Mineralogical Determinants of Cytotoxicity in Respirable Dust from Metal and Nonmetal Mines: A Multi-Technique Physicochemical Study

Mineralogical composition and crystal structure govern not only the geological classification of ore-derived dust but also its biological reactivity, yet the mineralogy–toxicity relationship of respirable dust from metal and nonmetal (MNM) mining operations remains poorly constrained. This study presents a mineralogical and physicochemical characterization of laboratory-generated respirable dust from bulk ore collected at one metal mine and four nonmetal mines, spanning five geological settings. Mineral phase and crystal structure were identified by XRD, with FTIR, SEM-EDX, and ICP-MS providing complementary structural, morphological, and elemental data. Crystalline silica (quartz) dominated four of five mine dust types (70.0%–88.3% in silica-rich nonmetal samples; 78.5%–86.6% in the metal mine), confirming pervasive respirable crystalline silica exposure regardless of commodity, while one nonmetal mine yielded a silica-free, carbonate-dominated dust as a reference material. In vitro MTT assays showed dose-dependent cytotoxicity across all samples, with viability at 100 µg/mL ranging from 31% to 71%. Quartz-rich nonmetal dust reduced viability to ~45% versus ~62% for carbonate-dominated dust (p ≤ 0.0001), while metal mine dust was most cytotoxic (31%–44%), coinciding with elevated surface manganese. This potency gradient (carbonate < silica-rich nonmetal < metal) establishes direct, mineralogically grounded structure–toxicity relationships and provides foundational data for occupational health risk assessment and dust control in MNM mining environments.