Suchergebnisse

The entry of pharmaceuticals into the aquatic environment has become a major concern in environmental research and has gained increasing public interest. Pharmaceuticals, both human and veterinary, find their way into water bodies through various routes such as wastewater treatment plants and agricultural activities, posing risks to aquatic organisms. In particular, hormone-active substances have been identified as potential threats, even at low concentrations in water. These pharmaceutical residues are known to persist in the environment and may cause adverse effects on non-target organisms. The objective of this project was to develop a tailored testing strategy for assessing the environmental risk of novel hormonal active substances, focusing on synthetic progestins and glucocorticoids, to aquatic organisms. In the initial phase of the project, a comprehensive literature review was conducted to gather and evaluate existing findings on the effects of these substances. Based on the literature review, two candidate substances representing both substance classes were selected for further study. Two long-term laboratory experiments were conducted using aquatic vertebrates, and an additional study with an aquatic invertebrate was carried out for the progestin. Dienogest and Dexamethasone were selected to represent progestins and glucocorticoids, respectively. For Dienogest, a Zebrafish one generation reproduction test (ZEOGRT) was performed, and a Chironomid Life Cycle Test was conducted for the invertebrates. For Dexamethasone, only the Zebrafish study was conducted. The experiments involved exposing the organisms to different concentrations of the test substances and measuring various endpoints related to growth, reproduction, and survival. The physical water parameters were monitored to ensure stable test conditions. For Dienogest, the results showed that it had no significant effects on the parental generation (F 0) of zebrafish but adversely affected the fertility and early larval survival in the first filial generation (F1 ). Hatching success of the second filial generation (F 2) was also reduced. Based on the endpoint hatching success of the second filial generation (F2 ), which was the most sensitive endpoint throughout the study, the overall NOEC of the ZEOGRT was determined to be 3.51 ng Dienogest/L and the LOEC was 10.3 ng Dienogest/L. In the Chironomid study, no effects were observed, indicating a lack of biological impact. Regarding Dexamethasone, it caused reduced growth in both F 0 and F1 generations of zebrafish, with males being more affected. However, reproductive capability and other endpoints were not negatively impacted. Based on the endpoint growth in terms of wet weight and total length the NOEC was determined to be 10.5 μg Dexamethasone/L. The LOEC was set at 34.7 μg Dexamethasone/L. The results indicate that synthetic progestins, such as Dienogest, can have similar effects to potent endocrine substances like estrogens and androgens. However, the underlying mechanism remain unclear. On the other hand, glucocorticoid exposure, specifically Dexamethasone, had effects on the growth of fish across different life stages, but did not significantly affect reproductive performance or sex ratios. The studies suggest that fish are more sensitive to endocrine impacts compared to other aquatic organisms, however, in order to identify the underlying mode of action, additional methodological approaches, such as innovative Omics methods or the immune challenge, could provide valuable information on the molecular effects of the substances. Thus, further research is necessary to improve the identification of underlying mechanisms and their acceptance in the regulatory context.

AbstractThe so-called EPT taxa have been shown to be highly sensitive to various environmental pollutants. However, there are only few published studies on toxicity testing with EPT representatives and there is a particular lack of protocols for chronic toxicity testing, e.g., for integration into species sensitivity distribution (SSD) approaches. To address this gap, we performed a long-term 38-day semi-static toxicity test with the European mayfly species Cloeon dipterum using the insecticide fipronil as model substance. The functionality of the test system was confirmed by the high emergence rate of 85% in the control condition. We found a high sensitivity with regard to larval development with an EC50 of 180 ng/L and a NOEC of 38.0 ng/L after 7 days exposure. After 38 days, an LC50 value of 185 ng/L and an EC50 value of 160 ng/L for emergence (both: NOEC = 38.0 ng/L) were calculated. In a short-term 7-day toxicity test, we found a similar effect on larval development. In addition to the physiological endpoints, we examined fipronil-induced gene expression changes at the transcriptome level in this test. Our results revealed a concentration-dependent increase in the number of differentially expressed genes, as well as observed effects on larval development. Notably, we identified marker gene candidates involved in nervous system development, mirroring the known mode-of-action of fipronil in C. dipterum. The affected genes primarily play crucial roles in neurological processes. Concluding, within this two-step approach we were able to identify fipronil effects on the sublethal physiological endpoint larval development and to complement these effects at the molecular level by gene expression changes in the transcriptome. Thus, this assay proved to be suitable to assess sublethal effects as well as the mode-of-action of substances in the non-standard organism C. dipterum already after a short-term exposure of 7 days. However, further testing is required to validate the procedure.