Study finds high levels of toxins in rocks from fracking target area
University of Aberdeen team warns of groundwater risks after selenium found in shale samples.
High levels of a toxic chemical have been discovered in rock samples taken from an area of the UK targeted for shale gas extraction.
The discovery, by researchers from the University of Aberdeen, could have serious implications for companies hoping to frack in Britain.
Scientists say the significance of the discovery lies in the risk of high levels of selenium being released into groundwater during drilling or fracking operations. Selenium is found in foods such as nuts and mushrooms, but excessive levels pose a serious risk to human health.
Professor John Parnell led the study at the Bowland Shale, a geological formation in the north of England rich in shale gas.
He said: "A major factor to be considered during shale gas drilling is the accompanying water, which may contain chemicals that require careful treatment. Recently, there was widespread concern in the US when water wells near a shale drilling site were found to contain selenium at levels that exceeded the maximum amount considered safe to drink, and this was assumed to have been released from the shale during drilling.
"The samples we have analysed from the Bowland Shale are some of the most selenium-rich in the British Isles, and far in excess of the levels of selenium found in the US example.
"Indeed, a number of the samples we tested exceeded the far stricter European Union limits, so it is clear that any drilling to extract shale gas in the Bowland Shale area must be carefully managed."
In addition to the UK, the study reveals similarly high levels of selenium existing in equivalent rocks in Ireland.
Despite these concerns, the study also highlights the opportunities that exist as a result of the high levels of selenium found in Bowland Shale.
Professor Parnell said: "While this is first and foremost an environmental issue, the concentration of selenium and other trace elements in extraction waters could be regarded as an opportunity.
"Selenium is a rare element for which demand is likely to increase, so there is a commercial incentive here which companies will no doubt be mindful of."