A recent interdisciplinary study, partially sponsored by the National Institutes of Health, has shed light on the negative impact dry air can have on healthy human airways. The research indicates that exposure to dry air can increase the risk of dehydration and inflammation in our airways, which could lead to conditions like asthma, allergic rhinitis, and chronic cough.
As the world continues to warm, the atmosphere’s thirst for water, referred to as Vapor Pressure Deficit (VPD), is increasing at a significant rate. Even with relative humidity staying constant, a higher VPD can result in faster evaporation and dehydration of earth’s ecosystems, including our upper airways. This, in turn, can trigger the body’s inflammatory and immune response.
The research, published in Communications Earth & Environment, suggests that such dehydration and inflammation in our airways can get worse with mouth breathing (which is also on the rise) and increased exposure to air-conditioned and heated indoor air.
“Air quality is not just about cleanliness, it’s also about the level of dryness in the air. Just like we need to keep our airways clean, keeping them hydrated is equally important,” says David Edwards, lead author and adjunct professor of medicine at Johns Hopkins University School of Medicine. Edwards further explains that the ocular mucosa, a part of our eye exposed to the atmosphere, is also at risk in dehydrating atmospheres.
In their research, the team investigated whether a water loss process called transpiration, common in plants, occurs in the mucus of our upper airways when exposed to dry air. They found that dry air exposure led to thinner mucus and higher concentrations of cytokines, proteins indicating cell inflammation, in human bronchial epithelium cells (cells that line the upper airway).
Furthermore, their study also revealed that inflammatory mucus transpiration happens during normal breathing when exposed to dry air. This was observed in an animal model, where mice with pre-existing airway dryness exhibited high inflammatory response, while those exposed only to moist air did not.
Looking at climate models, the team predicts that due to rising temperatures and drier air, most of America could face an increased risk of airway inflammation by the second half of the current century.
The researchers concluded that these findings have wider implications for other physiological mechanisms in the human body, particularly dry eye and the movement of water in the mucus lining of the eyes. “As global warming continues, human mucosa dehydration is becoming a significant threat to human health, leading to increased chronic inflammation and related diseases,” says Justin Hanes, Ph.D., the Lewis J. Ort Professor of Ophthalmology at the Wilmer Eye Institute, Johns Hopkins Medicine.
The study highlights the need for understanding how our airways dehydrate on exposure to dry air. This will help in developing effective behavioural changes, preventive measures, and therapeutic interventions to combat the detrimental effects of dehydration.
This research included contributions from various esteemed institutions like Boston University, Imperial College London, Sensory Cloud Inc., Illinois Institute of Technology, and University of North Carolina. The authors have reported no conflicts of interest. A part of this research was funded by NIH grants.
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