An overview of ethylene oxide testing in the United States and European Union
The European Union first banned ethylene oxide as a food fumigant in 1991. 
Recently, global concern for ethylene oxide (EtO) foods continues to rise. In 2020, routine testing of an Indian sesame seed import discovered ethylene oxide levels well above the detection limits. This spurred increased pressure for ethylene oxide testing in a variety of food matrices within the European Union and countries importing to its members. While the United States has not banned ethylene oxide use in foods, it is important to understand the allowed tolerances in the US and EU, especially as regulations continue to evolve and online sales contribute to increasing overseas exports.
What is ethylene oxide?
Ethylene oxide is a highly reactive compound that forms a colorless, flammable gas. It is the smallest epoxide, and its size and chemical properties make it easily volatilized. This means it evaporates quickly and does not remain on a solid surface for very long.
Is ethylene oxide toxic?
There is evidence that ethylene oxide is carcinogenic, and possibly mutagenic, via inhalation. Different regulatory agencies have assigned different toxicity levels to ethylene oxide:
- International Agency for Research on Cancer (IARC): Group 1 carcinogen (carcinogenic to humans)
- United States Environmental Protection Agency (US EPA): Carcinogenic to humans by the inhalation route of exposure with evidence supporting mutagenicity
- European Union: Category 1B mutagen, 1B carcinogen, and 1B toxic compound for reproduction
Why is ethylene oxide used for food products?
Ethylene oxide is a fumigant that inhibits microbial growth on dried foods; used properly, it can prevent disastrous foodborne illness outbreaks. Its small size provides high diffusivity and strong penetrating properties, effectively inhibiting bacteria (including spores), fungi, and virus growth. Ethylene oxide acts through the alkylation of organic compounds and denaturation of functional proteins and enzymes, ultimately causing DNA damage and alterations in microbial growth and reproduction.
What industries use ethylene oxide?
Ethylene oxide is a highly effective fumigant for the control of microbial growth on dried foods. It is used in various dried products, including:
- Spices
- Nuts
- Oilseeds
- Dried fruits and vegetables
- Herbs and botanicals
- Dietary supplements, including capsules and tablets
- Dried dairy products and infant formula
What is 2-chloroethanol and how is it related to ethylene oxide?
Ethylene oxide is highly reactive, and in the presence of chloride ions, it quickly converts to 2-chloroethanol. 2-chloroethanol is much less volatile and reactive than ethylene oxide, so it is less likely to fully evaporate from a product following aeration. This means 2-chloroethanol sticks around on products for longer time periods.
Since ethylene oxide either evaporates or reacts with other compounds during fumigation and aeration, 2-chloroethanol is often used as a marker compound to measure ethylene oxide levels. There is limited information about the safety of 2-chloroethanol, so it is only used to determine relative levels of ethylene oxide on a product.
What are the tolerance levels in the US?
The US-EPA sets tolerance levels of ethylene oxide on food in the United States; levels are reported as ethylene oxide and 2-chloroethanol (either separately or as a sum). The table below provides an overview of detection limits for ethylene oxide in different commodities, as defined in 40 CFR 180.151:
What are the tolerance levels in the EU?
Ethylene oxide use as a fumigant and pesticide has been banned in the EU since 1991. Although this restriction is not new, there has been a large increase in testing since 2020 when a screen of sesame seeds detected ethylene oxide used as a control agent before EU import.
The EU defines ethylene oxide residue as the sum of ethylene oxide and 2-chloroethanol, expressed as ethylene oxide. The maximum residue levels (MRLs) vary based on the commodity but are set at the level of quantification (LOQ). In other words, if ethylene oxide can be detected, then it has exceeded the tolerance level. It is important to understand the regulations for your specific raw ingredients and finished products because the LOQ may differ throughout production.
It should be noted that the MRL for food supplements in the EU is set at 0.1 mg/kg, including the capsules used in supplement formulations.
When should ingredients and products be tested?
Currently, ethylene oxide testing mainly occurs on products with historically high levels of the compound. However, testing is quickly becoming part of routine analysis with pesticides and other residues in the EU. This trend is spreading to the US, especially for products sold internationally. It is recommended to test raw materials before manufacturing to avoid wasting resources on production only to end up with a contaminated final product. Finished product testing is also valuable, especially for products with numerous reported cases of ethylene oxide issues. Agencies and raw material purchasers can request proof of testing, so it is important to stay vigilant with screening procedures.
How are ethylene oxide and 2-chloroethanol measured at Eurofins?
Eurofins scientists in Germany pioneered the development of analytical methods for ethylene oxide detection in food products. The current method involves converting any ethylene oxide in a sample to 2-iodoethanol, which is easier to detect. Following conversion, 2-iodoethanol and 2-chloroethanol are measured via gas chromatography-mass spectrometry (GC-MS/MS) and reported either individually or as a sum.
This method has a very low limit of quantification (0.01 mg/kg) which allows the detection of even trace levels of ethylene oxide. Currently, this GC-MS/MS method is validated for a variety of food matrices, including:
- Spices
- Sesame seeds
- Oilseeds
- Cereal products and thickeners (like gums)
- Dairy products
Why choose Eurofins as your third-party testing lab for residue and ethylene oxide analysis?
Since 1991, Eurofins has been at the forefront of ethylene oxide analysis. With 13 labs in 8 countries, we have the laboratory capacity to meet testing needs. Our team is devoted to working with you to clarify regulations, identify testing needs, and provide the most accurate analysis possible. Years of experience coupled with efficient communications make for a seamless testing experience.
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