Ever stepped outside on what should have been a sunny day, only to be greeted by a thick, grayish haze? That, my friend, is smog.

Smog isn’t just an aesthetic issue or a temporary nuisance. Its effects can range from breathing difficulties to long-term respiratory symptoms and environmental degradation.

But what exactly it is, and why does it blanket our cities? Let’s dive into the science behind this urban menace.

What is Smog?

The term “smog” originated in the early 20th century as a combination of the words “smoke” and “fog.” Modern smog, however, is more complex, consisting of a mixture of ground-level ozone (O₃), particulate matter (PM), nitrogen oxides (NOx), sulfur dioxide (SO2), and volatile organic compounds (VOCs).

These pollutants react under sunlight to produce harmful compounds that linger in the air, creating that familiar, hazy cloud.

How Smog Forms

There are two primary types of smog

Summer Smog:

Photochemical smog, often referred to as “summer smog,” is the more common and dangerous type in modern urban areas. It forms when sunlight reacts with nitrogen oxides (NOₓ) and volatile organic compounds (VOCs) in the atmosphere.

The primary sources of these pollutants are vehicle emissions, industrial processes, and gasoline vapors. When sunlight hits these pollutants, a series of complex reactions occur, leading to the formation of ground-level ozone and other secondary pollutants.

Ground-level ozone, unlike the protective ozone layer high in the atmosphere, is a harmful pollutant at the Earth’s surface.

The reaction can be summarized as follows:

Step 1: Nitrogen dioxide (NO₂) absorbs sunlight and splits into nitrogen oxide (NO) and a free oxygen atom (O).

Step 2: The free oxygen atom combines with molecular oxygen (O₂) to form ozone (O₃).

Step 3: Ozone reacts with VOCs, creating a range of harmful organic compounds, including peroxyacetyl nitrate (PAN), aldehydes, and more.

This cocktail of pollutants forms the brownish–yellow haze we associate with smog. The presence of heat and sunlight accelerates these reactions, which is why it is typically worse on hot, sunny days.

Sulfurous Smog:

Sulfurous smog, also known as “winter smog,” is less common today but still a concern in certain areas. It forms in cool, damp conditions and is primarily the result of burning fossil fuels, such as coal, that contain sulfur.

When sulfur dioxide (SO₂) is released into the air, it can react with water vapor to form sulfuric acid (H₂SO₄) and other sulfate compounds.

The reaction can be summarized as:

Step 1: Sulfur dioxide (SO₂) reacts with water vapor (H₂O) to form sulfurous acid (H₂SO₃).

Step 2: Sulfurous acid can further oxidize to form sulfuric acid (H₂SO₄), a major component of acid rain.

Particulate Matter (PM2.5 and PM10)
These tiny particles come from both natural and human sources, including dust, combustion processes, and industrial emissions. Particulate matter is small enough to penetrate deep into the lungs, posing serious health risks.

Contributing Factors

Smog formation is most likely in urban areas with high vehicle and industrial emissions, especially when weather conditions favor the stagnation of air.

This is particularly common during warm seasons when sunlight is more intense and atmospheric conditions can trap pollutants closer to the ground.

High Traffic and Industrial Activity: Areas with heavy traffic or extensive industrial operations are more prone to pollute air due to higher levels of NOx and VOC emissions.

Topography and Weather: Cities in valleys, such as Los Angeles, often experience temperature inversions where warm air traps pollutants close to the ground.

Warm and Sunny Days: Sunlight acts as a catalyst for the chemical reactions between NOx and VOCs, accelerating ozone formation.

Impact on Health

The health effects of smog are extensive and can affect nearly everyone, particularly those with pre-existing respiratory conditions.

Respiratory Problems: Ozone and particulate matter irritate the respiratory tract, causing symptoms like coughing, throat irritation, and shortness of breath. Long-term exposure can lead to chronic respiratory diseases like asthma and chronic bronchitis.

Cardiovascular Risks: Smog can increase the risk of heart attacks and other cardiovascular events by causing inflammation and constricting blood vessels.

Increased Mortality: In extreme cases, high levels of air pollution have been linked to increased mortality rates due to respiratory and cardiovascular complications.

Research shows that smog exposure can worsen asthma symptoms, reduce lung function, and increase the likelihood of hospitalization for individuals with lung or heart conditions (1)

Environmental Consequences

Reduced Visibility: The haze diminishes visibility, impacting both road safety and the enjoyment of natural scenery.

Crop Damage: Ground-level ozone is particularly harmful to crops, reducing yield and quality by interfering with photosynthesis.

Ecosystem Imbalance: Pollutants can deposit into soil and water, causing acidification and nutrient imbalances that affect plant and aquatic life.

Delhi in India or Lahore in Pakistan are one of the most polluted cities globally, experiences severe smog episodes, particularly in the winter months when crop-burning practices in surrounding states contribute to high levels of particulate matter. Coupled with vehicle emissions, industrial output, and seasonal weather conditions, smog often reaches hazardous levels.

Tips for Staying Safe

Limit Outdoor Activities

Stay Indoors: On days when smog levels are high, try to stay indoors as much as possible, especially during peak pollution hours (usually in the afternoon).

Close Windows and Doors: Keep your living space sealed to prevent smog from entering.

Use Air Purifiers

Invest in Air Purifiers: Use HEPA air purifiers in your home to reduce indoor pollution levels.

Keep Indoor Plants: Certain plants, like spider plants and peace lilies, can help improve indoor air quality.

Monitor Air Quality

Stay Informed: Regularly check air quality reports and forecasts for your area.
Apps and websites like AirVisual and IQAir can provide real-time updates.

Protect Your Lungs

Wear Masks: Use masks designed to filter out pollutants, such as N95 respirators, when going outside is unavoidable.

Stay Hydrated: Drink plenty of water to help your body flush out pollutants and maintain lung health.

Maintain Clean Air Indoors

Ventilation: Ensure good ventilation in your home without letting smoggy air in. Use exhaust fans and keep air filters clean.

Avoid Indoor Pollutants: Refrain from using candles, incense, and tobacco indoors, as they can add to indoor pollution levels.

Remember, while we can take steps to protect ourselves, addressing the root causes requires collective action.

What’s The Solution?

To be honest, We all know the deadly affects of smog on our daily lives but there is very little we all do to prevent that, so I would like to emphasize on the practical solution involving policy, technology, and individual actions, Let’s get into it!

Policy Measures

Governments play a critical role in reducing smog through regulations and policies.

Emission Standards: Implementing and enforcing stringent emission standards for vehicles, industries, and power plants to limit the release of NOₓ, VOCs, and SO₂.

Fuel Quality: Mandating the use of cleaner fuels with lower sulfur content to reduce sulfurous smog.

Public Transportation: Investing in public transportation infrastructure to reduce the number of vehicles on the road and decrease overall emissions.

Urban Planning: Promoting urban green spaces and implementing policies to reduce urban sprawl, which can help mitigate the heat island effect and reduce smog formation.

Technological Solutions:

Advances in technology offer promising solutions to combat smog:

Clean Energy: Transitioning to renewable energy sources, such as solar, wind, and hydroelectric power, reduces reliance on fossil fuels and decreases emissions.

Electric Vehicles (EVs): Promoting the adoption of electric vehicles, which produce zero tailpipe emissions, can significantly reduce the pollutants that contribute to smog.

Industrial Innovation: Implementing cleaner production technologies and practices in industries to minimize emissions and improve energy efficiency.

Individual Actions:

Individuals also have a role to play in reducing smog:

Vehicle Use: Limiting the use of personal vehicles by carpooling, using public transportation, biking, or walking can reduce emissions.

Energy Consumption: Conserving energy at home and work by using energy-efficient appliances and reducing unnecessary electricity use.

Support Clean Policies: Advocating for and supporting policies and initiatives that promote clean air and reduce pollution.

Conclusion

Smog formation is a complex interaction between natural and human factors, and addressing it requires a concerted effort to reduce pollutant emissions.

While we can make changes on an individual level, addressing smog on a broader scale involves policy changes, technological advancements, and increased awareness.

By tackling the sources of smog, we can work toward cleaner air, healthier lives, and a more sustainable future.