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Free Study Guide for Silent Spring by Rachel Carson - Book Summary

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CHAPTER 4 - Surface Waters and Underground Seas


Water is the most important of our natural resources and even though it covers the earth, its use for people is limited. Most of it is salt water and, now, more and more it is being contaminated with pollution by pesticides. The pollution of water happens in many forms. It comes from radioactive wastes, from nuclear explosions, from domestic waste, and from chemical sprays. The problem with the chemicals is increased when they are combined. People donít know all the bad effects of chemicals in the environment, yet they continue to use them in massive quantities.

Water purification plants have a hard time detecting what chemicals are in the water. Most of the synthetic chemicals canít be broken down or even identified. Chemicals in rivers are mixing to such a degree that scientists canít even analyze it properly to figure out what the combinations have created. Some chemicals are put in water deliberately to destroy organisms, plants, or unwanted fish. Some seep into the rivers from forest spraying. Most are residues of all the millions of pounds of chemicals put on farmlands. These residues have gotten into the underground water streams and moved slowly to the rivers and into the ocean.

There are many dramatic examples of chemicals found in water supplies. In Pennsylvania, water from an orchard area was tested and found to contain high degrees of insecticides. Water close to cotton fields that were sprayed with insecticides continued to be contaminated even after it was passed through a purifying plant. In Tennessee, the river that had received runoff from fields sprayed with one chemical was so toxic that it killed all the fish inhabiting its streams. Water supplies are usually untested. Chemists who watch the levels of toxicity often donít have the equipment to test for many of the pollutants. The United States Fish and Wildlife Service issued a report in 1960 which found that fish carry pesticides in their fat just like warm blooded animals do. Researchers have found DDT in streams far from spraying and cut off by natural barriers from water that is contaminated by spraying. These streams had to have been contaminated by groundwater, since there was no direct path for the contamination otherwise.

The threat to groundwater is the most disturbing of the water pollution problems. "It is not possible to add pesticides to water anywhere without threatening the purity of water everywhere." Nature doesnít operate in closed and separate compartments. Rain falls and settles into the soil and reaches a zone where there is something like a subterranean sea. Groundwater always moves, but often very slowly. It comes to the surface in some places where it is tapped to feed a water well or where it contributes to streams and rivers. Except for water that enters rivers and steams directly as rain, all the water on earth was once groundwater. Thus, the pollution of groundwater is the pollution of the entire earth.

In one example, poisonous chemicals flowed through the groundwater from a manufacturing plant in Colorado to a farming district miles away. It poisoned wells and made crops and animals die. There was an arsenal near Denver in 1943. After the war, the facilities of the arsenal were leased to a manufacturer of chemical pesticides. Soon, farmers miles from the plant reported strange illnesses in their livestock and extensive crop damage. These farms irrigated by the use of shallow wells. In 1959, the well waters were studied and found to contain many chemicals which had come from the arsenal and traveled through the groundwater. It had taken that water seven or eight years to get to the surrounding farms three miles distant. There was no way to contain or halt the chemicals from spreading further. The strangest discovery on these farms was of a chemical called 2,4-D in some wells. This chemical had never been produced at the arsenal or at the plant. Scientists realized that this chemical had come into being as a result of natural chemical processes operating on the chemicals leaked from the arsenal.

This problem of synthetic chemicals being released into the environment and then being transformed into other chemicals by the natural processes of air, light, and water on them is far reaching. The problem with all the chemicals in the environment at once is that once out there, they combine with other released chemicals to produce something no one ever guessed at. This makes the threat of chemical pollution uncontainable and unpredictable.

Not only groundwater, but streams, rivers and irrigation waters are contaminated. There are some wildlife refuges in California, at Tule Lake and at Lower Klamath. These are linked via water supply to another refuge called Upper Klamath Lake in Oregon. All of these refuges are surrounded by farmlands that use chemical pesticides heavily. In 1960, scientists at one of the refuges found hundreds of dead and dying birds. They were the kind of birds that lived on fish. A test found residues of Toxaphene, DDD, and DDE. The fish that were tested were contaminated with pesticides. Plankton in the lakes were also contaminated.

What are the results of the poisoning of waters set-aside for refuges? Duck hunters will no longer find so many ducks. No one will be able to enjoy the sight of waterfowl flying overhead. These refuges are extremely important strategically for the life of birds. They are resting places for three fourths of all waterfowl that move south in the Pacific Coastal states in the autumn.

Poisoned water also effects the chains of life. Life moves from the smallest life up through larger organisms until it reaches human beings. The best example of this process is the case of Clear Lake, California. It is a lake that is used by people who love to fish and by other resort dwellers. There was one problem with the lake. There was a small gnat that lived there and bothered people by its sheer numbers. The authorities used chlorinated hydrocarbon insecticides to kill the gnats. The particular chemical was called DDD, a relative of DDT. At first the gnats were brought under control, but soon their numbers increased. So the authorities increased the dosage of pesticides. The next winter, a favorite bird of the lake, the western grebe, began to die by the hundreds. Even so, the authorities put even more pesticides into the water to kill the gnats and predictably, more grebes died. Finally, someone examined the fatty tissue of the birds and found extraordinarily high levels of DDD, much higher than was ever put into the water. The reason for the increased level is that the birds eat the fish. Researchers realized that the chemical was picked up by the smallest life form, concentrated, and then passed on the next life form until its concentrations reached the phenomenal levels found in the birds.

The case of Clear Lake taught scientists other valuable lessons about the spread of chemical pesticides. Just after the chemical was dumped into the lake, water tests couldnít pick it up. The reason was not that the chemical had disappeared, but that it had gone into "the fabric of life the lake supports." Even after 23 months, the plankton of the lake still had the chemical in it. All the birds, fish, and frogs examined also had the chemical in them. The nesting colonies of grebes dwindled from more than 100 pairs before the first poisoning to only 30 pairs years after the last poisoning. The California Department of Public Health declared that there was no problem, but nevertheless, it ceased the use of DDD on the lake. Itís useful to realize what DDD does to a body. It destroys part of the adrenal gland, the part called the adrenal cortex which produces cortin. They found that the effect of DDD on dogs was very similar to that occurring in Addisonís disease in humans. Later they found that DDD does affect the human adrenal cortex.

The problems at Clear Lake teach many important lessons. Yet, the poisons are still being dumped into reservoirs. Often authorities want to support recreational use. Fishermen want one kind of fish and so they ask authorities to kill the less desirable fish in a reservoir. The public rarely learns of this solution and doesnít realize itís paying for the later purification of the same water. The use of pesticides in water also produces cancer-causing affects. Cities that receive their drinking supply from contaminated rivers have a higher death rate from cancer.


Carson begins a systematic treatment of all the areas of earthly life that are affected by pesticides. She begins here with the water, what she calls our greatest natural resource. In the previous chapter, she provided a knowledge of the kinds of chemicals being used and how they function. Here, her purpose is to show the widespread use of pesticides and the effects of that use on the environment. Carson is skilled at using a variety of means of persuasion. If the reader doesnít care about the graceful and beautiful birds that are being killed en mass, perhaps the reader will care about the fish that she or he takes home to eat after a day of fishing. She describes the path of a chemical from the tiniest microorganism that has been contaminated to the person who eats the fish freshly killed. She describes the efforts to control agencies to discover the causes of the deaths and mutations, thus making the reader see the difficulties of cleaning up after a mass infusion of poisons into the environment.

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