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The Beijing Marathon has gone ahead, despite warnings over the potentially-hazardous air quality in the Chinese capital.
More than 30,000 runners took to the streets wearing face masks and being handed sponges to clean their skin.
One of those taking part, engineer Liu Zhenyu, said on a normal day "nobody would run in such conditions". He added: "But the event is happening today, so what can we do?"
The smog level in Beijing was sufficiently bad to top China's poor air quality index, with warnings for children, the sick and elderly to stay indoors, and everyone else to avoid outdoor activities.
The US embassy, which uses a separate tracking system, said the air was hazardous, with 344 micrograms per cubic meter of PM2.5 particulate matter - a carcinogen.
The World Health Organisation considers 25 micrograms during a 24-hour period a safe level.
(Pictures: AP and Getty)