Acute and subacute toxicity studies were conducted with paraquat (1,1'-dimethyl-4,4'-dipyridylium dimethylsulfate) in adult Sherman rats. The single-dose oral LD50 was 100 mg.kg in females. The 90-dose oral LD50 in female rats was 21 mg/kg, giving a chronicity factor of 5.2. The acute dermal LD50 was 80 mg/kg in male rats and 90 mg/kg in females. Studies of lung tissue with the electron microscope after a single oral dose indicate that the first discernible changes are pulmonary edema, swelling of the epithelium, an increase in collagen, and an effect on the ribosomes of the membranous pneumocytes. Light microscopic studies of lungs affected by paraquat after po and iv administration or local instillation showed intra-alveolar hemorrhage, edema, extensive fibrosis, and changes in the epithelium. Local instillation of 0.05 mg/kg of paraquat into lung and 0.8 mg/kg into skeletal muscle caused local fibrosis.

contained in PB-280 889 titled Journal Articles on Toxicology. Group 14.