In 2008, EPA established a new primary 8-hour standard for ozone of 0.075 parts per million (ppm), and a new secondary standard set at a form and level identical to the new primary standard. The previous primary and secondary standards were identical 8-hour standards, set at 0.08 ppm. Because ozone is measured out to three decimal places, the standard effectively became 0.084 ppm; therefore, areas with ozone levels as high as 0.084 ppm were considered to have met the 0.08 ppm standard, due to rounding. (Earlier post.)

The 2008 standard was at the higher end of options proposed by EPA staff scientists in a paper submitted in 2007, and falls above the standard recommended by scientific and medical groups, including the Clean Air Scientific Advisory Committee (CASAC) which assists the Administrator of the EPA.

EPA will conduct a thorough review of the science that guided the 2008 decision, including more than 1,700 scientific studies and any public comments from that rulemaking process. The agency will also review the findings of EPA’s independent Clean Air Scientific Advisory Committee, which recommended stronger smog standards.

EPA will move quickly to implement any new standards that might result from the reconsideration. To reduce the workload for states during the interim period of reconsideration, the agency will propose to stay the 2008 standards for the purpose of attainment and nonattainment area designations. EPA will work with states, local governments and tribes to ensure that air quality is protected during that time. The agency will propose any revisions to the ozone standards by December 2009 and will issue a final decision by August 2010.

EPA sets primary air quality standards to protect public health, including the health of sensitive groups, such as children and people with asthma. The secondary standard is set to protect public welfare and the environment, including protection against visibility impairment, damage to animals, crops, vegetation, and buildings.

Earlier this year, EPA Administrator Lisa Jackson reinstated the role of a key policy document created by agency scientists (the Staff Paper) that contains staff analyses of options for the administrator to consider when setting National Ambient Air Quality Standards (NAAQS) to protect human health and the environment. (Earlier post.)

Ground-level ozone forms when emissions from industrial facilities, power plants, landfills and motor vehicles react in the presence of sunlight. Scientific studies have linked ozone exposure to respiratory health problems ranging from decreased lung function and aggravated asthma to increased emergency department visits, hospital admissions, and even premature death. Seasonal ozone exposure has also been linked to adverse effects on sensitive vegetation, forests and ecosystems.