Rethinking pesticide use

In Nature Wars, Mark L. Winston argues that the public’s equally intense phobias about pests and pesticides often result in irrational pest control decisions. In many situations our hatred of pests leads to unwarranted use of pesticides that poison the environment. In other cases, our fear of pesticides prompts us to let real pest problems grow out of control. Winston’s message is that effective education of public leaders as well as typical homeowners would do much to scale back the war on pests as well as unnecessary pollution.

Winston, professor of biological sciences at Simon Fraser University in British Columbia, Canada, uses a series of well-chosen anecdotes as the primary tool for conveying his message. For example, he tells how a media-fueled battle among scientists, politicians, and environmentalists in Vancouver, British Columbia, almost resulted in a ban on aerial spraying of the bacterial insecticide Bt. The spraying was aimed at eliminating a 1991 gypsy moth infestation that threatened lumber exports to the United States. To allay public concerns, the government chose a product widely used by organic farmers. But a few environmental groups, armed with one report of a harmless Bt bacteria isolated from a patient with an eye lesion, convinced many citizens that they and their children would be sprayed with harmful bacteria. The battle over spraying went on for months.

Although some Vancouver citizens were ready to risk their lumber industry to avoid the Bt spraying, others didn’t seem at all concerned about having hard-core insecticides sprayed inside their homes. A number of exterminators interviewed by Winston said they advised clients to use slow-acting alternatives to insecticides but were bluntly rebuffed. The customers wanted every roach gone by yesterday.

How serious a problem are the chemical tactics used to battle roaches versus the pests themselves? Winston reports that about one-quarter of all U.S. homes are treated for roaches and that 15 percent of all poisonings from five major insecticides (including those used on roaches) occur in homes. Scientific evidence, on the other hand, indicates that low levels of roach infestations do not cause disease to be transmitted. (The most serious concern is allergenicity for some individuals.)

Winston’s point in illustrating this contrast is basic: As long as people don’t have to come face to face with pests, they hate insecticides and are ready to believe that farmers and public officials are allowing the air, water, and food supply to be poisoned. But when a roach or spider is spotted in a kitchen, concern over cancer and the environment often seems to vanish. Because we don’t know how much Raid it takes to kill a spider, we buy the large can. And if we call the exterminator, we want quick service, although many of us would prefer that the technician show up in an unmarked car.

Rational pest control?

Because of this schizophrenic response by the public to pests and pesticides, Winston argues that it will be difficult to institute rational pest management programs. Effective public education is critical to progress on this front, he believes, and there is evidence that education can work. Farmers once sprayed pesticides on crops without even checking to see if a pest was present. But during the past 25 years, the U.S. Agricultural Extension Service has taught many farmers how to use integrated pest management (IPM). In its purest form, IPM involves determining why a pest problem exists and what combination of changes in a farming system, including pesticide use, would reduce the problem with the lowest environmental and economic costs. In cases in which specific IPM research and education programs have been practical and based on rigorous data, significant reductions in pesticide use have resulted and farmers have saved money. Unfortunately, IPM programs have received limited funding; many more farmers still need hands-on IPM training. IPM programs will not really flourish until the public has enough education to demand more funding for training programs.

It is widely acknowledged that a negative psychological response to insects is deeply imbedded in Western culture. Winston argues that this response cannot be overcome simply by accumulating more scientific data. In the short run, he says, money spent on good public relations efforts may be much more useful in establishing rational pest control programs than money spent on research. For example, Winston believes that without the public education campaign launched by the government of British Columbia, the environmentally benign gypsy moth spraying program would ultimately have crashed and burned.

Also imbedded in modern Western culture is a general distrust of technology. How can anyone trust scientists and government officials who used to say that DDT was safe? Unfortunately, the public, environmentalists, and sometimes even Winston seem too willing to trust scientists who find monumental problems with pesticide technology. Surely there are problems associated with pesticides, but I am concerned that some scientists draw unwarranted conclusions about their magnitude.

Dubious estimate

For example, Winston argues that there is a hidden cost to society of $8 billion per year from pesticide use. He bases this estimate on an analysis by David Pimentel and his Cornell University colleagues in their 1993 book The Pesticide Question. Yet there are problems with how these estimates were made. Pimentel et al. estimate that “pesticide cancers” cost society $700 million annually, a figure derived from an unpublished study that concluded that less than 1 percent of the nation’s cancer cases are caused by pesticides. Pimentel and his colleagues base their calculation on the assumption that 1 percent of people get cancer from pesticides, but they could just as justifiably have assumed that the number was zero and that there was no cost. They further estimate a $320 million annual loss caused by adverse pesticide effects on honeybees. But this ignores the fact that without the targeted spraying of bees with selective pesticides, the beekeeping industry recently would have been devastated by acarine pests of the bees.

The largest hidden cost revealed by the Pimentel study is from the death of birds in crop fields. The authors “conservatively” estimate that 10 percent of birds in crop fields die because of pesticide use. At an estimated cost to society of $30 per bird, the total cost is $2 billion. But nature doesn’t work that way. Since organochlorine pesticides were banned, reductions in bird populations have been linked to habitat loss, not to the toxicity of pesticides to vertebrates. Why do so many policymakers (and Winston) accept the Pimentel assessment? Maybe because we love to hate pesticides.

Although Winston believes that pesticide use needs to be reduced, he differs from many environmentally concerned citizens and governments in his ideas about how it should be done. He argues that the use of genetically engineered plants such as those that produce a toxin derived from the Bt bacteria would be far preferable to the spraying of chemical pesticides. Yet a large segment of the public has a different attitude. No matter what the data show about the positive attributes of Bt, anything that is genetically engineered can grab a negative sound bite on TV and be translated into a fear-producing fact. Public concern about the potential hazards of genetically engineered crops have halted commercialization in Europe. In the United States, bioengineered plants that target specific pests without damaging beneficial insects are expected to be planted on more than 10 million acres of farmland during the summer of 1998. The worst problem foreseen by U.S. scientists is that insects will rapidly adapt to the Bt toxins and put us back at square one.

In one of the book’s last chapters, “Moving beyond Rachel Carson,” Winston criticizes the Environmental Protection Agency (EPA) for its focus on regulatory protection instead of providing alternatives to pesticides. EPA, he writes, has become bogged down with the Sisyphean task of assessing the impacts of thousands of new pesticides pouring out of the industrial research pipeline.

In addition, Winston argues that since the publication of Silent Spring, most of the research on alternatives has been conducted and assessed by academic researchers who tend to discover “scientifically interesting but impractical alternatives.” If research were conducted and judged by a more diverse group of stakeholders, including farmers, Winston says, more viable alternatives would be developed. Although not mentioned by Winston, this idea is currently being tested in a Department of Agriculture grant program called Sustainable Agricultural Research and Education, which sponsors only research involving both farmers and scientists. Farmers judge the potential utility of each proposed project before it is funded.

Perhaps the most obvious reason why we haven’t replaced pesticides is because they are so damn cheap. Winston says that if the hidden costs of pesticides could be taxed, the alternatives would become more economically appealing. But taxing the environmental and health effects of pesticide use will be a tough battle. Unlike the case of cigarettes, in which rigorous and voluminous data on societal costs have been collected, the United States still does not have good data on pesticide costs. It is amazing that 35 years after Silent Spring was published, the most often quoted estimate is the dubious Pimentel number. I agree with Winston that it would be wonderful if EPA could offer more leadership in developing alternatives to pesticides. However, I also think it would be useful if EPA could offer leadership in determining what the real costs of current pesticide use are, so that we would actually know just how critical it is to replace specific pesticides or change general patterns of pesticide use.