Chlorine is used in the manufacture of chlorinated organic chemicals, plastics, and chlorinated lime. Other uses include water purification, shrink proofing wool, in flame-retardant compounds and batteries, processing of some foods, metal fluxing, as a bleaching agent, in pulp and paper manufacturing, and detinning and dezincing iron. It is used as a post-harvest disinfectant for fruits and vegetables, or as a disinfectant in human drinking water treatment systems, swimming pool water systems, industrial ponds, and sewage systems. Chlorine may also be used as an algaecide in commercial and industrial water-cooling tower systems.
Substance name: Chlorine
CASR number: 7782-50-5
Molecular formula: Cl2
Synonyms: Dichlorine; molecular chlorine; chlorinated water, bertholite, javelle water, and sodium hypochlorite.
Greenish-yellow diatomic gas, a liquid, or in rhombic crystals, The pungent odour is suffocating and very irritating by inhalation, Chlorine is soluble in water, alcohols, and alkalis, Evaporates into the air very quickly.
Melting Point: -100.98°C
Boiling Point: -34.6°C
Specific Gravity: 1.4085
Vapour Density: 2.5
Formula weight 70.906
It is a powerful oxidising agent, strongly electronegative, very reactive, and combines readily with all elements except the rare gases (xenon excluded) and nitrogen. Chlorine also acts as an electron-acceptor in forming complexes with many donor species. Monatomic chlorine is unstable under ordinary conditions and can be formed as a result of thermal or optical dissociation, by an electrical discharge, or as an intermediate during chemical reactions.
The National Pollutant Inventory (NPI) holds data for all sources of chlorine and compounds emissions in Australia.
Exposure to low concentrations can cause burning of eyes, nose, and mouth; as the concentration increases, the effects become more severe: lacrimation (tear formation) and rhinorrhea (streaming nose); coughing, sneezing, choking, and substernal (chest) pain; nausea and vomiting; headaches and dizziness; fainting; fatal pulmonary oedema; pneumonia; conjunctivitis; inflammation of the cornea; pharyngitis; burning chest pain; difficulty breathing; bleeding in the respiratory system; oxygen deficiency; dermatitis; and skin blisters.
When inhaled in high concentrations, chlorine causes emphysema and damage to the pulmonary blood vessels. Chronic exposure can cause corrosion of the teeth. Cardiac arrest may occur secondary to oxygen deficiency.
Inhalation of small amounts of chlorine causes few or no symptoms. In larger amounts, it is a powerful irritant to the mucous membranes of the eyes, nose, and throat.
Exposures of 1-3 ppm can cause mild mucous membrane irritation; 5-15 ppm, moderate irritation of upper respiratory tract; 30 ppm, immediate chest pain, vomiting, dyspnoea, and cough; 40-60 ppm, toxic pneumonitis and pulmonary oedema; 430 ppm, lethal over 30 minutes; and 1,000 ppm, death within a few minutes. Death is possible from asphyxia, shock, reflex spasm in the larynx, or massive pulmonary oedema.
Populations at special risk from chlorine exposure are individuals with pulmonary disease, breathing problems, bronchitis, or chronic lung conditions.
Limited information is available on adverse developmental or reproductive effects of chlorine in humans or animals via inhalation exposure.
Entering the body
Through inhalation, skin or eye contact with the gas, or ingestion, skin or eye contact with any of the numerous products that contain chlorine.
The dominant exposure for the general public is likely to be from drinking chlorinated drinking water and using household chemicals (such as bleach and pool chemicals) that may release chlorine during use. Living near industries or facilities (such as water and wastewater treatment plants) that produce or use chlorine can also result in exposure.
Workplace exposure standards
Safe Work Australia sets the workplace exposure standard for chlorine through the workplace exposure standards for airborne contaminants:
- Maximum eight hour time weighted average (TWA): 1 part per million (3 mg/m3)
- A peak limitation notice exists for this substance.
These standards are only appropriate for use in workplaces and are not limited to any specific industry or operation. Make sure you understand how to interpret the standards before you use them.
Drinking water guidelines
The Australian Drinking Water Guidelines include the following guidelines for acceptable water quality:
- Maximum of 5 milligrams per litre of water for health purposes
Chlorine persists for only minutes in the air, water, or land environments. Both chlorine itself, and some of its reaction products, are very harmful to the biota. These effects range from causing death to a range of sub-lethal effects including deformities and reproductive damage.
Entering the environment
Chlorine is carried in the air, where it rapidly reacts to form other compounds (see chemical properties). In water, it also reacts rapidly leading to a variety of organochlorine compounds, some of which are hazardous to the biota.
Where it ends up
Chlorine absorbs some wavelengths of ultraviolet and visible sunlight and undergoes rapid chemical reactions in the atmosphere. The atmospheric half-life and lifetime of chlorine due to these reactions is estimated to be about 10 minutes and 14 minutes, respectively. The chlorine atoms produced will then react with organic compounds (mainly alkanes in polluted urban areas) to form hydrogen chloride and organochlorine compounds.
No national guidelines.
Releases from industries producing, using or handling chlorine.
Diffuse sources, and industry sources included in diffuse emissions data
Sub-threshold industries or facilities (such as water and wastewater treatment plants) that produce or use chlorine.
There are no known natural sources of gaseous chlorine. Elemental chlorine makes up approximately 0.03 percent of the upper earth's crust. The crustal material contains chlorine mainly in the form of sodium, potassium, and manganese chlorides. Chlorine is a component of the minerals halite, sylvite, and carnallite and occurs as the chloride ion in seawater.
Chlorine has been identified but not quantified in motor vehicle exhaust.
A wide range of disinfecting and cleaning products. These include household bleaches and disinfectants (including those for cleaning babies nappies and kitchen and bathroom surfaces), and swimming pool disinfectants and algaecides.
Sources used in preparing this information
- Australian and New Zealand Environment and Conservation Council (ANZECC) (1992), Australian Water Quality Guidelines for Fresh and Marine Waters.
- ChemFinder WebServer Project (1995) (accessed, May, 1999)
- Chemical backgrounder (accessed, May, 1999)
- Cornell University, Planning Design and Construction, MSDS (accessed, May, 1999)
- Meagher, D (1991), The Macmillan Dictionary of The Australian Environment, Macmillan Education Australia Pty Ltd.
- New Hersey Health Fact Sheet (accessed, May, 1999)
- Scorecard - California Air Resources Board (accessed, May, 1999)
- Scorecard - industrial rank (on quantity) (accessed, May, 1999)
- Richardson, M (1992), Dictionary of Substances and their Effects, Royal Society of Chemistry, Clays Ltd, England.
- Sittig, M (1991), Handbook of Toxic and Hazardous Chemicals and Carcinogens, 3rd edition, Noyes Publications, USA.
- Technical Advisory Panel (1997), Report to the National Environment Protection Council.
- TRIFacts (accessed, May, 1999)
- US Department of Health and Human Services (1990), NIOSH Pocket Guide to Chemical Hazards, Publication No. 90-117.
- USEPA Chem Facts (accessed, May, 1999)
- USEPA Health Effects (accessed, May, 1999)
- Safe Work Australia, Workplace exposure standards for airborne contaminants, accessed June 2021.
- National Health and Medical Research Council (NHMRC), Australian Drinking Water Guidelines (2011) - Updated October 2017, accessed May 2018