People in China breathe more easily when dust-laden winds blow in from the Gobi desert. Paradoxical as it sounds, desert dust helps to keep human-made pollution down, a new study shows.

Air pollution is a big issue in China, with hundreds of millions of people suffering from respiratory problems. An estimated 1.6 million deaths (17% of mortalities) a year are attributed to China’s dirty air.

In particular, eastern China has had severe and persistent winter haze episodes in recent years, with cities, including Beijing, being regularly issued “red alerts” for air quality. Belching coal-fired power stations, traffic fumes and industrial chimneys are to blame, but it is the weather conditions that determine how long the pollution lingers.

Using historical data, Yang Yang, a scientist at the Pacific Northwest National Laboratory, in Washington State, US, and his colleagues, simulated 150 years of wind and dust patterns over eastern China.

Power stations and factories in operation in China, where 17% of mortalities a year are attributed to unclean air. Photograph: Imaginechina/Rex/Shutterstock

This research showed that when the winds were slack the lack of desert dust in the air allowed more solar radiation to reach the surface. This lessened the temperature difference between land and sea, reducing winds even further and helping the air to stagnate over east China, creating the perfect conditions for a build-up of pollutants produced by people. The effect was most pronounced during the winter monsoon season.

The findings, published in Nature Communications, suggest that air pollution in eastern China increases by as much as 13% when the desert winds are at their slackest.

Observational data from dozens of sites backed up the model findings, showing that the air became cleaner two or three days after the winds brought dust into the region.



