Running the Beijing marathon in a smog mask
The Chinese capital has been suffering under heavy smog for the past few weeks, but the 34th edition of the Beijing marathon still went ahead on Sunday.
Many of those taking part wore masks to try to protect themselves from pollution, but some pulled out of the race early because of the conditions.
Chas Pope planned to run the half marathon distance but decided to stop after 10km, near the half way point in his race. He spoke to the BBC about the event.