New research by Professor Eun-Jung Park and her team at the Graduate School of Medicine sheds light on the respiratory risks of microfiber exposure in indoor air

Professor Eun-Jung Park at the Graduate School of Medicine investigates the impact of household chemicals on our health. Her research interest includes the causative relationship between humidifier disinfectants and pulmonary fibrosis, as well as the potential for the chemicals in disinfectant sprays leading to respiratory diseases. Last year, the Human Health and Environmental Toxins Research Center was designated as a standard reference data center for respiratory safety data. Professor Park's research aims to raise awareness of ways to protect our health in daily life.

Most of the air in our living spaces contains small airborne fibers (nanofibers) that come from clothes and bedding. Clothing made from synthetic fibers has increasingly become the mainstream in recent times, driven by economic considerations and the superior durability of synthetic fibers over natural fibers. Face masks are no longer mandatory as of January 30, 2023, but wearing them is still recommended, and they are typically made of synthetic fibers. More attention should be paid to nanofibers, since they are a byproduct of petroleum refining, similar to microplastics that have become a global concern recently.

Professor Park's team joined forces with Professor Dong-Wan Kim at the School of Civil, Environmental and Architectural Engineering of Korea University to create two types of synthetic fibers through electrospinning and examine the potential health implications when these nanofibers are inhaled and enter the human body by way of the respiratory system. Their research findings were published in February 20 in Nanotoxicology (IF=5.913) under the title of “Comparison of toxicity and cellular responses following pulmonary exposure to different types of nanofibers.” The study was supported by the National Research Foundation of Korea and the Korea Institute of Toxicology.

Potential health risks of nanofibers in the indoor air of homes and offices
The researchers investigated the health impacts of polyethylene oxide fibroin (PEONF) nanofibers produced by electrospinning, as well as silk fibroin (SFNF) nanofibers obtained by removing the polyethylene framework used in electrospinning, on the lung when they were cut into smaller pieces and taken in via the respiratory system. Female mice that breathed in a high concentration of SFNF nanofibers for four weeks showed a significant loss in body weight when compared to the control group. Mice exposed to nanofibers exhibited a higher number of cells in the pulmonary alveoli compared to the unexposed group. However, the relative portion of neutrophils and eosinophils only substantially increased in female mice exposed to SFNF nanofibers.

Both types of nanofibers induced notable pathological changes in the lungs of all the exposed mice: (1) inflammatory cells infiltrated into the blood vessels, bronchioles, and interstitium; (2) macrophages coalesced in the alveoli; (3) arterial media degenerated and hypertrophied; (4) mucus-secreting cells proliferated and mucus plugs produced; and (5) multinucleated giant cells and foamy macrophages formed. Furthermore, only the concentration of MCP-1α and CXCL1, which contribute to the influx of neutrophils and macrophages, and TGF-β, which plays a role in damaged tissue repair, increased among the 12 inflammation-related markers involved in these changes. TGF-β is also considered a marker closely associated with the development of idiopathic pulmonary fibrosis.

Notable findings include an increase in the distribution of eosinophils, as well as changes in the concentrations of total bilirubin, glucose, sodium, chloride, calcium, and creatine kinase in the blood. These results suggest that synthetic nanofibers, when inhaled through the respiratory system, can induce changes in immune system and biochemical alterations in the bloodstream, which may have a systemic adverse effect on health.

To further investigate the toxic mechanism of the two nanofibers observed in animal testing, the research team exposed alveolar macrophages to the nanofibers for 24 hours and observed the resulting cellular responses. The nanofibers caused cells to die through necrosis and late apoptosis, which was accompanied by oxidative stress, increased production of nitric oxide, rupture of cell membranes, damage to intracellular organelles, and accumulation of intracellular calcium. Notably, multinucleated giant cells were formed in cells exposed to either PEONF or SFNF.

The durability of synthetic nanofibers raises concern about lower excretion potential once inside the body
Professor Park said, “The durability of fibers makes them resistant to physical and chemical stresses that can occur in the environment. On the flip side, it also means that highly durable materials have a very low chance of being broken down and excreted once they enter the body. When fibers enter the body through the respiratory tract, they are less likely to be excreted if not decomposed or dissolved, as this pathway has a low excretion potential.”

The study underscores the significance of indoor air management. Professor Park emphasized the importance of managing the air after drying clothes or using a dryer at home. As seen in a scene from a movie about the late labor activist Jeon Tae-il, many seamstresses and tailors working in sewing factories in the late 1960s suffered from respiratory diseases caused by exposure to synthetic nanofibers.

Professor Park concluded by stating, “While the exposure level to synthetic nanofibers in indoor settings may be lower than that of a factory setting, the potential risk of long and continuous exposure cannot be ignored. Thus, it is crucial to prevent the airborne release of nanofibers indoors by wiping down areas around dryers or where laundry is folded with a wet mop or by using other wet cleaning methods. Families with crawling babies or energetic children should be particularly cautious during the winter months, when indoor air tends to be dry so that the likelihood of airborne nanofibers increases. I am committed to conducting research that can help prevent respiratory diseases caused by the exposure to harmful substances in our daily lives.”