Recent radiobiological findings from spaceflight and ground-based studies--an overview.

With respect to radiation standards for manned space flight, we wish to address ourselves to the following topics that we consider pertinent for a realistic assessment of the risk to man when exposed to ionizing radiation under space flight conditions: 1) prediction and measurement of the spectra of the physical traits of cosmic radiation as a function of orbital parameters and the mass shielding of the spacecraft; 2) synergistic or antagonistic modification of radiation effects by dynamic flight conditions and by the space environment; 3) production of biological damage becoming manifest only long after exposure, especially to the heavy ions; and 4) demonstration of possibly specific radiobiological mechanisms for the densely ionizing heavy-ion component of the cosmic radiation. Some recent work referring to these topics will be presented and discussed with emphasis on the high LET component of the cosmic radiation.