“…Users directly exposed to combustion smoke may receive a large dose of these pollutants and be threatened by the carcinogenic risk associated with them. PAHs as well as numerous PAH derivatives, i.e., alkylated PAHs, nitro-PAHs, oxygenated PAHs, quinones, hydroxy and hydroxynitro compounds, are produced by the incomplete combustion of fuels such as coal, gasoline, diesel and biofuels (Beak et al, 1991;Matsumoto et al, 1998). The mutagenicity and carcinogenicity of PAHs associated with combustion and ambient aerosols have been conclusively demonstrated through bacterial assays, human cell mutagenicity assays, animal assays and epidemiological studies (Hannigan et al, 1998;Helmig et al, 1992;Kamens et al, 1984;Kleindienst et al, 1986;Mastrangelo et al, 1996;McCrillis et al, 1992;Moller and Alfheim, 1980).…”