''Radiation'' - the word has overtones of atomic power or nuclear war. But it can also mean electromagnetic waves that carry TV signals, probe radar targets, or cook food in microwave ovens.
Leakage of RF (radio frequency) radiation into our general environment has been considered benign, except where it directly interferes with electronic equipment. Yet there has been continuing speculation about possible hidden hazards.
Now there are indications that low levels of microwaves can set up oscillations in molecules of DNA - the material that contains the genetic ''blueprints'' of living organisms and determines the functioning of cells. As with other indications of biological effects - such as impaired hemoglobin synthesis or changes in the immune system in rodents - there is no more than a hint of any possible human health hazard. Yet it does show that subtle effects once thought improbable may well occur.
This adds weight to the health and safety guidelines for exposure to RF pollution, which the US Environmental Protection Agency should be ready to release for public comment this summer. The EPA study has been under way for several years. According to an agency spokesman, there is still debate within the EPA as to just what the health effects might be. So it will probably take a couple of more months to pull together the long-awaited recommendations.
There is no question that strong RF radiation can heat biological tissue: It is dangerous to stand in front of an air defense radar antenna; and in a microwave oven, food cooks. The concern, rather, is over possible hazards with radio-wave pollution too weak to cause heating.
Earl W. Prohofsky, a solid-state physicist at Purdue University, has been studying the properties of DNA as a material, rather than as a biologically active molecule. He suggested on theoretical grounds that RF radiation could make this molecule resonate in tune with certain frequencies. He says, however, that he and his co-workers were making predictions which they ''didn't think should be taken too seriously.''
DNA, packed in the nucleus of a cell and surrounded by protein material, is a complex system whose interaction with radio energy is hard to envision. ''Theory can be way off in such a complex system,'' Prohofsky says. Even in the case of DNA molecules in an aqueous solution - a much simpler system - he says that he and his co-workers doubted their prediction of a resonant effect. He adds that experimental evidence, not theory, is the touchstone.
Now a Food and Drug Administration biochemist, Mays Swicord, and colleagues have produced such evidence. They have shown that microwave radiation can indeed affect DNA in solution. The RF energy sets the molecules dancing in a resonant manner.
Earlier experiments had been ambiguous. This new work suggests that his theoretical predictions of such an effect are sound, Prohofsky says. Whether biologically active DNA within living cells also resonates to low levels of RF radiation remains to be shown. If it does, this could interfere with normal cell function.
Prohofsky warns against jumping to any conclusion about health risks. All the evidence does is to suggest that this is an important area for research. It also indicates that scientists have barely begun to discover how radio waves can interact with living material.
Whatever guidelines the EPA finally publishes, they will be tentative. We know too little about the subject for anyone to draw a definitive conclusion. At the same time, the possibility of subtle but significant hazards from radio-wave polluton can no longer be ignored.