Long-term carcinogenicity bioassays on methylene chloride administered by ingestion to Sprague-Dawley rats and Swiss mice and by inhalation to Sprague-Dawley rats.

ABSTRACT

Methylene chloride was administered to Sprague-Dawley rats and Swiss mice by ingestion (stomach tube), in olive oil, at the doses of 500, 100 and 0 mg/kg body weight, once daily, 4-5 days weekly, for 64 weeks, and to Sprague-Dawley rats by inhalation, at the concentration of 100 and 0 ppm, 7 hours daily, for 5 days weekly. The inhalatory treatment was started on 13-week-old breeders, and male and female offspring (12-day embryos). The breeders and part of the offspring were exposed for 104 weeks; the other part of the offspring was exposed for 15 weeks only. The most important findings were (1) the increased incidence of pulmonary tumors in male mice treated by ingestion at 500 mg/kg body weight; (2) a not-significant increase in total malignant tumors in rats exposed by inhalation at 100 ppm for 104 weeks; and (3) a not-significant increase in total malignant mammary tumors in female rats given methylene chloride by ingestion at 500 mg/kg body weight.