Lunar surface radiation environment simulation and health risk assessment for Chinese astronauts during lunar surface activities

0 Abstract: Objective To evaluate radiation exposure and lifetime cancer risk for Chinese astronauts during lunar surface activities, based on an integrated framework developed to combine lunar surface radiation transport, organ dosimetry, and population-specific health risk assessment. Methods A lunar surface radiation transport model was developed in Geant4 using the ICRP 145 adult male mesh-type reference computational phantom, shielded with 1 g/cm 2 aluminum and positioned on lunar soil based on the Chang’e-5 regolith composition. Under a Galactic Cosmic Ray (GCR) environment, organ absorbed dose, dose equivalent, and whole-body effective dose were calculated. For risk assessment, a population-adjusted cancer risk assessment framework was developed based on the NASA Space Cancer Risk model (NSCR-2012). By incorporating Chinese life-table data and background cancer incidence and mortality statistics, the model was used to estimate the Risk of Exposure-Induced Cancer (REIC) and the Risk of Exposure-Induced Death (REID) for a 30-day lunar surface mission. Results Under 1 g/cm 2 aluminum shielding, absorbed dose rates to major organs ranged from 0.174 to 0.196 mGy/d, organ dose equivalent rates ranged from 0.36 to 0.65 mSv/d, and the effective dose rate was 0.50 mSv/d, with protons contributing approximately 39%. Risk assessment based on Chinese population background data showed that both lifetime REIC and REID from a 30-day lunar surface mission decreased monotonically with increasing age at exposure. Specifically, REIC decreased from 0.1621% at 20 years to 0.0422% at 65 years, while REID decreased from 0.1060% to 0.0386%. In terms of site-specific risk composition, lung cancer was the leading contributor to mortality risk, whereas stomach, esophageal, and liver cancers, together with other cancers, also made substantial contributions to the total risk profile. Conclusion The integrated framework developed in this study provides a modeled, population-specific estimate of radiation-induced cancer risk for a Chinese adult male reference astronaut under a defined 30-day GCR-dominated lunar-surface scenario. These results may serve as a methodological reference for future comparative assessments of shielding, mission duration, and radiation-risk management.