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

A guest post by agricultural scientist Steve Savage, 
proprietor of Applied Mythology
(This post first appeared on Sustainablog 6/15/11)

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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 thirdage.com 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 savage.sd@gmail.com.  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


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Steven Novella: No Health Benefits from Organic Food

The recent review of organic vs conventional produce agrees with previous systematic reviews that there is insufficient evidence to conclude that organic produce is healthier or more nutritious that conventional produce. Despite the scientific evidence, the alleged health benefits of organic produce is the number one reason given by consumers for buying organic. This likely represents the triumph of marketing over scientific reality.

At Science-Based Medicine neuro-scientist Steven Novella recently took another skeptical look at organic benefits, including the Crystal Smith-Spangler meta-review. I was pleased to see Steve start off by flagging the naturalistic fallacy.

A recent review of 240 studies has concluded that:

 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.

Organic produce has become increasingly popular in recent years. There are several reasons that consumers might prefer organic produce, including the belief that organic farming is better for the environment and more sustainable. I am going to focus in this article about the health effects of organic produce. Environmental claims for organic farming are complex and controversial – I will just say that such claims largely fall prey to the naturalistic and false dichotomy fallacies. In my opinion, farming practices should be evaluated on their own merits individually, based on evidence rather than philosophy. Sustainable and environmentally friendly farming are certainly laudable goals and I support farming practices promote them, however they are labeled.

(…)

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.

Dangers of organic produce: the German beansprouts kill at least 48 in 2011

For reference, the May-June 2011 food poisoning outbreak killed at least 48 (in Germany; I’ve not researched the outcomes of affected travelers). The German panic was caused by organic bean sprouts – the Lower Saxony farm has been shut down. The lethality of the sprouts is attributed to an enteroaggregative E. coli (EAEC) strain that had acquired the genes to produce Shiga toxins.

Here is a snippet of the Wikipedia reference “2011 Germany E. coli O104:H4 outbreak“:

Epidemiological fieldwork suggested fresh vegetables were the source of infection. The agriculture minister of Lower Saxony identified an organic farm[2] in Bienenbüttel, Lower Saxony, Germany, which produces a variety of sprouted foods, as the likely source of the E. coli outbreak.[3] The farm has since been shut down.[3] Although laboratories in Lower Saxony did not detect the bacterium in produce, a laboratory in North Rhine-Westphalia later found the outbreak strain in a discarded package of sprouts from the suspect farm.[4] A control investigation confirmed the farm as the source of the outbreak.[5] On 30 June 2011 the German Bundesinstitut für Risikobewertung (BfR) (Federal Institute for Risk Assessment), an institute of the GermanFederal Ministry of Food, Agriculture and Consumer Protection), announced that seeds of fenugreek imported from Egypt were likely the source of the outbreak.[6]

In addition to Germany, where 3,785 cases and 48 deaths had been reported by the end of the outbreak,[7] a handful of cases were reported in several countries including Switzerland,[7] Poland,[7] the Netherlands,[7] Sweden,[7] Denmark,[7]the UK,[7][8] Canada[9] and the USA.[9][10] Essentially all affected people had been in Germany or France shortly before becoming ill.

David Tribe has been following the case, including here and here, where I obtained this update:

The E. coli (O104) outbreak is responsible for 48 deaths in Germany and one in Sweden. The total number of cases reported in the EU, Norway and Switzerland is 4,178.

As always, David offers thorough references. One from July 7, 2011 by Maryn McKenna that is accessible to the non-scientist is “E. coli: A Risk for 3 More Years From Who Knows Where”.

UK food agency report: organic food is not healthier

New news for me, perhaps old news for you – the results were announced by FSA in July 2009. the FSA announcement reads:

An independent review commissioned by the Food Standards Agency (FSA) shows that there are no important differences in the nutrition content, or any additional health benefits, of organic food when compared with conventionally produced food. The focus of the review was the nutritional content of foodstuffs.

Gill Fine, FSA Director of Consumer Choice and Dietary Health, said: ‘Ensuring people have accurate information is absolutely essential in allowing us all to make informed choices about the food we eat. This study does not mean that people should not eat organic food. What it shows is that there is little, if any, nutritional difference between organic and conventionally produced food and that there is no evidence of additional health benefits from eating organic food.

‘The Agency supports consumer choice and is neither pro nor anti organic food. We recognise that there are many reasons why people choose to eat organic, such as animal welfare or environmental concerns. The Agency will continue to give consumers accurate information about their food based on the best available scientific evidence.’

The study, which took the form of a ‘systematic review of literature’, was carried out by the London School of Hygiene and Tropical Medicine (LSHTM). LSHTM’s team of researchers, led by Alan Dangour, reviewed all papers published over the past 50 years that related to the nutrient content and health differences between organic and conventional food. This systematic review is the most comprehensive study in this area that has been carried out to date.

The FSA commissioned this research as part of its commitment to giving consumers accurate information about their food, based on the most up-to-date science.

This research was split into two separate parts, one of which looked at differences in nutrient levels and their significance, while the other looked at the health benefits of eating organic food. A paper reporting the results of the review of nutritional differences has been peer-reviewed and published today by the American Journal of Clinical Nutrition.

Dr Dangour, of the LSHTM’s Nutrition and Public Health Intervention Research Unit, and the principal author of the paper, said: ‘A small number of differences in nutrient content were found to exist between organically and conventionally produced crops and livestock, but these are unlikely to be of any public health relevance. Our review indicates that there is currently no evidence to support the selection of organically over conventionally produced foods on the basis of nutritional superiority.’