Analysis of the genotoxicity of municipal solid waste incinerator ash

Combined bottom and fly ash obtained from a Chicago, IL, municipal solid waste incinerator (MSWI) was extracted with organic solvents, water or acidified water. The mean amounts of organic material isolated from each extraction procedure were 688.2, 91.8 and 167.7 micrograms/g MSWI ash. These extracts were evaluated for toxicity and mutagenicity in Salmonella typhimurium strains TA98 and TA100. We developed and calibrated a micropreincubation assay to evaluate small concentrations of the organic extracts. No direct-acting mutagens were found, however the acid-treated aqueous extracts were toxic. Materials isolated with methylene chloride methanol were mutagenic after hepatic microsomal activation (S9). The mutagenic potencies of the organic extract normalized to a per gram ash basis was the induction of 103.46 revertants in TA98 and 247.5 revertants in TA100. The aqueous extracts were neither toxic nor mutagenic. However, the acid-treated aqueous extract was mutagenic to TA100. The organic material isolated from the acidic extract had an induced mutagenic potency of 44.2 revertants/mg extract. Normalizing these data indicate a mutagenic potency of 7.4 revertants/g MSWI ash leached.