The Science of Pesticides One of the great insights of Silent Spring is its grasp of the pesticide problem as a compound one. On one hand, there are the intrinsic dangers of these chemicals: their capacity to disrupt basic biological processes, their persistence in the environment, and so forth. But Carson knew that the manner in which a dangerous substance is employed is also crucial. To understand how compounds like DDT and malathion have come to threaten life on a global scale, one has to examine what has been done with them. Each of the major themes of Silent Spring belongs then to one of two lines of argument; the first concerns the raw toxicity of pesticides, the second the recklessness with which they have been employed.

Along with atomic fallout, the synthetic pesticides that came into wide use after World War II are the most dangerous substances man has ever created. The heart of the problem, science has shown, is the pesticides' unique capacity for disrupting critical biological processes like metabolism and cell division. Acute exposure can cause catastrophic systemic problems—paralysis, immune deficiency, sterility, etc.—and small doses repeated over time can lead to grave illnesses like cancer.

Carson attributes this radically disruptive potential to the distinctive molecular structure of synthetic pesticides. Part carbon, they mimic the substances that are crucial to life (enzymes, hormones, etc.) and so gain entrance to sensitive physiological systems. Once inside these vital systems, the elements to which the carbon is bound (chlorine and other deadly materials) wreak havoc on the organism.

Two other properties that increase the hazard of pesticides are, first, the slow rate at which they break down and become less toxic, and, second, their tendency to accumulate in fat tissue. It is these characteristics that make even low-level exposure to pesticides so dangerous. A dose that is too small to cause immediate harm is stored in the body and remains active for a considerable period; with each subsequent exposure the cumulative ‘‘body burden’’ increases, and along with it the chance of serious illness. These properties also put species at the top of the food chain at special risk because they absorb large amounts of pesticide from the lower organisms they consume, a process called "biomagnification."

The Culture of Pesticides Carson takes great pains to show that it is the imprudent use of pesticides, as much as their intrinsic properties, which makes them one of the worst health threats of the twentieth century. Dosing blankets with DDT, spraying densely populated neighborhoods from the air, and pouring pesticide into ponds to kill mosquitoes might have poisoned the planet if not for Silent Spring. From the vantage point of a more environmentally conscious age, it is difficult to understand how such practices could have been so popular. Years ahead of her time, Carson was dumbfounded.

As nearly as Carson could figure, mid-twentieth-century attitudes toward synthetic pesticides were warped by a trio of interacting forces: the chemical industry, government, and what she calls ‘‘Neanderthal science.’’ In calling science ‘‘Neanderthal,’’ she has two characteristics of contemporary methodology in mind. The first is the extraordinarily high degree of specialization. Knowledge might appear to advance at a faster pace along the narrow paths of modern research, but it has also become more fragmented; the entomologist developing a pesticide to control the hungry gypsy moth, for example, is unlikely to know much about the chemical's harmful effects on non-targeted organisms such as birds and fish. The second defect of science, especially in the applied areas, is its habit of conceiving problems in military terms, an outlook it shared...