Microplastics as a Vector for Exposure to Hydrophobic Organic Chemicals in Fish: A Comparison of Two Polymers and Silica Particles Spiked With Three Model Compounds

Giedrė Ašmonaitė,Emelie Westberg,Malin Tivefälth,Bethanie Carney Almroth,Thomas Backhaus,Jörgen Magnér

doi:10.3389/fenvs.2020.00087

Abstract

The role of microplastics as chemical vectors delivering environmental contaminants into biota has been proposed, but their environmental relevance remains an issue of a debate. In this paper we compared the propensity and relative importance of synthetic polymer microparticles (glassy polystyrene (PS) and rubbery polyethylene (PE)) and silica glass particles (SG) to act as vectors for hydrophobic organic chemicals (HOCs) into fish after ingestion. Particles were spiked with three HOCs (17α-ethinylestradiol, chlorpyrifos and benzo(α)pyrene), which differ in hydrophobicity and induce well-known biomarker responses. Three-spined stickleback were exposed to 8 different diets: control diets (1), diets with non-spiked particles (2-4), diets containing a mixture of particles spiked with 3 model contaminants (5-7) and, finally, diets loaded with only the chemical mixture (8), for 14 days. Chemical sorption onto the particles was quantified and chemical transfer into the fish was investigated via biomarkers (CYP1a, ERα, VTG and AChE) in fish intestine, liver and brain and quantification of HOCs in fish muscle. Results demonstrated particle-mediated chemical transfer of moderately hydrophobic contaminants into fish. While PS and PE particles mediated higher chemical transfer and tissue accumulation of 17α-ethinylestradiol and chlorpyrifos than SG, the overall chemical transfer was found to be very low. The present work suggested that chemical sorption, desorption and subsequent transfer of chemicals in vivo depends on multiple interconnected factors, including physicochemical properties of particles and contaminants, as well as toxicokinetic and toxicodynamic interactions. The biomarker approach was, however, suboptimal for assessing chemical transfer when addressing particle-associated chemical mixtures.

Highlights

Microplastics (MPs) are widely known to sorb and concentrate hydrophobic organic chemicals (HOCs) from the ambient environment (Mato et al, 2001; Teuten et al, 2007; Rochman et al, 2013a; Prokic et al, 2019)
Mass-based results showed that synthetic plastic polymer particles (PS and PE) absorbed more of CPS and BαP compared to inorganic silica glass particles (SG) (Figure 2A)
In regards to chemical sorption of HOCs on different types of synthetic polymers, we found that the glassy PS particles sorbed more chemicals than rubbery PE particles per mass unit (Figure 2A)

Summary

Introduction

Microplastics (MPs) are widely known to sorb and concentrate hydrophobic organic chemicals (HOCs) from the ambient environment (Mato et al, 2001; Teuten et al, 2007; Rochman et al, 2013a; Prokic et al, 2019). Some experimental data suggest that certain polymers have the ability to sorb and accumulate HOCs to a greater extent than sediments and suspended organic particles (Mato et al, 2001; Teuten et al, 2007; Wang and Wang, 2018), the comparative importance of chemical sorption to synthetic versus natural particulates, and subsequent transfer into organisms, remains relatively unknown. It is important to improve our understanding about the role and relative importance of MP-mediated contaminant transfer, compared to naturally occurring particulates

Methods

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Discussion

Conclusion