May, 2011

Fruits of Thought

Pesticide Usage Under Attack Again

Yogi Berra is a member of the baseball Hall of Fame; one of only four players to be named Most Valuable Player of the American League three separate times; one of just six managers to lead both an American League and a National League team to the World Series. Many consider him the best catcher in the history of baseball.

Yet he is, perhaps, most well known for his frequent malapropisms, or incorrect use of language. One of his most famous lines came from a time in the early 1960s when Mickey Mantle and Roger Marris seemed to constantly be hitting back to back home runs and Yogi declared that it was “déjà vu all over again.”

Those active in the produce industry for the past few decades are bound to start thinking about Yogi and that feeling of déjà vu all over again. With the release of a study by Brenda Eskenazi and various colleagues from the University of California at Berkley in a journal titled, Environmental Health Perspectives, proclaiming that there is a link between maternal exposure to pesticides — specifically organophosphate pesticides — and lower intelligence — specifically seven points lower on IQ tests given to the children when they reached seven years of age — the focus of activist interest in the produce industry is transitioning away from the pathogen concerns of the past few years to a new focus on pesticides.

This particular study is very weak and really tells nothing about the issue of eating fresh produce. The researchers did several studies, but the key one was a birth-cohort study drawn from a group of mostly Latino farm workers in an agricultural community in California. Right away, this means that whatever the issue might be regarding pesticides, it is more likely an issue related to those who have far greater exposure to pesticides — for example farm workers — than it is related to consumption of fresh produce.

Even on the issue of how pesticides affect the IQ of farm worker children, the research leaves much to be desired. We have extensive and well-documented research indicating that many variables can impact intelligence — use of drugs, consumption of alcohol, smoking, etc. — yet the study makes no attempt to control for these variables.

Strangely, though the researchers did adjust for the mother’s IQ and education, they did not adjust for the IQ or education of the father. This is odd. The fact the researchers made the adjustments on the maternal side clearly indicates that they thought it relevant, but there is no theory of genetics that holds that intelligence is only inherited down the maternal line.

The study was built around a urine analysis seeking metabolites of organophosphate — a metabolite is a substance produced as the body’s metabolism processes another substance. Yet this methodology does not establish any connection with any actual pesticide, much less with pesticide consumption on fruits and vegetables. In fact, the study clearly states: “These six metabolites cannot be traced back to individual pesticides...”

The researchers also decided to add in numbers when none exist. For example, there are limits in the ability to detect things in lab tests. That means we don’t know if the particular substance is present or not, or in what amount it is present if it is there at all, except to say that it is below the level of detectability. These researchers, perhaps looking to put a thumb on the scale, decided to impute the existence of these unknown and undetectable substances:

“Concentrations below the limit of detection (LOD) were randomly imputed based on a log-normal probability distribution whose parameters were estimated using maximum likelihood estimation.”

In other words, the results are phony and include imputed amounts that we don’t know exist.

Finally, the study authors have to acknowledge that “...children’s urinary DAP concentrations were not consistently associated with cognitive scores.” DAP stands for dialkyl phosphate, the key metabolite that was being studied. So the thesis is that children’s level of this metabolite — collected at six months, 1, 2, 31⁄2 and 5 years of age — has no impact on IQ scores and thus cognitive function, but that being the child of a mother in the highest quintile of organophosphate metabolite concentration causes a seven point differential, on the negative side, in IQ scores at age seven.

Of course, none of this may matter at all. Within moments of releasing the study, it was picked up by countless Web sites and publications with scary headline such as, “Pesticides Make Us Dumber,” and various talking heads were giving advice, such as urging people to consume only organically grown fruits and vegetables — although the study did not apply to men at all, nor to post-menopausal women and was dubious regarding any impact at all from consumption of produce.

Years ago, I would travel the country to speak and the focus was all on pesticides. I warned all my audiences that the real issue was pathogens. Now, like déjà vu all over again, we have studies like this, combining with enthusiasm for the “precautionary principle,” or the belief that if something can possibly have a bad impact, we shouldn’t do it. And now we will see a new focus on pesticides.

Of course, the real issue isn’t just the safety of pesticides; the real issue is the alternative. First, by focusing on one class of pesticides and one theorized side effect, we can’t know if eliminating this class of pesticides would be a net good or bad — that can only be done by comparing this class of chemicals to an alternative. Second, in a world without pesticides, we would have trouble raising enough food to feed the people of world. The implications of such a problem are chilling.                                                  pb