Effects of decabromodiphenyl ether (BDE-209) on the avoidance response, survival, growth and reproduction of earthworms (Eisenia fetida)

Copper toxicity on Eisenia fetida in a vineyard soil: a combined study with standard tests, genotoxicity assessment and gut metagenomic analysis

Copper (Cu) toxicity is a pressing concern for several soils, especially in organic viticulture. The objective of this work was to assess Cu toxicity on the non-target organism Eisenia fetida, employing both traditional and novel tools for early identification of Cu-induced damages. In addition to traditional tests like avoidance and reproductive toxicity experiments, other tests such as the single cell gel electrophoresis (SCGE) and gut microbiome analysis were evaluated to identify early and more sensitive pollution biomarkers. Four sub-lethal Cu concentrations were studied, and the results showed strong dose-dependent responses by the earthworm avoidance test and the exceeding of habitat threshold limit at the higher Cu doses. An inverse proportionality was observed between reproductive output and soil Cu concentration. Bioaccumulation was not detected in earthworms; soil concentrations of potentially bioavailable Cu were not affected by E. fetida presence or by time. On the contrary, the SCGE test revealed dose-dependent genotoxicity for the 'tail length' parameter already at the second day of Cu exposition. Gut microbiome analysis a modulation of microbial composition, with the most aboundant families being Pectobateriaceae, Comamonadaceae and Microscillaceae. Bacillaceae increased over time and showed adaptability to copper up to 165 mg/kg, while at the highest dose even the sensitive Acetobacteriaceae family was affected. The research provided new insights into the ecotoxicity of Cu sub-lethal doses highlighting both alterations at earthworms' cellular level and changes in their gut microbiota.

Aerobic Degradation Characteristics of Decabromodiphenyl ether through Rhodococcus ruber TAW-CT127 and Its Preliminary Genome Analysis

Decabromodiphenyl ether (BDE-209), a polybrominated diphenyl ether (PBDE) homolog, seriously threatens human health. In this study, a Rhodococcus ruber strain with high BDE-209 degradation activity, named TAW-CT127, was isolated from Tong’an Bay, Xiamen. Under laboratory conditions, the strain’s optimal growth temperature, pH, and salinity are 45 °C, 7.0, and 0–2.5%, respectively. Scanning electron microscopy (SEM) analysis shows that TAW-CT127 is damaged when grown in manual marine culture (MMC) medium with BDE-209 as the sole carbon source instead of eutrophic conditions. In the dark, under the conditions of 28 °C, 160 rpm, and 3 g/L (wet weight) TAW-CT127, the degradation rate of 50 mg/L BDE-209 is 81.07%. The intermediate metabolites are hexabromo-, octabromo-, and nonabromo-diphenyl ethers. Through whole-genome sequencing, multiple dehalogenases were found in the genome of TAW-CT127; these may be involved in the production of lower-brominated diphenyl ethers. Additionally, biphenyl-2,3-dioxygenase (BDO) in TAW-CT127 may catalyze the debromination reaction of BDE-209. Our research provides a new high-efficiency strain for bioremediation of BDE-209 pollution, and lays the foundation for the preliminary exploration of genes associated with BDE-209 degradation.

Behavioural changes and flight response of a mosquito (Culicidae) and an earthworm (Lumbricidae), respectively, after exposure to imidacloprid

A major point of concern in ecotoxicology is the effects of pesticides on nontarget organisms. This can impact the ecological role played by certain beneficial species in nature. Regarding neonicotinoid insecticides such as imidacloprid (IMI), several measures, including limited trade, restrictive use, and ban have been implemented in Europe and the USA but not globally. The goal of our study was to evaluate the potential risk of this still widely used agrochemical on the behaviour of mosquito larvae (Culicidae) and the escape behaviour of earthworms (Lumbricidae). Changes in breathing, swimming and resting were recorded in mosquitoes postexposure to 0, 1 and 2 mg IMI/L for 10 min. Earthworms were topically exposed in water for 2 minutes to 0, 5, 10 and 20 mg IMI/L. The escape behaviour (initial escape distance and speed) of the earthworms were recorded. In culicids, resting particularly was significantly increased by the exposure to imidacloprid (p < 0.05). In earthworms, the initial escape distance was statistically longer (p < 0.05) when fleeing from the 5 mg IMI/L solution than the solutions with the two highest concentrations. The worms exposed to the 5 mg IMI/L reacted faster than those exposed to the higher concentrations, which explained the long distance covered in the same amount of time. These results point to the relatively quick onset of the neurotoxic effects of imidacloprid, crippling earthworms and altering the buoyancy of mosquito larvae. The ecological consequences of these findings on the completion of life cycles and the survival of these species in nature are yet to be established.

Heavy Metals and Probabilistic Risk Assessment via Pheretima (a Traditional Chinese Medicine) Consumption in China

Earthworms are known to accumulate inorganic contaminants from the soil; they are also used as a traditional Chinese medicine (TCM) called Pheretima, which might cause safety problems with long-term exposure. Here, this study was conducted to determine and analyze the level of heavy metal contamination such as arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), manganese (Mn), nickel (Ni), and lead (Pb) in Pheretima and then explore the probabilistic health risks caused by 8 heavy metals in 98 batches of Pheretima using Monte Carlo simulation. A risk assessment strategy was conducted to assess heavy metal-associated health risk of Pheretima based on consumption data. For random consumption sampling, the results found that the non-carcinogenic risk of As is higher than the acceptable level, and the carcinogenic risk levels of As and Cr exceeded the acceptable risk recommended by the USEPA. Cr and As were regarded as the priority metals for risk control in the present study. Finally, it was recommended that the dosing frequency should be less than 24 d/y. In general, this study conducted a probabilistic risk assessment of heavy metals in Pheretima, which would be of significance for policy makers to take effective strategies to improve the quality and safety of Pheretima.

Polybrominated diphenyl ethers from automobile microenvironment: Occurrence, sources, and exposure assessment

To investigate the level of polybrominated diphenyl ether (PBDE) contamination in the automobile microenvironment, air and dust samples were collected from 15 family automobiles in Hangzhou City, China. The PBDE concentrations, distribution of congeners, and human exposure were determined; and the content and distribution of PBDEs in automotive interior materials were analyzed. The results revealed that the average and median concentrations of ∑₁₄PBDEs in the air in automobiles were 732 and 695 pg/m³, respectively, whereas those in automotive dust were 4913 and 5094 ng/g, respectively. Decabromodiphenyl ether (BDE-209) had the highest proportion, accounting for 61.3% and 88.8% of the ∑₁₄PBDEs in the air and dust, respectively. The potential primary sources of PBDEs in automobile air and dust were volatile polyurethanes in seat covers and foot pads, respectively. Human exposure calculations revealed that infants and toddlers in cars were most exposed to air and dust, respectively. BDE-47 and -99 were the primary sources of health risks related to air and dust in cars.

Exposure evaluation and risk assessment of polybrominated diphenyl ethers in dust from microenvironments in Nsukka, Nigeria

The health risks of polybrominated diphenyl ethers (PBDEs) to toddlers, children, and adults in creches, nursery schools, cars, and offices in Nsukka, Nigeria, via inhalation, ingestion, and dermal exposure pathways were evaluated. Eight PBDEs congeners (BDE-28, BDE-47, BDE-100, BDE-99, BDE-154, BDE-153, BDE-183, and BDE-209) were determined using gas chromatography-mass spectrometry. This is the first study on PBDEs in creches and nursery schools in Africa. The mean (median) ∑8PBDEs (ng/g) in creches, nursery schools, offices, and cars were 4355 (1850), 2095 (1130), and 37741 (2620) respectively. The concentrations of PBDEs between the three microenvironments were significantly different (p ˂ 0.05), and the highest concentration was found in cars. Ingestion of dust was the predominant pathway of exposure to PBDEs for toddlers and children, while dermal absorption was the dominant pathway for adults. Dermal absorption and ingestion in cars, creches, and nursery schools were of the same magnitude. Toddlers with the highest ingestion rate of PBDEs in creches, nursery schools, and cars are at risk especially from prolonged exposure.

Exposure pathways, levels and toxicity of polybrominated diphenyl ethers in humans: A review

Polybrominated diphenyl ethers (PBDEs) are extensively used as brominated flame retardants (BFRs) in different types of materials, which have been listed as Persistent Organic Pollutants (POPs) by the Stockholm Convention in 2009 and 2017. Due to their ubiquities in the environment and toxicities, PBDEs have posed great threat to both human health and ecosystems. The aim of this review is to offer a comprehensive understanding of the exposure pathways, levels and trends and associated health risks of PBDEs in human body in a global scale. We systematically reviewed and described the scientific data of PBDE researches worldwide from 2010 to March 2020, focusing on the following three areas: (1) sources and human external exposure pathways of PBDEs; (2) PBDE levels and trends in humans; (3) human data of PBDEs toxicity. Dietary intake and dust ingestion are dominant human exposure pathways. PBDEs were widely detected in human samples, especially in human serum and human milk. Data showed that PBDEs are generally declining in human samples worldwide as a result of their phasing out. Due to the common use of PBDEs, their levels in humans from the USA were generally higher than that in other countries. High concentrations of PBDEs have been detected in humans from PBDE production regions and e-waste recycling sites. BDE-47, -153 and -99 were proved to be the primary congeners in humans. Human toxicity data demonstrated that PBDEs have extensively endocrine disruption effects, developmental effects, and carcinogenic effects among different populations.

Enzyme assays and toxicity of pig abattoir waste in Eisenia andrei

Due to high global demand, large amounts of abbattoir waste are generated from pork production. Mismanagement of abattoir waste on agricultural lands can result in soil and water contamination with pathogens and contaminants like metals and nutrients. Therefore, possible effects on soil organisms prior to application should be evaluated. Thus, the aim of this study was to determine the effects of fresh pig abattoir waste (PAWf) and waste after stabilization processes on E. andrei through tests of avoidance behavior, acute toxicity and chronic toxicity. In order to do this, the waste was evaluated fresh (i.e., non-treated), and after aerated composting (PAWa), natural composting (PAWn) and vermicomposting (PAWv). In addition, we used a natural soil with no history of agricultural use as control soil. The evaluation was based on avoidance behavior, mortality, initial and final earthworm weight, and reproduction, in addition to a set of enzyme assays formed by acetylcholinesterase, lipid peroxidation, catalase and glutathione S-transferase measured over time. The ecotoxicological results showed that PAWf and PAWa increased AChE activity at different experimental periods, while PAWn decreased activity at 14 days compared to the control. PAWf and PAWa increased TBARS levels at 7 and 14 days, respectively. CAT activity decreased at 3, 7 and 14 days in PAWv, while GST activity increased at 3 days in PAWa and at 3 and 14 days in PAWf compared to the control. In the acute toxicity test, PAWa and PAWn had a toxic effect on E. andrei, resulting in 100% mortality at 14 days of exposure. Based on our findings, pig abattoir waste should undergo vermicomposting prior to agricultural application to soils.

Global trends and future prospects of e-waste research: a bibliometric analysis

Electronic waste (e-waste) has been widely studied by scholars all over the world, but the research topics and development trends in this field are still unclear. This study aimed to explore the status quo, hot topics, and future prospects in the field of e-waste. Data of publications were downloaded from the Web of Science Core Collection. We used CiteSpace V, Histcite, and VOSviewer to analyze literature information. A total of 2800 papers in e-waste research were identified, and the number of publications increased rapidly after 2004. Six thousand five hundred seventy-three authors participated in the e-waste research, but 70.01% of the authors published only 1 article. The most productive country in this field was China (1146 publications), and the most productive institution was the Chinese Academy of Sciences (370 publications). The Waste Management (225 publications) was the most productive journal, and Environment Science & Technology (9704 co-citations) was the most co-cited journal. The main hot topics in e-waste field were management and recycling of e-waste in developing countries, health risk assessment after exposure to organic pollutants, degradation and recovery of waste metal materials, and impact of heavy metals on children's health. The frontier topic was degradation.

Negligible effects of microplastics on animal fitness and HOC bioaccumulation in earthworm Eisenia fetida in soil

As one type of the most widespread and long-lasting anthropogenic contaminants, microplastics have become a global environmental concern. While numerous studies have demonstrated effects of microplastics on aquatic organisms, the potential influence on terrestrial faunas is relatively less known, even though soil is a primary recipient and sink of plastics. In this study, earthworm Eisenia fetida was exposed to different levels (0, 1, 5, 10, and 20% d.w.) of polyethylene (PE, ≤300 μm) and polystyrene (PS, ≤250 μm) particles in an agricultural soil to evaluate the oxidative stress. Fluorescence imaging, after dying with Nile Red, clearly indicated the ingestion of PE and PS particles by E. fetida. Exposure to PE or PS particles at the highest rate (20%) for 14 d significantly (p < 0.05) increased the activity of catalase and peroxidase and the level of lipid peroxidation, while inhibited the activity of superoxide dismutase and glutathione S-transferase in E. fetida. However, no discernible effect was detected at amendment rates ≤10% for the majority of biochemical endpoints, suggesting that microplastic-induced oxidative stress would not occur in E. fetida under most environmental conditions. The influence of microplastics on bioaccumulation of PAHs and PCBs was also evaluated in E. fetida exposed to different levels (0, 0.1, 1, 5, and 10% d.w.) of PE and PS particles. The tissue concentrations of PAHs and PCBs were reduced in the presence of microplastics at amendment rates ≥1%, suggesting that microplastics did not act as a carrier to enhance contaminant uptake. This was attributed to competitive sorption of microplastics for contaminants and the specific feeding behavior of earthworm. Biodynamic model analysis confirmed that ingestion of microplastics contributed negligibly to contaminant bioaccumulation. Findings of this study suggested that under environmentally relevant conditions, microplastics should not cause significant toxic effects to E. fetida, nor enhance its accumulation of hydrophobic contaminants.

Polybrominated diphenyl ethers (PBDEs) in dust in typical indoor public places in Hangzhou: Levels and an assessment of human exposure

Polybrominated diphenyl ethers (PBDEs) are organic pollutants (POPs) with the characteristics of environmental persistence, long-distance transmission in nature, biological accumulation and toxic effects on human health. To investigate the level of contamination due to PBDEs in typical indoor public places in Hangzhou, dust samples were collected from ten supermarkets, three electronic markets and five different areas throughout one commodity market. Based on sample pretreatment and GC-ECD instrumental analysis, the contamination characteristics, sources and the influencing factors of 14 PBDE congeners were analyzed. The results revealed that the mean of ∑₁₄PBDEs in dust in the supermarkets and electronic markets was 546.13 ng/g and 1140.05 ng/g, respectively, while in the commodity market the mean was 1005.42 ng/g and varied in the five different areas as follows: shoe areas (1367.22 ng/g) > parking lot (1001.05 ng/g) > waiting halls (970.31 ng/g) > packet areas (933.23 ng/g) > curtain areas (755.28 ng/g). The high levels of PBDE were attributed to the quantity of electrical appliances in the supermarkets (r = 0.708^*, p < 0.05) and the electronic markets (r = 0.799^**, p < 0.05) through Spearman correlation coefficient analysis. BDE-209 was the dominant congener, accounting for 53.72% in supermarkets and 64.25% in electronic markets. The calculated inhalation exposure revealed that the exposure level of PBDEs varied in supermarkets, electronic markets and commodity markets, with values of 0.476 ng/day/kg, 0.993 ng/day/kg and 0.876 ng/day/kg, respectively. Moreover, BDE-209's contribution to the total intake of PBDEs was the highest, with a value of 0.072-0.970 ng/day/kg, while the value of BDE-183 was the lowest, with a value of 0-0.020 ng/day/kg. The exposure level of PBDEs in the studied indoor public places was lower than the reference dose of EPA.

Multi-level ecotoxicological effects of imidacloprid on earthworm (Eisenia fetida)

As a neurotoxic insecticide, imidacloprid (IMI) has been widely used for crop protection. However, continuous application of such pesticide in the environment may damage the non-target organisms in soil. In the present study, we aimed to investigate the effects of IMI on earthworms in terms of survival, avoidance behavior, reproduction, detoxification enzyme activity and gene expression using a systematic experimental approach. The results showed that the 14-day LC₅₀ value of IMI was 2.26 (2.09-2.43) mg a.i. kg^-1, and the 2-day AC₅₀ value (concentration inducing an avoidance rate of 50%) of IMI was 1.34 (1.02-1.91) mg a.i. kg^-1 to E. fetida. For reproduction, the 56-day EC₅₀ value of IMI was 0.87 (0.66-1.33) mg a.i. kg^-1 to E. fetida, and there was a positive correlation between the growth rate of earthworms and the number of juveniles in IMI treatments. Activities of carboxylesterase (CarE) and glutathione-S-transferases (GST) in earthworms were disturbed by IMI exposure. Moreover, effects of IMI on the CarE activity in earthworms were more severe and sensitive compared with the GST activity. The expressions of annetocin (ann) and calreticulin (crt) at the transcriptional level were decreased upon IMI exposure, reaching the lowest levels of 0.09 fold and 0.16 fold on day 7 and day 14, respectively. Transcriptionally controlled tumor protein (tctp), heat shock protein 70 (hsp70) and gst exhibited relatively obvious variations (up-regulation or down-regulation) when the exposure duration was extended. Taken together, these results comprehensively contributed to further understandings of the impacts of IMI on earthworms.

Toxic effects of pentachlorophenol and 2,2',4,4'-tetrabromodiphenyl ether on two generations of Folsomia candida

The standard Folsomia candida test (ISO 11267), in which only the survival and reproduction of the parental generation (F0) were determined, is insufficient to assess the toxicity of chemicals, like endocrine disrupting chemicals (EDCs), since the effects of EDCs could last for several generations and sometimes can be transgenerational. It's necessary to assess the effects on subsequent generations to address the long-term consequences of these chemicals exposure. In this study, the effects of pentachlorophenol (PCP) and 2,2',4,4'-tetrabromodiphenyl (BDE47) were assessed on F0 and the first filial generation (F1) of F. candida after 28-day or 10-day exposure of F0. In the 28-day exposure method, F0 was exposed to PCP or BD47 for 28 days and F1 was exposed for about 21 days. In the 10-day exposure method, F0 was exposed for 10 days and F1 was not exposed. The F. candida reproduction of F0 and F1 can be assessed in both methods, while transgenerational effects can further be evaluated in the 10-day exposure method. The numbers of F1 and F2 (second filial generation) juveniles in the 28-day exposure method and F1 juveniles in the 10-day exposure method decreased significantly for the PCP treatment. For BDE47, only the number of F1 juveniles in the 28-day exposure method significantly decreased. The EC50 values of F0 reproduction (the number of F1 juveniles) in the 28-day exposure method were 89 and 306 mg/kg dry soil for PCP and BDE47, respectively. Results suggested that PCP could affect F. candida egg hatching or juvenile survival and adult reproductive capacity, while BDE47 was more likely to affect egg hatchability or juvenile survival rather than adult reproductive capacity. It also indicated that F. candida exposed to PCP or BDE47 could recover in clean soil. Transgenerational effects were not observed for neither PCP nor BDE47 in this study.

Allelopathic effects of volatile organic compounds from Eucalyptus grandis rhizosphere soil on Eisenia fetida assessed using avoidance bioassays, enzyme activity, and comet assays

Allelopathy has been identified as an underlying mechanism of detrimental environmental impacts within commercial plantations. Eucalyptus spp. are known to generate huge amounts of volatile organic compounds (VOCs) that can function as phytotoxins and thus inhibit other plants. In the present study, biochemical markers, including activities of acetylcholinesterase (AChE) and oxidative stress enzymes, such as superoxide dismutase (SOD) and glutathione S-transferase (GST), were assayed to assess changes in Eisenia fetida at the physiological level induced by different doses of VOCs as part of an acute toxicity test over 7 and 14-day exposures. In addition, the toxicities of VOCs were investigated using a soil avoidance test and comet assay. The results revealed that E. fetida exhibited significant avoidance behavior towards the highest concentrations of undecane, decane, 2,4-dimethyl heptane, and 2,2,4,6,6-pentametyl heptane. The tail DNA percentages were significantly increased for all experimental treatments relative to control. However, under the treatments of VOCs, Olive tail moment content and comet tail length also display an obvious increase compared to control, except for that of octane, undecane and decane treatments. As VOC concentrations and durations increased in the soil, activities of AChE, SOD, and GST were either stimulated or inhibited. Among the VOCs, decane, 2,4-dimethyl heptane, 2,2,4,6,6-pentamethyl heptane, and 2,4-di tert buyl phenol exerted stronger effects on enzymatic activities. In summary, VOCs in rhizosphere soils of E. grandis might exert a toxic impact on E. fetida, among which 2,4-dimethyl heptane, 2,2,4,6,6-pentamethyl heptane, and 2,4-di tert buyl phenol have the strongest effects.

Bioaccumulation and toxic effects of decabromodiphenyl ether in the presence of nanoscale zero-valent iron in an earthworm-soil system

In this study, the bioaccumulation and toxic effects of decabromodiphenyl ether (BDE209) (1 and 10 mg kg^-1) were investigated in the earthworm Eisenia fetida in the presence of different levels of nanoscale zero-valent iron (nZVI) (100, 500, and 1000 mg kg^-1) in an earthworm-soil system. The results demonstrated that compared to single BDE209 exposure, the addition of high levels of nZVI significantly (P < 0.05) inhibited growth and respiration, while increased the avoidance response of earthworms. The perturbations of antioxidant enzyme activities (superoxide dismutase (SOD) and catalase (CAT)) and the malondialdehyde (MDA) content clearly revealed that oxidative stress was induced by the two chemicals. The histopathological observations of the body wall of earthworms under a combined exposure of 10 mg kg^-1 BDE209 with 500 or 1000 mg kg^-1 nZVI illustrated the presence of a serious injury in the intestinal tissues after a 28-day exposure. Additionally, a gas chromatography-mass spectrometry analysis revealed that the coexistence of high level of nZVI significantly (P < 0.05) decreased the bioaccumulation of BDE209 in earthworms; BDE208 and BDE206 were the predominant congeners of debrominated metabolites, and 4,6-dibromobenzene-1,2,3,5-tetraol along with benzene-1,2,4,5-tetraol were determined as the two main intermediates. The possible degradation pathways were proposed on the basis of the identified products. This work provides useful information on the biological effects of BDE209 and nZVI.

Bioaccumulation and bound-residue formation of 14C-decabromodiphenyl ether in an earthworm-soil system

Decabromodiphenyl ether (DecaBDE) is one of the most frequently detected flame retardants in terrestrial environments. However, the fate of DecaBDE and its transport in an earthworm-soil system with and without a DecaBDE-degrading strain have rarely been evaluated. In this study, ¹⁴C-DecaBDE was self-synthesized, and a DBDE-degrading strain, Rhodococcus erythropolis, was used in an earthworm-soil system. DecaBDE showed limited degradation and mineralization after 35days of all treatments. The bound-residue (BR) formation in soil was <2.5% in the system containing earthworms, which was significantly higher (p<0.05) than that observed in the absence of earthworms (<0.45%). DecaBDE could be adsorbed by the earthworms with a BSAF of ≤0.31. The distribution of ¹⁴C-DecaBDE concentrations in the earthworm roughly followed the pattern of crop gizzard>digestive system>head>tail>body wall, suggesting that DecaBDE was mainly uptaken through ingestion. Up to 31% of the ¹⁴C-DecaBDE in the earthworms was not extractable, revealing that the total concentration of accumulated ¹⁴C-DecaBDE was underestimated. The results also showed that the presence of DecaBDE-degrading bacteria did not significantly affect the fate of DecaBDE and its accumulation in earthworms. The study indicates that the conventional assessment of the bioaccumulation and ecological effects of DecaBDE, which is based only on extractable concentrations, may underestimate the risks.

Oxidative damage of naphthenic acids on the Eisenia fetida earthworm

Naphthenic acids (NAs) have been gaining recognition in recent years as potentially harmful environmental contaminants. Few studies have focused on the potential ecotoxicity of NAs to terrestrial environment. In this study, the responses of antioxidant system and lipid peroxidation and DNA damage were investigated after exposing Eisenia fetida to soil contaminated with NAs. The results indicated that NAs induced a significant increase (p < 0.05) in superoxide dismutase and catalase enzyme activities. The glutathione peroxidase enzyme activities were significantly inhibited (p < 0.05) in the medium and high dose treatments. An increase in malondialidehyde indicated that NAs could cause cellular lipid peroxidation in the tested earthworms. The percentage of DNA in the tail of comet assay of coelomocytes as an indication of DNA damage increased after treatment with different doses of NAs, and a dose-dependent DNA damage of coelomocytes was found. In conclusion, oxidative stress caused by NAs exposure induces physiological responses and genotoxicity on earthworms. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1337-1343, 2016.

Effect of decabromodiphenyl ether (BDE-209) on a soil-biota system: Role of earthworms and ryegrass

In the present study, the toxic effect of decabromodiphenyl ether (BDE-209), an important brominated fire retardant, on soil was evaluated by amending with different concentrations (0 mg/kg, 1 mg/kg, 10 mg/kg, and 500 mg/kg dry wt) for 40 d. The activities of 3 soil enzymes (urease, catalase, and alkaline phosphatase) were measured as the principal assessment endpoints. Meanwhile, the effects of natural environmental factors, such as light conditions and soil biota, on BDE-209 intoxication were studied. For the latter, 30 earthworms (Metaphire guillelmi) with fully matured clitella or ryegrass (Lolium perenne) with fully matured leaves were exposed in soil amended with BDE-209. The activities of the soil enzymes were adversely affected by BDE-209, especially for the high-concentration treatments, with greater adverse effects in the dark than in the light. The presence of earthworms reduced toxicity to BDE-209, whereas ryegrass did not. The calculated integrated biomarker response index, which provides a general indicator of the health status of test species by combining different biomarker signals, further validated these findings. Moreover, the antioxidant status (oxidant-antioxidant balance) of these 2 biota was assessed. Results indicated that BDE-209 significantly affected the activities of antioxidant enzymes (superoxide dismutase and catalase) and enhanced the levels of malondialdehyde in both species. The present study may facilitate a better understanding of the toxicity of BDE-209 toward the soil environment. Environ Toxicol Chem 2016;35:1349-1357. © 2015 SETAC.

Impacts of BDE209 addition on Pb uptake, subcellular partitioning and gene toxicity in earthworm (Eisenia fetida)

Lead (Pb) and decabromodiphenyl ether (BDE209) are the mainly co-existed contaminants at e-waste recycling sites. The potential toxicity of Pb (250 μg g(-1)) to earthworm Eisenia fetida in the presence of BDE209 (1, 10 and 100 μg g(-1)) was determined during 14-d incubation period. Compared to Pb treatment alone, the co-exposure with 1 μg g(-1) BDE209 barely affected Pb uptake, subcellular partitioning and gene expression; however, histopathological changes in earthworms' body wall (epidermal, circular and longitudinal muscles) demonstrated that 10 and 100 μg g(-1) BDE209 additions enhanced Pb uptake and altered its subcellular partitioning, indicating that Pb redistributed from fractions E (cell debris) and D (metal-rich granules) to fraction C (cytosols); Additionally, BDE209 supply significantly inhibited (p<0.05) the induction of SOD (superoxide dismutase) and CAT (catalase) gene expressions (maximum down-regulation 59% for SOD gene at Pb+100 μg g(-1) BDE209 and 89% for CAT gene at Pb+10 μg g(-1) BDE209), while facilitated (p<0.05) Hsp90 (heat shock protein 90) gene expression with maximum induction rate of 120% after exposure to Pb+10 μg g(-1) BDE209. These findings illustrate the importance of considering environmental BDE209 co-exposure when assessing Pb bioaccumulation and toxicity in multi-contaminated soil ecosystems.

Responses of growth inhibition and antioxidant gene expression in earthworms (Eisenia fetida) exposed to tetrabromobisphenol A, hexabromocyclododecane and decabromodiphenyl ether

Tetrabromobisphenol A (TBBPA), hexabromocyclododecane (HBCD) and decabromodiphenyl ether (BDE 209), suspected ubiquitous contaminants, account for the largest volume of brominated flame retardants (BFRs) since penta-BDE and octa-BDE have been phased out globally. In this paper, the growth inhibition and gene transcript levels of antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT)) and the stress-response gene involved in the prevention of oxidative stress (Hsp70) of earthworms (Eisenia fetida) exposed to TBBPA, HBCD and BDE 209 were measured to identify the toxicity effects of selected BFRs on earthworms. The growth of earthworms treated by TBBPA at 200 and 400 mg/kg dw were inhibited at rate of 13.7% and 22.0% respectively, while there was no significant growth inhibition by HBCD and BDE 209. A significant (P<0.01) up-regulation of SOD expression level was observed in earthworms exposed to TBBPA at 50 mg/kg dw (1.77-fold) and to HBCD at 400 mg/kg dw (2.06-fold). The transcript level of Hsp70 gene was significantly up-regulated (P<0.01) when earthworms exposed to TBBPA at concentration of 50-200 mg/kg (2.16-2.19-fold) and HBCD at 400 mg/kg (2.61-fold). No significant variation of CAT gene expression in all the BFRs treatments was observed, neither does all the target gene expression level exposed to BDE 209. Assessed by growth inhibition and the changes at mRNA levels of encoding genes in earthworms, TBBPA showed the greatest toxicity, followed by HBCD and BDE 209, consistent with trends in molecular properties. The results help to understand the molecular mechanism of antioxidant defense.

Growth inhibition and altered gene transcript levels in earthworms (Eisenia fetida) exposed to 2,2',4,4'-tetrabromodiphenyl ether

The toxic effects of the ubiquitous pollutant 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) on the earthworm Eisenia fetida were assessed by determining growth-inhibition and gene transcript levels of superoxide dismutase (SOD), catalase (CAT), glutathione transferase (GST), and transcriptional changes of the stress-response gene (heat-shock protein 70 [Hsp70]). Somatic growth and growth-inhibition rates in all BDE-47-treated groups were significantly different from those of the controls. The SOD gene transcripts were upregulated at all exposure doses and reached the maximum at the concentration of 400 mg/kg dry weight (dw) (3.84-fold, P < 0.01), which protected earthworms from oxidative stresses. However, downregulation of CAT and Hsp70 was present in all exposure doses and reached to the minimum at concentrations of 400 mg/kg dw (0.07-fold, P < 0.01 and 0.06-fold, P < 0.01, respectively). Upregulation of GST gene transcript level presented significant changes at concentrations of 10 (2.69-fold, P < 0.05) and 100 mg/kg dw (2.55-fold, P < 0.05). SOD maintained a dynamic balance to upregulate SOD expression to eliminate superoxide radicals in all dosage treatments, but downregulation of CAT decreased the ability to eliminate hydrogen peroxide. These changes could result in biochemical and physiological disturbances in earthworms.

EPR detection of hydroxyl radical generation and oxidative perturbations in lead-exposed earthworms (Eisenia fetida) in the presence of decabromodiphenyl ether

Lead (Pb) and decabromodiphenyl ether (BDE209) are the main contaminants at e-waste recycling sites, and their potential toxicological effects on terrestrial organisms have received extensive attention. However, the impacts on the oxidative perturbations and hydroxyl radical (·OH) generation in earthworms of exposure to the two chemicals remain almost unknown. Therefore, indoor incubation tests were performed on control and contaminated soil samples to determine the effects of Pb in earthworms Eisenia fetida in the presence of BDE209 through the use of several biomarkers in microcosms. The results have demonstrated that the addition of BDE209 (1 or 10 mg kg(-1)) decreased the enzymatic activities [superoxide dismutase, catalase (CAT), peroxidase] and total antioxidant capacity (T-AOC) compared with exposure to BDE209 alone (50, 250 or 500 mg kg(-1)). Electron paramagnetic resonance spectra indicated that ·OH radicals in earthworms were significantly induced by Pb in the presence of BDE209. The changing pattern of malondialdehyde (MDA) contents was accordant with that of ·OH intensity suggested that reactive oxygen species might lead to cellular lipid peroxidation. Furthermore, CAT exhibited more sensitive response to single Pb exposure than the other biomarkers, while T-AOC, ·OH and MDA might be three most sensitive biomarkers in earthworms after simultaneous exposure to Pb and BDE209. The results of these observations suggested that oxidative stress appeared in E. fetida, and it may play an important role in inducing the Pb and BDE209 toxicity to earthworms.

Effects of two polybrominated diphenyl ethers (BDE-47, BDE-209) on the swimming behavior, population growth and reproduction of the rotifer Brachionus plicatilis

Polybrominated diphenyl ethers (PBDEs) are new kinds of persistent organic pollutants (POPs) and their potential threats to the equilibrium and sustainability of marine ecosystems have raised worldwide concerns. Here, two kinds of PBDEs, tetra-BDE (BDE-47) and deca-BDE (BDE-209) were applied, and their toxic effects on the swimming behavior, population growth and reproduction of Brachionus plicatilis were investigated. The results showed that: (1) The actual concentrations of BDE-47 and -209 in the seawater phase measured by GC-MS (Gas Chromatography-Mass Spectrometer) were much lower than their nominal concentrations. (2) In accordance with the 24-hr acute tests, BDE-209 did not show any obvious swimming inhibition to rotifers, but a good correlation did exist between the swimming inhibition rate and BDE-47 concentration suggesting that BDE-47 is more toxic than BDE-209. (3) Both BDE-47 and -209 had a significant influence on the population growth and reproduction parameters of B. plicatilis including the population growth rate, the ratio of ovigerous females/non-ovigerous females (OF/NOF), the ratio of mictic females/amictic females (MF/AF), resting egg production and the mictic rate, which indicate that these parameters in B. plicatilis population were suitable for monitoring and assessing PBDEs. Our results suggest that BDE-47 and -209 are not acute lethal toxicants and may pose a low risk to marine rotifers at environmental concentrations for short-term exposure. They also accumulate differently into rotifers. Further research data are needed to understand the mechanisms responsible for the effects caused by PBDEs and to assess their risks accurately.

Effects of the joint exposure of decabromodiphenyl ether and tetrabromobisphenol A on soil bacterial community structure

Decabromodiphenyl ether (BDE209) and tetrabromobisphenol A (TBBPA) are the main contaminants at electronic waste (e-waste) recycling sites (EWRSs), and their potential toxicological effects have received extensive attention. However, the impact on soil microorganism of joint exposure to the two chemicals remains almost unknown. Therefore, indoor incubation tests were performed on control and contaminated soil samples to determine the response of soil bacterial community structure in the joint presence of BDE209 and TBBPA for the first time. The results have demonstrated that the soil bacterial diversity generally declined with increasing BDE209 and TBBPA concentrations and moderate and high doses of both chemicals can cause inhibitory effects. PCR-DGGE analysis indicated that the correlations between Shannon-Weaver index and contaminant concentrations could be well represented by a second-order polynomial model. The combined toxicity of the two chemicals was antagonistic during the first 14 days and then synergistic. Pectobacterium carotovorum, Sinorhizobium fredii HH103, and Stenotrophomonas maltophilia were highly tolerant to joint exposure during the entire incubation period. Moreover, some Staphylococcus strains were enriched after 90 days exposed to TBBPA or low concentrations of BDE209, indicating that they might degrade the two chemicals effectively. The results of these observations have provided some basic understanding of potential ecological effects of joint exposure to BDE209 and TBBPA on soil microorganism at EWRSs.

A multi-biomarker risk assessment of the impact of brominated flame retardant-decabromodiphenyl ether (BDE209) on the antioxidant system of earthworm Eisenia fetida

Decabromodiphenyl ether (BDE209) is the major contaminant at e-waste recycling sites (EWRSs), and its potential toxicological effects on terrestrial organisms have received extensive attention. However, the impacts of BDE209 on the antioxidant defense system in terrestrial organisms remain vague. Therefore, indoor incubation tests were performed systematically on control and contaminated soil samples to determine the effects of BDE209 on the antioxidant system of earthworm Eisenia fetida. The results showed that compared to the controls, superoxide dismutase (SOD) activities in all treated groups were elevated significantly after 21 and 28 days exposure; catalase (CAT) activities were much higher in all tests during the entire exposure period; peroxidase (POD) and glutathione-s-transferase (GST) activities generally decreased and indicated contrary response trend; the total antioxidant capacity (T-AOC) after exposure to low level of BDE209 (1 mg kg(-1)) was induced, whereas at 10 and 100 mg kg(-1) concentrations it showed suppression status; electron paramagnetic resonance (EPR) spectra suggested that hydroxyl radicals (OH) in earthworms were significantly induced by BDE209; the changes in malondialdehyde (MDA) contents suggested that reactive oxygen species (ROS) might lead to cellular lipid peroxidation in earthworms. The results of these observations suggested that severe oxidative stress occurred in E. fetida, and it may play an important role in inducing the BDE209 toxicity to earthworms.

Bioaccumulation of decabromodiphenyl ether (BDE209) in earthworms in the presence of lead (Pb)

BDE209 (decabromodiphenyl ether) and lead (Pb) are the main contaminants at e-waste recycling sites, and their potential toxicological effects on terrestrial organisms have received extensive attention. However, the impact on earthworms of exposure to the two chemicals remains almost unknown. Therefore, indoor incubation tests were performed on control and contaminated soil samples to determine the uptake and transformation of BDE209 in the presence of Pb for the first time. The results have demonstrated that Pb addition can affect BDE209 bioaccumulation efficiency compared with exposure to BDE209 alone. For a low BDE209 concentration (1mgkg(-1)), Pb addition barely affected the uptake of BDE209, whereas for a high BDE209 concentration (100mgkg(-1)), Pb addition elicited a complex response. Scanning electron microscope (SEM) observation indicated that a higher level of Pb (250 and 500mgkg(-1)) facilitated the uptake of BDE209 through the skin. Gas chromatography/mass spectrometry (GC/MS) analysis showed that the peak of BDE209 accumulation usually appeared in the joint exposure groups involving 10 or 100mgkg(-1) BDE209 and 250mgkg(-1) Pb, and the average bioaccumulation factor (BAF) was 0.53, which is more than 1.2 times that of single exposure to BDE209 (average=0.44). Also, the earthworms eliminated more BDE209 after 21d, and the biodegradation products were mainly BDE206 and BDE208. Furthermore, Pb addition can affect the transformation efficiency of BDE209 in earthworms, and several lower bromodiphenyl ethers can be detected. The results of these observations have provided a basic understanding of the potential ecotoxicological effects of joint PBDE and heavy metal exposure on terrestrial invertebrates.

Lead accumulations and toxic effects in earthworms (Eisenia fetida) in the presence of decabromodiphenyl ether

Lead (Pb) and decabromodiphenyl ether (BDE209) are the main contaminants at e-waste recycling sites, and their potential toxicological effects on terrestrial organisms have received extensive attention. However, the impact on earthworms of exposure to the two chemicals remains almost unknown. Therefore, indoor incubation tests were performed on control and contaminated soil samples to determine the Pb accumulations and toxic effects by earthworms in the presence of BDE209 for the first time. The results have demonstrated that BDE209 presence can affect Pb bioaccumulation efficiency compared with exposure to Pb alone. The Pb contents in earthworms had a highly positive correlation with the Pb concentrations in soils. For different Pb doses, almost contrary response trends were found for Pb uptake examined separately on day 7 or 28, and dose-effect relationships were clearly observed in the presence of BDE209. After 7 days of exposure, the earthworm bodies receiving 1-mg kg(-1) BDE209 dose showed significantly lower Pb contents (average = 175.85 mg kg(-1)) and bioaccumulation factor (average = 0.574) than those receiving non-BDE209 treatments (217.39 mg kg(-1) and 1.209, respectively). As the incubation time extended, the influence of BDE209 presence on Pb uptake gradually declined. Additionally, either single or combined exposure to both chemicals can affect the protein synthesis in earthworms (p < 0.01), while different levels of BDE209 addition barely caused visible differences. The results of these observations have provided a basic understanding on the potential toxicological effects of joint Pb and BDE209 exposure on terrestrial invertebrates.