Table 3.
EPA regulations of drinking water contaminants.
| Contaminant group | Substance | MCL,a MRDLb or TTc | Standard (mg/l) |
|---|---|---|---|
| Disinfectants | Chloramines (as Cl2) | MRDL | 4.0 |
| Chlorine | MRDL | 4.0 | |
| Chlorine dioxide | MRDL | 0.8 | |
| Disinfection by-products | Bromate | MCL | 0.010 |
| Chlorite | MCL | 1.0 | |
| Haloacetic acids | MCL | 0.060 | |
| Total Trihalomethanes | MCL | 0.080 | |
| Inorganic chemicals | Antimony | MCL | 0.006 |
| Arsenic | MCL | 0.010 | |
| Asbestos | MCL | (fibers >10 micrometers) 7 million fibers per liter (MFL) | |
| Barium | MCL | 2 | |
| Beryllium | MCL | 0.004 | |
| Cadmium | MCL | 0.005 | |
| Chromium | MCL | 0.1 | |
| Copper | TT | d; Action Level = 1.3 | |
| Cyanide | MCL | 0.2 | |
| Fluoride | MCL | 4.0 | |
| Lead | TT | e | |
| Mercury (inorganic) | MCL | 0.002 | |
| Nitrate | MCL | 10 | |
| Nitrite | MCL | 1 | |
| Selenium | MCL | 0.05 | |
| Thallium | MCL | 0.002 | |
| Microorganisms | Cryptosporidium | TT | f |
| Fecal coliform & E. coli | MCL | g | |
| Giardia lamblia | TT | h | |
| Heterotrophic plate count | TT | i | |
| Legionella | TT | j | |
| Total Coliforms | MCL | 5.0%k | |
| Turbidity | TT | l | |
| Viruses | TT | m | |
| Organic chemicals | Acrylamide | TT | n |
| Alachlor | MCL | 0.002 | |
| Atrazine | MCL | 0.003 | |
| Benzene | MCL | 0.005 | |
| Benzo(a)pyrene (PAHs) | MCL | 0.0002 | |
| Carbofuran | MCL | 0.04 | |
| Carbon tetrachloride | MCL | 0.005 | |
| Chlordane | MCL | 0.002 | |
| Chlorobenzene | MCL | 0.1 | |
| 2,4-D | MCL | 0.07 | |
| Dalapon | MCL | 0.2 | |
| 1,2-Dibromo-3- chloropropane (DBCP) | MCL | 0.0002 | |
| o-Dichlorobenzene | MCL | 0.6 | |
| p-Dichlorobenzene | MCL | 0.075 | |
| 1,2-Dichloroethane | MCL | 0.005 | |
| 1,1-Dichloroethylene | MCL | 0.007 | |
| cis-1,2- Dichloroethylene | MCL | 0.07 | |
| trans-1,2, Dichloroethylene | MCL | 0.1 | |
| Dichloromethane | MCL | 0.005 | |
| 1,2-Dichloropropane | MCL | 0.005 | |
| Di(2-ethylhexyl) adipate | MCL | 0.4 | |
| Di(2-ethylhexyl) phthalate | MCL | 0.006 | |
| Dinoseb | MCL | 0.007 | |
| Dioxin (2,3,7,8-TCDD) | MCL | 0.00000003 | |
| Diquat | MCL | 0.02 | |
| Endothall | MCL | 0.1 | |
| Endrin | MCL | 0.002 | |
| Epichlorohydrin | TT | o | |
| Ethylbenzene | MCL | 0.7 | |
| Ethylene dibromide | MCL | 0.00005 | |
| Glyphosate | MCL | 0.7 | |
| Heptachlor | MCL | 0.0004 | |
| Heptachlor epoxide | MCL | 0.0002 | |
| Hexachlorobenzene | MCL | 0.001 | |
| Hexachlorocyclopentadiene | MCL | 0.05 | |
| Lindane | TT | 0.0002 | |
| Methoxychlor | MCL | 0.04 | |
| Oxamyl (Vydate) | MCL | 0.2 | |
| Pentachlorophenol | MCL | 0.001 | |
| Picloram | MCL | 0.5 | |
| Polychlorinated biphenyls (PCBs) | MCL | 0.0005 | |
| Simazine | MCL | 0.004 | |
| Styrene | MCL | 0.1 | |
| Tetrachloroethylene | MCL | 0.005 | |
| Toluene | MCL | 1 | |
| Toxaphene | MCL | 0.003 | |
| 2,4,5-TP (Silvex) | MCL | 0.05 | |
| 1,2,4- Trichlorobenzene | MCL | 0.07 | |
| 1,1,1- Trichloroethane | MCL | 0.2 | |
| 1,1,2- Trichloroethane | MCL | 0.005 | |
| Trichloroethylene | MCL | 0.005 | |
| Vinyl chloride | MCL | 0.002 | |
| Xylenes (total) | MCL | 10 | |
| Radionuclides | Alpha/photon emitters | MCL | 15 picocuries per Liter (pCi/L) |
| Beta photon emitters | MCL | 4 millirems per year | |
| Radium 226 and Radium 228 (combined) | MCL | 5 pCi/l | |
| Uranium | MCL | 30 µg/l |
aMCL: Maximum Contaminant Level. The highest level of a contaminant that is allowed in drinking water. MCLs are set as close to Maximum Contaminant Level Goals (MCLGs) as feasible using the best available treatment technology and taking cost into consideration. MCLs are enforceable standards.
bMRDL: Maximum Residual Disinfectant Level. The highest level of a disinfectant allowed in drinking water.
cTT: Treatment Technique. A required process intended to reduce the level of a contaminant in drinking water.
dTT for copper requires systems to control the corrosiveness of their water. If more than 10 percent of tap water samples exceed the action level of 1.3 mg/L, water systems must take additional steps.
eTT for lead requires systems to control the corrosiveness of their water. If more than 10 percent of tap water samples exceed the action level of 0.015 mg/L, water systems must take additional steps.
f99% removal for systems that filter. Unfiltered systems are required to include Cryptosporidium in their existing watershed control provisions.
gA routine sample that is fecal coliform-positive or E. coli-positive triggers repeat samples. If any repeat sample is total coliform-positive, the system has an acute MCL violation. A routine sample that is total coliform-positive and fecal coliform-negative or E. coli negative triggers repeat samples.
h99.9 percent removal/inactivation.
iNo more than 500 bacterial colonies per milliliter.
jNo limit.
kNo more than 5.0 percent samples total coliform-positive in a month.
lFor systems that use conventional or direct filtration, at no time can turbidity exceed 1 nephelometric turbidity unit (NTU), and samples for turbidity must be less than or equal to 0.3 NTU in at least 95 percent of the samples in any month. Systems that use filtration other than the conventional or direct filtration must follow state limits, which must include turbidity at no time exceeding 5 NTU.
m99.9 percent removal/inactivation.
nEach water system must certify annually, 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 percent dosed at 1 mg/L (or equivalent); Epichlorohydrin = 0.01 percent dosed at 20 mg/L (or equivalent).
oEach water system must certify annually 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 percent dosed at 1 mg/L (or equivalent); Epichlorohydrin = 0.01 percent dosed at 20 mg/L (or equivalent).