Thursday, December 6, 2012
Pesticide Residues on Organic: What Do We Know?
Are there really less pesticide residues on organic crops? The answer might not be as simple as you think.
A few weeks ago it was announced that for the first time in the history of USDA-Organic, there will be mandatory pesticide residue testing starting in 2013. This was always a theoretical possibility, but a government audit of certifiers showed that it essentially never happened. Now it will, at least to some extent (something like 5% of operations)
I wrote to the contact person at USDA to ask this question:
"will this new testing program look for any residues of the pesticides that are allowed on organic crop and thus applied frequently?"
Why Ask This Question?
Most consumers believe (erroneously) that organic crops are not sprayed with any pesticides at all. That is not true, and the criterion for what can be sprayed on organic has nothing to do with relative risk - it is simply based on whether the pesticide is deemed "natural." Knowing what is actually sprayed on organic crops, I was particularly interested in the copper-based fungicides because they are rather toxic by modern standards, and about Bt, protein insecticides because it would be helpful to calm people freaked out about Bt-biotech crops to be able to compare the exposure to this ultra-safe material when they probably consume farm more that is sprayed on crops vs when it is expressed by the crop.
Unfortunately, I learned that this new testing program is only there to encourage compliance with the organic rules, not to document anything about relative residue levels. There will be no testing for organically approved pesticides. In fact there won't be any public data-base generated and the sampling will be at the discretion of certifiers - not random.
This leaves us with the same situation we have had for a long time. Organic advocates and marketers make regular claims about the advantage of organic with regard to pesticide residues, and yet there is no actual data to support that claim - at least not for the US.
But Didn't That Stanford Study Compare Residues?
Remember the recent "Stanford Meta-Study" comparing organic and conventional that stirred so much controversy? They found lots of studies about nutrient content, but in their extensive search of the scientific literature they were only able to find 9 studies that compared pesticide residues in organic and conventional. Only one of those was even from the US and it was from the mid 1990s. It was based on a testing program at USDA called the PDP (Pesticide Detection Program). While that group does an excellent job of monitoring pesticide residues on conventional crops, it has never looked for the pesticides most likely to be found as residues on organic - things like copper salts. So even that one study that the Stanford group cited for the US was not a meaningful piece of data for residue comparison. So much for the scientific literature as a source on this question.
Why Doesn't the PDP Test For Copper, Bt, Biologicals Etc?
I contacted the USDA scientists who run the PDP to ask why they don't test for things like Copper fungicides, Bts or other biologicals. The answer was quite practical. They use something called multi-residues methods (MRMs) with which it is possible to simultaneously test for 2-300 different synthetic pesticides in a single analysis run. However, because of solubility issues and detection technology differences, many organic-approved pesticides cannot be extracted or measured by the same protocol. To do the testing for these individual categories of pesticides would be far too expensive for the budget of that agency. The random sampling method of PDP is also not well suited to getting enough organic samples for comparison.
Can We Compare Residues? No.
So, here is where we stand on the question of pesticide residues on food. The conventional supply is rigorously tested for the main products they intentionally apply as well as for any off-label or environmentally persistent products left over from the bad old days. We get a data set every year which essentially says that there isn't anything to keep consumers from confidently buying that food. The organic food supply is going to be tested to some degree for the first time, but we won't see any real summary of that data nor will we be able to compare it to conventional. We also know that there won't be any data generated about the pesticide residues most likely to be present on organic.
Do We Know Anything About Pesticide Residues On Organic Crops?
There was a relatively small, but high quality pilot study conducted by the USDA as background for their new testing regime. The authors were careful to point out the multiple reasons that their data is not really comparable to PDP (limited number of crops, smaller sample size not collected in the same fashion, fewer chemical tests conducted...). What they did find was that there were definitely some synthetic pesticide residues detected on organic crops - mostly consistent with spray drift, accidental contact in packing houses, persistent environmental pollutants.... The levels they found were not problematic from a safety point of view, but that is just as true for the PDP testing of conventional crops. This pilot program was like the PDP in that it used MRMs and so it didn't test for the majority of organic pesticides. So, bottom line, we still have no real data about the most likely pesticide residues that occur on organic crops and we are unlikely to get any.
What Would Happen If We Could Get Information About Organic Residue Status?
If organic were subjected to the same level of random and comprehensive testing that is used for conventional, and if all its pesticides were included, it would almost certainly come out "dirty" by the absurd and irresponsible methodology employed by the Environmental Working Group to create its annual "dirty dozen list". They just count detections without regard to the nature of the chemical in question or its concentration or its EPA tolerance. If there ever were a comparable pesticide residue database for organic it would force a far more scientific discussion of which residues matter and which do not. My guess is that both conventional and organic would come out as just fine for consumers to eat, but the "organic advantage" would disappear when both types of food had to be compared using scientifically sound assessments.
Bottom line. Just eat your fruits and vegetables and whole grains.... enjoy them!
You are welcome to comment here, and/or to write me at firstname.lastname@example.org
Organic produce image from Pculter's Photostream