China’s air quality has long been a major public health concern, with pollution levels historically among the worst in the world thanks to coal burning power plants, industrial growth, and urbanization. The crisis went largely unacknowledged for years. While the public knew the air was often dirty, they remained unaware of the true scale of the problem. 

But nearly two decades ago, a surprising outside source of air quality information brought the issue to light, leading to major policy shifts, greater public awareness, and a positive impact in both China’s air quality and people’s health outcomes.

U.S. Embassy monitoring changed the game

In April 2008, just months before the Beijing Olympics, the U.S. Embassy in Beijing installed a regulatory-grade air quality monitor and began sharing its data publicly on Twitter (1). The readings exposed alarming pollution levels—prompting widespread public attention and concern (2).

Twice daily, the embassy’s readings exposed stark differences from official Chinese air quality reports, highlighting a major discrepancy in PM2.5 levels. PM2.5 is so tiny that it can enter the lungs and the bloodstream, ultimately leading to respiratory illness, heart disease, and even premature death. It was a crucial contradiction; competing and conflicting air quality readings risked misrepresenting the seriousness of the health crisis and could keep the public in the dark about the air they were breathing.

In October 2010, one of the U.S. State Department's tweets noted “crazy bad” levels of PM2.5, - over 500 μg/m3 and well into the range of air quality considered “hazardous.” (3) Though the U.S. Embassy later deleted the tweet and replaced it with a note saying it was “beyond index,” the message resonated.

The viral tweet, combined with the embassy's contradictory data, fueled widespread public outcry. Frustrated by the lack of transparency, citizens turned to the embassy’s real-time data as a reliable source, and environmental activists began using this information to challenge the government’s portrayal of the air quality.

Policy reforms sparked by data transparency

Initially resistant to being contradicted, the Chinese government soon began to respond to the public outcry. U.S. Ambassador to China Gary Locke told the Washington Post in 2013, “I’ve never seen an initiative of the U.S. government have such an immediate, dramatic impact in a country (4).” 

“I’ve never seen an initiative of the U.S. government have such an immediate, dramatic impact in a country.”—Gary Locke, U.S. Ambassador to China

In 2012, China adopted PM2.5 as an official air quality metric within national air quality standards and announced ambitious plans to greatly expand air quality monitoring across the country (5). 

China then launched a multi-billion dollar “war on pollution” in 2013, aiming to tackle the environmental crisis head-on. China’s State Council released a national air quality action plan, and began to implement stricter regulations on industrial emissions, encouraged cuts to steel capacity, sought to reduce the number of cars on the road, banned coal-fired power plants in major cities, and pressured the plants to switch to renewables and natural gas. 

The Chinese government also greatly expanded the national air monitoring network.

How China’s air quality improved

Thanks to the embassy monitor and the Chinese government’s resulting policy shift, PM2.5 levels have improved significantly since 2013. In 2013, Beijing struggled with an ‘air-pocalypse’ so severe that the sky often turned yellow from pollution, and people avoided going outdoors (6). The government responded in Beijing and other large urban centers with targeted smog control policies, including limits on construction activities, enhanced dust control, and incentives for cleaner industrial technologies.

Between 2018 and 2024, China’s annual average PM2.5 concentration declined from 41.2 to 31 – improving from very unhealthy to unhealthy range of air quality. 

The positive health impacts have been startling. According to a University of Chicago study, a decade of air quality improvements led to a 41% reduction in air pollution by 2022 (7). As a result, the study suggested that Chinese people could expect to live an additional two years, thanks to cleaner air.

U.S. Embassy large-scale global air quality monitoring lowered pollution and "led to substantial health benefits enjoyed by the over 300 million people living in cities home to a US Embassy monitor as of 2019."

A 2022 study published by PNAS further noted that U.S. Embassy air quality tweeting and large-scale global air quality monitoring lowered pollution in low- to middle-income countries like China, and "led to substantial health benefits enjoyed by the over 300 million people living in cities home to a US Embassy monitor as of 2019." (8)

U.S. State Department monitoring program under threat

The U.S. State Department was expected to cease sharing data from regulatory-grade air quality monitors at embassies and consulates worldwide by the end of March, including the long-running program in Beijing.

The State Department informed news outlets that the decision was due to “funding constraints,” though those costs were not shared. A former administration official, Deputy Special Envoy for Climate Rick Duke, noted that the cost to maintain the systems was, in fact, “trivial (9).” 

The cost to maintain the systems was, in fact, "trivial.”

This decision marks a significant loss in China, where air quality data transparency played a pivotal role in both raising awareness and spurring policy change. Though low-cost air quality monitoring is important in promoting air quality awareness, regulatory-grade monitors like those installed at U.S. embassies help calibrate and validate low-cost sensors. Because it is illegal in China to publicly share air quality data from non-government monitors, the U.S. Embassy sensors served a unique and critical role. They were the only publicly accessible, independent source for verifying the accuracy of government-reported pollution levels.

The U.S. State Department’s independent data source allowed citizens, media, and environmental groups to hold authorities accountable and ensured that the reported improvements were genuinely reflective of the air quality on the ground. Local activists and researchers will be particularly affected, making it harder to study the complex links between air quality, public health, and pollution sources—potentially slowing environmental reforms. (10).

Although China has reduced air pollution, challenges remain. Winter smog, industrial rebound, dust storms, and the potential manipulation of local air quality data continue to be concerns.

The takeaway

The U.S. Embassy’s air quality monitor didn’t just track pollution—it ignited a movement. By exposing hidden dangers, it forced a policy reckoning that led to cleaner air and longer lives. But as the State Department shuts down its monitors and with no legal path forward for privately-owned air quality monitors to publicly share air quality data, the world risks backsliding into opacity.  Only by restarting the monitoring program will it be possible to have independently verifiable, transparent air quality monitoring in China.

Coming up in Part 2: Learn how U.S. embassies champion air quality in Africa—and why those efforts are more vital than ever.