Explain the preventive measures to control pollution in Delhi. 

Explanation

Delhi ranked fourth among the 41 most polluted cities in the world.
Delhi leads the country in its levels of air pollution.
Air pollution problems in Delhi became so serious that a public interest litigation (PIL) was filed in the Supreme Court of India.
Supreme Court has directed government to take, within a specificed time period, appropriate measures including switching over the entire fleet of public transport i.e, buses, from diesel to compressed natural gas (CNG).
All the buses of Delhi were converted to run on CNG by the end of 2002.
CNG burns most efficiently, unlike petrol or diesel.
Very little of it is left unburnt.
CNG is cheaper than petrol or diesel.
CNG can not be siphoned off by thieves and adulterated like petrol or diesel.
Phasing out of old vehicles.
Use of unleaded petrol.
Use of low sulphur petrol and diesel.
Use of catalytic converters in vehicles.
Application of stringent pollution-level norms for vehicles.