Mutagenicity, Carcinogenicity, and Human Cancer Risk from Indoor Exposure to Coal and Wood Combustion in Xuan Wei, China

Abstract

The residents in Xuan Wei County, China, have been exposed to high levels of combustion emissions from smoky and smokeless coal and wood combustion under unvented conditions in homes. An unusually high lung cancer mortality rate that cannot be attributed to tobacco smoke or occupational exposure was found. The communes using smoky coal, which emits more organics than smokeless coal, generally have a higher lung cancer rate than the communes using smokeless coal or wood. The mutagenicity and carcinogencity of organic extracts of indoor air particles collected from Xuan Wei homes during cooking were investigated. The objectives of this study were: (i) to investigate the characteristics of lung cancer mortality in Xuan Wei, (ii) to determine the genotoxicity and chemical and physical properties of the combustion emissions, and (iii) to link bioassay results to human lung cancer data. The organic extracts of these emission particles were, tested for mutagenicity in the Ames Salmonella and the L5178Y TK+/− mouse lymphoma assays, and for skin tumor-initiating activity and complete carcinogencity in SENCAR mice. The two coal samples showed higher activity in both mutagenicity and tumor initiation. When the emission rate of organics was taken into consideration, the smoky coal emission showed the highest potency of the three fuels. The smoky coal sample was also a more potent complete carcinogen than the wood sample. Higher mutagenicity and carcinogenicity of the smoky coal emission compared to wood or smokeless coal emissions are in agreement with the epidemiological data.