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

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, US ATSDR, US CDC, USGS and TerraGraphics Environmental Engineering (TG) have carried out a unique integrated health- and earth-science assessment of the crisis. In May 2010 CDC/ATSDR/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/ATSDR 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 and sent to the USGS for analysis 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 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 help guide 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 combine to cause similar lead poisoning. We are grateful for key contributions by many CDC, ATSDR, USGS, and TG scientists, as well as MSF and Nigerian Federal and State public health personnel.