Chemical smell in fridge/freezer?

Yesterday I noticed a strange pungent smell when I opening my fridge door, then I noticed that it had permiated into my food. Today it is just as bad, if not worse.

The Smell: It is a chemical, plastic/metal smell is the only way I can discribe it. Very different from any food smell.

The Fridge/Freezer: Daewoo No-Frost Fridge/Freezer (approx. 5-8 years old)

Before you ask, I have removed all the food from the fridge and freezer and there was nothing rotten, I have cleaned out the inside and the smell persists. I have checked the drip tray at the base of the unit at the back and this is not where the smell is coming from and there is nothing behind or under the unit that could cause the smell.

I am a little worried that as the smell has already got into my food (most of which I have thrown away) that it could be harmful. PLEASE could you give me a clue as to what it might be?