Air-pollution emissions and population urbanisation in China: provincial co-evolution under structural transformation

Urbanisation and environmental change are often modelled as a one-way relationship, yet both can be outcomes of the same structural transformation. This study distinguishes production-side air-pollution emissions from exposure-side environmental amenities and examines how provincial emissions and population urbanisation co-evolved in China. Using 31 provincial-level units from 2011 to 2023, the preferred emissions-based sample excludes 2018 because the compiled yearbook series reproduces the preceding year’s pollution-emissions values during a statistical transition. A reverse-coded principal-component index is constructed from provincial sulfur dioxide, nitrogen oxides, and particulate emissions, with higher values indicating lower emissions pressure. The empirical strategy combines two-way fixed effects with null-imposed wild cluster bootstrap-t inference, alternative emissions measures, a province-demeaned PCA that reduces dependence on persistent between-province scale differences, lagged controls, and province-specific linear trends. In the preferred conventional specification, lower emissions pressure is modestly associated with higher population urbanisation (beta = 0.0122; wild-bootstrap p = 0.046). The association remains visible with a two-pollutant index and with the province-demeaned emissions PCA, but becomes less precise with lagged controls and disappears after province-specific trends are absorbed. The central finding is therefore not a stable causal effect of pollution reduction on urbanisation. Rather, the conventional positive relationship is substantially embedded in slow-moving provincial development trajectories. By separating production-side emissions transition from exposure-side amenity mechanisms, the study develops a structural-transformation co-evolution framework for interpreting the urbanisation–environment nexus in long regional panels.