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Water Quality Parameters

Primary Drinking Water Standards

There are two categories of the EPA’s drinking water regulations. The National Primary Drinking Water Regulations include legally enforceable maximum contaminant levels (MCL) for hazardous contaminants in 6 broad categories: microorganisms, disinfection byproducts, disinfectants, inorganic chemicals, organic chemicals, and radionuclides.

Primary Contaminants

Microorganisms

ContaminantPrimary MCLEffects
Cryptosporidium0Gastrointestinal illness (such as diarrhea, vomiting, and cramps)
Giardia lamblia0Gastrointestinal illness (such as diarrhea, vomiting, and cramps)
Heterotrophic plate count (HPC)0HPC has no health effects; it is an analytic method used to measure the variety of bacteria that are common in water. The lower the concentration of bacteria in drinking water, the better maintained the water system is.
Legionella0Legionnaire’s Disease, a type of pneumonia
Total Coliforms (including fecal coliform and E. Coli)5.0%Not a health threat in itself; it is used to indicate whether other potentially harmful bacteria may be present
Turbidityn/aTurbidity is a measure of the cloudiness of water. It is used to indicate water quality and filtration effectiveness (such as whether disease-causing organisms are present).
Viruses (enteric)0Gastrointestinal illness (such as diarrhea, vomiting, and cramps)

Disinfection Byproducts

ContaminantPrimary MCLEffects
Bromate0.010 mg/LIncreased risk of cancer
Chlorite1.0 mg/LAnemia; infants and young children: nervous system effects
Haloacetic acids (HAA5)0.060 mg/LIncreased risk of cancer
Total Trihalomethanes (TTHMs)0.080 mg/LLiver, kidney or central nervous system problems; increased risk of cancer

Disinfectants

ContaminantMaximum Residual Disinfectant LevelEffects
Chloramines (as Cl2)4.0 mg/LEye/nose irritation; stomach discomfort, anemia
Chlorine (as Cl2)4.0 mg/LEye/nose irritation; stomach discomfort
Chlorine dioxide (as ClO2)0.08 mg/LAnemia; infants and young children: nervous system effects
Total Trihalomethanes (TTHMs)0.080 mg/LLiver, kidney or central nervous system problems; increased risk of cancer

Inorganic Chemicals

ContaminantMaximum Contaminant LevelEffects
Antimony0.006 mg/LIncrease in blood cholesterol; decrease in blood sugar
Arsenic0.010 mg/LSkin damage or problems with circulatory systems, and may have increased risk of getting cancer
Asbestos7 million fibers per literIncreased risk of developing benign intestinal polyps
Barium2 mg/LIncrease in blood pressure
Beryllium0.004 mg/LIntestinal lesions
Cadmium0.005 mg/LKidney damage
Chromium0.1 mg/LAllergic dermatitis
Copper1.3 mg/LShort term exposure: Gastrointestinal distress
Long term exposure: Liver or kidney damage
Cyanide0.2 mg/LNerve damage or thyroid problems
Fluoride4.0 mg/LBone disease (pain and tenderness of the bones); Children may get mottled teeth
Lead0.015 mg/LInfants and children: Delays in physical or mental development; children could show slight deficits in attention span and learning abilities
Adults: Kidney problems; high blood pressure
Mercury0.002 mg/LKidney damage
Nitrate10 mg/LInfants below the age of six months who drink water containing nitrate in excess of the MCL could become seriously ill and, if untreated, may die. Symptoms include shortness of breath and blue-baby syndrome.
Nitrite1 mg/LInfants below the age of six months who drink water containing nitrite in excess of the MCL could become seriously ill and, if untreated, may die. Symptoms include shortness of breath and blue-baby syndrome.
Selenium0.05 mg/LHair or fingernail loss; numbness in fingers or toes; circulatory problems
Thalium0.002 mg/LHair loss; changes in blood; kidney, intestine, or liver problems

Organic Chemicals

ContaminantMaximum Contaminant LevelEffects
Acrylamide0Nervous system or blood problems; increased risk of cancer
Alachor0.002 mg/LEye, liver, kidney or spleen problems; anemia; increased risk of cancer
Atrazine0.003 mg/LCardiovascular system or reproductive problems
Benzene0.005 mg/LAnemia; decrease in blood platelets; increased risk of cancer
Benzo(a)pyrene (PAHs)0.0002 mg/LReproductive difficulties; increased risk of cancer
Carbofuran0.04 mg/LProblems with blood, nervous system, or reproductive system
Carbon tetrachloride0.005 mg/LLiver problems; increased risk of cancer
Chlordane0.002 mg/LLiver or nervous system problems; increased risk of cancer
Chlorobenzene0.1 mg/LLiver or kidney problems
2,4-D0.07 mg/LKidney, liver, or adrenal gland problems
Dalapon0.2 mg/LMinor kidney changes
1,2-Dibromo-3-chloropropane (DBCP)0.0002 mg/LReproductive difficulties; increased risk of cancer
o-Dichlorobenzene0.075 mg/LAnemia; liver, kidney or spleen damage; changes in blood
1,2-Dichloroethane0.005 mg/LIncreased risk of cancer
1,1-Dichloroethylene0.007 mg/LLiver problems
cis-1,2-Dichloroethylene0.07 mg/LLiver problems
trans-1,2-Dichloroethylene0.1 mg/LLiver problems
Dichloromethane0.005 mg/LLiver problems; increased risk of cancer
1,2-Dichloropropane0.005 mg/LIncreased risk of cancer
Di(2-ethylhexyl) adipate0.4 mg/LWeight loss, liver problems, or possible reproductive difficulties.
Di(2-ethylhexyl) phthalate0.006 mg/LReproductive difficulties; liver problems; increased risk of cancer
Dinoseb0.007 mg/LReproductive difficulties
Dioxin (2,3,7,8-TCDD)0.00000003 mg/LReproductive difficulties; increased risk of cancer
Diquat0.02 mg/LCataracts
Endothall0.1 mg/LStomach and intestinal problems
Endrin0.02 mg/LLiver problems
Epichlorohydrin0Increased cancer risk, and over a long period of time, stomach problems
Ethylbenzene0.7 mg/LLiver or kidneys problems
Ethylene dibromide0.00005 mg/LProblems with liver, stomach, reproductive system, or kidneys; increased risk of cancer
Glyphosate0.7 mg/LKidney problems; reproductive difficulties
Heptachlor0.0004 mg/LLiver damage; increased risk of cancer
Heptachlor epoxide0.0002 mg/LLiver damage; increased risk of cancer
Hexachlorobenzene0.001 mg/LLiver or kidney problems; reproductive difficulties; increased risk of cancer
Hexachlorocyclopentadiene0.05 mg/LKidney or stomach problems
Hexachlorocyclopentadiene0.05 mg/LKidney or stomach problems
Lindane0.0002 mg/LLiver or kidney problems
Methoxychlor0.04 mg/LReproductive difficulties
Oxamyl (Vydate)0.2 mg/LSlight nervous system effects
Polychlorinated biphenyls (PCBs)0.0005 mg/LSkin changes; thymus gland problems; immune deficiencies; reproductive or nervous system difficulties; increased risk of cancer
Pentachlorophenol0.001 mg/LLiver or kidney problems; increased cancer risk
Picloram0.5 mg/LLiver problems
Simazine0.004 mg/LProblems with blood
Styrene0.1 mg/LLiver, kidney, or circulatory system problems
Tetrachloroethylene0.005 mg/LLiver problems; increased risk of cancer
Toluene1 mg/LNervous system, kidney, or liver problems
Toxaphene0.003 mg/LKidney, liver, or thyroid problems; increased risk of cancer
2,4,5-TP (Silvex)0.05 mg/LLiver problems
1,2,4-Trichlorobenzene0.07 mg/LChanges in adrenal glands
1,1,1-Trichloroethane0.2 mg/LLiver, nervous system, or circulatory problems
1,1,2-Trichloroethane0.005 mg/LLiver, kidney, or immune system problems
Trichloroethylene0.005 mg/LLiver problems; increased risk of cancer
Vinyl chloride0.002 mg/LIncreased risk of cancer
Xylenes (total)10 mg/LNervous system damage

Radionuclides

ContaminantPrimary MCLEffects
Alpha particles15 picocuries per Liter (pCi/L)Increased risk of cancer
Beta particles and photon emitters4 millirems per yearIncreased risk of cancer
Radium 226 and Radium 228 (combined)5 pCi/LIncreased risk of cancer
Uranium30 ug/LIncreased risk of cancer, kidney toxicity

Secondary Drinking Water Standards

Non-mandatory regulations provide secondary maximum contamination levels (SMCL) to suggest acceptable levels of 15 additional contaminants. The National Secondary Drinking Water Regulations help manage aesthetic qualities such as taste, color, and odor, rather than human health qualities.

Secondary Contaminants

ContaminantSecondary MCLEffects
Aluminum0.05 to 0.2 mg/Lcolored water
Chloride250 mg/Lsalty taste
Color15 color unitsvisible tint
Copper1.0 mg/Lmetallic taste; blue-green staining
CorrosivityNon-corrosivemetallic taste; corroded pipes/fixtures staining
Fluoride2.0 mg/Ltooth discoloration
Foaming Agents0.5 mg/Lfrothy, cloudy; bitter taste; odor
Iron0.3 mg/Lrusty color; sediment; metallic taste; reddish or orange staining
Manganese0.05 mg/Lblack to brown color; black staining; bitter metallic taste
Odor3 TON (threshold odor number)/L“rotten-egg”, musty or chemical smell
pH6.5 – 8.5low pH: bitter metallic taste; corrosion
high pH: slippery feel; soda taste; deposits
Silver0.1 mg/Lskin discoloration; graying of the white part of the eye
Sulfate250 mg/Lsalty taste
Total Dissolved Solids (TDS)500 mg/Lhardness; deposits; colored water; staining; salty taste
Zinc5 mg/Lmetallic taste
Citations

Environmental Protection Agency, National Primary Drinking Water Regulations, https://www.epa.gov/ground-water-and-drinking-water/national-primary-drinking-water-regulations (accessed September 19, 2017).

Images: “Pouring water from bottle” by Africa Studio via Shutterstock