Beijing's smog: When a scale of zero to 500 doesn't go high enough

In the space of an afternoon, Beijing vanished.

For days, the city was crisp and clear. Wind whipped down its ancient alleys and sprawling, 12-lane thoroughfares; an electric blue sky reflected in the glass walls of its postmodern office buildings. But by evening, all was gone, engulfed in a gauzy-white miasma. Buildings rose into hazy oblivion, and the sun became a dull yellow orb, like a flashlight shining from under a blanket.

That was Friday, when levels of PM2.5 — particularly noxious particulate matter, small enough to enter the bloodstream through the lungs — reached 429 micrograms per cubic meter, 17 times the World Health Organization’s recommended limit. By Monday, schools were closed; drivers were using their headlights at noon.

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