Safety evaluation of mechanical recycling processes used to produce polyethylene terephthalate (PET) intended for food contact applications
Résumé
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 0.0025gkg(-1)bwday(-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 3mgkg(-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 5kg and consuming every day powdered infant formula reconstituted with 0.75L 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 mu gkg(-1)bwday(-1) is not exceeded, is 0.017gkg(-1) food. The maximum residual content that would comply with this migration limit depends on molecular weight and is in the range 0.09-0.32mgkg(-1) PET for the typical surrogate contaminants.