The War Against Bugs : OUR CHILDREN’S TOXIC LEGACY: How Science and Law Fail to Protect Us From Pesticides.<i> By John Wargo (Yale University Press: $29.95, 380 pp.)</i>

At the core of every environmental debate lies an intractable conflict between scientific uncertainty and presumptive evidence. It explains almost everything about the way liberal democracies protect their environments, whether from resource exploitation, toxic pollution or global phenomena like ozone depletion and climate chaos.

Environmentalists pressure governments to act on evidence that presumes a risk, while regulated industries say to wait for certainty. When the regulated industries out-gun the enviros, as they do in America 10 to 1 with lobbyists and dollars, the result is a regulatory process that presumes great benefits for most technologies and barely keeps pace with their risks.

One of the best models for observing and understanding this bizarre conflict is pesticide management, as John Wargo attests in “Our Children’s Toxic Legacy,” a trenchant critique of America’s 100-year war against insects. The war has not been without its human casualties--innocent victims of friendly fire. But with the exception of a few hundred farm workers who die every year from immediate exposure, pesticide fatalities are delayed for so long that the proximate cause of death can be declared “‘uncertain.” Meanwhile, the benefits of pesticide use, though difficult to quantify, remain obvious and undeniable.

Like so many of our technologies, the upside of pesticides was immediately evident when arsenic-based chemicals were first sprayed on crops during the middle of the last century. Their risks to health and the environment appeared more gradually, and more ambiguously, over the century that followed. Thus, regulatory statutes created to protect human and wildlife from the carcinogens, mutagens and neurotoxins in pesticides were based on risk assessments that were often outdated even before they were signed into law.

As Wargo describes it, both the law and the science governing pesticides in the United States are fractured and inadequate for the task. He calls our 100-year experience with insecticides, herbicides and rodenticides “an act of human experimentation” and excoriates the federal government for allowing “massive exposure to evolve through thousands of disconnected incremental decisions” that have created a “crazy-quilt pattern of regulation.”

He criticizes environmental scientists as well, for underestimating “the diversity of ways that humans encounter and accumulate pesticide residues from exposures to contaminated food, water, air and soil.” And he chides them for their acceptance of one-by-one toxicological studies that skirt the issue of combinations and mixtures of pesticides and other environmental toxins. “Given the sheer number of pesticides that are permitted to contaminate food and water supplies,” Wargo writes, “we will never fully understand the toxicological implications of our exposure to complex mixtures . . . .”

Wargo’s strongest rebuke is reserved for policymakers who disregard “the fact that some people face far higher risks than others.” While his main concern in that regard is for children, who consume disproportionate quantities of many pesticides relative to their body weight, he also points to adult cultures and ethnicities whose food preferences and consumption patterns put them at higher risk.

Regulators, Wargo asserts, have also failed to take into account “the rapid evolution of insect and parasite resistance” that allowed super-strains of mosquitoes and other pests to survive DDT, forcing chemists to develop a stronger and more toxic arsenal of pesticides. Furthermore, “misunderstanding the potential for parasites to rapidly evolve new methods for evading attack by the human immune system, or by anti-malarial drugs,” Wargo believes, “will likely increase world reliance on pesticides as the dominant vector-control strategy.”

The result, he predicts, will be more cancer and neurological disorders and further disruption of human and wildlife endocrine systems. And even now that we are aware of the hazards of pesticide residues, particularly to children, the burden still remains on environmentalists to prove toxicity before a chemical is banned or restricted.

Wargo proposes a new architecture for pesticide risk assessment, management and regulation. At its heart is a challenge to the established federal practice of “risk averaging,” a procedure that focuses on single crop uses of single pesticides and assumes “an average level of food intake across the entire population and an average level of food contamination by pesticide residues.” This, he says, must stop if the government is to protect the public from the most significant hazards of pesticide exposure.

In the end, Wargo believes that it will be a consideration of “moral dimensions”--not science or policy--that will lead to true reform. We will look back from the 21st century, he says, “and wonder about our experimental arrogance, and will search for a moral logic more compelling and sensitive to distributive justice than simple utilitarianism.”

“Our Children’s Toxic Legacy” is a profound, disturbing and well-researched book, though redundant in places and at times difficult to read. Most careful readers who plow through it will come away hoping two things: that Wargo’s prescription for reform is seriously considered by policymakers, and that a less arcane version is written and published for the laity.