RALEIGH  This week the N.C. Department of Environmental Quality announced its new water purity standards for determining which homes within a half-mile Duke Energy’s 14 coal ash plants across the state will get water filtration systems or new hookups to public water. Under state law Duke Energy is required to provide an alternative source of drinking water for homes in that proximity, whether their water exceeds those standards or not.”We want every family in North Carolina to have access to safe, clean drinking water,” said Michael Regan, DEQ secretary. “We’ve set performance standards for coal ash contaminants to ensure that families who use these filtration systems will have water that meets or exceeds federal and state standards.”On DEQ’s new list of standards is chromium VI, or hexavalent chromium, listing 10 parts per billion as the limit. That is significantly less stringent than the 0.07 limit recommended by scientists at the Department of Health and Human Services last fall under the Pat McCrory administration. During the campaign for governor, then-Attorney General Roy Cooper openly chastised his opponent in televised debates saying he would have “listened to the scientists” and backed their figures.The controversy over what standard to use erupted in 2014 after a coal ash spill into the Dan River. At the time scientists, policymakers and politicians intensely debated the health ramifications of the spill, how to clean it up and how to prevent another.Scientists at DEQ and those at the Department of Health and Human Services disagreed on what was considered a “safe” level of chromium VI in drinking water. In one of the meetings, DHHS scientist Ken Rudo advocated for permissible chromium VI levels at 0.07 parts per billion, 1,400 times more stringent than the federal standard. DEQ at that time estimated that more than half of public water systems in the state would need to tell residents not to drink their tap water if Rudo’s standard was used.Much to the dismay of DEQ, Rudo moved forward with sending “do not drink” notices to 400 homeowners, but later had to rescind them. The controversy played out in media across the state as residents tried to decipher whether their water was safe.Cooper pulled the issue into a live campaign debate, saying he would have backed Rudo, supporting a chromium VI level that is much lower than that for bottled water.”One of the things I’m going to do is listen to the scientists,” Cooper said during a televised gubernatorial debate in October 2016. Environmental groups and Cooper’s supporters were equally fired up at the McCrory administration over the standards.Chromium is a naturally occurring mineral in everything from toothpaste to deodorant to bottled water. It is also in coal ash, a byproduct of coal-fired energy plants. Chromium VI, however, is a carcinogen in high concentrations. The Environmental Protection Agency sets a limit of 100 parts per billion for total chromium, but does not parse out chromium VI for a separate standard.Recently, a California state court knocked back efforts to establish a chromium VI limit of 10 parts per billion. In that case, the court ruled that the chromium level established by the state’s Department of Public Health was not economically feasible and efforts to comply with it would raise household water prices between $64 and $5,000 annually, depending on the size of their water system.Despite the interagency conflict under the McCrory administration, DHHS now seems in agreement with the DEQ standard of 10 parts per billion.”Clean drinking water is essential to public health, and our department will continue to work with DEQ to provide accurate and timely information about drinking water safety,” said Mandy Cohen, secretary of the N.C. Department of Health and Human Services.For households within a half-mile of a coal ash basin, state law requires that Duke Energy install whole-home filtration or provide for households to hook up to public water supply by October 2018 even if their water testing results do not exceed the DEQ standard.