Water utilities serving American cities use tests that downplay contamination

Guardian analysis reveals millions of customers were asked to used testing method condemned by the EPA which may flush out detectable lead content

Water utilities in some of the largest cities in the US that collectively serve some 12 million people have used tests that downplay the amount of lead contamination found in drinking water for more than a decade, a Guardian analysis of testing protocols reveals.

In the tests, utilities ask customers who sample their home's water for lead to remove the faucet's aerator screen and to flush lines hours before tests, potentially flushing out detectable lead contamination. The distorted tests, condemned by the Environmental Protection Agency, have taken place in cities including Chicago, New Orleans, Philadelphia and Columbus, Ohio. The improper screening could decrease the chance of detecting potentially dangerous levels of lead in water, the EPA has said.