Lead (Pb) exposure is a significant global concern due to its negative impact on neurological and cognitive development in children. Particularly, in many historic mining sites, high levels of lead (Pb) in the ingestible soil (<250 µm) and inhalable dust (<10 µm) have prompted the investigation into techniques for in-situ Pb immobilization using soil amendments. Although the efficacy of Pb immobilization using phosphates has been demonstrated via the ingestion pathway (e.g. by promoting the formation of insoluble Pb-phosphates in the soil), its efficacy in reducing Pb exposure via the inhalation pathway has received little attention. This is particularly relevant because 90% of the inhaled dust may be swallowed within 24 h and reach the gastro-intestinal (GI) tract where the Pb may be subjected to the same conditions as ingested soil. This study compared Pb immobilisation efficacies of phosphorus (P) and iron (Fe) amendments via ingestion and inhalation pathways using in-vitro and in-vivo assays in conjunction with Pb speciation and dynamics via X-ray based spectroscopic methodologies. Mining/smelting impacted soil from Broken Hill, Australia was amended with Phosphoric Acid (PA), Hydroxyapatite, Mono-Ammonium Phosphate (MAP), Triple Super Phosphate (TSP), bonemeal biochar and Fe2O3 at a molar ratio of Pb:P/Fe=1:5. Pb in-vitro bioaccessibility (IVBA) was conducted in the <250 µm ingestible soil particle fraction (ingestible fraction) using the solubility bioaccessibility research consortium assay, and in the <10 µm inhalable soil particle fraction (dust fraction) using inhalation-ingestion bioaccessibility assay and artificial lysosomal fluid assay. In-vivo bioassays were conducted in the mouse model [relative bioavailability (RBA) in the ingestible fraction and blood and tissue bioavailability via instillation in the dust fraction over a 24 h exposure period]. Spectroscopic methodologies utilised included assessment of Pb-phosphate formation by X-ray Absorption Spe