III. Late
Effects
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).
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IV.
Non-ionizing Radiation
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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 pro
liferation 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.