Pollution tweets from US embassies improved air quality in cities

Satellite data from 466 cities in low and middle-income countries shows that monitoring by US embassies led to better air quality compared with cities without public data

By Luke Taylor

The US embassy in Beijing began tweeting air pollution readings in 2008

Zihao Chen/Getty Images

US embassies’ tweets showing real-time air quality data resulted in lower levels of air pollution in cities around the world.

In 2008, the US embassy in Beijing installed an air quality monitor and began tweeting hourly readings. By 2020, more than 50 US embassies in 37 other countries had followed, creating a large data set that researchers could use to assess the impact of disseminating real-time pollution data.

Akshaya Jha at Carnegie Mellon University in Pittsburgh, Pennsylvania, and his colleagues analysed satellite data on air pollution in 466 cities in 136 low and middle-income countries, including 50 cities where US embassies installed monitors.

They focused on pollution particles with a diameter of 2.5 microns or less, known as PM2.5. These particles are particularly harmful because they penetrate the lung barrier and enter the bloodstream, contributing to respiratory and cardiovascular conditions such as heart disease and lung cancer.

In 2016, it was estimated that outdoor air pollution caused 4.2 million premature deaths worldwide per year, but only 32 per cent countries in the study sample had any form of air quality monitoring. Fewer countries still made that data public.

The study found that cities where US embassies tweeted air contamination data saw the levels of PM 2.5 drop by an average of 2 to 4 micrograms per cubic metre compared with those that didn’t.

The drop is small relative to the high levels of pollution in the most-contaminated cities – for example, in New Delhi, the average PM 2.5 level for 2020 was 89 micrograms per cubic metre of air. However, the researchers estimate this would have reduced the number of premature deaths caused by pollution each year by a median of 303 in each city.

Jha and his colleagues suspect that making the data accessible made people aware of low air quality and ramped up public pressure to address it through policy change.

The team recorded a steady increase in the number of Google searches where the monitors were installed and pollution levels subsequently dropped. “Once the information is out there, it may lead to more public press or even international pressure,” says Jha.

Various policy initiatives may have improved air quality, such as restricting the use of cars or moving industrial production further away from densely populated cities.

The data could also give members of local and federal governments the evidence they need to lobby for greener policies while providing journalists with authoritative findings they can use in media coverage.

The study suggests that publishing information on health risks can have a big impact, says Jha. “The overarching message of the paper is that information alone can help quite a bit more than was previously expected. It speaks to making air pollution salient to local populations and getting the adverse health effects of pollution on people’s minds.”

“Engaging with, and involving the public in, dialogue on the health impacts of air pollution is key to building pressure and momentum for authorities to act on the issue, as demonstrated in this new study,” says Frank Kelly at Imperial College London.

Journal reference: PNAS, DOI: 10.1073/pnas.2201092119