Genotoxic evaluation of the herbicide paraquat in cultured human lymphocytes

The widely used herbicide paraquat was evaluated for genotoxicity in peripheral blood human lymphocyte cultures. Sister-chromatid exchanges (SCE), chromosome aberrations (CA), and micronuclei (MN) were scored as genetic endpoints. Paraquat was administered either alone or in combination with an external source of metabolic activation. Our data indicate that paraquat induced slight but significant increases in the frequency of SCE. This genotoxic effect was not modified by cotreatments with S9 fraction from rat liver. However, paraquat did not increase the frequency of CA and MN, indicating that this bipyridylium compound is not effective in these assays, which would mean a general lack of effectiveness of the herbicide to induce clastogenic damage. In addition, cotreatments with the S9 fraction, did not modify the genotoxic ability detected in the SCE assay.