Evaluation of municipal waste incinerator fly ash toxicity and the role of cadmium by two aquatic toxicity tests

Fly ash from a municipal solid waste incinerator in Japan is regulated under the hazardous waste regulation ''Waste under Special Control'', according to the Amendment of the Waste Disposal and Public Cleansing Law, because it contains high concentrations of heavy metals which are available for leaching. To evaluate the toxicity of fly ash, a fly ash leachate was prepared according to the Japanese standard leaching procedure. The chemical analysis of the leachate showed that possibly one of the most toxic substances was cadmium. The toxicity of the leachate and the cadmium was determined by algal assay and a Daphnia acute toxicity test. The results showed that the leachate was about seven times more toxic to the growth of algae and 20 to 30 times more toxic to the survival of Daphnia than expected from its cadmium concentration. The toxicity interaction between cadmium and the other constituents in the leachate was also examined. The toxicity of cadmium showed an additive effect with the other constituents in the leachate in algal assay. In the Daphnia test, however, cadmium showed an antagonistic effect. (C) 1997 Elsevier Science Ltd.