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Fables About Toxic Substances

Without the use of massive quantities of pesticides, starvation would stalk the planet.

The truth is that we are already using far too great a tonnage of pesticides for the results achieved. Humanity now applies about 2.5 million tons of synthetic pesticides worldwide each year, and pesticide production is a multibillion dollar industry. Yet pests and spoilage still destroy about 25 to 50 percent of crops before and after harvest. That proportion, if anything, is higher than average crop losses before synthetic pesticides were widely introduced after World War II.

The strategy of large-scale broadcast spraying of pesticides has proven a poor one-except from the standpoint of petrochemical-company profits. An important reason for this lack of success is the rapidity with which pest populations evolve resistance: aided by short generation times and large populations, more than 500 species of insects and mites no longer respond to pesticides, and resistance to herbicides has been noted in more than 100 species of weeds and 150 species of plant pathogens.

Moreover, only a small proportion of the pesticides applied to fields ever actually reaches the target pest. For instance, of those delivered by aerial crop dusters, some 50 to 75 percent miss the target area and less than 0.1 percent may actually reach the pest. The remainder by definition is an environmental contaminant that can injure people and non-target species and in some cases migrate to the far reaches of the globe.

Yet in most cases, pests can be effectively controlled without heavy application of pesticides by using more biologically based methods. Known as integrated pest management (IPM), this approach involves various strategies such as encouraging natural enemies of pests, developing and planting pest-resistant strains of crops, fallowing, mixed cropping, destroying crop wastes where pests shelter, as well as some use of pesticides. IPM is generally vastly superior to chemical-based pest-control methods from both economic and environmental perspectives.

Indonesia, for example, has had remarkable success with IPM. In 1986, responding to the failure to chemically control the brown planthopper, a presidential decree banned 57 of 66 pesticides used on rice. Pesticide subsidies, which were as high as 80 percent, were phased out over two years, and some of the resources saved were diverted into IPM. Since then, more than 250,000 farmers have been trained in IPM techniques, insecticide use has plunged by 60 percent, the rice harvest has risen more than 15 percent, and farmers and the Indonesian treasury have saved more than $1 billion.

Pesticide use no doubt could be greatly reduced everywhere by wider adoption of IPM, which relies on synthetic pesticides as a scalpel only when needed rather than a bludgeon. Relaxing cosmetic standards on foods (such as allowing signs of minor insect damage) might also lead to reductions in pesticide use, as could the recent shift in public preferences toward “organically grown” foods. In fact, Americans increasingly distrust toxic chemicals, as is indicated by soaring sales of organically grown fruits and vegetables, which doubled to $7.6 billion from 1989 to 1994.

Overall, pesticide use in the United States could be reduced by 50 percent for a negligible increase (less than 1 percent) in food prices, according to calculations made in 1991 by the authors of the Handbook of Pest Management in Agriculture. Such a reduction could prove to be a great bargain if, as some scientists think, exposure to pesticide residues can impair the human immune system. And in view of today’s deteriorating epidemiological environment, in which new diseases are emerging and drug-resistant strains of bacteria are causing resurgences of diseases once believed conquered, any loss of immune function should be taken seriously.

Exposure to dioxin is now considered by some experts to be no more risky than spending a week sunbathing.

Of course, with the increase in ultraviolet radiation reaching the earth’s surface because of depletion of the ozone shield, a week of sunbathing is hardly a risk-free activity. But, more seriously, despite a recent barrage of misinformation, plenty of evidence shows that dioxin is a very dangerous chemical, especially in one of its more common forms, known by its chemical shorthand as TCDD.

Dioxin is a byproduct of the combustion of chlorine-containing substances-which are commonly formed when plastics are burned in incinerators and during the manufacture of the herbicide 2,4,5-T-and used in some industrial processes such as bleaching paper. People can absorb tiny amounts of dioxin by eating food contaminated by paper containers, by breathing air polluted with emissions from waste incineration, or handling some herbicides or bleached paper products.

Dioxin not only is easily absorbed and persistent in the body, it is also an extremely potent toxin. As little as one billionth of an ounce can cause chloracne (a severe form of acne) and various generalized complaints such as headaches, dizziness, digestive upsets, and pain. Animal studies and epidemiological investigations indicate that larger doses of dioxin can cause some kinds of cancer. Other effects that have been found include liver and kidney problems, stillbirths, birth defects, and immune suppression. And prenatal exposure to dioxin appears to have a variety of effects on hormone expression-as observed in laboratory animals and wildlife exposed to TCDD-that are sometimes feminizing, sometimes masculinizing.

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