As news about North Carolina's governor and his administration downplaying the risks of drinking water contaminated with hexavalent chromium unfolds, two leading environmental health advocates are pushing the Obama administration to finally set a nationwide standard for the highly toxic chemical.

Erin Brockovich, a noted environmental health advocate and the Environmental Working Group (EWG) President Ken Cook called on the U.S. Environmental Protection Agency (EPA) to stop dragging its feet and move quickly to set a tough national standard, known as a Maximum Contaminant Level or MCL, for the ubiquitous carcinogen found in millions of Americans' tap water.

In a joint letter to EPA Administrator Gina McCarthy, Brockovich and Cook wrote:

We write with deep concern about this continued delay. It is clear that the delay is sowing confusion among state and local regulators, utilities and the public about how much hexavalent chromium is safe in drinking water. This confusion is resulting in many Americans' exposure to unregulated levels of hexavalent chromium that federal, state and independent scientists agree pose health hazards.

The request comes as a top state health official in North Carolina resigned in protest over meddling by Gov. Pat McCrory and his staff. McCrory sought to retract "do-not-drink" warnings directed at some residents whose tap water comes from wells likely tainted by hexavalent chromium from nearby Duke Energy coal-burning facilities.

The situation in North Carolina is, in part, a result of the absence of a stringent nationwide health-protective EPA standard, argued Brockovich and Cook:

States like North Carolina, where industrial byproducts like coal ash increase the risk of hexavalent chromium contamination, need a federal mandate to set strong, health-protective standards for levels of the contaminant in drinking water. Without it, states will continue to use inconsistent and potentially unsafe guidelines and leave citizens confused about whether their drinking water is safe.

A report issued by EWG back in December 2010 found hexavalent chromium in tap water from 31 of 35 American cities.

"It's high time EPA put in place a stringent national standard to protect Americans from drinking water contaminated with hexavalent chromium," Cook said in a separate statement.

"A lack of a federal standard and the ongoing delay in setting one, are confusing utilities, states and citizens about what level of hexavalent chromium in drinking water is safe. Until EPA acts, we will likely continue to see the situation happening in North Carolina unfold in other states."