Context There is growing concern about the potential of various chemicals to produce changes in the functioning of the endocrine system of humans and animals. Known natural hormones as well as relatively unknown environmental pollutants seem to have the ability to potentially disrupt the endocrine system of man and animal in such a way that harmful effects on their development and reproduction can occur. The first indications of possible effects of endocrine disrupting substances and the presence of these substances in the Scheldt estuary have recently been published. The industrial areas of Ghent and Antwerp are to a large extent responsible for this pollution. Therefore, there is an obvious need to investigate the occurrence of endocrine disruption in the Scheldt estuary. In addition, a detailed knowledge of the distribution and long-term effects of these substances is needed in the framework of future-oriented policy measures at the national and European level. Project description Objectives The major objectives within the project are: - analyses of endocrine disrupters in water, suspended solids, sediment and biota (mysids, gobies); - in vitro evaluation of the estrogenic and androgenic potency of samples of water, suspended solids and sediment; - ecotoxicological and in situ evaluation of the effects on the resident mysid populations (short, intermediate and long-term); - risk assessment of endocrine disrupters in the Scheldt estuary. Methodology The proposed project can be divided into four different research phases: Phase I: Distribution of endocrine disrupting substances in the Scheldt estuary (chemical analyses, analyses on biota, in vitro analyses) The Scheldt estuary will be sampled three times a year (spring, summer and winter) for the duration of the project. On each sampling date, sediment, water, suspended solid and biota (mysid shrimp and gobies) will be collected. An extended list of natural hormones and endocrine disrupting chemicals will be measured in these samples. The different water, sediment and suspended solid extracts will be tested in vitro to assess their potential to bind with the (human) estrogen and androgen receptor. The results of these analyses will allow an identification of the estrogenic and androgenic potency in different environmental matrices of the Scheldt estuary. Phase II: Evaluation of the exposure of biota from the Scheldt estuary to endocrine disrupting substances Based on the results of the first sampling campaigns priority substances will be selected. These priority endocrine-disrupting chemicals will be used in laboratory experiments with mysid shrimp to assess acute and chronic effects (Phase III). Phase III: Ecotoxicological evaluation of the effects of endocrine disrupting substances occurring in the Scheldt estuary on resident mysid shrimp populations (laboratory and field studies) Acute and chronic laboratory tests with mysid shrimps To evaluate the possible effects of the pollutants (retained in phase II) on mysid shrimp, acute and chronic test will be performed in the laboratory. Mysid shrimp will also be exposed in multi-generation experiments during two generations (until the first generation of juveniles produces juveniles again) to assess the effects of endocrine disrupters during prolonged exposure. Population study of the native mysid shrimp in the Scheldt estuary The mysid shrimp population of the Scheldt estuary will be sampled and studied during one year. In this way, the present population dynamics can be compared with the available historical data and possible changes can be detected. In addition, a more in-depth field study on the possible endocrine disruption effects will be conducted based on the results of the laboratory toxicity experiments. Sensitive endpoints identified in the laboratory experiments will be validated in situ on the resident mysid shrimp population in the Scheldt estuary. Phase IV: Risk assessment In the last phase, the results of the previous phases will be incorporated into an integrated risk assessment for the Scheldt estuary with reference to endocrine disrupting substances. Moreover, an overall risk assessment for the Scheldt estuary will be conducted with these data in correlation with environmental concentrations of the tested endocrine disrupters. Recommendations for sustainable management and priority substances will be developed. The results of this study on "endocrine disruption in the Scheldt estuary: distribution, exposure and effects" will be used at different levels and in different ways. In order to ensure (rapid) dissemination and valorisation of the obtained results, the following actions will be undertaken: - all results will be published in peer-reviewed journals; - transfer (and discussion) of the obtained knowledge and insights to national and international representatives of policy-making and policy-supporting governmental services. This discussion will offer an essential contribution to the international contractual engagements of Belgium; - diffusion of data and results through scientific databases; - interactive communication forum during the project (project website); - the results of the project will be brought together in a book, which will include the datasets on CD-rom and the main research results. The diffusion and valorisation of the information as described above will be developed and maintained by the Flemish Institute for the Sea (VLIZ) (subcontracted) under supervision of the co-ordinator.