CHENNAI: Tamil Nadu’s coastline has emerged as one of the most severely affected microplastic pollution zones in the Bay of Bengal, with Chennai’s Muttukadu backwaters and the Thoothukudi coast recording some of the highest contamination levels in the sediments and water documented in a major regional study.
The study, titled 'Characterisation, Risk, and Pathway of Microplastics in Coastal Areas of the Bay of Bengal: A Systematic Review and Quantitative Synthesis', identified the Muttukadu estuary near Chennai as the most polluted sediment zone in the Bay of Bengal region, while the Thoothukudi coast recorded the highest concentration of floating microplastics in seawater samples. For the study, water and sediment samples were collected from 26 locations along the Bay of Bengal coast.
Researchers said the findings exposed the growing environmental burden caused by unmanaged urban waste, tourism activity, riverine plastic discharge, fishing operations and maritime traffic along the Tamil Nadu coast.
According to the study, sediment samples collected from the Muttukadu backwaters showed a peak concentration of 815 microplastic particles per kilogram, the highest recorded among all coastal sediment sites examined across the Bay of Bengal.
The study attributed the contamination mainly to land-based plastic waste entering the estuary through urban runoff, tourism-related littering and river systems carrying discarded packaging materials and household plastic debris from nearby settlements.
Situated along East Coast Road (ECR), south of Chennai, Muttukadu has witnessed rapid urban expansion and increasing tourist footfall over the last decade, with environmentalists repeatedly warning about unchecked waste disposal into the fragile backwater ecosystem.
Researchers noted that particles smaller than one millimetre dominated the samples, indicating prolonged degradation and fragmentation of larger plastic waste already accumulated in the ecosystem.
Transparent and white plastic fragments and fibres were the most common forms detected in both water and sediment samples. These were chemically identified as Polyethylene (PE) and Polypropylene (PP), polymers widely used in single-use plastic bags, food packaging, disposable containers and synthetic fishing materials.
The report stated that the prevalence of such polymers directly reflected the large-scale consumption and improper disposal of consumer plastics in coastal urban regions.
While Muttukadu topped the sediment pollution category, the Thoothukudi coast recorded the highest microplastic concentration in water samples, reaching 2,63,000 particles per cubic metre.
Researchers linked the unusually high concentration along the Thoothukudi coast to intense commercial shipping activity, fishing harbour operations, industrial discharge and maritime transport routes concentrated around the southern Tamil Nadu coastline.
The synthesis, based on peer-reviewed studies conducted over the past decade, examined microplastic pollution across beaches, estuaries, islands and coastal waters throughout the Bay of Bengal region.
The study also highlighted the transboundary nature of marine plastic contamination, warning that large river systems flowing into the Bay of Bengal continued to transport untreated solid waste from inland urban centres directly into coastal waters.
Apart from riverine discharge, the researchers identified tourism, municipal waste mismanagement, fishing activities and atmospheric deposition of microfibres as major pathways contributing to microplastic accumulation in Tamil Nadu’s marine ecosystems.
Using internationally recognised pollution assessment methods, including the Pollution Load Index (PLI), Polymer Hazard Index (PHI) and Ecological Risk Index (ERI), the researchers found that more than 75% of coastal water sites and 83% of sediment sites across the Bay of Bengal exceeded extreme pollution thresholds.
The study warned that such elevated contamination levels posed serious ecological threats to marine biodiversity and could lead to trophic transfer of plastic particles through the aquatic food chain.
Scientists cautioned that prolonged exposure to microplastics could eventually affect commercially important fish species and raise potential human health concerns through seafood consumption.
Neithal Makkal Katchi president K Bharathi told DT Next that fishermen were being severely affected by plastic pollution in the sea. He said fishermen frequently encountered large amounts of plastic waste accumulated in their fishing nets, while larger plastic debris often damaged their nets. He noted that the volume of plastic debris increased significantly after heavy rainfall.
According to him, this had affected fish resources along the coastal regions of Chennai, Tiruvallur and Chengalpattu, while also impacting the livelihood of fishermen.
Environmentalist Dr Selvam said microplastics were formed from the breakdown of macroplastics. Pointing out that much of the plastic waste was carried into the Bay of Bengal through the Adyar, Cooum and Kosasthalaiyar rivers, he attributed the situation to poor sewage and solid waste management in Chennai and several other coastal cities in Tamil Nadu.
He further noted that Tamil Nadu had one of the most densely populated and urbanised coastal stretches in the country, contributing to it becoming one of the most polluted coastal regions.
He said single-use plastics and plastic packaging materials were causing severe damage to the coastal environment and urged the government to implement stricter laws to ban single-use plastics.
Dr Selvam also said river systems were the primary source through which plastic waste entered the oceans. Referring to measures adopted in developed countries, he suggested that barrier systems should be installed in rivers to prevent garbage from flowing into the sea. Although such systems could involve high installation costs, he said they would deliver effective long-term results.
He added that the findings should serve as a wake-up call for Tamil Nadu’s coastal management agencies, especially in ecologically sensitive zones such as Muttukadu, Pulicat, Ennore Creek and the Gulf of Mannar region.