Pesky Pesticide Tests

by Howard Fienberg
June 3, 2002

One of the main reasons some consumers choose "organic" produce over conventionally-grown produce is to avoid the pesticides used in conventional farming. A study published last month in the Food Additives and Contaminants Journal (Vol. 19, No. 5), seemed to provide evidence in support of that choice. "The report shows what we suspected all along: if you want to reduce your exposure to pesticides, eating organic is a very good way," said Ken Cook, president of the Environmental Working Group.


Early critics of the study seized upon an obvious methodological problem, which The New York Times (May 8) mentioned in passing: organic produce represented only a minuscule portion of the study's data. Of the 94,227 samples studied, only 1,291 were grown organically (about 1.3 percent of the total).


That is not specifically the researchers' fault. They examined three sets of data: the USDA's Pesticide Data Program; the California Department of Pesticide Regulation's Marketplace Surveillance Program; and private tests on four selected foods carried out by Consumers Union. The California and USDA programs tend to sample close to the market share for the different kinds of produce. So since organic produce has such a small market share, it is only a tiny part of their samples. With a three-way comparison as the stated goal, a better study might have included equal amounts of the three categories of produce. (Note: the Consumers Union data, while only a small part of the total data set, at least included a near equal number from each category).


This sample disparity is not enough of a problem to discredit the study. However, there was a much more important methodological shortfall, ignored by the Times but highlighted by the Associated Press (AP). The study tested only for specific "synthetic" pesticides, neglecting "the many special pesticides that are approved for organic crops" derived from botanical and mineral sources, like rotenone, sulfur or copper-based fungicides, and biological preparations like the microbial insecticide BT.


When it comes to organic farming, the label "natural" does not mean a lack of pesticides, but a lack of a particular kind of pesticide.


The researchers claim in their study that "there is no basis to conclude that residues of natural pesticides in any foods... pose risks remotely comparable to those represented by residues of conventional (synthetic) pesticides." It is true that the EPA and FDA do not consider most "natural" pesticides worthy of analysis -- partly because the agencies feel they do not pose enough risk, partly because of the minuscule market share of organic farming that uses them. And yet, the AP reported that, while "government inspectors do not test for them," natural pesticides are not harmless. One "natural pesticide used by organic farmers, pyrethum, may cause cancer, and another is linked to neurotoxic effects in rats." The researchers dismiss such claims by pointing out the greater evidence in favor of effects from synthetic pesticides.


Such an argument is pointless without the right data on exposure. Thanks to studies such as this, we have some necessary data for "synthetic" pesticide residue. But data on "natural" pesticide residue, presumably highly prevalent in organic farming, is not so easy to find. The researchers point out that, "Few or no confirmed methods are available for these residues; consequently, they are generally not tested for by programmes [sic] and laboratories that routinely monitor foods for pesticides." They argue in favor of more research in this area.


Though it was glossed over in the media coverage, consumers should take home one over-riding point about this study: organic produce is not necessarily pesticide free, as many organic promoters would prefer. The tested pesticides may not have turned up as frequently in organic produce, but they did turn up, and often in higher concentrations than in the conventional produce.


Does that sully the reputation of organic produce? Commenting on the study to the AP, Edward Goth, president of Consumers Union, said organic produce is still the best. "Less is better... Fewer residues and lower levels of residues are better than higher levels of residues and more residues." Unfortunately, that is not necessarily true. The concentrations of "synthetic" (and presumably organic) pesticides in produce, no matter which way it was farmed, pose no known threat to human health. Bruce Ames, the famed biochemist and cancer researcher with the University of California at Berkeley, regularly stresses that Americans "consume more carcinogens in one cup of coffee than we get from the pesticide residues on all the fruits and vegetables we eat in a year." Mother Nature laces most of our food with oodles of "natural" carcinogens more powerful than just about anything we could add.


As the AP struggled to explain, the study's findings "don't mean that any of the produce is unsafe."


So please, eat more fruits and vegetables. They're good for you, plain and simple. Just don't presume you're making yourself healthier when you eat organic rather than conventional ones.

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