Toxic smog engulfs India's capital

A thick layer of toxic smog covered India's capital on Friday morning as the air quality index (AQI) entered the "severe" category in several parts of the city.

The smog forms over Delhi every winter as the cold, heavy air traps construction dust, pollution from vehicles and smoke from the burning of crop stubble in neighboring states. As a result, millions of residents face respiratory illnesses every year.

"Unfavourable meteorological conditions, sudden increase in the farm fire incidents and north-westerly winds moving the pollutants to Delhi are the major causes for sudden spike in AQI," the region's Commission for Air Quality Management said on Thursday.

Pollution a threat to the sick

On Friday morning, the AQI reached 480, according to local monitoring stations. A level of 0-50 is considered good. Anything between 400-500 presents a danger to those with existing diseases. Residents across the city complained of itchy throats, burning eyes and difficulty in breathing.

Air quality monitoring Swiss firm IQAir put Delhi's AQI at 611 in the "hazardous" category on Friday morning.

The PM2.5 particles — considered most dangerous since they are small enough to enter the bloodstream — were nearly 35 times the daily maximum recommended by the WHO, the Swiss company said

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