Monitoring of fish and human exposure to mercury due to gold mining in the Lake Victoria goldfields, Tanzania.

Monitoring of environmental and human exposure to mercury in the Nungwe Bay area of the Lake Victoria goldfields, Tanzania, has revealed low mercury concentrations in fish (range: 1.8-16.9 ppb, mean: 7.0 ppb) and human hair (range: 156-5433 ppb, mean: 947 ppb) that represent background levels. Gold mining has not produced a significant increase in environmental methylmercury that is available for bioaccummulation in aquatic food chains. Urinary mercury levels in gold mine workers frequently exposed to Hg vapour in amalgamation and burning of amalgam were significantly higher (mean: 241 ng/ml) than those in the general mine population not occupational exposed to Hg (mean: 2.6 ng/ml). Rotation of mine duties reduced Hg exposure levels and hence the risk of intoxication in the gold mine workers. The lowest urinary and hair mercury levels were found in the Nungwe Bay fishing village population. This was consistent with the low mercury content of fish consumed by the inhabitants of the Nungwe Bay.