An optimized method for the preliminary detection of Microplastics in the Indoor Environment

Abstract

Objective: Microplastics (MPs) are plastic particles with sizes between 100 nm and 5 mm, regarded as emerging contaminants and responsible for multiple deleterious effects on human health. Due to MPs ubiquity, humans are continuously exposed. However, exposure dosimetry is very rarely performed, particularly for the indoor environment. This work describes a simple protocol to evaluate the presence of MPs in the indoor environment. Methods: Passive dust samples were collected in two divisions (kitchen and bedroom) of the same house during one-week periods. Active dust samples were retrieved from the vacuum cleaner bag. Different methods for the extraction of MPs were tested, including the combination of density separation with sodium chloride and digestion with hydrogen peroxide. Since no standard protocol for MPs quantification in dust samples was available, the amount of dust to be used in the analysis was also optimized. The MPs were then visualized and identified by confocal microscopy after Nile Red staining. Results: For passive samples, only the oxidative digestion of the lipids content with H2O2 is necessary. For active samples, it is necessary to perform a density separation with NaCl prior to oxidative digestion. Overall, the results from the passive dust samples revealed that the bedroom exhibited a higher number of fibers than the kitchen and that the highest fluorescence intensity was also registered in the bedroom samples. Concerning the active samples, the optimization of the amount of dust to be analyzed indicated that a minimum of 0.5 g of the 63 µm dust fraction should be used. Conclusions: Nile Red visualization technique proved to be efficient in MPs detection and quantification. However, it cannot discern the composition of different MPs present in a sample. Hence, this technique should be used as a preliminary approach to confirm the existence/non-existence of MPs.