Pollutants Bioavailability and Toxicological Risk from Microplastics

Abstract

Microplastics (MPs, <5 mm in size) are considered to be one of today’s major environmental problems. They are a ubiquitous persistent pollutant group that has reached into all parts of the environment - from the highest mountain tops to the lowest depths of the ocean. In their production, plastics have added to them a number of chemical additives in the form of plasticizers, colorants, fillers, and stabilizers, some of which with known toxicological effects to biota. When released into nature, MPs are also likely to encounter and sorb to their surfaces a variety of established pollutants including hydrophobic organic contaminants, trace metals, and pharmaceuticals. Importantly, MPs have been shown to be readily ingested by a wide range of organisms and it is this combination of biotic ingestion and chemical association that gives credence to the notion that MPs may impact the bioavailability and toxicity of both endogenous and exogenous pollutants. This chapter provides an overview of the literature that has examined the role of MPs as chemical carriers to biota, with particular focus on aquatic organisms. The influence and interactions of MPs with endogenous and exogenous chemicals are reviewed before a more critical view of the relative importance of MPs as pathway for chemical transfer is provided. Lastly, the current state of the literature is placed into context of the needs of risk assessment highlighting the challenges to assessing the risk of MPs as chemical vehicles.