Microwaves, Radio Waves, and Other Types of Radiofrequency Radiation
What is radiofrequency (RF) radiation?
Radiation is the emission (sending out) of energy from any source. X-rays are an example of radiation, but so is the light that comes from the sun and the heat that is constantly coming off our bodies.
When talking about radiation and cancer, many people think of specific kinds of radiation such as x-rays or the radiation made by nuclear reactors. But there are other types of radiation that act differently.
Radiation exists across a spectrum from very high-energy (high-frequency) radiation to very low-energy (low-frequency) radiation. This is sometimes referred to as the electromagnetic spectrum.
Examples of high-energy radiation include x-rays and gamma rays. They, as well as some higher energy UV radiation, are called ionizing radiation, which means they have enough energy to remove an electron from (ionize) an atom or molecule. This can damage the DNA inside of cells, which can result in cancer.
Radiofrequency (RF) radiation is at the low-energy end of the electromagnetic spectrum and is a type of non-ionizing radiation. Non-ionizing radiation has enough energy to move atoms in a molecule around or cause them to vibrate, but not enough to ionize (remove charged particles such as electrons). RF radiation has higher energy than extremely low-frequency electromagnetic radiation, but lower energy than some other types of non-ionizing radiation, like visible light and infrared. Ionizing radiation has even higher energy.
If RF radiation is absorbed in large enough amounts by materials containing water, such as food, fluids, and body tissues, it can produce heat. This can lead to burns and tissue damage. Although RF radiation does not cause cancer by damaging DNA in cells the way ionizing radiation does, there has been concern that some forms of non-ionizing radiation might have biological effects that could result in cancer in some circumstances.
How are people exposed to RF radiation?
People can be exposed to RF radiation from both natural and man-made sources.
Natural sources include:
- Outer space and the sun
- The sky – including lightning strikes
- The earth itself – most radiation from the earth is infrared, but a tiny fraction is RF
Man-made RF radiation is used for many different things, such as
- Broadcasting radio and television signals
- Transmitting signals from cordless telephones, cellular phones and cell phone towers, satellite phones, and 2-way radios
- WiFi and Bluetooth
- Cooking food (in a microwave oven)
- Heating body tissues to destroy them in medical procedures
- “Welding” pieces of polyvinyl chloride (PVC) using certain machines
- Millimeter wave scanners (a type of full body scanner used for security screening)
Some people can have significant RF exposure as part of their jobs. This includes PVC welders, people who maintain antenna towers that broadcast communication signals, and people who use or maintain radar equipment.
Most people are exposed to much lower levels of man-made RF radiation every day due to the presence of RF signals all around us. They come from radio and television broadcasts, WiFi and Bluetooth, cell phones (and cell phone towers), and other sources.
Microwave ovens work by using very high levels of a certain frequency of RF radiation (in the microwave spectrum) to heat foods. When microwaves are absorbed by food containing water, it causes the water molecules to vibrate. This produces heat. Microwaves do not use x-rays or gamma rays, and they do not make food radioactive. Microwave ovens can cook food, but do not otherwise change the chemical or molecular structure of it.
Microwave ovens are designed so that the microwaves are contained within the oven itself. The oven only makes microwaves when the door is shut and the oven is turned on. When microwave ovens are used according to instructions, there is no evidence that they pose a health risk to people. In the US, the federal standards limit the amount of radiation that can leak from a microwave oven to a level far below what would harm people. Ovens that are damaged or modified, however, could allow microwaves to leak out, and so could pose a hazard to people nearby by potentially causing burns.
Although some people have been injured from microwave ovens, most often they have been burns from contact with steam or hot food.
In the past, there was a concern that leakage from microwave ovens could interfere with pacemaker function. Pacemakers are now designed to be shielded from outside electrical activity, so this is no longer a concern for most people. If you are worried, though, you can ask your doctor if being around a microwave is safe for you.
Full-body security scanners
In some airports in the United States, the Transportation Security Administration (TSA) uses full body scanners to screen passengers. The scanners currently used by the TSA use millimeter wave imaging. These scanners send out a small amount of millimeter wave radiation (a type of RF radiation) toward the person in the scanner. The RF radiation passes through clothing and bounces off the person’s skin as well as any objects under the clothes. The radiation is sensed by receivers that create images of the person.
Millimeter wave scanners do not use x-rays (or any other kind of high-energy radiation) and the amount of RF radiation used is very low – much less than that from a cell phone. According to the Food and Drug Administration, these scanners have no known health effects. However, TSA allows people to be screened in a different way if they object to screening with these scanners.
Cell phones and cell phone towers
Cell phones and cell phone towers use RF radiation to transmit and receive signals. Some concerns have been raised that these signals might increase the risk of cancer, and research in this area continues. For more detailed information, refer to our documents Cellular Phones and Cellular Phone Towers.
Does RF radiation cause cancer?
Researchers use 2 main types of studies to try to determine if something might cause cancer.
Lab studies usually expose animals to chemical or physical agents (such as RF energy) to see if it causes tumors or other health problems. It’s not always clear if the results from these types of studies will apply to humans, but lab studies allow researchers to carefully control for other factors that might affect the results and to answer some basic science questions.
Another type of study looks at cancer rates in different groups of people. Such a study might compare the cancer rate in a group exposed to something like RF energy versus the rate in a group not exposed to it, or compare it to what the expected cancer rate would be in the general population. But studies in people can sometimes be hard to interpret, because there may be other factors affecting the results that are hard to account for.
In most cases neither type of study provides enough evidence on its own to show if something causes cancer in people, so researchers usually look at both lab-based and human studies.
Studies done in the lab
Most animal and laboratory studies have found no evidence of an increased risk of cancer with exposure to RF radiation. A few studies have reported evidence of biological effects that could be linked to cancer..
Studies in people
Studies of people who may have been exposed to RF radiation at their jobs (such as people who work around or with radar equipment, those who service communication antennae, and radio operators) have found no clear increase in cancer risk.
A number of studies have looked at the possible link between cell phones and cancer. Although one large study showed a possible link, most studies did not. Still, many question the quality of these studies and their ability to find a link. The possible link between cell phones and cancer risk is discussed in detail in our document Cellular Phones.
What do expert agencies say?
Several agencies (national and international) study different substances in the environment to determine if they can cause cancer. (A substance that causes cancer or helps cancer grow is called a carcinogen.) The American Cancer Society looks to these organizations to evaluate the risks based on evidence from laboratory, animal, and human research studies.
The International Agency for Research on Cancer (IARC) is part of the World Health Organization. Its major goal is to identify causes of cancer. IARC has stated that there is limited evidence that RF radiation causes cancer in animals and humans, and classifies RF radiation as “possibly carcinogenic to humans” This was based on the finding of a possible link in at least one study between cell phone use and a specific type of brain tumor. IARC considers the evidence overall to be “limited” because of the conflicting findings and generally low quality of the studies that have been done.
The other main agencies that classify cancer-causing exposures (carcinogens), including the US Environmental Protection Agency (EPA) and the National Toxicology Program (NTP), have not formally classified RF radiation as to its cancer-causing potential.
(For more information on the classification systems used by these agencies, see our document Known and Probable Human Carcinogens.)
Does RF radiation cause any other health problems?
Studies in the lab
In animals, the main effects of exposure to RF are related to heating (sometimes called thermal effects). High doses of RF radiation can raise body temperature, even to the point of being fatal. Focusing RF radiation on one area of the body can lead to burns and the breakdown of tissue. When RF waves are focused on the eye, it can cause cataracts to form.
It isn’t clear what effects, if any, RF radiation has at levels of exposure too low to produce heating.
People have been exposed to large amounts of RF radiation through accidents involving radar equipment. This has led to severe burns.
People who are near microwave radar equipment can be exposed to enough pulsed microwave radiation (a type of RF radiation) that they begin to hear clicking noises. This is sometimes called RF hearing and does not seem to cause long term health problems.
Although there is concern that people exposed to low levels of microwaves over long periods of time in their jobs could have an increased risk of cataracts or loss of fertility (in men), this has not been seen in large studies.
How can I avoid exposure to RF radiation?
Because sources of RF radiation are so common in the modern environment, there is no way to completely avoid exposure to it. It may be possible to lower your exposure to RF radiation by avoiding jobs with increased RF exposure, keeping away from appliances and equipment that use RF, and using devices that allow mobile phones to be used without placing them against the ear. Still, it isn’t clear that doing so will be helpful in terms of health risks.
More information from your American Cancer Society
The following related information may also be helpful to you. These materials may be viewed on our website or ordered from our toll-free number, at 1-800-227-2345.
National organizations and websites*
In addition to the American Cancer Society, other sources of information and support include:
Centers for Disease Control and Prevention (CDC)
Toll-free number: 1-800-232-4636 (1-800-CDC-INFO)
Environmental Protection Agency (EPA)
Understanding Radiation: www.epa.gov/radiation/understanding-radiation-overview.html
National Cancer Institute (NCI)
Toll-free number: 1-800-422-6237 (1-800-4-CANCER)
Magnetic Field Exposure and Cancer: www.cancer.gov/cancertopics/factsheet/Risk/magnetic-fields
National Institute of Environmental Health Sciences
Electric and Magnetic Fields: www.niehs.nih.gov/health/topics/agents/emf/index.cfmww
*Inclusion on this list does not imply endorsement by the American Cancer Society.
No matter who you are, we can help. Contact us anytime, day or night, for information and support. Call us at 1-800-227-2345 or visit www.cancer.org.
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Last Revised: 10/16/2013