Edexcel iGCSE Biology-5.12 Biological Consequences of Air Pollution- Study Notes- New Syllabus
Edexcel iGCSE Biology-5.12 Biological Consequences of Air Pollution- Study Notes- New syllabus
Edexcel iGCSE Biology-5.12 Biological Consequences of Air Pollution- Study Notes -Edexcel iGCSE Biology – per latest Syllabus.
Key Concepts:
5.12 understand the biological consequences of pollution of air by sulfur dioxide and carbon monoxide
Air Pollution: Sulfur Dioxide & Carbon Monoxide
📝 Introduction
- Air pollution occurs when harmful gases or particles are released into the atmosphere.
- Some air pollutants can damage living organisms and reduce the quality of the environment.
- Two important air pollutants are sulfur dioxide (SO₂) and carbon monoxide (CO).
- These gases are produced mainly by burning fuels and can have harmful effects on humans, animals and plants.
🌫️ Sulfur Dioxide (SO₂)
What is Sulfur Dioxide?
- Sulfur dioxide is a colourless gas with a strong, irritating smell.
- It is released into the atmosphere when fuels containing sulfur are burned.
Common Sources
- Burning coal in power stations.
- Burning oil and diesel fuels.
- Industrial factories.
- Metal smelting industries.
- Some volcanic eruptions (natural source).
🧬 Biological Effects of Sulfur Dioxide
1. Irritates the Respiratory System
When sulfur dioxide is breathed in:
- It irritates the lining of the nose and throat.
- It causes irritation in the airways and lungs.
- Breathing may become uncomfortable, especially after long exposure.
2. Worsens Breathing Problems
People with respiratory diseases are more sensitive to sulfur dioxide.
Exposure can:
- Trigger asthma attacks.
- Make breathing more difficult.
- Increase coughing and wheezing.
- Irritate damaged lungs.
3. Damages Plant Leaves
Sulfur dioxide enters plants through the stomata.
It can:
- Damage leaf cells.
- Reduce the amount of chlorophyll.
- Slow down photosynthesis.
- Reduce plant growth.
- Cause yellowing or browning of leaves if exposure continues.
As a result, plants produce less food and may grow poorly.
4. Contributes to Acid Rain
- Sulfur dioxide reacts with water vapour and oxygen in the atmosphere to form acidic substances.
- These acids fall as acid rain.
Acid rain can:
- Damage forests.
- Harm crops.
- Reduce plant growth.
- Make soil more acidic.
- Kill aquatic organisms by lowering the pH of lakes and rivers.
5. Reduces Biodiversity
Long-term sulfur dioxide pollution can:
- Kill sensitive plant species.
- Damage forests.
- Reduce food sources for animals.
- Disrupt habitats.
This may lead to a decrease in biodiversity.
⚫ Carbon Monoxide (CO)
What is Carbon Monoxide?
- Carbon monoxide is a colourless, odourless and poisonous gas.
- It is produced when fuels burn incompletely because there is not enough oxygen.
Common Sources
- Car and motorcycle exhausts.
- Faulty gas heaters.
- Wood-burning stoves.
- Fires.
- Petrol and diesel engines.
🧬 Biological Effects of Carbon Monoxide
1. Reduces Oxygen Transport in the Blood
Red blood cells contain haemoglobin, which normally carries oxygen.
Carbon monoxide:
- Binds very strongly to haemoglobin.
- Forms carboxyhaemoglobin.
- Prevents haemoglobin from carrying enough oxygen.
As a result:
- Less oxygen reaches body tissues and organs.
- Cells receive less oxygen for respiration.
2. Reduces Energy Production
Because cells receive less oxygen:
- Aerobic respiration decreases.
- Less ATP is produced.
- Body cells have less energy for normal activities.
This affects the normal functioning of many organs.
3. Causes Symptoms of Oxygen Shortage
Low levels of carbon monoxide exposure may cause:
- Headache.
- Dizziness.
- Weakness.
- Tiredness.
- Difficulty concentrating.
These symptoms occur because the brain and muscles receive less oxygen.
4. Can Cause Serious Poisoning
High concentrations of carbon monoxide can:
- Cause confusion.
- Lead to unconsciousness.
- Stop vital organs from receiving enough oxygen.
- Be fatal if exposure continues.
🌍 Why are These Pollutants Harmful?
- Both sulfur dioxide and carbon monoxide interfere with the normal functioning of living organisms.
- Sulfur dioxide mainly damages the respiratory system and plants.
- Carbon monoxide mainly affects the transport of oxygen in the blood.
- Although they act in different ways, both reduce the health and survival of living organisms.
📊 Comparison of Sulfur Dioxide and Carbon Monoxide
| Feature | Sulfur Dioxide (SO₂) | Carbon Monoxide (CO) |
|---|---|---|
| Main source | Burning sulfur-containing fuels | Incomplete combustion of fuels |
| Colour | Colourless | Colourless |
| Smell | Strong, irritating smell | Odourless |
| Main target | Lungs and plants | Blood and body tissues |
| Effect on humans | Irritates airways and worsens breathing problems | Reduces oxygen transport in the blood |
| Effect on plants | Damages leaves, reduces photosynthesis and growth | No major direct effect on plants |
| Other environmental effect | Causes acid rain and reduces biodiversity | Mainly affects animals and humans through oxygen shortage |
🌱 Biological Consequences at a Glance
| Pollutant | Biological Consequences |
|---|---|
| Sulfur dioxide | Irritates lungs, worsens asthma, damages leaves, reduces photosynthesis, contributes to acid rain, harms ecosystems and reduces biodiversity. |
| Carbon monoxide | Binds to haemoglobin, reduces oxygen transport, decreases aerobic respiration, lowers ATP production, causes headaches, dizziness, unconsciousness and can be fatal at high concentrations. |
📝 Quick Recap
SO₂ → acid rain, respiratory issues, damages plants, lakes, and buildings.
CO → binds haemoglobin → blocks O₂ transport → toxic, deadly, reduces foetal oxygen supply.
Both → major pollutants, harmful to health and environment.