Haliday island in the Sunderbans has far fewer human footfalls than popular beaches, but that hasn’t insulated it from plastic debris, a snapshot study by researchers in Calcutta has suggested.

Environmental scientists who assessed plastic debris along Tajpur beach, a popular tourist destination in Bengal, and on the secluded Haliday island wildlife sanctuary say they have found “an abundance” of plastic waste on the island. However, the counts are fewer than those in Tajpur.

Their field surveys revealed both household and recreational (HR) as well as packaging and labelling (PL) plastic debris at both sites — adhesive tape, bags, bottles, glasses, plates and spoons, straws, food and shampoo packaging, cement bag films, for instance, at Tajpur, and bottles and wrappers, electrical casing, fishing gear, foam fragments, footwear, packaging material and plates on the island.

“Inadequate plastic waste management on the mainland is impacting even pristine islands,” Punarbasu Chaudhuri, associate professor of environmental sciences at the University of Calcutta who supervised the study, told The Telegraph.

The study’s findings were published on Wednesday in the scientific journal Marine Pollution Bulletin.

Haliday island in South 24-Parganas, about 50km from Gosaba and 48km from Canning, is an uninhabited degraded mangrove island with restrictions on visits for sightseeing.

The island experiences strong incoming tidal currents along its western edge and slow-moving ebb-tide currents along its eastern and northeastern margins, leading to an accumulation of plastic debris, the researchers said.

While local authorities periodically initiate action to clean coastal tracts such as the Tajpur beach, Haliday and other islands in the Sunderbans have not received any such attention and could be accumulating plastic debris, they said.

The Union environment ministry had in 2022 notified rules to prohibit from July 1, 2022, single-use plastic plates, cups, glasses, other cutlery, and wrapping films, and to change the minimum thickness of plastic carry bags from 75 microns to 120 microns by December 31, 2022. Thicker bags are intended to eliminate the use of lightweight single-use plastic.

The Calcutta scientists conducted their field surveys between March and June 2023, selecting multiple, random 5m by 5m grids along Tajpur beach and on Haliday island to count and classify plastic debris lying within the grids.

The grids on Haliday island contained nearly 108kg plastic debris, said Asit Roy, a post-doctoral research scholar at the University of Calcutta and the study’s lead author. The debris was probably dumped into rivers upstream and carried down to the estuaries and brought by tides to the island, Roy said.

Chaudhury said the long-term accumulation of plastic debris in the marine environment could lead to the consumption of microplastics by marine organisms, including fish. “Macroscopic debris breaks down into microplastic fibres and films that can accumulate in fish,” Chaudhuri said.

In an earlier study, Chaudhuri had detected microplastics in the gastrointestinal tracts of 13 species of edible fish caught by fisherfolk in the Sunderbans.

Humans are exposed to microplastics through ingestion, inhalation and skin contact but experts say the effects of microplastics on human health remain unclear.