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.
Exam tip: 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.
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.
Exam tip: Questions may ask about impacts on ecosystems, buildings, OR humans. Be ready to explain cause-effect chains for each type of impact.
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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.