I remember Adam Craig saying that the air during event he went to last Fall (a kind of goodwill pre-Olympic race either on the same course or in the same area) caused a lot of problems for him and other cyclists. Back in December he guessed his plan would be to fly in the day before the event, race and get out. And if the polution was too bad, just pull from the race. No one wanted to risk long term damage.
He was obviously very worried about the balancing act of health and wanting to race in the Olympics.
Frends know gud humors when dey is hear it. ~ Da Crockydiles of ZZE.