Since 2008, embassies and other diplomatic posts had been publishing data about local air quality. In many countries, it was the only reliable source of such information.

The program had used sensors at more than 80 U.S. embassies and consulates to track air quality, mostly in places where such data was unavailable.

The initiative helped pressure the Chinese government to clean up the air in Beijing and was later expanded to dozens of cities around the world. Now, it’s been abruptly halted.