Concentrations and trophic interactions of novel brominated flame retardants, HBCD, and PBDEs in zooplankton and fish from Lake Maggiore (Northern Italy)

Contamination characteristics and dietary intake risk of brominated flame retardants in fishes around a typical e-waste dismantling site in Southern China

Polybrominated diphenyl ethers (PBDEs) and their substitutes, novel brominated flame retardants (NBFRs), are ubiquitously present in the aquatic environment of electronic waste (e-waste) dismantling region, leading to their inevitable absorption and accumulation by aquatic organisms, which can be transferred to human via directly aquatic product consumption or through food chain, thereby posing potential health risks. This study focused on fish samples from Guiyu and its surrounding areas, and found the total PBDEs concentrations were 24-7400 ng/g lw (mean: 1800 ng/g lw) and the total NBFRs concentrations were 14 to 2300 ng/g lw (mean: 310 ng/g lw). Significant positive correlations were found among PBDE congeners, among different NBFRs, and between NBFRs and commercial PBDEs that they replace. ΣPBDEs and ΣNBFRs in the intestine were 620-350,000 and 91-81,000 ng/g lw (mean: 83000 and 12,000 ng/g lw, respectively), significantly exceeding those in the gills, where ΣPBDEs and ΣNBFRs were 14-37,000 and 39-45,000 ng/g lw (mean: 9200 and 2400 ng/g lw, respectively). The ΣPBDEs and ΣNBFRs showed no non-carcinogenic risks to the target population through dietary intake. Despite the significantly higher daily intake of decabromodiphenyl ethane (DBDPE) compared to decabromodiphenyl ether (BDE209), the non-carcinogenic risk associated with BDE209 remained higher than that of DBDPE. Our findings can assist researchers in understanding the presence of BFRs in aquatic organisms, inhabiting e-waste dismantling areas, and in evaluating the associated health risks posed to humans through dietary exposure.

Distribution and biomagnification of Hexabromocyclododecanes (HBCDs) in edible marine fish in the Beibu Gulf, China: Implication for seafood dietary risk

Hexabromocyclododecanes (HBCDs) are legacy additive brominated flame retardant. In present study, the distribution, biomagnification and potential human health risk associated with HBCDs were investigated in six edible marine fish species collected from three bays in the Beibu Gulf, China, between March and October 2021. The concentration of HBCDs ranged from 0.05 to 200 ng/g lipid weight (lw), with Scoliodon laticaudus and Trichiurus nanhaiensis having the highest and lowest concentration, respectively. The α-HBCD was dominant in most studied fish, expect for Scoliodon laticaudus. Dietary source was the primary factor for the diastereomeric profiles of HBCDs in fish. Only γ-HBCD demonstrated trophic magnification in the studied fish species. Finally, the estimated daily intake (EDI) was 0.18 ng/kg/day for adults, 0.17 ng/kg/day for teenager and children, and all corresponding margin of exposure (MOE) values were lager than 8 indicating relatively low human exposure risks from fish consumption.

Species-specific and habitat-dependent bioaccumulation of halogenated flame retardants in marine organisms from estuary to coastal seas

Halogenated flame retardants (HFRs) have attracted global attention owing to their adverse effects on ecosystems and humans. The Shandong Peninsula is the largest manufacturing base for HFRs in East Asia, yet its impacts on marine ecosystems are unclear. Seventeen HFRs were analyzed in organisms captured from the Xiaoqing River estuary, Bohai Sea (BS), Yellow Sea and Northern East China Sea to investigate the distribution and bioaccumulation of HFRs on a broad scale. The results showed a downward trend in ΣHFR concentrations from the estuary (37.7 ng/g lw on average) to Laizhou Bay (192 ng/g lw) and to coastal seas (3.13 ng/g lw). The concentrations of ΣHFRs were significantly higher in demersal fish (0.71-198 ng/g lw) and benthic invertebrates (0.81-3340 ng/g lw) than in pelagic fish (0.30-27.6 ng/g lw), reflecting a habitat dependence. The concentrations of higher-brominated homologs were greater in benthic invertebrates, whereas a greater level of lower-brominated PBDE congeners was observed in fish, suggesting different profiles between species. Furthermore, the analogue composition of HFRs in fish was similar to that in the dissolved phase of seawater, whereas the HFR pattern in benthic invertebrates was consistent with the profile in sediment. The concentrations of HFRs in organisms vary widely depending on emissions from anthropogenic activities, whereas bioaccumulation patterns are strongly influenced by species and habitat.

Bioaccumulation and biotransformation of 1,2-bis (2,4,6-tribromophenoxyethane) (BTBPE) and 1,2-dibromo-4-(1,2-dibromoethyl)-cyclohexane (TBECH) in zebrafish (Danio rerio)

Despite the increasing production, use, and ubiquitous occurrence of novel brominated flame retardants (NBFRs), little information is available regarding their fate in aquatic organisms. In this study, the bioaccumulation and biotransformation of two typical NBFRs, i.e., 1,2-bis (2,4,6-tribromophenoxyethane) (BTBPE) and 1,2-dibromo-4-(1,2-dibromoethyl)-cyclohexane (TBECH), were investigated in tissues of zebrafish (Danio rerio) being administrated a dose of target chemicals through their diet. Linear accumulation was observed for both BTBPE and TBECH in the muscle, liver, gonads, and brain of zebrafish, and the elimination of BTBPE and TBECH in all tissues followed pseudo-first-order kinetics, with the fastest depuration rate occurring in the liver. BTBPE and TBECH showed low bioaccumulation potential in zebrafish, with biomagnification factors (BMFs) < 1 in all tissues. Individual tissues' function and lipid content are vital factors affecting the distribution of BTBPE and TBECH. Stereoselective accumulation of TBECH enantiomers was observed in zebrafish tissues, with first-eluting enantiomers, i.e. E1-α-TBECH and E1-β-TBECH, preferentially accumulated. Additionally, the transformation products (TPs) in the zebrafish liver were comprehensively screened and identified using high-resolution mass spectrometry. Twelve TPs of BTBPE and eight TPs of TBECH were identified: biotransformation pathways involving ether cleavage, debromination, hydroxylation, and methoxylation reactions for BTBPE and hydroxylation, debromination, and oxidation processes for TBECH. Biotransformation is also a vital factor affecting the bioaccumulation potential of these two NBFRs, and the environmental impacts of NBFR TPs should be further investigated in future studies. The findings of this study provide a scientific basis for an accurate assessment of the ecological and environmental risks of BTBPE and TBECH.

Trophodynamics of halogenated organic pollutants (HOPs) in aquatic food webs

Halogenated organic pollutants (HOPs) represent hazardous and persistent compounds characterized by their capacity to accumulate within organisms and endure in the environment. These substances are frequently transmitted through aquatic food webs, engendering potential hazards to ecosystems and human well-being. The trophodynamics of HOPs in aquatic food webs has garnered worldwide attention within the scientific community. Despite comprehensive research endeavors, the prevailing trajectory of HOPs, whether inclined toward biomagnification or biodilution within global aquatic food webs, remains unresolved. Furthermore, while numerous studies have probed the variables influencing the trophic magnification factor (TMF), the paramount determinant remains elusive. Collating a compendium of pertinent literature encompassing TMFs from the Web of Science between 1994 and 2023, our analysis underscores the disparities in attention accorded to legacy HOPs compared to emerging counterparts. A discernible pattern of biomagnification characterizes the behavior of HOPs within aquatic food webs. Geographically, the northern hemisphere, including Asia, Europe, and North America, has demonstrated greater biomagnification than its southern hemisphere counterparts. Utilizing a boosted regression tree (BRT) approach, we reveal that the food web length and type emerge as pivotal determinants influencing TMFs. This review provides a valuable basis for gauging ecological and health risks, thereby facilitating the formulation of robust standards for managing aquatic environments.

The effects and mechanisms of the new brominated flame retardant BTBPE on thyroid toxicity

As an alternative to octabromodiphenyl ether (octa-BDE), 1, 2-bis (2,4, 6-tribromophenoxy) ethane (BTBPE) has been widely used in a variety of combustible materials, such as plastics, textiles and furniture. Previous studies have demonstrated the thyroid toxicity of traditional brominated flame retardants for example octa-BDE clearly. Nevertheless, little is known about the thyroid toxicity of alternative novel brominated flame retardants BTBPE. In this study, it was demonstrated that BTBPE in vivo exposure induced FT4 reduction in 2.5, 25 and 250 mg/kg bw treated group and TT4 reduction in 25 mg/kg bw treated group. TG, TPO and NIS are key proteins of thyroid hormone synthesis. The results of Western blot and RT-PCR from thyroid tissue showed decreased protein levels and gene expression levels of TG, TPO and NIS as well as regulatory proteins PAX8 and TTF2. To investigate whether the effect also occurred in humans, anthropogenic Nthy-ori 3-1 cells were selected. Similar results were seen in vitro condition. 2.5 mg/L BTBPE reduced the protein levels of PAX8, TTF1 and TTF2, which in turn inhibited the protein levels of TG and NIS. The results in vitro experiment were consistent with that in vivo, suggesting possible thyrotoxic effects of BTBPE on humans. It was indicated that BTBPE had the potential interference of T4 generation and the study provided more evidence of the effects on endocrine disorders.

Zooplankton as Mercury Repository in Lake Maggiore (Northern Italy): Biomass Composition and Stable Isotope Analysis

Total mercury (THg) and methylmercury (MeHg) concentrations were analyzed in zooplankton (≥450 and ≥850 µm size fractions) collected seasonally over 6 years in Lake Maggiore (Northern Italy), characterized by a legacy mercury contamination. Analysis of δ 15N and δ13C stable isotopes was carried out to trace how taxa with different trophic levels and carbon sources contributed to mercury concentrations and trends. THg ranged between 44–213 µg kg−1 d.w. and MeHg 15–93 µg kg−1 d.w., representing 24–61% of THg. Values showed strong seasonal variations, with peaks in winter, due to the high biomass of predator taxa (Bythotrephes longimanus, Leptodora kindtii) and of Daphnia longispina-galeata gr. A positive correlation between THg and MeHg and δ15N signature was observed. D. longispina-galeata gr. prevailed in both size fractions, substantially contributing to THg and MeHg concentrations. Δ13C signature was strictly bound to lake thermal circulation dynamics. Mercury stock in the zooplankton compartment ranged between 19–140 ng THg m−2 and 6–44 ng MeHg m−2 for the ≥450 µm size fraction and between 2–66 ng THg m−2 and 1–7 ng MeHg m−2 for the ≥850 µm fraction, with the highest values in spring when zooplanktivorous fish actively prey in the pelagic zone. The results highlighted the crucial role of zooplankton as a repository of mercury, easily available to higher trophic levels.

Significance of biotransformation and excretion on the enantioselective bioaccumulation of hexabromocyclododecane (HBCDD) in laying hens and developing chicken embryos

Although (-)-α-hexabromocyclododecane (HBCDD) and (+)-γ-HBCDD are preferentially enriched in chickens, the key factors contributing to their selective bioaccumulation in hens and their potential biotransformation in developing chicken embryos remain unclear. Herein, in vivo and in ovo exposure experiments using hens and fertilized eggs were conducted to investigate the absorption, excretion, and biotransformation of HBCDDs in chickens. γ-HBCDD (76%) exhibited a higher absorption efficiency than α- (22%) and β- (69%) HBCDDs. However, α-HBCDD was dominant in hen tissues, although γ-HBCDD accounted for >75% in the spiked feed. Moreover, chicken embryos biotransformed approximately 9.5% and 11.7% of absorbed α- and γ-HBCDDs, respectively, implying that diastereomer-selective elimination causes the predominance of α-HBCDD in hens. The concentration and enantiomer fraction (EF) of α-HBCDD in laid eggs were significantly positively correlated, suggesting enantioselective elimination. The EFs of α- and γ-HBCDDs varied between feces from the exposure and depuration periods, indicating the preferred excretion of (+)-α- and (-)-γ-HBCDDs. Furthermore, the enantioselective biotransformation of (-)-γ-HBCDD was confirmed in developing chicken embryos. These results show that excretion and biotransformation contribute to the diastereomer- and enantiomer-selective bioaccumulation of HBCDDs in chickens; The results may improve our understanding of the environmental fate and ecological risks of HBCDDs in biota.

Risk Characterization and Benefit-Risk Assessment of Brominated Flame Retardant in Commercially Exploited Freshwater Fishes and Crayfish of Lake Trasimeno, Italy

Among brominated flame retardants (BFRs), polybrominateddiphenyl ethers (PBDEs) and hexabromocyclododecanes (HBCDs) were the most widely used in past decades. BFRs not being chemically bonded to polymers means they can easily leach from the products into the environment and bioaccumulate. Humans are exposed to flame retardants mainly through food consumption, especially fish and fish products. In the present study, the occurrence of PBDEs and HBCDs in freshwater fishes and crayfish from Lake Trasimeno (Umbria region, central Italy) was assessed according to monitoring plans recommended by European competent authorities. The dietary exposure of the central Italian population to such molecules was calculated, and the risk characterization and the benefit–risk evaluation were also assessed. A total of 90 samples were analyzed by means of gas and liquid chromatography associated with triple quadrupole mass spectroscopy. A total of 51% of samples were found positive for at least one of the congeners; the most frequently found molecule was BDE-47. The data on dietary exposure ranged from 0.138 to 1.113 pg/kg body weight/day for ∑PBDE and from 0.805 to 0.868 pg/kg body weight/day for ∑HBCD. The data show no health risks for the central Italian population consuming freshwater fish products from Lake Trasimeno in relation to exposure to PBDE and HBCD.

BFRs (PBDEs and HBCDs) in freshwater species from Lake Trasimeno (Italy): The singular case of HBCDs in red swamp crayfish

Eighty-six samples belonging to five different species (crucian carp, Carassius carassius; European perch, Perca fluviatilis; tench, Tinca tinca; eel, Anguilla anguilla; red swamp crayfish, Procambarus clarkii) collected from Lake Trasimeno (Italy) were analyzed to assess polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecanes (HBCDs) contamination. The Trasimeno is the largest Italian peninsular lake located in Umbria (Central Italy), in a rural area with low anthropogenic impact. All the samples were analyzed by an in-house developed analytical procedure involving a single sample preparation with dual detection: Gas- and Liquid-Chromatography coupled to tandem Mass Spectrometry (GC-MS/MS for PBDEs and LC-MS/MS for HBCDs). BFRs levels in crucian carp, tench and European perch were negligible and mostly below quantification limits (LOQs). In eel, the species with the higher fat content, PBDE sum (15 congeners) ranged from 0.269 to 0.916 ng/g w.w. BDE-47, -100 and -154 accounted for roughly 57%, 16% and 11% of the PBDE sum, respectively, while BDE-99 (usually one of the most abundant congeners in biota), only for 3%. HBCDs (sum of α-, β-, γ-isomers) were found between 0.157 and 1.14 ng/g w.w. with α- as predominant isomer (92% of the sum), followed by γ- (5%) and β- (2%). Peculiar was the contamination in red swamp crayfish characterized by negligible PBDEs and very high HBCDs levels with a singular contamination pattern. In female pools (n = 9) the mean HBCDs sum was 0.150 ng/g w.w., while in males higher concentrations were measured (mean = 2.77 ng/g w.w.). A significant correlation seems to exist between the contamination level and the seasonal cycle only in male crayfish. Interestingly, among the HBCDs, the γ-isomer was the highest (67% of the total) while α- contributes only for 20%.

Brominated flame retardants and heavy metals in common aquatic products from the pearl river delta, south china: Bioaccessibility assessment and human health implications

Aquatic products are an important source of environmental pollutants to humans. This study was conducted to assess the bioaccessibility of selected brominated flame retardants and heavy metals in common aquatic products from the Pearl River Delta, South China, as well as associated human health risks. Based on a questionnaire survey, ten of the most consumed aquatic products were collected from local markets. The bioaccessibility of polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCDDs), and heavy metals was assessed using an in vitro gastrointestinal model. Bioaccessibility of heavy metals (33.0-84.0%) and HBCDDs (38.5-68.4%) was significantly higher than that of PBDEs (13.4-65.4%). Total non-carcinogenic and carcinogenic risks from heavy metal consumption were much higher than the threshold values due to excessive abundances of arsenic in shellfish (HQ = 2.45, CR = 1.1 ×10^-3). Furthermore, middle-aged populations and females were subjected to greater health risks due to different intakes of aquatic products among age and gender groups. Significant difference in bioaccessibility among analytes indicated that bioaccessibility of pollutants is non-negligible in health risk assessment. This is the first study systematically investigating health risks of aquatic products consumption and concludes that shellfish is a great cause for concern for the PRD residents.

Legacy and alternative halogenated flame retardants in Lake Geneva fish

Legacy (i.e., polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCDD)) and alternative halogenated flame retardants (HFRs) were analyzed in 31 whole fish samples from Lake Geneva in 2018. Two fish species, namely, the burbot (Lota lota) and the roach (Rutilus rutilus), were selected, hypothetically representing different habitats, feeding behaviors, and different metabolic capacities. Roach (N = 20) and burbot (N = 11) displayed similar size and mass, but the latter species was overall leaner than the former. The sum of individual PBDE concentrations (0.54-9.86 ng g^-1 wet weight (ww)) was similar in both species, but the respective molecular profiles suggested contrasted metabolic capacities. HBCDD sum of isomer concentrations ranged from non-detected to 3.477 ng g^-1 (ww), also similar in both species. Both PBDEs and HBCDD levels were far below the threshold that indicates a risk to fish predators. Referring to previous surveys, which involved a wider range of species, PBDE concentrations have declined or are stable. HBCDD concentrations remained low, despite the PBDE ban, which could have fostered the consumption of other HFRs. The occurrence of alternative HFRs was also low for most compounds analyzed. Only dechloranes and decabromodiphenyl ethane (DBDPE) had detection rates above 50%. Dechloranes spanned a concentration range between 5 and 10 times the quantification limits (0.002 to 0.005 ng g^-1 wet weight), lower than DBDPE (< 0.005 to 2.89 ng g^-1 wet weight). Quality standards targeting biota are currently missing for these emerging chemicals.

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

The study aimed to investigate temporal trends of "old" and "new" persistent halogenated organic pollutants (HOPs) in Taihu Lake, the third largest freshwater lake in China, and the associated health risks. Five fish species were consecutively collected from the lake every year during 2011-2018. HOPs including 37 polychlorinated biphenyls (PCBs), 10 organochlorine pesticides (OCPs), short- and medium-chain chlorinated paraffins (SCCPs and MCCPs), 19 polybrominated diphenyl ethers (PBDEs), and 10 new brominated flame retardants (NBFRs), were measured. The results showed that all the HOPs were detected, with MCCPs and NBFRs showing the highest and lowest concentrations, respectively. The levels of SCCPs and MCCPs were several orders of magnitude higher than those of the other HOPs. There were obvious increasing trends for SCCPs, MCCPs, and hexachlorobenzene, but a decreasing trend for PBDEs. No obvious increasing or decreasing trends were observed for the other HOPs. The present study indicated that the use of NBFRs to replace PBDEs was not yet clearly observed. Fish consumption did not result in non-carcinogenic risks, but posed low carcinogenic risks, with PCBs and DDTs being the highest-risk contaminants because of historical residues. This is the first study for the temporal variations of the HOPs in the lake.

Climate warming restructures an aquatic food web over 28 years

Climate warming can restructure lake food webs if trophic levels differ in their thermal responses, but evidence for these changes and their underlying mechanisms remain scarce in nature. Here we document how warming lake temperatures by up to 2°C, rather than changes in trophic state or fishing effort, have restructured the pelagic food web of a large European lake (Lake Maggiore, Italy). Our approach exploited abundance and biomass data collected weekly to yearly across five trophic levels from 1981 to 2008. Temperature generally had stronger effects on taxa than changes in fish predation or trophic state mediated through primary productivity. Consequently, we found that, as the lake warmed, the food web shifted in numerical abundance towards predators occupying middle trophic positions. Of these taxa, the spiny water flea (Bythotrephes longimanus) most prospered. Bythotrephes strongly limited abundances of the keystone grazer Daphnia, strengthening top-down structuring of the food web. Warmer temperatures partly restructured the food web by advancing peak Bythotrephes densities by approximately 60 days and extending periods of positive population growth by three times. Nonetheless, our results suggested that advances in the timing and size of peak Bythotrephes densities could not outpace changes in the timing and size of peak densities in their Daphnia prey. Our results provide rare evidence from nature as to how long-term warming can favour higher trophic levels, with the potential to strengthen top-down control of food webs.

First report on polybrominated diphenyl ethers in the Iranian Coral Islands: Concentrations, profiles, source apportionment, and ecological risk assessment

Coral reefs are challenged by multiple stressors due to the growing industrialization. Despite that, data on their environment are still scarce, and no research is yet performed on polybrominated diphenyl ethers in the Persian Gulf area. Seeking to fill in this gap, the present study aims to determine spatio-vertical distributions, source apportionment and ecological risk of polybrominated diphenyl ethers in the sediment cores and seawater samples from ten coral reef Islands in the Persian Gulf, Iran. Σ₁₂PBDEs concentrations ranged from 0.42 ± 0.04 to 47.14 ± 1.35 ng g^-1 dw in sediments, and from 1.17 ± 0.06 to 7.21 ± 1.13 ng L^-1 in seawater. The vertical polybrominated diphenyl ethers distribution varied significantly among the sampling stations and different depths with a decreasing trend towards the surface and peaks around 12-20 cm. Both in the seawater and sediment samples, elevated polybrominated diphenyl ethers loadings were observed in highly industrialized areas. Deca-bromodiphenyl ether-209 was the predominant congener along the sediment cores, whereas Tetra-bromodiphenyl ether-47 and Penta-bromodiphenyl ether-100 dominated in seawater samples. Commercial Deca-bromodiphenyl ether mixture was found to be the major source of polybrominated diphenyl ethers. Penta-bromodiphenyl ether was revealed to be the major ecological risk driver in the study area: it posed medium to high-risk quotient to sediment dwelling organisms. This study indicated that coral reefs are playing an important role in retaining polybrominated diphenyl ethers and highlighted the need to manage polybrominated diphenyl ethers contamination in the coral reef environment.

A Review of Environmental Occurrence, Fate, and Toxicity of Novel Brominated Flame Retardants

Use of legacy brominated flame retardants (BFRs), including polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCD), has been reduced due to adverse effects of these chemicals. Several novel brominated flame retardants (NBFRs), such decabromodiphenyl ethane (DBDPE) and bis(2,4,6-tribromophenoxy) ethane (BTBPE), have been developed as replacements for PBDEs. NBFRs are used in various industrial and consumer products, which leads to their ubiquitous occurrence in the environment. This article reviews occurrence and fate of a select group of NBFRs in the environment, as well as their human exposure and toxicity. Occurrence of NBFRs in both abiotic, including air, water, dust, soil, sediment and sludge, and biotic matrices, including bird, fish, and human serum, have been documented. Evidence regarding the degradation, including photodegradation, thermal degradation and biodegradation, and bioaccumulation and biomagnification of NBFRs is summarized. The toxicity data of NBFRs show that several NBFRs can cause adverse effects through different modes of action, such as hormone disruption, endocrine disruption, genotoxicity, and behavioral modification. The primary ecological risk assessment shows that most NBFRs exert no significant environmental risk, but it is worth noting that the result should be carefully used owing to the limited toxicity data.

Species and habitat-dependent accumulation and biomagnification of brominated flame retardants and PBDE metabolites

The occurrence, species- and habitat-dependent distribution of brominated flame retardants (BFRs) and PBDE metabolites comprising 27 polybrominated diphenyl ethers (PBDEs), 3 hexabromocyclododecanes (HBCDs), tetrabromobisphenol A (TBBPA), 17 methoxylated (MeO-) BDEs, and 8 hydroxylated (OH-) BDEs were determined in marine environments (sediment and seawater) and 20 biota species in food web in the southern part of Korea. The concentration of HBCDs was statistically higher in both pelagic (5.73-60.1 ng/g lipid weight [lw]) and demersal fish (2.45-31.3 ng/g lw), whereas a higher level of OH-BDEs was observed in benthic invertebrates (2.48-40.7 ng/g lw), suggesting different composition of BFRs and PBDE metabolites between species. The concentrations of TBBPA and MeO-BDEs were significantly higher in pelagic fish (1.31-11.3, 6.15-61.5 ng/g lw) than in demersal fish (not detected [N.D.]-4.45, 0.956-8.52 ng/g lw) and benthic invertebrates (N.D.-8.11, 0.182-4.65 ng/g lw), reflecting a dependence on habitat. Additionally, analogue distribution of PBDEs in pelagic fish was similar to that in seawater, whereas the distribution in demersal fish and benthic invertebrates was similar to the distribution in sediment. The bioconcentration factor (BCF) and trophic magnification factor (TMF) of α-HBCD, some of PBDEs, and 6-MeO-BDE47 were up to 5000 and 1, respectively, suggesting strong bioaccumulation and biomagnification.

Microplastic exposure and effects in aquatic organisms: A physiological perspective

The impact of microplastics (MPs) on aquatic life, given their ubiquitous presence in the water compartment, represents a growing concern. Consistently, scientific knowledge is advancing rapidly, although evidence on actual adverse effects is still highly fragmented. This paper summarizes the recent literature on MP impacts on aquatic organisms in an attempt to link routes of uptake, possible alterations of physiological processes, and outcomes at different levels of biological organization. Animal feeding strategies and MP biodistribution is discussed, alongside with relevant effects at molecular, cellular, and systemic level. Pathways from animal exposure to apical physiological responses are examined to define the relevance of MPs for animal health, and to point out open questions and research gaps. Emphasis is given to emerging threats posed by leaching of plastic additives, many of which have endocrine disruption potential. The potential role of MPs as substrates for microorganism growth and vehicle for pathogen spreading is also addressed.

Practical advice for selecting or determining trophic magnification factors for application under the European Union Water Framework Directive

European Union Directive 2013/39/EU, which amended and updated the Water Framework Directive (WFD; 2000/60/EC) and its daughter directive (2008/105/EC), sets Environmental Quality Standards for biota (EQSbiota ) for a number of bioaccumulative chemicals. These chemicals pose a threat to both aquatic wildlife and human health via the consumption of contaminated prey or the intake of contaminated food originating from the aquatic environment. EU member states will need to establish programs to monitor the concentration of 11 priority substances in biota and assess compliance against these new standards for the classification of surface water bodies. An EU-wide guidance effectively addresses the implementation of EQSbiota . Flexibility is allowed in the choice of target species used for monitoring to account for both diversity of habitats and aquatic community composition across Europe. According to that guidance, the consistency and comparability of monitoring data across member states should be enhanced by adjusting the data on biota contaminant concentrations to a standard trophic level by use of the appropriate trophic magnification factor (TMF), a metric of contaminant biomagnification through the food web. In this context, the selection of a TMF value for a given substance is a critical issue, because this field-derived measure of trophic magnification can show variability related to the characteristics of ecosystems, the biology and ecology of organisms, the experimental design, and the statistical methods used for TMF calculation. This paper provides general practical advice and guidance for the selection or determination of TMFs for reliable application within the context of the WFD (i.e., adjustment of monitoring data and EQS derivation). Based on a series of quality attributes for TMFs, a decision tree is presented to help end users select a reasonable and relevant TMF. Integr Environ Assess Manag 2019;15:266-277. © 2018 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals, Inc. on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Trophic transfer of persistent organic pollutants through a pelagic food web: The case of Lake Como (Northern Italy)

Despite DDT and PCB having been banned for about 40 years, they are still detectable in the environment. In the present research we specifically investigated the trophic transfer of these organochlorine contaminants (OC) through a pelagic food web of a deep lake in Northern Italy (Lake Como) over time. Zooplankton and fish were sampled each season of a year and OC concentrations and the carbon and nitrogen isotopic ratios were measured. By using stable isotopes, the direct trophic relationship between pelagic zooplankton and zooplanktivorous fish was confirmed for Alosa agone only in summer. Based on this result, the biomagnification factor normalized on the trophic level (BMF_TL) for organic contaminants was calculated. BMF_TL values were within the range 0.9-1.9 for DDT isomers and 1.6-4.9 for some PCB congeners (PCB 95, PCB 101, PCB 149, PCB 153, PCB 138 - present both in zooplankton and in fish and representing >60% of the PCB contamination), confirming the biomagnification of these compounds in one of the two zooplanktivorous fish species of the lake.

Stereoisomer-Specific Trophodynamics of the Chiral Brominated Flame Retardants HBCD and TBECH in a Marine Food Web, with Implications for Human Exposure

Stereoisomers of 1,2,5,6,9,10-hexabromocyclododecane (HBCD) and 1,2-dibromo-4-(1,2-dibromoethyl)-cyclohexane (TBECH) were determined in sediments and 30 marine species in a marine food web to investigate their trophic transfer. Lipid content was found to affect the bioaccumulation of ΣHBCD and ΣTBECH in these species. Elevated biomagnification of each diastereomer from prey species to marine mammals was observed. For HBCD, biota samples showed a shift from γ- to α-HBCD when compared with sediments and technical mixtures; trophic magnification potential of (-)-α- and (+)-α-HBCD were observed in the food web, with trophic magnification factors (TMFs) of 11.8 and 8.7, respectively. For TBECH, the relative abundance of γ- and δ-TBECH exhibited an increasing trend from abiotic matrices to biota samples; trophic magnification was observed for each diastereomer, with TMFs ranging from 1.9 to 3.5. The enantioselective bioaccumulation of the first eluting enantiomer of δ-TBECH in organisms at higher TLs was consistently observed across samples. This is the first report on the trophic transfer of TBECH in the food web. The estimated daily intake of HBCD for Hong Kong residents was approximately 16-times higher than that for the general population in China, and the health risk to local children was high, based on the relevant available reference dose.

Biomagnification of Hexabromocyclododecane (HBCD) in a coastal ecosystem near a large producer in China: Human exposure implication through food web transfer

Hexabromocyclododecane (HBCD) is a widely used brominated flame retardant which is mainly produced in China. Many HBCD facilities are located at the coast and the released HBCD may enter into the coastal ecosystem. There is a risk that HBCD can transfer through the food web to the diet of local population. Therefore, the coastal organisms near one of the biggest HBCD facilities in China were investigated. Variation was observed for the bioaccumulation of HBCD between the detrital food chain and the grazing food chain. In the studied species, the mullet was most contaminated which may be caused by its feeding on detritus. At the same time, the transfer of HBCD along the food web was investigated, and HBCD was biomagnified from the prey to the predator in the grazing food chains. Among the three diastereoisomers, α-HBCD was biomagnified with increasing trophic levels in the food web while β- and γ-HBCD were not. To assess the human dietary exposure, the dietary intake of HBCD from seafood was estimated, and the estimated daily intake (EDI) was 5.22ng/kg/day for adults, and 16.39ng/kg/day for children. The EDI for local residents were tens of times higher than that for general population in China, but the risk through dietary intake was very low in terms of existing reference dose.

Determination of legacy and novel brominated flame retardants in dust from end of life office equipment and furniture from Pretoria, South Africa

Indoor dust is known to be a source of human exposure to brominated flame retardants (BFRs) and these consists of the legacy polybrominated diphenyl ethers (PBDEs), total hexabromocyclododecane (T-HBCDD) and the "Novel or alternate" Brominated flame retardants (NBFRs). In this study, x-ray fluorescence (XRF) analyser was employed to measure elemental bromine contents in office furniture and electronics as the first indication of the possible presence of BFRs. To investigate the possible BFRs present, a total of 21 dust samples were collected from surfaces of electronic equipment and office furniture and were analysed using gas chromatography-mass spectrometry (GC-MS). The concentrations of ∑₇ BDE- congeners ranged from 50 to 3346ngng^-1. Of the ∑₇ BDE congeners analysed, BDE-209, -183 and -99 were the most dominant congeners. The concentrations observed ranged from <LOD - 1758, <LOD - 401 and <LOD-543ngg^-1, for BDE-209, -183 and -99, respectively. T-HBCDD and 2-ethyl-1-hexyl-2.3.4.5-tetrabromobenzoate (EH-TBB) were detected in 57 and 67% of the total dust samples analysed with concentrations ranging from <LOD - 673 and <LOD - 385ngg^-1, respectively. However, Bis (2-ethylhexyl) tetrabromophthalate (BEH-TEBP) was only detected in 24% of the 21 samples exhibiting a concentration range of <LOD - 63ngg^-1. The detection frequency of 1,2 Bis (2.4.6-tribromophenoxy) ethane (BTBPE) was 81% with concentrations of <LOD-1402ngg^-1. Alongside the legacy BFRs, NBFRs were the most detected indicating probably increased usage as replacements for the banned commercial PBDEs products namely, penta-, octa-, and deca-BDE mixtures. No correlation was observed between the bromine levels obtained using portable XRF and the BFRs detected using GC-MS (r=0.0073, p=0.076). The observed trend may be attributed to various factors including the sample matrix analysed and the number of BFRs analysed. The observed trend is consistent with those reported from other studies.

Hexabromocyclododecanes (HBCDs) in fish: Evidence of recent HBCD input into the coastal environment

Hexabromocyclododecanes (HBCDs) are flame retardants and emerging persistent organic pollutants. In the present study, α-, β-, and γ-HBCDs were measured in several fish species from rivers and an electronic waste (e-waste) recycling site in Pearl River Delta, South China. The concentrations of HBCDs were 12.8 to 640, 5.90 to 115, and 34.3 to 518ng/g lipid weight (lw) in mud carp (Cirrhinus molitorella), tilapia (Tilapia nilotica), and plecostomus (Hypostomus plecostomus), respectively. Plecostomus showed the highest HBCD concentrations among three fish species. The contributions of α-HBCD to total HBCDs were 78% to 97%, 93% to 99%, and 87% to 98% in carp, tilapia, and plecostomus, respectively. Fish samples from a harbor and the e-waste site exhibited the highest HBCD concentrations among all samples. The HBCD concentrations were not significantly correlated with the gross domestic product or population data. e-Waste recycling activities, harbor construction, and shipment might be recent HBCD sources.

How do measured PBDE and HCBD levels in river fish compare to the European Environmental Quality Standards?

This study evaluates the current situation regarding PBDE and HBCD levels in different river fish species. We collected published data in the last five years in different countries around the world. These levels of pollution were compared with Environmental Quality Standards (EQS) for biota established by the European Directive in the field of water policy. Although HBCD situation is not critical, with only some values exceeding the limit about 5 times, the PBDE levels clearly exceeded the established EQS, with 25% of fish samples exceeding up to ten thousand times. Although it is expected that levels of pollution by PBDEs will decrease over the next years due to the ban in their use, it is not expected that this decrease will reach the EQS values by the end of 2021, as demanded by the European Directive. Hence, it is necessary to implement new strategies in order to minimize the impact of PBDEs on the environment.

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

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

Hexabromocyclododecane diastereomers in fish and suspended particulate matter from selected European waters-trend monitoring and environmental quality standard compliance

The brominated flame retardant hexabromocyclododecane (HBCD) was monitored in fish and sediment (from one lake) or suspended particulate matter (SPM; from five rivers) at European freshwater sites to study the effects of reduction measures implemented by HBCD producers and users in recent years. Bream (Abramis brama) were sampled annually between 2007 and 2013 in the rivers Götaälv/SE, Rhône/FR, Western Scheldt/NL, Mersey/UK, and Tees/UK and in Lake Belau/DE. Sediment/SPM was taken every second year between 2008 and 2014. HBCD was analyzed by LC/MS/MS allowing the determination of the alpha-, beta-, and gamma-diastereomers. For most sites, a decrease in ∑HBCD was observed in fish (e.g., in the Rhône and Western Scheldt by about 80 and 60%, respectively, with significantly decreasing trends, p < 0.01). In the Rhône, HBCD also decreased in SPM. At the sampling site in the Tees which was impacted by a former HBCD point source, fish HBCD levels decreased only after a major flood event in 2013. While fish data indicate a decline in environmental HBCD concentrations at most sites with diffuse emissions, SPM data were less conclusive. The European environmental quality standard for HBCD in fish of 167 μg kg^-1 wet weight was met by all fish samples in 2013.

Distribution, isomerization and enantiomer selectivity of hexabromocyclododecane (HBCD) diastereoisomers in different tissue and subcellular fractions of earthworms

In this study, earthworms Eisenia fetida (E. fetida) were exposed to a soil artificially contaminated with individual hexabromocyclododecane (HBCD) diastereoisomers (α-, β- and γ-HBCDs) to investigate the distribution, isomerization and enantiomer selectivity of HBCDs at tissue and subcellular levels. At the tissue level, the concentrations of HBCDs all followed the order of gut>bodyfluid>body wall, which suggested that earthworms accumulated HBCDs mainly via ingesting soil particles. At the subcellular level, the concentrations of HBCDs in an extracellular fraction consisting of granules, tissue fragment, cell membrane and intact cells (fraction A) were higher than those in an intracellular fractions consisting of the microsomal and cytosol (fraction B+C). This confirmed the passive diffusion during the distribution of HBCDs into the intracellular compartment. The distribution proportions of HBCDs varied among different tissue and subcellular fractions, and all changed over time within 14 days. The variable distributions of HBCDs in different fractions were a result of the comprehensive effects of dynamics and thermodynamics processes. The β- and γ-HBCDs were isomerized to α-HBCD in all tissue and subcellular fractions except for fraction C, and the isomerization ratios varied a lot, which seemed to be related to HBCDs residence time. The selective enrichment of (-) α-, (-) β and (-) γ-HBCDs was found in all fractions and this is consistent with that in the whole earthworm. Besides, the extents of enantio-selectivity did not change significantly among different tissue and subcellular fractions.

Trophic transfer of hexabromocyclododecane in the terrestrial and aquatic food webs from an e-waste dismantling region in East China

Trophic transfer of hexabromocyclododecane (HBCD) was investigated in both the terrestrial and aquatic food webs from an e-waste dismantling region in East China. The mean Σ₃HBCD concentrations in the terrestrial species varied from 0.91 (0.16-1.85) ng g^-1 lipid weight (lw) in dragonflies (Pantala flavescens) to 40.3 (22.1-51.1) ng g^-1 lw in rats (Rattus norvegicus). The isomeric profile indicated that α-HBCD presented a decreasing trend along the trophic level (TL) (from 97.2% to 16.3% of Σ₃HBCDs), while γ-HBCD showed a reverse trend (from 2.8% to 73.6% of Σ₃HBCDs). The trophic magnification factor (TMF) derived from the slope of the regression line between TLs and ln-transferred Σ₃HBCDs was 0.10, suggesting a trophic dilution of HBCD in the terrestrial food web. By contrast, in the aquatic species, Σ₃HBCD concentrations varied from 5.02 (3.5-6.55) ng g^-1 lw in apple snails (Ampullaria gigas spix) to 45.9 (14.9-67.8) ng g^-1 lw in grass carps (Ctenopharyngodon idellus). α-HBCD was the dominant isomer, followed by γ-HBCD in the majority of species. A positive linear relationship was observed in the plots of ln Σ₃HBCDs versus TLs (R² = 0.81, p = 0.06). The TMF for Σ₃HBCDs was 6.36, indicating a trophic magnification of HBCD in the aquatic food web. Although these results demonstrated the distinct trophic transfer of Σ₃HBCDs in different ecosystems, further research is needed to eliminate the uncertainty of the tendencies, due to the non-significant relationship and limited species.

Quantification of polybrominated diphenyl ethers (PBDEs) in food. A review

The polybrominated diphenyl ethers (PBDEs), a class of brominated flame retardants (BFRs), are food contaminants of animal origin. Interest in food matrices analysis is growing due to the toxicity of PBDEs and European Commission (EC) recommendation (118/2014/EU). Here we review papers concerning methods of PBDEs analysis while focusing on extraction, clean up, chromatographic separation and detection techniques. The emphasis is put on EC recommendation, the congeners and the efficiency of different detection systems. Some analytical problems caused by differences between low- and high-molecular-mass congener properties, especially the possible limitations of BDE-209 analysis, are discussed. Detection techniques and mass spectrometry (MS) ionization modes applied to PBDE level determination in food of animal origin are compared. The gas chromatography (GC) coupled to high-resolution MS is undoubtedly fit for that purpose, but ion trap MS could be used to PBDEs determination as well. ECD is the most sensitive technique; however, other halogen compounds present in sample may interfere with PBDEs congeners necessitating results confirmation. Moreover, the novel atmospheric pressure chemical ionization (APCI) method applied to GC in tandem with MS places this technique in the top category of the most sensitive techniques which may be used.

Legacy and emerging flame retardants (FRs) in the freshwater ecosystem: A review

In this review article, we have compiled and reviewed the previously published available literature on environmental distribution, behaviour, fate and regional trends of legacy and emerging flame retardants (FRs) including brominated (BFRs), organo-phosphate (OPFRs), novel brominated flame retardants (NBFRs) and dechlorane plus (DP) in the freshwater ecosystem. Transport and fate is discussed briefly with the evidences of de-bromination, sedimentation and accumulation in biota. De-bromination of BDE-209 is considered of concern because the lower brominated congeners are more toxic and mobile thus posing increased risk to the freshwater ecosystem. The available data on temporal and spatial trends as yet, is too few to show any consistent trends, enabling only general conclusions to be drawn. There is a lack of temporal studies in Asia, while, overall the trends are mixed, with both increasing and decreasing concentrations of BFRs and OPFRs. OPFRs and NBFRs have replaced classical BFRs (polybrominated diphenyl ethers (PBDEs)) in some countries but the amount of PBDEs in the environment is still considerable. Knowledge gaps and recommendations for future research are discussed emphasizing on further monitoring, advanced analytical methodologies, and risk assessment studies to completely understand the science of flame retardants in the freshwater ecosystem.

Current levels and trends of selected EU Water Framework Directive priority substances in freshwater fish from the German environmental specimen bank

Under the German environmental specimen bank programme bream (Abramis brama) were sampled in six German rivers and analysed for the priority hazardous substances dicofol, hexabromocyclododecane (HBCDD), hexachlorobenzene (HCB), hexachlorobutadiene (HCBD), heptachlor + heptachlor epoxide (HC + HCE), polybrominated diphenylethers (PBDEs), polychlorinated dibenzo-p-dioxins and -furans and dioxin-like polychlorinated biphenyls (PCDD/Fs + dl-PCBs), and perfluorooctane sulfonic acid (PFOS). The aim was to assess compliance with the EU Water Framework Directive environmental quality standards for biota (EQSBiota) for the year 2013, and to analyse temporal trends for those substances that are of special concern. General compliance was observed for dicofol, HBCDD and HCBD whereas PBDEs exceeded the EQSBiota at all sites. For all other substances compliance in 2013 varied between locations. No assessment was possible for HC + HCE at some sites where the analytical sensitivity was not sufficient to cover the EQSBiota. Trend analysis showed decreasing linear trends for HCB and PFOS at most sampling sites between 1995 and 2014 indicating that the emission reduction measures are effective. Mostly decreasing trends or constant levels were also observed for PCDD/Fs and dl-PCBs. In contrast, increasing trends were detected for PBDEs and HBCDD which were especially pronounced at one Saar site located downstream of the industries and conurbation of Saarbrücken and Völklingen. This finding points to new sources of emissions which should be followed in the coming years.

Brominated flame retardants in the surrounding soil of two manufacturing plants in China: Occurrence, composition profiles and spatial distribution

Surface soil samples were collected surrounding two brominated flame retardants (BFRs) manufacturing plants in China in August 2014 and analyzed for 23 polybrominated diphenyl ethers (PBDEs) and 8 novel brominated flame retardants (NBFRs). BDE209 and decabromodiphenylethane (DBDPE) were the predominant compounds in soil with the median levels of 1600 and 560 ng/g dw, respectively. The PBDEs profiles in soil samples were consistent with that of commercial product (comDecaBDE). The percentage contributions to total PBDEs decreased from higher to lower brominated homologues. Lower concentrations of NBFRs (excluding DBDPE) were detected in soil surrounding the two plants, suggesting they are byproducts or degradation products of the manufacturing activities. The concentrations of most BFRs dropped exponentially within 3-5 km of the manufacturing plants, suggesting recent deposition of these compounds to the soil. Directional distribution indicated that PBDEs and DBDPE concentrations were highest in the north direction of Plants 1. Three-day air parcel forward trajectories confirmed that the air parcel was responsible for the higher concentration of BFRs in the soil of north direction of the plant.

Persistent organic pollutants (POPs) in fish with different feeding habits inhabiting a shallow lake ecosystem

The occurrence of persistent organic pollutants (POPs) in the environment can affect organisms inhabiting aquatic systems, in particular shallow lakes that are vulnerable to environmental stressors. This study aimed to assess POPs accumulation and changes at histological and physiological levels in tissues of three fish species with different trophic habits. Gills, brain, muscle, liver and gonads of Odontesthes bonariensis, Oligosarcus jenynsii and Cyphocharax voga were collected from the shallow lake La Peregrina, located in an agricultural area from Argentina. In addition, contaminant levels in surface water (SW), suspended particulate matter (SPM) and bottom sediments (BS) were assessed. Histological lesions were evaluated in fish tissues and levels of vitellogenin (VTG) were assessed in plasma of male fish in order to correlate these alterations with the presence of POPs in the environment. Organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) were determined by GC-ECD. Biotic and abiotic samples showed the same POPs distribution pattern: OCPs>PCBs>PBDEs. Although tissue distribution of OCPs was species-specific, muscle showed the lowest levels in all species. The most abundant contaminants were endosulfans, suggesting their widespread use in the area. O. bonariensis showed the highest endosulfans levels in liver (184.2-219ngg(-1)wet w), which was associated with the high SPM levels considering this species is a filter feeder. The occurrence of PCBs and PBDEs shows the ubiquity of these pollutants in the area. Histological lesions in gills and liver of O. bonariensis and O. jenynsii, might be related with the high levels of endosulfans in these organs. The detection of VTG in males warns about a possible exposure to estrogenic compounds in the environment. In conclusion, the simultaneous exposure of fish to multiple environmental pollutants leads to different alterations, so measures should be taken in order to prevent their occurrence and toxic effects.

Diastereomer- and enantiomer-specific accumulation, depuration, bioisomerization, and metabolism of hexabromocyclododecanes (HBCDs) in two ecologically different species of earthworms

In this study, two ecological types of earthworms were exposed to soil samples that were artificially contaminated with individual hexabromocyclododecane (HBCD) diastereomers (α-, β-, and γ-HBCDs) to investigate the bioaccumulation, depuration, enantiomer selectivity and isomerization of HBCDs in earthworms. The uptake rate constant (ku), bioaccumulation factor (BAF), biota soil accumulation factor (BSAF), and half-life (t1/2) for the α-HBCD were the highest among the three diastereomers. The bioaccumulation parameters of the three diastereoisomers differed between the two ecologically different species of earthworms. The BSAF values of α- and γ-HBCDs were substantially higher in Eisenia fetida than those in Metaphire guillelmi, with the higher lipid and protein contents in E. fetida as the primary reason for this difference. The other processes, such as uptake, depuration, metabolism and isomerization, also differed between the two species and led to a difference in the bioaccumulation of β-HBCD. The β- and γ-HBCDs were bioisomerized to α-HBCD in the earthworms, but to a greater extent in E. fetida. The highest BSAF, t1/2 of α-HBCD and the bioisomerization of β- and γ-HBCDs to α-HBCD might explain in part why α-HBCD was the dominant isomer in biota samples. Most of the enantiomer fractions (EFs) for the three HBCD diastereoisomers in the earthworms were different from those in standard samples (p<0.05), indicating that enantiomer selectivity occurred. Moreover, the trends and extent of the enantioselectivity were different between the two species. Additionally, the EFs of α-HBCD that was bioisomerized from β- or γ-isomers were also different from those in the standards (p<0.05), which likely reflect the integration of several processes, such as enantioselective isomerization and the subsequent selective metabolism of the produced α-HBCD or selective excretion of the enantiomers.