Acetaldehyde is a well known decomposition product of PET; what effect does this have?

Small amounts of acetaldehyde are formed during thermal degradation of PET, only when the polymer is in the molten state. Acetaldehyde is a simple, naturally-occurring, organic chemical present in many ripe fruits eg apples, grapes, and citrus fruits (up to 230 ppm).  It is produced during the fermentation of sugar to alcohol, and is a natural constituent of butter, olives, frozen vegetables, and cheese. It forms in wine and other alcoholic beverages after exposure to air (up to 140 ppm).  It even occurs as an intermediate in the metabolism of sugars in the body and hence can be found in human blood.  Acetaldehyde is listed as an approved food additive and is used to enhance citrus flavours, helping to create natural, fruity tastes and fragrances.  As a flavour ingredient, it can be found in ice creams, sweets, baked goods, chocolates, rum, and wine. Since it is present naturally in numerous foodstuffs at higher levels than in PET, acetaldehyde from PET will have a significantly lower effect on humans than that from natural sources.The safety of acetaldehyde is also demonstrated by the fact that it is an accepted raw material for the manufacture of food contact plastics. It is important that manufacturers and converters control the level of acetaldehyde in PET because, in its pure state, it has a flavour and a sharp penetrating aroma, therefore it has the ability to change the taste and flavour of foods packaged in PET, particularly mineral water.   Typical concentrations of acetaldehyde in PET containers used for beverage packaging are less than 10 ppm and probably closer to 4- 5 ppm.