40 CFR § 141.61 - Maximum contaminant levels for organic contaminants.

§ 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.	Contaminant	MCL (mg/l)
(1) 75-01-4	Vinyl chloride	0.002
(2) 71-43-2	Benzene	0.005
(3) 56-23-5	Carbon tetrachloride	0.005
(4) 107-06-2	1,2-Dichloroethane	0.005
(5) 79-01-6	Trichloroethylene	0.005
(6) 106-46-7	para-Dichlorobenzene	0.075
(7) 75-35-4	1,1-Dichloroethylene	0.007
(8) 71-55-6	1,1,1-Trichloroethane	0.2
(9) 156-59-2	cis-1,2-Dichloroethylene	0.07
(10) 78-87-5	1,2-Dichloropropane	0.005
(11) 100-41-4	Ethylbenzene	0.7
(12) 108-90-7	Monochlorobenzene	0.1
(13) 95-50-1	o-Dichlorobenzene	0.6
(14) 100-42-5	Styrene	0.1
(15) 127-18-4	Tetrachloroethylene	0.005
(16) 108-88-3	Toluene	1
(17) 156-60-5	trans-1,2-Dichloroethylene	0.1
(18) 1330-20-7	Xylenes (total)	10
(19) 75-09-2	Dichloromethane	0.005
(20) 120-82-1	1,2,4-Trichloro- benzene	.07
(21) 79-00-5	1,1,2-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
15972-60-8	Alachlor	X
116-06-3	Aldicarb	X
1646-88-4	Aldicarb sulfone	X
1646-87-3	Aldicarb sulfoxide	X
1912-24-9	Atrazine	X
71-43-2	Benzene	X	X
50-32-8	Benzo[a]pyrene	X
1563-66-2	Carbofuran	X
56-23-5	Carbon tetrachloride	X	X
57-74-9	Chlordane	X
75-99-0	Dalapon	X
94-75-7	2,4-D	X
103-23-1	Di (2-ethylhexyl) adipate	X	X
117-81-7	Di (2-ethylhexyl) phthalate	X
96-12-8	Dibromochloropropane (DBCP)	X	X
95-50-1	o-Dichlorobenzene	X	X
106-46-7	para-Dichlorobenzene	X	X
107-06-2	1,2-Dichloroethane	X	X
75-35-4	1,1-Dichloroethylene	X	X
156-59-2	cis-1,2-Dichloroethylene	X	X
156-60-5	trans-1,2-Dichloroethylene	X	X
75-09-2	Dichloromethane		X
78-87-5	1,2-Dichloropropane	X	X
88-85-7	Dinoseb	X
85-00-7	Diquat	X
145-73-3	Endothall	X
72-20-8	Endrin	X
100-41-4	Ethylbenzene	X	X
106-93-4	Ethylene Dibromide (EDB)	X	X
1071-83-6	Gylphosate			X
76-44-8	Heptachlor	X
1024-57-3	Heptachlor epoxide	X
118-74-1	Hexachlorobenzene	X
77-47-3	Hexachlorocyclopentadiene	X	X
58-89-9	Lindane	X
72-43-5	Methoxychlor	X
108-90-7	Monochlorobenzene	X	X
23135-22-0	Oxamyl (Vydate)	X
87-86-5	Pentachlorophenol	X
1918-02-1	Picloram	X
1336-36-3	Polychlorinated biphenyls (PCB)	X
122-34-9	Simazine	X
100-42-5	Styrene	X	X
1746-01-6	2,3,7,8-TCDD (Dioxin)	X
127-18-4	Tetrachloroethylene	X	X
108-88-3	Toluene	X	X
8001-35-2	Toxaphene	X
93-72-1	2,4,5-TP (Silvex)	X
120-82-1	1,2,4-Trichlorobenzene	X	X
71-55-6	1,1,1-Trichloroethane	X	X
79-00-5	1,1,2-Trichloroethane	X	X
79-01-6	Trichloroethylene	X	X
75-01-4	Vinyl chloride		X
1330-20-7	Xylene	X	X

(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.	Contaminant	MCL (mg/l)
(i) 15972-60-8	Alachlor	0.002
(ii) 116-06-3	Aldicarb	0.003
(iii) 1646-87-3	Aldicarb sulfoxide	0.004
(iv) 1646-87-4	Aldicarb sulfone	0.002
(v) 1912-24-9	Atrazine	0.003
(vi) 1563-66-2	Carbofuran	0.04
(vii) 57-74-9	Chlordane	0.002
(viii) 96-12-8	Dibromochloropropane	0.0002
(ix) 94-75-7	2,4-D	0.07
(x) 106-93-4	Ethylene dibromide	0.00005
(xi) 76-44-8	Heptachlor	0.0004
(xii) 1024-57-3	Heptachlor epoxide	0.0002
(xiii) 58-89-9	Lindane	0.0002
(xiv) 72-43-5	Methoxychlor	0.04
(xv) 1336-36-3	Polychlorinated biphenyls	0.0005
(xvi) 87-86-5	Pentachlorophenol	0.001
(xvii) 8001-35-2	Toxaphene	0.003
(xviii) 93-72-1	2,4,5-TP	0.05
(xix) 50-32-8	Benzo[a]pyrene	0.0002
(xx) 75-99-0	Dalapon	0.2
(xxi) 103-23-1	Di(2-ethylhexyl) adipate	0.4
(xxii) 117-81-7	Di(2-ethylhexyl) phthalate	0.006
(xxiii) 88-85-7	Dinoseb	0.007
(xxiv) 85-00-7	Diquat	0.02
(xxv) 145-73-3	Endothall	0.1
(xxvi) 72-20-8	Endrin	0.002
(xvii) 1071-53-6	Glyphosate	0.7
(xxviii) 118-74-1	Hexacholorbenzene	0.001
(xxix) 77-47-4	Hexachlorocyclopentadiene	0.05
(xxx) 23135-22-0	Oxamyl (Vydate)	0.2
(xxxi) 1918-02-1	Picloram	0.5
(xxxii) 122-34-9	Simazine	0.004
(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 applicable	Hazard Index PFAS (HFPO-DA, PFBS, PFHxS, and PFNA)	1 (unitless) ¹	Not applicable.
(ii) 122499-17-6	HFPO-DA	0.00001	0.00001.
(iii) 45187-15-3	PFBS	No individual MCL	0.002.
(iv) 108427-53-8	PFHxS	0.00001	0.00001.
(v) 72007-68-2	PFNA	0.00001	0.00001.
(vi) 45285-51-6	PFOA	0.0000040	Not applicable.
(vii) 45298-90-6	PFOS	0.0000040	Not 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

Contaminant	BAT
Hazard Index PFAS (HFPO-DA, PFBS, PFHxS, and PFNA)	Anion exchange, GAC, reverse osmosis, nanofiltration.
HFPO-DA	Anion exchange, GAC, reverse osmosis, nanofiltration.
PFHxS	Anion exchange, GAC, reverse osmosis, nanofiltration.
PFNA	Anion exchange, GAC, reverse osmosis, nanofiltration.
PFOA	Anion exchange, GAC, reverse osmosis, nanofiltration.
PFOS	Anion 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 Carbon	All size categories.
Anion Exchange	All size categories.
Reverse Osmosis, Nanofiltration ³	3,301-10,000.

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.

[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]