Because the harmful gases (Like carbon monoxide) gets into the air we breathe
Pollution.
Automobiles, burning of matter and using of natural resources at an exploiting level cause much pollution.
Because burning fuel (coal, oil, gasoline, petroleum, diesel and natural gas etc) releases carbon dioxide, a powerful greenhouse gas, which is overloading the carbon cycle and causing global warming. That answer is only partially correct. Yes, burning excessive fuel does cause air pollution but there is little proof scientifically that it has caused "global warming" alone in of itself.
Pollution is caused by many things such as factories, burning fuels, and even as much as forest fires.
Alot
*aeroplanes
Fuel efficiency determines how much useful energy you get out of each unit of fuel. If fuel efficiency drops you have to use more fuel to get the same job done. And fuel cost money, so you'll also have to pay more to get the same job done. And burning fossil fuels contributes to pollution, so with poorer fuel efficiency you have to put up with more pollution being released for thesame amount of useful work being done.
Electromagnetic waves only cause sound pollution because they are sound waves.
Talking too much could be considered noise pollution, but that's about it.
"It indicates how much a fuel swells after burning"
None.
If you put pollution in a box it is 2 litres