Heavy metals, PAHs and POPs in recycled polyethylene samples of agricultural, post-commercial, post-industrial and post-consumer origin

Abstract

In the present work, recycled polyethylene (LDPE) samples of agricultural, post-commercial, post-industrial and post-consumer origin were selected and analysed. The analysis comprised the determination of different contaminants such as metals, polycyclic aromatic hydrocarbons (PAHs), dioxin-like biphenyl polychlorides (PCBs), and polychlorinated-dibenzo-p-dioxins and furans (PCDD/Fs). A comparison with one sample of virgin plastic (unrecycled) was performed. The study aimed at stressing the importance of this type of analysis in recycled plastics. Indeed, such an examination will determine the material’s final destination, and the possible origin of the pollutants analysed is investigated. Black post-industrial and post-consumer samples presented the highest concentration of PCBs and PCDD/Fs, attaining a maximum value of 2.40 pg WHO-TEQ/g, while the least toxic sample (post-commercial) presented a toxicity of 0.38 pg WHO-TEQ/g. PAHs content was also much higher in black samples, reaching 514.41 ng/g, while the lowest concentrations were obtained for the post-commercial plastic sample, which did not exceed 38.98 ng/g. The higher PAHs concentrations in the black samples were related to the carbon black content of the black samples, which was 2.00% for black post-industrial sample and 1.51% for post-consumer sample. The PCDD/Fs congener profile observed in almost all samples was very similar to the profile found in the literature on urban air samples, indicating that the plastic is mainly influenced by the environment. The presence of some metals (mainly copper) showed a slight correlation with PCDD/Fs content. The pollutants analysed were found to be significantly reduced during the cleaning processes that are generally carried out in recycling companies.