Occurrence and causes of occupational asthma in South Africa - Results from SORDSA's occupational asthma registry, 1997-1999

Objective. To present results for the first 3 years of the occupational ast hma registry of the Surveillance of Work-related and Occupational Respirato ry Diseases in South Africa (SORDSA) programme, ending December 1999. Design. Surveillance was accomplished by collecting voluntary reports of oc cupational asthma cases from pulmonologists, occupational medicine practiti oners and occupational health nurses. Setting. Medical and occupational health referral centres in the nine provi nces of South Africa. Subjects. patients diagnosed with new-onset occupational asthma with latenc y or irritant-induced asthma, reported to SORDSA during 1997 - 1999. Outcome measures. Frequencies of cases, causative agents, industries causin g exposure and diagnostic methods. Average annual incidence rates by provin ce and by occupation. Results. During this period 324 cases of occupational asthma were reported. The average annual incidence rate of occupational asthma was estimated in the three best-reporting provinces, namely Gauteng, KwaZulu-Natal and the W estern Cape, as 17.5 per million employed people annually. This rate was hi ghest in the Western Cape (25.1 per million). Semi-skilled operators had th e highest incidence rate of 68.7 per million annually in the three province s. Isocyanates and latex were the most common agents. Low molecular weight causative agents predominated (68.8%) over high molecular weight agents. He alth care was the most frequently reported workplace for occupational asthm a (OA) development. Serial peak flow testing was the method most often used for diagnosis. One-fifth of the cases were still occupationally exposed to the causative agent at time of diagnosis. Conclusion. Despite underreporting, SORDSA's estimate of the occupational a sthma incidence rate was similar to that of the UK. SORDSA has also demonst rated that surveillance programmes in a developing country can provide usef ul information on which to base prevention activities.