Pollution normally refers to waste water discharged from factories or gases discharged from factory smoke stacks or car exhaust pipes. Pollution is a deliberate discharge. It is NOT considered to be contamination. Contamination is very specific and usually refers to a single element (iron, lead, mercury) or chemical that is accidentally (or intentionally by sabotage) introduced into a water or food source. Contamination is NOT considered to be pollution.

They are both similar and often mean the same thing. A couple of differences. Contaminate sometimes has more of a sense of "interfering with" or "making impure," not necessarily implying making something dirty or unhealthy. For example, a blood sample can become contaminated or tainted. It just means it's no longer pure or that something is interefering with the ratio of chemicals that was in the sample before and has made the sample no longer valid. Also, contamination almost always refers to a liquid or solid. If you're talking about a gas or air, it's going to be pollution. So, we don't normally say, air contamination (unless it's a very small and isolated sample of air being used for an experiment--see the exmaple of blood contaimination above). But most of the time their meaning and use are identical.