EPA’s independent science advisers say the agency has provided a “strong rationale” for tightening the federal limit for ground-level ozone, a lung-irritating air pollutant, to 60–70 ppb. In a review of the agency’s preliminary policy assessment, the Clean Air Scientific Advisory Committee says EPA has also provided “adequate justification” for considering concentrations in the 50–60-ppb range. The current ozone standard is 75 ppb, as established by the George W. Bush Administration in 2008. A year ago, EPA was prepared to finalize a revised standard of 70 ppb. But citing the slow economic recovery, the White House directed the agency not to take any action until at least 2013. At the time, EPA estimated that complying with the tighter standard would cost U.S. businesses up to $90 billion per year but said those costs would be offset by the benefits to public health. EPA now says it expects to complete the lengthy process of reviewing the national ozone standard by September 2014.