Uptake and accumulation of antimicrobials, triclocarban and triclosan, by food crops in a hydroponic system

Charged polystyrene microplastics inhibit uptake and transformation of 14C-triclosan in hydroponics-cabbage system

INTRODUCTION

Since the outbreak of COVID-19, microplastics (MPs) and triclosan in pharmaceuticals and personal care products (PPCPs) are markedly rising. MPs and triclosan are co-present in the environment, but their interactions and subsequent implications on the fate of triclosan in plants are not well understood.

OBJECTIVE

This study aimed to investigate effects of charged polystyrene microplastics (PS-MPs) on the fate of triclosan in cabbage plants under a hydroponic system.

METHODS

14C-labeling method and liquid chromatography coupled with quadrupole/time-of-flight mass spectrometry (LC-QTOF-MS) analysis were applied to clarify the bioaccumulation, distribution, and metabolism of triclosan in hydroponics-cabbage system. The distribution of differentially charged PS-MPs in cabbage was investigated by confocal laser scanning microscopy and scanning electron microscopy.

RESULTS

The results showed that MPs had a significant impact on bioaccumulation and metabolism of triclosan in hydroponics-cabbage system. PS-COO-, PS, and PS-NH3+ MPs decreased the bioaccumulation of triclosan in cabbage by 69.1 %, 81.5 %, and 87.7 %, respectively, in comparison with the non-MP treatment (control). PS-MPs also reduced the translocation of triclosan from the roots to the shoots in cabbage, with a reduction rate of 15.6 %, 28.3 %, and 65.8 % for PS-COO-, PS, and PS-NH3+, respectively. In addition, PS-NH3+ profoundly inhibited the triclosan metabolism pathways such as sulfonation, nitration, and nitrosation in the hydroponics-cabbage system. The above findings might be linked to strong adsorption between PS-NH3+ and triclosan, and PS-NH3+ may also potentially inhibit the growth of cabbage. Specially, the amount of triclosan adsorbed on PS-NH3+ was significantly greater than that on PS and PS-COO-. The cabbage biomass was reduced by 76.9 % in PS-NH3+ groups, in comparison with the control.

CONCLUSION

The uptake and transformation of triclosan in hydroponics-cabbage system were significantly inhibited by charged PS-MPs, especially PS-NH3+. This provides new insights into the fate of triclosan and other PPCPs coexisted with microplastics for potential risk assessments.

Accumulation of micropollutants, byproducts, and metabolites in vegetables cultivated with treated water

Due to a lack of water resources, people are starting to use treated wastewater to irrigate crops and vegetables. However, the risk of micropollutant exposure from vegetables cultivated with treated wastewater has been largely underestimated. To elucidate this underestimation, a hydroponic system for lettuce cultivation using a nutrient solution spiked with three pharmaceuticals with different log KOW values (acetaminophen (0.46), ketamine (2.18) and methadone (3.93)) was examined, and the total bioconcentration factors (BCFs) (including the transformation of metabolites) of the pharmaceuticals were found to be 0, 120 ± 7.76 and 176 ± 16.0 L/kg, respectively. To simulate treated wastewater, these nutrient solutions were first treated by sunlight photolysis, chlorination, and sunlight/chlorine before use in lettuce cultivation. During the treatment, ketamine and methadone were transformed into norketamine (up to 6.0 %) and 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) (up to 16 %), respectively; the BCF of norketamine (162 ± 22.6 L/kg) was found to be even greater than ketamine. In addition, other degradation byproducts (including 3 trace and 13 undetected byproducts in the nutrient solutions) were taken up by the lettuce. In parallel, ketamine and methadone can also undergo metabolism in lettuce; the conversion rate to norketamine increased from 22 ± 7.0 % to 45 ± 0.062 when the ketamine concentration decreased from 1000 to 50 μg/L.

Critical review on the environmental behaviors and toxicity of triclosan and its removal technologies

As a highly effective broad-spectrum antibacterial agent, triclosan (TCS) is widely used in personal care and medical disinfection products, resulting in its widespread occurrence in aquatic and terrestrial environments, and even in the human body. Notably, the use of TCS surged during the COVID-19 outbreak, leading to increasing environmental TCS pollution pressure. From the perspective of environmental health, it is essential to systematically understand the environmental occurrence and behavior of TCS, its toxicological effects on biota and humans, and technologies to remove TCS from the environment. This review comprehensively summarizes the current knowledge regarding the sources and behavior of TCS in surface water, groundwater, and soil systems, focusing on its toxicological effects on aquatic and terrestrial organisms. Effluent from wastewater treatment plants is the primary source of TCS in aquatic systems, whereas sewage application and/or wastewater irrigation are the major sources of TCS in soil. Human exposure pathways to TCS and associated adverse outcomes were also analyzed. Skin and oral mucosal absorption, and dietary intake are important TCS exposure pathways. Reducing or completely degrading TCS in the environment is important for alleviating environmental pollution and protecting public health. Therefore, this paper reviews the removal mechanisms, including adsorption, biotic and abiotic redox reactions, and the influencing factors. In addition, the advantages and disadvantages of the different techniques are compared, and development prospects are proposed. These findings provide a basis for the management and risk assessment of TCS and are beneficial for the application of treatment technology in TCS removal.

Personal care products in soil-plant and hydroponic systems: Uptake, translocation, and accumulation

Personal care products (PCPs) are organic compounds that are incorporated in several daily life products, such as shampoos, lotions, perfumes, cleaning products, air fresheners, etc. Due to their massive and continuous use and because they are not routinely monitored in the environment, these compounds are considered emerging contaminants. In fact, residues of PCPs are being discharged into the sewage system, reaching wastewater treatment plants (WWTPs), where most of these compounds are not completely degraded, being partially released into the environment via the final effluents and/or accumulating in the sewage sludges. Environmental sustainability is nowadays one of the main pillars of society and the application of circular economy models, promoting the waste valorisation, is increasingly encouraged. Therefore, irrigation with reclaimed wastewater or soil fertilization with sewage sludge/biosolids are interesting solutions. However, these practices raise concerns due to the potential risks associated to the presence of hazardous compounds, including PCPs. When applied to agricultural soils, PCPs present in these matrices can contaminate the soil or be taken up by crops. Crops can therefore become a route of exposure for humans and pose a risk to public health. However, the extent to which PCPs are taken up and bioaccumulated in crops is highly dependent on the physicochemical properties of the compounds, environmental variables, and the plant species. This issue has attracted the attention of scientists in recent years and the number of publications on this topic has rapidly increased, but a systematic review of these studies is lacking. Therefore, the present paper reviews the uptake, accumulation, and translocation of different classes of PCPs (biocides, parabens, synthetic musks, phthalates, UV-filters) following application of sewage sludge or reclaimed water under field and greenhouse conditions, but also in hydroponic systems. The factors influencing the uptake mechanism in plants were also discussed.

Health risk assessment of exposure to triclosan in pregnant women using Monte Carlo simulation techniques: based on biomonitoring data

This study aimed to assess the triclosan (TCS) health risk in an Iranian pregnant women sample by Monte Carlo simulation (MCS). The urinary TCS of 99 women after the 28th week of pregnancy was detected by gas chromatography/mass spectrometry detector (GC/MS), and the MCS model implemented a health risk assessment. The corresponding hazard quotient (HQ) and the sensitivity analysis were calculated. TCS was measured in 100% of the urine samples with a median concentration of 2.89 µg/L. The median of HQ was obtained at 1.93 × 10-4. The TCS exposure risk in the studied population was lower than the allowable limit. A comparison between HQ values in the two weight subgroups of pregnant women showed that the risk level is almost equal, and there was minimal health risk in pregnant women from exposure to TCS.

Acute exposure of triclocarban affects early embryo development in mouse through disrupting maternal-to-zygotic transition and epigenetic modifications

Triclocarban (TCC) is a broad-spectrum antibacterial agent used globally, and high concentrations of this harmful chemical exist in the environment. The human body is directly exposed to TCC through skin contact. Moreover, TCC is also absorbed through diet and inhaled through breathing, which results in its accumulation in the body. The safety profile of TCC and its potential impact on human health are still not completely clear; therefore, it becomes imperative to evaluate the reproductive toxicity of TCC. Here, we explored the effect of TCC on the early embryonic development of mice and its associated mechanisms. We found that acute exposure of TCC affected the early embryonic development of mice in a dose-dependent manner. Approximately 7600 differentially expressed genes (DEGs) were obtained by sequencing the transcriptome of 2-cell mouse embryos; of these, 3157 genes were upregulated and 4443 genes were downregulated in the TCC-treated embryos. GO and KEGG analysis revealed that the enriched genes were mainly involved in redox processes, RNA synthesis, DNA damage, apoptosis, mitochondria, endoplasmic reticulum, Golgi apparatus, cytoskeleton, peroxisome, RNA polymerase, and other components or processes. Moreover, the Venn analysis showed that the zygotic genome activation (ZGA) was affected and the degradation of maternal effector genes was inhibited. TCC induced changes in the epigenetic modification of 2-cell embryos. The level of DNA methylation increased significantly. Further, the levels of H3K27ac, H3K9ac, and H3K27me3 histone modifications decreased significantly, whereas those of H3K4me3 and H3K9me3 modifications increased significantly. Additionally, TCC induced oxidative stress and DNA damage in the 2-cell embryos. In conclusion, acute exposure of TCC affected early embryo development, destroyed early embryo gene expression, interfered with ZGA and maternal gene degradation, induced changes in epigenetic modification of early embryos, and led to oxidative stress and DNA damage in mouse early embryos.

Uptake and metabolism of 14C-triclosan in celery under hydroponic system

As triclosan is used extensively as an antimicrobial agent, it inevitably enters agroecosystems, when sewage and treated wastewater are applied to agricultural fields. As a result, triclosan can be accumulated into crops and vegetables. Currently, limited information is available on the metabolism of triclosan in vegetables. In this study, the fate of ¹⁴C-triclosan in celery under a hydroponic system was investigated in a 30-day laboratory test. Most (97.7 %) of the ¹⁴C-triclosan accumulated in celery. The bioconcentration factors of triclosan were up to 3140 L kg^-1 at day 30. The concentration of ¹⁴C-triclosan in roots (17.8 mg kg^-1) was 57- and 127-fold higher than that in stems (0.31 mg kg^-1) and leaves (0.14 mg kg^-1), respectively, at day 30, suggesting a higher accumulation of triclosan in celery roots and negligible transport to stems and leaves. Moreover, triclosan, as well as its eight metabolites, was detected and identified in celery tissues and the growth medium using ¹⁴C-labelling and LC-Q-TOF-MS analysis methods. Phase I metabolites in the growth medium were from hydroxylation, dechlorination, nitration, and nitrosylation. Phase II metabolism was the major pathway in celery tissues. Monosaccharide, disaccharide, and sulfate conjugates of triclosan were putatively identified. The results represent an important step toward a better evaluation of the behavior of triclosan in vegetables, with notable implications for environmental and human risk assessments of triclosan.

Triclosan and triclocarban as potential risk factors of colitis and colon cancer: Roles of gut microbiota involved

In recent decades there has been a dramatic increase in the incidence and prevalence of inflammatory bowel disease (IBD), a chronic inflammatory disease of the intestinal tissues and a major risk factor of developing colon cancer. While accumulating evidence supports that the rapid increase of IBD is mainly caused by exposure to environmental risk factors, the identities of the risk factors, as well as the mechanisms connecting environmental exposure with IBD, remain largely unknown. Triclosan (TCS) and triclocarban (TCC) are high-volume chemicals that are used as antimicrobial ingredients in consumer and industrial products. They are ubiquitous contaminants in the environment and are frequently detected in human populations. Recent studies showed that exposure to TCS/TCC, at human exposure-relevant doses, increases the severity of colitis and exacerbates colon tumorigenesis in mice, suggesting that they could be risk factors of IBD and associated diseases. The gut toxicities of these compounds require the presence of gut microbiota, since they fail to induce colonic inflammation in mice lacking the microbiota. Regarding the functional roles of the microbiota involved, gut commensal microbes and specific microbial β-glucuronidase (GUS) enzymes mediate colonic metabolism of TCS, leading to metabolic reactivation of TCS in the colon and contributing to its subsequent gut toxicity. Overall, these results support that these commonly used compounds could be environmental risk factors of IBD and associated diseases through gut microbiota-dependent mechanisms.

Correlation between human gut microbiome and diseases

Human gut microbiome is a major source of human bacterial population and a significant contribution to both positive and harmful effects. Due to its involvement in a variety of interactions, gut microorganisms have a great impact on our health throughout our lives. The impact of gut microbial population is been studied intensively in last two decades. Extensive literature survey focusing developments in the field were searched in English language Electronic Databases like PubMed, Google Scholar, Pubag, Google books, and Research Gate were mostly used to understand the role of human gut mirobiome and its role in different human diseases. Gut microbiome in healthy subjects differs from those who suffer from diseases. Type 2 diabetes, obesity, non-alcoholic liver disease, and cardiometabolic diseases have all been linked to dysbiosis of the gut microbiota. Pathogenesis of many disorders is also linked to changes in gut microbiota. Other diseases like cancer, arithritis, autism, depression, anxiety, sleep disorder, HIV, hypertension, and gout are also related to gut microbiota dysbiosis. We focus in this review on recent studies looking into the link between gut microbiome dysbiosis and disease etiology. Research on how gut microbiota affects host metabolism has been changed in past decades from descriptive analyses to high throughput integrative omics data analysis such as metagenomics and metabolomics. Identification of molecular mechanisms behind reported associations is been carried out in human, animals, and cells for measure of host physiology and mechanics. Still many the mechanisms are not completely understood.

Contaminants of emerging concern (CECs) in Zea mays: Uptake, translocation and distribution tissue patterns over the time and its relation with physicochemical properties and plant transpiration rate

Passive uptake of contaminants of emerging concern (CECs) and its relationship with physicochemical properties, such as lipophilicity (LogKow), ionization behavior (pKa), distribution coefficient (LogDow) and transpiration rate are scarcely studied. In the current study, hydroponically grown corn (Zea mays) was exposed to carbamazepine (CBZ), fluoxetine (FLX), gemfibrozil (GBZ), triclosan (TRI) and atrazine (ATZ)) at environmentally relevant concentrations (20 μg/L each one). Plant tissue concentrations of CECs were determined several times over 21 days. Eighteen plants were used, nine exposed to the CECs and nine untreated. Whole plants were harvested at 7, 14 and 21 days and separated into roots, stem, leaf and male bud flower (only at 21 days). Hydroponic solution was maintained at pH 5.5 throughout the study. CECs concentrations in the exposure solution and tissues were determined by LC-MS/MS. ATZ metabolites desisopropylatrazine (DIA) and desethylatrazine (DEA) were determined by LC-DAD. In shoot tissues, CBZ, FLX and ATZ were detected, while TRI and GBZ were detected only in roots. Root concentrations were related with LogKow (R²_ROOT = 0.415). Leaf and stem concentrations of CBZ, FLX and ATZ were linked with LogKow and strongly linked with pKa. Transpiration was related with CBZ and ATZ in shoot, but not related with FLX shoot levels. Neutral compounds such as CBZ (pKa = 13.94; 100% neutral) and ATZ (pKa = 1.6; 85% neutral) were taken up passively with transpiration. Root accumulation was related with CECs lipophilicity, while translocation and bioaccumulation in shoot were not only related with lipophilicity, but also with CECs ionization behavior and transpiration.

Distinct uptake and accumulation profiles of triclosan in youdonger (Brassica campestris subsp. Chinensis var. communis) under two planting systems: Evidence from 14C tracing techniques

Triclosan is a widely used biocide against microorganisms and is ubiquitously distributed in the environment. Triclosan can be accumulated into plants from soil and hydroponic media. However, little information is currently available on the comparative fate of triclosan in plants under soil and hydroponics cultivation conditions and factors governing uptake. Therefore, this study was designed to comparatively elucidate the uptake mechanism of ¹⁴C-triclosan in youdonger (Brassica campestris subsp. Chinensis var. communis) grown under different soils and hydroponics and clarify dominant uptake factors. Results showed that 77.2% of ¹⁴C were accumulated in youdonger grown in a hydroponic system, while only 1.24%-2.33% were accumulated in the two soil-planting systems. In addition, the bioconcentration factor (BCF) of ¹⁴C-triclosan in soil-plant systems was approximately 400-fold smaller than that in the hydroponics. In the soil-planting system, a strong linear correlation was found between concentrations of triclosan in soil pore water and youdonger plant (R² > 0.85, p < 0.01) at different incubation times. Therefore, triclosan in pore water might be a good indicator to estimate its accumulation in plants and is significantly affected by soil pH, clay, and organic matter contents. The estimated average dietary intakes of triclosan for youdonger grown in hydroponic and soil-planting systems were estimated to be 1.31 ng day^-1 kg^-1 and 0.05-0.12 ng day^-1 kg^-1, respectively, much lower than the acceptable dietary intakes of triclosan (83 μg day^-1 kg^-1), indicating no significant human health risks from youdonger consumption. This study provided insights into uptake routes of triclosan into youdonger plants from both soil and hydroponic systems, bioavailability of triclosan in different soils, and further assessment of human exposure to triclosan from youdonger.

Phytoremediation as an effective tool to handle emerging contaminants

Phytoremediation is a process which effectively uses plants as a tool to remove, detoxify or immobilize contaminants. It has been an eco-friendly and cost-effective technique to clean contaminated environments. The contaminants from various sources have caused an irreversible damage to all the biotic factors in the biosphere. Bioremediation has become an indispensable strategy in reclaiming or rehabilitating the environment that was damaged by the contaminants. The process of bioremediation has been extensively used for the past few decades to neutralize toxic contaminants, but the results have not been satisfactory due to the lack of cost-effectiveness, production of byproducts that are toxic and requirement of large landscape. Phytoremediation helps in treating chemical pollutants on two broad categories namely, emerging organic pollutants (EOPs) and emerging inorganic pollutants (EIOPs) under in situ conditions. The EOPs are produced from pharmaceutical, chemical and synthetic polymer industries, which have potential to pollute water and soil environments. Similarly, EIOPs are generated during mining operations, transportations and industries involved in urban development. Among the EIOPs, it has been noticed that there is pollution due to heavy metals, radioactive waste production and electronic waste in urban centers. Moreover, in recent times phytoremediation has been recognized as a feasible method to treat biological contaminants. Since remediation of soil and water is very important to preserve natural habitats and ecosystems, it is necessary to devise new strategies in using plants as a tool for remediation. In this review, we focus on recent advancements in phytoremediation strategies that could be utilized to mitigate the adverse effects of emerging contaminants without affecting the environment.

Metabolism and detoxification of pesticides in plants

Pesticides make indispensable contributions to agricultural productivity. However, the residues after their excessive use may be harmful to crop production, food safety and human health. Although the ability of plants (especially crops) to accumulate and metabolize pesticides has been intensively investigated, data describing the chemical and metabolic processes in plants are limited. Understanding how pesticides are metabolized is a key step toward developing cleaner crops with minimal pesticides in crops, creating new green pesticides (or safeners), and building up the engineered plants for environmental remediation. In this review, we describe the recently discovered mechanistic insights into pesticide metabolic pathways, and development of improved plant genotypes that break down pesticides more effectively. We highlight the identification of biological features and functions of major pesticide-metabolized enzymes such as laccases, glycosyltransferases, methyltransferases and ATP binding cassette (ABC) transporters, and discuss their chemical reactions involved in diverse pathways including the formation of pesticide S-conjugates. The recent findings for some signal molecules (phytohomormes) like salicylic acid, jasmonic acid and brassinosteroids involved in metabolism and detoxification of pesticides are summarized. In particular, the emerging research on the epigenetic mechanisms such DNA methylation and histone modification for pesticide metabolism is emphasized. The review would broaden our understanding of the regulatory networks of the pesticide metabolic pathways in higher plants.

Reviewing chemical and biological risks in urban agriculture: A comprehensive framework for a food safety assessment of city region food systems

Attention to urban agriculture (UA) has recently grown among practitioners, scientists, and the public, resulting in several initiatives worldwide. Despite the positive perception of modern UA and locally grown, fresh produce, the potential food safety risks connected to these practices may be underestimated, leading to regulatory gaps. Thus, there is a need for assessment tools to evaluate the food safety risks connected to specific UA initiatives, to assist practitioners in self-evaluation and control, and to provide policy makers and scholars a means to pursue and assess food safety in city regions, avoiding either a lack or an excess of regulation that could ultimately hinder the sector. To address this aim, this paper reviews the most recent and relevant literature on UA food safety assessments. Food safety indicators were identified first. Then, a food safety assessment framework for UA initiatives was developed. The framework uses business surveys and food analyses (if available) as a data source for calculating a food safety index for single UA businesses and the whole UA landscape of a given city region. The proposed framework was designed to allow its integration into the CRFS (City Region Food System) toolkit developed by FAO (Food and Agriculture Organization of the United Nations), RUAF foundation (Resource Centres on Urban Agriculture and Food Security) and Wilfrid Laurier University.

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Connection of several biological and chemical food safety risks to UA techniques.

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Identifiable food safety risk factors for diverse UA practices.

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Framework for the assessment of food safety levels of UA initiatives.

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Development of a risk-based assessment that can be integrated into the FAO CRFS framework.

Mechanism of growth amelioration of triclosan-stressed tobacco (Nicotiana tabacum) by endogenous salicylic acid

Among emerging organic contaminants (EOCs), triclosan (TCS) is an antibacterial agent and frequently detected in sludge. In this study, RNA sequencing (RNA-seq) was used to obtain the first transcriptomic profile of tobacco with TCS treatment in comparison with control. The results of transcriptome profiling indicated that salicylic acid (SA) signalling pathway actively participated in the tobacco's response to TCS treatment. The accumulation of endogenous SA in transgene tobacco lines transformed with a homologous gene of SA binding protein (LcSABP) was significantly enhanced. The resistance of transgenic tobacco lines to TCS was markedly enhanced revealed by morphological and physiological indexes while the total Chl level and Pn of transgenic individuals showed about 180% and 250% higher than that of WT on average, and the accumulation of H2O2 and O2- induced by TCS in SABP overexpressing tobacco was 35.3%-37.3% and 53.0%-56.0% lower than that of WT. In order to further explore the mechanism of TCS tolerance in transgenic plants, RNA-seq was then performed to obtain the second transcriptomic profile between wild type and transgenic samples with TCS exposure. The results indicated that differentially expressed genes (DEGs) were most highly enriched in MAPK signalling pathway, amino acid synthesis pathway and plant hormone transduction pathway. Especially, genes encoding key proteins such as cytochrome P450, laccase, peroxidase, glycosyl transferase, glutathione S-transferase and ATP-binding cassette were considered to be related to the increased tolerance ability of transgenic tobacco to the treatment of TCS stress. This research will likely provide novel insights into the molecular mechanism of SA-mediated amelioration of TCS stress on tobacco.

Triclocarban Exposure Exaggerates Spontaneous Colonic Inflammation in Il-10-/- Mice

Triclocarban (3,4,4'-trichlorocarbanilide, TCC) is a high-volume chemical used as an antimicrobial ingredient in many consumer and personal care products. In 2016, the Food and Drug Administration removed TCC from over-the-counter hand washing products. However, TCC remains approved to use in many other products and is a ubiquitous contaminant in the environment; furthermore, many common food crops can efficiently accumulate environmental TCC, resulting in potential human exposure through oral ingestion of contaminated food products. Therefore, human exposure to TCC could be a long-lasting and serious problem. A better understanding of its impact on human health could lead to important impact for public health and regulatory policy. Using a spontaneous colonic inflammation model in Il-10-/- mice, here we demonstrate that exposure to TCC, at doses relevant to human exposure, exaggerates spontaneous colonic inflammation in Il-10-/- mice, with reduced colon length, increase fecal concentration of lipocalin 2, enhanced gene expression of Il-6 and Ifn-γ in the colon, and exaggerated crypt damage in the colon. Collectively, these results support that TCC could be a potential environmental risk factor of colitis and associated gut diseases.

Comparative transcriptome combined with transgenic analysis reveal the involvement of salicylic acid pathway in the response of Nicotiana tabacum to triclosan stress

Triclosan (TCS) is a highly effective antibacterial agent, which is widely distributed in wastewater and sludge. The application of sludge containing high concentration TCS in agriculture will cause physiological damage to plants. Nevertheless, little is known about the physiological and molecular mechanism of TCS to plants. So firstly the physiological and biochemical indexes of tobacco with treatment of different concentrations of TCS were evaluated in this study. The results showed that tobacco plants with TCS treatment exhibited lower germination rate, root development, photosynthesis efficiency, and higher ROS accumulation in comparison with control group. The transcriptome analysis of tobacco plants was then performed to reveal the molecular mechanism in the response of tobacco to TCS. There were 3, 819 differentially expressed genes (DEGs) were identified between groups with or without TCS treatment. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis demonstrated that these DEGs were mainly enriched in groups of the plant hormone signal transduction pathway. To further investigate the role of plant hormone, transgenic tobacco overexpressing a homologous of salicylic acid (SA) binding protein gene was used to assess the SA-mediate TCS tolerance in plant. The results showed that transgenic plants exhibited enhanced activities of antioxidant enzymes and stronger TCS resistance than wild-type ones, which verify the important role of SA signal pathway in TCS response of tobacco plants. This study could be used to better understand the key roles of plant hormones in the TCS stress response of higher plants, and find key pathways and candidate genes for phytoremediation.

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

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

Triclocarban exposure exaggerates colitis and colon tumorigenesis: roles of gut microbiota involved

Triclocarban (TCC) is a widely used antimicrobial ingredient in consumer products and is a ubiquitous contaminant in the environment. In 2016, the FDA removed TCC from over-the-counter handwashing products, but this compound is still approved for use in many other personal care products. A better understanding of its impact on human health could lead to significant impact for public health and regulatory policies. Here we show that exposure to low-dose TCC exaggerated the severity of colitis and exacerbated the development of colitis-associated colon tumorigenesis, via gut microbiota-dependent mechanisms. Exposure to TCC increased dextran sodium sulfate (DSS)- and interleukin 10 (IL-10) knockout-induced colitis, and exaggerated azoxymethane (AOM)/DSS-induced colon tumorigenesis in mice. Regarding the mechanisms, TCC exposure reduced the diversity and altered the composition of gut microbiota and failed to promote DSS-induced colitis in mice lacking the microbiota, supporting that the presence of the microbiota is critical for the pro-colitis effects of TCC. Together, these results support TCC could be a novel risk factor for colitis and colitis-associated colon cancer, and further regulatory policies on this compound could be needed.

Reclaimed wastewater as a viable water source for agricultural irrigation: A review of food crop growth inhibition and promotion in the context of environmental change

The geographical and temporal distribution of precipitation has and is continuing to change with changing climate. Shifting precipitation will likely require adaptations to irrigation strategies, and because 35% of rainfed and 60% of irrigated agriculture is within 20 km of a wastewater treatment plant, we expect that the use of treated wastewater (e.g., reclaimed wastewater) for irrigation will increase. Treated wastewater contains various organic and inorganic substances that may have beneficial (e.g., nitrate) or deleterious (e.g., salt) effects on plants, which may cause a change in global food productivity should a large change to treated wastewater irrigation occur. We reviewed literature focused on food crop growth inhibition or promotion resulting from exposure to xenobiotics, engineered nanoparticles, nitrogen, and phosphorus, metals, and salts. Xenobiotics and engineered nanoparticles, in nearly all instances, were detrimental to crop growth, but only at concentrations much greater than would be currently expected in treated wastewater. However, future changes in wastewater flow and use of these compounds and particles may result in phytotoxicity, particularly for xenobiotics, as some are present in wastewater at concentrations within approximately an order of magnitude of concentrations which caused growth inhibition. The availability of nutrients present in treated wastewater provided the greatest overall benefit, but may be surpassed by the detrimental impact of salt in scenarios where either high concentrations of salt are directly deleterious to plant development (rare) or in scenarios where soils are poorly managed, resulting in soil salt accumulation.

Impact of biochar on plant growth and uptake of ciprofloxacin, triclocarban and triclosan from biosolids

Application of municipal biosolids in agriculture present a concern with potential uptake and bioaccumulation of pharmaceutical compounds from biosolids into agronomic plants. We evaluated the efficacy of biochar as a soil amendment to minimize uptake of antimicrobial agents (ciprofloxacin, triclocarban, and triclosan) in lettuce (Lactuca sativa) and carrot (Daucus carota) plants. Biochar reduced the concentration of ciprofloxacin and triclocarban in lettuce leaves and resulted in a 67% reduction of triclosan in carrot roots. There was no substantial difference in pharmaceutical concentrations in carrot and lettuce plant matter at low (2.0 g kg-1 soil) and high (20.4 g kg-1 soil) rates of applied biochar. The co-amendment of biochar and biosolids increased soil pH and nutrient content which were positively correlated with an increase in lettuce shoot biomass. Our results demonstrate the potential efficacy of using walnut shell biochar as a sorbent for pharmaceutical contaminants in soil without negatively affecting plant growth.

Rapid capture and SERS detection of triclosan using a silver nanoparticle core - protein satellite substrate

Triclosan (TCS) is a synthetic antimicrobial compound that has been widely used in consumer products. However, increasing evidence suggests adverse effects of TCS to human health and environment, raising great public concerns. The existing methods for detecting TCS are limited to time-consuming and complicated procedure. Here, we developed a rapid method for capture and detection of TCS using surface-enhanced Raman spectroscopy (SERS) based on a silver nanoparticle (Ag NP) core - protein satellite nanostructure. Bovine serum albumin (BSA) assembled on Ag NPs as satellites configuration could anchor a large number of TCS molecules close to the surface of Ag NPs, producing amplified SERS signals. As low as 50 nM TCS standard was successfully detected within 30 min. We also demonstrated its capability for TCS detection in pond water. The developed SERS method holds a great promise for rapid screening of TCS in environmental and food samples.

Fate, risk and removal of triclocarban: A critical review

The halogenated antimicrobial triclocarban (TCC) has large production and consumption over last decades. Its extensive utilization in personal care products and insufficient treatment in conventional wastewater treatment plants (WWTPs) has led to its listing as one of emerging organic contaminants (EOCs). Due to the hydrophobicity and chemical stability of TCC, it has been omnipresent detected in terrestrial and aquatic environments, and its prolonged exposure has thrown potential pernicious threat to ecosystem and human health. Considering its recalcitrance, especially under anoxic conditions, both biological and non-biological methods have been exploited for its removal. The efficiency of advanced oxidation processes was optimistic, but complete removal can rarely be realized through a single method. The biodegradation of TCC either with microbial community or pure culture is feasible but efficient bacterial degraders and the molecular mechanism of degradation need to be further explored. This review provides comprehensive information of the occurrence, potential ecological and health effects, and biological and non-biological removal of TCC, and outlines future prospects for the risk evaluation and enhanced bioremediation of TCC in various environments.

TraDIS-Xpress: a high-resolution whole-genome assay identifies novel mechanisms of triclosan action and resistance

Understanding the genetic basis for a phenotype is a central goal in biological research. Much has been learnt about bacterial genomes by creating large mutant libraries and looking for conditionally important genes. However, current genome-wide methods are largely unable to assay essential genes which are not amenable to disruption. To overcome this limitation, we developed a new version of "TraDIS" (transposon directed insertion-site sequencing) that we term "TraDIS-Xpress" that combines an inducible promoter into the transposon cassette. This allows controlled overexpression and repression of all genes owing to saturation of inserts adjacent to all open reading frames as well as conventional inactivation. We applied TraDIS-Xpress to identify responses to the biocide triclosan across a range of concentrations. Triclosan is endemic in modern life, but there is uncertainty about its mode of action with a concentration-dependent switch from bacteriostatic to bactericidal action unexplained. Our results show a concentration-dependent response to triclosan with different genes important in survival between static and cidal exposures. These genes include those previously reported to have a role in triclosan resistance as well as a new set of genes, including essential genes. Novel genes identified as being sensitive to triclosan exposure include those involved in barrier function, small molecule uptake, and integrity of transcription and translation. We anticipate the approach we show here, by allowing comparisons across multiple experimental conditions of TraDIS data, and including essential genes, will be a starting point for future work examining how different drug conditions impact bacterial survival mechanisms.

Salicylic acid application alleviates the adverse effects of triclosan stress in tobacco plants through the improvement of plant photosynthesis and enhancing antioxidant system

Triclosan (TCS) is a chlorophenol which is highly bacteriostatic and used in a wide array of consumer products. TCS is now one of the most commonly detected organic pollutants in the sewage sludges. The sludge utilization for fertilizers on agricultural land would pose the risk of causing adverse effects on plant growth and yield by TCS. However, the toxicity of TCS toward plants is comparatively less understood. In this study, we assessed the effects of TCS on tobacco plants which were grown in MS medium or soils containing various concentrations of TCS. Our results indicated that TCS at the concentration of 2 mg/L could strongly inhibit the tobacco seed germination. TCS could suppress tobacco plant growth in soil with different concentrations (10, 20, and 50 mg/kg) of TCS through the downregulation of chlorophyll contents, restricting photosynthesis and increasing generation of reactive oxygen species (ROS). Salicylic acid (SA) plays important roles in the stress response of plants. The role of exogenous SA application in protecting tobacco plants from TCS stress was also investigated in this study. SA application could significantly increase net photosynthesis, enhance antioxidant enzyme activity, and thereby enhancing tobacco plant tolerance to TCS. Moreover, the activation of MPK3 and MPK6 induced by TCS was downregulated in plants with the treatment of SA. It was thus referred that mitogen-activated protein kinases (MAPKs) might play a key role in the signal transduction of TCS stress, and this process might be regulated by SA signaling. Overall, our results demonstrated that TCS had negative impacts on tobacco plants and SA played a protective role on tobacco plants against TCS stress.

Examining plant uptake and translocation of emerging contaminants using machine learning: Implications to food security

When water and solutes enter the plant root through the epidermis, organic contaminants in solution either cross the root membranes and transport through the vascular pathways to the aerial tissues or accumulate in the plant roots. The accumulation of contaminants in plant roots and edible tissues is measured by root concentration factor (RCF) and fruit concentration factor (FCF). In this paper, 1) a neural network (NN) was applied to model RCF based on physicochemical properties of organic compounds, 2) correlation and significance of physicochemical properties were assessed using statistical analysis, 3) fuzzy logic was used to examine the simultaneous impacts of significant compound properties on RCF and FCF, 4) a clustering algorithm (k-means) was used to identify unique groups and discover hidden relationships within contaminants in various parts of the plants. The physicochemical cutoffs achieved by fuzzy logic for the RCF and the FCF were compared versus the cutoffs for compounds that crossed the plant root membranes and found their way into transpiration stream (measured by transpiration stream concentration factor, TSCF). The NN predicted the RCF with improved accuracy compared to mechanistic models. The analysis indicated that log K_ow, molecular weight, and rotatable bonds are the most important properties for predicting the RCF. These significant compound properties are positively correlated with RCF while they are negatively correlated with TSCF. Comparing the relationships between compound properties in various plant tissues showed that compounds detected in the edible parts have physicochemical cutoffs that are more like the compounds crossing the plant root membranes (into xylem tissues) than the compounds accumulating in the plant roots, with clear relationships to food security. The cluster analysis placed the contaminants into three meaningful groups that were in agreement with the results of fuzzy logic.

Uptake, translocation and accumulation of imidacloprid in six leafy vegetables at three growth stages

The uptake, translocation and accumulation behaviours of imidacloprid in six leafy vegetables, including Xiadi cabbage (XDC), Huaguan cabbage (HGC), Gaogengbai (GGB), Shanghaiqing (SHQ), Kangresijiqing (KRQ) and Ziyoucai (ZYC), were investigated under hydroponic conditions. Seedling stage (S-stage), rapid growth stage (R-stage) and maturation stage (M-stage) for each vegetable were considered. The root concentration factor (RCF), translocation factor (TF) and bioconcentration factor (BCF) were used to compare the difference. The results show that during 48 h of exposure, the total amount of imidacloprid taken up by the test vegetables increased with vegetable growth; however, the imidacloprid concentration in vegetable tissues varied significantly according to the variety and growth stage. For individual vegetables, imidacloprid was most easily accumulated into HGC and GGB shoots at R-stage, but into XDC, KRC and ZYC shoots at S-stage. For varieties, the ability of accumulating imidacloprid from solution to shoots seemed to follow the order of GGB > XDC > SHQ > KRQ > HGC > ZYC. Pearson's correlation analysis revealed significant negative correlations between daily transpiration and logBCF and between logRCF and logTF, indicating that the difference of uptake, translocation and accumulation behaviours of imidacloprid in vegetable varieties and growth stages may be related to the daily transpiration and the ability of concentrating imidacloprid in vegetable roots.

Transformation, Conjugation, and Sequestration Following the Uptake of Triclocarban by Jalapeno Pepper Plants

Plant uptake and metabolism of emerging organic contaminants, such as personal-care products, pose potential risks to human health. In this study, jalapeno pepper ( Capsicum annuum) plants cultured in hydroponic media were exposed to both ¹⁴C-labeled and unlabeled triclocarban (TCC) to investigate the accumulation, distribution, and metabolism of TCC following plant uptake. The results revealed that TCC was detected in all plant tissues; after 12 weeks, the TCC concentrations in root, stem, leaf, and fruit tissues were 19.74 ± 2.26, 0.26 ± 0.04, 0.11 ± 0.01, and 0.03 ± 0.01 mg/kg dry weight, respectively. More importantly, a substantial portion of the TCC taken up by plants was metabolized, especially in the stems, leaves, and fruits. Hydroxylated TCC (e.g., 2'-OH TCC and 6-OH TCC) and glycosylated OH-TCC were the main phase I and phase II metabolites in plant tissues, respectively. Bound (or nonextractable) residues of TCC accounted for approximately 44.6, 85.6, 69.0, and 47.5% of all TCC species that accumulated in roots, stems, leaves, and fruits, respectively. The concentrations of TCC metabolites were more than 20 times greater than the concentrations of TCC in the above-ground tissues of the jalapeno pepper plants after 12 weeks; crucially, approximately 95.6% of the TCC was present as metabolites in the fruits. Consequently, human exposure to TCC through the consumption of pepper fruits is expected to be substantially higher when phytometabolism is considered.

Efficiency of the formulated plant-growth promoting Pseudomonas fluorescens MC46 inoculant on triclocarban treatment in soil and its effect on Vigna radiata growth and soil enzyme activities

For bioaugmentation-based treatment of triclocarban (TCC), an emerging soil pollutant that is recalcitrant to biodegradation and phytotransformation, efficient TCC-degrading bacteria with an effective soil-delivering means are required. This work developed the formulated bacterial inoculant, and successfully demonstrated its TCC removal and detoxification performance in pot soil experiment with Vigna radiata plants. The soil bacterium Pseudomonas fluorescens MC46 was isolated as TCC-degrading, plant-growth promoting bacterium. The characterizations were conducted in vitro revealing that it could utilize TCC as a sole carbon source, and at a wide and higher concentration range from 1.6-31.6mgkg^-1 than those previously reported, while the detoxification was assessed by cytogenotoxicity and phytotoxicity tests. The developed sawdust-based inoculant formula combined with molasses (5% w/w), and either PEG or CMC-starch blend (1% w/w) could maintain a 20-week shelf-life inoculant stability in terms of cell viability, and TCC-degrading activity. Bioaugmentation of the formulated inoculants into TCC-contaminated soil efficiently removed TCC up to 74-76% of the initial concentration, mitigated toxicity, restored plant growth and health, and enhanced soil enzyme activities. This work is the first to demonstrate potential application of the formulated plant-growth promoting bacterial inoculant for the treatment and detoxification of a persistent TCC contaminated in soil.

Uptake and phytotoxic effect of benzalkonium chlorides in Lepidium sativum and Lactuca sativa

Cationic surfactants such as benzalkonium chlorides (BACs) are used extensively as biocides in hospitals, food processing industries, and personal care products. BACs have the potential to reach the rooting zone of crop plants and BACs might thereby enter the food chain. The two most commonly used BACs, benzyl dimethyl dodecyl ammonium chloride (BDDA) and benzyl dimethyl tetradecyl ammonium chloride (BDTA), were tested in a hydroponic system to assess the uptake by and phytotoxicity to lettuce (Lactuca sativa L.) and garden cress (Lepidium sativum L.). Individually and in mixture, BACs at concentrations up to 100 mg L-1 did not affect germination; however, emergent seedlings were sensitive at 1 mg L-1 for lettuce and 5 mg L-1 for garden cress. After 12 d exposure to 0.25 mg L-1 BACs, plant dry weight was reduced by 68% for lettuce and 75% for garden cress, and symptoms of toxicity (necrosis, chlorosis, wilting, etc.) were visible. High performance liquid chromatography-mass spectroscopy analysis showed the presence of BACs in the roots and shoots of both plant species. Although no conclusive relationship was established between the concentrations of six macro- or six micro-nutrients, growth inhibition or BAC uptake, N and Mg concentrations in BAC-treated lettuce were 50% lower than that of control, indicating that BACs might induce nutrient deficiency. Although bioavailability of a compound in hydroponics is significantly higher than that in soil, these results confirm the potential of BACs to harm vascular plants.

Antimicrobial compounds (triclosan and triclocarban) in sewage sludges, and their presence in runoff following land application

The reuse of treated municipal sewage ('biosolids') on land is an effective method to divert waste away from landfill and to use an alternative, low cost method of fertilisation. While legislation has mainly focused on the control of nutrient and metal application rates to land, other potentially harmful emerging contaminants (ECs) may be present in biosolids. Up to 80% of municipal sewage sludge is reused in agriculture in Ireland, which is currently the highest rate of reuse in Europe. However, unlike other countries, no study has been conducted on the presence of ECs across a range of wastewater treatment plants (WWTPs) in this country. This study evaluated the concentrations of two ECs in sewage sludge, the antimicrobials triclosan (TCS) and triclocarban (TCC), and their presence in surface runoff following land application in controlled rainfall simulation studies. In 16 WWTPs, concentrations of TCS and TCC were 0.61 and 0.08µgg^-1, which is at the lower end of concentrations measured in other countries. The concentrations in runoff post land application were also mainly below the limits of detection (90ngL^-1 for TCS, 6ngL^-1 for TCC), indicating that runoff is not a significant pathway of entry into the environment.

The Florence Statement on Triclosan and Triclocarban

The Florence Statement on Triclosan and Triclocarban documents a consensus of more than 200 scientists and medical professionals on the hazards of and lack of demonstrated benefit from common uses of triclosan and triclocarban. These chemicals may be used in thousands of personal care and consumer products as well as in building materials. Based on extensive peer-reviewed research, this statement concludes that triclosan and triclocarban are environmentally persistent endocrine disruptors that bioaccumulate in and are toxic to aquatic and other organisms. Evidence of other hazards to humans and ecosystems from triclosan and triclocarban is presented along with recommendations intended to prevent future harm from triclosan, triclocarban, and antimicrobial substances with similar properties and effects. Because antimicrobials can have unintended adverse health and environmental impacts, they should only be used when they provide an evidence-based health benefit. Greater transparency is needed in product formulations, and before an antimicrobial is incorporated into a product, the long-term health and ecological impacts should be evaluated. https://doi.org/10.1289/EHP1788.

Uptake and subcellular distribution of triclosan in typical hydrophytes under hydroponic conditions

The increasing discharge of pharmaceuticals and personal care products (PPCPs) into the environment has generated serious public concern. The recent awareness of the environmental impact of this emerging class of pollutants and their potential adverse effects on human health have been documented in many reports. However, information regarding uptake and intracellular distribution of PPCPs in hydrophytes under hydroponic conditions, and potential human exposure is very limited. A laboratory experiment was conducted using ¹⁴C-labeled triclosan (TCS) to investigate uptake and distribution of TCS in six aquatic plants (water spinach, purple perilla, cress, penny grass, cane shoot, and rice), and the subcellular distribution of ¹⁴C-TCS was determined in these plants. The results showed that the uptake and removal rate of TCS from nutrient solution by hydrophytes followed the order of cress (96%) > water spinach (94%) > penny grass (87%) > cane shoot (84%) > purple perilla (78%) > rice (63%) at the end of incubation period (192 h). The range of ¹⁴C-TCS content in the roots was 94.3%-99.0% of the added ¹⁴C-TCS, and the concentrations in roots were 2-3 orders of magnitude greater than those in shoots. Furthermore, the subcellular fraction-concentration factor (3.6 × 10²-2.6 × 10³ mL g^-1), concentration (0.58-4.47 μg g^-1), and percentage (30%-61%) of ¹⁴C-TCS in organelles were found predominantly greater than those in cell walls and/or cytoplasm. These results indicate that for these plants, the roots are the primary storage for TCS, and within plant cells organelles are the major domains for TCS accumulation. These findings provide a better understanding of translocation and accumulation of TCS in aquatic plants at the cellular level, which is valuable for environmental and human health assessments of TCS.

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.

Temporal Development of Gut Microbiota in Triclocarban Exposed Pregnant and Neonatal Rats

Alteration of gut microbial colonization process may influence susceptibility of the newborn/infant to infectious and chronic disease. Infectious disease risk leads to widespread use of non-prescription antimicrobials in household products such as Triclocarban (TCC), an antimicrobial compound in personal care products. TCC concentrates in and is transferred through the milk to suckling offspring. TCC exposure during gestation and lactation significantly reduced phylogenetic diversity (PD) among exposed dams and neonates. Among dams using weighted UniFrac distances, TCC induced significant dysbiosis of gut microbiota by gestational day (GD) 18, a trend that continued after delivery. Similarly, an overall restructuring of gut microbiota occurred in neonates. By postnatal day (PND) 12, communities separated based on exposure status and became significantly different at PND 16. The ability of TCC to drive microbial dysbiosis warrants future investigation to evaluate the safety of non-prescription antimicrobial use, including TCC, during critical exposure windows.

Application of matrix solid-phase dispersion followed by GC-MS/MS to the analysis of emerging contaminants in vegetables

A multiresidue method for the determination of 17 emerging contaminants in vegetables was developed based on ultrasound-assisted matrix solid-phase dispersion (MSPD). The analysis was performed using isotope dilution gas chromatography tandem mass spectrometry. In the development of the MSPD procedure, different parameters such as sonication and the type of sorbent or extraction solvent were assayed. Manual and in situ derivatization was assayed and the chromatographic response was higher when the reaction takes place in the injection port. The limits of detection obtained for the studied compounds were in the range of 0.1-0.4ngg(-1) for the different vegetables analyzed. The developed method was applied to vegetables obtained from several local markets. At least one of the organophosphates was detected in the analyzed samples at levels ranging from 0.6 to 4.6ngg(-1) and bisphenol A was detected in all the samples at concentration up to 16ngg(-1).

Fate of Triclosan in Irrigated Soil: Degradation in Soil and Translocation into Onion and Tomato

This study determined the fate of triclosan, a prevalent wastewater contaminant in recycled waters and surface streams, when soil and crop plants were irrigated at environmentally relevant concentrations. Soil triclosan concentrations were monitored in an 8-wk and in a 16-wk study without plants to determine triclosan degradation. Onion ( O. Fedtsch.) and tomato ( L.) were assessed for growth and triclosan accumulation at four levels of triclosan exposure (0, 0.015, 0.15, and 1.5 µg L) in irrigation waters within ranges of those found in recycled waters and associated receiving streams. Onions were grown for 8 wk and tomatoes were grown for 8 wk (short-term study) and 12 wk (long-term study) in potting soil. Soil triclosan concentrations increased (5-fold) with triclosan levels applied to soils alone. With repeated application, the half-life of triclosan was 18 d, with low-level accumulation in soil. Bioaccumulation of triclosan was observed in all edible portions of onions (115-435 ng g), primarily in bulbs, with no discernible impact on biomass. In both short- and long-term tomato studies, triclosan translocated to shoots and fruits (approaching a translocation factor of 1) at the highest level examined. Even at low triclosan concentrations typically found in recycled waters and receiving streams, agricultural irrigation presents an additional exposure route for organic contaminants to humans via commercial crops. Our study indicates that bulb crops, in particular, would likely accumulate high levels of triclosan. However, concentrations detected in both onions and tomato fruits determined here are below current human exposure limits.

Phytoremediation of imazalil and tebuconazole by four emergent wetland plant species in hydroponic medium

Pollution from pesticide residues in aquatic environments is of increasing concern. Imazalil and tebuconazole, two commonly used systemic pesticides, are water contaminants that can be removed by constructed wetlands. However, the phytoremediation capability of emergent wetland plants for imazalil and tebuconazole, especially the removal mechanisms involved, is poorly understood. This study compared the removal of both pesticides by four commonly used wetland plants, Typha latifolia, Phragmites australis, Iris pseudacorus and Juncus effusus, and aimed to understand the removal mechanisms involved. The plants were individually exposed to an initial concentration of 10 mg/L in hydroponic solution. At the end of the 24-day study period, the tebuconazole removal efficiencies were relatively lower (25%-41%) than those for imazalil (46%-96%) for all plant species studied. The removal of imazalil and tebuconazole fit a first-order kinetics model, with the exception of tebuconazole removal in solutions with I. pseudacorus. Changes in the enantiomeric fraction for imazalil and tebuconazole were detected in plant tissue but not in the hydroponic solutions; thus, the translocation and degradation processes were enantioselective in the plants. At the end of the study period, the accumulation of imazalil and tebuconazole in plant tissue was relatively low and constituted 2.8-14.4% of the total spiked pesticide in each vessel. Therefore, the studied plants were able to not only take up the pesticides but also metabolise them.

Removal of the pesticides imazalil and tebuconazole in saturated constructed wetland mesocosms

The aim of this study was to investigate the removal of the pesticides imazalil and tebuconazole at realistic concentration levels (10 and 100 μg L(-1)) in saturated constructed wetland (CW) mesocosms planted with five wetland plant species (Typha latifolia, Phragmites australis, Iris pseudacorus, Juncus effusus and Berula erecta) at different hydraulic loading rates during summer and winter. The removal of imazalil and tebuconazole was not influenced by the influent concentration, but the removal efficiency for both compounds was lower in winter than in summer. Planted mesocosms had significantly higher removal efficiencies than the unplanted controls only in summer. The first-order kinetics model fitted the tebuconazole removal in all mesocosms, and the reaction rate constants varied by plant species and season (0.1-0.7 d(-1) in winter and 0.6-2.9 d(-1) in summer). For imazalil, the first-order kinetics model fitted the removal only in mesocosms planted with Phragmites australis (k = 1.2 ± 0.4 d(-1)) and in the unplanted control (k = 1.2 ± 0.5 d(-1) in both summer and winter). The removal of imazalil and tebuconazole by sorption to the bed substrate and plant uptake were low, suggesting a high rate of metabolization in the saturated CW mesocosms. The removal of imazalil and tebuconazole correlated with the rate of evapotranspiration and the removal of nutrients (N and P) during summer and with the DO/oxygen saturation during winter. This reveals two possible metabolization pathways: degradation inside the plant tissue after uptake and plant-stimulated microbial degradation in the bed substrate. Furthermore, the results indicate that nitrifying bacteria may play an active role in the biodegradation of these pesticides.

Uptake of azoles by lamb's lettuce (Valerianella locusta L.) grown in hydroponic conditions

An uptake and translocation study of azole compounds was performed in lamb's lettuce (Valerianella locusta L.) grown in nutrient solution fortified with different azoles. Three azoles, (clotrimazole, fluconazole and propiconazole), which have different physico-chemical properties and are ubiquitous in the aquatic environment, were the compounds selected. An analytical method, based on matrix solid phase dispersion (MSPD) followed by LC-MS/MS determination, was developed to quantify these compounds in aqueous solution and in roots and leaves. The physicochemical properties of azoles are the main factors governing the uptake and plant accumulation. These azoles were detected in leaves indicating their transport within lamb's lettuce. Translocation from nutrient solution to the aerial part of lamb's lettuce was found to be highly dependent on the hydrophobicity of the azole. Clotrimazole accumulates in roots causing necrosis in roots and leaves, whereas fluconazole was the azole with the highest concentration in leaves without causing apparent phytotoxicity symptoms. The assessment of the levels of these azoles in leaves indicates that the risk for human health is negligible.

Root Uptake of Pharmaceuticals and Personal Care Product Ingredients

Crops irrigated with reclaimed wastewater or grown in biosolids-amended soils may take up pharmaceuticals and personal care product ingredients (PPCPs) through their roots. The uptake pathways followed by PPCPs and the propensity for these compounds to bioaccumulate in food crops are still not well understood. In this critical review, we discuss processes expected to influence root uptake of PPCPs, evaluate current literature on uptake of PPCPs, assess models for predicting plant uptake of these compounds, and provide recommendations for future research, highlighting processes warranting study that hold promise for improving mechanistic understanding of plant uptake of PPCPs. We find that many processes that are expected to influence PPCP uptake and accumulation have received little study, particularly rhizosphere interactions, in planta transformations, and physicochemical properties beyond lipophilicity (as measured by Kow). Data gaps and discrepancies in methodology and reporting have so far hindered development of models that accurately predict plant uptake of PPCPs. Topics warranting investigation in future research include the influence of rhizosphere processes on uptake, determining mechanisms of uptake and accumulation, in planta transformations, the effects of PPCPs on plants, and the development of predictive models.

Simple and cost-effective polycondensation routes to antimicrobial consumer products

Cost-effective macromolecular antimicrobials were synthesized to explore a variety of chemical functional groups that target antimicrobial performance and reduce cytotoxicity.

Extraction of 3,4,4'-Trichlorocarbanilide from Rat Fecal Samples for Determination by High Pressure Liquid Chromatography-Tandem Mass Spectrometry

Triclocarban (3,4,4'-Trichlorocarbanilide; TCC) in the environment has been well documented. Methods have been developed to monitor TCC levels from various matrices including water, sediment, biosolids, plants, blood and urine; however, no method has been developed to document the concentration of TCC in fecal content after oral exposure in animal studies. In the present study, we developed and validated a method that uses liquid extraction coupled with HPLC-MS/MS determination to measure TCC in feces. The limit of detection and limit of quantitation in control rats without TCC exposure was 69.0 ng/g and 92.9 ng/g of feces, respectively. The base levels of TCC in feces were lower than LOD. At 12 days of treatment, the fecal TCC concentration increased to 2220 µg/g among 0.2% w/w exposed animals. The concentration in fecal samples decreased over the washout period in 0.2% w/w treated animals to 0.399 µ/g feces after exposure was removed for 28 days. This method required a small amount of sample (0.1 g) with simple sample preparation. Given its sensitivity and efficiency, this method may be useful for monitoring TCC exposure in toxicological studies of animals.

Identifying bioaccumulative halogenated organic compounds using a nontargeted analytical approach: seabirds as sentinels

Persistent organic pollutants (POPs) are typically monitored via targeted mass spectrometry, which potentially identifies only a fraction of the contaminants actually present in environmental samples. With new anthropogenic compounds continuously introduced to the environment, novel and proactive approaches that provide a comprehensive alternative to targeted methods are needed in order to more completely characterize the diversity of known and unknown compounds likely to cause adverse effects. Nontargeted mass spectrometry attempts to extensively screen for compounds, providing a feasible approach for identifying contaminants that warrant future monitoring. We employed a nontargeted analytical method using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC/TOF-MS) to characterize halogenated organic compounds (HOCs) in California Black skimmer (Rynchops niger) eggs. Our study identified 111 HOCs; 84 of these compounds were regularly detected via targeted approaches, while 27 were classified as typically unmonitored or unknown. Typically unmonitored compounds of note in bird eggs included tris(4-chlorophenyl)methane (TCPM), tris(4-chlorophenyl)methanol (TCPMOH), triclosan, permethrin, heptachloro-1'-methyl-1,2'-bipyrrole (MBP), as well as four halogenated unknown compounds that could not be identified through database searching or the literature. The presence of these compounds in Black skimmer eggs suggests they are persistent, bioaccumulative, potentially biomagnifying, and maternally transferring. Our results highlight the utility and importance of employing nontargeted analytical tools to assess true contaminant burdens in organisms, as well as to demonstrate the value in using environmental sentinels to proactively identify novel contaminants.

Parallel evolutionary pathways to antibiotic resistance selected by biocide exposure

Objectives

Biocides are widely used to prevent infection. We aimed to determine whether exposure of Salmonella to various biocides could act as a driver of antibiotic resistance.

Methods

Salmonella enterica serovar Typhimurium was exposed to four biocides with differing modes of action. Antibiotic-resistant mutants were selected during exposure to all biocides and characterized phenotypically and genotypically to identify mechanisms of resistance.

Results

All biocides tested selected MDR mutants with decreased antibiotic susceptibility; these occurred randomly throughout the experiments. Mutations that resulted in de-repression of the multidrug efflux pump AcrAB-TolC were seen in MDR mutants. A novel mutation in rpoA was also selected and contributed to the MDR phenotype. Other mutants were highly resistant to both quinolone antibiotics and the biocide triclosan.

Conclusions

This study shows that exposure of bacteria to biocides can select for antibiotic-resistant mutants and this is mediated by clinically relevant mechanisms of resistance prevalent in human pathogens.