contamination caused by unwanted matter.
china
las Vegas
Mainly pollution.
Mainly exhaust from cars.
in some countries they can be by predators and mainly pollution
agriculture
the answer is about 5000000000000 pollution is made from cars each day mainly fat ones :-)
There are many pollutions factors in the US but it is mainly from cars.
Pollution mainly.
The gas that causes the biggest amount of air pollution has to be carbon dioxide. Due mainly to emissions from vehicles.
The smog mainly hits cities. This shows that cities create more pollution.
Mainly pollution and the link below will give further information.