Five years ago, the Indian capital was rated as one of the most polluted cities in the world, continually shrouded in an eye-stinging smog of foul gas and noxious fumes. No longer. Pollution levels in the wheezing metropolis of about 13 million people have come down significantly since the government cracked down on exhaust-belching vehicles and closed down smoke-spewing factories in the late 1990s. Today, about 6,000 buses have changed from diesel to CNG and thousands of three-wheelers have also adopted the cleaner fuel. "Today, if you are at a red light, your eyes don't water and you don't just see a haze around you," said coordinator of air pollution control at the Centre for Science and Environment's Roychowdhury.