Levels, spatial distribution, and exposure risks of decabromodiphenylethane in soils of North China

Response mechanism of lettuce (Lactuca sativa L.) under combined stress of Cd and DBDPE: An integrated physiological and metabolomics analysis

DBDPE and Cd are representative contaminants commonly found in electronic waste (e-waste), which tend to be gradually discharged and accumulated in the environment during e-waste dismantling, resulting in frequent outbreaks and detection of these pollutants. The toxicity of both chemicals to vegetables after combined exposure has not been determined. The accumulation and mechanisms of phytotoxicity of the two compounds, alone and in combination, were studied using lettuce. The results showed that the enrichment ability of Cd and DBDPE in root was significantly higher than that in aerial part. Exposure to 1 mg/L Cd + DBDPE reduced the toxicity of Cd to lettuce, while exposure to 5 mg/L Cd + DBDPE increased the toxicity of Cd to lettuce. The absorption of Cd in the underground part of lettuce of 5 mg/L Cd + DBDPE was significantly increased by 108.75 % compared to 5 mg/L Cd. The significant enhancement of antioxidant system activity in lettuce under 5 mg/L Cd + DBDPE exposure, and the root activity and total chlorophyll content were decreased by 19.62 % and 33.13 %, respectively, compared to the control. At the same time, the organelles and cell membranes of lettuce root and leaf were significantly damaged, which was significantly worse than that of single Cd and DBDPE treatment. Combined exposure significantly affected the pathways related to amino acid metabolism, carbon metabolism and ABC transport in lettuce. This study filled the safety gap of DBDPE and Cd combined exposure on vegetables and would provide a theoretical basis for the environmental behavior and toxicological study of DBDPE and Cd.

Investigating the adverse outcome pathways (AOP) of neurotoxicity induced by DBDPE with a combination of in vitro and in silico approaches

Current studies have shown an association between DBDPE and neurotoxicity. In this study, the adverse outcome pathway (AOP) and mechanistic analysis of DBDPE-induced neurotoxicity were explored by a combination of in vitro and in silico approaches in SK-N-SH cells. DBDPE-induced oxidative stress caused DNA strand breaks, resulting in the activation of poly (ADP-ribose) (PAR) polymerase-1 (PARP-1). Activation of PARP1 could cause toxic damage in various organ systems, especially in the nervous system. DBDPE-induced apoptosis via the caspase-dependent intrinsic mitochondrial pathway and the PARP1-dependent pathway. Activation of PARP1 by DBDPE was deemed the initiating event, thereby affecting the key downstream biochemical events (e.g., ROS production, DNA damage, membrane potential changes, and ATP reduction), which induced apoptosis. Furthermore, excessive activation of PARP1 was accompanied by the translocation of the apoptosis-inducing factor (AIF), which was associated with PARP1-dependent cell death. The inhibition of PARP1 by PJ34 reduced DBDPE-induced apoptosis and maintained cellular ATP levels. PJ34 also prevented the translocation of AIF from the mitochondria to the nucleus. These findings improve the understanding of the mechanism of DBDPE-induced neurotoxic effects and provide a theoretical basis for the ecological risk of DBDPE.

Exposure to novel brominated and organophosphate flame retardants and associations with type 2 diabetes in East China: A case-control study

The alternative flame retardants, novel brominated flame retardants (NBFRs) and organophosphate flame retardants (OPFRs) are ubiquitous in the environment and biota and may induce endocrine disruption effects. Associations between traditional endocrine-disrupting chemicals and type 2 diabetes have been extensively reported in epidemiological studies. However, the effects of NBFRs and OPFRs in humans have not been reported to date. This paper reports a case-control study of 344 participants aged 25-80 years from Shandong Province, East China, where potential associations between serum NBFR and OPFR concentrations and type 2 diabetes are assessed for the first time. After adjusting for covariates (i.e., age, sex, body mass index, smoking status, alcohol consumption, triglycerides, and total cholesterol), serum concentrations of pentabromotoluene, 2,3-dibromopropyl 2,4,6-tribromophenyl ether, tri-n-propyl phosphate, triphenyl phosphate, and tris (2-ethylhexyl) phosphate were significantly positively associated with type 2 diabetes. In the control group, decabromodiphenyl ethane and triphenyl phosphate were significantly positively associated with fasting plasma glucose, triglycerides, and high-density lipoprotein cholesterol. In the quantile g-computation model, significant positive mixture effect was found between the flame retardants mixtures and high-density lipoprotein cholesterol levels, and decabromodiphenyl ethane contributed the largest positive weights to the mixture effect. Overall, these findings suggest that exposure to NBFRs and OPFRs may promote type 2 diabetes.

Occurrence, spatial distribution, and risk assessment of brominated flame retardants in farmland soils of typical provinces in China

In the present study, we investigated the occurrence, distribution, and potential risks of 4 brominated flame retardants in farmland soils across 18 provinces of China. The total mean concentrations of the BFRs were in order as DBDPE > BDE209 > HBB > TBB. DBDPE concentration was highest at 177.208 ng/kg, revealing its long-term use and persistence across the study areas. In parts of China, DBDPE was highest in the south (Sichuan, Shaanxi and Guangdong provinces), BDE209 was highest in the south (Sichuan province) and north (Jilin province), while HBB was highest in the south (Sichuan province) and east (Anhui and Zhejiang provinces) of China. Comparisons of the results in this study to other reported studies in different regions indicated that the studied BFRs concentrations were higher in the studied provinces of China. Pearson correlation between BFRs revealed both positive and negative associations within the BFRs groups and between BFRs and soil properties (SOM, CEC, pH, EC and PS%). The mean hazard quotients (HQ) of ecological risks ranged from 8.76 × 10^-6 to 1.16 × 10^-2 (HQ < 1) while non-carcinogenic human health risk evaluation for adults ranged from 7.05 × 10^-7 - 7.48 × 10^-4 (HQ < 1) and for children 2.99 × 10^-4 - 4.30 × 10^-2 (HQ < 1). Although the risk evaluations of BFRs from farmland soils in this study were low, the results serve as useful indicators of potential cumulative and long-term threats of BFR to rural areas where there is a high conversion of agricultural lands to non-agricultural use.

Decabromodiphenyl ethane induces locomotion neurotoxicity and potential Alzheimer's disease risks through intensifying amyloid-beta deposition by inhibiting transthyretin/transthyretin-like proteins

As a major alternative to traditional brominated flame retardants (BFRs), decabromodiphenyl ethane (DBDPE) is widely used and has been commonly detected in various environmental media and organisms. Few previous studies have focused on DBDPE-induced locomotion neurotoxicity, and the exact molecular mechanisms and related health risks remain unclear. In this study, we first analyzed the locomotion indicators of nematodes following DBDPE exposure, demonstrated that DBDPE caused locomotion neurotoxicity, and identified that a series of the transthyretin (TTR)-like genes participated in the regulation of nematode motility by transcriptomic analysis, gene transcription validation and TTR-like mutant verification. Subsequently, this study demonstrated that DBDPE exacerbated amyloid-beta (Aβ) deposition by repressing TTR/TTR-like gene transcription based on Alzheimer's disease (AD) model nematodes and human SH-SY5Y cells following DBDPE exposure and further revealed that DBDPE reduced the binding between TTR and Aβ by competing with the strand G region sites on the TTR/TTR-like protein, ultimately exacerbating Aβ deposition and the risk of AD. In short, our study demonstrated that DBDPE induced locomotion neurotoxicity and potential AD risks through intensifying Aβ deposition by inhibiting TTR/TTR-like proteins, providing reference support for risk management and policy formulation related to DBDPE and similarly structured novel BFRs.

Cytotoxicity profiling of decabromodiphenyl ethane to earthworm (Eisenia fetida): Abnormity-recovery-dysregulation physiological pattern reflects the coping mechanism

Response of terrestrial invertebrates to decabromodiphenyl ethane (DBDPE) is an emerging field of research nowadays, while cytotoxicity of DBDPE and self-defense strategies of invertebrates are poorly understood. In this study, earthworms (Eisenia fetida) were incubated in the DBDPE-spiked soil system (10, 30, 50, 70, and 100 mg kg^-1 dw) for 28-d uptake. The bioaccumulation and distribution of DBDPE, a series of biomarkers associated with lysosomes/mitochondria, and the apoptosis rate of coelomocytes have been evaluated on the 7th, 14th, 21th, and 28th day. At experimental endpoint, the autophagy/apoptosis phenomena have been observed under transmission electron microscopy and the expression levels of six target genes have been explored. Findings in this paper revealed that: bioaccumulation factors decreased with the incremental DBDPE concentrations in the soil. Intestinal ingestion, but not epidermal contact predominated the absorption of DBDPE. The fluctuations of biomarkers and the apoptosis rate were described as the "abnormity-recovery-dysregulation" pattern. Intense oxidative stress, energy demands, membrane-system damage, pathological organelles, and apoptosis were observed in the treated groups. Conclusively, the cytotoxicity of DBDPE initiated the mitochondrial apoptosis pathway which affected the physiological status of lysosomes, autophagy, and the expression of genes. The coping mechanisms of Eisenia fetida to DBDPE included activating mitochondrial electron transport processes, reorganizing actin cytoskeleton, and initiating autophagy. Earthworms resisted the cytotoxicity of DBDPE to a certain extent, while long-term exposure still resulted in apoptosis of coelomocytes. This study works as a laboratory simulation for the environmental safety evaluation of DBDPE and the detoxification mechanisms for earthworm.

Reduced mitochondrial DNA copy number in occupational workers from brominated flame retardants manufacturing plants

Decabrominated diphenyl ether (BDE-209) and its substitute decabromodiphenyl ethane (DBDPE) are two flame retardants that have similar structure and are widely used in various industrial products. The accumulation and potential toxicity of them to human health have already aroused attention, and some research showed that they may affect mitochondrial function. Therefore, this study focused on the population with high exposure to brominated flame retardants (BFRs) and the related changes in mtDNA copy number (mtDNAcn) in whole blood. 334 blood samples were collected from three groups of people in Shandong Province, including 42 BDE-209 occupational exposure workers from the BDE-209 manufacturing plant, 131 DBDPE occupational exposure workers from the DBDPE manufacturing plant, and 161 non-BFRs occupational exposure residents from the BFRs contaminated area. We measured the levels of BDE-209, DBDPE in serum sample, and the mtDNAcn in whole blood sample and analyzed these data by multiple linear regression. The average concentrations of BDE-209, DBDPE and ∑(BDE-209 + DBDPE) in BDE-209 occupational workers were 3510, 639 and 4600 ng/g lw, respectively; the average concentrations of BDE-209, DBDPE and ∑(BDE-209 + DBDPE) in DBDPE occupational workers were 229, 4040 and 4470 ng/g lw, respectively; the average concentrations of BDE-209, DBDPE and ∑(BDE-209 + DBDPE) in non-BFRs occupational exposure residents were 66.3, 45.7 and 137 ng/g lw, respectively. The relative mtDNAcn was 0.823 in BDE-209 occupational workers, 0.845 in DBDPE occupational workers and 0.989 in non-BFRs occupational exposure residents. A 10-fold increase in BDE-209, DBDPE concentrations was separately associated with a 0.068 and 0.063 decrease in mtDNAcn. Therefore, our study implied that BFRs may affect mitochondrial function. As increasing BFRs exposure has emerged in recent years, the relationship between BFRs exposure and mitochondrial function needs further study.

Use of integrated biomarker response for evaluating antioxidant stress and DNA damage of earthworms (Eisenia fetida) in decabromodiphenyl ethane-contaminated soil

Decabromodiphenyl ethane (DBDPE) is a new and popular type of brominated flame retardant (BFR) with high bromine content, strong thermal stability, and ultraviolet resistance. To evaluated the potential toxicity of this new BFR to soil ecosystem, different concentrations of DBDPE were used to observe effects on earthworms (Eisenia fetida) in artificial soil. The reactive oxygen species (ROS) contents, activities of antioxidase system and detoxify enzyme, levels of malondialdehyde (MDA), as well as DNA damage in earthworms were measured after exposure to 0, 2.5, 5, 10, and 20 mg/kg DBDPE in artificial soil for 7, 14, 21, and 28 days. The results showed that ROS and MDA content significantly increased for all treatments from days 7-21, followed by a decrease. Throughout the experimental period, SOD, POD, and CAT activities increased. The GST activity was stimulated significantly from days 14-28. Besides, the olive tail moment (OTM) value in all treated groups was significantly higher than that in the control and exhibited a concentration-related and exposure time-related response. This is the first study evaluating the biological toxicity of BFR at different concentrations using an integrated biomarker response index. Our results show that DBDPE has biochemical toxicity on earthworms, which sheds some light on the potential risks of DBDPE in the soil environment and provides a basis for the monitoring and diagnosis of soils contaminated with DBDPE.

Occurrence of organophosphate flame retardants in farmland soils from Northern China: Primary source analysis and risk assessment

Ninety-eight soil samples were collected from farmland soils from Beijing-Tianjin-Hebei core area, Northern China, where agricultural lands were subjected to contamination from intense urban and industrial activities. Twelve organophosphates flame retardants (OPFRs) were analyzed with total soil concentrations ranging from 0.543 μg/kg to 54.9 μg/kg. Chlorinated OPFRs were dominating at mean level of 3.64 μg/kg and Tris(2-chloroisopropyl) phosphate contributed the most (mean 3.36 ± 5.61 μg/kg, 98.0%). Tris(2-ethylhexyl) phosphate was fully detected at levels of 0.041-1.95 μg/kg. Generally, tris(2-butoxyethyl) phosphate and triphenyl phosphate contributed the most to alkyl- (53.6%) and aryl-OPFRs (54.3%), respectively. The levels of ∑OPFRs close to the core urban areas were significantly higher than those from background sites. The occurrence and fate of OPFRs in soil were significantly associated with total organic carbon content and mostly with fine soil particles (<0.005 mm), and a transfer potential from the atmosphere was predicted with logK_SA values. Comparable soil levels with poly brominated diphenyl ethers s in other studies suggested that the contamination of OPFRs occurred in farmland soil with an increasing trend but currently showed no significant environmental risk based on risk quotient estimation (<1). This investigation warrants further study on behaviors of OPFRs in a soil system and a continual monitoring for their risk assessment.

Exploring the membrane toxicity of decabromodiphenyl ethane (DBDPE): Based on cell membranes and lipid membranes model

Decabromodiphenyl ethane (DBDPE) is widely used in industry as an alternative to the decabromodiphenyl ether (BDEs). The large-scale use of DBDPE could lead to rapid growth of the human accumulation level of DBDPE. However, the biophysics of accumulation of DBDPE in cell membranes, as one of determinants of DBDPE metabolism is not clear. In the present study, detailed observations of cell lactate dehydrogenase (LDH) and reactive oxygen species (ROS) levels measurements proved that the DBDPE exposure to cell could result in significant cell membrane damage by concentration-dependent manners. The fluorescence anisotropy analysis supported the evidence that high concentration DBDPE bound decreased membrane fluidity significantly. Besides it, a detailed molecular dynamic (MD) simulation was approached to investigate the effects of DBDPE on the DPPC (dipalmitoyl phosphatidylcholine) phospholipid bilayer, which was constructed as the model of cell membrane. The molecular dynamic simulation revealed that DBDPE molecules can easily enter the membrane from the aqueous phase. Under the concentration of a threshold, the DBDPE molecules tended to aggregate inside the DPPC bilayer and caused pore formation. The bound of high concentration of DBDPE could result in significant variations in DPPC bilayer with a less dense, more disorder and rougher layer. The knowledge about DBDPEs interactions with lipid membranes is fundamentally essential to understand the in vivo process of DBDPE and the physical basis for the toxicity of DBDPE in cell membranes.

Critical review of soil contamination by polybrominated diphenyl ethers (PBDEs) and novel brominated flame retardants (NBFRs); concentrations, sources and congener profiles

Polybrominated diphenyl ethers (PBDEs) have been used in a broad array of polymeric materials such as plastics, foams, resins and adhesives to inhibit the spread of fires since the 1970s. The widespread environmental contamination and well documented toxic effects of PBDEs have led to bans and voluntary withdrawals in many jurisdictions. Replacement novel brominated flame retardants (NBFRs) have, however, exhibited many of the same toxic characteristics as PBDEs and appear to share similar environmental fate. This paper presents a critical review of the scientific literature regarding PBDE and NBFR contamination of surface soils internationally, with the secondary objective of identifying probable pollution sources. An evaluation of NBFR distribution in soil was also conducted to assess the suitability of the newer compounds as replacements for PBDEs, with respect to their land contamination potential. Principle production of PBDEs and NBFRs and their consequent use in secondary polymer manufacture appear to be processes with strong potential to contaminate surrounding soils. Evidence suggests that PBDEs and NBFRs are also released from flame retarded products during disposal via landfill, dumping, incineration and recycling. While the land application of sewage sludge represents another major pathway of soil contamination it is not considered in this review as it is extensively covered elsewhere. Both PBDEs and NBFRs were commonly detected at background locations including Antarctica and northern polar regions. PBDE congener profiles in soil were broadly representative of the major constituents in Penta-, Octa- and Deca-BDE commercial mixtures and related to predicted market place demand. BDE-209 dominated soil profiles, followed by BDE-99 and BDE-47. Although further research is required to gain baseline data on NBFRs in soil, the current state of scientific literature suggests that NBFRs pose a similar risk to land contamination as PBDEs.

Occurrence and Source Effect of Novel Brominated Flame Retardants (NBFRs) in Soils from Five Asian Countries and Their Relationship with PBDEs

This paper presents the first comprehensive survey of 19 novel brominated flame retardants (NBFRs) in soil samples collected among five Asian countries. High variability in concentrations of all NBFRs was found in soils with the geometric mean (GM) values ranging from 0.50 ng/g dry weight (dw) in Vietnam to 540 ng/g dw in the vicinity of a BFR manufacturer in China. In urban, rural, and background locations, the GM concentrations of ∑₁₉NBFRs decreased in the order of Japan > South Korea > China > India > Vietnam. Correlations among different NBFR compounds were positive and statistically significant (p < 0.05), suggesting that they originate from similar sources. Evidence for simultaneous application between polybrominated diphenyl ethers (PBDEs) and NBFRs were also noted. Principal component analysis of NBFR concentrations revealed specific pollution sources for different NBFRs coming from urban, BFR-related industrial, and e-waste sites. For the first time, this study demonstrates a "point source fractionation effect" for NBFRs and PBDEs. The concentrations of all NBFRs and PBDEs were negatively and significantly correlated with the distance from BFR-related industrial and e-waste regions. Positive and significant correlation between population density and NBFR concentrations in soils was identified. Our study revealed that the primary sources effects were stronger than the secondary sources effects in controlling the levels and distribution of NBFRs and PBDEs in soils in these five Asian countries.

Occurrence, composition, source, and regional distribution of halogenated flame retardants and polybrominated dibenzo-p-dioxin/dibenzofuran in the soils of Guiyu, China

Guiyu, China, is well-known for the crude disposal of electronic waste (EW) and severe persistent organic pollutants (POPs). Therefore, in this study, the occurrence, composition, and source of polybrominated diphenyl ethers (PBDEs), 2,2',4,4',5,5'-hexabromobiphenyl (BB153), some novel brominated flame retardants (NBFRs), Dechlorane Plus (DP) and polybrominated dibenzo-p-dioxins/dibenzofurans (PBDD/Fs) in farmland soils covering Guiyu were studied. In EW disposal area soils, PBDEs were the most abundant FRs, with concentrations of 13-1014 ng g^-1. The primary PBDE sources were technical Penta- and Deca-BDE mixtures in northern and southern Guiyu, respectively. The levels of BB153 were relatively low, possibly because it has been banned in the 1970s. The concentrations of hexabromobenzene (HBB) were 0.048-3.3 ng g^-1, while pentabromoethylbenzene (PBEB) was almost not detected in the soils. Two alternatives to commercial PBDEs, decabromodiphenyl ethane (DBDPE) and 1,2-bis(2,4,6-tribromophenoxy) ethane (BTBPE), were the primary NBFRs, with concentrations of 1.8-153 ng g^-1 and 0.43-15 ng g^-1, respectively. DP was another primary FR, with concentrations of 0.57-146 ng g^-1. Moreover, syn-DP and anti-DP isomers were not stereoselectively decomposed during the EW disposal process and were therefore present in their original fractions in the soils. The levels of PBDD/Fs in EW disposal area soils were 2.5-17 pg TEQ g^-1. 1,2,3,4,6,7,8-HpBDF and OBDF were the dominant congeners, mainly derived from processing, pyrolysis and combustion of BFRs. The regional distribution of pollutants was shown to be related to the disposal manner of EW, with their open thermal disposal tending to release more highly brominated compounds such as BDE209, DBDPE, and 1,2,3,4,6,7,8-HpBDF. Additionally, some riverbank sites were heavily polluted because of nearby point sources, downwind Simapu (SMP) town without EW disposal activity was also contaminated by these pollutants.

Characterization of anthropogenic impacts in a large urban center by examining the spatial distribution of halogenated flame retardants

Anthropogenic impacts have continuously intensified in mega urban centers with increasing urbanization and growing population. The spatial distribution pattern of such impacts can be assessed with soil halogenated flame retardants (HFRs) as HFRs are mostly derived from the production and use of various consumer products. In the present study, soil samples were collected from the Pearl River Delta (PRD), a large urbanized region in southern China, and its surrounding areas and analyzed for a group of HFRs, i.e., polybrominated diphenyl ethers (PBDEs), decabromodiphenyl ethane, bis(hexachlorocyclopentadieno)cyclooctane (DP) and hexabromobenzene. The sum concentrations of HFRs and PBDEs were in the ranges of 0.66-6500 and 0.37-5700 (mean: 290 and 250) ng g(-1) dry weight, respectively, around the middle level of the global range. BDE-209 was the predominant compound likely due to the huge amounts of usage and its persistence. The concentrations of HFRs were greater in the land-use types of residency, industry and landfill than in agriculture, forestry and drinking water source, and were also greater in the central PRD than in its surrounding areas. The concentrations of HFRs were moderately significantly (r(2) = 0.32-0.57; p < 0.05) correlated with urbanization levels, population densities and gross domestic productions in fifteen administrative districts. The spatial distribution of DP isomers appeared to be stereoselective as indicated by the similarity in the spatial patterns for the ratio of anti-DP versus the sum of DP isomers (fanti-DP) and DP concentrations. Finally, the concentrations of HFRs sharply decreased with increasing distance from an e-waste recycling site, indicating that e-waste derived HFRs largely remained in local soil.