Everyday Exposure to Radiation

What do you do on a normal day?

Regardless of what you do on a typical day, go to school, work, or stay home, in each case you are being exposed to radiation. Whether you know it or not you are being exposed to radioactivity everyday of your life.

Nuclear radiation is all around us in the environment. Low-level radiation is found in the oceans and waterways, the rocks and soils, the plant materials and in the atmosphere surrounding the planet. The radiation that we are exposed to can be said to come from two sources, that which occur naturally and that which is due to the activities of man.

Natural Radiation
Radioactivity in nature comes from two main sources, terrestrial and cosmic. Terrestrial radioisotopes are found on the earth that came into existence with the creation of the planet. Although some are long gone, some radioisotopes take a long time to decay and become non-radioactive (on the order of hundreds of millions of years) and are still around today.

Radioactive elements found in rock, soil, water, air, and in food from the earth make there way in our bodies when we drink water, breath air or eat foods which contain them. These naturally occurring radioisotopes such as carbon-14, potassium-40, thorium-223, uranium-238, polonium-218, and tritium(hydrogen-3) expose us to radiation from within our bodies.

By far, the largest contributor to our daily exposure of radiation is the natural world, and the major form of natural radiation is radon gas. Radon-222 is a naturally occuring decay product of uranium-238 which is commonly found in soils and rocks. Radon-222 is a gas which is odorless, colorless, tasteless and chemically nonreactive. As it escapes from the soils and rocks of which it is trapped, it enters the water we drink and the air we breath.

Since distribution of uranium in the earth's crust varies from place to place, so does the prevalence of radon gas. In areas where surface rocks contain a high concentration of uranium, radon gas could enter a home through a crack in the foundation. A concern for homeowners is the possibility that radon gas could accumulate to dangerous levels. This is especially a problem during the winter months when windows and doors are tightly shut.

A survey conducted by the Environmental Protection Agency of radon gas in homes shows a wide distribution of levels across the United States. Click here to see what level of radon gas was found in the majority of homes in the state in which you live. [button]


Another source of natural radiation comes from the interaction of cosmic rays with the earth's upper atmophere. Cosmic rays permeate all of space and are composed of highly energized, positively charged particles as well as high energy photons. Approaching the earth at near the speed of light, most cosmic rays are blocked by the earth's protective atmosphere and magnetic field. As a byproduct of the interaction between cosmic rays (i.e. particles) and the atmosphere, many radioactive isotopes are formed such as carbon-14.

Cosmic rays are also composed of high energy photons, and not all are prevented from reaching the earth's surface. It makes sense that the higher you are in altitude, the more you are exposed to cosmic radiation. In fact, the average amount of exposure to cosmic radiation that a person gets in the Unites States roughly doubles for every 6,000 foot increase in elevation.

The highest mountain in the continental United States is 14,495 feet. It is not likely that very many people will ever find their way to its summit, but what mode of transportation often brings us to elevations greater than this? The answer is flying. Flying can indeed add a few extra units of exposure to one's daily exposure. Of course, the amount of extra exposure you get depends on how high the plane flies and how long you are in the air.

Think about this : Estimate how much cosmic radiation
that astronauts are exposed to during their flights.
Recall that astronauts fly at heights of about 160 miles

Nuclear Radiation from Human Activities

Although radioisotopes occur naturally in the environment, activities of humans have brought this radiation closer to us all. For examples, the bricks, stones, cements and drywalls that we use for the building of our homes, schools, offices frequently contain uranium ores and are thus sources of radon.

The human production of tobacco products introduces another way for us to get exposure to radiation. Smokers recieve a dose of radiation from polonium-210 which is naturally present in tobacco. Smokers also recieve an additional dose of radiation from the decay product of radon gas, polonium-218. Polonium-218 clings to aerosols such as tobacco smoke, and eventually winds up in the lungs. Once in the lungs, polonium decays by alpha particle emission and in the process may damage cells.

Although this does not contribute radiation on a daily basis, the medical field has several ways of causing exposure to an individual. This exposure results from the attempt to diagnose fractures or cavities using x-rays, or to diagnose or treat cancer using injected radioisotopes. Patients are exposed to nuclear radiation in the diagnosis and treatment of cancer. Additionally, radiologists routinely use radioisotopes of technetium or thorium to diagnose heart disease.

Depending on one's occupation, the risk of exposure can be greater that that of the average person. These higher risk occupations include underground miners, radiologists, medical technologists, nuclear plant operators, research scientists and pilots.

Is This Exposure Dangerous?

Any amount of radiation can be dangerous because of the potential effect that it has on living cells. Radiation can disrupt normal chemical processes of the cells, causing them to grow abnormally or to die. Cells that are altered by the radiation may go on to produce more abnormal cells - a process that could eventually lead to cancer.

At low doses, such as have been described here, cells are able to repair any damage rapidly. Any cells that die due to exposure can be replaced by the body. If one receives a very high dose, unlike any exposure mentioned here, the cells may not be able to be replaced fast enough and tissues or organs may fail to function properly.

Guidelines for levels of exposure have been set by the Deparment of Energy as means of protecting the public.

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