GEOLOGY AND HEALTH INSIGHTS INTO LEAD POISONING FROM ARTISANAL GOLD MINING, NW NIGERIA: SOURCES, EXPOSURE PATHWAYS, ADDITIONAL HEALTH CONCERNS, AND GLOBAL IMPLICATIONS

In spring 2010, Médecins Sans Frontières (MSF) discovered an unusual lead poisoning outbreak from artisanal gold processing in NW Nigeria that has killed ~400 young children and affected thousands more. Since 2010, the US Geological Survey has worked with US Centers for Disease Control and Prevention (CDC) and TerraGraphics Environmental Engineering (TG) on a unique integrated health- and earth-science assessment of the crisis. In May 2010 CDC/TG visited two heavily affected villages and found high levels of lead contamination and acute lead poisoning in surviving children <5 years old. In fall 2010, CDC visited 74 more NW Nigeria villages, finding ore processing and(or) lead contamination in over half and identifying ~ 2000 additional children <5 years old as lead poisoned and needing treatment. The teams collected raw and processed ore samples, composite soil samples within and outside villages, sweep samples of dust and loose soils from eating areas in family compounds, and samples of plant foodstuffs from local markets. The USGS analyzed these samples using diverse methods. The same suite of lead minerals found in all sample types confirms that processing of lead-rich gold ores caused extreme contamination, with up to 18,500 ppm lead in soil and sweep samples and up to 145 ppm lead in plant foodstuffs. Lead is abundant in highly gastric-bioaccessible lead carbonates formed by natural weathering of lead sulfides before mining. Incidental ingestion of soils via hand-mouth transmission and of dusts cleared from the respiratory tract is the dominant lead exposure pathway. Consumption of contaminated water and foodstuffs are lesser but significant exposure pathways. Older children, pregnant women, and adult workers are also at substantial risk for lead poisoning. Mercury, arsenic, manganese, antimony, and crystalline silica exposures present additional health threats. Results inform ongoing efforts in Nigeria to assess lead contamination and poisoning, treat victims, mitigate exposures, and remediate contamination. Other areas occur globally where ore deposit geology, pre-mining weathering, and burgeoning artisanal mining may cause similar lead poisoning. The speaker thanks many CDC, USGS, and TG scientists, as well as MSF and Nigerian Federal and State public health personnel, for key contributions.