl. 1974
03
I
U)
o
Shcepshcad minnow, 96 hrs
Cyprlnodon vartegatus
Pinfish,
La^odon rhonibotdos
96 hrs
Mean bioconcentration
factor = 2.254
Mean bioconcentration
factor = 15,203
''' All data are for hexachlorobenzene (I1CU)
.1 \<)
I' ' »'. ri /il . 1974
-------
CHLORINATED BENZENES
REFERENCES
Geike, F., and C.D. Parasher. 1976a. Effect of hexachloro-
benzene (HCB) on growth of Tetrahymena pyriformis. Bull.
Environ. Contam. Toxicol. 16: 347.
Geike, F., and C.D. Parasher. 1976b. Effect of hexachloro-
benzene on some growth parameters of Chlorella pyrenoidosa.
Bull. Environ. Contam. Toxicol. 15: 670.
Isensee, A.R., et al. 1976. Soil persistence and aquatic
r
bioaccumulation potential of hexachlorobenzene (HCB). Jour.
Agric. Food Chem. 24: 1210.
Laska, A.L., et al. 1978. Acute and chronic effects of
hexachlorobenzene and hexachlorobutadiene in Red Swamp Cray-
fish (Procambarus clarki) and selected fish species. Toxicol,
Appl. Pharmacol. 43: 1.
Parrish, P.R., et al. 1974. Hexachlorobenzene: effects
on several estuarine animals. Pages 179-187 in. Proc. 28th
Annu. Conf. S.E. Assoc. Game Fish Comm.
Pickering, Q.H., and C. Henderson. 1966. Acute toxicity
of some important petrochemicals to fish. Jour. Water Pollut.
Control Fed. 38: 1419.
B-31
-------
U.S. EPA. 1978. In-depth studies on health and environmental
impacts of selected water pollutants. U.S. Environ. Prot.
Agency, Contract No. 68-01-4646.
Zitko, V., and 0. Hutzinger. 1976. Uptake of chloro- and
bromobiphenyls, hexachloro- and hexabromobenzene by fish.
Bull. Environ. Contam. Toxicol. 16: 665.
B-32
-------
MONOCHLOROBENZENE
Mammalian Toxicology and Human Health Effects
EXPOSURE
Introduction
Monochlorobenzene (MCB) is used industrially both as a
synthetic intermediate and as a solvent. As a synthetic in-
termediate, it is primarily used in the production of phenol,
DDT and aniline. Because it is a solvent for a large variety
of compounds and is noncorrosive, it finds technological use
as a solvent in the manufacture of adhesives, paints, pol-
ishes, waxes, diisocyanates, Pharmaceuticals and natural
rubber.
Data derived from U.S. International Trade Commission
reports show that between 1969 and 1975, the U.S. annual pro-
duction of MCB decreased by 50 percent from approximately 600
million pounds to approximately 300 million pounds (U.S.
EPA, 1977). It is, as expected from its structure, highly
lipophilic and hydrophobic, its solubility in water being
about 100 parts per million. The octanol to water partition
coefficient for MCB is 2.83. Monochlorobenzene also has a
relatively high vapor pressure (9 torr at 20°C). As will be
seen from the next section, this is an important considera-
tion in estimating the: likely retention of MCB in surface
waters.
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Ingestion from Water
Based on the vapor pressure, water solubility and molec-
ular weight of chlorobenzene, Mackay and Leinonen (1975) esti-
mated the half-life of evaporation from water for MCB to be
5.8 hours. This is compared to 4.8 hours for benzene and
73.9 hours for DDT.
MCB has been detected in ground water, "uncontaminated"
upland water and in waters contaminated either by industrial,
municipal or agricultural waste. It has been identified in
textile plant effluents (Erisman and Goldman, 1975). Table 1
consists of a compilation of data from other EPA reports and
shows the results of various water surveys as related to MCB.
Considering the volatile nature of MCB,. these data should be
considered from a point of view of gross estimate of expo-
sure. For example, in the analysis of the water for Lawson's
Fork Creek, South Carolina, the range indicated is the result
of two analyses four days apart (U.S. EPA, 1977). The pre-
sence .of MCB at other sites has been demonstrated qualita-
tively by volatile organic analysis. It has been detected in
"uncontaminated" upland water in Seattle, Wash., (Erisman and
Goldman, 1975) and in raw water contaminated with agricultur-
al runoff in Ottumwa, Iowa and Grand Falls, North Dakota
(U.S. EPA, 1977). Some information is available which might
give insight as to the source of contamination. For example,
it has been estimated that during the manufacture of MCB, 800
mg escapes into column water streams for every kg manufactur-
ed. Another 4 g of MCB per kg manufactured is recovered from
fractionating columns for land disposal (U.S. EPA, 1977).
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TABLE 1
Examples of Occurrence of Monochlorobenzene
Source: EPA, 1975; EPA, 1977
Location
Source
Concentration
(ug/D
Miami, FL
Philadelphia, PA
Cincinnati, OH
New York, NY
i
Lawrence, MA
Terrebone Parish, LA
Lawsons Fork Creek, SC
Coosa River, GA
Ground water
Raw water contaminated
with municipal waste
Raw water contaminated
with industrial discharge
"Uncontaminated" upland
water
Raw water contaminated
with industrial discharge
Raw water contaminated
with municipal waste
Industrial discharge
Municipal
1.0
0.1
0.1 - 0.5
4.7
0.12
5.6
8.0 - 17.0
27.0
Ingestion from Food
There are data which imply and demonstrate that MCB in
water can bioaccumulate in the food chain (Neely, et al. 1974,
Lu and Metcalf, 1975). MCB is stable in water and, thus,
that which does not evaporate is available for bioconcentra-
tion, the amount of accumulation depending upon the physical
nature of the substance. Neely, et al. (1974) determined the
bioconcentration factor for MCB based on the partition coef-
ficient and assigned it a value of 46. For comparison, ben-
zene was 19 and DDT was 650. Lu and Metcalf (1975) deter-
C-3
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mined the ecological magnification of MCB in various aquatic
species. Their data are shown in Table 2. For purposes of
comparison, the ecological magnification of aldrin and DDT in
mosquito fish was 1,312 and 16,960, respectively.
Further data by Lu and Metcalf (1975) indicate that MCB
resists biodegradation. They determine the biodegradability
index (BI) which was defined as the ratio of polar products
of degradation to the nonpolar products. For MCB, BI ranges
from 0.014 to 0.063 in the organisms shown in Table 2. The
low value for BI was similar to that seen for DDT and aldrin.
For example, in mosquito fish the BI for MCB was 0.014, for
DDT it was 0.012 and for aldrin it was 0.015.
TABLE 2
Ecological Magnification of Monochlorobenzene
in Various Aquatic Organisms
(From Lu and Metcalf, 1975; U.S. EPA, 1977)
Species
Ecological Magnification
(corganisms/c H2°)
Mosquito fish
(Gambusia affinis)
Mosquito larvae
(Culex quinquifasciatus]
Snails
(Physa)
Daphnia
(Daphnia magna)
Algae
(Oedogonium cardiacum)
645
1292
1313
2789
4185
-------
A bioconcentration factor (BCF) relates the concentra-
tion of chemical in water to the concentration in aquatic or-
ganisms, but BCF's are not available for the edible portions
of all four major groups of aquatic organisms consumed in the
United States. Since data indicate that the BCF for lipid-
soluble compounds is proportional to percent lipids, BCF's
can be adjusted to edible portions using data on percent
lipids and the amounts of various species consumed by Ameri-
cans. A recent survey on fish and shellfish consumption in
the United States (Cordle, et al. 1978) found that the per
capita consumption is 18.7 g/day. From the data on the nine-
teen major species identified in the survey and data on the
fat content of the edible portion of these species (Sidwell,
et al. 1974), the relative consumption of the four major
groups and the weighted average percent lipids for each group
can be calculated:
Consumption Weighted Average
Group (Percent) Percent Lipids
Freshwater fishes 12 4.8
Saltwater fishes 61 2.3
Saltwater molluscs 9 1.2
Saltwater decapods 18 1.2
Using the percentages for consumption and lipids for each of
these groups, the weighted average percent lipids is 2.3 for
consumed fish and shellfish.
C-5
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No measured steady-state bioconcentration factor (BCF)
is available for chlorobenzene, but tha equation "Log BCF =
0.76 Log P - 0.23" can be used (Vei^h, et al. Manuscript) to
estimate the BCF for aquatic organ.' ms that contain about
eight percent lipids from the octanol-water partition coef-
ficient (P). An adjustment factor -.f 2.3/8.0 = 0.2875 can be
used to adjust the estimated BCF from the 8;0 percent lipids
on which the equation is based to the 2.3 percent lipids that
is the weighted average for consumed fish and shellfish.
Thus, the weighted average bioconcentration factor for the
edible portion of all aquatic organisms consumed by Americans
can be calculated.
Compound P BCF Weighted BCF
Chlorobenzene 288 44 13
Inhalation
No data have been found which deal with exposure to MCB
by air outside of the industrial working environment. The
information concerning the industrial exposure of workers has
come primarily from eastern European sources and is tabulated
in Table 3. In addition to that information, Girard, et al.
(1969) reported on a case of an elderly female who was ex-
posed to a glue/ containing 0.07 percent MCB, for a period of
six years (See Special Groups at Risk). Chopra, et al.
(1978) predicted a mathematical chance for MCB to be in smoke
from endosulfan treated tobacco.
C-6
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TABLE 3
Recorded Industrial Exposures to Monochlorobenzene
Plant Activity Concentration of Reference
MCB (mg/1)
Manufacture of DDT 0.020 - average Gabor and Raucher, 1960
0.300 - highest
Manufacture of monuron 0.001 .- 0.01 Levina, et al. 1966
0.004 - 0.01 Stepangan, 1966
Dermal
No reports were available concerning the dermal exposure
of MCB.
Summary and Conclusions
Environmental exposure to MCB must be considered to be
primarily via water. Because of the short half-life of MCB
in water, it would be relatively difficult to monitor likely
human exposure unless multiple sampling were done. Compared
to substances such as DDT, the accumulation of MCB within the
food chain is limited; however, even this accumulation tends
to magnify the possible human exposure to MCB via discharge
into water.
PHARMACOKINETICS
Absorption
There is little question, based on human effects and
mammalian toxicity studies, that MCB is absorbed through the
lungs and from the gastrointestinal tract (c.f. U.S. EPA,
1977). Based on what is known about congeners, it is also
probably absorbed from the surface of the skin.
C-7
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Distribution
Because MCB is highly lipophilic and hydrophobia, it
would be expected that it would be distributed throughout
total body water space, with body lipid providing a deposi-
tion site. The data available on the related halobenzene,
bromobenzene, show this to be the case (Reid, et al. 1971).
Barring some abnormal kinetic pattern, it would also be
expected that redistribution from tissue sites would reflect
plasma decay rates. Again, with bromobenzene this was the
case, the plasma tl/2 being 5.8 hours and the tl/2 for fat
being 6.2 hours.
Metabolism
Metabolism of MCB has been studied in a number of labor-
atories.. Hydroxylation occurs para to the chloride via an
NADPH-cytochrome P-448 dependent microsomal enzyme system.
Further hydroxylation then occurs to form the corresponding
catechol compound. The diphenolic derivative is a predomi-
nant form, quantitatively, in comparison to the monophenolic
compounds. Various conjugates of these phenolic derivatives
are the primary excretory products (Lu, et al. 1974). ,The
conjugates are formed by microsomal enzymes, in this case the
NADPH-cytochrome P-450 dependent system. However, it would
appear that the rate limiting step in metabolism of MCB is
original hydroxylation of the ring. There are some differ-
ences in the nature of the conjugates, depending upon the
species studied. Williams, et al. (1975) found that among
thirteen species of non-human mammals, 21 to 65 percent of
excreted radioactivity from the administration of 14C-MCB is
C-8
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present in the urine as p-chlorophenylmercapturic acid. The
output of this conjugate in man was only 16 percent of the
administered dose. Williams (1959) also reported that about
27 percent of MCB administered to the rabbit was expired un-
changed in the air over a one to two day period; 47 percent
of the dose was excreted as glucuronic acid or sulfate con-
jugate, and 25 percent as mercapturic acid conjugate. This
accounts for the total dose and would imply that very little
is excreted unchanged. This would be expected. The lipo-
philic nature of MCB would predict that it would be almost
totally reabsorbed by the renal tubules such that its decay
from the plasma would rely totally on metabolism and on
ventilatory excretion.
The ease with which MCB is metabolized or eliminated via
the lungs would predict that its bioaccumulation potential is
somewhat limited. Varshavskaya (Iroc) found that when MCB
were administered to rats at a dose of 0.001 mg/day for nine
months, the coefficient of accumulate . -, 7 1.25. This would
mean that accumulation is somewhat 1: ~. i. : " if the exposure
level is kept constant. For example, :: a single dose were
taken every 24 hours and this resulted in a total body accu-
mulation of 1.25 x the dcse, t>a tl/2 would be calculated to
be approximately eleven hours. This wcu.'1'" suggest that in
the rat, upon exposure tc c cr ^tant dose, maximum body con-
centration is reachc-d in abuu<: two days. The same numbers
cannot be applied to man be .at ": of differences in organ
clearance, but relatively s^ei .ing it would be expected that
C-9
-------
equilibrium would -be reached in a short time from an environ-
mental point of view and that prolonged exposure to constant
levels in the environment would not be expected to result in
continuous accumulation.
Evidence has been building which implies that the meta-
bolism of halogenated benzene compounds results in the forma-
tion of toxic intermediates. Brodie, et al. (1971) pre-
treated animals with phenobarbital to stimulate the activity
of drug metabolizing enzymes in the liver. This treatment
potentiated liver necrosis induced "by halogenated aromatic
compounds (of which monobromobenzene was the primary ex-
ample) . This is apparently related to the formation of metab-
olites capable of forming complexes with, cellular ligands.
The covalent binding of the metabolites of halogenated ben-
zene derivatives with protein has been correlated with the
ability of these compounds to induce hepatic necrosis (Reid,
et al. 1971, 1973; Reid and Krishna, 1973). Oesch, et al.
(1973) -has reported that rats pretreated with 3-methylcholan-
threne are protected from MCB evoked hepatotoxicity. This
was ascribed to the modification of a coupled monooxygenase
epoxidehydrase system (Oesch, et al. 1973). Carlson and
Tardiff (1976) reported that the oral administration of 10 to
40 mg/day of MCB to rats for 14 days induced a variety of
microsomal enzymes which metabolize foreign organic compounds
including benzpyrenehydroxylase. Cellular toxicity, includ-
ing carcinogenic and mutagenic activity, may be related to
the formation of highly active metabolic intermediates such
as epoxides. In this connection, Kohli, et al. (1976) have
C-10
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suggested that the metabolism of MCB occurs through arene
oxide intermediates as shown in Figure 1.
EFFECTS
Acute, Sub-acute and Chronic Toxicity
The acute toxic effects of MCB were qualitatively similar
in some cases to chlorinated hydrocarbons such as carbon
tetrachloride. The oral LDso of monochlorobenzene in the rat
is approximately 3 g/kg. When administered by subcutaneous
injection, the LD5Q increases by about 25 percent Von
Oettingen (1955) found that large doses of MCB (7 to 8 g/kg
subcutaneously) were fatal in a few hours as a result of CNS
depression. When the dose utilized was 4 to 5 g/kg, death
occurred after a few days and resulted from hepatic and/or
renal necrosis. Vecerek, et al. (1976) found the oral LD5Q
of MCB in rats to be 3.4 g/kg. At this dose, the animals
died after about seven days and showed signs of a number of
metabolic disturbances including elevated levels of SGOT,
lactate dehydrogenase, alkaline phosphatase, blood urea ni-
trogen and decreased levels of glycogen phosphorylase and
blood sugars. Yang and Peterson (1977) administered MCB 5
mmol/kg intraperitoneally to male rats and found an increase
in bile duct pancreatic fluid flow.
Data on the subchronic and chronic toxicity of MCB are
sparse and somewhat contradictory. Lecca-Radu (1959) admin-
istered MCB by inhalation to rats and guinea pigs for periods
C-ll
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SR
1
OH
.OH
Figure 1: Proposed routes for the biotransformation of
monochlorobenzene via arene oxides (Kohli, et al. 1976),
-------
up to one year in doses which did not affect the liver or the
kidney but did find modification of erythrocyte carbonic an-
hydrase activity and leukocyte indolephenol oxidase activity.
Knapp, et al. (1971) administered MCB orally by capsule to
dogs in doses of 27.25, 54.5 and 272.5 mg/kg/day five days.a
week over a 90-day period. Four out of eight of the animals
in the high dose group died after 14 to 21 daily doses.
Clinical studies prior to death revealed an increase in im-
mature leukocytes, low blood sugar, elevated SGPT and alka-
line phosphatase and in some dogs increases in total biliru-
bin and total cholesterol. "Gross and/or microscopic patho-
logical changes" were seen in the liver, kidneys, gastroin-
testinal mucosa and hematopoietic tissue of the dogs which
r
died and, less extensively, in the dogs which, were sacrificed
after 65 or 66 daily doses. No consistent signs of MCB tox-
icity were seen in dogs in the intermediate and low levels.
MCB was given by diet for a period of 93 to 99 days to rats
at doses of 12.5, 50 and 250 mg/kg/day. Growth was retarded
in male rats in the high dose group. There was an increase
in liver and kidney weight for rats in the high and intermed-
iate levels. This was not accompanied by any "histopatho-
logical" findings (Knapp, et al. 1971).
The toxicity of MCB following exposure by inhalation and
by oral administration has been studied at the Dow Chemical
Company (Irish, 1963). Rats, rabbits and guinea pigs were
exposed seven hours a day, five days a week, for a total of
32 exposures over a period of 44 days at concentrations of
200, 475, and 1,000 ppm. The response of the animals in the
C-13
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high dose group was characterized by "histopathological
changes" in the lungs, liver and kidneys. In the middle dose
group, there was an increase in liver weight and a slight
liver "histopathology". In the low dose group, no apparent
effects were observed. In none of 'he groups was a hemato-
logical change seen. MCB was administered orally to rats
five days a week for a total of 137 doses' over 192 days, in
dose groups of 14.4, 144 and 228 mg/kg. In the middle and
high dose groups there were significant increases in liver
and kidney weight and some "histopathological changes" in the
liver. Blood and bone marrow were normal in all animals
(Irish, 1963).
Rimington and Ziegler (1963), citing the widespread out-
break of human cutaneous porphyria in Turkey in 1959 appar-
ently caused by wheat treated with hexachlorobenzene fungi-
cide, examined a series of chlorinated benzene compounds in
rats with regard to experimental porphyria. MCB at an oral
dose of 1140 mg/kg for five days increased the excretion of
urinary coproporphyrin, porphorobilinogen and delta-aminole-
vulinic acid. Some hair loss was also observed due to fol-
licular hyperkeratosis.
A study by Varshavskaya (1968) describes the CNS, liver
and hematopoietic system changes in seven male rats per group
which received oral doses of 0.1 mg/kg to 0.001 mg/kg MCB for
a period of nine months. This report indicates that doses of
0.001 mg/kg MCB for seven months affected the CNS of rats,
and that similar effects resulted from similar o-dichloroben-
zene dosages. However, these results are somewhat unexpected
C-14
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in light of other studies in the literature. For example,
Hollingsworth, et al. (1956) reported results from an experi-
ment with o-dichlorobenzene which differed by over three
orders of magnitude from those of the Varshavskaya (1968)
study. This discrepancy in o-dichlorobenzene results leaves
the MCB results of the Varshavskaya study open to question.
Synergism and/or Antagonism
In general, the halogenated benzenes appear to increase
the activity of microsomal NADPH-cytochrome P-450 dependent
enzyme systems. Induction of microsomal enzyme activity has
been shown to enhance the metabolism of a wide variety of
drugs, pes.ticides and other xenobiotics. Exposure to mono-
chlorobenzene could therefore result in decreased pharmaco-
logic and/or toxicologic activity of numerous compounds.
Frequently, chemical agents are metabolized to more active or
toxic "reactive" intermediates. In this event, exposure to
monochlorobenzene would result in enhanced activity and/or
toxicity of these agents.
Teratogenicity, Mutagenicity and Carcinogenicity
There have been no studies conducted to evaluate the
teratogenic, mutagenic or carcinogenic potential of MCB.
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CRITERION FORMULATION
Existing Guidelines and Standards
The Threshold Limit Value (TLV) for MCB as adopted by
the American Conference of Governmental Industrial Hygienists
(1971) is 75 ppro (350 mg/m^). The American Industrial Hygiene
Association Guide (1964) considered 75 ppm to be too high.
The recommended maximal allowable concentrations in air in
other countries are: Soviet Union/ 10 ppm; Czechoslovakia,,
43 ppm; Romania, 0.05 mg/1. The latter value for Romania was
reported by Gabor and Raucher (1960) and is equivalent to 10
ppm.
Current Levels of Exposure
MCB has been detected in water monitoring surveys of
various U.S. cities (U.S. EPA, 1975; 1977) as was presented
in Table 1. Levels reported were: ground water - 1.0 ug/1;
raw water contaminated by various discharges - 0.1 to 5.6
ug/1; upland water - 4.7 ug/1; industrial discharge - 8.0 to
17.0 ug/1; and municipal water - 27 ug/1. These data show a
gross estimate of possible human exposure to MCB through the
water route.
Evidence of possible exposure from food ingestion is in-
direct. MCB is stable in water and thus could be bioaccumu-
lated by edible fish species.
The only data concerning exposure to MCB via air are
from the industrial working environment. Reported industrial
exposures to MCB are 0.02 mg/1 (average value) and 0.3 mg/1
(highest value) (Gabor and Raucher, 1960); 0.001 to 0.01 mg/1
(Levina, et al. 1966); and 0.004 to 0.01 mg/1 (Stepangen,
1966).
C-16
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Special Groups at Risk
The major group at risk of MCB intoxication are individ-
uals exposed to MCB in the workplace. Table 3 shows recorded
industrial exposures to MCB. Girard, et al. (1969) reported
the case of an elderly female exposed to a glue containing
0.07 percent MCB for a period of six years. She had symptoms
of headache, irritation of the eyes and the upper respiratory
tract, and was diagnosed to have medullary aplasia. Smirnova
and Granik (1970) reported on three adults who developed
numbness, loss of consciousness, hyperemia of the conjunctiva
and the pharynx following exposure to "high" levels of MCB.
Information concerning the ultimate course of these indivi-
duals is not available. Gabor, et al. (1962) reported on in-
dividuals who were exposed to benzene, chlorobenzene and
vinyl chloride. Eighty-two workers examined for certain bio-
chemical indices showed a decreased catalase activity in the
blood and an increase in peroxidase, indophenol oxidase and
glutathione noted levels. Dunaeveskii (1972) reported on the
occupational exposure of workers exposed to the chemicals in-
volved in the manufacture of chlorobenzene at limits below
the allowable levels. After over 3 years cardiovascular ef-
fects were noted as pain in the area of the heart, bradycar-
dia, irregular variations in electrocardiogram, decreased
contractile function of myocardium and disorders in adapta-
tion to physical loading. ?ij -itova, et al. (1973) reported
on the prolonged exposure of individuals involved in the pro-
duction of diisocyanates to the factory air which contained
MCB as well as other chemicals. Diseases noted include bron-
C-17
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chitis, sinus arrhythmia, tachycardia, arterial dystrophy and
anemic tendencies. Petrova and Vishnevskii (1972) studied
the course of pregnancy and deliveries in women exposed to
air in a varnish manufacturing factory where the air contain-
ed three times the maximum permissible level of MCB but also
included toluene, ethyl chloride, butanol, ethyl bromide and
orthosilisic acid ester. The only reported significant ad-
verse effect of this mixed exposure was toxemia of pregnancy.
Basis and Derivation of Criterion
There is no information in the literature which indi-
cates that monochlorobenzene is, or is not, carcinogenic.
There is enough evidence to suggest that MCB does cause dose
related target organ toxicity, though the data still want
for an acceptable chronic toxicity study. There is little,
if any, usable human exposure data primarily because the
exposure was not only to MCB but to other compounds of known
toxicity.
The no-observable-adverse effect level (NOAEL) for deri-
vation of the water quality criterion is derived from the
information in the studies by Knapp, et al. (1971) and Irish
(1963). These are 27.25 mg/kg/day for the dog (the next
highest dose was 54.5 mg/kg and showed an effect); 12.5
mg/kg/rat from the Knapp study (the next highest dose was 50
mg/kg arid showed an effect); and 14.5 mg/kg/rat from the
Irish study (the next highest dose was 144 mg/kg and showed
an effect). When toxic effects were observed at higher
doses, the dog was judged .to be somewhat more sensitive than
-------
rats. The Irish study ran over a period of six months which
was twice as long as the Knapp study of both species. Since
the Knapp and Irish studies appear to give similar results
and since there are no chronic toxicities to rely on, it was
decided to take the NOAEL level from the longest term study,
that is, 14.4 mg/kg for six months.
Considering that there are relatively little human expo-
sure data, that there is no long-term animal data, and that
some theoretical questions, at least, can be raised on the
possible effects of chlorobenzene on blood-forming tissue, it
was decided to use an uncertainty factor of 1,000. From this
the acceptable daily intake (ADI) can be calculated as
follows:
ADI = 7° k? f ^A4 = 1.008 mg/day
The average daily consumption of water was taken to be
two liters and the consumption of fish to be 0.0187 kg daily.
A bioconcentration factor of 13 was utilized. This is the
value reported by the Duluth EPA Laboratories (see Ingestion
from Foods section) . The following calculation results in an
acceptable criterion based on the available toxicologic data:
_ 1.008 _ ... ..
2 + (13 x 0.0187) = 45° ^g/1
Varshavskya (1968) has reported the threshold concentra-
tion for odor and tas.te of MCB in reservoir water as being 20
u.g/1 which is the only report available. This value is about
4.5 percent of the possible standard calculated above. It
C-19
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is, however, approximately 17 times greater than the highest
concentration of MCB measured in survey sites (see Table 1).
Since water of disagreeable taste and odor is of significant
influence on the quality of life, and thus, related to
health, it would appear that the organoleptic level of 20
ug/1 should be the recommended criterion.
-20
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REFERENCES
American Conference of Governmental Industrial Hygienists.
1971. Documentation of the threshold limit values for
substances in workroom air. 3rd Ed.
American Industrial Hygiene Association. 1964. Chloroben-*
zene. Am. Ind. Hyg. Assoc. Jour. 25: 97.
Brodie, B.B., et al. 1971. Possible mechanism of liver
necrosis caused by aromatic organic compounds. Proc. Natl.
Acad. Sci. 68: 160.
Carlson, G.P., and R.G. Tardiff. 1976. Effect of chlorinated
benzenes on the metabolism of foreign organic compounds.
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Chopra, N.M., et al. 1978. Systematic studies on the break-
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Cordle, F., et al. 1978. Human exposure to polychlorinated
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C-21
-------
Djinaeveskii, G.A. 1972. Functional condition of circulatory
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Gabor, S., and K. Raucher. 1960. Studies on the determina-
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Prof. Zabol. Khim. Etiol. SB 221.
Girard, R., et al. 1969. Serious blood disorders and expo-
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C-22
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benzene: Determination on experimental animals and human
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Knapp, W.K. Jr., et al. 1971. Subacute oral toxicity of
monochlorobenzene in dogs and rats. Toxicol. Appl.
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Kohli, I., et al. 1976. The metabolism of higher chlorinated
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C-23
-------
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C-24
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C-25
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-------
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«
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C-27
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TRICHLOROBENZ ENES
Mammalian. Toxicology and Human Health Effects
- /'.'- v
-'.- EXPOSURE
Introduction
There are three isomers of trichlorobenzene (TCB): 1,
t
2,3-trichlorobenzene, 1,2,4-trichlorobenzene and 1,3,,5-tri-
chlorobenzene. Of the three, 1,2,4-TCB is the most economi-
cally important (U.S. EPA, 1977). It is used as a dye car-
rier in the application of dyes to polyester materials, as an
intermediate in the synthesis of herbicides, as a flame re-
tardant and for other functional uses. The U.S. production
of 1,2,4-trichlorobenzene in 1973 was over 28 million pounds
(Synthetic Organic Chemicals. U.S. Production and Sales.
U.S. International Trade Commission, 1975). A mixture of the
three isomers is used as a solvent, a lubricant and as a
dielectric fluid. The 1,2,3 and 1,3,5-TCB isomers as indi-
vidual compounds are primarily used as intermediates in chem-
ical synthesis. TCB's are most probably intermediates in the
mammalian metabolism of lindane (Kujawa, et al. 1977).
28
-------
Ingestion from Water
Table 1 shows data from monitoring the various water
sites. These data suggest the possibility of TCB contamina-
tion of the drinking water. In a report (U.S. EPA, 1975) in
which the sample site was not identified, the highest re-
ported concentration of trichlorobenzene in drinking water
was 1.0 ug/1.
Ingestion from Foods
Whereas the bioaccumulation of some of the other members
of the chlorinated benzene series has been studied with re-
gard to model aquatic ecological systems, such has not appar-
ently been the case with the TCB's. The accumulation of
TCB's in the food chain depends upon their concentration in
aquatic organisms. Haas, et -al. (1974) has found that 40
percent of the remaining 1,2,4-TCB in wastewater was absorbed
by microorganisms and the suggestion has been made by EPA
that the material concentrates in the cell wall. This type
of information indicates that TCB's will persist in a water
environment and are available for incorporation into fish.
TCB has been detected in trout taken from Lake Superior and
turbot taken from Lake Huron (U.S. EPA, 1977).
Bioconcentration factors are not available for the
edible portions of all four major groups of aquatic organisms
consumed in the United States. Since data indicate that the
BCF for lipid-soluble compounds is proportional to percent
lipids, BCF's can be adjusted to edible portions using data
on percent lipids and the amounts of various species consumed
C-29
-------
occurrence or TLts-s in water
(Source: U.S. EPA, 1977)
Compound
Location
Source
Concentration'
(ug/D
o
i
CO
o
1,2,3-TCB
1,2,4-TCB
1,3,5-TCB
Catawba Creek, NC
Catawba Creek, NC
Chattanooga Creek, TN
Joint Water Pollution
Control Plant (JWPCP)
Hyperion Sewage Treatment
Works, LA (HSTW)
HSTW
Orange County Sewage
Department (OCSD)
Port Loma Sewage Treat-
ment Plant (PLSTP)
Oxnard, CA Sewage
Treatment Plant (OSTP)
Los Angeles River
Holston River, TN
JWPCP
HSTW
HSTW
OCSD
PLSTP
OSTP
Los Angeles River
Municipal discharge
Industrial discharge
Industrial discharge
Municipal waste water
5 mile effluent, municipal
waste water
7 mile effluent, municipal
waste water
Municipal waste water
Municipal waste water
Municipal waste water
Surface run off
Industrial discharge
Municipal waste water
5 mile effluent, municipal
waste water
7 mile effluent, municipal
waste water
Municipal waste water
Municipal waste water
Municipal waste water
Surface run off
21-46a
12a
500b
6.0; 1.8a
6.7; 3.1C
275; 130C
0.30a
0.23; <0.01C
0.9; 0.25C
0.007d
26
0.2; 0.8C
<0.0-1; <0.01C
0.9; <0.2C
0.2
0.02; <0.01C
0.4; <0.01C
0.006d
aSummer
bSpring
GSummer; Fall
dWinter
epall
-------
by Americans. A recent survey on fish and shellfish consump-
tion in the United States (Cordle, et al. 1978) found that
the per capita consumption is 18.7 g/day. From the data on
the nineteen major species identified in the survey and data
on the fat content of the edible portion of these species
(Sidwell, et al. 1974), the relative consumption of the four
major groups and the weighted average percent lipids for each
group can be calculated:
Consumption Weighted Average
Group (Percent) Percent Lipids
Freshwater fishes 12 4.8
Saltwater fishes 61 2.3
Saltwater molluscs 9 1.2
Saltwater decapods 18 1.2
Using the percentages for consumption and lipids for each of
these groups, the weighted average percent lipids is 2.3 for
consumed fish and shellfish.
No measured steady-state bioconcentration factor (BCF)
is available for 1,2,4-trichlorobenzene but the equation "Log
BCF = 0.76 Log P - 0.23" can be used (Veith, et al. Manu-
script) to estimate the BCF for aquatic, organisms that con-
tain about eight percent lipids from the octanol-water parti-
tion coefficient (P). An adjustment factor of 2.3/8.0 =
0.2875 can be used to adjust the estimated BCF from the 8.0
percent lipids on which the equation is based to the 2.3 per-
cent lipids that is the weighted average for consumed fish
and shellfish. Thus, the weighted average bioconcentration
factor for the edible portion of all aquatic organisms con-
sumed by Americans can be calculated.
C-31
-------
Compound
BCF
Weighted BCF
1/2,4-trichlorobenzene
18,000
1,000
290
There is some information on studies of biochemical oxy-
gen demand (BOD) in waste water containing microorganisms from
treatment plants. This information has been compiled previously
(U.S. EPA, 1977) and is reproduced in Table 2. This table sum-
marizes the 20-day BOD for 1,2,4-TCB. As can be seen, the re-
sults vary from no biodegradation to complete biodegradation of
the 1,2,4-TCB.
TABLE 2
Effects of 1,2,4-Trichlorobenzene on BOD
(From U.S. EPA, 1977)
Source of Organisms
BOD20 (percent of
theoretical value)
References
Microorganisms from 78
industrial waste treat-
ment plant
Microorganisms from 100
industrial waste treat-
ment plant
Mixture of microorganisms 50
from 4 different textile
treatment plants
Microorganisms from "typi- 0
cal" treatment plant (2 days)
Hintz, 1962
Alexander, 1972
Porter and Snider,
1974
Haas, et al. 1974
C-32
-------
Simmons, et al. (1976) also noted a lack of degradation
of 1,2,4-TCB based on BOD determinations. However, direct
chemical analysis indicated a 14 percent reduction in the
compound in industrial wastewater after 24 hours, a 36 per-
cent reduction in 72 hours and 43 percent reduction at 7
days.- This would indicate that the limitation in change of
BOD is due primarily to incompletely oxidized metabolites.
Inhalation and Dermal
Vapor pressures for TCB's are: 1,2,3-TCB, 0.07 mm Hg
(25°C), 1.0 mm Hg (40°C); 1,2,4-TCB, 0.29 mm Hg (25°C); 1.0
mm Hg (38.4°C); 1,3,5-TCB, 0.15 mm Hg (25°C), 10 mm Hg (78°C)
(U.S. EPA, 1977; Sax, 1975). This is relatively low compared
to mono- and dichlorobenzenes. Nevertheless, TCB's have been
detected in particulates from aerial fallout. In a study of
aerial fallout in southern California (spring, 1976), five
sampling sites showed median levels of "less than 11 ng/m2/
day" for 1,2,4-TCB and "less than 6 ng/m2/day" for 1,3,5-TCB
(U.S. EPA, 1977).
There have been no direct reports of exposure of humans
to TCB via inhalation resulting in toxicity. A recent study
by Coate, et al. (1977) has demonstrated that inhalation ex-
posure of rats, rabbits and monkeys will result in a toxic
effect (vide infra). The amount of TCB necessary to induce a
toxic reaction via application to the skin is quite high and
thus exposure to TCB via water on the skin is not considered
to be a significant factor in tne determination of criteria
standards (Brown, et al. 1969).
C-33
-------
PHARMACOKINETICS
Absorption
All three isomers of TCB are absorbed from the gastroin-
testinal tract, intact skin and lungs. However, the absorp-
tion is somewhat less than that seen for the monochlorinated
and dichlorinated benzenes (U.S. EPA, 1977)
Metabolism
The primary route of metabolism of TCB's is through the
formation of monophenols with very little, if any, formation
of mercapturic acid or catechols (Williams, 1959; Parke and
Williams, 1960; Kohli, et al. 1976). Kphli, et al. (1976)
reported that the major metabolite in the rabbit for 1,2,3-
TCB was 2,3,4-trichlorophenol (2,3,4-TCP) (11 percent of the
dose) with minor metabolites being 2,3,6-TCP (1 percent) and
3,4,5-TCP (2 percent). For 1,2,4-TCP, the monophenols were
in the form of 2,4,5-TCP and 2,3,5-TCP both present in ap-
proximately the same percentage of the original dose (five
and six percent, respectively). In the case of 1,3,5-TCB,
the two metabolites were 2,3,4-TCP and 2,4,6-TCP (1.5 and 3.0
percents, respectively). These authors proposed a pathway
for metabolism which goes through arene oxide steps as shown
in Figure 1. Parke and Williams (1960) have also described
small quantitites of monochlorobenzene and parachlorophenol
in the urine of rabbits following the administration of
1,3,5-TCB. It can be assumed that the TCB is transformed by
the NADPH-cytochrome P-450 microsomal enzyme system. The
overwhelming evidence points towards this direction, but in
actuality the experiments designed to demonstrate this point
C-34
-------
Cl
Cl
Cl
Cl
Cl
Cl
Cl
o
I
to
Figure 1: Proposed pathways for the biotransformation of trichlorobenzene
isomers through arene oxide intermediates (Kohli, et al. 1976)
-------
specifically have not been done. Egyankor and Franklin, et
al. (1977) incubated TCB isomers with rat hepatic microsomal
cytochrome P-450. He found that the order of affinity of the
isomers for cytochrome P-450 was 1,2,3-TCB greater than 1,2,
4-TCB greater than 1,3,5-TCB. Interestingly, this is the
same order which has been found for the metabolism of TCB
isomers to phenol. They also noted that 1,3,5-TCB inhibits
hepatic microsomal mixed function oxidase system while the
1,2,3-TCB and the 1,2,4-TCB enhanced it. Ariyoshi, et al.
(1975a,b,c) reported on the microsomal enzyme systems in in-
tact rats. They found that 1,3,5-TCB increased the amount of
microsomal protein, phospholipids and cytochrome P-450 as
well as stimulating the activities of aminopyrine demethy-
lase, aniline hydroxylase, and delta aminolevulinic acid syn-
thesis (Ariyoshi, et al. 1975a). Similar results were ob-
tained for 1,2,4-trichlorobenzene. Increases were observed
in cytochrome P-450 content of the liver, enhanced delta ami-
nolevulinic acid synthetase activity, aminopyrine demethylase
activity, microsomal protein, microsomal phosphate, liver
weight and aniline hydroxylase (Ariyoshi, et al. 1975).
Carlson and Tardiff (1976) reported that 1,2,4-TCB
caused a decrease in hexobarbital sleeping time and an in-
crease in the activities of cytochrome-c reductase, cyto-
chrome P-450 glucuronyl transferase, benzpyrene hydroxylase
and azoreductase. Carlson (1978) investigating the effect of
1,2,4-TCB on metabolism systems in the liver, concluded that
the compound induces xenobiotic metabolism of the phenobar-
bital type rather than the 3-methylcholanthrene type.
-------
There is a paucity of kinetic data concerning TCB's.
However, based on data from Williams (1959) and Parke and
Williams (1960) some estimates can be made as to the biologi-
cal half-life of the isqmers. From these data, it was esti-
mated that the approximate half-lives of the isomers are:
1,2,3-TCB, 2 days; 1,2,4-TCB, 5.5 days; 1,3,5-TCB, 8.5 days.
This is a consideration in the evaluation of toxicity studies
for all species, especially those which are considered sub-
chronic.
Excretion
Williams (1959) reported that five days after oral
administration of the compound to the rabbit, 78 percent of
the administered 1,2,3-TCB was excreted as monophenols; five
days after the administration of 1,2,4-TCB, 42 percent was
excreted as monophenols; five days after administration, 9
percent of administered 1,3,5-TCB was excreted as mono-
phenols. There was no evidence for the existence of signifi-
cant alternative metabolic pathways implying that the elimi-
nation of 1,3,5-TCB is significantly slower than the other
two isomers. This is related to the ease of oxidation of the
various isomers and reflected in the monophenol metabolites
excreted.
EFFECTS
Acute, Sub-acute, and Chronic Toxicity
There is a limited amount of relevant data on the toxi-
0
city of 1,2,4-TCB and essentially no data on the toxicity of
the other two isomers. Cameron, et al. (1937) first de-
scribed hepatotoxic effects of trichlorobenzene, finding it
C-37
-------
to be less than that of monochlorobenzene or orthodichloro-
benzene. Brown, et al. (1969) reported the single dose acute
oral LDso in rats to be 756 mg/kg (556 to 939 mgAg* 95 per-
cent confidence limits). In mice, the single dose acute oral
LDs0 was 766 mg/kg (601 to 979 mg/kg, 95 percent confidence
limits). With the rats, deaths occurred within five days of
exposure and in mice within three days of exposure. For both
species, intoxication was manifested as depression of activ-
ity at low doses and predeath extensor convulsions at lethal
doses. They also determined a single dose acute percutaneous
toxicity in rats. This was 6139 mg/kg (4299 to 9056 mg/kg,
95 percent confidence limits). From the same study, data on
skin irritation were reported. The authors concluded that
1,2,4-TCB was not very irritating, although fissuring typical
of a decreasing action was observed after prolonged contact
in rabbits and guinea pigs. Spongiosis, acanthosis and para-
keratosis were noted in both species along with some inflam-
mation of the superficial dermis in rabbits exposed daily for
three weeks. Some guinea pigs exposed to 0.5 ml/day for five
days/week for three weeks died following extensor convul-
sions. The livers of these animals were found to have necro-
tic lesions.
Coate, et al. (1977) reported on a chronic inhalation
exposure of rats (30 animals per group), rabbits (16 animals
per group) and monkeys (9 animals per group) to 0.25, 50 and
100 ppm of 1,2,4-TCB for periods up to 26 weeks. No exposure
C-38
-------
related ophthalmologic changes were detected in. rabbits and
monkeys after 26 weeks of exposure (rats were not examined),
and similarly, no exposure-related changes were detected in
BUN, total bilirubin, SCOT, SGPT, alkaline phosphatase and
LDH when determined at 4, 13 and 26 weeks of exposure. Hema-
tological values were also normal when examined at 4, 13 and
26 weeks. Pulmonary function tests were carried out on the
monkeys. No treatment associated changes were noted in
static compliance, carbon monoxide diffusion capacity, dis-
tribution of ventilation, transpulmonary pressure or a bat-
tery of lung volume determinations. Histological changes
were noted in the livers and kidneys of rats necropsied after
4 and 13 weeks of exposure. These changes were noted in
animals from all treatment groups and were manifested as an
increase in size and vacuolation of hepatocytes. However,
after 26 weeks, no compound related histopathological changes
were noted in rabbits or monkeys.
Rowe (written communication, April, 1975) reported that
persons exposed to 1,2,4-TCB vapor at 3 to 5 ppm experienced
minor eye and respiratory irritation. The odor was described
as easily noticeable at these concentrations. There was a
detectable odor at concentrations up to 2.4 ppm, but no eye
irritation was evident. No odor was noted at concentrations
up to 0.88 ppm.
Smith, et al. (1978) conducted a 90 day, daily oral dose
study of 1,2,4-TCB in rhesus monkeys (four animals per group)
for concentrations of 1, 5, 25, 90, 125 and 174 mg/kg. Their
report, which is an abstract, states that single oral daily
C-39
-------
doses of 25 mg/kg or less were nontoxic whereas doses of 90
mg/kg or higher were toxic and doses of 173.6 mg/kg were
lethal within 20 to 30 days. There were no deaths observed
in the 1, 5 and 25 mg/kg group and one death occurred in each
of the 90 mg/kg and 125 mg/kg groups and two deaths occurred
in the 174 mg/kg group. Animals on the highest dose exhi-
bited severe weight loss and predeath fine tremors. All of
the animals in the highest dose group had elevated BUN, Na,
K, CPK, SCOT, SGPT/ LDH and alkaline phosphatase as well as
hypercalcemia and hyperphosphatemia from 30 days on. Smith,
et al. (1978) have been using the urinary pattern of chlor-
guanide metabolites as an indication of cytochrome P-450 de-
pendent drug metabolism. The abstract states that at the
high doses monkeys showed evidence of the hepatic induction
as well as an increased clearance of intravenous doses of
labeled TCB. Further information on the study (Smith, per-
sonal communication) gave evidence of liver enzyme induction
in the 90, 125 and 174 mg/kg animals. There were some patho-
logical changes noted in the livers of the high dose groups,
primarily a fatty infiltration. The point at which there was
absolutely no effect related to the compound was at the 5
mg/kg level. Since further detailed information on the
results of this study are lacking no estimation of a NOAEL
can be made.
Rimington and Ziegler (1963) were able to induce an ex-
perimental porphyria in rats with 1,2,4-TCB which was marked
by an increased urinary coproporphyrin excretion and an in-
creased porphorobilinogen excretion in urine. This porphyria
C-40
-------
could be reversed by glutathione. They also noted a hair
loss due to hyperkeratosis.
Synergism and/or Antagonism
In general/ the halogenated benzenes appear to increase
the activity of microsomal NADPH-cytochrome P-450 dependent
enzyme systems. Induction of microsomal enzyme activity has
been shown to enhance the metabolism of a wide variety of
drugs/ pesticides and other xenobiotics. Exposure to TCB
could, therefore, result in decreased pharmacologic and/or
toxicologic activity of numerous compounds. Frequently,
chemical agents are metabolized to more active or toxic
"reactive" intermediates. In this event exposure to TCB
would result in enhanced activity and/or toxicity of these
agents.
Teratogenicity, Mutagenicity and Carcinogenicity
Studies have not been conducted primarily for the pur-
pose of determining the teratogenic or mutagenic properties
of trichlorobenzene isomers. Gotto, et al. (1972), in a
study to examine hepatomas caused by hexachlorocyclohexane,
administered 1,2,4-TCB at a dose of 600 ppm by inhalation
daily for six months to mice and reported no incidence of
hepatomas. There are no other studies which have been de-
signed for the purpose,of studying carcinogenicity of TC3 nor
have there been any other reports indicating such activity.
041
-------
CRITERION FORMULATION
Existing Guideline and Standards
A proposed American Conference of Governmental and Ind-
ustrial Hygienists Threshold Limit Value (TLV) standard for
TCB's is 5 ppm (mg/1) as a ceiling value (Am. Conf. Gov. Ind.
Hyg. 1977). Sax, et al. (1951) recommends a maximum allow-
able concentration of 50 ppm in air for commercial TCB, a
mixture of isomers. Coate, et al. (1977), citing their
studies, recommends that the TLV should be set below 25 ppm,
preferably 5 ppm (mg/1). Gurfein and Parlova (1962) indicate
that in the Soviet Union the maximum allowable concentration
for TCB in water is 30 v.g/1, which is an organoleptic limit.
They also report that in a study of 40 rats and 8 rabbits ad-
ministered TCB in drinking water at a concentration of 60
ug/1 for a period of seven to eight months, no effects were
observed. This information was obtained from an abstract and
evaluation of the study could not be done.
Basis -and Derivation of Criterion
While the committee recognizes a need for toxicological in-
formation in order to establish a criterion, there are no reli-
able published toxicological data on TCB. The studies by Smith,
et al. (1978), and Coate, et al. (1977) do not give suffiecient
basis for establishing a toxicological criterion. Therfore, in
lieu of a criterion based on toxicological information, an or-
ganoleptic level of 13 ug/1 (Varshavskaya, 1968) is recommended.
It should be emphasized that this is a criterion based on
aesthetic rather than on health effects. Data on human health
effects need to be developed as a more substantial basis for
setting a criterion for the protection of human health.
C-42
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REFERENCES
Alexander, M. 1972. Pollution characteristics of 1,2,4-tri-
chlorobenzene. Dow Chemical Co., Midland, Mich. (Unpublish-
ed.) Cited in U.S. EPA. 1977.
Ariyoshi, T., et al. 1975a. Relation between chemical struc-
ture and activity. I. Effects of the number of chlorine
atoms in chlorinated benzenes on the components of drug
metabolizing systems and hepatic constitutents. Chem. Pharm.
Bull. 23: 817.
Ariyoshi, T., et al. 1975b. Relation between chemical struc-
ture and activity. II. Influences of isomers of dichloro-
benzene, trichlorobenzene and tetrchlorobenzene on the activ-
ities of drug metabolizing enzymes. Chem. Pharm. Bull. 23:
824.
Ariyoshi, T., et al. 1975c. Relation between chemical struc-
ture and activity. III. Dose response on tissue course of
induction of microsomal enzymes following treatment with
1,2,4-trichlorobenzene. Chem. Pharm. Bull. 23: 831.
Brown, V.K.H., et al. 1969. Acute toxicity and skin irritant
properties of 1,2,4-trichlorobenzene. Ann. Occup. Hyg. 12:
209.
C-43
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Cameron, G.R., et al. 1937. The toxicity of certain chlorine
derivatives of benzene with special reference to o-dichloro-
benzene. Jour. Path. Bact. 44: 281.
Carlson, G.P. 1978. Induction of cytochrome P-450 by halo-
genated benzenes. Biochem. Pharmacol. 27: 361.
Carlson, G.P., and R.G. Tardiff. 1976. Effect of chlorinated
benzenes on the metabolism of foreign organic compounds.
Toxicol. Appl. Pharmacol. 36: 383.
Coate, W.B., et al. 1977. Chronic inhalation exposure of
rats, rabbits and monkeys to 1,2,4-trichlorobenzene. Arch.
Environ. Health. 32: 249.
Cordle, F., et al. 1978. Human exposure to polychlorinated
biphenyls and polybrominated biphenyls. Environ. Health
Perspect. 24: 157.
Egyankor, K.B., and C.S. Franklin. 1977. Interaction of the
trichlorobenzenes with cytochrome P-450. Biochem. Soc.
Trans. 5: 1519.
Girard, R., et al. 1969. Serious blood disorders and expo-
sure to chlorine derivatives of benzene. (A report of 7
cases). Jour. Med. Lyon 50: 771.
C-44
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Gotto, M., et al. 1972. Hepatoma formation in mice after ad-
ministration of high doses of hexachlorocyclohexane isomers.
Chemosphere 1: 279.
Gurfein, L.W., and Z.K. Parlova. 1962. The limit of allow-
able concentrations of chlorobenzenes in water basins. In'
B.S. Levine, ed. USSR literature on water pollution. Dep.
Commer., Washington, D.C.
Haas, J.M., et al. 1974. Environmental considerations con-
cerning the selection of dye carrier solvents. Presented at
the 1974 Am. Assoc. Textile Chem. Colourists Natl. Tech.
Conf. October 9-11. Cited in U.S. EPA, 1977.
Hintz, M. 1962. Pollution characteristics of 1,2,4-tri-
chlorobenzene. Dow Chemical Co. Midland, Mich. (Unpublish-
ed.) Cited in U.S. EPA, 1977.
Kohli, I., et al. 1976. The metabolism of higher chlorinated
benzene isomers. Can. Jour. Biochem. 54: 203.
Kujawa, M., et al. 1977. On the metabolism of lindane. Proc.
1st Int. Symp. Environ. Pollut. Human Health.
Lu, P.Y., and R.L. Metcalf. 1975. Environmental fate and
biodegradability of benzene derivatives as studied in a model
aquatic ecosystem. Environ. Health. Perspect.10: 269.
C-45
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Parke, D.V., and R.T. Williams. 1960. Studies in detoxica-
tion. Metabolism of halobenzenes: (a) Penta- and hexachloro-
benzene: (b) Further observations on 1,3,5-trichlorobenzene.
Biochem. Jour. 74: 1.
Rimington, C., and G. Ziegler. 1963. Experimental porphyria
in rats induced by chlorinated benzenes. Biochem. Pharmacol.
12: 1387.
Sax, N.I. 1975. Dangerous properties of industrial materi-
als. 4th ed. Van Nostrand Reinhold, New York.
Sidwell, V.D., et al. 1974. Composition of the edible por-
tion of raw (fresh or frozen) crustaceans, ffnfish, and mol-
lusks. I. Protein, fat moisture, ash, carbohydrate, energy
value, and cholesterol. Mar. Fish. Rev. 36: 21.
Simmons, P., et al. 1976. 1,2,4-trichlorobenzene: Biode-
gradable or not? Can. Assoc. Textile Colourists Chem. Int.
Tech. Conf. Quebec. October 13-15. Cited in U.S. EPA, 1977.
Smith, C.C., et al. 1978. Subacute toxicity of 1,2,4-tri-
chlorobenzene (TCB) in subhuman primates. Fed. Proc. 37:
248.
U.S. EPA. 1975. Preliminary assessment of suspected carcino-
gens in drinking water. Rep. Cong. No. PB-250961.
C-46
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U.S. EPA. 1977. Investigation of selected potential environ-
mental contaminants: Halogenated benzenes. EPA 560/2-77-004.
Varshavskaya, S.P. 1968. Comparative toxicological charac-
teristics of chlorobenzene and dichlorobenzene (ortho- and
para-isomers) in relation to the sanitary protection of water
bodies (Russian translation). Jour. Hyg. San. 33: 10.
Veith, G.D., et al. An evaluation of using partition coeffi-
cients and water solubility to estimate bioconcentration fac-
tors for organic chemicals in fish (Manuscript.)
Williams, R.T. 1959. The metabolism of halogenated aromatic
hydrocarbons. Page 237 _in "Detoxication mechanisms. 2nd ed.
John Wiley and Sons, New York.
C-47
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TETRACHLOROBENZENE
Mammalian Toxicology and Human Health Effects
EXPOSURE
Introduction
Tetrachlorobenzene (TeCB) exists as three isomers-1,2,
3,4-TeCB, 1,2,3,5-TeCB and 1,2,4,5-TeCB. Of these, 1,2,4,5-
TeCB is the most widely used. In the limited state, 1,2,3,5-
TeCB is used primarily in the manufacture of 2,4,5-trichloro-
phenoxyacetic acid (2,4,5-T) and 2,4,5-trichlorophenol (2,4,
5-TCP). In 1973, an estimated ten million pounds of 1,2,4,5-
TeCB were utilized in the manufacture of 2,4,5-T while six
million pounds were utilized in the manufacture of 2,4,5-TCP
(U.S. EPA, 1977). In the Soviet Union, 1,2,4,5-TeCB is used
9
as a soil and grain pesticide (Fomenko, 1965). It is not
used for this purpose in the United States.
Tetrachlorobenzene (TeCB) has been found to be among the
metabolites of hexachlorobenzene (Mehendale, et al. 1975;
Rozman, et al. 1975), lindane, pentachlorocyclohexane, penta-
chlorobenzene and pentachlorophenol (Engst, et al. 1976a,b).
1,2,4,5-TeCB has an extremely low vapor pressure, less
than 0.1 mm Hg at 25°C (Sax, 1975). The octanol-water parti-
tion coefficient for TeCB is 4.93.
C-48
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Ingestion from Water
No literature was found which identified TeCB in water
in the United States. However, a contamination of run-off as
a result of its industrial use is certainly feasible and may
in part, be responsible for the contamination of the aquatic
organisms described below. Soil microorganisms are capable
of metabolizing lindane to tetrachlorobenzene, among others
(Tu, 1976; Mathur and Saha, 1977). TeCB derived in this man-
ner is available from soil run-off.
Ingestion from Foods
There are some data to show that TeCB will concentrate
in fish exposed to industrial effluent discharge. Kaiser
(1977) identified two isomers of TeCB in three species of
fish caught at various distances from a pulp and paper mill.
Similarly, Lunde and Ofstad (1976) identified tetrachloro-
benzene in sprat (a small herring) from different locations
in southeastern Norway.
Qualitatively, tetrachlorobenzenes have been identified
in the food chain as a result of the biotransformation of
lindane. Saha and Burrage (1976) administered lindane to hen
pheasants and identified tetrachlorobenzene as part of the
array of metabolites found in eggs and chicks as well as in
the body tissues of the hens. Balba and Saha (1974) followed
the metabolism of 14C-lindane in wheat plants grown from
treated seeds and identified two and possibly three of the
isomers of TeCB. Kohli, et al. (1976 b,c) in laboratory
studies identified TeCB as a minor metabolite of lindane in
lettuce and endives.
C-49
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Tetrachlorobenzenes have also been identified as metabo-
lites of gamma pentachlorocyclohexane in corn and pea seed-
lings. Pentachlorbenzenes have also been identified in the
essential oil of marsh grass (Miles, et al. 1973).
There is legitimate doubt as to whether exposure to
TeCBs as breakdown products of lindane and other substances
represents a significant exposure, especially considering
that concentrations of the more toxic parent compounds are
higher.
A bioconcentration factor (BCF) relates the concentra-
tion of a chemical in water to the concentration in aquatic
organisms, but BCF's are not available for the edible por-
tions of all four major groups of aquatic organisms consumed
in the United States. Since data indicate that the BCF for
lipid-soluble compounds is proportional to percent lipids,
BCF's can be adjusted to edible portions using data on per-
cent lipids and the amounts of various species consumed by
Americans. A recent survey on fish and shellfish consumption
in the United States (Cordle, et al. 1978) found that the per
capita consumption is 18.7 g/day. From the data on the nine-
teen major species identified in the survey and data on the
fat content of the edible portion of these species (Sidwell,
et al. 1974), the relative consumption of the four major
groups and the weighted', average percent lipids for each group
can be calculated:
C-50
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Consumption Weighted Average
Groups (Percent) Percent Lipids
Freshwater fishes 12 4.8
Saltwater fishes 61 2.3
Saltwater molluscs 9 1.2
Saltwater decapods 18 1.2
Using the percentages for consumption and lipids for each of
these groups, the weighted average percent lipids is 2.3 for
consumed fish and shellfish.
No measured steady-state bioconcentration factor (BCF)
is available for 1,2,4,5-tetrachlorobenzene, but the equation
"Log BCF =0.76 Log P - 0.23" can be used (Veith, et al.
Manuscript) to estimate the BCF for aquatic organisms that
contain about eight percent lipids from the octanol-water
partition coefficient (P). An adjustment factor of 2.3/8.0 =
0.2875 can be used to adjust the estimated BCF from the 8.0
percent lipids on which the equation is based to the 2.3 per-
cent lipids that is the weighted average for consumed fish
and shellfish. Thus, the weighted average bioconcentration
factor for the edible portion of all aquatic organisms
consumed by Americans can be calculated:
Compound P BCF Weighted BCF
1,2,4,5-tetrachlorobenzene 93,000 3,500 1,000
C-51
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Inhalation and Dermal
No reliable information has been recovered dealing with
inhalation or dermal exposure to TeCB.
PHARMACOKINETICS
Absorption/ Distribution, Metabolism, Excretion
Jondorf, et al. (1958) administered each of the three
isomers of TeCB to three rabbits at an oral dose of 0.5 g/kg.
The animals were followed for six days after dosing. The
percentage of administered dose recovered in the feces over
this time for the respective compounds was: 1,2,3,4-TeCB, 5
percent; I,2,3,5-TeCBf 14 percent; 1,2,4,5-TeCB, 16 percent.
Considering that this is over a six-day period and that some
of the fecal content could possibly have been a result of
biliary excretion, it would appear that the gastrointestinal
absorption of TeCBs is relatively efficient.
Table 1 shows the distribution of unchanged TeCB in rab-
bit tissues six days after dosing. Comparative distribution
among the three isomers shows a relative degree of consis-
tency. The one exception is in the gut contents where 12
percent of the total remaining compound is present for 1/2,
4,5-TeCB which is about twice that for the other isomers.
This could reflect lesser absorption of 1,2,4,5-TeCB or,
possibly, biliary excretion.
Table 2 shows the extent of elimination of the isomers
in expired air.
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TABLE 1
Unchanged Tetrachlorobenzene in Rabbit Tissues,
Six Days After Dosing (0.5 g/kg orally)
(Jondorf, et al. 1958)
TeCB
1,2,3,4
1,2,3,5
1,2,4,5
Liver Brain
0.1
<0.5 <0.2
0.1 <0.1
Percentage of Dose
Depot Gut Rest of .
Skin Fat Contents Body
2 5 0.5 2.0
5 11 1.4 5.2
10 25 6.2 6.4
TABLE 2
Total
10
23
48
Elimination of Unchanged Tetrachlorobenzenes
in Expired Air of Rabbits Following Oral Dosing
(Jondorf, et al. 1958)
TeCB
1,2,3,4
1,2,3,5
1,2,4,5
Dose
(g/kg)
0.5
0.3
0.5
0.3
0.5
Percentage of Dose in Expired Air
. Days after Dosing
1 2 3_ ± 5
1.9 2.2 1.6 0.2
0.8 1.7 6.7
2.1 2.1 1.2 2.9 2.6
0.9 3.2 9.8
1.2 0.2 0.2
Total
5.9
9.2
10.9
13.9
1.6
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Table 3 shows the*urinary excretory pattern observed in
the three isomers. The 1,2,3,4-TeCB isomer is more freely
metabolized than the other two isomers, and 1,2,4,5-TeCB is
metabolized the least.
TABLE 3
Urinary Excretion of Metabolites of Tetrachlorobenzenes
in Rabbits Following Oral Dosing (0,. 5 g/kg/)
(Jondorf, et al. 1958)
Percentage of Dose Excreted
TeCB
Ethereals Mercapturic TeCP
Glucuronide Sulfate Acid Fece
Total
1,2,3,4 30(22-36)a 3(1-8)
(5)b
<1
8(7,9)
43(38,48)
(2)
1,2,3,4
1,2,4,5
6(2-10)
(9)
4(1-8)
(ID
2(1-6)
(9)
l«l-2)
(11)
0
(3)
0
' (3)
1.9(1.2,2.5)
(2)
1.3(0.9,1.6)
(2)
5(4.6)
(2)
2.2(0.9,
(2)
1.6)
Kohli, et al. (1976a) studied the metabolism of TeCB iso-
mers in rabbits and identified the nature of TCP metabolites.
A dose of 60 to 705 mg/kg was administered to rabbits by in-
traperitoneal injection and the urine and feces collected for
ten days. The metabolism of both 1,2,3,4-TeCB and 1,2,3,5-
TeCB yielded two common metabolites, 2,3,4,5- and 2,3,4,6-
tetrachlorophenol (TeCP). Another metabolite of 1,2,3,5-TeCB
was 2,3,5,6-TeCP. This metabolite 2,3,5,6-TeCP was also the
only metabolite identified following the administration of 1,
2,4,5-TeCB. The relationships among the various isomers were
strikingly similar to the data reported by Jondorf, et al.
(1958).
C-54
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Kohli, et al. (1976a) proposed the formation of the
phenol metabolites through corresponding arene oxides. The
authors suggest the involvement of an NIH shift of the
chlorine atom in the formation of the metabolites (except for
the formation of 2,3,5,6-TeCP from 1,2,3,5-TeCB which can be
derived from 2,3,5,6-TeCB and oxide without an NIH shift of
chlorine).
From the above information, it is reasonable to expect
that the metabolism of the TeCB is via liver microsomal
enzymes. Ariyoshi, et al. (1975) reported an increase in
cytochrome P-450 induced by all three isomers in the rat
liver as well as an increase in delta aminolevulinic acid
synthetase activity. Rimington and Ziegler (1963) showed
that urinary porphyria and porphyria precursors were in-
creased in rats by 1,2,3,4-TeCB but not by 1,2,4,5-TeCB.
This was correlated with an increase in porphyrins, porphoro-
bilinogen and catalase activity in rats treated with 1,2,3,4-
TeCB but not the 1,2,4,5 isomer.
EFFECTS
Acute, Sub-acute and Chronic Toxicity
Most of the information on tetrachlorobenzene comes
from studies done in the Soviet Union and is concerned with
1,2,4,5-TeCB. The LD$Q for white mice was reported to be
1035 mg/kg when the compound was administered in sunflower
oil orally or 2650 mg/kg as a suspension in a 1.5 percent
starch solution. In rats and rabbits, the LD$Q was reported
to be 1500 mg/kg when the compound was administered in sun
flower oil (Fomenko, 1965). The apparent cumulative activity
C-55
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of this isomer of TeCB was demonstrated by Fomenko (1965). A
dose of 300 mg/kg, 20 percent of the LDso, was administered
to rats daily; 50 percent of the animals died when a dose
equivalent to the LD$Q was obtained. The same investigator
administered 1,2,3,5-TeCB in oral doses of 75 mg/kg daily for
two months. While there were presumptive changes in liver
function/ prothrombin index, blood cholesterol and number of
reticulocytes, histopathological examination showed no signif-
icant change that would alter liver function. Adrenal
hypertrophy and decreased content of ascorbic acid in
adrenals were reported. Histopathological examinations did
not reveal appreciable differences between control and
experimental groups.
Further experiments are described in the foregoing re-
port from the Soviet Union in which 1,2,4,5-TeCB was adminis-
tered in oral doses of .001, .005, and 0.05 mg/kg to rats and
rabbits over an eight month period. The report states that
doses of 0.005 mg/kg and "especially" 0.05 mg/kg disrupted
the conditioned reflexes. It is stated that "formation of a
positive condition reflex became slower but the latent period
remained the same". It is also stated that rabbits treated
with doses of 0.05 mg/kg "began to display disorders in gly-
cogen-forming function in the liver only after six experi-
mental months". No hematologic changes were noted in the
animals. At the end of the dosing period, liver weights were
increased in animals receiving doses of 0.005 and 0.05 mg/kg.
The conclusion made was that the two higher doses were active
and that the lower dose was not.
C-56
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The data from the above studies (Fomenko, 1965) are only
partially presented and the bulk of the report consists of
the conclusions of the author. The studies done on condi-
tioned reflexes in rats were done on a control group of five
animals, low and middle dose groups of seven animals each,
and a high dose group of six animals. It is not clear as to
whether or not those represented the total number of animals
in a group.
Braun, et al. (1978) administered 1,2,4,5-TeCB in the
diet to beagles at a dose of 5 mg/kg/day for two years. No
changes in clinical chemistry parameters were noted after 18
months. At 24 months there was a slight elevation of serum
alkaline phosphatase activity and bilirubin levels. The ani-
mals were then allowed to recover. After three months the
serum chemistry changes noted were no longer evident. Gross
and histopathological studies were done 20 months after
cessation of exposure. No treatment related changes were
noted.
Synergism and/or Antagonism
Since TeCBs can increase cytochrome P-450 levels, it,
like other halogenated benzenes, appears to represent a drug
metabolizing enzyme inducer (Ariyoshi, et al. 1975). In gen-
eral, the halogenated benzenes appear to increase the activ-
ity of microsomal NADPH-cytochrome P-450-dependent enzyme
systems. Induction of microsomal enzyme activity has been
shown to enhance the metabolism of a wide variety of drugs,
pesticides and other xenobiotics. Exposure to TeCB could
C-57
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therefore result in decreased pharmacologic and/or toxico-
logic activity of numerous compounds. Frequently, chemical
agents are metabolized to more active or toxic "reactive"
intermediates. In this event/ exposure to TeCB would result
in enhanced activity and/or toxicity of these agents.
Teratogenicity, Mutagenicity and Carcinogenicity
No studies have been identified which directly or in-
directly address the teratogenicity or carcinogenicity of
TeCB. An abstract of a study by Kiraly/ et al. (1976) de-
scribes a study of chromatid disorders among workers involved
in the manufacture of an organophosphorus compound. Disor-
ders were said to be significantly higher in this group than
in a group involved in the manufacture of TeCB. However/ the
abstract concludes "The mutagenic properties of tetrachloro-
benzene were confirmed". This is the only reference seen
referring to mutagenic activity of TeCB's.
C-58
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CRITERION FORMULATION
Existing Guidelines and Standards
The maximal permissible concentration of TeCB in water
established by the Soviet Union is 0.02 mg/1 (U.S. EPA,
1977) .
Current Levels of Exposure
No data are available on current levels of exposure.
However, the report by Morita, et al. (1975) gives some in-
dication of exposure. Morita, et al. (1975) examined adipose
tissue samples obtained at general hospitals and medical ex-
aminers offices in central Tokyo. Samples from 15 individ-
uals were examined; this represented five males and ten fe-
males between the ages of 13 and 78. The tissues were ex-
amined for 1,2,4,5-TeCB as well as for 1,4-dichlorobenzene
and hexachlorobenzene. The TeCB content of the fat ranged
from 0.006 to 0.039 mg/kg of tissue; the mean was 0.019
mg/kg. The mean concentrations of 1,4-dichlorobenzene and
hexachlorobenzene were 1.7 mg/kg and 0.21 mg/kg respectively.
Interestingly, neither age nor sex correlated with the level
of any of the chlorinated hydrocarbons in adipose tissue.
Special Groups at Risk
The primary groups at risk from the exposure to TeCB are
those who deal with it in the workplace. Since it is a
metabolite of certain insecticides, it might be expected that
certain individuals exposed to those agents might experience
more exposure to TeCB especially since its elimination rate
might be relatively slow in man. Individuals consuming large
C-59
-------
quantities of fish may also be at risk due to the proven bio-
concentration of TeCB in fish. U.S. EPA Duluth laboratory
studies show that the bioconcentration factor for 1,2,4,5-
TeCB is 1,000 times, and for 1,2,3,5-TeCB is 4,100 times.
Basis and Derivation of Criterion
The dose of 5 mg/kg/day reported for beagles (Braun,
1978) was utilized as the NOAEL for criterion derivation. An
acceptable daily intake (ADI) can be calculated from the
NOAEL by using a safety factor of 1,000 based on a 70 kg/man:
,. _T 70 kg x 5 mg/kg « ->c /j
ADI = - 1000 *** ~ 0-35 mg/day
For the sake of establishing a water quality criterion,
it is assumed that on the average, a person ingests 2 liters
of water and 18.7 grams of fish. Since fish may biomagnify
this compound, a biomagnif ication factor (F) is used in the
calculation.
The equation for calculating an acceptable amount of
TeCB in water is:
Criterion = 2 3. + = 16'9 ^/l or 17
where:
21=2 liters of drinking water consumed
0.0187 kg = amount of fish consumed daily
1000 = biomagnif ication factor
ADI = Allowable Daily Intake (mg/kg for a 70 kg/person)
Thus, the recommended criterion for TeCB in water is 17
ug/1.
C-60
-------
o
I
Figure 1: Proposed routes for the biotransformation of tetrachlorobenzene
isomers via arene oxides (Kohli, et al. 1976a)
-------
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:
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Pollut. 9: 175.
Rimington, C., and G. Ziegler. 1963. Experimental porphyria
in rats induced by chlorinated benzenes. Biochem. Pharmacol.
12: 1387.
Rozman, K., et al. 1975. Separation, body distribution and
metabolism of hexachlorobenzene after oral administration to
rats and rhesus monkeys. Chemosphere 4: 289.
C-64
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Saha, J.G., and R.H. Burrage. 1976. Residues of lindane and
its metabolites in eggs, chicks and body tissues of hen
pheasants after ingestion of lindane carbon-14 via treated
wheat seed or gelatin capsules. Jour. Environ. Sci. Health
Bll: 67.
Sax, N.I. 1975. Dangerous properties of industrial mater-
ials; 4th Ed., Van Nostrand Reinhold, New York. p. 1145.
Sidwell, V.D., et al. 1974. Composition of the edible por-
tion of raw (fresh or frozen) crustaceans, finfish, and mol-
lusks. I. Protein, fat, moisture, ash, carbohydrate, energy
value, and cholesterol. Mar. Fish. Rev. 36: 21.
Tu, C.M. 1976. Utilization and degradation of lindane by
soil microorganisms. Arch. Microbiol. 108: 259.
U.S. EPA. 1977. Investigation of selected potential environ-
mental contaminants: halogenated benzenes. 560/2-77-004
U.S. Environ. Prot. Agency.
Veith, G.D., et al. An evaluation of using partition coeffi-
cients and water solubility to estimate bioconcentration fac-
tors for organic chemicals in fish. (.Manuscript).
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PENTACHLOROBENZENE
Mammalian Toxicology and Human Health Effects
EXPOSURE
Introduction
Pentachlorobenzene (QCB1) is used primarily as a pre-
cursor in the synthesis of the fungicide, pentachloronitro-
benzene (PCNB, Quintozene, Terraclor), and as a flame retar-
dant. It has been suggested as an intermediate in the pro-
duction of thermoplastics (Kwiatkowski, et al. 1976). QCB is
a white solid crystalline material at room temperature and,
like other halogenated benzenes, is both lipophilic and
hydrophobia. Approximately 1.4 x 10^ kg of pentachloroben-
zene was produced in 1972 and it is estimated that 16.6 x 10^
kg of the material was discharged into (ambient) water sources.
Much of the exposure of the population to QCB is derived from
exposure to lindane, hexachlorobenzerie (HCB), and PCNB. The
metabolism of lindane to QCB is well established and it has
been demonstrated in humans (Engst, et al. 1976a), rats
(Engst, et al. 1976b,c; Seidler, et al. 1975; Kujawa, et al.
1977), and rabbits (Karapally, et al. 1973). Biotransforma-
tion of lindane to QCB can occur earlier in the food chain.
1QCB (for quintochlorob'enzene) rather than PCB will be used
as the abbreviation for pentachlorobenzene to avoid confusion
with polychlorinated biphenyls.
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Engst, et al. (1977) identified QCB as a product of the metab-.
olism of lindane by mold grown spontaneously on grated car-
rots. Tu (1976) identified 71 soil microorganisms which would
biodegrade lindane. Thirteen of these were examined further
and were found to produce QCB as one of the metabolites of the
insecticide. Mathur and Saha (1977) have also reported QCB as
a soil degradation product of lindane.
QCB has been identified as a metabolite of HCB in rats
(Mehendale, et al. 1975; Engst, et al. 1976c) and rhesus mon-
keys (Rozman, et al. 1977, 1978; Yang, et al. 1975, 1978).
TCNB occurs as a residue in technical grade PCNB.
Borzelleca, et al. (1971) detected TCNB storage in tissue of
rats, dogs and cows following feeding studies with PCNB.
Rautapaa, et al. (1977) examined soil samples in Finland from
areas that have been treated with PCNB and found a maximum
PCNB level of 27 mg/kg of soil and the highest QCB level of
0.09 mg/kg of soil.
Igarashi, et al. (1975) identified QCB as a further
degradation product of pentachlorothioanisole in soil.
The importance of QCB as a contaminant of PCNB in treated
soil is demonstrated by the study of Beck and Hansen (1974).
They studied 22 soil samples from fields where technical PCNB
had been used regularly during the foregoing 11 years. The
concentration range for PCNB in the samples was 0.01 to 25.25
mg/kg of soil and a concentration range for QCB of 0.003 to
0.84 mg/kg of soil. The samples were studied for a period of
C-67
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600 days. The half-life of QCB in two separate determinations
was 194 and 345 days. The calculated log partition coefficent
for QBC OCT/H2O = 5.63.
C-68
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Ingestion from Water
The following discussion concerning the ingestion of QCB
from food, especially as relates to its presence in marine
organisms, also relates to the presence of the compound in
water. Burlingame (1977) has identified QCB in effluent from
a wastewater treatment plant in southern California. Access
to water by QBC can occur by a number of means including in-
dustrial discharge or as a breakdown product or contaminant of
widely used organochlorine compounds.
Ingestion from Foods
From the available information it would appear that the
appearance of QCB in soil and its persistence can result in an
accumulation within the food chain. This also holds true for
its ecological precursors. For example, Balba and Saha (1974)
treated wheat seed with isotopically labeled lindane and ob-
served a number of metabolites, including QCB, in the seed-
lings and mature plants. Kohli, et al. (1976a) found that
isotopically labeled lindane added to the nutrient medium for
lettuce was metabolized to a number of products including QCB.
Dejonckheere, et al. (1975, 1976) examined samples from soil
which had been used to grow lettuce and samples from soil used
to grow witloof-chicory. The soil had been treated with PCNB
for a six year period. Sample averages ranged from 0.25 to
0.85 ppm of QCB. Lunde (1976) has examined fish from south-
eastern Norway for the presence of polychlorinated aromatic
hydrocarbons. QCB was among a number of compounds identified
in extracts of plaice, eel, sprat, whiting, and cod. Lunde
and Ofstad (1976) quantitated the amount of chlorinated
C-69
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hydrocarbons in sprat oil. Six samples taken from different
locations and/or at different times contained 0.7 to 3.8 ppm
of QCB. Ten Berge and Hillebrand (1974) identified the pres-
ence of a number of organochlorine compounds, including QCB,
in plankton, shrimp, mussels/ and fish from the North Sea and
the Dutch Wadden Sea. The compounds were present in part per
billion levels.
Stijve (1971) detected QCB in chicken fat which was
ascribed to residues of HCB. Kazama, et al. (1972) admin-
istered QCB by intramuscular injection to hens .and recovered
7.3 percent of the dose in the yolk of the egg. No material
was found in the egg white. Saha and Burrage (1976) admin-
istered isotopically labeled lindane to hen pheasants via
treated wheat seed or gelatin capsules and recovered QCB as
one of the metabolites in the body of the hen, in the eggs and
in the chicks. Dejonckheere, et al. (1974) reported on the
presence of QCB in animal fat and suggested that it was 'de-
rived from pesticide residue in feed. That pesticide residue
included HCB and lindane. Greve (1973) identified QCB and HCB
in wheat products used for animal feed and detected QCB in the
fat of animals utilizing that feed.
A bioconcentration factor (BCF) relates the concentration
of a chemical in water to the concentration in aquatic organ-
isms, but BCF's are not available for the edible portion of
all four major groups.of aquatic organisms consumed in the
United States. Since data indicate that the BCF for lipid-
soluble compounds is proportional to percent lipids, BCF's can
be adjusted to edible portions using data on percent lipids
C-70
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and the amounts of various species consumed by Americans. A
recent survey on fish and shellfish consumption in the United
States (Cordle, et al. 1978) found that the per capita
consumption is 18.7 g/day. From the data on the nineteen
major species identified in the survey and data on the fat
content of the edible portion of these species (Sidwell, et
al. 1974), the relative consumption of the four major groups
and the weighted average percent lipids for each group can be
calculated:
Consumption Weighted Average
Group (Percent) Percent Lipids
Freshwater fishes 12 4.8
Saltwater fishes 61 2.3
Saltwater molluscs 9 1.2
Saltwater decapods 18 1.2
Using the percentages for consumption .and lipids for each of
these groups, the weighted average percent lipids is 2.3 for
consumed fish and shellfish.
A measured steady-state bioconcentration factor of 1,800
was obtained for pentachlorobenzene using bluegills containing
about one percent lipids (U.S. EPA, 1978). An adjustment fac-
tor of 2.3/1.0 = 2.3 can be used to adjust the measured BCF
from the 1.0 percent lipids of the bluegill to the 2.3 percent
lipids that' is the weighted average for consumed fish and
shellfish. Thus, the weighted average bioconcentration
factors for pentachlorobenzene and the edible portion of all
aquatic organisms consumed by Americans is calculated to be
7,800.
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Inhalation
There is very little, information concerning atmospheric
exposure to QCB. The primary site for such exposure could be
the workplace in industries utilizing and/or producing QCB.
Dermal
No information was obtained which concerns dermal
exposure to pentachlorobenzene.
PHARMACOKINETICS
Absorption, Distribution, Metabolism, Excretion
Table 1 presents data from Parke and Williams (1960) on
the metabolism of pentachlorobenzene by rabbits. It can be
seen that a substantial portion of the oral dose was recov-
ered in the gut contents three to four days after dosing.
Except for the possibility of biliary secretion, which ap-
pears unlikely from the data obtained after a parenterally
administered dose, it would appear that pentachlorobenzene is
very poorly absorbed from the gastrointestinal tract. It is
also evident that distribution favors deposition in the fat.
Engst, et al. (1976c) administered QCB orally to rats at a
dose of 8 mg/kg for 19 days. They identified 2,3,4,5-tetra-
chlorophenol and pentachlorophenol as the major urinary
metabolites. They also detected 2,3,4,6-tetrachlorophenol
"and/or" 2,3,5,6-tetrachlorophenol and unchanged QCB. They
reported the presence of 1,3,5-trichlorobenzene in the liver.
Kohli, et al. (1976b) described 2,3,4,5-tetrachlorophenol and
pentachlorophenol as urinary metabolites of QCB in the rab-
C-72
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bit. They were detected at yields of one percent each of the
administered dose. The authors suggest that the dechlorina-
tion hydroxylation step to the tetrachlorophenol derivative
proceeds through an arene oxide step. Koss and Koransky
(1977) reported pentachlorophenol and 2,3,4,5-tetrachloro-
phenol as metabolites of QCB in the rat. However, they
stated that the amount of pentachlorophenol recovered in the
urine represented about nine percent of the administered
dose. Quantitively, this is substantially greater than the
073
-------
TABLE 1
Disposition of Pentachlorobenzene in the Rabbit as Percentage
of Administered Dose (Parke and Williams, 1960)
Dose/Route
Time
After
Dose
rag/kg (Days)
o
i
-4
0.5 p.o.
0.5 p.o.
0.5 s.c.
*Located mainly
3
4
10
at site
Urine
Triorpenta
Ch lorophenol
0.2
0.2
0.7
of injection.
Other
Phenol Feces
1 5
1 5
1 1.5
Cut
Contents
45
31
0.5
Depot
Pelt Fat
1 15
5 9
47* 22*.
Rest
of Un-
Body changed
6 0
5.5 0
10 0
Other
Hydro-
carbons
9
21
L2
Total
Accumulated
For
82
78
85
-------
amounts of pentachlorophenol reported by Kohli, et al.
(1976b) for the rabbit. Parke and Williams (1960) reported
that less than 0.2 percent of the dose was recovered as
pentachlorophenol in rabbit urine, also a substantial dif-
ference from that observed in the rat. Rozman, et al. (in
press) found that biological half-life for QCB in rhesus mon-
keys to be two to three months. After 40 days ten percent of
the total dose was excreted in the urine; of this 58 percent
was pentachlorophenol. After the same period, about 40 per-
cent of the dose was excreted in the feces, 99 percent of
which was unchanged QCB. These authors believe this is made
up of unabsorbed QCB that is secreted by bile into the GI
tract. Ariyoshi, et al. (1975) reported that, in female
Wistar rats dosed with 250 mg/kg QCB for three days by intu-
bation, QCB increased the liver content of cytochrome P450
and increased the activities of aminopyrine demethylase and
aniline hydroxylase. The contents of microsomal protein and
phospholipids were also increased as was the activity of
delta aminolevulinic acid.
Further information on the biotransformation and accumu-
lation properties of QCB can be obtained from a study re-
ported by Villeneuve and Khera (1975). They studied the
placental transfer of halogenated benzene in rats. They
administered oral doses of QCB to pregnant rats on days 6
through 15 of gestation. Their data are shown in Table 2.
It can be seen that the accumulation in the organs is dispro-
portionate to the increasing dose implying that somewhere
between 100 and 200 mg/kg doses, elimination approaches zero
C-75
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order kinetic behavior. The ease of accumulation of the
compound within the fetus is also evident. This will be
discussed further below.
EFFECTS
Acute, Sub-acute and Chronic Toxicity
Goerz, et al. (1978) administered a diet of 0.05 percent
of QCB to female adult rats for a period of 60 days. They
were primarily interested in the comparative abilities of QCB
and HCB to induce porphyria. The treatment resulted in an
increased urinary excretion of porphyrins by the HCB treat-
ment, but none with the QCB treatment. It is uncertain from
these experiments whether the dosage levels for QCB are ade-
quate. Induction of experimental porphyria can be accom-
plished with all of the other chlorinated benzenes and it
would appear that a more detailed examination of pentachloro-
benzene should be done before any final conclusions are made
concerning its activity in this regard. A survey of the
literature has revealed no other published data on the acute,
subchronic or chronic toxicity of QCB. The only exceptions
to this are data which have been gathered in association with
pharmacokinetic and teratologic studies, but on the basis of
the number of animals utilized and the time of administration,
these are not particularly useful for establishing criterion
standards. For example, Khera and Villeneuve (1975) admin-
istered QCB in doses of 50, 100 and 200 mg/kg orally to preg-
nant rats during days 6 to 15 of gestation. The adult rats
(20 in each group) did not display any "overt" signs of
C-76
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TABLE 2
Tissue Distribution of Pentachlorobenzene (PPM wet tissue) Following
Oral Administration to Pregnant Rats (Villeneuve and Khera, 1975)
o
1
-J
-J
Dose
(mg/kg)
50
100
200
Represents
^Represents
cRepresents
Fata
470+106
824+116
3350+331
the mean of
the mean of
the mean of
Liver3
13.9+5.1
18.1+2.0
91.1+_6.6
5 animals +
two fetuses
five fetuses
Brain3 Heart3 Kidney3
6.9+ 1.2 6.2+1.0 6.0+1.1
12.0+ 1.7 12.6+2.0 10.6+1.5
62.5+10.2 57.5+9.6 43.5+2.6
o » ti *H
from 15 litters + S.E.H.
each from a different litter + S.E.M.
Whole3 Fetalc Fetalc
Spleen3 Fetus Liver Brain
4.5+1.1 9.65+^1.3 4.37+0.69 3.08+0.55
8.3+1.3 21.2 +2.1 10.4 +1.31 5.31+0.60
46.2+8.1 55.1 +6.7 40.4 +6.02 20.5 +2.64
-------
toxicity, though it is not certain whether the word overt re-
fers to any particularly informative toxicological examina-
tion.
There are no other studies which shed light as to the
chronic toxicity of pentachlororbenzene.
Koss and Koransky (1977) have suggested that a major con-
sideration in toxicity of pentachlorobenzene is its biotrans-
formation to pentachlorophenol. Considering that the findings
by Rozman/ et al. (in press); cited above, showing a half-life
of pentachlorobenzene to be two to three months/ and the urin-
ary excretion of pentachlorophenol to be six percent of the
administered dose/ it is questionable that over a period of 40
days a substantial quantity of pentachlorophenol might event-
ually be made available to the system.
Synergism and/or Antagonism
The interaction of QCB with microsomal enzyme systems
might result in effects on biotransformation and toxicity of
drugs and other chemicals. However/ there are no available
data on synergistic or antagonistic effects.
Carcinogenicity/ Mutagenicity/ Teratogenicity
There is one report that alludes to the carcinogenicity
of pentachlorobenzene in mice and the absence of this activ-
ity in ratd and dogs (Preussman/ 1975). This paper has not
been evaluated due to difficulties in locating the source.
When made available it will be evaluated as a possible basis
for a criterion standard.
Teratogenicity studies with QCB have been reported by
Khera and Villeneuve (1975). As indicated above/ doses of
C-78
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50, 100 and 200 mg/kg were administered to pregnant rats on
day 6 to 15 of gestation. The authors did not interpret these
data to demonstrate the teratogenicity of QCB. However, the
EPA feels that suprauni ribs represent an adverse effect on
fetal development. Table 3 represents findings resulting from
Cesarean sections done on day 22 of pregnancy. The high dose
of QCB produced an increased incidence of uni- or bilateral
extra rib, as well as sternal defects consisting of unossified
or nonaligned sternabrae with cartilagenous precursors
present. The authors considered that the sternal defects
suggested a retarded sternal development, and that these were
related to a decreased mean fetal weight. At lower doses the
sternal defects were not noted, but there was an increased
incidence of extra ribs. The number of litters with one or
more litter mates showing an anomalous rib number (14th and
15th combined), versus numbers of litters examined for each
dose group, was 3/19 for 0, 14/19 for 50, 11/19 for 100, and
15/19 for 200 mg/kg, showing an apparent dose-related
incidence.
No data have been found concerning the mutagenicity of
QCB.
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TABLE 3
Prenatal Data on Rats Dosed on Days 6 to 15 of
Gestation with Pentachlorpbenzene
(Khera and Villeneuve, 1975)
Dose mg/kg
0 50 100
200
No. of rats pregnant at term
No. of live fetuses, mean %
fetal death
(dead + deciduoma) 100
total implants
Fetal weight, g., mean
No. of fetuses examined
for skeletal anomalies
Anomalies, type and incidence
Extra ribs:
uni
bilateral
Fused ribs:
wavy ribs
sternal defects
No. of fetuses examined
for visceral defects
Runts
Cleft Palate
Other defects
19
12.1
1.3
4.8
127
2
2
5
5
67
1
18
12.5
4.2
4.9
129
18
10
2
4
69
2
1
19 17
11.5 10.7
3.1 3.2
4.8 4.4
122 100
10 17
11 46
2
31
67 52
2
2
-------
CRITERION FORMULATION
Current Levels of Exposure
Morita, et al. (1975) examined levels of QCB in adipose
tissue samples obtained from general hospitals and medical
examiners' offices in central Tokyo. The samples were from a
total of 15 people. The group found by gas chromatography a
residual level of QCB to be in the range of 0.004 y.g/g to
0.020 ug/g* with a mean value of 0.09 ug/g of fat. Lunde and
Bjorseth (1977) looked at blood samples from workers with
occupational exposure to pentachlorobenzene and found that
their blood samples contained higher levels of this compound
than a comparable group of workers not exposed to chloro-
benzene.
Special Groups at Risk
At risk groups would appear to be those in the indus-
trial setting. There might be an expected increase in body
burdens of QCB in individuals on diets high in fish due to
the persistence of the compound in the food chain and to
those on diets high in agricultural products containing QCB
as residues of PCNB spraying.
Basis and Derivation of Criterion
A survey of the QCB literature revealed no acute, sub-
chronic or chronic toxicity data with the exception of the
studies by Khera and Villeneuve (1975). These authors found
an adverse effect on the fetal development of embryos exposed
in utero to pentachlorobenzene. The adverse effect has not
been labeled teratogenic because the abnormality was an in-
creased incidence of extra ribs and sternal defects. The
C-81
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lowest level of exposure to the pregnant rat was 5 mg/kg.
The criterion rationale is based on this exposure level.
Since there was no "no observable adverse effect level"
(NOAEL) an uncertainty factor of 5000 is used. The use of
this factor has precedent in the pesticide literature.
From this, the acceptable daily intake (ADI) can be
calculated as follows:
ADI = = 0.07 mg
The average daily consumption of water was taken to be 2
liters and the consumption of fish to be 0.0187 kg daily.
The bioconcentration factor for QCB is 7800.
Therefore:
Recommended Criterion = 2 + (7800) x 0.0187 = °*47 ug//1 (°r~°'5 ug/D
The recommended water quality criterion for pentachloro-
benzene is 0.5 ug/1.
C-82
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Rautapaa, J., et al. 1977. Quintozene in some soils and
plants in Finland. Ann. Agric. Fenn. 16: 277.
Rozman, K., et al. 1977. Longterm feeding study of hexa-
chlorobenzene in rhesus monkeys. Chemosphere 6: 81.
Rozman, K., et al. 1978. Chronic low dose exposure of rhesus
monkeys to hexachlorobenzene. Chemosphere 7: 177.
C-87
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Tu, C.M. 1976. Utilization and degradation of Lindane by
soil microorganisms. Arch. Microbiol. 108: 259.
U.S. EPA. 1978. In-depth studies on health and environmental
impacts of selected water pollutants. U.S. Environ. Prot.
Agency, Contract No. 68-01-4646.
Villeneuve, D.C., and K.S. Khera. 1975. Placental transfer
of halogenated benzenes (pentachloro-, pentachloronitro-, and
hexabromo-) in rats. Environ. Physiol. Biochem. 5: 328.
Yang, R.S.H., et al. 1975. Chromatographic methods for the
analysis of hexachlorobenzene and possible metabolites in
monkey fecal samples. Jour. Assoc. Off. Anal. Chem. 56:
1197.
Yang, R.S.H., et al. 1978. Pharmacokinetics and metabolism
of hexachlorobenzene in the rat. Jour. Agric. Food Chem.
26: 1076.
C-89
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systems far removed from the original area of application.
HCB's impact on agriculture as a result of environmental con-
tamination may be much larger than its utility as a fungicide
to control smut diseases in cereal grains. Foodstuffs such
as eggs, milk, and meat become contaminated with HCB as a re-
sult of ingestion of HCB-treated cereals by livestock.
Commercial production of HCB in the United States was
discontinued in 1976 (Chem. Econ. Hdbk., 1977). However,
even prior to 1976, most HCB was produced as a waste by-
product during the manufacture of perchloroethylene, carbon
tetrachloride, trichloroethylene and other chlorinated hydro-
carbons. (This is still the major source of HCB in the U.S.)
In 1972, an estimated 2.2 x 106 kg of HCB were produced
from these industrial processes (Mumma and Lawless, 1975).
Its generation as a by-product remains unabated. HCB found
in Louisiana was apparently related to airborne industrial
emissions, while residues in sheep from Texas and California
were traced to pesticide contaminated with HCB. Until re-
cently, HCB was a major impurity in the herbicide dimethyl
tetrachloroterephthalate and the fungicide pentachloronitro-
benzene. HCB has been found in polyethylene plastic bottles
from one source (Rourke, et al. 1977). HCB is used in in-
dustry as a plasticizer for polyvinyl chloride as well as a
flame retardant.
C-91
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bodies of fresh water in cne world. The total population
density around the lake is low and the concentrations of
trace elements have remained relatively small compared to
those in other Great Lakes (Veith, et al. 1977). HCB was
detected in drinking water supplies at three locations, with
concentrations ranging from 6 to 10 ng/kg.. HCB was detected
in finished drinking water at two locations, with concentra-
tions ranging from 4 to 6 ng/kg (U.S. EPA, 1975).
HCB has considerable potential to bioaccumulate in the
aquatic environment and is very persistent. The combination
of these two attributes makes HCB a potentially hazardous
compound in the environment. Soil contaminated with HCB
would retain HCB for many years. If contaminated soil finds
its way into the aquatic environment, it will become avail-
able to aquatic organisms.
HCB enters the environment in the waste streams from the
manufacture of chlorinated,hydrocarbons and from its agricul-
tural use as a preemergence fungicide for small grains. HCB
becomes redistributed throughout the environment as a conse-
quence of its leaching from industrial waste dumps and its
volatilization from industrial sources and contaminated im-
poundments. HCB absorbed to soil may be transported long
distances in streams and rivers. HCB is now distributed
throughout the world. The solubility of HCB in water is low,
however, and its concentration in water rarely exceeds 2
ug/kg.
HCB is sufficently volatile so that one air drying of
moist soil or biological samples causes a 10 to 20 percent
C-93
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loss of HCB (vapor pressure 1.089xlO""5 mm Hg at 20°C). The
half-life of HCB in soil (incorporated at 10 kg/ha) stored in
plastic-covered plastic pots is about 4.2 years (Beck and
Hansen, 1976). HCB is not lost from soil two to four cm be-
neath the surface during 19 months, but 55 percent is lost
from the surface two cm of soil within two weeks (Beall,
1976). Clearly/ volatilization is a significant factor in
the loss of HCB from soil and for its entry into the atmos-
phere. No HCB is lost from soil treated with 0.1 to 100
mg/kg of HCB and stored under aerobic (sterile and non-
sterile) and anaerobic nonsterile conditions for one year in
covered containers to retard volatilization (Isensee, et-al.
1976). Degradation products of HCB have not been found in
plants and soil. Hexachlorobenzene is relatively resistant
to photochemical degradation in water. Photolysis of HCB oc-
curs slowly in methanol, 62 percent being degraded in 15
days. It is not known whether organic matter in natural
waters or natural photosensitizers in the environment can en-
hance the rate of degradation of HCB (Plimmer and Klingebiel,
1976). HCB may be even more stable than DDT or dieldrin in
the environment (Freitag, et al. 1974). HCB has been singled
out as the only organic chemical contaminant present in the
ocean at levels likely to cause serious problems (Natl. Acad.
Sci. 1975).
HCB, adsorbed to soil or sand, is released into water
and taken up by aquatic organisms such as algae, snails,
daphnids (Isensee, et al. 1976), and fish (Zitko and Hut-
zinger, 1976). The alga Chara, collected from the lower
Mississippi River (Louisiana) contained 563 ug/kg wet weight.
C-94
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An undefined planKtor. ... jIf* cont ; . a,
et al. 1976).
The aquatic plants Najas and Ellocharis contained 147 ug
HCB/kg and 423 ug HCB/kg wet weight respectively (Laseter, et
al. 1976). Three aquatic invertebrate genera: snail Physa,
crayfish Procambarus and dragonfly larvae Anisoptera, also
collected from the lower Mississippi River, contained 294
ug/kg, 48.67 ug/g and 4.7 ug/g respectively (Laseter, et al.
1976). The HCB levels in inland fish from the United States
ranged from "none detected" to 62 mg HCB/kg. The high mean
level of HCB in carp (16 mg/kg) was attributed to runoff from
an industrial chemical storage area. The mean HCB concentra-
tion in seven other inland fish ranged from <1 to 130 ug/kg
(Johnson, et al. 1974). The HCB level in fish collected from
the contaminated lower Mississippi River ranged from 3.3 to
82.9 mg/kg for fish. The HCB levels in mosquitofish col-
lected some distance from the site of the HCB industrial
source on the lower Mississippi River ranged from 71.8 to
379.8 ug/kg, about 100-fold lower than the HCB content in
fish near the site of industrial contamination (Laseter, et
al. 1976).
Marine invertebrates collected from the central North
Sea contained substantially less HCB than invertebrates from
the central contaminated lower Mississippi River (Schaefer,
et al. 1976). Residues of HCB were determined in 104 samples
of marine organisms collected at various sites off the At-
lantic Coast of Canada during 1971 and 1972. The results
C-95
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indicated a widespread, low-level distribution of HCB (<1 to
20 ug HCB/kg). The highest levels of HCB were in fatty sam-
ples (1 ug/kg in whole cod vs 39 ug/kg in cod liver; none
detected in whole lobster vs 54 ug/kg in lobster hepatopan-
creas). Herring contained the greatest whole body burden of
HCB (20 ug/kg) (Sims, et al. 1977). The HCB levels in marine
fish from the central North Sea ranged from 0.2 to 2.9 ug/kg
for muscle and from 2.9 to 10 ug/kg for liver. The organ
concentrations of HCB increased with increasing lipid content
of the organ (Schaefer, et al. 1976).
HCB has been detected in a number of water and land
birds. Carcasses of immature ducks contained HCB ranging
from >60 to 240 ugAg (White and Kaiser, 1976). The HCB
levels ranged from 110 to 500 ug/kg in carcasses of 4 of 37
bald eagles (Cromartie, et al. 1975). The HCB levels in the
eggs of the common tern Sterna ranged from 1.35 to 14.7 mg/kg
dry weight (Gilbertson and Reynolds, 1972). Eggs of double-
crested cormorants Phalacrocorax from the Bay of Fundy were
monitored from 1973 to 1975. The eggs contained 15 to 17 ug
HCB/kg wet weight (Zitko, 1976).
Foxes and wild boars, which feed on small animals such
as mice and invertebrates, accumulated large amounts of HCB.
Because predators and scavengers contain higher residues of
HCB than herbivores, it would seem that bioaccumulation
through the food chain is occurring (Koss and Manz, 1976).
Ingestion from Foods
Ingestion of excessive amounts of HCB has been a con-
sequence of carelessness, lack of concern, and ignorance.
C-96
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There is a tendency to dispose of excess wheat seed by feed-
ing it to stock without due recognition of the toxic proper-
ties of the compounds concerned. In the mid-1960's, a ship-
ment of Australian powdered eggs was rejected for importation
into the United States by the Food and Drug Administration on
the grounds of contamination with HCB. The New South Wales
Egg Marketing Board tests samples of eggs that it handles and
will not accept for distribution any eggs which contain sig-
nificant amounts of HCB.
Food materials were collected at retail and department
stores in Tokyo, Japan, and were weighed out in the amounts
consumed a day. The food materials were classified into four
categories: cereals, vegetal products (vegetables, vegetal
oils, seasoning and seaweed), marine animal products, and
terrestrial animal products including dairy products and
eggs. The dietary intake of HCB ranged from 0.3 ug/day to
0.8 ug/day. Contributions from cereals were low (<0.05
ug/day). The contribution from vegetal products ranged from
<0.05 ug/day to 0.4 ug/day; that for marine animal products
from <0.05 ug/day to 0.3 ug/day; and that for terrestrial
animal products from 0.3 ug/day to 0.4 ug/day (Ushio and
Doguchi, 1977).
Herds of cattle in Louisiana were condemned by the State
Department of Agriculture in 1972 for .excessive HCB residues,
that is, they exceeded 0.3 mg HCB/kg in fat. Levels as high
as 1.52 mg HCB/kg. were reported. Of 555 animals tested among
157 herds, 29 percent of the cattle sampled contained <0.5 mg
HCB/kg in fat. HCB residues apparently did not arise from
C-97
-------
agricultural application of HCB fungicide but from contamina-
tion of air, soil and grass by industrial sources (U.S. EPA,
1976). In a total diet study conducted in Italy between 1969
and 1974, the average intake was estimated to be 4.2 ug
(Leoni and D'Arca, 1976). In an effort to reduce the amount
of HCB entering the environment, the Federal Republic of Ger-
many no longer allows application of HCB-containing pesti-
cides (Geike and Parashar, 1976a). The New South Wales
Department of Health (Australia) has recommended that the
concentration of HCB in eggs must not exceed 0.1 mg/kg
(Siyali, 1973). The NHMRC (Australia) has set the tolerance
for cows' milk at 0.3 mg HCB/kg in fat (Miller and Fox,
1973). The Louisiana Department of Agriculture has set the
tolerance for meat at 0.3 mg HCB/kg in fat (U.S. EPA, 1976).
There is a substantial body of information on HCB levels
in human milk for a number of countries. In the United
States, human milk contained a mean concentration of 78 ppb
(Savage, 1976). Milk from 45 women living in a metropolitan
v
area (Sydney, Australia) was found to contain HCB. The mean
HCB concentration in human milk was 15.6 ug/kg, and seven
percent of the samples contained 51 to 100 ug HCB/kg. In ad-
dition, 49 human milk samples from France and 50 from the
Netherlands contained HCB, but no values were reported. Hu-
man milk samples from Germany contained 153 ug HCB/kg of
whole milk and those from Sweden 1 ug/kg (Siyali, 1973). HCB
was also detected .in all of 40 human milk samples from Bris-
bane, Australia, and a rural area (Mareeba on the Atherton
Tablelands). The excretion of HCB into human milk was higher
C-98
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Hexachlorobenzene Content of Food (u.g HCB/kg)
(Italy: 1969 - 1974)
Food
Bread 1.1 n.d.
Noodles 0.7 0.2
Maize flour
Rice 0.8 0.3
Preserved legumes 1.1 n.d.
Dry legumes 2.4 0.2
Fresh legumes
Fresh vegetables 0.5 n.d.
and artichokes
Tomatoes
Potatoes
Onions 0.6 0.6
Carrots and other
root vegetables
Fresh fruit
Dried fruit
Exotic fruit
Citrus fruit
Bovine meat
Mutton, game
and rabbits
Giblets
Pork meat
Chicken
Eggs
Fresh fish
Preserved fish
Whole milk
Butter
Cheese
Olive oil
Seed oil
Lard
Wine 0.1 n.d.
Beer
Sugar 0.2 n.d.
Coffee
Values in parentheses are for extracted fat.
(a)n.d. not detected
Adapted from Leoni and D'Arca, 1976.
Mean
1.1
0.7
n.d.
0.8
1.1
2.4
n.d.
0.5
n.d.
n.d.
0.6
n.d.
n.d.
n.d.
n.d.
n.d.
0.7
(33.6)
1.0
(25.4)
0.7
(27.0)
25.0
(96.3)
5.7
(49.0)
4.7
0.7
n.d.
4.1
133.0
12.6
(63.0)
13.1
4.7
46.2
63.4
0.1
n.d.
0.2
n.d.
Range
2.9
2.9
1.1
3.1
5.1
1.8
0.6
n.d .
n.d.
n.d.
9.1
(74.3)
n.d.
1.7
n.d.
0.2
n.d.
n.d.
n.d.
1.4
- (78.4)
2.6
- (51.3)
1.3
- (53.9)
- 40.9
-(118.3)
- 11.5
- (75.0)
7.5
1.8
- 17.2
- 25.1
-(126.0)
- 53.8
- 27.9
0.6
0.6
C-99
-------
in Brisbane samples than in Mareeba samples (2.22 versus 1.23
mg HCB/kg in milk fat). The higher levels of HCB in Brisbane
donors may be related to the close proximity to a major grain
growing area, the Darling Downs. The daily intake of HCB by
infants was estimated to be 39.5 ug per day per 4 kg baby in
Brisbane and 14 ug per day per 4 kg baby in Mareeba. The
calculated average daily intake of HCB by breast-fed babies
in both areas exceeded the acceptable daily intakes recom-
mended by the FAO/WHO (1974) (2.4 ug/kg/day). The HCB con-
tent of human milk also exceeded the Australian NHMRC toler-
ance for cows' milk (0.3 mg/kg in milk fat). The dietary in-
take by young adults (15-to-18-year old males) was estimated
to be 35 ug HCB per person per day (Miller and Fox, 1973).
Similarly, HCB was found in all of 50 samples of human breast
milk collected in Norway. The mean HCB level was 9.7 ug/kg,
with a maximum value of 60.5 ug/kg. The HCB content of colo-
strum (7.7 ug/kg) was within the range of that for milk 1 to
16 weeks after birth (5.9 to 10.0 ug/kg). The HCB content of
the human milk samples in this survey exceeded the maximum
concentration for cows' milk approved by FAO/WHO (20 ug/kg).
The milk sample with the highest HCB level exceeded this
standard by threefold (Bakken and Seip, 1976).
A bioconcentration factor (BCF) relates the concentra-
tion of a chemical in water to the concentration in aquatic
organisms, but BCF's are not available for the edible por-
tions of all four major groups of aquatic organisms consumed
in the United States. Since data indicate that the BCF for
lipid-soluble compounds is proportional to percent lipids,
-------
BCF's can be adjusted to edible portions using data on per-
cent lipids and the amounts of various species consumed by
Americans. A recent survey on fish and shellfish consumption
in the United States (Cordle, et al. 1978) found that the per
capita consumption is 18.7 g/day. From the data on the nine-
teen major species identified in the survey and data on the
fat content of the edible portion of these species (Sidwell,
et al. 1974), the relative consumption of the four major
groups and the weighted average percent lipids for each group
can be calculated:
Consumption Weighted Average
Group (Percent) Percent Lipids
Freshwater fishes 12 4.8
Saltwater fishes 61 2.3
Saltwater molluscs "9 1.2
Saltwater decapods 18 1.2
Using the percentages for consumption and lipids for each of
these groups, the weighted average percent lipids is 2.3 for
consumed fish and shellfish.
No measured steady-state bioconcentration factor (BCF)
is available for hexachlorobenzene but the equation "Log BCF
= 0.76 Log P - 0.23" can be used (Veith, et al., Manuscript)
to estimate the BCF for aquatic organisms that contain about
eight percent lipids from the octanol- water partition coef-
ficient (P). An adjustment factor of 2.3/8.0 = 0.2875 can be
used to adjust the estimated BCF from the 8.0 percent lipids
C-101
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m which the equation is based to the 2.3 percent lipids that
*-.
s the weighted average for consumed fish and shellfish.
'hus, the weighted average bioconcentration factor for the
;dible portion of all aquatic organisms consumed by Americans
:an be calculated:
:ompound P :BCF Weighted
' BCF
iexachlorobenzene 2,450,000 42,000 12,000
nhalation and Dermal
HCB enters the air by various mechanisms such as release
rom stacks and vents of industrial plants, volatilization
rom waste dumps and impoundments, intentional spraying and
usting, and unintentional dispersion of HCB-laden dust from
anufacturing sites, during transport of finished material or
astes, and by wind from sites where HCB has been applied.
lasma HCB levels in a sample of 86 individuals living in
ouisiana adjacent to a plant producing chlorinated
ut not occupationally exposed, averaged 3.6 up^>/ with a
aximum of 23 ug/kg. Plasma HCB concentr^xi^'s were higher
&~
n males than in females (4.71 ug/kg compared with 2.79
g/kg, respectively), but there was no significant difference
_ r-t; f*
etween age groups^ ... The re was no evidenc^^aJE--cutajno^j^
^"^ -- <^~~^L-^m'g*~w\*hhi$c\ plasma con-
:entrations of HCB showed elevated coproporphyrin and lactic
lehydrogenase levels. Only two of 48 household meals sampled
C-102
-------
contained significant quantities of nCii, L -: _.ie,.» ,4^^
correlation between concentration in plasma and the concen-
tration of HCB in household dust. Some household dust con-
tained as much as 3.0 mg/kg. Affected households were on the
route of a truck which regularly conveyed residues containing
HCB from a factory to a dump. Workers in the adjacent plant
engaged in manufacturing carbon tetrachloride and perchloro-
ethylene had plasma HCB concentrations from 14 to 233 ug/kg
(Burns and Miller, 1975).
Pest control operators in their day-to-day work handle a
variety of toxic chemicals, including chlorinated hydrocarbon
pesticides. Pesticide may enter the body by inhalation of
spray mist which exists in confined spaces. The levels of
HCB in blood of pest control operators in New South Wales/
Australia, were found to be elevated in a 1970-71 study (1 to
226 ug/kg). The pest control operators seldom used respira-
tors, and those in use appeared to be ineffective due to poor
service maintenance. It is essential that the respirator
cartridges be changed regularly. The respiratory exposure
values were many-fold higher than the acceptable daily intake
as applied to food by WHO (0.1 ug/kg/day or 7 ug/day intake
for a 70 kg man) (Simpson and Shandar, 1972).
HCB may enter the body by absorption through the intact
skin as a result of skin contamination. Workers involved in
the application or manufacture of HCB-containing products are
at greater risk.
HCB enters the body as a result of ingestion and presum-
ably by inhalation and absorption through the skin. HCB re-
C-103
-------
mains in the blood for only a short period before it is trans-
located to fatty tissues or is excreted. HCB blood levels
reflect either recent exposure or mobilization of HCB from
body fat depots. HCB finds its way into air, water and food
as a result of unintentional escape from industrial si^es,'
intended application of HCB containing prod-acts, volatiliza-
tion from waste disposal sites and impoundments and uninten-
tional dispersion during transport" and storage. The result
has been the worldwide dissemination of HCB and ubiquity in
man's food, at least in low
All blood samp^fr^taken from children (1 to 18 years
old) in upper B^^ia in 1975 contained HCB at 2.6 to 77.9
ug/kg. The^study included 90 males and 96 females. HCB
/'
levels in blood showed a positive, hyperbolic correlation
with age, tending to an uper limit of 22 ug/kg for boys and
increase, in HCB concentra-
inversely proportioria
JSJ*'-
stantial accumulation of HCB became evident nine to ten
months after birth (Richter and Schmid, 1976). HCB was found
in all of a series of human fat samples collected from au-
topsy material throughout Germany. The highest levels of HCB
were in specimens from Munster (22 mg HCB/kg in fat) and
Munich (21 mg HCB/kg in fat) (Acker and Schulte, 1974). The
presence of HCB in Japanese autopsy adipose tissue^ was"~dej:er-,
mined for a total of 241 samples from Aichi Cancer Center
Research Institute, Chikusa-Ka Nagoya, Japan. The concentra-
tion of HCB in these fat samples was 90 ug/kg + 6 ug/kg stan-
dard -error (Curley, et al. 1973).
C-104
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HCB was found in all of 75 specimens of Australian human
body fat (1.25 mg/kg). Perirenal fat was taken at autopsy
from a random selection of bodies at the City Morgue, Sydney,
Australia. All ages and both sexes were included in the
study (Brady and Siyali, 1972). The incidence (63 percent of
samples tested) and concentration of HCB (0.26 mg/kg) in 38
specimens of human body fat from Papua and New Guinea were
lower than the Australian values. The concentration of HCB
in whole blood of 185 people who had some occupational expo-
sure to organochlorine compounds in their working conditions
and of 52 who had no known exposure was determined. None of
the subjects displayed apparent signs of intoxication. Over
95 percent of the subjects had HCB in their blood. The HCB
blood level in the exposed population was 55.5 ug/kg, with
nine percent having more than 100 ug/kg. The HCB blood level
in the population with no known exposure was 22 ug/kg, with
none having as much as 100 ug/kg. Levels of 50 to 100 ug/kg
whole blood indicate either recent exposure over and above
that normally assimilated from the environment or the mobili-
zation of fat depots associated with a loss in total body
weight. The mean HCB level in 81 samples of human body fat
was 1.31 mg/kg, with a maximum of 8.2 mg/kg. All 81 human
fat samples contained HCB (Siyali, 1972).
The HCB levels in adipose tissue of Canadians, col-
lected in 1972 by Burns and Miller (1975), were determined.
The regional distribution of the samples was as follows: 16
from the eastern region (Newfoundland, Prince Edward Island,
Nova Scotia and New Brunswick), 50 from Quebec, 57 from
0105
-------
Ontario, 22 from the central region (Manitoba and Saskatche-
wan) and 27 from the western region (Alberta and British
Columbia). All of the adipose samples contained HCB, with an
overall mean value of 62 ug/kg. HCB values were lowest in
the samples from the eastern (25 ug/kg) and central (15
ug/kg) regions and highest in Quebec (107 ug/kg). The
Ontario samples averaged 60 ug HCB/kg and those from the
western region 43 ug/kg. The HCB content of adipose tissue
from females (82 ug/kg) was greater than that for males (52
ug/kg). The HCB content of human adipose tissue did not show
an age-related trend: 0 to 25 years, 76 ug/kg; 26 to 50
years, 45 ug/kg; and 51+ years, 70 ug/kg (Mes, et al. 1977).
In the study of Richter and Schmid, the'age-related accumula- .
tion of HCB was marked only for the first five years of life
(Richter and Schmid, 1976). Plasma HCB levels in a Louisiana
population exposed through the transport and disposal of
chemical waste containing HCB averaged 3.6 ug/kg in a study
of 86 subjects. The highest level was 345 ug/kg in a sample
from a waste disposal worker, while the highest level in a
sample from a member of the general population was 23 ug/kg
(Burns and Miller, 1975).
PHARMACOKINETICS
Absorption
To date, only absorption of HCB from the gut has been
examined in detail. Fish fed HCB-contaminated food take up
the material in a reasonably direct relationship to the con-
centration in the food (Sanborn, et al. 1977). Intestinal
absorption of HCB from an aqueous suspension was poor in both
-------
rabbits (Parke and Williams, 1960) and rats (Koss and
Koransky, 1975). The amount of HCB left in the intestinal
contents 24 hours after administration was small. Intestinal
absorption of HCB by rats was substantial when the chemical
was given in cotton seed oil (Albro and Thomas, 1974) or
olive oil (Koss and Koransky, 1975). Between 70 percent and
80 percent of doses of HCB ranging from 12 mg/kg to 180 mg/kg
were absorbed. The fact that HCB is well absorbed when dis-
solved in oil is of particular relevance for man. HCB in
food products will selectively partition into the lipid por-
tion, and HCB in lipids will be absorbed far better than that
in an aqueous milieu. This is consistent with the observa-
tion that the highest HCB levels ever observed have been in
tissues of carnivorous animals (Acker and Schulte, 1971;
Koeman, 1972). HCB is readily absorbed from the abdominal
cavity after intraperitoneal injection of the chemical dis-
solved in oil.
Data of toxicological experiments should take into ac-
count how HCB was administered. Relatively little HCB was
absorbed by the walls of the stomach and duodenum of rats one
hour after oral administration of HCB suspended in aqueous
methylcellulose. After three hours, the ingested HCB reached
the jejunum and ileum, resulting in increasing concentrations
in the walls of these parts of the intestine. Liver and kid-
ney contained some HCB; however, the concentrations in lymph
nodes and adipose tissue were much higher. During the re-
maining 45 hours, the concentrations in liver and kidney de-
creased, whereas those in lymph nodes and adipose tissue re-
C-107
-------
mained relatively constant or rose slightly. . Formal venous
transport to the liver seemed to be a minor pathway because,
in spite of its slow metabolism, HCB never achieved high con-
centrations in the liver. The majority of the ingested HCB
was absorbed by the lymphatic system in the region of the
duodenum and jejuno-ileum, and deposited in fat, bypassing
the systemic circulation and excretory organs. There1appears
to be an equilibrium between lymph nodes and fat (latropoulos,
et al. 1975) .
Distribution
It is well known that HCB has a low solubility in water
(6 y.g/kg) (Lu and Metcalf, 1975) and a high solubility in fat
(calculated log partition coefficient in octanol/H2O=6.43).
Accordingly, the highest concentrations of HCB are in fat
tissue (Lu and Metcalf, 1975). The concentration of HCB in
fish fed contaminated food (100 mg/kg) for three days was
4.99 mg/kg in liver and 1.53 mg/kg in muscle (Sanborn, et al.
1977). The concentration of HCB in Japanese quail fed con-
taminated food (5 mg/kg) for 90 days was 6.88 mg HCB/kg in
liver and 0.99 mg/kg in brain of female birds and 8.56 mg/kg
in liver and 1.44 mg/kg in brain of male birds (Vos, et al.
1971). As noted above, HCB accumulated in fatty tissues.
After prolonged feeding of a constant'level of HCB, the con-
centration of compound in the fat of laying hens reached a
plateau. This indicates that an equilibrium between uptake
and excretion can be achieved. This phenomenon allows one to
calculate the ratio of the concentration of HCB in fat to the
concentration in the feed. This accumulation or storage
C-108
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ratio apparently is independent of HCB concentration in the
feed over a wide range. The accumulation ratio for HCB in
laying hens is about 20 (Kan and Tuinstra, 1976).
The distribution of HCB in rat tissues was similar for
animals given a single oral dose or a single intraperitoneal
injection of HCB dissolved in olive oil. Adipose tissue con-
tained about 120-fold, liver, 4-fold; brain, 2.5-fold; and
kidney, 1.5-fold more HCB than muscle. The HCB content of
adrenals, ovaries and the Harderian gland was essentially the
same as skin whereas that for heart, lungs, and intestinal
wall corresponded to the level in liver. The thymus content
was similar to that of brain (Koss and Koransky, 1975).
The distribution of HCB in mice fed a diet containing
167 mg HCB/kg was determined after three and six weeks. The
HCB level in the serum was 23 mg/kg after three weeks and 12
mg/kg after six weeks; for liver, 68.9 mg/kg after three
weeks and 56 mg/kg at six weeks; for spleen, 20.9 mg/kg at
three weeks and 47 mg/kg at six weeks; for lung, 85.1 mg/kg
at three weeks and 269 mg/kg at six weeks; and for the
thymus, 48.6 mg/kg at three weeks and 152 mg/kg at six weeks.
The only histological alterations seen in tissues of mice fed
HCB for six weeks was a centrilobular and pericentral hepatic
parenchymal cell hypertrophy; hepatic Kupffer cells appeared
normal in number and morphology (Loose, et al. 1978).
Adipose tissue serves as a reservoir for HCB, and deple-
tion of fat depots results in mobilization and redistribution
of stored pesticide. For example, food restriction caused
mobilization of HCB stored within the fat depots of rats that
C-109
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had been fed HCB-contaminated food for 14 days. Although HCB
was redistributed into the plasma and other tissues of the
body, food restriction did not increase the excretion of HCB,
therefore the total body burden was not reduced. Rats re-
ceiving 100 mg HCB/kg/day orally for 14 days developed trem-
ors, lost appetite and some died during subsequent food re-
striction. Weight loss from whatever cause results in redis-
tribution of HCB contained in adipose tissue, and if the
initial level of the pesticide is sufficiently high, toxic
manifestations may develop (Villeneuve, 1975).
Metabolism
Although HCB appears to be relatively stable in the
soil, it is metabolized by a variety of animal species.
About half of HCB taken into the body of fish fed contami-
nated food is converted into pentachlorophenol (Sanborn, et
al. 1977). The rabbit does not appear to oxidize HCB to
pentachlorophenol (Kohli, et al. 1976). In rats given HCB
intraperitoneally on two or three occasions (total dose 260
to 390 mg HCB/kg), pentachlorophenol, tetrachlorohydroquinone
and pentachlorothiophenol were the major metabolites in
urine. More than 90 percent of the radiolabeled HCB material
in the urine had been metabolized whereas only 30 percent of
the starting radiolabeled HCB material in the feces was
metabolized. Of the HCB administered intraperitoneally, 65
percent was in the animal body (almost all as HCB), 6.5 per-
cent was excreted in the urine (mostly as metabolites) and
27.2 percent was excreted in the feces (about 70 percent as
HCB). The metabolites in feces were (in decreasing order)
C-110
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pentachlorophenol >
substance (Kpss, et al. 1976).
In organs of rats given 8 mg/HCB/kg dissolved in sun-
flower oil by gavage, only HCB, pentachlorobenzene and penta-
chlorophenol could be identified. The metabolites were pres-
ent in small concentrations. The HCB level in fat was 83
mg/kg, in muscle-17 mg/kg; in liver-125 ug total; in kidneys-
21 ug each; in spleen-9 ug total; in heart-1.5 ug total and
in adrenals-0.5 ug each. In urine, the main metabolites of
orally administered HCB were pentachlorophenol, tetrachloro-
phenol, trichlorophenol and pentachlorobenzene. Small
amounts of trichlorophenol and tetrachlorophenol were present
as glucuronide conjugates. The feces contained a little
pentachlorobenzene, but mostly the parent HCB (Engst, et al.
1976) .
HCB in corn oil given orally to rats at a dose of 20
mg/kg for 14 days caused an elevation of the levels of cyto-
chrome P-450 and NADPH-cytochrome c reductase activity. HCB
appears to be an inducer of the hepatic microsomal system
of the phenobarbital type (Carlson, 1978). In a separate
study, the cytochrome P-450 level was elevated in rats
(Porton strain) fed HCB mixed into the diet (dose about 19
mg/kg) for 14 days, but not in rats (Agus strain) fed HCB-
containing food for 90 days. In both HCB-exposed groups,
benzo(a)pyrene hydroxylation activity was elevated, but
aminopyrine N-demethylation activity was not significantly
enhanced. It has been proposed that HCB is an inducer of
hepatic microsomal enzyme activity having properties of both
C-lll
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the phenobarbital type and the 3-methylcholanthrene type
(Stonard, 1975; Stonard and Greig, 1976). Although HCB is a
well-documented inducer of hepatic microsomal enzyme activ-
ity, the hexobarbital sleeping times of rats fed 2000 mg
HCB/kg/day for 14 days were the same as unexposed control
rats. The duration of hexobarbital-induced sleep decreased
14 days after eliminating HCB from the diet. In rats fed 500
mg HCB/kg/day for 14 days, hepatic glucose-6-phosphatase
"1
activity was decreased and serum isocitrate dehydrogenase
activity remained undetectable. In rats fed 10 mg HCB/kg/day
for 14 days, the liver was enlarged; the cytochrome P-450
level, detoxification of EPN (O-ethyl O-p-nitrophenyl phenyl-
phosphonothioate) , benzpyrene hydroxylase activity and azore-
ductase activity were increased whereas cytochrome c reduc-
tase and glucuronyl transferase activities were unaltered.
Excretion
As described in earlier sections, HCB is excreted mainly
in the feces and to some extent in the urine in the form of
several metabolites that are more polar than the parent HCB.
Usually a plateau is reached in most tissues when the dose is
held relatively constant. If the exposure increases, how-
ever, the body concentrations will increase, and vice versa.
Fish fed HCB contaminated food (100 mg/kg) for three
days have relatively high levels of HCB and pentachlorophenol
in their stomach (27.16 mg/kg and 19.14 mg/kg, respectively)
and intestine (26.82 mg/kg and'15.94 mg/kg, respectively) on
the fourth day. The half-life of HCB in the stomach, intes-
tine and muscle was 8 to 8.5 days, that for the carcass 10
C-112
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days and that for the liver 19.6 days. During the initial
elimination period, the clearance of HCB in the intestine and
muscle lagged behind that for the stomach and liver, and may
indicate biliary excretion with enterohepatic recirculation
(Sanborn, et al. 1977). Biliary excretion and enterohepatic
recirculation of HCB have been described in dogs (Sundlof, et
al. 1976).
HCB accumulates in the eggs of laying hens fed contami-
nated food. The accumulation ratio (level of HCB in whole
egg/level in the feed) was 1.3. The actual HCB concentration
in eggs was 20 ug/kg for hens fed 10 ug HCB/kg of feed and
140 ug/kg for hens fed 100 ug HCB/kg. Although the concen-
tration of HCB in eggs is usually viewed from the perspective
of accumulation in a human food, it can also be viewed as an
excretion process. Whereas 10 percent of the daily HCB in-
take is excreted in the feces, 35 percent is excreted in the
eggs of laying hens (Kan and Tuinstra, 1976). The rate of
elimination of HCB from swine was greatest 48 to 72 hours
after a single intravenous injection of drug. The rate of
release of HCB from fat was the rate limiting factor for
excretion at later times. Half of the starting HCB material
in the feces was unmetabolized HCB. All of the HCB material
excreted in the urine was metabolites of HCB. Excretion of
HCB from swine was five to tenfold slower than excretion from
dogs (Wilson and Hansen, 1976).
Clearance of HCB from brain of rats given a single in-
jection intraperitoneally occurs in two steps: a slow phase
days 1 to 14 and a very slow phase thereafter. The half-life
C-113
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for the slow phase was ten days and that for the very slow
phase was 57 days. Similarly, the half-life of HCB in testes
was 15 days for the initial slow clearance and 62 days for
the later very slow phase. The initial clearance rates
(half-lives) for the heart, lung and kidney were 15, 13 and
16 days respectively. In contrast to the pattern for in-
dividual organs, the clearance of HCB from the whole body
proceeded as a single step process, with a half-life of 60
days. The initial clearance of HCB from individual organs
therefore reflects a redistribution of the chemical among the
tissues of the body (Morita and Oishi, 1975). Clearance of
HCB from organs of rats given a single dose of HCB dissolved
in olive oil by gavage occurred in two stages also: a very
slow phase between day two and day five or day eight, and a
slow phase thereafter. The overall half-life of HCB for fat,
skin, liver, brain, kidney, blood and muscle was eight to ten
days. The administered chemical was retained in the tissue
as unaltered HCB. During a two week period, five percent of
the administered HCB was excreted in the urine; essentially
all as metabolites of HCB, and 34 percent was excreted in the
feces, mostly as unaltered HCB. The fecal excretion of a
fairly high amount of unmetabolized HCB is presumed to be due
to biliary secretion. Unchanged HCB has been detected in
bile of rats after intraperitoneal administration of the
chemical (Koss and Koransky, 1975).
No radioactivity was detected in the expired air of rats
administered radiolabeled HCB (Koss and Koransky, 1975).
-------
EFFECTS
Acute, Sub-acute/ and Chronic Toxicity
Japanese quail are among the most sensitive species to HCB.
Japanese quail fed a diet containing 5 mg HCB/kg for 90 days de-
veloped enlarged livers, had slight liver damage and excreted
increased amounts of coproporphyrin in the feces. Increased ex-
cretion of coproporphyrin was noticeable after ten days (Vos, et
al. 1971).
The acute toxicity of HCB for vertebrates is low: 500 mg/
kg intrapertioneally is not lethal in rats; the oral lethal dose
in guinea pigs is greater than 3 g/kg; and the oral lethal dose
in Japanese quail is greater than 1 g/kg (Vos, et al. 1971). In
acute studies, HCB was more toxic for guinea pigs than rats, but
accumulated to a lesser degree in the guinea pig. Male rats ap-
peared to be more susceptible to HCB than females (Villeneuve
and Newsome, 1975). HCB is able to induce rat microsomal liver
enzymes; HCB was more effective in stimulating aniline hydroxy-
lase than aminopyrine demethylase or hexobarbital oxidase. HCB
is not a particularly effective inducer of these microsomal en-
zymes (den Tonkelaar and van Esch, 1974). Although HCB has a
low acute toxicity for most species (>1000 mg/kg), it has a wide
range of biological effects at prolonged moderate exposure.
Subacute toxic effects of HCB were examined in rats after
feeding with HCB for 15 weeks. Histopathological changes were
confined to the liver and spleen. In the liver, there was an
increase in the severity of centrilobular liver lesions with as
little as 2 mg HCB/kg/day in the food. In contrast to the re-
sults of others, females were more susceptible to HCB than male
C-115
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rats. It would appear that 0.5 mg HCB/kg/body weight per
day, where diet was adjusted weekly 3.4 to 11.6 mg HCB/kg, is
the no-effect level in the rat (Kuiper-Goodman, et al. 1977).
Unlike in the rat, it was not possible to induce porphyria in
dogs with HCB (Gralla, et al. 1977). Swine are more suscept-
ible to HCB in subacute studies than rats. Liver microsomal
enzymes were induced in swine and excretion of coproporphyrin
was increased by 0.5 mg HCB/kg/day after 13 and 8 weeks, re-
spectively. It would appear that 0.05 mg HCB/kg/day in the
diet is the "no-effect" level for swine (den Tonkelaar, et
al. 1978).
In rats given 50 mg HCB/kg every other day for 53 weeks,
an equilibrium between intake and elimination was achieved
after nine weeks. In general, the most changes observed in
the long term studies resembled those described for short
term studies. When the administration of HCB was discon-
tinued, elimination of the xenobiotic continued slowly for
many months (Koss, et al. 1978).
HCB caused a serious outbreak of hepatic porphyria in
Turkey involving cutanea tarda lesions and porphyrinuria (Cam
and Nigogosyan, 1963). This has been confirmed in a number
of laboratory animals including rats (San Martin de Viale, et
al. 1976), rabbits (Ivanov, et al. 1976), Japanese quail
(Vos, et al. 1971), guinea pigs (Strik, 1973), swine (den
Tonkelaar, et al. 1978), mice (Strik, 1973) and Rhesus mon-
keys (latropoulos, et al. 1976). Rats given 50 mg HCB/kg or-
ally for 30 days showed enlarged livers, elevated liver por-
phyrin and elevated urine porphyrin (Carlson, 1977). In both
-------
rabbits and rats, HCB produced an increase in the excretion
of uroporphyrin and coproporphyrin. The mechanism of action
of HCB is not known, but it elicits an increase in ^~- ami-
nolevulinic acid synthetase, which is the rate limiting en-
zyme in the biosynthesis of porphyrins (Timme, et al. 1974).
The development of HCB-induced porphyria is accompanied by a
progressive fall in hepatic uroporphyrinogen decarboxylase
activity. This change may be causally related to the disease
(Elder, et al. 1976). The mitochondrial membrane may also be
a factor in limiting the rate of porphyrin biosynthesis since
some critical enzymes are intramitochondrial and others are
cytoplasmic. It has been proposed that HCB may damage the
mitochondrial membrane thereby facilitating the flow of por-
phyrin intermediates through-it (Simon, et al. 1976). Con-
sistent with this proposal is the observation that HCB causes
marked enlargement of rat hepatocytes, proliferation of
smooth endoplasmic reticulum, formation of eosinophilic
bodies, generation of large lipid vesicles, and mitochondrial
swelling (Mollenhauer, et al. 1975).
It should be noted that the principal metabolite of HCB,
pentachlorophenol, is not porphyrinogenic in the rat, so the
formation of this metabolite is unlikely to play a role in
HCB-induced porphyria (Lui, et al. 1976). Nevertheless, it
is conceivable that metabolites of HCB, particularly as a re-
sult of microsomal enzyme induction, might be the actual por-
phyrogenic agent (Lissner, et al. 1975).
C-117
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An epidemic of HCB-induced cutanea tarda porphyria oc-
curred in Turkey during the period 1955 to 1959 (Cam and
Nigogosyan, 1963). More than 600 patients were observed dur-
ing a five year period, and it was estimated that a total of
3000 people were affected. The outbreak was traced to the
consumption of wheat as food after it had been prepared for
planting by treating it with hexachlorobenzene. The syndrome
involves blistering and epidermolysis of the exposed parts of
the body/ particularly the face and hands. It was estimated
that the subjects ingested 50 to 200 mg HCB/day for a rela-
tively long period before the skin manifestations became ap-
parent. The symptoms were seen mostly during the summer
months, having been exacerbated by intense sunlight. The
disease subsided and symptoms disappeared 20 to 30 days after
discontinuation of intake of HCB-contaminated bread. Re-
lapses were often seen, either because the subjects were eat-
ing HCB-containing wheat again, or because of redistribution
of HCB stored in body fat.
A disorder called pembe yara was described in infants of
Turkish mothers who either had HCB-induced porphyria or had
eaten HCB-contaminated bread (Cam, 1960). The maternal milk
contained HCB. At least 95 percent of these infants died
within a year and in many villages, there were no children
left between the ages of two and five during the period 1955-
60. With human tissue levels of HCB increasing measurably
throughout the world, the effect of low chronic doses of this
pesticide must be considered. HCB is stored in the body fat
and transmitted through maternal milk. It is not known
C-118
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whether HCB is responsible for genetic damage to the progeny
(Peters, 1976).
There was no evidence of cutaneous porphyria in 86
Louisiana residents having an average plasma HCB level of 3.6
ug/kg, with a maximum level of 345 u.g HCB/kg. There was a
possible correlation between plasma HCB levels and urinary
coproporphyrin excretion or plasma lactate dehydrogenase
activity, but none with urinary uroporphyrin excretion (Burns
and Miller, 1975). It should be noted that the people in
Turkey showing symptoms of porphyria had ingested 1 to 4 mg
HCB/kg/day for a relatively long period (Cam and Nigogosyan,
1963). It is speculated that some of the Louisiana workers
had taken in several mg HCB/kg/day, at least sporadically.
Synergism and/or Antagonism
HCB, at doses far below those causing mortality, en-
hances the capability of animals to metabolize foreign or-
ganic compounds (see section on Metabolism). This type of
interaction may be of importance in determining the effects
of other concurrently encountered xenobiotics on the animal
(Carlson and Tardiff, 1976). An increase in paraoxon dealky-
lation activity was a more sensitive indicator of induction
of microsomal enzyme activity in a liver fraction from rats
fed a diet containing 2 mg HCB/kg for two weeks than cyto-
chrome P-450 content or N-demethylase activity (Iverson,
1976) .
HCB elicits significant and rather selective changes in
Lindane metabolism in rats (Chadwick, et al. 1977). Rats ad-
ministered 7.5 mg HCB/kg/day orally for seven days had in-
creased capability to metabolize arid eliminate 1,2,3,4,5,6
C-119
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hexachlorocyclohexane (Lindane). As noted before, HCB caused
liver enlargement and enhanced EPN metabolism. Rats fed HCB
also had significantly increased ability to metabolize
p-nitroanisole, but not methyl orange. HCB-treated rats ex-
creted 35 percent of the administered Lindane in their feces
and 13.7 percent in their urine within 24 hr/ in contrast to
12.7 percent in feces and 5.0 percent in urine of unexposed
rats. The amount of Lindane in fat and liver 24 hr after
administering 12.5 mg of Lindane/kg orally was less in HCB-
treated rats than in unexposed controls (117 versus 60.7
mg/kg in fat and 9.57 versus 5.24 mg/kg in liver). The Lin-
dane content of the kidney was not significantly reduced
(6.91 versus 5.94 mg/kg for HCB-treated versus unexposed
rats). Rats pretreated with HCB excreted a significantly
higher proportion of free chlorophenols, with a corresponding
decrease in polar metabolites as compared to unexposed rats.
Prior exposure to HCB may alter the response of an ani-
mal to any of a variety of challenges. Mice fed a diet con-
taining 167 mg HCB/kg have altered susceptibility to Salmon-
ella typhosa 0901 lipopolysaccharide (endotoxin). The LDso
for exposed mice was about 40 mg endotoxin/kg, for mice fed
HCB for three weeks 7.4 mg/kg, and for mice fed HCB for six
weeks, 1.4 mg/kg. Mice fed HCB were also somewhat more sus-
ceptible to the malaria parasite Plasmodium than unexposed
mice (Loose, et al. 1978).
Teratogenicity
The effect of HCB on reproduction has received limited
atte'ntion. Dietary HCB adversely affected reproduction in
C-120
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the rat by decreasing the number of litters whelped and the
number of pups surviving to weaning (Grant, et al. 1977).
The fertility (numbers of litters whelped/number of females
exposed to mating) of rats fed a diet containing 320 mg
HCB/kg was decreased. This concentration of HCB in the food
led to accumulative toxicity (convulsions and death) in some
of the animals. The proportion of pups surviving five days
was reduced when the parents had been fed a diet containing
160 mg HCB/kg and when the rats had been fed a diet of 80 mg
HCB/kg for three generations. The birth weight of rats was
reduced in rats fed a diet containing 320 mg HCB/kg and in
rats fed a diet containing 160 mg HCB/kg for two generations.
The weight of five-day old pups was markedly less when the
parents had been fed a diet containing 80 mg HCB/kg. The
tissue of 21-day-old pups whose dam had been fed graded
dietary levels of HCB contained progressively more drug; for
example, the level of HCB in body fat was about 250 mg/kg
when the dietary level was 10 mg/kg; 500 mg/kg in fat for 20
mg/kg in diet; 800 mg/kg in fat for 40 mg/kg in diet; 1900
mg/kg in fat for 80 mg/kg in diet; and 2700 mg/kg in fat for
160 mg/kg in diet. The highest HCB levels were in the body
fat; for pups whose dam had been fed a diet containing 10 mg
HCB/kg, the body fat contained 250 mg HCB/kg, liver-9 mg/kg;
kidney and brain-4 mg/kg and plasma-1.3 mg/kg. HCB crossed
the placenta of rats and accumulated in the fetus in a dose-
related manner. HCB 'fed to pregnant mice and rats was de-
posited in the tissues in a dose-related manner. The HCB
content of placentas was greater than that of the correspond
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respect to the incidence of pregnancies, corpora lutea, live
implants or deciduoraas (Khera, 1974).
HCB injected intraperitoneally into rats at 10 mg/kg
elicited a marked induction of the hepatic cytochrome P-450
system. This liver microsomal fraction mediated the meta-
bolic activation of 2,4-diaminoanisole to a mutagen (as mea-
sured by the Ames test) (Dybing and Aune, 1977). The muta-
genic activities of several aromatic and polycyclic hydro-
carbons are not associated with the parent compound but with
metabolically activated products that react covalently with
nucleic acid. As noted previously, HCB stimulates the
hepatic cytochrome P-450 system and thereby has the potential
to enhance the mutagenicity of other chemicals.
Carcinogenicity
Two studies have been conducted which indicate that HCB
is a carcinogen. The carcinogenic activity of HCB in ham-
sters fed 4, 8, or 16 mg/kg/day for life was assessed
(Cabral, et al. 1977). HCB appears to have multipotential
carcinogenic activity; the incidence of hepatomas, haemangio-
endotheliomas and thyroid adenomas was significantly in-
creased. Whereas 10 percent of the unexposed hamsters de-
veloped tumors, 92 percent of the hamsters fed 16 mg HCB/kg/
day developed tumors. The incidence of tumor-bearing animals
was dose-related: 56 percent for hamsters fed 4 mg HCB/kg/day
and 75 percent for 8 mg/kg/day. No thyroid tumors, hepatomas
or liver haemangioendotheliomas were detected in the unex-
posed group. An intake of 4 to 16 mg HCB/kg/day in hamsters
is near the exposure range estimated for Turkish people who
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accidentally consumed KGB-contaminated grain (Cabral, et al.
1977).
The carcinogenic activity of HCB in mice fed 6.5, 13 or
26 mg/kg/day for life was assessed. The incidence of hepato-
mas was increased significantly in mice fed 13 or 26 mg
HCB/kg/ day. None of the hepatomas metastasized or occurred
in the untreated control groups. The results presented in
the abstract of Cabral, et al. (1978) confirm their earlier
conclusion that HCB is carcinogenic. However, the incidence
of lung tumors in strain A mice treated three times a week
for a total of 24 injections of 40 mg/kg each was not signif-
icantly greater than the incidence in control mice (Theiss,
et al. 1977). Moreover, HCB did not induce hepatocellular
carcinomas in ICR mice fed HCB at 1.5 or 7 mg/kg/day for 24
weeks (Shirai, et al. 1978).
-------
CRITERION FORMULATION
Existing Guidelines and Standards
As far as can be determined, the Occupational Safety and
Health Administration has not set a standard for occupational
exposure of HCB. HCB has been approved for use as a preemer-
gence fungicide applied to seed grain. The Federal Republic
of Germany no longer allows the application of HCB-containing
pesticides (Geike and Parasher, 1976a). The government of
Turkey discontinued the use of HCB-treated seed wheat in 1959
after its link to acquired toxic porphyria cutanea tarda was
reported (Cam, 1959). Commercial production of HCB in the
United Staes was discontinued in 1976 (Chem. Econ. Hdbk.,
1977). The Louisiana State Department of Agriculture has set
the tolerated level of HCB in-meat fat at 0.3 mg/kg (U.S.
EPA, 1976). The NHMRC (Australia) has used this same value
for the tolerated level of HCB in cows' milk (Miller and Fox,
1973). WHO has set the tolerated level of HCB in cows' milk
at 20 ug/kg in whole milk (Bakken and Seip, 1976). The New
South Wales Department of Health (Australia) has recommended
that the concentration of HCB in eggs must not exceed 0.1
mg/kg (Siyali, 1973). The value of 0.6 ug HCB/kg/day was
suggesce'd by FAO/WHO in -1-974 as a reasonable upper limit for
HCB residues in food for human consumption (FAO/WHO, 1974).
The FAO/WHO recommendations for residues in foodstuffs were
0.5 mg/kg in fat for milk and eggs, and 1 mg/kg in fat for
meat and poultry. Russia and Yugoslavia have set the maximum
tolerated'level of HCB in air at 0.9 mg/m3 (Int. Labor Off.
1977).
C-125
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Current Levels of Exposure
HCB appears to be distributed worldwide, with high
levels of contamination found in agricultural areas devoted
to wheat and related cereal grains and in industrial areas.
HCB is manufactured and formulated for application to seed
wheat to prevent bunt; however, most of the HCB in the en-
vironment comes from industrial processes. = HCB is used as a
starting material for the production of pentachlorophenol
which is marketed as a wood preservative. HCB is one of the
main substances in the tarry residue which results from the
production of chlorinated hydrocarbons. HCB is formed as a
by-product in the production of chlorine gas by the electrol-
ysis of sodium chloride using a mercury electrode (Gilbertson
and Reynolds, 1972).
People in the United States are exposed to HCB in air,
water.and food. HCB is disseminated in the air as dust par-
ticles and as a result of volatilization from sites having a
high HCB-concentration. Airborne HCB-laden dust particles
appear to have been a major factor in producing the blood
levels in the general public living near an industrial site
in Louisiana (Burns and Miller, 1975). HCB is found in river
water near industrial sites in quantities of as much as 2
ug/kg (Laska, et al. 1976) and even in finished drinking
water at 5 ng/kg (U.S. EPA, 1975). HCB occurs in a wide
variety of foods, in particular, terrestrial animal products,
including dairy products and eggs (U.S. EPA, 1976). The
dietary intake of HCB has been estimated to be 0.5 ug/day in
Japan (Ushio and Doguchi, 1977) and 35 ug/day in Australia
C-126
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(Miller and Fox, 1973). Breast-fed in^^ ,.^_^_u and
Norway may consume 40 ug HCB/day (Miller and Fox, 1973; Bakken
and Seip, 1076). HCB is found in human tissues collected
throughout the world.
The HCB content of human adipose tissue taken at autopsy
is as follows:
Mean Values
-(mg/kg in
Reference
Brady and Siyali, 1972
Siyali, 1972
Brady and Siyali, 1972
Curley, et al. 1973
Mes and Campbell, 1976
Mes, et al. 1977
Mes, et al. 1977
Mes, et al. 1977
Mes, et al. 1977
Mes, et al. 1977
Acker and Schulte, 1974
Acker and Schulte, 1974
Aoker and Schulte, 1974
Acker and Schulte, 1974
Acker and Schulte, 1974
Acker and Schulte, 1974
The maximum HCB level reported was 22 mg/kg (Acker and Schulte,
1974) .
Source
Australia
Papua and
New Guinea
Japan
Canada
»
»
-
"
"
Germany
"
"
»
"
n
No. samples
75
81
38
241
3
16
50
57
22
27
56
54
04 - . -
59
59
93
Human Fat)
1.25
1.31
0.26
0.08
0.09
0.025
0.107
0.060
0.015
0.043
2.9
8.2
- Q
4.8
6.4
4.8
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The HCB content of human blood samples is as follows:
Mean Values
(mg/kg
Source No. Samples in Blood) Reference
Bavaria 98 boys 0.022 Richter and Schmid, 1976
" 96 girls 0.017 Richter and Schmid, 1976
Australia 185 exposed 0.055 Siyali, 1972
" 52 unexposed 0.022 Siyali, 1972
" 76 0.058 Siyali and Ouw, 1973
Louisiana 86 0.0036 Burns and Miller, 1975
The maximum HCB level reported was 0.345 mg/kg, that in a
Louisiana waste disposal worker (Burns and Miller, 1975).
The levels of HCB in body fat of swine and sheep were
sixfold and eightfold greater, respectively than the dietary
level (Hansen, et al. 1977). If these comparisons are valid
when applied to man, it would appear that some adult humans
have been exposed to several mg HCB/kg/day. A similar con-
clusion is reached by extrapolating the values for human
blood. The HCB levels in blood of rats are about tenfold
less than the dietary level (Kuiper-Goodman, et al. 1977).
Current evidence would indicate that food intake may be
the primary source of the body burden of HCB for the general
population although inhalation and dermal exposure may be
more important in selected groups (e.g., industrial wor-
kers) .
Special Groups at Risk
Several groups appear to be at risk. These include wor-
kers engaged directly in: (1) the manufacture of HCB or in
processes in which HCB is a by-product, (2) the formulation
of HCB-containing products, (3) the disposal of HCB-containing
-------
wastes; and (4) the application of HCB-containing products.
Other groups at risk are the general public living near in-
dustrial sites, populations consuming large amounts of con-
taminated fish/ pregnant women, fetuses and breast-fed in-
fants. Two lines of evidence indicate that infants may be at
risk. It has been demonstrated that human milk contains HCB,
and some infants may be exposed to relatively high concentra-
tions of HCB from that source alone (Miller and Fox, 1973;
Bakken and Seip, 1976). Moreover, some infants of Turkish
mothers who consumed HCB-contaminated bread developed a fatal
disorder called pembe yara. In some Turkish villages in the
region most affected by HCB-poisoning, few infants survived
during the period 1955-1960 (Cam, 1960).
Occupational exposure is associated with an increased
body burden of HCB. Plant workers in Louisiana have about
200 ug HCB/kg in blood (Burns and Miller, 1975). The HCB
content of body fat exceeded 1 mg/kg in many parts of the
world where HCB contamination of the environment is extensive
(Brady and Siyali, 1972; Acker and Schulte, 1974).
The massive episode of human poisoning resulting from
the consumption of bread prepared from HCB-treated seed wheat
brought to light the misuse of HCB-treated grain (Cam and
Nigogosyan, 1963). In spite of warnings, regulations and
attempts at public education, HCB-treated grain apparently
still finds its way into the food chain, for example, in fish
food (Hansen, et al. 1976; Laska, et al. 1976). The diffi-
culty in tracing the source of HCB contamination in a diet
for laboratory animals emphasizes the difficulties encoun-
C-129
-------
tered in tracing the source of HCB in foodstuffs for man
(Yang, et al. 1976).
As noted previously, adipose tissue acts as a reservoir
for HCB. Deletion of fat depots can result in mobilization
and redistribution of stored HCB. Weight loss for any reason
may result in a dramatic redistribution of HCB contained in
adipose tissue; if the stored levels of HCB are high, adverse
effects might ensue. Many humans restrict their dietary in-
take voluntarily or because of illness. In these instances,
the redistribution of the HCB body burden becomes a potential
added health hazard (Villeneuve, 1975).
Basis and Derivation of Criterion
Among the studies reviewed by this document, only two
appear suitable for use in the risk assessment: the mouse
study of Cabral, et al. (1978) and the hamster study of
Cabral, et al. 1977. These two studies are described in
detail in Appendix I.
Under the Consent Decree in NRDC v. Train, criteria are
to state "recommended maximum permissible concentrations
(including where appropriate, zero) consistent with the pro-
tection of aquatic organisms, human health, and recreational
activities". HCB is suspected of being a human carcinogen.
Because there is no recognized safe concentration for a human
carcinogen, the recommended concentration of HCB in water for
maximum protection of human health is zero.
Because attaining a zero concentration level may be un-
feasible in some cases, and in order to assist the Agency and
States in the possible future development of water quality
C-130
-------
regulations/ the concentrations of HCB corresponding to
several incremental lifetime cancer risk levels have been
estimated. A cancer risk level provides an estimate of the
additional incidence of cancer that may be expected in an
exposed population. A risk of 10"^ for example, indicates a
probability of one additional case of cancer for every
100,000 people exposed, a risk of 10~6 indicates one addi-
tional case of cancer 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 consid-
ering setting criteria at an interim target risk level of
10~~5, 10~6, or 10"? as shown in the table below:
Exposure Assumption Risk Levels and Corresponding Criteria (1)
(per day)
2 10~7 IP"6 10~5
2 liters of drinking water 0 0.0125 ng/1 0.125 ng/1 1.25 ng/1
and consumption of 18.7 grams
fish and shellfish. (2)
Consumption of fish and 0 0.0126 ng/1 0.126 ng/1 1.26 ng/1
shellfish only.
(1) Calculated by applying a modified "one-hit" extrapola-
tion model described in the Federal Register, FR 15926,
1979. Appropriate bioassay data used in the calculation
of the model is presented in Appendix I. Since the ex-
trapolation model is linear at low doses, the additional
lifetime risk is directly proportional to the water
C-131
-------
concentration. Therefore,, water concentrations corres-
ponding to other risk levels can be derived by multiply-
ing 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) Ninety-nine percent of the HCB exposure results from the
consumption of aquatic organisms which exhibit an aver-
age bioconcentration potential of 12,000-fold. The re-
maining one percent of HCB exposure results from drink-
ing water.
Concentration levels were derived assuming a lifetime
exposure to various amounts of HCB, (1) occurring from the .
consumption of both drinking water and aquatic life grown in
waters containing the corresponding HCB concentrations and,
(2) occurring solely from consumption of-aquatic life grown
in the waters containing the corresponding HCB concentra-
tions. Because data indicating other sources of HCB exposure
and their contributions to total body burden are inadequate
for quantitative use, the figures reflect the incremental
risks associated with the indicated routes only.
-------
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SUMMARY-CRITERION FORMULATION
Existing Guidelines and Standards
Monochlorobenzene
The Threshold Limit Value (TLV) for MCB as adopted by
the American Conference of Governmental Industrial Hygienist.c
(1971) is 75 ppm (350 mg/m-^J. The American Industrial Hygiene
Association Guide (1964) considered 75 ppm to be too 'high.
The recommended maximal allowable concentrations in air in
other countries are: Soviet Union, 10 ppm; Czechoslovakia,
43 ppm; Romania, 0.05 mg/1. The latter value for Romania was
reported by Gabor and Raucher (1960) and is equivalent to 10
ppm.
Trichlorobenzene
A proposed ACGIH Threshold Limit Value (TLV) standard
for TCB's is 5 ppm (mg/1) as a cealing value (Am. Conf. Gov.
Ind. Hyg. 1977). Sax, et al. (1951) recommends a maximum
allowable concentration of 50 ppm in air for commercial TCB,
a mixture of isomers. Coate, et al. (1977), citing their
studies, recommends that the TLV should be set below 25 ppm,
preferably 5 ppm (mg/1). Gurfein and Parlova (1962) indicate
that in the Soviet Union the maximum allowable concentration
for TCB in water is 30 ug/1 which is an organoleptic limit.
They also report that in a study of 40 rats and 8 rabbits
administered TCB in drinking water at a concentration of 60
ug/1 for a period of seven to eight months, no effects were
observed. This information was obtained from an abstract and
evaluation of the study could not be done.
148
-------
suggested by FAO/WHO in 1974 as a reasonable upper limit for
HCB residues in food for human consumption (FAO/WHO), 1974).
The FAO/WHO recommendations for residues in foodstuffs were
o.5 mg/kg in fat for milk and eggs, and 1 mg/kg in fat for
meat and poultry. Russia and Yugoslavia have set the maximum
tolerated level of HCB in air at 0.9 mg/m3 (Int. Labor Off.
1977).
Current Levels of Exposure
Monochlorobenzene
MCB has been detected in water monitoring surveys of
various U.S. cities (U.S. EPA, 1975; 1977) as was presented
in Table 1. Levels reported were: ground water 1.0 ug/1;
raw water contaminated by various discharges - 0.1 to 5.6
ug/1; upland water - 4.7 ug/1; industrial discharge - 8.0 to
17.0 ug/1 and municipal water - 27 ug/1- These data show a
gross estimate of possible human exposure to MCB through the
water route.
Evidence of possible exposure from food ingestion is in-
direct. MCB is stable in water and thus could be bioaccumu-
lated by edible fish species.
The only data concerning exposure to MCB via air are
from the industrial working environment. Reported industrial
exposures to MCB are 0:. 02 mg/1 (average value) and 0.3 mg/1
(highest value) (Gabor and Raucher, 1960); 0.001 to 0.01 mg/1
(Levina, et al. 1966); and 0.004 to 0.01 mg/1 (Stepangen,
1966).
C-150
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Tetrachlorobenzene
The maximal permissible concentration of TeCB in water
established by the Soviet Union is 0.02 mg/1 (U.S. EPA,
1977).
Pentachlorobenzene
No guidelines or standards for pentachlorobenzene were
found.
Hexachlorobenzene
As far as can be determined, the Occupational Safety and
Health Administration has not set a standard for occupational
exposure of HCB. HCB has been approved for use as a preemer-
gence fungicide applied to seed grain. The Federal Republic
of Germany no longer allows the application of HCB-containing
pesticides (Geike and Parasher, 1976a). The government of
Turkey discontinued the use of HCB-treated seed wheat in 1959
after its link to acquired toxic porphyria cutanea tarda was
/reported (Cam, 1959). Commercial production of HCB in the
United States was discontinued in 1976 (Chem. Econ. Hdbk.,
1977). The Louisiana State Department of Agriculture has set
the tolerated level of HCB in meat fat at 0.3 mg/kg (U.S.
EPA, 1976). The NHMRC (Australia) has used this same value
for the tolerated level of HCB in cows' milk (Miller and Fox,
1973). WHO has set the tolerated level of HCB in cows' milk
at 20 ug/kg in whole milk (Bakken and Seip, 1976). The New
South Wales Department of Health (Australia) has recommended
that the concentration of HCB in eggs must not exceed 0.1
mg/kg (Siyali, 1973). The value of 0.6 ug HCB/kg/day was
-------
Trichlorobenzene
Possible human exposure to TCB's might occur from munici-
pal and industrial wastewater and from surface runoff (U.S.
EPA, 1977). Municipal and industrial discharges contained
from 0.1 ug/1 to 500 ug/1. Surface runoff has been found
to contain .006 to .007 ug/1.
In the National Organic Reconaissance Survey conducted
by EPA (1975) trichlorobenzene was found in drinking water
at a level of 1.0 ug/1.
Tetrachlorobenzene
No data are available on current levels of exposure.
However, the report by Morita, et al. (1975) gives some in-
dication of exposure. Morita, et al. (1975) examined adipose
tissue samples obtained at general hospitals and medical
examiners' offices in central Tokyo. Samples from 15
individuals were examined; this represented five males and
ten females between the ages of 13 and 78. The tissues were
examined for 1,2,4,5-TeCB as well as for 1,4-dichlorobenzene
and hexachlorobenzene. The TeCB content of the fat ranged
from 0.006 to 0.039 mg/kg of tissue; the mean was 0.019
mg/kg. The mean concentrations of 1,4-dichlorobenzene and
hexachlorobenzene were 1.7 mg/kg and 0.21 mg/kg respectively.
Interestingly, neither age nor sex correlated with the level
of any of the chlorinated hydrocarbons in adipose tissue.
-1.51
-------
Pentachlorobenzene
Morita, et al. (1975) examined levels of QCB in adipose
tissue samples obtained from general hospitals and medical
examiners' offices in central Tokyo. The samples were from a
total of 15 people. The group found by gas chromatography a
residual level of QCB to be in the range of 0.004 ug/g to
0.020 ug/g/ with a mean value of 0.09 ug/g of fat. Lunde and
Bjorseth (1977) looked at blood samples from workers with
occupational exposure to pentachlorobenzene and found that
their blood samples contained higher levels of this compound
than a comparable group of workers not exposed to chloro-
benzene.
Hexachlorobenzene
HCB appears to be distributed worldwide, with high
levels of contamination found in agricultural areas devoted
to wheat and related cereal grains and in industrial areas.
HCB is manufactured and formulated for application to seed
wheat to prevent bunt; however, most of the HCB in the
environment comes from industrial processes. HCB is used as
a starting material for the production of pentachlorophenol
which is marketed as a wood preservative. HCB is one of the
main substances in the tarry residue which results from the
production of chlorinated hydrocarbons. HCB is formed as a
by-product in the production of chlorine gas by the electrol-
ysis of sodium chloride using a mercury electrode (Gilbertson
and Reynolds, 1972).
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People in the United States are exposed to HCB in air,
water and food. HCB is disseminated in the air as dust par-
ticles and as a result of volatilization from sites having a
high HCB-concentration. Airborne HCB-laden dust particles
appear to have been a major factor in producing the blood
levels in the general public living near an industrial site
~fh Louisiana (Burns and Miller, 1975). HCB is found in river
water near industrial sites in quantities of as much as 2
ug/kg (Laska, et al. 1976) and even in finished drinking
water at 5 ng/kg (U.S. EPA, 1975). HCB occurs in a wide
variety of foods, in particular, terrestrial animal products,
including dairy products and eggs (U.S. EPA, 1976). The
dietary intake of HCB has been estimated to be 0.5 ug/day in
J*apan (Ushio and Doguchi, 1977) and 35 u.g/day in Australia
(Miller and Fox, 1973). Breast-fed infants in Australia and
Norway may consume 40 yg HCB/day (Miller and Fox, 1973; Bakken
Seip, 19761. HCB is found in human tissues collected
throughout the world.
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The HCB content of human adipose tissue taken at autopsy
is as follows:
Mean Values
(mg/kg in
Reference
Brady and Siyali, 1972
Siyali, 1972
Brady and Siyali, 1972
Curley, et al. 1973
Mes and Campbell, 1976
Mes, et al. 1977
Mes, et al. 1977
Mes, et al. 1977
Mes, et al. 1977
Mes, et al. 1977
Acker and Schulte, 1974
Acker and Schulte, 1974
Acker and Schulte, 1974
Acker and Schulte, 1974
Acker and Schulte, 1974
Acker and Schulte, 1974
The maximum HCB level reported was 22 mg/kg (Acker and Schulte,
1974) .
Source
;tralia
n
)ua and
/ Guinea
jan
lada
»
it
n
n
n
many
n
.11
it
ii
n
No. samples
75
81
38
241
3
16
50
57
22
27
56
54
54
59
59
93
Human Fat)
1.25
1.31
0.26
0.08
0.09
0.025
0.107
0.060
0.015
0.043
2.9
8.2
5.9
4.8
6.4
4.8
C-154
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Special Groups at Risk
Monochlorobenzene
The major group at risk of MCB intoxication are individ-
uals exposed to MCB in the workplace. Table 3 shows recorded
us trial expos 'u^-asT^o rr?-13 -- ^-ir.ard.^et al. (1969) reported
the case of an elderly female exposed to"aT g 1 ut 3
0.07 percent MCB for a period of six years. She had symptoms
of headache, irritation of the eyes and the upper respiratory
tract, and was diagnosed to have medullary aplasia. Smirnova
and Granik (1970) reported on three adults who developed
numbness, loss of consciousness, hyperemia of the conjunctiva
and the pharynx following exposure to "high" levels of MCB.
Information concerning the ultimate course of these individ-
uals is not available. Gabor, et al. (1962) reported on in-
dividuals who were exposed to benzene, chlorobenzene and
vinyl chloride. Eighty-two workers examined for certain bio-
chemical indices showed a decreased catalase activity in the
blood and an increase in peroxidase, indophenol oxidase and
glutathione levels. Dunaeveskii (1972) reported on the occu-
pational exposure of workers exposed to the chemicals in-
*
volved in the manufacture of chlorobenzene at limits below
the allowable levels. After over three years cardiovascular
effects were noted as pain in the area of the heart, brady-
cardia, irregular variations in electrocardiogram, decreased
contractile function of myocardium and disorders in adapta-
tion to physical loading. Filatova, et al. (1973) reported
on the prolonged exposure of individuals involved in the pro-
duction of diisocyanates to the factory- air which contained
C-155
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MCB as well as other chemicals. . Diseases noted include asth-
matic bronchitis, sinus arrhythmia, tachycardia, arterial
dystrophy and anemic tendencies. Petrova and Vishnevskii
(1972) studied the course of pregnancy and deliveries in
women exposed to air in a varnish manufacturing factory where
the air contained three times the maximum permissible level
of MCB but also included toluene, ethyl chloride, buta'nol,
ethyl bromide and orthosilisic acid ester. The only reported
significant adverse effect of this mixed exposure was toxemia
of pregnancy.
Tetrachlorobenzene
The primary groups at risk from the exposure to TeCB are
those who deal with it in the workplace. Since it is a
metabolite of certain insecticides, it might be expected that
certain individuals exposed to those agents might experience
more exposure to TeCB especially since its elimination rate
might be relatively slow in man. Individuals consuming large
quantities of fish may also be at risk due to the proven bio-
concentration of TeCB in fish. U.S. EPA Duluth laboratory
studies show that the bioconcentration factor for 1,2,4,5-
TeCB is 1,000 times, and for 1,2,3,5-TeCB is 4,100 times.
Pentachlorobenzene
At risk groups would appear to be'those in the indus-
trial setting. There might be an expected increase in body
burdens of QCB in individuals on diets high in fish due to
the persistence of the compound in the food chain and to
those on diets high in agricultural products containing QCB
as residues of PCNB spraying.
C-156
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Hexachlorobenzene
Several groups appear to be at risk; these include wor-
kers engaged directly in: (1) the manufacture of HCB or in
processes in which HCB is a byproduct; (2) the formulation of
HCB-containing products; (3) the disposal of HCB-containing
wastes; and (4) the application of HCB-containing products.
They also include the general public living near industrial
sites/ pregnant women, fetuses, and breast-fed infants and
populations consuming large amounts of contaminated fish.
Two lines of evidence indicate that infants may be at risk.
It has been demonstrated that human milk contains HCB, and
some infants may be exposed to relatively high concentrations
of HCB from that source alone (Miller and Fox, 1973; Bakken
and Seip, 1976). Moreover, some infants of Turkish mothers
who consumed HCB-contaminated bread developed a fatal disor-
der called pembe yara. In some Turkish villages in the re-
gion most affected by HCB-poisoning, few infants survived
during the period 1955-1960 (Cam, 1960).
Occupational exposure is associated with an increased
body burden of HCB. Plant workers in Louisiana have about
200 ug HCB/kg in blood (Burns and Miller, 1975). The HCB
content of body fat exceeds 1 mg/kg in many parts of the
world where HCB contamination of the environment is extensive
(Brady and Siyali, 1972; Acker and Schulte, 1974).
The massive episode of human poisoning resulting from
the consumption of bread prepared from HCB-treated seed wheat
C-157
-------
brought to light the misuse of KGB-treated grain (Cam and
Nigogosyan, 1963). In spite of warnings, regulations and
attempts at public education, HCB-treated grain apparently
still finds its way into the food chain, for example, in fish
food (Hansen, et al. 1976; Laska, et al. 1976). The diffi-
culty in tracing the source of HCB contamination in a diet
for laboratory animals emphasizes the difficulties encoun-
tered in tracing the source of HCB in foodstuffs for man
(Yang, et al. 1976).
As noted previously, adipose tissue acts as a reservoir
for HCB. Deletion of fat depots can result in mobilization
and redistribution of stored HCB. Weight loss for any reason
may result in a dramatic redistribution of HCB contained in
adipose tissue; if the stored levels of HCB are high, adverse
effects might ensue. Many humans restrict their dietary in-
take voluntarily or because of illness. In these instances,
the redistribution of the HCB body burden becomes a potential
added health hazard (Villeneuve, 1975).
C-158
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The HCB content of human bloodsamples is as follows:
Mean Values
(mg/kg
Source No. Samples in Blood) Reference
Bavaria 98 boys 0.022 Richter and Schmid, 1976
" 96 girls 0.017 Richter and Schmid, 1976
Australia 185 exposed 0.055 Siyali, 1972
11 52 unexposed 0.022 Siyali, 1972
" 76 0.058 Siyali and Ouw, 1973
Louisiana 86 0.0036 Burns and Miller, 1975
The maximum HCB level reported was 0.345 mg/kg, in a
Louisiana waste disposal worker (Burns and Miller, 1975).
The levels of HCB in body fat of swine and sheep were
sixfold and eightfold greater respectively than the dietary
level (Hansen, et al. 1977). If these comparisons are valid
when applied to man, it would appear that some adult humans
have been exposed to several mg HCB/kg/day. A similar con-
clusion is reached by extrapolating the values for human
blood. The HCB levels in blood of rats are about tenfold
less than the dietary level (Kuiper-Goodman, et al. 1977).
Current evidence would indicate that food intake may be
the primary source of the body burden of HCB for the general
population although inhalation and dermal exposure may be
more important in selected groups (e.g. industrial workers).
C-159
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Considering that there are relatively little human ex-
posure data, that there is no long-term animal data, and that
some theoretical questions, at least, can be raised on the
possible effects of chlorobenzene on blood-forming tissue, it
was decided to use an uncertainty factor of 1,000. From this
the acceptable daily intake (ADI) can be calculated as fol-
lows:
.._... 70 kg x 14.4 mg/kg . nAO .,
ADI = ? 1,000 ***- = 1.008 mg/day
The average daily consumption of water was taken to be
two liters and the consumption of fish to be 0.0187 kg daily.
A bioconcentration factor of 13 was utilized. "This is the
value reported by the Duluth EPA Laboratories (see Ingestion
from Foods section). The following calculation results in an
acceptable criterion based on the available toxicologic data:
1.008 A-.n ,,
2 + (13 x 0.0187) = 45° ug/1
Varshavskya (1968), the only report available, has re-
ported the threshold concentration for odor and taste of MCB
in reservoir water as being 20 ug/1. This value is about 4.5
percent of the possible standard calculated above. It is,
however, approximately 17 times greater than the highest con-
centration of MCB measured in survey sites (see Table 1).
Since water of disagreeable taste and odor is of significant
influence on the quality of life, and thus, related to
health, it would appear that the organoleptic level of 20
ug/1 should be the recommended criterion.
C-161
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Trichlorobenzene
While the committee recognizes a need for toxicological
information in order to establish a criterion, there are no
reliable published toxicological data on TCB. The studies by
Smith, et al. (1978), and Coate, et al. (1977) do not give
sufficient basis for establishing a toxicological criterion.
Therefore, in lieu of a criterion based on toxicological in-
formation, an organoleptic level of 13 y.g/1 (Varshavskaya,
1968) is recommended. It should be emphasized that this is a
criterion based on aesthetic rather than on health effects.
Data on human health effects need to be developed as a more
substantial basis for setting a criterion for the protection
of human health.
Tetrachlorobenzene
The dose of 5 mg/kg /day reported for beagles (Braun,
1978) was utilized as the NOAEL for criterion derivation. An
acceptable daily intake (ADI) can be calculated from the NOAEL
by using a safety factor of 1,000 based on a 70 kg/man:
. _T 70 kg x 5 mg/kg n c ' .,
ADI = - ** = °-35 mg/day
For the sake of establishing a water quality criterion,
it is assumed that on the average, a person ingests 2 liters
of water and 18.7 grams of fish. Since fish may biomagnify
this compound, a biomagnif ication factor (F) is used in the
calculation.
-------
The equation for calculating an acceptable amount of TeCB
in water is:
Criterion = 2 1 + (IQOO^CKOIS?) = 16-9 *g/l or 17 ug/1
where:
21=2 liters of drinking water consumed
0.0187 kg = amount of fish consumed daily
1000 = biomagnification factor
ADI = Allowable Daily Intake (mg/kg for a 70 kg/person)
Thus, the recommended criterion for TeCB in water is 17
ug/1.
Pentachlorobenzene
A survey of the QCB literature revealed no acute, sub-
chronic or chronic toxicity data with the exception of the
studies by Khera and Villeneuve (1975). These authors found
an adverse effect on the fetal development of embryos exposed
in utero to pentachlorobenzene. The adverse effect has not
been labeled teratogenic because the abnormality was an in-
creased incidence of extra ribs and sternal defects. The
lowest level of exposure to the pregnant rat was 5 mg/kg.
The criterion rationale is based on this exposure level.
Since there was .no no-observable-adverse effect level (NOAEL)
an uncertainty factor of 5000 is used. The use of this factor
has precedent in the pesticide literature.
C-163
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From this/ the acceptable daily intake (ADI) can be cal-
culated as follows:
ADI = 7° kg5Q0o "*'"* - 0.07 mg
The average daily consumption of water was taken to be 2
liters and the consumption of fish to be 0.0187 kg daily.
The bioconcentration factor for QCB is 7800.
Therefore:
Recommended Criterion = 2 + (7800)°x 0.0187 = *47 U9/1 (or °'5
The recommended water quality criterion for pentachloro-
benzene is 0.5 ug/1.
Hexachlorobenzene
Among the studies reviewed by this document, only two ap-
pear suitable for use in the risk assessment: the mouse study
of Cabral, et al. (1978) and the hamster study of Cabral, et
al. (1977). These two studies are described in detail in
Appendix I.
Under the Consent Decree in NRDC v. Train, criteria are
to state "recommended maximum permissible concentrations (in-
cluding where appropriate, . zero) consistent with the protec-
tion of aquatic.organisms, human health, and recreational
activities". HCB is suspected of being a human carcinogen.
Because there is no recognized safe concentration for a human
carcinogen, the recommended concentration of HCB in water for
maximum protection of human health is zero.
-------
Because attaining a zero concentration level may be un-
feasible in some cases, and in order to assist the Agency and
States in the possible future development of water quality
regulations, the concentrations of HCB corresponding to
several incremental lifetime cancer risk levels have been
estimated. A cancer risk level provides an estimate of the
additional incidence of cancer that may be expected in an
exposed population. A risk of 10"^ for example, indicates a
probability of one additional case of cancer for every
100,000 people exposed, a risk of 10~6 indicates one addi-
tional case of cancer 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 consid-
ering setting criteria at an interim target risk level of
10~5, 10~6, or 10~7 as shown in the table below:
sure Assumption Risk Levels and Corresponding Criteria (1)
(per day.) ,
£ IP"7 1Q-Q 1Q-5
ters of drinking water 0 0.0125 ng/1 0.125 ng/1 1.25 ng/1
consumption of 18.7 grams . . .
and shellfish. (2)
amption of fish and 0 0.0126 ng/1 0.126 ng/1 1.26 ng/1
Lfish only.
(1) Calculated by applying a modified "one-hit" extrapola-
tion model described in the Federal Register, FR 15926,
1979. Appropriate bioassay data used in the calculation
of the model is presented in Appendix I. Since the ex-
trapolation model is linear at low doses, the additional
lifetime risk is directly proportional to the water
C-165
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concentration. Therefore, water concentrations corres-
ponding to other risk levels can be derived by multiply-
ing 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) Ninety-nine percent of the HCB exposure results from the
consumption of aquatic organisms which exhibit an aver-
age bioconcentration potential of 12,000-fold. The re-
maining one percent of HCB exposure results from drink-
ing water.
Concentration levels were derived assuming a lifetime
exposure to various amounts of HCB, (1) occurring from the
consumption of both drinking water and aquatic life grown in
waters containing the corresponding HCB concentrations and,
(2) occurring solely from consumption of aquatic life grown
in the waters containing the corresponding HCB concentra-
tions. Because data indicating other sources of HCB exposure
and their contributions to total body burden are inadequate
for quantitative use, the figures reflect the incremental
risks associated with the indicated routes only.
C-166
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Summary of Recommended Criterion for Chlorinated Benzenes
Substance Criterion Basis for Criterion
Monochlorobenzenel 20 ug/1 organoleptic effects
Trichlorobenzene 13 ug/1 organoleptic effects
Tetrachlorobenzene 17 ug/1 toxicity studies
Pentachlorobenzene .5 ug/1 toxicity study
Hexachlorobenzene2 5 ng/1 carcinogenicity
IA toxicological evaluation of monochlorobenzene resulted
in a level of 450 ug/1; however, organoleptic effects have
been reported at 20 ug/1-
2The value 5 ng/1 is at a risk level of 1 in 100,000.
-------
APPENDIX I
Summary and Conclusions Regarding the
Carcinogenicity of Chlorinated Benzene*
Monochlorobenzene (MCB) is used industrially as a solvent,
and as a synthetic intermediate primarily for production
of phenol, DDT and aniline. MCB has been detected in water
contaminated by industrial or agricultural waste, and human
exposure is mainly via water. There are no studies available
concerning the mutagenic or carcinogenic potential of MCB,
so that it is not possible to calculate a water quality
criterion on the basis of an oncogenic effect.
There are three isomers of trichlorobenzene (TCB).
1,2,4-TCB is used as a carrier of dyes, as a flame retardant,
and in the synthesis of herbicides. 1,2,3-TCB and 1,3,5-
TCB are used as synthetic intermediates, while a mixture
of the three isomers is used as a solvent or lubricant.
TCB's are likely intermediates in mammalian metabolism of
lindane, and TCB's metabolize to trichlorophenols (TCP)
(e.g., 1,3,5-TCB produces 2,4,6-TCP). TCB is present in
drinking water, but there are no studies concerning the
mutagenicity or carcinogenicity of these compounds and,
hence, a criterion cannot be calculated on this basis.
Tetrachlorobenzene (TeCB) exists as three isomers.
Two of these, 1,2,4,5-TeCB and 1,2,3,6-TeCB, are used in
the manufacture of 2,4,5-trichlorophenoxyacetic acid (2,4,5-
*This summary has been prepared and approved by the Carcinogens
Assessment Group of EPA.
C-168
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T) and 2,4,5-trichlorophenol (2,4,5-TCP). TeCB is one of
the metabolites of hexachlorobenzene and lindane. TeCB
has not been identified in water in the United States.
However, industrial effluent may contain TeCB which causes
contamination of aquatic organisms. Soil microorganisms
can metabolize lindane to TeCB, which may further contaminate
water due to soil run-off. There are no carcinogenicity
studies available for TeCB's so that a water quality criterion
cannot be derived on this basis.
Pentachlorobenzene (QCB) is used mainly as a precursor
in the synthesis of the fungicide pentachloronitrobenzene,
and as a flame retardant. Lindane metabolizes i-n humans
to QCB. QCB has entered water from industrial discharge,
or as a breakdown product of organochlorine compounds.
There is no data available concerning the mutagenicity of
QCB. There is a translated abstract of an article by Preussman
(1975) which states that PCB is carcinogenic in mice, but
not in rats and dogs. The abstract does not report the
data and, since the article has been difficult to obtain,
the study is not yet available to evaluate for a water quality
criterion.
Hexachlorobenzene (HCB) is used as a fungicide and
industrially for the synthesis of chlorinated hydrocarbons,
as a plasticizer and as a flame retardant.. HCB has been
detected in water near sites of industrial discharge, and
leaches from industrial waste dumps. HCB is very stable
in the environment and bioaccumulates, so that it is present
C-169
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in many food sources (e.g., cereals, vegetables, fish, meat,
and dairy products). It is stored in human adipose tissue
and is present in human milk. There is only one mutagenicity
study reported for HCB which is negative for the induction
of dominant lethal mutations in rats.
Studies by Cabral, et al. (1977, 1978) indicated that
oral administration of HCB induced hepatomas and liver hemangio-
endotheliomas in male and female Syrian Golden hamsters,
and hepatomas in male and female Swiss mice. The data from
the hamster study was reported in detail for evaluation,
whereas the mouse study was only described in an abstract.
In the hamster study, there was a statistically significant
incidence of hepatomas in males fed 50, 100, and 200 ppm
(p =7.5 X 10~7, 2.45 X 10~15, and 1.30 X 10~19, respectively),
and of liver hemangioendtheoliomas in males fed 100 and
200 ppm (p = 4.5 X 10~3 and 4.0 X 10~6, respectively).
There was a statistically significant incidence of hepatomas
in females fed 50, 100, and 200 ppm (p = 7.5 X 10~7, 2.0
8 19
X 10 and 3.05 X 10 , respectively), and of liver hemangio-
endotheliomas in females fed 200 ppm (p = .026).
The water quality criterion for HCB is based on the
induction of hepatomas and nemangioendotheliomas in male
Syrian Golden hamsters given a daily oral dose of 100 ppm
(Cabral, et al. 1977) . The concentration of HCB in drinking
water calculated to limit human lifetime cancer risk from
HCB to less than 10~5 is 1.25 nanograms per liter.
C-170
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Summary of Pertinent Data
The water quality criterion for HCB is based on the
induction of hepatomas and hemangioendotheliomas in male
Syrian Golden hamsters given a daily oral dose of 100 ppm
for 80 weeks (Cabral, et al. 1977). The hepatoma incidence
was 26/30 in the treated group compared with 0/40 in the
control group, and the hemangioendothelioma incidence was
6/30 in the treated group compared with 0/40 in the control
group. The criterion was calculated from the following
parameters.
d = 100 ppm, X 0.8 = 8 mg/kg/day
W = .100 kg
F = .0187 kg
R = 12,000
nfc hepatoma = 26
N. hepatoma = 30
nc hepatoma = 0
N~ hepatoma = 40
c
n. hemangioendothelioma = 6
N. hemangioendothelioma = 30
n_ hemangioendothelioma = 0
C
No hemangioendothelioma = 40
Le = 80 wk
le = 80 wk
L = 80 wk
Based on these parameters, the one-hit slope (B^) is
2.2363 (mg/kg/day) for hepatomas and 0.2477 (mg/kg/day)
for hemangioendotheliomas. The resulting water concentration
of HCB calculated to keep the individual lifetime cancer
risk below 10~ is 1.25 nanogramj; per liter.
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