adjective (a)

• injurious to physical or mental health(adj.all)

  Example:
  Noxious chemical wastes.
  Noxious ideas.
  

  Antonym:
  innocuous
  

  source: wordnet30
• Hurtful; harmful; baneful; pernicious; injurious; destructive; unwholesome; insalubrious; as, noxious air, food, or climate; pernicious; corrupting to morals; as, noxious practices or examples.(adjective)

  source: webster1913