Substance 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 dioxide. It describes how you might be exposed to this substance, how exposure might effect you and the environment, common uses, comparative data about chlorine dioxide 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 dioxide emissions in Australia .
Acute health effects : The following acute (short-term) health effects may occur immediately or shortly after exposure to chlorine dioxide: irritate the nose and throat, causing coughing and chest pain; eye irritation with watery eyes and seeing halos around lights; breathing chlorine dioxide can irritate the lungs causing coughing and/or shortness of breath. Higher exposures can cause a build-up of fluid in the lungs (pulmonary oedema), a medical emergency but which might not occur for 24 hours, with severe shortness of breath and possibly death.
Chronic health effects : The following chronic (long-term) health effects can occur at some time after exposure to chlorine dioxide and can last for months or years: irritate the lungs; repeated exposure may cause bronchitis to develop with cough, phlegm, and/or shortness of breath. Permanent lung damage may occur, especially with repeated exposure to the vapours. There is limited evidence that chlorine dioxide may damage the developing foetus.
The substance can be absorbed into the body by inhalation, ingestion of food that has been treated with chlorine dioxide, or skin contact.
People living near industries that produce or use chlorine dioxide. From using disinfectants or bleaches that contain chlorine dioxide. From foods and drinking water that have been treated with chlorine dioxide.
See Sources for more information.
Australian Drinking Water Guidelines (NHMRC and ARMCANZ, 1996):
Maximum of 1 mg/L (i.e. 0.001 g/L)
Worksafe Australia
Maximum time weighted exposure (TWA) level: 0.1 ppm 0.28 mg/m³
Maximum short term exposure level (STEL): 0.3 ppm 0.83 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.
Chlorine dioxide is well established to be harmful to all forms of life. Ranked in the USA as one of the most hazardous compounds (worst 10%) to ecosystems.
Most releases will be as the gas to the atmosphere or in wastewater streams from plants that make or use chlorine dioxide. Because of its high reactivity chlorine dioxide will not persist long in the air, water, or soil environments - up to minutes in air and up to hours in the others.
In the atmosphere it will photolyze rapidly, with a tropospheric half-life of a few seconds. Because of its high reactivity, chlorine dioxide will breakdown rapidly in natural waters (that is, waters that contain moderate amounts of organic matter). Nevertheless, this substance is considered hazardous to the environment with special attention required for water organisms.
The breakdown products are chloride ion and oxidised products of organic matter.
No national guidelines.
The major use of chlorine dioxide is as a bleach in a number of industries: in cleaning and de-tanning of leather, and as a bleaching agent for wood pulp, fats and oils, cellulose, flour, textiles, and beeswax.
Chlorine dioxide is registered as a bactericide, fungicide and algaecide. It is used to disinfect human drinking water systems, commercial water cooling tower systems, and metal cutting fluids. It may also be used to disinfect dairy farm animals and milking equipment, in eating establishments and food processing/handling areas and around the house. It is used extensively in Europe for disinfecting drinking water, and its use there is increasing as well as in North America and Australia, as an alternative to chlorine due to lesser problems with disinfection by-products.
Approved food additive in Australia (No. 926).
Paper and allied products industries; textile mills; chemical industries: food processing industries; drinking water treatment plants; and commercial water-cooling tower systems.
Residues from food and drinking water that have been treated with chlorine dioxide.
No specific information. Because of the nature of its high chemical reactivity, it is unlikely to occur naturally.
None known.
Possibly in some disinfectants and bleaches. Foods and drinking water that have been treated with chlorine dioxide.
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 dioxide was ranked as 41out of 400. The total hazard score taking into account both human health and environmental criteria is 3.3.
On a health hazard rating of 0 - 3 chlorine dioxide registers 1.8. 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 dioxide 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.
| Substance name | Chlorine dioxide |
| CASR number |
10049-04-4 |
| Molecular formula | ClO2 |
| Synonyms |
Synonyms chlorine peroxide; chloroperoxyl; doxcide 50; chlorine oxide; chlorine(IV) oxide |
| Physical properties: Chlorine dioxide is a strongly oxidising, yellow to reddish-yellow gas or liquid with a pungent, sharp odour. The odour is similar to that of chlorine and nitric acid. Soluble in water, alkaline, and sulfuric acid solutions. It is normally supplied as a less than 10% solution in cold water. Melting Point (°C): -59 |
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| Chemical properties: Chlorine dioxide gas is flammable, and is violently explosive in air at concentrations over 10%. It can be ignited by almost any form of energy, including sunlight, heat, or sparks. Chlorine dioxide is strongly oxidising, and reacts violently with organic chemicals and can be detonated by sunlight, heat, or contact with mercury or carbon monoxide. |
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There is more information that may be useful in understanding some of the issues surrounding the NPI.