Factors affecting microplastic pollution of sandboxes in urban residential areas: Simple methodology for quality control in the context of potential exposure assessment for children.

Occurrence of microplastics in the environment is well studied, but our knowledge of their distribution in specific locations, such as the sandboxes, which are integral parts of popular playgrounds for children, is limited. Pioneering research on the factors affecting the microplastic pollution of sandboxes in urban residential areas was conducted within three estates in Kielce, Poland. Sand samples (Σ27) were collected from nine sandboxes and examined for the presence of microplastics, using a simple quality control methodology proposed by the authors. Microplastics were found in each sample and their contents ranged from 60 to 5,540 items/kg of sand. Fragments and fibers were the most prevalent types of microplastics in the samples. They contributed to approximately 95% of all microplastics found. Transparent fibers were the most abundant among fibers (63%) and red particles (57%) among fragments. A strong, positive, and significant correlation (rSpearman = 0.90) was found between the number of microplastic items and the location of sandboxes (above sea level). There was no correlation between the population density of the estates (rSpearman  =  0.03), the distance of the estates from the center (rSpearman  =  0.02), and the distance of the estates from main roads (rSpearman  =  0.43). Considering that sandboxes can be a potential source of microplastics for children, and assuming that sand ingestion by children is similar to the estimated daily soil ingestion rate, our results indicate that the number of microplastics ingested could be 1,106. Inhalation, dermal transport, and ingestion of microplastic particles from sandboxes pose a potential threat to children's health. However, more research is needed to better understand the health risks associated with this source of microplastics.