Discipline of Occupational and Environmental Health
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Department of Occupational and Environmental Health

Respiratory Health of South African Coalminers
 
Summary:

The study described the prevalence of dust related respiratory problems among living and deceased South African coal miners and investigated dose response relationships between health endpoints and respirable dust, adjusting for potential confounders.

This was achieved through a review of coalminer autopsies (n=7760) performed between 1975 and 1997 and the assessment of active (n=684) and ex-miners (n=212), employed for at least one year in underground mining between 1985 and 1998 in one of three mines in Mpumalanga province.
Associations were investigated between exposure measures and respiratory outcomes, based on questionnaires, spirometry and radiographs. Cumulative exposure to respirable dust was estimated through historical and current dust samples, work histories, miner interviews and other record reviews.

Historic exposure levels and investigator collected dust data across the mines ranged from averages of 1.30 - 2.56mg/m3 at the coalface. The prevalence of respiratory diseases ranged from 2.59% - 11.30%. The estimate of dust related effect on FEV1 for a 40 year old, 1.70m tall man, was 1.33ml per mg-years/m3, controlling for smoking and past history of TB. Past history of TB resulted in an average 698ml decline in FEV1. Miners with the most significant respiratory problems and the greatest sensitivity to dust exposure were likely to leave employment before normal retirement age or move from high to lower exposed jobs.

At autopsy, the prevalence of CWP (6.95%), silicosis (10.22%) and moderate to marked emphysema (6.45%) was relatively low. A high exposure category miner (12 to 55 years of work in a coalmine) had a 15 times greater chance of emphysema compared to one in a lower exposure category (0.1 to 3.5 years), adjusting for the effects of smoking. Smoking status (ever versus never smoker) resulted in a two times greater risk of emphysema.
Under currently prevailing conditions, coaldust exposures contribute to respiratory disease. This conclusion is reinforced by the independent, complementary findings of exposure related decrements in lung function and exposure related risk for emphysema. Recommendations include increased engineering controls and work practices designed to minimise exposure, enforcement of statutory occupational exposure aimed at progressive reduction and ensuring respiratory medical surveillance programmes are instituted.


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