Global scanning assessment of calcium channel blockers in the environment: Review and analysis of occurrence, ecotoxicology and hazards in aquatic systems

Environmental fate and risk evolution of calcium channel blockers from chlorine-based disinfection to sunlit surface waters

Organic micropollutants present in disinfected wastewater and discharged to sunlit surface waters may be transformed by multiple processes, such as chlorination due to the presence of chlorine residuals, solar irradiation as well as solar-irradiated chlorine residues. This study reports, for the first time, the multi-scenario degradation kinetics, transformation products, and risk evolution of calcium channel blockers (CCBs), a class of emerging pharmaceutical contaminants with worldwide prevalence in natural waters and wastewater. It was found that the chlorination of the studied CCBs (amlodipine (AML) and verapamil (VER)) was dominated by the reaction of HOCl with their neutral species, with second-order rate constants of 6.15×104 M-1 s-1 (AML) and 7.93×103 M-1 s-1 (VER) at pH 5.0-11.0. Bromination is much faster than chlorination, with the measured kapp,HOBr values of 2.94×105 M-1 s-1 and 6.58×103 M-1 s-1 for AML and VER, respectively, at pH 7.0. Furthermore, both CCBs would undergo photolytic attenuations with hydroxyl and carbonate radicals as the dominant reactive species in water. Notably, free chlorine mainly contributed to their abatement during the solar/chlorine treatment. Additionally, the halogen addition on the aromatic ring was observed during chlorination and bromination of the two CCBs. Cyclization was observed under solar irradiation only, while the aromatic ring was opened in the solar/chlorine system. Some products generated by the three transformation processes exhibited non-negligible risks of high biodegradation recalcitrance and toxicity, potentially threatening the aquatic environment and public health. Overall, this study elucidated the environmental fate of typical CCBs under different transformation processes to better understand the resulting ecological risks in these environmental scenarios.

What, How, When, and Where: Spatiotemporal Water Quality Hazards of Cyanotoxins in Subtropical Eutrophic Reservoirs

Though toxins produced during harmful blooms of cyanobacteria present diverse risks to public health and the environment, surface water quality surveillance of cyanobacterial toxins is inconsistent, spatiotemporally limited, and routinely relies on ELISA kits to estimate total microcystins (MCs) in surface waters. Here, we employed liquid chromatography tandem mass spectrometry to examine common cyanotoxins, including five microcystins, three anatoxins, nodularin, cylindrospermopsin, and saxitoxin in 20 subtropical reservoirs spatially distributed across a pronounced annual rainfall gradient. Probabilistic environmental hazard analyses identified whether water quality values for cyanotoxins were exceeded and if these exceedances varied spatiotemporally. MC-LR was the most common congener detected, but it was not consistently observed with other toxins, including MC-YR, which was detected at the highest concentrations during spring with many observations above the California human recreation guideline (800 ng/L). Cylindrospermopsin was also quantitated in 40% of eutrophic reservoirs; these detections did not exceed a US Environmental Protection Agency swimming/advisory level (15,000 ng/L). Our observations have implications for routine water quality monitoring practices, which traditionally use ELISA kits to estimate MC levels and often limit collection of surface samples during summer months near reservoir impoundments, and further indicate that spatiotemporal surveillance efforts are necessary to understand cyanotoxins risks when harmful cyanobacteria blooms occur throughout the year.

A new Wastewater-Based Epidemiology workflow to estimate community wide non-communicable disease prevalence using pharmaceutical proxy data

This manuscript introduces a new wastewater-based epidemiology workflow for estimation of non-communicable diseases (NCDs) prevalence by using wastewater-based epidemiology (WBE) and pharmaceuticals/their metabolites as proxies for NCDs prevalence. 83 targets were selected (54 parent pharmaceuticals and 29 metabolites). Three critical aspects were tested: (i) Solid-Phase Extraction - Ultra-Performance Liquid Chromatography and Tandem Mass Spectrometry (SPE-UHPLC-MS/MS) method performance, (ii) biomarker stability under variable storage conditions (during sampling and long-term storage) and (iii) accounting for human metabolism in WBE back-calculations. High stability of most analytes was observed under tested storage conditions. A few exceptions include diazepam, dihydroketoprofen and 5-hydroxy-lansoprazole. Analyte recoveries varied between 75% and 125% for most analytes. MDLs ranged from 0.2 ng L-1 to 5.6 ng L-1, while MQLs from 0.2 ng L-1 to 16.8 ng L-1. The overall average method accuracy and precision were: 99.5% and 4.0% respectively. A fully validated method was tested using community wastewater in the Southwest of England to estimate pharmaceutical usage, test metabolism correction factors established and compare results with prescription data. The new WBE method for NCD approximation allowed for the estimation of the daily usage/intake of 69 NCD targets with a standardized approach and a consistent reporting format.

Additive cardiotoxicity of a bisphenol mixture in zebrafish embryos: The involvement of calcium channel and pump

Bisphenol A (BPA) and its analogs, such as bisphenol F (BPF), bisphenol AF (BPAF), and bisphenol B (BPB), are often simultaneously detected in environmental and human specimens. Thus, assessing the toxicity of bisphenol (BP) mixtures is more relevant than assessing that of each BP type. Here, we found that BPs, individually or in a mixture, concentration-dependently and additively increased the mortality of zebrafish embryos (ZFEs) at 96 h post fertilization (hpf) and induced bradycardia (i.e., reduced heart rate) at 48 hpf, indicating their cardiotoxic potency. BPAF was the most potent, followed by BPB, BPA, and BPF. We then explored the mechanism underlying BP-induced bradycardia in ZFEs. Although BPs increased the mRNA expression of the estrogen-responsive gene, treatment with the estrogen receptor inhibitor ICI 182780 did not prevent BP-induced bradycardia. Because they did not change cardiomyocyte counts or heart development-related gene expression, BPs might not affect cardiomyocyte development. By contrast, BPs might impair calcium homeostasis during cardiac contraction and relaxation through the downregulation of the expression of the mRNAs for the pore-forming subunit of L-type Ca2+ channel (LTCC; cacna1c) and sarco/endoplasmic reticulum Ca2+-ATPase (SERCA; atp2a2a). BPs reduced SERCA activity significantly. BPs also potentiated the cardiotoxicity induced by the LTCC blocker nisoldipine, conceivably by inhibiting SERCA activity. In conclusion, BPs additively induced bradycardia in ZFEs, possibly by impeding calcium homeostasis during cardiac contraction and relaxation. BPs also potentiated the cardiotoxicity of calcium channel blockers.

Global occurrence of synthetic glucocorticoids and glucocorticoid receptor agonistic activity, and aquatic hazards in effluent discharges and freshwater systems

With a growing global population comes an increase in pharmaceutical usage and a concentration of pharmaceutical consumption in urban areas, which release diverse chemicals and waste to the environment. Because synthetic glucocorticoids have been identified as endocrine disruptors and environmental contaminants of emerging concern, we conducted a global scanning assessment of these pharmaceuticals in wastewater effluents and freshwater systems. Thirty-seven synthetic glucocorticoids were identified, and available information on environmental occurrence of specific substances was critically reviewed from the peer-reviewed literature. We developed probabilistic environmental exposure distributions for synthetic glucocorticoids, and further considered glucocorticoid receptor agonistic activity from biomonitoring efforts using in vitro methods. When sufficient data was available, we then performed probabilistic environmental hazard assessments using predicted no effect concentrations, therapeutic hazard values and in vitro bioactivity information (AC50 values) for specific glucocorticoids. We observed pronounced differences for aquatic monitoring data among geographic regions; information is not available from many regions where most of the global population resides. We identified differences between analytical chemistry derived occurrence values for specific chemicals and biomonitoring results from seven different in vitro assays, which suggests that compounds not previously preselected for targeted analyses contribute to glucocorticoid receptor agonism in effluent discharges and aquatic systems. Our observations further identify the importance of advancing nontargeted analyses and research on in vitro to in vivo extrapolation of aquatic hazards. Though aquatic toxicology information is lacking for most of these substances, we observed diverse aquatic hazards for several synthetic glucocorticoids, and these observations varied by aquatic matrix and among geographic regions. This study identifies timely data gaps and can inform future environmentally relevant chemistry and toxicology efforts examining synthetic glucocorticoids in aquatic systems.

Global occurrence and aquatic hazards of antipsychotics in sewage influents, effluent discharges and surface waters

Despite increasing reports of pharmaceuticals in surface waters, aquatic hazard information remains limited for many contaminants, particularly for sublethal, chronic responses plausibly linked to molecular initiation events that are largely conserved across vertebrates. Here, we critically examined available refereed information on the occurrence of 67 antipsychotics in wastewater effluent and surface waters. Because the majority of sewage remains untreated around the world, we also examined occurrence in sewage influents. When sufficient information was available, we developed probabilistic environmental exposure distributions (EEDs) for each compound in each matrix by geographic region. We then performed probabilistic environmental hazard assessments (PEHAs) using therapeutic hazard values (THVs) of each compound, due to limited sublethal aquatic toxicology information for this class of pharmaceuticals. From these PEHAs, we determined predicted exceedances of the respective THVs for each chemical among matrices and regions, noting that THV values of antipsychotic contaminants are typically lower than other classes of human pharmaceuticals. Diverse exceedances were observed, and these aquatic hazards varied by compound, matrix and geographic region. In wastewater effluent discharges and surface waters, sulpiride was the most detected antipsychotic; however, percent exceedances of the THV were minimal (0.6%) for this medication. In contrast, we observed elevated aquatic hazards for chlorpromazine (30.5%), aripiprazole (37.5%), and perphenazine (68.7%) in effluent discharges, and for chlorprothixene (35.4%) and flupentixol (98.8%) in surface waters. Elevated aquatic hazards for relatively understudied antipsychotics were identified, which highlight important data gaps for future environmental chemistry and toxicology research.

Antibiotic concentrations and antibiotic resistance in aquatic environments of the WHO Western Pacific and South-East Asia regions: a systematic review and probabilistic environmental hazard assessment

BACKGROUND

Antibiotic resistance poses human health risks, and there are concerns about the effect of environmental antibiotic residues in the selection and spread of antibiotic resistance. The aim of this study was to identify antibiotic residue levels that are likely to select for resistance and relative contributions from different aquatic sources, of various aquatic environmental compartments of the WHO Western Pacific region (WPR) and the WHO South-East Asia region (SEAR), including in China and India.

METHODS

A systematic review of empirical studies that measured antibiotic concentrations in aquatic environments, published between 2006 and 2019, and a probabilistic environmental hazard assessments approach, were used to identify antibiotic concentrations that are likely to select for resistance in various aquatic environmental compartments of the WPR and SEAR, including in China and India. The assessment involved the use of measured environmental concentrations and predicted no-effect concentrations (PNECs).

FINDINGS

The systematic review found 218 relevant studies of 5230 screened from the WPR and 22 relevant studies of 2625 screened from the SEAR; some of these relevant studies were largely from China (n=168) and India (n=15). 92 antibiotics in the WPR and 45 in the SEAR were detected in various aquatic compartments. Antibiotic concentrations that most likely exceeded PNECs (0-100%) were observed in wastewater, and influents and effluents of wastewater treatment plants. Antibiotic concentrations that most likely exceeded PNECs were also observed in aquatic environmental compartments. The highest risk for the development of resistance was in tap or drinking water of the WPR and China for ciprofloxacin (62·5%). The relative contributions of potential sources of antibiotic contamination in waterways, such as hospitals, municipals, livestock, and pharmaceutical manufacturing, was determined for each antibiotic.

INTERPRETATION

The concentrations of antibiotic residues found in wastewater and wastewater treatment plants of the WPR and SEAR make them potential hotspots for the development of antibiotic resistance, which creates human health risks from environmental exposure via drinking water. These findings can help decision makers to target risk reduction measures against environmental residues of priority antibiotics in high-risk sites, and help to focus research efforts in these world regions.

FUNDING

Swedish Research Council.

Factors Affecting the Binding of Diltiazem to Rainbow Trout Plasma: Implications for the Risk Assessment of Pharmaceuticals in Aquatic Systems

The accumulation of organic toxicants in fish plasma, and how they partition between the bound and unbound fraction once absorbed, are important metrics in models that seek to predict the risk of such contaminants in aquatic settings. Rapid equilibrium dialysis of diltiazem, an ionizable weak base and important human pharmaceutical contaminant of freshwaters, was conducted with rainbow trout (Oncorhynchus mykiss) plasma. The effect of fed state, fish sex, fish strain/size, and dialysis buffer pH on the binding of radiolabeled diltiazem (9 ng ml^-1 ) was assessed. In fed fish, 24.6%-29.5% of diltiazem was free, unbound to plasma proteins. Although starvation of fish resulted in a decrease in plasma protein, the bound fraction of diltiazem remained relatively constant. Consequently, the protein-bound concentration of diltiazem increased with length of starvation. In general, rainbow trout strain was a significant factor affecting plasma binding, although the two strains tested also differed markedly in size. Dialysis buffer pH significantly influenced plasma binding, with a higher unbound diltiazem fraction at pH 6.8 than pH 8.0. These data indicate that empirical measures of plasma binding in fish are important for accurate risk assessment and that the physiological status of a fish is likely to impact its sensitivity to toxicants such as diltiazem. Environ Toxicol Chem 2022;41:3125-3133. © 2022 SETAC.

First eco-toxicological evidence of ivabradine effect on the marine bacterium Vibrio fischeri: A chiral view

Ivabradine (S-ivabradine) is a contemporary antihypertensive drug designed and commercialized for cardiovascular diseases treatment over the world. In this work the enantiomer-specific stability and acute toxicity of ivabradine to the marine bacterium Vibrio fischeri as well as the potential mechanism of action were investigated for the first time. With this aim, real concentrations of ivabradine enantiomers under abiotic and biotic conditions were determined by Capillary Electrophoresis (CE) with cyclodextrins (CDs) as chiral selectors. A moderate chiral stability without enantiomeric interconversion was observed for ivabradine. The bioluminescence inhibition method revealed an enantioselective toxicity of ivabradine to marine bacterium. The order of ecotoxicity was R-ivabradine < racemic ivabradine < S-ivabradine with EC50 (t = 5 min) values about 75.98, 11.11 and 7.93 mg/L, respectively. Confocal Live/Dead stained images showed that bacterial envelops cells were seriously damaged after exposure to S-ivabradine. S-ivabradine also disturbed the esterase activity and significantly increased the ROS level compared with the control. Thus, oxidative stress originating membrane cells damage and enzymatic activity changes was shown to be the primary mechanism of S-ivabradine toxicity to marine bacterium. Our results highlight the need for more eco-toxicological evaluations of the cardiovascular drug S-ivabradine on other aquatic organisms to establish the risk on the environment.

Global occurrence and probabilistic environmental health hazard assessment of per- and polyfluoroalkyl substances (PFASs) in groundwater and surface waters

Per- and polyfluoroalkyl substances (PFASs) have been used in consumer and military products since the 1950s but are increasingly scrutinized worldwide because of inherent chemical properties, environmental contamination, and risks to public health and the environment. The United States Environmental Protection Agency (USEPA) identified 24 PFASs of interest for further study and possible regulation. We examined 371 peer-reviewed studies published since 2001 to understand the occurrence and distribution of 24 priority PFASs in global surface waters and groundwater. We identified 77,541 and 16,246 data points for surface waters and groundwater, respectively, with total PFAS concentrations ranging from low pg/L to low mg/L levels. Most data were from Asia, Europe, and North America with some reports from Oceania. PFAS information from other geographic regions is lacking. PFASs levels are consistently higher in rivers and streams followed by lakes and reservoirs and then coastal and marine systems. When sufficient data were available, probabilistic environmental hazard assessments (PEHAs) were performed from environmental exposure distributions (EEDs) to identify potential exceedances of available guideline values for each compound by matrix, region, and aquatic system. Specifically, exceedances of USEPA drinking water lifetime health advisory levels were up to 74% for PFOS in groundwater from Oceania and 69% for PFOA in North American groundwater. Our findings support selection of environmentally relevant experimental treatment levels for future toxicology, ecotoxicology and bioaccumulation studies, and potable source water exposure investigations, while highlighting PFASs and major geographic locations requiring additional study and inclusion in global monitoring and surveillance campaigns.

Interaction of the Olfactory System of Rainbow Trout (Oncorhynchus mykiss) with Diltiazem

Diltiazem is ubiquitously prescribed and has been reported in many effluents and freshwater bodies. Being a calcium channel blocker, diltiazem could disrupt the function of the sensory and central nervous systems. In the present study, using electro-olfactography (EOG), we investigated the interaction of diltiazem with the olfactory sensory neurons (OSNs) of rainbow trout by looking into the detection threshold and effects of immediate (~5 min) and acute (24 h) exposure to diltiazem at 6.6, 66, and 660 µg/L. We also studied the accumulation of the drug in fish plasma and whole body. Brief exposure to diltiazem impaired the OSN response to a chemosensory stimulus in a concentration-dependent manner at 6.6 µg/L and higher, whereas OSNs exposed for 24 h only displayed an impairment at 660 µg/L. Chemical analysis showed that the accumulation of diltiazem in fish plasma and body correlated with the EOG response because it was 10 times higher in the group that displayed a significant impairment (660 µg/L) compared to the other 2 groups (6.6, 66 µg/L). This correlation suggests that the impact of diltiazem on OSNs might partially be through the accumulated molecules in the fish bloodstream. Fish did not detect diltiazem as a sensory stimulus even at concentrations as high as 660 µg/L; thus, fish could potentially swim toward or fail to escape harmful concentrations of diltiazem. Environ Toxicol Chem 2022;41:554-550. © 2020 SETAC.

Water reuse for aquaculture: Comparative removal efficacy and aquatic hazard reduction of pharmaceuticals by a pond treatment system during a one year study

Aquaculture is increasing at the global scale, and beneficial reuse of wastewater is becoming crucial in some regions. Here we selected a unique tertiary treatment system for study over a one-year period. This experimental ecosystem-based approach to effluent management included a treated wastewater pond (TWP), which receives 100% effluent from a wastewater treatment plant, and an aquaculture pond (AP) that receives treated water from the TWP for fish production. We examined the fate of a wide range of pharmaceutically active compounds (PhACs) in this TWP-AP system and a control pond fed by river water using traditional grab sampling and passive samplers. We then employed probabilistic approaches to examine exposure hazards. Telmisartan, carbamazepine, diclofenac and venlafaxine, exceeded ecotoxicological predicted no effect concentrations in influent wastewater to the TWP, but these water quality hazards were consistently reduced following treatment in the TWP-AP system. In addition, both grab and passive sampling approaches resulted in similar occurrence patterns of studied compounds, which highlights the potential of POCIS use for water monitoring. Based on the approach taken here, the TWP-AP system appears useful as a tertiary treatment step to reduce PhACs and decrease ecotoxicological and antibiotic resistance water quality hazards prior to beneficial reuse in aquaculture.

Contribution of aged polystyrene microplastics to the bioaccumulation of pharmaceuticals in marine organisms using experimental and model analysis

Microplastics (MPs) in the environment would undergo extensive weathering, which can act as a vector affecting the accumulation of pollutants in organisms. However, the risk of organic pollutants adsorbed on aged MPs to marine organisms is poorly understood. This study revealed the contribution of aged polystyrene (PS) MPs to the total bioaccumulation of atorvastatin (ATV) and amlodipine (AML), and assessed the environmental risks via experimental and model analysis. The results showed that pharmaceuticals were more easily released in gastrointestinal fluids from aged MPs relative to that in simulated seawater. The hydrophobic pharmaceuticals were more bioaccessible than hydrophilic ones by organisms. Model analysis showed that ingestion of water and food were the most important uptake routes for pharmaceuticals in marine fish and seabirds, while aged PS MPs could decrease the bioaccumulation of pharmaceuticals (contributed for -2.9% and -1.2% for the total uptake of ATV, and -25.8% and -4.4% for AML), indicating the cleaning effect of aged MPs, and the potential higher exposure risks of pharmaceuticals in warm-blooded organisms than that in cold-blooded ones via ingested MPs. The study revealed the effect of aged MPs to the bioaccumulation of pharmaceuticals in marine organisms, and highlighted the combined risks of aged MPs and pharmaceuticals in the environment.

De facto reuse at the watershed scale: Seasonal changes, population contributions, instream flows and water quality hazards of human pharmaceuticals

With increasing population growth and climate change, de facto reuse practices are predicted to increase globally. We investigated a longitudinal gradient within the Uhlava River, a representative watershed, where de facto reuse is actively occurring, during Fall and Spring seasons when instream flows vary. We observed human pharmaceutical levels in the river to continuously increase from the mountainous areas upstream to downstream locations and a potable intake location, with the highest concentrations found in small tributaries. Significant relationship was identified between mass flow of pharmaceuticals and the size of human populations contributing to wastewater treatment plant discharges. Advanced ozonation and granular activated carbon filtration effectively removed pharmaceuticals from potable source waters. We observed a higher probability of encountering a number of targeted pharmaceuticals during colder Spring months when stream flows were elevated compared to warmer conditions with lower flows in the Fall despite a dilution paradigm routinely applied for surface water quality assessment and management efforts. Such observations translated to greater water quality hazards during these higher Spring flows. Future water monitoring efforts should account for periods when higher chemical uses occur, particularly in the face of climate change for regions experiencing population growth and de facto reuse.

Water reuse and aquaculture: Pharmaceutical bioaccumulation by fish during tertiary treatment in a wastewater stabilization pond

With increasing demand for aquaculture products, water reuse is likely to increase for aquaculture operations around the world. Herein, wastewater stabilization ponds (WSP) represents low cost and sustainable treatment technologies to reduce nutrients and various contaminants of emerging concern from effluent. In the present study, we examined bioaccumulation of selected pharmaceuticals from several therapeutic classes by two important fish species in aquaculture with different feeding preferences (Cyprinus carpio and Sander lucioperca) and their common prey to test whether species specific accumulation occurs. Forty and nineteen from 66 selected pharmaceuticals and their metabolites were positively found in water and sediment samples, respectively from the representative WSP. After a six-month study, which corresponds to aquaculture operations, fourteen pharmaceuticals and their metabolites were detected (at a frequency of higher than 50% of samples) in at least one fish tissue collected from the WSP. We observed striking differences for species and organ specific BAFs among study compounds. Though muscle tissues consistently accumulated lower levels of the target analytes, several substances were elevated in brain, liver and kidney tissues (e.g., sertraline) of both species. Low residual concentrations of these target analytes in aquaculture products (fish fillets) suggest WSPs are promising to support the water-food nexus in aquaculture.

Toxicity assessment of verapamil and its photodegradation products

Pathways of photochemical degradation of a cardiovascular drug verapamil under conditions relevant to natural waters and the toxicity of the photoproducts to Daphnia magna were investigated. Photodegradation was shown to proceed via photocatalysed mechanism. Two main photodegradation pathways were recognised: the first leading to hydroxylation at the methylamino position followed by splitting of verapamil molecule into two fragments, and the second providing the main active metabolite of verapamil, norverapamil, and a series of norverapamil isomers, followed again by their splitting at the amino group position. Twenty-two products of photodegradation were identified. Toxicity assays in sublethal concentrations of the parental drug, of the photoproduct mixture, and of norverapamil revealed no direct negative response in Daphnia magna to verapamil. On the other hand, photochemical products significantly lowered the number of juveniles, number of clutches, and body size of Daphnia. The exposition of Daphnia to norverapamil showed the same but even more pronounced effects than its exposition to the mixture of photoproducts, which leads to the conclusion that norverapamil is mainly responsible for the toxicity of photoproduct mixture and represents a noteworthy threat to aquatic invertebrates.

Psychoactive pharmaceuticals in aquatic systems: A comparative assessment of environmental monitoring approaches for water and fish

Environmental monitoring and surveillance studies of pharmaceuticals routinely examine occurrence of substances without current information on human consumption patterns. We selected 10 streams with diverse annual flows and differentially influenced by population densities to examine surface water occurrence and fish accumulation of select psychoactive medicines, for which consumption is increasing in the Czech Republic. We then tested whether passive sampling can provide a useful surrogate for exposure to these substances through grab sampling, body burdens of young of year fish, and tissue specific accumulation of these psychoactive contaminants. We identified a statistically significant (p < 0.05) relationship between ambient grab samples and passive samplers in these streams when psychoactive contaminants were commonly quantitated by targeted liquid chromatography with tandem mass spectrometry, though we did not observe relationships between passive samplers and tissue specific pharmaceutical accumulation. We further observed smaller lotic systems with elevated contamination when municipal effluent discharges from more highly populated cities contributed a greater extent of instream flows. These findings identify the importance of understanding age and species specific differences in fish uptake, internal disposition, metabolism and elimination of psychoactive drugs across surface water quality gradients.

Identifying bioaccessible suspect toxicants in sediment using adverse outcome pathway directed analysis

Chemical mixtures are a common occurrence in contaminated sediment and determining causal relationship between sediment contamination and adverse outcomes is challenging. The bioavailability and choice of bioassay endpoints played important roles in elucidating causality. As such, bioaccessibility-based XAD extraction and adverse outcome pathway (AOP) guided bioassays were incorporated into an effect-directed analysis to more effectively determine sediment causality. XAD extracts of sediments from urban waterways in Guangzhou, China were examined using cell viability bioassays with four human tumor cells from lung, liver, breast, and bone marrow. Pronounced effects to SH-SY5Y cells were noted, thus neurotoxicity was subsequently focused in the AOP-guided bioassays. Intracellular calcium influx, mitochondrial membrane potential inhibition, reactive oxygen species generation, and cell viability were utilized as evidence for neurotoxicity AOP-guided analysis. Suspect toxicants were identified in active fractions using GC-MS. Toxicity confirmation was performed by evaluating toxicity contributions of the candidates to the pathway. Cypermethrin, bisphenol A, galaxolide, tonalide, and versalide were found as the major stressors across key events of the studied pathway. Moreover, good correlations among key events validated the feasibility of method to predict in vivo response, suggesting that considering bioavailability and AOP improved environmental relevance for toxicant identification in a complex mixture.

Verapamil and Alzheimer's Disease: Past, Present, and Future

Verapamil is a phenylalkylamine class calcium channel blocker that for half a century has been used for the treatment of cardiovascular diseases. Nowadays, verapamil is also considered as a drug option for the treatment of several neurological and psychiatric disorders, such as cluster headache, bipolar disorders, epilepsy, and neurodegenerative diseases. Here, we review insights into the potential preventive and therapeutic role of verapamil on Alzheimer’s disease (AD) based on limited experimental and clinical data. Pharmacological studies have shown that verapamil has a wide therapeutic spectrum, including antihypertensive, anti-inflammatory, and antioxidative effects, regulation of the blood-brain barrier function, due to its effect on P-glycoprotein, as well as adjustment of cellular calcium homeostasis, which may result in the delay of AD onset or ameliorate the symptoms of patients. However, the majority of the AD individuals are on polypharmacotherapy, and the interactions between verapamil and other drugs need to be considered. Therefore, for an appropriate and successful AD treatment, a personalized approach is more than necessary. A well-known narrow pharmacological window of verapamil efficacy may hinder this approach. It is therefore important to note that the verapamil efficacy may be conditioned by different factors. The onset, grade, and brain distribution of AD pathological hallmarks, the time-sequential appearances of AD-related cognitive and behavioral dysfunction, the chronobiologic and gender impact on calcium homeostasis and AD pathogenesis may somehow be influencing that success. In the future, such insights will be crucial for testing the validity of verapamil treatment on animal models of AD and clinical approaches.

Low dissolved oxygen increases uptake of a model calcium channel blocker and alters its effects on adult Pimephales promelas

Human population growth accompanied with urbanization is urbanizing the water cycle in many regions. Urban watersheds, particularly with limited upstream dilution of effluent discharges, represent worst case scenarios for exposure to multiple environmental stressors, including down the drain chemicals (e.g., pharmaceuticals) and other stressors (e.g., dissolved oxygen (DO)). We recently identified the calcium channel blocker diltiazem (DZM) to accumulate in fish plasma exceeding human therapeutic doses (e.g., C_min) in coastal estuaries impaired due to nonattainment of DO water quality standards. Thus, we examined whether DO influences DZM uptake by fish, and if changes in DO-dependent upatke alter fish physiological and biochemical responses. Low DO (3.0 mg DO/L) approximately doubled diltiazem uptake in adult fathead minnows relative to normoxic (8.2 mg DO/L) conditions and were associated with significant (p < 0.05) increases in fish ventilation rate at low DO levels. Decreased burst swim performance (U_burst) of adult fathead minnows were significantly (p < 0.05) altered by low versus normal DO levels. DO × DZM studies reduced U_burst by 13-31% from controls, though not significantly (p = 0.06). Physiological responses in fish exposed to DZM alone were minimal; however, in co-exposure with low DO, decreasing trends in U_burst appeared inversely related to plasma lactate levels. Such physiological responses to multiple stressors, when paired with internal tissue concentrations, identify the utility of employing biological read across approaches to identify adverse outcomes of heart medications and potentially other cardiotoxicants impacting fish cardiovascular function across DO gradients.

Interactions of emerging contaminants with model colloidal microplastics, C60 fullerene, and natural organic matter - effect of surface functional group and adsorbate properties

Surface adsorption of two commonly detected emerging contaminants, amlodipine (AMP) and carbamazepine (CBZ), onto model colloidal microplastics, natural organic matter (NOM), and fullerene nanomaterials have been investigated. It is found that AMP accumulation at these colloidal-aqueous interfaces is markedly higher than that of CBZ. Measurements of surface excess and particle zeta potential, along with pH-dependent adsorption studies, reveal a distinct influence of colloidal functional group on the adsorption properties of these pharmaceuticals. AMP shows a clear preference for a surface containing carboxylic group compared to an amine modified surface. CBZ, in contrast, exhibit a pH-dependent surface proclivity for both of these microparticles. The type of interactions and molecular differences with respect to structural rigidity and charge properties explain these observed behaviors. In this work, we also demonstrate a facile approach in fabricating uniform microspheres coated with NOM and C₆₀ nanoclusters. Subsequent binding studies on these surfaces show considerable adsorption on the NOM surface but a minimal uptake of CBZ by C₆₀. Adsorption induced colloidal aggregation was not observed. These findings map out the extent of contaminant removal by colloids of different surface properties available in the aquatic environment. The methodology developed for the adsorption study also opens up the possibility for further investigations into colloidal-contaminant interactions.

Occurrence and treatment of contaminants of emerging concern in the African aquatic environment: Literature review and a look ahead

Awareness about the rising detection and reported (eco)toxicological effects of contaminants of emerging concern (CECs, e.g. pharmaceuticals and personal care products - PPCPs - and modern pesticides) in the aquatic environment is growing. CECs are increasingly reported in the African aquatic environment, although the amount of data available is still limited. In this work, a comprehensive review is presented on the occurrence of CECs in wastewater, sludge, surface water, sediment, groundwater and drinking water of Africa. Further attention is given to the performance of wastewater stabilization ponds (WSPs) and trickling filters (TF) with respect to CECs removal. For the first time, we also look at the state of knowledge on the performance of point-of-use technologies (POUs) regarding the removal of CECs in drinking water. Generally, CECs in Africa occur at the same order of magnitude as in the Western world. However, for particular groups of compounds and at specific locations such as informal settlements, clearly higher concentrations are reported in Africa. Whereas antiretroviral and antimalarial drugs are rarely detected in the Western world, occurrence patterns in Africa reveal concentrations up to >100 μg L^-1. Removal efficiencies of WSPs and TFs focus mainly on PPCPs and vary significantly, ranging from no removal (e.g. carbamazepine) to better than 99.9% (e.g. paracetamol). Despite the rising adoption of POUs, limited but promising information is available on their performance regarding CECs treatment in drinking water, particularly for the low-cost devices (e.g. ceramic filters and solar disinfection - SODIS) being adopted in Africa and other developing countries.

Influence of salinity and pH on bioconcentration of ionizable pharmaceuticals by the gulf killifish, Fundulus grandis

Estuaries routinely receive discharges of contaminants of emerging concern from urban regions. Within these dynamic estuarine systems, salinity and pH can vary across spatial and temporal scales. Our previous research identified bioaccumulation of the calcium channel blocker diltiazem and the antihistamine diphenhydramine in several species of fish residing in multiple urban estuaries along the Gulf of Mexico in Texas, where field-measured observations of diltiazem in fish plasma exceeded human therapeutic plasma doses. However, there remains a limited understanding of pharmaceutical bioaccumulation in estuarine environments. Here, we examined the influence of pH and salinity on bioconcentration of three pharmaceuticals in the Gulf killifish, Fundulus grandis. F. grandis were exposed to low levels of the ionizable pharmaceuticals carbamazepine, diltiazem, and diphenhydramine at two salinities (5 ppt, 20 ppt) and two pH levels (6.7, 8.3). pH influenced bioconcentration of select weak base pharmaceuticals, while salinity did not, suggesting that intestinal uptake via drinking does not appear to be a major exposure route of these pharmaceuticals in killifish. Compared to our previous pH dependent uptake observations with diphenhydramine in the fathead minnow model, killifish apparent volume of distribution values were markedly lower than fatheads, though killifish bioconcentration factors were similar at high pH and four fold higher at low pH than freshwater fish. Advancing an understanding of environmental gradient influences on pharmacokinetics among fish is necessary to improve bioaccumulation assessments and interpretation of toxicological observations for ionizable contaminants.

Global scanning of selective serotonin reuptake inhibitors: occurrence, wastewater treatment and hazards in aquatic systems

As the global population becomes more concentrated in urban areas, resource consumption, including access to pharmaceuticals, is increasing and chemical use is also increasingly concentrated. Unfortunately, implementation of waste management systems and wastewater treatment infrastructure is not yet meeting these global megatrends. Herein, pharmaceuticals are indicators of an urbanizing water cycle; antidepressants are among the most commonly studied classes of these contaminants of emerging concern. In the present study, we performed a unique global hazard assessment of selective serotonin reuptake inhibitors (SSRIs) in water matrices across geographic regions and for common wastewater treatment technologies. SSRIs in the environment have primarily been reported from Europe (50%) followed by North America (38%) and Asia-Pacific (10%). Minimal to no monitoring data exists for many developing regions of the world, including Africa and South America. From probabilistic environmental exposure distributions, 5th and 95th percentiles for all SSRIs across all geographic regions were 2.31 and 3022.1 ng/L for influent, 5.3 and 841.6 ng/L for effluent, 0.8 and 127.7 ng/L for freshwater, and 0.5 and 22.3 ng/L for coastal and marine systems, respectively. To estimate the potential hazards of SSRIs in the aquatic environment, percent exceedances of therapeutic hazard values of specific SSRIs, without recommended safety factors, were identified within and among geographic regions. For influent sewage and wastewater effluents, sertraline exceedances were observed 49% and 29% of the time, respectively, demonstrating the need to better understand emerging water quality hazards of SSRIs in urban freshwater and coastal ecosystems. This unique global review and analysis identified regions where more monitoring is necessary, and compounds requiring toxicological attention, particularly with increasing aquatic reports of behavioral perturbations elicited by SSRIs.

Corbicula fluminea rapidly accumulate pharmaceuticals from an effluent dependent urban stream

Freshwater bivalve populations are stressed by watershed development at the global scale. Though pharmaceuticals released from wastewater treatment plant effluent discharges are increasingly reported to bioaccumulate in fish, an understanding of bioaccumulation in bivalves is less defined. In the present study, we examined accumulation of 12 target pharmaceuticals in C. fluminea during a 42 day in situ study in Pecan Creek, an effluent dependent wadeable stream in north central Texas, USA. Caged clams were placed at increasing distances (5 m, 643 m, 1762 m) downstream from a municipal effluent discharge and then subsampled on study days 7, 14, 28 and 42. Acetaminophen, caffeine, carbamazepine, diltiazem, diphenhydramine, fluoxetine, norfluoxetine, sertraline, desmethylsertraline, and methylphenidate were identified in C. fluminea whole body tissue homogenates via isotope dilution liquid chromatography-tandem mass spectrometry. Tissue concentrations ranged from low μg/kg (methylphenidate) to 341 μg/kg (sertraline). By study day 7, rapid and apparent pseudo-steady state accumulation of study compounds was observed in clams; this observation continued throughout the 42 d study. Notably, elevated bioaccumulation factors (L/kg) for sertraline were observed between 3361 and 6845, which highlights the importance of developing predictive bioaccumulation models for ionizable contaminants with bivalves. Future research is also necessary to understand different routes of exposure and elimination kinetics for pharmaceutical accumulation in bivalves.

The role of freshwater copepods in the environmental risk assessment of caffeine and propranolol mixtures in the surface water bodies of Spain

In this study we aimed at assessing: (i) the environmental risk posed by mixtures of caffeine and propranolol to the freshwater ecosystems of Spain; (ii) the sensitivity of freshwater copepod species to the two compounds; (iii) if the toxicity of caffeine and propranolol to freshwater copepods contributes to the environmental risk posed by the two compounds in the freshwater bodies of Spain. The environmental risk was computed as the ratio of MECs (i.e. the measured environmental concentrations) to PNECs (i.e. the respective predicted no-effect concentrations). The effects of caffeine and propranolol on the freshwater cyclopoid Diacyclops crassicaudis crassicaudis were tested both individually and in binary mixtures. Propranolol posed an environmental risk in some but not in all the surface water ecosystems of Spain investigated in this study, while caffeine posed an environmental risk to all the investigated freshwater bodies, both as single compound and in the mixture with propranolol. Propranolol was the most toxic compound to D. crassicaudis crassicaudis, while caffeine was non-toxic to this species. The CA model predicted the toxicity of the propranolol and caffeine mixture for this species. D. crassicaudis crassicaudis was much less sensitive than several other aquatic species to both compounds. The sensitivity of D. crassicaudis crassicaudis does not increase the environmental risk posed by the two compounds in the freshwater bodies of Spain, however, further testing is recommended since the effect of toxicants on freshwater copepods can be more pronounced under multiple stressors and temperature increasing due to climate change.

Commentary: Perspectives on aquaculture, urbanization and water quality

Aquaculture presents essential opportunities to meet global food security needs, but adverse effects of aquaculture practices on ecological integrity and influences of existing waste management infrastructure on product safety must be understood in rapidly expanding urban and peri-urban regions. Concentration of, access to and use of chemical products is increasing in many urban areas faster than interventions are being implemented. Aquaculture farming is employing "non-traditional" (e.g., treated or untreated sewage) waters in some regions, but the spatial extent of these intentional or de facto water reuse practices with associated water quality and food safety systems are poorly understood around the world. Integrative water reuse, aquaculture product safety, ecological and public health research and advanced surveillance systems are needed. Such efforts appear particularly important because noncommunicable diseases are increasing and pollution is now recognized as one of the major global health threats, particularly in lower and middle income countries. Here we provide some modest perspectives and identify several research needs to support more sustainable aquaculture practices while protecting public health and the environment.

Emerging contaminants in a river receiving untreated wastewater from an Indian urban centre

Research over the last decade on emerging trace organic contaminants in aquatic systems has largely focused on sources such as treated wastewaters in high income countries, with relatively few studies relating to wastewater sources of these contaminants in low and middle income countries. We undertook a longitudinal survey of the Ahar River for a number of emerging organic contaminants (including pharmaceuticals, hormones, personal care products and industrial chemicals) which flows through the city of Udaipur, India. Udaipur is a city of approximately 450,000 people with no wastewater treatment occurring at the time of this survey. We found the concentrations of many of the contaminants within the river water were similar to those commonly reported in untreated wastewater in high income countries. For example, concentrations of pharmaceuticals, such as carbamazepine, antibiotics and non-steroidal anti-inflammatory drugs, ranged up to 1900 ng/L. Other organic contaminants, such as steroid estrogens (up to 124 ng/L), steroid androgens (up to 1560 ng/L), benzotriazoles (up to 11 μg/L), DEET (up to 390 ng/L), BPA (up to 300 ng/L) and caffeine (up to 37.5 μg/L), were all similar to previously reported concentrations in wastewaters in high income countries. An assessment of the population densities in the watersheds feeding into the river showed increasing population density of a watershed led to a corresponding downstream increase in the concentrations of the organic contaminants, with quantifiable concentrations still present up to 10 km downstream of the areas directly adjacent to the highest population densities. Overall, this study highlights how a relatively clean river can be contaminated by untreated wastewater released from an urban centre.

Influence of Diltiazem on Fathead Minnows Across Dissolved Oxygen Gradients

Water resources in many arid to semi-arid regions are stressed by population growth and drought. Growing populations and climatic changes are influencing contaminant and water chemistry dynamics in urban inland waters, where flows can be dominated by, or even dependent on, wastewater effluent discharge. In these watersheds, interacting stressors such as dissolved oxygen and environmental contaminants (e.g., pharmaceuticals) have the potential to affect fish physiology and populations. Recent field observations from our group identified the calcium channel blocker (CCB) diltiazem in fish plasma exceeding human therapeutic doses (e.g., C_min ) in aquatic systems impaired because of nonattainment of dissolved oxygen water quality standards. Therefore our study objectives examined: 1) standard acute and chronic effects of dissolved oxygen and diltiazem to fish, 2) influences of dissolved oxygen at criteria levels deemed protective of aquatic life on diltiazem toxicity to fish, and 3) whether sublethal effects occur at diltiazem water concentrations predicted to cause a human therapeutic level (therapeutic hazard value [THV]) in fish plasma. Dissolved oxygen × diltiazem co-exposures significantly decreased survival at typical stream, lake, and reservoir water quality standards of 5.0 and 3.0 mg dissolved oxygen/L. Dissolved oxygen and diltiazem growth effects were observed at 2 times and 10 times lower than median lethal concentration (LC50) values (1.7 and 28.2 mg/L, respectively). Larval fathead minnow (Pimephales promelas) swimming behavior following low dissolved oxygen and diltiazem exposure generally decreased and was significantly reduced in light-to-dark bursting distance traveled, number of movements, and duration at concentrations as low as the THV. Individual and population level consequences of such responses are not yet understood, particularly in older organisms or other species; however, these findings suggest that assessments with pharmaceuticals and other cardioactive contaminants may underestimate adverse outcomes in fish across dissolved oxygen levels considered protective of aquatic life. Environ Toxicol Chem 2018;37:2835-2850. © 2018 SETAC.

Occurrence, fate and removal of pharmaceuticals, personal care products and pesticides in wastewater stabilization ponds and receiving rivers in the Nzoia Basin, Kenya

Although there is increased global environmental concern about emerging organic micropollutants (EOMPs) such as pharmaceuticals, personal care products (PPCPs) and polar pesticides, limited information is available on their occurrence in Africa. This study presents unique data on concentrations and loads of 31 PPCPs and 10 pesticides in four wastewater stabilization ponds (WSPs) and receiving rivers (flowing through urban centres) in Kenya. The WSPs indicate a high potential to remove pharmaceutically active compounds (PhACs) with removals by up to >4 orders of magnitude (>99.99% removal), mainly occurring at the facultative stage. However, there are large differences in removal among the different classes, and a shift in the relative PhACs occurrence is observed during wastewater treatment. Whereas the influent is dominated by high-consumption PhACs like anti-inflammatory drugs (e.g. paracetamol and ibuprofen, up to 1000 μg L^-1), the most recalcitrant PhACs including mainly antibiotics (e.g. sulfadoxin and sulfamethoxazole) and antiretrovirals (e.g. lamivudine and nevirapine) are largely abundant (up to 100 μg L^-1) in treated effluent. Overall, concentrations of EOMPs in the Nzoia Basin rivers are the highest in dry season (except pesticides) and in small tributaries. They are of the same order of magnitude as those measured in the western world, but clearly lower than what we recently measured in the Ngong River, Nairobi region. Based on the specific consumption patterns and recalcitrant behavior, high concentrations (>1000 ng L^-1) are observed in the rivers for PPCPs like lamivudine, zidovudine, sulfamethoxazole and methylparaben. Concentration levels of pesticides are in general one order of magnitude lower (<250 ng L^-1). Our data suggest a continuous input of EOMPs to the rivers from both point (WSPs) and diffuse (urban centres) sources. To better understand and manage the impact of both sources, EOMP removal mechanisms in WSPs and their attenuation in rivers merit further research.

Pharmaceuticals in the aquatic environments: Evidence of emerged threat and future challenges for marine organisms

Pharmaceuticals are nowadays recognized as a threat for aquatic ecosystems. The growing consumption of these compounds and the enhancement of human health in the past two decades have been paralleled by the continuous input of such biologically active molecules in natural environments. Waste water treatment plants (WWTPs) have been identified as a major route for release of pharmaceuticals in aquatic bodies where concentrations ranging from ng/L to μg/L are ubiquitously detected. Since medicines principles are designed to be effective at very low concentrations, they have the potential to interfere with biochemical and physiological processes of aquatic species over their entire life cycle. Investigations on occurrence, bioaccumulation and effects in non target organisms are fragmentary, particularly for marine ecosystems, and related to only a limited number over the 4000 substances classified as pharmaceuticals: hence, there is a urgent need to prioritize the environmental sustainability of the most relevant compounds. The aim of this review is to summarize the main adverse effects documented for marine species exposed in both field and laboratory conditions to different classes of pharmaceuticals including non-steroidal anti-inflammatory drugs, psychiatric, cardiovascular, hypocholesterolaemic drugs, steroid hormones and antibiotics. Despite a great scientific advancement has been achieved, our knowledge is still limited on pharmaceuticals behavior in chemical mixtures, as well as their interactions with other environmental stressors. Complex ecotoxicological effects are increasingly documented and multidisciplinary, integrated approaches will be helpful to clarify the environmental hazard of these "emerged" pollutants in marine environment.

Experimental Protocol for Examining Behavioral Response Profiles in Larval Fish: Application to the Neuro-stimulant Caffeine

Fish models and behaviors are increasingly used in the biomedical sciences; however, fish have long been the subject of ecological, physiological and toxicological studies. Using automated digital tracking platforms, recent efforts in neuropharmacology are leveraging larval fish locomotor behaviors to identify potential therapeutic targets for novel small molecules. Similar to these efforts, research in the environmental sciences and comparative pharmacology and toxicology is examining various behaviors of fish models as diagnostic tools in tiered evaluation of contaminants and real-time monitoring of surface waters for contaminant threats. Whereas the zebrafish is a popular larval fish model in the biomedical sciences, the fathead minnow is a common larval fish model in ecotoxicology. Unfortunately, fathead minnow larvae have received considerably less attention in behavioral studies. Here, we develop and demonstrate a behavioral profile protocol using caffeine as a model neurostimulant. Though photomotor responses of fathead minnows were occasionally affected by caffeine, zebrafish were markedly more sensitive for photomotor and locomotor endpoints, which responded at environmentally relevant levels. Future studies are needed to understand comparative behavioral sensitivity differences among fish with age and time of day, and to determine whether similar behavioral effects would occur in nature and be indicative of adverse outcomes at the individual or population levels of biological organization.

Global review and analysis of erythromycin in the environment: Occurrence, bioaccumulation and antibiotic resistance hazards

Environmental observations of antibiotics and other pharmaceuticals have received attention as indicators of an urbanizing global water cycle. When connections between environment and development of antibiotic resistance (ABR) are considered, it is increasingly important to understand the life cycle of antibiotics. Here we examined the global occurrence of erythromycin (ERY) in: 1. wastewater effluent, inland waters, drinking water, groundwater, and estuarine and coastal systems; 2. sewage sludge, biosolids and sediments; and 3. tissues of aquatic organisms. We then performed probabilistic environmental hazard assessments to identify probabilities of exceeding the predicted no-effect concentration (PNEC) of 1.0 μg L^-1 for promoting ABR, based on previous modeling of minimum inhibitory concentrations and minimal selective concentrations of ERY, and measured levels from different geographic regions. Marked differences were observed among geographic regions and matrices. For example, more information was available for water matrices (312 publications) than solids (97 publications). ERY has primarily been studied in Asia, North America and Europe with the majority of studies performed in China, USA, Spain and the United Kingdom. In surface waters 72.4% of the Asian studies have been performed in China, while 85.4% of the observations from North America were from the USA; Spain represented 41.9% of the European surface water studies. Remarkably, results from PEHAs indicated that the likelihood of exceeding the ERY PNEC for ABR in effluents was markedly high in Asia (33.3%) followed by Europe (20%) and North America (17.8%). Unfortunately, ERY occurrence data is comparatively limited in coastal and marine systems across large geographic regions including Southwest Asia, Eastern Europe, Africa, and Central and South America. Future studies are needed to understand risks of ERY and other antibiotics to human health and the environment, particularly in developing regions where waste management systems and treatment infrastructure are being implemented slower than access to and consumption of pharmaceuticals is occurring.

Select antibiotics in leachate from closed and active landfills exceed thresholds for antibiotic resistance development

Though antibiotic resistance (ABR) represents a major global health threat, contributions of landfill leachate to the life cycle of antibiotics and ABR development are poorly understood in rapidly urbanizing regions of developing countries. We selected one of the largest active landfills in Asia and two landfills that have been closed for 20 years to examine antibiotic occurrences in leachates and associated hazards during wet and dry season sampling events. We focused on some of the most commonly used human antibiotics in Hong Kong, one of the most populous Asian cities and the fourth most densely populated cities in the world. Seven antibiotics (cephalexin [CLX], chloramphenicol [CAP], ciprofloxacin [CIP], erythromycin [ERY], roxithromycin [ROX], trimethoprim [TMP], sulfamethoxazole [SMX]) were quantitated using HPLC-MS/MS generally following previously reported methods. Whereas CLX, CAP, ROX and SMX in leachates did not exceed ABR predicted no effect concentrations (PNECs), exceedances were observed for CIP, ERY and TMP in some study locations and on some dates. In fact, an ABR PNEC for CIP was exceeded in leachates during both sampling periods from all study locations, including leachates that are directly discharged to coastal systems. These findings highlight the importance of developing an advanced understanding of pharmaceutical access, usage and disposal practices, effectiveness of intervention strategies (e.g., leachate treatment technologies, drug take-back schemes), and contributions of landfill leachates to the life cycle of antibiotics and ABR development, particularly in rapidly urbanizing coastal regions with less advanced waste management systems than Hong Kong.