Airborne mercury from gold mining is contaminating African food crops, study warns

IN recent study published in the magazine Biogeosciences, Scientists have confirmed that mercury pollution from artisanal and small-scale gold mining (ASGM) is contaminating food crops not through the soil, as previously thought, but directly from the air. The rapid expansion of unregulated mining in these regions, fueled by rising gold prices that have risen more than tenfold since 2000, raises urgent questions about food security, human health and environmental justice.

The study, conducted by an international team of scientists led by Exclusive O. Eboigbe and David McLagan from Queens University and Abiodun Odukoya Mary from the University of Lagos, focused on farming community in Nigeria, located close to artisanal and small-scale gold mining. The researchers compared crops from a field located 500 meters from the ASGM site with crops grown 8 kilometers away. The contrast was striking: mercury concentrations in leaves and grains were about 10 to 50 times higher on the farm closer to the mining site.

For decades, scientists have assumed that mercury enters food crops primarily through roots, after leaching into soil or water. But this new study, using sophisticated stable isotope analysis of mercury, shows that a very different mechanism is at work. Most of the mercury is found in plant tissue comes from the atmosphere and is absorbed by leaves during photosynthesis. In short: plants breathe mercury. David McLagan states that:

“The uptake of mercury by plants from the air represents the largest sink of mercury from the air to land-based objects. [land and freshwater] systems. While this essential ecosystem service helps reduce the amount of mercury that spreads throughout the world through the atmosphere, it increases human health it bothers me when it happens main crops This is a mechanism that cleanses the air of mercury.”

The research team found that the leafy parts of plants, which are often eaten by people and livestock, retained the highest levels. mercury concentrations. Edible, nonleafy plant parts, such as cassava roots or corn kernels, had lower concentrations but still had significant contamination.

Although levels remain below international mercury intake thresholds, the authors caution that health problems may still arise from consuming mercury-contaminated crops near ASGM sites, as international standards use conservative mercury intake limits, and that other studies have observed even greater contamination of air, soil, and crops. This is especially true for communities that depend on local agriculture for survival.

Mercury, used to extract gold from raw ore, is a potent neurotoxin. Long-term exposure, even at low levels, can damage the nervous system, impair cognitive development in children, and cause serious cardiovascular and reproductive problems. Due to its frequent use in artisanal and small-scale mining activities, vulnerable populations in low-income rural areas are at higher risk.

“Miners will not stop using mercury to extract gold until they have a readily available alternative that is also cost-effective,” Abiodun Mary said.

According to the United Nations Environment Programme, ASGM is currently the largest source of mercury emissions in the world. However, regulation and monitoring are limited in many parts of the Global South, where ASGM is often an economic lifeline for communities facing poverty and displacement. This study highlights a critical but overlooked consequence of this boom: food systems are being quietly and undetected by elevated levels of mercury in the air.

The study also serves as a call to action for governments and international organizations tasked with enforcing the Minamata Convention on Mercury. Current monitoring strategies focus primarily on water bodies, sediments, and seafood rather than crops. This research shows that these efforts are missing a key vector of impact.

“Because of the bioaccumulation toxicity and biomagnification potential of methylmercury, fish consumption in ASGM areas has been a major focus of epidemiological research in ASGM areas. However, this work shows that there are other food sources of mercury, and mercury from these different sources may have a cumulative effect,” Abiodun Mary said.

The study concludes that new policies are urgently needed to monitor and mitigate the effects of airborne mercury in agricultural regions near mining operations. Given the rapid growth of artisanal and small-scale gold miningmillions of people in Africa, South America and Asia could face long-term health risks from something as simple and important as growing and consuming local food.