Degradation of the Polymeric Brominated Flame Retardant "Polymeric FR" by Heat and UV Exposure

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.

Photolytic degradation of novel polymeric and monomeric brominated flame retardants: Investigation of endocrine disruption, physiological and ecotoxicological effects

Ecotoxicological effects of photolytic degradation mixtures of the two brominated flame retardants PolymericFR and Tetrabromobisphenol A-bis (2,3-dibrom-2-methyl-propyl) Ether (TBBPA-BDBMPE) have been studied in vitro and in vivo. Both substances were experimentally degraded separately by exposure to artificial UV-light and the resulting degradation mixtures from different time points during the UV-exposure were applied in ecotoxicological tests. The in vitro investigation showed no effects of the degraded flame retardants on the estrogenic and androgenic receptors via the CALUX (chemically activated luciferase gene expression) assay. Short-term exposures (up to 96 h) of Lumbriculus variegatus lead to temporary physiological reactions of the annelid. The exposure to degraded PolymericFR lead to an increased activity of Catalase, while the degradation mixture of TBBPA-BDBMPE caused increases of Glutathione-S-transferase and Acetylcholine esterase activities. Following a chronic exposure (28 d) of L. variegatus, no effects on the growth, reproduction, fragmentation and energy storage of the annelid were detected. The results indicate that the experimental degradation of the two flame retardants causes changes in their ecotoxicological potential. This might lead to acute physiological effects on aquatic annelids, which, however, do not affect the animals chronically according to our results.

Degradation of carbamazepine by high-voltage direct current gas-liquid plasma with the addition of H2O2 and Fe2

Carbamazepine (CBZ) is a typical psychotropic pharmaceutical which is one of the most commonly detected persistent pharmaceuticals in the environment. The degradation of CBZ in the aqueous solution was studied by a direct current (DC) gas-liquid phase discharge plasma combined with different catalysts (H₂O₂ or Fe²⁺) in this study. The concentrations of reactive species (H₂O₂, O₃, and NO₃^-) and •OH radical yield in the liquid were measured during the discharge process. The various parameters that affect the degradation of CBZ, such as discharge powers, initial concentrations, initial pH values, and addition of catalysts, were investigated. The energy efficiency was 25.2 mg·kW^-1·h^-1 at 35.7 W, and the discharge power at 35.7 W was selected to achieve the optimal balance on the degradation effect and energy efficiency. Both acidic and alkaline solution conditions were conducive to promoting the degradation of CBZ. Both H₂O₂ and Fe²⁺ at low concentration (10-100 mg/L of Fe²⁺, 0.05-2.0 mmol/L of H₂O₂) were observed contributing to the improvement of the CBZ degradation rate, while the promotional effect of CBZ degradation was weakened even inhibition would occur at high concentrations (100-200 mg/L of Fe²⁺, 2.0-5.0 mmol/L of H₂O₂). The degradation rate of CBZ was up to 99.1%, and the total organic carbon (TOC) removal efficiency of CBZ was up to 67.1% in the plasma/Fe²⁺ (100 mg/L) system at 48 min, which suggested that high degradation rate and mineralization efficiency on CBZ could be achieved by employing Fe²⁺ as a catalyst. Based on the intermediate products identified by Ultra Performance Liquid Chromatography Tandem Mass Spectrometry (UPLC-MS), the possible degradation pathways were proposed. Finally, the growth inhibition assay with Escherichia coli (E. coli) showed that the toxicity of plasma/Fe²⁺-treated CBZ solution decreased and a relatively low solution toxicity could be achieved. Thus, the plasma/catalyst could be an effective technology for the degradation of pharmaceuticals in aqueous solutions.

Metabolic transformation of environmentally-relevant brominated flame retardants in Fauna: A review

Over the past few decades, production trends of the flame retardant (FR) industry, and specifically for brominated FRs (BFRs), is for the replacement of banned and regulated compounds with more highly brominated, higher molecular weight compounds including oligomeric and polymeric compounds. Chemical, biological, and environmental stability of BFRs has received some attention over the years but knowledge is currently lacking in the transformation potential and metabolism of replacement emerging or novel BFRs (E/NBFRs). For articles published since 2015, a systematic search strategy reviewed the existing literature on the direct (e.g., in vitro or in vivo) non-human BFR metabolism in fauna (animals). Of the 51 papers reviewed, and of the 75 known environmental BFRs, PBDEs were by far the most widely studied, followed by HBCDDs and TBBPA. Experimental protocols between studies showed large disparities in exposure or incubation times, age, sex, depuration periods, and of the absence of active controls used in in vitro experiments. Species selection emphasized non-standard test animals and/or field-collected animals making comparisons difficult. For in vitro studies, confounding variables were generally not taken into consideration (e.g., season and time of day of collection, pollution point-sources or human settlements). As of 2021 there remains essentially no information on the fate and metabolic pathways or kinetics for 30 of the 75 environmentally relevant E/BFRs. Regardless, there are clear species-specific and BFR-specific differences in metabolism and metabolite formation (e.g. BDE congeners and HBCDD isomers). Future in vitro and in vivo metabolism/biotransformation research on E/NBFRs is required to better understand their bioaccumulation and fate in exposed organisms. Also, studies should be conducted on well characterized lab (e.g., laboratory rodents, zebrafish) and commonly collected wildlife species used as captive models (crucian carp, Japanese quail, zebra finches and polar bears).

Machine learning-assisted optimization of TBBPA-bis-(2,3-dibromopropyl ether) extraction process from ABS polymer

The increasing amount of e-waste plastics needs to be disposed of properly, and removing the brominated flame retardants contained in them can effectively reduce their negative impact on the environment. In the present work, TBBPA-bis-(2,3-dibromopropyl ether) (TBBPA-DBP), a novel brominated flame retardant, was extracted by ultrasonic-assisted solvothermal extraction process. Response Surface Methodology (RSM) achieved by machine learning (support vector regression, SVR) was employed to estimate the optimum extraction conditions (extraction time, extraction temperature, liquid to solid ratio) in methanol or ethanol solvent. The predicted optimum conditions of TBBPA-DBP were 96 min, 131 mL g^-1, 65 °C, in MeOH, and 120 min, 152 mL g^-1, 67 °C in EtOH. And the validity of predicted conditions was verified.

Stability Assessment of a Polymeric Brominated Flame Retardant in Polystyrene Foams under Application-Relevant Conditions

The flame retardant (FR) BLUEDGE polymeric flame retardant (PFR) has been in use since 2011 and was developed as a replacement FR for hexabromocyclododecane in polystyrene (PS)-based insulation foams. To better understand the degradation behavior of the PFR used within PS foams, we examined the degradation of PFR under application-relevant conditions. Thermo-oxidative and photolytic pathways represent the most relevant degradation pathways. Separately, both the thermal and oxidative degradations of PFR at ambient conditions were shown to be negligible based on kinetic models of thermogravimetric analysis data obtained at elevated temperatures; the models predict that it would take 100 years to degrade 1% of PFR at 50 °C and 1000 years at 20 °C. Photodegradation was shown to degrade PFR after accelerated ultraviolet (UV) aging/exposure. UV radiation did not significantly penetrate the foam insulation (<2000 μm); the degradation process took place primarily at the surface. The molecular weight of the polymer changed with degradation, but there was minimal loss of bromine from the foam with degradation. The data from the liquid chromatography-mass spectrometry analysis focused primarily on several small-molecule polar products formed, which included two brominated species. These species were predicted using computer-based modeling to be biodegradable, to not be persistent in the environment, and to exhibit a low toxicity to aquatic organisms.

Tris(2-chloroethyl) phosphate, a pervasive flame retardant: critical perspective on its emissions into the environment and human toxicity

Regulations and the voluntary activities of manufacturers have led to a market shift in the use of flame retardants (FRs). Accordingly, organophosphate ester flame retardants (OPFRs) have emerged as a replacement for polybrominated diphenyl ethers (PBDEs). One of the widely used OPFRs is tris(2-chloroethyl) phosphate (TCEP), the considerable usage of which has reached 1.0 Mt globally. High concentrations of TCEP in indoor dust (∼2.0 × 105 ng g-1), its detection in nearly all foodstuffs (max. concentration of ∼30-300 ng g-1 or ng L-1), human body burden, and toxicological properties as revealed by meta-analysis make TCEP hard to distinguish from traditional FRs, and this situation requires researchers to rethink whether or not TCEP is an appropriate choice as a new FR. However, there are many unresolved issues, which may impede global health agencies in framing stringent regulations and manufacturers considering the meticulous use of TCEP. Therefore, the aim of the present review is to highlight the factors that influence TCEP emissions from its sources, its bioaccessibility, threat of trophic transfer, and toxicogenomics in order to provide better insight into its emergence as an FR. Finally, remediation strategies for dealing with TCEP emissions, and future research directions are addressed.

The Potential for Bio-Sustainable Organobromine-Containing Flame Retardant Formulations for Textile Applications-A Review

This review considers the challenge of developing sustainable organobromine flame retardants (BrFRs) and alternative synergists to the predominantly used antimony III oxide. Current BrFR efficiencies are reviewed for textile coatings and back-coatings with a focus on furnishing and similar fabrics covering underlying flammable fillings, such as flexible polyurethane foam. The difficulty of replacing them with non-halogen-containing systems is also reviewed with major disadvantages including their extreme specificity with regard to a given textile type and poor durability.The possibility of replacing currently used BrFRs for textiles structures that mimic naturally occurring organobromine-containing species is discussed, noting that of the nearly 2000 such species identified in both marine and terrestrial environments, a significant number are functionalised polybrominated diphenyl ethers, which form part of a series of little understood biosynthetic biodegradation cycles.The continued use of antimony III oxide as synergist and possible replacement by alternatives, such as the commercially available zinc stannates and the recently identified zinc tungstate, are discussed. Both are effective as synergists and smoke suppressants, but unlike Sb₂0₃, they have efficiencies dependent on BrFR chemistry and polymer matrix or textile structure. Furthermore, their effectiveness in textile coatings has yet to be more fully assessed.In conclusion, it is proposed that the future of sustainable BrFRs should be based on naturally occurring polybrominated structures developed in conjunction with non-toxic, smoke-suppressing synergists such as the zinc stannates or zinc tungstate, which have been carefully tailored for given polymeric and textile substrates.

Co-pyrolysis of polyethylene with products from thermal decomposition of brominated flame retardants

Co-pyrolysis of brominated flame retardants (BFRs) with polymeric materials prevails in scenarios pertinent to thermal recycling of bromine-laden objects; most notably the non-metallic fraction in e-waste. Hydro-dehalogenation of aromatic compounds in a hydrogen-donating medium constitutes a key step in refining pyrolysis oil of BFRs. Chemical reactions underpinning this process are poorly understood. Herein, we utilize accurate density functional theory (DFT) calculations to report thermo-kinetic parameters for the reaction of solid polyethylene, PE, (as a surrogate model for aliphatic polymers) with prime products sourced from thermal decomposition of BFRs, namely, HBr, bromophenols; benzene, and phenyl radical. Facile abstraction of an ethylenic H by Br atoms is expected to contribute to the formation of abundant HBr concentrations in practical systems. Likewise, a relatively low energy barrier for aromatic Br atom abstraction from a 2-bromophenol molecule by an alkyl radical site, concurs with the reported noticeable hydro-debromination capacity of PE. Pathways entailing a PE-induced bromination of a phenoxy radical should be hindered in view of high energy barrier for a Br transfer into the para position of the phenoxy radical. Adsorption of a phenoxy radical onto a Cu(Br) site substituted at the PE chain affords the commonly discussed PBDD/Fs precursor of a surface-bounded bromophenolate adduct. Such scenario arises due to the heterogeneous integration of metals into the bromine-rich carbon matrix in primitive recycling of e-waste and their open burning.

Brain Bromine Levels Associated with Alzheimer's Disease Neuropathology

BACKGROUND

Bromine is a naturally occurring element that is widely present in the human environment in various chemical forms primarily as flame retardants, pesticides, and water treatments.

OBJECTIVE

In this exploratory study, we investigated the association of brain bromine concentrations on Alzheimer's disease (AD) neuropathology, cerebral infarcts, and Lewy bodies.

METHODS

The study was conducted in 215 deceased participants of the Memory and Aging Project, a clinical-pathologic cohort study. Brain bromine levels were measured using instrumental neutron activation analysis. Multiple brain regions were assessed for diffuse and neuritic plaques, neurofibrillary tangles, cerebral macro-and microinfarcts, and Lewy bodies. Standardized measures of AD pathology (Braak, CERAD, NIA-Reagan, global AD pathology) were computed.

RESULTS

In linear regression models, the higher brain bromine levels were associated with more AD neuropathology (Braak (p trend = 0.01); CERAD (p trend = 0.02); NIA-Reagan (p trend = 0.02).

CONCLUSION

Bromine accumulation in the brain is associated with higher level of AD neuropathology. The potential deleterious effects of this element on AD need further exploration.

Occurrence of hexabromocyclododecanes and tetrabromobisphenol A in fish and seafood from the sea of Sardinia - FAO 37.1.3 area: Their impact on human health within the European Union marine framework strategy directive

Levels of hexabromocyclododecane isomers α, β, γ, (HBCDDs) and tetrabromobisphenol A (TBBP-A) were determined in 24 representative samples of different wild fish and seafood species (benthic: N = 16; pelagic: N = 8) and 16 samples of farmed bivalve molluscs from the West Mediterranean Sea (FAO 37, 1.3 sub-area). An LC-MS/MS-based method with limits of quantification (LOQS) in the range of 0.01-0.05 ng g^-1 fresh weight (fw) was utilized. While α HBCDD was found in 80% of the 24 wild species samples, β and γ congeners were found in 33% and 25%, respectively. ΣHBCDD content ranged from 0.03 (Aristeus antennatus) to 0.68 (Sardina pilchardus) ng g^-1 fw as Upper Bound values across 2.00-4.46 trophic levels. In farmed molluscs, HBCDD congeners were always present and ranged from 0.22-0.52 ng g^-1 fw, with the exception of one farm (1.23-2.06 ng g^-1 fw), whose values suggest the presence of a regular emission source. TBBP-A levels always fell below the LOQ of 0.05 ng g^-1 fw in all samples. The results are in good agreement with results of previous studies from the Mediterranean Sea. The Environmental Quality Standard for human health from fish and seafood local consumption was set at 165 μg g^-1 fw. The Margin of Exposure of 490,020 as the ratio between the considered Health Based Guidance Level of 0.79 mg kg^-1 body weight and the geo-referenced HBCDD intake (P95 fish and seafood intake; mean ΣHBCDD contamination) indicates no threat to food safety.

Degradation of brominated polymeric flame retardants and effects of generated decomposition products

Brominated flame retardants are often associated with adverse environmental effects. Nevertheless, these chemicals are required in order to comply with fire safety standards. Therefore, a better environmental profile is desirable. A "new" class of flame retardants is claimed to fulfil this request while still being feasible for established industrial processes. Different to previous brominated flame retardants, this new group is based on a polymeric structure that could indeed lead to a better environmental profile. However, not much is known about the long-term behaviour of such flame retardants. This short review summarizes what has already been published. With an annual production volume of 26,000 metric tons, "Polymeric FR" is currently the only industrially produced representative of this group. It has been shown to degrade under specific circumstances (following UV and heat exposure). Detected degradation products cause almost no acute toxicity, whereas chronic toxicity might be relevant. Nevertheless, as long as polymeric flame retardants are only used in building insulation, the actual risk seems to be rather limited.

Ecotoxicological characterization of possible degradation products of the polymeric flame retardant "Polymeric FR" using algae and Daphnia OECD tests

History has shown that brominated flame retardants often pose risks to the environment. However, the new group of polymeric brominated flame retardants might be a safer alternative compared to previously used monomers due to their high molecular weight. An example for this new group is "Polymeric FR", which is persistent by design. Within this publication, we study the acute and chronic toxicity of possible degradation products that were previously described for this polymer following UV irradiation and heat exposure at 60 °C. We have applied the OECD tests No. 201 (Algae growth inhibition), 202 (Daphnia acute immobilisation), and 211 (Daphnia reproduction) to four individual substances, indicated to originate as degradation products of "Polymeric FR" as well as a combination of these. In addition, we have used trend analysis to predict effects on fish as an additional trophic level. The results suggest that acute toxicity to the aquatic organisms chosen is rather limited or even not occurring. Chronic exposure, however, does exert effects that might be relevant from an environmental perspective.