In light of a recent article in the Chicago Tribune about chromium levels in Lake Michigan water, the City of Evanston reported that drinking water here has been annually tested for chromium since 1979. What the level of chromium – particularly hexavalent chromium, the subject of the Tribune article – and whether that amount is similar to that in Chicago’s drinking water is not clear.
The Environmental Protection Agency requires only that total chromium levels be tested – which includes hexavalent and other forms of the metal, according to the City. Further, Underwriter’s Laboratory, the nationally recognized water quality laboratory utilized by Evanston for this type of water analysis, has equipment capable of measuring the level of total chromium in water only to 5.0 parts per billion (ppb). The chromium in Evanston’s water has always been below this detection level and reported as non-detectable, or less than 5.0 ppb, according to the City.
The Tribune article said that the hexavalent chromium level in Chicago’s drinking water was 0.18 ppb. Based on the proximity of Evanston’s water intakes to Chicago’s and similarities in the water treatment processes, the City said Evanston staff assumes that the level of hexavalent chromium in the Evanston drinking water would be approximately the same as Chicago’s.
The current maximum contaminant (MCL) level for chromium is 100.0 ppb under U.S. EPA and Illinois EPA standards. This standard is established in the National Primary Drinking Water Regulations and all public water supplies must abide by these regulations, the City said. MCLs are established to protect human health based on what the EPA believes, given present technology and resources to detect and treat, is the lowest level to which water systems can reasonably be required to remove a contaminant.
At this time, the City said, the EPA considers this level of protection adequate to avoid skin irritation or ulceration during short term exposure or damage to liver, kidney circulatory and nerve tissues during long term exposure.
Per the Tribune article, the Environmental Working Group (EWG) commissioned the testing for hexavalent chromium levels in tap water from 35 cities and then compared these results to a proposed California public health goal of 0.06 ppb. The EWG recommendation is that the EPA should move expeditiously to establish a legal limit for hexavalent chromium in tap water and require water utilities to test for it. The EWG report can be viewed at their website www.ewg.org.
If Evanston were required by the EPA to remove hexavalent chromium to 0.06 ppb, a reverse osmosis / membrane technology treatment process would be required. Based on the capacity of the Evanston water treatment plant, conversion to this technology would cost at a minimum $110 million to install. In addition, this type of treatment process would require an increase in maintenance expenditures of approximately $3 million annually.
Evanston’s Water Division staff is investigating what laboratories are capable of testing for hexavalent chromium at the levels indicated in the Tribune article. Pending laboratory availability and testing cost, the Water Division proposes to have the level of hexavalent chromium in the Evanston tap water determined and then make this information available.
Bottled water is not required to meet any higher standard than tap water, and the City cautions that people should not interpret a PHG as a reason to limit their water consumption from a community water system.