According to the United States Environmental Protection Agency, wastewater can contain endocrine disrupting chemicals (EDCs) that, when released in the environment, may negatively affect fish populations. Two of the primary dangers include feminization and disruption of fish populations.
Wastewater plants are designed to rid wastewater of pathogens, waste particles and nutrients, but potential EDCs are more difficult to eliminate. These chemicals end up in wastewater through a variety of ways, as they are present in pharmaceutical products, detergents, soaps, plastics, food and personal care products such as perfume. According to the EPA, the presence of EDCs has been shown to feminize fish populations that are downstream of wastewater treatment plants.
The other serious effect from EDCs in wastewater is their ability to disrupt fish populations. One study performed by the Department of Fisheries and Oceans Canada exposed fathead minnow in a lake to low concentrations of estrogen. Within 3 years, the reproductive development of both the male and female minnows had suffered from serious defects and led to a near extinction of the fish from the lake. The amount of estrogen used in the study was similar to the amount measured in sewage-infested waterways, which shows that EDCs present in wastewater have the potential to disrupt wild fish populations.