How Are People Exposed to X-rays and Gamma Rays?

Exposure to x-rays and gamma rays can come from several sources. The main 3 sources are natural background radiation, medical radiation, and radiation from other human-made sources, like nuclear power plants and nuclear weapons.

X-rays and gamma rays from natural background radiation

All people are exposed to some radiation just from being on this planet. This is known as background radiation. In the US, this amount averages to about 3 millisieverts (mSv) per year. For most people, background radiation will be most of their exposure to ionizing radiation during a year. It comes from several sources.

Cosmic rays

Cosmic rays are radioactive particles that hit the earth from outer space. They come from the sun and from other stars. The earth’s atmosphere blocks a portion of these rays, but some of them reach the ground.

Exposure is greater at higher altitudes. For example, people who live in Denver, a city with a high elevation, are exposed to more cosmic rays than people living at sea level.

Flying in a plane exposes people to higher levels of cosmic rays than being on the ground. Airline pilots and flight attendants, who spend many hours at high elevations, are exposed to more of these rays. However, it is not clear if they have an increased risk of cancer because of it. The Federal Aviation Administration (FAA) tracks flight crews’ exposure to cosmic radiation.

Radon

The largest source of natural background radiation for most people is radon. Radon is an odorless, colorless gas that is formed from the breakdown of radioactive materials in the ground.

Radon levels are usually higher inside buildings and homes, especially in spaces closer to the ground, such as basements. Radon levels vary a great deal, depending on where you live. Some people are exposed to higher radon levels on the job, especially if they work underground, like in some types of mines.

For more on radon and its possible health effects, see Radon and Cancer Risk.

Other sources of radiation in the earth

People are also exposed to small amounts of radiation from other radioactive elements that occur naturally in rocks and soil. Some of these may end up in building materials used in houses and other structures. Tiny amounts of radiation may even be found in drinking water, plants, and some plant-based foods.

For example, as tobacco plants grow, they can absorb radiation from the soil, as well as from fertilizers. Products made from tobacco contain this radiation. People who smoke or chew tobacco can be exposed to a significant amount. This radiation can also be found in secondhand smoke.

X-rays and gamma rays from medical radiation

X-rays, gamma rays, and other forms of ionizing radiation are used to diagnose and treat some medical conditions. Radiation can be directed at the body from a machine, or a person may have radioactive particles put inside their body.

Imaging tests

Certain types of imaging tests, such as x-rays, CT scans, and nuclear medicine tests (like PET scans and bone scans) expose people to low levels of radiation to create images of the inside of the body. Over the years, the amount of radiation used in many imaging tests has been reduced as technology has improved.

The amount of radiation a person is exposed to depends on the test being done, as well as on a person’s size and age. For children, concerns about these tests are increased because:

• Children, especially younger ones, are much more sensitive to radiation than adults.
• Children are expected to live longer than adults, so they have more time to develop problems from radiation exposure.
• With tests like CT scans, children might get a higher radiation dose than necessary if the CT scanner settings are not adjusted for their smaller body size.

A young child’s risk of developing a radiation-related cancer after an imaging test could be several times higher than for an adult who gets the same test.

To learn more, see Understanding Radiation Risk from Imaging Tests.

Radiation therapy

X-rays, gamma rays, and other forms of ionizing radiation are an effective way to treat some types of cancer. Radiation is also sometimes used to treat other serious medical conditions.

During radiation therapy, ionizing radiation is directed at the cancer, resulting in the death of the cancer cells. The doses of radiation used for this treatment are much higher than those used in imaging tests. Radiation therapy can sometimes lead to DNA changes (mutations) in cells that survive the radiation. It might lead to the development of a second cancer years later.

For more information about cancer risks from radiation therapy for cancer, see Second Cancers.

X-rays and gamma rays from other human-made sources

People may also be exposed to ionizing radiation from other human-made sources.

Nuclear weapons

In 1945, atomic bombs dropped on Nagasaki and Hiroshima, Japan, exposed many people to x-rays, gamma rays, and other types of radiation. Some people died quickly from burns and radiation sickness, but many survived.

The survivors were exposed to different amounts of radiation, depending on how far they were from the explosions. Today, much of the information known about radiation and cancer risk comes from studies of the people who survived.

Between 1945 and 1962, the United States government conducted above-ground nuclear tests in Nevada and in the South Pacific. At the time, many people in the military were part of training exercises in these areas. They were exposed to ionizing radiation from these tests. Others were exposed to radiation while working at facilities making the bombs or at other nuclear sites.

People living near or downwind of nuclear test sites may have also been exposed to radioactive byproducts. Some radioactive particles from the tests traveled great distances through the air, landing far away from the original site. While exposure levels were likely to be higher at the time of testing, some radiation in the soil today is the result of these tests.

Nuclear power plants

Emissions of radiation from nuclear power plants are carefully monitored and controlled. According to the US Environmental Protection Agency (EPA), nuclear power plant operations account for only a tiny amount of the average American’s total radiation exposure.

Accidents at nuclear power plants are rare, but they could possibly expose people to high levels of radiation.

In 1986, an accident at the nuclear power plant at Chernobyl (in Ukraine, which was then part of the Soviet Union) exposed millions of people in the area to radiation. This was from either direct exposure or from released radioactive elements that ended up on the ground. Emergency cleanup workers were exposed to the highest levels of radiation.

In 2011, an earthquake and tsunami struck the coast of Japan and damaged the Fukushima Daiichi Nuclear Power Plant. Radiation was released into the air, contaminating soil, food, and water (both fresh and seawater). An area of more than 300 square miles around the plant was found to be contaminated with radiation, although at lower levels than within the plant. Because of high radiation levels, many areas were evacuated. The health effects of this disaster are still being studied.

Workplace exposures

Some people can be exposed to radiation at work. For example:

• People who work in nuclear power plants may be exposed to higher levels of radiation than the general public. However, the exposure levels for these employees are monitored carefully.
• People who work in uranium mines are monitored because of their exposure to radiation in the form of radon.
• People who work in medical facilities and dental offices may also be exposed to radiation at work, particularly those who work with x-ray or other imaging test equipment or who work with radioactive isotopes. Radiation exposure may also occur at some research labs.

In the US, people who are likely to be exposed to radiation in the workplace are monitored carefully. Safety measures have been put into place to lower exposure as much as possible. Federal and international standards limit workplace radiation exposure to an effective dose of 100 mSv over 5 years, with a maximum of 50 mSv in any single year, to help prevent harm.

Consumer products

Some consumer products contain small amounts of ionizing radiation.

Tobacco products contain low levels of radiation, which may come from the soil it’s grown in or the fertilizer used to help it grow. Tobacco may account for a significant portion of the yearly radiation exposure for people who smoke or who are exposed to secondhand smoke.

Some building materials may contain low levels of naturally occurring radiation, which can be given off in the form of radon gas. These levels are most often found in brick, concrete, and granite and other types of stone used in buildings. The amount of radiation can vary depending on the materials used, but the levels are unlikely to add much to a person’s overall exposure to radiation.

Some smoke detectors contain a small amount of a very low-level radioactive material that helps detect smoke. This material is sealed in a container and does not pose a significant risk of radiation exposure.

Food irradiation

Ionizing radiation can be used to kill bacteria and other germs on certain foods, which may make them safer to eat and last longer. Some people may be concerned that irradiated food may contain radiation.

The radiation used to treat foods doesn’t stay in them. Irradiating food does not make it radioactive. It also does not change the nutritional value, Nuclear power plant accidents taste, texture, or appearance of the food.

Can I avoid x-rays and gamma rays or limit being exposed to them?

Every person will be exposed to some amount of radiation during their lifetime. You can, however, limit your exposure to some sources of radiation, such as radon in your home, tobacco, x-rays from imaging tests, and radiation in the workplace.

Radon

For most people, the largest potential source of radon exposure is in their home. You can check radon levels in your home, either with do-it-yourself kits or by hiring a professional. If the levels are high, you can take steps to lower them.

For more information, see Radon and Cancer.

Tobacco

If you smoke or chew tobacco, you can reduce your radiation exposure by quitting. The American Cancer Society provides many tools to help with quitting. It is also helpful to avoid secondhand smoke.

Radiation from imaging tests

The increased risk of cancer from exposure to any single imaging test is likely to be very small. But radiation exposure from all sources can add up over a lifetime. Imaging tests that use radiation should only be done if there is a good medical reason to do so.

Sometimes, other imaging tests that don’t use radiation, such as an ultrasound or MRI, might be an option. But if an x-ray or CT scan is the best test to look for cancer or other diseases, the imaging test is more likely to be helpful than to cause harm.

If you do need a test that will expose you to some radiation, ask if there are ways to shield parts of your body that aren’t being imaged. For example, a lead apron can sometimes be used to protect parts of your chest or abdomen from radiation. A lead collar, known as a thyroid shield or thyroid collar, can be used to protect your thyroid gland.

For children

Exposure to radiation from imaging tests is of particular concern in children. Their bodies are smaller and more sensitive to radiation. Before a child has an imaging test, parents should ask questions to make sure that the test is really needed. They should also ask if the facility is experienced in adjusting radiation doses for children.

For more detailed information, see Understanding Radiation Risk from Imaging Tests.

Radiation in the workplace

In the US, several federal agencies are charged with protecting workers from radiation exposure, including the Nuclear Regulatory Commission (NRC) and the Occupational Safety and Health Administration (OSHA). These agencies set limits on exposure to ionizing radiation in the workplace.

If you work someplace where radiation exposure is possible, your employer must have safety policies that address the risks and ways to minimize them. For example, employers need to monitor how much radiation their employees are exposed to and make sure that it stays below certain limits. Workers should learn about the risks and follow safety procedures, which may include using protective clothing and equipment.