Hepatocarcinogenicity of the herbicide maleic hydrazide following parenteral administration to infant Swiss mice

Random-bred infant Swiss mice were injected subcutaneously with maleic hydrazide in aqueous solution or tricaprylin suspension in varying doses. Maleic hydrazide in excess of 0.5 mg on the first day of life was lethal. Following a total maleic hydrazide dosage of 55 mg in the first 3 weeks of life, there was a high incidence of hepatomas, 65% of 26 male mice alive at 49 weeks, in contrast to solvent controls, 8% of 48 male mice. On the basis of these data, it is necessary to consider the possibility of carcinogenic hazard to man due to exposure to maleic hydrazide residues in root crops and tobacco.