An official website of the United States government.

This is not the current EPA website. To navigate to the current EPA website, please go to This website is historical material reflecting the EPA website as it existed on January 19, 2021. This website is no longer updated and links to external websites and some internal pages may not work. More information »

Monitoring Unregulated Drinking Water Contaminants

First Unregulated Contaminant Monitoring Rule

You may need a PDF reader to view some of the files on this page. See EPA’s About PDF page to learn more.

The 1996 Safe Drinking Water Act (SDWA) amendments require that once every five years EPA issue a new list of no more than 30 unregulated contaminants to be monitored by public water systems (PWSs). The first Unregulated Contaminant Monitoring Rule (UCMR 1) was published on September 17, 1999, and through supplemental actions on March 2, 2000, and January 11, 2001.

UCMR 1 required monitoring for 26 contaminants between 2001 and 2003 using analytical methods developed by EPA, consensus organizations, or both. This monitoring provides a basis for future regulatory actions to protect public health.

On this page:

UCMR 1 contaminants

Assessment Monitoring (List 1 contaminants)

The 12 contaminants were:

  • 2,4-dinitrotoluene
  • 2,6-dinitrotoluene
  • Acetochlor
  • DCPA mono-acid degradate
  • DCPA di-acid degradate
  • 4,4'-DDE
  • EPTC
  • Molinate
  • MTBE
  • Nitrobenzene
  • Perchlorate
  • Terbacil

Fact sheets for Assessment Monitoring of List 1 contaminants:

Screening Survey (List 2 contaminants)

The 14 contaminants were:

  • 1,2-diphenylhydrazine
  • 2-methyl-phenol
  • 2,4-dichlorophenol
  • 2,4-dinitrophenol
  • 2,4,6-trichlorophenol
  • Diazinon
  • Disulfoton
  • Diuron
  • Fonofos
  • Linuron
  • Nitrobenzene
  • Prometon
  • Terbufos
  • Aeromonas

Fact sheets for the Screening Survey of List 2 contaminants:

Top of Page

Federal Register Notices

On October 29, 2002, EPA published a final rule to approve EPA Method 1605 to monitor Aeromonas. The rule also specified that laboratories wishing to be approved for this method must participate in an Aeromonas proficiency testing (PT) program conducted by EPA.

On March 12, 2002, EPA published a rule to establish the electronic reporting date for monitoring results.

On March 7, 2002, EPA published a proposed rule to approve EPA Method 1605 to monitor Aeromonas.

On September 4, 2001, EPA published a direct final rule to amend the List 2 requirements and delay the requirements for the electronic reporting of monitoring results.

On January 11, 2001, EPA published analytical methods for several Screening Survey List 2 contaminants and described the required monitoring for those contaminants. In this notice, EPA also modified the UCMR to improve the implementation of monitoring for both List 1 and List 2 contaminants.

On March 2, 2000, EPA published a rule specifying the approved analytical methods for perchlorate and acetochlor. EPA included a notice about a laboratory approval process for laboratories interested in participating in perchlorate monitoring.

On January 8, 1999, EPA published a rule suspending unregulated contaminant monitoring for small public water systems.

Top of Page