CHICAGO — The U.S. Environmental Protection Agency says air monitors near a suburban Chicago plant recently detected the highest level of a cancer-causing chemical at the facility since the federal government began testing.

The Chicago Tribune reports the EPA released data Thursday pertaining to ethylene oxide levels at the Sterigenics U.S. facility in Willowbrook. The plant sterilizes medical instruments.

According to the data, the plant’s highest daily average concentration of the chemical in January was found to be 14.3 micrograms per cubic meter of air.

The Centers for Disease Control and Prevention says exposure to 2.1 micrograms could cause about six cases of cancer for every 1,000 people exposed.

The Illinois EPA ordered the facility to shut down a week ago because of the levels. A judge denied the company’s effort to lift the ban. Sterigenics officials have declined comment.