. >> reporter: it's colorless, at times odorless, difficult to contain, and even more difficult to detectn escaping as emissions out of a facility just outside their doorsteps. people in this neighborhood fear it may be threatening their lives. but it's essential for sterilizing medical equipment, ventilators, syringes, catheters, all treated with it. america's hospitals rely on eto to prevent infections and ensure patient safety. you can see it in use here in an ad for a company called medline. >> ethylene oxide is injected into the chamber -- >> reporter: according to the fda, half the sterile medical devices us you'ded every year in our country, around 20 billion, are treated with eto. >> ethylene oxide is the most widely used safe and effective, scientifically proven, modality for medical device sterilization not only in the united statesstates but worldwide. >> reporter: it's a double-edged sword. while there's no risk to doctors and patients using devices sterilized with eto, the gas is a known carcinogen and breathing it in over time increases the risk of some cancers, including ly