Delhi woke up to hazardous air quality on Sunday, with several areas reporting 'Very Poor' AQI levels. Residents expressed concern over the deteriorating air quality, particularly for early morning commuters and athletes.

A thick, toxic smog has enveloped India's capital, home to more than 33 million people. One technology firm which monitors air pollution ranked New Delhi as the most polluted city in the world.

Delhi was listed as India's most polluted city Thursday as a weeks-long air quality crisis gripping northern India has shown few signs of letting up.

Delhi's air quality plummeted to 'severe' on Saturday, with an AQI of 412, posing significant health risks. Twenty monitoring stations recorded 'severe' readings, primarily due to vehicular emissions and stubble burning.

The AQI in Anand Vihar was recorded as 457; the AQI in Ashok Vihar was 455; Chandni Chowk's AQI was 439 and RK Puram recorded an AQI of 421.

With the overall Air Quality Index (AQI) reading 422 at 6 AM on Saturday, Delhi was once again engulfed in a dense layer of poisonous haze as the air quality fell into the "Severe" category. According to the Central Pollution Control Board (CPCB),

Experts attribute the deteriorating conditions to a mix of vehicular emissions, industrial pollution, and unfavourable weather patterns

The Central Pollution Control Board data shows of the 38 monitoring stations in Delhi, nine reported AQI readings in the “severe” range.