Use of lead- free petrol or diesel is recommended to reduce the pollutant emitted by automobiles. What role does lead play?

Explanation

Catalytic converters , having expensive metals namely platinum , palladium and rhodoum as the catalysts are fitted into automobiles for reducing emission of poisonous gases and to convert unburnt hydrocarbons into `CO_(2) and H_(2)O`.
Motor vehicles equipped with catalytic to converter need to use unleaded petrol because lead in the petrol, inactivates the catalyst and increases the hydrocarbon emission , there by harming the environment.