Dangerously high levels of mercury and a related toxin are pervasive in rivers and soils near artisanal gold mines in Senegal, according to a new study from Duke University.

“Nearly every sample we collected from in and around four mining villages contained mercury concentrations higher than regulatory standards set by the World Health Organization and U.S. Environmental Protection Agency,” said Jacqueline Gerson, a PhD student in ecology at Duke.

The level of contamination was more than 10 times higher than these standards, with some cases up to 100 times higher – making them, among small gold mining sites, some of the highest levels ever reported in the world.

Gerson and her colleagues published their work in the journal Elementa: Science of the Anthropocene.

In May 2016, they collected soil, sediment and water samples from four artisanal gold-mining communities in southeastern Senegal, as well as from a control village where no mining took place. The highest median total mercury concentrations were found in huts where mercury-gold amalgams were burned (7.5 μg/g), while the highest median methylmercury concentrations, and percent of mercury in methylmercury, were found in river sediments (4.2 ng/g, 0.41 percent).

Artisanal miners in Senegal, the ‘galamsey’ miners of Ghana, some operations in Sudan and many other developing nations use mercury to separate gold ore from soil and sediments, but they often do so at risk to their health and the wider community and environment. A key effort to reduce the damaging and potentially fatal health risks is the Minamata Convention on Mercury, which went into effect last year.

The Senegal discovery raises concerns that villagers could be exposed to mercury not only by eating contaminated fish from the water, but also by eating crops grown on contaminated soil or livestock grazing on this land. Children might be at risk of accidental exposure during play.

Gerson has shared the team’s study with Senegalese government agencies and NGOs, and with Senegalese partners has reached out to the wider community with information and workshops.

Image: Jacqueline Gerson, Duke University