Bacterial mutagenicity of pyrolysis tars produced from chloro-organic fuels.

Abstract

Droplets of toluene and three chlorinated organics, oriho-dichlorobenzene, 1,2-dichloroethane, and trichloroethylene, were pyrolyzed in pure nitrogen. The composition and bacterial mutagenicity of the product tars were measured. The presence oforgmic chlorine was found to affect both pyrolysis product tar composition and total tar muagenicity. Pyrolysis in the absence of chlorine produced tars whose bacterial mutagenicity was found to be largely due to the presence of cyclopenta[cdlpyrene, fluoranthene, and benzolalpyrene. Small amounts ofchlorine inthe fuel (i.e., Cl/H molar ratios of less than 0.3) enhanced the formation of highly condensed polycyclic aromatic hydrocarbons (including cyclopentalcdlpyrene) and increased tar mutagenicity. LIarger amounts of organic chlorine (Cl/H ratios of between 0.3 and 0.6) resulted in significant yields of mono-and dichlorinated aromatics and higher levels oftarmutagenicity, which could not be accounted for by the presence ofmutagens produced by pyrolysis in the absence ofchlorine. Furthermore, unlike tars containing little or no chlorine, tars containing aryl chlorine were more mutagenic in the absence ofadded enzymes (intended tomimicin woo m ln o n) than in their presence. ehypothesizethat least one ofthe chlorinated aromatic products is strongly mutagenic. Two specific conditions that gave notably different results were a ) the lowtemperature (ixe, below 1400 K) pyrolysis ofotho-dichlorobenzene, which produced tri-and tetrachlorinated biphenyls almost exclusively; and b) the chlorine-rich pyrolysis oftrichloroethylene, during which mostly perchloroaromatics were formed. Neither of these tars was found to mutate bacteria.