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.
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)
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.
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.
The National Pollutant Inventory (NPI) holds data for all sources of Polychlorinated dioxins and furans in Australia.
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.
Entering the body
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.
Workplace exposure standards
Safe Work Australia sets the workplace exposure standards for airborne contaminants. There are no workplace exposure standards for polychlorinated dioxins and furans.
Drinking water guidelines
There is no guideline for polychlorinated dioxins and furans in the Australian Drinking Water 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.
Entering the environment
Dioxins may be transported by air, water and in soils or sediments.
Where it ends up
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.
The principal sources of dioxins are:
- Combustion and incineration sources such as: incineration of solid waste, sewerage sludge and hospital wastes; high temperature steel production, smelting operations and scrap metal recovery furnaces and the burning of coal, wood petroleum products and used tires for energy generation all result in emissions to air.
- Chemical manufacturing and process sources such as manufacture of chlorine, chlorinated organic compounds may result in emissions to air or water.
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.
Diffuse sources, and industry sources included in diffuse emissions data
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 occur in natural fires.
Dioxins may be formed during the combustion of automotive fuel.
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.
Sources used in preparing this information
- ChemFinder WebServer Project (1995), (accessed, May, 1999)
- Environmental Defense Fund (accessed, May, 1999)
- National Environment Protection Council (1998a), National Environment Protection Measure for the National Pollutant Inventory (accessed, May, 1999)
- Technical Advisory Panel (1999), Final Report to the National Environment Protection Council.
- US EPA (accessed, May, 1999)
- Safe Work Australia, Workplace exposure standards for airborne contaminants, accessed February 2019.
- National Health and Medical Research Council (NHMRC), Australian Drinking Water Guidelines (2011) - Updated October 2017, accessed May 2018.