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Frequently Asked Questions

What is Ethylene Oxide and what is it used for?

Ethylene Oxide (EO or EtO) is a highly toxic, flammable, and explosive chemical used as a fumigant and sterilant.  It is a gas at room temperature (1).

What is known about the hazards of this chemical?  

As one of the most hazardous air pollutants, and a class-one carcinogen, EtO poses great risk to human health (1).  Proven effects of chronic, low-level exposure by inhalation include, but are not limited to: breast and stomach cancer, leukemia, lymphoma, miscarriage, genetic mutation, chromosomal changes, respiratory disease, & organ damage (2, 3, 5, 6).

What is the risk level for residents due to EtO exposure?

The area surrounding Sterigenics in Willowbrook has the highest cancer risk in IL and 19th highest risk in the US. It is in the top 99.98% tracts for cancer risk in the country (13). Air samples from May 2018 indicated cancer risk levels at 64 times the EPA’s action level and 6,400 times the acceptable risk level (2). Since then, the US EPA has suggested  EtO is twice as potent a carcinogen as presumed in the ATSDR consultation, meaning the risk should be doubled (14).

What hours of the day is EtO emitted in Willowbrook?

Sterigenics, Willowbrook emits EtO 24 hours a day, 7 days a week and has done so for 34 years.

How are emissions of EtO measured?

EtO emissions are measured by stack test and ambient air assessments.   Existing monitoring methods are not sensitive enough to detect EtO to the level proven hazardous (7).

How far do emissions of EtO reach?

Air testing limitations restrict the capacity to understand the full reach of this toxin; however, people living in Willowbrook, Darien, Burr Ridge, Hinsdale, Clarendon Hills, Western Springs, La Grange, LaGrange Park, Indian Head Park, and Countryside have been identified for heightened cancer risk for because of EtO emissions from Sterigenics, Willowbrook (4).

What is known about the impact of EtO on children?

EtO can cross the placenta and impact prenatal development.  Mutagenic and chromosomal changes during this time have extreme ramifications, threaten quality of life, and impact future generations.  The effects are so severe, it can result in spontaneous abortion. Children exposed to carcinogens from birth to 2 years have a 10-fold increased risk for cancer.   With exposure from 2-16 years, there is 3-fold increased cancer risk (9, 11, 13).

How long does EtO stay present in the air?

Estimates of the half life of EtO in ambient air range from 69 to over 500 days and are temperature dependent. Rain does not appreciably remove EtO from the air. EtO is not absorbed by the soil. It is heavier than air and accumulates near the earth.  (17).

Is there a safe level of exposure of EtO?

Carcinogens are assumed to have no toxicity thresholds and are potential risk for causing cancer regardless of level of exposure (12).

Sterigenics, Willowbrook claims to have reduced emissions by 99.6%.  Is there still a health risk?

Yes.  The emissions by this company have been so large, that even decreasing them by 99.6% continues to put the community surrounding this facility at health risk.

Have there ever been hazardous spills of EtO from Sterigenics in Willowbrook?

Industry procedure allows Sterigenics to self-monitor and self-report.  They never notified the public of any increased risks when chemicals were spilled or leaked, including at least four times in Willowbrook: 1990 (70 lbs/16,100 liters EtO), 2006 (11.9 lbs/2,737 liters EtO) , 2007 (0.5 lbs/115 liters EtO) and 2013 (6 lbs/ 1380 liters of EtO) (16).

What alternatives for EtO exist?

In February 2019, the Illinois Medical Society filed a resolution urging, "The substitution of ethylene oxide with less toxic alternatives that are currently available...which do not release carcinogens into the workplace or community." They elaborated, "Safer substitution is the most effective means to address this problem of EtO community exposures...alternatives exist that are equally efficacious." Two major alternatives in hospitals include immersion in peracetic acid and chamber sterilization by hydrogen peroxide gas plasma, which is a direct replacement for EtO in terms of materials compatibility, ease of use, and sterile storage. Other FDA approved methods include heat and steam (traditional autoclave), dry heat, irradiation by gamma rays or electron beam, and ozone (18, 19, 20, 21).

What safety concerns exist with the storage and and transportation of EtO?  

In 2004, there was an explosion of EtO at a Sterigenics facility in California. In Willowbrook, the impact of an explosion could spread at least 1 mile in diameter, including 4 schools, a daycare, and homes and workplaces of over 20,000 people.

Sterigenics claims they follow IL EPA regulations.  What’s the problem?

Current regulations do not protect communities surrounding facilities like Sterigenics from health hazards and were written before EtO was classified as a class-one carcinogen.  EtO lobbyist groups, including the Ethylene Oxide Sterilization Association (EOSA) and American Chemistry Council (ACC), ignore decades of research proving the detrimental impact of this toxin and encourage the US EPA to lower EtO emission standards because it is better for their business.

What is the connection between Sterigenics and the EOSA?  

Kathleen Ann Hoffman, formerly Kathleen Ann Steilen, is a senior VP at Sterigenics.  She is a past president and still active member of the lobbyist group EOSA.

What can/should be done?

IEPA and Governor Rauner should immediately revoke the Sterigenics permit using public health rules under the Illinois Environmental Protection Act. Additionally, the Illinois legislature should act during veto session to strengthen the rules that allow permit revocation of an air permit.

1. IEPA must immediately draft rules to strengthen EtO emission limits under an emergency rulemaking. Should the IEPA fail to create rules or introduce ineffective rules, the state legislature should pass legislation requiring stronger regulations.

2. The legislature should pass legislation providing IEPA the authority to reopen an air pollution permit in specific instances where the carcinogenicity of an emitted chemical has been increased such that the allowable levels of emissions are found to create a public health hazard.

3. EtO itself should be regulated more stringently at all facilities. Regulation of EtO should account for short and long-term exposure to both employees of the facility and members of the surrounding community (10).


1.  International Agency for Research on Cancer.  (2008). Ethylene Oxide, IARC Monographs, 97. Retrieved from:

2. U.S. Department of Health and Human Services, Agency for Toxic Substances and Disease Registry. (2018, August 21). Evaluation of Potential Health Impacts from Ethylene Oxide Emissions, Sterigenics International, INC. Willowbrook, Illinois.  Retrieved from:

3. Jinot J, Fritz JM, Vulimiri SV, Keshava N. (2017). Carcinogenicity of Ethylene Oxide: Key Findings and Scientific Issues.  Toxicol Mech Methods. Retrieved from:

4. National Air Toxics Assessment Map. (2018).

5. Stop Sterigenics Fact Sheet. (2018). Retrieved from:

6. U.S. Environmental Protection Agency. (2016). Evaluation of the Inhalation Carcinogenicity of Ethylene Oxide Executive Summary. Retrieved from:

7. Illinois Environmental Protection Agency.  (2018, October). Sterigenics Willowbrook Facility - Latest Update. Retrieved from:

8. U.S. Environmental Protection Agency. (2005, March).  Supplemental Guidance for Assessing Susceptibility from Early-Life Exposure to Carcinogens. Retrieved from:

9. Carrington, Damian. (2018). Air Pollution Particles found in Mothers' Placentas.

10.  Walling, Jen.  (2018, October 4). Sterigenics, Ethylene Oxide and Human Health. Retrieved from:

11. International Agency for Research on Cancer.  (2012). Ethylene Oxide. IARC Monographs, 100.

12. M.Cristina Fondelli, Adele Seniori Constantin, M. Ercolanelli, Anna Maria Pizzo, Simona Alberchini Maltoni, Margaret M. Quinn. (2007). Exposure to Carcinogens and Mortality in a Cohort of Restoration Workers of Water-Damaged Library Materials Following the River Arno Flooding in Florence.  MedLav, 98,5:422-431

13. U.S. Environmental Protection Agency.  (2018). EPA’s 2014 National Air Toxics Assessment.  Retrieved from:

14. Illinois Environmental Protection Agency. (2018, Oct 2).  News Release. Retrieved from:

15. World Health Organization.  (2003). Ethylene Oxide. Retrieved from:

16. TRI Facility Report: STERIGENICS US LLC-WILLOWBROOK IL FACILITY(60521GRFFT7775Q). Accessed 10/16/2018.

17. U.S. Environmental Protection Agency. (1987). Atmospheric Persistence of Eight Air Toxins. Retrieved from:

18. Department of Health and Human Services, Centers for Disease Control and Prevention. (2008).  Guideline for Disinfection and Sterilization in Healthcare Facilities. Retrieved from:

19. Maxim Integrated. (2011, Aug 09). Sterilization Methods and Their Impact on Medical Devices Containing Electronics.  Retreived from:

20. Centers for Disease and Prevention. (2016, September). Guideline for Disinfection and Sterilization in Healthcare Facilities. Table 6. Summary of advantages and disadvantages of commonly used sterilization technologies.

21. Illinois Medical Society. (2019, February). Removing Ethylene Oxide as Sterilant From Healthcare.


This blog post is a representation of the author's opinion. Posts are intended for informational purposes only and not indented to provide medical or legal advice.

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