Statutes, codes, and regulations
Code of Federal Regulations
Title 40 - PROTECTION OF ENVIRONMENTChapter I - ENVIRONMENTAL PROTECTION AGENCYSubchapter D - WATER PROGRAMSPart 141 - NATIONAL PRIMARY DRINKING WATER REGULATIONS
Subpart G - NATIONAL PRIMARY DRINKING WATER REGULATIONS: MAXIMUM CONTAMINANT LEVELS AND MAXIMUM RESIDUAL DISINFECTANT LEVELS
Section 141.61 - Maximum contaminant levels for organic contaminants

40 C.F.R. § 141.61

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Current through September 30, 2024
Section 141.61 - Maximum contaminant levels for organic contaminants
(a) The following maximum contaminant levels for volatile organic contaminants apply to community and non-transient, non-community water systems.

Table 1 to Paragraph (a)-Maximum Contaminant Levels for Volatile Organic Contaminants

CAS No. ContaminantMCL (mg/l)
(1) 75-01-4Vinyl chloride0.002
(2) 71-43-2Benzene0.005
(3) 56-23-5Carbon tetrachloride0.005
(4) 107-06-21,2-Dichloroethane0.005
(5) 79-01-6Trichloroethylene0.005
(6) 106-46-7para-Dichlorobenzene0.075
(7) 75-35-41,1-Dichloroethylene0.007
(8) 71-55-61,1,1-Trichloroethane0.2
(9) 156-59-2cis-1,2-Dichloroethylene0.07
(10) 78-87-51,2-Dichloropropane0.005
(11) 100-41-4Ethylbenzene0.7
(12) 108-90-7Monochlorobenzene0.1
(13) 95-50-1o-Dichlorobenzene0.6
(14) 100-42-5Styrene0.1
(15) 127-18-4Tetrachloroethylene0.005
(16) 108-88-3Toluene1
(17) 156-60-5trans-1,2-Dichloroethylene0.1
(18) 1330-20-7Xylenes (total)10
(19) 75-09-2Dichloromethane0.005
(20) 120-82-11,2,4-Trichloro- benzene.07
(21) 79-00-51,1,2-Trichloro- ethane.005

(b) The Administrator, pursuant to section 1412 of the Act, hereby identifies as indicated in table 2 to this paragraph (b) granular activated carbon (GAC), packed tower aeration (PTA), or oxidation (OX) as the best technology, treatment technique, or other means available for achieving compliance with the maximum contaminant level for organic contaminants identified in paragraphs (a) and (c) of this section, except for per- and polyfluoroalkyl substances (PFAS).

Table 2 to Paragraph (b)-BAT for Organic Contaminants in Paragraphs (a) and (c) of This Section, Except for PFAS

BAT for Organic Contaminants Listed in § 141.61 (a) and (c)

CAS No. Contaminant GAC PTA OX
15972-60-8AlachlorX
116-06-3AldicarbX
1646-88-4Aldicarb sulfoneX
1646-87-3Aldicarb sulfoxideX
1912-24-9AtrazineX
71-43-2BenzeneXX
50-32-8Benzo[a]pyreneX
1563-66-2CarbofuranX
56-23-5Carbon tetrachlorideXX
57-74-9ChlordaneX
75-99-0DalaponX
94-75-72,4-DX
103-23-1Di (2-ethylhexyl) adipateXX
117-81-7Di (2-ethylhexyl) phthalateX
96-12-8Dibromochloropropane (DBCP)XX
95-50-1o-DichlorobenzeneXX
106-46-7para-DichlorobenzeneXX
107-06-21,2-DichloroethaneXX
75-35-41,1-DichloroethyleneXX
156-59-2cis-1,2-DichloroethyleneXX
156-60-5trans-1,2-DichloroethyleneXX
75-09-2DichloromethaneX
78-87-51,2-DichloropropaneXX
88-85-7DinosebX
85-00-7DiquatX
145-73-3EndothallX
72-20-8EndrinX
100-41-4EthylbenzeneXX
106-93-4Ethylene Dibromide (EDB)XX
1071-83-6GylphosateX
76-44-8HeptachlorX
1024-57-3Heptachlor epoxideX
118-74-1HexachlorobenzeneX
77-47-3HexachlorocyclopentadieneXX
58-89-9LindaneX
72-43-5MethoxychlorX
108-90-7MonochlorobenzeneXX
23135-22-0Oxamyl (Vydate)X
87-86-5PentachlorophenolX
1918-02-1PicloramX
1336-36-3Polychlorinated biphenyls (PCB)X
122-34-9SimazineX
100-42-5StyreneXX
1746-01-62,3,7,8-TCDD (Dioxin)X
127-18-4TetrachloroethyleneXX
108-88-3TolueneXX
8001-35-2ToxapheneX
93-72-12,4,5-TP (Silvex)X
120-82-11,2,4-TrichlorobenzeneXX
71-55-61,1,1-TrichloroethaneXX
79-00-51,1,2-TrichloroethaneXX
79-01-6TrichloroethyleneXX
75-01-4Vinyl chlorideX
1330-20-7XyleneXX

(c) The following maximum contaminant levels (MCLs) in paragraphs (c)(1) and (2) of this section for synthetic organic contaminants apply to community water systems and non-transient, non-community water systems; paragraph (c)(2) of this section also contains health-based water concentrations (HBWCs) for selected per- and poly-fluoroalkyl substances (PFAS) used in calculating the Hazard Index.
(1)MCLs for Synthetic Organic Contaminants, Except for PFAS.

CAS No. ContaminantMCL (mg/l)
(i) 15972-60-8Alachlor0.002
(ii) 116-06-3Aldicarb0.003
(iii) 1646-87-3Aldicarb sulfoxide0.004
(iv) 1646-87-4Aldicarb sulfone0.002
(v) 1912-24-9Atrazine0.003
(vi) 1563-66-2Carbofuran0.04
(vii) 57-74-9Chlordane0.002
(viii) 96-12-8Dibromochloropropane0.0002
(ix) 94-75-72,4-D0.07
(x) 106-93-4Ethylene dibromide0.00005
(xi) 76-44-8Heptachlor0.0004
(xii) 1024-57-3Heptachlor epoxide0.0002
(xiii) 58-89-9Lindane0.0002
(xiv) 72-43-5Methoxychlor0.04
(xv) 1336-36-3Polychlorinated biphenyls0.0005
(xvi) 87-86-5Pentachlorophenol0.001
(xvii) 8001-35-2Toxaphene0.003
(xviii) 93-72-12,4,5-TP0.05
(xix) 50-32-8Benzo[a]pyrene0.0002
(xx) 75-99-0Dalapon0.2
(xxi) 103-23-1Di(2-ethylhexyl) adipate0.4
(xxii) 117-81-7Di(2-ethylhexyl) phthalate0.006
(xxiii) 88-85-7Dinoseb0.007
(xxiv) 85-00-7Diquat0.02
(xxv) 145-73-3Endothall0.1
(xxvi) 72-20-8Endrin0.002
(xvii) 1071-53-6Glyphosate0.7
(xxviii) 118-74-1Hexacholorbenzene0.001
(xxix) 77-47-4Hexachlorocyclopentadiene0.05
(xxx) 23135-22-0Oxamyl (Vydate)0.2
(xxxi) 1918-02-1Picloram0.5
(xxxii) 122-34-9Simazine0.004
(xxxiii) 1746-01-6 2,3,7,8-TCDD (Dioxin)3 * 10 -8

(2)MCLs and HBWCs for PFAS.

CAS. No. Contaminant MCL (mg/l) (unless otherwise noted)HBWC (mg/l) for Hazard Index calculation
(i) Not applicableHazard Index PFAS (HFPO-DA, PFBS, PFHxS, and PFNA)1 (unitless) 1Not applicable.
(ii) 122499-17-6HFPO-DA0.000010.00001.
(iii) 45187-15-3PFBSNo individual MCL0.002.
(iv) 108427-53-8PFHxS0.000010.00001.
(v) 72007-68-2PFNA0.000010.00001.
(vi) 45285-51-6PFOA0.0000040Not applicable.
(vii) 45298-90-6PFOS 0.0000040Not applicable.

1 The PFAS Mixture Hazard Index (HI) is the sum of component hazard quotients (HQs), which are calculated by dividing the measured component PFAS concentration in water by the relevant health-based water concentration when expressed in the same units (shown in ng/l for simplification). The HBWC for PFHxS is 10 ng/l; the HBWC for HFPO-DA is 10 ng/l; the HBWC for PFNA is 10 ng/l; and the HBWC for PFBS is 2000 ng/l.

Hazard Index = ([HFPO-DAwater ng/l]/[10 ng/l]) + ([PFBSwater ng/l]/[2000 ng/l]) + ([PFNAwater ng/l]/[10 ng/l]) + ([PFHxSwater ng/l]/[10 ng/l])

HBWC = health-based water concentration

HQ = hazard quotient

ng/l = nanograms per liter

PFASwater = the concentration of a specific PFAS in water

(d) The Administrator, pursuant to section 1412 of the Act, hereby identifies in table 3 to this paragraph (d) the best technology, treatment technique, or other means available for achieving compliance with the maximum contaminant levels for all regulated PFAS identified in paragraph (c) of this section:

Table 3 to Paragraph (d)-Best Available Technologies for PFAS Listed in Paragraph (c) of This Section

ContaminantBAT
Hazard Index PFAS (HFPO-DA, PFBS, PFHxS, and PFNA)Anion exchange, GAC, reverse osmosis, nanofiltration.
HFPO-DAAnion exchange, GAC, reverse osmosis, nanofiltration.
PFHxSAnion exchange, GAC, reverse osmosis, nanofiltration.
PFNAAnion exchange, GAC, reverse osmosis, nanofiltration.
PFOAAnion exchange, GAC, reverse osmosis, nanofiltration.
PFOSAnion exchange, GAC, reverse osmosis, nanofiltration.

(e) The Administrator, pursuant to section 1412 of the Act, hereby identifies in table 4 to this paragraph (e) the affordable technology, treatment technique, or other means available to systems serving 10,000 persons or fewer for achieving compliance with the maximum contaminant levels for all regulated PFAS identified in paragraph (c) of this section:

Table 4 to Paragraph (e)-Small System Compliance Technologies (SSCTs) for PFAS

Small system compliance technology 1 Affordable for listed small system categories 2
Granular Activated CarbonAll size categories.
Anion ExchangeAll size categories.
Reverse Osmosis, Nanofiltration 33,301-10,000.

1 Section 1412(b)(4)(E)(ii) of SDWA specifies that SSCTs must be affordable and technically feasible for small systems.

2 The Act (ibid.) specifies three categories of small systems: (i) those serving 25 or more, but fewer than 501, (ii) those serving more than 500, but fewer than 3,301, and (iii) those serving more than 3,300, but fewer than 10,001.

3 "Technologies reject a large volume of water and may not be appropriate for areas where water quantity may be an issue.

40 C.F.R. §141.61

56 FR 3593, Jan. 30, 1991, as amended at 56 FR 30280, July 1, 1991; 57 FR 31846, July 17, 1992; 59 FR 34324, July 1, 1994; 89 FR 32744, Apr. 26, 2024; 89 FR 49102, June 11, 2024
89 FR 32744, 6/25/2024; 89 FR 49102, 6/25/2024