experience notable discomfort, irritation, or certain asymptomatic, nonsensory effects. However, the effects are not disabling and are transient and reversible upon cessation of exposure.

AEGL-2 is the airborne concentration (expressed as ppm or mg/m3) of a substance above which it is predicted that the general population, including susceptible individuals, could experience irreversible or other serious, long-lasting adverse health effects, or an impaired ability to escape.

AEGL-3 is the airborne concentration (expressed as ppm or mg/m3) of a substance above which it is predicted that the general population, including susceptible individuals, could experience life-threatening health effects or death.


Airborne concentrations below the AEGL-1 represent exposure levels that could produce mild and progressively increasing but transient and nondisabling odor, taste, and sensory irritation or certain asymptomatic, nonsensory effects. With increasing airborne concentrations above each AEGL, there is a progressive increase in the likelihood of occurrence and the severity of effects described for each corresponding AEGL. Although the AEGLs represent threshold levels for the general public, including susceptible subpopulations, such as infants, children, the elderly, persons with asthma, and those with other illnesses, it is recognized that individuals, subject to idiosyncratic responses, could experience the effects described at concentrations below the corresponding AEGL.

SUMMARY

Ethylene oxide is a highly flammable gas produced in very large quantities in the United States (5.3 to 6.3 billion pounds). It is very reactive with nucleophilic substances such as water, alcohols, halides, amines, and sulfhydryl compounds. Ethylene oxide is used as an intermediate in the production of ethylene glycol and nonionic surfactants; a small amount is used as a fumigant for sterilizing foods and heat-sensitive medical equipment.

The database on the toxicity of ethylene oxide vapor in humans and experimental animals is extensive, including data on all aspects of toxicity except lethality in humans. Pharmacokinetics data show that ethylene oxide is readily absorbed from the respiratory tract in humans and other animals. Ethylene oxide alkylates proteins and DNA, and it is metabolized primarily by nonenzymatic hydrolysis, enzymatic hydrolysis, and glutathione conjugation.

The odor detection threshold for ethylene oxide was reported to be 260 ppm by one investigator and 700 ppm by another. In humans, ethylene oxide vapors affect the eyes, respiratory tract, central and peripheral nervous systems, gastrointestinal tract (probably secondary effects to nervous system toxicity), hematopoietic system, and possibly the reproductive system and fetus. Acute exposure to ethylene oxide at the odor detection level (≥260 ppm) causes eye and upper respiratory tract irritation and signs and symptoms of effects on the central and peripheral nervous systems. Acute exposure to a calculated concen-



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