The study from the University of California, San Diego, tracked the ability of natural, synthetic and blended fabrics to biodegrade directly in the ocean.

It found that while natural and wood-based cellulose fabrics degraded within a month, synthetic textiles - including so-called compostable plastic materials like polylactic acid (PLA) and the synthetic portions of textile blends - showed no signs of degradation even after more than a year submerged in the ocean.

“This study shows the need for standardising tests to see if materials promoted as compostable or biodegradable actually do biodegrade in a natural environment,” said lead author Dr Sarah-Jeanne Royer.

“What might biodegrade in an industrial setting does not necessarily biodegrade in the natural environment and can end up as marine and environmental pollutants.”

An estimated 62 per cent of textiles - around 68 million tons - are now made from plastic fibres and plastic blends, which can persist...