Runners at this year's annual Beijing Marathon donned face masks due to thick smog, China Daily reported.
The athletic event, one of China's biggest, pushed through on Sunday from Tian'anmen Square to the Chinese National Stadium despite "hazardous" levels of air pollution, with smog also affecting the visibility of the surroundings.
More than 30,000 participants qualified for the marathon via lottery, but as thick smog enveloped the capital, many backed out for fear of health risks.
"A marathon represents a healthy way of living, not the opposite," said Chen Xiaohui, chief executive officer of Cheers Publishing. Chen was supposed to participate in his eighth Beijing marathon since September last year.
Some of those who decided to push through with their run cited the experience of joining as worthwhile despite the health risks posed by the smog.
"I also had concerns about air pollution before it started. But I had prepared for this for a long time and it would be a shame if I quit," said Jin Bo, a manager with Lenovo. It was his first time to join the even with friends, along with the company's CEO.
"After I started, it turned out to be not that horrible. For some time it was difficult to see what lay ahead, but that's OK," Jin said.
"This was an amazing experience, like a festival for runners. I mean, running on the roads which should be packed with cars and people if not for this marathon, it was great," the 33-year old manager said.
Li Ming, a correspondent in New York, said she understood why people backed out.
"I think what they did can also help society and the government pay more attention to air pollution in Beijing," Li said.
Wang Dawei, the event's secretary-general, said that the organizing committee did not foresee the smog a few days prior.
"We surely don't want this to happen. It has always been our goal to organize a great event for our participants," Wang said.
The organizing committee of the Beijing Marathon is considering holding the event in the future on a date that is not prone to thick smog.