A study conducted by Delhi University has found that freshwater fish caught in the Yamuna stretch flowing through Delhi contain a much higher amount of microplastic particles than the fish in Haryana, the upper reaches of the Yamuna River.
In the study titled ‘Environmental Factors and Bioaccumulation Pathways of Microplastics in Freshwater Fish in India’s Yamuna River’, these tiny microplastic particles were found in all the fish that were examined.
This study was conducted using 220 freshwater fish belonging to 12 species collected from four locations: Yamuna Nagar and Karnal in Haryana, and Sur Ghat and Sonia Vihar in Delhi. Researchers found a total of 1,678 microplastic particles in these fish. That is, an average of 7.6 particles per fish was detected. This shows that none of the fish included in the study escaped microplastic contamination.
Researchers have identified the Yamuna River, which flows through Delhi, as a zone with high microplastic pollution.
Speaking about this, they said, “These study findings indicate that the Delhi stretch of the Yamuna River is a zone with high microplastic pollution. They also highlight the impact of urban pollution and fish ecology together on the gradual accumulation of microplastic particles in the bodies of living organisms.”
Compared with fish collected from Haryana regions, fish caught in the Sonia Vihar and Sur ghat areas contained the highest levels of microplastic particles. This difference was statistically significant.
Researchers said that the high pollution in the Delhi area is due to untreated sewage, municipal wastewater, textile industry waste, rainwater mixing into the river, and improperly managed plastic waste entering the river.
Among the fish species studied, the highest contamination was found in ‘Tilapia’ fish caught at Sonia Vihar. A total of 436 microplastic particles were detected in 20 fish (an average of 21.8 particles per fish).
264 particles were found in tilapia fish from the Sur bathing ghat area, and 205 particles were found in ‘rohu’ fish from Sonia Vihar (an average of 10.25 particles per fish). The lowest level of contamination was recorded in ‘needle fish’ from the Karnal area. Only 37 particles were detected in 10 fish.
Researchers found the highest number of microplastic particles (751 particles) in the digestive systems of fish. In addition, 605 particles were found in the gills of fish and 322 particles in muscle tissues. This indicates that these particles may spread beyond the digestive system to the edible parts of the fish as well.
Of all the microplastics recovered from the fish, 77.8 percent were fibers or thread-like strands. Broken fragments of larger plastic items were the next most common type. Meanwhile, films, foam, and microbeads made up only a small share. Researchers said this shows that the most commonly found plastic fibers likely reached the river through synthetic clothing, household laundry, textile factories, and wastewater discharges.
Of the recovered microplastics, 44 percent were translucent particles, followed by 19.5 percent blue particles and 16.3 percent black particles.
Moreover, a greater variety of plastic colors and shapes was found in fish collected from Delhi than in fish collected from areas in Haryana. This indicates that the Yamuna River carries a large amount of plastic through Delhi.
Laboratory analysis identified 10 different polymer types, that is, plastic types. Polyethylene, commonly used in plastic bags and packaging, accounted for about 24 percent of the recovered particles, while polypropylene, used in food containers, bottle caps, and packaging, accounted for about 21 percent. Together, these two made up nearly half of the total particles identified.
Using the Polymer Hazard Index, an internationally accepted metric for ranking the environmental risk posed by different types of plastics, researchers classified this pollution as ‘Category 4’. This indicates a high ecological risk or a high potential threat to aquatic ecosystems.
The researchers said these findings underscore the need for continuous monitoring of microplastics in freshwater ecosystems, robust wastewater treatment, and measures to reduce plastic waste entering the Yamuna in order to prevent further pollution of the river and its aquatic life.