Effects of coal combustion products and metal compounds on sister chromatid exchange (SCE) in a macrophagelike cell line

Investigations of genotoxic effects of particles have almost exclusively been performed by organic extraction, while direct investigations in cells capable of engulfing particles have only been performed in few cases. Thus, in most studies, the eventual effects of particle-associated metal compounds have remained undiscovered. The present study attempted direct measurement of genotoxic effects of particulate coal combustion products by using the P388D(1) macrophage cell line. The capability of these cells for phagocytosis was demonstrated with insoluble particles. The sister chromatid exchange (SCE) test was used for measuring genotoxic effects of test compounds. Dimethylnitrosamine and benzo(a)pyrene did not increase SCE, indicating that the P388D(1) cell line has lost the capacity for metabolism of latent organic carcinogens, reducing the value of these cells for evaluating genotoxic effects of complex particles. Indirect evidence has been obtained that the cell line may be infected with a virus. Thus, interactions between virus and test compound may lead to erroneous results. This should be kept in mind during evaluation of the results. The effects of metals with reported carcinogenic or mutagenic effects on SCE were compared in P388D(1) cells and human lymphocytes: NaAsO(2), CdCl(2), K(2)Cr(2)O(7), CoCl(2), CH(3)HgCl and MnSO(4) increased SCE in both cell systems. Pb(CH(3)COO)(2), BeSO(4) and NiSO(4) had a weak effect on SCE in P388D(1). Pb(CH(3)COO)(2) and NiSO(4), but not BeSO(4), increased SCE in human lymphocytes. Cr(CH(3)COO)(3) increased SCE in human lymphocytes at high concentration, but was a strong inducer of increased SCE in P388D(1) cells, which take up Cr(III) by phagocytosis. This suggests that the Cr(III) ion is an ultimate carcinogenic form of chromium. Generally P388D(1) cells and human lymphocytes respond to in vitro exposure to metals in agreement with reported mutagenic/carcinogenic effects of the metals. Of four precipitated coal fly ash samples tested, only one sample (from an electrostatic precipitator downstream of a cyclone at an electricity generating plant burning pulverized coal) had a clear increasing effect on SCE in P388D(1). Extraction of this sample with medium with 10% serum yielded an extract capable of increasing SCE. The extracted particles still increased SCE, but less than unextracted particles. Emission samples taken with impactor sampler after a dilution probe using controlled cooling of the flue gas were obtained from an oil-fired (one sample) and a coal-fired (one sample < 3 μm and one sample < 3 μm) steam boiler. The only sample increasing SCE was the sample < 3 μm from the coal-fired boiler. Extract from this sample also increased SCE. The results demonstrated that the use of phagocytizing cells for assessment of genotoxic effects of particles offers a useful system, since the particles can be investigated directly. Furthermore, particles, extracted particles and extract can be investigated in the same system.