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  These are sorely outdated images.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  In fact, scores of old materials have been withdrawn from the market or banned long ago.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

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  Graphs are based on USDA-AMS pesticide data and USDA-ERS produce trend data.