A study out in the journal Nature today reveals that nearly a quarter of early deaths attributable to bad air quality worldwide happen because of products made in one region for consumers in another region.
It also found that around 1 in 10 early deaths related to air pollution happen because of pollutants emitted in a different part of the world.
For example, the study shows that in 2007 there were 108,600 premature deaths in China because of goods that were made for western Europe and the US. On the flip side of that example, pollution emitted in China caused 64,800 deaths in places other than China, including 3,100 in the US and western Europe.
"It's not a local issue any more, it requires global cooperation," Dabo Guan, an author on the paper and professor in climate change economics at the University of East Anglia, said at a briefing.
Western Europe and the US contributed the highest number of deaths outside of each region because of the products they consumed in 2007.
China and the "rest of Asia" region had the highest number of deaths in 2007 in each region because of products made for elsewhere.
The "rest of Asia" region covers central and southeast Asia.
The study only covers deaths from a type of air pollution called PM2.5, made up of small particles up to 2.5 micrometers across. It looked at 3.45 million global early deaths that were related to PM2.5 and happened in 2007, and tracked emissions of the pollutant in different regions across the globe.
Some kinds of pollution, like PM2.5 and ozone, can drift around the globe from where they were emitted. Others, like nitrogen dioxide, don't go very far.
Pollutants in the air affect everybody's health to some extent, but they have a much greater effect on vulnerable people, such as those who already have respiratory problems.
India and the rest of Asia caused the highest number of deaths outside each region due to their emissions in 2007.
The rest-of-Asia region and India also had the highest number of deaths because of other regions’ pollution emissions.
The study looked at deaths that happened in the year 2007, which was the latest data available when the study began. The authors said at a press briefing that they have started looking at data up to 2011 to see if anything has changed since 2007, but don't yet have the results of that analysis.
"Since 2013 China’s government has put tremendous effort on controlling emissions, and we expect a large decrease in emissions ... especially from large facilities like power plants.," said Qiang Zhang of Tsinghua University, Beijing, China, who is an author on the paper. "But we believe that the concept of how our global economy affects global health will still be there."
PM2.5 particles come from both traffic and industry, and in smaller amounts from other sources like wood burners in homes. A major industrial source of PM2.5 is coal burning.
"The numbers didn't surprise me at all," Martin Williams, a professor in the science policy group at King's College London, told BuzzFeed News. "The obvious question when you see a piece of science like this is, 'What are policymakers going to do about it?'"
A similar analysis has been done in Europe, Williams said: "Countries then sit round a table and negotiate emission reductions based on these calculations that show what impact one country has on another."
How exactly that would work on a global scale is another issue.
"What we’ve done here is really quantify, in terms of the numbers of deaths, this trade-off between economic development and environmental impact," Steven Davies, another author on the paper and professor at the University of California, Irvine, said at a briefing.
"But it’s not really up to us to say what’s fair or not, especially as it's not just that Chinese people dying when the US consumers buy Chinese goods, there's folks in Japan and Korea and other places downwind that also might suffer harm," he added. "It’s a more complicated issue and it involves some decision-making that’s going to happen at the policy level. What we hope we’ve done is give them some information to base their decisions on."