RSH > Documents > ANS National Meetings/Sessions > June 1999 >Robert G. Thomas

3. A Practical Threshold Dose for Bone Tumors in the Classic Study of Radium Dial Painters

                "Data from the painters of luminous dials, using radium as the radiation source, are presented. The study of these workers has been reported in the literature for decades, and it derives from what has to be a classic epidemiological study. In fact, this study may be superb among all radioepidemiological studies as it matches the individual’s skeletal radiation dose to the biomedical effect, in this case, tumors of the skeleton. Most of the workers, in the early part of this century, were female, and the data to be presented have been limited to this gender. The only data to be presented are from those dial painters in the United States and will not include those from studies in other countries.

                "Radium is a radionuclide that shows in humans a dose below which there should be little need for regulation. This practical threshold dose was first pointed out several decades ago, but the data have changed the initial considerations very little. The original estimates of a practical threshold were in the 10-Gy range, and although modern modeling techniques have been applied to the data, this threshold still holds. Many modelers apply a linear or linear-quadratic formulation to the data to make it fit with the premise that all radiation is injurious to human health. Such has not been borne out, and the analyses strengthen this point. A log-normal fit to the data has been shown to be the best fit.

                "A total of 1391 female dial painters still being followed into 1992 had average skeletal doses below 10 Gy and had shown no evidence of bone tumors at that time. No data have been collected since that time as a result of cessation of funding by the U.S. Department of Energy. This group was well along in life at that time, and it is since then that the most crucial data would have been obtained with regard to the low-level effects of internally deposited radium. The current controversy that compares the linear no-threshold theory against the practical evidence of a threshold has no basis for tumor genesis in the radium study. There is a clear-cut threshold below which there were no observed osteosarcomas or carcinomas of the nasal passages. The modeling done for this presentation will display these data in terms of tumor incidence as a function of radiation dose to the skeleton, using classic dosage functions. Although these data are from studies that were carried out over many decades and although they have been reported many times, the author feels it is important to show that these data from humans who were studied in detail display the practical threshold dose that appears to be prominent with many other radioelements."