Pollution is a pretty general term. In this instance you are referring to air pollution. Air pollution comes from a huge number of sources, the one you are most likely o have encountered are fires and diesel/oil burning combustion engines. If you turn all cars electric then the air in our cities will very quickly clear up. This would see huge health benefits and would reduce the smog hanging over our cities considerably. This would also be much better for the environment because we produce some of our electricity via renewables. However if we can get to an 100% renewable energy economy that would be the ideal.