By Aditya Kalra
NEW DELHI (Reuters) - Air quality in New Delhi will deteriorate to "severe" levels this week when Indians set off firecrackers to celebrate the Hindu festival of lights, a government scientist said, leaving many at risk of respiratory problems.
The warning, based for the first time on India's newly launched national Air Quality Index, is significant as New Delhi dismissed a World Health Organization study in May which found the capital to have the world's worst air pollution.
The study, which covered 1,600 cities, also said that India has 13 of the 20 cities with the worst air quality worldwide.
"Delhiites are going to breathe very poor-to-severe air at least for two days," said Gufran Beig, chief scientist at the Indian Institute of Tropical Meteorology, referring to Thursday, when the nation celebrates Diwali, and a day after.
The city of over 16 million people will see its air pollution index jump to 450 from 220 currently. A reading above 401 could put the healthy at risk for respiratory problems and seriously affect those already ill, the new index explains.
Pollution levels in Indian cities have often been compared to Chinese counterparts such as Beijing, notorious for the smog that prompted some Anglophone residents to dub it "Greyjing".
"Over the next three days the air quality will be worse than Beijing because of firecrackers," Beig said, adding that Delhi normally has better air quality than the Chinese capital.
However, a delay in the onset of the winter season will result in lower pollution levels this year as warmer temperature helps pollutants disperse faster, Beig said.
Indian government officials have appealed to the public to refrain from bursting firecrackers, with the health minister calling for a "silent Diwali" in Delhi to control sound levels.
(Editing by Malini Menon/Mark Heinrich)