Editing Natural experiment (section)

===Nuclear weapons testing===

[[Nuclear weapons testing]] released large quantities of radioactive [[isotope]]s into the atmosphere, some of which could be incorporated into biological tissues. The release stopped after the [[Partial Nuclear Test Ban Treaty]] in 1963, which prohibited atmospheric nuclear tests. This resembled a large-scale [[pulse-chase experiment]], but could not have been performed as a regular experiment in humans due to scientific ethics. Several types of observations were made possible (in people born before 1963), such as determination of the rate of replacement for cells in different human tissues.{{cn|date=April 2025}}