Work-related asthma symptoms and lung function among workers in the Norwegian salmon processing industry: a cross-sectional study.

Objectives: Exposure to bioaerosols from salmon processing is associated with occupational asthma. The prevalence of work-related asthma symptoms in fish processing workers has earlier been reported to be 12%-24%, but small sample sizes and heterogeneity in exposure across studies make generalisability to todays' salmon processing industry questionable. Studies comparing filleting workers and slaughtering workers have shown conflicting results.

Methods: Questionnaire and spirometry data from workers in nine different salmon processing plants were gathered during 2021-2023. Exposure to salmon bioaerosols was defined by work tasks and total time working with salmon. Asthma symptoms and lung function were compared between exposure groups using logistic regression and adjusting for relevant confounding variables.

Results: Of the 867 workers regularly or variably exposed to salmon bioaerosols, 170 (20%) had work-related asthma symptoms. Exposure was associated with symptoms, but not with lung function. Of the 440 exposed workers with spirometry data, 9.8% had expiratory airflow limitation, and all mean lung function measures were below the reference values. The prevalence of work-related asthma symptoms was slightly higher among gutting workers than filleting workers (OR 1.7, 95% CI 1.1 to 2.8).

Conclusions: The prevalence of work-related asthma symptoms is high in salmon processing, probably due to bioaerosol exposure. Salmon processing workers had more expiratory airflow limitation and lower lung function compared with the reference values. Although gutting workers had slightly higher risk for work-related asthma symptoms than filleting workers, all exposed workers seem to be at risk and preventive measures should be taken in all areas where bioaerosols are present.