noun (n)

• undesirable state of the natural environment being contaminated with harmful substances as a consequence of human activities(noun.state)

  source: wordnet30
• the state of being polluted(noun.state)

  Synonym:
  befoulment, defilement
  

  source: wordnet30
• the act of contaminating or polluting; including (either intentionally or accidentally) unwanted substances or factors(noun.act)

  Synonym:
  contamination
  Antonym:
  decontamination
  

  source: wordnet30
• The act of polluting, or the state of being polluted (in any sense of the verb); defilement; uncleanness; impurity.(noun)

  source: webster1913