Mucus and lung health: IIT Bombay researchers have reported findings that challenge a common assumption about how our lungs protect us. Mucus, the slippery fluid lining the airways, is meant to act like a natural shield. When dust, smoke, allergens, or any foreign material enters the breathing passages, the body responds by producing more mucus to trap those particles so they can be cleared out.
But the new work suggests that when mucus increases beyond a point, such as during exposure to heavy air pollution, this defence may not get stronger. It can become weaker.
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The researchers explain that a larger amount of mucus does not always spread out into a smooth, protective layer. Instead, it can pull itself into narrow, raised ridges or “humps.” These humps may be thicker in certain spots, but they also become tighter and more concentrated, leaving wider stretches of the airway surface uncovered. In other words, the coating turns uneven and patchy, exposing parts of the airway wall that would ideally remain protected.
That matters in real-world city air. Urban pollution often contains soot and other particles that are extremely small; many are far thinner than a human hair. Because of their size, these particles can drift and settle through diffusion, meaning they can land easily on any exposed areas inside the airways. If the mucus layer is patchy, it creates more opportunities for these fine particles to stick directly to the airway wall, potentially increasing irritation and making allergy symptoms more likely.
The findings may also help explain why people with asthma can experience sudden, fast-escalating attacks. During an allergic response, the body may release even more mucus. If that extra mucus gathers into narrow humps rather than forming an even layer, it could leave more of the airway surface exposed to the same allergen that triggered the reaction. More exposure can lead to more irritation, which can drive more mucus release and tighter airways, setting up a self-reinforcing cycle that worsens quickly.
The researchers add that excessive mucus can create another serious problem: physical blockage. Thick mucus can plug parts of the airways, restricting airflow and making breathing more difficult, even before inflammation is fully under control.
While more research is needed to connect these fluid patterns directly to immune and cellular behaviour, the study offers a practical physical explanation for why “more mucus” is not always helpful. It also points toward a potential future benefit: if scientists can predict where mucus collects and where the exposed zones appear, they may be able to design inhaled treatments that land more accurately in the areas that need medicine the most.
