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Is Philadelphia testing its drinking water correctly?

Documents obtained by NBC News show results from Philadelphia's last round of water testing may offer a misleading picture of the lead flowing from its taps.

The silhouettes of people are seen watching the sunset over the Schuylkill River in Philadelphia, May 8, 2015. Philadelphia. (Photo by Victor J. Blue/Bloomberg/Getty)
The silhouettes of people are seen watching the sunset over the Schuylkill River in Philadelphia, May 8, 2015. Philadelphia. Bloomberg via Getty Images

Lisa Riordan Seville