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Assessment of the Basis for Increased Illness in Workers Exposed to Biosolids

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2020, PhD, University of Cincinnati, Medicine: Industrial Hygiene (Environmental Health).
After being ingested, pharmaceuticals are excreted either unaltered in their parent form or as metabolites and collected into municipal wastewater. The technologies that are often used in our current wastewater treatment plants (WWTPs) are not explicitly designed to remove pharmaceuticals. Consequently, a portion of the antibiotics entering the wastewater system ends up accumulated in sewage sludge and could pose potential threats to workers in biosolids occupation. Occupational epidemiology studies have shown that the workers have an increased incidence of illness, potentially as a result of their exposure to biosolids. The health effects commonly seen are gastroenteritis and gastrointestinal symptoms, mainly attributed to enteric bacteria, viruses, and protozoa. The objective of this research was to investigate the risk of co-exposure to antibiotics and microbial pathogens in the biosolids that may contribute to the incidence of illness in wastewater treatment workers. The central hypothesis was that workers exposed to biosolids have higher exposures to antibiotics and antibiotic-resistant bacteria than workers not exposed to biosolids. The following three aims were completed. The first aim was to establish a traditional and microbiological occupational exposure limit (OEL) for the most common antibiotics found in biosolids, which are ciprofloxacin (CIP) and azithromycin (AZ). This would serve to protect workers from the adverse health effects of these drugs as well as unintended damage to gut microflora that could decrease the ability to combat the emergence of resistant pathogens. The traditional OEL was derived as 80 µg/m3 CIP, and 500 µg/m3 for AZ. For the microbiological OEL, the derived values were 25 µg/kg-BW/day for CIP and 2 µg/kg-body weight (BW)/day for AZ. The second aim was to estimate exposures of airborne ciprofloxacin and azithromycin found at human waste handling sites. An exposure factors approach suggested that inhalation route exposures to CIP and AZ are well below their chemical-specific occupational exposure limits (OELs) based on conventional risk assessment methodology, and likely too low to cause direct adverse health effects from antibiotic inhalation. Exposure data were not adequate to estimate exceedances of the microbiological OELs in the current research, but opportunities to evaluate this potential risk were identified. Finally, the third aim was to detect and quantify the concentrations of antibiotic-resistant bacteria in workplace breathing air as well as in different sludge sample types from an urban WWTP. There was a significant difference between the prevalence of azithromycin-resistant bacteria and ciprofloxacin-resistant bacteria in the three types of sludge that were sampled (raw, treated, and digested). Similarly, the prevalence of airborne azithromycin-resistant bacteria inside the belt filter press room was higher compared to the prevalence of airborne ciprofloxacin-resistant bacteria. The air concentrations of both antibiotic-resistant bacteria were higher in the filter press room than in the surrounding outdoor air. This dissertation project shows that the concentrations of antibiotic-resistant bacteria in the air and different sludge sample types are not negligible and could partly explain work-related gastrointestinal symptoms, impact treatment efficacy, and prolong illnesses in these industries.
Tiina Reponen, Ph.D. (Committee Chair)
M. Maier, Ph.D. (Committee Member)
John Reichard, PharmD Ph.D. (Committee Member)
Glenn Talaska, Ph.D. (Committee Member)
Jun Ying, Ph.D. (Committee Member)
123 p.

Recommended Citations

Citations

  • Niang, M. (2020). Assessment of the Basis for Increased Illness in Workers Exposed to Biosolids [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1602152859360418

    APA Style (7th edition)

  • Niang, Mamadou. Assessment of the Basis for Increased Illness in Workers Exposed to Biosolids. 2020. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1602152859360418.

    MLA Style (8th edition)

  • Niang, Mamadou. "Assessment of the Basis for Increased Illness in Workers Exposed to Biosolids." Doctoral dissertation, University of Cincinnati, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1602152859360418

    Chicago Manual of Style (17th edition)