Indoor Air Pollution (IAP) refers to the chemical, biological, and physical contamination of indoor air. It is often more lethal than outdoor pollution because pollutants are concentrated in confined spaces where people spend approximately 90% of their time. In India, it remains a leading cause of premature mortality, particularly among women and children in rural areas.
Major Sources and Pollutants
Indoor pollutants originate from fuel combustion, building materials, and biological agents.
Biomass and Household Combustion
- Solid Fuels: Use of wood, charcoal, animal dung, and crop residues in traditional cookstoves (Chulhas).
- Pollutants Emitted: Carbon Monoxide (CO), Particulate Matter (PM2.5), Polycyclic Aromatic Hydrocarbons (PAHs), and Formaldehyde.
- Impact: Incomplete combustion of biomass releases high concentrations of soot (Black Carbon), which is both a health hazard and a potent short-lived climate pollutant.
Chemical and Building Material Emissions
- Volatile Organic Compounds (VOCs): Emitted as gases from paints, lacquers, cleaning supplies, and pesticides.
- Radon Gas: A naturally occurring radioactive gas that seeps through soil and cracks in the foundation; it is the second leading cause of lung cancer globally.
- Asbestos: Found in older insulation and roofing materials; fibers cause asbestosis and mesothelioma when inhaled.
- Formaldehyde: Commonly found in pressed-wood products (plywood, particleboard) and certain textiles.
Biological Contaminants
- Allergens: Mold, mildew, dust mites, pet dander, and pollen.
- Factors: High humidity and poor ventilation promote the growth of biological pollutants, leading to Sick Building Syndrome (SBS).
Health Impacts of Indoor Pollution
The health burden of IAP is disproportionately high in developing nations due to lack of access to clean energy.
| Condition | Primary Causative Pollutant | Impact Detail |
| Respiratory Infections | PM2.5, NO2 | Acute Respiratory Infections (ARI) in children; pneumonia. |
| COPD | Biomass Smoke | Chronic Obstructive Pulmonary Disease; permanent lung damage. |
| Carboxyhemoglobin | Carbon Monoxide (CO) | CO binds with hemoglobin, reducing oxygen delivery to organs. |
| Sick Building Syndrome | VOCs, Poor Ventilation | Acute health effects (headache, dizziness) linked to time spent in a building. |
| Lung Cancer | Radon, Second-hand Smoke | Long-term exposure to carcinogens in enclosed spaces. |
Comparison: Indoor vs. Outdoor Air Pollution
| Feature | Indoor Air Pollution | Outdoor (Ambient) Air Pollution |
| Concentration | Can be 2–5 times higher than outdoors. | Diluted by wind and atmospheric volume. |
| Primary Victims | Women, children, and elderly. | General urban population, traffic workers. |
| Major Regulation | Building codes, PM Ujjwala Yojana. | NAAQS, NCAP, GRAP. |
| Key Source | Cooking, heating, building materials. | Vehicles, Industries, Dust. |
Government Initiatives and Policy Interventions
The Government of India has shifted focus toward “Energy Poverty” to address the root cause of IAP.
Pradhan Mantri Ujjwala Yojana (PMUY)
- Objective: To provide clean cooking fuel (LPG) to BPL (Below Poverty Line) households.
- Impact: Reduces reliance on solid biomass, significantly lowering indoor concentrations of PM2.5 and CO.
- Evolution: Ujjwala 2.0 focuses on migrant workers and provides the first refill and hot plate free of cost.
Unnat Chulha Abhiyan (UCA)
- Mechanism: Promotion of biomass-based cookstoves that use improved combustion technology.
- Goal: To provide “Improved Cookstoves” (ICS) in areas where LPG penetration is difficult or expensive.
National Tobacco Control Programme (NTCP)
- Goal: To reduce the prevalence of tobacco use, thereby decreasing second-hand smoke—a major indoor pollutant.
- Legislative Support: The Cigarettes and Other Tobacco Products Act (COTPA), 2003, bans smoking in public indoor places.
Trivia and Key Facts for Prelims
- Bio-aerosols: These are airborne particles that are biological in origin (bacteria, fungi, viruses). They are a major component of indoor pollution in poorly ventilated hospitals.
- Environmental Tobacco Smoke (ETS): Also known as second-hand smoke, it contains over 7,000 chemicals, including at least 70 known to cause cancer.
- Household Air Pollution (HAP): The WHO uses this term specifically to describe the pollution resulting from the use of inefficient solid fuels.
- Ventilation Rate: The rate at which indoor air is replaced by outdoor air. Low ventilation rates are the primary cause of pollutant buildup indoors.