wireless device radiation and health wireless device radiation and health the antennas contained in mobile phones, including smartphones, emit radiofrequency (rf) radiation (non-ionizing "radio waves" such as microwaves); the parts of the head or body nearest to the antenna can absorb this energy and convert it to heat. since at least the 1990s, scientists have researched whether the now-ubiquitous radiation associated with mobile phone antennas or cell phone towers is affecting human health. mobile phone networks use various bands of rf radiation, some of which overlap with the microwave range. other digital wireless systems, such as data communication networks, produce similar radiation. a man speaking on a mobile telephone part of a series onantennas common types dipole fractal loop monopole satellite dish television whip components balun block upconverter coaxial cable counterpoise (ground system) feed feed line low-noise block downconverter passive radiator receiver rotator stub transmitter tuner twin-lead systems antenna farm amateur radio cellular network hotspot municipal wireless network radio radio masts and towers wi-fi wireless safety and regulation wireless device radiation and health wireless electronic devices and health international telecommunication union(radio regulations) world radiocommunication conference radiation sources / regions boresight focal cloud ground plane main lobe near and far field side lobe vertical plane characteristics array gain directivity efficiency electrical length equivalent radius factor friis transmission equation gain height radiation pattern radiation resistance radio propagation radio spectrum signal-to-noise ratio spurious emission techniques beam steering beam tilt beamforming small cell bell laboratories layeredspace-time (blast) massive multiple-input multiple-output (mimo) reconfiguration spread spectrum wideband space divisionmultiple access (wsdma) 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 emf in the frequency range from 0 to 300 ghz. they have 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. 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. 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." 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, as non-thermal effects have not been conclusively demonstrated. the official stance of the british health protection agency (hpa) is that "here 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 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. effects studied