Natural history museums are a potential treasure trove for understanding how persistent pollutants move around the globe. Using feathers from white-tailed eagles in specimen collections, researchers have constructed a time series of per- and polyfluoroalkyl substances (PFAS) exposure going back to the late 1960s (Environ. Sci. Technol. 2019, DOI: 10.1021/acs.est.9b03514). The team measured the concentrations of 15 PFAS compounds and examined differences in PFAS concentrations in birds collected from Greenland, Norway, and Sweden. Almost every one of the 147 specimens contained at least one of the compounds. In birds from Greenland and Norway, concentrations of perfluorooctane sulfonate (PFOS) declined in the late 1990s, when the chemical was phased out by 3M. Interestingly, notes Aarhus University ecotoxicologist Igor Eulaers, PFOS exposure in the Swedish subpopulation did not decrease. That may be due to continued inputs from previously produced PFOS or to the relatively low circulation of water into and out of the Baltic Sea. University of Antwerp ecotoxicologist Jiachen Sun says museum collections allow researchers to look back in time and “see what has been imprinted on the environment.” Eulaers says this kind of information is critical for informing both national and international policy on these persistent pollutants.