Aquatic Toxicology 95 (2009) 173–181 Contents lists available at ScienceDirect Aquatic Toxicology journal homepage: www.elsevier.com/locate/aquatox Developmental effects of a municipal wastewater effluent on two generations of the fathead minnow, Pimephales promelas Anthony D. Sowers a,∗ , Kristen M. Gaworecki a , Marc A. Mills b , Aaron P. Roberts c , Stephen J. Klaine a a Institute of Environmental Toxicology, Department of Biological Sciences, Clemson University, 509 Westinghouse Road, Pendleton, SC 29670, USA b United States Environmental Protection Agency, Office of Research and Development, National Risk Management Research Laboratory, 26 W. Martin Luther King Dr., MS 420, Cincinnati, OH 45268, USA c Institute of Applied Sciences, Department of Biological Sciences, University of North Texas, 1155 Union Circle #310559, Denton, TX 76203-5017, USA article info Article history: Received 11 May 2009 Received in revised form 19 August 2009 Accepted 23 August 2009 Keywords: Wastewater effluent Endocrine disruption Fathead minnow abstract Municipal wastewater effluents have been shown to contain a variety of anthropogenic compounds, many of which are known to display estrogenic properties. While multiple laboratory studies have shown the effects of such compounds on an individual basis at elevated concentrations, little research has attempted to characterize the effects of exposure to environmentally relevant mixtures of estrogenic compounds. The current study examined the effects of long-term exposure to graded concentrations (0, 50, 100%) of wastewater effluent on the fathead minnow, Pimephales promelas. The F1 generation was cultured in control water to test for transgenerational effects from parental exposure to wastewater effluent. Total estrogenic activity in the wastewater was determined to be approximately 1.7 ng/L 17-estradiol equiv- alents. Survival, growth, and reproduction in the parent generation were not affected by exposure to the wastewater treatments. An increase in the gonadosomatic index and a reduction in the expression of secondary sex characteristics in male fathead minnows exposed to 100% wastewater in the parent gen- eration were observed. Conversely, the expression of secondary sex characteristics was greater in males from the F1 generation of wastewater-exposed parents. Additionally, a positive relationship between parental exposure to wastewater and the onset of reproductive activity in the F1 generation was observed. Results of this study suggest that exposure to wastewater effluent did not pose a significant threat to the successful growth, development, and reproduction of the fathead minnow. Early onset of reproductive activity observed in the F1 generation of wastewater-exposed parents in subsequent generations should be studied further. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Endocrine disrupting compounds (EDCs) can be defined as exogenous substances that disrupt endocrine system-mediated physiological functions. One of the major pathways for EDCs to enter the aquatic environment is through municipal wastewater effluents. Effluents around the world have been shown to con- tain measurable concentrations of pharmaceuticals, personal care products, and natural and synthetic hormones that are capable of acting as EDCs (Nakada et al., 2004, 2006; Snyder, 2008). A sur- vey conducted in the United States between 1999 and 2000 by the United States Geological Survey that targeted areas downstream of urbanization and/or livestock production found the presence of organic wastewater-derived contaminants, many of which are known EDCs, in 80% of 139 surface waters (Kolpin et al., 2002). ∗ Corresponding author. Fax: +1 864 646 2277. E-mail address: sowers@clemson.edu (A.D. Sowers). The presence of estrogenic compounds in wastewater effluents is a potential risk to aquatic ecosystems and has been studied exten- sively (Byrns, 2001; Murk et al., 2002; Nakada et al., 2004; Servos et al., 2005). Estrogenic compounds of interest include the natural estrogen, 17- estradiol (E2); the synthetic oral contraceptive- derived estrogen, 17- ethynylestradiol (EE2); bisphenol-A (BPA), which is a component of polycarbonate plastics; and a class of industrial compounds known as the alkylphenols, which include nonylphenol (NP) and octylphenol (OP). The estrogen receptor (ER) affinities of E2 and EE2 are orders of magnitude higher than those of BPA, NP, and OP (Rutishauser et al., 2004), although in some wastewater effluents such industrial compounds may reach con- centrations in the parts per billion range making them relevant to study as endocrine disruptors despite their low ER affinities. In addition to studying the occurrence of estrogenic EDCs, a great deal of research has focused on their effects on aquatic organisms. The developmental and reproductive status of EDC-exposed fish species has been studied in detail. Altered secondary sexual char- acteristics as well as a decrease in reproductive success have been observed in fathead minnows exposed to EE2 (Parrott and Blunt, 0166-445X/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.aquatox.2009.08.012