PESTICIDES IN FOOD: WHY GO ORGANIC

An Analysis of New Zealand's latest Total Diet Survey

by Alison White
Pesticide Action Network NZ/ Safe Food Campaign NZ
PO Box 9206, Wellington.

Executive summary

The Ministry of Health assures us that "the pesticide residue levels found in [the latest Total Diet Survey] are unlikely to have any adverse health implications for the New Zealand population." Their conclusions are based on the assumption that pesticide levels below the Acceptable Daily Intake are safe. But this is based in turn on several unscientific assumptions, such as that we are exposed to only one chemical at a time. Results from the survey are furthermore questionable with the very small sample sizes being analysed: 86% of the 114 foods tested had a mere two composite samples analysed.

Young children in New Zealand are getting about five times more pesticide residues than young American children. A sizable proportion of young NZ children could suffer from acute organophosphate poisoning from the residues in their food. The young child, aged 1-3 years old, takes in more pesticide residues than other age-sex groups, more than two and a half times more than men, for example.

The percentage of total samples with pesticide residues is significantly greater than some other countries, for example, the UK and the US. Wine, grains, especially wheat, and meat are more likely to contain pesticide residues than other food groups. When ranked according to the number of pesticides in combination with the percentage containing residues, bread and wheat products, wine, fruit and salad vegetables come out worst.

Recent findings concerning the endocrine disrupting potential of certain pesticides, eight of which are found in this survey, are a matter of grave concern, with disturbing consequences for the future of the individual, the family and society as a whole. A group of fungicides of concern, the most common of which is mancozeb, a known endocrine disruptor, continue to be used on a wide range of fruit and vegetables.

Analysis of the latest Total Diet Survey reveals tragically unnecessary pesticide residues in the New Zealand diet. With co-operation from regulatory authorities and growers and farmers, New Zealand can become an organic nation by 2020.

Shortcomings of the survey

90 pesticides of approximately 300 odd pesticide active ingredients registered in New Zealand were analysed for in this survey. Many pesticides may not have shown up because of the very small sample sizes. 98 out of 114 food groups had a sample size of 2, with the maximum sample size being 12.

Fewer pesticides would also not have been detected because of the large proportion of composite sampling done. Almost a third of the 460 samples analysed were composite samples, with between 6 and 10 samples combined together to form 2 samples that were analysed for pesticide residues. An effect of this is to dilute pesticide residues so they become undetectable. Also, it is not possible to obtain an accurate range of concentrations. A specific recommendation of the 1990/1 Total Diet Survey was to have "individualised sampling to maintain and improve sensitivity in future studies, and to enable worthwhile comparisons". No doubt for financial reasons, as it is very expensive to analyse for pesticides, this recommendation was not entirely followed for the latest total diet survey. The sample sizes in this survey compared to the last survey have been consistently reduced in size, suggesting that budgetary constraints have outweighed considerations of the accuracy of estimated dietary exposure to pesticides. Are we consuming fewer pesticide residues? Have fruitgrowers really reduced their pesticide residues? These questions cannot be answered with any confidence.

An assumption was made that if no residue was detected in a sample, the true concentration of the pesticide in that sample was zero. But the large proportion of composite sampling along with the very low sample sizes would mean zero results may not be a true zero. I believe a more accurate measure would have been to assign a value half way between the limit of detection and zero. As it is, the mean concentration of a residue would tend to be underestimated.

When pesticides are tested on animals, they are only tested individually, as if people were exposed to them one at a time. Studies are rarely done that reflect the reality of our exposure to a cocktail of chemicals over a life time. A typical lunch of a bread roll with butter, lettuce, tomato, luncheon sausage and an apple could have 16 different pesticides in it (data drawn from the Total Diet Survey 1990/1).

Research has found that mixtures of chemicals can be more potent than each individual one. An Italian study, for example, found that a mixture of 15 different pesticides commonly found in food caused liver and free radical damage of DNA, even at low doses. The study also found that when one pesticide, benomyl (a fungicide still used in NZ and never analysed for), was removed the mixture was much less toxic (Lodovic 1994).

Only the active ingredient of a pesticide is tested for long-term effects. The full pesticide formulation, containing secret and possibly very toxic ingredients, is not tested. No account is taken of the cumulative effects of a pesticide . Yet pesticides contain 'inert' as well as 'active' ingredients. There could be as many as 1700 different inert ingredients in the 700 pesticides on sale in New Zealand and many pesticides are almost entirely made up of these 'inert' ingredients. Yet by law they are not required to be listed on a label, even though the US Environmental Protection Agency acknowledges that some of them, such as mercury and lead, are dangerous.

What's wrong with an "Acceptable Daily Intake"?

The approach of the Ministry of Health, like other regulatory authorities around the world it must be said, is to assume the safety of a pesticide if it is below the Acceptable Daily Intake (ADI).

Acceptable Daily Intake is the daily intake of a chemical which, during the entire life-time of the consumer, appears to be "without appreciable risk" to health, as determined by experts meeting at the WHO/FAO. It is arrived at by taking the "no effect" level from animal studies and multiplying it, usually by a 100. It assumes that if we all eat less than, or up to, one hundredth of the daily dose that failed to provoke an obviously toxic effect in animals, then we will be adequately protected.

International regulatory agencies concede that the concept of an acceptable daily intake is a crude way of assessing toxicity. There is in fact no scientific justification for choosing a safety factor of 100 rather than 75 or even a 1000. It is little more than a calculated guess or a stab in the dark (chosen for political rather than scientific reasons) and is a nonsense in the real world, Professor Erik Millstone argues (Millstone 1986).

Risk assessments are generally based on animal tests, but then scientists disagree amongst themselves as to how reliable a guide these tests are in assessing the effects pesticides will have on humans. Because of the inexact nature of toxicology, precise and unequivocal risk assessments for some substances are difficult to do. Over time our knowledge about particular substances increases and technology and testing methods become more sophisticated, with the result that ADIs once thought to be acceptable no longer are.

The ADI in New Zealand of the chlorinated hydrocarbon insecticide dicofol has fallen from 25 micrograms/kg body weight/day in 1991, to 2 in 1998. In Australia it is 1, and there is a EU proposal to make it .4. Dicofol is an organochlorine contaminated with DDT and is a known endocrine disruptor. It was found in the latest survey in nectarines, pears and raisins and sultanas. DDT and its metabolites have an ADI of 20 micrograms/kg bw/day in New Zealand, in Australia it is 2.

Another flaw in the concept of an ADI is the fact that it is calculated on the basis of an "average" person, usually male, 60-70kg, and consuming an "average" diet. It's too bad if you happen to eat more than 180g sausages in a two-week period, which means that you could be getting a significantly higher dose of DDT. The largest dose of DDT, however, goes to the human baby, at the top of the food chain. ADIs do not take enough account of those most susceptible, like the sick, pregnant women, the developing foetus, the very young and the very old. It can be argued that there is no acceptable daily intake of a substance like DDT which bioaccumulates and causes endocrine disruption at very low levels.

As the survey acknowledges,relying on the supposed safety net of an ADI does not take into account the risk from acute or short term poisoning, . The survey fails to deal with this gap adequately, however. It recommends that "NZ maintains a watching brief". Increasing sample sizes and avoiding composite sampling would initially ensure a more accurate picture of the range of concentrations. Much lower collective ADIs should be used for pesticides which have a common effect and are likely to be found together, for example organophosphates.

Young children at risk

Young children in NZ are still getting about five times more pesticide residues than young American children. A similar calculation was made from data in the last survey, but this time comparing 13 pesticides. (See Figure 1.) While organochlorine levels continue to fall, and are now similar to US levels of the late 80s, the levels for organophosphates and fungicides have both disturbingly risen to almost twice the level, expressed as estimated daily intake for young children in micrograms/kg bw/day.

Young children are at special risk from acute poisoning from pesticide residues in food, especially from organophosphates. In this total diet survey young children are estimated to consume almost three times as many organophosphate residues as men. (See Figure 2.) US researchers from the National Research Council concluded that young children could suffer from acute poisoning from the residues in their food. They actually calculated that two-year-olds could exceed the ADI (of chlorpyrifos) 4.1% of the time, basing their figures on just five pesticides and eight foods (NRC 1993).

In Figure 1 we can see how the estimated daily intake of organophosphates in NZ young children is more than 20 times that of young US children. This means that a certain sizable proportion of NZ children could suffer from acute organophosphate poisoning. Common symptoms include tingling mouth, increased saliva, blurring of vision, sore stomach, nausea, diarrhoea. Two of the organophosphates found at high levels, pirimiphos methyl and chlorpyrifos methyl, are applied post harvest to grain in storage. Of concern is that young children have increased their intake of the organophosphate chlorpyrifos methyl more than elevenfold compared to the last total diet survey. This pesticide is now found in a wider range of foods (anything containing wheat) and at higher levels.

Young NZ children consume an estimated 20 times more fungicide when five fungicides are compared to US data (chlorothalonil, dichloran, diphenylamine, iprodione and vinclozolin). The estimated daily intake for young children in the case of iprodione has risen nearly five times compared to the last total diet survey. The mean concentration of this pesticide in food has also risen 80% compared to the last survey.

Compared to other age-sex groups, young children (1-3 year olds) have the highest levels of pesticide residues in their diets. In Figure 2 it can be seen that they have an estimated daily intake of pesticides which is more than two and a half times more than men. This is mainly because children eat more food in proportion to their body weight than other groups, but also because they tend to eat more food like fruit which is highly sprayed.

Interestingly, lacto-ovo-vegetarian females (dairy and egg eating), measured for the first time in this survey, consume about 50% more pesticide residues than other females. This seems to be due to the estimation that they eat more bread, more fruit and more of certain vegetables. This group does take in lower levels of DDT and other organochlorines due to their not eating meat.

Which foods have more pesticide residues?

Residues were found in 59% of the 460 samples taken in this survey, compared to 56% in the last survey. The slight increase may be misleading, because even though there were more levels detected due to lower limits of reporting for some pesticides, the greater composite sampling and smaller sample sizes would generally result in under reporting. Our food has more residues than either the US (33.5% - 1998) or the UK (25% - 1998).

Figure 3 shows which food groups contain a greater percentage of pesticide residues. Wine, grains and animals are more likely to have pesticide residues than other groups.

Animals included chicken, eggs (all two of them!), fish, meat as well as pizza. 79% of animal samples analysed had DDE, the persistent metabolite of DDT. This is comparable to the last survey where 80% had DDT (total), but the concentration has fallen and the limit of reporting is considerably lower (.003mg/kg compared to .01 mg/kg last time). New Zealand's levels of DDT are still high compared to overseas, but they are continuing to drop. The highest levels were found in butter (.04mg/kg or ppm), luncheon sausage and beef sausage (both .02mg/kg). It is worth seeking out organic butter and meat on the basis that you will get lower DDT residues. Biogro requires an initial soil sample test for DDT and metabolites.

DDT is the main contaminant of dairy products as well, especially ones with fat like butter, cheese, and whole milk. The fungicide iprodione was also found in yoghurt, presumably from the fruit. A comparison between American dairy products and New Zealand ones is startling: New Zealand's rate of contamination is so much higher: 68.2% as opposed to 3.4%.

Fruits from the US, on the other hand, have about the same percentage of samples containing pesticide residues as NZ. In this survey there were 11 different pesticides found in vegetables and 10 in fruit. (This compares to the last survey where there were 20 in fruit and 15 in vegetables.) A decrease in the percentage of samples with residues and also in the number of pesticides detected in fruit compared to the last survey may be due to fruitgrowers reducing their pesticide usage, or, it may be due to the greater composite sampling done with subsequent dilution. There is not enough evidence to decide.

"The Dirty Dozen"

Which foods is it especially good to avoid if non-organic and make an effort to buy organically? In Figure 4 are twelve foods analysed in the 97/98 Total Diet Survey which have been ranked according to the number of pesticides found and percentage with detectable pesticide residues. It is worthwhile to compare this list with the first dirty dozen list which is published in "Eating Safely in a Toxic World" (Kedgley 1998).

Bread and wheat products are at the top of the list, with residues detected in 94.4% of 90 samples. Wheat products include bran cereal, biscuits, flour, noodles, spaghetti, wheatbix, cake, pizza, sausages, luncheon sausage, muesli, hamburger, meat pie and the batter around fish. The chances are you are also taking in organophosphate or insecticide residues most of the time you eat something with flour in it. Most of these residues result from the post harvest application of a fumigant on the stored grain (chlorpyrifos methyl, pirimiphos-methyl, piperonyl butoxide, fenitrothion,).

The level of these insecticides does not seem to have decreased overall since the Total Diet Survey in 1990/91, even though New Zealand's residues are much higher than either the UK or US. The US had residues in 27% of wheat and wheat products, in contrast to New Zealand's 94%, for example! Other countries are increasingly using non-pesticide means of storage for their grain, for example, cold storage or carbon dioxide.

Wine is second on the list, with all 12 samples having iprodione, a fungicide in them. The good news is that the levels of vinclozolin, a known endocrine disruptor, have fallen. (It has just recently been deregistered.) The bad news is that grape growers seem to be substituting another fungicide, using more iprodione instead. Overall, levels of iprodione in food have increased 80% since the last Total Diet Survey. Iprodione, a chemical cousin to vinclozolin, can cause cancer.

The ranking of the rest of the foods on the dirty dozen list is not necessarily accurate because the sample sizes are small (most of them are eight), and with bigger sample sizes the ranking could easily change. It would be nice to think, for example, that apples have a lower ranking in this dirty dozen list because pesticide levels have reduced. Apples, like kiwifruit, now have a reduced pesticide programme in place for export fruit due to the overseas demand for lower pesticide residues. However, a comparison between the total diet surveys of 1997/8 and 1990/1 does not reveal much difference in regard to apples. It would be helpful if ENZA supplied details of the tests that they do for the export market to see whether pesticide residues on export apples at least have indeed decreased.

Close contenders for the dirty dozen list were lettuce, dairy products, meat and potatoes.

Health effects of these pesticides

Many of the pesticides found as residues in our food have been found in independent studies to have serious long term effects including hormonal disruption, cancer, immune system suppression, nervous system damage, genetic damage and birth defects.

The assumption is made that a continuous cocktail of these chemicals will have no effects at low doses. This assumption, however, is not based on solid scientific grounds, but more often than not, on whimsical political and economic grounds. Chemical substances which make a great deal of profit for powerful multi-national corporations in our modern society are less likely to be banned or restricted until the evidence of harm by them is overwhelmingly strong.

Children are at special risk with any substance capable of causing cancer and nervous system damage. A number of animal studies have shown that animals are at greater risk of developing cancer if exposure began in infancy rather than later in life. Of 14 carcinogens reviewed by the US Natural Resources Defense Council, the young were more susceptible to 12 (Whyatt 1989). The reason for such susceptibility may be linked with rapid cell division entailed in development and growth. Also children have more of their lives still to live during which exposure and carcinogenic action may occur.

The young are especially susceptible to the acute effects of organophosphate insecticides. Young rats are more susceptible than adults to the lethal effects of 15 out of 16 organophosphates tested. For some organophosphates, the fatal dose in immature animals has been reported to be only 1% of the lethal dose in adult animals (Calabrese 1986).

The authoritative study by the US National Research Council concluded: "The data strongly suggest that exposure to neurotoxic compounds at levels believed to be safe for adults could result in permanent loss of brain function if it occurred during the prenatal and early childhood period of brain development. This information is of particular relevance to dietary exposure to pesticides, since policies that established safe levels of exposures to neurotoxic pesticides for adults could not be assumed to adequately protect a child less than four years of age." (NRC 1993)

Endocrine disruption

Recent research has brought to light another class of adverse effects from various pesticides and other chemicals. Several pesticides (as well as some widely used industrial chemicals) can disrupt the body's endocrine or hormonal system - so crucial in growth and development. These endocrine disruptors can mimic or disrupt the normal functions of hormones, and tamper with this delicately balanced signaling system in the body, which governs a range of functions and developmental processes.

Though their effects in human beings are still being debated, the evidence is mounting. From wildlife and animal studies in laboratories, there is growing concern that these endocrine disruptors can cause developmental, reproductive, behavioural, immunological and physiological changes.

Particularly worrisome is the threat that endocrine disruptors pose on the unborn. When acting on a developing foetus at critical periods, they can cause lasting damage at minute doses, which were previously not thought to be harmful. As Theo Colborn, researcher and author of the book "Our Stolen Future", expressed: "[this calls] into question the adequacy and relevance of high-dose testing on adult animals. Some chemicals have effects at low doses that differ from those at higher doses, undermining reliance on extrapolation from high doses." (Nair & Mourin 1999)

Theo Colborn continues further: "We are neutering the population; we are making females more masculine and males more feminine." Further potential effects on human health are listed in Box 1. A recent study on how exposure to pesticides impairs children's brain development is detailed in Box 3. Pesticides registered in New Zealand known to cause endocrine disruption in animals are listed in Box 2.

Eight pesticides found in this survey are known endocrine disruptors: DDT, dicofol, endosulfan, chlorpyrifos, dimethoate, fenitrothion, mancozeb (as dithiocarbamates) and vinclozolin. There are various other pesticides structurally related to these which are suspect.

The dithiocarbamates are a group of fungicides including mancozeb, metiram, zineb and ziram which have a metabolite called ethylene thiourea (ETU). This breakdown product is a known endocrine disruptor, carcinogen, mutagen and teratogen, and can concentrate upon processing and heating. In other words, if you cook a vegetable which has been sprayed with mancozeb (the most common), you will be increasing the amount of the dangerous metabolite.

Over 60% of the 138 samples of fruit and vegetables analysed for dithiocarbamates in the latest total diet survey contained them. The 17 fruit and vegetables ranked in order according to occurrence and mean concentration are: broccoli, cabbage, tomato, celery, lettuce, onions, cucumber, apples, oranges, mushrooms, potatoes, courgettes, kumara, nectarines, pears, capsicum and kiwifruit.

Conclusion

The young, those who suffer from chronic illness and anyone who eats more bread, fruit and vegetables than average are more at risk both short term and long term from pesticide residues in their diet. For these people particularly it is important to increase the amount of organic food eaten, especially those foods which are heavily sprayed.

In general, if you are trying to reduce pesticide residues in your diet, especially seek out organic bread, fruit and salad vegetables, meat and butter. It is especially important for pregnant women and women who may conceive to eat organic wheat, fruit, vegetables, meat, cheese and butter. Ideally, a woman would detoxify before conceiving.

We can help protect ourselves from a toxic environment by eating organic food, and by demanding a benign system of agriculture and an economy and infrastructure that does not depend on pouring pollutants into the atmosphere, rivers and seas.

Recommendations

Grain merchants:

• urgently investigate and implement non-pesticide means of grain storage. This single measure could result in dramatically lower organophosate levels in New Zealand food.

Ministry of Health:

• assess cumulative exposures rather than individual exposures
• decrease ADIs to account for greater susceptibility of the young to endocrine disruption, nervous system damage and cancer.
• reduce use and exposure to endocrine disrupting pesticides.
• analyse for ETU
• increase sample sizes dramatically
• have more individualised samples analysed
• analyse for other pesticides, including paraquat, diquat, glyphosate and 24D

MAF, ENZA, Zespri and other exporting organisations:

• allow the public access to details of sampling for export. Australia does it.
• co-operate with organic growers to enable knowledge to be shared of how problems and pests can best be dealt with using the least toxic method of control.
• avoid use of the suspect pesticides such as endocrine disruptors, immunotoxins and carcinogens.

ERMA, Pesticides Board:

• deregister 24D.
• restrict and phase out the dithiocarbamates.
• phase out the organophosphates.

References

Calabrese, E.J. 1986: Age and Susceptiblity to Toxic Substances. New York: John Wiley & Sons.

Guillette, E.A.et al 1998: An anthropological approach to the evaluation of preschool children exposed to pesticides in Mexico. Environmental Health Perspectives 106: 237-347. In: Watts, M. 2000: Endocrine disruption: a case for the precautionary approach. Soil & Health March/April.

Kedgley, S. et al 1998: Eating Safely in a Toxic World: What really is in the food we eat. Penguin NZ.

Lodovic, M. et al 1994: Effect of a mixture of 15 commonly used pesticides on DNA levels of 8-hydroxy-2-deoxyguanosine and xenobiotic metabolizing enzymes in rat liver. Journal of Environmental Pathology, Toxicology and Oncology 13: 3, pp163-168.

Millstone, Erik 1986: Food Additives. Penguin Books.

Nair, K.P. & Mourin, J 1999: Introduction. In: Mourin, J (ed): Warning: Pesticides are Dangerous to Your Health! Pesticide Action Network Asia and the Pacific, Penang.

NRC (National Research Council) 1993: Pesticides in the diets of infants and children. Washington: National Academy Press.

Whyatt, R. 1993: The physiological susceptibility of children to pesticides. Journal of Pesticide Reform 9:3, pp5-9. 

Bibliography

Cressey, P. et al 2000: 1997/98 New Zealand Total Diet Survey. Part 1: Pesticide Residues. Ministry of Health.

National Office of Food Safety/ National Office of Animal & Plant Health 1999: Report on the Australian National Residue Survey: 1998 Results. Department of Agriculture, Fisheries and Forestry Australia.

FDA 1993: Food and Drug Administration: Pesticide Program: Residue Monitoring 1992. Journal of AOAC International 76.

MAF 1992: Pesticide Residues in NZ Food 1990-1991. Department of Health.

Vannort, R.W. et al 1995: 1990/1991 New Zealand Total Diet Survey: Part 1: Pesticide Residues. Ministry of Health.