Chlorine fact sheet

The National Pollutant Inventory (NPI) provides information on the types and amounts of pollutants being emitted in the Australian community.

This page provides facts about chlorine. It describes how you might be exposed to this substance, how exposure might effect you and the environment, common uses, comparative data about chlorine and its physical and chemical properties.

For more information about some of the terms used in this page, see the NPI glossary.

The National Pollutant Inventory (NPI) holds data for all sources of chlorine emissions in Australia .

Health effects

What effect might chlorine have on my health?

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.

How might chlorine enter my 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.

How might I be exposed to 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.

See Sources for more information.

What are the chlorine health guidelines?

Australian Drinking Water Guidelines (NHMRC and ARMCANZ, 1996):
Health: Maximum of 5 mg/L (i.e. 0.005 g/L)
Aesthetic: Maximum of 0.6 mg/L (i.e. 0.0006 g/L)
Worksafe Australia: Maximum eight hour time weighted average (TWA) exposure is 3 mg/m³

The Australian NOHSC National Exposure Standards Database link is probably the most useful source of information.

Note that the emissions data in the NPI database is not directly comparable with these guidelines.

Environmental effects

What effect might chlorine have on the environment?

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.

How might chlorine enter the environment?

Chlorine is carried in the air, where it rapidly reacts to form other compounds (see above). In water, it also reacts rapidly leading to a variety of organochlorine compounds, some of which are hazardous to the biota.

Where in the environment does chlorine end 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.

What are the chlorine environmental guidelines?

No national guidelines.

Common uses

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.

Sources of emissions

Industry sources

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.

Natural sources

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.

Transport sources

Chlorine has been identified but not quantified in motor vehicle exhaust.

Consumer products that may contain chlorine

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.

Comparison to other substances

NPI rank

Approximately 400 substances were considered for inclusion on the NPI reporting list. A ranking and total hazard score was given based on health and environmental hazards and human and environmental exposure to the substance.

Chlorine was ranked as 42 out of 400. The total hazard score taking into account both human health and environmental criteria is 2.7.

On a health hazard rating of 0 – 3 chlorine registers 1.2. A score of 3 represents a very high hazard to health, 2 represents a medium hazard and 1 is harmful to health.

On an environmental rating of 0 – 3 chlorine registers 1.5. A score of 3 represents a very high hazard to the environment and 0 a negligible hazard.

Factors taken into account to obtain this ranking and these scores include the extent of the material’s toxic or poisonous nature and/or its lack of toxicity, and the measure of its ability to remain active in the environment and whether it accumulates in living organisms. It does not take into account exposure to the substance. Environmental exposure is reflected in the NPI rank for this substance (see comparative data below). A substance that scores highly as an environmental hazard is oxides of nitrogen at 3.0 and one of the lower scores is carbon monoxide at 0.8. A substance that scores highly as a health hazard is arsenic at 2.3 and one of the lowest scores is ammonia at 1.0.

Total hazard rating

Physical and chemical properties

Substance name Chlorine
CASR number 7782-50-5
Molecular formula Cl2
Synonyms Dichlorine; molecular chlorine; chlorinated water, bertholite, javelle water, and sodium hypochlorite.
Physical properties:
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 (°C): -100.98
Boiling Point (°C): -34.6
Specific Gravity: 1.4085
Vapour Density: 2.5
Formula weight 70.906
Chemical properties:
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.

Sources of information used in preparing this fact sheet

  • 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.
  • National Health and Medical Research Council (NHMRC) and Agriculture and Resource Management Council of Australia and New Zealand (ARMCANZ) (1996), Australian Drinking Water Guidelines.
  • 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)
  • WorkSafe Australia (accessed, May, 1999)

There is more information that may be useful in understanding some of the issues surrounding the NPI.


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