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)
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

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