Prevalence and determinants of evidence of silicosis and impaired lung function among small scale tanzanite miners and the peri-mining community in northern Tanzania

Abstract

Limited data among miners in Tanzania suggests prevalence of silicosis, obstructive lung disease and restrictive lung disease to be around 1.6%, 1.9% and 8.8% respectively. Our study aimed to determine the prevalence and factors associated with silicosis and impaired lung function among tanzanite mining community in northern Tanzania. We conducted a cross-sectional study, involving 330 miners and 330 peri-mining community members in Mererani mines. Silicosis was defined based on study participants' history of exposure to mining dust and digital chest radiological findings with reference to the 2011 ILO classification of pneumoconiosis. Impaired lung function was determined by spirometry using American Thoracic Society/European Respiratory Society recommended system 3. Association between evidence of silicosis/impaired lung function and presumed risk factors were determined using binary logistic regression analyses. The study found that 99/330 (30.0%) of miners had silicosis. Total of 65 (9.8%) participants had impaired lung function, of whom 29 (4.4%) had Chronic Obstructive Pulmonary Disease, 32 (4.8%) had restrictive lung disease and 4 (0.6%) had both obstructive and restrictive lung diseases. Unexpectedly, miners who have worked for more than 10years and those worked for 6 to 10 years had 64% (aOR 0.34, CI = 0.17-0.67, p = 0.002) and 48% (aOR 0.52, CI = 0.30-0.89, p = 0.018) lower odds of having silicosis respectively compared those worked for up to 5 years. Participants with more than 10 years of work duration had more than 3-times higher odds of impaired lung function compared to those who had worked for up to 5 years (aOR 3.11, CI = 1.53-6.34, p<0.002). We found a concerningly high prevalence of silicosis despite short durations of exposure to occupational silica dust. Immediate dust control measures including deployment of wet drilling, wearing of personal protective equipment and regular monitoring of dust exposure need to be enforced by the Occupational Safety and Health Authority-Tanzania.

Fig 1. Duration of work in mines among mine workers found to have evidence of silicosis (N = 99).

Around 50% had a working duration of up to 5years while around 89% had a working duration of up to 10 years.

Fig 2. Chart showing the trend of various form of impaired lung function in relation to the ILO classes of silicosis.