A group of Edinburgh medical students dugup the facts on the Great London Smog of 1952 (the photos are fascinating;

几位爱丁堡大学医学院的学生发掘了1952年伦敦大雾霾的一些事实（其中的照片引人入胜；

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London, renowned for centuries for its infamous smog and severe pollution, today has the cleanest air that it has had since the Middle Ages.

伦敦，因其臭名昭著的烟雾和极其严重的污染而闻名几百年，今天有着自中世纪以来最干净的空气。

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However, Frank Kelly, director of environmental research at King's College London, says the smoke isn't as dangerous as the industrial smog seen in most cities.

不过，伦敦大学国王学院环境研究主任弗兰克·凯利说，这种烟雾并不像大多数城市看到的工业烟雾那么危险。

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The Global Times warns of "danger signals" after Chinese scientists find a "large number of toxic and hazardous particles" in polluted air samples from Beijing and Tianjin in January that are similar to deadly smog in Los Angeles and London in the 1950s.

BBC: China media: Pollution strikes again

Now London is known for its real fog, not smog.

CNN: China needs smog-free air in a can

And in Santiago, Chile, short-term emergency action was taken in the 90s when there were extraordinary bursts of smog, says Nigel Bell, professor of environmental pollution at Imperial College London.

BBC: The filthy air conundrum