Chronic Effects of 17a-Ethinylestradiol, Fluoxetine, and the Mixture on Individual and Population-Level End Points in Daphnia magna Tamara O. Luna • Stephanie C. Plautz • Christopher J. Salice Received: 20 June 2014 / Accepted: 10 December 2014 Ó Springer Science+Business Media New York 2015 Abstract Many pharmaceuticals and personal care pro- ducts (PPCPs) enter the environment continuously. Because these chemicals are not intended for environ- mental applications, testing for environmental effects is not mandatory, and thus relatively little is known about their ecological effects, particularly on invertebrate species. To better understand the effects of PPCPs on freshwater invertebrates, we exposed the water flea Daphnia magna to environmentally relevant concentrations of the pharma- ceuticals 17a-ethinylestradiol (EE2) and fluoxetine both individually and as a mixture for 40 days. Exposure to EE2 decreased the number of neonates produced per female at 0.1 and 1.0 lg/L EE2, whereas fluoxetine increased mor- tality and neonate production at 100 lg/L. Exposure to the mixture of EE2 ? fluoxetine increased time to first repro- duction in medium and high mixture treatments and decreased time to death and neonate production in the high mixture treatment. When these individual parameters were integrated into a demographic model, population growth rate decreased when D. magna were exposed to 0.1 and 1.0 lg/L EE2, 100 lg/L fluoxetine, and low and high mixture treatments. When we compared the results of our extended 40 day exposures with data from only the first 21 days, the standard duration of chronic toxicity tests with D. magna, the effects of pharmaceutical exposure were generally significant at lower chemical concentrations during the 21-day period compared with the 40-day exposures, which points to the importance of exposure duration in drawing inferences from toxicity studies. Pharmaceuticals and personal care products (PPCPs) are among the many organic chemicals that enter sewage systems and can subsequently be released to surface water (Kolpin et al. 2002). Wastewater-treatment plants are not designed to treat these compounds, so many PPCPs are not effectively removed and can be found in effluent as parent compounds and/or metabolites. This effluent eventually enters surface waters, in which low concentrations of many PPCPs have been measured (Kolpin et al. 2002). These compounds can then interact with numerous ecological receptors. Because PPCPs are not intended for application to the environment, testing for possible adverse ecological effects is not required as they are for pesticides. Thus, relatively little is known about the effects of PPCPs on aquatic organisms, particularly invertebrates. However, some PPCPs have been shown to exert sublethal endocrine- disrupting effects on ecological receptors at environmen- tally relevant exposure concentrations (Dietrich et al. 2010; Jobling et al. 2004; Luna et al. 2013). Endocrine disruptors in the environment are cause for concern because they can affect populations of vertebrate and invertebrate wildlife by causing changes in blood hormone levels, decreased fer- tility and fecundity, superfeminization or masculinization of females, and feminization of males (Vos et al. 2000 and references therein). T. O. Luna  S. C. Plautz Department of Environmental Toxicology, The Institute of Environmental and Human Health, Texas Tech University, Box 41163, Lubbock, TX 79409, USA e-mail: tluna@pacificecorisk.com S. C. Plautz e-mail: steph.plautz@gmail.com C. J. Salice (&) Environmental Science and Studies Program, Towson University, 8000 York Rd., Towson, MD 21252, USA e-mail: csalice@towson.edu 123 Arch Environ Contam Toxicol DOI 10.1007/s00244-014-0119-2