EPA has proposed the strictest health standards to date for smog. Smog, also known as ground-level ozone, is linked to a number of serious health problems, ranging from aggravation of asthma to increased risk of premature death in people with heart or lung disease. Ozone can even harm healthy people who work and play outdoors. The agency is proposing to replace the standards set by the previous administration, which many believe were not protective enough of human health.

“EPA is stepping up to protect Americans from one of the most persistent and widespread pollutants we face. Smog in the air we breathe poses a very serious health threat, especially to children and individuals suffering from asthma and lung disease. It dirties our air, clouds our cities, and drives up our health care costs across the country,” said EPA Administrator Lisa P. Jackson. “Using the best science to strengthen these standards is a long overdue action that will help millions of Americans breathe easier and live healthier.”

The agency is proposing to set the “primary” standard, which protects public health, at a level between 0.060 and 0.070 parts per million (ppm) measured over eight hours. Children are at the greatest risk from ozone, because their lungs are still developing, they are most likely to be active outdoors, and they are more likely than adults to have asthma. Adults with asthma or other lung diseases, and older adults are also sensitive to ozone.

EPA is also proposing to set a separate “secondary” standard to protect the environment, especially plants and trees. This seasonal standard is designed to protect plants and trees from damage occurring from repeated ozone exposure, which can reduce tree growth, damage leaves, and increase susceptibility to disease.

In September 2009 Administrator Jackson announced that EPA would reconsider the existing ozone standards, set at 0.075 ppm in March 2008. As part of its reconsideration, EPA conducted a review of the science that guided the 2008 decision, including more than 1,700 scientific studies and public comments from the 2008 rulemaking process. EPA also reviewed the findings of the independent Clean Air Scientific Advisory Committee, which recommended standards in the ranges proposed today.

Depending on the level of the final standard, the proposal would yield health benefits between $13 billion and $100 billion. This proposal would help reduce premature deaths, aggravated asthma, bronchitis cases, hospital and emergency room visits and days when people miss work or school because of ozone-related symptoms. Estimated costs of implementing this proposal range from $19 billion to $90 billion.

Ground-level ozone forms when emissions from industrial facilities, power plants, landfills and motor vehicles react in the sun.

EPA will take public comment for 60 days after the proposed rule is published in the Federal Register. The agency will hold three public hearings on the proposal: Feb. 2, 2010 in Arlington, Va. and in Houston; and Feb. 4, 2010 in Sacramento.