抄録
Trihalomethanes (THMs) are bi products formed when natural organic materials react with chlorine used to treat water. Chlorine has been used globally to disinfect water for almost a century. Its use has been instrumental in eliminating plagues such as cholera and typhoid and reducing the incidence of intestinal illness caused by waterborne pathogens.
Chlorodibromomethane (CDBM) is currently classified as a group 3 carcinogen by the U.S. EPA (1997) and by IARC as group 3 (1991). There is currently evidence of hepatocellular adenomas and carcinomas in mouse chronic gavage studies. However in rats no tumour incidences are reported and negative results were obtained in the mouse bone marrow micronucleus test and the rat liver UDS test and so CDBM has been assessed as a non-genotoxic carcinogen. However, studies by Sekihashi et al. (2002) using the in vivo COMET assay gave positive results in the multiple tissues, including liver, in both rats and mice. Clearly throwing some doubt upon the hazard assessment of CDBM. The aim of this study was to investigate the COMET assay in rats using the protocols defined by the IWGT guidelines (Burlinson et al (2006)) and the liver UDS assay.
Rats were dosed twice orally at the MTD and 0.5xMTD, the second dose being administered approximately 14 hours after the first dose with perfusion of the livers approximately 2 hours post second dose. Glandular stomach, bone marrow, peripheral blood, duodenum, jejunum, ileum, testes were then assessed for DNA damage using the comet assay and the isolated hepatocytes using the COMET and UDS assays.
