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Imidacloprid Imidacloprid
is a systemic, chloro-nicotinyl insecticide used for the control of sucking
insects such as fleas, aphids, whiteflies, termites, turf insects, soil
insects, and some beetles. It has not been fully evaluated for human health
and environmental effects. Mode of ActionIt
causes a blockage in a type of neural pathway that is more abundant in
insects than in warm-blooded animals, leading to an accumulation of acetylcholine,
a neurotransmitter, and resulting in the insect's paralysis and eventual
death. It is effective on contact and via stomach action. ToxicityImidacloprid
is classified by the Environmental Protection Agency (EPA) as both a toxicity
class II and class III pesticide (on a scale of I to IV, I being the highest
toxicity class), and must be labeled with the signal word "Warning"
or "Caution." Symptoms
of acute exposure are expected to be fatigue, twitching, cramps, and muscle
weakness including the muscles necessary for breathing. The LD50
is 450 mg/kg body weight in rats and 131 mg/kg in mice.
The 24-hour dermal LD50 in rats is >5,000 mg/kg.
The airborne concentration that resulted in mortality to half of the test
organisms (LC50) is >69 mg/meters cubed air in the form of an aerosol,
and >5323 mg/meters cubed in air in the form of dust. It is considered
non-irritating to eyes and skin, and non-sensitizing to skin, though some
granular formulations may contain clay as an inert ingredient, which may
act as an eye irritant. In
a study of rats fed up to 1,800 parts per million (ppm), the NOEL (No
Observable Effect Level) was found to be 100 ppm, with adverse effects
including decreased body weight gain in females at 900 ppm and 300 ppm
in males. A study of dogs fed up to 2,500 ppm resulted in a NOEL of 1,250
ppm, with adverse effects including some stress to the liver and increased
blood cholesterol levels. A reproduction study in rats fed up to 700 ppm
resulted in a NOEL of 100 ppm based on decreased pup body weight observed
at the 250-ppm dose level. A developmental toxicity study in rats given
doses up to 100 ppm during days 6 to 16 of gestation resulted in a NOEL
of 30 mg/kg/day based on skeletal abnormalities observed at the next highest
dose tested. Another developmental toxicity study with rabbits given doses
of imidacloprid during days 6 through 19 of gestation resulted in a NOEL
of 24 mg/kg/day based on decreased body weight and skeletal abnormalities
at the highest dose tested. Imidacloprid
was found to be weakly mutagenic, testing positive for causing changes
in human lymphocyte chromosomes and for genotoxicity in Chinese hamster
ovary cells. It categorized as a "Group E" carcinogen (evidence
of noncarcinogenicity for humans) by EPA. In feeding studies in rats,
very high doses of imidacloprid were associated with thyroid lesions. Imidacloprid
is quickly and nearly completely absorbed from the gastrointestinal tract
and eliminated in urine and feces.
Imidacloprid can be phytotoxic when not used according to the manufacturer's
specifications. Ecological EffectsIt
is considered toxic to upland game and birds, of moderately low toxicity
to fish, and highly toxic to bees if used as a foliar application, especially
during flowering. Environmental FateIn
soil, Imidacloprid has a half-life of 48-190 days, breaking down more
quickly in soils with plant ground cover. It degrades into the primary
metabolite 6-chloronicotinic acid, which eventually breaks down into carbon
dioxide. There is low risk for groundwater contamination, it is moderately
soluble, and has moderate binding affinity to organic materials in soil.
The half-life in water is myth greater than 31 days at a pH of 5, 7, and
9. Reference: Extension
Toxicology Network (ETN). 1995. Pesticide Information Profiles: Imidacloprid.
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BEYOND PESTICIDES |
