Biodosimetry results from space flight Mir-18

Area of Science:

• Space biology and radiation research.
• Cytogenetics and molecular biology.
• Astronaut health and radiation safety.

Background:

• Astronauts are exposed to space radiation, classified as radiation workers.
• Physical dosimetry for assessing space radiation exposure has limitations due to dosimeter placement and dose rate variations.
• Microgravity's biological effects introduce uncertainties in radiation exposure estimation.

Purpose of the Study:

• To investigate the cytogenetic effects of space radiation on human lymphocytes.
• To estimate the absorbed radiation dose received by astronauts during the Mir-18 mission.
• To compare biological dose estimates with physical dosimetry measurements.

Main Methods:

• Human lymphocytes were analyzed for chromosomal aberrations using fluorescence in situ hybridization (FISH) and Giemsa staining.
• Whole-chromosome painting probes were used to score chromosomal exchanges.
• Cell growth kinetics and sister chromatid exchanges (SCEs) were monitored to validate aberration scoring.

Main Results:

• A significant increase in chromosomal aberrations was observed in postflight lymphocyte samples compared to preflight samples.
• The frequency of sister chromatid exchanges (SCEs) remained similar between pre- and postflight samples.
• Biological dose estimation based on gamma-ray dose-response curves yielded approximately 14.75 cSv.

Conclusions:

• Space radiation exposure during the Mir-18 mission led to a measurable increase in chromosomal damage in astronauts.
• The estimated biological dose (14.75 cSv) significantly exceeded the physical dosimeter measurement (5.2 cGy).
• The relative biological effectiveness (RBE) of space radiation was estimated to be approximately 2.8, highlighting potential underestimation of biological risk by physical dosimeters.