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EXTOXNET PIP - IMIDACLOPRID Page 2 of 4 ,*.e %000 (223), and 131 mg/kg in mice (1). The 24-hour dermal LD50 in rats is >5,000 mg/kg. It is considered non-irritating to eyes and skin (rabbits), and non-sensitizing to skin (guinea pigs) (1). Some granular formulations may contain clays as inert ingredients that may act as eye irritants. In acute inhalation toxicity tests with rats, the airborne concentration of imidacloprid 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 air in the form of dust. These values represent the maximum attainable airborne concentrations (1). • Signs and Symptoms of Poisoning: Although no account of human poisoning was found in the literature, signs and symptoms of poisoning would be expected to be similar to nicotinic signs and symptoms, including fatigue, twitching, cramps, and muscle weakness including the muscles necessary for breathing (330). • Chronic Toxicity: A 2-year feeding study in rats fed up to 1,800 ppm resulted in a No Observable Effect Level (NOEL) of 100 ppm (5.7 mg/kg body weight in males and 7.6 mg/kg in females). Adverse effects included decreased body weight gain in females at 300 ppm, and increased thyroid lesions in males at 300 ppm and females at 900 ppm. A 1-year feeding study in dogs fed up to 2,500 ppm resulted in a NOEL of 1,250 ppm (41 mg/kg). Adverse effects included increased cholesterol levels in the blood, and some stress to the liver(measured by elevated liver cytochrome p-450 levels) (331). • Reproductive Effects: A three generation reproduction study in rats fed up to 700 ppm imidacloprid resulted in a NOEL of 100 ppm (equivalent to 8 mg/kg/day) based on decreased pup body weight observed at the 250 ppm dose level (331). • Teratogenic Effects: A developmental toxicity study in rats given doses up to 100 ppm by gavage on 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 of 100 ppm) (329). In a developmental toxicity study with rabbits given doses of imidacloprid by gavage during days 6 through 19 of gestation, resulted in a NOEL of 24 mg/kg/day based on decreased body weight and skeletal abnormalities observed at 72 mg/kg/day (highest dose tested) (331). • Mutagenic Effects: Imidacloprid may be weakly mutagenic. In a battery of 23 laboratory mutagenicity assays, imidacloprid tested negative for mutagenic effects in all but two of the assays. It did test positive for causing changes in chromosomes in human lymphocytes, as well as testing positive for genotoxicity in Chinese hamster ovary cells (331). • Carcinogenic Effects: Imidacloprid is considered to be of minimal carcinogenic risk, and is thus categorized by EPA as a "Group E" carcinogen (evidence of noncarcinogenicity for humans). There were no carcinogenic effects in a 2-year carcinogenicity study in rats fed up to 1,800 ppm imidacloprid (328). • Organ Toxicity: In short-term feeding studies in rats, there were thyroid lesions associated with very high doses of imidacloprid (331). • Fate in Humans and Animals: Imidacloprid is quickly and almost completely absorbed from the gastrointestinal tract, and eliminated via urine and feces (70-80% and 20-30%, respectively, of the 96% of the parent compound administered within 48 hours). The most important metabolic steps include the degradation to 6-chloronicotinic acid, a compound that acts on the nervous system as described above. This compound may be conjugated with glycine and eliminated, or reduced to guanidine (1). ECOLOGICAL EFFECTS • Effects on Birds: Imidacloprid is toxic to upland game birds. The LD50 is 152 mg/kg for bobwhite quail, and 31 mg/kg in Japanese quail (223, 1). In studies with red-winged blackbirds and brown-headed cowbirds, it was observed that birds learned to avoid imidacloprid treated seeds after experiencing transitory gastrointestinal distress (retching) and ataxia(loss of coordination). It was concluded that the risk of dietary exposure to birds via treated seeds was minimal. Based on http://extoxnet.orst.edu/pips/imidaclo.htm 11/22/2004