Answer to Question #824 Submitted to "Ask the Experts"

Q

Where can you find radiation in everyday life?

A

Radiation is everywhere. In fact, it can be said quite literally that we live in a "sea of radiation." Before identifying some of the components of this "sea," it is important to note that, without the use of monitoring equipment, humans are not able to "find" radiation. In contrast to heat, light, food, and noise, humans are not able to see, feel, taste, smell, or hear radiation. Natural Background The first, and largest, source of radiation in our everyday lives comes from what is called natural background. This source has been with us since the beginning of time. One example is a host of naturally occurring radioactive materials that are present in the soil. These materials emit radiation that exposes us from outside our bodies and are therefore referred to as external sources. Naturally occurring radioactive materials, originally present in the soil, also become airborne and are inhaled when we breathe. Through this process, they become what are called internal sources of radiation exposure. They are also taken up by food crops grown in the soil and are subsequently ingested when we eat various types of vegetables and nuts. In addition, they contaminate water in the ground and are consumed when we drink water from underground wells. Radioactive materials taken into the body through the consumption of food and water represent other types of internal sources of exposure. Humans are also exposed to external sources as a result of cosmic radiation coming from outer space. Although the magnitude of the dose from natural background varies from place to place, in general these sources contribute more than 80% of the total radiation dose received by the average member of the U.S. public. Of this total of more than 80%, about one-third comes from cosmic radiation, from external exposures due to the presence of radioactive materials in the soil, and from internal exposures due to the presence of naturally occurring radioactive materials deposited in our bodies through ingestion. About two-thirds of the total results from the inhalation of airborne naturally occurring radioactive materials, the most commonly known such source being the radioactive gas, radon, that is present in the air in many of our homes. Man-Made Radiation From the standpoint of man-made radiation, the largest contributor to the dose of average members of the U.S. public is the use of x rays and radioactive materials (the latter in the form of radiopharmaceuticals) in medicine and dentistry. On average these two sources contribute about 15% of the total annual dose received. The remaining man-made sources that make a significant contribution to the dose to the average member of the public are consumer products. These include radioactive smoke detectors, television sets, luminous watches and dials, and various products, such as glassware, that are glazed with uranium. On average, these contribute about 3% of the total dose. About two-thirds of this 3% comes from radioactive materials that are present in materials, such as brick and concrete block, used in building our homes. In contrast to what many people think, man-made sources such as commercial nuclear power plants, uranium mining and milling, nuclear waste disposal, and fallout from atmospheric nuclear weapons tests, contribute less than 1% of the total dose to average members of the U.S. public. Dade W. Moeller, Ph.D., CHP