Inorganic Contaminants


Inorganic Contaminants (IOCs) are elements or compounds found in water supplies and may be natural in the geology or caused by activities of man through mining, industry or agriculture.  It is common to have trace amounts of many Inorganic Contaminants in water supplies.  Amounts above the Maximum Contaminant Levels may cause a variety of damaging effects to the liver, kidney, nervous system circulatory system, blood, gastrointestinal system, bones, or skin depending upon the inorganic contaminant and level of exposure.  Some Inorganic Contaminants are more damaging to infants and pregnant women.  Because of some special aspects of the rules for asbestos, fluoride, and nitrates, separate pages can be found for them on this web site.

 

Do the inorganic contaminant regulations apply to my water system?

Yes, all community and non-transient non-community public water supply systems must monitor for regulated Inorganic Contaminants in their water supply.  At the present there are 15 regulated Inorganic Contaminants (including fluoride, arsenic, and nitrates).

 

Frequency of sampling

  • Samples are to be taken at the entry point where the source enters the distribution system after treatment.
  • Samples must be taken to an EPA approved laboratory for analysis.
  • Sampling continues yearly or every three years for currently regulated Inorganic Contaminants.
  • Ground water systems – sample every 3 years
  • Surface water supplies – sample annually
  • Waivers are available to reduce  inorganic contaminant sampling to once every nine years.

 

If your water system exceeds any of the Maximum Contaminant Levels they must:

  • Notify the Drinking Water Program and complete Public Notices as required.
  • Work with the Drinking Water Program to determine the best way to reduce the level of contaminant in your water supply.  A variety of options can be considered including a new treatment process, mixing your contaminated supply with another supply that does not exceed the Maximum Contaminant Level, or using a new source of water.
  • Contact resource agencies listed on the Resource Agencies page of this web site for help in planning and finding financing for your system improvements.
  • Monitor quarterly.

 

Inorganic Contaminants


 

Contaminants

Maximum Contaminant Level

 

 

 

 

 

 

Antimony

0.006 mg/L

 

 

Arsenic

0.01 mg/L

 

 

Asbestos

7 million fibers/L

 

 

Barium

2 mg/L

 

 

Beryllium

0.004 mg/L

 

 

Cadmium

0.005 mg/L

 

 

Chromium

0.1 mg/L

 

 

Cyanide

0.2 mg/L

 

 

Fluoride

4.0 mg/L

 

 

Mercury

0.002 mg/L

 

 

Nickel

0.1 mg/L

 

 

Nitrate

10 mg/L

 

 

Nitrite (as N)

1 mg/L

 

 

Nitrate & Nitrite (combined)

10 mg/L

 

 

Selenium

0.05 mg/L

 

 

Thallium

0.002 mg/L

 

 

Additional Information

The rules for Inorganic Contaminants are contained in 40 CFR 141.11, 141.23, 141.62.