Every breath you take: Study models the journey of inhaled plastic particle pollution

With recent studies having established the presence of nano and microplastic particles in the respiratory systems of both human and bird populations, a new University of Technology Sydney (UTS) study has modelled what happens when people breathe in different kinds of plastic particles and where they end up.

Led by Senior Lecturer of Mechanical Engineering Dr Suvash Saha, the UTS research team has used computational fluid-particle dynamics (CFPD) to study the transfer and deposition of particles of different sizes and shapes depending on the rate of breathing.

The results of the modelling, published in the journal Environmental Advances, have pinpointed hotspots in the human respiratory system where plastic particles can accumulate, from the nasal cavity and larynx and into the lungs.

Dr Saha said evidence was mounting on the significant impact of nano and microplastics on respiratory health and the UTS study would provide essential insights for the development of targeted strategies to mitigate potential risks and ensure effective health interventions.

"Experimental evidence has strongly suggested that these plastic particles amplify human susceptibility to a spectrum of lung disorders, including chronic obstructive pulmonary disease, fibrosis, dyspnea (shortness of breath), asthma, and the formation of what are called frosted glass nodules," Dr Saha said.

"Plastic particle air pollution is now pervasive and inhalation ranks as the second most likely pathway for human exposure.

"The primary types are intentionally manufactured, including a wide array of cosmetics and personal care products such as toothpaste.

"The secondary ones are fragments derived from the degradation of larger plastic products, such as water bottles, food containers and clothes.

"Extensive investigations have identified synthetic textiles as a principal source of indoor airborne plastic particles, while the outdoor environment presents a multitude of sources encompassing contaminated aerosols from the ocean to particles originating from wastewater treatment."

Dr Saha said the UTS team's modelling found that breathing rate along with particle size and shape determined where in the respiratory system plastic particles would be deposited.

"Faster breathing rates led to heightened deposition in the upper respiratory tract, particularly for larger microplastics, whereas slower breathing facilitated deeper penetration and deposition of smaller nanoplastic particles," he said.

"Particle shape was another factor, with non-spherical microplastic particles showing a propensity for deeper lung penetration compared to spherical microplastics and nanoplastics, potentially leading to different health outcomes.

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Scientists develop an RNA-based breath test to detect COVID-19

In a new study in The Journal of Molecular Diagnostics, published by Elsevier, investigators report on the design and testing of a breathalyzer, known as the Bubbler, that relies on viral RNA detection to diagnose SARS-CoV-2. Its name is derived from the bubbling sound that occurs when the patient exhales into the device.

The Bubbler not only reverse transcribes RNA from airborne virus particles into DNA to be tested via PCR but can also barcode that DNA, allowing samples to be linked directly to the patient they have come from and be used for sequencing. It can be used for simultaneous batches of pooled samples and provides additional information such as viral load and strain identity and eliminates the need for stabilizing a sample, potentially allowing the assay to be performed at home.

"Involvement of the lower respiratory tract is often a precursor to severe COVID-19, so there is an argument for a more direct sampling focused on exhaled breath," explained lead investigator William G. Fairbrother, PhD, professor in the department of molecular biology, cell biology and biochemistry at Brown University in Providence, RI, USA.

Virus detection by the Bubbler is similar to a hospital-swab PCR test; however, it is a better measure of risk of contagion as it detects airborne viral particles. Swab tests can return a positive result for months after infection as they detect viral RNA fragments in cells that persist in previously infected cells. The Bubbler can also be adapted for environmental sampling in hospitals, transportation hubs, and closed environments like offices, ships, and planes, the investigators report.

Seventy patients treated in the Emergency Department of Rhode Island Hospital between May 2020 and January 2021 were screened. The study tested samples from three points in the respiratory tract. Tongue scrapes from the mouth (saliva/tongue scrapes) and from 15 seconds of exhaled breath collected in the Bubbler were compared to those from a conventional nasopharyngeal swab PCR test. The Bubbler is a glass tube with a glass pipette through which patients can exhale. The tube is filled with a reverse transcription reaction mixture and cold mineral oil.

The study determined that SARS-CoV-2 can be readily detected in the breath and is more predictive of lower respiratory tract involvement. Viral RNA is more enriched in the breath relative to oral samples, while oral samples include cells involved with SARS-CoV-2 replication that breath samples do not. This suggests the viral signal detected in the Bubbler comes from active viral particles.

"The Bubbler is more likely to be a better indicator of current infection than nasopharyngeal swabs," said Dr. Fairbrother. "Another advantage is the barcoding, which enables high-throughput RNA virus testing at a fraction of the cost of conventional testing. The barcode returns a viral sequence that also supports strain identification, which may prove useful as more information is learned about transmissibility and possible strain-specific treatment decisions."

The investigators also demonstrated how the Bubbler might be adapted to detect virus in airborne samples. To model the movement of droplets exhaled in human breath, three unique nucleic acid samples were added to three personal humidifiers at different locations at varied distances from the Bubbler in a room with high airflow and a room with low airflow. Although a detailed exploration of this application was beyond the scope of the study, the results demonstrate the potential to use aerosolized nucleic acids to quantitatively map airflow in indoor spaces, and to detect SARS-CoV-2 in the air.

"Such technology could be useful in restoring service to industries such as hotels, cruise ships, and casinos," Dr. Fairbrother observed. "There is also an epidemiological benefit to routine testing of air at early warning sites such as transportation hubs and hospital emergency departments."

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