Hexavalent chromium has been in the spotlight for many years due to its toxicity, prevalence in our water bodies, and popularization by the movie industry in the film, titled, Erin Brockovich (link to Wikipedia page). At the U.S. federal level, the EPA has had a long-standing regulation for total chromium at 100 ppb using Inductively Coupled Plasma Mass Spectroscopy (ICP-MS) per EPA 200.8. This method tests for total chromium and water utilities are required to use this method.
Conversely, states, such as California, require a measurement exclusively for hexavalent chromium using EPA 218.6 and now EPA 218.7 which is specific for drinking waters. You can read a review of hexavalent chromium regulations and analysis by EPA method 218.6 and 218.7 using ion chromatography in this article, titled, Changes from EPA Method 218.6 to 218.7 (link to downloadable PDF). The logic of a total method is based on the possible conversion between trivalent and hexavalent chromium.
The EPA regularly re-evaluates drinking water standards and, based on new science on chromium-6, began a rigorous and comprehensive review of its health effects in 2008. The agency uses an Integrated Risk Information System (IRIS) process that is currently evaluating the long term health effects, including the possibility that hexavalent chromium is a carcinogen.
Chromium is currently part of the EPA’s Unregulated Contaminant Monitoring Rule Three (UCMR3) program and in January 2015 released a report providing the data summary for the most current results, titled, The Third Unregulated Contaminant Monitoring Rule (UCMR 3) Data Summary, (downloadable PDF). Monitoring will continue to occur through December with final results release in the summer of 2016. This invaluable information probably represents the most comprehensive comparison study for the oxidation state of chromium and detection capabilities for the two different EPA methods.
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Data from over 38,000 samples and roughly 3800 water utilities show positive for 18,780 samples and 29,120 samples for Total and hexavalent chromium, respectively. In other words, 70% of public water utilities have total chromium (above an MRL of 100 ppb) and 88% of public water utilities (using an MRL of 0.03 ppb) test positive when hexavalent chromium is measured. Care should be taken in these numbers in that the reference concentration and health effects should be taken into consideration. Are these concentrations significant to cause a health concern? More information on this will come to light when the final IRIS reports are released by the EPA. It will also remain to be seen if the regulations are affected once the final UCMR3 report is release in the summer of 2016. Stay tuned!
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