Occupational exposures and incidence of asthma over two decades in the European Community Respiratory Health Survey

Background While short-term occupational exposures to many agents are associated with increased risk of asthma, the long-term consequences of exposure have not been well understood. We investigated the effects of occupational exposures over two decades on the incidence of asthma. Methods This population-based, multicentre cohort was assessed at baseline (European Community Respiratory Health Survey (ECRHS)1) and followed up twice over 20 years (ECRHS2 and ECRHS3). This analysis included data for 5591 participants with complete work histories and free of asthma at baseline. Incident adult-onset asthma was defined as either an asthma attack, woken by an attack of shortness of breath and/or current asthma medication in the last 12 months before each timepoint, without asthma at a previous survey. An updated asthma-specific job exposure matrix was used to estimate exposures to asthmagens. Adjusted Poisson models were fitted with generalised estimating equations to estimate asthma incidence. Results Ever high exposure to high molecular weight sensitisers (rate ratio (RR)=1.31; 95% CI 1.15 to 1.63), irritants (RR=1.29; 1.09–1.54), biocides (RR=1.42; 1.12–1.79), only low exposure to low molecular weight sensitisers (RR=1.26; 1.08–1.47), mites (RR=1.48; 1.12–1.94) and reactive chemicals (RR=1.24; 1.06–1.45) were associated with increased incidence of asthma. Asthma incidence also increased with ever high or cumulative exposure to these exposures and for specific exposure to wood dust, cleaning agents and bleach. The population-attributable fraction for adult-onset asthma due to occupational exposures was 18% (16.9–19.4%). Conclusion This strengthens the evidence that occupational exposures to sensitisers and chemical irritants contribute substantial risk and a substantive attributable fraction of adult-onset asthma. Control of implicated hazardous exposures and periodic screening of exposed workers should be considered.