World Anti-Doping Agency says micro-doses could escape detection

MONTREAL -- The World Anti-Doping Agency has acknowledged that a French documentary "did raise questions" about the ability of athletes to take micro-doses of banned substances and escape detection under biological passport rules.

A week ago, WADA criticized the documentary on French TV network France 2. WADA director general David Howman said at the time the study "does not accurately follow the Athletes Biological Passport guidelines."

WADA backed off Tuesday and said the documentary indicated that athletes could take "minimal amounts of performance enhancing substances without testing positive."

In a statement, WADA says, "We are very alert to 'micro-dosing'; it is an issue that we are exploring in great detail with experts from across the anti-doping community."

In the documentary, eight athletes were given micro-doses of EPO, human growth hormones and blood transfusions.