The correlation between aerosol size and the deposited fraction within the lung can be used to greatly improve drug efficacy through fine tuning the hygroscopic properties of the aerosols used in drug delivery so as to specifically target locations within the lung to deliver the dose.  The rapid change in RH, from ambient to >99%, to which an aerosol is exposed affects its size, and the magnitude of size change will dictate the site of particle deposition. Currently, the degree to which the aerosol changes in size during the brief period of time that encompasses inhalation is not well understood.  In this preliminary study, we looked at the potential of using Pluronic polymers as the basis of an aerosol by which to deliver drugs to the lung.  A new type of electrodynamic balance (EDB) was used to probe these rapid changes in size of Pluronic polymer containing aerosols.