Letter Health Consultation
“Evaluation of Potential Health Impacts from Ethylene Oxide Emissions”
STERIGENICS INTERNATIONAL, INC.
WILLOWBROOK, ILLINOIS

AUGUST 21, 2018

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES
Agency for Toxic Substances and Disease Registry
Division of Community Health Investigations
Atlanta, Georgia 30333

 Health Consultation: A Note of Explanation
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request for information about health risks related to a specific site, a chemical release, or the
presence of hazardous material. In order to prevent or mitigate exposures, a consultation may
lead to specific actions, such as restricting use of or replacing water supplies; intensifying
environmental sampling; restricting site access; or removing the contaminated material.
In addition, consultations may recommend additional public health actions, such as conducting
health surveillance activities to evaluate exposure or trends in adverse health outcomes;
conducting biological indicators of exposure studies to assess exposure; and providing health
education for health care providers and community members. This concludes the health
consultation process for this site, unless additional information is obtained by ATSDR which,
in the Agency’s opinion, indicates a need to revise or append the conclusions previously
issued.

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or
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 LETTER HEALTH CONSULTATION

“Evaluation of Potential Health Impacts from Ethylene Oxide Emissions”
STERIGENICS INTERNATIONAL, INC.
WILLOWBROOK, ILLINOIS

Prepared By:
U.S. Department of Health and Human Services
Agency for Toxic Substances and Disease Registry
Division of Community Health Investigations

  

DEPARTMENT OF HEALTH & HUMAN SERVICES
Agency for Toxic Substances and Disease Registry,
Region 5

Public Health Service
77 W. Jackson Blvd., Room 413
Chicago, IL 60604

July 26, 2018 *
Ed Nam
Director, Air and Radiation Division
United States Environmental Protection Agency, Region 5
77 W. Jackson Blvd., MS A-18J
Chicago, IL 60604

Dear Mr. Nam:
Since February 2018, ATSDR has met with U.S. EPA Region 5 Air and Radiation Division (ARD) staff
regarding a change in the cancer risk basis for ethylene oxide (EtO) in the EPA Integrated Risk
Information System (IRIS) and how that change affects general population risks estimated from EtOemitting facilities in the draft 2014 National Air Toxics Assessment (NATA) update1. In December 2016,
IRIS changed EtO’s adult-based inhalation unit risk from 0.0001 per microgram per cubic meter
(µg/m3) to 0.003 per µg/m3, a 30-fold increase in cancer potency. It also changed EtO’s cancer weightof-evidence descriptor from “probably carcinogenic to humans” to “carcinogenic to humans”. These
changes could result in many census tracts having estimated cancer risks that are greater than 1 in
10,000 from EtO exposure identified through the draft NATA modeling of air emissions across the
United States.
Specifically, ARD decided to evaluate the implications of this change at two sites, Sterigenics
International, Inc. (referred to in the letter as “Sterigenics”) in Willowbrook, IL and the Elé Corporation
in McCook, IL. This letter addresses EtO emissions from the Sterigenics facility. In June 2018, after the
monitoring results were received and reviewed, ARD requested that ATSDR review air measurements
of EtO and modeling results of EtO emissions from Sterigenics and specifically answer the question: If
modeled and measured ethylene oxide concentrations represent long term conditions, would they pose
a public health problem for people living and working in Willowbrook?
The air modeling data that U.S. EPA provided to ATSDR estimated potential short-term and long-term
concentrations of EtO in ambient air surrounding the Sterigenics Corporation. Follow-up air
monitoring data confirm the presence of elevated EtO at concentrations within a similar range to
those estimated by the air modeling of Sterigenics emissions. Based on these measured and modeled
concentrations and the proximity to residences and other commercial structures, cancer risks higher
than 1 in 10,000 people may exist for some community members and workers exposed to airborne
EtO in this community. If these measured and estimated concentrations represent chronic exposures
* Minor edits to the reference list have been incorporated into the final posted ATSDR Letter Health Consultation.
1

The 2014 NATA is expected to be publicly available in the fall of 2018.

 in the surrounding community (with higher exposures likely for workers of the facility), EtO emissions
from the Sterigenics Corporation poses a public health hazard.
BACKGROUND
Sterigenics provides sterilization processes using gamma, ethylene oxide, Ebeam, and X-ray
sterilization and operates 46 facilities in 13 countries (Sterigenics, 2018). The facility stores ethylene
oxide that is sprayed into sealed chambers to sterilize medical equipment, pharmaceuticals, and
food/spice products contained on 40” x 48” pallets. The sterilization chambers are contained in two
buildings. Building 1 has fifteen chambers that can hold 1 to 13 pallets, while Building 2 has four
sterilization chambers that can hold 13 to 26 pallets (Illinois EPA, 2017). Building 1 chambers were
constructed in 1984, while Building 2 chambers were built in 1999 and 2012. Pollution control
technology includes acid water scrubbers and dry bed reactors that convert the ethylene oxide to
ethylene glycol after the sterilization process (Illinois EPA, 2015). Although back vents on the units
have historically been uncontrolled, Sterigenics is currently in the process of installing pollution
controls to control passive releases (ATSDR, 2018).
Figure 1 illustrates the total reported emissions in pounds per year (lbs/yr) of EtO from Sterigenics.

Figure 1. TRI Total Air Emissions Reported (in pounds), by Sterigenics Corporation for
Ethylene Oxide, 1995-2016

a

Source: Toxic Release Inventory (TRI): https://www.epa.gov/enviro/tri-overview
Dates for facility constructed and upgrades were identified according to Illinois EPA (2017) DRAFT/PROPOSED Clean Air
Act Permit Program (CAAPP) Permit
b

2

 The emissions data show a substantial reduction in total air releases after 1998. No data are available
before 1995 on ambient air releases, but the available data suggests that substantially higher ambient
releases prior to 1995 were likely. The Building 1 sterilization chambers were constructed in 1984,
therefore EtO has been emitted over the past 34 years from the Willowbrook facility.
Willowbrook, Illinois is a small suburb of Chicago with approximately 8,500 residents (U.S. Census,
2016). The Willowbrook industrial complex where Sterigenics is located is in a densely populated
metropolitan area, with 19,271 people living within 1 mile of the facility boundary. There are four
schools and one daycare facility within 1 mile of the facility. According to 2016 Census estimates,
Willowbrook residents are predominately white (73.3%), non-Hispanic (66.6%), educated (97.7%
graduate high school, and 48.9% graduated with a bachelor’s degree or higher), and middle class
(median household income was over $67,000 per year). Approximately 18.5% of the population is
identified as Asian, and 6.3% as black.

Figure 2. Aerial map of the community surrounding Sterigenics Corporation

Source: Google Earth

3

 ENVIRONMENTAL DATA
Air Modeling
U.S. EPA modeled short and long-term ambient EtO concentrations (AERMOD version 18081) to
evaluate the potential impact of site emissions. These scenarios estimated a 5-year average to
represent chronic exposures and maximum 1- and 8-hour averages to represent acute exposures at
882 community receptor points. An overlay of the modeling output is displayed in Figure 3, below.
The statistical distributions of the modeled air concentrations are presented in Table 1.
Figure 3. AERMOD modeling output: 5-year average exposure estimates

Source: U.S. EPA Air and Radiation Division, Region 5
Note: Source 1 is Sterigenics Willowbrook Building 1, and Source 2 is Sterigenics Willowbrook Building 2

4

 Table 1. Statistical distribution of EtO modeling*
Statistics
Minimum
25th Percentile
50th Percentile
75th Percentile
90th Percentile
95th Percentile
99th Percentile
Maximum
Mean
Geometric Mean

Modeled 1-hour
(µg/m3)

Modeled 8-hour
(µg/m3)

Modeled 5-year
(µg/m3)

2.17
4.62
9.72
18.88
33.90
45.22
134.73
249.77
15.75
10.13

1.02
2.26
4.07
7.29
12.62
18.83
61.39
123.89
6.72
4.41

0.03
0.09
0.17
0.31
0.57
0.91
2.97
13.32
0.32
0.18

*N= 882 modeled receptors
Air Measurements
U.S. EPA collected 39 validated samples May 16th and May 17th, 2018. These samples were collected
using SUMMA® canisters, and analyzed using U.S. EPA Compendium Method TO-15, Compendium of
Methods for the Determination of Toxic Organic Compounds in Ambient Air. A SUMMA® canister is an
airtight, stainless-steel container with an inner surface that has been electro-polished and chemically
deactivated. The laboratory is required to clean each canister and evacuate it to a high vacuum prior
to shipping it to the sampling location. A canister can hold the vacuum for up to 30 days. The air being
sampled is “drawn” into the canister by the high vacuum, thus eliminating the need for a pump. While
opening the inlet orifice fills the canister in less than a minute, yielding an instantaneous “grab”
sample, regulators can be added to the inlet orifice to draw the air into the canister over a designated
period, ranging from 1 to 24-hours.
Of the 39 samples collected at 26 discrete locations (Figure 4), 18 were 12-hour samples, and 21 were
grab samples (Table 2). Three of the 12-hour samples were collocated duplicates, and three of the
grab samples were collocated duplicates. Grab samples generally had lower EtO concentrations than
12-hour averaged samples (U.S. EPA, 2018). However, all grab samples were collected between 10:20
am and 3:05 pm. ARD staff noted that higher EtO concentrations were measured overnight than
during the day, and 12-hour samples were collected overnight in some locations. Since Sterigenics is a
24-hour operation, this may be due to calm meteorological conditions overnight with a higher
potential for inversions. Given the elevated detections over a limited duration, additional long-term
sampling is warranted to better characterize residential exposure to EtO.

5

 Table 2. Statistical distribution of residential and commercial EtO air sampling*
Statistics

Grab samples (µg/m3)

12-hour samples (µg/m3)

0.16
0.24
0.45
1.34
2.28
4.27
4.33
4.34
1.07
0.62

0.34
0.69
1.56
4.39
8.26
8.44
8.96
9.09
3.02
1.74

Min
25th Percentile
50th Percentile
75th Percentile
90th Percentile
95th Percentile
99th Percentile
Max
Mean
Geo Mean
*N=21 grab samples, 18 12-hour samples

Figure 4. Ambient air samples near the Sterigenics facility, Willowbrook, IL

Source: U.S. EPA, Region 5

6

 Figure 4, shows the location of discrete samples collected in the community. Given limited measured
data presented in Table 2, ATSDR used the maximum 12-hour residential sample concentration and
the maximum 12-hour commercial sample concentration to represent chronic upper bound
residential (2.1 µg/m3) and occupational (9.1 µg/m3) exposures in the community. These
concentrations represent maximums identified during a very temporally and spatially limited sampling
campaign and actual average long-term exposures may be higher or lower.
HEALTH IMPLICATIONS
Overview for identifying contaminants of concern and evaluating risk
To evaluate EtO exposures near Sterigenics, ATSDR considered its own health-based comparison
values as well as those published by other agencies. ATSDR uses comparison values for screening
purposes to determine whether a pollutant should be evaluated further. A CV was identified for both
an intermediate exposure duration (for non-cancer evaluation) as well as for a long-term (chronic)
exposure duration (for which we considered both cancer and non-cancer health effects). In this
evaluation, the air sampling results were compared to the ATSDR Cancer Risk Evaluation Guide (CREG)
and environmental media evaluation guide (EMEG) and California EPA Reference Exposure Level (REL)
for EtO.
▪

▪

▪

ATSDR CREGs are estimates of the concentrations of a carcinogen at which there is an
elevated risk for one additional case of cancer in one million people exposed over a lifetime.
ATSDR's CREG for EtO is calculated from the current U.S. EPA's adult-based inhalation unit risk
value (0.003 (µg/m3)-1) and is based on U.S. EPA evaluations and assumptions about
hypothetical cancer risks at low levels of exposure. ATSDR’s CREG for EtO is 0.00021 µg/m3.
ATSDR inhalation minimal risk levels (MRL)/EMEGs are estimates of the concentrations of
pollutants calculated that anyone could be exposed to where health effects are unlikely, based
on chronic, intermediate, and acute exposures (those occurring longer than 365 days, between
14-365 days, and 14 days of exposure or less, respectively). For EtO, ATSDR only has an
intermediate EMEG of 160 µg/m3 (ATSDR, 1990).
California RELs are concentrations that are unlikely to result in adverse non-cancer health
effects. The chronic California REL for EtO is 30 µg/m3 (California EPA, 2008).

All 5-year modeled and 12-hour measured averages exceeded the ATSDR CREG. Only maximum
modeled concentrations exceeded intermediate or chronic non-cancer screening values. The following
sections evaluate chronic non-cancer and cancer risks further.
Ethylene oxide properties
Ethylene oxide is a highly flammable gas that is highly reactive with nucleophilic substances such as
water, alcohols, halides, amines, and sulfhydryl compounds. It is used as an intermediate in the
production of ethylene glycol and surfactants as well as a fumigant for sterilizing foods and heatsensitive medical equipment.
EtO is highly reactive, readily absorbed, and easily distributed in the human body. The absolute odor
threshold has been reported in several studies to be about 470 milligrams per cubic meter (mg/m3)
7

 (or 470,000 µg/m3), with acute health effects possible in the range of the odor threshold (NRC, 2010).
Chronic exposures can result somatic cell damage at much lower concentrations (California EPA,
2008). EtO is mutagenic and causes chromosome damage in many species, including humans. EtO
exposure has widely been studied in scientific literature and its adverse health impacts are well
understood. The carcinogenic effects of EtO have been documented in human and animal studies
(U.S. EPA 2016).
Acute and intermediate exposure and health effects
Acute and intermediate effects have mostly been documented in hospital workers or in other
occupational settings that include sterilizing chambers. Short-term exposure (minutes to weeks or
months) above the odor threshold of 470 mg/m3 (into the thousands of mg/m3) include primarily
neurological effects (headache, dizziness, nausea, lethargy, fatigue, muscle weakness, numbness,
memory loss, incoordination, etc.), respiratory irritation (irritation of the nasal cavity, sinuses,
coughing, shortness of breath, wheezing, and bronchial constriction and hyperreactivity), excessive
thirst and dry mouth, and gastrointestinal effects (vomiting, diarrhea, stomach spasms, etc.). Some
studies reported skin rashes with short-term exposures (NRC, 2010).
All studies with documented health effects summarized above had substantially higher EtO
concentrations than what was observed in measured and modeled data in this assessment. ATSDR
does not have an acute health-based comparison value but does have an intermediate-duration
health-based comparison value of 160 µg/m3. No measured data and only the maximum 1-hour
modeled concentration of EtO exceeded this value and modeled and measured concentrations of EtO
in this investigation were well below the odor threshold. Thus, it is unlikely that the non-cancer health
effects noted above would occur in the general or off-site worker populations.
Chronic exposure and health effects
Cancer effects
The U.S. EPA IRIS released an “Evaluation of the Inhalation Carcinogenicity of Ethylene Oxide” in
December 2016. This evaluation summarizes the evidence that EtO is “carcinogenic to humans”
through a mutagenic mode of action (MOA) and derives an inhalation unit risk value for EtO (U.S. EPA,
2016). Many studies have identified the genotoxic potential and mutagenic mode of action of EtO
exposure via inhalation. There is clear evidence from multiple studies that EtO causes chromosomal
aberrations, sister chromatic exchanges, and micronuclei in peripheral blood lymphocytes and bone
marrow cells. Chromosomal aberrations and micronucleus frequency have been linked to increased
risk of cancer in a number of large human studies (Jinot et al., 2017). Mice and rats exposed to EtO
demonstrate cancers of the lymphohematopoietic system (cells involved in the production of
lymphocytes and cells of blood, bone marrow, spleen, lymph nodes, and thymus), brain, lung,
connective tissue, uterus, and mammary gland.
In humans, an increased incidence and mortality of breast and lymphohematopoietic system cancers
have been observed in workers in the EtO manufacturing and in sterilizing facilities (U.S. EPA, 2016).
U.S. EPA identified six studies evaluating breast cancer in women, with the largest being a study from
the National Institute of Occupational Safety and Health (NIOSH) of over 18,000 workers (45% male,
55% female) in 14 commercial sterilization plants. The NIOSH study reported statistically significant
8

 exposure-response relationships for breast cancer incidence and mortality (Steenland et al., 2003 and
Steenland et al., 2004). From assessing these studies, U.S. EPA (2016) determined that there is
sufficient evidence of a causal relationship between EtO exposure and breast cancer in women.
U.S. EPA used the cancer incidence data from the NIOSH study, using individual exposure estimates
for 17,530 workers from 13 plants, to calculate an inhalation unit risk value. A linear low-dose
extrapolation of the lowest effective concentration (LEC; defined here as the lower 95% confidence
limit on the EC01, the estimated effective concentration associated with 1% extra risk) for lymphoid
cancer was calculated as 2.9 x 10-3 per µg/m3. Using the same approach, the lifetime unit risk for
breast cancer was calculated as 8.1 x 10-4 per µg/m3. Combining the risk for lymphoid and breast
cancers in females U.S. EPA adopted an inhalation unit risk of 2.99 x 10-3 per µg/m3 (rounded to 3.0 x
10-3 per µg/m3). These adult-exposure only unit risk estimates were then rescaled to a lifetime, using
age-dependent adjustment factors (ADAF). ADAFs are used to incorporate the greater risk of early life
exposure to chemicals that have a mutagenic MOA. When applying the ADAFs, EPA calculated an
inhalation unit risk value over a 70-year lifetime of 5.0 x 10-3 per µg/m3 (U.S. EPA, 2016). Cancer risk
from measured and modeled EtO concentrations are estimated by multiplying the IUR by the EtO
concentrations.
U.S. EPA Cancer Risk Estimates Reviewed by ATSDR
U.S. EPA Region 5 air modelers estimated cancer risk assuming a 70-year lifetime from measured and
modeled data. Based on modeled EtO concentrations at over 882 specific locations around the
Sterigenics facility, U.S. EPA used the 5-year average EtO concentrations to calculate lifetime cancer
risks between 1.3 x 10-4 to 6.7 x 10-2, with a geometric mean risk of 9.1 x 10-4. Even though cancer
risks are not generally calculated for short term exposures, the estimated cancer risks associated with
the measured EtO air concentration (19 samples collected for 12 hours each) were similar (range: 7.9
x 10-4 to 4.5 x 10-2, geometric mean: 7.7 x 10-3; Table 3). Note that these cancer risks were calculated
using the lifetime ADAF-adjusted IUR of 5.0 x 10-3 per µg/m3.
Table 3. Range of measured and modeled EtO concentrations: U.S. EPA Cancer Risk Estimates
Statistics
Minimum
Maximum
Mean
Geometric Mean

Modeled 5-year
(µg/m3)
0.03
13.32
0.32
0.18

Modeled
cancer risk range
1.3E-04
6.7E-02
1.6E-03
9.1E-04

12-hour samples
(µg/m3)
0.16
4.34
1.04
0.61

Measured
cancer risk range*
7.9E-04
4.5E-02
1.4E-02
7.7E-03

*Cancer risk was calculated to estimate what long term exposures to the 12-hour concentration could look like if sustained
long term and does not represent actual exposures.

Cancer Risk Estimates Calculated by ATSDR
For ATSDR assessments, the reasonable maximum exposure (RME) scenario for residential exposure
duration is 33 years over a lifetime of 78 years, so ATSDR calculated an IUR based on 33-year
residential exposure using ADAFs. As mentioned previously, ATSDR’s RME exposure point
concentration (EPC) of 2.1 µg/m3 was used as a reasonable estimate of exposure for the most exposed
individual in the community. This EPC is the maximum residential sample concentration of EtO in the
May 2018 data collection period. Given these assumptions, the cancer risk for this residential sample
9

 location is 6.4 x 10-3—an additional lifetime risk of 6.4 cancers in a population of 1,000 residents who
could be exposed to EtO emissions from Sterigenics. This cancer risk exceeds U.S. EPA’s decisionmaking cancer risk range of 1.0 x 10-6 to 1.0 x 10-4, and adds to the lifetime background cancer risk of
an average American of 1 in 3 people (American Cancer Society, 2018).
Table 4. Site-specific ADAF calculations for residential exposure*
Age Range
0 to <2 yrs
2 to <16 yrs
16 to 33 yrs

ADAF
10
3
3

U.S. EPA
unadjusted IUR
2.99 x 10-3
2.99 x 10-3
2.99 x 10-3

EPC
(µg/m3)
2.1
2.1
2.1

Duration Adjustment
2 years/78 years
14 years/78 years
17 years/78 years
Lifetime Risk

Partial Risk
1.6 x 10-3
3.4 x 10-3
1.4 x 10-3
6.4 x 10-3

*Cancer risk was calculated to estimate what long term exposures to the 12-hour concentration could look like if sustained
long term and does not represent actual exposures.

Likewise, ATSDR assumed the maximum commercial 12-hour sample concentration in commercial
sample locations of 9.1 µg/m3 to represent RME occupational exposures to workers in nearby
facilities. Note that workers at the Sterigenics facility would be covered under the Occupational Safety
and Health Administration (OSHA) EtO standard (29 CFR 1910.1047). For the off-site worker scenario,
ATSDR assumed an 8.5-hour workday, 250 days a year, for 25 years (ATSDR, 2016), yielding an
exposure factor (EF) of 0.08.
EFcancer, chronic =

ℎ𝑟
𝑑
𝑤𝑘
𝑥5
𝑥 50
𝑥 25 𝑦𝑟
𝑑
𝑤𝑘
𝑦𝑟
ℎ𝑟
𝑑
𝑤𝑘
24 𝑥 7
𝑥 52.14
𝑥 78 𝑦𝑟
𝑑
𝑤𝑘
𝑦𝑟

8.5

= 0.08

Cancer risk for workers can be calculated by multiplying the long-term air concentration by the IUR,
adjusting the duration of exposure as appropriate using the exposure factor calculation, above:
Cancer risk= IUR x EPC (µg/m3) x EF
For the maximum commercial concentration of 9.1 µg/m3, this risk equation yields a lifetime
occupational cancer risk of 2.1 x 10-3, or an increased risk of cancer for 2.1 people in a population of
1,000 workers from chronic exposures to Sterigenics emissions:
Cancer riskoccupational = 0.00299 x 9.1 µg/m3 x 0.08 = 2.1 x 10-3
While a more complete database from which to characterize exposure is preferable, we used U.S.
EPA’s limited data for the Sterigenics investigation and applied the standard ATSDR evaluation
process. Note that in both ATSDR calculations, we made a very conservative assumption that a 12hour sample represents long term exposure. We felt this assumption was warranted because the
measured and modeled concentrations demonstrated consistency and provided support that this
range of exposure is possible in the area surrounding Sterigenics.

10

 Non-cancer effects
Workers exposed to ethylene oxide over a long-term duration experienced similar health effects to
those exposed over shorter durations (California EPA, 2008). Workers exposed to levels of EtO at
8,500 µg/m3 and higher over an average of 5-6.5 years demonstrated cognitive and motor impairment
compared to unexposed controls. At lower levels of EtO exposure (145-300 µg/m3), studies have
shown evidence of hemoglobin adducts, DNA damage effects (i.e. sister chromatid exchanges), and
hematological effects (i.e. increases in leukocytes and decreases in neutrophil counts; decreases in
hematocrit and hemoglobin) (California EPA, 2008). No measured EtO concentrations from the
residential or occupational sampling approached or exceeded effect levels in the long-term modeling
estimates or the 12-hour samples being used as chronic exposure surrogates, therefore, non-cancer
health effects are not expected. However, air sampling in this effort was extremely limited.
LIMITATIONS
ATSDR made several assumptions as part of this assessment that could lead to the over or
underestimation of risk. Some limitations of this assessment include:
1. To calculate risks, ATSDR assumed that the concentrations measured during this assessment
will continue, unchanged if no actions are taken, over 33 years for residents, and 25 years for
workers.
2. ATSDR assumed that the very limited sampling investigation of 26 discrete locations over 2
days throughout the community represents typical exposure conditions from Sterigenics EtO
emissions. Only one 12-hour residential sample was collected, and that sample was used to
represent the RME residential chronic exposure estimate. EtO concentrations from grab
samples at one other residential location were slightly higher than the 12-hour averaged
sample collected at this property.
3. ATSDR assumed that the highest EtO concentration in the commercial area surrounding
Sterigenics represents worst case off-site worker exposures. This is likely underestimating
worker exposures for some employees in this area.
4. Due to a lack of long term sampling, the temporal trends of EtO emissions could not be
evaluated. Fluctuations of seasons that affect temperatures, barometric pressure, wind speed
and direction, and other potential factors that could influence the transport of EtO into the
surrounding community were not assessed.
Despite these limitations, ATSDR acknowledges that the U.S. EPA modeling demonstrates similar
concentration ranges to community air measurements. Thus, ATSDR believes the exposure estimates
assumed in this assessment are reasonable. Historical emissions were higher before a substantial drop
in 1999 with the construction of aeration rooms in Building 1. EtO cancer risks may have been
substantially greater for the 14 years the facility operated before these emission controls were
implemented, but historical risk cannot be evaluated with available emissions data.

11

 Conclusions:
U.S. EPA asked ATSDR to answer the following question: “If modeled and measured ethylene oxide
concentrations represent long term conditions, would they pose a public health problem for people
living and working in Willowbrook?” U.S. EPA provided modeled and measured data for ATSDR to
evaluate and render a health opinion.
It is ATSDR’s conclusion that the data U.S. EPA provided suggests that residents and workers are
exposed to elevated airborne EtO concentrations from facility emissions. It is difficult to assess longterm public health implications from facility emissions because there has been no historical air
monitoring in the community. ATSDR assumed that these data represent long term exposures for area
residents and workers. Specifically, ATSDR concludes the following:
1) 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 elevated risks present a public health hazard to
these populations.
2) Measured and modeled ethylene oxide concentrations in ambient air indicate that non-cancer
health effects are unlikely for residents and off-site workers in the Willowbrook community
surrounding the Sterigenics facility.
Recommendations:
1) ATSDR recommends that Sterigenics take immediate action to reduce EtO emissions at this
facility.
2) ATSDR recommends that U.S. EPA work with the Sterigenics facility to initiate long-term air
monitoring as soon as possible to measure ambient air levels of EtO. Ongoing air monitoring
can demonstrate the effectiveness of actions taken by the company to reduce emissions and
subsequent exposures in the community.
3) ATSDR recommends that IDPH investigate whether there are elevated cancers in the
population surrounding the Sterigenics facility that are consistent with those associated with
chronic EtO exposures.

Please do not hesitate to contact ATSDR Region 5 to discuss this assessment further or to request
further public health assistance.
Sincerely,

Michelle Colledge, MPH, PhD
Environmental Health Scientist
Agency for Toxic Substances and Disease Registry
Division of Community Health Investigations
Central Branch, Region 5
12

 CC:
Ken Runkle, IDPH
Aaron Martin, IDPH
Kathryn Siegel, U.S. EPA
Margaret Sieffert, U.S. EPA
Alexis Cain, U.S. EPA
Mark Johnson, ATSDR/ DCHI/CB
Rick Gillig, ATSDR/ DCHI/CB
Tina Forrester, ATSDR/ DCHI/OD

13

  

References:
Agency for Toxic Substances and Disease Registry (ATSDR). 2018. Discussion between ATSDR and U.S. EPA
Region 5 Air and Radiation Division on 7/23/2018.
Agency for Toxic Substances and Disease Registry (ATSDR). 2016. Exposure Dose Guidance for Determining Life
Expectancy and Exposure Factor. Atlanta, GA: U.S. Department of Health and Human Services, Public Health
Service.
Agency for Toxic Substances and Disease Registry (ATSDR). 1990. Toxicological Profile for Ethylene Oxide.
Health and Human Services: Atlanta, GA. Accessed from:
https://www.atsdr.cdc.gov/toxprofiles/tp.asp?id=734&tid=133
American Cancer Society (ACS). 2018. Lifetime probability of developing or dying of cancer. Accessed from:
https://www.cancer.org/cancer/cancer-basics/lifetime-probability-of-developing-or-dying-from-cancer.html
California Environmental Protection Agency (California EPA). 2008. Determination of Noncancer Chronic
Reference Exposure Levels, Appendix D3, Ethylene Oxide. Accessed from:
https://oehha.ca.gov/chemicals/ethylene-oxide.
Illinois Environmental Protection Agency (Illinois EPA). 2017. DRAFT/PROPOSED Clean Air Act Permit Program
(CAAPP) PERMIT. Permit No. 95120085. Bureau of Air, Permit Section. April 17, 2017.
Illinois Environmental Protection Agency (Illinois EPA). 2015. Statement of Basis for the DRAFT CAAPP Permit
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