4.6 mm. the depth where maximum of the energy is deposited is significantly lower. the energy and penetration depth of several isotopes is as follows: 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. mev surfacedose % 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 causes radiation burns are caused by exposure to high levels of radiation. levels high enough to cause burn are generally lethal if received as a whole-body dose, whereas they may be treatable if received as a shallow or local dose. medical imaging fluoroscopy may cause burns if performed repeatedly or for too long. similarly, x-ray computed tomography and traditional projectional radiography have the potential to cause radiation burns if the exposure factors and exposure time are not appropriately controlled by the operator. a study of radiation-induced skin injuries has been performed by the food and drug administration (fda) based on results from 1994, followed by an advisory to minimize further fluoroscopy-induced injuries. the problem of radiation injuries due to fluoroscopy has been further investigated in review articles in 2000, 2001, 2009 and 2010. radioactive fallout 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. 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. 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 as if they had been scalded. 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 a layer of up to 2 cm. residents developed beta burns, mostly on the backs of their necks and on their feet, 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; the 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. the fishing ship daigo fukuryu maru was affected by the fallout as well; the crew suffered skin doses between 1.7 and 6.0 gy, with beta burns manifesting as severe skin lesions, erythema, erosions, sometimes necrosis, and skin atrophy. twenty-three u.s. radar servicemen of the 28-member weather station on rongerik were affected, experiencing discrete 1–4 mm 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. during the zebra test of the operation sandstone in 1948, three men had 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. a fourth man showed weaker burns after the earlier yoke test. the upshot–knothole harry test at the frenchman flat site released a large amount of fallout. a significant number of sheep died after grazing on contaminated areas. the aec however had a 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. during the operation upshot–knothole, sheep as far as 50 miles (80 km) from the test site developed beta burns to their backs and nostrils. during underground nuclear testing in nevada, several workers developed burns and skin ulcers, in part attributed to exposure to tritium. nuclear accidents 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 developed 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. the survivors have atrophied skin which is spider veined and with underlying fibrosis. 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. 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 had 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. the burns may be fairly deep and require skin grafts, tissue resection or even amputation of fingers or limbs. treatment radiation burns should be covered by a clean, dry dressing as soon as possible to prevent infection. wet dressings are not recommended. the presence of combined injury (exposure to radiation plus trauma or radiation burn) increases the likelihood of generalized sepsis. this requires administration of systemic antimicrobial therapy.