---
title: "Air pollution: causes, effects and mitigation"
subject: "Technology, Environment and Society"
chapter: 5
key: "semester_7/technology_environment_and_society:air-pollution-causes-mitigation"
source: https://www.bctengineer.com/q/semester_7/technology_environment_and_society/air-pollution-causes-mitigation
site: BCT Engineering
---

# Air pollution: causes, effects and mitigation

Technology, Environment and Society · Chapter 5: Water and Air Pollution

- Asked in: 2075 Asoj, 8 marks; 2073 Chaitra, 8 marks; 2074 Asoj, 4 marks (asked 3 times)
- Video: [Air Pollution](https://www.youtube.com/watch?v=_dTtvtlct9k) — Bozeman Science
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/technology_environment_and_society/air-pollution-causes-mitigation
- Whole chapter: https://www.bctengineer.com/md/semester_7/technology_environment_and_society/chapter-5

## Question

Write down causes, effects and mitigation measures of air pollution.

## Short answer

Air pollution is harmful gases and particles in the atmosphere. Main causes are vehicles, industry, biomass and fossil fuel burning, construction dust, open waste burning and indoor cooking smoke. Effects include respiratory and heart disease, acid rain, global warming and smog. Mitigation uses emission testing, clean energy, filters, dust control, green belts, monitoring and awareness.

## Answer

**Air pollution** is the presence in the atmosphere of harmful substances (gases, particles, biological matter) in amounts that damage human health, living things, materials or climate. Main pollutants: particulate matter (PM10, PM2.5), carbon monoxide (CO), sulphur dioxide (SO₂), nitrogen oxides (NOₓ), ground-level ozone (O₃), hydrocarbons/VOCs and lead.

#### Causes (sources)
**Natural sources:** volcanic eruption, forest fires, dust storms, pollen, sea salt.

**Man-made sources:**
1. **Vehicles** – burning of petrol and diesel gives CO, NOₓ, hydrocarbons and PM; old, poorly maintained vehicles are the worst.
2. **Industries and power plants** – cement, brick kilns, thermal plants release SO₂, NOₓ and dust.
3. **Burning of fossil fuels and biomass** – coal, firewood, dung and agricultural residue.
4. **Construction and road dust** – unpaved and dug-up roads, building works.
5. **Open burning of waste** – plastics release dioxins and toxic smoke.
6. **Agriculture** – ammonia from fertilisers, methane from livestock and rice fields, pesticide spraying.
7. **Indoor sources** – cooking with firewood and kerosene, smoking.

#### Effects
**On human health**
- Respiratory diseases: asthma, bronchitis, COPD, pneumonia, lung cancer.
- Heart disease and stroke (PM2.5 enters blood).
- CO reduces oxygen carrying capacity of blood; lead harms the brain of children.
- Eye irritation, headache, reduced life expectancy.

**On environment**
- **Acid rain** from SO₂ and NOₓ damages crops, forests, lakes and buildings.
- **Global warming** and climate change from CO₂, CH₄, black carbon.
- **Ozone layer depletion** by CFCs.
- **Smog** and reduced visibility, affecting flights and tourism.
- Damage to plants (reduced photosynthesis) and to monuments and metal structures.

**Economic** – medical costs, lost working days, lower tourism.

#### Mitigation measures
1. **Vehicle control** – emission testing and green stickers, phasing out old vehicles, better fuel quality (Euro standards), promoting electric vehicles and public transport.
2. **Industrial control** – filters, electrostatic precipitators, scrubbers, tall stacks, cleaner brick kiln technology (zig-zag kilns).
3. **Clean energy** – hydropower, solar, wind, biogas, LPG/electric cooking instead of firewood.
4. **Dust control** – paving roads, covering construction sites, water sprinkling, timely completion of road works.
5. **Waste management** – ban open burning, recycling, composting, sanitary landfill.
6. **Greenery** – tree plantation along roads and green belts.
7. **Monitoring and law** – air quality monitoring stations, National Ambient Air Quality Standards, strict enforcement.
8. **Awareness** – masks during high pollution, public information on AQI, behaviour change.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Which pollutants come from burning petrol and diesel in vehicles?
   A. CO, NOx, hydrocarbons and PM
   B. Only CO2 and water
   C. Ammonia only
   D. Dioxins only
   Answer: A. Vehicle exhaust has CO, NOx, hydrocarbons and particulates. (Key point: Vehicle pollutants)

2. How does carbon monoxide harm health?
   A. Causes eutrophication
   B. Reduces oxygen carrying capacity of blood
   C. Damages the ozone layer
   D. Causes acid rain
   Answer: B. CO binds haemoglobin and reduces oxygen transport. (Key point: Health effect of CO)

3. Which pollutants cause acid rain?
   A. Methane
   B. Lead
   C. SO2 and NOx
   D. CFCs
   Answer: C. SO2 and NOx form sulphuric and nitric acids. (Key point: Acid rain source)

4. Which is an industrial air pollution control measure?
   A. Rainwater harvesting
   B. Composting
   C. Wildlife corridors
   D. Electrostatic precipitators, scrubbers and zig-zag brick kilns
   Answer: D. These cut stack emissions and dust. (Key point: Industrial control)

## Related in Technology, Environment and Society

- [Kathmandu air pollution: causes, effects, mitigation](https://www.bctengineer.com/question.md?key=semester_7%2Ftechnology_environment_and_society%3Akathmandu-air-pollution-causes) — Technology, Environment and Society, chapter 5
- [Indoor air pollution in Nepal and counter measures](https://www.bctengineer.com/question.md?key=semester_7%2Ftechnology_environment_and_society%3Aindoor-air-pollution-nepal) — Technology, Environment and Society, chapter 5
- [Water pollution: sources, causes and impacts](https://www.bctengineer.com/question.md?key=semester_7%2Ftechnology_environment_and_society%3Awater-pollution-sources-impacts) — Technology, Environment and Society, chapter 5

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