The Dirty Dozen is a low blow to growers, we agree. But is the science behind it suspect? Here is a scientific perspective on the Environmental Working Group’s Dirty Dozen methodology.
The report, found in the Journal of Toxicology, is called “Research Article Dietary Exposure to Pesticide Residues from Commodities Alleged to Contain the Highest Contamination Levels” and was authored by Carl K. Winter and Josh M. Katz.
The report looked at the 2010 EWG rankings. From the research article:
In June 2010, the EWG released its most recent “Dirty Dozen” list . 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.”
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. 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).