Photochemical smog is a type of air pollution that occurs when sunlight reacts with pollutants like nitrogen oxides and volatile organic compounds. These pollutants often come from vehicle emissions, industrial activities, and other sources. The reaction produces harmful chemicals, including ozone, which can cause respiratory problems and other health issues. This smog is most common in urban areas with heavy traffic and sunny weather. It typically forms during the warmer months when sunlight is more intense. Reducing emissions from cars and factories can help decrease the formation of photochemical smog and improve air quality.