Tritium and deuterium in atmospheric methane

Ten samples of atmospheric methane collected at Oberhausen, Germany, and Gary, Indiana, between 1960 and 1963 have been analyzed for their tritium and deuterium content. The results show the tritium concentration in the northern hemisphere to have been essentially constant since 1958, the time the first samples were analyzed. Existing theories to explain the origin of tritiated methane are discussed and rejected as highly improbable. The data can best be explained by assuming that leakage of tritiated methane into the atmosphere from sources in nuclear industry located in the northern hemisphere occurred for a period of years prior to 1958, and then the leak was essentially closed.