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 for months or years. (120V power systems would be unable to reach this intensity unless an appliance has an internal voltage transformer.)
Overhead power lines 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. 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. Associations between exposure to extremely low frequency magnetic fields (ELF MF) and various health outcomes have been investigated through a variety of epidemiological studies. A pooled analysis found consistent evidence of an effect of ELF-MF on childhood leukaemia. An assessment of the burden of disease potentially resulting from ELF MF exposure in Europe found that 1.5–2% of childhood leukaemia cases might be attributable to ELF MF, but uncertainties around causal mechanisms and models of dose-response were found to be considerable. The International Agency for Research on Cancer (IARC) finds "inadequate evidence" for human carcinogenicity.
Shortwave Shortwave (1.6 to 30 MHz)
diathermy (where EM waves are used to produce heat) can be used as a therapeutic technique for its
analgesic effect and deep muscle relaxation, but has largely been replaced by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 and
muscle.
Adipose tissue (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 where 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 between 1.34 and 30 MHz.has been interpreted to mean that there is very little scientific evidence as to phone signal carcinogenesis. In 2011, the
International Agency for Research on Cancer (IARC) classified mobile phone radiation as
group 2B, "possibly carcinogenic," rather than
group 2A ("probably carcinogenic") or
group 1 ("is carcinogenic"). 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 and other radio frequencies cause heating, and this can cause
burns 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, 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 scanners. Likewise
WiGig 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 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, 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 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). As with its infrared and ultraviolet radiation dangers, welding creates an intense brightness in the visible light spectrum, which may cause temporary
flash blindness. 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 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 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 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 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 can lead to
melanoma and other skin malignancies. Clear evidence establishes ultraviolet radiation, especially the non-ionizing medium wave
UVB, as the cause of most non-melanoma
skin cancers, which are the most common forms of cancer in the world. Ultraviolet radiation of wavelengths shorter than 300 nm (
actinic rays) can damage the
corneal epithelium. 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. warning sign: Non-ionizing radiation
Fluorescent light bulbs and tubes internally produce
ultraviolet light. Normally this is converted to visible light by the
phosphor 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==