home edit2 whole TSD November 2002 PDF format - OEHHA

ETHYLENE OXIDE
CAS No: 75-21-8
I. PHYSICAL AND CHEMICAL PROPERTIES (From HSDB (1998) except as noted.)
Molecular weight 44.06
Boiling point
10.7 ºC at 760 mm Hg
Melting point -111 ºC
Vapor pressure 1314 mm Hg at 25 ºC
Air concentration conversion 1 ppm = 1.83 mg/m 3 (NIOSH, 1994)
II.
HEALTH ASSESSMENT VALUES
Unit Risk Factor: 8.8 E-5 (µg/m 3 ) -1
Slope Factor: 3.1 E-1 (mg/kg-day) -1
[Female rat mononuclear cell leukemia data (Snellings et al., 1984), analyzed by US EPA
(1985) using a linearized multistage procedure (GLOBAL82), reevaluated by CDHS (1987).]
III.
CARCINOGENIC EFFECTS
Human Studies
Epidemiologic evidence for the carcinogenic effects of ethylene oxide at the time the Toxic Air
Contaminant (TAC) document (CDHS, 1987) was written was based on five longitudinal studies of
occupational cohorts in Sweden, the United States and West Germany. Together the studies
demonstrate an association between exposure to ethylene oxide and cancer. Two additional studies,
which were cross-sectional in design, evaluated leukemia incidence as part of a health evaluation of two
separate occupational cohorts (Joyner 1964; Ehrenberg and Hallstrom, 1967). Neither of these studies
was adequate to evaluate the carcinogenic effect of ethylene oxide since they were not designed to
study this outcome.
The five longitudinal studies examined cancer outcomes for all sites and site-specific cancers, with
leukemia as a focus for all studies. Four studies reported excesses in leukemia, while one study found
no cases of leukemia. A discussion of these studies follows.
Hogstedt et al. (1979a) reported that three cases of leukemia had occurred between 1972 and 1977
among 230 Swedish workers exposed to 50% ethylene and 50% methyl formate at a factory that
sterilized hospital equipment. Exposure at the plant began in 1968 and measurements taken in 1977
indicated concentrations of ethylene oxide of approximately 20 ± 10 ppm (time-weighted average);
exposure levels prior to 1977 were not known. The expected number of leukemia cases at this factory
for 1968-1977 was 0.2 cases, based on national rates. Three cases were observed, including two
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