
As Air Quality Index in Delhi hit 500-mark in several locations, a Supreme Court-mandated panel declared a public health emergency in Delhi. (Express Photo by Neeti Nigam.)

Bangladesh players wear masks while practicing for India-Bangladesh series at Arun Jaitely stadium in New Delhi on Friday. (Express photo by Praveen Khanna)

Delhi Chief Minister Arvind Kejriwal also announced schools in the capital would be shut till November 5. (PTI Photo)

A woman and a child, wearing anti-pollution masks, walk along a road in New Delhi, Friday, Nov. 1, 2019. (PTI Photo.) The blanket of haze over Delhi thickened on Friday morning with the national capital's pollution levels increasing overnight. An AQI between 0-50 is considered 'good', 51-100 'satisfactory', 101-200 'moderate', 201-300 'poor', 301-400 'very poor' and 401-500 'severe'. Above 500 falls in the 'severe-plus emergency' category.

A security person, wearing anti-pollution mask, guards outside the Reserve Bank of India in New Delhi, Friday, Nov. 1, 2019, PTI Photo. Exposure to polluted air for such sustained periods of time can lead to breathing difficulties, lung damage and other adverse health effects, especially among children and the elderly.