The inhalable mycobiome of sawmill workers: Exposure characterization and diversity

Abstract

Exposure to fungal spores has been associated with respiratory symptoms and allergic alveolitis among sawmill workers, but the complexity of sawmill workers' fungal exposure has been poorly studied. We characterized the fungal diversity in air samples from sawmill workers' breathing zone, and identified differences in richness, diversity and taxonomic composition between companies, departments, wood types and seasons. Full-shift personal inhalable dust samples (n=86) collected from 11 industrial saw-, sorting-, and planer mill companies processing spruce and/or pine were subjected to DNA metabarcoding using the fungal Internal Transcribed Spacer (ITS) region 2. The workers were exposed to a higher total number of operational taxonomic units (OTUs) in summer compared to winter, and when processing spruce compared with pine. Workers in the saw department had the richest fungal exposure followed by workers in the planing department and sorting of dry timber department. Sawmills explained 11% of the variation in fungal community composition of the exposure, followed by season (5%) and departments (3%). The fungal composition of the exposure differed between season, sawmills, wood types and departments also at the taxonomic levels, from phylum to species level. The differences in exposure diversity suggests that potential health effects of fungal inhalation also may be different, hence a risk assessment based on the fungal diversity differences should be performed. This study may serve as a basis towards establishing a fungal profile of signature species that are specific for sawmills and can be measured quantitatively in future risk assessments of sawmill workers.

The inhalable mycobiome of sawmill workers: Exposure characterization and diversity