Suchergebnisse

Abstract
Background
The high production volume of engineered nanomaterials (ENMs) may lead to high pressure on the environment, and a scientific assessment of ENMs that bioaccumulate in organisms and biomagnify in the food web is necessary. Within the regulation of chemicals in several jurisdictions, such as the European regulation REACH, the bioconcentration factor is the standard endpoint. The bioconcentration factor is mostly determined by flow-through fish tests. However, nanomaterials tend to agglomerate, which may lead to sedimentation in aquatic environments. The bioavailability of the tested nanomaterials may be thus impaired for pelagic species, including fish, in comparison to benthic or filtrating species. Several risk assessment regulations allow the usage of data gained during tests using invertebrates and such data may allow a waiver of further tests using vertebrates. The aim of this study was to elucidate the potential of different freshwater invertebrate species to be used in laboratory bioaccumulation studies on ENMs and to give some guidance for the use of bioaccumulation endpoints derived from studies using aquatic invertebrate species in the risk assessment process for ENMs.

Results
The existing literature related to the testing of nanomaterial bioaccumulation with freshwater invertebrates was screened and reviewed to find suitable test species with regard to their ecology and physiology, as well as laboratory test systems allowing to investigate the bioavailability/bioaccumulation of nanomaterials with the respective species. Bivalvia, gastropoda, isopoda, amphipoda, and branchiopoda were reviewed and their suitability for bioaccumulation testing was assessed. Amphipods and bivalves represent worst-case scenarios and show clear advantages to be used as test organisms. However, only amphipods allow the examination of two clearly independent exposure pathways (water and diet).

Conclusion
Amphipods are suitable test organisms for bioaccumulation testing of ENMs. The results from amphipod bioconcentration and biomagnification tests can be included in a tiered assessment suggested at the end of this study allowing a clear grading of the tested nanomaterials as "bioaccumulative" or "non bioaccumulative." Due to the worst-case scenario of the amphipod test, this approach may allow a waiver of further vertebrate tests.

Abstract
Background
Manufactured nanomaterials (MNMs) are released into the environment in increasing quantities. Consequently, MNMs also reach the aquatic environment, where they can interact with different organisms. Previous studies have already shown that filter-feeding bivalves can ingest nanomaterials from the surrounding water leading to higher concentration of the material. Furthermore, they have been shown to be vectors for environmental chemicals and pathogens to other organisms, as their feces/pseudofeces (F/pF) play a crucial role as a food source for other species. We exposed bivalves (Corbicula sp.) to MNMs and performed experiments to investigate the possible transport of MNMs by their feces to the benthic amphipod Hyalella azteca. Silver (Ag) and gold (Au) nanoparticles (NPs) as well as fluorescent polystyrene nanoparticles were used in this study. They allowed the investigation of the metal content of the bivalves' feces and the amphipods feeding on it, as well as the localization of the fluorescent particles in the body of the animals.

Results
Examination of the feces by fluorescence microscope and determination of the total metal content by inductively coupled plasma mass spectrometry (ICP-MS) showed a high accumulation of the exposed MNMs in the F/pF. The examination of fecal matter, using transmission electron microscopy confirmed the nanoparticulate character of the metals in the examined fecal matter. After exposure of amphipods to the MNMs containing fecal matter, the fluorescent MNMs were localized in the animals gut. The chronic exposure of juvenile amphipods over 21 days to feces enriched with Au MNMs caused significant effects on the growth of the amphipods. The transfer of both metals (Ag and Au) from the fecal matter to the amphipods was confirmed after total metal measurements.

Conclusion
Probably, for the first time, it has been shown that when exposed to MNMs bivalves can transfer these particles to other benthic species. Transfer is via released F/pF upon which the benthic species feed and thus could ingest the particles. The high concentrations of MNMs in the fecal matter raises concerns about the potential accumulation and transfer of the materials and associated ecotoxicological effects in invertebrates such as benthic amphipods.

AbstractBackgroundThe trophic magnification factor (TMF) is a metric that describes the average trophic magnification of a chemical through a food web. TMFs may be used for the risk assessment of chemicals, although TMFs for single compounds can vary considerably between studies despite thorough guidance available in the literature to eliminate potential sources of error. The practical realization of a TMF investigation is quite complex and often only a few chemicals can be investigated due to low sample masses. This study evaluated whether a pragmatic approach involving the large-scale cryogenic sample preparation practices of the German Environmental Specimen Bank (ESB) is feasible. This approach could provide sufficient sample masses for a reduced set of samples allowing screenings for a broad spectrum of substances and by that enabling a systematic comparison of derived TMFs. Furthermore, it was assessed whether plausible TMFs can be derived with the 'Food web on ice' approach via a comparison with literature TMF values.ResultsThis investigation at Lake Templin near Potsdam is the first TMF study for a German freshwater ecosystem and aimed to derive TMFs that are appropriate for regulatory purposes. A set of 15 composite biota samples was obtained and analyzed for an extended set of benchmark chemicals such as persistent organic pollutants, mercury and perfluoroalkyl substances. TMFs were calculated for all substances that were present in > 80% of the biota samples. For example, in the case of polychlorinated biphenyls, TMFs from 1.7 to 2.5 were determined and comparisons to literature TMFs determined in other freshwater ecosystems showed similarities. We showed that 32 out of 35 compounds analyzed had TMFs significantly above 1. In the remaining three cases, the correlations were not statistically significant.ConclusionsThe derived food web samples allow for an on-demand analysis and are ready-to-use for additional investigations. Since substances with non-lipophilic accumulation properties were also included in the list of analyzed substances, we conclude that the 'Food web on ice' provides samples which could be used to characterize the trophic magnification potential of substances with unknown bioaccumulation properties in the future which in return could be compared directly to the benchmarking patterns provided here.

Abstract
Background
The assessment of persistence, bioaccumulation and toxicity (PBT) is part of the regulation process of ionic organic compounds (IOCs) and a major challenge, as a commonly acknowledged approach for the estimation of the bioaccumulation potential of IOCs is still missing. The goal of the present study was, therefore, to experimentally determine the bioaccumulation of fully ionized compounds and to identify screening parameters that can indicate high bioaccumulation potential of IOCs. Three feeding studies with rainbow trout (Oncorhynchus mykiss) were carried out according to OECD TG 305. Separation of liver, gastrointestinal tract (GIT) and carcass allowed to further elucidate the tissue distribution of the individual test substances. The chemicals chosen had characteristics that made them suspect for high bioaccumulation, and included two cations (tetrabutylphosphonium bromide (TBP), trimethyloctadecyl ammonium chloride (TMOA)) and four anions (benzotriazole, tecloftalam, pentachlorophenol (PCP), MEE-phosphonate). Data on the dietary biomagnification of IOCs (strong acids) were also collected from published literature.

Results
The highest distribution factors were found for the GIT, followed by liver. However, none of the tested IOCs showed a distinct biomagnification potential, as kinetic biomagnification factors (BMFk) ranged between 0.001 and 0.05 g/g (median 0.009 g/g). Cations showed lower assimilation efficiency (α) than anions, except for tecloftalam. In contrast, anions showed a considerably faster depuration rate (half-life less than 0.5 days) compared to cations (half-life of around 5 days). Sixteen potential screening parameters for BMF were calculated with a chemical property estimation tool (ACD/i-Lab) and correlated with the BMF data from this study and from literature. The number of hydrogen bond donors (nHBD) showed the highest correlation to measured BMF, but the prediction is only based on two values (one or two nHBD), while the other descriptors were insignificantly correlated.

Conclusion
The suspected dietary bioaccumulation potential of the six IOCs could not be confirmed in the feeding studies with rainbow trout. The more than twenty screening parameters showed no particularly high correlation neither with the test results nor with the BMF values collected from literature. The results corroborate earlier findings that ionization lowers the tendency of a chemical for dietary bioaccumulation, compared to non-ionized chemicals. In addition to the lipophobicity of ionic molecule moieties, fast depuration seems to be a major reason for the observed low dietary bioaccumulation of ionic compounds, in particular anions. Fast depuration may happen due to rapid metabolism of charged compounds, and future studies should test this hypothesis.

Abstract
Background
The European Water Framework Directive (WFD) requires the monitoring of biota—preferably fish—to check the compliance of tissue concentrations of priority substances (PS) against substance-specific environmental quality standards (EQSs). In monitoring programs, different fish species are covered, which often are secondary consumers with a trophic level (TL) of about 3. For harmonization, a normalization of monitoring data to a common trophic level is proposed, i.e., TL 4 (predatory fish) in freshwaters, so that data would be sufficiently protective. For normalization, the biomagnification properties of the chemicals can be considered by applying substance-specific trophic magnification factors (TMFs). Alternatively, TL-corrected biomagnification factors (BMFTLs) may be applied. Since it is impractical to derive site-specific TMFs or BMFTLs, often data from literature will be used for normalization. However, available literature values for TMFs and BMFTLs are quite varying. In the present study, the use of literature-derived TMFs and BMFTLs in data normalization is studied more closely.

Results
An extensive literature evaluation was conducted to identify appropriate TMFs for the WFD PS polybrominated diphenyl ethers (PBDE), hexachlorobenzene, perfluorooctane sulfonate (PFOS), dioxins and dioxin-like compounds (PCDD/F + dl-PCB), hexabromocyclododecane, and mercury. The TMFs eventually derived were applied to PS monitoring data sets of fish from different trophic levels (chub, bream, roach, and perch) from two German rivers. For comparison, PFOS and PBDE data were also normalized using literature-retrieved BMFTLs.

Conclusions
The evaluation illustrates that published TMFs and BMFTLs for WFD PS are quite variable and the selection of appropriate values for TL 4 normalization can be challenging. The normalized concentrations partly included large uncertainties when considering the range of selected TMFs, but indicated whether an EQS exceedance at TL 4 can be expected. Normalization of the fish monitoring data revealed that levels of substances accumulating in the food web (TMF or BMF > 1) can be underestimated when relying on fish with TL < 4 for EQS compliance assessment. The evaluation also revealed that TMF specifically derived for freshwater ecosystems in Europe would be advantageous. Field-derived BMFTLs seemed to be no appropriate alternative to TMFs, because they can vary even stronger than TMFs.

Kürzlich wurde ein Testkonzept für Biokonzentrationstests mit dem Süßwasserflohkrebs H. azteca (HYBIT) beschrieben. Dabei wurde gezeigt, dass Biokonzentrationsfaktoren (BCFs), die für Verbindungen mit unterschiedlichen hydrophoben Eigenschaften ermittelt wurden (log Kow 2,4 – 7,8), eine starke Korrelation zu denen aus Fischtests aufweisen. Das diesem Bericht zu Grunde liegende Projekt wurde durchgeführt, um die Eignung des HYBIT-Tests zur Prüfung eines erweiterten Kreises von Substanzklassen einschließlich solcher, die schwer zu testen sind, zu untersuchen und erforderlichenfalls das Testkonzept entsprechend zu erweitern. Das Bioakkumulationspotential von hoch lipophilen UV-Stabilisatoren und ionischen organischen PFAS-Verbindungen sowie Silber-, Titandioxid- und Goldnanomaterialien wurde getestet. Die zwei möglichen Ansätze zur Durchführung von Biokonzentrationsstudien mit H. azteca unter Verwendung eines semistatischen Testaufbaus oder eines Durchflussansatzes wurden angewendet. Der Einsatz von Lösungsvermittlern und die lösungsmittelfreie Applikation der hydrophoben Testverbindungen wurden verglichen. Wegen der Schwierigkeiten bei der wässrigen Exposition von Nanomaterialien wurden im Rahmen dieses Projekts auch Biomagnifikationsstudien durchgeführt. Wir konnten zeigen, dass der HYBIT-Ansatz die Testung schwer zu applizierender Substanzen ermöglicht und die Ermittlung regulatorischer Endpunkte für die Bioakkumulationsbewertung zulässt. Aufgrund der kürzeren Expositionszeiten und der kleineren verwendeten Versuchseinheiten bietet der HYBIT-Ansatz mehrere Vorteile gegenüber dem Durchfluss-Fischtest. Als Nicht-Wirbeltier-Test kann der Hyalella-Biokonzentrationstest (bzw. Biomagnifikationstest) dazu beitragen, die für die behördlichen Tests von Chemikalien erforderliche Fischmenge weiter zu reduzieren.

Trophic magnification factors (TMFs) have been derived in a variety of different aquatic eco-systems worldwide to investigate accumulation patterns of environmentally relevant chemicals. The TMF is defined as a metric that describes the average trophic magnification of a chemical through the analyzed food web under realistic environmental conditions. Not only is the TMF interesting for chemicals' risk assessment related questions, but also for monitoring aspects under the European Water Framework Directive (WFD). This study is the first TMF study con-ducted in a German freshwater ecosystem, that is, Lake Templin near Potsdam. Aim of the study was to investigate the food web magnification following existing guidance to derive reliable TMFs that could be used for regulatory purposes. A sampling campaign yielded 15 biota samples covering about three trophic levels, which have been processed and cryo-preserved following standardized protocols of the German Environmental Specimen Bank (ESB). The samples remain available for future analysis and, thus, form a "food web on ice". These large-scale food web samples are ready-to-use for a broad variety of analyses. In a first step, a plausibility check was performed. Different persistent organic pollutants (POPs), which are known to magnify in food webs and are not readily metabolized, serve as benchmarks. It could be shown that for nearly all of the POPs analyzed, the TMFs are significantly above 1. In a few cases, an enrichment is also seen, but not statistically relevant. Since not only POPs with lipophilic accumulation properties were analyzed, it could be concluded that the food web on ice samples from Lake Templin can be used to characterize the trophic magnification potential of further substances with less investigated bioaccumulation properties present in the samples. To this end, several PFAS, pharmaceuticals, pesticides and methyl siloxanes were investigated in the samples to derive their TMFs.

Increasing amounts of MNMs are produced for industrial purpose and released to the environment by their usage or disposal of the products. Due to the high production volume MNMs are subject to PBT-assessment to estimate their potential environmental impact. The classical method to elucidate the bioaccumulation potential of chemicals is the flow-through approach with fish according to OECD TG 305 providing a BCF estimate. However, most MNMs tend to sediment in the aquatic environment and are thus difficult to be tested following the established test concept where constant and continous exposure conditions need to be achieved. The freshwater filter feeding bivalve Corbicula fluminea has previously shown to ingest and accumulate MNMs present in the water phase. To investigate the suitability of C. fluminea as test organism for bioaccumulation studies we developed a new flow-through system to expose the mussels under constant expsosure conditions. Different MNMs, each having different characteristics, were applied to determine their bioaccumulation potential. The silver nanoparticle NM 300K (Ag NP) was tested as a well dispersable and ion releasing MNM. In addition, C. fluminea was exposed to AgNO3 as a source of dissolved Ag+ to compare the bioaccumulation of Ag from dissolved and nanoparticulate sources. The titanium dioxide NP NM 105 was used for testing a non ion releasing MNM and the polystyrene nanoparticle (nPS) Fluoro-Max™, containing a fluorescence dye, was tested representing MNMs that are based on organic polymers. The uptake and distribution of nPS in the mussel soft tissue were observed using a fluorescence microscope. Following exposure to metal and metal oxides we were able to determine BAFss and BCFss values. BAFss values of 31 and 128 for two NM 300K concentrations (0.624 and 6.177 μg Ag/L) and of 6,150 and 9,022 for two NM 105 concentrations (0.099 and 0.589 μg TiO2/L) showed that the BAFss depends on the exposure concentration. Also for AgNO3, concentration depending BCFss of 31 and 711 were estimated for the higher and lower concentration, respectively. The analysis of metals in the soft tissue of previously exposed mussels and the resulting compartment specific distribution factors provide clear indications, that the uptake of NPs was mainly driven by the simple ingestion of NPs rather than the accumulation of dissolved ions. This was supported by the measurement of particle concentrations in mussel tissue using single particle ICP-MS.