Drinking Water Standards and Guidelines

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.

[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, 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.

[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

[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] The MCL is equal to an adjusted gross alpha concentration of 15pCi/L, calculated by excluding radon and uranium, but including radium 226.

[13] 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.

[12] For additional information on the Total Coliform Rule/Revised Total Coliform Rule, go to 310 CMR 22.05 and to Public Drinking Water System Operations Federal Rules & Acts.

[13] For additional information on the Ground Water Rule, go to 310 CMR 22.26 and Public Drinking Water System Operations 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.

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) 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.

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 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).

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.

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.