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 low-energy (low-frequency) radiation to very high-energy (high-frequency) radiation. This is sometimes referred to as the electromagnetic spectrum. The electromagnetic spectrum illustration below shows all of the possible frequencies of electromagnetic energy. It ranges from extremely low frequencies (such as those from power lines) to extremely high frequencies (x-rays and gamma rays), and includes both non-ionizing and ionizing radiation. Examples of high-energy radiation include x-rays and gamma rays. These rays, as well as some higher energy UV radiation, are forms of ionizing radiation, which means they have enough energy to remove an electron from (ionize) an atom. This can damage the DNA (genes) inside of cells, which can sometimes result in cancer. Radiofrequency (RF) radiation, which includes radio waves and microwaves, is at the low-energy end of the electromagnetic spectrum.

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 Radiofrequency (RF) Radiation

The American Cancer Society

 

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 low-energy (low-frequency) radiation to very high-energy (high-frequency) radiation. This is sometimes referred to as the electromagnetic spectrum.

The electromagnetic spectrum illustration below shows all of the possible frequencies of electromagnetic energy.

It ranges from extremely low frequencies (such as those from power lines) to extremely high frequencies (x-rays and gamma rays), and includes both non-ionizing and ionizing radiation.

Examples of high-energy radiation include x-rays and gamma rays.

These rays, as well as some higher energy UV radiation, are forms of ionizing radiation, which means they have enough energy to remove an electron from (ionize) an atom.

This can damage the DNA (genes) inside of cells, which can sometimes result in cancer.

What is radiofrequency (RF) radiation?

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 does not have enough energy to remove electrons from an atom.

Visible light is another type of non-ionizing radiation. 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 by the body in large enough amounts, it can produce heat. This can lead to burns and body tissue damage.

Although RF radiation is not thought to cause cancer by damaging the DNA in cells the way ionizing radiation does, there has been concern that in some circumstances, some forms of non-ionizing radiation might still have other effects on cells that might somehow result in cancer.

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 sources include:

·          Broadcasting radio and television signals

·          Transmitting signals from cordless telephones, cell phones and cell phone towers, satellite phones, and 2-way radios

·          Radar

·          WiFi, Bluetooth^® devices, and smart meters

·          The heating of 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 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 devices, cell phones (and cell phone towers), and other sources.

Some common uses of RF radiation

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 food absorbs microwaves, it causes the water molecules in the food to vibrate, which produces heat. Microwaves do not use x-rays or gamma rays, and they do not make food radioactive.

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 RF 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.

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. Receivers sense the radiation and create an image of the outline 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 (base stations) 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 information, see Cellular Phones and Cell Phone Towers.

Does RF radiation cause cancer?

Researchers use 2 main types of studies to try to determine if something might cause cancer:

·               Studies done in the lab studies

·               Studies looking at groups of people

Often neither type of study provides enough evidence on its own, so researchers usually look at both lab-based and human studies when trying to figure out if something causes cancer.

The following is a brief summary of some of the major studies that have looked at this issue to date. However, this is not a comprehensive review of all studies that have been done.

Studies done in the lab

RF waves don’t have enough energy to damage DNA directly. Because of this, it’s not clear how RF radiation might be able to cause cancer.

Some studies have found possible increased rates of certain types of tumors in lab animals exposed to RF radiation, but overall, the results of these types of studies have not provided clear answers so far.

A few studies have reported evidence of biological effects that could be linked to cancer, but this is still an area of research.

In large studies published in 2018 by the US National Toxicology Program (NTP) and by the Ramazzini Institute in Italy, researchers exposed groups of lab rats (as well as mice, in the case of the NTP study) to RF waves over their entire bodies for many hours a day, starting before birth and continuing for at least most of their natural lives.

Both studies found an increased risk of uncommon heart tumors called malignant schwannomas in male rats, but not in female rats (nor in male or female mice, in the NTP study).

The NTP study also reported possible increased risks of certain types of tumors in the brain and in the adrenal glands.

While both of these studies had strengths, they also had limitations that make it hard to know how they might apply to humans being exposed to RF radiation.

A 2019 review of these two studies by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) determined that the limitations of the studies didn’t allow conclusions to be drawn regarding the ability of RF energy to cause cancer.

Still, the results of these studies do not rule out the possibility that RF radiation might somehow be able to impact human health.

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 for a possible link between cell phones and cancer. Although some studies have shown a possible link, many others have not.

For many reasons, it is hard to study if there might be a link between cell phones and cancer, including the relatively short time that cell phones have been in widespread use, changes in the technology over time, and difficulty in estimating each person’s exposure.

The topic of cell phones and cancer risk is discussed in detail in Cellular (Cell) Phones.

What do expert agencies say?

The American Cancer Society (ACS) does not have any official position or statement on whether or not radiofrequency radiation from cell phones, cell phones towers, or other sources is a cause of cancer. 

ACS generally looks to other expert organizations to determine if something causes cancer (that is, if it is a carcinogen), including:

·          The International Agency for Research on Cancer (IARC), which is part of the World Health Organization (WHO)

·          The US National Toxicology Program (NTP), which is formed from parts of several different government agencies, including the National Institutes of Health (NIH), the Centers for Disease Control and Prevention (CDC), and the Food and Drug Administration (FDA)

Other major organizations might also comment on the ability of certain exposures to cause cancer.

Based on a review of studies published up until 2011, the International Agency for Research on Cancer (IARC) has classified RF radiation as “possibly carcinogenic to humans,” based on limited evidence of a possible increase in risk for brain tumors among cell phone users, and inadequate evidence for other types of cancer. (For more information on the IARC classification system, see Known and Probable Human Carcinogens.) 

More recently, the US Food and Drug Administration (FDA) issued a technical report based on results of studies published between 2008 and 2018, as well as national trends in cancer rates.

The report concluded: “Based on the studies that are described in detail in this report, there is insufficient evidence to support a causal association between radiofrequency radiation (RFR) exposure and [tumor formation].”

So far, the National Toxicology Program (NTP) has not included RF radiation in its Report on Carcinogens, which lists exposures that are known to be or reasonably anticipated to be human carcinogens. (For more on this report, see Known and Probable Human Carcinogens.)

According to the US Federal Communications Commission (FCC):

“[C]urrently no scientific evidence establishes a causal link between wireless device use and cancer or other illnesses. Those evaluating the potential risks of using wireless devices agree that more and longer-term studies should explore whether there is a better basis for RF safety standards than is currently used.”

How can I avoid exposure to RF radiation?

Because sources of RF radiation are so common in the modern world, there is no way to completely avoid exposure to it.

There are some ways you can lower your exposure to RF radiation, such as:

·          Avoiding jobs with increased RF exposure

·          Limiting the time you spend near appliances, equipment, and other devices (such as WiFi routers) that give off RF radiation

·          Limiting the time you spend with a cell (mobile) phone placed against your ear (or close to another part of your body)

Still, it isn’t clear that doing these things will be helpful in terms of health risks. 

The American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

At the American Cancer Society, we're on a mission to free the world from cancer. Until we do, we'll be funding and conducting research, sharing expert information, supporting patients, and spreading the word about prevention. All so you can live longer — and better.

Whether we're working in a community near you or one halfway around the world, our mission remains the same: to save lives. See what we've been up to lately — and get to know the American Cancer Society a little bit better.

https://www.cancer.org/cancer/cancer-causes/radiation-exposure/radiofrequency-radiation.html

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MICROWAVE OVENS - How Do Microwave Ovens Work? - These handy kitchen appliances are actually packed with interesting science and physics. Microwaves are a very useful cooking device. They're compact, tiny, but incredibly versatile machines – so how do they work? There's an incredible amount of science and engineering behind microwaves, but it can all be broken down into easy to understand and digest bits. Microwave ovens mainly function by generating microwave radiation - which is passed through the food, cooking it. Microwaves aren't specific to microwave ovens, rather they are a form of electromagnetic waves with a wavelength in the frequency range of between 300 MHz and 300 GHz (a wavelength of around 1 m and 1 mm). Microwave ovens generally use a frequency of 2450 MHz (a wavelength of 12.24 cm). When compared to other types of radiation, microwaves fall between radio waves, which tend to be longer, and infrared waves, which are shorter. What makes microwaves so specialized for cooking is just how they interact with water molecules. Inside microwave ovens, the microwaves are created using a device called a magnetron. At their core, magnetrons are high-voltage motors that output energy in the form of microwaves rather than mechanical work. Inside the microwave oven, a transformer steps up electricity from the wall socket, 120V in the US, or 110V in Europe, to around 4000 volts.

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Microwave Ovens

How Do Microwave Ovens Work?

These handy kitchen appliances are actually packed with interesting science and physics.

By  Trevor English

Interesting Engineering

 

Microwaves are a very useful cooking device. They're compact, tiny, but incredibly versatile machines – so how do they work?

There's an incredible amount of science and engineering behind microwaves, but it can all be broken down into easy to understand and digest bits.

Microwave ovens mainly function by generating microwave radiation - which is passed through the food, cooking it.

Microwaves aren't specific to microwave ovens, rather they are a form of electromagnetic waves with a wavelength in the frequency range of between 300 MHz and 300 GHz (a wavelength of around 1 m and 1 mm).

Microwave ovens generally use a frequency of 2450 MHz (a wavelength of 12.24 cm).

When compared to other types of radiation, microwaves fall between radio waves, which tend to be longer, and infrared waves, which are shorter.

What makes microwaves so specialized for cooking is just how they interact with water molecules.

The science behind microwaves

Inside microwave ovens, the microwaves are created using a device called a magnetron.

At their core, magnetrons are high-voltage motors that output energy in the form of microwaves rather than mechanical work.

Inside the microwave oven, a transformer steps up electricity from the wall socket, 120V in the US, or 110V in Europe, to around 4000 volts.

This increased voltage is needed to power the magnetron, causing a filament to heat up at the core of the device.

As this filament heats up, electrons are released.

The microwave oven puts these electrons to work.

A circular magnet is located near the heated filament.

Normally, the electrons that are released by the filament would become attracted to the anode, but because of the positioning of the magnet, the electrons loop back to the filament itself.

This looping of electrons is what actually creates microwaves.

All of that may have sounded a little bit complex, and it can be when explained without diagrams.

For a deeper dive into the understanding of how magnetrons and, ultimately, microwaves work, take a look at the video below.

https://youtu.be/kp33ZprO0Ck

Are you safe to stand next to a microwave?

One popular myth about microwaves is that they can give you cancer.

This may stem from the use of the word 'radiation' in describing how they work, as well as a fear that this microwave radiation can leak out of the microwave.

Radiation, in this case, refers to energy that radiates from a source, and not to radioactivity.

However, microwaves do not contain enough energy to chemically change substances through ionization - they are an example of non-ionizing radiation.

Other types of electromagnetic waves such as ultraviolet and x-rays possess more energy per photon and thus can cause cancer.

Microwaves can, of course, cause heating and burns, but microwave ovens are all designed with a metal mesh on the door of the appliance to keep the microwaves from leaking out.

These metal meshes are large enough for you to see your food cooking, but the holes aren't large enough for the microwaves to slip through.

Microwave ovens also have built-in safety devices that do not allow the oven to work while the door is open.

So, at the end of the day, you won't get cancer from standing too close to a microwave because the rays aren't ionizing, and you won't get cooked either.

We've gotten through the basic science, but we still haven't covered why exactly microwaves work so well to heat food quickly.

How microwaves heat up water molecules

The microwaves used in a microwave oven are sent out through a type of antenna that channels them into the cooking area of the appliance.

The waves are contained inside of the appliance thanks to the solid metal walls (and mesh door).

These microwaves are then absorbed by the water molecules inside of the food.

The energy from the microwaves causes the water molecules to vibrate rapidly, which heats the food.

In essence, because water molecules easily absorb microwaves, which cause the molecules to start vibrating rapidly, this becomes a mechanism to turn microwave energy into thermal energy.

Just like a cam and roller is a mechanical device for converting rotational energy into linear motion, so too are the interactions of microwaves and water molecules a way of converting microwave energy into heat energy.

https://youtu.be/SlkLa9Ezt00

But why are just the water molecules vibrating?

Water molecules are polar, meaning they have a positively charged side and a negatively charged side.

Microwaves have a positive crest and a negative crest, just like any wave does.

As the microwaves move throughout the inside of the microwave oven, the water molecules will try to align their poles with that of the microwave.

Since microwaves move about rapidly inside of the appliance, the water molecules rapidly try to keep aligning themselves with the motion of the waves.

Just how fast is this happening?

Microwaves' positive and negative fields are moving at roughly 2.5 billion times per second.

When you combine this effect with the water molecule's reaction, you can start to realize how microwaves cook food so fast and effectively.

Why do microwaves cook unevenly?

The last question we need to answer is why there are often dead spots on the inside of microwave ovens.

For example, why is the center of your food often much colder than the edges?

This occurs because some of the microwaves end up canceling each other out.

Oftentimes, these places of cancelation are localized, meaning some areas of the microwave oven don't get any "heat".

In essence, when the peak  of one wave hits the valley of another wave, the result is a canceled-out wave. This is why most microwaves use a rotating dish in order to ensure even cooking.

So, that's how microwave ovens work.

They are appliances that use magnets to produce electromagnetic radiation at a particular wavelength, which is directed at water molecules  in food, causing them to vibrate and heat up rapidly.

Next time you cook something in a microwave, you won't look at it the same way.

Founded on the core mission of connecting likeminded engineers around the globe, Interesting Engineering is now a leading community with more than 15 million+ minds. Every day we share a new idea, a new thought, an upcoming technology OR an engineering breakthrough that will change the way you think about technology and engineering in today’s world and in the near future. Whether it’s a device that can charge your mobile in seconds or it’s the latest model of Boeing that has launched moments ago, we will bring everything up on your screen to view, to share and to grant you the power to comment. We believe that sharing information is the only way that can enrich and empower humans on this earth and we follow this as our core mission and responsibility. If you have got something that could entice the world, then Interesting Engineering is a perfect platform to show off your work to the outside world.

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