Mutagenicity and cytotoxicity of coal fly ash from fluidized‐bed and conventional combustion

Abstract

Two respirable coal fly-ash samples (.ltoreq. 3 .mu.m) were evaluated for physical properties, chemical composition, and biological activity, including cytotoxicity and mutagenicity. These 2 fly-ash samples were collected from a pressurized fluidized-bed combustion miniplant and from a conventional-combustion power plant, both burning eastern coal. All samples were collected by a fabric filter downstream of the plant particulate control devices at 165.degree. C (for fluidized-bed combustion fly ash) or 130.degree. C (for conventional combustion fly ash). The 2 coal fly-ash samples were found to have different properties. Scanning electron microscopy illustrated a high degree of irregularity in fluidized-bed combustion fly ash and sphericity in conventional-combustion fly ash. Elemental analysis showed that fluidized-bed combustion fly ash was higher in Ca, Fe, Cr, Ni, Se and Zn, and conventional combustion fly ash was higher in Al, Si, As, Va and Pb. Both fly-ash samples were toxic in 2 mammalian cell systems, rabbit alveolar macrophages and Chinese hamster ovary cells in vitro, with fuidized-bed combustion fly ash showing higher toxicity in both assay systems. The rabbit alveolar macrophage system was a more sensitive assay than the Chinese hamster ovary system. For measuring the cytotoxicity of fly ash, the most sensitive parameters were ADP in the rabbit alveolar macrophage system and viability index in the Chinese hamster ovary system. Intact fluidized-bed combustion fly-ash particles proved mutagenic only in tester strains TA98 and TA1538 without metabolic activation in the Ames Salmonella typhimurium plate incorporation assay. For conventional-combustion fly ash, no mutagenicity was detected in bioassay of the whole particles. A series of organic solvents with differing polarities was employed to identify the most efficient solvent for removing mutagens from coal fly ash. Soxhlet extraction yielded more extractable mass from fluidized-bed combustion fly ash than from conventional-combustion fly ash. The extracts of fluidized-bed combustion fly ash were found to be mutagenic when dichloromethane, acetone, or cyclohexane were employed. These samples contained direct-acting, frameshift mutagens. Much lower mutagenic activity was found in dichloromethane and acetone extracts of conventional-combustion fly ash. [This study may be applicable to humans.].