E-Waste Recycling Emits Large Quantities of Emerging Aromatic Amines and Organophosphites: A Poorly Recognized Source for Another Two Classes of Synthetic Antioxidants

Our previous work demonstrated that massive emissions of hindered phenol antioxidants and sulfur-containing antioxidants from e-waste recycling; however, it remains unclear whether e-waste recycling also results in the emission of substantial quantities of amine antioxidants (AAs) and organophosphite antioxidants (OPAs), another two major classes of under-researched antioxidants. In this study, we continued to screen the previously studied e-waste dusts for a broad range of 21 AAs, two p-phenylenediamine-derived quinones, and 15 OPAs. All 21 AAs and 12 out of the 15 OPAs were detected in the samples, with the total concentrations ranging from 511 to 10,600 ng/g for AAs and from 155 to 33,200 ng/g for OPAs. Among the detected chemicals, nine were identified for the first time in the environment. More importantly, N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine-quinone (6PPD-quinone), the causal toxicant of acute mortality in coho salmon, was pervasively detected with greater environmental abundance (median: 375 ng/g) than its parent chemical 6PPD (median: 113 ng/g), demonstrating that e-waste as another source of ubiquitous 6PPD-quinone in addition to tire rubber. Waste wires, cables, and electronic plastics were identified as the main sources for e-waste-derived AAs and OPAs. Our work highlights a large group of antioxidant chemicals, including their transformation products, as emerging e-waste pollutants that require more attention.