By Mary Ellen Ternes
Last year we talked about the glorious provision of precious, clean tap water by our municipalities, the significant effort required to achieve such a feat and complex regulations governing the process. In December 2010, Oklahoma received unfavorable national media attention regarding our drinking water that might have alarmed a few folks, so I thought an update might be welcome, at least to provide some perspective on the media coverage of Norman’s “hexavalent chromium” concentrations, and an explanation of the EPA’s recent reconsideration of fluoride standards.
First, let’s talk about “hexavalent chromium.” Chromium is a naturally occurring element. We actually need trace amounts of chromium in basic metabolism, and we live with low levels of chromium all around us in our air, soil, water and food. Chromium is naturally part of vegetables, fruits, meat, yeast and grain.
Chromium, like many other elements, can have several “oxidation states,” meaning that the chromium atom can exist in combination with other elements (chemically bonded into molecules), sharing electrons with these other elements in a manner that changes the number of electrons considered to be part of the chromium atom – remember “Lewis structures” and “valence electrons” from chemistry? According to the general literature, the most common oxidation states for chromium in the environment are “trivalent chromium” (or Cr+3) and “hexavalent chromium” (or Cr+6), and trivalent chromium is much more common in most locations in the United States. Industry uses chromium in all kinds of applications – most visibly in shiny chrome plating, but others as well, including processes which may use hexavelent chromium. This hexavalent form of chromium is more reactive and considered more toxic than the trivalent form. The relative proportions of trivalent and hexavalent chromium that occur naturally in the environment depend on the environment to which the chromium is exposed, particularly its pH and oxidative properties.
The EPA has set the Safe Drinking Water Act standard for “total” chromium (meaning chromium in all of its possible oxidation states) at 0.1 milligrams per liter (mg/l, which may be referred to as parts per million or ppm), which is the same as 100 micrograms per liter (ug/l, or parts per billion or ppb), conservatively assuming for purposes of setting the standard that all the chromium would be in hexavalent form. However, in response to new scientific research, EPA began to reconsider the health effects of hexavalent chromium and released a draft of this scientific review for public comment on September 30, 2010. The public comment period on the proposed standard expired on December 29, 2010. During the public comment period, the Environmental Working Group (EWG, a nonprofit environmental advocacy group) submitted comments that argued for even tighter standards relying on the new data. Many industry groups also submitted comments, with some questioning EPA’s timing and reliance on the new data. (I will spare you a dissertation on mouse livers, inhalation versus ingestion routes of exposure, etc.)
Just 10 days before the end of the public comment period, on December 20, 2010, the EWG released drinking water analytical data for 35 U.S. cities indicating existing concentrations of hexavalent chromium in those samples. Norman was one of the 35 cities sampled, and at 12.9 ppb, or 12.9 parts in 1,000,000,000 parts, the results for Norman were the highest of the 35 cities EWG tested.
Note that the EWG did not sample drinking water from all the cities in the United States, nor did its analysis demonstrate that any of the drinking water samples exceeded EPA’s drinking water standards, nor did the hexavalent chromium analysis indicate that Norman’s result of 12.9 ppb was close to exceeding EPA’s standard of 100 ppb, which was set assuming all chromium is in the hexavalent form. Thus, EWG’s report does not indicate that Norman has the highest concentrations of hexavalent chromium in the United States, or that Norman’s concentrations are anywhere close to exceeding EPA standards.
The next day, EPA issued reassurances regarding the appropriateness of the existing standard. And on January 11, 2011, it issued new guidance providing methods for municipalities to monitor specifically for hexavalent chromium, if they wish. But EPA will not require this specific analysis while considering the public comments received in response to its draft study. EPA might revise this standard, and it might not… we just don’t know yet.
Now a note on fluoride: fluorine, like chlorine, is an element and thus naturally found in our environment in many forms, including fluoride. While fluoride is in our drinking water naturally, for many decades we in the U.S. have intentionally added more to inhibit tooth decay. Like most folks, I probably owe the teeth in my head to fluoridation of tap water. But while a little fluoride may be a good thing, too much isn’t good for us, so EPA set the current primary drinking water standard at 4.0 milligrams per liter (mg/l, about 4,000 ppb) to protect against skeletal fluorosis caused by overconsumption, and the secondary standard of 2.0 mg/l to protect against tooth discoloration and other tooth damage. However, as part of its implementation of the Safe Drinking Water Act, EPA found new health effects data, as well as lots of new sources of fluoride in our environment, which might cause it to reconsider its fluoride drinking water standards also.
So right now, with hexavalent chromium and fluoride, EPA is doing its job: reviewing new health effects data for both chromium and fluoride like it’s supposed to do in implementing the Safe Drinking Water Act, which requires EPA to periodically review and update its drinking water standards. Am I concerned about it? Nope. This is the way the process works. Really, if I’m going to be concerned about anything, it ought to be the lead that’s probably in the pipe conveying water from the street main to my house, upon which I’m happy to lay blame for any misstatements in the foregoing.
STAY INFORMED
Mary Ellen Ternes, Esq. is a former chemical engineer from both the EPA and industry. She is currently a shareholder with McAfee & Taft and co-chair of its Renewable and Sustainable Energy Industry Group, and is serving a three-year term as City of Nichols Hills Environment, Health and Sustainability Commissioner.
This article was published in the March 2011 issue of Slice Magazine. It is reproduced with permission from the publisher. © 2011 Southwestern Publishing.