Dynamics of leaching of POPs and additives from plastic in a Procellariiform gastric model: Diet- and polymer-dependent effects and implications for long-term exposure

Abstract

Procellariiform seabirds are known to have high rates of plastic ingestion. We investigated the bioaccessibility of plastic-associated chemicals [plastic additives and sorbed persistent organic pollutants (POPs)] leached from plastic over time using an in vitro Procellariiform gastric model. High-density polyethylene (HDPE) and polyvinyl chloride (PVC), commonly ingested by Procellariiform seabirds, were manufactured with one additive [decabrominated diphenyl ether (PBDE-209) or bisphenol S (BPS)]. HDPE and PVC added with PBDE-209 were additionally incubated in salt water with 2,4,4'-trichloro-1,1'-biphenyl (PCB-28) and 2,2',3,4,4',5'-hexachlorobiphenyl (PCB-138) to simulate sorption of POPs on plastic in the marine environment. Our results indicate that the type of plastic (nature of polymer and additive), presence of food (i.e., lipids and proteins) and gastric secretions (i.e., pepsin) influence the leaching of chemicals in a seabird. In addition, 100% of the sorbed POPs were leached from the plastic within 100 hours, while only 2-5% of the additives were leached from the matrix within 100 hours, suggesting that the remaining 95% of the additives could continue to be leached. Overall, our study illustrates how plastic type, diet and plastic retention time can influence a Procellariform's exposure risk to plastic-associated chemicals.

Fig 1. Experimental design.

Two HDPE and PVC plastic plates were supplemented with decabrominated diphenyl ether (PBDE-209) or bisphenol S (BPS) at a concentration of 1% (w/w). Plastic plates were cut in 5 mm x 5 mm x 1 mm square pieces. A total of 300 pieces of each polymer with 1% PBDE-209 were incubated in 100 ml of salt water under agitation (150 rpm; RT; in the dark) for three weeks with polychlorinated biphenyl -28 and -138 (PCB-28 and PCB-138). To study the influence of lipids, enzymes, proteins and acidity, ten plastic pieces (HDPE or PVC) containing either 1% BPS or 1% PBDE-209 + PCBs-28 and -138 were exposed to either (i) salmon (ii) calanus oil, (iii) an acidic albumin-pepsin solution (iv) an acidic pepsin solution or (v) acidic water for 20 hours at 38°C. Hexane and milli-Q water were used as controls. To study the influence of contact time on the release of chemicals, 10 plastic pieces containing either 1% BPS or 1% PBDE-209 + PCB-28 and -138 were incubated in the Procellariiform gastric model (PGM), containing an acidic albumin-pepsin solution mixed either with salmon oil or calanus oil for 100 hours. This gastric solution was replaced every 20 hours. Controls of water mixed with hexane were run in parallel.

Fig 2

Percentage of plastic additives (A) and PCBs (B) released from HDPE and PVC in different solutions after 20h. HDPE and PVC pieces with 1% PBDE-209 + PCB-28 and -138 or HDPE and PVC pieces with 1% BPS were leached in hexane, salmon oil, calanus oil, an aqueous digestive solution made of albumin, pepsin, HCl and water (“Acid/pep/alb solution”), an acidic pepsin solution (“Acid/pep solution”), acidic water and water for 20h at 38°C (800 rpm; n = 3). Panel A) the concentrations of additives (PBDE-209 in black and BPS in white) leached from HDPE and PVC. Panel B) the concentrations of PCBs (PCB-28 in black and PCB-138 in white) leached from HDPE and PVC. Values with different uppercase letters (A, B, C, D, E, F for PBDE-209 or PCB-28) or lowercase letters (a, b, c, d, e, f for BPS or PCB-138) show significant differences between treatments (p-val < 0.05). Asterisk (*) (PBDE-209 or PCB-28) and pound sign (#) (BPS or PCB-138) depict significant differences between polymers for each chemical and treatment (p-val < 0.05). Error bars represent standard deviation, n = 3.

Fig 3. Percentage of plastic additives and PCBs released from HDPE and PVC in salmon or calanus gastric fluid over time.

HDPE and PVC pieces with 1% PBDE-209 + PCB-28 and -138 or HDPE and PVC pieces with 1% BPS were leached in the full PGM containing an acidic albumin-pepsin solution (pH 3) mixed with salmon oil (PGM-S) or calanus oil (PGM-C) at 38°C for 100h (800 rpm; n = 3). The mixture was renewed every 20h. Aqueous and lipidic phases were analyzed separately and concentrations were summed to give the total concentration leached in the digestive mixtures. Concentrations were below the detection limit in the aqueous phases for PBDE-209 and PCBs. Panel A and B) the percentage of PBDE-209 and BPS leached from HDPE and PVC. Panel C and D) the percentage of PCB-28 and PCB-138 desorbed from HDPE and PVC. Values with different uppercase letters (A, B, C, D, E) and lowercase (a, b, c, d, e) show significant differences in the percentage of chemicals released (additives or PCBs) over time for each treatment (p-val < 0.05). Asterisk symbols (*) show significant differences between salmon and calanus gastric fluid for each chemical at each timepoint (p-val < 0.05). Error bars represent standard deviation, n = 3.