Potential Contaminants

Every year, thousands of tests are conducted to monitor the quality of your water. If any contaminants are found, they are listed in the annual water quality report. However, most of the contaminants we test for are not found, so they are not listed in the water quality report.

The below table lists all of the contaminants that the Environmental Protection Agency requires New Mexico Water to test for, along with their maximum containment level (MCL). If you have any questions about this table or about the quality of your water, please contact us.

**Get more information on EPA’s adoption of MCLs for certain PFAS.**

EPA National Primary Drinking Water Standards

Contaminant MCL or TT1 (mg/L)2 Public Health Goal
Acrylamide TT8 zero
Alachlor 0.002 zero
Alpha particles 15 picocuries per Liter (pCi/L) zero
Antimony 0.006 0.006
Arsenic 0.010 as of 1/23/06 0
Asbestos (fibers >10 micrometers) 7 million fibers per Liter (MFL) 7 MFL
Atrazine 0.003 0.003
Barium 2 2
Benzene 0.005 zero
Benzo(a)pyrene (PAHs) 0.0002 zero
Beryllium 0.004 0.004
Beta particles and photon emitters 4 millirems per year zero
Bromate 0.010 zero
Cadmium 0.005 0.005
Carbofuran 0.04 0.04
Carbon tetrachloride 0.005 zero
Chloramines (as Cl2) MRDL=4.01 MRDLG=41
Chlordane 0.002 zero
Chlorine (as Cl2) MRDL=4.01 MRDLG=41
Chlorine dioxide (as ClO2) MRDL=0.81 MRDLG=0.81
Chlorite 1.0 0.8
Chlorobenzene 0.1 0.1
Chromium (total) 0.1 0.1
Copper TT7; Action Level = 1.3 1.3
Cryptosporidium TT3 zero
Cyanide (as free cyanide) 0.2 0.2
2,4-D 0.07 0.07
Dalapon 0.2 0.2
1,2-Dibromo-3-chloropropane (DBCP) 0.0002 zero
o-Dichlorobenzene 0.6 0.6
p-Dichlorobenzene 0.075 0.075
1,2-Dichloroethane 0.005 zero
1,1-Dichloroethylene 0.007 0.007
cis-1,2-Dichloroethylene 0.07 0.07
trans-1,2-Dichloroethylene 0.1 0.1
Dichloromethane 0.005 zero
1,2-Dichloropropane 0.005 zero
Di(2-ethylhexyl) adipate 0.4 0.4
Di(2-ethylhexyl) phthalate 0.006 zero
Dinoseb 0.007 0.007
Dioxin (2,3,7,8-TCDD) 0.00000003 zero
Diquat 0.02 0.02
Endothall 0.1 0.1
Endrin 0.002 0.002
Epichlorohydrin TT8 zero
Ethylbenzene 0.7 0.7
Ethylene dibromide 0.00005 zero
Fluoride 4.0 4.0
Giardia lamblia TT3 zero
Glyphosate 0.7 0.7
Haloacetic acids (HAA5) 0.060 n/a6
Heptachlor 0.0004 zero
Heptachlor epoxide 0.0002 zero
Heterotrophic plate count (HPC) TT3 n/a
Hexachlorobenzene 0.001 zero
Hexachlorocyclopentadiene 0.05 0.05
Lead TT7; Action Level = 0.015 zero
Legionella TT3 zero
Lindane 0.0002 0.0002
Mercury (inorganic) 0.002 0.002
Methoxychlor 0.04 0.04
Nitrate (measured as Nitrogen) 10 10
Nitrite (measured as Nitrogen) 1 1
Oxamyl (Vydate) 0.2 0.2
Pentachlorophenol 0.001 zero
Picloram 0.5 0.5
Polychlorinated biphenyls (PCBs) 0.0005 zero
Radium 226 and Radium 228 (combined) 5 pCi/L zero
Selenium 0.05 0.05
Simazine 0.004 0.004
Styrene 0.1 0.1
Tetrachloroethylene 0.005 zero
Thallium 0.002 0.0005
Toluene 1 1
Total Coliforms (including fecal coliform and E. coli) 5.0%4 zero
Total Trihalomethanes (TTHMs) 0.10, 0.080 after 12/31/03 n/a6
Toxaphene 0.003 zero
2,4,5-TP (Silvex) 0.05 0.05
1,2,4-Trichlorobenzene 0.07 0.07
1,1,1-Trichloroethane 0.2 0.20
1,1,2-Trichloroethane 0.005 0.003
Trichloroethylene 0.005 zero
Turbidity TT3 n/a
Uranium 30 ug/L as of 12/08/03 zero
Vinyl chloride 0.002 zero
Viruses (enteric) TT3 zero
Xylenes (total) 10 10


1 Definitions

  • Maximum Contaminant Level Goal (MCLG)—The level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety and are non-enforceable public health goals.
  • Maximum Contaminant Level (MCL)—The highest level of a contaminant that is allowed in drinking water. MCLs are set as close to MCLGs as feasible using the best available treatment technology and taking cost into consideration. MCLs are enforceable standards.
  • Maximum Residual Disinfectant Level Goal (MRDLG)—The level of a drinking water disinfectant below which there is no known or expected risk to health. MRDLGs do not reflect the benefits of the use of disinfectants to control microbial contaminants.
  • Maximum Residual Disinfectant Level (MRDL)—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.
  • Treatment Technique (TT)—A required process intended to reduce the level of a contaminant in drinking water.

2 Units are in milligrams per liter (mg/L) unless otherwise noted. Milligrams per liter are equivalent to parts per million (ppm).

3 EPA’s surface water treatment rules require systems using surface water or ground water under the direct influence of surface water to (1) disinfect their water, and (2) filter their water or meet criteria for avoiding filtration so that the following contaminants are controlled at the following levels:

  • Cryptosporidium (as of 1/1/02 for systems serving >10,000 and 1/14/05 for systems serving <10,000) 99% removal.
  • Giardia lamblia: 99.9% removal/inactivation
  • Viruses: 99.99% removal/inactivation
  • Legionella: No limit, but EPA believes that if Giardia and viruses are removed/inactivated, Legionella will also be controlled.
  • Turbidity: At no time can turbidity (cloudiness of water) go above 5 nephelolometric turbidity units (NTU); systems that filter must ensure that the turbidity go no higher than 1 NTU (0.5 NTU for conventional or direct filtration) in at least 95% of the daily samples in any month. As of January 1, 2002, for systems servicing >10,000, and January 14, 2005, for systems servicing <10,000, turbidity may never exceed 1 NTU, and must not exceed 0.3 NTU in 95% of daily samples in any month.
  • HPC: No more than 500 bacterial colonies per milliliter
  • Long Term 1 Enhanced Surface Water Treatment (Effective Date: January 14, 2005); Surface water systems or (GWUDI) systems serving fewer than 10,000 people must comply with the applicable Long Term 1 Enhanced Surface Water Treatment Rule provisions (e.g. turbidity standards, individual filter monitoring, Cryptosporidium removal requirements, updated watershed control requirements for unfiltered systems).
  • Filter Backwash Recycling: The Filter Backwash Recycling Rule requires systems that recycle to return specific recycle flows through all processes of the system’s existing conventional or direct filtration system or at an alternate location approved by the state.

4 No more than 5.0% samples total coliform-positive in a month. (For water systems that collect fewer than 40 routine samples per month, no more than one sample can be total coliform-positive per month.) Every sample that has total coliform must be analyzed for either fecal coliforms or E. coli if two consecutive TC-positive samples, and one is also positive for E. coli fecal coliforms, system has an acute MCL violation.

5 Fecal coliform and E. coli are bacteria whose presence indicates that the water may be contaminated with human or animal wastes. Disease-causing microbes (pathogens) in these wastes can cause diarrhea, cramps, nausea, headaches, or other symptoms. These pathogens may pose a special health risk for infants, young children, and people with severely compromised immune systems.

6 Although there is no collective MCLG for this contaminant group, there are individual MCLGs for some of the individual contaminants:

  • Haloacetic acids: dichloroacetic acid (zero); trichloroacetic acid (0.3 mg/L)
  • Trihalomethanes: bromodichloromethane (zero); bromoform (zero); dibromochloromethane (0.06 mg/L)

7 Lead and copper are regulated by a Treatment Technique that requires systems to control the corrosiveness of their water. If more than 10% of tap water samples exceed the action level, water systems must take additional steps. For copper, the action level is 1.3 mg/L, and for lead is 0.015 mg/L.

8 Each water system must certify, in writing, to the state (using third-party or manufacturers certification) that when it uses acrylamide and/or epichlorohydrin to treat water, 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).

National Secondary Drinking Water Standards

National Secondary Drinking Water Standards are non-enforceable guidelines regulating contaminants that may cause cosmetic effects (such as skin or tooth discoloration) or aesthetic effects (such as taste, odor, or color) in drinking water. EPA recommends secondary standards to water systems but does not require systems to comply. However, states may choose to adopt them as enforceable standards.

Contaminant Secondary Standard
Aluminum 0.05 to 0.2 mg/L
Chloride 250 mg/L
Color 15 (color units)
Copper 1.0 mg/L
Corrosivity noncorrosive
Fluoride 2.0 mg/L
Foaming Agents 0.5 mg/L
Iron 0.3 mg/L
Manganese 0.05 mg/L
Odor 3 threshold odor number
pH 6.5-8.5
Silver 0.10 mg/L
Sulfate 250 mg/L
Total Dissolved Solids 500 mg/L
Zinc 5 mg/L