Nanoplastics (NPs) and microplastics (MPs) are an emerging threat to global health. They negatively impact ecosystems and many physiological processes, causing alterations in xenobiotic metabolism, nutrient uptake, energy metabolism, or cytotoxicity. In humans, we are beginning to analyze these plastics for the mechanisms by which they enter the organism, accumulate, and diffuse as well as for their pathogenic potential. NP accumulation has been demonstrated in human tissues, such as blood or placenta, while in others it remains largely unstudied. In this work, we detected NP accumulation in bronchoalveolar lavage fluids (BALFs), cerebrospinal fluids (CSFs), lymph nodes (LNs), urine, pleural fluids (PFs), ascitic fluids (AFs), and peripheral blood (PB) by combining fluorescence and nanocytometry techniques. NP analysis was compared with two strains of mice, and the results support that inhalation is the main route of NP accumulation.