The most commonly encountered chlorides in nature are sodium, potassium and calcium chlorides. Chloride is an essential nutrient for plants and animals, including humans, but high concentrations can be harmful. The chloride salts mentioned above are white crystalline solids that dissolve readily in water. Hydrogen chloride, the acid from which these salts are derived, is a choking, irritant gas. It is highly soluble in water. Solutions of hydrogen chloride are called hydrochloric acid.
The major industrial use for sodium chloride (as rock salt) is as feedstock to produce chlorine gas and caustic soda. Chlorine is a major industrial chemical, e.g. being used to produce the plastic polyvinylchloride (PVC). Sodium chloride is also used for de-icing roads. Sodium chloride is also used in water softeners, both industrially and in domestic dishwashers. Inorganic chlorides have a variety of industrial uses, but most are released as waste products produced from other processes. Sodium chloride, as common salt, is used as a flavour enhancer for food and in commercial food production.
Chlorides are released with industrial waste waters (e.g. from flue-gas cleaning), agricultural run-off, landfill leachate, road salting, coal ash waste deposits and chloride-containing rocks.
Chloride is released naturally into the environment through the weathering of chloride containing minerals. The seas and oceans contain vast amounts of dissolved chloride. Coal also contains significant amounts of chloride that is released into the atmosphere as hydrogen chloride during combustion..
Impacts on human health and environment
Excessive exposure to some chemicals in this diverse group may cause effects on health, with the possible effects depending on the particular chemical.
Plants and animals show a wide range of tolerance to chloride and some, which live in saline lakes or coastal rock pools, may be extraordinarily resistant to very high concentrations. High levels of chloride discharged into freshwater bodies may be harmful to fish and other aquatic organisms which are not adapted to live in saline environments. Some terrestrial plants and animals may also be sensitive to chloride and be replaced by those that are more tolerant. For example, plants which are found usually in salt marshes may sometimes be found on roadside verges where there has been extensive run-off from de-icing salt, or on land contaminated from salty run-off from coal ash dumps.
Emission to water reporting threshold: 2000000 kg/year
Data source: European Pollutant Emission Register