Common Sense about Pesticides

by Dave Kopel

Relix magazine, 1992

Given the choice, would you prefer to be struck by lightening for a couple seconds, or to stick your hand in a household electrical outlet for the same amount of time? If you prefer being struck by lightening because it's "natural," then you're eminently suited to lead the current campaign to outlaw pesticides.

Pesticides have a lot of things wrong with them: After being applied to the land, they move through groundwater and into lakes and streams. As they pass through the plant and animal food chain, they can sometimes cause devastating effects on animal species, especially birds. Some vicious farmers spray pesticides while migrant workers are in the fields below, thereby dosing the workers which huge quantities of chemicals that are, after all, designed to kill.

But in very large part, current efforts to abolish pesticides focus on the alleged danger that pesticides pose to consumers. Pesticides must be totally outlawed, we are told, because trace pesticides in crops grown for human consumption pose a grave consumer health risk.

Years ago, Congress bought into the total prohibition theory by enacting the Delaney Amendment, which outlaws the use of any pesticide which leaves residues in food, if the residues pose any risk of cancer at all, no matter how small. After years of evasion, the federal government may soon be forced to start implementing the Delaney Amendment by a recent federal court of appeals decision.

Common sense to avoid any contact with food that contains even the slightest amount of pesticides? Not at all, say scientists like the University of California's Bruce Ames.

To most Americans, nature seems benign. Nature means a walk in the woods, or three days of camping in a wilderness area -- followed by going home to a house with hot water, climate control, and no predators. So great is humanity's ability to shield itself from most natural threats, and so spiritually powerful is nature itself, that we tend to forget what a dangerous place nature is, if you have to live there full time.

The natural world is a constant war of all against all. "Eat or be eaten," as the Firesign Theater put it. In the war for survival, animals try to eat plants, and plants try to kill the animals that eat them. Anyone who's raised a small child in a country environment knows how many plants there are that could kill a small child if they were ingested.

The poisonous plants didn't evolve that way simply out of perversity. Killing something that's eating you is a good way to live longer -- especially if you're a plant, and can't run away.

Because human manufacturers of pesticides have to comply with federal laws, almost all man-made pesticides have been tested for carcinogenity. In studies of laboratory rodents exposed to extremely high doses, about half of all man-made pesticides are found to be carcinogenic.

Plants (fortunately) aren't subject to federal law, and have been producing their own pesticides for hundreds of millions of years. Since plants (unlike artificial pesticides) don't need to be lab-tested in order to be sold, there's never been much economic incentive to analyze plants for carcinogenity.

Dr. Ames, however, identified 52 natural pesticides, and tested them the same way artificial pesticides are tested: high-dose rodent studies. Of the 52 natural pesticides, 27 caused cancer. The 52 pesticides Ames studied are only a fraction of all natural pesticides, and most plants contain a variety of pesticides. Thus, concludes Ames, "it is probable that almost every fruit and vegetable in the supermarket contains natural plant pesticides that are rodent carcinogens."

Ames' research is consistent with other work finding that high doses of certain foods can cause health problems. Monkeys fed large amounts of alfalfa sprouts develop lupus, an immune system disorder.

Thus, long before artificial pesticides were invented, humans consumed significant amounts of natural pesticides. In today's typical American diet, 99.99% of ingested pesticides (by weight) are natural. The average American eats 1 1/2 grams of natural pesticides a day -- about 10,000 times more than the amount of artificial pesticides consumed.

For example, roasted coffee contains 826 volatile chemicals. (Roasting causes the formation of new chemical compounds.) Twenty-one of those coffee chemicals have been tested on rodents, and 16 of those 21 cause cancer. A cup of coffee includes 10 milligrams of carcinogens.

Among the foods highest in natural pesticides are cabbage, collard greens, Brussels sprouts, brown mustard (extremely high), black pepper (also very high), nutmeg, jasmine tea, rosemary, and apples.

Does all this mean that you should give up apples, or abandon a vegetarian diet altogether, since vegetarians consume especially high doses of natural pesticides? Not at all. The anticarcinogenic effects of the vitamins found in fruit likely outweigh the carcinogenic effect of the fruit's natural pesticides.

The vitamin effect is one reason that vegetarians have lower cancer rates, even though they consume higher doses of carcinogenic pesticides. Most fruits and vegetables are also low in fat, which is a major cause of heart disease.

The point is that there's no such thing as a risk-free world. Every choice is a trade-off of one risk for another.

That's why absolutist approaches such as the Delaney Amendment are self-defeating. By focusing so intently on completely eliminating one small risk (cancer from artificial pesticide residues), absolutism causes other risks. Thanks to Delaney, as artificial pesticides are phased out, there will be greater crop losses caused by insects, and fruit and vegetables will become more expensive, and some people will not be able to afford to eat them as often. Since fruit and vegetables are, on the whole, good for you, human health will worsen as food prices rise.

What is perhaps most pernicious about the Delaney Amendment is that it deprives Americans of the choice to control their own bodies. Some folks, who shop at Safeway, are willing to accept minute health risks in order to afford fruit and vegetables. Other folks, who shop at organic groceries, would like to eliminate all exposure to man-made risks, and are willing to pay the higher price that raising food without pesticides entails. The Delaney Amendment, however, takes away the freedom of choice of the first group, and forces them to live like the second group.

Both the Delaney Amendment and consumer demand for plants grown without artificial pesticides encourage the cultivation of plants that manufacture much large doses of their own pesticides. Plants that are able to thrive without humans around to poison their predators take care of the job themselves.

For instance, normal supermarket celery contains 800 parts per billion of psoralens (a natural pesticide, and a carcinogen). A new brand of organic, celery, grown without the aid of artificial pesticides, contains 6,200 ppb psoralens -- nearly eight times as much. Farmworkers who handle large quantities of the organic celery develop skin rashes and burns. By any rational standard of risk assessment, the supermarket celery seems safer to eat than the stuff that burns its handlers.

So if we eat all these pesticides -- both natural and artificial -- why we aren't we dead of cancer already? First of all, some of the pesticides are only carcinogens at extremely high doses. At the much lower doses typical of human consumption, there may be no negative effect at all. By analogy, gigantic doses of sodium chloride (salt) are poisonous; large doses over extended periods can cause high blood pressure; and small doses are chemically necessary for survival.

Second, something that's a carcinogen in rats may not be in humans. Rats are only designed to live for a couple years, while humans are built to live for many decades. Accordingly, humans may have evolved natural resistances to pesticides, while rodents have never needed to.

Third, although many human cells live for years, the cells which suffer the most direct exposure to environmental toxins, such as the stomach lining, respiratory system linings, and the skin are constantly being replaced.

Understanding the complex interaction of animals, including human animals, with the natural and synthetic chemicals in the environment is very difficult. Good environmentalism -- and good nutrition -- require that we try to understand these complexities, rather than basing our behavior on simplistic and dangerous absolutism.

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