New-Generation Steroid Hormones

New-Generation Steroid Hormones– Tailored Assessment Strategies for Environmental Protection
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
(F0) of zebrafish but adversely affected the fertility and early larval survival in the first filial
generation (F1). Hatching success of the second filial generation (F2) 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 F0 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.