US EPA

29240 

Journal Article 

Inhalation toxicology and carcinogenesis studies of methylene chloride (dichloromethane) in F344/N rats and B6C3F1 mice 

Mennear, JH; McConnell, EE; Huff, JE; Renne, RA; Giddens, E 

1988 

Yes 

Annals of the New York Academy of Sciences
ISSN: 0077-8923
EISSN: 1749-6632 

534 

343-351 

English 

3389664 

10.1111/j.1749-6632.1988.tb30121.x 

The findings of the National Toxicology Program (NTP) 2 year inhalation studies of methylene-chloride (75092) (MC) in rodents were reported. Groups of 50 male and 50 female F344-rats were exposed to 1000, 2000, or 4000 parts per million (ppm) of MC for 6 hours per day, 5 days per week, for 102 weeks. Similar groups of B6C3F1-mice were exposed to 2000 or 4000ppm concentrations 6 hours a day, 5 days a week for 102 weeks. Mammary gland neoplasms were produced in both male and female rats and lung and liver neoplasms in male and female mice. A marginal increase was noted in male rats to subcutaneous tissue fibromas in the region of the mammary chain, which probably arose from mammary tissue. The mammary gland neoplasms of the female rats were clearly associated with the administration of MC. These observations in females lend support to the importance of MC associated increased incidences of mammary gland tumors in male rats. A high incidence of mononuclear cell leukemia was noted in all groups of male rats. Survival of females at 4000ppm was reduced, possibly because of a MC related increase in the incidence of leukemia. Dose related increases in the incidences of squamous metaplasia of the mucosal epithelium of the nasal cavity, renal tubular cell degeneration, and splenic fibrosis were noted and were interpreted to be related to the administration of MC. No treatment related neoplasms were observed in these tissues. In mice there were increased incidences of alveolar/bronchiolar and of hepatocellular adenomas and carcinomas in exposed groups of both males and females. MC produced hepatocellular degeneration and hepatocellular neoplasms in male and female mice. Exposed mice also experienced increased incidences of hemangiomas or hemangiosarcomas.