Impact of Atmospheric Pollution » Health Effects of Smog

What you'll learn this session

Study time: 30 minutes

The composition and formation of smog
Different types of smog (photochemical and industrial)
Health impacts of smog on respiratory and cardiovascular systems
Vulnerable populations most affected by smog
Major smog episodes and their consequences
Measures to reduce smog and protect public health

Understanding Smog and Its Health Effects

Smog is a type of air pollution that hangs like a thick blanket over many cities worldwide. The term "smog" comes from combining the words "smoke" and "fog", which perfectly describes its appearance. While it might just look like a hazy day, smog contains harmful chemicals that can seriously damage our health.

Key Definitions:

Smog: A form of air pollution consisting of a mixture of smoke, gases and particulates that forms a haze in the atmosphere.
Photochemical smog: Smog formed when sunlight reacts with pollutants from vehicles and industry, creating ground-level ozone and other harmful substances.
Industrial smog: Smog primarily composed of sulphur dioxide, particulates and nitrogen oxides from coal burning and industrial processes.
Particulate matter (PM): Tiny solid or liquid particles suspended in the air that can penetrate deep into the lungs.

★ Types of Smog

Photochemical Smog
Common in warm, sunny cities with lots of traffic. Forms when nitrogen oxides and volatile organic compounds (VOCs) from vehicle exhaust react with sunlight. Has a yellowish-brown colour and is worse during hot afternoons. Los Angeles is famous for this type of smog.

★ Types of Smog

Industrial Smog
Also called "classical" or "London-type" smog. Forms from burning coal and heavy fuels containing sulphur. Appears grey or black and gets worse in cold, damp conditions when more heating is used. Was common in industrial cities like London and Manchester.

What's in Smog?

Smog contains a cocktail of harmful substances that can damage our health. The exact mix depends on the type of smog and local pollution sources, but most smog contains:

Ground-level ozone (O₃): A reactive gas formed when pollutants react with sunlight. Unlike the protective ozone layer high in the atmosphere, ground-level ozone irritates the lungs.
Nitrogen dioxide (NO₂): A reddish-brown gas from vehicle exhaust and power plants that irritates the airways.
Sulphur dioxide (SO₂): A colourless gas with a sharp smell, mainly from burning coal and oil.
Particulate matter (PM₁₀ and PM_2.5): Tiny particles that can penetrate deep into the lungs. PM_2.5 (particles smaller than 2.5 micrometres) are especially dangerous as they can enter the bloodstream.
Carbon monoxide (CO): A colourless, odourless gas that reduces oxygen delivery in the body.
Volatile organic compounds (VOCs): Chemicals that easily become vapours or gases, released from paints, solvents and vehicle exhaust.

Health Effects of Smog

Breathing in smog can cause both immediate and long-term health problems. The severity depends on the concentration of pollutants, how long you're exposed and your personal health status.

♥ Respiratory Effects

Coughing and throat irritation
Chest tightness and difficulty breathing
Worsening of asthma symptoms
Increased risk of respiratory infections
Reduced lung function
Development of chronic bronchitis
Long-term exposure can lead to lung cancer

♥ Cardiovascular Effects

Increased blood pressure
Irregular heartbeat
Higher risk of heart attacks
Increased risk of stroke
Worsening of existing heart conditions
Blood vessel inflammation
Long-term exposure linked to heart disease

♥ Other Health Effects

Eye irritation and inflammation
Headaches and dizziness
Fatigue and weakness
Reduced immune function
Possible neurological effects
Low birth weight in newborns
Premature death in severe cases

Who's Most at Risk?

While smog affects everyone, certain groups are more vulnerable to its harmful effects:

! Vulnerable Groups

Children: Their lungs are still developing, they breathe more air per kilogram of body weight and they often spend more time outdoors.
Elderly people: May have weakened immune systems and often have pre-existing health conditions.
People with respiratory conditions: Those with asthma, COPD, or other lung diseases experience worsened symptoms.
People with heart disease: More susceptible to the cardiovascular effects of air pollution.

! High-Risk Activities

Outdoor exercise during smog alerts: Breathing harder means inhaling more pollutants.
Working outdoors: Construction workers, traffic police and street vendors have prolonged exposure.
Living near major roads: Pollution levels are typically higher within 500 metres of busy roads.
Living in valleys: Geographic features can trap smog and prevent it from dispersing.

Case Study Focus: The Great Smog of London (1952)

In December 1952, London experienced one of history's deadliest air pollution events. Cold weather combined with windless conditions trapped coal smoke from homes and factories close to the ground. The smog was so thick that visibility dropped to just a few metres – people couldn't see their feet while walking!

The smog lasted for five days and had devastating consequences:

At least 4,000 people died during the smog (recent research suggests up to 12,000 deaths)
Hospitals were overwhelmed with patients suffering from respiratory problems
Public transport stopped and even indoor events were cancelled as smog penetrated buildings
Cattle at a livestock show choked to death

This disaster led directly to the UK's Clean Air Act of 1956, which restricted coal burning in urban areas and marked a turning point in addressing air pollution.

Modern Smog Episodes

While regulations have improved air quality in many developed countries, smog remains a serious problem globally:

Beijing, China: Frequently experiences severe smog from coal-burning power plants, industry and increasing vehicle numbers. During the 2008 Olympics, the government temporarily shut down factories and restricted driving to improve air quality.
Delhi, India: Often records some of the world's worst air quality, especially after the autumn harvest when farmers burn crop stubble. Schools sometimes close during severe episodes and outdoor activities are restricted.
Mexico City, Mexico: Its high altitude (2,240m) and location in a valley make it prone to photochemical smog. The government has implemented driving restrictions and moved industries outside the city.
Los Angeles, USA: Though improved since the 1970s, still experiences photochemical smog due to heavy traffic and sunshine. The city pioneered many air quality regulations that were later adopted nationwide.

Protecting Yourself from Smog

While systemic changes are needed to truly solve smog problems, individuals can take steps to reduce their exposure and health risks:

✓ Personal Protection

Check air quality forecasts and limit outdoor activities when pollution levels are high
Exercise early in the morning or in parks away from traffic when air quality is better
Consider wearing a properly fitted N95 mask during severe smog episodes
Keep windows closed during high pollution periods
Use air purifiers with HEPA filters indoors
Stay well-hydrated to help your body clear toxins

✓ Reducing Your Contribution

Use public transport, cycle, or walk instead of driving when possible
If driving, avoid idling your engine unnecessarily
Maintain your vehicle properly to reduce emissions
Conserve energy at home to reduce power plant emissions
Avoid burning garden waste or using wood-burning stoves in urban areas
Support clean air policies in your community

Global Solutions to Smog

Tackling smog requires action at all levels of society:

Government regulations: Emission standards for vehicles and industry, clean fuel requirements and restrictions on burning
Urban planning: Creating car-free zones, improving public transport and increasing green spaces
Technology: Developing cleaner vehicles, renewable energy sources and better pollution monitoring
International cooperation: Air pollution crosses borders, so countries must work together on solutions
Public awareness: Educating people about the health risks of smog and how to reduce pollution

Success Story: London's Air Quality Improvement

London has made remarkable progress since the deadly smog of 1952. Key measures have included:

The Clean Air Act (1956) that restricted coal burning
Moving power stations away from the city centre
Introduction of the Ultra Low Emission Zone (ULEZ) in 2019, charging high-polluting vehicles
Electrification of the bus fleet
Promotion of cycling with dedicated lanes and bike-sharing schemes

While London still faces air quality challenges, deadly smog events are now history, showing that determined action can make a real difference.

Summary: The Impact of Smog on Health

Smog isn't just an unsightly haze – it's a serious health hazard that affects millions of people worldwide. From immediate symptoms like coughing and eye irritation to long-term effects including heart disease and lung cancer, the health impacts are wide-ranging and sometimes deadly.

While vulnerable groups like children, the elderly and those with pre-existing conditions are most at risk, smog affects everyone's health to some degree. Historical disasters like the Great Smog of London demonstrate the potential severity of the problem, while modern episodes in cities like Beijing and Delhi show that smog remains a pressing global issue.

The good news is that we know how to reduce smog through cleaner technologies, better regulations and changes in individual behaviour. Many cities have made significant progress, proving that cleaner air is possible with determined action.

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