Assessing the potential mutagenicity of pesticides.

Determining mutagenic profiles of pesticides requires tests of high sensitivity and specificity. An effective strategy uses tests that produce reproducible and biologically relevant data based upon three stages. Stage 1, in vitro, uses (i) bacterial gene mutation assays, (ii) assays measuring clastogenicity and aneugenicity, and (iii) assays measuring the induction of gene mutations in cultured mammalian cells. Stage 1 can detect most mutagenic hazards. Stage 2, in vivo testing in somatic cells of rodents, is required to determine whether in vitro positives are reproduced in vivo and to detect activity only produced in intact animals. Decisions on assay selection should be based on the in vitro profile. In most cases in vivo assessment is based on the micronucleus assay in rodent bone marrow. Stage 3, in vivo germ-cell testing, is rarely required for pesticides that have been shown to be mutagenic in somatic cells in vivo.