Like phosgene, the principal feature of DP is delayed pulmonary edema. Although the mechanism is not entirely clear, edema may be caused by direct alveolar damage when DP breaks down into hydrochloric acid and carbon dioxide in the presence of water. DP also causes irritation of the upper respiratory tract and rarely can cause airway obstruction. Respiratory effects occur at doses of 1-10 parts per million. Doses greater than 25 parts per million can be rapidly fatal.
Toxicity varies with both the concentration of vapor and the length of exposure.
Because of its low water solubility, patients often inhale significant amounts of vapor before symptoms appear. History likely reveals multiple casualties with respiratory complaints. Some patients also may report irritation of the eyes or skin. Victims likely will have been involved in a mass gathering or military event within the last 24 hours. Patients may report explosions, smoke, or a gas cloud.