Gov. J.B. Pritzker’s administration on Friday banned Sterigenics from using ethylene oxide at its Willowbrook sterilization plant, responding to an intense public outcry about toxic air pollution that left surrounding neighborhoods with some of the highest cancer risks in the nation.

Pritzker, the state’s new Democratic governor, ordered the Illinois Environmental Protection Agency to step in a week after the Trump administration told residents it still didn’t have enough evidence to take action against the Oak Brook-based company, which is owned in part by a private equity fund co-founded by former Republican Gov. Bruce Rauner.

Invoking rarely used authority in state law, Illinois EPA Director John Kim prohibited Sterigenics from pumping ethylene oxide gas into massive chambers used to sterilize medical equipment, pharmaceutical drugs, spices and food.

Kim’s order cited a federal study that said the chemical is so toxic that even tiny concentrations routinely leaking from the company’s two buildings pose a significant health risk.

“Governor Pritzker is committed to using every available tool to protect the health and well-being of Illinoisans,” spokeswoman Jordan Abudayyeh said in a statement. “The governor will continue to take any available and necessary action.”

Political appointees at the Trump EPA are taking a more cautious approach, even though testing in Willowbrook, Burr Ridge and Darien during late November and December revealed spikes of the volatile gas that were higher than concentrations detected before the company installed new pollution-control equipment last year.

William Wehrum, the administration’s top air official, said last week that the U.S. EPA will re-evaluate cancer risks in the Willowbrook area after collecting more air samples during the coming month and combining the results with computer modeling of pollution emitted by Sterigenics.

Samples analyzed so far suggest that on some days the air monitors are registering other, unknown sources of ethylene oxide, Wehrum said, meaning the agency needs more time to assess the dangers, determine the extent of Sterigenics’ responsibility and figure out how to limit future emissions. He also said there is no doubt that Sterigenics is responsible for alarming levels of the chemical in the community.

About 19,000 people in southeast DuPage County live within a mile of the Willowbrook facility. Four schools and a day-care center are close by, including Hinsdale South High School in Darien and Gower Middle School in Burr Ridge.

Sterigenics vowed to fight the order in court.

“The Illinois EPA’s actions to suspend operations at the Sterigenics Willowbrook facility are indefensible,” the company said in a statement. “Unilaterally preventing a business that is operating in compliance with all state permits and regulations from carrying out its vital function sets a dangerous precedent.”

Frustrated with the pace of federal and state investigations, Willowbrook officials hired their own consultants to collect air samples using the same type of equipment deployed in the community by the federal EPA. The village posted an update Friday showing that high levels of ethylene oxide were detected in early February outside the Willowbrook Police Department, across the street from Sterigenics in a cluster of government and industrial buildings near Illinois Route 83 and the Stevenson Expressway.

Pollution levels spiked as high as 160 micrograms per cubic meter of air, according to the village’s testing summary. Higher-than-expected levels also were detected at Gower Middle School (6.12) and Gower Elementary (3.1).

Regular exposure to 2.1 micrograms of ethylene oxide per cubic meter of air could trigger more than 6 cases of cancer for every 1,000 people exposed, according to the Agency for Toxic Substances and Disease Registry, an arm of the Centers for Disease Control and Prevention. Federal regulators generally target polluters when local cancer risks are greater than 100 in a million.

“We have to work to make sure they don’t reopen,” Willowbrook resident Melissa Alvarado said at news conference organized by the Stop Sterigenics community group. “We need to ban ethylene oxide emissions. No level of poison is safe.”

The Chicago Tribune first reported that federal and state officials began taking a closer look at Sterigenics in late 2017 after determining the cancer risks in one census tract near the facility are more than nine times higher than the national average.

By the time the U.S. EPA quietly posted its findings online in August, another federal agency had estimated the effects could be significantly more dire, prompting demands from local, state and federal lawmakers for an in-depth investigation.

John J. Kim / Chicago Tribune People protesting Sterigenics hold signs and wave at passing cars at the corner of Spring Road and Commerce Drive Saturday, Dec. 15, 2018, in Oak Brook. People protesting Sterigenics hold signs and wave at passing cars at the corner of Spring Road and Commerce Drive Saturday, Dec. 15, 2018, in Oak Brook. (John J. Kim / Chicago Tribune)

The Tribune reported in December that 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. After owners of the Willowbrook plant applied for a new permit in the mid-1980s, state regulators estimated that people living within a mile of the facility could end up breathing the highly toxic gas at concentrations 14 times higher than studies suggested was safe at the time.