Polycythemia vera among participants of a nuclear weapons test

Two cases of polycythemia vera and two cases of suspected polycythemia vera were found among 3,217 nuclear test participants present during the detonation of the nuclear device, "Smoky," on Aug 31, 1957, and traced through December 1981. The observed occurrence of four cases of polycythemia vera in a group this size significantly exceeds that expected. However, the small individual whole-body doses of radiation reported for these four participants makes the association with ionizing radiation tenuous, although this was the only known unusual risk factor.