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DARIEN, Ill. — The latest test results near the shuttered Sterigenics facility in suburban Willowbrook reveal the highest levels to date of ethylene oxide in the air.

The U.S. Environmental Agency has been conducting ongoing testing for the cancer-causing gas. Sterigenics was shut down last month by Gov. JB Pritzker amid public outcry.

The latest numbers, released this week, come from samples taken between Jan. 22 and Feb. 11 — shortly before the facility was closed.

The levels fluctuated, but the EPA said ethylene oxide levels found Feb. 5 were the highest since air monitoring began. Officials believe Sterigenics is responsible for the significant levels of the chemical, which was found in neighboring communities and at Hinsdale South High School.

One area recorded a reading of 26.4 micrograms per cubic meter of the chemical — which is more than 1,000 times the limit allowed by the EPA.

Sterigenics said it believes it complied with its EPA permit and called the variability of concentrations both “inexplicable and inconsistent.”

The EPA has promised more answers over the next few months after finishing a cancer-risk evaluation. Meanwhile, members of the Stop Sterigenics group are traveling to Washington, D.C., on Monday to speak with federal lawmakers.

To read the EPA test results and learn more about Sterigenics testing, click here.