"Nationwide, water is screened for lead by checking the first sample of water from homeowners' faucets. But results of recent federal testing in Chicago show that although all homes passed that first test, nearly 45 percent had lead levels spike when more water samples were taken directly afterward."
"Those results suggest that the way water is screened for lead nationwide may inaccurately gauge how much of the toxic metal leaches into our water.
For example, the highest lead levels in most of 29 Chicago homes tested were found in the sixth or seventh liter of water, which is not tested by water utilities. Some lead levels were more than twice the federal standard."