Authorities in India’s capital have shut schools, halted construction and banned non-essential trucks from entering the city after air pollution shot up to its worst level this season.

New Delhi has become the most polluted city in the world after its air quality turns ‘hazardous’ at 1,081 and the concentration of PM2.5 - particulate matter measuring 2.5 microns or less in diameter that can be carried into lungs,

India's capital New Delhi was wreathed in blanketing toxic smog this week as worsening air pollution surged past the grim mark of 50 times World Health Organization recommended daily maximum.

Toxic smog continues to plague most of northern India, including the capital, New Delhi. With levels of microparticles well over recommended limits in the city, schools have been ordered to hold classes online.

The smog, a toxic blend of smoke and fog, happens each year in winter as cold air traps dust, emissions, and smoke from illegal farm fires in some surrounding states. Visibility dropped to 100 m (109 yards) in Delhi and Chandigarh,

Delhi recorded air pollution more than 17 times above an acceptable level as worsening smog triggered curbs on trucking and shuttered construction sites and schools.