ASSESSING CONCENTRATION AND BIOACCESSIBILITY OF POTENTIALLY TOXIC ELEMENTS IN AFRICAN DUST

Exposure to fine particulate matter (PM) is generally acknowledged to increase risk for human morbidity and mortality. Research has generally examined PM from anthropogenic sources. Few studies consider contributions from geogenic PM (produced from the Earth by natural processes, e.g., volcanic ash, windborne ash from wildfires, and mineral dusts) or geoanthropogenic PM (produced from natural sources by processes that are modified or enhanced by human activities, e.g., dusts from lakebeds dried by human removal of water, dusts produced from areas that have undergone desertification as a result of human practices). The focus of this study was to elucidate relationships between dust aerosols and human and ecosystem health in a system transitioning from a dominantly geogenic to a geoanthropogenic source. There is increasing worldwide recognition of growing health concerns related to desertification (from changing land use practices) and climate change. As part of a larger study investigating the relationship between atmospheric transportation of African dust, human health, and coral reef declines, we examined mineral aerosol samples collected using high-volume samplers from three sites (one in West Africa and two in the Caribbean). Dust samples were extracted with simulated lung and gastrointestinal fluids to determine metals bioaccessibility (solubility in fluids compositionally similar to human body fluids). Although total chemistry results for these dust samples are above the U.S. mean concentration for many elements, they are not elevated when compared with US EPA soil screening level (SSL) guidelines for elements with known human health toxicity. However, such comparisons may not reflect risk from low-level chronic exposures. Some elements do exceed EPA Eco-SSL avian guidelines. Bioaccessibility varies by element and fluid.