Vehicles on Delhi roads generate roughly 20 percent of these tiny particles in the air, which can be absorbed into the bloodstream and which are linked to chronic bronchitis, lung cancer, and heart disease.
According to a report published by a research group Urban Emissions, as much as 5 million kilograms of firecrackers were burnt in the region leading to an emission of 150,000 kilograms of Particulate Matter (PM) 2.5 despite the Supreme Court's order stating that bursting of firecrackers will only be allowed from 8 pm to 10 pm on Diwali.
Hours after Diwali celebrations, a thick haze enveloped Delhi-NCR as the air quality Thursday morning plunged to "hazardous" - Anand Vihar and areas around Major Dhyan Chand National Stadium recorded 999 AQI and Chanakyapuri 459 - exposing people to major health risks.More news: Trump slaps down journalist for 'stupid' question
The Delhi police said it has registered over 550 cases and arrested more than 300 people for violating the court's order.
On Wednesday night Delhites largely defied a court order and set off an vast barrage of smoke-spewing firecrackers to celebrate the major Hindu festival of Diwali, sending pollution levels soaring. Police officers said they could not tell an environmentally-friendly banger from an unfriendly one so were unsure what action to take.
Forecasts suggest the air quality across northern cities will remain very poor till Sunday.More news: Lakers sign Chandler to fill need at center
A level of 50 or less is considered safe. Any reading between 301 and 400 is "very poor" and can cause "respiratory illness on prolonged exposure". In recent weeks Delhi doctors have reported an increase in the number of patients with respiratory problems due to a rise in pollution levels from burning crop residue, vehicle exhausts and industrial gases.
On Friday, levels of particulates 2.5 micrometers or less in diameter, the most harmful to human health, peaked at 845, according to the U.S. embassy website that monitors air quality independently.
More gentle winds and cool air, which can trap pollution, exacerbate the problem. Around this time previous year, he declared a public health crisis, shutting down schools for a week and told residents to remain indoors.More news: Pat Toomey's advice to next attorney general: Wrap up Trump probe