Jan Wölz

Effect-directed analysis of Ah receptor-mediated activities caused by PAHs in suspended particulate matter sampled in flood events

Suspended particulate matter (SPM) sampled during a flood event in the year 2004 at the rivers Neckar and Rhine (Southwest Germany) was assessed for aryl hydrocarbon receptor (AhR)-mediated activities using EROD induction in the rainbow trout liver cell line RTL-W1. All EROD inductions were normalized to the positive control TCDD and given as bio-TEQ values. Since all samples indicated elevated AhR-mediated toxicities, an effect-directed analysis (EDA) was applied to identify substances causing the effects. In three primary fractions (F1 to F3) non-polar aliphatics, non-polar aromatic substances and more polar substances were separated. Fraction F2, co-eluting with non-polar polyaromatic substances (PACs) including polycyclic aromatic hydrocarbons (PAHs) gave highest AhR-agonistic effects and, thus, were sub-fractionated into seven secondary fractions (F2-1 to F2-7). Fraction F2-1, co-eluting with PCBs and PCDD/Fs, did not cause AhR-agonist activities. F2-2 to F2-4 containing PACs of less than 16 aromatic C-atoms produced minor activities. Highest inductions were detected with fraction F2-5 to F2-7, containing substances of more than 16 aromatic C-atoms (bio-TEQs up to approximately 4500 pg/g). Concentrations and relative potencies (REPs) of priority EPA-PAHs allowed the calculation of chemical toxicity equivalent concentrations (chem-TEQ values). Based on the chem-TEQs, EPA-PAHs explained between 5 and 58% of crude extract bio-TEQs from both rivers. Whereas fractions F2-1 to F2-4 indicated no biological activities, EPA-PAHs in fraction F2-5 to F2-7 accounted for 2 to 137% of AhR-related activities.

Endocrine disrupting, mutagenic, and teratogenic effects of upper Danube River sediments using effect‐directed analysis

Effect-directed analysis (EDA) can be useful in identifying and evaluating potential toxic chemicals in matrixes. Previous investigations of extracts of sediments from the upper Danube River in Germany revealed acute nonspecific and mechanism-specific toxicity as determined by several bioassays. In the present study, EDA was used to further characterize these sediments and identify groups of potentially toxic chemicals. Four extracts of sediments were subjected to a novel fractionation scheme coupled with identification of chemicals to characterize their ability to disrupt steroidogenesis or cause mutagenic and/or teratogenic effects. All four whole extracts of sediment caused significant alteration of steroidogenesis and were mutagenic as well as teratogenic. The whole extracts of sediments were separated into 18 fractions and these fractions were then subjected to the same bioassays as the whole extracts. Fractions 7 to 15 of all four extracts were consistently more potent in both the Ames fluctuation and H295R assays. Much of this toxicity could be attributed to polycyclic aromatic hydrocarbons, sterols, and in fraction 7-naphthoic acids. Because the fraction containing polychlorinated biphenyls, polychlorodibenzodioxin/furan, dichlorodiphenyltrichloroethane, and several organophosphates did not cause any observable effects on hormone production or a mutagenic response, or were not detected in any of the samples, these compounds could be eliminated as causative agents for the observed effects. These results demonstrate the value of using EDA, which uses multiple bioassays and new fractionation techniques to assess toxicity. Furthermore, to our knowledge this is the first study using the recently developed H295R assay within EDA strategies.

How flood events affect rainbow trout: Evidence of a biomarker cascade in rainbow trout after exposure to PAH contaminated sediment suspensions

Increasing frequency and intensity of flood events are major concerns in the context of climate change. In addition to the direct hydrological implications of such events, potential ecotoxicological impacts are of increasing interest. It is vital to understand mechanisms of contaminant uptake from suspended particulate matter (SPM) and related effects in aquatic biota under realistic conditions. However, little is known about these processes. Due to recent changes in climate, during summer temperatures of German rivers frequently exceed 25°C. Effects of re-suspension of sediments on biota under elevated temperature regimes are likely to differ from those under lower temperature regimes. To elucidate this differential response of aquatic vertebrates, rainbow trout were exposed to suspensions of sediment from the Rhine River that was spiked with a mixture of polycyclic aromatic hydrocarbons (PAH). The experiments were conducted under two different temperature regimes (24°C or 12°C). Physicochemical parameters, including concentration of PAHs in SPM, and biomarkers in fish (biliary PAH metabolites, 7-ethoxyresorufin O-deethylase activity, lipid peroxidation (LPO), mRNA expression of some genes and micronuclei) were measured over the course of a 12d study. Concentrations of pyrene and phenanthrene decreased over time, while no decrease was observed for chrysene and benzo[a]pyrene. The biomarker cascades, more specifically the temporal dynamics of biomarker reactions, did not only show quantitative differences (i.e. different induction intensity or rate of biomarker responses) at the two temperatures but also qualitative differences, i.e. different biomarker responses were observed. A slight significant increase of biliary metabolites in fish was observed in un-spiked sediment at 24°C. In bile of fish exposed to PAH spiked sediment concentrations of 1-hydroxypyrene and 1-hydroxyphenanthrene increased significantly during the first two days, and then decreased. At 12°C uptake of PAHs was slower and maximum metabolite concentrations in bile were less than in fish exposed at 24°C. Following a latency of two days, concentrations of PAH metabolites in bile of fish exposed at 24°C were followed by a peak in LPO. PAHs spiked into sediments under laboratory conditions were significantly more bioavailable than the PAHs that were already present in un-spiked field-collected sediments.