Environment, Health and Safety Online
The site for free, objective information you can use!
Learn all about radioactive materials, radiation, nuclear waste, sources of radiation the relationship to human health and cancer here!
Nuclear waste overview
Types of radiation
Low-level radioactive wastes
Uranium mining - Uranium mill tailings
Nuclear waste from weapons production
Naturally-occurring radioactive waste
Nuclear / radioactive guidance documents
How to assess the danger from radiation
Links to many federal government, scientific and reputable sources of information about radioactive materials
Links to State nuclear agencies
Matter is composed of atoms. Some atoms are unstable. As these atoms change to become more stable, they give off invisible energy waves or particles called radiation.
There are different types of radiation, some more energetic than others. One type of radiation, non-ionizing radiation, has enough energy to move atoms but not enough to alter them chemically. This booklet discusses the most energetic form, known as ionizing radiation, which from here on will be referred to simply as radiation.
We measure radiation dose in units called rem. Scientists estimate that the average person in the United States receives a dose of about 360 millirem of radiation per year. Eighty percent of that exposure comes from natural sources: radon gas, the human body, outer space, and rocks and soil. The remaining 20 percent comes from man-made radiation sources, primarily medical x-rays.
Radiation is a carcinogen. In this respect, it is similar to many hazardous chemicals found in the environment that can cause cancer. It may also cause other adverse health effects, including genetic defects in the children of exposed parents or mental retardation in the children of mothers exposed during pregnancy. However, the risk of developing cancer due to radiation exposure is much higher than the risk of these other effects.
Much of our knowledge about the risks from radiation is based on studies of over 100,000 survivors of the atomic bombs at Hiroshima and Nagasaki. In these studies, which have continued over the last 40 years, scientists have been able to observe the effects of a wide range of radiation doses, including doses comparable to an average person's lifetime dose from naturally-occurring background radiation (about 20,000 millirem). We have learned many things from these studies. The most important are:
The more radiation dose a person receives, the greater the chance of developing cancer.
It is the chance of cancer occurring, not the kind or severity of cancer, that increases as the radiation dose increases.
Most cancers do not appear until many years after the radiation dose is received (typically 10 to 40 years).
Current evidence suggests that any exposure to radiation poses some risk, i.e., there is no level below which we can say an exposure poses no risk. For the entire dose of radiation we accumulate over a lifetime from natural background radiation, the risk of developing cancer is estimated to be about one in one hundred. Based on this estimate, several percent of all fatal cancers in the U.S. are caused by background radiation. The additional contribution from all man-made sources of radiation is much smaller.
Fifty-five percent of our exposure to natural sources of radiation usually comes from radon. Radon is a colorless, tasteless, and odorless gas that comes from the decay of uranium found in nearly all soils. Levels of radon vary throughout the country. Radon usually moves from the ground up and migrates into homes and other buildings through cracks and other holes in their foundations. The buildings trap radon inside, where it accumulates and may become a health hazard if the building is not properly ventilated.
When you breathe air containing a large amount of radon, the radiation can damage your lungs and eventually cause lung cancer. Scientists believe that radon is the second leading cause of lung cancer in the United States. It is estimated that 7,000 to 30,000 Americans die each year from radon-induced lung cancer. Only smoking causes more lung cancer deaths and smokers exposed to radon are at higher risk than nonsmokers.
Click here for more information about radon in your home.
Radon is found all over the United States. Scientists estimate that nearly one out of every 15 homes in this country has radon levels higher than four picocuries per liter, the level above which EPA recommends that homeowners take corrective action. Picocuries per liter is how radon in the air is measured. Testing your home is the only way to know if you and your family are at risk from radon.
Testing for radon is easy and only takes a few minutes of your time. There are many kinds of low-cost, "do-it-yourself," EPA-approved or state-certified radon test kits available through the mail or from retail outlets. You can also hire a professional to do the testing. EPA recommends choosing a state-certified and/or EPA-listed measurement company.
If you find high radon concentrations, you can reduce them in a variety of ways. Reduction methods can be as simple as sealing cracks in floors and walls or as complex as installing systems that use pipes and fans to draw radon out of the building.
EPA has a National Radon Program to inform the public about radon risks, train radon mitigation contractors, provide grants for state radon programs, and develop standards for radon-resistant buildings. EPA works with health organizations, state radon programs, and other federal agencies to make the program as effective as possible.
For more information about radon, its risks and what you can do to protect yourself, call 1-800-SOS-RADON or contact your state's radon office and request a free copy of EPA's A Citizen's Guide to Radon.
Radon gas is not the only source of natural radioactivity. We receive about eight percent of our exposure to radiation from other radioactive elements in the earth's crust, such as thorium and potassium. Radiation levels from these sources vary in different areas of the country.
Another eight percent of our radiation exposure comes from outer space. This cosmic radiation originates in our galaxy, other galaxies, and our own sun. Our exposure to cosmic radiation depends in part on the elevation where we live. For example, people who live in Denver, Colorado, which is more than 5,000 feet above sea level, are exposed to more cosmic radiation than people living in Chicago, Illinois. Because Chicago is only approximately 1,000 feet above sea level, it has a thicker atmosphere, which can filter out more cosmic radiation than Denver's thinner atmosphere.
Back to top
This page was updated on 23-Mar-2017
This page was updated on 23-Mar-2017