17 β-estradiol mineralization in human waste products and soil in the presence and the absence of antimicrobials.
TL;DR: It is unlikely for doxycycline and norfloxacin, or their mixtures, to have a significant effect on E2 mineralization in human waste products and soil, however, the potential for E2 to be persistent in biosolids, with and without the presence of antimicrobials, is posing a challenge for biosolid disposal to agricultural lands.
Abstract: Natural steroidal estrogens, such as 17 β-estradiol (E2), as well as antimicrobials such as doxycycline and norfloxacin, are excreted by humans and hence detected in sewage sludge and biosolid. The disposal of human waste products on agricultural land results in estrogens and antibiotics being detected as mixtures in soils. The objective of this study was to examine microbial respiration and E2 mineralization in sewage sludge, biosolid, and soil in the presence and the absence of doxycycline and norfloxacin. The antimicrobials were applied to the media either alone or in combination at total rates of 4 and 40 mg kg-1, with the 4 mg kg-1 rate being an environmentally relevant concentration. The calculated time that half of the applied E2 was mineralized ranged from 294 to 418 days in sewage sludge, from 721 to 869 days in soil, and from 2,258 to 14,146 days in biosolid. E2 mineralization followed first-order and the presence of antimicrobials had no significant effect on mineralization half-lives, except for some antimicrobial applications to the human waste products. At 189 day, total E2 mineralization was significantly greater in sewage sludge (38 ±0.7%) > soil (23 ±0.7%) > biosolid (3 ±0.7%), while total respiration was significantly greater in biosolid (1,258 mg CO2) > sewage sludge (253 mg CO2) ≥ soil (131 mg CO2). Strong sorption of E2 to the organic fraction in biosolid may have resulted in reduced E2 mineralization despite the high microbial activity in this media. Total E2 mineralization at 189 day was not significantly influenced by the presence of doxycycline and/or norfloxacin in the media. Antimicrobial additions also did not significantly influence total respiration in media, except that total CO2 respiration at 189 day was significantly greater for biosolid with 40 mg kg-1 doxycycline added, relative to biosolid without antimicrobials. We conclude that it is unlikely for doxycycline and norfloxacin, or their mixtures, to have a significant effect on E2 mineralization in human waste products and soil. However, the potential for E2 to be persistent in biosolids, with and without the presence of antimicrobials, is posing a challenge for biosolid disposal to agricultural lands.
Summary (2 min read)
- Estrogens are excreted by vertebrates in both urine and feces with an estimated global rate of 29,500 kg of natural estrogens being excreted by humans each year. .
- Drinking water contaminated with estrogens could pose health risk to humans. [7, 12].
- Antimicrobial additions to soil and other media has shown to reduce reduced E2 mineralization in some cases. [20, 23, 26].
- Doxycycline is commonly used to treat wide array of infections in humans (urinary tract, intestine and eye) and is also increasingly used as an anti-cancer therapeutic. .
- Tetracycline has shown to decrease soil bacterial diversity following its application to a plantsoil system. .
Chemicals and Media
- Analytical grade 17 β-estradiol (≥98% pure), doxycycline (≥98% pure) and norfloxacin (≥98% pure) were purchased from Sigma-Aldrich Chemical Company (Saint Louis, MO, USA).
- Sewage sludge was obtained from facultative lagoon-based sewage treatment facility in southern Manitoba, Canada that services approximately 8000 people.
- The soil was sampled (0-15 cm) from the Ap-horizon of a Newdale Clay Loam, which is recognized as the provincial soil of Manitoba and represents a large area of agricultural land in this province.
- Hormones were below detection limits in both samples.
- The impact of antibiotics on E2 mineralization in these media was quantified using a factorial design of antimicrobial additions plus controls without antimicrobials.
- Both radiolabeled and analytical grade E2 was applied and the E2 experiment was terminated at 189 days at which time E2 mineralization had slowed to <0.1% per day for all treatments.
- In a parallel experiment, only analytical E2 was applied, but the same factorial design plus control was utilized to quantify the impact of antibiotics on microbial respiration (CO 2 production) over 189 days.
- Microcosms were pre-incubated at 20˚C for seven days prior to E2 applications.
- Antibiotic stock solutions were prepared in milli-Q water that was acidified with 0.5 M HCl (pH 4) to help dissolve doxycycline and/or norfloxacin.
- The effect of media and antibacterial treatment on total E2 mineralization or total respiration was analyzed by ANOVA using PROC MIXED in SAS ver. 9.4 (SAS Institute Inc., 2013).
- All data respected normality based on Shapiro-Wilks statistic ≥ 0.9.
- Dissipation kinetics of E2 for each media was generated and compared using PROC NLIN in SAS.
- The calculated half-life is equivalent to the time that 50% of the radioactivity would have been mineralized in a media.
- The Tukey multiple comparison procedure was used for pairwise comparisons of treatment means.
RESULTS AND DISCUSSION
- Specifically, when norfloxacin or doxycycline were applied together, or when no antimicrobials were added, cumulative respiration was significantly greater in the sewage sludge than soil; however, when either norfloxacin or doxycycline were applied alone, sewage sludge and soil had a similar cumulative respiration (Fig. 3 ).
- Regardless of whether norfloxacin or doxycycline was applied alone or in combination, the antimicrobials did not supress microbial respiration and, consistently, antimicrobial applications had no pronounced effect on E2 mineralization.
- Biosolid showed a very small total E2 mineralization relative to sewage sludge and soil, yet this medium had a much greater microbial respiration.
- 3 LECO model CHN 600 carbon-hydrogen-nitrogen determinator.
- 8 Aqua regia digestion followed by Inductively Coupled Plasma Optical Emission Spectroscopy.
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Cites background from "17 β-estradiol mineralization in hu..."
...recovery of (14)CO2 indicates that the steroid molecule has been inactivated because of ring cleavage.() The time that 50% of the applied E2 is mineralized (E2-(1)/2) can be calculated from these laboratory data....
"17 β-estradiol mineralization in hu..." refers background in this paper
...abnormal secondary sexual characteristics in male and juvenile female fish,([10,11]) for example, the production of an egg yolk protein...
"17 β-estradiol mineralization in hu..." refers background in this paper
...Both antimicrobials have been detected in surface water following wastewater effluent discharge and following surface runoff from soils amended with biosolid.([31,32,36,37])...
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