Chlorine and inorganic compounds (as HCl)
Chlorine is a toxic, green-yellow gas and has a pungent odour. Chlorine is very reactive and oxidises e.g. metals already at room temperature. Chlorine gas dissolves in water (2.3 l in one liter of water).
Hydrogen chloride is a toxic, corrosive, colourless gas. It is strongly acidic and has a strong, pungent odour. It dissolves readily in water to form hydrochloric acid. In moist air, it forms dense clouds of hydrochloric acid. It has a choking, pungent odour.
Chlorine is one of the most important basic compounds of chemical industry.
The largest part of production is used for the production of polyvinylchloride (PVC) and other organic and inorganic intermediates and products as e.g. chloroform, trichlorobenzenes, propylenoxide, phosgene and silicium tetrachloride. Chlorine and other compounds which split off chlorine are used for bleaching of pulp, paper and cellulose as well as the chlorination of drinking and bathing water.
Hydrogen chloride is used in the hydrochlorination of rubber, in the production of vinyl and alkyl chlorides, in the separation of cotton from wool and in the delinting of cotton. It is also used for etching semiconductor crystals and is a chemical intermediate in many industrial production processes.
Since chlorine is very reactive it usually does not reach the environment. Small amounts dissolved in water could be discharged from bleaching processes. In rare cases accidents might be the cause of chlorine emissions.
Most hydrogen chloride released into the atmosphere is a result of burning coal. Mostly, these releases are from coal burning power stations or from power generation in other industrial plants. Waste incinerators also release hydrogen chloride. The emissions originate from sodium chloride (salt) in the coal or in incinerated food waste. The plastic PVC found in many products also contributes to hydrogen chloride emissions when waste is incinerated. Hydrogen chloride is also released from volcanoes.
Impacts on human health and environment
Chlorine gas destroys the tissue of humans, animals and plants by oxidation. Air, containing 0.5 -1.0 % chlorine, causes rapid death to humans mainly caused by generation of hydrogen chloride in the inhalation system and the lungs. Chlorine gas was used as a poison gas in First World War.
Excessive exposure to hydrogen chloride may cause health effects on the eye, lung, nose, skin and throat.
Hydrogen chloride is highly corrosive and attacks many metals and limestone, resulting in the corrosion of buildings and other cultural monuments. The gas dissolves in water to form a strong acid which at high concentrations is toxic to aquatic life. Acute harm to wildlife is unlikely to result from non-accidental emissions from combustion processes, but spillages leading to large discharges to water may be harmful to wildlife. Hydrogen chloride is very soluble in water and so tends to wash out of emissions into the air in rain. Certain types of soil and lakes may be particularly sensitive to inputs of acid rain above defined 'critical loads'.
The major gases involved with acid rain formation are sulphur dioxide, and nitrogen oxides, but hydrogen chloride may also play a part. Hydrogen chloride gas dissolves in the water droplets in clouds causing the rain to be more acidic than usual. Pollutants can be transported thousands of kilometers due to the introduction of tall chimneys dispersing pollutants high in the atmosphere. Acid rain affects the natural composition of rivers, lakes and soils, resulting in
Emission to air reporting threshold: 10000 kg/year
Data source: European Pollutant Emission Register