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1,4-DIOXANE
CAS No: 123-91-1
I. PHYSICAL AND CHEMICAL PROPERTIES (From ACGIH, 1994)
Molecular weight 88.1
Boiling point
101.1°C
Melting point
11.8°C
Vapor pressure 29 mm Hg @ 20°C
Air concentration conversion 1 ppm = 3.6 mg/m 3
II.
HEALTH ASSESSMENT VALUES
Unit Risk Factor: (7.7 E-6 µg/m 3 ) -1
Slope Factor: 2.7 E-2 (mg/kg-day) -1
[Calculated from a cancer potency factor derived by RCHAS/OEHHA (CDHS, 1989)]
III.
CARCINOGENIC EFFECTS
Human Studies
The two human epidemiological studies of the potential carcinogenicity of 1,4-dioxane (Thiess et al.
(1976); Buffler et al. (1978)) did not show significant changes in the incidence of carcinogenicity.
However, neither study had sufficient statistical power to detect moderate changes in cancer incidence
due to the small size of the sample groups or the short duration of the studies.
In the study by Thiess et al. (1976), 74 German workers were exposed to various concentrations of
1,4-dioxane for an average of 24.9 years. Of the 74 workers, 24 were working at the end of the
follow-up period (1964 - 1974), 23 were no longer working, 15 had retired, and 12 had died. Of the
12 deaths, two were attributed to neoplastic diseases (1 lamellar epithelial carcinoma and 1
myelofibrotic leukemia). The expected number of deaths during this period in the cohort was 14.5,
based on Federal Republic of Germany mortality statistics. The overall death rate and the cancer death
rate were not significantly increased over controls.
Buffler et al. (1978) studied the mortality of 165 workers exposed to 1,4-dioxane in a dioxanemanufacturing
and processing facility in Texas. The employees were exposed to dioxane for at least 1-
month up to 21 years (April, 1954 to June, 1975), and were divided into two cohorts. The cohort of
manufacturing workers was composed of 100 individuals, and the processing workers numbered 65.
The concentrations of dioxane in the workplaces were less than 25 ppm. Seven deaths occurred in the
manufacturing cohort (4.9 expected), two from neoplasms (0.9 expected). Five deaths occurred in the
processing cohort (4.9 expected), one from cancer (0.8 expected). These mortality and cancer rates
were not higher than the expected from Texas age- and sex-specific death rates for 1960-1969. Due
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