Steve Savage: “A Rational Analysis of the USDA Pesticide Residue Data”

A guest post by agricultural scientist Steve Savage,
proprietor of Applied Mythology.
(Updated 1/6/16 to reconnect missing illustrations. This post first appeared on Sustainablog 6/15/11)


When the Environmental Working Group (EWG) makes its annual “Dirty Dozen List” of fruits and vegetables with pesticide residues, it does so without paying any attention to which chemicals were found or what level was detected. This is why it is so misleading.  To do the analysis properly does take a lot more “work” – it took me much of the last two days to do it.

First I had to download the raw data which comes as a 5.5 MB ZIP File that expands to a 83 MB text file.  My son wrote a little Ruby On Rails script that sifts through the millions of rows of data to find the 30,000 actual “detections” of pesticide residues that the USDA reported for 2009.  That list has the identity of the pesticide and its concentration in parts per million, billion or sometimes trillion.  Next, I searched for anMSDS for each of the 300 or so different chemicals to get the specific acute toxicity (this is usually in section eleven of each document).  The acute toxicity is expressed as an LD50 – the milligrams of chemical it would take per kilogram of body weight to kill 1/2 of the rats in a feeding study (Oral LD50).  These are publicly available documents which are usually easy to find except for old, discontinued pesticides and some of the metabolites.  Dividing the LD50 by the detected amount gives you the multiple of its own body weight that the rat would have to eat to reach a toxic dose.

An Example You Can Blame on McDonald’s

As an example, an old, extremely toxic pesticide, aldicarb (Temik) has an LD50 of 1 mg/kg.  This is exactly what you imagine when you hear the word, “pesticide.”  In one sample of fresh potatoes, the USDA scientists detected 0.01 mg/kg of aldicarb sulfoxide – a metabolite which is just as toxic as the aldicarb.  For the rats to die from eating such potatoes would require that they rapidly consume 90 times their own weight of those particular potatoes.   The most toxic potato sample had 1.5mg/kg of the aldicarb sulfoxide which means that the rates could die by eating just one times their own body weight.  A rat might be able to do that.

The EWG essentially treats every one of the 30,000 detections as equal in risk to these worst-case potato values.  Because most pesticides are far, far less toxic than aldicarb, the average residue found by the USDA on potatoes has a safety margin of 595,163.   The only reason that aldicarb is still used on potatoes (and it will be phased out soon), is that for purely brand protection reasons, MacDonald’s asked it’s fry suppliers not to give them any more GMO potatoes (they had been using them for several years, and they still cook them in GMO soybean oil and serve up GMO sodas with corn sweetener).  Still, McDonalds killed the Bt-potato.  That is why potato growers plant their potatoes into a furrow with granular aldicarb so that the roots pick up the insecticide for ~60 days, protecting them from the Colorado Potato Beetle.  Still, potatoes are in about the middle of the pack in terms of average safety margin.  Oranges have a safety factor of nearly 1.5 million.

Sweet corn, which makes the “Clean Fifteen” list for EWG is actually the crop with the lowest average safety margin (8,909).  This demonstrates the meaninglessness of the Dirty Dozen list.

Beyond Averages

Of course, averages can be misleading.  It is more instructive to look at the full distribution of results.  The graph below summarizes all the sample results for fruit crops.  For this graph, values on the right side of the graph represent extremely low risk while those to the left represent relatively higher risk.  As you can see, even though these crops had many pesticide residues, they almost all were present at vanishingly levels meaning extremely minor risk.  People just don’t eat one hundred, one thousand or several million times their body weight of one food in a sitting!

The same is true for vegetables.  The few residues detected on lettuce have safety margins in the million-fold range and the non-Organic lettuce was actually a little better than the Organic lettuce.  By this methodology potatoes and spinach come out the worst with some safety margins in the thousand range.  Still, the message from the real data is completely different than what one gets from the EWG’s “analysis.”

When the EWG list is reported by the unsophisticated media, they say things about it which are completely false.  For instance said, “The “dirty dozen” list of the twelve fruits and vegetables with the highest amount of pesticide residue was released Monday by the Environmental Working Group (EWG).”  That would be impossible because the EWG did not access the raw data which would be necessary to identify how “high” the residues actually were.  They say that cherries “dropped off the list” without mentioning that cherries were not even one of the crops tested in 2009.

So, what does the USDA data actually tell us?  That we should feel confident that the fruits and vegetables available in our markets are perfectly safe, and we should be consuming them in ever greater quantities to take advantage of all the cancer- and other disease-fighting chemicals they naturally contain.  It also tells us that the EWG should be ashamed of their list, print a full retraction, and refund their ill-gotten financial gains.

If anyone would like a copy of the processed data or graphs I would be happy to email it from  Also if anyone would like to improve on my collection of LD50 values that would be much appreciated.  My website is Applied Mythology.

Crop dusting image from wikimedia

sustainablog (

Mary Magnan on the NEJM Fail — the Benbrook & Landrigan Non-Disclosures


Dear Reader, if you are a subscriber to The New England Journal of Medicine then I hope you will take the time to carefully read the preceding guest post by Dr. Mary Magnan. I anticipate that you will come to the same conclusion I did – that NEJM must, at the very least, publish a correction to the Benbrook & Landrigan article. And on the NEJM website the article should be prepended with a full disclosure of the blatant conflicts of interest that were not disclosed by the authors. I also hope that subscribers to NEJM will take the trouble to explain their strong feelings to the editors.

In the media there is clearly a “double standard” applied to discussions on genetic engineering – particularly in agriculture. The tacit assumption of the reporting journalist or editor is that the person taking the anti-GMO position is the innocent “good guy environmentalist”, who is just trying to inform the public of the dangers of this technology. Conversely, the person who discusses GMO risk v. benefits is presumed to be beholden to corporate interests. The code word “Monsanto” is usually considered sufficient to terminate rational discussion.

This specific case of the NEJM publication is an example of an article carefully crafted to appear to be a scientific reference for contrary-to-fact claims that herbicide-resistant crops are increasing the negative impact of pesticides. The trick the authors use is to tabulate only the time series total mass of the herbicide glyphosate. Not discussed are the important benefits of glyphosate – that in recommended application regimes glyphosate is one of the least toxic herbicides, that glyphosate is replacing significantly more toxic chemicals, resulting in much-increased conversion of acreage to environmentally beneficial “no-till farming”.

So the conclusions of the Benbrook & Landrigan article are exactly backwards from the perspective of a scientist objectively evaluating the before-after the introduction of the glyphosate-resistance trait.

What would motivate Benbrook & Landrigan to publish such nonsense? Well, particularly in the case of Benbrook – that is his job – to provide the “scientific references” to counter the conclusions of all the worlds major scientific institutions that GMO crops are as safe as non-GMO alternatives, and good for the environment and good for the farmers.

I appreciate Dr. Magnan’s significant effort invested to carefully document what Benbrook & Landrigan should have disclosed to NEJM. My reading of the evidence is that NEJM would have declined to publish this piece.

For an overview of the evidence on pesticides before/after GMO introduction, please Dr. Steve Savage: When Increased Pesticide Use Is A Good Thing which concludes with this:

To reiterate, pesticide use or its increase are not automatically undesirable things.  It depends on what is the alternative and what is the nature of the particular pesticide in question.  Plant biotechnology is just one important tool in the bigger tool box of agriculture.  Sometimes it allows farmers to use a more attractive pesticide option (Bt Sweet Corn would the be best example of this).  Sometimes it helps them with the adoption of sustainable practices that depend on relatively low risk herbicides.  For farmers, biotechnology and pesticides are not an either/or.  They are often partners.

Dr. Savage has published many articles on the complex subject of agricultural pests, IPM (Integrated Pest Management) and pesticides. Another useful perspective is The Muddled Debate About Pesticide Use And GM Crops:

Bottom line, a biotechnology trait may decrease or increases the need for a pesticide.  There will also be many cases where the biotech trait has nothing to do with pesticide use.  There is no necessary good or bad linkage between these two categories of agricultural technology – both can serve to make crop production better.  Both are options that should be available to those who farm.

Organic marketing: Not truthful, often misleading

I am supportive of those who choose to grow organic food and those who choose to buy it. However, I do not accept the organic industry’s attack on new tech agriculture. It is entirely without justification.

If the roles were reversed and conventional agriculture engaged in similar “black marketing” against organics, the regulatory authorities and consumer groups would come down like a ton of bricks.

One wonders why, then, this multibillion-dollar industry gets a free ride to propagate negative and false advertising denigrating the livelihood of the vast majority of America’s farmers.

It’s time for it to stop.

JOHN R. BLOCK was U.S. secretary of agriculture from 1981 to 1986. On the Academic Review report John begins with this 

As someone who has dedicated his career to agriculture, I’ve often wondered what drives the now double-digit growth in the $35 billion U.S. organic products industry. Why are so many people willing to pay premiums up to 100 percent or more for items that carry an organic label, and do they really understand what that label means and — even more important — what it doesn’t mean?

Many of these questions have now been answered in a blockbuster report by the scientific-integrity watchdog Academics Review. The report examines the last 25 years of academic and organic industry market research, public statements and often questionable marketing practices.

What they have found should be raising red flags for all of us.

The organic industry likes to project a friendly image of small farmers and contented cows. But as this report extensively documents, the behavior of this multibillion-dollar industry is considerably less benign.

Among the other findings is the extent to which the large organic food corporations engage in what it describes as deceptive advertising linked to scientifically baseless scares about conventional food.

Worse, this “black marketing” takes place with the implied approval of the U.S. Department of Agriculture’s Organic Seal and the silent acquiescence of the regulatory authorities charged with ensuring that all labeling and advertising be “truthful and non-misleading.”

As a leading consultant warned the organic industry in the 1990s, “If the threats posed by cheaper, conventionally produced products are removed, then the potential to develop organic foods will be limited.” Since then we’ve witnessed a remorseless campaign based on junk science or no-science attacking food grown with modern fertilizers, pesticides, GMOs and other technologies.

Advertising and promotional material — including “educational” materials developed for schools — suggest non-organic food is linked to almost every disease under the sun, including “developmental and learning problems such as ADHD,” “high blood pressure, type 2 diabetes, depression and cancer.”

Tens of millions of organic marketing dollars flow annually to activist organizations such as the Environmental Working Group which spread misinformation and fear. Unsupported, provably counter factual claims are so habitual to the industry that they are even included in official statements: “Not only is organic safer, healthier and more nutritious,” claims the Organic Consumer Association in testimony to USDA, but buying organic will “reduce food-borne illness and diet-related diseases.”

The Organic Seal does not and cannot signify any health or safety criteria whatsoever. It merely certifies that products were produced using less modern inputs.


Why Consumers Pay More for Organic Foods? Fear Sells and Marketers Know it.

You have probably noticed how much of the anti-GMO and organic industry advertising is based on fear-mongering. For a deep dive into how this works, I suggest the 2014 Academic Review report:

Why Consumers Pay More for Organic Foods? Fear Sells and Marketers Know it.

An academic review of more than 25 years of market research, marketing tactics and government programs driving sales in the organic and natural product industries

(April 8, 2014 Priest River, ID) An extensive review of more than 200 published academic, industry and government research reports into why consumers adopt organic product purchasing behaviors was conducted by Academics Review – a non-profit led by independent academic experts in agriculture and food sciences. This review was then supplemented with an assessment of more than 1,000 news reports, 500 website and social media account evaluations and reviews of hundreds of other marketing materials, advertisements, analyst presentations, speeches and advocacy reports generated between 1988 and 2014. Our findings were reviewed and endorsed by an international panel of independent agricultural science, food science, economic and legal experts from respected international institutions with extensive experience in academic food and agriculture research and publishing.

Our report finds consumers have spent hundreds of billion dollars purchasing premium-priced organic food products based on false or misleading perceptions about comparative product food safety, nutrition and health attributes. The research found extensive evidence that widespread, collaborative and pervasive industry marketing activities are a primary cause for these misperceptions. This suggests a widespread organic and natural products industry pattern of research-informed and intentionally-deceptive marketing and paid advocacy. Further, this deceptive marketing is enabled and conducted with the implied use and approval of the U.S. government endorsed and managed U.S. Department of Agriculture (USDA) Organic Seal and corresponding National Organic Standards Program (NOSP) in direct conflict with the USDA’s NOSP stated intent and purpose.

“It is our hope that responsible members of the organic food industry and government officials will use these findings to address consumer misperceptions about important issues of food safety and nutrition,” said Professor Bruce Chassy, professor emeritus University of Illinois, Department of Food Science & Human Nutrition. “Accurate food safety, nutrition and health information combined with consumer pocket book protections should be a threshold standard for any U.S. government program that cannot be coopted by special interest marketing groups.”

Dietary pesticides (99.99% all natural)

Plants are not just food for animals… The world is not green. It is colored lectin, tannin, cyanide, aflatoxin, and canavanine [Janzen (16)].

A false claim keeps crossing my desk: that organic foods are safer; and especially safer due to the prohibition of synthetic pesticides. This is false. In fact the motivation for development of many of the synthetic pesticides in use today is to reduce toxicity for both consumers and agricultural workers. This effort has been successful, but due to the vested interests in the “organic” marketing designation the prohibition against synthetic pesticides prevails.

John R. Block was U.S. secretary of agriculture from 1981 to 1986, so he is a good source for a concise summary of what “organic” really means:

The Organic Seal does not and cannot signify any health or safety criteria whatsoever. It merely certifies that products were produced using less modern inputs.

“Let me be clear about one thing,” said USDA Secretary Dan Glickman when organic certification was being considered. “The organic label is a marketing tool. It is not a statement about food safety. Nor is ‘organic’ a value judgment about nutrition or quality.”

Yet USDA’s own research shows consumers buy higher priced organic products because they mistakenly believe them safer and more nutritious.

The science is clear on this point: As numerous studies, USDA monitoring, and a massive “meta-analysis” recently conducted at Stanford University confirm, organic foods are no more nutritious, nor do they carry any fewer health risks, than conventional foods. In fact, a good case could be made that conventional food may be considerably safer.

 My quick summary is organic labeled products are limited to pre-scientific agriculture.

Are natural pesticides better? Definitely, not – though, because natural pesticides are not regulated,  we know much less about their toxicity. Bruce Ames is one of the heroes of environmentalism, so NY Times science writer John Tierney turned to the Ames et al 1999 paper to document his column Synthetic v. Natural Pesticides: the captioned Dietary pesticides (99.99% all natural). This paper is open access, free PDF here, by B N Ames, M Profet, and L S Gold: Division of Biochemistry and Molecular Biology, University of California, Berkeley.

When a toxicologist says “99.99%, by weight, of the pesticides we eat are natural” she is probably referring to this paper. I like the way John Tierney characterizes the Ames work

Dr. Ames was one of the early heroes of environmentalism. He invented the widely used Ames Test, which is a quick way to screen for potential carcinogens by seeing if a chemical causes mutations in bacteria. After he discovered that Tris, a flame-retardant in children’s pajamas, caused mutations in the Ames Test, he helped environmentalists three decades ago in their successful campaign to ban Tris — one of the early victories against synthetic chemicals.

But Dr. Ames began rethinking this war against synthetic chemicals after thousands of chemicals had been subjected to his test. He noticed that plenty of natural chemicals flunked the Ames test. He and Dr. Gold took a systematic look at the chemicals that had been tested on rodents. They found that about half of natural chemicals tested positive for carcinogencity, the same proportion as the synthetic chemicals. Fruits, vegetables, herbs and spices contained their own pesticides that caused cancer in rodents. The toxins were found in apples, bananas, beets, Brussel sprouts, collard greens, grapes, melons, oranges, parsley, peaches — the list went on and on.

Then Dr. Ames and Dr. Gold estimated the prevalence of these natural pesticides in the typical diet. In a paper published in 2000 in Mutation Research, they conclude:

About 99.9 percent of the chemicals humans ingest are natural. The amounts of synthetic pesticide residues in plant food are insignificant compared to the amount of natural pesticides produced by plants themselves. Of all dietary pesticides that humans eat, 99.99 percent are natural: they are chemicals produced by plants to defend themselves against fungi, insects, and other animal predators.

We have estimated that on average Americans ingest roughly 5,000 to 10,000 different natural pesticides and their breakdown products. Americans eat about 1,500 mg of natural pesticides per person per day, which is about 10,000 times more than the 0.09 mg they consume of synthetic pesticide residues.

Even though these natural chemicals are as likely to be carcinogenic as synthetic ones, it doesn’t follow that they’re killing us. Just because natural pesticides make up 99.99 percent of the pesticides in our diet, it doesn’t follow that they’re causing human cancer — or that the .01 percent of of synthetic pesticides are causing cancer either. Dr. Ames and Dr. Gold believe most of these carcinogenic pesticides, natural or synthetic, don’t present problems because the human exposures are low and because the high doses given to rodents may not be relevant to humans.

“Everything you eat in the supermarket is absolutely chock full of carcinogens,” Dr. Ames told me. “But most cancers are not due to parts per billion of pesticides. They’re due to causes like smoking, bad diets and, obesity.”

He and Dr. Gold note that “many ordinary foods would not pass the regulatory criteria used for synthetic chemicals,” but they’re not advocating banning broccoli or avoiding natural pesticides in foods that cause cancer in rodents. Rather, they suggest that Americans stop worrying so much about synthetic chemicals:

Regulatory efforts to reduce low-level human exposures to synthetic chemicals because they are rodent carcinogens are expensive; they aim to eliminate minuscule concentrations that now can be measured with improved techniques. These efforts are distractions from the major task of improving public health through increasing scientific understanding about how to prevent cancer (e.g., what aspects of diet are important), increasing public understanding of how lifestyle influences health, and improving our ability to help individuals alter their lifestyles.

You can read a detailed account of their work in the Handbook of Pesticide Toxicology.

Pesticide residues: what about chronic toxicity and accumulation?

In a prior post commenter “L” asked a question that worries a lot of people, especially moms.

I understand that one would need to eat multiple body weights in a day to die right away of acute toxicity, but what about chronic toxicity and accumulation of these substances in the body when consumed not over days but years? (Over several years I will consume multiples of my body weight of certain crops, so what could the consequences be in this case? Higher risk of cancer etc.? And I understand that actual toxicity is different from probabilities/risks in the future.) Thanks

Here’s what I wrote as a comment reply:

Good question. Ewan R’s answer illustrates how large the safety factors are – the ‘tolerances’ set by the EPA. The challenge posed by your lifetime exposure question is “how do we measure that?”. Even if willing to wait a century for the results, the cost of blind, controlled studies would be impossible to fund. Because of the practical impossibility of funding such long term studies, toxicologists developed the “factor of safety”, or some prefer “factor of ignorance”.

Possibly one reason that toxicologists are more relaxed about the cumulative or chronic toxicity issue is that they learn early on that humans have evolved to survive in a toxic world. Our DNA repair mechanisms reflect this constant barrage from background radiation to chemicals. 99.9% of pesticides are natural – the plants have evolved these chemicals because something is always trying to eat them.

For a quick, accessible read, I suggest Steve Savage’s discussion in What Are Your Favorite Toxins?

For further reading may I suggest the B N Ames, M Profet, and L S Gold paper Dietary pesticides (99.99% all natural), whose abstract reads:

The toxicological significance of exposures to synthetic chemicals is examined in the context of exposures to naturally occurring chemicals. We calculate that 99.99% (by weight) of the pesticides in the American diet are chemicals that plants produce to defend themselves. Only 52 natural pesticides have been tested in high-dose animal cancer tests, and about half (27) are rodent carcinogens; these 27 are shown to be present in many common foods. We conclude that natural and synthetic chemicals are equally likely to be positive in animal cancer tests. We also conclude that at the low doses of most human exposures the comparative hazards of synthetic pesticide residues are insignificant.

This lengthy paper is an edited version of a chapter titled ‘Cancer Prevention and the Environmental Chemical Distraction [PDF]‘, in the 2003 book Politicizing Science: the Alchemy of Policymaking. You can pay Amazon $9.99 for the Kindle or you can download the chapter “Cancer Prevention and the Environmental Chemical Distraction” [PDF] on the UC Berkeley site.

Distraction is the right word.

Steve Savage: “How The USDA Unwittingly Aids EWGs Pesticide Disinformation Campaign”

A guest post by agricultural scientist Steve Savage, 
proprietor of Applied Mythology
(This post first appeared on Applied Mythology 6/19/2012)

Each year, the Agricultural Marketing Service of the USDA (USDA-AMS) conducts an extensive sampling and analysis of items from the actual US food supply to determine what, if any, pesticide residues are present at the consumer level.  This information is published each year, and the actual raw data is also available for download.  The data for 2010 was just recently released.

What Does The Data Actually Tell Us?

For 2010, as for preceding years, the data demonstrates is that pesticide residues are only present at very low levels, usually dramatically below the conservative ‘tolerances’ set during the risk analysis by the EPA.  This is quite remarkable considering that pesticide use on crops depends on many thousands of independent decisions by many thousands of individual farmers both in the US and in dozens of countries from which we import food.

This year the USDA provided several summaries in an effort to be clear about what they have found.  In this years press release one finds the following, unambiguous statements:

The 2010 PDP report confirms that food does not pose a safety concern 
based upon pesticide residues.  
Statement from the EPA ‘The data confirms EPA’s success in phasing- out pesticides used in children’s food for safer pesticides and pest control techniques.  The very small amounts of pesticide residues found in the baby food samples were well below levels that are harmful to children.’  
Statement from FDA: ‘Based on the PDP data from this report, parents and 
caregivers can continue to feed infants their regular baby foods without being concerned about 
the possible presence of unlawful pesticide chemical residues.’ 

Statement from the USDA: ‘Age-old advice remains the same: eat more fruits and vegetables and wash them before you do so.  Health and nutrition experts encourage the consumption of fruits and vegetables in every meal as part of a healthy diet…’

Unambiguously positive assessments like this can also be found in the main data summary, the ‘What Consumers Should Know‘ highlights, and in the ‘Questions and Answers‘ link.

What Does The Press Tell Us?

As a typical example, CNN starts with the headline, ‘Watch out for the 2012 Dirty Dozen,’ and continues, ‘Apples and celery are still agricultures dirtiest pieces of produce according to the Environmental Working Groups annual ‘Dirty Dozen’ report.’  Its version of the baby food findings are, ‘For the first time this year, the USDA also collected data on pesticide residue in baby food, finding many of the studies samples to be contaminated with organophosphate pesticides.’

How can CNN report something so radically different than what the USDA said?  They simply are repeating what the Environmental Working Group has said in its press release of 6/19 and make no effort to compare it with the official document.

HuffPost Healthy Living starts with the headline, ‘Dirty Dozen: EWG Reveals List of Pesticide-Heavy Fruits and Veggies.’  Nowhere in this article is there even a reference to what the USDA, EPA and FDA said about the data.  It simply passes along the EWG interpretation as if it were gospel. 

This is the mainstream media.  You can well imagine what is said on various organic and Food Movement sites and blogs.

In contrast, Jon Hamilton writing for an NPR blog uses the headline, ‘Why you shouldnt panic about pesticide in produce.’  Jon notes that the EWG sends a ‘mixed message,’ saying ‘you should be concerned about pesticide residues in fruits and vegetables, but not so concerned that you stop eating these foods.’  Rather than simply parroting EWG, this writer demonstrates some journalistic mettle by interviewing a scientist at McGill University who can provide some perspective.  He also demonstrates that he read at least some of the USDA documentation by quoting specific numbers on apples and the non-alarm assessment for the baby food data.  Such efforts at balance are unfortunately rare.

Why Does The EWG’s Version Get So Much Attention vs The USDA’s?

Although sensationalism, low journalistic standards, and limited scientific background are certainly involved in the largely uncritical magnification of the EWGs message by the press (and particularly the blogosphere), Im afraid that UDSA-AMS is partially to blame.  Dont get me wrong, they do a rigorous collection and analysis of the data.  They are extremely clear in what they conclude with sound reasoning.  They are definitely transparent and unbiased in their presentation.  What what USDA does not do is provide a summary version of the data that is easily digestible by ordinary readers, including typical members of the press.  EWG provides a simple list with a one dimensional ranking.  It is a gross and misleading simplification, but that makes it easy to relay as if it was a real analysis.  Unfortunately, the summaries that the USDA presents are extremely detailed, extremely long, and not easy to interpret even for someone who wants to.  Let me explain.

A Document That I Doubt Many People Really Read and Digest

The annual summary document for each years PDP data is huge, in the range of 200 pages as a pdf (it is hard to tell, the appendices are numbered independently).  It starts with 28 pages of background on methodology and summary of sample types etc.  Then there are 9 pages of a historical appendix.  Finally the actual data begins in a 77 page appendix, but this is organized by chemical – nothing that most people would even begin to relate to.  For each chemical there is no information about whether that product is something toxic or not, nor is there information on any other dimension of its environmental profile.  To get that, someone would have to search for an MSDS and maybe an EPA RED – none of which are easy for any layman to interpret.  All this table lists are the number of samples, the number and percent of ‘detections,’  the range of those detections in PPM, the LOD (limit of detection), and the EPA tolerance (an extremely conservative level set by an elaborate risk analysis). Most people would have no idea what to do with those numbers.  In fact they show that the vast majority of ‘pesticide detections’ are at levels well below the tolerances, but it is tedious to do the comparisons by eye and there is nothing in the table to give the message of how far below any level of concern the vast majority of samples are actually shown to be.  Im not surprised that no independent journalistic interpretation of these data occur.

Below the chemical-by-chemical summary there are dozens of pages summarizing commodities other than fruits and vegetables.  That is followed by an appendix J which unhelpfully simply compares the ‘percent detections’ for imported and domestic samples (a summary level as seriously unhelpful as that by the EWG).

Finally, at the very end of this huge document there is a crop-by-crop summary with the same data columns as for each chemical (#samples, #detections…) which has the same tedious requirement to compare detections and tolerance that are all usually numbers to several decimal points.  I have never seen anyone in the press do much if anything with this data set.

What Does This Report Need?

To be fair, USDA-AMS has amassed such a huge body of data.  It is difficult to summarize it in a way that is intuitively meaningful.  Their bottom line conclusion, ‘produce is safe,’ is a perfectly valid, but some visual representation could go a long way towards getting that message across.  I acknowledge that this is difficult.  I have made some attempts to do so in the past.  I plan to do so again with this years data, but that will take time.  The same would be true for even an ambitious reporter, while simply reporting what the EWG says allows less ambitious reporters to keep up with the instant news cycle.

A Mountain of Data

It is a wonderful thing that the USDA makes the effort to analyze so many samples of so many crops and looks for so many different chemicals.  The downside is that this generates a database that is beyond what most of us even know how to process.  The file that one can download with the raw data has been getting bigger every year and has now reached 85MB.  Im used to dealing with large files, but none of my ordinary software can deal this this.  Ive gotten my son to write a program in RUBY to parse the data and only give me the tiny fraction which contains ‘detections’ and discard the millions of rows of data that effectively say, ‘we didnt find this chemical in this sample.’  Im going to ask him to modify the program this year with some additional summaries.  

When and if I get this done, I plan to make this available to anyone interested in doing an actually meaningful analysis of the data and to explore ways to present it graphically in ways that can compete with the egregiously trivialized ‘analysis’ done by EWG.  

You are welcome to comment here, and/or email me at

Produce stand image from Steve Savage

(Via Steve Savage Applied Mythology.)

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

What I found disappointing about the Stanford study was the weakness of its analysis of differences in pesticide residues. 

I was delighted to find that Steve Savage had posted a well-researched critique  Do You Really Need to Buy Organic Foods To Avoid Pesticide Residues? of the meta-analysis “Are Organic Foods Safer or Healthier Than Conventional Alternatives?” The main-stream media didn’t get much further than the “Conclusion” paragraph of the press release

Conclusion: The published literature lacks strong evidence that organic foods are significantly more nutritious than conventional foods. Consumption of organic foods may reduce exposure to pesticide residues and antibiotic-resistant bacteria.

Every media reference I’ve encountered emphasizes the “…may reduce exposure to pesticide residues”. Does that mean “reduce exposure” from safe-and-totally-insignificant to…? Perhaps – but that really isn’t the focus of the Stanford paper – which is the nutritional vector. Steve’s introduction gets right to the implied pesticide risk that concerns me:

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.

Please read Steve’s commentary with an open mind. If you are not completely persuaded, then for further reading may I suggest the B N Ames, M Profet, and L S Gold paper Dietary pesticides, which is an edited version of a chapter titled ‘Cancer Prevention and the Environmental Chemical Distraction‘, in the 2003 book Politicizing Science: the Alchemy of Policymaking. The Kindle edition is only $9.99, and a very good investment it is.