May 23, 2024
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Linking Northern and Central NJ, Bronx, Manhattan, Westchester and CT

Testing Cottonseed Oil for Pesticides

Spoiler alert: Cottonseed oil appears to be safe, as far as pesticide levels are concerned, from the results of a single test I did. But additional testing would raise my confidence level. There. Now you don’t have to read the rest of this article.

I remember about five decades ago a small scandal erupted regarding pesticide levels found in cottonseed oil. The problem stemmed from how cotton was grown—not as a food crop, and therefore not subject to the same rules and restrictions in the use of pesticides that normally applied to food crops. What was more, it was thought that cotton tended to concentrate various compounds and residues, such as pesticides, in its seeds. When these seeds were treated to express their oil, the pesticides came out along with the oil. So the combination of cotton grown with high exposure to pesticides, and oil derived from the seeds, led to extraordinarily high pesticide levels in cottonseed oil.

But, to repeat, all this was several decades ago. Changes were made to the industry to mitigate this problem. Today, cottonseed oil is now processed in a way that probably removes most or all of any pesticides. (This may be, in part, because raw cottonseed oil contains a component called gossypol, which is toxic, and the current methods of removing gossypol might also rid the oil of many other undesired impurities.)

Nevertheless, I decided to test a single sample of this year’s Passover cottonseed oil from my supermarket. I bought it, sent out a sample as soon as it appeared on supermarket shelves, and I recently got an answer from the lab. The results of a battery of screening tests for nearly 500 of the most commonly used pesticides and herbicides showed no detectable levels of any of them, within the limits of the lab’s ability to detect them. That was a welcome result.

Needless to say, those 500 pesticides are an alphabet soup of things I’d never heard of, as well as familiar ones such as pyrethrins, parathions, DDTs, dicloran, permethrin, etc. that you may have heard of. Each pesticide in that test has its own “Limit of Quantitation,” meaning the lowest level at which that chemical can reliably be detected by the test. For most pesticides, that level is on the order of 0.01 mg/kg, which is a fairly low level.

I still had to judge whether the lab’s tests were sufficiently sensitive compared with “safe” levels for these pesticides. Without getting into too much detail, for several of those 500 chemicals tested, I have looked up the levels considered terribly dangerous to ingest (technically called LD50 values), and this lab’s tests seemed sensitive enough, considering those LD50 values. For example, supposing a pesticide were present just barely below the detectable threshold: a typical adult would have to ingest 800 gallons or more of oil, to reach that LD50 level in their body. That seems safe —nobody is going to ingest anywhere near 800 gallons of oil during Pesach!

But I am not completely reassured as regards to public health in general. With many or most chemicals, our bodies are able to completely neutralize toxins quickly if the levels we ingest are low. But, with some chemicals (typically carcinogens), the danger might be proportional to the dosage, even in small amounts. That means the danger to one individual might be absolutely minimal, but the risks to the community as a whole might add up. Assuming that 500,000 Pesach-observers are using cottonseed oil for a full week every year, I cannot yet be certain that the tests for all these pesticides are perfectly reassuring. I feel the need to find laboratories that can do more sensitive testing.

Testing like this can be rather expensive, costing between $350 and $1,500 per sample, so for this initial project I chose to do only a single battery of tests, from a single laboratory (Columbia Laboratories, owned by Tentamus) which I found via a government-approved list of testing sites. I took a sample of pure cottonseed oil from one of the major Passover retailers. (I see no need to reveal the name of the company, and indeed, I would not have revealed it even if tests came back positive, there being so many ethical considerations at stake in such a preliminary stage.) Ideally, several samples should be obtained, from different retailers and from products besides pure oil, such mayonnaise, that are largely made from cottonseed oil. At least some samples should be sent to more than one lab for comparison between laboratories.

I would like to make a few additional comments. First, if you wish to support my process of spot-checking cottonseed oils, I have created a GoFundMe.com page, “Cottonseed Oil Testing,” where you may donate. My goals would be (1) confirming these initial results by sending samples to a second lab, (2) after-the-fact checking on this year’s cottonseed oil crop by testing samples from a few more products, and (3) similar testing in future years. I would suggest, however, that a professional chemist would be a far better person for such a project than an amateur like me. Perhaps some Jewish organization could get involved.

Second, if anyone wishes to avoid cottonseed oil despite these preliminary results indicating its use is likely quite safe, there are two simple things you can do: first, try to rely on olive oil, safflower oil, avocado oil, a nut oil, etc. Second, try making your own mayonnaise. After many years of doing this each Pesach, I’ve found one method that is reliable, easy, and fun: use an immersion blender with a jar that is just barely wider than it. Recipes abound on the internet, for example: into the narrow jar put a raw egg, then 1 cup mild oil (e.g. safflower), 1 Tbsp lemon juice, 1 Tbsp vinegar, 1/2 tsp kosher salt, 1 tsp wet mustard (optional). A few seconds’ blending will give you fresh mayonnaise. But this year, I’ve decided to buy a jar of mayonnaise!

Finally, I wish to gently mention corn oil, which is kitniyot. The decision to include New World foods such as corn in the category of kitniot is less than 600 years old (counting from 1492), and therefore has not yet acquired the force of minhag. So if any influential halachic authority were able to reverse the decision that declared corn to be kitniot, it would have to be done within the next few decades. After that, it will be too late.


Dan Dyckman received his M.D. from Brown University in 1984, followed by an internship year in a Connecticut hospital, a Masters Degree in Biostatistics from the Harvard School of Public Health in 1987, and a Computer Science degree from U.C.Berkeley in 1991. He is now retired.

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