Air pollution after the shutdown of US embassy monitoring

For more than a decade, US embassies and consulates provided independent, publicly accessible air-quality information in cities worldwide. In 2025, this program was abruptly suspended, generating sharp drops in the availability of trusted pollution information. We evaluate the consequences of this change using real-time satellite-derived aerosol optical depth (AOD) and a matched difference-in-differences design with same-country control cities. Across 46 cities, we find no systematic trends prior to the halt in US reporting, and a prompt 24 to 33% increase in local pollution levels after reporting stopped. Calibrating AOD to concurrent preshutdown embassy PM_2.5 readings, the main estimate corresponds to an approximate PM_2.5-equivalent increase of 1.9 [Formula: see text]g/m³ under our preferred conservative translation, with alternative approaches yielding values between 1.5 and 16.3 [Formula: see text]g/m³. Estimated effects are largest and most persistent in cities with poor substitutes for the US-provided data. The findings indicate that pollution reductions are not guaranteed by either previous air quality improvements or the legacy of reliable environmental data.