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 polychlorinated dioxins and furans. It describes how you might be exposed to these substances, how exposure might effect you and the environment, common uses, comparative data about polychlorinated dioxins and furans and their 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 polychlorinated dioxins and furans emissions in Australia.
For the NPI, polychlorinated dioxins and furans are reported as total emissions - ie, a total of the emissions kilograms (kg) of each of the species in this class of substances. However, dioxins and furans are often reported in toxic equivalents (TEQ), which is a means of scaling the emissions of each species of dioxin and furan according to their relative toxicity.
This concept allows the toxicity of a complex mixture to be estimated and expressed as a single number. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) is the most toxic and most extensively studied dioxin and is assigned a weighting factor(or toxic equivalency factor, TEF) of 1; all other dioxins have a TEF of less than 1.
Multiplication of the mass of a specific dioxin by its TEF yields the corresponding 2,3,7,8-TCDD mass (or TEQ). The total toxicity of any mixture is then simply the sum of the individual dioxin TEQs.
Hence, care should be taken when comparing NPI emissions of polychlorinated dioxins and furans with other sources of information.
The most noted health effect in people exposed to large amounts of 2,3,7,8-TCDD is chloracne. Chloracne is a severe skin disease with acne-like lesions that occur mainly on the face and upper body. Other skin effects noted in people exposed to high doses of 2,3,7,8-TCDD include skin rashes, discolouration, and excessive body hair. Changes in blood and urine that may indicate liver damage are also seen in people. Exposure to high concentrations of dioxin may induce long-term alterations in glucose metabolism and subtle changes in hormonal levels. In certain animal species, 2,3,7,8-TCDD is especially harmful and can cause death after a single exposure. Exposure to lower levels can cause a variety of effects in animals, such as weight loss, liver damage, and disruption of the endocrine system. In many species of animals, 2,3,7,8-TCDD weakens the immune system and causes a decrease in the system's ability to fight bacteria and viruses. In other animal studies, exposure to 2,3,7,8-TCDD has caused reproductive damage and birth defects. Some animal species exposed to dioxins during pregnancy had miscarriages and the offspring of animals exposed to 2,3,7,8-TCDD during pregnancy often had severe birth defects including skeletal deformities, kidney defects, and weakened immune responses.
Several studies suggest that exposure to 2,3,7,8-TCDD increases the risk of several types of cancer in people. Animal studies have also shown an increased risk of cancer from exposure to 2,3,7,8-TCDD. The World Health Organisation (WHO) has determined that 2,3,7,8-TCDD is a human carcinogen. The US Department of Health and Human Services (DHHS) has determined that 2,3,7,8-TCDD is known to cause cancer.
Polychlorinated dioxins and furans may enter your body through breathing, ingestion or absorption through the skin.
Eating food, primarily meat, dairy products, and fish, makes up more than 90% of the intake of dioxins for the general population. In addition breathing low levels in air and drinking low levels in water as well as skin contact with certain pesticides and herbicides may also be a source of exposure.
You may be exposed from living near an uncontrolled hazardous waste site containing dioxins or incinerators releasing dioxins.
You may be exposed from working in industries involved in producing certain pesticides containing dioxins as impurities, working at paper and pulp mills, or operating incinerators.
No national guidelines.
Dioxins are very toxic to certain animals. Studies have shown dioxins to have a range of adverse effects on a wide number of animals. Dioxins are known to bioaccumulate and therefore tend to be concentrated in the food chain.
Dioxins may be transported by air, water and in soils or sediments.
When released into the air, some dioxins may be transported long distances, even around the globe. When released in waste waters, some dioxins are broken down by sunlight, some evaporate to air, but most attach to soil and settle to the bottom sediment in water. CDD concentrations may build up in the food chain, resulting in measurable levels in animals.
No national guidelines.
Dioxins and furans are not manufactured intentionally other than for research. Their relevance to public and environmental health in Australia stems from their generation in small concentrations as by-products of chemical manufacture and incomplete combustion.
The principal sources of dioxins are:
Industrial and municipal processes including chlorinated bleaching processes used in pulp and paper production and in some cases municipal sewerage sludge may result in emissions to water. Dioxins may also be formed in water during chlorination of waste and drinking water treatment plants.
Dioxins and furans are ubiquitous and can be found in a wide range of environments and organisms though normally in very small quantities. The persistent and hydrophobic nature of dioxins mean that they can accumulate in soils sediments, organic matter and waste disposal sites. Disturbance of these sites, such as dredging may re-release the dioxins.
May be present in products (such as some pesticides) where it is an inadvertent contaminant produced during the manufacturing process. May be present in food substances due to contamination in the food chain.
Dioxins may be formed during the combustion of automotive fuel.
May occur in natural fires.
Approximately 400 substances were considered for inclusion on the NPI reporting list. A risk ranking was given based on health and environmental hazard identification and human and environmental exposure to the substance. Some substances were grouped together at the same rank with 208 ranks in total. Polychlorinated dioxins and furans was ranked as 83 out of the 208 ranks. Total hazard score (human health + environmental criteria) = 3.5.
On a health hazard spectrum of 0 - 3 polychlorinated dioxins and furans registers 2.8. 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 spectrum of 0 - 3 polychlorinated dioxins and furans registers 0.7. A score of 3 represents a very high hazard to the environment and 0 a negligible hazard.
Factors that are taken into account to obtain this ranking 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 | Polychlorinated dioxins and furans |
| CASR number | Not applicable |
| Molecular formula | Not applicable. This is a class of substances, the most toxic and widely studied is C12H4Cl4O2 or 2,3,7,8-tetrachlorodibenzo-p-dioxin (CASR# 1746-01-6) |
| Synonyms | 2,3,7,8-tetrachlorodibenzodioxin; Dioxin; TCDD; 2,3,7,8-tcdd; 2,3,7,8-T4CDD; 2,3,7,8-Tetrachlorodibenzo[b,e][1,4]dioxin; TCDBD; dibenzo-dioxin, 2,3,7,8-tetrachlorinated; 2,3,7,8-Tetrachlorodibenzo-1,4-dioxin; tetrachlorodibenzodioxin; tetradioxin; Tetrachlorodibenzo-1,4-dioxin polychlorinated dibenzo-p-dioxins (PCDDs) polychlorinated dibenzofurans (PCDFs) chlorinated dibenzo-p-dioxins (CDDs) |
| Physical properties: In the pure form dioxins are crystals or colourless solids. Generally present as mixtures containing a number of individual components. 2,3,7,8-TCDD is odourless, the odours of the other dioxins are not known. There are 75 compounds in the dioxin family and 135 compounds in the furan family. All have varying degrees of toxicity in comparison to the most toxic 2,3,7,8-TCDD. Melting point 305 - 306 (°C) Thermal decomposition 700 (°C) Other compounds in these families will have differing properties, depending on the number and position of chlorine atoms in the molecule. |
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| Chemical properties: Dioxins and furans are chemically classified as halogenated aromatic hydrocarbons. The most widely studied compound is 2,3,7,8-tetrachloro-p-dibenzodioxin which is often referred to simply as dioxin and is the reference for a number of compounds which are similar structurally and have dioxin-like toxicity. In general the compounds have low water solubility, low vapour pressure many are very stable and tend to bioaccumulate. There are also a number of dioxin-like PCBs, polybrominated biphenyls and mixed chlorinated and brominated congeners with dioxin-like properties. Compounds in these families will have differing properties, depending on the number and position of halogen atoms in the molecule. |
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There is more information that may be useful in understanding some of the issues surrounding the NPI.