The Washington Post reports many US cities have not reported real lead levels in their drinking water. Like DC, other cities are using regulatory loopholes to manipulate their lead level reports, so whether lead is a problem is not known:
Some cities, including Philadelphia and Boston, have thrown out tests that show high readings or have avoided testing homes most likely to have lead, records show. In New York City, the nation's largest water provider has for the past three years assured its 9.3 million customers that its water was safe because the lead content fell below federal limits. But the city has withheld from regulators hundreds of test results that would have raised lead levels above the safety standard in two of those years, according to records.
Several other points from the article