While the 2012 London Olympics was touted as being drug free, the WADA report revealed how Russian authorities had hid positive doping tests to allow cheating athletes to compete.
"Some of those would have competed in London when suspicions of doping were known to the Russian authorities and to other authorities and yet were not exposed," Howman said.
"Consequently there's been eight athletes referred for sanction processes, we're awaiting the outcomes of those eight.
"Some of those were medalists at the London Olympic Games."
Despite that admission, Howman defended the effectiveness of anti-doping measures and practices at the London Olympics and stressed the cheating and cover-ups between Russian athletes and officials had occurred prior to the event.
"You really have to fail an IQ test to go and commit a doping offence in an Olympic Games," he said.
"When you're looking at all the testing that's done outside of those big events, that's when the problems can arise and that seems to have occurred in Russia in a big way.
"And not only has the problem arisen, people have paid a lot of money to cover up some of the problems and that's the concern to us."
Discovering and revealing the full extent of doping within Russian athletics was not possible prior to the London Olympics, as WADA only gained the right to begin their investigation earlier this year.
"We didn't have the authority to conduct investigations prior to London, we only got that authority on the first of January this year," Howman explained.
"So this is the first enquiry or investigation that we've conducted under our new rules giving us the authority to do these things.
"In the past we've had to rely on those in the international federations and at national levels to do that sort of work. Now we have our own independent method of doing it."
