Estrogenic activity of plastic nanoparticle mixtures under in vitro settings

Abstract

The plastic value chain, a central part of modern living, causes environmental pollution and bioaccumulation of plastic nanoparticles (PNPs). Their ubiquitous presence in different environmental and biological compartments has become a serious threat to human health and ecosystems. Frequently used plastic materials such as polypropylene (PP), polystyrene (PS) and polyethylene (PE) have been detected in the form of PNPs in the food chain, soil, water and air, as well as in human feces and blood. In this study, we aimed to provide novel insights into the endocrine disrupting properties of PNPs using in vitro estrogen receptor (ER) transactivation assay. The effects of PP-NPs, PE-NPs and PS-NPs and their mixture on the T47D-KBluc cell line stably transfected with luciferase as a reporter enzyme were evaluated by means of cytotoxicity, cellular uptake and ER activation. The tested dose range for PNPs was 0.001–10 mg L⁻¹. Both cellular uptake and cytotoxicity for all PNPs were found to be dose-dependent. Only the highest dose of PP-NPs and PE-NPs induced apoptosis and cell death, while PS-NPs were not cytotoxic in the tested dose range. For tested concentrations, PP-NPs and PE-NPs showed significant agonistic activity on the ER, while PS-NPs cannot be considered ER active. When applied as a mixture, PNPs demonstrated additive toxicity effects compared to the effect of each individual PNP. Additivity was also observed for the ER agonistic effect of the PNP mixture according to the benchmark dose-addition modelling approach. This study provides missing science-based evidence on endocrine disrupting effects of PE-NPs, PP-NPs, PS-NPs and their mixtures and highlights the importance of considering unintentional, aggregate and combined exposure to different PNPs in risk management.