The Guardian claims that “at least 33” large American cities use testing methods deliberately designed to undercount the presence of lead in tap water:
Of these cities, 21 used the same water testing methods that prompted criminal charges against three government employees in Flint over their role in one of the worst public health disasters in US history.
….Testing methods that can avoid detecting lead include asking testers to run faucets before the test period, known as “pre-flushing”; to remove faucet filters called “aerators”; and to slowly fill sample bottles. The EPA reiterated in February that these lead-reducing methods go against its guidelines, and the Flint charges show they may now be criminal acts.
….The EPA has warned since 2008 that pre-flushing is problematic and goes against the “intent” of regulations designed to detect lead….Further distortion is achieved through the removal of “aerators” — the small metal filters at the tip of faucets. These filters can collect lead particles and add to lead detected in tests.
I don’t know how serious this is. I suppose no one will know until these cities collect data properly and compare it to their old results. The EPA says it plans to release new testing rules in 2017.