World women's marathon record holder Paula Radcliffe has said she is more concerned about heat and humidity at the Beijing Olympics than the Chinese capital's pollution despite suffering from asthma.

Ethiopian men's world record holder Haile Gebrselassie, who also has asthma, withdrew from the Beijing marathon last month because of concerns about the polluted air.

"I need the right dosages of my asthma medication but after that I don't think it's something you can worry about too much," Radcliffe told the BBC.

"It might not even be as bad as everyone thinks because I'm sure the Chinese will do everything they can to reduce the problem.

"We are all dealing with the same thing so I don't think worrying about it in advance is that productive.

"But heat and humidity are a different kettle of fish because they're things you can prepare for."

The 34-year-old Briton pulled out of the 2004 Athens Olympics marathon after 36 km because of a stomach complaint after starting the race as the favourite.

She was due to run in Sunday's London marathon on the course where she set her world record of 2:15.25 but has withdrawn because of a toe injury.