EPA Ethylene Oxide Air Sampling in Laredo, Texas
About the monitoring
From early September 2023 to early January 2024, EPA performed air monitoring for ethylene oxide (EtO) in areas around the Midwest Sterilization Corporation facility in Laredo, Texas to improve the understanding of EtO concentrations in the city of Laredo. In order to keep the community informed, we are providing these air monitoring results that have gone through EPA’s quality assurance process. The Clean Air Laredo Coalition, through the Rio Grande International Study Center, performed independent EtO monitoring in approximately the same timeframe as EPA, using funding from non-federal sources. More information on EPA's work in Laredo can be found here (pdf) .
Every three days, EPA collected 24-hour EtO air samples in canisters at four of the five monitoring sites in Laredo. Three monitoring locations were near or a short distance from Midwest. One monitor was about two miles away, in order to gather EtO data from areas that are not near a known source of EtO emissions. The locations of the four canisters changed over the course of the project due to collocation of EPA canisters with the community canisters and other logistical considerations. A map of the monitoring sites is on this webpage, below. For quality assurance purposes, EPA collected and analyzed one additional canister for most of the monitoring days, usually collocated with the canister at either site M3 or M5, along with two weekly canisters that traveled with the other canisters but were never opened to collect an air sample.
About the Data
After laboratory analysis, data from the air sampling underwent a rigorous quality assurance/quality control process. The data generally shows EtO concentrations in the air are similar to what was expected. The monitors closest to the Midwest facility typically show the highest concentrations. Less than one mile downwind from the facility, concentrations fall to those similar to EtO concentrations in areas in the U.S. that are not near a known source of EtO emissions.
To view EPA's EtO monitoring data, please see the following link for the EPA EtO Laredo Monitoring Data Summary (pdf) . The tab with the data summary shows the concentrations of EtO in air samples collected each monitoring day. The tab with the wind information shows the wind speed and direction on these days.
About EtO Regulations
In March 2024, EPA announced a Clean Air Act regulation to dramatically slash EtO emissions from commercial sterilizers, including from Midwest. Finalizing the 2024 sterilizers rule is one of the most important measures that EPA is taking to reduce emissions of EtO. Once implemented, this rule will reduce the lifetime cancer risk from EtO exposure for people living near commercial sterilization facilities.
Midwest has two years from the April 5, 2024 effective date of the final rule to install controls. After Midwest installs and starts operating the additional emissions controls required by this 2024 rule, EPA expects that no individual in Laredo will be exposed to EtO emissions from this facility in outdoor air at levels that correspond to a lifetime cancer risk of greater than 100-in-1 million. This is an important Clean Air Act metric for evaluating risk.
Continuous emissions monitoring and quarterly reporting for most commercial sterilizers will provide EPA and communities with data to ensure EtO emissions are controlled and not entering the outdoor air before being captured and controlled. Learn more about the 2024 final rule here.
EPA Ethylene Oxide Monitoring Site Location Map, Laredo, Texas
This map shows the sites of EPA’s EtO air monitoring in Laredo, all on city of Laredo right-of-way. EPA placed canisters at four of these sites per monitoring day to measure the concentration of EtO in the outside air. The sites were:
M1: Mines Road, near its southwest intersection with Interstate 69W
M2: Doc Adams Drive, near the intersection of Killam Industrial Boulevard
M3: Northern part of Jef Drive
M4: Northern part of Archer Drive
M5: Intersection of Jef Drive and Killam Industrial Boulevard
Additional Information
More information on EPA efforts to address emissions of EtO from commercial sterilizers.
For commonly asked questions about EtO, please see the EPA EtO Q&A.
If you have additional questions, please e-mail: r6ethyleneoxide@epa.gov and a staff member will contact you.