Most plastic trash on local beaches originates from offshore sources: Study

97% of waste from sea-based sources or transported across boundaries by currents

- Zachary Lim

Heaps of plastic trash on Singapore's beaches are a common sight during the country's two main monsoon seasons. Most of the debris originates from offshore sources, according to a new study.

A key finding was that 97 per cent of the plastic waste on Singapore's recreational beaches came from sea-based sources, such as ships, or were transported across boundaries by marine currents.

The study was published on the National Environment Agency's (NEA) website on Jan 13.

Commissioned by NEA in 2021, it was aimed at better understanding the possible sources of plastic waste on Singapore's shores and how the waste ended up there.

The study was led by NEA, which worked closely with other agencies including national water agency PUB, National Parks Board, the Maritime and Port Authority of Singapore and Singapore Food Agency.

Consultants from two organisations, DHI Water and Environment and SGS Testing and Control Services, were also involved.

NEA told The Straits Times that the study involved sampling various inland and coastal waters and recreational beaches monthly over a one-year period.

Information collected on the plastic debris, such as its size, as well as other factors like rainfall and surface wind speed, enabled researchers to model the amount of marine plastics on Singapore's beaches.

"The modelling found that only about 3 per cent of the macro- and micro-plastics found on our beaches were from inland waterways, while 97 per cent were from marine-based sources," said NEA.

The study used international classification standards to define macroplastics as being larger-sized plastic particles with diameters greater than 5mm, and microplastics as smaller fragments with diameters less than 5mm.

From the samples collected at the mouths of rivers, researchers found that over 90 per cent of the samples presented no trace of microplastics.