Science, Tech, Math › Science What Is Smog? Share Flipboard Email Print Alan Copson/Getty Images Science Weather & Climate Understanding Your Forecast Storms & Other Phenomena Chemistry Biology Physics Geology Astronomy By Rachelle Oblack Rachelle Oblack is a K-12 science educator and Holt McDougal science textbook writer. She specializes in climate and weather. our editorial process Rachelle Oblack Updated March 04, 2019 The formation of smog is hazardous to your health especially if you live in a big sunny city. Find out now how smog is formed and how you can protect yourself. The sun gives us life. But it also can cause lung cancer and heart attacks as it is a primary factor in creating smog. Learn more about this hazard. The Formation of Smog Photochemical smog (or just smog for short) is a term used to describe air pollution that is a result of the interaction of sunlight with certain chemicals in the atmosphere. One of the primary components of photochemical smog is ozone. While ozone in the stratosphere protects earth from harmful UV radiation, ozone on the ground is hazardous to human health. Ground-level ozone is formed when vehicle emissions containing nitrogen oxides (primarily from vehicle exhaust) and volatile organic compounds (from paints, solvents, and fuel evaporation) interact in the presence of sunlight. Therefore, some of the sunniest cities are also some of the most polluted. Smog and Your Health According to the American Lung Association, your lungs and heart can be permanently affected by air pollution and smog. While the young and the elderly are particularly susceptible to the effects of pollution, anyone with both short and long-term exposure can suffer ill health effects. Problems include shortness of breath, coughing, wheezing, bronchitis, pneumonia, inflammation of pulmonary tissues, heart attacks, lung cancer, increased asthma-related symptoms, fatigue, heart palpitations, and even premature aging of the lungs and death. How to Protect Yourself From Air Pollutants You can check the Air Quality Index (AQI) in your area. It may be reported on your weather app or local weather forecast or you can find it at the AirNow.gov website. 0 to 50: Green. Good air quality.51 to 100: Yellow. Moderate air quality. People who are unusually sensitive to ozone may experience respiratory symptoms.101 to 150: Orange. Unhealthy air quality for sensitive groups including people with lung disease or heart disease, older adults, and children.151 to 200: Red. Unhealthy for everyone, with special concern for sensitive groups.201 to 300: Purple. Health alert level indicating very unhealthy conditions, everyone may experience serious health effects.301 to 500: Maroon. Hazardous, an emergency condition for the entire population. Air Quality Action Days When air quality gets into unhealthy levels, local air pollution agencies declare an action day. These have different names depending on the agency. They may be called a Smog Alert, Air Quality Alert, Ozone Action Day, Air Pollution Action Day, Spare the Air Day, or many other terms. When you see this advisory, those sensitive to smog should reduce their exposure, including refraining from prolonged or heavy exertion outdoors. Become familiar with what these days are called in your area and pay attention to them in weather forecasts and on weather apps. You can also check the Action Days page at the AirNow.gov website. Where Can You Live to Avoid Smog? The American Lung Association provides air quality data for cities and states. You can check different locations for air quality when considering where to live. Cities in California lead the list due to the effects of sun and high levels of vehicular traffic.