ENVIRONMENT | Protecting our natural resources
26 May 2008
A Persistent Controversy, a Still Valid Warning
(The following article is taken from the U.S. Department of State publication, Rachel Carson.)
A Persistent Controversy, a Still Valid Warning
By May Berenbaum
Probably few people today remember the best-selling nonfiction book of 1962 despite the scandal that surrounded it. The book, a diet guide titled Calories Don't Count, sold more than two million copies. Its author, Herman Taller, was spectacularly convicted of mail fraud, drug violations, and conspiracy charges five years later over unsubstantiated claims regarding the efficacy of safflower-oil capsules in mitigating the effects of unfettered carbohydrate-free calorie intake.
Although it didn't sell nearly as well, another nonfiction book published that year has had a much more lasting impact; its title, Silent Spring, is recognizable today, and its author, already in 1962 a best-selling popular science writer, remains a household name 43 years after her death. Among the book's legacies are heightened public concern about the environmental consequences of pesticide abuse, including strengthened opposition to one pesticide in particular, the chlorinated hydrocarbon DDT, and more broadly a revitalized and empowered environmental movement.
The book's core message – that over-reliance on a particular pest-control strategy could have adverse environmental effects – was hardly novel. Indeed, it was well documented in the entomological journals of the time. But Carson, an inspired and gifted writer, explained this idea in terms the general public could comprehend and, more importantly, feel. Spraying to eliminate insects or other target species, she explained, also kills birds and other nontarget organisms, even as the target species evolves resistance to the chemicals. Although aimed at a crop pest, a pesticide can inadvertently contaminate earthworms, which in turn if eaten in sufficient quantity can kill robins. Without birdsong, a Silent Spring ensues.
The public took her words to heart. Less than a year after Silent Spring first appeared serialized in the New Yorker magazine, more than 40 bills aimed at controlling use of DDT and other synthetic organic insecticides had been introduced in state legislatures across the United States. In 1972, eight years after Carson's death, the newly established Environmental Protection Agency banned the domestic use of DDT.
Message Misunderstood
Silent Spring quickly proved a controversial book. The pesticide industry and other supporters of chemical controls of pests reacted swiftly and negatively to its publication. They branded Carson an irresponsible hysteric whose extremist views and selective presentation of scientific evidence threatened the health and welfare of the nation.
Even today Rachel Carson's name is a lightning rod for chemical pesticide supporters. Recent efforts to reintroduce DDT to control disease-carrying mosquitoes in malaria-ravaged parts of Africa have returned Silent Spring to center stage. The resulting often intemperate debate eerily mirrors the controversies of a half-century ago.
Oddly enough, many people on both sides of the debate still don't quite understand the central message of Silent Spring. Carson was no lover of mosquitoes, or of insects in general, and in fact never advocated abandoning chemical control methods. On page 12 of Silent Spring she unambiguously writes, “It is not my contention that chemical insecticides must never be used. I do contend that we have put poisonous and biologically potent chemicals indiscriminately into the hands of persons largely or wholly ignorant of their potential for harm.”
Indeed, in the context of malaria control, she argued that DDT users should “spray as little as you possibly can” rather than “spray to the limit of your capacity.”
Silent Spring was no extremist tract arguing for a chemical-free natural paradise; it was a compelling plea for “sparing, selective and intelligent use of chemicals,” as she wrote less famously in a 1963 article in Audubon magazine.
This “informed use” approach today underlies “integrated pest management” (IPM), the prevailing approach for controlling pests of all descriptions. IPM, as the name suggests, integrates a number of useful strategies – chemical, cultural, and biological – into an ecologically sound, socially acceptable, and economically viable program.
Carson's message was one of moderation. It was hardly radical – indeed its origins date back to ancient Greece – but it should resonate today in any discussion of environmental technology. For that matter, it applies equally well to ongoing and still controversial discussions of calories and weight control.
Research Continues
In the half-century since Silent Spring first appeared, knowledge of the toxicological and environmental effects of synthetic organic insecticides has grown, much of it acquired in studies inspired by Carson and those who embraced her message. DDT, the first and by far the most infamous of the chlorinated hydrocarbons, remains both newsworthy and controversial.
As it turns out, the causative links between DDT and cancer asserted by Carson have proved difficult to confirm, but cancers for which a causative factor has been definitively documented, such as lung cancer and smoking, remain the exception. As for ecosystem effects, epidemiological and animal studies have confirmed links between DDT exposure and reproductive disorders, although DDT is hardly alone in this attribute; new, more sophisticated analyses have revealed that many synthetic compounds and naturally occurring compounds disrupt human endocrine function.
Insect resistance to DDT, a major problem pointed out by Carson, and often forgotten in reexaminations of her central thesis, remains a problem a half-century later, even where DDT has not been used in years. This resistance can render DDT use ineffectual, as it already did in Carson's era for many different insect species. But then again, insects have evolved similar resistance against just about every other form of pest control, including crop rotation. And some new findings about DDT have even softened its image as the ultimate environmental pollutant; it degrades much more rapidly than expected, for example, in the warm, moist tropical environments where its use to combat malaria is most needed.
One thing about DDT that hasn't changed in the past half-century is its price; it remains one of the cheapest insecticides available. Its relatively low threat of acute toxicity to mammals and its affordability make DDT an appealing alternative for controlling insects that carry human diseases in desperately impoverished and disease-plagued regions of the world.
It's impossible to know what Rachel Carson would say today about the wisdom of re-deploying DDT in areas where other pest control measures have failed miserably, either due to cost, improper use, or resistance. It's likely, though, that whatever she advocated would be based on a careful examination of all of the evidence published since Silent Spring, consistent with her plea for “intelligent use of chemicals.” Whatever her position, it likely would be presented in the same elegant, compelling prose that changed history.
[May Berenbaum is head of the entomology department at University of Illinois, Urbana-Champaign.]
