Smog is a type of air pollution that combines smoke and fog, creating a thick, hazy atmosphere. It often occurs in urban areas where there are many vehicles and factories. When sunlight reacts with pollutants like carbon monoxide and nitrogen oxides, it can lead to the formation of smog, making it difficult to see and breathe. This phenomenon is especially common in cities like Los Angeles and Beijing, where high levels of traffic and industrial activity contribute to poor air quality. Smog can have serious health effects, including respiratory problems and eye irritation, making it important for communities to take action to reduce pollution.