The Collaborative International Dictionary of English v.0.48:

Noisome \Noi"some\, a. [For noysome, fr. noy for annoy. See
   Annoy.]
   1. Noxious to health; hurtful; mischievous; unwholesome;
      insalubrious; destructive; as, noisome effluvia. "Noisome
      pestilence." --Ps. xci. 3.
      [1913 Webster]

   2. Offensive to the smell or other senses; disgusting; fetid.
      "Foul breath is noisome." --Shak.
      [1913 Webster] -- Noi"some*ly, adv. -- Noi"some*ness,
      n.
      [1913 Webster]

   Syn: Noxious; unwholesome; insalubrious; mischievous;
        destructive.

   Usage: Noisome, Noxious. These words have to a great
          extent been interchanged; but there is a tendency to
          make a distinction between them, applying noxious to
          things that inflict evil directly; as, a noxious
          plant, noxious practices, etc., and noisome to things
          that operate with a remoter influence; as, noisome
          vapors, a noisome pestilence, etc. Noisome has the
          additional sense of disqusting. A garden may be free
          from noxious weeds or animals; but, if recently
          covered with manure, it may be filled with a noisome
          smell.
          [1913 Webster]

WordNet (r) 3.0 (2006):

noisomeness
    n 1: the quality of being noxious [syn: harmfulness,
         noisomeness, noxiousness]