The Air Quality Index (AQI) of Delhi refers to the measurement of air pollution levels in Delhi, one of the most populated cities in the world. AQI is a numerical scale used to indicate how clean or polluted the air is and what health effects might be associated with it. In India, AQI is monitored and reported by the Central Pollution Control Board (CPCB) under the National Air Quality Monitoring Programme.
Delhi’s AQI often reaches very high and hazardous levels, especially during the winter months (October to January). The main reasons for poor air quality include vehicle emissions, industrial pollution, construction dust, burning of crop stubble in nearby states like Punjab and Haryana, firecrackers during festivals, and unfavorable weather conditions that trap pollutants close to the ground.
The AQI scale in India is divided into six categories:
0–50 (Good) – Minimal impact
51–100 (Satisfactory) – Minor breathing discomfort to sensitive people
101–200 (Moderate) – Breathing discomfort to people with lung diseases
201–300 (Poor) – Discomfort to most people on prolonged exposure
301–400 (Very Poor) – Respiratory illness on prolonged exposure
401–500 (Severe) – Affects healthy people and seriously impacts those with existing diseases
In many winters, Delhi’s AQI crosses 400 and sometimes even touches 500, which falls under the “Severe” category. Major pollutants include PM2.5 (fine particulate matter), PM10, nitrogen dioxide (NO₂), sulfur dioxide (SO₂), carbon monoxide (CO), and ozone (O₃). Among these, PM2.5 is considered the most dangerous because its tiny particles can enter deep into the lungs and bloodstream.
The government has introduced measures such as the Odd-Even traffic rule, promotion of electric vehicles, restrictions on construction activities, and the Graded Response Action Plan (GRAP) to control pollution levels. Despite these efforts, controlling air pollution in Delhi remains a major environmental and public health challenge.
