Insights into human exposure to microplastics through drinking water: Current state of the science

Drinking water is one of the primary sources of microplastic exposure in humans. However, the extent to which microplastics in drinking water contribute to overall human health remains unclear. The aim of this work is to assess the characteristics of microplastic contamination in bottled and tap water, explore and explain the geographical distribution of the selected studies, evaluate the extent of human exposure to microplastics, and suggest areas for future research. Based on the latest literature from 2018 to 2023 (n = 66), we quantified the constituent profiles of microplastics in drinking water and explored their global distribution heterogeneity. The outcomes showed that microplastics in drinking water mainly comprised polyethylene terephthalate, polyethylene, and polypropylene. Notably, small-sized microplastic fractions (<300 μm) dominated all microplastics, often in the form of fragments and fibers. The average microplastic abundance in tap water was 62.38 particles/L, whereas in bottled water, it was 38.45 particles/L. The abundance of microplastics in drinking water varied globally from 0.0007 particles/L to 6,292 particles/L in Germany. Therefore, common consumers are estimated to ingest 175 particles/capita/day through drinking water. As expected, this review systematically provides scientific evidence for further high-quality research using standardized methods to increase the knowledge of microplastic exposure to humans through drinking water.