Long-distance atmospheric transport of African dust and chemical pollutants - implications for ecosystem and human health

Over the past 40 years, the quantities of desert dust eroded from the Sahara/Sahel of Africa and transported through the atmosphere to the Caribbean and Americas have increased and the composition of dust air masses has changed. Global climate, regional meteorology, local geomorphology and human activities have driven these changes. Dust-associated metals, organic contaminants and elevated concentrations of fine (respirable) dust particles during African dust events are potentially hazardous, individually and in combination, to humans and ecosystems in source (Africa) and distant downwind locations (the Americas, Europe and the Near East). Toxic persistent organic contaminants such as banned and current use pesticides, polycyclic aromatic hydrocarbons (from combustion) and polychlorinated biphenyls have been detected in dust air masses from source and downwind locations in the Caribbean. All are known to persist in the environment, bioaccumulate and be toxic to humans and other organisms (carcinogenic, mutagenic, teratogenic, neurotoxic, hepatotoxic and/or affect reproduction or immune function). Bioaccessibility of some metals (e.g., Fe and As) may be increased due to reduction-oxidation environments produced by geologic processes in the source region. To date, concentrations of organic and metal contaminants and fine particles in dust air masses have been found to be below current EPA threshold limits (inhalation) for human health, with two exceptions - particles and Pb in the dust source region. Two of the pesticides identified from all sites have been shown to interfere with reproduction in coral. Investigation of synergistic effects among metals, organics contaminants and fine particles is needed.