Is pendimethlin approved for pastures to control weedy grasses?

Answer 1

Increases in alkaline phosphatase level and liver weight were produced in dogs fed 50 and 200 mg/kg for 2 years. No effects were observed at 12.5 mg/kg/day (2, 4). In a 90 day feeding study of rats, the NOEL was 500 ppm (40 mg/kg/day) (4). Slightly fewer offspring with decreased weight gain from weaning to maturity were observed in a 3-generation reproductive study of rats tested at levels up to 250 mg/kg. No effects were observed at 30 mg/kg (40 mg/kg) (2, 4). No birth defects and no toxic effects on fetuses occurred when pregnant rats were given 500 mg/kg, the highest dose tested. The NOEL and the highest dose tested in a teratology study with rabbits was 60 mg/kg (4). EPA reports that several mutagenicity studies, including tests on live animals and mammalian and bacterial cell cultures, have all shown that pendimethalin is not mutagenic (4). EPA is currently reviewing the carcinogenicity data for pendimethalin. Increases in alkaline phosphatase level and liver weight were produced in dogs fed 50 and 200 mg/kg for 2 years (2, 4). By 24 hours after the administration of 37 mg/kg of radio-labeled pendimethalin to rats, 90.3% of the dose was recovered in the feces and urine. After 96 hours, 95.8% of the dose was recovered in the urine (20.9%) and feces (74.9%). When a lower dose was administered (7.3 mg/kg), 99.8% was recovered in the urine (21.8%) and feces (78.0%) after 12 hours. After 96 hours, residues were less than 0.3 ppm in all body tissues except fat, which had 0.9 ppm. This study indicates that ingested pendimethalin is largely unabsorbed by the bloodstream and excreted through the feces. Pendimethalin which does become absorbed into the bloodstream from the gastrointestinal tract is rapidly metabolized in the kidneys and liver and is then excreted in the urine (7).