4.3 Phosgene

Phosgene does not occur naturally, but since its initial preparation in the early 1800s it has become widely available in the chemical industry, where it is used as an intermediate in the manufacture of a wide range of other substances including dyes, pesticides and polymers. Annual production worldwide is in the millions of tonnes. When phosgene is used as a weapon rather than for beneficial purposes, the lung is the main target organ.

Descriptions of its smell range from decaying fruit to fresh cut grass or mouldy hay. Irritation of eyes, nose and throat together with chest tightness will occur rapidly when concentrations are greater than 3 parts per million (3 ppm), and these symptoms will be followed by shortness of breath and coughing. If these are the only symptoms, they will disappear rapidly after exposure ceases. If the dose is greater than 30 ppm a minute, victims experience severe lung damage and water on the lung, which is occasionally fatal. Although individuals can be trained to detect  phosgene at low concentrations, the sense of smell is a poor guide to interpreting what might be in the air. At high concentrations, individuals lose their sense of smell and their ability to assess danger.