What does smog indicate about air quality?

Smog is a visible indicator of severe air pollution, signaling the presence of harmful concentrations of ground-level pollutants. The term combines "smoke" and "fog," and modern smog typically forms when nitrogen oxides and volatile organic compounds from vehicles and industry react with sunlight to create photochemical smog. The presence of smog indicates elevated levels of ozone, particulate matter, and other pollutants that pose serious health risks, particularly for children, elderly individuals, and those with respiratory conditions. Persistent smog conditions suggest inadequate pollution controls, heavy traffic, industrial emissions, or unfavorable weather conditions that trap pollutants near the ground. Cities experiencing frequent smog events need to implement stricter emission standards and pollution reduction strategies.