Ecological risk assessment and testing for endocrine disruption in the aquatic environment

Field observations of endocrine disruption (ED) in fish and other aquatic species have contributed to a global effort to establish test methods for detecting ED effects in wildlife species. For ecological risk assessment, validated tests are needed for Amphibia, fish and aquatic invertebrates, supported by a tiered approach incorporating mechanistic data and exposure characterisation. The potential for extrapolation of ED data from mammalian to aquatic species may be limited, however, due to significant physiological differences in function and regulation of hormone systems in (aquatic) lower vertebrates and invertebrates. Presently, the OECD is considering a tiered approach for ED risk assessment, incorporating a fish 14-day screening assay (Tier 1); fish development and reproduction tests (both Tier 2); and a fish full life-cycle test (Tier 3). For detection of (anti-)oestrogens, the yolk-precursor protein vitellogenin is an ideal biomarker of exposure and functionally equivalent biomarkers are being sought for (anti-)androgens in fish. At the two higher tiers, impacts are assessed in terms of apical endpoints (e.g. development, breeding behaviour and fecundity) and also gonadal histopathology. Validation of these higher tier tests should include comparison of sensitivity of biochemical and apical endpoints to optimise the value of biomarkers for predicting adverse health effects (e.g. impaired reproduction). The specificity of future OECD fish and amphibian test guidelines for endocrine disrupters needs further consideration through inclusion of mechanistic endpoints based on state-of-the-art molecular endocrinology.