Impacts of urban air pollution at HL: The impacts of urban air pollution are the same for SL and HL. At HL you weigh these impacts against the economics of cleaning the air.
No HL-only material to add — just learn the main impacts of urban air pollution.
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Health impacts
Big idea: Air pollution is a major public health crisis, causing millions of premature deaths annually. Effects range from minor irritation to chronic diseases and death.
Respiratory impacts
- Acute effects: Coughing, wheezing, shortness of breath, asthma attacks
- Chronic effects: Reduced lung function, chronic bronchitis, emphysema (COPD)
- Lung cancer: Long-term PM2.5 and diesel exhaust exposure increases risk
- Vulnerability: Children, elderly, and those with existing conditions most affected
Cardiovascular impacts
- Heart disease: PM2.5 enters bloodstream, causes inflammation, increases heart attack risk
- Stroke: Air pollution is a significant stroke risk factor
- High blood pressure: Associated with long-term pollution exposure
Other health impacts
- Neurological: Links to dementia, cognitive decline, developmental delays in children
- Reproductive: Low birth weight, preterm birth, fertility impacts
- Mental health: Association with depression and anxiety
- Economic burden: Healthcare costs, lost productivity, reduced quality of life
The WHO estimates 7 million premature deaths per year from air pollution — more than AIDS, malaria, and tuberculosis combined. Its the worlds largest environmental health risk.
When explaining health impacts, use cause → effect chains. E.g., PM2.5 particles are inhaled → penetrate deep into lungs → enter bloodstream → cause inflammation → increase heart attack risk.
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Environmental impacts
Big idea: Urban air pollution damages ecosystems, buildings, and visibility both locally and at considerable distances from cities through acid deposition and ozone damage.
Acid deposition
- Formation: SO₂ and NOₓ react with water to form sulfuric and nitric acids
- Wet deposition: Acid rain, snow, fog — pH can drop below 4
- Dry deposition: Acidic particles settle directly on surfaces
- Effects on water: Lakes and streams become acidified; fish and invertebrates die
- Effects on soil: Nutrients leached; aluminium released (toxic to plants)
- Effects on forests: Leaf damage, weakened trees, forest decline
Other environmental impacts
- Ozone damage to plants: Ground-level O₃ damages crops and natural vegetation — reduces yields by 5-15%
- Reduced visibility: Particulates scatter light, creating haze
- Building damage: Acid deposition corrodes stone, metal, and paint; blackens surfaces
- Eutrophication: Nitrogen deposition fertilises ecosystems, altering species composition
- Climate effects: Black carbon (soot) absorbs heat; some aerosols cool by reflecting sunlight
Acid rain can travel hundreds of kilometres from pollution sources. Scandinavias acid rain problems came largely from UK and German industrial emissions.
Questions may ask about impacts on ecosystems, buildings, OR humans. Be ready to explain cause-effect chains for each type of impact.
IB-style question — Impacts of urban air pollution [3]
Mardelo sits in a steep-sided valley. Air-quality data show fine-particle (PM2.5) levels are far higher in winter than in summer.
Outline three reasons why air pollution is worse in this city during the colder months. [3]
How to answer it, step by step
- Why pollution gets trapped
• Valley shape + cold dense air → temperature inversion holds a 'lid' over the city
• Low winter sun and little wind mean poor mixing, so pollutants stay near the ground - Why more is emitted + less removed
• More fuel burned for heating raises emissions
• Less rainfall in winter means fewer particles are washed out of the air
Final answer
Examiner tip: 'Outline three' = three separate, marked points. Mix emission causes (more burning) with dispersal causes (inversion, no rain) rather than rewording one idea three times.