THANH HOA, Vietnam (Reuters) - There’s almost more plastic than sand on this long, tree-lined beach: Plastic helmets, plastic furniture and the plastic leg of a shop mannequin all jut out of an ocean of blue plastic bags.

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Just south of the capital Hanoi, the once-peaceful and clean beach of Da Loc in Vietnam’s Thanh Hoa province, has been slowly suffocating under the weight of plastic waste for decades.

“Plastic bags have been waste here since the first day we started using them,” said Pham Thi Lai, 60, a local seafood processor.

“They put everything in a plastic bag. If they’re preserving shrimp or preserving fish, they put it in a plastic bag,” Lai said of local fishermen, many of whom shuck clam shells and dry shrimp between the mounds of plastic waste on the beach.

“When they finish they just throw the bags into the ocean. The trash floats to wherever the sea level rises,” she said.

Vietnam is the fourth-largest contributor to marine plastic pollution globally, a 2015 study by the University of Georgia showed.

Globally, eight million tonnes of plastic is dumped into the ocean every year, killing marine life and entering the human food chain, according to the U.N. Environment Programme.

The latest example was a pilot whale that died in Thailand with some 80 pieces of plastic rubbish found in its stomach.

The theme of World Environment Day on Tuesday is beating plastic pollution, with a call for citizens, companies and civil society groups to organize the “biggest-ever worldwide cleanup”.

On Monday, 41 embassies and international organizations in Vietnam signed a pledge to combat plastic pollution in the country.

“As international partners, we have the privilege to work in Vietnam, and have a collective responsibility to reduce our plastic footprint in this beautiful country,” Canadian ambassador Ping Kitnikone said in a statement.

The problem in Vietnam has become so bad that some people in tourist areas have started handing out reusable bags made from rattan, and use newspapers to wrap market produce.

Officials in charge of the beach at Da Loc have struggled to keep up with the rising tide of waste.

“Water rises and falls everyday, how can we clean it all?” said Ngo Ngoc Dinh, head of Da Loc People’s Committee. “We can’t escape it, we have to solve it ourselves”.

“But we hope proper campaigns can help reduce environmental waste”.