HYDROXYL RADICAL GENERATION BY COAL-MINE DUST - POSSIBLE IMPLICATION TO COAL-WORKERS PNEUMOCONIOSIS (CWP)

Occupational exposure to coal mine dust causes coal workers' pneumocon iosis (CWP) and other pulmonary diseases by mechanisms that remain unc lear. Because the hydroxyl radicals (.OH) may play an important role i n the pathogenesis of CWP, we studied the potential role of bituminous coal mine dust samples for catalyzing the generation of .OH from hydr ogen peroxide (H2O2). These coal mine dusts evaluated represented two geographic areas with diversity in CWP prevalence. Electron spin reson ance (ESR), with the aid of spin trapping techniques, was used to meas ure the .OH radical generation. Bituminous coal mine dusts representin g the Pittsburgh seam in the eastern United States and Blind Canyon se am in the mid-western United States were used together with a standard coal dust obtained from the National Institute of Standards and Techn ology, Gaithersburg, MD. All the coal mine dust samples generated vary ing levels of .OH radicals from H2O2 in the presence of a .OH spin tra p 5,5,-dimethyl-1-pyrroline-N-oxide (DMPO). .OH radical generation by the coal from H2O2, was effectively inhibited by deferoxamine and cata lase, but only partially inhibited by superoxide dismutase. Metal chel ators DETAPAC and EDTA enhanced the radical generation. These results indicated that the Fenton reaction is predominantly involved in the ge neration of .OH radicals from H2O2 The .OH-generating potential of all the coal dusts showed a positive correlation with the surface iron co ntent of coal mine dusts. In addition, the potential to induce lipid p eroxidation by the coal samples exhibited a good correlation with the available surface iron. Based on the results presented here, we propos e that higher concentrations of surface iron in coal mine dust may be involved in tile generation of increased levels of .OH radicals and ma y play an important role in the development of CWP in different coal m ining areas.