Microplastics in the indoor environment

Microplastics are plastic particles with sizes between 100 nm and 5 mm, being consideredan emerging class of contaminants with deleterious effects on the environment and human health.Polyethylene (PE), Polyvinyl Chloride (PVC) and polyamide (PA-commonlyknown as nylon) are three of the most common polymers used in buildings and construction, packaging,personal careproducts and clothing. Due to MPs ubiquity in the environment, especiallyindoor, humans are continuously exposed. However, only a few studies regarding the contamination of the indoor environment by microplastics and their effects on health were performed to date. This work intends to develop an integrated strategy to study the microplastics present in the indoor environment and their potentialdeleterious effects.For this, the levels of MPs in airborn and house dust samples were estimated and the cytotoxicity of three different MPs (polyethylene, PVC and polyamide) was evaluated in three cell lines, namely intestinal epithelial cells (Caco-2), hepatocytes (HepG2) and dopaminergic neurons (N27).In addition, and givingthe limitations of currently existing quantification techniques, a new strategy for isolating and purifying MPs from complex samples was developed using two-phase aqueous systems made up of ionic liquids. The results obtained from the analysis of MPs in air and dust samples using sodium chloride (NaCl) density separation and digestion with hydrogen peroxide (H2O2), and subsequent microscopic visualization after Nile Red staining showed that the largest amount of MPs corresponds to samples collected in kitchens. The new procedure developed for sample preparation using ILs generally allowed to extract the MPs from the dust matrix.However, the separation in a single step of the different MPs was not achieved and requires further optimization. Nevertheless, Raman spectroscopy proved to be efficient to identify MPs in house dust samples. The cytotoxicity tests showed that the dopaminergic neuron cell line was the most sensitive to microplastics’ exposure, with polyamide being the least toxic microplastic tested and PE the most toxic. For the tested concentrations (0.01; 0.1; 1; 10; 100; 1000; 2000; 4000 mg.L-1) the toxicity of the three MPs for intestinal epithelial cells and for hepatocytes was reduced, which shows the low toxicity of these MPs when tested in its pure and isolated, that is its native form without the addition of plasticizers, colourants, flame retardants or stabilizers.