A COMPARISON OF TOXICOLOGICALLY IMPORTANT CHARACTERISTICS OF ATMOSPHERIC PARTICULATE MATTER FROM DIVERSE SOURCES

The air that people and animals breathe can contain complex mixtures of airborne particulate matter (PM) from diverse sources. Our USGS project has collaborated over the past decade with many colleagues in the earth and health sciences to measure toxicologically relevant mineralogical, physical, geochemical, biosolubility, bioaccessibility, and bioreactivity characteristics of diverse PM types or sources. These include a range of geogenic (produced from the Earth by natural processes), geoanthropogenic (produced from natural sources but that are modified by human activities) and anthropogenic PM and PM sources; all have either been shown or speculated to cause adverse health impacts. Diverse PM types (desert, glacial, intercontinental dusts; wildfire ash; volcanic ash, urban PM) can have abundant respirable particles (<2.5 µm, PM2.5) that may contribute to respiratory and related cardiovascular health problems due to their abundance, mineralogy, geochemistry, biosolubility, and bioreactivity. Some PM types can cause irritation of dermal, ocular, and respiratory tissues because of acutely bioreactive caustic alkali minerals (wildfire ash, concrete particles in building collapse dusts, cement dusts, coal fly ash) or caustic acid minerals (soluble metal salts in coal dust or weathered sulfide mine waste; volcanic ash; urban PM). Many PM types contain potentially toxic elements that can be bioaccessible (depending upon mineralogy) in simulated gastrointestinal fluids, and in some cases simulated lung fluids, e.g.: wildfire ash and ash from burned buildings (Cr[VI], As, Pb, Sb, Mn, Cu, Zn); PM from building collapse (Pb, Sb, Zn, Cu, Cr[VI]); coal fly ash (Pb, Tl, As, Cd, V, Cr[VI]); PM from metal mine wastes, ore roasting or smelting, or artisanal gold amalgamation (Pb, Hg, As, Cd, Cu, Zn, Mn, others); and volcanic ash (F, Mo, Mn, Cu, Zn, Si). Oxidative stress and lung toxicity may result from inhalation of PM that release Fe, Mn, or other redox-sensitive elements either acutely in high concentrations (e.g. biosoluble and bioreactive iron sulfides and sulfates in mine wastes or coal dusts) or chronically in lower concentrations (biodurable volcanic ash, asbestos, etc.). These results help public health experts understand better the nature of diverse PM exposures, and therefore if and how they may affect health.