Temporal trends of "old" and "new" persistent halogenated organic pollutants in fish from the third largest freshwater lake in China during 2011-2018 and the associated health risks

A nationwide characterization of organochlorine pesticides (OCPs) in livestock and poultry food products across China: Residual levels, origin and the associated health risks

Organochlorine pesticides (OCPs) are still occurring in various foodstuffs after the ban on their use. However, it remains unclear concerning the contamination source of OCPs in livestock and poultry food products and associated health risks. To fill this gap, we characterized the residual levels of 19 OCPs in multiple types of meats and eggs, which were sampled across China within the same period. Dichlorodiphenyltrichloroethanes (DDTs) were dominant in eggs, with the mean levels being 0.76 and 2.03 μg/kg for chicken eggs and duck eggs, respectively. By contrast, hexachlorocyclohexanes (HCHs) were the top one OCP in beef and lamb, with its mean levels being 0.51 and 0.65 μg/kg, respectively. Hexachlorobenzene (HCB) was rather detected in the poultry products. The componential ratio analysis implicated recent inputs of several banned OCPs including technical HCH and DDT, HCB and aldrin in multiple regions, which may origin from local industrial activities or possible illegal use. Risk assessment based on the risk quotient method suggested that daily consumption of cooked meats and eggs contaminated by dieldrin may pose a carcinogenic risk in adult residents of Jiangsu province. We concluded that OCPs remain present in meats and eggs at levels of health concern regionally in China.

A review of occurrence, bioaccumulation, and fate of novel brominated flame retardants in aquatic environments: A comparison with legacy brominated flame retardants

Novel brominated flame retardants (NBFRs) have been developed as replacements for legacy brominated flame retardants (BFRs) such as polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecanes (HBCDs). The prevalence of NBFRs in aquatic environments has initiated intense concerns that they resemble to BFRs. To comprehensively elucidate the fate of NBFRs in aquatic environments, this review summarizes the physico-chemical properties, distribution, bioaccumulation, and fates in aquatic environments. 1,2-bis(2,3,4,5,6-pentabromophenyl) ethane (DBDPE) as the major substitute for PBDEs is the primary NBFR. The release from industrial point sources such as e-waste recycling stations is the dominant way for NBFRs to enter the environment, which results in significant differences in the regional distribution of NBFRs. Sediment is the major sink of NBFRs attributed to the high hydrophobicity. Significantly, there is no decreasing trend of NBFRs concentrations, while PBDEs achieved the peak value in 1970-2000 and decreased gradually. The bioaccumulation of NBFRs is reported in both field studies and laboratory studies, which is regulated by the active area, lipid contents, trophic level of aquatic organisms, and the log KOW of NBFRs. The biotransformation of NBFRs showed similar metabolism patterns to that of BFRs, including debromination, hydroxylation, methoxylation, hydrolysis, and glycosylation. In addition, NBFRs show great potential in trophic magnification along the aquatic food chain, which could pose a higher risk to high trophic-level species. The passive uptake by roots dominates the plant uptake of NBFRs, followed by acropetal and basipetal bidirectional transportation between roots and leaves in plants. This review will provide the support to understand the current pollution characteristics of NBFRs and highlight perspectives for future research.

Novel ultrasound assisted extraction and d-SPE clean-up for the analysis of multiple legacy and emerging organic contaminants in edible fish

Polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), novel brominated flame retardants (NBFRs), phthalate esters (PAEs) are pervasive environmental pollutants, posing threats to both ecosystems and human health. Although several analytical methods were developed for these compounds, they are not performed simultaneously. This study addresses the need for a sustainable, novel, analytical approach capable of simultaneously determining these diverse chemical classes in edible fish muscles. Employing ultrasound extraction coupled with dispersive solid-phase extraction (d-SPE) as a cleanup procedure, the method was compared to conventional techniques, revealing significant improvements. Analytical parameters were thoroughly assessed, and the innovative method demonstrated notable advantages, reducing extraction and purification times by approximately 74-80 % and solvent consumption by around 94-97 %. Applied to Mediterranean Sea fish samples, the results underscore the method's potential as a viable, sustainable alternative to traditional approaches, promising enhanced efficiency and reduced environmental impact.

Health risk assessment and development of human health ambient water quality criteria for PCBs in Taihu Basin, China

Polychlorinated biphenyls (PCBs) are a class of typical persistent organic pollutants (POPs) with carcinogenicity and extensively found in diverse environmental mediums. The Taihu Basin is one of the most economically developed regions in China, and it has also caused a lot of historical legacy and unconscious emissions of PCBs, posing a threat to the health of people in the region. This study counted the concentrations of PCBs in five environmental media (water, soil, air, dust, and food) in the Taihu Basin from 2000 to 2020 and used Monte Carlo simulation to simulate the multi-channel exposure of PCBs in people of different ages (children, teenagers, and adults), and evaluated their noncarcinogenic and carcinogenic health risks. Finally, the human health ambient water quality standards (AWQC) for PCBs were obtained using regional exposure parameters and bioaccumulation factors. The results showed that the pollution of PCBs in the Taihu Basin was relatively serious in China. The concentration of PCBs in dust is higher than other environmental media. And exposure to water and food is the main exposure pathway for PCBs in the population of the region. Besides, PCBs pose no noncarcinogenic risk to people in this region, but their carcinogenic risk to residents exceeds the safety threshold. Among the three population groups, adults have the highest risk of cancer, and prevention measures need to be taken by controlling the intake of related foods and the concentration of PCBs in water. The following human health AWQC values of the PCBs in Taihu Basin is 3.2 × 10-9 mg/L.

Comprehensive characterization and prioritization of halogenated organic compounds in fish and their implications for exposure

Fish are an important pollution indicator for biomonitoring of halogenated organic compounds (HOCs) in aquatic environments, and HOCs in fish may pose health threats to consumers. This study performed nontarget and comprehensive analyses of HOCs in fish from an e-waste recycling zone by gas chromatography-high-resolution mass spectrometry, and further prioritized their human exposure risks. A total of 1652 formulas of HOCs were found in the fish, of which 1222, 117, and 313 were organochlorines, organobromines, and organochlorine-bromines, respectively. The total concentrations of HOCs were 15.4-18.7 μg/g (wet weight), and organobromines were the predominant (14.1-16.8 μg/g). Of the HOCs, 41 % were elucidated with tentative structures and divided into 13 groups. The estimated total daily exposures of HOCs via dietary consumption of the fish for local adult residents were 3082-3744 ng/kg bw/day. The total exposures were dominated by several groups of HOCs with the following contribution order: polyhalogenated biphenyls and their derivatives > polyhalogenated diphenyl ethers > halo- (H-)alkanes/olefines > H-benzenes > H-dioxins > H-polycyclic aromatic hydrocarbons > H-phenols. The comprehensive characterization and prioritization results provide an overview of the species and distributions of HOCs in edible fish, and propose an inventory of crucial HOCs associated with high exposure risks.

Review of scientific literature on available methods of assessing organochlorine pesticides in the environment

Organochlorine pesticides (OCPs) are persistent organic pollutants (POPs) widely used in agriculture and industry, causing serious health and ecological consequences upon exposure. This review offers a thorough overview of OCPs analysis emphasizing the necessity of ongoing work to enhance the identification and monitoring of these POPs in environmental and human samples. The benefits and drawbacks of the various OCPs analysis techniques including gas chromatography-mass spectrometry (GC-MS), gas chromatography-electron capture detector (GC-ECD), and liquid chromatography-mass spectrometry (LC-MS) are discussed. Challenges associated with validation and optimization criteria, including accuracy, precision, limit of detection (LOD), and limit of quantitation (LOQ), must be met for a method to be regarded as accurate and reliable. Suitable quality control measures, such as method blanks and procedural blanks, are emphasized. The LOD and LOQ are critical quality control measure for efficient quantification of these compounds, and researchers have explored various techniques for their calculation. Matrix interference, solubility, volatility, and partition coefficient influence OCPs occurrences and are discussed in this review. Validation experiments, as stated by European Commission in document SANTE/11813/2017, showed that the acceptance criteria for method validation of OCP analytes include ≤20 % for high precision, and 70-120 % for recovery. This may ultimately be vital for determining the human health risk effects of exposure to OCP and for formulating sensible environmental and public health regulations.

Short-chain fatty acids facilitated long-term dechlorination of PCBs in Taihu Lake sediment microcosms: Evidence from PCB congener and microbial community analyses

Microbial reductive dechlorination hosts great promise as an in situ bioremediation strategy for polychlorinated biphenyls (PCBs) contamination. However, the slow dechlorination in sediments limits natural attenuation. Short-chain fatty acids, as preferred carbon sources and electron donors for dechlorinating microorganisms, might stimulate PCB dechlorination. Herein, two sets of short-chain fatty acids, sole acetate and a fatty acid mixture (acetate, propionate, and butyrate), were amended periodically into Taihu Lake (China) sediment microcosms containing nine PCB congeners (PCB5, 12, 64, 71, 105, 114, 149, 153, and 170) after 24 weeks of incubation. Short-chain fatty acids facilitated the long-term PCB dechlorination and the promoting effect of the fatty acid mixture compared favorably with that of sole acetate. By the end of 108 weeks, the total PCB mass concentrations in acetate amended and fatty acid mixture amended microcosms significantly declined by 7.6% and 10.3% compared with non-amended microcosms (P < 0.05), respectively. Short-chain fatty acids selectively favored the removal of flanked meta and single-flanked para chlorines. Notably, a rare ortho dechlorination pathway, PCB25 (24-3-CB) to PCB13 (3-4-CB), was enhanced. Supplementary fatty acids significantly increased reductive dehalogenases (RDase) gene pcbA5 instead of improving the growth of Dehalococcoides. These findings highlight the merits of low cost short-chain fatty acids on in situ biostimulation in treating PCBs contamination.

Biomonitoring, exposure routes and risk assessment of chlorinated paraffins in humans: a mini-review

Chlorinated paraffins (CPs), which were conventionally classified into short- (SCCPs), medium- (MCCPs) and long- (LCCPs) chain CPs, have received growing attention due to their wide usage and extensive detection in environmental samples and biota. The number of studies regarding the biomonitoring of CPs in human beings increased rapidly and their health risk gained great concern. This review summarized their occurrence and homologue patterns in human matrices including blood/serum, placenta, cord serum and breast milk. As the production and usage of SCCPs was progressively banned after being listed in Annex A of the Stockholm Convention, the production of MCCPs and LCCPs was stimulated. Accordingly, the ratio of MCCPs/SCCPs in human samples has increased rapidly in the last 5 years. The current understanding of exposure routes and risk assessments of CPs was also reviewed. Oral dietary intake is the most predominant source of daily CP intake, but dust ingestion, inhalation and dermal exposure is also nonnegligible, especially for MCCPs and LCCPs. Furthermore, the reported upper bound of the estimated daily intakes (EDIs) in various risk assessment studies was close to or exceeded the tolerable daily intakes (TDIs). Considering the bioaccumulation and long-lasting exposure of CPs, their health impacts on humans and the ecosystem required continuous monitoring and evaluation.

The potential health risks of short-chain chlorinated paraffin: A mini-review from a toxicological perspective

Short-chain chlorinated paraffins (SCCPs) are ubiquitously distributed in various environmental matrics due to their wide production and consumption globally in the past and ongoing production and use in some developing countries. SCCPs have been detected in various human samples including serum, milk, placenta, nail, and hair, and internal SCCP levels were found to be positively correlated with biomarkers of some diseases. While the environmental occurrence has been reported in a lot of studies, the toxicity and underlying molecular mechanisms of SCCPs remain largely unknown. The current tolerable daily intakes (TDIs) recommended by the world health organization/international programme on chemical safety (WHO/IPCS, 100 μg/kg bw/d) and the UK Committee on Toxicity (COT, 30 μg/kg bw/d) were obtained based on a no observed adverse effect level (NOAEL) of SCCP from the repeated-dose study (90 d exposure) in rodents performed nearly 40 years ago. Importantly, the health risks assessment of SCCPs in a variety of studies has shown that the estimated daily intakes (EDIs) may approach and even over the established TDI by UK COT. Furthermore, recent studies revealed that lower doses of SCCPs could also result in damage to multiple organs including the liver, kidney, and thyroid. Long-term effects of SCCPs at environmental-related doses are warranted.

Legacy and novel brominated flame retardants in agricultural soils of eastern China (2011-2021): Concentration level, temporal trend, and health risk assessment

Polybrominated diphenyl ethers (PBDEs) and novel brominated flame retardants (NBFRs) have been extensively investigated in the terrestrial environment of China. However, little is known about how PBDEs and NBFRs burdens in agricultural soils altered over time. In this study, agricultural soils from different regions of China were collected from 2011 to 2021 to investigate the contamination levels and temporal variation of PBDEs and NBFRs. The concentrations of ∑₂₆PBDEs and ∑₅NBFRs ranged from 0.144 to 215 ng/g dry weight (d.w.) and 0.186-144 ng/g (d.w.), with a mean value of 9.27 ng/g (d.w.) and 8.22 ng/g (d.w.), respectively. Among PBDEs and NBFRs, BDE-209 and decabromodiphenylethane (DBDPE) were the most predominant compounds. The PBDE concentrations did not vary significantly during the past decade, whereas the lower brominated congeners increased with time (doubling times ranged from 5.46 to 8.56 years). Meanwhile, NBFR concentrations increased over time, with concentrations significantly higher in 2021, 2016, and 2013 than in 2011 (p < 0.05). Additionally, DBDPE, 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), and hexabromobenzene (HBB) had doubling times of 6.84, 11.2, and 7.37 years, respectively. Total organic matter (TOC) impacted the distribution and variation of PBDEs (particularly lower-brominated congeners), with soil organic matter (SOM)-sorption showing an increasing and then decreasing trend. Health risk assessment suggested that PBDEs and NBFRs did not pose non-carcinogenic risks to humans. Nevertheless, the long-term health risk of BFRs should be considered. Overall, this is the first study to comprehensively analyze the contamination burdens and temporal trends of PBDEs and NBFRs in Chinese agricultural soils over a long period, providing a fundamental basis for future BFR management.

Thin-layer chromatography coupled with HPLC-DAD/UHPLC-HRMS for target and non-target determination of emerging halogenated organic contaminants in animal-derived foods

In this study, a simple, solvent-saving, and sensitive method was established using high-performance liquid chromatography coupled with high-resolution mass spectrometry to quantitively determine 16 emerging halogenated organic contaminants (HOCs), including polyhalogenated carbazoles, halogenated phenols, and tetrabromobisphenol-A analogs, and to qualitatively identify non-target HOCs in animal-derived food samples. The sample extracts were physically frozen to remove most lipids and further purified by thin-layer chromatography according to the targets polarity. The method detection limit and method quantification limit of 16 HOCs were in the range of 0.003-9.168 and 0.010-30.601 ng·g-1 dry weight, respectively. The recoveries were within 69.1-111.0 %, the intra/inter-day precisions were 0.1-6.1 % and 0.1-6.7 %, and the matrix effects were between -12.1 and 10.8 %, all within the acceptable range. Finally, 16 HOCs were detected in nine actual samples in range of not detected-307.22 ng·g-1 dry weight. Moreover, five bromides and two chlorides were identified by using non-target analysis in animal-derived foods.

Temporal trends and health risks of organophosphorus flame retardants in fishes in Taihu Lake from 2013 to 2018

Organophosphorus flame retardants (OPFRs) are synthetic, physical additive flame retardants widely detected in the environment. To investigate the temporal trends of OPFRs in Taihu regions and the associated health risks from fish consumption, 150 fish samples of five species were collected from Taihu Lake in China from 2013 to 2018. Eight OPFRs were measured, having 2-ethylhexyl diphenyl phosphate (90.7%) and tris (1,3-dichloro-2 propyl) phosphate (21.5%) as the most and least frequently detected OPFRs, respectively. Among the eight OPFRs, tris (chloropropyl) phosphate concentration (446 pg/g, wet weight) was higher than others. The maximum cumulative concentration of the OPFRs (∑₈OPFRs) was observed in large icefish (1.69 × 10³ pg/g), while silver carp (841 pg/g) had the lowest. For the temporal trends, higher levels of ∑₈OPFRs (1.91 × 10³ pg/g) were detected in 2013 than in other years, although no significant change in the trend occurred over time. The estimated daily intake of OPFRs from large icefish consumption was 1.20 × 10³ pg/kg-bw/day, higher than that of other fish species. The Monte Carlo simulations showed that ≤0.3% of adults and children would suffer non-cancer health risks from OPFRs via fish consumption. This study provides the first data on temporal trends of OPFRs in Taihu Lake.

A large geographic-scale characterization of organochlorine pesticides (OCPs) in surface sediments and multiple aquatic foods of inland freshwater aquaculture ponds in China: Co-occurrence, source and risk assessment

Inland freshwater aquaculture ponds (IFAPs) represent the key component of the global lentic freshwater environment and are increasingly important for global aquaculture production, yet the occurrence of organochlorine pesticides (OCPs) in these pond systems remains largely unknown. Here, we characterized the residual concentrations of 19 individual OCPs in sediments and in cultured fish and crustacean species (crabs, shrimp, crayfish and lobster), which were on-spot sampled from the IFAPs at a large region-scale in China. The total OCP levels in sediments varied dramatically between regions. Crabs presented the greatest OCP contamination among the studied species. Dichlorodiphenyltrichloroethanes (DDTs) was the dominating contaminant in sediments and crabs and its stable degradation products 4,4'-DDE and 4,4'-DDD were co-occurrent between these two compartments. The diagnostic ratio analysis indicated fresh inputs of DDTs, lindane and aldrin in multiple regions, which may be resulted from agricultural soil erosion, surface runoff and local anthropogenic activities. Ecological impacts of these pesticides could be expected at some sites due to their levels in sediments above the risk level. Risk assessment based on the OCP levels corrected by the cooking loss revealed that daily consumption of the IFAPs-derived aquatic foods may pose carcinogenic risks in humans.

Perfluoroalkyl substances in freshwater and marine fish from northern Vietnam: Accumulation levels, profiles, and implications for human consumption

The accumulation profiles of nine perfluoroalkyl substances (PFASs) were determined in 95 muscle samples of seven freshwater (n = 65) and seven marine (n = 30) fish species collected in Northern Vietnam. In both groups of fish, perfluorooctane sulfonic acid (PFOS) was the most prevalent component, accounting for roughly 29 % of total PFASs. The total PFASs in freshwater fish species ranged from 0.08 to 8.06 ng/g wet weight (w.w), with the highest concentration found in topmouth culter (7.01 ± 1.23 ng/g w.w). In marine fish, the highest mean concentration of PFASs was detected in Asian sea bass (2.75 ± 0.54 ng/g, w.w). Estimation on the human dietary intake of PFASs from fish consumption resulted in hazard ratios (HR) ranging from 0.019 to 0.238 for freshwater fish and from 0.016 to 0.074 for marine fish, indicating low exposure risks associated with PFASs.

Brominated flame retardants (BFRs) in sediment from a typical e-waste dismantling region in Southern China: Occurrence, spatial distribution, composition profiles, and ecological risks

Our study evaluated the current occurrence, composition, and spatial distribution of eight congeners of polybrominated diphenyl ethers (PBDEs) and seven novel brominated flame retardants (NBFRs) in sediment from Guiyu, a typical e-waste dismantling region in China. PBDEs levels ranged from 0.345 to 401,000 ng/g dw and NBFRs levels ranged from 0.581 to 73,100 ng/g dw. Almost all sediment samples contained high levels of BDE-209 and DBDPE, and the ratio of DBDPE/BDE-209 in sediments ranged from 0.0814 to 2.80 (mean: 0.879). The concentration and composition profiles for BFRs in sediments from both mainstream and tributaries of two major rivers in Guiyu reach (and adjacent downstream locations) differed significantly from those far from Guiyu town. Whereas the high presence of BFRs in Guiyu reflected the historical crude e-waste dismantling activities in the region; the locations far from Guiyu town were likely to receive BFRs from atmospheric deposition, not originated from the region, as BFRs in water-sediment are known to be able to migrate a limited distance along the river. Ecological risk assessment revealed that the low brominated congeners of PBDEs and BDE-209 posed an unacceptable risk to the sedimentary life at multiple locations. Our results updated our knowledge of BFRs contamination in Guiyu, suggesting the necessity of continuous source monitoring, control procedures, and sediment cleanup for BFRs.

Spatiotemporal distribution and risk assessment of short-chain chlorinated paraffins in 30 major rivers in Taiwan

Because of their highly persistent, bioaccumulative and toxic properties, short-chain chlorinated paraffins (SCCPs) have become emerging contaminants and have been included in Annex A (elimination) of the Stockholm Convention since 2017. The contamination of SCCPs has been observed in the environment and biota worldwide but has not been detected in Taiwanese river ecosystems. Thus, this study aimed to determine the occurrence of SCCPs in sediments and fish from 30 major rivers in Taiwan and to evaluate the risk of SCCPs to river ecosystems and human health. The concentrations of SCCPs in sediments and fish ranged from ND (not detected) to 12.6 mg/kg dw and ND to 2.07 mg/kg ww, respectively. The concentrations of SCCPs in sediments were significantly correlated with some indicators of the discharge sources and water quality variables, indicating that SCCPs were released via human activities and various discharges into rivers and accumulated in sediments. The bioaccumulation of SCCPs in fish exhibited species-specific profiles and was related to environmental contamination levels and the living pattern and trophic level of the fish. The SCCP levels in sediments from 20 major rivers in Taiwan might pose a potential ecological risk to river ecosystems according to the criteria of the Federal Environmental Quality Guidelines in Canada, the biota-sediment accumulation factor and the risk quotient. Consumption of SCCP-contaminated river fish by different gender and age groups showed no significant health risk to residents in Taiwan evaluated by the estimated daily intake and hazard quotient. However, there was a health concern for the 0- to 3-year-old group due to the consumption of contaminated river fish at a bioaccessibility of 100% for SCCPs by the margin of exposure. Routine monitoring of SCCPs in river ecosystems is needed to protect aquatic organisms and human health.

Environmental contamination and human exposure of polychlorinated biphenyls (PCBs) in China: A review

Polychlorinated biphenyls (PCBs), together with 11 other organic compounds, were initially listed as persistent organic pollutants (POPs) by the Stockholm Convention because of their potential threat to ecosystems and humans. In China, many monitoring studies have been undertaken to reveal the level of PCBs in environment since 2005 due to the introduced stricter environmental regulations. However, there are still significant gaps in understanding the overall spatial and temporal distributions of PCBs in China. This review systematically discusses the occurrence and distribution of PCBs in environmental matrices, organisms, and humans in China. Results showed that PCB contamination in northern and southern China was not significantly different, but the PCB levels in East China were commonly higher than those in West China, which might have been due to the widespread consumption of PCBs and intensive human activities in East China. Serious PCB contamination was found in e-waste disassembling areas (e.g., Taizhou of Zhejiang Province and Qingyuan and Guiyu of Guangdong Province). Higher PCB concentrations were also chronicled in megalopolises and industrial clusters. The unintentionally produced PCBs (UP-PCBs) formed during industrial thermal processes may play an increasingly significant role in PCB pollution in China. Low PCB levels were recorded in rural and underdeveloped districts, particularly in remote and high-altitude localities such as the Tibetan Plateau and the South China Sea. However, these data are limited. Human exposure to PCBs is closely related to the characteristics of environmental pollution. This review also discusses existing issues and future research prospects on PCBs in China. For instance, the accumulation characteristics and migration regularities of PCBs in food webs should be further studied. More investigations should be undertaken to assess the quantitative relationship between external and internal exposure to PCBs. For example, bioaccessibility and bioavailability studies should be supplemented to evaluate human health risks more accurately.

Long-Term Dechlorination of Polychlorinated Biphenyls (PCBs) in Taihu Lake Sediment Microcosms: Identification of New Pathways, PCB-Driven Shifts of Microbial Communities, and Insights into Dechlorination Potential

Microbial reductive dechlorination of polychlorinated biphenyls (PCBs) is regarded as an alternative approach for in situ remediation and detoxification in the environment. To better understand the process of PCB dechlorination in freshwater lake sediment, a long-term (108 weeks) dechlorination study was performed in Taihu Lake sediment microcosms with nine parent PCB congeners (PCB5, 12, 64, 71, 105, 114, 149, 153, and 170). Within 108 weeks, the total PCBs declined by 32.8%, while parent PCBs declined by 84.8%. PCB dechlorinators preferred to attack meta- and para-chlorines, principally para-flanked meta and single-flanked para chlorines. A total of 58 dechlorination pathways were observed, and 20 of them were not in 8 processes, suggesting the broad spectrum of PCB dechlorination in the environment. Rare ortho dechlorination was confirmed to target the unflanked ortho chlorine, indicating a potential for complete dechlorination. PCBs drove the shifts of the microbial community structures, and putative dechlorinating bacteria were growth-linked to PCB dechlorination. The distinct jump of RDase genes ardA, rdh12, pcbA4, and pcbA5 was found to be consistent with the commencement of dechlorination. The maintained high level of putative dechlorinating phylum Chloroflexi (including Dehalococcoides and o-17/DF-1), genus Dehalococcoides, and four RDase genes at the end of incubation revealed the long-term dechlorination potential. This work provided insights into dechlorination potential for long-term remediation strategies at PCB-contaminated sites.

Legacy brominated flame retardants in human milk from the general population in Beijing, China: Biomonitoring, temporal trends from 2011 to 2018, and nursing infant's exposure assessment

Three kinds of legacy brominated flame retardants (BFRs), including eight polybrominated diphenyl ether (PBDE) congeners, tetrabromobisphenol A (TBBPA), and three hexabromocyclododecane (HBCDD) isomers, were analyzed in 105 human milk samples collected in 2018 from Beijing, China. The tested BFRs all showed high detection frequencies, and HBCDD was the most abundant BFR, with a median level of 7.64 × 10³ pg/g lipid, followed by BDE-153 (389 pg/g lipid), BDE-209 (283 pg/g lipid), and TBBPA (271 pg/g lipid). By comparing the results of the present study with those of our previous Beijing human milk surveys conducted in 2014 and 2011, the contamination of TBBPA and HBCDD increased steadily from 2011 to 2018, whereas that of PBDEs decreased sharply during this period. Our results suggested that the production and consumption of BFRs in China have shifted from PBDEs to other FRs. Education level and the consumption of animal-derived foods such as eggs and meat were identified as major influencing factors for some BFRs. For nursing infants, the median levels of lower bound BFR daily intake via human milk ingestion ranged from 4.62 × 10^-2 ng/kg bw/day for BDE-154 to 30.6 ng/kg bw/day for HBCDD. The daily intake of most BFRs by breastfeeding is unlikely to pose significant health risks for Beijing nursing infants. However, the minimum margin of exposure (MOE) of HBCDD was below its threshold value, which indicated that its daily intake might raise health concerns for some breastfed infants.

Occurrence, bioaccumulation, fate, and risk assessment of novel brominated flame retardants (NBFRs) in aquatic environments - A critical review

Novel brominated flame retardants (NBFRs), which have been developed as replacements for legacy flame retardants such as polybrominated diphenyl ethers (PBDEs), are a class of alternative flame retardants with emerging and widespread applications. The ubiquitous occurrence of NBFRs in the aquatic environments and the potential adverse effects on aquatic organisms have initiated intense global concerns. The present article, therefore, identifies and analyzes the current state of knowledge on the occurrence, bioaccumulation, fates, and environmental and health risks of NBFRs in aquatic environments. The key findings from this review are that (1) the distribution of NBFRs are source-dependent in the global aquatic environments, and several NBFRs have been reported at higher concentrations than that of the legacy flame retardants; (2) high bioaccumulative properties have been found for all of the discussed NBFRs due to their strong hydrophobic characteristics and weak metabolic rates; (3) the limited information available suggests that NBFRs are resistant to biotic and abiotic degradation processes and that sorption to sludge and sediments are the main fate of NBFRs in the aquatic environments; (4) the results of ecological risk assessments have indicated the potential risks of NBFRs and have suggested that source areas are the most vulnerable environmental compartments. Knowledge gaps and perspectives for future research regarding the monitoring, toxicokinetics, transformation processes, and development of ecological risk assessments of NBFRs in aquatic environments are proposed.

Potential health risk assessment of HFRs, PCBs, and OCPs in the Yellow River basin

The concentrations of PBDEs, NBFRs, DP, PCBs, and OCPs were analyzed in water samples of the Yellow River Basin (YRB) and in soil and maize samples collected from basin irrigation areas to understand the status of POPs and associated health risks. The results showed: (1) the congeners of eight PBDEs and seven NBFRs were detected in 10 tributaries, with average concentrations of 1575 and 4288 pg. L^-1. Thirty-three congeners of PCBs were detected, and the average concentration of PCB was 232 pg. L^-1. Five HCHs were the primary congeners among twenty-three congeners of OCPs in the ten tributaries, accounting for 79% of the total. The average concentration of OCPs was 8287 pg. L^-1. (2) Similar congeners of HFRs, PCBs, and OCPs were found in the trunk water. The ranking based on the HFR concentration was upstream > downstream > midstream, and that of the PCB and OCP concentration was downstream > upstream > midstream. (3) PCBs and OCPs in the trunk water of the YRB and in the soil and maize irrigated with river water pose potential carcinogenic and non-carcinogenic risks. The results indicate considerable organic pollution in the YRB, suggesting that national emission standards for POPs should be implemented soon.

Brominated flame retardants (BFRs) in PM2.5 associated with various source sectors in southern China

The present study investigates legacy and novel brominated flame retardants (BFRs) in atmospheric PM2.5 associated with various urban source sectors in a city and electronic waste (e-waste) recycling facilities in southern China. The concentrations of polybrominated diphenyl ethers (PBDEs) and novel BFRs (∑2NBFRs) at the urban industrial park (UIP) sites varied greatly from 22.0 to 105 pg m-3 and from to 29.7 to 459 pg m-3, respectively, and higher concentrations were generally found at sites involving industrial sectors of electronics, plastics, and machinery. Their spatial variations at other urban potential source sites were small suggesting a lack of strong point emissions. The levels of PBDEs and ∑2NBFRs at the e-waste facilities (220-2356 pg m-3 and 83.6-569 pg m-3) were significantly higher and did not temporally decline, indicating that improvement in e-waste recycling techniques does not significantly reduce emissions of PBDEs. NBFRs dominated the BFRs at the urban sites (55% on average), while PBDEs were still dominant (78%) at the e-waste sites. PBDE congener profiles in PM2.5 were substantially different from those in commercial mixtures. The congener profiles as well as their correlations suggested frequent formation of lower brominated PBDEs from degradation of highly brominated congeners in this region, which became appreciable due to the reduced emissions. The significant correlations among the lower brominated congeners also reflected similar environmental behaviors due to similar physicochemical properties.

A review of the transplacental transfer of persistent halogenated organic pollutants: Transfer characteristics, influential factors, and mechanisms

Persistent halogenated organic pollutants (HOPs) are a class of toxic chemicals, which may have adverse effects on fetuses via transplacental transfer from their mothers. Here, we review reported internal exposure levels of various HOPs (organochlorinated pesticides, polychlorinated biphenyls, polybrominated diphenyl ethers, short- and medium-chain chlorinated paraffins, and per- and poly-fluoroalkyl substances) in placenta, and both maternal and umbilical cord sera. We also present analyses of the transplacental transfer and placental distribution characteristics of each class of compounds, and discuss effects of several factors on the transfer and accumulation efficiencies of HOPs, as well as the main mechanisms of HOPs' transfer across the placental barrier. Reported compound-specific transplacental transfer efficiencies and distribution efficiencies, expressed as umbilical cord:maternal serum and placental:maternal serum concentration ratios (R_CM and R_PM, respectively), are summarized. Average published R_CM values of the HOPs range from 0.24 to 3.08 (lipid-adjusted) and from 0.04 to 3.1 (based on wet weights), and are highest for perfluoroalkylcarboxylates (PFCAs) and tetrabromobisphenol A. Average published R_PM values range from 0.14 to 1.02 (lipid-adjusted) and from 0.30 to 1.4 (based on wet weights). The broad R_CM and R_PM ranges may reflect effects of various factors, inter alia physicochemical properties of HOPs, metabolic capacities of mothers and fetuses, placental maturity, and differential expression of influx/efflux transporters in the placenta. Generally, HOPs' R_CM values decline linearly with molecular size, and are curvilinearly related to solubility. Plasma protein binding affinity and the difference between maternal and fetal metabolic capacities may also affect some HOPs' transfer efficiencies. HOPs' molecular size may be influential. Transplacental transport of HOPs likely occurs mostly through passive diffusion, although influx/efflux transporters expressed on maternal and/or fetal sides of the placenta may also facilitate or hinder their transport. Overall, the review highlights clear gaps in our understanding of mechanisms involved in HOPs' transplacental transport.