The study shows that although concentrations of arsenic are generally lower than the current EPA drinking water standard of 50 micrograms per litre, approximately 10% of the samples analysed exceed the WHO guideline of 10 micrograms per litre.

The study’s findings have also been expressed as a map. This shows that the highest concentrations of arsenic are found in groundwater in the western, midwestern and northeastern parts of the US.

The USGS study was conducted in order to discover where arsenic concentrations might exceed possible new standards, such as the WHO guideline.

The US National Academy of Sciences (NAS) released a report last year recommending that the EPA should reduce the allowable level of arsenic in drinking water supplies from 50 micrograms/litre to 10 micrograms/litre as soon as possible (see related story). The American Water Works Association (AWWA) also called on the USEPA to base its proposal to revise the current standard for arsenic levels in drinking water on the report.

AWWA said it was not concerned about the impact a lower standard would have on US water utilities. “The USGS survey shows that only 13% of sources have arsenic levels greater than 5 micrograms,” an AWWA spokesperson told edie. “That leaves around 85% with less than five, so the number of systems that would be out of compliance with the WHO standard would be very low. The AWWA strongly endorses moves to set the standard at lower levels as recommended by the NAS. We are willing to support the conclusions of the nation’s best health experts on that. But the question is at what level is health best protected? Our official line is that we would support a standard of no less than 10 micrograms.”

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