This article was first published in .
It is spring and that means a flood of questions come my way about pesticide residue on produce. That’s because it is at this time of the year the Environmental Working Group (EWG), a non-profit consumer advocacy organization in Washington, D.C., annually freaks out the public with a press release that unveils the fruits and vegetables with the highest levels of pesticide residues.
The “Dirty Dozen” is the name EWG has coined for its targets, pilfered from the 1967 movie by that title. This year, the ignominious pack is led by the strawberry, with spinach nipping at its heel. EWG does an excellent job garnering publicity for its Dirty Dozen, implying anyone concerned about health should choose organic versions of the condemned fruits and veggies. EWG presents itself as a knight in shining armour, a sentinel ready to slay all those dangerous products spewed out by companies that put profits ahead of safety.
The first thing I noted when I checked the list of the Dirty Dozen is the total absence of numbers. Curious, considering numbers are the currency when it comes to discussing toxicity. Actually, the absence of data was the second thing I noted. The first item that appeared when I Googled EWG’s list was a request for a donation so that these guardians of public health can continue to carry out their stated mission of “empowering consumers with breakthrough research to make informed choices and live a healthy life in a healthy environment.” However, sometimes those “informed choices” may be misinformed. Also, EWG’s claim of “breakthrough research” is a bit of a stretch. To arrive at the Dirty Dozen, they used information gleaned from the U.S Department of Agriculture’s annual testing of a random selection of fruits and vegetables for pesticide residues.
It is important to have a look at how pesticides are regulated. And they are, thoroughly. In Canada, the task falls to the Pesticide Management Regulatory Agency (PMRA), while in the U.S., responsibility lies with the Department of Agriculture (USDA) and the Food and Drug Administration (FDA). These bodies evaluate laboratory data, animal studies and potential human exposure to determine a risk/benefit ratio for each pesticide. A substance is allowed if its benefits are found to outweigh risks, but that does not mean free rein of use. How and when a chemical can be applied is carefully regulated, as are tolerable residues. A great deal of attention is paid to safety since pesticides are inherently toxic. After all, they are designed to kill insects, fungi and weeds.
Residue tolerance levels, also referred to as “maximum residue limits” (MRL), are determined by evaluating animal studies, chemical properties such as estrogenic effects, occupational exposure, and non-occupational exposure through diet and drinking water. It is common to determine a “no observed adverse effect level” NOAEL, which is the maximum amount that produces no effect in an animal. This is then divided by a safety factor of 100 to establish an MRL. Of course, no regulatory system is perfect, since so-called “cocktail effects” that may result from various combinations of chemicals, or subtle effects that may turn up after decades of exposure, are virtually impossible to predict.
So, how do tolerance levels stack up? Studies of produce randomly purchased both in North America and Europe consistently show only two to three per cent exceed the MRL (remember this has a 100-fold safety factor built-in) and roughly half have no detectable residue at all. But even within tolerance levels, produce can harbour more or less residue, which is the basis for EWG’s Dirty Dozen. Without any numbers, without any specification about whether produce in the Dirty Dozen exceeds maximum residue levels, the list is meaningless and creates unnecessary fear about eating fruits and vegetables.
This is not a trivial concern, since evidence linking fruit and vegetable consumption to health is overwhelming. Anyone who steers away from eating foods that appear on the Dirty Dozen list is doing themselves a disservice. As far as nutritional differences between organic and conventional produce go, studies can be dredged up to favour either one. In any case, whatever difference there may be is too small to have an effect on the overall diet. Where organic may have an advantage is in its reduced effect on the environment. To give EWG some credit, they do urge people to eat more fruits and veggies be they conventional or organic, but their whole approach casts a shadow on conventionally grown produce.
It is interesting to note most of the residue detected are fungicides to control the growth of mould that can produce potentially dangerous mycotoxins such as the carcinogenic ochratoxin A. Some studies have found higher concentrations of mycotoxins in organic produce since it is not protected by fungicides.
EWG’s Dirty Dozen lists only conventionally grown produce and implies organic foods are grown without pesticides. Indeed, EWG urges consumers to eat organic when possible for that reason. But the message pesticides are not used in organic agriculture is misinformed. There are many pesticides allowed, with the stipulation they come from a natural source. Copper sulfate, lime sulfur, neem oil, pyrethrins from chrysanthemums and spinosyn from a soil bacterium can all be used in organic agriculture and can, like any other pesticide, leave a residue.
Keep in mind that whether a chemical is natural or synthetic has no bearing on its potential toxicity. The reason there is no need to be concerned about organic pesticides is they are regulated the same way as any other pesticide. As far as establishing safety, regulatory agencies make no distinction between conventional or organic pesticides. Both have to jump through the same hoops and over the same hurdles.
That being said, there is no doubt a greater variety of residue can be found on conventional produce since there are far more pesticides approved for conventional than for organic agriculture. However, it is not the number of different pesticide residue that matters, but whether they exceed maximum residue limits. And, unless EWG can show that to be the case, its Dirty Dozen list amounts to no more than a ploy to raise funds.
