Former world 200m champion Ato Boldon says he has sympathy with athletes who fail drug tests by taking supplements. But former 100m Olympic and world champion Donovan Bailey insists there can be no excuses for athletes taking banned substances.Following sprinters Tyson Gay and Asafa Powell testing positive for banned drugs , Boldon said: “An athlete does not have a degree in pharmacology.” But Bailey said: “Athletes must know what is on the ‘banned’ list.” And he added it could be time to consider life bans for those caught taking banned substances.The Canadian, who will be a BBC Radio 5 live summariser for the Anniversary Games and World Championships, said: “Ultimately it could be the new false start rule—it doesn’t matter who you are, if you false start out of the blocks, you’re out.” It is not known which substance Gay, the fastest man in the world this year having run 9.75 seconds, has tested positive for—that should be confirmed after the result of analysis of his B sample.Powell, who has clocked 9.88 this year, was tested at the national trials in June and returned an adverse finding for oxilofrine (methylsynephrine), a stimulant that boosts fat-burning. Boldon said it was important to make a distinction between blood-doping and “people trying to push the envelope with their supplements”. He added:“An athlete is trusting of the person he is buying the supplements from, or the coach, or whoever is providing these supplements. “When you listen to Tyson, he is saying he put his faith in someone and they let him down. That says to me, OK somebody told me you can take this and it will be fine, there will be nothing to cause you to have a positive test—and obviously that was not the case.” Bailey, who won Olympic and world 100m gold medals, and has held the 100m world record, has a zero-tolerance policy on drug-taking. The 45-year-old said: “Every single athlete is given a banned list and they should look carefully down it. “When money is involved you are going to have cheats, people who push the envelope.We are in a sport where one thousandth of a second can be the difference between success and failure. “Athletes who take drugs tend to be insecure. They don’t believe they have the physical and/or mental capacity to do great things so they take another route—the pharmaceutical route, if you like.” On Gay claiming he was let down by someone he trusted, Bailey added: “You don’t go to an athletics meeting to watch the trainer, coach or masseur run a race.The onus is 100 per cent on the athlete to take responsibility for any substances going into their body.” Boldon suggested stimulants and supplements are here to stay and said it was naive to think they could be banned. He added: “I think the problem is in trying to push the envelope and get to the edge, several of the top names in the sport are falling over the edge.”