In this action, the Administrator finds that lead air pollution may reasonably be anticipated to endanger the public health and welfare within the meaning of the Clean Air Act. The Administrator also finds that engine emissions of lead from certain aircraft cause or contribute to the lead air pollution that may reasonably be anticipated to endanger public health and welfare under the Clean Air Act. These findings are effective on 20 November 2023. POC is Ken Davidson, Office of Transportation and Air Quality, Assessment and Standards Division (ASD), Environmental Protection Agency; tele: (415) 972–3633; email: davidson.ken@epa.gov. (Federal Register 20 October 2023 [Rule] Pages 72372-72404)