Since the early 1990s, information on radiation-exposed populations other than those exposed from the Chernobyl accident in 1986 has become increasingly available for international scientific research. It is essential to understand how the cohorts of exposed populations have been defined and what mechanisms can be used to study their health outcomes. Different international scientific research collaborations currently investigate four population groups chronically exposed to ionizing radiation during the late 1940s and early 1950s in the Russian Federation and in Kazakhstan. In this framework, collaborations have been established to develop cause-of-death registers in each of these four areas for future mortality follow-up purposes with the aim of studying the health effects of ionizing radiation. The emphasis of this effort is on assessing the information sources available, the mechanisms of data collection and coding, and the data quality and completeness of the information collected. One of the major challenges is the harmonization of all these aspects between the four different centers to the extent possible, taking into account that much of the actual data has been collected over many decades.

We briefly outline existing information about several cohorts in the Southern Urals, Semipalatinsk and the Altai regions, in addition to those discussed in the companion papers in this issue of Radiation and Environmental Biophysics. These include: (a) the East-Urals Radiation Trace (EURT) cohort of individuals (exposed to fallout from the September 1957 explosion of a storage tank containing liquid radioactive waste from the Mayak Production Association) as well as their offspring, (b) the cohort of exposed parents (i.e. workers of the Mayak facility) and their children, having been established with the aim of examining reproductive health, and (c) several additional cohorts in the Altai region and in Semipalatinsk, where investment of additional resources would greatly facilitate the progress of ongoing studies. Furthermore, we include a brief description of the Russian Human Radiobiology Tissue Repository, which has been established in the city of Ozyorsk and is in the process of making an inventory of autopsied tissues from 700 deceased Mayak workers and of collecting and storing donations of blood and tumor tissues from the members of the Mayak workers cohort currently residing in the city.