Interaction of Environmental Pollutants with Microplastics: A Critical Review of Sorption Factors, Bioaccumulation and Ecotoxicological Effects

Abstract

Microplastics have become one of the leading environmental threats due to their persistence, ubiquity and intrinsic toxic potential. The potential harm that microplastics impose on ecosystems varies from direct effects (i.e., entanglement and ingestion) to their ability to sorb a diversity of environmental pollutants (e.g., heavy metals, persistent organic compounds or pharmaceuticals). Therefore, the toxicological assessment of the combined effects of microplastics and sorbed pollutants can produce in biota is one of the hottest topics on the environmental toxicology field. This review aims to clarify the main impacts that this interaction could have on ecosystems by (1) highlighting the principal factors that influence the microplastics sorption capacities; (2) discussing the potential scenarios in which microplastics may have an essential role on the bioaccumulation and transfer of chemicals; and (3) reviewing the recently published studies describing toxicological effects caused by the combination of microplastics and their sorbed chemicals. Finally, a discussion regarding the need for a new generation of toxicological studies is presented.

Keywords: bioaccumulation; environmental pollutants; microplastics; sorption; toxicological studies.

Figure 1

(a) Global plastic production since the 1950s together with an estimate of the global plastic production until 2050. (b) Estimated percentage of primary microplastics (MPs) that ends up into oceans respect the total MPs materials released into marine ecosystems every year. The percentage of land-based and marine-based contributions are also presented. (c) Most important land-based and marine-based sources of primary MPs released into marine ecosystems.

Figure 2

Summary of the main factors influencing the interaction between MPs and chemical pollutants.

Figure 3

Standard isotherm models used in the study of sorption/desorption of environmental pollutants in MPs.

Figure 4

Overview of the main weathering processes and alterations produced on large plastic debris or primary MPs to form secondary MPs on marine environments.

Figure 5

Schematic representation of the three possible bioaccumulation scenarios to assess the role of MPs (blue circles) as vectors of environmental pollutants (red dots) in marine biota (green squares).