The nexus between urbanization and PM2.5 related mortality in China.

The launch of China's new national urbanization plan, coupled with increasing concerns about air pollution, calls for better understandings of the nexus between urbanization and the air pollution-related health. Based on refined estimates of PM2.5 related mortality in China, we developed an Urbanization-Excess Deaths Elasticity (U-EDE) indicator to measure the marginal PM2.5 related mortality caused by urbanization. We then applied statistical models to estimate U-EDE and examined the modification effects of income on U-EDE. Urbanization in China between 2004 and 2012 led to increased PM2.5 related mortality. A 1% increase in urbanization was associated with a 0.32%, 0.14%, and 0.50% increase in PM2.5 related mortality of lung cancer, stroke, and ischemic heart disease. U-EDEs were modified by income with an inverted U curve, i.e., lower marginal impacts at the lowest and highest income levels. In addition, we projected the future U-EDE trend of China as a whole and found that China had experienced the peak of U-EDE and entered the second half of the inverted U-shaped curve. In the near future, national average U-EDE in China will decline along with the improvement of income level if no dramatic changes happen. However, the decreased U-EDE only implies that marginal PM2.5-related mortality brought by urbanization would decrease in China. Total health damage of urbanization will keep going up in the predictable future because the U-EDE is always positive.