Fate and Transformation of an Estrogen Conjugate and Its Metabolites in Agricultural Soils

Abstract

In the environment, conjugated estrogens are nontoxic but may hydrolyze to their potent unconjugated, 'free' forms. Compared to free estrogens, conjugated estrogens would be more mobile in the environment because of their higher water solubility. To identify the fate of a conjugated estrogen in natural agricultural soils, batch experiments were conducted with a (14)C labeled prototype conjugate, 17β-estradiol-3-glucuronide (E2-3G). Initially, aqueous dissipation was dominated by biological hydrolysis of E2-3G and its oxidized metabolite, estrone glucuronide (E1-3G), both of which were transformed into the free estrogens, 17β-estradiol (E2) and estrone (E1), respectively. Following hydrolysis, hydrophobic sorption interactions of E2 and E1 dominated. Depending on soil organic matter contents, dissolved E2-3G persisted from 1-14 d, which was much longer than what others reported for free estrogens (generally <24 h). Biodegradation rate constants of E2-3G were smaller in the subsoil (0.01-0.02 h(-1)) compared to topsoil (0.2-0.4 h(-1)). Field observations supported our laboratory findings where significant concentrations (425 ng L(-1)) of intact E2-3G were detected in groundwater (6.5-8.1 m deep) near a swine (Sus scrofa domesticus) farm. This study provides evidence that conjugate estrogens may be a significant source of free estrogens to surface water and groundwater.

Fate and transport of free and conjugated estrogens during soil passage

“…Therefore, the knowledge of all compounds present along with the soil and hydrochemical properties is important to understand their fate and transport behavior. Recent studies have examined the fate and transport of sulfate-or glucuronide-conjugated estrogens in soils (Scherr et al, 2008(Scherr et al, , 2009a(Scherr et al, , 2009bShrestha et al, 2012). For example, in the study of Scherr et al (2008) which is based on batch experiments, a fast degradation of estrone-3-sulfate (E1-3S) to the metabolite E1 was observed; however, transport experiments were not performed.…”

Current trends in environmental analysis of human metabolite conjugates of pharmaceuticals

“…Notably, there is an absence of any passive sampling for conjugate quantification in the existing literature to date. This could be due to the relative infancy of techniques [57], liquid scintillation [20,58], Orbitrap TM [22,49], immunoassay [23], fluorescence [20], flame ionisation [20], Fourier transform-MS [43] available to analyze conjugates across multiple drug classes. Moreover, the potential labile nature of conjugates and their susceptibility to biodegradation or abiotic processes may make their longer-term passive uptake more problematic or inaccurate, although this hypothesis has not been evaluated to date.…”

“…In fact, most studies used some form of analyte pre-concentration (e.g., SPE cartridge or micro-elution well plate), with few exceptions: estrogen glucuronide analysis in soil [20], resveratrol conjugates isolated from heart, liver, and brain tissues [21,22]; and alcohol glucuronides assayed from urine by serial dilution for immunoassay [23]. Both cartridges and well plates used HLB stationary phase to isolate and concentrate conjugates.…”

Aerobic and Anaerobic Transformations in Estrogens and Nutrients in Swine Manure: Environmental Consequences

“…However, there were several folds differences in estrogen concentrations in swine manure, possibly due to: (1) rapid degradation of fE2 and fE1 bound to the soil [26][27][28]; (2) differential hydrolysis of cEs resulting in an increasing in free estrogens [29]; and (3) potentially higher mobility of conjugated estrogens compared to free estrogens (E2 and E1), because of their high water solubility [26,28,[30][31][32][33]. Based on these observations, it was expected that cEs, being water soluble estrogens, will remain in the aqueous phase and leach with water flow, while fEs, being lipophilic, remain bound to the solid particles and leach slowly.…”