Mutagenicity of monochlorodibenzofurans detected in the environment.

Recently, monochlorodibenzofuran, which is formed by the reaction of dibenzofuran with residual chlorine, has been detected in tap water in one region of Japan. The mutagenicities of 1-, 2-, 3-, and 4-chlorodibenzofuran were tested using Salmonella typhimurium TA98 and TA100. 1-Chlorodibenzofuran and 4-chlorodibenzofuran proved to be practically non-mutagenic, while 2-chlorodibenzofuran was weakly mutagenic. Unlike these three isomers, 3-chlorodibenzofuran was markedly mutagenic, and the intensity of its mutagenicity in TA98 was about one-fifth and in TA100 about one-twentieth of that of benzo[a]pyrene.