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The U.S. Embassy said the air quality monitor in Shanghai measures the air quality in the area around the consulate’s office. “The monitor is an unofficial resource for the health of the consulate community,” said Richard Buangan, embassy spokesman in Beijing.

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 contributed to this report.