Assessment of dust exposure and risk of chronic respiratory diseases among stone corrie quarry workers in Namibia, 2018.

Abstract

Quarry mining produces substantial dust amounts bearing an adverse effect on human health in several ways, mainly the respiratory system. Even though employers are obligated to protect their employees from occupational hazards, the quarry mining industry in Namibia has failed to honour that obligation. This study investigated quarry workers and the surrounding community’s exposure to dust as well as their risk of getting chronic respiratory diseases in the Erongo region of Namibia. Objectively the study assessed the amount of silica emitted in quarry dust emissions from selected Namibian quarry mines in compliance with national and WHO Air Quality Standards. Secondly, this study made an evaluation of health risks connected to dust exposure amid quarry workers and surrounding communities of 1km radius to selected quarry sites. Lastly, this study established appropriate interventions to deter dust exposure effects on quarry workers and the surrounding community. A cross-sectional descriptive study was done with 233 quarry workers and community members from selected quarry mines around Karibib. Self-administered interview questionnaires were used to both quarry workers and community members. Respirable dust levels were evaluated in different work stations using Spirometry. Binominal logistic regression analysis was used to predictable the overall outcome of quarry dust exposure on respiratory outcomes, while linear regression predicted the exposure-related effect on lung function. Workers were stratified according to the cumulative dust exposure category. The highest mean dust level, by quarry site, was 1.13 mg/m³ (SD: 0.58) recorded among workers from Site A and the lowest was 0.63 mg/m³ (SD=0.38) at Site B. In relation to job types, excavation had the highest mean dust level of 1.20 mg/m³ (SD: 0.65) and wire saw the lowest at 0.54 mg/m³ (SD=0.42). The most prevalent of the respiratory symptoms reported by the quarry workers were coughing (57%) and the corresponding percentage among the community members was lower (14%). There were more respondents with 10 or more years in quarrying (78%) who reported coughing compared to 58% or less among workers with less than 10 years in the job. Statistical links between the lung function assessments and quarry site, job specification, or years in quarrying among the quarry workers (p>0.05) were not established. Lung function outcomes between the quarry workers and community members (p>0.05) did not also show a substantive difference. However, a significant statistically difference between quarry workers and community members, with 13 of the 120 of quarry 8 workers (11%) diagnosed with obstructive or restrictive lung functioning compared to none of the 96 community members. There were statistically significant associations between smoking history and the lung function assessments FVC1 Pred% and FEV1 Pred%. Workers with 6-10 years of smoking history had significantly lower mean scores on both these measures compared to non-smokers. The study found that there were no medical examinations records at any of the studied sites. The study recommended that routine occupational medical check-up is performed for each and every worker of the quarry mines. Environmental administration systems, such as dust management plan, can be used in quarries to minimise the generation of dust. Regular environmental audit and monitoring of quarrying activities should be enforced in order to ensure adherence to the standards and limits of the concentrations of the dust generated from the different stages of their operations.