Biomonitoring of microplastics in saliva and hands of young children in kindergartens: identification, quantification, and exposure assessment.

Microplastics (MPs), small plastic particles increasingly accumulating in the environment and encountered by humans, pose a particular risk to children due to their heightened vulnerability compared to adults. This study pioneered biological monitoring of MPs and investigated the presence and potential exposure of MPs in the saliva and on the hands of young children attending kindergartens in Kerman, Iran. A sample of 100 children aged 3 to 6 years was randomly selected from five kindergartens across five districts (1, 2, 3, 4, and 5). Following sample digestion and filtration, MPs were identified and classified under an optical microscope. Micro-Raman spectroscopy was employed to analyze the composition of MPs. The study identified a total of 716 MPs, with the majority (299, 41.7%) being black. The number of microplastics on hands and saliva increased by 55.9% and 11.8%, respectively, after entering kindergarten. Most MPs observed were smaller than 100 µm. Micro-Raman spectroscopy analysis of six fibers revealed four composed of polystyrene (PS), one of nylon, and one of low-density polyethylene (LDPE). The average number of MPs on children's hands upon kindergarten entry was 1.85 ± 1.39, increasing significantly to 4.2 ± 3.05 after kindergarten entry (p-value < 0.0001). This research highlighted the significant role of kindergarten flooring in determining MPs' presence in children. Specifically, the presence of tatami flooring correlated with higher MPs' levels.