Microplastics are now ubiquitous on our planet – they’re found all over the place, including fresh Antarctic snow, and are also present in our bodies. We are thought to inhale a staggering amount of plastic, but where does it all end up?

In a new study, researchers have created a model to work out, for the first time, how these tiny plastic particles are transported in the upper airways, and, crucially, where they accumulate. 

Microplastics are extremely small pieces of debris generated by the disposal and breakdown of plastic products. They can pose a serious risk to our health when inhaled and there is concern about the long-term effects they may have on our bodies, especially as they amass within us.

“For the first time, in 2022, studies found microplastics deep in human airways, which raises the concern of serious respiratory health hazards,” Mohammad Islam, an author on the paper, said in a statement.

Understanding how they travel in the respiratory system is therefore of great importance; however, this represents a gap in the literature and has never before been studied.

Islam and co-authors sought to change this, creating a computational fluid dynamics model to explore the movement of differently shaped and sized microplastics in the upper airways under various breathing conditions. The plastic particles, they found, were most likely to build up in the nasal cavity and oropharynx  – the back of the throat.

“The complicated and highly asymmetric anatomical shape of the airway and complex flow behavior in the nasal cavity and oropharynx causes the microplastics to deviate from the flow pathline and deposit in those areas,” said Islam.

“The flow speed, particle inertia, and asymmetric anatomy influence the overall deposition and increase the deposition concentration in nasal cavities and the oropharynx area.”

A faster flow rate resulted in less microplastic accumulation, while a larger particle size (5.56 microns) led to increased deposition.

The researchers are now looking to investigate how these microplastics move around human lungs and how this might be impacted by environmental factors such as temperature and humidity. They hope, as microplastic production continues to rise, that their current research will help inform policy decisions surrounding microplastic pollution.

“Millions of tons of these microplastic particles have been found in water, air, and soil,” said Islam. “Global microplastic production is surging, and the density of microplastics in the air is increasing significantly.”

“This study emphasizes the need for greater awareness of the presence and potential health impacts of microplastics in the air we breathe,” author YuanTong Gu added.

The study is published in Physics of Fluids.

Correction 3/14/24: An earlier version of this article incorrectly claimed that humans inhale a credit card’s worth of microplastics every week. This was based on an overestimation in the press release, which has since been corrected; the actual amount is much lower. The header image, title, and first paragraph have been updated accordingly.