IN VIVO MEASUREMENT OF LEAD-210 AS AN INDICATOR OF CUMULATIVE RADON DAUGHTER EXPOSURE IN URANIUM MINERS

The accumulation of lead-210 in the human skeleton can be measured in uranium miners by in vivo techniques at body burdens greater than about 4 nCi using transportable equipment designed to detect the 47 keV gamma-ray from this nuclide. A burden of two nanocuries is shown to be equivalent to a calculated cumulative exposure of about 800 working-level months. The instrumentation utilizes the Laurer system of twin crystal gamma spectroscopy in which an 8 in. × 1 mm cesium iodide crystal is optically coupled to an 8 in. × 2 in. sodium iodide crystal and is operated in anti-coincidence on a single photomultiplier tube utilizing the principle of rise-time discrimination. The method of measuring 210Pb used and the equations used to estimate the cumulative exposure in working-level months are presented, with an evaluation of the uncertainties and the extent to which the estimates can be improved by additional experimental data. The results of field measurements undertaken on the Colorado Plateau showed that, among 37 control subjects with no history of employment in mines, only one individual had counts in excess of two sigma above the mean in the 47 keV region. In contrast, 26 out of 54 mean with uranium mining histories showed counts greater than two sigma above the mean. © 1969 Health Physics Society.