Every time we breathe, we could be inhaling tiny fragments of plastic. In recent years, concern about plastic pollution has grown, especially due to its accumulation in the oceans. However, what many people still don't realize is that plastics are also present in the air we breathe.

An adult can inhale more than 48,000 microplastic particles per year without even noticing it. These particles, imperceptible to the naked eye, float in the air as invisible dust that sneaks through our windows, settles on our furniture and, most disturbingly, enters our lungs.

This year, World Environment Day (June 5) focuses on plastic pollution. And perhaps it's time to look not just at the land and sea, but also at the sky.

The air route of microplastics

When we think of plastic pollution, we usually imagine bottles on the beach or bags floating in the sea. But plastics also fragment over time - due to solar radiation, wind or use - until they become particles of less than 5 mm: the so-called microplastics.

These are known as secondary microplastics, because they originate from the degradation of larger plastic objects. However, there is another subject of microplastics that do not originate from such decomposition, but are manufactured directly as tiny particles: primary microplastics. These are used intentionally in numerous industrial and commercial sectors. For example, as ingredients in cosmetic and staff care products such as scrubs or make-up. They are also common in textile coatings, paints, detergents, slow-release fertilizers and even as industrial abrasives.

These particles can end up in the air by various routes: direct emissions into the environment, tire wear on roads, washing and drying of synthetic clothing, urban dust, being expelled by waves at sea or being ripped up and washed from the sea by severe storms. Once there, they can be carried by the wind thousands of kilometers away.

It is already common to detect microplastics in densely populated urban areas. In Spanish cities it has been estimated that between 2,000 and 28,000 microplastic particles are deposited from the atmosphere per square meter per year, with the highest values in cities such as Madrid and Barcelona. But what is really worrying is that they have also been detected in remote places such as the cima of Mount Everest, in cloud water samples taken at the summits of the mountains of Japan or the atmosphere of both the Arctic and Antarctica. In other words: it doesn't matter whether we live by the sea, in the mountains or in the center of a city. Microplastics are already part of the atmospheric cycle.

What enters through the nose does not stay in the wind

The great challenge now is to understand what effects these microplastics have on our health. It is already known that they can reach the respiratory system, and that some, because of their size and shape, could even penetrate into the deepest tissues of the lung.

And it's not just the plastic itself that matters. Many microplastics travel "loaded" with chemical contaminants: heavy metals, pesticides, or toxic additives that can be released once inside the body. It's as if we're not just breathing dust, but also an invisible cocktail of unwanted substances.

Recent programs of study have shown that certain plastic particles can cause inflammation, oxidative stress and even altered immune responses in laboratory lung tissues. However, the long-term effects in humans are still under research.

The concern becomes greater when we think about the exhibition daily, especially in vulnerable people: children, the elderly, or those living in areas with high air pollution. Are we facing a new subject of invisible pollution that could chronically affect our health?

What can we do if we don't even see them?

Faced with this problem, the solution isn't (only) to stop using straws. We need to consider how we produce, consume, and dispose of plastics. As citizens, we can reduce the use of synthetic clothing, opt for public transportation (to limit tire wear), strategically ventilate, or support initiatives that promote biodegradable materials and public policies to combat pollution.

From a scientific perspective, we continue to investigate how much plastic is in the air to better understand how and where it originates, how it is transported, what factors drive these processes, and what consequences they have. In my case, I'm dedicated to studying atmospheric microplastics because I believe we can't protect what we can't see if we don't first understand it.

This June 5th, as we celebrate World Environment Day, let's remember that plastic pollution doesn't just float in the ocean: it also floats, silently, among us. And breathing should be a clean and safe act.

This article was originally published in The Conversation. Read the original.