- Sunday's Beijing Marathon hit by poor air quality in Chinese capital
- "Hazardous" smog made for testing conditions
- Many runners donned face and gas masks
- Ethiopian runners win men's and women's elite races
If running a 42 kilometer foot race was not tough enough, Sunday's Beijing International Marathon saw thousands of competitors brave a "hazardous" smog which engulfed the Chinese capital.
Many runners wore face or gas marks to attempt to protect themselves from the effects of the poor air quality but there were several withdrawals before and during the race as runners feared for their health.
It did not stop Ethiopia's Girmay Birhanu Gebru from winning the 34th edition of the race in two hours 10 minutes and 42 seconds, with his compatriot Fatuma Sado Dergo taking the women's title.
But many leading runners did stay away -- perhaps taking their cue from Gebru's compatriot, the great Haile Gebrselassie, who opted out of running the marathon in the 2008 Olympics in Beijing because he was asthmatic and feared the effects of smog.
This is caused by tiny particles known as PM2.5, which can embed themselves deep in the lungs, and had reached more than 400 micrograms per cubic meter as the runners lined up for the start in Tiananmen Square.
The recommended daily average maximum level of exposure as prescribed by the World Health Organization is just 25 micrograms.
The United States embassy in Beijing, which monitors air quality daily, described the conditions on its official website as "hazardous" -- with the advice to "avoid prolonged or heavy exertion."
The conditions proved too much for British runner Chas Pope, 39, who pulled out after 10km.
"When I looked at the state of the mask after 10 km I decided enough was enough," he tweeted.
"It felt pretty ridiculous given we're meant to be running for health and fitness."
Organizers reportedly decided against abandoning the race because of the large number of overseas entrants who had traveled to Beijing for the annual race.
But they made available 140,000 sponges so runners could get some relief on the course by hoping to wipe away the particles of smog at regular intervals.
At the finish near the Olympic Park many runners complained about the conditions, but there were no immediate reports of any serious health problems among competitors.
China, like many rapidly emerging economies, has suffered from poor air quality and pollution, particularly in its major cities.
Experts say it is caused, in the main, by the use of coal in electricity and power generation and emissions from the growing number of motor vehicles.
For the Beijing Games in 2008, the government imposed draconian restrictions on car use in the Chinese capital and factories were ordered to reduce their production.