EPA Adds Microplastics to Draft CCL 6: First-Ever Federal Drinking Water Watchlist Inclusion

On April 6, 2026, the U.S. Environmental Protection Agency released the draft of its Sixth Contaminant Candidate List (CCL 6) under the Safe Drinking Water Act. For the first time in the CCL's 30-year history, microplastics appear as a priority contaminant group — a significant signal that federal drinking water regulators are beginning to formalize concern about plastic particles in the water supply.

The draft CCL 6 includes four contaminant groups: microplastics, pharmaceuticals, per- and polyfluoroalkyl substances (PFAS), and disinfection byproducts. It also lists 75 individual chemicals and nine microbes that may be present in drinking water. Comments on the draft are due June 5, 2026, and EPA must consult its independent Science Advisory Board before finalizing the list — currently targeted for November 17, 2026.

What a CCL Listing Means

The Contaminant Candidate List is essentially a regulatory watchlist. Listing does not:

• Create enforceable Maximum Contaminant Levels (MCLs)
• Require water utilities to test for the listed contaminant
• Mandate treatment actions at public water systems

What a listing does do is prioritize a substance for future rulemaking. EPA is required to make a regulatory determination on a subset of CCL contaminants every five years under the Safe Drinking Water Act — potentially leading to National Primary Drinking Water Regulations down the road. PFAS was first listed on CCL 3 in 2009 before finalizing MCLs in 2024, so the path from CCL listing to enforceable regulation can take over a decade.

HHS Launches $144M STOMP Initiative

In a coordinated announcement, the Department of Health and Human Services launched Systematic Targeting of MicroPlastics (STOMP), a $144 million research program to measure microplastics in human tissue and study their biological effects. HHS Secretary Robert F. Kennedy Jr. announced STOMP in conjunction with EPA's CCL 6 release, framing both as part of the administration's Make America Healthy Again (MAHA) agenda.

STOMP funding flows through NIH institutes including NIEHS and NIAID. The program is expected to generate the exposure and toxicology data that EPA would need to move microplastics from CCL listing toward enforceable regulation in future rulemaking cycles.

Industries Most Directly Affected

Public water systems are the ultimate downstream party, but the CCL 6 announcement signals broader regulatory direction for:

• Municipal water utilities — may eventually need sampling, treatment, and reporting capacity for microplastics, PFAS, and pharmaceuticals.
• Industrial wastewater dischargers — especially chemical manufacturing, pharmaceutical production, and plastics processing — face increased scrutiny upstream of drinking water intakes.
• Water treatment chemistry suppliers — coagulants, activated carbon, oxidizers, and membrane cleaning chemistries will see shifting demand as utilities pilot new treatment approaches.
• Bottled water and food processing — may face secondary scrutiny as microplastics research matures.

What to Watch Next

Comments on the draft CCL 6 are due June 5, 2026. EPA's Science Advisory Board consultation and final list signing are targeted for November 17, 2026. After finalization, EPA must issue regulatory determinations for at least five contaminants by 2031. PFAS is the clearest precedent for how CCL listing eventually produces enforceable MCLs — a pathway microplastics are now on for the first time.