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Pesticide Facts

Over at his NYT blog, Mark Bittman weighs in on pesticide use in agriculture. It is really hard to know where to start to address the misnomers that are raised in his piece. Let me begin by saying, however, that no one (including myself) likes the thought of eating pesticides in food. But, we need to put things in perspective. Here are some UC Berkeley scientists:

We estimate that about 99.9% of the chemicals that humans ingest are naturally occurring. The amounts of synthetic pesticide residues in plant foods are low in comparison to the amount of natural pesticides produced by plants themselves.
Bittman begins by saying:
After the publication of “Silent Spring,” 50 years ago, we (scientists, environmental and health advocates, birdwatchers, citizens) managed to curb the use of pesticides[1] and our exposure to them — only to see their application grow and grow to the point where American agriculture uses more of them than ever before. And the threat is more acute than ever.
But if you click on the link he actually provides in the quote, you'll find front and center from the EPA that:
Total pounds of U.S. pesticide use decreased by approximately 8% from 1.2 to 1.1 billion pounds from 2000 to 2007.

Similarly, if you look at the USDA, you'll find that:

In 2007, roughly 877 million pounds of active ingredients were applied to U.S. cropland at a cost of roughly $7.9 billion. In comparison, in 1980, roughly 1.1 billion pounds of active ingredients were applied at a cost of roughly $7.1 billion (in inflation-adjusted dollars). During 1980-2007 the aggregate quantity of pesticides applied in the U.S. declined at an average rate of 0.6 percent per year
So, it appears the entire premise of the piece is off base. Still, I will briefly remark on some of the other claims raised in this piece:
  • Even if pesticide use were increasing (which according to the above it is not), you have to keep in mind that not all pesticides are created equal. The pesticides farmers now use include much more glyphosate (think Round-Up) than they once did, which is less toxic and environmentally damaging than options they use to use (think atrazine).
  • I agree integrated pest management (IPM) is a promising alternative and it is one that many farmers and food processors are already, voluntarily, pursuing because it can be profit enhancing. Pesticide resistance is a problem - always has been, always will be. Calling something a "superweed" makes it sound as if this is a new problem but it isn't. IPM can help mitigate resistance issues.
  • The piece tries to link trends in pesticide use with autism and IQ. Has anyone heard of the Flynn effect? IQ is rising not falling.
  • It is true that organics tend to (on average) use fewer total pesticides. But it is simply not true that organic farmers can't use pesticides. They can use "natural" pesticides like copper and sulfur, which are more toxic than many synthetics. There is really no way to tell when in the supermarket whether the organic has more or less pesticides than the non-organic.
  • If you want to read a really nice account about pesticide risks in food, see Bjorn Lomborg's book. There you'll find lots of data and statistics showing that the relative risks of food pesticides are very small in the grand scheme of things. Moreover, he shows that the bigger cancer risk is not ingesting too many pesticides but rather not ingesting enough fruits and veggies.
  • On an acre-per-acre basis, which commodities are the biggest users of pesticides? You might be surprised to find out that it is not corn, soybeans, or wheat but rather fruits and veggies like lemons, strawberries, etc. It is true that more pesticide is used in corn than strawberries but that's only because we grow a lot more corn than strawberries. If you look at pesticides per acres planted, a much different picture emerges.

Mark Twain on Smoking, Drinking, etc.

A colleague alerted me to this humorous piece by Mark Twain (from an essay titled The Moral Statistician written in 1893; it was partially reprinted in the WSJ a couple weeks ago).  Apparently Twain was a bit put off by the food police of his day . . .

I don't want any of your statistics. I took your whole batch and lit my pipe with it.
I hate your kind of people. You are always ciphering out how much a man's health is injured, and how much his intellect is impaired, and how many pitiful dollars and cents he wastes in the course of ninety-two years' indulgence in the fatal practice of smoking; and in the equally fatal practice of drinking coffee; and in playing billiards occasionally; and in taking a glass of wine at dinner, etc., etc., etc. And you are always figuring out how many women have been burned to death because of the dangerous fashion of wearing expansive hoops, etc., etc., etc. You never see but one side of the question.
You are blind to the fact that most old men in America smoke and drink coffee, although, according to your theory, they ought to have died young; and that hearty old Englishmen drink wine and survive it, and portly old Dutchmen both drink and smoke freely, and yet grow older and fatter all the time. And you never try to find out how much solid comfort, relaxation and enjoyment a man derives from smoking in the course of a lifetime, (and which is worth ten times the money he would save by letting it alone,) nor the appalling aggregate of happiness lost in a lifetime by your kind of people from not  smoking. Of course you can save money by denying yourself all these little vicious enjoyments for fifty years, but then what can you do with it? -what use can you put it to? Money can't save your infinitesimal soul; all the use that money can be put to is to purchase comfort and enjoyment in this life -therefore, as you are an enemy to comfort and enjoyment, where is the use in accumulating cash?
It won't do for you to say that you can use it to better purpose in furnishing a good table, and in charities, and in supporting tract societies, because you know yourself that you people who have no petty vices are never known to give away a cent, and that you stint yourselves so in the matter of food that you are always feeble and hungry. And you never dare to laugh in the daytime for fear some poor wretch, seeing you in a good humor, will try to borrow a dollar of you; and in church you are always down on your knees when the contribution box comes around; and you always pay your debts in greenbacks, and never give the revenue officers a true statement of your income. Now you know all these things yourself, don't you? Very well, then, what is the use of your stringing out your miserable lives to a lean and withered old age?
What is the use of your saving money that is so utterly worthless to you? In a word, why don't you go off somewhere and die, and not be always trying to seduce people into becoming as "ornery" and unloveable as you are yourselves, by your ceaseless and villainous "moral statistics?" Now I don't approve of dissipation, and I don't indulge in it, either, but I haven't a particle of confidence in a man who has no redeeming petty vices whatever, and so I don't want to hear from you any more. I think you are the very same man who read me a long lecture, last week, about the degrading vice of smoking cigars, and then came back, in my absence, with your vile, reprehensible fire-proof gloves on, and carried off my beautiful parlor stove.

Assorted Links

  • The journal Agricultural and Applied Economic Perspectives just released a new issue with several interesting papers.  Here are some excerpts of a few of the papers.

Our major findings are as follows: (1) if dietary requirements do not increase by more than 20% from the current level, crop yields from current cropland must increase by more than 57% just to meet dietary demand
Exercising short-run oligopsony power is inimical to the long-run interests of buyers in these settings because below-competitive returns will lead to the exodus of resources from input production. Policy proposals grounded in the presumed linkage between concentration, competition, and market power may well be misguided and detrimental to the objectives that proponents seek to advance.
Since U.S. domestic workers are unwilling to do farm work and the United States can feasibly import farm workers from only a few countries in close geographic proximity, the agricultural industry will eventually need to adjust production to use less labor. The decline in foreign labor supply to farms in the United States ultimately will need to be accompanied by farm labor conservation, switching to less labor intensive crops and technologies, and labor management practices that match fewer workers with more farm jobs.

Does Every Food Cause Cancer?

This study in the American Journal of Clinical Nutrition reveals the twin problems of: 1) selectivity bias in the academic publication process (papers finding positive results are more publishable than those finding negative results) and 2) epidemiological studies based on cross-sectional data and simple regression analysis (which confuse correlation with causation).

The study picked 50 common ingredients from random recipes in a cookbook and then scoured the published academic research to see if they could find studies purporting a link with cancer.  Here is what they found:

Forty ingredients (80%) had articles reporting on their cancer risk. Of 264 single-study assessments, 191 (72%) concluded that the tested food was associated with an increased (n = 103) or a decreased (n = 88) risk; 75% of the risk estimates had weak (0.05 > P ≥ 0.001) or no statistical (P > 0.05) significance. Statistically significant results were more likely than nonsignificant findings to be published in the study abstract than in only the full text (P< 0.0001).

Here are the authors in the Washington Post:

"I was constantly amazed at how often claims about associations of specific foods with cancer were made, so I wanted to examine systematically the phenomenon,” e-mails study author John Ioannidis ”I suspected that much of this literature must be wrong. What we see is that almost everything is claimed to be associated with cancer, and a large portion of these claims seem to be wrong indeed.”

For reference, here are the ingredients studied:

veal, salt, pepper spice, flour, egg, bread, pork, butter, tomato, lemon, duck, onion, celery, carrot, parsley, mace, sherry, olive, mushroom, tripe, milk, cheese, coffee, bacon, sugar, lobster, potato, beef, lamb, mustard, nuts, wine, peas, corn, cinnamon, cayenne, orange, tea, rum, and raisin

The conclusion isn't that nothing causes cancer.  Rather, one should be careful over-interpreting the results from one or two studies conducted using correlation analysis.  

The Value of Experts

It is often debated whether "experts" should be the ones that decide how to structure our food health, safety, and quality system.  The standard thought is that people are too busy and distracted to properly consider all the relevant evidence and make an informed decision.  As a specialist (dare I say "expert") myself, it is humbling to read pieces like this that show how wrong we often get it.  It is also useful to keep the following in mind when "experts" forecast the impact of some new food or farm policy.

The interview is with Jeremy Howard who works for a website (Kaggle.com) that pays people for correct predictions.  Here are some interesting bits:

and:

PA: That sounds very different from the traditional approach to building predictive models. How have experts reacted?

JH: The messages are uncomfortable for a lot of people. It's controversial because we're telling them: "Your decades of specialist knowledge are not only useless, they're actually unhelpful; your sophisticated techniques are worse than generic methods." It's difficult for people who are used to that old type of science. They spend so much time discussing whether an idea makes sense. They check the visualizations and noodle over it. That is all actively unhelpful.

PA: Is there any role for expert knowledge?
JH: Some kinds of experts are required early on, for when you're trying to work out what problem you're trying to solve. The expertise you need is strategy expertise in answering these questions.

It does make me wonder about the value of theory relative to trial-and-error empirical methods.