Metal Mining Contaminates Rivers and Floodplains Across the World

Metal mining is one of the most important economic activities in the world, providing essential raw materials for various industries and sectors.

However, metal mining also generates large amounts of waste that can pose serious environmental and health risks to millions of people living downstream from mining sites.

A new study, published in Science, has provided new insights into the extensive impact of metal mining contamination on rivers and floodplains across the world, with an estimated 23 million people believed to be affected by potentially dangerous concentrations of toxic waste.

How metal mining contaminates rivers and floodplains

The study, led by Professors Mark Macklin and Chris Thomas, Directors of the Lincoln Center for Water and Planetary Health at the University of Lincoln, UK, alongside Dr. Amogh Mudbhatkal from the University's Department of Geography, used a new georeferenced global database of 185,000 metal mines compiled by the team and employed a combination of process-based modeling and empirical testing to assess the global scale of metal mining contamination in river systems and its repercussions for human populations and livestock.

The study modeled contamination from all known active and inactive metal mining sites, including tailings storage facilities-used to store mine waste-and looked at potentially harmful contaminants, such as lead, zinc, copper, and arsenic, which are transported downstream from mining operations, and often deposited along river channels and floodplains for extended periods.

The researchers explained that their new method for predicting the dispersal of mine waste in river systems worldwide can help governments, environmental regulators, the mining industry, and local communities to evaluate the offsite and downstream impacts of mining on ecosystem and human health.

They added that this can make it easier to mitigate the environmental effects of historical and present mining and, most importantly, help to minimize the impacts of future mining development on communities, while also protecting food and water security.

The extent and consequences of metal mining contamination

Released against the backdrop of growing demand for metals and minerals to feed the demands of the green energy transition, the new results highlight the widespread reach of the contamination, affecting approximately 479,200 kilometers of river channels and encompassing 164,000 square kilometers of floodplains on a global scale.

According to the findings, approximately 23.48 million people reside on these affected floodplains, supporting 5.72 million livestock and encompassing over 65,000 square kilometers of irrigated land.

Due to a lack of available data for several countries, the team behind the study believe these numbers to be a conservative estimate.

Various pathways exist for humans to become exposed to these contaminant metals including from direct exposure through skin contact, accidental ingestion, inhalation of contaminated dust, and through the consumption of contaminated water and food grown on contaminated soils.

The study also found that worldwide, metal mines affect 479,200 kilometers of river channels and 164,000 square kilometers of floodplains.

The number of people exposed to contamination sourced from the long-term discharge of mining waste into rivers is almost 50 times greater than the number directly affected by tailings dam failures.

The study warns that metal mining contamination poses a serious threat to human health and well-being, especially in developing countries where environmental regulations are weak or poorly enforced.

It also calls for urgent action to prevent further contamination and remediate existing pollution sources.