Abstract
Objectives: This paper examines how the Linear No-Threshold hypothesis emerged in radiation research and why its adoption did not immediately translate into specific radiological protection guidelines for pregnant women and women of reproductive capacity. It analyses the tension between early scientific warnings about reproductive harm and the continued medical and institutional use of ionizing radiation.
Methods: The study is based on a historical reconstruction of medical and scientific debates on the reproductive risks of ionizing radiation from around 1900 to the 1960s. It draws on animal experiments, clinical practices, wartime and postwar research, and the positions of key institutions and scientists, including Hermann J. Muller, Alice Stewart, the Atomic Bomb Casualty Commission, and the International Commission on Radiological Protection.
Results: Despite early evidence of reproductive harm from animal studies, radiation was widely used in human medicine, including in potentially pregnant women, and even for pregnancy diagnosis. Nazi Germany exploited the sterilizing effects of radiation, and after World War II, the Atomic Bomb Casualty Commission reported increased risks of microcephaly in children born near atomic blast sites. Although Muller and Stewart strongly warned against radiation exposure to reproductive organs and supported a no-threshold interpretation of risk, conflicting analyses of epidemiological data – particularly at low doses – generated uncertainty. These disagreements delayed regulatory consensus within the International Commission on Radiological Protection.
Conclusion: The delay in issuing specific radiological protection recommendations for pregnant women until 1965 cannot be explained by ignorance of risk. Rather, it resulted from unresolved scientific disputes, institutional caution, and the difficulty of translating genetic theory and uncertain epidemiological evidence into binding regulatory standards. This case study thus highlights the intricate entanglement of scientific knowledge, political interests, and institutional authority in the making of regulatory standards.