The World Anti-Doping Agency (WADA) has added xenon gas to its 2014 prohibited list for the substance's potential to enhance performance. In a statement Sunday, WADA said its executive committee approved the modification of its 2014 prohibited list which will be effective following the required three-month notice period. Scientific studies suggest that the gas artificially increases the levels of erythropoietin (EPO) in the blood, which is forbidden under WADA's rules.