Background: Airborne fungi play an important role the quality of indoor and outdoor air. The aim of this study was to investigate the concentration of airborne fungi around different parts of the wastewater treatment plant (WWTP) in the west of Ahvaz and its relationship with some important meteorological parameters. Methods: This study was conducted on a WWTP in the west of Ahvaz during 4 months in both cold and warm seasons. Samples were collected from 2-and 10-m intervals of the grit chamber (GCh), primary sludge dewatering basin (PSDB), and aeration tank (AT), as well as 60 m upstream (US), downstream (DS), and administrative building (AB) of the WWTP. Bioaerosols were collected using passive sampling method. Temperature, humidity, wind speed, wind direction, and ultraviolet index (UV) were also measured at the time of sampling. Results: The total concentration of fungi was 46.1 ± 43 CFU/plate/h. The highest concentration of fungi (92.2 ± 28.12 CFU/plate/h) was found 2 m away from the GCh in the cold season and the lowest one (24.6 ± 6.67 CFU/plate/h) was found at the 10-m distance of the AT in the warm season. The dominant fungal genus included Cladosporium, Alternaria, Yeast, and Aspergillus, respectively. Also, there was a significant relationship between the degree of fungal contamination in different units, the US and DS of the WWTP, and there was a negative relationship between the release of fungi and UV. Conclusion: According to the results, grit chamber plays an important role in releasing airborne fungi. Also, airborne fungi were reduced with an increase in distance and UV.

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Introduction: Airborne Cladosporium spores in different regions of the world are known as the main cause of allergic diseases. This study aimed to identify the Cladosporium species airborne fungi in Ahvaz wastewater treat- ment plant area and its adjacent places and check the effect of some meteoro- logical parameters on their emissions. Materials and methods: Cladosporium spores were cultured on Sabouraud`s dextrose agar (SDA) medium in both cold and warm seasons. The passive sampling method was performed and after incubation, colonies were counted as CFU/Plate/h. Then, according to the macroscopic and microscopic charac- teristics of the genus, the fungal was studied. The meteorological parameters including temperature, humidity, air pressure, dew point, wind speed, and ultraviolet index were measured. Results: At least, 3358 colonies were counted. 1433 colonies were related  to the Cladosporium species. The amount of Cladosporium in indoor air was 46% of the total Cladosporium. The average of meteorological parameters includes temperature, humidity, air pressure, dew point, wind speed and UV index during the study were 27.8 °C, 32.9%, 548.7 °Kpa, 3.6°, 9.1 km / h and 3.9 respectively. 42.6% of the total number of colonies was related to the Cladosporium species. Cladospiromes had a direct correlation with the dew point, temperature, humidity, air pressure, wind speed, and ultraviolet index (Pvalue<0.05). Primary sludge dewatering has the greatest role in the Cladospo- rium spores emission. Conclusion: Considering the importance of Cladosporium spores in the ap- pearance of allergic diseases, and given that wastewater treatment workers spend most of their time outside, observing health and preventive measures is necessary in this regard.