Anyone wondering how convinced athletes are by Beijing's efforts to clear its smoggy air for the Olympics need only check their travelling luggage.

Despite years of official reassurance, many of the top teams will be packing breathing accessories or timing their arrival for the last possible moment. Haile Gebrselassie, the asthmatic holder of the men's marathon world record, has withdrawn from the event in Beijing though he still plans to compete in the 10,000m.