Health & cooking oils: Are PET bottles dangerous? 

A new study from the University of Vienna brings to light very interesting results

A new study from the University of Vienna tested the shelf life of cooking oil in different types of bottles. The study also found that the PET bottle releases carcinogenic benzene into the oil over its storage period. 

The researchers in this study tested the stored sunflower oil for benzene after 56 days and measured a concentration in the samples stored in PET bottles that is 140 times higher than permitted for drinking water. Recycled PET performed even worse. Benzene is a strong-smelling liquid that is contained in gasoline, for example. Even in small quantities, it poses a health risk because the substance is classified as carcinogenic.  

Further research on this topic shows that benzene is already contained in the plastic as part of the PET - but is normally bound harmlessly in the molecule. During the manufacturing process of the PET bottle, the plastic is melted at around 260°C so that it can be shaped. This heat damages the material, causing some of the PET molecules to break down, allowing the previously bound benzene to be released. The now unbound benzene is then released from the plastic over the storage period and remains in the oil. It's obvious why recycled PET performs even worse: During recycling, it is exposed to the melting heat a second time, whereby impurities such as PVC can further support the formation of benzene*. 

In comparison to the PET bottle, the NaKu bottle tested in this study is made of completely natural materials, which is why no harmful substances can be released from the bottle. This does not have an aromatic ring, as sugar is used as the starting material and not a “poisonous” raw material.  

The Study by the University of Vienna can be read here. 

* According to a study, one liter of oil contains as much benzene as is inhaled through more than 4 cigarettes.