Breast best despite danger from dioxin

Our contamination levels are too high ... but they could be a lot worse. MATHEW DEARNALEY reports.

Breast-fed infants, women and older people are the New Zealanders most exposed to dioxin, a highly toxic family of chemicals which infiltrates and confuses body cells.

Kiwis' exposure to dioxin is only a third of that for people living in Europe, but an Environment Ministry report notes that our dietary intake is still 70 times above a daily limit recommended by the US Environmental Protection Agency.

Dioxin also gives us a lifetime risk of up to three to seven more cancers for every 1000 people, the report says.

A Health Ministry study has, meanwhile, found that while the intake of dioxin through mothers' milk has been reduced to about a third of that estimated a decade ago, it is still at unacceptable levels.

That study has yet to be published, as have reports obtained by the Herald that Environment Minister Marian Hobbs put before a cabinet committee last year, with advice that their release would need to be carefully managed to avoid public alarm.

But the Health Ministry yesterday issued what amounted to a call for calm, emphasising that the nutritional and other health benefits of breast-feeding still far outweighed the risks.

This view was supported by anti-dioxin author and former Greenpeace campaigner Gordon Jackman, despite his call for a redoubling of Government efforts to reduce exposure to the population at large.

Although general exposure to dioxin has also been reduced in recent years, largely because of reduced levels in food, Mr Jackman pointed out that babies took their milk from adults with accumulated concentrations from the past.

But he agreed that losses of other health benefits from moving to bottle-feeding would outweigh risks from dioxin contamination.

One of the Environment Ministry draft reports obtained by the Herald says body concentrations of dioxin-like compounds in infants exceed those in the mother after about six months, as a consequence of their presence in breast milk.

That in itself is recommended as cause enough to seek a reduction in emissions to the environment, which will be the aim of an industry standard which Ms Hobbs says the Government will introduce this year.

But the Health Ministry's chief child and youth adviser, Dr Pat Tuohy, said yesterday that the risk to health was from any long-term build-up in a person's body, rather than from short-term poisoning.

By about age 7, dioxin levels in children who were breastfed as infants were similar to those who were bottlefed, he said.

Ms Hobbs acknowledged that dioxin exposure was a serious issue and was being addressed by the Government, but she counted backyard fires and cigarette smoking as emission sources as well as industrial processes such as chlorine bleaching.

Older people have higher dioxin levels because of exposure through the food chain to agricultural chemicals, notably 2,4,5-T, which New Zealand in 1987 became the last country in the world to stop manufacturing.

But dioxin remains a byproduct of a range of industrial processes including timber treatment and waste incineration.

Higher body fat in women means they have more dioxin in their systems than men.

What are these dioxins and dioxin-like PCBs that Government officials have been studying for their toxicity?


Persistent organochlorine chemicals include the dioxins and polychlorinated biphenyls (PCBs), as well as pesticides such as DDT and dieldrin.

Dioxins are unintentional products of processes which use or burn chlorine.

How are they persistent?


Organochlorines are a group of chemicals which break down only very slowly in the environment. Once released, they may remain in soil and sediments for tens to hundreds of years.

They are highly toxic substances that accumulate in the fat and tissues of people and wildlife. As such they are known to cause serious health effects in a variety of animal species - cancer, birth defects, reproductive problems. It is generally considered these same effects may occur in humans.

Where does dioxin in NZ come from?


Dioxin is a byproduct of the manufacture of the herbicide 2,4,5-T, which the Ivon Watkins-Dow plant in New Plymouth produced from the early 1960s to 1987. But there is also a broad range of other dioxin sources, according to a report to the cabinet finance, infrastructure and environment committee summarising work by Environment Ministry scientists.

The burning of waste material, wood and coal and metallurgical processes are the major sources of emissions to the air. Solid residues from these processes, such as ash, are an important source of dioxins discharged to land.

An inventory compiled by the ministry estimates that 47 per cent of dioxin emissions are to the air, 50 per cent to land and only 3 per cent to water.

Industry is reckoned to account for 60 per cent of total dioxin emissions, with domestic sources including backyard fires contributing 38 per cent and natural sources such as bush or scrub fires 2 per cent.

An estimated 286 sawmill and timber treatment sites are contaminated by the organochlorine PCP (pentachlorophenol) and dioxin associated with it, notably the Waipa sawmill near Rotorua.

Surplus stocks of the chlorinated pesticide dieldrin lie under former Lands and Survey blocks.

Despite the low percentage of emissions to water, Lake Rotorua and the Tarawera River have been contaminated by past usage of organochlorines, including for paper production.

Newsprint and toilet paper produced in New Zealand are no longer contaminated by dioxin as their manufacturers have stopped using chlorine bleach. But chlorine-bleached paper products are still imported.

Land at New Plymouth next to the Ivon Watkins-Dow herbicide plant has been identified as a remaining "hot spot," and the Government intends giving nearby residents blood tests after claims that some have suffered birth defects similar to those of children of Vietnam War veterans exposed to defoliants such as Agent Orange.

Agent Orange was made from a mixture of 2,4,5-T and the herbicide 2,4-D, both of which were produced at New Plymouth for farm use.

How do our dioxin emissions compare with overseas?


The report suggests that overall our background levels of dioxins and PCBs are low compared with Northern Hemisphere countries. That is said to be consistent with our comparatively small industrial base.

So how much risk is there to us from these so-called background levels?


The report suggests very low levels of dioxins and PCBs have been found in our retail foods. That is said to indicate the present level of exposure from these things is low. But higher levels of exposure have occurred in the past, indicated by the levels of dioxins and PCBs present in people's bodies. Remember that 2,4,5-T was once widely valued by farmers as an effective herbicide and some of them, 20 or so years ago, opposed stopping its use.

New Zealand dioxin serum (a liquid in blood) concentrations are on average half those measured in populations in Europe and North America.

An assessment of New Zealand data suggests there is a minimal risk to wildlife from the levels of our background dioxins.

But can there be a "safe" level for dioxins?


Scientists talk in infinitesimally small numbers when dealing with dioxins. The World Health Organisation in 1990 recommended a daily intake of no more than 10 picograms per kilogram of body weight, when a picogram works out at one-millionth of a millionth of a gram.

But about two years ago it concluded that dioxin was even more toxic than earlier feared and reduced its recommendation to between 1 and 4 picograms.

Now, the US Environmental Protection Agency believes the figure should be 10 times lower than even that figure and Mr Jackman says there can be no safe level because of the extremely disruptive effect these tiny particles have on cell behaviour.

They confuse signals within the cell, causing the immune system to malfunction, and interfere with the body's hormones.

How does dioxin get into our bodies?


New Zealand Government scientists estimate more than 90 per cent of exposure to dioxin-like compounds is through our diet, with foods such as meats, dairy produce and fish usually predominant sources.

Dr Tuohy says people can reduce dioxin intake by eating more cereals, fruits and vegetables, and choosing low-fat meats.

Mr Jackman says following a fully vegan diet, without eggs and dairy products, would be the ideal but that would avoid the bigger picture of having to reduce dioxin emissions to the environment.

How much of the stuff do we actually swallow or breathe?


A study led by Environment Ministry scientist Dr Simon Buckland found that the amount we eat with our food appears to be lower than exposures reported in any other country where comparable studies have been undertaken.

The Buckland study found the intake varied from a mean or midpoint of 0.37 picograms per kilogram of body weight from a median energy adult male diet, to 0.84pg eaten by a high-energy adolescent.

But a supplementary study last year led by Dr Buckland estimated the mean average lifetime daily exposure for New Zealanders as a whole, counting all sources of dioxin and including higher concentrations from bygone years, at 1.4pg.

A study in the late 1980s of two types of dioxin in New Zealand mothers' milk measured concentrations of between 6100 and 40,000pg in every kilogram of fat.

But preliminary indications from a second study, by the Ministry of Health, indicated that concentrations fell by about two-thirds in the 10 years to 1998.

The Environment Ministry says that, based on a median lifetime daily intake of 1.4 pg, the added cancer risk is about three to seven extra cases for every 1000 people.

But Mr Jackman points out that many other health problems, such as heart disease and diabetes, have been caused by dioxin exposure at lower levels than those that might trigger cancer.