Air Pollution
NCERT Class 12 • Biology • Chapter "Environmental Issues" | NCERT Class 8 • Science • Chapter "Pollution of Air and Water"
Air Pollution
Air pollution is the presence in the air of any substance in a concentration high enough to harm living things or property. Because air moves freely, pollution released in one place does not stay there, which makes air the hardest medium to manage.
Pollutants and Their Sources
- Primary pollutants are released directly, such as carbon monoxide, sulphur dioxide, oxides of nitrogen and particulate matter.
- Secondary pollutants form in the air from reactions between primary pollutants, as ozone does at ground level.
- Vehicles release carbon monoxide, oxides of nitrogen and unburnt hydrocarbons.
- Industry and thermal power plants release sulphur dioxide, oxides of nitrogen and fly ash.
- Burning of crop residue, firewood and waste is a major seasonal source in many regions.
- Particulate matter is measured by size, and the finer particles are more dangerous because they reach deep into the lungs.
- Indoor air pollution from cooking on biofuel in poorly ventilated rooms harms women and children most.
Effects and Control
- Health effects include respiratory disease, asthma, reduced lung function, heart disease and eye irritation.
- Sulphur dioxide and oxides of nitrogen dissolve in rain water to form acid rain, which damages crops, buildings and aquatic life.
- Smog is a mixture of smoke and fog; photochemical smog forms in sunlight from vehicle exhaust.
- Carbon monoxide is dangerous because it binds to haemoglobin far more strongly than oxygen does.
- Control at source uses cleaner fuel, better engines, catalytic converters and electrostatic precipitators.
- Scrubbers remove gases from industrial exhaust and electrostatic precipitators remove particles.
- Public transport, cleaner cooking fuel, afforestation and monitoring of air quality complete the response.
| Pollutant | Main Source | Main Effect |
|---|---|---|
| Carbon monoxide | Vehicle exhaust | Binds haemoglobin, reduces oxygen |
| Sulphur dioxide | Coal burning industry | Acid rain, lung damage |
| Particulate matter | Dust, smoke, construction | Deep lung damage |
| Ground level ozone | Secondary, from sunlight reactions | Eye and lung irritation |
Secondary pollutant — a pollutant that is not released directly but forms in the air through reactions between primary pollutants.
Hindi me samjhein
प्राथमिक प्रदूषक सीधे छोड़े जाते हैं, जैसे कार्बन मोनोऑक्साइड। द्वितीयक प्रदूषक वायु में अभिक्रिया से बनते हैं, जैसे धरातलीय ओजोन, इसीलिए उन्हें स्रोत पर रोकना कठिन होता है।
Exam me kaise aata hai
- Which gas binds strongly to haemoglobin — carbon monoxide
- Which pollutants cause acid rain — sulphur dioxide and oxides of nitrogen
- Which device removes particles from industrial exhaust — electrostatic precipitator
- Ozone at ground level is which kind of pollutant — secondary
UPSC/State PSC ke liye
- Fine particulate matter is the most harmful fraction because its small size lets it pass the body's natural filters and reach the deepest part of the lung.
- Secondary pollutants are hard to control because there is no single chimney to fit a filter on; the response must reduce the precursor emissions instead.
Yahan confuse hote hain
✗ All pollutants are released directly | Secondary pollutants form in the air itself | ✓
✗ Ozone is always harmful | Ozone high in the atmosphere protects us; at ground level it is a pollutant | ✓
✗ Indoor air is always safer than outdoor air | Cooking on biofuel indoors can make indoor air worse | ✓
Ek nazar me
- Primary pollutants are released directly; secondary ones form in the air.
- Vehicles, industry, power plants and burning of residue are the main sources.
- Effects include respiratory disease, acid rain and smog.
- Control uses cleaner fuel, catalytic converters, scrubbers and precipitators.