Our aim was to compare the dose-response relationship for the embryotoxic effects of 0.43 MeV neutrons with those of 240 kVp X rays after in utero exposures during early organogenesis in the rat. At 9.5 days after conception, pregnant rats were exposed to 0.025 to 0.35 Gy 0.43 MeV neutrons at a dose rate of 0.04 to 0.07 Gy/h. Comparable biological effects were produced using 0.50 to 2.05 Gy 240 kVp X rays. Neutron irradiation produced a greater proportion of offspring with very low body weight than with malformations when compared to X rays. There were no embryotoxic effects observed at neutron exposures of 0.025, 0.049, 0.079, 0.10, 0.15 and 0.20 Gy or X-ray exposures of 0.50 and 0.96 Gy. Taken together, the results suggest that the mechanisms by which neutron irradiation affects embryonic development may, in part, be both quantitatively and qualitatively different from those by which X irradiation affects development. These results support the generalization that the embryo exhibits a nonlinear response to increasing doses of ionizing radiations during the period of early organogenesis.
This study was set up to provide quantitative data to evaluate unsubstantiated claims that improper dermatologic radiation techniques may cause breast cancer. A thin mylar window ionization rate meter placed at the location of the right breast of an Alderson-RANDO anthropomorphic phantom was used to measure direct and scatter radiation reaching the female breast during radiotherapy of the facial region (as given for acne). The results indicate that scatter doses are very small; they are influenced by radiation quality and the use or nonuse of a treatment cone. Quantitative risk estimates show that the very small risk of breast cancer induction can be reduced even further by the use of proper radiation protection measures.
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