Occupational asthma in a highly industrialized region of UK: report from a local surveillance scheme.

Estimates of the incidence of occupational asthma may be derived from surveillance schemes established in several countries. SHIELD is a voluntary surveillance scheme for occupational asthma in the West Midlands, a highly industrialized region of UK. The aim of this study was to estimate the general and specific incidence of occupational asthma in the West Midlands in 1990-97. The annual incidence was 41.2/million. There was a two fold difference in the incidence by sex (male 59.6/million/yr; female 27.4/million/yr). The highest annual incidence (53.2/million) was observed in the age group 45-64 yr (male) and 45-59 yr (female). Spray painters were the occupation at the highest risk of developing occupational asthma, followed by electroplaters, rubber and plastic workers, bakery workers and moulders. Although the percentage of reported cases was low among healthcare workers, there was a raising trend. Isocyanates still remained the most common causative agents with 190 (17.3%) out of the total 1097 cases reported to the surveillance scheme in seven years. There was a decrease in the reported cases due to colophony (9.5% to 4.6%), flour & wheat (8.9% to 4.9%). There was an increase of reported cases due to latex (0.4% to 4.9%) and glutaraldehyde (1.3% to 5.6%). The serial mesurement of peak expiratory flow at and away from work was the most used method of diagnosis to confirm the occupational cause of asthma. Specific bronchial challenge test with the occupational agents were used when the serial measurement of peak expiratory flow was not able to confirm undoubtdely the diagnostic suspicion or when it was difficult to identify the possible causative agent due to multiple exposures in the workplace. Following diagnosis, 24% of the patients were moved away from exposure within the same workplace in 1997, compared to 15.8% in the previous years. Those remaining exposed to the causative agent in the same workplace decreased from 28.3% to 17.7% between 1990-97. The surveillance of occupational asthma trough this voluntary scheme has allowed to monitor the incidence of the disease in the region and to identify clusters of cases, where control measures are a priority.