High levels of microplastic and nanoplastic contamination in birds from remote Himalayan forests

The Himalayas are a biodiversity hotspot with high species richness and endemism. Despite its remoteness, substantial microplastic pollution has been observed in waterways and snow sediment of Mt. Everest. It is unclear, however, if and how microplastic (MP) and nanoplastic (NP) contamination is entering food webs in the region, and this study addresses this gap by quantifying and characterizing MP and NP contamination in 46 birds inhabiting Himalayan forests. Using laser direct infrared (LDIR) spectroscopy and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), We found 28 MP types in the intestines of 42 bird species and 4 NP types in 8 species. We found that MP abundance ranged from 9.33 to 2035.97 particles/g of sample weight, with particles predominantly 20-100 μm in size and mainly identifying as pellets and films. Additionally, bird species exhibited varying levels of plastic contamination due to differences in their morphological and ecological traits, with smaller, insectivorous and adult birds exhibited higher MP loads. The polymer hazard index for both MPs and NPs indicated that most species that were sampled fell into a hazard level III or IV. These results raise serious environmental and conservation concerns about the Anthropocene pollution, and future studies should focus on the long-term physiological and health effects of plastic pollution, as well as its trophic transfer mechanisms, in Himalayan flora and fauna.