Nuclear radiation can affect number of girls born

National Geographic : According to a new study, nuclear radiation from bomb tests and power plant accidents causes slightly more boys than girls to be born, writes Ker Than for National Geographic. Normally, male births outnumber female births by a ratio of 105 to 100, said one of the study’s coauthors, Hagen Scherb of the Institute of Biomathematics and Biometry at Helmholtz Zentrum München in Germany. The statistical bumps observed in the study are in addition to that slight natural imbalance. The study also found that while effects of nuclear incidents on the ground tend to be regional, atmospheric blasts can have a global effect. Analyzing population data from 1975 to 2007 for Europe and the US, Scherb and colleagues found two spikes in the number of male births relative to female births, which they attribute to atmospheric atomic bomb tests and the 1986 Chernobyl disaster. Despite the fact that in both instances the increase in the ratio of male-to-female births was meager—less than 1%—even such a small increase in the percentage of male births has led, over decades, to several million fewer girls being born worldwide than would otherwise have been expected. Although the biological mechanism behind the skewed sex ratio wasn’t investigated in the study, previous radiation experiments on animals suggest the boost in males may be due to damage to X chromosomes in sperm, Scherb said.