MONTREAL: The World Anti-Doping Agency (WADA) said the use of carbon monoxide rebreathers to measure blood values should have no impact on athletic performance but it is looking into the effects of frequent and repeated exposure to the gas. Carbon monoxide rebreathing is used to monitor athletes’ haemoglobin levels, which are a predictor of exercise performance but there has been suggestions that repeated inhalation can be used to improve athletic performance. Earlier this week, the International Cycling Union asked teams and riders to avoid repeated carbon monoxide inhalation and called on WADA to take a position on the use of the gas, which is not on its list of banned substances. “Exposure to carbon monoxide (CO) has been discussed by WADAs prohibited list expert advisory group on several occasions,” WADA said. “There is no general consensus on whether CO can have a performance enhancing effect and no sufficiently robust data currently supports that proposition.” When used to measure haemoglobin mass, the amount of CO used is low and should not be performance enhancing, it added. However, it said it was investigating the effects of repeated use of the rebreathing method with respect to, “Artificially enhancing the uptake, transport or delivery of oxygen” in its list of prohibited substances and methods.