The Environmental Protection Agency proposed Tuesday to limit the use of the chemical ethylene oxide after finding higher than expected cancer risk at facilities that use it to sterilize billions of medical devices each year. The EPA says its proposal will reduce ethylene oxide emissions from 86 medical sterilization facilities across the United States by roughly 80%. The companies will also have to measure the chemical, which is classified as a pesticide, in the air. The proposed change is based on EPA research that finds that as many as one in every ten workers in sterilization plants who is exposed to ethylene oxide could develop cancer, over and above their usual risk.