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A woman who lives across the river from the Three Mile Island nuclear plant said last week: "As long as that plant is out there, I'm going to live with some kind of fear."
The fear that she and millions of others felt last week was a new one for most Americans – a dread of the unseen, unfelt phenomenon called radiation.
The German professor, Wilhelm Konrad Roentgen, felt no such fear, only high excitement, when he discovered X-rays in 1895. But within four months, a Dr. J. Daniels of Vanderbilt University in Nashville, experimenting with the mysterious rays, found that they made a colleague's hair fall out.
Today scientists know that the radiation from an X-ray tube strips electrons from – or "ionizes" – the atoms of cells. If the ionization is extensive enough, it rearranges the cell's molecule, and can kill it.
Today, too, scientists know that some 60 substances in nature, like radium and uranium-235, and some 200 man-made substances, are radioactive, meaning they are gradually disintegrating and shooting off unseen, unfelt particles and rays that are physical cousins of Wilhelm Roetgen's unseen rays.
Various radioactive substances, like those produced in nuclear reactors, variously give off gamma rays, very much like X-rays, and three possible kinds of ray-like particles; alpha particles (nuclei of helium atom), beta particles (high energy electrons), and neutrons. For example, radioactive iodine – which emerged in small amount, at least, from Three Mile Island – emits beta and gamma rays.
When ionizing radiation enters a body cell, it can break down its membranes and internal structures and kill it. Or, at lower levels, it can alter the cell's metabolism or the way it uses the body's nutrients. And the radiation can disorder chromosomes, the threadlike units of heredity, and alter their tiny molecules of DNA (deoxyribonucleic acid), whose composition dictates the shape of our descendants.
The effect on an individual? Probably none, if the radiation is at low levels, like the 20 or so millirems – thousandths of radiation units – of an average chest X-ray. But one must say "probably" none, for most scientists think that a few individuals exposed to even the smallest amounts of ionizing radiation pass on a disordered bit of DNA to some descendant, or after 10 or 20 years develop a cancer
What are the odds? For the 2 million people living within a 50-mile radius of Three Mile Island, there should be no cancers at all, the radioactive emissions were so small, Health, Education and Welfare Secretary Joseph A. Califano Jr. estimated. Dr. Karl N. Morgan, an elder statesman among health physicists, thinks there may be one excess cancer. He also acknowledged that a few scientists, with whom most authorities disagree, think there may be as many as 50.
Some known facts about radiation are that:
We all live with an unavoidable radiation "background" from elements in rocks, soil and the air, and from man's works, like enclosing us in buildings made of ordinary granite and brick, which emit some radioactivity.
The natural background at Harrisburg, Pa., is 88 millirems an year, just about the same as the added manmade dose Califano says a Harrisburg area resident may have had in the first five days following the nuclear accident.
A resident of a high-altitude city like Denver unavoidably gets nearly twice the natural Harrisburg dose, or 147 millirems a year, because of more exposure to cosmic rays.
The average American gets half his annual radiation dose from natural background, and 90 per cent of the rest from medical and dental radiation. Doctors say: avoid unneeded medical radiation; accept it when necessary, since the probable benefit outweighs the possible risk.