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

Updates Since 2012

The ORSG for tetrahydrofuran has been updated.  The change reflects the latest toxicological information from the US EPA IRIS database, including a chronic oral reference dose (RfD) and a “suggestive” carcinogenicity weight-of-evidence designation.  The old value was based upon an RfD derived by ORS that was based on a 1990 study by Chhabra et al.

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:


The MMCLs listed in the drinking water regulations (310 CMR 22.00) pdf format of 310 CMR 22.00: Massachusetts Drinking Water Regulations
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 on December 25, 2009.

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.

Inorganic and Organic Chemicals 

SubstanceCASRNMMCL (mg/L)
Acrylamide [1]79061Treatment Technique
Alachlor 159726080.002
Antimony 74403600.006
Arsenic 74403820.010
Asbestos [2]13322147 million fibers/liter
Atrazine 19122490.003
Barium 74403932
Benzene 714320.005
Benzo(a)pyrene 503280.0002
Beryllium 74404170.004
Bromate 155414540.010
Cadmium 74404390.005
Carbofuran 15636620.04
Carbon tetrachloride 562350.005
Chloramines (as Cl2)N/A4.0 (MRDL [3])
Chlordane 577490.002
Chlorine (as Cl2)77825054.0 (MRDL)
Chlorine dioxide (as ClO2)100490440.8 (MRDL)
Chlorite 77581921.0
Chlorobenzene 1089070.1
Chromium (total) 74404730.1
Copper 7440508Treatment Technique, 1.3 (Action Level)
Cyanide (as free cyanide) 571250.2
2,4-D (2,4-Dichlorophenoxyacetic acid) 947570.07
Dalapon 759900.2
1,2-Dibromo-3-chloropropane (DBCP) 961280.0002
1,2-Dichlorobenzene (o-DCB) 955010.6
1,4-Dichlorobenzene (p-DCB) [4]1064670.005
1,2-Dichloroethane 1070620.005
1,1-Dichloroethylene 753540.007
1,2-Dichloroethylene(cis) 1565920.07
1,2-Dichloroethylene(trans) 1566050.1
Dichloromethane 750920.005
1,2-Dichloropropane 788750.005
Di(2-ethylhexyl)-adipate 1032310.4
Di(2-ethylhexyl)-phthalate 1178170.006
Dinoseb 888570.007
Diquat 850070.02
Endothall 1457330.1
Endrin 722080.002
Epichlorohydrin [5]106898Treatment Technique
Ethylbenzene 1004140.7
Ethylene dibromide (EDB) [6]1069340.00002
Fluoride [7]77824144.0
Glyphosate 10715360.7
Haloacetic acids (HAA5) (for chlorinated supplies only): including monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, bromoacetic acid and dibromoacetic acidN/A0.060
Heptachlor 764480.0004
Heptachlor epoxide 10245730.0002
Hexachlorobenzene 1187410.001
Hexachlorocyclopentadiene 774740.05
Lead 7439921Treatment Technique, 0.015 (Action Level)
Lindane 588990.0002
Mercury (inorganic)74399760.002
Methoxychlor 724350.04
Nitrate (As N) 1479755810
Nitrate/Nitrite (total) N/A10
Nitrite (As N) 147976501
Oxamyl (Vydate) 231352200.2
PCBs (Polychlorinated biphenyls) [8]13363630.0005
Pentachlorophenol 878650.001
Perchlorate [9]Various0.002
Picloram 1918021 0.5
Selenium 77824920.05
Simazine 1223490.004
Styrene 1004250.1
2,3,7,8-TCDD (Dioxin)  17460163 x 10-8 
Tetrachloroethylene 1271840.005
Thallium 74402800.002
Toluene 1088831
Total trihalomethanes (for chlorinated supplies only)N/A0.080
Including: Chloroform 67663N/A [10]
Toxaphene 80013520.003
2,4,5-TP (Silvex) 937210.05
1,2,4-Trichlorobenzene 1208210.07
1,1,1-Trichloroethane 715560.2
1,1,2-Trichloroethane 790050.005
Trichloroethylene 790160.005
Vinyl chloride 750140.002
Xylenes (total) 133020710

[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] The U.S. Environmental Protection Agency (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) recently recommended lowering the non-regulatory HHS limit for fluoride in drinking water to 0.7 mg/L, the lowest end of its previous recommended range of 0.7-1.2 mg/L. US EPA is currently considering whether to lower its fluoride MCL of 4 mg/L.

[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 mg/L. MassDEP recommends that no one consume water containing perchlorate concentrations greater than 18 mg/L.

[10] Not applicable


Beta particle and photon radioactivity N/AMMCLconcentration which produces an annual dose of 4 millirem/yr
Gross alpha radiation N/AMMCL15 pCi/L
Radium (226 228) 7440144MMCL5 pCi/L
Radon-222 [11]14859677ORSG10,000 pCi/L (ORSG)
Uranium 7440611MMCL0.030

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


Cryptosporidium N/ATreatment Technique
E. coliN/A310 CMR 22.05
Giardia lamblia N/ATreatment Technique
Heterotrophic plate count N/ATreatment Technique
Legionella N/ATreatment Technique
Turbidity N/ATreatment Technique
Viruses (enteric) N/ATreatment Technique
Total ColiformsN/AIndicator used in tiered monitoring protocol in the Total Coliform Rule [12]
Fecal Indicator (E. coli, enterococci, coliphage)N/AIndicator used in tiered monitoring protocol in the Ground Water Rule [13]

[12] For additional information on the Total Coliform Rule, go to 310 CMR 22.05 and to and scroll down to the "Total Coliform Rule" subheading.

[13] For additional information on the Ground Water Rule, go to 310 CMR 22.26 and to and scroll down to the "Ground Water Rule" subheading.


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

SubstanceCASRNORSG (mg/L)
Acetone 676416.3
Aldicarb [14]1160630.003
Aldicarb sulfone [15]16468840.002
Aldicarb sulfoxide [16]16468730.004
Bromomethane 748390.01
Chloroform [17]676630.07
Dichlorodifluoromethane 757181.4
1,1-Dichloroethane 753430.07
1,3-Dichloropropene 5427560.0004
1,4-Dioxane 1239110.0003
Ethylene glycol 10721114
Manganese [18]7439965---
Methyl ethyl ketone 789334.0
Methyl isobutyl ketone 1081010.35
Methyl tertiary butyl ether [19]16340440.07
Metolachlor 512184520.1
Naphthalene 912030.140
Nickel [20]74400200.1
n-Nitrosodimethylamine (NDMA) 627590.00001
Petroleum hydrocarbons: [21]
C9-C12 [22]N/A0.7
C9-C18 [23]N/A0.7
C6-C8N/Ause guidance for individual chemicals
Sodium [24]744023520
Tertiary-Amyl Methyl Ether (TAME)9940580.09
Tertiary Butyl Alcohol (TBA)756500.12
Tetrahydrofuran [25]1099990.6
1,1,2-Trichloro-1,2,2-trifluoroethane (FREON 113)76131210

All guidelines are current with the information listed in the U.S. EPA Integrated Risk Information System (IRIS) as of April 8, 2014, 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 ( 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.

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).

Secondary Maximum Contaminant Levels

Chemicals/ParameterStatusSMCL (mg/L)
AluminumF [26]0.05 to 0.2
ColorF15 Color Units
Foaming agentsF0.5
Manganese [27]F0.05
Methyl tertiary butyl ether [28]A [29]0.020-0.040
OdorF3 threshold odor numbers
pH [30]F6.5 - 8.5
SulfateF250 [31]
Total dissolved solids (TDS)F500

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

[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]:

[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.

Additional Information

A more detailed description of the methodology used by ORS to derive water guidance can be found in the Guide to the Regulation of Toxic Chemicals in Massachusetts Waters (ORS, 1990) pdf format of Toxic Chemical Reg in Massachusetts Waters
doc format of Toxic Chemical Reg in Massachusetts Waters (PDF, 416 KB).

The Department's Drinking Water Program provides a description of how ORSG and US EPA HA's are used in its regulatory oversight of water quality in public drinking water supplies (MassDEP 2009).


For more information about these standards please contact Michael Hutcheson, MassDEP Office of Research and Standards, at: or 617-292-5998.


MassDEP. 2009. DWP's Use of Office of Research and Standards Drinking Water Guidelines and US EPA Health Advisory Levels. Massachusetts Department of Environmental Protection ( ).

Office of Research and Standards, 1990. Toxic Chemical Regulation in Massachusetts Waters pdf format of Toxic Chemical Reg in Massachusetts Waters
doc format of Toxic Chemical Reg in Massachusetts Waters . Massachusetts Department of Environmental Protection. Boston, MA.

US EPA (US Environmental Protection Agency). 2005. Guidelines for Carcinogen Risk Assessment. 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.