Cross-shift peak expiratory flow changes are unassociated with respirable coal dust exposure among South African coal miners.
BACKGROUND
The objectives of this study were to determine whether cross-shift changes in peak expiratory flow rate (PEFR) were related to respirable dust exposure in South African coalminers.


METHODS
Fifty workers were randomly selected from a cohort of 684 miners from 3 bituminous coalmines in Mpumalanga, South Africa. Peak expiratory efforts were measured prior to the commencement of the shift, and at the end of the shift on at least two occasions separated by at least 2 weeks, with full shift personal dust sampling being conducted on each occasion for each participant. Interviews were conducted, work histories were obtained and cumulative exposure estimates were constructed. Regression models examined the associations of cross-shift changes in PEFR with current and cumulative exposure, controlling for shift, smoking and past history of tuberculosis.


RESULTS
There were marginal differences in cross-shift PEFR (ranging from 0.1 to 2 L/min). Linear regression analyses showed no association between cross-shift change in PEFR and current or cumulative exposure. The specific shift worked by participants in the study showed no effect.


CONCLUSIONS
Our study showed no association between current respirable dust exposure and cross-shift changes in PEFR. There was a non-significant protective effect of cumulative dust exposure on the outcome, suggesting the presence of a "healthy worker survivor effect" in this data.
Naidoo
Rajen N
RN
Centre for Occupational and Environmental Health, University of KwaZulu-Natal, Durban, South Africa. naidoon@ukzn.ac.za
Robins
Thomas G
TG
Becklake
Margaret
M
Seixas
Noah
N
Thompson
Mary Lou
ML
D000328:Adult; D003032:Coal Mining; D003430:Cross-Sectional Studies; D004391:Dust; D005260:Female; D006304:Health Status; D006306:Health Surveys; D006801:Humans; D007407:Interviews as Topic; D008171:Lung Diseases / Q000453:epidemiology* / Q000209:etiology; D009784:Occupational Diseases / Q000453:epidemiology* / Q000209:etiology; D016273:Occupational Exposure / Q000009:adverse effects*; D016272:Occupational Health; D010366:Peak Expiratory Flow Rate; D012140:Respiratory Tract Diseases / Q000453:epidemiology; D012307:Risk Factors; D013019:South Africa / Q000453:epidemiology; D011795:Surveys and Questionnaires
D004391:Dust