National Primary Drinking Water Regulations

The National Primary Drinking Water Regulations (NPDWR) are legally enforceable primary standards and treatment techniques that apply to public water systems. Primary standards and treatment techniques protect public health by limiting the levels of contaminants in drinking water.

Microorganisms

Contaminant	MCLG	MCL or TT	Potential Health Effects from Long-Term Exposure Above the MCL (unless specified as short-term)	Sources of Contaminant in Drinking Water	Treatment Method
Cryptosporidium	zero	TT	Gastrointestinal illness (such as diarrhea, vomiting, and cramps)	Human and animal fecal waste	UF/Microfiltration, can effectively capture the small Cryptosporidium oocysts. UV can inactivate the parasite.
Giardia lamblia	zero	TT	Gastrointestinal illness (such as diarrhea, vomiting, and cramps)	Human and animal fecal waste	UF/Microfiltration, can effectively capture the Giardia. UV can inactivate the cyst.
Heterotrophic plate count (HPC)	n/a	TT	HPC 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.	HPCmeasures a range of bacteria that are naturally present in the environment	Adding Chlorine will kill the bacteria. Ozone gases will oxidize and kill the bacteria. UV will inactivate bacteria.
Legionella	zero	TT	Legionnaire’s Disease, a type of pneumonia	Found naturally in water; multiplies in heating systems	Chlorine is commonly used and can effectively kill bacteria. UV may be used, but not effective in all water conditions.
Total Coliforms (including fecal coliform and E. Coli)	zero	5.00%	Not a health threat in itself; it is used to indicate whether other potentially harmful bacteria may be present	Coliforms are naturally present in the environment; as well as feces; fecal coliforms and E. coli only come from human and animal fecal waste.	UV light will damage the DNA of bacteria, rendering them unable to reproduce. Chlorine can be used as an effective disinfectant.
Turbidity	n/a	TT	Turbidity 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). Higher turbidity levels are often associated with higher levels of disease-causing microorganisms such as viruses, parasites and some bacteria. These organisms can cause symptoms such as nausea, cramps, diarrhea, and associated headaches.	Soil runoff	UF systems can filter out high levels of turbidity, bacteria, and viruses.  Sand, carbon, and multi-media filters use layers of media to trap and remove suspended particles.
Viruses (enteric)	zero	TT	Gastrointestinal illness (such as diarrhea, vomiting, and cramps)	Human and animal fecal waste	Chlorine, chlorine dioxide, iodine, monochloramine, and ozone can be used to kill pathogens in water. UV can be used to inactivate pathogens in water.

Disinfection Byproducts

Contaminant	MCLG (mg/L)	MCL or TT (mg/L)	Potential Health Effects from Long-Term Exposure Above the MCL (unless specified as short-term)	Sources of Contaminant in Drinking Water	Treatment Method
Bromate	zero	0.010	Increased risk of cancer	Byproduct of drinking water disinfection	Activated carbon filtration, GAC filtration can also contribute to bromate removal, especially when combined with other methods.  Membrane filtration, Reverse Osmosis systems are considered the most effective method for removing bromate due to their high rejection rate.
Chlorite	0.8	1.0	Anemia; infants and young children: nervous system effects	Byproduct of drinking water disinfection	The most effective method for removing chlorite from water is using activated carbon filtration. Advanced filtration systems like Reverse Osmosis can be used for home use.
Haloacetic acids (HAA5)	n/a	0.060	Increased risk of cancer	Byproduct of drinking water disinfection	Activated carbon filtration, granular activated carbon (GAC) filters are highly effective at adsorbing HAA5 molecules from water.  RO systems can significantly reduce HAA5 levels due to their high filtration capabilities.
Total Trihalomethanes (TTHMs)	n/a	0.080	Liver, kidney or central nervous system problems; increased risk of cancer	Byproduct of drinking water disinfection	Activated carbon filtration, is considered the most effective method for removing TTHMs

Disinfectants

Contaminant	MCLG (mg/L)	MCL or TT (mg/L)	Potential Health Effects from Long-Term Exposure Above the MCL (unless specified as short-term)	Sources of Contaminant in Drinking Water	Treatment Method
Chloramines (as Cl2)	MRDLG=4	MRDL=4.0	Eye/nose irritation; stomach discomfort, anemia	Water additive used to control microbes	Catalytic carbon, is a specialized form of activated carbon with enhanced capacity to remove chloramines.
Chlorine (as Cl2)	MRDLG=4	MRDL=4.0	Eye/nose irritation; stomach discomfort	Water additive used to control microbes	The most common method is using an activated carbon filter. This effectively absorbs chlorine molecules.

Inorganic Chemicals

Contaminant	MCLG (mg/L)	MCL or TT (mg/L)	Potential Health Effects from Long-Term Exposure Above the MCL (unless specified as short-term)	Sources of Contaminant in Drinking Water	Treatment Method
Antimony	0.006	0.006	Increase in blood cholesterol; decrease in blood sugar	Discharge from petroleum refineries; fire retardants; ceramics; electronics; solder	Activated carbon, activated alumina, and specialized anion exchange resins are the most common and commercially available adsorbents.
Arsenic	0	0.010 as of 01/23/06	Skin damage or problems with circulatory systems, and may have increased risk of getting cancer	Erosion of natural deposits; runoff from orchards, runoff from glass and electronics production wastes	Oxidation converts Arsenic 3 to 5. Anion exchange removes/reduces Arsenic 5. Reverse Osmosis can reduce Arsenic 5.
Asbestos (fiber > 10 micrometers)	7 million fibers per liter (MFL)	7 MFL	Increased risk of developing benign intestinal polyps	Decay of asbestos cement in water mains; erosion of natural deposits	The most effective is Reverse Osmosis due to its ability to trap most contaminants through a semipermeable membrane, significantly reducing asbestos levels in water.
Barium	2	2	Increase in blood pressure	Discharge of drilling wastes; discharge from metal refineries; erosion of natural deposits	The most effective water treatment methods for removing Barium from water are ion exchange (water softeners) and Reverse Osmosis.
Beryllium	0.004	0.004	Intestinal lesions	Discharge from metal refineries and coal-burning factories; discharge from electrical, aerospace, and defense industries	The most effective treatment methods include Reverse Osmosis, ion exchange (water softeners) and activated alumina.
Cadmium	0.005	0.005	Kidney damage	Corrosion of galvanized pipes; erosion of natural deposits; discharge from metal refineries; runoff from waste batteries and paints	The most effective methods include Reverse Osmosis and ion exchange (water softeners). With reverse osmosis generally considered the most efficient at removing high percentages
Chromium (total)	0.1	0.1	Allergic dermatitis	Discharge from steel and pulp mills; erosion of natural deposits	The most effective treatment methods include Reverse Osmosis, specialized anion exchange, membrane filtration (like nanofiltration).
Copper	1.3	TT; Action Level=1.3	Short term exposure: Gastrointestinal distress Long term exposure: Liver or kidney damage People with Wilson’s Disease should consult their personal doctor if the amount of copper in their water exceeds the action level	Corrosion of household plumbing systems; erosion of natural deposits	The most effective treatment methods include Reverse Osmosis and ion exchange. Reverse Osmosis is generally considered the most effective for removing high levels of copper from drinking water.
Cyanide (as free cyanide)	0.2	0.2	Nerve damage or thyroid problems	Discharge from steel/metal factories; discharge from plastic and fertilizer factories	The most effective treatment methods is using Ozone treatment in conjunction with adsorption using activated carbon.
Fluoride	4.0	4.0	Bone disease (pain and tenderness of the bones); Children may get mottled teeth	Water additive which promotes strong teeth; erosion of natural deposits; discharge from fertilizer and aluminum factories	Reverse Osmosis is considered the most effective method for removing fluoride from water. Activated Alumina is a solid adsorbent that binds to fluoride ions, but effectiveness can depend on pH levels.
Lead	zero	TT; Action Level=0.010	Infants 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	Corrosion of household plumbing systems; erosion of natural deposits	Reverse Osmosis is a process that uses a semipermeable membrane to filter out contaminants like lead, achieving high removal rates. Activated Carbon Filtration, while not as effective as RO, can still reduce lead levels to some extent.
Mercury (inorganic)	0.002	0.002	Kidney damage	Erosion of natural deposits; discharge from refineries and factories; runoff from landfills and croplands	Reverse Osmosis, a semipermeable membrane that filters out mercury ions, allowing clean water to pass through.  Specialty ion exchange resins are used to exchange mercury ions in the water with other ions, effectively removing the mercury.
Nitrate (measured as Nitrogen)	10	10	Infants 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.	Runoff from fertilizer use; leaking from septic tanks, sewage; erosion of natural deposits	The primary water treatment methods are Anion exchange and Reverse Osmosis. These technologies work by attracting and capturing nitrate ions from the water through various mechanisms.
Nitrite (measured as Nitrogen)	1	1	Infants 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.	Runoff from fertilizer use; leaking from septic tanks, sewage; erosion of natural deposits	The most effective treatment methods are Anion exchange and Reverse Osmosis being the most common choices for household applications
Selenium	0.05	0.05	Hair or fingernail loss; numbness in fingers or toes; circulatory problems	Discharge from petroleum refineries; erosion of natural deposits; discharge from mines	The most effective treatment methods include Reverse Osmosis, specialized ion exchange resin. Activated Alumina can adsorb selenium onto its surface, with removal efficiency depending on the water chemistry.
Thallium	0.0005	0.002	Hair loss; changes in blood; kidney, intestine, or liver problems	Leaching from ore-processing sites; discharge from electronics, glass, and drug factories	The most common treatment methods are specialized Ion exchange and activated alumina adsorption for removing thallium from water.

Selected Per- and poly-fluoroalkyl substances (PFA)

Contaminant	MCLG (mg/L)	MCL (mg/L)	HBWC (mg/L) for Hazard Index Calculation	Potential Health Effects from Long-Term Exposure Above the MCL (unless specified as short-term)	Sources of Contaminant in Drinking Water	Treatment Method
PFAS (HFPO-DA, PFBS, PFHxS, and PFNA)	1 (unitless)	1 (unitless)	Not applicable	Low levels of multiple PFAS that individually would not likely result in increased risk of adverse health effects may result in adverse health effects when combined in a mixture. Increased health risks include liver, immune, and thyroid effects. Additionally, developmental and thyroid effects following repeated exposure during pregnancy and/or childhood.	Human and animal fecal waste	The most effective treatment methods are granular activated carbon (GAC) adsorption, Reverse Osmosis and nanofiltration. Though nanofiltration may not be as efficient as RO depending on the specific PFAS compounds.
HFPO-DA (commonly knowns as GenX Chemicals	0.00001	0.00001	0.00001	Immune, liver and kidney effects; potential concern for cancer Developmental effects following repeated exposure during pregnancy and/or childhood	Human and animal fecal waste	The most effective treatment methods are Granular Activated Carbon (GAC) adsorption and Reverse Osmosis filtration. RO is often considered the best option for individual home filtration due to its high removal efficiency.
PFBS	No individual MCLG	No individual MCL	0.002	See Hazard Index PFAS information	HPCmeasures a range of bacteria that are naturally present in the environment	The most effective treatment methods are Granular Activated Carbon (GAC) adsorption and Reverse Osmosis filtration. RO is often considered the best option for individual home filtration due to its high removal efficiency.
PFHxS	0.00001	0.00001	0.00001	Immune, thyroid, and liver effects Developmental effects following repeated exposure during pregnancy and/or childhood	Found naturally in water; multiplies in heating systems	The most effective treatment methods are Granular Activated Carbon (GAC) adsorption and Reverse Osmosis filtration. RO is often considered the best option for individual home filtration due to its high removal efficiency.
PFNA	0.00001	0.00001	0.00001	Elevated cholesterol levels and immune and liver effects Developmental effects following repeated exposure during pregnancy and/or childhood	Coliforms are naturally present in the environment; as well as feces; fecal coliforms and E. coli only come from human and animal fecal waste.	The most effective treatment methods are Granular Activated Carbon (GAC) adsorption and Reverse Osmosis filtration. RO is often considered the best option for individual home filtration due to its high removal efficiency.
PFOA	zero	0.0000040	Not applicable	Cardiovascular, immune and liver effects; increased incidence of certain types of cancers including kidney and testicular Developmental and immune effects following repeated exposure during pregnancy and/or childhood	Soil runoff	The most effective treatment methods are Granular Activated Carbon (GAC) adsorption and Reverse Osmosis filtration. RO is often considered the best option for individual home filtration due to its high removal efficiency.
PFOS	zero	0.0000040	Not applicable	Cardiovascular, immune and liver effects; increased incidence of certain types of cancers including liver Developmental and immune effects following repeated exposure during pregnancy and/or childhood	Human and animal fecal waste	The most effective treatment methods are Granular Activated Carbon (GAC) adsorption and Reverse Osmosis filtration. RO is often considered the best option for individual home filtration due to its high removal efficiency.

Radionuclides

Contaminant	MCLG (mg/L)	MCL or TT (mg/L)	Potential Health Effects from Long-Term Exposure Above the MCL (unless specified as short-term)	Sources of Contaminant in Drinking Water	Treatment Method
Alpha particles	none ———- zero	15 picocuries per Liter (pCi/L)	Increased risk of cancer	Erosion of natural deposits of certain minerals that are radioactive and may emit a form of radiation known as alpha radiation	Reverse osmosis is considered the most reliable method for removing alpha particles due to its high filtration capability.
Beta particles and photon emitters	none ———- zero	4 millirems per year	Increased risk of cancer	Decay of natural and man-made deposits of certain minerals that are radioactive and may emit forms of radiation known as photons and beta radiation	Reverse Osmosis is considered the most effective method for removing a wide range of radionuclides, including beta and photon emitters, by filtering water through a semipermeable membrane, leaving contaminants behind.
Radium 226 and Radium 228 (combined)	none ———- zero	5 pCi/L	Increased risk of cancer	Erosion of natural deposits	The most effective water treatment methods for removing combined Radium 226 and Radium 228 from water are ion exchange (including water softeners) and Reverse Osmosis
Uranium	zero	30 ug/L as of 12/08/03	Increased risk of cancer; kidney toxicity	Erosion of natural deposits	Reverse osmosis (RO) and Anion exchange are the most common methods for removing uranium from water.