(CBS) — What is ethylene oxide, the cancer-causing agent at the center of the Sterigenics case?

The chemical is used to sterilize medical equipment.

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According to the Illinois Environmental Protection Agency, the chemical is linked to several cancers. The CBS 2 Investigators obtained documents showing the EPA warned the company 35 years ago that ethylene oxide caused stomach cancer.

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According to a 1984 Illinois EPA letter, the agency warned the company that the 40 tons of ethylene oxide released the previous year, was “several magnitudes higher than desirable.” The company was warned at that time that ethylene oxide could cause cancers of the pancreas, bladder, brain, and stomach. According to the letter, the EPA found the company was releasing it at levels 14 times to 445 times the acceptable level for people in a one-mile radius around the plant.

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Sterigenics denies all claims it dumped illegally or outside of any the controlled limits set by regulatory agencies