The antennas contained in mobile phones, and various other electronic devices, emit radiation which consists of non-ionising radiation or radiofrequency electromagnetic fields (RF EMF) such as microwaves. The parts of the head or body nearest to the antenna can absorb this energy in the form of heat. Since at least the 1990s, scientists have researched whether the now-ubiquitous radiation associated with mobile phone antennas, Wi-Fi routers or cell phone towers is affecting human health.What has research shown about the possible cancer-causing effects of radiofrequency energy?, United States National Cancer Institute Mobile phone networks use various bands of RF radiation, some of which overlap with the microwave range.
In response to public concern, the World Health Organization (WHO) established the International EMF (Electric and Magnetic Fields) Project in 1996 to assess the scientific evidence of possible health effects of RF EMF with a frequency range from 3 kilohertz (KHz) to 300 gigahertz (GHz). They have conducted a survey in 2019 among 300 radiofrequency scientists to prioritize the most important potential health effects from exposure to radiofrequency electromagnetic fields. The survey reported heat related effects, cancer, infertility, cognitive performance, symptoms and oxidative stress as the most important to study further.Verbeek J, Oftedal G, Feychting M, van Rongen E, Scarfì MR, Mann S, Wong R, van Deventer E. Prioritizing health outcomes when assessing the effects of exposure to radiofrequency electromagnetic fields: A survey among experts. Environment International, Volume 146, 2021, 106300. https://doi.org/10.1016/j.envint.2020.106300.
WHO has stated that although extensive research has been conducted into possible health effects of exposure to many parts of the frequency spectrum, all reviews conducted so far have indicated that, as long as exposures are below the limits recommended in the ICNIRP (1998) EMF guidelines, which cover the full frequency range from 0–300 GHz, such exposures do not produce any known adverse health effect. The WHO states that "A large number of studies have been performed over the last two decades to assess whether mobile phones pose a potential health risk. To date, no adverse health effects have been established as being caused by mobile phone use."
In 2024, the National Cancer Institute wrote: "The evidence to date suggests that cell phone use does not cause brain or other kinds of cancer in humans."
In 2011, International Agency for Research on Cancer (IARC), an agency of the WHO, classified wireless radiation as Group 2B – possibly carcinogenic. That means that there "could be some risk" of carcinogenicity, so additional research into the long-term, heavy use of wireless devices needs to be conducted.
International guidelines on exposure levels to microwave frequency EMFs such as ICNIRP limit the power levels of wireless devices and it is uncommon for wireless devices to exceed the guidelines. These guidelines only take into account thermal effects.
The official stance of the British Health Protection Agency (HPA) is that "there is no consistent evidence to date that Wi-Fi and WLANs adversely affect the health of the general population", but also that "it is a sensible precautionary approach ... to keep the situation under ongoing review ...".
In a 2018 statement, the FDA said that "the current safety limits are set to include a 50-fold safety margin from observed effects of Radio-frequency energy exposure".
Exposure
Mobile phones A mobile phone connects to the telephone network by radio waves exchanged with a local antenna and automated transceiver called a cellular base station (cell site or cell tower). The service area served by each provider is divided into small geographical areas called cells, and all the phones in a cell communicate with that cell's antenna. Both the phone and the tower have radio transmitters which communicate with each other. Since in a cellular network the same radio channels are reused every few cells, cellular networks use low power transmitters to avoid radio waves from one cell spilling over and interfering with a nearby cell using the same frequencies.
Mobile phones are limited to an effective isotropic radiated power (EIRP) output of 3 watts, and the network continuously adjusts the phone transmitter to the lowest power consistent with good signal quality, reducing it to as low as one milliwatt when near the cell tower. Tower channel transmitters usually have an EIRP power output of around 50 watts. Even when it is not being used, unless it is turned off, a mobile phone periodically emits radio signals on its control channel, to keep contact with its cell tower and for functions like handing off the phone to another tower if the user crosses into another cell. When the user is making a call, the phone transmits a signal on a second channel which carries the user's voice. Existing 2G, 3G, and 4G networks use frequencies in the UHF or low microwave bands, 600 MHz to 3.5 GHz. Many household wireless devices such as WiFi networks, garage door openers, and baby monitors use other frequencies in this same frequency range.
Radio waves decrease rapidly in intensity by the inverse square of distance as they spread out from a transmitting antenna. So the phone transmitter, which is held close to the user's face when talking, is a much greater source of human exposure than the tower transmitter, which is typically at least hundreds of metres away from the user. A user can reduce their exposure by using a wired headset and keeping the phone itself farther away from their body.
Next generation 5G cellular networks, which began deploying in 2019, use higher frequencies in or near the millimetre wave band, 24 to 52 GHz. Millimetre waves are absorbed by atmospheric gases so 5G networks will use smaller cells than previous cellular networks, about the size of a city block. Instead of a cell tower, each cell will use an array of multiple small antennas mounted on existing buildings and utility poles. In general, millimetre waves penetrate less deeply into biological tissue than microwaves, and are mainly absorbed within the first centimetres of the body surface.
Cordless phones The HPA also says that due to the mobile phone's adaptive power ability, a DECT cordless phone's radiation could actually exceed the radiation of a mobile phone. The HPA explains that while the DECT cordless phone's radiation has an average output power of 10 mW, it is actually in the form of 100 bursts per second of 250 mW, a strength comparable to some mobile phones.
Wireless networking Most wireless LAN equipment is designed to work within predefined standards. Wireless access points are also often close to people, but the drop off in power over distance is fast, following the inverse-square law. However, wireless laptops are typically used close to people. WiFi had been anecdotally linked to electromagnetic hypersensitivity but research into electromagnetic hypersensitivity has found no systematic evidence supporting claims made by affected people.
Users of wireless networking devices are typically exposed for much longer periods than for mobile phones and the strength of wireless devices is not significantly less. Whereas a Universal Mobile Telecommunications System (UMTS) phone can range from 21 dBm (125 mW) for Power Class 4 to 33 dBm (2W) for Power class 1, a wireless router can range from a typical 15 dBm (30 mW) strength to 27 dBm (500 mW) on the high end.
However, wireless routers are typically located significantly farther away from users' heads than a phone the user is handling, resulting in far less exposure overall. The Health Protection Agency (HPA) says that if a person spends one year in a location with a WiFi hot spot, they will receive the same dose of radio waves as if they had made a 20-minute call on a mobile phone.
The HPA's position is that "... radio frequency (RF) exposures from WiFi are likely to be lower than those from mobile phones." It also saw "... no reason why schools and others should not use WiFi equipment." In October 2007, the HPA launched a new "systematic" study into the effects of WiFi networks on behalf of the UK government, in order to calm fears that had appeared in the media in a recent period up to that time. Michael Clark of the HPA says published research on mobile phones and masts does not add up to an indictment of WiFi.
Health effects of RF
Heat-related effects There is general consensus that heating caused by RF EMF exposure can lead to heat-related effects such as pain, burns and heat stroke.
Cancer
There have been rumors that mobile phone use can cause cancer, but this has not been conclusively proven. In 2024, the National Cancer Institute wrote: "The evidence to date suggests that cell phone use does not cause brain or other kinds of cancer in humans."
In a 2018 statement, the US Food and Drug Administration said that "the current safety limits are set to include a 50-fold safety margin from observed effects of radiofrequency energy exposure".
In 2018 the US National Toxicology Program (NTP) published the results of its ten year, $30 million study of the effects of radio frequency radiation on laboratory rodents, which found 'clear evidence' of malignant heart tumors (schwannomas) and 'some evidence' of malignant gliomas and adrenal tumors in male rats. In 2019, the NTP scientists published an article stating that RF scientists found evidence of 'significant' DNA damage in the frontal cortex and hippocampus of male rat brains and the blood cells of female mice. In 2018, the Ramazzini Cancer Research Institute study of cell phone radiation and cancer published its results and conclusion that 'The RI findings on far field exposure to RFR are consistent with and reinforce the results of the NTP study on near field exposure, as both reported an increase in the incidence of tumors of the brain and heart in RFR-exposed Sprague-Dawley rats. These tumors are of the same histotype of those observed in some epidemiological studies on cell phone users. These experimental studies provide sufficient evidence to call for the re-evaluation of IARC conclusions regarding the carcinogenic potential of RFR in humans.'Belpoggi F et al 2018. Report of final results regarding brain and heart tumors in Sprague-Dawley rats exposed from prenatal life until natural death to mobile phone radiofrequency field representative of a 1.8 GHz GSM base station environmental emission. Environ Res Aug:165:496-503.
A 2021 review found "limited" evidence for radio frequencies in the range of 450 MHz to 6,000 MHz to be related to gliomas and acoustic neuromas in humans, however concluding also that "... the evidence is not yet sufficiently strong to establish a direct relationship". The report also states that there is "sufficient evidence" of carcinogenicity in experimental animals from radiofrequency in that same range. Conclusions could not be drawn for higher frequencies (24 to 100 GHz) due to insufficient adequate studies.
Fertility and reproduction A decline in male sperm quality has been observed over several decades. Studies on the impact of mobile radiation on male fertility are conflicting, and the effects of the radio frequency electromagnetic radiation (RF-EMR) emitted by these devices on the reproductive systems are currently under active debate. A 2012 review concluded that "together, the results of these studies have shown that RF-EMR decreases sperm count and motility and increases oxidative stress". A 2017 study of 153 men that attended an academic fertility clinic in Boston, Massachusetts found that self-reported mobile phone use was not related to semen quality, and that carrying a mobile phone in the pants pocket was not related to semen quality.