Respirable coal dust exposure and respiratory symptoms in South-African coal miners: a comparison of current and ex-miners.
OBJECTIVE
Dose-response associations between respirable dust exposure and respiratory symptoms and between symptoms and spirometry outcomes among currently employed and formerly employed South-African coal miners were investigated.


METHODS
Work histories, interviews, and spirometry and cumulative exposure were assessed among 684 current and 212 ex-miners.


RESULTS
Lower prevalences of symptoms were found among employed compared with ex-miners. Associations with increasing exposure for symptoms of phlegm and past history of tuberculosis were observed, whereas other symptom prevalences were higher in the higher exposure categories. Symptomatic ex-miners exhibited lower lung function compared to the nonsymptomatic.


CONCLUSIONS
Compared with published data, symptoms rates were low in current miners but high in ex-miners. Although explanations could include the low prevalence of smoking and/or reporting/selection bias, a "survivor" and/or a "hire" effect is more likely, resulting in an underestimation of the dust-related effect.
Naidoo
Rajen N
RN
Centre for Occupational and Environmental Health, University of KwaZulu-Natal, Congella, South Africa. naidoon@ukzn.ac.za
Robins
Thomas G
TG
Seixas
Noah
N
Lalloo
Umesh G
UG
Becklake
Margaret
M
D001991:Bronchitis / Q000453:epidemiology; D002908:Chronic Disease; D003031:Coal; D003032:Coal Mining; D004305:Dose-Response Relationship, Drug; D004391:Dust; D006801:Humans; D016015:Logistic Models; D016273:Occupational Exposure; D012129:Respiratory Function Tests; D012907:Smoking / Q000453:epidemiology; D013019:South Africa
D003031:Coal; D004391:Dust