Major origin of mutagenicity of chlorinated drinking water in China: humic acid or pollutants

Since Loper and Glatz (J. Toxicol. Environ. Health, 4;919–938;1978) discovered the presence of the mutagenicity in drinking water after chlorination in 1978, humic acid (HA) has been considered as an important source. But our research results show that only View the MathML source of observed direct frameshift mutagenicity in tap water originated from chlorination of HA isolated from raw water. Contamination from industrial waste and human settlement (night soil) are important potential sources of mutagenicity in chlorinated drinking water. The results show that mutagenicity from night soil after chlorination depended upon pH of sample. Production of mutagenicity at pH 6 is ten times of that at pH 8, and decomposition process is necessary condition for mutagenicity production. Season variation of mutagenicity of tap is also presented in the paper.