Ethylene oxide is a colorless gas used in some countries such as India, USA, Canada for spraying food to kill bacteria and fungi. It may therefore appear as a residue in these foods. In the EU, it has been banned in plant protection products since 1991. Ethylene oxide is permitted as a sterilizing agent (e.g., in medical devices) because, in order to prevent damage to the material or electronics, in many cases it cannot be replaced by other sterilization methods (hot steam, gamma rays, etc.). However, it must not come into contact with food, but also must not be applied to surfaces that come into contact with food.

Residues of ethylene oxide are found mainly in sesame seeds, in products containing sesame seeds such as bars, snacks or salad toppings, and in spices and additives, e.g. locust bean gum (E410), guar gum (E412).

Ethylene oxide is mutagenic and carcinogenic

Antigen test systems

We have already randomly analyzed swabs of commercially available SARS-CoV-2 antigen test systems with regard to ethylene oxide residues in 2021. For this purpose, we performed 15 swab analyses from 12 different products/manufacturers. In 13 swabs, no ethylene oxide was detectable. Ethylene oxide was detectable in two swabs, but in both cases the levels were well below the method's limit of quantitation of 1 µg/swab. These two results represent less than one-tenth of the limit allowed for medical devices.

We also evaluated the health risk: To do this, we assumed that a child weighing 30 kilograms would have a test stick containing 1 microgram of ethylene oxide in his or her nose for one hour every day. Even under this nevertheless unlikely duration of contact, the so-called "intake level of low concern" for ethylene oxide of 0.037 micrograms per kilogram of body weight per day is undercut. Since a test is not performed every day and the swab is usually in contact with the nasal mucosa for about 20 seconds when an antigen test is used, the actual risk is much lower.

Food

On July 16, 2021, the European Commission reiterated in a letter addressed to European authorities and food business operators that products contaminated with ethylene oxide above the applicable MRL under Regulation(EC) No. 396/2005 will be assessed as unsafe throughout the EU and therefore unfit for human consumption.

The responsibility for safe food lies primarily with food business operators. As part of their self-monitoring, they are now called upon to test their products for this banned substance. In case of contamination with ethylene oxide above the applicable maximum residue level according to Regulation(EC) No. 396/2005, these products must not be marketed.

Since contaminated food products were reported via the European Rapid Alert System, controls by the competent food authorities have been ongoing throughout Austria and will continue to be carried out in order to ensure the greatest possible safety for consumers.

Ethylene oxide is a mutagenic carcinogen with no threshold (RAC 2017, ATP). Mutagenicity (the potential to alter genetic material) is basically an acute effect occurring after a single exposure. However, secondary effects, such as tumor formation (carcinogenicity), occur after a delay and as a result of accumulated exposure over a lifetime. Therefore, even single high exposures by children should be avoided. Due to the mutagenic potential of ethylene oxide, it was not possible to define a health-based guideline value without health risk (EFSA, 2012, BPC 2020). However, as already stated in the BfR statement (BfR, 2020, 2021), the data situation on ethylene oxide allows the derivation of intake levels below which a "minimal additional cancer risk" can be assumed (EFSA, 2005). Following the elaboration of this concept by EFSA (2005), an intake level of "low concern" can be estimated by applying an extrapolation factor of 10000 (Margin of Exposure, MoE) to the relevant BMDL10 value from an appropriate animal study or from epidemiological surveys. The BMDL10 value describes the calculated lower limit of the confidence interval of that dose that causes a 10% increase in tumor incidence with lifetime intake. In the case of ethylene oxide, the National Institute for Public Health and the Environment (RIVM, the Netherlands) had available a 150-week study in rats (Dunkelberg, 1982) suitable for estimating cancer risk after oral intake. The findings from this study were re-evaluated with respect to the dose-response relationship according to the state of the art described by EFSA (2017) using benchmark dose modeling and found to be plausible by BfR (BfR, 2020, 2021). A BMDL10 of 0.37 mg/kg bw/day was determined for the increase in tumors in the stomach of lifelong exposed female animals (rats) in the study by Dunkelberg, 1982. Thus, by including the extrapolation factor of 10,000, the intake level of "low concern" for ethylene oxide is 0.037 µg/kg bw/day. Regarding the ethylene oxide degradation product 2-chloroethanol, the data situation is contradictory and partly incomplete. The BfR (BfR, 2020, 2021) also concludes that no reliable statement can currently be made on the mutagenic and carcinogenic properties of 2-chloroethanol and that the risk assessment for 2-chloroethanol should therefore follow the same principle as for ethylene oxide.

The use of ethylene oxide for sterilization of medical devices is an established procedure. The manufacturer must prove that the products are actually sterile after sterilization and that the outgassing time for ethylene oxide has been selected long enough to ensure that limit values that have been classified as harmless are also complied with. In addition, the involvement of a notified body (independent testing authority) is necessary as part of the conformity assessment procedure. If ethylene oxide were no longer allowed to be used for sterilization, many medical devices, especially high-class ones (implantable devices), would no longer be available, as most of them cannot be sterilized using other methods.