Unexpected nephrotoxicity induced by tetrabromobisphenol A in newborn rats

Update of the scientific opinion on tetrabromobisphenol A (TBBPA) and its derivatives in food

The European Commission asked EFSA to update its 2011 risk assessment on tetrabromobisphenol A (TBBPA) and five derivatives in food. Neurotoxicity and carcinogenicity were considered as the critical effects of TBBPA in rodent studies. The available evidence indicates that the carcinogenicity of TBBPA occurs via non-genotoxic mechanisms. Taking into account the new data, the CONTAM Panel considered it appropriate to set a tolerable daily intake (TDI). Based on decreased interest in social interaction in male mice, a lowest observed adverse effect level (LOAEL) of 0.2 mg/kg body weight (bw) per day was identified and selected as the reference point for the risk characterisation. Applying the default uncertainty factor of 100 for inter- and intraspecies variability, and a factor of 3 to extrapolate from the LOAEL to NOAEL, a TDI for TBBPA of 0.7 μg/kg bw per day was established. Around 2100 analytical results for TBBPA in food were used to estimate dietary exposure for the European population. The most important contributors to the chronic dietary LB exposure to TBBPA were fish and seafood, meat and meat products and milk and dairy products. The exposure estimates to TBBPA were all below the TDI, including those estimated for breastfed and formula-fed infants. Accounting for the uncertainties affecting the assessment, the CONTAM Panel concluded with 90%-95% certainty that the current dietary exposure to TBBPA does not raise a health concern for any of the population groups considered. There were insufficient data on the toxicity of any of the TBBPA derivatives to derive reference points, or to allow a comparison with TBBPA that would support assignment to an assessment group for the purposes of combined risk assessment.

Tetrabromobisphenol Exposure Impairs Bovine Oocyte Maturation by Inducing Mitochondrial Dysfunction

Tetrabromobisphenol (TBBPA) is the most widely used brominated flame retardant in the world and displays toxicity to humans and animals. However, few studies have focused on its impact on oocyte maturation. Here, TBBPA was added to the culture medium of bovine cumulus-oocyte complexes (COCs) to examine its effect on oocytes. We found that TBBPA exposure displayed an adverse influence on oocyte maturation and subsequent embryonic development. The results of this study showed that TBBPA exposure induced oocyte meiotic failure by disturbing the polar-body extrusion of oocytes and the expansion of cumulus cells. We further found that TBBPA exposure led to defective spindle assembly and chromosome alignment. Meanwhile, TBBPA induced oxidative stress and early apoptosis by mediating the expression of superoxide dismutase 2 (SOD2). TBBPA exposure also caused mitochondrial dysfunction, displaying a decrease in mitochondrial membrane potential, mitochondrial content, mtDNA copy number, and ATP levels, which are regulated by the expression of pyruvate dehydrogenase kinase 3 (PDK3). In addition, the developmental competence of oocytes and the quality of blastocysts were also reduced after TBBPA treatment. These results demonstrated that TBBPA exposure impaired oocyte maturation and developmental competence by disrupting both nuclear and cytoplasmic maturation of the oocyte, which might have been caused by oxidative stress induced by mitochondrial dysfunction.

Determination of Apoptotic Mechanism of Action of Tetrabromobisphenol A and Tetrabromobisphenol S in Human Peripheral Blood Mononuclear Cells: A Comparative Study

Background: Tetrabromobisphenol A (TBBPA) is the most commonly used brominated flame retardant (BFR) in the industry. TBBPA has been determined in environmental samples, food, tap water, dust as well as outdoor and indoor air and in the human body. Studies have also shown the toxic potential of this substance. In search of a better and less toxic BFR, tetrabromobisphenol S (TBBPS) has been developed in order to replace TBBPA in the industry. There is a lack of data on the toxic effects of TBBPS, while no study has explored apoptotic mechanism of action of TBBPA and TBBPS in human leukocytes. Methods: The cells were separated from leucocyte-platelet buffy coat and were incubated with studied compounds in concentrations ranging from 0.01 to 50 µg/mL for 24 h. In order to explore the apoptotic mechanism of action of tested BFRs, phosphatidylserine externalization at cellular membrane (the number of apoptotic cells), cytosolic calcium ion and transmembrane mitochondrial potential levels, caspase-8, -9 and -3 activation, as well as PARP-1 cleavage, DNA fragmentation and chromatin condensation in PBMCs were determined. Results: TBBPA and TBBPS triggered apoptosis in human PBMCs as they changed all tested parameters in the incubated cells. It was also observed that the mitochondrial pathway was mainly involved in the apoptotic action of studied compounds. Conclusions: It was found that TBBPS, and more strongly TBBPA, triggered apoptosis in human PBMCs. Generally, the mitochondrial pathway was involved in the apoptotic action of tested compounds; nevertheless, TBBPS more strongly than TBBPA caused intrinsic pathway activation.

Vascular Response of Tetrabromobisphenol a in Rat Aorta: Calcium Channels Inhibition and Potassium Channels Activation

Tetrabromobisphenol A (TBBPA) is a flame retardant widely used to reduce flammability. It is an endocrine disruptor, and due to constant human exposure, some concerns have been raised regarding its impact on human health. Studies showed that TBBPA affects oxidative stress, cell proliferation and intracellular calcium levels. However, the vascular consequences of TBBPA exposure are still relatively unexplored. Hence, this work aimed to analyse TBBPA effects on rat aortic smooth muscle and its action mechanisms. Through an ex vivo approach, Wistar rat aortas were used in an organ bath to evaluate the vascular effect of TBBPA (0.01-100 μM). Additionally, TBBPA's mode of action was studied through calcium and potassium channel inhibitors. Resorting to in vitro studies, A7r5 cells were used to analyse L-Type voltage-gated calcium channel (VGCC) activity through the whole-cell configuration of the patch clamp technique, and the mRNA expression of proteins and ion channels involved in vascular contractility. The results showed vasorelaxation of rat aorta induced by TBBPA exposure, involving the inactivation of L-Type VGCC and activation of potassium channels, and the modulation of mRNA expression of L-type calcium and large-conductance calcium 1.1 and the BK_Ca 1.1 α- and β₁ -subunit channels, soluble guanylyl cyclase and protein Kinase G.

Developmental Exposure to Endocrine Disrupting Chemicals and Its Impact on Cardio-Metabolic-Renal Health

Developmental origin of health and disease postulates that the footprints of early life exposure are followed as an endowment of risk for adult diseases. Epidemiological and experimental evidence suggest that an adverse fetal environment can affect the health of offspring throughout their lifetime. Exposure to endocrine disrupting chemicals (EDCs) during fetal development can affect the hormone system homeostasis, resulting in a broad spectrum of adverse health outcomes. In the present review, we have described the effect of prenatal EDCs exposure on cardio-metabolic-renal health, using the available epidemiological and experimental evidence. We also discuss the potential mechanisms of their action, which include epigenetic changes, hormonal imprinting, loss of energy homeostasis, and metabolic perturbations. The effect of prenatal EDCs exposure on cardio-metabolic-renal health, which is a complex condition of an altered biological landscape, can be further examined in the case of other environmental stressors with a similar mode of action.

Environmental pollution, a hidden culprit for health issues

The environmental and health impacts from the massive discharge of chemicals and subsequent pollution have been gaining increasing public concern. The unintended exposure to different pollutants, such as heavy metals, air pollutants and organic chemicals, may cause diverse deleterious effects on human bodies, resulting in the incidence and progression of different diseases. The article reviewed the outbreak of environmental pollution-related public health emergencies, the epidemiological evidence on certain pollution-correlated health effects, and the pathological studies on specific pollutant exposure. By recalling the notable historical life-threatening disasters incurred by local chemical pollution, the damning evidence was presented to criminate certain pollutants as the main culprit for the given health issues. The epidemiological data on the prevalence of some common diseases revealed a variety of environmental pollutants to blame, such as endocrine-disrupting chemicals (EDCs), fine particulate matters (PMs) and heavy metals. The retrospection of toxicological studies provided illustrative clues for evaluating ambient pollutant-induced health risks. Overall, environmental pollution, as the hidden culprit, should answer for the increasing public health burden, and more efforts are highly encouraged to strive to explore the cause-and-effect relationships through extensive epidemiological and pathological studies.

Transcriptomic Analysis of the Differential Nephrotoxicity of Diverse Brominated Flame Retardants in Rat and Human Renal Cells

Brominated flame retardants (BFRs) are environmentally persistent, are detected in humans, and some have been banned due to their potential toxicity. BFRs are developmental neurotoxicants and endocrine disruptors; however, few studies have explored their potential nephrotoxicity. We addressed this gap in the literature by determining the toxicity of three different BFRs (tetrabromobisphenol A (TBBPA), hexabromocyclododecane (HBCD), and tetrabromodiphenyl ether (BDE-47)) in rat (NRK 52E) and human (HK-2 and RPTEC) tubular epithelial cells. All compounds induced time- and concentration-dependent toxicity based on decreases in MTT staining and changes in cell and nuclear morphology. The toxicity of BFRs was chemical- and cell-dependent, and human cells were more susceptible to all three BFRs based on IC₅₀s after 48 h exposure. BFRs also had chemical- and cell-dependent effects on apoptosis as measured by increases in annexin V and PI staining. The molecular mechanisms mediating this toxicity were investigated using RNA sequencing. Principal components analysis supported the hypothesis that BFRs induce different transcriptional changes in rat and human cells. Furthermore, BFRs only shared nine differentially expressed genes in rat cells and five in human cells. Gene set enrichment analysis demonstrated chemical- and cell-dependent effects; however, some commonalities were also observed. Namely, gene sets associated with extracellular matrix turnover, the coagulation cascade, and the SNS-related adrenal cortex response were enriched across all cell lines and BFR treatments. Taken together, these data support the hypothesis that BFRs induce differential toxicity in rat and human renal cell lines that is mediated by differential changes in gene expression.

Health toxicity effects of brominated flame retardants: From environmental to human exposure

Hexabromocyclododecane (HBCD) and Tetrabromobisphenol A (TBBP-A) are brominated flame retardants widely used in variety of industrial and consumer products (e.g., automobiles, electronics, furniture, textiles and plastics) to reduce flammability. HBCD and TBBPA can also contaminate the environment, mainly water, dust, air and soil, from which human exposure occurs. This constant exposure has raised some concerns against human health. These compounds can act as endocrine disruptors, a property that gives them the ability to interfere with hormonal function and quantity, when HBCD and TBBPA bind target tissues in the body. Studies in human and animals suggest a correlation between HBCD and TBBPA exposure and adverse health outcomes, namely thyroid disorders, neurobehavior and development disorders, reproductive health, immunological, oncological and cardiovascular diseases. However, in humans these effects are still poorly understood, once only a few data evaluated the human health effects. Thus, the purpose of this review is to present the toxicity effects of HBCD and TBBPA and how these compounds affect the environment and health, resorting to data and knowledge of 255 published papers from 1979 to 2020.

Effects of tetrabromobisphenol A (TBBPA) on the reproductive health of male rodents: A systematic review and meta-analysis

Tetrabromobisphenol A (TBBPA) is a type of brominated flame retardant widely detected in the environment and organisms. It has been reported to cause cytotoxicity and disrupt endocrine system of animals. However, the effect of TBBPA on the reproductive system of male rodents is still controversial. Hence, this meta-analysis aims to determine whether TBBPA exposure damage to the reproductive system of male rodents. In this study, a thorough search of literatures was undertaken to select papers published before December 1st, 2020. The standard mean difference (SMD) and 95% confidence interval (CI) were calculated by random model. The results showed a statistically significant association between TBBPA exposure and the reproductive system health of male rodents (SMD = -0.35, 95% CI -0.50 to -0.19). The SMD for the reproductive system index organ weight, sperm quality, hormone levels, and gene expression were 0.03 (95% CI -0.18 to 0.23), -0.47 (95% CI -0.78 to -0.16), -0.51 (95% CI -0.75 to -0.27), and -0.98 (95% CI -1.36 to -0.60), respectively. There was a significant dose-effect relationship between TBBPA exposure and the reproductive health of male rodents, with the SMD values of low, medium, and high doses -0.20 (95% CI -0.34 to -0.05), -0.24 (95% CI -0.56 to 0.07), and -0.48 (95% CI -0.83 to -0.13), respectively. For exposure duration of TBBPA, an exposure time of >10 weeks (SMD = -0.33, 95% CI -0.54 to -0.12) showed more significant effect than an exposure time of ≤10 weeks (SMD = -0.22, 95% CI -0.43 to -0.02). Moreover, TBBPA exposure exhibited significant negative effects on sperm count (SMD = -0.49, 95% CI -0.82 to -0.17) while also reduced the content of triiodothyronine (T3), thyroxine (T4), and thyroid stimulating hormone (TSH) hormones. To summarize, our meta-analysis indicated that TBBPA had a toxicity effect to the reproductive system of male rodents.

Biotechnology-based microbial degradation of plastic additives

Plastic additives are agents responsible to the flame resistance, durability, microbial resistance, and flexibility of plastic products. High demand for production and use of plastic additives is associated with environmental accumulation and various health hazards. One of the suitable methods of depleting plastic additive in the environment is bioremediation as it offers cost-efficiency, convenience, and sustainability. Microbial activity is one of the effective ways of detoxifying various compounds as microorganisms can adapt in an environment with high prevalence of pollutants. The present review discusses the use and abundance of these plastic additives, their health-related risks, the microorganisms capable of degrading them, the proposed mechanism of biodegradation, and current innovations capable of improving the efficiency of bioremediation.

Tetrabromobisphenol A (TBBPA): A controversial environmental pollutant

Tetrabromobisphenol A (TBBPA) is one of the most widely used brominated flame retardants and is extensively used in electronic equipment, furniture, plastics, and textiles. It is frequently detected in water, soil, air, and organisms, including humans, and has raised concerns in the scientific community regarding its potential adverse health effects. Human exposure to TBBPA is mainly via diet, respiration, and skin contact. Various in vivo and in vitro studies based on animal and cell models have demonstrated that TBBPA can induce multifaceted effects in cells and animals, and potentially exert hepatic, renal, neural, cardiac, and reproductive toxicities. Nevertheless, other reports have claimed that TBBPA might be a safe chemical. In this review, we re-evaluated most of the published TBBPA toxicological assessments with the goal of reaching a conclusion about its potential toxicity. We concluded that, although low TBBPA exposure levels and rapid metabolism in humans may signify that TBBPA is a safe chemical for the general population, particular attention should be paid to the potential effects of TBBPA on early developmental stages.

Excretion characteristics and tissue accumulation of tetrabromobisphenol-A in male rats after sub-chronic inhalation exposure

Tetrabromobisphenol-A (TBBPA) is an emerging organic pollutant and a commonly used brominated flame retardant that has received much attention owing to its toxicity. Although TBBPA is ubiquitously detected in atmospheric particulate matter and dust, few studies have investigated the sub-chronic inhalation exposure to TBBPA. To further understand the excretion characteristics and tissue accumulation of TBBPA after inhalation exposure, we used the rat model to conduct a sub-chronic inhalation exposure study. Male rats were administered with different doses of aerosol TBBPA (12.9, 54.6, 121.6, and 455.0 mg/m³). TBBPA was found in the excretion (feces and urine) and all the target tissues (lung, liver, heart, thymus gland, spleen, testicles, muscles, kidneys, brain and serum). Feces were the main route of excretion, which contributed 19.18% to 72.54% (urine <0.10%). TBBPA excretion through feces following inhalation administration was much higher than that following oral and dermal exposure, thereby indicating lower bioavailability of TBBPA under inhalation exposure. Liver and serum showed higher levels of TBBPA compared with those of other tissues, thereby suggesting tissue-specific accumulation of TBBPA in rats. Owing to the relative non-invasiveness of serum sampling and greatest TBBPA concentration among the tissues, serum is a suitable matrix for estimation of TBBPA bioaccumulation after inhalation exposure.

Assessment of Tetrabromobisphenol and Hexabromocyclododecanes exposure and risk characterization using occurrence data in foods

Tetrabromobisphenol A (TBBPA) and Hexabromocyclododecanes (HBCDs) are two of the most used BFRs and they have cumulated in the environment. TBBPA and HBCDs in food were determined and their risks were assessed. The analytical method used was validated in different food categories, and the performance parameters were acceptable based on the criteria of AOAC. Fish and cephalopods were contaminated with TBBPA higher than other foods, and fish contained higher levels of HBCDs than other foods. α-HBCD was the predominant diastereomer in fish and meat and had strong correlations with HBCDs in fish and cephalopods. HBCDs accumulated easier than TBBPA in food. People were exposed to TBBPA from 0.125 ng kg^-1 b.w. day^-1 to 0.284 ng kg^-1 b.w. day^-1 and HBCDs from 0.353 ng kg^-1 b.w. day^-1 to 1.006 ng kg^-1 b.w. day^-1 via food and air. Food mainly contributed to exposure to TBBPA and HBCDs and vegetables were the main contributors for exposure to TBBPA and HBCDs in food. MOEs for the whole population were over 100, and the risks of exposure to TBBPA and HBCDs from food and the environment were of low concern to public health.

Sex-specific behavioral effects following developmental exposure to tetrabromobisphenol A (TBBPA) in Wistar rats

Tetrabromobisphenol A (TBBPA) has become a ubiquitous indoor contaminant due to its widespread use as an additive flame retardant in consumer products. Reported evidence of endocrine disruption and accumulation of TBBPA in brain tissue has raised concerns regarding its potential effects on neurodevelopment and behavior. The goal of the present study was to examine the impact of developmental TBBPA exposure, across a wide range of doses, on sexually dimorphic non-reproductive behaviors in male and female Wistar rats. We first ran a pilot study using a single TBBPA dose hypothesized to produce behavioral effects. Wistar rat dams were orally exposed using cookie treats to 0 or 0.1 mg TBBPA/kg bw daily from gestational day (GD) 9 to postnatal day (PND) 21 to assess offspring (both sexes) activity and anxiety-related behaviors. Significant effects were evident in females, with exposure increasing activity levels. Thus, this dose was used as the lowest TBBPA dose in a subsequent, larger study conducted as part of a comprehensive assessment of TBBPA toxicity. Animals were exposed to 0, 0.1, 25, or 250 mg TBBPA/kg bw daily by oral gavage starting on GD 6 through PND 90 (dosed dams GD 6 - PND 21, dosed offspring PND 22 - PND 90). Significant behavioral findings were observed for male offspring, with increased anxiety-like behavior as the primary phenotype. These findings demonstrate that exposure to environmental contaminants, like TBBPA, can have sex-specific effects on behavior highlighting the vulnerability of the developing brain.

Tetrabromobisphenol A: Disposition, kinetics and toxicity in animals and humans

Tetrabromobisphenol A (TBBPA) is a nonregulated brominated flame retardant with a high production volume, and it is applied in a wide variety of consumer products. TBBPA is ubiquitous in abiotic matrices, wildlife and humans around the world. This paper critically reviews the published scientific data concerning the disposition, metabolism or kinetics and toxicity of TBBPA in animals and humans. TBBPA is rapidly absorbed and widely distributed among tissues, and is excreted primarily in the feces. In rats, TBBPA and its metabolites have limited systemic bioavailability. TBBPA has been detected in human milk in the general population. It is available to both the developing fetus and the nursing pups following maternal exposure. It has been suggested that TBBPA causes acute toxicity, endocrine disruptor activity, immunotoxicity, neurotoxicity, nephrotoxicity, and hepatotoxicity in animals. Cell-based assays have shown that TBBPA can induce reactive oxygen species in a concentration-dependent manner, and it promotes the production of inflammatory factors such as TNF α, IL-6, and IL-8. Cells exposed to high levels of TBBPA exhibit seriously injured mitochondria and a dilated smooth endoplasmic reticulum. This review will enhance the understanding of the potential risks of TBBPA exposure to ecological and human health.

Rapid and simultaneous analysis of tetrabromobisphenol A and hexabromocyclododecane in water by direct immersion solid phase microextraction: Uniform design to explore factors

Direct immersion solid phase microextraction (DI-SPME) coupled to liquid chromatography-tandem mass spectrometry (LC-MS/MS) is of significant research interest because of its low solvent consumption, simple design, and efficient, sensitive, fast performance. In this work, a combination of these two methods (DI-SPME-LC-MS) for the determination of tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCD) in water was developed. Important factors, which included temperature, stirring rate, salt concentration, pH value and adsorption time, were evaluated in for the optimization of solid phase microextraction (SPME) method. The method was developed using spiked natural waters in a concentration range of 0.1-10 ng mL^-1, and showed notable linearity with regression coefficients ranging between 0.992 and 0.999. The limits of detection varied from 0.01 to 0.04 ng mL^-1 (at S/N = 3) and relative standard deviation (RSD < 11%) were obtained showing that the precision of the method was reliable. Recoveries were in relatively high levels for both analytes and ranged from 88% to 108%. Moreover, in comparison with the performance time of traditional sample pretreatment methods such as solid-phase extraction (SPE), accelerated solvent extraction (ASE), and liquid-liquid extraction (LLE), DI-SPME-LC-MS takes only approximately 35 min to perform. The optimized method was successfully applied for monitoring concentrations of TBBPA and HBCD in water.

Transcriptome profiling of HepG2 cells exposed to the flame retardant 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO)

The flame retardant, 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO), has been receiving great interest given its superior fire protection properties, and its predicted low level of persistence, bioaccumulation, and toxicity. However, empirical toxicological data that are essential for a complete hazard assessment are severely lacking. In this study, we attempted to identify the potential toxicological modes of action by transcriptome (RNA-seq) profiling of the human liver hepatocellular carcinoma cell line, HepG2. Such insight may help in identifying compounds of concern and potential toxicological phenotypes. DOPO was found to have little cytotoxic potential, with lower effective concentrations compared to other flame retardants studied in the same cell line. Differentially expressed genes revealed a wide range of molecular effects including changes in protein, energy, DNA, and lipid metabolism, along with changes in cellular stress response pathways. In response to 250 μM DOPO, the most perturbed biological processes were fatty acid metabolism, androgen metabolism, glucose transport, and renal function and development, which is in agreement with other studies that observed similar effects of other flame retardants in other species. However, treatment with 2.5 μM DOPO resulted in very few differentially expressed genes and failed to indicate any potential effects on biology, despite such concentrations likely being orders of magnitude greater than would be encountered in the environment. This, together with the low levels of cytotoxicity, supports the potential replacement of the current flame retardants by DOPO, although further studies are needed to establish the nephrotoxicity and endocrine disruption of DOPO.

In vivo assessment of dermal adhesion, penetration, and bioavailability of tetrabromobisphenol A

Individuals are exposed to brominated flame retardants (BFRs), including tetrabromobisphenol A (TBBPA), on a daily basis because of their widespread usage. These compounds may have adverse effects on human health. In the present study, dermal absorption experiments were conducted in vivo to predict the adhesion, penetration, and bioavailability of TBBPA. TBBPA was administered to Wistar rats for 6 h by repeated dermal exposure at doses of 20, 60, 200, and 600 mg of TBBPA per kg of body weight (bw). The skin adhesion coefficient (AC) was calculated using a difference-value method and ranged from 0.12 to 3.25 mg/cm² and 0.1 to 2.56 mg/cm² for the male and female rats, respectively. The adhesion rate was 70.92%. According to Fick's first law of diffusion, the diffusion constant (D) was 1.4 × 10^-4 cm²/h and the permeation coefficient (K_p) was 1.26 × 10^-5 cm/h for TBBPA. TBBPA levels in the blood, urine, and feces of the male rats were significantly higher than those in the female rats. The dermal bioavailability of TBBPA was 24.71% for male rats and 20.05% for female rats 24 h after exposure.

Exposure to tetrabromobisphenol A induces cellular dysfunction in osteoblastic MC3T3-E1 cells

This study was undertaken to investigate the possible involvement of oxidative stress in tetrabromobisphenol A (TBBPA)-induced toxicity in osteoblastic MC3T3-E1 cells. To examine the potential effect of TBBPA on cultured osteoblastic cells, we measured cell viability, apoptosis, reactive oxygen species (ROS), mitochondrial superoxide, and mitochondrial parameters including adenosine triphosphate (ATP) level, cardiolipin content, cytochrome c release, cyclophilin levels, and differentiation markers in osteoblastic MC3T3-E1 cells. TBBPA exposure for 48 h caused the apoptosis and cytotoxicity of MC3T3-E1 cells. TBBPA also induced ROS and mitochondrial superoxide production in a concentration-dependent manner. These results suggest that TBBPA induces osteoblast apoptosis and ROS production, resulting in bone diseases. Moreover, TBBPA induced cardiolipin peroxidation, cytochrome c release, and decreased ATP levels which induced apoptosis or necrosis. TBBPA decreased the differentiation markers, collagen synthesis, alkaline phosphatase activity, and calcium deposition in cells. Additionally, TBBPA decreased cyclophilin A and B releases. Taken together, these data support the notion that TBBPA inhibits osteoblast function and has detrimental effects on osteoblasts through a mechanism involving oxidative stress and mitochondrial dysfunction.

Excretion characteristics of tetrabromobisphenol-A in Wistar rats following mouth and nose inhalation exposure

Tetrabromobisphenol-A (TBBPA), a brominated flame retardant with the largest production volume worldwide, is employed as a reactive and additive flame retardant, and also as an intermediate in the production of other retardants. The constant release of TBBPA into the environment has attracted increasing attention to its potent health effects. To date, the vast majority of health-related research on TBBPA has focused on oral exposure. This study aims to explore the excretion characteristics of TBBPA in living organisms following inhalation exposure. An inhalation exposure system was established in which the experimental animal model was exposed to inhalable particles (diameter < 10 μm) of TBBPA. The TBBPA aerosol doses used were 12.9, 54.6, 121.6, and 455.0 mg/m³ according to tuning system parameters. Following 14 d (2 h/d) of repeated inhalational exposure, the primary route of elimination was in feces for all exposed groups, and the values showed a significant positive linear relationship with exposure dose. In contrast, the elimination amount in urine was less than 0.4% of the inhaled dose. Trace levels of TBBPA (less than 0.1% of the inhaled dose) were also detected in serum, with amounts varying from 0 to 844 ng (per rat) among all groups.

Whole-body aerosol exposure of cadmium chloride (CdCl2) and tetrabromobisphenol A (TBBPA) induced hepatic changes in CD-1 male mice

Cadmium (Cd) and tetrabromobisphenol A (TBBPA) are two prevalent contaminants in e-waste recycling facilities. However, the potential adversely health effect of co-exposure to these two types of pollutants in an occupational setting is unknown. In this study, we investigated co-exposure of these two pollutants on hepatic toxicity in CD-1 male mice through a whole-body aerosol inhalation route. Specifically, mice were exposed to solvent control (5% DMSO), Cd (8μg/m(3)), TBBPA (16μg/m(3)) and Cd/TBBPA mixture for 8h/day and 6days a week for 60 days. Hepatic changes include increased organ weight, focal necrosis, and elevated levels of liver enzymes in serum. These changes were most severe in mice exposed to TBBPA, followed by Cd/TBBPA mixture and Cd. These chemicals also led to suppressed antioxidant defensive mechanisms and increased oxidative stress. Further, these chemicals induced gene expression of apoptosis-related genes, activated genes encoding for phase I detoxification enzymes and inhibited genes encoding for phase II detoxification enzymes. These findings indicate that the hepatic damages induced by subchronic aerosol exposure of Cd and TBBPA may result from the oxidative damages caused by excessive ROS production when these chemicals were metabolized in the liver.

Zwitterionic Surfactant Modified Acetylene Black Paste Electrode for Highly Facile and Sensitive Determination of Tetrabromobisphenol A

A electrochemical sensor for the highly sensitive detection of tetrabromobisphenol A (TBBPA) was fabricated based on acetylene black paste electrode (ABPE) modified with 3-(N,N-Dimethylpalmitylammonio) propanesulfonate (SB3-16) in this study. The peak current of TBBPA was significantly enhanced at SB3-16/ABPE compared with unmodified electrodes. To further improve the electrochemical performance of the modified electrode, corresponding experimental parameters such as the length of hydrophobic chains of zwitterionic surfactant, the concentration of SB3-16, pH value, and accumulation time were examined. The peak currents of TBBPA were found to be linearly correlated with its concentrations in the range of 1 nM to 1 µM, with a detection limit of 0.4 nM. Besides, a possible mechanism was also discussed, and the hydrophobic interaction between TBBPA and the surfactants was suggested to take a leading role in enhancing the responses. Finally, this sensor was successfully employed to detect TBBPA in water samples.

Synergetic enhancement of gold nanoparticles and 2-mercaptobenzothiazole as highly-sensitive sensing strategy for tetrabromobisphenol A

Various gold nanoparticles (AuNPs) were in-situ prepared on the electrode surface through electrochemical reduction under different potentials such as −0.60, −0.50, −0.40, −0.30 and −0.20 V. The reduction potentials heavily affect the surface morphology and electrochemical activity of AuNPs such as effective area and catalytic ability, as confirmed using atomic force microscopy and electrochemical impedance spectroscopy. The electrochemical behaviors of tetrabromobisphenol A (TBBPA), a widely-existed pollutant with severe adverse health effects, were studied. The oxidation activity of TBBPA enhances obviously on the surface of AuNPs, and the signal improvements of TBBPA show difference on the prepared AuNPs. Interestingly, the existence of 2-mercaptobenzothiazole (MBT) further improves the oxidation signals of TBBPA on AuNPs. The synergetic enhancement effects of AuNPs and MBT were studied using cyclic voltammetry and chronocoulometry. The numerous nano-scaled gold particles together with the strong hydrophobic interaction between TBBPA and the assembled MBT on AuNPs jointly provide highly-effective accumulation for TBBPA. As a result, a sensitive and simple electrochemical method was developed for the direct determination of TBBPA, with detection limit of 0.12 μg L⁻¹ (0.22 nM). The practical applications in water samples manifest that this new sensing system is accurate and feasible.

Absorption and excretion of Tetrabromobisphenol A in male Wistar rats following subchronic dermal exposure

Tetrabromobisphenol A (TBBPA) is widely used as a flame retardant and frequently detected in environmental and biological samples. In this study, male Wistar rats were repeatedly exposed by dermal application to 20, 60, 200 and 600 mg TBBPA/kg body weight during 90 days. Concentrations of TBBPA in serum, urine and feces after dermal exposure were determined. TBBPA concentrations in serum ranged from 19.04 to 427.20 g/g lipids. The percentage of TBBPA dose recovered in serum on the 90th day varied from 0.002 ± 0.002% to 0.013 ± 0.008%, and the percentage of dose excreted in urine varied from 0.004 ± 0.002% to 0.072 ± 0.027%, while the percentage of dose recovered in feces were 3.30 ± 0.61% to 11.13 ± 3.16%. The results showed that about 3.31-11.21% TBBPA was absorbed dermally under different dosing regimens. TBBPA was excreted mainly in feces and small only amounts were recovered in urine.

Development of toxicity values and exposure estimates for tetrabromobisphenol A: application in a margin of exposure assessment

Tetrabromobisphenol A (TBBPA) is used in a diverse array of products to improve fire safety. The National Toxicology Program (NTP) recently completed a 2-year bioassay for TBBPA. The objective of the present study was to develop a cancer-based and a non-cancer based toxicity value and to compare such to appropriate estimates of human exposure. Data from the NTP 2-year and 13-week studies were selected to develop candidate toxicity values. Benchmark dose modeling and subsequent evaluation of candidate values resulted in selection of an oral reference dose (RfD) of 0.6 mg kg(-1) day(-1) based on uterine hyperplasia in rats and an oral cancer slope factor (OSF) of 0.00315 per mg kg(-1) day(-1) based on an increased incidence of uterine tumors in rats. Lifetime average daily dose (LADD) estimates ranged from 2.2 E(-7) to 3.9 E(-6) mg kg(-1) day(-1) based on age-adjusted exposures to TBBPA via breast milk consumption, dietary intake, soil/dust ingestion and drinking water ingestion in infants, young children, older children and adults. Average daily dose (ADD) estimates ranged from 3.2 E (-7) to 8.4 E(-5) mg kg(-1) day(-1). Resulting margin of exposure (MOE) values were > 800 000 for non-cancer endpoints and > 32,000,000 for cancer-based endpoints. These data collectively indicate a low level of health concern associated with exposures to TBBPA based on current data. It is anticipated that the exposure estimates, along with the toxicity values described within, should be informative for understanding human health hazards associated with TBBPA.

Hexabromocyclododecane and tetrabromobisphenol A alter secretion of interferon gamma (IFN-γ) from human immune cells

Hexabromocyclododecane (HBCD) and tetrabromobisphenol A (TBBPA) are brominated flame-retardant compounds used in a variety of applications including insulation, upholstery, and epoxy resin circuit boards. Interferon gamma (IFN-γ) is an inflammatory cytokine produced by activated T and NK cells that regulates immune responsiveness. HBCD and TBBPA are found in human blood, and previous studies have shown that they alter the ability of human natural killer (NK) lymphocytes to destroy tumor cells. This study examines whether HBCD and TBBPA affect the secretion of IFN-γ from increasingly complex preparations of human immune cells-purified NK cells, monocyte-depleted (MD) peripheral blood mononuclear cells (PBMCs), and PBMCs. Both HBCD and TBBPA were tested at concentrations ranging from 0.05 to 5 µM. HBCD generally caused increases in IFN-γ secretion after 24-h, 48-h, and 6-day exposures in each of the different cell preparations. The specific concentration of HBCD that caused increases as well as the magnitude of the increase varied from donor to donor. In contrast, TBBPA tended to decrease secretion of IFN-γ from NK cells, MD-PBMCs, and PBMCs. Thus, exposure to these compounds may potentially disrupt the immune regulation mediated by IFN-γ. Signaling pathways that have the capacity to regulate IFN-γ production (nuclear factor kappa B (NF-κB), p44/42, p38, JNK) were examined for their role in the HBCD-induced increases in IFN-γ. Results showed that the p44/42 (ERK1/2) MAPK pathway appears to be important in HBCD-induced increases in IFN-γ secretion from human immune cells.

Exposure of Chlamys farreri to tetrabromobisphenol A: accumulation and multibiomarker responses

Tetrabromobisphenol A (TBBPA) is currently the most widely used brominated flame retardant (BFR). To date, the toxic effects of TBBPA remains poorly understood in aquatic organisms, especially in bivalves. The objective of this experiment was to examine bioaccumulation and multibiomarker responses in the scallop Chlamys farreri exposed to TBBPA under laboratory conditions. The results showed that TBBPA was rapidly accumulated in and then eliminated from the gill and digestive gland of the scallops. TBBPA exposure invoked alterations in the detoxification system and induced oxidant stress and biomacromolecule damages in the gill and digestive gland of C. farreri. Additionally, glutathione-S-transferase (GST) activity, lipid peroxidation (LPO) level, cytochrome b5 (Cyt b5) content, and DNA strand break had good correlations with TBBPA accumulation levels in the gill and digestive gland of C. farreri. Summarizing, these results enabled us to hypothesize several toxic mechanisms of TBBPA and select potential biomarkers for TBBPA pollution monitoring.

Activation of protein kinase C and protein kinase D in human natural killer cells: effects of tributyltin, dibutyltin, and tetrabromobisphenol A

Up to now, the ability of target cells to activate protein kinase C (PKC) and protein kinase D (PKD) (which is often a downstream target of PKC) has not been examined in natural killer (NK) lymphocytes. Here we examined whether exposure of human NK cells to lysis sensitive tumor cells activated PKC and PKD. The results of these studies show for the first time that activation of PKC and PKD occurs in response to target cell binding to NK cells. Exposure of NK cells to K562 tumor cells for 10 and 30 min increased phosphorylation/activation of both PKC and PKD by roughly 2-fold. Butyltins (tributyltin (TBT), dibutyltin (DBT)) and brominated compounds (tetrabromobisphenol A (TBBPA)) are environmental contaminants that are found in human blood. Exposures of NK cells to TBT, DBT, or TBBPA decrease NK cell lytic function in part by activating the mitogen-activated protein kinases (MAPKs) that are part of the NK lytic pathway. We established that PKC and PKD are part of the lytic pathway upstream of MAPKs and thus we investigated whether DBT, TBT, and TBBPA exposures activated PKC and PKD. TBT-activated PKC by 2-3-folds at 10 min at concentrations ranging from 50 to 300 nM while DBT caused a 1.3-fold activation at 2.5 µM at 10 min. Both TBT and DBT caused an approximately 2-fold increase in phosphorylation/activation of PKC. Exposures to TBBPA caused no statistically significant changes in either PKC or PKD activation.

Bioaccumulation and detoxification responses in the scallop Chlamys farreri exposed to tetrabromobisphenol A (TBBPA)

Tetrabromobisphenol A (TBBPA) is currently the most widely used brominated flame retardant (BFR). In this study, the bioaccumulation of TBBPA and its consequent detoxification responses were examined in the scallop Chlamys farreri over 10 days' exposure. Chemical analysis showed that C. farreri absorbed TBBPA rapidly and an approximate steady state was achieved within 6 days. The mRNA expression levels of three important genes involved in aryl hydrocarbon receptor (AhR) pathway were down-regulated upon TBBPA exposure. Both CYP3A and CYP4 showed time-dependent responses to TBBPA exposure. Glutathione-S-transferase (GST) activity and gene expression level, and UDP-glucuronosyltransferase (UGT) activity were increased in time- and dose-dependent manners, confirming their role in the phase II metabolism of TBBPA. The TBBPA-elicited down-regulation of the P-glycoprotein (Pgp) gene was observed in all treatments. This study provides a preliminary basis for studying TBBPA detoxification mechanisms of marine bivalves.

Enhanced transformation of tetrabromobisphenol a by nitrifiers in nitrifying activated sludge

The fate of the most commonly used brominated flame retardant, tetrabromobisphenol A (TBBPA), in wastewater treatment plants is obscure. Using a (14)C-tracer, we studied TBBPA transformation in nitrifying activated sludge (NAS). During the 31-day incubation, TBBPA transformation (half-life 10.3 days) was accompanied by mineralization (17% of initial TBBPA). Twelve metabolites, including those with single benzene ring, O-methyl TBBPA ether, and nitro compounds, were identified. When allylthiourea was added to the sludge to completely inhibit nitrification, TBBPA transformation was significantly reduced (half-life 28.9 days), formation of the polar and single-ring metabolites stopped, but O-methylation was not significantly affected. Abiotic experiments confirmed the generation of mono- and dinitro-brominated forms of bisphenol A in NAS by the abiotic nitration of TBBPA by nitrite, a product of ammonia-oxidizing microorganisms (AOMs). Three biotic (type II ipso-substitution, oxidative skeletal cleavage, and O-methylation) and one abiotic (nitro-debromination) pathways were proposed for TBBPA transformation in NAS. Apart from O-methylation, AOMs were involved in three other pathways. Our results are the first to provide information about the complex metabolism of TBBPA in NAS, and they are consistent with a determining role for nitrifiers in TBBPA degradation by initiating its cleavage into single-ring metabolites that are substrates for the growth of heterotrophic bacteria.

Electrochemical enhancement of acetylene black film as sensitive sensing platform for toxic tetrabromobisphenol A

A sensitive and rapid electrochemical method was developed for TBBPA based on enhancement effects of acetylene black particles.

Brominated flame retardants, tetrabromobisphenol A and hexabromocyclododecane, activate mitogen-activated protein kinases (MAPKs) in human natural killer cells

Natural killer (NK) cells provide a vital surveillance against virally infected cells, tumor cells, and antibody-coated cells through the release of cytolytic mediators and gamma interferon (IFN-γ). Hexabromocyclododecane (HBCD) is a brominated flame retardant used primarily in expanded (EPS) and extruded (XPS) polystyrene foams for thermal insulation in the building and construction industry. Tetrabromobisphenol A (TBBPA) is used both as a reactive and an additive flame retardant in a variety of materials. HBCD and TBBPA contaminate the environment and are found in human blood samples. In previous studies, we have shown that other environmental contaminants, such as the dibutyltin (DBT) and tributyltin (TBT), decrease NK lytic function by activating mitogen-activated protein kinases (MAPKs) in the NK cells. HBCD and TBBPA also interfere with NK cell(s) lytic function. The current study evaluates whether HBCD and/or TBBPA have the capacity to activate MAPKs and MAPK kinases (MAP2Ks). The effects of concentrations of HBCD and TBBPA that inhibited lytic function on the phosphorylation state and total levels of the MAPKs (p44/42, p38, and JNK) and the phosphorylation and total levels of the MAP2Ks (MEK1/2 and MKK3/6) were examined. Results indicate that exposure of human NK cells to 10-0.5 μM HBCD or TBBPA activate MAPKs and MAP2Ks. This HBCD and TBBPA-induced activation of MAPKs may leave them unavailable for activation by virally infected or tumor target cells and thus contributes to the observed decreases in lytic function seen in NK cells exposed to HBCD and TBBPA.

Tetrabromobisphenol A activates inflammatory pathways in human first trimester extravillous trophoblasts in vitro

Tetrabromobisphenol A (TBBPA) is a widely used flame retardant. Despite the presence of TBBPA in gestational tissues and the importance of proper regulation of inflammatory networks for successful pregnancy, there is no prior study on the effects of TBBPA on inflammatory responses in gestational tissues. The present study aimed to investigate TBBPA activation of inflammatory pathways, specifically cytokine and prostaglandin production, in the human first trimester placental cell line HTR-8/SVneo. TBBPA enhanced release of interleukin (IL)-6, IL-8, and prostaglandin E2 (PGE2), and suppressed TGF-β release in HTR-8/SVneo cells. The lowest effective concentration was 10 μM TBBPA. A commercial immune response PCR array revealed increased expression of genes involved in inflammatory pathways stimulated by TBBPA in HTR-8/SVneo cells. Because proper regulation of inflammatory mediators in the gestational compartment is necessary for normal placental development and successful pregnancy, further investigation on the impact of TBBPA-stimulated responses on trophoblast function is warranted.

Deep sequencing of the scallop Chlamys farreri transcriptome response to tetrabromobisphenol A (TBBPA) stress

Tetrabromobisphenol-A (TBBPA) is currently the most widely used brominated flame retardant (BFR) and has been proven to have a very high toxicity to aquatic organisms including bivalves. However, molecular responses to TBBPA in bivalve remain largely unknown. Novel high-throughput deep sequencing technology has been a powerful tool for looking at molecular responses to toxicological stressors in organisms. Using Illumina's digital gene expression (DGE) system, we investigated TBBPA-induced transcriptome response in the digestive gland tissue of scallop Chlamys farreri. In total, 173 and 266 genes were identified as significantly up- or down-regulated, respectively. Functional analysis based on gene ontology (GO) classification system and Kyoto Encyclopedia of Genes and Genomes (KEGG) database revealed that TBBPA significantly altered the expression of genes involved in stress response, detoxification, antioxidation, and innate immunity which were extensively discussed. In particular, evidence for the endocrine disrupting effect of TBBPA on bivalve was first obtained in this study. Quantitative real-time PCR was performed to ascertain the mRNA expression of several genes identified by the DGE analysis. The results of this study may serve as a basis for future research on molecular mechanism of toxic effects of TBBPA on marine bivalves.

Two organobromines trigger lifespan, growth, reproductive and transcriptional changes in Caenorhabditis elegans

Organobromines of natural and artificial origin are omnipresent in aquatic and terrestrial environments. Although it is well established that exposure to high concentrations of organobromines are harmful to vertebrates, few studies have investigated the effect of environmentally realistic concentrations on invertebrates. Here, the nematode Caenorhabditis elegans was challenged with two organobromines, namely dibromoacetic acid (DBAA) and tetrabromobisphenol-A (TBBP), and monitored for changes in different life trait variables and global gene expression patterns. Fifty micromolar DBAA stimulated the growth and lifespan of the nematodes; however, the onset of reproduction was delayed. In contrast, TBBP changed the lifespan in a hormetic fashion, namely it was stimulated at 0.1 μM but impaired at 50 μM. The reproductive performance was even impaired at 2 μM TBBP. Moreover, DBAA could not reduce the toxic effect of TBBP when applied as a mixture. A whole-genome DNA microarray revealed that both organobromines curtailed signalling and neurological processes. Furthermore on the transcription level, 50 μM TBBP induced proteolysis and DBAA up-regulated biosynthesis and metabolism. To conclude, even naturally occurring concentrations of organobromines can influence the biomolecular responses and life cycle traits in C. elegans. The life extension is accompanied by negative changes in the reproductive behaviour, which is crucial for the stability of populations. Thus, this paper highlights that the effects of exposure to moderate, environmentally realistic concentrations of organobromines should not be ignored.

Mammalian toxicology and human exposures to the flame retardant 2,2',6,6'-tetrabromo-4,4'-isopropylidenediphenol (TBBPA): implications for risk assessment

The compound 2,2',6,6'-Tetrabromo-4,4'-isopropylidenediphenol (tetrabromobisphenol A, TBBPA) is used as a reactive and additive flame retardant. This review evaluates the mammalian toxicology of TBBPA and summarizes recent human exposure and risk assessments. TBBPA has a low potential for systemic or reproductive toxicity, and no-observed-adverse-effect-levels were greater than 1,000 mg/kg body weight (bw)/day in a 90-day oral toxicity study, a developmental toxicity study and a two-generation reproductive and developmental toxicity study. Some interactions of TBBPA with hormone-mediated pathways were noted in vitro; however, when studied in vivo, TBBPA did not produce adverse effects that might be considered to be related to disturbances in the endocrine system. Therefore, in accordance with internationally accepted definitions, TBBPA should not be considered an "endocrine disruptor." Furthermore, TBBPA is rapidly excreted in mammals and therefore does not have a potential for bioaccumulation. Measured concentrations of TBBPA in house dust, human diet and human serum samples are very low. Daily intakes of TBBPA in humans were estimated to not exceed a few ng/kg bw/day. Due to the low exposures and the low potential for toxicity, margins of exposures for TBBPA in the human population were between 6 × 10(4) (infants) to 6 × 10(7) (adults). Exposures of the general population are also well below the derived-no-effect-levels derived for endpoints of potential concern in REACH.

Molecular Mechanism of Tetrabromobisphenol A (TBBPA)-induced Target Organ Toxicity in Sprague-Dawley Male Rats

Brominated flame retardants (BFRs) are present in many consumer products ranging from fabrics to plastics and electronics. Wide use of flame retardants can pose an environmental hazard, which makes it important to determine the mechanism of their toxicity. In the present study, dose-dependent toxicity of tetrabromobisphenol A (TBBPA), a flame retardant, was examined in male prepubertal rats (postnatal day 18) treated orally with TBBPA at 0, 125, 250 or 500 mg/kg for 30 days. There were no differences in body weight gain between the control and TBBPA-treated groups. However, absolute and relative liver weights were significantly increased in high dose of TBBPA-treated groups. TBBPA treatment led to significant induction of CYP2B1 and constitutive androstane receptor (CAR) expression in the liver. In addition, serum thyroxin (T4) concentration was significantly reduced in the TBBPA treated group. These results indicate that repeated exposure to TBBPA induces drug-metabolising enzymes in rats through the CAR signaling pathway. In particular, TBBPA efficiently produced reactive oxygen species (ROS) through CYP2B1 induction in rats. We measured 8-hydroxy-2'-deoxyguanosine (8-OHdG), a biomarker of DNA oxidative damage, in the kidney, liver and testes of rats following TBBPA treatment. As expected, TBBPA strongly induced the production of 8-OHdG in the testis and kidney. These observations suggest that TBBPA-induced target organ toxicity may be due to ROS produced by metabolism of TBBPA in Sprague- Dawley rats.

Tetrabromobisphenol A decreases cell-surface proteins involved in human natural killer (NK) cell-dependent target cell lysis

Human natural killer (NK) lymphocytes are able to destroy tumor cells and virally-infected cells. Interference with their function can leave an individual with increased susceptibility to cancer development and/or viral infection. We have shown that the tumor-destroying (lytic) function of NK cells can be dramatically decreased by exposure to the environmental contaminant tetrabromobisphenol A (TBBPA). TBBPA is a flame retardant used in a variety of materials including circuit boards, carpeting, and upholstery and has been found in human blood samples. TBBPA interferes with NK cell lytic function, in part, by decreasing the ability of NK cells to bind to target cells. This study examines the effects of exposures to concentrations of TBBPA (i.e., that were able to decrease the binding capacity of NK cells) on the expression of cell-surface proteins (CD2, CD11a, CD16, CD18, and CD56) that are needed for NK cells to bind target cells. NK cells were exposed to TBBPA for 24 h, 48 h, and 6 days or for 1 h followed by 24 h, 48 h, and 6 days in TBBPA-free media. Twenty-four-hour exposures to 5 µM TBBPA caused decreases in four of the cell-surface proteins examined. CD16 was decreased by >35%. The decreases in cell-surface proteins after a 48-h exposure were similar to those seen after 24 h. The results indicate that TBBPA exposures that decrease the binding function of human NK cells do so by decreasing the expression of cell-surface proteins needed for attachment of NK cells to targets cells.

Tetrabromobisphenol A has immunosuppressive effects on human natural killer cells

Human natural killer (NK) cells are lymphocytes that destroy tumor cells, virally-infected cells, and antibody-coated cells. Tetrabromobisphenol A (TBBPA) is used both as a reactive and as an additive flame retardant in a variety of materials and appears to contaminate the environment. TBBPA has been found in human blood samples and if it interferes with NK cell function, this could increase the risk of tumor development and/or viral infection. The present study examines the effects of exposure to various concentrations of TBBPA for 24 hr, 48 hr, and 6 days on the lytic function, tumor-target-binding function, and ATP levels of NK cells. These same parameters were also monitored in NK cells that were exposed to TBBPA for 1 h followed by 24 hr, 48 hr, and 6 days in TBBPA-free media. A 24-h exposure of NK cells to 5 microM TBBPA caused a >95% decrease in NK lytic function, a 70% decrease in binding function, and a 34% decrease in ATP levels in NK cells. Exposure to 2.5 microM TBBPA for 24 h decreased lytic function by 76%, binding function by 20%, and had no effect on ATP levels. Exposure of NK cells to 5 microM TBBPA for 1 h followed by 24 h in TBBPA-free media caused a progressive and persistent loss of lytic function (41%) while not affecting either binding ability or ATP levels. The results indicate that TBBPA exposures decrease the lytic function of human NK cells and that an initial brief (1 hr) exposure can cause a progressive loss of function. In addition, the data also indicate that TBBPA-induced loss of NK lytic function can occur at a concentration of TBBPA that does not affect target-binding ability and ATP levels of NK cells.