Metro station free drinking water fountain- A potential "microplastics hotspot" for human consumption.

Microplastics have become an inevitable component of our environment. Worldwide, free public fountains are common and one of the best sources of drinking water which are being installed with one of the viewpoints of reducing single-use plastics bottle consumption. However, the state of knowledge on how microplastics might be affecting in those free public drinking fountains is unknown. In this study, free drinking water fountains from 42 metro stations in Mexico City were being looked into for the occurrence of microplastics and investigated their shape type, size, abundance, distribution, polymer composition and surface morphology. Microplastics were detected in all the samples analyzed. The results revealed the significant abundance of microplastics ranging from 5 ± 2 to 91 ± 14 L in drinking water with an overall average of 18 ± 7 microplastics L. Transparent fibers (69%) were predominant in the identified microplastics followed by blue (24%) and red colored (7%) fibers. The most frequent microplastics dimensions ranged between 0.1 and 1 mm which is approximately 75% of the total microplastics. Micro-Raman spectroscopy analysis indicated that microplastics contained in drinking water were mainly polyesters (poly (trimethylene terephthalate)) and epoxy resin suggesting the possible contribution of wastewater discharges for microplastics contamination. Thus, this study findings show that free public drinking water fountains are potential microplastics hotspot for human consumption and provide useful references for mitigation measures.