Exposure-response relationships for work-related asthma in fish processing workers

Introduction: Seafood processing workers are at increased risk of developing work-related allergy and asthma. The nature and the shape of the exposure-response relationships for various clinical endpoints especially among fish processing workers is not well characterised.  

Objectives: The aim of this study was to examine the association between exposure to fish aerosols and work-related asthma among workers processing pelagic fish.  

Methods: A cross-sectional study of 594 currently employed workers involved in fish canning (pilchard) and fishmeal processing (anchovy and pilchard offal) recorded work-related allergy and asthma endpoints. Exposure metrics were developed using fish antigen levels of personal samples collected during environmental sampling in various departments of the factory, the details of which have been previously reported. Exposure-response models used multivariate logistic regression and nonparametric regression modelling (smoothing).   Results: Workers involved in fishmeal processing and bagging had the highest risk of occupational fish-related rhino-conjunctivitis or probable asthma due fish. In multivariate logistic regression models workers with work-related asthma symptoms were 3 times more likely (OR=3.53, CI=1.56-7.96) to have fish antigen exposures >90 ng/m3 compared to <30 ng/m3. Using non-parametric smooth plots, the prevalence of work-related asthma symptoms increased with increasing fish antigen levels reaching  90-100 ng/m3, and then levelled off and decreased at higher exposure concentrations. Exposure-response curves showed a stronger pronounced bell-shape with cumulative exposure. These relationships were modified by atopic status.  

Conclusion: The study showed a bell-shaped exposure-response relationship especially for cumulative fish antigen exposure with work-related asthma symptoms. The non-linear exposure response relationship observed in this study needs further exploration. Both atopic and non-atopic workers are at increased risk of developing work-related asthma, possibly through different mechanisms.