Ethylene Oxide Exposures to Hospital Sterilization Workers from Poor Ventilation Design

Abstract

Employees in the central supply (CS) department of a Midwestern hospital, which used ethylene oxide (EtO) to sterilize medical supplies, reported experiencing multiple symptoms including headaches, dizziness, mucous membrane irritation, vomiting, and smelling a “sweet” odor during a portion of the operating cycle of the sterilizers. To identify the causative agent, air samples were collected and analyzed for EtO, organics, aldehydes, hydrochloric acid, chlorine, carbon monoxide, and carbon dioxide. In addition, air exhaust system flow rates were measured in and around the sterilizers, and the integrity of floor drains below the sterilizers was evaluated. Time-weighted average personal exposure concentrations for EtO ranged from 0.23 to 0.56 ppm among CS employees. These concentrations were below the Occupational Safety and Health Administration permissible exposure limit of 1 ppm, but above the National Institute for Occupational Safety and Health recommended criterion of maintaining EtO exposures at the lowest feasible level (<0.1 ppm). Short-term area concentrations of up to 77 ppm were detected at breathing zone height in the cart wash area. Area air concentrations of < 1.0 ppm for hydrochioric acid, < 0.2 ppm for chlorine, < 5.0 ppm for carbon monoxide, and up to 700 ppm for carbon dioxide were measured using gas detector tubes. The elevated EtO concentrations, suspected overexposures, and reported employee symptoms resulted from the connection of two sterilizer exhaust fans to an existing ventilation system, which had insufficient flow capacity at the point of connection. Some of the EtO exhausted from the large sterilizer was therefore forced into the cart wash area. A brief follow-up visit conducted 1 year after the last field survey indicated that employees had not experienced symptoms during the previous year. Following the last field survey the hospital staff had increased the ventilation system exhaust capacity and installed additional exhaust hoods and an EtO air monitoring system.