More research is needed to study the effects posed by microplastics in drinking water, the World Health Organisation (WHO) has said.

The international public health body has also called for a reduction in plastic pollution to reduce the global populations exposed to the substance.

Microplastics – which are tiny beads of the non-compostable material – are now found in oceans, fresh waterways, snow in the mountains, tap and bottled water.

Microplastics contained in drinking water pose a “low” risk to human health at current levels, but more research is needed to reassure consumers, the World Health Organization (WHO) said on Thursday.

Studies over the past year on plastic particles detected in tap and bottled water have sparked public concerns but the limited data appears reassuring, the UN agency said in its first report on potential health risks associated with ingestion.

Microplastics enter drinking water sources mainly through run-off and wastewater effluent, the WHO said. Evidence shows that microplastics found in some bottled water seem to be at least partly due to the bottling process and/or packaging such as plastic caps, it said.

The majority of plastic particles in water are larger than 150 micrometres in diameter and are excreted from the body, while “smaller particles are more likely to cross the gut wall and reach other tissues,” it said.