Has urbanization contributed to an increase in haze pollution?

To examine the impact mechanisms of urbanization on haze pollution, this study analyzes panel data from 269 prefecture-level cities in China from 2007 to 2021. We construct regression models that incorporate technological innovation and human capital accumulation as mediating and threshold variables to examine the influence of urbanization on haze pollution. The results reveal an inverted U-shaped relationship between urbanization levels and haze pollution, which initially increases before subsequently decreasing. During urbanization, haze pollution is mitigated through technological innovation and human capital accumulation, both serving as partial mediators. A dual-threshold effect of technological innovation significantly reduces pollution upon surpassing these thresholds, while human capital accumulation exhibits a single-threshold effect; its influence on reducing haze pollution gradually diminishes. Both eastern and western regions of China have surpassed the single-threshold effect for human capital accumulation, whereas the central region has exceeded the threshold for technological innovation, with trends being consistent across these regions. As levels of technological innovation and human capital increase, they contribute to haze reduction. Consequently, the paper advocates for China to prioritize technological innovation and talent development, implementing region-specific strategies tailored to the developmental phases of the eastern, central, and western regions, thereby enhancing urbanization levels and achieving sustainable development while continuously mitigating haze pollution.