London, Nov 3 (IANS): Air pollution reached the near-maximum level possible in Delhi on Friday as the national capital was blanketed by a thick layer of toxic haze, marking the start of the annual smog season, as per reports.

Schools were closed and non-essential construction was banned as the air quality index in the city reached almost 500 -- 100 times the limit deemed to be healthy by the World Health Organisation.

Air quality in Delhi had worsened over the last week, attributed to a dramatic rise to stubble burning by farmers in the neighbouring states of Punjab and Haryana, as well as winds that brought the pollutants into the capital and a decrease in temperatures keeping the particles trapped.

Delhi Chief Minister Arvind Kejriwal announced late Thursday that all primary schools would be closed across the capital for at least two days.

Many of the capital's 33 million residents complained of irritation to eyes and itchy throats as the air turned a dense grey, Daily Mail reported.

Doctors in the city said they had started to notice the damaging impact of pollution on the capital's residents.

Pollution levels in Delhi in October were at their worst since 2020, according to the Central Pollution Control Board.

Delhi is regularly ranked the most polluted city in the world.

Smoke from farmers burning crop stubble, vehicle exhaust and factory emissions combine every winter to blanket Delhi in a choking haze.

According to this year's air quality life index, compiled by the University of Chicago's energy policy institute, the people of Delhi could have their lives shortened by 11.9 years due to the poor air they breathe, Daily Mail reported.