Using reverse quantitative microbial risk assessment for estimating acceptable exposure time of bioaerosols in wastewater treatment plants

Bioaerosol emission from aeration ponds of wastewater treatment plants can cause serious health effects on staff and associated personnel. Therefore, this research focused on estimating the acceptable level of exposure to two bioindicators, mainly Staphylococcus aureus and Gram-negative bacteria bioaerosols for staff and associated personnel researchers. To do so, a reverse quantitative microbial risk assessment approach was used based on an annual infection risk benchmark. The results showed that the estimations of the acceptable exposure time for aerosolized Gram-negative bacteria and Staphylococcus aureus were similar. For each specific exposure scenario, the acceptable exposure time for males was always shorter than that for females. To satisfy the official recommended on-site working time, wearing N-95 masks should be mandatory for staff and researchers under the inverted umbrella aeration mode in the H wastewater treatment plant and the fine-pore aeration mode in the T wastewater treatment plant. Nevertheless, under the fine-pore aeration mode in the H wastewater treatment plant, the recommended working time was satisfied even for the worst estimate. In addition, the acceptable exposure time of the beta-Poisson dose–response model showed an order of magnitude shorter than that of the exponential dose–response model. In general, these reverse quantitative microbial risk assessment results could deliver a feasible guideline for directly helping the exposure population to control their exposure time and manage their health risks in wastewater treatment plants, as well as help decision-makers to regulate the recommended working time.