Abstract
After decades of research on low-Earth orbit, national space agencies and private entrepreneurs are investing in exploration of the Solar system. The main health risk for human space exploration is late toxicity caused by exposure to cosmic rays. On Earth, the exposure of radiation workers is regulated by dose limits and mitigated by shielding and reducing exposure times. For space travel, different international space agencies adopt different limits, recently modified as reviewed in this paper. Shielding and reduced transit time are currently the only practical solutions to maintain acceptable risks in deep space missions.
Highlights
The main uncertainty is related to the relative biological effectiveness (RBE) of space radiation [9], given the lack of epidemiological data
The 1 Sv limit, agreed with the ISS partner in the Medical Operation Board, was chosen in an attempt to harmonize the limits with European Space Agency (ESA), but it corresponds to an excess fatality risk around 7%, i.e., higher than the 3% recommended by NCRP to National Aeronautics and Space Administration (NASA)
500 mGy-Eq for cardiovascular disease (CVD) and 100 mGy for z > 10 for central nervous system (CNS) effects. These limits should be within the 600 mSv limit based on 3% cancer mortality, but the uncertainty of RBE of space radiation is even larger for normal tissue degenerative effects than for carcinogenesis
Summary
Laboratory (NSRL) in the Brookhaven National Laboratory (BNL) [2], while in Europe, European Space Agency (ESA) is supporting experimental studies on space radiation shielding (ROSSINI) [3] and radiobiology (IBER) [4] Considering their unavoidable exposure to space radiation during missions, astronauts are classified as radiation workers. It can be stated that almost everything we know on space radiation effects has been measured in ground experiments with high-energy accelerators [16] This implies that the extrapolation to human risk is complex, because we have to translate in vitro or animal data into human risk. For space radiation risk assessment, there are many sources of uncertainty, eventually leading to very large confidence intervals on risk estimates for different mission scenarios [9] For this very reason, dose limits should consider the acceptable risk and the uncertainty of the estimated risk, HT =
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