A Field Comparison of Methods for Monitoring Ethylene Oxide Concentration

Abstract

A variety of methods for monitoring ethylene oxide (ETO) in air have been developed and evaluated in the laboratory and in the field to provide the ability to monitor this compound at the increasingly lower levels required by current guidelines and regulations for exposure limits. The field evaluation described here compares results obtained using four techniques: two commercially manufactured passive monitors, the Crystal Diagnostics AirScan^[rgrave] and the 3M #3551 badge; the sorbent tube method currently being used by the Occupational Safety and Health Administration; and a portable gas chromatographic (GC) method published in the current edition of the Manual of Analytical Methods of the National institute for Occupational Safety and Health. Samples were collected at two commercial sterilization facilities that use ETO for sterilization of a variety of materials. Concentrations ranged from approximately 0.7 to 32 ppm for samples of 15-minute duration, and from approximately 0.5 to 1.6 ppm for samples of 8-hour duration. The precision and relative response of the various monitoring techniques were compared with one another because the true concentration of ETO was not known and therefore no measure of accuracy could be determined. At the first sampling site the AirScan passive sampler gave significantly higher results than the sorbent tube method, but neither of those methods could be statistically distinguished from the 3M passive sampler or the GC method. Results at the second site indicated all sampling techniques were equivalent except for the subset of 3M badges that were analyzed by one of two laboratories that analyzed the 3M badges. Precision ranged from <2 percent mean relative standard deviation for on-site GC analysis by one instrument to approximately 15 percent for the AirScan sample results. In general, although the AirScan monitoring method was less precise than the other methods, all the methods provided statistically equivalent measures of workplace ETO concentrations for both short-term and full-shift exposures under the conditions of this evaluation.