A thick layer of smog enveloped New Delhi on Friday after revelers celebrating Diwali, the Hindu festival of lights, ignored a ban on firecrackers.

The air quality index stood at more than 345 shortly after dawn, according to Swiss company IQ Air, bringing pollution in the sprawling Indian capital to “hazardous.” It also put New Delhi at the top of a real-time list as the world’s most polluted city, above Lahore in neighboring Pakistan.

In recent years, authorities in New Delhi have banned the use and sale of traditional firecrackers during Diwali and urged people to celebrate the festival of lights with more environmentally friendly options.

Why doesn’t the ban on firecrackers work?

The ban has proven difficult to enforce and is often violated.

Some Hindu groups have criticized the move, saying it interferes with their ability to observe the festival of lights celebrating the Hindu goddess Lakshmi.

Meanwhile, authorities say the ban is aimed at saving lives.

In many areas on Friday, levels of deadly particles, which can lodge deep in the lungs and cause a host of health problems, rose well above the daily maximum considered safe by the World Health Organization.

According to the AFP news agency, New Delhi police confiscated almost two tonnes of fireworks in the run-up to Diwali this year, but revelers were still able to travel to neighboring states to buy them.

Other sources of pollution

New Delhi, home to 33 million people, is often ranked as one of the most polluted urban areas in the world.

Smoke from its streets congested by traffic and factories only aggravate the problem.

Diwali also usually coincides with the burning of crop residue on farms in neighboring states. This can worsen air quality in early winter as colder temperatures trap smoke.

nm/kb (AFP, AP, Reuters)