1,2Epoxybutane [factsheet]

1,2-EPOXYBUTANE

Please Note: The main sources of information for this fact sheet are EPA's Integrated Risk Information System (IRIS), which contains information on inhalation chronic toxicity of 1,2-epoxybutane and the RfC, and NTP toxicology and carcinogenesis studies of 1,2-epoxybutane in rats and mice. Other secondary sources include the Hazardous Substances Data Bank (HSDB), a database of summaries of peer-reviewed literature, and the Registry of Toxic Effects of Chemical Substances (RTECS), a database of toxic effects that are not peer reviewed.

Environmental/Occupational Exposure

* Individuals will be primarily exposed to 1,2-epoxybutane by dermal contact or inhalation in occupational settings. (1)

Assessing Personal Exposure

* No information was located concerning the measurement of personal exposure to 1,2-epoxybutane.

Health Hazard Information

Acute Effects:

* Irritation and inflammation of the nasal passageways and lungs have been observed in animal studies following acute (short-term) inhalation exposure to 1,2-epoxybutane at high concentrations. (1)

* Brief dermal contact to 1,2-epoxybutane causes mild irritation in rabbits. (1)

* Tests involving acute exposure of animals, such as the LD₅₀ test in rats and rabbits, have demonstrated 1,2-epoxybutane to have moderate acute toxicity from oral and dermal exposure. (2)

Chronic Effects (Noncancer):

* Chronic (long-term) inhalation exposure of rats and mice to 1,2-epoxybutane causes degenerative lesions of the nasal cavity. Pulmonary hemorrhage has been observed in rats exposed to the highest levels. (3,4)

* Atrophy and necrosis of the spleen and thymus, and renal necrosis have been observed in mice chronically exposed to high concentrations of 1,2-epoxybutane in air. (3,4)

* Chronic inhalation exposure of rats to high levels has been reported to result in hematological effects. (4)

* Prolonged or repeated dermal exposure of humans to 1,2-epoxybutane may cause blistering and necrosis. (1)

* The RfC for 1,2-epoxybutane is 0.02 mg/m³ based on degenerative lesions of the nasal cavity in mice. (4)

* EPA has medium confidence in the study on which the RfC was based because although the study was well-conducted, used an appropriate number of animals, chose well-spaced exposure levels, and provided a thorough histopathological examination of the respiratory tract, it did not establish a no-observed-adverse-effect level (NOAEL); medium confidence in the database because there is a chronic inhalation study in two species supported by subchronic inhalation studies in several species and because inhalation studies are available on developmental effects although there are no multigenerational reproductive studies available; and, consequently, medium confidence in the RfC.

* EPA has not established an RfD for 1,2-epoxybutane. (4)

Reproductive/Developmental Effects:

* No information is available on the reproductive or developmental effects of 1,2-epoxybutane in humans.

* In a developmental inhalation study, the pregnancy rate of rabbits was reduced but birth defects were not observed at high doses; these results may be confounded by a high rate of maternal mortality. (1,3,4)

* No reproductive or developmental effects were observed in an inhalation study of rats. (1,3,4)

Cancer Risk:

* No information is available on the carcinogenic effects of 1,2-epoxybutane in humans.

* In an inhalation study of 1,2-epoxybutane in rats and mice, tumors of the nasal cavity and alveolar/bronchial tumors were produced in male rats, while no tumors were observed in mice. NTP noted that there was clear evidence of carcinogenic activity for male rats. (3)

* EPA has not classified 1,2-epoxybutane for potential carcinogenicity. (4)

Physical Properties

* The chemical formula for 1,2-epoxybutane is C₄H₈O, and its molecular weight is 72.1 g/mol. (3)

* 1,2-epoxybutane is a watery, white liquid that is highly flammable. (3)

* The odor of 1,2-epoxybutane is sweetish and disagreeable; the odor threshold has not been established.

* The vapor pressure for 1,2-epoxybutane is 176 mm Hg at 25 EC. (1,3)

Uses

* The primary use of 1,2-epoxybutane is as a stabilizer in chlorinated hydrocarbon solvents. (3)

* 1,2-epoxybutane is used in the production of the corresponding butylene glycols and their derivatives. It is also used to make butanolamines, surface-active agents, and gasoline additives. (1,3)

Health Data from Inhalation Exposure

Concentration (mg/m³)	Health numbers^a	Regulatory, advisory numbers^b	Reference
1,000.0
_ _ _ _ 100.0	* LOAEL (mice) (147 mg/m³)		4
_ _ _ _ 10.0
_ _ _ _ 1.0
_ _ _ _ 0.1	* RfC (0.02 mg/m³)		4

LOAELCLowest-observed-adverse-effect level.

RfCCReference concentration.

^a Health numbers are toxicological numbers from animal testing or risk assessment values developed by EPA.

^b Regulatory numbers are values that have been incorporated in Government regulations, while advisory numbers are nonregulatory values provided by the Government or other groups as advice.

References

1. U.S. Department of Health and Human Services. Hazardous Substances Data Bank (HSDB, online database). National Toxicology Information Program, National Library of Medicine, Bethesda, MD. 1993.

2. U.S. Department of Health and Human Services. Registry of Toxic Effects of Chemical Substances (RTECS, online database). National Toxicology Information Program, National Library of Medicine, Bethesda, MD. 1993.

3. National Toxicology Program. Toxicology and Carcinogenesis Studies of 1,2-Epoxybutane (CAS No. 106-88-7) in F344/N Rats and B6C3F₁ Mice (Inhalation Studies). NTP TR 329. U.S. Department of Health and Human Services, Public Health Service, National Institutes of Health, Bethesda, MD. 1988.

4. U.S. Environmental Protection Agency. Integrated Risk Information System (IRIS) on 1,2-Epoxybutane. Environmental Criteria and Assessment Office, Office of Health and Environmental Assessment, Office of Research and Development, Cincinnati, OH. 1993.