Mich. proposes tougher standard for hazardous chemical

Lansing — State officials are proposing a tougher cleanup standard for a toxic chemical that has contaminated groundwater beneath the city of Ann Arbor.

The chemical is known as 1,4-dioxane, an industrial solvent. Federal agencies say long-term exposure could cause health problems, including cancer.

The Michigan Department of Environmental Quality said its new standard would significantly lower the threshold for requiring cleanups of sites polluted with dioxane.

A plume of the chemical from a former Ann Arbor manufacturing plant has tainted three square miles of groundwater, although the DEQ said the city’s drinking water supply has not been affected.

DEQ remediation chief Bob Wagner said the action on dioxane is part of an update of cleanup standards for 308 hazardous substances in Michigan, based on scientific information about toxicity and exposure risks.