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