Microplastics: The Very Air We Breathe Is A Poisonous Fume

Examining the different ways in which microplastics enter our bodies

Every single one of us gets exposed to plastic every single day of our lives, to the point where it is in the very air we breathe. Where are all these particles coming from? What are the biggest exposure mediums? And what happens once these particles enter our body?

These are all important questions to consider when looking at the global microplastics problem, and none have easy answers. The goal of these articles is to give you an idea of the many factors, the many facets of microplastics pollution, and help you understand the possible consequences of humanity’s 230-fold increase in plastic production of the last 70 years.

Plastics break down when exposed to the sun/heat, the air, or water; they can be decomposed in the soil by bacteria and fungi, or fall apart when ingested or coming into contact with acidic compounds or certain chemicals. Basically, all the time everywhere but always in different ways—at different rates, leaching different chemicals in varying compositions and concentrations, with different particles shapes, sizes, and weights.

To better understand all these various aspects, we first looked at what micro- and nanoplastics (MNP) are. Now, we are going to dive deeper into the different ways in which we are exposed to them. Besides giving us a better understanding of the scale of this complex problem, this wider context will also help us later on when we examine the possible health and environmental consequences.

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💡In this series of posts you can expect to learn more about the following aspects of plastic pollution:

1. What are micro/nanoplastics

2. Looking beyond the headlines – avoiding sensationalism in reporting on scientific research

3. Health risks of microplastics

4. Environmental consequences of microplastics

5. What can we do to address plastic pollution?

If you would like to directly support me in these efforts, which involves time-consuming activities like reading through piles of scientific studies, please consider leaving a donation using the button below or taking a paid subscription, which also provides you with access to the fiction stories I’m currently writing. Sharing these articles is also greatly appreciated, so that more people can learn about this topic.

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Microplastics exposure

MNP exposure can come about through ingestion, inhalation, (skin) contact, and in utero. For now, let’s focus on what we know about how MNP enter and break down inside our bodies.

❗Reminder – I do not use the terms micro- and nanoplastic particles (MNP) and microplastics interchangeably in these posts. Due to the small size of nanoplastics (<1 micrometer), most studies have so far only examined microplastics (1 micrometer to 5 millimeters), and their findings therefore mainly apply to those, although we can to a large degree expect similar findings had they been studied. It is probably safe to assume that, had these studies been able to detect nanoplastic particles, their particle counts would have been much higher. What is much less clear is how the inclusion of nanoplastics might impact conclusions about health risks. 

Exposure medium 1: inhalation / air

As we have firmly established by now, MNP are everywhere. But how many particles we are exposed to can be highly variable, which is part of what makes it so difficult to figure out the harm they can cause.

In what situations can we expect to find more MNP? A 2024 systematic review of the current state of research regarding indoor and outdoor air exposure sheds some light on that question:

• Microplastic particle concentrations indoors > outdoors

• The highest microplastic particle concentrations were found in the vicinity of roads. The denser the traffic, the more microplastic particle particles are in the air.

• Certain occupations can increase your exposure to microplastic particle

• Children have the highest exposure rates. The researchers suggest that school could be a significant contributor to their higher microplastic particle exposure.

• Infants and pregnant women are particularly vulnerable to toxins, so even at low exposure rates there is a greater risk of health impacts. We will definitely go into the effects of MNP on fetal development and fertility once we get to the topic of health.

  Note: The findings above seem to be relatively consistent across most studies, despite different methodologies. Exact concentrations and exposures can vary widely based on geography, population, occupation, sex, activity, inhalation rate. As we saw in the previous post, the number and type of detected microplastic particles also vary depending on the methodology used, so it remains difficult to compare the results of different studies with a high degree of certainty. That is also why I tend to exclude more precise concentrations and particle counts, and instead talk about indications and trends.

Why are there so many MNP in the air?
Car tires appear to be a significant part of the answer to that question. As we see in the list above, the highest MP concentrations were found near roads. That is because when car tires shear past the road and are exposed to the elements, thousands of small particles are released into the air, including MNP. Over its lifetime, a tire loses about 10% of its weight this way. Estimations of the total contribution of airborne MNP from car tires can vary widely locally, but overall they seem to be one of the largest contributors. Other significant sources are litter, paints, nurdles (plastic pallets), cosmetics, laundry fibers, artificial turf, and detergents. Many (~34%) of these airborne MNP end up in the ocean, which means they eventually end up in even the remotest regions on Earth. The rest ends up in soil and surface waters, and inside our lungs and digestive system.

Based on measurements in the OSPAR maritime area, which spans the North-East Atlantic. Source

So how many MNP do we breathe in each day?
To get a clearer idea of our possible exposure, let’s examine this Danish study, which put a mannequin inside three different apartments that would ‘breathe in’ the air for 24 hours while the people who lived there went about their day. The membrane? Built into the doll was a membrane that captured the ‘inhaled’ particles. Using this method, the researchers were able to identify particles down to 11 micrometer. That means they were not able to detect nanoplastics, but were able to detect most of the smallest microplastics.

The researchers divided the detected particles into three groups: ‘protein-based’ (shed skin) ‘cellulose-based’ (cotton and paper), and ‘microplastic’ particles. Most of the detected particles were part of the protein-based group (91%), while cellulose and microplastic were both slightly above 4%. Polyester was by far the most abundant microplastic (59-92%), with the rest consisting of a wide range of different plastics like nylon (0-13%), polyethylene (5-28%) and polypropylene (0.4-10%). Based on their findings, they estimate an inhalation rate of 272 microplastic particles per day. It is important to note that the apartments had significant differences in microplastic concentrations and composition.

While I do not think we should see the quantities of inhaled particles as completely representative of what the average person inhales, they nonetheless give us some fascinating insights into the microscopic particles that are in the air we breathe every day.

💡Considering the importance of methodology, as we discussed in the previous post in this series, this is a good moment to put these results into perspective. If you are not familiar with this way of thinking, this can hopefully provide you with another concrete example of how to interpret these kinds of results.

As mentioned earlier, nanoplastics could not be detected, so the amount of plastic particles entering the mannequin’s lungs is likely much higher. On the other hand, a mannequin is obviously not a human being, and while the researchers took into consideration factors like air flow, body temperature, and mouth size, the plastic particles collected on the membrane inside the dummy cannot replicate the complexity of the human lung (the researchers acknowledge this). Besides, most of us are unlikely to sit in a chair inside our home for 24 hours straight, so we cannot assume these particle counts to be wholly representative of what we would inhale ourselves. Lastly, during the removal and transport of the membrane, and subsequent transfer and analysis of the particles, additional particles will have made their way onto (or out of) the sample. By comparing the membranes to blank ones, researchers estimated this contamination to be, on average, about 4.9±3.9% for the MP particles.

In conclusion, inhalation is one of the major ways in which MNPs enter our bodies. In terms of quantities, it could very well be our biggest exposure medium. On the other hand, MNPs ingested through food or bottled water may be less numerous, but have a higher mass. This of course begs the question what is potentially more harmful, having many tiny MNP inside our bodies that can potentially penetrate cell tissue, or having less but heavier MNP that can leach higher quantities of chemicals or carry more pollutants. I do not think that anyone has an answer to that, but it is an important distinction to keep in mind. In the next post, we are going to take a closer look at our MNP exposure through ingestion.

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You can find my other posts on microplastics here:

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