The interaction of model compounds with a polyolefin plastic material was examined in binary mixtures of ethanol/water to assess the impact of the solvent polarity on the magnitude of the interaction. The interactions investigated included both compound sorption from the solution by the plastic material and leaching of plastic components into the solution. The magnitude of the interaction at equilibrium, expressed as an equilibrium interaction constant, could be linearly related to the compound's octanol-water partition coefficient (P,I,) and the solvent's polarity (P.). The utility of the resulting mathematical interaction model was assessed by examining the compatibility of the sample plastic system with a simulated pharmaceutical product vehicle containing a typically encountered surfactant. The nature of the plastic-solution interaction in the surfactant was unlike that observed in the binary model systems, consistent with the expectation that a surfactant's behavior is mediated by mechanisms other than simple polarity. (C) 2003 Wiley Periodicals, Inc.