Methylbromide: carcinogenic effects in the rat forestomach.

Methylbromide (MB) administered by oral gavage as a solution in arachis oil was carcinogenic to rats in a 90-day experiment. In 13 of 20 animals of the highest dose group, 50 mg MB/kg body wt squamous cell carcinomas of the forestomach developed. All animals of this group showed a marked diffuse hyperplasia of the epithelium of the forestomach. A less pronounced hyperplasia was observed in high and lower incidence with respectively 10 and 2 mg MB/kg body wt. The lowest dose, 0.4 mg MB/kg body wt was without effects.