Drinking Water Standards and Guidelines

Massachusetts has set maximum contaminant levels and guidance levels for various contaminants that potentially could be found in public drinking water. This page lists the compounds and the established levels.

Table of Contents


The Drinking Water List of Standards and Guidelines is a convenient compendium of guidance values available for evaluating contaminants in drinking water in Massachusetts.

In addition to the drinking water standards and guidelines listed below, MassDEP has also derived Immediate Action Levels for routinely used water treatment chemicals, to enable water treatment plant operators to identify and address serious incidents of chemical overfeed or misuse.

Four primary types of guidance, designated as Standards or Guidelines, are available for assessing drinking water quality in the Commonwealth. The guidance values are contained in six separate lists and appear in the order listed below:

  • Standards
  • Massachusetts Maximum Contaminant Levels (MMCLs)
  • Massachusetts Maximum Contaminant Levels - Radionuclides
  • Massachusetts Maximum Contaminant Levels - Biologicals
  • Guidelines
  • Massachusetts Drinking Water Guidelines

Additional Resources   for Overview


The Massachusetts Maximum Contaminant Levels (MMCLs) listed in the drinking water regulations (310 CMR 22.00) consist of promulgated US EPA MCLs which have become effective, plus a few MCLs set specifically by Massachusetts. The standards are enforced by the Drinking Water Program (DWP). Massachusetts may adopt a more stringent standard than the US EPA based on an independent review of primary or secondary data. The regulations were last promulgated in March 2016.

The MMCLs listed in 310 CMR 22.00 apply to water that is delivered to any user of a public water system as defined in 310 CMR 22.02. More specific definitions and applications are in the regulations. Private residential wells are not subject to the requirements of 310 CMR 22.00. However, these drinking water standards are recommended for the evaluation of private drinking water and are often used to evaluate private residential contamination, especially in Federal Superfund and M.G.L Chapter 21E activities.

Additional Resources   for Standards

Massachusetts Maximum Contaminant Levels (MMCLs)

Inorganic & Organic Chemicals
Substance CASRN MMCL (mg/L)
Acrylamide [1] 79061 Treatment Technique
Alachlor 15972608 0.002
Antimony 7440360 0.006
Arsenic 7440382 0.010
Asbestos [2] 1332214 7 million fibers/liter
Atrazine 1912249 0.003
Barium 7440393 2
Benzene 71432 0.005
Benzo(a)pyrene 50328 0.0002
Beryllium 7440417 0.004
Bromate 15541454 0.010
Cadmium 7440439 0.005
Carbofuran 1563662 0.04
Carbon tetrachloride 56235 0.005
Chloramines (as Cl2) N/A 4.0 (MRDL [3])
Chlordane 57749 0.002
Chlorine (as Cl2) 7782505 4.0 (MRDL)
Chlorine dioxide (as ClO2) 10049044 0.8 (MRDL)
Chlorite 7758192 1.0
Chlorobenzene 108907 0.1
Chromium (total) 7440473 0.1
Copper 7440508 Treatment Technique, 1.3 (Action Level)
Cyanide (as free cyanide) 57125 0.2
2,4-D (2,4-Dichlorophenoxyacetic acid) 94757 0.07
Dalapon 75990 0.2
1,2-Dibromo-3-chloropropane (DBCP) 96128 0.0002
1,2-Dichlorobenzene (o-DCB) 95501 0.6
1,4-Dichlorobenzene (p-DCB) [4] 106467 0.005
1,2-Dichloroethane 107062 0.005
1,1-Dichloroethylene 75354 0.007
cis-1,2-Dichloroethylene 156592 0.07
trans-1,2-Dichloroethylene 156605 0.1
Dichloromethane 75092 0.005
1,2-Dichloropropane 78875 0.005
Di(2-ethylhexyl)-adipate 103231 0.4
Di(2-ethylhexyl)-phthalate 117817 0.006
Dinoseb 88857 0.007
Diquat 85007 0.02
Endothall 145733 0.1
Endrin 72208 0.002
Epichlorohydrin [5] 106898 Treatment Technique
Ethylbenzene 100414 0.7
Ethylene dibromide (EDB) [6] 106934 0.00002
Fluoride [7] 7782414 4.0
Glyphosate 1071536 0.7
Haloacetic acids (HAA5) (for chlorinated supplies only): including monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, bromoacetic acid and dibromoacetic acid N/A 0.060
Heptachlor 76448 0.0004
Heptachlor epoxide 1024573 0.0002
Hexachlorobenzene 118741 0.001
Hexachlorocyclopentadiene 77474 0.05
Lead 7439921 Treatment Technique, 0.015 (Action Level)
Lindane 58899 0.0002
Mercury (inorganic) 7439976 0.002
Methoxychlor 72435 0.04
Nitrate (As N) 14797558 10
Nitrate/Nitrite (total) N/A 10
Nitrite (As N) 14797650 1
Oxamyl (Vydate) 23135220 0.2
PCBs (Polychlorinated biphenyls) [8] 1336363 0.0005
Pentachlorophenol 87865 0.001
Perchlorate [9] Various 0.002
PFAS6 [26] N/A 0.00002
Picloram 1918021 0.5
Selenium 7782492 0.05
Simazine 122349 0.004
Styrene 100425 0.1
2,3,7,8-TCDD (Dioxin) 1746016 3 x 10-8
Tetrachloroethylene 127184 0.005
Thallium 7440280 0.002
Toluene 108883 1
Total trihalomethanes (for chlorinated supplies only) N/A 0.080
Including: Chloroform 67663 N/A [10]
Chlorodibromomethane 124481 N/A
Bromodichloromethane 75274 N/A
Bromoform 75252 N/A
Toxaphene 8001352 0.003
2,4,5-TP (Silvex) 93721 0.05
1,2,4-Trichlorobenzene 120821 0.07
1,1,1-Trichloroethane 71556 0.2
1,1,2-Trichloroethane 79005 0.005
Trichloroethylene 79016 0.005
Vinyl chloride 75014 0.002
Xylenes (total) 1330207 10

[1] Acrylamide = 0.05% dosed at 1 mg/L (or equivalent)[1] No numerical MCL is provided for these compounds. If detected, a treatment technique is specified. Each water system must certify, in writing, to the state (using third-party or manufacturer's certification) that when acrylamide and epichlorohydrin are used in drinking water systems, the combination (or product) of dose and monomer level does not exceed the levels specified, as follows:

  • Acrylamide = 0.05% dosed at 1 mg/L (or equivalent)
  • Epichlorohydrin = 0.01% dosed at 20 mg/L (or equivalent)

[2] For fibers longer than 10 microns.

[3] MRDL = maximum residual disinfectant level - the highest level of a disinfectant allowed in drinking water. There is convincing evidence that addition of a disinfectant is necessary for control of microbial contaminants.

[4] The MMCL for this chemical is more stringent than the federal MCL.

[5] See footnote 1 above.

[6] See footnote 4 above.

[7] US EPA completed a scientific assessment of fluoride in response to a 2006 National Academy of Sciences (NAS) report recommending that US EPA update its fluoride health and exposure assessments to take into account bone and dental effects and to consider all sources of fluoride. Based upon the NAS and US EPA information and its own independent assessment, the U.S. Health and Human Services (HHS) issued a final recommendation on April 27, 2015, lowering the non-regulatory HHS limit for fluoride in drinking water to 0.7 mg/L. US EPA is currently considering whether to lower its fluoride MCL of 4 mg/L. http://wayback.archive-it.org/3926/20170127185809/https://www.hhs.gov/about/news/2015/04/27/hhs-issues-final-recommendation-for-community-water-fluoridation.html

[8] The MCL for PCBs applies to the decachlorobiphenyl species.

[9] The MCL is directed at the sensitive subgroups of pregnant women, infants, children up to the age of 12, and individuals with hypothyroidism. They should not consume drinking water containing concentrations of perchlorate exceeding 2 ug/L. MassDEP recommends that no one consume water containing perchlorate concentrations greater than 18 ug/L.

[10] Not applicable

Massachusetts Maximum Contaminant Levels - Radionuclides

Substance CASRN Type of Guidance MMCL (mg/L)
Beta particle and photon radioactivity N/A MMCL concentration which produces an annual dose of 4 millirem/yr
Gross alpha radiation [11] N/A MMCL 15 pCi/L
Radium 226 & 228 7440144 MMCL 5 pCi/L
Radon-222 [12] 14859677 ORSG 10,000 pCi/L (ORSG)
Uranium 7440611 MMCL 0.030

[11] If the gross alpha result is equal to or greater than 5 pCi/L then testing for radium 226 and radium 228 should be requested of the laboratory. If the gross alpha result is equal to or greater than 15 pCi/L then testing for uranium should also be requested.

[12] Exceedance of this guideline indicates that indoor air sampling for Radon-222 should be done. US EPA proposed MCLs for radon (64 FR 211; Tuesday, November 2, 1999) which have not been finalized.

Additional Resources   for Massachusetts Maximum Contaminant Levels - Radionuclides

Massachusetts Maximum Contaminant Levels - Biologicals

Substance CASRN MMCL
Cryptosporidium N/A Treatment Technique
E. coli N/A 310 CMR 22.05
Giardia lamblia N/A Treatment Technique
Heterotrophic plate count N/A Treatment Technique
Legionella N/A Treatment Technique
Turbidity N/A Treatment Technique
Viruses (enteric) N/A Treatment Technique
Total coliforms N/A Indicator used in tiered monitoring protocol in the Revised Total Coliform Rule [12]
Fecal Indicator (E. coli, enterococci, coliphage) N/A Indicator used in tiered monitoring protocol in the Ground Water Rule [13]

[12] For additional information on the Total Coliform Rule/Revised Total Coliform Rule, go to 310 CMR 22.05 and to https://www.mass.gov/info-details/water-systems-operations-requirements-and-guidance#federal-rules-&-acts-.

[13] For additional information on the Ground Water Rule, go to 310 CMR 22.26 and to https://www.mass.gov/info-details/water-systems-operations-requirements-and-guidance#federal-rules-&-acts-.


The MassDEP Office of Research and Standards (ORS) issues guidance for chemicals other than those with Massachusetts MCLs in drinking water. These ORS guidance values are known as ORS Guidelines or ORSG and are usually developed for use by Departmental programs in the absence of any other federal standards or guidance. ORSG may be based upon US EPA IRIS toxicity values or derived based on a review and evaluation of all available data for the chemical of interest. Some ORSG may be based on US EPA Health Advisories. Standards promulgated by the US EPA but not yet effective may also be included on the list of Massachusetts Drinking Water Guidelines. ORSG are updated when IRIS toxicity values change so as to reflect the current toxicological guidance for the chemical.

ORS uses methodology similar to that used by the US EPA's Office of Groundwater and Drinking Water (OGWDW) when setting guidelines for chemicals in drinking water. Concentrations of chemicals having evidence of carcinogenicity are minimized as much as feasible; therefore, guidelines are set at a target excess lifetime cancer risk of one in one million (1 x 10-6) or at the lowest practical quantitation limit (PQL) if the concentration at 1 x 10-6 is below the PQL. This practice applies to chemicals classified as A or B carcinogens under the old cancer classification scheme of US EPA (US EPA, 1986). Class C carcinogens are individually evaluated for a decision regarding whether to set the guidelines on cancer effects. For carcinogens classified under US EPA’s Carcinogen Risk Assessment Guidelines (US EPA, 2005), MassDEP will follow US EPA OGWDW’s procedures for development of guidance.

To derive guidance for potential non-carcinogenic effects for a chemical, ORS applies a percentage (usually 20%) to published or derived route-specific reference doses and then uses standard exposure assumptions to convert the dose to a drinking water concentration. This practice allows for the possibility of human exposures from sources other than drinking water.

Massachusetts Drinking Water Guidelines
Substance CASRN ORSG (mg/L)
Acetone 67641 6.3
Aldicarb [14] 116063 0.003
Aldicarb sulfone [15] 1646884 0.002
Aldicarb sulfoxide [16] 1646873 0.004
Bromomethane 74839 0.01
Chloroform [17] 67663 0.07
Dichlorodifluoromethane 75718 1.4
1,1-Dichloroethane 75343 0.07
1,3-Dichloropropene 542756 0.0004
1,4-Dioxane 123911 0.0003
Ethylene glycol 107211 14
Manganese [18] 7439965 general population:
0.3 (lifetime);
1.0 (limit exposure to > 1.0 mg/L to 10 days)

infants < 1 yr old:
0.3 (limit exposure to > 0.3 mg/L to 10 days)
Methyl ethyl ketone 78933 4.0
Methyl isobutyl ketone 108101 0.35
Methyl tertiary butyl ether [19] 1634044 0.07
Metolachlor 51218452 0.1
Naphthalene 91203 0.140
Nickel [20] 7440020 0.1
n-Nitrosodimethylamine (NDMA) 62759 0.00001
Petroleum hydrocarbons: [21]
N/A 0.2
Aliphatics: N/A  
C5-C8 N/A 0.3
C9-C12 [22] N/A 0.7
C9-C18 [23] N/A 0.7
C19-C36 N/A 14.0
Aromatics: N/A  
C6-C8 N/A use guidance for individual chemicals
C9-C10 N/A 0.2
C11-C22 N/A 0.2
Sodium [24] 7440235 20
Tertiary-Amyl Methyl Ether (TAME) 994058 0.09
Tertiary Butyl Alcohol (TBA) 75650 0.12
Tetrahydrofuran [25] 109999 0.6
1,1,2-Trichloro-1,2,2-trifluoroethane (FREON 113) 76131 210

All guidelines are current with the information listed in the U.S. EPA Integrated Risk Information system (IRIS) as of May 3, 2017 except where noted.

[14] The MCLs for aldicarb, aldicarb sulfone and aldicarb sulfoxide have been stayed.

[15] See footnote 11 above.

[16] See footnote 11 above.

[17] This guideline applies to non-chlorinated water supplies. For chlorinated drinking water supplies, please contact the Drinking Water Program.

[18] See Secondary Maximum Contaminant Level below and endnote to US EPA Health Advisories.

[19] The health-based guideline for MTBE was reviewed by ORS in 2000.

[20] The MCL for Nickel has been remanded and is no longer in effect; however, the current EPA IRIS chronic oral reference dose for soluble salts of nickel (https://cfpub.epa.gov/ncea/iris2/chemicalLanding.cfm?substance_nmbr=271) supports this value and it is also the currently listed EPA Life-time Health Advisory value.

[21] Monitoring for these compounds is not required but is done on a case-by-case basis. These limits may be used when evaluating health risks posed by clearly identified mixtures of petroleum hydrocarbon compounds. The analytical methods to use to generate data to compare to the Drinking Water Guidelines are the Volatile Petroleum Hydrocarbon (VPH) and the Extractable Petroleum Hydrocarbon (EPH) methods developed by the MassDEP (MassDEP 1998).

[22] The overlap in the C9-C12 range is the result of the VPH and EPH analytical methods used to quantitate these ranges of petroleum hydrocarbons in drinking water. The choice of the most appropriate range to use is based on the identity of the petroleum product of concern and is therefore determined on a case-specific basis.

[23] See footnote 9 above.

[24] All detections of sodium must be reported. Please refer to 310 CMR 22.06A for the specific requirements. The sodium guideline of 20 mg/L is based on an eight (8) ounce serving.

[25] The ORSG for tetrahydrofuran was updated in April 2014.

[26] The ORSG level is for the sum of six PFAS compounds: PFDA, PFOA, PFOS, PFNA, PFHxS and PFHpA. When some or all of these compounds occur together in drinking water, the detected concentrations for these PFAS should be summed and compared to the ORSG. This value is also applicable to the individual compounds.

Secondary Maximum Contaminant Levels

SMCLs are guidance values issued by the US EPA representing levels of chemicals or parameters above which the aesthetic properties of the water can be affected (e.g., taste, odor, color) or cosmetic effects may occur (e.g., skin or tooth discoloration). The SMCLs are listed in 310 CMR 22.00.

Secondary Maximum Contaminant Levels
Chemicals/Parameter Status SMCL (mg/L)
Aluminum F [26] 0.05 to 0.2
Chloride F 250
Color F 15 Color Units
Copper F 1
Corrosivity F non-corrosive
Fluoride F 2
Foaming agents F 0.5
Iron F 0.3
Manganese [27] F 0.05
Methyl tertiary butyl ether [28] A [29] 0.020-0.040
Odor F 3 threshold odor numbers
pH [30] F 6.5 - 8.5
Silver F 0.10
Sulfate F 250 [31]
Total dissolved solids (TDS) F 500
Zinc F 5

Secondary Standards are referenced in the Massachusetts Drinking Water Regulations (310 CMR 22.07D).

[26] Final

[27] See also Secondary Maximum Contaminant Level listing and US EPA Health Advisory reference and modification.

[28] The secondary MCL for MTBE is based on the Drinking Water Advisory set by EPA and is based on taste and odor considerations.

[29] Advisory

[30] This range of values is set to avoid adverse aesthetic impacts. Alternate system-specific values for pH may be generated for other program areas (e.g., Lead and Copper Rule water quality parameters; Immediate Action Level for Water Treatment Plant Chemicals).

[31] An MCL of 500 mg/L has been proposed by USEPA (Federal Register 12/20/94).

US EPA Health Advisories

The US EPA provides drinking water guidance in the form of Health Advisories for different durations of exposure (i.e., one-day, ten-day and lifetime). These are based upon non-cancer health effects. They are used by MassDEP when evaluating the potential health risks from chemicals in drinking water when no MMCL or ORSG is available. A tabular compilation of US EPA Health Advisories is available from the EPA Website [32]: https://www.epa.gov/dwstandardsregulations/drinking-water-contaminant-human-health-effects-information#dw-standards.

[32] The Lifetime Health Advisory for manganese contains a precautionary statement that "for infants younger than 6 months, the lifetime Health Advisory of 0.3 mg/L be used even for an acute exposure of 10 days, because of the concerns for differences in manganese content in human milk and formula and the possibility of a higher absorption and lower excretion in young infants." MassDEP is extending that age to one year out of concerns for formula use up to that age and the potential susceptibility of this early life stage to excessive manganese exposure and potential resultant toxicity.


MassDEP. 2009. DWP's Use of MCLs, Office of Research and Standards Drinking Water Guidelines for Drinking Water (ORSGs) and US EPA Health Advisory (HA) Levels.

US EPA (US Environmental Protection Agency). 2005. Guidelines for Carcinogen Risk Assessment (PDF). EPA/630/P-03/001F. Risk Assessment Forum. US Environmental Protection Agency. Washington, D.C.

US EPA (US Environmental Protection Agency). 1986. Guidelines for Carcinogen Risk Assessment. Risk Assessment Forum. US Environmental Protection Agency. Washington, D.C.

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