Irritant asthma and work: cases from the UK SWORD reporting scheme from 1999 to 2018

Background Acute irritant asthma is a preventable health consequence of a workplace exposure and has a number of adverse outcomes. While cases and case series are reported, little is known about the causes and incidence of this condition over prolonged periods of time. Aims We aimed to estimate the reported incidence of irritant asthma referred to a national reporting scheme, and how this has changed over time. Methods Cases of irritant asthma reported to SWORD, the UK-based Surveillance of Work-related Occupational Respiratory Diseases scheme, were grouped into four 5-year time periods from 1999 onwards. Likely causative exposures, job, work sector and incidence rates were analysed over time. Results 307 actual cases equated to 1066 estimated cases; actual cases had a mean age of 46 years (SD 17.8); 70.7% were male. The annual incidence fell from 1.98 per million employed in the first 5-year period, to 0.56 in the most recent. Eleven occupational codes were associated with six or more attributed cases, and between them accounted for 38% of all cases. Thirteen exposure categories were associated with five or more cases. These were formaldehyde (n=5), cutting oils and coolants (n=6), isocyanates (n=6), pesticides and herbicides (n=6), welding fumes (n=7), paints (n=7), solder and colophony (n=7), solvents (n=9), fuel oil, diesel and ill-defined fumes (n=10), chlorine and hypochlorites (n=15), acids (n=23), smoke (n=25) and cleaning products and sterilising agents (n=39). Conclusions While the incidence of irritant asthma may have fallen, cases are persistently attributed to well-described causes. A persistence of cases attributed to cleaning agents was seen.