First Unregulated Contaminant Monitoring Rule

Access Results

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 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 2005 using analytical methods developed by the EPA and consensus organizations. This monitoring provides a basis for future actions to protect public health.

On this page:

UCMR 1 Scope, Analytical Methods, and Contaminants

Assessment Monitoring (AM)

All PWSs serving more than 10,000 people and 800 representative PWSs serving 10,000 or fewer people were required to monitor for 12 contaminants during a 12-month period from January 2001 through December 2005.

Fact Sheets for Assessment Monitoring:

Screening Survey (SS)

PWSs monitored during a 12-month period from January 2001 through December 2003. The EPA randomly selected PWSs from those PWSs that were required to conduct AM. A set of 300 representative PWSs monitored for the 12 chemical contaminants on the SS and a different set of 300 representative PWSs monitored for Aeromonas.

Fact Sheets for the Screening Survey:

The EPA paid all analytical costs associated with monitoring at PWSs serving 10,000 or fewer people.

Table 1. Contaminants, Minimum Reporting Levels, Sampling Locations1, and Analytical Methods

Contaminant CASRN2 Minimum Reporting Level3 Analytical Method Contaminant Classification Monitoring Requirement
perchlorate 14797-73-0 4 µg/L EPA 314.0 Solid rocket propellants, munitions, fireworks, airbag initiators for vehicles, matches, and signal flares AM
methyl-tertiary-butyl-ether (MTBE) 1634-04-4 5 µg/L EPA 502.2 or EPA 524.2 Fuel additive; solvent AM
molinate 2212-67-1 0.9 µg/L EPA 507 or EPA 525.2 Pesticide AM
s-ethyl-dipropylthiocarbamate (EPTC) 759-94-4 1 µg/L EPA 507 or EPA 525.2 Pesticide AM
terbacil 5902-51-2 2 µg/L EPA 507 or EPA 525.2 Pesticide AM
4,4’-dichloro dichlorophenyl ethylene (DDE) 72-55-9 0.8 µg/L EPA 508, EPA 508.1,
EPA 525.2, or AOAC 990.06		 Pesticide AM
dimethyl tetrachloroterephthalate (DCPA) mono/di-acid degradate 887-54-7; 2136-79-0 1 µg/L EPA 515.1, EPA 515.2, EPA 515.3, or EPA 515.4 Pesticide AM
nitrobenzene4 98-95-3 10 µg/L EPA 524.2 Industrial chemical AM
2,4-dinitrotoluene 121-14-2 0.5 µg/L EPA 525.2 Explosives and related compounds AM
2,6-dinitrotoluene 606-20-2 2 µg/L EPA 525.2 Explosives and related compounds AM
acetochlor 34256-82-1 2 µg/L EPA 525.2 Pesticide AM
1,2-diphenylhydrazine 122-66-7 2 µg/L EPA 526 Industrial chemical SS
diazinon 333-41-5 0.5 µg/L EPA 526 Pesticide SS
disulfoton 298-04-4 0.5 µg/L EPA 526 Pesticide SS
fonofos 944-22-9 0.5 µg/L EPA 526 Pesticide SS
prometon 1610-18-0 0.5 µg/L EPA 526 Pesticide SS
terbufos 13071-79-9 0.5 µg/L EPA 526 Pesticide SS
2-methyl-phenol 95-48-7 0.5 µg/L EPA 528 Chemical intermediate SS
2,4-dichlorophenol 120-83-2 1 µg/L EPA 528 Pesticide SS
2,4-dinitrophenol 51-28-5 1 µg/L EPA 528 Pesticide; explosives and related compounds SS
2,4,6-trichlorophenol 88-06-2 5 µg/L EPA 528 Pesticide SS
diuron 330-54-1 1 µg/L EPA 532 Pesticide SS
linuron 330-55-2 1 µg/L EPA 532 Pesticide SS
Aeromonas NA CFU/100mL4 EPA 1605 Bacteria SS

Notes

  1. The majority of UCMR 1 samples were collected at entry point to the distribution system (EP) locations. However, samples from source water (untreated water) (SR) locations are also included in the UCMR 1 dataset. Sample point type for UCMR 1 results can be found in the UCMR Archival Data Finder and UCMR 1 occurrence data text files. Refer to the UCMR 1 Data Summary for data definitions.
  2. Chemical Abstracts Service Registry Number (CASRN), Not Available (NA)
  3. 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, an 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).
  4. Nitrobenzene was also included as an SS contaminant using EPA Method 526. Results are reported as LL-nitrobenzene.
  5. CFU/100mL – Colony forming units per one hundred milliliters. See the UCMR 1 Data Summary for more information.

Federal Register Notices

On October 29, 2002, the 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 the EPA.

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

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

On September 4, 2001, the 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, the EPA published analytical methods for several Screening Survey List 2 contaminants and described the required monitoring for those contaminants. In this notice, the EPA also modified the UCMR to improve the implementation of monitoring for both List 1 and List 2 contaminants.

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

On January 8, 1999, the EPA published a rule suspending unregulated contaminant monitoring for small PWSs.

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Last updated on August 24, 2024