There are many ways our wastewater quality can affect us negatively if we do not treat it properly. In some cases, what we flush down the toilet may come back to us in other ways. A recent study suggested that human hormones found in wastewater from sewage treatment plants may have profound effects on aquatic wildlife, according to a biologist from the University of Cincinnati.
Latonya Jackson, a UC assistant professor, performed experiments with North American freshwater fish called least killifish. She discovered that killifish exposed to estrogen amounting to as small as 5 nanograms per liter under controlled lab conditions produced fewer males and less offspring. Scientists have determined that estrogen levels can be as much as 16 times that concentration in streams near sewage treatment plants. This can have profound consequences on wild fish populations found living beside wastewater facilities.
Jackson examined a synthetic estrogen called 17α-ethinylestradiol, the core ingredient found in oral contraceptives, as well as in hormone replacement therapies. It’s been determined to have concentrations as high as 60 nanograms or more per liter in streams next to sewage treatment plants.
She stressed that anything that is flushed down the toilet ends up in the water supply. This is true not only of medicines, but of unmetabolized chemicals as well.
“Our wastewater treatment systems are good at removing a lot of things, but they weren’t designed to remove pharmaceuticals. So, when women on birth control or hormone therapy go to the bathroom, it gets flushed into wastewater treatment plants.” Jackson said.
This constant exposure by fish to estrogen can lead to significantly reduced populations and gender imbalance because of the higher ratio of females compared to males.
Jackson has sought the help of the U.S. Environmental Protection Agency to determine how the hormonal exposure in a female fish affects her offspring. She focused her study on the waters around southwestern Ohio because they are common in the area and are easily found.
A unique characteristic about least killifish is they have a placenta and give birth to live offspring. This is not a common trait among fish, which are known to typically lay eggs.
Because the killifish are tiny creatures, examining their organs can be a challenge, but capturing the fish is surprisingly easy. Killifish in captivity are able to live more than three years, but in the wild, they are prone to a lot of predation from other fish. To counter this, they produce live young and reproduce with high propensity. They can give birth every 28 days.
Jackson stressed that the impact of hormones in the effluent originating from sewage treatment plants are not just limited to fish. These hormones and other chemicals can bioaccumulate in the food chain or end up in our drinking water.
She goes on to say that our drinking water is not a renewable resource. When the clean drinking water runs out, it’s gone for good, according to Jackson. She believes that it is especially important to keep this resource clean.
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