Study highlights threat posed by microplastics in Coimbatore tanks

A recently published study has highlighted that tanks in Coimbatore city face potential threat from microplastics pollution, posing ecological risks to freshwater organisms and possible implications on human health.

S. Raja, Assistant Professor with the Department of Zoology at Kongunadu Arts and Science College and Ephsy K. Davis, a research scholar, assessed the abundance, distribution, and characteristics of microplastics in surface water and sediment samples collected in 2018-2019 from Kumaraswamy tank, Ukkadam Big tank, Kuruchi tank, Singanallur tank and Sulur tank for the study — ‘The Seasonal variation and distribution of microplastics in surface water and sediments of Coimbatore Lakes, India’, published in the journal Gondwana Research.

As per the results, microplastic concentrations were high in the five tanks particularly in those that stood close to the terrestrial zone. According to the researchers, this could be due to the transfer of microplastics into the lake through wind, rain or direct dumping. Spatial distribution patterns indicated that tanks receiving urban run-off, domestic wastewater inflow, and inputs from fishing and recreational activities exhibited higher microplastic concentrations. Discarded fishing gear were found during field observations around the tanks. It was also found that strong winds facilitate the transport of terrestrial plastic waste into tanks. Overflowing waste bins near a tank led to direct dumping of plastic waste into the waterbody. Lower water levels and reduced rainfall in summer resulted in less turbulence that allow microplastics to settle in tank sediments. 

The study identified PE group, PET and PP as the major microplastic constituents in the Coimbatore tanks. Microplastic compositional analysis identified PET, PP, LLDPE and HDPE with the last two accounting for the majority of the polymers detected, consistent with their common use in packaging materials. Among them, LLDPE microplastics were more numerous in water and sediment samples from the five tanks. 

According to the researchers, the predominance of LLDPE microplastics is of particular ecological concern, as it has been proved to exert significant toxic effects on freshwater organisms. A previous study by the researchers on catla fish (Catla catla) had showed that exposure to virgin LLDPE microplastics induced pronounced adverse effects on fish growth, behaviour, antioxidant defence mechanisms, and haematological health. 

“As fishing is happening in some of the tanks in Coimbatore, there is a higher chance of microplastics being present in fishes caught from these waterbodies. Government and local bodies should consider taking measures to prevent pollution caused by microplastics in waterbodies,” said Mr. Raja.