Every year around this time, the air in north India changes. News reports from late September describe Delhi’s average air quality index rising from about 100 in September to about 212 in October, based on data from recent years, with other cities seeing similar jumps as winter approaches. If you’ve noticed a scratchy throat or a heavier chest as the season turns, you’re not imagining it. This guide explains what the numbers mean, who is most affected, and which protective steps are worth your effort.
What the AQI Numbers Mean
India’s National Air Quality Index turns pollution readings into six bands. A reading of 0 to 50 is Good, 51 to 100 Satisfactory, 101 to 200 Moderate, 201 to 300 Poor, 301 to 400 Very Poor and 401 to 500 Severe. In the Moderate band, people with asthma, lung disease or heart disease may start to have trouble breathing. In the Poor band, most people can feel discomfort after being outside for a while. Very Poor and Severe days are bad enough to affect healthy people too, and they can seriously worsen existing illness.
The pollutant that matters most is PM2.5, tiny particles less than 2.5 micrometres across, many times thinner than a hair. They’re small enough to travel deep into the lungs, and some pass into the bloodstream.
Why It’s More Than a Cough
It’s easy to think of pollution as a lung problem alone. The World Health Organization estimates that outdoor air pollution caused 4.2 million premature deaths worldwide in 2019, and about 99% of the global population lives in places that don’t meet WHO air quality guidelines. Of those deaths, roughly two-thirds were from heart disease and stroke, with the rest from chronic lung disease, lung infections and lung cancer.
That matters for how you think about protection. The American Lung Association notes that there is no safe threshold for breathing in fine particles. Short spikes lasting hours or days are linked to heart attacks, strokes, hospital visits and worse asthma attacks in children, and long-term exposure is linked to slower lung growth in children and to heart and lung disease in adults. If you want to look after the rest of your body too, our guide on protecting your heart is a good companion read.
Who Needs to Be Most Careful
Children, pregnant women, adults over 65 and anyone with asthma, COPD or heart disease are the groups health bodies single out, and people with diabetes or a smoking history are also at higher risk. The WHO describes air pollution as one of the greatest environmental risks to child health. If someone in your family is in one of these groups, plan around the AQI on bad days and not around the calendar.
What Helps
Check the AQI before you go out. Use a trusted app or the official CPCB readings, and make it a morning habit like checking the weather. The point is to decide the day’s plan with real numbers, not guesses.
Time and place your outdoor activity. On Poor days and worse, move exercise indoors or make it lighter and shorter, and avoid busy roads. Research on active travel found that the benefits of walking and cycling generally outweigh the risks from pollution, but that work modelled cities such as London, and it doesn’t mean a Severe Delhi morning is a good time for a hard run. If you’d rather keep moving without going outside, an indoor routine like interval walking works at home.
Use the right mask, and wear it properly. Respirators rated N95 or FFP2 are designed to filter at least 95% of fine particles, but only if they fit snugly with no gaps at the nose and cheeks. A thin cloth mask or a loose surgical mask does much less against PM2.5. A mask you can’t wear comfortably for the time you need it won’t protect anyone, so fit and comfort matter as much as the rating.
Clean the air indoors. Keep windows closed during the worst hours, usually early morning and late evening in the smog season. A HEPA air purifier sized for the room can lower indoor particle levels noticeably, and it helps most in the room where you sleep. Avoid adding indoor smoke from incense, mosquito coils and tobacco, and ventilate when you cook.
Skip the firecrackers. Smoke from Diwali firecrackers adds a sharp spike on top of an already bad season, and it hits children and people with asthma hardest.
Build a simple smog-day routine. Decide in advance what you’ll do when the AQI crosses a number you’ve set, for example 200: school bag and mask by the door, an indoor exercise plan, windows shut by evening, and an inhaler within reach if anyone in the house uses one. Having the plan ready means you won’t have to make a health decision while you’re rushing out of the door.
What Doesn’t Help
Many popular fixes sound reasonable and don’t have solid evidence behind them. There’s no good reason to expect steam inhalation, “lung detox” drinks, jaggery or herbal concoctions to clear pollution particles out of your lungs, and steam carries a risk of burns. A balanced diet, enough sleep and regular exercise support your overall health, but they’re not a shield against polluted air. The only reliable way to protect your lungs is to breathe less of the pollution in the first place.
Don’t Forget the Basics
Spending more time indoors in the smog season can also mean less sunlight and less movement, so it’s worth keeping an eye on your vitamin D and finding indoor ways to stay active.
When to See a Doctor
Don’t wait out chest pain, breathlessness at rest, wheezing, a cough that lingers for weeks, or any worsening of asthma or COPD that your usual inhaler doesn’t settle. If you have a lung or heart condition, ask your doctor now for a plan for smog days, including when to adjust medication and when to stay in. Pollution is a problem no single household can solve, and it needs policy changes. On the days when you can’t change the air outside, you can still control the air inside your home and how long you spend in the open.