The World Health Organization says there's not enough evidence to conclude that microplastics — which exist nearly everywhere in the environment and show up in drinking water — pose any risk to human health, but it cautions that more research is needed to draw firm conclusions.
In a new study, the WHO says that microplastics are "ubiquitous" and have been detected in fresh water, wastewater, food, air, bottled water, tap water and more.
However, despite widespread concern, "There is currently no evidence to suggest a human health risk from microplastics associated with biofilms in drinking-water," the study concludes, referring to microorganisms that attach to microplastics.
Instead, WHO suggests that diseases associated with untreated or poorly treated drinking water should remain a more urgent priority for public health officials. The risk posed by microplastics "is considered far lower than the well-established risk posed by the high concentration and diversity of pathogens in human and livestock waste in drinking-water sources," the study says.
Even so, WHO's director of public health, Dr. Maria Neira, acknowledges that the conclusions reached in the report are based on incomplete information.
"We urgently need to know more about the health impact of microplastics because they are everywhere — including in our drinking-water," she says in a statement. "Based on limited information we have, microplastics in drinking water don't appear to pose a health risk at current levels. But we need to find out more. We also need to stop the rise in plastic pollution worldwide."
Although there is no exact scientific definition of microplastics, they are formed when man-made plastics break down into tiny particles that measure less than 5 millimeters — about the size of the letters on a computer keyboard. Those plastics have gotten into oceans, rivers, lakes and streams and are consumed by humans and other animals.
"But just because we're ingesting them doesn't mean we have a risk to human health," says Bruce Gordon, WHO's coordinator of water, sanitation and hygiene, according to The Associated Press. "The main conclusion is, I think, if you are a consumer drinking bottled water or tap water, you shouldn't necessarily be concerned."
The report is WHO's first to cover potential health risks associated with microplastics. The organization recommends more studies of microplastics, developing new ways to remove them from drinking water and the establishment of standard methods for measuring microplastics in water.