"The pollution in China is a threat to my health and it would be difficult for me to run 42 kilometres in my current condition. This decision is not about Haile. It is about all athletes who will be competing. Our safety has to be protected." - Ethiopia's marathon world record holder Haile Gebrselassie
"His ideal picture was . . . for the next four years to try to break his own [ marathon] world record and try to win in London 2012 because Beijing is very risky. I'm not a scientist but how can you train for pollution?"
- Gebrselassie's manager, Jos Hermens
"Knowledge is key, so we're finding out as much as we can on how to counter the problem. We've taken advice from an array of people, from physiologists to people who have worked with the military."
- Gary Lough, Paula Radcliffe's husband and manager
"I had to go back and see a specialist to start other treatments but I'm feeling better now. I was pretty disappointed because I wanted to play the tournament and get used to the conditions."
- Justine Henin the world's top-ranked women's tennis player and the 2004 Olympic gold medallist, after withdrawing from the Beijing Open last September because of asthma
"My lungs stopped working. It started with a routine deep breath on a descent to recover a bit, which produced a sharp pain and a fit of hacking, then progressed rapidly to a state where I was unable to take more than a quarter of a breath."
- American mountain bike rider Adam Craig after a pre-Olympic event in Beijing last September