Plastic as a Carrier of POPs to Aquatic Organisms: A Model Analysis

TLDR

It has been hypothesized that persistent organic pollutants in microplastic may pose a risk to aquatic organisms. The study develops and analyzes a conceptual model simulating how plastic affects POP bioaccumulation. The model incorporates POP dilution, carrier, and cleaning processes, and evaluates scenarios with polystyrene, polyethylene, nanosized plastic, and open marine systems. Model results indicate that low‑affinity plastics like polystyrene marginally reduce bioaccumulation, while higher‑affinity plastics such as polyethylene produce more pronounced dilution, carrier, and cleaning effects, yet overall differences are too small to impact risk assessment.

Abstract

It has been hypothesized that persistent organic pollutants (POPs) in microplastic may pose a risk to aquatic organisms. Here we develop and analyze a conceptual model that simulates the effects of plastic on bioaccumulation of POPs. The model accounts for dilution of exposure concentration by sorption of POPs to plastic (POP "dilution"), increased bioaccumulation by ingestion of plastic-containing POPs ("carrier"), and decreased bioaccumulation by ingestion of clean plastic ("cleaning"). Dilution of exposure concentration by sorption of POPs to plastic (POP "dilution"). The model is parametrized for the lugworm Arenicola marina and evaluated against recently published bioaccumulation data for this species from laboratory bioassays with polystyrene microplastic. Further scenarios include polyethylene microplastic, nanosized plastic, and open marine systems. Model analysis shows that plastic with low affinity for POPs such as polystyrene will have a marginal decreasing effect on bioaccumulation, governed by dilution. For stronger sorbents such as polyethylene, the dilution, carrier, and cleaning mechanism are more substantial. In closed laboratory bioassay systems, dilution and cleaning dominate, leading to decreased bioaccumulation. Also in open marine systems a decrease is predicted due to a cleaning mechanism that counteracts biomagnification. However, the differences are considered too small to be relevant from a risk assessment perspective.