Explain pollution caused by automobiles and how the use of a catalytic converter in them reduces pollution.

(N/A) Automobiles are a major cause of atmospheric pollution in metropolitan cities.
Proper maintenance of automobiles,along with the use of lead-free petrol or diesel,can reduce the pollutants they emit.
Catalytic converters,which contain expensive metals like platinum-palladium and rhodium as catalysts,are fitted into automobiles to reduce the emission of poisonous gases.
As the exhaust passes through the catalytic converter,unburnt hydrocarbons are converted into carbon dioxide $(CO_2)$ and water $(H_2O)$,while carbon monoxide $(CO)$ and nitric oxide $(NO)$ are changed to carbon dioxide $(CO_2)$ and nitrogen gas $(N_2)$.
Vehicles fitted with catalytic converters must use unleaded petrol because lead in the petrol inactivates the catalyst.
In Delhi,the entire fleet of public transport was converted to Compressed Natural Gas $(CNG)$ mode to reduce the rapidly increasing pollution levels of the metro.