They reported that about 50% of the Haversian systems in the os pubis were hot spots, while hot spots constituted only about 2% of the Haversian systems in the femur shaft. The higher values of the ratios were associated with shorter exposure times, usually the order of a year or less. A more complete description of the radium-dial painter data and parallel studies with radium in laboratory animals, particularly the rat, would do much to further such efforts. A., P. Isaacson, W. J. Hausler, and J. Kohler. The alternative is to reanalyze all of the data on tumor induction for 224Ra by using the new algorithm before it is applied it to dose calculations for risk estimation in a population group different from the subjects in the study by Spiess and Mays.85. These were plotted against a variety of dose variables, including absorbed dose to the skeleton from 226Ra and 228Ra, pure radium equivalent, and time-weighted absorbed dose, referred to as cumulative rad years. The purpose of this chapter is to review the information on cancer induced by these three isotopes in humans and estimate the risks associated with their internal deposition. When examined in this fashion, questions arise. Over age 30, the situation is different. There may be an excess of leukemia among the adults, but the evidence is weak. These results are in marked contrast to those of Kolenkow30 and Littman et al.31 Under Schlenker's73 assumptions, the airspace is the predominant source of dose, with the exception noted, whether or not the airspace is ventilated. Otherwise, the retention in bone is estimated by models. cumulative exposure because lead accumulates in bone over the lifetime and most of the lead body burden resides in bone. No fitted value is given for doses below 1,000 rad, but all data points in this range are at zero incidence. In the case of 224Ra, the relatively short half-life of the material permits an estimation of the dose to bone or one that is proportional to that received by the cells at risk. The half lives are 3.5 days for radium-224, 1,600 years for radium-226, and 6.7 years for radium-228, the most common isotopes of radium, after which each forms an isotope of radon. Table 4-5, based on their report, illustrates their results. Some 55 sarcomas of bone have occurred in 53 of 898 224Ra-exposed patients whose health status is evaluated triennially.46 Two primary sarcomas occurred in 2 subjects. Each isotope of radium gives rise to a series of radioactive daughter products that leads to a stable isotope of lead (Figure 4-1a and 4-1b). Twenty-eight towns met the three criteria for the second study: a population between 1,000 and 10,000, water is obtained solely from wells greater than 500 ft (152 m) deep, and no water softening. The radiogenic risk equals the total risk given by one of the preceding expressions minus the natural tumor risk. Source: Mays and Spiess.45, Risk per person per gray versus mean skeletal dose. 2]exp(-1.1 10-3 l - 0.7 10-5) are used to determine a range of values based on the envelope boundaries, a measure of the uncertainty in estimated bone sarcoma risk at low doses can be formed as: where I is the best-fit function [0.7 10-5 + 7.0 10-8 Specific bone complications of radiation include osteopenia, growth arrest, fracture and malignancy. The complexity of the problem is illustrated by their findings for Chicago. In press. Pain, PSA flare, and bone scan response in a patient with metastatic This large difference has prompted theoretical investigations of the time dependence of hotspot dose rate and speculations on the relative importance of hot-spot and diffuse components of the radioactivity distribution for tumor induction. A recent examination of data on whole-body radium retention in humans revealed that the excretion rate diminished with increasing body burden.70 Absolute retention could not be studied, because the initial intake was unknown, but the data imply the existence of a dose-dependent retention similar to that observed in animals. In the subject without carcinoma, the measured radium concentration in the layer adjacent to the bone surface was only about 3 times the skeletal average. local 36 elevator apprenticeship. During the first few days after intake, radium concentrates heavily on bone surfaces and then gradually shifts its primary deposition site to bone volume. When the model is used for radium, careful attention should be paid to the constraints placed on the model by data on radium retention in human soft tissues.74 Because of the mathematical complexity of the retention functions, some investigators have fitted simpler functions to the ICRP model. The expected number, however, is only 1.31. The mucosal lining of the mastoid air cells is thinner than the lining of the sinuses. i). Mays, C. W., T. F. Dougherty, G. N. Taylor, R. D. Lloyd, B. J. Stover, W. S. S. Jee, W. R. Christensen, J. H. Dougherty, and D. R. Atherton. The same goals can be achieved if normal mortality is represented by a continuous function and radiation-induced mortality is so represented, as for 224Ra above, and the methods of calculus are used to compute the integrals obtained by the tabular method. Tumor frequencies for axial and appendicular skeleton are shown in Table 4-1. Human health studies have grown from a case report phase into epidemiological studies devoted to the discovery of all significant health endpoints, with an emphasis on cancer but always with the recognition that other endpoints might also be significant. Decay series for radium-228, a beta-particle emitter, and radium-224, an alpha-particle emitter, showing the principal isotopes present, the primary radiations emitted (, , or both), and the half-lives (s = second, m = minute, h (more). The practical threshold would be the dose at which the minimum appearance time exceeded the maximum human life span, about 50 rad. Mays, C. W., H. Spiess, and A. Gerspach. In the analyses, a linear dose-response relationship was postulated, and the data were sorted according to the time period over which 224Ra was administered. -kx), and a threshold function. . For example, if a person is exposed to 226Ra at time zero, the person is not considered to be at risk for 10 yr; the total number of carcinomas expected to occur among N people with identical systemic intakes D In addition, blood vessel cells themselves sometimes convert into bone-forming osteoblasts, producing extra calcium on the spot. A., P. Isaacson, R. M. Hahne, and J. Kohler. 2 Below this dose level, the chance of developing a radium-induced tumor would be very small, or zero, as the word threshold implies. It is absorbed from the soil by plants and passed up the food chain to humans. The chance that two independent initiations will occur close enough together to permit a short tumor appearance time increases with increasing dose rate, in agreement with the observations of Raabe et al.61,62 When the total dose is delivered over a period of time much shorter than the human life span, both initiations must occur within the period of dose delivery, and there is a high probability of short tumor appearance times, regardless of dose level, as confirmed by the human 224Ra data.46 Reasoning from the theory, there is always a nonzero chance for both initiations to occur close together, regardless of dose rate or total dose. where 3 10-5 is the natural risk adapted here. It is clear, therefore, that a nonzero function could be fitted to these data but would have numerical values substantially less than 28%. The resultant graph of dose-response curve slopes versus years of follow-up is shown in Figure 4-6. Kolenkow's work30 illustrated many of the complexities of sinus dosimetry and emphasized the rapid decrease of dose with depth in the mucous membrane. 1972. why does radium accumulate in bones? There is little evidence for an age or sex dependence of the cancer risk from radium isotopes, provided that the age dependence of dose that accompanies changes in body and tissue masses is taken into account. How are people exposed to radium? Both bones are important for proper motion of the elbow and wrist joints, and both bones serve as important attachments to muscles of the upper extremity. He pointed out that the reports of Martland4143 describe a regenerative leucopenic anemia, and he stated that "this syndrome has features of atypical (aleukemic) leukemia or myelosclerosis or both.". As the dose parameter, absorbed dose in endosteal tissue was used, computed from the injection levels, in micrograms per kilogram, using conversion factors based on body weight and relative distribution factors similar to those of Marshall et al.40 but altered to take into account the dependence of stopping power on energy. . The decay products of radium, except radon, are atoms of solid materials. It does, however, deposit in soft tissue and there is a potential for radiation effects in these tissues. However, 80% of the bone tumors in the this series, for which histologic type is known, are osteosarcomas, while fibrosarcomas and reticulum cell sarcomas each represent only about 2% of the total, and multiple myeloma was not observed at all. This study was aimed at the role, if any, of trihalomethanes resulting from the disinfection of water by chlorination. The identities of these cells are uncertain, and their movements and life cycles are only partly understood. In discussing these cases, Wick and Gssner93 noted that three cases of bone cancer were within the range expected for naturally occurring tumors and also within the range expected from a linear extrapolation downward to lower doses from the Spiess et al.88 series. Leukemia has not often been seen in the studies of persons who have acquired internally deposited radium. Sarcomas of the bones and joints comprise only 0.24% of microscopically confirmed malignancies reported by the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) program.52 The chance of contracting bone sarcoma during a lifetime is less than 0.1%. The cause of paranasal sinus and mastoid air cell carcinomas has been the subject of comment since the first published report,43 when it was postulated that they arise ''. i Following entry into the circulatory system from the gut or lungs, radium is quickly distributed to body tissues, and a rapid decrease in its content in blood occurs. The analysis of Marshall and Groer38 is noteworthy, not only because it provides a good fit to the data but also because it links dose and events at the cellular level to epidemiological data, an essential step if the results of experimental research at the cellular level are to play a serious role in the estimation of tumor risk at low doses. Radiation Safety Flashcards | Quizlet All towns, 1,000 to 10,000 population, with surface water supplies. 67,68 based on dose, equations that give an acceptable fit are: where the risk coefficient I equals the number of bone sarcomas per person-year at risk that begin to appear after a 5 yr latent period, and D Therefore, no judgment can be made as to whether such a layer would develop in response to a single injection of 224Ra or whether the layer could develop fast enough to modify the endosteal cell dosimetry for multiple 224Ra fractions delivered over an extended period of time. For 226Ra and 228Ra the constant tumor rates given by Rowland et al.68 as functions of systemic intake are computed for the intake of interest, and the results are worked out with a table such as Table 4-7. In contrast, mean skeletal dose changes with time, causing a gradual shift of cases between dose bands and confusing the intercomparison of data analyses carried out over a period of years. In the context of radioactive poisoning by Radium and Strontium, it is known that they accumulate in the human skeleton and thus have a cumulative effect over time. The British patients that Loutit described34 also may have experienced high radiation exposures; two were radiation chemists whose radium levels were reported to fall in the range of 0.3 to 0.5 Ci, both of whom probably had many years of occupational exposure to external radiation. The functional form in the analysis of Rowland et al. A total of almost 908,000 residents constituted the exposed population; the mean level of radium in their water was 4.7 pCi/liter. Thus, the absence of information on the tumor probability as a function of person-years at risk is not a major limitation on risk estimation, although a long-term objective for all internal-emitter analyses should be to reanalyze the data in terms of a consistent set of response variables and with the same dosimetry algorithm for both 224Ra and for 226Ra and 228Ra. When the size of the study group was reduced by changing the criterion for acceptance into the group from year of first entry into the industry to year of first measurement of body radioactivity while living, the observed number of bone tumors dropped from 42 to 13, because radioactivity in many persons was first measured after death. In general, the data from humans suffice to establish radium retention in the bone volume compartment. Also, they were continuously subjected to alpha radiation from another source: the radon in expired breath. Proper handling procedures are necessary to avoid radiation risks. U.S. white male mortality rates for 1982 from Statistical Abstract of the United States, 106th ed., U.S. Department of Commerce, Washington, D.C., 1986. Recall that the preceding discussion of tumor appearance time and rate of tumor appearance indicated that tumor rate increases with time for some intake bands, verifying a suggestion by Rowland et al.67 made in their analysis of the carcinoma data. For five subjects on whom he had autoradiographic data for the 226Ra specific activity in bone adjacent to the mastoid air cells, the dose rate at death from 222Rn and its daughters in the airspaces exceeded the dose rate from 226Ra and its daughters in bone. The typical adult maxillary cavity has a volume of about 13 cm3; one frontal sinus has a volume of about 4.0 cm3, and one sphenoid sinus has a volume of about 3.5 cm3. The primary sources of information on the health effects and dosimetry of radium isotopes come from extensive studies of 224Ra, 226Ra, and 228Ra in humans and experimental animals. However, calcium is ubiquitous in the human body, so small amounts of radium may accumulate in other tissues, causing toxicity. Mucosal dimensions for the mastoid air cells have been less well studied. Being an -emitting radionuclide, the radium irradiates bone surface-lining cells and has resulted in an excess incidence of osteogenic sarcomas. Environmental Research Division. Retention in tissues decreases with time following attainment of maximal uptake not long after intake to blood. In this way, some problems of selection bias could be avoided, because most radium-dial workers were identified by search, and coverage of the radium-dial worker groups was considered to be high. While five cases of leukemia were observed among 681 adults who received an average skeletal dose of 206 rad, none were observed among 218 1 to 20-yr-olds at an average skeletal dose of 1,062 rad. Groer and Marshall20 estimated the minimum time for osteosarcoma appearance in persons exposed to high doses of 226Ra and 228Ra. This keeps it from accumulating inside your home. Investigation of other dosimetric approaches is warranted. mobile roadworthy certificate sunshine coast. as result of the local effects of the radon . In contrast, 226Ra delivers most of its dose while residing in bone volume, from which dose delivery is much less efficient. Only the beta and gamma rays, which were of low intensity compared to the alpha rays, emitted by these radioactive materials in the adjacent bone could have reached these cells. Radon is gaseous at room temperature and is not chemically reactive to any important degree. 1982. Stebbings et al.89 published results of a mortality study of the U.S. female radium-dial workers using a much larger data base. If the survival adjacent to the diffuse component were 37%, as might occur for endosteal doses of 50 to 150 rad, the hot-spot survival would be 0.09%. Restated in more modern terms, the residual range from bone volume seekers (226Ra and 228Ra) is too small for alpha particles to reach the mucosal epithelium, but the range may be great enough for bone surface seekers (228Th), whose alpha particles suffer no significant energy loss in bone mineral;78 long-range beta particles and most gamma rays emitted from adjacent bone can reach the mucosal cells, and free radon may play a role in the tumor-induction process. As stated earlier, average hot-spot concentrations are about an order of magnitude higher than average diffuse concentrations, leading to the conclusion that the doses to bone surface tissues from hot spots over the course of a lifetime would also be about an order of magnitude higher than the doses from diffuse radioactivity. Shortly thereafter, experimental animal studies and the analysis of case reports on human effects focused on the determination of tolerance doses and radiation protection guides for the control of workplace exposure. 1962. The first analysis to take account of competing risks and loss to followup74 was based on a life-table analysis of data collected88 for persons 16 yr of age and older. The first widespread effort to control accidental radium exposure was the abandonment of the technique of using the mouth to tip the paint-laden brushes used for application of luminous material containing 226Ra and sometimes 228Ra to the often small numerals on watch dials. Equally important is ensuring the availability of information on the rate at which tumors have occurred in the populations at risk. However, Petersen55 wrote an interim report for a review board constituted to advise on a proposal for continued funding for this project. The natural tumor rate in these regions of the skull is very low, and this aids the identification of etiological agents. There were 11 bone marrow failures in the exposed group, and only 4 in the control group. Mays et al.47 showed that mean survival time increased with decreasing dose in beagles that had contracted osteosarcoma following radionuclide injection. There is no assurance that women exposed at a greater age or that men would have yielded the same results. To circumvent this problem, two strategies have been developed: (1) classification of the cases according to their epidemiological suitability, on a scale of 1 to 5, with 5 representing the least suitable and therefore the most likely to cause bias and 1 representing the most suitable and therefore the least likely to cause bias; and (2) definition of subgroups of the whole population according to objective criteria presumably unrelated to tumor risk, for example, by year of first exposure and type of exposure. In summary, hot spots may not have played a role in the induction of bone cancer among members of the radium population under study at Argonne National Laboratory because of excessive cell killing in tissues which they irradiate, and the carcinogenic portion of the average endosteal dose may have been about one-half of the total average endosteal dose.
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