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Thursday, December 6, 2012

Pesticide Residues on Organic: What Do We Know?



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

Organic produce image from Pculter's Photostream


  1. Do you have any idea which of the organic ones are used in the EU/know where i could find this information?

    1. Lea,
      I don't know of a public database for the EU. I did find a residue testing program from IFOAM (the group that certifies organic for much of Europe and import sources)

      I doubt that they look for the organic pesticides because this is also just about compliance with the rules

  2. Great blog post. Thank you for shedding some light on the organic vs. non-organic sampling and testing issues.


  3. Timely post, what with Dr. Oz getting everyones' bloomers in a twist.

    My friend in Germany sent me these two links just yesterday:

  4. An "official" I know in Maine sent me this information earlier this year. These are quotations from emails:

    "Just for fun I downloaded the 2010 USDA PDP database and checked out the organic food samples. The most interesting thing I found was that 52% (16 of 31 samples) of the Organic Baby Food Pear samples were positive for Spinosad B. Most of the residues (14 samples) were just at the detection limit of 0.0017 PPM. I was 0.0033 PPM and the other was 0.0052 PPM.

    "They also reported 160 samples of conventional baby food pears and 78% (126 of the160 samples) had at least one residue detected. 75 of the samples (75%) had Spinosad B. Most of those samples (65) were 0.0017 PPM, four were in the 0.0030s, two in the 0.0040s and two were in the 0.0050s. The highest was 0.0058 PPM.

    "Of course the tolerance in pome fruits is 0.2 PPM so none of the residues are even close to tolerance."

    "According to the 2008 USDA Pesticide Data Program Report:
    43% of organic spinach samples were positive for spinosad
    (13 of 30 samples positive)."

    1. Michael,
      Thanks for that. I'd like to know how you tell which samples in PDP are organic. I've got the data as well, but didn't know you could spot those. Your friend is right, Spinosad is one of the few pesticides used on organic that can be detected by this protocol. Of course it is super safe stuff and also very widely used in conventional.

    2. I forwarded your response to him. Hopefully he'll reply to you directly, because I know that he, like others in Maine, are interested in refuting the misinformation spread by the EWG.


  5. Great post. It always helps to debunk the misconception that organic foods contain absolutely no pesticides or fertilizers. However, it is depressing to learn that the USDA promises to "test" for residues there will not be testing for organically approved pesticides. So it kind of renders their program mute. So those involved in growing organics can contined to claim "our foods are 100 percent natural with absolutely no pesticides on them." I liked your comment about the flawed way EWG arrives at its dirty dozen list. And the fact needs to be driven home: regardless of conventional or organic grown, do eat your fruits and veggies.

  6. This is excellent information in this blog post, but if this provides a rationale to some to continue merrily spraying toxic synthetic chemical pesticides to the heart's desire, then this information has been twisted. If organic copper-based fungicides scare you (and they should), then we need to test for them as well. That's the whole point. We need safer food. It's not about "us versus them" winning or losing. Let's hold the organic farmers to the same standards. But let there continue to be standards by which we judge our food. Letting farmers use Americans as guinea pigs for modern industrial farming methods isn't the way to go. Waiting for 99% conclusive and complete information will take decades - long after the damage is done to millions of Americans. Nobody knows why obesity, diabetes, infertility, attention deficit, and thyroid illnesses are skyrocketing in the modern era. We need to be more respectful of our ecological limitations. Farmers need to use innovation to find safer ways to make the food that we eat. America deserves nothing less.

  7. A lot of people are worried about this, but a Home Pesticide can actually be considered organic. If it is made with natural ingredients and is used moderately, I think you can consider this to be a safe organic product.

  8. Well, the debate may go o and on and on.. Things are still up in the air.. But as for me, I really felt a healthy change in my life after turning towards organic food items.. They may have chemical residues too, but they are indeed better than conventional food.

    1. Sunny,
      I think the important conclusion is that everyone is better off if they eat a diverse diet including many fruits and vegetables. The one caution I would give you about organic (and I'm not the only one saying this - lots of serious organic advocates say the same) is that there are a growing number of organic foods based on ingredients (grains, fruit juice concentrates, frozen items) that come from places like China where the sort of paper-trail certification of USDA Organic is probably not so trustworthy. With the sort of minimal, discretionary testing that is being instituted, that concern continues

