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EPA in Illinois

Questions and Answers: Previous Monitoring

Previous Monitoring

Where were the outdoor air samples taken in May?

EPA collected air samples to test for ethylene oxide (EtO) in mid-May 2018. Sampling locations are shown in a map in EPA’s Sterigenics Air Sampling Summary.

EPA will collect additional air samples to test for EtO to evaluate the impact of the emissions control equipment.

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Did higher releases of ethylene oxide in the past have any long-term effects?

We are not aware of any historical monitoring for ethylene oxide (EtO) around this facility. Thus, we do not have information about the levels of exposure in the past.

Sterigenics’ EtO emissions reports to EPA’s Toxic Release Inventory (TRI) indicate that the levels of emissions have decreased as more stringent regulatory limits have been enacted and emissions controls have been installed.

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What are the EtO and formaldehyde levels in the Willowbrook area for 2017 and 2018?

We don’t have ethylene oxide or formaldehyde air concentrations for the Willowbrook area for 2017 or 2018. 

EPA began monitoring outdoor air near the Sterigenics facility to better understand the levels of ethylene oxide (EtO) in the air. The first monitors began collecting air samples on Nov. 13, 2018. EPA will use these data to estimate the uncontrolled EtO emissions at the facility. Once the monitoring is complete, EPA will conduct a refined risk assessment for the area near the Sterigenics, Willowbrook facility.  We expect the risk assessment to be complete by early spring 2019. The data is available on our website at:

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