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Bendiocarb Bendiocarb,
known to most consumers as Ficam DTM , is a widely used
carbamate insecticide with high acute toxicity. Due to AgrEvo’s,
bendiocarb manufacturer, request for voluntary cancellation of all
bendiocarb products on August 18, 1999, all products are being phased-out.
End use products used in and around homes have been prohibited to be sold
or distributed by the registrant since October 31, 2000 and all bendiocarb
products will be cancelled as of December 31, 2001 (U.S. EPA 1999). Data
gaps exists for acute and subchronic neurotoxicity studies in rats.
Occupational and residential exposure indicates risk of concern through
dermal and inhalation routes of exposure, especially for children and
workers. Usage
Consumers
are most familiar with Ficam DTM, a 1% dust, and Ficam WTM,
an 80% wettable powder, for use by professional applicators. Both
formulations are used in structural pest control against cockroaches,
ants, fleas and crickets. Ficam PlusTM, used with synergized
pyrethrins (NCAMP 1986). DycarbTM is registered for use on
plant insect pests like aphids, scale, whitefly, lace bugs and mealy bugs
on horticultural crops. TurcamTM is registered for use on turf
and ornamentals, and Turcam ULVTM, an ultra-low volume
formulation, is registered for mosquito control (U.S. EPA 1985). Toxicity
Carbamate
insecticides are nervous system poisons. They bind to the active site of
the enzyme acetylcholine esterase (AchE), which is necessary for normal
function of nerve impulses to other nerves and muscles. This causes an
accumulation of acetylcholine, an excitatory neurotransmitter, at nerve
muscle sites resulting in poisoning symptoms. Unlike their close
relatives, the organophosphates, examples of which include Dursban TM,
parathion, and diazinon, carbamates do not bind permanently to the enzyme
and can be “dislodged” from the active site, so that poisoning effects
are readily reversible, upon administration of the antidote atropine.
Carbamates, however, can be more acutely toxic. Bendiocarb has a
particularly high acute toxicity. The oral rat LD50 is
34-156mg/kg (lethal dose that will kill 50% of the test population); cats
are eight times more sensitive.
It is
suspected that carbamates can act at other sites in the nervous system as
well. Symptoms of poisoning include diarrhea, nausea, vomiting, stomach
cramps, sweating, blurred vision, muscle twitching or jerking, which last
only a few hours if exposure is interrupted. Continued exposure can result
in malaise, weakness and symptoms that mimic the flu. Because carbamates
dissociate so readily from AchE, blood tests for reduced activity of AchE
are of limited use in documentation of a poisoning episode. Bendiocarb
has been classified as a ‘Group E’ carcinogen by the EPA, showing no
evidence of carcinogenicity in laboratory animals or in humans (U.S. EPA
2000). Available information indicates that bendiocarb does not cause
reproductive effects or birth defects in animals. It can cause skin rashes
in rabbits, but is not a skin sensitizer. In one chronic study performed
in mice, hyperactivity and lenticular opacities (eye problems) are noted
in an interim report. There is no information on the outcome of this test.
Another chronic study performed on rats fed 10mg/kg/day showed various
changes in organ weights, blood, urine characteristics and increased
incidence of stomach and eye lesions. A metabolism study indicates that
bendiocarb clears within 3 hours in the urine of exposed men.
Moderate toxicity has been seen in birds with an LD50=3.1 mg/kg in
mallard ducks. Bendiocarb is also toxic to fish, earthworms and bees (U.S.
EPA 1985).
Environmental Fate
Other
insecticides of the carbamate class, aldicarb and carbofuran, are of
concern due to their demonstrated ability to contaminate groundwater.
According to an EPA official, information submitted in response to a Data
Call-In stated that bendiocarb is a potential leacher.
At pH
5, approximating that of rainwater, bendiocarb is fairly stable, showing
no appreciable breakdown after 30 days. Bendiocarb breaks down more
readily at more alkaline pHs, with a half-life of 10 days at pH 7, to
2,2-dimethyl1,3-benzodioxyl-4-ol, a phenol, and carbon dioxide. Bendiocarb
is metabolized by soil microorganisms in soils with organic content, but
in low-oxygen, low-organic content soils, this process is retarded. References: NCAMP.
1986. Pesticides and You. July. U.S.
EPA. 2000. List of Chemicals Evaluated for Carcinogenic Potential.
Office of Pesticide Programs. Washington, DC. U.S.
EPA. 1999. R.E.D. Facts: Bendiocarb. Office of Pesticide Programs.
Washington, DC.
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