Sunday, September 23, 2012

Pesticides: Probably Less Scary Than You Imagine

 The word "pesticide" conjures up negative, scary images. These images come from old organophosphate insecticides of the 1960s that killed fish and birds and caused farm worker illness.  These are sorely outdated images. What most people don't know is how much safer the new generations of pesticides are.  In fact, scores of old materials have been withdrawn from the market or banned long ago.  The new products are mostly compounds with extremely low mammalian toxicity and benign environmental profiles.  Today's pesticides are not your grandfather's or even your father's pesticides. Fortunately, you don't have to take my word for this.  There are some excellent sources of public data on this topic. These  products emerged from an on-going chemical discovery effort involving billions of dollars of investment over decades.  

Pesticides From A Consumer Perspective

One source of information about pesticides is a huge, annual sampling and testing exercise that the USDA carries out to look at what pesticide residues can be found in the food supply.  I have previously posted an analysis of that that data set from 2010 (latest available).  It shows that the residues that can be detected on US foods are at such low levels relative to conservative tolerances, there is no reason for US consumers to worry about them.  

What Sort of Pesticides Are Farmers Using Today?

When a recent, Stanford, meta-study cast doubt on the nutritional advantage of organic foods, some consumers stated that it is still worth it to buy organic because it doesn't have pesticides.   Many, perhaps most, consumers believe that organic means "no pesticides." This is simply not true - though it is a convenient fiction for some marketers and advocates. There are many pesticides that are allowed to be used on organic crops.   

One of the best ways to look at what is being used in both conventional and organic farming is to look at the extensive and transparent, California Pesticide Information Portal (CalPip).  California has a tremendous diversity of crops and also a very large share of the organic market.  It is a source for data which comes from mandatory reporting of all commercial pesticide use in the state.  CalPip posted two lists of the top 100 pesticides used - one based on total pounds applied and one based on the total number of acres treated.  I created a list that combined the two without the surfactants or other spray additives.  That left 104 materials.  I then looked up the publicly available, MSDS documents (Material Safety Data Sheets) to get the acute toxicity (oral ALD50) for each of the products (see graph below).  

The EPA defines a range of toxicity categories from I to IV, with IV being the least toxic (essentially non-toxic to mammals, but their terminology is classic regulatory-cautious).  On a weight basis, the largest share of pesticides used in California in 2010 fall into the least toxic category (62%).  The blue part of the bar includes products which allowed for both organic and conventional farms.  
About 1/3 of all the pesticides used in California in 2010 fall into the "slightly toxic" or "moderately toxic" categories.  Note that there are organic products in these toxicity categories as well.  Most of the organic pesticides in categories II and II are copper salts (copper sulfate, copper hydroxide...).  These are old products which the EPA still allows with some restrictions because of copper's issues with toxicity to aquatic invertebrates and environmental persistence.  Conventional growers can control the same plant diseases that organic growers treat with coppers using various category IV products which are less toxic which have benign environmental profiles.   Why would organic growers use pesticides with somewhat more risk issues than conventional?  Because the criterion for organic approval has nothing to do with safety as such.  It is all about whether it meets a certain definition of "natural."   As we will see later, categories II an III are not all that scary, but it is worth noting that organic does not automatically mean better from a pesticide perspective.
Note that only 0.2% of the commonly used chemicals in California fall into the "Highly Toxic" category, and those are used under strict limits to prevent any form of unwanted exposure.  Just for interest sake, however, Vitamin D3 would fall into this category if it were a pesticide.

How Toxic Are These Different Categories?

It is not that easy for most people to relate to these EPA category descriptions, so it is useful to make comparisons between pesticides and familiar chemicals in foods and pharmaceuticals (see graph below).

Vitamin C is something which many people take in large, 250-1000 mg doses on a regular basis.  Fifty-five percent (55%) of the pesticides used in California in 2010 were less toxic than Vitamin C. Sixty-four percents (64%) were less toxic than vitamin A.  Seventy-one percent (71%) were less toxic than the vanillin in ice cream or lattes. Seventy-six percent (76%) of the pesticides were less toxic than prozac and 89% were less toxic than the ibuprofen in products like Advil.  Ninety-seven percent (97%) of California pesticide use in 2010 was with products that are less toxic than the caffeine in our daily coffee, the aspirin many take regularly, or the capsaicin in hot sauces or curries.  This is not the sort of image that most people visualize when they hear the word "pesticides."

Of course, acute oral toxicity is only one of many dimensions of the EPA risk assessment that is behind all product registrations and reviews.  That is why, from a consumer health point of view, the comparison of residue levels to a tolerance is the most appropriate statistic by which to judge consumer safety (it factors in various forms of chronic exposure and the nature of the crop itself..).   People are also concerned about combinations of chemicals, but our diets contain more complex combinations of natural plant-made chemicals at much higher concentrations.   The beneficial aspects of eating things like fresh produce far outweigh any concerns about the pesticide residues that are in either organic or conventional foods.

What About Farm Workers or the Environment?

The people who tend our crops are certainly exposed to pesticides far more than any consumer.  What about them?  If one looks at the data for exposure via skin or breathing, a similar pattern emerges to that for oral toxicity - modern chemistries are low in hazard and thus in risk.  There are also label restrictions that prevent workers from being exposed to the more hazardous materials (e.g. what protective clothing is required and how long after a spray before anyone can re-enter the field).  All the registered pesticides are also extensively studied in terms of their effects on "non-target" organisms and their environmental fate.  The rules for how any given pesticide can be used (the label requirements) factor in worker and environmental risk.  Once again, the sort of issues that were common in the 1960s are not at all reflective of the modern situation.  Some organically approved pesticides have their own worker and environmental issues which are also mitigated by the same sorts of EPA label restrictions.

Are Pesticides Really Needed Anyway?

Yes, they certainly are.  Farmers use many other methods than pesticides to control pests (I'll be writing about that soon), but without pesticides our farms would be far less efficient in terms of resource-use-efficiency (land, water, fuel, fertilizers, labor).  That is why both organic and conventional farmers often need to use pesticides.  Again, the organic pesticide list was not created based on its risk profile, so there are many cases where the conventional options are as low or lower in risk than the organic option.  

So, overall, the “its all about pesticides” argument for buying organic is not compelling in a modern time-frame.  If someone wants to spend the extra money for organic, that is their choice. Someone who does not want to by organic should feel neither guilt nor fear about that decision.  It is a choice that is well supported by the science.

Spraying image from the USDA-ARS.  Graphs by Steve Savage based on CalPip Data.  I'm also happy to share my data files with those that are interested.  You are welcome to comment here and/or to write me at


  1. As usual, Steve, I've learned a lot from you.

    Before I "jumped ship" and left the organic movement, I worked at an organic farm that used pesticides. Now, there is nothing wrong with that, but the way organics advocates issue calumnies against so-called conventional farmers for their pesticides use just reeks of hypocrisy.

    I can remember the moment when the cognitive dissonance was so great that I simply couldn't continue the charade of believing organic was superior to other farming methods. It was at a training session for pesticide applicators: To work at the organic farm, I had to go to the state of Maine's organic center to learn the laws and be certified as a pesticides applicator. It was very weird.

    Another story of disillusionment: At a new farmers workshop in Maine, during the pesticides module, an orchardist got up to speak about conventional versus organic pesticides use on apples. His orchard has both organic and conventional fruit [that he could be both is a bit of silliness in itself, but topic for a separate discussion].

    This grower explained that he sprays his conventional crop 12 times a year to control disease, fungi, and insects.

    Then he explained that he sprays his organic apples 22 times a year! The reason, he stated, is "sulfur, sulfur, and more sulfur." It's basically the only way organic growers in the Northeast can control scab fungus.

    He also stated that his organic trees produce only 25% of what his conventional trees produce, and that "those trees are not healthy" as a result of their organic treatment.

    We have a tiny orchard of 65 heirloom trees here on our little CSA farm, and believe me I have no qualms about using "conventional" pesticides to take care of them.

    And yet the propaganda against any farming that doesn't uphold organic dogma is so pervasive that I've had a customer at a local farmers market ask me if my apples have been sprayed, and when I said yes, the customer said she would not feed them to her child.

    I'll bet she never even thinks to ask organic farmers whether they spray....

    1. Mike,
      You are right that most of your customers wouldn't even think to ask if the organic fruit was sprayed. If they do know they probably assume that because the things use in organic are "natural" they are automatically better. The fact is that both synthetic and natural chemicals come in the whole range of toxicity.

    2. I actually use/d a spray containing Sulfur for my bonsai trees (it's a 3 in 1 but i used it most for fungus) and noticed some degradation in health afterwords myself. Is there any conventional spray you could recommend that is less toxic?

    3. Dawshoss,
      Sulfur isn't very toxic, but it is highly irritating to skin and eyes. Depending on what the pest issue, there are some good conventional options. If its an insect problem, products with the active ingredient imidacloprid are quite effective systemically. If it is a disease like a powdery mildew, look for things with myclobutanil or tebuconazole. If its something like aphids or mealy bugs, insecticidal soap works if you can get very complete coverage (e.g. both sides of all leaves).

  2. This article is a place to start but when I am choosing a strawberry I really am much more concerned about how pesticides will effect ME than how they will effect aquatic life. Telling me how toxic something is to fish does not help me to decide. It is useful to know that both organic and non organic produce may contain pesticides but I want to know if the organic pesticides are safer to eat or not.

  3. Anonymous,
    For strawberries I would say that the risk from either organic or conventional are so low you need not hesitate to enjoy them. There are some relatively toxic soil fumigants used on conventional, but that is well before the crop is even planted and they break down as well. I did an analysis of the 2008 strawberry residue data for 2008 and found the smallest safety margin was such that you would need to eat 34 times your own body weight over a short time period to get a toxic dose. The safety factors for most of the residues were in the 100,000 to 1 million range. Just for reference, the caffeine in coffee is somewhat toxic and the safety margin for drinking that is such that if you drank one times your own body weight you could get the toxic dose.

    Organic strawberry growers often use copper-based fungicides. Those are 10-20 times as toxic to mammals as the conventional alternatives and they are used at rates of multiple pounds per acre vs ounces/acre. Even so, the copper salts are pretty water soluble and non-systemic, so they should be fairly easily washed off in your sink. If the residues were a real safety issue, they would not remain EPA registered.

    Bottom line, just enjoy the berries

  4. Thank you for this post. My biggest pet peeve with people talking about pesticides is they fail to put dosage & toxcity in normal people terms, like you did above with comparing toxic levels.

    Always enjoy your posts!

  5. This was helpful, but it would be nice to know more details about the variables, such as differences between insecticides, herbicides, fungicides, etc., which are bioaccumulative, when (during the growing season) they're applied, etc. Something that's used as a soil fumigant early in the season that breaks down regularly may be very different from something that is a foliar spray, has a different LD50, and is bioaccumulative.

    Another point is that label restrictions don't "prevent workers from being exposed" any more than label restrictions prevent any other behaviors or activities. There's plenty of work showing lax safety training by unethical growers, particularly of undocumented workers, who are reluctant to complain even if they understand the risks.

  6. Anonymous,
    Bioaccumulation was an issue with certain old pesticides, and to my knowledge that is really only a remaining issue with rodent baits.

    As for worker safety training. I think that your view is dated.

    I was once involved in an effort to improve that for workers exposed to a particular old chemical (which is now entirely gone). One of the biggest barriers was that workers were reluctant to come to officially sponsored training sessions because of risk of deportation. If we could establish a reasonable guest-worker program, we could efficiently train and far more efficiently deploy workers where they are needed. The grower community has been asking for this for decades.

  7. @California Pesticide Use in 2010 (Weight Basis)

    Are most of the pesticides approved for Organic use sprayed primarily on Organic farms?

    I'm curious what percentage of total pesticide by weight is sprayed on Organic acreage.

  8. Michael,
    I don't have any good source for that breakdown, but here is what I know. Sulfur is far an away the largest pesticide use by pounds and by acres. A great deal of that is for conventional grapes and some other crops. Of course it is used even more for the organic grapes, but at <5% of acres thats not much. Organic is relatively small for almost any crop except "spring mix" and "baby spinach."

    The really interesting issue would be where the copper fungicides are used. They are definitely used on both organic and conventional, but probably a bit more to the organic side because there are so much better options for conventional.

    I wish there was a good data set for this. Perhaps CalPip could start tracking this.

  9. Thanks Dr. Savage.

    If there aren't statistics by weight, I wonder if there's any historical data on pesticide application frequency for various crops.

    I'm also curious about the guidelines Organic producers have to follow in order to spray multiple times in a growing season.

    It's my understanding that some alternative approaches to chemical pest management must be documented before the first application, but afterward is the producer essentially free to spray multiple times throughout the season, i.e. without following additional Organic protocols?

  10. Michael

    There are lots of stats, at least for California, but it isn't broken down by what was on Organic, Transitional or Conventional acres.

    I'm not sure about that issue of first reporting and then free etc. My impression is that organic producers only have to be concerned about what is or isn't on the list (OMRI). There is no actual requirement for IPM methods etc.

  11. Mr. Savage. I just wanted to leave a quick comment and thank you for your blog! I hope you don't mind that I use it as a resource for my own (as a lawyer, science isn't something I'm super awesome at, haha). Keep up the good work! (

    1. The farmers daughter,
      Thanks for the feedback and for the nice mention on your blog. You are doing a great job defending ag from a personal and legal perspective!

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  13. Another point is that label restrictions don't "prevent workers from being exposed" any more than label restrictions prevent any other behaviors or activities. There's plenty of work showing lax safety training by unethical growers, particularly of undocumented workers, who are reluctant to complain even if they understand the risks.pest control minneapolis

    1. I'm sure that out of the thousands of growers there are bad actors, but based on my experience I don't think that is close to normative. I've had the chance to work in the past with a broad stake-holder group on the issue of safety training for farmworkers in the apple industry. I can assure that they take it very seriously. Honestly one of the biggest barriers to safety training is our dysfunctional immigration policy and our lack of a rational guest worker policy.

  14. One thing that's usually missed in these analysis's that I was wondering about, aside from LD50 levels, what are the comparative risks of birth defects due to exposure to these chemicals while pregnant? Is there a way to get a list or comparative graph about that?

    1. Dawshoss,

      Teratogenicity (causing birth defects) is definitely one of the risks that is part of what the EPA reviews. There isn't a quantitative index for this. Here is an example of an MSDS (Material Safety Data Sheet) for glyphosate that states that this compound was not found to be teratogenic. I'd be surprised if you found many if any commercial products for which that is not the same result. The EPA has done a good job of making sure that registered pesticides are not teratogenic.

      When women are pregnant, it is probably more important that they eat lots of fruits and vegetables because there is evidence that this will "program" their children to have a taste for those foods. That would give them a lifetime of protection from cancer and many other diseases

    2. Shoot so there is no risk index by which we can compare one to another, they are all at zero?

      Also by "The EPA has done a good job of making sure that registered pesticides are not teratogenic." do you also mean herbicides? As actually this is what I've heard most worries from.

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