Last week, a meta-analysis from a highly credible, academic source (Stanford University, its medical school and nearby institutions), raised serious questions about the often-touted, nutritional advantage of organic food. They digested the contents of 237 peer reviewed articles comparing organic and conventional foods and diets. They concluded that "the published literature lacks strong evidence that organic foods are significantly more nutritious than conventional foods." This drew a great deal of attention and organic advocate defense. Because even though Stanford is affectionately known by alums such as me as "the farm," it is certainly no ag-school promoting the status quo. Instead, it enjoys a very strong reputation for research excellence. It isn't easy to dismiss these findings.
What I found disappointing about the Stanford study was the weakness of its analysis of differences in pesticide residues. First of all, of the 9 papers it analyzed on this topic, only one was based on US crops. Seven were about European food and one was from Australia. The single US study used data from the 1990s. Since that time there have been significant declines in the usage of older, more toxic pesticides.
The Stanford-associated authors drew the cautious conclusion that "consumption of organic foods may reduce exposures to pesticide residues...", but they didn't do anything to put that statement in perspective. In fact, their analysis was only a comparison of the number of pesticide detections with no consideration of which pesticides were detected at at what levels. Without that information, one can easily be counting, as equivalent, chemical residues that could differ by a factor of a hundred thousand or million in terms of relative risk. The Stanford group may have been limited by doing meta-analysis instead of original research, but in any case this sort of "detection counting" is the same egregiously misleading "analysis" that is committed each year by the Environmental Working Group in compiling their "Dirty Dozen List."
How Would You Best Answer Questions About Pesticide Residue Safety
The truth is that at least for the US, there is a perfectly good way to answer the question, "Should we be concerned at all about pesticide residues on our conventional food?" There is a publically available, fully transparent, downloadable data-set that provides exactly the information needed to get those answers. Each year, a group in the US Department of Agriculture (USDA-AMS) conducts a huge effort called "The Pesticide Detection Program." (PDP). They collect thousands of samples of food commodities from commercial channels throughout the year, and then take them back to the lab and analyze each for hundreds of different pesticide residues. It is effectively a "report card" on the entire food production system about how well it protects consumers from undesirable pesticide exposure.
I've been working for a while to do a rigorous analysis of the latest available PDP data from 2010. It has been a daunting task, because it is a nearly 2 million row, 85MB document. It contains a great deal of useful information in a form not easily accessed or understood by the public. However; once this is data iscrunched; it is easy to see why the USDA, EPA, FDA conclude that consumers have no need to worry about the safety of their food supply from a pesticide residue point of view.
What Does The Residue Testing Say?
The Stanford study cited a 30% reduction pesticide residue detections which is essentially meaningless in the context of the miniscule risk associated. Unfortunately, many consumers have been convinced that there is a risk where there isn't one. They have gotten this from misleading promotion of organic as "pesticide-free" when it isn't, and by the scaremongering of groups like the EWG. The net effect of consumer concern about pesticide residues, driven by distorted messaging, may be a reduction in fresh fruit and vegetables consumption (see graph below). After some modest increases in fruit and vegetable per capita consumption in the 80s and 90s, those trends have ceased or even been reversed. How much of that is related to disinformation about the risks associated with pesticide residues? A study by the Hartman group found that some consumers said they reduced their produce purchases specifically because of the "dirty dozen list." The question needs more research.