Metal mining pollution threatens over 23 million people worldwide, according to a recent study by UK scientists. The study found that people living in flood-prone areas contaminated with hazardous levels of toxic waste from metal mining are at risk of environmental and health crises.

Led by Professor Mark Macklin from the University of Lincoln, the research team assessed global metal mining operations, mapping 22,609 active mines and 159,735 abandoned ones. The findings, published in Science, reveal the extent of pollution generated by these mining activities.

Toxic chemicals used in or resulting from mining operations can infiltrate the surrounding soil and water systems, posing environmental and health risks. This study underscores the pressing need for meticulous planning and responsible practices in future mining ventures, especially as the demand for metals crucial to battery technology and electrification, such as lithium and copper, continues to soar.

Professor Macklin noted that awareness of the pollution issue related to mining activities has persisted for years.

The research builds upon the team’s previous studies focused on understanding how pollution from mining operations spreads and accumulates within the environment. To gather their data, the scientists drew from various sources, including government publications, mining companies, and organisations like the US Geological Survey. This data included information about the location of each mine, the type of metal being extracted, and whether the mine was still active or abandoned.

A significant portion of the metals derived from metal mining become trapped in sediment within the ground. This sediment, whether eroded from mine waste tips or present in contaminated soil, ultimately finds its way into river channels or gets deposited across floodplains, contributing to environmental contamination.

Prof. Macklin and his research team used previously published field and laboratory analyses to determine the extent to which sediment contaminated with metals from mining activity travels within river systems.

Professor Chris Thomas, who specialises in water and planetary health at the University of Lincoln, explained that the study involved mapping areas likely to be affected by pollution linked to mining activities. When this information is cross-referenced with population data, it becomes evident that approximately 23 million people worldwide are residing on land that can be classified as “contaminated” due to mining-related pollution.

Professor Thomas emphasised the critical role of agriculture and irrigation in many of these contaminated regions. Crops cultivated in soils tainted by mining pollution or irrigated with water contaminated by mine waste have been found to accumulate elevated levels of metals.

The scientists underscored in their research paper that animals, such as livestock, grazing on floodplains in contaminated areas might inadvertently consume polluted plant material and sediment, especially following flooding events when fresh sediment rich in metals is deposited.

Offering his perspective on the matter, Professor Jamie Woodward from the University of Manchester, who was not directly involved in the study, stressed the significance of addressing what he called “silent pollution” that accumulates in floodplains. He explained that a significant portion of river monitoring efforts typically focuses on water quality, while the true environmental hazards often originate from contaminants associated with river sediments.

Professor Woodward further emphasised the importance of gaining a deeper understanding of how contaminants are transported within the environment and where they are retained. Such knowledge is essential for assessing potential hazards and implementing strategies to mitigate them. For example, floodplain areas heavily contaminated by mining waste should be avoided for purposes such as livestock grazing to prevent exposure to contaminated resources.

Metal mining has a history dating back as far as 7,000 years.