Exploratory Study of Microplastics in the Eastern Himalayas of Nepal

There is currently a lack of data on the occurrence of microplastics in the river systems of the Himalaya Mountains. This exploratory study looks at the occurrence of plastics in the range of ≤5mm to ≥250µm in three one-liter surface water samples taken from the Dud Khosi, Sagarmatha National Park, Nepal.

The samples and various blanks were filtered using MF-Millipore™ 0.45 µm pore size mixed cellulose acetate membrane filters. Steps were taken with respect to controlling contamination of samples. A total of four blanks were created to assess possible contamination during the filtering process. An additional two filters were left exposed to the lab environment. Visual identification of microplastics was done using a stereo microscope at 45x magnification. Identification was made based on the Marine & Environmental Institute's Guide to Microplastic Identification.

Microplastics above 250µm were not found in surface samples collected from the Sagarmatha National Park. However, there were microplastics visually identified below the 250μm limit. Identification of microplastics smaller than 500μm is problematic due to significantly higher rates of misidentification. The presence of microplastics suggests that further studies, focusing on the microplastics under 250μm, are warranted.

Microplastics is a growing concern as a contaminant due to its pervasive existence across the Earth. There is a need to establish a baseline for environmental concentration of microplastics, as they can vary due to geographical location. Once this baseline has been established future mitigation, if needed, can be discussed. The results of this exploratory study provide the initial data towards establishing a baseline for future work.