From the Daily Mail:
Parts of China have been blanketed by thick yellowish cloud this week - sparking fears of pollution among its millions of inhabitants.
Witnesses in the metropolis of Wuhan said the haze appeared suddenly yesterday morning, with residents rushing to put on face masks.
'I looked out of my office window and couldn't believe my eyes,' said Li Yunzhong, describing the haze as opaque, with yellowish and greenish tinges.
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France's consulate-general in the central city advised residents to stay at home, close their windows and limit the use of air-conditioning. It said on its website: 'The source of the thick cloud that has covered the city of Wuhan since this morning is at present unknown.Not as bad as the Great Smog of 1952 that hit London. But this may be precursor of worse to come.
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'Local authorities have promised us the information as soon as possible.'
Air pollution is increasingly acute in major Chinese cities and authorities are frequently accused of underestimating the severity of the problem in urban areas, especially in Beijing.
Official statistics are sometimes at odds with non-government measurements, and are often viewed with distrust.
While I have never been to China, I think the worst air pollution I've ever experienced was in Tokyo (and I say this having grown up on a city that had some of the worst air pollution in the U.S. at the time). Millions of people and cars, with most houses, apartments and other buildings heated with small kerosene heaters and stoves. It would look like the photo above sometimes for days on end. Your skin would darken during the day; you'd blow you nose and it would just be black gunk; poor visibility and smell. Ugh.