Workers in wastewater treatment plants (WWTP) are facing an overwhelming threat due to heavy exposure to fungal bioaerosol, mainly Aspergillus, released into the surrounding environment for a long time. This results in critical respiratory problems, especially for workers suffering from immunodeficiency. 60 out of 85 WWTP workers were selected for this study. The study's goal was to find out which Aspergillus species were prevalent among those plant exposed workers. For the detection of the sputum PCR results and serum specific IgE (sIgE) of three Aspergillus species (A. fumigatus, A. niger, and A. flavus) for the aforementioned selected workers, nested PCR and ELISA techniques were utilized. Our study revealed that 76.6% of the workers' sputum specimens were positive for Aspergillus. 21.7% of total positive samples tested positive for A. niger, 19.6% for A. flavus, and 2.2% for A. fumigatus. Additionally, 56.5% of workers showed mixed positive results. Furthermore, sIgE of A. niger increased significantly among A. niger positive workers compared to negative workers. Intriguingly, sIgE for different species of Aspergillus exhibited increasing levels among positive workers than among negative ones. Thus, both the significance and non-significance results of sIgE have to be seriously taken into consideration. To summarise, prolonged fungal exposure in WWTPs could be regarded as a potential health hazard. In addition, the results of the Aspergillus sIgE test should not be overlooked and thus should be considered a warning sign. Further investigations were recommended for those who have elevated Aspergillus sIgE.