Microbial exposure and diversity in Norwegian shrimp processing plants

Seafood processing workers have a high prevalence of respiratory symptoms and occupational asthma, primarily attributed to allergenic protein exposure. However, exposure to airborne microorganisms from raw materials can also contribute to allergic sensitization and other respiratory ailments. This study aimed to assess microbial exposure in shrimp processing plants and identify susceptible work tasks. Full-shift personal air samples were collected from two Norwegian shrimp processing plants across five distinct work processes: thawing, truck driving, cooking-peeling (technician), packing, and flour production. The samples were analyzed for the presence of endotoxin, Toll-Like Receptor (TLR) activation, bacterial and fungal DNA copies, and microbial composition. Endotoxin levels were generally low, with only one sample (98 EU/m³) exceeding the recommended occupational exposure limit (OEL). A significant TLR2 activation was observed among thawers, indicating the presence of microbial ligands capable of triggering an immune response. The median bacterial (75 × 10³ DNA copies/m³) and fungal (3,301 × 10³ DNA copies/m³) exposure were highest among the flour production workers, while the lowest bacterial and fungal exposure was among packers (1.5 × 10³ DNA copies/m³) and technicians (337 DNA copies/m³), respectively. Several bacterial and fungal species were identified, including ten allergenic and sixteen pathogenic species. Sporobolomyces roseus and Saccharomyces cerevisiae were the two most frequently identified allergenic fungal species. Among the pathogenic bacterial species, Prevotella nigrescens and Roseomonas gilardii were the two most detected species. While the pathogenic species were identified mainly in the packing, truck driving, and flour production work processes, most of the allergenic species were found in all work processes. Altogether, work processes before the cooking of shrimp (thawing and truck driving) had higher endotoxin, bacterial load, and species richness than after cooking, suggesting that these work tasks are susceptible to bacterial exposure and that the cooking process significantly reduces bacterial exposure. By shedding light on microbial exposure and identifying high-exposure work tasks, this study enables the development of targeted interventions and implementation of measures for the prevention of occupational diseases.