Rare earth elements in plastics

Because of their unique properties, rare earth elements (REEs), comprising the lanthanide elements plus Sc and Y, have a variety of integral applications in modern electronic equipment. Consequently, it has been suggested that REEs may act as contaminants of and tracers for recycled electrical and electronic plastics in consumer goods. In this study, REEs have been determined in a range of consumer plastics of different polymeric makeup (n = 31), and purchased new and in societal circulation, by inductively coupled plasma-mass spectrometry following acid digestion. Samples were also screened by X-ray fluorescence spectrometry for Br and Sb as markers of brominated flame retardants and the retardant synergist, Sb₂O₃, respectively. One or more REE was detected in 24 samples, with four samples returning detectable concentrations of all REEs analysed and with total REE concentrations up to 8 mg kg⁻¹. REEs were most commonly observed in samples containing Br and Sb at levels insufficient to effect flame retardancy and, therefore, likely derived from recycled electronic plastic, but were not detectable in new electrical plastics. Various REEs were also present in plastics with no detectable Br and Sb, however, and where unregulated recycling is prohibited (e.g. food packaging). This observation, and correlations between pairs of REEs for all samples considered, suggests a more generic source of these elements in consumer plastics in addition to the recycling of electrical and electronic waste. REEs reported in the literature for beached marine plastics were characterised by similar concentrations and inter-element correlations, suggesting that REEs are ubiquitous and pervasive contaminants of both contemporary and historical consumer and environmental plastics.