Phosgene originally was manufactured as a war gas. It is now used in the manufacture of dyes, resins, and pesticides. It is also commonly produced when chlorinated compounds are burned, such as in a fire, or in the process of welding metal that has been cleaned with chlorinated solvents.
Mechanism of toxicity. Phosgene is an irritant. However, because it is poorly water-soluble, in lower concentrations it does not cause immediate upper airway or skin irritation. Thus, an exposed individual may inhale phosgene for prolonged periods deeply into the lungs, where it is slowly hydrolyzed to hydrochloric acid. This results in necrosis and inflammation of the small airways and alveoli, which may lead to noncardiogenic pulmonary edema.
Toxic dose. The ACGIH-recommended workplace exposure limit (TLV-TWA) is 0.1 ppm (0.4 mg/m3) as an 8-hour time-weighted average. The level considered immediately dangerous to life or health (IDLH) by NIOSH is 2 ppm. Exposure to 50 ppm may be rapidly fatal.
Clinical presentation. Exposure to moderate concentrations of phosgene causes mild cough and minimal mucous membrane irritation. After an asymptomatic interval of 30 minutes to 8 hours (depending on the duration and concentration of exposure), the victim develops dyspnea and hypoxemia. Pulmonary edema may be delayed up to 24 hours. Permanent pulmonary impairment may be a sequela of serious exposure.
Diagnosis is based on a history of exposure and the clinical presentation. Many other toxic gases may cause delayed-onset pulmonary edema (See Hypoxia).
Specific levels. There are no specific blood or urine levels.
Other useful laboratory studies include chest radiography and arterial blood gases or oximetry.
Emergency and supportive measures
Maintain an open airway and assist ventilation if necessary (See Airway and Breathing). Administer supplemental oxygen, and treat noncardiogenic pulmonary edema (See Hypoxia) if it occurs.
Monitor the patient for at least 12–24 hours after exposure because of the potential for delayed-onset pulmonary edema.
Specific drugs and antidotes. There is no specific antidote.
Decontamination. Remove the victim from exposure and give supplemental oxygen if available. Rescuers should wear self-contained breathing apparatus.
Enhanced elimination. These procedures are not effective.