Propylene Glycol Degradation due to Sunlight
The thermal degradation of propylene glycol and its uses in e-cigarettes has been a discussed in a previous question here on Chem.SE.


  Upon complete oxidation and degradation, propylene glycol will fully
  decompose to carbon dioxide and oxygen. However, if there is partial
  oxidation, you will get some intermediate species - formaldehyde or
  acetaldehyde.(1st answer)
  
  Propylene glycol does not decompose on heating, it simply boils. In
  theory, under certain conditions (pressure/encapsulation/catalysts) it
  could dehydrate to either acetone or Propionaldehyde, probably the
  former.(2nd answer)


Also, this link shows the decomposition products of propylene glycol which are all acid based:


  The main degradation product of propylene glycol was lactic acid (2-hydroxypropionic
  acid), with formic, acetic, and oxalic acids as minor products.


So, mainly degradation of propylene glycol in sunlight would yield a bunch of acids and small amounts of acetone. Worrying about the odors is a personal medical question and is off-topic in Chem.SE.