Chem. Res. Toxicol. 2000, 13, 161-164
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Communications Mo1 ssbauer Spectroscopy Indicates That Iron in an Aluminosilicate Glass Phase Is the Source of the Bioavailable Iron from Coal Fly Ash John M. Veranth,† Kevin R. Smith,‡ Frank Huggins,§ Autumn A. Hu,† JoAnn S. Lighty,† and Ann E. Aust*,‡ Department of Chemical and Fuels Engineering, University of Utah, Salt Lake City, Utah 84112, Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322-0300, and Department of Chemical and Materials Engineering, University of Kentucky, Lexington, Kentucky 40536-0082 Received December 29, 1999
Iron speciation by Mo¨ssbauer spectroscopy indicates that ferric iron in an aluminosilicate glass phase is the source of the bioavailable iron in coal fly ash and that this iron species is associated with combustion particles, but not with crustal dust derived from soil minerals. Urban particulate has been shown to be a source of bioavailable iron and has been shown to be able to induce the formation of reactive species in cell culture experiments. Crustal dust and laboratory-generated coal fly ash have been studied as surrogates for two sources of metalbearing particles in ambient air. As much as a 60-fold difference in the amount of iron mobilized by the chelator citrate was observed between fly ash and crustal dust samples with similar total iron contents. The extent of iron mobilization by citrate in vitro has been shown to correlate with indirect measures of excess iron in cultured cells and with assays for reactive oxygen species generation in vitro. Mo¨ssbauer spectroscopy of coal fly ash, before and after treatment with the chelator desferrioxamine B, showed that the iron in an aluminosilicate glass phase was preferentially removed. The removal of the glass-phase iron greatly reduced the amount of iron that could be mobilized by citrate and prevented the particles from inducing interleukin-8 in cultured human lung epithelial (A549) cells. Ferric iron in aluminosilicate glass is associated with particles formed at high temperatures followed by rapid cooling. The observation that ferric iron in aluminosilicate glass is the source of bioavailable iron in coal fly ash suggests that particles from ambient sources and other specific combustion sources should be examined for the presence of this potential source of bioavailable iron.
Introduction Studies of PM10 and PM2.51 have found statistical correlations between particulate air pollution and human health effects (1), but the inconsistent correlations between deaths and monthly pollution levels (2) indicate that particle mass within the inhalable size range is not the only important factor. Ambient particles vary in size, morphology, elemental composition, and chemical speciation depending on the source. Typical data apportion * To whom correspondence should be addressed: Department of Chemistry and Biochemistry, Utah State University, Logan, UT 843220300. Phone: (435) 797-1629. Fax: (435) 797-3390. E-mail: AAUST@ cc.usu.edu. † University of Utah. ‡ Utah State University. § University of Kentucky. 1Abbreviations: CFA, coal fly ash; DF, desferrioxamine B, N-[5-[3[(5-aminopentyl)hydroxycarbamoyl]propioamido]pentyl]-3-[[5-(N-hydroxyacetamido)pentyl]carbamoyl]propionohydroxamic acid; IL-8, interleukin-8; PM2.5, particulate air pollution with a mean aerodynamic diameter of 10 µm UT PM 2.5-10 µm crustal dust
