Air Pollution is becoming a huge threat for our healths. Every winter, as a thick gray veil descends upon the city, the residents brace themselves for another season of smog, irritation, and illness. The poor air quality is primarily due to particulate matter (PM 2.5 and PM 10) levels soaring to many times above permissible limits. While the immediate effects—cough, watery eyes, breathlessness—are well recognized, what often escapes notice is how this toxic air silently weakens our body's natural defense systems, making us more prone to infections, especially of the respiratory tract.
The human respiratory system is designed with remarkable efficiency to filter, humidify, and warm the air we breathe. Tiny hair-like structures called cilia, lining the airways, trap dust and microbes, moving them upward to be expelled. However, prolonged exposure to polluted air disrupts this delicate mechanism. Fine particulate matter—PM2.5—penetrates deep into the lungs, lodging in the bronchioles and alveoli, where gas exchange occurs. These particles cause chronic inflammation and damage the epithelial lining, compromising the very barrier meant to protect against invading pathogens.
As a result, viruses and bacteria that would normally be cleared by the body's defense mechanisms gain easy entry, leading to more frequent and severe respiratory infections. In fact, hospital data during Delhi's pollution peaks often shows a spike in cases of bronchitis, pneumonia, sinusitis, and asthma exacerbations.
Polluted air doesn't just weaken our defenses—it actually creates an environment more favorable for viruses to thrive and spread. Studies have shown that exposure to high levels of air pollutants can alter the immune response in the respiratory tract, reducing the activity of macrophages and natural killer cells—the body's frontline soldiers against infections. When these are suppressed, viruses such as influenza, adenovirus, and even SARS-CoV-2 can replicate more easily.
Moreover, the winter months, when pollution levels are at their peak, coincide with lower humidity and temperature inversions. These conditions allow both pollutants and viruses to linger in the air longer, increasing exposure risk. This is one of the reasons why flu-like illnesses surge in Delhi every winter—pollution acts as both a facilitator and amplifier.
It's not just the lungs that suffer. Prolonged exposure to polluted air triggers systemic inflammation—elevating oxidative stress and inflammatory markers throughout the body. This chronic inflammation can dysregulate immune function, making it less efficient in responding to new infections. For those with pre-existing respiratory conditions like asthma or COPD, pollution can cause frequent flare-ups and further compromise their already fragile immune systems.
Children, the elderly, and those with diabetes or heart disease are particularly vulnerable. In children, repeated exposure to polluted air interferes with lung development and reduces lung capacity, making them more susceptible to both infections and long-term respiratory illnesses. For the elderly, pollution aggravates chronic diseases and weakens immune resilience.
An emerging area of concern is the link between air pollution and antimicrobial resistance. Pollutants like heavy metals and hydrocarbons in Delhi's air can promote genetic exchanges between bacteria, fostering the emergence of drug-resistant strains. This means that infections not only become more frequent but also harder to treat. The intersection of pollution, weakened immunity, and antibiotic resistance could evolve into a major public health challenge if not addressed urgently.
While the respiratory tract is the primary entry point, the impact of polluted air extends far beyond it. Ultrafine particles can enter the bloodstream, reaching organs such as the heart, brain, and kidneys. This widespread oxidative stress suppresses immune regulation, increasing vulnerability to infections in general—not just those affecting the lungs. Even the skin, our first line of defense, suffers from inflammation and impaired barrier function in polluted environments, predisposing to allergies and infections.
Individuals especially the more vulnerable ones can take measures to mitigate the effects of pollution:
1. Use air purifiers indoors, especially in bedrooms and living spaces.
2. Avoid early morning and late evening outdoor activities during high pollution days, when particulate matter levels peak.
3. Wear N95 or equivalent masks when outdoors—these can filter fine particles effectively.
4. Maintain good indoor ventilation, but avoid opening windows during severe smog episodes.
5. Boost your immunity through a balanced diet rich in antioxidants, regular exercise, adequate hydration, and sufficient sleep.
6. Get vaccinated against influenza and pneumococcal infections, especially if you belong to a vulnerable group.
(By Dr Vivek Nangia, Vice Chairman & Head, Pulmonology, Max Super Speciality Hospital, Saket)
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