New Delhi's air quality has already reached its worst level this year. And the Hindu festival of lights, Diwali, which starts this weekend, is likely to make things even worse as the traditional rounds of firecrackers add to the air pollution.
During the five-day festival, revelers set off smoke bombs, sparklers and aerial fireworks that spew clouds of noxious gas.
"It's a very critical, dangerous week ahead of us," said Delhi-based environmental activist Vimlendu Jha.