Ozone Annual Average
Ground-level ozone, widely known as smog, is formed when sunlight triggers chemical reactions between nitrogen oxide and volatile organic compounds emitted from industrial plants, electric utilities, motor vehicles and other sources. Ozone pollution travels with the breeze and can affect downwind counties and states. Breathing ozone particularly irritates the respiratory tract. Short-term exposure can exacerbate asthma and trigger attacks and other health problems. The U.S. Environmental Protection Agency lowered the health-based ozone standard from a maximum daily 8-hour average of no greater than .075 parts per million to .070 ppm in 2015.