Two Chicago-area companies — Sterigenics and Medline Industries — are facing more stringent air quality regulations and new worker protections after federal officials found higher-than-expected cancer risks in dozens of American communities where ethylene oxide is used to sterilize medical equipment.

Changes in federal policy proposed by the U.S. Environmental Protection Agency would reduce emissions of the toxic gas by about 80%, in part by requiring dozens of sterilization plants across the nation to cut back on the amount of ethylene oxide used and by mandating more effective pollution control equipment industrywide.

The new regulations come more than four years after an EPA analysis found that Sterigenics and Medline were responsible for some of the nation’s highest cancer risks from toxic air pollution.

Under intense pressure from politicians and community groups, Sterigenics closed a sterilization plant in west suburban Willowbrook during 2019 and took steps to reduce pollution from eight other facilities across the country. A state law prompted by Chicago Tribune reporting required Northfield-based Medline to dramatically reduce EtO emissions at its Waukegan facility.

EPA officials said other sterilization companies also have reduced emissions in recent years. The new regulations would set uniform pollution standards, require rigorous air quality monitoring and demand more protective gear for workers, agency officials said.

“Failing to take action to address these risks is simply unacceptable,” Janet McCabe, the agency’s deputy administrator, told reporters Tuesday during a media briefing. “At EPA, we are committed to following the law and following the science to safeguard public health.”

Chemical companies and government health agencies have known since at least the late 1970s that ethylene oxide mutates genes and causes breast cancer, leukemia and lymphomas.

Time and time again, a 2019 Tribune investigation found, the multibillion-dollar chemical industry and its political allies in Washington have thwarted, weakened or delayed efforts to limit exposure to EtO, relying on the same tactics used to stall action on more well-known hazards such as lead and asbestos.

After reviewing studies of animals and sterilization workers, EPA scientists concluded in 2006 that EtO was far more dangerous than previously thought. But it took the agency another decade to formally adopt a more protective limit intended to protect plant workers and neighbors.

Two panels of independent scientists generally agreed with the agency’s findings and rejected industry-financed studies that claimed to show EtO isn’t harmful at typical exposure levels. Chemical manufacturers and the sterilization industry continue to cite those studies as proof the new regulations aren’t necessary.

“Sterigenics supports EPA’s mission and is firmly committed to regulation based on sound science,” the company said in a statement that once again criticized what it calls the agency’s “flawed” conclusions about ethylene oxide.

Medline noted in its own statement that the company already reduced its Waukegan emissions by 95%. “Our top priority continues to be the safety of our employees, the communities where we operate and the healthcare providers and patients we serve,” the company said.

Based on air quality monitoring at parks, schools and homes when Sterigenics still operated in Willowbrook, the EPA concluded the facility’s pollution could trigger more than 10 cases of cancer for every 10,000 people exposed during their lifetimes — a rate 10 times higher than what the agency considers acceptable.

The Willowbrook plant increased the risk of cancer for people living up to 25 miles away, EPA officials said during a 2019 community forum.

In September, a Cook County jury ordered Sterigenics and two corporate predecessors to pay a Willowbrook breast cancer survivor $363 million for exposing her to ethylene oxide. The Oak Brook-based company later agreed to settle lawsuits filed by nearly 900 other neighbors for $408 million.

Sterilization companies contend they need to continue using ethylene oxide to fumigate about half of the medical devices and related products manufactured in the United States each year. The Food and Drug Administration has been nudging the industry to find safer alternatives.

National and local environmental groups sued the EPA last year demanding more aggressive action to protect Americans from exposure.

“Ethylene oxide sterilizers emit harmful air emissions day in and day out, endangering those living, working or going to school nearby,” said Celeste Flores, an activist with the nonprofit group Clean Power Lake County. “We’re looking forward to ensuring that the EPA is held accountable and enacts the strongest protection possible.”

mhawthorne@chicagotribune.com