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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 recently been negotiated.

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, chlorine bleaching of pulp and paper, and some industrial processes can all create small quantities of dioxins. They may also be formed from natural sources such as forest fires.

Most dioxins escape into the environment from air emissions. 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. A recent study by the Ministry of Health has measured the levels of dioxins in the breast milk of nursing mothers.

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. A 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 that the level of dioxins in New Zealanders’ bodies continues to reduce over time.

The Ministry has also investigated dioxin emissions from industry and domestic activity, as well as natural events such as forest and scrub fires.

It was 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, are the major sources of dioxin emissions to air.

Industrial sources are estimated to produce approximately 60% of New Zealand’s total emissions to air. Domestic activities (for example, backyard burning of waste and burning wood to heat our homes) are also important sources of dioxins.

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.

What is the Ministry for the Environment doing?

Contamination levels in our environment are generally low, but New Zealand research indicates that we should aim to minimise emissions of dioxins so that the level of dioxins in people reduces over time. Industrial emissions, particularly from combustion sources, are identified as one of the priorities for action.

Action on waste disposal and other sources

In October 2001, the Ministry for the Environment released a proposal for a national environmental standard under the Resource Management Act to regulate dioxin emissions from industrial facilities. Other actions to further reduce dioxin emissions in our environment were also proposed as part of the Dioxin Action Plan.

The Dioxin Action Plan is supported by technical and economic information on the applicability and implementation of national environmental standards in New Zealand.

The following reports are available:

Metallurgical processes

The action plan highlighted the potential for dioxin discharges from secondary metal processing as a particular area of uncertainty that needed to be addressed. Consequently, the Ministry for the Environment has funded a study on the Dioxin and Furan Emissions to Air from Secondary Metallurgical Processes in New Zealand. This study was undertaken by Sinclair Knight Merz.

Studies of land contamination

An investigation of dioxin soil contamination at sawmill sites where pentachlorophenol may have been used is underway.

The Ministry has recently reported on a study that measured dioxin in soils at residential properties in the New Plymouth suburb of Paritutu. For more information see Dioxin Soil Investigations in New Plymouth.

What else is the Government doing?

Other government departments are also involved in dioxins at a number of levels. The Ministry of Health is coordinating a whole of government approach to dioxin and has convened an Organochlorines Technical Advisory Group (OTAG). The Ministry is currently undertaking a number of studies of non-occupational health effects in the population from dioxin exposure. For more information visit the Ministry of Health dioxin webpages.

In June 2002, following a recommendation from OTAG, the Ministry of Health established an Interim Maximum Monthly Intake for dioxin (IMMI) (see Public Health Perspectives, Vol 5, No. 4). This IMMI replaces the 1990 tolerable daily intake value of the World Health Organisation, which has previously been adopted by the Ministry to assess a person’s exposure to dioxin.

Last updated: 17 October 2007