Occurrence and environmental behavior of the bactericide triclosan and its methyl derivative in surface waters and in wastewater

A Unique Monitoring Method for Fecal and Sewage-Derived Chemical Pollution Utilizing International Pellet Watch Approach

This study established a unique approach to assess fecal contamination by measuring fecal sterols, especially coprostanol (5β-cholestanol-3β-ol, 5β) and cholestanol (5α-cholestan-3β-ol, 5α) and their ratio 5β/(5β + 5α) alongside triclosan (TCS) and methyl-triclosan (MTC) in beached plastic pellets across 40 countries. Coprostanol concentrations ranged from 3.6 to 8190 ng/g pellet with extremely high levels in densely populated areas in African countries. The 5β/(5β + 5α) ratio was not affected by the difference in residence time of pellets in aquatic environments, and their spatial pattern showed a positive correlation with that of sedimentary sterols, demonstrating its reliability as an indicator of fecal contamination. Pellets from populated areas of economically developing countries, i.e., Africa and Asia, with lower coverage of wastewater treatment exhibited higher 5β/(5β + 5α) ratios (∼0.7) corresponding to ∼1% sewage in seawater, while pellets from developed countries, i.e., the USA, Canada, Japan, and Europe, with higher coverage of modern wastewater treatment displayed lower ratios (∼0.5), corresponding to the first contact limit. Triclosan levels were higher in developing countries (0.4-1298 ng/g pellet), whereas developed countries showed higher methyl-triclosan levels (0.5-70 ng/g pellet) due to TCS conversion during secondary treatment. However, some samples from Japan and Europe displayed higher TCS levels, suggesting contributions from combined sewage overflow (CSO). Combination of 5β/(5β + 5α) and MTC/TCS ratios revealed extreme fecal contamination from direct input of raw sewage due to inadequate treatment facilities in some African and South and Southeast Asian countries.

Effects of weathering on the properties and fate of secondary microplastics from a polystyrene single-use cup

In this work, we probed the changes to some physicochemical properties of polystyrene microplastics generated from a disposable cup as a result of UV-weathering, using a range of spectroscopy, microscopy, and profilometry techniques. Thereafter, we aimed to understand how these physicochemical changes affect the microplastic transport potential and contaminant sorption ability in model freshwaters. Exposure to UV led to measured changes in microplastic hydrophobicity (20-23 % decrease), density (3% increase), carbonyl index (up to 746 % increase), and microscale roughness (24-86 % increase). The settling velocity of the microplastics increased by 53 % after weathering which suggests that UV aging can increase microplastic deposition to sediments. This impact of aging was greater than the effect of the water temperature. Weathered microplastics exhibited reduced sorption capacity (up to 52 % decrease) to a model hydrophobic contaminant (triclosan) compared to unaged ones. The adsorption of triclosan to both microplastics was slightly reversible with notable desorption hysteresis. These combined effects of weathering could potentially increase the transport potential while decreasing the contaminant transport abilities of microplastics. This work provides new insights on the sorption capacity and mobility of a secondary microplastic, advances our knowledge about their risks in aquatic environments, and the need to use environmentally relevant microplastics.

Metabolic disturbance and transcriptomic changes induced by methyl triclosan in human hepatocyte L02 cells

PURPOSE

Methyl triclosan (MTCS) is one of the biomethylated by-products of triclosan (TCS). With the increasing use of TCS, the adverse effects of MTCS have attracted extensive attention in recent years. The purpose of this study was to investigate the cytotoxicity of MTCS and to explore the underlining mechanism using human hepatocyte L02 cells as in vitro model.

RESULTS

The cytotoxicity results revealed that MTCS could inhibit cell viability, disturb the ratio of reduced glutathione (GSH) and oxidized glutathione (GSSG), and reduce the mitochondrial membrane potential (MMP) in a dose-dependent manner. In addition, MTCS exposure significantly promoted the cellular metabolic process, including enhanced conversion of glucose to lactic acid, and elevated content of intracellular triglyceride (TG) and total cholesterol (TC). RNA-sequencing and bioinformatics analysis indicated disorder of glucose and lipid metabolism was significantly induced after MTCS exposure. Protein-protein interaction network analysis and node identification suggested that Serine hydroxy methyltransferase 2 (SHMT2), Methylenetetrahydrofolate dehydrogenase 2 (MTHFD2), Asparagine synthetase (ASNS) and Phosphoglycerate dehydrogenase (PHGDH) are potential molecular markers of metabolism imbalance induced by MTCS.

CONCLUSION

These results demonstrated that oxidative stress and metabolism dysregulation might be involved in the cytotoxicity of MTCS in L02 cells.

A review on triclosan in wastewater: Mechanism of action, resistance phenomenon, environmental risks, and sustainable removal techniques

Triclosan, belonging to the bisphenols, is a known antiseptic broad-spectrum biocide. It has a very wide range of applications, both in health care and in the household. Triclosan enters the environment, both water bodies and soil, because of its high prevalence and the ability to accumulation. Excessive use of antimicrobial formulations may cause the generation of resistance among microorganisms. Reduced susceptibility to triclosan is observed more frequently and in an expanded group of microorganisms and is conditioned by a number of different mechanisms occurring on the molecular level. Conventional wastewater treatment processes are not always able to provide a reliable barrier to triclosan. Therefore, additional advanced treatment technologies are being considered in areas, where a triclosan contamination problem has been identified. Removal of triclosan from wastewater is carried out using different biological and chemical techniques; however, it should be pointed out that physico-chemical methods often generate toxic by-products. Toxicity of triclosan and its degradation products, bacterial resistance to this compound, and evident problems with triclosan elimination from wastewater are currently the main problems faced by companies creating products containing triclosan. PRACTITIONER POINTS: Triclosan is an emerging pollutant in the environment because of its ability to accumulation and high prevalence. Reduced susceptibility to triclosan is being observed more frequently. Conventional wastewater treatment processes are not always able to provide a reliable barrier to triclosan. Additional advanced treatment technologies should be implemented to remove triclosan from wastewater.

Antimicrobial Transformation Products in the Aquatic Environment: Global Occurrence, Ecotoxicological Risks, and Potential of Antibiotic Resistance

The global spread of antimicrobial resistance (AMR) is concerning for the health of humans, animals, and the environment in a One Health perspective. Assessments of AMR and associated environmental hazards mostly focus on antimicrobial parent compounds, while largely overlooking their transformation products (TPs). This review lists antimicrobial TPs identified in surface water environments and examines their potential for AMR promotion, ecological risk, as well as human health and environmental hazards using in silico models. Our review also summarizes the key transformation compartments of TPs, related pathways for TPs reaching surface waters and methodologies for studying the fate of TPs. The 56 antimicrobial TPs covered by the review were prioritized via scoring and ranking of various risk and hazard parameters. Most data on occurrences to date have been reported in Europe, while little is known about antibiotic TPs in Africa, Central and South America, Asia, and Oceania. Occurrence data on antiviral TPs and other antibacterial TPs are even scarcer. We propose evaluation of structural similarity between parent compounds and TPs for TP risk assessment. We predicted a risk of AMR for 13 TPs, especially TPs of tetracyclines and macrolides. We estimated the ecotoxicological effect concentrations of TPs from the experimental effect data of the parent chemical for bacteria, algae and water fleas, scaled by potency differences predicted by quantitative structure-activity relationships (QSARs) for baseline toxicity and a scaling factor for structural similarity. Inclusion of TPs in mixtures with their parent increased the ecological risk quotient over the threshold of one for 7 of the 24 antimicrobials included in this analysis, while only one parent had a risk quotient above one. Thirteen TPs, from which 6 were macrolide TPs, posed a risk to at least one of the three tested species. There were 12/21 TPs identified that are likely to exhibit a similar or higher level of mutagenicity/carcinogenicity, respectively, than their parent compound, with tetracycline TPs often showing increased mutagenicity. Most TPs with increased carcinogenicity belonged to sulfonamides. Most of the TPs were predicted to be mobile but not bioaccumulative, and 14 were predicted to be persistent. The six highest-priority TPs originated from the tetracycline antibiotic family and antivirals. This review, and in particular our ranking of antimicrobial TPs of concern, can support authorities in planning related intervention strategies and source mitigation of antimicrobials toward a sustainable future.

Adsorptive and photocatalytic degradation potential of porous polymeric materials for removal of pesticides, pharmaceuticals, and dyes-based emerging contaminants from water

Life on earth is dependent on clean water, which is crucial for survival. Water supplies are getting contaminated due to the growing human population and its associated industrialization, urbanization, and chemically improved agriculture. Currently, a large number of people struggle to find clean drinking water, a problem that is particularly serious in developing countries. To meet the enormous demand of clean water around the world, there is an urgent need of advanced technologies and materials that are affordable, easy to use, thermally efficient, portable, environmentally benign, and chemically durable. The physical, chemical and biological methods are used to eliminate insoluble materials and soluble pollutants from wastewater. In addition to cost, each treatment carries its limitations in terms of effectiveness, productivity, environmental effect, sludge generation, pre-treatment demands, operating difficulties, and the creation of potentially hazardous byproducts. To overcome the problems of traditional methods, porous polymers have distinguished themselves as practical and efficient materials for the treatment of wastewater because of their distinctive characteristics such as large surface area, chemical versatility, biodegradability, and biocompatibility. This study overviews improvement in manufacturing methods and the sustainable usage of porous polymers for wastewater treatment and explicitly discusses the efficiency of advanced porous polymeric materials for the removal of emerging pollutants viz. pesticides, dyes, and pharmaceuticals whereby adsorption and photocatalytic degradation are considered to be among the most promising methods for their effective removal. Porous polymers are considered excellent adsorbents for the mitigation of these pollutants as they are cost-effective and have greater porosities to facilitate penetration and adhesion of pollutants, thus enhance their adsorption functionality. Appropriately functionalized porous polymers can offer the potential to eliminate hazardous chemicals and making water useful for a variety of purposes thus, numerous types of porous polymers have been selected, discussed and compared especially in terms of their efficiencies against specific pollutants. The study also sheds light on numerous challenges faced by porous polymers in the removal of contaminants, their solutions and some associated toxicity issues.

Triclosan and related compounds in the environment: Recent updates on sources, fates, distribution, analytical extraction, analysis, and removal techniques

Triclosan (TCS) has been widely used in daily life because of its broad-spectrum antibacterial activities. The residue of TCS and related compounds in the environment is one of the critical environmental safety problems, and the pandemic of COVID-19 aggravates the accumulation of TCS and related compounds in the environment. Therefore, detecting TCS and related compound residues in the environment is of great significance to human health and environmental safety. The distribution of TCS and related compounds are slightly different worldwide, and the removal methods also have advantages and disadvantages. This paper summarized the research progress on the source, distribution, degradation, analytical extraction, detection, and removal techniques of TCS and related compounds in different environmental samples. The commonly used analytical extraction methods for TCS and related compounds include solid-phase extraction, liquid-liquid extraction, solid-phase microextraction, liquid-phase microextraction, and so on. The determination methods include liquid chromatography coupled with different detectors, gas chromatography and related methods, sensors, electrochemical method, capillary electrophoresis. The removal techniques in various environmental samples mainly include biodegradation, advanced oxidation, and adsorption methods. Besides, both the pros and cons of different techniques have been compared and summarized, and the development and prospect of each technique have been given.

Acute toxicity, oxidative stress, and apoptosis due to short-term triclosan exposure and multi- and transgenerational effects on in vivo endpoints, antioxidant defense, and DNA damage response in the freshwater water flea Daphnia magna

In this study, we measured the acute toxicity of triclosan (TCS) in neonate and adult Daphnia magna water fleas. The median lethal concentrations were 184.689 and 349.511 μg/L, respectively. Oxidative stress induced by TCS was analyzed based on changes in reactive oxygen species (ROS) content and antioxidant enzymatic activities in D. magna. Based on these endpoints, TCS concentrations of 50 and 100 μg/L induced oxidative stress. However, several apoptosis-mediated proteins showed TCS-induced oxidative-stress damage in response to 25 μg/L, indicating that apoptotic proteins were the most sensitive mediators. We also evaluated the multi- and transgenerational effects of TCS on D. magna over three generations in terms of various in vivo endpoints, DNA damage responses, and biochemical reactions. The transgenerational group exposed to TCS exhibited greater negative impacts on antioxidant responses, DNA fragmentation status, and biological endpoints compared with the multigenerational exposure group, leading to decreased reproductive rates and higher ROS content. The transcriptional expression levels of glutathione S-transferase genes in the transgenerational exposure group were upregulated compared to those in the multigenerational group but were fully recovered in F2 offspring. Our findings provide an in-depth understanding of the adaptive effects of multigenerational exposure to TCS.

Triclosan and Methyl Triclosan in Prey Fish in a Wastewater-Influenced Estuary

While the antimicrobial ingredient triclosan has been widely monitored in the environment, much less is known about the occurrence and toxicity of its major transformation product, methyl triclosan. An improved method was developed and validated to effectively extract and quantify both contaminants in fish tissue and used to characterize concentrations in small prey fish in areas of San Francisco Bay where exposure to triclosan via municipal wastewater discharges was expected to be highest. Concentrations of triclosan (0.44-57 ng/g wet wt, median 1.9 ng/g wet wt) and methyl triclosan (1.1-200 ng/g wet wt, median 36 ng/g wet wt) in fish tissue decreased linearly with concentrations of nitrate in site water, used as indicators of wastewater influence. The total concentrations of triclosan and methyl triclosan measured in prey fish were below available toxicity thresholds for triclosan, but there are few ecotoxicological studies to evaluate impacts of methyl triclosan. Methyl triclosan represented up to 96% of the total concentrations observed. These results emphasize the importance of monitoring contaminant transformation products, which can be present at higher levels than the parent compound. Environ Toxicol Chem 2023;42:620-627. © 2023 SETAC.

Growth, ROS accumulation site, and photosynthesis inhibition mechanism of Chlorella vulgaris by triclosan

Although the addition of triclosan (TCS) in consumer products has been strictly restricted, its continuous applications in hospitals and other medical facilities and its numerous residues still pose a potential risk to aquatic organisms and aquatic ecosystems. In this study, we investigated the growth, biochemical alterations, and physiological responses of Chlorella vulgaris exposed to different concentrations of TCS. The potential toxicity mechanisms associated with excessive production of reactive oxygen species (ROS) and disruption of photosynthetic system II (PSII) were also analyzed. The results indicated that the growth, cellular ultrastructure, and physiology of C. vulgaris were severely affected by TCS in a dose-effect dependent manner. TCS inhibited the growth of C. vulgaris, leading to mitochondria enlargement, the disordering of the arrangement of thylakoids, cell wall rupture, organelles loss, and the cytoplasm lysis. TCS induced severe oxidative damage characterized by ROS accumulation, elevated malondialdehyde (MDA), and up-regulation of antioxidant enzyme activities. Moreover, in TCS-induced algal cells, the main sites of ROS accumulation were chloroplasts, mitochondria, and cell membranes, with ROS accumulating most in the mitochondria. In addition, TCS caused damage to the reaction center (RC inactivation), donor side (OEC damage), and accepted side (electron transport from Q_A to Q_B) of PSII in C. vulgaris, leading to inhibition of photosynthetic activity. These results could provide novel insights into the mechanisms of TCS-induced ROS accumulation and photosynthetic inhibition in C. vulgaris, which would contribute to a deep understanding of TCS toxicity on algae.

Occurrence and distribution of triclosan and its transformation products in Taihu Lake, China

The transformation products of triclosan (5-chloro-2-(2,4-dichlorophenoxy)phenol) may be more persistent and toxic than their parent compound, yet their occurrence in aquatic environments is poorly understood. In this study, we identified three transformation products in sediment samples from Taihu Lake and compared their concentrations with the parent compound triclosan. Triclosan in Taihu Lake was at low level, ranging from 0.086 to 1.1 ng/L in surface water and 0.0058-8.3 ng/g in sediments. The three detected transformation products included methyl triclosan, chlorinated triclosan derivatives, and methyl chlorinated triclosan derivatives. Those transformation products constituted 0.73-87.5% of the total triclosan (total triclosan is the sum of triclosan, methyl triclosan, chlorinated triclosan derivatives, and methyl chlorinated triclosan derivatives on a molar basis), indicating that the ecological risk of transformation products should be considered in addition to the parent compound. Different transformation products had distinct spatial distributions. Chlorinated triclosan derivatives had the highest concentration in samples from the northwest region (0.016-0.21 ng/g) of the lake and were positively correlated with triclosan, which may indicate the possible transformation from triclosan to chlorinated triclosan derivatives. Methyl triclosan and methyl chlorinated triclosan derivatives were generally higher in samples from the center of the lake (0.22-0.28 ng/g for methyl triclosan and 0.017-0.021 ng/g for methyl chlorinated triclosan derivatives, respectively), indicating the possible occurrence of in situ microbial methylation of triclosan and chlorinated triclosan derivatives and the accumulation of those methylated analogues in Taihu Lake.

Laccase-assisted degradation of emerging recalcitrant compounds - A review

The main objective of this review is to provide up to date, brief, irrefutable, organized data on the conducted experiments on a range of emerging recalcitrant compounds such as Diclofenac (DCF), Chlorophenols (CPs), tetracycline (TCs), Triclosan (TCS), Bisphenol A (BPA) and Carbamazepine (CBZ). These compounds were selected from the categories of pharmaceutical contaminants (PCs), endocrine disruptors (EDs) and personal care products (PCPs) on the basis of their toxicity and concentration retained in the environment. In this context, detailed mechanism of laccase mediated degradation has been conversed that laccase assisted degradation occurs by one electron oxidation involving redox potential as underlying element of the process. Further, converging towards biotechnology, laccase immobilization increased removal efficiency, storage and reusability through various experimentally conducted studies. Laccase is being considered noteworthy as mediators facilitate laccase in oxidation of non-phenolic compounds and thereby increasing its substrate range which is being discussed in further in the review. The laccase assisted degradation mechanism of each compound has been elucidated but further studies to undercover proper degradation mechanisms needs to be performed.

Triclosan uptake and transformation by the green algae Euglena gracilis strain Z

Triclosan is an antimicrobial chemical present in consumer products that is frequently detected in aquatic environments. In this research, we investigated the role of a common freshwater microalgae species, Euglena gracilis for triclosan uptake and transformation in open-water treatment wetlands. Lab-scale wetland bioreactors were created under various conditions of light (i.e., continuous (white) light, red light, and in the dark), media (i.e., wetland, autoclaved wetland, Milli-Q, and growth media water), and presence or absence of algae. Triclosan and its potential transformation products were identified in the water and algae phases. Triclosan transformation occurred most rapidly with reactors that received continuous (white) light, with pseudo first-order rate constants, k, ranging from 0.035 to 0.292 day^-1. This indicates that phototransformation played a major role in triclosan transformation during the day, despite light screening by algae. Algae contributed to the uptake and transformation of triclosan in all reactors, and algae and bacteria both contributed to triclosan biotransformation under dark conditions, representative of nighttime conditions. Some transformation products were formed and further transformed, e.g., triclosan-O-sulfate, methoxy and diglucosyl conjugate of hydroxylated triclosan, and dimethoxy and glucosyl conjugate of 2,4-dichlorophenol, suggesting their minimal accumulation over the 25 days of the experiments. This study shows that the combined action of light, microbes, and algae allows the safe transfer and transformation of triclosan in open-water treatment wetlands.

Removal of Carbamazepine in Aqueous Solution by CoS2/Fe2+/PMS Process

Carbamazepine (CBZ), as a typical pharmaceutical and personal care product (PPCP), cannot be efficiently removed by the conventional drinking water and wastewater treatment process. In this work, the CoS2/Fe2+/PMS process was applied for efficient elimination of CBZ. The CBZ removal efficiency of CoS2/Fe2+/PMS was 2.5 times and 23 times higher than that of CoS2/PMS and Fe2+/PMS, respectively. The intensity of DMPO-HO• and DMPO-SO4•− followed the order of Fe2+/PMS < CoS2/PMS < CoS2/Fe2+/PMS, also suggesting the CoS2/Fe2+/PMS process has the highest oxidation activity. The effects of reaction conditions (e.g., CoS2 dosage, Fe2+ concentration, PMS concentration, initial CBZ concentration, pH, temperature) and water quality parameters (e.g., SO42−, NO3−, H2PO4−, Cl−, NH4+, humic acid) on the degradation of CBZ were also studied. Response surface methodology analysis was carried out to obtain the best conditions for the removal of CBZ, which are: Fe2+ = 70 µmol/L, PMS = 240 µmol/L, CoS2 = 0.59 g/L. The sustainability test demonstrated that the repeated use of CoS2 for 8 successive cycles resulted in little function decrease (<10%). These findings suggest that CoS2/Fe2+/PMS may be a promising method for advanced treatment of tailwater from sewage treatment plant.

A comprehensive review on current technologies for removal of endocrine disrupting chemicals from wastewaters

In the recent years, endocrine disrupting compounds (EDCs) has received increasing attention due to their significant toxic effects on human beings and wildlife by affecting their endocrine systems. As an important group of emerging pollutant, EDCs have been detected in various aquatic environments, including surface waters, groundwater, wastewater, runoff, and landfill leachates. Their removal from water resources has also been an emerging concern considering growing population as well as reducing access to fresh water resources. EDC removal from wastewaters is highly dependent on physicochemical properties of the given EDCs present in each wastewater types as well as various aquatic environments. Due to chemical, physical and physicochemical diversities in these parameters, variety of technologies consisting of physical, biological, electrochemical, and chemical processes have been developed for their removal. This review highlights that the effectiveness of EDC removal is highly dependent of selecting the appropriate technology; which decision is made upon a full wastewater chemical characterization. This review aims to provide a comprehensive perspective about all the current technologies used for EDCs removal from various aquatic matrices along with rising challenges such as the antimicrobial resistance gene transfer during EDC treatment.

Delineating the impact of COVID-19 on antimicrobial resistance: An Indian perspective

The COVID-19 pandemic has shattered millions of lives globally and continues to be a challenge to public health due to the emergence of variants of concern. Fear of secondary infections following COVID-19 has led to an escalation in antimicrobial use during the pandemic, while some antimicrobials have been repurposed as treatments for SARS-CoV-2, further driving antimicrobial resistance. India is one of the largest producers and consumers of antimicrobials globally, hence the task of curbing antimicrobial resistance is a huge challenge. Practices like empirical antimicrobial prescription and repurposing of drugs in clinical settings, self-medication and excessive use of antimicrobial hygiene products may have negatively impacted the prevalence of antimicrobial resistance in India. However, the expanded production of antimicrobials and disinfectants during the pandemic in response to increased demand may have had an even greater impact on the threat of antimicrobial resistance through major impacts on the environment. The review provides an outline of the impact COVID-19 can have on antimicrobial resistance in clinical settings and the possible outcomes on the environment. This review calls for the upgrading of existing antimicrobial policies and emphasizes the need for research studies to understand the impact of the pandemic on antimicrobial resistance in India.

Research on freshwater water quality criteria, sediment quality criteria and ecological risk assessment of triclosan in China

Triclosan (TCS) is a broad-spectrum antimicrobial agent commonly used in pharmaceuticals and personal care products (PPCPs). The widespread use of TCS makes it frequently detected in various environmental mediums. In view of the high detection frequency of TCS in the aquatic environment and sediments, and its toxic effects on aquatic species, it is critical and necessary to derive Chinese TCS water quality criteria (WQC) and sediment quality criteria (SQC) for protecting Chinese aquatic organisms, and perform the ecological risk assessment. In fact, former research had derived the WQC of TCS mainly based on acute and chronic toxicity data. As an endocrine disrupting chemical (EDC), TCS poses adverse effects on the growth, development and reproduction of aquatic organisms at much lower concentration. Considering nonlethal endpoints are sensitive endpoints for EDCs, TCS long-term water quality criteria (LWQC) was derived based on reproduction and growth related endpoints. In this work, the acute toxicity data of 19 aquatic organisms and the chronic toxicity data of 15 aquatic organisms were obtained through collection and screening. The best fitting model of species sensitivity distribution (SSD) models including Normal, Log-Normal, Logistic and Log-Logistic of toxicity data was selected to derive WQC. The short-term and long-term WQC of TCS for Chinese aquatic organisms were 6.22 μg/L and 0.25 μg/L, respectively. Furthermore, through the phase-equilibrium partitioning method, SQC was derived based on WQC. SQC-low (SQC-L) and SQC-high (SQCH) were 0.13 mg/kg and 3.26 mg/kg, respectively. Moreover, the exposure concentration (EPC) data of TCS in Chinese rivers and sediments were collected. And through the hazard quotient (HQ) method and the joint probability curve (JPC) method we found that there were certain TCS ecological risks in Chinese rivers and sediments. Our work will provide a valuable reference for protecting aquatic organisms and minimizing TCS ecological risk in China.

Characterization of the effects of triclosan on sperm and embryos of Mytilus and Perna mussel species

The Greenshell™ mussel (GSM), Perna canaliculus, is a culturally and commercially important species in New Zealand. Declines in spat settlement of GSM have been observed in important growing areas and the cause(s) have not been identified. One hypothesis is that chemical contaminants could be a contributing factor. The aim to this study was to investigate the effects of acute exposure on early life stages using the anti-microbial triclosan (TCS) as a benchmark toxicant and the blue mussel (BM), Mytilus galloprovincialis, as a reference species. Sperm and embryos of BM and GSM were exposed to TCS for 1 h and 48 h, respectively. Following exposures, a range of parameters were investigated including spermatozoa cellular characteristics via flow cytometry, fertilization success, larval mortality and size. Exposure to TCS negatively impacted functional parameters of sperm, reduced the fertilization success and larval size, and increased larval mortality in both BM and GSM with LC50_48h of 94.3 and 213 µg L^-1, respectively. Triclosan increased sperm ROS production in both species, which could cause destabilisation of mitochondrial and other cellular membranes, resulting in reduced mitochondrial membrane potential (BM) and increased sperm size (GSM), leading to apoptosis in both species. Fertilization success of GSM was only affected at the highest TCS concentration tested (391 µg L^-1), but development of larvae derived from exposed sperm was affected from the lowest concentrations tested (0.5 and 5.2 µg L^-1) in both species. This highlights the importance of assessing the sensitivity of contaminants across developmental stages. Results of this study confirm that TCS causes oxidative stress and has membranotropic effects, and that early life stages of the endemic GSM are suitable to assess ecotoxicity of contaminants such as TCS.

Watershed-Scale Risk to Aquatic Organisms from Complex Chemical Mixtures in the Shenandoah River

River waters contain complex chemical mixtures derived from natural and anthropogenic sources. Aquatic organisms are exposed to the entire chemical composition of the water, resulting in potential effects at the organismal through ecosystem level. This study applied a holistic approach to assess landscape, hydrological, chemical, and biological variables. On-site mobile laboratory experiments were conducted to evaluate biological effects of exposure to chemical mixtures in the Shenandoah River Watershed. A suite of 534 inorganic and organic constituents were analyzed, of which 273 were detected. A watershed-scale accumulated wastewater model was developed to predict environmental concentrations of chemicals derived from wastewater treatment plants (WWTPs) to assess potential aquatic organism exposure for all stream reaches in the watershed. Measured and modeled concentrations generally were within a factor of 2. Ecotoxicological effects from exposure to individual components of the chemical mixture were evaluated using risk quotients (RQs) based on measured or predicted environmental concentrations and no effect concentrations or chronic toxicity threshold values. Seventy-two percent of the compounds had RQ values <0.1, indicating limited risk from individual chemicals. However, when individual RQs were aggregated into a risk index, most stream reaches receiving WWTP effluent posed potential risk to aquatic organisms from exposure to complex chemical mixtures.

Exposure to a mixture of benzo[a]pyrene and triclosan induces multi-and transgenerational metabolic disorders associated with decreased female investment in reproduction in Silurana (Xenopus) tropicalis

Animals must partition limited resources between their own growth and subsequent reproduction. Endocrine disruptors (ED) may cause maternal metabolic disorders that decrease successful reproduction and might be responsible for multi- and transgenerational effects in amphibians. We found that the frog Silurana (Xenopus) tropicalis, exposed to environmentally relevant concentrations of benzo[a]pyrene and triclosan throughout its life cycle, produced F1 females with delayed sexual maturity and decreased size and weight. These F1 females displayed a marked metabolic syndrome associated with decreased fasting plasma cholesterol and triglyceride concentrations and decreased gonadal development. F1 females from F0 exposed animals also had decreased reproductive investment highlighted by a decrease of oocyte lipid reserves associated with significant F2-tadpole mortality. F2 females from F0 exposed animals also displayed a marked metabolic syndrome but were able to correctly direct liver lipid metabolism to the constitution of fat bodies and oocyte yolk stores. In addition, the F2 females produced progeny that had normal mortality levels at 5 days post hatching compared to the controls suggesting a good reproductive investment. Our data confirmed that these ED, at concentrations often found in natural ponds, can induce multi- and transgenerational metabolic disorders in the progeny of amphibians that are not directly exposed. We present a hypothesis to explain the transmission of the metabolic syndrome across generations through modification of egg reserves. However, when high mortality occurred at the tadpole stage, surviving females were able to cope with metabolic costs and produce viable progeny through sufficient investment in the contents of oocyte reserves.

Biomarkers-based assessment of triclosan toxicity in aquatic environment: A mechanistic review

Triclosan (TCS), an emergent pollutant, is raising a global concern due to its toxic effects on organisms and aquatic ecosystems. The non-availability of proven treatment technologies for TCS remediation is the central issue stressing thorough research on understanding the underlying mechanisms of toxicity and assessing vital biomarkers in the aquatic organism for practical monitoring purposes. Given the unprecedented circumstances during COVID 19 pandemic, a several-fold higher discharge of TCS in the aquatic ecosystems cannot be considered a remote possibility. Therefore, identifying potential biomarkers for assessing chronic effects of TCS are prerequisites for addressing the issues related to its ecological impact and its monitoring in the future. It is the first holistic review on highlighting the biomarkers of TCS toxicity based on a comprehensive review of available literature about the biomarkers related to cytotoxicity, genotoxicity, hematological, alterations of gene expression, and metabolic profiling. This review establishes that biomarkers at the subcellular level such as oxidative stress, lipid peroxidation, neurotoxicity, and metabolic enzymes can be used to evaluate the cytotoxic effect of TCS in future investigations. Micronuclei frequency and % DNA damage proved to be reliable biomarkers for genotoxic effects of TCS in fishes and other aquatic organisms. Alteration of gene expression and metabolic profiling in different organs provides a better insight into mechanisms underlying the biocide's toxicity. In the concluding part of the review, the present status of knowledge about mechanisms of antimicrobial resistance of TCS and its relevance in understanding the toxicity is also discussed referring to the relevant reports on microorganisms.

Multibiomarker responses in Danio rerio after exposure to sediment spiked with triclosan

Triclosan (TCS) is an antimicrobial and antimycotic agent widely used in personal care products. In aquatic environments, both TCS and its biomethylated more persistent form, methyl-triclosan (MeTCS), are usually detected in wastewater effluents and rivers, where are commonly adsorbed to suspended solids and sediments. The aim of this study was to evaluate biochemical and physiological effects in Danio rerio after a short term (2 days) and prolonged (21 days) exposures to sediment spiked with TCS acting as the source of the pollutant in the assay. The activities of catalase (CAT), glutathione-s transferase (GST) and superoxide dismutase (SOD), lipid peroxidation levels (LPO), total capacity against peroxyl radicals (ACAP), and acetylcholinesterase enzymatic activity (AChE) were measured in liver, gills, and brain. Most of TCS on the spiked sediment was biotransformed to MeTCS and promoted different adverse effects on D. rerio. Gills were the most sensitive organ after 2 day-exposure, showing lipid damage and increased SOD activity. After 21 days of exposure, liver was the most sensitive organ, showing lower ACAP, increased LPO levels, and SOD and CAT activities. This is the first study reporting the effects on biochemical markers in D. rerio from a MeTCS sink resulting from sediment spiked with TCS.

Ecotoxicogenomic analysis of zebrafish embryos exposed to triclosan and mixture triclosan and methyl triclosan using suppression subtractive hybridization and next-generation sequencing

Triclosan (TCS) and methyl-triclosan (MTCS), an environmental transformation product of biocide of TCS, have been detected in water, sediment, fish, and invertebrates. In this study, the key pathway perturbation in zebrafish (Danio rerio) embryos exposed to TCS (300 μg/L) and TCS/MTCS mixture (300 μg/L TCS + 30 μg/L MTCS) was assessed by integrating the metabolomic and transcriptomic dysregulation. The differential expressed genes (DEGs) were obtained from the subtracted cDNA libraries by using the suppression subtractive hybridization and next-generation sequencing approach. The dysregulation of twenty-eight GO terms and four KEGG pathways, including oxidative phosphorylation and cardiac muscle contraction, were shown in the TCS treatment group, indicating that TCS could disrupt the mitochondrial inner membrane function by downshifting the electrochemical gradient. Meanwhile, the addition of MTCS in the exposure would cause fourteen additional significant KEGG pathway changes, demonstrating the different effects between two exposure. A pathway-based analysis using the identified DEGs and the altered metabolites in zebrafish embryos treated with TCS and TCS/MTCS mixture, collectively, has been applied. This study demonstrated that the integration of SSH-NGS and metabolomics could reveal toxic effects and potential diseases associated with the exposures of TCS and MTCS in aquatic environments.

Evaluation of Triclosan-induced reproductive impairments in the accessory reproductive organs and sperm indices in the mice

Highly effective antimicrobial properties of triclosan (TCS) make its use as a widely used preservative in different types of consumer products. TCS is reported as an emerging endocrine disruptor causing reproductive impairments in the males as well as in the females. The present study describes the adverse effects of various doses of TCS (40, 80, 160 and 320 mg/kg BW/day, for 42 consecutive days) on the weights and histopathology of the epididymis and seminal vesicle, sperm indices (motility, viability, count and morphology), concentrations of epididymal sialic acid and seminal vesicular fructose, along with TCS accumulated in these accessory reproductive organs of the laboratory mouse. TCS induced significant reductions in the weights of the epididymis and seminal vesicle along with noticeable histopathological alterations in these organs. TCS caused significant reductions in the count, percentage of motile and viable spermatozoa while a significant increase in the percentage of abnormal spermatozoa in the epididymis. Concentrations of epididymal sialic acid and seminal vesicular fructose declined significantly in the treated mice. A significant increase was noticed in the concentration of TCS, accumulated in the epididymis and seminal vesicle following TCS exposure at a high dose (320 mg/kg BW/day). The results thus suggest that the accessory sex organs are also affected deleteriously following TCS exposure, leading to impairment in the male reproductive health.

Degradation of triclosan by anodic oxidation/in-situ peroxone process: Kinetics, pathway and reaction mechanism

Triclosan (TCS) is an emerging contaminant that threatens the environment and human health. This study was conducted to investigate TCS abatement by a novel electro-oxidation (EO) process, which used a Ti-based nickel and antimony doped tin oxide (NATO/Ti) anode and a carbon nanotubes (CNTs) doped carbon/PTFE (CNTs-C/PTFE) gas diffusion electrode (GDE) for oxygen reduction reaction (ORR). A comparative study was also performed for TCS degradation by using a traditional EO with a nickel foam cathode, termed as HER-EO. The optimal initial TCS concentration, current density and solution pH for TCS degradation during the ORR-EO and HER-EO were investigated. Results showed that ORR-EO removed more than 98% of TCS in 10-60 min under the concentration of 5-50 mg/L. The TCS degradation followed pseudo-first-order kinetics and its main intermediates were observed during the ORR-EO and HER-EO using liquid chromatography combined mass (LC-MS). The results of FED analysis and toxicity prediction by ECOSAR software showed that less intermediates accumulated during the ORR-EO and the residues were less harmful. The ORR-EO degradation mechanism for TCS was attacking on the ether bond and the benzene ring by ^•OH. This novel ORR-EO process exhibits a great merit in the field of emerging contaminants abatement.

Microplastics can act as vector of the biocide triclosan exerting damage to freshwater microalgae

Despite the large number of recent studies on microplastics (MPs) and their ability to act as carriers of pollutants, the knowledge about the biological effects of MPs loaded with chemicals is scarce. The aim of this study was to evaluate the potential of MPs as vectors for the antimicrobial triclosan (TCS). For it, we tested low-density polyethylene (LDPE), polyamide (PA), polyethylene terephthalate (PET), polyoxymethylene (POM), polypropylene (PP), polystyrene (PS) and the biodegradable polylactic acid (PLA). Thus, chemical analysis of sorption and desorption of TCS by these MPs was evaluated. The effect of TCS-loaded MPs to Anabaena sp. PCC7120, a cyanobacterium model of primary producers in freshwater ecosystems, was investigated. Chemical analyses showed different capacity of sorption depending on the MP type, which was related to some of their physicochemical properties. PA (104.7 μg/g), POM (57.4 μg/g) and LDPE (18.3 μg/g) were the polymers that sorbed the highest amounts of TCS. Glass transition temperature of polymers and their physicochemical interaction with TCS explained the extent of sorption. Significant decreases were found in growth, 22.3%, 94.6% and 81.0%, and chlorophyll a content, 58.4%, 95.0% and 89.6%, of Anabaena when exposed to TCS-loaded LDPE, PA and POM beads, respectively, which were the only MPs displaying significant sorption-desorption of TCS, implying that these MPs could act as vectors of TCS towards freshwater microalgae. This finding is of fundamental relevance as microalgae are at the base of the aquatic trophic chain and support growth of upper organisms.

Environmental Distribution of Personal Care Products and Their Effects on Human Health

Personal care products (PCPs) are generally used for personal hygiene, cleaning, grooming, and beautification. These include hair and skin care products, baby care products, UV blocking creams, facial cleansers, insect repellents, perfumes, fragrances, soap, detergents, shampoos, conditioners, toothpaste, etc., thus exposing humans easily. Personal preferences related to PCPs usage frequency are highly variable and depend on socioeconomic status and lifestyle factors. The increasing availability and diversity of PCPs from the retailer outlets consequently result in higher loading of PCPs into wastewater systems and, therefore, the environment. These compounds persistently and continuously release biologically active and inactive ingredients in the atmosphere, biosphere, geosphere, and demonstrating adverse effects on human, wild, and marine life. Advanced techniques such as granular activated carbon filtration and algae-based system may help biotransformation and remove PCP contaminants from water with improved efficiency. Additionally, harmony among PCPs related regulations of different countries may encourage standard checks to control their manufacturing, sale, and distribution across the borders to ensure consumers' safety. Furthermore, all intended ingredients, their concentrations, and instructions for frequency of use as per age groups may be clearly labeled on packages of PCPs. In conclusion, the emerging environmental contaminants of PCPs and their association with the growing risks of negative effects on human health and globally on the environment emphasize the chemical-free simple lifestyle.

Toxicity evaluation and by-products identification of triclosan ozonation and chlorination

Triclosan (TCS) has attracted increasing concern due to its ubiquitous occurrence in aquatic environments as well as its potential adverse effects on human health. This study investigated the toxicity and transformation characteristics of triclosan ozonation and chlorination. The results showed that two hydroxylated by-products were formed via nucleophilic substitution during ozonation, while three chlorinated compounds were generated via electrophilic substitution during chlorination. The toxicity results demonstrated that the parent compound, triclosan, exhibited mild genotoxicity and anti-estrogenic activity. The chlorination of triclosan resulted in a 30-fold increase in anti-estrogenic activity owing to the generation of toxic polychlorinated transformation by-products. In addition, the chlorination by-products were found to be genotoxic like the parent compound. Fortunately, in contrast to chlorination, ozonation could mitigate the genotoxicity and anti-estrogenic activity of triclosan-containing water.

A Review on the Fate of Legacy and Alternative Antimicrobials and Their Metabolites during Wastewater and Sludge Treatment

Antimicrobial compounds are used in a broad range of personal care, consumer and healthcare products and are frequently encountered in modern life. The use of these compounds is being reexamined as their safety, effectiveness and necessity are increasingly being questioned by regulators and consumers alike. Wastewater often contains significant amounts of these chemicals, much of which ends up being released into the environment as existing wastewater and sludge treatment processes are simply not designed to treat many of these contaminants. Furthermore, many biotic and abiotic processes during wastewater treatment can generate significant quantities of potentially toxic and persistent antimicrobial metabolites and byproducts, many of which may be even more concerning than their parent antimicrobials. This review article explores the occurrence and fate of two of the most common legacy antimicrobials, triclosan and triclocarban, their metabolites/byproducts during wastewater and sludge treatment and their potential impacts on the environment. This article also explores the fate and transformation of emerging alternative antimicrobials and addresses some of the growing concerns regarding these compounds. This is becoming increasingly important as consumers and regulators alike shift away from legacy antimicrobials to alternative chemicals which may have similar environmental and human health concerns.

Rapid destruction of triclosan by Iron(III)-Tetraamidomacrocyclic ligand/hydrogen peroxide system

Iron(III)-tetraamidomacrocyclic ligand (Fe(III)-TAML) activators can activate hydrogen peroxide to oxidize many kinds of organic pollutants. In this study, we investigated the degradation of triclosan, a widely used broad-spectrum bactericide, under the treatment of Fe(III)-TAML/H₂O₂ system at different pH conditions. We also studied the influence of natural organic matter (NOM) on the degradation process. Our results showed that complete removal of triclosan could be obtained within several minutes under the optimal conditions. The degradation of triclosan by Fe(III)-TAML/H₂O₂ system exhibited strong pH-dependence and the degradation rate increased with the increase in pH level from 7.0 to 10.0. When adding fulvic acid (FA) or humic acid (HA) in the reaction system, the degradation of triclosan could be suppressed slightly, and HA exhibited stronger inhibition than FA. Based on the analysis of reaction intermediates, phenoxyl radical reaction and ring open reaction were involved in the decomposition of triclosan. Significant inhibition of overall toxicity to Photobacterium phosphoreum further confirmed the high efficiency of Fe(III)-TAML/H₂O₂ system for the removal of antibiotic activities resulting from the parent triclosan molecule and its degradation products.

Linking Triclosan's Structural Features to Its Environmental Fate and Photoproducts

Triclosan is a high-production volume chemical, which has become widely detected in environmental systems because of its widespread usage. Photodegradation has been identified as a major degradation pathway, but the identified photoproducts are also chemicals of concern. In this study, lower chlorinated derivatives of triclosan were synthesized to investigate the impact the chlorine substituents have on the photodegradation rate and the photoproducts produced. In addition, the photodegradation of two classes of photoproducts-dibenzo-p-dioxins (DDs) and 2,2'-dihydroxylated biphenyls-was also investigated. Degradation of triclosan in near-surface sunlit waters was relatively fast (t_1/2 < 5 h). Calculated degradation rates were slower for DDs and faster for dihydroxylated biphenyls in comparison to that for triclosan. In addition, the 2'-Cl substituent was critical for the high quantum yield measured for triclosan and necessary for the photodegradation mechanism that forms DDs and dihydroxylated biphenyls. The 4-Cl substituent was responsible for higher rates of light absorption and the environmentally relevant pK_a. Without either of these substituents, the environmental fate of triclosan would be markedly different.

Organic Micropollutants in Wastewater Effluents and the Receiving Coastal Waters, Sediments, and Biota of Lyttelton Harbour (Te Whakaraupō), New Zealand

Coastal ecosystems are receiving environments for micropollutants due to high levels of associated anthropogenic activities. Effluent discharges from wastewater treatment plants are a significant source of micropollutants to coastal environments. Wastewater effluents, seawater, sediments, and green-lipped mussels (Perna canaliculus) in Lyttelton Harbour (Te Whakaraupō), Christchurch, New Zealand, were analysed for a suite of personal care products and steroid hormones during a 1-year period. In wastewater effluents, the concentration of methyl paraben (mParaben), ethyl paraben (eParaben), propyl paraben (pParaben), butyl paraben (bParaben), 4-t-octylphenol (OP), 4-methylbenzylidene camphor (4-MBC), benzophenone-3 (BP-3), benzophenone-1 (BP-1), triclosan, methyl triclosan (mTric), Bisphenol A (BPA), Estrone (E1), 17β-estradiol (E2), 17α-ethinyl estradiol (EE2), and Estriol (E3) ranged from < 0.6 to 429 ng L^-1 and was dominated by OP, 4-MBC, BP-3, triclosan, BP-1, and BPA. In seawater, 4-MBC, BP-3, BPA, and E1 were the most frequently detected contaminants (< 0.2-9.4 ng L^-1). Coastal sediment samples contained mParaben, OP, 4-MBC, BP-3, BP-1, BPA, OMC, and E1 (< 0.2-11 ng g^-1 d.w.), and mParaben, OP, and BP-3 were found to bioaccumulate (3.8-21.3 ng g^-1 d.w.) in green lipped mussels.

Halogenated organic contaminants of concern in urban-influenced waters of Lake Ontario, Canada: Passive sampling with targeted and non-targeted screening

Passive samplers are useful tools for monitoring hydrophobic, persistent, and potentially bioaccumulative contaminants in the environment. In this study, low density polyethylene passive samplers were deployed in urban-influenced and background nearshore freshwaters of northwestern Lake Ontario and analyzed for a broad range of both legacy halogenated organic contaminants (HOCs) and halogenated flame retardants (HFRs). Non-targeted analysis was conducted for screening additional halogenated substances. For most compounds, concentrations were greatest in the industrialized Hamilton Harbour and more generally at sites that have stronger influences of wastewater effluent discharges and stormwater run-off through rivers and creeks. Polychlorinated biphenyls (PCBs) remain the dominant class of HOCs in water, with dissolved-phase concentrations ranging from 10 to 4100 pg/L (ΣPCBs), followed by polybrominated diphenylethers (ΣPBDEs; 14-960 pg/L) and the organochlorine pesticides (OCPs; 22-290 pg/L). Several non-PBDE brominated flame retardants (nBFRs) and chlorinated Dechlorane-related compounds were detected, with hexabromocyclododecanes (ΣHBCDD; sum of 3 diastereoisomers) the most abundant (1.0-21 pg/L). Non-targeted screening of samples by high resolution mass spectrometry using Kendrick mass defect plots for data analysis indicated that several other halogenated compounds were present in waters at relatively high abundances compared to the flame retardants, based on semi-quantitative estimates. These included methyl-triclosan, four halogenated anisoles (2,4,6-tribromoanisole, dimethyl-trichloroanisole, pentachloroanisole, and pentachlorothioanisole), and pentachloro-aniline. Dissolved-phase methyl-triclosan was estimated to contribute up to approximately 40% of the summed target HOC concentrations. Polyethylene passive samplers provided an excellent medium for both non-targeted screening of HOCs not currently included in monitoring programs and tracking brominated and chlorinated chemicals slated for reductions in uses and emissions through international (Stockholm Convention) and binational (Great Lakes) agreements.

The role of PFOS on triclosan toxicity to two model freshwater organisms

Surface-active substances may enhance the bioavailability of certain pollutants by modifying the permeability of cell membranes. However, they could also interact in a positive manner by increasing toxicity to aquatic organisms. A comparative effects assessment of waterborne exposure to triclosan (TCS) alone vs. combined with perfluorooctanesulfonic acid (PFOS) was herein investigated in daphnids (Daphnia magna) and medaka (Oryzias latipes) early life stages (ELS) using a battery of non-invasive behavioral, physiological and anatomical endpoints. Additionally, TCS bioaccumulation was evaluated in medaka embryos to help discern differences in effects caused by either, changes in TCS permeability or by a positive interaction with PFOS. The TCS analytical measurements in the medaka ELS exposure media revealed fast dissipation with half-lives < 12 h. The D. magna immobilization and feeding inhibition assays suggested an increased response when TCS (≥200 and 37.50 μg/L, respectively) was co-exposed with PFOS. Concentrations <800 μg TCS/L did not affect medaka ELS. However, exposures to ≥400 μg TCS/L + PFOS had effects on the embryo and eleutheroembryo viability. The morphometric analysis of the embryonic gallbladder area and the oxidative stress, determined in vivo by the manifestation of reactive oxygen species (ROS), revealed a hormetic response in both experimental sets. The TCS + PFOS experimental set generally resulted in increased gallbladder areas and ROS activity levels compared to those quantified in the corresponding TCS set. The bioaccumulation studies in the medaka embryos revealed comparable TCS levels regardless of PFOS presence. Without disregarding any TCS's enhanced bioavailability caused by the surface-active substance, overall results primarily indicate increased biological effects of TCS due to a potentiation action of PFOS as a binary mixture with TCS.

Changes of the acute and chronic toxicity of three antimicrobial agents to Daphnia magna in the presence/absence of micro-polystyrene

The effects of microplastics on aquatic organisms are drawing growing attention, but little has been focused on their effects on the toxicity of other chemicals. In this study, we examined the acute and chronic toxicity of micro-polystyrene (5.8 μm dia.), and its effects on the toxicity of three antimicrobial agents (triclosan, triclocarban and methyl-triclosan) to Daphnia magna. Results indicated that polystyrene had a low acute toxicity with an EC₅₀ of 36.5 mg/L. The presence of polystyrene (1 mg/L) did not produce significant effect on the acute toxicity of three chemicals, because the 95% confidence intervals of their EC₅₀ values had a large overlap of 11.3%-48.3%. For the 21 day chronic toxicity, polystyrene alone had significant toxicity with concentrations of at least 2 mg/L, which prolonged the time of the first brood, limited the number of broods, and reduced the total number of neonates. Compared with the chemicals alone, the addition of polystyrene enhanced their reproduction toxicity. Based on the various reproduction indicators, an intrinsic rate of natural increase (r_m) was calculated to assess the rate of population growth. Results suggested that the r_m values of three chemicals decreased in the presence of PS, and further decreased with increasing PS concentrations. Among the three chemicals, methyl-triclosan was the most affected. These results suggested that the presence of microplastics would exacerbate the detrimental influence of pollutants on Daphnia magna.

Garbage in garbage out: the contribution of our industrial advancement to wastewater degeneration

Natural water sources are habitually marred by insidious anthropogenic practices and municipal wastewater discharges that contain either of xenobiotic pollutants and their sometimes more toxic degradation products, or both. Although wastewater is considered as both a resource and a problem, as explained in this review, it is however daunting that, while the global village is still struggling to decipher the mode of proper handling, subsequent discharge and regulation of already established aromatic contaminants in wastewater, there emanates some more aggressive, stealth and sinister groups of compounds. It is quite ironic that majority of these compounds are the 'go through' consumables in our present society and have been suspected to pose several health risks to the aquatic ecosystem, eliciting unfavourable clinical manifestations in aquatic animals and humans, which has heightened the uncertainties conferred on freshwater use and consumption of some aquatic foods. This review therefore serves to give a brief account on the metamorphosis of approach in detection of aromatic pollutants and ultimately their implications along the trophic chains in the community.

Triclosan-loaded pH-responsive copolymer to target bacteria and to have long bacteriostatic efficacy

It is important to reduce side effects and to explore novel usage for hydrophobic broad-spectrum antibacterial agent triclosan (TCS). In this study, a new amphiphilic copolymer with tertiary amine groups, monomethyl ether poly(ethylene glycol)-b-poly{α-[4-(diethylamino)methyl-1,2,3-triazol]-caprolactone-co-caprolactone} (mPEG-PDCL) was designed and synthesized, and its micelles were applied as carries of TCS to enhance antimicrobial and bacteriostatic action. mPEG-PDCL and its contrastive copolymer mPEG-PCL could form uniform spherical micelles with sizes 50-110 nm. The zeta potential of mPEG-PDCL micelles was positive and changed from 7.00 ± 0.67 mV at pH 7.5 to 24.67 ± 1.23 mV at pH 5.5. Both TCS-loaded micelles displayed quite high drug loading content (approx. 15%) and drug loading efficiency (more than 85%). In comparison with pH 7.4, TCS released faster in acidic environment which was induced by bacteria metabolism. MIC values of both TCS-loaded micelles against S. aureus and E. coli were as low as free TCS. TCS-loaded micelles showed much better antibacterial activity than free TCS, especially, mPEG-PDCL/TCS micelles displayed long bacteriostatic efficacy in 60 h against S. aureus and in 54 h against E. coli. mPEG-PDCL micelles preferred targeting to both S. aureus and E. coli due to positive zeta potential. In in vivo experiment, the purulence of the infected wound almost disappeared for SD rats treated with mPEG-PDCL/TCS micelles. Therefore, mPEG-PDCL micelles may be used as good carriers for antimicrobial agents, and the TCS-loaded micelles possess long antimicrobial/bacteriostatic efficacy.

Fate and impact of pharmaceuticals and personal care products during septage co-composting using an in-vessel composter

The present study aimed at understanding the impact of pharmaceutical and personal care product (PPCP) load on compost dynamics and fate of PPCPs during the composting. In addition, the compost dynamics during single PPCP degradation and multiple PPCPs degradation were investigated. Results revealed that co-composting could degrade the pharmaceutical, carbamazepine (CBZ) up to 83% during single pollutant degradation while it was 66% during multiple pollutant system, at an initial concentration (IC) of 5 mg/kg dw. In case of personal care product, namely triclosan (TCS), single pollutant degradation resulted in 86% removal whereas the removal efficiency was 83% in multiple pollutant system. Relatively high concentration of CBZ showed a negative impact on compost dynamics compared to that of TCS. Higher IC resulted in lower temperature development and relatively lower pollutant removal. The study on pollutant transfer in compost solid surface and in leachate revealed that TCS was not leached out while the leaching of CBZ was significant during composting process. The various transformation products formed during composting were identified and tentative pathways for CBZ and TCS degradation were proposed.

Adsorption of triclosan onto different aged polypropylene microplastics: Critical effect of cations

Adsorption of organic contaminants onto aged microplastics (MPs) may be important in understanding their transport potential and ecological risks in aquatic environment. Cations of Na⁺ and Ca²⁺ are common electrolytes in water, which can greatly influence the adsorption behavior of MPs by impacting the electrostatic interaction between MPs and organic contaminants. The results of this study showed that aged isotactic polypropylene (iPP) MPs exhibited higher adsorption capacity to triclosan (TCS) than pristine ones, and the sorption affinity was enhanced with the increase of ionic concentrations. The crucial influence of cations on the adsorption behavior of aged MPs mainly depended on the changed properties of TCS and interactions between MPs and TCS. Salting out effect induced the precipitation of TCS from water and facilitated the partition of TCS onto MPs in high salinity water. Besides, compressing electrostatic double layer of MPs via squeezing out effect and bridging effect between functional groups of aged MPs and contaminants may also be significant factors in the sorption process. These findings will be helpful for understanding the role of cations on the transport of pollutants, the fate of MPs and their associated environmental risks in aquatic ecosystems.

Critical review on the mechanistic photolytic and photocatalytic degradation of triclosan

The environmentally extended presence of triclosan, TCS, component of many pharmaceutical and personal care products, and its known persistent character have awoke the scientific and social concern leading to the study of effective remediation techniques. Advanced oxidation techniques stand out for the effectiveness in degrading many persistent compounds, and as a result, they have been addressed by many researchers. However, the powerful oxidation media might lead to the formation of undesirable by-products, concern that has also been widely addressed. With regard to the presence of TCS, photolytic and photocatalytic processes provide a very effective degradation yield and rate, with a large number of reports addressing its removal from different environmental matrices. But currently, there is no clear understanding of the mechanisms involved and the routes responsible for the formation of degradation products. Thus, this work presents an exhaustive and critical analysis of the state of the art related to the photo-degradation of TCS, with special focus on the formation of oxidation by-products, on the phenomena responsible and on the influence of operation variables. This report aims at offering valuable information to researchers dealing with this environmentally relevant problem.

Triclosan export from low-volume sources in an urban to rural watershed

Triclosan (TCS), an emerging contaminant linked to antimicrobial resistance, has been the focus of many surface water studies to date. However, these initial studies have predominantly used sampling locations downstream of large volume (i.e., >0.5 million gallons per day) wastewater treatment plants (WWTPs). This approach overlooks potential inputs from their low volume counterparts as well as non-point sources, such as sewage network leaks, biosolid application to agricultural fields and leach fields associated with septic systems. Here we examine the range of concentrations, overall loading, and potential controls on TCS delivery to the East Branch of the Brandywine Creek (EBBC), a rural to suburban watershed located in southeastern Pennsylvania. TCS measurements were collected from 13 locations in the EBBC during baseflow conditions and immediately following a storm event. A regulatory database review identified WWTP density an order of magnitude greater than the national average, thereby confirming their pervasiveness in rural to urban systems. Detectable concentrations of TCS in the EBBC ranged from 0.2 to 0.6 ng/L during baseflow conditions and 0.5 to over 1000 ng/L following a storm event. The lack of a statistical relationship between TCS concentrations and yields with the number of upstream WWTPs and/or volume of treated effluent during both sampling periods confirm the importance of individual WWTP practices and the volume of the receiving water body, while a positive statistically-significant relationship between TCS concentrations and upstream developed open space following the storm event was likely influenced by runoff of spray-applied treated wastewater and/or sewage network leaks. Furthermore, the presence of detectable concentrations of TCS in sub-watersheds with no WWTP systems implies field applied biosolids or treated wastewater, as well as septic tank related leach fields are all viable sources of TCS. These findings suggest we must greatly expand our consideration of sources for emerging contaminants in waterways.

Determination of non-extractable residues in soils: Towards a standardised approach

After exposure of soils to anthropogenic organic chemicals non-extractable residues (NER) can be formed. The quantitative proportion of a compound which remains non-extractable is operationally defined by the extraction procedure employed and can be quantified only when using isotope labelled compounds (e.g. ¹⁴C or ¹³C). In Germany and the EU, there is no standardised procedure, how to determine NER, especially when different legal regulations apply. Consequently, the comparability of NER data is low. Hence, a major task of this study was the development of a general approach for the quantification of non-extractable residues (NER) in soils using radiotracer analysis. For that, extraction efficiencies were determined for 42 non-labelled organic chemicals spiked onto 3 soils applying a number of extraction techniques and conditions, developing an extraction procedure which provides high extraction efficiencies and a low variability for a broad spectrum of analytes. Additionally, NER generated within soil transformation studies according to OECD 307 using ¹⁴C-triclosan, ¹⁴C-fenoxycarb and ¹⁴C-acetaminophen were analysed using sequential batch extraction and pressurised liquid extraction (PLE). Depending on the extraction procedure used, the NER fraction related to ¹⁴C-triclosan in a soil varied greatly between 96% and 28%. In this study a widely universal extraction procedure was developed to improve the comparability of the NER data and limit overestimation of NER, which can be of enormous consequence for the assessment of persistence and environmental risk of organic chemicals. Furthermore, silylation, EDTA-extraction and HCl-treatment were compared regarding a further analysis of NER using radiotracer analysis.

Enhanced degradation of triclosan by cobalt manganese spinel-type oxide activated peroxymonosulfate oxidation process via sulfate radicals and singlet oxygen: Mechanisms and intermediates identification

Spinel is a kind of desirable catalyst to activate peroxymonosulfate (PMS) for chemical oxidation of organic contaminants in wastewater treatment. However, apart from classic sulfate radical based AOPs (SR-AOPs), the generation and oxidative pathways of singlet oxygen (¹O₂) by Co/Mn spinels have been little explored in PMS catalysis. In this study, spinel-type oxide Co₂Mn₁O₄ was successfully synthesized, and used as highly effective catalyst in PMS activation for heterogeneous degradation of TCS (up to 96.4% within 30 min) at initial pH of 6.8, which was also slightly impacted by coexisting ions. Based on radical scavengers and electron paramagnetic resonance (EPR) experiments, sulfate radicals and singlet oxygen (¹O₂) were unveiled to be the dominant reactive oxygen species (ROS) in Co₂Mn₁O₄/PMS system. Co₂Mn₁O₄ catalyst exhibited reversible redox properties based on the results of cyclic voltammetry (CV). More importantly, the generation of ¹O₂ might not only promote the TCS removal rate directly, but also facilitate the metal redox cycle in spinel structure in Co₂Mn₁O₄/PMS system. Finally, degradation pathways of TCS in Co₂Mn₁O₄/PMS system were proposed, which involved the breakage of ether bond and cycloaddition reaction.

Polyelectrolyte Based Sensors as Key to Achieve Quantitative Electronic Tongues: Detection of Triclosan on Aqueous Environmental Matrices

Triclosan (TCS) is a bacteriostatic used in household items that promotes antimicrobial resistance and endocrine disruption effects both to humans and biota, raising health concerns. In this sense, new devices for its continuous monitoring in complex matrices are needed. In this work, sensors, based on polyelectrolyte layer-by-layer (LbL) films prepared onto gold interdigitated electrodes (IDE), were studied. An electronic tongue array, composed of (polyethyleneimine (PEI)/polysodium 4-styrenesulfonate (PSS))₅ and (poly(allylamine hydrochloride/graphene oxide)₅ LbL films together with gold IDE without coating were used to detect TCS concentrations (10⁻¹⁵–10⁻⁵ M). Electrical impedance spectroscopy was used as means of transduction and the obtained data was analyzed by principal component analysis (PCA). The electronic tongue was tested in deionized water, mineral water and wastewater matrices showing its ability to (1) distinguish between TCS doped and non-doped solutions and (2) sort out the TCS range of concentrations. Regarding film stability, strong polyelectrolytes, as (PEI/PSS)_n, presented more firmness and no significant desorption when immersed in wastewater. Finally, the PCA data of gold IDE and (PEI/PSS)₅ sensors, for the mineral water and wastewater matrices, respectively, showed the ability to distinguish both matrices. A sensitivity value of 0.19 ± 0.02 per decade to TCS concentration and a resolution of 0.13 pM were found through the PCA second principal component.

Four typical personal care products in a municipal wastewater treatment plant in China: Occurrence, removal efficiency, mass loading and emission

The occurrence, removal efficiency, mass loading and environmental emission of four categories (benzotriazoles; parabens; antimicrobials; benzophenones) of personal care products were simultaneously determined along the whole process line through an integrated approach (involving both dissolved and adsorbed phase) at a typical wastewater treatment plant in Hunan Province, Southern China. The results showed the prevalence of 13 and 11 target compounds in wastewater and suspended particulate matter, respectively. Twelve substances were detected in the sludge with the mean concentrations ranging from 0.12 to 591.23 ng/g dry weight. Benzotriazoles were the dominant compounds existing in water and antimicrobials were readily being absorbed onto suspended particulate matter and sludge. The overall removal efficiencies of compounds in the total treatment were -84.06%-98.53%. Mass balance results revealed that 85.17%-98.73% of the parabens and benzophenones were removed by degradation, while antimicrobials were removed by being adsorbed onto sludge. However, benzotriazoles could not be efficiently removed and the mass loss was lower than 61.03%. Although ultraviolet radiation played a limited role in removing most target compounds, it still had an impact on removing antimicrobials, 5,6-dimethyl-1H-benzotriazole and 2-hydroxy-4-methoxybenzophenone. The total mass loading and emission of personal care products were 506.35 mg/d/1000 people and 357.56 mg/d/1000 people, respectively. This work would help understand the removal approaches and real pollution of personal care products in the water environment.

Optimizing Constructed Wetlands for Safe Removal of Triclosan: A Box-Behnken Approach

Traditional constructed wetland designs typically result in variable efficiencies for trace organic contaminant removal. In this work, we used a Box-Behnken experimental design for optimizing the conditions of pH, nitrate concentration, and dissolved organic carbon (DOC) concentration that would maximize the rate of triclosan phototransformation while minimizing the accumulation of toxic byproducts. Triclosan is a frequently detected and toxic antimicrobial agent present in many consumer and industrial products. The results showed that high pH values (9.9) and low DOC concentration (11 mg/L^-) would maximize triclosan phototransformation rate while minimizing the accumulation of toxic byproducts. As long as DOC concentrations were larger than 33 mg/L, nitrate concentration did not show a significant effect on triclosan phototransformation rate. The major transformation products detected were 2,4-dichlorophenol and compounds with chemical formulas C₁₂H₈Cl₂O₂ and C₁₂H₉ClO₃, resulting from a chlorine loss or replacement by a OH group. In addition, 4-chlorocatechol was mainly detected during direct photolysis and 2,8-dichlorodibenzo-p-dioxin was only found during direct photolysis at pH 8. This study showed that wetland efficiency at removing triclosan can theoretically be increased by limiting DOC-contributing factors, e.g., emergent vegetation, and supporting pH-increase processes, e.g., via algae growth or by incorporating alkaline geomedia.

Removal of triclosan during wastewater treatment process and sewage sludge composting-A case study in the middle reaches of the Yellow River

Triclosan (TCS) is widely used as an antibacterial disinfectant in personal care products, especially in rapidly-urbanizing countries, such as China. Almost all TCS enters wastewater treatment plants (WWTPs), but the fate of the TCS in the WWTPs is unclear. TCS may be present in sewage sludge or in effluent, and the discharge of TCS into an ecosystem can pose environmental risks. In the present study, influent, effluent, and sewage sludge were collected from four typical urban WWTPs, and the fate of TCS in the plants was investigated. The study was conducted in Zhengzhou, a city in the middle reaches of the Yellow River in China. The sewage sludge was used for aerobic composting to study the influences of different ventilation treatments on the biodegradation effects of TCS and the changes in the microbial community during the composting process. The results showed that the mean concentration of TCS in the influent of the four typical WWTPs was 397.1 ng/L. The mean level of TCS in the effluent was 8.0 ng/L. The mean concentration of TCS in the sewage sludge was 814.4 ng/g. For the four WWTPs, the percentages of TCS removal were 97.6% (Nansanhuan), 97.6% (Xinzheng), 98.8% (Wulongkou), and 97.9% (Chenyu), respectively. The sewage sludge enrichment rates for TCS ranged between 36.4% and 49%. Therefore, there is a need to focus on the environmental risks from sewage sludge. During aerobic composting, the TCS was effectively degraded under three ventilation strategies. Thus, improved ventilation could enhance the degradation rate of TCS. Moreover, TCS degradation occurred in the mesophilic period and in the early stage of the thermophilic phase period. Finally, the degradation rates of TCS in sewage sludge samples composted with low-, medium-, and high-ventilation treatments were 48.1%, 59.0%, and 59.5%, respectively. Thus, high ventilation could provide enough oxygen for the pile and enhanced microorganism activity, benefiting the degradation of TCS. In addition, the microbial communities change during the composting process, and a diversity index of the changes can help explain the composting process.

Mechanisms of pharmaceutical and personal care product removal in algae-based wastewater treatment systems

The widespread distribution of pharmaceuticals and personal care products (PPCPs), particularly in the built environment, has led to increased concern about their effects on both human and ecosystem health. In this research, we investigated the role of algae species Scenedesmus obliquus and Chlorella vulgaris in governing PPCP transfer and transformation mechanisms in algae-containing environments. Lab-scale algal bioreactors were created under various conditions of light, water matrix, and sterilization method to isolate and elucidate reaction mechanisms affecting carbamazepine, ibuprofen, gemfibrozil, and triclosan. The parent compounds and their potential transformation products were analyzed in both the water and algae phases. The results showed that ibuprofen was primarily biotransformed due to synergistic relationships between the algae and the bacteria. Ibuprofen biotransformation products tentatively identified as hydroxy-ibuprofen, carboxy-ibuprofen, and 4-isobutylcatechol were detected in several samples. In all the reactors exposed to light, triclosan underwent both phototransformation and biotransformation. Triclosan biotransformation took place in Scenedesmus obliquus, as demonstrated by the presence of triclosan-O-sulfate in the algae extracts. No evidence of significant carbamazepine and gemfibrozil transfer or transformation was observed under the experimental conditions tested. These results suggest that microalgal-bacterial consortia can facilitate PPCP transformation in algae-based passive water treatment systems.

Concomitant exposure to benzo[a]pyrene and triclosan at environmentally relevant concentrations induces metabolic syndrome with multigenerational consequences in Silurana (Xenopus) tropicalis

Numerous studies suggest that amphibians are highly sensitive to endocrine disruptors (ED) but their precise role in population decline remains unknown. This study shows that frogs exposed to a mixture of ED throughout their life cycle, at environmentally relevant concentrations, developed an unexpected metabolic syndrome. Female Silurana (Xenopus) tropicalis exposed to a mixture of benzo[a]pyrene and triclosan (50 ng·L^-1 each) from the tadpole stage developed liver steatosis and transcriptomic signature associated with glucose intolerance syndrome, and pancreatic insulin hyper secretion typical of pre-diabetes. These metabolic disorders were associated with delayed metamorphosis and developmental mortality in their progeny, both of which have been linked to reduced adult recruitment and reproductive success. Indeed, F1 females were smaller and lighter and presented reduced reproductive capacities, demonstrating a reduced fitness of ED-exposed Xenopus. Our results confirm that amphibians are highly sensitive to ED even at concentrations considered to be safe for other animals. This study demonstrates that ED might be considered as direct contributing factors to amphibian population decline, due to their disruption of energetic metabolism.