11.2.6 Ground Level Ozone (O₃)

• Nitrogen oxides (NOₓ)
• Volatile organic compounds (VOC)

under the influence of sunlight.

These reactions occur mainly in industrial and urban areas where emissions from vehicles and industries are high.

• Photochemical smog
• Respiratory problems

Simple explanation: Ground-level ozone is formed when NOₓ and VOCs react in sunlight — it's a major component of smog.

Intermediate Level

Sources of Air Pollutants

Effects of Air Pollutants

What Is Particulate Matter?

• Soot
• Smoke
• Dust
• Other solid or liquid substances

• Respiratory problems
• Lung cancer

Simple explanation: Particulate matter is tiny particles in the air that can damage your lungs.

Why CO Is So Dangerous

• Is colourless and odourless — you can't see or smell it.
• Combines with hemoglobin (the oxygen carrier in blood).
• Forms carboxyhemoglobin, which cannot carry oxygen.
• Causes loss of consciousness, suffocation, and death.

Simple explanation: CO is a silent killer — it takes the place of oxygen in your blood.

Important Points

• - Pollutant: anything in air, water, or soil that has a harmful effect on the environment.
• - Air pollutants: substances in air that harm the environment and health.
• - Major air pollutants: SO₂, NOₓ, CO₂, CO, CH₄, ground-level O₃.
• - SO₂: from burning fossil fuels; causes acid rain and breathing problems.
• - NOₓ: from car engines; causes acid rain, smog, respiratory problems.
• - CO₂: from burning fossil fuels and deforestation; causes global warming.
• - CO: from incomplete combustion; toxic, combines with hemoglobin.
• - CH₄: from decomposition and livestock; contributes to global warming.
• - Ground-level O₃: from NOₓ + VOCs + sunlight; causes smog.
• - Particulate matter: fine particles (soot, smoke, dust) that harm lungs.

Remember

• - Pollutant = harmful substance in the environment.
• - SO₂ → acid rain, breathing problems.
• - NOₓ → acid rain, smog, breathing problems.
• - CO₂ → global warming.
• - CO → toxic; combines with hemoglobin.
• - CH₄ → global warming.
• - O₃ (ground level) → smog.
• - Particulate matter → respiratory problems, lung cancer.

Common Mistakes

• 1. Thinking CO₂ is not a pollutant. CO₂ is a major air pollutant linked to climate change.
• 2. Thinking CO is safe because it's colourless and odourless. CO is highly toxic and can cause death.
• 3. Confusing ground-level ozone with the ozone layer. Ground-level ozone is a pollutant (smog); the ozone layer is protective.
• 4. Thinking SO₂ and NOₓ have no health effects. Both cause respiratory problems.
• 5. Forgetting that methane comes from livestock. Cows, goats, and sheep produce large amounts of methane.
• 6. Thinking particulate matter is harmless. Particulate matter can cause lung cancer and other respiratory problems.

Quick Revision

• Sulphur oxides (SO₂): from burning fossil fuels; causes acid rain, haze, and respiratory problems.
• Oxides of nitrogen (NO, NO₂): from car engines, power plants; cause acid rain, photochemical smog, and respiratory problems.
• Carbon dioxide (CO₂): from burning fossil fuels, deforestation, industrial processes; contributes to global warming and climate change.
• Carbon monoxide (CO): from incomplete combustion; toxic gas; combines with hemoglobin, causing suffocation and death.
• Methane (CH₄): from decomposition of vegetation and waste, wetlands, rice fields, livestock; contributes to global warming.
• Ground-level ozone (O₃): secondary pollutant from reactions of NOₓ and VOCs in sunlight; causes photochemical smog and respiratory problems.

60-Second Revision

• SO₂ → acid rain, breathing problems.
• NOₓ → acid rain, smog, breathing problems.
• CO₂ → global warming.
• CO → toxic; silent killer.
• CH₄ → global warming.
• O₃ → smog.
• Warning: CO is colourless and odourless — you can't detect it without a detector.