Confirmation of the formation of dichlorodibenzo-p-dioxin in the photodegradation of triclosan by photo-SPME

Removal of pharmaceutical and personal care products (PPCPs) by MOF-derived carbons: A review

Nowadays, the increasing demand for pharmaceuticals and personal care products (PPCPs) has resulted in the uncontrolled release of large amounts of PPCPs into the environment, which poses a great challenge to the existing wastewater treatment technologies. Therefore, novel materials for efficient treatment of PPCPs need to be developed urgently. MOF-derived carbons (MDCs), have many advantages such as high mechanical strength, excellent water stability, large specific surface area, excellent electron transfer capability, and environmental friendliness. These advantages give MDCs an excellent ability to remove PPCPs. In this review, the effects of different substances on the properties and functions of MDCs are discussed. In addition, representative applications of MDCs and composites for the removal of PPCPs in the field of adsorption and catalysis are summarized. Finally, the future challenges of MDCs and composites are foreseen.

Tracking photodegradation products and bond-cleavage reaction pathways of triclosan using ultra-high resolution mass spectrometry and stable carbon isotope analysis

Triclosan (TCS) is an antimicrobial compound ubiquitously found in surface waters throughout the world. Although several studies have focused on the photochemical degradation of TCS, there is still limited knowledge about its environmental fate. In this study, we got molecular-level insights into the photochemical degradation of TCS. Significant stable carbon isotope fractionation was observed during photodegradation; different bond-cleavage reaction pathways under different photolytic conditions were characterized, using compound specific isotope analysis (CSIA). Photochemical modeling of TCS photodegradation showed that direct photolysis would be the main transformation pathway if pH > 7, even in presence of dissolved organic matter. Moreover, by use of ultrahigh resolution mass spectrometry, FT-ICR-MS, a broad and complex spectrum of organic by-products (some of which potentially toxic, as assessed by a quantitative structure-activity relationship approach) were identified. A detailed reaction mechanism was developed on the basis of the detected compounds. A possible sequence of steps leading to some of the detected product compounds in aqueous solution is suggested.

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.

PCDD/Fs traceability during triclosan electrochemical oxidation

5-Chloro-2-(2,4-dichlorophenoxy)phenol (TCS) is a persistent organic pollutant (POP) widely used in different consumer goods. Its recalcitrant nature demands the application of effective remediation technologies in order to avoid the negative environmental impact associated to the discharge of contaminated waters. Although advanced oxidation technologies have been considered the best alternative to destroy bio-recalcitrant compounds, the likely formation of high toxicity byproducts must be analysed before large-scale deployment. In this work, we aim to trace the presence of chlorinated compounds during the electro-oxidation of aqueous TCS samples. First, we analyze the influence of the initial concentration of TCS on the toxicity of the oxidation medium expressed by the International-Toxicity Equivalency Factor (I-TEF); second, we have detected the formation of intermediate organo-chlorinated compounds by GC-MS supported by HPLC and finally, we have quantified the concentration of highly-polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) by HRGC-HRMS within the oxidation treatment. In those samples where TCS had been completely degraded the concentration of PCDD/Fs showed a high increase, especially when NaCl was used as electrolyte, with the initial concentration of TCS. Under these conditions the I-TEF achieved values up to 3.8 × 10² pg L^-1.

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.

Degradation of triclosan by chlorine dioxide: Reaction mechanism,2,4-dichlorophenol accumulation and toxicity evaluation

The mechanism and toxicity of TCS degradation by ClO₂ was investigated. Intermediate products during the oxidation process were identified by GC/MS and LC/MS. A microtox bioassay and a SOS/umu assay were employed to evaluate the acute toxicity and genotoxicity of the resulting solutions during the chlorination process. The results showed that the reaction between TCS and ClO₂ was of second-order overall. The pseudo first-order rate constants (k_obs) exhibited significant dependence on solution pH and chlorine dioxide concentration, with the apparent second-order rate constant, k_app, being 7.07 × 10⁴ M^-1s^-1 in the pH range of 6.80-7.02. TCS decomposition was accompanied by the accumulation of 2,4-dichlorophenol (2,4-DCP), and the maximum molar yield ratios of 2,4-DCP/TCS were in the range of 31.71%-35.43%. The major intermediates identified were 2,7/2,8-dichlorodibenzop-dioxin (2,7/2.8-Cl₂DD), 2,4-DCP, 2,4,6-trichlorophenol (2,4,6-TCP), tetraclosan and pentaclosan. The proposed mechanism for TCS oxidation involved the cleavage of the ether link in TCS, chlorination of the phenolic ring and ring closure of a single TCS molecule. The transformation and degradation of TCS led to reduction of the acute toxicity and genotoxicity. However, irregular fluctuations in the toxicity changes indicated that the oxidation of TCS was not a simultaneous detoxification process.

Spectrophotometric determination of triclosan based on diazotization reaction: response surface optimization using Box-Behnken design

A spectrophotometric method based on diazotization of aniline with triclosan has been developed for the determination of triclosan in water samples. The diazotization process involves two steps: (1) reaction of aniline with sodium nitrite in an acidic medium to form diazonium ion and (2) reaction of diazonium ion with triclosan to form a yellowish-orange azo compound in an alkaline medium. The resulting yellowish-orange product has a maximum absorption at 352 nm which allows the determination of triclosan in aqueous solution in the linear concentration range of 0.1-3.0 μM with R² = 0.998. The concentration of hydrochloric acid, sodium nitrite, and aniline was optimized for diazotization reaction to achieve good spectrophotometric determination of triclosan. The optimization of experimental conditions for spectrophotometric determination of triclosan in terms of concentration of sodium nitrite, hydrogen chloride and aniline was also carried out by using Box-Behnken design of response surface methodology and results obtained were in agreement with the experimentally optimized values. The proposed method was then successfully applied for analyses of triclosan content in water samples.

Triclosan exposure, transformation, and human health effects

Triclosan (TCS) is an antimicrobial used so ubiquitously that 75% of the US population is likely exposed to this compound via consumer goods and personal care products. In September 2016, TCS was banned from soap products following the risk assessment by the US Food and Drug Administration (FDA). However, TCS still remains, at high concentrations, in other personal care products such as toothpaste, mouthwash, hand sanitizer, and surgical soaps. TCS is readily absorbed into human skin and oral mucosa and found in various human tissues and fluids. The aim of this review was to describe TCS exposure routes and levels as well as metabolism and transformation processes. The burgeoning literature on human health effects associated with TCS exposure, such as reproductive problems, was also summarized.

A model assessment of the ability of lake water in Terra Nova Bay, Antarctica, to induce the photochemical degradation of emerging contaminants

The shallow lakes located in Terra Nova Bay, Antarctica, are free from ice for only up to a couple of months (mid December to early/mid February) during the austral summer. In the rest of the year, the ice cover shields the light and inhibits the photochemical processes in the water columns. Previous work has shown that chromophoric dissolved organic matter (CDOM) in these lakes is very reactive photochemically. A model assessment is here provided of lake-water photoreactivity in field conditions, based on experimental data of lake water absorption spectra, chemistry and photochemistry obtained previously, taking into account the water depth and the irradiation conditions of the Antarctic summer. The chosen sample contaminants were the solar filter benzophenone-3 and the antimicrobial agent triclosan, which have very well known photoreactivity and have been found in a variety of environmental matrices in the Antarctic continent. The two compounds would have a half-life time of just a few days or less in the lake water during the Antarctic summertime, largely due to reaction with CDOM triplet states ((3)CDOM*). In general, pollutants that occur in the ice and could be released to lake water upon ice melting (around or soon after the December solstice) would be quickly photodegraded if they undergo fast reaction with (3)CDOM*. With some compounds, the important (3)CDOM* reactions might favour the production of harmful secondary pollutants, such as 2,8-dichlorodibenzodioxin from the basic (anionic) form of triclosan.

Pressurized liquid extraction-gas chromatography-mass spectrometry for confirming the photo-induced generation of dioxin-like derivatives and other cosmetic preservative photoproducts on artificial skin

The stability and photochemical transformations of cosmetic preservatives in topical applications exposed to UV-light is a serious but poorly understood problem. In this study, a high throughput extraction and selective method based on pressurized liquid extraction (PLE) coupled to gas chromatography-mass spectrometry (GC-MS) was validated and applied to investigate the photochemical transformation of the antioxidant butylated hydroxytoluene (BHT), as well as the antimicrobials triclosan (TCS) and phenyl benzoate (PhBz) in an artificial skin model. Two sets of photodegradation experiments were performed: (i) UV-Irradiation (8W, 254nm) of artificial skin directly spiked with the target preservatives, and (ii) UV-irradiation of artificial skin after the application of a cosmetic cream fortified with the target compounds. After irradiation, PLE was used to isolate the target preservatives and their transformation products. The follow-up of the photodegradation kinetics of the parent preservatives, the identification of the arising by-products, and the monitorization of their kinetic profiles was performed by GC-MS. The photochemical transformation of triclosan into 2,8-dichloro-dibenzo-p-dioxin (2,8-DCDD) and other dioxin-like photoproducts has been confirmed in this work. Furthermore, seven BHT photoproducts, and three benzophenones as PhBz by-products, have been also identified. These findings reveal the first evidences of cosmetic ingredients phototransformation into unwanted photoproducts on an artificial skin model.

Environmental chemicals active as human antiandrogens do not activate a stickleback androgen receptor but enhance a feminising effect of oestrogen in roach

Sexual disruption is reported in wild fish populations living in freshwaters receiving discharges of wastewater treatment works (WwTW) effluents and is associated primarily with the feminisation of males by exposure to oestrogenic chemicals. Antiandrogens could also contribute to the feminisation of male fish, but there are far less data supporting this hypothesis and almost nothing is known for the effects of oestrogens in combination with antiandrogens in fish. We conducted a series of in vivo exposures in two fish species to investigate the potency on reproductive-relevant endpoints of the antiandrogenic antimicrobials triclosan (TCS), chlorophene (CP) and dichlorophene (DCP) and the resin, abietic acid (AbA), all found widely in WwTW effluents. We also undertook exposures with a mixture of antiandrogens and a mixture of antiandrogens in combination with the oestrogen 17α-ethinyloestradiol (EE2). In stickleback (Gasterosteus aculeatus), DCP showed a tendency to reduce spiggin induction in females androgenised by dihydrotestosterone (DHT), but these findings were not conclusive. In roach (Rutilus rutilus), exposures to DCP (178 days), or a mixture of TCS, CP and AbA (185 days), or to the model antiandrogen flutamide (FL, 178 days) had no effect on gonadal sex ratio or on the development of the reproductive ducts. Exposure to EE2 (1.5ng/L, 185 days) induced feminisation of the ducts in 17% of the males and in the mixture of antiandrogens (TCS, CP, AbA) in combination with EE2, almost all (96%) of the males had a feminised reproductive ducts. In stickleback androgen receptor (ARα and ARβ) transactivation assays, the model antiandrogens, FL and procymidone inhibited 11-ketotestosterone (11-KT) induced receptor activation, but none of the human antiandrogens, TCS, CP, DCP and AbA had an effect. These data indicate that antimicrobial antiandrogens in combination can contribute to the feminisation process in exposed males, but they do not appear to act through the androgen receptor in fish.

GC/MS analysis of triclosan and its degradation by-products in wastewater and sludge samples from different treatments

A gas chromatography/mass spectrometry (GC/MS)-based method was developed for simultaneous determination of triclosan (TCS) and its degradation products including 2,4-dichlorophenol (2,4-DCP), 2,8-dichlorodibenzo-p-dioxin (2,8-DCDD), and methyl triclosan (MTCS) in wastewater and sludge samples. The method provides satisfactory detection limit, accuracy, precision and recovery especially for samples with complicated matrix such as sewage sludge. Liquid-liquid extraction and accelerated solvent extraction (ASE) methods were applied for the extraction, and column chromatography was employed for the sample cleanup. Analysis was performed by GC/MS in the selected ion monitoring (SIM) mode. The method was successfully applied to wastewater and sludge samples from three different municipal wastewater treatment plants (WWTPs). Satisfactory mean recoveries were obtained as 91(±4)-106(±7)%, 82(±3)-87(±4)%, 86(±6)-87(±8)%, and 88(±4)-105(±3)% in wastewater and 88(±5)-96(±8)%, 84(±2)-87(±3)%, 84(±7)-89(±4)%, and 88(±3)-97(±5)% in sludge samples for TCS, 2,4-DCP, 2,8-DCDD, and MTCS, respectively. TCS degradation products were detected based on the type of the wastewater and sludge treatment. 2,8-DCDD was detected in the plant utilizing UV disinfection at the mean level of 20.3(±4.8) ng/L. 2,4-DCP was identified in chemically enhanced primary treatment (CEPT) applying chlorine disinfection at the mean level of 16.8(±4.5) ng/L). Besides, methyl triclosan (MTCS) was detected in the wastewater collected after biological treatment (10.7 ± 3.3 ng/L) as well as in sludge samples that have undergone aerobic digestion at the mean level of 129.3(±17.2) ng/g dry weight (dw).

Triclosan: current status, occurrence, environmental risks and bioaccumulation potential

Triclosan (TCS) is a multi-purpose antimicrobial agent used as a common ingredient in everyday household personal care and consumer products. The expanded use of TCS provides a number of pathways for the compound to enter the environment and it has been detected in sewage treatment plant effluents; surface; ground and drinking water. The physico-chemical properties indicate the bioaccumulation and persistence potential of TCS in the environment. Hence, there is an increasing concern about the presence of TCS in the environment and its potential negative effects on human and animal health. Nevertheless, scarce monitoring data could be one reason for not prioritizing TCS as emerging contaminant. Conventional water and wastewater treatment processes are unable to completely remove the TCS and even form toxic intermediates. Considering the worldwide application of personal care products containing TCS and inefficient removal and its toxic effects on aquatic organisms, the compound should be considered on the priority list of emerging contaminants and its utilization in all products should be regulated.

Overview of the PCDD/Fs degradation potential and formation risk in the application of advanced oxidation processes (AOPs) to wastewater treatment

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) are a family of unintentionally produced persistent organic pollutants (POPs) that have received considerable public and scientific attention due to the toxicity of some of their congeners, more specifically those with chlorine substitution in the 2,3,7,8 positions. The environmental management and control of PCDD/Fs is addressed at a global level through the Stockholm Convention that establishes that POPs should be destroyed or irreversibly transformed in order to reduce or eliminate their release to the environment. Several technologies, including advanced oxidation processes (AOPs) such as photolysis, photocatalysis and Fenton oxidation, have been considered as effective methods for destroying PCDD/Fs in polluted waters. Nevertheless, during the remediation of wastewaters it is critical that the treatment technologies applied do not lead to the formation of by-products that are themselves POPs, especially if PCDD/Fs precursors or chlorine are present in the reaction medium. Despite the high effectiveness of AOPs in the oxidation of major contaminants, scarce references deal with the monitoring of PCDD/Fs in the course of the oxidation process, revealing that a detailed assessment of non-combustion technologies with respect to PCDD/Fs formation is still lacking. This study reports a review of the state of the art related to the potential remediation and/or formation of PCDD/Fs as a result of the application of AOPs for the treatment of polluted waters, warning on the correct selection of the operating conditions.

Substance flow analysis and assessment of environmental exposure potential for triclosan in mainland China

Triclosan (TCS) is a widely-used antimicrobial agent in many consumer products around the world, and China is a major producer and consumer of TCS. In this study substance flow analysis (SFA) was used to construct a static model of anthropogenic TCS metabolism in China in 2008. The systematic SFA results were used to determine possible exposure pathways and trends in environmental exposure potential through different pathways. TCS discharged in wastewater mainly flowed into surface water sediment, ocean, and soil, where it accumulates in aquatic and agricultural products that may pose a higher risk to human health than brief exposure during consumption. Only 22% of TCS discharged was removed in the built environment with the remainder discharged into the natural environment, indicating that anthropogenic TCS metabolism in China is unsustainable. Per capita TCS consumption increased 209% from 2003 to 2012, resulting in increased discharge and accumulation in the environment. If current trends continue, it will increase to 713 mg capita(-1) yr(-1) in 2015 and 957 mg capita(-1) yr(-1) in 2020. Accordingly, annual environmental exposure potential will increase from 388 mg capita(-1) in 2008 to 557 mg capita(-1) in 2015 and 747 mg capita(-1) in 2020, indicating an increasing trend of exposure to environmental TCS. Results of Pearson correlation analysis suggested that feasible countermeasures to reduce environmental exposure potential for triclosan would include encouraging the development of small cities, raising awareness of health risks, nurturing environmentally-friendly consumer values, and improving the environmental performance of TCS-containing products.

Sonoelectrochemical degradation of triclosan in water

The sonoelectrochemical degradation of triclosan in aqueous solutions with high-frequency ultrasound (850kHz) and various electrodes was investigated. Diamond coated niobium electrode showed the best results and was used as standard electrode, leading to effective degradation and positive synergistic effect. The influence of different parameters on the degradation degree and energy efficiency were evaluated and favorable reaction conditions were found. It could be shown that 92% of triclosan (1mgL(-1) aqueous solution) was degraded within 15min, following pseudo-first order kinetics.

A novel antibiotic-delivery system by using ovotransferrin as targeting molecule

Synthetic antibiotics and antimicrobial agents, such as sulfonamide and triclosan (TCS), have provided new avenues in the treatment of bacterial infections, as they target lethal intracellular pathways. Sulfonamide antibiotics block synthesis of folic acid by inhibiting dihydrofolate reductase (DHFR) while TCS block fatty acid synthesis through inhibition of enoyl-ACP reductase (FabI). They are water-insoluble agents and high doses are toxic, limiting their therapeutic efficiency. In this study, an antibiotic drug-targeting strategy based on utilizing ovotransferrin (OTf) as a carrier to allow specific targeting of the drug to microbial or mammalian cells via the transferrin receptor (TfR) is explored, with potential to alleviate insolubility and toxicity problems. Complexation, through non-covalent interaction, with OTf turned sulfa antibiotics or TCS into completely soluble in aqueous solution. OTf complexes showed superior bactericidal activity against several bacterial strains compared to the activity of free agents. Strikingly, a multi-drug resistant Salmonella strain become susceptible to antibiotics-OTf complexes while a tolC-knockout mutant strain become susceptible to OTf and more sensitive to the complexes. The antibiotic bound to OTf was, thus exported through the multi-drug efflux pump TolC in Salmonella wild-type strain. Further, antibiotics-OTf complexes were able to efficiently kill intracellular pathogens after infecting human colon carcinoma cells (HCT-116). The results demonstrate, for the first time, that the TfR mediated endocytosis of OTf can be utilized to specifically target drugs directly to pathogens or intracellularly infected cells and highlights the potency of the antibiotic-OTf complex for the treatment of infectious diseases.

Triclosan occurrence in freshwater systems in the United States (1999-2012): a meta-analysis

Recently, concern has grown regarding the presence of triclosan (TCS) in waters because of its potential for causing ecological and human health effects. The authors present a statistical analysis of TCS concentrations reported between 1999 and 2012 in freshwater environments in the United States and provide a comparison with available health-based and aquatic guidance values. Data from 46 peer-reviewed and unpublished investigations from 45 states and 1 US territory were included in the meta-analysis, encompassing the following coded water types: untreated (raw wastewater), effluent (wastewater treatment plant effluent), effluent-impacted environmental, environmental, and finished drinking water (total n = 2305). Triclosan was most frequently detected in untreated waters (92% detection frequency; mean ± standard error, 11 270 ± 2925 ng/L; n = 237), but concentrations were significantly reduced in effluent waters (83% detection frequency 775 ± 311 ng/L; n = 192, α = 0.05). Triclosan concentration in effluent-impacted environmental waters (62% detection frequency; 130 ± 17 ng/L; n = 228) was not significantly reduced from effluent waters but was significantly greater than TCS in environmental waters not classified as effluent impacted (11% detection frequency; 13 ± 3 ng/L; n = 1195). In finished drinking water, TCS was largely undetected (1% detection frequency; 4 ± 2 ng/L n = 453), suggesting that for the United States, drinking water is not an appreciable source of TCS exposure. In posttreatment waters, average TCS concentrations were below part-per-billion levels. Although no US regulatory standard exists for TCS in aquatic systems, comparison of averages reported in the present study with a predicted-no-effect concentration (PNEC) of 500 ng/L showed that 5.3% of effluent-impacted environmental waters were above the PNEC for changes in algal biomass, while only 0.25% of environmental waters surpassed this value.

Drought episode modulates the response of river biofilms to triclosan

The consequences of global change on rivers include altered flow regime, and entrance of compounds that may be toxic to biota. When water is scarce, a reduced dilution capacity may amplify the effects of chemical pollution. Therefore, studying the response of natural communities to compromised water flow and to toxicants is critical for assessing how global change may affect river ecosystems. This work aims to investigate how an episode of drought might influence the response of river biofilms to pulses of triclosan (TCS). The objectives were to assess the separate and combined effects of simulated drought (achieved through drastic flow alteration) and of TCS exposure on biofilms growing in artificial channels. Thus, three-week-old biofilms were studied under four conditions: Control (normal water flow); Simulated Drought (1 week reduced flow+2 days interrupted flow); TCS only (normal water flow plus a 48-h pulse of TCS); and Simulated Drought+TCS. All channels were then left for 2 weeks under steady flow conditions, and their responses and recovery were studied. Several descriptors of biofilms were analyzed before and after each step. Flow reduction and subsequent interruption were found to provoke an increase in extracellular phosphatase activity, bacterial mortality and green algae biomass. The TCS pulses severely affected biofilms: they drastically reduced photosynthetic efficiency, the viability of bacteria and diatoms, and phosphate uptake. Latent consequences evidenced significant combined effects caused by the two stressors. The biofilms exposed only to TCS recovered far better than those subjected to both altered flow and subsequent TCS exposure: the latter suffered more persistent consequences, indicating that simulated drought amplified the toxicity of this compound. This finding has implications for river ecosystems, as it suggests that the toxicity of pollutants to biofilms may be exacerbated following a drought.

Triclosan reduces the levels of global DNA methylation in HepG2 cells

Triclosan (TCS), an antibacterial agent, is widely used in a variety of personal care and industrial products. TCS is associated with the development of liver tumors in rodents and has become a concern to environmental and human health. This study is aimed at investigating whether TCS could modulate the levels of global DNA methylation (GDM) in human hepatocytes. We found that treatment with different doses (1.25-10 μM) of TCS did not affect HepG2 cell viability, but significantly reduced the levels of GDM in HepG2 cells, and inhibited DNMT1 activity. Furthermore, treatment with TCS significantly inhibited the methylated DNA-binding domain 2 (MBD2), MBD3, and MeCP2 mRNA transcription. In addition, treatment with TCS promoted the accumulation of 8-hydroxy-2-deoxyguanosine (8-OHdG) in a dose-dependent manner, which was abrogated by treatment with an antioxidant, N-acetylcysteine (NAC). Collectively, our data indicated that TCS reduced the levels of GDM and down-regulated the MBD2, MBD3, and MeCP2 gene expression by increasing 8-OHdG levels and inhibiting the DNMT1 activity in HepG2 cells.

Occurrence and toxicity of antimicrobial triclosan and by-products in the environment

INTRODUCTION AND AIMS

A review was undertaken on the occurrence, toxicity, and degradation of triclosan (TCS; 5-chloro-2,4-dichlorophenoxy)phenol) in the environment. TCS is a synthetic, broad-spectrum antibacterial agent incorporated in a wide variety of household and personal care products such as hand soap, toothpaste, and deodorants but also in textile fibers used in a range of other consumer products (e.g., toys, undergarments and cutting boards among other things).

OCCURRENCE

Because of its partial elimination in sewage treatment plants, most reports describe TCS as one of the most commonly encountered substances in solid and water environmental compartments. It has been detected in a microgram per liter or microgram per kilogram level in sewage treatment plants (influents, effluents, and sludges), natural waters (rivers, lakes, and estuarine waters), and sediments as well as in drinking water.

TOXICITY

Moreover, due to its high hydrophobicity, TCS can accumulate in fatty tissues and has been found in fish and human samples (urine, breast milk, and serum). TCS is known to be biodegradable, photo-unstable, and reactive towards chlorine and ozone.

DISCUSSION

As a consequence, it can be transformed into potentially more toxic and persistent compounds, such as chlorinated phenols and biphenyl ethers after chlorination, methyl triclosan after biological methylation, and chlorinated dibenzodioxins after photooxidation. The toxicity of TCS toward aquatic organisms like fish, crustaceans, and algae has been demonstrated with EC50 values near TCS environmental concentrations. It has even been shown to produce cytotoxic, genotoxic, and endocrine disruptor effects.

CONCLUSION

Furthermore, the excessive use of TCS is suspected to increase the risk of emergence of TCS-resistant bacteria and the selection of resistant strains.

Emerging pollutants in sewage, surface and drinking water in Galicia (NW Spain)

A monitoring programme was carried out on wastewater, surface and drinking water on the NW area of Spain during the four seasons of a year period (November 2007-September 2008). This study covered a series of emerging pollutants of different classes, including pharmaceuticals, neutral and acidic organophosphorus flame retardant/plasticizers (OPs), triclosan, phenoxy-herbicides, insect repellents and UV filters. From the total set of 53 compounds, 19 were found in raw wastewater with median concentrations higher than 0.1 μg L(-1). Among them, salicylic acid, ibuprofen and the UV filter benzophenone-4 (BP-4) were the most concentrated, exceeding the 1 μg L(-1) median value. Subsequently, 11 of these contaminants are not efficiently enough removed in the small WWTPs tested and their median concentrations in effluents still surpassed the 0.1 μg L(-1), so that they can spread through surface water. These chemicals are the pharmaceuticals naproxen, diclofenac and atenolol; the OPs tri(2-chloroethyl) phosphate (TCEP), tri(chloropropyl) phosphate (TCPP), tri-n-butyl phosphate (TnBP), diphenyl phosphate (DPhP) and diethylhexyl phosphate (DEHP); and the sulphonate UV filters BP-4 and 2-phenylbenzimidazole-5-sulphonic acid (PBSA). These OPs were then the dominant emerging pollutants occurring in surface and drinking water, where they are detected in the 20-200 ng L(-1) range. Pharmaceuticals and UV filters are typically below the 10 ng L(-1) level. Finally, herbicides were only detected in the last sampling campaign under the 100 ng L(-1) drinking water European Union limit.

Triclosan: environmental exposure, toxicity and mechanisms of action

Triclosan [5-chloro-2-(2,4-dichlorophenoxy)phenol; TCS] is a broad spectrum antibacterial agent used in personal care, veterinary, industrial and household products. TCS is commonly detected in aquatic ecosystems, as it is only partially removed during the wastewater treatment process. Sorption, biodegradation and photolytic degradation mitigate the availability of TCS to aquatic biota; however the by-products such as methyltriclosan and other chlorinated phenols may be more resistant to degradation and have higher toxicity than the parent compound. The continuous exposure of aquatic organisms to TCS, coupled with its bioaccumulation potential, have led to detectable levels of the antimicrobial in a number of aquatic species. TCS has been also detected in breast milk, urine and plasma, with levels of TCS in the blood correlating with consumer use patterns of the antimicrobial. Mammalian systemic toxicity studies indicate that TCS is neither acutely toxic, mutagenic, carcinogenic, nor a developmental toxicant. Recently, however, concern has been raised over TCS's potential for endocrine disruption, as the antimicrobial has been shown to disrupt thyroid hormone homeostasis and possibly the reproductive axis. Moreover, there is strong evidence that aquatic species such as algae, invertebrates and certain types of fish are much more sensitive to TCS than mammals. TCS is highly toxic to algae and exerts reproductive and developmental effects in some fish. The potential for endocrine disruption and antibiotic cross-resistance highlights the importance of the judicious use of TCS, whereby the use of TCS should be limited to applications where it has been shown to be effective.

New drug-targeting strategy from beneath the shell of egg

IMPORTANCE OF THE FIELD

Antibiotic resistance is a serious problem that continues to challenge the healthcare sectors and has become increasingly alarming in the past few years. To face this emerging global crisis, there is a need to find a new class of antibiotics that act on new microbial targets and/or harness existing antibiotics by developing new drug-targeting strategies.

AREAS COVERED IN THIS REVIEW

This review: explores an innovative drug-delivery strategy of using hen egg lysozyme as a carrier to enable water solubilization and to allow specific targeting to the microbial cells of a water-insoluble antimicrobial agent with a powerful killing action; addresses potentials for lysozyme in antibiotics drug targeting; and provides insight for the future direction of this highly prospective technology.

WHAT THE READER WILL GAIN

The unique features and advantages of lysozyme-based drug delivery system are highlighted. The efficiency of lysozyme in solubilization and delivery of lipophilic antibiotics, to reformulate drugs that may fail clinical trials owing to low solubility, is emphasized.

TAKE HOME MESSAGE

Fewer pharmaceutical companies are inventing new antibiotics because of long development times and high failure rates. Combining lysozyme with a powerful old antibiotic may open doors to revolutionizing medicine, particularly in the treatment of deadly infections.

Environmental implications of the surfactant effect on the photochemistry of (substituted) 4-chlorophenols in water

The effect of surfactants (cationic, anionic, and nonionic) on the direct photochemistry of selected chlorophenol antimicrobials in aqueous solution has been investigated. The inclusion of the starting aromatics into micelles markedly directs the reaction towards a cleaner process (mainly photoreduction), contrasting with the variety of processes observed when the irradiation is carried out in neat water. This could have some implications from the environmental point of view because such paths may be significant in natural aquatic systems.

Potent antimicrobial action of triclosan-lysozyme complex against skin pathogens mediated through drug-targeted delivery mechanism

Triclosan (TCS), an antimicrobial agent that inhibits bacterial fatty acid synthesis by blocking the active site of enoyl-ACP reductase (FabI), is a water-insoluble agent that limits its therapeutic candidacy. We have recently shown that the water solubility and antimicrobial activity of TCS were greatly enhanced when complexed to lysozyme (LZ). This study is to examine the therapeutic potential of triclosan-lysozyme (T-LZ) complex against common skin pathogens expressing different levels of FabI, and to delineate the drug-targeting mechanism by lysozyme. The T-LZ exhibited superior antimicrobial activity against two bacterial skin pathogens, Propionibacterium acnes and Corynebacterium minutissimum, while yeast pathogens, Candida albicans and Malassezia furfur lacking FabI enzyme were insensitive to the complex. Unlike free TCS or LZ, the T-LZ complex exhibited a potent antibacterial activity under a wide range of pH condition and salt concentration. Interestingly, P. acnes expressing greater amount of FabI was more susceptible to the T-LZ complex than C. minutissimum that produces lesser amount of the enzyme. A sensitive assay of FabI activity revealed that P. acnes and C. minutissimum treated with the complex exhibited significant inhibition of the intracellular FabI activity than cells treated with free TCS, indicating the efficiency of lysozyme to specifically deliver TCS to its target (FabI) in the cytoplasm of bacterial cells. These results demonstrate, for the first time, that lysozyme is a potential drug carrier that allows specific targeting to the microbial cells of the water-insoluble triclosan and highlights the potency of the complex for the treatment of skin bacterial infections.

Occurrence, efficacy, metabolism, and toxicity of triclosan

Triclosan has broad-spectrum anti-microbial activity against most gram-negative and gram-positive bacteria. It is widely used in personal care products, household items, medical devices, and clinical settings. Due to its extensive use, there is potential for humans in all age groups to receive life-time exposures to triclosan, and, indeed, triclosan has been detected in human tissues and the environment. Data gaps exist regarding the chronic dermal toxicity and carcinogenicity of triclosan, which is needed for the risk assessment of triclosan. The US Food and Drug Administration (FDA) nominated triclosan to the National Toxicology Program (NTP) for toxicological evaluations. Currently, the NTP is conducting several dermal toxicological studies to determine the carcinogenic potential of triclosan, evaluate its endocrine and developmental-reproductive effects, and investigate the potential UV-induced dermal formation of chlorinated phenols and dioxins of triclosan. This paper reviews data on the human exposure, environmental fate, efficacy of anti-microbial activity, absorption, distribution, metabolism and elimination, endocrine disrupting effects, and toxicity of triclosan.

Mass loadings of triclosan and triclocarbon from four wastewater treatment plants to three rivers and landfill in Savannah, Georgia, USA

Triclosan (TCS) and triclocarbon (TCC) are bactericides used in various consumer and personal-care products. Recent studies have revealed considerable levels of these bactericides in wastewater, aquatic wildlife, and human samples. Consequently, in this study we measured TCS and TCC in influent and effluent, sludge, and pond water/sediment samples from four wastewater treatment plants (WWTPs) and three major rivers in Savannah, Georgia (USA). Among these treatment plants, the Wilshire plant showed elevated concentrations of TCS (influent, 86,161; effluent, 5370 ng/L), whereas TCC was greater in the Georgetown plant (influent, 36,221) and the Wilshire plant effluent (3045 ng/L). Clearance of TCS and TCC were 95 and 92%, respectively, in the President Street plant, 94 and 85%, respectively, in the Wilshire plant, 99 and 80%, respectively, in the Travis Field plant, and 99 and 99%, respectively, in the Georgetown plant. Based on the mass flow estimate, 138 g/day of TCS and 214 g/day TCC are released into the Savannah River from the President Street, Travis Field, and Wilshire plants and 1.60 g/day TCS and 1.64 g/day TCC are released to the Ogeechee River from the Georgetown plant. Based on the sludge data, the loading estimate can be calculated that 32 and 0.004 g/day TCS and 53 and 0.01 g/day TCC (nonincinerated and incinerated, respectively) are deposited in landfill from the President Street plant alone, whereas 4.6, 26, and 6.8 g/day TCS and 3.8, 23, and 5.9 g/day TCC (wet sludge) were produced and dumped in landfill from the rest of the WWTPs. Incineration of wet sludge can eliminate 99.99% of TCS and TCC. Concentrations of TCS and TCC in water and sediment were greater in the Vernon River, followed by the Savannah River and the Ogeechee River.

Passive sampling as a tool for obtaining reliable analytical information in environmental quality monitoring

Passive sampling technology has been developing very quickly for the past 20 years, and is widely used for monitoring pollutants in different environments, for example air, water, and soil. It has many significant advantages, including simplicity, low cost, no need for expensive and complicated equipment, no power requirements, unattended operation, and the ability to produce accurate results. The present generation of passive samplers enables detection and analysis of bioavailable pollutants at low and very low concentrations and investigation of the environmental concentration of organic and inorganic pollutants not only on the local scale but also on continental and global scales. This review describes the current application of passive sampling techniques in environmental analysis and monitoring, under both equilibrium and non-equilibrium conditions.

Simultaneous determination of parabens, triclosan and triclocarban in water by liquid chromatography/electrospray ionisation tandem mass spectrometry

A method for the determination of several household biocides in water by liquid chromatography/electrospray ionisation tandem mass spectrometry (LC/ESI-MS/MS) is presented. It permits the simultaneous determination of triclosan (TCS), triclocarban (TCC) and seven parabens, including the distinction between branched and linear isomers of propyl (i-PrP and n-PrP) and butyl parabens (i-BuP and n-BuP). Prior to LC/MS/MS, analytes are preconcentrated by solid-phase extraction (SPE) on Oasis HLB (60 mg) cartridges at natural sample pH and subsequently eluted with 4 mL of methanol. This simple SPE procedure provides extraction recoveries above 85% except for raw wastewater, where it falls to 65% for TCC. The performance of the method was tested with two triple-quadrupole LC/MS instruments from a low/mid and mid/high market range: a Varian 1200L and an API-4000. The latter system provided between 3 and 80 times lower limits of quantification (LOQs) than the first one, in the 0.08-0.44 ng/L range for surface water. Moreover, a comparison of matrix effects on both instruments showed a very different behaviour, particularly in the case of parabens. For these compounds signal suppression was observed in the 1200L instrument and signal enhancement with the 4000 instrument. As a result, different calibration approaches were chosen for them and this pointed to the need of matrix effect re-evaluation in method transfer between different LC/MS systems. The application of the method to real samples showed the ubiquity of methyl paraben (MeP) and n-PrP (at the 1-6 microg/L in raw wastewater) and the coexistence of i-BuP and n-BuP at similar levels (ca. 100-200 ng/L in raw wastewater).

Biodegradation of pharmaceutical and personal care products

Medical treatments and personal hygiene lead to the steady release of pharmaceutical and personal care products (PPCPs) into the environment. Some of these PPCPs have been shown to have detrimental environmental effects and could potentially impact human health. Understanding the biological transformation of PPCPs is essential for accurately determining their ultimate environmental fate, conducting accurate risk assessments, and improving PPCP removal. We summarize the current literature concerning the biological transformation of PPCPs in wastewater treatment plants, the environment, and by pure cultures of bacterial isolates. Although some PPCPs, such as ibuprofen, are readily degraded under most studied conditions, others, such as carbamazepine, tend to be recalcitrant. This variation in the biodegradability of PPCPs can be attributed to structural differences, because PPCPs are classified by application, not chemical structure. The degradation pathways of octylphenol by Sphingomonas sp. strain PWE1, ibuprofen by Sphingomonas sp. strain Ibu-2, and DEET by Pseudomonas putida DTB are discussed in more detail.

Spectroscopic, kinetic and dosimetric features of the radical species produced after radiodegradation of solid triclosan

In the present work, spectroscopic, kinetic and dosimetric features of the radicalic intermediates produced after gamma irradiation at room temperature of solid triclosan (2,4,4-trichloro-2-hydroxydiphenyl ether; TCS) were investigated by means of electron spin resonance spectroscopy (ESR) at various temperatures. The same material was also irradiated with UV light, and an ESR spectrum very similar to that obtained for gamma-irradiated TCS, was recorded. The ESR spectrum of TCS is characterized by an unresolved doublet with resonance lines split into other doublets. An evaluation technique based on variations of four assigned peak-to-peak amplitudes and signal intensity was adopted, to monitor the evolution of the spectrum under different experimental conditions. Radicals of one type were proposed to be created upon irradiation exhibiting decays via intra-track and inter-track recombination reactions with activation energies of 43 +/- 2 and 139 +/- 6 kJ/mol, respectively. A radical exhibiting axial g anisotropy and interacting with two un-equivalent protons was found to describe the experimental spectrum well. The sensitivity of TCS to gamma radiation was high (G = 0.12) suggesting TCS to be a suitable dosimetric material in measuring normal and accidental radiation doses in the range of (1-25 kGy).

Sonochemical degradation of triclosan in water and wastewater

The sonochemical degradation of 5 microg l(-1) triclosan, a priority micro-pollutant, in various environmental samples (seawater, urban runoff and influent domestic wastewater) as well as in model solutions (pure and saline water) was investigated. Experiments were conducted with a horn-type sonicator operating at 80 kHz frequency and a nominal applied power of 135 W, while solid-phase microextraction coupled with gas chromatography-electron capture detector (SPME/GC-ECD) was employed to monitor triclosan degradation. The latter followed pseudo-first order kinetics with the rate constant being (min(-1)): 0.2284 for seawater>0.1051 for 3.5% NaCl in deionised water>0.0597 for centrifuged urban runoff approximately 0.0523 for untreated urban runoff >0.0272 for deionised water >0.0063 for wastewater influent. SPME/GC-ECD and SPME coupled with gas chromatography-mass spectrometry (SPME/GC-MS) were also used to check for the formation of chlorinated and other toxic by-products; at the conditions in question, the presence of such compounds was not confirmed.

Electrostatic accumulation and determination of triclosan in ultrathin carbon nanoparticle composite film electrodes

A film composed of carbon nanoparticles and poly(diallyldimethylammonium chloride) or CNP-PDDAC is formed in a layer-by-layer deposition process at tin-doped indium oxide (ITO) substrates. Excess positive binding sites within this film in aqueous phosphate buffer at pH 9.5 are quantified by adsorption of iron(III)phthalocyanine tetrasulfonate and indigo carmine. Both anionic redox systems bind with Langmuirian characteristics (K approximately 10(5) mol(-1) dm3) and show electrochemical reactivity throughout the film at different thicknesses. Therefore, the electrical conductivity in CNP-PDDAC films is good and the positive binding sites are approximately 140 pmol cm(-2) per layer. Structural instability of the CNP-PDDAC film in the presence of high concentrations of iron(III)phthalocyanine tetrasulfonate or indigo carmine is observed. Triclosan, a widely used anti-bacterial and anti-fungal agent, exists in aqueous media at pH 9.5 as a negatively charged chlorinated poly-aromatic phenol. Due to the negative charge, triclosan is readily accumulated into CNP-PDDAC films with an efficiency consistent with that expected for simple electrostatic interaction with the cationic binding sites. Oxidation of bound triclosan occurs at 0.6 V versus SCE in a chemically irreversible process. The CNP-PDDAC film electrode is renewed by rinsing in organic solvent and the triclosan oxidation response is shown to correlate with the triclosan concentration in solution from 0.5 to 50 microM. Applications of the CNP-PDDAC film electrode (or improved versions of it) in analysis or in anodic extraction are proposed.

Nonequilibrium hollow-fiber liquid-phase microextraction with in situ derivatization for the measurement of triclosan in aqueous samples by gas chromatography-mass spectrometry

Hollow-fiber liquid-phase microextraction (HF-LPME), a relatively new sample preparation technique, has attracted much interest in the field of environmental analysis. In the current study, a novel method based on hollow-fiber liquid-phase microextraction with in situ derivatization and gas chromatography-mass spectrometry for the measurement of triclosan in aqueous samples is described. Hollow-fiber liquid-phase microextraction conditions such as the type of extraction solvent, the stirring rate, the volume of derivatizing reagent, and the extraction time were investigated. When the conditions had been optimized, the linear range was found to be 0.05-100 microg l(-1) for triclosan, and the limit of detection to be 0.02 microg l(-1). Tap water and surface water samples collected from our laboratory and Wohushan reservoir, respectively, were successfully analyzed using the proposed method. The recoveries from the spiked water samples were 83.6 and 114.1%, respectively; and the relative standard deviation (RSD) at the 1.0 microg l(-1) level was 6.9%.

Online phototransformation-flow injection chemiluminescence determination of triclosan

A highly selective and sensitive chemiluminescence method for the determination of triclosan is proposed. The method is based on the phototransformation of triclosan to a light-emitting precursor in the presence of fluorescein in alkaline medium and the chemiluminescence reaction is then triggered by strong base or oxidants such as N-bromosuccinimide. Based on this reaction an online phototransformation-flow injection manifold was developed, in which the photoreactor comprises a 150-cm-long x 0.8-mm-i.d. piece of PTFE tubing coiled around a 25-W fluorescent lamp, and the phototransformed products were then injected into a carrier stream of borate buffer. After mixing with the oxidant stream the produced light was detected by a photomultiplier. A wide calibration range from 8.0 x 10(-8) to 1.0 x 10(-4) mol L(-1) was obtained under the optimized conditions, and the detection limit was as low as 5.0 x 10(-8) mol L(-1). The whole process of analysis, including the online phototransformation and subsequent chemiluminescence detection, could be completed in 6 min. Most of the foreign substances tested showed high tolerance levels, and the proposed method was directly applied to the determination of triclosan in toothpaste samples without any pre-separation procedure. Figure Schematic representation of the phototransformation of triclosan and subsequent chemiluminescence reaction.

Alternative sample preparation method for photochemical studies based on solid phase microextraction: synthetic pyrethroid photochemistry

An alternative sample preparation method for photochemical studies, which overcomes all the disadvantages associated with classical approaches, is proposed. The method is based on Solid Phase Microextraction (SPME) and can be considered as being within the scope of "green photochemistry", especially when it is combined with sunlight irradiation. To demonstrate the potential of the procedure, photochemical studies of synthetic pyrethroids were carried out. Photodegradation pathways for five dihalogenovinyl-substituted pyrethroid pesticides: permethrin, deltamethrin, cyfluthrin, cypermethrin and lambda-cyhalothrin, are proposed, and kinetic curves and parameters provided. This information, obtained by rapidly carried out, green experiments, allows us to corroborate photoproducts reported by other authors and to identify the photoproducts proposed for the first time in the present study.

Further research on the photo-SPME of triclosan

In this study the photoinduced degradation of triclosan has been investigated by photo-solid-phase microextraction (photo-SPME). In photo-SPME, photodegradation is carried out on the SPME fibre containing the target compound. Triclosan was extracted from aqueous solutions by use of polydimethylsiloxane SPME fibres and these were subsequently exposed to UV irradiation (power 8 W, wavelength 254 nm) for different times (from 2 to 60 min). The photodegradation kinetics of triclosan were investigated, the photoproducts generated were tentatively identified, and the photochemical behaviour of these products was studied by use of this on-fibre approach followed by gas chromatographic-mass spectrometric analysis. Eight photoproducts were tentatively identified, including chlorinated phenols, chlorohydroxydiphenyl ethers, 2,8-dichlorodibenzo-p-dioxin, and a possible dichlorodibenzodioxin isomer or dichlorohydroxydibenzofuran. The main photodegradation mechanisms were postulated and photodegradation pathways proposed. The effect of pH on triclosan degradation and on triclosan-to-dioxin conversion was also investigated. Triclosan degradation occurred, and generation of 2,8-dichlorodibenzo-p-dioxin was confirmed, throughout the pH range studied (from 3 to 9).