Leaks from defunct Welsh metal mines pose health threat

The Welsh Affairs Committee will investigate the impact of metal mine pollution on human health and explore whether existing regulations and standards are fit for purpose

A UK parliamentary committee has launched an investigation into the human health risks posed by abandoned metal mines in Wales after a Financial Times (FT) investigation revealed that they leak at least 500 tonnes (t) of harmful metals into the environment each year. 

A Freedom of Information request filed by the FT disclosed that 129 abandoned mine sites across Wales are contributing to poor water quality. Natural Resources Wales (NRW) told the FT that it estimates that 350–500t of metal leaks into the water supply each year, stating that the abandoned sites are “certainly, or highly likely, to be causing failures of water quality criteria”. 

The toxic metals can be absorbed into plants and livestock to be consumed by humans. Indeed, in 2023 a study funded by NRW uncovered harmful levels of lead in eggs on two small farms downstream from abandoned lead mines in west Wales. It found that a young child eating one to two of the eggs per day “could become cognitively impaired”.

Rt Hon Stephen Crabb MP, Chair of the Welsh Affairs Committee said the information revealed by the FT was “deeply concerning.” He added, “Given the reported volumes of harmful metals being discharged from abandoned mines, there is an urgent need for transparency about the scale of the problem and especially the potential health impacts.”

Sean Comber, Professor in Environmental Chemistry at the University of Plymouth acknowledged that mine water discharges are a major challenge, citing a few problematic areas: “Point sources such as the mines themselves are not the only input – the diffuse wash out from mine waste heaps, old working etc may be 50% of the issue and is much less easily dealt with.”

He added that abandoned mine sites are remote and without power, and costs are high and must be funded by the public purse. “Passive treatment (where ideally contaminated water passes via gravity, through an adsorbent bed of material to remove metals of interest) is cheaper but hard to achieve at scale, and needs maintenance.  Although shown to work on circum [nearly] neutral pH water in the North of the UK, they do not work as efficiently on acid mine drainage in Wales.

“Red media (bauxite waste) is highly alkaline so can neutralise the pH, but you still end up with a contaminated media that needs disposal, which presents another challenge.”

“Approximately 1,300 sites are estimated to have an impact on water quality and the ecology of over 700 km of watercourses.”

Dave Johnston, Natural Resources Wales’ Senior Specialist Advisor for abandoned metal mines said Wales’ industrial past presents “a significant legacy of abandoned metal mines which cause extensive pollution to rivers and streams across Wales. Approximately 1,300 sites are estimated to have an impact on water quality and the ecology of over 700 km of watercourses.”

He added that, funded by Welsh Government, Natural Resources Wales (NRW) and the Coal Authority are working together to try to reduce the pollution of land and rivers and mitigate other hazards and risks from abandoned metal mines.

Crabb added, “Following the Committee’s work last year on water quality in Wales, the Welsh Affairs Committee will investigate the impact of metal mine pollution on human health, plans for remediation, the information available to the public, and whether existing regulations and standards are fit for purpose.”

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