Understanding the Difference Between AQI and Indoor Air Quality
Outdoor air pollution remains a significant concern across the Indian subcontinent, particularly in northern states where the Air Quality Index frequently falls into the poor to severe category throughout the year. However, while outdoor air quality garners much attention, indoor air quality is equally critical and often overlooked. A fictional story illustrates this point: a man living in Delhi always wears a mask outdoors and monitors the AQI on his phone, shutting doors and windows when conditions worsen. Yet he neglected the polluted indoor air, which can be harmful over long exposure. Eventually, he installed an air purifier for home to improve indoor air quality. This article explores the differences between indoor and outdoor pollution, their sources, and strategies to manage indoor air.
What Is the Air Quality Index (AQI) and What Does It Indicate?
The Air Quality Index is a standardized tool used by governments to assess air quality in a given area. India launched its AQI in 2014, based on eight key pollutants: Particulate Matter (PM2.5 and PM10), Nitrogen Dioxide (NO2), Sulfur Dioxide (SO2), Carbon Monoxide (CO), Ozone (O3), Ammonia (NH3), and Lead (Pb). The index ranges from 0 to 500, with categories: Good (0-50), Satisfactory (51-100), Moderately Polluted (101-200), Poor (201-300), Very Poor (301-400), and Severe (401-500). However, the AQI captures only part of the picture, as monitoring stations are located at specific points and provide data for that location only. For example, a station at Pari Chowk in Greater Noida reflects air quality there, not in Delta 1. Moreover, the AQI does not account for indoor air quality, which includes pollutants like cooking fumes, volatile organic compounds, dust mites, and molds. Consequently, a city may report an AQI of 50-70, while indoor AQI could exceed 70.
Indoor Air Quality: Key Contributors to Poor Indoor AQI
Consider the activities in an average home: dusting, sweeping, cooking, and sometimes painting walls. These actions create a cocktail of indoor pollutants. Major contributors include:
- Particulate Matter (PM2.5, PM10): Emitted from incense sticks, candles, and cooking fumes.
- Carbon Monoxide: Released from gas stoves and heaters.
- Carbon Dioxide: Accumulates in closed rooms.
- Volatile Organic Compounds (VOCs): Found in adhesives, cleaning sprays, air fresheners, and paints.
- Biological Pollutants: Pet dander, fungal molds, and dust mites.
- Formaldehyde: Released from plywood and pressed furniture.
How Outdoor and Indoor Pollutants Differ: A Direct Comparison
Outdoor air pollution primarily stems from vehicular emissions, industrial activities, construction dust, and stubble burning. The dominant outdoor pollutants are particulate matter, ground-level ozone, carbon dioxide, and carbon monoxide. In contrast, indoor pollution is a diverse mixture of chemicals and gases, with VOCs playing a prominent role. Key differences include:
Primary Sources
- Outdoor AQI: Vehicular emissions, industrial emissions, construction dust.
- Indoor AQI: Cooking and cleaning activities.
Key Pollutants
- Outdoor AQI: NO2, PM10, PM2.5, SO2, CO, O3.
- Indoor AQI: CO2, VOCs, PM2.5, formaldehyde.
Measurement
- Outdoor AQI: Monitored by government agencies.
- Indoor AQI: Measured at the household level.
Visibility
- Outdoor AQI: Published and updated regularly.
- Indoor AQI: Displayed via air purifier indicators or personal monitors.
Control
- Outdoor AQI: Limited individual control.
- Indoor AQI: Manageable through personal actions.
Why People Are More Vulnerable to Indoor Air Pollution and Its Health Effects
Indian cooking involves high-heat techniques like deep frying, tadka (tempering spices in oil), and cooking on open flames (mitti ka chulha), generating substantial particulate matter. LPG gas stoves release large amounts of nitrogen dioxide and carbon monoxide, especially in compact, poorly ventilated kitchens. Research shows gas stoves can push indoor NO2 levels above outdoor standards within minutes. Additionally, daily practices like burning agarbatti, dhoop, and incense sticks, along with dry dusting and brooming, contribute to indoor pollution. These pollutants have both short-term and long-term health impacts:
Short-Term Effects
- Persistent headaches.
- Irritation of eyes, nose, and throat.
- Worsening allergies and asthma.
Long-Term Effects
- Kidney and liver damage from prolonged VOC exposure.
- Lung and cardiovascular issues from extended particulate matter exposure.
Certain groups are at higher risk: children (developing immune systems), elderly individuals (compromised immunity), pregnant women (VOC and PM exposure linked to adverse birth outcomes), and people with asthma, COPD, bronchitis, or other respiratory conditions. For these individuals, maintaining better indoor air quality through ventilation, regular cleaning, and air purifiers can reduce exposure.
Practical Steps to Manage Indoor Air Pollution
Improving indoor air quality does not require extreme measures; consistent small steps can be effective:
- Use an exhaust fan or chimney while cooking to remove fumes.
- Ensure proper ventilation by opening windows periodically, except when outdoor AQI is severe.
- Opt for wet dusting instead of dry dusting to prevent scattering dust.
- Clean thoroughly to prevent mold and fungal growth.
- Invest in an air purifier with four-stage filtration: pre-filter, HEPA filter, activated carbon filter, and plasma filtration. Replace filters periodically to maintain performance.
When choosing an air purifier, consider factors like room size and existing air quality, rather than focusing solely on price.
Conclusion
Many people feel reassured when their phone shows an AQI of 55, but this reflects only outdoor air. Indoor air quality can differ significantly and is equally important. By taking steps such as installing an air purifier, maintaining ventilation, and using exhaust systems, you can protect your family's health and well-being.
