Scientists have begun to expose a global horror show: microplastic pollution. Tiny bits of plastic have been showing up in unlikely places, including Arctic ice floes. The particles are blowing in the air, so we’re breathing microplastic and eating it and drinking plastic-infused water.
The implications for human health are potentially huge. Potentially. The problem is that little is known about how microplastics affect the human body. That makes things difficult for the World Health Organization, which today released an exhaustive report on the state of research on microplastics in drinking water. The takeaway: As the limited science stands now, there’s no evidence that drinking microplastics is a threat to human health.
“We know from the data that we’ve reviewed that we’re ingesting them, and we know that’s caused concern among consumers,” says Bruce Gordon, who helped assemble the report as a coordinator with the WHO. “The headline message is to reassure drinking-water consumers around the world that based on our assessment of the risk, that it is low.”
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The report urges the scientific community to further study the potential impact of microplastics on human health, and fast. And it pleads for the world at large to rein in its plastic pollution catastrophe, because human beings aside, microplastics have poisoned even remote reaches of this planet. They’re swirling deep in ocean currents and showing up in the seafood we eat. The pervasiveness of microplastic particles is horrifying, and there’s no way we can scrub the planet of them.
“What we don’t know is enormous,” says University of Strathclyde environmental pollution scientist Deonie Allen, who wasn’t involved in the report.
Humans produce an astounding amount of plastic—nearly 400 million tons of the stuff in 2015, and production is expected to double by 2025. An estimated 8 million tons enter the ocean every year, yet researchers can only account for 1 percent of that. The rest has seemingly disappeared.
Microplastics are getting into drinking water in a number of ways. Some of it is carried in the air—“city dust,” as it’s called, all the particles flying off shoes and tires and whatnot—and landing in freshwater sources like reservoirs. Plastic trash gets in there as well, growing brittle as it bakes in the sun, and breaking down over time into tinier and tinier pieces. Textiles like yoga pants slough off microplastic fibers, which flow out with laundry water.
Freshwater sources are, of course, treated before being distributed to customers, which removes most of the microplastic, the new report says. But it also cautions that in the developing world, people don’t always have access to this kind of water treatment. Also, treatment equipment that is itself made of plastic may contribute microplastics to the water supply.
At this early stage of research, the number of studies is small, and researchers have not yet settled on consistent methodologies. The nine studies compiled by the WHO report reflect the scattered nature of the work so far. Some looked at bottled water, others tap water. Some filtered their water samples down to micron-scale particles, others included particles 100 times bigger than that. Some determined the types of plastic they found, others didn’t. Unsurprisingly, the level of contamination they report ranges from zero to thousands of particles per liter. The upshot is that the findings are almost impossible to compare.
Then there’s the range of effects the particles might have in the human gut. The WHO report notes that most microplastic particles appear to pass through harmlessly. But we need more research about how the size of the particles affects their passage, or if gut tissue might absorb the smaller ones. And then there’s the stuff that comes along with plastic— the chemicals they leach, known as leachates, and also the foreign organisms like bacteria and viruses, known as biofilm, that may hitch a ride on the particles.
