Risk Factors Associated with Silicosis in Zambin former Mineworkers

The risk of silicosis depends on a number of factors which include among others; the nature of the dust, the intensity and duration of exposure as well as individual susceptibility. The association of these factors with silicosis vary from country to country and between regions being influenced mainly by work culture, environmental and safety conditions prevailing at worksites. This study aimed to determine the risk factors of silicosis in Zambian former copper mineworkers.
A retrospective cross-sectional study involving the review of 476 randomly selected records of all Zambian former copper mineworkers who attended medical examinations at Occupational Health Management Board in Kitwe, between the periods 1st January 2004 and 31st December 2008. Data was analysed using Epi Info version 3.3.2 statistical package. Data was described for silicosis by; current age, dates of certification and discharge, sex, service in various mining divisions, work-sites, job categories, and mean percent silica concentration.
The results showed a silicosis prevalence of 8.8percent (CI = 6.27 to 11.38). The study established an average age of 66 years in silicotics, as compared to 56 years in non-silicotics (p-value <0.001). The silicotics were found to have worked for a median 26 years while the non-silicotics’ median service stood at 21 years (p-value <0.001). For each additional year spent working for Mufulira or Chibuluma divisions, miners were16percentmore likelyto develop silicosis (OR = 1.16; CI = 1.06 to 1.26 and OR = 1.16; CI = 1.04 to 1.30 respectively). On each additional year spent working in the underground production areas, miners were 14percent (OR = 1.14; CI = 1.06 to 1.24) more likely to develop silicosis. Each year spent working as a lasher increased miners’ chances of developing silicosis by 31percent (OR = 1.31; CI = 1.12 to 1.54). Silicotics were exposed to 825percent silica-years as compared to 507percent silica-years in non-silicotics (p-value < 0.001).
Long service, working in Mufulira or Chibuluma division, working in the production area, working as a lasher and exposure to dust with high percent silica concentration are associated with silicosis in Zambian former miners. Efforts to reduce the silicosis burden among the former miners should address the above identified risk factors. These include reducing years of service and providing personal protective equipment for workers in work-areas with high silica content