Good Chemistry: The Dirty Dozen is well-titled, but like a list of pesticide residues

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Spring is here and that means a flood of questions about pesticide residues on produce. That's because this time of year, the Environmental Working Group (EWG), a Washington, D.C.-based consumer advocacy nonprofit, surprises the public with its annual press release revealing the top fruits and vegetables. pesticide residues.

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The “Dirty Dozen” is a name coined by the EWG for its own purposes, taken from the 1967 film of that title. This year, the disgraced group is led by a strawberry with a spinach bite at its heels. EWG does promotional work for the Dirty Dozen, which suggests that anyone concerned about their health should choose organic versions of condemned fruits and vegetables. EWG presents itself as a knight in shining armor, a watchdog ready to destroy all dangerous products produced by companies that put profit before safety.

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The first thing I noticed when I checked the Dirty Dozen list was the complete absence of numbers. Interestingly, considering the numbers is the currency when discussing toxicity. Actually, the lack of data was the second thing I mentioned. The first item that came up when I googled the EWG list was a request for donations so that these public health advocates can continue their mission of “empowering consumers with breakthrough research to make informed choices and lead healthier lives.” environment.” However, sometimes these “informed choices” can be misinformed. Also, EWG's claim of “breakthrough research” is a bit of a stretch. To come up with the Dirty Ten, they used information from the US Department of Agriculture's annual testing of a random selection of fruits and vegetables for pesticide residues.

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It is important to consider how pesticides are regulated. And they are careful. In Canada, the responsibility rests with the Pesticide Management Regulatory Agency (PMRA), while in the US, the responsibility rests with the Department of Agriculture (USDA) and the Food and Drug Administration (FDA). These agencies evaluate laboratory data, animal studies, and potential human exposure to determine the risk/benefit ratio for each pesticide. A substance is permitted if its benefits outweigh the risks, but this does not mean freedom of use. How and when chemicals can be used is carefully regulated, as is persistent waste. Because pesticides are naturally toxic, much attention is paid to safety. After all, they are designed to kill insects, fungi and weeds.

Residue tolerance levels, also known as “Maximum Residue Limits” (MRLs), are determined by evaluating chemical properties such as animal studies, estrogenic effects, occupational exposure, and non-occupational exposure through diet and drinking water. It is customary to define a “no observed adverse effect level” as the NOAEL, which is the highest level at which an animal will not be affected. This is then divided by a safety factor of 100 to establish the MRL. Of course, no regulatory system is perfect, as it is virtually impossible to predict the “cocktail effects” that may result from different combinations of chemicals, or the subtle effects that may emerge after decades of exposure.

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So how do endurance levels stack up? Studies of randomly purchased products in both North America and Europe consistently show that only two to three percent are above the MRL (remember it's set at a 100-fold safety factor), and about half have no detectable residue at all. But even at tolerance levels, a product can contain more or less residue, which is the basis for EWG's Dirty Dozen. Without any numbers, without any specification of whether Dirty Dezen products exceed the maximum residue level, the list is meaningless and creates unnecessary fear about eating fruits and vegetables.

This is not a big deal because there is so much evidence linking fruit and vegetable consumption to health. Anyone who refuses to eat foods that appear on the Dirty Ten list is doing themselves a disservice. When it comes to nutritional differences between organic and conventional produce, research can be done to favor one of them. In any case, whatever the difference is, it is too small to affect the overall diet. The advantage of organic matter is to reduce its impact on the environment. To give the EWG some credit, they do encourage people to eat more conventional or organic fruits and vegetables, but their entire approach casts a shadow over conventionally grown produce.

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It is interesting to note that most of the residues detected are fungicides that control mold growth, which can produce potentially dangerous mycotoxins such as carcinogenic ochratoxin A. Some studies have found higher concentrations of mycotoxins in organic produce because they are not protected by fungicides.

EWG's Dirty Dozen lists only conventionally grown produce and means that organic foods are grown without pesticides. Indeed, the EWG encourages consumers to eat organic whenever possible for this reason. But the message that pesticides are not used in organic farming is not true. Many pesticides are approved and are obtained from natural sources. Copper sulfate, lime sulfur, neem oil, pyrethrins from chrysanthemums, and spinosyn from a soil bacterium can be used in organic agriculture and leave residues like any other pesticide.

Remember that whether a chemical is natural or synthetic has nothing to do with its potential toxicity. You don't have to worry about organic pesticides because they are regulated like any other pesticide. When it comes to establishing safety, regulatory authorities make no distinction between conventional or organic pesticides. Both must jump through the same hoop and hurdles.

It is important to note that there is no doubt that more residues can be found in conventional produce, as there are far more conventionally approved pesticides than in organic farming. However, it is not the quantity of different pesticide residues that is important, but whether they exceed the maximum residue limit. And, if the EWG can't demonstrate this, its Dirty Dozen list is nothing more than a fundraising ploy.

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Joe Schwartz is director of the Office of Science and Society at McGill University (mcgill.ca/oss). He hosts “The Dr. Joe Show” every Sunday from 3:00 PM to 4:00 PM on CJAD Radio on 800 AM.

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