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How much hexavalent chromium is in NC public drinking water supplies?

Is your water safe Environmental Working Group has released a new interactive map and report showing all the public water systems that have reported detecting hexavalent chromium at any level. This may leave North Carolinians wondering if they should be concerned about the amounts of hexavalent chromium found in their own local NC water supplies.

Last year, the NC Department of Health and Human Services (DHHS) warned well users near coal ash dumps with more than 0.07 parts per billion (ppb) hexavalent chromium not to drink their water. This concentration represents a 1 in 1 million increased lifetime cancer risk. (The Department later rescinded those letters, a decisions that has errupted into a major controversy).

Besides being associated with coal ash, hexavalent chromium can come from other industrial sources; non-toxic forms of chromium can also react with some drinking water disinfectants to create the toxic hexavalent form. Under current–but outdated–federal law, total chromium up to 100 ppb is allowed in drinking water. All of that could be the hexavalent form, leading to an estimated cancer risk of 1 in 700! Thankfully, no NC water supplies are close to that, but some have been found to exceed the DHHS health screening level (and even more are above California’s public health goal of 0.02 ppb, which is even more health-protective).

Out of 143 publicly and privately owned supplies tested from 2013-2015 under EPA’s Unregulated Contaminant Monitoring Rule, 48 (33%) had an average concentration above 0.07 ppb, but mostly far below the high concentrations detected in wells around coal ash sites. The majority of public water systems in NC (66%) averaged below 0.07 ppb. Private company Aqua NC’s Bayleaf Master system in North Raleigh, with a history of water quality violations for other contaminants, had the highest average concentration (0.62 ppb), and some of the highest individual sample results – up to 11 ppb at one well, and 3.1 ppb in the distribution system!

Among NC’s ten most populous cities, only Greensboro’s water supply averaged – barely – above 0.07 ppb during the 2-year period. Officials there recently identified the cause of the 2014 hexavalent chromium spike that led to the higher average – a specific liming agent they had used to treat the water, which has since been discontinued.

As federal standards for hexavalent chromium and many other substances fail to protect public health, often by factors of hundreds or thousands, CWFNC is advocating for health-based notifications to both private well users and public water customers for possibly harmful contaminants, whether there is a standard or not! See how your water supplier’s average compares at bit.ly/Cr6NC.

Thanks to Jennifer Liming for contributing to this article.

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