Each recycled polymer displays specific contamination and decontamination behaviour governed by physical processes: sorption (contamination), diffusion and migration (release into foodstuff). Only a small number of studies has investigated safety issues related to the use of recycled polyolefins. Most studies extrapolate to polyolefins the results obtained for PET, but this approach can be erroneous. The post-condensation steps of PET recycling processes allow elimination of possible contaminants of concern. The diffusion coefficient of a given substance is lower in PET than in polyolefins by orders of magnitude, so that the possible migration of absorbed contaminants is much higher for poliolefins.

Moreover, polyolefins have a reduced thermal stability and degradation products are formed during the processes. Stabilizers, which are used to protect polyolefins from oxidation and degradation during processing also give rise to reaction products. These become even more important when the materials are recycled and processed several times. Neoformed substances formed from both polymers and stabilizers may migrate into the packaged food.