pollution-n; 3 Senses

Sense Number 1: being polluted

Commentary: befoulment, defilement - undesirable state of being contaminated; especially in nature

When George throws his trash on the ground he is contributing to the pollution of the environment.
Air pollution reduced visibility.
Sewage is one of the yuckiest types of water pollution.
Video games led to the pollution of his young mind.

WordNet 2.0 Sense Numbers: 1 2

Sense Number 2: act of polluting

Commentary: contamination the act of contaminating or polluting; including (either in intentionally or accidentally) unwanted substances or factors

George's act of throwing his trash on the ground is pollution of the environment.
There's a $2,000 fine for pollution.
Pollution of our children's minds by video games must be stopped.

WordNet 2.0 Sense Numbers: 3

Sense Number 3: the stuff

Commentary: the trash - this usage is quantifiable (unlike sense 1)

Look at all the pollution on the ground.
There is a lot of pollution in the river these days.

WordNet 2.0 Sense Numbers: -