Nainital, a major tourist hub that receives 7-8 lakh visitors annually, showed the highest levels of pollution. The lake’s watershed includes extensive built-up areas, roads and boating activity, all contributing to the introduction of plastic waste. A major scientific contribution of the study is the integration of land use/land cover (LULC) analysis. “We demonstrate that watershed development and built-up areas are the main drivers of microplastic accumulation in lake systems,” noted the lead author.
In contrast, Garudtal Lake, located in a forested region with no permanent population, had the lowest levels of microplastics, although pollution was still detectable. “The presence of microplastics even in Garudtal highlights the role of atmospheric deposition and indirect human impacts, including nearby roads and limited tourism,” said Dr Neelavannan.
The study further noted that “abundance of microplastics was positively associated with watershed development and anthropogenic activities such as waste management, transport and fishing”.
A striking finding is the dominance of microplastic fibers, which make up 84% of all particles, followed by fragments (12%). These fibers are mainly associated with synthetic textiles, released during washing and entering water bodies through sewage and runoff.
“Textile-derived microfibers appear to be a major contributor, particularly in urbanized lake catchments,” the researchers noted.
Microplastics enter these lake systems through multiple pathways, including surface runoff, sewage discharge, atmospheric deposition, and tourism-related activities, making the lakes effective long-term sinks of plastic pollution. Polymer analysis showed that the most common material is polyester (31%), followed by polypropylene (15%), rayon (8%) and polyethylene (6%). The dominance of polyester is of particular concern because of its higher hazard potential.
Most of the particles were in the 1000-5000 micrometer size range (53%), suggesting relatively slow degradation under cold, high-altitude conditions.
While the pollution load index (PLI) indicated relatively low levels of contamination, the polymer hazard index (PHI) exceeded 1000 in many samples, indicating potentially serious ecological risks.
