Carcinogenicity study of the pesticide maleic hydrazide in mice.

The carcinogenicity of the pesticide maleic hydrazide (MH) was studied in C57BL/B6 mice. After subcutaneous (s.c.) administration no significant increase in the incidence of liver-cell tumours was seen over that in solvent-treated controls, and although a statistically significant difference in the incidence of liver-cell tumours was observed between treated and untreated males, this was considered biologically inadequate as evidence of carcinogenic effect. When MH was administered orally, no significant increase in the incidence of liver-cell tumours was seen. These results partially confirm the negative finding of a recent parallel study in rats [1].