Nearly every new sample showed lead well above the redline. Edwards implored the agency to test the whole city. Cadmus didn't renew his contract.

On January 31, 2004, The Washington Post exposed the subsequent cover-up. According to a later congressional report, tens of thousands of homes—two-thirds of those tested—had tap water that registered above the legal action limit. Some samples tripped 5,000 ppb, the technical definition of hazardous waste. Worse still, the EPA was giving out bad health advice, telling people to flush their water lines in a way that actually increased exposure.

Edwards, meanwhile, had become so obsessed with the problem that he'd forgotten to maintain the well water for his own house, which had plunged to a dangerously low pH. "I wasn't taking care of myself or my family or my job," he says. "I had this moment of total panic where maybe I'd just poisoned my family with lead." He couldn't take it. One night Edwards thought he was having a heart attack; he'd developed an arrhythmia.

Marc Edwards begged the EPA to test all of Washington, DC, for lead, but it didn't listen.