NEW DELHI — It is a seemingly intractable annual drawback: India’s capital is engulfed in a poisonous haze so extreme that colleges are closed and residents are suggested to remain indoors.

The smog spreads as farmers within the northwest of the nation burn stubble, setting hearth to leftover paddy straw after harvesting rice. Despite repeated official clampdowns, this burning throughout an estimated 2 million farms releases dangerous pollution that specialists say improve the danger of demise from respiratory and cardiovascular ailments, not only for Delhi’s roughly 35 million residents however different elements of South Asia.