The U.S. Environmental Protection Agency ( will reconsider the 2008 national smog standards to ensure they are scientifically sound and protective of human health. Smog, which is also known as ground level ozone, has been linked to asthma and other respiratory illnesses.

The reconsideration, announced this week by EPA Administrator Lisa Jackson, covers both the primary and secondary ozone standards. The 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. The agency will propose any revisionsto the ozone standards by December 2009 and will issue a final decision by August 2010.

The reconsideration will be comprised of a 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.

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.