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Electromagnetic radiation can be classified into two types: ionizing radiation and non-ionizing radiation, based on the capability of a single photon with more than 10  eV energy to ionize atoms or break
chemical bond A chemical bond is a lasting attraction between atoms or ions that enables the formation of molecules and crystals. The bond may result from the electrostatic force between oppositely charged ions as in ionic bonds, or through the sharing o ...
s. Extreme ultraviolet and higher frequencies, such as
X-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10  picometers to 10 nanometers, corresponding to frequencies in the range 30  ...
s or gamma rays are ionizing, and these pose their own special hazards: see '' radiation poisoning''. The most common health hazard of radiation is
sunburn Sunburn is a form of radiation burn that affects living tissue, such as skin, that results from an overexposure to ultraviolet (UV) radiation, usually from the Sun. Common symptoms in humans and animals include: red or reddish skin that is ho ...
, which causes between approximately 100,000 and 1 million new skin cancers annually in the United States. In 2011, the World Health Organization (WHO) and the
International Agency for Research on Cancer The International Agency for Research on Cancer (IARC; french: Centre International de Recherche sur le Cancer, CIRC) is an intergovernmental agency forming part of the World Health Organization of the United Nations. Its role is to conduct and ...
(IARC) have classified radiofrequency electromagnetic fields as possibly
carcinogenic A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive substan ...
to humans (Group 2B).


Hazards

Dielectric heating from electromagnetic fields can create a biological hazard. For example, touching or standing around an antenna while a high-power transmitter is in operation can cause burns (the mechanism is the same as that used in a microwave oven). The heating effect varies with the power and the frequency of the electromagnetic energy, as well as the
inverse square In science, an inverse-square law is any scientific law stating that a specified physical quantity is inversely proportional to the square of the distance from the source of that physical quantity. The fundamental cause for this can be understoo ...
of distance to the source. The eyes and testes are particularly susceptible to radio frequency heating due to the paucity of blood flow in these areas that could otherwise dissipate the heat buildup. Radio frequency (RF) energy at power density levels of 1–10 mW/cm2 or higher can cause measurable heating of tissues. Typical RF energy levels encountered by the general public are well below the level needed to cause significant heating, but certain workplace environments near high power RF sources may exceed safe exposure limits. A measure of the heating effect is the
specific absorption rate Specific absorption rate (SAR) is a measure of the rate at which energy is absorbed per unit mass by a human body when exposed to a radio frequency (RF) electromagnetic field. It can also refer to absorption of other forms of energy by tissue, inc ...
or SAR, which has units of watts per kilogram (W/kg). The IEEE and many national governments have established safety limits for exposure to various frequencies of electromagnetic energy based on SAR, mainly based o
ICNIRP
Guidelines, which guard against thermal damage.


Low-level exposure

The World Health Organization (WHO) began a research effort in 1996 to study the health effects from the ever-increasing exposure of people to a diverse range of EMR sources. In 2011
the WHO/International Agency for Research on Cancer (IARC)
has classified radiofrequency electromagnetic fields as possibly carcinogenic to humans (Group 2B), based on an increased risk for glioma, a malignant type of brain cancer, associated with wireless phone use. Epidemiological studies look for statistical correlations between EM exposure in the field and specific health effects. As of 2019, much of the current work is focused on the study of EM fields in relation to cancer. There are publications which support the existence of complex biological and neurological effects of weaker ''non-thermal'' electromagnetic fields (see
Bioelectromagnetics Bioelectromagnetics, also known as bioelectromagnetism, is the study of the interaction between electromagnetic fields and biological entities. Areas of study include electromagnetic fields produced by living cells, tissues or organisms, the ...
), including weak
ELF An elf () is a type of humanoid supernatural being in Germanic mythology and folklore. Elves appear especially in North Germanic mythology. They are subsequently mentioned in Snorri Sturluson's Icelandic Prose Edda. He distinguishes ...
electromagnetic fields and modulated RF and
microwave Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency rang ...
fields.


Effects by frequency

While the most acute exposures to harmful levels of electromagnetic radiation are immediately realized as burns, the health effects due to chronic or occupational exposure may not manifest effects for months or years.


Extremely-low frequency

Extremely low frequency EM waves can span from 0 Hz to 3 kHz, though definitions vary across disciplines. The maximum recommended exposure for the general public is 5 kV/m. ELF waves around 50 Hz to 60 Hz are emitted by
power generator Electricity generation is the process of generating electric power from sources of primary energy. For utilities in the electric power industry, it is the stage prior to its delivery ( transmission, distribution, etc.) to end users or its sto ...
s,
transmission lines In electrical engineering, a transmission line is a specialized cable or other structure designed to conduct electromagnetic waves in a contained manner. The term applies when the conductors are long enough that the wave nature of the transmis ...
and distribution lines,
power cable A power cable is an electrical cable, an assembly of one or more electrical conductors, usually held together with an overall sheath. The assembly is used for transmission of electrical power. Power cables may be installed as permanent wiring w ...
s, and electric appliances. Typical household exposure to ELF waves ranges in intensity from 5 V/m for a light bulb to 180 V/m for a stereo, measured at and using 240V power. (120V power systems would be unable to reach this intensity unless an appliance has an internal voltage transformer.)
Overhead power line An overhead power line is a structure used in electric power transmission and distribution to transmit electrical energy across large distances. It consists of one or more uninsulated electrical cables (commonly multiples of three for three-p ...
s range from 1kV for local distribution to 1,150 kV for ultra high voltage lines. These can produce electric fields up to 10kV/m on the ground directly underneath, but 50 m to 100 m away these levels return to approximately ambient. Metal equipment must be maintained at a safe distance from energized high-voltage lines. Exposure to ELF waves can induce an electric current. Because the human body is conductive, electric currents and resulting voltages differences typically accumulate on the skin but do not reach interior tissues. People can start to perceive high-voltage charges as tingling when hair or clothing in contact with the skin stands up or vibrates. In scientific tests, only about 10% of people could detect a field intensity in the range of 2-5 kV/m. Such voltage differences can also create electric sparks, similar to a discharge of
static electricity Static electricity is an imbalance of electric charges within or on the surface of a material or between materials. The charge remains until it is able to move away by means of an electric current or electrical discharge. Static electricity is na ...
when nearly touching a grounded object. When receiving such a shock at 5 kV/m, it was reported as painful by only 7% of test participants and by 50% of participants at 10 kV/m.Extremely Low Frequency Fields Environmental Health Criteria Monograph No.238
chapter 5, page 121, WHO
The International Agency for Research on Cancer (IARC) finds "inadequate evidence" for human carcinogenicity.


Shortwave

Shortwave Shortwave radio is radio transmission using shortwave (SW) radio frequencies. There is no official definition of the band, but the range always includes all of the high frequency band (HF), which extends from 3 to 30 MHz (100 to 10 me ...
(1.6 to 30 MHz)
diathermy Diathermy is electrically induced heat or the use of high-frequency electromagnetic currents as a form of physical therapy and in surgical procedures. The earliest observations on the reactions of high-frequency electromagnetic currents upon the ...
(where EM waves are used to produce heat) can be used as a therapeutic technique for its
analgesic An analgesic drug, also called simply an analgesic (American English), analgaesic (British English), pain reliever, or painkiller, is any member of the group of drugs used to achieve relief from pain (that is, analgesia or pain management). It i ...
effect and deep muscle relaxation, but has largely been replaced by ultrasound. Temperatures in muscles can increase by 4–6 °C, and subcutaneous fat by 15 °C. The FCC has restricted the frequencies allowed for medical treatment, and most machines in the US use 27.12 MHz. Shortwave diathermy can be applied in either continuous or pulsed mode. The latter came to prominence because the continuous mode produced too much heating too rapidly, making patients uncomfortable. The technique only heats tissues that are good electrical conductors, such as
blood vessels The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away f ...
and muscle.
Adipose tissue Adipose tissue, body fat, or simply fat is a loose connective tissue composed mostly of adipocytes. In addition to adipocytes, adipose tissue contains the stromal vascular fraction (SVF) of cells including preadipocytes, fibroblasts, vascular e ...
(fat) receives little heating by induction fields because an electrical current is not actually going through the tissues. Studies have been performed on the use of shortwave radiation for cancer therapy and promoting wound healing, with some success. However, at a sufficiently high energy level, shortwave energy can be harmful to human health, potentially causing damage to biological tissues, for example by overheating or inducing electrical currents. The FCC limits for maximum permissible workplace exposure to shortwave radio frequency energy in the range of 3–30 MHz has a plane-wave equivalent power density of (900/''f''2) mW/cm2 where ''f'' is the frequency in MHz, and 100 mW/cm2 from 0.3 to 3.0 MHz. For uncontrolled exposure to the general public, the limit is 180/''f''2 between 1.34 and 30 MHz.


Radio and microwave frequencies

The designation of mobile phone signals as "possibly
carcinogen A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive substa ...
ic to humans" by the World Health Organization (WHO) (e.g. its IARC, see below) has often been misinterpreted as indicating that some measure of risk has been observed however the designation indicates only that the possibility could not be conclusively ruled out using the available data. In 2011, International Agency for Research on Cancer (IARC) classified mobile phone radiation as Group 2B "possibly carcinogenic" (rather than Group 2A "probably carcinogenic" nor the "is carcinogenic" Group 1). That means that there "could be some risk" of carcinogenicity, so additional research into the long-term, heavy use of mobile phones needs to be conducted. The WHO concluded in 2014 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." Since 1962, the microwave auditory effect or tinnitus has been shown from radio frequency exposure at levels below significant heating. Studies during the 1960s in Europe and Russia claimed to show effects on humans, especially the nervous system, from low energy RF radiation; the studies were disputed at the time. In 2019, reporters from the Chicago Tribune tested the level of radiation from smartphones and found that certain models emitted more than reported by the manufacturers and in some cases more than the U.S. Federal Communications Commission exposure limit. It is unclear if this resulted in any harm to consumers. Some problems apparently involved the phone's ability to detect proximity to a human body and lower the radio power. In response, the FCC began testing some phones itself rather than relying solely on manufacturer certifications.
Microwave Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency rang ...
and other radio frequencies cause heating, and this can cause
burns Burns may refer to: * Burn, an injury (plural) People: * Burns (surname), includes list of people and characters Business: * Burns London, a British guitar maker Places: ;In the United States * Burns, Colorado, unincorporated community in Eagle ...
or eye damage if delivered in high intensity, or hyperthermia as with any powerful heat source. Microwave ovens use this form of radiation, and have shielding to prevent it from leaking out and unintentionally heating nearby objects or people.


Millimeter waves

In 2009, the US TSA introduced full-body scanners as a primary screening modality in
airport security Airport security includes the techniques and methods used in an attempt to protect passengers, staff, aircraft, and airport property from malicious harm, crime, terrorism, and other threats. Aviation security is a combination of measures and hum ...
, first as backscatter X-ray scanners, which use ionizing radiation and which the European Union banned in 2011 due to health and safety concerns. These were followed by non-ionizing
millimeter wave scanner A millimeter wave scanner is a whole-body imaging device used for detecting objects concealed underneath a person’s clothing using a form of electromagnetic radiation. Typical uses for this technology include detection of items for commercial ...
s. Likewise
WiGig WiGig, alternatively known as 60 GHz Wi-Fi, refers to a set of 60 GHz wireless network protocols. It includes the current IEEE 802.11ad standard and also the IEEE 802.11ay standard. The WiGig specification allows devices to communicate wi ...
for personal area networks have opened the 60 GHz and above microwave band to SAR exposure regulations. Previously, microwave applications in these bands were for point-to-point satellite communication with minimal human exposure.


Infrared

Infrared wavelengths longer than 750 nm can produce changes in the lens of the eye. Glassblower's cataract is an example of a heat injury that damages the
anterior lens Ectopia lentis is a displacement or malposition of the eye's crystalline lens from its normal location. A partial dislocation of a lens is termed lens subluxation or subluxated lens; a complete dislocation of a lens is termed lens luxation or lux ...
capsule among unprotected glass and iron workers. Cataract-like changes can occur in workers who observe glowing masses of glass or iron without protective eyewear for prolonged periods over many years. Exposing skin to infrared radiation near visible light (IR-A) leads to increased production of free radicals. Short-term exposure can be beneficial (activating protective responses), while prolonged exposure can lead to photoaging. Another important factor is the distance between the worker and the source of radiation. In the case of
arc welding Arc welding is a welding process that is used to join metal to metal by using electricity to create enough heat to melt metal, and the melted metals, when cool, result in a binding of the metals. It is a type of welding that uses a welding power ...
, infrared radiation decreases rapidly as a function of distance, so that farther than three feet away from where welding takes place, it does not pose an ocular hazard anymore but, ultraviolet radiation still does. This is why welders wear tinted glasses and surrounding workers only have to wear clear ones that filter UV.


Visible light

Photic retinopathy Photic retinopathy is damage to the eye's retina, particularly the macula, from prolonged exposure to solar radiation or other bright light, e.g., lasers or arc welders. The term includes solar, laser, and welder's retinopathy and is synonymous ...
is damage to the macular area of the eye's retina that results from prolonged exposure to sunlight, particularly with dilated pupils. This can happen, for example, while observing a solar eclipse without suitable eye protection. The Sun's radiation creates a photochemical reaction that can result in visual dazzling and a scotoma. The initial lesions and edema will disappear after several weeks, but may leave behind a permanent reduction in visual acuity. Moderate and high-power lasers are potentially hazardous because they can burn the retina of the eye, or even the skin. To control the risk of injury, various specifications – for example ANSI Z136 in the US, EN 60825-1/A2 in Europe, and IEC 60825 internationally – define "classes" of lasers depending on their power and wavelength. Regulations prescribe required safety measures, such as labeling lasers with specific warnings, and wearing laser safety goggles during operation (see
laser safety Laser radiation safety is the safe design, use and implementation of lasers to minimize the risk of laser accidents, especially those involving eye injuries. Since even relatively small amounts of laser light can lead to permanent eye injuries, t ...
). As with its infrared and ultraviolet radiation dangers, welding creates an intense brightness in the visible light spectrum, which may cause temporary
flash blindness Flash blindness is an either temporary or permanent visual impairment during and following exposure of a varying length of time to a light flash of extremely high intensity, such as a nuclear explosion, flash photograph, lightning strike, or extre ...
. Some sources state that there is no minimum safe distance for exposure to these radiation emissions without adequate eye protection.


Ultraviolet

Sunlight includes sufficient ultraviolet power to cause
sunburn Sunburn is a form of radiation burn that affects living tissue, such as skin, that results from an overexposure to ultraviolet (UV) radiation, usually from the Sun. Common symptoms in humans and animals include: red or reddish skin that is ho ...
within hours of exposure, and the burn severity increases with the duration of exposure. This effect is a response of the skin called erythema, which is caused by a sufficient strong dose of UV-B. The Sun's UV output is divided into
UV-A Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30  PHz) to 400 nm (750  THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...
and UV-B: solar UV-A flux is 100 times that of UV-B, but the erythema response is 1,000 times higher for UV-B. This exposure can increase at higher altitudes and when reflected by snow, ice, or sand. The UV-B flux is 2–4 times greater during the middle 4–6 hours of the day, and is not significantly absorbed by cloud cover or up to a meter of water. Ultraviolet light, specifically UV-B, has been shown to cause
cataracts A cataract is a cloudy area in the lens of the eye that leads to a decrease in vision. Cataracts often develop slowly and can affect one or both eyes. Symptoms may include faded colors, blurry or double vision, halos around light, trouble wi ...
and there is some evidence that sunglasses worn at an early age can slow its development in later life. Most UV light from the sun is filtered out by the atmosphere and consequently airline pilots often have high rates of cataracts because of the increased levels of UV radiation in the upper atmosphere. It is hypothesized that
depletion of the ozone layer Ozone depletion consists of two related events observed since the late 1970s: a steady lowering of about four percent in the total amount of ozone in Earth's atmosphere, and a much larger springtime decrease in stratospheric ozone (the ozone la ...
and a consequent increase in levels of UV light on the ground may increase future rates of cataracts. Note that the lens filters UV light, so if it is removed via surgery, one may be able to see UV light. Prolonged exposure to ultraviolet radiation from the
sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
can lead to melanoma and other skin malignancies. Clear evidence establishes ultraviolet radiation, especially the non-ionizing medium wave
UVB Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30  PHz) to 400 nm (750  THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...
, as the cause of most non-melanoma skin cancers, which are the most common forms of cancer in the world. UV rays can also cause wrinkles,
liver spot The liver is a major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it i ...
s, moles, and freckles. In addition to sunlight, other sources include tanning beds, and bright desk lights. Damage is cumulative over one's lifetime, so that permanent effects may not be evident for some time after exposure. Ultraviolet radiation of wavelengths shorter than 300 nm ( actinic rays) can damage the
corneal epithelium The corneal epithelium (epithelium corneæ anterior layer) is made up of epithelial tissue and covers the front of the cornea. It acts as a barrier to protect the cornea, resisting the free flow of fluids from the tears, and prevents bacteria fr ...
. This is most commonly the result of exposure to the sun at high altitude, and in areas where shorter wavelengths are readily reflected from bright surfaces, such as snow, water, and sand. UV generated by a welding arc can similarly cause damage to the cornea, known as "arc eye" or welding flash burn, a form of
photokeratitis Photokeratitis or ultraviolet keratitis is a painful eye condition caused by exposure of insufficiently protected eyes to the ultraviolet (UV) rays from either natural (e.g. intense sunlight) or artificial (e.g. the electric arc during welding) ...
. Fluorescent light bulbs and tubes internally produce ultraviolet light. Normally this is converted to visible light by the
phosphor A phosphor is a substance that exhibits the phenomenon of luminescence; it emits light when exposed to some type of radiant energy. The term is used both for fluorescent or phosphorescent substances which glow on exposure to ultraviolet or ...
film inside a protective coating. When the film is cracked by mishandling or faulty manufacturing then UV may escape at levels that could cause sunburn or even skin cancer.


Regulation

In the United States, nonionizing radiation is regulated in the Radiation Control for Health and Safety Act of 1968 and the
Occupational Safety and Health Act of 1970 The Occupational Safety and Health Act of 1970 is a US labor law governing the federal law of occupational health and safety in the private sector and federal government in the United States. It was enacted by Congress in 1970 and was signed by P ...
.


See also

*
Background radiation Background radiation is a measure of the level of ionizing radiation present in the environment at a particular location which is not due to deliberate introduction of radiation sources. Background radiation originates from a variety of source ...
* Bioinitiative Report *
Biological effects of radiation on the epigenome Ionizing radiation can cause biological effects which are passed on to offspring through the epigenome. The effects of radiation on cells has been found to be dependent on the dosage of the radiation, the location of the cell in regards to tissue ...
* Central nervous system effects from radiation exposure during spaceflight * Cosmic ray * COSMOS cohort study *
Electromagnetic hypersensitivity Electromagnetic hypersensitivity (EHS) is a claimed sensitivity to electromagnetic fields, to which negative symptoms are attributed. EHS has no scientific basis and is not a recognised medical diagnosis. Claims are characterized by a "variet ...
*
Electromagnetism In physics, electromagnetism is an interaction that occurs between particles with electric charge. It is the second-strongest of the four fundamental interactions, after the strong force, and it is the dominant force in the interactions of ...
*
EMF measurement EMF measurements are measurements of ambient (surrounding) electromagnetic fields that are performed using particular sensors or probes, such as EMF meters. These probes can be generally considered as ''antennas'' although with different charac ...
*
Health threat from cosmic rays Health threats from cosmic rays are the dangers posed by cosmic rays to astronauts on interplanetary missions or any missions that venture through the Van-Allen Belts or outside the Earth's magnetosphere. They are one of the greatest barriers s ...
* Light ergonomics *
Magnetobiology Magnetobiology is the study of biological effects of mainly weak static and low-frequency magnetic fields, which do not cause heating of tissues. Magnetobiological effects have unique features that obviously distinguish them from thermal effects; ...
*
Microwave Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency rang ...
*
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 t ...
*
Personal RF safety monitor Electromagnetic field monitors measure the exposure to electromagnetic radiation in certain ranges of the electromagnetic spectrum. This article concentrates on monitors used in the telecommunication industry, which measure exposure to radio spectru ...
*
Specific absorption rate Specific absorption rate (SAR) is a measure of the rate at which energy is absorbed per unit mass by a human body when exposed to a radio frequency (RF) electromagnetic field. It can also refer to absorption of other forms of energy by tissue, inc ...


References


Further reading

* (over 100 pages) *


External links


Information page
on electromagnetic fields at the World Health Organization web site
CDC – Electric and Magnetic Fields – NIOSH Workplace Safety and Health Topic
* {{DEFAULTSORT:Electromagnetic Radiation And Health Environmental controversies Medical physics Radiation health effects Radiobiology Health effects by subject