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Dioxin - Frequently asked questions
General Facts
What is dioxin?
Dioxin belongs to a larger family of chemicals called organochlorines, which contain carbon and chlorine atoms joined together. Dioxin is toxic. Because it is a stable chemical, it does not break down easily and can stay in the environment for a long time. Dioxin can also build up in people's bodies and in animals, where it can remain for many years.
Where does dioxin come from?
Dioxin is created by any kind of burning process. It is released into the air from fires at landfills, the burning of rubbish in commercial incinerators and from backyard fires. The burning of coal and wood and, to a much lesser extent, the combustion of petrol and diesel in motor vehicles are also a source of dioxin. Dioxin may also enter the environment through forest fires.
Metal processing, especially the smelting and refining of scrap metal can also release dioxin.
Previously, dioxin was made during the bleaching of pulp and paper. This dioxin was released into waterways, such as rivers. Also in the past, dioxin was released into the environment when people manufactured or used certain chemicals, especially:
- polychlorinated biphenyls (PCBs), which were used in transformers and capacitators in the electrical industry
- 2,4,5-T, a herbicide used to control gorse and other woody weeds
- pentachlorophenol (PCP), a fungicide used to treat timber.
Since 1994 the use of PCBs has been illegal in New Zealand. Neither PCP nor 2,4,5-T are used here anymore.
How does dioxin pollute the environment?
Dioxin released into air eventually settles on vegetation, soil or water. It is then taken up from the land by grazing animals and from aquatic and marine environments by fish. In animals, dioxin is stored mainly in the fatty tissue.
Dioxin may also enter our soil and then the food chain by recycling material, such as sewage sludge, back to land. It can also be released directly to water, such as from industry discharges, in landfill leachate or in run-off from soil.
How long has dioxin been in our environment?
As dioxin can be produced by natural events such as forest fires, it is likely there have always been very small amounts of dioxin in the environment. However, as our society became more industrialised, more dioxin would have been released. The amount of dioxin released is thought to have reached a peak in the 1960s and 1970s. Now that we know about the toxic effects of dioxin, government and industry in New Zealand and other countries are working successfully to cut back the amount of this chemical released into our environment.
How does dioxin get into our bodies?
For most people, about 90% of dioxin intake is through the diet. Animal-based foods (such as meats, dairy products and fish) have the highest amounts of dioxin. Unborn children are exposed to dioxin via the placenta while in the womb, and breastfed babies absorb dioxin from breast milk.
A dietary survey found that levels of dioxin in New Zealand food were lower than levels found in foods from Europe and North America. As a result, our dietary intake of dioxin is about one half to one fifth the intake reported in countries from these regions. Some groups of people will absorb more dioxin if they eat unusually high amounts of foods from polluted sources, or if they are exposed through their work.
Dioxin in New Zealand
Overseas, less dioxin is being released into the environment. Is the same happening here?
Yes. Over the past few years, the release of dioxin into our environment has fallen. The reasons for this include:
- phasing out leaded petrol from 1996
- stopping the use of PCP in the timber industry in 1988 and the deregistration of PCP in 1991
- discontinuing the manufacture of 2,4,5-T in 1987
- upgrades of industrial plants that historically emitted dioxin
- prohibiting the import (1987) and use (1994) of PCBs
- running PCB collection schemes and shipping PCBs overseas for destruction
- the closure of many smaller hospital waste incinerators which were poorly designed and/or operated.
The presence of dioxin in the environment in New Zealand is largely due to past behaviour and practice.
Where in the environment does dioxin go?
What can I do to reduce dioxin in our environment?
There are many simple things we can do that will cut back the amount of dioxin released into our environment. For example:
- make sure any motor vehicle is well maintained, especially if it uses diesel fuel
- do not burn driftwood (which contains high levels of chlorine from sea salt)
- make sure that anything containing PCBs, such as capacitors and light fittings, are disposed of safely. The Ministry of Health has published guidelines on the identification and disposal of PCB - containing electrical units titled Phasing out small PCB Holdings: Information Booklet for the Technical and Trade Association (1995 3rd edition). A copy of these guidelines can be obtained from Wickcliffe Press, P O Box 932, Dunedin or email moh@wickcliffe.co.nz.
To find out about storage and disposal arrangements, contact the local public health service of your District Health Board or ERMA New Zealand.
The Ministry of Health has published guidelines on the identification and disposal of PCB-containing electrical units. These guidelines are available from the local public health service of your District Health Board - avoid open fires as a method of heating. Use modern, efficient enclosed burners.
These initiatives will also reduce the release of other pollutants to the environment.
What has the government done to check the dioxin levels in our environment?
Over the past six years, the Ministry for the Environment has been checking the levels of dioxin in New Zealand. A major environmental survey has measured the amount of dioxin present in our soil, air, rivers and estuaries. The level of dioxin discharged to air, land and water has also been estimated as part of a dioxin inventory.
Reports on the environmental survey and dioxin inventory are available from the Ministry's website. A summary report is available from the Ministry for the Environment (Organochlorines Programme), PO Box 10-362, Wellington.
How safe is our environment?
The soil survey found that dioxin throughout New Zealand was either not detectable or present at only very low levels. Overall, the New Zealand soil environment is relatively free from dioxin contamination. The exceptions include sawmill sites where pentachlorophenol was historically used and the area in the immediate vicinity of a chemical manufacturing plant in New Plymouth. One soil sample on a Northland farm had higher than normal dioxin levels. This may have been because concentrated 2,4,5-T had been spilled there.
Some urban areas were found to have higher levels of dioxin in the air in winter time, probably as a result of people burning wood to heat their homes. Dioxin levels in our rivers and estuaries and in fish living in these water bodies were very low.
What are the main culprits in terms of polluting the environment with dioxin?
The research (in particular the dioxin inventory) shows that dioxin primarily gets into the environment via air and land, with smaller amounts entering water.
The dioxin inventory estimates that industrial sources, including landfills, account for about 60% of the total discharges to air, with domestic sources (eg, backyard burning of waste and accidental building fires) and natural sources (such as scrub and bush fires) accounting for the remainder.
Because it is often difficult to link any given source with any area of land contamination, scientists look at the national trends for emissions and pollution of land and air and estimate the relative contributions of different factors, like open fires and factory chimneys.
Do we still use any chemicals that contain dioxin?
PCP was voluntarily withdrawn from use by the timber industry in 1988 and deregistered by the Pesticides Board in 1991. The manufacture of 2,4,5-T in New Zealand ceased in 1987 and this herbicide is no longer sold in this country.
The herbicide 2,4-D, which is contaminated with small amounts of dioxin, is still used in New Zealand. However, the dioxin inventory estimated that this pesticide is a relatively minor source of all dioxin released to the environment. The Pesticides Board recently looked at the use of 2,4-D in New Zealand and decided not to prohibit the use of this chemical.
The Organochlorines Programme - what is it?
The Organochlorines Programme in the Ministry for the Environment was set up in 1995 because of the need to reduce emissions of dioxin in New Zealand and to clean up sites contaminated with organochlorines. The Programme has:
- studied the levels of organochlorines in the New Zealand environment
- identified sources and estimated quantities of dioxin emitted to air, land and water
- measured the levels of dioxin and PCBs in our diet and the levels of organochlorines present in our bodies
- helped industry to develop technologies that can be used to clean up contaminated sites.
The Programme is taking action to reduce New Zealanders' exposure to dioxin, including developing national standards for dioxin under the Resource Management Act (RMA) 1991.
Does the government regularly check dioxin levels across the country?
No. The environmental survey of the Organochlorines Programme was a one-off nationwide check on organochlorine levels in our environment. Other government work has also looked at dioxin in New Zealand, including a Ministry of Health survey on dioxin in breast milk. A copy of this report is available from the Ministry of Health's website at: www.moh.govt.nz
Risks to New Zealanders from dioxin
Why are people concerned about dioxin?
We know that dioxin can affect health. How dioxin affects people's health will depend on:
- how much dioxin the person was exposed to
- when the exposure happened, and
- the length of time the person was exposed for.
People and animals that have been exposed to high levels of dioxin have a greater risk of cancer.
The United States Environmental Protection Agency (EPA) lists known health effects in people exposed to high levels of dioxin, including:
- chloracne (a severe acne-like skin disease)
- skin rashes
- skin discolouration
- excessive body hair
- possibly mild liver damage.
The World Health Organisation (WHO) has classified one of the dioxin chemicals as a human carcinogen. There is also concern that lower level exposure over a long period can result in adverse effects on a person's immune system, as well as reproductive, neurobehavioural and developmental changes.
What can I do to reduce my family's dioxin intake?
The best way to reduce your intake of dioxin is by eating a diet low in animal fat. The Ministry of Health sets out nutrition guidelines recommending New Zealanders eat a healthy diet high in cereals, fruits and vegetables and low in fats. Following these guidelines will also mean that you are reducing your dioxin intake.
Does dioxin concentrate through the food chain?
Yes, and for humans at the top of the food chain this is particularly significant. Dioxin also builds up in our bodies over time. So an older person will tend to have higher levels of dioxin in their body than a younger person.
Do vegetarians have lower levels of dioxin in their bodies?
This has not been extensively studied, but one would expect that reducing meat/fat intake (and, therefore, dioxin intake) would over time result in lower levels of dioxin in a person's body.
Is dioxin excreted from people's bodies?
Yes, but only very slowly. For example, the most toxic dioxin is estimated to take about 7.5 years to reduce to half its initial concentration in a person's body, if there is no further exposure. For some of the other dioxin compounds, there is evidence that it takes even longer than this.
How does dioxin get into the air?
What are the primary sources of dioxin pollution to land?
How does dioxin get into the air?
What is the government doing to reduce dioxin levels in New Zealand?
As part of the Organochlorines Programme, the government has carried out research into dioxin in New Zealand. On the basis of this research, the Ministry for the Environment is developing national environmental standards and guidelines for levels of dioxin. The aim is to reduce dioxin in our environment to protect the health of New Zealanders.
What do we know about the health risks to New Zealanders from dioxin?
We know that dioxin is a very toxic chemical.
To assess risks to the New Zealand population from dioxin, the Ministry commissioned an independent Health Risk Appraisal, Evaluation of the toxicity of dioxins and dioxin-like PCBs: A health risk appraisal for the New Zealand population. This work looked at the current level of exposure for the population and compared this with levels that have been shown to cause health effects in laboratory animals and in people who had been occupationally exposed.
What does the Health Risk Assessment say about the cancer effects of dioxin?
The report estimates the cancer risk for the general New Zealand population and says this indicates a high potential risk of cancer for people exposed to dioxin. At the current level of exposure, one extra cancer could be expected for 1000 people exposed over a lifetime. This cancer estimate is about 100 times larger than the level of safety usually adopted in relation to exposure to carcinogenic chemicals in New Zealand. For the New Zealand population, this represents about 50 extra cancer deaths per year as a result of dioxin exposure. Although the actual rate of occurrence of cancers directly attributable to dioxin exposure is not known, it is unlikely to exceed the current estimates, and may be substantially less.
What does the Health Risk Assessment say about the non-cancer effects of dioxin?
The Health Risk Assessment says that there is not a big enough margin of safety between the concentration of dioxin in the body of the average New Zealander and the concentration of dioxin in the bodies of animals showing adverse health effects (including decreased sperm count, immune system suppression, genital malformations and abnormal behaviour). The report concludes by saying that although there is no clear evidence to show these effects are occurring in New Zealanders as a direct result of dioxin, people's exposure to this chemical should be reduced so that the margin of safety is improved.
What does the Health Risk Assessment say about former chemical plant and timber workers?
The Health Risk Assessment says that some people may have had higher exposure to dioxin than most New Zealanders because of their occupation. For example, it reports dioxin levels in former timber workers that are higher than levels in the general population. The report goes on to say that it is unknown whether these people would experience health effects and recommends that further assessment of timber workers be carried out.
General questions on dioxin and other organochlorines
Where can I get copies of the Ministry reports (either in summary or in full)?
These reports are all available on the Ministry's website, at www.mfe.govt.nz/issues/waste/ocreports. Summary reports are available from the Ministry for the Environment (Organochlorines Programme), PO Box 10-362, Wellington.
What other types of persistent organochlorines are there?
PCP, or pentachlorophenol, is a fungicide that was used extensively by sawmills in New Zealand in the treatment of freshly cut timber. PCP was also used to a smaller extent in New Zealand by the pulp and paper industry, in mushroom culture and in home gardens to control moss and algae. The use of PCP in the timber industry ceased in 1998 and it was withdrawn from sale in 1991. Although not itself persistent, PCP was contaminated with dioxin as a result of its manufacture.
PCBs (polychlorinated biphenyls) contain dioxin and were used in the electrical supply industry from the 1930s, mainly in transformers and capacitors. The use of PCBs has been illegal in New Zealand since 1994, and most stocks have now been shipped overseas for destruction. In the past, PCBs were also used as heat exchange fluids, as paint additives, in carbonless copy paper and in plastics.
Dieldrin was used as an agricultural insecticide and, with chlordane, was used in the timber processing industry. The sale of dieldrin in agriculture was banned in New Zealand in 1968, and its sale for all other purposes was banned in 1989.
DDT is an insecticide that has been used worldwide in horticulture and agriculture. It is still used in some tropical countries for the control of insects that transmit malaria. In New Zealand, the use of DDT was prohibited on farmland in 1970, and its sale for all other purposes was banned in 1989.
Lindane was used as an insecticide in agriculture for the control of lice on cattle and grass grub in pasture, and for insect control on vegetables and in orchards. As with DDT, the use of lindane was progressively restricted under a permit system and its sale for use was banned in 1989.
The other organochlorine pesticides being studied in the Organochlorines Programme are aldrin, hexachlorobenzene and heptachlor. These pesticides were used to only a limited extent in New Zealand.
Does the burning of pesticides or pesticide residues release dioxin?
Yes. Burning any material where carbon and chlorine are present can release dioxin. The amount of dioxin produced depends on what is burnt and how it is burnt (for example, whether these wastes are burnt in an incinerator where you can control the temperature and treat the gases discharged, or in an uncontrolled backyard fire).
What destruction options exist for waste organochlorine pesticides that have been collected?
As present there is no technology commercially set up and permitted under the Resource Management Act (RMA) that allows New Zealanders to destroy unwanted organochlorine pesticides within New Zealand. In recent years, PCB containing wastes have been shipped to Europe and destroyed there by means of high temperature incineration. Some small-scale tests have been run on non-incineration technologies in New Zealand and these and other options are operating in Australia and the USA.
What is the availability in New Zealand of clean-up technology for sites contaminated by organochlorines?
Commercial-scale clean-up technologies have yet to be established in New Zealand but are currently being used overseas.
Minimising dioxin releases
Dioxin releases occur from a wide range of industrial and household activities, including vehicle transport, incineration, the burning of wood and wastes, and the smelting of recycled metals.
Domestic activity contributes roughly 50% of all dioxin released in New Zealand on a daily basis. Therefore, in minimising dioxin releases, everyone has a role to play. For example, keeping vehicle engines tuned to minimise exhaust emissions, not burning refuse and plastics, and using a modern and efficient appliance if burning coal or wood for home heating (never burn chemically-treated timber or driftwood as burning salty wood releases dioxin). These actions all help to keep dioxin releases to a minimum level that will protect the health of New Zealanders and our environment. If industrial and domestic sources of dioxins are minimised, then the level of dioxins in people and in wildlife will reduce over time.
Last updated: 24 January 2006
