Small-scale gold-mining: a mercury risk in Tanzania

The Geological Survey of Denmark and Greenland (GEUS) and the National Environmental Research Institute (NERI) have carried out a pilot study for a joint research project to be carried out with the University of Dar es Salaam and the Geological Survey of Tanzania aimed at assessing the health risk associated with gold-mining. The pilot study was financed by a Foreign Ministry programme under Danida.

The pilot study was carried out in western Tanzania, where numerous small gold deposits are mined by smallscale miners. The gold is extracted using metallic mercury, which forms an amalgam with the gold. The amalgam is subsequently heated over open fires causing the mercury to evaporate while leaving the gold behind.

The workers extracting the gold were found to have the highest hair mercury concentrations (average 3 mg/kg) – 30-fold more than in control persons. The mercury concentration in the amalgamation pools was about 50 mg/kg, and high mercury concentrations were found in the river sediment close to the pools.

Although low-price gadgets able to reduce mercury discharge during extraction of the gold are available, these are not widely used, mainly for financial reasons.

Further information: Peter Appel, GEUS. Phone: +45 3814 2214. E-mail: pa@geus.dk, or Christian Glahder, NERI. Phone: +45 4630 1946. E-mail: cmg@dmu.dk. See also: Reference: “A pilot study in Tanzania” by P. Appel, C. Glahder et al., GEUS rapport 2000/16, 155 pp.


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