Largely overlooked after a 5-year battle, state officials this week backed off a plan to deregulate 500 types of toxic air pollutants, a move that was declared a “major win” for environmentalists.

The proposal was initiated in 2011 by Gov. Rick Snyder’s Office of Regulatory Reinvention (ORR), an effort by the administration to remove regulations that were considered burdensome to business. If approved, the rule change would have nearly halved the number of contaminants subject to scrutiny and would have dropped Michigan from a list of 9 states that currently regulate all potentially toxic airborne chemicals.

The Department of Environmental Quality announced on Monday that, in response to strong pushback from environmental advocates and the public,  it is sticking with the regulatory process that has been in place for 25 years.

“The DEQ’s decision to continue regulating these chemicals is consistent with the best available science on the health risks of exposure to toxic substances, and it’s the right decision for Michigan residents,” said Michigan Environmental Council policy director James Clift.

“We hope this is a sign that the department is putting its focus back where it belongs, on protecting Michigan’s environment and the health of people who live here.”

At a time when southwest Detroit’s air pollution “disaster” was the subject of the cover story in this week’s Newsweek, the MEC and other environmental group’s had argued that deregulation would  disproportionately affect the health of  low-income residents and minority communities.

“The region is among the most polluted in the nation, with little access to health care for those in need,” Newsweek reported, referring to the southwest section of the city and surrounding Downriver area suburbs.

The Snyder administration plan to deregulate air emissions would have meant oversight at the minimum federal standards — approximately 750 chemicals instead of the 1,200 the DEQ now regulates.

According to the MEC, it would have allowed unchecked air emissions of about 250 chemicals that have never been tested for their impact on human health and could be cancer-causing. It also would have deregulated emissions of another 250 chemicals that, while not carcinogenic, are known to be somewhat toxic, allowing industry to emit them in any quantity. Environmentalists warned that even mildly toxic chemicals can have serious health impacts if people are exposed at high enough levels.