; (2) ambient lead concentrations at and around airports where piston-powered general aviation aircraft are used; and (3) mitigation measures to reduce ambient lead concentrations, including increasing the size of run-up areas, relocating run-up areas, imposing restrictions on aircraft using aviation gasoline, and increasing the use of motor gasoline in piston-powered general aviation aircraft. (c) Report to Congress Not later than 1 year after the date of enactment of this Act, the Secretary shall submit to the appropriate committees of Congress the study developed by the National Research Council pursuant to this section. 178. Terminal sequencing and spacing Not later than 60 days after the date of enactment of this Act, the Administrator of the Federal Aviation Administration shall provide a briefing to the appropriate committees of Congress on the status of Terminal Sequencing and Spacing (TSAS) implementation across all completed NextGen metroplexes with specific information provided by airline regarding the adoption and equipping of aircraft and the training of pilots in its use. 179. Airport noise mitigation and safety study (a) Study Not later than 1 year after the date of enactment of this Act, the Administrator of the Federal Aviation Administration shall initiate a study to review and evaluate existing studies and analyses of the relationship between jet aircraft approach and takeoff speeds and corresponding noise impacts on communities surrounding airports. (b) Considerations In conducting the study initiated under subsection (a), the Administrator shall determine— (1) whether a decrease in jet aircraft approach or takeoff speeds results in significant aircraft noise reductions; (2) whether the jet aircraft approach or takeoff speed reduction necessary to achieve significant noise reductions— (A) jeopardizes aviation safety; or (B) decreases the efficiency of the National Airspace System, including lowering airport capacity, increasing travel times, or increasing fuel burn