Until now the blame for the excessive air pollution has been pinned on coal-fired power stations and China’s booming construction industry. But the new research shows that exports to developed countries are also responsible for a significant proportion of China’s small particulate emissions.

Beijing regularly makes international headlines because of the intense smogs that frequently blanket the city. In January 2013 the concentration of PM2.5 (particulate matter smaller than 2.5 µm) in Beijing passed 1000 µg per cubic metre – 40 times higher than the World Health Organization standard for good health.

These miniscule particles, which can include sulphates, black carbon, organics and trace metals, are the major component of smog. Their small size means they can cause respiratory damage and enter the bloodstream relatively easily.

It isn’t just Beijing that suffers. During the same episode in January 2013 smog suffocated more than 70 major cities in north China, smothering 15% of China’s land mass. Meanwhile, estimates indicate that outdoor air pollution contributed to 1.25 million premature deaths in China in 2010. Sometimes that air pollution drifts long distances, even crossing the Pacific Ocean and bringing extra smog days to the west coast of the US.

In recent years China has invested significant resources to try and clean up the problem. Since 1998 the country has designated around 11% of its territory as acid rain and sulphur dioxide pollution control zones. And Chinese electricity plants have been installing flue gas de-sulphurization systems: by 2010 more than 85% of plants had them in place.

But still the pollution problem grows. So what is driving the increase in small particulates? Dabo Guan from the University of Leeds, UK, and his colleagues used regional emissions figures from 1997 to 2010 to tease out the socioeconomic factors that are driving changes in PM2.5.

During the study period, China achieved double digit economic growth, which should have pushed pollution sky high. However, the researchers found that the significant efficiency measures offset the additional emissions that would otherwise have accompanied the growth.

Delving deeper into the data, Guan and his colleagues showed that capital formation (construction of infrastructure, for example) was the largest source of PM2.5, contributing nearly 40% of PM2.5 emissions every year. And within that capital formation, more than 65% came from the construction industry. “This is because the supply chain for construction activities is very emission intensive,” explained Guan. “Construction requires cements, steel, glass, bricks and so on, all of which require massive electricity demand to produce them.”

In second place came exports, contributing 18% of primary PM2.5 emissions in 2010). While capital formation-related emissions fell steadily from 1997 to 2010, export-related emissions crept higher and higher. “In 2010, exports were responsible for 1.8 million tonnes of PM2.5 emissions, mainly from producing electronic and electrical products, metals, mineral materials and chemical products,” said Guan.

So what can be done to reduce emissions? While China can continue to improve production efficiency and switch over to lower carbon fuels, ultimately consumer habits need to change too. “Consumers need to start thinking about consuming less emission-intensive products and increasing recycling and reusing,” said Guan. What’s more, Chinese manufacturers could start to cherry-pick the products they export. Right now, China exports a number of resource-intensive and relatively low-value products. By focusing more on the high value, and minimal energy and resource consumption products, China could maintain its thriving export market yet reduce its emissions. “By shifting its export structure China may hurt total trade a little, but long term it is a more sustainable way to do exporting,” Guan told environmentalresearchweb.

The team reported the results in Environmental Research Letters (ERL).

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