New Delhi (CNN) Naresh Kumar Rana's day begins early. Every morning, he leaves his home at 6.30 a.m. and will drive across the vast Indian capital of Delhi for the next 10 hours.

Rana, 42, is an auto rickshaw driver. The three-wheeled taxicabs, with their distinctive green and yellow livery, are a common sight on the streets of Delhi, where they provide a cheap and ready available means of transport on the city's heavily congested roads.

The job provides Rana with a steady income to help support his family, but it comes with a risk -- especially during winter -- when the city's already toxic air becomes even more lethal.

On Thursday morning, the day after Diwali , the Hindu festival of lights that is celebrated with fireworks, parts of the capital reported levels almost 40 times those considered "safe" by the World Health Organization.

"I have trouble breathing. By the time I return home, I have chest pain, I'm coughing," Rana, who has been a auto rickshaw driver for 24 years, told CNN of his experience driving during the winter smog.

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