Biological responses of workplace particles and their association with adverse health effects on miners

Abstract

Epidemiological research has demonstrated the relationship between exposure to quartz dust and an elevated risk of pneumoconiosis and possible elevated risk of cancer. The current study was designed to evaluate the biological responses of workplace particles containing crystalline silica using an in vitro cell test. Respirable particle samples were sampled from four tin mines, where the standardized mortality ratio (SMR) for pneumoconiosis was 51.6 and SMR for lung cancer was 2.2 in dust-exposed miners. Alveolar macrophages (AM) are considered as the target cells for primary dust effects. The samples were then measured at 15, 30, 60 and 120 μg particle per 10⁶ AM for cytoxicity with the release of glucuronidase, lactate dehydrogenase, for reactive oxygen damage with H₂O₂ release, and for ability to induce fibrosis using the secretion of tumor necrosis factor-alpha (TNF-α). Pure quartz (DQ12) and corundum were used as controls. The results showed the samples from tin mines caused a higher cytoxicity when compared to corundum, yet lower when compared to quartz. However, reactive oxygen species release (148–177 nmol/3 × 10⁵ AM in high concentration of 120 μg/10⁶ AM) induced by the samples were significantly higher than that induced by quartz (57 nmol/3 × 10⁵ AM) and corundum (62 nmol/3 × 10⁵ AM). Furthermore, particle samples induced higher TNF-α secretion than corundum, the samples from Limu tin mine induced much higher TNF-α levels than that induced by DQ12 quartz. The results from the in vitro tests help elucidate the degree of hazard of dust particles in tin mines. The in vitro reaction patterns of AM also constitute a powerful tool to monitor biological and pathogenic responses of humans following dust particle exposure.