Urban Health Inequality Relation to Climate Change and Air Quality: Evidence from Urban Air Quality Surveillance System in 120 Cities of China

Background: In addition to a significant health inequality in life expectancy across the country, China has had a rapid increase in its economy over the past 3 decades. However, the economic boom comes at the cost of worsening air quality. We aimed to examine the complex association of climate change, air pollution and health outcomes using Chinese national surveillance data.

Methods: City-level daily air quality data (assessed by air pollution index, API) for 120 cities from 2012 to 2013 in China, and relevant meteorological factors, socioeconomic status and total morality were obtained from Chinese environmental protection, meteorology and health statistics agencies. Weekly, monthly and seasonal changes in API and their correlation with meteorological factors were examined using multiple linear regression analysis, spatial autocorrelation analysis and panel fixed models. Ecological association between API and total mortality was tested using correlation analysis method.

Results: Among the 120 cities, annual average API significantly increased from 2012 to 2013 (65.05 vs. 75.99, p<0.0001). The highest average API was in winter, and the lowest in summer. A significant spatial-clustering distribution of elevated API was observed in both 2012 and 2013, with the highest API in northern China. Among the 120 cities,  5 cities (4%) in 2012 and 21 cities (18%) in 2013 had API >100 (defined as slightly polluted reference value) for ≥60 days in a year. Of the 120 cities, 16 (13%) in 2012 and 35 (29%) in 2013 experienced maximum API >300 (defined as severely polluted) in a year. Heat index, precipitation and sunshine hours were negatively and significantly, but air pressure was positively correlated with API. Cities with higher API concentrations had significantly higher total mortality than those with lower API. This API – mortality association remained significant after adjustment for city-level socioeconomic status. More than 8% of the variation in total mortality could be explained by the difference in air pollution concentration across the nation.   

Conclusion:  Using data from national air quality surveillance systems, the study provides new evidence of an increasing trend of air pollution from 2012 to 2013. Air pollution may contribute to more than 8% of the urban health inequality in total mortality across China.