Thousands of runners have took part in the 34th Beijing International Marathon, many wearing face masks amid concerns about pollution.
The organizers warned runners to expect slight or moderate smog, but the U.S. embassy in Beijing said air quality early on the day of the race was "hazardous". One resident in the city told reporters that the air smelt like burnt coal.
Some athletes gave up the race altogether because of the pollution. British runner Chas Pope tweeted that he was only able to do 10km (6 miles) of the race in a pollution mask before he was forced to pull out. He said that race should have been cancelled because the air quality was "not suitable for outdoor activities".
Beijing resident Neil Holt told reporters that although the air quality was better than last year, it was still very polluted. "You can hardly see [the stadium] through the smog. It's really hard to breathe when it is like this," he said.