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The smog over Beijing at the minute is thick and grey. It hangs in the air, obscuring the view of the city. And it seems to seems to coat the back of your throat.

Over the past few weeks there have been times when the air pollution was truly awful, and it has covered swathes of northern China.

The US embassy, which monitors pollution levels, said the air quality was hazardous on Sunday and Monday, and improved slightly so the levels that were described as "very unhealthy" today. China's authorities have blamed weather conditions.

In Durban in South Africa the world is talking about how to tackle climate change. China, though, is still reluctant to sign up to binding emissions targets anytime soon. Economic development still comes first.

But Beijing now ranks, environmentalists say, among the world's most polluted cities. The rush for growth has come at a cost and it's one that many people are now starting to question. So here's taste of what it's like out on the streets of Beijing today: