The interaction of silica and kaolin with dipalmitoylphosphatidylcholine (DPPC) has been studied using C-13 and P-31 solid state nuclear magnetic resonance spectroscopy. These studies explore the molecular interactions of these respirable dusts with a model lung surfactant species to characterize silica toxicity in mixed systems. The choline head group of DPPC was found to remain mobile when adsorbed on kaolin, in contrast to an immobile head group on silica. Further, glycerol carbon intensities were greatly diminished relative to that of choline carbons, a result attributed to broadening effects. These preliminary findings suggest that silica toxicity may not be related to choline mobility as previously noted [J. Colloid Interface Sci. 172 (1995) 536-538]. Published by Elsevier Inc.