[Biodegradation of herbicide chlornitrofen (CNP) and mutagenicity of its degradation products].

Mutagenicities of three diphenyl ether-derived herbicides, chlornitrofen (CNP), nitrofen and chlormethoxynil, and their amino derivatives were assayed by the Ames test using TA98, TA100 and YG strains, recently developed tester strains. As for CNP, mutagenicities of its biodegradation products were also assayed, and biodegradation of CNP and change in mutagenic potency were examined using river water to which CNP was added. CNP was weakly mutagenic in YG1029, and nitrofen was weakly mutagenic in YG1029, while highly mutagenic in YG1026. But neither of three herbicides were mutagenic using TA98 and TA100. All of their amino derivatives were mutagenic especially in YG1024 and YG1029, acetyltransferase-rich mutants of TA98 or TA100. In YG1029, mutagenic potency of the amino derivatives was relatively high compared with that of each parent compound. Concerning biodegradation products of CNP, amino-CNP was highly mutagenic and acethylamino-CNP was moderately mutagenic in YG 1026, but others were non-mutagenic. In river water, CNP was degraded rapidly and converted to amino-CNP. Change in mutagenicity of river water to which CNP was added seemed to reflect changes in amino-CNP concentration in river water. Therefore, assessing health impact of chemicals released in natural environment, their degradation products must be considered along with parent compounds.