In 2024, the facility began installing new air pollution control equipment and implement additional measures to comply with requirements under Rule 1405.
In August 2025, Ethylene Oxide (EtO) operations were shut down at the 49th St. location to install new equipment, and to complete connections between upgraded air pollution control systems and its existing equipment for both facilities.
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March 2022 – Investigation initiated
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June 2022 – Facility designated as high risk
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December 2023 – Rule 1405 strengthened
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2022–2025 – Emission controls installed and upgraded
South Coast AQMD began investigating facilities that emit Ethylene Oxide (EtO) in March 2022, following the U.S. Environmental Protection Agency’s (U.S. EPA) reconsideration of the potential toxicity of EtO. For more information on the overall initiative please visit: www.aqmd.gov/eto.
Sterigenics conducts sterilization of medical equipment using a gas called EtO. The Vernon facility is housed in two buildings between 49th and 50th Street on Gifford Avenue. The nearest residential area is about 500 feet away, and the nearest school is 1700 feet away.
Air sampling around the facility identified elevated levels of EtO, and South Coast AQMD took immediate action to identify sources and reduce emissions as quickly as possible, including:
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Air monitoring efforts at the facility
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Issuing a Proposition 65 Notice
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Investigating equipment and permit compliance
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Requiring leak detection and source testing to reduce fugitive emissions
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Strengthening Rule 1405 for sterilization operations
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Designating the facility as a Potentially High Risk Level Facility under Rule 1402, with accelerated timelines to address their emissions.
South Coast AQMD continues to conduct a full investigation and evaluation of all equipment to ensure that the Vernon facilities are adhering to permit conditions, meeting rule requirements, complying with the EARP, and using proper air pollution controls.
During a visit to the Sterigenics buildings in Vernon on March 31, 2022, South Coast AQMD detected odors near various equipment. Initial air samples were taken directly outside the facilities, and results showed elevated levels of EtO, prompting more comprehensive air monitoring and further investigation.
South Coast AQMD has worked with the operator on immediate and near-term actions. A source test was required and has been conducted on the wet scrubber at the 50th Street building. Additionally, South Coast AQMD conducted an assessment to identify potential emission sources that are contributing to the elevated levels, and to identify measures to further reduce EtO emissions.
South Coast AQMD inspectors issued a Notice of Violation (NOV) to the Sterigenics 50th Street building on May 5, 2022 for failure to operate the air pollution control system in accordance with the facility’s permit; for failure to maintain the air pollution control system in good operating condition; and for failure to equip control equipment with a pressure gauge and a pH meter, both of which were required in the permit. Inspectors also issued Notices to Comply requiring the facility to provide operating records.
On June 30, 2022, additional NOVs were issued to Sterigenics for installing control equipment at both buildings without first obtaining air quality permits. For the 50th Street facility, during an on-site visit on June 17, 2022, inspectors also observed equipment operating in violation of permit conditions.
On March 7, 2024, South Coast AQMD was notified by Sterigenics that the facility exceeded the lower trigger value threshold of 10 parts per billion under the Early Action Reduction Plan (EARP). The facility was required to curtail operations by 20% within 24 hours of receiving the exceedance notification and conduct additional air monitoring. Curtailment ended on March 14, 2024.
On August 2, 2024, following a review of historical data obtained from Sterigenics, NOVs were issued to the 49th Street and 50th Street facilities for operating air pollution control equipment contrary to permit conditions by failing to maintain minimum scrubbing solution flow rates on multiple dates in 2022 and 2023. Additionally, on August 6, 2024, a NOV was issued to the 49th Street facility for the failure to conduct an asbestos survey prior to renovation activities that took place at the site in January 2023.
The investigation is ongoing, and additional enforcement actions may be taken as necessary.
Notices of Violation:
On June 7, 2022, the Sterigenics facility (49th and 50th Street buildings) was designated as a Potentially High Risk Level Facility. A facility is designated a Potentially High Risk Level Facility when emissions data show either a potential to exceed or that emissions have already exceeded cancer risk thresholds (greater than 100 chances in a million). As a Potentially High Risk Level Facility, Sterigenics was required to:
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Develop an Early Action Reduction Plan (EARP), including measures that can be taken immediately to reduce health risks.
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Submit an Air Toxics Emissions Inventory Report (ATIR)
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Conduct a Health Risk Assessment (HRA)
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Submit a Risk Reduction Plan (RRP)
ATIR: Sterigenics submitted the ATIR on November 4, 2022. South Coast AQMD identified deficiencies and rejected the ATIR on December 2, 2022. A revised ATIR was not submitted, therefore South Coast AQMD modified the document to fix the deficiencies and approved it on May 26, 2023.
EARP: Sterigenics submitted the EARP on September 2, 2022 and it was approved by South Coast AQMD on September 9, 2022. On December 29, 2023, the facility submitted a request to modify the EARP to update the fenceline monitoring plan and curtailment provisions. The amended EARP was approved on February 6, 2024.
HRA: Sterigenics submitted the HRA on December 6, 2022. South Coast AQMD identified deficiencies in the HRA and rejected it on June 15, 2023. A revised HRA was submitted on August 15, 2023; however, it did not address all deficiencies identified in the rejection letter. South Coast AQMD modified the HRA and approved it on June 12, 2024. The results of the HRA exceeded the Rule 1402 notification and risk reduction thresholds. A public notification meeting was held on August 7, 2024 to inform the public of potential health risks posed by the facility.
RRP: Sterigenics submitted the RRP on December 6, 2022. South Coast AQMD required revisions to the RRP to incorporate additional controls installed by the facility and ensure consistency with the amended EARP. A revised RRP was received on July 12, 2024 and was conditionally approved on September 12, 2024. The approval was contingent upon the facility conducting source testing of the Permanent Total Enclosure (PTE) and newly installed control equipment to verify EtO emissions. South Coast AQMD also published modified residual risk values in the RRP approval letter.
AB 2588 Documents:
South Coast AQMD is required to use methodologies developed by the Office of Environmental Health Hazard Assessment in its health risk programs. Based on monitoring data estimates, the primary concern is off-site worker exposure.
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2022 estimates: Worker cancer risks could be as high as 750 excess cancers per million.
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2025 estimates: Workers at facilities adjacent to Sterigenics could be experiencing cancer risks as high as about 44 chances in-one-million, if they are or have been exposed for long periods (i.e., a 25-year worker exposure).
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Regional average lifetime cancer risk from all sources (excluding EtO): ~450 chances in-one-million
This significant decrease from 2022 to 2025 is due to emission control measures implemented at the facility. Monitoring data trends collected by the facility also show substantial decreases in average concentrations, supporting the conclusion that potential cancer risks have declined.
South Coast AQMD issued a Proposition 65 notice on May 5, 2022 notifying the Los Angeles County Board of Supervisors, the Los Angeles County Health Officer, and the City of Vernon Director of Health and Environmental Control of the illegal discharge likely to impact public health or safety.
The Vernon facility’s 49th Street building currently has active permits for eight EtO sterilization chambers, one heated aeration room, and three air pollution control equipment which includes one scrubber system, one catalytic oxidizer and one PTE/Dry Bed control system. The 50th Street building currently has active permits for six EtO sterilization chambers, one heated and one ambient aeration room, and three air pollution control equipment which includes one scrubber system, one catalytic oxidizer and one PTE/Dry Bed control system.
Products are loaded into sealed sterilization chambers where EtO is injected. EtO emissions from the sterilizers are vented and controlled by each building’s scrubber system, which includes a wet scrubber with two dry bed polishing scrubbers. When the sterilization cycle is complete, the chamber is opened and vented by back vents to each facility’s catalytic oxidizers. Any fugitive emissions generated from their sterilization processes are captured and controlled by a dry bed scrubber system which maintains the facility under a PTE. The PTE for 49th Street encompasses the sterilization chambers, one aeration room, one process storage area, one shipping area and one dry scrubber area. The PTE for 50th Street encompasses the sterilization chambers, aerations rooms, a transfer corridor, one process storage and shipping area, and one dry scrubber area.
All control systems are required to:
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Achieve at least 99.99% reduction in EtO emissions, or
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Limit emissions to 0.01 parts per million (ppm) at the stack
Recent Permitting Actions
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May 25, 2022: Applications submitted in response to NOVs issued for operating control equipment without first obtaining permits.
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June 7, 2022: Applications submitted for the construction and installation of new control equipment and the PTEs for both buildings. Permits to Construct were issued on January 27, 2023.
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September 28, 2022: Applications submitted for the modification of exhaust piping for several existing control systems. Permits to Construct/Operate were issued on December 13, 2022. November 2, 2023: Applications submitted to finalize the construction of their PTEs for both buildings. The modifications included adding a new dry bed scrubber to each building, constructing a new heated aeration room in the 49th Street building, and modifying some of the air pollution control systems’ exhaust stacks. Permits to Construct for these applications were issued on April 30, 2024.
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March 3, 2025: Applications submitted for both facilities to further modify their existing wet scrubber system to include an additional polishing dry scrubber for further EtO control. The Permits to Construct were issued for this modification on May 21, 2025.
From April 2022 through April 2024, South Coast AQMD conducted local air sampling to determine levels of EtO in the surrounding community and evaluate potential sources of emissions coming from the Sterigenics facilities. Early in this investigation, individual grab samples (an air sample collected at one location at one point in time) were taken near the facilities (Figure 1). Grab samples were also collected near the surrounding community and the closest school (Figure 2).
Additionally, mobile monitoring was conducted to collect data on volatile organic compounds (VOCs) around the facilities and the surrounding community. VOC signals associated with EtO were elevated near the facilities; however, levels in the community were within typical background levels.
As a result of these survey activities, air samplers were placed near Sterigenics’ facilities and in the community (Figure 3) to collect 24-hour samples (Figure 4). Sampling at Site #2 concluded on May 5, 2022; sampling at site #3 concluded on February 12, 2024; sampling at Site #4 concluded February 18, 2024; and sampling at Site #1 concluded on April 18, 2024.
South Coast AQMD worked with Sterigenics’ Vernon facility operator to identify potential sources of EtO from their operations and the facility implemented actions to reduce EtO emissions. As part of the facility’s EARP, the facility installed air samplers around the facility adjacent to agency monitors and data collected was compared to ensure accuracy. The facility monitors, along with the strengthened requirements on the facility under the recently amended Rule 1405, led to South Coast AQMD concluding its sampling activities. Sterigenics is responsible for continuing to collect and analyze 24-hour samples near their Vernon facility and provide that data to South Coast AQMD.
The agency will continue to work with Sterigenics Vernon as needed to identify the source(s) of EtO and determine measures to reduce EtO emissions.
Grab Samples
Figure 1. Map of grab samples. Concentrations are in parts per billion volume (ppbv).
Community Grab Samples
Figure 2. Map of community grab samples. Concentrations are in parts per billion volume (ppbv).
24-Hour Integrated Sample Locations
Figure 3. Map of 24-hour sampling locations.
This plot is interactive, individual data points can be viewed with a mouse hover. The view can be reset by selecting the circular arrows to the right of the plot.
Figure 4. 24-hour samples - South Coast AQMD air monitoring data can be found here (PDF).
As part of the facility’s Early Action Reduction Plan the facility has installed four air monitors around the facility (see figure 5) and provides that data to South Coast AQMD.
Data from the air monitors operated by the facility can be found here. (PDF).
Ramboll Sampling Sites
Figure 5. Map of Early Action Reduction Plan
EtO sterilization and aeration facilities are subject to local, state, and federal regulations.
During South Coast AQMD's monitoring efforts at several commercial EtO sterilization facilities, the agency became aware of fugitive emissions from sources that were not previously known. South Coast AQMD’s investigation has identified that existing pollution controls will need to be upgraded and measures will be needed to reduce fugitive emissions.
South Coast AQMD amended Rule 1405 on December 1, 2023 to:
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Strengthen emission control requirements for sterilization and storage facilities
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Upgrade existing or add new pollution controls and measure to monitor and minimize stack and fugitive emissions.
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Require enhanced monitoring and reporting
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Require storage facilities that receive products sterilized by EtO to monitor fenceline emissions.
The updated rule applies to 15 sterilization facilities. More details related to Rule 1405 requirements can be found on the Rule 1405 webpage.