At least 33 US cities used water testing 'cheats' over lead concerns

Exclusive: Guardian investigation reveals testing regimes similar to that of Flint were in place in major cities including Chicago, Boston and Philadelphia

• Water departments to change lead-testing methods after investigation

At least 33 cities across 17 US states have used water testing "cheats" that potentially conceal dangerous levels of lead, a Guardian investigation launched in the wake of the toxic water crisis in Flint, Michigan, has found.

Related: Chicago residents take action to be rid of lead pipes as fear of toxic water grows