Abstract
Coal, which contains significant amounts of water, can be ground and dried to produce an efficient fuel for electric power plants; however, spontaneous combustion can occur in the dried coal. Liquid petroleum hydrocarbons inhibit this combustion, but not all petroleum streams are effective. No. 6 fuel oil, a readily available and inexpensive stream, provides an effective coating, but the carcinogenic potential of coal particles treated with No. 6 fuel oil, which contains polynuclear aromatic hydrocarbons (PNAs), was undefined. As part of the assessment process, a series of studies was conducted to compare this treated coal with similar particles (petroleum coke) that had been tested by chronic inhalation in monkeys and rats. The amounts of PNAs in petroleum coke and treated coal were compared in extraction studies; the treated coal had only two-thirds of the organics extractable with benzene compared with coke and only 7% as much of the 3–7 ring PNAs, the likely tumorigenic compounds. In addition, the analytical profile of 3–7 ring PNAs was of lower molecular weights in the coal treated with fuel oil. The mutagenicity of extracts from treated coal was much less than with petroleum coke and markedly less than that of No. 6 fuel oil itself. The percutaneous absorption of 3H-benzo(a)pyrene from both particles and from their benzene extracts, as measured in vitro, was approximately eight times greater with petroleum coke than with treated coal. Based on these preliminary results, there is no evidence suggesting that the treated coal would pose any greater carcinogenic risk than petroleum coke.