Fifteen-year trends in occupational asthma: data from the Shield surveillance scheme

Trends of occupational asthma (OA) differ between regions depending on local industries, provisions for health and safety at the workplace and the availability of a reporting scheme to help in data collection and interpretation.

To assess trends in OA in an industrialized part of the UK over a 15-year period.

Occupational and chest physicians in the West Midlands were invited to submit details of newly diagnosed cases with OA. Data were then transferred to the regional centre for occupational lung diseases for analysis.

A total of 1461 cases were reported to the scheme. Sixty-eight per cent were males with mean (standard deviation) age of 44 (12) years. The annual incidence of OA was 42 per million of working population (95% CI = 37-45). OA was most frequently reported in welders (9%) and health care-related professions (9%) while < 1% of cases were reported in farmers. Isocyanates were the commonest offending agents responsible for 21% of reports followed by metal working fluids (MWFs) (11%), adhesives (7%), chrome (7%), latex (6%) and glutaraldehyde (6%). Flour was suspected in 5% of cases while laboratory animals only in 1%.

Our data confirm a high annual incidence of OA in this part of the UK. MWFs are an emerging problem, while isocyanates remain the commonest cause. Incidence remained at a fairly stable background level with many small and a few large epidemics superimposed. Schemes like Midland Thoracic Society's Rare Respiratory Disease Registry Surveillance Scheme of Occupational Asthma could help in identifying outbreaks by linking cases at the workplace.