A carcinogenesis bioassay of blocky (nonfibrous) tremolite was conducted with male and female F344/N rats. Tremolite was administered at a concentration of 1% in pelleted diet for the entire lifetime of the rats, starting with the dams of the study animals. The studies were started in 1978 and ended in 1981. Group sizes were 118 male and female controls and 250 male and female tremolite-exposed rats.
Litter size was not effected by the administration of tremolite to the dams. The offspring from mothers exposed to tremolite were the same size at birth as the controls but were slightly smaller at weaning and remained so throughout their life. Survival was similar in the exposed and control groups. No toxicity or increase in incidence of neoplasia was observed in the tremolite-exposed animals compared with the concurrent controls.
Conclusions: Under the conditions of these feed studies, nonfibrous tremolite was not overly toxic or carcinogenic for male or female F344/N rats, following lifetime ingestion of a diet containing 1% tremolite.