New Information

02/15/2019 - Illinois EPA Director seals portions of Sterigenics due to public health hazards from ethylene oxide emissions.  Additional information can be found in the News Release and Seal Order.  Illinois EPA's recent inspection reports are available in the Documents section below.


Illinois EPA

The Illinois EPA upholds those standards established by the state Environmental Protection Act, the federal Clean Air Act and the corresponding regulations. Illinois EPA is the regulatory agency that inspects, permits and ensures that facilities comply with the applicable rules and regulations. 


Sterigenics US LLC operates a hospital implement sterilization facility at 7775 Quincy Street and 830 Midway in Willowbrook. The facility uses ethylene oxide to sterilize hospital equipment/implements.  Implements to be sterilized are placed in a chamber and ethylene oxide is introduced to the chamber.  After a certain residence time, the chamber is evacuated of ethylene oxide.  After the gas is pumped out of the chamber, air is introduced into the chamber.  When air is introduced into the chamber, residual amounts of ethylene oxide are vented through a “back vent.” 

Sterigenics is currently controlling the back vents at the facility with a scrubber. The company recently had stack testing of back vent emissions done, as required by Illinois EPA permit #18060020, to verify the performance of the scrubber.  The stack testing was performed in accordance with USEPA stack test guidance and the stack test plan was approved by Illinois EPA.  Both Illinois EPA and USEPA observed the stack testing.  Final results from the stack test showed no measurable EtO emissions after the scrubber.  A full stack test report will be submitted to the Illinois EPA in the next few weeks.


USEPA identifies certain chemicals as hazardous air pollutants (HAPs). One such chemical is Ethylene Oxide (EtO). USEPA regulates facilities that have emissions of HAPs by setting National Emission Standards for Hazardous Air Pollutants (NESHAP). The intent of a NESHAP is to protect public health by requiring existing and new major sources to control emissions to the level achievable by the maximum achievable control technology (MACT).   

Periodically, USEPA reevaluates HAPs by reviewing the most recent scientific studies to ensure up-to-date risk categorizations and to determine if updates need to be made to a NESHAP. USEPA recently updated the risk profile for EtO, significantly reducing the acceptable exposure level. As a result of the updated risk profile, USEPA has begun to assess sources that use EtO for purposes of updating the NESHAP.   Hospital equipment sterilization facilities are a user of EtO.  The NESHAP for sterilization facilities has not yet been changed.

As part of its review, USEPA identified Sterigenics in Willowbrook as a user of EtO and conducted modeling of the emissions from the facility. USEPA then performed ambient air sampling around the facility in May of 2018 and forwarded that information to the Agency for Toxic Substance and Disease Registry (ATSDR), the federal public health agency, for a public health assessment to help USEPA evaluated the need for regulatory changes that may be needed to the sterilization facility NESHAP.  ATSDR produced a Health Consultation Report and summarized its findings in an e-mail to the Village of Willowbrook,

“The emissions of ethylene oxide from the Sterigenics International, Inc. facility in Willowbrook, IL are not an immediate threat to public health and are not considered to be an emergency situation. ATSDR recommended to U.S. EPA that actions be taken to reduce emissions of ethylene oxide from this facility to protect the public from long-term exposures that could harm their health.

The conclusion in the ATSDR Letter Health Consultation report,

“If measured and modeled data represent typical EtO ambient concentrations in ambient air, an elevated cancer risk exists for residents and off-site workers in the Willowbrook community surrounding the Sterigenics facility. These evaluated risks present a public health hazard to these populations”

is to inform and support the regulatory decisions being made by the state and EPA to reduce emissions from that facility to protect public health.

ATSDR based this conclusion on estimated cancer risks that are calculated using conservative assumptions about a lifetime exposure to the highest levels of ethylene oxide that were measured in Willowbrook commercial and residential areas near the facility. The highest measured levels of ethylene oxide in those areas were about 1,000 times lower than levels associated with cancer risks in scientific studies of workers with industrial exposure to EtO.”

In June 2018, Sterigenics requested a construction permit from the Illinois EPA to control emissions of EtO from the back vents with a scrubber. Illinois EPA issued a construction permit for the scrubber and it has been in operation since the end of July.  Scrubbers are a known technology for controlling emissions and typically have a greater than 90% efficiency.  The scrubber has reduced emissions from the facility.  Sterigenics is required to stack test to verify the level of control from the stack.

As noted above, USEPA previously conducted modeling and sampling. It is important that any additional sampling and modelling conform to the same criteria that was previously used so that the results may be directly correlated to the previous sampling event.  The Illinois EPA has requested that USEPA perform additional modeling and monitoring and reassess the risk assessment now that emissions from the facility have been significantly reduced. 

Questions the Illinois EPA has received from the Public

  1. Has the company always been in compliance with air regulations?

    Sterigenics is currently in compliance with applicable environmental regulations including USEPA’s National Emission Standard for Hazardous Air Pollutants (NESHAP). They have not always been in compliance. Please see question two for additional information.

  2. The facility had a release of EtO in 2013. Did the emissions exceed the 10 lbs. of EtO that requires the company to notify the EPA? When was Sterigenics given the first notice of violation for the emission of EtO?

    On October 21, 2013, Sterigenics reported a release of EtO to the Agency.  The release was estimated to be between 10 and 30 pounds. The Illinois EPA issued a notice of violation to the company on November 12, 2013 and referred the violation to the Illinois Attorney General’s Office.  The AGO, Illinois EPA and the company signed a Consent Order including a penalty in September 2015.

  3. When is Sterigenics or the EPA going to retest the emissions? When would at least the preliminary results be available to the public?

    Third-party stack testing as required by the 2018 construction permit occurred on September 20th & 21st. Illinois EPA and USEPA had staff on-site during the stack testing and all indications are that the scrubber performed as designed, i.e. significantly reducing emissions. The Illinois EPA has demanded the final stack test results be provided as soon as possible.

  4. Are the controls installed in July working?

    The pollution control equipment in operation are scrubbers. Scrubbers are known technology for controlling emissions. Scrubbers typically have a 90+% efficiency at reducing emissions. To verify the exact efficiency, IEPA required the company to conduct stack testing. Testing was completed on September 20th & 21st. Illinois EPA has demanded the final stack test results be provided as soon as possible.

  5. What periods throughout the day and days of the week was EtO being emitted?

    The facility’s permit does not limit the operating hours of the facility. Rather, the permit addresses the conditions to which the source must adhere when operating.

  6. How long has this plant been emitting EtO into the surrounding neighborhoods?

    The facility uses EtO to sterilize hospital implements. One of the facility buildings has been operating since 1984 and the other since 1999.

  7. Why is the facility operating in close proximity to schools? Facilities like this should not be located with residential areas within a certain radius.

    Neither the Illinois EPA nor USEPA regulate land use decisions or the appropriateness of zoning. There are no federal or state laws that provide setback requirements to separate commercial/industrial zones from residential areas.

  8. Will the Illinois EPA shut the facility down?

    The Illinois EPA has received this question from numerous residents.  The Agency is seeking an order enjoining Sterigenics from continuing operations that result in any emissions of ethylene oxide either until a complete review of additional modeling and risk assessment is completed by U.S. EPA or until U.S. EPA otherwise assures the community that resumed operations would not present an elevated health risk.

    The suggestion has been made that the Clean Air Act (CAA) or the CAAPP permit contain a provision that allows the shutdown of the facility.  The Illinois EPA believes this comment refers to administrative and civil actions during air pollution emergencies covered by Section 303 of the CAA.  Section 303 authority is a federal authority when there is imminent or substantial endangerment.  The CAAPP permit does not provide this authority to the state, but includes a provision that no condition in the CAAPP permit will preclude USEPA’s use of that authority.  While guidance for Section 303 addresses the risk posed by carcinogenic substances, this is a federal authority that does not extend to state jurisdiction.


Questions about the permit, inspections and stack testing

Illinois EPA

Brad Frost


Documents & Links

Illinois EPA Inspection Report - February 25, 2019

Illinois EPA Inspection Report - March 12, 2019

Illinois EPA Inspection Report - March 19, 2019

Illinois EPA Inspection Report - March 26, 2019

Illinois EPA Inspection Report - March 29, 2019

Illinois EPA Inspection Report - April 5, 2019

Illinois EPA Inspection Report - April 16, 2019

Illinois EPA Inspection Report - April 24, 2019

Illinois EPA Inspection Report - April 26, 2019

USEPA's Outdoor Air Monitoring in Willowbrook webpage

Transmittal Letter, Willowbrook I Stack Test Report, and Willowbrook II Stack Test Report

Illinois EPA Letter to Sterigenics, September 25, 2018

Illinois EPA Letter to USEPA, September 25, 2018

USEPA Response to Director Messina, September 27, 2018

Sterigenics' letter transmitting stack test results to Illinois EPA, September 27, 2018

USEPA's Sterigenics website:

USEPA information on ethylene oxide:

USEPA frequently asked question on ethylene oxide:

ATSDR factsheet on ethylene oxide:

OSHA factsheet on ethylene oxide:

Clean Air Act Permit Program Permit (CAAPP) – the operating permit for Sterigenics

Construction Permit #18060020 – the construction permit to control emissions from the back vents

Illinois EPA’s 2016 Inspection Report – the last facility inspection report

2013 Violation Notice & resulting 2015 Consent Order

Annual Emission Reports 1995 - 2017