Health Hazard Information
Acute Effects:
• Acute inhalation exposure of workers to high levels of ethylene oxide has resulted in nausea, vomiting,
neurological disorders, bronchitis, pulmonary edema, and emphysema. (2)
• Dermal or ocular contact with solutions of ethylene oxide has caused irritation of the skin and eyes in humans. (2)
• Tests involving acute exposure of animals have shown ethylene oxide to have high acute toxicity from inhalation
exposures. (2)
Chronic Effects (Noncancer):
• Major effects observed in workers exposed to ethylene oxide at low levels for several years are irritation of the
eyes, skin, and respiratory passages and effects to the nervous system (e.g., headache, nausea, memory loss,
numbness). (2)
• EPA has not established a Reference Dose (RfD) or a Reference Concentration (RfC) for ethylene oxide.
• The California Environmental Protection Agency (CalEPA) has established a chronic inhalation reference exposure
level of 0.03 milligrams per cubic meter (mg/m
3
) (18 parts per billion [ppb]) for ethylene oxide based on
nervous system effects in mice. The CalEPA reference exposure level is a concentration at or below which adverse
health effects are not likely to occur. It is not a direct estimator of risk, but rather a reference point to gauge the
potential effects. At lifetime exposures increasingly greater than the reference exposure level, the potential for
adverse health effects increases. (3)
• ATSDR has established an intermediate inhalation minimal risk level (MRL) of 0.2 mg/m
3
(0.09 parts per million
[ppm]) based on an exposure below that associated with renal effects in mice. The MRL is an estimate of the
daily human exposure to a hazardous substance that is likely to be without appreciable risk of adverse noncancer
health effects over a specified duration of exposure. The exposure period for an intermediate MRL is from two
weeks to a year. (2)
Reproductive/Developmental Effects:
• Some evidence exists indicating that inhalation exposure to ethylene oxide can cause an increased rate of
miscarriages in female workers. (2)
• Various reproductive effects have been noted in inhalation exposure studies of animals, including decreased
number of implantation sites, decreased testicular weights and sperm concentration, and testicular
degeneration. (2)
Cancer Risk:
• Human occupational studies have shown elevated cases of lymphoid cancer and, also breast cancer in female
workers. (1)
• Ethylene oxide has been shown to cause lymphoid cancer and tumors of the brain, lung, connective tissue, uterus,
and mammary gland in animals exposed to ethylene oxide by inhalation. (1)
• EPA has concluded that ethylene oxide is carcinogenic to humans by the inhalation route of exposure. (1)
• EPA additionally concludes that the weight of evidence supports a mutagenic mode of action for ethylene oxide
toxicity. (1)
• EPA uses mathematical models, based on human and animal studies, to estimate the probability of a person
developing cancer from breathing air containing a specified concentration of a chemical. EPA has calculated an
inhalation unit cancer risk estimate of 3 × 10
-3
per µg/m
3
(6 × 10
-3
per ppb) for ethylene oxide for both cancer
types combined (lymphoid cancer and, in females, breast cancer). Taking into account the mode of action
conclusion, EPA estimates that if an individual were to continuously breathe air containing ethylene oxide at an
average of 2 × 10
-4
µg/m
3
(1 × 10
-4
ppb) over his or her entire lifetime, that person theoretically would have no
more than a one-in-a-million increased chance of developing cancer as a direct result of breathing air containing
this chemical. Similarly, EPA estimates that a lifetime of continuously breathing air containing
2 × 10
-3
µg/m
3
(1 × 10
-3
ppb) ethylene oxide would result in not greater than one-in-a-hundred thousand