Assessment of endocrine disruptor effects of levonorgestrel and its photoproducts: Environmental implications of released fractions after their photocatalytic removal
Introduction
A wide range of pharmaceutical and personal care products have been categorized as endocrine disruptor micro-pollutants. These molecules interrupt or stop the synthesis, degradation, and release of hormones that regulate biological processes such as metabolism and reproduction [1,2].
Many substances are discharged into water bodies directly or via human excretion. However, many persistent micro-pollutants are not degraded completely by conventional methods applied in wastewater treatment plants (WWTPs) [3]. Thus, pharmaceutical compounds may be taken up by aquatic biota or humans and may exert effects that are yet to be characterized [4]. Some steroid hormones have been detected in the influent and effluent of WWTPs in South Africa, with a removal rate of approximately 65% [5]. Therefore, the degraded and undegraded fractions of such hormones may provide continuous dosing to biota, having potential adverse effects. In addition, lipophilic pollutants may bioaccumulate in different species; therefore, the toxicity in the food chain can be biomagnified. Some pharmaceutical compounds have been detected in fish filet and liver by high performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) at a level close to 200 ng g−1 [6].
Levonorgestrel (LNG) is a pharmaceutical molecule widely used as a contraceptive and which steroid core structure which is widely [7] (for the chemical structure, refer Fig. 1). This pollutant has been found in the effluent of a WWTP in Montreal at a concentration of 30 ng L−1. Therefore, large amounts of LNG may be distributed freely and may be able to exert toxic effects on the environment [8]. Particularly, the levels in such effluents may have effects on aquatic species. For instance, the effects of LNG at concentrations of 0.8, 3.3, and 29.6 ng L−1 were tested in adult fathead minnows (Pimephales promelas) and were reported to cause the inhibition of reproduction in this species [9]. Additionally, this molecule is known to affect male fertility by inducing azoospermia upon exposure to high levels [10].
Even at low levels, LNG may affect the growth, development, and reproduction of aquatic organisms continuously exposed to this parent compound and its degradation products [11].
To reduce the high level of LNG in water bodies, many degradation procedures have been implemented for its removal [12]. However, this molecule is quite stable and persistent. For instance, Eichhornia crassipes has been applied for the phytoremediation of LNG, with a reported removal rate close to 80% [13]. However, this rate may be inadequate because low levels may have adverse effects on aquatic species, causing feminization. Some advanced oxidation processes (AOPs), such as Fenton and photo-Fenton oxidation, have been investigated to removal pollutants waterborne, but ineffective methods for assessment of endocrine disruption as an acceptable degradation have been applied [14]. However, the effects of the complexity of components within the discharged degraded fraction are still unknown, and many studies have not considered that incompletely removed compounds may be more toxic to biota than their initial parent compounds. Thus, more efficient methods for degradation and endocrine disruptor assays in final degraded fractions should be applied to ensure the acceptable degradation of LNG.
The present study provides a method to assay the environmental implications of released degraded fractions of LNG on exposed species. The experimental methodology includes the photocatalytic removal and endocrine disruptor assay of LNG and its photoproducts based on β-hCG hormone production, which is related to trophoblastic implantation in different reproductive pathways. Incomplete mineralization of LNG may produce a complex mixture, which could still lead to endocrine disorders in aquatic species.
Section snippets
Chemicals and reagents
The parent compound LNG was obtained from the commercial product Cerciorat® from Exeltis Laboratory at 0.75 mg. Potassium persulfate was used as a catalyst and was purchased from Sigma-Aldrich (San Luis, MO, USA). Milli-Q water was purified in a Thermo Scientific® Barnstead 50131217 GenPure™ UV/UF Water Purification System for Type I Water, whereas solvents, such as methanol, ethanol, dimethyl sulfoxide, and acetonitrile were supplied by Sigma-Aldrich (San Luis, MO, USA). Fetal bovine serum
LNG analysis
The scanning in the wavelength range of 200–400 nm showed a spectrum and maximum wavelength adsorption at 247 nm, similar to those presented in the literature for LNG [17]. Thus, the maximum wavelength found were applied with quality and quantitative purposes for LNG by spectrophotometry analysis. From the regression line plot at 247 nm, %RA was >99.1%; therefore, the quantification was found to be acceptable to describe the GOF of the calibration curve. Normally, when the xi,true and xi calc
Discussion
Many steroid hormones have been detected in water bodies, and their environmental risks in aquatic ecosystems are complex and diverse [20]. Some reports have described the effects of endocrine disruptors, such as causing reproductive and metabolic variation in species exposed to these molecules [21]. For instance, after the excretion of LNG, a synthetic progestin used as an oral contraceptive, from the human body, it may enter streams and rivers by sewage effluent discharge due to inefficient
Conclusions
Degradation of LNG was performed under a UV-C lamp at 265 nm but not at UVA wavelength (365 nm), which may be related to the stable steroidal ring in the molecule and thus under sunlight effects LNG is a recalcitrant pollutant. Although, more than 90% of LNG is degraded using a persulfate catalyst and even by applying direct photolysis, during persulfate photocatalysis some photoproducts arise and therefore, more complex fraction may be found in waterbodies after similar treatments with complex
Acknowledgments
We thank Hospital General de Medellín for measuring β-hCG hormone levels in the cell medium. We also thank the project entitled “Preliminary screening of organic pollutants and endocrine disruptor assay” (project code 4000000087) and the research project code 4000000098 which were funding by Corporación Universitaria Remington.
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