Glyoxal Derivatives as Ozonation Products: The Biodegradation, DNA Lesion in Rat Hepatocytes and the Occurrence in Water Purification Process.

The occurrence, biodegradation and DNA lesion of glyoxal derivatives as ozonation products, glyoxal and methylglyoxal were compared from the viewpoint of consequences for human health effect. The ozonation of three kinds of humic acids from different origins resulted in the tendency of more formation of glyoxal than methylglyoxal. Methylglyoxal showed high basepair substitution mutagenicity but was easily decomposed by glyoxalase system or S9 mix, compared to glyoxal. In rat hepatocytes, glyoxal induced 2-3 times more apparent frequency of DNA single-strand breaks than methylglyoxal, while only methylglyoxal induced DNA crosslink at about 1/10 frequency of the DNA single-strand breaks. During the process of ozone treatment pilot-scale plant, glyoxal showed 2 times higher formation after ozonation than methylglyoxal, and the concentration after chlorination was higher than that of chlorinated water from the conventional process because of less elimination of glyoxal by granular activated carbon-filtration. Therefore, all the results indicate that glyoxal should be prior to methylglyoxal as regards the toxicological assessment of ozonation products in drinking water.