There are hundreds of millions vehicle on the road every day throughout the world and each one is a prevalent source of pollution. Especially in terms of larger cities and metro areas, the amount of air pollution is significantly higher than what you would find in rural areas.
Considering that there are far more populated cities than rural ones in the world, it is important that government implement clean air tools and laws to reduce the amount of toxic emissions created by vehicles which is where catalytic converters come into play.
In 1975, changes were made to the way that car engines were developed to ensure that they reduced the amount of toxic emissions in the air. The catalytic converter is used to help convert the harmful pollutants into less harmful emissions even before these pollutants leave the exhaust system. It is quite interesting how a simple catalytic converter has such a large impact on your vehicle.