More people feel there is to much dirty air in big cities.求全

More people feel there is too much dirty air in big cities.Some of the dirty air comes from cars.The more cars there arein cities,the more dirty air we will have So some people suggest we should go to work by bike,because no dirty air is from bike.The more people go to work by bike,the fewer cars there will be in cities,so the dirty air will not be much.Do you think it is a good idea?