Huge quantities of nitrate chemicals from farm fertilisers are polluting the rocks beneath our feet, a study says.
Researchers at the British Geological Survey say it could have severe global-scale consequences for rivers, water supplies, human health and the economy.
They say the nitrate will be released from the rocks into rivers via springs.
That will cause toxic algal blooms and fish deaths, and will cost industry and consumers billions of pounds a year in extra water treatment.
In a paper in Nature Communications, the scientists from BGS and Lancaster University estimate that up to 180 million tonnes of nitrate are stored in rocks worldwide – perhaps twice the amount stored in soils.