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Monitoring Unregulated Drinking Water Contaminants
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Second Unregulated Contaminant Monitoring Rule

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 second Unregulated Contaminant Monitoring Rule (UCMR 2) was published on January 4, 2007. UCMR 2 required monitoring for 25 contaminants between 2008 and 2010 using analytical methods developed by EPA, consensus organizations, or both. This monitoring provides a basis for future regulatory actions to protect public health.

  • Federal Register Notice: Revisions to the UCMR 2 for Public Water Systems, January 4, 2007
  • UCMR 2 Basic Information Fact Sheet (PDF)(2 pp, 9.5 K, About PDF)

UCMR 2 contaminants and analytical methods

  • Assessment Monitoring (List 1 contaminants)
  • Screening Survey (List 2 contaminants)
  • Notes

Assessment Monitoring (List 1 contaminants)

All PWSs serving more than 10,000 people and 800 representative PWSs serving 10,000 or fewer people were required to monitor for 10 List 1 contaminants during a 12-month period from January 2008 through December 2010.

  • UCMR 2: Fact Sheet for Assessment Monitoring of List 1 Contaminants (PDF)(2 pp, 9.2 K, About PDF)

Two Insecticides

Contaminant

CAS Registry Number1

Minimum Reporting Level

Sampling Points2

Analytical Methods

Dimethoate

60-51-5

0.7 µg/L

EPTDS

EPA 527

Terbufos sulfone

56070-16-7

0.4 µg/L

EPTDS

EPA 527

Five Flame Retardants

Contaminant

CAS Registry Number1

Minimum Reporting Level

Sampling Points2

Analytical Methods

2,2',4,4'-tetrabromodiphenyl ether (BDE-47)

5436-43-1

0.3 µg/L

EPTDS

EPA 527

2,2',4,4',5-pentabromodiphenyl ether (BDE-99)

60348-60-9

0.9 µg/L

EPTDS

EPA 527

2,2',4,4',5,5'-hexabromobiphenyl (HBB)

59080-40-9

0.7 µg/L

EPTDS

EPA 527

2,2',4,4',5,5'-hexabromodiphenyl ether (BDE-153)

68631-49-2

0.8 µg/L

EPTDS

EPA 527

2,2',4,4',6-pentabromodiphenyl ether (BDE-100)

189084-64-8

0.5 µg/L

EPTDS

EPA 527

Three Explosives

Contaminant

CAS Registry Number1

Minimum Reporting Level

Sampling Points2

Analytical Methods

1,3-dinitrobenzene

99-65-0

0.8 µg/L

EPTDS

EPA 529

2,4,6-trinitrotoluene (TNT)

118-96-7

0.8 µg/L

EPTDS

EPA 529

Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)

121-82-4

1 µg/L

EPTDS

EPA 529


Screening Survey (List 2 contaminants)

All PWSs serving more than 100,000 people, 320 representative PWSs serving 10,001 to 100,000 people, and 480 representative PWSs serving 10,000 or fewer people were required to monitor for 15 List 2 contaminants during a 12-month period from January 2008 through December 2010.

  • UCMR 2: Fact Sheet for Screening Survey of List 2 Contaminants (PDF)(2 pp, 8.5 K, About PDF)

Three Parent Acetanilides

Contaminant

CAS Registry Number1

Minimum Reporting Level

Sampling Points2

Analytical Methods

Acetochlor

34256-82-1

2 µg/L

EPTDS

EPA 525.2

Alachlor

15972-60-8

2 µg/L

EPTDS

EPA 525.2

Metolachlor

51218-45-2

1 µg/L

EPTDS

EPA 525.2

Six Acetanilide Degradates

Contaminant

CAS Registry Number1

Minimum Reporting Level

Sampling Points2

Analytical Methods

Acetochlor ethane sulfonic acid (ESA)

187022-11-3

1 µg/L

EPTDS

EPA 535

Acetochlor oxanilic acid (OA)

184992-44-4

2 µg/L

EPTDS

EPA 535

Alachlor ethane sulfonic acid (ESA)

142363-53-9

1 µg/L

EPTDS

EPA 535

Alachlor oxanilic acid (OA)

171262-17-2

2 µg/L

EPTDS

EPA 535

Metolachlor ethane sulfonic acid (ESA)

171118-09-5

1 µg/L

EPTDS

EPA 535

Metolachlor oxanilic acid (OA)

152019-73-3

2 µg/L

EPTDS

EPA 535

Six Nitrosamines

Contaminant

CAS Registry Number1

Minimum Reporting Level

Sampling Points2

Analytical Methods

N-nitroso-diethylamine (NDEA)

55-18-5

0.005 µg/L

EPTDS & DSMRT

EPA 521

N-nitroso-dimethylamine (NDMA)

62-75-9

0.002 µg/L

EPTDS & DSMRT

EPA 521

N-nitroso-di-n-butylamine (NDBA)

924-16-3

0.004 µg/L

EPTDS & DSMRT

EPA 521

N-nitroso-di-n-propylamine (NDPA)

621-64-7

0.007 µg/L

EPTDS & DSMRT

EPA 521

N-nitroso-methylethylamine (NMEA)

10595-95-6

0.003 µg/L

EPTDS & DSMRT

EPA 521

N-nitroso-pyrrolidine (NPYR)

930-55-2

0.002 µg/L

EPTDS & DSMRT

EPA 521


Notes

  1. Chemical Abstract Service (CAS) Registry Number
  2. Sample point:
    • Entry points to the distribution system (EPTDS)
    • Distribution system maximum residence time (DSMRT)
  • Monitoring Unregulated Drinking Water Contaminants Home
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Last updated on November 25, 2022
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