What initiatives was taken for reducing vehicular air pollutin in Delhi? Has air quality improved in Delhi?

The alternative fuel used in automobiles in Delhi to reduce air pollution.

In 1990s Delhi ranked 4th among the most polluted cities of the world. But now, air quality of Delhi has significantly improved mainly by switching vehicles from diesel to CNG. (a) Expand CNG (b ) CNG is better than diesel. Comment

What happens when Na is heated in free supply of air

What are the deleterious effects of air pollution