How concerned should we be about microplastics?

A few years ago, traces of microplastics were detected for the first time in the lungs of some patients. In the past, they had already been found in the respiratory systems of various deceased individuals. Recently, as reported by the New York Times, a research group from the University of New Mexico also recorded the presence of microplastics in several brain samples, noting that those from people with dementia contained a higher amount than those from individuals without neurodegenerative diseases. The researchers also observed that, in the brain samples examined, the concentration of microplastics in 2024 was higher than in those dating back to 2016, indicating a growing accumulation over time. The discovery provides new insights into the widespread presence of microplastics and their possible impacts on human health. It is estimated that more than 40 million tons of microplastics end up in the environment each year, but measurements vary greatly and the problem is difficult to quantify.

The scientific community is nevertheless in agreement in stating that microplastics are present in almost all environments where we live, due to pollution. As more sensitive systems to detect their presence have been developed, microplastics have been discovered practically everywhere – from the oceans to the highest mountain ranges on the planet. Their presence has also been detected in the bodies of over a thousand species – including humans. Despite this data, it is still not entirely clear what actual impact these materials have on a physical level. Many variables are at play, such as the size and quantity of individual microplastics, as well as the pathways through which they were absorbed by the body. What makes the issue even more complex is the fact that there is no single definition of microplastics, also due to margins of error in measurements: generally, particles smaller than 5 millimeters are considered microplastics.

Microplastics mainly come from the deterioration of larger plastic objects, which release tiny particles into the environment that can then come into contact with our bodies. Microplastics can be found in the air, water, or soil, and in some cases are so small that they can pass through the natural barriers of our body, such as the blood-brain barrier – which normally prevents many substances from entering the brain. The evidence gathered by the University of New Mexico team suggests that the greater porosity of the blood-brain barrier in the brains of people with dementia might facilitate the entry of microplastics into the body. This, in turn, could promote the development or worsening of neurodegenerative diseases.

That we could inhale microplastics by breathing had already been known for some time, thanks to other studies. In 2021, a research group in Brazil conducted several autopsies, finding traces of microplastics in the lung tissues of over 50% of the bodies analyzed – but even in that case, the researchers were very cautious about any potential health effects. In 2022, another study detected the presence of microplastics in the bloodstream. The study showed that these particles can move through the human body, potentially accumulating in some organs. However, their widespread presence in the environment does not automatically imply a high health risk. A few years ago, the World Health Organization (WHO) had published a first assessment on the topic, concluding that – based on the available knowledge – microplastics did not represent a significant threat to humans. That same analysis, however, contained numerous caveats, especially due to the lack of data available at the time.