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

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.

Methods
The concentrations of PBDE-209 and PCB released in the different gastric solutions, and in the Procellariiform gastric model (PGM-S or PGM-C) were analysed with GC/MS. The concentrations of BPS released in the different gastric solutions, and in the Procellariiform gastric model (PGM-S or PGM-C) were analysed with LC/MS (for more detail, see Material and Method of the paper). Regarding data processing, the area obtained for each chemical was normalized with the area obtained for the C13- (for PBDE-209 and PCBs) or d8- (for BPS) labelled chemical and according to the RRF obtained from a calibration curve. The concentration of chemicals measured within the solutions was then transformed to the concentration of chemical leached per gram of plastic according to the mass of the plastic sample that was incubated in that same solution. Then the % of chemical released was measured according to the total concentration of additives (10,000 µg/g plastic) or PCBs (1695.6 ng PCB-28/g HDPE, 1088.7 ng PCB-28/g PVC, 1426.8 ng PCB-138/g HDPE and 925.0 ng PCB-138/g PVC) present within or at the surface of the plastic before incubation into the different gastric solutions.