Summary of U.S. EPA's Risk Assessment of Ethylene Oxide Emissions
from the Sterigenics Commercial Sterilizer in Willowbrook, Illinois
About U.S. EPA's risk assessment:
U.S. EPA used the same, standard methods that we use when we conduct risk assessments for regulations
to assess risk from lifetime exposure to ethylene oxide emissions from the Sterigenics Commercial
Sterilizer in Willowbrook, Illinois. The assessment:
•	For people living near the facility, assumes people are exposed to ethylene oxide 24 hours a day, 365
days a year for 70 years (to represent lifetime exposure)
•	For people working near, but not in, the facility, assumes assumed people were exposed for 8.5 hours
a day, five days a week, 50 weeks a year for 25 years.
•	Estimates the risk of getting cancer that is in addition to people's overall risk of getting cancer for
other reasons.
•	Focuses on the risk from ethylene oxide emissions from the Sterigenics facility; it does not address
comprehensive risk from all pollutants and all air pollution sources
•	Projects risk going forward. It does not estimate past risk.
•	Provides general estimates of risk to populations. It cannot predict any one person's risk of developing
cancer.
•	Is more likely to over-estimate risk than underestimate risk due to what we call 'health-protective
assumptions
•	The full risk assessment report is available at www.epa.gov/il/risk-assessment-report-sterigenics-facility-
willowbrook-il
What we assessed
U.S. EPA assessed the risk of getting cancer from lifetime exposure to ethylene oxide emitted from the
Sterigenics Willowbrook facility.
We looked at two scenarios:
1.	A scenario focused on what risks would be if the facility was operating - after the back vent was
controlled and before the Illinois EPA issued a seal order preventing the facility from using ethylene
oxide.
2.	An example future scenario, called the "illustrative future case." This scenario looked at what future
risks could be if the facility was more highly controlled.
For each scenario, U.S. EPA estimated risk for people who live in the area, including communities in
Willowbrook, Burr Ridge, Hinsdale, Darien and Indian Head Park. We also estimated risk for people who
work close to the facility (but not at the facility).
What we found
• Estimated risks would be below 100 in 1 million - and potentially as low as 1 in 1 million
- if the facility was more highly controlled.
o A 1-in-a-million risk means that 1 person out of a million people who were breathed air
containing ethylene oxide for a lifetime could develop cancer as a result of that exposure.
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• For residential areas, the estimated risks from lifetime exposure while the facility was operating
ranged from less than 100 in 1 million to 1,000 in a million in areas closest to the facility. The
assessment estimated that future risks would be below 100 in million - and potentially as low as 1
in 1 million -- if the facility was more highly controlled.
Estimated cancer risk in residential areas
based on operations before seal order, and reflecting
emission controls installed in Summer 2018
Illustrative future case: estimated cancer risk in residential
areas if the facility were highly controlled
Lifetime
Ethylene Oxide
Cancer Risk
(in 1 million)
HI 100 - 200
200 - 500
500 - 1000
.. . Non-Residential
8558 Areas
¦I Sterigenics
Willowbrook
• For areas where people work near the facility, the estimated risks while the facility was
operating ranged from 200 in 1 million to 1,000 in a million just outside the facility. Estimated
future risks would be below 100 in million - and potentially as low as 1 in 1 million - if the facility
was more highly controlled.
Occupational
Ethylene Oxide
Cancer Risk
(in 1 million)
¦I 100 - 200
200 - 500
500 - 1000
Estimated cancer risks for people working near the
Sterigenics facility, based on operations before seal order,
and reflecting emission controls installed in Summer 2018
Illustrative future case: estimated cancer risks for people
working near, but not at, the Sterigenics facility
if the facility were highly controlled
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