530R86104
ATER QUALITY
ADVISORY
DCPA
Criteria and Standards Division
Df-fice a -F Water Regulations and Standards
United States
EIn v ir anrnen t al Protection Rgency
MRRCH 1 3 8 G
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WATER QUALITY ADVISORY
Number 3 .
DCPA
Criteria and Standards Division
Office of Water Regulations and Standards
United States Environmental Protection Agency
The advisory concentration for DCPA in ambient water for the
protection of freshwater aquatic life is estimated to be 14.3 mg/L. No
saltwater data were reviewed, and no advisory concentration for the
protection of saltwater aquatic organisms is estimated. Care should
be taken in the application of this advisory, with consideration of
its derivation, as stated in the attached support document.
A value given to protect aquatic life can be derived from no
observed effect levels (NOEL), the lowest concentration found in the
data which has been observed to cause acute or chronic toxicity or
other experimental data which may be applicable. When there is no
valid experimental evidence, a value may be derived from a model
which uses structure-activity relationships (SAR) as its basis. The
advisory concentrations should be used with caution, since they are
derived from minimal experimental evidence, or in the case of SAR
derived values, no data on the specific chemical.
The advisory concentration for DCPA in ambient water for the
protection of human health is estimated to be 0.008 ug/L, based on
data and information which are available to the U.S. EPA. Care should
be taken in the application of this advisory, with consideration of
its derivation, as stated in the attached support document.
An advisory concentration can be derived from a number of
sources: The Office of Drinking Water Health Effects Advisories;
Acceptable Daily Intake(ADI) values from EPA; Office of Pesticides
and Toxic Substances risk assessments; Carcinogen Assessment Group
(CAG) cancer risk estimates; risk estimates derived from the open
literature; or other sources which will be given in the support
document. The advi-sory concentrations derived from these sources
will vary in confidence and usefulness, based on the amount and
quality of data used as well as the assumptions behind the original
estimates. The user is advised to read the background information
carefully to determine the strengths or deficiencies of the values
given in the advisory.
U.S. Environmental Protection Agency
Region 5, Library (PL-12J)
77 West Jackson Boulevard, 12th Floor
Chicago, IL 60604-3590
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HUMAN HEALTH AND AQUATIC LIFE
LITERATURE SEARCH AND DATA
BASE EVALUATION FOR
DCPA
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF WATER REGULATION AND STANDARDS
CRITERIA AND STANDARDS DIVISION
WASHINGTON, D.C. 20460
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TABLE OF CONTENTS
INTRODUCTION ,
SCOPE OF SEARCH
SUMMARY OF FINDINGS ,
Aquatic Toxicity ,
Health Effects ,
CRITERIA EVALUATION AND RECOMMENDATIONS
REFERENCES
1
1
2
2
5
5
9
LIST OF TABLES
Table I. Summary of Aquatic Toxicity Literature Review of DCPA
Table 2. Summary of Health Effects Literature Review of DCPA ..
Table 3. Data Requirements for Calculation of Aquatic Life
Interim Criteria—DCPA
Table 4. Data Requirements for Calculation of Human
Interim Criteria—DCPA
3
4
7
8
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HUMAN HEALTH AND AQUATIC LIFE
LITERATURE SEARCH AND DATA
BASE EVALUATION FOR
DCPA
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF WATER REGULATION AND STANDARDS
CRITERIA AND STANDARDS DIVISION
WASHINGTON, D.C. 20460
INTRODUCTION
Dimethyl tetrachloroterephthalate (DCPA) is a chlorinated benzoic
acid used as a selective pre-emergent herbicide for control of annual
grasses, and certain broadleaf weeds (McEwen and Stephenson, 1979;
WSSA, 1974). DCPA is used commercially on turf, ornamentals,
strawberries, soy and field beans, onions, cabbage, and cotton. The
basic producer of DCPA is Diamond Shamrock, U.S.A., and the most
frequently encountered common and trade names are Dacthal, DCPA, DAC
893, chlorathal dimethyl, and Fatal. DCPA has an estimated half life
of 100 days in most soil types and is either adsorbed to or absorbed
by organic matter (WSSA, 1979).
DCPA is an odorless, white crystalline compound with the following
physical and chemical properties:
Molecular weight 332
Melting point 156 C
Vapor pressure <0.01 mm Hg at 40 C
Solubility in water at 25 C 0.5 ppm.
Hexachlorobenzene may be a contaminant of DCPA (8-9 percent). The
toxicity of hexachlorobenzene may need to be considered for criteria
calculation (Burns et al., 1974).
SCOPE OF SEARCH
Computerized literature searches and printed abstracts of TOXLINE,
TOXBACK, NTIS, and the Toxicology Data Base were used as primary
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sources for identifying data on aquatic toxicity and human health
effects, focusing primarily on laboratory studies of dose-response of
aquatic organisms and mammalian species. The quality assurance/
quality control measures used in these studies were evaluated for
their use of positive and negative controls, replication, and chemical
analysis of test concentrations.
Additionally, the quality of experimental methods was evaluated by
comparison to guidelines established by the U.S. EPA in "Guidelines
and Methodology Used in Preparation of Health Effect Assessment
Chapters of the Consent Decree Water Quality Criteria Documents" (FR
45:79347, November 28, 1980) and the "Guidelines for Deriving
Numerical National Water Quality Criteria for the Protection of
Aquatic Life and Their Uses" (Stephan et al., 1985). Data other than
dose-response relationships (e.g., metabolic studies and field obser-
vations) were also collected to provide ancillary information relevant
to aquatic toxicity and human health effects.
SUMMARY OF FINDINGS
Aquatic Toxicity
Few data are available concerning the toxicity of DCPA to aquatic
life (Table 1). In general, the herbicide is reported to be of low
toxicity to these species tested (WSSA, 1979).
An LC50 (estimated concentration at which 50 percent of the test
animals die) of DCPA for Tubifex tubifex, an aquatic oligochaete worm,
was reported at 286 ppm, indicating low toxicity (Voronkin and
Loshakov, 1973). However, DCPA inhibited the activity of the enzyme
succinate dehydrogenase in these worms.
Only one study was found that reported the toxicity of DCPA to
fish (>500 ppm); however, neither the species tested nor the original
study was cited (WSSA, 1979).
Miller and Gomes (1974) collected five species of fish from the
lower Rio Grande River Valley, Texas, and analyzed them for tissue
residues of DCPA. The herbicide was used in this region for weed
control in onions and cotton. From this study, a bioconcentration
factor was estimated for menhaden (Brevoortia tyrannus) by averaging
the mean waterborne and fish residue levels of DCPA per month for a 2-
year period (Table 1). These data indicate that DCPA concentrates
significantly in fish (about 3,000 times the concentration of the
surrounding water).
DCPA residues in fish tissues from waters averaging 0.5 ppb DCPA
concentration showed maximum concentrations ranging from 132 ppb in
testes to 555 ppb in liver (Table 1).
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Health Effects
The toxicity of DCPA to mammals appears to be relatively low, with
LD50 (estimated dosage at which 50 percent mortality occurs) values
ranging from 320 mg/kg for mice to 3,000 mg/kg for rats (Table 2).
Additionally, a no-observed-effect level (NOEL) of 10,000 ppm in diet
was found for dogs and rabbits fed DCPA for a 2-year period. A
probable oral lethal dose of 500-5,000 mg/kg was reported for humans
(CTCP, 1976). Cytogenetic toxicity of DCPA is indicated by an
increase in the number of metaphase stages with multiple aberrations
in bone marrow cells of mice (Kurinnyi et al., 1982). All literature
sources from which health effects data were collected either cited
results from other studies (WSSA, 1979) or did not document methods
adequately (Kurinnyi et al., 1982). Thus, these data were difficult
to evaluate with respect to quality assurance, quality control, and
other parameters.
DCPA exposures may have public health significance because
hexachlorobenzene (HCB) has been found to be an important contaminant
of DCPA. One study has found that HCB increased the incidence of
hepatomas and hemangioendotheliomas in golden hamsters and mice fed 50
to 200 ppm HCB in diet for durations between 80 weeks to the entire
life span of the animals (Cabral et al., 1977 and 1978). A study of
residues in workers exposed to DCPA detected no levels of DCPA in
blood, whereas concentrations of HCB averaged 40 ppb in blood, with a
maximum level of 310 ppb (Burns et al., 1974). Although no adverse
effects were detected in these workers, HCB may be carcinogenic
(Cabral et al., 1977 and 1978).
CRITERIA EVALUATION AND RECOMMENDATIONS
No water-quality criterion for DCPA was found in the literature
search or in various water quality criteria documents. The lack of
adequate data makes recommendation of criteria difficult. No
verifiable toxicity data were found for aquatic organisms although
there is an indication (see Table 1) that levels as high as 500 ppm
DCPA are not toxic to fish. Furthermore, the formulas stipulated by
the guidelines (Stephan et al., 1985) are not operable because of the
lack of data.
However, because fish can concentrate DCPA at waterborne levels of
0.5 ppb, bioaccumulation of DCPA in aquatic organisms may pose a
health risk to humans who consume these animals from areas where the
herbicide is used regularly (Miller and Gomes, 1974). Consumption of
fish with these levels may result in exposure to elevated levels of
DCPA although the toxicity to humans of DCPA may be quite low (500-
5, 000 mg/kg).
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The potential for cytogenetic toxicity (mutagenesis) of DCPA has
been implied (Kurinnyi et al., 1982); however, the methods of these
determinations and the significance of these results for human health
was not reported. Furthermore, no appropriate data were found
concerning carcinogenicity or long-term effects for mammals. The
absence of appropriate chronic parameters (i.e., NOAEL, LOEL, LOAEL)
does not allow calculation of a water quality criterion for human
health.
Potential carcinogenicity of hexachlorbenzene (HCB), a contaminant
of DCPA, has been reported for hamsters and mice at levels of 50 ppm
during long exposures (Cabral et al., 1977 and 1978). Because HCB
comprised 8-9 percent of DCPA used for weed control in Texas during
the early 1970's (Burns et al., 1974), it may be an important
contaminant of DCPA for human health. The U.S. EPA (1980) has
established a recommended criteria for HCB of 0.72 ng/L based on a
cancer risk of 10~6 for a lifetime exposure. This should be taken
into account if HCB contamination is suspected.
In summary, no adequate data were found for any aquatic species
(Table 3) nor were any found for adequately assessing human health
effects (Table 4). Given the minimal data base, it is suggested that
the advisory be based on the LC50 concentrations found in the aquatic
data, that of 286 ppm for Tubifex tubifex. The advisory concentration
would be calculated by dividing this value by 2, to approximate an
LCI, then by 10 to estimate a possible chronic value. This would mean
a maximum allowable concentration of 14.3 mg/L to protect aquatic
life.
A value designed to protect human health should take into account
the bioconcentration factor, and potential contamination by HCB. If
HCB is assumed to comprise 9% of DCPA by weight, assuming consumption
of contaminated organisms and water, then, the maximum concentration
which would not exceed the 10~6 risk level is 8 ng/L. This value,
derived from the AWQ Criteria Document for Chlorinated Benzenes (U.S.
EPA, 1980) takes into account a bioconcentration potential for HCB of
8,690.
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TABLE 3. DATA REQUIREMENTS FOR CALCULATION OF AQUATIC LIFE
INTERIM CRITERIA—DCPA
Criterion Requirements
Aquatic Toxicity
Acute Test Results from tests on:
A salmonid (class Osteichthyes)
A warm water species
commercially or recreationally
important (class Osteichthyes)
Another family in the phylum
Cordata (fish, amphibian, etc.)
A planktonic crustacean
(cladoceran, copepod, etc.)
Benthic crustacean (ostracod,
isopod, scud, crayfish, etc.)
Insect (mayfly, dragonfly,
damselfly, stonefly, mosquito,
etc.)
Phylum other than Arthropoda/
Chordata (Rotifera, Annelida,
Mollusca)
Another family of insect
Acute-chronic ratios with species from
three different families:
One fish
One invertebrate
Acutely sensitive freshwater
animal species
Acceptable test results from a
test with:
Freshwater algae
A vascular plant
Bioaccumulation factor with a
freshwater species (if a maximum
permissible tissue concentration
is available)
Available
Data
NO
NO
NO
NO
NO
NO
YES
NO
Data
Acceptability
NO
NO
NO
NO
NO
YES
NO; QA/QC
not reported
NO; not a
freshwater species
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TABLE 4. DATA REQUIREMENTS FOR CALCULATION OF HUMAN
INTERIM CRITERIA—DCPA
Criterion Requirements
Human Health Effects
Available
Data
Data
Acceptability
Non-Threshold:
Carcinogen NO
Tumor incidence tests (Incidence of
tumor formation significantly more
than the control for at least one N/A
dose level, or
Data set which gives estimate of
carcinogenetic risk, or N/A
Lifetime average exposure tests, or N/A
Human epidemiology studies
(if available, not required) N/A
Threshold:
Non-carcinogens YES*
No observed adverse effect level
(at least 90-day), or NO
Lowest observed effect level NO
Lowest observed adverse effect level NO
Acceptable Daily Intake:
Daily water consumption YES
Daily fish consumption YES
Bioconcentration factor NO
Non-fish dietary intake YES
Daily intake by inhalation NO
Threshold Limit Value:
(Based on 8-hour time-weighted
average concentrations in air) NO
Inhalation Studies:
Available pharmacokinetic data NO
Measurements of absorption efficiency NO
Comparative excretion data NO
YES
(EPA assumption)
YES
(EPA assumption)
YES
(EPA assumption)
N/A = Not Applicable
* NOEL available (not acceptable data)
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U.S. Environmental Protection ARency
Region 5, Library (PL-12J)
77 West Jackson Boulevar.d, 12th Floor
Chicago, IL 60604-3590
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REFERENCES
Burns, J.E., F.M. Miller, E.D. Gomes, and R.A. Albert. 1974.
Hexachlorobenzene exposure from contaminated DCPA in vegetable
spraymen. Arch. Environ. Health 29:192-194.
Cabral, J.R.P., P. Shubik, T. Mollner, and F. Raitano. 1977.
Carcinogenesis study in hamsters with hexachlorobenzene. Toxicol.
Appl. Pharmacol 41:155.
Cabral, J.R.P., T. Mollner, F. Raitano, and P. Shubik. 1978.
Carcinogenesis study in mice with hexachlorobenzene. Toxicol. Appl.
Pharmacol. 45:323.
CTCP. 1976. 4th ed. Article by Gosselin. Abstracted from
Toxicology Data Base.
Federal Register (FR). 1980. U.S. Government Printing Office,
Washington, D.C. November 28, 45(231) :79347-79356.
Kurinnyi, A.I., M.A. Pilinskaya, I.V. German, and T.S. L'vova. 1982.
Implementation of a program of cytogentic activity and potential
mutagenic hazard of 24 pesticides.. Cytol Genet 16:50-53.
McEwen, F.L. and G.R. Stephenson. 1979. The use and significance of
Pesticides in the environment. John Wiley and Sons, Inc., New York.
Miller, F.M. and E.D. Gomes. 1974. Detection of DCPA residues in
environmental samples. Pestic. Monit. J. 8:53-58.
NIOSH RTECS ONLINE File. 82/8007. Abstracted from Toxicology Data
Base.
Stephan, C. E., D. I. Mount, D. J. Hansen, J. N. Gentile, G. A.
Chapman, and W. A. Brungs. 1985. Guidelines for deriving numerical
national water quality criteria for the protection of aquatic
organisms and their uses. Draft. U.S. Environmental Protection
Agency, Office of Research and Development, Environmental Research
Laboratories, Duluth, Minnesota.
U.S. EPA. 1980. Ambient Water Quality Criteria Document for
Chlorinated Benzenes. Available through National Technical
Information Service - PB81-117392.
Voronkin, A.S., and Y.T. Loshakov. 1973. Toxic effect of pesticides
on Tubifex tubifex. ESKP. Vodn. Toksikol. 5:169-178.
Weed Science Society of America (WSSA). 1979. Herbicide Handbook 4th
ed.
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