Arsenic is a naturally-occurring element found in soil and minerals.

Some Maine and New Hampshire wells exhibit triple the national average amount of arsenic, thanks to our unique geology of arsenic-rich bedrock.  To view Maine’s “Arsenic Belt”, see this article in the Bangor Daily News, “‘Arsenic Belt’ in Eastern Maine Means High Rate of the Poison in Well Water, Study Finds”

Exposure to arsenic can cause many health problems.  Arsenic accumulates in body tissues. In high concentrations, arsenic can damage the skin, digestive tract, liver, heart and circulation. Studies suggest that arsenic is associated with skin cancer and bladder cancer.

Sources of Arsenic:

Arsenic contamination of water is most often caused by natural groundwater conditions, leachate from solid waste landfills, or from use of arsenic-based pesticides, which were commonly used in orchards at one time. In addition, compounds containing arsenic are used to preserve wood (e.g. pre-2004 pressure treated wood), as pesticides, and in some industries, including glass and electronics production.  Arsenic can get into air, water, and the ground from wind-blown dust. [source: the Agency for Toxic Substances Disease Registry]

Exposure Limits:

Maine Maximum Exposure Guideline limit: 10ppb (= 10ug/L = .010 mg/L)

USA Primary Drinking Water Standard limit: 10ppb (= 10ug/L = .010 mg/L) (This limit is proposed to be significantly lowered in the next few years.)



LOCAL: Maine DHHS Arsenic Fact Sheet (website)

LOCAL: What to do if your well has too much arsenic. / Maine CDC, 1 pg. pdf

LOCAL: Maine Geological Survey / Bob Marvinney, "Arsenic in Maine's Groundwater" (2016, 8 pg. pdf)

REGIONAL: Massachusetts’ Arsenic in Private Well–Water FAQ” (website)

NATIONAL: Toxic Substances Portal: Arsenic (website)

NATIONAL: Medline Plus: Arsenic (website).

IN DEPTH: Guidelines for Canadian Drinking Water Quality: Arsenic / Health Canada, 2006, 38 pg. pdf

ACADEMIC and much plagiarized: Determination of Arsenic and Other Trace Elements in Bottled Waters by High Resolution Inductively Coupled Plasma Mass Spectrometry / Croatia, 2007, 10 pg. pdf

Wikipedia: “Arsenic”

Treatment options:

The State of Massachusetts offers a good overview of arsenic treatment options here:

What can I do if my water has high arsenic levels?

If the arsenic level in your well water is above 10 ppb there are a number of treatment methods available.

However, before selecting a treatment method, there are a number of factors that need to be considered.

First, there are typically two varieties, or species, of arsenic in water: “arsenic 3” and “arsenic 5.” This is significant because “arsenic 3” is very difficult to remove from water and must be changed or “oxidized” to “arsenic 5” before it can be removed. A laboratory can determine how much of each kind of arsenic is in your water, with a method called “speciation.” Speciation will add additional cost to the analysis. Ask the laboratory what they require for this process as it may require additional samples. See MassDEP’s Certified Laboratories That Test for Arsenic Speciation web page. Oxidants that can convert arsenic 3 to 5 include: liquid chlorine (bleach), hydrogen peroxide, and ozone. Chlorine is the most readily available oxidant for home water treatment.

The second factor is whether you want point-of-use (at the tap) treatment that is installed under the kitchen sink and that has a special tap for drinking water, or whole house treatment (point-of-entry) that treats all the water that enters the house.

The third factor is the possible presence of other constituents in the water, such as iron and manganese, which might hinder the effectiveness of arsenic removal and will need to be removed before the arsenic treatment.

Arsenic removal methods or systems include anion exchange, reverse osmosis, activated alumina, and other types of adsorptive media filters. Each method has its advantages and disadvantages. Information on these treatment methods is listed below:

Anion exchange units operate using the same principle as a water softener. In this case the arsenic is exchanged for chloride. The systems are generally used to treat water for the entire house and generally require little maintenance.

Reverse osmosis (RO) is generally installed as a point-of-use treatment system and usually requires pre-filtration to remove sand and grit that might foul the RO membrane. RO is considered ineffective at removing arsenic 3.

Adsorptive filter media are used in both point-of-use and whole house treatment systems. There are several varieties of adsorptive media available including activated alumina (AA) and other types of media including some with proprietary ingredients. Activated alumina and most of the other adsorptive media will either not remove arsenic 3 or are not very efficient at the removal of arsenic 3.

The efficiency of removal is dependent on the pH of the water, and may require pre-treatment to adjust pH. If substantial arsenic 3 removal is required a typical installation would consist of a single adsorptive media cartridge with a pre-oxidation cartridge ahead of the adsorptive media cartridge. There is an ongoing cost of replacing the adsorptive media cartridges about every six months. The used media can be disposed of as a non-hazardous waste.

Reverse osmosis (RO) and adsorptive media are most commonly used for point-of-use systems. A recent cost survey conducted by New Hampshire Department of Environmental Services (NHDES) indicated that the median cost to install a point-of-use treatment system was $1,200, with median annual maintenance costs of $343. RO treatment systems are generally less expensive than adsorptive media systems. Adsorptive media and anion exchange are most commonly used for whole house treatment systems. The same NHDES survey indicated a median cost of $3,000 to install a whole house treatment system, with median annual maintenance costs of $550. Anion exchange treatment systems are generally less expensive than adsorptive media systems. The above costs from the NHDES survey did not include costs for the installation and maintenance of pre-oxidation treatment which may be required depending upon the concentration of arsenic 3. –Massachusetts’ “Arsenic in Private Well–Water FAQ” (website)

MEL Test Method for Arsenic:

Drinking Water – EPA 200.5 Rev. 4.4 (SDWA Compliant)
Wastewater – EPA 200.7 Rev. 4.4 (NPDES Compliant)
Solids & NPW – EPA 6010C Rev. 3 (SW846) (RCRA Compliant)

Sample Requirements


Container: plastic, glass
Volume: 250mL
Hold Time: 6 months if preserved with HNO3 to pH<2, otherwise 2 weeks Preservation: HNO3 to pH<2


Container: plastic, glass, baggie
Volume: a least 150g
Hold Time: 6 months
Preservation: n/a

(Chart courtesy U.S. Geological Survey)

Blue and teal colors show ‘Arsenic Belt’ across New England.