The U.S. Dept. of Agriculture’s new MyPlate initiative recommends that consumers “make half your plate fruits and vegetables.” This practical and simple message, if followed, should result in significant health benefits for consumers. Unfortunately, unfounded yet highly publicized warnings for consumers to avoid conventionally produced fruits and vegetables due to the presence of pesticide residues may serve to undermine the MyPlate message while increasing consumer fear and guilt.
On the same day that White House Chef Sam Kass discussed the MyPlate program at a press conference during the 2011 IFT Annual Meeting in New Orleans, the Environmental Working Group (EWG), a Washington D.C.-based environmental advocacy organization, released its annual “Shoppers Guide to Pesticides in Produce.” This guide contained the notorious “Dirty Dozen” list of fruits and vegetables showing the highest “loads” of pesticide residues and urged consumers to purchase more expensive organic forms of such commodities rather than eat these foods in their conventional forms. Although EWG has been releasing a similar Dirty Dozen list annually since 1995, media coverage of this latest list was widespread and uncritically delivered EWG’s recommendations to millions of Americans.
EWG implies that pesticide residues in foods present health risks to consumers and that their rankings of the Dirty Dozen commodities are based upon a scientifically rigorous and meaningful methodology that identifies the fruits and vegetables of greatest health concern. If true, the EWG shoppers guide would be of value to consumers. Sadly, EWG misses the mark on both counts.
From a toxicological perspective, the key components of consumer risk from pesticides in foods are the toxicity of the pesticides, the levels of the pesticides found in the foods, and the amount of the foods that are consumed. The EWG methodology, however, focuses specifically upon the presence of pesticide residues detected on foods rather than amounts of individual pesticides and completely ignores food consumption and pesticide toxicity.
Just how risky are pesticide residues on the Dirty Dozen fruits and vegetables? Work I recently published with graduate student Josh Katz in the peer-reviewed Journal of toxicology sheds some light on this question (http://www.hindawi.com/journals/jt/2011/589674/).
In our study, we identified the 10 most frequently detected pesticides on each of the 2011 Dirty Dozen fruits and vegetables based upon results of the USDA’s Pesticide Data Program. (The EWG used the same pesticide residue database to generate its rankings.) Rather than focusing upon just pesticide detection rates, we performed probabilistic exposure assessments where the actual levels of pesticides detected were combined with food consumption estimates. This allowed us to develop estimates of actual consumer exposure to the pesticides and to compare such exposures with toxicological indicators of safety in the form of the Reference Doses (RfDs) for each of the pesticides. The RfDs are established by the U.S. Environmental Protection Agency and represent levels not considered to pose any health concern for consumers.
What did our study find? As expected, consumer exposure to the pesticides most frequently detected on the Dirty Dozen produce was extremely low and well below the RfDs in all cases. In 75% of the pesticide/commodity combinations, exposure estimates were below 0.01% of the RfD, representing exposures at least one million times lower than doses that do not show any toxicological effects in lab animals when exposed throughout their lifetimes.
Here’s how the EWG’s Shopper’s Guide webpage (http://www.ewg.org/foodnews/) summarizes the three “riskiest” foods on the 2011 Dirty Dozen list:
• Apples. Eaten daily by children, 98% of conventional apples had pesticides.
• Celery. Highly contaminated, celery tested positive for 57 different pesticides.
• Strawberries. A delicious snack for kids and pests, some strawberries had as many as 13 different pesticides.
Substituting our findings for the EWG summaries paints a more reassuring picture:
• Apples. Consumer exposure to the 10 most frequently detected pesticides on apples was between 20,000 and 30,000,000 times lower than doses that don’t affect lab animals in long-term studies.
• Celery. Consumer exposure to the 10 most frequently detected pesticides on celery was between 60,000 and 100,000,000 times lower than doses that don’t affect lab animals in long-term studies.
• Strawberries. Consumer exposure to the 10 most frequently detected pesticides on strawberries was between 800,000 and 6,000,000 times lower than doses that don’t affect lab animals in long-term studies.
The MyPlate message to “make half of your plate fruits and vegetables” is sound dietary advice, regardless of whether the produce is grown organically or conventionally. Solid science casts serious doubts on the validity of the Dirty Dozen rankings. Consumers choosing conventionally grown fruits and vegetables should be able to do without fear or guilt.
Carl K. Winter, Ph.D., an IFT Fellow, and an Extension Food Toxicologist, Dept. of Food Science and Technology, University of California, Davis, CA ([email protected]).