The genotoxicity of the waste water discharged from paraquat manufacturing and its pyridyl components.

The genotoxic potencies of waste water condensate from paraquat manufacturing and its pyridyl components on V79 cells were evaluated using the alkaline elution assay and 6-thioguanine resistance mutation assay. Although 2,2'-dipyridyl and 2,2',2"-tripyridyl both were highly cytotoxic to the cells, only 2,2'-dipyridyl induced moderate DNA-cleaving activity and a low frequency of thioguanine resistance mutation in V79 cells. However, equally toxic doses of waste water condensate exhibited highly DNA-damaging and mutagenic activities in the same cell system. After chelation of ferrous ions, the number of DNA lesions and frequency of 6-TGr mutations induced by waste water condensate were slightly suppressed, whereas by contrast those induced by 2,2'-dipyridyl were significantly potentiated. These results indicate that the coordination compound formation of pyridyl derivatives of waste water with metal ions, especially ferrous ions, in biological systems may be closely related to these genotoxic mechanisms. Finally, it was found that DMSO (a scavenger of hydroxyl radical) and catalase could remarkably protect cells from genotoxic damage induced by waste water condensate, 2,2'-dipyridyl and their ferrous complexes, but this protection was not observed in cells which were treated with SOD (superoxide dismutase). This suggests that the generation of some unknown active oxygen species may be involved in the genotoxic mechanisms of waste water condensate and its constituent 2,2'-dipyridyl.