Emission inventory and environmental distribution of decabromodiphenyl ether in China

Deca-BDE emissions, validation, and environmental fate in China

Decabromodiphenyl ether (Deca-BDE) was officially listed in Annex A of the Stockholm Convention for persistent organic pollutants (POPs). It is necessary to establish its emission inventory to help reduce Deca-BDE contamination in the environment. We established a comprehensive Deca-BDE emission inventory in China. The results reveal that, from 2015 to 2017, the Deca-BDE emissions in its production source (source I) were less altered but increased annually in flame retarded plastics processing (source II), Deca-BDE-containing products usage (source III), and electronic waste (e-waste) treatment (source IV). We show that Deca-BDE emissions declined significantly in sources I and II but grew in source III and source IV from 2017 to 2018. We set up the provincial emission inventory to a gridded map on a spatial resolution of 0.25°× 0.25° latitude/longitude. The gridded inventory was incorporated into ChnMETOP model to simulate Deca-BDE concentrations in air and soil, and the modeled concentrations were compared to field-sampling data. The results show that the Deca-BDE emission inventory developed in this study agreed well with observed data, demonstrating that the Deca-BDE inventory in China developed in the present study is reliable. The inventory provides a support for quantifying human exposure risk to Deca-BDE and developing effective mitigation measures to mitigate Deca-BDE emissions.

Emission and environmental distribution of decabromodiphenyl ethane (DBDPE) in China from 2006 to 2026: Retrospection, forecasting, and implications for assessment and management

Decabromodiphenyl ethane (DBDPE) is the main alternative to decabromodiphenyl ether (deca-BDE) in commercial use. However, there is increasing evidence show that DBDPE is a potential persistent organic pollutant, and it has been found ubiquitously in environmental media across China in recent years. Monitoring studies have not been able to determine the overall levels and temporal trends of DBDPE contamination in China, and have been unable to explain how emission patterns can affect their environmental distribution. Therefore, this study estimated the temporal variance of DBDPE emissions and environmental concentrations in five regions of China from 2006 to 2026 using the PROduction-To-EXposure (PROTEX) mass balance model. The results showed that Guangdong Province was the greatest DBDPE pollution hotspot in China due to emissions from plastics manufacturing and e-waste disposal; there was also severe pollution in Shandong Province, where almost all the DBDPE in China is produced. The DBDPE concentrations in indoor and outdoor environments increased substantially in all regions during 2006-2021. Furthermore, in Guangdong Province and Shandong Province, the ratio of indoor/outdoor air concentrations was greater than or close to 1, indicative of significant outdoor emission sources of DBDPE. In contrast, the ratios for the Beijing-Tianjin-Hebei region, East China, and Southwest China were below 1 due to the indoor use of electronic equipment containing DBDPE. The temporal trends of these ratios indicated that DBDPE contamination has gradually spread from high-concentration environments with strong emission sources to low-concentration environments. The outcomes of this study have important implications for the risk assessment of DBDPE use in China and can be used to establish contamination-mitigation actions.

Global PBDE contamination in cetaceans. A critical review

This review summarizes the most relevant information on PBDEs' occurrence and their impacts in cetaceans at global scale, with special attention on the species with the highest reported levels and therefore the most potentially impacted by the current and continuous release of these substances. This review also emphasizes the anthropogenic and environmental factors that could increase concentrations and associated risks for these species in the next future. High PBDE concentrations above the toxicity threshold and stationary trends have been related to continuous import of PBDE-containing products in cetaceans of Brazil and Australia, where PBDEs have never been produced. Non-decreasing levels documented in cetaceans from the Northwest Pacific Ocean might be linked to the increased e-waste import and ongoing production and use of deca-BDE that is still allowed in China. Moreover, high levels of PBDEs in some endangered species such as beluga whales (Delphinapterus leucas) in St. Lawrence Estuary and Southern Resident killer whales (Orcinus Orca) are influenced by the discharge of contaminated waters deriving from wastewater treatment plants. Climate change related processes such as enhanced long-range transport, re-emissions from secondary sources and shifts in migration habits could lead to greater exposure and accumulation of PBDEs in cetaceans, above all in those species living in the Arctic. In addition, increased rainfall could carry greater amount of contaminants to the marine environment, thereby, enhancing the exposure and accumulation especially for coastal species. Synergic effects of all these factors and ongoing emissions of PBDEs, expected to continue at least until 2050, could increase the degree of exposure and menace for cetacean populations. In this regard, it is necessary to improve current regulations on PBDEs and broader the knowledge about their toxicological effects, in order to assess health risks and support regulatory protection for cetacean species.

Current pollution status, spatial features, and health risks of legacy and emerging halogenated flame retardants in agricultural soils across China

Soil is a major reservoir and a secondary source of semi-volatile organic chemicals, while studies on the pollution status of halogenated flame retardants (HFRs) in agricultural soils are limited. In this study, a total of twenty-five chemicals including novel brominated flame retardants (NBFRs), polybrominated diphenyl ethers (PBDEs), and dechlorane plus (DPs) was analyzed in the agricultural soils across China to investigate the occurrence, spatial distribution, potential sources, influencing factors and their associated human health risks. The results showed that BDE-209 (125-130,183 pg/g, dry weight, d.w.) was the most abundant flame retardant of PBDEs, followed by decabromodiphenyl ethane (DBDPE) (9.27-22,864 pg/g, d.w.). Meanwhile, the DPs (anti-DP plus syn-DP) were in the range of ND-1229 pg/g (d.w.), and the range of f_anti values (the concentration of anti-DP divided by the sum of the concentrations of two isomers) in this study greatly matched those of commercial products, suggesting the effect of proximity to the source region. The higher levels of HFRs were found in Eastern and Southern regions of China. Spatial distribution implied that e-waste recycling activities and plastic processing have shown more importance in releasing legacy flame retardants (FRs) into the environment than the manufacturing process, while all are important for novel FRs. Correlation analysis between influencing factors and HFRs indicated that the distribution of most pollutants was more affected by anthropogenic source factors than environmental factors. The results of the principal component analysis demonstrated that deca-BDE and its alternative products were the major contributors to the sources of HFRs pollution. Human health risks assessment via oral intake and dermal contact pathways presented that the selected pollutants posed a no-carcinogenic risk to children and adults. It is worth noting that supervision of the disposal process of the NBFRs should be strengthened in the future.

Comprehensive Identification of Liquid Crystal Monomers-Biphenyls, Cyanobiphenyls, Fluorinated Biphenyls, and their Analogues-in Waste LCD Panels and the First Estimate of their Global Release into the Environment

Our previous study demonstrated massive emissions of liquid crystal monomers (LCMs) from liquid crystal display (LCD)-associated e-waste dismantling; however, the compositions, priority list, and inventory of LCMs in waste LCD panels remain unknown. Herein, we conducted the first comprehensive identification covering a broader range of LCMs, including 21 biphenyls and analogues (BAs), 28 cyanobiphenyls and analogues (CBAs), and 44 fluorinated biphenyls and analogues (FBAs), in waste television/computer LCD panels. A total of 64 of the 93 target LCMs, including 19 BAs, 6 CBAs, and 39 FBAs, were widely detected in collected waste LCD panels. Approximately 10-18 of the 64 detectable LCMs were identified as the main compositions in various waste LCD panels, which contributed to >90% of the total LCMs. Total concentrations of FBAs in the television/computer LCD panel samples were comparable to those of BAs but much higher than those of CBAs, indicating FBAs and BAs being the commonly used LCM categories. The composition distribution of LCMs varied between television/computer LCDs and among different brands of television/computer LCDs. A preliminary estimate of the globally direct release of LCMs from waste television/computer LCD panels into various environmental compartments was about 1.07-107 kg/year, which will increase considerably in the near future.

Trends of production, consumption and environmental emissions of Decabromodiphenyl ether in mainland China

Decabromodiphenyl ether (DecaBDE) is a brominated flame retardant belonging to the group of polybrominated diphenyl ethers. DecaBDE has been widely used for various applications, such as plastics, textiles, and building and construction materials. Limited information on DecaBDE production and usage inventory has been elaborated, however. Therefore, this work aimed to produce a preliminary emissions inventory of DecaBDE in mainland China by estimating production and consumption amounts of DecaBDE, and characterizing its emission factors during production and usage, based on industrial investigation and theoretical prediction. It was indicated that the total production of DecaBDE reached 464.68 thousand metric tons (kt), of which 62.72 kt were exported, since the beginning of its production. Shandong and Jiangsu provinces dominate the production, with proportions of 77.95% and 18.45%, respectively. The production stage releases most of the DecaBDE to the atmosphere, with an emissions factor of 23 ± 1.9 kg/t, followed by 20 ± 0.9 kg/t DecaBDE to waste water and 16 ± 1.0 kg/t DecaBDE as solid residue. DecaBDE emissions in the consumption stage-namely the plastic production process-are 0.17 ± 0.06-0.23 ± 0.08 kg DecaBDE to the atmosphere and 1.72 ± 0.58-2.29 ± 0.77 kg DecaBDE to solid residue, for each metric ton of plastic produced. The total annual DecaBDE emissions to waste water are 93.98-1140.9 mg-negligible. The results showed that the sources of DecaBDE environmental pollution are its manufacturing and flame-retardant plastic modification plants, which are easily overlooked by both the government and the public. Yet DecaBDE emissions elimination and the environmentally sound management of the DecaBDE waste generated from these two processes are crucial for environmental protection.

Stocks, flows and emissions of DBDPE in China and its international distribution through products and waste

Decabromodiphenyl ethane (DBDPE) is an alternative to the commercial decabromodiphenyl ether (deca-BDE) mixture but has potentially similar persistence, bioaccumulation potential and toxicity. While it is widely used as a flame retardant in electrical and electronic equipment (EEE) in China, DBDPE could be distributed globally on a large scale with the international trade of EEE emanating from China. Here, we performed a dynamic substance flow analysis to estimate the time-dependent mass flows, stocks and emissions of DBDPE in China, and the global spread of DBDPE originating in China through the international trade of EEE and e-waste. Our analysis indicates that, between 2006 and 2016, ∼230 thousand tonnes (kt) of DBDPE were produced in China; production, use and disposal activities led to the release of 196 tonnes of DBDPE to the environment. By the end of 2016, ∼152 kt of the DBDPE produced resided in in-use products across China. During the period 2000-2016, ∼39 kt of DBDPE were exported from China in EEE products, most of which (>50%) ended up in North America. Based on projected trends of China's DBDPE production, use and EEE exports, we predict that, by 2026, ∼74 and ∼14 kt of DBDPE originating in China will reside in in-use and waste stocks, respectively, in regions other than mainland China, which will act as long-term emission sources of DBDPE worldwide. This study discusses the considerable impact of DBDPE originating in China and distributed globally through the international trade of EEE; this is projected to occur on a large scale in the near future, which necessitates countermeasures.

Global Historical Stocks and Emissions of PBDEs

The first spatially and temporally resolved inventory of BDE28, 47, 99, 153, 183, and 209 in the anthroposphere and environment is presented here. The stock and emissions of PBDE congeners were estimated using a dynamic substance flow analysis model, CiP-CAFE. To evaluate our results, the emission estimates were used as input to the BETR-Global model. Estimated concentrations were compared with observed concentrations in air from background areas. The global (a) in-use and (b) waste stocks of ∑₅BDE(28, 47, 99, 153, 183) and BDE209 are estimated to be (a) ∼25 and 400 kt and (b) 13 and 100 kt, respectively, in 2018. A total of 6 (0.3-13) and 10.5 (9-12) kt of ∑₅BDE and BDE209, respectively, has been emitted to the atmosphere by 2018. More than 70% of PBDE emissions during production and use occurred in the industrialized regions, while more than 70% of the emissions during waste disposal occurred in the less industrialized regions. A total of 70 kt of ∑₅BDE and BDE209 was recycled within products since 1970. As recycling rates are expected to increase under the circular economy, an additional 45 kt of PBDEs (mainly BDE209) may reappear in new products.

State of knowledge on current exposure, fate and potential health effects of contaminants in polar bears from the circumpolar Arctic

The polar bear (Ursus maritimus) is among the Arctic species exposed to the highest concentrations of long-range transported bioaccumulative contaminants, such as halogenated organic compounds and mercury. Contaminant exposure is considered to be one of the largest threats to polar bears after the loss of their Arctic sea ice habitat due to climate change. The aim of this review is to provide a comprehensive summary of current exposure, fate, and potential health effects of contaminants in polar bears from the circumpolar Arctic required by the Circumpolar Action Plan for polar bear conservation. Overall results suggest that legacy persistent organic pollutants (POPs) including polychlorinated biphenyls, chlordanes and perfluorooctane sulfonic acid (PFOS), followed by other perfluoroalkyl compounds (e.g. carboxylic acids, PFCAs) and brominated flame retardants, are still the main compounds in polar bears. Concentrations of several legacy POPs that have been banned for decades in most parts of the world have generally declined in polar bears. Current spatial trends of contaminants vary widely between compounds and recent studies suggest increased concentrations of both POPs and PFCAs in certain subpopulations. Correlative field studies, supported by in vitro studies, suggest that contaminant exposure disrupts circulating levels of thyroid hormones and lipid metabolism, and alters neurochemistry in polar bears. Additionally, field and in vitro studies and risk assessments indicate the potential for adverse impacts to polar bear immune functions from exposure to certain contaminants.

Designing modified polybrominated diphenyl ether BDE-47, BDE-99, BDE-100, BDE-183, and BDE-209 molecules with decreased estrogenic activities using 3D-QSAR, pharmacophore models coupled with resolution V of the 210-3 fractional factorial design and molecular docking

A 3D-QSAR model was constructed to predict polybrominated diphenyl ether (PBDE) estrogenic activities expressed as median effective concentrations (pEC₅₀), and resolution V of the 2^10-3 fractional factorial design and a pharmacophore model were used to modify the target PBDE molecules BDE-47, BDE-99, BDE-100, BDE-183, and BDE-209 to decrease the estrogenic activities. The persistent-organic-pollutant-related and flame-retardant properties of the modified molecules were evaluated. The mechanisms involved in decreasing PBDE estrogenic activities were explored through molecular docking. The 3D-QSAR model gave a cross-validated correlation coefficient (q²) of 0.682 (i.e., >0.5) and a non-cross-validated correlation coefficient (r²) of 0.980 (i.e., >0.9). Mono- and di-substitutions and hydrophobic substituent groups gave 40 modified molecules with decreased estrogenic activities, including modified BDE-47 and BDE-99 with pEC₅₀ decreased by >10% and modified BDE-100, BDE-183, and BDE-209 with pEC₅₀ decreased by >20%. The modified molecules had similar flame-retardancy to the unmodified molecules, and lower biotoxicities (by a maximum of 17.27%), persistences (by a maximum of 55.68%), bioconcentration (by 4.28%-23.91%), and long-range transport potentials (by 0.72%-18.47%). Docking indicated that hydrophobic interactions were the main factors affecting PBDE estrogenic activities. The results provide a theoretical basis for designing less estrogenic flame retardants than are currently available.