Safety evaluation of mechanical recycling processes used to produce polyethylene terephthalate (PET) intended for food contact applications

Abstract

The development of a scheme for the safety evaluation of mechanical recycling processes for polyethylene terephthalate (PET) is described. The starting point is the adoption of a threshold of toxicological concern such that migration from the recycled PET should not give rise to a dietary exposure exceeding 0.0025 μg kg(-1) bw day(-1), the exposure threshold value for chemicals with structural alerts raising concern for potential genotoxicity, below which the risk to human health would be negligible. It is practically impossible to test every batch of incoming recovered PET and every production batch of recycled PET for all the different chemical contaminants that could theoretically arise. Consequently, the principle of the safety evaluation is to measure the cleaning efficiency of a recycling process by using a challenge test with surrogate contaminants. This cleaning efficiency is then applied to reduce a reference contamination level for post-consumer PET, conservatively set at 3 mg kg(-1) PET for a contaminant resulting from possible misuse by consumers. The resulting residual concentration of each contaminant in recycled PET is used in conservative migration models to calculate migration levels, which are then used along with food consumption data to give estimates of potential dietary exposure. The default scenario, when the recycled PET is intended for general use, is that of an infant weighing 5 kg and consuming every day powdered infant formula reconstituted with 0.75 L of water coming from water bottles manufactured with 100% recycled PET. According to this scenario, it can be derived that the highest concentration of a substance in water that would ensure that the dietary exposure of 0.0025 µg kg(-1) bw day(-1) is not exceeded, is 0.017 μg kg(-1) food. The maximum residual content that would comply with this migration limit depends on molecular weight and is in the range 0.09-0.32 mg kg(-1) PET for the typical surrogate contaminants.

Rational Design of Packaging: Toward Safer and Ecodesigned Food Packaging Systems

“…In the case of PET bottles, the capacity to estimate the best ratio of virgin (high impact) and mechanically recycled (low impact) materials will be significant. In this particular case, current EU regulation requires a design and storage conditions, which would ensure a migration lower than 0.017 μg·kg −1 in the beverage for a residual post-consumer contamination of recycled PET conservatively set at 3 mg·kg −1 (Barthélémy et al, 2014). The chief difficulty at this stage is the absence of standardized templates and non-commercial licenses for food packaging design.…”

A focused review on recycling and hydrolysis techniques of polyethylene terephthalate

“…MR requires sorting into individual plastics, washing and drying, size reduction, and melting to reproduce polymer pellets for further processing. [45][46][47] As PET waste has contaminants and other materials such as polymers and metals, the sorting facilities separate the PET from metal and other polymers using a variety of methods including accounting the density and the waste size. The PET waste is washed and dried to remove the contaminants and prepared for the size reduction process.…”

Occurrence, toxicity and remediation of polyethylene terephthalate plastics. A review

“…The EFSA evaluated the risks of recycling processes and managed them by an appropriate quality assurance system (Barthélémy et al 2014 ). Welle ( 2016 ) determined the cross-contamination amount during the recycling process of PET between noncontaminated and contaminated flakes.…”