A new study in PNAS has found that air pollution went up in the months following the Trump administration’s decision to stop embassy air quality monitoring in cities across the globe. Scientists examined satellite data before and after the U.S. stopped releasing information from its diplomatic posts, and discovered pollution increased by 24 to 33 percent in those months. The figure 46 refers to the number of cities involved.
The research indicates that public information about air quality has a larger effect than anticipated. Once the U.S. ceased publishing these reports, the figures rose.
The Embassy Monitoring Program
In 2008, U.S. officials put an air quality monitor on the embassy in Beijing and made the data available to the public for the first time. This move shifted how people perceived the smog.
An environmental economist at the University of Michigan who grew up in Shanghai in the early 1990s recalls what the air was like back then. Eric Zou lived close to a chemical plant, where visibility was poor even at midday. People often referred to the smog as “fog”, treating it as bad weather rather than pollution.
“Once you have pollution information, it tends to be that it actually helps people to realize, ‘Oh I actually value air quality,'” Zou says.
The program grew to cover more than 80 embassies and consulates around the world over time. Studies indicate that tracking helped produce better air quality, particularly in nations with modest resources that lacked their own monitoring systems.
The Shutdown
The program was shut down in March 2025, with the Trump administration pointing to financial expenses as the reason. When contacted by the State Department, no response was received in time for publication.
At Columbia University, climate researcher Zoe Yiyuan Zhou viewed the shutdown as a chance to study something unusual. She pointed to plenty of proof that more monitoring pays off, yet she found almost no cases where surveillance dropped suddenly.
How the Study Worked
Zhou and her colleagues drew upon satellite data to measure air pollution levels in two separate time frames: before the U.S. stopped reporting, and after, when ground-level measures were no longer available.
For the period before the end of U.S. reporting, which spanned roughly 300 days, there were no discernible patterns in air pollution levels. However, around three to four months after reporting stopped, pollution levels rose, with an average increase of approximately 30 percent.
Ground monitors provide direct readings, while satellite data offers an approximation of air quality from above. Researchers estimate that their satellite-based measurements correspond to roughly a 4 percent rise in PM2.5 levels — those tiny airborne particles capable of penetrating the lungs and entering the bloodstream, where they can trigger serious health issues.
“That magnitude is certainly concerning,” says Andrea La Nauze, an environmental economist at Deakin University in Australia who has researched the benefits of the program but was not involved in this study. “Particulate matter is a serious and dangerous thing, and being exposed to it is not good.”
Where the Increase Was Highest
Among the cities where the increase was greatest were Manila in the Philippines, Rangoon in Myanmar and Vientiane in Laos, all of which sit within Southeast Asia. Pollution also rose more sharply in places that had fewer monitoring options available to them.
Researchers aren’t able to explain why pollution rose after monitoring was discontinued. They do, however, put forward possible explanations for the trend.
Zou says that for nations without established or fledgling monitoring programs, U.S. data likely spurred more regulatory action. “Maybe the U.S. embassy was a really strong force, in terms of a third-party auditing mechanism, and once that’s removed people are like ‘Now I can just pollute, right?'”
Zhou argues that in numerous fields, reducing pollution expenses carries a price tag. Companies can regard the suspension of oversight as a chance to trim those expenses.
A Silver Lining
While the research did uncover some grounds for optimism, it also found that pollution levels seemed to decline somewhat after reaching a peak around three or four months following the end of monitoring.
Zhou says she cannot explain the decline or predict if it will keep falling. Her guess is that it might be tied to other kinds of oversight stepping up after the United States pulled out.
She points out that some places might lack the capacity to easily replace what has been lost, particularly in parts of the world where air quality tracking is still a recent development.
What the Numbers Mean
Satellite measurements show a rise in pollution levels of between 24 and 33 percent. Researchers calculated an estimated increase in PM2.5 of 4 percent using that same satellite data.
While satellite measurements aren’t perfect, they remain the most reliable means of tracking how pollution changes across several cities from year to year.
What Happens Next
The study poses a question regarding the part played by public information in environmental policy, and it makes clear that without oversight, there can be no responsibility.
“Data is just so important,” says Zhou. “Having access to information is necessary to make sure that these previous gains can continue. Public information creates accountability.”
La Nauze agrees. She calls the study “a great study, high quality. And it’s a real pity.” The program “led to sustained improvements in air quality that were continuing to increase after 10 years,” she says.
The new findings indicate that gains may not hold up once oversight is abandoned.
Key Dates
| Date | Event |
|---|---|
| 2008 | U.S. officials install air quality monitor on the Beijing embassy and begin public reporting |
| March 2025 | Trump administration shuts down the embassy monitoring program, citing monetary costs |
| 300 days | Period with no significant air pollution trends before U.S. reporting ended |
| Three to four months | Period when satellite-measured pollution increased 24 to 33 percent |
| Monday in the journal PNAS | Study published |
According to the research, openness is important. The air grew worse after the U.S. stopped sharing information.
The outcome hinges on what comes after. A few places might plug the hole with their own local tracking systems. Other places might leave it unfilled.
It’s a plain idea: the air grows worse when there’s no one around to take notice.
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