Air quality progress in North American megacities: A review

Air quality progress in the North American megacities of Los Angeles, New York, and Mexico City is reviewed, compared, and contrasted. Enormous progress made in North America over the last 5 decades provides a template for other megacities of the world, especially in developing countries, attempting to achieve rapid economic growth without compromising air quality. While the progress to date has been impressive, many challenges remain including the need to improve air quality while simultaneously mitigating climate change. The impact of pollutant emissions from megacities is felt long distances away from the local sources but no policy mechanisms currently exist to mitigate air quality impacts resulting from such pollution transport.

► Air quality progress in three North American megacities is reviewed.
► Enormous progress has been made over the last 5 decades.
► Further progress is required to meet health-based standards.
► North American progress can provide a template for developing megacities.
► A remaining challenge is to improve air quality while mitigating climate change.