Human Activities Increased Microplastics Contamination in the Himalaya Mountains

Microplastic pollution is an emerging environmental concern, and has been found in remote regions, including the high Himalaya mountains. However, the abundance and sources of microplastics in the region are not well documented. This research investigated the abundance, types, and potential sources of microplastics in the Sagarmatha National Park (SNP), a rural and sparsely populated region of Nepal on the southern side of the Himalaya mountains. Water samples were collected from streams and tributaries in SNP in May of 2022. The average microplastic concentration among all samples was 2.0 ± 1.7 pieces/L, similar to that of water samples collected in other high mountain areas and is in the lower range of that found in water samples across the globe. Microplastic abundance is higher in water samples collected near settlements than in streams far from human settlements, indicating the impact of human activities. The presence of microplastics in all samples, including headwaters immediately beneath glaciers, illustrates the widespread distribution of microplastics and suggests the potential for airborne sources. While the concentration of microplastics does not change dramatically from upstream tributaries to downstream rivers, the total load of microplastics increases due to higher discharge downstream. This research demonstrates the anthropogenic and air-borne influences on microplastics contamination on the southern side of the Himalayan range and contributes to filling the data gaps towards a better understanding of the global fate and transport of microplastics.