Lung function loss in relation to silica dust exposure in South African gold miners.
OBJECTIVE
To estimate exposure-response relationships between respirable dust, respirable quartz and lung function loss in black South African gold miners.


METHODS
520 mineworkers aged >37 years were enrolled in a cross-sectional study. Gravimetric dust measurements were used to calculate cumulative respirable dust and quartz exposures. Excess lung function loss was defined as predicted minus observed forced expiratory volume in one second (FEV(1)) and forced vital capacity (FVC). The association between excess loss and exposure was estimated, adjusting for smoking, tuberculosis and silicosis.


RESULTS
Mean service length was 21.8 years, mean respirable dust 0.37 mg/m(3) and mean respirable quartz 0.053 mg/m(3). After adjustment, 1 mg-yr/m(3) increase in cumulative respirable dust exposure was associated with 18.7 ml mean excess loss in FVC [95% confidence interval (CI) 0.3, 37.1] and 16.2 ml in FEV1 (95% CI -0.3, 32.6). Mean excess loss with silicosis was 224.1 ml in FEV1 and 123.6 ml in FVC; with tuberculosis 347.4 ml in FEV1 and 264.3 ml in FVC.


CONCLUSIONS
Despite a healthy worker effect, lung function loss was demonstrable whether due to silicosis, tuberculosis or an independent effect of dust. A miner working at a respirable dust intensity of 0.37 mg/m(3) for 30 years would lose on average an additional 208 ml in FVC (95% CI 3, 412) in the absence of other disease, an impact greater than that of silicosis and comparable to that of tuberculosis. Improved dust control on the South African gold mines would reduce the risk of silicosis, tuberculosis and lung function impairment.
Ehrlich
R I
RI
School of Public Health and Family Medicine, University of Cape Town, Observatory 7925, South Africa. rodney.ehrlich@uct.ac.za
Myers
J E
JE
te Water Naude
J M
JM
Thompson
M L
ML
Churchyard
G J
GJ
D000328:Adult; D004391:Dust; D004784:Environmental Monitoring / Q000379:methods; D004812:Epidemiologic Methods; D062665:Epidemiological Monitoring; D005541:Forced Expiratory Volume / Q000502:physiology; D006046:Gold; D015989:Healthy Worker Effect; D006801:Humans; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D008906:Mining; D016273:Occupational Exposure / Q000009:adverse effects* / Q000032:analysis; D012822:Silicon Dioxide / Q000633:toxicity*; D012829:Silicosis / Q000503:physiopathology; D012907:Smoking / Q000503:physiopathology; D013147:Spirometry / Q000379:methods; D014397:Tuberculosis, Pulmonary / Q000503:physiopathology; D014797:Vital Capacity / Q000502:physiology
D004391:Dust; D006046:Gold; D012822:Silicon Dioxide