History and program of biophysical examinations in an epidemiological cohort of Mayak PA workers

One of the internationally recognized cohorts included in the studies of ionizing radiation-induced pathology risks is a cohort of Mayak PA workers who had contact with ionizing radiation sources in the early years of the enterprise operation. Individual biophysical examinations of the cohort registrants serve as a source of data to estimate internal exposure doses accumulated due to the chronic inhalation intake of 239Pu in a production environment. This paper discusses the methods of individual control of 239Pu content in excreta samples and monitoring programs performed at different stages of the development of the Mayak PA personnel dosimetry register. The programs aimed at both the increase of the monitoring period for previously examined individuals and the examination of those cohort representatives who had no previous individual control data. The work represents the quantitative results of individual control and their dynamics over time. Analysis of the individual monitoring results of the main production cohort registrants shows a downward trend in detecting the 239Pu activity in daily urine amount above the measurement method detection limit in workers employed in the later years of operation of the plants under consideration. Expanding the amount of dosimetry data on the individuals included in the epidemiological cohort of radiation risk study remains an urgent task for providing the most cohort representatives with the dosimetry results, increasing the monitoring period and reducing the dose estimate uncertainties, as well as providing data for verification and the development of actinide biokinetic models.