Space

A critical gap in understanding the health effects of gradual, low-dose radiation exposure has been addressed through the Million Person Study (MPS), the largest study of its kind. This study, involving over 360,000 U.S. Department of Energy workers and other exposed individuals, provides substantial statistical power to quantify risks associated with prolonged, low-dose radiation exposure. Unlike terrestrial-based organizations that rely on dose limits, NASA employs an individual risk-based system for astronauts, allowing a 3% risk of exposure-induced death (REID) from cancer. The MPS aims to reduce uncertainty in risk estimates, enabling longer space missions by narrowing the 95% confidence interval. Additionally, it offers insights into gender differences in radiation response and evaluates non-cancer outcomes such as neurological disorders and cardiovascular disease.

Boice, J. D. (2017). Space. Health Physics, 112(4), 392–397. https://doi.org/10.1097/hp.0000000000000656