This is a monitoring rule, not a drinking-water standard. EPA uses UCMR to gather occurrence data on contaminants that are not currently regulated under federal drinking-water rules.

Who would have to monitor

Under the proposal, all large public water systems serving more than 10,000 people would have to monitor. EPA also would require all smaller systems serving 3,300 to 10,000 people to participate, along with a nationally representative sample of smaller systems serving fewer than 3,300 people.

EPA proposes that sampling run from January 1, 2028, through December 31, 2030, with monitoring completed by December 31, 2031. The agency also says the rule is open for public comment, and it plans two virtual public meetings on August 11 and August 12.

Why microplastics are out for now

One closely watched part of the proposal is what EPA left out: microplastics. In the proposal, EPA says there is no validated drinking-water analytical method with the quality control, accuracy, and precision needed for UCMR 6, and that it is not feasible to develop one within the rule’s statutory timeframe.

EPA says it will keep evaluating methods and laboratory capacity so microplastics could be considered in a future UCMR cycle if national monitoring becomes scientifically feasible.

What this means for utilities and consumers

For utilities, the immediate issue is planning and reporting, not a new treatment mandate. For consumers, the practical takeaway is simpler: this proposal would collect more data, but it would not change household drinking-water standards today.

The next step is the final EPA rule. Until then, UCMR 6 remains a proposal.

Sources

• EPA news release: proposed UCMR 6 action
• Federal Register text of the UCMR 6 proposed rule
• C&EN report on the UCMR 6 proposal