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Ecosystems & Environment: Wastewater Treatment

EPA researchers assess wastewater effluents to measure effects on ecosystems


Wastewater treatment plants are designed to eliminate pathogens, waste particles and nutrients like nitrogen. But other types of contaminants are more difficult to treat. Chemicals present in water in low concentrations may have an effect on the environment when released into waterways such as lakes and streams. Among these chemicals are potential endocrine disrupting chemicals (EDCs).

EDCs can end up in wastewater through a variety of routes. Wastewater can contain natural human hormones, hormones from pharmaceutical products like birth control pills, and potential EDCs present in detergents, soaps, plastics, food, and personal care products such as fragrances. EPA researchers have documented that chemical mixtures in some wastewater effluents (or outflows) can result in feminization of fish populations downstream of treatment plants. Additional ecological impacts of these effluents, and of effluents from other sources such as from concentrated animal feeding operations, are still being assessed.

However, it is clear that EDCs have the potential to disrupt fish populations. One 7 year study conducted by the Department of Fisheries and Oceans Canada and their EPA partners examined a lake in the Experimental Lake Area in Ontario, Canada, that was dosed for 3 years with a potent estrogen, 17-ethynylestradiol. The findings showed that chronic exposure of fathead minnow (Pimephales promelas) to low concentrations (ethynylestradiol EE2) led to defects in the reproductive development of females and males, and, ultimately, a near extinction of this species from the lake. The concentrations of the hormone used in this lake were similar to those measured in effluent-dominated waterways, suggesting that EDCs present in the environment can impact the sustainability of wild fish populations.


Given such concerns, EPA researchers are assessing wastewater effluents to measure their effects on ecosystems and aquatic animals while also developing innovative solutions to reduce concentrations of potential EDCs. EPA researchers are deploying a range of techniques to examine effluents from waste water treatment facilities. One fundamental approach involves chemistry-based assessments of the concentration of various known and potential endocrine-disrupting drugs or chemicals in effluents. This approach provides valuable information on the chemicals present, but is limited because methods have not been developed for measuring many chemicals of interest. In addition, mixtures of chemicals (rather than a single chemical acting alone) can have unpredictable effects on hormonal systems.

Researchers are also examining the properties of effluents using various biochemical and biological assays that describe how the effluents might affect hormonal systems. For instance, one test that assesses whether male fish have been exposed to estrogens is an assay that measures whether the gene for vitellogenin, the egg yolk protein, has been induced at levels similar levels to females or similar to a known concentration of ethynylestradiol tested in the Canadian study. Another assay under development assesses whether estrogen is turned on in human cells. Assays such as these are being used by EPA researchers to examine various types of effluents. Researchers are also studying the extent of the problem of potential EDCs in the nation's waterways. A national survey of water collected from 50 wastewater treatment plant effluents found that 13 had endocrine disruption activity, as measured by the vitellogenin gene assay in male fish. Another study took a broader approach, and showed that 5 percent of 113 samples from various California rivers and lakes had detectable endocrine disruption activity, as measured by the vitellogenin gene assay.

More comprehensive studies are now underway as these earlier studies did not test samples over different time periods or in different seasons and did not evaluate the concentrations of the various chemicals present. One current research study focuses on examining effluents on a small river in New England that has four waste treatment plants on its banks. EPA researchers along with other federal agencies (USGS, USFWS, NPS) are examining the types of chemicals in the effluents and comparing the health of fish kept in cages upstream and downstream of the treatment plants, using the vitellogenin test and other assays. Scientists are also conducting a battery of laboratory tests on the effluents, such as their effect on cells grown in the lab. Another EPA research project examines effluents from hospitals, long-term care facilities and industrial facilities to assess the composition of that wastewater. Effluents from these types of institutions may produce particularly high concentrations of EDCs - and so may represent potential targets for minimizing discharges.

Results and Impact

EPA's analysis of effluents from a range of treatment plants is the first step to understanding which endocrine disruptors are present in wastewater. By comparing the results from these various studies, researchers can begin to address whether certain types of water treatment processes might be more effective at reducing concentrations of EDCs. Data from these studies are complemented by projects at the EPA examining various types of treatment systems that can be used to reduce concentrations of potential EDCs. The development of new screening methods, such as bioassays, will help researchers assess endocrine-disrupting potential of the thousands of compounds that may be in wastewater. These screening methods can be used by EPA's Endocrine Disrupting Screening Program in a variety of ways, from analyzing mixtures of compounds to testing the activity of individual uncharacterized chemicals. Research results will help EPA better understand the sources of endocrine disrupting chemicals in effluents and aid in developing innovative solutions that municipalities can use to reduce the concentrations of these chemicals.

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