Microplastics, Polycyclic Aromatic Hydrocarbons, and Heavy Metals in Milk: Analyses and Induced Health Risk Assessment

Abstract

The current study aims to develop isolation protocols for several contaminants of emerging concern (i.e., microplastics (MPs), polycyclic aromatic hydrocarbons (PAHs), and heavy metals (HMs)) from different commercial brands and raw milk samples and also to quantify and characterize the risks of these contaminants pose to human health. The quantification, shape, color, and chemical composition of MPs were achieved using optical microscopy, micro-Fourier transform infrared spectroscopy, and scanning electron microscopy coupled with energy-dispersive spectroscopy. Based on the MP dimensions highlighted by the aforementioned techniques, it can be stated that their length ranges between tens of micrometers and a few centimeters; plus, the thickness in some cases reaches more than 15 µm, and the structure of the MPs can be mostly described as a fibriform with a glossy/matte aspect. The polymeric structures identified were polyamides, poly(methyl methacrylate), polyurethane, polyester, and polyethylene. Chemical investigations (PAHs and HMs concentrations) were performed by high-performance liquid chromatography with fluorescence detection and inductively coupled plasma mass spectrometry, respectively. The pollution load index (1.091–7.676) and daily intake of MPs for adults (0.021–1.061 n·kg−1·d−1) and children (0.089–4.420 n·kg−1·d−1) were calculated. It can be concluded that the presence of MPs in milk supports the hypothesis that microplastics can act as carriers for other contaminants (HMs and PAHs), thus increasing the threat to health.