Chlorate and perchlorate in tea leaves from major producing regions in China and related human exposure risk.

Chlorate and perchlorate are emerging pollutants that may interfere with thyroid function. Since they are highly water soluble, chlorate and perchlorate in tea leaves cause health concerns but have scarcely been studied. In this study, chlorate and perchlorate concentrations in 216 tea samples from different regions of China were determined. Perchlorate was detected in all the samples with a median concentration of 44.1 µg kg-1, while the chlorate detection frequency was 15.7%. We observed regional differences in perchlorate contents in tea leaves, with the highest quantity found in the central region of China. Except for dark tea, the concentration of perchlorate in tea infusions decreased with the increased number of times the tea leaves were brewed. The hazard quotients (HQs) of chlorate and perchlorate in all the samples were less than 1, suggesting negligible health risks caused by these pollutants from tea consumption. To the best of our knowledge, this is the first study to investigate chlorate and perchlorate contamination in tea infusions by simulating brewing behavior.

Investigation of black phosphorus anodic catalyst for electrolysis: Degradation of organics via a perchlorate-free oxidant activation.

This study investigated the potential of a novel fabricated black phosphorus (BP) nanoparticle electrode as an alternative to noble metal-based catalysts for application in electrolysis. The BP electrode was compared with other conventional catalysts (boron-doped diamond (BDD) and a dimensional stable electrode (DSA)) under different electrolyte conditions for the generation of specific oxidants (e.g., OH•, HOCl, OCl-, SO4• -) in the bulk phase during electrolysis. In the presence of sulfate-based electrolyte, results on the electrochemical oxidation showed that the BP not only resulted in an 8-fold increase in the current efficiency compared to DSA, but also reduced energy consumptions by approximately 30-fold. Moreover, electrolysis using certain electrodes (i.e., BDD) under high current densities in the presence of chlorine-based electrolyte has been reported to be hazardous to the water system due to the generation of toxic chlorine oxyanions (i.e., perchlorate), which necessitates the operation of a post-treatment process. Likewise, application of the BDD electrode was confirmed to produce perchlorate under high current densities, while no by-product was generated by electrolysis with the BP electrode. Finally, multiple degradation pathways for selective water treatment was monitored under oxidation with the BP electrode. To the best of our knowledge, this study is the first to apply the novel fabricated BP electrode as the anodic catalyst for the treatment of a water system.

Monitoring and risk assessment of perchlorate in tea samples produced in China.

Accumulation of potentially perchlorate in tea is a new concern for tea consumers. The information on perchlorate contamination in tea is highly limited. This study aimed to investigate the occurrence and accumulation of perchlorate in tea samples from China and to assess human exposure risks. A total of 288 tea samples collected from 16 provinces of China were tested, and nearly 94.8% of the samples were found to have detectable perchlorate contamination. Concentrations of perchlorate ranged from below LOQ to 1274.3 µg/kg, with a mean value of 294.6 µg/kg. Tea samples collected from Central China had the highest mean perchlorate concentration (403.4 µg/kg). The mean and median perchlorate levels in the dark and black samples were much higher than that of other types of tea samples. After brewing tea, the dissolution rates of perchlorate from the dried tea ranged from 58.9% to 89.2%. For the worst-case scenario, the estimated daily intakes (EDIs) of tea samples in 16 investigated provinces ranged from 25.9 to 157.8 ng/kg bw/day and 29.7-180.7 ng/kg bw/day for male and female respectively, indicating no significant health risks to local residents via tea consumption.

Comprehending the Role of Endocrine Disruptors in Inducing Epigenetic Toxicity.

Endocrine disruptors are natural or man-made chemicals that interfere with the body's endocrine system leading to hormone synthesis and production defects. These chemicals are categorized as plasticizers and cosmetic chemicals, heavy metals, phytoestrogens, pesticides, detergents, surfactants, and flame retardants. Some of the most common endocrine disruptors are dioxins, bisphenol A, phthalates, perchlorate, perfluoroalkyl, and poly-fluoroalkyl substances (PFAs), phytoestrogens, polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCB), triclosan, atrazine, lead, arsenic, mercury, organophosphate pesticides, and glycol ethers. Epigenetic alterations such as DNA methylation, histone modification, and miRNA regulation have been observed to play a major role in many diseases such as cancer, neurodegenerative diseases, PCOS, cardiovascular diseases, and various other disorders. In recent times, there has been a focus on endocrine-disrupting chemicals in epigenetic alterations. This review concentrates on estrogen and androgen disrupting effects, placental, and fetal effects, thyroid disrupting effects, and transgenerational effects of endocrine disruptors.

Accumulation and distribution of perchlorate in spinach and chard growing under greenhouse: Implications for food safety in baby foods commodities.

Very little information is available with regards to the bioavailability of perchlorate in spinach or chard used in the production of baby foods commodities. In the present study, the uptake and accumulation of perchlorate were compared under two different treatments (T1: 1 and T2: 10 mg L-1 ClO4-). Our results indicate that spinach has a higher capacity to accumulate perchlorate than chard (p < 0.0185). Concentrations of perchlorate in leaves, stems and roots (leaves > stem > roots) all gradually increased (p < 0.0001) as vegetable growing and treatment (T2 > T1). No significant differences were found between the control and T1. The daily intake for perchlorate (control) is below the proposed international standard, however, it was exceeded in T1 and T2. The results suggested that perchlorate is actively accumulate in high concentrations in vegetables used in the production of baby food commodities and the exposure of perchlorate via the food consumption (baby foods) was evaluated as not safe.

Modeling principles of protective thyroid blocking.

PURPOSE: In the case of a nuclear incident, the release of radioiodine must be expected. Radioiodine accumulates in the thyroid and by irradiation enhances the risk of cancer. Large doses of stable (non-radioactive) iodine may inhibit radioiodine accumulation and protect the thyroid ('thyroid blocking'). Protection is based on a competition at the active carrier site in the cellular membrane and an additional temporary inhibition of the organification of iodide (Wolff-Chaikoff effect). Alternatively, other agents like e.g. perchlorate that compete with iodide for the uptake into the thyrocytes may also confer thyroidal protection against radioiodine exposure.Biokinetic models for radioiodine mostly describe exchanges between compartments by first order kinetics. This leads to correct predictions only for low (radio)iodide concentrations. These models are not suited to describe the kinetics of iodine if administered at the dosages recommended for thyroid blocking and moreover does not permit to simulate either the protective competition mechanism at the membrane or the Wolff-Chaikoff effect. Models adapted for this purpose must be used. Such models may use a mathematical relation between the serum iodide concentration and a relative uptake suppression or a dependent rate constant determining total thyroidal radioiodine accumulation. Alternatively, the thyroidal uptake rate constant may be modeled as a function of the total iodine content of the gland relative to a saturation amount. Newer models integrate a carrier-mechanism described by Michalis-Menten kinetics in the membrane and in analogy to enzyme kinetics apply the rate law for monomolecular irreversible enzyme reactions with competing substrates to model the competition mechanism. An additional total iodide uptake block, independent on competition but limited in time, is used to simulate the Wolff-Chaikoff effect. CONCLUSION: The selection of the best model depends on the issue to be studied. Most models cannot quantify the relative contributions of the competition mechanism at the membrane and the Wolff-Chaikoff effect. This makes it impossible or exceedingly difficult to simulate prolonged radioiodine exposure and the effect of repetitive administrations of stable iodine. The newer thyroid blocking models with a separate modeling of competition and Wolff-Chaikoff effect allow better quantitative mechanistic insights and offer the possibility to simulate complex radioiodine exposure scenarios and various protective dosage schemes of stable iodine relatively easily. Moreover, they permit to study the protective effects of other competitors at the membrane carrier site, like e.g. perchlorate, and to draw conclusions on their protective efficacy in comparison to stable iodine.

Biosynthesized silver nanoparticle-coated electro-membrane extraction of perchlorate in different seafood samples.

In this work we developed a rapid and straightforward technique in which biosynthesized silver nanoparticles (Ag-NPs) were coated on a porous membrane utilizing electrical potential to extract perchlorate from seafood samples. The biosynthesized Ag-NPs were well characterized using UV-Vis. spectrophotometry, X-ray diffraction, and scanning electron microscopy. After extraction, analyses were performed using ion chromatography. The Ag-NP-coated porous polypropylene membrane shows higher extraction efficiency due to the high electrical conductivity of the Ag-NPs. The performance of this efficient technique was compared with those previously reported in the literature. The extraction variables that affect extraction of the target analyte and influence percentage recovery, such as pH of the sample solution, extraction time, and applied voltage, were investigated and optimized. The results demonstrated optimum conditions to achieve low detection limits [LODs (limits of detection)]: sample solution (pH = 6), short extraction time (10 min), and applied voltage (5 V). The developed method shows excellent linearity for perchlorate ion in the range from 0.001 to 350 µg L-1 with a coefficient of determination (r2 ) of 0.9991. The detection limit (LODs) and quantification limits (limits of quantification) were found to be 0.04 and 0.1225 µg kg-1 , respectively. The mean recovery percentages for three replicates of 10 different spiked fish samples by 3 µg g-1 of perchlorate were between 92.2 and 106.2%, with an observed relative standard deviation in the range of 0.8-3.7%. The proposed method is rapid, sensitive, inexpensive, environmentally friendly, and highly effective in extracting perchlorate from different seafood samples.

A comparison of thyroidal protection by iodine and perchlorate against radioiodine exposure in Caucasians and Japanese.

Radioactive iodine released in nuclear accidents may accumulate in the thyroid and by irradiation enhances the risk of cancer. Radioiodine uptake into the gland can be inhibited by large doses of stable iodine or perchlorate. Nutritional iodine daily intake may impact thyroid physiology, so that radiological doses absorbed by the thyroid as well as thyroid blocking efficacy may differ in Japanese with a very rich iodine diet compared to Caucasians. Based on established biokinetic-dosimetric models for the thyroid, we derived the parameters for Caucasians and Japanese to quantitatively compare the effects of radioiodine exposure and the protective efficacy of thyroid blocking by stable iodine at the officially recommended dosages (100 mg in Germany, 76 mg in Japan) or perchlorate. The maximum transport capacity for iodine uptake into the thyroid is lower in Japanese compared to Caucasians. For the same radioiodine exposure pattern, the radiological equivalent thyroid dose is substantially lower in Japanese in the absence of thyroid blocking treatments. In the case of acute radioiodine exposure, stable iodine is less potent in Japanese (ED50 = 41.6 mg) than in Caucasians (ED50 = 2.7 mg) and confers less thyroid protection at the recommended dosages because of a delayed responsiveness to iodine saturation of the gland (Wolff-Chaikoff effect). Perchlorate (ED50 = 10 mg in Caucasians) at a dose of 1000 mg has roughly the same thyroid blocking effect as 100 mg iodine in Caucasians, whereas it confers a much better protection than 76 mg iodine in Japanese. For prolonged exposures, a single dose of iodine offer substantially lower protection than after acute radioiodine exposure in both groups. Repetitive daily iodine administrations improve efficacy without reaching levels after acute radioiodine exposure and achieve only slightly better protection in Japanese than in Caucasians. However, in the case of continuous radioiodine exposure, daily doses of 1000 mg perchlorate achieve a high protective efficacy in Caucasians as well as Japanese (> 0.98). In Caucasians, iodine (100 mg) and perchlorate (1000 mg) at the recommended dosages seem alternatives in case of acute radioiodine exposure, whereas perchlorate has a higher protective efficacy in the case of longer lasting radioiodine exposures. In Japanese, considering protective efficacy, preference should be given to perchlorate in acute as well as prolonged radioiodine exposure scenarios.

Uptake, Accumulation, Translocation, and Subcellular Distribution of Perchlorate in Tea (Camellia sinensis L.) Plants.

Perchlorate, emerging pollution with thyroid toxicity, has a high detection rate in fresh tea leaves. What needs attention is that the uptake characteristic is insufficiently understood. Herein, the uptake, accumulation, and translocation of perchlorate in a tea plant-hydroponic solution system were investigated, of which the mechanism was further lucubrated by subcellular distribution. The perchlorate concentration in tea tissues is ramped up along with the increase in the exposure level and time. The bioaccumulation factor of tea tissues followed the rank: mature leaves > tender leaves > roots. After the seedlings have been transplanted to a perchlorate-free solution, the perchlorate in mature leaves is reduced significantly, accompanied by a progressive increase in perchlorate in new shoots and solutions. The cell-soluble fractions are the major reservoir of perchlorate both for roots (>59%) and leaves (>76%), which precisely explained the translocation within the tea plant-hydroponic solution system. These results not only illuminate the uptake characteristic in tea plants but also improve the understanding of the behavior of perchlorate in higher plants.

Determination of perchlorate in tea using SERS with a superhydrophobically treated cysteine modified silver film/polydimethylsiloxane substrate.

Perchlorate is a new type of persistent pollutant, which interferes with the synthesis and secretion of thyroxine and affects human health. The EU's limit for perchlorate in tea is 750 µg kg-1. The surface-enhanced Raman scattering (SERS) technique has the characteristics of a simple pretreatment method, rapid detection, high sensitivity, high specificity and great stability in the detection of perchlorate. This study proposed a novel superhydrophobic SERS substrate, which can be used to detect perchlorate in tea. Firstly, a chemical deposition method was used to deposit a silver film on the surface of a thin layer of polydimethylsiloxane. After drying, the substrate was immersed in 1H,1H,2H,2H-perfluorodecyltriethoxysilane aqueous solution for 15 hours to make the surface of the substrate superhydrophobic. Then cysteine molecules were deposited on the surface of the silver film/polydimethylsiloxane by incubation. The superhydrophobic surface has a unique enrichment effect on the highly diluted solution, and perchlorate has a strong affinity for the amino group of cysteine. We collected the Raman spectra of 9 gradient concentrations (1-100 µmol L-1) of perchlorate-spiked tea samples on the hydrophobic substrate, and a linear model of the relationship between the SERS spectral intensity and the concentrations of perchlorate in tea was established. This method reached a good limit of detection of 0.0067 µmol L-1 (0.82 µg kg-1) in tea, which showed that the developed sensor has high sensitivity and could be used as a fast and simple technique for quantitative detection of perchlorate based on SERS technology.

A comparison of thyroidal protection by stable iodine or perchlorate in the case of acute or prolonged radioiodine exposure.

In the case of a nuclear power plant accident, repetitive/prolonged radioiodine release may occur. Radioiodine accumulates in the thyroid and by irradiation enhances the risk of cancer. Large doses of non-radioactive iodine may protect the thyroid by inhibiting radioiodine uptake into the gland (iodine blockade). Protection is based on a competition at the active carrier site in the cellular membrane and the Wolff-Chaikoff effect, the latter being, however, only transient (24-48 h). Perchlorate may alternatively provide protection by a carrier competition mechanism only. Perchlorate has, however, a stronger affinity to the carrier than iodide. Based on an established biokinetic-dosimetric model developed to study iodine blockade, and after its extension to describe perchlorate pharmacokinetics and the inhibition of iodine transport through the carrier, we computed the protective efficacies that can be achieved by stable iodine or perchlorate in the case of an acute or prolonged radioiodine exposure. In the case of acute radioiodine exposure, perchlorate is less potent than stable iodine considering its ED50. A dose of 100 mg stable iodine has roughly the same protective efficacy as 1000 mg perchlorate. For prolonged exposures, single doses of protective agents, whether stable iodine or perchlorate, offer substantially lower protection than after acute radioiodine exposure, and thus repetitive administrations seem necessary. In case of prolonged exposure, the higher affinity of perchlorate for the carrier in combination with the fading Wolff-Chaikoff effect of iodine confers perchlorate a higher protective efficacy compared to stable iodine. Taking into account the frequency and seriousness of adverse effects, iodine and perchlorate at equieffective dosages seem to be alternatives in case of short-term acute radioiodine exposure, whereas preference should be given to perchlorate in view of its higher protective efficacy in the case of longer lasting radioiodine exposures.

A highly-efficient and cost-effective pretreatment method for selective extraction and detection of perchlorate in tea and dairy products.

In view of the high polarity and ubiquitous occurrence of perchlorate, achieving an ultra-trace analysis has become a challenging task. The present study aimed to develop a simple and generic pretreatment protocol based on cold-induced liquid-liquid extraction to efficiently extract perchlorate from tea and dairy products and remarkably decrease potential matrix interferences and laborious cleanup. By optimizing the pretreatment conditions, the enrichment factor of perchlorate increased by 7.79 times under the compromise between the matrix effect and extraction recovery. The validated method presented satisfactory selectivity, linearity, accuracy, precision, and matrix effect, providing recoveries of 78.2%-106.2% with RSDr ranging from 1.2% to 7.9% and RSDR less than 10.7% for tea and dairy products. This pretreatment protocol depended only on shaking, freezing, and centrifugation in one step, without additional equipment or tedious operations, which will be explored to a greater extent in complex biological or food matrices.

Heterologous expression of the gene for chlorite dismutase from Ideonella dechloratans is induced by an FNR-type transcription factor.

Regulation of the expression of the gene for chlorite dismutase (cld), located on the chlorate reduction composite transposon of the chlorate reducer Ideonella dechloratans, was studied. A 200 bp upstream sequence of the cld gene, and mutated and truncated versions thereof, was used in a reporter system in Escherichia coli. It was found that a sequence within this upstream region, which is nearly identical to the canonical FNR-binding sequence of E. coli, is necessary for anaerobic induction of the reporter gene. Anaerobic induction was regained in an FNR-deficient strain of E. coli when supplemented either with the fnr gene from E. coli or with a candidate fnr gene cloned from I. dechloratans. In vivo transcription of the suggested fnr gene of I. dechloratans was demonstrated by qRT-PCR. Based on these results, the cld promoter of I. dechloratans is suggested to be a class II-activated promoter regulated by an FNR-type protein of I. dechloratans. No fnr-type genes have been found on the chlorate reduction composite transposon of I. dechloratans, making anaerobic upregulation of the cld gene after a gene transfer event dependent on the presence of an fnr-type gene in the recipient.

Field study on the uptake, accumulation and risk assessment of perchlorate in a soil-chard/spinach system: Impact of agronomic practices and fertilization.

The application of excessive fertilizer represents a primary source of entry for perchlorate into crop systems and thus has raised widespread concern regarding food safety. Several studies have reported the occurrence of perchlorate in vegetables. However, limited information is available on the fate of perchlorate in the soil-plant system. In this study, we performed field experiments to evaluate the effects of the application rate of Chilean nitrate fertilizer and the type of fertilization (manual or fertigation) on the uptake of perchlorate by plants grown in open fields. Interestingly, in the control, chard and spinach accumulated 21.3 and 25.9 µg kg-1, respectively. For both agronomic practices, the content of perchlorate in chard and spinach increased as the fertilizer application rate increased, with fertigation promoting more significant accumulations. Spinach accumulated almost two times more perchlorate than chard for all treatments; however, the concentrations generally remained below regulatory values. The intake of spinach and chard presented a low risk to human health for all age groups. These findings enhance our understanding of the environmental impact of the use of fertilizers in agriculture and food safety.

Macrocycle-Directed Construction of Tetrahedral Anion-π Receptors for Nesting Anions with Complementary Geometry.

Manipulation of the emerging anion-π interactions in a highly cooperative manner through sophisticated host design represents a very challenging task. In this work, unprecedented tetrahedral anion-π receptors have been successfully constructed for complementary accommodation of tetrahedral and relevant anions. The synthesis was achieved by a macrocycle-directed approach by using large macrocycle precursors bearing four reactive sites, which enabled a kinetic-favored pathway and afforded the otherwise inaccessible tetrahedral cages in considerable yields. Crystal structure suggested that the tetrahedral cages have an enclosed three-dimensional cavity surrounded by four electron-deficient triazine faces in a tetrahedral array. The complementary accommodation of a series of tetrahedral and relevant anions including BF4 - , ClO4 - , H2 PO4 - , HSO4 - , SO4 2- and PF6 - was revealed by ESI-MS and DFT calculations. Crystal structures of ClO4 - and PF6 - complexes showed that the anion was nicely encapsulated within the tetrahedral cavity with up to quadruple cooperative anion-π interactions by an excellent shape and size match. The strong anion-π binding was further confirmed by negative ion photoelectron spectroscopy measurements.

LC-ESI-MS/MS determination of oxyhalides (chlorate, perchlorate and bromate) in food and water samples, and chlorate on household water treatment devices along with perchlorate in plants.

The results of the validation study of the LC-ESI-MS/MS method for the determination of chlorate (ClO3-), perchlorate (ClO4-) and bromate (BrO3-) in water and food samples are summarized. Towards this, 284 samples of drinking water were analysed, out of which the 69% contained chlorate above the limit of quantitation (LOQ) of 0.01 mg/L, with maximum amount of 1.1 mg/L. Only 6 samples were found to be positive with perchlorate at levels <0.01 mg/L. Bromate was detected in 5 drinking water samples at levels above the LOQ, at concentrations up to 0.026 mg/L. For the validation of the method in food, 108 blank samples were spiked with chlorate and perchlorate for the LC-MS/MS analysis at two levels. In total 247 food samples from the market of 19 different commodities including fruits, vegetables, cereals and wine, were analysed. The maximum concentration of chlorate was found at 0.83 mg/kg in a sample of cultivated mushrooms. The number of samples contaminated with perchlorate was also small, with all the determined concentrations below the LOQ of 0.05 mg/kg. Experiments for the chlorate reduction in drinking water, showed that reverse osmosis treatment is effective in particular with newly installed cartridges. Finally, according to the results of the pilot study when chlorinated water is used for the plant irrigation, accumulation of chlorate is observed, especially in the green parts of the plant. Perchlorate was also detected in leafy samples, although it was not present in the irrigation water.

Combined in-situ bioremediation treatment for perchlorate pollution in the vadose zone and groundwater.

Perchlorate is considered a rapidly spreading environmental pollutant. In Israel, it has been found at high concentrations in the vadose zone (up to 30,000 mg/L) and groundwater (up to 800 mg/L) underlying former industrial waste ponds. A perchlorate-reduction method that utilizes the high degradation potential of shallow soil and the high mobility of perchlorate across the deep unsaturated zone has been proposed. The combined treatment method includes recurrent pumping and application of polluted groundwater amended with an electron donor to the shallow soil layers. As a result, perchlorate is biodegraded in the upper soil, and the treated water drains through the unsaturated zone, displacing the pollutant toward the water table, where it is immediately pumped back to the surface for further treatment through a cyclic process. In the current study, the combined treatment approach was tested in a full-scale unsaturated zone (40 m), long-term (1 year) field experiment. Results showed a daily reduction in perchlorate concentration from 800 mg/L to practically zero. A total of ˜330 kg of perchlorate was reduced during the experiment. Nevertheless, competitive reduction (iron and sulfate) and soil acidification were found to be limiting factors. The study demonstrates a potentially efficient way to overcome these limitations by optimizing electron donor concentration.

Quantitative determination and contamination pattern of perchlorate in tea by ultra performance liquid chromatography and tandem mass spectrometry.

Perchlorate causes great health concerns for its inhibition on the iodide intake of human. However, the contamination pattern of perchlorate in tea remains unclear although tea is substantially consumed worldwide. Thus, the present study established an efficient method using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) in combination with external standard method, and further lucubrated the contamination level of perchlorate in made tea, fresh tea leaves, along with the waters and soils from tea gardens. Fresh tea leaves with higher maturity generally contains more perchlorate. The observation explains well why the residual of perchlorate in dark tea is generally higher than that in black tea or green tea from the perspective of raw material. In consideration of the ubiquitous existence of perchlorate in waters and soils from tea gardens, perchlorate might accumulate in tea leaves via soil. This study not only provides an alternative quantification method of perchlorate when the isotope internal standard is out of stock, but also illuminates the contamination pattern of perchlorate in tea from planting process.

Determination of perchlorate from tea leaves using quaternary ammonium modified magnetic carboxyl-carbon nanotubes followed by liquid chromatography-tandem quadrupole mass spectrometry.

The novel quaternary ammonium modified magnetic carboxyl-carbon nanotubes (QA-Mag-CCNTs) have been synthesised and characterized. QA-Mag-CCNTs were applied in magnetic dispersive solid phase extraction (Mag-dSPE) for preconcentration of perchlorate from tea leaves prior to liquid chromatography-tandem quadrupole mass spectrometry (LC-MS/MS) analysis. The Mag-dSPE procedure for preconcentration of perchlorate succeed in overcoming the flaw (containing target analyte randomly) of commercially available SPE cartridge. Under optimal conditions, the results showed higher extraction efficiency of QA-Mag-CCNTs, with recoveries between 85.2% and 107%. And the satisfactory precision with inter-day and intra-day RSD values were lower than 8.0%. Furthermore, QA-Mag-CCNTs were evaluated for reuse up to 20 times. The limit of quantification (LOQ) for perchlorate was 8.21 ng kg-1. The developed method was successfully applied in tea leaves for food-safety risk monitoring in Zhejiang province, China. The results showed the concentrations of perchlorate in 229 out of 240 collected samples were in the range of 0.082-988 µg kg-1. It was confirmed that QA-Mag-CCNTs were highly effective materials used for preconcentration of perchlorate.

Evaluation of hypothalamus-pituitary-thyroid axis function by chronic perchlorate exposure in male rats.

Perchlorate is a widespread endocrine disruptor that was previously correlated with increased serum TSH levels and decreased thyroid hormones production both in animals and humans. Even so, the regulation of gene/protein expression in the hypothalamus, pituitary and thyroid by chronic perchlorate exposure was not completely elucidated. Therefore, this study aimed to investigate the underlying mechanisms involved in the disruption of hypothalamus-pituitary-thyroid axis by chronic perchlorate exposure. Male Wistar rats were treated or not with NaClO4 in the drinking water (35 mg/Kg/day) for 60 days. Thereafter, hormone/cytokines serum levels were measured through multiplex assays; genes/proteins expression were investigated by qPCR/Western Blotting and thyroid morphology was evaluated through histological analysis. Serum TSH levels were increased and serum T4 /T3 levels were decreased in perchlorate-treated animals. This treatment also altered the thyrotropin-releasing hormone mRNA/protein content in the hypothalamus. Additionally, the expression of both subunits of TSH were increased in the pituitary of perchlorate-treated rats, which also presented significant alterations in the thyroid morphology/gene expression. Furthermore, perchlorate exposure reduced liver Dio1 mRNA expression and increased the content of pro-inflammatory cytokines in the thyroid and the serum. In conclusion, our study adds novel findings about the perchlorate-induced disruption of the hypothalamus-pituitary-thyroid axis gene/protein expression in male rats. The data presented herein also suggest that perchlorate induces thyroid and systemic inflammation through the increased production of cytokines. Taken together, our results suggest that perchlorate contamination should be monitored, especially in the individuals most susceptible to the deleterious effects of reduced levels of thyroid hormones.