Checking the daily air pollution report has become a routine for many in India's metro cities. But what do the numbers and colours really mean? Understanding the data is the first step to protecting your health from the rising threat of air pollution.
The Big Number: What is AQI?
The Air Quality Index, or AQI, is a single number that simplifies complex air pollution data. Launched by India's Central Pollution Control Board (CPCB) in 2014, its goal is to provide 'One Number - One Colour - One Description' for easy public understanding. The AQI value is calculated based on the concentration of up to eight key pollutants, including PM2.5, PM10, Nitrogen Dioxide, and Carbon Monoxide. The final AQI number reported for your city is typically the highest value among these individual pollutant sub-indices, meaning it reflects the day's worst-performing pollutant.
Decoding the Six Colour Categories
The AQI scale from 0 to 500 is divided into six colour-coded categories, each with a clear health advisory. Good (0-50, Green): The air quality is excellent with minimal health impact. Outdoor activity is safe for everyone. Satisfactory (51-100, Light Green): Air quality is acceptable, but it may cause minor breathing discomfort for very sensitive individuals. Moderate (101-200, Yellow): This can cause breathing discomfort for people with existing lung conditions like asthma, as well as heart disease. Children and older adults may also be affected. Poor (201-300, Orange): Most people will experience breathing discomfort on prolonged exposure. It's advisable to reduce heavy outdoor exertion. Very Poor (301-400, Red): This level of pollution can lead to respiratory illness after prolonged exposure. People with lung or heart disease are at high risk and should avoid outdoor activities. Severe (401-500, Maroon): The air is hazardous. It can affect even healthy people and seriously impact those with existing diseases. Everyone should avoid all outdoor physical activity.
The Pollutants to Watch: PM2.5 and PM10
While the AQI measures multiple pollutants, particulate matter (PM) is often the primary concern in Indian cities. These are tiny solid and liquid particles suspended in the air, coming from sources like vehicle exhaust, industrial emissions, construction dust, and stubble burning. PM10: These are coarse particles with a diameter of 10 micrometres or less. They can irritate your eyes, nose, and throat. PM2.5: These are fine particles with a diameter of 2.5 micrometres or less—about 30 times smaller than a human hair. Because they are so small, they can bypass the body's natural defences, penetrate deep into the lungs, and even enter the bloodstream. Long-term exposure to PM2.5 is linked to serious health issues, including asthma, chronic bronchitis, heart attacks, strokes, and lung cancer.
Other Harmful Pollutants in the Mix
Beyond particulate matter, the AQI also tracks several harmful gases that impact health: Ozone (O3): Ground_level ozone is a lung irritant that can cause chest pain, coughing, and throat irritation. It can worsen bronchitis and asthma. Carbon Monoxide (CO): This gas, primarily from vehicle exhaust, reduces the amount of oxygen that can be transported in the bloodstream to critical organs like the heart and brain.* Nitrogen Dioxide (NO2) & Sulphur Dioxide (SO2): These gases, often from fuel combustion in vehicles and power plants, can irritate the respiratory system and worsen conditions like asthma.
Where to Find Reliable Pollution Data
To get accurate, real_time information, rely on official sources. The CPCB provides live AQI data for hundreds of cities across India on its website. Another excellent resource is SAFAR (System of Air Quality and Weather Forecasting and Research), an initiative by the Ministry of Earth Sciences. SAFAR provides location_specific air quality data and forecasts for major metros like Delhi, Mumbai, Pune, and Ahmedabad, helping you plan your activities up to three days in advance.
Practical Steps Based on the AQI
Reading the report is one thing; acting on it is what truly matters. When the AQI is 'Moderate' or worse, consider taking precautions. For 'Poor' to 'Severe' days, limit or avoid strenuous outdoor exercise, especially during morning and evening hours when pollution often peaks. Keep windows closed and use an air purifier indoors if you have one. When you must go out, wearing a well_fitted N95 or FFP2 mask can significantly reduce your exposure to harmful PM2.5 particles. Sensitive groups, including children, the elderly, and those with respiratory or cardiovascular conditions, should be especially cautious.
