Occupational Asthma and Its Causation in the UK Seafood Processing Industry

The processing of seafood (fish and shellfish) for human consumption can lead to health consequences, including occupational asthma (OA). Several non-UK studies have reported both respiratory outcomes and airborne levels of major allergens in seafood processing. However, there is a paucity of such evidence in the UK land-based seafood processing sector, which employs some 20 000 workers.

University of Manchester's Surveillance of Work-related and Occupational Respiratory Disease (SWORD) reporting system has been interrogated over the period 1992-2017 to define the incidence rate of OA cases that can be ascribed to the UK land-based processing sector, and the seafood species implicated. Airborne allergen monitoring data undertaken at Health and Safety Executive's laboratory from 2003 to 2019 have also been collated.

The estimated annual OA incidence rate in seafood processors was 70 [95% confidence intervals (CIs) 48.9, 91.1] per 100 000 workers compared with 2.9 (95% CIs 2.8, 3.1) in 'all other industries'. The annual calculated percentage trend in OA (1992-2017) was -8.1% (95% CIs -15.9, 0.4) in seafood processing showing a similar trend to 'all other industries' (mean -7.0%; 95% CIs -7.8, -6.1). Prawns and salmon/trout were notably implicated by SWORD as causative species related to OA. There is a general paucity of available UK airborne allergen monitoring data, particularly concerning processing salmon or trout. Available airborne monitoring for salmon parvalbumin in seven processors ranged between the limit of detection and 816 ng m-3 (n = 64). Available air monitoring levels of the major shellfish allergen (tropomyosin) during processing of crabs and prawns ranged between 1 and 101 600 ng m-3 (n = 280), highlighting that high levels of exposure can occur.

These data show an excess incidence of OA in the UK seafood processing industry during 1992-2017, with limited airborne monitoring data for the processing of prawn, crab, and salmon suggesting that significant exposure to major seafood allergens can occur in this industry. Further investigation of current levels of respiratory ill-health and the sources of allergen exposure are warranted.