EPA emerging contaminants

April 13, 2026

The EPA uses the Safe Drinking Water Act (SDWA) to identify and regulate emerging contaminants in drinking water that pose new risks to public health. Through the Contaminant Candidate List (CCL) and Unregulated Contaminant Monitoring Rule (UCMR 5), the EPA collects data to set future standards (e.g., Maximum Contaminant Levels).

Key Aspects of EPA Emerging Contaminants Actions include:

• Contaminant Candidate List (CCL): Every five years, the EPA publishes a CCL listing unregulated contaminants known or anticipated to occur in public water systems.
• Unregulated Contaminant Monitoring Rule (UCMR 5): This rule requires public water systems to perform monitoring and reporting for CCL constituents. 

Emerging contaminants identified under the SDWA CCL and UCMR often have environmental implications that reach far beyond drinking water – e.g., wastewater/leachate, stormwater, environmental assessment and remediation, waste characterization, etc.

EPA recently proposed a list of emerging contaminants for its Sixth Contaminant Candidate List (CCL 6), now open for public comment. Comments must be received on or before June 01, 2026. The draft CCL 6 list includes four chemical groups –   microplastics, pharmaceuticals,  per- and polyfluoroalkyl substances (PFAS), and disinfection byproducts—as well as 75 chemicals and nine microbial contaminants that may be found in drinking water.

A few additional details:

• Microplastics, are tiny plastic particles that have been detected in human blood, breast milk, and organs—are now officially on EPA’s radar as a drinking water priority. This is the first time the agency has elevated microplastics to the CCL as a contaminant group, unlocking focused research and potential future regulation. Read the SCS article.
• Pharmaceuticals, including antidepressants, hormones, antibiotics, and other drugs that enter water systems through human waste and improper disposal—are also being prioritized as a group for the first time. EPA is simultaneously releasing human health benchmarks for 374 pharmaceuticals, giving states, Tribes, and local water systems a critical new tool to assess risk and take action when drug residues are found at concerning levels.
• PFAS, while select PFAS constituents were addressed under CCL 5 and recent MCLs, CCL 6 proposes to address PFAS as a group.

For additional information regarding the CCL 6 proposal, see the following EPA webpages:

• https://www.epa.gov/newsreleases/epa-hhs-announce-historic-actions-protect-americans-microplastics-and-safeguard
• https://www.epa.gov/ccl/draft-contaminant-candidate-list-6-ccl-6, and
• The docket folder EPA-HQ-OW-2022-0946 at regulations.gov.
• Contact an SCS Engineers expert near you.

About the Author: Jeff Marshall, PE, is a Vice President of SCS Engineers and our National Expert on Emerging Contaminants (e.g., PFAS) and Innovative Technologies. He has over four decades of experience with emphasis on environmental chemistry (e.g., hydrogen sulfide generation at MSW landfills), environmental permitting and compliance (e.g., fumigation facilities), hazardous materials/waste management. site assessment/remediation, treatment technologies, and human health risk issues. He is a licensed professional engineer in five states. Contact Jeff or an SCS Engineers expert near you.