Photodegradation of 1,3,5-Tris-(2,3-dibromopropyl)-1,3,5-triazine-2,4,6-trione and decabromodiphenyl ethane flame retardants: Kinetics, Main products, and environmental implications

Degradation processes of brominated flame retardants dispersed in high impact polystyrene under UV-visible radiation

In order to protect human health and the environment, several regulations have been introduced in recent years to reduce or even eliminate the use of some brominated flame retardants (BFRs) due to their toxicity, persistence and bioaccumulation. Dispersions of these BFRs in polymers are widely used for various applications. In this report, four different brominated molecules, decabromodiphenyl ether (DBDE), hexabromocyclododecane (HBCDD), decabromodiphenyl ethane (DBDPE) and tris(tribromophenoxy)triazine (TTBPT), were dispersed in the solid matrix of an industrial polymer, high impact polystyrene (HIPS). The possibility of degradation of these BFRs within HIPS under UV-visible irradiation in ambient air was investigated. The degradation kinetics of DBDE and HBCDD were followed by Fourier transform infrared spectroscopy (FTIR) and high-resolution two-step laser mass spectrometry (L2MS). The thermal properties of the pristine and irradiated polymer matrix were monitored by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), which showed that these properties were globally preserved. Volatile photoproducts from the degradation of DBDE, DBDPE and TTBPT were identified by headspace gas chromatography/mass spectrometry analysis. Under the chosen experimental conditions, BFRs underwent rapid degradation after a few seconds of irradiation, with conversions exceeding 50% for HIPS/DBDE and HIPS/HBCDD systems.

Assessing the environmental impact due to photolytic degradation of ethane-bis(pentabromophenyl) in plastics

Photolytic degradation of brominated flame retardants is one of the potential decomposition pathways in the environment, and for some flame retardants such as ethane-bis(pentabromophenyl) (EBP), also called decabromodiphenyl ethane, there are concerns that degradation products may be harmful. In this paper, we present photolytic studies of EBP in high-impact polystyrene (HIPS) and polypropylene impact copolymer (PP) using accelerated weatherometry. The half-life of photolytic debromination of EBP in HIPS was estimated to be more than 200 years, which can be contrasted with half-lives of minutes for photolysis conducted on dilute EBP solutions. Perhaps more importantly, there was no subsequent debromination to the octabrominated congeners or lower. No evidence of debromination was seen in PP, which confirms the importance of matrix effects. We also saw no evidence of accelerated resin photooxidation caused by EBP. These studies demonstrate that EBP is much more photolytically stable in resins than structurally-similar decabromodiphenyl ether, and a read-across comparison between the two flame retardant molecules for this degradation pathway is misleading.

Associations between environmental exposure to polybrominated diphenyl ethers and nodular goiter risk: A case-control study

Polybrominated diphenyl ethers (PBDEs) are widespread and persistent environmental contaminants, but their association with nodular goiter (NG) remains unknown. The present case-control study of 179 NG cases and 358 matched normal controls aimed to investigate the association between PBDEs and risk of NG. The plasma concentrations of 8 PBDEs congeners (BDE-28, -47, -99, -100, -153, -154, -183, and -209) were determined by gas chromatograph-mass spectrometer. Conditional logistic regression model was used to evaluate the odds ratio (OR) and 95% confidence interval (CI) for the association between each PBDEs congener and NG. Bayesian kernel machine regression (BKMR) was used to evaluate the association between overall levels of 8 PBDEs mixture and NG. The results of logistic model suggested that increased risk of NG was associated with elevated concentrations of all PBDEs congeners, except for BDE-209. In BKMR model, the risk of NG increased with the increase in overall exposure level of 8 PBDEs mixture. Compared to when all PBDEs mixture were at their median value, the risk of exposure-response function for NG increased by 0.34 units when all PBDEs were at their 75th percentile. In women, the results showed similar trends after additional adjustment for age at menarche and menopausal status. These findings provide novel epidemiological evidence for the prevention of NG. However, larger prospective studies are required to address the associations between PBDEs exposure and NG risk.

Investigation of novel brominated triazine-based flame retardant (TDBP-TAZTO) and its transformation products emitted from fire-retarded textile manufacturing facility and its downstream sewage treatment plant

Investigation of transformation products from novel flame retardants emitted throughout their life cycles is crucial for understanding and predicting environmental and human health risks posed by them during the material and product life cycle. Here, to understand more about the emission of TDBP-TAZTO to the environment, we investigated the presence of novel brominated triazine-based flame retardant 1,3,5-tris-(2,3-dibromopropyl)-1,3,5-triazine-2,4,6-trione (TDBP-TAZTO) and its transformation products in the effluent from a facility manufacturing fire-retarded textiles, and in the influent, effluent, and sludge of its closest downstream sewage treatment plant. To acquire mass spectra data of the transformation products in the influent, effluent, and sludge, non-target analysis was carried out by electrospray ionization-quadrupole time-of-flight-high-resolution mass spectrometry with liquid chromatography (LC-ESI-QTOF-HRMS). Then, the HaloSeeker 2.0 software was used to filter the mass spectrometry data for signals attributable to halogenated compounds. Combination of LC-ESI-QTOF-HRMS accurate mass measurements and HaloSeeker screening allowed us to determine the most probable elemental compositions and structures of 11 transformation products from TDBP-TAZTO and to construct a possible transformation pathway that included dehydrobromination, hydroxylation, and decarbonylation reactions. Based on analysis of the absolute intensities, we found that TDBP-TAZTO and its transformation products may not be easily removed by current sewage treatment plant process. There are increasing concerns about environmental contamination by TDBP-TAZTO and its transformation products different from the one which have previously been considered to be c-decaBDE and its lower brominated congeners. However, the present data suggest that concern is also warranted over the presence of TDBP-TAZTO and its transformation products in the environment. The present data will be useful for assessing, predicting, and understanding the environmental contamination and human health risks posed by TDBP-TAZTO, and for considering appropriate measures to control the emission of TDBP-TAZTO and its transformation products during product life cycles.

Tris (2,3-Dibromopropyl) Isocyanurate (TDBP-TAZTO or TBC) Shows Different Toxicity Depending on the Degree of Differentiation of the Human Neuroblastoma (SH-SY5Y) Cell Line

Tris (2,3-dibromopropyl) isocyanurate (TDBP-TAZTO or TBC) is a heterocyclic hexabromated flame retardant. It is widely used during the production of many synthetic compounds. High concentrations of TDBP-TAZTO were found in river water, surface sediments, soil, earthworms, and carp tissues. Moreover, it has been shown that this compound can cross the blood–brain barrier and accumulate in the gut and brain of carp. The aryl hydrocarbon receptor (AhR) has been characterized as a multifunctional intracellular sensor and receptor. AhR is an activator of cytochrome P450 1A1 and 1A2, which metabolize various toxic compounds. The aim of the study was to explain how/whether TDBP-TAZTO increases the expression and/or activity of the CYP1A1 enzyme and the AhR and TUBB3 expression during SH-SY5Y cell differentiation. SH-SY5Y cells were differentiated for 7 and 14 days using retinoic acid. Cell viability, ethoxyresorufin-O-deethylase (EROD) activity, and mRNA expression of CYP1A1, AhR, and TUBB3 were assessed. Our experiment showed that, during the differentiation process, the ability of TDBP-TAZTO to induce EROD activity in SH-SY5Y cells subsequently decreased, which may have been an effect of cell differentiation into neurons. Moreover, the results suggest that TDBP-TAZTO can affect the differentiation process. Since no CYP2B6 mRNA expression was detected, the CAR receptor may not be involved in the TDBP-TAZTO mechanism of action. However, more research is needed in this field to elucidate this mechanism precisely.

Potential health risk assessment of HFRs, PCBs, and OCPs in the Yellow River basin

The concentrations of PBDEs, NBFRs, DP, PCBs, and OCPs were analyzed in water samples of the Yellow River Basin (YRB) and in soil and maize samples collected from basin irrigation areas to understand the status of POPs and associated health risks. The results showed: (1) the congeners of eight PBDEs and seven NBFRs were detected in 10 tributaries, with average concentrations of 1575 and 4288 pg. L^-1. Thirty-three congeners of PCBs were detected, and the average concentration of PCB was 232 pg. L^-1. Five HCHs were the primary congeners among twenty-three congeners of OCPs in the ten tributaries, accounting for 79% of the total. The average concentration of OCPs was 8287 pg. L^-1. (2) Similar congeners of HFRs, PCBs, and OCPs were found in the trunk water. The ranking based on the HFR concentration was upstream > downstream > midstream, and that of the PCB and OCP concentration was downstream > upstream > midstream. (3) PCBs and OCPs in the trunk water of the YRB and in the soil and maize irrigated with river water pose potential carcinogenic and non-carcinogenic risks. The results indicate considerable organic pollution in the YRB, suggesting that national emission standards for POPs should be implemented soon.