From inhabitat: Already a large number of athletes are severely concerned about how competing in the Olympics will harm their health and chances at winning. The Australian track and field team, and the Canadian athletics team are skipping the opening ceremony due to concerns about pollution. [Link]
Hopefully the air in the Watercube is filtered. If smog screws up these Olympic Games then the IOC royally screwed up by choosing a country devoid of air clean enough to compete in. The blame should be placed on the IOC rather than China.