As world leaders — China’s included — meet in Paris at the U.N. Climate Summit, Beijing has raised its air pollution alert to “orange” — the highest level reached so far this year.

Over the last few days a thick, grey fog has enveloped the Chinese capital, sending levels of particulate matter — the unit of measuring air pollution — into deeply hazardous territory. Levels of particulate matter 2.5, which can penetrate human lungs and cause respiratory ailments, heart attacks and other health impacts, peaked near 600 micrograms per cubic meter of air in the city. The World Health Organization standard for healthy air is just 25 micrograms per cubic meter. Read more…

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