The information in this profile may be out-of-date. It was last revised
in 1996. EXTOXNET no longer updates this information, but it may be useful
as a reference or resource.
Please visit the National Pesticide Information Center (NPIC) to find
updated pesticide fact sheets.
If you don't find a fact sheet related to
your question, feel free to call 1-800-858-7378.
NPIC is open five days
a week from 8:00am to 12:00pm Pacific Time.
E X T O X N E T
A Pesticide Information Project of Cooperative Extension
Offices of Cornell University, Oregon State University, the
University of Idaho, and the University of California at Davis
and the Institute for Environmental Toxicology, Michigan State
University. Major support and funding was provided by the
USDA/Extension Service/National Agricultural Pesticide Impact
EXTOXNET primary files maintained and archived at Oregon State
Revised June 1996
Trade and Other Names:
Trade names include Agridip, Asunthol, Bay 21, Baymix, Co-Ral,
Dilice, Meldame, Muscatox, Negashunt, Resistox, Suntol, and
The U.S. Environmental Protection Agency (EPA) classifies most
formulations of coumaphos as General Use Pesticides (GUPs). The
formulations 11.6% EC and 42% flowable concentrate end-use
products have been classified as Restricted Use Pesticides (RUPs)
because they pose a hazard of acute poisoning from ingestion.
RUPs may be purchased and used only by certified applicators.
Coumaphos is classified as toxicity class II - moderately toxic.
Products containing coumaphos bear the Signal Word WARNING.
Coumaphos is an organophosphate insecticide used for control of a
wide variety of livestock insects, including cattle grubs, screw
worms, lice, scabies, flies, and ticks. It is used against
ectoparasites, which are insects that live on the outside of host
animals such as sheep, goats, horses, pigs, and poultry. It is
added to cattle and poultry feed to control the development of
fly larvae that breed in manure. It is also used as a dust, dip,
or spray to control mange, horn flies, and face flies of cattle.
Because of its low toxicity to fish, it is also used in water as
an agent to control mosquito larvae. Coumaphos is considered a
selective insecticide because it kills specific insect species
while sparing other non-target organisms.
Formulation: It is
added to catte and poultry feed to control the development of fly
larvae that breed in manure. It is also used as a dust, dip, or
spray to control mange, horn flies, and face flies of cattle.
Because of its low toxicity to fish, it is also used in water as
an agent to control mosquito larvae.
- Acute toxicity: Coumaphos is highly
toxic by ingestion, and moderately toxic by inhalation
and dermal absorption . As with all organophosphates,
coumaphos is readily absorbed through the skin. Skin and
eye contact with this insecticide may cause mild
irritation, as well as cholinesterase inhibition.
Coumaphos does not cause skin sensitization allergies
. Toxic symptoms in humans are largely caused by the
inhibition of cholinesterase. Individuals with
respiratory ailments, impaired cholinesterase production,
or with liver malfunction may be at increased risk from
exposure to coumaphos. High ambient temperatures or
exposure to UV light may increase the toxicity of
coumaphos . Signs of poisoning include diarrhea,
drooling, difficulty in breathing, and leg and neck
stiffness . Some of the symptoms of acute inhalation
of coumaphos include headaches, dizziness and
incoordination. Moderate poisoning is characterized by
muscle twitching and vomiting. Severe poisoning is
indicated by diarrhea, fever, toxic psychosis, fluid
retention (edema) of the lungs, and high blood pressure.
Symptoms of sublethal poisoning may continue for 2 to 6
weeks . Some organophosphates may cause delayed
symptoms beginning 1 to 4 weeks after an acute exposure
that may or may not have produced immediate symptoms. In
such cases, numbness, tingling, weakness, and cramping
may appear in the lower limbs and progress to
incoordination and paralysis. Improvement may occur over
months or years, and in some cases residual impairment
will remain . The oral LD50 for coumaphos is 13 41
mg/kg in rats, 28 to 55 mg/kg in mice, 58 mg/kg in guinea
pigs, and 80 mg/kg in rabbits [8,2]. The dermal LD50 is
860 mg/kg in rats, and 500 to 2400 mg/kg in rabbits .
The 1-hour inhalation LC50 for coumaphos is 0.34 mg/L in
female and 1.1 mg/L in male rats .
- Chronic toxicity: Repeated or prolonged
exposure to organophosphates may result in the same
effects as acute exposure, including the delayed
symptoms. Other effects reported in workers repeatedly
exposed include impaired memory and concentration,
disorientation, severe depressions, irritability,
confusion, headache, speech difficulties, delayed
reaction times, nightmares, sleepwalking, and drowsiness
or insomnia. An influenza-like condition with headache,
nausea, weakness, loss of appetite, and malaise has also
been reported .
- Reproductive effects: Once in the
bloodstream, coumaphos may cross the placenta. Mice fed
coumaphos at a dietary level of 100 mg/kg/day exhibited a
decrease in the number of pregnancies, litter size, and
surviving offspring. No reproductive effects were
observed in three generations of mice fed dietary doses
of 1.25 mg/kg/day . Coumaphos is unlikely to cause
reproductive effects in humans at expected exposure
- Teratogenic effects: Based on studies
with rats and rabbits, coumaphos does not appear to be
teratogenic . No developmental effects occurred in
rat offspring at maternal doses up to 25 mg/kg/day.
Similar results were observed when pregnant rabbits were
given doses of up to 18 mg/kg/day on days 7 to 19 of
pregnancy . No increase in embryonic deaths or
teratogenesis was observed in heifers given dermal
applications of coumaphos during various stages of
- Mutagenic effects: Gene mutations and
DNA damage studies performed on bacterial cultures showed
no evidence of mutagenicity [18,54].
- Carcinogenic effects: Coumaphos was not
found to be carcinogenic in tests done on mice and rats.
There was no increase in the number of tumors reported in
rats given doses of 1.25 or 5 mg/kg/day of coumaphos in a
2-year chronic feeding study .
- Organ toxicity: Coumaphos primarily
affects the nervous system through cholinesterase
inhibition, the blockage of an enzyme required for proper
nerve functioning. No organ effects were seen in acute or
chronic studies of coumaphos.
- Fate in humans and animals: Following
oral administration to mammals, coumaphos is rapidly
broken down into nontoxic products which are eliminated
in urine and feces with no evidence of bioaccumulation
. Some 70% of an oral dose given to rats was
eliminated in 7 days. With dermal doses, 5% was
eliminated. Single oral doses produced no changes in
metabolism and no evidence of bioaccumulation in rats
. Coumaphos was found in the milk of dermally treated
cows . Unchanged coumaphos and other breakdown
products were found in the excreta of hens that were
dusted with the insecticide. Similar results were found
after oral treatment of hens with coumaphos .
- Effects on birds: Coumaphos is highly
toxic to birds . The symptoms of acute toxicity in
mallards given a dietary concentration of 29.8 mg/kg
include spraddle-legged walking, wing twitching, wing
drop, tearing of the eyes, and spread wings. These
symptoms persisted in some survivors for up to 13 days,
accompanied by weight loss. Death usually occurred
between 2 and 12 hours after treatment. Severe acute
toxicity, and eventual death, was caused in hens after
they were given daily oral doses of 10 mg/kg/day for 1 to
8 days. Hens given single oral doses of 50 mg/kg
recovered from the initial effects of cholinesterase
inhibition and developed signs of delayed nerve poisoning
. The oral LD50 for coumaphos is 3 mg/kg in wild
birds, 29.4 mg/kg in mallard ducks, 7.94 mg/kg in
pheasants, and 14 mg/kg in chickens [8,13].
- Effects on aquatic organisms: Coumaphos
is moderately toxic to fish and highly toxic to aquatic
invertebrates . The LC50 (96-hour) in channel catfish
is 0.8 mg/L, in largemouth bass is 1.1 mg/L, and in
walleye is 0.8 mg/L [27,13]. The LC50 (96-hour) in
rainbow trout is 5.9 mg/L, in bluegill sunfish is 5 mg/L,
and in freshwater invertebrates (amphipods) is 0.00015
mg/L . Coumaphos tends to accumulate slightly in
fish. For example, bluegill sunfish showed a
bioconcentration factor of 331 times the ambient water
concentration; however, mortality was high among the fish
at the concentrations tested (0.1 mg/L).
- Effects on other organisms: Coumaphos
poses a moderate hazard to honeybees and a slight hazard
to other beneficial insects .
- Breakdown in soil and groundwater: Based
on the general characteristics of organophosphates,
coumaphos is expected to have low to moderate persistence
in soil. Coumaphos was relatively immobile in a sandy
loam soil and is unlikely to contaminate groundwater. A
general characteristic of organophosphates such as
coumaphos is that they bind fairly well to soil
particles. Therefore, they do not readily move (leach)
with water percolating through the soil .
- Breakdown in water: Coumaphos is
resistant to breakdown in water (hydrolysis). It is
nearly insoluble in water, and is stable over a wide pH
- Breakdown in vegetation: No data are
- Appearance: Technical coumaphos is a tan
crystalline solid with a slight sulfur odor .
- Chemical Name:
- CAS Number: 56-72-4
- Molecular Weight: 362.50
- Water Solubility: i.s. in water ;
1.5 mg/L at 20 C 
- Solubility in Other Solvents: acetone
s.s.; chloroform s.s.; ethanol s.s. 
- Melting Point: 90-92 C (technical) 
- Vapor Pressure: 0.013m Pa @ 20 C 
- Partition Coefficient: Not Available
- Adsorption Coefficient: Not Available
- ADI: Not Available
- MCL: Not Available
- RfD: Not Available
- PEL: Not Available
- HA: Not Available
- TLV: Not Available
Shawnee Mission, KS 66201
- Phone: 913-631-4800
- Emergency: Not Available
References for the information in this PIP can be found in
Reference List Number 5
information in this profile does not in any way replace or
supersede the information on the pesticide product labeling or
other regulatory requirements. Please refer to the pesticide