Document zZVYgVwpjjkr6KN6q1rjQ1qm

Silicosis elimination in South Africa David Rees National Institute for Occupational Health School of Public Health, University of the Witwatersrand Risk of silicosis in 2 235 white South African gold miners (1993) Historical cohort study First employed 1940-1970 1991 or death Estimated mean resp dust: 0.29 mg/m3 Silicosis in 14% Highest risk group: silicosis risk = 77% Hnizdo 1993 AJIM Silicosis prevalence at autopsy in black miners by age group Silicosis rates in former southern African gold miners _ibode, Eastern Cape Former miners: prevalence 22- 37% 480 000 cases in southern Africa Trapido, 1999 Thamanga, Botswana Former miners: prevalence 26- 31% Steen, 1998 Silicosis prevalence in SA goldminers 520 black mineworkers returning from leave > 37 years Mean length of service 21.8 years Chest x-rays - read by two readers using ILO Classification Churchyard et al. Occup Envir Med 2004 1 Results Silicosis prevalence (= or > 1/1) Reader 1: 18.3 % (95% CI 15.0 -21.9) Reader 2: 19.9 % (95% CI 16.5-23.6) Silicosis in # sectional surveys of foundries ' 1984 1987 1992 2003 Silicosis by work years Years % >10-20 7 >20 24 >15 38 >15 4 >10 7 INCIDENCE OF TB BY SEVERITY OF SILICOSIS IN BLACK GOLD MINERS 7 year follow-up period Cowie RL. Am J Respir Crit Care Med. 1994 42% RISK OF TB RELATIVE TO SILICOSIS AND SILICA DUST EXPOSURE IN SOUTH AFRICAN WHITE GOLD MINERS Silicosis Cumulated dust quartiles (mg/m3 yrs) OR Absent Present <=9 10-13 14-17 18+ <=9 10-13 14-17 18+ 1.0 4.1 2.8 4.5 4.5 4.4 8.4 11.2 Hnizdo and Murray. Occup Environ Med 1998 HIV PREVALENCE IN A COHORT OF BLACK MINERS % HIV positive 40 I 35 30 25 20 15 10 - 50 Year Gold FieldsLtd. Unpublished data Occupational Risk of tuberculosis modified by HIV. Source: SIMRAC Handbook of Occupational Health Practice in the SA Mining Industry. Ch 6. Tuberculosis and Associated Diseases. Churchyard GJ, Corbett L. 2 Silicosis and TB mortality 30 No silicosis silicosis 25 20 15 P erce rtage 10 5 0 Churchyard GJ.Riskfac HIV-negative mortality with in first 6 months ofTB treatmei HIV-positive 0 Int J Tubercl LungDis. L How many South Africans exposed and where? Census 2001 Usual silica industries 20% 50% and 80% Estimates of occupational silica Agriculture? Dismiss? Maybe not NIOH Clinic no cases since 1975 Quartz % in respirable fraction North Carolina sandy-loam soils: 9.1 21.3% Respirable silica 5 sweet potato transplanters: mean 3.91 mg/m3 Case reports: tractor drivers' silicosis Archer et al. AIHA 2002 Elimination of Silicosis Programme: scope, focus areas and deliverables 3 Template training materials Work and Health Southern Africa (WAHSA) Sida-sponsored NIWL NIPH NIOH Project 7 Action on silica, silicosis and tuberculosis 1 2 years Objectives: Reduction of silica dust in key industries Improved prevention of PTB in silica exposed workers Considerations Occupational exposure limit OEL O. I mg/m3 Prevent silicosis? Prevent PTB? but Practicable to lower OEL? Onset of silicosis Sectoral prioritisation Clay example Quartz in Grahamstown deposits: but Worker exposure? Modification of risk? up to 30% common 60% recorded Good case for simple silicosis and quartz surveys of sectors with poorly defined risk (former workers) 4 Innovative activities Biomarkers project evaluation of 10 contenders risk assessment tool Non-mining industry: Foundries Awareness Targets Research Reasons? Less well organised and resourced Incidence low Threat of litigation ''absent" 5