Mangroves in danger: Plastic dust drifting in air deep inside Sundarbans, find IISER scientists

Kolkata: The Sundarbans, long seen as one of the planet's last wild fortresses, is now revealing a quieter, more unsettling intrusion — plastic dust drifting through its air. A new study by the Indian Institute of Science Education and Research (IISER) Kolkata has detected airborne microplastics over a completely uninhabited mangrove island deep inside the Sundarbans Biosphere Reserve.Published in Science of the Total Environment, the study marks the first evidence of atmospheric microplastics inside a protected natural ecosystem in India. During an intensive eight-day winter campaign in Jan 2025, scientists used high-volume air samplers to record an average of 10 ± 6 microplastic particles per 100 cubic metres of air — levels significantly higher than those reported from several remote regions worldwide."What we are seeing is profoundly disturbing — even the air above the Sundarbans is contaminated," said Abhinandan Ghosh, lead author of the study. "Plastic particles are now travelling through the atmosphere, reaching places once believed to be beyond human influence."The study was carried out at an isolated site — the Chula Kathi Protection Camp (21.35°N, 88.32°E) deep within the Indian Sundarbans mangrove ecosystem.The team found that tiny fibres and fragments — many of them black — dominated the samples. These were traced to everyday materials such as single-use plastic bags, fishing nets, textile fibres and packaging waste. Using advanced Raman spectroscopy, the researchers identified industrial polymers like polypropylene (PP) and polyethylene (PE), both widely used in households and industry."The Raman spectra gave each particle a chemical fingerprint," said Abhishek Mandal, research scholar at IISER. "It was startling to see field samples match the same polymers we handle every day. Human activity leaves a molecular footprint even in places we never enter."For many on the team, the filtering process itself was an eye-opener. "Every filter told a story of long-distance travel," said Jay Karmakar. "It's humbling to realise that plastic from our cities can drift into these deep mangrove islands."The study also revealed a powerful atmospheric engine that moves plastics between land and sea. During land-breeze hours, microplastics from urban South Bengal — including Kolkata — were pushed into the forest interior. Sea-breeze hours, meanwhile, carried marine microplastics inland, lifted from the ocean surface by bubble bursting and wave action.Even more striking was the role of fog, which the researchers found was trapping plastic particles in calm, humid air. "Fog acts like a sponge," said Swadhin Majumdar. "Once trapped, the plastics linger near the mangrove canopy, increasing the chances of deposition on leaves and sediments."This dual land-sea influence means the Sundarbans now receives both continental and marine plastic signatures — a rare convergence documented for the first time. Airborne microplastics can settle on mangrove leaves, disrupt microbial cycles, contaminate soils and eventually enter the estuarine food chain through fish and shellfish. Adding to the concern, the study also recorded average PM₁₀ levels of 144 ± 14 µg/m³, far above India's permissible limit of 80 µg/m³ — indicating considerable chemical stress even inside a designated ecological sanctuary."The atmosphere connects continents and oceans. Once plastics enter this cycle, they can reach anywhere on Earth," said Gopala Krishna Darbha, principal investigator. "Protecting ecosystems like the Sundarbans now means understanding not only the water around them but the air above them."The researchers have urged policymakers to include airborne microplastics in India's National Clean Air Programme (NCAP) and in coastal pollution frameworks, stressing that plastic pollution has now become a multi-domain environmental challenge. "Plastic has become part of the air we breathe," Ghosh warned. "Even the sky above the Sundarbans is no longer free from human pollution."

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