Introduction
The possibility of suffering adverse health effects as a result of exposure to radiation is a cause of concern and fear for many people. They may think that little is known about the health effects of exposure to radiation and that exposure to even low levels of radiation can be disastrous. Neither of these beliefs is true, and they shouldn’t cause people to make unwise decisions such as foregoing beneficial medical procedures that involve radiation. This pamphlet by the American Council on Science and Health will summarize the scientific facts about the health effects of exposure to low levels of radiation.
What Is Radiation and How Is It Measured?
The word “radiation” refers to energy that travels in the form of waves or highspeed particles. Many different types of radiation exist including visible light, microwaves, and radio waves. We will use the term “radiation” to refer only to the types of radiation classified as “ionizing” radiation, including some ultraviolet radiation, x-rays, and the type of radiation given off by radioactive elements (alpha, beta, and gamma radiation).
In this pamphlet, the principle term used to express radiation doses is the rem, a measure of the biological risk resulting from exposure to radiation. Low levels of radiation are often expressed in millirems (mrem), 1/1000 of a rem. On average, one year of exposure to natural background radiation results in a radiation dose of 300 mrem. A chest x-ray exposes a person to about 5 mrem.
Sources of Radiation
Most of the radiation to which people are exposed comes from the natural environment (called background radiation) and includes cosmic rays from the sun and stars, radionuclides (radioactive forms of stable atoms) naturally present in our bodies, and naturally-occurring radioactive materials in rocks and soil including radon.
The chief sources of radiation exposure from human activity are medical procedures, such as x-rays. People are also exposed from some consumer products, nuclear power plants, fallout from nuclear weapons testing, and other sources. In North America, the average radiation dose from medical sources is 53 mrem/year; total exposure from human activity averages 65 mrem/year.
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