A potentially dangerous chemical was discovered in drinking water in a number of cities nationwide, creating concerns for Madison residents serviced by city wells.

In a recent national study conducted by the Environmental Working Group, researchers found hexavalent chromium, or chromium-6, in tap water the tap water of 31 of 35 American cities – including Madison.

Following the Environmental Working Group’s research, the State Laboratory of Hygiene conducted further testing on a broader sample of Madison’s drinking water to determine more accurate levels of chromium-6.

Test results published Jan. 11 showed the level of chromium-6 in Madison’s drinking water was much higher than the level of the carcinogen in other cities throughout the country, but still below the federal limitations.

The test examined four Madison wells and found the level of chromium-6 in the drinking water ranged from .41 parts per billion to 1.79 ppb in comparison with the federal limitations that require general chromium contaminant not to exceed 100 ppb.

Scientists have yet to determine the level at which chromium-6 in drinking water can affect humans, according to a statement from the City of Madison Water Utility.

The Environmental Protection Agency performed a draft toxicological review that showed chromium-6 in tap water was likely to be carcinogenic to humans and laboratory animals.

Tom Heikkinen, Madison Water Utility’s general manager, said the city’s water is still safe to drink despite these findings.

“Madison’s drinking water meets or exceeds all current standards mandated by the Environmental Protection Agency and the Wisconsin Department of Natural Resources, and we have never had a drinking water violation,” Heikkinen said in a statement.

Heikkinen said the amount of testing Madison performs to monitor its water quality exceeds the regulatory requirements established by the EPA and the Department of Natural Resources.

The Environmental Working Group tested a single sample from one of the city’s taps, which Heikkinen said is an inaccurate representation of the city’s water system.

Madison will support outside testing for different chemicals in the city’s water and the utility will perform a more thorough examination of the level of chromium-6 in drinking water, Heikkinen said.

According to an EPA statement, the agency is currently analyzing new information about the effects chromium-6 has on humans and will release its findings later this year.

Following the Environmental Working Group’s study, EPA administrator Lisa Jackson met with U.S. senators to discuss the growing concerns about chromium-6 in drinking water.

The meeting concluded the EPA would work with local and state officials to develop monitoring programs specifically for the carcinogen in water systems, Jackson said in a statement.

The EPA will provide special assistance to the communities the Environmental Working Group cited as having the highest levels of chromium-6. Madison had the fourth-highest level of chromium-6 compared to the other cities tested in the study.

Once the risk analysis of chromium-6 is completed, Jackson said the EPA would determine whether new standards for levels of the chemical need to be established for drinking water.

Studies have found chromium-6 is carcinogenic when inhaled. It is used in the production process for materials such as dyes, stainless steel and leather.