Pigment-derived polychlorinated biphenyls in plastic bottle labels from marine plastic debris

Plastics contain various chemicals, including additives and their by-products, some of which are toxic. Although a congener of polychlorinated biphenyls (PCBs), PCB-11-known as a by-product in certain pigments-has been detected in marine plastics, its sources remain unidentified. Here, we conducted a screening analysis for PCBs in 12 plastic bottle labels collected from marine plastic debris and in 4 labels from new commercial products of the same brands, followed by a segmented analysis of different parts with varying pigment compositions to investigate the correlation between PCBs and pigments. PCBs were detected in 6 of the 12 label samples from marine plastic debris. Segmented analysis (n = 17) of the 6 labels revealed that PCB-11 was the dominant congener, and total PCB concentrations ranged from 0.284 to 394 μg/g. PCB levels increased in the order of transparent < white/black < colored parts, and appeared to be associated with yellow pigments. The concentrations were unexpectedly high compared with previous surveys and exceeded the 50 μg/g limit applied in regulations such as the Stockholm Convention. We therefore identified pigments as sources of PCB-11 in marine plastics and found significant contamination in pigmented products. The production dates of the labels suggest that the issue of PCB contamination in pigments persists. A more comprehensive investigation of upstream manufacturing processes is needed to identify the origins of the PCB-11, and the environmental and human health impacts of this pollution should be quantitatively assessed.