In this research, we investigate whether urban rail transit expansion improves air quality. We also compare the magnitudes of the effects across cities and explain the variation. The results suggest that opening subways alleviated air pollution, especially during non-rush hours in the daytime. We find that the effects are smaller in the cities with higher income and more subway lines, while the effects are larger in the cities with higher population density. Furthermore, the effect of the first subway line opening is stronger, compared to expansion of an existing subway system.

The high rates of economic activity and environmental degradation in Asia demand the implementation of creative and cost-effective environmental policy instruments that provide polluters with more flexibility to find least-cost solutions to pollution reduction. Despite their many theoretical advantages, the use of market-based instruments (MBIs) is a relatively recent phenomenon in Asia, partly due to policymakers being unfamiliar with MBIs and countries lacking the institutional capacity to implement and enforce them.

We combine survey responses to subjective well-being (SWB) questions with air pollution data to recover Chinese residents' valuation of air quality improvements. Motivated by theoretical models of ‘projection bias’ and ‘recency bias’, we posit that one's SWB (and valuation) is affected disproportionately by more recent experiences with air pollution, even though long-term air pollution is more detrimental to one's actual well-being.

A large body of literature estimates the effect of air pollution on health. However, most of these studies have focused on physical health, while the effect on mental health is limited. Using the China Family Panel Studies (CFPS) covering 12,615 urban residents during 2014 – 2015, we find significantly positive effect of air pollution – instrumented by thermal inversions – on mental illness.

Identifying a demand function for air quality is a key input to calculate welfare measurements of pollution abatement policies. We defined intra-urban housing submarkets to apply a Second Stage hedonic pricing model that allowed us to identify an inverse demand function for PM10 reductions in Bogotá. The monthly benefits of compliance with the U.S. Environmental Protection Agency standard (50 μg/m3 – annual average), and the far more stringent World Health Organization standard (20 μg/m3 – annual average) are valued at US$12.16 and US$189.64 per household, respectively.