US moves to monitor microplastics in water

The U.S. Environmental Protection Agency on April 2 said it had added microplastics and pharmaceuticals for the first time to its draft Sixth Contaminant Candidate List, a federal watchlist of substances that may later face drinking-water regulation under the Safe Drinking Water Act. (epa.gov) The draft list, known as CCL 6, is not a new limit on utilities and does not by itself require treatment or reporting, but it marks the substances for further review in EPA’s regulatory process. The Department of Health and Human Services announced the same day that its health-research arm, ARPA-H, was starting a separate program to measure and study microplastics in the human body. (federalregister.gov) The move puts two strands of federal work on the same track: EPA’s drinking-water screening process and ARPA-H’s effort to build tools for detecting microplastics in people. EPA said the draft CCL 6 includes 75 chemicals, four chemical groups — microplastics, pharmaceuticals, PFAS and disinfection byproducts — and nine microbes. Comments on the draft are due by June 5. ### What exactly did EPA add this spring? EPA’s April 6 Federal Register notice said the draft CCL 6 covers contaminants “not subject to any proposed or promulgated” national primary drinking-water regulations but known or anticipated to occur in public water systems. For the first time, the agency listed microplastics and pharmaceuticals as contaminant groups on that draft list. (epa.gov) EPA said contaminants placed on the CCL may require future regulation under the Safe Drinking Water Act. The agency is seeking public comment on both the draft list and the method it used to select contaminants before issuing a final version. (epa.gov) ### Does this mean water systems must start testing for microplastics now? The draft CCL 6 notice does not itself create a testing mandate for public water systems. EPA describes the CCL as a screening tool used to drive research, funding and later decisions on whether to regulate contaminants. EPA’s separate page on Unregulated Contaminant Monitoring Rule meetings shows the agency has been discussing possible approaches for UCMR 6, including analytical methods and contaminants under consideration, in pre-proposal webinars since April 2024. (federalregister.gov) That indicates method development and monitoring design remain part of a later process, not something triggered automatically by the CCL notice. (epa.gov) ### What is ARPA-H doing on the human-testing side? ARPA-H on April 2 launched STOMP, short for Systematic Targeting of Microplastics, which EPA and HHS described as a nationwide initiative to build tools for measuring, researching and removing microplastics and nanoplastics from the human body. (epa.gov) The program’s “Measure” track is aimed at deploying detection technology to quantify microplastics in water and human tissue. HHS and EPA said the program’s other tracks are “Target,” to identify the most harmful plastic contaminants and how they move through the body, and “Remove,” to develop and validate methods to eliminate them. (epa.gov) That makes the federal effort broader than environmental sampling alone. ### How far along is the science on measuring a person’s microplastic burden? Scientific reviews have described human microplastic biomonitoring as an active but still developing field, with researchers working on methods to characterize internal exposure and accumulation in the body. A review in *Science of the Total Environment* said integrated exposure assessment through biomonitoring has become an important goal for understanding internal microplastic exposure in humans. (epa.gov) A 2025 review in *Nature Medicine* said there are strong indications that microplastic and nanoplastic exposure may harm human health, but that the evidence base is still not robust. (epa.gov) That gap helps explain why federal agencies are pairing environmental monitoring with efforts to improve detection methods in human tissue. ### What happens next, and where can people track it? June 5, 2026, is EPA’s deadline for public comments on draft CCL 6, under docket EPA-HQ-OW-2022-0946 in the Federal Register notice. After that, EPA will review comments and decide on a final CCL 6, while ARPA-H’s STOMP program proceeds with its measurement and research work announced on April 2. (sciencedirect.com) (federalregister.gov) (nature.com)