The accumulation of plastic waste fragments in sea sediment has sharply increased around the world in the 21st century, according to a recent study on microplastic litter.

The study, led by Hideshige Takada, a professor at Tokyo University of Agriculture and Technology, found the concentration of microplastics, defined as plastic particles up to 5 mm in size, is higher in sediment than in sea water, raising concerns that it could affect organisms living in and on the bottom of the ocean.

"Sediment is becoming one of the places where microplastics build up. There is an urgent need to deal with the situation by reducing the use of plastic," Takada said.