Dioxins
Dioxins can be found throughout the world in air, soil, sediment and water. Once in the environment, dioxins accumulate in the fatty tissue of wildlife, such as birds, fish, shellfish and marine mammals, and in people. Dioxins break down only very slowly and can remain in the environment, in wildlife and in people's bodies for a very long time.
Dioxins are highly toxic chemicals that are known, from studies with animals, to cause serious health effects such as cancer, birth defects, and reproductive and developmental problems. Dioxins can travel great distances on air currents, affecting people and wildlife far from their point of release – even in polar regions.
Because of these properties, when we release dioxins into the environment, we are burdening future generations with our pollution and its effects. Since the early 1970s dioxins have caused a great deal of public concern, and have been the subject of extensive investigation by the scientific community and regulatory agencies. Dioxins are a focus of international concern as one of the group of persistent organic pollutants (POPs). An international convention on POPs, the Stockholm Convention, has been in force since 2004.
New Zealand's efforts to minimise and eliminate releases of dioxins are set out in New Zealand's National Implementation Plan under the Stockholm Convention on Persistent Organic Pollutants (POPs).
Where do dioxins come from and how are people exposed?
Dioxins are not produced deliberately, but are created by some industrial processes and when organic material is burnt in the presence of chlorine. Burning wastes, and some industrial processes can all create small quantities of dioxins. They may also be formed from natural sources such as forest fires.
Dioxins are released into the environment mainly within emissions to air, and as a constituent of some solid wastes (eg, ash, sewage sludge, and scrap metal processing). Dioxins may stay in the air for a long time and be carried a great distance before settling on soil or water. If dioxins settle on pastoral land, they may be taken up by grazing animals and stored in the animals’ meat and milk. Dioxins can also enter our rivers, lakes and estuaries in effluent discharges, where they may be taken up by fish and shellfish.
For most New Zealanders, over 90% of our exposure to dioxins comes from eating foods of animal origin, such as meats, dairy products and fish. To a much lesser extent, we may also be exposed when we breathe air and come into contact with contaminated materials. Unborn children can be exposed to dioxins and nursing infants are exposed to the dioxins present in breast milk. The Ministry of Health has carried out a number of surveys of dioxins in breast milk. The most recent survey was published in 2010 and a copy of the report is available from the Ministry of Health's website.
Further information is available on the Ministry's Stockholm Convention web page.
What do we know about dioxins in New Zealand?
From scientific studies carried out by the Ministry for the Environment, we know that the background levels of dioxins in the New Zealand environment are generally low compared with the levels recorded in many other countries. The levels of dioxins in New Zealand foods, including our meats, dairy products and fish, are also low. Nevertheless, even a low level of dioxins in our environment does result in their accumulation in people’s bodies. An independent report to the Ministry for the Environment on the health risks of dioxin concluded that the current background exposures to dioxin-like compounds for the New Zealand population has an insufficient margin of safety and steps should be taken to further reduce exposures. The Ministry thinks that it is necessary to further reduce ongoing emissions so the level of dioxins in New Zealanders’ bodies continues to reduce over time.
The Ministry has investigated dioxin emissions from industry and domestic activity, as well as natural events such as forest and scrub fires. These investigations were first reported in 2000, followed by an update report in 2011.
The 2000 investigation found that burning waste material in incinerators, uncontrolled fires at landfills and domestic backyard fires, along with burning of wood and coal and processing of metal, were the major sources of dioxin emissions to air. However, the releases from the first two of these sources have since been considerably reduced, as a result of regulations applied under the national environmental standard on air quality.
Open burning processes are estimated to account for almost 70% of New Zealand's current total emissions to air. This includes landfill fires, forest, grass and scrub burning, backyard rubbish burning, and vehicle and building fires. The burning of wood to heat our homes is another significant contributor.
The two most significant sources of releases to land are the sludge produced by municipal wastewater treatment plants and the disposal of industrial and domestic wastes to landfill. Together these account for about 60% of all releases to land. Other significant sources are the solid wastes produced from the processing of scrap metals and the open burning processes noted above for releases to air.
New Zealand also has reservoirs of dioxin in contaminated soils, waste dumps, and landfills. The dioxins present in these reservoirs can potentially be redistributed back into our environment over a long period of time. The importance of these reservoirs relative to current ongoing emissions is unknown.
For more information on the New Zealand research see the Organochlorines Programme pages of this website.
Is it possible to eliminate dioxins?
Eliminating dioxins is not a realistic option. Dioxins in New Zealand come from both industrial and household activities. To eliminate dioxin emissions, most industrial activity involving vehicle transport, incineration, combustion, and the smelting of recycled metals would need to stop.
Domestic activities also produce dioxins. In New Zealand, they add up to roughly the same amount produced by all industrial activity. Therefore, eliminating dioxins could also mean that many domestic activities we take for granted would also need to be banned (for example, burning wood or coal to heat our homes, and driving motor vehicles).
Eliminating the release of dioxins to our environment would not be possible without causing major impacts on our economy and way of life. However, a practical approach is to reduce emissions to a level that will protect the health of New Zealanders and our environment.
The Ministry thinks that if industrial and domestic sources of dioxins are minimised, then the levels of dioxins in people and in wildlife will reduce over time.
What has New Zealand done to control dioxins?
New Zealand has already taken some important steps to reduce people’s exposure to dioxins, including:
- phasing out leaded petrol in 1996
- closing many smaller and/or poorly controlled waste incinerators, such as those commonly found in provincial hospitals
- replacing waste incinerators with an autoclave system, which treats the waste by sterilisation rather than burning
- stopping the use of the pesticide pentachlorophenol by the timber industry in 1988
- ceasing the manufacture of the herbicide 2,4,5-T in 1987
- no longer using elemental chlorine in New Zealand’s two pulp and paper mills
- prohibiting the importation of polychlorinated biphenyls from January 1987 and prohibiting their use since January 1994.
The Ministry for the Environment has recently developed Regulations for controlling some of the more significant sources of dioxins. These Regulations form part of the national environmental standards for air quality. The specific actions taken in relation to dioxins are discussed on the Ministry’s Stockholm Convention web page.
Levels of dioxin in our environment are generally low, but New Zealand research indicates that we should further minimise emissions of dioxins so the level of dioxins in people reduces over time. (See also Dioxins – Frequently Asked Questions)
Last updated: 29 March 2012
