U.S. Census tracts near the Sterigenics sterilization facility in Smyrna were among several locations flagged in Georgia by the EPA last year for elevated cancer risk from ethylene oxide. The gas, which was reclassified in 2016 as a carcinogen, is used by the company to sterilize medical equipment and other products.

Sterigenics has said it is in full compliance with state and federal emissions regulations and is in the process of upgrading its emissions controls. Sources of the gas also include petroleum refining and vehicle exhaust, and its presence in the atmosphere has been found to be more pervasive than previously thought.