Microplastics can stick in human airways, new study finds

A new study from an international group of researchers has found that microplastics can stick in our respiratory system, posing potentially serious health risks.

According to the researchers, microplastics, which are small fragments resulting from the breakdown of plastic items of industrial waste, often contain harmful pollutants.

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In a study, researchers say that humans may unknowingly breathe in approximately 16.2 bits of microplastic per hour. This amount is equivalent to the size of a credit card over the course of a week.

Published in the Journal Physics of Fluids on Tuesday, the authors say this is the first study to analyze the microplastic transport within the upper lung airways.

Researchers from the University of Technology Sydney, Western Sydney University, Urmia University, Islamic Azad University, the University of Comilla, and the Queensland University of Technology used a computational fluid dynamics model to analyze how microplastics move and accumulate in the upper airway.

“Millions of tons of these microplastic particles have been found in water, air, and soil. Global microplastic production is surging, and the density of microplastics in the air is increasing significantly,” Mohammad S. Islam, one of the study authors, explained in a news release. “For the first time, in 2022, studies found microplastics deep in human airways, which raises the concern of serious respiratory health hazards.”

For this study, the team studied the movement of microplastics of different shapes and sizes during slow and fast breathing. They found that these microplastics tended to gather in specific areas called hot spots in the nose and back of the throat (oropharynx).

“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.”

Researchers say the size of microplastics and the way we breathe can affect how much they stick to our airways. For instance, when we breathe faster, fewer microplastics get deposited, and the largest microplastics (5.56 microns) are more likely to get stuck in our airways compared to smaller ones.

The authors say the study signifies the real concern of potential risks of breathing in microplastics, particularly in areas with lots of plastic pollution or industrial activity. They hope their findings can help inform targeted drug delivery devices and improve health risk assessment.

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

The researchers say they intend to study in the future how microplastics move in a detailed model of the entire lung, while considering factors like humidity and temperature to better understand the movement of microplastics.