Question

Which of the following city was ranked 4th out of the 41 most polluted cities of the world, in the 1990s?

• A. Kolkata
• B. Ahmedabad
• C. Mumbai
• D. Delhi

Answer 1

The correct option is D Delhi

Any undesirable change in the physical, chemical or biological characteristics of air is called air pollution.

Delhi is one of the largest cities of India and is famous for its heavy vehicular traffic. Automobiles are a major cause for air pollution in the metro cities. Incomplete combustion of fuels such as petrol or diesel results in the formation of pollutants such as unburnt carbon particles, carbon monoxide, aromatic hydrocarbons (naphthalene, anthracene), nitrogen dioxide, sulphur dioxide, etc.

In the 1990s, Delhi was ranked as the 4th most polluted city out of 41 polluted cities of the world. In subsequent years, the level of air pollution in Delhi became serious enough to file a public interest litigation in the Supreme court of India. Hence option d is correct.

Under the directives of the Supreme court, the Government of Delhi was asked to take necessary steps to control air pollution and switch over the fuel used in all public transport vehicles (buses), from diesel to compressed natural gas (CNG). CNG burns more efficiently than petrol or diesel and releases less smoke and harmful gases into the air.

Figure : CNG vs Petrol

Apart from this, other measures such as using unleaded petrol, catalytic converters (it converts toxic substances into less harmful byproducts, such as water vapour and carbon dioxide) in vehicles, low sulphur diesel, etc., were also adopted to reduce the degree of air pollution in Delhi.