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Five pesticides (carbaryl, DDT, parathion, chlordimeform, and ametryne) were tested for their effects on the immunocompetence of Balb/c mice. All five of the test pesticides were observed to induce statistically significant suppression of the humoral immune response if administered orally, at near lethal doses, during an ongoing immune response. Ametryne and chlordimeform were also observed to have a suppressive effect on humoral immune competence if orally administered in a sufficiently large quantity, 1 LD50, at the time of, or prior to, immunization. Administration of 0.1 LD50 parathion per day, over an extended period of time, resulted in a statistically significant suppression of the humoral immune response.

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The mutagenic activity of chlordimeform and two of its breakdown products, 4-chloro-o-toludine and 4-chloro-N-formyl-o-toluidine were determined with five histidine dependent strains of Salmonella typhimurium (TA1535, TA1537, TA1538, TA98, TA100) and five tryptophan dependent strains of E. coli WP2 (WP2, WP2uvrA, WP67, CM611, CM571) with and without rat liver microsomal enzymes. 4-chloro-o-toluidine increased the number of the reversions of the S. typhimurium strain TA1535 more than two fold over spontaneous at the concentration of 400 micrograms/plate. The results of the DNA repair tests in the Salmonella TA1538/TA1978 and E. coli multirepair deficient systems showed that both breakdown products were active in inducing damage not repaired in at least one repair deficient strain while chlordimeform itself was inactive.