EPA staff have concluded that there is adequate evidence for lowering the existing ozone standard from 75 parts per billion to somewhere between 60 and 70 ppb. “The available scientific evidence and exposure/risk information provide strong support for considering a primary O3 standard with a revised level to increase public health protection, including for at-risk populations,” according to a policy assessment prepared by EPA staff. The final decision on where to set the revised ozone standard will be made by EPA Administrator Gina McCarthy. The agency has a court-ordered deadline of Dec. 1 to issue a proposal on whether to retain or revise the existing ozone standard. A tighter standard would lead to new emissions control requirements for sources that emit ozone precursors—nitrogen oxides and volatile organic compounds—such as power plants, industrial facilities, and motor vehicles. The range identified in the final policy assessment matches the range identified as appropriate by EPA’s Clean Air Scientific Advisory Committee.