Rising concerns about cancer from sterilizing gas prompt new pollution limits

A sterilizing chemical used to clean 20 billion medical devices in the United States each year also poses a significant cancer risk to people who inhale it — and federal regulators are cracking down on plants where the gas can seep into surrounding neighborhoods.

The Environmental Protection Agency announced last week that it plans to tighten rules for emitters of ethylene oxide, an odorless, colorless gas.

A few of the roughly 86 plants across the country that use the chemical have generated public opposition — including sites in the Atlanta and Chicago regions run by Sterigenics, an Illinois company that sterilizes medical tools, devices, biopharmaceuticals, foods and packaging.

The new rules will affect three plants in the Twin Cities, according to the EPA's website — although six metro-area facilities had previously been listed as using ethylene oxide. Sterilizers would have to install new equipment to limit emissions, test it and continuously monitor releases on-site.

The three sites that would be regulated under the new rule are Boston Scientific's Cardiac Pacemakers Inc. in Arden Hills; Medtronic's facility in Fridley; and Steris Inc. in Coon Rapids.

Ethylene oxide is commonly used to sterilize medical devices and instruments used in hospitals and other medical settings. It's also used to fumigate some spices. The EPA's proposed rule would cut emissions by 84% at commercial sites that use the gas for sterilization, or a reduction of 77 tons a year across the country, EPA Deputy Administrator Janet McCabe told reporters last week.

The new rule and a separate action that would target plastics makers and chemical plants caps years of concern over the gas. EPA considered banning it from new sterilizers in 2005. It abandoned the idea after pushback from industry groups like the American Chemistry Council.

The agency completed an analysis last year that showed 23 plants across the country released enough of the gas that 100 people in a million could develop cancer if exposed over a lifetime by living nearby. Those cancers affect the blood, bone marrow and lymph systems, according to the Centers for Disease Control and Prevention.

For people exposed at higher levels, such as workers in sterilization plants, breathing in the gas can damage the nervous system, according to the CDC.

None of the plants that exceeded the EPA's health limit are in Minnesota — but the agency did not consider the effects of several lower-emitting plants that might be close together, said Darya Minovi, a senior analyst at the Union of Concerned Scientists (UCS).

She added that many advocates say the EPA needs a lower threshold for protection than 100 cases of cancer in a million. The agency uses that level to focus on the biggest emitters.

A UCS report from earlier this year highlighted that in some places the plants are clustered — including in the Twin Cities, where four facilities are in a roughly 10-mile corridor from Shoreview to Coon Rapids.

That report was based on the six facilities the EPA used to list as ethylene oxide emitters in Minnesota. When the agency released its new rule last week, it removed three sites from the list.

All three sites removed from the list are research facilities, which are not subject to the proposed rule, EPA spokeswoman Shayla Powell wrote in an email. The exempted sites include a research and development lab owned by Maplewood-based 3M, a Medtronic physiological research lab in Coon Rapids, and Interventional Cardiology in Maple Grove.

Kari Palmer, air assessment section manager with the Minnesota Pollution Control Agency, said that an exemption for scientific labs is written into the Clean Air Act.

At the state level, regulators start looking at an emitter if its pollution could lead to 10 cases of cancer in a million people, or one-tenth of the EPA's threshold, Palmer said.

But the most the state can do is ask for a voluntary change in operation or emissions control — Minnesota's laws and regulations don't let the MPCA force reductions in toxic air pollutants, Palmer said.

"When some of this is a little less clear and not in rule, it can definitely make it a little more challenging to make these reductions quickly," she said.

As is the case in most states, the MPCA carries out EPA programs, and would implement the new rule.

Some change has happened already. In Coon Rapids, the Steris plant installed new equipment in 2021 to scrub ethylene oxide from the air, Palmer said. Steris is a medical equipment sterilizer registered in Ireland. A media representative did not respond to requests for comment.

Before the controls were installed, ethylene oxide accounted for about 40% of the airborne cancer risk in the census tract where Steris is located, according to the most recent EPA modeling available.

The MPCA has not yet determined how much the new equipment has reduced emissions, spokeswoman Hannah Sabroski said.

Daily Memphian reporter Keely Brewer contributed to this story.