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

A polylactic acid-carbon nanofiber-based electro-conductive sensing material and paper-based colorimetric sensor for detection of nitrates

Plastics are ubiquitous in today's lifestyle, and their indiscriminate use has led to the accumulation of plastic waste in landfills and oceans. The waste accumulates and breaks into micro-particles that enter the food chain, causing severe threats to human health, wildlife, and the ecosystem. Environment-friendly and bio-based degradable materials offer a sustainable alternative to the vastly used synthetic materials. Here, a polylactic acid and carbon nanofiber-based membrane and a paper-based colorimetric sensor have been developed. The membrane had a surface area of 3.02 m2 g-1 and a pore size of 18.77 nm. The pores were evenly distributed with a pore volume of 0.0137 cm3 g-1. The membrane was evaluated in accordance with OECD guidelines and was found to be safe for tested aquatic and terrestrial models. The activated PLA-CNF membrane was further used as a bio-based electrode for the electrochemical detection of nitrates (NO3-) in water samples with a detection limit of 0.046 ppm and sensitivity of 1.69 × 10-4 A ppm-1 mm-2, whereas the developed paper-based colorimetric sensor had a detection limit of 156 ppm for NO3-. This study presents an environment-friendly, low-carbon footprint disposable material for sensing applications as a sustainable alternative to plastics.

In Silico Acute Aquatic Hazard Assessment and Prioritization Using a Grouped Target Site Model: A Case Study of Organic Substances Reported in Permian Basin Hydraulic Fracturing Operations

Hydraulic fracturing (HF) is commonly used to enhance onshore recovery of oil and gas during production. This process involves the use of a variety of chemicals to support the physical extraction of oil and gas, maintain appropriate conditions downhole (e.g., redox conditions, pH), and limit microbial growth. The diversity of chemicals used in HF presents a significant challenge for risk assessment. The objective of the present study is to establish a transparent, reproducible procedure for estimating 5th percentile acute aquatic hazard concentrations (e.g., acute hazard concentration 5th percentiles [HC5s]) for these substances and validating against existing toxicity data. A simplified, grouped target site model (gTSM) was developed using a database (n = 1696) of diverse compounds with known mode of action (MoA) information. Statistical significance testing was employed to reduce model complexity by combining 11 discrete MoAs into three general hazard groups. The new model was trained and validated using an 80:20 allocation of the experimental database. The gTSM predicts toxicity using a combination of target site water partition coefficients and hazard group-based critical target site concentrations. Model performance was comparable to the original TSM using 40% fewer parameters. Model predictions were judged to be sufficiently reliable and the gTSM was further used to prioritize a subset of reported Permian Basin HF substances for risk evaluation. The gTSM was applied to predict hazard groups, species acute toxicity, and acute HC5s for 186 organic compounds (neutral and ionic). Toxicity predictions and acute HC5 estimates were validated against measured acute toxicity data compiled for HF substances. This case study supports the gTSM as an efficient, cost-effective computational tool for rapid aquatic hazard assessment of diverse organic chemicals. Environ Toxicol Chem 2024;00:1-12. © 2024 ExxonMobil Petroleum and Chemical BV. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

A review of polybrominated diphenyl ethers and novel brominated flame retardants in Chinese aquatic environment: Source, occurrence, distribution, and ecological risk assessment

Due to the widespread commercial production and use of brominated flame retardants (BFRs) in China, their potential impact on human health development should not be underestimated. This review searched the literature on Polybrominated diphenyl ethers and Novel brominated flame retardant (PBDEs and NBFRs) (broad BFRs) in the aquatic environment (including surface water and sediment) in China over the last decade. It was found that PBDEs and NBFRs entered the aquatic environment through four main pathways, atmospheric deposition, surface runoff, sewage effluent and microplastic decomposition. The distribution of PBDEs and NBFRs in the aquatic environment was highly correlated with the local economic structure and population density. In addition, a preliminary risk assessment of existing PBDEs and PBDEs in sediments showed that areas with high-risk quotient values were always located in coastal areas with e-waste dismantling sites, which was mainly attributed to the historical legacy of electronic waste. This research provides help for the human health development and regional risk planning management posed by PBDEs and NBFRs.

Polylactic acid/tapioca starch/banana peel-based material for colorimetric and electrochemical biosensing applications

The rapidly growing electronic and plastic waste has become a global environmental concern. Developing advanced and environmentally safe agro-based materials is an emerging field with an enormous potential for applications in sensors and devices. Here, an agro-based material as membrane has been developed by incorporating tapioca starch and banana peel powder in polylactic acid, with uniform dispersibility and amorphous nature. The material was used for the development of electrochemical sensor for S-gene of SARS-CoV-2. Further, the membrane was used for the development of a non-invasive, colorimetric skin patch for the detection of glucose and a sensor for the assessment of fruit juice quality. Using OECD-recommended model systems, the developed membrane was found to be non-toxic towards aquatic and terrestrial non-target organisms. The developed conductive material opens new avenues in various electrochemical, analytical, and biological applications.

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.

Effects and mechanisms of decabromodiphenyl ethane on Chlorella sorokiniana: Transcriptomics, proteins and fatty acid production

Decabromodiphenyl ethane is a novel brominated flame retardant, that has always been dissolved in organic solvents to explore its activities on aquatic organisms. In this study, the influences of decabromodiphenyl ethane on the microalga Chlorella sorokiniana (C. sorokiniana) were studied, and three microalgae treatments, including decabromodiphenyl ethane dissolved in dimethyl sulfoxide solvent (DBDPE treatment), dimethyl sulfoxide alone (control II) or untreated (control I) were used in the experiment, respectively. The results showed that the growth of C. sorokiniana was remarkably enhanced in the DBDPE treatment compared with the control I and II groups. Conjoint analysis of transcriptomics and quantitative proteome displayed that the upregulated differentially expressed genes and proteins of DBDPE:control I were enriched in 6 pathways, and downregulated genes/proteins of DBDPE:control I were enriched in 3 pathways. The upregulated differentially expressed genes and proteins of DBDPE:control II were enriched in 4 pathways, and downregulated genes/proteins of DBDPE:control II were enriched in 6 pathways. In addition, decabromodiphenyl ethane changed the fatty acid concentration in C. sorokiniana cells. The activities of superoxide dismutase were enhanced when C. sorokiniana were treated by decabromodiphenyl ethane. The data highlighted that the mRNA and protein expression relating to the fatty acid production, of C. sorokiniana were significantly affected by decabromodiphenyl ethane, and decabromodiphenyl ethane pollution changed the physiological metabolism of microalgae and had harmful effects on natural environments.

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).

Matrix composition during ozonation of N-containing substances may influence the acute toxicity towards Daphnia magna

Micropollutants reach the aquatic environment through wastewater treatment plant effluents. Ozonation, applied in wastewater treatment for micropollutants abatement, can yield transformation products (TP), which might be of ecotoxicological concern. Previous studies on TP formation were mostly performed in ultrapure water. However, the water matrix can have a substantial influence and lead to unpredictable yields of TPs with toxicological potential. In this study the acute toxicity (immobilization) of the parent substances (isoproturon and metoprolol) and also of available TPs of isoproturon, metoprolol and diclofenac towards Daphnia magna (D. magna) were investigated. Further, the acute toxicity of TP mixtures, formed during ozonation of isoproturon, metoprolol and diclofenac was evaluated in the following systems: in the presence of radical scavengers (tert-butanol and dimethyl sulfoxide) and in the presence of hypobromous acid (HOBr), a secondary oxidant in ozonation. For all tested substances and TP standards, except 2,6-dichloroaniline (EC₅₀ 1.02 mg/L (48 h)), no immobilization of D. magna was detected. Ozonated pure water and wastewater did not show an immobilization effect either. After ozonation of diclofenac in the presence of dimethyl sulfoxide 95% (48 h) of the daphnids were immobile. Ozonation of parent substances, after the reaction with HOBr, showed no effect for isoproturon but a high effect on D. magna for diclofenac (95% immobilization (48 h)) and an even higher effect for metoprolol (100% immobilization (48 h)). These results emphasize that complex water matrices can influence the toxicity of TPs as shown in this study for D. magna.

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.

Ecotoxicological effects of micropollutant-loaded powdered activated carbon emitted from wastewater treatment plants on Daphnia magna

In order to eliminate micropollutants from wastewater, the use of powdered activated carbon (PAC) is a suitable and common technique. Many studies already proved the successful elimination of micropollutants from wastewater using PAC. However, it still remains a challenge to completely retain the applied PAC within the wastewater treatment plant (WWTP) without considerable emission of PAC into receiving waters. The present study investigates possible toxic effects of micropollutant-loaded PAC from a WWTP in acute and chronic tests with the aquatic organism Daphnia magna. Furthermore, the well-studied micropollutant diclofenac as well as unloaded, native PAC and experimentally diclofenac-loaded PAC were tested. The acute tests resulted in median effect concentrations (EC₅₀) after 48 h of 53 mg/L for diclofenac, 217 mg/L for native PAC and 414 mg/L for diclofenac-loaded PAC. No effects were detected for the loaded PAC from the WWTP although D. magna ingested the PAC. The chronic tests revealed that diclofenac had effects on growth, reproduction and mortality (median lethal concentration 17.0 mg/L). Exposure to native and diclofenac-loaded PAC showed clear effects on growth and a reproduction inhibition of 80% in the highest tested concentrations. The calculated reproduction EC₁₀ values were 0.8 mg/L for native PAC and 0.3 mg/L for diclofenac-loaded PAC. For the loaded PAC from the WWTP, no effects were observed on reproduction, growth and mortality during the 21-day exposure albeit the fact that the animals ingested the PAC into their gastrointestinal system. Based on these findings PAC from WWTP can be considered as not harmful to D. magna even if complete retention of the PAC at the WWTP cannot be guaranteed.

Distribution behaviour in body compartments and in ovo transfer of flame retardants in North American Great Lakes herring gulls

Polybrominated diphenyl ethers (PBDEs) and other halogenated flame retardants (HFRs) continue to be an environmental concern. In the Laurentian Great Lakes, herring gulls (Larus argentatus) are an important wildlife sentinel species, although very little information is available regarding the body distribution (limited to e.g. liver and blood) of these contaminants and in relation to depuration via in ovo transfer. Maternal transfer rates and distribution were presently determined in six body compartments from eight female, Great Lakes herring gulls and separate egg compartments from their entire clutch. Among the 25 PBDEs and 23 non-PBDE HFRs assessed, only six PBDE congeners (BDE-47/99/100/153/154/209), hexabromocyclododecane (HBCDD), and Dechlorane Plus (syn- and anti-DDC-CO) were frequently detectable and quantifiable. Σ₆BDE concentrations were an order of magnitude greater than non-PBDE HFR concentrations, and were greatest in the adipose (9641 ± 2436 ng/g ww), followed by egg yolk (699 ± 139 ng/g ww) > muscle (332 ± 545 ng/g ww) > liver (221 ± 65 ng/g ww) > plasma (85.4 ± 20.4 ng/g ww) > brain (54.6 ± 10.6 ng/g ww) > red blood cells (RBCs; 23.5 ± 5.6 ng/g ww) > albumen (7.3 ± 1.3 ng/g ww). Σ₂DDC-CO and HBCDD were frequently below the method limit of quantification in the brain, RBCs, plasma, and albumen. Additionally, novel methoxylated-polybrominated diphenoxybenzene contaminants were detected and quantified in herring gull tissues and eggs. The primary difference in PBDE congener profiles was the resistance of both BDE-153 and -154 towards accumulation in the brain, and a corresponding increase in BDE-209 accumulation, which may suggest congener-specific differences in crossing the blood-brain barrier in herring gulls. Maternal transfer rates of PBDEs and non-PBDE HFRs were low (∼4.7 and ∼2.9 % respectively), suggesting that in ovo transfer is not a significant mode of depuration for these compounds.

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.