Sterigenics Emissions Investigation in Vernon

South Coast AQMD is conducting special air monitoring in the City of Vernon to assess Ethylene Oxide emissions

Información en español

Recent Activity

Amended Early Action Reduction Plan:


South Coast AQMD has an ongoing investigation into emissions of EtO from facilities within our jurisdiction. For more information on the overall initiative please visit:

Sterigenics conducts sterilization of medical equipment using a gas called Ethylene Oxide (EtO) and operates in Vernon within two buildings between 49th St. and 50th St. on Gifford Ave in an industrial area. The nearest residential area is about 500 feet away, and the nearest school is 1700 feet away.

Based on sampling around the facilities, high levels of EtO have been discovered, and South Coast AQMD is taking several actions to identify emission sources and reduce emissions as quickly as possible including:

  • Air monitoring efforts at the facilities and near the surrounding community.

  • Proposition 65 Notice

  • A complete investigation into the facilities’ equipment and compliance with South Coast AQMD rules, regulations and permit requirements.

  • Evaluation of immediate actions to be taken by the facilities to reduce leaks or fugitive emissions, including leak and source testing.

More Information

  • For more information, please contact the South Coast AQMD Public Advisor at

  • To receive notifications related to the Sterigenics Vernon facilities, please fill out the form at

Comments from Local Officials & Community Groups

Response Letters to Local Officials & Community Groups

South Coast AQMD has provided informational letters to local officials to address concerns regarding Sterigenics: 

Ongoing Investigation

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 is working 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, a team of South Coast AQMD engineers and inspectors 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 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. 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 and using proper emissions control equipment.

On June 30, 2022, additional Notices of Violation 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.

Notices of Violation:

AB 2588 Air Toxic “Hot Spots” program

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 develop an Early Action Reduction Plan that includes measures that can be taken immediately to reduce health risks. In addition, the facility was required to submit an Air Toxics Inventory Report (ATIR), conduct a Health Risk Assessment (HRA), and submit a Risk Reduction Plan (RRP). As of early December 2022, these documents have all been submitted by the facility, and are under various stages of review and approval.

South Coast AQMD staff identified deficiencies and rejected the ATIR on December 2, 2022. Sterigenics did not submit a revised ATIR, therefore South Coast AQMD modified the ATIR to fix the deficiencies and approved it on May 26, 2023.  Staff also identified deficiencies with the HRA and rejected it on October 31, 2023. A revised HRA was received on August 15, 2023 which did not address all of the deficiencies. Staff is currently modifying the HRA.

Amended Early Action Reduction Plan


The approved Amended Early Action Reduction Plan set a temporary threshold for EtO emissions from the facility of 10 parts per billion (ppb) over a 24-hour period (see below). This temporary threshold ensures that the facility does not reverse any emission reductions that have been achieved recently while more permanent engineering controls are put into place. If air monitoring results near the facility show one EtO value at 10 ppb or higher, the facility must initiate curtailment of its operations. Repeated exceedances of the threshold within a rolling 15-day period may result in a temporary shutdown of the facility.

EtO Level ≥ 10 ppb
but <16 ppb


EtO Level ≥ 16 ppb


First Sample

20% Curtailment of Operations
(maximum 800 lbs of EtO usage per day)

First Sample

40% Curtailment of Operations
(maximum 600 lbs of EtO usage per day)

Second Sample

40% Curtailment of Operations

Second Sample

80% Curtailment of Operation
(maximum 200 lbs of EtO usage per day)

Third Sample

60% Curtailment of Operations
(maximum 400 lbs of EtO usage per day)

Third Sample

100% Curtailment of Operations 

 Fourth Sample

80% Curtailment of Operations
(maximum 200 lbs of EtO usage per day)



 Fifth Sample

100% Curtailment of Operations



Curtailment begins after South Coast AQMD is notified of an exceedance of the threshold. Laboratory analysis can take many days to complete. Sterigenics must provide results for sites M1, M2, M3 and M5 (see figure 5 below) within 10 days of collecting the sample. Sterigenics must also provide sample data within three hours of receiving results from their laboratory analysis when levels are above curtailment thresholds.

Sterigenics may resume normal operations once data from the same monitor that triggered the curtailment shows EtO levels are below the thresholds set under the plan.

Sterigenics Vernon Curtailment

EtO Sample Level That Required Curtailment

Curtailment Sample Date

Monitor Location


Start Date*

EtO Sample to End Curtailment

Date of Sample

End Date

20 ppb


Sterigenics Monitor M1

20% Curtailment of Operations


1.8 ppb



 13 ppb


 Sterigenics Monitor M5

20% Curtailment of Operations 


1.8 ppb 




Air Monitoring Efforts

South Coast AQMD is conducting local air sampling to determine levels of EtO in the surrounding community and evaluate potential sources of emissions coming from the Sterigenics buildings. Earlier 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 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, monitors 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. 


Grab Samples

Grab Samples
Figure 1.
Map of grab samples. Concentrations are in parts per billion volume (ppbv).

Community Grab Samples

Community Grab Samples

Figure 2. Map of community grab samples. Concentrations are in parts per billion volume (ppbv).

24-Hour Integrated Sample Locations

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).

Facility Air Monitoring

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
Ramboll Sampling Sites
Figure 5. Map of Early Action Reduction Plan

Health Impacts

South Coast AQMD is required to use methodologies developed by OEHHA in its health risk programs. Based on preliminary monitoring data, the primary concern is off-site worker exposure. This data indicates that workers at facilities adjacent to the Sterigenics facilities could be experiencing cancer risks as high as about 750 in a million, if they are or have been exposed for long periods (i.e., a 25-year worker exposure). This risk level is more than one and a half times higher than the average lifetime cancer risk throughout the region according to South Coast AQMD’s Multiple Air Toxics Exposure Study V. The preliminary air monitoring results also show that EtO levels and off-site worker cancer risk drops off substantially (about 50 times lower) a short distance away (about 150 feet), from the facility.

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.

South Coast AQMD has also notified the California Division of Occupational Safety and Health Administration (Cal/OSHA) of potential exposure to employees at the Vernon facilities. Cal/OSHA subsequently launched its own investigation and has visited the Sterigenics facility. Additionally, South Coast AQMD is working closely with the Los Angeles County Department of Public Health and is providing data to public health officials for additional risk assessment.


The Vernon facility consists of two buildings (49th St. and 50th St.). The 49th St. building currently has active permits for eight EtO sterilization chambers, one ambient temperature aeration room, and air pollution control equipment which includes one wet scrubber and one catalytic oxidizer. The 50th St. building currently has active permits for six EtO sterilization chambers, one ambient temperature and two heated aeration rooms, and air pollution control equipment which includes one wet scrubber and one catalytic oxidizer. Construction is in progress for the PTE/Dry Bed control system. 

Products are loaded into sealed sterilization chambers where EtO is injected. Chambers are required to meet strict requirements to capture the EtO gas and prevent 99.9% of emissions. The PTE/Dry Bed control system will be required to control at least 95% of EtO emissions from operations within the building. Additionally, it will require the facility to maintain negative air pressure to prevent fugitive EtO emissions from escaping the building. The additional layer of controls will result in higher control efficiencies, which will be verified through Source Tests.

On May 25, 2022, the facility submitted four applications as a result of the NOVs issued for operating equipment without first obtaining a permit. On June 7, 2022, the facility submitted five permit applications. Three of the applications are for the construction and installation of new control equipment and two applications are to update the buildings to PTEs. On November 2, 2023, the facility submitted four permit applications to add a new dry bed scrubber to each building and to modify some of the air pollution control systems at the facility. 

The facilities’ permits can be accessed through South Coast AQMD’s Facility Information Detail (F.I.N.D.) using the facility address or ID numbers (126191 and 126197).


EtO sterilization and aeration facilities are subject to local, state, and federal regulations. South Coast AQMD Rule 1405 (PDF) - Control of Ethylene Oxide Emissions from Sterilization and Related Operations.
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. Rule 1405 was amended on December 1, 2023 to strengthen requirements for sterilization and storage facilities. The updated rule applies to 15 sterilization facilities which are required to upgrade existing or add new pollution controls and implement measures to monitor and minimize stack and fugitive emissions. Additionally, storage facilities that receive products sterilized by EtO may also be required to monitor emissions at the fenceline. More details related to Rule 1405 requirements can be found on the Rule 1405 webpage

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