Release of chemical additives and potentially toxic elements from plastics under ambient outdoor environmental conditions

Plastic pollution of water environments remains a widespread environmental concern. Previous studies of release of additives from plastics either utilised microplastics particles (<5 mm) or were conducted under artificial conditions, such as microwaving, boiling, or UV exposure. However, in reality, plastics are disposed of as large items and seen in the natural environment for long periods. In this study, we employed natural outdoor environmental conditions to investigate and quantify the release of specific organic chemical additives (phthalates, phenolic compounds and polybrominated diphenyl ethers, PBDEs) from large plastic pieces of seven commercial polymers. The release of potentially toxic elements (PTEs - As, Cd, Cr, Cu, Fe, Pb, Sb, Sn and Zn) was also assessed. The results revealed the plastic polymers that were responsible for releasing the different additive contaminants under natural conditions. Polystyrene (PS) released the greatest variety and highest concentration of all the organic chemicals. Bis (2-ethyhexyl) phthalate (BEHP) at 26.9 mg/L, BDE-153 at 11.1 mg/L, and bisphenol-A (BPA) at 0.85 mg/L, were the dominant phthalate, PBDE and phenolic compounds released by PS plastic. Different patterns of release of the PTEs were also observed from the plastics, with high-density polyethylene (HDPE) leaching out the highest amount of PTEs. This was evidenced by Sn and Fe concentrations, which were measured in the HDPE leachate at up to 1.77 and 2.11 mg/L, respectively. This study provides realistic understanding of the characteristics of leachates from plastic polymers, and will be invaluable in curbing chemical pollution of the aquatic environment.