Bioaccessibility and concentration of metal(loids) in African Dust

Exposure to fine particulate matter (PM) is acknowledged as a risk factor for human morbidity and mortality. Research has generally examined PM from anthropogenic sources and few studies consider naturally produced (geogenic) contributions, or PM produced from natural sources as a result of human activities (geoanthropogenic PM), such as dusts from lakebeds dried by human removal of water, or dusts produced from areas that have undergone desertification as a result of human practices). The focus of this study was to elucidate relationships between human/ecosystem health and dusts produced by a system transitioning from a dominantly natural to a geoanthropogenic PM source. There is increasing concern about health effects 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 sourced in Mali, Africa. Samples were collected using high-volume samplers from three sites, one in West Africa and two in the Caribbean. A significant fraction of the dust collected was estimated to be in the respirable range. Inhalation and ingestion exposure pathways were explored by extraction of the filters using simulated lung and gastric fluids. Bioaccessibility of some metals with known or suspected human/ecosystem health risks generally increased from the dust source region to the Caribbean. For example, total arsenic concentrations ranged from 5 to 8 mg/kg with greater than 40% bioaccessibility similar to what we have observed with salt-rich mineral dusts from dry lakebeds.