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Sunday, September 9, 2012

Do You Really Need to Buy Organic Foods To Avoid Pesticide Residues?


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.

Many commentators, confronted with the highly credible de-mythification of the nutritional advantage of organic, jumped to the paper's slight evidence supporting a 30% reduction in exposure to pesticide residues as a way to justify paying extra for organic. Does the science really support that claim?  No.

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.


The graph above shows that the vast majority of the residues that the USDA scientists detect are at less than one part per million (1 milligram/kilogram).  There really are not very many chemicals, synthetic or natural, that are of concern at these levels, but fortunately the USDA data does identify what the chemicals were and one can find out about them by searching for an MSDS (Material Safety Data Sheet).




When most people hear the word, "pesticide" they imagine something quite dangerous.  What they don't know is that over the last several decades, the old chemicals have been steadily replaced by much less hazardous ones that have emerged from a multi-billion dollar discover effort.  That is why 36.6% of the residues detected in 2010 were for chemicals that are less toxic to mammals than things like salt, or vinegar or the citric acid in your lemons (see graph above).   73 percent of the detections  were for pesticides that are less toxic than the vanilla that is in your ice cream.  90.5 percent of the pesticides detected were less toxic gram per gram than the ibuprofen that is in the Advil tablets that tens of millions of people take on a regular basis.  95.4% of the detected residues were from chemicals that are less toxic than the caffeine that is in your coffee each morning.  "Pesticide" does not equal "danger."

Even so, the best way to answer the question, "should I worry about pesticide residues?" is to compare what was detected to something called the "EPA tolerance."  Companies that want to register new pesticides or to continue to use older ones spend well over $100 million dollars and several years of research to characterize the hazards (or lack thereof) that are associated with each chemical.  These are used to inform a sophisticated, EPA-driven  "Risk Assessment" process that determines if the chemical can be used and with which restrictions (e.g. how long the use must stop before the crop is harvested.)  The "tolerance" that comes out of this process is designed to set a maximum level of that pesticide residue that should be detected in practice. This value includes a generous safety margin (on the order of 100x).  Anything that is detected which is below the tolerance is not of any concern.  The tolerances are set specifically by chemical with differences for each crop to reflect  differences in the amount people would eat and which crops tend to be consumed the most by children.  

What Does The Residue Testing Say?


The reason that the USDA can look at their data and make strong statements about safety is that the residues they find are virtually all below the tolerances, mostly far below (see graph above.)  Only 7.8% of the residues detected in 2010 were even within the range of 0.1 to 1 times the tolerance.  More than half were less than 1% of the tolerance (see graph above).

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.

This new study, even if it is from Stanford, does not provide consumers meaningful guidance on the question of whether they should spend more to avoid pesticide residues.  The more relevant USDA data says that they don't need to hesitate to buy and consume "conventional" foods.

You are welcome to comment here or to email me at savage.sd@gmail.com.  Graphs are based on USDA-AMS pesticide data and USDA-ERS produce trend data.


39 comments:

  1. This is the perfect rebuttal, concise and trenchant.

    Thanks, Steve.

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  2. Anytime I don't see the dosage of pesticide one might ingest (Dirty Dozen?) I'm skeptical. Thanks for this post. Great stuff once again.

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  3. Excellent work putting the relative exposure in perspective.

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  4. Excellent job putting the exposure in perspective.

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  5. Steve--I have a question for you: does this count "organic" pesticides? Or is there a separate data set that counts those?

    That was something I actually didn't know from the Stanford study either.

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  6. Mary,

    The Stanford study didn't pay any attention to the identity of the chemicals. The PDP testing battery includes some organic approved actives (like natural pyrethroids and spinosad), but not the copper compounds, Bts, biologicals... As far as I can tell, one can't tell if any of the samples were organic.

    Steve

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  7. Thanks--exactly what I was wondering (and suspected).

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  8. I have found over the last 60 years organic food tastes much better and has no chemical aftertaste . But you'd have to have the experience to know what youre talking about.and not work for a chemical company

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  9. Has anyone here ate organic? Or chemical-free ? 60 yrs of experience tells me - you probably haven't noticed the chemicals in your food anyway - your tastebuds must be shot - and as you say you "its hard to know" what they've been doing to your analytics or your justification.its just a matter of time.

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    1. As I understand it from my organic farmer friends, they use Pyganic on kale , Spinosad on potatoes, and BT on hornworms and still are considered organic. You can't be assured even organic is an assurance of being chemical free.

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    2. Nothing is "chemical free." Everything is made of chemicals. Crops like kale and potatoes actually contain many compounds which are somewhat toxic if there were consumed at too high a dose. Solanine in the potatoes in destroyed by cooking otherwise there is enough that you could get sick from eating lots of raw potatoes. Your organic farmer friends have to deal with pests just like conventional growers. Those products you mention are low toxicity chemicals and are used by both kinds of growers. Of the three, spinosad is the most effective as an insecticide, but it is essentially non-toxic to mammals and has no bad environmental effects either. It was developed by Dow AgroSciences by the way.

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  10. A wonderfully researched and well-written article. If more readers in the general public would take the time to "digest" scientific details that you have highlighted then organizations such as the Environmental Working Group would be put out of business.

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  11. You need to drink a gallon of this stuff for it to have an adverse effect. Eating organic is like drinking 1 drop. Eating conventional is like drinking 3 drops. So, conventionals may have 3 times the level of pesticide as do organics, but in the end, neither comes remotely close to what it takes to harm you.

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  12. Here is a good article showing just how much conventional food you would have to eat to obtain toxic levels of pesticide exposure: http://edibleintelligence.blogspot.com/2011/06/coming-clean-about-dirty-fruit.html

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  13. You should go to the NY Times and view the comments under Marion Nestle's recent paean to organic food. People are completely ignorant and irrational about the issue of pesticides. I've commented there (Mike Bendzela), to little effect.

    http://www.nytimes.com/roomfordebate/2012/09/10/is-organic-food-worth-the-expense/buying-organic-fruits-and-vegetables-is-a-personal-choice

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  14. Dr. Savage,

    Thanks for another thoughtfully researched post.

    Can you offer some insight on the comparative toxicity / environmental impact of commonly used organic pesticides? How do the LD50s and ecological effects stack up?

    Michael

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  15. Michael,
    I'm working on a post that will cover that, but I can tell you that they cover a wide range. Many are in the >5000 mg/kg range which is essentially non-toxic. That is also the biggest category for conventional and many of the most important products are the same ones used in conventional. Some organic pesticides are in the 3-4000 mg/kg range which is only as toxic as table salt or vinegar. Some are in the range of 250-300 mg/kg which gets you to EPA's "moderately toxic" category (as toxic as caffeine or capsaicin) . That isn't actually that big a deal for our diets, but from an environmental point of view these are not wonderful. These products are mostly copper salts (copper hydroxide, copper sulfate...) and they are not things you want to get into water ways because they are really hard on invertebrates. Also, copper is an element, so it does not break down into harmless things as most pesticides do.

    There are a few, mostly bacterial diseases for which copper is one of the only viable options, but for most of the diseases for which copper is used in organic, there are many far, far safer and more effective conventional options (mostly in the >5000 mg/kg range and with no environmental persistence issues and which are used at a fraction of the rate per acre - ounces vs multiple pounds).

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  16. "The net effect of consumer concern about pesticide residues, driven by distorted messaging, is a reduction in fresh fruit and vegetables consumption (see graph below)."

    Strange statement to be found in an article talking about conclusions being improperly drawn from insufficient or non-existent evidence.

    Particularly since in the very next statement you then say "hard to know" when discussing the same causal relationship.

    You can't make such conclusions about cause-and-effect if you haven't controlled for variables. Correlation does not equal causation. Why does that need to be pointed out to someone writing this kind of analysis?

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    1. Joshua,
      I certainly understand that correlation does not equal causation, but there is some polling data that directly supports the link. I don't think it was extensive enough to fully answer the question because it just considered the EWG Dirty Dozen List. I've modified the text. I'm looking into this question on a crop-by-crop basis now.

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  17. Seems that if you really want to evaluate the trends related to pesticide in our environment - particularly since the concentrations in the human body are cumulative - simply analyzing the amount detected in commodities is interesting but certainly not sufficient. The most important measure would be the levels found in human tissue, breast milk, etc. Have you looked at those data?

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    1. Joshua,
      Not all chemicals coming into the human body are cumulative - in fact most aren't. We have lots of liver enzymes that break things down and also mechanisms to eliminate chemicals in urine. Things that bioaccumulate are not that common and we know what sort of chemical properties are associated with that. The metabolism of new pesticide candidates is very well studied. Other than old things like DDT or organophosphates, what literature do you know of saying there is a cumulative effect?

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    2. S.D. Savage -

      Thanks for the responses.

      "...what literature do you know of saying there is a cumulative effect?"

      Er.....actually, I don't know of any.

      My statement was based on things that I've read on the Internet!!! That information may have not been well-supported by evidence.

      Mea culpa. I should be more careful.

      I do still think that to the most important trend to evaluate is how much of these chemicals accumulate in our bodies (to the extent that they do accumulate). The other data are interesting and instructive, but if data on biological accumulation are measurable (particularly for organisms high on the food chain), isn't that really the bottom line?

      As for my first point: It would be interesting to see evidence of variables associated with changes in consumption of vegetables - in particular if it is controlled for SES or other factors.

      I would hazard a guess that there would be increases in vegetable consumption, certainly in a relative sense if not an absolute sense, among those who consume more organic vegetables. So, then, the merits and rhetoric of organic food may take on a different hue if, in spite of organic food not containing more nutrients, it is associated (as a mediator? or moderator?) with people that are eating healthier.

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  18. s.d. savage -

    As for the link you added about evidence linking fear about pesticides with reduced consumption of vegetables - yes, that evidence looks pretty weak.

    My guess is that the people most concerned about pesticides in vegetables probably consume more vegetables, on average, than those who aren't concerned about pesticides. They are more likely to be people who are health conscious, foodies, vegetarians, vegans, people who eat organic vegetables, etc. - i.e., precisely those more likely to be those folks who eat more vegetables.

    What would the related mechanism for alternative caloric intake in those eating fewer veggies because they are concerned due to media hype about pesticides in veggies? Are they going to turn, then, to meat, or processed foods? Wouldn't you say that that same media also hypes concerns about those alternatives? What are they eating because of pesticide-related health concerns? Big Macs? Will they reduce their caloric intake more generally?

    I'm not sure that linking that study is any better than implying a causation without supporting data. Speculation is fine - why go any farther than that without some sort of validated evidence?

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    1. There is some state-specific data on consumption from the CDC, but I'm not sure it helps.

      http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5935a1.htm

      The real question here is not what one eats instead for calories. Fresh fruits and vegetable are more about healthy benefits from all the nice chemicals that they contain which do everything from reducing cancer to improving vein health... I have met many people who feel guilty because they don't want to spend the extra for organic and some good social scientist or psychologist needs to design a way to see what effect that has. When I explain that Organic is also sprayed with pesticides, most people are shocked. The organic advocates and promoters have been quite content to let that bit of misinformation persist. When I also explain that most of the pesticides used on conventional are as safe or often safer than what is used on organic, they are quite relieved because, again, it has convenient for organic backers to reinforce the idea that all pesticides are something like parathion or DDT.

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  19. Hey Steve.........spot on comment. The U.S. food supply is the safest in the world and we need more people spreading the word. The only way we ever feed the hungry and impoverished in our own country is with a conventional food supply. I eat it, my kids eat it, and I believe it is safe. Thanks for you views and being vocal.

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  20. A very large percentage of conventional produce in the US comes from outside the country, especially in the winter. Do you know if the FDA tests them for residue? I imagine they can't regulate what chemicals they use.

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    1. Actually the USDA data includes lots of imports and yes, we do regulate what can be used on crops that are for export to the us. The fact is that a great deal of imported produce is from the same companies that operate in the US or their partners

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  21. very nice and informative blog..Previous study looked at organic food and found that they contain high level of nutrients like vitamins and minerals.But recent Stanford study reveals that organic produce is 30% less likely to be contaminated with pesticide than conventional fruits and vegetables but also pointed out that organic food aren't necessarily 100% free of pesticides..
    I appreciate for your great writing..keep sharing such useful post

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    1. The Stanford study looked at a handful of pesticide studies, only one of which was from the US and it was old. The USDA "PDP" data is much more relevant and it clearly shows that residue levels are too low to be of any concern.

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  22. Hello,
    I am so impressed by this post .
    Thanks for the sharing.
    Organic Food Toowoomba

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  23. How could we ignore the dangerous effects of pesticides and insecticides on our ECO system???? Why shouldn't we choose the safe way of having healthy organic food products to live healthy life??? Just think about this.

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  24. Very good post, informative and thorough.

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  25. Great post full of useful tips! My site is fairly new and I am also having a hard time getting my readers to leave comments. Analytics shows they are coming to the site but I have a feeling “nobody wants to be first” reputation repair

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  26. It's a nice blog to provide a good information. Hope more people reaching your blog because you are sharing a good information.

    Organic products

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  27. Organic food production is free of antibiotics, anti-microbials, hormones and other growth promotants.

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    1. Wholesale,
      Lets consider what you just said. Plants make many anti-microbial substances and both plants and animals make anti-microbial peptides. Plants and animals make hormones and other growth promoters. So if organic food is "free" of these things then it isn't based on natural plants or animals? I think there is something fundamentally sick about a culture where food are sold, not for what they provide us, but for what they do not contain. I call that the "marketing of non-existance." Personally, I grow and buy food for what is in it and I enjoy it. I'm sorry that your are dedicated to the wholesaling of food sold as what does not contain when it actually does contain these things provided by nature itself.

      What you are selling is "Truth Free."

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