A study released by the Washington D.C.-based Environmental Working Group found that Chicago's water contains a carcinogen called chromium-6 at three times the proposed limit.
The California Environmental Protection Agency proposes the safe limit for chromium 6 should be set at 0.06 parts per billion. According to the study, Chicago water contains 0.18 parts per billion.
The Illinois EPA and the national EPA require the testing of total chromium, but not the sub-species chromium-6.
Thomas Powers is the commissioner for Chicago's Department of Water Management.
"Our water is safe. It's safe per those standards. And we test it every single day. Public health is the driving factor behind this department," he said.
The study recommends the EPA establish a legal limit for the contaminant. Powers says Chicago is ready to comply with any changes the EPA puts forth.
The report sites Norman, Oklahoma; Honolulu, Hawaii and Riverside, California as having the highest levels of contamination.