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The term \u201cair quality\u201d refers to the degree to which ambient (outdoor) air is free of pollution. Air pollutants are those substances present in ambient air that negatively affect human health and welfare, animal and plant life, property, and the enjoyment of life or use of property. The Clean Air Act of 1970 and its amendments require the US Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards (NAAQS) for criteria pollutants. Criteria pollutants are those that endanger public health or welfare and are widely emitted. The EPA has established NAAQS for six criteria pollutants: ozone (O<\/span>3<\/span>), carbon monoxide (CO), nitrogen dioxide (NO<\/span>2<\/span>), sulfur dioxide (SO<\/span>2<\/span>), particulate matter (PM), and lead (Pb). Ambient pollutant concentrations result from interaction between meteorology and pollutant emissions. Because meteorology can\u2019t be controlled, emissions must be managed to control pollutant concentrations. The purpose of air quality conformity regulations, enforced by the EPA and the Utah Division of Air Quality (DAQ), is to protect public health and welfare by lowering pollutant emissions to reduce the severity and number of violations of the NAAQS.<\/span><\/p>\n Related resources for County planning include:<\/p>\n