View all text of Subpart G [§ 141.60 - § 141.66]

§ 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) 75-01-4Vinyl 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. Contaminant MCL
(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) 1746-01-62,3,7,8-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) 45298-90-6PFOS0.0000040Not 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

Contaminant BAT 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.

[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]