Background: During day to day mining activities, miners are exposed to different airborne pollutants, which may result in occupational lung diseases (OLDs). In South Africa mining is a primary industrial activity that contributes significantly to the gross domestic product (GDP). Mine related lung diseases depend on the type of commodity that is mined, aerodynamic size of airborne pollutants, exposure time, environmental conditions and the employee’s lifestyle.
Aim and Objectives: To determine the prevalence of obstructive airway disease amongst load haul drivers (LHD) occupationally exposed to mineral dusts and diesel particulate matter (DPM) in trackless mines. The study was also aimed at determining the relationship of selected epidemiological determinants on the status of obstructive airway disease in LHD and to determine whether a difference existed between employees that worked only day or night shift.
Methodology: The study area was a platinum mine in Mpumalanga. The study population comprised of underground LHD drivers who were frequently exposed to mineral dust and DPM during loading and off-loading of raw minerals. The study population was divided into two groups: day shift and night shift, a questionnaire was used to obtain information on demographics; self-reported social and health history, including respiratory symptoms. Spirometry was performed to determine the Forced Vital Lung Capacity (FVC) and Forced Expiratory Volume 1 sec (FEV1). Employees who presented an FEV1/FVC of <70% underwent a second spirometry after using a bronchodilator (Combivent, 0.5mg ipratropium bromide anhydrous, 2.5mg salbutamol base, & 0.52mg ipratroniumbromide).This was done to rule out reversible obstructive lung cases.
Results: Employees on night shift had a significantly higher prevalence of obstructive airway disease patterns (32.6%) compared to the day shift prevalence (12.5%). There was a significantly higher (p = 0.009) prevalence of acute coughing in night shift LHD (41.3%) compared to day shift LHD drivers (15.0%)). Over 3 months, night shift workers (73.68%) also presented with significantly more (p = 0.036) symptoms of chronic coughing than day shift workers (0.00%) night shift workers (47.83%) presented sputum production while day shift workers presented only 14.29%. Furthermore, night shift LHD showed a significance change (p = 0.729) in measured lung function of FEV1/FVC, in comparison with day shift LHD. Multivariate regression analysis also showed that night shift LHD had a 3 times higher odds of developing obstructive airway disease than day shift workers (OR 3.30, 95% Cl 1.08, 10.04, p = 0.036).
Conclusion: The night shift LHD drivers presented a marked reduction in lung function as well as acute and chronic respiratory symptoms. It is therefore concluded that night shift LHD are at higher risk of developing obstructive airway disease when exposed to diesel particulate matter as compared to day shift workers.