; (2) an assessment of the sources, prevalence, and causes of microfiber pollution; (3) a recommendation for a standardized methodology to measure and estimate the prevalence of microfiber pollution; (4) recommendations for reducing microfiber pollution; and (5) a plan for how Federal agencies, in partnership with other stakeholders, can lead on opportunities to reduce microfiber pollution during the 5-year period beginning on such date of enactment. 503. Study on United States plastic pollution data (a) In general The Under Secretary, in consultation with the EPA Administrator, shall seek to enter into an arrangement with the National Academies of Sciences, Engineering, and Medicine under which the National Academies will undertake a multifaceted study that includes the following: (1) An evaluation of United States contributions to global ocean plastic waste, including types, sources, and geographic variations. (2) An assessment of the prevalence of marine debris and mismanaged plastic waste in saltwater and freshwater United States waterways. (b) Report Not later than 18 months after the date of the enactment of this Act, the Under Secretary shall submit to Congress a report on the study conducted under subsection (a) that includes— (1) the findings of the National Academies; (2) recommendations on knowledge gaps that warrant further scientific inquiry