Global Study Reveals Extensive Impact of Metal Mining Contamination on Rivers and Floodplains

A groundbreaking study, published today 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.

Led by Professors Mark Macklin and Chris Thomas, Directors of the Lincoln Centre for Water and Planetary Health at the University of Lincoln, UK – working with Dr Amogh Mudbhatkal from the University’s Department of Geography – the study offers a comprehensive understanding of the environmental and health challenges associated with metal mining activities.

Using a new georeferenced global database of 185,000 metal mines compiled by the team and employing a combination of process-based modelling and empirical testing, the research assessed the global scale of metal mining contamination in river systems and its repercussions for human populations and livestock.

The study modelled 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.

“Our new method for predicting the dispersal of mine waste in river systems worldwide provides governments, environmental regulators, the mining industry and local communities with a tool that, for the first time, will enable them to assess the offsite and downstream impacts of mining on ecosystem and human health.” said Professor Mark Macklin, who led the multi-disciplinary, international team behind the research:

“We expect that this will make it easier to mitigate the environmental effects of historical and present mining and, most importantly, help to minimise the impacts of future mining development on communities, while also protecting food and water security.”

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 kilometres of river channels and encompassing 164,000 square kilometres of floodplains on a global scale.

According to the findings released today, approximately 23.48 million people reside on these affected floodplains, supporting 5.72 million livestock and encompassing over 65,000 square kilometres 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.

This poses an additional hazard to the health of urban and rural communities in low-income countries and communities dependent on these rivers and floodplains, especially in regions already burdened with water-related diseases. In industrialised nations in Western Europe, including the UK, and the United States, this contamination constitutes a major and growing constraint to water and food security, compromises vital ecosystem services, and contributes to antimicrobial resistance in the environment.

“Rapid growth in global metal mining is crucial if the world is to make the transition to green energy.”, said Professor Chris Thomas who led the analysis and modelling, “Much of the estimated global contamination we have mapped is a legacy from the industrial era – rightly, modern mining is being encouraged to prioritise environmental sustainability. Our methods, which also work at local scales, add an important new approach in this process for which have set up an applied unit of our research centre ‘Water and Planetary Health Analytics’ to work with the sector.”

Professor Deanna Kemp from the University of Queensland’s Sustainable Minerals Institute, who was part of the team behind the study, called the results “sobering.”

“At a basic level, these findings remind us that mining can cause extensive downstream damage over long periods of time.” Kemp said. “Many people benefit from mining and metals, but we must do more to understand and prevent the negative effects on people who live and work in affected areas.”

Professor Paul Brewer from Aberystwyth University commented: “These very significant findings demonstrate the scale of the threat posed to people, ecosystems, and the wider environment from metal mining activity across the world.  For the first time, we have been able to establish that the number of people exposed to contaminant metals sourced from the long-term discharge of mining waste into rivers is almost 50 times greater than the number directly affected by acute tailings dam failures. The new modelling approach used in this study provides industry and regulatory agencies with a tool for assessing the potential downstream impacts of metal mining activity on human populations and the environment. This will benefit future generations as we will be able to develop better, data-informed strategies for identifying and managing land contaminated by metal mining.”

Professor Karen Hudson-Edwards, co-author of the study and an expert in Sustainable Mining, from the University of Exeter, added: “As the mining industry moves towards sustainability, protection of the environment and people is more important than ever. Our study provides data and models to inform risk management strategies for river systems that could be affected by mining-related contamination.”

Co-author Professor Graham Bird of Bangor University commented: “We have been mining metal resources for millenia and that activity has left a widespread pollution legacy, especially within floodplain sediments. Indeed we can see examples of that legacy across the UK, including in North Wales. This study for the first time quantifies the extent of that legacy on a global scale, including the number of people living in areas polluted by metal mining activity.

“It also serves as an important reminder of the risks posed by poorly manged mining activities. This is especially relevant given that technological approaches to tackling climate change, such as renewable energy and electric vehicle technology, require certain metal resources that we will need to mine. We need to do so as sustainably as possible and so that we do not add to the existing legacy present within our environment.”

The full study – Impacts of metal mining on river systems: a global assessment – can be found here: www.science.org/doi/10.1126/science.adg6704

Image: Firefighters from Minas Gerais conduct searches following the dam rupture in Brumadinho, Minas Gerais, Brazil – photo reproduced with permission from the Fire Department of Minas Gerais