Microwaves and Health Effects

Abstract

Microwaves an Nestled snugly between ordinary radio waves and the infrared in the electromagnetic spectrum is the wilderness of microwaves. Even the boundaries are not clearly defined: Just where the microwave region begins and ends is still not universally agreed upon since measurements of it are influenced by the technique used. But the National Bureau of Standards places microwaves, which are really a type of high-frequency radio waves, between 300 million and 300 billion cycles a second. first major application of radio frequencies in this range came in the 1930's, when they were used in radar. World War II gave them a boost, but their real growth came after the war. Today 90 percent of all TV transmission and two-thirds of all long-distance communication, including telephone data transmission and fascimile, are done by microwave. Microwaves are the medium for radio telescopes and for satellite communications. A linear accelerator at Stanford is unraveling the nature of matter with their help. Because they produce intense heat by molecular agitation, they are being drafted for industrial processes: Microwaves cure plastics, dry lumber, drugs and textiles, precook foods, warm food in canteens and cafeterias and cook it at institutions and in a growing number of private homes. Some British newspapers are drying newsprint with them; a microwave pasteurization process for bakery products has been developed; and in September, a microwave kiln for enameling glass, ceramics and metal was patented. Their medical applications have been mainly relegated to the area of diathermy treatments where deep heat penetration is required. For the future, the big promise of microwave technology will be in electric power transmission and production. Some plans call for harnessing the sun's energy with microwaves and transporting billions of watts underground (SN: 4/12, p. 353). But there is one black cloud on an otherwise bright horizon: safety. It has been known for a long time that microwaves in sufficient amounts and over a long enough period can be harmful to biological systems; cataracts and damage to the testes are two of their reported effects in humans. And despite the fact that there are an estimated 10,000 people working directly with microwave devices and untold numbers coming in contact with them in schools, hospitals, cafeterias and even the home, information on the biological effects of microwaves is about as scanty as are precautions against undue exposure. The knowledge of biological effects is inadequate, biophysicist Dr. Stephen F. Cleary of Virginia Commonwealth University said in Richmond, Va., at a recent symposium on microwaves' biological effects. don't know the biological mechanisms. main problem is the effect on the central nervous system. We don't know if microwaves interfere with neural transmissions. It was in an effort to learn more about the potential hazards of microwave radiation, as well as the mechanism of damage, and to set future research directions, that 400 scientists, medical and health specialists and engineers from all over the United States came to Richmond. meeting indicated that certain organs, such as the eyes, testes, gall and urinary bladders and the digestive tract, show more susceptibility to microwave damage than other organs; the smaller blood vessels of these organs make them less able to cool themselves after exposure to the heat produced by microwaves. And, since water is a microwave absorber, it makes tissues such as eye, skin and muscle, more susceptible to microwave damage than bone marrow or fat, which have less water. Microwave heat works against the body by heating it to the point where the metabolic rate is raised. This results in a compensatory increase in respiration and blood circulation. At the same time that the blood is speeding more quickly through the lungs, the ability of hemoglobin, the blood's oxygen carrier, to transport oxygen diminishes. Furthermore, the blood hurtling through the lungs now has less time to load up on oxygen. effects observed are similar to those of a high fever in extreme cases: degeneration and death of heart tissue and bleeding in the digestive tract, lungs, liver and brain. But these and other known effects stem from large doses of microwaves. Scientists are not certain about the effects either short term or cumulative -of low-level doses of microwaves.