Detection of Benzotriazole UV-stabilizers (BUVSs) in PP pellets from remote island

International Pellet Watch has been analyzing polyethylene (PE) pellets because of their sorptive nature.  However, the present study focused on polypropylene (PP) pellets, because PP is less resistant to weathering and more UV stabilizers could be compounded to PP than PE.  We analyzed 10 benzotriazole UV stabilizers (BUVSs) including UVP, UVPS, UV329, UV9, UV320, UV350, UV326, UV327, UV328, UV234 in 36 PP pellet samples (each sample consists of basically 50 pellets) collected from beaches across the globe (Europe, Africa, middle east, Asia, Oceania, north, middle and south America).  Among them, 17 samples collected from remote islands were included to examine potential of microplastic-mediated long-range transport of the additives.  In the 36 PP pellet samples, 14 samples showed extremely high concentrations of BUVSs over 1000 ng/g (sum of the 10 BUVSs : total BUVSs), while 20 samples showed trace levels of BUVSs below 200 ng/g, as shown in Fig.1 and Fig.2.

The highest one was up to 70000 at Belize. Higher concentrations of BUVSs than sorption-derived maximum concentrations of BUVSs (~4000 ng/g) which were established based on total BUVSs concentrations for PE pellets from world beaches (78 ng/g to 3981 ng/g; Fig.3), were observed for 10 samples.  Thus, the sporadic high concentrations of BUVSs observed in the 10 locations are likely to be derived from additives industrially compounded to the pellets. Interestingly, such sporadic high concentrations of BUVSs were found in pellets even from the remote islands, i.e., Macquarie Island, Hawaii Island, Ogasawara Island, and Hachijo Island.  The concentrations of BUVSs in the remote island were in similar orders of magnitude to those observed in coastal areas where is close to industrial areas such as Sydney or Tokyo.  These means that BUVSs are long-range-transported across the borders for thousands kilometers without drastic desorption or degradation.  The sporadic high concentrations were observed only for single or two BUVS compounds for individual samples. This pattern is consistent with their origin of industrial compounding.  Based on the compound-specific relation of BUVSs concentrations in PP pellets with those in PE pellets, the following compounds were suspected to be derived from industrially-compounded additives, as shown in Fig.4.  They include UV326 at Macquarie Island, Ogasawara Island, and Kenya; UV327 at Hachijo Island, Belize, and Kenya; UV329 at Oahu Island, Malaysia, Japan (Fujisawa); UV328 at Mexico (PunTa Herradura). The present analysis demonstrated that microplastics long-range-transport hydrophobic additives across the borders and the international regulation on plastics and associated chemicals is necessary.