Formation of non-volatile potent mutagens in domestic sewage by chlorination

XAD extracts obtained from chlorinated domestic sewage samples were evaluated for mutagenicity by Ames test. The sewage before chlorination did not show obvious mutagenicity in S. typhymurium TA 100. The sewage after chlorination exhibited dose-related mutagenic activity ( 5000 ∼ 30000 rev./ 1 ) in S. typhimurium TA 100 without S9 mix. The activity was enhanced 5 ∼ 50 fold over that of non-chlorinated sewage. Formation of both volatile and non-volatile mutagens by the chlorination of sewage was confirmed by a taped plate assay and Ames assay of the XAD extracts. It was estimated that the mutagens consisted of several substances from results of fractionation of the XAD extracts.