Ethylene oxide sterilisation examined

Healthcare facilities worldwide use Ethylene Oxide (EtO or EO) sterilisers to process sensitive devices. Used as a sterilant for nearly eighty years, EtO has stood the test of time – proving effective at killing a wide range of pathogens. It continues to be a major technology for the sterilisation of medical devices worldwide – in fact, some 70% of packages containing devices for use in surgery include the statement “Sterile EO”. EtO is very good at reaching all parts of the most complicated of shapes, which means that long, narrow lumens present no problem. For example, a Line-Pickerill helix, comprising a 1m stainless steel tube, with a 2 mm lumen open only at one end, can be readily sterilised with EtO. In addition, EtO has no effect on the item being sterilised, so designers are not restricted in the plastics they can use, as they are when sterilising with gamma irradiation. Although EtO has global dominance in the sterilisation of single-use devices, it does not enjoy the same position in re-sterilisation. Its adoption has an irregular global pattern, with widespread use in the Americas (including the US), Middle East and Far East (excluding Japan). It is less widely used in Europe, and is not used at all in Japan, however. The successful adoption of EtO technology has been driven by its: • Low cost. • High effectiveness. • Low environmental impact.

Toxicity

As with any other sterilisation process, ethylene oxide must be used carefully. Because ethylene oxide is a toxic substance, users must pay attention to correct usage guidelines to avoid adverse effects for          operators or patients. The only statistically significant epidemiological study on the carcinogenicity of EtO, Mortality Among Workers Exposed To Ethylene Oxide (Steenland 1991), was conducted by NIOSH (National Institute of Safety and Health in the US). This study was updated in 2003 and covered 18,235 men and women who had worked at 14 plants (belonging to 10 different companies) from the early 1940s through to the 1980s. The study compared the death rates and causes of death in the general US population with those in the study. The study found that, overall, the occurrence of cancer in the study population (that had been exposed to EtO) was lower than in the general population. It also found that there was a trend of increased cancer incidence with increasing years of exposure. With less than ten years’ exposure the incidence of cancer in the study population was 77% of that in the general population. This rose to 91% for those exposed for 10-20 years, and reached 103% for those exposed for more than 20 years. It is this trend that led NIOSH to classify ETO as a “potential human carcinogen”. However, within the context of a sterilisation facility, the operator is not exposed to any EtO, giving rise to the question: “Are Europe and Japan missing out on the potential benefits?”