Arsenic Water Contamination

US Geological Survey Arsenic Map

What is the significance of the USGS map?

The U.S. Geological Survey map above (PDF version available here) provides a national snapshot of arsenic concentrations in the Nation’s groundwater. The map is based on 31,350 groundwater samples and shows arsenic concentrations found in at least 25% of samples per county.

What is the source of arsenic?

Arsenic is a naturally occurring element in the environment. Its presence in groundwater largely is the result of arsenic-bearing minerals dissolving naturally over time as certain types of rocks and soils are weathered.

What are the human health concerns?

The public’s greatest exposure to arsenic is via drinking water. Long-term exposure to arsenic via drinking water causes cancer of the skin, lungs, urinary bladder, and kidney, and causes serious skin problems. In addition, arsenic has been reported to affect the central and peripheral nervous systems, as well as heart and blood vessels. It has been associated with the development of diabetes, and it also may cause birth defects and reproductive problems.

How many Americans are exposed to arsenic in drinking water?

The National Resources Defense Council (NRDC) analyzed data compiled by the USEPA on arsenic and estimates that 34 million to as many as 56 million people drink tap water containing average levels of arsenic that pose unacceptable cancer risks.

What are the consequences of the level of arsenic in my drinking water?

According to National Academy of Sciences estimates, one out of 100 people who drinking water containing 50 parts per billion (50 ppb) will get cancer (based on drinking two liters of water per day over the course of a lifetime). The lifetime risk of dying of cancer from arsenic in tap water at la level of 10 ppb is one in 500.

How can I find out whether my drinking water contains arsenic?

First, contact your local water utility --it is required by law to provide a report on all regulated (only) contaminants and toxins found in your local drinking water. If you have a private well, your public health departments may help in locating laboratories to have your water tested. In addition, the USGS District Office in your State might have information from ongoing or previous arsenic investigations.

What is the regulated concentration of arsenic?

The current EPA standard for arsenic is a maximum of 10 ppb, reduced from 50 ppb in 2006.

Where can I get more information about arsenic in ground water?

Additional information is available online at:

  • U.S. Environmental Protection Agency (USEPA) 
  • U.S. Geological Survey (USGS)
  • World Health Organization (WHO) 
  • Natural Resources Defense Council

    What are the types of arsenic?

    Inorganic arsenic can occur in the environment in several forms but in drinking water it is mostly found as Arsenic III (trivalent arsenite) or Arsenic V (pentavalent arsenate). Arsenic III will convert to Arsenic V in water that is oxidized. Water treatment chemicals or processes such as chlorine (when there is a free chlorine residual), potassium permanganate, and ozone will change trivalent arsenic to pentavalent arsenic. A combined chlorine residual (i.e. chloramine) may not convert all the Arsenic III. It may be advisable to contact your public water utility to find out if free chlorine, or some other oxidizer, is used in your water system.

    Will Multipure Drinking Water Systems remove arsenic?

    The Multipure Aquaperform series has been tested and certified to effectively remove pentavalent arsenic (Arsenic V). The Aquaperform may remove some trivalent arsenic; however, a standard has not been established for Arsenic III. If Arsenic III has been converted to Arsenic V, then the Multipure Aquaperform systems will remove it as Arsenic V.

  • USGS Arsenic Map - County PDF (407 Kb)
  • USGS Arsenic Map - Equal Area PDF (1,920 Kb)
  • USGS Web Site

    Facts About Arsenic

    Arsenic (abbreviated As) is a naturally occurring contaminant found in many ground waters. Arsenic in water has no color, taste or odor. It must be measured by a lab test. Public water utilities must have their water tested for arsenic. You can get the results from your water utility. If you have your own well, you can have the water tested. The local health department or the state environmental health agency can provide a list of certified labs. The cost is typically $15 to $30. Information about arsenic in water can be found on the Internet at the U.S. Environmental Protection Agency website:

    There are two forms of arsenic: pentavalent arsenic (also called As(V), As(+5), and arsenate) and trivalent arsenic (also called As(III), As(+3), and arsenite). In well water, arsenic may be pentavalent, trivalent, or a combination of both. Special sampling procedures are needed for a lab to determine what type and how much of each type of arsenic is in the water. Check with the labs in your area to see if they can provide this type of service.

    Specially formulated Carbon Block systems are very effective at removing pentavalent arsenic. A free chlorine residual will rapidly convert trivalent arsenic to pentavalent arsenic. Other water treatment chemicals such as ozone and potassium permanganate will also change trivalent arsenic to pentavalent arsenic. A combined chlorine residual (also called chloramine) may not convert all the trivalent arsenic. If you get your water from a public water utility, contact the utility to find out if free chlorine or combined chlorine is used in the water system.

    The Multipure Aquaperform models are designed to remove only pentavalent arsenic. It will not convert trivalent arsenic to pentavalent arsenic. The system may remove some trivalent arsenic, however, it has not been evaluated for its ability to remove trivalent arsenic. The system was tested in a laboratory to remove pentavalent arsenic. Under lab conditions, as defined in ANSI/NSF Standard 53, the system reduced 0.050 mg/L (ppm) pentavalent arsenic to 0.010 mg/L (ppm) (the U.S. EPA standard for drinking water) or less. The performance of the system may be different at your installation. Have the treated water tested for arsenic to check if the system is working properly.

    The Carbon Block filter component of the Multipure Aquaperform filter system must be replaced as indicated in the Owner's Manual to ensure the system will continue to remove arsenic and other contaminants. The component identification and locations where you can purchase the component are listed in the installation/operation manual.

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    Multipure's Solid Carbon Block Filters provide clean, delicious, healthier water for drinking, cooking, beverages, food preparation, and more. And refreshing Multipure water is available whenever you need it, right at your kitchen sink. Multipure’s exclusive three-stage, compressed, activated solid carbon block filter does not remove healthful minerals, but it does reduce a wide range of contaminants of health concern.

    All units include hardware and materials needed for installation, and the filter is easy to replace. Plus, Multipure Drinking Water Systems come with a 90-day money-back guarantee, a lifetime warranty on the housing, and a one year warranty on all accessories.

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