The United States Environmental Protection Agency (EPA) has recently proposed strategies to reduce emissions and exposure to ethylene oxide (EtO) gas, commonly used in commercial sterilization facilities. This is an important decision because EtO is associated with many health hazards. Implementing the strategies proposed by EPA will ensure a safer community and environment for workers to maintain a steady supply chain for sterilized medical equipment.
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Use of EtO in Commercial Sterilization Facilities and their Associated Risks
EtO is commonly used in commercial sterilization facilities due to its bactericidal, sporicidal, and virucidal properties.
The four main parameters of EtO that influence its sterilization effectiveness are temperature (37 °C – 63 °C), gas concentration (450 - 1200 mg/l), exposure time (1-6 hours), and relative humidity (40-80%). Typically, an increase in temperature and gas concentration reduces the sterilization time.
Since 1950, EtO has been used as a low-temperature sterilizing agent. Besides sterilization of medical equipment, it is also used as a fumigant for food, particularly spices and cosmetics.
The key mechanism associated with EtO’s microbiocidal activity is the alkylation of the microbes' DNA, RNA, and protein. This process prevents cellular metabolism and replication, which leads to microbial inactivation. Microbial inactivation also results from EtO’s high reactivity and diffusivity.
Over the years, research has shown the hazards associated with the emission and exposure to EtO. For instance, it is highly explosive and flammable, which increases handling risk. The reaction between EtO and its derivatives (e.g. ethylene chlorohydrin) with water also results in toxic residues. In addition to toxicity, EtO is also a mutagenic gas.
Individuals who work in EtO manufacturing or processing plants, or those involved in fumigation and sterilization are at a high risk of EtO exposure. Acute inhalation of this gas causes nausea, neurological disorders, bronchitis, pulmonary edema, and emphysema. EtO has been characterized as a carcinogenic chemical to humans.
Despite EtO’s toxicity and safety concerns, it is a preferred sterilization method because of its greater compatibility with materials than other techniques (e.g., irradiations and heat sterilizations). Therefore, monitoring the emission levels and formulating effective strategies to protect workers exposed to EtO due to their occupation is important.
EPA’s Proposed Strategies to Reduce EtO Emission from Commercial Sterilizing Facilities
The critical role of the EPA is to protect the environment and people from health risks and develop effective environmental regulations.
EPA has regulated 188 hazardous air pollutants and EtO is one of them. In April 2023, the EPA proposed a comprehensive series of actions to regulate EtO emissions under the Clean Air Act and the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA).
The EPA’s latest proposed strategies have focused on developing stringent national emission standards for hazardous air pollutants (NESHAP) for commercial sterilization facilities. In addition, new Clean Air Act rules would be formulated for manufacturing plants associated with the synthesis of polymers and resins, and synthetic organic chemicals. The EPA has also proposed stricter standards for workplaces handling EtO.
Following the Clean Air Act, the EPA is required to perform a risk-and-technology review (RTR) eight years post-NESHAP issuance. If RTR uncovers residual or new risks and identifies cost-effective technology improvements to control EtO emission, it must review and establish the same.
Conducting technology reviews every eight years after the latest RTR is mandatory. After 2006, there has been no revision in the NESHAP for commercial sterilizers. In April 2023, the EPA announced its latest proposed revisions to the NESHAP for commercial sterilization facilities. The proposal focused on controlling EtO emissions from these facilities by implementing numeric emission limits, operating limits, and stringent management practices.
The EPA has proposed establishing standards for unregulated sources, such as aeration room vents, sterilization chamber vents, and chamber exhaust vents at commercial sterilization facilities where EtO use is less than 1 ton per year (tpy) to at least 10 tpy.
The latest proposal by the EPA provided clarification that includes amendments and exemptions of regulatory provisions related to EtO emission for startup, shutdown, and malfunction (SSM).
According to the new proposal, commercial sterilization facilities must either install an EtO continuous emissions monitoring system (CEMS) or conduct initial and annual EtO emission assessments based on continually monitoring relevant parameters.
The EPA also proposes an expedited timeline for commercial sterilization facilities to meet the new emission and operating requirements. After regulations are approved, commercial sterilization facilities must install pollution controls within 18 months of the final ruling. Compliance status reports must be submitted within 60 days following the final rule's effective date.
Industry Response and Challenges to EPA Proposals
Many commercial sterilization facilities that use EtO have been identified in the United States.
The EPA expects businesses using EtO to challenge the proposed rules. In the past, chemical manufacturers had filed lawsuits against EPA over the final miscellaneous organic chemical manufacturing (MON) rule. However, people living close to commercial sterilization facilities urged the EPA to implement stringent rules and conduct frequent assessments. It also must be noted that many commercial sterilization facilities have already taken necessary steps to reduce EtO emissions.
Current Status of the EPA’s Proposal
If the EPA’s proposals are finalized, EtO emission is expected to decrease by 80% from commercial sterilization facilities. The EPA has requested stakeholders, such as industry, community, and public health leaders, to comment on the proposed strategies to reduce EtO emissions.
The EPA has conducted a public hearing and hosted webinars to discuss their proposal and risk assessment. It expects to finalize the proposals to reduce EtO emissions by 2024.
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References and Further Reading
Proposal to Reduce Ethylene Oxide Emissions from Commercial Sterilization Facilities. (2023) [Online] Available at: https://www.epa.gov/hazardous-air-pollutants-ethylene-oxide/proposal-reduce-ethylene-oxide-emissions-commercial
Anthonijs, S. (2023) EPA proposes rule to reduce ethylene oxide emissions from commercial sterilizers [Online] Available at: https://www.barr.com/Insights/Insights-Article/ArtMID/1344/ArticleID/566/EPA-proposes-rule-to-reduce-ethylene-oxide-emissions-from-commercial-sterilizers
Brightbill, J.D. (2023) EPA Announces Series of New Actions to Address Ethylene Oxide Emissions [Online] Available at: https://www.winston.com/en/winston-and-the-legal-environment/epa-announces-series-of-new-actions-to-address-ethylene-oxide-emissions.html
Actions to Protect Workers and Communities from Ethylene Oxide (EtO) Risk. (2023) [Online] Available at: https://www.epa.gov/hazardous-air-pollutants-ethylene-oxide/actions-protect-workers-and-communities-ethylene-oxide-eto
Sterilization for Medical Devices. (2023) [Online] Available at: https://www.fda.gov/medical-devices/general-hospital-devices-and-supplies/sterilization-medical-devices
Our Current Understanding of Ethylene Oxide (EtO) (2023) [Online] Available at: https://www.epa.gov/hazardous-air-pollutants-ethylene-oxide/our-current-understanding-ethylene-oxide-eto
Ethylene Oxide "Gas" Sterilization. (2008) [Online] Available at: https://www.cdc.gov/infectioncontrol/guidelines/disinfection/sterilization/ethylene-oxide.html