Ethylene oxide is a highly penetrating, chemically reactive flammable gas or liquid that is used widely as a sterilizer of medical equipment and supplies. It is also an important industrial chemical that is used as an intermediate in the production of ethylene glycol, solvents, surfactants, and multiple other industrial chemicals. Ethylene oxide liquid has a boiling point of 10.7°C (760 mm Hg) and is readily miscible with water and organic solvents. Ethylene oxide in air poses a risk for fire/explosion at concentrations greater than 2.6%.
Mechanism of toxicity. Ethylene oxide is an alkylating agent and reacts directly with proteins and DNA to cause cell death. Direct contact with the gas causes irritation of the eyes, mucous membranes, and lungs. Ethylene oxide is mutagenic, teratogenic, and carcinogenic (regulated as a carcinogen by OSHA and categorized by IARC as a known human carcinogen). It may be absorbed through intact skin.
Toxic dose. Occupational exposure to ethylene oxide is regulated by OSHA, whose standard and excellent supporting documentation can be found at www.osha.gov. The workplace permissible exposure limit (PEL) in air is 1 ppm (1.8 mg/m3) as an 8-hour time-weighted average (TWA). The air level immediately dangerous to life or health (IDLH) is 800 ppm. Occupational exposure above OSHA-determined trigger levels (0.5 ppm as an 8-hour TWA) requires medical surveillance (29 CFR 1910.1047). The odor threshold is approximately 500 ppm, giving the gas poor warning properties. High levels of ethylene oxide can occur when sterilizers malfunction or during opening or replacing ethylene oxide tanks. Exposure may also occur when fumigated or sterilized materials are inadequately aerated. A minute amount of ethylene oxide is produced endogenously in humans from the metabolism of ethylene.
Ethylene oxide is a potent mucous membrane irritant and can cause eye and oropharyngeal irritation, bronchospasm, and pulmonary edema. Cataract formation has been described after significant eye exposure. Exposure to ethylene oxide in solution can cause vesicant injury to the skin. Ethylene oxide can cause CNS depression, seizures, or coma.
Neurotoxicity, including convulsions and delayed peripheral neuropathy, may occur after exposure.
Other systemic effects include cardiac arrhythmias when ethylene oxide is used in combination with freon (See Freons and Halons) as a carrier gas.
Leukemia has been described in workers chronically exposed to ethylene oxide.
Diagnosis is based on a history of exposure and typical upper airway irritant effects. Detection of ethylene oxide odor indicates significant exposure. Industrial hygiene sampling is necessary to document air levels of exposure.
Specific levels. Blood levels are not available. Ethylene oxide DNA or hemoglobin adducts may indicate exposure but are not available for clinical use.
Other useful laboratory studies include CBC, glucose, electrolytes, arterial blood gases or pulse oximetry, and chest radiography.
Emergency and supportive measures. Monitor closely for several hours after exposure.
Maintain an open airway and assist ventilation if necessary (See Airway and Breathing). Treat bronchospasm (See Hypoxia) and pulmonary edema (See Hypoxia) if they occur.