A proof-of-principle experiment to use the convenient scattering length of perfluorinated alkyl surfactants to measure partitioning to lipids at the air-water interface, representative of lung ling. The partitioning of Perfluorooctadecanoic acid and perfluorooctadecanoic sulphate to a monolayer of the lipid DPPC at the air-water interface will be measured at biological temperature as a function of perfluorinated compound concentration. The partition constant and adsorption kinetics will be measured and will be used in ecotoxicological models to understand the bioaccumulation of perfluorinated surfactants in biological organs.