Print
Effects
Choking agent poisoning results in the lungs filling with fluid (massive pulmonary edema). Exposure to very high concentrations may result in death within several hours; in most fatal cases pulmonary edema reaches a maximum in 12 hours followed by death in 24-48 hours. If the casualty survives, resolution commences within 48 hours and, in the absence of complicating infection, there may be little or no residual damage.
Signs and Symptoms
- Coughing
- Choking
- Tightness in the chest
- Nausea
- Occasionally vomiting
- Headache
- Tearing
The presence or absence of these symptoms is of little value in immediate prognosis. Some casualties with severe coughs fail to develop serious lung injury, while others with little sign of early respiratory tract irritation develop fatal pulmonary edema.
A period follows during which abnormal chest signs are absent and the casualty may be symptom-free. This interval commonly lasts 2 to 24 hours but may be shorter. It is terminated by the signs and symptoms of pulmonary edema. These begin with cough (occasionally painful), difficulty breathing, rapid, shallow breathing and cyanosis. Nausea and vomiting may appear. As the edema progresses, discomfort, apprehension and difficulty breathing increase and frothy sputum develops.
The casualty may develop shock-like symptoms and pale, clammy skin, low blood pressure and feeble, rapid heartbeat. During the acute phase, casualties may have minimal signs and symptoms and prognosis should be guarded. Casualties may very rapidly develop severe pulmonary edema. If casualties survive more than 48 hours they usually recover.
Lung-damaging agents are not commonly mentioned as major chemical threats. Phosgene was a major threat in World War I until mustard was introduced. Phosgene and similar agents have since not been used on the battlefield, primarily because other agents are more effective.
Phosgene is an industrial hazard used in many manufacturing processes. More importantly, it is released from heating or burning many common chemicals or solvents. Carbon tetrachloride, perchloroethylene (a degreasing compound), methylene chloride (used in paint removal), and many other compounds break down to phosgene with fl ame or heat. Also, common substances such as foam plastics release phosgene when they burn.
A casualty with shortness of breath in the absence of a chemical attack or other obvious cause should be questioned very carefully about whether he has been near any burning substances or chemical vapors that were near flame or other hot materials (e.g., a heater with open coils).
Detection
Phosgene smells like newly cut grass or freshly cut hay, but odor is not a reliable detection method. There are no fi eld detection devices for these compounds.
Physical Properties
Phosgene is very volatile. Under temperate conditions, it evaporates very quickly. Liquid phosgene may get on clothing and continue to release vapor. Although skin decontamination after vapor exposure is not a high priority, clothing should be removed and the underlying skin decontaminated with soap and water.
Mechanism of Action
Phosgene is the most studied compound in this category. Less is known about the other compounds; however, it is believed that they are very similar.