Are there airborne microbial hotspot areas over Iran's Sistan region?: A spatial analysis of microbe concentrations and relationships with dust

During 18 dust storms from June 2022 to September 2023, bacterial and fungal concentrations were measured in dust collected in different parts of the Sistan region of Iran, including Zabol and Zahak (i.e., urban environments) and Ghorghori, Adimi, and Aliakbar (i.e., non-urban environments). The goal was to assess (a) the spatial distribution of airborne microbes across Sistan to identify hotspots of high levels, (b) airborne microbe concentrations in urban and non-urban environments, and (c) the influence of Hamoun lakes on airborne microbial concentrations. The highest bacterial and fungal concentrations per gram of dust were observed in Zabol (3.5 $\times {10}^6$ and 1.2 $\times {10}^4$ cfu g⁻¹) and the lowest in Ghorghori (1.16 $\times {10}^4$ and 1.1 $\times {10}^3$ cfu g⁻¹). The highest bacterial and fungal concentrations per sampled area were found in Aliakbar (4.7 $\times {10}^7$ and 8.6 $\times {10}^4$ cfu g⁻¹) and the lowest in Ghorghori (1.9$\times {10}^7$ and 3.2 $\times {10}^4$ cfu g⁻¹). Aliakbar and Zahak were the most serious airborne microbial hazard sites based on high loads of dust and, consequently, microbes. Hamoun lakes contribute to airborne microbial pollution across Sistan. Management of lakes is suggested as a key path forward to reduce dispersal of microbes.