(SevinTM) is said by EPA to be “one of the most widely applied
insecticides in the US,” since use began in 1959, with 10-15 million pounds
used annually. This widespread use is a major reason why carbaryl may
pose more dangers than most other pesticides. Manufactured by Union Carbide,
this broad-spectrum insecticide is used on a variety of crops, in forestry
and on ornamentals, in home gardens, and on livestock and pets. One manufacturing
method uses methyl isocyanate (MIC), the agent responsible for thousands
of deaths in Bhopal, India when a Union Carbide plant leaked the deadly
1980, five years after the special review process was initiated due to
concerns regarding teratogenicity, fetotoxicity, mutagenicity,
oncogenicity, neurotoxicity, and viral enhancement, the review was
abruptly withdrawn. Criticizing the action, Janette Sherman, M.D., then a
member of EPA’s Advisory Committee on Toxic Substances, commented that,
“it was a political and economic decision.” In April 1991, during an
assessment of data needs for the reevaluation process (reregistration),
EPA concluded that there were serious data gaps in all disciplinary areas,
including chronic toxicity studies, carcinogenicity studies in rats and
mice and a teratogenicity study in dogs. Nonetheless, there is an
extensive body of literature on the toxicity of carbaryl.
a carbamate, is a contact nerve toxin that inhibits the enzyme
cholinesterase, with a resulting disruption of nerve impulse
routine use of insecticides, such as carbaryl, in the home where they
contaminate indoor air and do not readily dissipate, exposes a substantial
proportion of the population, particularly the young and the elderly, to
considerable risk. Carbaryl is considered very toxic, with a rat oral LD50
(dose needed to kill 50% of the test population) of 225 mg/kg. The World
Health Organization has established an acceptable daily intake (ADI) of
0.01 mg/kg/day, while EPA’s ADI is 0.1 mg/kg/day. Carbaryl is readily
absorbed through the skin, with almost total absorption through the
forearm and scrotum. A skin sensitizer in guinea pigs, it causes allergic
dermatitis in dogs, and dermatitis and acute irritations in humans. Acute
signs and symptoms of carbaryl poisoning include blurred vision, nausea,
headache, salivation, breathing difficulties, muscle twitching, and
causes an array of serious neurotoxic effects in animals, including
irreversible neurological damage and behavioral disturbances. Humans and
cats develop aggressive behavior with irritability, paranoia and physical
assaults, while learning and response rates are slowed in rats given small
doses. Physicians may often fail to diagnose carbaryl poisoning. In one
case, despite the “opinions of an internist, cardiologist, neurologist
and orthopedist, it was an observation by the patient’s wife that
established the diagnosis of carbaryl poisoning.
long ago as 1969, a Health Education and Welfare Department (HEW) report
recommended that the use of carbaryl “should be immediately restricted
to prevent risk of human exposure,” because low doses cause birth
defects when given to pregnant dogs. So far, the HEW warning has been
ignored. Carbaryl is also a mutagen, toxic to the kidney and liver,
damages ovaries and testes, and causes behavioral problems in humans and
animals. Children, women, pregnant women, older persons, and those whose
health is compromised are particularly susceptible to carbaryl’s
1975, EPA concluded that “carbaryl has been shown to produce birth
defects in guinea pigs, rabbits and dogs; and fetotoxicity in mice, rats
and gerbils.” Defects included lack of intestines and failure to form
skeletal tissues. EPA felt that carbaryl was not a potent teratogen
because the effects generally occurred at levels that were toxic to the
pregnant animal. Carbaryl causes abortions in monkeys. It causes severe
effects on the formation of sperm in male rats and on the ovary of female
rats. Sperm abnormalities have been described in carbaryl production
workers as well. According to EPA, “The results of cytogenetic tests
imply that carbaryl may induce chromosomal effects in mammalian cells in
culture, in whole animals, and in plants, and carbaryl has been shown to
cause primary DNA damage in cultured human cells.” Despite this and the
human evidence of spermatogenic effects, the agency concludes that it
“probably only acts as a weak mutagen.” EPA’s Scientific Advisory
Panel recommended that carbaryl carry a warning regarding the hazard to
pregnant women. However, only a warning not to use carbaryl on pregnant
dogs appears on the label.
years, EPA accepted invalid rat and mice carcinogenicity studies as
showing that carbaryl was not carcinogenic. The agency stated that
although individually the studies were unacceptable, collectively they
provided sufficient evidence of non-carcinogenicity. In 1991, EPA reversed
itself and issued a data call-in on both carcinogenicity studies. The
breakdown product nitrosocarbaryl, formed in the stomach, is highly
mutagenic and carcinogenic.
Carbaryl is highly toxic to bees, killing more bees in California than any other pesticide. It is highly toxic to aquatic invertebrates, LC50 is 6.4 ppb (parts per billion) for Daphnia (the common water flea), and its breakdown product, alpha-naphthol, is quite toxic to mollusks and other estuarine organisms. Moderately toxic to fish (LC50 is 1.95-6.76 ppm), it may also bioaccumulate. Carbaryl acts synergistically to increase the toxicity of other pesticides such as 2,4-D, rotenone or pentachlorophenol in trout.
W.K. 1981. “Effects of carbaryl on variable interval response rates in
rats.” Neurobehavioral Toxicology 2:21-24.
D. 1986. “Aggression in cat and human precipitated by a cholinesterase
inhibitor.” Psychosomatics 27:535-536.
R.A. 1986. “Is carbaryl as safe as its reputation? Does it have a
potential for causing chronic neurotoxicity in humans?” American
Journal of Medicine 80:659-664.
C.P. et al. 1961. “Mammalian toxicity of 1-naphthyl-N-methyl carbamate (Sevin
insecticide).” Journal of Agriculture Food Chemistry 9:30-39.
W.J. 1971. “The effect of carbaryl on reproduction in the monkey.” Toxicology
Applications in Pharmacology 19:365.
M.J. et al. 1988. “Medical toxicology: diagnosis and treatment of human
poisoning.” Elsevier Science Publishing Co., Inc. New York.
Toxicology Network (EXTOXNET) Pesticide Information Profiles. 2001. “Carbaryl.”
W. 1978. “Carcinogenesis by nitroso derivatives of methylcarbamate
insecticides and other nitrosamides in rats and mice. In: Environmental
aspects of N-nitroso compounds.” IARC Scientific Publishing
A.I. et al. 1971. Vopr. Pitan. 30:42-49.
J.M. 1973. “Decreased performance behavior with carbaryl-an indication
of clinical toxicity.” Clinical Toxicology 6:97-108.
H.E. et al. 1968. “Teratogenic action of carbaryl in Beagle dogs.” Toxicological
Applications in Pharmacology 13:392-403.
H.E. et al. 1969. “The effects of chronic carbaryl administration on the
neuromuscular system of swine.” Toxicological Applications in
C.N. et al. 1975. “Potentiation of the acute toxicity of several
pesticides and herbicides in trout by carbaryl.” Toxicological
Applications in Pharmacology 34:83-87.
J.H. et al. 1968. “Effects of oral doses of carbaryl on man.” Clinical
A.J. et al. 1981. Environmental Health Perspective 40:255-265.
Department of Health Education and Welfare. 1969. “Report of the
secretary’s commission on pesticides and their relationship to
environmental health.” Washington D.C.
EPA. 1991. “Reregistration Eligibility Document: carbaryl.” Office of
Pesticide Programs. Washington D.C. <http://www.epa.gov/oppsrrd1/REDs/>.
EPA. 1991. “Data call-in chemical status sheet: carbaryl.”
EPA. 1991. “Personal communication with OPP/RD product manager.”
EPA. 1984. “Chemical Factsheet for carbaryl.” Office of Pesticide
Programs. Washington D.C.
EPA. 1983. “Guidance for the reregistration of manufacturing-use and
certain end-use pesticide products containing carbaryl.” Office of
Pesticide Programs. Washington D.C.
EPA. 1980. “Determination not to initiate a rebuttable presumption
against registration of pesticide products containing carbaryl.” 45 FR
U.S. EPA. 1975. “Pesticide Fact Sheet: carbaryl.” Washington D.C.