Jeffrey M. Sanders says US EPA issues new guidance on hexavalent chromium for public drinking water systems.

U.S. EPA issued guidance recommending how public water systems might enhance monitoring and sampling programs specifically for hexavalent chromium. The recommendations are in response to emerging scientific evidence that chromium-6 could pose health concerns if consumed over long periods of time. Apparently, EPA has figured out that if chromium-6 is in a public water supply, it may likely be ingested over a long period of time.

EPA’s enhanced monitoring guidance provides recommendations on where the systems should collect samples and how often they should be collected, along with analytical methods for laboratory testing. Systems that perform the enhanced monitoring will be able to better inform their consumers about any presence of chromium-6 in their drinking water, evaluate the degree to which other forms of chromium are transformed into chromium-6, and assess the degree to which existing treatment affects the levels of chromium-6 in drinking water.

EPA currently has a drinking water standard for total chromium, which includes chromium-6, and requires water systems to test for it. Testing is not required to distinguish what percentage of the total chromium is chromium-6 versus other forms such as chromium-3, so EPA’s regulation assumes that the sample is 100 percent chromium-6. This means the current chromium-6 standard has been as protective and precautionary as the science of that time allowed.

EPA’s latest data show that no public water systems are in violation of the standard. However, the science behind chromium-6 is still evolving. When the human health assessment is finalized in 2011, EPA will determine if a new standard needs to be set. More information on the new guidance to drinking water systems: http://water.epa.gov/drink/info/chromium/guidance.cfm