Microwave burn – Wikipedia

This article is about injury from direct microwave exposure. For early microwave-oven relate injuries, see Microwave oven § Hazards Microwave burns are sunburn injuries caused by thermal effects of microwave radiation absorbed in a living organism. In comparison with radiation burns caused by ionizing radiation, where the prevailing mechanism of weave damage is internal cell damage caused by free radicals, the elementary wrong mechanism of microwave radiation is by hotness. Microwave damage can manifest with a delay ; pain or signs of skin damage can show some clock after microwave exposure. [ 1 ]

Frequency vanadium depth [edit ]

The depth of penetration depends on the frequency of the microwaves and the tissue type. The Active Denial System ( “ pain ray ” ) is a less-lethal directed energy weapon that employs a microwave radio beam at 95 GHz ; a two-second collapse of the 95 GHz focused beam heats the skin to a temperature of 130 °F ( 54 °C ) at a depth of 1/64th of an edge ( 0.4 millimeter ) and is claimed to cause bark pain without survive damage. conversely, lower frequencies penetrate deep ; at 5.8 GHz ( 3.2 millimeter ) the depth most of the energy is dissipated in the first millimeter of the skin ; the 2.45 GHz frequency microwaves normally used in microwave ovens can deliver department of energy deep into the tissue ; the generally accepted value is 17 millimeter for muscleman tissue. [ 2 ]

As lower frequencies penetrate deep into the weave, and as there are fewer heart endings in deeper-located parts of the torso, the effects of the radio frequency waves ( and the damage caused ) may not be immediately obtrusive. The lower frequencies at eminent might densities present a significant risk. The microwave assimilation is directed by the insulator constant of the weave. At 2.5 GHz, this ranges from about 5 for adipose weave to about 56 for the cardiac muscle. As the speed of electromagnetic waves is proportional to the reciprocal of the square root of the insulator changeless, the resulting wavelength in the weave can drop to a divide of the wavelength in vent ; e.g. at 10 GHz the wavelength can drop from 3 curium to about 3.4 millimeter. [ 3 ] The layers of the body can be approximated as a thin layer of epidermis, dermis, adipose tissue ( hypodermic fat ), and muscle tissue. At dozens of gigahertz, the radiation is absorbed in the clear fraction to top few millimeters of skin. Muscle tissue is a a lot more efficient absorber than fatness, therefore at lower frequencies that can penetrate sufficiently deep, most energy gets deposited there. In a homogeneous average, the energy/depth addiction is an exponential bend with the exponent depending on the frequency and weave. For 2.5 GHz, the inaugural millimeter of muscleman tissue absorbs 11 % of the heat energy, the first two millimeters together absorb 20 %. For lower frequencies, the attenuation factors are much lower, the accomplishable inflame depths are higher, and the temperature gradient within the weave is lower. [ 2 ] [ 4 ]

tissue damage [edit ]

The weave damage depends primarily on the absorb energy and the tissue sensitivity ; it is a serve of the microwave ability concentration ( which depends on the distance from the generator and its power output ), frequency, concentration rate in the given tissue, and the tissue sensitivity. Tissues with high gear water system ( resp. electrolyte ) content show higher microwave absorption. The degree of the tissue damage depends on both the achieved temperature and the length of exposure. For curtly times, higher temperatures can be tolerated. The damage can be spread over a big area, when the beginning is a relatively aloof energy radiator, or a identical small ( though possibly deep ) area, when the body comes to a send contact with the source ( e.g. a wire or a connection pin ). [ 5 ] The epidermis has high electric resistance for lower frequencies ; at higher frequencies, the energy penetrates through by capacitive couple. wrong to epidermis has low extent unless the epidermis is very damp. The characteristic depth for lower-frequency microwave injury is about 1 curium. The heating pace of adipose tissue is much slower than of muscle tissue. Frequencies in millimeter wave range are absorbed in the topmost layer of skin, rich people in thermal sensors. At lower frequencies, between 1–10 GHz, most of the energy is however absorbed in deeper layers ; the threshold for cellular injury there lies at 42 °C while the pain threshold is at 45 °C, so a subjective perception may not be a dependable indicator of a harmful level of photograph at those frequencies. [ 6 ]

skin [edit ]

exposure to frequencies park in domestic and industrial sources rarely leads to meaning skin damage ; in such cases, the damage tends to be limited to upper limbs. significant injury with erythema, blisters, pain, steel price and tissue necrosis can occur even with exposures equally short as 2–3 seconds. Due to the deep penetration of these frequencies, the skin may be minimally affect and show no signs of wrong, while muscles, nerves, and lineage vessels may be importantly damaged. sensational nerves are particularly sensitive to such price ; cases of persistent neuritis and compression neuropathy were reported after significant microwave exposures. [ 7 ]

muscle and fatty tissue [edit ]

Microwave burns show some similarities with electrical burns, as the weave damage is deep rather than superficial. Adipose weave shows less degree of price than muscles and other water-rich tissues. ( In line, beaming inflame, liaison burns and chemical burns damage hypodermic adipose weave to higher extent than deeper brawn tissue. ) Full-thickness biopsy of the area between burned and unburned clamber shows layers of more and less damaged weave ( “ tissue sparing ” ), layers of undamaged fatness between damaged muscles ; a design that is not deliver in conventional thermal or chemical burns. Cells subjected to electrical burns show microscopic nuclear streaming on histology examination ; this feature is not salute with microwave burns. Microwaves besides deposit more energy to areas with abject lineage supply and to tissue interfaces. [ 1 ] [ 8 ] Hot spots may be formed in the weave, with a attendant higher absorption of microwave energy and even higher temperature achieved, with localize necrosis of the involve tissue following. [ 9 ] Sometimes, the moved tissue can even be charred. [ 10 ] Muscle tissue destruction can lead to myoglobinuria, with nephritic failure following in severe cases ; this is similar to burns from electric current. urinalysis and serum CPK, BUN and creatine tests are used to check for this condition. [ 11 ]

Eyes [edit ]

Cases of austere conjunctivitis were reported after technicians looked into powered waveguides. [ 4 ] Microwave-induced cataracts have been reported. [ 12 ] Experiments on rabbits and dogs, largely in the UHF crop of frequencies, shown that the eyepiece effects are confined to eyelids and conjunctiva ( as e.g. anterior segment keratitis or iritis ). [ 7 ] Cataracts were observed at several workers exposed to radiofrequency radiation, but in some of the cases the causal agent was unrelated to the RF exposure and in the early cases the attest was incomplete or inconclusive. [ 9 ] Some sources however mention incidence of microwave-related injuries of eyepiece lens and retina [ 13 ] and the possibility of thermal effects to cause cataracts or focal tissue burns ( incl. keratitis ). [ 14 ] For the dear field 2.45 GHz frequency, the minimal ability density to cause cataracts in rabbits was found to be 150 mW/cm2 for 100 minutes ; a retrolental temperature of 41 °C was necessary to be achieved. When the eye temperature was kept humble by external cooling, cataracts were not produced by higher field intensities ; that supports the hypothesis of a thermal mechanism being involved. [ 15 ]

Nerves [edit ]

sensory nerves are peculiarly sensitive to microwave price. Cases of haunting neuritis and compression neuropathy were reported after meaning microwave exposures. [ 7 ] When the temperature of the brain is raised to or above 42 °C, the blood–brain barrier permeability increases. [ 15 ] A neuropathy due to peripheral steel lesion, without visible external burns, can occur when the nerve is subjected to microwaves of sufficient might concentration. The damage mechanism is believed to be thermal. Radiofrequency waves and sonography can be used for impermanent block of peripheral nerves during neurosurgical operations. [ 16 ]

early tissues [edit ]

The thermal effects of microwaves can cause testicular degeneration and lower sperm count. [ 14 ] pneumonic bite can be present when lungs are exposed ; chest roentgenogram is used for diagnosing. [ 11 ] exposure of abdomen may lead to bowel obstruction due to stenosis of the moved intestine ; two-dimensional and upright abdominal x-ray is used to check for this condition. [ 11 ]

injury cases [edit ]

Household microwave ovens have shielding around the inside of the oven that prevents microwaves from leaking out, american samoa well as safety interlocks that prevent the oven from operate on when the door is open. therefore, burns due to calculate exposure to microwave energy ( as opposed to touching hot food ) should not occur under normal circumstances .

Infants and microwave ovens [edit ]

There are several cases of child abuse where an baby or child has been placed in a microwave oven. The typical feature of such injuries are well-defined burns on the skin nearest to the microwave emitter, and histology interrogation shows higher damage extent in tissues with senior high school content of water ( for example, muscles ) than in tissues with less water ( for example, adipose tissue ). [ 17 ]

One such case involved a adolescent babysitter who admitted to having placed a child in the microwave oven for approximately sixty seconds. The child developed a one-third degree burn to the back, measuring 5 inches x 6 inches. The babysitter late took the child to the emergency department, where multiple skin grafts were placed on the back. There were no signs of lasting emotional, cognitive or physical effects. CT scan of the head was convention, and there were no cataracts. [ 1 ] Another case involved a five-week-old female baby that had multiple full-thickness burns totaling 11 % of the soundbox surface area. The mother claimed the baby had been near a microwave oven, but not inside it. The baby survived but necessitate amputations of parts of one stage and one hand. [ 1 ] besides, there have been two alleged baby deaths caused by microwave ovens. [ 18 ] [ 19 ] [ 20 ] In all these cases, the babies were placed within microwaves and died of subsequent injuries .

Adults and microwave ovens [edit ]

A event of nerve damage by an exposure to radiation sickness from a malfunctioning 600 watt microwave oven, operated for five seconds with the doorway receptive, with both arms and hands exposed, was reported. During exposure, there was a pulsate, burning sense in all fingers. Erythema appeared on the back sides of both hands and arms. Four years later, denervation of median boldness, ulnar nerve, and radial steel in both arms was shown on an electromyography screen. [ 1 ] [ 21 ] The inaugural microwave oven injury was reported in 1973. Two women operated a microwave oven in a department store nosh bar. After several years, the oven showed a malfunction attest by burning the food. The first charwoman noticed burning sensations in her fingers and very little pain or softheartedness when nearby to the function oven. A small wound appeared on her left index finger, near the base of the fingernail. In the adjacent four weeks, three fingers of her right hand became affect vitamin a well. Transverse ridge and deformations close to the collar base appeared on her fingernails. After five months since the initial symptoms, she visited a repair ; the examination found no abnormalities other than the nails. topical steroid cream used over six weeks led to gradual improvement. The second charwoman experienced complete distortion at the same time as the first one, with the same clinical findings. The oven was returned to the manufacturer before the participation of the doctor, and the come of escape could not be assessed. [ 21 ] On July 29, 1977, H.F., a 51-year-old teacher, was attempting to remove a casserole dish from her newly 600-watt microwave oven. The oven signaled the end of the heat cycle, but the light and the cook blower were on. During recovery of the serve, she inserted two thirds of her unsheathed forearms into the oven, for a sum fourth dimension of about five seconds. The oven was still operating. She felt “ hot pulsate sense ” and burning in fingers and fingernails and a sensation of “ needles “ over the expose areas. Jabbing pain, swelling, and red-orange discoloration of abaxial sides of both hands and forearms appeared curtly afterwards. The future day she sought aesculapian help. Since then, she has undergo treatment with oral and topical cortisone, Grenz rays, sonography, and late acupuncture, without relief. Symptoms persisted, including high sensitivity to radiant estrus ( sun, desk lamp, etc. ) and growing intolerance to press of clothes and to touch in hands and forearms. neurological examinations in 1980 and 1981 did not yield a definite diagnosis. neural latencies were within average. Electromyography discovered denervation in the medial boldness, ulnar nerve, and radial heart on both arms. austere reduction of count of sweat glands in the feel pulp, in comparison with a random dominance, was besides found. The injury was determined to be caused by the fully power of the magnetron ; the pulsate sensation was caused either by the stirrer ( a mechanical mirror distributing the microwave beam across the oven space to prevent geological formation of hot and cold spots ), or by the arterial pulsation in combination with increased nerve sensitivity. damage to the A beta fibers, A delta fibers, and group C nerve fibers was the lawsuit of the burn ace. The increased hypersensitivity to radiant heat is caused by the wrong to the A beta, A delta, and polymodal nociceptors ( the group C fibers ) ; this damage is induced by a single-time overheating of the bark to 48.5–50 °C, and the resulting sensitivity persists for a long time. degeneration of the alpha motive neurons is besides caused by the exposure to heat and radiation. Most of the major boldness trunks were not affected. damage to the A beta fibers ( located in the skin ), discovered by the two-point discrimination test, is permanent wave ; the Pacinian corpuscles, Meissner corpuscles, and Merkel steel endings, which degenerated after denervation, do not regenerate. The sympathetic anxious organization was involved american samoa well ; the reduction in active sweat glands was caused by end of their innervation, the initial edema and blush was besides caused by sympathetic steel damage. [ 22 ] In 1983, a 35-year-old male was heating a sandwich in a microwave oven at oeuvre. After opening the door, the magnetron did not shut off and his right hand was exposed to microwave radiation as he retrieved the sandwich. After exposure, his hired hand was pale and cold ; 30 minutes late the man presented himself to a doctor, with paresthesia in all fingers and the hand still pale and cold. An Allen ‘s test showed a return to normal color after 60 seconds ( normal is 5 seconds ). By 60 minutes after exposure the bridge player was normal again, and the affected role was discharged without treatment. A week late there was no paresthesia, motive weakness nor sensational deficit. [ 21 ]

other [edit ]

An engineer replaced a woodpecker -damaged fertilize horn of a high-octane microwave antenna, a 15-meter dish at an Earth station of a television receiver network, using a cherry picker. After finishing, he sent his technician to power up the vector, and attempted to lower the cherry picker down. The locomotive failed and the engineer was stuck following to the antenna, outside of its main lobe but well within the first sidelobe. The technician, unaware that the engineer was still close to the antenna, powered it up. The engineer was exposed to an acute microwave field for about three minutes, until the error was realized. There were no immediate symptoms ; the following good morning the mastermind detected blood and solid matter in his urine, and visited a sophisticate, who found blood in toilet and massive intestine adhesions. The engineer ‘s medical problems lasted for many years. [ 23 ]

aesculapian uses [edit ]

Dielectric heating system ( diathermy ) is used in medicine ; the frequencies used typically lie in the supersonic, shortwave, and microwave ranges. Careless application, specially when the patient has implanted metallic conductors ( e.g. cardiostimulator leads ), can cause burns of hide and deeper tissues and even death. [ 24 ] Microwave damage to tissues can be intentionally exploited as a remedy technique, e.g. radiofrequency ablation and radiofrequency lesioning. Controlled end of tissue is performed for treatment of cardiac arrhythmia. [ 25 ] Microwave curdling can be used for some kinds of surgeries, for example, stopping bleed after a dangerous liver injury. [ 26 ] Microwave heat seems to cause more damage to bacteria than equivalent thermal-only heat. [ 27 ] however food reheated in a microwave oven typically reaches lower temperature than classically reheated, consequently pathogens are more likely to survive. Microwave heat of blood, e.g. for transfusion, is contraindicated, as it can cause hemolysis and hyperkalemia. [ 8 ] Microwave heat is one of the methods for inducing hyperthermia for hyperthermia therapy. high-energy microwaves are used in neurobiology experiments to kill belittled testing ground animals ( mouse, rats ) in club to fix brain metabolites without the loss of anatomic integrity of the tissue. The instruments used are designed to focus most of the office to the animal ‘s head. The unconsciousness and death is closely blink of an eye, occurring in less than one second, and the method acting is the most effective one to fix brain tissue chemical action. A 2.45 GHz, 6.5 kilowatt source will heat the brain of a 30 gravitational constant mouse to 90 °C in about 325 milliseconds ; a 915 MHz, 25 kilowatt source will heat the brain of a 300 g rat to the same temperature in a second. extra devices designed or modified for this function have to be used ; use of kitchen-grade microwave ovens is condemned. [ 28 ]

percept thresholds [edit ]

Safety limits exist for microwave exposure. The U.S. Occupational Safety and Health Administration defines department of energy concentration limit for exposure periods of 0.1 hours or more to 10 mW/cm2 ; for shorter periods the specify is 1 mW-hr/cm2 with limited excursions above 10 mW/cm2. The U.S. Food and Drug Administration ( FDA ) standard for microwave oven escape puts specify to 5 mW/cm2 at 2 inches from the oven ‘s open. [ 24 ] For 5.8 GHz, exposure to 30 mW/cm2 causes increase of facial skin temperature by 0.48 °C, corneal open heats by 0.7 °C, and the temperature of retina is estimated to increase by 0.08–0.03 °C. [ 9 ] exposure of skin to microwaves can be perceived as a sensation of inflame or trouble. Due to lower penetration of higher frequencies, perception threshold is lower for higher frequencies as more energy is dissipated closer to the body surface. When the entire face is exposed to 10 GHz microwaves, the feel of heat is evoked at energy densities of 4–6 mW/cm2 for 5 or more seconds, or about 10 mW/cm2 for a half second base. Experiments on six volunteers exposed to 2.45 GHz microwaves shown sensing thresholds on forearm clamber to be at the average of 25–29 mW/cm2, ranging from 15.40 to 44.25 mW/cm2. The sensation was indistinguishable from heat delivered by infrared radiation, though the infrared radiotherapy required about five times lower energy density. Pain threshold for 3 GHz was demonstrated to range from 0.83–3.1 W/cm2 for 9.5 cm2 of expose area, depending on duration of the exposure ; other source says the dependence is not directly on the power concentration and exposure length, but primarily on the critical bark temperature. [ 9 ] Microwave energy can be focused by alloy objects in the vicinity of the body or when implanted. such concentrate and attendant increased heat can importantly lower the perception, pain and damage thresholds. Metal-framed glasses perturb microwave fields between 2–12 GHz ; individual components were found to be evocative between 1.4 and 3.75 GHz. [ 9 ] A security guard with a metallic element plate in his leg experienced heat of the plate when patrolling near tropospheric disperse sender antenna ; he had to be removed from their vicinity. In the 30–300 GHz band, dry clothing may serve as an electric resistance transformer, facilitating more efficient energy coupling to the underlying hide. [ 4 ] Pulsed microwave radiation can be perceived by some workers as a phenomenon called “ microwave hearing “ ; the irradiate personnel perceive auditory sensations of clicking or buzzing. The lawsuit is thought to be thermoelastic expansion of portions of auditory apparatus. [ 14 ] The auditory system answer occurs at least from 200 MHz to at least 3 GHz. In the tests, repetition rate of 50 Hz was used, with pulse width between 10–70 microseconds. The sensed flashiness was found to be linked to the peak power density alternatively of average power concentration. At 1.245 GHz, the peak power concentration for perception was below 80 mW/cm2. The broadly accepted mechanism is rapid ( but small letter, in the range of 10−5 °C ) heat of genius by each pulse, and the result pressure wave traveling through skull to cochlea. [ 4 ]

early concerns [edit ]

Some vacuum tube deliver in microwave installations tend to generate bremsstrahlung x-rays. Magnetrons and specially hydrogen thyratrons tend to be the worst offenders. [ 29 ]

low-level exposure [edit ]

As the energy of radio frequency waves and microwaves is insufficient to directly disrupt individual chemical bonds in minor or stable molecules, the effects are considered limited to thermal. Energy densities that are not sufficient to overheat the tissues are not shown to cause survive damage [ citation needed ]. To clarify, the deep-red light bulb in a black-and-white photographic darkroom produces a higher-energy human body of radiotherapy than microwaves. Like a microwave, this light bulb can burn, particularly if touched, but the tan is only possible due to excessively a lot estrus. A study of 20,000 radar technicians of the US Navy, who were chronically exposed to high levels of microwave radiation sickness, did not detect increase incidence of cancer. [ 30 ] Recent epidemiologic evidence besides led to the consensus that exposure to electromagnetic fields, e.g. along might lines, did not raise incidence of leukemia or other cancers. [ 31 ]

Myths [edit ]

A coarse myth among radar and microwave communication workers is that the exposure of the genital area to microwaves renders a man sterile for about a day. The might concentration necessity for this effect is however sufficient to besides cause permanent damage. [ 23 ]

References [edit ]