PESTICIDE REPORT BY MERIEL WATTS 15 March 2001

Reprinted from Soil & Health 2001, Vol 60 No.2, p.14-15.

Dioxin And Cancer In New Zealand

It's all happening with dioxin: it's now been officially linked to cancer. In the USA, the National Toxicology Programme has at last added dioxin to the federal list of substances "known to be human carcinogens", specifically the TCDD type of dioxin. This announcement was due to be made eight months ago, but was delayed by a legal bid by a group of New York restaurateurs (among others) who argued they would suffer economically from the announcement because people would avoid eating food!

Meanwhile, across the other side of the world, negotiators from 122 countries, including New Zealand, have finally agreed on the phase-out and ultimate elimination of persistent organic pollutants such as DDT, and including dioxin, with the rider "where possible". That means that the New Zealand government should now eliminate the use of 2,4-D because it contains dioxin, including the TCDD form, and its use is not necessary.

It was a hard fought battle in this country to get our government to agree to that elimination, and congratulations to those activists here who undertook that work. The treaty still has to be ratified and signed by 50 countries so the pressure needs to be maintained to ensure that New Zealand signs on fast - and then does its utmost to reduce exposure to dioxin in this country, because we have a serious problem.

Unacceptably High Rates

Unpublished government documents state quite clearly that the New Zealand population's body burdens of dioxin are unacceptably high. No longer will the soothing, placatory comparisons with other countries where the pollution is worst, suffice. At last there is a realisation that the pollution is unacceptably bad in this country. It is a government recognition that we are not clean and green at all.

The documents state that there appears to be a small margin of safety, if any, between New Zealand intakes of dioxin and some non-cancer health effects. According to animal studies these non-cancer effects can include decreased sperm count, increased genital malformations, suppression of the immune system, neurobehavioural effects and endometriosis. There is particular concern for the health of the babies of exposed mothers, because of the concentration of dioxin in breast milk (women have higher levels of dioxin than men). There is acknowledgement that there is no threshold level of dioxin below which it can be said that cancer won't happen: in other words there is no safe level of dioxin. It is now acknowledged that there is no tolerable daily intake of dioxin, and that people in New Zealand may be experiencing adverse health effects from dioxin exposure. This includes an estimated 1-7 out of every 1000 people developing cancer from dioxin exposure. That's between 3844 and 26,910 cases of cancer in New Zealand caused by dioxin alone. This is regarded as being 100-fold greater than the "acceptable" level of cancer from exposure to environmental chemicals, according to the government papers.

Excuse me, acceptable to whom? In my view no cases of cancer caused by man-made chemicals liberated into the environment are acceptable. The government papers also contained the advice that the release of this information should be carefully managed so as not to alarm the public. I guess Soil & Health will be called alarmist for telling you the barefaced truth: instead the government should be thanking organisations like Soil & Health and Greenpeace, and all the others who have been politely pointing out for many years that there is a dioxin problem in this country. The good news is the government is planning a strategy to reduce dioxin exposure in New Zealand to "acceptable" levels - presumably that means only 38 to 269 cases of cancer from dioxin each year.

Meanwhile, readers need to be aware that the main intake of dioxin occurs through meat, dairy products and fish. The main sources of dioxin contamination in New Zealand are incineration, including backyard burning and landfill fires, the pulp and paper industry (chlorine bleaching), and some industrial processes.

Parkinson's Disease & Residues In Food

A superb new piece of research has highlighted the very real possibility of Parkinson's disease resulting from eating conventionally produced food containing pesticide residues. The research, carried out by the USA's University of Rochester and National Institute of Environmental Health Sciences, found that low doses of the herbicide paraquat and the fungicide maneb, in combination, caused key brain cells, known as dopamine neurons, to die.

1. This is the hallmark of Parkinson's disease. Mice exposed to these chemicals showed no effect when exposed to each chemical by itself, but did when exposed to the two chemicals together. This is evidence of a synergistic effect, where one chemical heightens the adverse effect of another, and has serious implications for our pesticide registration system. The system is only capable of looking at (some of) the effects of a single chemical at a time, hence it cannot judge the implications of exposure to multiple chemicals, which is the reality of human existence. The doses of maneb and paraquat that caused the death of brain cells in mice were only a fraction of those usually regarded as being toxic - for maneb it was only one per cent of the LD50, the standard measure of acute toxicity. This is compelling evidence that exposure to low doses of mixtures of chemicals, such as pesticide residues in food, is dangerous to your health. Worldwide, scientists are increasingly concerned about such exposures. The government authorities in this country are yet to show any concern or to take any action on the problem. Matters get worse. The research found that ongoing exposure to the combination of chemicals resulted in progressive neurotoxicity - and they only tested the chemicals for six weeks. Imagine the potential neurotoxicity for humans eating conventional produce containing these chemicals day after day after day, all their lives. Dithiocarbamate fungicides, of which maneb is one, have been found in virtually all fruit and vegetables tested during the Ministry of Health's Total Diet Survey (for a full list of these check Soil & Health 1999 Vol. 58(1) and (2). Paraquat wasn't included in the testing, so there's no knowing what residues might be present, or in which food combinations. But wait, there's more, as they say on a well-known TV advertisement: "I think what we have found is the tip of the ice-berg," said Cory Slechta, one of the reseachers.
2. There are thousands upon thousands of combinations of chemicals, any of which may produce similar effects. "I don't think we just happened to pick the right chemicals to see such an effect," says Slechta. These combinations have not been tested, so nobody knows whether or not the low dose mixtures of pesticides, other than paraquat and maneb, in the average New Zealander's daily diet are causing Parkinson's disease. This latest research suggests that they might well do so. So why don't all New Zealanders get Parkinson's disease? It is probable, according to the researchers, that these pesticide combinations would act in conjunction with a susceptible genetic pre-disposition. The genetic predisposition would likely include deficiencies in enzyme systems involved in detoxifying chemicals.
3. There's another interesting twist to this story: maneb contains manganese, that element claimed by Mark Purdey to be involved in BSE, a progressive neurology disorder not too dissimilar to Parkinson's disease (see page X for more on this theory). A higher incidence of Parkinson's has also been found in welders, and welding fumes contain high levels of manganese.
4. For more information on Parkinson's disease and pesticides check Soil & Health 2000, Vol. 59(5) and 2001, Vol. 60(1).

References

1. Thiruchelvam M, Richfield EK, Baggs RB, Tank AW, Cory-Slechta DA. 2000. The nigrostriatal dopaminergic system as a preferential target of repeated exposure to combined paraquat and maneb: implications for Parkinson's disease. J Neuroscience 20(24):9207-14. 2. Lazaroff C. 2001. Combination of pesticides linked to Parkinson's disease. Environmental News Service, January 3, Rochester, New York. 3. Betarbet R, Sherer TB, MacKenzie G, Garcia-Osuna M, Panov AV, Greenamyre T. 2000. Chronic systemic pesticide exposure reproduces features of Parkinson's disease. Nature Neuroscience 3(12):13012-6. 4. Lazaroff C.2001. Researchers link welding and Parkinson's disease. Environmental News Service, January 23, Rochester, New York