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2007 PROPOSED REVISIONS TO GROUND-LEVEL OZONE: BACKGROUND AND PROCESS Background On The 2007 Proposed Revisions To Ground-Level Ozone Standards ........................... 1 Proposed Revisions ........................................................................................................................................... 2 Estimated Timeline For Implementing The Proposed Standards ............................................................. 2 Process of Reviewing The Standards ..................................................................:.......................................... 3 How to Comment ............................................................................................................................................. 3 History of Ground-level Ozone Standards ................................................................................................... 4 Background On The 2007 Proposed Revisions To Ground-Level Ozone Standards Background: "Ozone (03) is a gas composed of three oxygen atoms. It is not usually emitted dixecdy into the air, but at ground-level is created by a chemical reaction between oxides of nitrogen (NOx) and volatile organic compounds (VOC) in the presence of sunlight. Ozone has the same chemical structure whether it occurs miles above the earth or at ground-level and can be `good' ox `bad,' depending on its location in the atmosphere. "Motor vehicle exhaust and industrial emissions, gasoline vapors, and chemical solvents as well as natural sources emit NOx and VOC that help form ozone. Ground-level ozone is the primary constituent of smog. Sunlight and hot weather cause ground-level ozone to form in harmful concentrations in the air. "Breathing ozone can trigger a variety of health problems including chest pain, coughing, throat irritation, and congestion. It can worsen bronchitis, emphysema, and asthma. Ground-level ozone also can reduce lung function and inflame the linings of the lungs. Repeated exposure may permanently scar lung tissue. "To protect public health and welfare, EPA issues National Ambient Air Quality Standards (NAAQS) for six criteria pollutants; ground-level ozone is one of these. EPA first issued standards for ground-level ozone in 1971; and revised the standard in 1979 and 1997. In June 2007, the Agency proposed to revise the 1997 standards. "The proposed revisions would strengthen the standards to increase public health protection and prevent environmental damage from ground-level ozone. The proposed revisions would affect two types of ozone standards: G - 1'--t