Abandoned lead mines are leaving a toxic legacy on Wales’s farmland, wildlife and rivers

Ten days into starting my PhD to research trace metal pollution, I found myself at a beautiful small private farm in rural Wales. A clear stream flowed past lush pastures and copses of trees, while sheep and horses grazed nearby. Even the nearby abandoned mine site, the reason for my visit, looked more like an old ruin than a toxic waste site, with abandoned buildings and gravel mounds studded across heather-covered hills.

But once I started my investigation into the environmental impact of this old lead mine, I uncovered a completely different tale. Underneath this idyllic landscape was a longstanding legacy of metal pollution from centuries of mining. The stream and pastures were contaminated with notably high concentrations of lead and other toxic trace metals. Worst of all, I found evidence of these metals transferring into local wildlife and domestic animals, with potentially devastating effects.

Before starting my PhD project, I hadn’t given lead pollution much thought. In my mind, it was rooted in the past – an issue that affected Romans using lead pipes or Elizabethans using white lead makeup. I soon realised that lead pollution is not just reserved for the history books.

Despite its past prevalence, lead and other metal pollution continues to be a major global problem. Active mining and metalworking is currently prevalent in Africa, Asia and the Americas, frequently causing pollution and major health effects in surrounding communities.

Even though most metal mines in the UK closed more than a century ago, the resulting pollution remains in our environments because trace metals do not degrade.

As part of my research, I investigated the extent and possible impacts of the legacy pollution from abandoned metal mines. I collected environmental and animal samples from two Welsh mine sites and areas downstream.

In conjunction with a multidisciplinary team of researchers, I found extremely high concentrations of lead and other metals, including cadmium, zinc and copper in the water, sediment and soil at the mine sites. These concentrations did not markedly decline in the areas I surveyed downstream of the mine sites including at the farm I had admired during my first field visit, where levels remained high. I was surprised to find that sites appearing pristine and located miles downstream of a mine could still be contaminated.

Next, I collected aquatic invertebrates, including caddisflies, mayflies and stoneflies, plus mice and voles to assess whether metals were transferring into wild animals. Lab tests showed that the invertebrates contained extremely high metal concentrations, sometimes even above those found in the local sediments. Mice and voles showed a similar pattern – while they appeared able to regulate some metals, we found particularly high, and potentially toxic, lead concentrations in their tissues.

Chickens and eggs

Finding these elevated metal concentrations in local wildlife made me wonder whether domestic animals were similarly affected. We examined chickens living approximately 0.6km downstream from an abandoned lead mine. While these chickens appeared healthy, their blood and feathers contained high lead concentrations, potentially indicating lead poisoning.

I found that the eggs these chickens laid were similarly contaminated with lead concentrations much higher than those found in supermarket eggs. Based on thresholds by the European Food Standards Agency, human adults regularly consuming these eggs could be at risk of developing chronic kidney disease. Meanwhile, in children, regularly eating only one or two eggs per day could result in lower IQ scores because lead poisoning can affect their brain development.

My study is one of many globally highlighting the extent and potential impacts of metal pollution, whether it is from an abandoned or working mine, a factory, or a landfill. With metal recycling on the rise, electronic waste recycling points are carving out their own legacy of metal pollution.

While remediation efforts are needed to clean up sites polluted by metal, this can be challenging and expensive. Metal contamination cannot be destroyed, though it can be covered and sealed or moved to another more secure location. But it’s hard to contain - my studies illustrate how metal contamination can extend far beyond the original source, so remediating one site may not address the full extent of that pollution.

Climate change will also exacerbate contamination, as more frequent storms could disturb and further move metal pollution through the soil, air, and water. Far from being an artefact of the past, metal pollution is present in our environment. It has to be addressed, both now and in the future.

Andrea Sartorius received funding from NERC and NRW.