BIODOSIMETRY RESULTS FROM SPACE-FLIGHT MIR-18

Astronauts are classified as radiation workers due to the presence of ionizing radiation in space. For the assessment of health risks, physi cal dosimetry has been indispensable. However, the change of the locat ion of dosimeters on the crew members, the variation in dose rate with location inside the spacecraft and the unknown biological effects of microgravity can introduce significant uncertainties in estimating exp osure. To circumvent such uncertainty, a study on the cytogenetic effe cts of space radiation in human lymphocytes was proposed and conducted for Mir-18, a 115-day mission. This study used fluorescence in situ h ybridization (FISH) with whole-chromosome painting probes to score chr omosomal exchanges and the Giemsa staining method to determine the fre quency of dicentrics. The growth kinetics of cells and sister chromati d exchanges (SCEs) were examined to ensure that chromosomal aberration s were scored in the first mitosis and were induced primarily by space radiation. Our results showed that the frequency of chromosomal aberr ations increased significantly in postflight samples compared to sampl es drawn prior to flight, and that the frequency of SCEs was similar f or both pre- and postflight samples. Based on a dose-response curve fo r preflight samples exposed to gamma rays, the absorbed dose received by crew members during the mission was estimated to be about 14.75 cSv . Because the absorbed dose measured by physical dosimeters is 5.2 cGy for the entire mission, the RBE is about 2.8. (C) 1997 by Radiation R esearch Society.