Seven Governors Push for Microplastics Monitoring in UCMR 6

With concern related to the presence of microplastics in the environment coming to the forefront, a group of seven governors led by New Jersey’s Phil Murphy have signed a petition to monitor the existence of microplastics in drinking water across the United States.

Microplastics – A Brief Summary

The U.S. Environmental Protection Agency (U.S. EPA) defines microplastics as plastic particles ranging in diameter from one nanometer to five millimeters. Wind, currents, and other natural factors break down plastic of any size into small, ingestible pieces that meet the definition of microplastics. Some of the largest contributors to microplastic formation are cosmetic microbeads, the wearing of car tires, synthetic clothing, and fertilizers, though almost every source of plastic has the capability to degrade into microplastics.

Microplastics are found across nearly every corner of the earth, accumulating and inadvertently being consumed by most organisms. Trophic effects magnify the amount of plastic ingested by animals in the upper levels of the food chain, including humans. Several materials used in the manufacturing of plastic are known to be carcinogenic and can present a variety of health issues in humans and in nature. Microplastics also have an affinity to bind to other hazardous chemicals and can act as a vector to bring these materials into contact with humans.

Whether it be due to runoff, wastewater effluent, or aerial deposition, most water bodies inevitably contain microplastics. Ground, surface, and desalinated tap water have all been demonstrated to contain microplastic concentrations ranging from 0.0001 to 930 microplastic particles per liter (MP/L). Bottled water has been shown to contain between 1.4 and 6,292 MP/L. Research is currently being undertaken to determine how particle size, concentration, structure, and other properties of microplastics pose health risks to humans. Currently, much remains unknown until more standardized, conclusive studies can be completed. As testing methods improve and the effects of microplastics on human health have become better studied, regulating their presence in drinking water has become an increasing concern worldwide.

Regulations to reduce overall plastic use in the United States have recently become stricter, but, as of January 2026, cohesive and broad regulations for microplastics are scarce. Federal regulations include the Microbead-Free Waters Act of 2015, which banned the manufacturing and use of plastic microbeads five millimeters or less in diameter. The Infrastructure Investment and Jobs Act of 2022, which allocated $50 billion for U.S. EPA to invest in drinking water and wastewater, lists microplastics as an emerging contaminant. Several states including California, Virginia, New Jersey, and Illinois, have laws adopting procedures for testing microplastics in drinking water. Due to the current lack of unified regulations surrounding microplastics, the signing of this petition may have significant long-term ramifications on improving environmental policy and protecting human health.

Implications of the Petition – Unregulated Contaminant Monitoring Rule 6 (UCMR 6)

The request of those who signed the petition is for U.S. EPA to include microplastics in the 2027 renewal of U.S. EPA’s Unregulated Contaminant Monitoring Rule 6 (UCMR 6), which may act as a first step towards establishing a microplastics drinking standard. Pursuant to 42 U.S. Code (U.S.C.) §300j-4(a)(2)(B)(i), a UCMR is required to be released every five years with up to 30 unregulated contaminants to be monitored by public water systems and to be included in the National Contaminant Occurrence Database (NCOD). UCMR 6 will be the sixth edition of this list of contaminants and will run from 2027 until 2031. The monitoring will include sample collection from 2028-2030 with reporting concluding in 2031. Data collected from monitoring will then be considered in future U.S. EPA regulatory decisions regarding these contaminants.

The petition was signed by the following seven governors: Phil Murphy (New Jersey), Matt Meyer (Delaware), J.B. Pritzker (Illinois), Wes Moore (Maryland), Tony Evers (Wisconsin), Gretchen Whitmer (Michigan), and Ned Lamont (Connecticut). According to 42 U.S.C. §300j-4(a)(2)(B)(ii), the administrator of U.S. EPA shall include among the list of contaminants in the UCMR each contaminant recommended in a petition signed by the governor of each of seven or more states, unless the administrator determines that the action would prevent the listing of other contaminants of a higher public health concern. This places microplastics into current consideration for addition to UCMR 6.

It is worth noting that of the 30 unregulated contaminants included in UCMR 5, which contains the current contaminants subject to monitoring, 29 are comprised of perfluoroalkyl substances (PFAS). PFAS are a group of compounds that, like microplastics, persist in and pollute the environment heavily and have been shown to negatively affect human and ecosystem health. Because more than 15,000 distinct types of PFAS have been identified, it is currently unclear whether microplastics will qualify as one of the 30 contaminants that command scrutiny in UCMR 6 or if future monitoring will continue to focus on PFAS.

Should microplastics be included in UCMR 6, managers of public water systems (PWS) may be required to monitor microplastics depending on the number of people those systems provide drinking water for. Managers of large PWS (greater than 10,000 people) and of small PWS (between 3,300 and 10,000 people) must follow monitoring plans according to their states’ discretion to assess the occurrence of unregulated contaminants. A nationally representative sample of PWS serving less than 3,300 people will also be selected to monitor. Analytical results will then be made publicly available quarterly in the NCOD. Because UCMR 6 is specific to unregulated contaminants, data gathered is strictly informational and would be used to guide future decision making for how to regulate microplastics. UCMR 6 may lead to the future development of, and therefore enforcement of, Maximum Contaminant Levels (MCL) like those promulgated for PFAS in 2023. Owners and operators of all PWS should therefore stay posted for updates to the contaminants to be included in UCMR 6 and what testing and monitoring requirements will apply to their facilities.

Final Thoughts

Though the complex issues caused by microplastics will not be fully solved by an elevation to inclusion in UCMR 6, the potential to sample and monitor them over a three-year period is a critical first step in their future regulation. Much of the discourse surrounding microplastics stems from how little is known about their long-term effects on humans and the environment, gaps in data required to create clear regulations, and difficult detection methods obstructing the formation of a robust data set. While UCMR 6 represents a preliminary step towards analyzing and tracking microplastics, regulations related to microplastics and their potential inclusion in future permits and enforcement is likely years away. Collecting as much information as possible and keeping microplastics in the public eye will be key to creating stringent drinking water standards and eventually limiting contact with microplastics in our daily lives.

ALL4 continues to track and keep our readers informed about important environmental regulatory updates. For questions related to the content in this article or about microplastics in drinking water, please reach out to Aidan Decker at adecker@all4inc.com or 571-554-8246. For any regulatory questions related to water or for strategical support on water-related issues, please refer to our Water Tech Team Lead, Lizzie Smith, at lsmith@all4inc.com or 770-999-0269.