Yes, POLLUTION is a Scrabble word!

Letter values in Scrabble US: P 3, O 1, L 1, L 1, U 1, T 1, I 1, O 1, N 1.

Is it a valid word?

POLLUTION is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

undesirable state of the natural environment being contaminated with harmful substances as a consequence of human activities
the state of being polluted
the act of contaminating or polluting; including (either intentionally or accidentally) unwanted substances or factors

Not playable in Scrabble US: BEFOULMENT.