Every time you put a glass of water to your lips, you may actually be consuming hundreds of tiny flakes and fibres of microplastic, according to a report by the WHO.
As plastic waste has degraded in the environment, tiny and invisible fragments of plastic have infiltrated the world’s water supply, reaching densities of up to 1000 particles per litre.
Microplastics, particles 5mm in size or less, are now “ubiquitous” in the environment and have been detected in the air, the oceans, rivers and in bottled and tap water, the WHO’s report says.
There are few high-quality studies on the impact of microplastics on human health, the WHO said.
Ingesting microplastics could be toxic if particles are absorbed through the digestive tract in high concentrations or if pathogens hitch a ride on the microplastic biofilm.
But all the available evidence suggested the risk to human health from microplastics was low, the WHO said.
While microplastics promote pathogens growth, their contribution is dwarfed by that of plumbing pipes, which have much larger surface areas and therefore make better breeding grounds for bacteria, the WHO said.
There are few studies that investigate what happens to microplastics once they are ingested.
But it was unlikely that particles larger than 150?m would be absorbed through the digestive tract, the WHO said.
Animal studies suggested the uptake of nanoplastics only “occurred under extremely high exposures that would not occur in drinking-water”, the WHO said.
The chemical toxins from microplastic (such as additives, monomers and accumulated hydrophobic persistent organic pollutants) were “a low health concern … even in extreme exposure circumstances”, according to the WHO analysis.
While the organisation did call for more research into microplastics it did not recommend that microplastics in drinking water be monitored routinely because there was “no evidence to indicate a human health concern”.
Currently, two billion people worldwide relied on drinking water that was contaminated with sewerage, the WHO said.
The microbial pathogens living in drinking water caused around half a million diarrhoeal-related deaths in 2016.
By addressing this bigger problem of untreated wastewater, communities could simultaneously address the smaller concern related to microplastics, the WHO said.
Standard water treatment systems already remove more than 90% of microplastics through filtration.
Dr Paul Harvey (PhD), an environmental scientist at Macquarie University, said the WHO’s report was “reminiscent of the ‘no data, no problem’ paradigm”.
“While it is encouraging to see the WHO take the lead on this issue… the conclusions could be better refined. The report highlights a paucity of research… however errs on the side of microplastics in drinking water being of no health concern.”
Sydney Water reviewed the risks of microplastics in its drinking water catchments in 2017.
“Microplastics have been an issue of emerging concern in the water industry for several years,” a spokesperson said.
“Given the largely protected nature of our catchments and based on current evidence, the risk to Sydney’s water supplies is low.”
There are currently no guidelines in Australia for regulating microplastics contamination in drinking water.
Sydney Water is currently working on a project with NSW Environment Protection Authority to examine microplastics in wastewater systems that discharge into marine environments.