Characterizing bioaerosols in PM2.5 in a semi-arid region experiencing desert dust events
Hossein Karimi, Mahnaz Nikaeen, Zahra Shamsizadeh, Yaghoub Hajizadeh
Abstract
Introduction: Fine particulate matter (PM 2.5 ) pollution is a global public health concern, particularly in arid and semi-arid regions that experience dust events. Exposure to PM 2.5 has been associated with various short- and long-term health effects, which can be attributed to the composition of the fine particles. This study aimed to assess the concentration of bacteria and fungi in PM 2.5 in the air of Isfahan, Iran which experiences air pollution. Methods: A total of thirty-nine PM 2.5 samples were collected over 1 year. Bacterial and fungal concentrations associated with PM 2.5 were measured using both culture-based method and real-time polymerase chain reaction (PCR). Results: The average concentration of PM 2.5 was found to be 56 μg m −3 , with many samples exceeding the recommended limit of 15 μg m −3 set by the World Health Organization for PM 2.5 in ambient air. The mean culturable bacterial and fungal concentrations were 39 and 4 CFU m −3 , respectively which showed a significant difference compared to the results obtained through real-time PCR. No significant correlation was found between the levels of bacterial and fungal cells and PM 2.5 concentrations. The dominant phyla found in PM 2.5 were Firmicutes and Actinobacteria, while Proteobacteria as Gram-negative bacteria were rarely detected. Discussion: The findings suggest that the climate conditions in Isfahan, characterized by its semi-arid nature with low humidity content, influences the activity and viability of microbial populations, resulting in low concentrations of bioaerosols in PM 2.5 . Furthermore, it seems that desert dust events do not contribute to increasing the potential health risks associated with bacterial and fungal bioaerosols in PM 2.5 .