Measurements of the whole-body content of 241Am and its distribution in the body were made at 8, 10 and 12yr following inhalation of the insoluble dioxide by a worker in 1%5. Chelation therapy was administered at another center from 1%7 to 1974 and excretion of over one-half the initial body burden of 2.1 pCi (77.7 kBq) was obtained. Since the cessation of therapy, a very slow decrease in body content was observed indicating a retention half-time of more than I 0 0 yr.Longitudinal profile scans showed that the distribution of activity in the body remained essentially the same from 1973 to 1977. About one-fourth of the total body burden was in the chest region, and transverse profile scans of the chest showed that the majority of activity in that region was in the lungs; a slight decrease in the lung content was observed. The distribution of activity in the skeleton was extremely well correlated with the distribution of available bone surface area.An increase in the ratio of counts obtained from the liver region to those from the left side of the abdomen since the chelation therapy was halted indicated that there was redistribution of activity still taking place. The amount of activity translocated to the liver may justify the resumption of chelation therapy in the future.
From the results of serial measurements of body 226Ra activity in 13 former luminous dial workers 30-60 y after relatively brief periods of intake of luminous compounds in adolescence or young adulthood, we determined the postmenopausal rate of elimination of Ra in percent of contemporary body Ra content per year. This rate was negatively correlated with the "reduced x-ray score," a measure of radiation osteonecrosis observed radiographically in the 13 subjects (r = -0.85, P less than 0.001). The clearance rates of subjects retaining low Ra activity were greater than predicted by retention models. We conclude that for those members of the Ra-exposed population under study for health effects at our institution who sustained the lesser degrees of macroscopic skeletal damage, present estimates of skeletal absorbed dose are systematically low, by at most a factor of 2.
We made radiochemical determinations of 226Ra and the 228Ra-decay product, 228Th, in samples of bone from former Ra dial workers who belonged to a major cohort of Ra-exposed persons under study for health effects at our institution. Most of the former workers were long-term residents of two communities supplied with drinking water containing elevated natural levels of 228Ra and 226Ra, so determinations also were made of radioactivity in samples of bone from long-term residents not occupationally exposed to Ra. The 228Th activity of the bones of the former workers, after correction for the presence of natural radioactivity, showed that some had significant occupational intakes of 228Ra, contrary to published reports that 228Ra was never used by the Illinois company that had employed the cohort of early workers. For 14 workers hired in the years 1920-23, the calculated ratio of the occupational intake of 228Ra to 226Ra activity averaged 0.15 (coefficient of variation 0.65), whereas for three workers hired in 1924, it was not significantly different from zero (mean 0.05, coefficient of variation 1.5). The risk of radiogenic cancer for the typical worker hired before 1924 may have been nearly twice that incurred in the absence of the 228Ra component of the Ra intakes.
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