Under standard conditions, chlorine exists as a diatomic molecule. Chlorine is a highly toxic, pale yellow-green gas that has a specific strong smell similar to the smell of bleach. In nature, chlorine is most abundant as a chloride ion. In industry, elemental chlorine is usually produced by the electrolysis of sodium chloride dissolved in water. This method, the chloralkali process industrialized in 1892, now provides essentially all industrial chlorine gas. Along with chlorine, the method yields hydrogen gas and sodium hydroxide (with sodium hydroxide actually being the most crucial of the three industrial products produced by the process. Principal applications of chlorine are in the production of a wide range of industrial and consumer products. For example, it is used in making plastics, solvents for dry cleaning and metal degreasing, textiles, agrochemicals and pharmaceuticals, insecticides, dyestuffs, household cleaning products, etc. Chlorine is added both to pesticides and pharmaceuticals to make the molecules more resistant to enzymatic degradation by bacteria, insects, and mammals, but this property also has the effect of prolonging the residence time of these compounds when they enter the environment. In this respect chlorinated organics have some resemblance to fluorinated organics. Chlorine is used to prepare sodium and calcium hypochlorites. It is used as a disinfectant in water treatment, especially to make drinking water and in large public swimming pools . Chlorine was used extensively to bleach wood pulp, but this use has decreased significantly due to environmental concerns.
belongs to the class of inorganic compounds known as homogeneous halogens. These are inorganic non-metallic compounds in which the largest atom is a nobel gas.
Chlorine is a strong oxidizer that hydrolyzes in water forming hydrochloric and hypochlorous acids. In this form, it can penetrate the cell and form N-chloro-derivatives that can damage cellular integrity. Chlorine reacts with water in the epithelial lining of the upper respiratory airways. The mechanism of toxicity of aqueous chlorine or a hypochlorous acid/sodium hypochlorite is basically the same as that for chlorine gas. However, hypochlorous acid is a stronger oxidant than chlorine gas as reflected by its higher redox potential. Damage to the upper gastrointestinal tract, as may occur following ingestion of sodium hypochlorite bleach, is likely the result of oxidation reactions of hypochlorous acid with a range of biological molecules.
Metabolism
Hypochlorous acid reacts with proteins, amino acids, and unsaturated lipids to form chlorinated compounds, whereas the reaction with carbohydrates yields oxidation products. Metabolisation of chlorine results in the production of N-chloramines, tentatively identified as N-chloroalanine, N-chloroglycine, and N-chlorophenylalanine. (1)
Toxicity Values
Coughing and vomiting may occur at 30 ppm and lung damage at 60 ppm. About 1000 ppm can be fatal after a few deep breaths of the gas.
Lethal Dose
A few deep breaths of chlorine gas at 1000 ppm is usually fatal.
No indication of carcinogenicity (not listed by IARC). (3)
Uses/Sources
Chlorine is used in making plastics, solvents for dry cleaning and metal degreasing, textiles, agrochemicals and pharmaceuticals, insecticides, dyestuffs, household cleaning products. Chlorine is also used to prepare sodium and calcium hypochlorites. It is used as a disinfectant in water treatment, especially to make drinking water and in large public swimming pools. Chlorine was used extensively to bleach wood pulp, but this use has decreased significantly due to environmental concerns. Exposure usually results from inhaling contaminated air, ingesting chlorine bleach or directly contacting the skin with aqueous chlorine. (1)
The principal targets of exposure to chlorine gas are the respiratory airways and the eyes. Exposure to chlorine gas can lead to mild irritation of the nose, eye irritation and headache and throat irritation. Pulmonary edema and hypoxia can follow and further increase capillary permeability. Further complications can lead to pneumonia and even death. The principal targets of exposure to aqueous chlorine are the upper gastrointestinal tract and the skin. Ingestion of chlorine can lead to esophageal and gastric mucosal erosions, perforations at the gastroesophageal junction, and extensive necrosis of adjacent soft tissue. (1)
Symptoms
If inhaled, chlorine can trigger cough, substernal pain, respiratory distress, shortness of breath, and wheezing. Symptoms may be delayed. Nausea and vomiting are reflex in origin, and headache and loss of consciousness are probably due to the hypoxia caused by pulmonary edema. Dermal contact can lead to redness, pain, and redness of the exposed surface. Eye contact can lead to watering of the eyes. (1, 2)
Treatment
In case of inhalation, move patient to fresh air. Monitor for respiratory distress. If cough or difficulty breathing develops, evaluate for respiratory tract irritation, bronchitis, or pneumonitis. Administer oxygen and assist ventilation as required. Treat bronchospasm with an inhaled beta2 agonist and oral or parenteral corticosteroids. Examine mucous membranes, eyes and skin to be certain that corrosive effects have not occurred. In case of acute lung injury, maintain ventilation and oxygenation and evaluate with frequent arterial blood gas or pulse oximetry monitoring. In case of eye exposure, irrigate exposed eyes with copious amounts of room temperature water for at least 15 minutes. In case of dermal exposure, remove contaminated clothing and wash exposed area thoroughly with soap and water.
