Toxic and harmful gas in the environment and its detection - phosgene

1. the source of pollution

Phosgene is produced by carbon monoxide and chlorine under the action of sunlight or activated carbon at 200 ° C. It is a widely used organic chemical raw material. Phosgene is used as a raw material to produce a variety of organic compounds such as pesticides, dyes, pharmaceuticals, rubber, plastics and synthetic fibers. The annual production capacity of phosgene in the United States is more than 1 million tons. Decomposition of chloroform, carbon tetrachloride, etc. also produces phosgene. Phosgene is often emitted into the air during manufacturing and use, causing atmospheric pollution.

2. physical and chemical properties

Phosgene (cobalt chloride), also known as carbonyl chloride, is carbonyl chloride. It is a colorless gas with a boiling point of 7.60C and a melting point of 127.9°C. It is easily liquefied, has strong irritancy and suffocation, is non-flammable, slightly soluble in water, and easily soluble in benzene, toluene, xylene, chloroform and carbon tetrachloride. And organic solvents such as acetic acid. Phosgene can react with alcohol to form an ester. It easily decomposes to form carbon dioxide and hydrogen chloride when it meets water, and can react with ammonia to form urea.

Phosgene is toxic to the respiratory system, and the target organ is mainly the lung. Phosgene can directly damage the intima of the alveolar capillaries and cause pulmonary edema. The study found that under the scanning electron microscope, the damage of phosgene to the lower respiratory tract is characterized by cleavage, loss and lodging of cilia, and necrosis and shedding of ciliated cells, that is, damage to cilia-mucus delivery system after phosgene poisoning. Pulmonary capillary contraction; the number of pulmonary neuroendocrine cells (NE cells) and the number of particles of intracellular bioactive substances are significantly reduced. The activity of angiotensin-converting enzyme in the lung is increased, which causes the concentration of angiotensin in the lung to be greatly increased. In addition, in the study of pulmonary edema caused by phosgene poisoning, it is found that drugs capable of reducing free radical production or having free radical scavenging can be reduced. , can significantly reduce pulmonary edema caused by phosgene. This indicates that the generation of free radicals plays an important role in the development of phosgene-induced pulmonary edema.

3. the toxic effect

Phosgene is a highly toxic gas that enters the body mainly through the respiratory tract and has a cumulative effect. When the concentration reaches 5 mg/m3 in the production environment, it can smell rotten apple; when it is 10~20 mg/m3, it can cause eyes and upper Respiratory irritation symptoms; 20~50 mg/m3 can cause acute poisoning; 100~300 mg/m3 contact 15~30 seconds can cause severe poisoning or even death. The main symptoms of acute poisoning are tearing and coughing in the early stage of contact. Chest tightness, nausea and other symptoms after 1.5 to ~3d incubation period, shortness of breath, frequent cough, cyanosis, irritability and other symptoms. X-ray can be seen abnormal chest, susceptible to bronchitis, pulmonary edema, tonsillitis, and even acute Respiratory Compression Syndrome (ARDS).