Survey of heavy metal contamination in recycled polyethylene terephthalate used for food packaging

Polyethylene terephthalate food-product containers made with post-consumer materials have been found contaminated with heavy metals due to the recycling and sorting process. The increased use of recycled plastic flake from international suppliers, and subsequent commingling with electronic waste, has been suspected as the source of the increased levels of heavy metal contamination. In this study, nickel, chromium, cadmium, antimony, and lead were quantified in post-consumer polyethylene terephthalate extruded sheet and thermoformed samples, using inductively coupled plasma-atomic emission spectrometry. Recycled polyethylene terephthalate samples were digested using trace-metal grade hydrochloric, perchloric, and nitric acids. Samples were analyzed per ASTM E1613-04, standard test method for determination of lead by inductively coupled plasma atomic emission spectrometry, flame atomic absorption spectrometry, or graphite furnace atomic absorption spectrometry techniques. Two hundred samples were tested of which 29 were found to be contaminated with heavy metals. Chromium and cadmium were found in all 29 sample replicates. Nickel was found in 96.4% of the sample replicates and when it was found, the concentration averaged 11.59 ppm. Lead was found in 90.4% of the sample replicates and the average concentration was 0.15 ppm. Antimony was found in 97.6% of the sample replicates and concentrations were higher in rigid recycled polyethylene terephthalate containers compared to films. It was noted that the total contamination in all 29 samples was well below the threshold level set for the incidental presence of heavy metals in packaging materials as set forth in California’s Toxics in Packaging Prevention Act of 2006. The percentage of each heavy metal that would actually leach from the plastics to contaminate food products during normal processing, packaging, marketing, and consumer use was not determined in this study.