The Traditional Purpose of Ethylene Oxide in Food
Historically, ethylene oxide (EtO) was employed in the food industry as an effective pesticide and sterilizing agent. Its primary function was to curb microbial loads, which include harmful bacteria, molds, and yeast. For low-moisture foods, this treatment served as a critical line of defense against foodborne illnesses caused by pathogens like Salmonella and E. coli, which can survive for long periods in a dried state. By disrupting the reproductive processes of these microorganisms, EtO effectively extended the shelf life of food products and helped prevent spoilage during transport and storage.
What Foods Were Treated with Ethylene Oxide?
Due to its gaseous state, EtO could easily penetrate breathable packaging and sterilize the contents within. This made it a particularly useful treatment for a range of products that are difficult to sterilize by other means, such as steam or heat, without compromising quality.
Commonly treated food products included:
- Spices and dried herbs: Items like sesame seeds, paprika, curry powder, and black pepper were frequently fumigated.
- Nuts and oilseeds: Walnuts, sesame seeds, and similar products were treated to prevent microbial growth.
- Dried fruits and vegetables: This included dried figs and prunes, where EtO was used to prevent spoilage.
- Food additives and thickeners: Substances such as locust bean gum (E410) and guar gum (E412) have been a source of recent contamination concerns.
Health Concerns and Carcinogenic Classification
Despite its effectiveness, ethylene oxide is not a benign substance. The primary reason for its phase-out in many regions is its classification as a mutagenic and carcinogenic substance. The International Agency for Research on Cancer (IARC) classifies EtO as a Group 1 carcinogen, meaning it is carcinogenic to humans. Continuous or long-term exposure has been linked to increased cancer risk, particularly lymphomas and leukemia.
Another significant health concern is the formation of toxic byproducts. Ethylene oxide is highly reactive and can transform into other harmful compounds, most notably 2-chloroethanol (2-CE), in the presence of chloride ions. This compound is less volatile than EtO and can persist in food products for longer periods, posing a continued health risk. Due to the lack of conclusive data on the toxicity of 2-CE, regulatory bodies in the EU treat it with the same caution as the parent compound.
Varying Global Regulations and Bans
The regulatory landscape surrounding ethylene oxide in food is highly fragmented, leading to significant challenges in international food trade. Different countries and regions have adopted vastly different approaches based on their risk assessments.
European Union's Stance
The EU has one of the strictest approaches to ethylene oxide. The use of EtO as a pesticide and fumigant on food has been banned for years (pesticide use banned in 1991, feed fumigation since 2011). The EU sets maximum residue levels (MRLs) at the analytical limit of quantification (LOQ), which is the lowest level that can be reliably detected. For most products, this level is extremely low, and any detection of EtO or its metabolite 2-chloroethanol above this limit triggers market withdrawal and recall actions. This strict policy has resulted in thousands of recalls involving products like sesame seeds and thickeners since 2020.
Regulations in North America
In contrast, the United States and Canada take a different approach. The US Environmental Protection Agency (EPA) allows the use of EtO on specific dried foods, such as certain herbs, spices, and walnuts, with established maximum residue levels. While these MRLs are still regulated, they are significantly higher than the EU's detection-based limits. The EPA acknowledges the risks but has not implemented an outright ban, arguing that for some products, no viable alternatives currently exist without compromising food safety.
Safer Alternatives to Ethylene Oxide
The global shift away from ethylene oxide has spurred the adoption of safer, yet equally effective, decontamination methods. These alternatives must address microbial risk without introducing carcinogenic residues.
- Heat or Steam Pasteurization: Applying controlled heat or steam can effectively reduce microbial load in many dried foods and spices. This process is well-established and widely used. However, it is not suitable for all products, as it can sometimes affect the flavor or texture of delicate spices.
- Food Irradiation: This process involves exposing food to a controlled amount of ionizing radiation to eliminate bacteria, fungi, and insects. Irradiation is highly effective, but consumer acceptance and labeling requirements can sometimes be a barrier.
- Ozone Treatment: Gaseous ozone can be used to sterilize food products. It is a powerful oxidant that breaks down quickly, leaving no harmful residues.
- Propylene Oxide (PPO): Similar to EtO but with lower toxicity concerns, PPO is used to treat certain low-moisture foods like nuts and spices in some jurisdictions.
Comparison Table: Ethylene Oxide vs. Alternative Methods
| Feature | Ethylene Oxide (ETO) | Heat/Steam Pasteurization | Food Irradiation | Ozone Treatment |
|---|---|---|---|---|
| Effectiveness | Highly effective against a wide range of microorganisms. | Very effective, particularly for surface contamination. | Highly effective at eliminating pathogens and insects. | Effective as a potent antimicrobial agent. |
| Health Risk | Classified as carcinogenic and mutagenic; forms toxic byproducts. | Minimal health risk; heat treatment is a standard practice. | Widely considered safe by regulatory bodies; no harmful residues. | Breaks down into oxygen, leaving no toxic residues. |
| Effect on Product | Minimal impact on heat-sensitive materials but can affect volatile compounds in spices. | Can alter sensory qualities (flavor, texture) of some sensitive foods. | Preserves freshness and texture; can be applied to a wide range of products. | Minimizes impact on product quality compared to heat. |
| Regulatory Status | Largely banned or heavily restricted in many regions (e.g., EU). | Widely accepted and regulated for food safety. | Approved in many countries but often subject to labeling requirements. | Approved for use in food processing in many regions. |
| Cost and Complexity | Relatively straightforward to implement in industrial settings. | Can be complex depending on scale and product type. | Requires specialized, heavily regulated, and expensive equipment. | Requires specialized equipment and careful monitoring. |
Conclusion
While ethylene oxide was once a staple in food sterilization due to its efficacy and versatility, modern understanding of its significant health risks has rendered it an undesirable and, in many regions, illegal treatment for food products. The discovery of carcinogenic properties and the persistence of toxic residues have fueled stringent regulations, most notably in the European Union, which has led to numerous high-profile product recalls. In its place, the food industry has increasingly turned to safer alternatives like steam pasteurization and irradiation. However, the variation in global regulations continues to pose a challenge, with countries like the US and Canada still permitting its use under specific conditions. This regulatory divergence, combined with global supply chains, means that vigilance and strict testing are essential for ensuring consumer safety worldwide. As public awareness grows and analytical methods become more sophisticated, the use of ethylene oxide in the food sector will continue to shrink, replaced by methods that do not compromise consumer health.
An excellent resource for monitoring global food alerts is the EU's Rapid Alert System for Food and Feed (RASFF), which has tracked many ethylene oxide-related incidents.
