Evaluating the threshold limit value of acceptable exposure concentration for exposure to bioaerosols in a wastewater treatment plant: Reverse-quantitative microbial risk assessment and sensitivity analysis

Agitation operations produce numerous pathogenic bioaerosols in WWTPs11Wastewater treatment plants.. QMRA22Quantitative microbial risk assessment. can determine risks of persons exposed to these bioaerosols. However, QMRA framework cannot help stakeholders in immediately deciding whether a risk is intolerable. Thus, evaluating threshold of acceptable exposure concentration is an urgent issue but is still rarely addressed in WWTPs. This study analyzed TLV33Threshold limit value. benchmarks of E. coli and S. aureus bioaerosols emitted from a WWTP by reverse-QMRA. Furthermore, variance of input parameters was clarified by sensitivity analysis. Results showed that, under conservative and optimistic estimates, TLV of technicians was 1.52–2.06 and 1.26–1.68 times as large as those of workers, respectively; wearing mask drive TLV up to 1–2 orders of magnitude; TLV of M44Microporous aeration tank. was at most 1.33 and 1.31 times as large as that of RD55Rotating-disc aeration tank., respectively. For sensitivity analysis, removal fraction by equipping PPE enlarge TLV for effortlessly obtaining an acceptable assessment result; exposure time was dominant when without PPE excepting the scenario of technicians exposed to E. coli bioaerosol. This study helps establish threshold guidelines for bioaerosols in WWTPs and contribute innovative perspectives for stakeholders. [Display omitted] •TLV of technicians was 1.52–2.06 and 1.26–1.68 times as large as that of workers.•Wearing mask can drive TLV benchmarks up to one to two orders of magnitude.•TLV of microporous aeration tank was always higher than rotating-disc aeration tank.•FPPE can enlarge TLV for obtaining an acceptable assessment result on health risk.•T or Ag was dominant when exposure to S. aureus or E. coli bioaerosols without PPE.