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See detailTowards a harmonized method for the global reconnaissance of multi-class antimicrobials and other pharmaceuticals in wastewater and receiving surface waters
Singh, Randolph UL; Angeles, Luisa; Butryn, Deena et al

in Environment International (2019), 124

Antimicrobial resistance is a worldwide problem that is both pressing and challenging due to the rate at which it is spreading, and the lack of understanding of the mechanisms that link human, animal and ... [more ▼]

Antimicrobial resistance is a worldwide problem that is both pressing and challenging due to the rate at which it is spreading, and the lack of understanding of the mechanisms that link human, animal and environmental sources contributing to its proliferation. One knowledge gap that requires immediate attention is the significance of antimicrobial residues and other pharmaceuticals that are being discharged from wastewater treatment plants (WWTPs) on the dissemination of antimicrobial resistance in the environment. In this work we provide an approach to develop a harmonized analytical method for 8 classes of antimicrobials and other pharmaceuticals that can be used for global monitoring in wastewater and receiving waters. Analysis of these trace organic chemicals in the influent and effluent wastewater, and in the respective upstream and downstream receiving waters from different countries across the globe is not trivial. Here, we demonstrated that sample preparation using solid-phase extraction (SPE) not only provides a convenient and cost-effective shipping of samples, but also adds stability to the analytes during international shipping. It is important that SPE cartridges are maintained at cold temperature during shipment if the duration is longer than 7 days because a significant decrease in recoveries were observed after 7 days in the cartridges stored at room temperature, especially for sulfonamides and tetracyclines. To compensate for sample degradation during shipment, and matrix effects in liquid chromatography/mass spectrometry, the use of stable isotope labeled compounds should be employed when available and affordable. The importance of applying a defined tolerance for the ion ratios (Q/q) that have been optimized for wastewater and surface water is discussed. The tolerance range was set to be the mean Q/q of the analyte standard at various concentrations ±40% for the influent, and ±30% for the effluent, upstream, and downstream samples; for tetracyclines and quinolones, however, the tolerance range was ±80% in order to minimize false negative and false positive detection. The optimized procedures were employed to reveal differences in antimicrobial and pharmaceutical concentrations in influent, effluent, and surface water samples from Hong Kong, India, Philippines, Sweden, Switzerland, and United States. The antimicrobials with the highest concentrations in influent and effluent samples were ciprofloxacin (48,103 ng/L, Hong Kong WWTP 1) and clarithromycin (5178 ng/L, India WWTP 2), respectively. On the other hand, diclofenac (108,000 ng/L, Sweden WWTP 2), caffeine (67,000 ng/L, India WWTP 1), and acetaminophen (28,000 ng/L, India WWTP 1) were the highest detected pharmaceuticals in the receiving surface water samples. Hong Kong showed the highest total antimicrobial concentrations that included macrolides, quinolones, and sulfonamides with concentrations reaching 60,000 ng/L levels in the influent. Antidepressants were predominant in Sweden, Switzerland, and the United States. [less ▲]

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See detailBinding of iodinated contrast media (ICM) and their transformation products with hormone receptors: Are ICM the new EDCs?
Singh, Randolph UL; Rajnarayanan, Rajendram; Aga, Diana

in Science of the Total Environment (2019)

Iodinated contrast media (ICM) have been detected at high concentrations (as high as about 3 μg/L) in surface water systems, and recently in fish brains and gonad. The mismatch between the polarity of ICM ... [more ▼]

Iodinated contrast media (ICM) have been detected at high concentrations (as high as about 3 μg/L) in surface water systems, and recently in fish brains and gonad. The mismatch between the polarity of ICM and the high lipid content of brain raises questions on whether their bioaccumulation is receptor-mediated. Furthermore, the structural similarity of ICM to the natural thyroid hormones thyroxine and triiodothyronine suggest potential binding of ICM to nuclear receptors in the endocrine system. Therefore, an in silico approach based on Surflex-Dock module of SYBYL was used to investigate the molecular docking of selected ICM (diatrizoic acid, iohexol, iopamidol, and iopromide). These ICM showed interaction with nuclear receptors that play key roles in endocrine regulation, including the androgen and estrogen receptors. Furthermore, the results indicate peroxisome proliferator-activated receptor gamma (PPARg) as one of the viable targets in the endocrine disrupting potential of ICM with higher Cscores for the ICM and iopromide transformation products than the reference ligand for the receptor. The data obtained from in silico calculations showed stronger binding of iohexol to the transthyretin-binding pocket compared to the natural hormones, thyroxine and triiodothyronine, suggesting the potential of ICM to act as endocrine disrupting chemicals (EDCs) in the environment. [less ▲]

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