Airborne particulate material collected from seventeen rural unsurfaced roads in Missouri's agricultural and resource mining areas were characterized using the BCR sequential extraction procedure and simulated invitro body fluids to determine the phase partitioning and bioaccessibility of Pb associated with roadway dusts. Results show that dusts produced from driving over unsurfaced roads in the mining area has a substantial portion of the Pb concentration associated with the more mobile exchangeable-plus-carbonate and reducible geochemical phases. By comparison, unsurfaced road dusts outside the resource mining area have lower metal contents, as expected, and a larger portion of the total Pb concentration associated with the immobile oxidizable and non-silicate bound residual phases. SEM/EDS analysis suggests the minerals associated with the more mobile Pb components include cerussite, Pb oxides and sulfates. Compared with the coarser >1μm size fraction of dust, the <1μm fraction contains a substantially higher concentration of Pb in association with clay minerals. Extraction tests using simulated body fluids show that gastric fluid can mobilize as much as 69% of the total Pb concentration in mining area road dust samples after five hours. Simulated alveolar lung fluid also was an efficient extractor of Pb from the <1μm sample dust fraction, dissolving up to 100% of the available Pb after 100h. Regression analysis suggests that aqua regia total Pb concentration is a good predictor of mobility and bioaccessibility and can be used to minimize costs associated with monitoring suspended dust contamination.