Microplastics in water, from treatment process to drinking water: analytical methods and potential health effects

Aim: The commonly used analytical methods for microplastic (MPs) detection in drinking water and the threat of MP pollution in water intended for human consumption to human beings are presented through a systematic review. Furthermore, MP occurrence, transport, and fate from raw to treated drinking water, tap water, and bottled water, as well as the possible health impacts of MPs on human beings, are also evaluated. Methods: Systematic review included articles published in scientific journals that contain specific keywords in the title and were searched in Web of Science (WOS) and Scopus. The literature was selected and extracted by two reviewers based on the PRISMA-A guidelines, which recommend including 57 items. Results: The experimental studies pointed out that sampling is performed using grab or reduced samples, and sample treatment involves mostly oxidation with hydrogen peroxide and density separation. The minimum sample size obtainable in the extraction and the maximum density of the polymer separable from the matrix provided different results. Clearly, the determination of MPs involves the simultaneous application of several analytical techniques, including optical, fluorescence, and electronic microscopies, µFTIR, µ-Raman, and pyrolysis gas chromatography-mass spectrometry. The determination technique also provides different results according to the sensitivity as well as the minimum size determinable. These studies are mostly devoted to establishing the occurrence, transport, and fate within the supply network, the efficiency in removal of MPs from drinking water by treatment plants, and the risk to humans. The MP concentration in drinking water reservoirs is highly variable. However, tap water always presents lower concentrations of MPs than the water that enters the drinking water treatment plants because the different treatments are efficient at removing MPs. Although it has not been fully demonstrated that MPs are toxic to humans, the effects point to oxidative stress, gastrointestinal irritation, microbiome irregularities, and changes in lipid metabolism. Conclusion: Analytical methods present some common features as a first step towards harmonization. However, it is still unknown whether the analytical methods could influence the disparity of the results. The MP concentration in drinking water is low in comparison to other types of water. MPs are not exempt from hazards to human health.