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Pesticides And Food – Conference At The Royal Medical Society Reveals Some Uncomfortable Truths

Pesticides And Food

Conference At The Royal Medical Society Reveals Some Uncomfortable Truths


We know that direct exposure to pesticides is harmful, the warning is on the label – a pesticide is a poison, it’s used to kill ‘things’. But what about low dose pesticide exposure from the food we eat? That’s the question scientists addressed at the conference.

More farmland is being treated with pesticides than ever before, says Professor Carlo Leifert from the Australian Southern Cross University. Some pesticides like DDT have been banned in a lot of countries, a lot of pesticides are used in smaller doses because their toxicity is higher, but from seeding to harvest, crops get treated multiple times. The use of the world’s most widely used pesticide, glyphosate, has increased 250 times over the last 20 years, not just the US use huge amounts, Europe does too, often right before harvest. Unsurprisingly glyphosate residue is found in 60% of the bread sold in the UK, in the urine of 75% of Germans tested, and in 45% of all top soil.

But are these residual levels harmful to humans? That’s a very hard question to answer, says Leifert because it is everywhere. In order to test the effect of any substance scientists need a control group that is not exposed to the substance in question. Because glyphosate is so widely used it is virtually impossible to find people who are not exposed to it. Scientists have compared people who eat organic produce with those who have consumed conventionally produced food. But people who eat organic food usually lead a healthier life style, too, they exercise more and are less often overweight. To compensate for such a bias, studies would have to run over a long period (i.e. several years) and a lot of people (i.e. thousands or more) would have to take part. That’s difficult to achieve, says Carlo Leifert, and it is expensive.

What we do know, though, is that many pesticides act as endocrine disrupters: they can mimic, block or in other ways affect the hormones in our body. We also know that even minute quantities – parts per billion – can have a sizable effect. And what’s worse: like most chemical products (like household cleaners) commercially available pesticides don’t contain just one ingredient but different chemicals. The combined toxicity of these chemicals often is a lot higher than the effect of each individual chemical. Take glyphosate, the active ingredient in the weed killer Roundup. The Conference heard that there are only a few animal studies that suggest glyphosate on its own causes cancer, and the verdict whether it is an endocrine disruptor is still out. However, the commercially available products used by farmers and gardeners are a combination of glyphosate with a number of other chemicals. These adjuvants can make the ‘active ingredient’ more effective, for example by removing the protective layer on leaves so that glyphosate can penetrate the plant’s cells or they make the pesticide easier to spray. According to IARC, the cancer research agency which is part of the WHO this pesticide cocktail is in all probability carcinogenic.

Dr Michael Antoniou from King’s College in London reported on at least one proven impact Roundup has on health: exposure to environmentally relevant amounts causes non-fatty liver syndrome in rats.

Almost every speaker at the conference emphasised that the combined effect of chemicals is insufficiently studied. One reason for that is the regulatory process. Take glyphosate: In December the license for glyphosate in the EU runs out. So why were politicians fighting for months over whether a new one should be issued for 10 years, 5 years or not at all? EFSA (the European Food Safety Authority) only assesses the safety of active ingredients – e.g. glyphosate – it does not look at the commercially available product, explained Dave Bench, director for Brexit and chemicals at HSE (Health and Safety Executive). Professor Leifert drew a simple conclusion: ‘The regulatory process is failing us’.

The final speaker was Peter Melchett from the Soil Association and he summed things up: today most crops are sprayed multiple times, wheat for example on average has 12 times the number of active ingredients applied today than 40 years ago, onions and leeks 18 times. Some toxic chemicals accumulate in the environment and in people; very low doses build up over time. And adjuvants, those chemicals that are part of all commercially available pesticides, can be extremely toxic. Peter Melchett called for pesticides to be tested as rigorously as pharmaceuticals before they are released for use, including in long term impact studies. So is low dose pesticide exposure harmful? The evidence is mounting, and there are an awful lot of factors we are not (yet) looking at.

PS: Exactly one week after the London conference on food and pesticides the EU voted to license glyphosate for another five years. Nine countries voted against the renewal, one abstained.