The Duke Energy coal ash spills have led to high concentrations of vanadium and hexavalent chromium in North Carolina surface waters, resulting in legitimate public health concerns. In response, NCDEQ representatives correctly noted that vanadium and hexavalent chromium are not regulated in the current U.S. Drinking Water Standards, implying that waters containing these chemicals are safe to drink. This implication is false.
I have worked with the USEPA on the identification of chemicals that should be considered for inclusion in the U.S. Drinking Water Standards.
Two essential attributes of candidate contaminants are: (1) the contaminant is toxic to humans; (2) and the contaminant may be found in natural waters of the U.S. at concentrations approaching harmful levels.
Vanadium and hexavalent chromium are toxic to humans at relatively low concentrations, which satisfies attribute 1. However, these contaminants are typically found in natural waters to be at concentrations well below health advisories (attribute 2), so they are not currently regulated in the U.S. Drinking Water Standards. A contaminant that satisfies attribute 1 but not attribute 2 results in precisely the circumstance where health advisories make sense.
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It is regrettable that the NCDEQ did not acknowledge this situation and retain the health advisory.