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1 Introduction

This paper presents a national action plan for reducing discharges of dioxin to air.

'Dioxin' is used as shorthand for a family of 210 chemical compounds that belong to a class of environmental pollutants known as organochlorines. Organochlorines are toxic, do not break down in the environment, and accumulate in human and animal tissue. In New Zealand, residues of persistent organochlorines can be found in our environment, in food and in people. This environmental health problem is being addressed at a national level in New Zealand through the Organochlorines Programme in the Ministry for the Environment.

1.1 Dioxin in New Zealand's organochlorines programme

New Zealand's Organochlorines Programme was begun by the Ministry for the Environment in 1995. The focus of the programme is on:

In New Zealand the use of PCBs and persistent organochlorine pesticides has largely ceased, so the main task is to collect the existing stocks within the community and to clean up or secure reservoirs of these pollutants.(See footnote 4) This will require actions that are likely to include the development of environmental guidelines, and the formal banning of the use of these specific organochlorine pesticides under the Hazardous Substances and New Organisms Act 1996.

'Old' dioxin is also stored in reservoirs, but in contrast with PCBs and organochlorine pesticides, 'new' dioxin flows from many sources into the New Zealand environment. Of all these persistent organochlorines, action on dioxin is seen as the highest priority.

Flows and reservoirs of dioxin

Flows of new dioxin

Dioxin is still being created and released for the first time into the environment. This new dioxin is created as an unwanted byproduct of industrial and domestic activities and is discharged primarily to air and land. Much smaller amounts are discharged to water. 'Flows' of dioxin also occur when reservoirs are breached.

Reservoirs of old dioxin

Some reservoirs of dioxin, such as those left behind from the use of the pesticide 2,4,5-T and from the combustion of wastes, are dispersed widely throughout the environment. Other reservoirs, such as sawmill and timber treatment sites where pentachlorophenol was used, are relatively localised and more concentrated.

An inventory has been made of the flows and reservoirs of dioxin in New Zealand. How dangerous a particular flow or reservoir of dioxin is depends on how likely it is to travel along a pathway that ends in human or animal body tissue.

Summary of the New Zealand science on dioxin

The Organochlorines Programme has undertaken national surveys to identify the sources of dioxin in New Zealand, and to measure the levels in our atmosphere, in our terrestrial and aquatic ecosystems, and in our foods and the bodies of New Zealanders. The overall findings of this work are as follows.

  1. There is a broad range of dioxin sources in New Zealand. The burning of wastes, wood and coal, and metallurgical processes are the major sources of discharges to air. Compared to inventories from northern hemisphere countries, New Zealand's discharges are low, consistent with our comparatively limited industrial base and low population density.
  2. The background levels of dioxin in our environment are generally low relative to other countries. With the possible exception of coastal marine mammals such as Hectors dolphin, there is minimal risk to wildlife from background exposures to dioxin.
  3. Very low levels of dioxin were measured in retail foods, indicating that the current level of exposure for the population is low relative to other countries. Nevertheless, because dioxin is stored in people's bodies and only slowly eliminated, and because higher levels of exposure have occurred in the past, the levels of dioxin present in New Zealanders are, on average, half those measured in populations from Europe and North America.
  4. Although dioxin levels are believed to have fallen in New Zealand over the last decade, and despite the fact that our environmental levels and dietary intakes are low relative to other countries, the margin of safety to protect New Zealanders' health is judged to be small.

The technical reports on these studies are listed in Appendix 1, and are available from: http://www.mfe.govt.nz/issues/waste/ocreports.htm.

1.2 Objectives for action on dioxin

The objectives of New Zealand's action on dioxin are to:

  1. protect the health of New Zealanders by reducing their exposure to dioxin
  2. protect future generations of New Zealanders by reducing the creation of dioxin and its release into the environment
  3. safeguard the quality of our foods, especially meat and dairy products
  4. prevent the accumulation of dioxin in our environment and, where possible, reduce its concentration in reservoirs
  5. strengthen and protect New Zealand's clean green image.

These objectives can be achieved by developing action plans focused on four areas:

  • discharge to air
  • discharge on to land and into landfills
  • soil concentrations appropriate for different land uses
  • direct entry into food manufacturing processes.

No action on releases of dioxin to water is planned at this time. Current discharges from high-profile sources, such as bleached pulp and paper mill effluent, are only a very small source of dioxin. The major source of discharges to water is wastewater treatment, and this source is expected to decrease due to current industry improvements in treatment processes. However, reducing dioxin in wastewater can lead to increased levels in sewage sludge, and since sewage sludge is increasingly being applied to food-producing land, this must be addressed in an action plan.(See footnote 5)

The first stage of New Zealand's initiatives is an action plan that deals with the discharge of dioxin to air.

1.3 Dioxin discharge to air is a priority

There are good reasons for choosing the discharges of dioxin to air as the first priority for action.

  • The sources of dioxin discharges to air and the pathways of population exposures are relatively well understood.
  • Most of the dioxin stored in body tissue of the average New Zealander has originated from processes that discharged this dioxin to air.
  • Most dioxin discharged to air is newly created. Because dioxin persists in the environment, reducing dioxin discharges to air will diminish the amount of dioxin that ends up being stored in the environment.
  • Analysis has shown that certain discharges of dioxin to air can be reduced substantially at relatively little cost.
  • New Zealand would be following other countries, where the primary focus has been on reducing dioxin discharges to air from industrial sources. For example, Europe and North America have already set compulsory limits on discharges of dioxin to air from waste incinerators.
  • Dioxin discharges to air result in contamination of meats and dairy products. In Europe there is a high level of concern about food safety as a result of recent food contamination problems, several of which have involved dioxin. It is therefore economically prudent to minimise the discharge of dioxin to air to protect New Zealand's export markets.
  • Dioxin control technologies may also reduce other pollutants such as airborne particulates.
  • PCBs may sometimes be discharged from the same industrial processes as dioxin, but because the pathways by which dioxin and PCBs are formed in these processes are similar, control of dioxin will also control these PCBs.

1.4 Aim of this action plan

This paper is concerned with the unwanted creation of dioxin and its release to air. The aim of this action plan is to:

  1. find efficient and effective ways of reducing the discharge of dioxin to air from point and non-point sources
  2. identify sources where:
    • dioxin reduction initiatives can be established immediately
    • the gathering of additional information is warranted before initiatives can be proposed
    • no action is justified solely for controlling dioxin discharges
  3. contribute to fulfilling New Zealand's future obligations under the Stockholm Convention on persistent organic pollutants.

Footnotes:
2 Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), referred to collectively as 'dioxin'.

3 Aldrin, dieldrin, chlordane, DDT, lindane, hexachlorobenzene and heptachlor.

4 Reservoirs of organochlorines are places or materials that contain these chemicals. They include contaminated sites, waste dumps and landfills.

5 Other contaminants are present in sewage sludge, including the persistent organochlorine pesticides, PCBs and metals, so any action would have additional environmental benefits.

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