| Radiation burn | |
|---|---|
| Classification and external resources | |
| ICD-9 | 990 |
A radiation burn is damage to the skin or other biological tissue caused by exposure to radio frequency energy or ionizing radiation.
The most common type of radiation burn is a sunburn caused by UV radiation. High exposure to X-rays during diagnostic medical imaging or radiotherapy can also result in radiation burns. As the ionizing radiation interacts with cells within the body—damaging them—the body responds to this damage, typically resulting in erythema—that is, redness around the damaged area. Radiation burns are often associated with cancer due to the ability of ionizing radiation to interact with and damage DNA, occasionally inducing a cell to become cancerous. Cavity magnetrons can be improperly used to create surface and internal burning. Depending on the photon energy, gamma radiation can cause very deep gamma burns, with 60Co internal burns common. Beta burns tend to be shallow as beta particles are not able to penetrate deep into the person; these burns can be similar to sunburn.
Radiation burns can also occur with high power radio transmitters at any frequency where the body absorbs radio frequency energy and converts it to heat.[1] The U.S. Federal Communications Commission (FCC) considers 50 watts to be the lowest power above which radio stations must evaluate emission safety. Frequencies considered especially dangerous occur where the human body can become resonant, at 35 MHz, 70 MHz, 80-100 MHz, 400 MHz, and 1 GHz.[2] Exposure to microwaves of too high intensity can cause microwave burns.
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"Beta burns" are shallow surface burns, usually of skin and less often of lungs or gastrointestinal tract, caused by beta particles, typically from hot particles or dissolved radionuclides that came to direct contact with or close proximity to the body. They can appear similar to sunburn. Unlike gamma rays, beta emissions are stopped much more effectively by materials and therefore deposit all their energy in only a shallow layer of tissue, causing more intense but more localized damage. On cellular level, the changes in skin are similar to radiodermatitis.
High doses of radiation can cause rapid browning of skin, known as "nuclear tan".
The dose is influenced by relatively low penetration of beta emissions through materials. The cornified keratine layer of epidermis has enough stopping power to absorb beta radiation with energies lower than 70 keV. Further protection is provided by clothing, especially shoes. The dose is further reduced by limited retention of radioactive particles on skin; a 1 millimeter particle is typically released in 2 hours, while a 50 micrometer particle usually does not adhere for more than 7 hours. Beta emissions are also severely attenuated by air; their range generally does not exceed 6 feet (1.8 m) and intensity rapidly diminishes with distance.[3]
The eye lens seems to be the most sensitive organ to beta radiation,[4] even in doses far below maximum permissible dose. Safety goggles are recommended to attenuate strong beta.[5]
Beta burns can occur also to plants.
The beta activity diminishes rapidly. Dose ratios from smaller radioactive particles are higher than from large particles. As early as 17 minutes after the blast, single particles 0.5mm or less in diameter do not cause skin ulceration anymore. Deposition of 100 mg of fallout per square foot of skin, with particles smaller than 0.25 mm, will cause beta burns up to 3 hours after the blast.[6]
Careful washing of exposed body surface, removing the radioactive particles, may provide significant dose reduction. Exchanging or at least brushing off clothes also provides a degree of protection.
If the exposition to beta radiation is intense, the beta burns may first manifest in 24–48 hours by itching and/or burning sensation that last for one or two days, sometimes accompanied by hyperaemia. After 1–3 weeks burn symptoms appear; erythema, increased skin pigmentation (dark colored patches and raised areas), followed by epilation and skin lesions. Erythema occurs after 5–15 Gy, dry desquamation after 17 Gy, and bullous epidermitis after 72 Gy.[3] Chronic radiation keratosis may develop after higher doses. Primary erythema lasting more than 72 hours is an indication of injury severe enough to cause chronic radiation dermatitis. Edema of dermal papillae, if present within 48 hours since the exposition, is followed by transepidermal necrosis. After higher doses, the malpighian layer cells die within 24 hours; lower doses may take 10–14 days to show dead cells.[7] Inhalation of beta radioactive isotopes may cause beta burns of lungs and nasopharyngeal region, ingestion may lead to burns of gastrointestinal tract; the latter being a risk especially for grazing animals.
Lost hair begins regrowing in 9 weeks and is completely restored in about half a year.[8]
The acute dose-dependent effects of beta radiation on skin are as follows:[9]
| 0–6 Gy | no acute effect |
| 6–20 Gy | moderate early erythema |
| 20–40 Gy | early erythema in 24 hours, skin breakdown in 2 weeks |
| 40–100 Gy | severe erythema in less than 24 hours |
| 100–150 Gy | severe erythema in less than 4 hours, skin breakdown in 1–2 weeks |
| 150–1000 Gy | blistering immediate or up to 1 day |
According to other source:[10]
| 2–6 Gy | transient erythema 2–24 h |
| 3–5 Gy | dry desquamation in 3–6 weeks |
| 3–4 Gy | temporary epilation in 3 weeks |
| 10–15 Gy | erythema 18–20 days |
| 15–20 Gy | moist desquamation |
| 25 Gy | ulceration with slow healing |
| 30–50 Gy | blistering, necrosis in 3 weeks |
| 100 Gy | blistering, necrosis in 1–3 weeks |
As shown, the dose thresholds for symptoms vary by source and even individually. In practice, determining the exact dose tends to be difficult.
Similar effects apply to animals, with fur acting as additional factor for both increased particle retention and partial skin shielding. Unshorn thickly wooled sheep are well protected; while the epilation threshold for sheared sheep is between 23–47 Gy (2500–5000 rep) and the threshold for normally wooled face is 47–93 Gy (5000–10000 rep), for thickly wooled (33mm hair length) sheep it is 93–140 Gy (10000–15000 rep). To produce skin lesions comparable with contagious pustular dermatitis, the estimated dose is between 465–1395 Gy.[11]
| Prop: Unit: |
t½ a |
Yield % |
Q * keV |
βγ * |
|---|---|---|---|---|
| 155Eu | 4.76 | .0803 | 252 | βγ |
| 85Kr | 10.76 | .2180 | 687 | βγ |
| 113mCd | 14.1 | .0008 | 316 | β |
| 90Sr | 28.9 | 4.505 | 2826 | β |
| 137Cs | 30.23 | 6.337 | 1176 | βγ |
| 121mSn | 43.9 | .00005 | 390 | βγ |
| 151Sm | 90 | .5314 | 77 | β |
The effects depend on both the intensity and the energy of the radiation. Low-energy beta (sulfur-35, 170 keV) produces shallow ulcers with little damage to dermis, while cobalt-60 (310 keV), caesium-137 (550 keV), phosphorus-32 (1.71 MeV), strontium-90 (650 keV) and its daughter product yttrium-90 (2.3 MeV) damage deeper levels of the dermis and can result in chronic radiation dermatitis. Very high energies from electron beams from particle accelerators, reaching tens of megaelectronvolts, can be deeply penetrating. Conversely, megavolt-scale beams can deposit their energy deeper with less damage to the dermis; modern radiotherapy electron beam accelerators take advantage of this. At yet higher energies, above 16 MeV, the effect does not show significantly anymore, limiting the usefulness of higher energies for radiotherapy. As a convention, surface is defined as the topmost 0.5 mm of skin.[12] High-energy beta emissions should be shielded with plastic instead of lead, as high-Z elements generate deeply penetrating gamma bremsstrahlung.
The electron energies from beta decay are not discrete but form a continuous spectrum with a cutoff at maximum energy. The rest of the energy of each decay is carried off by an antineutrino which does not significantly interact and therefore does not contribute to the dose. Most energies of beta emissions are at about a third of the maximum energy.[5] Beta emissions have much lower energies than what is achievable from particle accelerators, no more than few megaelectronvolts.
The energy-depth-dose profile is a curve starting with a surface dose, ascending to the maximum dose in a certain depth dm (usually normalized as 100% dose), then descends slowly through depths of 90% dose (d90) and 80% dose (d80), then falls off linearly and relatively sharply though depth of 50% dose (d50). The extrapolation of this linear part of the curve to zero defines the maximum electron range, Rp. In practice, there is a long tail of weaker but deep dose, called "bremsstrahlung tail", attributable to bremsstrahlung. The penetration depth depends also on beam shape, narrower beam tend to have less penetration. In water, broad electron beams, as is the case in homogeneous surface contamination of skin, have d80 about E/3 cm and Rp about E/2 cm, where E is the beta particle energy in MeV.[13]
The penetration depth of lower-energy beta in water (and soft tissues) is about 2 mm/MeV. For a 2.3 MeV beta the maximum depth in water is 11 mm, for 1.1 MeV it is 4.6 mm. The depth where maximum of the energy is deposited is significantly lower.[14]
The energy and penetration depth of several isotopes is as follows:[15]
| isotope | half-life | specific activity (TBq/g) |
avg. (keV) |
max. (keV) |
in air (mm) |
in tissue (mm) |
comment |
|---|---|---|---|---|---|---|---|
| tritium | 12.3 years | 357 | 5.7 | 18.6 | 6 | 0.006 | no beta passes the dead layer of skin; however tritium and its compounds may diffuse through skin |
| carbon-14 | 5730 years | 0.165 | 49 | 156 | 240 | 0.28 | about 1% of beta passes through the dead layer of skin |
| sulfur-35 | 87.44 days | 1580 | 48.8 | 167.47 | 260 | 0.32 | |
| phosphorus-33 | 25.3 days | 5780 | 76.4 | 248.5 | 500 | 0.6 | |
| phosphorus-32 | 14.29 days | 10600 | 695 | 1710 | 6100 | 7.6 | risk of bremsstrahlung if improperly shielded |
For a wide beam, the depth-energy relation for dose ranges is as follows, for energies in megaelectronvolts and depths in millimeters. The dependence of surface dose and penetration depth on beam energy is clearly visible.[13]
| MeV | surface dose % |
max. depth |
90% | 80% | 50% | 10% | Rp |
|---|---|---|---|---|---|---|---|
| 5 | 74% | 9 | 12 | 14 | 17 | 22 | 23 |
| 7 | 76% | 16 | 20 | 22 | 27 | 33 | 34 |
| 10 | 82% | 24 | 31 | 34 | 39 | 48 | 49 |
| 13 | 88% | 32 | 40 | 43 | 51 | 61 | 64 |
| 16 | 93% | 34 | 51 | 56 | 65 | 80 | 80 |
| 19 | 94% | 26–36 | 59 | 67 | 78 | 95 | 95 |
| 22 | 96% | 26–36 | 65 | 76 | 93 | 113 | 114 |
| 25 | 96% | 26–36 | 65 | 80 | 101 | 124 | 124 |
Radiation burns should be covered by a clean, dry dressing as soon as possible to prevent infection. Wet dressings are NOT recommended. Of The Army, United States. Dept (1982). Nuclear handbook for medical service personnel. http://books.google.com/?id=CAUYAAAAYAAJ&pg=PA18&dq=%22beta+burns%22&cd=65#v=onepage&q=%22beta%20burns%22&f=false. The presence of combined injury ( exposure to radiation plus trauma or radiation burn) increases the likelihood of generalized sepsis.[16] This requires administration of systemic antimicrobial therapy.[17]
Beta burns are frequently the result of exposure to radioactive fallout after nuclear explosions or nuclear accidents. Shortly after the explosion, the fission products have very high beta activity, with about two beta emissions per each gamma photon.
After the Trinity test, the fallout caused localized burns on the backs of cattle in the area downwind.[18] The fallout had the appearance of small flaky dust particles. The cattle showed temporary burns, bleeding, and loss of hair. Dogs were also affected; in addition to localized burns on their backs, they also had burned paws, likely from the particles lodged between their toes as hoofed animals did not show problems with feet. About 350–600 cattle were affected by superficial burns and localized temporary loss of dorsal hair; the army later bought 75 most affected cows as the discolored regrown hair lowered their market value.[19] The cows were shipped to Los Alamos and Oak Ridge, where they were observed. They healed, now sporting large patches of white fur; some looked like being scalded.[20]
The fallout produced by the Castle Bravo test was unexpectedly strong. A white snow-like dust, nicknamed by the scientists "Bikini snow" and consisting of contaminated crushed calcined coral, fell for about 12 hours upon the Rongelap Atoll, depositing layer of up to 2 cm. Residents suffered beta burns, mostly on the backs of their necks and on their feet,[18] and were resettled after three days. After 24–48 hours their skin was itching and burning; in a day or two the sensations subsided, to be followed after 2–3 weeks by epilation and ulcers. Darker-colored patches and raised areas appeared on their skin, blistering was uncommon. Ulcers formed dry scabs and healed. Deeper lesions, painful, weeping and ulcerated, formed on more contaminated residents; majority healed with simple treatment. In general, the beta burns healed with some cutaneous scarring and depigmentation. Individuals who bathed and washed the fallout particles from their skin did not develop skin lesions.[9] The fishing ship Daigo Fukuryu Maru was affected by the fallout as well; the crew suffered skin doses between 1.7–6.0 Gy, with beta burns manifesting as severe skin lesions, erythema, erosions, sometimes necrosis, and skin atrophy. 23 U.S. radar servicemen of the 28-member weather station on Rongerik[21] were affected, experiencing discrete 1-4mm skin lesions which healed quickly, and ridging of fingernails several months later. Sixteen crew members of the aircraft carrier USS Bairoko received beta burns and there was an increased cancer rate.[3]
During the Zebra test of the Operation Sandstone in 1948 three men suffered beta burns on their hands when removing sample collection filters from drones flying through the mushroom cloud; their estimated skin surface dose was 28 to 149 Gy and their disfigured hands required skin grafts. Fourth man shown weaker burns after the earlier Yoke test.[22]
The Upshot-Knothole Harry test at the Frenchman Flat site released large amount of fallout. Significant amount of sheep died after grazing on contaminated areas. The AEC however had policy to compensate farmers only for animals showing external beta burns, so many claims were denied. Other tests on the Nevada Test Site also caused fallout and corresponding beta burns to sheep, horses and cattle.[23] During the Operation Upshot-Knothole, sheep as far as 50 miles (80 km) from the test site suffered beta burns to their backs and nostrils.[22]
During underground nuclear testing in Nevada, several workers developed burns and skin ulcers, in part attributed to exposure to tritium.[24]
Beta burns were a serious medical issue for some victims of the Chernobyl disaster; from 115 patients treated in Moscow, 30% had burns covering 10–50% of body surface, 11% were affected on 50–100% of skin; the massive exposure was often caused by clothes drenched with radioactive water. Some firefighters suffered beta burns of lungs and nasopharyngeal region after inhalation of massive amounts of radioactive smoke. Out of 28 deaths, 16 had skin injuries listed among the causes. The beta activity was extremely high, with beta/gamma ratio reaching 10–30 and beta energy high enough to damage basal layer of the skin, resulting in large area portals for infections, exacerbated by damage to bone marrow and weakened immune system. Some patients received skin dose of 400–500 Gy. The infections caused more than half of the acute deaths. Several died of fourth degree beta burns between 9–28 days after dose of 6–16 Gy. Seven died after dose of 4–6 Gy and third degree beta burns in 4–6 weeks. One died later from second degree beta burns and dose 1-4 Gy.[24] The survivors have atrophic skin which is telangiectactic and with underlying fibrosis.[3]
The burns may manifest at different times at different body areas. The Chernobyl liquidators burns first appeared on wrists, face, neck and feet, followed by chest and back, then by knees, hips and buttocks.[25]
Industrial radiography sources are a common source of beta burns in workers.
Radiation therapy sources can cause beta burns during exposure of the patients. The sources can be also lost and mishandled, as in the Goiânia accident, during which several people suffered external beta burns and more serious gamma burns, and several died. Numerous accidents also occur during radiotherapy due to equipment failures, operator errors, or wrong dosage.
Electron beam sources and particle accelerators can be also sources of beta burns.[26] The burns may be fairly deep and require skin grafts, tissue resection or even amputation of fingers or limbs.[27]