Scientists find how microplastics stick around in human airways

Scientists have found that tiny bits of plastic particles that we inhale from the environment collect in hot spots in the nasal cavity and oropharynx, or back of the throat.

The findings that were published recently in the journal Physics of Fluids warned that the tiny particles generated from the degradation of plastic products can pose serious health risks, including to the respiratory system.

A computer model to analyse microplastic transport and deposition in the upper airway was developed by scientists, including those from the University of Technology Sydney in Australia.

Microplastics are tiny plastic particles usually classed as less than 5mm in length that mostly result from the breakdown of larger plastic products over time.

Scientists have warned over recent years that there are a number of potential health risks from ingesting these particles as their chemical constituents, such as bisphenols and phthalates, are known to disrupt hormones and are linked to cancer, infertility and early puberty.

Recent studies have also shown that microplastics deep in human airways can pose significant respiratory health hazards.

“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,” study co-author Mohammad S Islam said in a statement.

Researchers explored the movement of microplastics with different shapes – spherical, tetrahedral and cylindrical – and sizes from 1.6 to 5.56 microns under slow and fast breathing conditions.

The new study found that these plastic particles containing toxic pollutants tend to collect in hotspots in the nasal cavity or the back of the throat, with their deposition rate dependent on breathing conditions and particle size.

“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,” Dr Islam said.

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

Scientists found that an increased flow rate led to less deposition and the largest microplastics about 5.56 micron in size were deposited in the airways more often than their smaller counterparts.

The findings highlight the “real concern” of exposure to and inhalation of microplastics, especially among people living in areas with high levels of plastic pollution or industrial activity.

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

This article was amended on 13 March 2024. It originally reported that the study said humans might inhale up to a credit card’s worth of microplastics every week, however, this was inaccurate. A press release issued in relation to the study contained the over-estimate but was corrected on 12 March 2024, and this article amended accordingly.