United States Office of Pesticides and Toxic Substances
Environmental Protection Office of Pesticide Programs (H7508C)
Agency Washington, DC 20460
*£EPA Pesticide
Fact Sheet
540/FS-89-067
Name of Chemical: COUMAPHOS
Reason for Issuance: REGISTRATION STANDARD
Date Issued: SEP 2T l989
Fact Sheet Number: 207
1. DESCRIPTION OF CHEMICAL
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Common Name: Coumaphos
Chemical Family: Organophosphate
Pesticide Type: Insecticide/acaricide
Chemical Name: 0,0-diethyl 0-(3-chloro-4-methyl-2-oxo-
2H-i-benzopyran-7-yl) phosphorothioate
Trade Names: Bay 21/199, Asuntol, Muscatox, Resitox,
Baymix, Meldane, Co-Ral and Negashunt
Other Chemical
Nomenclature: 0-3-chloro-4-methylcoumarin-7-yl
0,0-diethyl phosphorothioate; 3-chloro-7-
diethoxyphosphino-thioyloxy-4-
methylcoumarin; 0-(3-chloro-4-methyl-2-
oxo-2H-l-benzopyran-7-yl) 0,0-diethyl
phosphorothioate (Chemical Abstracts,
9th Collective Index); 3,chloro-7-hydroxy-
4-methylcoumarin 0-ester with 0,0-diethyl
phosphorothioate (8th Collective Index);
0,3-chloro-4-methyl-2-oxo-2H-chromen-7-y1
0-0-diethyl phosphorothioate;
[0-(3-chloro-4-methyl-7-coumarinyl)]
0,0-diethyl phosphorothioate; 0,0-diethyl
0-(3-chloro-4-methyl-7-courmarinyl)
phosphorothioate; phosphorothioic acid 0-
(3-chloro-4-methyi-2-oxo-2H-l-benzopyran-
7-yl) 0,0-diethyl ester; 3-chloro-4-
methylumJhelliferone, 0-ester with 0,0-
dietyl phosphorothioate; 0,0-diethyl
0-(3-chloro-4-methylumbelliferone
thiophosphate
Year of Initial Registration: 1958
CAS Registry Number: 56-72-4
EPA Pesticide Chemical Code (Shaughnessy Number): 036501
U.S. Manufacturer: Bayvet, a division of Cutter Laboratories
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USE PATTERNS AMD FORMULATIONS
Coumaphos is applied as a direct animal treatment to control
arthropod pests of beef cattle, dairy cattle, sheep, goats,
horses and swine. Jt is used to treat swine bedding. Registered
control claims are for face flies, horn flies, fly larvae, cattle
grubs, ticks (including ear tick), lice, mites, screwworms, sheep
keds and fleeceworms. Methods of application consist of dusts,
sprays, dips, pour-ons, dust bags and backrubber oilers. Annual
usage is 264,000 to 525,600 Ibs (1986 estimate). The
predominate use is on beef cattle (98%). A relatively small
amount is used on dairy cattle «2%) and swine (
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cattle which have entered a body of water. Aquatic residue
monitoring is required to assess the potential hazards. Due to
the potential for avian exposure resulting from birds feeding in
cattle lots and on the backs of cattle, Tier I avian field
testing is required to assess possible effects to birds resulting
from the direct treatment to livestock.
The environmental fate profile for coumaphos is adequately
delineated for the registered use pattern, except for a
groundwater assessment. Coumaphos is relatively immobile in aged
sandy loam soil, based on findings in a column leaching study.
There are no immediate concerns for groundwater contamination
from non-point source application of coumaphos. However, the
potential does exist for localized, point source contamination in
animal treatment areas (particularly where animals are dipped),
and as a result of associated disposal practices. Due to
increased Agency sensitivity in the area of pesticides and
groundwater contamination, environmental fate studies are
required so that the Agency can assess coumaphos's potential for
point source contamination.
Most of the residue chemistry conclusions drawn in the 1981
Standard have been reversed in the current Standard. Residue
chemistry data requirements were not imposed in the 1981
Standard. Since issuance of that Standard, the Agency has
published residue chemistry guidelines (Pesticide Assessment
Guidelines, Subdivision 0, 1982, EPA-540/9-82-023) and other
Federal Register (FR) Notices which provide a more stringent
interpretation of the existing regulations. As a result of these
new guidelines, data are now required in the area of animal
metabolism, storage stability and method validation. No changes
to coumaphos tolerances are indicated at this time.
The Agency is unable to totally assess the safety of current
tolerances and establish an acceptable daily intake (ADI) value
for coumaphos because of the absence of chronic toxicity studies
(reproduction and dog chronic toxicity), and outstanding residue
chemistry data. However, a preliminary dietary exposure
analysis has been performed for coumaphos. Based on the results
of this analysis, current coumaphos tolerances are considered to
be adequate to protect the public health. When the remaining
data requirements have been fulfilled, the Agency will perform a
final reassessment of coumaphos tolerances.
Chemical/Physical Characteristics of the Technical Material
Empirical Formula: C14H16C105PS
Molecular Weight: 362.8
Color: grey to tan
Physical state: powder to granules
Odor: characteristic sulfur
Melting Point: 90 to 95 °C
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Boiling Point: 20 °C at 10"7 rrunHg
Solubility: (at 20 °C) : g/100 mL at 20 C
acetone 23.82
methylene chloride 6.39
denatured alchohol 0.90
xylenes 0.90
hexanes 0.07
water insoluble at 0.002
octanol 0.13
odorless mineral spirits 0.09
diethyl phthalate 21.50
Vapor Pressure: 1 X 10 7 mmHg
Density, Bulk Density, or
Specific Gravity: granules: 30.06 Ib/cu ft, loose; 30.85
Ib/cu ft, packed, mhajranermiiled: 24.35
Ib/cu ft, loose; 30.51 Ib/cu ft, packed
pH: 7.23 at 1 g/100 mL
Stability: hydrolyses slowly under alkaline conditions;
stable under normal storage conditions and
use; incompatible with piperonyl butoxide
Storage Stability: Stable (<6% loss) in glass vials up
to 8 weeks at -12 to 50 C, dry and
at pH 4-10, at 83% moisture, exposed
to aluminum, and stainless steel;
stable exposed to sunlight for 4
days.
Toxicology Characteristics
Acute Oral: Toxicity Category I (LD50 of greater than 240 mg/kg
in males rats and 17 mg/kg in female rats)
Acute dermal: Toxicity Category III (LD50 of greater than 2400
mg/kg in rabbits
Acute inhalation: Toxicity Category II (LC50 dose for a 1-hour
is 341 mg/m3 in female rats and
greater than 1080 mg/m3 in male rats)
Primary eye irritation: Toxicity Category III, mild
eye irritation reported
Primary dermal irritation: Toxicity Category IV, very minor
dermal irritation reported
Skin sensitization: No observable evidence of dermal
sensitization
Delayed Neurotoxicity: Did not induce delayed rieurotoxicity in
an acceptable study in hens.
Subchronic non-rodent/
rodent studies: None available. Not required
since chronic data supercede
need for subchronic testing.
21-day dermal toxicity: Required Study
Chronic toxicity: Dog study is required. Rat study NOEL is 0.07
mg/kg for decreased cholinesterase activity.
Oncogenicity: The mouse and rat chronic toxicity/
oncogenicity studies did not reveal any evidence
that coumaphos is oncogenic.
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Mutagenicity: Negative in all areas of mutagenicity tested. A
structural chromosomal abberation study is
required.
Teratogenicity: Rat teratology study NOEL and LEL were 5 and 25
mg/kg (based on the observation of cholinergic
effects), respectively. The developmental NOEL
was greater than 25 mg/kg (HDT). Rabbit
teratology study maternal NOEL and LEL were
2.0 and 18.0 mg/kg, respectively;
developmental NOEL was greater than 18.0 mg/kg
(HDT).
Reproduction: Required study
Metabolism: In a rat metabolism study, coumaphos was rapidly
excreted. No dose-related changes in metabolism or
evidence of activation/bioaccumulation were noted
in this study.
Environmental Characteristics
t
Based on the results of a column leaching study, coumaphos
can be characterized as persistent, but immobile in sandy loam
soils. There are no immediate concerns for groundwater
contamination from non-point source application of coumaphos.
However, the potential does exist for localized, non-point source
contamination in animal treatment areas (particularly where
animals are dipped), and as a result of associated disposal
practices. In order to evaluate the potential for point source
contamination, special studies are required: a photodegradation
study in soil, a photodegradation study in water, an
adsorption/desorption study, a hydrolysis study and a
retrospective field dissipation study.
Ecological Characteristics
Based on the results of acceptable laboratory data,
technical coumaphos is characterized as highly to very highly
toxic to birds, moderately toxic to fish and highly toxic to
aquatic invertebrates:
- Acute LD50 (mallard): 29.4 mg/kg
- Acute LD50 (pheasant): 7.94 mg/kg
- Dietary LC50:
401 ppm (mallard)
82 ppm (bobwhite)
- Freshwater invertebrates toxicity (96-hr LC50) for
amphipods: 0.15 ppb
- Fish acute toxicity (96-hr LC50) for rainbow trout: 5900
ppb
- Fish acute toxicity (96-hr LC50) for bluegill sunfish:
5000 ppb
Results of laboratory testing, in conjunction with
theoretical monitoring, indicate that aquatic invertebrates may
be potentially exposed to hazardous levels of coumaphos resulting
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from washing-off of the material from the backs of newly treated
cattle which have entered a body of water, such as a pond or
stream. To evaluate the potential risk, a residue monitoring
study is required. There is a potential for avian exposure
resulting from birds feeding in cattle feedlots and on the backs
of cattle. Tier I avian field testing is required to assess
possible effects to birds resulting from direct treatment to
livestock.
Tolerance Assessment
U.S. tolerances are established for residues of the
insecticide coumaphos, 0,0-diethyl 0-(3-chloro-4-methyl-2-oxo-2H-
l-benzopyran-7-yl) phosphorothioate, and its oxygen analog, 0,0-
diethyl 0-3-chloro-4,-methyl-2-oxo-2H-l-benzopyran-7-yl-phosphate,
in or on raw agricultural products as follows (40 CFR 180.189):
o 1 ppm in or on meat, fat, and meat byproducts of
cattle, goats, hogs, horses, poultry , and sheep
o 0.5 ppm in milk fat (reflecting negligible residues in
milk)
o 0.1 ppm in eggs
Most of the residue chemistry conclusions drawn in the 1981
Standard have been reversed. No residue chemistry data
requirements were imposed in the 1981 Standard. Since issuance
of that Standard, the Agency has published residue chemistry
guidelines (Pesticide Assessment Guidelines, Subdivision 0, 1982,
EPA-540/9-82-023) and other FR Notices which provide a more
stringent interpretation of the existing regulations. As a
result of these new guidelines, data are now needed in the area
of animal metabolism, storage stability and method validation.
The Provisional Acceptable Daily Intake (PADI) for coumaphos
is 0.0007 mg/kg/day and is based on the 2-year rat
feeding/oncogenicity study NOEL of 0.07 mg/kg/day (based on
plasma cholinesterase inhibition in females) and uncertainty
factor of 100. The Anticipated Residue Contribution (ARC) for
the United States population is 0.000127 mg/kg/day, occupying
18.2% of the PADI. The two highest calculated exposures for the
population subgroups are children 1 to 6 years of age [ARC
occupies 33.6% of the PADI] and children 7 to 12 years of age
[ARC occupies 25.6% of the PADI]. Based on these calculations,
coumaphos applied at the currently registered application rates
would not be expected to exceed established tolerances.
The Agency is unable to totally assess the safety of current
tolerances and establish an acceptable daily intake (ADI) value
for coumaphos because of the absence of chronic toxicity studies
(reproduction and dog chronic toxicity), and outstanding data in
1 There are no longer any federally registered uses for
poultry/poultry houses. Therefore, the Agency intends to revoke
the tolerances for poultry and eggs.
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the area of animal metabolism, method validation and storage
stability. When the required data have been submitted and
evaluated, the Agency will perform a final reassessment of
coumaphos tolerances.
4. SUMMARY OF REGULATORY POSITIONS AND RATIONALES
The Agency is not initiating a Special Review for coumaphos.
No Special Review concerns were identified for this chemical by
the Agency during its review of the current data base.
The Agency is classifying coumaphos 11.6% EC and 42%
flowable concentrate end-use products as restricted use due to
acute oral hazards.
The Agency will approve new food/feed tolerances for
coumaphos on a case-by-case basis.
Environmental fate testing is'required to evaluate the
potential for coumaphos to impact groundwater or surface water
resulting from point source application.
A special aquatic residue monitoring study is required.
Special Tier I avian field testing is required.
- The Agency will revoke the poultry and egg tolerances,
since coumaphos is no longer federally registered for use on
poultry or in poultry houses.
Unique labeling statements are required:
o Restricted-use classification is required for coumaphos
11.6% EC and 42% flowable concentrate formulations.
o Special disposal instructions are required for products
bearing directions for use a livestock dip treatment.
o Labels bearing directions for use on goats and sheep must
be amended to specify a preslaughter interval (PSI) of 3 days.
o Product labels must bear revised and updated fish and
wildlife statments.
o Worker safety and protective clothing statements are
required for products falling in Toxicity Category I or II.
o Each end-use product label must be revised to reflect the
appropriate signal word and precautionary statements assigned to
it based on the results of acceptable acute toxicity testing.
o Revised labeling must be submitted for those products
which do not contain directions for use specifying a maximum
single application rate expressed in terms of: (1) amount of
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active ingredient per animal; (2) a maximum seasonal application
rate or number of applications permitted per season; and (3) a
minimum interval between applications, revised labeling must be
submitted.
SUMMARY OF OUTSTANDING DATA REQUIREMENTS
Toxicology
21-Day Dermal Toxicity
Dog Chronic Toxicity
Reproduction Study
Chromosome Aberration
Environmental Fate/Exposure
Photodegradation in Water and Soil
Adsorption/Desorption
Special Retrospective Field Dissipation
Study
Hydrolysis Study
Fish and Wildlife
Monitoring for Aquatic Invertebrate
Mortality and Residues in Water
Tier I avian field testing
Residue Chemistry
Metabolism data - Animals
Residue Analytical Methods
Storage Stability Data
Product Chemistry
Remaining Data Gaps
6. Contact Person at EPA
George LaRocca.
Product Manager (15)
Insecticide-Rodenticide Branch
Registration Division (H7505C)
Environmental Protection Agency
Washington, DC 20460
Tel. No. (703) 557-24006
DISCLAIMER: The information presented in this Chemical
Information Fact Sheet is for informational purposes only and may
not be used to fulfill data requirements for pesticide
registration and reregistration.
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Environmental Protection Agency
Office of Pesticide Program (H7504C)
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Washington, DC 20460
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