Background
Radiation is all around us. It is naturally present in our environment and has been since the birth of this planet. Consequently, life has evolved in an environment which has significant levels of ionizing radiation. It comes from outer space (cosmic), the ground (terrestrial), and even from within our own bodies. It is present in the air we breathe, the food we eat, the water we drink, and in the construction materials used to build our homes. Certain foods such as bananas and brazil nuts naturally contain higher levels of radiation than other foods. Brick and stone homes have higher natural radiation levels than homes made of other building materials such as wood. Our nation's Capitol, which is largely constructed of granite, contains higher levels of natural radiation than most homes.
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How does radiation have an impact on health?
Too much radiation, like too much of anything, is harmful.
We know about this harm from research and from accidents, and from the effects of the two atomic bombs dropped on Japan in 1945. The effects can range from mild gastrointestinal problems (such as nausea and vomiting) to changes in the blood, to damage to the central nervous system.
Too little radiation, likewise, is also harmful.
The world's flora and fauna, including human beings, have grown up in a radioactive environment. We know from research in which organisms have been shielded from everyday radiation that their growth is stunted. We also know it from comparing populations that receive different levels of radiation because of their location. Often, the populations receiving the most radiation are healthier and suffer fewer cancers. In between these extremes, it is usual to protect workers when they work in industries that use sources of radiation.
Radioactive materials decay spontaneously to produce