A city in northwest China has come under fire for hosting a mass marathon event during a time of extreme air pollution.

Lanzhou, the capital city of Gansu province, celebrated the New Year by mobilizing about 10,000 citizens, including children and the elderly, into an around-the-city marathon on Sunday, Jan. 1. [Xinhua]

Although known for its generally poor air quality, Lanzhou, the capital city of Gansu province, celebrated the New Year by mobilizing about 10,000 citizens, including children and the elderly, into an around-the-city marathon on Sunday.

The day's air quality was rated "poor," with the level of PM10 exceeding 200, triggering online protests over the health risks imposed on the race's participants.

Ma Qizhi, a professor at Northwest University for Nationalities, called the race "a harmful showcase" on Sina Weibo, China's most popular Twitter-like microblog.

In a fiercely-phrased post that was widely forwarded, Ma asked the citizens of Lanzhou to stop being "human dust cleaners" and reprimanded parents who sent their children to participate in the harmful activity.

On his Weibo, Ma also posted pictures showing participants running against the background of a hazy, darkened city and senior runners wearing face masks during the race.

"AN UNHEALTHY PRACTICE"

Health experts echoed Ma's objection, saying that extended outdoor exercise could be unhealthy when the level of air pollution is high.

"Long-distance running can increase the inhalation of pollutants, so doing it in a polluted environment is detrimental to health," said Shi Junnian, a physician at No. 2 Affiliated Hospital of Lanzhou University.

A WHO survey last year showed that Lanzhou ranked the worst among Chinese cities in terms of air pollution. Its annual average of PM10, or particles smaller than 10 micrometers, was 150 micrograms per cubic meter, while the WHO-recommended upper limit stands at 20 micrograms per cubic meter.

Experts said the elevated PM10 level would increase the risk of heart disease, lung cancer, asthma, and respiratory infection.

Meanwhile, Sunday's air pollution was particularly bad. The city was enveloped in a dense, dirty haze, prompting local environmental authorities to advise against outdoor exercise.

The Lanzhou Municipal Bureau of Sports, the race's organizer, said in a written statement to Xinhua that holding the around-the-city race in Lanzhou on the first day of the year has been a 40-year-old tradition and that a temporary change in schedule was impractical.

Furthermore, this year's New Year race was intended as a warm-up event for the 2012 Lanzhou International Marathon that is scheduled for June.

Officials had not anticipated the heated reactions of Internet users this year, who rallied against the combination of the extremely poor air quality and the mass participation of children.

According to the official response, the race participants included 1,332 middle school students and 610 primary school pupils, and the youngest participant was seven years old. But officials refused to comment on how many children had been voluntary participants.

"It is unreasonably dogmatic that they stuck to the schedule regardless of the adverse weather conditions and public opinion. They should have at least kept the children from harm," Ma said.