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.

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.

U.S. embassies and consulates have stopped monitoring air quality abroad, ending a program that had provided essential public health data for more than a decade.