Radiation
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, which includes radio waves and microwaves, is at the low-energy end of the electromagnetic spectrum. It 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 lower energy than some other types of non-ionizing radiation, like visible light and infrared, but it has higher energy than extremely low-frequency (ELF) radiation.
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:
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
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, which produces heat. Microwaves do not use x-rays or gamma rays, and they do not make food radioactive. Microwave ovens can cook food, but they 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, 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.
Full-body security scanners
In many 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. According to the US Food and Drug Administration (FDA), these scanners have no known health effects. However, TSA often 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, see Cellular Phones and Cellular Phone Towers.
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, which includes radio waves and microwaves, is at the low-energy end of the electromagnetic spectrum. It 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 lower energy than some other types of non-ionizing radiation, like visible light and infrared, but it has higher energy than extremely low-frequency (ELF) radiation.
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, cell phones and cell phone towers, satellite phones, and 2-way radios
- Radar
- 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
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, which produces heat. Microwaves do not use x-rays or gamma rays, and they do not make food radioactive. Microwave ovens can cook food, but they 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, 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.
Full-body security scanners
In many 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. According to the US Food and Drug Administration (FDA), these scanners have no known health effects. However, TSA often 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, see Cellular Phones and Cellular Phone Towers.