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

Abstract

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.

First Report on the Occurrence of N-(1,3-Dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD) and 6PPD-Quinone as Pervasive Pollutants in Human Urine from South China

“…In this study, the positive concentration correlations observed between 6PPD and 6PPD-Q in urine ( p < 0.01, Figure S3) also suggested some co-exposure pathways. Indeed, 6PPD and 6PPD-Q can be detected simultaneously in various environmental matrices including dust, air, and water; ,,− thus, direct human intake via these contaminated matrices should be responsible for the presence of both 6PPD and 6PPD-Q in urine. In some cases, ,,, the concentration of 6PPD-Q in the environmental matrices was higher than that of 6PPD (Figure S4), which should be an important reason for the higher abundance of 6PPD-Q than 6PPD found in human urine.…”

“…Briefly, 1 mL of thawed urine sample was transferred to a 10 mL glass centrifuge tube and spiked with 20 ng surrogate standard of 13 C 6 -6PPD-Q. After equilibration for 30 min, 0.2 mL of 1 mmol/L glutathione solution was added considering it could suppress potential oxidative transformations of 6PPD during sample preparation . After addition of 0.4 g of NaCl, the sample was extracted with 3 mL acetonitrile by vortexing for 10 min and ultrasonication for 10 min.…”

“…More recently, 6PPD and 6PPD-Q have been found in a variety of environmental matrices, including atmospheric particles, ,− indoor dust, ,, road dust, , playground dust, roadside soil, runoff water, ,, and surface water. − In most cases, 6PPD and 6PPD-Q coexisted in these environmental matrices at comparable concentrations. For instance, Zhang et al demonstrated ubiquitous distributions of 6PPD and 6PPD-Q in fine particulate matters (PM 2.5 ) from six Chinese cities, and the atmospheric concentrations of 6PPD (median 0.9–8.4 pg/m 3 ) were found to be similar to those of 6PPD-Q (median 1.7–6.7 pg/m 3 ) .…”

Screening p-Phenylenediamine Antioxidants, Their Transformation Products, and Industrial Chemical Additives in Crumb Rubber and Elastomeric Consumer Products

“…IPPD showed 14-d LC 50 of 90 μg/L for fathead minnow ( Pimephales promelas ), although the stability of reactive PPD antioxidants throughout these longer term exposures remains unclear. Global reports now document PPD antioxidants and TPs, including the toxic 6PPDQ and quinones generated from other PPDs (PPDQs), ubiquitously in roadway-impacted air, − dust, − soil, and water, ,− with growing concern for the environmental dispersal, fate, and exposure implications of tire tread wear particles (TWPs) and associated chemicals …”

“…PPD antioxidants are additionally used in other rubber and elastomeric products, including pipes, belts, hoses, and footwear. ,,, Both virgin and recycled rubber consumer products are often human proximate, raising concerns over human exposures to PPD antioxidants and toxic TPs, such as 6PPDQ. For example, PPD antioxidants and PPDQs were recently reported in wastewater, house dusts, e-waste dusts, and human urine . 6PPD and 6PPDQ in crumb rubbers were recently shown to be orally bioaccessible using synthetic body fluids. , IPPD has been linked to contact dermatitis in tire rubber workers and people wearing rubber boots .…”