Tuesday, January 11, 2011 - 12:17pm
Madison Water Utility (MWU) has received the results of water samples analyzed for (hexavalent) chromium-6 by the Wisconsin State Laboratory of Hygiene. The utility sampled four wells plus three other locations in the city. The data can be found at http://www.cityofmadison.com/water/waterQuality/Chromium.cfm.
While total chromium results have consistently been well below the allowable level of 100 ppb, the levels of Chromium-6 are relatively high in relation to test results from other parts of the country in a study done by an environmental group. The highest level detected in samples from seven locations in the City of Madison was 1.79 micrograms per liter, or parts per billion (ppb). Chromium-6 has been measured in other parts of the country at levels of 600 to 1,500 ppb.
The EPA does not have a health standard for chromium-6, nor does it require water utilities to test for the metal. The Madison Water Utility voluntarily tested seven sites within the City. No states in the country currently have a standard, but the State of California is currently proposing a health standard.
"These recent test data indicate that chromium-6 makes up the majority of total chromium in our water, and that it is present throughout our aquifer. Based on current science, we have no reason to believe that there is any health risk from the levels of chromium 6 in Madison's drinking water supply," said General Manager Tom Heikkinen. "We will continue to work closely with federal EPA officials on implementing any testing or treatment protocols they adopt."
Dr. Tom Schlenker, Director of Public Health for Madison and Dane County said, "Stomach cancer rates in Dane County are very low, significantly lower than the U.S. average rate. It is unlikely that one part per billion chromium in our drinking water poses a risk but we must be attentive to what the EPA analysis will show."
The U.S. Environmental Protection Agency is currently assessing the risk associated with chromium-6 in drinking water; a report should be available later this year. In the meantime MWU is working with Public Health Madison and Dane County to follow the evolving science closely and will be prepared to meet any future regulations regarding chromium-6, should they be deemed necessary. In addition, the Utility will continue to develop and implement a monitoring program for chromium-6 that will include all wells.
- Gail Gawenda, Water Utility PIO608:266-9129