Just the facts. Just Science.
Electromagnetic waves (also known as electromagnetic radiation or EMR) are comprised of oscillating electric and magnetic fields that travel through space carrying energy as they radiate from their source. Waves are measured by frequency or wavelength, which are related. Wavelength is the distance between the crests of a wave, and frequency is the number of times a crest passes a point each second, Figure 1. Longer wavelengths have a lower frequency and less energy than shorter waves. The intensity or power of the EMR is represented by the wave’s height, as shown in Figure 2. The shortest wavelengths have the highest frequencies and the most energy among the full range of electromagnetic waves referred to as the electromagnetic spectrum, Figure 3.
Electromagnetic fields (EMFs) are simply the combined electric and magnetic forces created whenever electricity is generated, transmitted, or used. Electric and magnetic fields are tied together — one creates the other as they spread out from their origin at the speed of light. The strength of an electric field is measured in volts per meter (V/m). Magnetic fields are generated by moving electric charges or by the motion of electrons. Magnetic fields exert forces on other moving charged particles and can also affect magnetic materials like iron. The strength of a magnetic field is measured in ampere per meter (A/m).
Electromagnetic waves are also referred to as “radiation” because waves radiate from a source such as a cell phone, the sun, or radioactive materials, but not all radiation acts the same. There are two broad categories of radiation at the opposite ends of the electromagnetic spectrum: ionizing radiation and non-ionizing radiation, as seen in Figure 3.
Figure 3 Electromagnetic energy is integral to our quality of life, health, and well-being. Our modern way of life depends on energy in the electromagnetic spectrum such as when you use GPS to get directions, make a call with your mobile phone, or listen to the radio. Gamma rays, X rays, and ultraviolet rays are ionizing radiation because they have energy sufficient to alter the chemistry of atoms and molecules, which can cause damage at the cellular level. Non-ionizing radiation at intensities commonly encountered by the public does not have enough energy to cause cellular damage.
Ionizing radiation is what most people think of when they hear the word “radiation”. They might think of radiation associated with atomic bombs, nuclear power plants, or radiation therapy, which can have an ionizing effect. Ionization is the process of removing one or more electrons from an atom or molecule, creating charged particles (ions), Figure 4.
The most familiar form of non-ionizing radiation is visible light. The different wavelengths and frequencies of visible light make up the colors of the rainbow or the visible light spectrum. Colors range in frequency from around 400 to 800 THz and have wavelengths between 400 and 750 nm. Colors with shorter wavelengths, like violet and purple, have a higher frequency and more energy. Longer wavelengths, like red, have a lower frequency and less energy. Another common example is infrared radiation (heat) radiating from fire.
The spectrum of RF frequencies is divided into bands based on their applications and characteristics of their frequencies, such as range, penetration through obstacles, and data capacity. For example, lower frequencies have a longer range, but higher frequencies can carry more data. This chart of United States frequency allocations in the radio spectrum Figure 5 shows the variety of applications and their positions in the spectrum.
Heinrich Hertz was the first to generate radio waves in the laboratory, and his experiments confirmed that electric and magnetic fields couple together to form electromagnetic waves (Figure 6). Radio waves are just one type of electromagnetic radiation across a spectrum of waves that vary in wavelength and frequency. Hertz’s success in generating and detecting radio waves laid the foundation for understanding how electromagnetic waves move (radiate) through space at the speed of light. Electromagnetic waves can propagate through empty space (a vacuum) as well as through various materials.
Figure 6 Antenna and Propagating Electromagnetic Field: A radio wave is generated within an antenna by the movement of electrons in a conductor back and forth, creating an oscillating or alternating electric current. As the electric current in the antenna oscillates, it creates a changing electric field around the antenna. A changing electric field generates a changing magnetic field, and vice versa. The changing electric and magnetic fields propagate away from the antenna, forming an electromagnetic wave. The frequency of the wave corresponds to the frequency of the oscillating electric current and is measured in Hertz units.
Because RF radiation does not have the energy to ionize atoms, it is considered non-ionizing. RF radiation primarily interacts with charged particles (such as electrons) within the body by inducing oscillations in their motion. This interaction results in the absorption of RF energy as heat in the body, but it does not produce ions or cause damage associated with ionizing radiation. The human body can absorb radio waves at various frequencies, but the extent to which absorption occurs depends on the frequency of the radio waves, the intensity of the signal, and the specific tissues involved.
Electromagnetic waves and sound waves are fundamentally different in how they travel and interact with the world. Electromagnetic waves, like light, radio waves, and X-rays, do not need a medium to travel and can move through empty space. They consist of oscillating electric and magnetic fields that move together at the speed of light, about 300 million meters per second in a vacuum. Microwaves are a subset of radio frequencies and are used for a variety of wireless applications. Cell phones are designed to emit RF (including microwave) radiation at a low power level, typically much less than 1 watt. These power levels are far too low to generate the significant heat required for cooking food or causing harm to biological tissues.
In contrast, sound waves require a medium such as air, water, or solid materials to propagate. They move by vibrating particles in the medium, which means they cannot travel through a vacuum. Sound waves are much slower than electromagnetic waves, traveling at about 343 meters per second in air and even faster in water or solids. Electromagnetic waves can be seen in the form of visible light, but cannot, under normal circumstances, be heard, while sound waves are heard as different pitches depending on their frequency. Because they interact differently with materials, electromagnetic waves can be reflected, diverted, or absorbed, while sound waves can produce echoes or be absorbed depending on the material they encounter.
Wireless technology using Radio Frequency (RF) has been a fundamental part of our communication and entertainment landscape for over a century. Commercial AM (amplitude modulation) radio started broadcasting in the 1920s, and FM (frequency modulation) radio in the 1930s. By the 1940s, television started broadcasting and expanded into rural areas in the 1950s. We live in a world where RF frequencies are all around us and were broadcast into our homes for decades before the adoption of modern mobile phones.
The foundation of wireless communication was laid with the discovery of electromagnetic waves by scientists like Heinrich Hertz and James Clerk Maxwell in the late 19th century. This led to the development of wireless telegraphy, pioneered by Guglielmo Marconi. The first broadcast radio transmissions used amplitude modulation (AM) in the 1920s, providing news, entertainment, and music to a growing audience.
Edwin Armstrong’s invention of frequency modulation (FM) revolutionized radio broadcasting. FM radio offered clearer, static-free audio compared to AM radio because it was less susceptible to interference. FM radio stations expanded, offering a wider range of music and programming, leading to the development of stereo FM broadcasts in the 1950s, further enhancing audio quality.
Early (1930s) television broadcasts also used radio frequencies to transmit both audio and video signals, which were displayed in black-and-white using cathode-ray tube (CRT) technology. Only a handful of television stations were operating in major cities, and coverage was limited primarily to urban areas. By the 1960s, the popularity of television exploded and had become a mainstream form of entertainment and information. The number of television stations expanded significantly, with multiple regional and local stations expanding to serve a growing and diverse audience.
By the 1980s, wireless communication using mobile phones and cellular technology (see section 4.6) started gaining momentum. Cellular technology allowed for mobile voice communication and later data services, revolutionizing the way people communicate and access information. Some of the most essential wireless communications uses include emergency response and satellite navigation using GPS (Global Positioning System) satellites. RF technology for wireless communications continued to evolve with the development of Wi-Fi, Bluetooth, and satellite internet, which have become essential to our daily lives.
Throughout this history, radio frequencies have been around us, serving as the foundation for various forms of wireless communication and entertainment. They have connected people, provided information, and shaped the way we live and interact with the world. The adoption of mobile phones and cellular technology represented a significant milestone in this ongoing evolution, as it brought personal communication devices into the mainstream and paved the way for the digital age.
Like all electromagnetic waves, radio waves can travel through the vacuum of space at the speed of light. However, unlike many other forms of electromagnetic waves, RF signals can propagate through Earth’s atmosphere without significant signal degradation. They can tolerate various forms of interference, such as atmospheric conditions and signal blockage by objects. This makes RF suitable for reliable communication.
RF signals can transport a large amount of data at a very fast rate over large distances. This speed allows for virtually instantaneous communication between Earth and satellites and between transmitters and receivers within a cellular network. RF antennas can be designed to focus and direct signals accurately toward specific locations. This directional control helps to establish a strong and stable connection, even in the presence of interference or other sources of RF noise.
Radio frequency communication encompasses a wide range of frequencies that can support various data rates and provide different frequency bands to accommodate a wide range of applications.
All of these characteristics of radio waves make them ideal for telecommunications and wireless technology.
RF Safety guidelines and limits are established to assure safe levels of exposure to radiofrequency (RF) energy in occupational and public exposure settings. The terms “limits” and “guidelines” are sometimes used interchangeably, often with guidelines considered as a set of recommendations and limits specific for certain scenarios. It is important to understand that exposure limits are not set at the threshold beyond which RF exposure is believed to be hazardous to human health but include precautionary safety factors (factors of 50 and 10 for public and occupational exposures, respectively, are common) to ensure exposure conditions are not hazardous.
Exposure limits depend on several factors, including the frequency and intensity of the RF signal. Since RF energy is used in various technologies, including wireless communication devices, microwave ovens, and medical equipment, standards have been established to ensure human safety. Studies have shown that environmental levels of RF energy routinely encountered by the public are typically far below levels known to cause adverse health effects.
Several organizations, such as the American National Standards Institute (ANSI), the Institute of Electrical and Electronics Engineers (IEEE), the International Commission on Non-Ionizing Radiation Protection (ICNIRP), and the National Council on Radiation Protection and Measurements (NCRP) have issued scientifically based recommendations for safe levels of human exposure to RF electromagnetic fields.
In the United States, the Federal Communications Commission (FCC) has adopted safety standards for limiting RF environmental exposure for different frequency ranges. The National Environmental Policy Act (NEPA) requires the FCC to evaluate the effect of emissions from FCC-regulated transmitters on the quality of the human environment. While the FCC has the regulatory authority to issue safety standards, it relies on Federal Health and Safety agencies to recommend standards for safe levels of exposure to RF energy.
The Environmental Protection Agency (EPA), the U.S. Food and Drug Administration (FDA), the National Institutes of Health (NIH), the National Institute for Occupational Safety and Health (NIOSH), and the Occupational Safety and Health Administration (OSHA) are consulted on safety issues related to RF exposure.
The FDA states that the “current limit on radio frequency (RF) energy set by the Federal Communications Commission remains acceptable for protecting the public health.” And based on FDA’s evaluation “the weight of scientific evidence has not linked exposure to radio frequency energy from cell phone use with any health problems at or below the radio frequency exposure limits set by the FCC.” The NIH’s National Cancer Institute concludes that “no consistent evidence for an association between any source of non-ionizing EMF and cancer has been found.”
The FCC’s exposure standards specify limits for human exposure to RF emissions and are designed to protect against adverse health effects of RF radiation exposure. These limits are expressed in Specific Absorption Rate (SAR), a measure of the rate of RF energy absorption. For frequencies above 6 GHz, where the majority of the energy is absorbed in the skin, limits are expressed as Power Density, a measure of RF energy intensity. The limits vary depending on the frequency range of the RF-emitting device.
For information about studies on the environmental and health effects of RF radiation exposure that led to these limits, visit this site’s Research section.
Exposure guidelines and standards for RF levels establish exposure limits to protect against adverse outcomes that could result from such exposure. The human body absorbs RF energy most efficiently in a frequency range known as the “Resonance Absorption Frequency” or “Resonant Frequency.” This frequency range falls between ~70 and 110 MHz. Some television and all FM radio broadcasts use these frequencies. At other frequencies the absorption by the human body decreases. Exposure to radio frequency levels below established guidelines results in a negligible temperature rise in the human body.
Exposure limits are set to protect against established adverse health effects associated both with whole-body and partial-body exposures. Limits for partial-body exposures are higher than those of whole-body averaged exposures.
Cell phones emit low levels of radio frequency energy. As stated by the National Cancer Institute, “there is currently no consistent evidence that non-ionizing radiation increases cancer risk in humans. The only consistently recognized biological effect of radiofrequency radiation in humans is heating.” To induce potentially adverse or even noticeable heating from RF energy, exposures would have to be well above the current exposure limits. Public exposure to RF energy from cell phones and cell sites is below (often well below) the limits set by international guidelines and standard-setting organizations.
The FCC exposure limit for a mobile phone user is a SAR of 1.6 watts per kg (1.6 W/kg), averaged over one gram of tissue in the shape of a cube, and compliance with this limit must be demonstrated before FCC approval is granted for marketing of a mobile phone in the United States. See Specific Absorption Rate (SAR) for Cellular Telephones regarding SAR and cellphones.
Today, most individuals’ RF exposure is primarily from their cell phones. Exposure from cell sites, Wi-Fi routers, and other sources tends to be much less than an individual’s exposure from their cell phone, due to the proximity of the device. While there is no established health benefit from reducing an individual’s RF exposure from cell phones, there are simple actions to reduce exposure. One can reduce the amount of time spent using a cell phone; use speaker mode, headphones, or earbuds to place more distance between your body and the cell phone; avoid making calls when the signal is weak (fewer bars) as this causes cell phones to boost RF transmission power; and use text functions rather that voice.
Imagine making a cell phone call to a friend in another country. You dial their number and wait for your friend to pick up, and then you have a conversation in real time with very little delay. That is because your voice – or data from your phone – is being transmitted to your friend over electromagnetic waves that travel at the speed of light. This technology not only allows you to text your favorite picture to your friend, but is essential for emergency services, disaster response, and even providing phone service in developing countries that do not have extensive infrastructure for landlines.
Cell phones convert your voice into digital signals and transmit this information over radio frequencies to a cellular network, which then transmits the data to its destination. Just as radios and televisions use antennas to receive signals from a local broadcast station, cell phones use antennas that receive signals from nearby cell sites. In both examples, the RF signals have low frequencies and long wavelengths that can pass through clouds, rain, smoke, dust, and other atmospheric interference. These characteristics of RF waves make them perfect for wireless communications.
Common frequency bands used by cell phones and their network include the frequencies in Table 1
A cell phone antenna emits low levels of RF radiation that are only effective in communicating over short ranges. The cell phone automatically connects with the best cell sites in the network to get the call to your destination. The cell site antennas are located on top of towers or buildings and geographically situated in a network of cells to provide complete coverage. Like all electromagnetic energy, RF signals get weaker the further you get from the source. The greater the distance a cell phone is from a cell site, the more power the cell phone needs to use for its signal to reach the tower. A cell phone varies its power output when connecting to a cell site based on the distance between the phone and the cell site. 5G cell phones have a maximum power of 2/10th of a Watt but the average power in an urban area is less than 1/100th of a Watt, based on reports of actual measurements.
Cellular networks use a feature called “adaptive power control” to manage the transmission power of mobile devices to ensure that the mobile device’s signal is strong enough for reliable communication with the cell site while minimizing interference with neighboring cells and conserving battery life. Your cell phone continuously monitors the signal strength and quality of the connection. If the signal weakens or gets stronger, your phone adjusts its transmit power accordingly to maintain a reliable connection. When your cell phone is close to a cell site (i.e., you have a strong signal), it reduces the transmit power because it doesn’t need to use high power to reach the nearby tower.
When your cell phone is far away from the nearest cell site (i.e., you have a weak signal), it increases its transmit power. This is necessary because the signal must overcome the increased distance. By boosting its power output, your phone attempts to establish a reliable connection with the tower and ensure that your call or data transmission is successful. A cell phone with a weak signal emits higher power and increases the user’s exposure to RF radiation. However, power levels are still well within the regulated RF exposure safety limits. This adaptive power control saves battery and prolongs usage.
It is important to understand the difference between exposure and absorption. For example, if two people are out in the sun, they are exposed to the same energy, but the one wearing sunscreen absorbs much less.
Specific Absorption Rate (SAR) is a measure of the rate at which electromagnetic energy is absorbed by the human body when exposed to radiofrequency (RF) electromagnetic fields. SAR is typically used to assess the potential health risks associated with the use of devices that emit RF radiation, such as mobile phones, wireless routers, and microwave ovens. It is expressed in watts per kilogram (W/kg) and represents the amount of RF energy absorbed per unit mass of body tissue over a specific time period.
At RF frequencies above 6 GHz, such as those used by 5G millimeter wave devices, most energy is absorbed within just a few millimeters of the skin, causing surface heating instead of deep tissue heating. As a result, power density (watts per square meter, W/m²) at the skin’s surface is the safety metric—rather than SAR. SAR is not appropriate when penetration is shallow and heating effects are localized to the skin. This approach helps prevent excessive heating at the body’s surface and is reflected in guidelines from organizations like ICNIRP and the FCC for frequencies above 6 GHz.
Cell phones can have different SAR levels, and manufacturers are required to report the maximum SAR level of their products to the US Federal Communications Commission (FCC). The measurement of SAR uses international standard techniques that are established by the FCC. The SAR value of a cellular phone can be searched through the FCC ID database using the device’s FCC ID number. According to FCC safety guidelines, the upper limit of SAR allowed in the United States is 1.6 watts per kilogram (W/kg) averaged over 1 gram tissue. See Specific Absorption Rate (SAR) for Cellular Telephones for more information regarding SAR and cellphones.
Public exposure to RF energy in the vicinity of wireless communications facilities is very low due to several factors. Cellular wireless communications is a low-power technology. The typical power can be as low as a few watts up to a few hundred watts. By comparison, AM/FM radio and TV typically broadcast with power levels of 1,000 or more watts. In addition, cell sites typically utilize directional antennae that focus the RF energy toward the horizon (i.e., parallel with but above ground level), with the maximum exposure occurring in front of and at the level of the antenna. Thus, only a tiny percentage of the RF energy is emitted toward the ground. This is similar to a lighthouse beacon that sends most of its light out toward the horizon with very little reaching the base of the lighthouse or people living nearby (Figure 7 A). At ground level near a typical cellular site, the amount of energy is hundreds to thousands of times less than that set by the FCC (Figure 7B).
Finally, as one gets farther away, there is a very rapid decrease in exposure intensity. Like all forms of electromagnetic energy, including light, the reduction in exposure is proportional to the square of the increased distance. Thus, if the exposure at one point was 1% of the public exposure standard and one doubled the distance (all other conditions being the same), the exposure would be (1/2)2 or one quarter 1/4 as much (i.e., 0.25% of the public exposure standard).
Electromagnetic radiation can be described by frequency, wavelength, or energy, but the intensity affects the amount of exposure. Intensity can be measured as the magnitude of the electric field, magnetic field, or electromagnetic power density. Power is the speed at which energy is created, moved, or used. Think of it like water flowing through a hose: power is how much water flows out in a certain amount of time (like gallons per second).
Because an electromagnetic wave has both an electric and a magnetic component, its strength can be measured by the strength of the electric field in units of “volts per meter” (V/m) or the strength of the magnetic field in units of “amperes per meter” (A/m). A measurement of the total strength of the electromagnetic field is called power density. Power density is the power flow (watts) per unit area (square meter) and is used to express the intensity of exposure (W/m2).
Figure 8 This image shows an example of frequency reuse in cellular networks Source https://commons.wikimedia.org/wiki/File:Frequency_reuse.svg
A cellular network is a telecommunications network that enables mobile communication using cell phones and other wireless devices. It’s called a “cellular” network because the coverage area is divided into small geographic regions called “cells” Figure 8. Each cell is served by a base station, also known as a cell tower or cell site, equipped with antennas and radios. The antennas are usually outdoors on rooftops, sides of buildings, towers, or monopole structures. These cell sites are interconnected to provide seamless communication as you move from one coverage area to another.
The cell site receives your signals, processes them, and forwards them to a central mobile switching center (MSC). The MSC connects your call to the appropriate destination, whether it’s another mobile phone, a landline phone, or a networked device. It also manages tasks like call routing, handovers between cells, and call setup. The recipient’s phone or device receives the incoming call signal.
Cellular networks have evolved through several generations primarily because of the need for continuous improvement and adaptation to meet evolving technology, user demands, and new applications. Each generation refers to a set of protocols for how information is transmitted over radio waves. Early generations were analog and have since evolved to digital. Capabilities were incorporated into each new generation to meet the growing needs for telecommunications, such as increased network capacity to accommodate more users and higher data traffic. Increased data speed helped minimize latency and supported new services beyond voice calls. Energy efficiency, security, and global standardization also contributed to the evolution of networks.
New generations also optimize the available frequency spectrum, making more efficient use of the radio frequencies allocated for wireless communication. The first generation of wireless phone technology (1G) was launched in the 1980s. The newest generation is 5G, which began rolling out in the late 2010s.
5G, or fifth generation, is the latest wireless mobile phone technology and was first widely deployed in 2019. 5G antennas are designed to support the unique characteristics and requirements of 5G technology, including higher data speeds, lower latency, and the ability to connect a massive number of devices. In addition to traditional sub-6 GHz frequency bands, 5G can utilize millimeter wave (mmWave) spectrum with much higher frequencies and shorter wavelengths than previous generations.
5G technology uses high-frequency waves to deliver extremely fast data speeds. However, these waves have a shorter range and struggle to penetrate obstacles. To address this, more infrastructure is required, including smaller and more numerous mmWave cell sites and antennas, to expand the coverage.
mmWave antennas have a higher antenna gain and concentrate signal power in specific directions. Many 5G antennas incorporate advanced beamforming and Massive MIMO (Multiple-Input Multiple-Output) technology. Beamforming allows antennas to focus signals on specific directions, enhancing signal strength and reducing interference. Massive MIMO uses multiple antenna elements to improve coverage (the area served by a cell site) and capacity (the number of simultaneous user the cell site can support).
Exposure limits and standards are based on established science and are not dependent on specific technologies or communications protocols. Whether the RF signal is 4G or 5G, or AM or FM, etc., the established exposure limits are protective.
5G mmWaves have higher frequencies than previous generations of cellular networks. However, these frequencies have been used for other technologies and have long-established exposure limits. Cell phone signals at these higher frequencies, in the range of 30 GHz, have considerable difficulty in penetrating most materials. Just as these waves can’t penetrate leaves on trees, they also can’t penetrate beyond human skin. Additionally, 5G networks have lower power and use small cells with short-range cell sites.
Cell phones and networks are designed and installed to ensure that RF exposure limits are not exceeded. Typically, exposure levels encountered by the public are well below these limits.
Findings from a 2020 study in Health Physics by the IEEE Engineering in Medicine and Biology Society Committee on Man and Radiation (COMAR) suggest that the added transmission signals from multiple small 5G cell sites will most likely not change the overall levels of public exposure to RF radiation. Public exposure levels are expected to remain well below the exposure limits mentioned above. Subsequent measurement studies support this view.
A wide range of radio frequency (RF) technologies and devices play an essential role in modern life. From broadcast radio and television to millimeter wave security scanners and microwave ovens, each operates within specific RF bands and is subject to established safety standards. These technologies vary in their applications, power levels, and safety profiles, providing valuable services while maintaining public health protection.
Radio broadcasts have been in operation for over 100 years. These typically use high-powered transmitters and are mounted away from the public on tall towers, large parcels of land, or mountain tops. They are all engineered so that publicly accessible areas have RF levels below exposure limits. Radios and television sets are receivers only, which do not transmit RF energy.
AM (Amplitude Modulation) radio is one of the earliest forms of radio broadcasting. It modulates the amplitude of the carrier wave to transmit audio information. AM radio is known for its long-range reception, especially at night, and its simple and inexpensive receivers. However, it has lower audio quality than FM and is more susceptible to noise and interference. The frequency range for AM radio is typically from 530 to 1700 kHz.
FM (Frequency Modulation) radio broadcasting modulates the frequency of the carrier wave to transmit audio signals, offering better sound quality than AM radio. FM radio is less susceptible to noise and interference but has a shorter range and is limited by line-of-sight constraints. The frequency range for FM radio is from 87.5 to 108 MHz.
Digital TV (DTV) broadcasting uses digital encoding to transmit television signals, providing higher quality video and audio than previous analog methods. This technology supports high-definition television (HDTV), allows for more efficient use of the broadcast spectrum, and enables multiple channels to be transmitted within the same frequency band (multicasting). Additionally, DTV offers enhanced services like electronic program guides (EPGs) and interactive TV. The frequency range for DTV includes VHF bands (54-88 MHz for channels 2-6 and 174-216 MHz for channels 7-13) and UHF bands (470-608 MHz for channels 14-36).
In summary, AM radio offers long-range reception with simpler technology, FM radio delivers superior sound quality with a shorter range, and digital TV provides high-quality video and audio with efficient spectrum use. Each broadcasting method serves different purposes and operates within specific radiofrequency bands to meet various media consumption needs.
Wi-Fi is a technology that enables devices to connect to the internet or communicate with each other wirelessly over a local area network (LAN). It has become an integral part of modern life and is commonly used in homes, businesses, schools, and public places like cafes and airports.
Wi-Fi operates using radio frequencies within the 2.4 GHz and 5 GHz bands, which are available for use without a license. This technology allows multiple devices to use Wi-Fi without significant interference.
Online gaming consoles, streaming devices, and smart speakers commonly use Wi-Fi to access online gaming services, stream content, and listen to music. Many smartphones can act as Wi-Fi access points or hot spots, allowing other devices to connect to the internet through the phone’s cellular data connection.
RF exposure from Wi-Fi devices, whether in schools, public buildings, or homes, is common and is typically thousands of times lower than the regulatory limits. While there are not many laboratory studies or studies on human exposure to low levels of Wi-Fi, there have been many studies at higher intensities at the same frequencies that do not provide any meaningful support for potential health harm in the form of sleep disturbance, symptoms such as headaches or fatigue, or physiologic effects such as changes in blood pressure or heart rate. Experimental Studies with Human Volunteers.
Bluetooth technology operates in the 2.4 GHz frequency range and allows electronic devices to connect and exchange data over short distances, typically within a range of about 30 feet for class 2 (2.5 mW), without the need for cables. Bluetooth devices provide a convenient and efficient way to communicate wirelessly between devices. Popular wireless devices such as headphones, earbuds, speakers, keyboards, game controllers, and printers use Bluetooth to connect wirelessly to smartphones and computers.
Bluetooth technology is also used for hands-free communication in cars to allow drivers to make and receive calls, access navigation, and control audio systems without taking their hands off the steering wheel. Bluetooth can be used to synchronize data between devices, such as transferring contacts, calendars, and other information between a smartphone and a laptop. Various health and fitness gadgets, like watches, fitness trackers, and smart scales, use Bluetooth to synchronize data with other devices for analysis and tracking.
As Bluetooth uses the same frequency as Wi-Fi at even lower power levels, the same conclusions regarding RF health effects are applicable.
Satellite navigation systems, like the Global Positioning System (GPS), use radio frequency signals to determine the precise location, speed, and time information for users on Earth’s surface. GPS consists of a constellation of satellites orbiting the Earth. These satellites are positioned in specific orbits, usually at altitudes of approximately 20,000 kilometers (12,000 miles).
Each GPS satellite continuously broadcasts radio frequency (RF) signals in the microwave band. These signals contain precise timing and positioning information. GPS receivers are used in smartphones, vehicles, and navigation devices to receive signals from multiple GPS satellites simultaneously. To determine its position, the GPS receiver combines the distance measurements and the timing information from multiple satellites.
Common GPS receivers operate at a frequency of approximately 1.5 GHz and can receive a GPS satellite’s identity and the precise time the signal was transmitted. GPS receivers that operate around 1.2 GHz are used for more advanced applications such as military use and scientific research requiring additional information to improve accuracy.
GPS receivers do not transmit, so they have no RF exposure impact. Exposure from the satellites is vanishingly small, even lower than Bluetooth.
Satellite radio and satellite television services use distinct radio frequency bands and satellite systems for their transmissions. Satellite radio, such as XM, focuses on audio content, while satellite television services, such as Dish and DIRECTV, provide a wide range of video and audio content.
All satellite radio and television services operate in the microwave portion of the radio spectrum. These services rely on satellites in orbit around the Earth placed at specific positions in the sky, ensuring that they remain fixed relative to the Earth’s surface. RF is transmitted from the satellite to the user’s equipment, which is used as a receiver only and does not transmit RF energy.
Starlink and other providers are advanced satellite communication systems designed to provide internet and communication services in remote and underserved areas. Starlink, developed by SpaceX, is a satellite internet constellation that delivers high-speed broadband internet globally, particularly in remote and rural locations. Starlink uses a network of low Earth orbit (LEO) satellites to ensure consistent and high-speed internet coverage. Its primary frequency ranges are the millimeter wave band (12-18 GHz and 26.5-40 GHz). Starlink is used for high-speed internet access for residential, commercial, and government users, as well as for emergency and disaster recovery communications.
These satellite networks play a crucial role in providing reliable connectivity in remote and underserved areas, supporting a wide range of applications from everyday internet access to emergency communication and disaster recovery.
Exposure from satellite terminals is low and directed primarily toward the satellite, not the surrounding environment. While there is some RF emission during operation, the exposure levels are below international exposure limits, especially at ground level or in typical user environments. Proper installation and operation reduce any potential risks. Each terminal is required to have a report filed with the Federal Communications Commission (FCC) detailing the RF exposure conditions and how the device meets the regulatory safety guidelines.
Radio remote controllers (RC) use RF signals to wirelessly operate devices such as remote-controlled vehicles, drones, toys, industrial machinery, home automation systems, smart home hubs, and some gaming consoles. RF provides longer-range and more reliable communication than infrared light, commonly used in television remotes. The specific frequency a remote controller uses may vary depending on factors such as the intended application, region, local regulations, and allocation of frequency bands. The exact frequencies can vary, but the following frequency bands are commonly used for radio remote controllers:
– 27 and 49 MHz Bands: These bands are widely used for radio remote-controlled toys and low-power applications.
– 72 MHz Band: This frequency band is commonly used for hobby-grade radio-controlled aircraft and helicopters. It offers more channels and allows for greater range.
– 433 MHz Band: In some regions, the 433 MHz band is used for low-power radio remote control systems. It’s commonly used in home automation and industrial applications.
– 900 MHz Band: This frequency band is utilized for long-range consumer and industrial remote-control applications. It provides a greater range than higher-frequency bands but may have limited channels available. Examples range from baby monitors to Smart Meters.
– 2.4 GHz Band: The 2.4 GHz band is one of the most popular frequency bands for radio remote controllers, especially for hobby-grade and consumer-grade applications. It provides a wide range of channels, reduces interference, and allows for more complex control systems. It’s commonly used for radio-controlled (RC) cars, drones, boats, and more. This band is also used for Wi-Fi networks.
Because of the extremely low power and intermittent RF transmissions from these devices, RF exposure near them is far below safety standards..
Smart meters are devices used to measure and monitor electricity, gas, or water consumption in homes and businesses. They use RF signals to communicate and send consumption data to utility companies or local service providers. Smart meters are equipped with sensors and measurement capabilities to record the consumption of utilities, such as electricity, gas, or water. At regular intervals, the smart meter uses RF emissions to transmit the collected data. This transmission is typically done in short bursts or packets of data at 900 MHz, 2.4 GHz, and/or 5.8 GHz radio frequencies.
In 2011, the California Council on Science and Technology, a non-profit organization established in 1988 at the request of the California State Government, published a report, Health Impacts of Radio Frequency Exposure from Smart Meters. The CCST Project Team, after carefully reviewing the available literature on the current state of science on the health impacts of radiofrequency from smart meters and input from a wide array of subject matter experts, concluded that:
1. ‘’The FCC standard provides a currently accepted factor of safety against known thermally induced health impacts of smart meters and other electronic devices in the same range of RF emissions. Exposure levels from smart meters are well below the thresholds for such effects.
2. There is no scientific evidence that additional standards are needed to protect the public from smart meters.”
A 2013 study in the IEEE Electromagnetic Compatibility Magazine by the IEEE Engineering in Medicine and Biology Society Committee on Man and Radiation (COMAR) found that “RF fields near Smart Meters are far below both U.S. and international RF safety limits.”.
Radio-Frequency Identification (RFID) is a technology that uses radio frequency signals to identify, track, and manage objects, animals, or people. It is commonly used in various applications, such as inventory management, access control, contactless payment systems, and supply chain logistics.
RFID systems consist of tags or transponders and RFID readers or interrogators. RFID tags are small electronic devices that contain a microchip and an antenna. These tags come in various forms, including stickers, cards, and key fobs. RFID readers are devices that send out RF signals to interact with RFID tags. When an RFID reader emits radio waves, RFID tags within range of the reader receive this energy and use this energy to power up and transmit their stored data back to the reader. Data can include unique identification numbers, sensor readings, or other information stored on the tag.
RFID technology operates in various frequency bands. The choice of frequency bands depends on factors such as the required read range, interference considerations, and regulatory requirements in a specific region. Because of the extremely low-power RF transmissions from RFID tags and readers, RF exposure near them is far below safety standards.
Millimeter wave (mmW) scanners used at airports emit extremely low-level, non-ionizing radio frequency radiation, Figure 9. Most of the energy from these scanners is absorbed by or reflected off the skin’s surface and does not penetrate deeply into body tissues, making them safe for repeated public use. Federal health organization, including the CDC and EPA, consistently report that mmW scanners pose negligible health risks, with exposure levels far below established safety limits.
