Smog is a type of air pollution formed by the interaction of sunlight with pollutants such as nitrogen oxides (NOx), volatile organic compounds (VOCs), and particulate matter. The word “smog” comes from “smoke” and “fog,” describing the hazy brown or gray air that often blankets urban areas. In IB Environmental Systems & Societies (ESS), understanding smog formation helps students explore atmospheric systems, pollution, and sustainability solutions.
Quick Start Checklist for IB ESS Students
- Define smog and identify its major components
- Learn the difference between photochemical and industrial smog
- Understand the chemical reactions that produce smog
- Analyze human and environmental effects
- Review mitigation strategies with RevisionDojo’s IB ESS course
Types of Smog
- Photochemical Smog:
- Common in sunny, warm climates (e.g., Los Angeles).
- Forms when sunlight reacts with nitrogen oxides and VOCs from vehicles and industrial emissions.
- Produces harmful substances such as ozone (O₃), PANs, and nitric acid.
- Industrial Smog (Sulfurous Smog):
- Common in cooler, humid climates with high coal burning (e.g., London historically).
- Results from burning fossil fuels that release sulfur dioxide (SO₂) and particulates.
- Combines with fog and smoke to form thick gray smog.
How Smog Forms
Smog formation is a complex chemical process influenced by sunlight, temperature, and topography.
- In photochemical smog, UV radiation splits nitrogen dioxide (NO₂) into nitrogen oxide (NO) and oxygen (O).
- Free oxygen atoms then combine with O₂ to form ozone (O₃), which reacts with VOCs to produce secondary pollutants.
- These reactions create a visible haze and harmful air conditions.
Effects of Smog
Human Health:
- Causes respiratory problems, eye irritation, and long-term lung damage.
- Increases rates of asthma and cardiovascular diseases.
Environmental Impacts:
- Damages plant tissues and reduces photosynthesis.
- Contributes to acid rain formation and ecosystem stress.
- Degrades materials and reduces visibility.
Economic Costs:
- Reduces worker productivity and increases healthcare costs.
- Affects tourism and outdoor activities in polluted regions.
Managing and Preventing Smog
Controlling smog involves reducing emissions and improving energy efficiency:
- Vehicle emission standards and catalytic converters lower NOx output.
- Renewable energy reduces fossil fuel dependency.
- Urban planning encourages public transport and reduces congestion.
- Legislation, such as the Clean Air Acts, limits industrial emissions.
The IB ESS Connection
In the IB ESS curriculum, smog ties directly to Topic 6.3: Photochemical Smog under Atmospheric Systems. Students must understand the causes, effects, and management of air pollution, using systems thinking to analyze how atmospheric inputs and outputs influence global health.
Through RevisionDojo’s IB ESS course, students can study interactive diagrams of smog formation, practice data interpretation questions, and explore real-world case studies of urban air pollution.
FAQs
What are the main pollutants that cause smog?
Nitrogen oxides (NOx), volatile organic compounds (VOCs), and particulate matter from vehicles and industry.
How does sunlight contribute to smog formation?
UV radiation triggers chemical reactions that produce ozone and other secondary pollutants.
Can smog be prevented?
Yes, through cleaner energy, strict emissions control, and sustainable urban policies.
