Baseline assessment of microplastic contamination in water, sediment, and biotic compartments of the Indus River at Mianwali, Pakistan

Microplastics are significant contaminants in freshwater ecosystems, yet baseline data for the Indus River are limited. This first comprehensive assessment of MPs across four sampling sites (S1–S4) along the Indus River near Mianwali, analysing water, sediments, fish , and freshwater mussels. A total of 861 particles were detected, confirming a 100% contamination prevalence. Water showed the highest abundance (37.40%), followed by fish gastrointestinal tissues (19.74%), sediments (17.89%), gills (14.40%), and mussels (10.57%). Colour profiling revealed black (31.13%) and red (28.11%) particles were dominant, while green (9.52%), transparent (9.41%), and dark blue (9.30%) were moderate. Morphologically, fibres were excessively dominant (87.85%), followed by fragments (10.82%), indicating strong input from textile effluent, fishing gear abrasion, and domestic wastewater. FTIR confirmed the presence of polyethylene, polypropylene, and polystyrene among others, while SEM showed weathering features such as pits, cracks, and abrasion. MPs in edible aquatic tissues highlights potential food-chain transfer and public health risks. This study establishes baseline dataset for MP contamination in the Indus River, providing a reference for tracking trends and informing regulatory measures. Furthermore, it contributes valuable insights into the MP pollution in a key South Asian river system, supporting management strategies for similar freshwater environments globally.HighlightsRiver bed sediment, water, fish, and mussels are affected by MPs.The levels of MPs decreased in the order water > fish > sediments > mussels.Fibres and fragments were the most common, followed by films and beads.Brightly coloured MPs, including blue, black, and red, were the main types found in all samples.First comprehensive MP assessment in the Indus River near Mianwali.