---
title: "Emission hazards and health impact"
subject: "Energy Environment and Society"
chapter: 4
key: "semester_7/energy_environment_and_society:emission-hazard-health-impact"
source: https://www.bctengineer.com/q/semester_7/energy_environment_and_society/emission-hazard-health-impact
site: BCT Engineering
---

# Emission hazards and health impact

Energy Environment and Society · Chapter 4: Environmental Impact of Energy sources

- Asked in: 2074 Asoj, 4 marks; 2070 Asar, 4 marks; year not given (asked 2 times)
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/energy_environment_and_society/emission-hazard-health-impact
- Whole chapter: https://www.bctengineer.com/md/semester_7/energy_environment_and_society/chapter-4

## Question

What are the common pollutants for the emission hazard? How can they affect health?

## Short answer

Common pollutants include PM2.5/PM10, CO, SO₂, NOₓ, ground-level ozone, VOCs, lead, and black carbon. They cause respiratory diseases (asthma, COPD, lung cancer), cardiovascular disease, eye irritation, and premature death. PM2.5 enters lungs and blood; CO reduces oxygen delivery; SO₂ and NOₓ irritate airways; lead damages children's brains.

## Answer

Air pollutants from fuel combustion (vehicles, industries, power plants, brick kilns, biomass burning) harm health and the environment.

#### Common pollutants and their health effects
| Pollutant | Main source | Health effect |
|---|---|---|
| **Particulate matter (PM10, PM2.5)** | Diesel vehicles, brick kilns, biomass burning, dust | Enters lungs and blood; asthma, bronchitis, lung cancer, heart disease, premature death |
| **Carbon monoxide (CO)** | Incomplete combustion; vehicles, stoves | Binds with haemoglobin and reduces oxygen delivery; headache, dizziness, death at high levels |
| **Sulphur dioxide (SO₂)** | Coal, diesel, smelters | Irritates eyes and respiratory tract, worsens asthma; acid rain |
| **Nitrogen oxides (NOₓ)** | Vehicles, power plants | Lung irritation, reduced lung function; leads to smog and ozone |
| **Ground-level ozone (O₃)** | Reaction of NOₓ and VOC in sunlight | Chest pain, cough, asthma attacks |
| **Volatile organic compounds (VOC), benzene** | Petrol, solvents | Cancer (benzene), nervous system effects |
| **Lead (Pb)** | Leaded petrol (banned in Nepal since 1999), batteries | Brain damage in children, anaemia |
| **Carbon dioxide (CO₂) and CH₄** | All fuels | Climate change (global warming) |
| **Smoke and black carbon** | Firewood, dung | Respiratory infection, eye disease, low birth weight |

#### Health consequences in general
- Respiratory diseases (asthma, COPD, pneumonia in children).
- Cardiovascular diseases and stroke.
- Lung cancer and other cancers.
- Eye and skin irritation; reduced life expectancy.
- Air pollution is among the leading risk factors of death in Nepal; the Kathmandu valley and Tarai cities have very high PM2.5 in winter.

Control: cleaner fuels (electric and gas), emission standards, vehicle inspection, scrubbers and filters, and clean cooking.

## Check yourself

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

1. How does carbon monoxide harm health?
   A. It forms acid rain in the lungs
   B. It damages the lungs by forming ozone
   C. It causes brain damage in children by lead accumulation
   D. It binds with haemoglobin and reduces oxygen delivery
   Answer: D. CO arises from incomplete combustion and reduces oxygen delivery causing headache, dizziness and death. (Key point: Carbon monoxide)

2. Why is PM2.5 especially dangerous?
   A. It enters the lungs and blood, causing asthma, heart disease and lung cancer
   B. It only discolours buildings
   C. It only causes global warming
   D. It is harmless below 100 µm
   Answer: A. Fine particles penetrate deep into lungs and blood. (Key point: Particulate matter)

3. How is ground-level ozone formed?
   A. Direct emission from tailpipes
   B. Reaction of NOx and VOC in sunlight
   C. Burning of leaded petrol
   D. Incomplete combustion giving CO
   Answer: B. Ozone is a secondary pollutant causing chest pain, cough and asthma attacks. (Key point: Ozone formation)

4. What is the health effect of lead?
   A. Acid rain
   B. Lung irritation from smog
   C. Brain damage in children and anaemia
   D. Global warming
   Answer: C. Lead from leaded petrol (banned in Nepal since 1999) and batteries damages the nervous system. (Key point: Lead)

## Related in Energy Environment and Society

- [Health impacts of indoor air pollutants](https://www.bctengineer.com/question.md?key=semester_7%2Fenergy_environment_and_society%3Aindoor-air-pollutants-health) — Energy Environment and Society, chapter 4
- [Short note: SO2 emission and impact](https://www.bctengineer.com/question.md?key=semester_7%2Fenergy_environment_and_society%3Aso2-emission-impact) — Energy Environment and Society, chapter 4

## Related in other subjects

- [Exhaust pollutants and emission norms](https://www.bctengineer.com/question.md?key=semester_5%2Fautomotive_technology%3Aemission-norms-and-pollutants) — Automotive Technology, chapter 10
- [Hazard types and hazard cover in K-maps](https://www.bctengineer.com/question.md?key=semester_3%2Fdigital_logic%3Ahazards-hazard-cover) — Digital Logic, chapter 3
- [Soil pollutants, effects and remedies](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Asoil-pollutants-effects-remedies) — Engineering Chemistry, chapter 3, asked 5×
- [Particulate pollutants: sources and effects](https://www.bctengineer.com/question.md?key=semester_7%2Fenvironment_and_pollution_control%3Aparticulate-pollutants-sources-effects) — Environment and Pollution Control, chapter 1