Toxicity of 2,6-dichloro-1,4-benzoquinone and five regulated drinking water disinfection by-products for the Caenorhabditis elegans nematode

Scarce toxicological data are available for 2,6-dichloro-1,4-benzoquinone (DCBQ), an emerging water disinfection by-product (DBP) that is of potential public health concern. This study investigated the effects of DCBQ on the lethality, respiration rate, and DNA damage in the Caenorhabditis elegans nematode. Meanwhile, the toxic effects of five regulated DBPs, dichloroacetic acid (DCA), trichloroacetic acid (TCA), monobromoacetic acid (MBA), dibromoacetic acid (DBA), and N-nitrosodimethylamine (NDMA), have also been evaluated. The tested DBPs increased the lethality and inhibited the respiration of C. elegans with an identical order of toxicity as follows: DCBQ > MBA > DBA > DCA > TCA > NDMA. The EC50 value (median concentration causing 50% reduction in respiration compared with untreated C. elegans) is at least 30-fold lower than the corresponding LC50 value (median lethal concentration). Exposure to DCBQ and NDMA, but not to MBA, DBA, DCA, or TCA, resulted in DNA damage to C. elegans. The study suggested that DCBQ was more potent in inducing general toxicity than some regulated DBPs, and it revealed the in vivo genotoxic effect of DCBQ. Furthermore, the C. elegans-based bioassays may provide potentially useful tools for the toxicology assessment and ranking of DBPs.