New Delhi (CNN) — It’s easy to tell when it’s smog season in New Delhi; the air gets darker, heavier and starts scratching the throats and testing the lungs of the city’s 34 million residents.

Dhaka, Feb. 16 -- Dhaka, the densely populated capital of Bangladesh, ranked third among the world's most polluted cities on Monday morning, recording an Air Quality Index (AQI) of 248 at 8:11 am.

Some countries have to choose between development and the environment. We don't.

Smog settles around Delhi's famed Red Fort in the early hours of November. - Sanchit Khanna/Hindustan Times/Getty Images It’s easy to tell when it’s smog season in New Delhi; the air gets darker, ...