Chapter 8: THE DESIGNED WORLD
The world we live in has been shaped in many important ways by human action. We have created technological options to prevent, eliminate, or lessen threats to life and the environment and to fulfill social needs. We have dammed rivers and cleared forests, made new materials and machines, covered vast areas with cities and highways, and decidedsometimes willy-nillythe fate of many other living things.
In a sense, then, many parts of our world are designedshaped and controlled, largely through the use of technologyin light of what we take our interests to be. We have brought the earth to a point where our future well-being will depend heavily on how we develop and use and restrict technology. In turn, that will depend heavily on how well we understand the workings of technology and the social, cultural, economic, and ecological systems within which we live.
This chapter sets forth recommendations about certain key aspects of technology, with emphasis on the major human activities that have shaped our environment and lives. The chapter focuses on eight basic technology areas: agriculture, materials, manufacturing, energy sources, energy use, communication, information processing, and health technology.
Throughout history, most people have had to spend a great deal of their time getting food and fuel. People began as nomadic hunters and gatherers, using as food the animals and plants they found in the environment. Gradually, they learned how to expand their food supplies by using processing technology (such as pounding, salting, cooking, and fermenting). And they also learned how to use some usually inedible parts of animals and plants to make such things as tools, clothes, and containers. After many thousands of years of hunting and gathering, the human species developed ways of manipulating plants and animals to provide better food supplies and thereby support larger populations. People planted crops in one place and encouraged growth by cultivating, weeding, irrigating, and fertilizing. They captured and tamed animals for food and materials and also trained them for such tasks as plowing and carrying loads; later, they raised such animals in captivity.
More advances in agriculture came over time as people learned not only to use but also to modify life forms. At first, they could control breeding only by choosing which of their animals and plants would reproduce. Combinations of the natural variety of characteristics could thus be attempted, to improve the domesticity, hardiness, and productivity of plant and animal species. To preserve the great variety of naturally adapted crop species that are available for crossbreeding, seed banks are set up around the world; their importance is evident in the international negotiations about who has what rights to those genetic resources.
In the twentieth century, the success of modern genetics has helped to increase the natural variability within plant species by using radiation to induce mutations, so that there are more choices for selective breeding. Scientists are now learning how to modify the genetic material of organisms directly. As we learn more about how the genetic code works (it is virtually the same for all life forms), it is becoming possible to move genes from one organism to another. With knowledge of what genetic code sequences control what functions, some characteristics can be transferred from one species to another; this technique may eventually lead to the design of new characteristics. For example, plants can be given the genetic program for synthesizing substances that give them resistance to insect predators.
One factor in improved agricultural productivity in recent decades has been the control of plant and animal pests. In the United States in the past, and elsewhere in the world still, a large fraction of farm products was lost to weeds, rodents, insects, and disease-causing microorganisms. The widespread use of insecticides, herbicides, and fungicides has greatly increased useful farm output. There are problems, however. One is that pesticides may also act harmfully on other organisms in the environment, sometimes far from where they are used, and sometimes greatly concentrated by water runoff and the food web. Insecticides used to control the boll weevil, for instance, killed off its natural predators, making the weevil problem worse. Another problem is that the effectiveness of the pesticides may diminish as organisms develop genetically determined resistance to them, thereby requiring increased amounts of pesticides or the development of new ones.
Consequently, more environmentally harmonious use of technology is being explored. This work involves the careful design and use of chemicals and a more knowledgeable diversification of crops, changing the crops planted on a particular tract of land from crops that deplete some constituent of the soil to crops that replenish it. Changing crops can also reduce the likelihood that particular crop diseases will get a foothold. An alternative to the chemical control of pests is introducing organisms from other ecosystems in an effort to reduce the number of pests in the agricultural ecosystem (such as by using foreign insects that feed on local weeds). This approach also carries some risk of an introduced organism's becoming a pest itself.
Agricultural productivity has grown through the use of machines and fertilizers. Machines and the fossil-fuel engines needed to power them have made it possible for one person to cultivate and harvest more land, to cultivate more different kinds of land, and to feed and use the parts and products of greater numbers of plants and animals. Chemical fertilizers are widely used in the western hemisphere to supplement inadequate soil nutrients, in place of the manure used in many other parts of the world. One risk in the heavy use of machinery and fertilizers is the temptation to exhaust the soil from overuse. For that reason, the U.S. government encourages agricultural producers to take land out of production periodically and to take steps to restore the natural richness of the soil.
For many centuries, most food was consumed or marketed within a few dozen miles of where it was grown. Technology has revolutionized agricultural markets through transportation and communication. The many improvements in land productivity have led to availability of far more food in some areas than is needed for the local population. The development of rapid and cheap transportation reduces spoilage of food, as do treatment, additives, refrigeration, and packaging. But rapid, long-distance distribution of farm products also requires rapid, long-distance communication for selling and routing them. Together, modern transportation and communication systems enable food to be marketed and consumed thousands of miles from where it is produced.
When most markets were local, bad weather could cause great ups and downs in well-being for farmers and consumers. Now, because food is distributed through a worldwide market, consumers in wealthy nations have much less worry about an inadequate food supply. On the other hand, bad weather anywhere in the world can affect markets elsewhere. The concern of government for maintaining the national food supply for consumers and for protecting farmers from disastrous ups and downs in income has led to many forms of control of agriculture, which include controlling how land is used, what products are sold, and at what prices.
Only a century ago, a majority of workers in the United States were engaged in farming. Now, because technology has so greatly increased the efficiency of agriculture, only a tiny proportion (only about 2 percent) of the population is directly involved in production. There are, however, many more people involved in producing agricultural equipment and chemicals, and in the processing, storage, transportation, and distribution of food and fiber. The rapid reduction in the number of farmers needed to produce the nation's food has caused great shifts of population out of rural communities, resulting in the virtual disappearance of what was only recently the predominant way of life.
Technology is based on the use and application of a great variety of materials, some of which occur naturally, some of which are produced by means of mixing or treating, and some of which are synthesized from basic materials. All materials have certain physical properties, such as strength, density, hardness, flexibility, durability, imperviousness to water and fire, and ease of conducting a flow of heat or electric current. These properties determine the use to which the materials are put by manufacturers, engineers, and others involved in technology.
For much of human history, materials technology was based chiefly on the use of natural materials such as plants, animal products, and minerals. Over time, people learned that the characteristics of natural materials could be changed by processing, such as the tanning of leather and the firing of clay. Later, they discovered that materials could be physically combinedmixed, layered, or bonded togetherto get combinations of the characteristics of several different materials (for example, different kinds of wood laminated in a bow, steel rods embedded in concrete, zinc plated onto steel, and fibers interwoven in cloth). They also learned that the fine control of processes such as the tempering of steel or the annealing of glass could significantly improve some properties.
Since the 1960s, materials technology has focused increasingly on the synthesis of materials with entirely new properties. This process usually involves mixing substances together, as has been done for thousands of years with metal alloys. Typically, though, chemical changes are involved, and the properties of the new material may be entirely different from those of its constituents. Some new materials, such as plastics, are synthesized in chemical reactions that link long chains of atoms together. Plastics can be designed to have a wide variety of properties for different uses, from automobile and space vehicle parts, to food packaging and fabrics, to artificial hip joints and dissolving stitches. Ceramics, too, can be designed to have a variety of properties, and they can even be made such that the properties differ greatly from one ceramic to another (for example, the extremely low electrical conductivity of ceramic insulators, the controllable conductivity of ceramic semiconductors, and the virtually infinite conductivity of ceramic superconductors). Some materials can even be designed to adapt to various environmentssuch as all-weather motor oil and variable-density sunglasses.
The growth of technology has led us to use some materials from the environment much more rapidly than they can be replaced by natural processes. Forests in many countries have been greatly reduced during the past few hundred years, and ore deposits are being depleted. There is a continuing search for substitute materialsand in many cases they have been found or invented.
Increasingly, the disposal of used materials has become a problem. Some used materials, such as organic wastes, can be returned safely to the environmentalthough as the population grows, the task becomes more difficult and more expensive. But some materials, such as plastics, are not easily recycled; nor do they degrade quickly when returned to the environment. Still other used materialsradioactive waste being the most dramatic but not the only exampleare so hazardous for such a long time that how best to dispose of them is not clear and is the subject of widespread controversy. Solving these problems of disposal will require systematic efforts that include both social and technological innovations.
Making things requires a great variety of tools. The growth of technology in general has been greatly helped by improvement in the fineness and sharpness of cutting tools, the force that can be applied, the temperature at which heat can be concentrated, the swiftness with which operations can occur, and the consistency with which operations can be repeated. Such tools are an essential factor in modern manufacturing, which is based largely on the need to produce great numbers of products of uniform quality (such as automobiles and wristwatches) and much smaller numbers of products of extremely high quality (such as space vehicles and atomic clocks).
Modern manufacturing processes usually involve three major steps: (1) obtaining and preparing raw materials; (2) mechanical processing such as shaping, joining, and assembling; and (3) coating, testing, inspecting, and packaging. In all of these steps, there are choices for how to sequence tasks and how to perform them, so the organization of tasks to optimize productivity is another major component of manufacturing.
Modern factories tend to specialize in making specific products. When a large number of nearly identical things are made on a continuous basis at the same place, it is possible to make them much more cheaply than if they were made separately. Such cost-effectiveness is achieved by bringing workers together with machines, energy sources, and raw materials or component parts. The maintenance and repair of products are also likely to be easier when production is centralized because parts can be made that are interchangeable between units and even between different models.
Production is increasingly automated. In some settings, robots are used to perform the repetitive tasks of mass production. Instructions for processing are used to control the processes electronically, rather than having to be interpreted and carried out by people. The flexibility in control makes it possible to design and use multipurpose machines that can customize a line of products. Such machines may also enable manufacturers to introduce a new line of products without first making a special set of new machines.
The design of manufacturing systems, whether automated or not, can be highly complex. First, the sequence of operations admits of many possibilities, from which highly efficient and cost-effective ones must be selected. Then, for any chosen sequence, a great number of flows of materials and timings of operations must be controlled, monitored, and coordinated. Many subtleties of human skill and judgment may be difficult to specify precisely; often, experts are not able to explain exactly what they do or how they do it. Control by computers makes efficient operation of highly complex manufacturing systems possible, but it still requires human supervision to deal with the unforeseen or unforeseeable.
The evolution of production has changed the nature of work. In the past, a craft worker could work at the same tasks for a lifetime with little change in product or technique. Large-scale production in one place led to an extreme of specialization: each worker doing just one simple task over and over again, rather than putting together complete products. Increasing automation requires less direct labor and fewer skilled crafts, but more engineering, computer programming, quality control, supervision, and maintenance. Although it may reduce workers' feelings of boredom and unimportance that result from endlessly repeating the same minor tasks, automation also reduces the workers' control and may eliminate some workers' jobs even while it creates others. Flexibility and skill in learning a succession of new job roles have become increasingly important as the pace of technological change quickens.
Industry, transportation, urban development, agriculture, and most other human activities are closely tied to the amount and kind of energy available. Energy is required for technological processes: taking apart, putting together, moving around, communicating, and getting raw materials, and then working them and recycling them.
Different sources of energy and ways of using them have different costs, implications, and risks. Some of the resourcesdirect sunlight, wind, and waterwill continue to be available indefinitely. Plant fuelswood and grassesare self renewing, but only at a limited rate and only if we plant as much as we harvest. Fuels already accumulated in the earthcoal, oil and natural gas, and uraniumwill become more difficult to obtain as the most readily available sources run out. When scarcity threatens, new technology may make it possible to use the remaining sources better by digging deeper, processing lower concentration ores, or mining the ocean bed. Just when they will run out completely, however, is difficult to predict. The ultimate limit may be prohibitive cost rather than complete disappearancea question of when the energy required to obtain the resources becomes greater than the energy those resources will provide.
Sunlight is the ultimate source of most of the energy we use. It becomes available to us in several ways: The energy of sunlight is captured directly in plants, and it heats the air, land, and water to cause wind and rain. But the flux of energy is fairly weak, and large collection systems are necessary to concentrate energy for most technological uses: Hydroelectric energy technology uses rainwater concentrated in rivers by runoff from vast land areas; windmills use the flow of air produced by the heating of large land and ocean surfaces; and electricity generated from wind power and directly from sunlight falling on light-sensitive surfaces requires very large collection systems. Small-scale energy production for household use can be achieved in part by using windmills and direct solar heating, but cost-efficient technology for the large-scale use of windmills and solar heating has not yet been developed.
For much of history, burning wood was the most common source of intense energy for cooking, for heating dwellings, and for running machines. Most of the energy used today is derived from burning fossil fuels, which have stored sunlight energy that plants collected over millions of years. Coal was the most widely used fossil fuel until recently. But in the last century, oil and its associated natural gas have become preferred because of their ease of collection, multiple uses in industry, and ability to be concentrated into a readily portable source of energy for vehicles such as cars, trucks, trains, and airplanes. All burning of fossil fuels, unfortunately, dumps into the atmosphere waste products that may threaten health and life; the mining of coal underground is extremely hazardous to the health and safety of miners, and can leave the earth scarred; and oil spills can endanger marine life. Returning to the burning of wood is not a satisfactory alternative, for that too adds so-called greenhouse gases to the atmosphere; and overcutting trees for fuel depletes the forests needed to maintain healthy ecosystems both locally and worldwide.
But there are other sources of energy. One is the fission of the nuclei of heavy elements, whichcompared to the burning of fossil fuelsreleases an immense quantity of energy in relation to the mass of material used. In nuclear reactors, the energy generated is used mostly to boil water into steam, which drives electric generators. The required uranium is in large, although ultimately limited, supply. The waste products of fission, however, are highly radioactive and remain so for thousands of years. The technical problem of reasonably safe disposal of these fission products is compounded by public fear of radioactivity and worry about the sabotage of nuclear power plants and the theft of nuclear materials to make weapons. Controlled nuclear fusion reactions are a potentially much greater source of energy, but the technology has not yet proved feasible. Fusion reactions would use fuel materials that are safer in themselves, although there would still be a problem of disposing of worn-out construction materials made radioactive by the process. And as always with new technology, there may be some unanticipated risks.
Energy must be distributed from its source to where it is to be used. For much of human history, energy had to be used on siteat the windmill or water mill, or close to the forest. In time, improvement in transportation made it possible for fossil fuels to be burned far from where they were mined, and intensive manufacturing could spread much more widely. In this century, it has been common to use energy sources to generate electricity, which can deliver energy almost instantly along wires far from the source. Electricity, moreover, can conveniently be transformed into and from other kinds of energy.
As important as the amount of energy available is its quality: the extent to which it can be concentrated and the convenience with which it can be used. A central factor in technological change has been how hot a fire could be made. The discovery of new fuels, the design of better ovens and furnaces, and the forced delivery of air or pure oxygen have progressively increased the temperature available for firing clay and glass, smelting metal ores, and purifying and working metals. Lasers are a new tool for focusing radiation energy with great intensity and control, and they are being developed for a growing number of applicationsfrom making computer chips and performing eye surgery to communicating by satellite.
During any useful transformation of energy from one form to another, there is inevitably some dissipation of energy into the environment. Except for the energy bound in the structure of manufactured materials, most of our uses of energy result in all of it eventually dissipating away, slightly warming the environment and ultimately radiating into space. In this practical sense, energy gets "used up," even though it is still around somewhere.
People have invented ingenious ways of deliberately bringing about energy transformations that are useful to them. These ways range from the simple acts of throwing rocks (which transforms biochemical energy into motion) and starting fires (chemical energy into heat and light), to using such complex devices as steam engines (heat energy into motion), electric generators (motion into electrical energy), nuclear fission reactors (nuclear energy into heat), and solar converters (radiation energy into electrical energy). In the operation of these devices, as in all phenomena, the useful energy outputthat is, what is available for further changeis always less than the energy input, with the difference usually appearing as heat. One goal in the design of such devices is to make them as efficient as possiblethat is, to maximize the useful output for a given input.
Consistent with the general differences in the global distribution of wealth and development, energy is used at highly unequal rates in different parts of the world. Industrialized nations use tremendous amounts of energy for chemical and mechanical processes in factories, creating synthetic materials, producing fertilizer for agriculture, powering industrial and personal transportation, heating and cooling buildings, lighting, and communications. The demand for energy at a still greater rate is likely as the world's population grows and more nations industrialize. Along with large-scale use, there is large-scale waste (for example, vehicles with more power than their function warrants and buildings insufficiently insulated against heat transfer). But other factors, especially an increase in the efficiency of energy use, can help reduce the demand for additional energy.
Depletion of energy sources can be slowed by both technical and social means. Technical means include maximizing the usefulness that we realize from a given input of energy by means of good design of the transformation device, by means of insulation where we want to restrict heat flow (for example, insulating hot-water tanks), or by doing something with the heat as it leaks out. Social means include government, which may restrict low-priority uses of energy or may establish requirements for efficiency (such as in automobile engines) or for insulation (as in house construction). Individuals also may make energy efficiency a consideration in their own choice and use of technology (for example, turning out lights and driving high-efficiency cars)either to conserve energy as a matter of principle or to reduce their personal long-term expenses. As always, there are trade-offs. For example, better-insulated houses stay warmer in winter and cooler in summer, but restrict ventilation and thus may increase the indoor accumulation of pollutants.
People communicate frequently, if not always well. Hundreds of different languages have evolved to fit the needs of the people who use them. Because languages vary widely in sound, structure, and vocabulary and because language is so culturally bound, it is not always easy to translate from one to another with precision. Written communicationsfrom personal letters to books and junk mailcrisscross continents and reach the farthest outposts. Telephones, radio, television, satellites, sound and optical recordings, and other forms of electronic communication have increased the options and added to the flow of information.
Communication involves a means of representing information, a means of transmitting and receiving it, and some assurance of fidelity between what is sent and what is received. Representation requires coding information in some transmission medium. In human history, the natural media have been mechanical contact (touch), chemicals (smell), sound waves (speech and hearing), and visible light (vision). But reliability and permanence require a medium for recording information. The reliable medium that developed first was the marking of solid materialswood, clay, stone, and eventually paper. Today, we also mark, microscopically, plastic disks and magnetic tape. These modified materials can endure for many years, and can be moved great distances with their encoded information intact.
With the invention of devices to generate and control electric current, information could be encoded as changes in current and could be conveyed over long distances by wire almost instantaneously. With the discovery of radio waves, the same information could be encoded as changes in wave pattern and distributed in all directions through the atmosphere without the need of connecting wires. Particularly important was the invention of electronic amplifiers, in which a weak electrical signal controls the flow of a much stronger electric current, impressing it with the same pattern of information. Recently, the efficient control of light waves in lasers has made possible the encoding and transmitting of information as pulses in light intensity over optical fibers.
Information can be coded in analog or digital form. For example, originally both wired and wireless electric communication were only in the digital form of off-and-on bursts, requiring an artificial code to represent letters and numbers. A great advantage came with the invention of electronicsdevices to transform sound and light signals into electrical signals, and vice versa. Electronics made it possible to transmit analog signals that represent subtle variations in sound or light and to transcribe those signals as continuous variations in some medium. The ability to transcribe information microscopically and to transmit information at very high rates now makes possible the reduction of distortion and noise in processing analog signals by returning to the reliability of off-and-on digital signals. Analog signals of all sorts can now be sampled and represented as numbers, stored or transmitted in that form, and conveniently processed by computers, and perhaps returned to analog form for sound or graphic display.
The basic technical challenge of communication is to keep the signal large compared to the noise, which always tends to increase when information is recorded, transformed, or transmitted. The ratio of signal to noise can be improved by boosting the signal or by reducing the noise. Signals can be kept strong by amplification or by preventing energy loss (as by focusing them in a narrow beam of waves). Noise can be limited by isolating the signal from external noise sources (as by shielding microphone cables) or by reducing internal sources of noise (as by cooling an amplifier). A very different way to minimize errors from noise in communication is by means of repetition or some other form of redundancy that allows comparison and detection of errors. Some redundancy is always desirable in communication, because otherwise a single error may completely change the meaning of a message.
Communication sometimes requires security. Mail can be intercepted and copied, telephone wires can be tapped, over-the-air communications can be monitored. Privacy can be protected by preventing access to signals (for example, by using locks and passwords) or by preventing interpretation of them (such as by using secret codes). The creation of secret codes that are extremely difficult to figure out is an interesting application of number theory in mathematics. As the techniques of providing security improve, however, so do techniques for penetrating it.
Technology has long played an important role in collecting, storing, and retrieving information, as well as in transporting it. The invention of writing, tables of data, diagrams, mathematical formulas, and filing systems have all increased the amount of information we can handle and the speed with which we can process it. Large amounts of information are essential for the operation of modern societies; indeed, the generation, processing, and transfer of information is becoming the most common occupation of workers in industrialized countries.
Information is most useful when it is organized and represented by orderly collections of symbols. People use tables, indexes, alphabetical lists, and hierarchical networks to organize large amounts of data. The best way to store information depends on what is to be done with it. Information stored with one purpose in mind may be very troublesome to retrieve for other purposes (for example, the alphabetical listing of telephone numbers is ideal if one knows a person's name, but not if one knows only the address). Multipurpose data bases enable the information to be located in several different ways (for example, books listed by author or title or subject). A typical feature of such information systems is attaching to each data entry a prescribed set of key words that a computer can search for matching items.
Mechanical devices to perform mathematical or logical operations have been around for centuries, but it was the invention of the electronic computer that revolutionized information processing. One aspect of mathematical logic is that any information whatsoeverincluding numbers, letters, and logical propositionscan be coded as a string of yes-or-no bits (for example, as dots and dashes, 1's and 0's, or on/off switches). Electronic computers are essentially very large arrays of on/off switches connected in ways that allow them to perform logical operations. New materials and techniques have made possible the extreme miniaturization and reliability of no-moving-parts switches, which enable very large numbers of connected switches to be fitted into a small space. Very small size also means very short connections, which in turn mean very brief travel time for signals; therefore, miniaturized electronic circuits can act very quickly. The very short times required for processing steps to occur, together with the very large number of connections that can be made, mean that computers can carry out extremely complicated or repetitive instructions millions of times more quickly than people can.
The activity of computers is controlled partly by how they are wired, partly by sets of coded instructions. In general-purpose computers, instructions for processing information are not wired in but are stored temporarily (like other information). This arrangement permits great flexibility in what computers can do. People give instructions to computers through previously programmed software or by means of original programs written in a programming language. Programming languages enable a programmer to compose instructions with something like English or algebra, or geometrical manipulation of diagrams. Those instructions are then translated by another program into machine language for the computer. Often, the program calls for other inputs in the form of data entered by keyboard, from an information-storage device, or from an automatic sensing device. The output of a computer may be symbolic (words, numbers) or graphic (charts, diagrams), or it may be the automatic control of some other machine (an alarm signal, an action of a robot) or a request to a human operator for more instructions.
An important role of computers is in modeling or simulating systemsfor example, the economy or the weather, a grid of traffic lights, a strategic game, or chemical interactions. In effect, the computer computes the logical consequences of a set of complicated instructions that represent how the system works. A computer program is written that specifies those instructions and is then run, beginning with data that describe an initial state of the system. The program also displays subsequent states of the system, which can be compared to how the systems actually behave to see how good our knowledge of the rules is and to help correct them. If we are sure we know all the rules well, we can use the consequence-deducing power of computers to aid us in the design of systems.
An important potential role for computer programs is to assist humans in problem solving and decision making. Computers already play a role in helping people think by running programs that amass, analyze, summarize, and display data. Pattern-searching programs help to extract meaning from large pools of data. An important area of research in computer science is the design of programsbased on the principles of artificial intelligencethat are intended to mimic human thought and possibly even improve on it. Most of human thought is not yet well understood, however. As is true for simulations of other complex systems such as the economy or the weather, comparison of the performance of programs with the phenomena they represent is a technique for learning more about how the system works.
In mechanical systems that are well understood, computers can provide control that is as good as, or more precise and rapid than, deliberate human control. Thus, the operation of automobile engines, the flight control of aircraft and spacecraft, and the aiming and firing of weapons can be computerized to take account of more information and to respond much more rapidly than a human operator could. Yet, there are also risks that the instructions or the information entered may contain errors, the computer may have malfunctions in its hardware or software, and even that perfectly reliable computers, programs, and information may still give faulty results if some relevant factors are not included in the programs or if any values of included factors fall outside of their expected range. Even if the whole system is technically flawless, though, a very complex high-speed system may create problems because its speed of response may exceed human ability to monitor or judge the output.
The complexity of control in today's world requires vast computer management of information. And as the amount of information increases, there is increasing need to keep track of, control, and interpret the informationwhich involves still more information, and so on through more layers of information. This flood of information requires invention of ways to store it in less space, to categorize it more usefully, to retrieve it more quickly, to transmit it at a higher rate, to sort it and search it more efficiently, and to minimize errorsthat is, to check for them and to correct them when they are found. As for communication, information storage also involves issues of privacy and security. Computer-managed information systems require means for ensuring that information cannot be changed or lost accidentally and that it will be unintelligible if unauthorized access does occur.
Health technology is concerned with reducing the exposure of humans to conditions that threaten health, as well as with increasing the body's resistance to such conditions and minimizing the deleterious effects that do occur.
Historically, the most important effect of technology on human health has been through prevention of disease, not through its treatment or cure. The recognition that disease-causing organisms are spread through insects, rodents, and human waste has led to great improvements in sanitation that have greatly affected the length and quality of human life. Sanitation measures include containment and disposal of garbage, construction of sewers and sewage processing plants, purification of water and milk supplies, quarantine of infectious patients, chemical reduction of insect and microorganism populations (insecticides and antiseptics), and suppression of the population of rats, flies, and mosquitoes that carry microorganisms. Just as important in the prevention of illness has been furnishing an adequate food supply containing the variety of foods required to supply all the body's needs for proteins, minerals, and trace substances.
Health technology can be used to enhance the human body's natural defenses against disease. Under conditions of reasonably good nutrition and sanitation, the human body recovers from most infectious diseases by itself without intervention of any kind, and recovery itself often brings immunity. But the suffering and danger of many serious diseases can be prevented artificially. By means of inoculation, the immune system of the human body can be provoked to develop its own defenses against specific disease without the suffering and risk of actually contracting the disease. Weakened or killed disease microorganisms injected into the blood may arouse the body's immune system to create antibodies that subsequently will incapacitate live microorganisms if they try to invade. Next to sanitation, inoculation has been the most effective means of preventing early death from disease, especially among infants and children.
Molecular biology is beginning to make it possible to design substances that evoke immune responses more precisely and safely than current vaccines. Genetic engineering is developing ways to induce organisms to produce these substances in quantities large enough for research and applications.
Many diseases are caused by bacteria or viruses. If the body's immune system cannot suppress a bacterial infection, an antibacterial drug may be effectiveat least against the types of bacteria it was designed to combat. But the overuse of any given antibacterial drug can lead, by means of natural selection, to the spread of bacteria that are not affected by it. Much less is known about the treatment of viral infections, and there are very few antiviral drugs equivalent to those used to combat bacterial infections.
The detection, diagnosis, and monitoring of disease are improved by several different kinds of technology. Considerable progress in learning about the general condition of the human body came with the development of simple mechanical devices for measuring temperature and blood pressure and listening to the heart. A better look inside the body has been provided by imaging devices that use slender probes to supply visible light or (from outside the body) magnetic fields, infrared radiation, sound waves, x rays, or nuclear radiation. Using mathematical models of wave behavior, computers are able to process information from these probes to produce moving, three-dimensional images. Other technologies include chemical techniques for detecting disease-related components of body fluids and comparing levels of common components to normal ranges.
Techniques for mapping the location of genes on chromosomes make it possible to detect disease-related genes in children or in prospective parents; the latter can be informed and counseled about possible risks. With ever-growing technology for observing and measuring the body, the information load can become more than doctors can easily consider all at once. Computer programs that compare a patient's data to norms and to patterns typical of disease are increasingly aiding in diagnosis.
The modern treatment of many diseases also is improved by science-based technologies. Knowledge of chemistry, for example, has improved our understanding of how drugs and naturally occurring body chemicals work, how to synthesize them in large quantities, and how to supply the body with the proper amounts of them. Substances have been identified that are most damaging to certain kinds of cancer cells. Knowledge of the biological effects of finely controlled beams of light, ultrasound, x rays, and nuclear radiation (all at much greater intensities than are used for imaging) has led to technological alternatives to scalpels and cauterization. As the knowledge of the human immune system has grown and new materials have been developed, the transplantation of tissue or whole organs has become increasingly common. New materials that are durable and not rejected by the immune system now make it possible to replace some body parts and to implant devices for electrically pacing the heart, sensing internal conditions, or slowly dispensing drugs at optimal times.
Effective treatment of mental disturbance involves attention not only to the immediate psychological symptoms but also to their possible physiological causes and consequences, and to their possible roots in the individual's total experience. Psychological treatment may include prolonged or intensive personal interviews, group discussions among people with similar problems, or deliberately programmed punishment and reward to shape behavior. Medical treatment may include the use of drugs, or electric shock, or even surgery. The overall effectiveness of any of these treatments, even more than in the case of most other medical treatment, is uncertain; any one approach may work in some cases and not in others.
Improved medical technologies raise ethical and economic issues. The combined results of improved technology in public health, medicine, and agriculture have increased human longevity and population size. This growth in numbers, which is very unlikely to end before the middle of the next century, increases the challenge of providing all humans with adequate food, shelter, health care, and employment, and it places ever more strain on the environment. The high costs of some treatments forces society to make unwelcome choices about who should be selected to benefit and who should pay. Moreover, the developing technology of diagnosing, monitoring, and treating diseases and malfunctions increases society's ability to keep people living when they otherwise would have been unable to sustain their lives themselves. This raises questions as to who should decide whether and for how long extraordinary care should be provided and to whom. There is continuing debate over abortion, intensive care for infants with severe disabilities, maintaining the life functions of people whose brains have died, the sale of organs, altering human genes, and many other social and cultural issues that arise from biomedical technology.
An increasingly important adjunct to preventive and corrective health care is the use of statistics to keep track of the distribution of disease, malnutrition, and death among various geographic, social, and economic groups. They help determine where public health problems are and how fast they may be spreading. Such information can be interpreted, sometimes with the help of mathematical modeling, to project the effects of preventive and corrective measures and thus to plan more effectively.
Copyright © 1989, 1990 by American Association for the Advancement of Science