Plants Could Solve the Microplastics Problem

Plastics are the most prevalent type of marine debris found in the Great Lakes and in the oceans. Plastic pollution pieces come in all shapes and sizes, but those that are less than 0.2 inches (or five millimeters) in length—about the size of a sesame seed—are called “microplastics.”

The sources of microplastics are varied; some examples include clothing, fishing nets, larger plastic items that degrade into smaller pieces and microbeads. Microbeads are very tiny pieces of manufactured polyethylene plastic that are added as exfoliants to some beauty and health products, such as cleansers and toothpastes. And like plastic pieces of any size, microbeads do not readily break down into harmless molecules. Microplastics can take hundreds or thousands of years to decompose. In the meantime, these tiny particles can easily pass through water filtration systems, ending up in our waterways and posing a threat to aquatic life, that can mistake microplastics for food.

In fact, microscopic plastic particles have now been found in the fats and lungs of two-thirds of marine mammals, suggesting that microplastics can travel out of the digestive tract and lodge in the tissues.

That’s not all: researchers have recently discovered that microplastics can be detected in the air far away from ocean coastlines. These bits are not only escaping into the atmosphere from seawater, but they are also being carried by the wind.

However, there is encouraging and exciting news. Is there any answer to the ever-growing threat of microplastics pollution? Yes, there is: plants.

Microplastics in the tissues

In a paper that’s slated to be published in the October 15, 2023, edition of the journal Environmental Pollution (and that recently appeared online), scientists say that microplastics were found embedded in the tissues of dolphins and whales. The samples they studied were acquired from 32 stranded or subsistence-harvested animals between 2000 and 2021 in Alaska, California and North Carolina. Twelve species were represented in the data, including one bearded seal, which also had plastic in its tissues.

Plastics are lipophilic, which means that they’re attracted to fats—such as blubber, the sound-producing melon on a toothed whale’s forehead and the fat pads along its lower jaw that focus sound to the whale’s internal ears. The scientists sampled those three kinds of fats, plus the lungs, and found plastics in all four tissues that ranged on average from 198 microns to 537 microns (a human hair is about 100 microns in diameter). The most common type of microplastics found in the tissue samples was polyester fibers, a byproduct of laundry machines; as was polyethylene, which is a component of beverage containers. Blue plastic was the most common color found in all four kinds of tissue.

It’s known that plastic pieces can abrade and tear tissues. What other harms that embedded microplastics might cause to marine mammals are yet to be determined, but they have been implicated in other studies as possible endocrine disruptors and hormone mimics.

In a 2022 paper published in the scientific journal Nature Communications, it was estimated, based on known concentrations of microplastics off the Pacific Coast of California, that a filter-feeding blue whale might be gulping down 95 pounds of plastic waste per day as it catches tiny creatures in the water column. Other whales and dolphins that prey on fish and larger organisms might also be acquiring accumulated plastic in the animals they eat.

On top of the challenges of climate change, ocean noise and water pollution, then, marine animals are also currently contending with ingesting plastic, having big pieces of it in their stomachs and now having it being internalized into their tissues. Some proportion of most marine animals’ mass, therefore, is now plastic.

Microplastics in the air

Not only are microplastics infiltrating our oceans and marine animals, but they’ve also been found in the air—even some air that’s far from coasts—according to a study published in Nature Communications in June 2023. And the plastic bits come from some unexpected sources.

In 2021, a team of German and Norwegian researchers collected air samples from various sites along the Norwegian coast up to the Arctic region during an expedition with the research vessel Heincke. The northernmost destination was Bear Island, the most southerly in the Svalbard archipelago and which lies halfway between the mainland and the archipelago’s largest island, Spitsbergen. To collect the air samples, the team used two different devices mounted on the bow of the ship at a height of 40 feet.

For analyzing the air samples, the researchers used pyrolysis-gas chromatography-mass spectrometry. With this method, they were able to identify and quantify the different types of plastics in the atmosphere through thermal degradation and selective analysis. They then performed model calculations and reconstructed the sources and distribution paths of the particles.

The analysis revealed the omnipresence of polyethylene terephthalate particles (polyester), which presumably entered the atmosphere in the form of textile fibers. Other plastic types were also present, including polystyrene (such as Styrofoam) and tire-wear particles, the tiny debris abraded from tires during driving and especially braking. The scientists measured concentrations of up to 37.5 nanograms (one nanogram equals one-billionth of a gram) of microplastics per cubic meter of air.

Until now, little was known about microplastics pollution levels in the atmosphere. The team posits that plastic particles floating near the sea surface enter the atmosphere via sea spray and bursting air bubbles produced during stormy weather, for example. These calculations, however, indicate that the microplastics in the atmosphere also come from direct sources on the land, as well.

Microplastics in retreat?

So, what can we do about the looming threat of microplastics pollution? Scientists at the University of British Columbia’s BioProducts Institute think they may have the answer.

For a study that will be published in the October 2023 issue of the journal Environmental Pollution, the institute’s researchers found that if you add tannins—natural plant compounds that make your mouth pucker if you bite into an unripe fruit—to a layer of wood dust, you can create a filter that traps virtually all microplastic particles present in water.

For their study, the scientists analyzed microparticles released from popular tea bags made of polypropylene. They found that their method (called “bioCap”) trapped 95.2 percent to as much as 99.9 percent of plastic particles in a column of water, depending on the plastic type. When tested in mouse models, the process was proven to prevent the accumulation of microplastics in the organs.

This is quite a feat, as it’s difficult to capture all the different kinds of microplastics in one solution, since microfibers from clothing, microbeads from cleansers and pellets from packaging come in different shapes, sizes and electrical charges. But by taking advantage of the different molecular interactions of tannic acids, the bioCap solution was able to remove virtually all of these varied microplastic types.

And while most solutions proposed so far are costly or difficult to scale up, the BC team is convinced that their solution—which is only a lab setup at this stage—can be adapted, for example, for municipal treatment systems and scaled down for home use easily and inexpensively once they find the right industry partner. And the filter, unlike plastic filters, does not contribute to further pollution because it uses biodegradable and renewable materials: tannic acids from bark, plants, leaves, wood and wood sawdust—a forestry byproduct that is both widely available and renewable.

Microplastics in the past

Today, virtually all tap water is contaminated by microplastics, and it’s estimated that more than 10 billion tons of mismanaged plastic waste will be dispersed in the environment by 2025. The problem demands innovative solutions.

Perhaps those answers will be found in plants. And then plants will save us—and the world—from our plastics.

Here’s to finding your true places and natural habitats,

Candy