Relative Importance of Microplastics as Vectors of Hydrophobic Organic Chemicals to Marine Fish and Seabirds

Microplastics are suspected to deliver hydrophobic organic chemicals (HOCs) to marine organisms as it has high sorption capacity towards HOCs. In this study, the roles of microplastics ingestion in the overall uptake of HOCs by fish and seabird were evaluated quantitatively using mass-balance models including their biological features and possible HOCs intake routes (i.e., air, seawater, food, and microplastics). HOCs having wide range of partitioning properties (n = 203) were chosen and the contribution of microplastics was compared with other intake routes and further visualized using 2-dimensional contour diagrams. For most of the non-additives (n = 170), the contribution of microplastics was observed to be negligible (< 5%), as compared to the other intake routes. On the other hand, plastic-bound intake can be important for plastic additives (n = 33) with high log octanol–water partition constant (log Kow) when the fugacity in microplastics is significantly greater than in other media, indicating the importance of further studies on leaching of hydrophobic additives under various conditions.