RT Journal Article
SR Electronic
T1 Tuberculosis and silica exposure in South African gold miners
JF Occupational and Environmental Medicine
JO Occup Environ Med
FD BMJ Publishing Group Ltd
SP 187
OP 192
DO 10.1136/oem.2004.018614
VO 63
IS 3
A1 J M teWaterNaude
A1 R I Ehrlich
A1 G J Churchyard
A1 L Pemba
A1 K Dekker
A1 M Vermeis
A1 N W White
A1 M L Thompson
A1 J E Myers
YR 2006
UL http://oem.bmj.com/content/63/3/187.abstract
AB Aims: To examine the effect of silica exposure, in the absence of silicosis, on the prevalence of pulmonary tuberculosis (PTB), which is epidemic among South African gold miners. Methods: Cross-sectional study of 520 gold miners over 37 years of age. Length of service, and cumulative and average dust and quartz exposure indices were derived for each miner. Chest radiographs were read for PTB by two NIOSH “B” readers. PTB was defined as a self-reported history of PTB or PTB on chest radiograph. Logistic regression was used to adjust for age, smoking, and silicosis. PTB effects of different exposure metrics for silica, scaled on their interquartile range (IQR), were compared. Results: Means (ranges) were: age 46.7 (37.1–59.9) years; length of service 21.8 (6.3–34.5) years; average intensity of respirable quartz 0.053 (0–0.095) mg/m3. PTB prevalence was 19.4% (95% CI 16.0 to 22.8) on history alone, and 35.2% (95% CI 31.1 to 39.3) on history or on chest radiograph. Length of service was poorly predictive of PTB, while all exposure indices which included dust or quartz yielded prevalence odds ratios (PORs) of approximately 1.4 (95% CI ∼1.1 to 1.8) for changes of one interquartile range in exposure. Controlling for silicosis—by adjustment or restriction—did not modify these results. Drillers and winch operators had the highest PTB prevalences and the highest dust and silica exposures. Conclusion: Older in-service gold miners in South Africa have a high prevalence of PTB, which is significantly associated with dust and silica exposure, even in the absence of silicosis. Limitations include a survivor workforce and the use of cumulative exposures based on current exposures. Dust control is an important component in control of the PTB epidemic in South African gold mines.