Environmental fate of Triclosan in the River Aire Basin, UK

A novel cobalt-iron bimetallic hydrochar for the degradation of triclosan in the aqueous solution: performance, reusability, and synergistic degradation mechanism

Low activation performance is a critical issue limiting the practical application of low-cost biochar in the advanced oxidation. Given the high potential of transition metals in the persulfate activation process and abundant oxygen-containing groups of hydrochar, hydrochar derived from cobalt (Co)-modified iron (Fe)-enriched sludge was synthesized and its performance and activation mechanism for the degradation of triclosan were investigated. Co modification significantly altered the morphology of hydrochar, and the increased Co-Fe mass ratios transformed hydrochar from granular to rose-shaped lamellar and then to helical sheet structures. Specific surface area, defect degree, and oxygen-containing groups of hydrochar increased with increasing cobalt-iron mass ratios. The highest removal of triclosan was up to 98% in the hydrochar/peroxymonosulfate (PMS) system under a wide range of pHs (3-10) and still remained higher than 90% after four cycles. Both Radical (mainly hydroxyl radical) and nonradical pathways (singlet oxygen and electron transfer) were evidenced to play roles in the triclosan removal. Fe3+ promoted the regeneration of Co2+ and realized the efficient circulation of Co3+/Co2+. A ternary system consisting of electron donor (triclosan)-electron mediator (hydrochar)-electron acceptor (PMS) provided channels for electron transfer. No measurable Co and Fe were released during the reaction, and the toxicity of degradation intermediates was lower than that of triclosan. Beside triclosan, rhodamine B, bisphenol A, sulfamethoxazole, and phenol were also almost degraded completely in this oxidation system. This study provides a promising way for the enhancement of catalytic activity of carbonaceous material.

Ecotoxicological effects of triclosan on Lemna minor: bioconcentration, growth inhibition and oxidative stress

Triclosan (TCS), an emerging pollutant, is a notable contributor to adverse impacts on aquatic organisms due to its widespread use during COVID-19 and hydrophobic properties. There is extensive documented literature on TCS toxicity in commercially important fish species; however, studies on aquatic plants remain limited. In this prelude, the present study aims to evaluate the effect of TCS on Lemna minor, a commercially important aquatic plant species for 7 days. The results showed dose-dependent significant alterations in growth, pigments and stress enzymes of L. minor at varied concentrations of TCS (1 to 8 mg L-1). Median inhibitory concentration (IC50) was found to be 4.813 mg L-1. Total chlorophyll and carotenoid levels decreased 73.11 and 81.83%, respectively after 7 days of TCS exposure. A significant increase in catalase and superoxide dismutase activity was observed in TCS exposed groups as compared to the control. Bioconcentration factor was found to be in the range of 5.855 to 37.129 signifying TCS ability to accumulate and transfer through the food chain. Scanning electron microscopy (SEM) analysis showed deformation in the cell surface and alteration of stroma morphology of TCS exposed groups. Furthermore, the Fourier transform infrared spectroscopy (FTIR) study also revealed that higher concentrations of TCS could cause alteration in the functional groups in the plant. This study demonstrates that TCS negatively impacts the growth and metabolism of primary producers, offering crucial insights into its interactions with aquatic plants and establishing baseline information essential for crafting effective mitigation strategies for TCS contamination in aquatic environments.

Ecotoxicological risk assessment of triclosan, an emerging pollutant in a riverine and estuarine ecosystems: A comparative study

Triclosan (TCS), an antibacterial biocide, pervades water and sediment matrices globally, posing a threat to aquatic life. In densely populated cities like Mumbai, rivers and coastal bodies demand baseline TCS data for ecotoxicological assessment due to the excessive use of personal care products comprising TCS. This pioneering study compares spatiotemporal TCS variations and risks in freshwater and marine ecosystems employing multivariate analysis of physicochemical parameters. Over five months (January to May 2022), Mithi River exhibited higher TCS concentrations (water: 1.68 μg/L, sediment: 3.19 μg/kg) than Versova Creek (water: 0.49 μg/L, sediment: 0.69 μg/kg). Principal component analysis revealed positive correlations between TCS and physicochemical parameters. High-risk quotients (>1) underscore TCS threats in both water bodies. This study furnishes crucial baseline data, emphasizing the need for effective treatment plans for TCS in effluent waters released into the adjacent aquatic systems.

Optimized preparation of Ni-Febm bimetallic particles by ball milling NiSO4 and iron powder for efficient removal of triclosan

The excessive usage and emissions of triclosan (TCS) pose a serious threat to aquatic environments. Iron-based bimetallic particles (Pd/Fe, Ni/Fe, and Cu/Fe, etc.) were widely used for the degradation of chlorophenol pollutants. This study proposed a novel synthesis method for the preparation of Ni/Fe bimetallic particles (Ni-Febm) by ball milling microscale zero valent iron ZVI (mZVI) and NiSO4. Ball-milling conditions such as ball-milling time, ball-milling speed and ball-to-powder ratio were optimized to prepare high activity Ni-Febm bimetallic particles. During the ball-milling process, Ni2+ was reduced to Ni0 and formed a coupled structure with ZVI. The amount of Ni0 on ZVI significantly affected the activity of Ni-Febm bimetallic particles. The highest activity Ni-Febm bimetallic particles with Ni/Fe ratio of 0.03 were synthesized under optimized conditions, which could remove 86.56% of TCS (10 μM) in aerobic aqueous solution within 60 min. In addition, higher particle dosage, lower pH condition and higher reaction temperature were more conducive for TCS degradation. The higher corrosion current and lower electron transfer impedance of Ni-Febm bimetallic particles were the main reasons for its high activity. The hydrogen atom (•H) on the surface of Ni-Febm bimetallic particles was mainly contributed to the removal of TCS, as reductive transformation products of TCS were detected by LC-TOF-MS. Notably, a small amount of oxidation products were discovered. The total dechlorination rate of TCS was calculated to be 39.67%. After eight reaction cycles, the residual Ni-Febm bimetallic particles could still degrade 28.34% of TCS within 6 h. Low Ni2+ leaching during reaction indicated that Ni-Febm bimetallic particles did not pose potential environmental risks. The prepared environmental-friendly Ni-Febm bimetallic particles with high activity have great potential in the degradation of other chlorinated organic compounds in wastewater.

Modeling and optimization of triclosan biodegradation by the newly isolated Bacillus sp. DL4: kinetics and pathway speculation

Triclosan is a widely used antibacterial agent and disinfectant, and its overuse endangered ecological safety and human health. Therefore, reducing residual TCS concentrations in the environment is an urgent issue. Bacillus sp. DL4, an aerobic bacterium with TCS biodegradability, was isolated from pharmaceutical wastewater samples. Response surface methodology (RSM) and artificial neural network (ANN) were carried out to optimize and verify the different condition variables, and the optimal growth conditions of strain DL4 were obtained (35 °C, initial pH 7.31, and 5% v/v). After 48 h of cultivation under the optimal conditions, the removal efficiency of strain DL4 on TCS was 95.89 ± 0.68%, which was consistent with the predicted values from RSM and ANN models. In addition, higher R2 value and lower MSE and ADD values indicated that the ANN model had a stronger predictive capability than the RSM model. Whole genome sequencing results showed that many functional genes were annotated in metabolic pathways related to TCS degradation (e.g., amino acid metabolism, xenobiotics biodegradation and metabolism, carbohydrate metabolism). Main intermediate metabolites were identified during the biodegradation process by liquid chromatography-mass spectrometry (LC-MS), and a possible pathway was hypothesized based on the metabolites. Overall, this study provides a theoretical foundation for the characterization and mechanism of TCS biodegradation in the environment by Bacillus sp. DL4.

Global insight into the occurrence, treatment technologies and ecological risk of emerging contaminants in sanitary sewers: Effects of the SARS-CoV-2 coronavirus pandemic

The SARS-CoV-2 pandemic caused changes in the consumption of prescribed/non-prescribed drugs and the population's habits, influencing the detection and concentration of emerging contaminants (ECs) in sanitary sewage and harming environmental and health risks. Therefore, the present work sought to discuss current literature data on the effects of the "COVID-19 pandemic factor" on the quality of raw sewage produced over a five-year period (2018-2019: pre-pandemic; 2020-2022: during the pandemic) and biological, physical, chemical and hybrid treatment technologies, influencing factors in the removal of ECs and potential ecological risks (RQs). Seven hundred thirty-one publications correlating sewage and COVID-19 were identified: 184 pre-pandemic and 547 during the pandemic. Eight classes and 37 ECs were detected in sewage between 2018 and 2022, with the "COVID-19 pandemic factor" promoting an increase in estrogens (+31,775 %), antibiotics (+19,544 %), antiepileptics and antipsychotics (+722 %), pesticides (+200 %), analgesics, anti-inflammatories and anticoagulants (+173 %), and stimulant medications (+157 %) in sanitary sewage. Among the treatment systems, aerated reactors integrated into biomembranes removed >90 % of cephalexin, clarithromycin, ibuprofen, estrone, and 17β-estradiol. The absorption, adsorption, and biodegradation mechanisms of planted wetland systems contributed to better cost-benefit in reducing the polluting load of sewage ECs in the COVID-19 pandemic, individually or integrated into the WWTP. The COVID-19 pandemic factor increased the potential ecological risks (RQs) for aquatic organisms by 40 %, with emphasis on clarithromycin and sulfamethoxazole, which changed from negligible risk and low risk to (very) high risk and caffeine with RQ > 2500. Therefore, it is possible to suggest that the COVID-19 pandemic intensified physiological, metabolic, and physical changes to different organisms in aquatic biota by ECs during 2020 and 2022.

Examining the association between urinary triclosan levels and menopausal status: results from the National Health and Nutrition Examination Survey, 2003 to 2016

OBJECTIVE

To examine the association between urinary levels of triclosan (TCS), a ubiquitous endocrine disrupter, and menopausal status using the National Health and Nutrition Examination Survey.

METHODS

A retrospective cross-sectional study from 2003 to 2016 was conducted among US female participants who completed the reproductive health questionnaire and provided TCS-level measurements. Exposure was assessed by urinary TCS levels adjusted for urinary creatinine; levels were log-transformed to achieve normal distribution for parametric analyses. Menopausal status was based on participants' responses to: "What is the reason that you have not had a period in the past 12 months?" Multivariable linear regression analyses examined the association between creatinine-adjusted urinary TCS levels and menopausal status after adjusting for age at survey completion, body mass index, race, ethnicity, and smoking exposure.

RESULTS

Of the final sample of female participants (n = 6,958), 40% identified as postmenopausal, of whom 60% had experienced natural menopause, and of these, 11% had become menopausal at under 40 years of age. Triclosan levels correlated positively with advancing age (r = 0.09, P < 0.001) and inversely with body mass index (r = -0.09, P < 0.001). Smoking exposure was associated with significantly lower TCS levels (P < 0.001). Compared with premenopausal women, postmenopausal women had significantly higher log-transformed, creatinine-adjusted TCS levels (mean, -1.22 ± 1.79 vs -1.51 ± 1.79 ng/mg creatinine; P < 0.001). Triclosan levels were unrelated to the duration of menopause and did not differ between women who underwent natural versus surgical menopause, and premature menopause versus menopause at 40 years or older. In unweighted multivariate linear regression analyses, menopausal status was independently associated with higher urinary TCS levels after adjusting for covariates (β coefficient, 0.17; 95% CI, 0.020-0.323; P = 0.026).

CONCLUSIONS

In a nationally representative sample, postmenopausal status was associated with higher urinary TCS levels, observations that merit further investigation into potential exposures and health consequences.

Neurotoxic mechanisms of triclosan: The antimicrobial agent emerging as a toxicant

Several scientific studies have suggested a link between increased exposure to pollutants and a rise in the number of neurodegenerative disorders of unknown origin. Notably, triclosan (an antimicrobial agent) is used in concentrations ranging from 0.3% to 1% in various consumer products. Recent studies have also highlighted triclosan as an emerging toxic pollutant due to its increasing global use. However, a definitive link is missing to associate the rising use of triclosan and the growing number of neurodegenerative disorders or neurotoxicity. In this article, we present systematic scientific evidence which are otherwise scattered to suggest that triclosan can indeed induce neurotoxic effects, especially in vertebrate organisms including humans. Mechanistically, triclosan affected important developmental and differentiation genes, structural genes, genes for signaling receptors and genes for neurotransmitter controlling enzymes. Triclosan-induced oxidative stress impacting cellular proteins and homeostasis which triggers apoptosis. Though the scientific evidence collated in this article unequivocally indicates that triclosan can cause neurotoxicity, further epidemiological studies may be needed to confirm the effects on humans.

The environmentally friendly approaches based on the heterojunction interface of the LaFeO3/Fe2O3@g-C3N4 composite for the disposable and laboratory sensing of triclosan

Triclosan (TCS) is a polychlorinated phenoxy phenol (PCPPs) used as a disinfectant and a broad-spectrum antibacterial and antifungal agent in personal hygiene products. TCS easily forms diphenyl ethers and dioxins, which are persistent organic pollutants. This work used a double approach for the TSC sensing: a) screen-printed (SPE) electrochemical platform for on-site application, modified with lanthanum iron oxide and graphitic carbon nitride composite (LaFeO₃/Fe₂O₃@g-C₃N₄/SPE); and b) carbon paste electrode (CPE), modified with the same material and used in laboratory conditions. Linear range from 0.1 μM to 10 μM, the limit of detection (LOD) of 29 nM and the limit of quantification (LOQ) of 91 nM were obtained for CP electrode in BRBS pH 8. SPE showed the best analytical parameters in BRBS at pH 3, with a linear range from 0.3 μM to 7 μM, LOD of 0.09 μM and LOQ of 0.28 μM. Furthermore, the influence of potential interferents was investigated and proven to be negligible. Determination of TSC was performed to estimate the environmental impact of this compound as well as the practical usefulness of the proposed sensor in the real sample analysis, confirmed with a HPLC analysis.

Organophosphate flame retardants in Hangzhou tap water system: Occurrence, distribution, and exposure risk assessment

The usage of Organophosphorus flame retardants (OPFRs) is gradually increased as the ban on brominated flame retardants (BFRs) worldwide. The frequent accessibility of OPFRs in aquatic environment poses potential risk to human. Previous studies have concerned on surface water, while studies on tap water are limited. In this research, we aim to evaluate the removal efficiency of the tap water treatment process and investigate the exposure risk of OPFRs in tap water. Herein, we collected 14 samples from water source, 10 samples from water treatment plants and 47 from tap to analyze the concentrations and removal efficiency of OPFRs in Hangzhou tap water supply system. The results showed the concentrations of ∑OPFRs ranged from 9.25 to 224.74 ng/L in all samples, with Tris(1-chloro-2-propyl) Phosphate (TCPP), Tris(2-chloroethyl) phosphate (TCEP), Triphenyl phosphate (TPHP), and Tributyl phosphate (TBP) being the predominant compounds. Levels of the OPFRs had a 10.0 % - 50.4 % declination when compared samples after treatment with that before. The maximum exposure doses of ∑OPFRs via tap water for both adults and children were much lower than the reference dose (RfD). As a result, the hazard index (HI) and the carcinogenic risk (CR) pinpointed a negligible non-carcinogenic and carcinogenic risk for the residents. Even so, given the pervasive usage of OPFRs, the residual levels and the potential risk of OPFRs in watershed should be continuously concerned.

Implications of triclosan for female fertility: results from the National Health and Nutrition Examination Survey, 2013-2016

Objective

To examine and further characterize the association between urinary levels of triclosan (TCS), a ubiquitous putative endocrine-disrupting chemical, and the risk of infertility.

Design

A retrospective cross-sectional study using the Centers for Disease Control and Prevention's National Health and Nutrition Examination Survey.

Setting

Not applicable.

Patients

Female participants in the United States who completed the reproductive health questionnaire and provided urine samples for TCS level measurement from 2013 to 2016.

Interventions

None.

Main Outcome Measures

Rates of presumed infertility based on participants' affirmative response to survey question RHQ074 ("Have you ever attempted to become pregnant over a period of at least a year without becoming pregnant?").

Results

A total of 11.7% of the overall female and 12.5% of the eligible study population met the criterion for presumed infertility. Creatinine-adjusted urinary TCS levels were significantly higher among those meeting the criterion for infertility compared with the levels among those who did not. On multivariable-adjusted analyses, individuals with undetectable levels of urinary TCS were 35% less likely to meet the specified infertility criterion compared with those with detectable TCS levels. The magnitude of association between TCS levels and infertility was strongest when comparing the lowest and highest quartiles. The directionality and magnitude of the relationship between TCS levels and infertility were maintained on age-restricted and weighted analyses; however, the associations did not retain statistical significance.

Conclusions

In a nationally representative sample of women in the United States, an association between TCS exposure and inability to conceive over a period of 1 year is suggested by our analysis of the National Health and Nutrition Examination Survey data. The data infer a dose-response relationship.

Mass trends of parabens, triclocarban and triclosan in Arizona wastewater collected after the 2017 FDA ban on antimicrobials and during the COVID-19 pandemic

Antimicrobials like parabens, triclosan (TCS), and triclocarban (TCC) are of public health concern worldwide due to their endocrine-disrupting properties and ability to promote antimicrobial drug resistance in human pathogens. The overall use of antimicrobials presumably has increased during the COVID-19 pandemic, whereas TCS and TCC may have experienced reductions in use due to their recent ban from thousands of over-the-counter (OTC) personal care products by the U.S. Food and Drug Administration (FDA). No quantitative data are available on the use of parabens or the impact the FDA ban had on TCC and TCS. Here, we use wastewater samples (n = 1514) from 10 different communities in Arizona to measure the presence of the six different antimicrobial products (TCS, TCC, and four alkylated parabens [methylparaben (MePb), ethylparaben (EtPb), propylparaben (PrPb), butylparaben (BuPb)]) collected before and during the COVID-19 pandemic using a combination of solid-phase extraction, liquid chromatography/tandem mass spectrometry (LC-MS/MS), and isotope dilution for absolute quantitation. The average mass loadings of all antimicrobials combined (1,431 ± 22 mg/day per 1,000 people) after the onset of the local epidemic (March 2020 - October 2020) were significantly higher (945 ± 62 mg/day per 1,000 people; p < 0.05) than before the pandemic (January 2019 - February 2020). Overall, parabens (∑Pbs = 999 ± 16 mg/day per 1,000 people) were the most used antimicrobials, followed by TCS (117 ± 14 mg/day per 1,000 people) and TCC (117 ± 14 mg/day per 1,000 people). After the 2017 U.S. FDA ban, we found a statistically significant (p < 0.05) reduction in the mass loadings of TCS (-89%) and TCC (-80%) but a rise in paraben use (+72%). Mass flows of 3 of a total of 4 parabens (MePb, EtPb, and PrPb) in wastewater were significantly higher upon the onset of the epidemic locally (p < 0.05). This is the first longitudinal study investigating the use of antimicrobials during the COVID-19 pandemic by employing wastewater-based epidemiology. Whereas an overall increase in the use of antimicrobials was evident from analyzing Arizona wastewater, a notable reduction in the use of TCS and TCC was evident during the pandemic, triggered by the U.S. FDA ban.

An amidase and a novel phenol hydroxylase catalyze the degradation of the antibacterial agent triclocarban by Rhodococcus rhodochrous

Triclocarban (TCC) is an emerging and intractable environmental contaminant due to its hydrophobicity and chemical stability. However, the antibacterial property of TCC limits its biodegradation, and only the functional enzyme TccA involved in TCC degradation has been characterized to date. In this study, we report a highly efficient TCC-degrading bacterium, Rhodococcus rhodochrous BX2, that could degrade and mineralize TCC (10 mg/L) by 76.8% and 56.5%, respectively, within 5 days. Subsequently, the TCC biodegradation pathway was predicted based on the detection of metabolites using modern mass spectrometry techniques. Furthermore, an amidase (TccS) and a novel phenol hydroxylase (PH_IND) encoded by the tccS and PH_IND genes, respectively, were identified by genomic and transcriptomic analyses of strain BX2, and these enzymes were further unequivocally proven to be the key enzymes responsible for the metabolism of TCC and its intermediate 4-chloroaniline (4-CA) by using a combination of heterologous expression and gene knockout. Our results shed new light on the mechanism of TCC biodegradation and better utilization of microbes to remediate TCC contamination.

Barley Straw Biochar and Compost Affect Heavy Metal Transport in Soil and Uptake by Potatoes Grown under Wastewater Irrigation

Wastewater can supplement freshwater in agriculture; however, it contains toxic heavy metals such as cadmium, chromium, and lead that are hazardous to humans and the environment. We investigated the effects of barley straw biochar, green and table waste compost, and their mix on heavy metal transport in soil and uptake by potatoes (Solanum tuberosum L.) irrigated with synthetic wastewater for two years. In both years, amending soil with compost significantly reduced (p ≤ 0.05) cadmium uptake in potato flesh, skin, roots, and stems; zinc uptake in potato skin and roots; and copper uptake in potato flesh due to increased soil cation-exchange capacity, dissolved organic carbon, and soil pH. Co-amending the soil with compost and 3% biochar significantly reduced (p ≤ 0.05) the bioavailability of cadmium, copper, and zinc in the contaminated soil. Relative to the non-amended soils, soil amendment with biochar, compost, and their mix affected neither the transport of chromium, iron, and lead in the soils nor their uptake by potatoes. It was concluded that amending soil with barley straw biochar and/or compost produced from city green table waste could be used to improve the safety of wastewater irrigated potatoes, depending on the biochar application rate and heavy metal type.

Genomic markers for the biological responses of Triclosan stressed hatchlings of Labeo rohita

Triclosan (TCS) used commonly in pharmaceuticals and personal care products has become the most common pollutant in water. Three-day-old hatchlings of an indigenous fish, Labeo rohita, were given 96h exposure to a nonlethal (60 μg L^-1) and two moderately lethal concentrations (67 and 97 μg L^-1) of TCS and kept for 10 days of recovery for recording transcriptomic alterations in antioxidant/detoxification (SOD, GST, CAT, GPx, GR, CYP1a and CYP3a), metabolic (LDH, ALT and AST) and neurological (AchE) genes and DNA damage. The data were subjected to principal component analysis (PCA) for obtaining biomarkers for the toxicity of TCS. Hatchlings were highly sensitive to TCS (96h LC₅₀ = 126 μg L^-1 and risk quotient = 40.95), 96h exposure caused significant induction of CYP3a, AChE and ALT but suppression of all other genes. However, expression of all the genes increased significantly (except for a significant decline in ALT) after recovery. Concentration-dependent increase was also observed in DNA damage [Tail Length (TL), Tail Moment (TM), Olive Tail Moment (OTM) and Percent Tail DNA (TDNA)] after 96 h. The damage declined significantly over 96h values at 60 and 67 μg L^-1 after recovery, but was still several times more than control. TCS elicited genomic alterations resulted in 5-11% mortality of exposed hatchlings during the recovery period. It is evident that hatchlings of L. rohita are a potential model and PCA shows that OTM, TL, TM, TDNA, SOD and GR (association with PC1 during exposure and recovery) are the biomarkers for the toxicity of TCS. Graphical abstract.

Sublethal and environmentally relevant concentrations of triclosan and triclocarban induce histological, genotoxic, and embryotoxic effects in Clarias gariepinus (Burchell, 1822)

Antimicrobial additives in personal care products (PCPs) such as triclosan (TCS) and triclocarban (TCC) are of environmental concern due to their potential toxicity in non-target aquatic organisms. In this study, the histological, genotoxic (micronucleus assay), and embryotoxic effects of sublethal and environmentally relevant concentrations of TCS and TCC were evaluated in Clarias gariepinus (the African sharptooth catfish) over a period of 28 days. The 96 hLC50 values of TCS and TCC against fingerlings of C. gariepinus were 16.04 mg/L and 41.57 mg/L respectively. The 24 hLC50 and 26 hEC50 (non-hatching) values for C. gariepinus embryos were 16.48 mg/L and 11.08 mg/L for TCS and 46.08 mg/L and 41.93 mg/L for TCC respectively. TCS was ×3 to ×4 more toxic to C. gariepinus fingerlings and embryos than TCC. Gill histological alterations ranged from mild to severe lamellar necrosis in the exposed fishes with Gill Alteration Index (GAI) of 1.60 on day 14 and 3.20 on day 28. There were significant dose-dependent increases (p < 0.05) in micronuclei and binucleated cells in the erythrocytes of exposed fishes compared to control. Embryotoxic effects assessed from 0 to 72 h post fertilization showed significant decreases (p < 0.05) in hatching success and number of heartbeats per minute, and significant increase (p < 0.05) in percentage abnormalities in the exposed embryos compared to control. The study demonstrates the need for regulatory measures and monitoring of the use of TCS and TCC in PCPs in order to mitigate potential adverse effects to non-target aquatic organisms. This will support the United Nations Sustainable Development Goal 14 on sustaining life below water.

Occurrence and removal of micropollutants in full-scale aerobic, anaerobic and facultative wastewater treatment plants in Brazil

This study aims to evaluate micropollutant occurrence and removal in a low-middle income country (LMIC) by investigating the occurrence of 28 chemicals from different classes (triclosan, 15 polycyclic aromatic hydrocarbons (PAHs), 4 estrogens and 8 polybrominated diphenyl ether (PBDE) congeners) in three technologically diverse full-scale Brazilian wastewater treatment plants (WWTPs). These chemicals were detected at concentrations similar to those reported in other low-middle income countries (LMICs) and high-income countries (HICs) (0.1-49 μg/L) indicating their widespread use globally and the need for more studies in LMICs that are typically characterized by relatively inadequate wastewater treatment barriers. Among the three different WWTPs investigated for removal of these chemicals, the least energy intensive system, waste stabilization ponds (WSPs), was the most effective (95-99%) compared to the activated sludge (79-94%), and Up-flow sludge blanket reactor (UASB) with trickling filters system (89-95%). These results highlight the potential of WSPs for micropollutant removal-especially in warm climates. However, the effluent from all three WWTP could pose a risk to aquatic organisms when discharged into the receiving waters as the effluent concentrations of triclosan, some estrogens, PAHs and BDE 209 were above European environmental quality standards (EQS) or predicted no effect concentration (PNEC values), indicating that receiving water bodies could benefit from further treatment. In combination, these results help to further understand prevailing concentrations of micropollutants globally and fate in current wastewater treatment systems.

Occurrence, seasonal variations, and ecological risk of pharmaceuticals and personal care products in River Ganges at two holy cities of India

Occurrence of 15 different pharmaceuticals and personal care products (PPCPs) (ibuprofen, diclofenac, ketoprofen, acetaminophen, ciprofloxacin, erythromycin, amoxicillin, ofloxacin, tetracycline, metoprolol, triclosan, salicylic acid, N, N diethyl-meta-toluamide, caffeine and β-Estradiol) belongs to eight different classes in an urban stretch of River Ganges were detected for three seasons in two holy cities Rishikesh and Haridwar (India). The overall concentration of PPCPs in the River Ganges ranged between Below Detectable Limit (BDL) to 1104.84 ng/L, with higher concentrations at anthropogenically influenced lower reaches of the River Ganges at Haridwar. Acetaminophen, triclosan, N, N diethyl-meta-toluamide (DEET), tetracycline, and caffeine showed the highest detection frequency (>90-100%) in the river. PPCPs concentration, especially for NSAIDs (Ibuprofen, ketoprofen and acetaminophen), antibiotics (ciprofloxacin, tetracycline and ofloxacin) and metabolite (salicylic acid) was found to be higher in winter compared to summer in the Ganges, possibly due to the lower biodegradation efficiency related to lesser temperatures and inadequate sunlight. While metoprolol (beta-blockers), triclosan (antibacterial), DEET (insect repellent) and caffeine (human indicator) showed a higher load in summer, possibly due to their intense uses during this period. Results of risk quiescent (RQ) revealed higher ecological risk for algae while the moderate risk for river fish biota.

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.

Pyrolysis of Triclosan and Its Chlorinated Derivatives

Triclosan (TCS) is a commonly used antimicrobial agent which persists in the environment and may undergo chlorination and/or photodegradation to produce toxic polychlorinated dibenzo-p-dioxins and polychlorinated benzenes. TCS accumulates in wastewater treatment biosolids, which may be used to fuel waste-to-energy plants, although little is known about the fate of TCS at high temperatures. Here, we have studied the thermal decomposition of TCS and chlorinated TCS derivatives in the gas phase using computational chemistry coupled with reaction rate theory calculations to predict rate coefficients and develop a chemical kinetic model to simulate TCS pyrolysis in a plug flow reactor. TCS is shown to interconvert with 4-chloro-2-(2,4-dichlorophenoxy)phenol (TCSi) with a relatively low barrier, achieving equilibrium at temperatures of around 900 K and above. Dissociation of TCS and TCSi proceeds in parallel with barriers of ca. 60-65 kcal/mol to produce dichlorodibenzo-p-dioxin chlorobenzoquinone isomers. Reactor simulations demonstrate that TCS incineration at a temperature of 1100 K or higher leads to the formation of toxic chlorinated aromatics.

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.

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.

Risk assessment of contaminants of emerging concern in the context of wastewater reuse for irrigation: An integrated modelling approach

Direct reuse of reclaimed wastewater (RWW) in agriculture has recently received increasing attention as a possible solution to water scarcity. The presence of contaminants of emerging concern (CECs) in RWW can be critical, as these chemicals can be uptaken in irrigated crops and eventually ingested during food consumption. In the present study, an integrated model was developed to predict the fate of CECs in water reuse systems where RWW is used for edible crops irrigation. The model was applied to a case study where RWW (originating from a municipal wastewater treatment plant) is discharged into a water channel, with subsequent irrigation of silage maize, rice, wheat and ryegrass. Environmental and human health risks were assessed for 13 CECs, selected based on their chemical and hazard characteristics. Predicted CEC concentrations in the channel showed good agreement with available measurements, indicating potential ecotoxicity of some CECs (estrogens and biocides) due to their limited attenuation. Plant uptake predictions were in good agreement with existing literature data, indicating higher uptake in leaves and roots than fruits. Notably, high uncertainties were shown for weakly acidic CECs, possibly due to degradation in soil and pH variations inside plants. The human health risk due to the ingestion of wheat and rice was assessed using the threshold of toxicological concern and the hazard quotient. Both approaches predicted negligible risk for most CECs, while sulfamethoxazole and 17α-ethinylestradiol exhibited the highest risk for consumers. Alternative scenarios were evaluated to identify possible risk minimization strategies (e.g., adoption of a more efficient irrigation system).

First nationwide investigation and environmental risk assessment of 72 pharmaceuticals and personal care products from Sri Lankan surface waterways

Pharmaceuticals and personal care products (PPCPs) are known as an emerging class of water contaminants due to their potential adverse effects on aquatic ecosystems. In this study, we conducted the first nationwide survey to understand the distribution and environmental risk of 72 PPCPs in surface waterways of Sri Lanka. Forty-one out of 72 targeted compounds were detected with total concentrations ranging between 5.49 and 993 ng/L in surface waterways in Sri Lanka. The highest level of PPCP contamination was detected in an ornamental fish farm. Sulfamethoxazole was found with the highest concentration (934 ng/L) followed by N,N-diethyl-meta-toluamide (202 ng/L) and clarithromycin (119 ng/L). Diclofenac, mefenamic acid, ibuprofen, trimethoprim, and erythromycin were detected ubiquitously throughout the country. Our data revealed that hospital and domestic wastewater, and aquaculture activities potentially contribute to the presence of PPCPs in Sri Lankan waterways. The calculated risk quotients indicated that several locations face medium to high ecological risk to aquatic organisms from ibuprofen, sulfamethoxazole, diclofenac, mefenamic acid, tramadol, clarithromycin, ciprofloxacin, triclocarban, and triclosan. The aforementioned compounds could affect aquatic organisms from different trophic levels like algae, crustacean and fish, and also influence the emergence of antibiotic resistant bacteria. These findings emphasize that a wide variety of pharmaceuticals have become pervasive environmental contaminants in the country. This data will serve to expand the inventory of global PPCP pollution. Further monitoring of PPCPs is needed in Sri Lanka in order to identify PPCP point sources and to implement strategies for contaminant reduction in wastewater to protect the aquatic ecosystem, wildlife, and human health.

Fate of Triclocarban (TCC) in aquatic and terrestrial systems and human exposure

Triclocarban (TCC) is considered as contaminant of emerging concern (CEC), and ranked in the top 10 CEC occurrence. TCC is a high production volume synthetic chemical used extensively in various personal care products. This chemical will be released into the environment via incomplete wastewater treatment and untreated wastewater discharge. TCC and its transformation products (4,4'-dichlorocarbilide (DCC),1-(3-chlorophenyl)-3-phenylurea (MCC) and carbanilide (NCC),2'OH-TCC, 3'OH-TCC) were detected in the environmental matrices. Sediment organic carbon will influence TCC concentrations in suspended and bed sediments. TCC is an antimicrobial agent and also emerging endocrine disruptor that can cause immune dysfunction and affect human reproductive outcomes. Furthermore, TCC alters the expression of proteins related to binding and metabolism, skeletal muscle development and function, nervous system development and immune response. TCC has potential health risks in wildlife and humans. Several animal studies illustrate that it can cause various adverse effects, which can be monitored by antioxidant biomarkers (CAT, GST and LPO). Accumulation of TCC in organisms depends on the lipophilicity and bioavailability of TCC in sediment and water. TCC was continuously detected in aquatic system. TCC is a lipophilic compound, which can efficiently bind with lipid content. Women are more vulnerable to TCC due to substantially higher frequency and extended exposure to TCC. This review provides basic information of occurrence of TCC and the exposure levels in aquatic organisms. Several literature have shown the higher usage and human exposure levels of TCC, which provides useful information for the chemical management approaches.

DNA damage and physiological responses in an Indian major carp Labeo rohita exposed to an antimicrobial agent triclosan

This study is aimed to evaluate the toxic effects of triclosan (TCS) in an Indian major carp Labeo rohita. The 96-h LC₅₀ value of triclosan to L. rohita was found to be 0.39 mg L^-1. Fish were exposed to two sublethal concentrations (0.039 mg L^-1, treatment I and 0.078 mg L^-1, treatment II) of TCS for 35 days, and certain hematobiochemical, antioxidant, histopathological responses were measured. Compared to the control group, there was a significant (p < 0.05) decrease in the values and genotoxicity of hematological parameters such as hemoglobin (Hb), hematocrit (Hct), and erythrocyte (RBC) in TCS-exposed fish, but the values of leucocyte count (WBC), mean corpuscular volume (MCV), and mean corpuscular hemoglobin (MCH) were found to be increased. A biphasic response in mean corpuscular hemoglobin concentration (MCHC) value was observed during the study period (35 days). Significant (p < 0.05) alterations in plasma biochemical parameters (glucose and protein), electrolytes (Na⁺, K⁺, and Cl^-), and transaminases (GOT and GPT) were observed in fish treated with TCS in both treatments. Gill Na⁺/K⁺-ATPase activity was found to be decreased in fish treated with TCS in both treatments. Enzymatic and nonenzymatic antioxidant index levels have also fluctuated in all the tissues (gill, liver, and kidney). The histological lesions were comparatively more severe in the gill than the liver and kidney. Comet assay showed DNA damage on exposure at two sublethal concentrations. The present results suggest that TCS is highly toxic to fish even at sublethal concentrations.

Sonochemical degradation of triclosan in water in a multifrequency reactor

Degradation of triclosan (TCS) by multifrequency ultrasound (US) was studied at high and low frequencies. Frequency effect on initial degradation rates was analyzed, and an optimum frequency was found. Power density always has a positive effect on degradation rates over the whole equipment work range. A reaction mechanism similar to that proposed by Serpone resulted in a pseudo-linear model that fitted statistically better than the nonlinear model proposed by Okitsu. Pulsed US showed a positive effect on degradation rates; however, simultaneous analysis of the effect of power, frequency, pulse time, and silent time did not show a clear trend for degradation as a function of pulse US variables. According to these results and those for degradation in the presence of radical scavengers, it was concluded that US TCS degradation was taking place in the bubble/liquid interface. A toxicity test was conducted by Microtox®, showing a decrease in toxicity as TCS concentration decreased and increase in toxicity after total depletion of TCS. Eight possible degradation by-products were identified by GC-MS analysis, and a degradation pathway was proposed.

Performance and kinetics of triclocarban removal by entrapped Pseudomonas fluorescens strain MC46

This study investigated removal of triclocarban (TCC) from contaminated wastewater by Pseudomonas fluorescens strain MC46 entrapped in barium alginate. Appropriate entrapped cell preparation conditions (cell-to-entrapment material ratio and cell loading) for removing TCC were examined. The highest TCC removal by the entrapped and free cell systems at the initial TCC concentration of 10 mg/L was 72 and 45%, respectively. TCC was degraded to less toxic compounds. Self-substrate inhibition was found at TCC concentration of 30 mg/L. The kinetics of TCC removal by entrapped and free cells fitted well with Edwards model. Scanning and transmission electron microscopic observations revealed that entrapment matrices reduced TCC-microbe contact, which lessened TCC inhibition. A live/dead cell assay also confirmed reduced microbial cell damage in the entrapped cell system compared to the free cell system. This study reveals the potential of entrapment technology to improve antibiotic removal from the environment.

Environmental risk assessment of triclosan and triclocarban from personal care products in South Africa

Trends in the widespread use of personal care products (PCPs) containing triclosan (TCS) and triclocarban (TCC) have led to continuous emissions of these chemicals into the environment. Consequently, both chemicals are ubiquitously present at high concentrations in the aquatic systems based on widely reported measured environmental concentration (MECs) data in different environmental systems (e.g. freshwater) worldwide, especially in developed countries. In developing countries, however, lack of MECs data is a major issue, and therefore, inhibits effective risk assessment of these chemicals. Herein, TCS and TCC releases from personal care products (PCPs) were quantified, using a modelling approach to determine predicted environmental concentrations (PECs) in wastewater, freshwater, and soils, and likely risk(s) were estimated by calculating risk quotient (RQs). TCS and TCC in freshwater had RQs >1 based on estimated PECs with wide variations (≈2-232) as performed across the three dilutions factors (1, 3, and 10) considered in this study; an indicator of their likely adverse effect on freshwater organisms. In untreated and treated wastewater, TCS RQs values for bacteria were >1, but <1 for TCC, implying the former may adversely affect the functioning of wastewater treatment plants (WWTPs), and with no plausible impacts from the latter. In terrestrial systems, RQ results for individual chemicals revealed no or limited risks; therefore, additional investigations are required on their toxicity, as effects data was very limited and characterised by wide variations. Future national monitoring programs in developing countries should consider including TCS and TCC as the results suggest both chemicals are of concern to freshwater, and TCS in WWTPs. Potential risks of their metabolites remain unquantified to date.

Triclosan - an antibacterial compound in water, sediment and fish of River Gomti, India

Triclosan (TCS), the antibacterial agent commonly used in personal care products is highly toxic to aquatic lives particularly algae, zooplankton and fish. It is bio-accumulative and has endocrine disruptive properties. In this present study, we monitored the occurrence of TCS in water, sediment and fish samples collected from stretch of about 450 km of River Gomti, a major tributary of River Ganga, in India. An isocratic reversed-phase HPLC method was standardized for determination of TCS in samples. In water, TCS was detected in the range of 1.1-9.65 μg/l while in sediments the level was 5.11-50.36 μg/kg. It was also found in fishes of different species in concentrations ranging from 13 to 1040 μg/kg on wet weight basis. However, estimated daily intake of TCS through contaminated fish was much below the acceptable daily intake (50 μg/kg body wt/day) and thus safe from human health hazard point of view.

Contamination and risk profiles of triclosan and triclocarban in sediments from a less urbanized region in China

Triclosan and triclocarban are priority environmental contaminants of increasing concern to environmental health. After application, the chemicals enter the aquatic environment and easily distribute in bed sediment due to their hydrophobicity, and thus pose potential ecological risks. This study investigated the distribution and risks of triclosan and triclocarban in the sediment environment of a less urbanized region in South China. The sampling sites with high levels of triclosan and triclocarban were found to locate in the tributaries. When compared to other monitoring results obtained from more densely populated regions, the residues of triclosan and triclocarban in the investigated region were low, suggesting that these two chemicals conservation in sediment is related to anthropic activities. The results of risk quotients showed that high risks to aquatic organisms were posed by triclosan residues in sediment, while the risks to benthic organisms were quite low. Triclocarban residues in sediment posed minimal to medium risks to aquatic and benthic organisms. In summary, using either of the calculation methods of risk quotients, medium risks posed by the antimicrobials can be found in certain sampling sites with low population densities. The results may be useful in the development of evidence-based policies for the government.

Triclosan toxicity alters behavioral and hematological parameters and vital antioxidant and neurological enzymes in Pangasianodon hypophthalmus (Sauvage, 1878)

Triclosan and its metabolites are detected in a diverse aquatic environment and are major concerns for various aquatic organisms. The present study investigated the impact of acute and sub-lethal exposure of triclosan on behaviour, activities of acetylcholinesterase and selected antioxidant enzymes, haematological and serum gas-electrolyte parameters of Pangasianodon hypophthalmus. The 96 h LC₅₀ of triclosan for P. hypophthalmus was estimated as 1458 μg L^-1. Further, sub-lethal triclosan exposure to 1/15th (97 μg L^-1), 1/10th (145 μg L^-1) and 1/5th (291 μg L^-1) of 96 h LC₅₀ concentration for a period of 45 days lead to decrease in total erythrocyte count, haemoglobin content and packed cell volume of blood while total leukocyte count increased significantly (p < 0.05) as compared to control. A concentration-dependent increase in the serum chloride and decrease in partial pressure of oxygen in blood serum was noted on 45th day. An increased activity of catalase and superoxide dismutase in gill and liver tissues and inhibition of acetylcholinesterase activity in brain was observed on 15th, 30th and 45th day of exposure which was dependent on both - concentration of triclosan and duration of exposure. A significant high activity of glutathione-S-transferase in gill and liver tissue was observed in triclosan exposed groups in comparison to control during the experimental period. The study shows that long-term sub-lethal exposure of triclosan to fish can lead to several physiological alterations such as enzymatic scavenging of oxygen radicals and the normal neurological functions mediated by the enzyme acetylcholinesterase. With increasing anthropogenic activity, the study provides a convincing evidence for the necessity of a regulated use and safer disposal of triclosan to the environment.

Fate of triclosan in laboratory-scale activated sludge reactors - Effect of culture acclimation

Triclosan (TCS); a widely used antimicrobial biocide, exists in several pharmaceutical and personal care products. Due to its wide usage, TCS is detected in wastewater at varying concentrations. Biological treatability of TCS and its effect on chemical oxygen demand (COD) removal efficiency were investigated running laboratory-scale pulse-fed sequencing batch reactors with acclimated and non-acclimated cultures. The culture was acclimatized to TCS by gradually increasing its concentration in the synthetic feed wastewater from 100 ng/L to 100 mg/L. There were no effects of TCS on COD removal efficiency up to the TCS concentration of 500 ng/L for both acclimatized and non-acclimatized cases. However, starting from a concentration of 1 mg/L, TCS affected the COD removal efficiency adversely. This effect was more pronounced with non-acclimatized culture. The decrease in the COD removal efficiency reached to 47% and 42% at the TCS concentration of 100 mg/L, under acclimation and non-acclimation conditions respectively. Adsorption of TCS into biomass was evidenced at higher TCS concentrations especially with non-acclimated cultures. 2,4-dichlorophenol and 2,4-dichloroanisole were identified as biodegradation by-products. The occurrence and distribution of these metabolites in the effluent and sludge matrices were found to be highly variable depending, especially, on the culture acclimation conditions.

Degradation of triclosan by environmental microbial consortia and by axenic cultures of microorganisms with concerns to wastewater treatment

Triclosan is an antimicrobial agent, which is widely used in personal care products including toothpaste, soaps, deodorants, plastics, and cosmetics. Widespread use of triclosan has resulted in its release into wastewater, surface water, and soils and has received considerable attention in the recent years. It has been reported that triclosan is detected in various environmental compartments. Toxicity studies have suggested its potential environmental impacts, especially to aquatic ecosystems. To date, removal of triclosan has attracted rising attention and biodegradation of triclosan in different systems, such as axenic cultures of microorganisms, full-scale WWTPs, activated sludge, sludge treatment systems, sludge-amended soils, and sediments has been described. In this study, an extensive literature survey was undertaken, to present the current knowledge of the biodegradation behavior of triclosan and highlights the removal and transformation processes to help understand and predict the environmental fate of triclosan. Experiments at from lab-scale to full-scale field studies are shown and discussed.

River export of triclosan from land to sea: A global modelling approach

Triclosan (TCS) is an antibacterial agent that is added to commonly used personal care products. Emitted to the aquatic environment in large quantities, it poses a potential threat to aquatic organisms. Triclosan enters the aquatic environment mainly through sewage effluent. We developed a global, spatially explicit model, the Global TCS model, to simulate triclosan transport by rivers to coastal areas. With this model we analysed annual, basin-wide triclosan export for the year 2000 and two future scenarios for the year 2050. Our analyses for 2000 indicate that triclosan export to coastal areas in Western Europe, Southeast Asia and the East Coast of the USA is higher than in the rest of the world. For future scenarios, the Global TCS model predicts an increase in river export of triclosan in Southeast Asia and a small decrease in Europe. The number of rivers with an annual average triclosan concentration at the river mouth that exceeds a PNEC of 26.2ng/L is projected to double between 2000 and 2050. This increase is most prominent in Southeast Asia, as a result of fast population growth, increasing urbanisation and increasing numbers of people connected to sewerage systems with poor wastewater treatment. Predicted triclosan loads correspond reasonably well with measured values. However, basin-specific predictions have considerable uncertainty due to lacking knowledge and location-specific data on the processes determining the fate of triclosan in river water, e.g. sorption, degradation and sedimentation. Additional research on the fate of triclosan in river systems is therefore recommended.

CAPSULE

We developed a global spatially explicit model to simulate triclosan export by rivers to coastal seas. For two future scenarios this Global TCS model projects an increase in river export of triclosan to several seas around the world.

Degradation behavior of triclosan by co-exposure to chlorine dioxide and UV irradiation: influencing factors and toxicity changes

This study investigated the transformation of triclosan (TCS) following co-exposure to UV irradiation and ClO₂. Special attention was given to understand the influencing of water quality parameters and toxicity changes during the co-exposure process. The results show that the co-exposure process prompted TCS elimination quickly and effectively, with more than 99% of TCS degraded under the experimental conditions. The molar yield ratios of 2,4-dichlorophenol/TCS (2,4-DCP/TCS) were calculated to be 35.81-74.49%; however, the by-product of 2,8-dichlorodibenzop-dioxin (2,8-Cl₂DD) was not detected. The TCS degradation was sensitive to ClO₂ dosage, pH, H₂O₂, and natural organic matter (NOM), but not to the carbonate (CO₃^2-) concentration. Neutral and slightly alkaline condition were favorable to TCS elimination. The TCS removal rate increased from 85.33 to 99.75% when the ClO₂ concentration increased from 0.25 to 1.5 mg L^-1. TCS degradation can be promoted at low NOM level (1, 3, and 5 mg L^-1), whereas was inhibited at high NOM concentrations of 7 and 9 mg L^-1. While adding H₂O₂, the degradation rate of TCS increased with increasing H₂O₂ concentration from 1 to 3 mg L^-1; however, too low or overdosed H₂O₂ (0.5 and 5 mg L^-1) hindered TCS degradation. Based on the results of a microtox bioassay, the toxicity did not change following the co-exposure process.

Effects of triclosan (TCS) on hormonal balance and genes of hypothalamus-pituitary- gonad axis of juvenile male Yellow River carp (Cyprinus carpio)

Triclosan (TCS) is a broad spectrum antimicrobial agent which has been widely dispersed and determinated in the aquatic environment. However, the effects of TCS on reproductive endocrine in male fish are poorly understood. In this study, male Yellow River carp (Cyprinus carpio) were exposed to 0, 1/5, 1/10 and 1/20 LC₅₀ (96 h LC₅₀ of TCS to carp) TCS under semi-static conditions for 42 d. Vitellogenin (Vtg), 17β-estradiol (E₂), testosterone(T), gonadotropin (GtH), and gonadotropin-releasing hormone (GnRH) levels were measured by enzyme-linked immunosorbent assay (ELISA). Meanwhile, we also examined the mRNA expressions of aromatase, GtHs-β, GnRH, estrogen receptor (Er), and androgen receptor (Ar) by quantitative Real-time Polymerase Chain Reaction (qRT-PCR). TCS induced Vtg levels of hepatopancreas, E₂ levels of serum, and inhibited Ar and Er mRNA levels, suggesting that the induction of Vtg production by TCS was indirectly caused by non-Er pathways. TCS-induced Vtg levels by interfering with the reproductive axis at plenty of latent loci of male carps: (a) TCS exposure increased the aromatase mRNA expression of hypothalamus and gonad aromatase, consequently increasing serum concentrations of E₂ to induce Vtg in hepatopancreas; (b) TCS treatment changed GtH-β and GnRH mRNA expression and secretion, causing the disturbance of reproductive endocrine; (c) TCS exposure decreased Ar mRNA levels, indicating potential Ar-mediated antiandrogen action. These mechanisms showed that TCS may induce Vtg production in male carp by non-Er-mediated pathways.

Triclosan-induced transcriptional and biochemical alterations in the freshwater green algae Chlamydomonas reinhardtii

Triclosan (TCS) is an antibacterial and antifungal agent widely used in personal care products (PCPs). We investigated the effects of TCS (20μg/L, 100μg/L and 500μg/L) on Chlamydomonas reinhardtii by measuring the algal growth, chlorophyll content, lipid peroxidation, and transcription of the antioxidant-related genes (superoxide dismutase (SOD), glutathione peroxidase (GPX), catalase (CAT), glutathione S-transferase (GST), plastid terminal oxidase 2 (PTOX) and thioredoxin (TRX)) as well as biochemical alterations. The results showed significant dose-related effects of TCS on the algal species in terms of growth and chlorophyll content. Malondialdehyde (MDA) increased with increasing TCS concentrations and showed significant difference between the treatment of 405.3μg/L TCS and control group. Transcription analysis revealed that the expression of SOD mRNA was most sensitive to TCS among the selected genes. In addition, Fourier-transform infrared spectroscopy showed time- and concentration-specific biochemical responses in C. reinhardtii when exposed to TCS. The biochemical alterations associated with different doses of TCS were mainly attributed to structural changes associated with lipid, protein, nucleic acid and carbohydrate. The findings from this study reveal that TCS in the aquatic environment may affect algal growth, chlorophyll synthesis, oxidative stress responses and cause biochemical alterations. This study provided important information to achieve a better understanding of the toxic mechanism of triclosan on algae Chlamydomonas reinhardtii.

Multigenerational effects of triclosan on the demography of Plationus patulus and Brachionus havanaensis (ROTIFERA)

Triclosan is a personal care product widely used in North America, Europe and Asia as antimicrobial ingredient in many consumer chemical products. In Mexico concentrations of triclosan have been reported in aquatic systems. However, there is no law regulating the presence of chemicals such as triclosan, in aquatic systems. The scarce data about this chemical has increased concern among ecotoxicologists regarding possible effects on aquatic organisms. Moreover, multigenerational studies are rarely studied and the results vary depending on the contaminant. Rotifers, are a dominant group of zooplankton, and have been used in aquatic risk assessments of personal care products due to their sensitivity and high reproductive rates. Plationus patulus and Brachionus havanaensis are common rotifers distributed in aquatic ecosystems of Mexico and have been used in ecotoxicological bioassays. In this study, the median lethal concentration (LC50, 24h) of P. patulus and B. havanaensis exposed to triclosan was determined. Based on the LC50, we tested three sublethal concentrations of triclosan to quantify the demographic responses of both rotifers for two successive generations (F0, and F1). The 24h LC50 of triclosan for P. patulus and B. havanaensis were 300 and 500µgL^-1 respectively. Despite the concentration, triclosan had an adverse effect on both Plationus patulus and Brachionus havanaensis in both generations exposed. Experiments show that P. patulus was more sensitive than B. havanaensis when exposed to triclosan. When exposed to triclosan the parental generation (F0) of P. patulus was far more affected than F1.

Evaluating the impacts of triclosan on wastewater treatment performance during startup and acclimation

Triclosan (TCS) is a broad range antimicrobial agent used in many personal care products, which is commonly discharged to wastewater treatment facilities (WWTFs). This study examined the impact of TCS on wastewater treatment performance using laboratory bench-scale sequencing batch reactors (SBRs) coupled with anaerobic digesters. The SBRs were continuously fed synthetic wastewater amended with or without 0.68 μM TCS, with the aim of determining the effect of chronic TCS exposure as opposed to a pulse TCS addition as previously studied. Overall, the present study suggests inhibition of nitrogen removal during reactor startup. However, NH₄⁺ removal fully rebounded after 63 days, suggesting acclimation of the associated microbial communities to TCS. An initial decrease in microbial community diversity was observed in the SBRs fed TCS as compared to the control SBRs, followed by an increase in community diversity, which coincided with the increase in NH₄⁺ removal. Elevated levels of NO₃^- and NO₂^- were found in the reactor effluent after day 58, however, suggesting ammonia oxidizing bacteria rebounding more rapidly than nitrogen oxidizing bacteria. Similar effects on treatment efficiencies at actual WWTFs have not been widely observed, suggesting that continuous addition of TCS in their influent may have selected for TCS-resistant nitrogen oxidizing bacteria.

Application of a spatially resolved model to contextualise monitoring data for risk assessment of down-the-drain chemicals over large scales

Many regulatory screening level exposure assessments are based on simple large scale conceptual scenarios. However, exposure, and therefore risks associated with chemicals, are characterised by high spatial variability. The Scenario assembly tool (ScenAT) is a global screening level model to enable spatially resolved local predictions of environmental concentrations of home and personal care chemicals. It uses the European Union Technical Guidance Document (TGD) equation to predict local scale freshwater concentrations (predicted environmental concentrations - PECs) of chemicals discharged via wastewater. ScenAT uses Geographic Information System (GIS) layers for the underlying socio-economic (population) and environmental parameters (per capita water use, sewage treatment plant connectivity, dilution factor). Using a probabilistic approach, we incorporate sources of uncertainty in the input data (tonnage estimation, removal in sewage treatment plants and seasonal variability in dilution factors) for two case-study chemicals: the antimicrobial triclosan (TCS) and the anionic surfactant linear alkylbenzene sulphonate (LAS). We then compare model estimates of wastewater and freshwater concentrations of TCS and LAS to UK monitoring data. Comparison showed that modeled PECs were on average higher than mean measured data for TCS and LAS by a factor 1.8 and 1.4, respectively. Considering the uncertainty associated with both model and monitoring data, the use of a probabilistic approach using the ScenAT model for screening assessment is reasonable. The combination of modelled and monitoring data enables the contextualisation of monitoring data. Spatial PECs can be used to identify areas of elevated concentration for further refined assessment.

A Random Forest approach to predict the spatial distribution of sediment pollution in an estuarine system

Modeling the magnitude and distribution of sediment-bound pollutants in estuaries is often limited by incomplete knowledge of the site and inadequate sample density. To address these modeling limitations, a decision-support tool framework was conceived that predicts sediment contamination from the sub-estuary to broader estuary extent. For this study, a Random Forest (RF) model was implemented to predict the distribution of a model contaminant, triclosan (5-chloro-2-(2,4-dichlorophenoxy)phenol) (TCS), in Narragansett Bay, Rhode Island, USA. TCS is an unregulated contaminant used in many personal care products. The RF explanatory variables were associated with TCS transport and fate (proxies) and direct and indirect environmental entry. The continuous RF TCS concentration predictions were discretized into three levels of contamination (low, medium, and high) for three different quantile thresholds. The RF model explained 63% of the variance with a minimum number of variables. Total organic carbon (TOC) (transport and fate proxy) was a strong predictor of TCS contamination causing a mean squared error increase of 59% when compared to permutations of randomized values of TOC. Additionally, combined sewer overflow discharge (environmental entry) and sand (transport and fate proxy) were strong predictors. The discretization models identified a TCS area of greatest concern in the northern reach of Narragansett Bay (Providence River sub-estuary), which was validated with independent test samples. This decision-support tool performed well at the sub-estuary extent and provided the means to identify areas of concern and prioritize bay-wide sampling.

Biofilm phosphorus uptake capacity as a tool for the assessment of pollutant effects in river ecosystems

Biofilms are a key component in the nutrient removal from the water column. However, nutrient uptake by biofilms may be hampered by the occurrence of pollutants or other stressors. This study aimed: (i) to investigate the biofilm phosphorus (P) uptake capacity as a relevant process for the maintenance of fluvial water quality and (ii) to explore the sensitivity of this process to different chemical and environmental stressors. We conducted chamber experiments to test for the relevance of biofilm P uptake capacity (PUC) as a tool to detect effects of pollutants on river self-depuration. PUC was calculated by measuring P temporal decay after performing controlled P-spikes in chambers with biofilm-colonized tiles. Four different experiments were conducted to evaluate the response of PUC to: (a) several river waters from increasing polluted sites; (b) the effect of the bactericide triclosan (TCS); (c) the combined effect of TCS and grazers; and (d) the effect of TCS after a drought episode that affected the biofilms. These experiments showed that biofilms decreased their PUC along the pollution gradient. The biofilm PUC was significantly reduced after receiving high TCS concentrations, though lower TCS concentrations also affected the biofilm when this was submitted to grazing pressure. PUC decrease was induced by flow interruption which further enhanced the TCS negative effects. Overall, PUC was sensitive to the effects of pollutants like TCS as well as to the action of biological (grazing) and environmental (drought) factors. The study also showed that multiple stressors enhance the negative effects of pollutants on the PUC of biofilms. Our study values the use of biofilms' PUC as a sensitive ecological-based tool to assess the effects of chemicals on freshwater communities and their derived functioning in river ecosystems.

Degradation of triclosan in the presence of p-aminobenzoic acid under simulated sunlight irradiation

This study aimed to investigate the degradation of triclosan (TCS) in the presence of p-aminobenzoic acid (PABA) under simulated sunlight irradiation (λ ≥ 290 nm). The effect of PABA concentration, pH, dissolved organic matter (DOM), and DOM-hydrolytic Fe(III) species complexes on the photodegradation of TCS in the presence of PABA (TCS_-PABA) was also studied. The photolysis of TCS_-PABA obeyed pseudo-first-order kinetics well, and the degradation of TCS_-PABA enhanced with increasing solution pH (from 3.0 to 11.0). The presence of PABA inhibited the degradation of TCS_-PABA, and the weakest inhibitory effect was observed while the concentration of PABA was 5 mg L^-1. The addition of DOM (Suwannee River fulvic acid standard I [SRFA], Suwannee River HA standard II [SRHA], and Suwannee River natural organic matter [SRNOM]) showed different inhibition effects on TCS_-PABA degradation. However, higher Fe(III) concentration at the DOM concentration of 5 mg L^-1 could favor the formation of DOM-hydrolytic Fe(III) species complexes, further accelerating the degradation of TCS_-PABA. In comparison with deionized water (DI water), TCS_-PABA could be better photodegraded in river water nearby the effluent of a wastewater treatment plant. This study provides useful information for understanding the natural behavior of TCS in the presence of other organic contaminants.

Effects of triclosan on bacterial community composition and Vibrio populations in natural seawater microcosms

Pharmaceuticals and personal care products, including antimicrobials, can be found at trace levels in treated wastewater effluent. Impacts of chemical contaminants on coastal aquatic microbial community structure and pathogen abundance are unknown despite the potential for selection through antimicrobial resistance. In particular, Vibrio, a marine bacterial genus that includes several human pathogens, displays resistance to the ubiquitous antimicrobial compound triclosan. Here we demonstrated through use of natural seawater microcosms that triclosan (at a concentration of ~5 ppm) can induce a significant Vibrio growth response (68-1,700 fold increases) in comparison with no treatment controls for three distinct coastal ecosystems: Looe Key Reef (Florida Keys National Marine Sanctuary), Doctors Arm Canal (Big Pine Key, FL), and Clam Bank Landing (North Inlet Estuary, Georgetown, SC). Additionally, microbial community analysis by 16 S rRNA gene sequencing for Looe Key Reef showed distinct changes in microbial community structure with exposure to 5 ppm triclosan, with increases observed in the relative abundance of Vibrionaceae (17-fold), Pseudoalteromonadaceae (65-fold), Alteromonadaceae (108-fold), Colwelliaceae (430-fold), and Oceanospirillaceae (1,494-fold). While the triclosan doses tested were above concentrations typically observed in coastal surface waters, results identify bacterial families that are potentially resistant to triclosan and/or adapted to use triclosan as a carbon source. The results further suggest the potential for selection of Vibrio in coastal environments, especially sediments, where triclosan may accumulate at high levels.