Pollution levels in India's capital New Delhi have hit their worst for the second time in October -- earning a "very poor" rating and indicating air quality could deteriorate further after the Hindu festival of Diwali, reports Reuters.
The air quality index, which measures the concentration of poisonous particulate matter, touched 388 in New Delhi on Friday, according to US embassy data, way above the "safe" limit of 60.
The index measures the concentration of tiny poisonous particulate matter -- PM2.5, particles that are less than 2.5 microns in diameter and can be carried deep into the lungs, causing deadly diseases including cancer and cardiac problems.
Senior government officials, who did not wish to be identified because they are not authorised to talk to media, said the main reason behind the sharp deterioration in air quality was a lack of wind speed.
A thick, toxic haze could envelop New Delhi and neighbouring cities if the authorities fail to clamp down on fireworks to celebrate Diwali, the Hindu festival of light that falls on Sunday.
Air quality usually starts worsening in New Delhi ahead of Diwali.
The Supreme Court last year allowed the use of only "safe and green firecrackers", for a maximum two hours, and only in designated areas such as parks, aiming to lessen the risk to health.
But authorities failed to enforce the decree and crackers continued to crackle late into the night. As a result, PM 2.5 levels in some parts of the city soared to 689 the next day, indicating emergency conditions.
To avoid a repeat of last year and wean residents away from bursting tens of thousands of firecrackers, New Delhi authorities are offering residents laser light shows to mark Diwali this weekend.
Other than the smog triggered by firecrackers, smoke from the surrounding countryside, where farmers at this time of the year burn the crop residue in their fields to prepare for winter sowing, causes pollution in New Delhi and surrounding cities.
Among a host of measures to curb pollution, the city government of New Delhi has decided to restrict use of private cars between Nov 4-15.
Some of the other steps include banning diesel-run generators and burning of garbage.