Introduction
Air pollution has become one of the most pressing environmental and health challenges of our time. With rapid urbanization, industrialization, and deforestation, the air we breathe is increasingly contaminated with harmful pollutants. The Air Quality Index (AQI) is a key tool used globally to monitor and communicate the quality of the air and its potential effects on public health.
What is the Air Quality Index (AQI)?
The Air Quality Index (AQI) is a numerical scale that helps the public understand how polluted or clean the air is in a given location. The AQI is calculated based on the levels of key air pollutants present in the atmosphere.
AQI Scale and Categories
The AQI scale generally ranges from 0 to 500, with higher values indicating worse air quality. Each range corresponds to a color-coded category that indicates health risks.
| AQI Value | Air Quality Category | Color Code | Health Implications |
|---|---|---|---|
| 0 – 50 | Good | Green | Air quality is satisfactory, with little or no health risk. |
| 51 – 100 | Moderate | Yellow | Air quality is acceptable, but sensitive individuals may experience minor effects. |
| 101 – 150 | Unhealthy for Sensitive Groups | Orange | Sensitive groups (children, elderly, and those with lung diseases) may experience health effects. |
| 151 – 200 | Unhealthy | Red | Everyone may experience adverse health effects. |
| 201 – 300 | Very Unhealthy | Purple | Health alerts issued, and outdoor activities should be avoided. |
| 301 – 500 | Hazardous | Maroon | Emergency situation: entire population at risk. |
Major Air Pollutants and Their Sources
The AQI is based on the concentration of several key pollutants. Each of these pollutants has different sources and health effects.
| Pollutant | Primary Sources | Health Effects |
|---|---|---|
| Particulate Matter (PM2.5 & PM10) | Vehicle emissions, industrial processes, wildfires, dust storms | Respiratory diseases, lung cancer, cardiovascular diseases |
| Ground-Level Ozone (O3) | Vehicle exhaust, industrial emissions, chemical reactions in sunlight | Lung irritation, asthma, reduced lung function |
| Carbon Monoxide (CO) | Incomplete combustion from vehicles, generators, household appliances | Dizziness, confusion, headaches, risk of heart diseases |
| Sulfur Dioxide (SO2) | Burning of fossil fuels (coal, oil), industrial emissions | Eye irritation, respiratory problems, acid rain |
| Nitrogen Dioxide (NO2) | Vehicle exhaust, power plants, industrial activity | Lung inflammation, increased risk of respiratory infections |
AIQ in India
As of March 5, 2025, air quality across various states in India varies significantly. Below is a detailed overview of the current Air Quality Index (AQI) readings for select states and their major cities:
| State | City | AQI | Air Quality Level |
|---|---|---|---|
| Delhi | New Delhi | 350 | Hazardous |
| Maharashtra | Mumbai | 180 | Unhealthy |
| Uttar Pradesh | Lucknow | 200 | Very Unhealthy |
| West Bengal | Kolkata | 160 | Unhealthy |
| Tamil Nadu | Chennai | 90 | Moderate |
| Karnataka | Bangalore | 85 | Moderate |
| Gujarat | Ahmedabad | 120 | Unhealthy for Sensitive Groups |
| Rajasthan | Jaipur | 110 | Unhealthy for Sensitive Groups |
Note: AQI values are subject to change based on real-time data.
Understanding AQI Levels:
- Good (0-50):
- Air quality is satisfactory, posing minimal or no risk.
- Moderate (51-100):
- Air quality is acceptable; however, some pollutants might pose a moderate health concern for sensitive individuals.
- Unhealthy for Sensitive Groups (101-150):
- Sensitive groups may experience health effects, while the general public is less likely to be affected.
- Unhealthy (151-200):
- Everyone could experience health effects; sensitive groups might face more severe impacts.
- Very Unhealthy (201-300):
- A health warning where everyone may suffer more serious health effects.
- Hazardous (301-500):
- Emergency conditions with a high likelihood of severe health effects across the entire population.
Health Recommendations:
- Moderate AQI (51-100):
- Individuals with respiratory conditions should consider reducing prolonged outdoor activities.
- Unhealthy for Sensitive Groups (101-150):
- Sensitive individuals should limit outdoor exertion.
- Unhealthy (151-200):
- Everyone should reduce prolonged outdoor activities; sensitive groups should avoid them.
- Very Unhealthy (201-300):
- Everyone should avoid outdoor activities; sensitive groups should remain indoors.
- Hazardous (301-500):
- Everyone should stay indoors and limit physical exertion.
Recent Developments:
- New Delhi’s Severe Pollution:
- The 33 million residents of New Delhi are enduring the worst levels of toxic smog in the city’s history, prompting politicians to question the suitability of the city as the national capital. With the AQI skyrocketing over 1700 in recent weeks—far above the “good” level of less than 50—residents face severe health risks, leading to the closure of schools, restricting truck traffic, and advising businesses to have half their employees work from home. citeturn0news12
- Mumbai’s Consideration to Ban Petrol and Diesel Vehicles:
- The state of Maharashtra is considering a proposal to ban petrol and diesel vehicles in Mumbai to combat worsening air quality, forming a seven-member committee to study the feasibility of allowing only electric or gas-driven vehicles. This action follows a directive from the Bombay High Court, which highlighted vehicle emissions as a major source of pollution amidst severe traffic congestion and ongoing infrastructure projects.
Health Effects of Air Pollution
Exposure to air pollution can have short-term and long-term effects on human health.
Short-Term Effects:
- Irritation of the eyes, nose, and throat
- Shortness of breath
- Coughing and wheezing
- Increased frequency of asthma attacks
- Headaches and dizziness
Long-Term Effects:
- Respiratory Diseases:
- Chronic obstructive pulmonary disease (COPD), lung infections
- Cardiovascular Diseases:
- Increased risk of heart attacks, high blood pressure
- Cancer:
- Long-term exposure to PM2.5 is linked to lung cancer
- Neurological Disorders:
- Studies show links between air pollution and cognitive decline, including dementia
Who is Most at Risk?
Some groups are more vulnerable to poor air quality:
- Children –
- Developing lungs make them more sensitive to pollutants.
- Elderly individuals –
- Weakened immune systems and existing health conditions worsen effects.
- People with pre-existing conditions –
- Those with asthma, heart disease, or COPD face increased risks.
- Outdoor workers –
- Constant exposure to pollutants increases their health risks.
Global Air Quality Trends (2025)
Most Polluted Cities in 2025
Recent air quality reports show that many cities across Asia, Africa, and South America continue to face hazardous air pollution levels.
| City | Country | AQI (Recent Data) | Primary Pollutant |
|---|---|---|---|
| Delhi | India | 350 (Hazardous) | PM2.5 |
| Beijing | China | 275 (Very Unhealthy) | PM2.5 & NO2 |
| Lahore | Pakistan | 290 (Very Unhealthy) | PM2.5 |
| Jakarta | Indonesia | 180 (Unhealthy) | Ozone |
| Mexico City | Mexico | 150 (Unhealthy for Sensitive Groups) | Ozone & NO2 |
Most Polluted Countries by Average AQI (2025)
| Rank | Country | Annual AQI Average |
|---|---|---|
| 1 | India | 180 (Unhealthy) |
| 2 | Pakistan | 175 (Unhealthy) |
| 3 | Bangladesh | 170 (Unhealthy) |
| 4 | China | 160 (Unhealthy for Sensitive Groups) |
| 5 | Nigeria | 155 (Unhealthy for Sensitive Groups) |
Government Actions & Policies to Improve AQI
1. Pollution Control Regulations
- Stricter vehicle emission norms (e.g., Euro 6 standards in Europe)
- Banning coal-fired power plants in major cities
- Monitoring and enforcing industrial emission limits
2. Green Energy and Transportation
- Promotion of electric vehicles (EVs) and public transport
- Investments in renewable energy (solar, wind, hydro)
- Expanding cycling lanes and pedestrian-friendly areas
3. Afforestation and Green Initiatives
- Large-scale tree plantation drives
- Green building policies requiring urban gardens and rooftop greenery
- Development of urban forests to absorb pollutants
How Individuals Can Reduce Air Pollution ?
1. Transportation Choices
- Use public transport, cycling, or walking
- Switch to electric or hybrid vehicles
- Carpool or use ride-sharing services
2. Energy Consumption
- Reduce electricity consumption to lower emissions from power plants
- Use energy-efficient appliances
- Install solar panels for renewable energy
3. Lifestyle Changes
- Avoid burning waste, wood, or coal
- Reduce use of firecrackers and bonfires
- Grow indoor plants that purify the air (e.g., Aloe Vera, Peace Lily)
Conclusion
The Air Quality Index (AQI) is a crucial tool in understanding and addressing air pollution. With the increasing health risks posed by poor air quality, it is essential that both governments and individuals take action to reduce pollution levels.
