Authors: Nelson G, Girdler-Brown B, Ndlovu N, Murray J
Source: Environ Health Perspect doi:10.1289/ehp.0900918 available via http://dx.doi.org/ [Online 23 November 2009]
South Africa joined the Global Programme for the Elimination of Silicosis and developed its own national initiative under the auspices of the Department of Labour in collaboration with the Department of Mineral Resources in 2004. The success of this initiative can only be measured by surveillance programmes such as the National Institute for Occupational Health’s occupational respiratory autopsy surveillance programme that provides an opportunity to measure disease trends. We thus undertook to describe trends in silicosis at autopsy in South African gold miners from 1975 to 2007, and to quantify the contributions of age at autopsy and employment duration (as proxy measurements for cumulative dust exposure) to these trends.
South African miners and ex-miners are eligible for autopsy examination for compensable lung disease, regardless of the clinical cause of death. Miners who died from external causes and had worked in the gold mines for more than one year were stratified by population group because of differences in exposure, patterns of employment and autopsy referral patterns. Trends in relative proportions of silicosis, standardized for age and employment duration, were estimated.
The mean age of black miners at death rose from 33.0 years in 1975 to 43.4 in 2007, while the mean age of white miners rose from 44.1 to 54.4 years. The mean duration of employment increased from 5.6 to 13.4 years for black miners, and from 17.5 to 20.1 years for white miners.
The crude proportion of silicosis in white miners was six times that in black miners in 1975. By 2007, it was 1.5 times higher in black miners. The proportion of white miners with silicosis increased from 18% to 22% and that of black miners, from 3% to 32%. The increase in white miners was due to increasing age and length of employment. For black miners, it can be only partly explained by these two factors. The higher proportions of black miners with silicosis, after adjusting for age and duration of employment, suggest that black miners had higher intensities of exposure to silica than white miners.
As miners continue to age and work for longer periods, the burden of silicosis will continue to rise which, together with the HIV epidemic, will result in an ever increasing burden of tuberculosis in the gold mines. We will continue to monitor rates of silicosis in miners, using the autopsy database.