Collapse of a fish population after exposure to a synthetic estrogen

Abstract

Municipal wastewaters are a complex mixture containing estrogens and estrogen mimics that are known to affect the reproductive health of wild fishes. Male fishes downstream of some wastewater outfalls produce vitellogenin (VTG) (a protein normally synthesized by females during oocyte maturation) and early-stage eggs in their testes, and this feminization has been attributed to the presence of estrogenic substances such as natural estrogens [estrone or 17␤-estradiol (E2)], the synthetic estrogen used in birth-control pills [17␣-ethynylestradiol (EE2)], or weaker estrogen mimics such as nonylphenol in the water. Despite widespread evidence that male fishes are being feminized, it is not known whether these low-level, chronic exposures adversely impact the sustainability of wild populations. We conducted a 7-year, wholelake experiment at the Experimental Lakes Area (ELA) in northwestern Ontario, Canada, and showed that chronic exposure of fathead minnow (Pimephales promelas) to low concentrations (5-6 ng⅐L ؊1 ) of the potent 17␣-ethynylestradiol led to feminization of males through the production of vitellogenin mRNA and protein, impacts on gonadal development as evidenced by intersex in males and altered oogenesis in females, and, ultimately, a near extinction of this species from the lake. Our observations demonstrate that the concentrations of estrogens and their mimics observed in freshwaters can impact the sustainability of wild fish populations.endocrine disrupters ͉ fathead minnow ͉ municipal wastewaters ͉ population-level effects ͉ whole-lake experiment

Derivation of an Aquatic Predicted No-Effect Concentration for the Synthetic Hormone, 17α-Ethinyl Estradiol

“…NOECs range between 0.3 (or a calculated value of 0.16) and 1 ng/L, yet 100% feminization occurs at 3 ng/L and above. A SSD derived from the reproduction NOECs allows for a statistical derivation of the HC 5,50 and, therefore, a PNEC by considering all existing, relevant data for the 26 species that have been studied for reproductive effects. This approach further reduces the uncertainty associated with the fish data by considering data from other chordata demonstrating similar sensitivity to EE2 (e.g., frogs).…”

“…The bootstrap simulation consisted of taking 2000 sets of n () 52) samples from the fitted distribution (with n ) 52 ) the number of data points used for the determination of the Best Fit distribution), and each time, the fifth percentile is calculated. The resulting distribution of HC5's is used to calculate the 50% confidence interval and the median value determined (HC 5,50).…”

“…A species sensitivity distribution was constructed using no observed effect concentrations (NOECs) for reproductive effects from 39 papers in 26 species, resulting in a median hazardous concentration at which 5% of the species tested are affected (HC 5,50 ) of 0.35 ng/L. After comparing this HC 5,50 to all of the laboratory and field-derived toxicity information available for EE2, we recommend using 0.35 ng/L as the PNEC for EE2 in surface water. This PNEC is below 95% of the existing NOECs for effects on reproduction and is also below virtually all of the NOECs for vitellogenin induction in the key fish reproduction studies.…”

Occurrence of endocrine-disrupting chemicals in riverine sediments from the Pearl River Delta, China

“…EDCs consist of a wide range of natural and man-made chemicals, most of which are released to natural waters by anthropogenic activities and whose adverse effects on normal reproductive functions of aquatic species have widely been confirmed (Jobling et al, 1996;Routledge et al, 1998;Oehlmann, 2000;Irwin et al, 2001;Levy et al, 2004). For instance, widespread estrogenic chemical input has been regarded as an important factor related to the decline of fish abundance in freshwater systems (Jobling et al, 1998;Burkhardt-Holm et al, 2005;Kidd et al, 2007). Among this group of chemicals, steroid estrogens (e.g.…”

Evaluation of estrogenic activity in the Pearl River by using effect-directed analysis

“…Despite small bioconcentration factors (BCFs 4-123), bioaccumulation of these seven target estrogenic chemicals could indeed occur in fish organisms (Chen et al 2014a, b;Lai et al 2002;Liu et al 2012;Huang et al 2015). Previous studies have reported adverse effects of estrogens, for example, feminization of fathead minnow in a lake by EE2 (Kidd et al 2007) and suppression of sexual behavior in male Japanese medaka by E2 (Oshima et al 2003). Xie et al (2010) observed fish feminization and altered development and reproduction in western mosquitofish (Gambusia affinis) from the Hanxi River (part of the Shima River) of the same region as the present study.…”