ABSTRACT
Progressive massive pulmonary fibrosis among coal miners has unexpectedly increased. It would likely due to the greater generation of smaller rock and coal particles produced by powerful equipment used in modern mines. There is limited understanding of the relationship between micro- or nanoparticles with pulmonary toxicity. This study aims to determine whether the size and chemical characteristics of typical coal-mining dust contribute to cellular toxicity. Size range, surface features, morphology, and elemental composition of coal and rock dust from modern mines were characterized. Human macrophages and bronchial tracheal epithelial cells were exposed to mining dust of three sub- micrometer and micrometer size ranges at varying concentrations, then assessed for cell viability and inflammatory cytokine expression. Coal had smaller hydrodynamic size (180-3000 nm) compared to rock (495-2160 nm) in their separated size fractions, more hydrophobicity, less surface charge, and consisted of more known toxic trace elements (Si, Pt, Fe, Al, Co). Larger particle size had a negative association with in-vitro toxicity in macrophages (p < 0.05). Fine particle fraction, approximately 200 nm for coal and 500 nm for rock particles, explicitly induced stronger inflammatory reactions than their coarser counterparts. Future work will study additional toxicity endpoints to further elucidate the molecular mechanism causing pulmonary toxicity and determine a dose-response curve.
Subject(s)
Coal Mining , Drug-Related Side Effects and Adverse Reactions , Humans , Particle Size , Dust/analysis , Lung/chemistry , Coal/analysisABSTRACT
Concerns have been raised regarding small respirable particles, i.e. sub-micrometer-sized particles, associated with mining activities. This evaluation was designed to investigate the emissions from jackleg drilling and diesel engines and to characterize the nature of emitted particles using gravimetric analysis and number metrics. The mass concentration to which workers are potentially exposed was determined from a 4-h sampling in the vicinity of drilling activities in an underground metal mine; this concentration was found to be lower than 0.6 mg m-3 of total respirable dust. This mass concentration is low; however, the number concentrations of emitted particles from drilling exceeded 1 × 106 particles cm-3 in areas 7-9 m downwind from the drilling operation. Sub-micrometer-sized particles were also observed in aerosol samples collected using a specialized sampler, and various elements associated with drilling were found among these emitted particles. Finally, the particles in the diesel exhaust were collected, and the exhaust was found to contain nanometer-sized particles.
