Person: Polleichtner, Christian
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Veröffentlichung An alternative approach to overcome shortcomings with multiple testing of binary data in ecotoxicology(2017) Lehmann, René; Bachmann, Jean; Karaoglan, Bilgin; Lacker, Jens; Polleichtner, ChristianBinary data such as survival, hatching and mortality are assumed to be best described by a binomial distribution. This article provides a simple and straight forward approach for derivation of a no/lowest observed effect level (NOEL/LOEL) in a one-to-many control versus treatments setup. Practically, NOEL and LOEL values can be derived by means of different procedures, e.g. using Fisher̷s exact test in coherence with adjusted p values. However, using adjusted p values heavily decreases statistical power. Alternatively, multiple t tests (e.g. Dunnett test procedure) together with arcsin-square-root transformations can be applied in order to account for variance heterogeneity of binomial data. Arcsin-square-root transformation, however, violates normal distribution because transformed data are constrained, while normal distribution provides data in the range (-8,8). Furthermore, results of statistical tests relying on an approximate normal distribution are approximate too. When testing for trends in probabilities of success (probs), the step down CochranŃArmitage trend test (CA) can be applied. The test statistic used is approximately normal. However, if probs approach 0 or 1, normal approximation of the null-distribution is suboptimal. Thus, critical values and p values lack statistical accuracy. We propose applying the closure principle (CP) and FisherŃFreemanŃHalton test (FISH). The resulting CPFISH can solve the problems mentioned above. CP is used to overcome a-inflation while FISH is applied to test for differences in probs between the control and any subset of treatment groups. Its applicability is presented by means of real data sets. Additionally, we performed a simulation study of 81 different setups (differing numbers of control replicates, numbers of treatments etc.), and compared the results of CPFISH to CA allowing us to point out the advantages and disadvantages of the CPFISH. Quelle: linkspringer.comVeröffentlichung Abschätzung der Umweltgefährdung durch Silber-Nanomaterialien - vom chemischen Partikel bis zum technischen Produkt - UMSICHT(2013) Polleichtner, Christian; Völker, Doris; Deutschland. UmweltbundesamtVeröffentlichung Abschätzung der Umweltgefährdung durch Silber-Nanomaterialien - vom chemischen Partikel bis zum technischen Produkt - UMSICHT(2013) Polleichtner, Christian; Völker, Doris; Deutschland. UmweltbundesamtVeröffentlichung Zur Sonderstellung von Antibiotika bei der Gewässerbelastung durch Arzneimittel(2016) Baumann, Michaela; Weiß, Klaus; Maletzki, Dirk; Schuessler, Walter; Polleichtner, Christian; Schudoma, DieterVeröffentlichung Four selected high molecular weight heterocyclic aromatic hydrocarbons: Ecotoxicological hazard assessment, environmental relevance and regulatory needs under REACH(2018) Brendel, Stephan; Einhenkel-Arle, Doreen; Hassold, Enken; Polleichtner, ChristianLittle is known about the ecotoxicity of heterocyclic aromatic hydrocarbons (NSO-HETs) to aquatic organisms. In the environment, NSO-HETs have been shown to occur in a strong association with their unsubstituted carbocyclic analogues, the polycyclic aromatic hydrocarbons (PAH), for which much more information is available. The present study addressed this issue by investigating the toxicity of four selected NSO-HETs in green algae (Desmodesmus subspicatus), daphnids (Daphnia magna) and fish embryos (Danio rerio). The four high molecular weight NSO-HETs dibenz[a,j]acridine (DBA), 7H-dibenzo[c,g]carbazole (DBC), benzo[b]naphtho[2,1-d]thiophene (BNT) and benzo[b]naphtho[1,2-d]furan (BNF) were selected, based on the results of a previous research project, indicating a lack of toxicity data and a high potential for persistence and bioaccumulation. The solubilities of the NSO-HETs in the test media were determined and turned out to be comparatively low (2.7-317ng/L) increasing in the following order: DBA < BNT " DBC " BNF. Exposure concentrations during the toxicity tests were quantified with GC-MS and decreased strongly possibly due to sorption or metabolising during the test periods (48-96 h). Therefore, the estimated effect concentrations were related to the mean measured concentrations, as endpoints related to nominal concentrations would have underestimated the toxicity many times over. Within the range of the substance solubilities, BNF affected all test organisms with fish embryos being the most sensitive (fish: EC50 6.7 ng/L, algae: EC10 17.8 ng/L, daphnids: EC50 55.8 ng/L). DBC affected daphnids (EC50 2.5 ng/L,) and algae (EC10 3.1 ng/L), but not fish embryos. The lowest toxicity endpoint was observed for BNT affecting only algae (NOEC 0.556 ng/L) and neither daphnids nor fish embryos. DBA did not show any effects on the tested organisms in the range of the water solubility. However, we would expect effects in long-term toxicity studies to fish and aquatic invertebrates for all substances at lower concentrations, which needs further investigation. All four NSO-HETs were identified in mussels (Mytilus edulis) from the German coasts, in green kale (Brassica oleracea var. acephala) and in freshwater harbor sediment in concentrations between 0.07 and 2 ng/kg, highlighting their relevance as environmental contaminants. There is a need to regulate the four NSO-HETs within the REACH regulation due to their intrinsic properties and their environmental relevance. However, acquisition of additional experimental data appears to be pivotal for a regulation under REACH. © 2018 The Authors. Published by Elsevier Inc.Veröffentlichung The CPCAT as a novel tool to overcome the shortcomings of NOEC/LOEC statistics in ecotoxicology(2018) Lehmann, René; Bachmann, Jean; Karaoglan, Bilgin; Lacker, Jens; Polleichtner, ChristianSpecies reproduction is an important determinant of population dynamics. As such, this is an important parameter in environmental risk assessment. The closure principle computational approach test (CPCAT) was recently proposed as a method to derive a NOEC/LOEC for reproduction count data such as the number of juvenile Daphnia. The Poisson distribution used by CPCAT can be too restrictive as a model of the data-generating process. In practice, the generalized Poisson distribution could be more appropriate, as it allows for inequality of the population mean ÎÌ and the population variance ÏĆ2 . It is of fundamental interest to explore the statistical power of CPCAT and the probability of determining a regulatory relevant effect correctly. Using a simulation, we varied between Poisson distribution ( ÎÌ=ÏĆ2 ) and generalized Poisson distribution allowing for over-dispersion ( ÎÌ<ÏĆ2 ) and under-dispersion ( ÎÌ>ÏĆ2 ). The results indicated that the probability of detecting the LOEC/NOEC correctly was â 0.8 provided the effect was at least 20% above or below the mean level of the control group and mean reproduction of the control was at least 50 individuals while over-dispersion was missing. Specifically, under-dispersion increased, whereas over-dispersion reduced the statistical power of the CPCAT. Using the well-known Hampel identifier, we propose a simple and straight forward method to assess whether the data-generating process of real data could be over- or under-dispersed.Veröffentlichung Prospective environmental risk assessment of mixtures in wastewater(2018) Coors, Anja; Vollmar, Pia; Sacher, Frank; Hassold, Enken; Polleichtner, Christian; Gildemeister, Daniela; Kühnen, UteThe aquatic environment is continually exposed to a complex mixture of chemicals, whereby effluents of wastewater treatment plants (WWTPs) are one key source. The aim of the present study was to investigate whether environmental risk assessments (ERAs) addressing individual substances are sufficiently protective for such coincidental mixtures. Based on a literature review of chemicals reported to occur in municipal WWTP effluents and mode-of-action considerations, four different types of mixtures were composed containing human pharmaceuticals, pesticides, and chemicals regulated under REACH. The experimentally determined chronic aquatic toxicity of these mixtures towards primary producers and the invertebrate Daphnia magna could be adequately predicted by the concept of concentration addition, with up to 5-fold overestimation and less than 3-fold underestimation of mixture toxicity. Effluents of a municipal WWTP had no impact on the predictability of mixture toxicity and showed no adverse effects on the test organisms. Predictive ERAs for the individual mixture components based on here derived predicted no effect concentrations (PNECs) and median measured concentrations in WWTP effluents (MCeff) indicated no unacceptable risk for any of the individual chemicals, while MCeff/PNEC summation indicated a possible risk for multi-component mixtures. However, a refined mixture assessment based on the sum of toxic units at species level indicated no unacceptable risks, and allowed for a safety margin of more than factor 10, not taking into account any dilution of WWTP effluents by surface waters. Individual substances, namely climbazole, fenofibric acid and fluoxetine, were dominating the risks of the investigated mixtures, while added risk due to the mixture was found to be low with the risk quotient being increased by less than factor 2. Yet, uncertainty remains regarding chronic mixture toxicity in fish, which was not included in the present study. The number and identity of substances composing environmental mixtures such as WWTP effluents is typically unknown. Therefore, a mixture assessment factor is discussed as an option for a prospective ERA of mixtures of unknown composition. © 2018 Elsevier Ltd. All rights reserved.