Wednesday, June 13, 2012

What We Have NOT Recently Learned About Pesticide Risk

A few weeks ago, the readers of various "Food Movement" and "Health" blogs (and unfortunately some news sources) were treated to a major dose of fear mongering.  It had to do with an old agricultural fungicide that was tested at an extremely high, non-contextual dosage in a scientific study that looked at "chemical effects on epigenetic change."  What the study demonstrated was interesting, but it's interpretation in various circles has been completely out of context.  For example, self-described "Health Ranger," Mike Adams of Natural News started off with the headline:

"Red alert for humanity: Chemical damage can be inherited by offspring through unlimited generations"

Under the section heading, "Why chemicals threaten the future of the human species," Adams concludes:"  we are, in essence, ChemHumans, forever imprinted with the toxic burden of all the tens of thousands of synthetic chemicals we have foolishly unleashed onto our world, our environment and food supply".  

What inspired this sort of "the sky is falling" rant?  A classic failure to put a scientific finding into any sort of rational perspective.

The Journal Article That Got This Started

On May 21st of this year, scientists from the University of Texas, Austin, and Washington State University published a paper in the prestigious journal, PNAS (Proceedings of the National Academy of Sciences).  It was titled: "Epigenetic transgenerational inheritance of altered stress responses."  Epigenetics is a relatively new field of science.  It is the study of heritable traits which are not produced by changes in the sequence of DNA, but rather by modifications of that DNA such as methylation.  Some of the same mechanisms are involved in how cells differentiate into different body parts even though all cells have the same total set of genes.  Many things can lead to Epigenetic change.  For instance it was found that there were inherited traits for the offspring of people in Sweden who experienced famine and that the traits were passed down several generations.   The recent PNAS study showed an epigenetic change related to exposure to a particular chemical - an old agricultural fungicide called vinclozolin.    Mother rats were exposed to a single, very large dose of that chemical.  This induced an epigenetic change, and the body weight and stress responses of the rat's offspring were altered in a way that was passed from generation to generation thereafter.  

This is an interesting finding, but it is important to be clear about what this study does and does not show.  It shows that a substantial chemical exposure can lead to epigenetic change.  It does not in any way demonstrate that this or any other chemical can do this at the doses that we humans would ever receive in real life.  To investigate the question of whether a chemical might actually have epigenetic effects on humans would require a "risk assessment," and the authors have stated that that they were not attempting to do that.  However; when interviewed, one of the authors, David Crews, theorized that environmental exposure to things like DDT in the 1940s lead to increases in obesity and autism.  This leads one to wonder why the experiment was not done using DDT.  Andrew Feinberg of the Johns Hopkins Epigenetics center says that the theory is premature and cautioned about overstating what has actually been demonstrated.  The PNAS authors have overstated their case, and unleashed a storm of unhelpful speculation.

Dose Matters

What Adams and many other writers classically (and irresponsibly) failed to do was to consider how much this experiment differs from real world chemical exposures.  Many chemical effects that occur at high dosages become irrelevant when the dose if low.  A high enough dose of many, ordinary, natural, chemicals (caffeine, capsaicin, even table salt) can kill rats in a lab study.  That does not mean that they pose any risk at the doses in which we often consume them.  The saying, "the dose makes the poison" is a bit of classic wisdom, but not something that a writer like Adams would consider (besides, a terrified readership makes better customers for the home delivered Organic and Non-GMO foods that Adams is hocking on his "informational" site).

Here Comes The Disinformation

I knew as soon as I heard about the PNAS article that people would begin to assume that this potential for chemically-induced epigenesis is a new worry with regard to pesticides.  After all, the study was done with an agricultural fungicide.  Fortunately, there is a great deal of publicly available information to demonstrate that the amount of vinclozolin that was given to these rats was huge in comparison to any relevant exposure for food consumers.

Understanding This Dosage

I wrote to the authors of the study to learn what actual dose of vinclozolin they had fed the rats (it was in an appendix I was unable to see on-line).  The dose was 100 milligrams per kilogram of body weight.  To put that in perspective, to give a 100 pound human female (45.4 Kg)  an equivalent dose to what the rats received, would require 4.5 grams of pure vinclozolin.  To visualize this a little, I weighed 4.5 grams of salt (see picture below).  That is a lot of any individual chemical to consume at one time!

Next, I went to the data from the USDA's Pesticide Detection Program (PDP), the large sampling effort they conduct each year to find out exactly what pesticide residues occur in foods of various types (the same data set perennially misused by the Environmental Working Group to make their "Dirty Dozen" list.  During the years 1995 to 2008, trace vinclozolin residues were detected 1,058 times in crops like strawberries, table grapes, and green beans.  The average quantity of the fungicide detected was 0.13 parts per million.  It is better to look at the entire distribution of results.    The highest level of vinclozolin ever detected was 5.2 parts per million in one batch of strawberries in 1998.  Even if our imaginary 100 pound person ate strawberries from that worst-case batch, they would have to eat 1,923 pounds of them at a sitting to get the 100 mg/kg dose the rats got in the PNAS study.  The graph below shows the entire distribution of pounds of produce needed to deliver the study dose to a 100 lb human from actual residues.

Clearly, there is no reason to think that real-world exposure to pesticide residues might cause the sort of epigenetic changes seen in the PNAS study.

What Would An Actual Risk Analysis Entail?

To do a risk analysis of this epigenetic phenomenon, vinclozolin would need to be fed to the rats at a series of different, lower doses in order to find the "No Effect Level."  It is almost certain that actual human exposure to vinclozolin in food is far, far below that level.  There is no rational reason to believe that pesticides like vinclozolin are "threatening the extinction of the human species."  Instead, they are making it possible for growers to provide us with food of high quality at a reasonable cost.  Vinclozolin served that role for a while; but not any more in the US.

A Short History of Vinclozolin

Vinclozolin was discovered by the German company, BASF in the 1970s and first registered for use in the US in 1981.  It was a fungicide that was active on a specific group of plant diseases caused by fungi such as Botrytis and Sclerotinia.  Every consumer that buys fresh produce has probably seen Botrytis which produces as a powdery mass of grey spores as it rots things (see effected strawberries below - Image from University of Florida).  Botrytis is one of the major causes of food wastage both before and after harvest of many crops.  There were not many very effective fungicides for these diseases in the 1980s, so the introduction of vinclozolin was welcomed by growers.  It was used for a period, but it has since been replaced by even better and safer options.

Vinclozolin is essentially non-toxic in acute, mammalian testing.  Rats can consume 50 times as much vinclozolin as in the PNAS study with no short-term effects.  However, over time, as EPA risk analysis became more and more comprehensive and risk tolerances were adjusted to safer and safer standards, it turned out that vinclozolin had some issues at high doses.  In an abundance of caution, actions were taken to make sure that risk was extremely low.  At first, certain uses of vinclozolin were restricted and extra worker safety standards were required.  Eventually, the manufacturer decided to simply withdraw the product and its use was phased out.  You can read the details of that history on the EPA website. Vinclozolin was never documented to cause any actual health problems, but it is a good example of our highly protective regulatory progress over time.  You can see how vinclozolin use declined in California in the graph below.

So, as interesting as this PNAS study is (a very high dose of a chemical can lead to epigenetic change), it is not a reason to conclude that this phenomenon is any sort of threat to human existence or the cause of a host of ills.  If chemically induced epigenetic change does occur, it is probably only relevant for vastly higher chemical exposures than ever occur with agricultural pesticide residues in food.   Humans can actually be exposed to far higher doses of certain nasty, natural chemicals like mycotoxins or certain phytochemicals.  Those would actually be a logical classes of chemicals to study for real-world epigenetic effects.

This recent PNAS article does not change the reality that we do not need to fear agricultural pesticide residues in our food, and that such fears only serve the economic interests of fear-based marketers.

You are welcome to comment on this site or to email me at  "Scream" image from Christopher Macsurak


  1. Great article, as usual.

    It sure was poor form of Crews to speculate that DDT exposure of parents could cause autism, obesity and depression in later generations. There is always someone waiting to pounce on unfounded comments like that, who then uses the sound bites to inflame the public for their his gain. This reminds me of the vaccine-autism problem.
    Also, why not look at the epigenetic effects of smoking. There is a lot more exposure of mothers and their fetuses to tobacco toxins than there is to most agriculturally-used compounds. And there aren't too many people up in arms over that.
    Keep up the good fight!

  2. Thanks Eleanor,

    Good point about smoking. I hope that this does not become something like the vaccine-autism thing because no amount of information can ever convince some people. Of course in that case, many people have ended up endangering their communities by not having their kids vaccinated.

  3. Nice post and thanks for the analysis of the PNAS publication !

  4. It has been circa 1200 years since Nicander described the consequences of lead poisoning, and mankind has not yet learned the lesson. It was not until 1980 that leaded gasoline began to be seen as a real health problem. Still we dispose of wasted batteries inapproprietely in parts of the world today. I think it should also take us many decades to start to realize the wrongs we are doing with all the chemichals in use today (not only vinclozolin). Sure we can benefit from science and the artificial interference over natural processes. This has been proven over and over. But it also seems clear to me that we have lost respect by going large scale too fast. There will probably be a price to be paid for it.

    1. Anonymous (I accidently deleted your comment but rescued it from the email notification)

      Actually the vinclozolin story is an excellent example of how far we have come since 1980. There is no comparison between the lead exposure back in the day and what ever happened with vinclozolin (as the data here demonstrates). I certainly won't deny that mistakes were made decades ago, but you could say that about all sorts of things from politics to race relations to women's rights. We have come a long way on many of those dimensions - particularly on pesticide safety

    2. Ok, I just cited lead to make a philosophical argument. When you recognize that mistakes were made decades ago, it sounds like something you're likely to continue to say decades from now. Just to keep the philosophical line of thinking, every time we make a mistake we are less like Prometheus and more like his brother Epimetheus. Just now, are we evolving towards Prometheus or Epimetheus ?

    3. Anonymous,
      So you don't believe that humans ever learn? There have been some big mistakes in Pharma like thalidomide (sic?). Does that mean we should never develop any new drugs? There were certain car designs that rendered them "death traps." Does that mean we should never develop new, safer cars based on what was learned? There have been some big mistakes in organic farming with human pathogens (e.g. the sprouts in Europe). Does that mean we should never grow sprouts?

      In all these cases, we have learned from mistakes and made progress on things that matter.

    4. I am sorry to see that you miss my point. What I believe is that humans learn much slower than we care to consider. That due to economic pressures, vanity or simply greed, changes to natural processes that are not fully understood have and are being made overnight and we only realize that years, decades or even centuries latter. By now, what we should be learning from our past mistakes is how to make no further mistakes. Instead we are making some new mistakes and then waiting for them to reveal themselves. Do you really think there is anything still "organic" nowadays ? Any pathogens still not exposed to man made chemichals ? Have you seen the New York Times article on how babies are being born experiencing opiate drugs withdrawal symptoms ? That is about 1.5 babies every hour in the US. That is the kind of thing I'm talking about ... I am not saying that we should not study, try, experience, learn, but that we should be more responsible and refrain from going large scale too quickly. I think that we are pushing the limits of nature that is all, and it might be that the means to correct any future consequences could be out of our reach. Well, that is about all the philosophical reasoning I dare to put forward. Thank you for the discussion.

  5. Anonymous,
    I don't disagree with the idea that we have to proceed with caution. At this point for any new agricultural chemical there the process of being careful is already up to seven years of testing and ~250 million dollars spent to do it. We always have to be open to phenomena we have not seen before, but the point of this article is that epigenetic effects has not been demonstrated to be one of those new things in an ag chem context. It might be for some far higher exposure scenario

  6. Hmm...well, I believe the author frames this subject in a very unintelligent perspective, massively.

    Is agriculture, promoted on massive, corporatized, corrupt, and polluting scale by the most violent and criminal organizations on the planet improve the health and beauty of the Earth?

    The answer is no--and the fact that these forces promoting oppression, ignorance and greed don't clean up their damage as they create it points up that the system is diseased. We see this in the collapsing health of the Earth.

    More, you make huge generalizations as you sneer at intelligent behavior by some to avoid exposure to pesticides--these are not compelling, and only reinforce the naïveté, or, will to believe, on the part of the readers that enable the profit feed-back loops that provide income for this portal.

    Current ideologies and violent tyrannies are making our planet less healing--as has been the undeniable trend.

    But you appear to support this trend--and that shows your core thinking and believe as ecocidal and diseased.

    Indeed, I am eager to review your replies to my core point on the part of your readership here. There actually is no argument that the system and ideology you have internalized is not irreparably harming the health of our planet--and that the major players have never been successful in any significant repair.

    Meanwhile, the pathological egoists stuff the gains in their pocket--and we all have to pay for any cleanup of the toxic messes created. What a brazen scam.

    When you die of cancer--the pesticide promoters will rest assured that their hands are clean--and everyone is safe.

    You are insane, and will leave this life supporting the trend toward decreased long-term survival--and the evisceration of ecosystems and beautiful species.

    All you know is the ugly--and we see the evidence everywhere you lay your hands.

    Deep, through layers of denial and paroxysms of fallacious and weak argument--you know this, of course.

    1. Swamp,

      I suspect that you are so deep into conspiracy theory thinking about these topics that there is no reason to discuss it. I've posted your diatribe - let readers judge for themselves

  7. Lol, you will love my reply to your lack of cogency and smear..

    Stay tuned, and drop that bottle of pesticide--that is not beer.

    Just saved your life..

    1. Swamp...
      Are you actually sober when writing these comments?

  8. Given that I have the capacity to offer a semblance of coherent comment, with rhyme schema, I would say that I am swimmingly sober.

    I divide my reply to your response to my first post on your site, with respect to the tread you have developed herein, focusing on pesticides and food safety. My main criticism is that you erect a caricature of the trend of thinking that strives to avoid food produced with pesticides to maximize production. The weak oppositional anecdotes you highlight generalize way too broadly with respect to the myriad and cogent criticisms that exist in the public sphere. Your selected anecdotes are from cherry-picking so as to present the most sloppy presentations that function to inform and warn the population. This presentation and your critique develops a.caricature--to the point that your loyal guests are ready to burn tree-buggers at the stake. (ok, I exaggerate--but not far off the mark.). This selective presentation of hack science shown( pesticides influencing epigenetic Alteration that influences the genetic coding of subsequent generations of humans exposed to pesticides) and the subsequent line of argument that smacks down the facile target, lacks cogency--is unscrupulous, thus unscientific, and suffers the taint of being pesticide industry aligned propaganda.

    I divide my response into two sections because of the constraints of this format.

    1. Swamp...

      Your language is rather convoluted, but do I hear you saying that the study was an example of "hack science?" I guess I wouldn't be quite that harsh, but some of the author's public comments have crossed a line.

      In this post I was only addressing this one example of data that should not be over-interpreted because it was generated with a dosage that it completely out of range for reality.

      As for the general issue of chemical toxicity, I fully recognize that there are many real historical examples of real, and even tragic problems. Fortunately, we have been in a continuous learning process over the last 30+ years and lots of "bad actor" chemicals are now off the market. We now have lots of really good choices for pest control chemicals and those are critical to making good use of all the other resources (land, water, fuel, labor...) that go into feeding us.

      I have no interest in poisoning anyone, but I do have a strong interest in enabling farmers to feed us.

  9. Critique the ideas and major points presented, as such communication would be logical, and possibly cogent.

    However, instead, your strategy I'd to impunge my person, my ability to engage and present ideas in a civilized, honorable fashion. 

    Corrupt logic..  Though I haven't enough experience with your ideas, as a whole, to present a psycho-ideological analysis in the form of argument to confidently present the roots and ligatures that can be helpful to significantly expose your motives and goals.

    "Follow the money" is too easy and trite--as thie scope of such explanation doesn't bring to the fore the deeper social and familial influences that come to bear on your presenting such grotesque, fallacious, and  reductive reasoning as standard given the weight of the issues you seek to influence the perception of other humans. 

    Talk radio squalor. 

  10. Well, I could engage critique of big, corporate ag, and present points and arguments that promote the idea that humans don't need big ag or synthetic chemicals to survive ( to the point that allows us humans to become more intelligent and thrive)--but this is actually well known.

    What we are facing are oppressive political tyrannies that increase ecological and human squalor so as to protect and project status quo patters of wealth and power.

    If these forces actually repaired significant amounts of their damage as our common reality unfolds--then my primary criticism of this system would be undermined by dint of ample example, and, unfortunately for all life and human society, this is not the reality we must face at this moment with courage, empathy, and applied

    How do these ecocide systems reproduce--with respect to education, the flow of information, through the dynamic of institutions, the culture industry, etc. How do patterns of ignorance spread and reproduce? We don't educate and form citizens that can develop sound lines of argument--and, thus, they are manipulated and coerced by undemocratic and corrupt patters that hold sway over our collective course.

    There exists a corruption in our basic cultural coding that sustains what is clearly a pathology and threat to our long-term survival.

    These matters are dire, and not reducible to feces flinging.



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