Polycyclic aromatic hydrocarbons and thiaarenes in the emission from hard‐coal combustion†

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Abstract
In order to identify the polycyclic aromatic compounds (PAC) responsible for the carcinogenicity of hard‐coal effluents, the emission condensate was separated by Chromatographic techniques into a PAC‐free and various PAC‐containing fractions. At a detection limit of 0.1 mg per kg of burned coal, more than 170 neutral PAC and about 70 basic N‐PAC were found by GC/MS. Within the neutral fraction, 111 PAH, 57 S‐PAC and 6 O‐PAC were detected. In total 80 compounds could be positively identified by comparison with synthetic standards. The subfraction containing PAH of molecular weight 300 and 302 was particularly complex; 8 homologs of pyrene, fluoranthene and perylene not earlier encountered in environmental matrices were identified. The PAC‐free fraction and that containing PAC with only 2 or 3 condensed rings showed no noticeable carcinogenicity upon testing them on the dorsal skin of mice, although present to 77% by weight in the emission condensate. Likewise, the subfraction containing N‐PAC and nitro‐PAC accounted for only 4–7% of the total carcinogenicity. The subfraction containing PAH, S‐PAC and O‐PAC with 4 and 5 rings was almost as active as the subfraction containing compounds with 6 and more rings, each contributing by almost 50% to the total carcinogenicity. While the potency of the former subfraction can be partially explained by the occurrence of known carcinogens such as benzo(a)pyrene and dibenz(a,h)anthracene, the origin for the high effect of the latter subfraction remains elusive. The desirability of further analytical and biological studies focussing on these high‐molecular weight PAH is emphasized.