Residents in India's northern states woke up to another day of poor air quality on Tuesday, as a layer of dense fog shrouded most of the region and pollution in the capital Delhi remained severe.India battles air pollution every winter as cold,

Parts of South Asia are filled with toxic smog, hurting not only residents' health, but the economies of India and Pakistan.

Toxic smog engulfed much of northern India on Monday and pollution readings in New Delhi hit their highest of this pre-winter season.