Nonmalignant delayed effects of ionizing radiation are manifested in many organsˇXparticularly bone marrow, kidneys, lungs, and the lens of the eyeˇXby degenerative changes and impaired function; these are largely secondary to radiation-induced damage to blood vessels.
The most important late effect of radiation exposure, however, is an increased incidence of leukemia and other cancers. Statistically significant increases in leukemia and of cancers of the thyroid, the lung, and the female breast have been demonstrated in populations exposed to relatively high doses (greater than 1 gray).
IV. Non-ionizing Radiation
The radio-frequency radiation, or electromagnetic fields (EMFs), from sources such as power lines, radar, communications networks, cellular phones, and microwave ovens is non-ionizing, and for many years only high doses of such radiation were known to be harmful, causing burns, cataracts, temporary sterility, and other effects. In the 1980s and early 1990s, however, with the proliferation of such devices, the possible effects of long-term exposure to low levels of non-ionizing radiation began to be a matter of scientific concern and controversy. Subtle biological effects were reported in some studies, while other studies failed to find these effects. In 1996 the National Academy of Sciences reviewed more than 500 scientific papers addressing the health effects of non-ionizing radiation and concluded that they do not pose a hazard to human health. Similarly, a major study by the National Cancer Institute, published in 1997, found no evidence that residential levels of non-ionizing radiation increased the risk of childhood leukemia.