Every year, higher pollution levels shave off $1.3 billion from India's IT sector in lost productivity, said the study by industry group CII; Clean Air Fund, a charity; and consulting firm Dalberg.

If New Delhi fails to clean its toxic air, the booming IT sector could lose more than $2.5 every year, the study warned.

New Delhi is the world's most polluted capital, and India is home to 35 of the world's 50 most polluted cities.

(Reporting by Mayank Bhardwaj; Editing by Richard Chang)