What is ethylene oxide?
At room temperature, ethylene oxide is a flammable colorless gas with a sweet odor. It is used primarily to produce other chemicals, including antifreeze. In smaller amounts, ethylene oxide is used as a pesticide and a sterilizing agent. The ability of ethylene oxide to damage DNA makes it an effective sterilizing agent but also accounts for its cancer-causing activity.
Copied from the national cancer institute
https://www.cancer.gov/about-cancer/causes-prevention/risk/substances/ethylene-oxide
