title: The risk of pulmonary tuberculosis in underground copper miners in Zambia exposed to respirable silica: a cross-sectional study.
abstract: Pulmonary tuberculosis (PTB) among underground miners exposed to silica remains a global problem. Although well described in gold and coal mining, risk in other mining entities are not as well documented. This study aims to determine dust-related dose response risk for PTB among underground miners exposed to silica dust in Zambia's copper mines.
  
  
  
  A cross sectional study of in-service miners (n = 357) was conducted at Occupational Health and Safety Institute (OHSI), Zambia. A systematic review of medical data over a 5-year period from assessments conducted by doctors at OHSI and statutory silica exposure data (n = 16678) from the Mine Safety Department (MSD) were analysed. Lifetime cumulative exposure metrics were calculated. Multivariate logistic regression analysis was used to determine the association between PTB and lifetime exposure to silica, while adjusting for various confounders.
  
  
  
  The median respirable silica dust level was 0.3 mg/m(3) (range 0.1-1.3). The overall prevalence of PTB was 9.5 % (n = 34). High cumulative respirable silica dust category showed a statistically significant association with PTB (OR = 6.4 (95 % CI 1. 8-23)) and a significant trend of increasing disease prevalence with increasing cumulative respirable silica dust categories was observed (ptrend < 0.01). Smoking showed a statistically significant association with PTB with OR = 4.3 (95 % CI 1.9-9.9).
  
  
  
  Our results demonstrate the association of increased risk for certified active TB with cumulative respirable dust in a dose related manner among this sample of copper miners. There is need to intensify dust control measures and incorporate anti-smoking interventions into TB prevention and control programmes in the mines.
authors.affiliation: Occupational Health and Safety Institute, P.O. Box 20205, Kitwe, Zambia. kingsleyngosa@gmail.com.
authors.forename: Kingsley
authors.initials: K
authors.lastname: Ngosa
authors.affiliation: Discipline of Occupational and Environmental Health, University of KwaZulu-Natal, Durban, 4041, South Africa.
authors.forename: Rajen N
authors.initials: RN
authors.lastname: Naidoo
mesh_terms: D000328:Adult; D003032:Coal Mining / Q000706:statistics & numerical data; D003300:Copper; D003430:Cross-Sectional Studies; D004391:Dust / Q000032:analysis; D006801:Humans; D008297:Male; D008875:Middle Aged; D000067572:Miners / Q000706:statistics & numerical data*; D009784:Occupational Diseases / Q000453:epidemiology*; D016273:Occupational Exposure / Q000009:adverse effects*; D015995:Prevalence; D012822:Silicon Dioxide / Q000633:toxicity*; D014397:Tuberculosis, Pulmonary / Q000139:chemically induced / Q000453:epidemiology*; D055815:Young Adult; D015024:Zambia
chemical_list: D004391:Dust; D012822:Silicon Dioxide; D003300:Copper
keywords: Cumulative exposure; Pulmonary Tuberculosis; Silica dust; Smoking; Underground copper miners