SCIENCE / Live dangerously, eat your greens: Pesticides cut prices, create more choice and give food a longer shelf-life - but at what cost to our health? David Nicholson-Lord on an inexact science shrouded in secrecy

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SUPPOSE you invented a chemical toxin and administered it in small doses over a lifetime to millions of people in their food and drink. These people were not asked for their consent. If they sought information, they were refused it. If they expressed doubts, they were told not to worry. A large bureaucracy was created to deliver these reassurances and a special form of words devised. 'There is no evidence,' it ran, 'that exposure at such levels poses a risk to human health.' But behind the words and the men in suits and white coats, there lurked a dreadful possibility: nobody was really sure.

The Government will next month release the annual report of the Working Party on Pesticide Residues. This will state that there are chemical residues in food - in 37 per cent of the bread, milk and potatoes sampled; in 30 per cent of the cereals; in 29 per cent of the fruit and vegetables (1991 figures) - but that we should not be concerned. The amounts are tiny - say one part in 10 million or 100 million for bread. The important figure - for the working party at least - is the so-called maximum residue level (MRL). Typically, 1 or 2 per cent of foods sampled exceed their MRLs.

You might find that figure reassuring. For instance, three of the 256 potatoes sampled in 1991 exceeded their MRLs for tecnazene, a chemical used to stop potatoes sprouting when they are stored after harvest. The average Briton eats about 235 pounds of potatoes a year. If the results of sampling by the Ministry of Agriculture Fisheries and Food (Maff) were extrapolated to all potatoes eaten in Britain, this would mean each of us was consuming roughly three pounds of potatoes containing 'unsafe' levels of tecnazene.

Or not, as the case may be. For MRLs are not safety limits. Maff accords MRLs a high profile. For some pesticides, MRLs represent a legal limit. Yet exceeding the MRL, according to Maff, does not imply a health hazard. In that case, argue critics, why have them?

MRLs are linked to acceptable daily intakes (ADIs) and 'good agricultural practice' and determined by judgements based on the toxicity of the pesticide and its likely consumption by humans. The judgements are made by committees, much of whose work is confidential: data on 90 per cent of pesticides is secret, according to the Campaign for Freedom of Information. The lack of consumer representatives on either the Advisory Committee on Pesticides (ACP) or the Maff working party has also provoked criticisms. On the working party, representatives of Maff - a department dominated, according to critics, by business and farming interests - hold sway. Hence the suspicion at some of the results produced.

A study in the late 1980s, for example, showed 37 out of 67 samples of potatoes contained tecnazene above the MRL. By 1990 this had decreased dramatically: 130 samples were analysed and in none did tecnazene breach its MRL. Heartening progress, one might think. In fact, Maff had simply moved the goalposts. By 1990 the MRL had been raised, from one to five milligrams per kilogram. Similarly with carrots: after finding residues of triazo-phos - an insecticide which is a chemical descendant of nerve gas - at 10 times the MRL, Maff raised the MRL by a factor of 20.

Tecnazene is not classed as a particularly dangerous chemical. It is irritating to eyes and lungs and harmful to fish. The World Health Organisation says it is 'unlikely to present acute hazard under normal use' but wants more studies on possible cancer-causing properties. The ACP is to examine new data on its carcinogenicity. It is one of up to 660 pesticides under review by Maff. Forty-three pesticides have been investigated in the past seven years, 23 are currently under investigation. About 250 are older pesticides approved on the basis of data now regarded as inadequate. The review is expected to take 10 years. In the meantime, pesticide-free eating may be impossible.

The first modern pesticide was probably Paris Green, an insecticide for potatoes developed in the 1860s. Twenty years later came Bordeaux Mixture, treating mildew. In the 1930s the organophosphates - used in nerve gases and sheep dips - arrived. Then, in 1939, came the discovery of the 'wonder chemical', DDT, the first organochlorine pesticide.

Consumers in northern Europe probably ingest more than 40 different pesticide residues in food and drink each day, according to Greenpeace. In 1990 almost 25,000 tonnes of pesticide was used in the UK - about a pound per person. In the past three decades pesticide sales worldwide have increased 31 times. Dr Peter Stanley, chairman of the Maff working party, has acknowledged that 'there is no such thing as pesticide-free food in Britain'.

Does this matter given the microscopic amounts involved and the benefits conferred? According to industry, consumers benefit through lower prices, longer shelf-life, more blemish-free food, wider choice. In the developing world, meanwhile, food production has been increased enormously. A leading American toxicologist, Bruce Ames, has produced calculations that suggest a person can consume 1.5 grams of natural toxins a day through foods such as coffee, tomatoes, wheat, rice and potatoes - about 10,000 times the average amount of pesticide residues consumed. Only 52 of these natural toxins have been tested - on animals - and half were carcinogenic. Diet, heredity and lifestyle - smoking, for instance - probably have more effect on health than pesticide residues. Indeed, if people stopped eating fruit and vegetables because of pesticide scares, death rates might increase because of worsening diets.

But pesticides are artificial - our bodies have not had thousands of years to adapt (possibly) to them. They are additions to our diet - perhaps unnecessary ones. They are involuntary - we consume them whether we like it or not. And when they are eaten, cooked, combined with each other or dispersed into earth, air and water, their toxicity can increase unpredictably. America's Environmental Protection Agency has classed 66 pesticides as suspected of causing cancer. According to the US National Academy of Sciences, this might mean up to 5,800 cases of cancer for every million people eating residues for a lifetime.

The environmental lobby questions the benefits of pesticides. According to the International Food Policy Research Institute in Washington, every dollar spent on pesticides causes dollars 5-dollars 10 dollars' worth of damage in poisonings, accidents, contamination and pollution. One of Maff's research projects has concluded that using less pesticide could improve farmers' profits; another Maff study found one fungicide used on wheat crops reduced yields. There are also diminishing returns: the number of insect species estimated to have developed resistance to pesticides has risen from 12 in 1946 to 829 by 1980.

What is not in dispute is their ubiquity. In 1962 Rachel Carson's classic, Silent Spring, detailed the damage wrought by pesticides on wildlife. Nine of the 23 pesticides she identified as hazardous are still permitted in the UK. Pesticides have penetrated every corner of the planet, turning up in underground wells, Arctic snows, the body tissue of whales, penguins and polar bears, falling in rain, pumped out to sea by rivers - the Rhine dumps more than 80 tonnes in the North Sea every year - or hanging suspended in 'toxic fogs'. Long-life chemicals such as DDT turn up in human body tissue and breast milk. According to Christopher Robbins, author of Poisoned Harvest and a founder member of the Centre for Agricultural Strategy at Reading University, if the bodies of American consumers were sold as meat in the EC, they would be declared unfit for consumption because of DDT contamination.

Most pesticide development has been concentrated in a tiny slice of human history - the past 50 years. In effect, we have been part of a vast unplanned experiment into the capacity of the biosphere and its inhabitants to withstand attack by chemicals designed to destroy living tissue and injure reproductive and nervous systems. There is speculation that the rise in cancer rates, the halving of male fertility since 1940 and the growth in allergy-related diseases are linked to chemical attack. Low-level pesticide exposure can produce symptoms similar to colds or stomach upsets - hence the under- reporting of poisoning incidents. And however small the amounts, American legislation is based on the premise that there is no 'safe' level of exposure to cancer-causing agents.

The arguments about pesticide use will probably not be resolved for a long time. The scope for paranoia and food fetishism is correspondingly immense. In the UK the 'Food Scare' has become a well-established ritual of public life. Fortunately, there is a growing consensus in favour of pesticide reduction policies and more efficient and less chemically intensive methods, such as integrated pest management or IPM - once satirised by farmers as 'I Pay More'. Since the food scares of the late 1980s, Maff has doubled the number of scientists working on pesticide safety to 100, and increased research spending to pounds 20m a year.

Nevertheless, if an international league table of enlightenment were drawn up for pesticides, the UK would rank well below the leaders. Sweden claims to have cut pesticide usage by a third in the second half of the 1980s. In a series of well-publicised cases - including the weedkiller 2,4,5-T and the pesticide Alar, which is used to 'plump up' apples - the Government has been put in the embarrassing position of having to discount evidence which led to a ban in the US, refuse calls for a ban in the UK, and then see the product withdrawn by manufacturers and rejected by supermarkets. Many supermarket chains now insist on tecnazene-free potatoes.

Testing for the long-term health impact of pesticides is fraught with difficulty. According to the British Toxicology Society, there is 'no reliable method' to extrapolate data from laboratory animals to human beings. To this intrinsic problem, the UK adds its own culture of secrecy: the British Medical Association is among critics wanting to see approval procedures opened up and taken away from Maff. Calls for labelling on products to show which pesticides have been used - similar to those introduced for food additives - have been ignored. What is the consumer to do?

Choosing organic food is one option: the more organic food people eat, the faster the price will come down. By-passing the middlemen, through co-operative bulk-buying from local organic farmers, will help to cut costs. Shopping in supermarkets is another. Most have responded much faster to consumer worries than the Government and run their own extensive testing programmes. The top four, according to a survey by Robbins for his book, are Safeway, Sainsbury, Tesco and Waitrose. Marks & Spencer and the Co-op come next. Consumers, and stores, could also reduce their obsession with 'blemish-free' fruit and vegetables - often a sign of over-spraying.

Washing fruit and vegetables has little effect, peeling more so - but at a price. According to the National Academy of Sciences, the worst foods for residues are, in descending order, tomatoes, beef, potatoes, oranges, lettuces, apples, peaches, pork, wheat, soybeans, beans, carrots, chicken, corn and grapes. A survey by Which? found that 10-25 per cent of 'post-harvest' pesticides applied to the skin during storage had seeped into the flesh. Washing apples and potatoes left residues largely unaffected: many will not dissolve, others are inside the skin. Peeling removed about 85 per cent of apple residues and 75-90 per cent of those in potatoes, but it also removes up to a fifth of the product as well as important fibre and nutrients. Cooking, Which? pointed out, often increases residues.

If much of this seems unsatisfactory, then spare a thought for Paul Mueller, the Swiss chemist who discovered DDT and was awarded a Nobel prize for it in 1948. DDT, despite its success in controlling malaria, is now banned throughout much of the world because of its devastating effects on the environment. If we had known half a century ago what we now know about pesticides, Mueller might never have received his prize.

'Poisoned Harvest' by Christopher Robbins (Gollancz pounds 5.99); 'P is for Pesticides' by Tim Lang and Charles Clutterbuck (Ebury Press pounds 6.99).

(Photograph omitted)