Sumiko Koikawa-Mutoh*, Takashi Someya**, Ayako Tachifuji*, Yasushi Matsufuji*, Masataka Hanashima*

*Faculty of Engineering, Fukuoka University
**Department of Microbiology, School of Medical Technology, University of Occupational & Environmental Health

+ Correspondence should be adressed to Sumiko Mutoh:
(53-2, Wakakusa 406, Kitanosyo-cho, Nara 630 Japan)

Abstract

Mutagenicity in solvent extracts of leachate from a municipal solid waste landfill was characterized by the Ames assay using five tester strains of Salmonella typhimurium. Of 36 leachate samples, 12 (33%) showed significant mutagenicity for both tester strains TA98 and TA100, and 3 (8%) for TA98 but not for TA100. The mutagenicity of these leachate samples was observed mostly without metabolic activation by liver homogenates from rats (S9) . Further examinations with selected samples showed mutagenicity for TA1537, a frameshift mutant, but not for TA1535, a base-pair mutant, nor TA1977, a frameshift mutant which had an excision repair system. The increase in a concentration of S9 up to 150 [micro]l/plate caused the decrease in mutagenicity for both TA98 and TA100 down to 40%-70%. The addition of a low concentration of S9 (20 [micro]l/plate), however, decreased markedly bactericidal effects observed under higher concentrations of extracts than ca. 250 [micro]g/plate. These results indicate the active ingredients of leachate extracts consisted mainly of direct mutagens which induce frameshift mutation by reacting with Salmonella DNA with covalent bond.

Key words: Ames Salmonella assay, landfill, leachate, municipal solid waste, mutagen