India now has the world's dirtiest air

The Delhi government has put in place a number of short-term policy measures — including restricting driving to alternate days based on license plate numbers — to reduce traffic emissions when other factors such as low winds, garbage burning for heat and stubble burning on farms north of the city become a problem. Even though these measures reduce daily concentration, they have not had a lasting impact. And Delhi is just the tip of the iceberg: Smaller towns and cities such as Kanpur are even worse off.

What's next: Based on the available data, Indian scientists and policy advisors have made a number of recommendations, many of which have gone unheeded since the 1990s. If rich cities like Delhi can’t manage pollution, the prospect for poorer ones is dim. Perhaps Indian politicians need to take a page out of the Beijing playbook and learn how China's government has managed to dramatically improve air quality through a combination of tough industrial and traffic control measures.

Tanvi Nagpal is acting director of the International Development Program and practitioner in residence at Johns Hopkins SAIS.