Associations of Occupational Exposure to Respirable Crystalline Silica with Pulmonary Function and Liver-related Biochemical Markers Among Gol-e-Gohar Iron Ore Miners

Abstract

Background: Occupational exposure to airborne dust in iron ore mining is a well-established risk factor for pulmonary impairment. However, its potential systemic effects, particularly on hepatic function, have received considerably less attention. Objectives: This study evaluated the associations between occupational exposure to respirable dust and crystalline silica and pulmonary function and liver-related biochemical parameters among workers at the Gol-e-Gohar mining complex using personal exposure monitoring, spirometry, and plasma biochemical analyses. Methods: This cross-sectional study measured aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase (ALP), cholesterol, and triglycerides in blood samples from 211 individuals (71 controls and 140 exposed workers). Spirometry was used to assess forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), FEV1/FVC, forced expiratory flow at 25% - 75% of FVC (FEF25 - 75), and peak expiratory flow rate. Respirable dust and crystalline silica exposure were evaluated using National Institute for Occupational Safety and Health (NIOSH) Method 0600 and an optimized NIOSH Method 7602, respectively. Data were analyzed using SPSS V21 at the 95% confidence level. Results: Respirable dust exposure was not significantly correlated with pulmonary function indices (P > 0.05). However, respirable crystalline silica exposure was significantly negatively correlated with %FVC (r = −0.40, P = 0.01), %FEV1 (r = −0.45, P = 0.024), and %FEF25 - 75 (r = −0.46, P = 0.02).

The mean ALP level was significantly higher in the exposure group than in the control group (P = 0.007). No statistically significant between-group differences were observed in the remaining liver-related biochemical markers.

Triglyceride levels were negatively correlated with respirable dust exposure (r = -0.23, P = 0.01), whereas the other liver-related parameters showed no significant associations. Conclusions: Respirable crystalline silica exposure was associated with a spirometric pattern compatible with possible restrictive pulmonary impairment. Liver-related biochemical markers were largely unchanged, apart from an isolated elevation in ALP, which may indicate subclinical hepatic stress. Longitudinal studies incorporating multivariable adjustment and more advanced hepatic assessment are needed to clarify the systemic risks of mining-related pollutant exposure.