China requires concentrations of PM2.5 to be kept below daily averages of 75 micrograms per cubic meter — more than twice as lenient as the U.S. Environmental Protection Agency's standard of 35 micrograms.
PM2.5 are believed to be a health risk because they can lodge deeply in the lungs, and have been linked to increased cardiovascular and respiratory diseases as well as lung cancer.
Associated Press writer Gillian Wong in Beijing and Matthew Pennington in Washington contributed to this report.
U.S. Embassy Beijing air quality monitor: https://twitter.com/(hashtag)!/BeijingAir
U.S. Consulate Guangzhou air quality monitor: https://twitter.com/(hashtag)!/Guangzhou_Air
U.S. Consulate Shanghai air quality monitor: https://twitter.com/(hashtag)!/cgshanghaiair
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