We tend to associate microplastics just with the marine environment, but these small pieces of plastic are also accumulating in soils and at a higher level. Now, a group of researchers has found an unexpected solution. Birch trees, found in the Northern Hemisphere, were found to remediate the soils by absorbing microplastics through their roots.

Microplastics are contaminants of growing concern. They originate from the breakdown of larger plastic and from the release of primary materials, which makes them easily transported in water, air, and soil and can accumulate and persist in the environment. Microplastics are everywhere, from the depths of the oceans to the top of Mount Everest.

Most research on the influence of microplastic has focused on how they interact with plants and animals in seas and oceans. While less obvious than in oceans, microplastics also accumulate in soils at levels between four to 23 times higher than in marine ecosystems, either being transported through the atmospheric or by direct deposition.

Microplastics alter the properties of the soil and can also affect plant growth and microbial community. However, not much is known about how microplastics interact with higher-order terrestrial plants such as trees. Recent studies have shown, for example, that microplastics are taken up by agricultural plants such as wheat.

As part of an interdisciplinary project, a group of German researchers has shown that longer-lived woody plants, specifically birch trees (Betula), can absorb and store microplastics in their tissue. The roots of this tree species grow close to the soil surface, where microplastic is the highest, making it a good choice for a study.

“The uptake rate of microplastics and the effects on the short- and long-term health of the trees still need to be studied. But this pilot study suggests birch has real potential for long-term soil remediation solutions – including reducing the number of microplastics in soil and possibly water,” Kat Austen, the lead author, said in a statement.

Birch trees and microplastics

Birch trees are a group of 40 species of ornamental and timber trees and shrubs, generally found in cool regions of the Northern Hemisphere. They have been used to remediate polluted land in the past as they can sequester and store pollutants and heavy metals in their tissues. Plus, they were found in previous studies to be very good at reducing air pollution. So it makes a lot of sense to see if they can help with microplastics.

For their study, the researchers added microplastic beads with fluorescent dyes to the soil of potted birch trees, which enabled them to see where the microplastic pieces were going. After five months, they analyzed the root system using fluorescence and confocal laser scanning microscopy, finding microplastics in different sections of the root system in between 5% and 17% in the experimental trees — enough to show that birch trees can be helpful with microplastic bioremediation.

“These results give a strong indication for the uptake and incorporation of soil-derived microplastic into juvenile birch roots and suggest that further investigations addressing the rate of uptake of microplastic and its implications for long term tree health are necessary to determine if birch trees are suitable microplastic remediators.,” the researchers wrote.

However, this doesn’t mean that we suddenly have a solution for microplastics pollution. If we want to truly address this problem, we need to tackle it at its root and think about producing less plastic in the first place.

The study was published in the journal Science of the Total Environment.

We know microplastics are a big environmental problem and that they can now be found almost everywhere, including our food and water — and inside our bodies. But just how harmful are they? Since it’s a problem we’ve only recently started to realize, we don’t know yet — but the data is coming in, and it doesn’t look too good. At least in a petri dish, microplastics have the potential to cause significant damage to human cells in the laboratory, a new study found.

The study is the first to quantify the levels of microplastics (plastic particles measuring less than five millimeters) that may lead to harmful effects in human cells.

“This is the first-time scientists have attempted to quantify the effects of the levels of microplastics on human cells using a statistical analysis of the available published studies,” Evangelos Danopoulos, lead author and PhD student, said in a statement. “We are seeing reactions including cell death and allergic reactions as potential effects.”

Not only are microplastics everywhere already, but the contamination is expected to rise as plastic production and use around the world also increase. Within a century, the ecological risks of microplastics could be widespread in ecosystems across the world. So researchers are trying to understand just how dangerous these microplastics really are.

Exposure and contamination

Humans have two main routes of exposure to microplastics: ingestion and inhalation; we either ingest or inhale microplastics — and concerningly, both seem to be widespread. The presence of microplastics has been verified in human lung tissue, placenta, and colectomy samples.

Danopoulos and his team first reviewed a set of 17 previous studies that looked at the toxicological impact of microplastics on human cell lines. This allowed them to compare the level of microplastics consumed by people through polluted seafood, table salt, and drinking water with the level at which damage is caused to human cells.  

They found that four specific types of harm to human cells (cell death, damage to cell membranes and allergic response) were directly caused by the microplastic that people eat. The study also showed that microplastics with an irregular shape cause more cell death than spherical ones. Most laboratory studies focus on spherical ones. At the levels already found inside human bodies, these particles seem to be causing significant cellular damage.

“Our analysis of the data showed that cell viability depends on the shape of the microplastics. Irregularly shaped microplastics, which are the majority found in the environment, are more hazardous than spherical,” Danopoulos said. “So far, most toxicology studies have been testing spherical microplastics. There needs to be a shift.”

For the researchers, the findings show that we are eating microplastics at levels consistent with harmful effects on our cells, which could then trigger other health effects. Nevertheless, he highlighted the high level of uncertainty regarding how ingested microplastics are excreted from the body – crucial to better understand the true risk that microplastics pose to our health.

The study was published in the Journal of Hazardous Materials.