8292635 Development of a job exposure matrix (JEM) for inhalable total protein for studying association between exposure to bioaerosols and respiratory health outcomes among salmon processing workers

<h3>Objective</h3> Workers in the salmon processing industry are at elevated risk of asthma and other respiratory illnesses. This study aimed to develop an industry-specific job exposure matrix (JEM) to assess exposure to inhalable total protein. <h3>Material and Methods</h3> The JEM was developed based on 372 full-shift personal air samples collected in the breathing zones of 222 workers across nine salmon processing plants in Norway between 2001 and 2022. At the end of each shift, contextual data were gathered to classify each sample into one of four a priori exposure groups at each of the nine plants: slaughtering, filleting, miscellaneous processes, or assumed non-exposed. A linear mixed-effects model was used to estimate exposure levels. In these models, workers were treated as random effects and sampling time and exposure group within plant were treated as fixed effects, yielding 35 group-specific shift-long exposure estimates. The estimates were ranked and subsequently grouped into three exposure categories—low, medium, and high. Repeated modeling was conducted to estimate exposure levels for these three categories. Contrast in exposure was estimated as: between-group variance/(within-group variance + between-group variance). <h3>Results</h3> Estimated exposure levels for inhalable protein in the final JEM were 1.2 µg/m³ (low exposed), 2.3 µg/m³ (medium exposed), and 5.0 µg/m³ (high exposed). Reducing the number of exposure groups from 35 to 3 increased the contrast in exposure between groups from 0.60 to 0.70. The JEM will be further refined with the inclusion of an additional 390 measurements collected during a second sampling campaign in 2022–2023. <h3>Conclusion</h3> The JEM provides quantitative estimates of bioaerosol exposure which are essential for evaluating the exposure-response relationship between exposure and respiratory health outcomes in salmon processing workers. Such knowledge forms the basis for the establishment of health-based exposure limits, which are currently lacking in this industry.