Alkylphenol ethoxylates (APEs) and related compounds recently have been reported to be estrogenic because it has been demonstrated in laboratory studies that they mimic the effects of estradiol both in vitro and in vivo. Chemicals referred to as "environmental estrogens" are suspected of causing health effects in both humans and wildlife through disruption of the endocrine system. In this review, the occurrence, environmental fate, and biological effects of APEs are presented. To provide understanding of the potential for endocrine disruption due to environmental estrogens, the physiology of estrogens in mammals and fish is also reviewed. The estrogenic potency of other environmental estrogens is compared to the potency of APE degradation products. The reproductive effects of estrogenic compounds are considered when evaluating the potential health effects of APEs. Given the reported environmental concentrations and bioconcentration factors of APE products, the potential for these compounds to produce estrogenic effects in the environment appears low. Although questions concerning the physiological effects of APEs and other environmental estrogens remain unanswered, there are indications that research is in progress that will lead to better understanding of the risks to humans and wildlife.

Abstract-Endocrine-disrupting compounds have the potential to alter hormone pathways that regulate reproductive processes. With the exception of endocrine effects leading to reproductive impairment and population declines in a few wildlife species (e.g., Great Lake [USA] bald eagles, Lake Apopka [Florida, USA] American alligators), the ecological implications of exposure to endocrine disrupting compounds has not been adequately investigated. For example, male fish exposed to estrogenic compounds show induced production of vitellogenin, an egg yolk precursor, but the biological significance of elevated vitellogenin levels is speculative. The development of techniques to predict and more accurately assess the ecological relevance of exposure to endocrinedisrupting compounds is needed. In this review, we focus on fish reproduction as an ecologically relevant indicator of endocrine disruption, specifically estrogenic activity. The following will provide a brief review of gonochoristic reproductive and endocrine physiology, as well as outline some of the commonly used techniques to screen for estrogenic activity in fish. Last, a proposed model reproductive assay using Japanese medaka (Oryzias latipes) is presented.

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BackgroundIn this commentary we present the findings from an international consortium on fish toxicogenomics sponsored by the U.K. Natural Environment Research Council (Fish Toxicogenomics—Moving into Regulation and Monitoring, held 21–23 April 2008 at the Pacific Environmental Science Centre, Vancouver, BC, Canada).ObjectivesThe consortium from government agencies, academia, and industry addressed three topics: progress in ecotoxicogenomics, regulatory perspectives on roadblocks for practical implementation of toxicogenomics into risk assessment, and dealing with variability in data sets.DiscussionParticipants noted that examples of successful application of omic technologies have been identified, but critical studies are needed to relate molecular changes to ecological adverse outcome. Participants made recommendations for the management of technical and biological variation. They also stressed the need for enhanced interdisciplinary training and communication as well as considerable investment into the generation and curation of appropriate reference omic data.ConclusionsThe participants concluded that, although there are hurdles to pass on the road to regulatory acceptance, omics technologies are already useful for elucidating modes of action of toxicants and can contribute to the risk assessment process as part of a weight-of-evidence approach.