For a cleaner, more prosperous world, ACC mobilizes conservatives around environmental issues, fostering collaboration in the pursuit of environmental conservation.
June 4, 2026
U.S. Environmental Protection Agency
EPA Docket Center, Water Docket
1200 Pennsylvania Ave. NW
Washington, DC 20460
Re: Response to Docket ID Number EPA-HQ-OW-2022-0946
Introduction
The American Conservation Coalition (ACC) appreciates the opportunity to comment on the Environmental Protection Agency’s (EPA’s) proposed Draft Contaminant Candidate List 6 (CCL 6). ACC is a nonprofit organization dedicated to building the conservative environmental movement, with more than 100,000 grassroots members nationwide. We recognize that water is one of our most precious natural resources, sustaining human life, supporting ecosystems, and powering communities and industries across the country. All Americans deserve access to safe, reliable water, and we commend EPA’s leadership in updating the Contaminant Candidate List and recognizing emerging concerns such as PFAS, microplastics, and pharmaceutical contaminants.
Specifically, ACC submits this response to encourage EPA to maintain a transparent, evidence-based approach in evaluating contaminants, ensuring that assessment decisions are grounded in scientific data on exposure and potential impacts to human health and the environment, rather than extraneous considerations such as political factors.
Comments
EPA’s draft CCL 6 appropriately reflects growing concern around emerging contaminants such as microplastics, PFAS, and pharmaceuticals by identifying them as a distinct category. These additions are grounded in increasing evidence of their occurrence and potential health concerns, which may warrant further study and possible regulation. As EPA continues its directive to update and maintain the CCL, it must do so in a science-based manner that squarely focuses on the best available data.
An example of a contaminant EPA should continue to evaluate carefully is mifepristone. While the drug itself has been the subject of significant controversy regarding its use as an abortifacient, if it is detected in drinking water systems and there is evidence of potential risks to human health, EPA should ensure appropriate regulatory processes are followed to assess and mitigate any such risks.
Within the last decade, a growing body of research has demonstrated that mifepristone possesses significant biological potency at low concentrations, raising critical questions regarding its potential long-term impacts on human health via public water systems. A 2024 study on African clawed frogs found that exposure to mifepristone reduced female reproductive success, with only about half of exposed females successfully reproducing. Exposed frogs also laid fewer eggs overall. Specifically, researchers found that mifepristone disrupted hormone signaling pathways involved in reproduction and caused primarily hormonal and functional effects rather than visible physical damage. While this study highlighted the compound’s impact on amphibian reproductive decline, its relevance is what it reveals about the drug’s high degree of biological activity and its potential to interact with hormone pathways.
Another study conducted in 2013 on zebrafish found that exposure to environmentally relevant concentrations of mifepristone altered reproductive processes, even at low levels. Female fish experienced changes in egg production and ovarian abnormalities, including disrupted follicle development and oocyte maturation, while male fish showed fewer effects. Although short-term exposure did not significantly affect embryo fertility or hatching success, the researchers concluded that trace levels of mifepristone can still disrupt fish reproduction. Again, these findings underscore how trace residues of the drug can act as potent hormone disruptors, highlighting a potential need for a closer look at potential human health impacts.
Because mifepristone use has scaled from a strictly controlled clinical drug in 2000 to a widely accessible medication frequently prescribed via telehealth over the last several years, the baseline volume entering wastewater systems nationwide has experienced a multi-year shift. While current data suggest environmental levels remain trace and low, the lack of long-term monitoring at this new scale supports EPA’s broader inclusion of pharmaceuticals in CCL 6 as a necessary step toward proactive monitoring and data collection to ensure water safety standards keep pace with evolving patterns of pharmaceutical use.
While mifepristone has not been comprehensively monitored in U.S. drinking water supplies, some studies indicate that pharmaceuticals can enter wastewater systems and persist through treatment processes. Specifically, a wastewater treatment plant study conducted in Europe found the presence of multiple pharmaceutical compounds in wastewater, with evidence of partial removal during treatment and trace residues remaining in discharge effluent. Still, there is limited U.S. data on whether mifepristone is present in treated wastewater or freshwater systems. Because it is not part of routine EPA monitoring programs, it is not consistently tracked in national drinking water datasets. Strengthening EPA’s evaluation of pharmaceuticals under the Contaminant Candidate List could help address these data gaps for all pharmaceuticals, including mifepristone, by improving monitoring and occurrence information. This is particularly important because according to the EPA itself, pharmaceuticals have been shown to pose emerging risks to public health and the environment.
Further, recent modeling studies of unregulated contaminants in U.S. drinking water systems suggest that individual chemicals may have limited activity on their own, but cumulative exposure to multiple contaminants may increase the importance of evaluating combined effects rather than single chemicals in isolation. This highlights the importance of considering mixture-based exposure scenarios in drinking water risk assessment. Incorporating this perspective into EPA’s evaluation process would better reflect real-world exposure conditions and improve understanding of how contaminants behave alongside other contaminants in drinking water systems.
Conclusion
As an environmental organization, we support a science-based, comprehensive approach to protecting water quality and public health. We appreciate EPA’s work to update the Contaminant Candidate List and its focus on emerging categories like PFAS, microplastics, and pharmaceuticals. Pharmaceuticals, including chemicals such as mifepristone, should be carefully considered in this review, not because of politics, but because understanding what is present in our water systems is essential to sound, unbiased environmental and natural resource protection. We look forward to continuing to engage with the EPA to ensure clean water for all Americans.