Biological Consequences of Air Pollution

Section 1 of 6Carbon monoxide

Source

• Source Carbon monoxide (CO) is a poisonous gas made when fuels such as petrol, gas or wood burn in too little oxygen, for example in car engines and faulty heaters.

Effect on the blood

• Effect on the blood CO binds to haemoglobin in red blood cells far more strongly than oxygen does.
  • This reduces the amount of oxygen the blood can carry to the body's tissues.

Consequences

• Consequences Tissues receive too little oxygen for aerobic respiration, causing headaches, dizziness and tiredness.
  • At high concentrations it can cause suffocation and death.

Section 2 of 6Sulfur dioxide and acid rain

1Release

• Release Burning fossil fuels that contain sulfur, such as coal, releases sulfur dioxide (SO₂) into the air.

2Reaction

• Reaction The gas dissolves in water droplets in clouds and forms acidic solutions.

3Acid rain

• Acid rain The rain that falls has a low pH and lands on plants, soil and water.

4Damage

• Damage Leaves and roots are damaged, soil minerals are washed out and lakes become too acidic for many aquatic organisms to survive.

Section 3 of 6Effects on living things

Pollutant	Affected organisms	Biological effect
Carbon monoxide	Humans and other animals	Less oxygen carried by the blood; suffocation at high levels
Sulfur dioxide	Humans	Irritates the airways and causes breathing problems such as asthma attacks
Acid rain from SO2	Plants	Damaged leaves, poor growth and nutrient loss from the soil
Acid rain from SO2	Aquatic life	Fish and other organisms die as water pH falls

Section 4 of 6Why acid rain harms ecosystems

1

Acid rain damages the waxy surface of leaves, so plants photosynthesise less and grow more slowly.

2

It dissolves essential mineral ions in the soil, such as magnesium and calcium, which are then washed away.

3

Poor soil and damaged trees mean less food and shelter for animals, so food webs are disrupted.

4

Run-off lowers the pH of ponds and lakes, killing sensitive organisms such as fish eggs and invertebrates.

5

Loss of those species affects every organism that feeds on them.

Section 5 of 6Key terms

Term	Meaning
Pollutant	A substance in the environment that causes harm to living things.
Carbon monoxide	A poisonous gas made by incomplete combustion of carbon-containing fuels.
Haemoglobin	The red pigment in red blood cells that carries oxygen.
Sulfur dioxide	A gas released when fossil fuels containing sulfur are burned; it causes acid rain.
Acid rain	Rain with a low pH caused by dissolved gases such as sulfur dioxide.

Section 6 of 6Exam technique

1

Writing that carbon monoxide 'reduces the oxygen in the air'; it reduces the oxygen carried by the blood.

2

Saying that carbon monoxide is made by complete combustion; it is made by incomplete combustion.

3

Mixing up carbon monoxide (CO) with carbon dioxide (CO₂) in the formula or effects.

4

Linking acid rain to carbon dioxide and the greenhouse effect instead of sulfur dioxide.

5

Failing to explain the harmalways say what happens to the organism, not just that it is 'damaged'.