Laura Alcocer Quinones presented her work on the challenges of aggregating source-level measurements of PFAS for use in policy analysis. Although monitoring for PFAS is common around the United States, the methods and frequency of monitoring are not standardized. Laura showed how the distribution of aggregated PFAS levels changes significantly, depending upon the assumptions over missing data and attrition. Her work highlights how our choices as researchers when cleaning and aggregating concentration data have the potential to lead us to different conclusions.