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Endocrine Disruption Found in Fish Exposed to Municipal Wastewater

Aquariums where male fathead minnows were exposed to the effluent from a wastewater treatment plant.
Aquariums where male fathead minnows were exposed to the effluent from a wastewater treatment plant.

USGS scientists and their colleagues reported in the journal Aquatic Toxicology that exposure to the wastewater from a major metropolitan sewage treatment plant caused endocrine disruption in male fathead minnows. After exposure to the wastewater the male minnows started producing vitellogenin--a female egg-yolk protein. Treated wastewater discharge has been identified as a source of endocrine disrupting chemicals to the aquatic environment, and this study documents some of the potential effects, both positive and negative, in fish due to exposure to wastewater.

Wastewater Exposure Experiments

The on-site wastewater exposure experiments consisted of several duplicated aquariums containing male fathead minnows. Wastewater discharged from a wastewater treatment plant (WWTP) was continuously pumped through the aquariums for 28 days. This design allowed the fish to be exposed to the normal day-to-day changes in the complex mixture of chemicals contained in wastewater. Parallel experiments were conducted exposing fish to wastewater effluent treated to remove estrogenic compounds, groundwater with a mixture of endocrine disrupting chemicals added to it (positive control), and groundwater with nothing added (negative control). The wastewater in the experiment contained 61 of the 169 chemicals analyzed. Several chemicals known to be potential endocrine disruptors were found, such as surfactant (detergent) compounds and their degradation products and bisphenol A (a chemical used in the production of plastics). Although an endocrine disrupting response was observed in the fish exposed to wastewater, determining the exact causative factors or which chemicals within the mixture of chemicals were responsible for the response is very difficult. This difficulty arises because of continual changes in the presence and levels of chemicals and nutrients in the wastewater and the corresponding changes in the multiple biological responses of the fish. In some cases, beneficial effects (such as increased gonadosomatic index – the ratio between gonad weight and body weight – a sign of healthy growth) were observed along with detrimental effects (such as male minnows producing vitellogenin). This study does, however, increase the scientific communities' understanding of the potential effects of wastewater on fish in streams, and this information can be use to make better decisions regarding the discharge of wastewater to the environment.

Endocrine Disruption
Exposure to low-levels of some contaminants can cause disruption of endocrine functions in animals, such as reproduction. This is done by modulating, mimicking, or interfering with normal hormonal activity.

Selected USGS Information on Endocrine Disruption


Barber, L.B., Lee, K.E., Swackhamer, D.L., Schoenfuss, H.L., 2007, Reproductive responses of male fathead minnows exposed to wastewater treatment plant effluent, effluent treated with XAD8 resin, and an environmentally relevant mixture of alkylphenol compounds: Aquatic Toxicology, v. 82, no. 1, p. 36-46, doi: doi:10.1016/j.aquatox.2007.01.003.

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