Monitoring Unregulated Drinking Water Contaminants

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.


UCMR 2 contaminants and analytical methods

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.

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

Top of Page


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.

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

Top of Page


Notes

  • Chemical Abstract Service (CAS) Registry Number
  • Sample point:
    • Entry points to the distribution system (EPTDS)
    • Distribution system maximum residence time (DSMRT)

Top of Page