Subways and Urban Air Pollution

61 Pages Posted: 9 Jan 2018 Last revised: 31 Jul 2022

See all articles by Nicolas Gendron-Carrier

Nicolas Gendron-Carrier

University of Toronto

Marco Gonzalez-Navarro

UC Berkeley

Stefano Polloni

Brown University

Matthew Turner

Brown University - Department of Economics

Date Written: January 2018


We investigate the effect of subway system openings on urban air pollution. On average, particulate concentrations are unchanged by subway openings. For cities with higher initial pollution levels, subway openings reduce particulates by 4% in the area surrounding a city center. The effect decays with distance to city center and persists over the longest time horizon that we can measure with our data, about four years. For highly polluted cities, we estimate that a new subway system provides an external mortality benefit of about $1b per year. For less polluted cities, the effect is indistinguishable from zero. Back of the envelope cost estimates suggest that reduced mortality due to lower air pollution offsets a substantial share of the construction costs of subways.

Suggested Citation

Gendron-Carrier, Nicolas and Gonzalez-Navarro, Marco and Polloni, Stefano and Turner, Matthew, Subways and Urban Air Pollution (January 2018). NBER Working Paper No. w24183, Available at SSRN:

Nicolas Gendron-Carrier (Contact Author)

University of Toronto ( email )

Toronto, M5S 3G8

Marco Gonzalez-Navarro

UC Berkeley ( email )

207 Giannini Hall
Berkeley, CA 94720
United States


Stefano Polloni

Brown University ( email )

Box 1860
Providence, RI 02912
United States

Matthew Turner

Brown University - Department of Economics ( email )

64 Waterman Street
Providence, RI 02912
United States

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