Ambient air pollution and socioeconomic status in China

Abstract

BACKGROUND AND AIM: Air pollution disparities by socioeconomic status (SES) are well documented for the US, with most literature indicating an inverse relationship (i.e., higher concentrations for lower-SES populations). Limited knowledge exists for China, a country accounting for 26% of global premature deaths from ambient air pollution. We propose and test the opposite relationship as in the US: in China, air pollution exposures are higher for high-SES than for the low-SES populations. Underlying this framework is that in China’s current industrialization and urbanization stage, economic development is correlated with both SES and air pollution. METHODS: We test our air pollution inequality theory by combining estimated 2015 annual-average ambient concentrations for nitrogen dioxide (NO2) and fine particulate matter (PM2.5), derived from a national empirical model for China with 1 km spatial resolution, with demographic information derived from national gridded GDP per capita at 1 km resolution and (separately) a national representative sample of 21,095 individuals from the China Health and Retirement Longitudinal Study (CHARLS) 2015 cohort. We quantify the air pollution disparities among individual’s rural-to-urban migration status and SES factors (education, occupation, and income). We compare results using three approaches to SES measurement (individual SES score; community-averaged SES score; gridded GDP per capita). RESULTS:Consistent with our theory, ambient NO2 and PM2.5 concentrations are higher for higher-SES populations than for lower-SES population, and higher for long-standing urban residents than for rural-to-urban migrant populations. For example, for the three SES measurements, a 1-IQR increase in SES corresponds to concentration (units: μg/m3) increases of 5.6 - 9.4 NO2 and 3.5 - 6.0 PM2.5. This pattern holds in rural and urban locations, across geographic regions, across levels of spatial resolution, and for modeled versus measured pollution concentrations. CONCLUSIONS:Multiple analyses reveal that in China, ambient NO2 and PM2.5 air pollution levels are higher for high-SES than for low-SES individuals. KEYWORDS: Ambient air pollution, Socioeconomic status, NO2, PM2.5