Exposure of human tissues to stratosphere radiation behind different shielding from a campaign of three balloon flights

Abstract While some physico-chemical features of the stratosphere are similar to those existing at the equatorial surface of Mars, few balloon campaigns have dealt with the biological effect of stratosphere radiation on human cells. Here, we present data from a campaign of 3 stratospheric balloon flights launched from Timmins (Canada) and Kiruna (Sweden) bases during which quiescent human cutaneous fibroblasts, epithelial lens, osteoblasts and heart myocytes and fibroblasts were exposed frozen to stratosphere in multi-alveolar containers containing boxes made of different shielding materials. In parallel, Monte-Carlo simulations were performed to better identify the potential secondary particles that can impact cells. Active and passive dosimetry was ensured all along the flights. Once returned in the laboratory, cells were thawed and a 30 min–24 h repair time was applied to them. Recognition and repair of the DNA double-strand breaks (DSB) were investigated by immunofluorescence. Despite a relatively low dose, flights revealed that stratosphere radiation can produce severe DSB: their severity increases with repair time according to the nature of shielding and the exposed tissues until the formation of unrepairable highly damaged cells. Lens and bones cells appeared to be the most radiosensitive tissues.