Fog vs. Smog: What is the Difference?

Fog is a natural atmospheric phenomenon, while smog is a type of air pollution:

• Origin: Fog is caused by water vapor condensing into water droplets or ice crystals. Smog is a combination of fog and smoke, which is created by human activities like burning coal, crop burning, and using poisonous gases in factories.
• Appearance: Fog is white, while smog is gray.
• Smell: Smog can be smelled, while fog cannot.
• Impact on visibility: Fog reduces visibility to less than 1 km (3,300 ft). Smog is air pollution that reduces visibility.
• Health effects: Smog can cause eye irritation, coughing, difficulty breathing, congestion, and other respiratory problems.
• Persistence: Fog eventually dips down, while smog persists in the air.
• Temperature: Smog can worsen with lower temperatures, like in the winter.  

The term “smog” comes from the words “smoke” and “fog”. It was first used in the early 1900s to describe a mix of smoke and fog that was common in industrial areas

Composition:

Smog (Smoke + Fog): Smog is a type of air pollution that results from the combination of smoke and fog. It often contains pollutants such as sulfur dioxide, nitrogen oxides, and particulate matter. Smog is typically found in urban areas with high levels of industrial and vehicular emissions.
Fog: Fog, on the other hand, is a natural atmospheric phenomenon. It is a collection of water droplets or ice crystals suspended in the air near the ground, reducing visibility. Fog is formed when moist air cools and condenses, especially during temperature inversions or when warm, moist air moves over a cooler surface.

Cause:

Smog: Primarily caused by human activities, such as the burning of fossil fuels, industrial processes, and vehicular emissions.
Fog: Formed by natural atmospheric processes, usually as a result of cooling air, often during the night.

Visibility:

Smog: While smog can reduce visibility, it is more associated with a hazy appearance due to the presence of pollutants.
Fog: Fog significantly reduces visibility, often to a few hundred meters or less.

Location:

Smog: Typically found in urban and industrial areas with high levels of pollution.
Fog: Can occur in various environments, including rural areas, valleys, and coastal regions, and is not necessarily linked to pollution.

Types:

Smog: There are two main types of smog: photochemical smog and sulfurous smog. Photochemical smog is common in sunny areas and forms when pollutants react with sunlight, while sulfurous smog is associated with coal-burning and industrial emissions.
Fog: There are different types of fog, such as radiation fog (forms on clear nights when the ground loses heat), advection fog (forms when warm, moist air moves over a cooler surface), and upslope fog (forms as air rises over a topographic barrier).

In summary, smog is a type of air pollution resulting from human activities, while fog is a natural atmospheric phenomenon caused by the condensation of water vapor. While they can share visual similarities, their origins, compositions, and impacts on visibility differ.