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- All Subjects: Biosolids
- Creators: Halden, Rolf U.
Description
Many manmade chemicals used in consumer products are ultimately washed down the drain and are collected in municipal sewers. Efficient chemical monitoring at wastewater treatment (WWT) plants thus may provide up-to-date information on chemical usage rates for epidemiological assessments. The objective of the present study was to extrapolate this concept, termed 'sewage epidemiology', to include municipal sewage sludge (MSS) in identifying and prioritizing contaminants of emerging concern (CECs). To test this the following specific aims were defined: i) to screen and identify CECs in nationally representative samples of MSS and to provide nationwide inventories of CECs in U.S. MSS; ii) to investigate the fate and persistence in MSS-amended soils, of sludge-borne hydrophobic CECs; and iii) to develop an analytical tool relying on contaminant levels in MSS as an indicator for identifying and prioritizing hydrophobic CECs. Chemicals that are primarily discharged to the sewage systems (alkylphenol surfactants) and widespread persistent organohalogen pollutants (perfluorochemicals and brominated flame retardants) were analyzed in nationally representative MSS samples. A meta-analysis showed that CECs contribute about 0.04-0.15% to the total dry mass of MSS, a mass equivalent of 2,700-7,900 metric tonnes of chemicals annually. An analysis of archived mesocoms from a sludge weathering study showed that 64 CECs persisted in MSS/soil mixtures over the course of the experiment, with half-lives ranging between 224 and >990 days; these results suggest an inherent persistence of CECs that accumulate in MSS. A comparison of the spectrum of chemicals (n=52) analyzed in nationally representative biological specimens from humans and MSS revealed 70% overlap. This observed co-occurrence of contaminants in both matrices suggests that MSS may serve as an indicator for ongoing human exposures and body burdens of pollutants in humans. In conclusion, I posit that this novel approach in sewage epidemiology may serve to pre-screen and prioritize the several thousands of known or suspected CECs to identify those that are most prone to pose a risk to human health and the environment.
ContributorsVenkatesan, Arjunkrishna (Author) / Halden, Rolf U. (Thesis advisor) / Westerhoff, Paul (Committee member) / Fox, Peter (Committee member) / Arizona State University (Publisher)
Created2013
Description
This dissertation studies the larger issue of antibiotic resistance with respect to how antibiotics are being introduced into the environment, focusing on two major anthropogenic pathways: animal husbandry for human consumption, and the recycling of wastewater and municipal sludge generated during conventional biological sewage treatment.
For animal production on land (agriculture) antibiotics are often used for growth enhancement and increased feed efficiency. For animal production in water (aquaculture) antibiotics are often used as a prophylactic. I found that the same antibiotics are being used in both industries and that the same strains of human pathogens have also been isolated from both sources, expressing identical resistance mechanisms. In U.S. seafood, five out of 47 antibiotics screened for were detected at levels of 0.3 to 7.7 ng/g fresh weight. Although compliant with FDA regulations, the risk for resistance still exists, as even low antibiotic concentrations have been shown to exert selective pressure on bacteria.
Similarly low concentrations of antibiotics were found in U.S. biosolids at levels of 0.6 to 19.1 ng/g dry weight. Of the five antibiotics detected, two have never been reported before in biosolids. Three have never been reported before in U.S. biosolids. Using the raw numbers obtained from antibiotic screenings in biosolids, I assessed the impact of employing four different LC-MS/MS methods, concluding that analysts should experimentally determine the most appropriate quantitation method based on the analyte targeted, matrix investigated, and research goals pursued. Preferred quantitation approaches included the isotope dilution method with use of an analogous standard and, although time and resource demanding, the method of standard addition.
In conclusion, antibiotics introduced into the environment via agriculture, aquaculture, and wastewater recycling pose a combination of chemical and biological threats. Aside from exerting outright chemical toxicity to non-target organisms, antibiotic residues can promote the development of multi-drug resistance in human pathogens. Public health protection approaches to stem the risks posed by animal husbandry may include reserving drugs for exclusive, human use, decreasing their usage altogether, improving reporting efforts, reevaluating existing regulations on agricultural and aquacultural antibiotic usage, and improved risk assessment for biosolids application on land.
For animal production on land (agriculture) antibiotics are often used for growth enhancement and increased feed efficiency. For animal production in water (aquaculture) antibiotics are often used as a prophylactic. I found that the same antibiotics are being used in both industries and that the same strains of human pathogens have also been isolated from both sources, expressing identical resistance mechanisms. In U.S. seafood, five out of 47 antibiotics screened for were detected at levels of 0.3 to 7.7 ng/g fresh weight. Although compliant with FDA regulations, the risk for resistance still exists, as even low antibiotic concentrations have been shown to exert selective pressure on bacteria.
Similarly low concentrations of antibiotics were found in U.S. biosolids at levels of 0.6 to 19.1 ng/g dry weight. Of the five antibiotics detected, two have never been reported before in biosolids. Three have never been reported before in U.S. biosolids. Using the raw numbers obtained from antibiotic screenings in biosolids, I assessed the impact of employing four different LC-MS/MS methods, concluding that analysts should experimentally determine the most appropriate quantitation method based on the analyte targeted, matrix investigated, and research goals pursued. Preferred quantitation approaches included the isotope dilution method with use of an analogous standard and, although time and resource demanding, the method of standard addition.
In conclusion, antibiotics introduced into the environment via agriculture, aquaculture, and wastewater recycling pose a combination of chemical and biological threats. Aside from exerting outright chemical toxicity to non-target organisms, antibiotic residues can promote the development of multi-drug resistance in human pathogens. Public health protection approaches to stem the risks posed by animal husbandry may include reserving drugs for exclusive, human use, decreasing their usage altogether, improving reporting efforts, reevaluating existing regulations on agricultural and aquacultural antibiotic usage, and improved risk assessment for biosolids application on land.
ContributorsDone, Hansa Yi-Yun (Author) / Halden, Rolf U. (Thesis advisor) / Haydel, Shelley E (Committee member) / Abbaszadegan, Morteza (Committee member) / Arizona State University (Publisher)
Created2015