Introduction to the U.S. Million Person Study of health effects from low-level exposure to radiation

The epidemiologic study of one million U.S. radiation workers and veterans on health effects following low-level radiation exposure (Boice, Cohen, et al. 2019), or the Million Person Study (MPS 1 ), has been underway in some form for more than a quarter of a century. The MPS was designed to examine health effects after chronic exposure to low dose-rates of radiation, in contrast to the brief exposure at a high dose-rate experienced by the Japanese atomic bomb survivors. The study will provide important scientific evidence needed for sound radiation protection policy and recommendations (NCRP 2018a; Boice, Held, et al. 2019). This special issue consists of 26 articles, including this introduction and an editorial (Wakeford 2021). The aim for this special issue is to present a comprehensive overview of the MPS with regard to: its conceptual development and historical perspectives, methodological approaches for both epidemiology and dosimetry, the first publications of quantitative results to date, as well as a summary of the first international virtual symposium with key stakeholders and researchers on the MPS that also casts a vision for the future.