The general public often construes the word "chemical" to mean a harmful synthetic substance. In fact, however, the term applies to any element or compound, either natural or synthetic. The thousands of compounds that make up the human body are all chemicals, as are the products of scientific research. A more accurate description, however, can be found in the dictionary. Thus, aspirin is a chemical by this definition, since it is the product of a series of chemical reactions.
The story of chemicals began with the rise of human society. Indeed, early stages of human history, such as the Iron, Copper , and Bronze Ages reflect humans' ability to produce important new materials. In the first two eras, people learned how to purify and use pure metals. In the third case, they discovered how to combine two to make an alloy with distinctive properties.
The history of ancient civilizations is filled with examples of men and women adapting natural resources for their own uses. Egyptians of the eighteenth dynasty (1700–1500 B.C.), for example, knew how to use cobalt compounds to glaze pottery and glass. They had also developed techniques for making and using a variety of dyes.
Over the next 3,000 years, humans expanded and improved their abilities to manipulate natural chemicals. Then, in the 1850s, a remarkable breakthrough occurred. A discovery by young British scientist William Henry Perkin led to the birth of the synthetic chemicals industry.
Perkin's great discovery came about almost by accident, an occurrence that was to become common in the synthetics industry. As an 18-year-old student at England's Royal College of Chemistry, Perkin was looking for an artificial compound that could be used as a quinine substitute. Quinine, the only drug available for the treatment of malaria , was itself in short supply.
Following his teacher's lead, Perkin carried out a number of experiments with compounds extracted from coal tar, the black, sticky sludge obtained when coal is heated in insufficient air. Eventually, he produced a black powder which, when dissolved in alcohol, created a beautiful purple liquid. Struck by the colorful solution, Perkin tried dyeing clothes with it.
His efforts were eventually successful. He went on to mass produce the synthetic dye—mauve, as it was named—and to create an entirely new industry. The years that followed are sometimes referred to as The Mauve Decade because of the many new synthetic products inspired by Perkin's achievement. Some of the great chemists of that era have been memorialized in the names of the products they developed or the companies they established: Adolf von Baeyer (Bayer aspirin), Leo Baekeland (Baekelite plastic), Eleuthère Irénéedu Pont (DuPont Chemical), George Eastman (Eastman 910 adhesive and the Eastman Kodak Company), and Charles Goodyear (Goodyear Rubber ).
Chemists soon learned that from the gooey, ugly byproducts of coal tar, a whole host of new products could be made. Among these products were dyes, medicines, fibers, flavorings, plastics , explosives, and detergents . They found that the other fossil fuels—petroleum and natural gas—could also produce synthetic chemicals.
Today, synthetic chemicals permeate our lives. They are at least as much a part of the environment , if not more, than are natural chemicals. They make life healthier, safer, and more enjoyable. People concerned about the abundance of "chemicals" in our environment should remember that everyone benefits from anti-cancer drugs, pain-killing anesthetics, long-lasting fibers, vivid dyes, sturdy synthetic rubber tires, and dozens of other products. The world would be a much poorer place without them.
Unfortunately, the production, use, and disposal of synthetic chemicals can create problems because they may be persistent and/or hazardous. Persistent means that a substance remains in the environment for a long time: dozens, hundreds, or thousands of years in many cases. Natural products such as wood and paper degrade naturally as they are consumed by microorganisms . Synthetic chemicals, however, have not been around long enough for such microorganisms to evolve.
This leads to the familiar problem of solid waste disposal. Plastics used for bottles, wrappings, containers, and hundreds of other purposes do not decay. As a result, landfills become crowded and communities need new places to dump their trash.
Persistence is even more of a problem if a chemical is hazardous. Some chemicals are a problem, for example, because they are flammable. More commonly, however, a hazardous chemical will adversely affect the health of a plant or animal. It may be (1) toxic, (2) carcinogenic, (3) teratogenic, or (4) mutagenic.
Toxic chemicals cause people, animals, or plants to become ill, develop a disease, or die. DDT, chlordane , heptachlor, and aldrin are familiar, toxic pesticides. Carcinogens cause cancer ; teratogens produce birth defects . Mutagens, perhaps the most sinister of all, inflict genetic damage.
Determining these effects can often be very difficult. Scientists can usually determine if a chemical will harm or kill a person. But how does one determine if a chemical causes cancer twenty years after exposure, is responsible for birth defects, or produces genetic disorders? After all, any number of factors may have been responsible for each of these health problems.
As a result, labeling any specific chemical as carcinogenic, teratogenic, or mutagenic can be difficult. Still, environmental scientists have prepared a list of synthetic chemicals that they believe fall into these categories. Among them are vinyl chloride , trichloroethylene, tetrachloroethylene , the nitrosamines, and chlordane and heptachlor.
Another class of chemicals are hazardous because they may contribute to the greenhouse effect and ozone layer depletion . The single most important chemical in determining the earth's annual average temperature is a naturally-occurring compound, carbon dioxide . Its increased production is believed to be responsible for a gradual increase in the planet's annual average temperature.
But synthetic compounds may also play a role in global warming. Chlorofluorocarbons (CFCs) are widely used in industry because of their many desirable properties, one of which is their chemical stability . This very property means, however, that when released into the atmosphere , they remain there for many years. Since they capture heat radiated from the earth in much the way carbon dioxide does, they are probably important contributors to global warming.
These same chemicals, highly unreactive on earth, decompose easily in the upper atmosphere. When they do so, they react with the ozone in the stratosphere , converting it to ordinary oxygen. This may have serious consequences, since stratospheric ozone shields the earth from harmful ultraviolet radiation .
There are two ways to deal with potentially hazardous chemicals in the environment. One is to take political or legal action to reduce the production, limit the use, and/or control the disposal of such products. A treaty negotiated and signed in Montreal by more than forty nations in 1987, for example, calls for a gradual ban on CFC production. If the treaty is honored, these chemicals will eventually be phased out of use.
A second approach is to solve the problem scientifically. Synthetic chemicals are a product of scientific research, and science can often solve the problems these chemicals produce. For example, scientists are exploring the possibility of replacing CFCs with related compounds called fluorocarbons (FCs) or hydrochloroflurocarbons (HCFCs). Both are commercially appealing, but they have fewer harmful effects on the environment.
[David E. Newton ]
Giddings, J. Calvin. Chemistry, Man, and Environmental Change: An Integrated Approach. San Francisco: Canfield Press, 1973.
Joesten, M. D., et al. World of Chemistry. Philadelphia: Saunders College Publishing, 1991.
Newton, David E. The Chemical Elements. New York: Franklin Watts, 1994.
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chem·i·cal / ˈkemikəl/ (abbr.: chem.) • adj. of or relating to chemistry or the interactions of substances as studied in chemistry. ∎ of or relating to chemicals: chemical treatments for killing fungi. ∎ relating to, involving, or denoting the use of poison gas or other chemicals as weapons of war: the manufacture of chemical weapons. • n. a compound or substance that has been purified or prepared, esp. artificially: never mix disinfectant with other chemicals controversy arose over treatment of apples with this chemical. DERIVATIVES: chem·i·cal·ly / -ik(ə)lē/ adv.