Olympic host city Beijing was shrouded in haze yesterday 11 days before the Games begin, raising anxieties about whether it can deliver the clean skies promised for the world's top athletes.
The city's chronic pollution, a sometimes acrid mix of construction dust, vehicle exhaust and factory and power plant fumes, has been one of the biggest worries for Games organisers.
Beijing has ordered many of its 3.3 million cars off roads and halted much construction and factory production in an effort to cut pollution before the Games open on August 8.
But a sultry haze persisted yesterday, and state media said Beijing might be forced to restrict more cars and shut more factories if the pollution persists.
City officials had earlier said the haze was due to humid weather, not pollution. But state media suggested Games organisers were also worried and considering more pollution cuts.
"More vehicles could go off the roads and all construction sites and some more factories in Beijing and its neighbouring areas could be closed temporarily if the capital's air quality deteriorates during the Olympic Games," the China Daily said.
Xinhua said air quality in Beijing yesterday was Grade II, making it officially a "blue sky day" despite the grey haze, with the main pollutant being particulate matter.
Many athletes have delayed arriving in Beijing until the last minute to avoid bad air and the International Olympic Committee said it may reschedule endurance events to prevent health risks to athletes if pollution is bad.
Marathon world record holder Haile Gebrselassie has already pulled out of the marathon over fears of damaging his health.
Yesterday, the Australian Olympic Committee said its athletes would be allowed to withdraw if pollution poses a threat.
"For us the athlete's attitude to the event is paramount," AOC vice-president Peter Montgomery told reporters.
For four days up to yesterday, Beijing had not experienced a "blue sky day", when the pollution index meets the national standard for "good air quality." Hong Kong, host of the equestrian events, was also badly polluted yesterday after a week of clear, blustery weather.
Unusual weather
Zhu Tong, a Peking University professor advising Games organisers on air quality, said an unusually long bout of still, humid weather was trapping in pollution.
"Although the restriction measures have reduced pollution emissions, if weather conditions are not favourable to dispersal, the build-up effect will be extremely considerable," Zhu said.
Cars in Beijing are now banned on alternate days depending on their licence plate number - odd or even - and many government cars have been ordered off the roads.
Taxis, buses and Olympic vehicles are exempt. Around Beijing, heavily polluting factories, such as steel plants, also have been closed.
The city has invested billions of dollars in public transport too, especially on upgrading and expanding the subway network, hoping to encourage people not to use their cars.
A spur line up to the main Olympic Green opened yesterday, Xinhua news agency said, which will feature airport-like security checks.
A city environment official said last week that air was improving, with a 20 percent cut in carbon monoxide, nitrogen dioxide and particulate matter since the same time last year.
But Greenpeace gave Beijing a mixed assessment. It noted energy-saving technology in Olympic venues, stricter vehicle emissions standards and expanded public transport.