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Table of Regulated Drinking Water Contaminants

Related Info

Regulation Development for Drinking Water Contaminants

Code of Federal Regulations: Title 40 - Protection of the Environment(full publication)

The National Primary Drinking Water Regulations (NPDWRs or primary

standar ds) are legally enforceable standards that apply to public water systems.Primar y standards protect public health by limiting the levels of contaminants indrinking water. Visit the list below of regulated contaminants for details.

On this page:

MicroorganismsDisinfectantsDisinfection ByproductsInorganic ChemicalsOrganic Chemicals

Radionuclides

Microorganisms

Contaminant  MCLG1

(mg/L)2

MCL

or TT1

(mg/L)2

Potential Health Eff ects fromLong-Term Exposure Above

the MCL (unless specified asshort-term)

Sources of Contaminant

in DrinkingWater

Cryptosporidium zero   TT3  Gastrointestinal illness (such as

diarrhea, vomiting, and cramps)

Human andanimal fecal

waste

Giardia lamblia   zero   TT3  Gastrointestinal illness (such as

diarrhea, vomiting, and cramps)

Human andanimal fecalwaste

Heterotrophic

 

HPC has no health effects; it isan analytic method used tomeasure the variety of bacteria

 

HPCmeasures arange of 

 

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 plate count(HPC)

n/a   TT that are common in water. Thelower the concentration of 

 bacteria in drinking water, the better maintained the water system is.

 bacteria thatare naturally

 present in theenvironment

 Legionella   zero   TT3  Legionnaire's Disease, a type of 

 pneumonia

Found

naturally inwater;multiplies inheatingsystems

Total Coliforms(including fecalcoliform and E.Coli)

zero   5.0%4 Not a health threat in itself; it isused to indicate whether other 

 potentially harmful bacteria

may be present5

Coliforms arenaturally

 present in theenvironment;

as well asfeces; fecalcoliforms and

 E. coli onlycome fromhuman andanimal fecalwaste.

Turbidity   n/a   TT3

Turbidity is a measure of the

cloudiness of water. It is used toindicate water quality andfiltration effectiveness (such aswhether disease-causingorganisms are present). Higher turbidity levels are oftenassociated with higher levels of disease-causing microorganismssuch as viruses, parasites andsome bacteria. These organisms

can cause symptoms such asnausea, cramps, diarrhea, andassociated headaches.

Soil runoff 

Viruses (enteric) zero   TT3  Gastrointestinal illness (such as

diarrhea, vomiting, and cramps)

Human andanimal fecalwaste

Disinfection Byproducts

 

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Contaminant  MCLG1

(mg/L)2

 or

TT1

(mg/L)2

 

from Long-Term ExposureAbove the MCL (unlessspecified as short-term)

 

Contaminantin DrinkingWater

Bromate   zero 0.010 Increased risk of cancer 

Byproduct of drinkingwater disinfection

Chlorite   0.8 1.0Anemia; infants and youngchildren: nervous systemeffects

Byproduct of drinkingwater disinfection

Haloacetic acids(HAA5)   n/a

6 0.060 Increased risk of cancer 

Byproduct of drinkingwater disinfection

TotalTrihalomethanes(TTHMs)

--> n/a6  ========-->--> 0.080

Liver, kidney or centralnervous system problems;increased risk of cancer 

Byproduct of drinkingwater disinfection

Disinfectants

ContaminantMCLG1

(mg/L)2

MCL or

TT1

(mg/L)2

Potential Health Effectsfrom Long-TermExposure Above theMCL (unless specified

as short-term)

Sources of Contaminantin DrinkingWater

Chloramines(as Cl2)

  MRDLG=41 MRDL=4.01Eye/nose irritation;stomach discomfort,anemia

Water additive usedto controlmicrobes

Chlorine (asCl2)

  MRDLG=41 MRDL=4.01Eye/nose irritation;stomach discomfort

Water additive usedto controlmicrobes

Chlorine

dioxide (asClO2)

  MRDLG=0.81 MRDL=0.81

Anemia; infants andyoung children: nervoussystem effects

Water additive usedto control

microbes

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Inorganic Chemicals

ContaminantMCLG1

(mg/L)2

MCL or

TT1

(mg/L)2

Potential HealthEffects from Long-Term Exposure Abovethe MCL (unlessspecified as short-

term)

Sources of Contaminant inDrinking Water

Antimony   0.006 0.006Increase in bloodcholesterol; decrease in

 blood sugar 

Discharge from petroleum refineries;fire retardants;ceramics;electronics; solder 

Arsenic   0  0.010 as of 

01/23/06

Skin damage or 

 problems withcirculatory systems,and may haveincreased risk of getting cancer 

Erosion of natural

deposits; runoff fromorchards, runoff fromglass andelectronicsproductionwastes

Asbestos(fiber > 10micrometers)

7millionfibers

 per liter (MFL)

7 MFLIncreased risk of developing benignintestinal polyps

Decay of asbestoscement in water mains; erosion of natural deposits

Barium   2 2  Increase in blood

 pressure

Discharge of drillingwastes; dischargefrom metalrefineries; erosion of natural deposits

Beryllium   0.004 0.004 Intestinal lesions

Discharge frommetal refineries and

coal-burningfactories; dischargefrom electrical,aerospace, anddefense industries

 

Corrosion of galvanized pipes;

erosion of natural

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a m um   . . ney amage  deposits; discharge

from metalrefineries; runoff from waste batteriesand paints

Chromium(total)

  0.1 0.1 Allergic dermatitis

Discharge from steel

and pulp mills;erosion of naturaldeposits

Copper    1.3   TT7; Action

Level=1.3

Short term exposure:Gastrointestinaldistress

Long term exposure:Liver or kidney

damage

People with Wilson'sDisease should consulttheir personal doctor if the amount of copper intheir water exceeds theaction level

Corrosion of 

household plumbingsystems; erosion of natural deposits

Cyanide (asfree cyanide)

  0.2 0.2  Nerve damage or 

thyroid problems

Discharge from

steel/metal factories;discharge from

 plastic and fertilizer factories

Fluoride   4.0 4.0

Bone disease (pain andtenderness of the

 bones); Children may

get mottled teeth

Water additive which promotes strongteeth; erosion of natural deposits;discharge fromfertilizer andaluminum factories

Lead   zero   TT7; Action

Infants and children:Delays in physical or mental development;children could show

slight deficits inattention span and

 

Corrosion of household plumbing

s stems erosion of 

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eve = .  

Adults: Kidney problems; high blood pressure

 natural deposits

Mercury(inorganic)

  0.002 0.002 Kidney damage

Erosion of naturaldeposits; dischargefrom refineries andfactories; runoff fromlandfills andcroplands

 Nitrate(measured as

 Nitrogen)10 10

Infants below the ageof six months whodrink water containing

nitrate in excess of theMCL could becomeseriously ill and, if untreated, may die.Symptoms includeshortness of breath and

 blue-baby syndrome.

Runoff from

fertilizer use; leakingfrom septic tanks,sewage; erosion of natural deposits

 Nitrite(measured as

 Nitrogen)1 1

Infants below the ageof six months who

drink water containingnitrite in excess of theMCL could becomeseriously ill and, if untreated, may die.Symptoms includeshortness of breath and

 blue-baby syndrome.

Runoff fromfertilizer use; leakingfrom septic tanks,sewage; erosion of natural deposits

Selenium   0.05 0.05Hair or fingernail loss;numbness in fingers or toes; circulatory

 problems

Discharge from

 petroleum refineries;erosion of naturaldeposits; dischargefrom mines

Thallium   0.0005 0.002   Hair loss; changes in blood; kidney,

intestine or liver 

Leaching from ore- processing sites;

dischar e from

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  problems

 electronics, glass,and drug factories

Organic Chemicals

Contaminant  MCLG1

(mg/L)2

MCL orTT1

(mg/L)2

PotentialHealthEffects from

Long-TermExposure

Above theMCL (unlessspecified asshort-term)

Sources of Contaminant in

Drinking Water

Acrylamide   zero   TT8

 Nervoussystem or 

 blood problems;increased risk of cancer 

Added to water duringsewage/wastewater treatment

Alachlor    zero 0.002

Eye, liver,kidney or spleen

 problems;anemia;increased risk 

of cancer 

Runoff fromherbicide used onrow crops

Atrazine   0.003 0.003

Cardiovascular system or reproductive

 problems

Runoff fromherbicide used onrow crops

Benzene   zero 0.005

Anemia;decrease in

 blood platelets;increased risk of cancer 

Discharge from

factories; leachingfrom gas storagetanks and landfills

Benzo(a)pyrene (PAHs)   zero 0.0002

Reproductivedifficulties;increased risk of cancer 

Leaching fromlinings of water storage tanks anddistribution lines

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Carbofuran   0.04 0.04

Problems with blood, nervoussystem, or reproductivesystem

Leaching of soilfumigant used onrice and alfalfa

Carbon tetrachloride   zero 0.005

Liver  problems;increased risk of cancer 

Discharge fromchemical plantsand other industrial activities

Chlordane   zero 0.002

Liver or nervoussystem

 problems;

increased risk of cancer 

Residue of bannedtermiticide

Chlorobenzene   0.1 0.1Liver or kidney

 problems

Discharge fromchemical andagriculturalchemical factories

2,4-D   0.07 0.07

Kidney, liver,

or adrenalgland

 problems

Runoff fromherbicide used onrow crops

Dalapon   0.2 0.2  Minor kidney

changes

Runoff fromherbicide used onrights of way

1,2-Dibromo-3-chloropropane (DBCP)

  zero 0.0002Reproductivedifficulties;increased risk of cancer 

Runoff/leaching

from soil fumigantused on soybeans,cotton, pineapples,and orchards

o-Dichlorobenzene   0.6 0.6

Liver, kidney,or circulatorysystem

 problems

Discharge fromindustrial chemicalfactories

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 p-Dichlorobenzene   0.075 0.075

Anemia; liver,kidney or spleendamage;changes in

 blood

Discharge fromindustrial chemicalfactories

1,2-Dichloroethane   zero 0.005  Increased risk 

of cancer 

Discharge fromindustrial chemicalfactories

1,1-Dichloroethylene   0.007 0.007  Liver 

 problems

Discharge fromindustrial chemicalfactories

cis-1,2-Dichloroethylene   0.07 0.07  Liver 

 problems

Discharge fromindustrial chemicalfactories

trans-1,2-Dichloroethylene   0.1 0.1  Liver 

 problems

Discharge fromindustrial chemicalfactories

Dichloromethane   zero 0.005

Liver 

 problems;increased risk of cancer 

Discharge fromdrug and chemicalfactories

1,2-Dichloropropane   zero 0.005  Increased risk 

of cancer 

Discharge fromindustrial chemicalfactories

Di(2-ethylhexyl) adipate   0.4 0.4

Weight loss,

liver problems,or possiblereproductivedifficulties.

Discharge fromchemical factories

Di(2-ethylhexyl) phthalate   zero 0.006

Reproductivedifficulties;liver 

  Discharge fromrubber andchemical factories

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 problems;increased risk 

of cancer 

Dinoseb   0.007 0.007  Reproductive

difficulties

Runoff fromherbicide used onsoybeans and

vegetables

Dioxin (2,3,7,8-TCDD)   zero 0.00000003

Reproductivedifficulties;increased risk of cancer 

Emissions fromwaste incinerationand other combustion;discharge fromchemical factories

Diquat   0.02 0.02 Cataracts   Runoff fromherbicide use

Endothall   0.1 0.1

Stomach andintestinal

 problems

Runoff fromherbicide use

Endrin   0.002 0.002  Liver 

 problems

Residue of banned

insecticide

Epichlorohydrin   zero   TT8

Increasedcancer risk,and over along period of time, stomach

 problems

Discharge fromindustrial chemicalfactories; animpurity of somewater treatmentchemicals

Ethylbenzene   0.7 0.7 Liver or kidneys problems

Discharge from petroleumrefineries

Ethylene dibromide   zero 0.00005

Problems withliver, stomach,reproductivesystem, or 

Discharge from petroleumrefineries

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kidneys;increased risk 

of cancer 

Glyphosate   0.7 0.7

Kidney problems;reproductive

difficulties

Runoff fromherbicide use

Heptachlor    zero 0.0004Liver damage;increased risk of cancer 

Residue of bannedtermiticide

Heptachlor epoxide   zero 0.0002Liver damage;increased risk of cancer 

Breakdown of heptachlor 

Hexachlorobenzene   zero 0.001

Liver or kidney

 problems;reproductivedifficulties;increased risk of cancer 

Discharge frommetal refineriesand agriculturalchemical factories

Hexachlorocyclopentadiene 0.05 0.05

Kidney or stomach

 problems   Discharge fromchemical factories

Lindane   0.0002 0.0002Liver or kidney

 problems

Runoff/leachingfrom insecticideused on cattle,

lumber, gardens

Methoxychlor    0.04 0.04  Reproductive

difficulties

Runoff/leachingfrom insecticideused on fruits,vegetables, alfalfa,livestock 

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Oxamyl (Vydate)   0.2 0.2   Slight nervoussystem effects

Runoff/leachingfrom insecticideused on apples,

 potatoes, andtomatoes

Polychlorinated biphenyls(PCBs)

  zero 0.0005

Skin changes;

thymus gland problems;immunedeficiencies;reproductiveor nervoussystemdifficulties;increased risk of cancer 

Runoff fromlandfills; dischargeof waste chemicals

Pentachlorophenol   zero 0.001

Liver or kidney

 problems;increasedcancer risk 

Discharge fromwood preservingfactories

Picloram   0.5 0.5  Liver 

 problems  Herbicide runoff 

Simazine   0.004 0.004  Problems with

 blood  Herbicide runoff 

Styrene   0.1 0.1

Liver, kidney,or circulatorysystem

 problems

Discharge fromrubber and plasticfactories; leachingfrom landfills

Tetrachloroethylene   zero 0.005

Liver  problems;increased risk of cancer 

Discharge fromfactories and drycleaners

Toluene   1 1

 Nervoussystem,

kidne , or 

Discharge from

etroleum factories

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liver problems

 

Toxaphene   zero 0.003

Kidney, liver,or thyroid

 problems;increased risk of cancer 

Runoff/leachingfrom insecticideused on cotton andcattle

2,4,5-TP (Silvex)   0.05 0.05  Liver 

 problemsResidue of bannedherbicide

1,2,4-Trichlorobenzene   0.07 0.07  Changes in

adrenal glands

Discharge fromtextile finishingfactories

1,1,1-Trichloroethane   0.20 0.2

Liver, nervoussystem, or circulatory

 problems

Discharge frommetal degreasingsites and other factories

1,1,2-Trichloroethane   0.003 0.005

Liver, kidney,or immunesystem

 problems

Discharge fromindustrial chemicalfactories

Trichloroethylene   zero 0.005

Liver  problems;increased risk of cancer 

Discharge frommetal degreasingsites and other factories

Vinyl chloride   zero 0.002  Increased risk 

of cancer 

Leaching fromPVC pipes;discharge from

 plastic factories

Xylenes (total)   10 10 Nervoussystemdamage

Discharge from petroleumfactories;discharge fromchemical factories

Radionuclides

 

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ContaminantMCLG1

(mg/L)2

MCL or

TT1

(mg/L)2

 

Effects from Long-Term ExposureAbove the MCL

(unless specified asshort-term)

Sources of Contaminantin Drinking Water

Alpha particles

none7 ----------zero

15 picocuries per Liter (pCi/L)

Increased risk of cancer 

Erosion of naturaldeposits of certainminerals that areradioactive and may emita form of radiationknown as alpha radiation

Beta particlesand photon

emitters

none7 ----------

zero

4millirems

 per year 

Increased risk of cancer 

Decay of natural andman-made deposits of 

certain minerals that areradioactive and may emitforms of radiation knownas photons and betaradiation

Radium 226and Radium228(combined)

none7 ----------zero

5 pCi/L  Increased risk of 

cancer Erosion of naturaldeposits

Uranium   zero

30 ug/L

as of 12/08/03

Increased risk of 

cancer, kidneytoxicity

Erosion of natural

deposits

Notes

1Definitions:

Maximum Contaminant Level Goal (MCLG) - The level of a contaminantin 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 healthgoals.Maximum Contaminant Level (MCL) - The highest level of a contaminantthat is allowed in drinking water. MCLs are set as close to MCLGs asfeasible using the best available treatment technology and taking cost intoconsideration. MCLs are enforceable standards.Maximum Residual Disinfectant Level Goal (MRDLG) - The level of adrinking water disinfectant below which there is no known or expected risk to health. MRDLGs do not reflect the benefits of the use of disinfectants tocontrol microbial contaminants.

https://safewater.zendesk.com/hc/en-us/sections/202346157https://safewater.zendesk.com/hc/en-us/sections/202366238https://safewater.zendesk.com/hc/en-us/sections/202346477https://safewater.zendesk.com/hc/en-us/sections/202366578

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Treatment Technique (TT) - A required process intended to reduce the levelof a contaminant in drinking water.Maximum Residual Disinfectant Level (MRDL) - The highest level of adisinfectant allowed in drinking water. There is convincing evidence thataddition of a disinfectant is necessary for control of microbialcontaminants.

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

a. Disinfect their water, and b. Filter their water, or c. Meet criteria for avoiding filtration so that the following contaminants are

controlled at the following levels:

Cryptosporidium: Unfiltered systems are required toinclude Cryptosporidium in their existing watershed control provisions

Giardia lamblia: 99.9% removal/inactivation.

Viruses: 99.99% removal/inactivation.

 Legionella: No limit, but EPA believes that if Giardia and viruses areremoved/inactivated, according to the treatment techniques in the SurfaceWater Treatment Rule, Legionella will also be controlled.

Turbidity: For systems that use conventional or direct filtration, at no timecan turbidity (cloudiness of water) go higher than 1 NephelometricTurbidity Unit (NTU), and samples for turbidity must be less than or equalto 0.3 NTUs in at least 95 percent of the samples in any month. Systemsthat use filtration other than the conventional or direct filtration must followstate limits, which must include turbidity at no time exceeding 5 NTUs.

Heterotrophic Plate Count (HPC): No more than 500 bacterial colonies per milliliter.

Long Term 1 Enhanced Surface Water Treatment: Surface water systems or 

groundwater under the direct influence (GWUDI) systems serving fewer than 10,000 people must comply with the applicable Long Term 1Enhanced Surface Water Treatment Rule provisions (such as turbiditystandards, individual filter monitoring, Cryptosporidium  removalrequirements, updated watershed control requirements for unfilteredsystems).

Long Term 2 Enhanced Surface Water Treatment Rule: This rule applies toall surface water systems or ground water systems under the directinfluence of surface water. The rule targets additionalCryptosporidium treatment requirements for higher risk systems and

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includes provisions to reduce risks from uncovered finished water storagefacilities and to ensure that the systems maintain microbial protection asthey take steps to reduce the formation of disinfection byproducts.

Filter Backwash Recycling: This rule requires systems that recycle to returnspecific recycle flows through all processes of the system's existingconventional or direct filtration system or at an alternate location approved

 by the state.

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

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 areindividual MCLGs for some of the individual contaminants:

Trihalomethanes: bromodichloromethane (zero); bromoform (zero);dibromochloromethane (0.06 mg/L): chloroform (0.07 mg/L.

Haloacetic acids: dichloroacetic acid (zero); trichloroacetic acid(0.02 mg/L); monochloroacetic acid (0.07mg/L). Bromoacetic acid and

dibromoacetic acid are regulated with this group but have no MCLGs.

7 Lead and copper are regulated by a treatment technique that requires systems tocontrol the corrosiveness of their water. If more than 10% of tap water samplesexceed the action level, water systems must take additional steps. For copper, theaction 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 manufacturer's certification) that when acrylamide and epichlorohydrin are usedto 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)

Last updated on February 18, 2016

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