Boiling Tap Water Could Help Remove 80 Percent of Its Microplastics, Study Suggests

Minerals in some tap water can capture tiny plastic particles when the water is boiled, making them easier to filter away, according to a new study

A close-up of a blue-flame burner on a stove, with water boiling in a clear glass pot.
Boiling and filtering tap water, researchers suggest, could reduce concentrations of microplastics by more than 80 percent. Ervins Strauhmanis via Flickr under CC BY 2.0

Microplastics have become a pervasive source of pollution across the Earth—these tiny fragments have settled in the deep sea and on Mount Everest, stuck inside volcanic rocks, filled the guts of seabirds and even fallen in fresh Antarctic snow. The problem is so widespread that some scientists are using the tiny plastics to try to define the Anthropocene,proposed environmental epoch marked by human activity.

With so many of these minuscule plastics available to be inhaled or ingested, they are even appearing inside humans. Now, new research suggests that a simple, cheap measure may significantly reduce the level of microplastics in water from your tap: boiling and filtering it.

In a study published Wednesday in Environmental Science & Technology Letters, researchers found that boiling tap water for just five minutes—then filtering it after it cools—could remove at least 80 percent of its microplastics.

To test this, the researchers began with samples of “hard” tap water, which has a high concentration of minerals such as calcium carbonate, and contaminated them with nano and microplastics (NMPs), writes the Hill’s Saul Elbein.

When they boiled the water, the calcium carbonate naturally formed a solid, chalky substance called limescale, which trapped the plastic particles. Removing this “encrustant” using a simple coffee filter also removes the captured NMPs, researchers say.

“We estimated that intakes of NMPs through boiled water consumption were two to five times less than those through tap water on a daily basis,” Eddy Zeng, an environmental chemist at Jinan University in China and an author of the study, tells New Scientist’s Chris Stokel-Walker. “This simple but effective boiling-water strategy can ‘decontaminate’ NMPs from household tap water and has the potential for harmlessly alleviating human exposure to NMPs through water consumption.”

A variety of small plastic bits, many round, in a variety of colors, spread before a white surface
Microplastics have been found miles underneath the sea and even inside volcanic rocks. Oregon State University via Flickr under CC BY-SA 4.0

Crucially, this process relies on the water containing enough calcium carbonate to trap the plastics. In the study, boiling hard water containing 300 milligrams of calcium carbonate led to an almost 90 percent drop in plastics. But in samples with less than 60 milligrams of calcium carbonate, boiling reduced the level of plastics by just 25 percent, reports Healthline’s Julia Ries.

“What’s important to note here is that the effectiveness of trapping these micro/nano plastics in these mineral solids is tied to how hard the water is—the harder the water, the more solids are formed, the more microplastics are trapped,” Anja Brandon, associate director of U.S. plastics policy at the nonprofit Ocean Conservancy who was not involved in the study, tells Healthline.

Additionally, the research wasn’t all-encompassing. The team focused only on three common types of plastics—polystyrene, polyethylene and polypropylene—and they didn’t study other chemicals previously found in water such as vinyl chloride, per the Hill.

Still, the findings show a potential path forward for reducing microplastic exposure—a task that’s becoming increasingly difficult. Even bottled water, scientists found earlier this year, contains 10 to 1,000 times more microplastics than originally thought.

And in a study published this month focusing on 62 human placentas, researchers detected microplastics inside every single one. Another new study found the tiny contaminants in all 17 human arteries examined.

Scientists are still trying to determine how harmful microplastics are—but what they do know has raised concerns. The new study suggests boiling tap water could be a tool to limit intake.

“The way they demonstrated how things were deposited through the boiling process was nice,” Caroline Gauchotte-Lindsay, an environmental engineer at the University of Glasgow in Scotland who was not involved in the research, tells New Scientist. “We should be looking into modifying drinking water treatment plants so they remove microplastics.”

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