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Pesticides

MagazineJuly 1995 (Vol. 6 Issue 4)Pesticides

Levels of pesticides found in our bodies are dangerously above those reckoned to be safe and could be responsible for many cancers and the epidemic of infertility

Levels of pesticides found in our bodies are dangerously above those reckoned to be safe and could be responsible for many cancers and the epidemic of infertility.

Lately, the British press has sounded warnings about the dangers of excessive pesticide levels in carrots and lettuce. But researcher Tuula Tuormaa, on behalf of Foresight, the Association of Preconceptual Care, has discovered that pesticide dangers lurk in everything we put on the table.

Nowadays, it's estimated that the industry worldwide is producing about 45-50,000 different pesticides based on about 600 active ingredients. In one year alone, 23,504 tonnes of active ingredients were sold by the UK pesticide manufacturers, which translates into 420g of chemicals for every man, woman and child in Britain.

During crop growth, pesticides are used as insecticides, herbicides and fungicides.

Most of what we eat is subject to multiple doses of the chemicals. Cereal crops such as wheat get doused an estimated five to eight times during growing season; with some vegetables and fruit crops, 10 to 15 sprays are the norm.

Then, after harvesting, most cereal, fruit and vegetable crops are dosed again with several pesticides to protect them from storage diseases. This particular treatment, dubbed the "bucket and shower" method, is a fairly crude affair: the pesticides, mixed with no freshly harvested produce, are poured into the storage container with food that has already been treated. So even though the actual harvest may have been relatively uncontaminated with pesticides, the casual way that it is treated in storage can add a considerable amount of pesticide residues in the food by the time it reaches your table.

Pesticides are also used during livestock production, either as preventive "animal medicines", such as sheep dips, warble-fly dressings and lice treatments, or as veterinary pesticides for controlling flies and other insects in the livestock houses.

But of course pesticides aren't simply used in food. Local authorities use a great variety of different pesticides in their parks, gardens, lawns, golf courses and other recreation. Besides railroad contractors, which spray thousands of kilos of pesticides, largely atrazine and simazine, into railways and their embankments, herbicides and chemicals such as sodium chlorate, dichlorobenzil and diquat are applied around canals and various waterways to remove excessive weeds.

Modern building practices use lindane as an active ingredient in their current wood-preservation treatments. Electric cables are doused with an insecticide called aldrin.

Different pesticides are also widely used at all stages of forest management. And of course, these days most home owners spread pesticides around their own domestic gardens.

Pesticides are also present in a vast number of different manufactured products, such as wallpaper pastes, wooden furniture, DIY products and natural-fibre textiles. New carpets are often treated with moth-proofing chemicals, including common insecticides such as pyrethrums and lindane. Pesticides even seem to be present in our bathroom cabinets and medicine chests; warfarin, widely used in the prevention of blood clots, originally was a rodenticide.

Organochlorides (OC), one of the earliest mass-produced pesticides, include DDT, lindane, dieldrin and aldrin. OCs are particularly harmful because they tend to collect in fatty tissue and don't readily break down. Because they are so tenacious, this group of pesticides are able to accumulate along the food chain from insects to birds, to fish, and finally to larger mammals, including humans (MAFF: Report of Working Party on Pesticide Residues, HMSO, 1989). Because of this cumulative danger, the use of OCs was eventually banned in 1971 in the United States. In the UK they were subject to a voluntary ban from 1974 to 1978, after which they were finally removed by law. Even though they are no longer used, since the 1980s, the levels of OCs in food have remained fairly static, mainly because OCs are still used in industry or used illegally in farming.

In 1979, a study which analyzed foods found high levels of dieldrin in some milk and potato, as well as lindane in some meat, milk and poultry; some samples exceeded the current EC recommended Maximum Residue Level (MRL) (WPRR Report of the Working Party on Pesticide Residues, London, 1988-89).

Furthermore, OC residues such as DDT have been found in the fat tissue of all people tested. In 1977 the average DDT contamination in men was 2.6ppm (parts per million) and in women 1.6 ppm both levels exceeding the current official EC MRL. In some men the DDT levels were found to exceed 15 times the EC legal limit; some women had levels 17 times over the limit (MAFF Working Party on Pesticides Residues (1977-81), HMSO, 1982). More worrying, traces of lindane and dieldrin were detected in a 1979/80 UK survey of human milk samples.

Even some infant foods have been found to be contaminated with pesticides. A 1987 Ministry of Agriculture, Fisheries and Food (MAFF) survey on 50 infant foods detected that 18 out of 31 samples of infant rusks contained pirimiphos methyl, and three samples of cow's milk contained dieldrin at levels exceeding the EC MRL. These findings are particularly alarming, because they show that exposure to pesticides can begin at the very beginning of your life, when you are most vulnerable to the effects of pesticides.

New evidence also suggests that organochloride pesticides, which seem to have mild estrogenic properties, can even bring on labour. Studies in Brazil and in India have shown that levels of DDT are significantly higher both in miscarried fetuses and in premature babies, compared with those born full-term (Acta Paediatrics Scand, 1981; 700:925-8).

You and I are exposed to excessive levels of pesticides because the levels in our food and water are poorly controlled. The 1985-1988 report of the MAFF Working Party on Pesticide Residues on animal products found that the most commonly detected pesticide residues in animal meat were pp'DDE, a metabolite of DDT, and gamma-HCH, a form of hexachlorocylocohexane. Because these residues were most commonly found in lamb, it's likely that they get into the food chain through the use of DDT and HCH in sheep dip. The same 1982-1986 survey on vegetables and fruit found that 37 out of 67 samples of potatoes analyzed contained residues of tecnazene in the excess of the EC recommended MRL. Tecnazene is widely used for the prevention of various storage diseases. In fact, pure bran, because it is positioned outside the grain, has been found to be contaminated with pesticides at levels that are three to four times higher than that of the whole grain. The same was found with apple and pear crops, of which approximately 80 per cent are held in long-term storage before distribution. A survey conducted by the Association of Public Analysts in 1983 found that one-third of all fruit and vegetables sampled were found to be contaminated with pesticide residues (The BMA Guide to Pesticides, Chemicals and Health, Edward Arnold, 1992).

A recent survey conducted on drinking water quality identified 298 water supplies in the UK that were contaminated with pesticides, with nearly a quarter exceeding the Maximum Admissible Concentration (MAC) of pesticide residues. Sixteen different active pesticide ingredients were detected.

Besides pesticides and other industrial pollutants, nitrates are also widely detected in drinking water supplies. This is due to ever increasing amounts of nitrogen based fertilizers being added to the soil. In the late 1930s, 60,000 tonnes of nitrogen fertilizers were spread on agricultural land in the UK each year. By 1985, this had increased 250 times to 1,580,000 tonnes (Town and Country Planning, 1987; 56:131-2). Because only about half of the fertilizers applied are taken up by the crop, the other half is lost into the atmosphere or leaches into surface or ground water reservoirs (Assoc Quarterly Rev, September 16-18, 1985). Presently, it's estimated that approximately one million people in the UK are exposed to nitrate levels in drinking water exceeding the present MAC level, which may quadruple by the turn of the century.

Considering how pervasive pesticides use is these days, what is this long-term exposure doing to you? The London Food Commission conducted a thorough toxicological survey on active ingredients currently permitted to be used by UK pesticide manufacturers. Almost 40 per cent of pesticides currently in use were linked with at least one adverse effect. Out of 426 chemicals listed, 68 were found to be carcinogenic, 61 capable of mutating genes, 35 to have various reproductive effects, ranging from impotence to a variety of birth defects, and 93 to cause skin irritations and similar milder complications. The most frequently used and troublesome pesticides are herbicides, especially the carboxyacid and phenylurea groups, as well as chlorinated solvents.

Numerous studies show a higher incidence of cancers and related disorders in individuals occupationally exposed to pesticides (J Cancer Inst, 1981; 66:461-4). These include cancers of the lung (J of Toxicology and Environ Health, 1981; 8:1027-40), kidney and testicular cancers (Scand J Work Environ and Health,1986; 12:630-1) leukemias and multiple types of tumours (Am J Epidem, 1971; 94:307-10) non-Hodgkin's lymphomas and malignant lymphomas (Lancet, 1981; ii: 579) soft-tissue sarcomas (Br J Cancer, 1979; 39:711-17) and brain tumours (J Occup Med, 1982; 26:906-8).

Beside occupational exposures, pesticides seem able to cause cancer if you are chronically exposed from babyhood (Natural Resources Defence Council, Intolerance Risk: Pesticides in our Children's Food, Washington, DC: NRDC, 1989).

Equally worrying are the effects of pesticides on your fertility. The London Food Commission has listed 35 different pesticides that have been linked with adverse reproductive effects in animal studies, including such widely used formulations as aldrin, benomyl, captan, carbaryl, diel-drin, dinoseb, ioxynil, lindane, maneb and paraquat (The London Food Commission, Food Adulteration and How to Beat it, Unwin Paperbacks, 1988).

A number of studies suggest that chronic exposure to pesticides can cause damage to the genetic material of your children. This problem became particularly noticeable when it was found that babies born to the US servicemen, who were exposed during the Vietnam war to a defoliant called Agent Orange (2,4,5-T, mixed with dieldrin), were found to have an extremely high overall rate of birth defects, including spina bifida and facial clefts. The partners of these men also suffered a high rate of miscarriages and stillbirths (Nature, 1983; 302:208-9).

Besides cleft lip and/or palate, babies suffered from hydrocenchepaly (Ann Esp Pediatr, 1979; 12:529-33), and various congenital long bone and limb defects (Community Health Studies, 1986; 10:1-11).

OCs can also have a toxic effect on the brain of your children. Chronic post-natal exposure to organophosphates has been linked with long-term, measurable changes in brain function (Neurotoxicology, 1980; 1: 667-89), aggression, memory difficulties, depression, emotional instability and schizophrenic reactions (Lancet, 1961; i:1371-4).

Organophosphates have also been shown to cause brain degeneration. This includes a number of the "sclerosing" diseases such as multiple sclerosis, muscular dystrophy, Wernick's encephalopathy and Guillan Barre-like syndromes (J Nutr Med, 1994; 4:43-82).

We also now know that chronic exposure to organophosphates is able to disrupt regulation of our immune systems (J Nutr Med, 1994; 4: 43-82). This may be one reason that chronic exposure has been linked to the development of allergies and other immuno-regulatory disorders, such as chronic fatigue syndrome and myalgic encephalomyelitis (ME) (Behan: Data presented at first international research conference on chronic fatigue syndrome, Albany, New York, 1992).

The N-nitroso group are considered to be among the most powerful chemical carinogens; they've been found to cause cancer in 39 animal species studied, including primates (Nutrition and Health, 1983; 2:1). High nitrite, derived from high nitrate, has been linked with the "blue baby" syndrome.

The use of nitrogen fertilizers also affects the nutritional value of crops. With the help of the fertilizers, farmers are able to grow an abundance of green foliage that is practically devoid of essential trace elements (Pfeiffer CC, Mental and Elemental Nutrients, Keats Publishing, Inc, New Canaan, Connecticut, 1975). Recent crop and soil investigations found particularly low levels of manganese, zinc and iron in the samples studied (Nutrition and Health, 1992; 8:1-16). Manganese deficiency has been linked with congenital malformations (Am J Clin Nutr, 1985; 41:1042-44), and zinc deficiency can lead to premature delivery and small-for-gestational-age babies (J Orthomolecular Med, 1994; 9:225-243).

Currently, scientists have sacrificed a great number of animals in the cause of attempting to figure out what constitutes a lethal dose of pesticides. However, these animal tests tell us virtually nothing. Unlike study animals, which are exposed to high levels over the short term, we are exposed intermittently to a great combination of pesticide residues for many years at very low doses. Furthermore, humans do not necessarily seem to respond to substances in the same way as animals do. For example, 2-Napthylamine has been found to be a bladder carcinogen in humans and dogs, but not in mice, rats, guinea pigs and rabbits (Matsumura F, Toxicology of Pesticides, New York, Plenum, 1975).

Despite what is supposed to be a scientific advance, pesticides may have only made the insect problem worse. At least 50 different species of weeds are resistant to herbs, while the number of insecticide resistant insects are also growing at an alarming rate (Phytoparasitica, 1988; 16: 364; Pesticides Science, 1989; 26: 333-58).

Furthermore, pesticides seem to be unnecessary. The US National Academy Sciences monitored 14 successful organic farms over five years. Some of the farms, which had not used agrochemicals for 15 years, had corn yields that were 32 per cent higher and soya bean yields that were 40 per cent higher than local farms using pesticides (Nat Acad Sci, Alternative Agriculture, Washington, DC: NAS, 1989). Another study found that cutting herbicides by 87 per cent did nothing to reduce yields of either wheat or barley (Farmers Weekly, April 6, 1990).

!ATuula Tuormaa


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