The exfoliating facial wash that makes your skin feel smooth can cause a host of problems down the food chain. They contain tiny balls of plastic, called microbeads, which can kill marine life and may even pass toxic chemicals to humans.

Several countries have vowed to ban products like facial washes, toothpaste and cosmetics that contain them. Now, the authorities here are studying their environmental threat and ways to prevent them from entering surrounding waters.

The National Parks Board told The Sunday Times it is "currently looking into assessing the status and impact of marine debris and microplastics on Singapore's marine environment". The National Environment Agency is monitoring international developments in legislation and domestic research on microplastics.

Last December, a law was passed in the United States to ban the production of personal care products and cosmetics containing plastic microbeads from 2017. Last month, Britain said it would follow suit.

Microbeads typically range in size from 1mm - about the size of a pinhead - to 1 micron or 100 times thinner than a strand of human hair. They are able to evade wastewater treatment filters and end up in rivers, seas and oceans. There, they are eaten by marine organisms, including fish and seabirds, blocking or damaging feeding appendages and digestive tracts.

Microbeads can also absorb and concentrate harmful compounds, said Associate Professor He Jianzhong from the National University of Singapore's Department of Civil and Environmental Engineering. The compounds include organic pollutants that can cause conditions like cancer. When eaten by fish, the toxins remain in them and can later be passed to humans.

But there are few large-scale studies with concrete findings on how chemicals in microplastics affect human health. A United Nations Environment Programme Frontiers 2016 Report said, for now, "the risk to human health appears to be no more significant than via other exposure routes". Still, it said harmful and persistent substances can amplify as predators eat prey.

Singapore's Agri-Food and Veterinary Authority said its food safety tests include chemical contaminants found in microplastics. It said it will keep a close watch on the microplastics issue and "will enhance or implement appropriate food safety programmes" if necessary.

According to Dr Jeffrey Obbard, who published a study on microplastics in Singapore's coastal marine environment in 2014, tiny plastic fragments including microbeads can be found in beach sand, seawater and drainage canals.

National water agency PUB gave the assurance that no microplastics are in Singapore's drinking water as any collected in reservoirs will be clumped with other impurities, which will sink and get filtered out.

But it said a small amount may enter the marine system when excess treated used water is discharged into the sea. It is looking into upgrading its water reclamation plants to filter out particles as small as 0.1 to 0.4 micron in diameter.

Singaporeans should be worried about plastics seeping into surrounding waters. "The microplastic might shift to Malaysia or Indonesia waters where people do fish and where we might get our fish too," Prof He said.