Every person on earth is contaminated with dangerous chemicals to one degree or another. Even though, at the time of the writing, synthetic pesticides have only been distributed for twenty years, they have already saturated the human, plant, and animal worlds. They occur in underground streams and they occur in mothers' milk. The industry for making and selling synthetic chemicals has grown enormously. These chemicals came into use by private industry after World War II. They had been used for chemical warfare and scientists discovered that they could be used to kill insects, too. These human-made chemicals differ greatly from naturally occurring chemicals which people used to use to kill unwanted organisms.
The main difference of synthetic pesticides is their power not only to poison but to enter into the body and change its processes. They destroy enzymes of the body, enzymes that are supposed to protect the body. They also block oxidation, thus blocking the body's ability to receive energy. They make organs malfunction. They cause cancer.
Even so, more chemicals are added each year. In the United States from 1947 to 1960 the production of synthetic pesticides increased by five times. It is important to learn about these chemicals we live with.
Most are synthetic, but one organic chemical is still used. It is arsenic. It is used in weed killers and insect killers. From early human history, people used arsenic to kill other people because it is mostly tasteless. It is also present in chimney soot. We know of epidemics of chronic arsenic poisoning in human populations. Arsenic has also killed all kinds of livestock and wildlife. Even so, arsenic is widely used in sprays and dusts around the house. It was used to kill insects on cotton in the south and as a result, the bee keeping industry all but died because the bees all but died. Farmers have long used arsenic formulas to dust crops and farmers have long gotten sick and died from this practice. Dusters and sprayers use arsenical insecticides with supreme carelessness for the ways this chemical gets carried to surrounding areas.
However deadly arsenic is, synthetic insecticides are much more so. One of these is DDT. It is one of a group of chemicals called chlorinated hydrocarbons. A second kind of chemicals is called organic phosphorus insecticides. These chemicals are built on the basis of carbon atoms. Carbon is an atom which has an almost infinite capacity to unite with atoms of other substances. Carbon is found in almost all forms of life and non-life. One kind of organic chemical compound that uses carbon is called methane. It has one carbon atom and four hydrogen atoms. Chemists have realized that they can substitute one or more of these hydrogen atoms to make other things. For example, they substitute one atom of chlorine for one hydrogen atom and they make methyl chloride. There are many examples of these simple permutations on the carbon atom, but there are extremely complex ones as well. These kinds of changes are how so many kinds of poisons are produced.
DDT (dichloro-diphenyl-trichloror-ethane) was first created in 1874, but not until 1939 was it used as an insecticide. Now it is used so much that it seems safe to most people. During the war, soldiers, refugees, and prisoners were dusted with it to kill their lice. They didn't get sick immediately, so it was presumed that they would never get sick and that DDT was harmless to people. It was used in powder form then. If DDT were to be dissolved in oil, it would be definitely toxic. The body stores DDT in its fat cells and in its organs. It doesn't just stay in the body in the same proportion as went into the body.
Fat serves as a biological magnifier. It increases the amount of DDT originally deposited. The smallest amount of DDT has been shown to hurt animals that were tested. It inhibited an essential enzyme in the heart muscle; it disintegrated the liver cells, and produced other ill effects in animals tested. Because small amounts of pesticides are accumulated over time and stored all that time and because these pesticides are very slowly excreted, people are under threat of chronic poisoning. Scientists disagree about how much DDT is poisonous, but it is known that the average person is storing potentially harmful amounts.
DDT and other chemicals are passed from one organism to another through links in the food chains. It is common practice, for instance, to dust alfalfa fields with DDT. Alfalfa is fed to chickens. The hens lay eggs which contain DDT. Insecticides have been found in human milk. By this we know that the infant child is receiving regular doses of toxic chemicals. This isn't the child's first exposure. Scientists have found that insecticides freely move across the wall of the placenta.
Chlordane is another chlorinated hydrocarbon. Like that described above, its residues are persistent and it is transmitted across organisms. Its deposits build up in the body in a cumulative way. A scientist in 1950 declared it one of the most toxic of insecticides, yet it is used liberally in lawn treatments. Some people store the chemicals in their bodies for a log time and then are taken with some kind of disorder and some people are struck down almost immediately.
Heptachlor is an ingredient of Chlordane, but it is also marketed separately. It has a high capacity to be stored in fat. It also goes through a change into Heptachlor epode, a more toxic chemical.
There is a special group of hydrocarbons called the chlorinated naphthalene's. They have been found to cause hepatitis and a rare form of liver disease. Workers in the electronic and the agricultural fields have been killed and these hydrocarbons have also killed cattle. There are three chlorinated napthalenes that are the most poisonous: dieldrin, aldrin, and endrin.
Dieldrin is five times as toxic as DDT when swallowed and 40 times as toxic as DDT when absorbed through the skin. People who are poisoned usually go into convulsions. They usually recover slowly and suffer chronic effects. Dieldrin is one of the most widely used insecticides. It has caused an appalling destruction of wildlife. Scientists don't know much about how Dieldrin is stored in the body. They know that it is like a sleeping volcano. Its effects are felt when people go through physical stress in which they have to draw on fat reserves. Scientists learned a lot about it when it was substituted for DDT to fight malarial mosquitoes that had become resistant to DDT. The people who did the spraying had seizures and some died.
Aldrin has the strange quality that it often changes into Dieldrin. If Aldrin is used to spray carrots, for example, tests will not find Aldrin, but will find Dieldrin. It is extremely toxic, causing degeneration of the liver and kidneys. It has harmed and killed many people who handle it in the factories as it is produced. It causes sterility. Even so, Aldrin has been sprayed from airplanes over suburban areas and farmlands.
Endrin is the most toxic of this group. It is five times as poisonous as Dieldrin. It is 15 times as poisonous as DDT to mammals, 30 times as poisonous to fish, and 300 times as poisonous to birds. In one sad case, a child was debilitated when the family had the house sprayed for cockroaches. Even though they took the child out of the house during the spraying and washed the floors afterwards, the child went into convulsions and lost consciousness. The child entered into a vegetative state and remained there for life.
The second group of pesticides is called organic phosphates. People who have to handle these chemicals are at serious risk. Two children in Florida found a bag that had contained one of the organic phosphates. They handled the bag and later died. In another incident, two farm boys were contaminated when their father sprayed a field with one of the organic pesticides. Organic pesticides originated in the 1930s and the German government used them in war.
Organic phosphorus insecticides act on a living organism by destroying enzymes. They target the nervous system. In normal bodies, there is a chemical transmitter which sends impulses from nerve to nerve. Normally, that transmitter disappears after it is used. If it doesn't the body becomes uncoordinated and suffers spasms and convulsions. An enzyme destroys this transmitting chemical as soon as it has done its work, thus protecting the body. Organic phosphorus insecticides kill this enzyme so the body builds up a dangerous amount of the transmitting chemical.
Parathion is one of the most used organic phosphates. Honeybees become extremely agitated and then die upon exposure to it. One chemist tried to test its danger and swallowed a minute amount. Before he could reach for the antidote, he died. The rate of death by Parathion is startling. Even so, 7 million pounds of it is being applied to fields and orchards in the United States. Parathion decomposes fairly quickly. However, it is not quickly enough for farm workers to be safe.
Malathion is another organic phosphate. It is used very widely by gardeners and in households as an insecticide. It is considered to be the safest of its group of chemicals. It is considered so because the human liver has an enzyme that renders it harmless. However, if something happens to that enzyme, the person exposed is poisoned. The Food and Drug Administration discovered that when Malathion and other chemicals are administered at the same time, there is massive poisoning. This discovery made scientists begin to explore what happens when other kinds of chemicals are combined. They found out many pairs of these chemicals are much more poisonous. The two chemicals don't have to be administered at the same time. If a person is exposed to one and then to the other, the combination of the two is effective. They've even found that an organic phosphate is made even more toxic when it is combined with a chemical that is normally considered harmless.
There is a sorceress in Greek mythology named Medea. When her husband betrayed her and decided to marry another woman for political gain, she sent his bride a poisoned gown. When the bride put it on, she suffered a horrible death. There are chemicals now being produced that act like this robe. They convert plants and animals into a sort of Medea's robe so that they will kill the insects that come to eat them. These are called systemic insecticides. They have used it one wheat, so that the wheat is poisonous to aphids. A systemic insecticide permeates all the tissues of a plant or animal and makes them toxic. Farmers also use systemics by applying them directly to seeds so that they will produce seedlings that are poisonous to insects. This has proven extremely dangerous for farm workers who have to handle these seeds and the plants that grow from them. Soon, Carson predicts, dogs will be given a systemic insecticide so that any flea that bites them will die. She wonders if people will some day be given a systemic to kill mosquitoes.
There are also problems with the war against weeds. Herbicides are the chemicals that are used to kill weeds. It is not true that herbicides are only toxic to plants, not animals. These chemicals also act on animal tissue. One weed killer is arsenic. Arsenic has been sprayed on roadsides and has killed cattle. They have made water unsuitable for swimming or fishing. Another kind of herbicide is a group of chemicals called "dinitro" compounds. They are some of the most dangerous in use in the U.S. They are a strong metabolic stimulant. Once, people even used it to lose weight. Several people died from it. Another one is called Pentachlorophenol, and it is used as a weed killer. It has killed people who handle it. One of the more safe-sounding weed killers is called Aminotriazole or amitrol. It is used very widely, but has been shown to cause malignant tumors of the thyroid. Some herbicides are classified as "mutagens." They cause problems in the next generations of organisms that are exposed to them.
Here, Carson describes the main chemical poisons which are used often in the world. It can be a difficult chapter to read since it includes scientific descriptions of the properties of the chemicals and their action. Carson makes it as simple as possible without oversimplifying. She describes the chemical, indicates how widespread is its use, and then often gives anecdotes detailing its dangers for human beings.