Higher air pollution in Chinese cities tied to higher mortality rate

Study authors examined daily air quality data from more than 100 cities in China between 2012 and 2015 and compared the data with mortality numbers available from the Chinese Center for Disease Control and Prevention. Air quality was measured with the air quality index, a pollution yardstick that includes ground-level ozone, particle pollution, carbon monoxide, sulfur dioxide and nitrogen dioxide. A higher air quality index value indicates a greater amount of pollution.

When researchers compared higher air quality index valued cities with mortality rates, they found that the two measures were significantly correlated. They also confirmed that cities with lower air quality index values had lower mortality rates. This correlation remained significant after researchers adjusted for covariates. Significantly, more than 5 percent of the variation in all-cause mortality could be explained by the difference in air quality index across China.

"Our research shows that air pollution is not just significantly linked to health problems like cardiovascular disease, diabetes and asthma, but also to a significantly higher rate of death," said Longjian Liu, MD, PhD, MSc, who presented the study and serves as a visiting associate professor at Harvard University T.H. Chan School of Public Health and associate professor at Drexel University Dornsife School of Public Health. "People living in cities across the globe need to know how air pollution can harm them long term. They are the ones who will pay the price of poor air quality if action isn't taken to clean up their air."

The study observed that the monthly average air quality index of cities differed significantly by temperature, with the highest air quality index values occurring in winter and the lowest in summer. The study also showed significant geographic clustering of cities by air quality index, with the highest values in northern cities and the lowest in southeast China.

Researchers also found that heat index, precipitation and sunshine hours were negatively associated with air quality index.