Lead tests in New York City school buildings’ drinking water may have given inaccurately low results, experts say. The night before samples of water were taken, the schools ran every water outlet fully for two hours. This practice, known as “flushing”, can temporarily lower lead levels because it flushes out most soluble lead and lead particles from pipes. When the results of lead testing were released in July, parents were told that the drinking water in schools was generally safe. Officials said less than 1 percent of all samples taken from over 1,500 schools exceeded guidelines set by the Environmental Protection Agency.
Marc Edwards, a civil engineering professor at Virginia Tech, said to NYT, “The results should be thrown into the garbage, and the city should start over,” Edwards helped identify the dangerously high levels of lead in Flint, Michigan, which triggered concerns about drinking water across the country. Lead exposure is particularly harmful in children, leading to developmental delays.
Yanna Lambrinidou, an anthropologist and an affiliate faculty member at Virginia Tech’s Department of Science and Technology in Society who has worked with Dr. Edwards to identify lead contamination, also criticized the practice. In an email to NYT she said that NYC schools “may have just broken the national record for flawed testing.”
“Flushing is inappropriate any time you want to assess lead concentrations coming out of individual taps,” Dr. Lambrinidou told NYT in an email. “Unless N.Y.C. schools flush every drinking water tap every evening for 2 hours routinely, their sampling technique is both unreliable and scientifically and morally indefensible,”
The EPA’s “action level” for lead in municipal water systems is 15 parts per billion. In 510 out of 1,520 school buildings, there was at least one outlet where the first sample exceeded this limit. In 153 buildings, there was at least one outlet where the second sample exceeded the cutoff. In eight buildings, at least one outlet had first and second samples exceeding 500 parts per billion.
In February, EPA recommended against flushing when sampling for lead in houses because it “may potentially lower the lead levels as compared to when it is not practiced.” The EPA does not regulate school drinking water, but the agency’s voluntary guidelines advise against flushing. Samples should be taken under normal consumption patterns, EPA said.