Mutagenicity of exhaust gas from municipal waste incineration

The mutagenicity was bioassayed by the Ames test using TA98 and TA100 Salmonella strains with or without the S9 mixture. We developed a method obtaining samples of mutagenic substances in the exhaust gas from municipal waste incinerators. Mutagenic substances in the exhaust gas were collected by using a condensed bottle and a silica wool column, a diaphragmpump and a wet gas flow meter. All the mutagenic substances were extracted with ethylacetate. The ethylacetate solution was dehydrated with sodiumsulfate and the concentrated by the evaporator. The concentrated ethylacetate solution was used for the Ames test and the chemical analysis. The exhaust gas showed high mutagenicity levels, especially the mutagenicity of the flame shift type with metabolic activation (TA98+S9) was high. The exhaust gas from fluidized-bed type incinerators showed higher mutagenicity than those from storker type incinerators, and exhaust gas from old plants also showed higher mutagenicity. Since many mutagenic substances were produced under conditions of incomplete combustion, the mutagenicity levels could be decreased by secondary combustion and a sufficient supply of air. The ethylacetate solution was separated into six fractions by HPLC (High performance liquid chromatograghy) using a silicagel column and 5% ethylacetate in hexane. Each fraction was analysed qualitatively by GC/MS (Gas chromatography mass spectrography) and quantitatively by GC-FID (Gas chromatography with flame ionization detector). The mutagenic compounds for TA100-S9 and TA100+S9 were separated into former and latter fractions, respectively, but the mutagenic compounds for TA98-S9 and TA98+S9 were not separated clearly. 62 compounds were identified in the solution and among them 29 compounds showed mutagenicity. The identified mutagenic compounds were mainly PAHs (Poly aromatichydrocarbons) and chlorinated PAHs.