Silent Spring

by Rachel Carson

There is still very limited awareness of the nature of the threat. This is an era of specialists, each of whom sees his own problem and is unaware of or intolerant of the larger frame into which it fits.

Almost immediately the German government recognized the value of these same chemicals as new and devastating weapons in man’s war against his own kind, and the work on them was declared secret. Some became the deadly nerve gases. Others, of closely allied structure, became insecticides.

To an ever-increasing degree, chemicals used for the control of insects, rodents, or unwanted vegetation contribute to these organic pollutants.

When the fish of Clear Lake also were analyzed the picture began to take form—the poison being picked up by the smallest organisms, concentrated and passed on to the larger predators.

It was a house-that-Jack-built sequence, in which the large carnivores had eaten the smaller carnivores, that had eaten the herbivores, that had eaten the plankton, that had absorbed the poison from the water.

The land of the sage is the land of the high western plains and the lower slopes of the mountains that rise above them, a land born of the great uplift of the Rocky Mountain system many millions of years ago.

It was no accident, but rather the result of long ages of experimentation by nature, that the great plains of the West became the land of the sage.

The bitter upland plains, the purple wastes of sage, the wild, swift antelope, and the grouse are then a natural system in perfect balance.

As the chemical penetrated the soil the poisoned beetle grubs crawled out on the surface of the ground, where they remained for some time before they died, attractive to insect-eating birds.

For other birds, too, the once beneficial rain had been changed, through the evil power of the poison introduced into their world, into an agent of destruction.

Evidently some spray had drifted across the road into the pasture, for the sheep began to show symptoms of intoxication almost at once . . . They lost interest in food and displayed extreme restlessness, following the pasture fence around and around apparently searching for a way out

These insecticides are not selective poisons; they do not single out the one species of which we desire to be rid. Each of them is used for the simple reason that it is a deadly poison.

By acquiescing in an act that can cause such suffering to a living creature, who among us is not diminished as a human being?

In England the major problem seems to be a specialized one, linked with the growing practice of treating seed with insecticides before sowing. Seed treatment is not a wholly new thing, but in earlier years the chemicals principally used were fungicides.

Then about 1956 there was a change to dual-purpose treatment; in addition to a fungicide, dieldrin, aldrin, or heptachlor was added to combat soil insects.

Deaths were heaviest in the same counties from which sparrow hawks, kestrels, and other birds of prey virtually disappeared, suggesting that the poison was spreading through the food chain, reaching out from the seed eaters to the furred and feathered carnivores.

This is not surprising, because in time of physiological stress the organism, be it fish or man, draws on stored fat for energy. This exposes it to the full lethal effect of the DDT stored in the tissues.

It is human nature to shrug off what may seem to us a vague threat of future disaster. “Men are naturally most impressed by diseases which have obvious manifestations,” says a wise physician, Dr. René Dubos, “yet some of their worst enemies creep on them unobtrusively.”

When one is concerned with the mysterious and wonderful functioning of the human body, cause and effect are seldom simple and easily demonstrated relationships. They may be widely separated both in space and time.

To discover the agent of disease and death depends on a patient piecing together of many seemingly distinct and unrelated facts developed through a vast amount of research in widely separated fields.

The lack of sufficiently delicate methods to detect injury before symptoms appear is one of the great unsolved problems in medicine.

The whole problem of pesticide poisoning is enormously complicated by the fact that a human being, unlike a laboratory animal living under rigidly controlled conditions, is never exposed to one chemical alone. Between the major groups of insecticides, and between them and other chemicals, there are interactions that have serious potentials. Whether released into soil or water or a man’s blood, these unrelated chemicals do not remain segregated; there are mysterious and unseen changes by which one alters the power of another for harm.

The ultimate work of energy production is accomplished not in any specialized organ but in every cell of the body. A living cell, like a flame, burns fuel to produce the energy on which life depends. The analogy is more poetic than precise, for the cell accomplishes its “burning” with only the moderate heat of the body’s normal temperature. Yet all these billions of gently burning little fires spark the energy of life.

Knowing that DDT and other (perhaps all) chlorinated hydrocarbons stop the energy-producing cycle by inactivating a specific enzyme or uncoupling the energy-producing mechanism, it is hard to see how any egg so loaded with residues could complete the complex process of development: the infinite number of cell divisions, the elaboration of tissues and organs, the synthesis of vital substances that in the end produce a living creature. All this requires vast amounts of energy—the little packets of ATP which the turning of the metabolic wheel alone can produce.

The history of cancer is long, but our recognition of the agents that produce it has been slow to mature. The first awareness that external or environmental agents could produce malignant change dawned in the mind of a London physician nearly two centuries ago. In 1775 Sir Percivall Pott declared that the scrotal cancer so common among chimney sweeps must be caused by the soot that accumulated on their bodies. He could not furnish the “proof” we would demand today, but modern research methods have now isolated the deadly chemical in soot and proved the correctness of his perception.

According to the mutation theory of the origin of cancer, a cell, perhaps under the influence of radiation or of a chemical, develops a mutation that allows it to escape the controls the body normally asserts over cell division. It is therefore able to multiply in a wild and unregulated manner.

This situation also explains the otherwise mystifying fact that certain outstanding entomologists are among the leading advocates of chemical control. Inquiry into the background of some of these men reveals that their entire research program is supported by the chemical industry.

“We must change our philosophy, abandon our attitude of human superiority and admit that in many cases in natural environments we find ways and means of limiting populations of organisms in a more economical way than we can do it ourselves.”

It need have surprised no one with even the simplest knowledge of insects or of the dynamics of animal populations that within a matter of a very few years an ugly and dangerous problem had clearly defined itself.

The world has heard much of the triumphant war against disease through the control of insect vectors of infection, but it has heard little of the other side of the story—the defeats, the short-lived triumphs that now strongly support the alarming view that the insect enemy has been made actually stronger by our efforts.

Silent Spring continues to be worthy of our attention because it marks an important moment in history, just as Harriet Beecher Stowe’s Uncle Tom’s Cabin and John Muir’s Our National Parks do.