Current status of French research on the biological effects of heavy ions in cosmic radiation as observed in high-altitude balloons.

On casual inspection, cosmic rays may not be considered to pose a biological hazard. Nevertheless, the heavy ion component does produce a significant but very local irradiation. This has been confirmed by the hair whitening in black-haired animals. Experiments with black C 57 mice in balloons at 30,000 m altitude show white-haired tufts along the tracks of heavy ions. Histological and radioautographic studies were carried out; the results are reported. Similar investigations on black rabbits gave similar results and confirm those obtained previously with black mice. In the discussion, we report that tissue damage is amplified. This fact is not yet explained, but suggests reconsideration of the calculation of radiation dosage. The ionization distribution induced by heavy ions is analyzed. We point out that along their tracks the dosage is very important; therefore it is necessary to investigate their biological action, particle by particle, according to their energy and their charge.