Almost five years after first proposing to strengthen the national air quality standard for ozone pollution, the U.S. Environmental Protection Agency (EPA) announced on Nov. 25 that it intends to again propose a more health-protective air quality standard for ground-level ozone pollution. Breathing ozone, also known as smog, can cause health issues ranging from asthma attacks to early death from heart and lung disease.

Depending on the level EPA chooses for the final standard, the Thanksgiving-eve announcement holds the promise of either a relatively modest or potentially substantial improvement in public health protection from this widespread air pollutant. The agency announced that it is considering revising the ozone standard from the current 75 parts per billion (ppb) to between 65 to 70 ppb, while also asking for comment on keeping the current standard or setting a standard at 60 ppb, the lowest level in the range recommended by its science advisors. Those advisors have already told EPA that a new standard at the high end of the proposed range would not provide the “margin of safety” required under the Clean Air Act.

People most at risk from breathing ozone include: children; people with asthma and other respiratory diseases; older adults; and people who are active outdoors, especially outdoor workers. Air pollution controls needed to reduce ozone levels will also result in reducing levels of toxic particles in the air. EPA expects that air pollution control efforts to comply with already existing or proposed rules and programs limiting air pollution from power plants and vehicles will result in most areas of the country meeting the new standard by 2025, when all areas in the U.S. except those in California will need to be in compliance.

EPA estimates that the combined effect of tightening the ozone standard and reductions in particle pollution will prevent 730 to 4,300 premature deaths, 320,000 to 960,000 asthma attacks in children, and 1,400 to 4,300 asthma-related emergency room visits each year, among other health benefits.

These estimates exclude the health benefits in California, which, due to its severe ozone problems, will have an extra seven to 12 years to meet the new standard. Once targeted areas in the state meet the new standard, the nation will avoid 110 to 430 additional premature deaths, 99,000 to 210,000 additional asthma attacks in children, and 340 to 740 more asthma-related emergency room visits each year.

Depending on whether EPA selects the higher or lower end of the proposed range, the health benefits will amount to between $6.4 to $38 billion each year, with the eventual benefits in California adding an additional $1.1 to $4.1 billion annually.

As I discussed in an article this summer, EPA’s past efforts to set a science- and health-based ozone standard have been battered by political forces. Ignoring the recommendations of its science advisors and bowing to pressure from industry and the George W. Bush White House, the agency in 2008 set the current ozone standard at a level characterized as “legally indefensible” by the Obama administration’s first EPA administrator, Lisa Jackson. Administrator Jackson committed to expediting a new standard, only to have the rug pulled out from underneath her by President Obama’s 2011 decision to postpone the final rule.

Once the proposed standard is published in the Federal Register, EPA will accept public comments for 90 days. A final decision on the ozone standard is due under a court-ordered deadline by Oct. 1, 2015. Big industry and their proxies in Congress have already started a drumbeat opposing any change to the current standard. It will be essential for the public to weigh in with comments on the importance of EPA selecting the most health-protective standard under consideration.