Are you inhaling plastics?

Title: Microplastics in the atmosphere of Ahvaz City, Iran
Authors: Sajjad Abbasi, Neamatollah Jaafarzadeh, Amir Zahedi, Maryam Ravanbakhsh, Somayeh Abbaszadeh & Andrew Turner.
Journal: Journal of Environmental Sciences
Year: 2023

Since the invention of plastics, humanity has found countless uses for this class of wonder-materials. From drinking straws to cars, plastic is everywhere. But the longevity of plastic has raised concerns from many people. As plastic objects degrade, they may release small plastic particles known as microplastics which have been observed in environments around the globe. Much of the focus around plastic pollution is on the marine environment, due to the well documented impacts of plastic pollution on aquatic life. However, there is growing evidence that microplastics can exist as suspended particles in the atmosphere. Atmospheric scientists are used to investigating particles in the air, for example soot formed from the burning of wood. Such particles are known to cause a myriad of health issues, but the potential impacts of airborne microplastics are much less certain.

In their recent publication, Abbasi et al. present their measurements of airborne microplastics collected at an urban site in Iran in order to characterise this underexplored and diverse category of air pollution. The researchers filtered air over the course of multiple days to collect atmospheric particles, including airborne microplastics, onto the filter samples. These filters were then processed to isolate plastic particles by soaking the filters in water and reacting the residues with H2O2 to remove organic matter in the sample. The microplastics were then collected by a density-based separation method using a saturated ZnCl2 solution.

A visual inspection of 322 particles under a microscope revealed that all of the microplastics collected were fibrous in nature, rather than being films or spheres, for example. Combining this with an analysis of the types of plastic that were detected (polyethylene terephthalate (PET), polypropylene, nylon, or polystyrene) indicates that the major source of these airborne microplastics is from synthetic fabrics used in clothing and furnishings. The team were also able to identify the colour of each fibre, finding that most were black or grey in colour, with others being white, transparent, red, pink, blue, or green.

The findings of this work are generally in agreement with previous investigations, which showed a dominance of fibres in the collected material, as well as similar plastic types. However, previous studies did detect morphologies other than fibres and the concentrations of microplastics in the air seem to be far lower than those detected in previous studies, particularly those conducted indoors. This may be partially explained by the method used to collect the samples, which exclusively collected small particles (so-called PM10) that are most significant for human exposure as they are more readily inhaled. The authors note that the low concentrations they observed may demonstrate that human exposure to airborne microplastics is more significant in indoor environments than outdoors. However, the choice of sampling location will also impact the concentration of microplastics, with some areas being more polluted than others.

There are large uncertainties around the impact of airborne microplastics on human health and the natural world and further research will help to reveal the effect of these widespread microplastics and inform the next steps in our development and use of plastics.

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