Feminization responses have been observed in some wild populations of fish living in rivers and streams, some of which have been shown to arise as a consequence of exposure to sewage treatment (STP) effluent discharges and the endocrine disrupting chemicals (EDCs) they contain which mimic or antagonize the actions of steroid hormones. The synthetic estrogen, 17α-ethinylestradiol (EE2), commonly used in oral contraceptives, is present in surface waters receiving STP effluents at concentrations ranging from non-detectable to 5 ng/L. Despite extensive evidence that EE2 negatively affects the reproductive health of fishes, relatively little is known about effects at the population level – and especially so for live-bearing fishes. To investigate the potential for such impacts, populations of the least killifish (Heterandria formosa) were exposed to 0 or 5 ng/L EE2. Exposures were started with newborn fish and continued for seven months. Chronic exposure to 5 ng/L EE2 caused significant reductions in population size, in abundances of newborns and males, and in population growth rates. The exposure also resulted in a female-biased sex ratio. However, individuals’ survival rates were not affected. This study showed that chronic exposure to 5 ng/L EE2 negatively affected population dynamics in a live-bearing fish, demonstrating that the levels of EE2 detected near STPs have the potential to impact wild populations of these fish.

在生活在河流和溪流中的一些野生鱼类中，观察到女性化反应，其中一些显示出是由于暴露于污水处理（STP）废水排放以及其中所含的模拟内分泌干扰物（EDC）的结果或拮抗类固醇激素的作用。通常用于口服避孕药的合成雌激素17α-炔雌醇（EE2）存在于接受STP废水的地表水中，浓度范围为不可检测到5 ng / L。尽管有大量证据表明EE2对鱼类的生殖健康有负面影响，但对种群水平的影响知之甚少，尤其是对于活鱼。为了调查这种影响的可能性，使用最少的鱼类（福建杂种）暴露于0或5 ng / L EE2。从新生鱼开始接触，持续七个月。长期暴露于5 ng / L EE2导致人口规模，新生儿和男性数量以及人口增长率显着下降。暴露也导致女性偏向性别比。但是，个人的生存率没有受到影响。这项研究表明，长期暴露于5 ng / L EE2会对活鱼的种群动态产生负面影响，表明在STP附近检测到的EE2含量有可能影响这些鱼类的野生种群。