Traces of pesticides, chloroform and arsenic have been discovered in samples of water taken from some north state wells in the US.
However, the US Geological Survey said the concentration of these chemicals was below levels which would cause any safety concern, Redding.com reports.
The survey is conducting research of north state wells as part of state-funded efforts to assess the
water quality.
Water monitoring efforts have taken place at 66 wells in Shasta and Tehma, with a focus on public service wells serving at least 25 people each.
George Bennett, a hydrologist with the US Geological Survey, said: "We want to assess the resource currently being used for water supply."
He added that trace amounts of pesticides Deethylatrazine and Atrazine were found in more than 20 per cent of the wells sampled.
In 2006, the Environment Agency in the UK said around 6.5 per cent of its indicator samples of rivers contained pesticide samples of above 0.1 microgrammes per litre, a lower figure than that seen in previous years.
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