New Delhi: Pollution levels in the Delhi dropped barely on Monday morning due to a slight increase in wind speed, yet the air quality remained in the 'severe' category.

At 4.38 am, Delhi's air quality index (AQI) was recorded at 438. The AQI at Alipur, Narela and Bawana were enrolled  at 493, 486 and 472 individually.

On Sunday, the Delhi average AQI stood at 494, the highest since 6 November, 2016 when it was 497.

An AQI between 0-50 is considered 'good', 51-100 'satisfactory', 101-200 'moderate', 201-300 'poor', 301-400 'extremely  poor' and 401-500 'severe'. Above 500 falls in the 'severe plus' category.

In the National Capital Region (NCR), Noida (452), Ghaziabad (474) and Greater Noida (454), Gurgaon (396), Faridabad (426) were breathing exceedingly polluted air.

On Sunday, 21 of the 37 air quality observing  stations recorded AQI between 490 and 500 with air quality sensors at Aya Nagar, Ashok Vihar, Anand Vihar and Aurobindo Marg peaking out at 7 pm.

The Delhi government had on Friday coordinated closure of schools till Tuesday and banned construction works after the Supreme Court-mandated Environment Pollution (Prevention and Control) Authority declared a public health emergency as air quality plummeted.