- Practice · 6 marks
Indoor air pollutants and their sources
Short answer
Major indoor pollutants include CO, PM, NO2, radon, formaldehyde/VOCs, biological agents, asbestos/lead, tobacco smoke and CO2. Sources are combustion appliances, building materials, occupant activities, outdoor air and HVAC systems; effects range from respiratory irritation and asthma to cancer and poisoning.
List the major indoor air pollutants and describe their sources and health effects in homes and offices.
Indoor air is often more polluted than outdoor air because people spend 80-90% of their time indoors and pollutants build up where ventilation is poor.
| Pollutant | Main sources | Health effects |
|---|---|---|
| Carbon monoxide | Faulty stoves, heaters, attached garages, tobacco | Headache, dizziness, death at high levels |
| Particulate matter (PM2.5/PM10) | Biomass/coal cooking, tobacco smoke, candles, dust | Respiratory infection, asthma, COPD, heart disease |
| Nitrogen dioxide | Gas stoves and heaters, kerosene lamps | Lung irritation, reduced resistance to infection |
| Radon | Soil gas from rock entering through cracks in floors; building materials | Lung cancer (second leading cause after smoking) |
| Formaldehyde and other VOCs | Plywood, particle board, paints, adhesives, carpets, cleaning products | Eye and throat irritation, headache, cancer risk |
| Biological agents | Mould, dust mites, bacteria, pollen, pets, damp walls | Allergy, asthma, infections (e.g. Legionella from cooling towers) |
| Asbestos and lead | Old insulation, roofing sheets, old paint | Asbestosis, lung cancer, lead poisoning |
| Environmental tobacco smoke | Cigarettes | Lung cancer, heart disease, respiratory illness in children |
| Carbon dioxide | Human breathing, combustion | Drowsiness and poor concentration at high levels (> 1000 ppm indicates poor ventilation) |
Classification of sources
- Building materials and furnishings: formaldehyde, asbestos, radon, VOCs.
- Combustion: cooking and heating appliances.
- Occupants and activities: CO, bio-effluents, smoking, cleaning, hobbies.
- Outdoor air entering the building: vehicle exhaust, pollen, dust.
- HVAC systems: contaminated ducts, filters and humidifiers.
✓ Answer checked by Claude Opus 5.5 (high effort)
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