The National Academy of Sciences Biological Effects of Atomic Radiation(BEAR) Genetics Panel recommended no second-generation genetic damage study of the offspring of the atomic bombings in Japan

Scientific Basis: The recommendation was primarily based on a 1962 memorandum by James V. Neel and William Schull, which argued that because the first-generation (F1) study of 75,000 children showed no significant genetic damage, a study of the F2 generation was highly unlikely to yield statistically significant results.
Logistical Challenges: Neel noted that demonstrating genetic effects in the F2 would be hindered by administrative problems, specifically the expected dispersal of survivors’ children throughout Japan, making them difficult to track.
Quantitative Assessment: Neel and Schull’s analysis estimated a potential F2 sample size of approximately 27,000 individuals, but they concluded that any induced genetic effect would naturally be weaker in the second generation than in the first.
The “Noise” Factor: Researchers highlighted that detecting radiation-induced mutations in humans is exceptionally difficult due to high levels of genetic “noise”—preexisting and spontaneous mutations in the human population that obscure the signal of radiation damage.
Consensus Among Experts: The decision was supported by a subcommittee of elite geneticists (Neel, Stern, and Sturtevant) and was not challenged by other members of the BEAR I Genetics Panel, including Nobel Laureates like Hermann J. Muller and Joshua Lederberg.