Microbial Indoor Air Quality Within Greenhouses and Polytunnels Is Crucial for Sustainable Horticulture (Malopolska Province, Poland Conditions)

Sustainable horticulture is crucially based on the greenhouse production of vegetables under controlled conditions. In this study, we wanted to learn how cultivated plants may impact indoor air quality and whether the workers can be exposed to bioaerosols in a similar way in these settings. The study objective was to test the hypothesis that the microbial concentrations, distribution of bioaerosol particle sizes, and composition of the airborne microbiome are specific to greenhouses, polytunnels, and open-air sites. The air samples were collected to assess the concentration of total culturable bacteria (TCB), fungi, actinomycetes, and β-haemolytic bacteria and for the identification of bacterial and fungal strains. Higher concentrations of TCB and fungi were found in the greenhouse (log 3.71 and 3.49 cfu m −3 , respectively) than in polytunnels (log 2.60–2.48 and 2.51–2.31 cfu m −3 , respectively) during the vegetation of cucumbers. These airborne microbes were represented by a significant contribution of the respirable fraction with a distinct contribution of fine particles in size below 4.7 µm. Cultivation of cucumbers resulted in the higher emission of airborne microorganisms in contrast with growing herbs such as oregano and basil. In total, 35 different bacteria and 12 fungal species, including pathogenic or allergenic agents, were identified within the studied sites. The workers can be exposed to increased concentrations of TCB and fungi in the greenhouse during the plant vegetation. It might be recommended to properly manage greenhouses and polytunnels, dispose of dust sources, and maintain appropriate ventilation to sustain relevant air quality.