Traces of a chemical listed as a probable carcinogen have been detected in four of Madison's city wells, prompting the city to conduct further testing.
Madison city officials said the chemical 1,4 dioxane is a man-made chemical often used as a stabilizer for a solvent.
Testing for the chemical wasn't required in Madison in 2015, according to EPA standards, but city officials said the water utility wanted to conduct the testing early.
The tests revealed trace amounts of 1,4 dioxane at the following levels measured by parts per billion:
? Well 9 (Spaanem Avenue): 0.12 ppb
? Well 11 (near east side Woodman's): 0.39 - 0.63 ppb
? Well 14 (University Avenue near Whitney Way): 0.29 ppb
? Well 15 (East Washington Avenue near Lien Road): 0.17 ppb
State's that have set guidelines for 1,4 dioxane set limits ranging from 2 ppb to 30 ppb.