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

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