Harmful effects of air pollutants

An invisible gas that can kill

Every winter, news reports tell of families harmed by a gas heater left on in a closed room. The gas has no colour and no smell. What is it, and what does it do inside the body?

Carbon monoxide is an extremely poisonous gas. It stops red blood cells from carrying the oxygen the body needs, and can cause suffocation and death. Carbon dioxide is far less poisonous, but higher levels increase global warming. Ice caps melt, oceans warm, sea levels rise, and heat waves, heavy rains and wild fires become more common.

Oxides of nitrogen and of sulphur irritate the eyes, cause breathing problems and produce acid rain, which damages limestone buildings and statues; NOx also harms vegetation. Hydrocarbons cause coughing, pneumonia and lung diseases and add to global warming. Particulates irritate the eyes, worsen asthma, dirty clothes and make haze that cuts visibility. Ozone causes chest pain, coughing and throat irritation.

Smog brings allergies, asthma and lung infections. It also slows plant growth by reducing the carbon dioxide plants absorb for photosynthesis.

CO poisons the blood; NOx and SOx bring acid rain; CO₂, methane and hydrocarbons warm the planet; particulates and ozone hurt the lungs.

Key terms

Toxic

Describing CO.

Global warming

Effect of CO₂ and methane.

Acid rain

Damage to stone and life.

Haze

Effect of particulates.

Short questions with model answers

1. Q1. Which gas is more poisonous, CO₂ or CO? (Short question iii, p. 143)

   • CO
   • CO₂

   Carbon monoxide, CO.

2. Q2. How does air pollution affect plants? (Exercise, p. 134)

   • Directly
   • Through smog

   NOx damages plants, and smog slows their growth by cutting photosynthesis.

Common mistakes

• ✗ CO₂ is the most poisonous gas from burning fuel.

  ✓ CO is the poisonous one; CO₂ mainly causes global warming.

• ✗ Acid rain is caused mainly by carbon dioxide.

  ✓ Oxides of nitrogen and sulphur cause it (Table 10.2).

• ✗ Dust in the air only makes things dirty.

  ✓ Particulates also irritate eyes and cause severe breathing problems (Table 10.2).

MCQs

1. 1. Which pollutant stops red blood cells carrying oxygen?

   1. (a) CO₂
   2. (b) CO
   3. (c) SO₂
   4. (d) O₃
   Show answer

   (b) Table 10.2.

2. 2. Which gases contribute to acid rain? (Exercise x, p. 143)

   1. (a) Oxides of carbon
   2. (b) Oxides of sulphur only
   3. (c) Oxides of nitrogen only
   4. (d) Both oxides of nitrogen and sulphur
   Show answer

   (d) Table 10.2 and p. 134.

3. 3. Haze that reduces visibility is caused by:

   1. (a) Particulate matter
   2. (b) Nitrogen
   3. (c) Oxygen
   4. (d) Argon
   Show answer

   (a) Table 10.2.

4. 4. Higher carbon dioxide levels lead to:

   1. (a) Rising sea levels
   2. (b) Cleaner air
   3. (c) More ozone in the stratosphere
   4. (d) Less rain everywhere
   Show answer

   (a) Ice caps melt and oceans warm (Table 10.2).

5. 5. Breathing ozone can cause:

   1. (a) Chest pain and coughing
   2. (b) Stronger bones
   3. (c) Better eyesight
   4. (d) Nothing at all
   Show answer

   (a) p. 134.

Quick revision

• CO is extremely poisonous: it stops the blood carrying oxygen.
• NOx and SOx irritate eyes and lungs and cause acid rain; CO₂, methane and hydrocarbons add to global warming.
• Particulates, ozone and smog harm breathing; smog also slows plant growth.