Published On: 27 August 2025

  • CSIC scientists compile research on the presence and effects of plastic particles on ecosystems and human health in the latest title in the “¿Qué sabemos de…?” series (CSIC-Catarata)

  • M. Victoria Moreno-Arribas, Cinta Porte, Amparo López-Rubio, and M. Auxiliadora Prieto are the authors of Micro- y Nanoplásticos, a book in which they highlight the urgent need to reduce single-use plastic consumption and to develop improved analytical methods

     

Packaging, toys, cars, furniture… wherever we look, we find objects made from plastic materials. There is such a vast quantity and variety, and sometimes they are so small, that we ingest them, inhale them, and they come into contact with our bodies through the skin. The latest volume in the series ¿Qué sabemos de…? (CSIC-Catarata) focuses on micro- and nanoplastics, those fragments originating from plastic products that have not been recycled and end up in the environment. CSIC researchers M. Victoria Moreno-Arribas, Cinta Porte, Amparo López-Rubio and M. Auxiliadora Prieto explain their properties, how they become part of ecosystems, and the pathways of human exposure to these particles. In the book Micro- y Nanoplásticos, the scientists also describe existing studies on micro- and nanoplastic pollution, known risks, and highlight the gaps that still remain regarding their presence, exposure, potential effects, and regulation. “Although we still have more questions than answers, the evidence accumulated in recent years clearly indicates that micro- and nanoplastics are not harmless,” the authors state.

Microplastics (MPs) are fragments smaller than 5 millimetres, while nanoplastics (NPs) include particles smaller than 1 micron, meaning they are a thousand times smaller than 1 millimetre. In terms of their origin, a distinction is made between primary microplastics, which are manufactured in small formats and added to products such as fertilisers, cosmetics or detergents, and secondary microplastics, which come from items such as bags, toys or clothing and progressively break down into increasingly smaller pieces through the action of air, sunlight and water.

According to the researchers, the main concern regarding these materials — invisible to the naked eye — stems, on the one hand, from their ubiquity — they have been found virtually everywhere on the planet where they have been sought — and, on the other, from the fact that they are not biodegradable. “It has been shown that microplastic pollution is extremely persistent, almost impossible to eliminate once released, and that it accumulates progressively in the environment.” Furthermore, “the structure of these materials enables them to absorb or adsorb pollutants from the environment and to transport or release them, thereby acting as vectors for the distribution of toxins, pests, or even pathogenic microorganisms,” they warn.

And all of this happens because of our ‘addiction’ to plastic. Its versatility, durability, and low cost are some of the properties that have made it one of the most widely used materials. It is estimated that since the mid-20th century, more than 8 billion tonnes of plastic have been produced — equivalent to more than one tonne per person on the planet. However, not all plastics are used in the same way or have the same environmental impact. The CSIC experts point out that there is a big difference between plastics used in the electrical sector — which have a long useful life and excellent insulating properties — and so-called single-use plastics, mainly used in packaging. The latter quickly contribute to the enormous volume of waste generated every day and are the main source of pollution. In fact, packaging accounts for more than 40% of total global plastic consumption.

By land, sea, and air

Recent studies show that the entry of plastics into terrestrial ecosystems amounts to between 10 and 40 million tonnes per year — that is, between three and ten times more than the estimated amount reaching seas and oceans. In the case of terrestrial ecosystems, the authors highlight agricultural practices such as the use of encapsulated fertilisers and plastic soil coverings, as well as irrigation with contaminated water, as major sources of MP and NP entering the soil. Another route is through plastic waste landfills, where ultraviolet radiation, moisture, or erosion break down the material, allowing it to spread to new areas through the action of wind — or even animals.

In aquatic ecosystems, the presence of plastics is illustrated by now-iconic images such as the vast Great Pacific Garbage Patch — but these formations are just the tip of the iceberg. “It is estimated that 85% of the plastic entering the oceans remains hidden underwater, accumulated in deep-sea sediments,” the authors explain. Ocean waste is proliferating to such an extent that even the World Economic Forum predicts that by 2050, the oceans could contain more tonnes of plastic than of fish.

Plastics come into contact with organisms and can even enter their bodies. Plastic particles have been reported in more than 1,300 aquatic and terrestrial species, including fish, mammals, birds, and insects. In the case of fish, it has been shown that they can accumulate higher levels of microplastics from contaminated prey than directly from the water, highlighting the role of the food chain in their accumulation. Exposure studies have found that smaller particles tend to accumulate in deep tissues such as the liver, brain, and muscle, whereas larger particles are found mainly in the gills, stomach, and intestines. Particles smaller than 100 nanometres (nm) can penetrate cells, potentially causing effects such as oxidative stress or DNA damage.

Despite progress, one of the main challenges for the scientific community is to identify and quantify micro- and nanoplastics in ecosystems. The experts, with many hours of laboratory work behind them, emphasise that the analytical process involves handling extremely small particles, extracting them from highly complex environmental matrices, and precisely identifying their polymer type, size, and shape. “This is especially difficult in the case of nanoplastics, as their physical and chemical behaviour differs from that of larger particles,” they state.

We ingest them, inhale them, and touch them

By mouth, by nose, and also through the skin. The human body is potentially exposed continuously to small plastic particles, either through marine and terrestrial organisms we consume, which carry microplastics, or through drinking water, both tap and bottled, to name just a couple of examples. These sources of exposure via ingestion are not mutually exclusive, and in addition, other routes such as inhalation of air and dust add to this, which means not only the entry of particles but also of chemical contaminants they may carry. The third ‘channel’ for penetrating our body is contact with the skin. In this case, the researchers suggest that it would be nanoparticles, especially the smallest ones, that could cross the skin barrier.

Besides the presence of MPs and NPs in food and drinks, it is important to consider bioaccessibility—that is, the fraction of particles and chemical compounds that can actually be released during digestion and absorbed by the body. The authors emphasize that not only the plastic particles themselves but also chemical additives like plasticizers and flame retardants can be a source of exposure through the diet. “The problem is that these compounds are not firmly bound to the plastic and can be released over time, especially when heating food or during digestion,” they clarify.

Health risks: what is known and what remains uncertain

What happens when plastic particles enter our bodies? Are they absorbed or easily eliminated? Can they accumulate in organs and tissues? Answering these questions is very difficult because microplastics (MP) and nanoplastics (NP) come in multiple forms, cover a wide range of sizes, and occur as complex mixtures that produce combined effects that are hard to study.

So far, plastic particles have been detected in various human tissues and fluids, including blood, lungs, liver, kidneys, spleen, placenta, intestines, colectomy samples, sputum, semen, breast milk, and faeces, among others. Available data suggest that the intestine is one of the main sites of accumulation, although accurately quantifying particles—especially the smallest ones—in faeces remains a challenge. “Ingestion is considered a very important exposure route, but it is still uncertain to what extent MP and NP can be significantly absorbed by the human body and under what conditions.” What is known is that “throughout the digestive process, these particles can interact with various molecules present in the digestive system, such as digestive enzymes, bile salts, and organic and inorganic compounds, forming a biological or (eco)corona on their surface, which could alter the way they are recognised by the body’s cells and, consequently, affect their biological behaviour and potential toxicity,” the researchers explain.

The study of the impact of MP and NP on the gut microbiota is an emerging research area due to its possible link with intestinal and systemic health disorders. A pioneering study carried out by the CSIC within the European PlasticsFatE project showed that polyethylene terephthalate (PET) microplastics modify the human colon microbiota during simulated gastrointestinal digestion. Other recent studies have shown that, beyond PET, exposure to MPs from other polymers can also alter the composition of the gut microbiome, even in disease contexts, causing a decrease in beneficial bacteria and an increase in pathogens and antibiotic-resistant microorganisms. Beyond these effects, researchers are also investigating the potential role of the gut microbiota in the biotransformation or elimination of these particles from the body, which could modulate their bioavailability and toxicity.

Reducing their use and better understanding their effects

Although many questions remain, current studies reflect a growing interest from the scientific community and regulatory bodies in better understanding the fate and effects of MPs and NPs in the human body. Among the challenges in this field, the CSIC scientists highlight the need for integrated tools that allow prioritising the most relevant particle types, improving detection methods, establishing comparable standards across studies, and more accurately assessing potential risks to human health.

Moreover, there is much to be done in terms of prevention: from drastically reducing the production and consumption of single-use plastics to improving water and waste treatment technologies. Likewise, the role of governments is crucial, although the outlook is not very positive at present. On 15 August, negotiations around an international treaty to tackle plastic pollution, sponsored by the United Nations (UN), once again failed during the meeting of the Intergovernmental Negotiating Committee (INC5-2) and were suspended without consensus. “There are many science-based strategies that can be followed, but the next steps are now in the hands of the international negotiators,” the scientists assert.

The book is available at the Editorial CSIC website.

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