Levels of polybrominated diphenyl ethers and hexabromocyclododecane in the atmosphere and tree bark from Beijing, China

A level IV fugacity-based multimedia model based on steady-state particle/gas partitioning theory and its application to study the spatio-temporal trends of PBDEs in atmosphere of northeast China

Particle/gas (P/G) partitioning can significantly affect the environmental behavior of atmospheric pollutants. In this study, we established a large-scale level IV fugacity-based multimedia model (the S-L4MF Model) based on the steady-state P/G partitioning theory. The spatial and temporal trends with the atmospheric contamination of polybrominated diphenyl ethers (PBDEs) in northeastern China under various climate conditions were simulated by the model. There is a reasonable agreement between the simulated and measured gaseous and particulate concentrations of 3 selected PBDE congeners (BDE-47, -99 and -209). For BDE-47, -99 and -209, 91.9 %, 94.8 % and 86.2 % of data points in the evaluation of the spatial trend, whereas 97.4 %, 98.2 % and 91.6 % of data points in the evaluation of the temporal trend, exhibit discrepancies between the modeled and measured data within 1 order of magnitude. The S-L4MF Model performed better than the other model with the same configuration but an equilibrium-state P/G partitioning assumption. The sensitivity and uncertainty analysis indicated that the air temperature and hexadecane-air partition coefficient were the dominant influencing factors on atmospheric concentrations. In addition, the model was successfully applied to study the inter-annual and seasonal variations of gaseous and particulate concentrations of the three PBDEs during 1971-2020 in Harbin, a northeastern Chinese city. Finally, we illustrated the potential to use the model to understand P/G partitioning behavior and the effects of snow and ice on atmospheric concentrations. In summary, the S-L4MF Model provided a powerful and effective tool for studying the environmental behavior of atmospheric organic pollutants, especially in cold regions.

A Review of Distribution and Profiles of HBCD in Different Environmental Media of China

Hexabromocyclododecane (HBCD) is the most important flame retardant that has been used in Expanded Polystyrene foam and Extruded Polystyrene foam in the past forty years across the world. China was the major producer and user of HBCD, and the total HBCD production was about 0.3 million tons. Although HBCD was completely banned in China in 2021 because of its long-range transport, bioaccumulation and toxicity, there is still a lot of residue in the environment. Therefore, we reviewed multiple studies concerning the distribution of HBCD in diverse environmental matrices, such as in the air, dust, soil, water, sediment, and biota. Results revealed that HBCD levels in different environments in China present geographical variation and were at a high level compared with other countries. In all environmental media, relatively high HBCD concentrations have been found in industrial and urban areas. Industrialization and urbanization are two important factors that influence the concentration and distribution of HBCD in the environment. In terms of isomer, γ-HBCD was the dominant isomer in soil, water, and sediment, while in the biota α-HBCD was the predominant isomer.

Occurrence, correlation, and partitioning of organophosphate esters in soil and tree bark from a megacity, Western China

Concern over the influences of constant addition of emerging anthropogenic chemicals to the environment has become a public issue during the rapid urbanization. Here, we investigated the occurrence of organophosphate esters (OPEs) in soil and corresponding tree bark in a megacity, Western China. Our results showed levels of OPEs in tree bark (1250 ± 573 ng/g dry weight (dw)) were 1-2 orders of magnitude higher than those in soil (40.4 ± 30.8 ng/g dw). Rooster Mountain is a background mountain area, exhibiting significantly lower concentrations of OPEs in soil and tree bark than those in other sites with relatively high population density. This result highlights the effect of human activities on the distribution of OPEs in environmental matrices. Alkyl-OPEs were predominant compounds in soil, whereas halogenated- (Cl-) OPEs were characterized in tree bark. Furthermore, tris(2-chloroethyl) phosphate (TCEP) positively correlated with tris(2-chloroisopropyl) phosphate (TCIPP) in soil (r² = 0.43, P < 0.05) while negatively correlated with TCIPP in tree bark (r² = 0.31, P < 0.05). The ratios of logarithm concentrations of OPEs in tree bark to those in soil correlated well with logK_OA values of OPEs from 6 to 10, indicating the equilibrium status was achieved between OPE partitioning in soil and in tree bark. Nevertheless, tris (2-butoxyethyl) phosphate (TBEP) and tris(2-ethylhexyl) phosphate (TEHP) with high values of logK_OA deviated from this linear tendency, which was possibly due to the fact that they were subjected to the particle-bound deposition process, leading to partition into the soil.

Occurrence of persistent organic pollutants (POPs) in the atmosphere of South Korea: A review

Numerous studies found the presence of persistent organic pollutants (POPs) in various environmental compartments, including air, water, and soil. POPs have been discovered in various industrial and agricultural products with severe environmental and human health consequences. According to the data, South Korea is a hotspot for POP pollution in the southern part of Asia; hence, South Korea has implemented the Stockholm Convention's National Implementation Plan (NIP) to address this worldwide issue. The purpose of this review is to assess the distribution pattern of POPs pollution in South Korea's atmosphere. According to findings, PAHs, PCBs, BFRs, and PBDEs significantly polluted the atmosphere of South Korea; however, assessing their exposure nationwide is difficult due to a shortage of data. The POPs temporal trend and meta-analysis disclosed no proof of a decrease in PAHs and BFRs residues in the atmosphere. However, POP pollution in South Korea tends to decrease compared to contamination levels in neighboring countries like Japan and China.

Atmospheric concentrations of polychlorinated biphenyls, brominated flame retardants, and novel flame retardants in Lagos, Nigeria indicate substantial local sources

Polychlorinated biphenyls (PCBs), brominated flame retardants (BFRs) like polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCDD), and novel flame retardants (NFRs) like decabromodiphenyl ethane (DBDPE) are ubiquitous environmental pollutants. Despite this, little is known about their concentrations in outdoor air in the African continent. To address this knowledge gap, concentrations of BFRs, NFRs, and PCBs were measured in outdoor air at 8 sites located within the metropolitan area of Lagos, Nigeria. Concentrations of ∑₈BDEs, ∑HBCDD, ∑₇NFRs and ∑₈PCBs were: 21-750 (median = 100) pg/m³, <12-180 (median = < 12) pg/m³, 34-900 (median = 300) pg/m³ and 85-460 (median = 300) pg/m³, respectively. Decabromodiphenyl ether (BDE-209, range: <16-620 pg/m³, median = 71 pg/m³) and DBDPE (range: <37-890 pg/m³, median = 280 pg/m³) were the dominant BFRs detected, while the non-Arochlor PCB 11 (range: 49-220 pg/m³, median = 100 pg/m³) was the dominant PCB. To the authors' knowledge, these are the first data on the non-Arochlor PCB 11 in outdoor air in Africa. In general, concentrations of all target contaminants in this study were within the range reported elsewhere in Africa and worldwide. Likely due to the tropical climate of Lagos, no seasonal variation in concentrations was discernible for any of the target contaminants. While concentrations of PBDEs and some NFRs were correlated with population density, concentrations of PCBs appear more impacted by leaks from electrical transformers and for PCB 11 to proximity to activities like textile factories that produce and use dyes.

Plant accumulation and transformation of brominated and organophosphate flame retardants: A review

Plants can take up and transform brominated flame retardants (BFRs) and organophosphate flame retardants (OPFRs) from soil, water and the atmosphere, which is of considerable significance to the geochemical cycle of BFRs and OPFRs and their human exposure. However, the current understanding of the plant uptake, translocation, accumulation, and metabolism of BFRs and OPFRs in the environment remains very limited. In this review, recent studies on the accumulation and transformation of BFRs and OPFRs in plants are summarized, the main factors affecting plant accumulation from the aspects of root uptake, foliar uptake, and plant translocation are presented, and the metabolites and metabolic pathways of BFRs and OPFRs in plants are analyzed. It was found that BFRs and OPFRs can be taken up by plants through partitioning to root lipids, as well as through gaseous and particle-bound deposition to the leaves. Their microscopic distribution in roots and leaves is important for understanding their accumulation behaviors. BFRs and OPFRs can be translocated in the xylem and phloem, but the specific transport pathways and mechanisms need to be further studied. BFRs and OPFRs can undergo phase I and phase II metabolism in plants. The identification, quantification and environmental fate of their metabolites will affect the assessment of their ecological and human exposure risks. Based on the issues mentioned above, some key directions worth studying in the future are proposed.

Atmospheric particulate represents a source of C8-C12 perfluoroalkyl carboxylates and 10:2 fluorotelomer alcohol in tree bark

In this study, we analyzed 30 legacy and emerging poly- and perfluoroalkyl substances (PFASs) in paired atmospheric particulate and bark samples collected around a Chinese fluorochemical manufacturing park (FMP), with the aim to explore the sources of PFASs in tree bark. The results showed that PFASs in atmospheric particulate and tree bark samples were consistently dominated by perfluorooctanoate (mean 73 ng/g; 44 pg/m3), perfluorohexanoate (47 ng/g; 36 pg/m3), perfluorononanoate (9.1 ng/g; 8.8 pg/m3), and 10:2 fluorotelomer alcohol (10:2 FTOH; 5.6 ng/g; 12 pg/m3). Spatially, concentrations of C8-C12 perfluoroalkyl carboxylates (PFCAs) and 10:2 FTOH all showed a similar and exponentially decreased trend in both bark and atmospheric particulate samples with the increasing distance from the FMP. For the first time, we observed strongly significant (Spearman's correlation coefficient = 0.53-0.79, p < 0.01) correlations between bark and atmospheric particulate concentrations for C8-C12 PFCAs and 10:2 FTOH over 1-2 orders of magnitude, suggesting that the continues trapping of atmospheric particulates resulted in the accumulation of these compounds in bark. Overall, this study provides the first evidence that atmospheric particulate is an obvious source of C8-C12 PFCAs and 10:2 FTOH in tree bark. This result may further contribute to the application of tree bark as an indicator of certain PFASs in atmospheric particulate.

Spatial distribution patterns and human exposure risks of polycyclic aromatic hydrocarbons, organochlorine pesticides and polychlorinated biphenyls in Nepal using tree bark as a passive air sampler

Nepal is abutted between the populated Indo-Gangetic Plain (IGP) and Himalayan mountains. Currently, knowledge on the country-wide distribution and cancer risks of atmospheric organic toxicants in Nepal remains limited. In this study, the concentrations, sources, and distributions of polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs), and polychlorinated biphenyls (PCBs), along with their cancer risks, were investigated in Nepal by using tree bark as a passive air sampler. After transferring by a bark/air partitioning model, the averaged concentrations of ∑PAHs, ∑DDTs, ∑HCHs, HCB, ∑Endo and ∑PCBs in the atmosphere of Nepal were 3.71 × 10⁴ pg/m³, 1.10 × 10³ pg/m³, 2.92 × 10² pg/m³, 4.38 × 10² pg/m³, 4.66 pg/m³ and 65.8 pg/m³, respectively. Source diagnosis suggested that biomass burning is the major source for PAHs, while local application and long-range transport jointly contribute to the high levels of DDT and HCH in the air. The ILCR (incremental lifetime cancer risk) value was used to assess the risks of various chemicals. Adults have a higher risk than other age groups; the major exposure pathway for risk is by inhalation; and PAHs and HCHs are the dominant chemical classes that lead to risk. It was also found that, in certain hotspots in south Nepal, the carcinogenic risks caused by DDT and HCH were particularly high (>1 × 10^-4). Given that illegal and disordered use of legacy POPs in south Nepal and the IGP region is common, our results highlight an urgent need for voluntary regulation of the ongoing use of pesticides.

Polybrominated diphenyl ethers in the environment and human external and internal exposure in China: A review

Polybrominated diphenyl ethers (PBDEs) are widely used as brominated flame retardants. Because of their toxicity and persistence, some PBDEs were restricted under the Stockholm Convention in 2009. Since then, many studies have been carried out on PBDEs in China and in many other countries. In the present review, the occurrences and contamination of PBDEs in air, water, sediment, soil, biota and daily food, human blood, hair, and other human tissues in China are comprehensively reviewed and described. The human exposure pathways and associated health risks of PBDEs are summarized. The data showed no obvious differences between North and South China, but concentrations from West China were generally lower than in East China, which can be mainly attributed to the production and widespread use of PBDEs in eastern regions. High levels of PBDEs were generally observed in the PBDE production facilities (e.g., Jiangsu Province and Shandong Province, East China) and e-waste recycling sites (Taizhou City, Zhejiang Province, East China, and Guiyu City and Qingyuan City, both located in Guangdong Province, South China) and large cities, whereas low levels were detected in rural and less-developed areas, especially in remote regions such as the Tibetan Plateau. Deca-BDE is generally the major congener. Existing problems for PBDE investigations in China are revealed, and further studies are also discussed and anticipated. In particular, non-invasive matrices such as hair should be more thoroughly studied; more accurate estimations of human exposure and health risks should be performed, such as adding bioaccessibility or bioavailability to human exposure assessments; and the degradation products and metabolites of PBDEs in human bodies should receive more attention. More investigations should be carried out to evaluate the quantitative relationships between internal and external exposure so as to provide a scientific basis for ensuring human health.

Distribution and diastereoisomeric profiles of hexabromocyclododecanes in air, water, soil, and sediment samples in South Korea: Application of an optimized analytical method

In this study, the levels and distribution patterns of HBCD diastereoisomers in air, water, soil, and sediment samples in South Korea were investigated after optimizing the UPLC-MS/MS analytical process. Extraction and cleanup efficiencies were tested using several different extraction solvents and adsorbents. Dichloromethane was selected as the base extraction solvent, and multi-layer silica gel (MSG) and MSG-alumina columns were selected for the removal of HBCDs from complex environmental matrices. The concentration of Ʃ₃ HBCDs was 22-133 pg/m³, 10-128 ng/g, 0.2-151 ng/L, and 0.5-552 ng/g dw for air, soil, water, and sediment samples, respectively. Relatively higher concentrations of Ʃ₃ HBCDs were observed at stations adjacent to industrial facilities (e.g., rubber and plastic, textile, chemical, fabricated metal, and wholesale trade factories) associated with the use of commercial HBCDs. The proportion of γ-HBCD in the soil (48.3-86.2%) and sediment (54.2-78.1%, except for one station) samples was similar to that found in technical and commercial HBCDs. In contrast, α-HBCD (52.3-71.2%) was dominant in all air samples, while the water samples displayed no clear trend in their diastereoisomer profiles. As the first nationwide report on HBCD diastereoisomers in the environment, this study demonstrates that most environmental compartments in South Korea are moderately contaminated with HBCDs.

Bioaccumulation and translocation of tetrabromobisphenol A and hexabromocyclododecanes in mangrove plants from a national nature reserve of Shenzhen City, South China

Brominated flame retardants (BFRs) such as tetrabromobisphenol A (TBBPA) and hexabromocyclododecanes (HBCDs) are of ecological concern due to their ubiquitous presence and adverse effects. There is a paucity of data on environmental fate of such compounds in mangrove wetlands, which are unique ecosystems in coastal intertidal areas and act as natural sinks for many pollutants. In this study, mangrove plants and sediments were collected from an urban nature reserve in South China to investigate bioaccumulation and translocation of TBBPA and HBCDs. The mean (range) concentrations of TBBPA and ΣHBCD in roots, stems and leaves were 67 (<MDL-999), 174 (0.73-1105) and 20 (0.59-250) pg/g dry weight (dw), and 329 (15.6-2234), 766 (32.9-3255) and 298 (19.9-1520) pg/g dw, respectively. Tissue-specific accumulations were observed, varying with plant species and compounds. HBCD diastereoisomer patterns were similar for all plant species. γ-HBCD was the major diastereoisomer in roots, while α-HBCD dominated in stems and leaves. The predominance of α-HBCD in aboveground tissues may be ascribed to diastereoisomer-specific translocation, isomerization and/or metabolization in mangrove plants. Preferential enrichment of (-)-α-, (-)-β- and (+)-γ-HBCDs was found in all mangrove plant tissues, suggesting the enantioselectivity for HBCDs in mangrove plants. Translocation factors (log TF, root to stem) of HBCD diastereoisomers and log K_ow were negatively correlated (p = 0.03), indicating passive translocation of HBCDs, driven by water movement during transpiration. Sediment-root bioaccumulation factors and log TFs (stem to leaf) both showed no obvious correlation with log K_ow of HBCD diastereoisomers. These results reflected the complex behavior of HBCDs in mangrove plants, which have not been sufficiently captured in laboratory-based studies of plant contaminant accumulation.

Contamination of polybrominated diphenyl ethers (PBDEs) in urban mangroves of Southern China

Mangroves are threatened due to urban development and human activities in coastal regions. Four urban mangroves in Shenzhen (rapidly developing city of China) were selected according to urban functional zoning, namely, Shajing mangrove (SJM) and Xixiang mangrove (XXM) featured with industry district, Futian mangrove (FTM) and Baguang mangrove (BGM) featured with central business district and ecological preserve. Eight BDE congeners (BDE-28, -47, -99, -100, -153, -154, -183, and -209) in mangrove sediments and leaves were determined. The highest level of BDE-209 in SJM was proximate to areas of point-source discharges of Dongbao River in Pearl River Estuary, China. Total organic carbon (TOC) was influential in BDE-209 accumulations in SJM, XXM, and FTM. Multiple variate analysis implied that PBDEs in SJM, XXM and FTM mainly composed of penta-, octa-, and deca-BDEs, with surface runoff to be the main contamination sources; while BGM was contaminated by penta- and octa-BDEs. Ecological risk of BDE-209 was high in SJM, with medium/negligible risk in the other urban mangroves. The transfers of BDE-209 from sediment to leaf were weak (BGM and FTM), improved (XXM), and restricted (SJM), respectively. This is the first reports of spatial distribution and bioaccumulation of PBDEs in urban mangroves featured with different urban functional zonings. More attention is required to reduce emission of PBDEs into the environment and manage PBDEs contamination in urban mangroves.

A contemporary assessment of polybrominated diphenyl ethers (PBDE) in the ambient air and soil of Azerbaijan

PBDEs were measured in air and soil across Azerbaijan to establish contemporary concentrations at 13 urban and rural sites. Polyurethane foam passive air samplers (PUF-PAS) were deployed for a period of a month with surface soil samples collected at the same sites. Unlike organochlorine pesticides previously surveyed by our group, PBDE concentrations in both contemporary air and soil were low in comparison to recent European and Asian studies. For example, mean ∑₉PBDE concentrations in air and soil were 7.13 ± 1.66 pg m^-3 and 168 ± 57 pg g^-1, respectively. The fully brominated BDE-209 was the most abundant congener observed in soil (174.8 ± 58.5 pg g^-1), comprising ~ 96% of ∑₁₀PBDE. However, the PAS-derived air concentrations for highly brominated congeners must be viewed with caution as there is uncertainty over the uptake rates of particle-bound chemicals using these devices. Some of the highest concentrations in air were observed at sites with the highest wind speeds and at several remote locations in the north of the country and this requires further research. Levels of BDE-47 and 99 (the two most abundant congeners in the widely used penta-formulation) were lower than levels reported elsewhere suggesting limited use/import of the penta-BDE formulation in Azerbaijan.

Levels and gas-particle partitioning of hexabromocyclododecanes in the urban air of Dalian, China

The concentrations of α-, β-, and γ-hexabromocyclododecane diastereomers (HBCDs) in gas phase and particulate phase of Dalian urban air, China, were monitored from September 2016 to August 2017 with high-volume active sampler. The total concentration of ∑HBCDs (gas phase + particulate phase) ranged from 15.47 to 43.57 pg m^-3, with an average of 27.07 pg m^-3, and 73.39-96.76% of the total HBCDs were found in the particulate phase. No matter in gas phase or in particulate phase, α-HBCD was the predominant component in all, and there was a good negative correlation between the relative contribution of α-HBCD to ∑HBCDs and that of γ-HBCD to ∑HBCDs. The average ratios of the air concentration of α-HBCD to γ-HBCD were comparable with those found in decorative polystyrene, which indicated that HBCDs in outdoor air of Dalian probably came from indoor air and ventilation air from inside of buildings coupled with the already present contamination in background air. There were clear seasonal differences in the HBCD concentrations. Spearman's rank correlation analysis between the concentrations of HBCDs with meteorological parameters was conducted. The exposure risk of HBCDs was evaluated, which illustrated that the estimated exposure of HBCDs via the outdoor air in Dalian was well below the reference doses (200 ng kg^-1 bw day^-1) derived by the US National Research Council.

Hazy Weather-Induced Variation in Environmental Behavior of PCDD/Fs and PBDEs in Winter Atmosphere of A North China Megacity

Haze is a serious pollution problem during the wintertime in North China. In this study, we investigated how the periodic cycle of winter haze events affect the environmental behaviors of two typical persistent organic pollutants, namely, polychlorinated dibenzo- p-dioxins and dibenzofurans (PCDD/Fs) and polybrominated diphenyl ethers (PBDEs), in the atmosphere of a typical megacity, Beijing. The average atmospheric concentrations of the total di- to octa-CDD/Fs (∑PCDD/Fs: 378.0 pg/m³) and the total mono- to nona-BDEs (∑_9hPBDEs: 166.5 pg/m³) during haze episodes increased by 3.6-fold and 1.9-fold compared with those during the nonhaze periods, respectively; and their concentrations both linearly increased with PM_2.5 levels and decreased as a power function of the atmospheric boundary layer height. The elevated concentrations could be clearly attributed to the vertically sinking motion of airflow in the midlower troposphere. When a haze event occurred, the partitioning rate of PCDD/Fs and PBDEs into particles was reduced; the largest fraction of the particle-bound ∑PCDD/Fs was shifted from ultrafine particles to accumulation mode particles; and a steady-state model (Li-Ma-Yang model) satisfactorily described the gas-particle partitioning of the PCDD/F and PBDE homologues. The inhalation exposure risk evaluation indicated that special attention should be paid to the increased cancer risk induced by the elevated inhalation intake of PCDD/Fs during haze episodes.

Atmospheric concentrations of hexabromocyclododecane (HBCDD) diastereomers in the Great Lakes region

The concentrations of α-, β-, and γ-hexabromocyclododecane (HBCDD) diastereomers in atmospheric particle phase samples were determined at four United States Integrated Atmospheric Deposition Network (IADN) sites located in the North American Great Lakes basin collected between 1 January and 31 December 2014. The concentrations ranged from 0.37 to 8.9 pg/m³, 0.12-4.0 pg/m³, and 0.26-22 pg/m³ for α-, β-, and γ-HBCDD, respectively among the four sampling sites. The median ΣHBCDD concentrations for the four sites were 2.0 pg/m³, 2.1 pg/m³, 1.7 pg/m³ and 5.2 pg/m³ for Chicago, Cleveland, Sturgeon Point and Sleeping Bear Dunes, respectively. Higher levels of ∑HBCDD were observed at the remote site of Sleeping Bear Dunes with comparable levels at the remaining three sites. α-HBCDD and γ-HBCDD were the dominant isomers with an average contribution of about 40% and 50% to ΣHBCDD concentrations, respectively. These HBCDD concentrations were compared with the levels of other brominated flame retardants measured in these samples, including polybrominated diphenyl ethers (PBDEs), 2,3,4,5-tetrabromoethylhexyl benzoate (EHTBB), bis(2-ethylhexyl) tetrabromophthalate (BEHTBP), and decabromodiphenylethane (DBDPE). ∑HBCDD concentrations were significantly lower than or indistinguishable from those of PBDEs, EHTBB, BEHTBP, and DBDPE at all sites except Sleeping Bear Dunes. No significant correlations were found between ΣHBCDD and ΣPBDE, EHTBB, BEHTBP, and DBDPE concentrations, suggesting a different source of HBCDD contamination. This is the first study reporting concentrations of HBCDD isomers in the Great Lakes ambient air, and our results indicate that HBCDD is ubiquitous in the Great Lakes basin, including at remote sites.

An overview of hexabromocyclododecane (HBCDs) in environmental media with focus on their potential risk and management in China

Hexabromocyclododecanes (HBCDs) are the subject of recent interest and potential risk assessment particularly in China due to its ubiquitous existence in a variety of environmental media. This paper reviews the recent studies conducted on HBCDs in different environmental media (air, soil, water, river sediment, sewage sludge, biota and daily food) in China. At the same time, human health risks via food and occupational exposure of HBCDs in production plants, expanded polystyrene (EPS) and extruded polystyrene (XPS) plants were assessed. The review reveals that HBCDs levels of air, soil, sediment, sewage sludge, biota and food presented a geographical variation in the eastern coastal regions of China. There were many factors resulting in the variation, such as sampling sites, climate and analytical method. In terms of diastereoisomer, α-HBCD and γ-HBCD were the predominant diastereoisomers in air, soil, sediment, and sewage sludge. In the water, α-HBCD and γ-HBCD shared the major proportion to the total HBCDs. However, only α-HBCD was the predominant diastereoisomer in biota. With regard to human exposure pathway to HBCDs, food was the major route for human exposure to HBCDs, especially meat. In addition, soil and road dust were also important exposure pathways. Furthermore, workers and residents, especially infants in and around waste dumping sites and industrial areas are exposed to the highest HBCDs levels among all the populations studied thus far. HBCDs posed a potential threat to the environment and human health. Therefore, risk assessment and management have an important role to play in preventing and mitigating HBCDs risks.

Hexabromocyclododecanes in breast milk from residents in Shenzhen, China: Implications for infant exposure

Hexabromocyclododecanes (HBCDs) are widely used as flame retardants for various products and have become ubiquitous pollutants in environmental media. However, little is known about HBCD exposure for humans, especially in China. This study aimed to investigate the levels and profiles of hexabromocyclododecanes (HBCDs) in human breast milk and to estimate the daily HBCD intake for infants in Shenzhen, China. Levels of the HBCD diastereoisomers α-, β-, and γ-HBCD in 180 breast milk samples collected from primiparas in Shenzhen were measured. The concentrations of α-, β-, and γ-HBCD (ΣHBCDs) ranged within 0.103-15.1ng/g lipid and had a median of 1.82ng/g lipid. ΣHBCDs levels in milk in the present study are comparable to those in milk from other countries and regions but are markedly higher than those for most populations in other regions of China. Among the diastereoisomers, α-HBCD was predominant, accounting for 97.6% of the concentration of ΣHBCDs. The estimated daily intake of ΣHBCDs via breast milk for infants in Shenzhen ranged from 0.481 to 100ng/kgbw/day with a median of 8.40ng/kgbw/day, however, which was unlikely to raises a health concern based on the margin of exposure (MOE) approach. The duration of residence was found to have a significant positive correlation with the HBCD levels in the human breast milk (p<0.05). To our knowledge, this is the first report on HBCD levels in breast milk from Shenzhen residents.

Hexabromocyclododecane and tetrabromobisphenol A in tree bark from different functional areas of Shanghai, China: levels and spatial distributions

The concentrations and spatial distributions of hexabromocyclododecane (HBCDD) and tetrabromobisphenol A (TBBPA) were measured in tree bark from different functional areas of Shanghai. ΣHBCDD (sum of α-, β-, and γ-HBCDD) concentrations ranged from 1.2 × 10² to 6.6 × 10³ ng g^-1 lw (median 5.7 × 10² ng g^-1 lw) and TBBPA concentrations ranged from 48 to 7.2 × 10⁴ ng g^-1 lw (median 2.8 × 10² ng g^-1 lw). The concentrations of ΣHBCDD and TBBPA all followed the order of industrial areas > commercial areas > residential areas. The mean percentage of α-HBCDD in bark samples (44%) from Shanghai was higher than that in technical HBCDD products, but comparable with that in air. The concentrations of TBBPA and individual HBCDD diastereoisomers between industrial areas and commercial areas were correlated. Based on the concentrations of HBCDD in the bark, the corresponding atmospheric HBCDD concentrations were estimated. Compared with the published data for HBCDD in urban air, the estimated atmospheric HBCDD concentrations in Shanghai had a relatively high level, and more attention should be paid to the pollution status of HBCDD in Shanghai.

Airborne persistent toxic substances (PTSs) in China: occurrence and its implication associated with air pollution

In recent years, China suffered from extensive air pollution due to the rapidly expanding economic and industrial developments. Its severe impact on human health has raised great concern currently. Persistent toxic substances (PTSs), a large group of environmental pollutants, have also received much attention due to their adverse effects on both the ecosystem and public health. However, limited studies have been conducted to reveal the airborne PTSs associated with air pollution at the national scale in China. In this review, we summarized the occurrence and variation of airborne PTSs in China, especially in megacities. These PTSs included polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), halogenated flame retardants (HFRs), perfluorinated compounds (PFCs), organochlorine pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs) and heavy metals. The implication of their occurrence associated with air pollution was discussed, and the emission source of these chemicals was concluded. Most reviewed studies have been conducted in east and south China with more developed economy and industry. Severe contamination of airborne PTSs generally occurred in megacities with large populations, such as Guangzhou, Shanghai and Beijing. However, the summarized results suggested that industrial production and product consumption are the major sources of most PTSs in the urban environment, while unintentional emission during anthropogenic activities is an important contributor to airborne PTSs. It is important that fine particles serve as a major carrier of most airborne PTSs, which facilitates the long-range atmospheric transport (LRAT) of PTSs, and therefore, increases the exposure risk of the human body to these pollutants. This implied that not only the concentration and chemical composition of fine particles but also the absorbed PTSs are of particular concern when air pollution occurs.

Matrix-specific distribution and diastereomeric profiles of hexabromocyclododecane (HBCD) in a multimedia environment: Air, soil, sludge, sediment, and fish

Hexabromocyclododecane (HBCD) contamination and its diastereomeric profile were investigated in a multi-media environment along a river at the local scale in air, soil, sludge, sediment, and fish samples. The spatial distribution of HBCD in each matrix showed a different result. The highest concentrations of HBCD in air and soil were detected near a general industrial complex; in the sediment and sludge samples, they were detected in the down-stream region (i.e., urban area). Each matrix showed the specific distribution patterns of HBCD diastereomers, suggesting continuous inputs of contaminants, different physicochemical properties, or isomerizations. The particle phases in air, sludge, and fish matrices were dominated by α-HBCD, owing to HBCD's various isomerization processes and different degradation rate in the environment, and metabolic capabilities of the fish; in contrast, the sediment and soil matrices were dominated by γ-HBCD because of the major composition of the technical mixtures and the strong adsorption onto solid particles. Based on these results, the prevalent and matrix-specific distribution of HBCD diastereomers suggested that more careful consideration should be given to the characteristics of the matrices and their effects on the potential influence of HBCD at the diastereomeric level.

Multi-year air monitoring of legacy and current-use brominated flame retardants in an urban center in northeastern China

The occurrence and temporal trends of polybrominated diphenyl ethers (PBDEs) and non-PBDE brominated flame retardants (NBFRs) were investigated in an urban atmosphere of Northeast China in consecutive six years (2008-2013). Among all chemicals, BDE-209, l,2,5,6,9,10-hexabromocyclododecane (HBCD), and decabromodiphenylethane (DBDPE) were the three most dominant compounds. During the period, the levels of pentabromodiphenyl ethers in the gas-phase and octabromodiphenyl ethers in the particle-phase significantly decreased, while the levels of BDE-209 and NBFRs increased in either the gas-phase or particle-phase. Ambient temperature was the most significant variable that influenced the gas-phase and particle-phase concentrations of BFRs, followed by wind speed and relative humidity. A stronger temperature dependence of the atmospheric concentrations was found for lower mass BFRs. Gas-particle partitioning studies suggested PBDEs in the urban atmosphere of Northeast China were at steady-state. Steady-state equation can also well describe the partitioning behavior for NBFRs, suggesting that the atmospheric partitioning behaviors of NBFRs were similar to those of PBDEs.

Concentrations and distributions of polybrominated diphenyl ethers and novel brominated flame retardants in tree bark and human hair from Yunnan Province, China

The concentrations and distributions of polybrominated diphenyl ethers (PBDEs) and novel brominated flame retardants (NBFRs) in tree bark and hair samples from the same area in Yunnan Province, China, were determined. The total PBDE and NBFR concentrations in the tree bark samples were 3.8 ng/g lipid weight to 91 ng/g lipid weight and 0.23 ng/g lipid weight to 5.0 ng/g lipid weight, respectively. The total PBDE and NBFR concentrations in the hair samples were 2.1 ng/g dry weight to 14 ng/g dry weight and 0.083 ng/g dry weight to 0.29 ng/g dry weight, respectively. Decabromodiphenyl ether had similar distributions in the tree bark and hair samples, but other PBDE congeners and NBFRs had different distributions in the tree bark and hair samples. External exposure was found to be mainly responsible for the total PBDE and pentabromotoluene concentrations in hair, but both external and internal exposure were responsible for the pentabromophenyl and hexabromobenzene concentrations in hair.

Polybrominated diphenyl ethers and new polybrominated flame retardants in tree bark from western areas of China

Tree bark samples were collected from 15 sites across western China in 2013, and the polybrominated diphenyl ether (PBDE) and new polybrominated flame retardant (NBFR) concentrations in the samples were determined. The mean total PBDE concentration was 51.8 ng/g lipid weight, which was 85.2% to 99.4% lower than in Chinese eastern coastal areas and the E-waste recycling areas. The dominant PBDE congener was BDE209, and its mean concentration was 49 ng/g lipid weight. The mean 2,3,5,6-tetrabromo-p-xylene, pentabromobenzene, pentabromotoluene, and hexabromobenzene concentrations were 0.61 ng/g, 0.97 ng/g, 0.68 ng/g, and 0.68 ng/g lw, respectively. The PBDE and NBFR concentrations in the air at the sampling sites were estimated from the concentrations in the tree bark samples. The estimated mean total PBDE and total NBFR concentrations in air were 58.5 pg/m(3) and 2.76 pg/m(3) , respectively. The sources of NBFR emissions were found to be different from the sources of PBDE emissions, as no relationship was found between the NBFR and PBDE concentrations, and it appeared that sources of measured hexabromobenzene, pentabromobenzene, and pentabromotoluene in tree bark in western China include industrial activity related to the aluminum industry. Environ Toxicol Chem 2016;35:1364-1370. © 2015 SETAC.

Concentrations of legacy and emerging flame retardants in air and soil on a transect in the UK West Midlands

Passive air samples were collected monthly for 6 months from 8 sites along a transect of Birmingham, United Kingdom between June 2012 and January 2013. Soil samples were collected once at each site. Average concentrations of BDE-209, ΣPBDEs17:183 and ΣPBDEs in ambient air were 150, 49, and 180 pg m(-3), respectively. Atmospheric concentrations of PBDEs were negatively correlated with distance from the city centre, exhibiting an "urban pulse". The average ΣHBCDD air concentration was 100 pg m(-3), however concentrations were not correlated with distance from the city centre. Several emerging flame retardants (EFRs) were identified in air and/or soil samples: 2,3,4,5-tetrabromo-bis(2-ethylhexyl) phthalate (BEH-TEBP), 1,2-dibromo-4-(1,2 dibromoethyl)cyclohexane (TBECH or DBE-DBCH), allyl 2,4,6-tribromophenyl ether (ATE), 2-bromoallyl 2,4,6-tribromophenyl ether (BATE), decabromodiphenyl ethane (DBDPE), and dechlorane plus (DP or DDC-CO). Average concentrations of BDE-209, ΣPBDEs17:183 and ΣPBDEs in soil were 11, 3.6, and 15 ng g(-1) soil organic matter. PBDE concentrations in soil were higher at sites closest to the city centre, however correlations with distance from the city centre were not significant. BDEs-47 and -99 contributed more to ΣPBDEs in soil samples than air samples, but in both, the predominant congener was BDE-209. BATE was more abundant in air than soil but ATE was abundant in soil but not air.

Polybrominated diphenyl ethers in sediments from the Southern Yellow Sea: Concentration, composition profile, source identification and mass inventory

The Southern Yellow Sea (SYS) is believed to be influenced by the contaminants from mainland China and the Korean peninsula. Here we report the first record about concentrations of polybrominated diphenyl ethers (PBDEs) in the sediments of the SYS. The concentrations of ∑(7)PBDEs (BDE-28, 47, 99, 100, 153, 154, 183) and BDE-209 were 0.064-0.807 ng g(-1) (dry weight) and 0.067-1.961 ng g(-1) with a mean value of 0.245 ng g(-1) and 0.652 ng g(-1), respectively. These are distinctively low compared with the PBDE levels previously reported in other regions of the world. PBDE concentrations gradually increased from the coastal areas to the central mud area. BDE-209 was the dominant congener, accounting for 70.2-91.6% of the total PBDEs. Congener profiles of PBDEs were similar to those in sediments from the Bohai Sea (BS), Laizhou Bay and modern Yellow River, which might be a tentative indication that they shared similar sources. Principal component analysis (PCA) revealed that PBDEs in the SYS were mainly from continental runoff (69.0%) and atmospheric deposition (31.0%). Depth profile of PBDEs in a sediment core collected from the edge of the central mud area showed that concentration of BDE-209 rapidly increased in recent years, which is in accordance with the replacement in demand and consumption of Penta- and Octa-BDEs by the Deca-BDE. Compared with BS, East China Sea, Erie and Ontario, the SYS was a relatively weak sink of PBDEs (0.102-1.288 t yr(-1) for ∑(7)PBDEs and 0.107-3.129 t yr(-1) for BDE-209) in the world.

Dechlorane Plus and decabromodiphenyl ether in atmospheric particles of northeast Asian cities

Atmospheric particles were collected in several cities in Japan (Sapporo, Sagamihara, Kanazawa, and Kitakyushu), Korea (Busan), and China (Beijing) using a high-volume air sampler equipped with a quartz fiber filter. The summer and winter samples were analyzed using gas chromatography-high-resolution mass spectrometry for Dechlorane Plus (DP). Decabromodiphenyl ether (BDE-209) was also analyzed for the samples from Kanazawa and Beijing. DP was detected in all samples. The mean total DP (ΣDP) concentration was highest (6.7 pg/m(3)) and lowest (0.87 pg/m(3)) in the winter samples from Sagamihara and Busan, respectively. The seasonal variation of DP concentrations varied by sampling site in this study. BDE-209 was detected in all the analyzed samples except for one of the Kanazawa winter samples. BDE-209 concentration was considerably higher in Beijing than in Kanazawa. Significant correlations were found between the concentrations of ΣDP and BDE-209 in the winter samples from Kanazawa and in both summer and winter samples from Beijing. This similarity in the atmospheric behavior of DP and BDE-209, especially in winter, is assumed to reflect a common end usage and release mechanism.

Tree bark as a biomonitor for the determination of polychlorinated biphenyls and polybrominated diphenyl ethers from Southern Jiangsu, China: levels, distribution, and possible sources

Tree bark was used as the passive air sampler to evaluate polychlorinated biphenyl (PCB) and polybrominated diphenyl ether (PBDE) pollution and possible sources in Southern Jiangsu. The concentrations of PCBs and Σ7PBDEs were in the range of 0.58-5.19 ng/g dry weight (dw; mean 1.79 ng/g dw) and 17.9-243 pg/g dw (mean 74.7 pg/g dw), respectively. Tri-PCBs were the major PCB homologs, and technical PCB product Ar1242 was identified as the main source. BDE209 concentrations (4.29-456 ng/g dw) were relatively high, indicating that BDE209 pollution was serious in this region. The deca-BDE commercial mixture was the predominant commercial PBDE product used in this region. A good correlation was found between tree bark and polyurethane foam (PUF) disks in Σ6PCB monitoring, suggesting that both of them respond well to the gas-phase PCB monitoring.

Insights into spatially and temporally co-occurring polybrominated diphenyl ethers in sediments of the East China Sea

In this study, twenty-four core sediment samples were collected from monitoring stations in the East China Sea (ECS) to investigate the spatial and temporal distributions of polybrominated diphenyl ethers (PBDEs) and their potential sources. In surface sediment samples (the top 0-3 cm segment), the concentrations of Σ8PBDEs (sum of BDE15, 28, 47, 99, 100, 153, 154 and 183) and BDE209 were between 0.03 and 1.26 ng g(-1) d.w., and 0.20 and 3.15 ng g(-1) d.w., respectively. The PBDEs concentrations were decreased generally from the shore towards the sea, indicating that PBDEs are mainly derived from anthropogenic sources. As the predominant congener, BDE209 was primarily distributed in the nearshore regions, suggesting that it might be derived from runoff and sewage. In contrast, higher levels of BDE99 and BDE47 were detected in the offshore samples, and the concentrations of BDE47 were higher than those of BDE99. All of their concentrations were poorly correlated with TOC, suggesting BDE47 and BDE99 might be transferred mainly along with the atmosphere. In most sediment cores, the Σ8PBDEs and BDE209 concentrations increased from the bottom (18-30 cm), reached their maximum concentrations in the middle (6-15 cm) or upper (0-6 cm) sections, and leveled off near the surface (0-3 cm). This trend is consistent with the phasing-out of PBDEs and the strict management of recycling e-waste. This is the first study for network used to analyze the distribution properties of pollutant congeners in environment, which facilitates the visualization of cluster results among multivariable data and helps in tracing the potential sources of pollutants.

Particle size distribution of halogenated flame retardants and implications for atmospheric deposition and transport

This study investigates the distribution of polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCD) and a group of novel flame retardants (NFRs) on atmospheric aerosols. Two high volume cascade impactors were used to collect particulate fractions of ambient air over a one year period at urban and rural sites. The majority of FRs were found on the finest aerosols (<0.95 μm). Concentrations of HBCD were higher than those of ΣPBDEs. Moreover, we noted seasonality and spatial differences in particle size distributions, yet a large portion of the observed differences were due to differences in particulate matter (PM) itself. When normalized by PM, the size distributions of the FRs exhibited much greater heterogeneity. Differences existed between the FR distributions by molecular weight, with the higher molecular weight FRs (e.g., BDE-209, Dechlorane Plus) distributed more uniformly across all particulate size fractions. The seasonal, spatial, and compound-specific differences are of crucial importance when estimating dry and wet deposition of FRs as smaller aerosols have longer atmospheric residence times. Estimated wet and dry deposition of four representative FRs (BDE-47, BDE-209, HBCD, and Dechlorane Plus) using size-segregated aerosol data resulted in lower deposition estimates than when bulk aerosol data were used. This has implications for estimates of long-range atmospheric transport and atmospheric residence times, as it suggests that without size-specific distributions, these parameters could be underestimated for FRs.

Polybrominated diphenyl ethers, dechlorane plus, and polychlorinated biphenyls in tree bark near the upper Yellow River, China

Willow tree bark samples from urban and rural sites in Inner Mongolia, Ningxia Province, and Gansu Province, in the Yellow River basin, were analyzed for polybrominated diphenyl ethers (PBDEs), dechlorane plus (DP), and dioxin-like polychlorinated biphenyls (DL-PCBs) to compare their relative levels in air in these areas (i.e., treating bark as a passive air sampler). No difference was found between the pollutant concentrations in Salix matsudana and Salix babylonica bark samples. The mean concentrations of the total PBDEs, DP, and total DL-PCBs were 13000 ± 6400, 46 ± 44, and 26 ± 17 pg/g dry weight, respectively, with urban samples containing much higher concentrations (19000 ± 5700 pg/g, 51 ± 27 pg/g, and 37 ± 29 pg/g dry wt in PBDEs, DP, and DL-PCBs, respectively) than rural samples (10000 ± 5200 pg/g, 45 ± 53 pg/g, 22 ± 9 pg/g dry wt). A strong positive correlation between PBDEs and DP was found in all of the samples (r=0.712, p=0.006), but correlations between PCBs and the other pollutants were only found in the rural samples. The total DL-PCB concentration in the tree bark correlated with population density.

Tree bark as a passive air sampler to indicate atmospheric polybrominated diphenyl ethers (PBDEs) in southeastern China

The different barks were sampled to discuss the influence of the tree species, trunk circumference, and bark thickness on the accumulation processes of polybrominated diphenyl ethers (PBDEs) from air into the bark. The results of different PBDE concentrations indicated that barks with a thickness of 0-3 mm collected from weeping willow, Camphor tree, and Masson pine, the trunk circumferences of which were 100 to 150 cm, were better PBDEs passive samplers. Furthermore, tree bark and the corresponding air samples were collected at Anji (AJ), Hangzhou (HZ), Shanghai (SH), and Wenling (WL) to investigate the relationship between the PBDE concentrations in bark and those in air. In addition, the significant correlation (r (2) = 0.906; P < 0.05) indicated that atmospheric PBDEs were the principle source for the accumulation of PBDEs in the barks. In this study, the log K BA (bark-air partition coefficient) of individual PBDE congeners at the four sites were in the range from 5.69 to 6.79. Finally, the total PBDE concentration in WL was 5 to 20 times higher than in the other three cities. The result indicated that crude household workshops contributed a heavy amount of PBDEs pollution to the environment, which had been verified by the spatial distribution of PBDEs levels in barks collected at Wenling (range, 26.53-1317.68 ng/g dw). The good correlation between the PBDE concentrations in the barks and the air samples and the variations of the PBDE concentrations in tree barks collected from different sites reflected that the bark could be used as a passive sampler to indicate the atmospheric PBDEs.

Organohalogen contamination in passerine birds from three metropolises in China: geographical variation and its implication for anthropogenic effects on urban environments

Contamination of organohalogen pollutants (OHPs), including dichlorodiphenyl trichloroethane and its metabolites (DDTs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), decabromodiphenylethane (DBDPE), hexabromocyclododecanes (HBCDs), and dechlorane plus (DP) in three metropolises of China, Beijing, Wuhan, and Guangzhou, and a reference rural site were determined using terrestrial residential passerine species as bioindicator. DDTs dominated in Wuhan whereas flame retardants dominated in Guangzhou and Beijing. No geographical variation was found for PCB levels but it exhibited different homologue profiles among different sites which could be attributed to different dietary sources of birds. Industry characteristics of the sampling location contributed to the geographical differences in the occurrence and contamination profile of OHPs. The transformation of traditional agriculture characterized contamination profiles to industry characterized profiles in Beijing and Guangzhou implicates significantly environmental concern on the flame retardants contamination in non-hot-spot regions of China.

Brominated and chlorinated flame retardants in tree bark from around the globe

Brominated and chlorinated flame retardants were measured in about 40 samples of tree bark from 12 locations around the globe. The analytes were polybrominated diphenyl ethers (PBDE), Dechlorane Plus (DP), decabromodiphenylethane (DBDPE), hexabromocyclododecane (HBCD), hexabromobenzene (HBB), pentabromoethylbenzene (PBEB), pentabromobenzene (PBBz), and tetrabromo-p-xylene (pTBX). The highest concentrations of these compounds were detected at an urban site in Downsview, Ontario, Canada. Total PBDE and DP concentrations ranged from 2.1 to 190 ng/g lipid weight and from 0.89 to 48 ng/g lipid weight, respectively. Relatively high levels of DP (46 ± 4 ng/g lipid weight) were found at a remote site at Bukit Kototabang in Indonesia. The concentrations of total PBDE, DP, PBEB, and HBCD in the tree bark samples were significantly associated with human population in the nearby areas (r(2) = 0.21-0.56; P < 0.05). In addition, the concentrations of total PBDE and DP were significantly associated (r(2) = 0.40-0.64; P < 0.05). with the corresponding atmospheric concentrations of these compounds over a concentration range of 2-3 orders of magnitude.

Summer atmospheric polybrominated diphenyl ethers in urban and rural areas of northern China

High levels of polybrominated diphenyl ethers (PBDEs) have been extensively reported in urban areas and at e-waste recycling sites in coastal China. However, data are scarce in northern China and are not available in rural areas at all. In addition, it is often believed that air concentrations in rural areas are lower than those in urban areas without distinguishing rural residential areas and open fields. In this study, air samples were collected at 17 sites covering urban and rural (residential and open field) areas in northern China using active samplers. With BDE-209 dominated in all congeners, the average concentrations of BDE-209 (41 ± 72 pg/m(3)) and other 13 PBDEs (16 ± 12 pg/m(3)) were significantly lower than those found in south China, such as in Guangzhou or Hong Kong. On average, the total PBDE concentrations at the urban sites were 2.2 and 2.9 times of those at the rural residential and field sites, respectively.

State of polybrominated diphenyl ethers in China: an overview

Polybrominated diphenyl ethers (PBDEs), extensively used as flame retardants, are ubiquitous environmental contaminants that are found in both abiotic and biotic environmental samples. Sufficient evidence shows that PBDEs have been rapidly accumulating in the environment of China, especially in the Southeast regions. This paper summarizes and critically reviews the published scientific data on PBDEs in China, including the levels of PBDEs in the air, soil, water, sediment, the terrestrial and marine organisms, and human samples in China. The data preliminarily reveal the state of PBDEs in China.

Levels, isomer profiles and chiral signatures of particle-bound hexabromocyclododecanes in ambient air around Shanghai, China

Hexabromocyclododecanes (HBCDs) have been considered candidate persistent organic pollutants, however, environmental data on their presence in China, a major world market, are limited. In this study, airborne particle-bound HBCDs in Shanghai, China were quantified with liquid chromatography-tandem mass spectrometry, and their total concentrations varied from 3.21 to 123 pg/m(3). The industrial area showed about three times higher HBCD levels than the urban areas. Gamma-HBCD dominated in particle-associated HBCDs in the industrial area, while α-HBCD was the major diastereomer of the urban areas, which is quite different from the pattern of technical products. Besides α-, β- and γ-HBCDs, δ-HBCD was also detected in all samples (0.09-6.31 pg/m(3)), while no ɛ-HBCD was found. Airborne β- and γ-HBCDs were racemic in most studied areas due to their chiral signatures showing no significant difference from commercial mixture. Fractions of (+)-α-HBCD (0.417-0.467), however, suggested the enrichment of (-)-α-HBCD and the involvement of enantioselective bioprocesses.