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:
•	Assumes people are exposed to ethylene oxide 24 hours a day, 365 days a year for 70 years
(to represent lifetime exposure)
•	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 will be posted shortly at
https://www.epa.gov/il/sterigenics-willowbrook-facility-updates
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).
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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.
•	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.
•	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.
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