Metabolic responses of Eisenia fetida after sub-lethal exposure to organic contaminants with different toxic modes of action

Nuclear magnetic resonance (NMR) - based metabolomics has the potential to identify toxic responses of contaminants within a mixture in contaminated soil. This study evaluated the metabolic response of Eisenia fetida after exposure to an array of organic compounds to determine whether contaminant-specific responses could be identified. The compounds investigated in contact tests included: two pesticides (carbaryl and chlorpyrifos), three pharmaceuticals (carbamazephine, estrone and caffeine), two persistent organohalogens (Aroclor 1254 and PBDE 209) and two industrial compounds (nonylphenol and dimethyl phthalate). Control and contaminant-exposed metabolic profiles were distinguished using principal component analysis and potential contaminant-specific biomarkers of exposure were found for several contaminants. These results suggest that NMR-based metabolomics offers considerable promise for differentiating between the different toxic modes of action (MOA) associated with sub-lethal toxicity to earthworms.     

Decabromodiphenyl ethane and decabromodiphenyl ether in Swedish background air

Decabromodiphenyl ethane (DPDPE) is a flame retardant that has been on the market for more than 20 years and is used as a replacement for decabromodiphenyl ether (BDE-209). Environmental data on DPDPE are scarce but for BDE-209, studies have shown that long-range transport in the atmosphere leads to contamination of remote regions. Given their similar physical-chemical properties, we hypothesized that this is also true for DPDPE. In this study we explored the European continent as a source for DBDPE by collecting air samples at a back-ground location in southern Sweden. Twelve samples with stable air mass back trajectories over the 24 h sampling period were analysed. BDE-209 and 5 polycyclic aromatic hydrocarbons (PAHs) were also included in the study. The concentration ranges of DBDPE and BDE-209 were similar, 0.077-7.9 and 0.093-1.8 pg m⁻³ air, respectively. The highest concentrations were detected when the air originated from the European continent and the lowest during periods with rather stagnant air over southern Scandinavia. The concentrations of DBDPE and BDE-209 did not co-vary, indicating that there are different major sources of the two compounds. In air, the compounds measured in this study are predominantly associated with particles. PAHs in the atmosphere are known to originate primarily from combustion processes and their concentrations were highly correlated with several measures of atmospheric particle concentration, i.e. PM 10, PM 2.5, soot, and N 450 (number of particles in the size range approximately 420-450 nm). No clear correlations were found between the concentrations of DBDPE or BDE-209 and any of the measures of particle concentrations, indicating that the emissions of these are not related to the major sources of emissions of soot or small particles.     

Debrominated and methoxylated polybrominated diphenyl ether metabolites in rainbow trout (Oncorhynchus mykiss) after exposure to decabromodiphenyl ether

Decabromodiphenyl ether (BDE209) is the primary component in a commonly used flame retardant. Previous studies had proved that BDE209 itself was not toxic, while its metabolites including debrominated diphenyl ethers (De-BDEs) and methoxylated brominated diphenyl ethers (MeO-BDEs) posed a potential threat to organisms. Many studies had indicated that BDE209 could metabolize quickly in mammals, but lacking in the basic data about the metabolism of BDE209 in fish. In the present study, two replicate treatment groups of rainbow trout (Oncorhynchus mykiss) were exposed to BDE209 via a single intraperitoneal injection approximately 100 and 500 ng/g, respectively. Muscle, liver and blood samples were collected to analyze the specific metabolites on day 1 and day 28 post injection. The highest concentration of BDE209 was detected in muscle tissues, from 796.1 ng/g wet weight (day 1) to 687.1 ng/g wet weight (day 28) in high dose group, suggesting that BDE209 could accumulate slightly in muscle tissues. However, BDE209 was not detected in the blood for all treatments. Most congeners of De-BDEs were found in muscle and liver tissues, with the highest concentration in the liver. The main De-BDEs were nona-, octa-, hepta- and penta-De-BDEs. A total of seven MeO-BDE metabolites were observed among di erent fish tissues. Blood had the highest contribution of the MeO-BDE metabolites. Each MeO-BDE congener increased over the 28 days. These results in contrast to other studies suggested possible species-specific di erences in metabolic abilities.     

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.