Proposed Sixth Unregulated Contaminant Monitoring Rule

The Safe Drinking Water Act (SDWA) requires that once every five years the EPA issue a list of unregulated contaminants to be monitored by public water systems (PWSs).

The sixth Unregulated Contaminant Monitoring Rule (UCMR 6) was proposed on July 1, 2026. UCMR 6 proposes sample collection for 30 chemical contaminants between 2028 and 2030 using analytical methods developed by the EPA. This monitoring provides a basis for future actions to protect public health.

• Federal Register Notice: Proposal - Revisions to Establish the Sixth Unregulated Contaminant Monitoring Rule (UCMR 6) for Public Water Systems
• UCMR 6 Proposal Webinar Registration: August 11 and 12, 2026

On this page:

• UCMR 6 Scope, Analytical Methods, and Contaminants
  • Proposed Monitoring Design
  • Proposed Contaminants, Minimum Reporting Levels, Sampling Locations, and Analytical Methods

UCMR 6 Scope, Analytical Methods, and Contaminants

Assessment Monitoring

Public water systems (PWSs) subject to UCMR 6 monitoring include:

• All community water systems (CWSs) and non-transient non-community water systems (NTNCWSs) serving more than 10,000 people
• All CWSs and NTNCWSs serving 3,300 to 10,000 people, and a representative sample of 800 CWSs or NTNCWSs serving fewer than 3,300 people, subject to the availability of annual appropriations and sufficient laboratory capacity
  • PWS Types

As proposed, PWSs will monitor for ultrashort organofluorine compounds (including certain per- and polyfluoroalkyl substances [PFAS]), pesticides, pesticide metabolites, industrial solvents, and chemical intermediates in drinking water during a 12-month period from January 2028 through December 2030. Large PWSs serving more than 10,000 people are responsible for all analytical costs associated with their UCMR monitoring requirements. The EPA continues to be responsible for all analytical costs associated with monitoring at small PWSs serving 10,000 or fewer people. If the EPA does not receive the appropriations needed in a given year, then a reduced number of small PWSs will perform monitoring. As the EPA finalizes its sampling design plan for each sample collection year, the agency will notify the participating small PWSs. See table below for the proposed monitoring design.

Table 1. Proposed Monitoring Design

Monitoring by all small PWSs serving between 3,300 and 10,000 people is subject to the availability of appropriations and sufficient laboratory capacity. 

Table 2. Proposed Contaminants, Minimum Reporting Levels, Sampling Locations, and Analytical Methods

Notes

1. Chemical Abstracts Service Registry Number (CASRN)
2. The EPA-established UCMR Minimum Reporting Level (MRL) is the lowest concentration that laboratories may report to the EPA during UCMR monitoring. UCMR MRLs are determined using data from multiple laboratories that participate in the EPA’s MRL-setting studies and are not associated with contaminant health effects information. More specifically, this multi-laboratory calculated MRL is the quantitation limit for a contaminant that is considered achievable, with 95% confidence, by at least 75% of laboratories nationwide using a specified analytical method (recognizing that individual laboratories may be able to measure at lower levels).
3. Sample Point Location - Entry point to the distribution system (EP)
4. EPA Analytical Methods
   1. EPA 524.3
      1. EPA 524.3 Recommended Parameters to Enhance Sensitivity
   2. EPA 525.3
   3. EPA 540
   4. EPA 563