Drinking Water Contaminants

The information below has been provided by the U.S. Environmental Protection Agency.

 

Contaminant

Potential Health Effects from Ingestion of Water

Sources of Contaminant in Drinking Water

Maximum

Contaminant

Level1

Maximum

Contaminant

Level Goal2

 

Concentration Units

A.  Sediment

Turbidity

Turbidity is a measure of the cloudiness of water.  It is used to indicate water quality and filtration effectiveness (e.g., 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

1 NTU; <0.3 NTU in 95% of samples collected

n/a

Nephelometric Turbidity Unit

 

B.  Microbial Cysts

Cryptosporidium

 

Gastrointestinal illness (e.g., diarrhea, vomiting, cramps)

Human and fecal animal waste

99% removal

zero

%

 

Giardia lamblia

Gastrointestinal illness (e.g., diarrhea, vomiting, cramps)

Human and animal fecal waste

99.9% removal

zero

%

 

C.  Bacteria

Total Coliforms (including fecal coliform and E.  Coli)

Not a health threat in itself; it is used to indicate whether other potentially harmful bacteria may be present5

Coliforms are naturally present in the environment; as well as feces; fecal coliforms and E.  coli only come from human and animal fecal waste.

5.0%3

zero

%

 

D.  Chlorine and Chlorination Byproducts

Haloacetic acids (HAA5)

Increased risk of cancer

Byproduct of drinking water disinfection

60

n/a4

ppb

Total Trihalomethanes (TTHMs)

Liver, kidney or central nervous system problems; increased risk of cancer

Byproduct of drinking water disinfection

80

n/a4

ppb

Chlorine (as Cl2)

Eye/nose irritation; stomach discomfort, anemia

Water additive used to control microbes

4.0

4

ppm

 

E.  Inorganic Chemicals/Heavy Metals

Arsenic

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 & electronics production wastes

0.010

n/a5

ppb

Copper

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

TT6;
Action

Level=1.3

 

1.3

ppm

Lead

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

TT6;
Action Level=0.015

 

Zero

ppm

Nitrate (measured as Nitrogen)

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; leaching from septic tanks, sewage; erosion of natural deposits

10

10

ppm

 

 

1.  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.
2.  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.

3.  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
4. 
Although there is no collective MCLG for this contaminant group, there are individual MCLGs for some of the individual contaminants:

  • Trihalomethanes: bromodichloromethane (zero); bromoform (zero); dibromochloromethane (0.06 mg/L). Chloroform is regulated with this group but has no MCLG.
  • Haloacetic acids: dichloroacetic acid (zero); trichloroacetic acid (0.3 mg/L). Monochloroacetic acid, bromoacetic acid, and dibromoacetic acid are regulated with this group but have no MCLGs.

5.  MCLGs were not established before the 1986 Amendments to the Safe Drinking Water Act. Therefore, there is no MCLG for this contaminant.

6. 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.

 UC