A report released last week found the presence of an unexpected contaminant in the water of four wells throughout the city.
After testing six wells, the Madison Water Utility found the chemical 1,4-dioxane in four of the wells, according to Joseph Grande, water quality manager for the Water Utility.
Wells on both the east and west sides of the city showed small levels of the chemical present in both drinking water and groundwater, he said.
The chemical is a solvent found in industrial products, such as cosmetics, and involves a volatile organic compound, according to Jeffrey Lefferty, an environmental epidemiologist for Public Health Madison and Dane County.
The well with the highest level of 1,4-dioxane was Well 11 near Woodman’s Market on the east side, Lefferty said. Test results showed the well had 0.63 parts per billion of 1,4-dioxane, more than double the amount the U.S. Environmental Protection Agency lists as a contaminant level, he said.
The EPA is unsure what effects the contaminant could have on humans, Lefferty said. Conclusive testing of the chemical has only been conducted on animals, he said. Based on the animal research, the EPA listed the chemical as a likely human carcinogen, he said.
“The U.S. EPA states that at a level of 0.35 parts per billion [the contaminant] could cause cancer risk,” Lefferty said. “To have this risk, they use the model of a 70-kilogram, roughly 150-pound, human drinking two liters of water at that level, 0.35, every day for 70 years.”
However, Lefferty said the amount of 1,4-dioxane found in the wells is very minor. He said the amount is about equivalent to one grain of sand in an Olympic-sized swimming pool.
The wells that were initially selected for screening were ones that had shown previous detections of man-made contaminants, Grande said. Other wells around the city, including those in the campus area, will be tested later this year, he said.
“Madison decided to do some prescreening in December of 2012 and we did additional testing in February based on the results in December,” Grande said. “There was the belief by the EPA as part of this rule that there may be some detection at these low levels.”
Grande said he would be surprised to find 1,4-dioxane in other wells throughout the city because they have not shown presence of man-made contaminants in the past.
The most common contaminants in the city wells influenced by human activity are elevated levels of nitrate, elevated levels of chloride generally from road salt, and trichloroethylene, according to Grande.
Although Madison Water Utility was not expecting to find the chemical, they will continue to monitor the wells to ensure the safety of drinking water, Grande said. He added the utility company is committed to providing safe, high-quality water to the community.
