Do microplastics mediate the effects of chemicals on aquatic organisms?

Abstract

Microplastics are ubiquitous in both marine and freshwater ecosystems, where they can act as a physical contaminant, as well as interact with chemicals present in the environment. It has been suggested that chemical contaminants can sorb to microplastics, such that microplastics act as a vector for chemicals into aquatic biota and enhance their negative effects. It has been repeatedly suggested that the main factors underpinning the binding of chemicals to microplastics are hydrophobic partitioning and the size of microplastic particles.Therefore, we used the hydrophobicity of chemicals, as log Kow, as well as the size of microplastic particles to conduct a quantitative analysis of published results to evaluate the influence of microplastics on chemical toxicity. We collated data from 39 laboratory studies that assessed the effects of microplastics, chemicals and their combination on several ecotoxicological responses of freshwater and marine organisms. Each chemical was assigned the relevant octanol / water partition coefficient (log KOW) as a measure of its hydrophobicity, and the mean size of microplastics particles used in each study was recorded. We found no effect of log KOW or the size of microplastic particles on the interaction between microplastics and chemicals with regards to any of the relevant ecotoxicological responses (behaviour, growth, survival and cellular) considered in this study. These findings are significant in showing that the effect of microplastics on the toxicity of chemicals is more complex than just considering hydrophobicity of chemicals and size of microplastics. We call for more mechanistic experiments to motivate a robust risk assessment and mitigation of microplastic toxicity in the environment.

Factors Affecting the Adsorption of Heavy Metals by Microplastics and Their Toxic Effects on Fish

“…The adsorption of HMs by MPs in water involves a variety of mechanisms, which can be divided into two categories: physical adsorption and chemical adsorption [ 24 ]. Physical adsorption mainly includes electrostatic interactions and internal and external diffusion, while chemical adsorption mainly involves interaction through complexation and cation-π bonds [ 24 , 25 ]. On the other hand, the HM adsorption mechanism of MPs can include both physical adsorption and chemical adsorption, and it is specific due to the different physical and chemical properties of MPs [ 26 ].…”

Recent Study of Separation and Identification of Micro- and Nanoplastics for Aquatic Products

“…In industrial production, social activities, and daily home life, plastic products and various types of plastic-containing wastes are generated and infiltrate aquatic environments through methods like direct discharge, intentional dumping, wind-driven transport, rainfall erosion, fishing and shipping activities, sewage discharges, and drifting movements [2][3][4][5]. During this process, plastics gradually degrade into tiny particles known as micro-and nanoplastics (MNPs).…”

“…Another critical issue is the lack of a standardized evaluation system. Universally applicable standards for the health and environmental hazard assessment of MNPs are currently absent [2], posing difficulties in data comparison and potentially leading to errors.…”