Dr Fay Couceiro, Senior Research Fellow in Biogeochemistry in the School of Civil Engineering and Surveying, writes on the widespread presence of airborne microplastics and their potential impact on human health.
Microplastics in air, what are they? What is known about them? Are they a danger to our health? These are just some of the questions I am trying to answer at the University of Portsmouth. So let’s start at the beginning:
What are airborne microplastics?
Microplastics are defined as any plastic below 5mm in size. They are separated into 2 types, primary and secondary microplastics.
Primary microplastics are below 5mm when they enter the environment, such as nurdles and those found in face scrubs and toothpastes. Secondary microplastics are larger than 5mm when they enter the environment but, over time, degrade into smaller pieces, such as fragments of plastic bags and bottles.
Airborne plastics are much smaller particles that are light enough to be carried in the air. Most airborne microplastics are below 1mm in length and are categorised by shape as fibres (long and thin) and non-fibres.
What is known about them?
Unfortunately not that much, but we do know that airborne microplastics are found everywhere. They have been found in every place that has been sampled so far. It is not just cities that are affected. Airborne microplastics have been found in remote mountain ranges, the arctic and even sea spray.
Most research on microplastics has focussed on plastics in water. Airborne microplastics is a relatively new but rapidly growing area of research. Those studies that have examined microplastics in the air have been undertaken outdoors. In the UK, however, 90% of our time is spent indoors. Most of the air we breathe is therefore indoor air, yet very little research has taken place on microplastics indoors.
That is why the University has begun research in this area. We are measuring microplastics in different indoor environments, looking at the type, size and shape of the plastics found. Although very little data exists, what we know so far is that the concentration of microplastics indoors is much higher than the concentration outdoors. Some studies have shown that it is 60 times higher than outdoors, while other research points to an even higher concentration!
Are they a danger to our health?
We simply don’t know yet. Airborne microplastics research is in its infancy and there are many factors to consider. That is what we are doing now — devising studies to see if there is an impact on human health.
Some studies have looked at the impacts of microfibers (natural and plastic) on human health in working conditions with very high concentrations of airborne fibres, such as fabric manufacturing and carpet laying. In such jobs, a detrimental effect on lung health has been shown due to microfiber inhalation. What we are unsure of is whether there is an effect at normal levels, not just the very high concentrations encountered by people working in these industries.
We know that particles (any particles, not just plastics) longer than 10µm are unlikely to get past our upper airways, particles below 2.5µm can get deep into our lungs, and particles less than 1µm can breach cell walls. To give context, the average width of a human hair is 75µm so, at the smallest range we are looking at, 1/100th of the width of a hair. Unfortunately due to difficulties in measuring, most studies have only measured microplastics 10µm and above.
To enhance our research, the University has purchased a specialist microscope that can reveal tiny pieces of plastic below 1 micrometre in size. This will enable us to identify microplastics at the size range which is most likely to impact our health, such as those with the ability to enter the bloodstream.
While there is currently no evidence for negative health impacts in our homes, we are working with the Portsmouth Hospitals NHS Trust to investigate the presence of microplastics in the lungs of chronic obstructive pulmonary disease (COPD) and asthma patients. Ultimately, this research may help alert patients of risk factors or triggers for their condition. For example, avoiding places that have recently been carpeted where there may be a high number of fibres in the air, ensuring adequate ventilation when hoovering or when there is a lot of activity within carpeted areas.