Does sunlight change the material and content of polyethylene terephthalate (PET) bottles?

A simple water treatment process called SODIS (solar water disinfection) consists of filling polluted water in PET bottles that are exposed to sunlight for 5–6 hours. However, sunlight does not only destroy disease-causing microorganisms found in the water but also transforms the plastic material into photoproducts. Laboratory and field tests revealed that these photoproducts are generated at the outer surface of the bottles. No indication for migration of possible photoproducts or additives from PET bottles into water was observed with the applied analytical methods.