In Singapore, 9 per cent of plastic waste was recycled in 2014, according to the National Environment Agency (NEA). The remainder was burnt in waste-to-energy plants. A small amount of plastic is dumped as litter and most of it is captured before it reaches the sea.

Last year, the NEA collected about 920 tonnes of plastic waste from rivers and canals cleaned by the NEA Department of Public Cleanliness, a spokesman for the agency said.

The bulk of the collected waste is sorted and sent for recycling if deemed suitable.

The Government uses litter traps and float booms in most waterways to minimise litter flowing into reservoirs or the sea.

The Government also tries to minimise waste from ships anchored in Singapore's waters.

The Maritime and Port Authority of Singapore (MPA) enforces strict regulations on pollution of the sea from ships within port waters, an MPA spokesman said. The agency also monitors the ships in port to ensure compliance with the regulations and employs a contractor who provides services daily to collect garbage from ships, ensuring proper disposal and flotsam retrieval.

The MPA does not track the amount of plastic waste from Singapore sources that escapes out to sea, the spokesman said.