"Organic" fanatics get a black eye

The great Satan against which "organic" farmers fight is PESTICIDES. And they never cease their criticism of conventional farming on the grounds that the products of conventional farming have dangerous quantities of pesticides in them.

A major organic advocacy organization is the Environmental Working Group (EWG), who regularly demonize common foods, claiming that consumption of them is "dirty".

A couple of food scientists (C. K. Winter and J. M. Katz) have however just taken EWG on and tested their claims. I reproduce below an excerpt from their recent report in the Journal of Toxicology. The report and the findings are crystal clear.

Probabilistic techniques were used to characterize dietary exposure of consumers to pesticides found in twelve commodities implicated as having the greatest potential for pesticide residue contamination by a United States-based environmental advocacy group. Estimates of exposures were derived for the ten most frequently detected pesticide residues on each of the twelve commodities based upon residue findings from the United States Department of Agriculture's Pesticide Data Program.

All pesticide exposure estimates were well below established chronic reference doses (RfDs). Only one of the 120 exposure estimates exceeded 1% of the RfD (methamidophos on bell peppers at 2% of the RfD), and only seven exposure estimates (5.8 percent) exceeded 0.1% of the RfD. Three quarters of the pesticide/commodity combinations demonstrated exposure estimates below 0.01% of the RfD (corresponding to exposures one million times below chronic No Observable Adverse Effect Levels from animal toxicology studies), and 40.8% had exposure estimates below 0.001% of the RfD.

It is concluded that (1) exposures to the most commonly detected pesticides on the twelve commodities pose negligible risks to consumers, (2) substitution of organic forms of the twelve commodities for conventional forms does not result in any appreciable reduction of consumer risks, and (3) the methodology used by the environmental advocacy group to rank commodities with respect to pesticide risks lacks scientific credibility.

1. Introduction

Since 1995, the Environmental Working Group (EWG), a United States-based environmental advocacy organization, has developed an annual list of fruits and vegetables, frequently referred to as the “Dirty Dozen,” suspected of having the greatest potential for contamination with residues of pesticides. The EWG cautions consumers to avoid conventional forms of these fruits and vegetables and recommends that consumers purchase organic forms of these commodities to reduce their exposure to pesticide residues.

The annual release of the report has traditionally generated newspaper, magazine, radio, and television coverage, and the report is considered to be quite influential in the produce purchasing decisions of millions of Americans.

In June 2010, the EWG released its most recent “Dirty Dozen” list [1]. Topping the list as the most contaminated commodity was celery, followed by peaches, strawberries, apples, blueberries, nectarines, bell peppers, spinach, cherries, kale, potatoes, and grapes (imported). According to an EWG news release, “consumers can lower their pesticide consumption by nearly four-fifths by avoiding conventionally grown varieties of the 12 most contaminated fruits and vegetables” [2].

It is unclear how the EWG could make such a statement since the methodology used to rank the various fruits and vegetables did not specifically quantify consumer exposure to pesticide residues in such foods. Instead, the methodology provided six separate indicators of contamination, including (1) percentage of samples tested with detectable residues, (2) percentage of samples with two or more pesticides detected, (3) average number of pesticides found on a single sample, (4) average amount of all pesticides found, (5) maximum number of pesticides found on a single sample, and (6) total number of pesticides found on the commodity [1]. Each of these indicators was normalized among the 49 most frequently consumed fruits and vegetables, and a total score was developed to form the basis for the rankings.

Since none of these indicators specifically considered exposure (the product of food consumption and residue levels), it is difficult to see how the EWG could substantiate the claim that consumers could lower their pesticide consumption by nearly four-fifths by avoiding conventional forms of the “Dirty Dozen” commodities.

Additionally, the toxicological significance of consumer exposure to pesticides in the diet is also not addressed through an appropriate comparison of exposure estimates with toxicological endpoints such as the reference dose (RfD) or the acceptable daily intake (ADI).

To more accurately assess the potential health impacts from consumer exposure to pesticide residues from the “Dirty Dozen” commodities, this study utilized a probabilistic modeling approach to estimate exposures. The exposure estimates were then compared with toxicological endpoints to determine the health significance of such exposures.

2. Materials and Methods

The EWG rankings were derived from the results of residue findings of the United States Department of Agriculture (USDA) Pesticide Data Program (PDP) and the United States Food and Drug Administration (FDA) Pesticide Program Residue Monitoring from 2000 to 2008 [1, 3, 4]. The PDP is more appropriate for risk assessment as it is not developed for enforcement, provides residue findings for produce in ready-to-eat forms (i.e., washed or peeled), includes many more samples than the FDA program, and relies upon more sensitive analytical methods. As a result, our study relied entirely upon results from the most recent PDP data collected from 2004 to 2008.

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