Imidacloprid - Toxicology

Toxicology

Based on laboratory rat studies, imidacloprid is rated as "moderately toxic" on an acute oral basis to mammals and low toxicity on a dermal basis by the World Health Organization and the United States Environmental Protection Agency (class II or III, requiring a "Warning" or "Caution" label). It is rated as an "unlikely" carcinogen and as weakly mutagenic by the U.S.EPA (group E). It is not listed for reproductive, or developmental toxicity, but is listed on EPA's Tier 1 Screening Order for chemicals to be tested under the Endocrine Disruptor Screening Program (EDSP). Tolerances for imidacloprid residues in food range from 0.02 mg/kg in eggs to 3.0 mg/kg in hops.

Animal toxicity is moderate when ingested orally and low when applied dermally. It is not irritating to eyes or skin in rabbits and guinea pigs (although some commercial preparations contain clay as an inert ingredient, which may be an irritant). The acute inhalation LD₅₀ in rats was not reached at the greatest attainable concentrations, 69 milligrams per cubic meter of air as an aerosol, and 5,323 mg a.i./m³ of air as a dust. In rats subjected to a two-year feeding study, no observable effect was seen at 100 parts per million (ppm). In rats, the thyroid is the organ most affected by imidacloprid. Thyroid lesions occurred in male rats at a LOAEL of 16.9 mg a.i./kg/day. In a one-year feeding study in dogs, no observable effect was seen at 1,250 ppm, while levels up to 2,500 ppm led to hypercholesterolemia and elevated liver cytochrome p-450 measurements.