When the wind blows: spatial spillover effects of urban air pollution in China

This paper estimates air pollution spillover effects in Chinese cities. Estimation of this spillover effect is complicated because neighboring cities share similar business/pollution cycles, and changes in wind direction can be frequent. To circumvent these empirical challenges, we propose a new approach exploiting spatial and temporal variations in PM_2.5 concentrations for major cities in China’s Eastern Monsoon Region during the monsoon season. We find large pollution spillover effects. Estimates based on our preferred model specification suggest that a city’s average PM_2.5 concentration increases by 0.33 (or 0.26) units during the winter (or summer) monsoon season, if PM_2.5 concentrations in cities upwind of this city increase by one unit. Estimated spillover effects in plain and non-plain regions are 14%–16% larger and 45%–71% smaller, respectively, than the baseline estimates. The percentage contributions of PM_2.5 pollution from upwind cities to local PM_2.5 levels vary by region and can be as large as 50%.

本文旨在估算中国城市间的大气污染溢出效应。该溢出效应的测算存在多重实证难点：相邻城市共享相似的经济与污染周期，且风向变动频繁。为规避上述难题，我们提出一种全新研究方法，利用中国东部季风区主要城市在季风季内的细颗粒物（PM₂.₅）浓度时空变化特征开展分析。研究结果显示，我国城市间存在显著的大气污染溢出效应：基于优选模型设定的测算结果表明，若某城市上风方向城市的PM₂.₅浓度每提升1单位，则该城市冬季（夏季）季风季内的平均PM₂.₅浓度将上升0.33（0.26）个单位。平原与非平原区域的污染溢出效应测算值分别较基准估计结果高出14%~16%与低45%~71%。此外，上风方向城市排放的PM₂.₅对本地PM₂.₅浓度的贡献占比存在显著区域异质性，最高可达50%。