One potential drinking water regulation that is seeing an uptick in activity is hexavalent chromium (Cr-VI), though the most immediate action may come in California, not at the federal level. On July 18, the California Superior Court ruled that the state’s Department of Public Health must act on an expedited schedule to propose a drinking water maximum contaminant level (MCL) for Cr-VI. The ruling stems from a Natural Resources Defense Council (NRDC) lawsuit (NRDC v. California Department of Public Health, Cal. Super. Ct., No. RG12643520), seeking enforcement of a California state law that required a Cr-VI standard to be set by January 1, 2004. In 2011, California’s Office of Environmental Health Hazard Assessment set a public health goal for Cr-VI of 0.02 parts per billion, and state law requires California drinking water standards to be set as close to that goal as economically and technically feasible.
Although the health effects of CR-VI exposure at high doses are fairly well documented, California’s push towards a Cr-VI MCL comes as EPA continues to assess potential health impacts at the very low doses that may be found in drinking water supplies. Though this assessment process is moving much slower than California’s regulatory process, EPA’s efforts at vetting the available science on low-dose Cr-VI exposures is a vital step in ensuring an MCL is set at a level that is both scientifically and economically defensible.
As part of its assessment process, EPA has scheduled a two-day “state of the science workshop” to inform its Integrated Risk Information System (IRIS) assessment of Cr-VI. Divided into two sessions held via webinar/teleconference only on September 19 and 25 (9:30 am – 12:30 pm EDT each day), the workshop will focus on key scientific issues expected to inform EPA’s IRIS assessment and, eventually, any potential federal regulation of Cr-VI in drinking water.
The first workshop session will focus on gastrointestinal tract processes that affect the absorption and transmission of Cr-VI and it’s conversion into non-toxic trivalent chromium, especially at low doses. The second session will explore exposure factors affecting susceptible human populations and lifestages. Each session will feature a panel of experts “representing scientific areas related to the reduction and absorption of ingested hexavalent chromium, including metals chemistry, toxicokinetics, and GI physiology and pathology.”
The workshops are open to public and should provide a good preview of the latest science that may be used to develop a federal-level drinking water standard for Cr-VI in the future. Additional information on the workshop, including registration information, is available at EPA’s Hexavalent Chromium Workshop webpage.